Folding At Home: Fact of the Day Log

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Folding fact #12
Glycine is the smallest amino acid. Chemically, it looks like this:
Picture- Click Here
The side chain is just a single hydrogen atom! Because of its diminuative size, glycine is very flexible and can be found in linker regions in proteins.

 

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Folding fact #13
The First Protein Structure was of myoglobin, determined by John Kendrew and his coworkers laying the foundation for an era of biological understanding. Myoglobin,a small, bright red protein that gives meat much of its red color. Its job is to store oxygen. Protein sequence databases grew from 1 in 1972 to 21390 as of June 17, 2003 in Protein Data Bank. Protein Data Bank is a worldwide depository of 3D structural databases of proteins. Database holds the coordinate data of each atom in a protein as determined by various experimental methods.

 

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Folding fact #14
Hydrogen Bond is key to the protein structures. A hydrogen atom is nothing more than a proton with a surrounding electron cloud. When one of these atoms is chemically bonded to an electron-withdrawing atom such as nitrogen or oxygen, much of the electron cloud moves toward the nitrogen or oxygen. The proton is thus left almost bare, with its positive charge largely unshielded. If it comes close to another atom with a bit of extra negative charge (typically, an oxygen or nitrogen atom), the partial positive and negative charges will attract each other and form the hydrogen bond.

 

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Folding fact #15
Distributed Computing: a type of system that divides a workload to computers connected to a network. The network may be either be enclosed in a room or out in the open, like the Internet. Distributed computing is also referred to as distributed processing, cooperative computing, and collective computing.

 

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Folding fact #16
Work-units: The data that is sent by Folding@home servers to users running the software. The work-units are pieces that a computer will process in its idle time and then send back to Folding@home.

 

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Folding fact #17
Milestones in the history of Internet:1969- The Department of Defense commissions ARPAnet for research in networking. The ARPAnet becomes 4-noded, as UCLA, Stanford, UCSB and the University of Utah hook up.1982- The ARPAnet has grown to 100 nodes when it switches from NCP to TCP/IP. 1986- NFSnet is created. Non-military research funding to the network marks the beginning of the Internet. 1991- The World Wide Web is released by Tim Berners-Lee, a physicist at CERN at the time who also creates world's first web page. 1992- Number of hosts exceeds 1,000,000.

 

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New Facts will start here, The FAH Site Has no More.

 

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Gravity has an effect on everyone and everything on Earth. Although we can't see it, smell it, taste it or touch it, we know it's there. Although scientists already know quite a bit about this invisible force, many aspects of this fundamental force of nature remain mysterious. In 2002 NASA teamed-up with the German Space Agency to launch the dual satellites that make up GRACE, short for the Gravity Recovery And Climate Experiment. These uniquely-designed twin satellites were developed to provide detailed measurements of Earth's gravity field that help scientists better understand the effects gravity has on Earth's global climate change.

Scientists have studied Earth's gravity for more than 30 years, using both satellite and ground measurements that were of uneven quality,' said Dr. Michael Watkins, GRACE project scientist at NASA's Jet Propulsion Laboratory in California. Errors in some locations were off by as much as 3 feet. Now, these measurements can be taken to within about 1 centimeter (0.4 inches) of accuracy. 'That's progress,' Watkins said. Why do the sensors need to be that sensitive? Because the variations in gravity across Earth's surface are very small and the weight of an object is not the same at every point on Earth. We live on a lumpy, bumpy planet scattered with mountains, valleys and caverns. These features have slightly different masses so as a result, the gravitational force changes ever so slightly across the surface of the Earth.

GRACE maps out these sensitive gravitational changes. GRACE can detect changes as small as one-tenth of the width of a human hair in the separation of the two spacecraft. This distance measurement is combined with Global Positioning data that gives the precise location of the measurement over Earth's surface. Every 30 days, scientists produce gravity maps that are 1,000 times more accurate then maps previously produced that had errors too large to be useful. GRACE monitors the mass and location of water as it moves around on the surface of the Earth, cycling between the land, oceans, and polar ice caps. Scientists also know that gravity is responsible for keeping the air and clouds from drifting away into space, creating the ups and downs of the ocean tides and a force that pulls two objects together. Gravity may be known as the weakest force in all of nature, but it still keeps our feet on the ground and manages to hold our galaxies and solar system together.
Gravity Map of the Earth

 

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Diadromous fish are fish that migrate between freshwater and saltwater. The migration patterns differ for each species and have seasonal and lifecycle variations. Only one percent of all fish in the world are diadromous. Some diadromous fish migrate great distances, while others migrate much shorter distances. In either case, these fish undergo physiological changes that allow them to survive as they migrate from freshwater to saltwater or vice versa. There are several types of diadromous fish, differing in their specific migration patterns.

Anadromous fish spend most of their adult lives in salt water, and migrate to freshwater rivers and lakes to reproduce. East Coast anadromous fish species include alewife, striped bass, Atlantic salmon, and shortnose sturgeon. West Coast anadromous species include five salmon species, steelhead, white sturgeon, and American shad (not native to the West Coast). Once the eggs of an anadromous fish hatch, the juvenile fish spend varying lengths of time in freshwater before migrating to saltwater, where they mature. The fish eventually return to freshwater to spawn. Some anadromous fish die after spawning (as with most salmon species), while others make the journey several times in their life. About half of all diadromous fish in the world are anadromous.

Catadromous fish spend most of their adult lives in freshwater, and migrate to saltwater to spawn. Juvenile fish migrate back upstream where they stay until maturing into adults, at which time the cycle starts again. The only catadromous species in the United States is the American eel. A fascinating aspect of the American eel's life history is that they migrate thousands of miles to spawn in the Sargasso Sea, located in the mid-Atlantic Ocean, south of Bermuda and north of the Bahamas. American eels do not eat once they leave the freshwater. Having spent so much energy to migrate and spawn, they die soon after. About one quarter of all diadromous fish in the world are catadromous. Amphidromous species move between estuaries and coastal rivers and streams, usually associated with the search for food and/or refuge rather than the need to reproduce. Amphidromous fish can spawn in either freshwater or in a marine environment. About one fifth of all diadromous fish are amphidromous.

 

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Why do you often wake up moments before your alarm clock goes off?

There are actually two functions in play here ? your circadian rhythms, and the Pavlovian effect. Complicated? Not really; here we go:

The brain has a sort of built-in pacemaker called the suprachiasmatic nuclei. Scientists can't explain exactly how this area keeps time, but it does, on a 24 hour clock. The brain keeps track of body temperature, hormone levels, reaction to outside light, and digestive patterns. It also sends your body into appropriate levels of sleep. Once the body feels fully rested, it slowly rises to a state of alertness.

In addition, all mechanical and most electronic alarm clocks give some sort of signal shortly before the actual alarm goes off, whether it's a faint "click" or a change in the glow of the digital display. Eventually our subconscious mind grows accustomed to and anticipates this foretelling of the "Get the Heck Out of Bed!" signal.

 

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A new form of radiation was discovered in 1895 by Wilhelm Roentgen, a German physicist. He called it X-radiation to denote its unknown nature. This mysterious radiation had the ability to pass through many materials that absorb visible light. X-rays also have the ability to knock electrons loose from atoms. Over the years these exceptional properties have made X-rays useful in many fields, such as medicine and research into the nature of the atom. Eventually, X-rays were found to be another form of light. Light is the by-product of the constant jiggling, vibrating, hurly-burly of all matter.

Like a frisky puppy, matter cannot be still. The chair you are sitting in may look and feel motionless. But if you could see down to the atomic level, you would see atoms and molecules vibrating hundreds of trillions of times a second and bumping into each other, while electrons zip around at speeds of 25,000 miles per hour.

When charged particles collide - or undergo sudden changes in their motion - they produce bundles of energy called photons that fly away from the scene of the accident at the speed of light. In fact they are light, or electromagnetic radiation, to use the technical term. Since electrons are the lightest known charged particle, they are most fidgety, so they are responsible for most of the photons produced in the universe.


Photgraph

 

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The number of hairs on the head varies with colour, for reasons still unknown. Blondes have 140,000 hairs, dark-haired people have around 108,000, while redheads have fewest at 90,000.



I guess blonds spend more time growing hair cells than brain cells!

 

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The term Global Warming refers to the observation that the atmosphere near the Earth's surface is warming, without any implications for the cause or magnitude. This warming is one of many kinds of climate change that the Earth has gone through in the past and will continue to go through in the future. Temperature increases will have significant impacts on human activities: where we can live, what food we can grow and how or where we can grow food, and where organisms we consider pests can thrive. To be prepared for the effects of these potential impacts we need to know how much the Earth is warming, for how long the Earth has been warming, and the cause of the warming. Answers to these questions provide us with a better basis for making decisions related to issues such as water resource management and agricultural planning.

The Greenhouse Effect is a term that describes how water vapor, carbon dioxide, and other gases in the atmosphere help maintain the temperature at the Earth's surface. The atmosphere approximates the function of a greenhouse by first letting sunlight (solar or short wave radiation) pass through to warm the Earth, while absorbing much of the heat (thermal or long wave radiation) radiated up from the surface of the Earth. Life on Earth would be very different without the Greenhouse Effect. The Greenhouse Effect serves to keep the long term annual average temperature of the Earth approximately 32 degrees C higher than the Earth's temperature would be without the Greenhouse Effect. Scientific evidence has shown that the Earth should warm as concentrations of greenhouse gases in the atmosphere increase above natural levels, much like what happens when the windows of a greenhouse are closed on a warm, sunny day. This additional warming is commonly referred to as Greenhouse Warming.

Greenhouse Warming is global warming due to increases in atmospheric greenhouse gases (e.g., carbon dioxide, methane, chlorofluorocarbons, etc.), whereas Global Warming refers only to the observation that the Earth is warming, without any indication of what might be causing the warming. Global Warming is accepted as fact by most of the scientific community. However, Greenhouse Warming is more controversial because it implies that we know what is causing the Earth to warm. Although it is known for certain that atmospheric concentrations of these greenhouse gases are rising dramatically due to human activity, it is less well known exactly how increases in these greenhouse gases factor in the observed changes of the Earth's climate and global temperatures. The majority of scientific evidence supports the theory that human activity is a major factor in currently observed global warming, but some of the warming may also be due to natural causes.

Fact Credit:
NOAA National Oceanic & Atmospheric Administration

Global Warming Photograph

 

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As any object moves through the air, the air near the object is disturbed. The disturbances are transmitted through the air at a distinct speed called the speed of sound, because sound itself is just a sensation created in the human brain in response to small pressure fluctuations in the air. Sound moves through the air as a series of waves. When the waves pass our ears, a sound is detected. The distance between any two waves is called the wavelength and the time interval between waves passing is called the frequency. The wavelength and the frequency are related by the speed of sound; high frequency implies short wavelength and low frequency implies a long wavelength. The brain associates a certain musical pitch with each frequency; the higher the frequency, the higher the pitch. Similarly, shorter wavelengths produce higher pitches. The speed of transmission of the sound remains a constant regardless of the frequency or the wavelength.

The speed of sound only depends on the state of the air (or gas) medium, not on the characteristics of the generating source. Because the speed of sound depends only on the state of the gas, some interesting physical phenomena occur when a sound source moves through a uniform gas. You can study some of these phenomena by using the interactive sound wave simulator. As the source moves, it continues to generate sound waves which move at the speed of sound. Since the source is moving slower than the speed of sound, the waves move out away from the source. Upstream (in the direction of the motion), the waves bunch up and the wavelength decreases. Downstream, the waves spread out and the wavelength increases. The sound that our ear detects will change in pitch as the object passes. This change in pitch is called a doppler effect. There are equations that describe the doppler effect.

As the moving source approaches our ear, the wavelength is shorter, the frequency is higher and we hear a higher pitch. If we let (fa) be the approaching frequency, (a) be the speed of sound, (u) be the velocity of the approaching souce, and (f) be the frequency of the sound at the source, then fa = [f * a] / [a - u]. As the moving source leaves us, the wavelength is longer, the frequency is lower and the pitch is lower. Again. if (fl) is the leaving frequency, then fl = [f * a] / [a + u].

Photgraph

Fact Credit:
NASA Glenn Research Center
Glenn Research Center Web Site

 

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Legionnaires' disease, which is also known as Legionellosis, is a form of pneumonia. It is often called Legionnaires' disease because the first known outbreak occurred in the Bellevue Stratford Hotel that was hosting a convention of the Pennsylvania Department of the American Legion. In that outbreak, approximately 221 people contracted this previously unknown type of bacterial pneumonia, and 34 people died. The source of the bacterium was found to be contaminated water used to cool the air in the hotel's air conditioning system.

Legionnaires' disease is most often contracted by inhaling mist from water sources such as whirlpool baths, showers, and cooling towers that are contaminated with Legionella bacteria. There is no evidence for person-to-person spread of the disease. Symptoms of Legionnaires' disease include fever, chills, and a cough that may or may not produce sputum. Other symptoms include abdominal pain, diarrhea, and confusion. This list of symptoms, however, does not readily distinguish Legionnaires' disease from other types of pneumonia. Legionnaires' disease is confirmed by laboratory tests that detect the presence of the bacterium, Legionella pnuemophila, or the presence of other bacteria in the family Legionellaceae. It is the most often treated with the antibiotic drug Erythromycin.

Although Legionnaires' disease has a mortality rate of 5 to 15 percent, many people may be infected with the bacterium that causes the disease, yet not develop any symptoms. It is likely that many cases of Legionnaires' disease go undiagnosed. Legionnaires' disease can be viewed as an example of how our physical environment affects our health. Relative humidity, temperature, and other environmental factors can alter the incidence and the fatality rates of infectious diseases, including Legionnaires' disease. For example, cooling towers and evaporative condensers of large air conditioning systems have been associated with outbreaks of the disease, and the highest incidence of Legionnaires' disease occurs in the warmest months of the year, the time when air conditioning systems are used the most.

Photograph

 

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The next time you notice that your cat's litter box doesn't smell bad, you can thank NASA astronauts. You can also thank them when you see lush green golf courses, or when you use air fresheners and laundry detergents. The common link in these products isn't immediately obvious: it's zeolites. The link still won't be obvious until you learn more about how zeolites work. Picture a sponge. When it's dry and hard, it doesn't soak up much water. As soon as it gets wet and squeezed, though, it can absorb and trap more than its weight in liquid. It also filters impurities; when you squeeze water out of sponge, the bits and pieces of other things stay in the sponge. Think of zeolites as sponges made out of rock. Zeolites don't use squeezing to release their liquids, however; they respond to heat. In fact, the name zeolite comes from the Greek words zeo (to boil) and lithos (stone) so it means 'the rock that boils.'

Zeolites aren't really rocks in the sense most people think; zeolites are rigid crystal structures. They have networks of interconnected tunnels and cages, similar to honeycomb. There are about 50 different types of zeolites that occur naturally. Another important feature: zeolites are small. Most zeolite molecules are about 2 to 8 microns in size, and that makes it difficult to study them accurately (a human hair is about 120 microns in diameter). That's where the astronauts can help. Because they're crystals, zeolites form gradually. In space, microgravity makes that crystallization happen at a slower pace, so more materials accumulate during the crystal-forming process. More material means larger, higher quality zeolites; the ones grown in space can be up to 1,000 times the size of ones on Earth. If scientists can see the zeolites better, they can study and manipulate them better.

What do zeolites do when heated? Their pores open. They act like sponges that have been squeezed, and expel water, gas or whatever is inside. Zeolites also filter substances by trapping large molecules. This helps some chemical reactions take place. Zeolites have ions loosely attached to their framework, and they can exchange their ions with ions from other materials. For instance, zeolites in laundry detergent exhange magnesium and calcium ions from hard water with their own sodium ions. That exchange improves the lathering effect of the detergent. Since zeolites absorb liquids and gases, that makes them useful in many everyday products that need this ability. Kitty litter requires substances that absorb liquids, for example, and air fresheners absorb foul-smelling gases. Because zeolites have small pores, that keeps some molecules from entering a zeolite structure. That means zeolites can be used to filter air and water to help clean up the environment.

Photgraph

 

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Nitrogen is a very interesting element. It is the seventh element of the periodic table, with seven electrons in its atoms. The somewhat unique combination of electronic structure and small atomic size makes it possible for as many as five of its electrons to be involved in bonding with other atoms. Nitrogen bonds very readily with other atoms to produce a bewildering variety of compounds, and is one essential component of amino acids, which are necessary for all life as we know it. Fortunately, there is no shortage of nitrogen in the world; the air that surrounds the planet is about 78% nitrogen. But there is a huge difference between the nitrogen we breathe and the nitrogen in amino acids.

Nitrogen gas is a diatomic molecule consisting of just two nitrogen atoms bonded very strongly to each other, while the nitrogen in amino acids and other compounds is just a single nitrogen atom bonded relatively weakly to a carbon atom and two other atoms. There are no chemical mechanisms in our bodies to convert nitrogen gas into free nitrogen atoms. In fact, the N to N bond in nitrogen gas is so strong that the single nitrogen atoms in amino acids and other compounds will spontaneously reform into nitrogen gas as those compounds break down. So how do we get those single atoms in the first place?

All life on this planet and probably wherever else there is life in the universe, owes its continued existence to a few varieties of bacteria that live in the soil. These are the 'nitrogen fixing' bacteria. Part of the life process of these bacteria is to 'fix' or 'tie down' free nitrogen gas from the air by converting it into atomic forms that can be taken up and used by plants and other organisms. Nitrogen-fixing bacteria use an enzyme-catalyzed biochemical process to carry out this conversion. Plants then use the fixed nitrogen to produce chlorophyll and other nitrogen-containing compounds. Animals that eat the plants thus acquire that nitrogen and use it to build amino acids and proteins, and life goes on.

 

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NASA's Chandra X-ray Observatory has discovered rich deposits of neon, magnesium, and silicon in a pair of colliding galaxies known as The Antennae. The deposits are located in vast clouds of hot gas. When the clouds cool, say scientists, a great number of stars and planets should form. These results may foreshadow the fate of our own Milky Way and its future collision with the Andromeda Galaxy. When galaxies collide, direct hits between stars are extremely rare, but collisions between huge gas clouds in the galaxies trigger a stellar baby boom. Massive newborn stars race through their evolution in a few million years and explode as supernovas. Heavy elements manufactured in these stars are blown away by the explosions and enrich the surrounding gas for thousands of light years.

The supernova rate in The Antennae is about 30 times that of the Milky Way. Supernova explosions heat the gas in these galaxies to millions of degrees Celsius--so hot that they emit X-rays. Such clouds are mostly invisible to optical telescopes, but they are easy targets for the Chandra X-ray Observatory. Chandra data reveal regions of high and varying enrichment. In one cloud, for instance, magnesium and silicon are 16 and 24 times as abundant as in the Sun. As the enriched gas cools, a new generation of stars will form, and with them new planets. A number of studies indicate that clouds enriched in heavy elements are more likely to form stars with planetary systems, so in the future an unusually high number of planets may form in The Antennae. At a distance of about 60 million light years, The Antennae system is the nearest example of a collision between two large galaxies.

The collision, which began a couple of hundred million years ago, has been so violent that gas and stars from the galaxies have been ejected into the two long arcs that give the system its name. The Antennae give a closeup view of the type of collisions that were common in the crowded early universe and likely led to the formation of many of the stars that exist in the universe today. They might also provide a glimpse of the future of our Milky Way galaxy, which is on a collision course with the Andromeda galaxy. At the present rate, a crash such as the one now occurring in the Antennae could happen in about 3 billion years. Tremendous gravitational forces will disrupt both galaxies and reform them, probably as a giant elliptical galaxy peppered with hundreds of millions of young Sun-like stars. And maybe hundreds of millions of habitable planets, too. These violent crashes aren't an end, after all. They're a new beginning.


Photgraph

 

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Ozone is a molecule containing three oxygen atoms. It is blue in color and has a strong odor. Normal oxygen, which we breathe, has two oxygen atoms and is colorless and odorless. Ozone is much less common than normal oxygen. Out of each 10 million air molecules, about 2 million are normal oxygen, but only 3 are ozone. However, even the small amount of ozone plays a key role in the atmosphere. The ozone layer absorbs a portion of the radiation from the sun, preventing it from reaching the planet's surface. Most importantly, it absorbs the portion of ultraviolet light called UVB. UVB has been linked to many harmful effects, including various types of skin cancer, cataracts, and harm to some crops, certain materials, and some forms of marine life.

At any given time, ozone molecules are constantly formed and destroyed in the stratosphere. The total amount, however, remains relatively stable. The concentration of the ozone layer can be thought of as a stream's depth at a particular location. Although water is constantly flowing in and out, the depth remains constant. While ozone concentrations vary naturally with sunspots, the seasons, and latitude, these processes are well understood and predictable. Scientists have established records spanning several decades that detail normal ozone levels during these natural cycles. Each natural reduction in ozone levels has been followed by a recovery. Recently, however, convincing scientific evidence has shown that the ozone shield is being depleted well beyond changes due to natural processes.


Photograph

 

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What Is A Mole?

No, it's not the furry little burrowing rodent with the star-shaped nose, from 'Wind In The Willows'... In chemistry, a mole is strictly defined as the number of particles of a pure material equal to the number of atoms in exactly 12 grams of carbon-12. This is the standard convention used by chemists throughout the world.

It is no accident that the mole and atomic mass are based on the same element. This was done to harmonize definitions so that chemists everywhere work with the same standards. A third feature can be added to further standardize the definition. This amount of carbon-12, exactly 12 grams, is said to contain exactly the number of particles (atoms in this case) equal to Avogadro's Number, that being 6.02252 X 1023. Because of this standardization the terms 'mole' and 'gram molecular weight' are used interchangeably. A gram molecular weight (or gram atomic weight when speaking of elements and single-atom structures) is the weight of the material in grams that corresponds to the molecular (or atomic) mass of the material.

For example, the atomic mass of the element neon is 20.183 atomic mass units. One mole (or gram atomic weight) of this material contains 6.02252 X 1023 atoms, and weighs exactly 20.183 grams. Another example, the molecular mass of the compound 1,3-dimethylpyrazole, C5H8N2, is 96.14 atomic mass units. One mole (or one gram molecular weight) of this material contains Avogadro's Number of molecules and weighs exactly 96.14 grams.

Mole Photgraph

 

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Atoms are the extremely small particles of which we, and everything around us, are made. A single element, such as oxygen, is made up of similar atoms. Different elements, such as oxygen, carbon, and uranium contain different kinds of atoms. There are 92 naturally occurring elements and scientists have made another 17, bringing the total to 109. Atoms are the smallest unit of an element that chemically behaves the same way the element does. When two chemicals react with each other, the reaction takes place between individual atoms--at the atomic level. The processes that cause materials be radioactive--to emit particles and energy--also occur at the atomic level.

In the early 20th century, an English scientist, Ernest Rutherford, and a Danish scientist, Niels Bohr, developed a way of thinking about the structure of an atom that described an atom as looking very much like our solar system. At the center of every atom was a nucleus, which is comparable to the sun in our solar system. Electrons moved around the nucleus in 'orbits' similar to the way planets move around the sun. (While scientists now know that atomic structure is more complex, the Rutherford-Bohr model is still a useful approximation to begin understanding about atomic structure.)

Opposite electrical charges of the protons and electrons do the work of holding the nucleus and its electrons together. Electrons closer to the nucleus are bound more tightly than the outer electrons because of their distance from the protons in the nucleus. The electrons in the outer orbits, or shells, are more loosely bound and affect an atom's chemical properties. A delicate balance of forces among nuclear particles keeps the nucleus stable. Any change in the number, the arrangement, or energy of the nucleons can upset this balance and cause the nucleus to become unstable or radioactive. (Disruption of electrons in the inner orbits can also cause an atom to emit radiation.) The amount of energy required to break up the nucleus into its parts is called the binding energy; it is often referred to as 'cosmic glue'. This is the same amount of energy given off when the nucleus formed.

 

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The hydrocarbons are the most broadly used organic compounds known, and are quite literally the driving force of western civilization. The greatest amounts of hydrocarbons are used as fuel for combustion, particularly in heating and motor fuel applications. The primary components of natural gas are methane and ethane. We are all familiar with the use of propane in gas barbecues, lanterns, and as a fuel for internal combustion engines and heating systems. Butane is also a readily available fuel, familiar to everyone in the form of the pocket lighter.

With pentane, the saturated hydrocarbons enter the realm of room-temperature liquids. This makes them useful as organic solvents, cleaners, and transport fuels. Gasoline for internal combustion engines in cars, trucks, tractors, lawnmowers, and so on, is rated in combustion properties relative to octane. It is in fact a combination of liquid hydrocarbons ranging from hexanes to decanes. Slightly larger hydrocarbons are known as kerosene or jet fuel, diesel fuel and heating oil. Still larger hydrocarbon molecules serve as lubricating oils, and greases. Eventually a point is reached at which the materials are solids at room temperature. These are the waxes. Hydrocarbon molecules larger than those of the waxes are the heavy greases and the tars commonly used in roofing applications and highway construction.

Most hydrocarbons are generated from the thermal 'cracking' and fractional distillation of crude oil. Another major source is the industrial alteration of ethanol to produce ethylene. The ethylene so produced becomes a feedstock for the industrial synthesis of other hydrocarbons up to and including polyethylene.

 

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You might wonder what the Northern Lights and neon signs have in common. Actually, a lot! What makes luminous colors shimmer across the Northern sky? The answer is in the Sun. Charged particles are constantly ejected from the Sun. These particles, collectively called solar winds, travel toward Earth with an average speed of 400 kilometers per second. Earth is shielded from the solar winds by its atmosphere and magnetic field. The magnetic field pulls the charged particles toward the North and South poles. As the particles strike atoms in the upper atmosphere, electrons are knocked free. We call atoms whose electrons have been knocked free 'ionized'. When the electrons re-unite with the ionized gas, they emit light.

In a neon tube, light is produced by a similar mechanism. The tube contains a low-pressure gas that is under high voltage. The high voltage ionizes the gas, and when the electrons recombine, they emit light. The color of the light depends upon the type of gas that is ionized: Oxygen emits bluish light, and neon emits reddish light. Because the chemical makeup of the Earth's atmosphere changes with altitude, the color of the aurora depends on altitude. The most spectacular auroras occur at elevations of 75 to 150 kilometers, and can produce red, green, yellow, blue and violet light. The shimmering is due to motion of the ionized gas as it is pulled by the Earth's magnetic field. And what is our planetary sign saying? Come and see and learn!

 

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In medical testing, ultrasound equipment is used to produce a sonogram, or a picture of organs inside the body. Ultrasound scanners do not use X-rays. They use waves of such high frequency that they cannot be heard. (Frequency is the number of sound wave cycles per second. The highest frequency humans can hear is 20 thousand Hertz. The sound waves used for ultrasound exams have a frequency of one to seven million Hertz.) The amount of energy they contain is low. The sound waves are made in a device called a transducer. It contains one or more quartz crystals that vibrate in response to an electrical current. This vibration changes electrical energy into the mechanical energy of sound.

When sound waves from the transducer enter the body, they travel through different materials at different speeds. When they hit a boundary between one kind of tissue and another--such as bone and muscle, or fluid and membrane--some bounce back, like an echo. The transducer receives those that bounce back, and the crystals work in reverse. They convert the mechanical energy of sound into an electrical current. A computer translates the electrical signals into a picture on a monitor. The picture is called a sonogram.

Ultrasound exams can yield several different kinds of information. Still pictures show individual structures inside the body. The pictures can be saved, enlarged, or printed just like any other photograph. Or, they can be viewed in rapid sequence, showing movement. Another type of sonogram is the Doppler. It works because sound waves bounce back to the transducer at a slightly different frequency than they had when they left it. The frequency shift can be used to produce colored images of problems such as clots in blood vessels or weaknesses in artery walls. Doppler techniques provide data on heart rate and blood flow.

 

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There's No Such Thing as a Safe Suntan:

Every time you step outdoors, you are bombarded by ultraviolet (UV) radiation from the sun. UV rays cause the number of free radicals in cells to increase. Free radicals are atoms or molecules that contain oxygen in a highly reactive form. They are the same kinds of compounds that cause iron to rust, stone to crumble, and paint to peel. In living cells, they damage membranes, alter DNA, and interfere with life-sustaining chemical reactions. The visible result is a suntan, which is simply the skin's less-than-adequate way of trying to protect itself from further damage. Over time, the damage adds up, and skin cancer is too often the result.

Two (and possibly three) types of UV radiation damage human skin. UVA (wavelength 320 to 400 nanometers) causes oxygen to combine with the brown pigment melanin in the skin. Melanin is the cause of the tanning response. The rays penetrate deep into the support layers under the skin's surface, causing wrinkles and skin cancers. UVA rays are strongest in summer around midday. UVB rays (280 to 320 nanometers) are strong all day long and all year round. They penetrate less deeply into the skin than UVA, but they are a thousand times more powerful. They cause skin cells to make enzymes that destroy collagen and elastin, the proteins that make skin elastic and supple. UVC rays (200 to 280 nanometers) may be the most dangerous of all. That's because the shorter the wavelength, the more energy the radiation possesses. Experts disagree about whether any UVC radiation filters through the atmosphere to the Earth's surface.

Between 1979 and 1995, deaths from malignant melanoma (the most deadly form of skin cancer) rose in the U.S. At the same time, the death rate from most other forms of cancer was declining. Experts say the best treatment for skin cancer is prevention. That means staying out of the sun whenever possible, applying sunscreens with a SPF (Sun Protection Factor) number greater than 30, and wearing protective clothing. Not just any clothing will do. If light passes through the fabric when it's held up to the sun, the clothing will let UV rays through to the skin. It's important to protect the eyes, too, with sunglasses that block all UV rays.