Atomic Energy of Canada Limited

About: Atomic Energy of Canada Limited is a company organization based out in Ottawa, Ontario, Canada. It is known for research contribution in the topics: Zirconium alloy & Neutron. The organization has 4845 authors who have published 4826 publications receiving 102951 citations.

Momentum Distributions of Photons from Positrons Annihilating in Alkali Halides

Abstract: The angular correlation of photons from the two-gamma decay of positrons in all sodium halides and all alkali chlorides has been measured. The data yields the momentum distribution of the two gamma rays which is also the momentum distribution of the annihilating electron-positron pairs. It is seen that the positive ion has very little influence on the momentum distribution in comparison with the negative ion. These distributions in momentum are compared with the distributions calculated from various models of electron and positron wave functions in the crystal. For fluorides and chlorides the electron-positron wave-function products which yield fits to the experimental data resemble Hartree-Fock free-ion electron wave functions. Both the wave-function products and the free-ion wave functions yield density distributions which are similar to the electron densities obtained by x-ray measurements. This conclusion makes improbable a model of single-particle wave functions describing both the electrons and the positron tightly bound to the negative ion.

Method and apparatus for tig tube welding

Abstract: Described herein is a method and apparatus for fully automatically weld-joining lengths of metal instrument tubing employing the TIG welding process to advance a weld puddle about the periphery of the junction of aligned ends of straight tubing, respective end portions of which are held in a closed chamber rigidly clamped in spaced seats of a robust metal head to resist elongation by heating; the unit comprises a handle portion axially separably joined with the head and providing drive to a rotating electrode carrier spool therein about the work, angular interval marking signals being transmitted to a remote control unit from which welding current and gas is supplied to the head according to a weld program selected for the material being joined. A welding cycle commences with a stationary arc developing a weld pool, followed by advance at uniform speed of the arc with controlled current levels over sectors, the arc being sustained beyond 360* and the complete cycle spanning two revolutions of the carrier and terminating with a bead-cooling gas flow. Repeatable welds of high quality on a production basis may be obtained, characterized by minimal fall-in of bead, full area fusion of faces, and constant internal diameter.

The dose window for radiation-induced protective adaptive responses.

Abstract: Adaptive responses to low doses of low LET radiation occur in all organisms thus far examined, from single cell lower eukaryotes to mammals. These responses reduce the deleterious consequences of DNA damaging events, including radiation-induced or spontaneous cancer and non-cancer diseases in mice. The adaptive response in mammalian cells and mammals operates within a certain window that can be defined by upper and lower dose thresholds, typically between about 1 and 100 mGy for a single low dose rate exposure. However, these thresholds for protection are not a fixed function of total dose, but also vary with dose rate, additional radiation or non-radiation stressors, tissue type and p53 functional status. Exposures above the upper threshold are generally detrimental, while exposures below the lower threshold may or may not increase either cancer or non-cancer disease risk.