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Human Backbone?
Human back bone is a column consisting of 24 vertebrae and nine fused vertebrae in the sacrum and the coccyx. It is separated by intervertebral discs and is located in the torso. It protects and houses the spinal cord in its spinal canal.
1 Additional Answer Answer for: what is a human backbone
Vertebral Column
The spinal cord links the brain to the body. Without it, the brain would not be able to receive sensory data or communicate commands to the body. More »
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It depends on how tall the person is. The spinal column varies widely depending on a person's height (specifically how long the person's torso is)
The vertebral column consists of 24 vertebrae. Regions of the column
Education. In other words, doing whatever is possible to provide large numbers of individuals with the tools to discover the truth about the world for themselves, thereby promoting
The spine is divided into four parts (going from the head to the low back) Cervical: 7 vertebrae Thoracic: 12 vertebrae Lumbar: 5 vertebrae Sacrum: 5 vertebrae, fused There are newer
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There are 33 vertebrae in the human backbone. These vertebrae are irregularly shaped bones. There are five categories of vertebrae in the backbone, divided by ...
The human spine, also known as backbone, is made up of components called vertebrae. The spine contains 33 of these components and is used as a messaging system ...
The human back bone, which is also known as the spine is strong as well as flexible, and it plays a major role as part of the human skeleton that protects the ...
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Jpn J Ophthalmol. 2007 Sep-Oct;51(5):347-52. Epub 2007 Oct 5.
Changes in contrast sensitivity function and ocular higher order aberration by conventional myopic photorefractive keratectomy.
Author information
• 1Department of Ophthalmology, Institute of Clinical Medicine, University of Tsukuba, Ibaraki, Japan.
To evaluate the relation between induced changes in ocular higher order aberrations and changes in the contrast sensitivity function in patients undergoing excimer laser photorefractive keratectomy (PRK).
Myopic PRK using excimer laser was performed in 31 patients (56 eyes). The preoperative refractive error was -6.2 +/- 2.9 diopters. Before and 1 month after surgery, we measured the ocular higher order aberrations for a 4-mm pupil, and three indices of contrast sensitivity function. From the data collected, the area under the log contrast sensitivity function (AULCSF) was calculated.
PRK significantly reduced AULCSF (P = 0.004), low-contrast visual acuity (P = 0.004), and letter-contrast sensitivity (P = 0.013). Coma-like (P < 0.001) and spherical-like (P < 0.001) aberrations were significantly increased by surgery. The change in AULCSF by surgery significantly correlated with the change in coma-like (r = -0.468, P < 0.001) and spherical-like (r = -0.291, P = 0.033) aberrations. The change in low-contrast visual acuity by PRK significantly correlated with the change in coma-like aberration (r = 0.599, P < 0.007), but not with change in spherical-like aberrations (r = 0.136, P = 0.326). There were significant correlations between changes in letter-contrast sensitivity and changes in coma-like (r = -0.450, P < 0.001) and spherical-like (r = -0.255, P = 0.048) aberrations.
PRK significantly increases ocular higher order aberrations, which compromise contrast sensitivity function after surgery.
[PubMed - indexed for MEDLINE]
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Permalink for comment 343866
Member since:
Teach students skills not brand names.
The current aproach is to teach a brand name. Students don't learn computers and office programs, they learn Microsoft Windows and Microsoft Office. This is like teaching all the shop kids to use a hammer but only if it's a B&D #4 hammer with B&D #4 nails.
Students come out of school and sit infront of a machine that isn't Office and they have a panic attack; "but this isn't Word, how can it possible write words?"
Stick them infront of anything but WindowsXP desktop and they can't even figure out how to reach out and touch the bloody mouse.
Teach students how to use word processors not Word. They should use two or three at least during the yer they do word processing, spreadsheets and basic databases (this was Grade10 around here). If a file format can not be opened in multiple word processors; it's not accepted within the schools; sort of like all those government offices deciding that documents to and from constituents should be accessible on more than just Windows/Office crippled systems.
Reply Parent Score: 8
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Permalink for comment 446745
Richard Dale
Member since:
Just $0.02 from an old engineer...
I think it is a characteristic of the Python community in that they will say that everyone should use Python and be rude about other languages. Whereas Ruby guys will say use Ruby if it suits you, but feel free to use something else like Python if it doesn't suit you, and we won't hold it against you. In fact we will be interested to hear how you get on.
The is a current C#/.NET Qt bindings project called Qyoto. When KDE moves from svn to git Qyoto will be re-engineered somewhat. Instead of generating the C# classes from the Qt header sources, it will generate the bindings directly from the language independent 'Smoke' libraries that various Qt/KDE language bindings projects use. This should make it much easier to maintain, and easier to add new libraries to the bindings.
Reply Parent Score: 3
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[10] Now, behold, I have brought the first of the fruit of the ground, which you, Yahweh, have given me. You shall set it down before Yahweh your God, and worship before Yahweh your God:
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Special Nonexistent Furniture
Unfortunately, we no longer carry the Bordeaux Single Handle Kitchen Faucet with Side Spray from Danze® (SKU#: DNZ5005), but here are some Kitchen Faucets you might like:
Kitchen Faucets
Your Search
Faucet Spread refers to how wide the faucet is from handle to handle.
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1 in.24 in.
to GO
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Spout Height refers to how high the faucet spout is from the base to the top.
Spout Height
1 in.31 in.
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Spout Reach refers to how far the faucet spout comes out over the sink.
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Symbiosis in marine microorganisms fertilises ocean: Study
Symbiosis in marine microorganisms fertilises ocean: Study Washington: Scientists have discovered an unusual symbiosis between tiny single-celled algae and nitrogen-fixing bacteria that helps fertilise the oceans.
Researchers led by University of California, Santa Cruz found that tiny single-celled algae and highly specialised bacteria exchange carbon and nitrogen in a mutually beneficial relationship.
This partnership plays an important role in marine ecosystems, fertilising the oceans by taking nitrogen from the atmosphere and "fixing" it into a form that other organisms can use.
The discovery emerged after investigation of a mysterious nitrogen-fixing microbe with a drastically reduced genome.
First detected in 1998 by Jonathan Zehr, a professor of ocean sciences at UC, Santa Cruz, it now appears to be the most widespread nitrogen-fixing organism in the oceans.
The microbe belongs to a group of photosynthetic bacteria known as cyanobacteria, but it lacks the genes needed to carry out photosynthesis and other essential metabolic pathways.
Apparently, its association with a photosynthetic host cell makes those genes unnecessary.
"The cyanobacterium is a nitrogen-fixer, so it provides nitrogen to the host cell, and the host cell provides carbon to the cyanobacterium, which is lacking the metabolic machinery to get its own carbon," said lead author, Anne Thompson.
Although the partners in the symbiosis have not been grown in the laboratory, the researchers were able to characterize both partners using cell sorting, gene sequencing, and other techniques.
The host cell is a type of single-celled algae in a class known as "prymnesiophytes," which are found throughout the world's oceans.
In seawater samples sorted by flow cytometry, which separates cells by size and colour, the host cells were discovered among the "photosynthetic picoeukaryotes," a mixed population of tiny single-celled algae in the 1- to 3-micron size range.
"Aside from the importance of nitrogen fixation in marine ecosystems, this is such an interesting symbiosis from an evolutionary perspective, because it can be seen as analogous to an early stage in the endosymbiosis that led to chloroplasts," Zehr said in a statement.
Chloroplasts, which carry out photosynthesis in all plants, evolved from symbiotic cyanobacteria that eventually became incorporated into their host cells in a process known as endosymbiosis.
The study was published in the journal Science.
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smallstring-0.1.0: A string type optimized for size in memory
The SmallString type is for storing small identifiers. We do not provide fast operations on strings - what we offer is low memory overhead.
The Ord instance is not guaranteed to be the same as that of the corresponding string.
data SmallString Source
A space efficient representation of text. This is like a strict ByteString, but with fewer features, and UTF preserving. Fow ASCII data, we're slightly smaller than ByteStrings for small strings.
fromString :: String -> SmallStringSource
Convert a String into a SmallString.
toString :: SmallString -> StringSource
Convert a SmallString into a String.
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Skip to content
Video: Jimmy Kimmel has ideas to fill time on NBA TV
Nov 19, 2011, 12:30 PM EDT
Jimmy Kimmel has some ideas to fill all that air time, and we thought we’d pass them along. They should go with them, we’ll watch anything Jack Nicholson does.
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How much can Andrew Bynum help Pacers?
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Full description for Truth Machine
• DNA profiling - commonly known as DNA fingerprinting - is often heralded as unassailable criminal evidence, a veritable "truth machine" that can overturn convictions based on eyewitness testimony, confessions, and other forms of forensic evidence. But DNA evidence is far from infallible. "Truth Machine" traces the controversial history of DNA fingerprinting by looking at court cases in the United States and United Kingdom beginning in the mid-1980s, when the practice was invented, and continuing until the present. Ultimately, "Truth Machine" presents compelling evidence of the obstacles and opportunities at the intersection of science, technology, sociology, and law.
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Half-time: Tottenham 0 - 0 Swansea
It's goalless between Swansea City and Tottenham at the end of the first half.
Swansea City lose to Spurs
Swansea City failed to make an impact as they took on Spurs at White Hart Lane, losing 1 - 0. It's a result that leaves them at the bottom of the table.
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Between Worlds: Jilbab and Transgender in Indonesia
It is a scene that wouldn’t be unfamiliar in France or Belgium: a woman’s hijab is snatched away by strangers on the street from her head despite her protest. She is told she shouldn’t wear it, or rather, she has no right to because her wearing it mocks other women and femininity itself. But it is not an episode of Islamophobic rage that is recounted by Shuniyya Rumaha Haiibalah, but an incident in her native Indonesia that would later become the title of her best-selling memoir, Jangan lepas jilbabku! (Please do not remove my jilbab!)
Haiibalah is Muslim and transgender. The hostile reactions from other women and men towards her decision to wear the jilbab (hijab) in public was based on the belief of the irreconcilability of being waria* (transgender) and expressing religiosity in the gender of choice.
While other waria do not mix gender identity with religious identity (as the video above shows, some transwomen dress as men in places of worship), women like Haiibalah attend prayers at the mosque alongside other cis-gender women much to disapproval of some, particularly those who argue that physical contact with Haiibalah’s biologically male body can render another woman’s prayers annulled.
Jangan lepas jilbabku! begins in 1997 when Haiibalah turns 16. The writer describes her gradual transition from male to female as eventful as the moment Indonesia regains its democracy at the end of Suharto’s dictatorial regime in 1998. She describes the kind of woman she wants to be: an ordinary woman, good-looking even without make-up, someone who wears the jilbab, independent, headstrong, and accepted. In school, Haiibalah is an active editor of the school’s Islamic magazine, and a popular student. Using her popularity and religious image as a social buffer, Haiibalah began experimenting with her appearance. She plucked her eyebrows into a pair of thin, arching crescents; suffice it to say, this led to other arched eyebrows. After being told that her eyebrows were seen as “inappropriate” for young men, Haiibalah went on to tackle what ostensibly is taboo: she, a transwoman, wearing a jilbab.
[Read more...]
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Last updated on March 13, 2014 at 15:19 EDT
Researchers Make Older Beta Cells Act Young Again
October 12, 2011
By manipulating a well-known molecular pathway, JDRF-funded scientists breathe new life into aging beta cells
As a person ages, the ability of their beta cells to divide and make new beta cells declines. By the time children reach the age of 10 to 12 years, the ability of their insulin-producing cells to replicate greatly diminishes. If these cells, called beta cells, are destroyed–as they are in type 1 diabetes–treatment with the hormone insulin becomes essential to regulate blood glucose levels and get energy from food. Now, longtime JDRF-funded researchers at Stanford University have identified a pathway responsible for this age-related decline, and have shown that they can tweak it to get older beta cells to act young again–and start dividing.
In the past, researchers have used other techniques to trigger older beta cells to start dividing, but they have been met with challenging results, explains Dr. Kim, who is also a Howard Hughes Medical Institute investigator. “You can get these cells to grow but they will literally lose their specific identity as a beta cell,” he says. “They will either stop making insulin, or they’ll grow just fine but they will grow uncontrollably or into other cell types.”
But with the advent of better genetic tools and the completion of the human genome project, that era has come to pass, he explains. “With these advanced technologies, we are now able to get a comprehensive view–at the genetic level–of the changes beta cells undergo as they age, and we can track these changes and study them in a systematic way,” he adds. “By understanding what genes are turned on and off in a young beta cell, we can try to recreate that genetic environment in older beta cells such that they divide in a desirable, controlled manner.”
By better understanding the mechanisms that control and govern pancreatic ï¢-cell proliferation, researchers could transform treatments for diabetes. The cascade leading from PDGF binding to its receptor on the beta cell’s surface to changes in protein levels within the nucleus could inspire scientists with new ideas on how to discover new drugs to safely promote beta cell regeneration to replace those lost in diabetes.
“A major goal of JDRF’s regeneration program is to find ways to preserve and restore functional beta cells as a cure for type 1 diabetes. One of the challenges is that adult beta cells do not readily replicate, and these new findings provide key insight on how the body regulates beta cell growth and replication,” says Patricia Kilian, Ph.D., JDRF’s scientific program director of regeneration research. “Based on these key scientific insights, we hope the new findings will help enable the discovery of safe therapies to promote beta cell regeneration.”
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The ‘Yeah, That Kind of Rich’ ad campaign for the New York lottery is an epitomization of a wealthy lifestyle by using money typography to script clever slogans.
In a sly attempt to help the public wrap their heads around how the lottery money could change their lives, the campaign released posters with slogans like “Banks ask you for a bailout,” or “You shop, the market rises.” Using dollar bills to create thick stacks of money, the letters in these one-liners were created using a super rich font. It is estimated that around $1,000 to $1,500 dollars worth of money was used to create each ad.
These comical posters can be seen on buses, shelters and in subway stations in New York.
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Charmed and Legend of Zelda Crossovers
Zelda: The Charmed Ones by Ilovesnurtlez reviews
"Not again!" Paige screamed. Then a transparent image of a dark skinned man, with flame colored hair appeared. He stretched out his hand, and large triangular light engulfed the women. The next moment they were standing in the middle of a field.
Rated: T - English - Adventure/Fantasy - Chapters: 8 - Words: 18,590 - Reviews: 4 - Favs: 5 - Follows: 7 - Updated: 7/8/2012 - Published: 8/7/2011
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Switch to Desktop Site
What Germany could teach America about health-care reform and government's role
Page 2 of 2
About these ads
France is not Germany
Then there is the second common mistake Americans make about Europe: They see a collective continent in place of a collection of countries. Britain is not Denmark; Denmark is not France; and France is not Germany. Eastern and southern European countries, though increasingly part of the same economic union, are in many ways a world apart from their western neighbors.
Failing to see differences within the eurozone is akin to drawing no contrast between New Hampshire (New England’s often Republican outcast) and Vermont (just across the border, yet one of the more socially liberal states in the union.)
Germany's federal system and unease with too-strong of a central government may actually put it closer to the United States than its European neighbors. The parts of both America's and Germany's contemporary whole were once autonomous entities. Germany enjoys a huge economy, a famed manufacturing base, and a love for Volkswagen on par with America's fealty to GM. It juggles a large, diverse population that in many regions is more conservative and religious than Europe is often generalized as being.
What ties these disparate threads together is the understanding that government exists to carry out certain responsibilities, and Germany’s state and federal governments have a definitive mandate to do so. Germans may debate how government conducts business, but not that it does.
America needs nation balancing at home
The absence of a similar mandate in the United States has become exponentially more acute. Preoccupied with nation building other countries, the United States is in dire need of nation balancing at home.
This is not a new challenge, of course, but one that has shaped American history since the beginning. The inability to define government's end of the social contract came close to halting the colonial independence movement before it began, later resulted in a constitution left wide open to interpretation, and culminated in civil war. Today, government can't keep lead out of toys, oil out of the Gulf, financial services out of the backroom, and put all Americans under private insurance policies not because it's too small or too big, as some would have us believe, but because we still haven't decided whether government should be small or big.
IN PICTURES: Germany sinkhole
It's the limbo that's wrecking us. Wrestling with policy is a normal, and necessary, component of any democracy, but an ideological standoff disconnected from evolving social and economic realities stymies progress and further polarizes and paralyzes the political system.
There needs to be some essential consensus that government has a specific role to play. America needs a framework within which the government can serve as a representative and protector of the individual against the overreach of market and global forces.
Until then, ambiguity will remain a fundamental obstacle to finding solutions for America’s mounting problems.
Bill Glucroft is an English trainer and consultant in Berlin. He blogs at mediabard.org.
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cbs4 My 33 Header Logo
Freediving Could Lead To “Drowning at the Surface”
Extreme diving daredevils can hold their breath for up to 4 minutes at a time. (CBS4)
Diving Daredevils Plunge Deep For Thrills
Some of us can hold our breath for 45 seconds, maybe one minute. If we’re lucky. Can you imagine doing it for four minutes?
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Mar 13, 2014
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Know Your Market
RSS By: Dairy Today: Know Your Market, Dairy Today
Popular Tactic: Offset Premiums While Establishing a Milk Price
Jul 02, 2010
By Jon Spainhour, Rice Dairy
Over the course of the past few months, we have discussed two types of risk management tools that dairy producers can use to help manage their output and input prices on their farm.
At first we discussed fixed priced contracts, called futures, which allow for dairy producers to establish a set selling price for their milk or a set buying price for their corn or soymeal. In either case, the ultimate price that the producer will sell his milk at or buy his inputs at will be determined by where he contracted them, regardless of where the spot price is at the contract expiration.
We also discussed contracts, called options, which act more like insurance than fixed price contracts. Producers can buy puts on specific price levels, called the strike price, which will establish insurance against their milk check going below that level. Puts are commonly referred to as floors. They can also buy calls, which is insurance against prices moving up, against their expected soymeal and corn input prices. Calls are commonly referred to as ceilings.
The beauty of options contracts is that they establish minimum prices of milk while still allowing the producer to benefit from upwards price movements. They also establish maximum prices for their input costs while still allowing them to benefit from downwards price movements. In both cases, the producer must pay a premium for their insurance.
So far, we have discussed the issue of options strictly from the perspective of buying insurance. However, in order for you to buy insurance, someone else has to sell it to you.
The person that sells a dairy producer a put/floor is essentially betting that the spot price will not go below the strike level. He is compensated for that risk by the premium that he collects. If the market goes below the strike level, he assumes all the risk below the strike level minus the premium that he collected. If the market settles higher than the strike level, he gets to keep the entire premium that he collected.
Dairy producers often times find the premiums that they have to pay for puts as being too expensive. One tactic they can employ is to sell calls/ceilings and use the premium that they collect to offset the cost of the puts/floors.
In this case, they are establishing a floor, which is the lowest price they will receive for their milk and paying for it by selling a ceiling, which is the highest price that they will receive for their milk.
This type of structure has several different names that you may have heard of at some point: windows, fences or risk reversals. Regardless of what name you use, it is a fairly straightforward structure that establishes a minimum and a maximum milk price.
For example, a dairy producer who wants to set a floor for his September milk production can buy $14.00/cwt. puts for $0.20/cwt. This means that the minimum price that he will receive for his production will be $14.00/cwt. He can offset the cost of the $0.20/cwt. premium by selling $16.00/cwt. calls and collecting $0.20/cwt. Under this structure, the maximum price that he will receive is $16.00/cwt. This means that for a net cost of zero, the producer has set a floor at $14.00/cwt. and a ceiling at $16.00/cwt.
The exact same type of strategy can be employed on the input side of the equation, only the producer can offset the cost of purchasing corn and soymeal calls by selling puts and collecting a premium.
I hope this was helpful, since I know that this can seem like a complicated subject matter. However, when broken down into simple components, I think it paints a more clear picture of a time-tested risk management structure that many dairy producers have been using for years to help manage their profitability.
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Miss Carole's Macaroni Soup!
Sing, dance, and move with Carole Stephens. The concert will include songs from her six award-winning albums, such as Sticky Bubble Gum, that are popular with young children. For ages 17.
Fri, 05/11/2012 - 4:00pm - 4:45pm
Due to the popularity of this program, please register each child and adult attending.
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mofette, ( French: “noxious fume”) , also spelled moffettefumarole, or gaseous volcanic vent, that has a temperature well below the boiling point of water, though above the temperature of the surrounding air, and that is generally rich in carbon dioxide and perhaps methane and other hydrocarbons. When the winds are right, the issuing gases may drift and settle into nearby hollows or small valleys and cause the asphyxiation of animals and birds wandering in the areas. Such potentially deadly hollows have been noted in the Absaroka Range near Yellowstone National Park in Wyoming, U.S., and at the base of Iceland’s Hekla volcano.
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Phytopathology. 2003 Jul;93(7):874-80. doi: 10.1094/PHYTO.2003.93.7.874.
Diversity of Epidemic Populations of Gibberella zeae from Small Quadrats in Kansas and North Dakota.
ABSTRACT Gibberella zeae (anamorph Fusarium graminearum) causes Fusarium head blight (FHB) of wheat and barley and has been responsible for several billion dollars of losses in the United States since the early 1990s. We isolated G. zeae from the top, middle, and bottom positions of wheat spikes collected from 0.25-m(2) quadrats during severe FHB epidemics in a single Kansas (KS) field (1993) and in a single North Dakota (ND) field (1994). Three amplified fragment length polymorphism (AFLP) primer pairs were used to resolve 94 polymorphic loci from 253 isolates. Members of a subset of 26 isolates also were tested for vegetative compatibility groups (VCGs). Both methods indicated high levels of genotypic variability and identified the same sets of isolates as probable clones. The mean number of AFLP multilocus haplotypes per head was approximately 1.8 in each population, but this value probably underestimates the true mean due to the small number of samples taken from each head. Isolates with the same AFLP haplotype often were recovered from different positions in a single head, but only rarely were such apparently clonal isolates recovered from more than one head within a quadrat, a pattern that is consistent with a genetically diverse initial inoculum and limited secondary spread. The KS and ND samples had no common AFLP haplotypes. All G. zeae isolates had high AFLP fingerprint similarity (>70%, unweighted pair group method with arithmetic means similarity) to reference isolates of G. zeae lineage 7. The genetic identity between the KS and ND populations was >99% and the estimated effective migration rate was high (Nm approximately 70). Tests for linkage disequilibrium provide little evidence for nonrandom associations between loci. Our results suggest that these populations are parts of a single, panmictic population that experiences frequent recombination. Our results also suggest that a variety of population sampling designs may be satisfactory for assessing diversity in this fungus.
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Protecting astronauts beyond the ISS
Astronauts venturing beyond the safety of the International Space Station (ISS) will face increased exposure to cosmic radiation.
Water-mining lunar robot revealed
Carnegie Mellon University spinoff Astrobotic Technology has now completed a full-size prototype of a solar-powered robot designed to search for water ice at the moon's poles.
Exploring the moon in 3D
Could alien soils make spacecraft heat shields?
NASA scientists will next week test whether a heat shield made from the soil of the moon, Mars or an asteroid could stand up to a plunge through Earth's atmosphere.
Blue moon will light up the sky tonight
A phenomenon will occur tonight that only happens once in a blue moon - literally.
Space elevator planned for the moon
The latest Kickstarter project, looking for crowd funding, is a little different to most - a space elevator to be built on the moon.
The man who walked the moon passes away
Neil Armstrong - the first man to walk on the moon - has passed away at the age of 82 following complications resulting from cardiovascular procedures.
Helium found in moon's atmosphere
Observations from NASA's Lunar Reconnaissance Orbiter (LRO) have revealed the presence of helium in the thin atmosphere surrounding the moon.
Perseid meteor shower will hit peak on Saturday
If you want a good look at a meteor shower, you'd better head outside this Saturday.
US flags still standing strong on the moon
Harsh conditions and extreme temperatures are nothing in the face of symbols of American pride.
Just how poisonous is the moon?
The moon could be a highly toxic place, say scientists, warning of cancer and breathing problems even when astronauts remain in their space suits.
Hubble spots fifth Pluto moon
NASA has confirmed the discovery of a fifth moon orbiting the icy dwarf planet Pluto.
Extensive water ice found in lunar crater
Almost a quarter of a crater near the moon's south pole is covered with ice, scientists using NASA's Lunar Reconnaissance Orbiter (LRO) spacecraft have found.
Glass bubble find may explain weird lunar soil
NASA completes main Grail mission ahead of time
NASA's Grail mission to study the moon from crust to core has completed its main task ahead of schedule, gathering information about the internal structure and evolution of the moon in unprecedented detail.
From lunar rovers to wet wipes: protecting artifacts on the moon
NASA's a bit concerned that the rush to the moon created by Google's Lunar X Prize could damage historic sites there.
NASA uses moon as mirror to watch Venus transit sun
Just like human eyes, the Hubble Space Telescope can't observe the sun directly - so NASA scientists plan to study Venus's solar transit in June by using the moon as a mirror.
NASA says the moon's crust is being stretched
New images snapped by NASA's Lunar Reconnaissance Orbiter (LRO) indicate the moon's crust is actually being stretched - forming minute valleys in a few small areas on the lunar surface.
Moon 'wasn't created by giant collision'
A new chemical analysis of lunar material collected by Apollo astronauts in the 1970s appears to disprove theories that the moon was created through a massive collision between Earth and a Mars-sized object 4.5 billion years ago.
Cosmic rays alter chemistry of lunar ice
A bombardment of cosmic rays on the moon's surface could be creating complex carbon chains similar to those that form the foundations of biological life.
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The short and spoiler filled answer is: not much at all. The laws of physics would require both to have an infinite amount of mass and energy, but would not allow their velocities to change, so in theory they would simply just pass right through each other. Yawn. No catastrophic universe-ending explosions or anything like that, which is probably for the best. [YouTube]
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In your house, which has more germs - the toilet seat or the kitchen sink?
Surprise! It's the sink, but that doesn't mean you shouldn't wash your hands after going. Turns out germs from raw meat linger in the sink and on the kitchen sponge, making them ickier than the toilet.
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1: Learn to develop your own film
2: Learn to print your own photos in the darkroom, or if you don't want to do that, get a GOOD film scanner and learn to use it.
3: Practice. A lot. Years of practice are needed to get really good. Its worth it. Don't be stingy about film, waste a lot of it, its not really waste, its practice and if you learn from your mistakes you will get very good.
4: Learn to get perfect exposure every time, it makes a big difference in your image quality. Either use an incident meter like 2f/2f suggested or learn the zone system and use a spotmeter.
5: The true speed of a black and white film is not what is marked on the box. Different developers affect the speed of the film, and you may need to use a lower or higher speed if your light meter is not in agreement with the meter used by the manufacturer to determine speed. Test your film.
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Forgot your password?
Under a Cruel Star: A Life in Prague 1941-1968 Test | Mid-Book Test - Hard
Heda Margolius Kovaly
Purchase our Under a Cruel Star: A Life in Prague 1941-1968 Lesson Plans
Mid-Book Test - Hard
Name: _____________________________ Period: ___________________________
Short Answer Questions
1. What are the living conditions in the ghetto?
2. Where are the camp inmates staying when Kovály and her acquaintances decide to escape?
3. After wandering Prague looking for help, where does Kovály find herself doubting her faith in God?
4. Surviving the initial selection at Auschwitz, Kovály is assigned what work?
5. What is the apartment like that Kovály is assigned?
Short Essay Questions
1. Describe the mass meeting Kovály attended in 1967.
2. What happens to Kovály's family at Auschwitz?
3. Who is arrested in November 1951 and how does it affect Margolius?
4. What is contained in the note that Ruda sends Kovály after she settles in his apartment?
5. What happens economically in Prague shortly after the war's end?
6. At the beginning of the book, what does Kovály say shapes her life?
7. What does Kovály realize by attending Communist Party meetings?
8. Why is Communism appealing to the Czech people after the war?
9. What does Kovály say many industrialists are unaware of during the war?
10. Why do Kovály and her friends decide to try to escape the camp guards?
Essay Topics
Discuss the struggles that Kovály faces. How does she overcome these obstacles? Are the struggles similar to others in Czechoslovakia? If not, why is she experiencing them?
Discuss the motif of fear and terror in "Under A Cruel Star." Of what is Kovály and the citizens of Czechoslovakia fearful? How is their fear conveyed to others? How does Kovály experience the fear of others? How does this fear affect her? Who is terrorizing Czechoslovakia and why? How are they spreading terror?
Discuss the theme of ostracism in "Under a Cruel Star." How is Kovály ostracized throughout the narrative? Why is she ostracized? How does this ostracism affect her life?
(see the answer keys)
This section contains 808 words
(approx. 3 pages at 300 words per page)
Under a Cruel Star: A Life in Prague 1941-1968 from BookRags. ©2009 BookRags, Inc. All rights reserved.
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| 0.722091 |
Feral Dragon (CR +Varies)
*Editor's Note
The challenge rating adjustment for this template is very approximate. Losing spellcasting and all abilities other than breath weapons will have a much greater impact on older dragons and ones that rely more on spellcasting so consider this carefully when applying this template.
Seemingly all scales, wings, fangs, and claws, feral dragons exist as pale reflections of true dragons. Some are actually cousins of true dragons, in the same way that apes are cousins to humankind. Others are degenerate descendents of dragons as they existed in an older age. Rapacious and voracious, feral dragons are awful carnivores that hunt beasts and sentient creatures alike. They love bright, shiny objects and often devastate caravans and entire settlements to steal even small amounts of treasure.
Like true dragons, feral dragons come in several hues, both chromatic and metallic, and can breathe great gouts of fire, ice, acid, or other energy. Though they are fully as perceptive as true dragons, they lack the intelligence and spellcasting ability of their more advanced cousins.
Creating a Feral Dragon
“Feral dragon” is an inherited template that can be added to any true dragon (referred to hereafter as the base creature). A feral dragon uses all the base creature's statistics and special abilities except as noted here.
Challenge Rating*: A feral dragon's challenge rating equals its racial Hit Dice divided by 2 or the base creature's CR –4, whichever is greater.
Alignment: Usually neutral, but feral dragons often grow closer to the base creature's alignment as they age and gain Intelligence.
Armor Class: The feral dragon's natural armor bonus is equal to the base creature's –2 (minimum +0). If the base creature had no natural armor bonus, this feature of the template causes no change.
Special Attacks: The feral dragon loses all the base creature's supernatural and spell-like special attacks except its breath weapons. It also loses the ability to cast spells. It retains all the base creature's other special attacks.
Special Qualities: The feral dragon loses the base creature's damage reduction and spell resistance (if any), and all its supernatural and spell-like special qualities. It retains all other special qualities the base creature had.
Abilities: Str +4, Dex –4 (minimum 1), Con +4, Int –15 (minimum 1), Wis –4 (minimum 1).
Skills: Recalculate the feral dragon's skill points for its racial Hit Dice according to the following formula (6 + new Int modifier) x HD. Then spend its skill points afresh, using Dragon type guidelines for class skills.
Feats: A feral dragon has the same number of feats as the base creature does, though they should be chosen with an eye toward which ones are most useful with its diminished abilities.
Treasure: Double standard.
Using the Feral Dragon Template
The feral dragon template was designed to give players the chance to fight big dragons at lower levels than normal. Both players and GMs can use these creatures to enjoy dragon slayer scenarios akin to those in European myth and popular culture. Feral dragons are still tough monsters for their CRs, but characters facing them can worry more about how dangerous a combatant their foe is and less about whether or not it uses scrying to learn their plans and prepares to use spells against them.
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| 0.857722 |
הרשמה Hebrew
חפשו מילה כלשהי, כמו fuck:
2 definitions by Misty De Meo
Onos - oh'noss - n. - A Greek concept of rational worry; represented by Homer's Odyssey in Athena, a Greek Goddess, and many Greek heroes in other traditional works, it is considered a positive attribute.
Romans considered "onos" a negative attribute, like Odysseus' intelligence, and it became transmuted into the less-positive "onus," or "burden."
Athena's onos was manifested in her fear of Poseidon's threat to Odysseus' homecoming.
מאת Misty De Meo 20 במרץ, 2004
32 20
"Have you heard the new T-Square album?"
מאת Misty De Meo 26 במאי, 2004
19 8
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| 0.862067 |
where the writers are
Brad Olsen's Books
Sacred Places Europe
Combining current trends, academic theories, and historical insights, this travel guide brings both lesser-known and famous European spiritual locales into perspective by explaining the significance of each sacred site. The cultural relevance, history, and spirituality of each site—including Stonehenge, the Acropolis, Mont Saint Michel, Pompeii, and Saint Peter’s Basilica—are...
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| 0.999884 |
Letter case
From Wikipedia, the free encyclopedia
(Redirected from Sentence case)
Jump to: navigation, search
The upper-case "A" and lower-case "a" are the two case variants of the first letter in the English alphabet.
In orthography and typography, letter case (or just case) is the distinction between the letters that are in larger upper case (also capital letters, capitals, caps, majuscule, or large letters) and smaller lower case (also minuscule or small letters) in certain languages. In the Latin script, upper case letters are A, B, C, etc., whereas lower case includes a, b, c, etc. Here is a comparison of the upper and lower case versions of each letter included in the English alphabet (the exact representation will vary according to the font used):
The lower case is the normal and more common variant, contrasted by the upper case, which is used for special purposes, for example as the first letter of a sentence or a proper noun. Languages have capitalisation rules to determine whether an upper or lower case letter is to be used in a given context, but there can also be stylistic variation.
Divided upper and lower type cases for movable type
Bicameral script[edit]
Williamsburg 18th-century press letters
Most Western languages (particularly those with writing systems based on the Latin, Cyrillic, Greek, Coptic, and Armenian alphabets) use letter cases in their written form as an aid to clarity. Scripts using two separate cases are also called bicameral scripts. Many other writing systems (such as the Georgian, Glagolitic, Arabic, Hebrew, Devanagari, and Hangul alphabets, not to mention Chinese or Kana character sets), make no distinction between capital and lowercase letters – a system called unicameral script or unicase.
If an alphabet has case, all or nearly all letters have both forms. Both forms in each pair are considered variants of the same letter: they have the same name and pronunciation and will be treated identically when sorting in alphabetical order.
In scripts with a case distinction, lower case is generally used for the majority of text; capitals are used for capitalisation, acronyms, and emphasis (in some languages).
Capitalisation is the writing of a word with its first letter in uppercase and the remaining letters in lowercase. Capitalisation rules vary by language and are often quite complex, but in most modern languages that have capitalisation, the first letter of every sentence is capitalised, as are all proper nouns.
Capitalisation in English, in terms of the general orthographic rules independent of context (e.g., title vs heading vs text), is universally standardized for formal writing (informal communication, such as texting, instant messaging, or a handwritten sticky note, may not bother, but that is because its users usually do not expect it to be formal). In English, capital letters are used as the first letter of a sentence, a proper noun, or a proper adjective. There are a few pairs of words of different meanings whose only difference is capitalisation of the first letter. The first-person pronoun "I" and the interjection "O" are also capitalised. Initialisms or acronyms are generally written in all-caps in American English, whereas British English only capitalises the first letter of an acronym (pronounced as a word) – or none if it is regarded as an everyday word.[3] Lower case letters are normally used for all other purposes. There are however situations where further capitalisation may be used to give added emphasis, for example in headings and titles or to pick out certain words (often using small capitals). In some traditional forms of poetry, capitalisation has conventionally been used as a marker to indicate the beginning of a line of verse independent of any grammatical feature.
Other languages vary in their use of capitals. For example, in German the first letter of all nouns is capitalised (this was previously common in English as well), while in Romance and most other European languages the names of days of the week, months of the year, and adjectives of nationality, religion and so on generally begin with a lower case letter.
Exceptional letters[edit]
• The German letter "ß" primarily exists in lower case and is capitalised as "SS" (but see Capital ß).
• The Greek letter "Σ" has two different lower case forms: "ς" in word-final position and "σ" elsewhere. In a similar manner, the Latin letter "S" used to have two different lower case forms: "s" in word-final position and "ſ" elsewhere. The latter form, called the long s, fell out of general use before the middle of the 19th century.
• The Cyrillic letter "Ӏ" usually has only a capital form, which is also used in lower case text.
• Unlike most Latin-script languages, which link the dotless upper case "I" with the dotted lower case "i", Turkish has both a dotted and dotless I in upper and lower case. Each of the two pairs ("İ/i" and "I/ı") represent a distinctive phoneme.
• In Dutch, the digraph "ij" is capitalised as a single entity, "IJ".[4]
Related phenomena[edit]
Similar orthographic conventions are used for emphasis or following language-specific rules, including:
Stylistic or specialised usage[edit]
Case styles[edit]
All-caps and title case in New York Times (10 November 1919, on Arthur Eddington's solar eclipse experiment).
• ALL CAPS: only capital letters are used. Capital letters were sometimes used for typographical emphasis in text made on a typewriter. However, long spans of Latin-alphabet text in all upper-case are harder to read because of the absence of the ascenders and descenders found in lower-case letters, which can aid recognition. With the advent of the Internet, all-caps is more often used for emphasis; however, it is considered poor netiquette by some to type in all capitals, and said to be tantamount to shouting.[5]
Example Rule
The Vitamins Are In My Fresh California Raisins Start case – capitalisation of all words, regardless of the part of speech
The Vitamins Are in My Fresh California Raisins Capitalisation of the first word, and all other words, except for articles, prepositions, and conjunctions
The Vitamins are in my Fresh California Raisins Capitalisation of the first word, and all other words, except for closed-class words
The Vitamins are in my fresh California Raisins Capitalisation of all nouns and the first word
the Vitamins are in my fresh California Raisins Capitalisation only of nouns
The vitamins are in my fresh California raisins Sentence case – capitalisation of only the first word, proper nouns and as dictated by other specific English rules
the vitamins are in my fresh California raisins Mid-sentence case – capitalisation of proper nouns only
Headings and publication titles[edit]
In English-language publications, varying conventions are used for capitalising words in publication titles and headlines, including chapter and section headings. The rules differ substantially between individual house styles.
The convention followed by many British publishers (including scientific publishers, like Nature, magazines, like The Economist and New Scientist, and newspapers, like The Guardian and The Times) is to use sentence-style capitalisation in titles and headlines, where capitalisation follows the same rules that apply for sentences. This convention is usually called sentence case. It is also widely used in the United States, especially in newspaper publishing, bibliographic references and library catalogues. Examples of global publishers whose English-language house styles prescribe sentence-case titles and headings include the International Organization for Standardization.
Among U.S. book publishers, it is a common typographic practice to capitalise significant words in titles and headings. This is an old form of emphasis, similar to the more modern practice of using a larger or boldface font for titles. This family of typographic conventions is usually called title case. The rules for which words to capitalise are not based on any grammatically inherent correct/incorrect distinction and are not universally standardized; they are arbitrary and differ between style guides, although in most styles they tend to follow a few strong conventions, as follows:
• Most styles capitalise all words except for closed-class words (certain parts of speech, namely, articles, prepositions, and conjunctions); but the first word (always) and last word (in many styles) are also capped, regardless of part of speech. Many styles capitalise longer prepositions such as "between" or "throughout", but not shorter ones such as "for" or "with".[6] Among such styles, "four or more letters (≥4)" or "more than four letters (>4)" are the typical (although arbitrary and conflicting) threshold rules.
One British style guide mentions a form of title case: R. M. Ritter's Oxford Manual of Style (2002) suggests capitalising "the first word and all nouns, pronouns, adjectives, verbs and adverbs, but generally not articles, conjunctions and short prepositions".[7]
Special case styles[edit]
• CamelCase: first letter of each word is capitalised, spaces and punctuation removed. If the very first letter is capitalized, as in "CamelCase" (or "PowerPoint"), the term upper camel case may be used; this is also known as Pascal case or bumpy case. Lower camel case describes a variation, as in "camelCase" (or "iPod" or "eBay"), in which the very first letter is in lower case. CamelCase derives from computer programming, but it has also become rather common in brand names of information technology products.
• Train-Case or spinal-case (depending on whether or not the first letter of each word is in upper case, respectively): similar to snake case, but spaces are replaced by hyphens, instead of underscores.
Metric system[edit]
In the International System of Units (SI), a letter usually has a different meaning in upper and lower cases when used as a unit symbol. A unit symbol is normally written in lower case, but if the name of the unit is derived from a proper noun, the first letter of the symbol is written in upper case (nevertheless, the name of the unit, if spelled out, is always considered a common noun and written accordingly):[9]
• 1 mS, a small measure of electric conductance.
• 1 MS, a large measure of electric conductance.
• 1 Mm, a large measure of length.
Case folding[edit]
Methods in word processing[edit]
Methods in programming[edit]
UpperA$ = UCASE$("a")
LowerA$ = LCASE$("A")
char upperA = toupper('a');
char lowerA = tolower('A');
This only works because the letters of upper and lower cases are spaced out equally. In ASCII they are consecutive, whereas with EBCDIC they are not; nonetheless the upper case letters are arranged in the same pattern and with the same gaps as are the lower case letters, so the technique still works.
Unicode case folding and script identification[edit]
Latin majuscule inscription on the Arch of Titus (82 AD)
Type cases[edit]
Combined case with capital letters above small letters
Late 19th-century mixed cases
See also[edit]
3. ^ "The Guardian and Observer Style Guide". Retrieved 5 March 2014.
5. ^ RFC 1855 "Netiquette Guidelines"
8. ^ "Ruby Style Guide". Retrieved 11 November 2013.
External links[edit]
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| 0.855515 |
Web Server Printing Expert
Job Description
Looking for someone who has experience printing from a web server. We are looking for someone who can develop a routine to print from a websever to a specific printer.
The use case is as follows:
A user places an order on a website, the order is processed by the site and an
entry is made in the mysql database. Logic which uses information about the order and fulfillment ques will determine where the order needs to be dispatched.
Once it is determined which Location will receive the order, the webserver will print the order information on a dedicated printer in that Store.
The printers for each store will be dedicated to this process and information about the printer will be stored in a table within the mysql db.
If you have done this in the past or know how to perform these task, please apply for the job.
Skills: systems-programming, web-services
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| 0.910857 |
Hartog, Dirckalso spelled Dirk Hartog or Dyrck Hartoochz ( flourished 1616Dutch explorer who made the first recorded exploration of the western coast of Australia.
Traveling an eastward route from Amsterdam around the Cape of Good Hope to Java, Hartog sighted and explored the western Australian coastline. He landed (October 1616) and spent three days exploring a desolate offshore island that he named for himself. To mark his landing, he left a flattened pewter plate, inscribed with the details of the visit, nailed on a post on the northern end of the island, now called Cape Inscription. In 1696 another Dutch explorer, Willem de Vlamingh, landed on Dirk Hartogs Island, found Dirck’s Hartog’s plate, replaced it with a newly inscribed dish, and sent the original to Amsterdam, where it can now be seen in the Rijksmuseum.
Until the 19th century the coast of Australia parallel to Dirk Hartogs Island was called Eendrachtsland, in honour of the explorer’s ship, Eendracht.
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Advantages of Afforestation?
Afforestation is the process of planting of trees for the purpose of creating woodland or forest. In the context of the common agricultural policy, the term refers to measures co-financed by the European Union to encourage new woodland development with a view to its beneficial effects for the environment.
1 Additional Answer Answer for: what is the definition of afforestation
[uh-fawr-ist, uh-for-]
Q&A Related to "Advantages of Afforestation?"
afforest: establish a forest on previously unforested land
Explore this Topic
Afforestable is the adjective form of afforestation, which means to turn fallow land into a forest. Any land with the capacity to be converted into a forest is ...
Afforest means to establish a forest on previously unforested land. Example of a sentence with the word afforest is: 'We are going to afforest the area that was ...
Afforestment is defined as the act of establishing a forest on a land that has never been forested before. Many governments and non-governments organisations encourage ...
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| 0.995211 |
You are here
Linearity, Simmetry, and Prediction in The Hydrogen Atom
Stephanie Frank Singer
Springer Verlag
Publication Date:
Number of Pages:
Undergraduate Texts in Mathematics
[Reviewed by
William J. Satzer
, on
Linearity, Symmetry, and Prediction in the Hydrogen Atom, a volume in Springer’s series of Undergraduate Texts in Mathematics, is about representation theory and the fundamental role it plays in quantum mechanics and the prediction of quantum phenomena. The author concentrates on one example of a quantum system with symmetry, namely a hydrogen atom with a single electron. There are digressions aplenty, but the main goal is to make predictions of the numbers that characterize the basic state of a quantum system using only symmetry and the linear model of quantum mechanics.
The intended audience for this text includes advanced undergraduates or beginning graduate students in mathematics, physics or chemistry. For physics and chemistry students, the author offers mathematical foundations for calculations that they may have already learned to do. Mathematics students get to see a powerful application of “pure” mathematics in an extraordinary story of a mathematical success.
After some preliminary background material on quantum mechanics and linear algebra over the complex numbers, we are introduced to Lie groups and Lie group representations. Right away we meet the major players: the special orthogonal groups SO(3) and SO(4) and the special unitary group SU(2). The next couple of chapters describe how new representations are created from old ones, what irreducible representations are, and why we should care about invariant integration. The book culminates with three chapters on the hydrogen atom, its symmetry and representations. A key piece of this is a presentation of Fock’s original construction of a representation of SO(4) on L2 (R3), the phase space of the hydrogen atom. Two final chapters look at projective representations, electron spin and quantum computing.
This is an attractive text with much to offer anyone interested in the interplay of mathematics, physics and chemistry. The author suggests that the book is ideally suited for mixed groups of science and mathematics students who can benefit by sharing and pooling their expertise. Nonetheless, the approach is rigorous and most results are proved, with the exception of a few things like the Stone-Weierstrass and Fubini theorems. Prerequisites include a strong background in calculus and linear algebra; a nodding acquaintance with differentiable manifolds and the Lebesgue integral would also be useful.
Setting the Stage.- Linear Algebra over the Complex Numbers.- Complex Scalar Product Spaces (a.k.a. Hilbert Spaces).- Lie Groups and Lie Group Representations.- New Representations from Old.- Irreducible Representations and Invariant Integration.- Represenatations and the Hydrogen Atom.- The Algebra so(4) Symmetry of the Hydrogen Atom.- The Group SO(4) Symmetry of the Hydrogen Atom.- Projective Representations and Spin.- Independent Events and Tensor Products.- A. Spherical Harmonics.- B. Proof of the Correspondence.- C. Suggested Paper Topics.- Bibliography.- Index.- References.
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Connect With Blountville Nonprofits and Charities
Blountville Nonprofits and Charities
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| 0.937353 |
Let's Make Robots!
Fading an LED with hardware
Gillerire's picture
Hi guys,
I am trying to get an LED (attached to the i/o port of a microcontroller) to fade in and fade out without using PWM. I hooked up a resistor and LED pair in parallel with a large-ish polarised capacitor, thinking that as the cap charged it would prevent some current getting to the LED, resulting in a fade up to full brightness. When power was removed the cap would then slowly empty it's charge through the LED, resulting in a fade out. It worked for the fade out but not the fade in; it simply went to full brightness when power was applied.
I realised I would need another resistor between power and the cap to limit the speed at which he cap could charge. I set this up (see figure below) and it is kind of working; I get both a fade in and a fade out. But the fade in speed is not the same as the fade out speed.
I'm wondering if anybody knows if there is a way to calculate what resistor/capacitor values will give different fade in/out speeds? I'm also curious if it's possible to calculate how much current is passing through the LED? I used a 220 ohm to set a current of 20mA when supplied with 5V, but I'm guessing this all goes out the window now that the cap and extra resistor are attached.
LED fade circuit
Comment viewing options
rik's picture
Charge throught D1 + R1.
Discharge through D2 + R2.
Fiddle the R-values.
Almost sounds like a 555 PWM circuit.
rik's picture
A schematic say more than a thousand words.
This is what I tried to suggest, but now I think it won't work. Look at this:
It's the equivalent schematic. Current will flow directly through diodes and resistors to the LED. Sure, the discharge and charge times will be different, but the required resistors will also resist the LED current. So let's try to isolate R1 and R2 from the LED current.
This one might work. I have no idea. R1 and R2 could be combined into one potmeter. Give it a try! And while you're at it...
Replace D1 and D2 with LEDs. These will glow only shortly after a change in the switch position. But wait. How is C1 ever gonna discharge? Oh right!
Don't forget to model your output pin as a double throw switch connected to either V+ or GND. Your MCU will sink approx. as much current as it will source. There's our discharge path!
But will it work? You might have to use a much bigger capacitor! Or smaller LEDs.
antonio.caciuc's picture
your problem is that the voltage does not drop linearly with time
see this link for details http://www.technologyuk.net/electronics/electrical_principles/rc_circuits.shtml
I think the most important graph on that page is this:
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__label__pos
| 0.796898 |
Take the 2-minute tour ×
We have two functions:
$$\begin{align*} y &= x^4-5x^3+2x^2-5 \\ y &= -11x-20 \end{align*}$$
My task is to find two closest points that can be found on these two functions.
Can somebody give any hints on how to solve these type of exercises?
Thank you!
share|improve this question
Do you mean the closest points of the curves, or the minimum difference between the two functions? – copper.hat Feb 8 '13 at 8:17
The minimum difference between the two functions. :) – Trom Feb 8 '13 at 8:23
add comment
2 Answers
up vote 2 down vote accepted
You want to minimize $x^4-5 x^3+2 x^2+11 x+15$. Take the derivative, set that to $0$, and solve. Unfortunately this is an irreducible cubic, so the solutions are not very nice. There are three real roots: approximately $-.6828742578$, $1.275428188$, $3.157446070$. I'll leave it to you to find which of these gives the minimum.
share|improve this answer
add comment
Since you want the minimum difference between $$\begin{align*} y_1(x) &= x^4-5x^3+2x^2-5 \text{ and }\\ y_2(x) &= -11x-20 \end{align*}$$ you are looking for the minimum of $$ \left| y_1(x) - y_2(x) \right|$$ which will be a max / min of $$ z(x) = y_1(x) - y_2(x).$$ So write down the equation for $z$ as Robert Israel has done for you, differentiate $z$ and find its turning points.
share|improve this answer
add comment
Your Answer
|
__label__pos
| 0.99188 |
Take the 2-minute tour ×
In Euclidean space, There is a classic Theorem claims that: The length of every rectifiable curve can be approximated by sufficiently small straight line segment with ends on the curve.
Now, The question is that: Is there a similar thing happen on plane of constant curvature? I.e., Can the length of every rectifiable curve on the plane of constant curvature be approximated by sufficiently small geodesic line segment?
share|improve this question
Yes, this is normally how the length of the curve would be defined, if it is not assumed to be smooth. – yasmar Nov 11 '11 at 18:26
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Your Answer
Browse other questions tagged or ask your own question.
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__label__pos
| 0.90182 |
NAME: ________________________
Midterm English Vocab Test
Question Types
Start With
Question Limit
of 51 available terms
Remove ads
5 Written Questions
5 Matching Questions
1. stagnate
2. furor
3. craven
4. verbose
5. radical
1. a using or expressed in more words than are needed
2. b to cease, to run, flow, or move
3. c cowardly; a coward
4. d advocating through political or social reform; political extreme. departing from tradition
5. e an outbreak of public anger or excitement
5 Multiple Choice Questions
1. wild and noisy, disorder or confusion; upraor
2. cool and formal in manner
3. take a position or power illegally or by force
4. to tease, torment by teasing
5. full of sorrow, miserable
5 True/False Questions
1. ingeniousclever, origional, and inventive
2. obtuseelaborate or highly decorated
3. ludicrousbright of shining, especially in the dark
4. luminousbright of shining, especially in the dark
5. querulousupsurd; ridiculous, silly, laughable
Create Set
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__label__pos
| 0.99826 |
Midnight News, 20/01/2011 QR code
What is this?
This code will link to the page for Midnight News, 20/01/2011 when read using a QR code reader.
You may save, print or share the image.
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| 0.865153 |
Showcase & Discover Creative Work Sign Up For Free
Hiring Talent? Post a Job
Natura Morta
• G3002
• F58
• D0
• “Natura Morta” is a musical concert where the only instruments used are real fruits and the sound we’ll hear is exclusively the electric energy contained within them.
The elettric power of the humans getting mixed with the energy of the fruits makes the sound audible, is the fisical contact between human and nature that generate the music.
Each fruit has acid in it that produces electrical tension, using a special technique we can boost these frequencies making the inaudible audible,
the sound of the vital energy of nature.
The individual fruits are raised on wooden platforms, standing on a transparent plexiglass plate lit from under. Each time a fruit plays its base will lit up, staining the surrounding space, making it changeable and dinamic. Each platform is a home made midi controller which allow us to modulate the sound wave’s, creating more complex rhythms and sounds.
The sound frequencies are emphasized by a large videoprojection representing a macro vision of the fruits.
Slowly the concrete images becomes abstract, the Natura morta (Still life) picture changes reacting precisely to the sound vawes,
crashing and dissolving into pure shapes of colors and lights.
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Shift (Rufus Mason)
Rufus Mason
Religion: tabula rasa CBR Scale: M
Name: Shift
Alter Ego: Rufus Mason
Other Names: Metamorpho; Metamorpho II
Classification: hero hero
Publisher(s): DC
First Appearance: Titans/Young Justice: Graduation Day #3 (Aug. 2003)
Creators: Judd Winick
Number of Appearances: 38
Teams/Affiliations: The Outsiders
Allies: Indigo
Race: white
Gender: male
Note: Metamorpho fragment that grew, gained sentience
During his brief life, Shift engaged in a considerable amount of soul-searching and trying to find meaning to his life.
Shift (Rufus Mason)
This character is in the following 38 stories which have been indexed by this website:
Teen Titans / Outsiders Secret Files 2003 (Dec. 2003): "A Day After"
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By CountryLady on August 06, 2003
25 Characters Max
Enter Time:
You can create up to five timers
1. 4 boneless chicken breasts
1. 1/4 cup lime juice ( or lemon)
2. 1/4 cup water
3. 2 tablespoons vegetable oil
4. 2 teaspoons curry powder
5. 1/2 teaspoon salt
1. 1/3 cup smooth peanut butter
2. 1/3 cup water
3. 1 clove garlic
4. 2 tablespoons lime juice ( or lemon)
5. 2 tablespoons soy sauce
6. 1 teaspoon sugar
1. Cut the chicken lengthwise into 1/4 inch (1/2 cm) strips- you'll get about 4 or 5 strips from each breast.
2. Thread these strips zigzag fashion onto bamboo skewers, about 3 or 4 strips per skewer.
3. Don't squash the zigzags too tightly- leave them loosely threaded so the marinade can soak in.
4. Arrange the skewers in a glass baking dish.
5. In a small bowl, combine the marinade ingredients& pour over the chicken skewers in the baking dish; allow to marinate, refrigerated, for at least one hour, but no longer than three or else the chicken will disintegrate.
6. Meanwhile, make the dipping sauce.
7. In a blender combine all the sauce ingredients and blend until completely smooth.
8. Pour into a small bowl.
9. Preheat the barbecue, then grill chicken skewers over medium heat, brushing lightly with the marinade, about 5 minutes per side.
10. The chicken should be cooked through but not dried out.
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Thursday 13 March 2014
Billions of habitable planets 'may exist within our galaxy'
BILLIONS of potentially habitable planets may exist in our galaxy, the Milky Way, according to a new study.
Around 100 'super-Earths' may be found on our galactic doorstep, at distances less than 30 light years from the sun.
Astronomers came up with the prediction after conducting a survey of red dwarf stars, which account for 80pc of stars in the Milky Way.
They calculate that around 40pc of red dwarfs have a rocky planet not much bigger than Earth orbiting the "habitable zone" where liquid surface water can exist.
Where there is water, there could be life -- although being in the habitable zone is no guarantee that life has evolved on a planet.
Dr Xavier Bonfils, from Grenoble University in France, who led the international team, said: "Because red dwarfs are so common -- there are about 160 billion of them in the Milky Way -- this leads us to the astonishing result that there are tens of billions of these planets in our galaxy alone."
The astronomers surveyed a carefully chosen sample of 102 red dwarfs using the European Southern Observatory's 3.6-metre telescope at La Silla, Chile. A total of nine super-Earths -- planets with masses between one and 10 times that of Earth -- were found.
Two were within the habitable zones of the stars Gliese 581 and Gliese 667 C.The astronomers found that habitable zone super-Earths orbiting red dwarfs occurred with a frequency of around 41pc.
On the other hand, massive planets similar to Jupiter and Saturn were rare around red dwarfs.
Because red dwarfs are common near the sun, many "super-Earths" may not be far away in astronomical terms. The scientists estimate there could be around 100 habitable zone planets within 30 light years.
Red dwarfs are cooler than the sun, which means that planets must orbit close to their parent stars to be warm enough to sustain life. This might not be good news for life.
"The habitable zone around a red dwarf, where the temperature is suitable for liquid water to exist on the surface, is much closer to the star than the Earth is to the sun," said team member Dr Stephane Udry, from Geneva Observatory.
The research is reported in the journal Astronomy & Astrophysics.
Irish Independent
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March 13, 2014
Posts by Noemi
Total # Posts: 9
pre cal
A punter kicks a football at an angle of 45 degrees to the ground. The football has an initial velocity of 25 m/s, make a diagram and calculate: a) How long was the football in the air? b) How far does the football travel horizontally? c) What is the maximum height of the foot...
describe how you would prepare 250.0 mL of a .500 M solution of NaCl by using apparatus found in a chemistry lab.
An elavater m=800kg has a maximum load of 8 people of 600kg. The elevatorgoes up to 10 stories = 30m at a costant speed of 4m/s. what is the average power output of the elevater motor if the elevater is fully loaded with its maximum weight? (neglect friction)
How do you turn an improper fraction into a mixed number?
At 850 C, the equilibrium constant Kp for the reaction: C(s)+CO2(g) >< 2CO(g) has a value of 10.7. If the total pressure in the system at equilibrium is 1.000 atm, what is the partial pressure of carbon monoxide.
First grade social studies
my son is in first grade and has to do a project as the curator for the american symbols. I am looking for a reputable website and having difficulty sorting out which ones to use. Can anyone help?
multiplying fraction
what is 3/7 * 2/10= and 5/6*2/3= , 1/2*1/4=,4/5*3/5=,2/3*3/8=,1/7*5/9= (Broken Link Removed) 3*2 = 6 7*10 = 70 Answer to the first one is 6/70. Then you'll need to reduce the answer; divide both parts by two, and you'll have 3/35. Do the others the same way. =) need he...
Pages: 1
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Nature and Environment
Because at 160,000 years, the party is just getting started.
Global Warming, Weather and Climate Change
7/31/2011 7:08:34 PM
Tags: Heat Wave, Weather, Climate, atmospheric carbon dioxide, the future, Richard Hilderman
The United States is currently experiencing an extreme heat wave! At one time 32 states were under either a heat advisory or heat warning covering about 100 million square miles and affecting about 141 million people. At least 12 deaths have been attributed to this heat wave. Furthermore, parts of the midwest and southeast are experiencing severe drought conditions. What is the relationship between heat waves, weather, climate change and global warming? To address this question we must understand the link between weather and climate.
Weather is comprised of temperature, wind speed, humidity, precipitation, etc that occurs over only a few days. Climate, on the other hand, is the average weather patterns that occur over decades. In other words weather is concerned about the immediate whereas climate is more focused on the long term. The climate is currently evolving because of the human induced burning of fossil fuel that releases carbon dioxide into the atmosphere. This release of carbon dioxide is responsible for the current atmospheric carbon overload which triggers the current global warming trend (my postings entitled Fossil Fuel and Atmospheric Levels of Carbon Dioxide and Solar Activity, Greenhouse Gas Levels and Climate Change on Our Earth). Since global warming occurs over decades, it represents a shift to a warmer climate. This shift to a warmer climate increases the frequency of powerful storms and extreme weather events which is something we have experienced in the past several years.
Since climate change represents what is happening in the future, there is only one possible future if we continue in our use of fossil fuels. The continued burning of fossil fuel is triggering climate change by shifting the global temperature to a higher level. Some people believe we don’t have to worry about global warming until climate change triggers events that are harmful to us personally. Unfortunately this will be too late! The climate system has a time lag because it will take thousands of years to remove the excess carbon dioxide we are pumping into the atmosphere by burning of fossil fuel (my posting entitled Carbon Cycle). Thus, when we see the effects of global warming in the weather on a daily basis it will be too late to fix the problem!
If we want to see an increase in the frequency of heat waves like the one we are currently experiencing, all we have to do is continue our use of fossil fuel.
More information on the relationship of weather and the climate can be found in the book entitled THE WEATHER OF THE FUTURE: Heat Waves, Extreme Storms and Other Scenes from a Climate-Changed Planet by Heidi Cullen.
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Math rock
From Wikipedia, the free encyclopedia
Jump to: navigation, search
Math rock
Stylistic origins Experimental rock, indie rock, post-hardcore, post-punk, noise rock, minimalism, progressive rock, art rock, avant-garde jazz
Cultural origins Late 1980s United States (Chicago, Pittsburgh, San Diego and Los Angeles) and Japan
Typical instruments Vocals, guitar, bass, drums
(complete list)
Fusion genres
Regional scenes
Chicago - San Diego - South Atlantic States - Pittsburgh - Boston - St. Louis - Japan
Other topics
Post-rock - Minimalist music - Instrumental rock
Slint performing Spiderland in its entirety at the Pitchfork Music Festival
Math rock is a rhythmically complex, often guitar-based, style of experimental rock and indie rock[1] music that emerged in the late 1980s, influenced by progressive rock bands like King Crimson and 20th century minimalist composers such as Steve Reich. It is characterized by complex, atypical rhythmic structures (including irregular stopping and starting), counterpoint, odd time signatures, angular melodies, and extended, often dissonant, chords.
Whereas most rock music uses a basic 4/4 meter (however accented or syncopated), math rock frequently uses asymmetrical time signatures such as 7/8, 11/8, or 13/8, or features constantly changing meters based on various groupings of 2 and 3. This rhythmic complexity, seen as "mathematical" in character by many listeners and critics, is what gives the genre its name.
The sound is usually dominated by guitars and drums as in traditional rock, and because of the complex rhythms, drummers of math rock groups have a tendency to stick out more often than in other groups. It is commonplace to find guitarists in math rock groups using the "tapping" method of guitar playing, and loop pedals are occasionally incorporated, as by the band Battles. Guitars are also often played in clean tones more than in other upbeat rock songs, but some groups also use distortion.
Lyrics are generally not the focus of math rock; the voice is treated as just another sound in the mix. Often, lyrics are not overdubbed, and are positioned low in the mix, as in the recording style of Steve Albini. Many of math rock's most famous groups are entirely instrumental such as Don Caballero or Hella, though both have experimented with singing to varying degrees.
The term math rock has often been passed off as a joke that has developed into what some believe is a musical style. An advocate of this is Matt Sweeney, singer with Chavez, who themselves were often linked to the math rock scene:[2]
Early influences[edit]
Some rock musicians who emerged in the 1960s and '70s experimented with unusual meters and structures. Notable examples include Frank Zappa, Henry Cow, Cream, Captain Beefheart, Emerson, Lake & Palmer, Genesis, Kansas, Jethro Tull, Gentle Giant, Yes, Rush, King Crimson, Gong, The Police, Mahavishnu Orchestra and Pink Floyd. The music of these and others from this era sometimes had hard rock or metal leanings, but such groups were generally classified as "progressive rock".
The Canadian punk rock group Nomeansno (founded in 1979 and active as of 2013) have been cited by music critics[3] as a "secret influence" on math rock, predating much of the genre's development by more than a decade. Though never finding or even seeking mainstream attention, Nomeansno's music typically blends dark humor, punk energy and aggression, drastic shifts in tempo and structure and acclaimed instrumental prowess in their quest for transcendence. An even more avant-garde group of the same era, Massacre, featured the guitarist Fred Frith and the bassist Bill Laswell. With some influence from the rapid-fire energy of punk, Massacre's influential music used complex rhythmic characteristics. Black Flag's 1984 album My War also included unusual polyrhythms.[4]
In the 1990s, a heavier, rhythmically complex style grew out of the broader noise rock scenes active in Chicago and other Midwestern cities, with influential groups also coming from Japan and Southern California. These groups shared influences ranging from the music of 20th-century composers such as Igor Stravinsky, Béla Bartók, John Cage, and Steve Reich, as well as the chaotic free-jazz approach of John Zorn's Naked City and Miles Davis´s later work, and critics soon dubbed the style "math rock".
Australian groups[edit]
Bands such as Because of Ghosts, The Sinking Citizenship, and My Disco emerged in the early 2000s in Melbourne.
European groups[edit]
The European math rock scene started in the late 90s to early 2000, including bands such as Adebisi Shank (Ireland), Kobong (Poland), The Redneck Manifesto (Ireland), It Was All A Bit Black & White (Ireland), Three Trapped Tigers and This Town Needs Guns (United Kingdom) and Uzeda (Italy).
Japanese groups[edit]
The most important Japanese groups include Ruins, Zeni Geva, Boredoms, Aburadako, and Doom. Yona-Kit is a collaboration between Japanese and U.S. musicians. Other Japanese groups which incorporate math rock in their music include Toe, Zazen Boys, and Lite. Skin Graft Records and Tzadik Records have released Japanese math rock albums in the United States.
United States[edit]
During the 1990s, the greatest concentration of math rock bands was in the urban centers of the U.S.'s Midwestern "Rust Belt", ranging from Minneapolis to Buffalo. Chicago was a central hub. The Chicago-based sound engineer Steve Albini is a key figure in the scene, and many math rock bands from around the country have enlisted him to record their albums, giving the genre's recorded catalog a certain uniformity of sound, and lumping his bands past and present—Shellac, Rapeman, and Big Black—into the pigeonhole as well. Also, many math rock records were released by Chicago-based Touch and Go Records, as well as its sister labels, Quarterstick Records and Skin Graft Records. Bands from Chicago include Sweep the Leg Johnny. Several other math rock groups of the 1990s were based in Midwestern cities: Cleveland's Craw and Keelhaul, St. Louis's Dazzling Killmen, and Minneapolis's Colossamite.
Outside the Midwest, the city of Pittsburgh is home to Don Caballero—whose drummer, Damon Che, is also involved with the international math rock band Bellini as well as Black Moth Super Rainbow, Tabula Rasa, and Knot Feeder.[5] Bands from Washington, D.C. include The Dismemberment Plan, Shudder to Think, Hoover, Faraquet, 1.6 Band, Autoclave, later Jawbox, and Circus Lupus. The Richmond, VA-based Breadwinner inspired bands such as Fulflej and Lamb of God. Polvo of Chapel Hill, North Carolina is often considered math rock, although the band has disavowed that categorization.[6] The success of Louisville, Kentucky's Slint inspired bands such as Rodan, Crain, The For Carnation, June of 44, Sonora Pine, Roadside Monument, and Shipping News.
In California, math rock groups from San Diego include Drive Like Jehu, Antioch Arrow, Tristeza, No Knife, Heavy Vegetable and Sleeping People. Northern California was the base of Game Theory and The Loud Family, both led by Scott Miller, who was said to "tinker with pop the way a born mathematician tinkers with numbers."[7] The origin of Game Theory's name is mathematical, suggesting a "nearly mathy" sound cited as "IQ rock."[8]
Contemporary math rock[edit]
By the turn of the 21st century, most of the later generation bands such as Sweep the Leg Johnny had disbanded and the genre had been roundly disavowed by most bands labeled with the "math rock" moniker. Many more bands, consisting of both those from the original wave of the genre and those of the new generation, have managed to be tagged with the moniker of "math-rock". The British band Foals exemplify the angular guitar sections and start/stop dynamics of the math rock sound particularly in their earlier demos; however they lack the mixture of time signatures or the odd time signatures needed to be thought of as a proper math rock band. The Edmund Fitzgerald is a band containing members of the band Foals, with the addition of the use of complex time signatures and time changes. Youthmovie Soundtrack Strategies are another British band who use angular guitar sections, as well as some post-rock techniques and the use of different time signatures. This Town Needs Guns, an Oxford based band, predominantly use asymmetrical time signatures, typical math rock characteristics, as well as complex finger picking.
In the mid-2000s, many math rock bands enjoyed renewed popularity. Slint and Chavez embarked on reunion tours, while Shellac toured and released their first album in seven years. Don Caballero reunited with a new lineup and released an album in 2006, while several of its original members joined new projects, such as the band Knot Feeder.
See also[edit]
Notes and references[edit]
1. ^ "Math Rock". Allmusic. Retrieved 2007-08-01.
2. ^ "Interview: Chavez". Pitchfork Media. 2006-08-12. Retrieved 2007-08-01.
3. ^ "Live and Cuddly". Allmusic. Retrieved 2007-08-01.
4. ^ "its seven-minute Metal dirges and Fusion-style time signatures proved too much for many fans" Steven Blush, American Hardcore: A Tribal History, "Thirsty and Miserable", Los Angeles: Feral House, 2001, p. 66
5. ^ Math & Noise: Knot Feeder
6. ^ You can call Polvo math rock, but the numbers just don't add up | Atlanta|Music|Feature
7. ^ Schoemer, Karen (April 2, 1993). "Sounds Around Town: Miller Writ Loud". New York Times. Archived from the original on 2013-11-13.
8. ^ Amar, Erin (July 2011). "Music: What Happened? Scott Miller on 50 Years of Singles in 258 Pages". Rocker Magazine. Archived from the original on 2013-11-01.
External links[edit]
Math Rock at AllMusic
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How Does Mitosis Result in Tissues and Organs?
Mitosis is the process of cell division which is the mechanism that eukaryotic cells use to replicate themselves. During cell division or mitosis, a cell will make two exact copies of itself before the original cell eventually dies. It is this process that results in the regeneration of parts of the human body such as tissues and organs.
Q&A Related to "How Does Mitosis Result in Tissues and Organs?"
From the division of somatic cells.
Mitosis allows for the division and "bulking" of many cells into
Ah interesting question. As you may know mitosis is the division of somatic (non-sex) cells. Mitosis is needed to build up the bulk of cells that make us up. Upon fertilization of
White Blood Cells< along with the immune system.
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| 0.938488 |
What a Great Idea
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What a Great Idea
Explores the fine line between reality and fiction by following a group of LA artists (actors/writers/musicians/dancers) involved in a private workshop (or with each other). As their paths intertwine, six degrees of separation becomes more like two degrees of separation and the questions raised are: is it on the page or improvisation, artistic endeavor or foreplay, experimentation or manipulation, art or life?
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Rustic Grilled Cheese
By ElizabethKnicely on March 12, 2013
25 Characters Max
Enter Time:
You can create up to five timers
1. 2 slices multi-grain bread
2. 1 teaspoon grey poupon savory honey mustard
3. 6 slices oscar mayer deli fresh shaved rotisserie seasoned chicken breasts
4. 2 slices tomatoes
5. 1 slice American cheese
6. 2 teaspoons butter, softened
1. Spread 1 bread slice with mustard; fill bread slices with all remaining ingredients except butter.
2. Spread outside of sandwich with butter.
3. Cook in skillet on medium heat for 3 minutes on each side or until golden bown on both sides.
5. Serving Suggestion: Serve with an ice-cold glass of fat-free milk and a mixed green salad to round out the meal.
6. Substitute: Prepare using thinly sliced red or green peppers instead of the tomato.
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Game To Nominate: Can you name the significant events in the life of Late Show host David Letterman?
Why? (optional):
You must be logged in to nominate a quiz.
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| 0.999694 |
What Is Direct and Indirect Employment?
Direct employment refers to employment directly related to the production of products or services or when a person is permanently employed in a firm. Indirect employment refers to when the business generates employment in other businesses to supply or produce goods and services or when a firm contracts some work to a person.
1 Additional Answer
Direct employment refers to the total number of persons employed in an organisation and belongs to a certain sector. Indirect employment is employment throughout the chain of production and it refers to people contracted by a firm to provide intermediate components or products or services to an organisation.
Q&A Related to "What Is Direct and Indirect Employment"
An object is a noun, pronoun, or noun phrase that receives the actions of a verb or a preposition. A direct object receives the action of a verb. An indirect object indicates to or
Indirect employment is when you contract with a search firm to get you work. When you get a job on your own efforts, that is direct employment. Source(s) Former recruiter.
Discrimination occurs when an employer or other institution makes decisions about people based on sex, national origin, race, color, ethnicity, age, disability or religion. This is
So many different possibilities here. In many cases, it's very much cultural - some cultures value directness as politeness in not wasting a person's valuable time. (New Yorkers in
Explore this Topic
A compensation package is a sum of the benefits, direct and indirect, that an employee receives from an employer. Examples of benefits include: salary, allowance ...
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Baylor > Mathematics > Research > Representation Theory
Representation Theory
Mathematics has enjoyed truly remarkable success in describing the universe in which we live. The fundamental laws often display a wonderful elegance and symmetry. The area of mathematics that studies this amazing symmetry is called Lie theory or representation theory. Loosely speaking, the objects possessing symmetry are called Lie groups and the ways in which they manifest themselves are called representations. Baylor has an active group working in this area.
Representation Theory Group: Markus Hunziker, Mark Sepanski, Ron Stanke
Rep Theory
From left to right: Ron Stanke, Markus Hunziker, Mark Sepanski
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PowerPoint Presentation - Michigan Technological University
Document Sample
PowerPoint Presentation - Michigan Technological University Powered By Docstoc
Quantum Mechanics
Robert Nemiroff
Michigan Technological University
Physics X: About This Course
• Officially "Extraordinary Concepts in Physics"
• Being taught for credit at Michigan Tech
o Light on math, heavy on concepts
o Anyone anywhere is welcome
• No textbook required
o Wikipedia, web links, and lectures only
o Find all the lectures with Google at:
"Starship Asterisk" then "Physics X"
o http://bb.nightskylive.net/asterisk/viewforum.php?f=39
Symmetry and Conservation:
Noether's Theorem
Symmetries underlie conservation laws
(assumes principle of least action)
Symmetry Conservation law
Rotation Angular momentum
Translation Linear momentum
Time Energy
Many others involving more complex symmetries.
Acceleration, Jerk, and Snap:
The Movement Paradox
To move from rest, and object must have change its position
over time, which means it must attain a velocity v.
To attain velocity v from rest, the object must accelerate, a.
But how does an object attain acceleration from rest?
Higher order motion: jerk = da/dt, snap = d(jerk)/dt .
Snap is also called "jounce".
All orders are needed for motion from rest, but these are the only ones with
Charge versus Mass
Although both electric charge and gravitational mass appear in similar
inverse square laws, there are differences.
Speed invariant Changes relativistically
charge mass
spin energy
magnetic moment wavelength
Experimental Relativity
E = m c2 is a theorist's equation
E = α m β c2γ + δ is more experimental
where α, β, and γ are near 1, and δ is near 0.
I don't know what the current experimental limits on these "free
parameters" are. This might make an interesting research
Quantum Effects:
As plain as the nose on your face?
Quantum effects have been observable since humans began, just not
understood. Using one eye, one can align a point source (say a star)
just over the nose on your face and see diffraction rings. Try it!
Quantum Effects:
Visible with imperfect lens and blurry vision?
To see quantum effects, you don't even have to have a nose! Assuming
your eye's lens is imperfect and your vision is even a little bit blurry, look
closely at a distant point light source. You will notice several "speckels"
that are caused by the fluid in your eye. But notice that each of these
speckels have a diffraction pattern around them. Try it!
P versus NP Problem
Technically the premiere problem in computer science but might be relevant to
physics one day.
Can answers be generated as quickly as they can be verified?
In particular, if answers can be verified in polynomial time on a computer, can the
answers be generated in polynomial time as well?
(Seems like "no" to me: one can open a lock quickly, given a key, but one can't
generate a key as quickly.)
Related to the arrow of time? Wave function collapse?
Holographic Principle
A conjecture that states that a volume of space has all its information
encoded on the area that bounds it.
Originally used to describe the entropy of black holes -- the entropy
inside a black hole can be computed from its bounding event horizon.
Extended to string theory and the universe in general.
Might be applicable to cosmology.
Unruh Effect
Accelerating observers measure different blackbody radiation than non-
accelerating observers
Accelerated observers see a different type of underlying background
vacuum than non-accelerating observers.
Say a thermometer at rest in a vacuum reads zero temperature. If that
same thermometer is waved about in the vacuum, it will read a finite
Unruh Effect
Unruh temperature: What temperature will the thermometer read?
• h is reduced Planck's constant
• a is acceleration
• c is the speed of light
• k is Boltzmann's constant
Higgs Mechanism
A leading mechanism for how (some) particles have inertial mass.
Space is filled with a virtual sea of Higgs bosons (among other
things). Fundamental particles perturb this sea so that a crowd of
virtual Higgs particles surrounds it. Slogging through this field creates
inertial mass.
For protons and neutrons, inertial mass is thought to be mostly
provided by the exchange of virtual color gluons.
Strangelets are a form of matter not seen on Earth consisting of equal
numbers of up, down, and strange quarks. Standard nucleons don't
contain strange quarks.
• are more compact than nuclear matter
• may grow to arbitrary size
o involves runaway reaction
o might make massive "strange stars"
• might convert any nucleon to a strangelet upon contact
Large Hadron Collider
• Currently largest collider, started in 2009
• Frequently known by abbreviation LHC
• Located in Switzerland
• Find or rule out predicted Higgs boson
o Bolster the Higgs mechanism
• Search for supersymmetric particle partners
• Search for extra space dimension
• Search for dark matter particles
Large Hadron Collider:
Black Hole Controversy
Black Holes
• LHC will create micro black holes that will devour the Earth
• Such mBHs should have been created already in cosmic rays, but
the Earth remains.
Large Hadron Collider:
Strangelet Controversy
Strangelets formed in the LHC could change the Earth into one big
strange particle
• Stranglets might not be found in cosmic rays since they would have
decayed before striking the Earth
• But still some of them should survive, as does the Earth -- so little
• Strangelets are more likely to have been created in other colliders,
but have never been found
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Alternative Mortgage Transaction Parity Act - AMTPA
Dictionary Says
Definition of 'Alternative Mortgage Transaction Parity Act - AMTPA'
An act from 1982 that over-rode many state laws that prevented banks from using mortgages other than conventional fixed-rate mortgages. This act allowed for the total costs of loans to become obscured, and led to the availability of various new mortgages such as adjustable rate mortgages (ARMs), interest only mortgages, and ballon payment mortgages.
Investopedia Says
Investopedia explains 'Alternative Mortgage Transaction Parity Act - AMTPA'
Many believe that this act is the basis of the sub-prime crisis of 2007, which led to the financial crisis of 2007-2009. Many mortgage borrowers in the early 21st century obtained mortgages that they failed to understand. As borrowers began to lose their homes due to defaulting on their mortgages, house prices began to spiral downward making it even more difficult for people to refinance their homes into more affordable mortgages.
Articles Of Interest
1. Interest-Only Mortgages: Home Free Or Homeless?
These loans can be beneficial, but for many borrowers, they present a financial trap.
2. ARMed And Dangerous
3. Option ARMs: American Dream Or Mortgage Nightmare?
4. Who Is To Blame For The Subprime Crisis?
5. This ARM Has Teeth
Find out how to avoid getting bitten when your mortgage rate resets.
6. What Is A Pyramid Scheme?
7. The Best-Performing Sectors Of 2013
A sector represents a high-level way in which analysts and investors group similar companies together. Analyzing Standard & Poor’s Depositary Receipts, or SPDRs, serves as one of the best proxies ...
8. How To Rent Your Home So You Can Pay Your Mortgage
9. Why Americans Still Can't Escape The Recession
National statistics indicate that the U.S. economy is finally gaining momentum. So why doesn't it feel that way for many Americans?
10. 10 Steps To Tax Preparation
Follow these simple steps to get you ready for the income tax deadline of April 15.
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5. Yield Elbow
6. XDIS
Trading Center
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New! Read & write annotations
I've touched some objects of faith more precious than pieces of eight.
Seen sacred places and ritual ways, but for communion let's go to my place.
I learned to pray on my knees.
Been taken in hand, if you please.
Had my own revelations, ideas about fate, but for communion let's go to my place.
So as the body, so as the blood, sacred as the soul is to love.
Don't be mistaken if you don't understand, divinely simple.
Part of the plan.
This is my body!
I give it to you.
This is my blood.
Do it in remembrance of me (so you won't forget me).
Now, I've been a witness of grace.
Iêve stared sacred days in the face.
The long long parade of ritual ways, but for communion let's go to my place.
Sacred stories are told.
They're passed on like pieces of gold.
So make your conclusions, consider your fate, and for communion let's go to my place.
Are you ready?
Are you ready for communion?
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| 0.981549 |
Spina Bifida Causes, Treatment, Symptoms, Diagnosis, Complications - MedicineNet
Spina Bifida
(Neural Tube Defect)
Introduction to spina bifida
What is spina bifida?
Spina bifida, which literally means "cleft spine," is characterized by the incomplete development of the brain, spinal cord, and/or meninges (the protective covering around the brain and spinal cord). It is the most common n eural tube defect in the United States -- affecting 1,500 to 2,000 of the more than 4 million babies born in the country each year. There are an estimated 166,000 individuals with spina bifida living in the United States.
What are the different types of spina bifida?
Occulta is the mildest and most common form in which one or more vertebrae are malformed. The name "occulta," which means "hidden," indicates that the malformation, or opening in the spine, is covered by a layer of skin. This form of spina bifida is present in 10 to 20 percent of the general population and rarely causes disability or symptoms.
In the third type, meningocele, spinal fluid and the meninges protrude through an abnormal vertebral opening. The malformation contains no neural elements and may or may not be covered by a layer of skin. Some individuals with meningocele may have few or no symptoms while others may experience symptoms similar to closed neural tube defects.
Myelomeningocele, the fourth form, is the most severe and occurs when the spinal cord or neural elements are exposed through the opening in the spine, resulting in partial or complete motor paralysis and sensory deficits within the parts of the body below the spinal opening. The paralysis may be so severe that the affected individual is unable to walk and may have urinary and bowel dysfunction.
Medically Reviewed by a Doctor on 9/1/2013
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Viewers share their comments
Anencephaly Definition
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Last updated on March 13, 2014 at 18:18 EDT
The Answer is in the Crests and Troughs
760 of 942
The Answer is in the Crests and Troughs
December 19, 2004
This microscopic image taken by the Mars Exploration Rover Spirit shows the troughs between the waves of windblown soil that characterize the surface of Gusev Crater, Mars. The fine-grained soil in the troughs, combined with the coarse grains observed in a similar microscopic image taken of the waves' crests, indicate that the waves are geologic features known as ripples, and not dunes. Dunes contain a more uniform distribution of material. This information helps scientists better understand the winds that shape the landscape of Mars. The image was taken on the 41st martian day, or sol, of the rover's mission by its microscopic imager. The observed area is 3 centimeters (1.2 inches) across.
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| 0.986683 |
Drifter (floating device)
From Wikipedia, the free encyclopedia
Jump to: navigation, search
A drifter nicknamed holey sock. Typical sensors acquire air pressure, sea surface temperature, irradiance and CTD.
A drifter (also float) is an oceanographic device floating on the surface or at a given water depth to investigate ocean currents and other parameters like temperature or salinity. They are also called Lagrangian drifters since they follow the flow in a Lagrangian manner. The depth of drifter is defined by its neutral buoyancy. The device stops sinking when its buoyancy force is in equilibrium with its gravitational force.[1]
Construction principle[edit]
The major component of a drifter are hollow bodies that ensure flotation, underwater-sails to catch water currents, instruments (e.g., data collecting instruments, transmitters to transmit the collected data, and GPS devices), and waterproof containers for instruments.[2][3] Drifters are a hi-tech evolution of the ocean current analysis by means of drift bottles, which in their turn evolved from simple collection of data about messages in a bottle.
Drifters provide real-time information about ocean circulation. The data is a valuable input for weather forecasts as meteorological satellites can at maximum measure the sea surface temperature or the surface roughness of the world oceans, but it is not possible to look into the water column. Data from inside the ocean is helpful for hurricane prediction as well.
Drifters may also collect information about marine life, such as distribution of plankton.[2]
Different types[edit]
An Argo float
• ALACE (Autonomous Lagrange Circulation Explorer)[4]
• Argo float[5]
• PALACE (Profiling Autonomous Lagrange Circulation Explorer)
• Davis drifter[6]
• Polar Profiling Float
• SOFAR float[7]
• SOLO
• Swallow float
See also[edit]
1. ^ Budeus, Gereon. "Floats – free drifting underwater buoys". Alfred-Wegener-Institute for Polar- and Marine Research. Retrieved 2012-09-13.
2. ^ a b "Drifters"
3. ^ "Dissect a Drifter"
4. ^ [1]
5. ^ "Argo-float design". Retrieved 2012-09-17.
6. ^ [2]
7. ^ [3]
External links[edit]
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__label__pos
| 0.899353 |
Take the 2-minute tour ×
I am using Isapi Rewrite for IIS, and I want to make SEO friendly URLs for a dynamic product page.
I need to replace spaces differently in two query string parameters.
In the first param, \s should be replaced with + In the second, all \s should be replaced with -
#seo. 2 conditions. split on _ delimiter.
RewriteRule ^Store/([^_]+)_([^/]+) Store/Details.aspx?id=$1&name=$2 [QSA,NC]
#replace spaces with + in first condition (doesn't work)
#RewriteRule ^Store/([^\w\s]+)\s(.+)$ Store/Details.aspx?id=$1+$2 [QSA, NC]
#replace spaces with dash in second condition ???
Store/NP SP_name name
//$1: NP+SP
//$2: name-name
// output: Store/NP+SP_name-name
//$1: mn+98+765
//$2: name-name-name
//output: Store/mn+98+765_name-name-name
share|improve this question
add comment
1 Answer
up vote 0 down vote accepted
I've done smth like that the other day, but there was a simplier task with only one type of replacement. Try using the following for basic redirect(if it works, we'll think of a more complex, multiple-parameters scenario):
RewriteRule ^Store/(.+)\s([^_]+)_(.+)\s(.+) /Store/$1+$2_$3-$4 [NC,R=301,L]
Make sure you put in on top of the existing rewrite.
share|improve this answer
Hi, That worked for NP SP_name name, but did not work for NP SP_name name name or mn%2098%20765_name%20name%20name. – User970008 Jul 26 '12 at 2:24
Is there a way to replace all spaces in the condition? not just the first one – User970008 Aug 2 '12 at 17:47
add comment
Your Answer
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__label__pos
| 0.70747 |
Take the 2-minute tour ×
I have three models (tables):
1. content
2. category
3. contentCategory
The contentCategory have content_id and category_id that related to each other.
How I must write relation in each model to select content of specific category?
public function relations()
return array(
share|improve this question
if you define the relationship(PK, FK) while designing the database, yii will automatically build the relationship, which is better than defining manually... yiiframework.com/doc/guide/1.1/en/database.arr the above doc explains cleary about building relations.... – Neeraj Dangol Jan 20 '13 at 9:50
add comment
1 Answer
up vote 2 down vote accepted
If your table contentCategory has only 2 fields content_id and category_id then u don't need to create a model for this table and in the other models you'll have
'contentCategory(content_id, category_id)'),
'contents'=>array(self::MANY_MANY, 'Content',
'contentCategory(category_id, content_id)'),
If your table contentCategory has more content then you'll need to use through:
Link to the guide
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| 0.787431 |
Business Description
PT Sumber Alfaria Trijaya Tbk is an Indonesia-based company primarily engaged in operating convenience store chain and managing its franchise. The convenience store chain is operated under the brand name Alfamart. The Company classifies its business into two operating segments: food and non-food. Its outlets is available in various areas in Indonesia, such as Jakarta, Bogor, Tangerang and Bekasi (Jabotabek), Medan, Pekan Baru, Bandung, Cilacap, Semarang, Denpasar, Makassar, among others. Its subsidiaries include PT Sumber Indah Lestari and PT Midi Utama Indonesia Tbk.
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What Does Preceding Mean?
Preceding is a word used in reference to order or arrangement. It can be used as an adjective to mean or show that something happens before the other does. For example, the preceding protests led to the resignation of the prime minister.
1 Additional Answer
Ask.com Answer for: what does preceding mean
that precedes; previous: Refer back to the footnote on the preceding page.
Source: Dictionary.com
Q&A Related to "What Does Preceding Mean"
Precedent is a rule that a court uses in similar court cases. It is commonly used in divorce, murder, and child custody cases. Many lawyers also use this rule to win cases.
When you use a cell in a formula located within another cell, it's a precedent cell. Likewise, the cell that contains the formula is a dependent cell. So if cell A2 has the formula
a legal case establishing a principle or rule that a court or other judicial body adopts when deciding subsequent cases with similar issues or facts. Court decision that stands as
The paleontologist Steven Mithen speculates that music is the evolutionary bridge between the calls and gestures of our fellow primates and human language. There's much to recommend
Explore this Topic
The word precede” may be used to mean “come or go before something” that is to come, go, be or happen before somebody or something else in time ...
The word preceded means came before or happened before. it is used to refer to positioning where it shows that one act or occurrence came before another. A synonym ...
Precedence is order observed in acknowledgement of people of different ranks in reference to an acknowledged or legal system. It also refers to a right of preferential ...
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According to scientists from Nasa and the National Snow and Ice Data Center in Boulder, Colorado, the ice cover is the smallest in the three decades since the polar cap has been monitored by satellite.
The ice is measured by a Special Sensor Microwave Imager, on a US spacecraft. The ice is currently 1.58 million square miles.
nasa ice
Sunset in the Arctic: Each year, the ice cap melts throughout the summer months before expanding through winter
Today's ice is 27,000 square miles smaller than 2007, when 1.61 million square miles of ice were measured.
And the 2012 "melt season" could still continue for several weeks, resulting in an even larger loss of ice.
But over the last three decades, satellites have observed a 13% decline per decade in the sea ice, which is measured when it is at its smallest, and the ice is steadily getting thinner.
ice caps
Joey Comiso, senior research scientist at Nasa, said the results were particularly unusual, because temperatures had not been exceptionally warm.
He said: "The persistent loss of perennial ice cover - ice that survives the melt season - led to this year's record summertime retreat. Unlike 2007, temperatures were not unusually warm in the Arctic this summer."
"In 2007, it was actually much warmer. We are losing the thick component of the ice cover.
ice cap
The sea ice concentration from September 21, 1979, which is much larger than 2012
NSIDC research scientist Walt Meier said: "By itself it's just a number, and occasionally records are going to get set.
Rod Downie, Polar Programme Manager for WWF-UK said the new research was concerning.
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Subscribe English
look up any word, like drinking watermelon:
Originating from high-fives. It's considered rude to not return a high-five when someone puts their hand in the air—there's no graceful way for them to lower it without someone returning their high-five. Their hand is left hanging in the air. So, whenever a person leaves another person in a situation where the first person is waiting for a response--and not getting it from the second person--it's referred to as being left hanging.
"Yo, dude, don't leave me hanging!"
by aidenfire April 19, 2006
213 67
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| 0.979263 |
Python indentation deters newbies?
beliavsky at beliavsky at
Mon Aug 16 15:12:07 CEST 2004
Peter Hansen <peter at> wrote in message news:<AuWdnUL93se81L3cRVn-hQ at>...
> For example, if 90% of people who have the "indentation rash"
> had previous encounters with FORTRAN IV, then it ought to
> be possible to make it obvious in the early documentation
> (tutorial, intro page, etc) that Python is not FORTRAN and
> doesn't suffer from the same limitations with respect to
> indentation/whitespace significance as FORTRAN does.
Uh oh, people are picking on my beloved Fortran :).
Fortran IV was standardized as Fortran 66. Even the following Fortran
standard, Fortran 77, had only "fixed format" with the rigid column
restrictions. The Fortran 90 standard introduced free format, and I
think such code resembles Python more closely than other compiled
languages, because there are no semicolons needed to terminate lines,
and curly braces are not used to delimit blocks.
It would be misleading to discuss certain flaws of earlier versions of
Fortran without mentioning that they have long since been corrected.
Btw, the official spelling has been "Fortran" (not all uppercase)
since the 1990 standard.
I have done a good bit of coding in both Python and Fortran and still
(mildly)prefer using key words rather than indentation to terminate
blocks, for example
do i=0,9
! some code
compared to
for i in range(10):
# some code
In Fortran you easily wrap a do-enddo or if-endif around a block of
code without touching the interior lines. This is useful for
debugging. If the change is permanent, the code should be re-indented.
In Python the indentation must be correct at all times, which can be
More information about the Python-list mailing list
|
__label__pos
| 0.81004 |
Take the 2-minute tour ×
I've in my logback.xml configuration file this appender:
<appender name="FILE"
<encoder class="ch.qos.logback.classic.encoder.PatternLayoutEncoder">
<Pattern>%d{dd MMM yyyy;HH:mm:ss} %-5level %logger{36} - %msg%n
<rollingPolicy class="ch.qos.logback.core.rolling.FixedWindowRollingPolicy">
so that I specify path to file in which to print logs in a relative way through classpath, but it doesn't work, no file addressbookLog.log is created and written. It only works with absolute paths like /home/andrea/.../resources/addressbookLog.log Have you any ideas on how to make it work with classpath?
share|improve this question
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2 Answers
The Chapter 3: Logback configuration: Variable substitution told us the various ways to refer to the variable defined outside, e.g. system properties and classpath.
The significant configuration is creating a separate file that will contain all the variables. We can make a reference to a resource on the class path instead of a file as well. e.g.
The logback.xml
<property resource="resource1.properties" />
<!-- Here we can refer to the variable
defined at the resource1.properties -->
<root level="debug">
<appender-ref ref="FILE" />
The external properties file (resource1.properties)
Please note that the resource1.properties is a resource which available at the classpath.
You may refer to the full version at Chapter 3: Logback configuration: Variable substitution. I hope this may help.
share|improve this answer
That's not really what he is asking. He wants to know how to use the classpath to specify where the destination log file is. For example, the log file in his example would be "WEB-INF/classes/addressbookLog.log" under Tomcat. But it could be in a different location in a different environment. I'm looking for the answer to the same question... – jsumners Jul 3 '13 at 17:45
add comment
You defined the resource1.properties is absolute path.
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Your Answer
|
__label__pos
| 0.919061 |
From Uncyclopedia, the content-free encyclopedia
Jump to: navigation, search
This picture of the August 11, 1999 solar eclipse was one of the last ever taken from the Mir space station. NASA image.
An eclipse is an astronomical event that occurs when one celestial object moves into the shadow of another. The term is derived from the ancient Greek noun ἔκλειψις, "I cease to exist," a combination of prefix ἐκ, from preposition ἐκ, ex, "I ate your dog," and of verb λείπω, "where's my popcorn"
The term eclipse is most often used to describe either a solar eclipse, when the Moon's shadow crosses the Earth's surface, or a lunar eclipse, when the Moon moves into the shadow of Earth. However, it can also refer to such events beyond the Earth-Moon system: for example, a planet moving into the shadow cast by one of its moons, a moon passing into the shadow cast by its parent planet, or a moon passing into the shadow of another moon. A binary star system can also produce eclipses if the plane of their orbit intersects the position of the observer.
edit Syzygy
This article is based on the Désencyclopédian text Éclipse, made freely available to French-speaking wildebeest gnus under the GFDL.
A syzygy is the alignment of three or more celestial bodies in the same gravitational system along a straight line. The word is usually used in context with the Sun, Earth, and the Moon or a planet, where the latter is in conjunction or opposition. Solar and lunar eclipses occur at times of syzygy, as do Astronomical transits and occultations.
An eclipse occurs when there is a syzygy between a star and two celestial bodies, such as a planet and a moon. The shadow cast by the object closest to the star intersects the more distant body, lowering the amount of luminosity reaching the latter's surface. The region of shadow cast by the occulting body is divided into an umbra, where the radiation from the star's radiation-emitting photosphere is completely blocked, and a penumbra, where only a portion of the radiation is blocked
A total eclipse will occur when the observer is located within the umbra of the occulting object. Totality occurs at the point of maximum phase during a total eclipse, when the occulted object is completely covered. When the star and a smaller occulting object are nearly spherical, the umbra forms a cone-shaped region of shadow in space.
Beyond the end of the umbra is a region called the antumbra, where a planet or moon will be seen transiting across the star but not completely covering it. For an observer inside the antumbra of a solar eclipse, for example, the Moon appears smaller than the Sun, resulting in an annular eclipse. The remaining volume of shadowed space, where only a fraction of the occulting object overlaps the star, is called the penumbra. An eclipse that does not reach totality, such as when the observer is in the penumbra, is called a partial eclipse.
For spherical bodies, when the occluding object is smaller than the star, the length (L) of the Umbra's cone-shaped shadow is given by:
where Rs is the radius of the star, Ro is the occulting object's radius, and r is the distance from the star to the occulting object. For Earth, on average L is equal to 1.384×106 km, which is much larger than the Moon's semimajor axis of 3.844×105 km. Hence the umbral cone of the Earth can completely envelop the Moon during a lunar eclipse. If the occulting object has an atmosphere, however, some of the luminosity of the star can be refracted into the volume of the umbra. This occurs, for example, during an eclipse of the Moon by the Earth—producing a faint, ruddy illumination of the Moon even at totality.
An astronomical transit is also a type of syzygy, but is used to describe the situation where the nearer object is considerably smaller in apparent size than the more distant object. Likewise, an occultation is a syzygy where the apparent size of the nearer object appears much larger than the distant object, and the distant object becomes completely hidden during the event.
An eclipse cycle takes place when a series of eclipses are separated by a certain interval of time. This happens when the orbital motions of the bodies form repeating harmonic patterns. A particular instance is the Saros cycle, which results in a repetition of a solar or lunar eclipse every 6,585.3 days, or a little over 18 years. However, because this cycle has an odd number of days, a successive eclipse is viewed from a different part of the world
edit Earth-Moon System
An eclipse involving the Sun, Earth and Moon can occur only when they are nearly in a straight line, allowing the shadow cast by the Sun to fall upon the eclipsed body. Because the orbital plane of the Moon is tilted with respect to the orbital plane of the Earth (the ecliptic), eclipses can occur only when the Moon is close to the intersection of these two planes (the nodes). The Sun, Earth and nodes are aligned twice a year, and eclipses can occur during a period of about two months around these times. There can be from four to seven eclipses in a calendar year, which repeat according to various eclipse cycles, such as the Saros cycle.
edit Solar eclipse
Solar eclips 1999 4
Totality during the 1999 solar eclipse. Solar prominences can be seen along the limb (in red) as well as extensive coronal filaments.
An eclipse of the Sun by the Moon is termed a solar eclipse. Records of solar eclipses have been kept since ancient times. A Syrian clay tablet records a solar eclipse on March 5, 1223 BCE, while Paul Griffin argues that a stone in Ireland records an eclipse on November 30, 3340 BCE. Chinese historical records of solar eclipses date back over 4,000 years and have been used to measure changes in the Earth's rate of spin. Eclipse dates can also be used for chronological dating of historical records.
The type of solar eclipse event depends on the distance of the Moon from the Earth during the event. A total solar eclipse occurs when the Earth intersects the umbra portion of the Moon's shadow. When the umbra does not reach the surface of the Earth, the Sun is only partially occluded, resulting in an annular eclipse. Partial solar eclipses occur when the viewer is inside the penumbra.
The eclipse magnitude is the fraction of the Sun's diameter that is covered by the Moon. For a total eclipse, this value is always greater than or equal to one. In both annular and total eclipses, the eclipse magnitude is the ratio of the angular sizes of the Moon to the Sun.
Solar eclipses are relatively brief events that can only be viewed in totality along a relatively narrow track. Under the most favorable circumstances, a total solar eclipse can last for 7 minutes, 31 seconds, and can be viewed along a track that is up to 250 km wide. However, the region where a partial eclipse can be observed is much larger. The Moon's umbra will advance eastward at a rate of 1,700 km/h, until it no longer intersects the Earth.
During a solar eclipse, the Moon can sometimes perfectly cover the Sun because its apparent size is nearly the same as the Sun when viewed from the Earth. A solar eclipse is actually a misnomer; the phenomenon is more correctly described as an occultation of the Sun by the Moon or an eclipse of the Earth by the Moon.
edit Lunar eclipse
Eclipse lune
The progression of a lunar eclipse. Totality is shown with the last two images to lower right. These required a longer exposure time to make the details visible.
Lunar eclipses occur when the Moon passes through the Earth's shadow. Since this occurs only when the Moon is on the far side of the Earth from the Sun, lunar eclipses only occur when there is a full moon. Unlike a solar eclipse, an eclipse of the Moon can be observed from nearly an entire hemisphere. For this reason it is much more common to observe a lunar eclipse from a given location. A lunar eclipse also lasts longer, taking several hours to complete, with totality itself usually averaging anywhere from about 30 minutes to over an hour.
There are three types of lunar eclipses: penumbral, when the Moon crosses only the Earth's penumbra; partial, when the Moon crosses partially into the Earth's umbra; and total, when the Moon circles entirely within the Earth's umbra. Total lunar eclipses pass through all three phases. Even during a total lunar eclipse, however, the Moon is not completely dark. Sunlight refracted through the Earth's atmosphere intersects the umbra and provides a faint illumination. Much as in a sunset, the atmosphere tends to scatter light with shorter wavelengths, so the illumination of the Moon by refracted light has a red hue.
edit Other planets
Phobos transits Sun, as seen by Mars Rover Opportunity
Saturn eclipse
Saturn eclipses the Sun as seen from the Cassini–Huygens space probe
Eclipses are impossible on Mercury and Venus, which have no moons. However, both have been observed to transit across the face of the Sun. There are on average 13 transits of Mercury each century. Transits of Venus occur in pairs separated by an interval of eight years, but each pair of events happen less than once a century
On Mars, only partial solar eclipses are possible, because neither of its moons is large enough, at their respective orbital radii, to cover the Sun's disc as seen from the surface of the planet. Eclipses of the moons by Mars are not only possible, but commonplace, with hundreds occurring each Earth year. There are also rare occasions when Deimos is eclipsed by Phobos. Martian eclipses have been photographed from both the surface of Mars and from orbit.
The gas giant planets (Jupiter, Saturn, Uranus, and Neptune) have many moons and thus frequently display eclipses. The most striking involve Jupiter, which has four large moons and a low axial tilt, making eclipses more frequent as these bodies pass through the shadow of the larger planet. Transits occur with equal frequency. It is common to see the larger moons casting circular shadows upon Jupiter's cloudtops.
The eclipses of the Galilean moons by Jupiter became accurately predictable once their orbital elements were known. During the 1670s, it was discovered that these events were occurring about 17 minutes later than expected when Jupiter was on the far side of the Sun. Ole Rømer deduced that the delay was caused by the time needed for light to travel from Jupiter to the Earth. This was used to produce the first estimate of the speed of light.
On the other three gas giants, eclipses only occur at certain periods during the planet's orbit, due to their higher inclination between the orbits of the moon and the orbital plane of the planet. The moon Titan, for example, has an orbital plane tilted about 1.6° to Saturn's equatorial plane. But Saturn has an axial tilt of nearly 27°. The orbital plane of Titan only crosses the line of sight to the Sun at two points along Saturn's orbit. As the orbital period of Saturn is 29.7 years, an eclipse is only possible about every 15 years.
The timing of the Jovian satellite eclipses was also used to calculate an observer's longitude upon the Earth. By knowing the expected time when an eclipse would be observed at a standard longitude (such as Greenwich), the time difference could be computed by accurately observing the local time of the eclipse. The time difference gives the longitude of the observer because every hour of difference corresponded to 15° around the Earth's equator. This technique was used, for example, by Giovanni D. Cassini in 1679 to re-map France.
Pluto, with its proportionately large moon Charon, is also the site of many eclipses. A series of such mutual eclipses occurred between 1985 and 1990. These daily events led to the first accurate measurements of the physical parameters of both objects.
edit Eclipsing binaries
A binary star system consists of two stars that orbit around their common center of mass. The movements of both stars lie on a common orbital plane in space. When this plane is very closely aligned with the location of an observer, the stars can be seen to pass in front of each other. The result is a type of extrinsic variable star system called an eclipsing binary.
The maximum luminosity of an eclipsing binary system is equal to the sum of the luminosity contributions from the individual stars. When one star passes in front of the other, the luminosity of the system is seen to decrease. The luminosity returns to normal once the two stars are no longer in alignment.
The first eclipsing binary star system to be discovered was Algol, a star system in the constellation Perseus. Normally this star system has a visual magnitude of 2.1. However, every 2.867 days the magnitude decreases to 3.4 for more than 9 hours. This is caused by the passage of the dimmer member of the pair in front of the brighter star. The concept that an eclipsing body caused these luminosity variations was introduced by John Goodricke in 1783.
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__label__pos
| 0.998837 |
BBC Radio 3
Through the Night, 02/10/2012 QR code
What is this?
This code will link to the page for Through the Night, 02/10/2012 when read using a QR code reader.
You may save, print or share the image.
|
__label__pos
| 0.999682 |
Ladon basin in full colour
The fractured features of Ladon basin
2 August 2012
ESA’s Mars Express has observed the southern part of a partially buried approx. 440-km wide crater, informally named Ladon basin.
The images, near to where Ladon Valles enters this large impact region reveal a variety of features, most notably the double interconnected impact craters Sigli and Shambe, the basins of which are criss-crossed by extensive fracturing.
This region, imaged on 27 April by the high-resolution stereo camera on Mars Express is of great interest to scientists since it shows significant signs of ancient lakes and rivers.
Both Holden and Eberswalde Craters were on the final shortlist of four candidate landing sites for NASA’s Mars Science Laboratory, which is due now to land in Gale Crater on 6 August.
Large-scale overview maps show clear evidence that vast volumes of water once flowed from the southern highlands. This water carved Ladon Valles, eventually flowing into Ladon basin, an ancient large impact region.
Sigli and Shambe perspective view
Ladon basin in context
The interconnected craters Sigli and Shambe are thought to have formed later when an incoming projectile split into two pieces just before impact. The joined craters were then partly filled with sediments at some later epoch.
Ladon Basin perspective view
Deep fractures can be seen within the craters whilst in the central and right part of the image, smaller craters and more subtle curved fractures appear. These fractures on the basin floor extend beyond the image borders and form concentric patterns. The fractures are believed to have evolved by compaction of the huge sediment loads deposited within the impact basin
Topographical view
The outflow of Ladon Valles in to Ladon basin is located towards the east of Sigli and Shambe Craters, towards the bottom of this image. Here, and in several other parts of the image, lighter-toned layered deposits can be seen. Researchers have detected clay minerals within these deposits, suggesting a relatively long-lasting presence of liquid water in the region’s past.
3D anaglyph view
In addition, winding, valley-like dendritic structures running into the larger basin can be seen above Sigli and Shambe Craters, running in to the larger impact basin, again indicating flowing water at some distant epoch.
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| 0.999395 |
Research Article
A Peak-Clustering Method for MEG Group Analysis to Minimise Artefacts Due to Smoothness
• Jessica R. Gilbert mail, (JRG); (LRS)
Affiliation: School of Life and Health Sciences, Aston University, Birmingham, United Kingdom
• Laura R. Shapiro mail, (JRG); (LRS)
• Gareth R. Barnes
Affiliation: The Wellcome Trust Centre for Neuroimaging, University College London, London, United Kingdom
• Published: September 14, 2012
• DOI: 10.1371/journal.pone.0045084
Magnetoencephalography (MEG), a non-invasive technique for characterizing brain electrical activity, is gaining popularity as a tool for assessing group-level differences between experimental conditions. One method for assessing task-condition effects involves beamforming, where a weighted sum of field measurements is used to tune activity on a voxel-by-voxel basis. However, this method has been shown to produce inhomogeneous smoothness differences as a function of signal-to-noise across a volumetric image, which can then produce false positives at the group level. Here we describe a novel method for group-level analysis with MEG beamformer images that utilizes the peak locations within each participant’s volumetric image to assess group-level effects. We compared our peak-clustering algorithm with SnPM using simulated data. We found that our method was immune to artefactual group effects that can arise as a result of inhomogeneous smoothness differences across a volumetric image. We also used our peak-clustering algorithm on experimental data and found that regions were identified that corresponded with task-related regions identified in the literature. These findings suggest that our technique is a robust method for group-level analysis with MEG beamformer images.
The use of magnetoencephalography (MEG) as a research tool for brain-imaging in both normal and clinical populations is burgeoning. With advances in signal processing, beamforming has gained traction as a meaningful approach to source-localization in MEG. In beamforming, a weighted sum of field measurements is used as a spatial filter to tune an estimate of neural activity (i.e.,power) in a pre-specified time and frequency band window on a voxel-by-voxel basis. This produces a whole-brain volumetric image of signal power change which can be used for group-level analyses.
One problem in conventional MEG group analysis is that individual beamformer images are not homogeneously smooth; the images are information rich around strong sources, yet very smooth elsewhere [1], [2]. These smoothness differences have been found to range over two orders of magnitude within an image [3]. This inverse relationship between source strength and smoothness can lead to unpredictable effects at a group-imaging level. For example, at moderate signal strengths, artefactual group effects can occur. These arise because the true peaks within each source reconstruction have broad maxima (and sidelobes) whose shapes differ across participants. Through the overlap of these smooth maxima (or their sidelobes), secondary, apparently disconnected peaks can arise at a group level. A related problem of non-isotropic or inhomogeneous smoothness has been studied in the context of fMRI to correct for cluster size statistics in cases where, for example, the underlying isotropic image has been inhomogeneously resampled onto a cortical surface [4], [5]; indeed, similar solutions have been proposed for MEG [2], [6]. These solutions based on random field theory assume that voxel-to-voxel covariance can be summarized by local smoothness measures. However, the relationship between two image voxels in MEG is not just a function of their proximity (as in fMRI/PET), but also of the orientation of the dipole at that location, and therefore covariant voxels are not necessarily part of the same contiguous cluster. This is an inevitable problem in MEG source reconstruction where a large number of voxel estimates are made from a small number of channels.
In this paper, we try to step around this reconstruction problem by compressing the volumetric image to a point list of local maxima, which in turn simplifies the statistics. This is advantageous as one often ultimately wishes to interrogate individual participant beamformer estimates of electrical activity, which have been shown to be only truly reliable at the image peaks [3] (note that a similar approach has been used previously for a dipole fit analysis [7]; see discussion section for a full comparison). In brief, we assume that, under the null hypothesis, rank-ordered (e.g., by power) image peaks across participants will be no more closely grouped than any random selection of peaks.
The paper is divided into three sections. In the first section, we describe the peak-clustering algorithm and define a method for correcting for multiple comparisons when testing over a range of peaks for group-level effects. In the second section, we compare our peak-clustering algorithm against SnPM using simulated data. In the third section, we utilize our algorithm to test for group-level effects in experimental data.
Methods and Results
Peak Clustering Algorithm
To compare the distribution of the M top-ranked image peaks (per person) over a group of participants against any random selection of peaks, we used the following algorithm. (The matlab code is available from the corresponding author on request.):
1. 1. Rank order the image peaks for each participant and store their corresponding locations. Since the test is based on rank order, the user must specify an interest in positive or negative peaks. The data presented in this manuscript used normalized t-tests between conditions to create images.
2. 2. Take the coordinates of the top M peaks from each of N participants. Construct the smallest possible ellipsoid that contains a single peak from each participant. The issue here is that the top peak in participant 1 may be at the same location as the 3rd peak in participant 3, etc. By selecting from M peaks, one trades off the precise peak order against spatial resolution (see later).
3. 3. Establish if this ellipsoid is smaller (in terms of the major radius) than one would expect by chance. The computation of this radius under the null hypothesis is done by randomly assigning ranks to peak locations and repeating step 2 a large number of times (e.g., 500 in this paper). This produces a distribution of radii which one would expect due to chance (if peak rank were not important).
To give a simple example, how likely is it that the image maxima for ten participants (N = 10, one peak so M = 1) are within 1 cm of one another? To answer this, one can compute how close the image maxima will be by chance by simply taking a random image peak from each participant and repeating this process to get a null distribution of ellipsoid radii. Now one computes the same size metric using ranked peaks from each participant, then reads off the number of randomly drawn ellipsoids that are smaller than this (e.g., p<0.01).
Ellipsoid computation.
For a given number of participants (N) and peaks (M), a k-means clustering procedure was iteratively used to derive M separate ellipsoids (ideally each of N points) from N*M points. Clusters were trimmed such that each set contained at maximum one point per participant (selecting the point closest to the centroid). At the end of the iterative procedure (typically 30 iterations), one is left with a set of the smallest (based on standard deviation of the point list) clusters for varying numbers of participants (from a user specified minimum up to a maximum of N). For these point lists, ellipsoid axes were computed from the eigenvectors and the standard deviation in each direction (and hence the 95 percentiles) computed from the corresponding eigenvalues.
Correcting for Arbitrary Number of Peaks
The peak clustering algorithm requires some a-priori selection of the parameter M, or the number of top-ranked peaks to consider in the analysis. Typically, therefore, it is necessary to test a range of values of M, and hence there is a corresponding multiple comparisons penalty. In this section, we examine the dependence of our results on this parameter and propose an approximate heuristic for dealing with it in the future.
Figure 1 shows the dependence of the 95th percentile of the confidence radius (R) (maximum radius (in mm) of the ellipsoid defining the confidence volume) on M for positive peaks in our experimental data analysis (see below for more information on the experimental study). Statistics are automatically produced for all subgroups from N = 5–10 participants but only N = 5, 7, and 10 are shown here for clarity. Intuitively, the smaller the number of subjects (N), the smaller an ellipsoid will be by chance (e.g., in the case of just 2 subjects, one could imagine that some peaks will be almost adjacent by chance).
Figure 1. Dependence of the confidence radius on parameter M.
The relationship between the number of peaks used (M) and the 95% significant (maximum) radius of the confidence ellipsoid (in mm) for subgroups of N = 5 (blue), 7 (green) and 10 (red). Intuitively, the larger the N, the larger the size of the cluster one would expect to occur by chance. In contrast, the larger the number of peaks per subject (M) considered, the easier it will be to reach a given cluster size, hence the 95% threshold decreases as more peaks are included in the analysis.
The parameter M determines the trade-off between the importance assigned to rank order and the importance assigned to tight clustering of peaks across participants. If there is high importance assigned to rank order (smaller M), then relatively larger clusters of peaks across participants will be acceptable (although these may have little anatomical consistency). However, if the effect in question does not reach the top M peaks in most participants, it will be completely missed by the analysis. By contrast, if M is set to be too large, then the inclusion of many superfluous (i.e., low rank) peaks will mean that a very tight spatial distribution is required to distinguish a functionally meaningful cluster from one occurring by chance. This is an analogous problem to the choice of image smoothing parameters in fMRI, and analogously the choice depends on the question asked. As a starting point, we propose a simple heuristic to choose a value of M which balances dependence on peak rank against cluster size. If we take the knee of the curve in Figure 1 to represent some optimal balance between dependence on peak magnitude (small M) and anatomical consistency across participants (small R), we can compute a parameter J which quantifies the distance of the curves from the knee,
where M and R are the number of peaks and the confidence radius respectively. Now plotting J against M gives a curve with a clear minimum (see Figure 2). For each sub-group (N), crosses on the curve indicate that at least one significant (p<0.05) cluster was found for this choice of M when analyzing positive peaks. Importantly, and giving some validiation of our choice of heuristic, these significant excursions predominate around the minimum of the function.
Figure 2. Peak amplitude and anatomical consistency trade-off.
A plot of the heuristic to optimize the balance between peak magnitude and anatomical consistency across subjects. J increases for large numbers of peaks (where there is a very tight distance threshold (R) on how close the peaks must be) and also increases when M is small due to the corresponding decrease in anatomical specificity (due to increase in threshold R shown in Figure 1). Alternatively, one can choose to test a range of M (2–30 in this case), produce significant clusters (for each M; shown by crosses), and then correct for multiple comparisons. After multiple comparison correction (for M), two significant clusters were found which are denoted by the circles and squares around these points. These are the same two clusters identified in our experimental data.
The next problem is how to set an appropriate significance level. There is a single univariate null hypothesis–that the peaks are clustered by chance. However, as we change (increase) M, we are re-testing the same hypothesis with different subsets of data. Hence, a multiple comparisons penalty is necessary. One simple solution would be to only examine the function minima at each value of N. One problem here is that the minima are relatively flat and the smoothness depends on the number of random permutation steps performed, which is processing intensive. Also, one can see from Figure 2 that each subgroup curve N has a different optimal M value (the larger the number of participants in the group, the larger the optimal number of peaks).
Another possibility is to consider the range of M which defines this minimum. This approach does not rely on the identification of minima (so it is more robust) and can be computed for all N at once. However, there is a multiple comparisons penalty. It is important to note, however, that a completely new (i.e., independent) set of data is only introduced each time the number of peaks is doubled.
Making a Bonferroni correction, the significance level should be decreased by a factor each time the number of peaks is doubled. This means that the test wise error rate to give a family wise error rate of 0.05 is based on the following Bonferroni correction:
where log2 is log to the base 2, pcorr is the corrected significance level and Mstart and Mend define the range of M we pre-specify an interest in. The circles and squares around the crosses in Figure 2 show the two significant ellipsoids found after multiple comparisons correction for the range of peaks tested (for Mstart = 2 and Mend = 30).
Measuring Algorithm Performance: Simulated Data
In order to test algorithm performance against some ground truth we simulated a single dipolar source across a group of participants. The same single sphere head model and sensor locations were used for each simulated participant. System white noise was simulated at 10 fT/sqrt (Hz) over a bandwidth of 80 Hz. Data for 10 participants were simulated, differing only in the simulated source location and white noise realization. In each simulated participant, a random seed location was generated, drawn from a Gaussian distribution of standard deviation 5 mm, centered on MNI location x = 52, y = −29, z = 13. The nearest canonical mesh location [8] to this seedpoint and the corresponding surface normal were used to set the location and orientation of the single simulated dipole in each participant. Our simulated sources were normal to the cortical mesh, but as location was jittered, both source location and orientation changed over participants. The dipolar source was driven with a 40 Hz sinusoid over a period of 200 ms (sample rate = 200 Hz). The source was active for 30 of 60 epochs and a linearly constrained minimum variance (LCMV) beamformer was used to produce a volumetric beamformer image of the change in power in the 0–300 ms, 0–80 Hz band in terms of a normalized difference (or pseudo-t) image [9] on a 10 mm grid. The beamformer has been described extensively [2], [3], [9], [10], and an abbreviated version is presented here.
The beamformer is simply a spatially filtered expression of the MEG sensor data.
where W is a vector of weighting coefficients and m(t) is the measurement vector at time t. To obtain the weighting coefficients, power is minimized over the covariance window subject to the constraint of unit gain at a specified coordinate θ:
where H is the forward solution for an equivalent current dipole (ECD) at coordinates and orientations specified by the vector θ. The solution to the equation is:
where C is the covariance matrix of the measurements calculated over the specified covariance window (Tcov). The 2 (i.e., single-sphere) or 3 (i.e., multiple spheres) orthogonally oriented components of W at each location can be estimated independently to produce a vector beamformer. In this case, we used a scalar beamformer in which optimal source orientation at each voxel was estimated through the method of Sekihara et al. [11]. A normalized source power estimate can be obtained over any test period (within the covariance window) through the estimation of the sensor level covariance matrix Ctest over this period, and an estimate of the sensor noise εtest (in this case, we used identity) matrix over this period:
We should note that in the experimental data analysis stage, we used the proprietary software (SAM) to analyze the data [9]. This computes separate covariances (and hence weights) for both active and passive periods. In the simulation stage, however, we computed a single covariance matrix (based on both active and passive periods), but as there was only white noise in the passive period, this should have marginal effect on the power difference calculation (see discussion).
Different participant groups were constructed by drawing 8 of these 10 images randomly twenty times. For each participant group, we used SnPM (multiple participant, one sample t-test, variance smoothing 25 mm) to identify significant (family wise error = 0.05) positive effects across the normalized power difference images. Using the peak clustering algorithm, we used the same data to look for clusters within the top 5 image peaks that were smaller than one would expect by chance (i.e., M = 5 peaks, N = 8 participants). For each simulated group, we compiled a list of the significant local maxima (p<0.05 corrected) in the SnPM images and a list of the centers of the peak-clusters deemed significant. We classed a hit as a peak/ellipse center closer than 20 mm to the initial MNI seed location and a miss to be any significant peak or ellipsoid center outside this range. The peaks were defined by local image maxima identified using the SPM function spm_max based on 18 neighbors. This means that two local maxima can be as close as a single (non-maximal) voxel apart.
Measuring Algorithm Performance: Experimental Data
We assessed the performance of our peak-clustering algorithm on experimental data. In our experiment, ten right-handed volunteers (Mean Age = 29.4 years, range = 20–36 years; 2 males) gave written informed consent following Aston University ethical guidelines and participated in the MEG study. The protocol was approved by the Aston University Institutional Review Board and complied with all guidelines expressed in the Declaration of Helsinki. Briefly, participants (N = 10) performed a superordinate-level categorization task on pictures of objects drawn from 3 living and 3 nonliving categories (see Figure 3). A total of 78 pictures were selected, half of which depicted a living object and half a nonliving object. Each picture was shown twice, half with a congruent label and half with an incongruent label. Therefore, a total of 156 trials were shown during the scan. The order of trial presentation was randomized across participants. We recorded neuromagnetic data at a 600 Hz sampling rate with a bandwidth of 0–150 Hz using a CTF 275 MEG system (VSM MedTech Ltd., Canada) composed of a whole-head array of 275 radial 1st order gradiometer channels housed in a magnetically shielded room (Vacuumschmelze, Germany). Synthetic 3rd gradient balancing was used to remove background noise on-line. Fiducial coils were placed on the nasion, left preauricular, and right preauricular sites of each participant. These coils were energized before each run to localize the participant’s head with respect to the MEG sensors. Total head displacement was measured after each run and could not exceed 5 mm for inclusion in the source analyses. Prior to scanning, participants’ head shapes and the location of fiducial coils were digitized using a Polhemus Isotrak 3D digitizer (Kaiser Aerospace Inc.). These were then coregistered to high-resolution T1-weighted anatomical images for each participant acquired with a 3-Tesla whole-body scanner (3T Trio, Siemens Medical Systems) using in-house coregistration software.
Figure 3. Example experimental data trial.
During study 1, participants were shown a 1000 ms red fixation cross, followed by a 300 ms category probe. After a variable (1000, 1050, or 1100 ms) delay interval, participants were shown a target object for 800 ms.
Data for each participant were edited and filtered to remove environmental and physiological artefacts. A LCMV beamformer was then used to produce 3-dimensional images of cortical power changes [9]. We utilized a wide frequency band (1–80 Hz) to compute source power from 120–220 ms after stimulus onset (i.e., a 100 ms window surrounding the M170), directly contrasting living (‘active’) to nonliving (‘control’) target objects. Spectral power changes between the ‘active’ and ‘control’ periods were calculated as a pseudo t-statistic [9]. Each participant’s data were then normalized and converted to Talairach space using statistical parametric mapping (SPM99, Wellcome Department of Imaging Neuroscience, London, UK, for group-level comparisons.
We used SnPM (multiple participant, one sample t-test, variance smoothing 6, 12, and 24 mm) to identify significant (family wise error = 0.05) positive effects across the normalized power difference images. We also used our peak-clustering algorithm to test over a range of M values from M = 2 through 40 (we utilized only positive peaks in the analysis), which means that in order to maintain a family wise error rate of 0.05, our test wise error rate was adjusted to p = 0.0094. After multiple comparisons correction, we were left with a number of significant clusters of peaks (see Table 1). The remaining volumes decreased in size spatially as M increased so if the same region was identified as showing a significant difference across a range of M values, we selected the region for reporting purposes that yielded the largest N. In some cases, several M values yielded the same N. We then chose the volume for reporting purposes that had the smallest spatial extent (in terms of the major radius).
Table 1. Experimental Results.
Simulation Results
Figure 4 (top) shows the number of hits and misses summed over the 20 participant groups for the two methods. At moderate SNR, the number of misses for SnPM is much higher than for the peak-clustering approach. This is due to extra peaks appearing in the SnPM images due to artefacts of smoothness. Figure 4 (bottom) shows binarized (thresholded at p<0.05 corrected) SnPM significance images summed over the 20 groups (and then normalized to the maximum count). That is, the maps show the spatial distribution of significant regions and the grey scale shows their relative frequency (over groups). For moderate source strengths (i.e., 10–20 nAm), one can see the appearance of extra significant clusters, which give rise to the inflated miss rate. Note that these misses are not false positives in the statistical sense, but simply image features that persist over participants due to the source reconstruction method. The peak-clustering approach is immune to these extra features as there are no consistent local maxima in these vicinities across participants. In this particular example, the peak-clustering approach is also more sensitive (i.e., a maximum of 20 hits reached before SnPM). Note, however, that in this case we have prior knowledge of how many of the top peaks to consider.
Figure 4. Data simulation findings.
Top panel shows the total number of significant local maxima over 20 simulated subject groups (with a single simulated source) identified using SnPM (dotted) and the peak clustering method (solid) as source magnitude is increased. Local maxima within 2 cm of the simulated source are defined as hits and those greater than 2 cm misses. Note that both methods consistently identify the correct source location at high SNR (20 hits, 0 misses) but that SnPM tends to produce a large number of artefactual significant regions at moderate SNR. This error rate is due to the smoothness of the beamformer images that gives rise to statistically significant overlapping side-lobes. These effects are shown in the lower panel, where maps of the percentage of significant voxels (from the 20 groups) are shown in the glass-brain.
Experimental Results
The SnPM analysis did not identify any regions showing significant positive power differences when using 6 or 12 mm variance smoothing. However, a single region centered in right anterior middle to superior temporal gyrus (Talairach coordinates of center = 48, 3, −18) was identified when we set variance smoothing to 24 mm (see Figure 5). The peak-clustering analysis of positive peaks identified two separate regions showing greater power for living objects (see Figure 5). The region with the largest N was centered in left inferior occipital gyrus, and using the top 8 positive peaks in each image, 7 of our 10 participants were found to have a peak falling within the region (major radius = 22.3 mm, mean value = 1.84). In addition to this region, when using the top 15 positive peaks in each image (i.e., a less stringent magnitude criterion), 6 of our 10 participants were found to have a peak falling within a region in right anterior superior temporal gyrus (major radius = 12.4 mm, mean value = 1.7). This region overlapped with the region identified in the SnPM analysis.
Figure 5. Experimental data findings.
A) The region in right anterior middle to superior temporal gyrus identified by the SnPM analysis as showing significantly greater power for living compared with nonliving objects. B) The two regions identified by the peak-clustering algorithm as showing significantly greater power for living compared with nonliving objects. Red = Inferior Occipital Gyrus; Blue = Superior Temporal Gyrus. The sagittal images show the approximate slice locations (z coordinates are given below each slice) shown on the corresponding axial image (at right, blue lines, arranged inferior to superior) on a template brain.
We have presented a peak-clustering algorithm for group-level analysis with MEG beamformer images. Our algorithm determines whether a range of image peaks (M) is closer than expected by chance. We compared the peak-clustering algorithm performance to a more traditional group imaging method (SnPM) and found the algorithm to be robust to artefacts of smoothness that can give rise to erroneous MEG beamformer group effects. There is an important distinction here between false positives due to type 1 error and the effects we are trying to correct for. Both SnPM and the peak-clustering algorithm have, by definition, the correct type 1 error rate (as it is set in both cases by permutation). Neither is there a problem with SnPM. The issue we are trying to correct for here is one of source reconstruction, where a small number of data channels are projected into a large number of voxels, resulting in images which are very smooth in certain regions. It is therefore a way of pruning away redundant information from beamformer images to reduce the likelihood that these smooth and information sparse regions of source space contribute to the group effect.
Our approach is similar to a dipole fit analysis approach used previously [7]. In the Litvak paper, the focus was on identifying the differences between experimental conditions through the permutation of condition labels to create sensor-time and dipole fit clusters. By comparing this null (e.g., in terms of distances between dipole clusters) to the true distribution, the authors were able to put a significance level on how likely the conditions were to be the same. The main differences between the Litvak technique and our own are that we shuffle peak rank rather than data labels, and we do not have a theoretical source model (e.g., 1 or 2 dipoles) but are looking for consistency over images which may contain large numbers of sources. That said, the same approach of shuffling data labels (rather than peak rank) to generate the null could also be used here to make inferences on whether the ellipsoids due to separate stimulus conditions were any larger than that due to their mixture.
As mentioned previously, in the algorithm we are effectively trying to compensate for the few (i.e., channel) to many (i.e., voxel) mapping in M/EEG volumetric source reconstruction. This problem is exacerbated in beamformer analyses because of the dependence of spatial resolution not only on system sensitivity, but also on source power [1], [2]. An additional problem not addressed here is that in the SAM implementation used for the experimental data (i.e., CTF version), different covariance matrices are used to construct different beamformer weights for different task labels (in contrast to a single set of weights for all tasks, cf. [2]). That is, the statistical image is a test between two non-stationary images. For the purposes of this study, the distinction is not important because either way the images are inhomogeneous. We are not proposing a new or improved inversion algorithm, simply a method by which some of the smoothness inhomogeneities (due to any volumetric reconstruction) can be discarded. Also, for our beamformer analysis, we used no regularization. This gives maximum spatial resolution at the expense of noisy images and time-series estimates. It would also give rise to the maximum number of peaks per image. A higher regularization constant would reduce the number of peaks, removing some that were potentially just due to sensor noise, but potentially risk discarding signal peaks. At some ideal level, one would expect the highest ratio of signal to noise peaks [12]. We do know that there can be a maximum N channels minus 1 nulls in the beamformer image [10]; so, for a simple (i.e., unregularized) power image one would expect approximately the same number of local maxima.
The algorithm requires a parameter that defines the number of top-ranked peaks to consider (M) for each participant. This parameter has important implications for cluster size. Since the algorithm first computes chance volume sizes using a random selection of peaks, using a small number of peaks can produce a large cluster size for the null distribution. Rather than arbitrarily determining the number of peaks for the algorithm to consider, we developed a heuristic that balances peak rank against cluster size that requires the user to test over a range of M values and use a Bonferroni correction for multiple comparisons. For example, to maintain a family wise error rate of 0.05 when testing over 38 P-values (i.e., 2–40), the test wise error rate becomes 0.0094. It is important to note that the choice of M can be made based on simulations or on the data themselves, as long as an appropriate multiple comparisons correction is made. For this reason we had expected the algorithm to be more conservative than volumetric approaches (like SnPM), but by only dealing with the image in its compressed point-list form, rather than all voxels, we have also considerably reduced the multiple comparison correction necessary. This may explain why, counter to our expectation, the algorithm picked out significant features in the experimental dataset that were not apparent in (the volume corrected) SnPM tests.
In our experimental study, participants were required to perform a superordinate-level categorization task on pictures of living and nonliving objects. The SnPM analysis yielded mixed results based on the variance smoothing used. When using both 6 and 12 mm, no regions survived statistical significance. However, when using 24 mm, a single region in right anterior middle to superior temporal gyrus showed significantly greater power for living than nonliving objects. Using the peak-clustering algorithm, we also found a significant cluster of activity in right anterior superior temporal gyrus, overlapping with the region identified by the SnPM analysis. In addition, we identified a region in left inferior temporal gyrus showing greater power for living than nonliving objects, which we did not find in our SnPM analysis. In order to determine whether the SnPM analysis yielded a peak in left inferior temporal gyrus that simply did not survive whole-brain correction, we looked at the t map produced in our SnPM analysis. We found a cluster of activity centered in left inferior temporal gyrus (peak value = 2.95), which suggests that left inferior temporal gyrus would be significant if we performed a region-of-interest analysis (rather than a whole-brain analysis) using roughly 7 independent voxels (or ROIs). This would be in accord with our explanation that the peak clustering analysis has a less stringent multiple comparisons penalty, as it considers only a limited number of image peaks per subject (indeed for these analyses there were 8 peaks per participant). Both of these regions we would expect to be active based on previous neuroimaging studies which have suggested that the inferior temporal/occipital gyri are important for form recognition, and that reliance on visual form is more important for living than nonliving objects [13], [14]. In addition, studies have also suggested that the anterior superior temporal gyri are important for object recognition, including making fine-grained distinctions amongst objects [15]. Several studies have also suggested that identifying living objects requires greater fine-grained discrimination than nonliving objects, perhaps due to greater structural (and semantic) similarity among living than nonliving things [16], [17].
As with many non-parametric techniques, the peak clustering method sacrifices some sensitivity for an increase in robustness, and requires that some feature of interest (here, each peak) is identifiable in the majority of individuals. This would not be the case in standard random or fixed effects models in which sub-threshold effects in the individual can be picked up in the group. Allowing the algorithm to identify smaller subgroups is a matter for debate. In some cases, the objective identification of subgroups might be a useful feature of the algorithm. Forcing the algorithm to be selective to only those regions in every participant that have a local maximum makes it extremely conservative. Once could also argue that a group effect is meaningless if one does not include the whole group. Yet, in classical volumetric approaches, random effects analysis allows some heterogeneity in the effects over the population. As long as the values of N (e.g., N = 9 for a group of 10) are reported then the reader can make his/her own inference on the strength of the finding (e.g., an effect in 90% of the participants). Also, the technique will not be sensitive to truly spatially extended regions of electrical activity that are not artefacts of smoothness, as only the peaks within each image are considered in the analysis.
In sum, we have found that our peak-clustering technique offers a number of advantages over current group-level analysis approaches with MEG. The method is immune to inhomogeneous smoothness introduced by imperfect volumetric M/EEG source reconstruction and exacerbated in beamformer implementations, and indeed it makes no assumptions about the underlying image properties. In addition, the null distributions of source locations are constructed from the data itself and the randomization testing takes into account the multiple comparisons problem (for a given M). As the test is based on rank, it should be relatively robust to physiological artefacts and as a default we would leave the artefact identification until the post-hoc analyses. For example, eyeball artefacts should result in significant clusters in the eyes. Subgroup statistics are also available, so, for example, bounds for any 5 of N participants having significantly clustered peaks can automatically be tested. Finally, by providing confidence intervals on peak location, the technique would be well suited to situations in which one would like to make some spatial inference concerning peak location. For example, whether peaks from a particular subject group derive from a specific cortical location.
Author Contributions
Conceived and designed the experiments: JRG LRS GRB. Performed the experiments: JRG GRB. Analyzed the data: JRG GRB. Contributed reagents/materials/analysis tools: LRS GRB. Wrote the paper: JRG LRS GRB.
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Conceptual illustration showing many different types of power generation, including nuclear, fossil fuel, wind power, photovoltaic cells, and hydro electric water power
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Take the 2-minute tour ×
Currently I'm using UISwipeGestureRecognizer to view the left or right each image, but the image move very fast.
Which way to hold and move the image slowly like iPhone Photos gallery?
On iPhone Photos we can move the image to left or right very slow and can see a part of next image. How can we do that?
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Use a UIScrollView. There's a tutorial here - http://www.raywenderlich.com/10518/how-to-use-uiscrollview-to-scroll-and-zoom-content .
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Very great. Thanks mattjgalloway so much. – jimmy Oct 25 '12 at 8:03
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antiHT which stands for anti- Human Trafficking, is an effort to stop and prevent such activities going on there in your vicinity or the outside world of yours. As people and humans we have this right and hence duty to prevent such shameful acts being undertaken for money and sexual motives.
We have setup a group for information providing, and discussions at Google Groups, voluteers may join the group and help the cause of humanity.
Group address is:
We shall be very thankful of your role in stopping/preventing these nefarious activities.
antiHT is an effort to prevent such nefarious acts going on out there.
Give me a Gun, a ship and few tactical skills and just see how i blast these monsters.
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NASA is restarting a mission with greater capability for usinghigh-energy X-rays to detect black holes.
The Nuclear Spectroscopic Telescope Array, or NuSTAR, is an X-ray telescope designed to answer fundamental questions about the universe, such as how black holes are distributed through the cosmos.
Funding pressures forced NASA cancel the NuSTAR mission in 2006, but the restarted mission is expected to be up and running in 2011.
"NuSTAR has more than500 times the sensitivity of previous instruments that detect black holes. It's a great opportunity for us to explore an important astronomical frontier," Alan Stern, associate administrator for the Science MissionDirectorate at NASA Headquarters in Washington, said in a release.
Black holes can't be seen directly because they're so dense not even light can escape their pull. Instead, astronomers use X-ray telescopes to detect the X-rays given off when objects fall into black holes.
By focusing X-rays at higher energy, NuSTAR will also answer questions such as: How were the elements that compose our bodies and the Earth forged in the explosions of massive stars? What powers the most extreme active galaxies?
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