.... of a gas in a container and then wighing it. In the 20th century, most scientists used oxygen as the standard gas to compare other gases' weights. It is relativly easy to measure the weights of liquids and sloids, the same procedure for gas is followed, more or less. In the early 1960s, though, the international union of chemistry and physics agreed that there would be a new standard, carbon isotope (carbon-12). British physicist Ernest Rutherford found and proved that an atom's mass is concentrated in its its nucleus, which is the center of the atom. He al .....

.... this process is repeated over, it becomes a self-sustaining chain reaction. This energy producing process is called a chain reaction. uses the uranium-235 element because it is the easiest of all atoms to split apart. Uranium-235 is made up of many protons and few neutrons. Protons naturally repel one another so a nucleus made up of many protons tends to ‘fly apart’ more easily. In addition, uranium makes a good nuclear reactor because it can sustain a series of fission reactions, each time producing more neutrons in chain reaction. Therefore, uranium-235 c .....

.... to high levels of radiation. Even the government declared that nuclear powers were safe and efficient. The truth is that accidents do happen at nuclear power plants and at other facilities all the time. An accident at a nuclear power plant has the potential to be much more harmful than an accident at a coal or gas plant because of the radiation that could be released. An example of this is Three Mile Island in Pennsylvania where there was a partial core meltdown in march of 1979 caused large amounts of radiation to be released into the atmosphere. Accidents .....

.... difficulties. This understanding often brings a solution to the problems. A psychologist's specialty and place of employment determines their working conditions. Clinical, school, and counseling psychologists in private practice have pleasant, comfortable offices and set their own hours. However, they often must offer evening hours to accommodate their clients. Those employed in hospitals, nursing homes, and other health facilities may work evenings and weekends, while those who work in schools and clinics generally work regular hours. Psychologists employed as .....

.... population was dramatically reduced when about 300,00 of its inhabitants died from some sickness. Some people now believe that this great plague was really Ebola. The first recorded outbreak of the Zaire string of the Ebola virus was in Zaire, in 1976. The doctors didn't know how to treat it and that meant that they didn't know how to contain it either. As infected people met in public places the virus spread. In Western Sudan, the same year, the Sudan string of the Ebola virus emerged with similar results. Both casts together had about a total of .....

.... of metal sulfate ore produces pure metal. This causes the release of sulfur dioxide. Sulfur dioxide can also be emitted into the atmosphere ny natural disasters or means. This ten percent of all sulfur dioxide emission comes from volcanoes, sea spray, plankton, and rotting vegetation. The oxides of nitrogen are by-products of firing processes of extreme high temperatures, for example: automobiles, and utility plants; and in chemical industries, for example: fertilizer production, etc. Also, natural processes such as bacterial action in soil, forest fir .....

.... to categorize cs as all those who merely complain about their sleep. The currently accepted definition, to become known as DIMS (Difficulty Initiating or Maintaining Sleep). Several surveys have tried to pin down the exact cause of sleep problems. Of 1,000 households, one third had someone with current problems and in 42 percent someone had suffered from sleep disorders at sometime. Some doctor's polls have been revealing yet somewhat disparate. In one survey, roughly 19 percent of the patients seen by the 3,000 doctors had complaints of some type of . That .....

.... red-cockaded woodpecker (Picoides borealis) is an endangered species that inhabits pine forests in an historical range from Texas to the Atlantic coast (Jackson, 1986; Reed et al., 1988). Picoides borealis nest in clans or family groups that usually consist of one breeding pair and 2 non-breeding male helpers (Jackson, 1986 ). This group establishes and defends a territory that includes foraging habitat and nesting "cavity trees" (Copeyon et al., 1991; Jackson et al., 1986; Rossell and Gorsira, 1996). Red-cockaded woodpecker clans excavate .....