text:
Der Chevrolet Bison – auch verkauft als GMC General – war ein schwerer Lkw, den General Motors in den Modelljahren 1977 bis 1988 herstellte. Beide Modelle waren Hauben-Lkws.

Es gab Dieselmotoren von Caterpillar, Cummins und Detroit Diesel zur Auswahl.

Die GMC-Version war häufiger anzutreffen als die von Chevrolet.

Trivia
Ein GMC General war 1980 im Film Das ausgekochte Schlitzohr ist wieder auf Achse und in der Serie Knight Rider, die von 1982 bis 1986 produziert wurde, zu sehen.

Weblinks

Bison
Lkw-Modell

redpajama_set_name: RedPajamaWikipedia


Moral norms tell you to keep your promises, respect others, be sincere, and help those in need. But such norms can seem mysterious. What justifies their authority over us? Many philosophers reflecting about this foundational question of ethics have recently turned to metaethical constitutivism for an answer. According to an influential formulation, constitutivism is the view that we can justify the authority of moral norms by showing them to be internal to or constitutive of the nature of action and agency. However, with the rise of interest in constitutivism, skepticism about the project's viability has grown. Moreover, it's not clear exactly how constitutivism should be understood. One can now find Aristotelian, Humean, Kantian, and post-Kantian varieties of constitutivism. This workshop seeks to investigate the nature, varieties, and overall viability of metaethical constitutivism. To do so, it brings together some of the leading voices from these diverse traditions.
This one day workshop is open to the public and free of charge. However, registration is necessary. Papers will be pre-circulated among participants and should be read in advance. Only a brief summary will be provided during the workshop. To register, please visit the event's website.
This workshop has been made possible by the generous support provided by UAlbany Philosophy Department, UAlbany's Conference Support Award, and the UAlbany Auxiliary Services.


text:
Q: ¿Cómo crear un arreglo asociativo en C#? Estoy leyendo un archivo excel que contiene fecha y hora, por ejemplo:
Id | fecha
1    2018-06-01 08:00
1    2018-06-01 12:00
1    2018-06-02 08:10
1    2018-06-02 12:40

Lo que quiero es obtener un arreglo del tipo:
[
  "2018-06-01" => [08:00, 12:00],
  "2018-06-02" => [08:10, 12:40]
]

Lo que tengo hasta el momento es:
Dictionary<string, ArrayList> test = new Dictionary<string, ArrayList>();
ArrayList listahora = new ArrayList();

for (int iRow = 2; iRow <= xlWorkSheet.Rows.Count; iRow++){  // inicia desde la segunda fila.
  DateTime f = xlWorkSheet.Cells[iRow, 4].value; //Aquí obtengo el valor del archivo excel
  string fecha = f.ToString().Split(' ')[0];
  string hora = f.ToString().Split(' ')[1];

  if (!test.ContainsKey(fecha))
  {
    listahora.Add(hora);
    test.Add(fecha, listahora);
  }
  else
  {
    listahora.Add(hora);
    test[fecha] = listahora;
  }
}

Sin embargo esto me crea un arreglo del tipo:
[
  "2018-06-01" => [08:00, 12:00, 08:10, 12:40],
  "2018-06-02" => [08:00, 12:00, 08:10, 12:40]
]

¿Cómo podría obtener el arreglo que necesito?

A: Lo que tienes que hacer es vaciar la lista en cada iteracion.  Eso lo puedes lograr simplemente moviendo la declaracion dentro del bucle.  Algo asi:
Dictionary<string, ArrayList> test = new Dictionary<string, ArrayList>();

for (int iRow = 2; iRow <= xlWorkSheet.Rows.Count; iRow++){  // inicia desde la segunda fila.
  ArrayList listahora = new ArrayList();
  DateTime f = xlWorkSheet.Cells[iRow, 4].value; //Aquí obtengo el valor del archivo excel
  string fecha = f.ToString().Split(' ')[0];
  string hora = f.ToString().Split(' ')[1];

  if (!test.ContainsKey(fecha))
  {
    listahora.Add(hora);
    test.Add(fecha, listahora);
  }
  else
  {
    test[fecha].Add(hora);
  }
}

redpajama_set_name: RedPajamaStackExchange


text:
Folk Culture
Religion Place
Park Garden
Categories: AcademicEnvironmentPhysics
Light is electromagnetic radiation within a certain portion of the electromagnetic spectrum. The word usually refers to visible light, which is the visible spectrum that is visible to the human eye and is responsible for the sense of sight. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), or 4.00 × 10−7 to 7.00 × 10−7 m, between the infrared (with longer wavelengths) and the ultraviolet (with shorter wavelengths). This wavelength means a frequency range of roughly 430–750 terahertz (THz).
The main source of light on Earth is the Sun. Sunlight provides the energy that green plants use to create sugars mostly in the form of starches, which release energy into the living things that digest them. This process of photosynthesis provides virtually all the energy used by living things. Historically, another important source of light for humans has been fire, from ancient campfires to modern kerosene lamps. With the development of electric lights and power systems, electric lighting has effectively replaced firelight. Some species of animals generate their own light, a process called bioluminescence. For example, fireflies use light to locate mates, and vampire squids use it to hide themselves from prey.
The primary properties of visible light are intensity, propagation direction, frequency or wavelength spectrum, and polarization, while its speed in a vacuum, 299,792,458 metres per second, is one of the fundamental constants of nature. Visible light, as with all types of electromagnetic radiation (EMR), is experimentally found to always move at this speed in a vacuum.
In physics, the term light sometimes refers to electromagnetic radiation of any wavelength, whether visible or not. In this sense, gamma rays, X-rays, microwaves and radio waves are also light. Like all types of EM radiation, visible light propagates as waves. However, the energy imparted by the waves is absorbed at single locations the way particles are absorbed. The absorbed energy of the EM waves is called a photon, and represents the quanta of light. When a wave of light is transformed and absorbed as a photon, the energy of the wave instantly collapses to a single location, and this location is where the photon "arrives." This is what is called the wave function collapse. This dual wave-like and particle-like nature of light is known as the wave–particle duality. The study of light, known as optics, is an important research area in modern physics.
Electromagnetic spectrum and visible light
Generally, EM radiation, or EMR (the designation "radiation" excludes static electric and magnetic and near fields), is classified by wavelength into radio, microwave, infrared, the visible region that we perceive as light, ultraviolet, X-rays and gamma rays.
The behavior of EMR depends on its wavelength. Higher frequencies have shorter wavelengths, and lower frequencies have longer wavelengths. When EMR interacts with single atoms and molecules, its behavior depends on the amount of energy per quantum it carries.
EMR in the visible light region consists of quanta (called photons) that are at the lower end of the energies that are capable of causing electronic excitation within molecules, which leads to changes in the bonding or chemistry of the molecule. At the lower end of the visible light spectrum, EMR becomes invisible to humans (infrared) because its photons no longer have enough individual energy to cause a lasting molecular change (a change in conformation) in the visual molecule retinal in the human retina, which change triggers the sensation of vision.
There exist animals that are sensitive to various types of infrared, but not by means of quantum-absorption. Infrared sensing in snakes depends on a kind of natural thermal imaging, in which tiny packets of cellular water are raised in temperature by the infrared radiation. EMR in this range causes molecular vibration and heating effects, which is how these animals detect it.
Above the range of visible light, ultraviolet light becomes invisible to humans, mostly because it is absorbed by the cornea below 360 nanometers and the internal lens below 400. Furthermore, the rods and cones located in the retina of the human eye cannot detect the very short (below 360 nm) ultraviolet wavelengths and are in fact damaged by ultraviolet. Many animals with eyes that do not require lenses (such as insects and shrimp) are able to detect ultraviolet, by quantum photon-absorption mechanisms, in much the same chemical way that humans detect visible light.
Various sources define visible light as narrowly as 420 to 680 to as broadly as 380 to 800 nm. Under ideal laboratory conditions, people can see infrared up to at least 1050 nm; children and young adults may perceive ultraviolet wavelengths down to about 310 to 313 nm.
Plant growth is also affected by the color spectrum of light, a process known as photomorphogenesis.
The speed of light in a vacuum is defined to be exactly 299,792,458 m/s (approx. 186,282 miles per second). The fixed value of the speed of light in SI units results from the fact that the metre is now defined in terms of the speed of light. All forms of electromagnetic radiation move at exactly this same speed in vacuum.
Different physicists have attempted to measure the speed of light throughout history. Galileo attempted to measure the speed of light in the seventeenth century. An early experiment to measure the speed of light was conducted by Ole Rømer, a Danish physicist, in 1676. Using a telescope, Rømer observed the motions of Jupiter and one of its moons, Io. Noting discrepancies in the apparent period of Io's orbit, he calculated that light takes about 22 minutes to traverse the diameter of Earth's orbit. However, its size was not known at that time. If Rømer had known the diameter of the Earth's orbit, he would have calculated a speed of 227,000,000 m/s.
Another, more accurate, measurement of the speed of light was performed in Europe by Hippolyte Fizeau in 1849. Fizeau directed a beam of light at a mirror several kilometers away. A rotating cog wheel was placed in the path of the light beam as it traveled from the source, to the mirror and then returned to its origin. Fizeau found that at a certain rate of rotation, the beam would pass through one gap in the wheel on the way out and the next gap on the way back. Knowing the distance to the mirror, the number of teeth on the wheel, and the rate of rotation, Fizeau was able to calculate the speed of light as 313,000,000 m/s.
Léon Foucault carried out an experiment which used rotating mirrors to obtain a value of 298,000,000 m/s in 1862. Albert A. Michelson conducted experiments on the speed of light from 1877 until his death in 1931. He refined Foucault's methods in 1926 using improved rotating mirrors to measure the time it took light to make a round trip from Mount Wilson to Mount San Antonio in California. The precise measurements yielded a speed of 299,796,000 m/s.
The effective velocity of light in various transparent substances containing ordinary matter, is less than in vacuum. For example, the speed of light in water is about 3/4 of that in vacuum.
Two independent teams of physicists were said to bring light to a "complete standstill" by passing it through a Bose–Einstein condensate of the element rubidium, one team at Harvard University and the Rowland Institute for Science in Cambridge, Massachusetts, and the other at the Harvard–Smithsonian Center for Astrophysics, also in Cambridge. However, the popular description of light being "stopped" in these experiments refers only to light being stored in the excited states of atoms, then re-emitted at an arbitrary later time, as stimulated by a second laser pulse. During the time it had "stopped" it had ceased to be light.
The study of light and the interaction of light and matter is termed optics. The observation and study of optical phenomena such as rainbows and the aurora borealis offer many clues as to the nature of light.
An example of refraction of light. The straw appears bent, because of refraction of light as it enters liquid from air.
Refraction is the bending of light rays when passing through a surface between one transparent material and another. It is described by Snell's Law:
where θ1 is the angle between the ray and the surface normal in the first medium, θ2 is the angle between the ray and the surface normal in the second medium, and n1 and n2 are the indices of refraction, n = 1 in a vacuum and n > 1 in a transparent substance.
When a beam of light crosses the boundary between a vacuum and another medium, or between two different media, the wavelength of the light changes, but the frequency remains constant. If the beam of light is not orthogonal (or rather normal) to the boundary, the change in wavelength results in a change in the direction of the beam. This change of direction is known as refraction.
The refractive quality of lenses is frequently used to manipulate light in order to change the apparent size of images. Magnifying glasses, spectacles, contact lenses, microscopes and refracting telescopes are all examples of this manipulation.
There are many sources of light. A body at a given temperature emits a characteristic spectrum of black-body radiation. A simple thermal source is sunlight, the radiation emitted by the chromosphere of the Sun at around 6,000 kelvins (5,730 degrees Celsius; 10,340 degrees Fahrenheit) peaks in the visible region of the electromagnetic spectrum when plotted in wavelength units and roughly 44% of sunlight energy that reaches the ground is visible. Another example is incandescent light bulbs, which emit only around 10% of their energy as visible light and the remainder as infrared. A common thermal light source in history is the glowing solid particles in flames, but these also emit most of their radiation in the infrared, and only a fraction in the visible spectrum.
The peak of the blackbody spectrum is in the deep infrared, at about 10 micrometre wavelength, for relatively cool objects like human beings. As the temperature increases, the peak shifts to shorter wavelengths, producing first a red glow, then a white one, and finally a blue-white colour as the peak moves out of the visible part of the spectrum and into the ultraviolet. These colours can be seen when metal is heated to "red hot" or "white hot". Blue-white thermal emission is not often seen, except in stars (the commonly seen pure-blue colour in a gas flame or a welder's torch is in fact due to molecular emission, notably by CH radicals (emitting a wavelength band around 425 nm, and is not seen in stars or pure thermal radiation).
Atoms emit and absorb light at characteristic energies. This produces "emission lines" in the spectrum of each atom. Emission can be spontaneous, as in light-emitting diodes, gas discharge lamps (such as neon lamps and neon signs, mercury-vapor lamps, etc.), and flames (light from the hot gas itself—so, for example, sodium in a gas flame emits characteristic yellow light). Emission can also be stimulated, as in a laser or a microwave maser.
Deceleration of a free charged particle, such as an electron, can produce visible radiation: cyclotron radiation, synchrotron radiation, and bremsstrahlung radiation are all examples of this. Particles moving through a medium faster than the speed of light in that medium can produce visible Cherenkov radiation. Certain chemicals produce visible radiation by chemoluminescence. In living things, this process is called bioluminescence. For example, fireflies produce light by this means, and boats moving through water can disturb plankton which produce a glowing wake.
Certain substances produce light when they are illuminated by more energetic radiation, a process known as fluorescence. Some substances emit light slowly after excitation by more energetic radiation. This is known as phosphorescence. Phosphorescent materials can also be excited by bombarding them with subatomic particles. Cathodoluminescence is one example. This mechanism is used in cathode ray tube television sets and computer monitors.
There are two types of color mixing: Additive and Subtractive. In both cases, there are…
Standard illuminant
A standard illuminant is a theoretical source of visible light with a profile (its spectral…
Certain other mechanisms can produce light:
Bioluminescence
Cherenkov radiation
Electroluminescence
Scintillation
Sonoluminescence
Triboluminescence
When the concept of light is intended to include very-high-energy photons (gamma rays), additional generation mechanisms include:
Particle–antiparticle annihilation
Radioactive decay
Light pressure
Light exerts physical pressure on objects in its path, a phenomenon which can be deduced by Maxwell's equations, but can be more easily explained by the particle nature of light: photons strike and transfer their momentum. Light pressure is equal to the power of the light beam divided by c, the speed of light. Due to the magnitude of c, the effect of light pressure is negligible for everyday objects. For example, a one-milliwatt laser pointer exerts a force of about 3.3 piconewtons on the object being illuminated; thus, one could lift a U.S. penny with laser pointers, but doing so would require about 30 billion 1-mW laser pointers. However, in nanometre-scale applications such as nanoelectromechanical systems (|NEMS), the effect of light pressure is more significant, and exploiting light pressure to drive NEMS mechanisms and to flip nanometre-scale physical switches in integrated circuits is an active area of research. At larger scales, light pressure can cause asteroids to spin faster, acting on their irregular shapes as on the vanes of a windmill. The possibility of making solar sails that would accelerate spaceships in space is also under investigation.
Although the motion of the Crookes radiometer was originally attributed to light pressure, this interpretation is incorrect; the characteristic Crookes rotation is the result of a partial vacuum. This should not be confused with the Nichols radiometer, in which the (slight) motion caused by torque (though not enough for full rotation against friction) is directly caused by light pressure. As a consequence of light pressure, Einstein in 1909 predicted the existence of "radiation friction" which would oppose the movement of matter. He wrote, "radiation will exert pressure on both sides of the plate. The forces of pressure exerted on the two sides are equal if the plate is at rest. However, if it is in motion, more radiation will be reflected on the surface that is ahead during the motion (front surface) than on the back surface. The backwardacting force of pressure exerted on the front surface is thus larger than the force of pressure acting on the back. Hence, as the resultant of the two forces, there remains a force that counteracts the motion of the plate and that increases with the velocity of the plate. We will call this resultant 'radiation friction' in brief."
Historical theories about light, in chronological order
In the fifth century BC, Empedocles postulated that everything was composed of four elements; fire, air, earth and water. He believed that Aphrodite made the human eye out of the four elements and that she lit the fire in the eye which shone out from the eye making sight possible. If this were true, then one could see during the night just as well as during the day, so Empedocles postulated an interaction between rays from the eyes and rays from a source such as the sun.
In about 300 BC, Euclid wrote Optica, in which he studied the properties of light. Euclid postulated that light travelled in straight lines and he described the laws of reflection and studied them mathematically. He questioned that sight is the result of a beam from the eye, for he asks how one sees the stars immediately, if one closes one's eyes, then opens them at night. If the beam from the eye travels infinitely fast this is not a problem.
In 55 BC, Lucretius, a Roman who carried on the ideas of earlier Greek atomists, wrote that "The light & heat of the sun; these are composed of minute atoms which, when they are shoved off, lose no time in shooting right across the interspace of air in the direction imparted by the shove." (from On the nature of the Universe). Despite being similar to later particle theories, Lucretius's views were not generally accepted. Ptolemy (c. 2nd century) wrote about the refraction of light in his book Optics.
Classical India
In ancient India, the Hindu schools of Samkhya and Vaisheshika, from around the early centuries AD developed theories on light. According to the Samkhya school, light is one of the five fundamental "subtle" elements (tanmatra) out of which emerge the gross elements. The atomicity of these elements is not specifically mentioned and it appears that they were actually taken to be continuous. On the other hand, the Vaisheshika school gives an atomic theory of the physical world on the non-atomic ground of ether, space and time. (See Indian atomism.) The basic atoms are those of earth (prthivi), water (pani), fire (agni), and air (vayu) Light rays are taken to be a stream of high velocity of tejas (fire) atoms. The particles of light can exhibit different characteristics depending on the speed and the arrangements of the tejas atoms. The Vishnu Purana refers to sunlight as "the seven rays of the sun".
The Indian Buddhists, such as Dignāga in the 5th century and Dharmakirti in the 7th century, developed a type of atomism that is a philosophy about reality being composed of atomic entities that are momentary flashes of light or energy. They viewed light as being an atomic entity equivalent to energy.
René Descartes (1596–1650) held that light was a mechanical property of the luminous body, rejecting the "forms" of Ibn al-Haytham and Witelo as well as the "species" of Bacon, Grosseteste, and Kepler. In 1637 he published a theory of the refraction of light that assumed, incorrectly, that light travelled faster in a denser medium than in a less dense medium. Descartes arrived at this conclusion by analogy with the behaviour of sound waves. Although Descartes was incorrect about the relative speeds, he was correct in assuming that light behaved like a wave and in concluding that refraction could be explained by the speed of light in different media.
Descartes is not the first to use the mechanical analogies but because he clearly asserts that light is only a mechanical property of the luminous body and the transmitting medium, Descartes' theory of light is regarded as the start of modern physical optics.
Particle theory
Pierre Gassendi (1592–1655), an atomist, proposed a particle theory of light which was published posthumously in the 1660s. Isaac Newton studied Gassendi's work at an early age, and preferred his view to Descartes' theory of the plenum. He stated in his Hypothesis of Light of 1675 that light was composed of corpuscles (particles of matter) which were emitted in all directions from a source. One of Newton's arguments against the wave nature of light was that waves were known to bend around obstacles, while light travelled only in straight lines. He did, however, explain the phenomenon of the diffraction of light (which had been observed by Francesco Grimaldi) by allowing that a light particle could create a localised wave in the aether.
Newton's theory could be used to predict the reflection of light, but could only explain refraction by incorrectly assuming that light accelerated upon entering a denser medium because the gravitational pull was greater. Newton published the final version of his theory in his Opticks of 1704. His reputation helped the particle theory of light to hold sway during the 18th century. The particle theory of light led Laplace to argue that a body could be so massive that light could not escape from it. In other words, it would become what is now called a black hole. Laplace withdrew his suggestion later, after a wave theory of light became firmly established as the model for light (as has been explained, neither a particle or wave theory is fully correct). A translation of Newton's essay on light appears in The large scale structure of space-time, by Stephen Hawking and George F. R. Ellis.
The fact that light could be polarized was for the first time qualitatively explained by Newton using the particle theory. Étienne-Louis Malus in 1810 created a mathematical particle theory of polarization. Jean-Baptiste Biot in 1812 showed that this theory explained all known phenomena of light polarization. At that time the polarization was considered as the proof of the particle theory.
Wave theory
To explain the origin of colors, Robert Hooke (1635-1703) developed a "pulse theory" and compared the spreading of light to that of waves in water in his 1665 work Micrographia ("Observation IX"). In 1672 Hooke suggested that light's vibrations could be perpendicular to the direction of propagation. Christiaan Huygens (1629-1695) worked out a mathematical wave theory of light in 1678, and published it in his Treatise on light in 1690. He proposed that light was emitted in all directions as a series of waves in a medium called the Luminiferous ether. As waves are not affected by gravity, it was assumed that they slowed down upon entering a denser medium.
Christiaan Huygens.
The wave theory predicted that light waves could interfere with each other like sound waves (as noted around 1800 by Thomas Young). Young showed by means of a diffraction experiment that light behaved as waves. He also proposed that different colours were caused by different wavelengths of light, and explained colour vision in terms of three-coloured receptors in the eye. Another supporter of the wave theory was Leonhard Euler. He argued in Nova theoria lucis et colorum (1746) that diffraction could more easily be explained by a wave theory. In 1816 André-Marie Ampère gave Augustin-Jean Fresnel an idea that the polarization of light can be explained by the wave theory if light were a transverse wave.
Later, Fresnel independently worked out his own wave theory of light, and presented it to the Académie des Sciences in 1817. Siméon Denis Poisson added to Fresnel's mathematical work to produce a convincing argument in favour of the wave theory, helping to overturn Newton's corpuscular theory. By the year 1821, Fresnel was able to show via mathematical methods that polarisation could be explained by the wave theory of light and only if light was entirely transverse, with no longitudinal vibration whatsoever.
The weakness of the wave theory was that light waves, like sound waves, would need a medium for transmission. The existence of the hypothetical substance luminiferous aether proposed by Huygens in 1678 was cast into strong doubt in the late nineteenth century by the Michelson–Morley experiment.
Newton's corpuscular theory implied that light would travel faster in a denser medium, while the wave theory of Huygens and others implied the opposite. At that time, the speed of light could not be measured accurately enough to decide which theory was correct. The first to make a sufficiently accurate measurement was Léon Foucault, in 1850. His result supported the wave theory, and the classical particle theory was finally abandoned, only to partly re-emerge in the 20th century.
Electromagnetic theory
A 3–dimensional rendering of linearly polarised light wave frozen in time and showing the two oscillating components of light; an electric field and a magnetic field perpendicular to each other and to the direction of motion (a transverse wave).
In 1845, Michael Faraday discovered that the plane of polarisation of linearly polarised light is rotated when the light rays travel along the magnetic field direction in the presence of a transparent dielectric, an effect now known as Faraday rotation. This was the first evidence that light was related to electromagnetism. In 1846 he speculated that light might be some form of disturbance propagating along magnetic field lines. Faraday proposed in 1847 that light was a high-frequency electromagnetic vibration, which could propagate even in the absence of a medium such as the ether.
Faraday's work inspired James Clerk Maxwell to study electromagnetic radiation and light. Maxwell discovered that self-propagating electromagnetic waves would travel through space at a constant speed, which happened to be equal to the previously measured speed of light. From this, Maxwell concluded that light was a form of electromagnetic radiation: he first stated this result in 1862 in On Physical Lines of Force. In 1873, he published A Treatise on Electricity and Magnetism, which contained a full mathematical description of the behaviour of electric and magnetic fields, still known as Maxwell's equations. Soon after, Heinrich Hertz confirmed Maxwell's theory experimentally by generating and detecting radio waves in the laboratory, and demonstrating that these waves behaved exactly like visible light, exhibiting properties such as reflection, refraction, diffraction, and interference. Maxwell's theory and Hertz's experiments led directly to the development of modern radio, radar, television, electromagnetic imaging, and wireless communications.
In the quantum theory, photons are seen as wave packets of the waves described in the classical theory of Maxwell. The quantum theory was needed to explain effects even with visual light that Maxwell's classical theory could not (such as spectral lines).
In 1900 Max Planck, attempting to explain black body radiation suggested that although light was a wave, these waves could gain or lose energy only in finite amounts related to their frequency. Planck called these "lumps" of light energy "quanta" (from a Latin word for "how much"). In 1905, Albert Einstein used the idea of light quanta to explain the photoelectric effect, and suggested that these light quanta had a "real" existence. In 1923 Arthur Holly Compton showed that the wavelength shift seen when low intensity X-rays scattered from electrons (so called Compton scattering) could be explained by a particle-theory of X-rays, but not a wave theory. In 1926 Gilbert N. Lewis named these light quanta particles photons.
Eventually the modern theory of quantum mechanics came to picture light as (in some sense) both a particle and a wave, and (in another sense), as a phenomenon which is neither a particle nor a wave (which actually are macroscopic phenomena, such as baseballs or ocean waves). Instead, modern physics sees light as something that can be described sometimes with mathematics appropriate to one type of macroscopic metaphor (particles), and sometimes another macroscopic metaphor (water waves), but is actually something that cannot be fully imagined. As in the case for radio waves and the X-rays involved in Compton scattering, physicists have noted that electromagnetic radiation tends to behave more like a classical wave at lower frequencies, but more like a classical particle at higher frequencies, but never completely loses all qualities of one or the other. Visible light, which occupies a middle ground in frequency, can easily be shown in experiments to be describable using either a wave or particle model, or sometimes both.
In February 2018, scientists reported, for the first time, the discovery of a new form of light, which may involve polaritons, that could be useful in the development of quantum computers.
Source From Wikipedia
Tags: LightRadiation
Rose color
Rose is the color halfway between red and magenta on the HSV color wheel, also…
Tuscan red is a shade of red that was used on the passenger cars of…
Tie A String Around the World, Philippine Pavilion, Venice Biennale 2015
The Philippines be back with the theme "Tie A String Around the World" to the…
Environmentalism or environmental rights is a broad philosophy, ideology, and social movement regarding concerns for…
Geocriticism
Geocriticism is a method of literary analysis and literary theory that incorporates the study of…
Sustainability reports emerged as an evolution of the environmental reports published in the 1990s by…
Impossible color
Impossible colors or forbidden colors are supposed colors that cannot be perceived in normal seeing…
Planetary boundaries is a concept involving Earth system processes which contain environmental boundaries, proposed in…
Low-energy house
A low-energy house is any type of house that from design, technologies and building products…
Zoology in Mexican art, Museum of Popular Art in Mexico City
The exhibition "Zoology in Mexican art", has an area of insects, mammals, amphibians and reptiles…
Categories Select Category 360 Video Academic America Ancient art Applied Archeology Architecture Art Art Gallery Artwork Asia Pacific Biology Business Chemistry Component Computing Contemporary art Costume Culture Decorative Arts Design Development East Asia Eastern Europe Education Element Energy Engineering Entertainment Environment Ethnography Europe Event Exhibition Exterior Fashion Folk Culture Geography Guide Tour Handicrafts Health Historic Sites History Indigenous art Industry Instrument Interior Islamic art Landmark Law Lifestyle List Literature Material Mathematics Medical Middle East Military Modern art North America Northern Europe Object Oceania Organic Organization Oriental art Ornament Park Garden People Performance Philosophy Physics Politics Product Psychology Public Religion Religion Place Science Nature Showcase Skill Society South America South Asia Southeast Asia Style Technology Theme Tool Tour Transportation Travel Trends Uncategorized Western art Western Europe

redpajama_set_name: RedPajamaCommonCrawl


text:
Author Archive: Anthony Schewe
Perseverance rover hightails it to Martian delta
Posted on March 20, 2022 March 20, 2022 by Anthony Schewe
NASA's Perseverance Mars rover looks back at its wheel tracks on March 17, 2022, the 381th Martian day, or sol, of the mission. Credit: NASA/JPL-Caltech
NASA's Perseverance Mars rover is trying to cover more distance in a single month than any rover before it—and it's doing so using artificial intelligence. On the path ahead are sandpits, craters, and fields of sharp rocks that the rover will have to navigate around on its own. At the end of the 3-mile (5-kilometer) journey, which began March 14, 2022, Perseverance will reach an ancient river delta within Jezero Crater, where a lake existed billions of years ago.
This delta is one of the best locations on Mars for the rover to look for signs of past microscopic life. Using a drill on the end of its robotic arm and a complex sample collection system in its belly, Perseverance is collecting rock cores for return to Earth—the first part of the Mars Sample Return campaign.
"The delta is so important that we've actually decided to minimize science activities and focus on driving to get there more quickly," said Ken Farley of Caltech, Perseverance's project scientist. "We'll be taking lots of images of the delta during that drive. The closer we get, the more impressive those images will be."
The science team will be searching these images for the rocks they'll eventually want to study in closer detail using the instruments on Perseverance's arm. They'll also hunt for the best routes the rover can take to ascend the 130-foot-high (40-meter-high) delta.
But first, Perseverance needs to get there. The rover will do this by relying on its self-driving AutoNav system, which has already set impressive distance records. While all of NASA's Mars rovers have had self-driving abilities, Perseverance has the most advanced one yet.
"Self-driving processes that took minutes on a rover like Opportunity happen in less than a second on Perseverance," said veteran rover planner and flight software developer Mark Maimone of NASA's Jet Propulsion Laboratory in Southern California, which leads the mission. "Because autonomous driving is now faster, we can cover more ground than if humans programmed every drive."
NASA's Perseverance Mars rover will follow the proposed route to Jezero Crater's delta shown in this animation. The delta is one the most important locations the rover will visit as it seeks signs of ancient life on Mars. Credit: NASA/JPL-Caltech/ASU/MSSS/University of Arizona
How rover planning works
Before the rover rolls, a team of mobility planning experts (Perseverance has 14 who trade off shifts) writes the driving commands the robotic explorer will carry out. The commands reach Mars via NASA's Deep Space Network, and Perseverance sends back data so the planners can confirm the rover's progress. Multiple days are required to complete some plans, as with a recent drive that spanned about 1,673 feet (510 meters) and included thousands of individual rover commands.
Some drives require more human input than others. AutoNav is useful for drives over flat terrain with simple potential hazards—for instance, large rocks and slopes—that are easy for the rover to detect and work around.
Thinking while driving
AutoNav reflects an evolution of self-driving tools previously developed for NASA's Spirit, Opportunity, and Curiosity rovers. What's different for AutoNav is "thinking while driving"—allowing Perseverance to take and process images while on the move. The rover then navigates based on those images. Is that boulder too close? Will its belly be able to clear that rock? What if the rover wheels were to slip?
Upgraded hardware allows "thinking while driving" to happen. Faster cameras mean Perseverance can take images quickly enough to process its route in real-time. And unlike its predecessors, Perseverance has an additional computer dedicated entirely to image processing. The computer relies on a single-purpose, super-efficient microchip called a field-programmable gate array that is great for computer vision processing.
"On past rovers, autonomy meant slowing down because data had to be processed on a single computer," Maimone said. "This extra computer is insanely fast compared to what we had in the past, and having it dedicated for driving means you don't have to share computing resources with over 100 other tasks."
Of course, humans aren't completely out of the picture during AutoNav drives. They still plan the basic route using images taken from space by missions like NASA's Mars Reconnaissance Orbiter. Then, they mark obstacles such as potential sand traps for Perseverance to avoid, drawing "keep out" and "keep in" zones that help it navigate.
Another big difference is Perseverance's sense of space.
Curiosity's autonomous navigation program keeps the rover in a safety bubble that is 16 feet (5 meters) wide. If Curiosity spots two rocks that are, say, 15 feet (4.5 meters) apart—a gap it could easily navigate—it will still stop or travel around them rather than risk passing through.
But Perseverance's bubble is much smaller: A virtual box is centered on each of the rover's six wheels. Mars' newest rover has a more sensitive understanding of the terrain and can get around boulders on its own.
"When we first looked at Jezero Crater as a landing site, we were concerned about the dense fields of rocks we saw scattered across the crater floor," Maimone said. "Now we're able to skirt or even straddle rocks that we couldn't have approached before."
While previous rover missions took a slower pace exploring along their path, AutoNav provides the science team with the ability to zip to the locations they prioritize the most. That means the mission is more focused on its primary objective: finding the samples that scientists will eventually want to return to Earth.
Perseverance rover hightails it to Martian delta (2022, March 18)
retrieved 20 March 2022
from https://phys.org/news/2022-03-perseverance-rover-hightails-martian-delta.html


text:
Reading & Study
Statements & Letters
Ministry Topics
Black Ministry
Life Ministry
Ministry to the Armed Forces
School Ministry
Recognized Service Organizations
Rural and Small Town Mission
Urban & Inner-City Mission
Witness & Outreach Ministry
About Reporter
Subscribe to Reporter
Advertise in Reporter
Reporter Apps
© 2003 – 2020 The Lutheran Church—Missouri Synod. All Rights Reserved.
Soldiers of the Cross: caring for caregivers
lcms.org
Lutherans Engage the World
Youth E-Source
LCMS Resources
MDFL Resource Center
KFUO Radio
Paula Schlueter Ross
Since 2012, Soldiers of the Cross has granted $1.1 million to pastors, teachers and other church workers facing a financial crisis. (lightstock)
By Paula Schlueter Ross (paula.ross@lcms.org)
"We've got to remember that pastors are people, too."
"Pastor Tom" (a pseudonym) laughs when he recalls those words of a concerned parishioner a few years ago when his health was a roller coaster with dips so low he was at heaven's door more than once.
Diagnosed with two "very deadly" and rare cancers, he says it was "like winning the lottery in reverse." Very uncertain. Very scary. And with myriad doctors and medical procedures, very expensive — especially when you're unable to work.
Desperate, he and his wife — once caregivers to others, now needing care themselves — packed up their belongings and moved thousands of miles back to his home state to be near family.
As he explains it, "there was a gap between coming back [home] and not being able to work, and actually getting the disability that was needed to pay the bills."
Enter Soldiers of the Cross, one of two LCMS mercy programs that assist church workers with financial needs. While "Soldiers" helps active workers facing emergencies such as serious illness, Veterans of the Cross provides grants to retirees who are struggling with basic living expenses.
Both programs depend on contributions from donors, and Soldiers of the Cross also works in conjunction with workers' districts, which typically provide matching funds to boost the initial $1,000 to $3,000 individual grants.
The total $6,000 that Pastor Tom received from Soldiers and his district provided a much-needed feeling of "relief." But he also "felt very supported by the church." It wasn't "just lip-service, but action," he noted, and he said he's especially grateful to his district president and the Rev. Dr. Carlos Hernandez — who receives and administers the funding requests — for their care and concern.
"It does make you feel that you are valued by the church. It does. And that they care about you."
Today his health is "stable" and he is able to serve a local congregation part time, about 10 to 15 hours a week, leading worship and Bible study, working with confirmands, and — with a "unique perspective on illness" — visiting members who are sick and those in nursing homes.
"The service I get to do, I tell you, is really a joy," he says, and "a great honor."
Since 2012, Soldiers of the Cross has granted $1.1 million to pastors, teachers and other church workers in crisis, according to Hernandez, director of Church and Community Engagement with the Synod's Office of National Mission.
That figure doesn't include matching funds from LCMS districts, a "very important and very valuable" partnership, he notes, especially in light of the ever-increasing needs.
"In reality, what we're trying to do through Soldiers of the Cross is help the districts help their workers," Hernandez says, and the "ideal situation" is when a district president requests an application for assistance for a worker. District presidents are familiar with their workers' circumstances, he explains, and so they are ideally situated to serve as liaisons between the workers and the Soldiers program.
Sometimes workers are reluctant to accept the grants, so Hernandez tells them, "Look, this is not our money — this is God's money. You've been praying to God for help? This is God helping you. He's just using us as a conduit. Know that this is a prayer that's been answered. And we're just here as servants of God."
As Hernandez sees it, "we're all part of the body of Christ, and when one part of the body is hurting, the rest comes to help."
Church workers facing financial stress "are not at their full capacity to proclaim and share the Gospel," he adds, so he considers the grants "an investment in the church worker and in the proclamation of the Gospel."
The Rev. "Tim and Linda Smith" (not their real names) had never heard of Soldiers of the Cross until they were contacted by Hernandez.
Fresh off the mission field because of Tim's debilitating illness, the couple was living with their grown children, seeing doctors, trying to figure out their next steps.
It was "a really tough time," says Tim. "We didn't really know where to turn [for help], we didn't know what we were going to do."
Soldiers of the Cross was a godsend, say the Smiths, who received a total of some $6,000 from the program and their district — enough to purchase a much-needed electric wheelchair and pay some medical bills.
"They've helped us out in so many ways and been so kind to us — and said prayers for us, as well. It's really great, and I didn't even know it existed," said Tim.
He's convinced that if more people and congregations knew about the Soldiers program — and the "incredible blessing" it is to hurting church workers — "they would get involved in it and want to help out with it."
Linda agrees, adding that if you're interested in contributing to a human-care ministry, "this is really [a valuable] one."
For more information about Soldiers of the Cross, contact Hernandez at carlos.hernandez@lcms.org or visit lcms.org/SoldiersoftheCross.
For information about Veterans of the Cross, which is administered by Concordia Plan Services for retired church workers, visit lcms.org/VeteransoftheCross.
Tags church workers concordia plan services Soldiers of the Cross Veterans of the Cross
Paula Schlueter Ross (1953–2019), former managing editor of Reporter, was a magna cum laude graduate of Webster University, with a Bachelor of Arts in Journalism. During her nearly 35-year career with the LCMS, she wrote for both Reporter and The Lutheran Witness and often took photos to accompany her stories. Ross won 17 national writing awards from the Associated Church Press, including seven first-place "Awards of Excellence."
In April's 'Lutheran Witness'
Journal critiques seminary models, theological education
Million Dollar Life Match applications now open
Wife of Synod's longest-serving alliance missionary laid to rest in Jamaica
Ministerial Care Coalition holds annual meeting
From the mission field: Youth ministry in Dominican Republic
Campus clips: Schools highlight creativity, liberty
Deadline to apply for national development grant extended to March 1
Call for nominations/applications — Executive director, Internal Audit
The gift of life: A letter from President Harrison
Start a Print Subscription
Authors & Contributors
Sign up for Reporter updates
Follow Us @thelcms
© 2003-2022 The Lutheran Church—Missouri Synod All Rights Reserved.


We at Buy'n'Sell Vanuatu are dedicated to making it easier to find items to buy Locally in Vanuatu.
Whether you are a local, moving to Vanuatu or just coming for a short time, it can be quite difficult locating a car, boat, electronic items, fridges, washing machines or furniture etc.
Buy'n'Sell Vanuatu is supporting Ni-Vanuatu locals & their businesses also Ex-pats & their businesses to locate things they need to buy and Sell locally.


This Wednesday (10/4): Albacore Tuna - Plus New Seasonal Options!
This month we have several squid boats going out multiple times a week as well as our rock crab boat in Santa Cruz going out twice a week. This allows us to always pick up our catch on a Monday or Tuesday to be delivered Wednesday, guaranteeing a fresh selection every week for our members!
This weeks' "Catch of the Week" is beautiful Albacore Tuna from Ft. Bragg.
In addition we have fresh Market Squid from Monterey and Cooked Rock Crab Claws from Santa Cruz for our "Seasonal Selection!"
Albacore Tuna landed in Ft. Bragg caught on long-lines is considered a Best Choice by our partners at the Monterey Bay Aquariums Seafood Watch.
Albacore is the lightest of the Tuna with a beautiful mild flavor which lends itself to many flavors and applications. Once cooked the meat is firm and flakey - this is a great fish people just getting into seafood because it is very meaty and succulent without a strong flavor. We love our Albacore seared over salads, cured as gravlax, grilled and on sandwiches, in curries, kebobs, and burgers, you name it - this fish can do it all!