Showing papers in "Science in 1953"

A Production of Amino Acids Under Possible Primitive Earth Conditions

Abstract: atmosphere of methane, ammonia, water, and hydrogen instead of carbon dioxide, nitrogen, oxygen, and water was suggested by Oparin (1) and has been-given emphasis recently by Urey (2) and Bernal (3) In order to test this hypothesis, an apparatus was built to circulate CHI4, NH3, H2O, and H2 past an electric discharge The resulting mixture has been tested for amino acids by paper chromatography Electrical discharge was used to form free radicals instead of ultraviolet light, because quartz absorbs wavelengths short enough to cause photo-dissociation of the gases Electrical discharge may have played a significant role in the formation of compounds in the

Regularly occurring periods of eye motility, and concomitant phenomena, during sleep.

Abstract: obtain their surface in square centimeters. This simple method provides a means by objective measurements to make evident changes in the surface of wounds that are not apparent to the naked eye. Figure 1 shows the observations recorded with this method in a man of 42 years of age with hemiplegia and a decubital ulcer over the right buttock. The clinicians who had observed this wound daily had not noticed any remarkable change; however, it is quite obvious that the wound grew larger each time the treatment was changed, and that the use of an antibiotic was followed by a particularly striking enlargement of the lesion. In this instance the procedure of projection and gravimetric planimetry was repeated by different operators and a variation of ±5% was found (indicated by a cross-hatched area on Fig. 1). Figure 2 shows the same type of observation in a woman with hemiplegia and a decubital ulcer. This patient died from septicemia, and the decubital ulcer worsened with the general condition of the patient. A method of gravimetric planimetry by standard photographs offers a means to study the course of surface wounds more accurately than by clinical observation or by the pictorial record alone. References

Thermoluminescence as a Research Tool

Abstract: THERMOLUMIXESCENCE IS T H E EMISSION O F LIGHT produced by heating a solid to a temperature below that of incandescence. It is exhibited by crystals, such as alkali halides, that have been exposed to x-rays or radioactivity and then heated rapidly. The high-energy radiation dislodges electrons, some of which become trapped in lattice imperfections, and are later driven out with the accompanying emission of light when the temperature is raised to supply the necessary amount of kinetic energy. Thermoluminescence is a property that is extremely sensitive to changes in the structure of crystals. Changes in minor impurity concentrations, crystallization techniques, and physical treatments all produce profound effects. This structure sensitivity is found in other solid state properties such as catalytic activity, dielectric constant, magnetic susceptibility, light absorption, fluorescence, and phosphorescence. Because of the similarities between thernioluminescence and these other properties i t is thought that thermoluininescence measurenlents inay be of value in their interpretation. The application of thermoluminescence in the analysis of lilinerals and control of feldspars in the ceramics ~ndns t ry has been described by Deribere (1,2). I t has been used in the interpretation of phosphorescence nlechanisms by Garlick and others (3).Further interesting uses of this phenomenon were suggested in preliminary reports (4-6), and it is the purpose of the present cominunication to outline progress in the application of thermolurninescence to a variety of re-

Irradiation of parts of individual cells.

Abstract: SELECTIVE EXPOSURE of fractions of intact individual cells to high-energy radiation is of interest fo r two reasons. First, i t has obvious use in radiobiology as a means of gaining information about the mechanisms by which radiations produce their strikingly injurious effects on living systems. Second, and of much more general application, it can aid in analyzing the normal functions of the various cell parts by selectively altering them. I n this respect it complements microsurgery. Irradiation of parts of single intact cells has been done before, both with ultraviolet light (1)and with high-energy radiation (2-7) ,3 but in each instance the success of the technique has been largely dependent on some peculiarity of cell structure, e.g., exceptionally large size (2, 7) or a n eccentric nucleus (2, 3), and accordingly has been quite'limited in application. Also the cell fraction irradiated has in most cases been quite large (25-50 per cent). This paper contains a brief description of a new and widely applicable method with which considerably smaller fractions of average-sized cells can be bombarded, and mention of some of the results obtained.

The Population Reference Bureau

Abstract: Guidance exists on the acceptable and unacceptable levels of risk behaviors for individuals but it is very challenging to translate those risks to a population. For example, if a young person smokes cigarettes, it is clear that in order to protect their health, they should quit. However, at what level should a larger group identify youth/adolescent smoking as a problem? The Global Tobacco Atlas has divided countries into four groups; low, medium, high, and exceedingly high prevalence. The population levels of smoking (for all ages) are below 7%, 7-15%, 16-29.9%, and 30% and above. Virtually no countries – and none in LAC – are in the high-prevalence category, so we used three levels of smoking for populations to identify low, medium, and high prevalence on our data sheet.