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.

Formation of Kinetically Trapped Nanoscopic Unilamellar Vesicles from Metastable Nanodiscs

Abstract: Zwitterionic long-chain lipids (e.g., dimyristoyl phosphatidylcholine, DMPC) spontaneously form onion-like, thermodynamically stable structures in aqueous solutions (commonly known as multilamellar vesicles, or MLVs). It has also been reported that the addition of zwitterionic short-chain (i.e., dihexanoyl phosphatidylcholine, DHPC) and charged long-chain (i.e., dimyristoyl phosphatidylglycerol, DMPG) lipids to zwitterionic long-chain lipid solutions results in the formation of unilamellar vesicles (ULVs). Here, we report a kinetic study on lipid mixtures composed of DMPC, DHPC, and DMPG. Two membrane charge densities (i.e., [DMPG]/[DMPC] = 0.01 and 0.001) and two solution salinities (i.e., [NaCl] = 0 and 0.2 M) are investigated. Upon dilution of the high-concentration samples at 50 °C, thermodynamically stable MLVs are formed, in the case of both weakly charged and high salinity solution mixtures, implying that the electrostatic interactions between bilayers are insufficient to cause MLVs to unbind. Impo...

Central mode and spin confinement near the boundary of the superconducting phase in YBa2Cu3O6.353 (Tc=18 K)

Abstract: We have mapped the neutron scattering spin spectrum at low energies in $\mathrm{Y}{\mathrm{Ba}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{6.353}$ $({T}_{c}=18\phantom{\rule{0.3em}{0ex}}\mathrm{K})$, where the doping $\ensuremath{\sim}0.06$ is near the critical value $({p}_{c}=0.055)$ for superconductivity. No coexistence with long-range-ordered antiferromagnetism is found. The spins fluctuate on two energy scales: one a damped spin response with a $\ensuremath{\simeq}2\phantom{\rule{0.3em}{0ex}}\mathrm{meV}$ relaxation rate and the other a central mode with a relaxation rate that slows to less than $0.08\phantom{\rule{0.3em}{0ex}}\mathrm{meV}$ below ${T}_{c}$. The spectrum mirrors that of a soft mode driving a central mode. Extremely short correlation lengths, $42\ifmmode\pm\else\textpm\fi{}5\phantom{\rule{0.3em}{0ex}}\mathrm{\AA{}}$ in-plane and $8\ifmmode\pm\else\textpm\fi{}2\phantom{\rule{0.3em}{0ex}}\mathrm{\AA{}}$ along the $c$ direction, and isotropic spin orientations for the central mode indicate that the correlations are subcritical with respect to any second-order transition to N\'eel order. The dynamics follows a model where damped spin fluctuations are coupled to the slow fluctuations of regions with correlations shortened by the hole doping.

Spontaneously Formed Unilamellar Vesicles

Abstract: Mixtures of long- and short-chain phospholipids can spontaneously form uniform unilamellar vesicles (ULVs) with diameters 50 nm (polydispersities of <0.3) or less. The morphology of these ULVs has mainly been characterized using small angle neutron scattering (SANS), a technique highly suited for the study of hydrogenous materials. Once formed, these ULVs have turned out to be highly stable and show great promise as imaging and therapeutic carriers.