A calorie is a unit of measurement for energy. Calorie is French and derives from the Latin calor (heat). In most fields, it has been replaced by the joule, the SI unit of energy. However, the kilocalorie or Calorie (capital "C") remains in common use for the amount of food energy.
Definitions for calorie fall into 3 classes:
The small calorie or gram calorie approximates the energy needed to increase the temperature of 1 gram of water by 1 °C. This is about 4.184 joules.
The large calorie or kilogram calorie approximates the energy needed to increase the temperature of 1 kg of water by 1 °C. This is about 4.184 kJ, and exactly 1000 small calories.
The mega calorie or ton calorie[citation needed] approximates the energy needed to increase the temperature of 1 ton of water by 1 °C. This is about 4.184 MJ, and exactly 1000 large calories.
In scientific contexts, the name "calorie" refers strictly to the gram calorie, and this unit has the symbol cal. SI prefixes are used with this name and symbol, so that the kilogram calorie is known as the "kilocalorie" and has the symbol kcal. In non-scientific contexts the kilocalorie is often referred to as a Calorie (capital "C"), or just a calorie, and it has to be inferred from the context that the small calorie is not intended.
The conversion factor between calories and joules is numerically equivalent to the specific heat capacity of liquid water (in SI units).
1 calINT = 4.1868 J (1 J = 0.23885 calIT)
1 calth = 4.184 J (1 J = 0.23901 calth)
1 cal15 = 4.18580 J (1 J = 0.23890 cal15)
Saturday, August 25, 2007
minerals(fluorescent)
There are several ways that minerals can emit light, besides the light that is emitted from exposure to daylight or the light from normal light bulbs. Some of these ways involve special lamps that emit non-visible ultraviolet light (at least not visible to humans). The light from these ultraviolet lamps reacts with the chemicals of a mineral and causes the mineral to glow; this is called fluorescence. If the mineral continues to glow after the light has been removed, this is called phosphorescence. Some minerals will glow when heated; this is called thermoluminescence. And there are some minerals that will glow when they are stuck or crushed; this is called triboluminescence.
The fluorescent minerals are minerals that emit visible light when activated by invisible ultraviolet light (UV), X-rays and/or electron beams. Certain electrons in the mineral absorb the energy from these sources and jump to a higher energy state. The fluorescent light is emitted when those electrons jump down to a lower energy state and emit a light of their own. Although most collectors do not have access to X-ray or high energy electron emitters, they do have access to affordable ultraviolet lamps. The visible light emitted after being activated by UV light is sometimes very colorful and can often be very different from the normal color of the mineral. Collecting fluorescent minerals is a popular hobby and experienced collectors can use fluorescence for identification purposes. At night or in dark mines or caves, fluorescence can be used to find certain mineral deposits and is a viable prospecting technique.
There are two kinds of ultraviolet light, longwave and shortwave. Longwave UV light is known as "black light" and most people are familiar with its effects of making white clothing glow in the dark. This is due to whitening chemicals in detergents. Remember the slogan "Whiter than white"? See the table of longwave fluorescent minerals.
Shortwave UV light is by definition of a shorter wavelength than the longwave UV light. Shortwave lamps which are available to collectors, can be very entertaining and useful to identify minerals, however it is dangerous to look at the shortwave light source (it can cause blindness) and they should not be used without adult supervision. See the table of shortwave fluorescent minerals. A lamp that can emit longwave and shortwave light is preferred as many fluorescent minerals emit different colors under different wave lengths and some only fluoresce under one but not the other.
Activator elements are responsible for fluorescence. But not all specimens have these activator elements. Care in identifying minerals, using UV fluorescence, should therefore be taken. Some minerals will have consistent colors as in they will always fluoresce red for example while other minerals may have many different colors from one locality to another. Also, one specimen may fluoresce and another specimen of the same mineral may not fluoresce at all. So how can fluorescence help in identifying minerals?
Well, fluorescence is not a common phenomenon being found in only certain minerals. If two minerals are similar and yet one is listed as a possible fluorescent mineral, a fluorescence test could prove important. However if an unknown mineral does not fluoresce, it should not so quickly be dismissed as not being the suspected fluorescing mineral, unless that mineral is reported to always fluoresce. Fluorescence is not usually an absolute property found in all specimens of even a named fluorescent mineral, but there do exist some minerals that are so reliably fluorescent that fluorescence is the best test to use. The tables to the left include the more common fluorescent minerals that are popular with collectors. Compare the minerals found in different wavelengths and in different colors
The fluorescent minerals are minerals that emit visible light when activated by invisible ultraviolet light (UV), X-rays and/or electron beams. Certain electrons in the mineral absorb the energy from these sources and jump to a higher energy state. The fluorescent light is emitted when those electrons jump down to a lower energy state and emit a light of their own. Although most collectors do not have access to X-ray or high energy electron emitters, they do have access to affordable ultraviolet lamps. The visible light emitted after being activated by UV light is sometimes very colorful and can often be very different from the normal color of the mineral. Collecting fluorescent minerals is a popular hobby and experienced collectors can use fluorescence for identification purposes. At night or in dark mines or caves, fluorescence can be used to find certain mineral deposits and is a viable prospecting technique.
There are two kinds of ultraviolet light, longwave and shortwave. Longwave UV light is known as "black light" and most people are familiar with its effects of making white clothing glow in the dark. This is due to whitening chemicals in detergents. Remember the slogan "Whiter than white"? See the table of longwave fluorescent minerals.
Shortwave UV light is by definition of a shorter wavelength than the longwave UV light. Shortwave lamps which are available to collectors, can be very entertaining and useful to identify minerals, however it is dangerous to look at the shortwave light source (it can cause blindness) and they should not be used without adult supervision. See the table of shortwave fluorescent minerals. A lamp that can emit longwave and shortwave light is preferred as many fluorescent minerals emit different colors under different wave lengths and some only fluoresce under one but not the other.
Activator elements are responsible for fluorescence. But not all specimens have these activator elements. Care in identifying minerals, using UV fluorescence, should therefore be taken. Some minerals will have consistent colors as in they will always fluoresce red for example while other minerals may have many different colors from one locality to another. Also, one specimen may fluoresce and another specimen of the same mineral may not fluoresce at all. So how can fluorescence help in identifying minerals?
Well, fluorescence is not a common phenomenon being found in only certain minerals. If two minerals are similar and yet one is listed as a possible fluorescent mineral, a fluorescence test could prove important. However if an unknown mineral does not fluoresce, it should not so quickly be dismissed as not being the suspected fluorescing mineral, unless that mineral is reported to always fluoresce. Fluorescence is not usually an absolute property found in all specimens of even a named fluorescent mineral, but there do exist some minerals that are so reliably fluorescent that fluorescence is the best test to use. The tables to the left include the more common fluorescent minerals that are popular with collectors. Compare the minerals found in different wavelengths and in different colors
GEMSTONES
AMethyst Galleries' Mineral Gallery "The First Internet Rock Shop!"THE GEMSTONES "The Flowers of the Mineral Kingdom"
As colorful as the rainbow and as sparkling as fine leaded crystal, gemstones have captured the imaginations and desires of men and perhaps especially, women, for ages. The pursuit of gems have become the subject of legends, fairy tales, epics, and major motion pictures ("Romancing the Stone", for one). Today, more fine gemstone specimens are available to the average person than at any time in history.
What makes a gemstone?
Generally speaking, a gemstone is a stone that is beautiful, rare, and durable (resistant to abrasion, fracturing and chemical reactions). Some minerals can be very beautiful, but they may be too soft and will scratch easily (such as the mineral fluorite). Fluorite is extremely colorful and pretty but has a hardness of only 4 on the Moh's hardness scale and has four perfect cleavage directions, which makes it only an oddity as a cut gem. Others are too common and are given a semi-precious status (such as agate). Most gemstones have good hardness (above 5) and a high index of refraction (the higher the index of refraction the greater the sparkle). All gemstones have some characteristics falling short of perfection though; even the seemingly perfect Diamond has four directions of cleavage.
Most gems are silicates which can be very stable, hard minerals. A few gems are oxides and only one gem, diamond, is composed of a single element, carbon. There are also a few gemstones that are not true minerals (called mineraloids) but are included here: opal, amber, and moldavite. While almost any mineral can be cut in the manner of a gemstone, below is a list of some of the gem kingdom's more prized and recognized members:
What makes a Precious Metal
Like gemstones, one of the characteristics of a precious metal is its rarity. It could not be "precious" if it were common! Two other characteristics are also important. Foremost is durability - it must not easily corrode away, nor can it be brittle. And that is related to the third characteristic, ductility. This means that the metal must be malleable, that it can be bent, hammered, or otherwise shaped. Gold is the most malleable of metals (it can be hammered into incredibly thin foils or drawn into extremely fine wires), it does not corrode or dissolve except under the most extreme conditions. It is so durable that nearly all of the gold ever mined is still in circulation or storage.
As colorful as the rainbow and as sparkling as fine leaded crystal, gemstones have captured the imaginations and desires of men and perhaps especially, women, for ages. The pursuit of gems have become the subject of legends, fairy tales, epics, and major motion pictures ("Romancing the Stone", for one). Today, more fine gemstone specimens are available to the average person than at any time in history.
What makes a gemstone?
Generally speaking, a gemstone is a stone that is beautiful, rare, and durable (resistant to abrasion, fracturing and chemical reactions). Some minerals can be very beautiful, but they may be too soft and will scratch easily (such as the mineral fluorite). Fluorite is extremely colorful and pretty but has a hardness of only 4 on the Moh's hardness scale and has four perfect cleavage directions, which makes it only an oddity as a cut gem. Others are too common and are given a semi-precious status (such as agate). Most gemstones have good hardness (above 5) and a high index of refraction (the higher the index of refraction the greater the sparkle). All gemstones have some characteristics falling short of perfection though; even the seemingly perfect Diamond has four directions of cleavage.
Most gems are silicates which can be very stable, hard minerals. A few gems are oxides and only one gem, diamond, is composed of a single element, carbon. There are also a few gemstones that are not true minerals (called mineraloids) but are included here: opal, amber, and moldavite. While almost any mineral can be cut in the manner of a gemstone, below is a list of some of the gem kingdom's more prized and recognized members:
What makes a Precious Metal
Like gemstones, one of the characteristics of a precious metal is its rarity. It could not be "precious" if it were common! Two other characteristics are also important. Foremost is durability - it must not easily corrode away, nor can it be brittle. And that is related to the third characteristic, ductility. This means that the metal must be malleable, that it can be bent, hammered, or otherwise shaped. Gold is the most malleable of metals (it can be hammered into incredibly thin foils or drawn into extremely fine wires), it does not corrode or dissolve except under the most extreme conditions. It is so durable that nearly all of the gold ever mined is still in circulation or storage.
minerals
Dietary minerals are the chemical elements required by living organisms, other than the four elements carbon, hydrogen, nitrogen, and oxygen which are present in common organic molecules. The term "mineral" is archaic, since the intent of the definition is to describe ions, not chemical compounds or actual minerals. Furthermore, once dissolved, so-called minerals do not exist as such, sodium chloride breaks down into sodium ions and chloride ions in aqueous solution. Some dieticians recommend that these heavier elements should be supplied by ingesting specific foods (that are enriched in the element(s) of interest), compounds, and sometimes including even minerals, such as calcium carbonate. Sometimes these "minerals" come from natural sources such as ground oyster shells. Sometimes minerals are added to the diet separately from food, such as mineral supplements, the most famous being iodine in "iodized salt." Dirt eating, called pica or geophagy is practiced by some as a means of supplementing the diet with elements. The chemical composition of soils will vary depending on the location.
Vitamins, which are not considered minerals, are organic compounds, some of which contain heavy elements such as iodine and cobalt. The dietary focus on "minerals" derives from an interest in supporting the biosynthetic apparatus with the required elemental components.[1] Appropriate intake levels of certain chemical elements is thus required to maintain optimal health. Commonly, the requirements are met with a conventional diet. Excessive intake of any element (again, usually as an ion) will lead to poisoning. For example, large doses of selenium are lethal. On the other hand, large doses of zinc are less dangerous but can lead to a harmful copper deficiency (unless compensated for, as in the Age-Related Eye Disease Study).
Dietary minerals classified as "macromineral" are required in relatively large amounts. Conversely "microminerals" or "trace minerals" are required relatively in minute amounts. There is no universally accepted definition of the difference between "large" and "small" amounts.
Vitamins, which are not considered minerals, are organic compounds, some of which contain heavy elements such as iodine and cobalt. The dietary focus on "minerals" derives from an interest in supporting the biosynthetic apparatus with the required elemental components.[1] Appropriate intake levels of certain chemical elements is thus required to maintain optimal health. Commonly, the requirements are met with a conventional diet. Excessive intake of any element (again, usually as an ion) will lead to poisoning. For example, large doses of selenium are lethal. On the other hand, large doses of zinc are less dangerous but can lead to a harmful copper deficiency (unless compensated for, as in the Age-Related Eye Disease Study).
Dietary minerals classified as "macromineral" are required in relatively large amounts. Conversely "microminerals" or "trace minerals" are required relatively in minute amounts. There is no universally accepted definition of the difference between "large" and "small" amounts.
Friday, August 24, 2007
What is ICMP?
ICMP is Internet Control Message Protocol, a network layer protocol of the TCP/IP suite used by hosts and gateways to send notification of datagram problems back to the sender. It uses the echo test / reply to test whether a destination is reachable and responding. It also handles both control and error messages.
What is autonomous system?
It is a collection of routers under the control of a single administrative authority and that uses a common Interior Gateway Protocol.
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