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The characteristics of plants give us clues as to how some plants are similar to and different from others. Classification of plant species depends upon common and unique features that are used to identify plants by their characteristics. Scientists and plant experts have collected data on numerous plant species from studying the plants in their natural habitats and recording information about their characteristics in scientific literature and databases for future reference.
What Are the Plant's Features?
Plant features include the color, shape, size and orientation of the plant's leaves on the stem and the color of its stem, branches and/or trunk. Is the plant evergreen, or do its leaves change color in the fall? Whether the plant's leaves fall or not identifies the plant as deciduous or evergreen.
Plants are also identified by the shape and color of their fruits and the seeds they contain. Fruit and seed colors include black, brown, green, orange, yellow, red and white.
How Does the Plant Grow and Change?
Plant types are identified by their active growth seasons, which vary at different times of the year and in different parts of the world. Some actively grow during the spring and summer, while others grow during the winter months.
The height of the plant is an identifying characteristic that defines its variety within a species. Some plants grow to a minimum height in dry soils but to a towering height in moist soil conditions.
What Are Its Growth Requirements?
The types of soil and soil conditions that support a plant's growth are identifying characteristics that define where a plant will and will not grow. Soil types include varying degrees and combinations of sand, loam, silt and clay. Soil pH levels and levels of potassium, phosphorus, nitrogen and salt are also characteristics that help to identify a plant.
How Does The Plant Reproduce?
Plants are identified by their reproduction characteristics. Plants naturally reproduce by seed, through the spreading of their roots or through their bulb or corm production. Some plants are propagated through cuttings as well.
Flowering plants bloom before the formation of their fruits and seeds. Plants are identified by the shapes of their flowers and their color, whether white, yellow, orange, red, purple, brown, green or blue. Plant identification includes the times when the plants are in full bloom and for how long. The fruiting characteristics of plants--the season when the fruits form, their shape, size, color and whether the fruit is edible or poisonous---describe and identify plants.
Observe and make notes about your plant. Take measurements of its leaves, its height and spread, the circumference of its base or trunk, and describe the plant's colors and distinguishing features. Compare your plant specimens to the records found in plant identification resource materials. These include reference books and online databases. | <urn:uuid:2ada8ed4-fed6-442b-9ce9-2e40e2a6ca09> | CC-MAIN-2013-20 | http://www.gardenguides.com/100709-plant-identification-characteristics.html | 2013-05-19T02:08:35 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368696383156/warc/CC-MAIN-20130516092623-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.95132 | 569 | 4.15625 | 4 |
Definition of Immunization
Immunization: Vaccination. Immunizations work by stimulating the immune system, the natural disease-fighting system of the body. The healthy immune system is able to recognize invading bacteria and viruses and produce substances (antibodies) to destroy or disable them. Immunizations prepare the immune system to ward off a disease. To immunize against viral diseases, the virus used in the vaccine has been weakened or killed. To immunize against bacterial diseases, it is generally possible to use only a small portion of the dead bacteria to stimulate the formation of antibodies against the whole bacteria. In addition to the initial immunization process, it has been found that the effectiveness of immunizations can be improved by periodic repeat injections or "boosters." Also see Immunizations (in the plural) and Immunization of a specific type (such Immunization, Polio).
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A tsunami is a series of waves most commonly caused by violent movement of the sea floor. In some ways, it resembles the ripples radiating outward from the spot where stone has been thrown into the water, but a tsunami can occur on an enormous scale. Tsunamis are generated by any large, impulsive displacement of the sea bed level. The movement at the sea floor leading to tsunami can be produced by earthquakes, landslides and volcanic eruptions.
Most tsunamis, including almost all of those traveling across entire ocean basins with destructive force, are caused by submarine faulting associated with large earthquakes. These are produced when a block of the ocean floor is thrust upward, or suddenly drops, or when an inclined area of the seafloor is thrust upward or suddenly thrust sideways. In any event, a huge mass of water is displaced, producing tsunami. Such fault movements are accompanied by earthquakes, which are sometimes referred to as “tsunamigenic earthquakes”. Most tsunamigenic earthquakes take place at the great ocean trenches, where the tectonic plates that make up the earth’s surface collide and are forced under each other. When the plates move gradually or in small thrust, only small earthquakes are produced; however, periodically in certain areas, the plates catch. The overall motion of the plates does not stop; only the motion beneath the trench becomes hung up. Such areas where the plates are hung up are known as “seismic gaps” for their lack of earthquakes. The forces in these gaps continue to build until finally they overcome the strength of the rocks holding back the plate motion. The built-up tension (or comprehension) is released in one large earthquake, instead of many smaller quakes, and these often generate large deadly tsunamis. If the sea floor movement is horizontal, a tsunami is not generated. Earthquakes of magnitude larger than M 6.5 are critical for tsunami generation.
Tsunamis produced by landslides:
Probably the second most common cause of tsunami is landslide. A tsunami may be generated by a landslide starting out above the sea level and then plunging into the sea, or by a landslide entirely occurring underwater. Landslides occur when slopes or deposits of sediment become too steep and the material falls under the pull of gravity. Once unstable conditions are present, slope failure can be caused by storms, earthquakes, rain, or merely continued deposit of material on the slope. Certain environments are particularly susceptible to the production of landslide-generated earthquakes. River deltas and steep underwater slopes above sub-marine canyons, for instance, are likely sites for landslide-generated earthquakes.
Tsunami produced by Volcanoes:
The violent geologic activity associated with volcanic eruptions can also generate devastating tsunamis. Although volcanic tsunamis are much less frequent, they are often highly destructive. These may be due to submarine explosions, pyroclastic flows and collapse of volcanic caldera.
(1) Submarine volcanic explosions occur when cool seawater encounters hot volcanic magma. It often reacts violently, producing stream explosions. Underwater eruptions at depths of less than 1500 feet are capable of disturbing the water all the way to the surface and producing tsunamis.
(2) Pyroclastic flows are incandescent, ground-hugging clouds, driven by gravity and fluidized by hot gases. These flows can move rapidly off an island and into the ocean, their impact displacing sea water and producing a tsunami.
(3) The collapse of a volcanic caldera can generate tsunami. This may happen when the magma beneath a volcano is withdrawn back deeper into the earth, and the sudden subsidence of the volcanic edifice displaces water and produces tsunami waves. The large masses of rock that accumulate on the sides of the volcanoes may suddenly slide down slope into the sea, causing tsunamis. Such landslides may be triggered by earthquakes or simple gravitational collapse. A catastrophic volcanic eruption and its ensuing tsunami waves may actually be behind the legend of the lost island civilization of Atlantis. The largest volcanic tsunami in historical times and the most famous historically documented volcanic eruption took lace in the East Indies-the eruption of Krakatau in 1883.
Tsunami waves :
A tsunami has a much smaller amplitude (wave height) offshore, and a very long wavelength (often hundreds of kilometers long), which is why they generally pass unnoticed at sea, forming only a passing "hump" in the ocean. Tsunamis have been historically referred to tidal waves because as they approach land, they take on the characteristics of a violent onrushing tide rather than the sort of cresting waves that are formed by wind action upon the ocean (with which people are more familiar). Since they are not actually related to tides the term is considered misleading and its usage is discouraged by oceanographers.
These waves are different from other wind-generated ocean waves, which rarely extend below a dept of 500 feet even in large storms. Tsunami waves, on the contrary, involvement of water all the way to the sea floor, and as a result their speed is controlled by the depth of the sea. Tsunami waves may travel as fast as 500 miles per hour or more in deep waters of an ocean basin. Yet these fast waves may be only a foot of two high in deep water. These waves have greater wavelengths having long 100 miles between crests. With a height of 2 to 3 feet spread over 100 miles, the slope of even the most powerful tsunamis would be impossible to see from a ship or airplane. A tsunami may consist of 10 or more waves forming a ‘tsunami wave train’. The individual waves follow one behind the other anywhere from 5 to 90 minutes apart.
As the waves near shore, they travel progressively more slowly, but the energy lost from decreasing velocity is transformed into increased wavelength. A tsunami wave that was 2 feet high at sea may become a 30-feet giant at the shoreline. Tsunami velocity is dependent on the depth of water through which it travels (velocity equals the square root of water depth h times the gravitational acceleration g, that is (V=√gh). The tsunami will travel approximately at a velocity of 700 kmph in 4000 m depth of sea water. In 10 m, of water depth the velocity drops to about 35 kmph. Even on shore tsunami speed is 35 to 40 km/h, hence much faster than a person can run.It is commonly believed that the water recedes before the first wave of a tsunami crashes ashore. In fact, the first sign of a tsunami is just as likely to be a rise in the water level. Whether the water rises or falls depends on what part of the tsunami wave train first reaches the coast. A wave crest will cause a rise in the water level and a wave trough causes a water recession.
Seiche (pronounced as ‘saysh’) is another wave phenomenon that may be produced when a tsunami strikes. The water in any basin will tend to slosh back and forth in a certain period of time determined by the physical size and shape of the basin. This sloshing is known as the seiche. The greater the length of the body, the longer the period of oscillation. The depth of the body also controls the period of oscillations, with greater water depths producing shorter periods. A tsunami wave may set off seiche and if the following tsunami wave arrives with the next natural oscillation of the seiche, water may even reach greater heights than it would have from the tsunami waves alone. Much of the great height of tsunami waves in bays may be explained by this constructive combination of a seiche wave and a tsunami wave arriving simultaneously. Once the water in the bay is set in motion, the resonance may further increase the size of the waves. The dying of the oscillations, or damping, occurs slowly as gravity gradually flattens the surface of the water and as friction turns the back and forth sloshing motion into turbulence. Bodies of water with steep, rocky sides are often the most seiche-prone, but any bay or harbour that is connected to offshore waters can be perturbed to form seiche, as can shelf waters that are directly exposed to the open sea.
The presence of a well developed fringing or barrier of coral reef off a shoreline also appears to have a strong effect on tsunami waves. A reef may serve to absorb a significant amount of the wave energy, reducing the height and intensity of the wave impact on the shoreline itself.
The popular image of a tsunami wave approaching shore is that of a nearly vertical wall of water, similar to the front of a breaking wave in the surf. Actually, most tsunamis probably don’t form such wave fronts; the water surface instead is very close to the horizontal, and the surface itself moves up and down. However, under certain circumstances an arriving tsunami wave can develop an abrupt steep front that will move inland at high speeds. This phenomenon is known as a bore. In general, the way a bore is created is related to the velocity of the shallow water waves. As waves move into progressively shallower water, the wave in front will be traveling more slowly than the wave behind it .This phenomenon causes the waves to begin “catching up” with each other, decreasing their distance apart i.e. shrinking the wavelength. If the wavelength decreases, but the height does not, then waves must become steeper. Furthermore, because the crest of each wave is in deeper water than the adjacent trough, the crest begins to overtake the trough in front and the wave gets steeper yet. Ultimately the crest may begin to break into the trough and a bore formed. A tsunami can cause a bore to move up a river that does not normally have one. Bores are particularly common late in the tsunami sequence, when return flow from one wave slows the next incoming wave. Though some tsunami waves do, in deed, form bores, and the impact of a moving wall of water is certainly impressive, more often the waves arrive like a very rapidly rising tide that just keeps coming and coming. The normal wind waves and swells may actually ride on top of the tsunami, causing yet more turbulence and bringing the water level to even greater heights. | <urn:uuid:87a817df-e201-474d-b964-dcde3f8d1a17> | CC-MAIN-2013-20 | http://www.osdma.org/ViewDetails.aspx?vchglinkid=GL002&vchplinkid=PL009 | 2013-05-19T02:39:17 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368696383156/warc/CC-MAIN-20130516092623-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.942164 | 2,112 | 4.90625 | 5 |
The hoary marmot (Marmota caligata), the Alaska marmot (M. broweri), and the woodchuck (M. monax) are the three species of marmots that live in Alaska. The hoary marmot can be found at the bases of active talus slopes in the mountains of central, southeastern, and southwestern Alaska. It also occurs down to sea level along some areas of the coast. The Alaska marmot lives in similar talus habitat throughout much of the Brooks Range. The woodchuck digs its den in loess (wind-deposited soils) along river valleys in the dry lowlands of eastcentral Alaska.
General description: Large relatives of the squirrel, the hoary and closely related Alaska marmots weigh 10 pounds (4.5 kg) or more and may exceed 24 inches (61 cm) in total length. The woodchuck weighs between 2 and 6 pounds (.4-2.7 kg). They may grow to be 20 inches (50.8 cm) long. The animals attain their maximum weight in late summer, when they accumulate thick layers of fat that will sustain them through winter hibernation. Body shape is similar in all three species: head short and broad, legs short, ears small, body thickset, tail densely furred, and front paws clawed for digging burrows. Hoary and Alaska marmots are predominantly gray with a darker lower back and face and a dark, reddish tail. The hoary marmot has a white patch above its nose and usually has dark brown feet, giving it the Latin name caligata, meaning “booted.” The Alaska marmot does not have a white face patch, its feet may be light or dark, and its fur is much softer than the stiff fur of the hoary marmot. A uniform reddish brown, the woodchuck has an unmarked brown face. The name woodchuck originated as a Cree Indian word used to describe a number of similar-sized animals and does not describe characteristics of the woodchuck's behavior or habitat preference.
Life history: In Alaska, all marmots mate in April or May. About a month later, two to six young are born hairless and blind. The young disperse two months after birth and may breed for the first time when they are 2 or 3 years old. Marmots may live to 5 years or more. They feed on grasses, flowering plants, berries, roots, mosses, and lichens.
Hoary and Alaska marmots make their summer homes on the bases of active talus slopes, where the rocks protect them from predators and provide lookout stations. Woodchuck dens may be up to 30 feet long, are dug in the loamy soils of river valleys in Interior Alaska, and end with a chamber containing a large grass nest. Most marmot dens have a main entrance with a mound of dirt near the hole and a number of concealed entrances. Marmots are social animals. Although each family has a separate burrow, these burrows are located near each other, forming a colony.
True hibernators, marmots enter a state of torpor in winter during which all bodily functions are reduced. Hoary marmots and woodchucks hibernate alone in the same burrows in which they spent the summer. To protect themselves from the cold, they plug the tunnel leading to the nest chamber with a mixture of dirt, vegetation, and feces. They emerge from their winter hibernation in April or early May to find food and mates. Adapted to the harsher winter climate of the Brooks Range, Alaska marmots create a special winter den which has a single entrance and is characteristically located on an exposed ridge that becomes snow-free in early spring. The entrance is plugged after all colony members are inside, and no animals can leave until the plug thaws in early May. Consequently, Alaska marmots mate before they emerge from their winter den. These dens are relatively permanent for each colony, and some are used for more than 20 years. Because hibernation begins in September, most marmots in Alaska spend two-thirds of each year locked in their winter dens.
Marmots are most active in early morning and late afternoon, although they may leave their burrows during other daylight hours. Marmots need wind to control mosquito levels and rarely venture out on calm days. The Alaska marmot marks its territory by rubbing its face and glands on rocks and along trails. The hoary marmot probably marks its territory in the same way.
The pelt colors of marmots help them blend with the lichen-colored rocks or rusty-brown soil of their surroundings. Nevertheless, marmots remain alert for predators including eagles, foxes, coyotes, wolves, and bears. When the Alaska marmot is alarmed, it produces a slurred, low-pitched warning call. The alarm call of both hoary marmot and the woodchuck is a loud whistle. They also hiss, squeal, growl, and yip. In areas where marmots are hunted by humans, they have learned to remain quiet when humans approach. Good climbers and swimmers, woodchucks may also take to trees or water to avoid predators.
Marmots often secondarily benefit other animals and plants. Abandoned marmot holes can become homes for small mammals. In moderation, their digging and defecation loosen, aerate, and improve the soil. Alaska Natives have long relished marmot meat and used its thick coat for warm clothing. Although these wary animals are difficult to approach closely, persistent observers are rewarded by the fascinating sight of a marmot community.
The northern flying squirrel (Glaucomys sabrinus yukonensis) is a gliding (volplaning) mammal that is incapable of true flight like birds and bats. There are 25 subspecies across North America with Interior Alaska being the most northern and western limit of the species' range. The generic name, Glaucomys, is from the Greek glaukos (silver, gray) and mys (mouse). Sabrinus is derived from the latin word sabrina (river-nymph) and refers to the squirrel's habit of living near streams and rivers.
General description: Adult flying squirrels average 4.9 ounces (139 gm) in weight and 12 inches (30 cm) in total length. The tail is broad, flattened, and feather-like. A unique feature of the body is the lateral skin folds (patagia) on each side that stretch between front and hind legs and function as gliding membranes. This squirrel is nocturnal and has large eyes that are efficient on the darkest nights. Eye shine color is a distinctive reddish-orange. Flying squirrel pelage is silky and thick with the top of the body light brown to cinnamon, the sides grayish, and the belly whitish.
Habitat requirements: Flying squirrels require a forest mosaic that includes adequate denning and feeding areas. Den sites include tree cavities and witches' brooms. Tree cavities are most numerous in old forests where wood rot, frost cracking, woodpeckers, and carpenter ants have created or enlarged cavities. Witches' brooms, clumps of abnormal branches caused by tree rust diseases, are the most common denning sites of flying squirrels in Interior Alaska. About November or December, when temperatures begin to drop sharply, flying squirrels move out of cavities and into brooms. In the coldest periods of winter, they form aggregations of two or more individuals in the brooms and sleep in torpor.
Feeding areas preferred by flying squirrels contain fungi (mushrooms and truffles), berries, and tree lichens and may be in either young or old forests. Dried fungi cached in limbs by red squirrels are sometimes stolen by flying squirrels.
Flying squirrels probably get water from foods they eat and rain, dew, and snow. Constant sources of free water (lakes, ponds, and watercourses) do not appear to be a stringent habitat requirement.
In a year's time, a flying squirrel in Interior Alaska may use as many as 13 different den trees within 19.8 acres (8 ha). On a night foray, a squirrel may travel as far as 1.2 miles (2 km) in a circular route and be away from its den tree for up to 7 hours. It may change den trees at night and move to different ones more than 20 times over a year, staying in each for a varying numbers of days. Den trees with brooms are used more than twice as much as trees with cavities.
Fairly dense, old closed-canopy forests with logs and corridors of trees (especially conifers) that are spaced close enough to glide between are needed for cover from predators. High quality flying squirrel habitat can be a community mosaic of small stands of varying age classes in which there is a mix of tall conifers and hardwoods. Part of the mosaic must be old coniferous forest with den trees containing witches' brooms, woodpecker cavities, and natural cavities for nesting sites. Riparian zones provide excellent habitat in all coniferous forest associations.
Life history: Flying squirrels in Alaska may breed anytime from March to late June, depending on length and severity of the winter. The female can breed before 11 months of age and give birth at about 1 year of age. Gestation requires about 37 days, so the young are born from May to early July. One litter of two per year is probably the usual case for Alaska, but they are known to have litters ranging from one to six in other parts of their range. At birth, the young flying squirrel (nestling) is hairless, and its eyes and ears are closed. Development is slow in comparison with other mammals of similar size. Their eyes open at about 25 days, and they nurse for about 60 to 70 days. By day 240, the young are fully grown and cannot be distinguished from adults by body measurements and fur characteristics. Mortality rate for flying squirrels 1 and 2 years old is about 50 percent, and few live past 4 years of age. Complete population turnover can occur by the third year.
Individual flying squirrels nest in tree cavities, witches' brooms, and drays. In Interior Alaska, most brooms and cavity entrances have southerly exposures. Nests in cavities are usually located about 25 feet above the ground but may range between 5 and 45 feet. Flying squirrels excavate chambers in witches' brooms and line them with nesting materials. A dray nest is a ball-like mass of mosses, twigs, lichens, and leaves with shredded bark and lichens forming the lining of the chamber. Flying squirrels build drays entirely by themselves or modify the nests of other species (e.g., bird nests, red squirrel nests). The dray is usually positioned close to the trunk on a limb or whorl of branches with its entrance next to the trunk. Most drays in Alaska are probably conifers.
Food habits: The flying squirrel is omnivorous. While little is known about its diet in Alaska, the food it consumes in other parts of its range include mushrooms, truffles, lichens, fruits, green vegetation, nuts, seeds, tree buds, insects, and meat (fresh, dried, or rotted). Nestling birds and birds' eggs may also be eaten. Those observed foraging in the wild in Interior Alaska ate mushrooms (fresh and dried), truffles, berries, tree lichens, and the newly flushed growth tips on white spruce limbs. In spring, summer, and fall the diet is mostly fresh fungi. In winter it's mostly lichens. Flying squirrels are not known to cache fungi for winter in Alaska, but they are known to do so elsewhere in their range. Witches' brooms and tree cavities would be likely places to find their caches.
Predators and parasites: Owls, hawks, and carnivorous mammals prey on flying squirrels. Primary predators are probably the great horned owl, goshawk, and marten due to their common occurrence and widespread range in Alaska's forests. Three different flea species may infest a single squirrel.
Economic and ecological value: Flying squirrels are important to forest regeneration and timber production because they disperse spores of ectomycorrhizal fungi like truffles. Truffles are fruiting bodies of a special type of fungus that matures underground. They are dependent upon animals to smell them out, dig them up, consume them, and disperse their spores in fecal material where the animal travels. The animal serves to inoculate disturbed sites (e.g., clearcuts, burned areas) with mycorrhizae that join symbiotically with plant roots and enhance their ability to absorb nutrients and maintain health. The flying squirrel's ecological role in forest ecosystems, therefore, gives it economic value. In addition, they may be important prey for a variety of hawks, owls, small carnivores, and furbearers like marten, lynx, and red fox. Many Alaskans value flying squirrels just for their interesting habits and aesthetic qualities.
Management considerations: Logging for house logs, wood for fuel, and lumber can have devastating effects on flying squirrel populations if clearcut size is too large or if some scattered tall conifers in large cuts are not retained as cover and for travel across the open spaces. Management should include retention of other squirrel species in shared habitats. Snags with woodpecker holes or other natural cavities and coniferous trees with witches' brooms must also be maintained in managed forests in order to provide adequate habitat for flying squirrels.
The red squirrel (Tamiasciurus hudsonicus) makes itself quite conspicuous with its lively habits and noisy chatter. Cone cuttings on stumps or rocks are common and tracks in snow are numerous where this squirrel occurs. It can be found in spruce forests over most of Alaska and has a wide range in North America. It occupies a wide variety of forest habitat, occurring in the hardwood forests of eastern North America and the coniferous forests of the west and north.
General description: The active rodent averages 11 to 13 inches in length (28-33 cm), including tail, and is a rusty-olive color on the upper parts of its body with a whitish belly and underparts. In summer, a dark stripe on the side separates the upper rusty color from the white of the belly. The bushy tail is often a lighter orange or red with light tipped hairs.
Life history: Red squirrels are solitary but pair for mating in February and March. Females usually breed when they are 1 year old. Three to seven young are born after a gestation period of 36 to 40 days. The young are born blind and hairless, weighing about ¼ ounce at birth. They are weaned at about 5 weeks but remain with the female until almost adult size.
The young leave the female and are independent during their first winter. This means that they have to be successful at gathering and storing a winter's supply of food.
Behavior: Much of the red squirrel's time in the summer is spent cutting and storing green spruce cones. There may be several bushels of cones stored in a cache. Caches may attain a diameter of 15 to 18 feet and a depth of 3 feet. Red squirrels also cache mushrooms on tree branches. They eat seeds, berries, buds, fungi, and occasionally insects and birds' eggs. They are busy collecting and storing food from early morning until dusk and also on moonlit nights.
Nests may be a hole in a tree trunk or a tightly constructed mass of twigs, leaves, mosses, and lichens in the densest foliage of a tree (making the nest almost completely weatherproof). A loose mass of twigs and leafy debris in a high tree is used as a “fair weather” nest. Their ground burrows, also known as middens, are used mostly for food storage. There is usually one large active midden in each territory with perhaps an inactive or auxiliary midden.
The home range of red squirrels is about ½ to 1 acre, and each squirrel knows its territory well. Each squirrel has several nests in its territory and always seems to know which retreat is nearest. Territorial behavior seems to be most rigid during caching of food and relaxes somewhat in the spring.
The red squirrel is active all year but may remain in its nest during severe cold spells and inclement weather. They are agile climbers and, being extremely curious, will often attempt to enter buildings, upsetting anything they can move and gnawing on woodwork. Once in a house or cabin, they can be very destructive, tearing out insulation and mattress stuffing for use as nesting material and caching food stores in any available niche.
Predators: The main predators of red squirrels are hawks, owls, and marten. Other predators may occasionally take a squirrel but are not serious threats. Around populated areas, one of the predators is the domestic housecat.
Human use: The red squirrel is used to a limited extent by man for food and fur. Squirrels may be small but the meat is good eating. In parts of Canada and Alaska the pelts are sold for their fur. Red squirrels may damage trees, cutting off twigs by the bushel, but they are also helpful because they distribute and plant seeds of spruce and other trees.
The Arctic Ground Squirrel (Spermophilus Parryii) was named "tsik-tsik" by the Inupiat Eskimos on account of a call this little rodent makes when it is alarmed?
Tsik-tsiks are found in both arctic and alpine tundra. They fatten themselves on seeds, mushrooms and berries—almost doubling their body weight over the summer—in preparation for fall hibernation. Although they insulate their winter burrows with grasses and block the entrances with dirt, winter temperatures inside the burrows still fall well below 0° F.
During hibernation, the body temperature of the arctic ground squirrel drops from 98.6° F to 26.4° F—that's below the freezing point of water and is the lowest known body temperature of any living mammal. Most mammals, including people, would be frozen solid at that body temperature! Scientists aren't sure just how these diminutive rodents do it, but they apparently have developed a unique mechanism that allows their body fluids to become supercooled—to fall below the freezing point without crystallizing into ice and damaging cell tissue.
Periodically throughout the winter, the tsik-tsik will rouse itself, briefly raising its body temperature more than 70° F in four hours, before going back into hibernation. Not until late March or early April does the arctic ground squirrel finally emerge from its winter den to the light of another spring and six months of intense activity.
Arctic ground squirrels are the largest and most northern of the North American ground squirrels. This species is common in the ice-free mountainous regions of Denali. Permafrost and soil type are two of the most important factors limiting ground squirrel distribution in Denali.
Arctic ground squirrels are burrowing animals and they establish colonies in areas with well-drained soils and views of the surrounding landscape. Colonies often consist of multiple burrows and a maze of tunnels beneath the surface. Well-drained soils are important, as flooding of these burrows causes considerable problems for squirrels. Accordingly, squirrels usually avoid establishing colonies or excavating burrows where permafrost is close to the surface.
Like many other arctic animals, arctic ground squirrels have unique physiological adaptations that allow them to survive during winter. Arctic ground squirrels are obligate hibernators and spend 7 to 8 months in hibernation. Researchers at the University of Alaska at Fairbanks have shown that during hibernation, arctic ground squirrels adopt the lowest body temperature ever measured in a mammal. The body temperature of hibernating squirrels drops below freezing, a condition referred to as supercooling. At intervals of two to three weeks, still in a state of sleep, hibernating squirrels shiver and shake for 12 to 15 hours to create heat that warms them back to a normal body temperature of about 98 degrees Fahrenheit. When the shivering and shaking stops, body temperature drops back to the minimal temperature. This type of hibernation is rare among mammals and scientists are still studying this unique physiological behavior.
In Denali, ground squirrels are active from late April to early October, but the sexes and age-classes show some differences in their annual activity patterns. Adult males are usually the first to emerge from hibernation. They dig their way through the snow and stay relatively close to their burrows until the snow cover melts. Breeding occurs in May and a single litter of 5 to 10 pups is born in June. The young develop rapidly and usually emerge from their burrows in mid-July. By late summer, young abandon their natal burrow and occupy a neighboring, empty burrow or excavate a new one.
Adults start hibernating as soon as they have enough body fat to survive the winter, often in late August when plenty of foods are still available. It is probably safer to enter hibernation early, even when foods are accessible, than to remain on the surface vulnerable to predators. Youngsters, however, take much longer to find foods and put on body fat and they are often active until late September. This means that youngsters are more vulnerable to predation than adults.
The diet of arctic ground squirrels is diverse and opportunistic. They eat many types of vegetation including the leaves, seeds, fruits, stems, flowers, and roots of many species of grasses, forbs, and woody plants. They also eat mushrooms and meat from freshly killed animals (including ground squirrels). Because they are active only during the short subarctic summer, arctic ground squirrels must be efficient foragers. As summer progresses, they put on a tremendous amount of fat stores for the winter and often double their body weight by the time they enter hibernation in fall.
The social behavior of arctic ground squirrels is complex. This species is highly territorial and squirrels may kill other squirrels over territorial disputes. However, other related females in the colony often care for orphaned youngsters. Further, territorial behavior lessens during late summer, and male squirrels may move between colonies or establish colonies of their own.
So many different predators eat arctic ground squirrels that Adolph Murie called them the "staff of life" in Denali. They are one of the most important summer food sources for golden eagles, gyrfalcons, foxes, and grizzly bears. | <urn:uuid:d873cdc6-8d07-4cc3-bc37-832d9f00ff94> | CC-MAIN-2013-20 | http://www.rso.cornell.edu/squirrelclub/squirrelmap/states/AK.htm | 2013-05-19T02:32:42 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368696383156/warc/CC-MAIN-20130516092623-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.955089 | 4,751 | 4.0625 | 4 |
Science: Balls and Ramps
These resources explore basic concepts of science related to balls and ramps. Learn about the characteristics and properties of balls and ramps, relationship between the physical properties of balls and their motion, and some of the factors that affect the way balls behave. Includes lesson plans, experiments, and simulations. There are also links to eThemes Resources on force and motion, and gravity.
TEACHEngineering: How High Can a Super Ball Bounce?
Students learn about elasticity for super balls; includes: prerequisite knowledge, learning objectives, materials list, introduction, vocabulary, procedures, safety issues, troubleshooting tips, investigating questions, assessment, activity extensions,and activity scaling advice.
PBS Kids: Balls and Ramp
This lesson introduces students to the concept of gravity; includes materials needed and activity instructions.
NOTE: This site includes a discussion board (message board, forum, etc).
In this experiment, students learn about factors such as temperature and construction that affect the height of a ball bouncing.
Basketball: A Physicist Party Trick
Through these activities, students learn the relationship between energy of a basketball and how high it bounces.
BBC: Force and Movement
Play an interactive game and observe the relationship between force, size of a car, and steepness of a ramp. NOTE: The "Talk" link leads to a discussion forum.
BBC: Forces in Action
Observe how far the truck travels with changing the gradient. Note: The "Talk" link is a link to discussion forum.
Ramps 1: Let it Roll
In this lesson, students will explore and measure the rate of spherical objects rolling down a ramp.
This experiment aims to help students understand things that affect the distance and speed of objects rolling from ramps.
eThemes Resource: Physics: Force and Motion
These sites cover the basic concepts of physics. Learn about force, motion, and friction using interactive simulations where you can manipulate the variables. Includes links to an eThemes on Simple Machines, Magnets, and Gravity.
eThemes Resource: Physics: Gravity
These sites explain how the earth's gravity works. Includes photographs, simulations, videos, hands-on activities, and online quizzes. Included are eThemes resources on mass versus weight and force. | <urn:uuid:f91f7a48-0901-4a85-a050-4188ec805b64> | CC-MAIN-2013-20 | http://ethemes.missouri.edu/themes/393?locale=zh | 2013-05-22T00:08:13 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368700958435/warc/CC-MAIN-20130516104238-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.886993 | 467 | 4.46875 | 4 |
May 04 2010
Today we talked about hydrogen and how it can be used to power vehicles. Of the forty-four free response questions on previous A.P. exams, none have addressed hydrogen power, so Mr. Willard said this would be “good knowledge to have in our pockets.”
First we reviewed what we already knew about hydrogen. Hydrogen is the most abundant element in the universe. Despite this fact, there is almost none in the troposphere, and this is because hydrogen has a very low density and so it rises. Additionally, hydrogen is very unstable, so it likes to bond with things (i.e. with oxygen, thus water).
In a hydrogen-powered car, the traditional internal combustion engine is replaced with a fuel cell. Here is a link to a video we watched in class about how a fuel cell works: How A Fuel Cell Works: Inside A Hydrogen-Powered Car (http://auto.howstuffworks.com/fuel-efficiency/alternative-fuels/dangerous-hydrogen-fuel1.htm)
As with every energy source, there are pros and cons. The pros to a hydrogen-powered car is that water is its only emission, it is a strategy for reducing fossil fuel use, and hydrogen is the most abundant element in the universe. On the flip side, the cons to a hydrogen-powered car are that we have to harvest the hydrogen or “make it” (which requires energy input), since this source of energy is new, the infrastructure for hydrogen power is not there, and that we can’t simply convert petro-gas stations to hydrogen gas stations. Perhaps we can add on to our petro-gas stations, and if we harvest the hydrogen or “make” the hydrogen by generating energy from renewable resources such as wind or solar power, technically the energy is still clean. But if we generate the energy for hydrogen from a coal-based power plant, then we’re just moving the source, but the impact is still the same.
Hydrogen can be “harvested” or “made” from electrolysis (splitting water), from biomass, and from fuel.
The U.S. Government is currently funding research on hydrogen power in the state of California. Hydrogen power is still very much in the research and development stage. Hope this helped!
Below is a picture of a typical hydrogen fuel cell: | <urn:uuid:d2593b31-f83e-45c5-92d3-66550eb9883c> | CC-MAIN-2013-20 | http://pdsblogs.org/pdsapes810/category/maggie/ | 2013-05-22T00:35:57 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368700958435/warc/CC-MAIN-20130516104238-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.946262 | 505 | 4.0625 | 4 |
Avian flu, also known as “bird flu,” is caused by influenza viruses that occur naturally among wild birds. Normally, wild birds across the globe are carriers of a harmless form of these viruses, which don’t sicken them. But recently, a new strain of the virus, H5N1 (named for the proteins on the surface of the virus), has killed birds of more than 80 wild species and flocks of domestic fowl, in Asia, Europe, and Africa.
Some human cases, primarily in Asia, have developed from contact with these birds, or their saliva or feces. More than half of the human victims have died after suffering fever, cough, muscle aches, and pneumonia. The disease has not appeared in the United States in either humans or birds.
At this time, avian flu is not easily transmitted from human to human, although experts are considering whether prolonged and intimate contact with a sick person may indeed make a caregiver vulnerable, since family clusters have been found in Indonesia. Still, human cases are rare and have been confirmed only in Azerbaijan, Cambodia, China, Djibouti, Egypt, Indonesia, Iraq, Thailand, Turkey, and Vietnam.
But because viruses often mutate, it is feared that H5N1 may some day turn into one that will quickly spread from human to human, perhaps around the globe. Such a pandemic is expected to be widespread and deadly.
Medical researchers are working on preparing a vaccine, but because the exact nature and virulence of the virus that may mutate into the human-to-human form isn’t known, the effectiveness of a vaccine prepared in advance isn’t known either. Typically, it takes six months to develop a vaccine, once the pathogen is known.
Many international agencies, as well as the federal government, local and state governments, businesses, schools, and hospitals are readying plans to deal with the possibility of an avian flu pandemic. The University of Pittsburgh and the University of Pittsburgh Medical Center are making plans as well. These plans primarily deal with how to efficiently treat the sick and limit exposure to the well.
In this country at this time, the only precautions to take are to observe wildlife from a distance and avoid touching wildlife. If contact occurs, wash hands with soap and water before you rub your eyes, eat, drink, or smoke.
Although there are no international travel restrictions as a result of avian flu, public health officials urge travelers to higher-risk areas of the world to avoid contact with live animal markets and poultry farms, and any free-ranging or caged poultry. In addition, visitors to affected areas should not consume under-cooked poultry and egg products.
Upon their return, travelers should monitor their health for 10 days. If illness is present (including fever plus cough, sore throat, or trouble breathing) during the 10-day period, a doctor should be consulted and informed of symptoms, location of travel, and whether there was direct contact with poultry or close contact with a severely ill person.
While health officials are watching the course of avian flu and making plans to deal with it, even though it may not happen, they are also preparing for the yearly occurrence of seasonal flu, usually between December and May.
Seasonal flu can also cause serious illness and death in the young, the elderly, or those with impaired resistance. But, in contrast to avian flu, vaccines do exist, and are offered at campus sites.
Seasonal flu is transmitted by coughing and sneezing or other close contact, or from contact with an object contaminated by flu viruses, which can live on surfaces for as long as two hours. Health officials are advising that everyone get a flu shot this year and be meticulous about hand-washing. | <urn:uuid:88ebe6e7-8490-4047-9655-e502312d6cb8> | CC-MAIN-2013-20 | http://pitt.edu/avianflu/overview.html | 2013-05-22T00:29:34 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368700958435/warc/CC-MAIN-20130516104238-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.963886 | 775 | 4 | 4 |
Lichen love space
Scientist have found the most complex organism to date that can survive direct exposure to space: lichen.
The European Space Agency (ESA), which sponsored the research, says the findings bolster the possibility that life was transferred between planets.
Researchers from Spain flew samples of lichen, which are made of algal cells in a mat of fungus, on the outside of a Russian capsule that spent two weeks in orbit.
The organisms survived the high levels of ultraviolet radiation, as well as the vacuum and extreme temperatures of space.
Dr Rosa de la Torre, from Spain's National Institute for Aerospace Technology in Madrid, says post-flight analysis shows the lichens not only survived, but still had the ability to photosynthesise upon their return.
Images taken by electron microscopes showed no cell damage.
"[The experiment shows] for the first time that complex organisms integrated by the association of seaweed and fungi, are able to resist the conditions of space without showing apparent damage," says Professor Leopoldo Sancho, with Complutense University of Madrid.
Sealed in a capsule
Two species of lichen, Rhizocarpon geographicum and Xanthoria elegans, were sealed in a capsule and launched on Russian Soyuz rocket on 31 May 2005.
Upon reaching orbit, the lid of the container holding the lichen was opened, exposing the samples to the space environment for 14.5 days.
The lid was then closed to protect the samples while the capsule returned to Earth.
"The lichens are probably some of the most resilient organisms that you can find," says astrobiologist Professor Charles Cockell, with the UK's Open University, who is familiar with the Madrid team's work.
Lichens have a mineral coating that apparently shields the organisms from the ultraviolet radiation of space, says Dr Rene Demets, who oversaw the project for the ESA.
On Earth, lichens are typically found on the surfaces of rocks and survive extreme conditions, such as high on mountaintops.
Previous studies have shown that simple organisms such as bacteria can survive in space and possibly even on the surface of Mars. Other organisms, such as plant seeds, have not fared as well.
"They could resist the absolute emptiness and the extreme temperatures, but not the radiation," Sancho says.
Follow-up ground and flight studies are planned for September 2007 to determine how long lichens might survive in space, and if they could survive re-entry forces if, for example, they are transported on a meteorite. | <urn:uuid:4d05952d-e1e3-4e24-b34a-454e5e481960> | CC-MAIN-2013-20 | http://www.abc.net.au/science/articles/2005/11/22/1514148.htm?site=science&topic=latest | 2013-05-22T00:29:55 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368700958435/warc/CC-MAIN-20130516104238-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.95543 | 526 | 4.21875 | 4 |
LEDs are commonly used in all kinds of applications. The tiny red and green indication lights found here and there on electronic equipment such as TVs and computers are LEDs. They are very efficient in converting an electric current directly into light, but their use was limited by technical constraints preventing the creation of colors other than red and green. In the 1990s, LED color display was made possible by the development of blue LEDs, and we are now witnessing rapid growth in LED applications. The outdoor displays you see on the sides of buildings and other locations on city streets use LEDs. They are also employed in the optical scanning units of color copying machines and image scanners.
Mechanism by Which Light Exposure Produces an Electric Current
To understand LEDs, let's first take a look at the mechanism by which light exposure produces an electric current, such as in solar batteries. Semiconductors, a term you probably hear daily, are a key component of electric circuits, including computers, and they are commonly made from silicon. Semiconductors either use "n-type" silicon, in which there are extra electrons, or "p-type" silicon, in which there are missing electrons that form "electron holes" or simply "holes." Combining these two types of silicon produces a "pn junction diode." When the pn junction is exposed to light, the p-type silicon becomes an anode and the n-type silicon a cathode. Attaching electrodes to either side and then connecting them to an external electrical conductor produces a current. This is also the principle behind solar batteries.
What do you suppose goes on inside a pn junction diode? When silicon is exposed to light such as that from the sun, electrons and electron holes are produced therein. Connecting the p-type silicon and n-type silicon to an external electrical conductor causes electrons in the electron-rich n-type silicon to move to the p-type silicon and the electron holes in the hole-rich p-type silicon to move to the n-type silicon. This in turn causes the excess electrons to flow out over the electrical conductor from the electrode attached to the n-type silicon and head towards the electrode on the p-type silicon, thereby generating an electric current. The flow of an electric current is defined as heading in the opposite direction of the flow of electrons, thus we get an electric current in which the p-type silicon is an anode and the n-type silicon a cathode.
Mechanism by Which Application of a Current Produces Light
Since exposing a pn junction diode to light produces an electric current just like a solar battery, the reverse should also hold true, i.e. applying an external electric current in the opposite direction should cause light to emit from the pn junction. This phenomenon does in fact occur. Making the n-type silicon the cathode and the p-type silicon the anode produces light. This is known as a light-emitting diode (LED). However, light emission from such rudimentary LEDs is inefficient, making them ill suited for practical applications. Only after creating pn junctions using semiconductor materials made of the compounds gallium arsenide, gallium phosphide, and gallium arsenide phosphide did LEDs become practical.
Semiconductor Lasers also Use pn Junctions
The semiconductor laser is another technology that uses pn junctions. Creating a pn junction within a semiconductor brings about "population inversion" by means of the electrons that flow into n-type silicon and the electron holes in p-type silicon. By skillfully placing two perpendicular mirrors with cleavage planes of semiconductor crystal on either end of the pn junction, we can intensify light by making it bounce back and forth between the planes, thus producing a laser beam comprising light with uniform phase and direction. Such semiconductor lasers are also called laser diodes. These devices are only about 300 micrometers square and 80 micrometers thick. Laser diodes using gallium arsenide phosphide, which emit a laser beam with a wavelength of 700 nanometers, are being mass produced for use in compact disc (CD) players and laser beam printers. | <urn:uuid:5b328f78-51eb-4863-9128-c6b167353bad> | CC-MAIN-2013-20 | http://www.canon.com/technology/s_labo/light/002/04.html | 2013-05-22T00:30:03 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368700958435/warc/CC-MAIN-20130516104238-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.927939 | 854 | 4.03125 | 4 |
The unique design of Literature & Thought provides the literature and teaching support you need to meet the challenges of the Common Core English Language Arts curriculum.
Close reading strategies
Writing to sources
Appropriate text complexity
Academic vocabulary support
Text dependent questions and tasks
Essential questions (whole book) and cluster questions (units) focus on developing specific critical thinking skills through careful reading,
textual analysis, discussion, and writing activities.
Outstanding literature and content-rich nonfiction and informational texts engage student's interest and focus attention on the critical thinking questions.
Selections provide the text complexity and academic vocabulary required by the Common Core State Standards (CCSS).
NEW! Professional learning—interactive online courses with experts from the Great Books Foundation in close reading of literary texts, strategic reading of informational texts, and more are included with each Teacher Package.
NEW! Interactive whiteboard lessons—explicit modeling and instruction of critical thinking and reading skills, writing rubrics, and much more.
NEW! Expanded Teacher Guides—informational text strategies, citing evidence to support analyses and claims, practice with academic vocabulary, specific support for CCSS in each selection (including detailed CCSS correlations), and multiple assessment options.
Great Books Discussion Guides for Teachers—specific questioning strategies developed by the Great Books Foundation supporting close text reading and discussion. | <urn:uuid:ffe10044-cb7d-4de7-91a3-892bae9c0285> | CC-MAIN-2013-20 | http://www.perfectionlearning.com/literature | 2013-05-22T00:09:50 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368700958435/warc/CC-MAIN-20130516104238-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.867638 | 275 | 4 | 4 |
Source: Garland Science/Taylor and Francis Books, Inc.
In this animation adapted from Garland Science Publishing, a detailed look at DNA reveals the structural features that make up the famed double-helix molecule. The animation shows how the ladder-shaped DNA is constructed from chemical building blocks, including phosphates, sugars, and bases, held together by different kinds of chemical bonds. The narration further explains how the overall structure determines the charge and stability of the molecule, and how structure predicts key cellular functions of replication and transcription.
Every living thing contains building and operating instructions from a molecule inside all cells called deoxyribonucleic acid (DNA). DNA contains regions called genes that tell the cells which proteins to produce. At all levels of organization in the living world, structure and function are related. Thanks to the work of many researchers using different technologies, scientists now understand the structure and function of DNA at the molecular level.
DNA is a double-stranded molecule made up of two helical chains of nucleotides. This structure enables several important functions related to heredity and evolution. To enable these functions, the structure allows certain kinds of proteins, called regulatory proteins, to bind to and interact directly with the DNA. These regulatory proteins help to dictate replication and transcription (information encoding) by relaxing the DNA structure in the region where they are bound. The double-helix structure of DNA contains a major (wider) groove and a minor (narrower) groove. Because the nucleotide sequence is more accessible in the major groove, many proteins that bind to and interact with DNA do so here.
Through the process of DNA replication, genetic information is passed from parent cell to daughter cell whenever the parent cell divides. Complementary base pairing ensures that DNA strands are copied quickly and accurately. The DNA double-helix molecule is unzipped by the enzyme helicase, resulting in two strands that will act as templates for new DNA strands. These strands are referred to as antiparallel; they are oriented side by side, but their respective nucleotide sequences read in opposite directions. A DNA polymerase enzyme controls the replication of each strand, which occurs as free-floating nucleotides move in one by one to match up with the nucleotides present on each “old” strand of the unzipped ladder. This creates two identical DNA molecules, each made of an “old” strand and a “new” complementary strand.
The arrangement of bases in a DNA molecule determines the genetic code. Approximately once every 100,000,000 bases or so, this copying process makes errors, so that the wrong nucleotide is placed in position. These errors are called mutations. The cell corrects many of the mutations itself. When specialized repair proteins identify a mismatched base pair, they remove the incorrect nucleotide and give DNA polymerase a chance to correct the sequence.
To manufacture the proteins it needs, the cell must transcribe or copy the instructions contained in its DNA into RNA (ribonucleic acid). It uses the sequence of nucleotides in a given gene to produce a single-stranded complementary messenger RNA (mRNA). The mRNA is then translated by structures called ribosomes from the language of nucleotides into the amino acid sequence of proteins. Each amino acid is specified by a combination of three of the chemical bases (A, T, C, or G), called codons. The codons determine the sequence of the amino acids that are put together in a long chain to form the protein that the cell uses to perform specific jobs for the body.
Academic standards correlations on Teachers' Domain use the Achievement Standards Network (ASN) database of state and national standards, provided to NSDL projects courtesy of JES & Co.
We assign reference terms to each statement within a standards document and to each media resource, and correlations are based upon matches of these terms for a given grade band. If a particular standards document of interest to you is not displayed yet, it most likely has not yet been processed by ASN or by Teachers' Domain. We will be adding social studies and arts correlations over the coming year, and also will be increasing the specificity of alignment. | <urn:uuid:bea57faf-a75a-4bbc-8b16-ac29ed5368b9> | CC-MAIN-2013-20 | http://www.teachersdomain.org/resource/biot11.sci.life.gen.structureofdna/ | 2013-05-22T00:34:48 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368700958435/warc/CC-MAIN-20130516104238-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.921504 | 860 | 4.4375 | 4 |
Learn something new every day More Info... by email
A predicate is part of a sentence or clause in English and is one of two primary components that serves to effectively complete the sentence. Sentences consist of two main components: subjects and predicates. Subjects are the primary “thing” in a sentence which the rest of the words then describe through either a direct description or by indicating what type of action that subject is performing. The predicate is this secondary aspect of the sentence and usually consists of a verb or adjective, though complicated sentences may have multiple verbs and a number of descriptions affecting the subject.
It can be easiest to understand predicates by first understanding subjects and how sentences are constructed. A sentence just about always has a subject, though it can be implied in some way and not necessarily directly stated. In a simple sentence like “The cat slept,” the subject is “the cat,” which is a noun phrase consisting of the direct article “the” and the noun “cat.” Subjects can be longer and more complicated, but they are usually fairly simple in nature.
The predicate of a sentence is then basically the rest of the sentence, though this is not always the case for longer and more complicated sentences. In “The cat slept,” the predicate is quite simple and merely consists of the word “slept.” This is simple because “slept” is an intransitive verb, which means that it requires no further description or objects to make it complete. The sentence could be expanded as “The cat slept on the bed,” but this is not necessary and merely adds a descriptive component to the predicate through the prepositional phrase “on the bed.”
In a somewhat more complicated sentence, such as “The man gave the ball to his son,” the subject of the sentence is still quite simple: “The man.” The predicate in this sentence, however, has become substantially more complicated and consists of the rest of the sentence: “gave the ball to his son.” This has been made more complicated because the verb “gave” is transitive, specifically ditransitive, which indicates both a direct object and an indirect object.
The act of “giving” requires that there is a direct object, which is the item given, and an indirect object, which is who or what it is given to. In this instance, the predicate consists of the verb “gave” and the direct object “the ball” with a connecting preposition “to” and the indirect object “his son.” Predicates can become even more complicated as an idea expands, such as a sentence like “The rock rolled off the table, landed on top of a skateboard, and proceeded to roll down the hill until it was stopped by a wall.” In this sentence, the subject is only “The rock,” which means that the rest of the sentence is the predicate. | <urn:uuid:b6182938-d2ed-4d47-a28c-9ae9952dbc8d> | CC-MAIN-2013-20 | http://www.wisegeek.com/what-is-a-predicate.htm | 2013-05-22T00:22:27 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368700958435/warc/CC-MAIN-20130516104238-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.971761 | 633 | 4.59375 | 5 |
|Module 3: Interpreting Data|
2. Using data to support an argument
To test a theory or answer a question a study is designed, sampling is conducted and the data is collected. The process of descriptive statistics then involves presenting the data in tables and graphs. The data may seem to indicate a clear conclusion about the population which has been sampled. But how strongly do the data support that conclusion? Is there strong evidence for the link between data and conclusion? How can you be sure that the effect observed is due to the experimental treatment and is not just an accidental result?
Deciding on the strength of the link between data - and making conclusions about the population - involves interpretation. The basis of how to make interpretation lies in another statistical process called inferential statistics. Inferential statistics involves the use of statistical methods and models to make measurable claims about populations (and population parameters) on the basis of samples (and sample statistics).
Usually researchers do not know the value of population parameters - they have to estimate them. But they do have measurements made on a sample -these are sample statistics. Researchers also realise that if they used a different sample from the same population to produce more data, the new sample statistics would be different to the first ones.
Inference uses probability to account for this sample variability. However, to make inferences you need to have designed a reliable, unbiased study so that the data that are produced are accurate and valid. Therefore, in order to make useful interpretations about data, or to assess the appropriateness of other interpretations, you need to first ask about how the data were produced and presented.
This page last updated 31 August 2009 | <urn:uuid:a6bea8fa-367c-49d6-8f25-41e8746417ff> | CC-MAIN-2013-20 | http://abs.gov.au/websitedbs/a3121120.nsf/4a256353001af3ed4b2562bb00121564/408aa41fb3568e68ca257617000027a2!OpenDocument | 2013-05-24T08:43:13 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368704392896/warc/CC-MAIN-20130516113952-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.937203 | 337 | 4.15625 | 4 |
An Efficient Solar Harvest
Solar power could be harvested more efficiently and transported over longer distances using tiny molecular circuits based on quantum mechanics, according to research inspired by new insights into natural photosynthesis. Incorporating the latest research into how plants, algae and some bacteria use quantum mechanics to optimize energy production via photosynthesis, UCL scientists have set out how to design molecular circuitry that is 10 times smaller than the thinnest electrical wire in computer processors. Published in Nature Chemistry, the report discusses how tiny molecular energy grids could capture, direct, regulate and amplify raw solar energy.
Solar fuel production is all about energy from light being absorbed by an assembly of molecules; this electronic excitation is subsequently transferred to a suitable acceptor. For example, in photosynthesis, antenna complexes capture sunlight and direct the energy to reaction centers that then carry out the associated chemistry.
In photosynthesis chlorophyll captures sunlight and directs the energy to special proteins that help make oxygen and sugars. This is no different in principle than a solar cell.
In natural systems energy from sunlight is captured by colored molecules called dyes or pigments, but it is only stored for a billionth of a second. This leaves little time to route the energy from pigments to the molecular machinery that produces fuel or electricity.
The key to transferring and storing energy very quickly is to harness the collective quantum properties of antennae, which are made up of just a few tens of pigments.
Recent studies have identified quantum coherence and entanglement between the excited states of different pigments in the light-harvesting stage of photosynthesis. Although this stage of photosynthesis is highly efficient, it remains unclear exactly how or if these quantum effects are relevant.
Dr Alexandra Olaya-Castro, co-author of the paper from UCL’s department of Physics and Astronomy said: “On a bright sunny day, more than 100 million billion red and blue colored photons strike a leaf each second.”
“Under these conditions plants need to be able to both use the energy that is required for growth but also to get rid of excess energy that can be harmful. Transferring energy quickly and in a regulated manner are the two key features of natural light harvesting systems.
“By assuring that all relevant energy scales involved in the process of energy transfer are more or less similar, natural antennae manage to combine quantum and classical phenomena to guarantee efficient and regulated capture, distribution and storage of the sun’s energy.”
Summary of lessons from nature about concentrating and distributing solar power with nanoscopic antennae:
The basic components of the antenna are efficient light absorbing molecules.
Take advantage of the collective properties of light-absorbing molecules by grouping them close together. This will make them exploit quantum mechanical principles so that the antenna can: i) absorb different colors ii) create energy gradients to favour unidirectional transfer and iii) possibly exploit quantum coherence for energy distribution.
Make sure that the relevant energy scales involved in the energy transfer process are more or less resonant. This will guarantee that both classical and quantum transfer mechanisms are combined to create regulated and efficient distribution of energy.
Article by Andy Soos, appearing courtesy Environmental News Network.
|Tags: energy distribution energy production photosynthesis quantum mechanics solar cell solar energy||[ Permalink ]| | <urn:uuid:5650b21a-52be-4f3e-bbd4-894e5d1fd662> | CC-MAIN-2013-20 | http://blog.cleantechies.com/2011/09/25/an-efficient-solar-harvest/ | 2013-05-24T08:56:15 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368704392896/warc/CC-MAIN-20130516113952-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.90946 | 683 | 4.28125 | 4 |
Some time in the past, before the ice age, most of western North America (and probably the whole world) was accurately mapped by a technologically advanced people. Who these people were and what technology they used is lost to us, but their maps remain as evidence that they did indeed accomplish the task. These ancient source maps were used by mapmakers in the 1600 to 1700s to fill in the vast unknown areas on the western side of North America. The recent mapmakers had no idea what was there, nor did anyone else, but they had source maps that showed the area as an island and they used them to fill in the gaps.
When were these source map made? They had to be made before the end of the ice age, because at the end of the ice age, the great ice dam holding back water in a huge lake finally gave way and the Grand Canyon was carved in just a few weeks. The Grand Canyon does not appear on any maps of California as an island that I have found, and is certainly not on the map used for this study, the Vingboons map of 1651. In fact, on the Vingboons map, two rivers cross the location of the Grand Canyon. This creates a problem, because the ice age supposedly reached a maximum 18,000 years ago (see Wikipedia article), putting the date for modern man well before that. This pushes the date back into the realm of the Neanderthals, or even into the Paleolithic period, when we were supposed to be only capable of using stone tools.
An even greater problem is that the map also had to predate the uplift of the Nevada-Utah-Wyoming area that followed the end of the latest continental drift event in North America. (see Wikipedia, Farallon plate) According to continental drift theory, when the continents spread apart, the North America continental plate was pushed over an oceanic plate, which was forced down into the mantle of the earth. The lighter minerals floated up against the bottom of North America, under the Nevada-Utah-Wyoming area. This area was lifted up from sea level (at least in Nevada, where the map shows where the sea encroached) to over 7,000 feet elevation in central Nevada, and similarly across all three states. The routes of rivers changed. The Rio Grande, shown on the Vingboons map as the Rio de Norte, which used to flow into the Gulf of California, was forced to flow to the Gulf of Mexico. The map places a geologically recent date on continental uplift, the uplift having happened after the map was made, putting it within the historical presence of humans on earth. Unfortunately, geology dates the North American continental drift events to the Jurassic period, 200,000,000 to 150,000,000 years ago. How will Science deal with the loss of 150,000,000 years? Since it requires abandoning a well entrenched worldview, it is most likely that the vast majority of academia will simply ignore this study and its implications.
In the following series of articles, I analyze the Johannes Vingboons “California as an Island” map area by area. We will see that the makers of the original map possessed a detailed knowledge of the geography of western North America. Correlation of features on the map to actual locations demonstrates that the map is very accurate. After the analysis of the map I have included some information on the historical mapmaking and exploration of this area by the Spanish after the arrival of Columbus. The Spanish were extremely slow to explore this area, and the information they had was not allowed to be made public because they needed to protect information on their trade routes from their competitors. Vingboons was not using Spanish information to present California as an island.
These articles are my work and the result of my research. I have referenced all the sources I have used. None of these sources presents “California as an Island” as anything more than a myth.
I graduated from UCLA in 1976 from the School of Engineering. I followed the course of study in chemical engineering. I was introduced to the whole topic of California as an island in about 2008 by Cliff Paiva, who was also researching the locations of features on the map. We have taken different paths in our efforts to decipher the map, but I much appreciate Cliff’s getting me started.
If you have any questions regarding these articles, you can email me at [email protected] | <urn:uuid:cf82d215-d0db-47f5-900c-89a2c31ef0f9> | CC-MAIN-2013-20 | http://californiaasanisland.org/ | 2013-05-24T08:52:14 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368704392896/warc/CC-MAIN-20130516113952-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.972555 | 912 | 4.03125 | 4 |
Transformations in the Coordinate Plane
Transformations in the coordinate plane are often represented by "coordinate rules" of the form (x, y) --> (x', y'). This means a point whose coordinates are (x, y) gets mapped to another point whose coordinates are (x', y').
When possible, simple formulas are given for x' and y' in terms of x and y. For example, (x, y) --> (x + y, x – y) is a coordinate rule for some transformation and maps the points (0, 0), (2, 0), (2, 5), and (0, 5) as follows:
(0, 0) --> (0, 0)
(2, 0) --> (2, 2)
(2, 5) --> (7, –3)
(0, 5) --> (5, –5)
This transformation is not an isometry (it changes the size of any figure) and the image of the blue rectangle with those vertices is the red rectangle:
Translations of geometric figures in the coordinate plane can be determined by translating the x- and y-coordinates of points. Horizontal and vertical translations are the easiest. All other translations can be thought of as a composition of horizontal and vertical translations. The following examples illustrate this.
Example 1: Give a coordinate rule for translating a figure horizontally by 3 units.
Solution: A horizontal translation just changes the x-coordinates of all points, so the rule is (x, y) à (x + 3, y). To illustrate, the blue rectangle with vertices (0, 0), (2, 0), (2, 5), and (0, 5) is translated to the red rectangle with coordinates (3, 0), (5, 0), (5, 5), and (3, 5):
Example 2: Give a coordinate rule for a translation by a distance of 4 units at 30o.
Solution: Consider a point with coordinates (x, y) and its image with coordinates (p, q)
Draw a right triangle with the point and its image as the endpoints of the hypotenuse. This is a 30-60-90 triangle, so the side opposite the 30o angle is half the hypotenuse and the other side is that times the square root of 3. Therefore we have the following picture:
From this picture we see that
and q = x + 2
Therefore the coordinate rule is: (x, y) -->
When a point is reflected in a line, the line is the perpendicular bisector of the segment joining the point and its image. We will only consider coordinate rules for reflections in horizontal and vertical lines, and in the lines y = x and y = –x since the rules for lines in general involve messy details beyond the scope of this course.
Example 3: Give a coordinate rule for reflecting in the line vertical line x = 3.
Solution: Consider a point (x, y) and its image (p, q):
The y-coordinate of the image is the same as the y-coordinate of the preimage, so q = y. Since the line x = 3 bisects the segment from the point to its image, the horizontal distances from the point to the line and its image to the line are equal, so
3 – x = p – 3
Adding 3 to both sides tells us that p = 6 – x. Therefore the coordinate rule is:
(x, y) --> (6 – x, y)
Example 4: Give a coordinate rule for reflecting in the line y = x.
Solution: Again let the point and its image have coordinates (x, y) and (p, q), respectively. The line y = x is a 45o line through the origin, and the relation between the point and its image looks like this:
If we draw horizontal and vertical segments from the axes through the points and to the line y = x, we have the following:
Since the green line is at 45o, we can focus on two squares to see that q = x and p = y:
Thus, the coordinate rule is: (x, y) --> (y, x)
That is, when reflected in the line y = x, the coordinates of any point are transposed.
Coordinate Rules for Reflections
In general, the following coordinate rules for reflections can easily be established:
Reflection in x-axis: (x, y) --> (x, –y)
Reflection in y-axis: (x, y) --> (–x, y)
Reflection in y = x: (x, y) --> (y, x)
Reflection in y = –x: (x, y) --> (–y, –x)
We will only consider rotations about the origin of multiples of 90o.
Example 5: Give a coordinate rule for a rotation about the origin of 90o (counterclockwise).
Solution: Such a rotation is equivalent to reflections in two lines that intersect at the origin and are 45o apart. We could use the x-axis as the first line and the line y = x as the second. The composite of these reflections is:
(x, y) --> (x, –y) --> (–y, x)
That is, a rotation about the origin of 90o has the coordinate rule: (x, y) --> (–y, x)
Coordinate Rules for Rotations
In general, we can state the following coordinate rules for (counterclockwise) rotations about the origin:
For a rotation of 90o: (x, y) --> (–y, x)
For a rotation of 180o: (x, y) --> (–x, –y)
For a rotation of 270o: (x, y) --> (y, –x)
Dilations in the Coordinate Plane
First consider dilations with the origin as center. Then the coordinate rule for a dilation with scale factor k is simply this:
(x, y) --> (kx, ky).
Example 6: Triangle ABC has coordinates A(–1, –3), B(1, 1) and C(2, –3). Triangle DEF has coordinates D(2, 6), E(–4, 6) and F(–2, –2). Show that triangle DFE is the image of triangle ABC under a dilation with center at the origin, and find the scale factor.
Solution: The image of A is given by (–1, –3) --> (–1k, –3k). If D is that image, then –1k = 2 and –3k = 6. Both give k = –2. If we apply this dilation to B and C, we find that F is the image of B and E is the image of C.
Dilations with Center other than the Origin
A dilation with any point other than the origin as the center of dilation can be accomplished by first translating the center of dilation and figure so the origin becomes the center, and then translating back:
Example 7: Find a coordinate rule for the dilation with center (5, –3) and scale factor 2.
Solution: If (x, y) is a point on a figure to be dilated, we first translate left 5 and up 3. This gives us the point (x – 5, y + 3), and the origin becomes the center of the dilation. The dilation now gives us (2x – 10, 2y + 6). Then we translate back--that is, right 5 and down 3, which gives us (2x – 10 + 5, 2y + 6 – 3). So the coordinate rule is:
(x, y) --> (2x – 5, 2y + 3)
Return to Lesson 5 | <urn:uuid:5a87378c-8f3a-440e-b812-447617fb0107> | CC-MAIN-2013-20 | http://ceemrr.com/Geometry2/Coordinate_Transformations/Coordinate_Transformations_print.html | 2013-05-24T09:03:48 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368704392896/warc/CC-MAIN-20130516113952-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.878896 | 1,660 | 4.40625 | 4 |
The Pasterze Glacier in western Austria has been receding since 1856. A combination of higher summer temperatures and lower winter snowfall is causing the retreat. Glaciers in nearby Switzerland receded more rapidly in 2003 than in any other year since annual measurements began in 1880. Despite the record heat in Europe that summer, scientists from the Swiss Academy of Natural Sciences attributed the melting to long-term climate change.
NASA scientists use satellite data to measure the advance and retreat of glaciers all around the world. This true-color image was acquired by Space Imaging’s Ikonos satellite on October 3, 2001. The full-resolution image has a resolution of 4 meters per pixel.
For more information about monitoring Glaciers, read At the Edge: Monitoring Glaciers to Watch Global Change.
Image by Robert Simmon, NASA’s Earth Observatory, based on data copyright Space Imaging | <urn:uuid:3bd74f56-0527-4a18-8035-023e5cfe289a> | CC-MAIN-2013-20 | http://earthobservatory.nasa.gov/IOTD/view.php?id=4549 | 2013-05-24T08:43:46 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368704392896/warc/CC-MAIN-20130516113952-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.932739 | 180 | 4.40625 | 4 |
General Chemistry/Periodicity and Electron Configurations
Blocks of the Periodic Table
The Periodic Table does more than just list the elements. The word periodic means that in each row, or period, there is a pattern of characteristics in the elements. This is because the elements are listed in part by their electron configuration. The Alkali metals and Alkaline earth metals have one and two valence electrons (electrons in the outer shell) respectively. These elements lose electrons to form bonds easily, and are thus very reactive. These elements are the s-block of the periodic table. The p-block, on the right, contains common non-metals such as chlorine and helium. The noble gases, in the column on the right, almost never react, since they have eight valence electrons, which makes it very stable. The halogens, directly to the left of the noble gases, readily gain electrons and react with metals. The s and p blocks make up the main-group elements, also known as representative elements. The d-block, which is the largest, consists of transition metals such as copper, iron, and gold. The f-block, on the bottom, contains rarer metals including uranium. Elements in the same Group or Family have the same configuration of valence electrons, making them behave in chemically similar ways.
Causes for Trends
There are certain phenomena that cause the periodic trends to occur. You must understand them before learning the trends.
Effective Nuclear Charge
The effective nuclear charge is the amount of positive charge acting on an electron. It is the number of protons in the nucleus minus the number of electrons in between the nucleus and the electron in question. Basically, the nucleus attracts an electron, but other electrons in lower shells repel it (opposites attract, likes repel).
Shielding Effect
The shielding (or screening) effect is similar to effective nuclear charge. The core electrons repel the valence electrons to some degree. The more electron shells there are (a new shell for each row in the periodic table), the greater the shielding effect is. Essentially, the core electrons shield the valence electrons from the positive charge of the nucleus.
Electron-Electron Repulsions
When two electrons are in the same shell, they will repel each other slightly. This effect is mostly canceled out due to the strong attraction to the nucleus, but it does cause electrons in the same shell to spread out a little bit. Lower shells experience this effect more because they are smaller and allow the electrons to interact more.
Coulomb's Law
Coulomb's law is an equation that determines the amount of force with which two charged particles attract or repel each other. It is , where is the amount of charge (+1e for protons, -1e for electrons), is the distance between them, and is a constant. You can see that doubling the distance would quarter the force. Also, a large number of protons would attract an electron with much more force than just a few protons would.
Trends in the Periodic table
Most of the elements occur naturally on Earth. However, all elements beyond uranium (number 92) are called trans-uranium elements and never occur outside of a laboratory. Most of the elements occur as solids or gases at STP. STP is standard temperature and pressure, which is 0° C and 1 atmosphere of pressure. There are only two elements that occur as liquids at STP: mercury (Hg) and bromine (Br).
Bismuth (Bi) is the last stable element on the chart. All elements after bismuth are radioactive and decay into more stable elements. Some elements before bismuth are radioactive, however.
Atomic Radius
Leaving out the noble gases, atomic radii are larger on the left side of the periodic chart and are progressively smaller as you move to the right across the period. Conversely, as you move down the group, radii increase.
Atomic radii decrease along a period due to greater effective nuclear charge. Atomic radii increase down a group due to the shielding effect of the additional core electrons, and the presence of another electron shell.
Ionic Radius
For nonmetals, ions are bigger than atoms, as the ions have extra electrons. For metals, it is the opposite.
Extra electrons (negative ions, called anions) cause additional electron-electron repulsions, making them spread out farther. Fewer electrons (positive ions, called cations) cause fewer repulsions, allowing them to be closer.
|Ionization energy is the energy required to strip an electron from the atom (when in the gas state).
Ionization energy is also a periodic trend within the periodic table organization. Moving left to right within a period or upward within a group, the first ionization energy generally increases. As the atomic radius decreases, it becomes harder to remove an electron that is closer to a more positively charged nucleus.
Ionization energy decreases going left across a period because there is a lower effective nuclear charge keeping the electrons attracted to the nucleus, so less energy is needed to pull one out. It decreases going down a group due to the shielding effect. Remember Coulomb's Law: as the distance between the nucleus and electrons increases, the force decreases at a quadratic rate.
It is considered a measure of the tendency of an atom or ion to surrender an electron, or the strength of the electron binding; the greater the ionization energy, the more difficult it is to remove an electron. The ionization energy may be an indicator of the reactivity of an element. Elements with a low ionization energy tend to be reducing agents and form cations, which in turn combine with anions to form salts.
Electron Affinity
|Electron affinity is the opposite of ionization energy. It is the energy released when an electron is added to an atom.
Electron affinity is highest in the upper left, lowest on the bottom right. However, electron affinity is actually negative for the noble gasses. They already have a complete valence shell, so there is no room in their orbitals for another electron. Adding an electron would require creating a whole new shell, which takes energy instead of releasing it. Several other elements have extremely low electron affinities because they are already in a stable configuration, and adding an electron would decrease stability.
Electron affinity occurs due to the same reasons as ionization energy.
Electronegativity is how much an atom attracts electrons within a bond. It is measured on a scale with fluorine at 4.0 and francium at 0.7. Electronegativity decreases from upper right to lower left.
Electronegativity decreases because of atomic radius, shielding effect, and effective nuclear charge in the same manner that ionization energy decreases.
Metallic Character
Metallic elements are shiny, usually gray or silver colored, and good conductors of heat and electricity. They are malleable (can be hammered into thin sheets), and ductile (can be stretched into wires). Some metals, like sodium, are soft and can be cut with a knife. Others, like iron, are very hard. Non-metallic atoms are dull, usually colorful or colorless, and poor conductors. They are brittle when solid, and many are gases at STP. Metals give away their valence electrons when bonding, whereas non-metals take electrons.
The metals are towards the left and center of the periodic table—in the s-block, d-block, and f-block . Poor metals and metalloids (somewhat metal, somewhat non-metal) are in the lower left of the p-block. Non-metals are on the right of the table.
Metallic character increases from right to left and top to bottom. Non-metallic character is just the opposite. This is because of the other trends: ionization energy, electron affinity, and electronegativity. | <urn:uuid:7ab562e2-c61b-4988-9c51-24c5b3cb1d20> | CC-MAIN-2013-20 | http://en.wikibooks.org/wiki/General_Chemistry/Periodicity_and_Electron_Configurations | 2013-05-24T08:58:15 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368704392896/warc/CC-MAIN-20130516113952-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.917487 | 1,666 | 4.4375 | 4 |
Most Atlantic hurricanes start to take shape when thunderstorms along the west coast of Africa drift out over warm ocean waters that are at least 80 degrees Fahrenheit (27 degrees Celsius), where they encounter converging winds from around the equator.
Warm Air, Warm Water Make Conditions Right for Hurricanes
Hurricanes start when warm, moist air from the ocean surface begins to rise rapidly, where it encounters cooler air that causes the warm water vapor to condense and to form storm clouds and drops of rain. The condensation also releases latent heat, which warms the cool air above, causing it to rise and make way for more warm humid air from the ocean below.
As this cycle continues, more warm moist air is drawn into the developing storm and more heat is transferred from the surface of the ocean to the atmosphere. This continuing heat exchange creates a wind pattern that spirals around a relatively calm center, or eye, like water swirling down a drain.
Converging Winds Create Hurricanes
Converging winds near the surface of the water collide, pushing more water vapor upward, increasing the circulation of warm air, and accelerating the speed of the wind. At the same time, strong winds blowing steadily at higher altitudes pull the rising warm air away from the storms center and send it swirling into the hurricanes classic cyclone pattern.
High-pressure air at high altitudes, usually above 30,000 feet (9,000 meters), also pull heat away from the storms center and cool the rising air. As high-pressure air is drawn into the low-pressure center of the storm, the speed of the wind continues to increase.
As the storm builds from thunderstorm to hurricane, it passes through three distinct stages based on wind speed:
- Tropical depressionwind speeds of less than 38 miles per hour (61.15 kilometers per hour)
- Tropical stormwind speeds of 39 mph to 73 mph (62.76 kph to 117.48 kph)
- Hurricanewind speeds greater than 74 mph (119.09 kph)
Scientists Debate Cause of Temperature Changes that Create Hurricanes
While scientists agree on the mechanics of hurricane formation, and they agree that hurricanes are becoming more frequent and severe, thats where consensus ends.
Some scientists believe that human activity already has contributed significantly to global warming, which is increasing air and water temperatures worldwide and making it easier for hurricanes to form and gain destructive force.
Other scientists believe that the increase in severe hurricanes over the past decade is due to natural salinity and temperature changes deep in the Atlanticpart of a natural environmental cycle that shifts back and forth every 40-60 years.
Frequency and Severity of Hurricanes Likely to Increase
While the scientific community debates the root cause of the temperature changes that are contributing to the current increase in destructive hurricanes, three things are apparent:
- Air and water temperatures are rising worldwide.
- Human activities such as deforestation and greenhouse gas emissions from a wide range of industrial and agricultural processes are contributing to those temperature changes at a greater rate today than in the past.
- Failure to take action now to lower atmospheric levels of greenhouse gases is likely to lead to more frequent and severe hurricanes in the future. | <urn:uuid:2529c9ff-fac1-4c7a-81c9-51e424e73008> | CC-MAIN-2013-20 | http://environment.about.com/od/globalwarming/a/hurricanecauses.htm | 2013-05-24T08:36:25 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368704392896/warc/CC-MAIN-20130516113952-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.907633 | 647 | 4.21875 | 4 |
We recognise that early childhood is key to young children’s development. By the age of 3 years 80% of their brain is developed and so it is important that the foundations of mathematical thinking, language and skills are supported from birth. So, how can we as practitioners (and parents) help children become confident in using and thinking about numbers and maths.
Follow and build on children’s interest – notice their interests and extend them. An example of this is seen in the Learning Story The Yoghurt Tubs which started when a bag of yoghurt tubs was brought into pre-school. Look at the story and see where the practitioner and children brought the activity.
Make sure that language and activities are integrated and embedded within the curriculum – in other words make the experience real and relevant for children. Remember, they learn best when they can connect or identify with ideas. In one of the Learning Stories a child asked ‘Can I bring Rainbow(a Teddy) on a trip?’ This started the children thinking about travel, distance, countries and led them on to making flags.
Equip and prepare the environment – Think about materials that engage or fascinate children, that stimulate their thinking and provide some element of challenge. Remember, mathematical thinking, language and activities happen in every area of the service
Tea sets, pots, pans and cooking containers – a great opportunity to match up cups and saucers (have enough for a group) to put lids on pots, to use baking implements such as measuring jugs and spoons, timers,pastry shape cutters
Dressing-up clothes and jewellery
Pencils and paper (making lists, taking orders)
Cash register and money
Empty boxes / packages of different sizes (organising the stock by size)
Large hollow blocks, ramps, boards
Lego , stickle bricks, interlocking train tracks
Tape measure, spirit level
Plastic plumbing pipes and connectors
Pictures of different buildings
Table Top Toy Area
Deck of card, jig-saws, floor puzzles, board games, games with dice,
Peg board, threading, sorting sets, sequencing games (dominos), mosaics,magnetic shapes and tiles
Creative Art Area:
Paint and a variety of brushes (chubby to fine)
Markers, crayons, chalk, pencils, charcoal, pastels
Paper – a variety of sizes, shapes, textures, colours (sugar, crepe, tissue, card, paper plates)
Used cards and magazines
Sellotape, glue, insulating tape
Different fabrics, buttons,sequins, collage materials
A water tray that allows 3 or 4 children play together
A sand tray that allows a number of children play together
Jugs, funnels, water wheels, water pump,
Sieve, moulds, spades, bucket/container
Items that float and sink
Assortment of items that are the same but different (stones of different shapes, weights and sizes)
Swings, slides (learn about movement, speed, force, push-pull), bikes and trikes (direction and speed), sand and water area (volume, displacement
Kites (wind, velocity), Skittles (number,force)
Taking and making opportunities to help children think logically and solve problems
Equipping the setting both indoors and outdoors with interesting open ended materials that offer possibilities for the children
Introducing mathematical language in very real contexts so that children have plenty of experience in understanding concepts of up and down; in and out; over and under; more and less and so on
Allowing time and space for children to think, process and ask questions
Encouraging thinking skills by asking real and relevant questions, in constructing, the question can be asked ‘how many wheels do you need to build the truck?’
For Maths Week 2012 we have been sharing ideas on promoting the following maths concepts in your service –
number, pattern, shape and space, and measuring and comparisons. We hope you find these find these useful in supporting positive attitudes and confidence in maths for the children in your care.
A very big THANK YOU to the children and staff at The ABC Club in Meath, and all the Learning Story participants, for the use of their photo’s, video’s and wonderful stories.
When early years educators have a sound knowledge of mathematics and the benefits of play, and the connections between them, there is great potential for early childhood experiences that extend young children’s mathematical understandings and attitudes.
Last but not least, an important part of mathematical play is that it should be fun! “We can influence young children’s keenness to learn mathematics by making the tasks we do of interest to them … by showing that we really think maths is important and fun”1
1Montague-Smith,Ann.Mathematics in Nursery Education.London:David Fulton Publishers, 2nd ed.2003 | <urn:uuid:846c8561-96f6-4633-b2bf-446b5139429a> | CC-MAIN-2013-20 | http://www.earlychildhoodireland.ie/supporting-maths-in-early-childhood/ | 2013-05-24T08:58:02 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368704392896/warc/CC-MAIN-20130516113952-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.924586 | 1,034 | 4.09375 | 4 |
Sea ice is frozen seawater that floats on the ocean surface. Blanketing millions of square kilometers, sea ice forms and melts with the polar seasons, affecting both human activity and biological habitat. In the Arctic, some sea ice persists year after year, whereas almost all Southern Ocean or Antarctic sea ice is "seasonal ice," meaning it melts away and reforms annually. While both Arctic and Antarctic ice are of vital importance to the marine mammals and birds for which they are habitats, sea ice in the Arctic appears to play a more crucial role in regulating climate.
Because they are composed of ice originating from glaciers, icebergs are not considered sea ice. Most of the icebergs infesting North Atlantic shipping lanes originate from Greenland glaciers.
Global Sea Ice Extent and Concentration: What sensors on satellites are telling us about sea ice
Sea ice regulates exchanges of heat, moisture and salinity in the polar oceans. It insulates the relatively warm ocean water from the cold polar atmosphere except where cracks, or leads, in the ice allow exchange of heat and water vapor from ocean to atmosphere in winter. The number of leads determines where and how much heat and water are lost to the atmosphere, which may affect local cloud cover and precipitation.
The seasonal sea ice cycle affects both human activities and biological habitats. For example, companies shipping raw materials such as oil or coal out of the Arctic must work quickly during periods of low ice concentration, navigating their ships towards openings in the ice and away from treacherous multi-year ice that has accumulated over several years. Many arctic mammals, such as polar bears, seals, and walruses, depend on the sea ice for their habitat. These species hunt, feed, and breed on the ice. Studies of polar bear populations indicate that declining sea ice is likely to decrease polar bear numbers, perhaps substantially (Stirling and Parkinson 2006).
Ice thickness, its spatial extent, and the fraction of open water within the ice pack can vary rapidly and profoundly in response to weather and climate. Sea ice typically covers about 14 to 16 million square kilometers in late winter in the Arctic and 17 to 20 million square kilometers in the Antarctic Southern Ocean. The seasonal decrease is much larger in the Antarctic, with only about three to four million square kilometers remaining at summer's end, compared to approximately seven to nine million square kilometers in the Arctic. These maps provide examples of late winter and late summer ice cover in the two hemispheres.
Monitoring sea ice
Passive microwave satellite data represent the best method to monitor sea ice because of the ability to show data through most clouds and during darkness. Passive microwave data allow scientists to monitor the inter-annual variations and trends in sea ice cover. Observations of polar oceans derived from these instruments are essential for tracking the ice edge, estimating sea ice concentrations, and classifying sea ice types. In addition to the practical use of this information for shipping and transport, these data add to the meteorological knowledge base required for better understanding climate.
Decline in Arctic sea ice extent
Passive microwave satellite data reveal that, since 1979, winter Arctic ice extent has decreased about 3.6 percent per decade (Meier et al. 2006). Antarctic ice extent is increasing (Cavalieri et al. 2003), but the trend is small.
Satellite data from the SMMR and SSM/I instruments have been combined with earlier observations from ice charts and other sources to yield a time series of Arctic ice extent from the early 1900s onward. While the pre-satellite records are not as reliable, their trends are in good general agreement with the satellite record and indicate that Arctic sea ice extent has been declining since at least the early 1950s.
In recent years, satellite data have indicated an even more dramatic reduction in regional ice cover. In September 2002, sea ice in the Arctic reached a record minimum (Serreze et al. 2003), 4 percent lower than any previous September since 1978, and 14 percent lower than the 1979-2000 mean. In the past, a low ice year would be followed by a rebound to near-normal conditions, but 2002 was followed by two more low-ice years, both of which almost matched the 2002 record. Taking these three years into account, the September ice extent trend for 1979-2004 declined by 7.7 percent per decade (Stroeve et al. 2005). The year 2005 set a new record, dropping the estimated decline in end-of-summer Arctic sea ice to approximately 8 percent per decade. Although sea ice did not set a new record low in 2006, it did fall below normal for the fifth consecutive year. In 2007, sea ice broke all prior satellite records, reaching a record low a month before the end of melt season. Through 2007, the September decline trend is now over 10 percent per decade. (For current sea ice trends, visit NSIDC's Sea Ice Index Cryospheric Climate Indicators.)
Combined with record low summertime extent, Arctic sea ice exhibited a new pattern of poor winter recovery. In the past, a low-ice year would be followed by a rebound to near-normal conditions, but 2002 was followed by two more low-ice years, both of which almost matched the 2002 record (see Arctic Sea Ice Decline Continues). Although wintertime recovery of Arctic sea ice improved somewhat after 2006, wintertime extents have remained well below the long-term average.
Decline in Arctic Sea Ice Thickness
Sea ice thickness has likewise shown substantial decline in recent decades (Rothrock et al. 1999). Using data from submarine cruises, Rothrock and collaborators determined that the mean ice draft at the end of the melt season in the Arctic has decreased by about 1.3 meters between the 1950s and the 1990s.
Estimates based on measurements taken by NASA's ICESat laser altimeter, first-year ice that formed after the autumn of 2007 had a mean thickness of 1.6 meters. The ice formed relatively late in the autumn of 2007, and NSIDC researchers had actually anticipated this first-year ice to be thinner, but it nearly equaled the thickness of 2006 and 2007. Snow accumulation on sea ice helps insulate the ice from frigid air overhead, so sparse snowfall during the winter of 2007-2008 might have actually accelerated the sea ice's growth.
Greenhouse gases emitted through human activities and the resulting increase in global mean temperatures are the most likely underlying cause of the sea ice decline, but the direct cause is a complicated combination of factors resulting from the warming, and from climate variability. The Arctic Oscillation (AO) is a see-saw pattern of alternating atmospheric pressure at polar and mid-latitudes. The positive phase produces a strong polar vortex, with the mid-latitude jet stream shifted northward. The negative phase produces the opposite conditions. From the 1950s to the 1980s, the AO flipped between positive and negative phases, but it entered a strong positive pattern between 1989 and 1995. So the acceleration in the sea ice decline since the mid 1990s may have been partly triggered by the strongly positive AO mode during the preceding years (Rigor et al. 2002 and Rigor and Wallace 2004) that flushed older, thicker ice out of the Arctic, but other factors also played a role.
Since the mid-1990s, the AO has largely been a neutral or negative phase, and the late 1990s and early 2000s brought a weakening of the Beaufort Gyre. However, the longevity of ice in the gyre began to change as a result of warming along the Alaskan and Siberian coasts. In the past, sea ice in this gyre could remain in the Arctic for many years, thickening over time. Beginning in the late 1990s, sea ice began melting in the southern arm of the gyre, thanks to warmer air temperatures and more extensive summer melt north of Alaska and Siberia. Moreover, ice movement out of the Arctic through Fram Strait continued at a high rate despite the change in the AO. Thus warming conditions and wind patterns have been the main drivers of the steeper decline since the late 1990s. Sea ice may not be able to recover under the current persistently warm conditions, and a tipping point may have been passed where the Arctic will eventually be ice-free during at least part of the summer (Lindsay and Zhang 2005).
Examination of the long-term satellite record dating back to 1979 and earlier records dating back to the 1950s indicate that spring melt seasons have started earlier and continued for a longer period throughout the year (Serreze et al. 2007). Even more disquieting, comparison of actual Arctic sea ice decline to IPCC AR4 projections show that observed ice loss is faster than any of the IPCC AR4 models have predicted (Stroeve et al. 2007).
Disclaimer: This article is taken wholly from, or contains information that was originally published by, the National Snow and Ice Data Center. Topic editors and authors for the Encyclopedia of Earth may have edited its content or added new information. The use of information from the National Snow and Ice Data Center should not be construed as support for or endorsement by that organization for any new information added by EoE personnel, or for any editing of the original content. | <urn:uuid:b5246854-fe77-4d8a-96ae-2c3df064ab3d> | CC-MAIN-2013-20 | http://www.eoearth.org/article/Climate_change_and_sea_ice | 2013-05-24T08:57:05 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368704392896/warc/CC-MAIN-20130516113952-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.942156 | 1,885 | 4.1875 | 4 |
Electrical inductance sensors are non-contact devices that measure the inductance of an electrical component or system. They consist of a wire loop or coils and are relatively inexpensive. Inductance, the property of a circuit or circuit element to oppose a change in current flow, refers to the capacity of a conductor to produce a magnetic field. The standard unit of inductance is the Henry (H). Because the Henry is a large unit, electrical inductance sensors often measure inductance in microhenry (µH) or millihenry (mH) levels.
Electrical inductance sensors contain a nickel-iron core shaft that rotates within the coil around the material. The inductance measured by an electrical inductance sensor depends on the number of turns in the coil, the type of material around which the coil rotates, and the radius of the coil. With the rotation of the shaft, displacement occurs within the coil and generates inductance. This displacement produces signals that can be measured by an inductance meter and recorded. Most inductance meters are digital, hand held devices suitable for measuring inductance of very low value. The results of the inductance calculation can be plotted as a graph for future study.
Selecting electrical inductance sensors requires a careful analysis of product specifications and application requirements. Most electrical inductance sensors have a standard accuracy variance of less than 0.5% when measured on full scale. For best results, an electrical inductance sensor should be able to generate an output signal of at least 4-20 mA. Typically, a sensor’s measurement range is approximately 30% of the coil diameter. For high precision measurements, the thickness of the coil should be at least 0.025 inches (in.).
Electrical inductance sensors are used in many different applications. Some electrical sensors are used in the automotive industry and the power industry. Other electrical sensors are used in constructing planar transformers, generating electrical magnetic fields, and monitoring the inductance of an electrical component. Electrical sensors such as electrical inductance sensors are widely used for detecting the presence of electrical voltage in equipments, and defective grounds. | <urn:uuid:bfe63548-3bc5-44fa-be93-553592b82423> | CC-MAIN-2013-20 | http://www.globalspec.com/learnmore/sensors_transducers_detectors/electrical_electromagnetic_sensing/electrical_inductance_sensors | 2013-05-24T08:44:49 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368704392896/warc/CC-MAIN-20130516113952-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.904317 | 433 | 4 | 4 |
From 4th century B.C to fourth century A.D a number early empires emerged in the Indian subcontinent. The earliest of these was the Mauryan Empire (c-324-187BC). Then there came satvahanas(c-324-250 A.D), kushanas (c.AD-50-320), and guptas (c.AD320-570) successively. Kushanas, originally a central Asian nomadic tribe, established a huge empire with Bactrian (Balk in north Afghanistan) as its main centre. Under kanishka 1 (c.AD100-123) this empire extended over a large area by encroaching extensive areas of north India up to Champa or Bhagalpur in the east, the lower Indus valley and Gujarat in the west, Chinese Turkistan and areas lying to the north of the river oxus. The successors of kanishka 1 had little control over the areas to the east of Matura.
The economy of Kushana Empire can be best known from literature, epigraphy and numismatics, various archaeological sites explored and excavated in the later period also acts as good source for the study of the economy of the Kushana Empire.
The kushana period was remarkable as kushana monarchs issued a large number of coins. Besides, there were numerous inscriptions, most of which are donatives in nature. Some of the Indian literatures like the Jatakas, the Angavijja, and the Lalitavistara highlights on the economy of the period.
Very little is known about the land system under the kushanas. During kushana reign agriculture was given due importance. No evidence can be put forward to prove this statement; in the north western part of the Kushana Empire a survey conducted by different scholars helped them to locate remains old canals, agricultural lands on the river courses and plain areas on the terraces of hills with means to canalized rain water from top to bottom.
It is evident from, archaeological evidences that agriculture was not the principal source of income in the kushana reign. Trade was given utmost importance both internally and externally huge amount of resources were mobilized through trade. Besides crafts production mining and different kinds of taxes were imposed on the subjects carved bone and ivory products, potteries excavated from different areas within the kushana realm shows influence of ancient Matura and Taxila art. Movements of ideas and people in the form of merchants’ artists inside the Kushana Empire resulted in exchange of ideas related to culture, art and literature.
Besides internal trade, external trade both over land and maritime played a great role in the kushana economy. Roman Empire had trade links with china. There was a great demand for Chinese silk in roman market. The famous Silk Road from loyang in china reached the two Mediterranean parts of Antioch and Alexandria by passing through central Asia, west Asia and Eurasia. Chinese silk had a great demand not only in the roman but also ion the European markets besides Indian wares, crafts, gems and spices were sold in the overseas markets. Better knowledge and utilization of the monsoon wind system through the Red sea cannels gave a fresh impetus to the flourishing trade during the kushana period. To maintain overseas trade with European countries two major parts of north India known as Barbaricum at the north of the river Indus and Barygara on the mouth of the river Narmada played a vital role and it was quite evident from perilous and Ptolemy’s geography. The city of Matura was a major political center. In case of trade with central and west Asia the cities of Taxila and pushkalavati acted as gateways.
Large scale commercial prosperity during the kushana period led to extensive monetization of the whole economy. kushana gold coins found in Ethiopia proves the value of kushana gold coins in international arena. These gold coins were mainly used in the overseas trade. The kushanas themselves struck silver coins only in the lower Indus area. Large number of copper coins were also struck and used copper coins and Bartend system which were very much in practice indicate that the impact of monetization ran parallel with system of exchange of goods on the basis of needs.
With the expansion of trade proliferation of crafts also took place. Crafts in practice during the kushana period were varied in nature and form. There were different occupations like constructions (navakarmikah), actors (sailakah), carpenters (vaddhaki), perfumers(gamdhika), goldsmith (suvarnakara), clothmakers9pravarika), ironsmith (lohakara), jewelers (manikara0 etc. the mining industry was directly under the state control. the of the state was augmented through mining and marketing of precious stones. Guilds mostly called srenis acted as an early form of bank in which money was deposited and only the interest could be utilized. Cities like Taxila, Matura, Bactra were well planned and blossomed further during the kushana period. | <urn:uuid:f0988e44-e9e4-496a-8e5d-1da7a3966d7d> | CC-MAIN-2013-20 | http://www.indiainfodir.com/Arts-blog/ | 2013-05-24T08:59:16 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368704392896/warc/CC-MAIN-20130516113952-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.963847 | 1,069 | 4.15625 | 4 |
XII. This activity involves reading a scenario and discussing the correct way for a school bus driver to handle it. Options for using the scenarios can be found on page 5.
Follow these steps to conduct the activity.
- Review the instructions (XII.A-D) with the participants.
- Read the scenario slowly.
NOTE: There are 10 scenarios, covering the various conditions addressed in the module. You will not need to use all of them. If you have presented the entire module, you can choose 5-6 of the scenarios. If you have only presented one section of the module, you can use a scenario that corresponds to that section. You may choose to develop your own scenarios using weather conditions particular to your local area.
- Ask participants to say how that scenario should be handled by the school bus driver. In each scenario the school bus is a medium-sized conventional bus equipped with a two-way radio and carrying middle school students.
NOTE: One alternative would be to first have each participant write down how he or she would handle the situation. Then discuss the scenario as a group. This process ensures that each school bus driver will have had to think about the scenario.
- Record the responses on a flip chart.
- After all the responses are listed, ask if certain actions need to happen before others. Starting with #1, indicate the order in which the actions should happen.
NOTE: With each scenario, the correct actions are listed in the order in which they should occur. If the order isnít important, the actions are preceded by a bullet instead of a number. | <urn:uuid:de7f7c6e-412e-420f-a12d-c5fe444c5a57> | CC-MAIN-2013-20 | http://www.nhtsa.gov/people/injury/buses/UpdatedWeb/topic_8/page12.html | 2013-05-24T09:04:14 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368704392896/warc/CC-MAIN-20130516113952-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.92154 | 329 | 4.34375 | 4 |
If astronomy and outerspace interest you, then this activity set will fascinate you. You'll learn about the planets, stars, sun, moon, and even rockets - all through fun, hands-on experiments. Activities include using balloons and chemically powered rockets to study rocket propulsion, building a telescope and star map to investigate the stars and constellations, assembling a model of the solar system to about the planets that share it,and more. Once you work through all the activities, you will understand how Earth’s axis and revolution around the sun causes the seasons, how the moon’s rotation around Earth gives us the phases of the moon, how meteorites formed the craters on the moon, how meteoroids become falling stars, and so much more. Includes a full-color, 32-page experiment book to guide your space exploration. Ages 8 and up.
WARNING: CHOKING HAZARD — Children under 8 yrs. can choke or suffocate on uninflated or broken balloons. Adult supervision required. Keep uninflated balloons from children. Discard broken balloons at once.
- launch three types of rockets
- build a telescope and star map
- model the solar system
- investigate the revolution and rotation of Earth
- swing a moon sling
- find the man in the moon
- recreate lunar and solar eclipses
- learn about falling stars
- discover how the universe is expanding | <urn:uuid:ed799365-aaf6-44a3-9da2-8f42750a83fe> | CC-MAIN-2013-20 | http://www.scientificsonline.com/review/product/list/id/4943/?price=1%2C1000&robotics_level=79 | 2013-05-24T08:38:37 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368704392896/warc/CC-MAIN-20130516113952-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.888303 | 292 | 4.21875 | 4 |
Functions and Variables in Physical Science Experiments
Almost all true science experiments involve designing a series of trials where one variable is manipulated and another variable changes as a result of this manipulation. All other variables are held constant. A variable is said to be a function of another variable if, for various values of x, it is possible to establish corresponding values of y, i.e. y = 6x.
In todayıs lab you will be working with various weights that can be hung on a spring. Work in pairs to determine any connections between the variables that you choose to investigate. Any spring will deform if you put a large amount of weight on it. The purpose of this lab is NOT to see how much weight a spring will take before it breaks or deforms. Deforming a spring by using an excess of weight, will ruin your experiment and it will force us to buy new springs. You can keep the lab fees from increasing if you use a reasonable amount of weight on the springs. Be nice to your springs.
When you have written a question and identified the variables you want to investigate, conduct an experiment to see what effect changing one variable has on another variable. Prior to beginning your experiment, you need to check your question and your procedure with your instructor. Please be sure to describe what experiment you are conducting and what materials you are using (the procedure) in your lab notebook (or if this is the first lab, use this sheet of paper). The level of detail you include in your procedure should allow someone to repeat your experiment just by reading your procedure. All data, observations, calculations, graphs, diagrams, etc. should be recorded in your lab notebook as well. Be sure to include appropriate units with all measurements and results of calculations. You will need to follow the rules for working with significant figures.
The expectations for this lab experiments are: a) you need to run a minimum of two different experiments, b) you need to collect a minimum of five data points for each experiment, c) you need to run each experiment twice and average your data, d) record your data for each experiment in a data table, e) there are at least two different types of springs, use them, describe them, make a comparison, f) for each experiment you do, plot a graph using the average values of your variables (when appropriate), g) identify at least two resulting relationships, h) include an algebraic expression (a mathematical equation and a written statement) describing the correlation between your variables, i) show how your data fits the equation.
Beginning Questions: In this lab you are faced with determining relationships between multiple variables. What are two initial questions that can be answered by doing this lab activity?
Procedure. Identify your dependent variable and your independent variable. What variables are kept constant?
Data/ Observations: (attach a separate piece of paper) Record all data and observations. Include appropriate units.
Graphs (attach graph paper). The dependent variable is plotted on the _____ axis and the independent variable is plotted on the _____ axis. Be sure to calculate the slope of each graph.
Claims: Based on the data collected, the graphs, etc. what claims can be made?
Evidence: Support your claims with appropriate evidence.
Reading/ Reflection: What are some of the principles that you have learned or applied in this lab? How does this compare to other groups? How does this compare to information found in a physics textbook? Compare graphs when using the thick wire/heavy spring vs. the thin wire/light spring, what physical variable does the slope of these graphs represent?
Please show how you arrived at your answers to each of the following questions using a) your algebraic expression, b) your graph. How does your equation or graph tell the difference between the two springs?
If a 63 gram weight is hung on the longer spring, what would be the amount of stretching? What would be the length of the spring? Does it make a difference if you investigate the length of the spring or the amount of stretching of the spring?
If a 63 gram weight is hung on the shorter spring, what would be the amount of stretching? What would be the length of the spring? | <urn:uuid:6f94b2b9-5fbc-4865-99d3-00a46b0e2828> | CC-MAIN-2013-20 | http://group.chem.iastate.edu/Greenbowe/sections/projectfolder/FunctionsVariables2.htm | 2013-06-18T22:50:57 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368707435344/warc/CC-MAIN-20130516123035-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.924953 | 865 | 4.03125 | 4 |
Photo: Scott Zona
There is nothing more emblematic of spring and summer than flowers, but why do plants have flowers, and how did they evolve?
Botanists know that flowering plants, that is, plants that reproduce by producing seeds, evolved from non-flowering plants. According to evolutionary theory, nature would have selected plants with flowering tendencies because it gave these plants a reproductive advantage. It’s within the protective casing of flower petals, after all, that flowers are pollinated and make seeds. The strategy has been hugely successful. The vast majority of plants today are flowering plants.
The precise origin of flowering plants, though, is puzzling. In fact, exactly when, how, and why plants first developed flowers remains one of the biggest mysteries of evolutionary paleontology.
However, two discoveries have begun to unravel the mystery of how plants got flowers. Four years ago, scientists in China found a fossil of the oldest known flowering plant. The reed-like plants lived at least 125 million years ago in a lake, suggesting that flowering plants first evolved in water. The scientists speculate that the plant’s seeds floated along the shore and germinated near the banks.
More recently, scientist William Friedman of the University of Colorado found a clue in a plant called Amborella trichopoda, which grows in South Pacific rain forests. The plant’s female reproductive system has an extra, sterile egg cell. Friedman thinks that the extraneous part is a remnant from a more primitive reproductive apparatus and could link the plant to non-flowering plants like pines and firs.
The origin of flowers is still a difficult puzzle, of course, but with further discoveries and research, flowering plants will become a bit less mysterious. | <urn:uuid:8a9b6621-ec71-444c-9309-238303e6477a> | CC-MAIN-2013-20 | http://indianapublicmedia.org/amomentofscience/the-first-flowers/ | 2013-06-18T22:53:45 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368707435344/warc/CC-MAIN-20130516123035-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.956253 | 359 | 4.28125 | 4 |
Sunlight is Earth’s most abundant energy source and is delivered everywhere free of charge. Yet direct use of solar energy—that is, harnessing light’s energy content immediately rather than indirectly in fossil fuels or wind power—makes only a small contribution to humanity’s energy supply. In 2008, about 0.1% of the total energy supply in the United States came from solar sources. In theory, it could be much more. In practice, it will require considerable scientific and engineering progress in the two ways of converting the energy of sunlight into usable forms.
Photovoltaic systems are routinely employed to power a host of devices—from orbiting satellites to pocket calculators—and many companies make roof-sized units for homes and office buildings.
Photovoltaic (PV) systems exploit the photoelectric effect discovered more than a century ago. In certain materials, the energy of incoming light kicks electrons into motion, creating a current. Sheets of these materials are routinely employed to power a host of devices—from orbiting satellites to pocket calculators—and many companies make roof-sized units for homes and office buildings.
At the present time, however, the best commercial PV systems produce electricity at five to six times the cost of other generation methods, though if a system is installed at its point of use, which is often the case, its price may compete successfully at the retail level. PV is an intermittent source, meaning that it’s only available when the Sun is shining. Furthermore, unless PV energy is consumed immediately, it must be stored in batteries or by some other method. Adequate and cost-effective storage solutions await development. One factor favoring PV systems is that they produce maximum power close to the time of peak loads, which are driven by air-conditioning. Peak power is much more expensive than average power. With the advent of time-of-day pricing for power, PV power will grow more economical.
Sunlight can also be focused and concentrated by mirrors and the resulting energy employed to heat liquids that drive turbines to create electricity—a technique called solar thermal generation. Existing systems produce electricity at about twice the cost of fossil-fuel sources. Engineering advances will reduce the cost, but solar thermal generation is unlikely to be feasible outside regions such as the southwestern United States that receive substantial sunlight over long time periods.
Despite the challenges, the idea of drawing our energy from a source that is renewable and that does not emit greenhouse gases has powerful appeal. | <urn:uuid:515d3239-de8f-40e7-adc5-50e951db0245> | CC-MAIN-2013-20 | http://needtoknow.nas.edu/energy/energy-sources/renewable-sources/solar/ | 2013-06-18T22:45:00 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368707435344/warc/CC-MAIN-20130516123035-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.942625 | 508 | 4.09375 | 4 |
NASA has released a computer visualization project called "Perpetual Ocean" that presents a data-created time lapse of the Earth's ocean and sea surface currents over a two-year period.
The animation (see below) shows the globe slowly spinning as white swirls curl and move in the water around landmasses. It looks as if Vincent van Gogh had painted into the oceans -- from the Gulf of Mexico to the Indian Ocean to the Black Sea.
Typically, NASA uses ECCO2 to model global ocean and sea-ice to better understand ocean eddies and other current systems that move heat and carbon in the oceans. The end goal is to study the ocean's role in future climate change scenarios. | <urn:uuid:2f1474e5-3ee2-4c33-a54a-89813f786382> | CC-MAIN-2013-20 | http://news.cnet.com/8301-11386_3-57406143-76/nasa-video-visualizes-a-perpetual-ocean/ | 2013-06-18T22:59:21 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368707435344/warc/CC-MAIN-20130516123035-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.933865 | 145 | 4.03125 | 4 |
From Ohio History Central
Youngstown is the county seat of Mahoning County, Ohio.
Youngstown was founded by John Young in 1797 and is within the original Western Reserve of Connecticut. . Young had purchased an entire township from the Connecticut Land Company. He paid $16,085 for 15,560 acres of land. Within a short period of time, ten families settled in the village along the Mahoning River. Youngstown continued to grow and was officially incorporated in 1802.
In that same year Daniel and James Heaton built the Hopewell Furnace. Iron ore and coal deposits had been discovered near Youngstown, and an early iron industry flourished. With the completion of the Pennsylvania and Ohio Canal in the 1830s and the construction of railroads beginning in the 1850's, Youngstown continued to grow. By 1860, the population had reached 5,300, and by 1870, 8,075 people lived in the community. By the second half of the nineteenth century, Youngstown had become an important intersection of a number of major railway lines, including the Baltimore & Ohio, the Erie Lackawana, the New York Central, and the Pennsylvania Railroad. As a result of the city's growth, the Mahoning County seat was moved from Canfield to Youngstown in 1876. The population reached 33,220 in 1890.
In the late 1800s, the first steel mills were constructed in Youngstown, signaling the new influence of that industry on the city's development. The new industry attracted many immigrants to the community, including Poles, Italians, and Hungarians. In the early twentieth century, the steel workers began to demand better wages and working conditions. There were a number of strikes in this era
During World War I, the steel mills produced materiel for the war effort. As a result of this increased production, there were a number of new jobs. Youngstown's population swelled so rapidly that there was not enough housing for everyone. When the war ended, a number of workers were laid off. Once again, workers went on strike. They demanded that the companies institute an eight-hour day and a six-day week. In addition, workers wanted extra pay for working overtime. When mill owners did not respond, there were violent confrontations.
By the 1920s, Youngstown was second only to Pittsburgh in terms of total steel production in the United States. At the same time, the industry faced some significant challenges. After the closing of the canal, the city no longer had access to water transportation. In addition, there was a shortage of water for use in the mills. In spite of these problems, the city continued to grow. The population in 1920 was 132, 358 people, and Youngstown was ranked as the fiftieth largest city in the nation. The population reached its peak in 1930 at just over 170,000 residents.
The Great Depression hit Youngstown hard. Because the city's economy relied so much on the steel industry, its unemployment rate was approximately three times the national average during the 1930s. Unions were gaining popularity among workers during this era, but several steel companies in Youngstown had resisted unionization. They were collectively known as the Little Steel Companies. Workers at these mills went on strike on March 26, 1937. Although the "Little Steel" strike, as it became known, was not very successful in the short-term, it led to the creation of the Congress of Industrial Organizations, commonly known as the CIO. The CIO was able to force the Little Steel Companies to accept unionization in 1941.
During World War II, Youngstown's industries once again contributed to the American war effort. Prosperity returned to the city. With the further growth of the automobile industry in the years following the war and its demand for steel, Youngstown's economy continued to grow. This economic growth slowed in the late twentieth century, as the steel industry across the United States began to decline. Cities such as Pittsburgh and Youngstown became part of the "Rust Belt" during this era. Youngstown's population also decreased. According to the 2000 census, the city had 82,026 residents.
In recent years, the city of Youngstown has seen some economic revitalization as new industries and enterprises have been attracted to the area.
- Great Depression
- World War I
- Hopewell Furnace
- Pennsylvania and Ohio Canal
- Connecticut Land Company
- Connecticut Western Reserve
- Iron Production
- Steel Mills
- zzHungarian Immigrants
- Italian Ohioans
- Polish Ohioans
- Slavic Ohioans
- Great Steel Strike of 1919
- Little Steel Strike of 1937
- Congress of Industrial Organizations
- World War II
- Mahoning County
- Eaton, Ohio
- [The Center of Industry and Labor]
- [Mahoning Valley Historical Society]
- [City of Youngstown]
- [Wikipedia: Youngstown, Ohio] | <urn:uuid:f66e737f-7c83-496e-a189-120a85a52392> | CC-MAIN-2013-20 | http://ohiohistorycentral.org/w/Youngstown,_Ohio?rec=826&nm=Youngstown-Ohio | 2013-06-18T22:45:28 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368707435344/warc/CC-MAIN-20130516123035-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.974771 | 1,005 | 4.125 | 4 |
Early galaxies full of cosmic dust
Space dust Astronomers have found dusty giant galaxies were already in existence 13 billion years ago, far earlier than previously thought.
The discovery reported in the Astrophysical Journal, means planets, which are made from coalescing dust particles, may also have already formed that far back in time.
The study's lead author Assistant Professor Steven Finkelstein from the University of Texas, says the discovery came as a complete surprise.
"I don't think we really expected that," says Finkelstein.
"We thought that 13 billion years ago would have been so early in the universe, that dust really didn't have a chance to form."
"But we now know that's simply not the case, at least in the most massive galaxies."
Using NASA's Hubble Space Telescope, Finkelstein and colleagues found that on average, galaxies appear less dusty the further back in time they look.
"If you go far enough back, dust doesn't exist in galaxies," says Finkelstein.
"That's what you would expect, because only hydrogen and helium were made in the big bang, and dust is made up of heavier elements like carbon, silicon and magnesium produced by the first generations of stars."
Finkelstein hypothesises why dust is only found in these early massive galaxies.
"Galaxies have large outflows of gas and dust from their interstellar medium, and it's a lot easier for that outflow to occur in low mass galaxies, where there's less gravity," says Finkelstein.
"Dust may be forming in all early epoch galaxies, but it's only sticking around in big galaxies because they have enough mass to hang on to their dust."
The findings are based on data from CANDELS, the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey, a huge two-month study carried out by the Hubble Space Telescope.
Finkelstein and colleagues examined the colour of galaxies in the Hubble images to see how red they look.
"Dust makes things appear red, so the redder a galaxy looks, the more dust it has," says Finkelstein.
"As well as being important for planet formation, the dust also blocks out some of the light, making it more difficult to determine how luminous a galaxy is, and consequently how much star formation is taking place in it."
Finkelstein and colleagues have more work to do, including taking spectroscopy of these galaxies to work out what they're made of.
"We can do some of that now with today's ten-metre telescopes," says Finkelstein.
"But we're really waiting for the next generation of big telescopes, such as the 25-metre Giant Magellan Telescope, and the space-based James Webb Telescope which will let us look even farther back in space-time to see what's there." | <urn:uuid:d1f94744-89f3-420a-93aa-2d160fb48f7b> | CC-MAIN-2013-20 | http://www.abc.net.au/science/articles/2012/10/16/3609580.htm?topic=space | 2013-06-18T22:57:55 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368707435344/warc/CC-MAIN-20130516123035-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.964141 | 588 | 4.0625 | 4 |
Oxygen Fuels the Fires of Time
Scientists from The Field Museum in Chicago and Royal Holloway University of London, publishing their results this week in the journal Nature Geoscience, have shown that the amount of charcoal preserved in ancient peat bogs, now coal, gives a measure of how much oxygen there was in the past.
Until now scientists have relied on geochemical models to estimate atmospheric oxygen concentrations. However, a number of competing models exist, each with significant discrepancies and no clear way to resolve an answer. All models agree that around 300 million years ago, in the Late Paleozoic, atmospheric oxygen levels were much higher than today. These elevated concentrations have been linked to gigantism in some animal groups, in particular insects, the dragonfly Meganeura monyi with a wingspan of over two feet epitomizing this. Some scientists think these higher concentrations of atmospheric oxygen may also have allowed vertebrates to colonize the land.
These higher levels of oxygen were a direct consequence of the colonization of land by plants. When plants photosynthesize they evolve oxygen. However, when the carbon stored in plant tissues decays atmospheric oxygen is used up. To produce a net increase in atmospheric oxygen over time organic matter must be buried. The colonization of land by plants not only led to new plant growth but also a dramatic increase in the burial of carbon. This burial was particularly high during the Late Paleozoic when huge coal deposits accumulated.
Dr. Ian J. Glasspool from the Department of Geology at the Field Museum explained that: "Atmospheric oxygen concentration is strongly related to flammability. At levels below 15% wildfires could not have spread. However, at levels significantly above 25% even wet plants could have burned, while at levels around 30 to 35%, as have been proposed for the Late Paleozoic, wildfires would have been frequent and catastrophic".
However, there were periods in Earth's history when the charcoal percentage in the coals was as high as 70%. This indicates very high levels of atmospheric oxygen that would have promoted many frequent, large, and extremely hot fires. These intervals include the Carboniferous and Permian Periods from 320-250 million years ago and the Middle Cretaceous Period approximately 100 million years ago.
"It is interesting", Professor Scott points out, "that these were times of major change in the evolution of vegetation on land with the evolution and spread of new plant groups, the conifers in the late Carboniferous and flowering plants in the Cretaceous".
These periods of high fire resulting from elevated atmospheric oxygen concentration might have been self-perpetuating, with more fire meaning greater plant mortality, and in turn more erosion and therefore greater burial of organic carbon, which would have then promoted elevated atmospheric oxygen concentrations.
"The mystery to us", Scott states, "is why oxygen levels appear to have more or less stabilized about 50 million years ago". | <urn:uuid:b82f6dde-52a7-4c70-a146-bfaf0d7d1e3b> | CC-MAIN-2013-20 | http://www.astrobio.net/includes/html_to_doc_execute.php?id=3574&component=news | 2013-06-18T22:25:26 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368707435344/warc/CC-MAIN-20130516123035-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.962289 | 598 | 4 | 4 |
Phytoplankton Under Ice
Beneath the Arctic ice—over 12 feet deep in some areas—lies a dark, cold and lifeless sea. Or so we thought.
“If someone had asked me before the expedition whether we would see under-ice blooms, I would have told them it was impossible,” says Arrigo. “This discovery was a complete surprise.”
The researchers discovered an abundance of phytoplankton—microscopic life that forms the base of the marine food chain. Phytoplankton require sunlight for photosynthesis, just like plants. And sunlight has a tough time penetrating thick sea ice.
But that thick sea ice is changing. Not only are warmer temperatures thinning the ice, but as the ice melts in summer, it forms pools of water that act like transient skylights and magnifying lenses. These pools focus sunlight through the ice and into the ocean, where currents steer nutrient-rich deep waters up toward the surface. Phytoplankton under the ice evolved to take advantage of this narrow window of light and nutrients.
The phytoplankton displayed extreme activity, doubling in number more than once a day. Blooms in open waters grow at a much slower rate, doubling in two to three days. These growth rates are among the highest ever measured for polar waters. Researchers estimate that phytoplankton production under the ice in parts of the Arctic could be up to 10 times higher than in the nearby open ocean.
The phytoplankton bloom discovered by Arrigo and his colleagues in the Chukchi Sea (just north of Alaska) extends tens of meters deep in spots and about 100 kilometers (62 miles) across.
“At this point we don’t know whether these rich phytoplankton blooms have been happening in the Arctic for a long time and we just haven’t observed them before,” Arrigo says. “These blooms could become more widespread in the future, however, if the Arctic sea ice cover continues to thin.”
The discovery of these previously unknown under-ice blooms could have serious implications for the broader Arctic ecosystem, including migratory species such as whales and birds. Phytoplankton are eaten by small ocean animals, which are eaten by larger fish and ocean animals.
“It could make it harder and harder for migratory species to time their life cycles to be in the Arctic when the bloom is at its peak,” Arrigo says. “If their food supply is coming earlier, they might be missing the boat.”
The research is published this week in Science. | <urn:uuid:dda98bee-cbfe-4019-acc9-adace79b16b1> | CC-MAIN-2013-20 | http://www.calacademy.org/sciencetoday/phytoplankton-under-ice/ | 2013-06-18T22:44:13 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368707435344/warc/CC-MAIN-20130516123035-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.946405 | 565 | 4.15625 | 4 |
Dinosaurs' active lifestyles suggest they were warm-blooded
H. Pontzer, V. Allen, J.R. Hutchinson/PLoS ONE
Whether dinosaurs were warm-blooded or cold-blooded has been a long-standing question in paleobiology. Now, new research on how two-legged dinosaurs walked and ran adds new evidence to the argument for warm-bloodedness, and suggests that even the earliest dinosaurs may have been warm-blooded.
Warm-blooded (or endothermic) dinosaurs — able to regulate their own body temperatures — would have been more active and could have inhabited colder climates than cold-blooded (or ectothermic) dinos, which would have functioned more like modern reptiles — animals that become animated only as temperatures warm. Endothermic dinosaurs would have also required more energy to maintain their higher metabolic rates. Evidence such as rapidly growing bones, bird-like feathers and athletic builds have led most paleontologists to believe that dinosaurs were endothermic, says paleobiologist Greg Erickson of Florida State University in Tallahassee, Fla., who was not involved in the new research.
But many scientists are still averse to the idea of warm-blooded dinosaurs. For example, some researchers have suggested that larger, more massive dinosaurs may have radiated much less heat than smaller dinosaurs — and thus, they could have been cold-blooded while still able to maintain relatively high body temperatures.
In the new study, published today in PLoS ONE, biomechanist Herman Pontzer of Washington University in St. Louis, Mo., and colleagues sought to figure out whether the lower metabolism of an ectotherm would have afforded dinosaurs the energy they needed to walk and run. To test this possibility, the team looked at two factors thought to be linked with energy requirements in modern animals: hip height and the volume of muscle used to hold up and move an animal’s body forward. If the limb length and active muscle volumes of dinosaurs required more energy than an ectotherm’s metabolism would have been able to provide, Pontzer and colleagues reasoned, then the dinosaurs were likely endothermic.
The team studied 13 different two-legged dinosaur species, ranging in size from Tyrannosaurus to the tiny, bird-like Archaeopteryx, as well as one early dinosaur relative, Marasuchus. Based on hip height, the results showed that the five largest dinosaurs (including Tyrannosaurus) would have needed endothermic metabolisms just to have the energy to walk, and all of the dinosaurs would have required endothermy to run at a moderate speed. Results based on estimated active muscle volume revealed a similar pattern: The five largest dino species would have needed to be endothermic to walk or run, while smaller, very active dinosaurs such as Velociraptor, must have been endothermic to be able to run.
In addition, even the most ancient dinosaur-like relative, Marasuchus, may have been endothermic based on the data from the hip study, Pontzer says, suggesting that endothermy evolved very early on in the dinosaur lineage. Therefore, the results also suggest that all dinosaurs were endothermic, the team wrote.
“I think their study is pointing to what a lot of other studies are saying — that these animals were endothermic,” Erickson says. “It’s just, what grade of endothermy were we dealing with?” For example, modern marsupials, although endothermic, generally grow more slowly and have lower metabolic rates than other mammals, he says.
The study may not put the final "nail in the coffin" for the idea that large dinosaurs could have been ectothermic, but it does provide positive evidence for an alternative metabolic strategy, says Patrick O’Connor, a paleontologist at the Ohio University College of Osteopathic Medicine in Athens who was also not involved in the new research. "Studies like this add crucial new lines of evidence that help us refine existing hypotheses," O'Connor says.
Estimating dinosaur metabolisms based on modern animals can only go so far, according to Erickson. For example, Pontzer and colleagues focused on two-legged dinosaurs because if they had used four-legged dinosaurs, they would have also needed to estimate how the dinosaurs’ weight was distributed across all four legs.
But because all modern ectotherms, such as alligators, are four-legged, Pontzer and colleagues had to gauge the hypothetical ectothermic capacity for the two-legged dinosaurs against four-legged modern animals, Erickson notes. Moreover, even the largest modern ectotherms are much smaller than a 6-metric-ton Tyrannosaurus. “There are limitations from living organisms that make it so we may never be able to test all these ideas,” Erickson says.
Still, Erickson says he thinks scientists are “honing in on the real answer” on the question of when endothermy evolved in dinosaurs and other ancient vertebrates. Other evidence, such as rates of bone growth, suggests pterosaurs, or flying reptiles, were also endothermic. “When you have all these different lines of evidence kind of pointing towards [endothermy],” he says, “I think it’s fairly compelling collectively.” | <urn:uuid:a459a3fc-e2ca-4318-b2d2-359bd270ce2f> | CC-MAIN-2013-20 | http://www.earthmagazine.org/article/dinosaurs-active-lifestyles-suggest-they-were-warm-blooded | 2013-06-18T22:39:32 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368707435344/warc/CC-MAIN-20130516123035-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.963021 | 1,101 | 4.40625 | 4 |
Lesson plans for teaching organization
A collection of LEARN NC's lesson plans for teaching organization, the second of the five features of effective writing.
- Getting Paragraphing Down P.A.T.
- One way to remember when to indent and begin a new paragraph is when (P) the place changes, (A) the action changes, and (T) the time changes (P-A-T). In this lesson, students will learn how to identify appropriate places to indent new paragraphs in their writing.
- Great beginnings
- Good beginnings hook readers and make them want to continue reading. Students will learn the features of good beginnings by reading the beginnings of several narrative picture books, and then writing good beginnings for their own narratives.
- Great endings
- Sometimes authors end their stories with a memory, a feeling, a wish, or a hope. Other times they end the story by referring back to the language of the beginning. In this lesson, students will examine the characteristics of good endings by reading good endings of narrative picture books. They will then practice writing good endings for their own narratives.
- Little Bit ? BIG BIT ? Little Bit
- This lesson helps students who tend to jump right in and tell their entire story in the first few sentences and then struggle to complete their story. Students will learn to start and end their stories with just a “Little Bit” about the setup and closure of the story.
- Meanwhile - Transition Words that Connect Ideas
- Students will identify transition words in picturebooks that they can use in their own writing. Transition words are the glue that holds sentences and paragraphs together. They signal that this is a new part of the story.
- Transition Words and Phrases
- Students will learn to combine sentences using two kinds of transition words: time transitions and thought (logical) transitions. Transition words link related ideas and hold them together. They can help the parts of a narrative to be coherent or work together to tell the story. Coherence means all parts of a narrative link together to move the story along. Think of transition words as the glue that holds a story together. Using transition words helps avoid the “Listing” problem in stories.
- Cause and effect writing: What it looks like and who reads it
- Students examine the causes and effects presented in a brochure called “Ozone: The Good and the Bad.” They also examine the language of the brochure with regard to audience appropriateness. Students then write their own brochures examine their classmates’ brochures for cause and effect and for audience appropriateness.
- Helping Students Understand Text Structures: Informational Problem/Solution
- This exercise teaches students to understand the organizational structure of problem/solution essays by having them write “what it says” and “what it does” statements about a text. Asking students to write these statements about a text will enable students to read the text closely and will ensure that they understand the structure of a problem/solution text.
- Examining effective openers and closures in writings
- Students will listen to a reading of Dr. Seuss’ and Jack Prelutsky’s Hooray for Difendoofer Day! Students will then work cooperatively to edit one another’s rough drafts of analytical essay, focusing on openers and closures.
- Practicing Elaboration in a Problem/Solution Essay
- One theory suggests that students tend to list in an essay because they lack the tools to elaborate. Because they do not have the strategies, they attempt to fill up the empty space by introducing new primary ideas instead of fleshing out the ideas they have already presented. This activity attempts to make students aware of the need to elaborate and to provide students with some workable strategies for elaborating. Using a PowerPoint presentation, the teacher demonstrates the necessity for elaboration in a problem/solution essay. Students then choose a particular point in the PowerPoint presentation to expand through elaboration.
- Making Patterns, Make Sense
- Students will analyze organizational patterns in analytical writing by reading, Oh, the Places You’ll Go! by Dr. Seuss. Students will then apply these patterns to their own writing by creating children’s books about success.
- Thematic and Organizational Patterns in McLaurin’s “The Rite Time of Night”
- Students will learn to identify and color-code thematic and organizational patterns found in the narrative and then use two-column notetaking to highlight how these patterns helped McLaurin give his story focus and organization. As a suggested follow-up activity, students are given ideas for writing their own narratives, using similar techniques as McLaurin. | <urn:uuid:e3c8f011-1af4-424e-89b8-b37560a91447> | CC-MAIN-2013-20 | http://www.learnnc.org/lp/pages/2741 | 2013-06-18T22:58:28 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368707435344/warc/CC-MAIN-20130516123035-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.929796 | 981 | 4.125 | 4 |
because accumulation exceeds ablation in a location. This
accumulation zone after it thickens to more than 30 m begins to
For a glacier to survive it must have a consistent and
persistent accumulation zone.
To diagnose a glacier
that is disappearing look for
1) Emergence of rock
outcrops in upper region of the glacier.
2) Recession of the
margin of the glacier in upper reaches of the glacier.
3) Lack of consistent
snowcover at the end of the summer in the accumulation zone of
Published Paper in The Cyrosphere 2010
Quaternary International Paper 2011
Why these criteria?
Glaciers respond to climate in an attempt to achieve
equilibrium. A glacier advances due to a climate
cooling/snowfall increase that causes positive mass balance.
A climate warming/snowfall decrease leads to negative mass
balances and glacier retreat. To reestablish equilibrium a
retreating glacier must lose enough of its highest ablating
sections, usually at the lowest elevations, so that accumulating
snows in the near the head of the glacier once again are
equivalent to overall ablation, and an equilibrium balance is
approached. If a glacier cannot retreat to a point where
equilibrium is established, it is in disequilibrium with the
climate system. A glacier that is in disequilibrium with present
climate will melt away with a continuation of this climate.
We often focus on
terminus change of a glacier which tells us how the glacier is
currently responding to recent climate. A glacier can retreat
rapidly and still survive if it has an accumulation zone.
Thus, to forecast survival we need to focus on the accumulation
zone, not just the terminus. If the accumulation zone no
longer retains accumulation consistently it will begin to thin.
A glacier needs 50-70% of its surface area to be snowcovered
event at the end of the summer to be healthy. A thinning accumulation zone is evident when the margins of
the glacier in this accumulation zone-upper potion of the glacier recede.
Also new outcrops of rock maybe exposed in the accumulation
zone due to thinning. This has been
observed both in the North Cascades and on Swiss glaciers.
Below are examples
of glaciers that have disappeared, will disappear and that can
retreat to a new position of equilibrium with current climate.
This is not to say that further warming will not eliminate many of
the the glaciers that have an accumulation zone today. Sometimes adjacent glaciers can have
differing forecasts based on their varied response to recent
climate. It is unusual for an entire mountain range to be
inhospitable to glaciers today.
of the rapid loss of all glaciers in Glacier National Park or the
Nepal Himalaya are exaggerated. In each case the glaciers
are retreating notably, but some of the glaciers still have
persistent accumulation zones. In the Himalaya the most
photographed glacier is probably the
Glacier on the south
side of Mount Everest. Above the famed Khumbu Icefall
there is a persistent accumulation zone, indicating it can
retreat to a new point of equilibrium with current climate.
Above is Foss Glacier in 1985, still
covering a large area of the east slope of Mount Hinman. | <urn:uuid:f43774c9-7747-41d3-8bfc-66df060ce147> | CC-MAIN-2013-20 | http://www.nichols.edu/departments/glacier%20survival.html | 2013-06-18T22:31:57 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368707435344/warc/CC-MAIN-20130516123035-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.913356 | 697 | 4.09375 | 4 |
Riparian and Wetland Management
Riparian areas are lands adjacent to creeks, streams, lakes, and rivers that support vegetation dependent upon free water in the soil. They are sometimes called "Ribbon-of-Green" because the vegetation on waterway banks forms a ribbon-like pattern when seen from the air. These areas, containing water and vegetation in the otherwise arid Western United States, are important to fish and wildlife species, as well as to livestock. Since they dissipate water energy and filter the water flowing through them, riparian-wetland areas can affect the health of entire watersheds. Wetlands are generally defined as areas inundated or saturated by surface or ground water at a frequency and duration sufficient to support vegetation this is typically adapted for life in saturated soil. Wetlands include bogs, marshes, shallows, muskegs, wet meadows, estuaries, and riparian areas.
A riparian-wetland area is healthy and functioning when adequate vegetation, landform, or large woody debris is present to dissipate energy associated with high water flow. A healthy riparian-wetland area exhibits certain characteristics, such as:
- Purifying water by filtering sediments as water moves through;
- Reducing the risk of flood damage;
- Reducing streambank erosion;
- Increasing water holding water in streambanks;
- Maintaining instream flows and streambanks;
- Increasing ground water supplies;
- Supporting a diversity of wildlife and plant species;
- Maintaining habitat for healthy fish populations;
- Providing water, forage, and shade for livestock;
- And creating opportunities for recreationists to fish, camp, picnic, and relax.
The BLM's National Science and Technology Center in Denver has a The technical reference library with a listing of available publications for integrated resource management, inventory and monitoring classification, riparian area management, stream channel surveys, and rangeland inventory monitoring and evaluation.
The Reference Guides section of this website has documents concerning wetlands identification, activities, and financial and technical assistance for conservation and management. | <urn:uuid:6d09527b-2b18-4bc1-a4e3-5c64e490c504> | CC-MAIN-2013-20 | http://www.oneplan.org/Water/Wetlands.asp | 2013-06-18T22:57:26 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368707435344/warc/CC-MAIN-20130516123035-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.927425 | 438 | 4.21875 | 4 |
In the cities and countryside section of Busy Teacher, there are 78 FREE worksheets to choose from
. They range from very simple word searches to detailed activities related to these topics. This activity
, for example, was created for Russian ESL learners but can serve as a model for you to create a similar activity more appropriate for your students. Some nice details on this worksheet include the translations of important words, the colorful images, and the fact that after completing this exercise, students should be able to create a similar article about the town they live in. You could do this as a class, in groups, or individually depending on your students and class size. Take a look at other worksheets to find something your students will enjoy.
It is good to talk about different places, compare them, and be able to describe them to people. Students will enjoy sharing their views of certain locations and some will certainly feel very strongly about cities while others will prefer the countryside. This division could set you up for a debate about the positive and negative characteristics of each. Despite your personal opinion, try to remain neutral and simply facilitate the discussion. This is just one way to incorporate this topic into your lessons. | <urn:uuid:f96e5d95-4d79-4709-bf16-5ebd19b0893e> | CC-MAIN-2013-20 | http://busyteacher.org/classroom_activities-vocabulary/city_and_countryside-worksheets/ | 2013-05-19T09:54:19 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368697380733/warc/CC-MAIN-20130516094300-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.961906 | 243 | 4.375 | 4 |
Free Blacks in the North and South, The Liberator, January 22, 1831
William Lloyd Garrison, a leading northern abolitionist, began publishing his anti-slavery newspaper, The Liberator, in January 1831. In this early article he compares the conditions of free blacks in the North and the South and the differences in the discrimination and prejudice they faced. As Garrison noted, freedom did not afford African Americans either civil rights or justice.
In most of the States in which slavery is tolerated, the laws in relation to free colored persons are severe in the extreme. Though their freedom is recognized, yet they have not the rights of other freemen. . . .
Few whites will eat with blacks. Even where blacks and whites are domestics in the same kitchen, the blacks, as I have been told, are often compelled to eat at a separate table. So it is said that white journeymen and apprentices of mechanics often refuse to work with blacks. The prejudice has taken two different forms in the different parts of our country. At the North, few blacks are mechanics, because the whites will not allow them to work with them. At the South, on the contrary, few of the mechanics are whites, because they will not do the same sort of work as blacks.
Source: Foner, Philip S., and Lewis, Ronald L., The Black Worker: A Documentary History from Colonial Times to the Present, Volume 1 The Black Worker to 1869. Philadelphia: Temple University Press, 1978 p. 157 | <urn:uuid:d9d4e9b7-c7ff-452a-ab8b-cb2016ef438c> | CC-MAIN-2013-20 | http://chnm.gmu.edu/lostmuseum/lm/119/ | 2013-05-19T10:03:50 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368697380733/warc/CC-MAIN-20130516094300-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.964786 | 309 | 4 | 4 |
Reading Skills: Making Connections
These sites provide various activities involving the reading stragey with connections to text-to-text, text-to-self, and text-to-world. Includes modeling scenarios as well as interactive activities for teachers.
Into The Book: Strategies for Learning
This site from Wisconsin Education Communication Board features interactive activities to teach questioning, visualizing, inferring, summarizing, evaluation, and synthesizing. Videos model teaching lessons.
READWRITETHINK: Making Connections: Strategy Guide
Here is a strategy guide to learn how to model the three different kinds of connections (text-to-text, text-to-self and text-to-world). Students then use the strategies to look for their own personal connections to a text. Three downloadable posters describing the connections are available.
Reading Response Logs - Making Connections
This PDF helps students connect to the texts they are reading.
Teaching Reading Comprehension: A Look At Reading Comprehension Strategies
Learn more about the following reading comprehension strategies: making connections, visualizing, questioning, inferring, evaluating, and synthesizing.
NOTE: This site includes ads.
Scholastic: Making Connections - Self-Monitoring
See this series of seven lessons provides independent activities to engage students in making connections to text. NOTE: This site contains ads.
READWRITETHINK: Digging Deeper: Developing Comprehension Using "Thank You, Mr. Falker"
This lesson provides strategies for students to make personal connections to text by using "Thank You, Mr. Falker". Response journals may be used for recording student connections to the character and themes in the book.
READWRITETHINK: Boars and Baseball: Making Connections
This lesson uses "In the Year of the Boar and Jackie Robinson" to teach reading strategies of text-to-self, text-to-text, and text-to-world. An extension activity is given.
READWRITETHINK: Family Ties: Making Connections to Improve Reading Comprehension
In this activity, students are engaged with picture books about families to make text-to-self, text-to-text, and text-to-world connections by reading and responding to those books.
Revisiting Read-Aloud: Instructional Strategies That Encourage Students' Engagement With Text
Use this article for teaching examples of modeling text-to-text, text-to-self, and text-to-world strategies. Several student activities are provided.
This site provides information on six comprehension strategies and activities for students. NOTE: This site contains ads.
Request State Standards | <urn:uuid:913cce12-9999-4a3b-b918-8339eeaa953a> | CC-MAIN-2013-20 | http://ethemes.missouri.edu/themes/1915?locale=en | 2013-05-19T10:16:45 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368697380733/warc/CC-MAIN-20130516094300-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.842571 | 554 | 4.09375 | 4 |
A volcano is a hole where melted rock called magma or rock and ashes are
thrown up from inside the earth. Volcanoes are commonly known around the
world for bringing huge destruction as they erupt. When most people think
of volcanoes they think of hot boiling lava. Many people do not realize
that instead of only erupting lava, it also erupts ash and gas. A volcano
works in the following sequence.
1. Melted rock called magma rises from deep within the earth to near the
2. Some of it cools and becomes solid within the crust, but some erupts
on the surface as lava.
3. When two plates with ocean crust move apart magma from the mantle bubbles
up to the surface to fill it.
Because of this factor, the Atlantic Ocean is widening by three-fourths
of an inch per year. The Pacific is widening much, much more as well.
is widening by eight inches every year.
There are many different types of volcanoes. Some volcanoes are dormant,
some are active, and some are dead or extinct. Volcanoes are very
different; they are responsible for shaping many of Earth’s
islands, mountains, and plains. They have also been responsible for
changing weather, burying
cities, and killing people who live near by. Volcanic gases are deadly
poisons. For example, in August 1986, a small eruption in Lake Nyons
Cameroon, located in West Africa, signaled the release of a cloud
of volcanic gases. The noxious fumes killed over 1,700 people.
are born in different ways; hotspot volcanoes, though spectacular,
are rather less
violent. They erupt in different ways from cone shaped volcanoes. Molten
lava rises to the surface from deep within the Earth’s mantle.
It then pierces the plate like a blowtorch and erupts in a lava flow
Though it may seem that hotspots move with the plates, they do not. The
hotspots stay still but the plates keep moving. Eventually chains of
islands, like Hawaii, form. Active volcanoes in Hawaii will soon become
dormant as Hawaii moves off the hotspot.
Its important to know how to stay
safe before a volcanic eruption, during a volcanic eruption, and after
a volcanic eruption.
Before the Eruption:
- Take Red Cross first aid, CPR, and fire safety classes.
- Call a family meeting and discuss where to go, what to take, where to
meet if separated, and what to do about pets.
- Plan escape routes - one by foot and two by car.
- Know where to go and what you will take in case of an evacuation.
- Store emergency supplies, food, and water.
- Post by every phone a number to call in case of a fire.
- Install portable smoke detectors outside every sleeping area and on
every level of your home, garage, and workshop.
- Use button to test smoke alarms twice a year.
- Store extra smoke alarm batteries.
- Keep fire extinguishers in the kitchen and hallways. Test and replace
immediately if faulty.
- Conduct fire drills, including walking or driving evacuation routes.
- Draw a floor plan and find two ways to escape from every room and conduct
- Get rope or chain ladders for upper stories and practice using.
During the Eruption:
- Turn off gas at the meter to avoid danger of explosion.
- Put on heavy shoes and protective clothing.
- Take your stored supplies and complete evacuation procedures.
- Listen to the radio for updates on the volcano.
- Do not return home until the eruption is declared over and lava flow
and fires have stopped.
- Prepare to travel on a confirmed route.
- If driving, use extreme caution and take only confirmed routes. Abandon
your car if lava and fire encroaches and take a route away from the fire.
- Assist others and render first aid as safety permits.
- Listen to the radio reports for confirmed information and instructions,
including location of Red Cross Disaster Stations, shelters, and animal
- Use caution when going home. Do not return unless advised by authorities
that conditions are safe and roads are clear.
- If driving is necessary, drive with caution. Visibility may be poor
if it is raining volcanic ash, and mud slides and landslides can occur.
- Avoid volcano damaged areas and lava flow areas.
- Go to the Red Cross Disaster Station for emergency treatment.
- Check your home’s exterior for damage and stability. If an earthquake
has occurred, use due caution and follow procedures.
- Do not go inside if it appears unsafe.
- If other family members are not there, follow your plan for locating
one another, including calling your out-of-the-area contact person.
- Approach animals with caution and comfort and contain them as much as
- Check and repair fenced areas for animals.
- Temporarily contain pets and livestock.
- Beware of loose or dangling electrical wires. Do not touch.
- Check gas appliance connections for signs of gas leaks. Do not light | <urn:uuid:46a560ea-cfbf-40c8-a71f-e4bbe34f338b> | CC-MAIN-2013-20 | http://library.thinkquest.org/03oct/01352/Volcanoes.htm | 2013-05-19T09:54:32 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368697380733/warc/CC-MAIN-20130516094300-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.92013 | 1,089 | 4.09375 | 4 |
But Keller and her colleagues say their research proves otherwise.
Keller has studied the Chicxulub site and other impact-crater sites around the world for the past decade. She believes that the asteroid impact behind Chicxulub coincided with a "time of massive volcanism, which led to greenhouse warming."
Keller says those three eventsthe Chicxulub asteroid impact, volcanism, and climate change"led to high biotic stress and caused the decline of many tropical species populations," but not mass extinctions. That die-off didn't occur until later. However, Keller does believe that the initial confluence of volcanic activity, global warming, and the Chicxulub asteroid impact ultimately contributed to the mass extinction.
Key to Keller's assertions is a 20-inch-thick (50-centimeter-thick) layer of limestone found between the K-T boundary and the impact breccia, or molten lava and rocky debris, laid down when the Chicxulub asteroid collided with Earth.
Keller and her colleagues believe that the thickness of the limestone layera type of sedimentary rock characteristically formed under large bodies of water like oceans, seas, and lakesindicates that it accumulated in the crater over some 300,000 years after the impact. As proof, Keller points to fossils of microscopic organisms called foraminifera and fossil burrows present in the limestone layer.
According to Keller, those fossils indicate the sediment was deposited after the asteroid impact but before the period of mass extinction that marked the end of the Cretaceous.
Many other scientists disagree with that interpretation, however. They say the layer of fossil-rich limestone was deposited quickly as backwash and infill caused by a huge tsunami that followed the Chicxulub asteroid's impact with Earth. The layer, they say, did not take 300,000 years to accumulate.
In her defense, Keller says the quick-accumulation theory is unsupported by evidence that would have been found during her analysis of core samples gathered at Chicxulub and 45 localities in northeast Mexico.
But Alan Hildebrand, a proponent of the quick-accumulation theory, says the burrows were "made by organisms digging after the fireball layer was deposited."
Thomas R. Holtz, Jr., a vertebrate paleontologist at the University of Maryland in College Park, supports the view that the limestone was quickly laid down as crater infill. He said he is not surprised that Cretaceous fossils were found in the limestone layer.
"If an asteroid clobbered the Eastern seaboard of the U.S. today, I would expect that most of the infilling would be Chevys and Hondas and shopping malls and houses and cows and McDonald's burger wrappers," Holtz said. "Only a tiny bit might be mastodons and Clovis points and Miocene whales." In other words, the crater would quickly fill with objects common on Earth at the time of impact.
So where do researchers in the Keller camp look next for the possible K-T crater? Keller says she's unsure, although "some scientists have suggested it could be a structure called Shiva, in India. We have no convincing evidence so far that this is the case."
SOURCES AND RELATED WEB SITES | <urn:uuid:4d9d2441-762a-4bf0-bbc6-64a734349fda> | CC-MAIN-2013-20 | http://news.nationalgeographic.com/news/2004/03/0309_040309_chicxulubdinos_2.html | 2013-05-19T09:56:45 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368697380733/warc/CC-MAIN-20130516094300-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.956261 | 683 | 4.0625 | 4 |
by Anne E. Egger, Ph.D.
We all see changes in the landscape around us, but your view of how fast things change is probably determined by where you live. If you live near the coast, you see daily, monthly, and yearly changes in the shape of the coastline. Deep in the interior of continents, change is less evident – rivers may flood and change course only every 100 years or so. If you live near an active fault zone or volcano, you experience infrequent but catastrophic events like earthquakes and eruptions.
Throughout human history, different groups of people have held to a wide variety of beliefs to explain these changes. Early Greeks ascribed earthquakes to the god Poseidon expressing his wrath, an explanation that accounted for their unpredictability. The Navajo view processes on the surface as interactions between opposite but complementary entities: the sky and the earth. Most 17th century European Christians believed that the earth was essentially unchanged from the time of creation. When naturalists found fossils of marine creatures high in the Alps, many devout believers interpreted the Old Testament literally and suggested that the perched fossils were a result of the biblical Noah’s flood.
In the mid-1700’s, a Scottish physician named James Hutton (see Biography link to the right) began to challenge the literal interpretation of the Bible by making detailed observations of rivers near his home. Every year, these rivers would flood, depositing a thin layer of sediment in the floodplain. It would take many millions of years, reasoned Hutton, to deposit a hundred meters of sediment in this fashion, not just the few weeks allowed by the Biblical flood. Hutton called this the principle of uniformitarianism: processes that occur today are the same ones that occurred in the past to create the landscape and rocks as we see them now. By comparison, the strict biblical interpretation, common at the time, suggested that the processes that had created the landscape were complete and no longer at work.
Figure 1: This image shows how James Hutton first envisioned the rock cycle.
Hutton argued that, in order for uniformitarianism to work over very long periods of time, earth materials had to be constantly recycled. If there were no recycling, mountains would erode (or continents would decay, in Hutton’s terms), the sediments would be transported to the sea, and eventually the surface of the earth would be perfectly flat and covered with a thin layer of water. Instead, those sediments once deposited in the sea must be frequently lifted back up to form new mountain ranges. Recycling was a radical departure from the prevailing notion of a largely unchanging earth. As shown in the diagram above, Hutton first conceived of the rock cycle as a process driven by earth’s internal heat engine. Heat caused sediments deposited in basins to be converted to rock, heat caused the uplift of mountain ranges, and heat contributed in part to the weathering of rock. While many of Hutton’s ideas about the rock cycle were either vague (such as “conversion to rock”) or inaccurate (such as heat causing decay), he made the important first step of putting diverse processes together into a simple, coherent theory.
Hutton’s ideas were not immediately embraced by the scientific community, largely because he was reluctant to publish. He was a far better thinker than writer – once he did get into print in 1788, few people were able to make sense of his highly technical and confusing writing (see the Classics link to the right to sample some of Hutton's writing). His ideas became far more accessible after his death with the publication of John Playfair’s “Illustrations of the Huttonian Theory of the Earth” (1802) and Charles Lyell’s “Principles of Geology” (1830). By that time, the scientific revolution in Europe had led to widespread acceptance of the once-radical concept that the earth was constantly changing.
A far more complete understanding of the rock cycle developed with the emergence of plate tectonics theory in the 1960’s (see our Plate Tectonics I module). Our modern concept of the rock cycle is fundamentally different from Hutton’s in a few important aspects: we now largely understand that plate tectonic activity determines how, where, and why uplift occurs, and we know that heat is generated in the interior of the earth through radioactive decay and moved out to the earth’s surface through convection. Together, uniformitarianism, plate tectonics, and the rock cycle provide a powerful lens for looking at the earth, allowing scientists to look back into earth history and make predictions about the future.
The rock cycle consists of a series of constant processes through which earth materials change from one form to another over time. As within the water cycle and the carbon cycle, some processes in the rock cycle occur over millions of years and others occur much more rapidly. There is no real beginning or end to the rock cycle, but it is convenient to begin exploring it with magma. You may want to open the rock cycle schematic below and follow along in the sketch, click on the caption to open this diagram in a new window.
Figure 2: A schematic sketch of the rock cycle. In this sketch, boxes represent earth materials and arrows represent the processes that transform those materials. The processes are named in bold next to the arrows. The two major sources of energy for the rock cycle are also shown; the sun provides energy for surface processes such as weathering, erosion, and transport, and the earth's internal heat provides energy for processes like subduction, melting, and metamorphism. The complexity of the diagram reflects a real complexity in the rock cycle. Notice that there are many possibilities at any step along the way.
Magma, or molten rock, forms only at certain locations within the earth, mostly along plate boundaries. (It is a common misconception that the entire interior of the earth is molten, but this is not the case. See our Earth Structure module for a more complete explanation.) When magma is allowed to cool, it crystallizes, much the same way that ice crystals develop when water is cooled. We see this process occurring at places like Iceland, where magma erupts out of a volcano and cools on the surface of the earth, forming a rock called basalt on the flanks of the volcano. But most magma never makes it to the surface and it cools within the earth’s crust. Deep in the crust below Iceland’s surface, the magma that doesn’t erupt cools to form gabbro. Rocks that form from cooled magma are called igneous rocks; intrusive igneous rocks if they cool below the surface (like gabbro), extrusive igneous rocks if they cool above (like basalt).
Figure 3: This picture shows a basaltic eruption of Pu'u O'o, on the flanks of the Kilauea volcano in Hawaii. The red material is molten lava, which turns black as it cools and crystallizes.
Rocks like basalt are immediately exposed to the atmosphere and weather. Rocks that form below the earth’s surface, like gabbro, must be uplifted and all of the overlying material must be removed through erosion in order for them to be exposed. In either case, as soon as rocks are exposed at the earth’s surface, the weathering process begins. Physical and chemical reactions caused by interaction with air, water, and biological organisms cause the rocks to break down. Once rocks are broken down, wind, moving water, and glaciers carry pieces of the rocks away through a process called erosion. Moving water is the most common agent of erosion – the muddy Mississippi, the Amazon, the Hudson, the Rio Grande, all of these rivers carry tons of sediment weathered and eroded from the mountains of their headwaters to the ocean every year. The sediment carried by these rivers is deposited and continually buried in floodplains and deltas. In fact, the U.S. Army Corps of Engineers is kept busy dredging the sediments out of the Mississippi in order to keep shipping lanes open.
Figure 4: Photograph from space of the Mississippi Delta. The brown color shows the river sediments and where they are being deposited in the Gulf of Mexico.
Under natural conditions, the pressure created by the weight of the younger deposits compacts the older, buried sediments. As groundwater moves through these sediments, minerals like calcite and silica precipitate out of the water and coat the sediment grains. These precipitants fill in the pore spaces between grains and act as cement, gluing individual grains together. The compaction and cementation of sediments creates sedimentary rocks like sandstone and shale, which are forming right now in places like the very bottom of the Mississippi delta. Because deposition of sediments often happens in seasonal or annual cycles, we often see layers preserved in sedimentary rocks when they are exposed. In order for us to see sedimentary rocks, however, they need to be uplifted and exposed by erosion. Most uplift happens along plate boundaries where two plates are moving towards each other and causing compression. As a result, we see sedimentary rocks that contain fossils of marine organisms (and therefore must have been deposited on the ocean floor) exposed high up in the Himalaya Mountains – this is where the Indian plate is running into the Eurasian plate.
Figure 5: The Grand Canyon is famous for its exposures of great thicknesses of sedimentary rocks.
If sedimentary rocks or intrusive igneous rocks are not brought to the earth’s surface by uplift and erosion, they may experience even deeper burial and be exposed to high temperatures and pressures. As a result, the rocks begin to change. Rocks that have changed below the earth’s surface due to exposure to heat, pressure, and hot fluids are called metamorphic rocks. Geologists often refer to metamorphic rocks as “cooked” because they change in much the same way that cake batter changes into a cake when heat is added. Cake batter and cake contain the same ingredients, but they have very different textures, just like sandstone, a sedimentary rock, and quartzite, its metamorphic equivalent. In sandstone, individual sand grains are easily visible and often can even be rubbed off; in quartzite, the edges of the sand grains are no longer visible, and it is a difficult rock to break with a hammer, much less rubbing pieces off with your hands.
Some of the processes within the rock cycle, like volcanic eruptions, happen very rapidly, while others happen very slowly, like the uplift of mountain ranges and weathering of igneous rocks. Importantly, there are multiple pathways through the rock cycle. Any kind of rock can be uplifted and exposed to weathering and erosion; any kind of rock can be buried and metamorphosed. As Hutton correctly theorized, these processes have been occurring for millions and billions of years to create the earth as we see it: a dynamic planet.
The rock cycle is not just theoretical; we can see all of these processes occurring at many different locations and at many different scales all over the world. As an example, the Cascade Range in North America illustrates many aspects of the rock cycle within a relatively small area, as shown in the diagram below.
Figure 6: Cross-section through the Cascade Range in Washington state. Image modified from the Cascade Volcano Observatory, USGS.
The Cascade Range in the northwestern United States is located near a convergent plate boundary, where the Juan de Fuca plate, which consists mostly of basalt saturated with ocean water is being subducted, or pulled underneath, the North American plate. As the plate descends deeper into the earth, heat and pressure increase and the basalt is metamorphosed into a very dense rock called eclogite. All of the ocean water that had been contained within the basalt is released into the overlying rocks, but it is no longer cold ocean water. It too has been heated and contains high concentrations of dissolved minerals, making it highly reactive, or volatile. These volatile fluids lower the melting temperature of the rocks, causing magma to form below the surface of the North American plate near the plate boundary. Some of that magma erupts out of volcanoes like Mt. St. Helens, cooling to form a rock called andesite, and some cools beneath the surface, forming a similar rock called diorite.
Storms coming off of the Pacific Ocean cause heavy rainfall in the Cascades, weathering and eroding the andesite. Small streams carry the weathered pieces of the andesite to large rivers like the Columbia and eventually to the Pacific Ocean, where the sediments are deposited. Continual deposition of sediments near the deep oceanic trench results in the formation of sedimentary rocks like sandstone. Eventually, some sandstone is carried down into the subduction zone, and the cycle begins again (see Experiment! link to the right).
The rock cycle is inextricably linked not only to plate tectonics, but to other earth cycles as well. Weathering, erosion, deposition, and cementation of sediments all require the presence of water, which moves in and out of contact with rocks through the hydrologic cycle; thus weathering happens much more slowly in a dry climate like the desert southwest than in the rainforest (see our The Hydrologic Cycle module for more information). Burial of organic sediments takes carbon out of the atmosphere, part of the long-term geological component of the carbon cycle (see our The Carbon Cycle module); many scientists today are exploring ways we might be able to take advantage of this process and bury additional carbon dioxide produced by the burning of fossil fuels (see News and Events link to the right). The uplift of mountain ranges dramatically affects global and local climate by blocking prevailing winds and inducing precipitation. The interactions between all of these cycles produce the wide variety of dynamic landscapes we see around the globe.
Anne E. Egger, Ph.D. "The Rock Cycle: Uniformitarianism and Recycling," Visionlearning Vol. EAS-2 (7), 2005. | <urn:uuid:1d8cdccb-098e-46d2-97a3-50a9d15430c5> | CC-MAIN-2013-20 | http://visionlearning.org/library/module_viewer.php?c3=&mid=128&l= | 2013-05-19T09:46:25 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368697380733/warc/CC-MAIN-20130516094300-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.951345 | 2,938 | 4.0625 | 4 |
Graph the Asymptote of a Tangent Function
An asymptote is a line that helps give direction to a graph of a trigonometry function. This line isn’t part of the function’s graph; rather, it helps determine the shape of the curve by showing where the curve tends toward being a straight line — somewhere out there. Asymptotes are usually indicated with dashed lines to distinguish them from the actual function.
The asymptotes for the graph of the tangent function are vertical lines that occur regularly, each of them π, or 180 degrees, apart. They separate each piece of the tangent curve, or each complete cycle from the next.
The equations of the tangent’s asymptotes are all of the form
where n is an integer. Under that stipulation for n, the expression 2n + 1 always results in an odd number. By replacing n with various integers, you get lines such as
The reason that asymptotes always occur at these odd multiples of
is because those points are where the cosine function is equal to 0. As such, the domain of the tangent function includes all real numbers except the numbers that occur at these asymptotes.
The preceding figure shows what the asymptotes look like when graphed alone.
The first figure isn’t all that exciting, but it does show how many times the tangent function repeats its pattern. Now take a look at the second preceding figure, which shows one cycle of the tangent function on a graph. The tangent values go infinitely high as the angle measure approaches 90 degrees. The values go infinitely low as the angle measure approaches –90 degrees.
In the third figure, there is more of the tangent on a graph, asymptotes included, to give you a better idea of what’s going on.
As you can see, the tangent function repeats its values over and over. The main difference between this function and the sine and cosine functions is that the tangent has all these breaks between the cycles. As you move from left to right, the tangent appears to go up to positive infinity. It actually disappears at the top of the graph and then picks up again at the bottom, where the values come from negative infinity. Graphing calculators and other graphing utilities don’t usually show the graph disappearing at the top, so it’s up to you to know what’s actually happening, even though the picture may not look exactly that way.
One of the peculiarities of graphing calculators is that they try to connect the tangent function to make it continuous across the screen. For this reason, you’ll usually see some lines between the different parts of the curve. In a way, these lines are errors — they aren’t the asymptotes, although you may be tempted to think they are. The only way to get rid of those extra lines is to turn your calculator to the dot mode (as opposed to the connected mode). Most calculators have ways to set the settings (or mode) for things such as degrees and radians, dotted graphs and connected graphs, floating decimals and fixed decimals, and so on. The changes are usually easy to do — just see your calculator’s manual for specific instructions. The hard part is remembering what setting you’re in. | <urn:uuid:8dec08bf-06f6-42d9-b382-8778f2fa5ff3> | CC-MAIN-2013-20 | http://www.dummies.com/how-to/content/graph-the-asymptote-of-a-tangent-function.html | 2013-05-19T10:19:13 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368697380733/warc/CC-MAIN-20130516094300-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.929057 | 715 | 4.1875 | 4 |
This lesson introduces the concept of monopoly. It calls upon students to consider how monopoly power might affect the quality and price of goods and services offered to consumers. In light of what they learn about the history of trusts and the Sherman AntiTrust Act, the students write editorials, stating and explaining their views about laws prohibiting monopolies. Finally, students consider the effect that the Internet has had on the potential of companies to become entrenched as monopolies in our national and global economies.
- Define monopoly.
- Explain the market power that monopolies can exert.
- Evaluate American laws prohibiting monopolies.
This lesson is intended to help students will develop an understanding of economic monopolies. It introduces the Sherman Anti-Trust Act, which forbade the establishment and practices of economic monopolies in the United States. Working as newspaper editorialists, students explain whether or not they believe that monopolies should be prohibited in free market economic systems. The students also consider the ways in which today's technological infrastructure has influenced the capacity of companies to establish themselves as monopolies. Finally, the students create radio broadcasts explaining the nature of monopolies today.
Monopoly: This EconEdLink glossary provides a large number of definitions of economic concepts.
Monopoly Defined: This page provides a print-out for students that defines monopolies.
Monopoly Defined Handout
Standard Oil and the Sherman Anti-Trust Act: This EconEdLink worksheet provides information and questions for students to answer related to monopolies.
Student Responses to Editorials: This worksheet allows students to write if they felt that the editorial that they read was well-written or not.
Student Responses to Editorials
Edublogs: At this site, students and teachers can set up their own blogs and post their own editorials.
Technology and Monopolies: This worksheet helps students to understand how advances in technology are related to monopolies.
Technology and Monopolies
Odeo Enterprise: This site allows students to create their own podcasts.
Creating a Monopoly: This EconEdLink worksheet asks students to develop their own monopoly.
Creating a Monopoly
To begin this lesson, tell the students that you want to purchase a pen from somebody. Ask whether any of them would be pen that they would be willing to sell. After the students have completed this short exercise ask them what they wrote willing to sell you a pen. Tell them to write down on a piece of paper the price that they would charge for a pen--using the down. Also ask them to help you decide which pen to purchase: what information should you think about in making your decision about which pen to purchase? The students may suggest that you should think about which pen you want, and that you should try to purchase it for the lowest possible price. If the students do not suggest these ideas on their own, raise them for the students. Ask them to explain why these ideas make sense.
Now tell the students to imagine that one student in the class owned all of the pens in the classroom. And you have decided that you would buy a pen only from somebody in the class. Ask them how this scenario might influence the price of the pen and the quality of the pen being sold. Here you would like to thear the students state that if one person owned all of the pens, that person could charge more money for them and sell lower-quality pens. Ask the students to explain why this is true. They should recognize that since only one person was selling pens, this individual would not have to worry about either the price set by other people or the quality of the pens that other people were selling. Tell the students that this scenario is an example of a monopoly.
Now show the students the definition of monopoly and use it as a transparency. Ask the students to explain this definition in their own words. Then shift the discussion: ask the students if they think it is fair for monopolies to exist. Urge them to support their opinions. As the students share their opinions take notes on the board. Encourage the students to express ideas that both support and oppose monopolies.
Now tell students that they should learn how the U.S. government views economic monopolies. Invite them to read and complete the worksheet entitled Standard Oil and the Sherman Anti-Trust Laws , available here. After the students have completed this work, reconvene the class. Call on students to share their answers with one another. Click here to view possible answers to the Standard Oil and Sherman Anti-Trust Laws worksheet.
Ask the students why companies might to be monopolies. Help them understand that in a free-market economic system, people work to make money and companies exist to make profit: individual companies want to make as much profit as possible. Certainly companies would love to be monopolies if this meant that they could make greater profits, as it most certainly would.
Ask the students how companies might try to become monopolies. There are several possible answers. Companies might lower their prices in order to attract customers away from their competition. Companies might also try to produce the best product or service available at the lowest cost in order to attract new customers. Companies can also become monopolies by inventing new products and acquiring a patent to prevent others from copying their products. At times the government establishes monopolies when policy makers believe it is in the public's best interest. For example, municipalities typically grant monopoly status to electric companies since it would be too expensive for several electric companies to compete in the same community. When the government does establish monopolies, it typically regulates them to insure that they do not unfairly raise prices or lower quality.
Help the students understand that, without government regulation, companies that become monopolies may lower the quality of their products or services (perhaps by spending less money producing them), or they may raise the price of the goods and services that they sell. Ask the students why companies might do this. The students should recognize that companies can reduce quality or raise prices if they no longer face competition. As appropriate refer to the pen-selling example to underscore this point.
Introduce the point that the U.S. government seeks in various ways to foster competition. Help the students understand that while individual firms might want to be monopolies and enjoy the benefits of monopoly status U.S. government does not think that monopolies are good for our nation since monopolies can raise prices and lower the quality of goods and services.
Now introduce a writing assignment. Tell the students that for the next part of this assignment they should pretend they are newspaper editorialists. To clarify the task, ask the students what they know about the job of a newspaper editorialist. If anybody states that editorialists write opinion pieces for the newspaper, underscore that response. If the students do not know this, tell them. Remind the students, however, that editorialists cannot simply write their opinion and expect others to accept it. They must justify their opinions with high quality reasoning. Remind the students that editors write for the public. On this assignment, therefore, classmates will read one another's editorials, and comment on them, upon completion. Ask the students to respond to the interactive question below.
- Pretend that you are an editorialist, and write an editorial considering whether or not you believe that monopolies should be illegal.
After the students have completed this work, tell them to form groups of three. Explain that in these groups they should read one another's opinions and respond to them. They should state whether the agree or disagree with the writer's conclusion. They also should explain why they agree or disagree by commenting on how the writer uses facts and reasons to support his or her conclusion. The Student Responses to Editorials can be used as a handout. Be sure to encourage the students to read the comments that their group mates write about their opinions.
[NOTE: As an alternative to the above interactive you may choose to have the students work in a "blog" setting. Using the website Edublogs
or another "blog" site of your choice set up a "blog" and have the students create their editorials. Once each student has created an editorial have the students comment on one another's editorial piece so they can complete the group work portion of the class.]
Now remind the students that the U.S. government outlawed monopolies at the end of the nineteenth century. Suggest that much has changed in American society between the 1890s and today. Ask the students what they can think of that has changed. Among many other things, the students may mention an infusion of computer technology. They should recognize that not all of the innovations we take for granted today--the personal computer, the World Wide Web, e-mail, instant text messaging, podcasts, open-source materials, etc.--were widely available 10 years ago, let alone 110 years ago. Ask the students to complete the worksheet entitled Technology and Monopolies , working in groups of two to three. This worksheet asks the students to consider whether or not they think recent technological advances would make it easier and cheaper to start businesses. They are then asked how these advances might affect the ability of individual companies to establish themselves as monopolies. After the students have completed this work, reconvene the class and invite students to share their answers with one another. Lead a discussion in which students consider the influence that the technology available in recent years has had on firms seeking to establish themselves as monopolies. During this discussion, ask the students if they think it is important for the U.S. government to continue to still have a law prohibiting the establishment of monopolies. During this discussion, urge the students to support their opinions thoughtfully.
In this lesson, students have learned about the role that monopolies play in economies. They have learned that monopolies are outlawed by the U.S. government. They have learned why companies would want to be monopolies -- i.e., because monopoly power sometimes enables companies to charge higher rates for their products/services, generating greater profit. In addition to considering their own perspectives on monopolies, the students have thought about their classmates' perspectives. Finally, the students have examined the influence of today's technology has on the ability of companies to establish themselves as monopolies.
Tell the students that in order to demonstrate their knowledge of monopolies, they should develop a radio interview, working in groups of two or three, in which the participants explain the nature of monopolies, the ways in which today's technological infrastructure has influenced the establishment of monopolies and whether or not they think monopolies should be illegal today. The students might particularly enjoy making podcast interviews. If you choose to have them make podcasts, consider using Odeo, an excellent resource. You can link to the Odeo site from here . The Odeo website has very user-friendly directions. Students can even call into Odeo via telephone to create their podcasts. If you would prefer not to use podcasts, you can simply ask the students to develop presentations which they can perform before the class. If you choose to do the activity in this way, ask the students who are not performing to write down one idea they learn from each presentation.
Assign the students to develop a plan to create their own monopoly. Having created their palns, they should also analyze their plans to determine what effect the plans might have on the greater economy. To begin this step, ask the students, working in groups of two or three, to complete the worksheet entitled Creating a Monopoly . After the students have completed this worksheet, reconvene the class. Invite students to share their answers with one another. During this discussion encourage the students to consider how efforts to create a monopoly might negatively influence the quality of goods and services that would be available to consumers. Urge the students to support their ideas thoughtfully.
“It seems like a very good lesson. I wish I had been able to print the material to use in my classroom.”
“Great lesson. I used this for a group of middle school students. I'm glad I noticed the student's version. I also used the board game Monopoly as an extension. Students grasped the concept more fully after playing the game.” | <urn:uuid:a26fec87-9c62-43ee-9542-9794a96ec19a> | CC-MAIN-2013-20 | http://www.econedlink.org/lessons/index.php?lid=686&type=educator | 2013-05-19T10:23:47 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368697380733/warc/CC-MAIN-20130516094300-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.964025 | 2,510 | 4.1875 | 4 |
Growth and Development, Ages 6 to 10 Years (cont.)
Promoting Healthy Growth and Development
Although your child between the ages of 6 and 10 may seem very independent at times, he or she still needs your constant guidance. Being present is the most important thing you can do to help your child grow in healthy ways. Knowing that you are "around" and available provides him or her with a sense of security. Although your child's world is expanding, you remain his or her primary influence.
You can do many things to help your child grow and develop.
- Promote physical development by encouraging and modeling healthy eating habits. Also, foster a healthy body image by talking about and showing how it is important to accept people of all colors, shapes, and sizes. For more information, see the topic Healthy Habits for Kids.
- Promote cognitive development—thinking and reasoning skills—by being involved in your child's school. Volunteer if possible, cultivate good relationships with teachers and other staff members, and show your interest in what your child is learning. Also, work on skills at home, such as simple math problems, money handling, reading, and writing. Age-appropriate workbooks are widely available. But be careful not to pressure your child. Simply spending time with him or her is an important part of setting a foundation for cognitive growth.
- Promote language development by reading to your child every day. Make reading a routine, even as he or she gets older and seems to lose interest. Set aside time that you and your child can look forward to and talk about stories, words, and ideas. Visit your local library and try finding books with new subjects that you think might interest your child.
- Promote social and emotional development by being aware of sibling rivalry, which can become a problem around this age. Also help your child learn social skills, such as by showing your acceptance of others and not gossiping or saying mean things about other people.
- Promote sensory and motor skill development by encouraging exercise every day. It doesn't have to be highly structured: the main point is to move around. Practicing somersaults, playing catch, going to the park, or riding a bike are all helpful in developing muscular skill and endurance. Also, encourage your child to create art projects, such as drawing, cutting with safety scissors, gluing, and stringing beads. These and similar activities help improve eye-hand coordination and fine motor skills. For more information, see the topic Physical Activity for Children and Teens.
Also, you can help your child in other general ways.
- Deal with fears. Understand that your child may become extremely interested in scary subjects or images as a way to overcome them. Help your child as much as you can by answering questions and providing reassurance as needed.
- Discourage physical violence and show your child ways to deal with anger without being violent. Protect your child from violent media as much as you can. Some TV programs, movies, video games, and websites show a lot of violent acts. Children who watch a lot of this violence may come to believe that such behavior is okay. This can make them more likely to act violently themselves. It can also lead to nightmares, aggression, or fears of being harmed.1 Music lyrics affect children's behavior and emotions, too.2 Monitor the type of music that your child is exposed to, and be aware of the music your child buys.
- Establish limits. Set limits for your children to show them that you love and care about them. Make sure your rules are reasonable and that your child understands them. It is important to follow through on any consequences you have established for failing to follow rules.
- Recognize and develop special talents. Help your child discover interests and practice skills. For example, kick a soccer ball around the yard with your child or help him or her practice printing letters.
- Recognize his or her curiosity about the body and sexuality. You can help your child gain basic knowledge and a healthy attitude toward these issues by showing a willingness to listen and discuss them.
- Before your child starts middle school, teach him or her how to resist using tobacco and other drugs.
You can also help your child through each stage of development by evaluating your relationship from time to time. In many ways, you have to "get to know" your child over and over again. Think about:
- What do I like most about my child?
- What could be triggering bad behavior? Are any of these new triggers?
- What new skills has my child developed within the past year? Six months? Three months?
- What tasks can I encourage my child to do for himself or herself? How can I encourage him or her?
- When am I happy about how I treat my child?
- What don't I like about some of our interactions? When do these episodes tend to occur?
As a parent or caregiver of children, it is also important for you to:
- Learn and use effective parenting and discipline techniques and avoid the use of corporal punishment. Parenting classes are offered in most communities. Ask your doctor or call a local hospital for more information.
- Learn healthy techniques to resolve conflicts and manage stress. For more information, see the topic Stress Management.
- Ask for help when you need it. Call a family member or friend to give you a break if you feel overwhelmed. Find out about community resources that are available to help you with child care or other necessary services. Call a doctor or local hospital to find out about a place to start. Some communities have respite care facilities for children, which provide temporary child care during times when you need a break.
eMedicineHealth Medical Reference from Healthwise
To learn more visit Healthwise.org
© 1995-2012 Healthwise, Incorporated. Healthwise, Healthwise for every health decision, and the Healthwise logo are trademarks of Healthwise, Incorporated. | <urn:uuid:0e2177aa-3fef-46ee-a4a6-acabac086287> | CC-MAIN-2013-20 | http://www.emedicinehealth.com/growth_and_development_ages_6_to_10_years-health/page4_em.htm | 2013-05-19T10:25:39 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368697380733/warc/CC-MAIN-20130516094300-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.960972 | 1,221 | 4.1875 | 4 |
Rhenium is a rare, silvery-white metallic element. Its atomic number is 75 and its symbol is Re. Rhenium was discovered in 1925 by a team of German scientists named Walter Noddack, Ida Tacke-Noddack, and Otto Berg. They discovered rhenium as a trace element in platinum ores and the mineral columbite. It is very dense. It has a melting temperature of 3,186 degrees Celsius (5,767 degrees Fahrenheit). It is not known to have any health benefit for animals or plants. Rhenium does not form minerals of its own, but it does occur as a trace element in columbite, tantalite and molybdenite. These minerals are the principal sources of columbium (commonly called niobium), tantalum and molybdenum metals.
Rhenium is a very rare element that is produced principally as a by-product of the processing of porphry copper-molybdenum ores. Because it is scarce, very little rhenium is actually processed and isolated each year as compared to the millions of tons of copper and millions of pounds of molybdenum that are extracted from these same porphry copper deposits. As a result, the processing of rhenium poses no environmental threat. The equipment that reduces sulfur dioxide in these processing plants also removes any rhenium that may escape through the smokestacks.
|Previous Element: Tungsten|
Next Element: Osmium
|Phase at Room Temp.||solid|
|Melting Point (K)||3453.2|
|Boiling Point (K)||5923|
|Heat of Fusion (kJ/mol)||33.054|
|Heat of Vaporization (kJ/mol)||707|
|Heat of Atomization (kJ/mol)||770|
|Thermal Conductivity (J/m sec K)||48|
|Electrical Conductivity (1/mohm cm)||51.813|
|Number of Isotopes||45 (2 natural)|
|Electron Affinity (kJ/mol)||14|
|First Ionization Energy (kJ/mol)||760|
|Second Ionization Energy (kJ/mol)||---|
|Third Ionization Energy (kJ/mol)||---|
|Atomic Volume (cm3/mol)||8.9|
|Ionic Radius2- (pm)||---|
|Ionic Radius1- (pm)||---|
|Atomic Radius (pm)||137|
|Ionic Radius1+ (pm)||---|
|Ionic Radius2+ (pm)||---|
|Ionic Radius3+ (pm)||---|
|Common Oxidation Numbers||+4|
|Other Oxid. Numbers||-3, -1, +1, +2, +3 +5, +6, +7|
|In Earth's Crust (mg/kg)||7.0x10-4|
|In Earth's Ocean (mg/L)||4.0x10-6|
|In Human Body (%)||0%|
|Regulatory / Health|
|OSHA Permissible Exposure Limit (PEL)||No limits|
|OSHA PEL Vacated 1989||No limits|
|NIOSH Recommended Exposure Limit (REL)||No limits|
University of Wisconsin General Chemistry
Mineral Information Institute
Jefferson Accelerator Laboratory
Rhenium was named after the Greek word for the Rhine River, Rhenus.
Rhenium is obtained almost exclusively as a by-product of the processing of a special type of copper deposit known as a porphyry copper deposit. Specifically, it is obtained from the processing of the mineral molybdenite (a molybdenum ore) that is found in porphyry copper deposits. A porphyry copper deposit is a valuable copper-rich deposit in which copper minerals occur throughout the rock. The copper in these deposits occurs as primary chalcopyrite (CuFeS2) or the important secondary copper mineral chalcocite (Cu2S).
The identified rhenium resources in the United States are estimated to total 5 million kilograms. These resources are found in the southwestern United States. The identified rhenium resources in the rest of the world are estimated to total 6 million kilograms. Countries producing rhenium include Armenia, Canada, Chile, Kazakhstan, Mexico, Peru, Russia, and Uzbekistan. Even though the United States has significant rhenium resources, the majority of the rhenium consumed in the U.S. is imported. Chile and Kazakhstan provide the majority of the imported rhenium. The rest is imported from Mexico and other nations.
Because of its very high melting point, rhenium is used to make high temperature alloys (an alloy is a mixture of metals) that are used in jet engine parts. It is also used to make strong alloys of nickel-based metals. Rhenium alloys are used to make a variety of equipment and equipment parts, such as temperature controls, heating elements, mass spectrographs, electrical contacts, electromagnets, and semiconductors. An alloy of rhenium and molybdenum is a superconductor of electricity at very low temperatures. These superalloys account for the majority of the rhenium use each year.
Rhenium is also used in the petroleum industry to make lead-free gasoline. In this application, rhenium compounds act as catalysts. (A catalyst is a chemical compound that takes part in a chemical reaction, and can often make the reaction proceed more quickly, but the chemical is not consumed in the chemical reaction.)
Substitutes and Alternative Sources
Substitutes for rhenium as a catalyst are being researched. Iridium and tin have been found to be a good catalyst for at least one reaction. Cobalt, tungsten, platinum and tantalum can be used in some of the other applications for rhenium.
- Common Minerals and Their Uses, Mineral Information Institute.
- More than 170 Mineral Photographs, Mineral Information Institute.
Disclaimer: This article is taken wholly from, or contains information that was originally published by, the Mineral Information Institute. Topic editors and authors for the Encyclopedia of Earth may have edited its content or added new information. The use of information from the Mineral Information Institute should not be construed as support for or endorsement by that organization for any new information added by EoE personnel, or for any editing of the original content. | <urn:uuid:c664e83e-de9f-4793-8ec6-412b4f0d26e6> | CC-MAIN-2013-20 | http://www.eoearth.org/article/Rhenium | 2013-05-19T10:23:32 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368697380733/warc/CC-MAIN-20130516094300-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.861598 | 1,404 | 4.21875 | 4 |
Well baby care
How do vaccines work?Tiny organisms (like viruses and bacteria) can attack your body and cause infections that make you sick. When you get an infection, your body makes special disease-fighting substances called antibodies to fight the organism. In many cases, once your body has made antibodies against an organism, you become immune to the infection it causes. Immune means you are protected against getting an infection. If you're immune to an infection, it means you can't get the infection.
Vaccines usually have a small amount or piece of the organism that causes an infection. The organisms used in vaccines are generally weakened or killed so they won’t make you sick. The vaccine causes your body to make antibodies against the organism. This allows you to become immune to an infection without getting sick first.
Some vaccines have a live but weakened organism. These are called live-virus vaccines. While live-virus vaccines are usually safe for most babies and adults, they’re not generally recommended for pregnant women.
See also: Vaccinations and pregnancy, Your baby’s vaccinations | <urn:uuid:9c78e97f-c6fb-411a-b4df-d92d9c2e6e29> | CC-MAIN-2013-20 | http://www.marchofdimes.com/baby/faq_vaccineswork.html | 2013-05-19T09:48:26 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368697380733/warc/CC-MAIN-20130516094300-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.949717 | 227 | 4.03125 | 4 |
The Plasma Spray – Physical Vapor Deposition (PS-PVD) rig at NASA's Glenn Research Center uses new technology to create super thin ceramic coatings. Here, Bryan Harder, the lead for the PS-PVD, installs a sample in the rig. Image Credit: NASA
Turbines, or rotary engines that create power, have a multitude of uses. They are used in machines that perform work on Earth and are essential components of airplanes. Currently, most turbines are built using metallic based components, and these metal components require cooling to avoid reaching their thermal limits. New, more efficient engine technology requires components that can survive higher temperatures and reduced cooling.
Silicon based ceramic components show great potential for use in advanced, higher efficiency engines, as they are capable of withstanding higher temperatures and weigh less than metal components. However, when unprotected, these silicon based ceramic components react and erode in turbine engine environments due to the presence of water vapor.
New coating processing technology is being pioneered at NASA Glenn's Research Center in Cleveland. The technology is used to protect advanced silicon based ceramic engine components that are being developed for future engines. This coating processing technology will enable more complex and thinner coatings than are currently possible. This is important for coating turbine blades, which need to endure engine environments and stress conditions, while still remaining smooth to avoid the disruption of airflow. This coating processing technology, called Plasma Spray – Physical Vapor Deposition (PS-PVD), has the potential to radically improve the capabilities of ceramic composite turbine components.
"PS-PVD technology is really necessary for the integration of silicon-based ceramic airfoil components into turbine engines. The use of these silicon-based ceramics as engine airfoil components would increase engine operation temperature, which translates into higher efficiencies," says Bryan Harder, the lead for the PS-PVD Facility at Glenn.
Plasma Spray – Physical Vapor Deposition
The PS-PVD rig uses a system of vacuum pumps and a blower to remove air from the chamber, reducing the pressure to one Torr (1/760th of normal atmospheric pressure). Image Credit: NASA
It has been known for decades that enveloping metals and other substances, such as silicon based ceramic components, with a ceramic coating can protect them. But there is new, cutting-edge technology that can create ceramic coatings in an extremely precise, uniform fashion—the coatings can be controlled to a thickness of ten microns (a micron is one-millionth of a meter). This technology is made possible by Glenn's Plasma Spray – Physical Vapor Deposition (PS-PVD) Facility.
The Plasma Spray – Physical Vapor Deposition (PS-PVD) Coater was completed at Glenn in 2010. Created in collaboration with Sulzer Metco, the PS-PVD rig is one of only two such facilities in the U.S.A. and one of four in the entire world. The PS-PVD rig, which is currently a research and development facility, uses a state of the art processing method of creating thin ceramic coatings. Planning began for the facility in 2007, and construction began in 2008 (previously constructed infrastructure was reused and is now the base for the new rig).
The rig is nearing completion of its capabilities testing and assessment phase. A team of five, led by Bryan Harder, a materials research engineer, has put the rig through its paces. The rig will soon begin supporting the Supersonic Project within NASA's Aeronautics Research Mission Directorate at Glenn. Eventually, the rig could be of service to many other areas and projects within Glenn, other NASA centers and governmental entities, and private industry partners.
"When you have something that has broad capabilities like this, it really allows us to work with a lot of different areas, which is a great thing," says Bryan Harder.
Super Thin Ceramic Coatings
Ceramic powder is pumped into the PS-PVD rig. It will be transformed inside the chamber to become a thin, precise, accurate ceramic coating. Image Credit: NASA
The Plasma Spray-Physical Vapor Deposition (PS-PVD) rig creates thin, extremely precise ceramic coatings. These coatings are created on metal, ceramic, or other appropriate materials.
"To create these coatings, ceramic powder is injected into a very high power plasma flame under a vacuum. During operation, the plasma is approximately 7 feet long and 3 feet wide. The ceramic material is vaporized within the plasma, and condenses onto the target component," says Bryan Harder.
The coatings can be single or multilayer, and they protect the components from environmental and thermal impact. The extremely high heat and the vacuum within the chamber allow the ceramic coating to be precisely applied, creating durable, long-lasting, effective coatings.
"If you can reduce the thickness, and still provide an effective barrier layer — you can reduce the weight, you can reduce your cost. There are a lot of benefits that come from this technology," Harder says.
Inside the Chamber
Within the PS-PVD, an extremely hot plasma flame is created. The plasma can reach a temperature of 10,000 degrees Celsius—ten times hotter than a candle flame. Image Credit: NASA
Located at Glenn, the Plasma Spray – Physical Vapor Deposition (PS-PVD) is installed in a dedicated room. A large, blimp-shaped chamber is made of stainless steel. The exterior metal, which is welded to a second sheet of stainless steel beneath, has cool water pumped through it to keep the chamber from getting too warm.
Inside the chamber is a steel arm which holds a plate made of a nickel-based superalloy. This plate holds the component that will be coated. Several feet away from this plate is the torch, where the ceramic powder is injected into the plasma. Once the chamber is closed, a system of vacuum pumps and a blower remove air from the chamber, reducing the pressure to one Torr (1/760th of normal atmospheric pressure). Then, helium and argon gases are introduced to the torch. An arc is created between the anode and cathode inside the chamber, ionizing the gases and creating the high temperature plasma.
The plasma, which can grow to seven feet in length, can be observed through one of three portals on the side of the rig. Its steady, fierce, concentrated glow resembles a Lightsaber from the Star Wars movies. Once the vacuum and plasma are stable, the ceramic powder is introduced to the torch. The plasma immediately begins to change colors. Depending on which ceramic powder is introduced, the plasma dramatically erupts into oranges, yellows, aquas, purples and blues.
The gas stream moves at a speed of Mach 2 — a rate of more than 2,000 feet per second. As the ceramic powder and the plasma blast the arm and plate where the component being coated is attached, the plasma appears to envelop the component and splash around it. The plasma, which appeared like a Lightsaber, seems to morph into the effect of the undulating stream of magic that occurs when Harry Potter's wand meets with Lord Voldemort's wand, in the Harry Potter movies.
Inside the PS-PVD, ceramic powder is introduced into the plasma flame. The plasma vaporizes the ceramic powder, which then condenses to form the ceramic coating. Image Credit: NASA
The entire process is over in about five minutes. The plasma is extinguished and the exhaust system clears the chamber. The pressure is returned to normal atmospheric conditions, and then the chamber can be opened. The newly-coated component glows red hot and must cool down for an hour before it can be handled. The plasma within the chamber can reach a scorching 10,000 degrees Celsius — ten times hotter than a candle flame.
After the sample cools, it will be tested and evaluated to ensure the coating is an effective barrier. And then the sample — be it a small test button or an essential component of a supersonic aircraft — is ready to go. The front, sides and inside of the sample can be coated — a capability never previously available from vapor deposition techniques.
"The PS-PVD allows us to do things that you can't do anywhere else," Harder says.
This newly developed technology could have myriad applications, both within NASA and with potential industry partners. The potential applications are only beginning to be discovered — from membrane technology to fuel cells to ion conductors and beyond.
The rig is a game-changing technology; Glenn is maturing and developing a technology that doesn't exist elsewhere, while making direct contributions to the NASA mission.
"This is new ground," Bryan Harder says. "This was only developed in the last couple of years… and we don't even know the limits of what it [PS-PVD] is capable of."
-Tori Woods, SGT Inc. NASA's Glenn Research Center | <urn:uuid:f1431e61-97ca-4d5d-8075-51f535c02fe1> | CC-MAIN-2013-20 | http://www.nasa.gov/topics/technology/features/ceramic_coatings.html | 2013-05-19T10:18:08 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368697380733/warc/CC-MAIN-20130516094300-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.937292 | 1,834 | 4.15625 | 4 |
Chemical Principles/Will It React? An Introduction to Chemical Equilibrium
And so, nothing that to our world appears,
Perishes completely, for nature ever
Upbuilds one thing from another's ruin;
Suffering nothing yet to come to birth
But by another's death.
Lucretius (95-55 B.C.)
The main question asked in Chapter 2 was "If a given set of substances will react to give a desired product, how much of each substance is needed?" Our basic assumptions were that matter cannot be arbitrarily created or destroyed, and that atoms going into a reaction must come out again as products.
In this chapter we ask a second question: "Will a reaction occur, eventually?" Is there a tendency or a drive for a given reaction to take place, and if we wait long enough will we find that reactants have been converted spontaneously into products? This question leads to the ideas of spontaneity and of chemical equilibrium. A third question, "Will a reaction occur in a reasonably short time?" involves chemical kinetics, which will be discussed in Chapter 22. For the moment, we will be satisfied if we can predict which way a chemical reaction will go by itself, ignoring the time factor.
Spontaneous Reactions
A chemical reaction that will occur on its own, given enough time, is said to be spontaneous. In the open air, and under the conditions inside an automobile engine, the combustion of gasoline is spontaneous:
C7H16 + 11 O2 → 7CO2 + 8 H2O
(The reaction is exothermic, or heat emitting. The enthalpy change, which was defined in Chapter 2, is large and negative: = -4812 kJ mole-1 of heptane at 298 K. The heat emitted causes the product gases to expand, and it is the pressure from these expanding gases that drives the car.) In contrast, the reverse reaction under the same conditions is not spontaneous:
7CO2 + 8H2O C7H16 + 11 O2
No one seriously proposes that gasoline can be obtained spontaneously from a mixture of water vapor and carbon dioxide.
Explosions are examples of rapid, spontaneous reactions, but a reaction need not be as rapid as an explosion to be spontaneous. It is important to understand clearly the difference between rapidity and spontaneity. If you mix oxygen and hydrogen gases at room temperature, they will remain together without appreciable reaction for years. Yet the reaction to produce water is genuinely spontaneous:
2H2 + O2 → 2H2O
We know that this is true because we can trigger the reaction with a match, or catalyst of finely divided platinum metal.
The preceding sentence suggests why a chemist is interested in whether a reaction is spontaneous, that is, whether it has a natural tendency to occur. If a desirable chemical reaction is spontaneous but slow, it may be possible to speed up the process. Increasing the temperature will often do the trick, or a catalyst may work. We will discuss the functions of a catalyst in detail in Chapter 22. But in brief, we can say now that a catalyst is a substance that helps a naturally spontaneous reaction to go faster by providing an easier pathway for it. Gasoline will burn rapidly in air at a high enough temperature. The role of a spark plug in an automobile engine is to provide this initial temperature. The heat produced by the reaction maintains the high temperature needed to keep it going thereafter. Gasoline will combine with oxygen at room temperature if the proper catalyst is used, because the reaction is naturally spontaneous but slow. But no catalyst will ever make carbon dioxide and water recombine to produce gasoline and oxygen at room temperature and moderate pressures, and it would be a foolish chemist who spent time trying to find such a catalyst. In short, an understanding of spontaneous and nonspontaneous reactions helps a chemist to see the limits of what is possible. If a reaction is possible but not currently realizable, it may be worthwhile to look for ways to carry it out. If the process is inherently impossible, then it is time to study something else.
Equilibrium and the Equilibrium Constant
The speed with which a reaction takes a place ordinarily depends on the most concentrations of the reacting substances. This is common sense, since most reactions take place when molecules collide, and the more molecules there are per unit of volume, the more often collisions will occur.
The industrial fixation of atmospheric nitrogen is very important in the manufacture of agricultural fertilizers (and explosives). One of the steps in nitrogen fixation, in the presence of a catalyst, is
N2 + O2 → 2NO (4-1)
If this reaction took place by simple collision of one molecule of N2 and one molecule of O2, then we would expect the rate of collision (and hence the rate of reaction) to be proportional to the concentrations of N2 and O2:
Rate of NO production
R1 = k1[N2][O2] (4-2)
The proportionality constant k1 is called the forward-reaction rate constant, and the bracketed terms [N2][O2] represent concentrations in moles per liter. This rate constant, which we will discuss in more detail in Chapter 22, usually varies with temperature. Most reactions go faster at higher temperatures, so k1 is larger at higher temperatures. But k1 does not depend on the concentrations of nitrogen and oxygen gases present. All of the concentration dependence of the overall forward reaction rate, R1, is contained in the terms [N2] and [O2]. If this reaction began rapidly in a sealed tank with high starting concentrations of both gases, then as more N2 and O2 were consumed, the forward reaction would become progressively slower. The rate of reaction would decrease because the frequency of collision of molecules would diminish as fewer N2 and O2 molecules were left in the tank.
The reverse reaction can also occur. If this reaction took place by the collision of two molecules of NO to make one molecule of each starting gas,
2NO → N2 + O2 (4-3)
then the rate of reaction again would be proportional to the concentration of each of the colliding molecules. Since these molecules are of the same compound, NO, the rate would be proportional to the square of the NO concentration:
Rate of NO removal [NO][NO]
R2 = k2[NO]2 (4-4)
where R2 is the overall reverse reaction rate and k2 is the rev~rse-reaction rate constant. If little NO is present when the experiment begins, this reaction will occur at a negligible rate. But as more NO accumulates by the forward reaction, the faster it will be broken down by the reverse reaction.
Thus as the forward rate, R1, decreases, the reverse rate, R2 , increases. Eventually the point will be reached at which the forward and reverse reactions exactly balance (4-5):
R1 = R2 [N2][O2]k1 = k2[NO]2
This is the condition of equilibrium. Had you been monitoring the concentrations of the three gases, N2 O2, and NO, you would have found that the composition of the reacting mixture had reached an equilibrium state and thereafter ceased to change with time. This does not mean that the individual reactions had stopped, only that they were proceeding at equal rates; that is, they had arrived at, and thereafter maintained, a condition of balance or equilibrium.
The condition of equilibrium can be illustrated by imagining two large fish tanks, connected by a channel (Figure 4-1). One tank initially contains 10 goldfish, and the other contains 10 guppies. If you watch the fish swimming aimlessly long enough, you will eventually find that approximately 5 of each type of fish are present in each tank. Each fish has the same chance of blundering through the channel into the other tank. But as long as there are more goldfish in the left tank (Figure 4-la), there is a greater probability that a goldfish will swim from left to right than the reverse. Similarly, as long as the number of guppies in the right tank exceeds that in the left, there will be a net flow of guppies to the left, even though there is nothing in the left tank to make the guppies prefer it. Thus the rate of flow of guppies is proportional to the concentration of guppies present. A similar statement can be made for the goldfish.
At equilibrium (Figure 4-1b), on an average there will be 5 guppies and 5 goldfish in each tank. But they will not always be the same 5 of each fish. If 1 guppy wanders from the left tank into the right, then it or a different guppy may wander back a little later. Thus at equilibrium we find that the fish have not stopped swimming, only that over a period of time the total number of guppies and goldfish in each tank remains constant. If we were to fill each tank with 9 goldfish and then throw in 1 guppy, we would see that, in its aimless swimming, it would spend half its time in one tank and half in the other (Figure 4-1 c).
In the NO reaction we considered, there will be a constant concentration of NO molecules at equilibrium, but they will not always be the same NO molecules. Individual NO molecules will react to re-form N2 and O2, and other reactant molecules will make more NO. As with the goldfish, only on a head-count or concentration basis have changes ceased at equilibrium.
The equilibrium condition for the NO-producing reaction, equation 4-1, can be rewritten in a more useful form:
in which the ratio of forward and reverse rate constants is expressed as a simple constant, the equilibrium constant, Keq. This equilibrium constant will vary as the temperature varies, but it is independent of the concentrations of the reactants and products. It tells us the ratio of products to reactants at equilibrium, and is an extremely useful quantity for determining whether a desired reaction will take place spontaneously.
General Form of the Equilibrium Constant
We derived the equilibrium-constant expression for the NO reaction by assuming that we knew the way that the forward and reverse steps occurred at the molecular level. If the NO reaction proceeded by simple collision of two molecules, the derivation would be perfectly correct. The actual mechanism of this reaction is more complicated. But it is important, and fortunate for chemists, that we do not have to know the reaction mechanism to write the proper equilibrium constant. The equilibrium-constant expression can always be written from the balanced chemical equation, with no other information, even when the forward and reverse rate expressions are more complicated than the balanced equation would suggest. (We shall prove this in Chapter 16.) In our NO example, the forward reaction actually takes place by a series of complicated chain steps. The reverse reaction takes place by a complementary set of reactions, so that these complications cancel one another in the final ratio of concentrations that gives us the equilibrium constant. The details of the mechanism are "invisible" to the equilibrium-constant expression, and irrelevant to equilibrium calculations.
A general chemical reaction can be written as
In this expression, A and B represent the reactants; C and D, the products. The letters a, b, c, and d represent the number of moles of each substance involved in the balanced reaction, and the double arrows indicate a state of equilibrium. Although only two reactants and two products are shown in the general reaction, the principle is extendable to any number. The correct equilibrium-constant expression for this reaction is
It is the ratio of product concentrations to reactant concentrations, with each concentration term raised to a power given by the number of moles of that substance appearing in the balanced chemical equation. Because it is based on the quantities of reactants and products present at equilibrium, equation 4-8 is called the law of mass action.
|Give the equilibrium-constant expression for the reaction|
The equilibrium constant is given by
Since all four substances have a coefficient of 1 in the balanced equation, their concentrations are all raised to the first power in the equilibrium-constant expression.
|What is the equilibrium-constant expression for the formation of water from hydrogen and oxygen gases? The reaction is|
Since two moles of hydrogen and water are involved in the chemical equation, their concentrations are squared in the Keq expression.
|Give the equilibrium-constant expression for the dissociation (breaking up) of water into hydrogen and oxygen. The reaction is|
An important general point emerges here. This reaction is the reverse of that of Example 2, and the equilibrium-constant expression is the inverse, or reciprocal, of the earlier one. If a balanced chemical reaction is reversed, then the equilibrium-constant expression must be inverted, since what once were reactants now are products, and vice versa.
|The dissociation of water can just as properly be written as
What then is the equilibrium-constant expression?
Notice that when the reaction from Example 3 is divided by 2, resulting in the Example 4 reaction, the equilibrium constant is the square root of the old value, or the old Keq to the one-half power. Similarly, if the reaction is doubled, the Keq must be squared. In general, it is perfectly proper to multiply all the coefficients of a balanced chemical reaction by any positive or negative number, n, and the equation will remain balanced. (Multiplying all the coefficients of an equation by - 1 is formally the same as writing the equation in reverse. Write out a simple equation and prove to yourself that this is so.) But if all the co1ficients of an equation are multiplied by n, then the new equilibrium-constant expression is the old one raised to the nth power. Hence, when working with equilibrium constants, one must keep the corresponding chemical reactions clearly in mind.
|The reaction for the formation or the breakdown of ammonia can be written in a number of ways:
(Each of these expressions might be appropriate, depending on whether you were focusing on nitrogen, ammonia, hydrogen, or the dissociation of ammonia.) What are the equilibrium-constant expressions for each formulation, and how are the equilibrium constants related?
Notice that there is nothing wrong with fractional powers in the equilibrium-constant expression.
Using Equilibrium Constants
Equilibrium constants have two main purposes:
- 1. To help us tell whether a reaction will be spontaneous under specified conditions.
- 2. To enable us to calculate the concentration of reactants and products that will be present once equilibrium has been reached.
We can illustrate how equilibrium constants can be used to achieve these ends, and also the fact that an equilibrium constant is indeed constant, with real data from one of the most intensively studied of all reactions, that between hydrogen and iodine to yield hydrogen iodide:
If we mix hydrogen and iodine in a sealed flask and observe the reaction, the gradual fading of the purple color of the iodine vapor tells us that iodine is being consumed. This reaction was studied first by the German chemist Max Bodenstein in 1893. Table 4-1 contains the data from Bodenstein's experiments. The experimental data are in the first three columns. In the fourth column, we have calculated the simple ratio of product and reactant concentrations, [HI]/[H2][I2], to see if it is constant. It clearly is not, for as the hydrogen concentration is decreased and the iodine concentration is increased, this ratio varies from 2.60 to less than 1. The law of mass action (Section 4-3) dictates that the equilibrium-constant expression should contain the square of the HI concentration, since the reaction involves 2 moles of HI for every mole of H2 and I2 , The fifth column shows that the ratio [HI]2/[H2][I2] is constant within a mean deviation of approximately 3%. * Therefore, this ratio is the proper equilibrium-constant expression, and the average value of Keq for these six runs is 50.53.
The equilibrium constant can be used to determine whether a reaction under specified conditions will go spontaneously in the forward or in the reverse direction. The ratio of product concentration to reactant concentration, identical to the equilibrium constant in form but not necessarily at equilibrium conditions, is called the reaction quotient, Q:
Q = (not necessarily at equilibrium) (4-10)
If there are too many reactant molecules present for equilibrium to exist, then the concentration terms in the denominator will make the reaction quotient, Q, smaller than Keq. The reaction will go forward spontaneously to make more product. However, if an experiment is set up so that the reaction quotient is greater than Keq, then too many product molecules are present for equilibrium and the reverse reaction will proceed spontaneously. Therefore, a comparison of the actual concentration ratio or reaction quotient with the equilibrium constant allows us to predict in which direction a reaction will go spontaneously under the given set of circumstances:
Q < Keq (forward reaction spontaneous) Q > Keq (reverse reaction spontaneous) (4-11) Q = Keq (reactants and products at equilibrium)
- These are Bodenstein's original numbers. Modern data can be much more accurate, with
less deviation in Keq. The mean deviation is the average of the deviations of individual calculated Keq from the average Keq.
|If 1.0 X 10-2 mole each of hydrogen and iodine gases are placed in a I-liter flask at 448°C with 2.0 X 10-3 mole of HI, will more HI be produced?|
The reaction quotient under these conditions is
This is smaller than the equilibrium value of 50.53 in Table 4-1, which tells us that excess reactants are present. Hence, equilibrium will not be reached until more HI has been formed.
|If only 1.0 X 10-3 mole each of H2 and I2 had been used, together with 2.0 X 10-3 mole of HI, would more HI have been produced spontaneously?|
You can verify that the reaction quotient is Q = 4.0. Because this is less than Keq, the forward reaction is still spontaneous.
|If the conditions of Example 7 are changed so that the HI concentration is increased to 2.0 X 10-2 mole liter-1 , what happens to the reaction?|
The reaction quotient now is Q = 400. This is greater than Keq- There are now too many product molecules and too few reactant molecules for equilibrium to exist. Thus the reverse reaction occurs more rapidly than the forward reaction. Equilibrium is reached only by converting some of the HI to H2 and 12, so the reverse reaction is spontaneous.
|If the conditions of Example 7 are changed so that the HI concentration is 7.1 X 10-3 mole liter-1 , in which direction is the reaction spontaneous?|
Under these conditions,
Since Q equals Keq within the limits of accuracy of the data, the system as described is at equilibrium, and neither the forward nor the backward reaction is spontaneous. (Both reactions are still taking place at the molecular level, of course, but they are balanced so their net effects cancel.)
The second use for equilibrium constants is to calculate the concentrations of reactants and products that will be present at equilibrium.
|If a 1-liter flask contains 1.0 X 10-3 mole each of H2 and I2 at 448°C, what amount of HI is present when the gas mixture is at equilibrium?|
The Keq expression is treated as an ordinary algebraic equation, and solved for the HI concentration:
You can verify that in Example 7 the HI concentration was less than this equilibrium value; in Example 8 it was more; and in Example 9 it was just this value.
|One-tenth of a mole, 0.10 mole, of hydrogen iodide is placed in an otherwise empty 5.0 liter flask at 448°C. When the contents have come to equilibrium, how much hydrogen and iodine will be in the flask?|
From the stoichiometry of the reaction, the concentrations of H2 and I2 must be the same. For every mole of H2 and I2 formed, 2 moles of HI must decompose. Let y equal the number of moles of H2 or I2 per liter present at equilibrium. The initial concentration of HI before any dissociation has occurred is
Begin by writing a balanced equation for the reaction, then make a table of concentrations at the start and at equilibrium:
The HI concentration of 0.020 mole liter-1 has been decreased by 2y for every y moles of H2 and I2 that are formed. The equilibrium-constant expression is
We immediately see that we can take a shortcut by taking the square root of both sides:
For 5 liters, 5 0.0022 = 0.011 mole of H2 and of I2 will be present at equilibrium. Only (0.020 - 0.0044) 5 = 0.080 mole of HI will be left in the 5-liter tank, and the fraction of HI dissociated at equilibrium is
Shortcuts such as taking the square root in the preceding example are not always possible, yet part of the skill of solving equilibrium problems lies in recognizing shortcuts when they occur and using them. The key is often a good intuition about what quantities are large and small relative to one another, and this intuition comes from thoughtful practice and understanding of the chemistry involved. You should remember that these are chemical problems, not mathematical ones.
In many cases a quadratic equation must be solved.
|If 0.00500 mole of hydrogen gas and 0.0100 mole of iodine gas are placed in a 5.00 liter tank at 448°C, how much HI will be present at equilibrium?|
The initial concentrations of H2 and I2 are
This time, let the unknown variable y be the moles per liter of H2 or I2 that have reacted at equilibrium:
The quilibrium expression is
The square-root shortcut is now impossible because the starting concentrations of H2 and I2 are unequal. Instead we must reduce the equation to a quadratic expression:
A general quadratic equation of the form ay2 + by + c = 0 can be solved by the quadratic formula,
Thus for this problem
The first solution is physically impossible since it shows more H2 reacting than was originally present. The second solution is the correct answer: y=0.935 10-3 mole liter-1. Therefore, the equilibrium concentrations are
Units and Equilibrium Constants
As we have seen, the square brackets around a chemical symbol, as in [N2], represent concentrations, usually but not exclusively in units of moles liter-1. Concentrations expressed as moles liter-1 are often given the special symbol c, as in cN2, the concentrations measured in these units is denoted by Kc.
An equilibrium constant as we have defined it thus far may itself have units. In Example 1, Keq is unitless since the moles2 1iter-2 of the numerator and denominator cancel. In Example 2, the units of Keq are moles-1 liter since concentration occurs to the second power in the numerator and to the third power in the denominator. In Example 3 the units of Keq are the inverse: moles liter-1. The units demanded by Example 4, moles1/2 liter-1/2, may seem strange but they are perfectly respectable.
|What are the units for the equilibrium constants in the four reactions of Example 5?|
The Keq expression is treated as an ordinary algebraic equation, and solved for the HI concentration:
The question of units for Keq becomes important as soon as we realize that we can measure concentration in units other than moles liter-1. The partial pressure in atmospheres is a convenient unit when dealing with gas mixtures, and the equilibrium constant then is identified by Kp. Since the numerical values of Kp and Kc in general will be different, one must be sure what the units are when using a numerical constant.
|One step in the commercial synthesis of sulfuric acid is the reaction of sulfur dioxide and oxygen to make sulfur trioxide:
At 1000 K, the equilibrium constant for this reaction is Kp = 3.50 atm-1. If the total pressure in the reaction chamber is 1.00 atm and the partial pressure of unused 02 at equilibrium is 0.10 atm, what is the ratio of concentrations of product (S03) to reactant (S02)?
The equilibrium mixture has 0.59 mole of S03 for every 1 mole of S02.
The ideal gas law permits us to convert between atmospheres and moles liter-1, and between Kp and Kc:
PV = nRT (3-8) (4-12)
In the general chemical reaction written earlier,
Δn (read "delta n"), the increase in number of moles of gas during the reaction, is n = c + d - a - b (4-13)
The equilibrium-constant expression in terms of partial pressures is
With the ideal gas law applied to each gas component, we can convert this expression to Kc:
(RT)Δn = Kc(RT)Δn (4-15)
(Do not confuse the two uses of the symbol c in equation 4-15: one is for concentration in moles liter-1 and the other for the number of moles of substance C.)
|What is the numerical value of Kc for the reaction of Example 14?|
Three moles of reactant gases are converted into only 2 moles of product, so Δn = - 1. Hence at 1000 K,
Although the numerical answers that result when different units are used may differ, the physical reality must be the same.
|What is the concentration of oxygen in Example 14, in moles liter-1? Solve Example 14 again using Kc from Example 15.|
Three moles of reactant gases are converted into only 2 moles of product, so Δn = - 1. Hence at 1000 K,
This is the same ration of SO_3 to SO_4 as was obtained when atmospheres were used. The choice is one of convenience.
Equilibrium Involving Gases with Liquids or Solids
All the examples considered so far have involved only one physical state, a gas, and are examples of homogeneous equilibria. Equilibria that involve two or more physical states (such as a gas with a liquid or a solid) are called hetergenous equilibria. If one or more of the reactants or products are solids or liquids, how does this affect the form of the equilibrium constant?
The answer, in short, is that any pure solids or liquids that may be present at equilibrium have the same effect on the equilibrium no matter how much solid or liquid is present. The concentration of a pure solid or liquid can be considered constant, and for convenience all such constant terms are brought to the left side of the equation and incorporated into the equilibrium constant itself. As an example, limestone (calcium carbonate, CaCO3), breaks down into quicklime (calcium oxide, CaO) and carbon dioxide, CO2:
The simple equilibrium-constant expression is
- K'eq =
As long as any solid limestone and quicklime are in contact with the gas, their effect on the equilibrium is unchanging. Hence the terms [CaCO3] and [CaO] remain constant and can be merged with K'eq:
- Keq = K'eq [CO2(g)]
This form of the equilibrium-constant expression tells us that, at a given temperature, the concentration of carbon-dioxide gas above limestone and calcium oxide is a fixed quantity. (this is true only as long as both solid forms are present.) Measuring concentration in units of atmospheres, we get
- Kp = pCO2
with the experimental value 0.236 atm at 800°C.
We can see what this means experimentally by considering a cylinder to which CaCO, and CaO have been added. The cylinder has a movable piston, as shown in Figure 4-2. If the piston is fixed at one position, then CaCO3 will decompose until the pressure of CO2 above the solids is 0.236 atm (if the temperature is 800°C). If you try to decrease the pressure by raising the piston, then more CaCO3 will decompose until the pressure again rises to 0.236 atm. Conversely, if you try to increase the pressure by lowering the piston, some of the CO2 gas will react with CaO and become CaCO3 decreasing the amount of CO2 gas present until the pressure once more is 0.236 atm. The only way to increase pCO2, is to raise the temperature, which increases the value of Kp itself to 1 atm at 894°C and to 1.04 atm at 900°C.
An even simpler example is the vaporization of a liquid such as water:
This process can be treated as a chemical reaction in a formal sense even though bonds within molecules are not made or broken. Imagine that the cylinder shown in Figure 4-2 is half-filled with water rather than with CaCO3 and CaO, and that the piston is initially brought down to the surface of the water. As the piston is raised, liquid will evaporate until the pressure of water vapor is a constant value that depends only on the temperature. This is the equilibrium vapor pressure of water at that temperature. At 25°C, the vapor pressure of water is 0.0313 atm. At 100°C, the vapor pressure reaches 1 atm and, as we shall see in Chapter 18, this is just the definition of the normal boiling point of water. The pressure of water vapor above the liquid in the cylinder does not depend on whether the water in the cylinder is 1 cm or 10 cm deep; the only requirement is that some water be present and capable of evaporating to make up any decrease in vapor pressure. Only when the piston is raised to the point where no more liquid exists can the pressure of water vapor fall below 0.0313 atm, if the cylinder is at 25°C. Similarly, if the piston is lowered, some of the vapor condenses, keeping the pressure at 0.0313 atm. Only when all vapor has condensed and the piston is resting on the surface of the liquid can the pressure inside the cylinder be raised above 0.0313 atm.
The formal equilibrium treatment of the evaporation of water would be
- K'eq =
- [H2O(l)] = constant , as long as liquid is present
- Keq = K'eq[H2O(l)] = [H2O(g)]
In pressure units, the expression would be
- Kp = pH2O(g)
From a practical standpoint, what the preceding discussion means is that the concentration terms for pure solids and liquids are simply eliminated from the equilibrium-constant expression. (They are present, implicitly, in the Keq.)
|If the hydrogen iodide reaction previously discussed in this chapter is carried out at room temperature, then iodine is present as deep purple crystals rather than as vapor. What then is the form of the equilibrium-constant expression, and does the equilibrium depend on the amount of iodine crystals present?|
The reaction is
and the equilibrium-constant expression is:
As long as some I2(s) crystals are present, the quantity is immaterial as far as equilibrium is concerned.
|Tin(IV) oxide reacts with carbon monoxide to form metallic tin and CO2 by the reaction
What is the equilibrium-constant expression?
|What is the equilibrium-constant expression for the following reaction leading to liquid water?
What would the expression be if the product were water vapor?
If the product is H2O(l), the equilibrium-constant expression is
If the product is H2O(g), the equilibrium-constant expression is
The preceding example shows that as long as liquid water is present the gas-phase concentration is fixed at the vapor pressure of water at that temperature. Hence the water contribution, being constant, can be lumped into Keq.
Factors Affecting Equilibrium: Le Chatelier's Principle
Equilibrium represents a balance between two opposing reactions. How sensitive is this balance to changes in the conditions of a reaction? What can be done to change the equilibrium state? These are very practical questions if, for example, one is trying to increase the yield of a useful product in a reaction.
Under specified conditions, the equilibrium-constant expression tells us the ratio of product to reactants when the forward and backward reactions are in balance. This equilibrium constant is not affected by changes in concentration of reactants or products. However, if products can be withdrawn continuously, then the reacting system can be kept constantly off-balance, or short of equilibrium. More reactants will be used and a continuous stream of new products will be formed. This method is useful when one product of the reaction can escape as a gas, be condensed or frozen out of a gas phase as a liquid or solid, be washed out of the gas mixture by a spray of a liquid in which it is especially soluble, or be precipitated from a gas or solution.
For example, when solid lime (CaO) and coke (C) are heated in an electric furnace to make calcium carbide (CaC2),
the reaction, which at 2000-3000°C has an equilibrium constant of close to 1.00, is tipped toward calcium carbide formation by the continuous removal of carbon monoxide gas. In the industrial manufacture of titanium dioxide for pigments, TiCl4 and O2 react as gases:
The product separates from the reacting gases as a fine powder of solid Ti02 , and the reaction is thus kept moving in the forward direction. When ethyl acetate or other esters used as solvents and flavorings are synthesized from carboxylic acids and alcohols,
the reaction is kept constantly off-balance by removing the water as fast as it is formed. This can be done by using a drying agent such as Drierite (CaS04), by running the reaction in benzene and boiling off a constant-boiling benzene-water mixture, or by running the reaction in a solvent in which the water is completely immiscible and separates as droplets in a second phase. A final example: Since ammonia is far more soluble in water than either hydrogen or nitrogen is, the yield of ammonia in the reaction
can be raised to well over 90% by washing the ammonia out of the equilibrium mixture of gases with a stream of water, and recycling the nitrogen and hydrogen.
All the preceding methods will upset an equilibrium (in our examples, in favor of desired products) without altering the equilibrium constant. A chemist can often enhance yields of desired products by increasing the equilibrium constant so that the ratio of products to reactants at equilibrium is larger. The equilibrium constant is usually temperature dependent. In general, both forward and reverse reactions are speeded up by increasing the temperature, because the molecules move faster and collide more often. If the increase in the rate of the forward reaction is greater than that of the reverse, then Keq. increases with temperature and more products are formed at equilibrium. If the reverse reaction is favored, then Keq. decreases. Thus Keq for the hydrogen- iodine reaction at 448°C is 50.53, but at 425°C it is 54.4, and at 357°C it increases to 66.9. Production of HI is favored to some extent by an increase in temperature, but its dissociation to hydrogen and iodine is favored much more.
The hydrogen iodide-producing reaction is exothermic or heat emitting:
(If you check this figure against Appendix 3, remember that this reaction involves gaseous iodine, not solid.) If the external temperature of this reaction is lowered, the equilibrium is shifted in favor of the heat-emitting or forward reaction; conversely, if the temperature is increased, the reverse reaction, producing H2 and I2 is favored. The equilibrium shifts so as to counteract to some extent the effect of adding heat externally (raising the temperature) or removing it (lowering the temperature).
The temperature dependence of the equilibrium point is one example of a more general principle, known as Le Chatelier's principle: If an external stress is applied to a system at chemical equilibrium, then the equilibrium point will change in such a way as to counteract the effects of that stress. If the forward half of an equilibrium reaction is exothermic, then Keq will decrease as the temperature increases; if it is endothermic, Keq will increase. Only for a heat-absorbing reaction can the equilibrium yield of products be improved by increasing the temperature. A good way to remember this is to write the reaction explicitly with a heat term:
Then it is clear that adding heat, just like adding HI, shifts the reaction to the left. (see Figure 4-3.)
Le Chatelier's principle is true for other kinds of stress, such as pressure changes. The equilibrium constant, Keq, is not altered by a pressure change at constant temperature. However, the relative amounts of reactants and products will change in a way that can be predicted from Le Chatelier's principle.
The hydrogen- iodine reaction involves an equal number (2) of moles of reactants and product. Therefore, if we double the pressure at constant temperature, the volume of the mixture of gases will be halved. All concentrations in moles liter-1 will be doubled, but their ratio will be the same. In Example 12, doubling the concentrations of the reactants and product does not change the equilibrium constant:
- Keq =
- = 50.51
Thus the hydrogen- iodine equilibrium is not sensitive to pressure changes. Notice that in this case Keq does not have units, since the concentration units in the numerator and denominator cancel.
In contrast, the dissociation of ammonia is affected by changes in pressure because the number of moles (2) of reactant does not equal the total number of moles (4) of products:
The equilibrium constant for this reaction at 25°C is
- Keq = 2.5 10-9 mole2 liter -2
One set of equilibrium conditions is
- N2 = 3.28 10-3 mole liter-1
- H2 = 2.05 10-3 mole liter-1
- NH3 = 0.106 mole liter-1
(Can you verify that these concentrations satisfy the equilibrium condition?) If we now double the pressure at constant temperature, thereby halving the volume and doubling each concentration,
- N2 = 6.56 10-3 mole liter-1
- H2 = 4.10 10-3 mole liter-1
- NH3 = 0.212 mole liter-1
the ratio of products to reactants, the reaction quotient, is no longer equal to Keq:
- Q = 1.0 10-8 mole2 liter-2
Since Q is greater than Keq, too many product molecules are present for equilibrium. The reverse reaction will run spontaneously, thereby forming more NH3 and decreasing the amounts of H2 and N2. Consequently, part of the increased pressure is offset when the reaction shifts in the direction that lowers the total number of moles of gas present. In general, a reaction that reduces the number of moles of gas will be favored by an increase in pressure, and one that produces more gas will be disfavored. (See Figure 4-4.)
|If the hydrogen iodide reaction were run at a temperature at which the iodine was a solid, would an increase in pressure shift the equilibrium reaction toward more HI, or less? What would be the effect of pressure on Keq?|
Since the reaction of 2 moles of gaseous HI now yields 1 mole of gaseous H2 and 1 mole of solid I2 the stress of increased pressure is relieved by dissociating HI to H2 and I2. However, Keq will be unchanged by the pressure increase.
What effect does a catalyst have on a reaction at equilibrium? None. A catalyst cannot change the value of Keq, but it can increase the speed with which equilibrium is reached. This is the main function of a catalyst. It can take the reaction only to the same equilibrium state that would be reached eventually without the catalyst.
Catalysts are useful, nevertheless. Many desirable reactions, although spontaneous, occur at extremely slow rates under ordinary conditions. In automobile engines, the main smog-producing reaction involving oxides of nitrogen is
(Once NO is present, it reacts readily with more oxygen to make brown N02.) At the high temperature of an automobile engine, Keq for this reaction is so large that appreciable amounts of NO are formed. However, at 25°C, Keq= 10-30. (Using only the previous two bits of information and Le Chatelier's principle, predict whether the reaction as written is endothermic or exothermic. Check your answer using data from Appendix 3.) The amount of NO present in the atmosphere at equilibrium at 25°C should be negligible. NO should decompose spontaneously to N2 and O2 as the exhaust gases cool. But any Southern Californian can verify that this is not what happens. Both NO and N02 are indeed present, because the gases of the atmosphere are not at equilibrium.
The rate of decomposition of NO is extremely slow, although the reaction is spontaneous. One approach to the smog problem has been to search for a catalyst for the reaction
that could be housed in an exhaust system and could break down NO in the exhaust gases as they cool. Finding a catalyst is possible; a practical problem arises from the gradual poisoning of the catalyst by gasoline additives, such as lead compounds. This is the reason why new cars with catalytic converters only use lead-free gasoline.
A proof of the assertion that a catalyst cannot change the equilibrium constant is illustrated in Figure 4-5. If a catalyst could shift the equilibrium point of a reacting gas mixture and produce a volume change, then this expansion and contraction could be harnessed by mechanical means and made to do work. We would have a true perpetual-motion machine that would deliver power without an energy source. From common sense and experience we know this to be impossible. This "common sense" is stated scientifically as the first law of thermodynamics, which will be discussed in Chapter 15. A mathematician would call this a proof by contradiction: If we assume that a catalyst can alter Keq, then we must assume the existence of a perpetual-motion machine. However, a perpetual-motion machine cannot exist; therefore our initial assumption was wrong, and we must conclude that a catalyst cannot alter Keq.
In summary, Keq is a function of temperature, but it is not a function of reactant or product concentrations, total pressure, or the presence or absence of catalysts. The relative amounts of substances at equilibrium can be changed by applying an external stress to the equilibrium mixture of reactants and products, and the change is one that will relieve this stress. This last statement, Le Chatelier's principle, enables us to predict what will happen to a reaction when external factors are changed, without having to make exact calculations.
A spontaneous reaction is one that will take place, given enough time, without outside assistance. Some spontaneous reactions are rapid, but time is not an element in the definition of spontaneity. A reaction can be almost infinitely slow and still be spontaneous.
The net reaction that we observe is the result of competition between forward and reverse steps. If the forward process is faster, then products accumulate, and we say that the reaction is spontaneous in the forward direction. If the reverse process is faster, then reactants accumulate, and we say that the reverse reaction is the spontaneous one. If both forward and reverse processes take place at the same rate, then no net change is observed in any of the reaction components. This is the condition of chemical equilibrium.
The ratio of products to reactants, each concentration term being raised to a power corresponding to the coefficient of that substance in the balanced chemical equation, is called the equilibrium constant, Keq. (See equation 4-8.) It can be used to predict whether a given reaction under specified conditions will be spontaneous, and to calculate the concentrations of reactants and products at equilibrium. The reaction quotient, Q, has a form that is identical with that of the equilibrium constant, Keq, but Q applies under nonequilibrium conditions as well. For a given set of conditions, if Q is smaller than Keq, the forward reaction is spontaneous; if Q is greater than Keq, the reverse reaction is spontaneous; and if Q = Keq, the system is at equilibrium.
The equilibrium constant can be used with any convenient set of concentration units: moles liter-1 , pressure in atmospheres, or others. Its numerical value will depend on the units of concentration, so one must be careful to match the proper values of Keq and units when solving problems. If gas concentrations are expressed in moles liter-1, the equilibrium constant is designated by Kc; if in atmospheres, by Kp. Just as partial pressure of the jth component of a gas mixture is related to moles per liter by pj = cjRT, so Kp and Kc are related by Kp = Kc(RT)Δn, in which Δn is the net change in number of moles of gas during the reaction.
When some of the reactants or products are pure solids or liquids, they act as infinite reservoirs of material as long as some solid or liquid is left. Their effect on equilibrium depends only on their presence, not on how much of the solid or liquid is present. Their effective concentrations are constant, and can be incorporated into Keq. In practice, this simply means omitting concentration terms for pure solids and liquids from the equilibrium-constant expression. Evaporation of a liquid can be treated formally as a chemical reaction with the liquid as reactant and vapor as product. These conventions for writing concentration terms for a liquid permit us to write the equilibrium constant for evaporation as Kp = pj where pj is the equilibrium vapor pressure of substance j.
Le Chatelier's principle states that if stress is applied to a system at equilibrium the amounts of reactants and products will shift in such a manner as to minimize the stress. This means that for a heat-absorbing, or endothermic, reaction, Keq increases as the temperature is increased, since carrying out more of the reaction is a way of absorbing some of the added heat. Similarly, cooling increases Keq for a heat-emitting or exothermic reaction. Although the equilibrium constant Keq is independent of pressure, and changing the total pressure on a reacting system does not alter Keq directly, an increase in pressure does cause the reaction to shift in the direction that decreases the total number of moles of gas present.
A catalyst has no effect at all on Keq or the conditions of equilibrium. All that a catalyst can do is to make the system reach equilibrium faster than it would have done otherwise. Catalysts can make inherently spontaneous but slow reactions into rapid reactions, but they cannot make nonspontaneous reactions take place of their own accord. | <urn:uuid:0380ba0a-eb55-47d7-9ade-aefc9151e100> | CC-MAIN-2013-20 | http://en.wikibooks.org/wiki/Chemical_Principles/Will_It_React%3F_An_Introduction_to_Chemical_Equilibrium | 2013-05-22T07:34:40 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368701459211/warc/CC-MAIN-20130516105059-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.934596 | 9,948 | 4.25 | 4 |
The set of Hamming
codes are called 'Forward Error Correction
' and give the ability for the receiving station
to correct a transmission error
. While this takes more bits to send the information
, it means fewer retransmits and thus can actually speed up a noisy connection.
The number of parity bits in the hamming code is given by the Hamming rule. This is a function of the number of bits of information transmitted in a block and is represented by the following inequality:
d + p + 1>= 2p
'd' is the number of data bits and 'p' is the number of parity bits. Hamming codes are identified by the ordered set (c,d) where 'c' = 'd' + 'p'. The Hamming code (7,4) is the classic example used which describes a word of 4 data bits long and 3 error check bits. This satisfies the above inequality:
4 + 3 + 1 >= 23
The hamming code word is created by multiplying the data bits by a generator matrix using modulo-2 arithmetic. The result of this is called a code word vector which consists of the original data bits and the parity bits.
The generator matrix used in constructing the hamming code consists of I (the identity matrix) and a parity generation matrix A. For a data size of 4 the following matrix is created:
1 0 0 0 | 1 1 1
0 1 0 0 | 0 1 1
G = 0 0 1 0 | 1 0 1
0 0 0 1 | 1 1 0
Multiplying a 4 bit vector (d1, d2, d3, d4) by G results in
a 7 bit vector of the form (d1, d2, d3, d4, p1, p2, p3). The A portion is what generates the parity bits. If the selection of the columns of A are unique
, it is true that (p1, p2, p3) is the parity calculations of three distinct subsets of the original data.
To validate the code word, it is necessary to multiply the data word by 'H' which is the [inverse A | I] check to form the parity check vector.
H r |1| s
| 1 0 1 1 | 1 0 0 | |0| |0|
| 1 1 0 1 | 0 1 0 | * |1| = |0|
| 1 1 1 0 | 0 0 1 | |0| |0|
If all the elements of s are 0, then the entire set has been received correctly. If there are any '1's in s, then there is an error which can be determined by looking at the parity pits that have failed.
If r = s will be This matches the third colum of 'H' which corresponds to the bit that has the error.
The (7,4) Hamming code, while good for demonstrations is not the best choice for practical communications - it has allot of overhead and has a non-standard length. The number of parity bits goes up with the log of the number of data bits. Hence, there is less overhead for longer words than shorter words.
The hamming code can detect and fix single bit errors, and detect double bit errors. For the (7,4) hamming code, the following table (error correcting bits are in bold):
decimal binary Hamming(7,4)
0 0000 0000000
1 0001 0001110
2 0010 0010101
3 0011 0011011
4 0100 0100011
5 0101 0100011
6 0110 0110110
7 0111 0111000
8 1000 1000111
9 1001 1001001
10 1010 1010010
11 1011 1011100
12 1100 1100100
13 1101 1101010
14 1110 1110001
15 1111 1111111
The hamming distance from one valid error correcting set to another for the same data is three. This means that it would take three errors to go from one valid message to another. Example:
0100010 (not valid - correctable)
0100000 (not valid - not correctable)
It is left an excercise to the reader to demonstrate this is the case for all 127 possible cases that the minimum hamming distance between any two valid messages is three. | <urn:uuid:720bdb8d-81e2-40ec-b246-8ae6e494c893> | CC-MAIN-2013-20 | http://everything2.com/title/Hamming+code | 2013-05-22T07:15:08 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368701459211/warc/CC-MAIN-20130516105059-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.85488 | 918 | 4.40625 | 4 |
The Heating System of the Winter Moth
When winter comes, many insect species inhabiting cold regions of the world die from cold or lack of food. That is because insects are delicate creatures, but there are some exceptions to this rule. For example, owl moths look like butterflies and at first sight seem very delicate. In reality, however, they are strong enough to survive tough winter conditions. Therefore these moths are also called "winter moths".
Like butterflies, a winter moth has two wings and a trunk to which these wings are joined. In order for this moth to fly, the temperature of its thorax to which its wings are joined should be 30oC (86oF). But the temperature where they live is usually 0oC (32oF) and even drops below zero degrees from time to time. How can winter moths survive such cold? What prevents them from freezing when they are motionless, and what enables them to fly in cold weather?
This moth species is created together with a special heating system that enables it to live under winter conditions. This system consists of several complementary features.
Before flight winter moths continuously tense the main muscles that are connected to the wings and make their wings vibrate. The rapid vibrating of the wings leads to an increase in the temperature of the insect's thorax. As a result of this increase, the temperature of the thorax may rise from 0oC (32oF) to 30oC (86oF) or even more. However, this is only one of the features that the moth needs to survive. In order to fly it is not sufficient for the winter moth merely to increase its body temperature. That is because the difference between the temperatures of the insect's body and of the atmosphere will result in loss of heat. In the same way as a glass of hot tea cools after a while, the moth's body will also cool. Therefore it will not help even if the moth keeps its wings vibrating. In order for the winter moth to fly and thus survive, another method is required to maintain the heat it has produced. This need is also met by a special structure that Allah created in the moth's body. Moths are covered with dense scales that reduce heat loss. Scientists have determined after research that a moth without scales cools twice as fast as those with scales.
These are some of the mechanisms in a winter moth that protect it from cold. The features mentioned above must have existed since this moth species came into being. Otherwise, the moth would have died of cold and this species would be extinct. One does not need to reflect at great length to understand that it is not a coincidence that only those species inhabiting cold regions possess these features that make them different from all other moths. Taking all kinds of measures to enable these creatures to survive in cold, Allah introduces Himself to us. In the Qur'an, Allah reveals that He knows where all creatures live:
There is no creature on the earth which is not dependent upon Allah for its provision. He knows where it lives and where it dies. They are all in a Clear Book. (Surah Hud: 6)
Such features in living creatures enable us to grasp Allah's power and artistry, and increase our faith in and love for our Lord. Communicating the amazing information you read to others, you may also be the means to increase other people's faith in Allah. | <urn:uuid:44af0f56-e442-414d-aa95-49fc8928cca9> | CC-MAIN-2013-20 | http://harunyahya.com/en/books/1021/Wonderful-Creatures/chapter/975/The-Heating-System-of-the-Winter-Moth | 2013-05-22T07:34:30 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368701459211/warc/CC-MAIN-20130516105059-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.971889 | 701 | 4.375 | 4 |
Note: This lesson was originally published on an older version of The Learning Network; the link to the related Times article will take you to a page on the old site.
Teaching ideas based on New York Times content.
Overview of Lesson Plan: In this lesson, students use prototypical fantasy themes to create an original role-playing game and cast of characters based on their own community.
Rachel McClain, The New York Times Learning Network
Suggested Time Allowance: 45 minutes
1. Explore the importance of characters in Dungeons and Dragons and other role-playing games.
2. Learn about the new movie “Dungeons and Dragons” by reading and discussing the article “‘Dungeons and Dragons’: After D and D, You May Need R and R.”
3. As a class, create the outline for a role-playing game based on their own community.
4. In groups, create character profiles for the game.
5. Write a dialogue between two of the characters from the game.
Resources / Materials:
-copies of the article “‘Dungeons and Dragons’: After D and D, You May Need R and R” (one per student)
Activities / Procedures:
1. WARM-UP/DO NOW: In their journals, students respond to the following prompt (written on the board prior to class): “If you could choose to be a character from any book or movie, who would you choose and why? How does your chosen character impact the plot and the other characters in the book or movie?” After 5-10 minutes, have some students read their journals aloud. As a class, discuss Dungeons and Dragons and how it offers people the opportunity to role-play fantastical and magical characters. Discuss the appeal of this and other role-playing games.
2. As a class, read the article “‘Dungeons and Dragons’: After D and D, You May Need R and R,” focusing on the following questions:
a. What is Dungeons and Dragons?
b. According to the article, what are some archetypes upon which Dungeons and Dragons is based?
c. How does A.O. Scott describe the special effects in the movie?
d. According to the article, why was the movie shot in Prague?
e. Which line of dialogue does A.O. Scott cite to show the low quality of the script? Why do you think he chose this line?
f. What is the main conflict in the plot of the film?
g. What phrase is used to advertise the film? How does A.O. Scott use this phrase to criticize the film?
3. Create a class role-playing game set in a mythical city that parallels the real one in which the students live. Have the class choose a name for their mythical city and create a map, including at least five key locations where action might take place(examples are a pizza shop, a school, a forest, etc.). The class should also brainstorm possible characters that might be included in the game, keeping in mind the types of characters usually found in such games (examples are an Evil Sorcerer Mayor, or the Wizard of the Pizza Shop). Avoid a sensitive situation by having students create prototypical characters and not ones based directly on actual people in the community. Divide the class into groups of 3 or 4. Each group creates a character profile of one of the characters discussed in class. The profile should consist of a brief description of the character, the character’s strengths and weaknesses, and an illustration of the character complete with the character’s mode of dress and special weapons or other articles that might assist him or her throughout the game.
4. WRAP-UP/HOMEWORK: Write a dialogue between two of the characters created by your class. Use a prototypical fantasy game conflict (such as the battle over the rod in the “Dungeons and Dragons” movie,) and set it in one of the key locations chosen in class. Keep in mind A.O. Scott’s criticism of the dialogue in the movie Dungeons and Dragons, and try to make your dialogue more realistic and compelling than the examples from the article.
Further Questions for Discussion:
– What do you think A.O. Scott is trying to achieve by using parentheses throughout the article?
– What is the overall tone of A.O. Scott’s review? How does he reveal his opinion of the movie?
– Do you think that role-playing games are a healthy outlet for the imagination? Do you think such games can have a negative effect on a person? How?
– Do you play or know people who play interactive role-playing games over the Internet? Do you think this is more or less exciting than playing these games on a board with a live group of people all in the same room?
– Are there certain modes of dress or behaviors that accompany being a player of games such as Dungeons and Dragons? Do the players of these games develop distinct social groups? If so, why do you think this is the case?
Evaluation / Assessment:
Students will be evaluated on completion of the journal entry, participation in class discussions, creation of a character profile, and completion of a dialogue between two of the characters created in class.
virtual, fantasy, sci-fi, jargon, grok, tedium, adherents, sorcery, murky, clotted, understatement, provocation, vexation, mages, antagonists, pontificate, raiment, conviction, plucky, mayhem
1. With a partner, perform the dialogue you wrote for homework for the class. Prepare the appropriate costumes and props based upon the profiles created for each character.
2. Movies based on books often do not live up to the expectations and imaginations of readers. This is especially true for movies based on fantasy books where elements like magical spells and mythical creatures are commonplace. Based on A.O. Scott’s criticism of the “Dungeons and Dragons” film, predict whether the Harry Potter film, expected to be released within the year, will impress or disappoint movie-goers who have already read the book.
3. Read a fantasy novel by J.R.R. Tolkien. Write a movie pitch for a film version of the novel. Describe who you would cast the main roles and why, and how you would successfully recreate the fantasy world depicted by Tolkien on screen.
4. It is often difficult to differentiate between the literary genres of fantasy, science fiction, legend, and myth. Create a dictionary of terms defining each genre and explaining how each one differs from the others.
-Research fantastical creatures from different cultures. Create a poster with an illustration and short description of each creature, including the culture from which it originates. (Some examples of fantastic and/or mythical creatures from various cultures are the Loch Ness Monster, Chupacabra, Big Foot, and Aswang.)
-Compare and contrast the themes and characters found in Arthurian and other Medieval legends (such as Sir Gawain and the Green Knight or Beowulf) to those in Dungeons and Dragons. Create a chart displaying your findings.
Journalism- See the movie “Dungeons and Dragons” and write your own movie review. Refer to A.O. Scott’s review by supporting or refuting his claims regarding the film.
Mathematics- The Dungeons and Dragons game uses numerical values to assess a character’s strengths and weaknesses. These values are initially chosen by rolling special dice with differing numbers of sides. Learn about how this process works and create a chart showing the various attributes chosen by this method, and the average number expected for each attribute when dice are rolled.
Social Studies- As A.O. Scott mentions in the article, an entire sub-culture has developed around fantasy and role-playing games. Research this culture and write a short (2-3 page) essay describing its development and characteristics since the introduction of Dungeons and Dragons in the 1970’s.
Other Information on the Web:
DnDMovie.com (more. http://www.dndmovie.com/) features updated news, photos, cast information, and more.
Dungeons and Dragons (http://www.seednd.com/) is the official movie site from New Line.
Academic Content Standards:
Language Arts Standard 1- Demonstrates competence in the general skills and strategies of the writing process. Benchmarks: Uses a variety of prewriting strategies; Uses a variety of strategies to draft and revise written work; Evaluates own and others’ writing; Uses style and structure appropriate for specific audiences and purposes; Writes narrative accounts; Writes in response to literature
(CTSS – ‘english’, ’6-8’, ’1’)
Language Arts Standard 6- Demonstrates competence in the general skills and strategies for reading a variety of literary texts. Benchmarks: Knows the defining characteristics of a variety of literary forms and genres; Identifies specific questions of personal importance and seeks to answer them through literature; Understands the effects of the author’s style on a literary text; Understands that people respond differently to literature
(CTSS – ‘english’, ’6-8’, ’6’)
Language Arts Standard 1- Demonstrates competence in the general skills and strategies of the writing process. Benchmarks: Uses a variety of prewriting strategies; Uses a variety of strategies to draft and revise written work; Uses a variety of strategiesto edit and publish written work; Evaluates own and others’ writing; Writes compositions that fulfill different purposes; Writes fictional, biographical, autobiographical, and observational narrative compositions; Writes descriptive compositions; Writes in response to literature
(CTSS – ‘english’, ’9-12’, ’1’)
Language Arts Standard 6- Demonstrates competencein the general skills and strategies for reading a variety of literary texts. Benchmarks: Knows the defining characteristics of a variety of literaryforms and genres; Understands historical and cultural influences on literary works; Relates personal response to the text with that seemingly intended by the author
(CTSS – ‘english’, ’9-12’, ’6’) | <urn:uuid:32f50486-ddfc-4bb0-a712-3a1c0b23b5c2> | CC-MAIN-2013-20 | http://learning.blogs.nytimes.com/2000/12/08/imagine-that/ | 2013-05-22T07:13:22 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368701459211/warc/CC-MAIN-20130516105059-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.915257 | 2,162 | 4.125 | 4 |
Socrates, an Athenian Greek of the second half of the fifth century bc, wrote no philosophical works but was uniquely influential in the later history of philosophy. His philosophical interests were restricted to ethics and the conduct of life, topics which thereafter became central to philosophy. He discussed these in public places in Athens, sometimes with other prominent intellectuals or political leaders, sometimes with young men, who gathered round him in large numbers, and other admirers. Among these young men was Plato. Socrates' philosophical ideas and - equally important for his philosophical influence - his personality and methods as a 'teacher' were handed on to posterity in the 'dialogues' that several of his friends wrote after his death, depicting such discussions. Only those of Xenophon (Memorabilia,Apology, Symposium) and the early dialogues of Plato survive (for example Euthyphro, Apology, Crito). Later Platonic dialogues such as Phaedo, Symposium and Republic do not present the historical Socrates' ideas; the 'Socrates' appearing in them is a spokesman for Plato's own ideas.
Socrates' discussions took the form of face-to-face interrogations of another person. Most often they concerned the nature of some moral virtue, such as courage or justice. Socrates asked what the respondent thought these qualities of mind and character amounted to, what their value was, how they were acquired. He would then test their ideas for logical consistency with other highly plausible general views about morality and goodness that the respondent also agreed to accept, once Socrates presented them. He succeeded in showing, to his satisfaction and that of the respondent and any bystanders, that the respondent's ideas were not consistent. By this practice of 'elenchus' or refutation he was able to prove that politicians and others who claimed to have 'wisdom' about human affairs in fact lacked it, and to draw attention to at least apparent errors in their thinking. He wanted to encourage them and others to think harder and to improve their ideas about the virtues and about how to conduct a good human life. He never argued directly for ideas of his own, but always questioned those of others. None the less, one can infer, from the questions he asks and his attitudes to the answers he receives, something about his own views.
Socrates was convinced that our souls - where virtues and vices are found - are vastly more important for our lives than our bodies or external circumstances. The quality of our souls determines the character of our lives, for better or for worse, much more than whether we are healthy or sick, or rich or poor. If we are to live well and happily, as he assumed we all want to do more than we want anything else, we must place the highest priority on the care of our souls. That means we must above all want to acquire the virtues, since they perfect our souls and enable them to direct our lives for the better. If only we could know what each of the virtues is we could then make an effort to obtain them. As to the nature of the virtues, Socrates seems to have held quite strict and, from the popular point of view, paradoxical views. Each virtue consists entirely in knowledge, of how it is best to act in some area of life, and why: additional 'emotional' aspects, such as the disciplining of our feelings and desires, he dismissed as of no importance. Weakness of will is not psychologically possible: if you act wrongly or badly, that is due to your ignorance of how you ought to act and why. He thought each of the apparently separate virtues amounts to the same single body of knowledge: the comprehensive knowledge of what is and is not good for a human being. Thus his quest was to acquire this single wisdom: all the particular virtues would follow automatically.
At the age of 70 Socrates was charged before an Athenian popular court with 'impiety' - with not believing in the Olympian gods and corrupting young men through his constant questioning of everything. He was found guilty and condemned to death. Plato's Apology, where Socrates gives a passionate defence of his life and philosophy, is one of the classics of Western literature. For different groups of later Greek philosophers he was the model both of a sceptical inquirer who never claims to know the truth, and of a 'sage' who knows the whole truth about human life and the human good. Among modern philosophers, the interpretations of his innermost meaning given by Montaigne, Hegel, Kierkegaard, and Nietzsche are especially notable.
Socrates, an Athenian citizen proud of his devotion to Athens, lived his adult life there engaging in open philosophical discussion and debate on fundamental questions of ethics, politics, religion and education. Going against the grain of the traditional education, he insisted that personal investigation and reasoned argument, rather than ancestral custom, or appeal to the authority of Homer, Hesiod and other respected poets, was the only proper basis for answering these questions. His emphasis on argument and logic and his opposition to unquestioning acceptance of tradition allied him with such Sophists of a generation earlier as Protagoras, Gorgias and Prodicus, none of whom was an Athenian, but all of whom spent time lecturing and teaching at Athens (see Sophists). Unlike these Sophists Socrates did not formally offer himself or accept pay as a teacher. But many upper-class young Athenian men gathered round him to hear and engage in his discussions, and he had an inspirational and educational effect upon them, heightening their powers of critical thought and encouraging them to take seriously their individual responsibility to think through and decide how to conduct their lives. Many of his contemporaries perceived this education as morally and socially destructive - it certainly involved subverting accepted beliefs - and he was tried in 399 bc before an Athenian popular court and condemned to death on a charge of 'impiety': that he did not believe in the Olympian gods, but in new ones instead, and corrupted the young. Scholars sometimes mention specifically political motives of revenge, based on guilt by association: a number of prominent Athenians who were with Socrates as young men or were close friends did turn against the Athenian democracy and collaborated with the Spartans in their victory over Athens in the Peloponnesian war. But an amnesty passed by the restored democracy in 403 bc prohibited prosecution for political offences before that date. The rhetorician Polycrates included Socrates' responsibility for these political crimes in his Accusation of Socrates (see Xenophon, Memorabilia I 2.12), a rhetorical exercise written at least five years after Socrates' death. But there is no evidence that, in contravention of the amnesty, Socrates' actual accusers covertly attacked him, or his jurors condemned him, on that ground. The defences Plato and Xenophon constructed for Socrates, each in his respective Apology, imply that it was his own questioning mind and what was perceived as the bad moral influence he had on his young men that led to his trial and condemnation.
Socrates left no philosophical works, and apparently wrote none. His philosophy and personality were made known to later generations through the dialogues that several of his associates wrote with him as principal speaker (see Socratic dialogues). Only fragments survive of those by Aeschines of Sphettus and Antisthenes, both Athenians, and Phaedo of Elis (after whom Plato's dialogue Phaedo is named). Our own knowledge of Socrates depends primarily on the dialogues of Plato and the Socratic works of the military leader and historian Xenophon. Plato was a young associate of Socrates' during perhaps the last ten years of his life, and Xenophon knew him during that same period, though he was absent from Athens at the time of Socrates' death and for several years before and many years after.
We also have secondary evidence from the comic playwright Aristophanes and from Aristotle. Aristotle, although born fifteen years after Socrates' death, had access through Plato and others to first-hand information about the man and his philosophy. Aristophanes knew Socrates personally; his Clouds (first produced c.423 bc) pillories the 'new' education offered by Sophists and philosophers by showing Socrates at work in a 'thinkery', propounding outlandish physical theories and teaching young men how to argue cleverly in defence of their improper behaviour. It is significant that in 423, when Socrates was about 45 years old, he could plausibly be taken as a leading representative in Athens of the 'new' education. But one cannot expect a comic play making fun of a whole intellectual movement to contain an authentic account of Socrates' specific philosophical commitments.
However, the literary genre to which Plato's and Xenophon's Socratic works belong (along with the other, lost dialogues) also permits the author much latitude; in his Poetics Aristotle counts such works as fictions of a certain kind, alongside epic poems and tragedies. They are by no means records of actual discussions (despite the fact that Xenophon explicitly so represents his). Each author was free to develop his own ideas behind the mask of Socrates, at least within the limits of what his personal experience had led him to believe was Socrates' basic philosophical and moral outlook. Especially in view of the many inconsistencies between Plato's and Xenophon's portraits (see §7 below), it is a difficult question for historical-philosophical interpretation whether the philosophical and moral views the character Socrates puts forward in any of these dialogues can legitimately be attributed to the historical philosopher. The problem of interpretation is made more difficult by the fact that Socrates appears in many of Plato's dialogues - ones belonging to his middle and later periods (see Plato §§10-16) - discussing and expounding views that we have good reason to believe resulted from Plato's own philosophical investigations into questions of metaphysics and epistemology, questions that were not entered into at all by the historical Socrates. To resolve this problem - what scholars call the 'Socratic problem' - most agree in preferring Plato to Xenophon as a witness. Xenophon is not thought to have been philosopher enough to have understood Socrates well or to have captured the depth of his views and his personality. As for Plato, most scholars accept only the philosophical interests and procedures, and the moral and philosophical views, of the Socrates of the early dialogues, and, more guardedly, the Socrates of 'transitional' ones such as Meno and Gorgias, as legitimate representations of the historical personage. These dialogues are the ones that predate the emergence of the metaphysical and epistemological inquiries just referred to. However, even Plato's early dialogues are philosophical works written to further Plato's own philosophical interests. That could produce distortions, also; and Xenophon's relative philosophical innocence could make his portrait in some respects more reliable. Moreover, it is possible, even probable, that in his efforts to help his young men improve themselves Socrates spoke differently to the philosophically more promising ones among them - including Plato - from the way he spoke to others, for example Xenophon. Both portraits could be true, but partial and needing to be combined (see §7). The account of Socrates' philosophy given below follows Plato, with caution, while giving independent weight also to Xenophon and to Aristotle.
Xenophon's Apology of Socrates, Symposium and Memorabilia (or Memoirs) may well reflect knowledge of Plato's own Apology and some of his early and middle period dialogues, as well as lost dialogues of Antisthenes and others. Xenophon composed the Memorabilia over many years, beginning only some ten years after Socrates' death, avowedly in order to defend Socrates' reputation as a good man, a true Athenian gentleman, and a good influence upon his young men. The same intention motivated hisApology and Symposium. Anything these works contain about Socrates' philosophical opinions and procedures is ancillary to that apologetic purpose. Plato's Apology, of course, is similarly apologetic, but it and his other early dialogues are carefully constructed discussions, strongly focused upon questions of philosophical substance. Plato evidently thought Socrates' philosophical ideas and methods were central to his life and to his mission. Xenophon's and Plato's testimony are agreed that Socrates' discussions consistently concerned the aretai, the recognized 'virtues' or excellences of character (see Aret), such as justice, piety, self-control or moderation (sophrosyn), courage and wisdom; what these individual characteristics consist in and require of a person, what their value is, and how they are acquired, whether by teaching or in some other way. In his Apology and elsewhere Plato has Socrates insist that these discussions were always inquiries, efforts made to engage his fellow-discussants in coming jointly to an adequate understanding of the matters inquired into. He does not himself know, and therefore cannot teach anyone else - whether by means of these discussions or in some other way - either how to be virtuous or what virtue in general or any particular virtue is. Furthermore, given his general characterization of virtue (see §§4-5), Plato's Socrates makes a point of suggesting the impossibility in principle of teaching virtue at all, by contrast with the Sophists who declared they could teach it. Virtue was not a matter of information about living or rote techniques of some sort to be handed on from teacher to pupil, but required an open-ended personal understanding that individuals could only come to for themselves. Xenophon, too, reports that Socrates denied he was a teacher of aret, but he pays no attention to such issues of philosophical principle. He does not hesitate to show Socrates speaking of himself as a teacher (see Apology 26, Memorabilia I 6.13-14), and describes him as accepting young men from their fathers as his pupils (but not for a fee), and teaching them the virtues by displaying his own virtues to them for emulation, as well as through conversation and precepts. Perhaps Socrates did not insist on holding to strict philosophical principles in dealing with people on whom their point would have been lost.
In his Apology Plato's Socrates traces his practice of spending his days discussing and inquiring about virtue to an oracle delivered at the shrine of Apollo at Delphi. Xenophon also mentions this oracle in his Apology. A friend of Socrates', Chaerephon, had asked the god whether anyone was wiser than Socrates; the priestess answered that no one was. Because he was sure he was not wise at all - only the gods, he suspected, could actually know how a human life ought to be led - Socrates cross-examined others at Athens with reputations for that kind of wisdom. He wanted to show that there were people wiser than he and thus discover the true meaning of the oracle - Apollo was known to speak in riddles requiring interpretation to reach their deeper meaning. In the event, it turned out that the people he examined were not wise, since they could not even give a self-consistent set of answers to his questions: obviously, true knowledge requires at least that one think and speak consistently on the subjects one professes to know. So he concluded that the priestess's reply had meant that of all those with reputations for wisdom only he came close to deserving it; he wisely did not profess to know these things that only gods can know, and that was wisdom enough for a human being. Because only he knew that he did not know, only he was ready earnestly to inquire into virtue and the other ingredients of the human good, in an effort to learn. He understood therefore that Apollo's true intention in the oracle had been to encourage him to continue his inquiries, to help others to realize that it is beyond human powers actually to know how to live - that is the prerogative of the gods - and to do his best to understand as far as a human being can how one ought to live. The life of philosophy, as led by him, was therefore something he was effectively ordered by Apollo to undertake.
We must remember that Socrates was on trial on a charge of 'impiety'. In tracing his philosophical vocation back to Apollo's oracle, and linking it to a humble recognition of human weakness and divine perfection, he was constructing a powerful rebuttal of the charges brought against him. But it cannot be literally true - if that is what he intended to say - that Socrates began his inquiries about virtue only after hearing of the oracle. Chaerephon's question to Apollo shows he had established a reputation in Athens for wisdom before that. That reputation cannot have rested on philosophical inquiries of another sort. In Plato's Phaedo Socrates says he had been interested as a young man in philosophical speculations about the structure and causes of the natural world, but he plainly did not take those interests very far; and in any event, his reputation was not for that kind of wisdom, but wisdom about how to lead a human life. In fact we do not hear of the duty to Apollo in Xenophon, or in other dialogues of Plato, where we might expect to find it if from the beginning Socrates thought Apollo had commanded his life of philosophizing. However, we need not think Socrates was false to the essential spirit of philosophy as he practised it if in looking back on his life under threat of condemnation for impiety he chose, inaccurately, to see it as initially imposed on him by Apollo's oracle.
Despite its impressiveness, Socrates' speech failed to convince his jury of 501 male fellow citizens, and he died in the state prison by drinking hemlock as required by law. His speech evidently offended the majority of the jurors by its disdain for the charges and the proceedings; Xenophon explains his lofty behaviour, which he thinks would otherwise have been lunatic - and damaging to his reputation - by reporting that he had told friends in advance that as a 70-year-old still in possession of his health and faculties it was time for him to die anyhow, before senility set in. Furthermore, his 'divine sign' - the 'voice' he sometimes heard warning him for his own good against a contemplated course of action - had prevented him from spending time crafting a defence speech. (This voice seems to have been the basis for the charge of introducing 'new' gods.) So he would do nothing to soften his manner in order to win his freedom. Even if this story is true, Plato could be right that Socrates put on a spirited, deeply serious defence of his life and beliefs - one that he thought should have convinced the jurors of his innocence, if only they had judged him intelligently and fairly.
In cross-examining those with reputations for wisdom about human affairs and showing their lack of it, Socrates employed a special method of dialectical argument that he himself had perfected, the method of 'elenchus' - Greek for 'putting to the test' or 'refutation'. He gives an example at his trial when he cross-examines Meletus, one of his accusers (Plato, Apology 24d-27e). The respondent states a thesis, as something he knows to be true because he is wise about the matter in question. Socrates then asks questions, eliciting clarifications, qualifications and extensions of the thesis, and seeking further opinions of the respondent on related matters. He then argues, and the respondent sees no way not to grant, that the original thesis is logically inconsistent with something affirmed in these further responses. For Socrates, it follows at once that the respondent did not know what he was talking about in stating his original thesis: true knowledge would prevent one from such self-contradiction. So the respondent suffers a personal set-back; he is refuted - revealed as incompetent. Meletus, for example, does not have consistent ideas about the gods or what would show someone not to believe in them, and he does not have consistent ideas about who corrupts the young, and how; so he does not know what he is talking about, and no one should take his word for it that Socrates disbelieves in the gods or has corrupted his young men. In many of his early dialogues Plato shows Socrates using this method to examine the opinions of persons who claim to be wise in some matter: the religious expert Euthyphro on piety (Euthyphro), the generals Laches and Nicias on courage (Laches), the Sophist Protagoras on the distinctions among the virtues and whether virtue can be taught (Protagoras), the rhapsodist Ion on what is involved in knowing poetry (Ion), the budding politician Alcibiades on justice and other political values (Alcibiades), the Sophist Hippias on which was the better man, Odysseus or Achilles (Lesser Hippias), and on the nature of moral and aesthetic beauty (Greater Hippias). They are all refuted - shown to have mutually inconsistent ideas on the subject discussed (see Plato §§4, 6, 8-9).
But Socrates is not content merely to demonstrate his interlocutor's lack of wisdom or knowledge. That might humiliate him into inquiring further or seeking by some other means the knowledge he has been shown to lack, instead of remaining puffed up with self-conceit. That would be a good thing. But Socrates often also indicates clearly that his cross-examination justifies him and the interlocutor in rejecting as false the interlocutor's original thesis. Logically, that is obviously wrong: if the interlocutor contradicts himself, at least one of the things he has said must be false (indeed, all of them could be), but the fact alone of self-contradiction does not show where the falsehood resides. For example, when Socrates leads Euthyphro to accept ideas that contradict his own definition of the pious as whatever pleases all the gods, Socrates concludes that that definition has been shown to be false (Euthyphro 10d-11a), and asks Euthyphro to come up with another one. He does not usually seem to consider that perhaps on further thought the additional ideas would seem faulty and so merit rejection instead.
Socrates uses his elenctic method also in discussion with persons who are not puffed up with false pride, and are quite willing to admit their ignorance and to reason out the truth about these important matters. Examples are his discussions with his long-time friend Crito on whether he should escape prison and set aside the court's death sentence (Plato, Crito), and with the young men Charmides, on self-control (Charmides), and Lysis and Menexenus, on the nature of friendship (Lysis). Socrates examines Crito's proposal that he escape on the basis of principles that he presents to him for his approval, and he, together with Crito (however half-heartedly), rejects it when it fails to be consistent with them. And he examines the young men's successive ideas about these virtues, rejecting some of them and refining others, by relying on their own acceptance of further ideas that he puts to them. Again, he is confident that the inconsistencies brought to light in their ideas indicate the inadequacy of their successive proposals as to the nature of the moral virtue in question.
In many of his discussions, both with young men and the allegedly wise, Socrates seeks to know what some morally valuable property is - for example, piety, courage, self-control or friendship (see §5). Rejecting the idea that one could learn this simply from attending to examples, he insisted on an articulated 'definition' of the item in question - some single account that would capture all at once the presumed common feature that would entitle anything to count as a legitimate instance. Such a definition, providing the essence of the thing defined, would give us a 'model' or 'paradigm' to use in judging whether or not some proposed action or person possesses the moral value so defined (Euthyphro 6d-e). Aristotle says (in Metaphysics I, 6) that Socrates was the first to interest himself in such 'universal definitions', and traces to his interest in them Plato's first impetus towards a theory of Forms, or 'separated' universals (see Plato §10).
In none of his discussions in Plato's early works does Socrates profess to think an adequate final result has actually been established - about the nature of friendship, or self-control, or piety, or any of the other matters he inquires about. Indeed, on the contrary, these works regularly end with professions of profound ignorance about the matter under investigation. Knowledge is never attained, and further questions always remain to be considered. But Socrates does plainly think that progress towards reaching final understanding has taken place (even if only a god, and no human being, could ever actually attain it). Not only has one discovered some things that are definitely wrong to say; one has also achieved some positive insights that are worth holding onto in seeking further systematic understanding. Given that Socrates' method of discussion is elenctic throughout, what does he think justifies this optimism?
On balance, our evidence suggests that Socrates had worked out no elaborate theory to support him here. The ideas he was stimulated to propound in an elenctic examination which went against some initial thesis seemed to him, and usually also to the others present, so plausible, and so supportable by further considerations, that he and they felt content to reject the initial thesis. Until someone came up with arguments to neutralize their force, it seemed the thesis was doomed, as contrary to reason itself. Occasionally Socrates expresses himself in just those terms: however unpalatable the option might seem, it remains open to someone to challenge the grounds on which his conclusions rest (see Euthyphro 15c, Gorgias 461d-462a, 509a, Crito 54d). But until they do, he is satisfied to treat his and his interlocutor's agreement as a firm basis for thought and action. Later, when Plato himself became interested in questions of philosophical methodology in his Meno, this came to seem a philosophically unsatisfactory position; Plato's demand for justification for one's beliefs independent of what seemed on reflection most plausible led him to epistemological and metaphysical inquiries that went well beyond the self-imposed restriction of Socratic philosophy to ethical thought in the broadest sense. But Socrates did not raise these questions. In this respect more bound by traditional views than Plato, he had great implicit confidence in his and his interlocutors' capacity, after disciplined dialectical examination of the issues, to reach firm ground for constructing positive ideas about the virtues and about how best to lead a human life - even if these ideas never received the sort of final validation that a god, understanding fully the truth about human life, could give them.
The topics Socrates discussed were always ethical, and never included questions of physical theory or metaphysics or other branches of philosophical study. Moreover, he always conducted his discussions not as theoretical inquiries but as profoundly personal moral tests. Questioner and interlocutor were equally putting their ways of life to what Socrates thought was the most important test of all - their capacity to stand up to scrutiny in rational argument about how one ought to live. In speaking about human life, he wanted his respondents to indicate what they truly believed, and as questioner he was prepared to do the same, at least at crucial junctures. Those beliefs were assumed to express not theoretical ideas, but the very ones on which they themselves were conducting their lives. In losing an argument with Socrates you did not merely show yourself logically or argumentatively deficient, but also put into question the very basis on which you were living. Your way of life might ultimately prove defensible, but if you cannot now defend it successfully, you are not leading it with any such justification. In that case, according to Socrates' views, your way of life is morally deficient. Thus if Menexenus, Lysis and Socrates profess to value friendship among the most important things in life and profess to be one another's friends, but cannot satisfactorily explain under pressure of elenctic investigation what a friend is, that casts serious doubt on the quality of any 'friendship' they might form (Plato, Lysis 212a, 223b). Moral consistency and personal integrity, and not mere delight in argument and logical thought, should therefore lead you to repeated elenctic examination of your views, in an effort to render them coherent and at the same time defensible on all sides through appeal to plausible arguments. Or, if some of your views have been shown false, by conflicting with extremely plausible general principles, it behoves you to drop them - and so to cease living in a way that depends upon accepting them. In this way, philosophical inquiry via the elenchus is fundamentally a personal moral quest. It is a quest not just to understand adequately the basis on which one is actually living, and the personal and moral commitments that this contains. It is also a quest to change the way one lives as the results of argument show one ought to, so that, at the logical limit of inquiry, one's way of life would be completely vindicated. Accordingly, Socrates in Plato's dialogues regularly insists on the individual and personal character of his discussions. He wants to hear the views of the one person with whom he is speaking. He dismisses as of no interest what outsiders or most people may think - provided that is not what his discussant is personally convinced is true. The views of 'the many' may well not rest on thought or argument at all. Socrates insists that his discussant shoulder the responsibility to explain and defend rationally the views he holds, and follow the argument - reason - wherever it may lead.
We learn a good deal about Socrates' own principles from both Plato and Xenophon. Those were ones that had stood up well over a lifetime of frequent elenctic discussions and had, as he thought, a wealth of plausible arguments in their favour. Foremost is his conviction that the virtues - self-control, courage, justice, piety, wisdom and related qualities of mind and soul - are essential if anyone is to lead a good and happy life. They are good in themselves for a human being, and they guarantee a happy life, eudaimonia - something that he thought all human beings always wanted, and wanted more than anything else. The virtues belong to the soul - they are the condition of a soul that has been properly cared for and brought to its best state. The soul is vastly more important for happiness than are health and strength of the body or social and political power, wealth and other external circumstances of life; the goods of the soul, and pre-eminently the virtues, are worth far more than any quantity of bodily or external goods. Socrates seems to have thought these other goods are truly good, but they only do people good, and thereby contribute to their happiness, under the condition that they are chosen and used in accordance with virtues indwelling in their souls (see Plato, Apology 30b, Euthydemus 280d-282d, Meno 87d-89a).
More specific principles followed. Doing injustice is worse for oneself than being subjected to it (Gorgias 469c-522e): by acting unjustly you make your soul worse, and that affects for the worse the whole of your life, whereas one who treats you unjustly at most harms your body or your possessions but leaves your soul unaffected. On the same ground Socrates firmly rejected the deeply entrenched Greek precept to aid one's friends and harm one's enemies, and the accompanying principle of retaliation, which he equated with returning wrongs for wrongs done to oneself and one's friends (Crito 49a-d). Socrates' daily life gave witness to his principles. He was poor, shabbily dressed and unshod, and made do with whatever ordinary food came his way: such things matter little. Wealth, finery and delicacies for the palate are not worth panting after and exerting oneself to enjoy. However, Socrates was fully capable of relishing both refined and plain enjoyments as occasion warranted (see §7).
The Greeks recognized a series of specially prized qualities of mind and character as aretai or virtues. Each was regarded as a distinct, separate quality: justice was one thing, concerned with treating other people fairly, courage quite another, showing itself in vigorous, correct behaviour in circumstances that normally cause people to be afraid; and self-control or moderation, piety and wisdom were yet others. Each of these ensured that its possessor would act in some specific ways, regularly and reliably over their lifetime, having the justified conviction that those are ways one ought to act - agathon (good) and kalon (fine, noble, admirable or beautiful) ways of acting. But each type of virtuous person acts rightly and well not only in regularly recurring, but also in unusual and unheralded, circumstances; the virtue involves always getting something right about how to live a good human life. Socrates thought these virtues were essential if one was to live happily (see §4). But what exactly were they? What was it about someone that made them just, or courageous, or wise? If you did not know that, you would not know what to do in order to acquire those qualities. Furthermore, supposing you did possess a virtue, you would have to be able to explain and defend by argument the consequent ways in which you lived - otherwise your conviction that those are ways one ought to act would be shallow and unjustified. And in order to do that you would have to know what state of mind the virtue was, since that is essential to them (see Plato, Charmides 158e-159a). Consequently, in his discussions Socrates constantly asked for 'definitions' of various virtues: what is courage (Laches); what is self-control or moderation (Charmides), what is friendship (Lysis) and what is piety (Euthyphro). As this context shows, he was asking not for a 'dictionary definition', an account of the accepted linguistic understanding of a term, but for an ethically defensible account of an actual condition of mind or character to which the word in common use would be correctly applied. In later terminology, he was seeking a 'real' rather than a 'nominal' definition (see Definition; Plato §§6-9).
Socrates objected to definitions that make a virtue some external aspect of a virtuous action (such as the manner in which it is done - for example its 'quiet' or measured quality in the case of moderation, Charmides 160b-d), or simply the doing of specific types of action, described in terms of their external circumstances (such as, for courage, standing one's ground in battle; Laches 190e-191d). He also objected to more psychological definitions that located a virtue in some non-rational and non-cognitive aspect of the soul (for example, in the case of courage, the soul's endurance or strength of resistance) (Laches 192d-193e). For his own part, he regularly shows himself ready to accept only definitions that identify a virtue with some sort of knowledge or wisdom about what is valuable for a human being. That 'intellectualist' expectation about the nature of virtue, although never worked out to his satisfaction in any Platonic dialogue, is central to Socrates' philosophy.
Given that in his discussions he is always the questioner, probing the opinions of his respondent and not arguing for views of his own, we never find Socrates stating clearly what led him to this intellectualism. Probably, however, it was considerations drawn from the generally agreed premise that each virtue is a condition motivating certain voluntary actions, chosen because they are good and fine or noble. He took it that what lies behind and produces any voluntary action is the idea under which it is done, the conception of the action in the agent's mind that makes it seem the thing to do just then. If so, each virtue must be some state of the mind, the possessor of which constantly has certain distinctive general ideas about how one ought to behave. Furthermore, since virtues get this right, these are true ideas. And since a virtuous person acts well and correctly in a perfectly reliable way, they must be seated so deeply in the mind as to be ineradicable and unwaveringly present. The only state of mind that meets these conditions is knowledge: to know a subject is not just to be thoroughly convinced, but to have a deep, fully articulated understanding, being ready with explanations to fend off objections and apparent difficulties and to extend old principles into new situations, and being prepared to show with the full weight of reason precisely why each thing falling under it is and must be so. Each virtue, then, must be knowledge about how one ought to behave in some area of life, and why - a knowledge so deep and rationally secure that those who have it can be counted upon never to change their minds, never to be argued out of or otherwise persuaded away from, or to waver in, their conviction about how to act.
In Plato's Protagoras Socrates goes beyond this, and identifies himself with the position, rejected by Protagoras in their discussion, that the apparently separate virtues of justice, piety, self-control, courage and wisdom are somehow one and the same thing - some single knowledge (361a-b). Xenophon too confirms that Socrates held this view (Memorabilia III 9.5). Protagoras defends the position that each of the virtues is not only a distinct thing from each of the others, but so different in kind that a person could possess one of them without possessing the others (329d-e). In opposing him, Socrates sometimes speaks plainly of two allegedly distinct virtues being 'one' (333b). Given this unity of the virtues, it would follow that a person could not possess one without having them all. And in speaking of justice and piety in particular, Socrates seems to go further, to imply that every action produced by virtue is equally an instance of all the standardly recognized virtues: pious as well as just, wise and self-controlled and courageous also. Among his early dialogues, however, Plato's own philosophical interests show themselves particularly heavily in the Protagoras, so it is doubtful how far the details of his arguments are to be attributed to the historical Socrates. The issues raised by Socrates in the Protagoras were, none the less, vigorously pursued by subsequent 'Socratic' philosophers (as Plutarch's report in On Moral Virtue 2 demonstrates). And the positions apparently adopted by Plato's Socrates were taken up and ingeniously defended by the Stoic philosopher Chrysippus (see Stoicism §16). As usual, because of his questioner's role, it is difficult to work out Socrates' grounds for holding to the unity of virtue; and it is difficult to tell whether, and if so how, he allowed that despite this unity there were some real differences between, say, justice and self-control, or courage and piety. Apparently he thought the same body of knowledge - knowledge of the whole of what is and is not good for human beings, and why it is so or not - must at least underlie the allegedly separate virtues. If you did not have that vast, comprehensive knowledge you could not be in the state of mind which is justice or in that which is courage, and so on; and if you did have it you would necessarily be in those states of mind. It seems doubtful whether Socrates himself progressed beyond that point. Efforts to do that were made by Chrysippus and the other philosophers referred to above. And despite denying that all virtues consist in knowledge, Plato in the Republic and Aristotle in Nicomachean Ethics VI follow Socrates to the extent of holding, in different ways, that you need to have all the virtues in order to have any one.
In Plato's Protagoras Socrates also denies the possibility of weakness of will - being 'mastered' by some desire so as to act voluntarily in a way one knows is wrong or bad (see also Xenophon, Memorabilia III 9.4, IV 5.6.) All voluntary wrongdoing or bad action is due to ignorance of how one ought to act and why, and to nothing else. This would be easy to understand if Socrates were using 'knowing' quite strictly, to refer to the elevated and demanding sort of knowledge described in §5 (sometimes called 'Socratic knowledge'). Someone could know an action was wrong or bad, with full 'Socratic knowledge', only if they were not just thoroughly convinced, but had a deep, fully articulated understanding, being ready with explanations to fend off objections and apparent difficulties, and prepared to show precisely why it was so. That would mean that these ideas were seated so deeply in the mind as to be ineradicable and unwaveringly present. Accordingly, a person with 'Socratic knowledge' could not come to hold even momentarily that the action in question would be the thing to do, and so they could never do it voluntarily.
However, Plato's Socrates goes further. He explains his denial of weak-willed action by saying that a person cannot voluntarily do actions which, in doing them, they even believe to be a wrong or bad thing to do (Protagoras 358c-e). He gives a much-discussed, elaborate argument to establish this stronger conclusion, starting from assumptions identifying that which is pleasant with that which is good (352a-357e). These assumptions, however, he attributes only to ordinary people, the ones who say they believe in the possibility of weak-willed action; he makes it clear to the careful reader, if not to Protagoras, that his own view is simply that pleasure is a good thing, not 'the' good (351c-e; see 354b-d). Although some scholars have thought otherwise, Socrates himself does not adopt a hedonist analysis of the good in the Protagoras or elsewhere either in Plato or Xenophon; indeed, he speaks elsewhere against hedonist views (see Hedonism). The fundamental principle underlying his argument - a principle he thinks ordinary people will accept - is that voluntary action is always 'subjectively' rational, in the sense that an agent who acts to achieve some particular sort of value always acts with the idea that what they are doing achieves more of that value than alternatives then thought by them to be available would achieve. If someone performs an overall bad action because of some (lesser) good they think they will get from it, they cannot do it while believing it is bad overall. That would mean they thought they could have got more good by refraining, and their action would violate the principle just stated. Instead, at the time they acted (despite what they may have thought before or after acting), they believed (wrongly and ignorantly) that the action would be good overall for them to do. Thus ignorance, and only ignorance, is responsible for voluntary error. Weakness of will - knowingly pursuing the worse outcome - is psychologically impossible: 'No one does wrong willingly'.
The details of this argument may not represent explicit commitments of the historical Socrates. None the less, his denial of weakness of will, understood as presented in Plato's Protagoras, was the centre of a protracted debate in later times. First Plato himself, in Republic IV, then Aristotle in Nicomachean Ethics VII, argued against Socrates' conclusion, on the ground that he had overlooked the fact that human beings have other sources of motivation that can produce voluntary actions, besides their ideas about what is good or bad, or right or wrong to do. 'Appetites' and 'spirited desires' exist also, which can lead a person to act in fulfilment of them without having to adopt the idea, in their beliefs about what is best to do, that so acting would be a good thing (see Plato §14; Aristotle §20, 22-23). The Stoics, however, and especially Chrysippus, argued vigorously and ingeniously in defence of Socrates' analysis and against the Platonic-Aristotelian assumption of alternative sources of motivation that produce voluntary action on their own (see Stoicism §19). In fact, during Hellenistic times it was the Socratic, 'unitary' psychology of action that carried the day; the Platonic-Aristotelian alternative, dominant in the 'common sense' and the philosophy of modern times, was a minority view. The issues Socrates raised about weakness of will continue to be debated today.
Socrates drew to himself many of the brightest and most prominent people in Athens, securing their fascinated attention and their passionate friendship and support. His effectiveness as a philosopher, and the Socratic 'legend' itself, depended as much on the strength and interest of his personality as on the power of his mind. Plato's and Xenophon's portraits of Socrates as a person differ significantly, however. Plato's Socrates is aloof and often speaks ironically, although also with unusual and deeply held moral convictions; paradoxically, the depth and clarity of his convictions, maintained alongside the firm disclaimer to know what was true, could seem all the stronger testimony to their truth, and made them felt the more strongly as a rebuke to the superficiality of one's own way of living. In Xenophon, Socrates is also sometimes ironical and playful, especially in the Symposium, but his conversation is usually direct, even didactic, and often chummy in tone; his attitudes are for the most part conventional though earnest; and there is nothing to unsettle anyone or make them suspect hidden depths. It is much easier to believe that the Socrates of Plato's dialogues could have had such profound effects on the lives of the brightest of his contemporaries than did the character in Xenophon. That is one reason given for trusting Plato's more than Xenophon's portrait of the historical personage. But perhaps Socrates used the more kindly and genial manner and conventional approach depicted by Xenophon to draw out the best in some of his young men and his friends - ones who would have been put off by the Platonic subtleties. The historical Socrates may have been a more complex person than even Plato presents.
Plato and Xenophon both represent Socrates as strongly attracted to good-looking young men in the 'bloom' of their middle to late teens, just the period when they were also coming of age morally and intellectually. In both he speaks of himself as unusually 'erotic' by temperament and constantly 'in love'. But he explains his 'erotic' attachments in terms of his desire to converse with bright and serious young men, to question them about virtue and how best to live a human life, and to draw out what was best in their minds and characters. In Xenophon he describes his love as love for their souls, not their bodies, and he vigorously condemns sexual relations with any young man: using him that way disgraces him and harms him by encouraging a loose attitude as regards physical pleasures Symposium 8). The overheated sexuality of Plato's own accounts (Symposium and Phaedrus) of eros, sexual love, for a young man's beauty as motivating an adult male to pursue philosophical truth into an eternal realm of Forms (see Plato §12) is to be distinguished sharply from Socrates' ideas, as we can gather them from Xenophon and from Plato's own early dialogues.
Xenophon emphasizes Socrates' freedom from the strong appetites for food, drink, sex and physical comfort that dominate other people; his enkrateia or self-mastery is the first of the virtues that Xenophon claims for him (Memorabilia I 2.1). He was notorious for going barefoot even in winter and dressing always in a simple cloak. Socrates' self-mastery was at the centre of Antisthenes' portrayal, and is reflected also in several incidents reported in Plato, such as his serene dismissal of the young Alcibiades' efforts to seduce him sexually (Plato, Symposium 217b-219e), or, perhaps when engrossed in a philosophical problem, his standing in the open (during a break in the action while on military service) from morning to night, totally indifferent to everything around him (Symposium 220c-d). This 'ascetic' Socrates, especially as presented by Antisthenes - rejecting conventional comforts and conventional behaviour - became an inspiration for the 'Cynics' of later centuries (see Cynics).
Looking back on the early history of philosophy, later philosophers traced to Socrates a major turn in its development. As Cicero puts it: 'Socrates was the first to call philosophy down from the heavens... and compel it to ask questions about life and morality' (Tusculan Disputations V 10-11). Previously it had been concerned with the origins and nature of the physical world and the explanation of celestial and other natural phenomena. Modern scholarship follows the ancients' lead in referring standardly to philosophers before Socrates collectively as 'Presocratics' (see Presocratic philosophy). This includes Democritus, in fact a slightly younger contemporary of Socrates; Cicero's verdict needs adjustment, in that Democritus, independently of Socrates, also investigated questions about ethics and morality. With the sole exception of Epicureanism, which developed separately out of Democritean origins, all the major movements of Greek philosophy after Socrates had roots in his teaching and example. This obviously applies to Plato, whose philosophical development began with a thorough reworking and assimilation of Socratic moral inquiry, and through him to Aristotle and his fellow members of Plato's Academy, Speusippus and Xenocrates and others, as well as to later Platonists. Among Socrates' inner circle were also Aristippus of Cyrene, who founded the hedonist Cyrenaic school (see Aristippus the Elder; Cyrenaics), and Antisthenes, an older rival of Plato's and major teacher in Athens of philosophical dialectic. Both of these figure in Xenophon's Memorabilia (Antisthenes also in his Symposium), where they are vividly characterized in conversation with Socrates. Another Socratic, Euclides, founded the Megarian school (see Megarian school). These 'Socratic schools' developed different themes already prominent in Socrates' own investigations, and competed in the claim to be his true philosophical heirs (see Socratic schools; Dialectical School).
In the third to first centuries bc, both the Stoics and their rivals the Academic sceptics claimed to be carrying forward the Socratic tradition. In both cases this was based upon a reading of Plato's dialogues and perhaps other eye-witness reconstructions of Socrates' philosophy. The Academic Arcesilaus interpreted the Platonic Socrates as a sceptical inquirer, avidly searching but never satisfied that the truth on any disputed question had been finally uncovered. He could point to much about Plato's Socrates in support: his modest but firm denial that he possessed any knowledge, and his constant practice of inquiring into the truth by examining others' opinions on the basis of ideas which they themselves accepted, without formally committing himself to these ideas even when he was the one to first suggest them. Arcesilaus, however, applied his sceptical Socratic dialectic to more than the questions of ethics and human life about which Socrates himself had argued, making it cover the whole range of philosophical topics being investigated in his day. The Stoics read the dialogues (especially the Euthydemus and Protagoras) quite differently. They found Socrates espousing a complete doctrine of ethics and the psychology of human action. He posed his questions on the basis of this doctrine, leaving the respondent (and the reader) to recover for themselves the philosophical considerations underlying it. They thus emphasized the conceptions of virtue as knowledge, of virtue as unified in wisdom, and of voluntary action as motivated always by an agent's beliefs about what is best to do, that emerged through Socrates' examination of Protagoras (see §§6-7). They thought these constituted a positive, Socratic moral philosophy, and in their own moral theory they set out to revive and strengthen it with systematic arguments and with added metaphysical and physical speculations of their own. Later Stoics regularly referred to Socrates as a genuine wise man or 'sage', perhaps the only one who ever lived. He had brought to final, systematic perfection his knowledge, along Stoic lines, of what is good and bad for human beings, and what is not, and therefore possessed all the virtues and no vices, and lived unwaveringly the best, happy life, free from emotion and all other errors about human life. It is a tribute to the complexity and enigmatic character of Socrates that he could stand simultaneously as a paragon both of sceptical, non-committal inquiry and life led on that uncommitted basis, and of dogmatic knowledge of the final truth about all things human.
The figure of Socrates has continued to fascinate and to inspire ever-new interpretations of his innermost meaning. For Montaigne, he proved that human beings can convincingly and attractively order their own lives from their own resources of mind, without direction from God or religion or tradition. In the nineteenth century Kierkegaard and Nietzsche offered extensive interpretations of him, both heavily dependent upon Hegel's absolute-idealist analysis. Hegel interpreted Socrates as a quintessentially negative thinker, aiming at making people vacillate in their superficial moral beliefs and endorse none of them wholeheartedly, thus hinting that the truth, although universal and objective, lies deep within the freedom of their own subjectivity. For Kierkegaard he represents, on the contrary, the possibility of living wholeheartedly by occupying an unarticulated position somehow beyond the negative rejection but expressed through it: 'infinite absolute negativity'. In Die Geburt der Tragödie (The Birth of Tragedy) Nietzsche treats Socrates principally as having poisoned the 'tragic' attitude that made possible the great achievements of classical culture, by insisting that life should be grounded in rational understanding and justified by 'knowledge'; but his fascinated regard for Socrates led him to return to him repeatedly in his writings. Socrates was paradigmatically a philosopher whose thought, however taken up with logic and abstract argument, is inseparable from the search for self-understanding and from a deeply felt attachment to the concerns of human life. His power to fascinate and inspire is surely not exhausted.JOHN M. COOPER | <urn:uuid:50ef9d50-2a81-471d-b070-9d33b96d1771> | CC-MAIN-2013-20 | http://muslimphilosophy.com/ip/rep/A108.htm | 2013-05-22T07:26:41 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368701459211/warc/CC-MAIN-20130516105059-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.976473 | 11,184 | 4.21875 | 4 |
News > Scientists reconstruct Red Sea parting
Researchers at the US National Center for Atmospheric Research (NCAR) have produced a computer simulation that demonstrates how the parting of the Red Sea described in the Book of Exodus could have been caused by strong winds.
The study, which is part of a larger project looking into the impact of winds on water depths, was published in the open-access journal Plos One. In it, researchers produced a reconstruction of the likely geography of the Nile Delta during the Old Testament period, which has changed considerably over the intervening centuries. The researchers have identified a stretch of the Nile where a strong east wind could conceivably have pushed the river back at a bend, opening up a walkway across the exposed mud flats and allowing the Israelites to flee the approaching Egyptians.
"The simulations match fairly closely with the account in Exodus," Carl Drews of the NCAR told the BBC. "The parting of the waters can be understood through fluid dynamics. The wind moves the water in a way that's in accordance with physical laws, creating a safe passage with water on two sides and then abruptly allowing the water to rush back in."
With the burning bush also potentially linked to freak environmental conditions, it remains to be seen how much else of the bible story can be explained by meteorology. | <urn:uuid:61945547-f2cd-4b80-b43e-e7d82c52b051> | CC-MAIN-2013-20 | http://theweatherclub.org.uk/news/article/scientists-reconstruct-red-sea-parting | 2013-05-22T07:47:57 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368701459211/warc/CC-MAIN-20130516105059-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.95224 | 264 | 4.09375 | 4 |
Autism spectrum disorders (ASDs) involve a wide range of clinical diagnoses, including
- Asperger syndrome (a mild form of autism)
- childhood degenerative disorder
- pervasive developmental disorder not otherwise specified (PDD-NOS)
Although the severity of the symptoms that occur with each of these disorders will be different, all ASDs result in specific impairments. These are commonly seen in three specific areas:
- social interaction
- language and communication
- engagement in repetitive behavior
The Centers for Disease Control and Prevention estimates that about one in every 88 children have an ASD (CDC, 2012).
The term autistic behavior is used to describe the actions of a child with an ASD.
Doctors do not know for certain what causes autistic behavior. Genetics may play a role. Research examining the brains of children with autism has shown abnormalities in several different regions. Environment may also play a part in the development of autism. Exposure of the fetus to certain toxins or viruses may increase the chances of developing autism.
Autism may also be passed down through families. If an identical twin has autism, there is a 90 percent chance that his or her twin will have the disorder. Families with a child who has autism have a one in 20 chance of having another child with autism. Even though this is only a five percent risk, it is higher than the risk for families that do not have a child with autism (NINDS, 2012).
For unknown reasons, boys are significantly more likely to have autism. Studies show that one in 54 boys is diagnosed with an ASD, while only one in 252 girls suffer from an ASD (CDC, 2012).
Many people believe that autistic behavior is caused by vaccines. The link between vaccines and autism has received much media attention in recent years. However, there is no evidence that suggests that childhood immunizations cause autism. If you are concerned about this issue, talk with your doctor.
The symptoms of autistic behavior vary depending on your specific diagnosis. The most common feature of autistic behavior is difficulty with social interaction. Infants and children who display this behavior may:
- not respond when their names are called
- avoid eye contact
- not respond appropriately to social cues, such as someone being angry or upset
- engage in self-injurious behavior, such as biting
- engage in repetitive behaviors, such as rocking back and forth
As autistic children grow, they may develop problems in other areas, including language and communication. Children with ASDs typically learn to speak later than children without the disorder.
In addition, children with ASDs:
- may refer to themselves by name instead of using pronouns such as “I” or “me”
- will not know how to play with other children
- appear disinterested when being engaged by other children or adults
- may not smile or respond to others
- may have specific interests or habits that are more important to them than interacting with others
- may have sensitivity to loud sounds or bright lights
Autistic behavior can be diagnosed by your doctor. Infants typically reach developmental milestones by certain ages. Examples include:
- babbling by 12 months
- gesturing and pointing by 12 months
- saying single words by 16 months
- saying two-word phrases by 24 months
If your child does not develop these behaviors or has other symptoms of autism, your doctor may order additional tests. Tests will be used to rule out other health problems and may include:
- hearing tests (to rule out a hearing problem may cause similar behaviors)
- blood tests (to look for lead toxicity, which may cause similar behaviors)
Your doctor may also screen your child for autism using the Checklist for Autism in Toddlers (CHAT) or the Autism Screening Questionnaire. Your doctor may refer you to a developmental psychologist for further evaluation. This specialist can provide you with a more accurate diagnosis.
Treatment for autistic behavior will depend on the severity of the symptoms. Young children diagnosed with an ASD are typically provided with early intervention services. These can include:
- occupational therapy
- social skills training
- physical therapy
- speech-language therapy
In some cases, your doctor may recommend medication to control certain behaviors. These might include:
- risperidone for irritability and aggression
- selective serotonin reuptake inhibitors (SSRIs) to stabilize mood
- methylphenidate, a stimulant
Treatment may also include changes in diet. Gluten has been postulated to be associated with certain autistic behaviors. There is no evidence to support this reasoning; however removing gluten from the diet may reduce symptoms of ASDs. Treatment works best when it is tailored to meet the needs of the individual with autism.
The long-term outcome for a child with autistic behavior is better today than it was a generation ago. In the past, children with autism were typically placed in institutions. Today, early diagnosis and treatment can improve outcomes.
The prognosis for a person with autism will depend on the severity of the disorder. It will also depend on how early treatment is provided. Autistic behavior can cause emotional problems for children and family members. Getting help and support for these challenges from doctors, therapists, and family members can be beneficial. | <urn:uuid:bf4bf857-684e-43d3-a7bd-f6ef95734f7c> | CC-MAIN-2013-20 | http://www.healthline.com/health/autistic-behavior | 2013-05-22T07:21:35 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368701459211/warc/CC-MAIN-20130516105059-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.955729 | 1,072 | 4.15625 | 4 |
Tiny phytoplankton in the oceans of the Northern Hemisphere had far larger extinction rates during the mass extinction event 65 million years ago than those living in the Southern Hemisphere, according to a paper published online this week in Nature Geoscience. The recovery of the Northern Hemisphere phytoplankton also occurred significantly later than recovery in the southern oceans.
Populations of phytoplankton smaller than 20 micrometres were decimated during the Cretaceous/Tertiary mass extinction, which is linked to an impact event. Timothy Bralower and colleagues propose that the clouds of debris from the impact ― which would have blocked the sunlight that these phytoplankton needed to grow, and poisoned them as the metal-laden dust fell to the ocean surface ― were concentrated in the Northern Hemisphere, leading to the higher extinction rates. The team also suggests that the recovery of marine diversity in the north may have been hindered by the phytoplankton's slower start in this region. | <urn:uuid:f5fa14c6-eceb-476d-a47f-2b67315b738c> | CC-MAIN-2013-20 | http://www.natureasia.com/en/research/highlight/660 | 2013-05-22T07:47:43 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368701459211/warc/CC-MAIN-20130516105059-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.969065 | 209 | 4.03125 | 4 |
In the simplest of terms, a virus is an infectious agent. It operates like a computer virus, replicating and dispersing itself in all directions, while crippling the normal function of the host. A virus has genes, but no cellular structure, so it's not considered a living organism. And like parasites, viruses can't survive on their own. Bacteria, on the other hand, are tiny cells that reproduce and can survive independently, with the ability to transport dangerous toxins.
Epidemiologists generally rely on an international but informal network of colleagues to get wind of a disease outbreak fast, even when it starts in a remote corner of the world. But while patients may be lining the hospital corridors in Jakarta, Veracruz or Pittsburgh, activating a worldwide emergency response protocol is not instantaneous. Laboratory tests must first isolate the virus, microbe, toxin or other mechanism of injury. Usually, scientists in the field must collaborate with researchers in other countries to identify the culprit. And only when the team is absolutely sure about the agent and its cause will entities like the Centers for Disease Control (CDC) and World Health Organization (WHO) spring into action. That's when the country alerts go out, a vaccine (or other remedy) gets developed, and the counterattack begins.
Getting Ahead of The Curve
In 1999, the CDC initiated the Laboratory Response Network (LRN), a group of local, state, federal, and international labs that can test for disease agents and develop vaccines in a fast, efficient manner. An estimated ninety percent of the U.S. population now live within a 100 miles of a designated lab. This close proximity insures a quick turnaround as evidence in the field is procured, then shipped to epidemiologists ready to analyze it.
To help get a jump on the next global pandemic, the CDC also dispatches scientists worldwide each year to sniff out virulent strains that may be on the prowl. The Epidemic Intelligence Service (EIS) recruits 70-80 college graduates annually for two-year, post-graduate assignments performing surveillance and study in the field.
Influenza viruses that affect humans are divided into two basic groups. "A" viruses have pandemic potential. "B" viruses don't. To qualify as a pandemic, an "A" virus must also be "novel", which means there's no pre-disposed immunity to it and no existing vaccines. Furthermore, the bug must have the potential for human to human transmission.
Diagram of the 1918 H1N1 Spanish Flu Virus. Photo: University of Washington School of Medicine
Other things to note about pandemic virus:
According to the U.S. Department of Health and Human Services, the continued spread of the avian H5N1 virus across much of eastern Asia, Russia, and eastern Europe represents the most significant pandemic threat out there today. Human avian H5N1 influenza infection was first recognized in 1997 when it infected 18 people in Hong Kong, causing 6 deaths. Concern has increased in recent years as avian H5N1 infections have killed poultry flocks in countries throughout Asia and in parts of Europe. Since 2003, over 100 human H5N1 cases have been diagnosed in Thailand, Vietnam, Cambodia, and Indonesia. HHS believes the virus is worrisome because:
Reports of new cases worldwide have continued to pour in through 2011. In March alone, Egypt reported its 131th case, Bangladesh reported its 67th outbreak, while public health officials in Japan, Myanmar, South Korea, India, Israel and Gaza all discovered its presence in poultry and other species. See the timeline (PDF) prepared by WHO.
While cases of human infection are rare, avian influenza is very contagious among birds and some of these viruses can sicken certain domesticated species, like chickens, ducks, and turkeys.
While H5N1 remains the top pandemic threat today, additional avian flu subtypes are entering the fray. In 1999, H9N2 infections were identified in Hong Kong; in 2003, H7N7 infections occurred in the Netherlands; and in 2004, H7N3 infections occurred in Canada. Such outbreaks have the potential to generate a pandemic, the CDC claims, reinforcing the need for continued surveillance and ongoing vaccine research.
In the case of a major nationwide pandemic, the CDC has established the following priority groups for vaccine distribution:
Vaccines are produced by pharmaceutical companies, often under a contract from the U.S. Government. Over 200 million doses, for instance, were ordered at the start of the H1N1 pandemic. In addition to pandemic vaccines, drug manufacturers produce the annual flu shot vaccine and chilhood immunization drugs for polio, chicken pox, German measles, etc. Immunizations for adults include hepatitus, malaria and tetanus. Some of these shots have only a short-term effectiveness. In the case of tetanus, for instance, a "booster" shot is recommended every ten years.
Vaccines are divided into other categories based on how the drug intends to destroy the targetted microbe or pathogen. Since viruses, bacteria and toxins attack the body in different ways, the epidemiologist must design a solution that works best for the circumstances. Here are his choices:
Live, attenuated vaccines
These contain a version of the living microbe that has been weakened in the lab so it can’t cause disease. Like firefighters setting small fires in advance of a mega-blaze, this small dose of the killer pathogen is easy for the immune system to fight off, thereby achieving lifelong immunity with one or two doses. However, people with compromised immune systems are considered too weak to overcome a live vaccine. Besides that, the microbe that's injected may on occasion morph into something worse than it was initially. These vaccines are likewise not suitable for some geographical locations, since a "live" vaccine must be kept alive through refrigeration.
Samples of the disease-causing microbe are first destroyed with chemicals, heat, or radiation. These vaccines are more stable and safer than live vaccines, since the dead microbes can’t mutate back to their disease-causing state. Inactivated vaccines usually don’t require refrigeration, and they can be easily stored and transported in a freeze-dried form, which makes them accessible to people in developing countries. On the down side, they trigger a weaker immune system response and therefore require multiple doses over time or booster shots to be effective.
These use only parts of the killer microbe, specifically the antigens, which are responsible for triggering the production of antibodies to fight the microbe. It takes a long time to develop a subunit vaccine, but once it's perfected, adverse reactions are much lower than with live or inactivated vaccines. These vaccines are a good choice for people with compromised immune systems.
Some bacteria secrete toxins or harmful chemicals, which can cause a serious illness all by themselves. The toxins can in some cases be neutralized by treating them with formalin, which is a solution of formaldehyde and sterilized water. Such “detoxified” toxins are called toxoids and are safe for use as vaccines.When injected, the toxoid causes the immune system to fight off the natural toxin and produce antibodies that will block the real toxin. Diphtheria and tetanus are examples of diseases that toxoid vaccines can prevent.
The immature immune systems of infants and younger children don't always recognize or respond to certain types of coatings around bacteria, so this special type of subunit vaccine has been developed to address the problem.
Still in the experimental stages, these vaccines show great promise (according to NIH), and several types are currently being tested in humans. These vaccines dispense with the microbe and its parts, and instead use the genes of those all-important antigens.
Recombinant vector vaccines
Also in the experimental stage, these are similar to DNA vaccines, but they use an attenuated virus or bacterium to introduce microbial DNA to cells of the body. “Vector” refers to the virus or bacterium used as the disease carrier. (For instance, mosquitoes carry malaria, so it's considered a "vector-bourne" disease.)
In addition to antigens that alert the immune system to an infectious agent, vaccines may also contain substances called adjuvants, which NIH says improve the immune response produced by the vaccines. Currently, the only adjuvant licensed for human use in the United States is an “alum” adjuvant, which is composed of aluminum salts.
Vaccines may also contain substances to prevent contamination, as well as maintain a vaccine’s potency at less-than-optimal temperatures, or act as a preservative. One such controversial ingredient in this catgegory is a compound call thimerosal.
Autism advocacy organizations oppose the use of thimerasol and other mercury-based additives in vaccines. They allege that autism is caused in part by these ingredients when multiple childhood immunizations are administered at one time. The claim is virulently rejected by the CDC and much of the western medical establishment. In recent years, however, thimerasol use in vaccines has been reduced. Autism advocates urge parents to observe the following cautions when getting vaccines for their kids or themselves:
For information on specific bacterial diseases and viruses, please check the second column on this page.
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"New Strain of Bird Flu Causing Deaths in China." Asian Pacific Post 4/17/13.
"Sri Lanka Red Rain may have a cosmic connection." Sinhalaya News 11/18/12
"Yosemite tourist dies after contracting hantavirus." Associated Press 8/17/12
"Amid severe outbreak, is it time for a whooping cough booster?"Los Angeles Times 7/20/12.
"Sepsis: An Infection, Unnoticed, Turns Unstoppable." By Jim Dwyer. New York Times 7/9/12.
"How the Swine Flu Pandemic Got Started." by Michael Friscolanti and Charlie Gillis. Macleans 5/1/09.
"1918 Influenza: the Mother of All Pandemics." By Jeffery K. Taubenberger and David M. Morens (2006)
"Health officials issue alert about Valley fever in County." Stockton Record 6/12/12.
Omaha sees outbreak of flesh-eating bacteria cases." Radio Iowa 6/11/12
Epidemics and Plagues
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Mega Disasters: "Pandemics and Alien Infection" - Season 2, Episode 7. The History Channel At Amazon...
After Armageddon. 2-hour docudrama examines the potential of a lethal flu virus spreading quickly across the United States.
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The Plague. 2-hour documentary tracks the 15th Century pandemic that killed tens of millions.
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How A Virus Invades Your Body
H1N1 virus and the 1918 pandemic
The Bubonic Plague
Epidemics - Old and New
The Plague, which still claims thousands of victims each year, has been traced not to a virus but to a bacteria called Yersinia pestis. It typically originates in the Indian rat flea, known scientifically as Xenopsylla cheopsis, of which only the adult females live off their hosts. This dreaded world traveler can survive up to a year on a host (especially rodunts), in dung, an abandoned rodent's nest or in textile bales.
Xenopsylla cheopsis, the killer flea.
Historically, human infection has occurred in three different ways:
Bubonic Plague - Caused when the victim gets bit by an infected flea. Here, the trademark symptom is painful swelling of the lymph glands in the armpits, groin or neck. The swelling creates ball-like buboes, hence the name bubonic plague. Red spots also appear on the skin and eventually turn black. Victims usually vomit blood and die within about three days without antibiotics.
Pneumonic Plague - The bacteria in this case is transmitted primarily through air, usually coughing, thus entering the respiratory tract. People who dissect or handle contaminated animal tissue are also susceptible. Symptoms include fever, coughing up blood and pneumonia leading to respiratory failure and shock within a few days. Most modern cases have occurred in Africa.
Septicemic Plague - Most often transmitted to humans through the bite of an infected rodent or bug, or through an opening in the skin or by cough from another infected human. This is the rarest type of Plague but the deadliest, as it causes sepsis. Cities along trade routes, especially Venice and Florence, were hit hardest during the Medieval epidemic. Symptoms include stomach ache, diarrhea, fever, nausea, vomiting, low blood pressure and lack of blood clotting.
Today, most cases of Plague occur in Africa, but 10-15 reports are logged in the United States annually, mostly in rural areas of the western states. Bats and rats are known to carry the flea.
Now for the big epidemics caused by viruses:
1918 Spanish Influenza - Still cloaked in mystery, this virus was responsible for infecting half a billion people worldwide, killing 50 million. Unlike other pandemics, this one struck on multiple continents on the same day. The infectious agent triggers an overreaction in the human immune system of mostly young, healthy adults. Like the simultaneous appearance, this feature of H1N1 (1918) also also diverges from the usual pattern. The lungs often became inflamed, leading to death. The original virus struck remote corners of the world, especially Alaska, leading a few researchers to suggest that it must have passed down through the atmosphere from outer space.
A theory known as Panspermia alleges that microbes are transmitted onto Earth via passing comets. Microbes may even be the source of all biological life on the planet. Professor Chandra Wickramasinghe of the Buckingham Centre for Astrobiology is the leading authority on comet-based microbes and viruses. (For more on his work, here's the school's website.)
Smallpox - An estimated 300 million deaths were recorded in the 20th Century alone. Because naturally occurring smallpox was wiped out worldwide by the 1970's, vaccinations stopped. According to the CDC, a case of smallpox today would be the result of an intentional act. Strains of the virus are kept in two approved labs in the U.S. and Russia. The CDC also states that "credible concern exists that the virus was made into a weapon by some countries and that terrorists may have obtained it. "
Polio - Largely unrecorded until the 19th century, recurring epidemics of the Poliomyelitis virus continued into the 20th until a vaccine was discovered. The disease is also known as infantile paralysis, but affects adults as well as children. In a typical case, a fever and other flu symptoms set in, followed eventually by paralysis in the lower half of the body.
Viral Hemorrhagic Fevers - A mostly rodunt-borne set of viruses made its first curtain call in the latter twentieth century, appearing on all continents. However cases usually remain localized. Ticks and mosquitoes may also carry the bug, which targets the vascular system, along with several organs in the body. The bleeding for which the disease is named is itself rarely life-threatening. Slaughterhouse workers have a much greater chance of contracting the virus than others.
HIV - Human Immunodeficiency Virus is a retrovirus discovered in the 1980s by Robert Gallo, but that identification was immediately surrounded in controversy. In particular, the so-called "father of retroviruses" Peter Duesberg dismissed Gallo's conclusions, claiming there was no virological evidence to back-up the HIV-AIDS connection. (This led many African governments to ban the use of anti-HIV drugs.) Duesberg believes HIV is biochemically inactive and harmless, and that the cause of AIDS may be toxicological (i.e. a toxic substance). There is still no satisfactory treatment, although a variety of new drugs has vastly reduced the number of fatalitiies.
West Nile Virus - Carried by mosquitoes, this virus first appeared in the United States in 1999, but got its start seventy years earlier in Uganda. It can produce a mild fever and other flu symptoms, and sometimes a rash, but 80 percent of those infected have no adverse reaction. In severe cases, encephalitis or meningitis may develop, but only one person out of every 150 infected falls into this category. Here's a CDC map of most recently reported cases.
SARS - Severe acute respiratory syndrome started in Hong Kong in 2002 and eventually infected a relatively small number of individuals in 37 countries. It targetted the lungs, caused fever and low white blood cell counts. There were appoximately 8,500 cases and 900 deaths. SARS is considered contained and there's no screening for it.
H1N1 Swine Flu - First appearing in Veracruz, Mexico, this 2009 version of an H1N1virus is thought to be a mutation or combination of previous bird, swine and human flu viruses. A Eurasian pig flu virus was also involved, hence the term "Swine Flu". H1N1 was not spread through eating pork products, however, but contracted through respiratory droplets circulating in the air (like other most other forms of influenza). In a small percentage of people exposed, the virus caused pneumonia or acute respiratory problems. The widespread public emergency surrounding it was offically put to rest by WHO in 2010.
Valley Fever - While not a contagion, Valley fever is carried by spores of the fungus Coccidioides immitis, found in soils of the southwestern United States and Central Valley of California, as well as parts of Africa, Central and South America. Wind is generally credited with transporting the spores, but digging, construction work or farming can likewise cause the spores to become airborne.
Dust containing the spores enters a person's lungs, which can sometimes lead to illness. Exposure is most common in the dry, late summer months, with most cases reported to medical personnel in the fall and early winter. It takes 5-21 days on average for flu-like symptoms to show up.
Those exposed to dust while working outside should consider wearing a close-fitting mask. Early recognition and treatment of Valley fever's flu-like symptoms is important to avert more serious complications.
Flesh-Eating Bacteria - Formally known as necrotizing fasciitis, it's caused by a toxin found in several types of bacteria. Infection is rare, with 500-1,000 cases per year reported in the United States. Aimee Copeland, a young Georgia woman, recently put this dirge on the map after a zipline accident and 22 stitches led to an infection. Open wounds and hospital surgery are the prime vehicles, with 25 percent of victims dying.
If you get a cut or wound that becomes increasingly painful, red and swollen, the bacteria may be present. Go to the emergency room immediately, as time is of the essence. First aid for any wound should always include thorough washing of the exposed area with soap and water, and if possible, application of an anti-biotic ointment.
- - - - - - - - - - - - - - - - - - - - - | <urn:uuid:2f85c88d-17d0-48a2-8c64-3a22dbfb158c> | CC-MAIN-2013-20 | http://www.thecityedition.com/Pages/Archive/2010/Pandemic_page2.html | 2013-05-22T07:41:39 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368701459211/warc/CC-MAIN-20130516105059-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.935572 | 4,234 | 4.09375 | 4 |
Start Your Visit WithHistorical Timelines
General Interest Maps
Fidel Castro was a young Cuban lawyer when he decided to begin an armed struggle against dictator Fulgencio Batista in 1953. He failed at the time and was nearly killed, but lived to lead a second and successful rebellion. Those who hoped that Castro would become a democratic reformer, however, were disappointed when he instead became the hemisphere's longest-serving dictator.
Fidel Alejandro Castro Ruz was born on August 13, 1926, near Mayari, Cuba. His parents owned a sugarcane plantation and the family lived moderately prosperous lives. He attended Catholic schools and enrolled in the University of Havana in 1945, where he studied law. At the university, Castro joined groups opposed to the government. He received his law degree in 1950 and planned to run for a seat in the legislature, but his plans were frustrated when Batista overthrew the government and stopped the elections.
Castro charged Batista with violating the constitution, but his case was refused by the court. With political action impossible, Castro switched to violent opposition. On July 26, 1953, he led a group of armed rebels in an attack on the Moncada army garrison in Santiago. They were defeated by the army, which murdered dozens of the captured rebels in reprisal. Castro was sentenced to 15 years in prison.
Following two years in prison, Castro was released by Batista as a gesture of reconciliation. Not at all reconciled, Castro left for Mexico to train a fresh rebel army. On December 2, 1956, they returned by boat. The army confronted them and they were defeated again, but this time Castro escaped into the mountains with a handful of supporters. From the mountains, they began to amass an army of more than 800 men and employed guerrilla military tactics that Bastista’s men were unequipped to handle. They began to win support among peasants, students, and even Catholic priests, from an additional propaganda campaign.
By the end of 1958, Castro had made Batista's position untenable. On the morning of January 1, 1959, the dictator left Cuba for the Dominican Republic, and from there to Madeira Island in Portugal, where he died. Castro entered Havana in triumph on January 8 to begin his more than 40-year rule. He promised to maintain the democratic constitution of 1940, but quickly imposed authoritarian socialist rule. Thousands of Batista supporters were executed, foreign holdings were confiscated, and American companies lost over a billion dollars in assets. On January 31, 1961, the United States imposed an economic embargo on Cuba. As a result, Cuba became more dependent on Soviet and Eastern bloc nations for economic aid. Many Cubans fled the island for the United States and some established an anti-Castro organization in Miami, Florida.
Stirrings of Castro’s overthrow began publicly when American presidential candidate John F. Kennedy criticized then president Dwight D. Eisenhower, during the 1960 presidential campaign, for not doing more about Castro. Kennedy decided early in his administration that Castro needed to be ousted, by force if necessary. He inherited a CIA plan for the Bay of Pigs Invasion from the Eisenhower administration and followed through on the covert attack in April 1961. Castro's military defeated the Cuban exiles and humiliated the United States. The United States got a measure of revenge the following year when they forced U.S.S.R. general secretary Nikita Khrushchev to withdraw Soviet missiles from Cuba during the October Cuban Missile Crisis.
Castro adopted the attitude that Cuba was "non-aligned" despite its close ties with other communist regimes around the world. He was elected head of Nonaligned Nations Movement and has been a strong voice against American imperialism. Until the fall of the Soviet Union, Cuba relied on Soviet subsidies to maintain its economy. With money received from sugar sales and economic aid from the Soviet Union, Castro implemented such social programs as his war on illiteracy and no-cost universal health care. Without their economic support, the Cuban economy has suffered, but Castro has maintained tight control. Castro's regime also has assisted with revolutions in Angola and Ethiopia.
From the American side, the economic embargo seems firmly in place, despite being supported by no other government in the world. The status quo seems likely to remain, at least until Fidel Castro finally passes from the scene.
---- Selected Quotes ----
Quotes by Fidel Castro.
I feel my belief in sacrifice and struggle getting stronger. I despise the kind of existence that clings to the miserly trifles of comfort and self-interest. I think that a man should not live beyond the age when he begins to deteriorate, when the flame that lighted the brightest moment of his life has weakened.
Letter from prison, 1953
Regarding Human Rights
With what moral authority can they speak of human rights — the rulers of a nation in which the millionaire and beggar coexist; the Indian is exterminated; the black man is discriminated against; the woman is prostituted; and the great masses of Chicanos, Puerto Ricans, and Latin Americans are scorned, exploited, and humiliated?
Speech in 1978
Quotes regarding Fidel Castro.
By Jesse Jackson
The most honest, courageous politician I have ever met.
During 1984 visit to Havana
- - - Books You May Like Include: ----
One Minute to Midnight: Kennedy, Khrushchev and Castro on the Brink of Nuclear War by Michael Dobbs.
In October 1962, at the height of the Cold War, the United States and the Soviet Union appeared to be sliding inexorably toward a nuclear conflict ove...
The Dark Side of Camelot by Seymour M. Hersh.
If the Kennedys are America's royal family, then John F. Kennedy was the nation's crown prince. Magnetic, handsome, and charismatic, his perfectly coi...
Brothers: The Hidden History of the Kennedy Years by David Talbot.
For decades, books about John or Robert Kennedy have woven either a shimmering tale of Camelot gallantry or a tawdry story of runaway ambition and rec...
One Hell of a Gamble: Khrushchev, Kennedy, and Castro, 1958-1964 by Aleksandr Fursenko.
The Berlin Wall has been rubble for a decade and the memories of the cold war are growing dim. And yet no one is ever likely to forget the Cuban Miss... | <urn:uuid:cc96fffd-2179-4169-8436-08117e3daeaa> | CC-MAIN-2013-20 | http://www.u-s-history.com/pages/h1766.html | 2013-05-22T07:13:59 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368701459211/warc/CC-MAIN-20130516105059-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.968298 | 1,304 | 4 | 4 |
This teacher-submitted, secondary lesson plan appeared in the Badger History Bulletin. Please adapt it to fit your students' needs.
Author: Joni Shahrani, Sennett Middle School, Madison
Students will investigate the meaning of "change" in our society and grasp the way Wisconsin's progressive traditions have affected changes in many aspects of life. They will make the connection between Wisconsin as a progressive leader, and the inventions and legislative acts that are documented on the Wisconsin Firsts poster. Then students will choose one of the items listed on the poster to research and report on in class. This lesson plan requires two to three class periods.
Students will gain a greater understanding of how change can be viewed in society.
Students will think critically and make intelligent inferences.
Students will be able to distinguish between industrial and legislative firsts.
Students will analyze and draw conclusions about how these "firsts" reflect the Wisconsin people who made and used them.
The Wisconsin Firsts Poster has been created by The Office of School Services for students of all ages. The following lesson idea can motivate middle-level students to discuss and research the great state of Wisconsin.
- Begin the lesson by asking students these questions:
- What is change?
- Why is there change?
- Lead students to the idea that change can be anything new and innovative.
- Once students understand a good working definition of change, ask them if change will happen more easily if it benefits an individual or a large number of people? Why?
Now have students also generate a working definition for the word "progressive."
At this point, ask students to draw parallels between their working definitions of "change" and "progressive."
Enable students to understand that the state of Wisconsin is seen as a progressive state in many areas.
Display the Wisconsin Firsts poster to show the many Wisconsin Firsts. These "firsts" exhibit why Wisconsin is considered a progressive state.
Now ask students to brainstorm categories of "firsts" from the poster. Two categories that work well are "Inventions" and "Legislative Firsts." There will be a few "firsts" that will not fit into these two categories.
Direct individual or pairs of students to research the "first" of their choice. Their research should explain what the innovation was and its impact on industry and human rights, or laws.
The information from these reports can be related to middle school history curriculum such as Industrialism and Reforms in the United States.
- Help students to see that change is much easier on a society if many people benefit as opposed to a few. | <urn:uuid:89eb0c56-407c-4dd6-b2dd-d9e6cbb84e8a> | CC-MAIN-2013-20 | http://www.wisconsinhistory.org/teachers/lessons/secondary/firsts.asp | 2013-05-22T07:48:02 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368701459211/warc/CC-MAIN-20130516105059-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.953566 | 537 | 4.0625 | 4 |
In a typical year, it is not uncommon for a dozen or so comets to come within range of amateur telescopes. During the month of October, 2010, a small comet will pass unusually close to Earth. On Oct. 20, Comet Hartley 2 will pass just over 11 million miles (18 million km) from Earth. That is close enough for the comet to be seen through binoculars or even, in the darkest skies, with the naked eye.
Amateur stargazers aren’t the only ones looking out for Hartley 2 this month. In September 2007, NASA woke up its hibernating DI spacecraft and, in November, sent it the maneuvering instructions to intercept Hartley 2. The spacecraft is precisely on schedule to rendezvous with the comet on November 4 as it approaches the sun.
This week’s online current events activity is a study of comets, the Hartley 2 Comet, and NASA’s attempt to study it.
Begin your investigation into comets by visiting Worldbook@NASA, which features excellent overviews on many topics related to space and astronomy, including Comets. As you read this page, look for answers to the following questions:
- What are some of the ingredients that make up a comet?
- How big are most comets?
- How does a comet tail form, and which direction does it always point?
- What is the relationship between comets and meteor showers?
- What have scientists learned about the nucleus of a comet?
More information about comets can be found at the Nine Planets site. As you read, look for answers to these questions:
- Name two examples of comet appearances in antiquity (ancient human history)
- How many comets have been cataloged?
- What are the five parts of a comet?
- How do comets “die”?
Comet Hartley 2
Now that you have some solid background information about comets in general, let’s see what we can learn about Comet Hartley 2. Start by going to the web site of Sky and Telescope magazine, and read Comet Hartley 2 At Its Best, written by Greg Bryant. This first half of the page is an ongoing blog with dated status updates, followed by the original article. As you read, just understand that you are reading backwards in time.
When you get to the October 8 update, watch the wide-field animation created by Ernesto Guido and Giovanni Sostero. Can you see the slight movement of the comet against the stationary star field?
As you read the original article, look for answers to the following questions:
- In what year was Hartley 2 discovered?
- Why does the moon play a factor in viewing comets?
- What does the EPOXI spacecraft’s name stand for?
- How close will the spacecraft get to the comet?
- What does the number 2 mean in “Hartley 2”?
- Why was this comet beyond visual discovery until after 1982?
Learn more about the EXOXI mission by visiting the official mission web site. From the home page, click Mission on the left and read the 10 phases of the mission. What is the purpose of the Earth fly-bys? What happens during the Comet Approach Phase? What will scientists be looking for during the Encounter Phase? What data will be gathered?
Finish your online study of comets this week by Comparing Comets. This is a student activity developed by NASA in which students can make their own observations based on photos of two different comet nuclei. Print this worksheet or follow along online and record your answers separately. Follow the directions on each page. On page 2, as you are looking at the two photos of comet surfaces, listen to this audio recording of students making their own observations about the comets in a teacher-led discussion.
Comets are not easy to study. Because of their speed and orbit, it is (currently) impossible for humans to travel to comets to make firsthand observations. Instead, scientists send up remotely controllable probes to intercept comets, take photographs, and make a variety of different measurements. This practice is not limited to astronomers. For centuries humans have been creating tools used to measure, weigh, count, or in many other ways analyze things that are beyond our physical senses. In a current or recent issue of the e-edition, look for news stories that cite examples of people using tools to measure or analyze. A good example might be DNA testing for criminal evidence, but you will find many others. Based on your findings, how important have these tools become in our daily lives? Why is it becoming increasingly important to measure, collect, and analyze information? | <urn:uuid:bae30682-110c-416b-bf84-eaae0f65eb55> | CC-MAIN-2013-20 | http://cincinnati.com/niecincy/archive/2010/10/11/ | 2013-05-24T15:36:20 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368704713110/warc/CC-MAIN-20130516114513-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.945656 | 978 | 4.28125 | 4 |
Concept 39 A genome is an entire set of genes.
Cross pure-bred pea plants to identify dominant flower color.
HI! One of the first steps in locating a disease gene is screening families with the disease for markers that are linked to the gene. Scientists use short tandem repeats (STR) as markers. These repeats can vary from ten to hundreds of base pairs, and are usually found in multiple copies. Different people will have different numbers of these repeats. In this example, A has two copies and B has four copies of the tandem repeat. The DNA sequences flanking the repeats are unique sequences found in everyone. PCR primers can be made to the unique flanking sequences and the intervening fragments can be amplified. These fragments are different sizes because of the number of repeats present in the individuals. The size difference can be seen when the fragments are electrophoresed on a gel. Assuming that A and B are homozygous for the length of an STR, what would the gel pattern look like for their progeny C? No, if C is the progeny of A and B, then it should have both bands. No, if C is the progeny of A and B, then it should have two bands. No, if C is the progeny of A and B, then it should not have a different size band. A progeny from a cross between A and B will be heterozygous for the length of the STR. In other words, C will have the smaller-size fragment from A and the larger-size fragment from B. The size differences of STRs are markers that can be associated with the occurrence of a disease or genetic trait. Which of the following gels and associated pedigrees shows an STR linked with an autosomal, recessive disease gene? No, two affected individuals have different STR patterns; there is no linkage. No, two unaffected individuals have different STR patterns; there is no linkage. No, both the affected and unaffected parent have the same STR pattern; there is no linkage. In this example, the STR is linked to an autosomal, recessive disorder. Carriers and the affected individual all have the same STR fragment. This is only a very small sample size. Larger, multi-generational analysis can confirm the linkage of this STR with the disease trait. Gene hunters try to find two markers linked to one gene. Which two markers (labeled 1 and 2) will be most useful? Gene hunters look for markers that are tightly linked to the disease gene. This indicates that the gene is nearby. By finding two flanking markers, gene hunters narrow their search to a defined stretch of DNA. Though the flanking markers are relatively close together, there may be a million base pairs and a hundred genes to wade through. Your next step is to find the coding sequences in this region. First you need to clone the DNA between the two markers, and order them with additional markers. If your biggest clone is 150,000 bp, which of the following "clone maps" is most useful in your hunt? No, there are gaps between the clones. No, the clones are too big. Remember, you don't know where the gene is, so you have to clone the entire region. Overlapping clones are needed to put each clone in the proper order. Now, you need to locate the coding sequences on the clones. What method CANNOT be used to identify coding sequences? A) Look for hybridization between cloned DNA and a human cDNA library. (No, human cDNA will identify coding sequences by hybridization.) B) Look for hybridization between cloned DNA and DNA from other species. (No, DNA from other species will identify coding sequences by hybridization if the genes are conserved.) C) Sequence the clones and look for tell-tale signs of coding sequences. (No, common promoter sequences can be used to find the beginnings of coding sequences.) D) Look for hybridization between cloned DNA and DNA from patients with the disease. B and D. (No, only one of these is incorrect.) When using DNA instead of cDNA, hybridization will reveal noncoding as well as coding sequences. Suppose you get lucky, and your analysis only reveals three candidate genes. For each, you compare sequences of unaffected people and disease patients. Candidate Gene #1 No differences found. Candidate Gene #3 Disease patients are missing an exon. Candidate Gene #2 Single nucleotide polymorphisms found in some disease patients. Which candidate is most likely the disease gene? Candidate #1 No differences found. (No, that is incorrect.) Candidate Gene #2 Single nucleotide polymorphisms found in some disease patients. (No, that is incorrect.) Candidate Gene #3 Disease patients are missing an exon. (That is correct) Single nucleotide polymorphisms between the two groups — unaffected and disease individuals — do not always point to a disease gene. Remember, there are redundancies in the codons and some changes are tolerated. However, if an exon is missing, chances are the protein has been altered and this could lead to a disease phenotype. | <urn:uuid:59b92788-caf3-4195-b3ca-4aeaa8169a52> | CC-MAIN-2013-20 | http://dnaftb.org/39/problem.html | 2013-05-24T15:30:25 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368704713110/warc/CC-MAIN-20130516114513-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.936339 | 1,044 | 4.03125 | 4 |
Tuesday, April 19, 2011
Three Billion Years B.C.
As we turn back the cosmic clock the rate of accumulation of material increases. The pockmarked lunar surface has served as a proxy for reconstructing the history of asteroidal and cometary impact on the Earth. Without an atmosphere or significant geophysical activity the Moon has an excellent memory of impacts, while the Earth had eroded and resurfaced itself in continual reinvention. This record has indicated that during a period between about 4.1 and 3.8 billion years ago the Earth must have been subject to a particularly brutal pummeling. A substantial fraction of the outer shell of our planet could have been laid down during what has become known as the Late Heavy Bombardment.
It's a fascinating time in the history of our world. The first indications that microbial life might have been at work come not so very long after this quite cataclysmic episode ended.
The reason for this infall of material seems likely to be connected to a period of dynamical evolution in the outer planets. Models suggest that both Neptune and Uranus could have migrated outwards and dug into a rich belt of outer, Kuiper or trans-Neptunian objects. Many of those distant small bodies would have been pushed into orbital paths that would eventually lead to passage through the inner solar system and collision with the Earth. At the same time, Jupiter and Saturn would have migrated inwards and could have scattered material from the asteroid belt onto inbound trajectories. Once the dynamical reorganization of the giant planets was finished the Late Heavy Bombardment would have tailed off. A settling planet Earth then gave rise to the tentative steps of biochemistry and single-celled organisms.
Or so we thought. New evidence is emerging from the terrestrial rock record that the Earth actually continued to be pounded by very significant impacts from 3.8 billion years ago all the way up to around 2.5 billion years ago. "Life Killer" type asteroid impacts seem to have happened roughly every 40 million years during this timespan, rather than every 500 million years as had previously been thought.
So what gives? Where did these chunks of material come from? W. Bottke and colleagues have studied the gravitational dynamics of the teenage solar system and suggest that a now-depleted inner belt of material between Mars and Jupiter could have been scattered onto an inclined set of orbits - out of the plane of the planets. This population would then slowly "leak" into Earth-crossing paths, thereby greatly extending the tail of the Late Heavy Bombardment over another billion years or so. The leftovers of these bodies are still there, known as the Hungaria asteroids.
It all looks to fit rather well. The dynamics are believable, and provide a mechanism for the impacts that littered the planet with the molten globs of rock that geologists find in layers of ancient strata. There's just one teensy question. What are the implications for the evolution of life on Earth? While evidence of microbe-built structures like stromatolites from 3.5 to 3.8 billion years ago remain a little controversial, the presence of a diverse planet-wide biosphere is pretty incontrovertible in the 3 to 2.5 billion year ago span. Apparently microbial life not only dealt with continual destructive asteroid impacts but really did rather well for itself.
This raises another intriguing issue. As W. Bottke and colleagues point out, this prolonged period of heavy impacts does effectively stop around 2.5 billion years ago. That is suspiciously coincident with the first signs of a rising oxygen content in the Earth's atmosphere (the "Great Oxidation Event"), and the eventual emergence of multi-cellular life somewhere around 1.6 to 2 billion years ago. Is there a connection? Could the continual accumulation of planetary material have held back the full-on evolutionary party of early life? It's highly speculative, but one is tempted to think that this might be further evidence for the incredible resilience of life and its near-relentless nature once it becomes entrenched on a planet. | <urn:uuid:1c251bf2-0608-4aae-b35f-0909a02d592e> | CC-MAIN-2013-20 | http://lifeunbounded.blogspot.com/2011/04/three-billion-years-bc.html?showComment=1308169042689 | 2013-05-24T15:57:29 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368704713110/warc/CC-MAIN-20130516114513-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.961679 | 835 | 4 | 4 |
The factors behind the calving process were not well understood
US researchers have come up with a way to predict the rate at which ice shelves break apart into icebergs.
These sometimes spectacular occurrences, called calving events, are a key step in the process by which climate change drives sea level rise.
Computer models that simulate how ice sheets might behave in a warmer world do not describe the calving process in much detail, Science journal reports.
Until now, the factors controlling this process have not been well understood.
Ice sheets, such as those in Antarctica and Greenland, spread under their own weight and flow off land over the ocean water.
Ice shelves are the thick, floating lips of ice sheets or glaciers that extend out past the coastline.
Timelapse footage of an iceberg breaking away from a glacier in July 2008. The event took approximately 15 minutes (Video: Fahnestock/UNH)
The Ross Ice Shelf in Antarctica floats for as much as 800km (500 miles) over the ocean before the edges begin to break and create icebergs. But other ice shelves may only edge over the water for a few kilometres.
A team led by Richard Alley at Pennsylvania State University, US, analysed factors such as thickness, calving rate and strain rate for 20 different ice shelves.
"The problem of when things break is a really hard problem because there is so much variability," said Professor Alley.
"Anyone who has dropped a coffee cup knows this. Sometimes the coffee cup breaks and sometimes it bounces."
The team's results show that the calving rate of an ice shelf is primarily determined by the rate at which the ice shelf is spreading away from the continent.
The researchers were also able to show that narrower shelves should calve more slowly than wider ones.
Ice cracking off into the ocean from Antarctica and Greenland could play a significant role in future sea level rise.
Floating ice that melts does not of itself contribute to the height of waters (because it has already displaced its volume), but the shelf from which it comes acts as a brake to the land-ice behind. Removal of the shelf will allow glaciers heading to the ocean to accelerate - a phenomenon documented when the Larsen B shelf on the Antarctic Peninsula shattered in spectacular style in 2002. This would speed sea level rise.
The UN Intergovernmental Panel on Climate Change in its 2007 assessment forecast that seas could rise by 18 to 59 cm (7-23ins) this century. However, in giving those figures, it conceded that ice behaviour was poorly understood.
This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so. | <urn:uuid:345a4045-6f1f-4b6d-b5c0-385afebb5719> | CC-MAIN-2013-20 | http://news.bbc.co.uk/2/hi/science/nature/7753228.stm | 2013-05-24T15:30:04 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368704713110/warc/CC-MAIN-20130516114513-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.951253 | 592 | 4.1875 | 4 |
Prefixes, Suffixes, Inflectional Endings, and Root Words
Spelling Words Correctly Using Prefixes This strategy will focus on the prefix "re-" to help predict the meaning of words. The same strategy can be used to introduce other common prefixes such as "dis-", "in-" and "im-".
Prefixes and Suffixes Students will create two Mini Books. One will incorporate prefixes and the other will focus on suffixes. Each book will include the meanings, sample words, and two well- written sentences for each suffix or prefix. Also supports Tech COS 12
Making Singular Nouns Plural This lesson involves the use of the Structural Analysis element of the Inflectional Ending "-s" to make singular nouns plural.
Vocabulary Root Word Drawing A Lesson Plans Page lesson plan, lesson idea, thematic unit, or activity in Language Arts and Art called Vocabulary Root Word Drawing.
Forming Possessives Showing possession in English is a relatively easy matter (believe it or not). By adding an apostrophe and an s we can manage to transform most singular nouns into their possessive form:
Word Confusion: Students choose the correct word to complete the sentence in this online game.
Inflected Endings: Some languages, such as Chinese, Hmong, and Vietnamese do not use inflected endings to form verb tenses. Students may need help understanding that adding -ed to a verb indicates that the action happened in the past. Spelling changes in inflected verbs may be difficult for ELLs to master.
Prefixes and Suffixes: Some English prefixes and suffixes have equivalent forms in the Romance languages. For example, the prefix dis- in English (disapprove) corresponds to the Spanish des- (desaprobar), the French des- (desapprouver), and the Haitian Creole dis- or dez- (dezaprouve). Students who are literate in a Romance language may be able to transfer their understanding of prefixes and suffixes much easier than those from non-Romance languages.
E/B, D, E: Help ELLs classify English words into meaningful categories. Use word walls, graphic organizers, and concept maps to group related words, record them in meaningful ways, and create visual references that can be used in future lessons. Teachers can help students group and relate words in different ways. For example, place a large picture of a tree on the wall. Place prefix and suffix cards on the different branches (i.e. prefixes: pre-, re- un-; suffixes: -ful, -less) and root words on the roots (write, view, paint). This visual representation can help students conceptualize that prefixes and suffixes are added on to root words.
E/B, D, E: The teacher creates a display of words containing Greek and Latin roots and adds to it during the school year. ELLs can refer to the display to help in understanding new words. (Example of display: the tree display above, or a poster with three columns - Root, Meaning, and Word, i.e. aqua, water, aquarium)
E/B: Read one's own writing or simple narrative text and begin to produce phonemes appropriately.
E/B: Recognize and produce English phonemes students already know, and possibly use them in simple phrases or sentences.
E/B: Recognize sounds in spoken words with accompanying illustrations
E/B: Use cues for sounding out unfamiliar words with accompanying illustrations
E/B: Blend sounds together to make words, shown visually
D: Remove or add sounds to existing words to make new words, shown visually (i.e. "Cover up the t in cart. What do you have now?")
D: Use letter-sound relationships and word roots to produce and understand multi-syllabic words; E: Use letter-sound relationships and word roots to produce and understand new word families.
D, E: Recognize and use prefixes and suffixes to find meanings of unknown words.
E: Segment illustrated sentences into words and phrases.
E: Identify and analyze sentence and context clues to find meanings of unknown words.
E/B, D, E: When sharing new vocabulary words, make sure to write each word divided into syllables (i.e. dic-tion-ar-y). When introducing each word, sound it out, pausing between each syllable, and then blend the syllables together. Have students repeat after you. Ask students how many syllables the word has. Tell students: Pay attention to the syllables in a word. This will help you spell the word, and it will help you pronounce it, too.
E/B, D, E: Before teaching the phonics skills, introduce the target words orally to students by using them in activities such as chants and riddle games, or asking and answering questions that use the words.
Some of the above ELL suggestions came from the following resources:
WIDA Consortium's English Language Proficiency Standards and Resource Guide, PreK - Grade 12
Scott Foresman Reading Street ELL and Transition Handbook Grades 3-6
A Guide to the Standard Course of Study for Limited English Proficient Students / Grades K-5 (Public Schools of N.C.) | <urn:uuid:facadd23-cb41-43f7-ae40-908f685d2f5d> | CC-MAIN-2013-20 | http://trip.schoolinsites.com/Default.asp?PN=Pages&SubP=Level2&DivisionID='3932'&DepartmentID='3769'&SubDepartmentID=''&PageID='6099'&SubPageID='4149' | 2013-05-24T15:43:09 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368704713110/warc/CC-MAIN-20130516114513-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.882967 | 1,126 | 4.59375 | 5 |
Although researchers can't be exactly sure how old the bacteria are — or how they reproduce — microbiologists at Aarhus University in Denmark posit that the ancient organisms could be anywhere from several thousand to millions of year old, The Washington Post's Joel Achenback reports.
The bacteria, found living in sediments that formed 86 million years ago, have extremely slow metabolisms and are able to survive by living on very small amounts of energy.
"The slow rate of reproduction means that they cannot evolve at the same speed as bacteria in friendlier, energy-rich, nutrient-thick settings. That means, in turn, that they may preserve more primitive genetic features than other bacteria," scientist Robert Hazen told Achenback.
The ability of bacteria to stay alive in such a nutrient-starved environment supports the idea that similar organisms could live on other planets, requiring very little to sustain life. | <urn:uuid:dcd7cbcc-ad75-4944-973e-9572ff78a9ba> | CC-MAIN-2013-20 | http://www.businessinsider.com/bacteria-found-under-the-ocean-floor-hasnt-had-fresh-food-since-the-age-of-the-dinosaurs-2012-5 | 2013-05-24T15:57:12 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368704713110/warc/CC-MAIN-20130516114513-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.95476 | 183 | 4.0625 | 4 |
The ecliptic is the geometric plane that contains the orbit of the Earth. The orbits of most planets in the Solar System lie very close to it. Seen from the Earth, this is a bisecting great circle, superimposed upon the celestial sphere, which contains the different points of the Sun's path, relative to the background stars, over the course of a year. The zodiac also lies along the ecliptic plane. The ecliptic plane is inclined by ~23.5°, with respect to the celestial equator; a result of axial tilt. The orbital plane of Luna is inclined by ~5°, with respect to the ecliptic.
The plane of the Ecliptic is well seen in this picture from the 1994 lunar prospecting Clementine spacecraft. Clementine's camera reveals (from right to left) the Moon lit by Earthshine, the Sun's glare rising over the Moon's dark limb, and the planets Saturn, Mars and Mercury (the three dots at lower left).
Because there are ~365.25 days in a year and 360 degrees in a circle, the Sun appears to move along the ecliptic at a rate of about 1° per day. This motion is from west to east, in opposition to the apparent east-west movement of the celestial sphere.
The ecliptic and the celestial equator intersect at two points, directly opposite one another. These are the equinoxes and when the Sun appears at these points, day and night are each about 12 hours long at all locations on Earth.
The point on the ecliptic that is farthest north of the celestial equator is called the summer solstice in the northern hemisphere, and the winter solstice in the southern hemisphere. When the Sun is farthest south of the celestial equator the reverse is true. | <urn:uuid:32dbb9c8-2347-4665-89b2-bf09d902a84a> | CC-MAIN-2013-20 | http://www.neohumanism.org/e/ec/ecliptic.html | 2013-05-24T15:56:57 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368704713110/warc/CC-MAIN-20130516114513-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.943708 | 383 | 4.21875 | 4 |
I have chosen to study the history of stone walls in the town of Thompson, Conn. Many of the stone walls have a historical perspective behind them, and to know how they were built can be interesting. Many were used as lines of demarcation, and still stand in their original form today.
Stone walls are the boundaries in fields built by the first settlers in the area. Fields were cleared of trees; many were plowed and planted, and "rockpicked."
(Connecticut Past and Present, prologue)
Wherever we see a stone wall today, there had to have been a field. These stone walls stand as evidence that many people lived off the rocky land in New England.
According to one author, Curtis Fields, the following steps should be considered in the careful construction of stone walls:
Many of the stonewalls which were built have markings with initials, and these initials, usually on a square stone, tell who built them and in what year (McGee 87). A great amount of human strength went into the building of these walls. "The early craftsman took thirty minutes to drill a hole through a stone and hundreds of hammer blows on a three-foot, star-pointed iron drill, turning the drill with a slight twist of the wrist between blows." (McGee 86. Each stone wall was prepared by a trench a foot wider than the top stones, and two feet deep for the foundation. These stone walls would not be standing today if it were not for these underground bases.
A good stone wall is said to last a couple of hundred years. Many of the stone walls are two feet wide at the top and five feet high in some places. Many were built by Civil War veterans in the 19th century.
"Some of the stone walls in Connecticut towns contain, it has
been estimated, over six thousand tons of rock, averaging
forty inches wide and rise as high as six feet to form an even
surface without mortar in its entire length, with each stone
used as fitting tightly, most of the stones having been cut to
size and shape in a quarry." (McGee 87)
Thompson contains many packets of swampland and wetlands, and these swamp areas are said to be a product of the last "ice-age." (McDonough 18) Glacial ice sheets wore down hills and left mounds of debris which blocked drainage and formed the wetlands. The glacial sheets also were known to have stripped away much of the topsoil, and left behind what is known as "glacial till."
"Till is a chaotic mixture of sand, clay, silt and --most notably-- rocks of all sizes and description." (McDonough 18). It is this glacial debris that has been held responsible for bent plows, and curses over the last three centuries. A nineteenth-century journalist, John Warner Barber, describes Thompson's soil in this manner: "There is a great supply of valuable stone for walls and buildings..." (McDonough 19) Another historian gave the opinion that the town's fields were so burdened with stone that cultivation was seen as impossible. (McDonough 19).
As I began my journey investigating the stone walls in Thompson, I found it fascinating to see the different widths and heights of these walls. The set of stone walls in Rte. 200 were used as a trail-guide, for it was these walls that settlers followed into neighboring towns in Massachusetts. These stone walls I found to be in excellent shape, and I found from talking to local townspeople, many folks have contributed to keeping them rebuilt.
I began to notice different types of stone used depending upon where the wall was built. Many of the stone walls built around farms seemed to be made from rounded stones,
and the ones around the center of town were flatter. The old town library was mostly made from round stones, and the foundation was flat stones. The stone walls built around farms were also narrow, and most were not very high.
I found a few walls in the woods that were quite wide, and built mostly of flat stones. In this one section, the walls seemed to divide at one point, and then rejoin.
I was disappointed not to find as much historical information as I had anticipated. I enjoyed this study, and enjoyed both the research and the picture taking involved.
Click on Any Thumbnail Below
Fields, Curtis, The Forgotten Art of Building a Stone Wall
Maine: Yankee Books, 1971.
Mc Donough, Mark, Townside Historical and Architectural Survey of
Thompson, CT. July 1986.
Mc Gee, Donald J. Towers of Brick, Walls of Stone: A History of the
Textile industry in New England with Thompson CT. as a Prism
of the Factory Town. New York: Vintage Press, 1991.
Shepard, Odell, Connecticut Past and Present.
Canada: Ryerson Press, 1939.
Click Here to Go Back... | <urn:uuid:15fa7879-f139-4d62-8ff4-5af8ed272993> | CC-MAIN-2013-20 | http://www.qvcc.commnet.edu/brian/smith/stone.html | 2013-05-24T15:29:08 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368704713110/warc/CC-MAIN-20130516114513-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.978422 | 1,028 | 4.09375 | 4 |
The Age of Reason, as it was called, was spreading rapidly across Europe. In the late 17th century, scientists like Isaac Newton and writers like John Locke were challenging the old order. Newton's laws of gravity and motion described the world in terms of natural laws beyond any spiritual force. In the wake of political turmoil in England, Locke asserted the right of a people to change a government that did not protect natural rights of life, liberty and property. People were beginning to doubt the existence of a God who could predestine human beings to eternal damnation and empower a tyrant for a king. Europe would be forever changed by these ideas.
In America, intellectuals were reading these ideas as well. On their side of the Atlantic, Enlightened ideas of liberty and progress had a chance to flourish without the shackles of Old Europe. Religious leaders began to change their old dogmatic positions. They began to emphasize the similarities between the Anglican Church and the Puritan Congregationalists rather than the differences. Even Cotton Mather, the Massachusetts minister who wrote and spoke so convincingly about the existence of witches advocated science to immunize citizens against smallpox. Harvard ministers became so liberal that Yale College was founded in New Haven in 1707 in an attempt to retain old Calvinist ideas. This attempt failed and the entire faculty except one converted to the Church of England in 1722. By the end of the century, many New England ministers would become Unitarians, doubting even the divinity of Christ.
New ideas shaped political attitudes as well. John Locke defended the displacement of a monarch who would not protect the lives, liberties, and property of the English people. Jean-Jacques Rousseau stated that society should be ruled by the "general will" of the people. Baron de Montesquieu declared that power should not be concentrated in the hands of any one individual. He recommended separating power among executive, legislative, judicial branches of government. American intellectuals began to absorb these ideas. The delegates who declared independence from Britain used many of these arguments. The entire opening of the Declaration of Independence is Thomas Jefferson's application of John Locke's ideas. The constitutions of our first states and the United States Constitution reflect Enlightenment principles. The writings of Benjamin Franklin made many Enlightenment ideas accessible to the general public.
The old way of life was represented by superstition, an angry God, and absolute submission to authority. The thinkers of the Age of Reason ushered in a new way of thinking. This new way championed the accomplishments of humankind. Individuals did not have to accept despair. Science and reason could bring happiness and progress. Kings did not rule by divine right. They had an obligation to their subjects. Europeans pondered the implications for nearly a century. Americans put them into practice first. | <urn:uuid:0d886c6c-db7f-47ef-9267-c6e050d8d105> | CC-MAIN-2013-20 | http://www.ushistory.org/us/7a.asp | 2013-05-24T15:30:16 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368704713110/warc/CC-MAIN-20130516114513-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.960294 | 560 | 4 | 4 |
The Array object is used to store multiple values in a single variable.
Create an array, and assign values to it:
You will find more examples at the bottom of this page.
An array is a special variable, which can hold more than one value at a time.
If you have a list of items (a list of car names, for example), storing the cars in single variables could look like this:
However, what if you want to loop through the cars and find a specific one? And what if you had not 3 cars, but 300?
The solution is an array!
An array can hold many values under a single name, and you can access the values by referring to an index number.
An array can be created in three ways.
The following code creates an Array object called myCars:
You refer to an element in an array by referring to the index number.
This statement access the value of the first element in myCars:
This statement modifies the first element in myCars:
| is the first element in an array. is the second . . . . . (indexes start with 0)|
Because of this, you can have variables of different types in the same Array.
You can have objects in an Array. You can have functions in an Array. You can have arrays in an Array:
The Array object has predefined properties and methods:
For a complete reference of all properties and methods, go to our complete Array object reference.
The reference contains a description (and more examples) of all Array properties and methods.
The example above makes a new array method that transforms array values into upper case.
Your message has been sent to W3Schools. | <urn:uuid:ce9fe621-e329-44db-acf6-98f01c2ee7b3> | CC-MAIN-2013-20 | http://www.w3schools.com/jS/js_obj_array.asp | 2013-05-24T16:04:56 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368704713110/warc/CC-MAIN-20130516114513-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.869112 | 360 | 4.28125 | 4 |
|Life depends on an essentially continuous exchange of
mass and energy between living organisms and their environment.
Human impact on this vital exchange has occurred on a global or
macroclimate scale. Understanding the physical principles
involved in heat transfer and absorption in the atmosphere is critical
to understanding how these physical factors affect living
organisms. The specific objectives of this section are to explain
the properties of heat transfer, and to describe laboratory activities
that can be used at a variety of academic levels with only slight
Described below are three series of experiments performed in
the laboratory to address questions that emphasize the underlying
principles of heat transfer. These hands-on experiments focused
on principles that relate to conduction and convection. The object was to identify the method of heat transfer
through solids, liquids, gases, and between boundaries.
Understanding these concepts gave us a better understanding of how heat
is transferred between our environment and living
organisms. These experiments were used as an integral part
of the workshop, which consisted of reflections on redesigning or
modifying lab exercises to fit personal needs of workshop
teachers. These exercises could be adapted for middle
school, high school, and college level courses.
The methods utilized for the three experiments involved increasing
or decreasing the temperature of a solid or liquid, and where
applicable, observing the motion of a dye caused by the changes in
temperature and density of the medium.
|Modes of Heat Transfer:
- Conduction: heat transfer resulting from direct contact
between substances of different temperatures; heat is transferred
from the high-temperature substance to the low by direct molecular
- Convection: heat transport by a moving fluid (gas of
liquid). The heat is first transferred to the fluid by
conduction, but the fluid motion carries the heat away.
- Radiative exchange: heat transfer via electromagnetic
waves, the amount of radiant energy emitted, transmitted, or
(Figure from Microsoft Encarta)
Return to Top
Laboratory Apparatus for Labs 1-3
|Lab 1: Heating
from Below: Convection
In this experiment, water was heated from below to produce
convection. Although the atmosphere is composed of air, this
experiment was relevant to atmospheric motion as well. The lower
atmosphere (troposphere) is mostly heated from below because the
oceans and continents absorb radiation from the sun and then transfer
some of the resulting heat energy to the lower atmosphere.
In Lab 1, a beaker was heated (see figure below). Thermometers were placed in 1/2 cm
below water surface and 1/2 cm above the bottom of the beaker.
The temperature was recorded at 30 second intervals. Drops of
dye were added to the bottom of the beaker between intervals.
After three minutes the beaker was removed from the hot plate and
temperature reading recorded for another five minutes.
Convection was visualized by observing the motion of the
The motion of the dye was circular from bottom to top and returning to
the bottom of the beaker. The energy from heating created a less
dense liquid at the bottom, thus causing the upward motion of the
dye. Upon reaching the surface, the dye was now in the denser
medium and therefore returned to the bottom. This motion is an
example of convection. This phenomenon is evident in the motion
of wind. The difference in densities and kinetic movement of the
water molecules driven by temperature change resulted in the movement of
air molecules. This lab can be used at lower levels to
demonstrate simple properties of heat transfer and convection.
At higher levels, this lab illustrates these basic principles, and
could be extended to address more complex applications related to
convection such as the Coriolis
1. Explain the process by which the water is heated.
2. Describe the motion of the water as made visible by the
3. Why does convection occur?
4. Did convection cease? When? Why?
Environmental Applications of Principles
of Radiative Exchange, Conduction and Convection (Figure from E. Zerba, Princeton University; [email protected])
Return to Top
|Lab 2: Conduction
Comparison of this experiment with the first illustrated the
difference between the rate of heat transfer by conduction and that of
convection. It also illustrated the difference in heat
capacities between water and the solid materials of the
Lab 2 was configured similarly to Lab 1, but looked at the effect of
heating and cooling temperature difference using sand of equal weight
as water used in experiment 1. No dye was used in this experiment, as convection was not a
The temperature difference between the top and bottom layers of sand
indicated that sand heats and cools at a faster rate compared to
water. When the beaker was removed from the heat, the
temperature continued to increase via conduction from the bottom of the
beaker. This lab exercise is useful for demonstrating the concept of conduction to lower level students. Upper level
students can use this lab to make the connections between conduction and
heat capacity of various substances related to heat transfer that occurs between the
earth's surfaces and the surface of living organisms.
1. Is there any convection in the sand? Explain.
2. Why did the temperature recorded by the lower thermometer
continue to rise dramatically after the heating ceased?
3. On the basis of heat capacity, explain why the temperature
changes for the sand and water were different.
4. Using what you have observed in the two experiments, predict
whether a cold front will lower temperatures more at inland locations
or on the coast. Explain your answer.
Return to Top
|Lab 3: Cooling From Above
In lakes and oceans, convection is generally the result of cooling
from above rather than heating from below. This was demonstrated
by adding ice to the water.
Using an experimental setup that allowed
measurement of temperature at the top and the bottom of a beaker of
water, ice was added to the top of the beaker. This experiment
illustrated the concept that at 4 °C, water
has higher density and sinks. Convection was
visualized by the movement of dye added to the bottom of the beaker
which was displaced by the cooler more dense water.
This lab demonstrates several physical principles associated with heat
transfer, including density, kinetic molecular theory, and
convection. On a larger scale, this laboratory exercise
demonstrates the process by which seasonal turnovers occur in ponds
and lakes. At
lower levels, teachers may choose to discuss physical principles of
heat transfer only, while at upper levels, teachers may choose to
integrate this small-scale investigation with the study of climate
processes and lake nutrient stratification and mixing.
1. Why does ice float?
2. Is there any evidence of convection? Why does or does
it not occur?
3. Draw a diagram to explain how seasonal turnover occurs in a
Return to Top
to The Passerine Birds home | <urn:uuid:77831d47-ed83-47e1-aa8f-16bc431d8619> | CC-MAIN-2013-20 | http://www.woodrow.org/teachers/esi/2001/Princeton/Project/zerba/activities/activities.htm | 2013-05-24T15:43:44 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368704713110/warc/CC-MAIN-20130516114513-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.932497 | 1,503 | 4 | 4 |
Introduction to Enzymes
The following has been excerpted from a very popular Worthington publication which was originally published in 1972 as the Manual of Clinical Enzyme Measurements. While some of the presentation may seem somewhat dated, the basic concepts are still helpful for researchers who must use enzymes but who have little background in enzymology.
Enzyme Kinetics: Energy Levels
Chemists have known for almost a century that for most chemical reactions to proceed, some form of energy is needed. They have termed this quantity of energy, "the energy of activation." It is the magnitude of the activation energy which determines just how fast the reaction will proceed. It is believed that enzymes lower the activation energy for the reaction they are catalyzing. Figure 3 illustrates this concept.
The enzyme is thought to reduce the "path" of the reaction. This shortened path would require less energy for each molecule of substrate converted to product. Given a total amount of available energy, more molecules of substrate would be converted when the enzyme is present (the shortened "path") than when it is absent. Hence, the reaction is said to go faster in a given period of time. | <urn:uuid:cb68bdbc-cf40-4d1b-ba86-741aa42fc245> | CC-MAIN-2013-20 | http://www.worthington-biochem.com/introbiochem/energy.html | 2013-05-24T15:29:41 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368704713110/warc/CC-MAIN-20130516114513-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.966327 | 234 | 4.09375 | 4 |
A thorough knowledge of the root system of plants is
essential if their growth, flowering, and fruiting responses are
to be understood. The structure and growth habits of roots have a
pronounced effect on the size and vigor of the plant, method of
propagation, adaptation to certain soil types, and response to
cultural practices and irrigation. The roots of certain vegetable
crops are important as food. Roots typically originate from the
lower portion of a plant or cutting. They possess a root cap, have
no nodes and never bear leaves or flowers directly. The principal
functions of roots are to absorb nutrients and moisture, to anchor
the plant in the soil, to furnish physical support for the stem,
and to serve as food storage organs. In some plants they may be
used as a means of propagation.
Types of Roots
A primary (radicle) root originates at the lower end of
the embryo of a seedling plant. A taproot is formed when the
primary root continues to elongate downward. This makes them
difficult to transplant and necessitates planting only in deep,
well-drained soil. The taproot of carrot, parsnip, and salsify
is the principal edible part of these crops.
A lateral, or secondary root is a side or
branch root which arises from another root. A fibrous root
system is one in which the primary root ceases to elongate,
leading to the development of numerous lateral roots. These then
branch repeatedly and form the feeding root system of the plant. A
fibrous root is one which remains small in diameter because of a
lack of significant cambial activity. One factor which causes
shrubs and dwarf trees to remain smaller than standard trees is
the lower activity rate of the cambium tissue which produces a
smaller root system.
If plants that normally develop a taproot are undercut
so that the taproot is severed early in the plants life, the
root will lose its taproot characteristic and develop a fibrous
root system. This is done commercially in nurseries so that trees,
which naturally have tap roots, will develop a compact, fibrous
root system. This allows a higher rate of transplanting success.
The quantity and distribution of plant roots is very
important because these two factors have a major influence on the
absorption of moisture and nutrients. The depth and spread of the
roots is dependent on the inherent growth characteristics of the
plant and the texture and structure of the soil. Roots will
penetrate much deeper in a loose, well-drained soil than in a
heavy, poorly-drained soil. A dense, compacted layer in the soil
will restrict or stop root growth.
During early development, a seedling plant nutrients
and moisture from the few inches of soil surrounding it.
Therefore, the early growth of most horticultural crops which are
seeded in rows benefits from band applications of fertilizer,
placed several inches to each side and slightly below the seeds.
As plants become well-established, the root system
develops laterally and usually extends far beyond the spread of
the branches. For most cultivated crops roots meet and overlap
between the rows. The greatest concentration of fibrous roots
occurs in the top foot of soil but significant numbers of laterals
may grow downward from these roots to provide an effective
absorption system a couple of feet deep.
Parts of a Root
Internally, there are three major parts of a root. The meristem
is at the tip and manufactures new cells. It is an area of cell
division and growth. Behind it is the zone of elongation,
in which cells increase in size through food and water absorption.
These cells by increasing in size, push the root through the soil.
The third major root part is the maturation zone, in which
cells undergo changes in order to become specific tissues such as
epidermis, cortex, or vascular tissue. The epidermis is the
outermost layer of cells surrounding the root. These cells are
responsible for the absorption of water and minerals dissolved in
water. Cortex cells are involved in the movement of water from the
epidermis and in food storage. A layer of suberized (a fatty
material in some cells), known as the Casparian strips, has
regulatory effect on the types of minerals absorbed and
transported by the roots to stems and leaves.
Vascular tissues conduct food and water and are
located in the center of the root. However, some monocots have the
vascular system of their roots distributed around the root center.
Externally there are two areas of importance. Root
hairs are found along the main root and perform much of the actual
work of water and nutrient absorption. The root cap is the
outermost tip of the root, and consists of cells that are sloughed
off as the root grows through the soil. The root cap covers and
protects the meristem and also senses gravity and directs in what
direction the root grows.
Roots as Food
The enlarged root is the edible portion of several vegetable
crops. The sweet potato is a swollen root, called a tuberous root,
which serves as a food storage area for the plant. Carrot,
parsnip, salsify, and radish are elongated taproots. | <urn:uuid:0eca56df-1124-4677-b593-dc9ee2f39c81> | CC-MAIN-2013-20 | http://ag.arizona.edu/pubs/garden/mg/botany/roots.html | 2013-06-19T06:01:57 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368708142388/warc/CC-MAIN-20130516124222-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.931994 | 1,139 | 4.1875 | 4 |
Karst diagram courtesy of Vancouver Island University.
Although the Cowling Arboretum does not exhibit any karst topography, much of Southern Minnesota does. Karst is a geological feature formed by the dissolution of soluble bedrock such as carbonates like limestone and dolostone. Karst formations lead to the formations of caves, disappearing streams, underground streams, sinkholes and other landforms in Southern Minnesota. The longest cave system in the world, the Mammoth-Flint Ridge Cave System in Kentucky was formed through the dissolution of carbonate rocks in its karst area.
Karst country in Southern Minnesota coincides with the Driftless Area that covers Southeastern Minnesota, Northwestern Iowa and Western Wisconsin. Glacial drift no younger than 500,000 years old has been discovered in Southern Minnesota Driftless Area, meaning it has not been glaciated in that time. Other geologists believe that the Driftless Area has not been glaciated in at least 2 million years. However, the Driftless Area has been subject to glacial lake outburst floods when titanic lakes like proglacial Lake Duluth began to cataclysmically drain about 9,500 years ago.
Karst forms when slightly acidic water meets a weakly soluble carbonate rock. Rainwater acidifies ever so slightly as it passes through the atmosphere and takes up CO2. As rainwater travels through the soil it picks up more CO2 and forms a weak carbonic acid solution, which readily dissolves carbonate rocks over time. Limestone is removed from the site in the form of calcium and bicarbonate.
A good way to spot a karst sinkhole in Southern Minnesota is to look for a tree covered area in the middle of a farmer’s field that she is wise not to plow.
- Callum McCulloch '15, for the Cole Student Naturalists | <urn:uuid:0e553886-7f5e-4949-ab87-98b017803aba> | CC-MAIN-2013-20 | http://apps.carleton.edu/campus/arb/programs/student_naturalists/arbtalk/?story_id=950716 | 2013-06-19T06:04:24 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368708142388/warc/CC-MAIN-20130516124222-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.938945 | 380 | 4.09375 | 4 |
In Journey into the Cell, we looked at the structure of the two major types of cells: prokaryotic and eukaryotic cells. Now we turn our attention to the "power houses" of a eukaryotic cell, the mitochondria.
Mitochondria are the cell's power producers. They convert energy into forms that are usable by the cell. Located in the cytoplasm, they are the sites of cellular respiration which ultimately generates fuel for the cell's activities. Mitochondria are also involved in other cell processes such as cell division and growth, as well as cell death.
Mitochondria: Distinguishing Characteristics
Mitochondria are bounded by a double membrane. Each of these membranes is a phospholipid bilayer with embedded proteins. The outermost membrane is smooth while the inner membrane has many folds. These folds are called cristae. The folds enhance the "productivity" of cellular respiration by increasing the available surface area.
The double membranes divide the mitochondrion into two distinct parts: the intermembrane space and the mitochondrial matrix. The intermembrane space is the narrow part between the two membranes while the mitochondrial matrix is the part enclosed by the innermost membrane. Several of the steps in cellular respiration occur in the matrix due to its high concentration of enzymes.
Mitochondria are semi-autonomous in that they are only partially dependent on the cell to replicate and grow. They have their own DNA, ribosomes and can make their own proteins. Similar to bacteria, mitochondria have circular DNA and replicate by a reproductive process called fission.
Journey into the Cell:
To learn more about cells, visit: | <urn:uuid:725b19ff-601b-4c5b-9e4d-2293b902f895> | CC-MAIN-2013-20 | http://biology.about.com/od/cellanatomy/ss/mitochondria.htm | 2013-06-19T06:02:09 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368708142388/warc/CC-MAIN-20130516124222-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.939032 | 351 | 4.0625 | 4 |
Want to know how to conquer kids' learning obstacles? If after
every lesson your kids can say, "We came, we saw, we heard, we
touched," they'll also be able to say, "We conquered!"
Kids experience their world through their senses, and each child
has a favored sense that sends more information to the brain than
the other senses.
The three primary perceptual preferences or "learning styles" are
visual, auditory and kinesthetic.
By understanding these three learning styles, you can create
lessons that'll give all your children a better chance of
*Characteristics-Visual learners need to see or observe
things closely. Visual learners recognize words by sight, remember
faces but forget names, take notes, make lists, have vivid
imaginations and think in pictures. Visual learners express emotion
through facial expressions.
Jonna is a visual learner. She's distracted by visual disorder or
movement and prefers a neat, meticulous environment. She doesn't
talk at length and becomes impatient when she has to listen for a
long time. While her teacher lectures, Jonna will stare, daydream
*Lesson Design-In every lesson, provide pictorial or
graphic representations and demonstrations. Allow visual learners
to read and look at illustrations, charts and other visual aids.
Don't just tell kids about a topic, but allow them to also read
*Characteristics-Auditory learners learn best by reading
aloud or listening. Auditory learners remember things they hear
better than things they see. These students move their lips or
subvocalize as they talk out situations and problems. They hum and
are easily distracted by sounds. They remember names by auditory
repetition but forget faces. Auditory learners express emotion
verbally through changes in tone, volume and pitch of voice.
Brad is an auditory learner. He often talks to others during class
because, even though he enjoys listening, he can't wait to talk.
Brad enjoys the sound of his own voice.
*Lesson Design-Provide opportunities for kids to listen
to oral reading or a taped presentation. Ask questions and form
group discussions to get these kids talking. Encourage dramatic
presentations or role-plays. Always read aloud any
*Characteristics-Kelly is a kinesthetic learner. She sits
at the front of a group so she can touch the object of the lesson.
In a line, Kelly is frequently told to "keep your hands to
yourself!" Kinesthetic learners enjoy touching or doing things.
These children aren't attentive to visual or auditory presentations
and so seem distracted.
Kinesthetic learners attack problems physically, impulsively
trying things out-touching, feeling and manipulating. When bored,
they fidget or find reasons to move. When happy, they jump for joy.
When angry, they stomp off.
*Lesson Design-Structure "real-life" situations such as
field trips and allow kids to make things. Give these kids objects
to touch or feel what they're learning about. Make lessons active
by having kids play educational games or run relays.
Joyce Platek works with children in Ohio.
Copyright© 1992 Group Publishing, Inc. / Children's Ministry | <urn:uuid:31b12466-250b-4389-a5cb-2c260620247c> | CC-MAIN-2013-20 | http://childrensministry.com/articles/how-to-tailor-your-lessons-to-kids-learning-styles | 2013-06-19T14:31:26 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368708142388/warc/CC-MAIN-20130516124222-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.92921 | 684 | 4.25 | 4 |
In fourth grade, students learn to use a variety of sentence structures in their narratives, summaries, responses to literature and information reports. They learn to use compound sentences, and may also learn to use complex sentences. Students learn to combine short, related sentences with appositives, participial phrases, adjectives, adverbs, and prepositional phrases. When introducing a new type of sentence structure, the teacher should provide adequate practice in writing sentences before requiring students to use the new sentence type in writing passages. Those assignments should be structured to prompt usage of the new sentence type. In addition, the teacher should provide adequate cumulative review to facilitate understanding and retention as well as exercises requiring the students to revise existing passages by combining sentences and thereby create a new type of sentence structure. Students should be taught not only how to create new sentence types but when to use them. For example, some students will need careful instruction to determine when words, phrases, or clauses should be joined by and, or, or but.
the Reading/Language Arts Framework for California Public Schools) | <urn:uuid:177b0b71-a442-4447-9a6f-fb432a48c646> | CC-MAIN-2013-20 | http://dixiesd.marin.k12.ca.us/dixieschool/classrooms/Rechtfertig/sentstructure.html | 2013-06-19T14:19:06 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368708142388/warc/CC-MAIN-20130516124222-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.934725 | 215 | 4.4375 | 4 |
The number of hurricanes occurring annually on a global basis varies widely from ocean to ocean. Globally, about 80 tropical cyclones occur annually, one-third of which achieve hurricane status. The most active area is the western Pacific Ocean, which contains a wide expanse of warm ocean water. In contrast, the Atlantic Ocean averages about ten storms annually, of which six reach hurricane status. Compared to the Pacific Ocean, the Atlantic is a much smaller area, and therefore supports a smaller expanse of warm ocean water to fuel storms. The Pacific waters also tend to be warmer, and the layer of warm surface waters tends to be deeper than in the Atlantic. The frequency and intensity of hurricanes varies significantly from year to year, and scientists haven’t yet figured out all the reasons for the variability.
Hurricanes and El Niño
Scientists continue to investigate the interactions between hurricane frequency and El Niño. El Niño is a phenomenon where ocean surface temperatures become warmer than normal in the equatorial East Pacific Ocean. In general, El Niño events are characterized by an increase in hurricane activity in the eastern Pacific and a decrease in activity in the Atlantic, Gulf of Mexico, and the Caribbean Sea. During El Niño years, the wind patterns are aligned in such a way that there is an increase in vertical wind shear (upper level winds) over the Caribbean and Atlantic. The increased wind shear helps to prevent tropical disturbances from developing into hurricanes. Oppositely, in the eastern Pacific, El Niño alters wind patterns in a way that reduces wind shear, contributing to more storms.
Hurricanes and Global Warming
Since warm ocean waters and warm, moist air fuel storms, theory predicts that global warming should increase the number and intensity of tropical cyclones. As the oceans soak up extra heat from the atmosphere, ocean surface temperatures rise, increasing the extent of warm water that can support a hurricane. Not only should this mean that more hurricanes can form, but increased ocean surface temperatures could also increase a storm’s maximum potential intensity, the strongest a storm can get in ideal conditions.
Models based on scientists’ current understanding of hurricanes suggest that if ocean temperatures increased by 2-2.5 degrees, the average intensity of hurricanes would increase by 6 to 10 percent. Since 1970, the average ocean temperature has warmed about half a degree, which means that theoretically, storms could be one to three percent stronger. Such an increase translates to a few knots in wind speed, too small a change to accurately measure. Hurricane wind speeds have historically been measured in increments of five knots, so any increase in intensity that has already occurred as a result of global warming would, in theory, be too small to detect yet.
However, in 2005 and 2006, several studies suggested that global warming may be impacting hurricanes more than theory predicts. In an analysis of the historical record, there appeared to be an increase in the number of intense (Category 4 and 5) storms in recent years. Another analysis charted sea surface temperatures and the number of tropical cyclones. It revealed that as sea surface temperatures went up, the number of cyclones went up. Was the increase in sea surface temperatures responsible for the increased number of storms or did some outside factor drive both?
The studies triggered many questions. Both theory and the studies suggested that there should be a link between global warming and hurricanes, but the studies showed a much greater increase in storm frequency and intensity than theory predicted. What caused the discrepancy? Is humanity’s current understanding of hurricanes flawed? Can the theory be adjusted to explain why hurricanes would have a stronger reaction to warming than previously predicted?
One theory put forth to explain the recent increase in storm intensity and frequency in the Atlantic basin is the multi-decadal oscillation. Storms in the Atlantic may go through a natural cycle of 20-30 years of increased activity followed by a quieter period. The record seems to show such a cycle, with more intense hurricanes in the 1950s and 1960s followed by two decades of relative quiet, and then increased intensity from the mid-1990s to the present. Some scientists argue that this natural cycle may actually be a product of global warming and atmospheric aerosols. In the 1970s and 1980s, aerosol pollution may have “shaded” the Earth, keeping temperatures cooler than they had been in previous decades. This cooling would have suppressed hurricane formation. In the 1990s, global warming may have increased enough to overcome aerosol cooling and allowed hurricane intensity and frequency to climb again.
Other scientists argued that the flaw isn’t necessarily in the theory, but in the historical records. Satellite data used to estimate hurricane intensity only goes back to the 1970s for the Atlantic basin, and other basins have a shorter record. A thirty-year record may not be long enough to coax out real trends. Further, satellite technology and the methods used to estimate a storm’s intensity have improved, so a storm that may have been classified a Category 1 or 2 in the 1970s through the mid-1980s would be classified as a much stronger storm today. The change in intensity-predicting methods could skew the record to show fewer intense storms in the 1970s and 1980s than there are today.
From the 1940s to the 1970s, hurricane intensity estimates were based on aircraft and ship data. This means that fewer storms were recorded than probably actually occurred. The intensity records may also be skewed because the early flights did not go directly over the eye of the hurricane, but measured winds in safer flying areas farther from the center of the storm. From those measurements, wind speeds at the center of the storm and thus the storm’s intensity were estimated. As a result, many storms may have been stronger than they were estimated to have been.
Before the 1940s, intensity estimates were made based on surviving ship’s records. It is likely that any ship at the center of a Category 4 or 5 storm didn’t survive, so the record probably contains fewer big storms than actually occurred. From changes in the methods used to estimate hurricane intensity to spotty ship records, the historical record may well be skewed towards weaker storms, argue many scientists. If all these factors were accounted for, the trend toward greater hurricane frequency and intensity could disappear.
Regardless of their position, scientists need a longer and more accurate data record to fully understand the connection between global warming and other factors that may influence hurricane intensity and frequency. A longer, more accurate record will help improve theory and models, and it will amplify or flatten the currently observed trends. | <urn:uuid:0788c2d8-b4c3-485e-875b-d43d7b2f6669> | CC-MAIN-2013-20 | http://earthobservatory.nasa.gov/Features/Hurricanes/hurricanes_3.php | 2013-06-19T14:26:14 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368708142388/warc/CC-MAIN-20130516124222-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.955144 | 1,333 | 4.09375 | 4 |
The percentage of overweight children in the United States is growing at an alarming rate, with 1 out of 3 kids now considered overweight or obese.
Many kids are spending less time exercising and more time in front of the TV, computer, or video-game console. And today's busy families have fewer free moments to prepare nutritious, home-cooked meals. From fast food to electronics, quick and easy is the reality for many people.
Preventing kids from becoming overweight means adapting the way your family eats and exercises, and how you spend time together. Helping kids lead healthy lifestyles begins with parents who lead by example.
Is Your Child Overweight?
Body mass index (BMI) uses height and weight measurements to estimate a person's body fat. But calculating BMI on your own can be complicated. An easier way is to use a BMI calculator.
Once your child's BMI is known, it can be plotted on a standard BMI chart. Kids ages 2 to 19 fall into one of four categories:
underweight: BMI below the 5th percentile
normal weight: BMI at the 5th and less than the 85th percentile
overweight: BMI at the 85th and below 95th percentiles
obese: BMI at or above 95th percentile
BMI calculations aren't used to estimate body fat in babies and young toddlers. For kids younger than 2, doctors use weight-for-length charts to determine how a baby’s weight compares with his or her length. Any child who falls at or above the 85th percentile may be considered overweight.
BMI is not a perfect measure of body fat and can be misleading in some situations. For example, a muscular person may have a high BMI without being overweight (extra muscle adds to body weight — but not fatness). Also, BMI might be difficult to interpret during puberty when kids are experiencing periods of rapid growth. It's important to remember that BMI is usually a good indicator — but is not a direct measurement — of body fat.
If you're worried that your child or teen may be overweight, make an appointment with your doctor, who can assess eating and activity habits and make suggestions on how to make positive changes. The doctor also may decide to screen for some of the medical conditions that can be associated with obesity.
Depending on your child's BMI (or weight-for-length measurement), age, and health, the doctor may refer you to a registered dietitian for additional advice and, possibly, might recommend a comprehensive weight management program.
Obesity increases the risk for serious health conditions like type 2 diabetes, high blood pressure, and high cholesterol — all once considered exclusively adult diseases. Obese kids also may be prone to low self-esteem that stems from being teased, bullied, or rejected by peers.
Kids who are unhappy with their weight may be more likely than average-weight kids to:
develop unhealthy dieting habits and eating disorders, such as anorexia nervosa and bulimia
be more prone to depression
be at risk for substance abuse
Overweight and obese kids are at risk for developing medical problems that affect their present and future health and quality of life, including:
high blood pressure, high cholesterol and abnormal blood lipid levels, insulin resistance, and type 2 diabetes
bone and joint problems
shortness of breath that makes exercise, sports, or any physical activity more difficult and may aggravate the symptoms or increase the chances of developing asthma
restless or disordered sleep patterns, such as obstructive sleep apnea
tendency to mature earlier (overweight kids may be taller and more sexually mature than their peers, raising expectations that they should act as old as they look, not as old as they are; overweight girls may have irregular menstrual cycles and fertility problems in adulthood)
liver and gall bladder disease
Cardiovascular risk factors present in childhood (including high blood pressure, high cholesterol, and diabetes) can lead to serious medical problems like heart disease, heart failure, and stroke as adults. Preventing or treating overweight and obesity in kids may reduce the risk of developing cardiovascular disease as they get older.
A number of factors contribute to becoming overweight. Genetics, lifestyle habits, or a combination of both may be involved. In some instances, endocrine problems, genetic syndromes, and medications can be associated with excessive weight gain.
Much of what we eat is quick and easy — from fat-laden fast food to microwave and prepackaged meals. Daily schedules are so jam-packed that there's little time to prepare healthier meals or to squeeze in some exercise. Portion sizes, in the home and out, have grown greatly.
Plus, now more than ever life is sedentary — kids spend more time playing with electronic devices, from computers to handheld video game systems, than actively playing outside. Television is a major culprit.
Kids younger than 6 spend an average of 2 hours a day in front of a screen, mostly watching TV, DVDs, or videos. Older kids and teens average 4.5 hours a day watching TV, DVDs, or videos. When computer use and video games are included, time spent in front of a screen increases to over 7 hours a day! Kids who watch more than 4 hours a day are more likely to be overweight compared with kids who watch 2 hours or less.
Not surprisingly, TV in the bedroom is also linked to increased likelihood of being overweight. In other words, for many kids, once they get home from school, virtually all of their free time is spent in front of one screen or another.
The American Academy of Pediatrics (AAP) recommends that kids over 2 years old not spend more than 1-2 hours a day in front of a screen. The AAP also discourages any screen time for children younger than 2 years old.
Many kids don't get enough physical activity. Although physical education (PE) in schools can help kids get up and moving, more and more schools are eliminating PE programs or cutting down the time spent on fitness-building activities. One study showed that gym classes offered third-graders just 25 minutes of vigorous activity each week.
Current guidelines recommend that kids over 2 years old get at least 60 minutes of moderate to vigorous physical activity on most, preferably all, days of the week. Babies and toddlers should be active for 15 minutes every hour (a total of 3 hours for every 12 waking hours) each day.
Genetics also play a role — genes help determine body type and how your body stores and burns fat just like they help determine other traits. Genes alone, however, cannot explain the current obesity crisis. Because both genes and habits can be passed down from one generation to the next, multiple members of a family may struggle with weight.
People in the same family tend to have similar eating patterns, maintain the same levels of physical activity, and adopt the same attitudes toward being overweight. Studies have shown that a child's risk of obesity greatly increases if one or more parent is overweight or obese.
The key to keeping kids of all ages at a healthy weight is taking a whole-family approach. It's the "practice what you preach" mentality. Make healthy eating and exercise a family affair. Get your kids involved by letting them help you plan and prepare healthy meals, and take them along when you go grocery shopping so they can learn how to make good food choices.
And avoid falling into these common food/eating behavior traps:
Don't reward kids for good behavior or try to stop bad behavior with sweets or treats. Come up with other solutions to modify their behavior.
Don't maintain a clean-plate policy. Be aware of kids' hunger cues. Even babies who turn away from the bottle or breast send signals that they're full. If kids are satisfied, don't force them to continue eating. Reinforce the idea that they should only eat when they're hungry.
Don't talk about "bad foods" or completely eliminate all sweets and favorite snacks from kids' diets. Kids may rebel and overeat these forbidden foods outside the home or sneak them in on their own.
Recommendations by Age
Additional recommendations for kids of all ages:
Birth to age 1: In addition to its many health benefits, breastfeeding may help prevent excessive weight gain. Though the exact mechanism is not known, breastfed babies may be more able to control their own intake and follow their own internal hunger cues.
Ages 1 to 5: Start good habits early. Help shape food preferences by offering a variety of healthy foods. Encourage kids' natural tendency to be active and help them build on developing skills.
Ages 6 to 12: Encourage kids to be physically active every day, whether through an organized sports team or a pick-up game of soccer during recess. Keep your kids active at home, too, through everyday activities like walking and playing in the yard. Let them be more involved in making good food choices, such as packing lunch.
Ages 13 to 18: Teens like fast food, but try to steer them toward healthier choices like grilled chicken sandwiches, salads, and smaller sizes. Teach them how to prepare healthy meals and snacks at home. Encourage teens to be active every day.
All ages: Cut down on TV, computer, and video game time and discourage eating while watching the tube. Serve a variety of healthy foods and eat meals together as often as possible. Encourage kids to have at least five servings of fruits and vegetables a day, limit sugar-sweetened beverages, and eat breakfast every day.
If you eat well, exercise regularly, and incorporate healthy habits into your family's daily life, you're modeling a healthy lifestyle for your kids that will last. Talk to them about the importance of eating well and being active, but make it a family affair that will become second nature for everyone.
Most of all, let your kids know you love them — no matter what their weight — and that you want to help them be happy and healthy. | <urn:uuid:5eb915a6-c76f-4779-adba-6350bba34181> | CC-MAIN-2013-20 | http://kidshealth.org/PageManager.jsp?dn=Nemours&lic=60&cat_id=20743&article_set=30265&ps=104 | 2013-06-19T14:38:28 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368708142388/warc/CC-MAIN-20130516124222-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.950773 | 2,037 | 4.03125 | 4 |
Science Fair Project Encyclopedia
Knot theory is a branch of topology that was inspired by observations, as the name suggests, of knots. But progress in the field no longer depends on experiments with twine. Knot theory concerns itself with abstract properties of theoretical knots — the spatial arrangements that in principle could be assumed by a loop of string.
In mathematical jargon, knots are embeddings of the closed circle in three-dimensional space. An ordinary knot is converted to a mathematical knot by splicing its ends together. The topological theory of knots asks whether two such knots can be rearranged to match, without opening the splice. The question of untying an ordinary knot has to do with unwedging tangles of rope pulled tight. A knot can be untied in the topological theory of knots if and only if it is equivalent to the unknot, a circle in 3-space.
Knot theory originated in an idea of Lord Kelvin's (1867), that atoms were knots of swirling vortices in the æther (also known as 'ether'). He believed that an understanding and classification of all possible knots would explain why atoms absorb and emit light at only the discrete wavelengths that they do (i.e. explain what we now understand to depend on quantum energy levels). Scottish physicist Peter Tait spent many years listing unique knots under the belief that he was creating a table of elements. When ether was discredited through the Michelson-Morley experiment, vortex theory became completely obsolete, and knot theory fell out of scientific interest. Only in the past 100 years, with the rise of topology, have knots become a popular field of study. Today, knot theory is inextricably linked to particle physics, DNA replication and recombination, and to areas of statistical mechanics.
An introduction to knot theory
Creating a knot is easy. Begin with a one-dimensional line segment, wrap it around itself arbitrarily, and then fuse its two free ends together to form a closed loop. One of the biggest unresolved problems in knot theory is to describe the different ways in which this may be done, or conversely to decide whether two such embeddings are different or the same.
The unknot, and a knot
equivalent to it
Before we can do this, we must decide what it means for embeddings to be "the same". We consider two embeddings of a loop to be the same if we can get from one to the other by a series of slides and distortions of the string which do not tear it, and do not pass one segment of string through another. If no such sequence of moves exists, the embeddings are different knots.
A useful way to visualise knots and the allowed moves on them is to project the knot onto a plane - think of the knot casting a shadow on the wall. Now we can draw and manipulate pictures, instead of having to think in 3D. However, there is one more thing we must do - at each crossing we must indicate which section is "over" and which is "under". This is to prevent us from pushing one piece of string through another, which is against the rules. To avoid ambiguity, we must avoid having three arcs cross at the same crossing and also having two arcs meet without actually crossing (we would say that the knot is in general position with respect to the plane). Fortunately a small perturbation in either the original knot or the position of the plane is all that is needed to ensure this.
In 1927, working with this diagrammatic form of knots, J.W. Alexander and G.B. Briggs , and independently Kurt Reidemeister, demonstrated that two knot diagrams belonging to the same knot can be related by a sequence of three kinds of moves on the diagram, shown right. These operations, now called the Reidemeister moves, are:
- Twist and untwist in either direction.
- Move one loop completely over another.
- Move a string completely over or under a crossing.
Knot invariants can be defined by demonstrating a property of a knot diagram which is not changed when we apply any of the Reidemeister moves. Some very important invariants can be defined in this way, including the Jones polynomial.
You can unknot any circle in four dimensions. There are two steps to this. First, "push" the circle into a 3-dimensional subspace. This is the hard, technical part which we will skip. Now imagine temperature to be a fourth dimension to the 3-dimensional space. Then you could make one section of a line cross through the other by simply warming it with your fingers.
Two knots can be added by breaking the circles and connecting the pairs of ends. Knots in 3-space form a commutative monoid with prime factorization. The trefoil knots are the simplest prime knots. Higher dimensional knots can be added by splicing the spheres. While you cannot form the unknot in three dimensions by adding two non-trivial knots, you can in higher dimensions.
- The Knot Book: An Elementary Introduction to the Mathematical Theory of Knots, Colin Adams , 2001, ISBN 0716742195
- Knots: Mathematics With a Twist, Alexei Sossinsky , 2002, ISBN 0674009444
- Knot Theory, Vassily Manturov , 2004, ISBN 0415310016
The contents of this article is licensed from www.wikipedia.org under the GNU Free Documentation License. Click here to see the transparent copy and copyright details | <urn:uuid:5224c8e3-2023-4490-bcb0-4fefe395a832> | CC-MAIN-2013-20 | http://www.all-science-fair-projects.com/science_fair_projects_encyclopedia/Knot_theory | 2013-06-19T14:31:28 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368708142388/warc/CC-MAIN-20130516124222-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.925185 | 1,141 | 4.03125 | 4 |
Say it with FEELING!!
Rationale: “Fluency means reading faster, smoother, more expressively, or more quietly with the goal of reading silently. Fluent reading approaches the speed of speech.” (Murray) At this development stage, fluency is a major goal of the student and the teacher. This lesson is aimed to teach and emphasize one aspect of fluency: expression. Reading with expression brings a story, and its characters, to life, making reading more enjoyable for everyone. The teacher will read a story, showing great expression, to model for children.
Materials: Copy of Tiki Tiki Tembo, various classroom library books, notebook paper, pencils
1. Review with students the difference that punctuation makes make at the end of a sentence. Read the following sentences twice through. The first time, pay NO ATTENTION to the punctuation marks at the end of the sentence. The second time, use the correct inflection in your voice, depending on the punctuation mark at the end of the sentence. “JIMMY WENT RUNNING., JIMMY WENT RUNNING?, JIMMY WENT RUNNING!. CAN ANYONE TELL ME THE DIFFERENCES IN THOSE SENTENCES?” Hopefully children will answer that the first was a statement, the second was a question, and the third was an exclamation.
2. “WHAT A WONDERFUL DAY WE HAVE!!!” After you have excited the kids with that exclamation, the teacher says ‘“NOW THAT WAS LOUD AND FULL OF EXCITEMENT WASN’T IT? THAT WAS HAPPY EXPRESSION. WHEN WE TALK OR READ WITH EXPRESSION, WE CHANGE THE TONE OF OUR VOICE (HAPPY TO SAD), THE VLOUME OF OUR VOICE (LOUD TO SOFT), AND USE OUR FACES TO SHOW THE FEELING OF THE BOOK. DIFFERENT FEELINGS HAVE DIFFERENT SOUNDS AND FACIL LOOKS.”
3. “CAN SOMEONE TELL ME WHY WE SHOULD USE EXPRESSION WHEN WE READ? Students will offer their own explanations. “GREAT! WE USE EXPRESSION TO MAKE THE STORY MORE INTERESTING AND FUN TO READ!!!”
4. “WHAT WOULD MY VOICE SOUND LIKE IF I WERE SCARED?” Children raise their hands and answer, using facial expressions and vocal tones. “WHAT ABOUT IF I WERE ANGRY? WOULD I YELL OR WHISPER?” Children will answer correctly to the question.
5. Now, gather the children around your reading center and read ‘“Tiki Tiki Tembo’”. Make sure to OVEREXAGGERATE your expressions. (vocal tone, facial expressions, and volume) When done reading, ask children what emotions you were trying to convey at different parts of the story. Have a mini group discussion.
6. Pair children up and have them select a book from the classroom library to read. Set a timer for 5-8 minutes and let each child read to their partner. “REMEMEBER TO READ TO YOUR READING BUDDY WITH LOTS OF EXPRESSION! MAKE YOUR READING BUDDY FEEL LIKE THEY ARE IN THE STORY.” Teacher circulates with rubric and evaluates each child as they read. Now have the kids switch roles. Reading buddy becomes reader and reader becomes reading buddy.
7. After the children are done with the reading, have each child individually write three sentences about their book that end with various punctuation marks. “OKAY CLASS, NOW THAT WE HAVE LEARNED TO READ WITH EXPRESSION, I WANT US TO WRITE WITH EXPRESSION. TAKE OUT PAPER AND A PENCIL. WRITE THREE SENTENCES ABOUT THE STORY YOU JUST READ. ONE SHOULD BE A STATEMENT AND END WITH A PERIOD. ONE SHOULD BE A QUESTION AND END WITH A QUESTION MARK. ONE SHOULD BE AN EXCLAMATION AND END WITH AN EXCLAMATION POINT.”
Have each child come to your desk or reading table and have them read, with expression, their original sentences. This will assess their grasp of punctuation and also the concept of expression: how to write it and convey it to the reader. You also have the checklist rubric that you evaluated their oral reading on.
www.auburn.edu/rdggenie The Reading Genie Website
Click here to return to Openings | <urn:uuid:6bb0bc1f-3587-407e-bca0-a705fa87ab31> | CC-MAIN-2013-20 | http://www.auburn.edu/academic/education/reading_genie/openings/tragesergf.html | 2013-06-19T14:37:57 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368708142388/warc/CC-MAIN-20130516124222-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.903687 | 973 | 4.59375 | 5 |
In order to understand solving logarithmic equations, students must understand the basics of logarithms, and how to use exponentiation to access the terms inside the logarithm. Some more complicated instances of solving simple logarithmic equations require knowledge of the product, quotient and power rules of logarithms in order to simplify complex terms.
Solving simple logarithm equations and what I mean by simple logarithm equations is basically logarithm equation that is in logarithm form. so basically you have a log, a base, your term and then an answer. So basically, 3 things, I'll call this a simple logarithmic equation.
Really all you have to do whenever you're solving something in this form is put into exponential form, okay? No matter what the x is we're going to deal with x's in all 3 of these spots. Just put into exponential form and solve, okay? So this one the 3 is going to come up and around leaving us with x=3 to the -2 and this problem has now just turned into evaluating an exponent. The negative puts everything in the bottom, the 2 squares it and we end up with x=1 over 9.
So whenever we ha- any time we have an equation in logarithm form, in order to solve it put an exponential and then solve it as you would in the other exponential equations. | <urn:uuid:9f3a4359-4581-4247-8531-bfa934ef3fa7> | CC-MAIN-2013-20 | http://www.brightstorm.com/math/precalculus/exponential-and-logarithmic-functions/solving-simple-logarithmic-equations-problem-3/ | 2013-06-19T14:31:42 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368708142388/warc/CC-MAIN-20130516124222-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.956464 | 296 | 4.28125 | 4 |
This tutorial, developed for high school physics students, uses multiple graphs and animations to study the relationship between the motion of an object and its graph of Velocity vs. Time. Users explore the relationship between position and velocity, positive and negative velocities, slope and shape of graphs, and acceleration. Interactive self-evaluations are included. See Related Materials for an accompanying lab by the same author.
This item is part of The Physics Classroom, a comprehensive set of tutorials and multimedia resources for high school physics.
Editor's Note:Education research indicates that many students have difficulty differentiating velocity and acceleration, and often plot velocity graphs as the path of an object. See Related Materials for a free research-based diagnostic tool to probe misconceptions related to velocity.
6-8: 4F/M3b. If a force acts towards a single center, the object's path may curve into an orbit around the center.
9-12: 4F/H1. The change in motion (direction or speed) of an object is proportional to the applied force and inversely proportional to the mass.
9-12: 4F/H8. Any object maintains a constant speed and direction of motion unless an unbalanced outside force acts on it.
9. The Mathematical World
9B. Symbolic Relationships
6-8: 9B/M3. Graphs can show a variety of possible relationships between two variables. As one variable increases uniformly, the other may do one of the following: increase or decrease steadily, increase or decrease faster and faster, get closer and closer to some limiting value, reach some intermediate maximum or minimum, alternately increase and decrease, increase or decrease in steps, or do something different from any of these.
9-12: 9B/H4. Tables, graphs, and symbols are alternative ways of representing data and relationships that can be translated from one to another.
9-12: 9C/H3c. A graph represents all the values that satisfy an equation, and if two equations have to be satisfied at the same time, the values that satisfy them both will be found where the graphs intersect.
Common Core State Standards for Mathematics Alignments
Expressions and Equations (6-8)
Represent and analyze quantitative relationships between
dependent and independent variables. (6)
6.EE.9 Use variables to represent two quantities in a real-world problem that change in relationship to one another; write an equation to express one quantity, thought of as the dependent variable, in terms of the other quantity, thought of as the independent variable. Analyze the relationship between the dependent and independent variables using graphs and tables, and relate these to the equation.
Understand the connections between proportional relationships,
lines, and linear equations. (8)
8.EE.5 Graph proportional relationships, interpreting the unit rate as the slope of the graph. Compare two different proportional relationships represented in different ways.
Use functions to model relationships between quantities. (8)
8.F.5 Describe qualitatively the functional relationship between two quantities by analyzing a graph (e.g., where the function is increasing or decreasing, linear or nonlinear). Sketch a graph that exhibits the qualitative features of a function that has been described verbally.
High School — Functions (9-12)
Interpreting Functions (9-12)
F-IF.4 For a function that models a relationship between two quantities, interpret key features of graphs and tables in terms of the quantities, and sketch graphs showing key features given a verbal description of the relationship.?
Linear, Quadratic, and Exponential Models? (9-12)
F-LE.1.b Recognize situations in which one quantity changes at a constant rate per unit interval relative to another.
F-LE.1.c Recognize situations in which a quantity grows or decays by a constant percent rate per unit interval relative to another.
F-LE.2 Construct linear and exponential functions, including arithmetic and geometric sequences, given a graph, a description of a relationship, or two input-output pairs (include reading these from a table).
Common Core State Reading Standards for Literacy in Science and Technical Subjects 6—12
Craft and Structure (6-12)
RST.9-10.4 Determine the meaning of symbols, key terms, and other domain-specific words and phrases as they are used in a specific scientific or technical context relevant to grades 9—10 texts and topics.
Range of Reading and Level of Text Complexity (6-12)
RST.9-10.10 By the end of grade 10, read and comprehend science/technical texts in the grades 9—10 text complexity band independently and proficiently.
This resource is part of a Physics Front Topical Unit.
Topic: Kinematics: The Physics of Motion Unit Title: Graphing
A companion to the resource above, this online tutorial explores the importance of the slope of v-t graphs as a representation of an object's acceleration. Self-guided evaluations help students overcome common misconceptions.
%0 Electronic Source %A Henderson, Tom %D June 1, 2011 %T The Physics Classroom: The Meaning of Shape for a v-t Graph %V 2013 %N 19 June 2013 %8 June 1, 2011 %9 text/html %U http://www.physicsclassroom.com/Class/1DKin/U1L4a.cfm
Disclaimer: ComPADRE offers citation styles as a guide only. We cannot offer interpretations about citations as this is an automated procedure. Please refer to the style manuals in the Citation Source Information area for clarifications. | <urn:uuid:9c52facc-6efa-4158-bbd2-7f8905b6f5a6> | CC-MAIN-2013-20 | http://www.compadre.org/Precollege/items/detail.cfm?ID=3313 | 2013-06-19T14:19:20 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368708142388/warc/CC-MAIN-20130516124222-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.894268 | 1,174 | 4.3125 | 4 |
A new tool to identify the calls of bat species could help conservation efforts.
Because bats are nocturnal and difficult to observe or catch, the most effective way to study them is to monitor their echolocation calls. These sounds are emitted in order to hear the echo bouncing back from surfaces around the bats, allowing them to navigate, hunt and communicate.
Many different measurements can be taken from each call, such as its minimum and maximum frequency, or how quickly the frequency changes during the call, and these measurements are used to help identify the species of bat.
However, a paper by an international team of researchers, published in the Journal of Applied Ecology, asserts that poor standardisation of acoustic monitoring limits scientists’ ability to collate data.
Kate Jones, chairwoman of the UK-based Bat Conservation Trust
told the BBC that “without using the same identification methods everywhere, we cannot form reliable conclusions about how bat populations are doing and whether their distribution is changing.
"Because many bats migrate between different European countries, we need to monitor bats at a European - as well as country - scale.”
The team selected 1,350 calls from 34 different European bat species from EchoBank, a global echolocation library containing more than 200,000 bat call recordings. This raw data has allowed them to develop the identification tool, iBatsID
, which can identify 34 out of 45 species of bats.
This free online tool works anywhere in Europe, and its creators claim can identify most species correctly more than 80% of the time.
There are 18 species of bat residing in the UK, including the common pipistrelle and greater horseshoe bat.
Monitoring bats is vital not just to this species, but also to the whole ecosystem. Bats are extremely sensitive to changes in their environment, so if bat populations are declining, it can be an indication that other species might be affected in the future. | <urn:uuid:293a002d-f152-4885-9293-13b158f7cec0> | CC-MAIN-2013-20 | http://www.countryfile.com/news/bats | 2013-06-19T06:08:09 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368708142388/warc/CC-MAIN-20130516124222-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.93685 | 398 | 4.46875 | 4 |
What is the media? What does it do? Students examine the types and roles of the media by taking on the role of newsmaker and agenda setter.
Students will be able to:
ANTICIPATE by asking students if they’ve ever seen a television newscast. Ask students to recall any details they remember (graphics, music, story topics). Ask students who they think makes decisions about what stories television newscasts discuss.
DISTRIBUTE the Reading pages to each student.
READ the two reading pages with the class, pausing to discuss as necessary.
CHECK for understanding by doing the T/F Active Participation activity. Have students respond “True” or “False” as a chorus or use thumbs up/thumbs down.
DISTRIBUTE scissors, glue, and the Agenda Cutout Activity pages. Students can complete this activity individually or in pairs.
READ the directions for the cutout activity.
ALLOW students to complete the cutout activity.
REVIEW the answers to the cutout activity.
DISTRIBUTE one worksheet to each student and review the directions for the activities.
ALLOW students to complete the worksheet.
DISTRIBUTE one Extension Activity to each student and review the directions.
ALLOW students to complete the extension activity.
CLOSE by asking students to silently recall as many roles of the media as they can. Call on students until all roles have been named. | <urn:uuid:0ed2aa07-2935-4e0f-8814-0064087833ed> | CC-MAIN-2013-20 | http://www.icivics.org/teachers/lesson-plans/role-media | 2013-06-19T06:03:00 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368708142388/warc/CC-MAIN-20130516124222-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.927136 | 304 | 4.59375 | 5 |
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Interstellar and Intergalactic Distances
— Using a Film Clip from Cosmic Voyage
Subject: Science & Technology — Interstellar & Intergalactic Distances;
Ages: 10+; Middle and High School;
Length: Film Clip: approximately 12 minutes or a shorter clip of approximately five minutes will also work; Lesson: One 50 minute class period.
Excerpts from the Snippet Lesson Plan
Learner Outcomes/Objectives: Students will get a feeling for the relative sizes and distances of stars and of galaxies and of the vastness of space as compared to the small world of planet Earth.
Rationale: Cosmic Voyage describes in a very attractive way the huge distances of deep space. Students usually know that stars are in galaxies and that there are huge numbers of galaxies in the universe. However it is usually not so easy to convey a feeling of the relative scales and distance of stars and galaxies: whereas galaxies densely populate the universe, stars are very far away from each other within a galaxy.
Description of the Film Clips: Viewers are taken on a journey through the distances of space changing magnification of one scene by a factor of ten at each step. . . .
The "Cosmic Voyage" taken in the film contains "landmarks" to enable the viewer to keep in mind the scale of things in the universe in terms of powers of ten. The journey has two major thresholds: first, the point at which stars begin to be seen in groups, at 1015 meters, and second, when the same thing happens with galaxies, several powers of ten later, at 1023 meters.
There is a fundamental difference between these two scales: the distances between stars are huge with respect to their sizes. . . .
The complete Snippet Lesson Plan provides additional helpful background on Interstellar and Intergalactic distances. Links to websites providing stunning photographs of colliding galaxies are also included.
TeachWithMovies.com's Movie Lesson Plans and Learning Guides are used by thousands of teachers in their classrooms to motivate students. They provide background and discussion questions that lead to fascinating classes. Parents can use them to supplement what their children learn in school.
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Snippet Lesson Plans are based on short subjects or film clips. They are ideal for classroom use because the video segments are less than 40 minutes in length.
Each TWM Snippet Lesson Plan Contains:
- Learner Outcomes/Objectives
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Interstellar and Intergalactic distances are truly astonishing in their magnitude.
A subscription to TeachWithMovies.com will give teachers access to 350 Snippet Lesson Plans, Learning Guides, and Movie Lesson Plans. Subscribe Today and give students a graphic sense of the distances in interstellar and intergalactic space using a film clip from Cosmic Voyage.
Already a Member? Login Here | <urn:uuid:742bdb16-533e-4d17-b0da-8fab352bffcc> | CC-MAIN-2013-20 | http://www.teachwithmovies.org/snippets/sn-sci-astronomy-space-distances-cosmic-voyage.html | 2013-06-19T14:39:02 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368708142388/warc/CC-MAIN-20130516124222-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.891313 | 850 | 4.03125 | 4 |
It may not be the most charismatic species, but the endangered California condor, a bird with an incredible wingspan of nearly 10 feet, has received a lot of attention over the years. After dropping to a population of just 22 individuals in the early 1980s, captive breeding programs have boosted their numbers to around 400, with some 200 living in the wild. Even that small population is extremely high-maintenance, however. All the birds are tracked by radio or GPS tags, and are frequently caught for medical examination and treatment.
As is the case with most birds that eat carrion, lead poisoning has long been a concern for the condors. When large animals are killed by a hunter’s lead bullet but not harvested, they can become a dangerous meal. When the birds eat the meat, they can ingest lead particles along with it.
When the condors get their medical checkup, a blood sample is analyzed for lead. If the levels are dangerously high, the birds are given treatment. The impact of lead poisoning on the condor population has long been debated, but a study published this week in the Proceedings of the National Academy of Sciences provides some clarity. It shows that many condors are suffering the effects of lead poisoning, suggesting the population will continue to struggle as long as lead ammunition remains in use.
Researchers compiled the results of over 1,100 blood samples taken from 150 California condors between 1997 and 2010. The US Centers for Disease Control and Prevention recommends that children with blood lead levels above 450 ng/ml undergo treatment, and this is roughly the level at which the condors are taken in for treatment as well. About 20 percent of the birds sampled each year exceeded this level, and 48 percent of individuals living in the wild exceeded it at some point during the 14-year period. Blood lead levels as high as 6,100 ng/ml were seen.
Because blood samples only provide a snapshot of lead levels, the group also analyzed feathers from 18 condors. The concentration of lead in each segment of the feather depends on the concentration in the body at the time that segment formed. That means that each feather records a few months of exposure history. From comparisons of the most recent segment to blood levels, they were able to estimate blood lead levels over the duration of the feather.
The feathers showed that after ingesting lead, the birds’ blood concentrations exceeded 450 ng/ml for about a month. Unsurprisingly, blood samples often miss the peak lead concentrations, which were 1.4x to 14.4x higher. About 34 percent of the average feather history was higher than the level at which the condors are treated.
Lead poisoning has consequences at concentrations lower than those that are lethal, but they are difficult to determine in wild populations. To get a handle on how sensitive California condors were to lead poisoning, the researchers measured a biomarker (δ-aminolevulinic acid dehydratase, or ALAD, enzyme activity) in 60 blood samples from 34 birds. That enzyme is important in a number of biochemical pathways, and its activity is strongly inhibited by lead, making it a great indicator of the effect of lead in the body. At blood lead levels of 450 ng/ml, the activity of ALAD was suppressed by 90 percent. Even at 200 ng/ml (a level exceeded by about 30 percent of blood samples each year, and for more than half of the duration of the feather records), activity was down 60 percent.
But how can we be sure the lead in those condors came from ammunition in carcasses and not some natural source? To see, the researchers measured the lead-207/lead-206 isotopic signature in 132 blood samples. Of those samples, 79 percent were consistent with lead ammunition and 27 percent were within the range of “background” ratios in captive birds (there’s some overlap). Several birds had isotopic signatures similar to lead-based paint, and had been observed roosting in an old fire tower with peeling lead paint.
If lead ammunition is a real problem for California condors, where does that leave the effort to restore the population? To answer that question, the group used population models and several scenarios. If present conditions continue, with the same lead exposure and active care of the birds, the wild population would just barely grow. The authors write, “without future releases of captive-reared birds, the population would take ∼1,800 [years] to meet the recovery goal of a noncaptive population of 150 individuals within California.”
If, instead, we gave up on the expensive work of capturing birds and treating those with high blood lead levels, the population would decline back to 22 in one to six decades. Finally, if lead exposure was eliminated, the wild population would grow at a rate of about 2 percent per year. And that’s a conservative estimate, the researchers say, because their “estimated rate of lead-caused mortality is based on the actual deaths that occurred despite intensive management interventions to mitigate lead poisonings; if lead was truly removed as an environmental hazard, the increase in condor health and survival should be substantially greater than modeled here.”
That is likely the outcome that California authorities were hoping for when, in 2008, they instituted a ban on lead ammunition for hunting many species within the condor’s range in southern California. But when the researchers compared blood lead levels in condors before the ban (2006-2007) and after (2009-2010), they found no improvement.
The researchers are currently evaluating the ineffectiveness of the ban so far, including a look at whether hunters are fully complying with the new rule. Myra Finkelstein, a University of California-Santa Cruz researcher involved in the project, told Ars that “even if only a few people are still using lead ammunition, there will be enough contaminated carcasses to cause lead poisoning in a significant number of condors. We found that over the course of ten years, if just one half of one percent of carcasses have lead in them, the probability that each free-flying condor will encounter a contaminated carcass is 85 to 98 percent, and one exposure event could kill a condor.”
On the national stage, 100 conservation groups recently filed a lawsuit against the US Environmental Protection Agency for denying petitions asking it to regulate lead ammunition used for hunting. The agency says it has no authority to do so, a fact the groups are challenging in court. | <urn:uuid:44d8062c-5790-4e4a-8a4b-1a852cc22433> | CC-MAIN-2013-20 | http://arstechnica.com/science/2012/06/endangered-california-condors-still-face-lead-poisoning-threat/?comments=1&post=22995313 | 2013-05-19T19:07:36 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368697974692/warc/CC-MAIN-20130516095254-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.965838 | 1,328 | 4.0625 | 4 |
In this lesson, our instructor Laura Ryan gives an introduction to music theory. She gives an overview of the grand staff, major scales, and minor scales before discussing the names of white and black keys. She concludes the video with chords, chord progressions, and examples of each concept covered in the lesson.
The grand staff is made of both Treble and Bass clefs.
When reading notes separately from left to right, they are played in succession.
When reading notes stacked vertically on top of one another, they are played simultaneously.
One can use simple chord progressions and only a few notes to create catchy and memorable tunes.
Lecture Slides are screen-captured images of important points in the lecture. Students can download and print out these lecture slide images to do practice problems as well as take notes while watching the lecture. | <urn:uuid:f18b30b5-45af-49ad-8c1b-cb175f53dbba> | CC-MAIN-2013-20 | http://educator.com/music-theory/ryan/music-theory.php?ss=1429 | 2013-05-19T18:33:19 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368697974692/warc/CC-MAIN-20130516095254-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.937212 | 172 | 4.125 | 4 |
Surface Ocean Currents
In the Northern Hemisphere, warm air around the equator rises and flows north toward the pole. As the air moves away from the equator, the Coriolis effect deflects it toward the right. It cools and descends near 30 degrees North latitude. The descending air blows from the northeast to the southwest, back toward the equator (Ross, 1995). A similar wind pattern occurs in the Southern Hemisphere; these winds blow from the southeast toward the northwest and descend near 30 degrees South latitude.
These prevailing winds, known as the trade winds, meet at the Intertropical Convergence Zone (also called the doldrums) between 5 degrees North and 5 degrees South latitude, where the winds are calm. The remaining air (air that does not descend at 30 degrees North or South latitude) continues toward the poles and is known as the westerly winds, or westerlies. The trade winds are so named because ships have historically taken advantage of them to aid their journies between Europe and the Americas (Bowditch, 1995). | <urn:uuid:04296702-4413-41d7-82cb-41486186afef> | CC-MAIN-2013-20 | http://oceanservice.noaa.gov/education/tutorial_currents/04currents2.html | 2013-05-19T18:49:59 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368697974692/warc/CC-MAIN-20130516095254-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.940754 | 219 | 4 | 4 |
What's a Mangrove? And How Does It Work?
If you've ever spent time by the sea in a tropical place, you've probably noticed distinctive trees that rise from a tangle of roots wriggling out of the mud. These are mangroves—shrub and tree species that live along shores, rivers, and estuaries in the tropics and subtropics. Mangroves are remarkably tough. Most live on muddy soil, but some also grow on sand, peat, and coral rock. They live in water up to 100 times saltier than most other plants can tolerate. They thrive despite twice-daily flooding by ocean tides; even if this water were fresh, the flooding alone would drown most trees. Growing where land and water meet, mangroves bear the brunt of ocean-borne storms and hurricanes.
There are 80 described species of mangroves, 60 of which live exclusively on coasts between the high- and low-tide lines. Mangroves once covered three-quarters of the world's tropical coastlines, with Southeast Asia hosting the greatest diversity. Only 12 species live in the Americas. Mangroves range in size from small bushes to the 60-meter giants found in Ecuador. Within a given mangrove forest, different species occupy distinct niches. Those that can handle tidal soakings grow in the open sea, in sheltered bays, and on fringe islands. Trees adapted to drier, saltier soil can be found farther from the shoreline. Some mangroves flourish along riverbanks far inland, as long as the freshwater current is met by ocean tides.
One Ingenious Plant
How do mangroves survive under such hostile conditions? A remarkable set of evolutionary adaptations makes it possible. These amazing trees and shrubs:
- cope with salt: Saltwater can kill plants, so mangroves must extract freshwater from the seawater that surrounds them. Many mangrove species survive by filtering out as much as 90 percent of the salt found in seawater as it enters their roots. Some species excrete salt through glands in their leaves. These leaves, which are covered with dried salt crystals, taste salty if you lick them. A third strategy used by some mangrove species is to concentrate salt in older leaves or bark. When the leaves drop or the bark sheds, the stored salt goes with them.
- hoard fresh water: Like desert plants, mangroves store fresh water in thick succulent leaves. A waxy coating on the leaves of some mangrove species seals in water and minimizes evaporation. Small hairs on the leaves of other species deflect wind and sunlight, which reduces water loss through the tiny openings where gases enter and exit during photosynthesis. On some mangroves species, these tiny openings are below the leaf's surface, away from the drying wind and sun.
- breathe in a variety of ways: Some mangroves grow pencil-like roots that stick up out of the dense, wet ground like snorkels. These breathing tubes, called pneumatophores, allow mangroves to cope with daily flooding by the tides. Pneumatophores take in oxygen from the air unless they're clogged or submerged for too long.
Roots That Multitask
Root systems that arch high over the water are a distinctive feature of many mangrove species. These aerial roots take several forms. Some are stilt roots that branch and loop off the trunk and lower branches. Others are wide, wavy plank roots that extend away from the trunk. Aerial roots broaden the base of the tree and, like flying buttresses on medieval cathedrals, stabilize the shallow root system in the soft, loose soil. In addition to providing structural support, aerial roots play an important part in providing oxygen for respiration. Oxygen enters a mangrove through lenticels, thousands of cell-sized breathing pores in the bark and roots. Lenticels close tightly during high tide, thus preventing mangroves from drowning.
The mangroves' niche between land and sea has led to unique methods of reproduction. Seed pods germinate while on the tree, so they are ready to take root when they drop. If a seed falls in the water during high tide, it can float and take root once it finds solid ground. If a sprout falls during low tide, it can quickly establish itself in the soft soil of tidal mudflats before the next tide comes in. A vigorous seed may grow up to two feet (about 0.6 m) in its first year. Roots arch from the seedling to anchor it in the mud. Some tree species form long, spear-shaped stems and roots while still attached to the parent plant. After being nourished by the parent tree for one to three years, these sprouts may break off. Some take root nearby while others fall into the water and are carried away to distant shores.
A World Traveler
Botanists believe that mangroves originated in Southeast Asia, but ocean currents have since dispersed them to India, Africa, Australia, and the Americas. As Alfredo Quarto, the head of the Mangrove Action Project, puts it, “Over the millions of years since they've been in existence, mangroves have essentially set up shop around the world.” The fruits, seeds, and seedlings of all mangrove plants can float, and they have been known to bob along for more than a year before taking root. In buoyant seawater, a seedling lies flat and floats fast. But when it approaches fresher, brackish water—ideal conditions for mangroves—the seedling turns vertical so its roots point downward. After lodging in the mud, the seedling quickly sends additional roots into the soil. Within 10 years, as those roots spread and sprout, a single seedling can give rise to an entire thicket. It's not just trees but the land itself that increases. Mud collects around the tangled mangrove roots, and shallow mudflats build up. From the journey of a single seed a rich ecosystem may be born.
More About This Resource...
Our innovative Science Bulletins are an online and exhibition program that offers the public a window into the excitement of scientific discovery. This essay was published in May 2004 as part of the Mangroves: The Roots of the Sea Bio Feature.
- It begins by explaining that these remarkably tough shrub and tree species can live in water up to 100 times saltier than most other plants can tolerate and thrive despite twice-daily flooding by ocean tides.
- It then details the remarkable set of evolutionary adaptations that allow mangroves to survive under such hostile conditions.
- The essay concludes with a note about how botanists believe that mangroves originated in Southeast Asia, but ocean currents have since dispersed them to India, Africa, Australia, and the Americas.
Supplement a study of biology with a classroom activity drawn from this Science Bulletin essay.
- Have students read the essay (either online or a printed copy).
- Working individually or in small groups, have them investigate the Explore a Mangrove Forest interactive. | <urn:uuid:0f198350-c837-4dc6-bdfe-ac3b5bfad431> | CC-MAIN-2013-20 | http://www.amnh.org/explore/science-bulletins/bio/documentaries/mangroves-the-roots-of-the-sea/what-s-a-mangrove-and-how-does-it-work | 2013-05-19T18:57:57 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368697974692/warc/CC-MAIN-20130516095254-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.934988 | 1,472 | 4.0625 | 4 |
An ombudsman is a government official charged with representing the interests of the public by investigating and addressing complaints reported by individual citizens. The term arose from its use in Sweden, with the Parliamentary ombudsman instituted in 1809 to safeguard the rights of citizens by establishing a supervisory agency independent of the executive branch. The word ombudsman and its specific meaning has since been adopted in to English as well as other languages, and ombudsmen has been instituted by other governments and organizations such as the European Union.
The origin of the word is found in Old Norse and the word umbuds man, meaning representative. The first preserved use in Swedish is from 1552. It is also used in the other Scandinavian languages such as the Icelandic "umboðsmaður", the Norwegian "ombudsmann" and the Danish "ombudsmand". An ombudsman doesn't necessarily have to be appointed by government, but an ombudsman of an non-governmental organization, whether working only for the own members or for the general public, does obviously not carry any special powers or sanction abilities.
In 1713 King Charles XII of Sweden, preoccupied with fighting the Great Northern War, was residing in Bendery and had not set foot in Sweden in over a decade. In order to reestablish the domestic administration, which had fallen into disarray, he instituted the office of His Majesty's Supreme Ombudsman. The role of the King's Ombudsman was to ensure that judges and public officials acted in accordance with the laws, proficiently discharged their tasks, and if not he could initiate legal proceedings for dereliction of duty.
The autocratic rule of Gustav III of Sweden, that ended half a century of parliamentary supremacy in 1772, prompted the Riksdag of the Estates to institute an Ombudsman who was independent of the executive power when his son Gustav IV Adolf of Sweden was deposed in 1809. The King's Ombudsman, who in 1719 had been given a new title; Chancellor of Justice, was to be accompanied by a Parliamentary Ombudsman . The office of the Parliamentary Ombudsman was established by the Instrument of Government of 1809 and its role preserved in the new Instrument of Government in 1974.
Apart from this there are also a number of more specialized ombudsmen that operate under the authority of the Government of Sweden:
- Swedish Ombudsman for Equal Opportunities , or Jämställdhetsombudsmannen (JämO)
- Swedish Ombudsman for Children , or Barnombudsmannen. Observes matters affecting the rights and interests of children and young people.
- Swedish Disability Ombudsman , or Handikappombudsmannen. Monitors issues relating to the rights and interests of persons with disabilities.
- Swedish Ombudsman against Discrimination on Grounds of Sexual Orientation, or Ombudsmannen mot diskriminering på grund av sexuell läggning (HomO)
- Swedish Ombudsman against Ethnic Discrimination , or Ombudsmannen mot etnisk diskriminering
The Director-General of the Swedish Consumer Agency is also designated as a Consumer Ombudsman.
The European Ombudsman was established by the Maastricht treaty, the treaty establishing the European Union.
The Office of Ombudsman was set up under the terms of The Ombudsman Act, 1980. The Ombudsman, who is appointed by the President of Ireland upon the nomination of both Houses of the Oireachtas, deals with complaints against Government Departments, local authorities, health boards and An Post.
The Spanish laws translate "ombudsman" as defensor del pueblo ("People's defender").
There is a general Defensor del Pueblo for issues with the Spanish administration, and regional ones for the autonomous communities of Spain:
The Spanish Defensor can start processes at the Constitutional Court .
In the United Kingdom a post of Ombudsman is attached to the Westminster Parliament with additional posts at the Scottish Parliament, the Welsh Assembly and other government institutions.
List of all Ombudsman in the United Kingdom
- Estate Agents Ombudsman, Financial Ombudsman Service, Financial Services Ombudsman Scheme for the Isle of Man, Health Service Ombudsman - England, , Health Service Ombudsman - Wales, Housing Ombudsman Service (HOS), Independent Police Complaints Commission, Legal Services Ombudsman, Local Government Ombudsman - England, Local Government Ombudsman - Wales , Northern Ireland Ombudsman, Northern Ireland Police Ombudsman, Parliamentary Ombudsman, Welsh Administration Ombudsman , Pensions Ombudsman, Removals Industry Ombudsman Scheme, Scottish Legal Services Ombudsman, Scottish Public Services Ombudsman, Telecommunications Ombudsman (OTELO)
Many private companies also have an ombudsman (or a ombudsman department). Like the government official, they receive complaints and resolve them. Though they are not legally independent, they are part of a company's customer service strategy. Some companies treat their ombudsman very seriously and the ombudsman is very independent.
Newspaper ombudsman are especially valuable to newspapers by promoting journalistic integrity to their readers. There is an international Organization of News Ombudsmen. The press in Sweden is self-regulated through the Public Press Ombudsman (Allmänhetens Pressombudsman) and the Swedish Press Council (Pressens Opinionsnämnd). | <urn:uuid:e737e063-bd47-470d-be08-1cfc65945d2b> | CC-MAIN-2013-20 | http://www.biologydaily.com/biology/Ombudsman | 2013-05-19T18:41:41 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368697974692/warc/CC-MAIN-20130516095254-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.929055 | 1,088 | 4 | 4 |
Continental CongressArticle Free Pass
Continental Congress, in the period of the American Revolution, the body of delegates who spoke and acted collectively for the people of the colony-states that later became the United States of America. The term most specifically refers to the bodies that met in 1774 and 1775–81 and respectively designated as the First Continental Congress and the Second Continental Congress.
In the spring of 1774 the British Parliament’s passage of the Intolerable (Coercive) Acts, including the closing of the port of Boston, provoked keen resentment in the colonies. The First Continental Congress, convened in response to the Acts by the colonial Committees of Correspondence, met in Philadelphia on September 5, 1774. Fifty-six deputies represented all the colonies except Georgia. Peyton Randolph of Virginia was unanimously elected president, thus establishing usage of that term as well as “Congress.” Charles Thomson of Pennsylvania was elected secretary and served in that office during the 15-year life of the Congress.
To provide unity, delegates gave one vote to each state regardless of its size. The First Continental Congress included Patrick Henry, George Washington, John and Samuel Adams, John Jay, and John Dickinson. Meeting in secret session, the body rejected a plan for reconciling British authority with colonial freedom. Instead, it adopted a declaration of personal rights, including life, liberty, property, assembly, and trial by jury. The declaration also denounced taxation without representation and the maintenance of the British army in the colonies without their consent. Parliamentary regulation of American commerce, however, was willingly accepted.
In October 1774 the Congress petitioned the crown for a redress of grievances accumulated since 1763. In an effort to force compliance, it called for a general boycott of British goods and eventual nonexportation of American products, except rice, to Britain or the British West Indies. Its last act was to set a date for another Congress to meet on May 10, 1775, to consider further steps.
Before that Second Continental Congress assembled in the Pennsylvania State House, hostilities had already broken out between Americans and British troops at Lexington and Concord, Massachusetts. New members of the Second Congress included Benjamin Franklin and Thomas Jefferson. John Hancock and John Jay were among those who served as president. The Congress “adopted” the New England military forces that had converged upon Boston and appointed Washington commander in chief of the American army on June 15, 1775. It also acted as the provisional government of the 13 colony-states, issuing and borrowing money, establishing a postal service, and creating a navy. Although the Congress for some months maintained that the Americans were struggling for their rights within the British Empire, it gradually cut tie after tie with Britain until separation was complete. On July 2, 1776, with New York abstaining, the Congress “unanimously” resolved that “these United Colonies are, and of right ought to be, free and independent states.” Two days later it solemnly approved this Declaration of Independence. The Congress also prepared the Articles of Confederation, which, after being sanctioned by all the states, became the first U.S. constitution in March 1781.
The Articles placed Congress on a constitutional basis, legalizing the powers it had exercised since 1775. To underline this distinction, the Congress that met under the Articles of Confederation is often referred to as the Congress of the Confederation, or the Confederation Congress. This Congress continued to function until the new Congress, elected under the present Constitution, met in 1789.
What made you want to look up "Continental Congress"? Please share what surprised you most... | <urn:uuid:7a956338-e7f7-4e3b-9c6e-b3a742460ce6> | CC-MAIN-2013-20 | http://www.britannica.com/EBchecked/topic/134850/Continental-Congress | 2013-05-19T19:06:20 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368697974692/warc/CC-MAIN-20130516095254-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.963599 | 738 | 4.375 | 4 |
Refraction at a Boundary
Need to see it? View The Broken Pencil animation from the Multimedia Physics Studios.Flickr Physics
Visit The Physics Classroom's Flickr Galleries and enjoy a photo overview of the topic of refraction and lenses.Flickr Physics
Visit The Physics Classroom's Flickr Galleries and enjoy the terrific display of photos showing the refraction of light by dew drops.Flickr Physics
View a collection of incredible photos of reflection and refraction phenomena from TPC's Flickr Pool.
Looking for a lab that coordinates with this page? Try the Refraction Action Lab from The Laboratory.Flickr Physics
View a collection of incredible photos of reflection and refraction phenomena from TPC's Flickr Pool.Curriculum Corner
Learning requires action. Give your students this sense-making activity from The Curriculum Corner.Treasures from TPF
Need ideas? Need help? Explore The Physics Front's treasure box of catalogued resources on ray optics, including the topic of refraction.
Refraction and Sight
In Unit 13 of The Physics Classroom Tutorial, it was emphasized that we are able to see because light from an object can travel to our eyes. Every object that can be seen is seen only because light from that object travels to our eyes. As you look at Mary in class, you are able to see Mary because she is illuminated with light and that light reflects off of her and travels to your eye. In the process of viewing Mary, you are directing your sight along a line in the direction of Mary. If you wish to view the top of Mary's head, then you direct your sight along a line towards the top of her head. If you wish to view Mary's feet, then you direct your sight along a line towards Mary's feet. And if you wish to view the image of Mary in a mirror, then you must direct your sight along a line towards the location of Mary's image. This directing of our sight in a specific direction is sometimes referred to as the line of sight.
As light travels through a given medium, it travels in a straight line. However, when light passes from one medium into a second medium, the light path bends. Refraction takes place. The refraction occurs only at the boundary. Once the light has crossed the boundary between the two media, it continues to travel in a straight line. Only now, the direction of that line is different than it was in the former medium. If when sighting at an object, light from that object changes media on the way to your eye, a visual distortion is likely to occur. This visual distortion is witnessed if you look at a pencil submerged in a glass half-filled with water. As you sight through the side of the glass at the portion of the pencil located above the water's surface, light travels directly from the pencil to your eye. Since this light does not change medium, it will not refract. (Actually, there is a change of medium from air to glass and back into air. Because the glass is so thin and because the light starts and finished in air, the refraction into and out of the glass causes little deviation in the light's original direction.) As you sight at the portion of the pencil that was submerged in the water, light travels from water to air (or from water to glass to air). This light ray changes medium and subsequently undergoes refraction. As a result, the image of the pencil appears to be broken. Furthermore, the portion of the pencil that is submerged in water appears to be wider than the portion of the pencil that is not submerged. These visual distortions are explained by the refraction of light.
In this case, the light rays that undergo a deviation from their original path are those that travel from the submerged portion of the pencil, through the water, across the boundary, into the air, and ultimately to the eye. At the boundary, this ray refracts. The eye-brain interaction cannot account for the refraction of light. As was emphasized in Unit 13, the brain judges the image location to be the location where light rays appear to originate from. This image location is the location where either reflected or refracted rays intersect. The eye and brain assume that light travels in a straight line and then extends all incoming rays of light backwards until they intersect. Light rays from the submerged portion of the pencil will intersect in a different location than light rays from the portion of the pencil that extends above the surface of the water. For this reason, the submerged portion of the pencil appears to be in a different location than the portion of the pencil that extends above the water. The diagram at the right shows a God's-eye view of the light path from the submerged portion of the pencil to each of your two eyes. Only the left and right extremities (edges) of the pencil are considered. The blue lines depict the path of light to your right eye and the red lines depict the path of light to your left eye. Observe that the light path has bent at the boundary. Dashed lines represent the extensions of the lines of sight backwards into the water. Observe that these extension lines intersect at a given point; the point represents the image of the left and the right edge of the pencil. Finally, observe that the image of the pencil is wider than the actual pencil. A ray model of light that considers the refraction of light at boundaries adequately explains the broken pencil observations.
Flickr Physics Photo
The broken pencil phenomenon occurs during your everyday spearfishing outing. Fortunately for the fish, light refracts as it travels from the fish in the water to the eyes of the hunter. The refraction occurs at the water-air boundary. Due to this bending of the path of light, a fish appears to be at a location where it isn't. A visual distortion occurs. Subsequently, the hunter launches the spear at the location where the fish is thought to be and misses the fish. Of course, the fish are never concerned about such hunters; they know that light refracts at the boundary and that the location where the hunter is sighting is not the same location as the actual fish. How did the fish get so smart and learn all this? They live in schools.
Now any fish that has done his/her physics homework knows that the amount of refraction that occurs is dependent upon the angle at which the light approaches the boundary. We will investigate this aspect of refraction in great detail in Lesson 2. For now, it is sufficient to say that as the hunter with the spear sights more perpendicular to the water, the amount of refraction decreases. The most successful hunters are those who sight perpendicular to the water. And the smartest fish are those who head for the deep when they spot hunters who sight in this direction.
Since refraction of light occurs when it crosses the boundary, visual distortions often occur. These distortions occur when light changes medium as it travels from the object to our eyes. | <urn:uuid:f573244e-5ac3-4fed-b8f9-567bac22c4bf> | CC-MAIN-2013-20 | http://www.physicsclassroom.com/class/refrn/U14L1b.cfm | 2013-05-19T18:33:44 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368697974692/warc/CC-MAIN-20130516095254-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.942208 | 1,417 | 4.09375 | 4 |
MAKING GRAPHENE NANORIBBONS: The process for tailoring of the silicon carbide crystal for selective graphene growth and device fabrication is illustrated, starting with the top left figure. (A) A nanometer-scale step is etched into the silicon carbide crystal by a fluorine-based reactive ion etch (RIE). (B) The crystal is heated to about 1200-1300 degrees Celsius (at low vacuum), inducing step flow and relaxation to the etching. (C) When the crystal is further heated to about 1450 degrees Celsius, a graphene nanoribbon forms. (D) From there the source and drain contacts, graphene nanoribbon channel, aluminum oxide gate dielectric and metal top gate are added. Image: COURTESY OF WALTER DE HEER
For years researchers have held out hope that graphene would be the material to pick up the mantle in the electronics industry when silicon hits its limits as the material of choice for making devices smaller, faster and cheaper. Yet, turning graphene's promise into a reality has been difficult to say the least, in part because of the inherent difficulty of working with a substance one atom thick.
Methods of cutting graphene into useable pieces tend to leave frayed edges that mitigate the material's effectiveness as a conductor. Now, a team of researchers at Georgia Institute of Technology led by Walter de Heer claims to have made a significant advance in that area by developing a technique for creating nanometer-scale graphene ribbons without rough edges. (A nanometer is one billionth of a meter.)
Graphene has, of course, made headlines throughout the scientific world this week, thanks to the awarding of the Nobel Prize in Physics to two researchers at the University of Manchester in England who in 2004 pioneered a way of isolating graphene by repeatedly cleaving graphite with adhesive tape. The Nobel Prize committee recognized Andre Geim and Konstantin Novoselov "for groundbreaking experiments regarding the two-dimensional material graphene."
Unlike the approach taken by Geim and Novoselov, de Heer and his team in the past have created graphene sheets by heating a silicon carbide surface to 1,500 degrees Celsius until a layer of graphene formed. The graphene was then cut to a particular size and shape using an electron beam. "This was a serious problem because cutting graphene leaves rough edges that destroy a lot of graphene's good properties, making it less conductive," says de Heer, regents' professor in Georgia Tech's School of Physics.
De Heer's new approach, described October 3 in Nature Nanotechnology, is to etch patterns into the silicon carbide and then heat that surface until graphene forms within the etched patterns. (Scientific American is part of Nature Publishing Group.) In this way graphene forms in specific shapes and sizes without the need for cutting. "The whole philosophy has changed," he says. "We're not starting with an infinite sheet of graphene; we're growing it where we want to grow it."
The researchers claim to have used the technique to fabricate a densely packed array of 10,000 top-gated graphene transistors on a 0.24-square-centimeter chip, a step toward their ultimate goal of creating graphene components that can be integrated with silicon for new generations of electronics. Such a consolidation would be a key milestone towards making microprocessors able to operate at terahertz speeds, 1,000 times faster than today's chips (whose speeds are clocked at billions of hertz). Another goal is to reduce heat generation as an increasing number of transistors are packed onto each chip. Such advances would continue to validate Moore's law even as silicon circuits reach their miniaturization limit. "In principle, graphene can overcome silicon's limitation," de Heer says. "If we completely succeed [only] time will tell."
Graphene and silicon will be able to coexist much the same way that airplanes and freight ships are used for transporting cargo. "They move at different speeds, but both are important because they have different costs," de Heer says. "I think a similar thing will happen in electronics."
De Heer is also quick to acknowledge that, although the study of graphene dates back to the 1970s, the field still has a long way to go. He and his team are now investigating how the ribbons they created will perform over time and to what degree their new approach improves on cutting pieces of graphene out of larger sheets.
With so many open questions about graphene's viability, de Heer says he was surprised that the Nobel selection committee recognized graphene at this time. The technology has tremendous potential but only a fraction of that potential has been realized to date. "It's a little early," he says. "If you ask me the bottom line—What has graphene accomplished?—it's still trying to find its way." | <urn:uuid:6708de11-4253-4cbc-926a-ece70408faa5> | CC-MAIN-2013-20 | http://www.scientificamerican.com/article.cfm?id=nobel-graphene-spotlight | 2013-05-19T18:28:00 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368697974692/warc/CC-MAIN-20130516095254-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.958932 | 997 | 4.1875 | 4 |
Now is the time of year when snake sightings become more common at Naval Base Ventura County (NBVC).
California has a variety of snakes, most of which are harmless. The exceptions are California’s only native venomous snakes — rattlesnakes. At NBVC Point Mugu there is only one native species, the Southern Pacific Rattlesnake.
Rattlesnakes can cause serious injury to humans — on rare occasions even death. Generally not aggressive, rattlesnakes strike when threatened or deliberately provoked, but given room they will retreat.
Most snake bites occur when a rattlesnake is handled or accidentally touched by someone walking or climbing.
Approximately 8,000 people annually are treated for poisonous snake bites in the United States. However, the California Poison Control Center notes that rattlesnakes account for only about 800 of those bites each year with about one to two deaths.
See if you’ve heard any of these common myths about rattlesnakes:
Myth: Baby rattlesnakes are more deadly than the adults.
Fact: Baby rattlesnake venom has the same concentration and formulation as the adults. The truth is it doesn’t take very much venom to create a full reaction in an adult human. So even the smaller amount injected by a young rattlesnake will cause a full reaction, giving people the impression they must be more deadly.
Myth: Rattlesnakes can jump.
Fact: Rattlesnakes, when fully coiled like a hose, can strike half the totally length of their body. For example, a striking distance for a 3-foot rattlesnake is 1½ feet away. The lower half of their body will propel the upper half forward in a full strike. However, the lower half of their body never leaves the ground.
Myth: Rattlesnakes always rattle before they strike.
Fact: When given enough time, a rattlesnake will warn anything around it that it feels is a direct threat by rattling its tail. It sounds more like a buzzer than a rattle. Mostly they hide and hope whatever is coming near them continues to walk by without noticing them. If surprised, they will strike without rattling their tail.
Rattlesnakes are nocturnal hunters. Sometimes they will come out during the day to warm themselves, especially in the mornings.
Take the following precautions:
Step on logs and rocks, never over them, as a snake could be coiled up behind the barrier where you cannot see it. Also be careful when stepping over the doorstep. Snakes like to crawl along the edge of buildings where they are protected on one side.
Keep an eye out when walking through dense brush, and watch where you put your feet. If you are out in the brush wear over-the-ankle boots and loose-fitting long pants.
Discourage snakes by removing piles of boards or rocks around buildings. But use caution when removing those piles as there may already be a snake there.
If you see a rattlesnake in occupied areas of NBVC, such as housing or in administrative offices, call 911. Dispatchers will alert the proper responder to handle the snake. If you are out in the natural areas and see a rattlesnake, leave it alone and go a safe distance around it. | <urn:uuid:ede1c232-22d7-4fb9-81c7-f9cb5466ce06> | CC-MAIN-2013-20 | http://www.thelighthousenews.com/news/2012/jun/27/snakes-on-the-base-heres-what-to-do/?lighthouse=1 | 2013-05-19T18:34:41 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368697974692/warc/CC-MAIN-20130516095254-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.94814 | 693 | 4.0625 | 4 |
German soldiers lead Jews captured during the Warsaw ghetto uprising to the assembly point for deportation. Poland, May 1943.
National Archives and Records Administration, College Park, Md.
The Nazi regime used rail transport as one method to forcibly rearrange the ethnic composition of eastern Europe within the framework of World War II. In 1941, the Nazi leadership decided to implement the "Final Solution," the systematic mass murder of European Jewry. The German authorities used rail systems across the continent to transport, or deport, Jews from their homes, primarily to eastern Europe. Once they had begun to methodically kill Jews in specially constructed killing centers, German officials deported Jews to these facilities by train or, when trains were not available or the distances were short, by truck or on foot.
OFFICIALS COORDINATE MASS TRANSPORT BY TRAIN
At the Wannsee Conference on January 20, 1942, held near Berlin, SS, Nazi Party, and German state officials met to coordinate the deportation of European Jews to killing centers (also known as “extermination camps”) already in operation or under construction in German-occupied Poland. The participants of the conference estimated that the "Final Solution" would involve the deportation and murder of 11 million Jews, including Jewish residents of nations outside German control, such as Ireland, Sweden, Turkey, and Great Britain.
Deportations on this scale required the coordination of numerous German government agencies including the Reich Security Main Office (Reichssicherheitshauptamt--RSHA), the Main Office of the Order Police, the Ministry of Transportation, and the Foreign Office. The RSHA or regional SS and police leaders coordinated and often directed the deportations. The Order Police, often reinforced by local auxiliaries or collaborators in occupied territories, rounded up and transported the Jews to the killing centers. Working with department IV B 4 of the RSHA commanded by SS Lieutenant Colonel Adolf Eichmann, the Ministry of Transportation coordinated train schedules. The Foreign Office negotiated with Germany's Axis partners over the transfer of their Jewish citizens to German custody.
The Germans attempted to disguise their intentions. They sought to portray the deportations as a "resettlement" of the Jewish population in labor camps in the "East." In reality, the "resettlement" in the "East" became a euphemism for transport to the killing centers and mass murder.
INSIDE THE RAILCARS
German railroad officials used both freight and passenger cars for the deportations. German authorities generally did not give the deportees food or water for the journey, even when they had to wait for days on railroad spurs for other trains to pass. Packed in sealed freight cars and suffering from overcrowding, they endured intense heat during the summer and freezing temperatures during the winter. Aside from a bucket, there was no sanitary facility. The stench of urine and excrement added to the humiliation and suffering of the deportees. Lacking food and water, many of the deportees died before the trains reached their destinations. Armed police guards accompanied the transports; they had orders to shoot anyone who tried to escape.
Between December 1941 and July 1942, the SS and police officials established five killing centers in German-occupied Poland: Chelmno, Belzec, Sobibor, Treblinka 2 (Treblinka 1 was a forced-labor camp for Jews), and Auschwitz-Birkenau, also known as Auschwitz II. SS and police authorities in the Lublin District of the Generalgouvernement (that part of German-occupied Poland not directly annexed to Germany, attached to German East Prussia, or incorporated into the German-occupied Soviet Union) managed and coordinated the deportations to Belzec, Sobibor, and Treblinka within the framework of “Operation Reinhard.”
The principal victims at Belzec were Jews from southern and southeastern Poland, but also Jews deported from the so-called Greater German Reich (Germany, Austria, the Sudetenland, and the Protectorate of Bohemia and Moravia) to District Lublin between October 1941 and the end of summer 1942. Most Jews deported to Sobibor came from the Lublin District; but German authorities also transported French and Dutch Jews to Sobibor in spring and summer 1943 and small groups of Soviet Jews from Belorussian and Lithuanian ghettos in late summer 1943. German officials transported the Jews from the Warsaw and Radom districts of the Generalgouvernement and from the Bialystok administrative district to Treblinka 2, where SS and police officials murdered them. German authorities deported most of the Jewish residents of the Lodz ghetto as well as the ghetto's surviving Roma and Sinti (Gypsy) residents to Chelmno between January 1942 and spring 1943, and then in early summer 1944.
In 1943 and 1944, the Auschwitz-Birkenau killing center played a significant role in the German plan to kill the European Jews. Beginning in late winter 1943, trains arrived at Auschwitz-Birkenau on a regular basis carrying Jews from virtually every German-occupied country of Europe -- from as far north as Norway to the Greek island of Rhodes off the coast of Turkey in the south, from the French slopes of the Pyrenees in the west to the easternmost reaches of German-occupied Poland and the Baltic states. Another concentration camp, located near Lublin and known as Majdanek, served as a site for murdering targeted groups of Jewish and non-Jewish prisoners by gas and other means.
The Germans killed nearly three million Jews in the five killing centers.
WESTERN AND NORTHERN EUROPE
German officials and local collaborators deported Jews from western Europe via transit camps, such as Drancy in France, Westerbork in the Netherlands, and Mechelen (Malines) in Belgium. Of the approximately 75,000 Jews deported from France, more than 65,000 were deported from Drancy to Auschwitz-Birkenau, and approximately 2,000 to Sobibor. The Germans deported over 100,000 Jews from the Netherlands, almost all from Westerbork: about 60,000 to Auschwitz and over 34,000 to Sobibor. Between August 1942 and July 1944, 28 trains transported more than 25,000 Jews from Belgium to Auschwitz-Birkenau via Mechelen.
In the autumn of 1942, the Germans seized approximately 770 Norwegian Jews and deported them by boat and train to Auschwitz. An effort to deport the Danish Jews in September 1943 failed when the resistance in Denmark, alerted to the impending roundup, assisted the mass escape of Danish Jews to neutral Sweden.
The Germans deported Jews from Greece, from Italy, and from Croatia. Between March and August 1943, SS and police officials deported more than 40,000 Jews from Salonika, in northern Greece, to Auschwitz-Birkenau, where the camp staff killed most of them in the gas chambers upon arrival. After the Germans occupied northern Italy in September 1943, they deported about 8,000 Jews, most of them to Auschwitz-Birkenau. Based on an agreement with their Croatian Axis partner, German officials took custody of around 7,000 Croat Jews and deported them to Auschwitz-Birkenau.
Bulgarian gendarmes and military units rounded up and deported around 7,000 Jewish residents of Bulgarian-occupied Macedonia, formerly a part of Yugoslavia, via a transit camp at Skopje. Bulgarian authorities concentrated approximately 4,000 Jews residing in Bulgarian-occupied Thrace at two assembly points in Bulgaria and transferred them to German custody. In all, Bulgaria deported more than 11,000 Jews to German-controlled territory. The German authorities deported these Jews to Treblinka 2 and killed them in the gas chambers.
German authorities began to deport Jews from the Greater German Reich in October 1941, while the construction of the killing centers was still in the planning stage. Between October 15, 1941, and November 4, 1941, German authorities deported 20,000 Jews to the Lodz ghetto. Between November 8, 1941, and October 1942, German authorities deported approximately 49,000 Jews from the Greater German Reich to Riga, Minsk, Kovno, and Raasiku, all in the Reich Commissariat Ostland (German-occupied Belorussia, Lithuania, Latvia, and Estonia). SS and police officials shot the overwhelming majority of the deportees upon arrival in the Reich Commissariat Ostland. German authorities deported another approximately 63,000 German, Austrian, and Czech Jews to the Warsaw ghetto and to various locations in District Lublin, including the transit camp-ghettos at Krasnystaw and Izbica and the killing center in Sobibor, between March and October 1942. German Jewish residents of the Lodz and Warsaw ghettos were later deported with Polish Jews to Chelmno, Treblinka 2, and, in 1944, to Auschwitz-Birkenau.
The first transport of Jews from the Greater German Reich directly to Auschwitz arrived on July 18, 1942, from Vienna. From late October 1942 until January 1945, German authorities deported more than 71,000 Jews remaining in the Greater German Reich to Auschwitz-Birkenau. The Germans deported elderly or prominent Jews from Germany, Austria, the Protectorate of Bohemia and Moravia, and western Europe to the Theresienstadt ghetto, which also served as a transit camp for deportations further east, most often to Auschwitz-Birkenau.
Between May and July 1944, Hungarian gendarmes, in cooperation with German security police officials, deported nearly 440,000 Jews from Hungary. Most of them were sent to Auschwitz-Birkenau. With the cooperation of Slovak authorities, the Germans deported more than 50,000 Slovak Jews to the concentration camps of Auschwitz-Birkenau and Majdanek. The Slovak Jews were the first to be selected for the gas chambers at Birkenau. In the autumn of 1944, German SS and police officials deported 10,000 Slovak Jews to Auschwitz-Birkenau during the Slovak uprising. This deportation was the last major one to a killing center.
Between March 1942 and November 1943, the SS and police deported approximately 1,526,000 Jews, most of them by train, to the killing centers of Operation Reinhard: Belzec, Sobibor, and Treblinka. Between December 8, 1941, and March 1943 and again in June-July 1944, SS and police officials deported approximately 156,000 Jews and a few thousand Roma and Sinti to the killing center at Chelmno by train, by truck, and on foot. Between March 1942 and December 1944, the German authorities deported approximately 1.1 million Jews and 23,000 Roma and Sinti to Auschwitz-Birkenau, the overwhelming majority by rail. Fewer than 500 survived the Operation Reinhard killing centers. Only a handful of Jews survived the transports to Chelmno. Perhaps as many as 100,000 Jews survived deportation to Auschwitz-Birkenau by virtue of having been selected for forced labor upon arrival. | <urn:uuid:35528fe2-8d9d-4615-b7d2-f8ad93be5e24> | CC-MAIN-2013-20 | http://www.ushmm.org/wlc/en/article.php?ModuleId=10005405 | 2013-05-19T18:59:27 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368697974692/warc/CC-MAIN-20130516095254-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.954529 | 2,267 | 4.15625 | 4 |
One of the Best Science Encyclopedia and Reference Book Sets for Students
The Student Discovery Science Encyclopedia is designed to meet the science information needs of both young learners and visual learners. This 13-volume set features easy-to-understand language, fun facts, and thousands of colorful illustrations and diagrams. Special features and engaging articles make science for young learners accessible and fun.
Key features of the set include more than 2,100 entries, 3,300 illustrations, and over 60 experiments and activities. The articles provide up-to-date, accurate, and clear information on hundreds of high-interest subjects—from space science and physics to biology and zoology—relevant to science curriculums for young learners. The Student Discovery Science Encyclopedia also includes many of the features also found in adult reference products, such as cross-references, guide words, and pronunciation guides. Volume 13 also contains a cumulative index. These elements promote familiarity with reference sources and develop research skills.
Several special features make the Student Discovery Science Encyclopedia a standout science resource for young learners. The Science Guide in Volume 13 functions as a guide to the dozens of activities and experiments in the set. It provides information on how to prepare the experiments and activities, as well as tips on how to plan a science fair project. Throughout the set, biographies of important scientists from the past and present provide fascinating insight into the people behind the technology, medicine, and scientific discoveries that have built and changed our world. Lastly, the stunning cover design draws readers in while thousands of colorful illustrations and diagrams provide both visual interest and scientific information. These features make the Student Discovery Science Encyclopedia a perfect addition to home or school libraries.
Browse through all of World Book's kids' science books! | <urn:uuid:3c0ca164-4f19-41a1-9bb5-5614ca566dfd> | CC-MAIN-2013-20 | http://www.worldbook.com/all/item/37-student-discovery-science-encyclopedia | 2013-05-19T18:35:25 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368697974692/warc/CC-MAIN-20130516095254-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.900405 | 350 | 4.1875 | 4 |
During their embryonic development, all chordates pass through a stage called the pharyngula [View] with these features:
There are three subdivisions of the chordates:
- a dorsal, tubular nerve cord ("1") running from anterior to posterior. At its anterior end, it becomes enlarged to form the brain.
- a flexible, rodlike notochord ("2") that runs dorsal to the digestive tract and provides internal support. In vertebrate chordates, it is replaced by a vertebral column or backbone long before maturity.
- pairs of gill pouches. These lateral outpocketings of the pharynx are matched on the exterior by paired grooves. In aquatic chordates, one or more pairs of gill pouches break through to the exterior grooves, forming gill slits ("3"). These provide an exit for water taken in through the mouth and passed over the gills.
- a tail that extends behind the anus
The cephalochordates and tunicates never develop a vertebral column. They are thus "invertebrates" and are discussed with the other invertebrates. [Link]
The vast majority of chordates have a skull enclosing their brain, eyes, inner ear, etc.). All but one group of these (the hagfishes) also convert their notochord into a vertebral column or backbone thus qualifying as vertebrates.
Although hagfishes, never replace their notochord with a vertebral column, and thus might seem not to qualify as vertebrates, they share a number of other features with other vertebrates and certainly should be classified with them. Still uncertain is whether they represent the most primitive vertebrates or are simply degenerate vertebrates (probably the latter).
All the other members of the craniata convert their notochord into a vertebral column or "backbone" (even though in some it is made of cartilage not bone). They also differ from all other animals in having quadrupled their HOX gene cluster; that is, they have 4 different clusters of HOX genes (on 4 separate chromosomes). Perhaps this acquisition played a key role in the evolutionary diversity that so characterizes the vertebrates.
The vertebrates are subdivided into the
- jawless vertebrates (Agnatha) and the
- jawed vertebrates (Gnathostomata)
Lampreys and hagfishes are the only jawless vertebrates to survive today. They both have a round mouth and for this reason are often referred to as cyclostomes. They are the most primitive of the vertebrates. By "primitive", a biologist means that they are the least changed from the first vertebrates.
Besides lacking jaws,
- They have no paired pectoral (shoulder) or pelvic (hip) fins.
- Their notochord persists for life, never being completely replaced by a backbone even in the lampreys.
- They have no scales.
- The axons of their neurons are unmyelinated (like those of all invertebrates).
- Lampreys have both an innate immune system and an adaptive immune system, but the latter is entirely different from that found in the jawed vertebrates.
The photo (courtesy of the Carolina Biological Supply Company) is of the West Coast lamprey. Note the gill slits and the absence of paired pectoral and pelvic fins.
As well as having jaws, all the members of this group have
Fossils of cartilaginous fishes become abundant in deposits dating to the Devonian period. They were very much like the sharks of today.
The group, which today is made up of some 800 species of
gets its name from the fact that their skeleton is made of cartilage, not bone.
- myelin sheaths around the axons of their neurons. This permits much more rapid transmission of nerve impulses — a trait probably as important for active vertebrates as their jaws.
- an adaptive immune system backing up their innate immune system.
With their gills exposed to sea water, all marine fishes are faced with the problem of conserving body water in a strongly hypertonic environment. Sea water is about 3.5% salt, over 3 times that of vertebrate blood. The cartilaginous fishes solve the problem by maintaining such a high concentration of urea in their blood (2.5% — far higher than the ~0.02% of other vertebrates) that it is in osmotic balance with — that is, is isotonic to — sea water.
This ability develops late in embryology, so the eggs of these species cannot simply be released in the sea. Two solutions are used:
- Enclose the egg in an impervious case filled with isotonic fluid before depositing it in the sea.
- Retain the eggs and embryos within the mother's body until they are capable of coping with the marine environment.
Both these solutions require internal fertilization, and the cartilaginous fishes were the first vertebrates to develop this. The pelvic fins of the male are modified for depositing sperm in the reproductive tract of the female.
As their name indicates, the skeleton in this group is made of bone.
The group is subdivided into the
- ray-finned fishes (Actinopterygii) and
- lobe-finned fishes (Sarcopterygii)
- Their fins are thin and supported by spines.
- There are over 30,000 species (representing more than half of all living vertebrates).
- They are an important part of the human diet in many areas of the world and, in affluent nations, support a large sports fishing industry.
Although the earliest bony fishes may have appeared late in the Silurian period, their fossils become abundant in freshwater deposits of the Devonian period. In addition to gills, these fishes had a pair of pouched outgrowths from the pharynx which served as lungs. They were inflated with air taken in through the mouth and may have provided a backup gas exchange organ when the water became too warm and stagnant to carry enough dissolved oxygen. Their kidneys were adapted for the hypotonic environment in which they lived. [Illustrated discussion]
These animals diversified through the remainder of the Devonian period (which is often called the "Age of Fishes"). Some migrated to the oceans. In this more stable environment, their lungs became transformed into a swim bladder with which they could alter buoyancy. Their kidneys became transformed as well adapting them to their new — hypertonic — surroundings. [Link to discussion]
The only ones to survive today are:
- two species of coelacanths. Coelacanths were long thought to have become extinct at the end of the Mesozoic era, some 70 million years ago. But in December 1938, a living coelacanth, Latimeria chalumnae, was pulled up from the depths of the ocean off the east coast of Africa. Since then, over 200 additional specimens have been caught.
- several species of lungfish found in Africa, South America, and Australia.
The nostrils of bony fishes open only to the outside and are used for smelling. Some of the lobe-finned fishes developed internal openings to their nostrils. This made it possible to breath air with the mouth closed as modern lungfishes do.
Judging from present-day lungfishes, two other significant adaptations evolved in this group:
- two atria and a partial septum in the ventricle of the heart (similar to the frog heart). This permitted a partial separation of oxygenated blood returning from the lung(s) and the deoxygenated blood returning from the rest of the body.
- an enzyme system to convert ammonia into the less toxic urea. This mechanism is highly-developed in the African and South American lungfishes. While in the water, these fishes excrete their waste nitrogen as ammonia, just as most ray-finned fishes do. In time of drought, these animals burrow in the mud and switch to urea production.
These rare modern lobe-finned fishes are the sole survivors of once-flourishing groups that also gave rise to the tetrapods — the four-legged vertebrates. In the Devonian (perhaps as early as 395 million years ago), the paired fins of some sarcopterygians moved under the body and developed limbs (complete with digits). This enabled them to venture out on land. So once again, evolution was opportunistic giving rise to the first land vertebrates, the amphibians.
The figure shows the relationship between the bones of two tetrapod forelegs and the pectoral fin of a sarcopterygian.
With their bony limbs and lungs inherited from their lobe-finned ancestors, amphibians were so successful during the Carboniferous (Mississippian and Pennsylvanian periods) that these periods are known as the Age of Amphibians.
The Carboniferous was followed by the Permian, when the earth became colder and dryer. The fortunes of the amphibians began to decline until only three groups — totaling about 6500 species — remain today:
As the name suggests, amphibians are only semiterrestrial:
- frogs and toads (Anura) (The one pictured is Rana pipiens, the leopard frog.)
- salamanders and newts (Urodela)
- caecilians (Apoda), which are rare, limbless, tropical animals.
- Their skin is soft and moist so they are at risk of desiccation in dry surroundings.
- Their eggs have no waterproof covering so
- they must be laid in water (which makes them useful animals for studying embryonic development) where they are fertilized or
- placed within the mother's body (some use a pouch in the skin, some use their mouth, some even use their stomach — which stops secreting acid and enzymes for the duration!) after external fertilization.
Some 310 million years ago (in the Pennsylvanian), some amphibians evolved the ability to lay shelled, yolk-filled eggs.
The embryo developing within the egg produces 4 extraembryonic membranes: the
|Link to descriptions of the heart and kidneys of amphibians.|
- amnion, which surrounds the embryo with a fluid as watery as the pond water around a frog's egg (and accounts for the name amniota);
- chorion, which serves for gas exchange;
- allantois, which serves both for gas exchange and to store metabolic wastes;
- yolk sac, which supplies the embryo with food.
A shelled egg is just as impervious to sperm as to water, so its arrival coincided with the development of internal fertilization.
The early aminotes soon diverged into two major lines of descent:
- the synapsids (the ancestors of the mammals) and the
With the arrival of the cold, dry Permian, reptiles were well-adapted to survive because of their development of a shelled, yolk-filled egg which could be deposited on land without danger of drying out.
The photo (courtesy of the Carolina Biological Supply Company) shows an American chameleon emerging from its egg.
Other adaptations that enabled the reptiles to flourish for the next 220 million years were:
Beginning late in the Paleozoic era and exploding in the Triassic period, the reptiles underwent a remarkable adaptive radiation producing the diapsids.
- a dry, water-impermeable skin;
- lungs inflated by expansion of the rib cage [View];
- a partial septum in the ventricle reducing the mixing of oxygenated and deoxygenated blood [Link to illustrated discussion.]
This group developed the ability to convert their nitrogenous waste into uric acid. Uric acid is almost insoluble in water so its excretion involves little loss of water. (It is the whitish paste that pigeons leave on statues.) This modification largely freed the diapsids and their descendants from a dependence on drinking water; the water in their food is usually sufficient.
Diapsid evolution soon produced:
Thecodonts were able to run fast by rising up on their hind legs, which became larger than their front legs, and using their long tail for balance. The group diversified into:
- lizards and snakes (Squamata — some 6,300 species survive today);
- crocodiles and alligators (Crocodilia — 22 species survive today);
- an extraordinary array of dinosaurs from some of which evolved today's birds.
The dominance of the reptiles during the Mesozoic era has giving it the name, the Age of Reptiles.
Feathers are the feature that most clearly distinguishes the birds from their dinosaur ancestors. These scaly skin outgrowths provide
Other adaptations are:
- a light, strong surface for the wings;
- heat insulation, making it possible to be small but still warm-blooded.
All of these adaptations help birds to fly (to escape predators and find suitable food and nesting sites). Almost 10,000 species are known today.
The early synapsids had their legs under, rather than at the sides of, the body. This permitted more rapid running on land.
- hollow bones;
- a single gonad (in females), which becomes enlarged and active only during the breeding season;
- no teeth (their function is replaced by the gizzard);
- powerful breast muscles attached to an enlarged sternum;
- a four-chambered heart.
- Soon a group of small, active land-dwelling therapsids evolved from these and, by the Jurassic, they had produced the
Mammals first appeared early in the Mesozoic. By ~220 million years ago, they had diverged into the
- milk secreted from mammary glands;
- hair; conserves body heat permitting even tiny mammals to be warm-blooded;
- teeth specialized for cutting (incisors), tearing (canines) and grinding (molars) their food;
- some 5,400 species living today.
The only prototheria to survive until now are the monotremes: the duckbill platypus and three species of spiny anteaters (echidnas). These animals retain several traits of their therapsid ancestors including
- Prototheria ("first beasts") and
Although the therians diverged into the
- a cloaca — the final segment of the digestive tract into which both the urinary and reproductive tracts empty (monotreme = single hole);
- lay shelled eggs.
some 190 million years ago, it was not until the extinction of the dinosaurs at the end of the Cretaceous (~66 million years ago — Link) that they began to diversify into the various orders that we see today.
- marsupials (Marsupialia) and
- placental mammals (Placentalia)
Their amniotic egg has no shell and develops for only a brief time within the reproductive tract of the mother. During this time they receive some nourishment from the yolk sac which grows into the wall of the uterus. They are born at such an early stage of development [View] that they must crawl into a pouch on the mother's abdomen, attach themselves to one of her milk-dispensing nipples, and complete development there.
Outside of Australia, the only marsupials found today are the opossums — one species in North America, some 69 species in South America. In Australia, however, where they were protected far longer from an influx of placental mammals, there is still an broad array of marsupials. [View, for example, the wombat.]
The placental mammals, with some 4,500 species living today, retain their shell-less amniotic egg within the mother. The egg contains little yolk, but the extraembryonic membranes form an
through which the young secure nourishment (and oxygen) from their mother until they are well-developed and ready to be born.
- umbilical cord and
The table shows the orders of placental mammals and representatives of each.
The members of orders shown with the same color belong to a single clade; that is, they are more closely related to each other than to the mammals in any other orders.
These clades are based on the most recent analysis of DNA sequences of several genes — both nuclear and mitochondrial — and the building of phylogenetic trees from these data.
||lemurs, New World monkeys, Old World monkeys, great apes (hominoids), humans
||rats, mice, squirrels, beaver
||dogs, cats, lion, skunk, walrus, sea lion
|horse, zebra, rhinoceros
(even-toed ungulates and
|cow, sheep, pig
giraffe, hippopotamus and whales, dolphins, porpoises
The 5 orders shown in yellow are found in Africa. They appear to be the most primitive of the placental mammals.
The 2 orders shown in red (armadillos, sloths, giant anteaters) probably arose in the part of Gondwana that today is South America.
The hugely-successful glires (rodents and rabbits) form a clade (light blue) that is so closely related to the clade (dark blue) that includes the tree shrews, the flying lemurs, and all our primate relatives, that they are grouped together. [Link to page on primate evolution.]
These 6 orders, shown in green, have been assigned to the Laurasiatheria because they are first found in the supercontinent of Laurasia. [ map and discussion ]
The even-toed ungulates and the cetaceans turn out to be so closely related that they are placed in a single order the Cetartiodactyla. In fact, hippos appear to be more closely related to the cetaceans than they are to the other even-toed ungulates.
23 April 2013 | <urn:uuid:db17c627-2bc4-43a0-b14d-2d4ed651cb57> | CC-MAIN-2013-20 | http://home.comcast.net/~john.kimball1/BiologyPages/V/Vertebrates.html | 2013-05-22T14:25:05 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368701852492/warc/CC-MAIN-20130516105732-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.935197 | 3,801 | 4.09375 | 4 |
Illinois Learning Standards
Stage C - Fine Arts—Music
Students who meet the standard understand the sensory
elements, organizational principles, and expressive qualities
of the arts.
- Distinguish between loud/soft, high/low sounds.
- Distinguish between fast/slow music.
- Distinguish between same and different tone colors (timbres)
of voices, classroom instruments, and environmental sounds.
- Distinguish between long and short sounds.
- Echo a rhythm pattern.
- Replicate the beat in a musical composition.
- Identify simple music forms (e.g. rondo, ostinato) when
- Identify different sensory elements that create a mood,
emotion, or idea in a simple musical selection.
Students who meet the standard understand the similarities,
distinctions, and connections in and among the arts.
- Compare sensory elements, organizational principles, and
expressive qualities shared among several art forms that
express a similar idea (e.g. beginning, middle, and end
in music, dance, and drama).
- Compare the use of sound, movement, action, or visual
images to express similar ideas (e.g., subject matter such
as night, ocean; emotions/moods such as sad, scary).
Students who meet the standard understand processes,
traditional tools, and modern technologies used in the arts.
- Distinguish between the sounds of two different voices
(e.g., man and child).
- Distinguish between the sounds of two different environmental
sounds (e.g., pencil sharpener and chalkboard).
- Distinguish between the sounds of two different classroom
instruments (e.g., tambourine and drum).
- Identify orchestral/band instruments visually.
- Use appropriate vocal timbre and volume when singing classroom
- Use correct technique (e.g., holding mallets, striking
drums) when playing classroom instruments.
- Echo, read, and/or write accurately rhythm patterns with
whole, half, quarter, and eighth notes and rests in 2/4,
3/4, 4/4 meter signatures.
- Sing or play accurately simple pitch notation in the treble
clef using a symbol system (e.g., icons, syllables, numbers,
Students who meet the standard can apply skills
and knowledge necessary to create and perform in one or more
of the arts.
- Sing on pitch or play on classroom instruments songs of
various cultures in rhythm, with appropriate timbre and
maintaining a steady tempo.
- Improvise rhythmic and melodic accompaniments for songs
of various cultures.
- Create short songs or instrumental pieces within specified
Students who meet the standard can analyze how the
arts function in history, society and everyday life.
- Distinguish between appropriate and inappropriate audience
- React to performances/ art works in a respectful, constructive,
and supportive manner.
- Match the types of occupations with their art form (e.g.,
actor, director, playwright, designer with drama).
- Compare ways the arts are used in a celebration (e.g.,
masks, costumes, banners, songs, dances).
- List the things that artists make or do when they communicate
through the arts (e.g., pictures, songs, advertisements,
stories, movements, buildings).
- Point out ways the arts are used for personal time and
enrichment (e.g., concerts, plays, exhibits, broadcasts,
social dances, choirs, lessons).
- Describe occupations that are related to the arts (e.g.,
photographer, illustrator, composer, playwright, choreographer,
Students who meet the standard understand how the
arts shape and reflect history, society and everyday life.
- Identify cultural characteristics of a work of art.
- Describe how the arts inform viewers about people and
events from history.
- Name significant artists in dance, drama, music, or visual
Return to Fine Arts Classroom
Assessments and Performance Descriptors | <urn:uuid:e59bfa48-3fef-4180-a2cb-e2b4b5dc02fc> | CC-MAIN-2013-20 | http://isbe.net/ils/fine_arts/music/stage_C/descriptor.htm | 2013-05-22T14:45:29 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368701852492/warc/CC-MAIN-20130516105732-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.845272 | 873 | 4.28125 | 4 |
Return to Physics Index
Monegain, Louise J. Park Manor
1) Students will learn basic understanding of inertia.
2) Students will demonstrate some activities illustrating inertia.
3) Students will develop a basic understanding of Newton's laws of motion.
Balls various sizes, pie pans with one fourth slice removed, pennies, heavy paper
circle, checkers, skate board, stuffed animal, glass, two eggs (one boiled, one raw),
cloth napkin, glass of water and straws.
Students should have prior knowledge of speed, force, acceleration, gravity and
friction. Demonstrate inertia by snatching a cloth napkin from under a glass of
water, and a paper circle from under a checker so that the checker falls into the
glass and spinning the two eggs. Group students into cooperative groupings to carry
out the following activities:
Activity 1 - Place a ball in the pie pan and spin the ball. Repeat this activity
using two balls of different mass.
Activity 2 - Put a ball in motion and try to blow it off of its path with a straw.
Repeat this activity using balls of various masses.
Activity 3 - Stack five checkers one on top of the other. Using your fore-finger
flick another checker sharply against the bottom checker of the stack to move it from
pile keeping pile undisturbed.
Discuss Newton's first law of motion with students. Have students answer these three
questions: 1) How does the pie pan and ball activity help prove the first law of
motion? 2) Which ball was the hardest to move off of the straight path? 3) Does
inertia increase with mass? | <urn:uuid:36e6f5ef-921e-4991-8a06-69f079752c70> | CC-MAIN-2013-20 | http://mypages.iit.edu/~smile/ph8912.html | 2013-05-22T14:52:59 | s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368701852492/warc/CC-MAIN-20130516105732-00000-ip-10-60-113-184.ec2.internal.warc.gz | en | 0.883569 | 354 | 4.3125 | 4 |
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