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.

Synthetic MgGa 2 O 4 -Mg 2 GeO 4 spinel solid solution and β-Mg 3 Ga 2 GeO 8 : chemistry, crystal structures, cation ordering, and comparison to Mg 2 GeO 4 olivine

Abstract: Structural parameters and cation ordering are determined for four compositions in the synthetic MgGa2O4-Mg2GeO4 spinel solid solution (0, 8, 15 and 23 mol% Mg2GeO4; 1400 °C, 1 bar) and for spinelloid β-Mg3Ga2GeO8 (1350 °C, 1 bar), by Rietveld refinement of room-temperature neutron diffraction data. Sample chemistry is determined by XRF and EPMA. Addition of Mg2GeO4 causes the cation distribution of the MgGa2O4 component to change from a disordered inverse distribution in end member MgGa2O4, [4]Ga = x = 0.88(3), through the random distribution, toward a normal cation distribution, x = 0.37(3), at 23 mol% Mg2GeO4. An increase in ao with increasing Mg2GeO4 component is correlated with an increase in the amount of Mg on the tetrahedral site, through substitution of 2 Ga3+⇄ Mg2++Ge4+. The spinel exhibits high configurational entropy, reaching 20.2 J mol−1 (four oxygen basis) near the compositional upper limit of the solid solution. This stabilizes the spinel in spite of positive enthalpy of disordering over the solid solution, where ΔH D = αx + βx 2, α = 22(3), β = −21(3) kJ mol−1. This model for the cation distribution across the join suggests that the empirically determined limit of the spinel solid solution is correlated with the limit of tetrahedral ordering of Mg, after which local charge-balanced substitution is no longer maintained. Spinelloid β-Mg3Ga2GeO8 has cation distribution M1[Mg0.50(2)Ga0.50(2)] M2[Mg0.96(2)Ga0.04(2)] M3[Mg0.77(2) Ga0.23(2)]2 (Ge0.5Ga0.5)2O8 (tetrahedral site occupancies are assumed). Octahedral site size is correlated to Mg distribution, where site volume, site distortion, and Mg content follow the relation M1

Phase transformation in magnesium hydride induced by ball milling

Abstract: Changement de phase induit par broyage mecanique dans l'hydrure de magnesium. La synthese de l'hydrure de magnesium par broyage reactif mene a la formation d'une phase orthorhombique metastable (γ-MgH 2 ) en plus de la phase quadratique β-MgH 2 . Les structures des phases β-MgD 2 et γ-MgD 2 du MgD 2 nanocristallin broye ont ete etudiees par diffraction de neutrons sur poudre. Les structures de β-MgD 2 et γ-MgD 2 prepares par broyage mecanique sont deformees par rapport aux memes phases synthetisees par haute pression et haute temperature. Dans la phase β-MgD 2 les liaisons Mg-D sont symetriquement deformes alors que dans la phase γ-MgD 2 seule une liaison est deformee. Les microcontraintes associees aux champs de deformation et aux defauts causes par le broyage a billes sont vraisemblablement la force motrice de cette transformation de phase.

Karyotype analysis and optimization of mitotic index in Picea mariana (black spruce) preparations from seedling root tips and embryogenic cultures

Abstract: Karyotype analysis and optimization of mitotic index in Picea mariana (black spruce) preparations from seedling root tips and embryogenic cultures

Ethanol enhances collective dynamics of lipid membranes.

Abstract: From inelastic neutron-scattering experiments and all atom molecular dynamics simulations we present evidence for a low-energy dynamical mode in the fluid phase of a 1,2-dimyristoyl-sn-glycero-3-phoshatidylcholine (DMPC) bilayer immersed in a 5% water/ethanol solution. In addition to the well-known phonon that shows a liquidlike dispersion with energies up to 4.5 meV, we observe an additional mode at smaller energies of 0.8 meV, which shows little or no dispersion. Both modes show transverse properties and might be related to molecular motion perpendicular to the bilayer.