Showing papers by "Chalk River Laboratories published in 1972"

Microanalysis of materials by backscattering spectrometry.

Abstract: After its successful soft landing on the moon on 9 September 1967, Surveyor 5 transmitted back to earth signals which contained the first factual information on the chemical composition of the lunar soil. The data were obtained from the "alpha-scattering experiment" performed by a relatively simple instrument placed on the lunar soil. A radioactive source emitted alpha particles which were directed at the lunar surface. The particles were then scattered back by collisions with the constituent atoms of the lunar material and counted by suitably positioned, energy-sensitive detectors. From such measurements one can determine the mass of the collision partner and therefore identify the elements present in the soil (1, 2). These backscattering analyses agree remarkably well with the chemical analyses later made on samples of moon rocks returned to earth by the Apollo 11 and Apollo 12 missions (3).

Comparison of two methods of estimating efficiency of funnel extractors for soil microarthropods

Abstract: Tullgren funnels and a high-gradient apparatus, with a printed circuit-board heater, were used to evaluate the efficiency of funnel extractors for soil microarthropods by two methods: (i) sterile cores into which known numbers of animals were introduced, and (ii) field soils with their natural populations. After extraction, the field samples were examined microscopically for residual animals. Qualitatively, extraction was 100% for methods in both instruments, but the number of specimens per species recovered was less than 100%. There was no significant difference between the total numbers of mites obtained by the two extractors, recoveries ranging from 85 to 98 %. However, from field soils, the high-gradient apparatus recovered about 73 % of the Collembola, a significantly higher proportion than the 45 % recovered by the Tullgren funnels. The two methods of testing efficiency showed general agreement for most species and orders of mites, but known introductions usually gave significantly lower estimates than field populations. Discrepancies between methods were observed for Discourella modesta, Alicorhagia fragilis, Carabodes sp., Malaconothrus sp., Nanhermannia dorsalis, Oribatella sp. and Phthiracaridae species. Further refinements in technique are required for these species and certain groups within the Collembola.

Dechanneling of MeV protons in tungsten

Abstract: A systematic investigation of the dechanneling of protons in tungsten has been completed for the axial direction and also for the (110) plane. Measurements at room temperature have been made at energies of 0.5, 2.0, 3.5, 8.0 and 12.0 MeV; at 2.0 MeV, the effect of target temperature has been investigated over the range 77–873°K. In the axial case, the dechanneling rate increases strongly with the vibrational amplitude ρ, but not as strongly as the ρ2 dependence reported by the Catania group (Refs. 4–7) for silicon and germanium. Also, unlike silicon and germanium, the tungsten axial data exhibit practically no energy dependence and so cannot be fitted by the zρ2/E scaling parameter suggested by the Catania group. On the other hand, the planar dechanneling data in tungsten exhibit the predicted (E −1)dependence and relatively littie temperature dependence, in good agreement with previous work.

Fluid modeling of critical heat flux in uniformly heated annuli.

Abstract: This paper presents the results of an experimental and analytical program to develop Freon-water modeling of critical heat flux in annular geometries. Experimental critical heat flux data were obtained with Freon-12 over a wide range of pressure and mass flux. These were compared with water data using Ahmad's compensated distortion model. A critical heat flux correlation for annular geometries which is independent of fluid types was developed from the Freon data and subsequently applied to published water data. It is concluded that adequate modeling of critical heat flux in an annular geometry can be obtained provided the size of the model and prototype is identical.

The nature of replicating instability in yeast

Abstract: The nature of replicating instability was studied in an adenine-requiring strain of Schizosaccharomyces pombe . The instability was recognized by the presence of mosaic (part red, part white) colonies when cells of mosaic colonies, obtained by ethylmethanesulfonate (EMS) treatment, were replated. It was found that the instability was not more closely associated with the cells of the mutant white portion of primary mosaics than with those of the red portion. Data conformed to the supposition that replicating instability is expressed by mutations from unstable to stable “red” and to stable “white”. Calculations indicated that the spontaneous mutation rate from unstable to stable may be in the order of 0.2 to 0.4, per cell per generation.

Damage caused by the fungus Scleroderris in plantations and nurseries in Europe and North America

Abstract: This communication deals with the damage caused by Scleroderris lagerbergii in nurseries as well as in plantations of Europe and North America. Roughly a two million dollar damage which easily may be higher, has been estimated by the author.

Natural frequencies of a hemispherical shell

Abstract: An experimental study of the natural frequencies of a hemispherical thin shell with a clamped edge is described. For the particular shell model studied, the four lowest symmetric modes were identified conclusively by establishing the node-line patterns. The associated natural frequencies were found to be in excellent agreement with theoretical predictions. A great number of higher modes were also excited but could not be conclusively identified due to difficulties in establishing the node-line patterns. The symmetric frequency spectrum up to and including the 23rd mode was, however, established by means of a qualitative argument and showed good correlation with the theoretical spectrum. A number of natural frequencies were found to be present in a particular frequency band for the test shell resulting in a severe crowding in this region. This was found to be in agreement with the more general results for hemispherical shells which indicate that the crowding takes place around a frequency parameterp=1.0.

Influence of Dislocations on Electron Microscope Crystal Lattice Images

Abstract: A brief description is given of (1) the electron-optics of lattice image formation, (2) the electron-microscope facility used to obtain these images, and (3) some unexpected oscillations in lattice plane spacing observed near end-on dislocations in germanium and aluminum.