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.

What determines the thickness of a biological membrane.

Abstract: Membrane thickness is thought to play a key role in protein function. Thus understanding the cell's ability to modulate the thickness of its membranes is essential in elucidating the structure/function relationship in biological membranes. We have investigated the influence of cholesterol on the structure of "thin" (diC14:1PC) and "thick" (diC22:1PC) phospholipid bilayers using oriented multibilayers and small angle neutron diffraction. Neutron contrast variation was used to determine the structure factors and the distribution of water across the bilayers. We found that in response to cholesterol, bilayer thickness changed in a similar fashion in both systems. The thickening of bilayers was rationalized in terms of cholesterol's ordering effect on the lipid's acyl chains, which dominates over the other option of rectifying the hydrophobic mismatch, surprisingly even in the case of diC22:1PC and cholesterol.

Frustration driven lattice distortion: an NMR investigation of Y(2)Mo(2)O(7).

Abstract: We have investigated the ${}^{89}\mathrm{Y}$ NMR spectrum and spin lattice relaxation, ${T}_{1}$, in the magnetically frustrated pyrochlore ${\mathrm{Y}}_{2}{\mathrm{Mo}}_{2}{\mathrm{O}}_{7}$. We find that upon cooling the spectrum shifts, and broadens asymmetrically. A detailed examination of the low $T$ spectrum reveals that it is constructed from multiple peaks, each shifted by a different amount. We argue that this spectrum is due to discrete lattice distortions and speculate that these distortions relieve the frustration and reduce the system's energy.

New insights into particle detection with superheated liquids

Abstract: We report new results obtained from calibrations of superheated liquid droplet detectors used in dark matter searches with different radiation sources (n, α, γ). In particular, detectors were spiked with α-emitters located inside and outside the droplets. It is shown that the responses have different temperature thresholds, depending on whether α-particles or recoil nuclei create the signals. The measured temperature threshold for recoiling 210Pb nuclei from 214Po α-decays was found to be in agreement with test beam measurements using mono-energetic neutrons. A comparison of the threshold data with theoretical predictions shows deviations, especially at high temperatures. It is shown that signals produced simultaneously by recoil nuclei and α-particles have more acoustic energy than signals produced by one or the other separately. A model is presented that describes how the observed intensities of particle-induced acoustic signals can be related to the dynamics of bubble growth in superheated liquids. A growth scenario that is limited by the inertia of the surrounding liquid shows a trend that is supported by the data. An improved understanding of the bubble dynamics is an important first step in obtaining better discrimination between particle types interacting in detectors of this kind.