Showing papers by "Atomic Energy of Canada Limited published in 1976"
TL;DR: Direct biochemical evidence is provided that diploid strains from AT donors are indeed impaired in DNA repair; in particular, these cell lines possess an enzymatic defect in an excision-type repair process operating on γ-modified nitrogenous base residues.
Abstract: ATAXIA telangiectasia (AT) (Louis–Bar syndrome) is a rare human neurovascular disease displaying an autosomal recessive pattern of inheritance1–3. Affected individuals, although clinically normal at birth, symptomatically develop cerebellar ataxia (loss of muscular coordination) and oculocutaneous telangiectasis (chronic dilation of the small blood vessels) in early childhood. The course of the disease follows a variable progression commonly leading to total neurological incapacitation before puberty. Accessory complications include lymphoreticular neoplasia2,3, bronchiectasis1,2, recurrent sinopulmonary infections1,2, decreased levels of serum immunoglobulins IgA and IgE (refs 3 and 4), impaired cellular immunity3,4, and widespread chromosomal instability5. AT patients, on receiving conventional radiotherapy for tumour treatment, tend to develop unusually severe complications often culminating in premature death6–8. Pronounced radiosenitivity is also observed at the cellular level in laboratory studies; the number of radiation-induced chromosomal aberrations is enhanced in leukocytes obtained from AT donors9. Moreover, diploid fibroblasts cultured from affected individuals exhibit a reduced ability to form colonies following exposure to γ radiation10 and radiomimetic chemicals11. Since the principal damage induced by both types of agents occurs in the DNA and seems to be acted on by the same enzymatic repair mechanisms12,13, it would seem probable that the molecular basis for the clinical radiosensitivity of AT patients stems from a deficient DNA repair mechanism. We therefore measured the DNA repair properties of AT fibroblasts after exposure to γ radiation. Data presented below provide direct biochemical evidence that diploid strains from AT donors are indeed impaired in DNA repair; in particular, these cell lines possess an enzymatic defect in an excision-type repair process operating on γ-modified nitrogenous base residues.
347 citations
TL;DR: In this paper, the role of excited states in the radiation chemistry of O 2, NH 3, CO, CO 2, H 2 S, H 2 O and NH 3 is discussed.
156 citations
TL;DR: Comparison with cell survival measurements at much lower doses suggests that loss of reproductive capacity corresponds to induction of approximately one double-strand break, which suggests that, in mammalian cells, most double- Strand breaks are not repairable, while all single-strands are repaired except those that are sufficiently close on complementary strands to constitute double-Strand breaks.
Abstract: The yields of unrepairable single-and double-strand breaks in the DNA of x-irradiated Chinese hamster cells were measured by low-speed neutral and alkaline sucrose density gradient sedimentation in order to investigate the relation between these lesions and reproductive death. After maximal single-strand remoining, at all doses, the number of residual single-strand breaks was twice the number of residual double-strand breaks. Both double-strand and unrepairable single-strand breaks were proportional to the square of absorbed dose, in the range 10-50 krad. No rejoining of double-strand breaks was observed. These observations suggest that, in mammalian cells, most double-strand breaks are not repairable, while all single-strand breaks are repaired except those that are sufficiently close on complementary strands to constitute double-strand breaks. Comparison with cell survival measurements at much lower doses suggests that loss of reproductive capacity corresponds to induction of approximately one double-strand break.
146 citations
TL;DR: The enzyme protected membranes after an acute exposure and from low level radiation at natural background while its inactivated form sensitized.
127 citations
TL;DR: In this article, a method of evaluating the non-equilibrium in vapor enthalphy (due to vapor superheating) from experimentally obtained post-dryout data is presented.
122 citations
01 Jan 1976
TL;DR: The oxidation behavior of zirconium and its alloys in both gaseous and aqueous environments is summarized, and how other environments, such as liquid metals, can be considered as special cases of one or other of the main classes is shown.
Abstract: I have tried to summarize the oxidation behavior of zirconium and its alloys in both gaseous and aqueous environments, and to show how other environments, such as liquid metals, can be considered as special cases of one or other of the main classes. It will be appreciated from the extent of the literature on zirconium alloys (the over-600 references are by no means a complete bibliography) that it was impossible to discuss the details of many of the studies reported. To achieve a comprehensive survey in the space available it has been necessary to present a single coherent view of the field, without perhaps devoting sufficient space to opposing views and the evidence adduced in their favor. I have endeavored to make the references as comprehensive as possible, however, only omitting some early ones that are cited in later publications, which adequately summarized their contents. Readers who may be stimulated to pursue the details of any particular aspect of the field should have little difficulty tracing these other references from the bibliographies of the works that are cited. Finally, if the gaps in our knowledge, which I have attempted to illuminate, provide the inspiration for even one reader to devise experiments which can unambiguously resolve some of the many still unanswered questions, then I will consider this review to have been worthwhile.
117 citations
TL;DR: In this article, the pzc values of Co(OH)2, Co3O4, NiO, and NiO have been determined between 25 and 80°C.
114 citations
99 citations
TL;DR: In this article, the stopping power of six materials (i.e., 19 F, 24 Mg, 27 Al, 32 S and 35 Cl) were measured for energies ∼ 0.2 to ∼ 3.5 MeV/nucleon in the range 8 ≤ Z ≤ 20.
98 citations
TL;DR: In this paper, the adsorption of CO and CO 2 on platinum, nickel and copper was studied by X-ray and UV photoelectron spectroscopy, and the results indicated that CO 2 is physisorbed on platinum and copper and that the bonding of CO on all three metals involves the metal d-electrons and particularly the 5σ level of CO.
87 citations
TL;DR: In this paper, small violations of the additivity rule for isomeric two-proton states in 202, 208, 208 and 210Po were observed and the relative g-factors of the 110 ns 8+ and 24 ns 13 2 − states were measured for the first time.
TL;DR: In this paper, a mathematical model to describe the contamination of steel surfaces by 60Co in high-temperature water is developed, assuming that 60Co is incorporated into the growing oxide film on the s...
Abstract: A mathematical model to describe the contamination of steel surfaces by 60Co in high-temperature water is developed. The model assumes that 60Co is incorporated into the growing oxide film on the s...
TL;DR: In this paper, X-ray line broadening measurements and electron microscopy have been used to characterize the dislocation substructures in extruded, cold-worked and stress relieved Zr-2.5 wt% Nb pressure tube materials.
TL;DR: The inelastic scattering of thermal neutrons from liquid helium at 1.2 K has been measured for wavevector transfers in the range 6.0 ≤ Q ≤ 12.0 »−1.
Abstract: The inelastic scattering of thermal neutrons from liquid helium at 1.2 K has been measured for wave-vector transfers in the range 6.0 ≤ Q ≤ 12.0 »−1. Oscillations in the widths of the scattered-neutron distributions as a function of Q are observed to persist at least up to 12.0 »−1. A simple physical model suggests that these oscillations, which reflect the presence of final-state interactions and interference effects, have their origin in similar oscillations which occur in the He-He scattering cross section. Detailed measurements at Q = 10.0»−1 show no evidence of a well-defined condensate peak, and calculations suggest that Q values in the range 50–100 »−1 or greater may be required to observe a separate condensate component in the line shape. A method is developed for eliminating a major part of the effects of final-state interactions from the Doppler part of the distributions, and the corrected data at Q = 10.0 »−1 are analyzed to determine the momentum distribution in liquid helium at 1.2 K. The resulting distribution is found to be non-Gaussian with a well-defined high-momentum tail. The result is compared with the momentum distribution obtained recently by Mook from thermal neutron time-of-flight data near Q = 15 »−1 and with theoretical calculations of McMillan and of Kalos.
TL;DR: In this article, a zirconium single crystal was irradiated at 473-523 K and its growth measured by transmission electron microscopy (TEM) at various fluences by TEM, and an explanation for the measured growth was given in terms of defects that are too small to be seen in the electron microscope, i.e. point defects or very small defect clusters.
TL;DR: In this article, the static fatigue limit is determined by measuring the change in strength distribution of a representative sample after a high-temperature anneal under a fixed tensile stress.
Abstract: After a review of the literature on the static fatigue limit, it was concluded that the normal method for its determination, using time-to-rupture data, is inadequate. There are very few experimental demonstrations of the existence of a true fatigue limit, and it is difficult to measure its value with any statistical confidence. An alternative experimental approach is suggested which is based on measuring the change in strength distribution of a representative sample after a high-temperature anneal under a fixed tensile stress. This stress weakens weak specimens in the as-received distribution, whereas strong specimens gain in strength. Those specimens whose strength remains constant demonstrate the existence of a fatigue limit and can be used to calculate a numerical value. The results are analyzed on the basis of the Charles-Hillig stress corrosion theory, which has been slightly modified to facilitate the examination of the parameters associated with the fatigue limit. This analysis relates the static fatigue limit to the effective surface energy appropriate to the fatigue mechanism, i.e. corrosion caused by water vapor. Some implications of the modified model are discussed.
TL;DR: Bovine superoxide dismutase, injected intravenously at 35 μg/g body weight 1 h before and after the X-irradiation, hastened the recovery such that at 22 days post-exposure, the erythrocyte count and percentage reticulocytes were both significantly different from the control values.
TL;DR: In this article, the peritectoid transformation Zr + Zr2Al → Zr3Al has been examined in Zr 7.6 to 9.0 wt.% Al ingots using isothermal annealing and optical microscopy.
TL;DR: Electron-affinic nitrofuran derivatives interfere with normal cellular metabolism by providing an electron shunt, apparently via free radical intermediates, between endogenous cellular reducing species and oxygen, in a manner analogous to that of vitamin K 3 .
TL;DR: Pulse radiolysis has been used to measure the rates of reactions of O 2 − with electron donors and acceptors, either directly or by a competition kinetic method using p -benzoquinone.
TL;DR: In this article, the authors calculated the effective number of immobile layers in a film of constant thickness, assuming that the surfaces of the film surfaces are slightly immobile and using a form of Vrij's theory for the inherent breaking time of films.
Abstract: Coalescence times are reported for bubbles of H2S and CO2 formed on adjacent nozzles in water. With CO2, times were small (1–3 ms) at pressures below 2 MPa, and rose to 20 ms at 3.4 MPa. With H2S, the logarithm of the coalescence time was proportional to pressure, and coalescence times reached 100 ms at 1.7 MPa. Film stretching rates were calculated assuming that the film surfaces were slightly immobile. By using a form of Vrij's theory for the inherent breaking time of films of constant thickness, the effective number of immobile layers could be calculated. Since these were in the range 10−2 to 10−3, only a small amount of “stiffness” in the film surface is enough to cause large changes in coalescence time.
On rapporte les temps de coalescence dans le cas de bulles de H2S et de CO2 formees dans l'eau sur des ajutages adjacents. Pour CO2, les temps de coalescence se sont averes faibles (1 a 3 minisecondes) a des pressions absolues inferieures a 2MP; ils se sont accrus a 20 minisecondes a une pression absolue de 3.4. Dans le cas de H2S, le logarithme du temps de coalescence a ete proportionnel a la pression et les temps de coalescence ont atteint 100 minisecondes a une pression absolue de 1.7MP. On a calcule les taux d'etirage des pellicules en supposant que les surfaces de celles-ci etaient legerement immobiles. En employant une forme de la theorie de Vrij Telativement au temps inherent de rupture des pellicules d'epaisseur constante, on a pu calculer le nombre effectif des couches immobiles; vu que celles-ci variaient entre 10−2 et 10−3, měme une faible quantite de rigidite dans la surface de la pellicule s'est averee suffisante pour produire des changements considerables dans le temps de coalescence.
TL;DR: Differential cross sections have been measured for the ground state transitions at a bombarding energy of 93 MeV; the cross section leading to the first excited state of 212 Po was also measured as mentioned in this paper.
TL;DR: In this article, an experimental study of the relaxation of a (111) platinum surface using MeV He + backscattering was carried out and an outward relaxation of (0.31 ± 0.06) was obtained for surfaces with monolayer coverages of adsorbed oxygen.
TL;DR: In this paper, the authors used channeling and Rutherford backscattering of 1 MeV He ions to measure the terminal solid solubility of hydrogen in niobium and of deuterium in Niobium over the concentration range 0.24 to 3.45 at percent and temperature range of 161 to 249/sup 0/K.
TL;DR: In this article, a dynamic process of oxide crystallite nucleation, recrystallization and growth was found for oxide films of less than 365 nm due to the presence of a dense network of amorphous oxide protusions at the oxide/metal interface.
TL;DR: In this article, high-temperature mechanical properties were studied in Zr--2.5 percent Nb alloy, in which the cap alpha....-->....beta.. transformation range covers 880 to 1160/sup 0/K.
TL;DR: In this article, the authors used high-speed liquid chromatography for the analysis of elemental sulfur in styrene-divinylbenzene (SDSN) packings.
TL;DR: Isotopic oxygen targets, 1 cm 2 with up to 50 μg oxygen/cm 2 measured with a standard error of 1%, can be prepared by anodizing tantalum in 0.5 ml enriched water.
TL;DR: In this article, the shapes of crystal-blocking angular distributions have been used to study the fission decay of excited compound nuclei produced by bombardment of tungsten with $ √ O$ ions.
Abstract: The shapes of crystal-blocking angular distributions have been used to study the fission decay of excited compound nuclei produced by bombardment of tungsten with $^{16}\mathrm{O}$ ions. The results show that while most of the fission decays (\ensuremath{\sim}80%) occur with lifetimes too short to be measured by the blocking technique ($\ensuremath{\tau}\ensuremath{\lesssim}{10}^{\ensuremath{-}18}$ sec), a large fraction (\ensuremath{\sim}20%) corresponds to lifetimes $\ensuremath{\tau}\ensuremath{\gtrsim}{10}^{\ensuremath{-}16}$ sec. This indicates a significant contribution from fission after evaporation of several neutrons.