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EFFECTS OF IONIZING RADIATION 1 Everyone on Earth is continually exposed to small, relatively harmless amounts of ionizing radiation, known as background radiation, from natural sources such as soil and rock. However, other types of ionizing radiation--x-rays, ultraviolet radiation from the sun, and alpha, beta, and gamma radiation emitted by radioactive isotopes--have the potential to harm the human body. Ionizing radiation has enough energy to remove one or more electrons from the atoms it hits to form positively charged ions that can react with and damage living tissue. Most damage occurs in tissues with rapidly dividing cells, such as the bone marrow, where blood cells are made, and the digestive tract, whose lining must be constantly renewed. 2 Exposure to ionizing radiation can damage cells in two ways. The first is genetic damage, which alters genes and chromosomes. This can show up as a genetic defect in children or in later generations. The second type of damage is somatic, which causes victims direct harm in the form of bums, miscarriages, eye cataracts, some types of leukemia, or cancers of the bone, thyroid, breast, skin, and lung. Small doses of ionizing radiation over a long period of time cause less damage than the same total dosage given all at once. Exposure to a large dose of ionizing radiation over a short time can be fatal within a few minutes to a few months later. Which exposure to ionizing radiation causes the most serious damage to humans
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Our company is ______ of other makers of spare parts for the airplane.
EFFECTS OF IONIZING RADIATION 1 Everyone on Earth is continually exposed to small, relatively harmless amounts of ionizing radiation, known as background radiation, from natural sources such as soil and rock. However, other types of ionizing radiation--x-rays, ultraviolet radiation from the sun, and alpha, beta, and gamma radiation emitted by radioactive isotopes--have the potential to harm the human body. Ionizing radiation has enough energy to remove one or more electrons from the atoms it hits to form positively charged ions that can react with and damage living tissue. Most damage occurs in tissues with rapidly dividing cells, such as the bone marrow, where blood cells are made, and the digestive tract, whose lining must be constantly renewed. 2 Exposure to ionizing radiation can damage cells in two ways. The first is genetic damage, which alters genes and chromosomes. This can show up as a genetic defect in children or in later generations. The second type of damage is somatic, which causes victims direct harm in the form of bums, miscarriages, eye cataracts, some types of leukemia, or cancers of the bone, thyroid, breast, skin, and lung. Small doses of ionizing radiation over a long period of time cause less damage than the same total dosage given all at once. Exposure to a large dose of ionizing radiation over a short time can be fatal within a few minutes to a few months later. According to the passage, what is one difference between background radiation and other types of ionizing radiation
ICE 1 Two conditions are necessary for the formation of ice: the presence of water and temperatures below freezing. Ice in the atmosphere and on the ground can assume various forms, depending on the conditions under which water is converted to its solid state~ Ice that forms in the atmosphere can fall to the ground as snow, sleet, or hail. Snow is an assemblage of ice crystals in the form of flakes; sleet is a collection of frozen raindrops, which are actually ice pellets. Hail consists of rounded or jagged lumps of ice, often in layers like the intemal structure of an onion. Ice also forms directly on the ground or on bodies of water. In North America, ice forms in late autumn, winter, and early spring. On very large bodies of water, it may not form until late winter because there must be several months of low temperatures to chill such large amounts of water. 2 On puddles and small ponds, ice first freezes in a thin layer with definite crystal structure that becomes less apparent as the ice thickens. On lakes large enough to have waves, such as the Great Lakes, the first ice to form is a thin surface layer of slush, sometimes called grease ice, which eventually grows into small floes of pancake ice. If the lake is small enough or the weather cold enough, the floes may freeze together into a fairly solid sheet of pack ice. Pack ice may cover the entire lake or be restricted to areas near the shore. 3 Because water expands when it freezes, ice is less dense than liquid water and therefore floats rather than sinks in water. As ice floats on the surface of a lake, ocean, or river, it acts as an insulator and is thus important in maintaining the balance of the ecosystem. Without the insulating effect of floating ice sheets, surface water would lose heat more rapidly, and large bodies of water such as the Arctic Ocean and Hudson Bay might freeze up completely. When ice starts to form on small bodies of water,
RURAL CANADA 1 In the 1880s, over three-fourths of Canada’s population lived outside urban centers. One view of rural Canada at that time portrays it as a vast wasteland of isolated farm communities. However, a more accurate view shows that rural Canadians had access to considerable information. The postal service was efficient and inexpensive and connected rural Canadians with the outside world. Many farm families received at least one newspaper through the mail, usually within a day of publication. The daily newspapers of the period were more substantial than those of today, and many reproduced precise accounts of court trials and public events. Rural Canadians read magazines and books and held discussions about them at club meetings. 2 Rural Canadians were also able to get together socially. The local school served other functions besides providing formal education, and school districts were often the only sign of political organization in vast regions of the country. Every community valued its one- room schoolhouse as a meeting place, especially during the winter, when work on the farm was much lighter and people had more time for a variety of social and cultural events. People of all ages got together to sing and play musical instruments, perform skits, and play parlor games. 3 Between 1880 and 1920, there was a growing exodus from farms to the city, mainly because smaller farms could not afford to modernize their technology and were no longer able to support the entire family. However, most Canadians continued to hold rural values, and artists and writers romanticized the family farm. In the novel Anne of Green Gables (1908), Lucy Maud Montgomery wrote about a young woman who strove to reconcile the beauty and peace of the rural landscape with the need to leave it in order to fulfill her ambitions. For large numbers of young Canadians, growing up meant leaving the farm to find work in the city. According to the passage, rural Canada in the 1880s was not an isolated wasteland because
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