.... in the late 1960's. The interconnection of computer systems over telecommunication networks soon became a requirement. Modems were used at first to generate analogue signals compatible with the PSTNs from the digital computer data to allow such interconnections. The already wide spread use of the PSTNs was an advantage of this scheme, however it was soon recognized as not being an optimum solution for data transfer. The analogue PSTNs were unsuitable in terms of switching, capacity (bandwidth) and channel noise. In data communication applications, data tends to be transferred in bursts, separated by silence. The constant conn .....

.... energy that is being supplied to the cell. This cellular degeneration may be set into action by highly reactive chemicals known as free radicals. These molecules have an unpaired electron in the outermost valence shell. This causes the molecule to grab electrons from other molecules, setting into motion a chain reaction that destabilizes them, and causes death of the cell. These free radicals are the normal by-product of metabolism, and can also form due to exposure to radiation or toxic chemicals. Enzymes that usually inactivate these free radicals diminish in later years, thus increasing their danger. The active process of a .....

.... see only half of her teacher and bright lights and flashes up to 20 minutes before her Migraine began. These symptoms are called auras and once they are gone the Migraine begins. The Migraine itself can lead to vomiting, slurred speech, makes the sufferer sensitive to light and worsens when there is a lot of noise. The mechanism is not completely understood, but many women have their most severe attacks during or just before their menstrual period. This is supposedly due to the hormonal imbalance during that time. So, what can we do to prevent Migraines? Because Migraine headaches can recur for years and medication may lead to .....

.... It was therefore fortunate that Miller changed the species name to esculentum which roughly means "edible". The common cultivated tomato belongs to the genus Lycopersicon. This genus exhibits a vast reservoir of genetic variability which remains largely underexploited. Some disease resistance, which is now a part of most commercially available cultivars, has been derived from related species of Lycopersicon. However, these other species may provide other potential benefits such as heat or cold tolerance, salt tolerance, higher nutrient amounts and possibly other yet undiscovered potentials. Some of these species cross readily to .....

.... two captive nuclei leading them to overcome their natural repulsion of each other and fuse. This reaction produces a larger nucleus that almost immediately shatters, releasing energy. It also frees the muon, which can then repeat the cycle, causing several hundred more such fusions. The fact that the muon is 207 times heavier than an electron gives support for this theory. A nuclei is orbited by an electron making a mini- solar system. If a muon is shot at the nuclei, it will bump the electrons into a smaller orbit and replace their orbit with muons. This then closes tightly around the atom, crushing the atom and nuc .....

.... miles. When there is enough food, the tiger lives in a much smaller territorty. It lives in the forest, the grassland, or the swamps. The tiger attacks a variety of prey, mainly deer, antelopes, pigs and buffalo. Once in awhile, it will attack cattle and even humans. There are many stories about the evils done by "man-eating" tigers. They're usually old tigers that are sick or wounded, and cannot hunt normally. The destruction of their usual prey may also cause them to attack humans. As soon as the tiger spots prey, it begins a slow and silent approach. When it is near it's prey, it charges. It may jump onto the prey's back o .....

.... as 30 percent for up to three hours. Large fluid losses on a hot day can lead to dehydration. Increased stomach acid can aggravate ulcers or hightail hernia, and cause nausea, vomiting and diarrhea. can cause an accelerated and irregular heartbeat. Where lifts your spirits, when it wears off there can be bouts of depression. If drank too close to bedtime, can disrupt your sleep. You can get the shakes from . Recent studies have failed to find any relationship between and strokes or increased risk of heart attack. There is no evidence that causes cancer, elevated cholesterol or high blood pressure. You can have , b .....

.... animals, thousands of forest and brush fires, as well as millions of dollars in damage to buildings, communications systems, power lines, and electrical systems are also the result of lightning. Finally, the threat of lightning causes many work stoppages and lost production increasing the time and cost required to prepare NASA spacecraft for flight. Benjamin Franklin performed the first systematic, scientific study of lightning during the second half of the 18th century. Prior to that time, electrical science had developed to the point where positive and negative charges could be separated. Electrical machines could, by rubbing to .....

.... McAuliffe, born in 1948, was the famous winner of the teacher-in-space program, was a high school teacher at Concord, N. H., a wife, and a mother of two children. She touched the lives of all those she knew and taught. As a school official in Concord said after her death, "To us, she seemed average. But she turned out to be remarkable. She handled success so beautifully." She also wanted everyone to learn more, including herself. Demonstrating her aspirations after entering the space program, she is quoted saying, "What are we doing here? We're reaching for the stars." Also, after reflecting on her position, she .....

.... allotropes, normal oxygen and ozone. Pure carbon also has two allotropes, diamond and graphite. A crystal of diamond is in fact a single giant molecule in which every carbon atom is linked to four other, by four equal, strong bonds. These bonds are arranged tetrahedrally round each atom and there are no planes along which the giant molecule can easily be split. This quality is what gives diamond its tremendous hardness. Graphite on the other hand, consists of flat sheets of carbon atoms arranged in adjoining rings. Each carbon atom is linked to three others by fairly strong bond that all lie in the same plane. These can easily be .....