Showing papers by "Atomic Energy of Canada Limited published in 1973"
TL;DR: The radiosensitizing and radioprotective effects of various compounds have been characterized in Chinese hamster fibroblasts growing in vitro and in a model chemical system utilizing DNA as target, and Cysteamine is shown to protect primarily by adding to the pool of radical-reducing species, resulting in enhanced repair of free-radical damage in the targets.
Abstract: The radiosensitizing and radioprotective effects of various compounds have been characterized in Chinese hamster fibroblasts growing in vitro and in a model chemical system utilizing DNA as target. The contribution to the lethal action of ionizing radiation in mammalian cells from the indirect effect of OH has been measured. The data are consistent with the “oxygen fixation hypothesis,” whereby target free radicals react either with radical-reducing species, resulting in “chemical repair,” or with radical-oxidizing species, resulting in “fixation” of radical damage to a potentially lethal form. Radical repair–fixation competition has been demonstrated in the in vitro chemical system with a sensitizer other than O2. Dimethyl sulfoxide is shown to radioprotect in both the cellular and chemical systems by scavenging OH. Cysteamine, on the other hand, is shown to protect primarily by adding to the pool of radical-reducing species, resulting in enhanced repair of free-radical damage in the targets. Electron-af...
331 citations
TL;DR: In this paper, it was shown that from the energy spectra of He ions backscattered from aluminum, recorded before and after anodic oxidation, the thickness of the oxide films and the positions of ion-implanted foreign atoms within the films can be determined.
Abstract: It is shown that from the energy spectra of He ions backscattered from aluminum, recorded before and after anodic oxidation, the thickness of the oxide films and the positions of ion‐implanted foreign atoms within the films can be determined. Information on the composition and uniformity of the films is also obtained. The scope, limitations, and precision of the method are predictable and are discussed. As model experiments the behavior of ion‐implanted noble gases was studied. The results agree with previous work and can be interpreted to show that, as expected, both aluminum and oxygen are mobile during the oxidation. The behavior of ion‐implanted alkali metals and halogens was also studied. These species were found to be mobile during oxidation and behaved in a manner consistent with their expected ionic charges.
224 citations
TL;DR: In this paper, the unconstrained misfit strains associated with the formation of zirconium hydride precipitates in Zr have been calculated with respect to directions.
208 citations
01 Jan 1973
TL;DR: In this article, the distribution of reduced radiation width, particularly for E1 and M1 radiation, in the less well-known “tail region” well below the peak of the E1 giant resonance was studied.
Abstract: The study of the energy dependence of multipole transition probabilities is a broad subject in which certain subfields have progressed much more rapidly than others. Thus for gamma rays ≲2 MeV, E1, M1, and E2 transition probabilities have been well studied (Per 66, SHR 66, SG 65), and at higher energies, ≳10 MeV, the absorption cross section and other properties of the E1 giant resonance are well known (Fir 70), but between these energies there are large gaps in our knowledge. In the present review we are concerned with the distribution of reduced radiation width, particularly for E1 and M1 radiation, in the less well-known “tail region” well below the peak of the E1 giant resonance. We will concentrate on elements with mass number A≳ 90, where a statistical description of radiative processes is appropriate, and on γ-ray energies above ~2 MeV.
153 citations
TL;DR: There is an annual cycle of intraspecific aggression syn- chronized with the breeding season in male M. pennsylvanicus, which supports studies on Peromyscus and shows that aggression increased with spring breeding and declined as reproduction ceased in fall; thus, behavioral density regulation seems most likely to occur during the breeding period.
Abstract: Intraspecific aggression of male Microtus pennsylvanicus drummondii was ob- served in 320 10-minute paired encounters in a neutral arena, during 17 months. Voles were drawn from a population live-trapped biweekly at Pinawa, Manitoba. The 17 months were divided into the following reproductive periods: non-breeding, testes scrotal, and littering. There were two non-breeding, two testes scrotal periods, and a single littering period. Threats, vocalizing, and "mutual uprights" were significantly and positively associated in all but one of the periods. Together with fighting, these three acts formed the aggressive component of the behavior recorded. All aggressive acts increased in frequency as males became reproduc- tively active, and decreased as the breeding season ended. Latencies to aggressive acts were negatively related to the acts' frequencies. Less frequent acts (fighting, "grooming other," and "submissives") also showed seasonal changes associated with breeding: fighting was com- mon throughout the breeding period, submissives most common early in the reproductive period, and grooming other most prevalent when juveniles were present in the population. Incidences of tail-wounding in the field population were significantly more common during the breeding season, and in males. A comprehensive Index of Aggression was devised by means of principal component analysis, based on the total frequencies of aggressive acts. Mean Indices of Aggression for the five periods showed that aggressive levels in the three breeding periods were significantly higher than in the two non-breeding periods. Re-tests of 53 voles showed scorn-. ii)m their two encounters to be positively correlated. Aggression mea,,:10 i n the encounters was related to population parameters derived from live-trapping results. Breeding season home ranges were larger than winter home ranges. Overwintered adults were more aggressive, had larger home ranges and survived longer than young of the year. Aggression and survival were positively related in adults but not in young. Resident voles were more aggressive than non-residents. Dominant voles were usually slightly heavier. Pairs of voles of similar weight exhibited more aggressive acts, but "following" was more frequent in dissimilar weight pairs. Aggressive levels did not vary consistently with population density. These observations demonstrate there is an annual cycle of intraspecific aggression syn- chronized with the breeding season in male M. pennsylvanicus. They support studies on Peromyscus, which also showed that aggression increased with spring breeding and declined as reproduction ceased in fall; thus, behavioral density regulation seems most likely to occur during the breeding period.
118 citations
TL;DR: In this paper, the Mechanism of Chemical Radioprotection by Dimethyl Sulphoxide (DSP) has been studied in the context of radiation biology and related studies in physics, chemistry and medicine.
Abstract: (1973). Studies on the Mechanism of Chemical Radioprotection by Dimethyl Sulphoxide. International Journal of Radiation Biology and Related Studies in Physics, Chemistry and Medicine: Vol. 24, No. 5, pp. 533-536.
117 citations
TL;DR: In this article, a generalized technique for fluid modeling of critical heat flux is developed from classical dimensional analysis and theory of models, and the problem of multiple distortion is solved by introducing a modeling parameter which is a function of Weber number and liquid and vapor superficial Reynolds numbers.
114 citations
TL;DR: Seven compounds which are more effective than PNAP at a given non-toxic concentration are reported and one of these, 1-(2,4-dinitrophenyl)pyridinium chloride (DNPC), approaches the nitrofuran class of radiosensitizers in effectiveness.
Abstract: SummaryNitrobenzene analogues of p-nitroacetophenone (PNAP) have been tested on Chinese-hamster cells for their ability to sensitize hypoxic cells to x-rays. Seven compounds which are more effective than PNAP at a given non-toxic concentration are reported. One of these, 1-(2,4-dinitrophenyl)pyridinium chloride (DNPC), approaches the nitrofuran class of radiosensitizers in effectiveness. A correlation between cellular radiosensitization and drug electron affinity is examined for its usefulness in predicting radiosensitizing potential of compounds in the nitrobenzene series.
111 citations
TL;DR: In this paper, adopted values for the static charge quadrupole moments Q2+ of first excited states of even-even nuclei are given in Table I and the adopted values of the reduced electromagnetic transition probabilities B(E2, 0+→2+) and corresponding values |Q2+rot | derived with the adiabaticrotational model.
100 citations
TL;DR: Analysis of the proteins present in intact virions and in the different SVP reveals clear differences which indicate that the conversions are accomplished by removal or cleavage of particular species of polypeptides.
Abstract: Reovirus virions, grown in suspension cultures of L cells and extensively purified by density gradient and velocity gradient centrifugation after their release from cell debris by fluorocarbon extraction, are characterized by a mean particle diameter of 73 nm and a density in CsCl of 136 to 137 g/cm3 Treatment of intact virions by chymotrypsin (CHT) digestion in vitro converts them to subviral particles (SVP) having characteristics which are determined by the species of monovalent cation present during the digestion In the presence of Cs+ ions, CHT converts the virions to SVP of mean diameter 51 nm and density 143 to 144 g/cm3 In the presence of K+ ions, the conversion is to SVP of diameter 51 nm and density 139 to 140 g/cm3 The SVP made in the presence of either Cs+ or K+ possess an extremely active RNA polymerase and nucleoside triphosphate phosphohydrolase (NTPase) activity in vitro and are resistant to further digestion by CHT Treatment of intact virions with CHT in the presence of Na+ or Li+ ions results in their conversion to SVP of mean diameter 64 nm and density 137 to 138 g/cm3 Such SVP are not active in in vitro RNA synthesis or NTP hydrolysis and are resistant to further digestion by CHT even during prolonged exposure to high concentrations of enzyme Addition of Cs+ or K+ ions to the digestion mixture allows conversion of the 64-nm diameter SVP to 51-nm diameter SVP in which the RNA polymerase and NTPase are active in vitro Analysis of the proteins present in intact virions and in the different SVP reveals clear differences which indicate that the conversions are accomplished by removal or cleavage of particular species of polypeptides
96 citations
TL;DR: In this article, the character of dislocations emitted during the precipitation of γ-zirconium hydride in zircimium, Zircaloy-2, Zr-1% Al and Zr 1% Cr has been determined.
TL;DR: In this paper, the ground-band level sequence in Hg has been identified to spin up to 14.5% and possibly to 10% of the original Hg at the same time.
Abstract: The ground-band level sequence in $^{184}\mathrm{Hg}$ has been identified to spin ${10}^{+}$ and possibly to ${14}^{+}$. Lifetimes for the ${2}^{+}$, ${4}^{+}$, and ${6}^{+}$ states have been measured. The results imply the onset of a permanent deformation above the ${2}^{+}$ level.
TL;DR: In this paper, the effect of Coulomb corrections on superallowed Fermi β-decays is investigated, including the contribution of charge-dependent configuration mixing, in a simple model, which relates δc with Coulomb displacement energies of 0+ states in isotriplets and to off-diagonal Coulomb matrix elements.
TL;DR: In this paper, the effects of porosity, pore distribution, and grain size on fracture energy were evaluated and a grain-size effect dominates in dense material; the fracture energy decreases with increasing grain size.
Abstract: Alumina specimens were fabricated under a wide range of conditions using cold-pressing and sintering techniques. Fracture energies were measured by an analytical technique (notched beam) and by the Tattersall-Tappin method. Problems in using the latter method are discussed. The effects of porosity, pore distribution, and grain size on fracture energy are evaluated. Connected porosity has a deleterious effect on fracture energy. A grain-size effect dominates in dense material; the fracture energy decreases with increasing grain size.
TL;DR: In this paper, the Morse potentials for the (100, (110), and (111) surfaces of seven f.c.c and 9 b.c metals were calculated and the surface binding energies were found to be greater than the sublimation energy per atom.
Abstract: Surface binding energies are calculated using Morse potentials for the (100), (110) and (111) surfaces of seven f.c.c. and 9 b.c.c. metals. Estimates are made for a further seven metals. Surface relaxation effects are included and their effect discussed. The surface binding energies are found to be greater than the sublimation energy per atom of the solid. Qualitative arguments are proposed to explain the ordering of binding energies between crystal faces. Comparison with experimental data for the adsorption energies of tungsten atoms on tungsten crystal faces indicates the plausibility of the calculated valucs.
TL;DR: In this paper, an experimental apparatus was described for studying channeling in a clean environment at temperatures as low as 25 K. The target is mounted on a standard 2-axis goniometer and is almost completely surrounded by a large cryoshield at 20 K.
TL;DR: In this article, potential pH diagrams have been derived for the aluminium-water system at temperatures between 25 and 300°C by integrating free energy functions using the Criss and Cobble "correspondence principle".
TL;DR: The data indicate that the effect of the cations is exerted on activation of the polymerase activity by CHT as opposed to an effect on polymerization per se, which may be important biologically in that it provides a mechanism whereby the virion can sense whether it is in an intracellular or an extracellular environment and thereby can avoid premature uncoating.
Abstract: Activation of reovirus transcriptase activity, latent in intact virions, by digestion of purified virions with chymotrypsin (CHT) in vitro shows a stringent requirement for specific monovalent cations. Cs(+), Rb(+), or K(+) ions are capable of facilitating activation by chymotryptic digestion. Na(+), Li(+), or NH(4) (+) ions are not capable of facilitating the CHT activation of polymerase activity and are antagonistic towards the effects of the facilitating ions. The data indicate that the effect of the cations is exerted on activation of the polymerase activity by CHT as opposed to an effect on polymerization per se. This effect may be important biologically in that it provides a mechanism whereby the virion can sense whether it is in an intracellular or an extracellular environment and thereby can avoid premature uncoating.
TL;DR: In this paper, the gamma-ray efficiency measurements of cooled Si(Li), Ge, CdTe and HgI2 spectrometers and detectors of comparable sizes for gamma ray energies from 60 keV to 3.85 MeV were made.
Abstract: Gamma-ray efficiency measurements were made for Si(Li), Ge, CdTe and HgI2 spectrometers and detectors of comparable sizes for gamma ray energies from 60 keV to 3.85 MeV. Full energy efficiency measurements of cooled Si(Li) and Ge spectrometers and a room temperature CdTe spectrometer show that the efficiencies improve in going from silicon (Z= 14) to germanium (Z= 32) to cadmium telluride (Z= 50) in agreement with the photoelectric cross-sections which vary as Z5. Because of its shorter carrier drift lengths, the CdTe spectrometer must be operated at the highest practical voltages. The detection efficiencies, based on all pulses above a threshold set by noise, were measured for Si(Li), CdTe and HgI2 detectors at room temperature. A 30 keV threshold and small photoelectric cross-section combine to give an efficiency minimum for the Si(Li) detector for 100 keV < E? < 200 keV. Both CdTe and HgI2 detectors iave no such minimum. In addition the higher electronic stopping powers of HgI2 and CdTe in comparison with Si reduce edge effects - an important factor in high energy ?-ray efficiency.
TL;DR: In this article, DWBA predictions were used to obtain l n transfers and absolute spectroscopic factors for the (p, d) reaction at 20 MeV, and the center-of-gravity energies and filling coefficients of the 2p 3 2, 1 f 5 2, 2 p 1 2 and 1 g 9 2 neutron Subshells calculated from these measurements are in generally goo agreement with the existing information on Ni, Zn and Se.
Patent•
13 Jul 1973TL;DR: A bithermal, catalytic, hydrogen isotope exchange process between liquid water and hydrogen gas to effect concentration of the deuterium isotope of hydrogen is described in this article.
Abstract: A bithermal, catalytic, hydrogen isotope exchange process between liquid water and hydrogen gas to effect concentration of the deuterium isotope of hydrogen, wherein liquid water and hydrogen gas are contacted with one another and with at least one catalytically active metal selected from Group VIII of the Periodic Table, the catalyst body has a water repellent, gas and water vapour permeable, organic polymer or resin coating, preferably a fluorinated olefin polymer or silicone resin coating, so that the isotope exchange takes place by two simultaneously occurring, and closely coupled in space, steps namely, using protium (H) and deuterium (D) as the example, HD gas + H2O vapour catalyst H2 gas + HDO vapour
Patent•
12 Dec 1973
TL;DR: In this paper, a process for the exchange of hydrogen isotopes between streams of gaseous hydrogen and liquid water is described, wherein the streams at a temperature in the range 273 to 573 K are brought into contact with one another and a catalytically active mass comprising an inherently hydrophobic, porous, polytetrafluoroethylene matrix and partially platinized carbon particles dispersed throughout the whole of the porous polyto-platinized high surface area carbon particles in the weight ratio of 1:1 to 3:1.
Abstract: A process for the exchange of hydrogen isotopes between streams of gaseous hydrogen and liquid water is described, wherein the streams at a temperature in the range 273 to 573 K are brought into contact with one another and a catalytically active mass comprising an inherently hydrophobic, porous, polytetrafluoroethylene matrix and partially platinized carbon particles dispersed throughout the whole of the porous polytetrafluoroethylene matrix in the weight ratio of 1:1 to 3:1 of polytetrafluoroethylene to partially platinized high surface area carbon particles. The inherently hydrophobic, porous polytetrafluoroethylene matrix allows the catalytically active metal to catalyze the hydrogen isotope exchange reaction between hydrogen gas and water vapor in the presence of liquid water while retarding loss of activity of the catalytically active metal by contact of the metal catalyst with liquid water. This catalyzed chemical isotope exchange proceeds simultaneously with isotope exchange from water vapor to liquid water by a non-catalyzed, physical evaporation and condensation exchange reaction. The efficient coupling of these two isotopic transfer steps which results in a rapid overall isotopic exchange between hydrogen and liquid water without a pronounced loss of activity of the catalyst is dependent upon the weight ratio of the catalytically active platinized carbon to the polytetrafluoroethylene matrix being in the above mentioned range of 1:1 to 3:1.
TL;DR: Comparison of radiosensitization for different phosphate esters shows that the degree of sensitization is strongly determined by the structure of the phosphate ester, which increases with the electron affinity of the added radiosensitizers.
Abstract: SummaryThe action of ionizing radiation on aqueous solutions of phosphate esters, including nucleotides and model phosphate ester derivatives of phospholipid membranes, causes the release of inorganic phosphate. Studies with selective radical scavengers implicate hydroxyl radicals as the principal reactive species in this process. In the presence of compounds of high electron affinity, an enhanced radiolytic yield of inorganic phosphate is observed in anoxic and nitrous oxide-saturated solutions. In the radiolysis of 10−2 M phosphate ester solutions, optimum radiosensitization occurs at sensitizer concentrations between 1 and 5 × 10−4 M. The degree of radiosensitization increases with the electron affinity of the added radiosensitizers. Comparison of radiosensitization for different phosphate esters shows that the degree of sensitization is strongly determined by the structure of the phosphate ester.
Patent•
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TL;DR: In this article, a He-Xe laser scans a number of retroreflectors which are strategically located around a D2O plant to detect H2S leaks, and the reflected beam is focussed by a telescope, filtered, and passed into an infra-red detector.
Abstract: The gas detection system provides for the effective detection of gas leaks over a large area. It includes a laser which has a laser line corresponding to an absorption line of the gas to be detected. In the instant case, a He-Xe laser scans a number of retroreflectors which are strategically located around a D2O plant to detect H2S leaks. The reflected beam is focussed by a telescope, filtered, and passed into an infra-red detector. The laser may be made to emit two frequencies, one of which corresponds with an H2S absorption line; or it may be modulated on and off the H2S absorption line. The relative amplitude of the absorbed light will be a measure of the H2S present.
TL;DR: In this paper, it was shown that the linear dependence of In σ σ 0 on time and the independence of the stress-relaxation behaviour on the initial stress implies that the creep rate in the steady-state period can be given by the expression, e = A σ.
TL;DR: SLOWPOKE as discussed by the authors is a new type of nuclear reactor for laboratories, universities, hospitals and research institutes, which is a safe, reliable, low-cost source of neutrons for isotope production and neutron activation analysis.
TL;DR: In this paper, a model for the rigid layer and conjugate modes is used to obtain the interlayer interaction which is shown to be of short range, and a discussion of the identification of polytypes in GaSe in also given.
TL;DR: In this article, the creep curves of Zircaloy-2, 23 mm diameter, have been tested in-reactor at 260 to 300°C (530 to 570 K), with transverse stresses from 100 to 300 MN/m 2.