Showing papers by "Atomic Energy of Canada Limited published in 1974"
TL;DR: Bothe's formula for the angular distribution of multiply scattered particles in the small-angle limit has been evaluated numerically for ion-atom potentials of Thomas-Fermi and Lenz-Jensen type, and analytically for power potentials as discussed by the authors.
438 citations
TL;DR: In this paper, a simple-minded decoupled oscillator model was used to calculate the effective surface Debye temperatures of several low-index fcc and bcc metal surfaces.
154 citations
TL;DR: In this paper, a model which considers the effects of deep acceptors which slowly ionize (~103 s) to an equilibrium concentration ~5 × 1011/cm3 can explain the changes of pulse shape, pulse amplitude, capacitance, energy resolution, and?-ray efficiency with time.
Abstract: Nuclear radiation detectors made from high resistivity chlorine doped cadmium telluride grown by the travelling heater method were evaluated. Short term performance for ?, s, and ? radiations was good but the long term performance (>1 min) was degraded by a decrease in the full energy pulse height and ?-ray efficiency with time after the bias voltage was applied. A model which considers the effects of deep acceptors which slowly ionize (~103 s) to an equilibrium concentration ~5 × 1011/cm3 can explain the experimental findings on the changes of pulse shape, pulse amplitude, capacitance, energy resolution, and ?-ray efficiency with time. The operating conditions required for satisfactory stability in these detectors may be inconvenient to the user.
114 citations
TL;DR: The frequencies of occurrence of various types of genetic disease have been derived from a number of successive annual birth cohorts from a well‐defined geographic region with a current population in excess of two million people to indicate the risk to human health from these diseases may be some 12 times too high.
Abstract: SUMMARY
The frequencies of occurrence of various types of genetic disease have been derived for a number of successive annual birth cohorts from a well-defined geographic region with a current population in excess of two million people. The results indicate that about 9·4 individuals out of every 100 liveborn will have serious genetic diseases or handicaps and that another 2·7 persons out of every 100 born alive suffer from disorders of unknown aetiology. However, the incidence of simple, dominant conditions is probably very close to 8 in every 10,000 liveborn, or about 12 times lower than previously believed. Accordingly, estimates of the risk to human health from these diseases, due to an artificially induced increase in mutation rate in man, may be some 12 times too high.
106 citations
TL;DR: In this article, studies on the radiosensitizing effect of oxygen in Chinese hamster cells were conducted, and the results showed that the effect of ozone on Chinese hamsters was negligible.
Abstract: (1974). Studies on the Radiosensitizing Effect of Oxygen in Chinese Hamster Cells. International Journal of Radiation Biology and Related Studies in Physics, Chemistry and Medicine: Vol. 26, No. 4, pp. 383-389.
92 citations
TL;DR: In this article, the authors attributed delayed failures at welds in components of Zi-2.5 wt % Nb are attributed to zirconium hydride forming at the root of a notch adjacent to the welds.
80 citations
TL;DR: In this paper, a weak beam image of long and relatively straight dislocation lines in annealed Zr3Al was obtained to obtain information on the equilibrium width of the extended dislocations.
79 citations
TL;DR: In this article, the products of the slower part of the ion recombination are affected by an applied magnetic field, and the fluorescence yield increases by a factor of about 1.5 whereas the triplet yield decreases.
75 citations
TL;DR: In this paper, the heat of hydrogen adsorption on clean polycrystalline platinum filaments has been determined as a function of the coverage (θ), temperature and method of preadsorption using UHV adiabatic calorimetric techniques.
67 citations
TL;DR: In this paper, reaction-bonded SiC loses nearly 50% of its fracture strength when exposed to neutron irradiation, and the damage occurs soon after exposure and levels out with continuing exposure up to 3 × 10 21 n/cm 2.
56 citations
TL;DR: Mechanistically, these results require reactions involving the superoxide radical both during and after the irradiation and implicate sulphydryl oxidation as well as peroxidation of membrane phospholipids.
Abstract: SummaryIrradiation of Acholeplasma laidlawii B cells in air in the presence of superoxide dismutase produced a protective effect that had two components. The smaller component manifested itself immediately after the irradiation and depended on the buffer used. In Tris NaCl, pH 7·6, it amounted to an increase in D0 of 7·5 per cent or less; in phosphate glycerol buffer, pH 7·0, the increase amounted to 10·5–18·9 per cent, depending on the enzyme concentration. The larger component was elicited over a 4-hour period after irradiation and amounted to an increase in D0 of 17–52 per cent, depending on the enzyme concentration. A major portion of this component was also elicited by the enzyme when added to the cells 10 min after irradiation. Inactivated enzyme was generally ineffective. Mechanistically, these results require reactions involving the superoxide radical both during and after the irradiation and implicate sulphydryl oxidation as well as peroxidation of membrane phospholipids.
TL;DR: In this paper, a cyclotron was used for medical therapy purposes, consisting of an iron metal housing acting as a magnetic yoke, magnetic shield, radiation shield, and vacuum vessel, and a pair of superconducting coils mounted in a cavity in the housing.
Abstract: A neutron source for medical therapy purposes comprising a cyclotron comprising an iron metal housing acting as a magnetic yoke, magnetic shield, radiation shield, and vacuum vessel, a pair of superconducting coils mounted in a cavity in the housing said coils being cooled to superconducting temperatures by passage of a refrigerant fluid therethrough and connected to an electrical energy source such that a high current flows in the coils producing an intense magnetic field inwardly between the coils, an ion orbiting region defined by pairs of sectoral-shaped RF electrode structures energized at an RF frequency and focussing flutter poles mounted in the intense magnetic field between coils, a source of ions positioned centrally of the ion orbiting region to provide a stream of ions that will be orbited in the orbit region; an ion target positioned internally of said iron housing at an outer position in the orbit region such that orbiting ions strike the target and produce neutrons; a channel formed in the iron housing from the target to the exterior for passage of the beam of neutrons formed at the target, said channel acting as a beam collimator; and a mounting structure for movably mounting the cyclotron and target such that the neutron beam produced can be employed at more than one position.
TL;DR: In this paper, a polyphase alloys based on ordered Zr3Al (Ll2 type) have been deformed in tension at 20 to 600°C and exposed to moist air (300°C), pressurized water and atmospheric pressure steam (400°C).
TL;DR: In this paper, a framework for calculating spectroscopic amplitudes for α-transfer reactions is developed in the framework of the j - j coupled harmonic oscillator shell model. But the amplitudes can be expressed as a sum of coupled two-neutron and two-proton spectroscopy amplitudes.
TL;DR: In this article, the sticking coefficient of H 2 on polycrystalline platinum and its variation with temperature and coverage are compared with the exchange and equilibration f H 2 and D 2 under similar experimental conditions.
TL;DR: In this article, a simple band-crossing model of back bending was used to identify high spin states in 156 Dy using (HI, x n) reactions and γγ coincidence techniques.
TL;DR: In this article, the root-crack-notch-radius relation is proposed for the application of this technique to ceramics and the effects of notch width and depth are examined for Al2O3, graphite, and SiC.
Abstract: The mathematical analysis of the notched-beam specimen for fracture-energy determination considers a beam containing a zero-volume crack, i.e. a crack with zero width. Such a configuration is difficult to reproduce in practice with ceramics, and artificially cut notches with widths large relative to the scale of the ceramic microstructure are usually used. Evidence is presented which suggests that incorrect results can be obtained using such notches even when real cracks exist at the notch root. The effects of notch width and depth are examined for Al2O3, graphite, and SiC. A tentative specification of a root-crack-notch-radius relation is proposed for the application of this technique to ceramics.
TL;DR: In this article, the surface instability of an isotropic half-space under biaxial plane stress is studied for compressible elastic materials in finite strain, where Euler's method is used to derive the general form of the stability criterion, and analytical details are exhibited by special application to the class of hyperelastic Hadamard materials.
Abstract: The phenomenon of surface instability of an isotropic half-space under biaxial plane stress is studied for compressible elastic materials in finite strain. Euler's method is used to derive the general form of the stability criterion, and analytical details are exhibited by special application to the class of hyperelastic Hadamard materials in two complementary cases: (i) the full solution is derived for the compressible, neo-Hookean members, and (ii) the plane deformation solution is provided for every isotropic, elastic material and specific results are presented for the full Hadamard class. Results appropriate to incompressible Mooney-Rivlin materials are herein obtained as special limit cases. Several theorems are established and some of the conclusions are illustrated graphically.
TL;DR: Observations indicate that the presently available radiation sensitive mutants represent defects in only two major pathways for repair of radiation damage in the wild type S. pombe.
Abstract: Different compounds known to inhibit dark repair in bacterial and mammalian systems have been tested for a similar effect in the yeast Schizosaccharomyces pombe. A marked inhibition of growth by these different drugs indicated that these were taken up by the cell, yet none except caffeine reduced the colony forming ability when present in the post-irradiation plating medium. The response of 22 different radiation sensitive mutants to the presence of caffeine in the plating medium was tested to investigate the probable number of pathways for repair of radiation damage in this organism. In some of the genetic crosses among single gene mutants showing a differential caffeine-response, supersensitive double mutants were obtained. Strains obtained either by additional crosses or by further mutagenic treatment of the supersensitive double mutants did not show a highly significant increase in radiation sensitivity. These observations indicate that the presently available radiation sensitive mutants represent defects in only two major pathways for repair of radiation damage in the wild type S. pombe.
TL;DR: In this article, a two-dimensional transient heat conduction model for rewetting a hot surface by a falling liquid film predicts that for stainless steel, Inconel or Zircaloy only a wall thickness of some 0.020 in.
TL;DR: In this paper, an expression for the boundary value of the chemical driving force at the crack tip is derived for the flux of vacancies to the crack and hence the crack-tip velocity.
TL;DR: In this paper, the excitation energies and L -transfers obtained in the present work are found to be in generally good agreement with previous data, and a comparison of the experimental angular distributions with those calculated assuming a closed 70 Ge core indicates that only ≈ 15% of the observed ground state L = 0 transition strength comes from (1 g 9 2 ) 2 and (2 p 1 2 )2 pick up.
TL;DR: In this paper, the same post-irradiation annealing treatments produced a larger fractional recovery of the critical resolved shear stress at 4 K than at 295 K. In polycrystalline copper, migrating grain and twin boundaries were quite effective in sweeping out the irradiation-produced defects.
Abstract: Irradiation hardening has been investigated in copper crystals irradiated at ∼325 K with 4 × 1020 and 8 × 1020 n cm−2. In the as-irradiated crystals, cleared channels were produced due to the sweeping up of the irradiation damage by the glide dislocations. The slip band width, spacing and height all increased with increasing testing temperature. Identical post-irradiation annealing treatments produced a larger fractional recovery of the critical resolved shear stress at 4 K than at 295 K. This indicates that the damage removed in the early stages of annealing acts as a more effective obstacle to dislocation glide at 4 K than at 295 K. For certain combinations of annealing treatment and low temperature testing, the initial stage of deformation was characterized by the bowing of the glide dislocations around the defects rather than sweeping them up. In polycrystalline copper, migrating grain and twin boundaries were quite effective in sweeping out the irradiation-produced defects.
TL;DR: In this article, high voltage electron microscopy revealed that the cavities could be nucleated at twin boundary/grain boundary intersections and that the maximum elongation occurs at a higher temperature than that of the maximum strain-rate sensitivity and this is explained in terms of grain-boundary migration, at the higher temperature, which restricts the cavitation process.
Abstract: Intergranular cavitation has been observed during the superplastic deformation of a fine grain sized (1 μm) Cu-2.8% Al-1.8% Si-0.4% Co alloy when tested at temperatures ≥500° C. High voltage electron microscopy revealed that the cavities could be nucleated at twin boundary/grain boundary intersections. The maximum elongation occurs at a higher temperature than that of the maximum strain-rate sensitivity and this is explained in terms of grain-boundary migration, at the higher temperature, which restricts the cavitation process. This explanation was put forward on the basis of texture analysis which was used to study the deformation characteristics at the temperatures of maximum elongation and strain-rate sensitivity. The final fracture mode is shown to change with test temperature: (i) at 400° C no cavitation occurs and fracture is by ductile rupture, (ii) at 500 to 550° C cavitation occurs and fracture is by the interlinkage of voids by an intergranular void sheet (IVS) mechanism and (iii) at 800° C grain growth occurs and fracture occurs by the propagation and interlinkage of grain-boundary cracks along the grain boundaries.
TL;DR: In this paper, the mean lifetimes of the first excited states of 24 Mg and 38 Ar were measured using Doppler broadened lineshapes and scaled experimental stopping powers.
TL;DR: In this article, the in-reactor stress relaxation of zirconium alloys can be represented by the equation σ/σ 0 = D exp (−Kt) where the unrelaxed stress ratio is equal to a factor times the exponential of the relaxation rate.
TL;DR: In this paper, the electron spin resonance spectra were directly observed during radiolysis of t-BuNO solutions with a 3 MeV electron beam from an accelerator, and it was shown that methoxy, CH3O·, and hydroxy methyl ·CH2OH, are formed in approximately equal amounts and that both are primary radicals in agreement with gas phase mass spectrometry data.
TL;DR: In this paper, the reorientation effect in Coulomb excitation has been used to measure the following static quadrupole moments: Q 2 + ( 32 S ) = −0.066 ± 0.017 b, Q 2+ ( 34 S )= 0.19 ± 0.14 b.