Chalk River Laboratories

About: Chalk River Laboratories is a based out in . It is known for research contribution in the topics: Neutron diffraction & Neutron scattering. The organization has 2297 authors who have published 2700 publications receiving 73287 citations.

Photoreversal of ultraviolet-induced mutagenic and lethal effects in Escherichia coli.

Abstract: When living cells are irradiated with ultraviolet, some of the individuals are killed and some are caused to mutate. Further, the ultraviolet wave lengths that are most active in producing the two effects are essentially the same and are those that are most readily absorbed by the nucleic acids. This implies a relationship between the induced killing and mutation, but the nature of the relationship is not known. Recently it has been found that both the lethal and the mutagenic effects of irradiation with 2,537 A ultraviolet (which is strongly absorbed by the nucleic acids) can be partially reversed by posttreatment with visible light and with near ultraviolet. The reversal of the lethal effect, which is termed \"photoreactivation,\" was demonstrated in Streptomyce8 griseus by Kelner (1949a) and was later shown to occur in a wide range of organisms including the bacterial viruses, bacteria, yeasts, molds, and protozoa (Kelner, 1949b; Novick and Szilard, 1949; Dulbecco, 1950; Goodgal, 1950; Kimball and Gaither, 1950). A corresponding reversal of the mutagenic effect has now been reported in bacteria (Novick and Szilard, 1949; Newcombe, 1950; see also Kelner, 1949b, 1950), in molds (Goodgal, 1950; Roegner, unpublished), and in Paramecium (Kimball and Gaither, 1950; Kimball, 1950). The present report deals with the probable nature of the relationship between the lethal and the mutagenic effects.

Excitations in KCoF3-I. Experimental

Abstract: Dispersion curves for magnons and phonons propagating in KCoF3 at low temperatures have been determined by means of neutron inelastic scattering techniques. Two branches of magnetic excitations have been observed corresponding to a transition between the two members of the ground state doublet (j=1/2) of the Co2+ ion and a transition between the ground state and the lowest member of the j=3/2 spin-orbit level. Neither branch shows evidence for the directional anisotropy which has been suggested for the exchange interactions in KCoF3; any splitting of the doubly degenerate magnon branch is shown to be less than 8% in frequency. The magnon branch of lowest frequency interacts with a phonon branch in the vicinity of the magnetic zone centre. The strength of the magnon-phonon interaction is found to be 0.35+or-0.10 THz and from the temperature dependence of the modes the magnon-phonon interaction is shown to be appreciable only within a radius 0.2*2 pi /a of the magnetic zone centre. The magnetic modes of higher frequency show a market decrease in intensity with increasing temperature but little change in frequency in accordance with expectations for a transition that depends strongly on the spin-orbit coupling but only weakly on the exchange.

The development of intergranular strains in a high-strength steel

Abstract: In situ neutron diffraction measurements have been made on a high-strength low-alloy steel to study the generation of intergranular strains under uniaxial load. Intergranular strains were found to be actively developed at small plastic deformation (< 4.5 per cent) and stay unchanged in subsequent loadings. Large tensile strains of an average 7 × 10−4 were observed for the (002) reflections transverse to the stress axis whereas intergranular effects are comparatively insignificant for other reflections. Experimental results were found to be in excellent agreement with the predictions based on the elastoplastic self-consistent model.

Accelerated Removal of Fe-Antisite Defects while Nanosizing Hydrothermal LiFePO4 with Ca(2).

Abstract: Based on neutron powder diffraction (NPD) and high angle annular dark field scanning transmission electron microscopy (HAADF-STEM), we show that calcium ions help eliminate the Fe-antisite defects by controlling the nucleation and evolution of the LiFePO4 particles during their hydrothermal synthesis. This Ca-regulated formation of LiFePO4 particles has an overwhelming impact on the removal of their iron antisite defects during the subsequent carbon-coating step since (i) almost all the Fe-antisite defects aggregate at the surface of the LiFePO4 crystal when the crystals are small enough and (ii) the concomitant increase of the surface area, which further exposes the Fe-antisite defects. Our results not only justify a low-cost, efficient and reliable hydrothermal synthesis method for LiFePO4 but also provide a promising alternative viewpoint on the mechanism controlling the nanosizing of LiFePO4, which leads to improved electrochemical performances.