American Scientist

Online ISSN: 1545-2786
Print ISSN: 0003-0996
Evidence for the fluid-like flow of rock debris is discussed, together with a conceptual model for the underlying processes. The phenomenon occurs with both crater walls and long-runout landslides. It is suggested that individual rocks in a debris mass may possess a degree of random motion and act like a dense gas, thereby being capable of flowing like a fluid. A sound wave propagating through a pile of rocks in contact and supporting an overburden of debris can be separated by half the sound wavelength and relieve the immobilizing overburden pressure. Exceeding the pressure permits the rocks to flow. The debris can be located on a gentle slope because of the efficiency of the conversion of gravitational potential energy to acoustic energy. The distance the mass will slide forward is proportional to its thickness. Applications of the principle for moving grain, sugar, and coal in storage bins are suggested.
An overview is presented of the problems related to air travel. It seems that disruptions of body rhythms and normal oxygen intake are an unavoidable aspect of long distance air travel. The primary objective of this paper is to highlight some of the more than 200 recent studies that throw light on the problems encountered by the modern jet air traveller.
The sources of exposure to ionizing radiation and the measuring methods for radiation are discussed. The mechanism of action of the radiation on biological systems is described, along with dose-response relationships. Symptoms of varying degrees of exposure and radiation effects on cells and studies using bacteria are also discussed and the degradation of DNA by radiation is described. A hypothesis for observed mutations caused by radiation is put forth. 19 references, 14 figures.
In this paper we have tried to explain the behavioral effects of LSD in terms of changes in the activity of single brain cells. As with any complex behavioral process and any centrally acting drug, a complete explanation will, of necessity, involve a good deal more then the activity of one set of neurons. There are also many unanswered questions about the actions of LSD, such as the precise mechanism underlying tolerance. An important sign of health and vitality in any scientific field is the ability to undergo change and revision. Neuroscience is at present one of the more vigorous fields of scientific investigation, and we therefore have no doubt that the story we have told will undergo significant modification and extension.
The article discusses how to address the problem of shortage of women in mathematics-intensive fields. Much has been written about the under-representation of women professors in math-intensive fields, particularly in upper-level positions. Despite the substantial amount of high-quality data on this issue, however, myths and misunderstandings prevail. Potentially addressable issues that limit women are often ignored, and efforts and resources are misdirected toward solving problems that no longer exist. The usual explanations for the shortage of women focus squarely on sex discrimination at various life stages. As a result of such discrimination, the argument goes, girls and women drop out of math-based endeavors or change their focus. The GRE-Quantitative scores of graduate students in math- intensive fields at our own university are very high across the board. There is no direct evidence that men's math-score advantage explains this shortage of women.
An outbreak of a type of food poisoning known as convulsive ergotism may have led to the 1692 accusations of witchcraft.
There are at least four main structural constituents to consider in the aging brain: the nerve cells, or neurons; the neuroglia, or glia (the structural and functional supporting cells of the nervous system); the blood vascular system, including the blood-brain; and the connective tissue. Because each one is dependent upon the other aging in one will undoubtedly affect the others. One of the most fundamental manifestations of aging is decreasing homeostatic adaption to environmental challenges. Some of the major environmental variables-affecting brain aging include nutrition, exercise, stress, drugs, accidents, radiation, infectious diseases and immunological changes, temperature, oxygen pressure, and the immediate social and cultural living conditions. Environmental factors influencing the brain are undoubtedly as important as genetic factors. For over fifteen years we have studied the effects of the external environment on the cerebral cortex of the male rat - the thin layer of gray matter that overlies the surface of the cerebrum and is responsible for the mammalian brain's highest functions. Littermates were separated into one of three environments: a standard colony setting, an enriched environment, and an improverished condition. In the enriched environment twelve rats were housed in a large wire-mesh cage (70 x 70 x 46 cm) equipped with ladders, small mazes, and tunnels. Animals in the impoverished environment were kept singly in small cages (34 x 20 x 20 cm). The standard colony included three rats in a similar small cage. All groups had free access to food and water. In our experiments in which the external environments were not impoverished but kept at the standard colony level, the thickness of the rat cerebral cortex diminished by only 6% (p<0.01) from 108 to 650 days of age, and the neurons and glia decreased by only a nonsignificant 4%. In the absence of disease, impoverished environment, or poor nutrition, the nervous system apparently does have the potential to oppose marked deterioration with aging. There has to be some reason for the remarkable human beings who keep their brains in good condition for almost ten decades.
An attempt is made to explain the atmosphere's role in influencing the distribution of the materials which cause air pollution and the uses to which an understanding of meteorological factors can be put in air pollution control. The state of the atmosphere affects many types of sources of pollution. Also, solar radiation, which is affected by cloudiness, has an influence on smog production. Atmospheric conditions determine the behavior of pollutants after they leave the source until they reach receptors, such as people, animals, or plants. In addition, the effect of the pollution on the receptor may depend on atmospheric conditions.
A discussion of the major sources of air pollution and methods used (in 1971) for its measurment and control are presented.
Both man-made and natural processes contribute to the concentration of particulate matter in the atmosphere; the effects of this aerosol on human health, environment, and climate are just beginning to be understood.
Refined tests have been used to explore the subtle disorders that manifest themselves as memory impairment in alcoholics with Korsakoff's syndrome
Top-cited authors
Howard Browman
  • Institute of Marine Research in Norway
Barbara I Evans
  • Lake Superior State University
Jesse Ausubel
  • The Rockefeller University
Simon Iain Hay
  • Institute for Health Metrics and Evaluation (IHME)
Andrew Tatem
  • University of Southampton