Friday, May 18, 2007
Emerging Paradigm
Network-on-Chip is an emerging paradigm for communications within large VLSI systems implemented on a single silicon chip. In a Network-on-Chip system, modules such as processor cores, memories and specialized IP blocks exchange data using a network as a "public transportation" sub-system for the information traffic. A Network-on-Chip is constructed from multiple point-to-point data links interconnected by switches, such that messages can be relayed from any source module to any destination module over several links, by making routing decisions at the switches. A Network-on-Chip is similar to a modern telecommunications network, using digital bit-packet switching over multiplexed links. Although packet-switching is sometimes claimed as necessity for a Network-on-Chip, there are several Network-on-Chip proposals utilizing circuit-switching techniques. This definition based on routers is usually interpreted so that a single shared bus, a single crossbar switch or a point-to-point network are not Network-on-Chip s but practically all other topologies are. This is somewhat confusing since all above mentioned are networks but they are not considered as network-on-chips. Note that some articles erroneously use Network-on-Chip as a synonym for mesh topology although Network-on-Chip paradigm does not dictate the topology. Likewise, the regularity of topology is sometimes considered as a requirement which is, obviously, not the case in research concentrating on "application-specific Network-on-Chip topology synthesis".
Sunday, May 13, 2007
Vitamins
Vitamins are nutrients required in minute amounts for essential metabolic reactions in the body. The term vitamin does not consist of other essential nutrients such as dietary minerals, essential fatty acids, or essential amino acids, nor does it include the large number of other nutrients that promote health but that are not essential for life. Vitamins are bio-molecules that act both as catalysts and substrates in chemical reactions. When acting as a catalyst, vitamins are bound to enzymes and are called cofactors. Vitamins also act as coenzymes to hold chemical groups between enzymes. Folic acid, for example, carries various forms of carbon groups–methyl, firmly or ethylene in the cell. Vitamins have been created as commodity chemicals and prepared widely available as inexpensive pills for several decades allowing supplementation of the dietary intake.
Wednesday, May 09, 2007
Bag
A bag is a container that is typically used for storing or holding something. Bags are non-rigid, usually made of paper, cloth, thin plastic or some other flexible material. A bag may have one or two handles or none at all. Sometimes a money bag or travel bag has a lock. Sachets may be fabric bags that are filled with pot pourri and tied off with ribbons. Youth giving a purse to a sitting courtesan the word probably has its origins in the Norse word baggy. Although paper had been used for purposes of wrapping and padding in ancient China since the 2nd century BC, the first use of paper bags in China came during the later Tang Dynasty.
Bags vary from small ones, like purses to large ones for use in traveling like a suitcase. Cheap disposable paper bags and plastic shopping bags are very common in the retail trade as a convenience for shoppers, and are often supplied by the shop for free or for a small fee. Customers may also take their own shopping bags to the shop. There are environmental concerns regarding use and disposal of plastic shopping and trash bags. Efforts are being taken to control and reduce their use in some European Union countries, including Ireland and the Netherlands. In some cases the cheap bags are taxed so the customer must pay a fee where they may not have done previously
Tuesday, May 01, 2007
Description of Willamette River
The Willamette rises in three separate forks in the mountains south and southeast of Eugene, at the southern termination of the Willamette Valley. The Middle Fork and North Fork increase on the western side of the Cascades between Three Sisters south to Diamond Peak, with the Middle Fork in receipt of the North Fork northwest of Oakridge and flowing northwest through the mountains to the southern end of the Willamette Valley. The Coast Fork rises in the lower mountains south of Cottage Grove, sinuous north to connect the Middle Fork 2 mi southeast of Eugene.
From Eugene, the joint river flow NNW across the plain of the southern Willamette Valley to Corvallis, and then follows a zigzag course past Albany and around the isolated hills in the middle valley, passing west of downtown Salem. From Salem it flows north in a not direct course across the northwest plain of the valley, reaching the hills at Newberg, where it turns sharply ENE along the hills, passing through an opening in the hills at Oregon City, the location of the Falls of the Willamette and the head of navigation. From Oregon City it flows northwest, past Lake Oswego and Milwaukee on the south edge of Portland, then passing between east and west Portland, where it is spanned by a series of urban bridges. Downstream of downtown Portland it flows northwest through the industrial port area of Portland Harbor, then splitting into two channels around Sauvie Island, both of which hook around to enter the Columbia from the west, with the main channel entering on the north edge of Portland and the smaller Multnomah Channel entering approximately 15 mi NNW at St.Helens.
From Eugene, the joint river flow NNW across the plain of the southern Willamette Valley to Corvallis, and then follows a zigzag course past Albany and around the isolated hills in the middle valley, passing west of downtown Salem. From Salem it flows north in a not direct course across the northwest plain of the valley, reaching the hills at Newberg, where it turns sharply ENE along the hills, passing through an opening in the hills at Oregon City, the location of the Falls of the Willamette and the head of navigation. From Oregon City it flows northwest, past Lake Oswego and Milwaukee on the south edge of Portland, then passing between east and west Portland, where it is spanned by a series of urban bridges. Downstream of downtown Portland it flows northwest through the industrial port area of Portland Harbor, then splitting into two channels around Sauvie Island, both of which hook around to enter the Columbia from the west, with the main channel entering on the north edge of Portland and the smaller Multnomah Channel entering approximately 15 mi NNW at St.Helens.
Friday, April 27, 2007
Transportation
Transportation is the movement of people and goods from one place to another. The term is derived from the porter ("to carry") and Latin Trans ("across"). Industries which have the business of providing equipment, actual transport, transport of people or goods and services used in transport of goods or people make up a huge broad and important segment of most national economies, and are collectively referred to as transport industries.
The field of transport has several aspects: loosely they can be divided into a triad of infrastructure, vehicles, and operations. Infrastructure includes the transport networks (roads, railways, airways, waterways, canals, pipelines, etc.) that are used, as well as the nodes or terminals (such as airports, railway stations, bus stations and seaports). The vehicles generally traverse on the networks, such as automobiles, bicycles, buses, trains, and aircrafts.
The field of transport has several aspects: loosely they can be divided into a triad of infrastructure, vehicles, and operations. Infrastructure includes the transport networks (roads, railways, airways, waterways, canals, pipelines, etc.) that are used, as well as the nodes or terminals (such as airports, railway stations, bus stations and seaports). The vehicles generally traverse on the networks, such as automobiles, bicycles, buses, trains, and aircrafts.
Tuesday, April 24, 2007
Corydon Airport
Corydon Airport is in south London on the limits of the London Boroughs of Corydon and Sutton. It was once the main airport for London, before it was replaced by Northolt Aerodrome, London Heathrow Airport and London Gatwick Airport.
It originated as two adjacent World War I airfields. Bedding ton Aerodrome, one of a number of small airfields around London which had been created for security against the Zeppelin raids in about May 1915, and Wad don Aerodrome of 1918, a test-flight aerodrome adjoining National Aircraft Factory No1.
At the end of that war, the two airfields were mutual into London's official airport as the gateway for all worldwide flights to and from the capital. Corydon Aerodrome opened on 29 March 1920.
It stimulated a growth in regular scheduled flights transport passengers, mail and freight, the first destinations being Paris, Amsterdam and Rotterdam. In 1923 Berlin flights were added. It was the operating base for Imperial Airways - remembered in the road name imposing Way on the site today.
In the mid 1920s, the airfield was extended, some adjacent roads being permanently closed to allow heavier airliners to land and depart safely. A new complex of buildings was constructed adjoining Purley Way, including the first purpose-designed air terminal in the world, the Aerodrome Hotel and extensive hangars, all opening on 2 May 1928.
The terminal building, the booking hall within it with its gallery balustraded in the geometrical design typical of the period, and the Aerodrome hotel were all built in the Art Deco style of the 1920s and 1930s. A further item that caught the eye of visitor and traveller alike was the time zone tower in the booking hall with its dials depicting the times in different parts of the world.
It originated as two adjacent World War I airfields. Bedding ton Aerodrome, one of a number of small airfields around London which had been created for security against the Zeppelin raids in about May 1915, and Wad don Aerodrome of 1918, a test-flight aerodrome adjoining National Aircraft Factory No1.
At the end of that war, the two airfields were mutual into London's official airport as the gateway for all worldwide flights to and from the capital. Corydon Aerodrome opened on 29 March 1920.
It stimulated a growth in regular scheduled flights transport passengers, mail and freight, the first destinations being Paris, Amsterdam and Rotterdam. In 1923 Berlin flights were added. It was the operating base for Imperial Airways - remembered in the road name imposing Way on the site today.
In the mid 1920s, the airfield was extended, some adjacent roads being permanently closed to allow heavier airliners to land and depart safely. A new complex of buildings was constructed adjoining Purley Way, including the first purpose-designed air terminal in the world, the Aerodrome Hotel and extensive hangars, all opening on 2 May 1928.
The terminal building, the booking hall within it with its gallery balustraded in the geometrical design typical of the period, and the Aerodrome hotel were all built in the Art Deco style of the 1920s and 1930s. A further item that caught the eye of visitor and traveller alike was the time zone tower in the booking hall with its dials depicting the times in different parts of the world.
Wednesday, April 18, 2007
Satellite phone
A satellite telephone, satellite phone, or satphone is a mobile phone that communicates directly with orbiting communications satellites. Depending on the architecture of a particular system, coverage may comprise the entire Earth, or only specific regions.Satellite phone (Inmarsat)The mobile equipment, also known as a terminal or earth station, varies generally. A satellite phone handset has a size and weight comparable to that of a late 1980s or early 1990s cell phone, but with a large retractable antenna. These are popular on expeditions into remote areas where terrestrial cellular service is unavailable.A fixed installation, such as used shipboard, may include large, rugged, rack-mounted electronics, and a steerable microwave antenna on the mast that mechanically tracks the overhead satellites.
Monday, April 09, 2007
Columbia River
100 The Columbia River is a river located in British Columbia and the Pacific Northwest of the United States. It is the biggest river in volume flowing into the Pacific Ocean from North America, and the second largest in the United States. It is the largest hydroelectric power producing river in North America. From its headwaters to the Pacific Ocean it flows 1,270 miles, and drains 258,000 square miles.
Geography
Columbia River, Revelstoke, BCColumbia Lake forms the Columbia's headwaters in the Canadian Rockies of southern British Columbia. The river then flows through Windermere Lake and the town of Invermere, then northwest to Golden and into Kinbasket Lake. The river then turns south all the way through Revelstoke Lake and the Arrow Lakes to the BC–Washington border.
The river then flows throughout the east-central portion of Washington State. The last 300 miles of the Columbia form the Washington-Oregon border line. The river goes into the Pacific Ocean at Ilwaco, Washington and Astoria, Oregon.
For its first 200 miles the Columbia flows northwest; it then bends to the south, crossing from Canada into the United States, where the river meets the Clark Fork. The Clark Fork River begins near Butte, Montana and flows through western Montana before entering Pend Oreille Lake. Water demanding from the lake forms the Pend Oreille River, which flows across the Idaho panhandle to Washington's northeastern curve where it meets the northern Canadian fork.
Columbia River Gorge, Oregon or South SideThe River then runs southsouthwest through the Columbia Plateau, changing to a southeasterly direction near the Columbia Basin, where the magnificent Gorge at George is situated. The Gorge Amphitheater, which looks out over the gorge, is a spectacular 40,000 person concert venue.
Geography
Columbia River, Revelstoke, BCColumbia Lake forms the Columbia's headwaters in the Canadian Rockies of southern British Columbia. The river then flows through Windermere Lake and the town of Invermere, then northwest to Golden and into Kinbasket Lake. The river then turns south all the way through Revelstoke Lake and the Arrow Lakes to the BC–Washington border.
The river then flows throughout the east-central portion of Washington State. The last 300 miles of the Columbia form the Washington-Oregon border line. The river goes into the Pacific Ocean at Ilwaco, Washington and Astoria, Oregon.
For its first 200 miles the Columbia flows northwest; it then bends to the south, crossing from Canada into the United States, where the river meets the Clark Fork. The Clark Fork River begins near Butte, Montana and flows through western Montana before entering Pend Oreille Lake. Water demanding from the lake forms the Pend Oreille River, which flows across the Idaho panhandle to Washington's northeastern curve where it meets the northern Canadian fork.
Columbia River Gorge, Oregon or South SideThe River then runs southsouthwest through the Columbia Plateau, changing to a southeasterly direction near the Columbia Basin, where the magnificent Gorge at George is situated. The Gorge Amphitheater, which looks out over the gorge, is a spectacular 40,000 person concert venue.
Monday, April 02, 2007
Lightning
Lightning is an influential natural electrostatic release produced during a thunderstorm. Lightning's abrupt electric release is accompanied by the emission of visible light and other forms of electromagnetic radiation. The electric current passing through the release channels quickly heats and expands the air into plasma, producing acoustic shock waves in the atmosphere.
Early lightning investigate
During early investigations into electricity via Leyden jars and other instruments, a number of people planned that small scale sparks shared some similarity with lightning.
Benjamin Franklin, who also imaginary the lightning rod, endeavored to test this theory by using a spire which was being erected in Philadelphia. Whilst he was waiting for the spire completion some others conducted at Marly in France, what became to be known as the Philadelphia experiments that Franklin had optional in his book?
Franklin typically gets the credit for being the first to perform this research. The Franklin myth goes like this:
Whilst coming up for completion of the spire, he got the idea of using a flying object, such as a kite in its place. During the next shower, in June 1752, he raised a kite, accompanied by his son as an assistant. On his end of the string he emotionally involved a key and tied it to a post with a silk thread. As time passed Franklin noticed the loose fibers on the string stretching out; he then brought his hand close enough to the key and a flash jumped the gap. The rain which had fallen during the storm had covered with water the line and made it conductive.
However, in his memoirs, Franklin obviously states that he only performed this research after those made in France.
As news of the research and its specifics spread, it was met with attempts at duplication. Experiments involving lightning are always risky and commonly fatal. The most well known death during the rash of Franklin-imitators was Professor George Richman, of Saint Petersburg, Russia. He had shaped a setup similar to Franklin's, and was attending a meeting of the Academy of Sciences, when he heard thunder. He ran home with his engraver to capture the event for posterity. While the research was underway, a large ball lightning showed up, collided with Richman's head, and killed him, leaving a red spot. His shoes were blown open, parts of his clothes singed, the engraver knocked out, the doorframe of the room was split, and the door itself ragged off its hinges.
Early lightning investigate
During early investigations into electricity via Leyden jars and other instruments, a number of people planned that small scale sparks shared some similarity with lightning.
Benjamin Franklin, who also imaginary the lightning rod, endeavored to test this theory by using a spire which was being erected in Philadelphia. Whilst he was waiting for the spire completion some others conducted at Marly in France, what became to be known as the Philadelphia experiments that Franklin had optional in his book?
Franklin typically gets the credit for being the first to perform this research. The Franklin myth goes like this:
Whilst coming up for completion of the spire, he got the idea of using a flying object, such as a kite in its place. During the next shower, in June 1752, he raised a kite, accompanied by his son as an assistant. On his end of the string he emotionally involved a key and tied it to a post with a silk thread. As time passed Franklin noticed the loose fibers on the string stretching out; he then brought his hand close enough to the key and a flash jumped the gap. The rain which had fallen during the storm had covered with water the line and made it conductive.
However, in his memoirs, Franklin obviously states that he only performed this research after those made in France.
As news of the research and its specifics spread, it was met with attempts at duplication. Experiments involving lightning are always risky and commonly fatal. The most well known death during the rash of Franklin-imitators was Professor George Richman, of Saint Petersburg, Russia. He had shaped a setup similar to Franklin's, and was attending a meeting of the Academy of Sciences, when he heard thunder. He ran home with his engraver to capture the event for posterity. While the research was underway, a large ball lightning showed up, collided with Richman's head, and killed him, leaving a red spot. His shoes were blown open, parts of his clothes singed, the engraver knocked out, the doorframe of the room was split, and the door itself ragged off its hinges.
Thursday, March 29, 2007
Giotto mission
100 Giotto was a European unmanned space mission from the European Space Agency planned to flying by and studies Halley's Comet.
Mission
On March 13, 1986, Giotto approached at a 596 kilometer detachment from Halley's nucleus.
The space probe "Giotto" from the European Space Agency was planned to study Halley's Comet. The spaceship was named after the medieval Italian painter Giotto di Bondone. He had observed Halley's Comet in 1301 and was stimulated to depict it as the star of Bethlehem in his painting The Christmas Story.
Originally a United States partner probe was intended that would accompany Giotto, but this fell from side to side due to budget cuts at NASA. There were plans to have watching equipment on-board a Space Shuttle in low-Earth orbit around the time of Giotto's fly-by, but they fell through with the Challenger disaster.
Mission
On March 13, 1986, Giotto approached at a 596 kilometer detachment from Halley's nucleus.
The space probe "Giotto" from the European Space Agency was planned to study Halley's Comet. The spaceship was named after the medieval Italian painter Giotto di Bondone. He had observed Halley's Comet in 1301 and was stimulated to depict it as the star of Bethlehem in his painting The Christmas Story.
Originally a United States partner probe was intended that would accompany Giotto, but this fell from side to side due to budget cuts at NASA. There were plans to have watching equipment on-board a Space Shuttle in low-Earth orbit around the time of Giotto's fly-by, but they fell through with the Challenger disaster.
Sunday, March 25, 2007
Atomic clock
An atomic clock is a type of clock so as to uses an atomic resonance frequency standard as its counter. Early atomic clocks were masers by means of attached equipment. Today's best atomic frequency standards (or clocks) are based on more advanced physics involving cold atoms and atomic fountains. National standards agencies maintain an accuracy of 10-9 seconds per day, and a precision equal to the frequency of the radio transmitter pumping the maser. The clocks keep up a continuous and stable time scale, International Atomic Time (TAI). For civil time, another time scale is disseminated, Coordinated Universal Time (UTC). UTC is derived from TAI, but coordinated with the passing of day and night based on astronomical observations.
Tuesday, March 20, 2007
Nectarines
Nectarine tree in full flower The nectarine is a variation of peach that has a fuzzless skin. Though grocers treat fuzzy peaches and nectarines as dissimilar fruits, they belong to the same species. Nectarines have arisen many times from fuzzy peaches, often as bud sports. Nectarines can be white, yellow, clingstone, or freestone. Regular peach trees infrequently produce a few nectarines, and vice versa. Nectarines are more simply damaged than fuzzy peaches. The history of the nectarine is unclear; the first recorded mention is from 1616 in England, but they had probably been grown very much earlier in central Asia.
Wednesday, March 14, 2007
Places to see in Jaipur
Places to see in Jaipur
Amber Palace The Amber Palace complex overlooking the artificial lake south of the town of Amber is one of the most well-liked tourist sites in the city, famous for its mixture of Hindu and Muslim architecture, and offering elephant rides from the town up to the palace courtyard. Although the structure is today known as Amber Fort, the complex was at first a Palace Complex within the Fort of Amber which is today known as Jaigarh fort.
Jaigarh Fort The Jaigarh Fort on the hills above the Amber Palace complex offers stunning views of the foothills of the Aravalli range, as well as attractions such as vast underground water-storage tanks, a medieval canon foundry and an impressive collection of medieval cannons with the Jaivana which is supposed to be the world's largest cannon on wheels. in the past this was the original Amber Fort, although it became known as Jaigarh from the time of Sawai Jai Singh II onwards.
Jal Mahal is located in Jaipur India, which is the capital of the State of Rajasthan. It is on the way to Sisodia garden. The rajput style "Water Palace" sits in the center of the Man Sarobar lake. The lake is frequently dry in the summer but winter monsoons frequently turn it into a beautiful lake filled with water hyacinths.
Amber Palace The Amber Palace complex overlooking the artificial lake south of the town of Amber is one of the most well-liked tourist sites in the city, famous for its mixture of Hindu and Muslim architecture, and offering elephant rides from the town up to the palace courtyard. Although the structure is today known as Amber Fort, the complex was at first a Palace Complex within the Fort of Amber which is today known as Jaigarh fort.
Jaigarh Fort The Jaigarh Fort on the hills above the Amber Palace complex offers stunning views of the foothills of the Aravalli range, as well as attractions such as vast underground water-storage tanks, a medieval canon foundry and an impressive collection of medieval cannons with the Jaivana which is supposed to be the world's largest cannon on wheels. in the past this was the original Amber Fort, although it became known as Jaigarh from the time of Sawai Jai Singh II onwards.
Jal Mahal is located in Jaipur India, which is the capital of the State of Rajasthan. It is on the way to Sisodia garden. The rajput style "Water Palace" sits in the center of the Man Sarobar lake. The lake is frequently dry in the summer but winter monsoons frequently turn it into a beautiful lake filled with water hyacinths.
Friday, March 09, 2007
Recreation
Recreation is the use of time in a non-profitable way, in many ways also therapeutic refreshment of one's body or mind. While leisure is more likely a type of entertainment or rest, recreation is active for the participant but in a refreshing and diverting manner. As people in the world's richer regions lead increasingly sedentary life styles, the need for recreation has grown. The rise of so called active vacations exemplifies this trend.
Monday, March 05, 2007
Air pollution
Air pollution is a chemical, physical (e.g. particulate matter), or biological agent that modifies the normal characteristics of the atmosphere. Stratospheric ozone depletion due to air pollution has long been known as a threat to human health as well as to the earth's ecosystems.
Worldwide air pollution is in charge for large numbers of deaths and cases of respiratory disease. Enforced air quality standards, like the Clean Air Act in the United States, have reduced the occurrence of some pollutants. While major stationary sources are often identified with air pollution, the greatest source of emissions are in fact mobile sources, principally the automobile. Gases such as carbon dioxide, which contribute to global warming, have newly gained recognition as pollutants.
Worldwide air pollution is in charge for large numbers of deaths and cases of respiratory disease. Enforced air quality standards, like the Clean Air Act in the United States, have reduced the occurrence of some pollutants. While major stationary sources are often identified with air pollution, the greatest source of emissions are in fact mobile sources, principally the automobile. Gases such as carbon dioxide, which contribute to global warming, have newly gained recognition as pollutants.
Thursday, March 01, 2007
Magnets
Magnets are materials that creates a magnetic field of their own. Extreme examples of magnets are "hard", or "permanent" magnets (like refrigerator magnets), which remember how they have been magnetized, and "soft", or "impermanent" magnets (like the material of the refrigerator door), which lose their memory of previous magnetizations. "Soft" magnets are often used in electromagnets to enhance (often by factors of hundreds or thousands) the magnetic field of a current-carrying wire that has been wrapped in the region of the magnet; when the current increases, so does the field of the "soft" magnet, which is much larger than the field due to the current. Permanent magnets occur naturally in some rocks, mainly lodestone, but they are now more commonly manufactured.
Materials without a permanent magnetic moment can, in the occurrence of magnetic fields, be attracted (paramagnetic), or repelled (diamagnetic). Liquid oxygen is paramagnetic; graphite is diamagnetic. "Soft" magnets, which are powerfully attracted to magnetic fields, can be thought of as strongly paramagnetic; superconductors, which are strongly repelled by magnetic fields, can be thought of as strongly diamagnetic.
Materials without a permanent magnetic moment can, in the occurrence of magnetic fields, be attracted (paramagnetic), or repelled (diamagnetic). Liquid oxygen is paramagnetic; graphite is diamagnetic. "Soft" magnets, which are powerfully attracted to magnetic fields, can be thought of as strongly paramagnetic; superconductors, which are strongly repelled by magnetic fields, can be thought of as strongly diamagnetic.
Friday, February 23, 2007
Desalination
Desalination refers to any of several processes that take away the excess salt and other minerals from water in order to obtain fresh water fit for animal consumption or irrigation, and if almost all of the salt is removed, for human consumption, sometimes producing table salt as a by-product. Desalination of brackish water is previously commonplace in the U.S., where it is used to meet treaty obligations for river water
entering Mexico. Indeed, desalination has spread into use in over a hundred countries, with Saudi Arabia accounting for about 24% of total world capacity. Kuwait built the world's first large-scale desalination plant in the 1960s. Kuwait's energy reserves are so great that Kuwait is unique in using desalinated water for agriculture. The world's largest desalination plant is in Ashkelon, Israel. It began in use on August 4, 2005, and it is capable of producing 100 million cubic meters of water per year.
entering Mexico. Indeed, desalination has spread into use in over a hundred countries, with Saudi Arabia accounting for about 24% of total world capacity. Kuwait built the world's first large-scale desalination plant in the 1960s. Kuwait's energy reserves are so great that Kuwait is unique in using desalinated water for agriculture. The world's largest desalination plant is in Ashkelon, Israel. It began in use on August 4, 2005, and it is capable of producing 100 million cubic meters of water per year.
Monday, February 19, 2007
Mercury (element)
Mercury also called quicksilver, is a chemical component in the periodic table that has the symbol Hg (Latinized Greek: hydrargyrum, meaning watery or liquid silver) and atomic number 80. A important, silvery transition metal, mercury is one of five elements that are liquid at or near standard room temperature and pressure (the others are the metals caesium, francium, and gallium, and the nonmetal bromine). Mercury is used in thermometers, barometers and other scientific apparatus, although the use of mercury in thermometers has been mostly phased out in clinical and scientific environments (in favor of alcohol-filled, digital or thermistor-based replacements) due to concerns about the element's toxicity. Mercury is still used in dental amalgam. Mercury is frequently obtained by reduction from the mineral cinnabar. Mercury, like lead, is a neurotoxin, and elevated blood mercury levels have led to retardation and deformities in children.
Tuesday, February 13, 2007
Massive stars
During their helium-burning phase, very high mass stars with more than nine solar masses increased to form red supergiants. Once this fuel is exhausted at the core, they can carry on to fuse elements heavier than helium. The core contracts until the temperature and pressure are enough to fuse carbon. This process continues, with the consecutive stages being fueled by oxygen, neon, silicon, and sulfur. Near the end of the star's life, fusion can occur along a series of onion-layer shells within the star. Each shell fuses a different element, with the outermost shell fusing hydrogen; the next shell fusing helium, and so forth.The final stage is reached when the star begins producing iron. Since iron nuclei are more tightly bound than any heavier nuclei, if they are fused they do not release energy — the process would, on the contrary, consume energy. Likewise, since they are more tightly bound than all lighter nuclei, energy cannot be free by fission.In relatively old, very massive stars, a large core of inert iron will accumulate in the center of the star. The heavier elements in these stars can work their way up to the surface, forming evolved objects known as Wolf-Rayet stars that have a dense stellar wind which sheds the outer atmosphere.
Tuesday, February 06, 2007
gold
Gold is a extremely sought-after valuable metal that for many centuries has been used as money, a store of value and in ornaments. The metal occurs as nugget or grains in rocks and in alluvial deposits and is one of the coinage metals. It is a soft, glossy, yellow, dense, malleable, and ductile (trivalent and univalent) change metal. Modern manufacturing uses include dentistry and electronics. Gold forms the basis for a financial typical used by the International Monetary Fund (IMF) and the Bank for International resolution (BIS). Its ISO currency code is XAU.
Gold is a tinny element with a trait yellow color, but can also be black or ruby when finely alienated, while colloidal solutions are intensely tinted and often purple. These colors are the effect of gold's plasmon frequency lying in the visible range, which causes red and yellow glow to be reflected, and blue light to be engrossed. Only silver colloids show the same interactions with light, albeit at a shorter occurrence, making silver colloids yellow in color.
Gold is a good conductor of temperature and electricity, and is not precious by air and most reagents. Heat, damp, oxygen, and most corrosive agents have very little chemical effect on gold, making it well-suited for use in coins and jewelry; equally, halogens will chemically alter gold, and aqua regia dissolve it.
Pure gold is too soft for ordinary use and is hard-boiled by alloying with silver, copper, and other metals. Gold and its lots of alloys are most often used in jewelry, coinage and as a typical for monetary exchange in various countries. When promotion it in the form of jewelry, gold is calculated in karats (k), with pure gold being 24k. However, it is more commonly sold in lower capacity of 22k, 18k, and 14k. A lower "k" indicates a higher percent of copper or silver assorted into the alloy, with copper being the more typically used metal between the two. Fourteen karat gold-copper alloy will be almost identical in color to definite bronze alloys, and both may be used to produce polish and added badges. Eighteen karat gold with a high copper content is establish in some traditional jewelry and will have a distinct, though not dominant copper cast, giving an attractively warm color. A comparable karat weight when alloyed with silvery metals will appear less humid in color, and some low karat white metal alloys may be sold as "white gold", silvery in exterior with a slightly yellow cast but far more resistant to decay than silver or sterling silver. Karat weights of twenty and higher is more general in modern jewelry. Because of its high electrical conductivity and confrontation to decay and other desirable combinations of physical and chemical properties, gold also emerged in the late 20th century as an vital industrial metal, particularly as thin plating on electrical card associates and connectors.
Gold is a tinny element with a trait yellow color, but can also be black or ruby when finely alienated, while colloidal solutions are intensely tinted and often purple. These colors are the effect of gold's plasmon frequency lying in the visible range, which causes red and yellow glow to be reflected, and blue light to be engrossed. Only silver colloids show the same interactions with light, albeit at a shorter occurrence, making silver colloids yellow in color.
Gold is a good conductor of temperature and electricity, and is not precious by air and most reagents. Heat, damp, oxygen, and most corrosive agents have very little chemical effect on gold, making it well-suited for use in coins and jewelry; equally, halogens will chemically alter gold, and aqua regia dissolve it.
Pure gold is too soft for ordinary use and is hard-boiled by alloying with silver, copper, and other metals. Gold and its lots of alloys are most often used in jewelry, coinage and as a typical for monetary exchange in various countries. When promotion it in the form of jewelry, gold is calculated in karats (k), with pure gold being 24k. However, it is more commonly sold in lower capacity of 22k, 18k, and 14k. A lower "k" indicates a higher percent of copper or silver assorted into the alloy, with copper being the more typically used metal between the two. Fourteen karat gold-copper alloy will be almost identical in color to definite bronze alloys, and both may be used to produce polish and added badges. Eighteen karat gold with a high copper content is establish in some traditional jewelry and will have a distinct, though not dominant copper cast, giving an attractively warm color. A comparable karat weight when alloyed with silvery metals will appear less humid in color, and some low karat white metal alloys may be sold as "white gold", silvery in exterior with a slightly yellow cast but far more resistant to decay than silver or sterling silver. Karat weights of twenty and higher is more general in modern jewelry. Because of its high electrical conductivity and confrontation to decay and other desirable combinations of physical and chemical properties, gold also emerged in the late 20th century as an vital industrial metal, particularly as thin plating on electrical card associates and connectors.
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