Showing papers by "Atomic Energy of Canada Limited published in 1971"
TL;DR: In this paper, a detailed analysis of the grain-boundary sliding occurring during diffusion creep in simple tension has been made, based on this point of view, and it is concluded that the relative velocities of displacement by grain boundary sliding and by diffusion at a particular point on a grain boundary are fixed by the geometry of the grains.
Abstract: The diffusion creep of polycrystalline materials must be accompanied by grain-boundary sliding in order that material continuity be preserved. Since both grain-boundary sliding and the addition of atoms to a boundary between two grains result in a relative translation of the grains, it is possible to regard the material as deforming by the motion of its constituent crystals. A detailed analysis of the grain-boundary sliding occurring during diffusion creep in simple tension has been made, based on this point of view. It is concluded that the relative velocities of displacement by grain-boundary sliding and by diffusion at a particular point on a grain boundary are fixed by the geometry of the grains. The relationship between these relative displacement velocities is found and it is concluded that sliding is occurring at most grain boundaries in a normal polyerystalline material undergoing diffusion creep. It is also shown that sliding on most boundaries makes a positive contribution to specimen s...
93 citations
TL;DR: It is concluded that O2 sensitizes Chinese hamster cells in a dose-modifying fashion, irrespective of position in the cell-cycle.
Abstract: SummaryThe effectiveness of p-nitroacetophenone (PNAP) as a sensitizing agent to x-rays has been measured in asynchronous and synchronous populations of Chinese hamster cells. PNAP was found to sensitize hypoxic cells selectively (those equilibrated with an environment of 96 per cent N2 + 4 per cent CO2 containing less than 2 p.p.m. O2) with a maximum dose-modifying factor (DMF) of ∼ 1·50 at concentrations of 400 µM and greater in complete medium. In a parallel radiation scheme, the DMF for cells saturated with air was consistently between 2·75 and 3·05. In synchronously-growing Chinese hamster cells, the cyclic variation in surviving fraction measured for cells in air experiencing a radiation dose of 1055 rads could be reproduced for cells irradiated in hypoxic conditions with 2840 rads. We conclude that O2 sensitizes Chinese hamster cells in a dose-modifying fashion, irrespective of position in the cell-cycle. Hypoxic synchronized cells irradiated in the presence of PNAP with 1980 rads are also sensitiz...
80 citations
TL;DR: In this article, a least-mean-square fit of the data points yields The present results are in fair agreement with the work of Fricke (1967), they are not, however, consistent with previous 54Mn tracer diffusion studies in Al made by Lundy and Murdock (1962).
Abstract: Measurements of 55Mn and 56Mn tracer diffusion in single crystal and polycrystalline specimens of 99.999% pure Al have been made in the range 460 to 660°C. A least-mean-square fit of the data points yields The present results are in fair agreement with the work of Fricke (1967). They are not, however, consistent with previous 54Mn tracer diffusion studies in Al made by Lundy and Murdock (1962). It appears that the discrepancy may have resulted from the presence of an isotopic impurity in the work of Lundy and Murdock.
79 citations
TL;DR: In this paper, a thermodynamic and kinetic model is developed which predicts the high temperature behavior of cracks under conditions of tensile and compressive stress, and expressions for the time to rupture following the propagation of Griffith cracks by lattice diffusion, surface diffusion and vapour phase transport.
77 citations
TL;DR: In this paper, a summary of the predicted image properties arising from the calculations is given, by examining lattice fringe images of inclined dislocations in deformed Ge, these properties are verified experimentally.
Abstract: Recently several very clear lattice fringe images have been published in which the perturbing influence of lattice defects is evident in the form of bending and terminating fringes. Detailed analyses of these images have been given, based on the assumption that there exists a one-to-one correspondence between fringe distribution and lattice plane distribution. From studies of the properties of calculated images, doubt has been cast upon the validity of such a straightforward interpretation. Analysis of these calculated images suggested that a change in the diffraction geometry could produce changes in the number of terminating fringes and in the fringe bending which were not related to the lattice plane geometry in any simple way. In this paper a summary of the predicted image properties arising from the calculations is given. By examining lattice fringe images of inclined dislocations in deformed Ge, these properties are verified experimentally. As a result it is shown that it is not correct to ...
74 citations
TL;DR: In Rhodnius, a volatile substance produced by mating pairs is attractive to male insects; the pheromone acts also as a sexual stimulant; males respond in the absence of females by attempting copulation with other males.
Abstract: In Rhodnius, a volatile substance produced by mating pairs is attractive to male insects. The pheromone acts also as a sexual stimulant; males respond in the absence of females by attempting copulation with other males. Air swept over mating pairs and conducted to a cage at a considerable distance proved to be highly attractive to males. Proximity of the sexes, without opportunity for actual contact, does not stimulate production of the pheromone. Since males and females will copulate only after a blood meal, feeding is a prerequisite to pheromone production. Also, unfed males will not respond to the attractant. Males of this nocturnal species were stimulated only in complete darkness.
52 citations
TL;DR: In this paper, the current status of the theory of anharmonic effects in insulators is reviewed, mainly from the simplest insulators, namely rare gas solids (RGS) and alkali-halides (AH) mostly of the rocksalt structure.
Abstract: Anharmonic effects manifest themselves in everyday properties of solids. Two of the more obvious examples are thermal expansion and heat conductivity. More sophisticated examples anharmonicity are provided by the direct measurement of the lifetimes and of the pressure and temperature dependence of modes of vibration solids by infrared, Raman, Brillouin, or neutron spectroscopy. The present article reviews current status of the theory of anharmonic effects in insulators. We will draw our examples almost exclusively from the simplest insulators, namely the fcc rare gas solids (RGS) and alkali-halides (AH) mostly of the rocksalt structure. Much what we have to say is applicable to other kinds solids also, but we shall not dwell on this aspect. We shall arbitrarily exclude perhaps the two most interesting classes of anharmonic solids, that ferroelectrics and quantum solids. These subjects are sufficiently developed as to warrant reviews their own and it would be impossible to do them justice in the s...
51 citations
TL;DR: In this article, a relationship between diameter and Young's modulus and tensile strength of graphite fibres, manufactured from both polyacrylonitrile and rayon precursors, is demonstrated.
Abstract: A relationship between diameter and both Young's modulus and tensile strength of graphite fibres, manufactured from both polyacrylonitrile and rayon precursors is demonstrated. Thin fibres exhibit higher values of Young's modulus and tensile strength than thick fibres. The observed relationship is deduced to be a consequence of the “sheath” and “core” type structure which is characteristic of these fibres.
48 citations
TL;DR: It is generally agreed that lateral vibration of nuclear fuel elements is random in nature and is caused by random pressure fluctuations acting on the element surface as discussed by the authors, and a series of tests have been con...
Abstract: It is generally agreed that lateral vibration of reactor fuel elements is random in nature and is caused by random pressure fluctuations acting on the element surface.A series of tests has been con...
42 citations
TL;DR: In this paper, it was found that two branches of well-defined magnetic excitatios, both of which exhibit propagating character, occur at certain compositions, and an extension of Anderson's criterion for localization in disordered alloys gave approximate agreement with the observed character.
Abstract: Magnetic excitations in several single crystals of the systems K(Co,Mn)${\mathrm{F}}_{3}$ and (Co, Mn)${\mathrm{F}}_{2}$ have been studied by neutron inelastic scattering. It is found that two branches of well-defined magnetic excitatios, both of which exhibit propagating character, occur at certain compositions. The dispersion relation for two branches of propagating excitations cannot be adequately described by current theories, but an extension of Anderson's criterion for localization in disordered alloys gives approximate agreement with the observed character.
38 citations
TL;DR: It is shown that a qualitatively similar, GI-blocked population of cells is shown to be produced by growing mammalian cells in script in preparation for manucan production.
Abstract: Many cell lines grown in tissue culture accumulate in a postmitotic, preDNA-synthetic part of the cell cycle when brought to a nonproliferating state by a variety of techniques (1-5) . In our laboratory we have recently shown that a qualitatively similar, GI-blocked population of cells I Chapman, J. D ., R . G. Webb, and J . Borsa. Manucan be produced by growing mammalian cells in script in preparation .
TL;DR: By expanding in appropriate series of singular harmonic functions, a solution to the equipotential problem for four circular poles (or electrodes) with quadrupole symmetry was found in this paper, where the duodecapole term in the potential was absent when the ratio of pole diameter to throat diameter is 1.14511; the contributions from multipoles of higher order are found to be small.
TL;DR: In this article, a theory for the size distributions of voids produced in metals by fast-neutron irradiation was developed, which can be interpreted directly in terms of the nucleation rate and the "equivalent" vacancy concentration.
TL;DR: In this article, a consistent explanation for the diffraction structure at large momentum transfer can be obtained in terms of the short-range correlations in the nuclear wave function, and the experimental results for the charge form factor are quite well reproduced.
TL;DR: In this article, Doppler-shift attenuation measurements on deexcitation γ-rays in three Ge(Li) detectors at 0°, 90° and 125° yielded mean lifetimes (in ps) of levels at 1.633 MeV (1.15 ± 0.20).
TL;DR: In this paper, the static quadrupole moments of the first excited states in 32 S and 112 Cd have been measured using a 100 MeV 32 S beam and the results indicate that 32 S deviates strongly from a purely vibrational nucleus.
TL;DR: The effect of fast neutron irradiation at 420 and 500 °C on the structure and mechanical properties of RAE type, high modulus graphite fibers is discussed and discussed in this paper.
TL;DR: In this article, the stopping cross sections of deutrons in titanium have been measured from 30-200 keV. Oxidation of the titanium film was eliminated by measuring the energy loss in thin Al-Ti-Al sandwiches.
TL;DR: A new method for extracting ribosomal ribonucleic acid (RNA) and polyribosomes from Schizosaccharomyces pombe, a fission yeast, has been developed.
Abstract: A new method for extracting ribosomal ribonucleic acid (RNA) and polyribosomes from Schizosaccharomyces pombe, a fission yeast, has been developed. Cells grown in the presence of 2-deoxyglucose were found to be more sensitive to the action of Glusulase; a short period of treatment (10 to 20 min) at 0 C was sufficient to convert the cells to osmotically sensitive structures. From these, ribosomal RNA and polyribosomes were readily prepared.
TL;DR: In this paper, the absence of dark field images indicates that an amorphous state has been formed where areas of atomic order are ⩽ 20 A in diameter and the unaccounted volume increase of 2.4% which occurs in U 3 Si irradiated under similar conditions might be explained in terms of vacancy clusters, a size that is less than can be resolved by the microscope technique used.
TL;DR: The structural changes of U 3 Si under argon ion bombardment and subsequent annealing have been examined by X-ray diffraction as discussed by the authors, showing that the structure degenerates through disordered cubic modification to an amorphous phase; the change may involve faulting on prism planes.
TL;DR: In this article, three cold-worked pressure tubes of Zr-2.5 wt% Nb were irradiated as components of Chalk River reactor loops, under operating conditions similar to those in the Canadian design of heavy water cooled, heavy water moderated power reactor.
TL;DR: In this article, the level densities that control statistical proton emission depend on the (n, p) Q -value, the pairing energy and a shell-dependent parameter a.
TL;DR: This chapter discusses that, by far the strongest stimulus for research in radiation genetics, in terms of financial support, has occurred because of concern over the consequences for man of the increasingly widespread use of major sources of radiation and radioactive materials, as a result of the development of nuclear energy.
Abstract: Publisher Summary This chapter explores that radiations are being used, as in the past, to investigate the origins and nature of genetic diversity and the role of selective forces in perpetuating or suppressing newly arisen changes. They are being applied to studies of the structure of genes and chromosomes, and the changes, which these structures are capable of undergoing. With more practical ends in view, the genomes of living cells are being altered by irradiation to improve agricultural crop plants, and to cause death or sterility for the purpose of destroying cancer cells or controlling insect pests. The chapter discusses that, by far the strongest stimulus for research in radiation genetics, in terms of financial support, has occurred because of concern over the consequences for man of the increasingly widespread use of major sources of radiation and radioactive materials, as a result of the development of nuclear energy. It also explored that no conceptual changes that seem likely to affect the field, it constitutes a special reason to re-examine current strategies in radiation genetics.
TL;DR: In this paper, the γ-ray energies of the 4 1 + → 2 1 + and 2 2 + → O 1 + transitions have been determined, with a branching ratio of 5.9 ± 0.3.
TL;DR: In this paper, the effect of temperature on the fracture strength and work of fracture of a self-bonded SiC has been measured from room temperature to 1100° C, and it was shown that over the same temperature range the fracture was observed to increase twofold.
Abstract: The effect of temperature on the fracture strength and work of fracture of a self-bonded SiC has been measured from room temperature to 1100° C. Over the same temperature range the work of fracture was observed to increase twofold. These phenomena were accounted for in terms of the behaviour of the free-silicon phase. In addition, electron microscopy of the fractured surface was undertaken. Fracture chips showed that dislocations were generated during the failure process in both the secondary SiC and silicon phases. Stacking faults were observed in the SiC phases, and some of these were shown to have formed during the fracture process.
TL;DR: In this paper, the structure of effective operators in the spherical shell model was determined in time-dependent perturbation theory and compared with the approach using Bloch-Horowitz theory discussed in paper I.
TL;DR: From a two-beam approximation of the dynamical theory of the relative backscattered electron intensity as a function of direction of incidence, the angular width of electron channelling lines on SEM images can be given by the expression: 2 ωg = 2/ξg|g|, where ξg and g are the extinction distance and the reciprocal lattice vector respectively of the strongly excited reflection.
Abstract: From a two beam approximation of the dynamical theory of the relative backscattered electron intensity as a function of direction of incidence, it is shown that the angular width of electron channelling lines on SEM images can be given by the expression: 2 ωg = 2/ξg|g|, where ξg and g are the extinction distance and the reciprocal lattice vector respectively of the strongly excited reflection. The expression is verified by comparing calculated line-widths with measured widths from silicon as a function of incident beam energy and reflection excited. An appendix is given discussing quantitatively the degradation effects of beam divergence on electron channelling lines. It is suggested that line broadening might be a possible method for assessing lattice distortions.
Durch eine Zweistrahlnaherung der dynamischen Theorie der relativen, ruckgestreuten Elektronenintensitat als Funktion der Einfallsrichtung wird gezeigt, das die Winkelbreite der Elektronen-Channelling-Linien auf SEM-Diagrammen durch den Ausdruck 2ωg = 2/ξg|g| gegeben ist, wobei ξg und g der Extinktionsabstand bzw. der reziproke Gittervektor der stark angeregten Reflexion ist. Der Ausdruck wird durch den Vergleich der berechneten Linienbreiten mit gemessenen Breiten von Silizium als Funktion der einfallenden Strahl-energie und der angeregten Reflexion gepruft. In einem Anhang werden Degradations-effekte der Strahldivergenz in Anwendung auf Elektron-Channelling-Linien quantitativ diskutiert. Es wird gezeigt, das Linienverbreiterung eine mogliche Methode zur Abschatzung von Gitterverzerrungen sein kann.