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.

Partitioning of ethanol into lipid membranes and its effect on fluidity and permeability as seen by X-ray and neutron scattering

Abstract: We present a combined neutron and X-ray scattering investigation to study the effect of ethanol on the molecular structure and dynamics of lipid membranes. 1,2-Dimyristoyl-sn-glycero-3-phoshatidylcholine (DMPC) powder hydrated with a 5 wt% ethanol solution (corresponding to 2 mol% of ethanol) was used in this study. From high-resolution X-ray experiments the position and partitioning of the ethanol molecules in the phospholipid bilayers was determined in their gel and fluid phases. We find that the ethanol molecules reside in the head group region of the bilayers, with 1.6 ethanol molecules per lipid molecule in the gel phase and 1.2 ethanol molecules per lipid molecule in the fluid phase. We find evidence for enhanced permeability in both fluid and gel phases of the phospholipid bilayers in the presence of ethanol molecules. Elastic and quasi-elastic neutron scattering data, obtained using a neutron backscattering spectrometer, was used to study slow, nanosecond molecular dynamics on length scales corresponding to lipid diffusion, acyl chain dynamics and solvent dynamics. While the presence of ethanol molecules had no observable effect on these types of dynamics in the fluid (Lα) phase, the membranes appeared to have a higher degree of order in gel (Lβ) and ripple (Pβ′) phases. In particular, lipid diffusion was found to be slower by a factor of two in the more rigid gel phase when ethanol was present.

Evaluation of somaclonal variation during somatic embryogenesis of interior spruce (Picea glauca engelmannii complex) using culture morphology and isozyme analysis.

Abstract: Somaclonal variation during interior spruce (Picea glauca engelmannii complex) somatic embryogenesis was evaluated using culture morphology and isozyme analysis. Genotype-specific abscisic acid-dependent developmental profiles and isozyme patterns were similar for subclone and parent line embryogenic cultures and cotyledonary somatic embryos. Extensive analysis of fifteen hundred subclone embryos of one genotype revealed no isozyme pattern variation. Initiation of embryogenic cultures was dependent on the developmental stage of the explant although cultures derived from different stages were morphologically similar. The embryogenic cultures initiated from interior spruce embryos show a high degree of genetic stability in that the morphological behavior and isozyme phenotype were always consistent with that of the explant genotype. These results support the conclusion that this culture system is appropriate for clonal propagation of interior spruce.

Corrosion Behavior of Uranium Dioxide in Alpha Radiolytically Decomposed Water

Abstract: The response of the corrosion potential of a UO 2 electrode to oxidants (H 2 O 2 ,O 2 ) produced by the alpha radiolysis of water has been measured in a thin-layer electrochemical cell. This cell allows the electrode to be brought within ∼25 μm of a gold-plated alpha source, thereby ensuring the uniform distribution of radiolytic oxidants in the aqueous solution filling the gap. The kinetics of water radiolysis, coupled with the surface-catalyzed decomposition of H 2 O 2 and diffusive transport of radiolytic species out of the electrode-source gap, was modeled using a finite difference description of the cell and the commercial numerical integration software, Facsimile. Using this approach, the mechanism of UO 2 corrosion in the presence of alpha radiolysis was shown to be dominated by reaction of the fuel with radiolytically produced H 2 O 2 . To explain the results, two surface-catalyzed H 2 O 2 decomposition processes were invoked: one with H 2 to produce H 2 O, and a second process leading to the production of O 2 and H 2 O. For sufficiently high alpha source strengths, the fuel behavior becomes redox-buffered, i.e., independent of alpha source strength, due to the presence of a corrosion product deposit.