Shape oscillations of a charged diamagnetically-levitated droplet

We investigate the effect of electrical charge on the normal mode frequencies of electrically-charged diamagnetically levitated water droplets with radii 4.5-7.5 mm using diamagnetic levitation. This technique allows us to levitate almost spherical droplets and therefore to directly compare the measured vibrational frequencies of the first seven modes of the charged droplet with theoretical values calculated by Lord Rayleigh, for which we find good agreement

Molecular Density Functional Theory of Water describing Hydrophobicity at Short and Long Length Scales

We present an extension of our recently introduced molecular density functional theory of water [G. Jeanmairet et al., J. Phys. Chem. Lett. 4, 619, 2013] to the solvation of hydrophobic solutes of various sizes, going from angstroms to nanometers. The theory is based on the quadratic expansion of the excess free energy in terms of two classical density fields, the particle density and the multipolar polarization density. Its implementation requires as input a molecular model of water and three measurable bulk properties, namely the structure factor and the k-dependent longitudinal and transverse dielectric susceptibilities. The fine three-dimensional water structure around small hydrophobic molecules is found to be well reproduced. In contrast the computed solvation free-energies appear overestimated and do not exhibit the correct qualitative behavior when the hydrophobic solute is grown in size. These shortcomings are corrected, in the spirit of the Lum-Chandler-Weeks theory, by complementing the functional with a truncated hard-sphere functional acting beyond quadratic order in density. It makes the resulting functional compatible with the Van-der-Waals theory of liquid-vapor coexistence at long range. Compared to available molecular simulations, the approach yields reasonable solvation structure and free energy of hard or soft spheres of increasing size, with a correct qualitative transition from a volume-driven to a surface-driven regime at the nanometer scale.Comment: 24 pages, 8 figure

Performance of a cryogenic system prototype for the XENON1T Detector

We have developed an efficient cryogenic system with heat exchange and associated gas purification system, as a prototype for the XENON1T experiment. The XENON1T detector will use about 3 ton of liquid xenon (LXe) at a temperature of 175K as target and detection medium for a dark matter search. In this paper we report results on the cryogenic system performance focusing on the dynamics of the gas circulation-purification through a heated getter, at flow rates above 50 Standard Liter per Minute (SLPM). A maximum flow of 114 SLPM has been achieved, and using two heat exchangers in parallel, a heat exchange efficiency better than 96% has been measured

Seasonal Ice Cycle at the Mars Phoenix Landing Site: 2. Postlanding CRISM and Ground Observations

The combination of ground observations from the Mars Phoenix Lander and orbital data from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) provided a detailed view of the formation of late summer surface water ice at the landing site and surrounding regions. CRISM observations of the landing site during and immediately after Phoenix operations were analyzed to track the seasonal and diurnal ice cycles during the late spring to late summer, and a nonlinear mixing model was used to estimate grain sizes and relative abundances of water ice and dust. The surface around the Phoenix landing site was ice-free from late spring through midsummer, although transient patches of mobile ices were observed in an 85 m diameter crater to the northeast of the landing site. At the ∼10 km diameter Heimdal Crater, located ∼10 km east of the landing site, permanent patches of water ice were observed to brighten during the late spring and darken during the summer, possibly as fine-grained water ice that was cold trapped onto the ice during late spring sintered into larger grains or finally sublimated, exposing larger-grained ice. CRISM spectra first show evidence of widespread ice during the night at solar longitude (Ls) ∼ 109°, ∼9 sols before Phoenix’s Surface Stereo Imager detected it. CRISM spectra first show evidence of afternoon surface ice and water ice clouds after Ls ∼ 155°, after Phoenix operations ended

Seasonal Ice Cycle at the Mars Phoenix Landing Site: 2. Postlanding CRISM and Ground Observations

The combination of ground observations from the Mars Phoenix Lander and orbital data from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) provided a detailed view of the formation of late summer surface water ice at the landing site and surrounding regions. CRISM observations of the landing site during and immediately after Phoenix operations were analyzed to track the seasonal and diurnal ice cycles during the late spring to late summer, and a nonlinear mixing model was used to estimate grain sizes and relative abundances of water ice and dust. The surface around the Phoenix landing site was ice-free from late spring through midsummer, although transient patches of mobile ices were observed in an 85 m diameter crater to the northeast of the landing site. At the ∼10 km diameter Heimdal Crater, located ∼10 km east of the landing site, permanent patches of water ice were observed to brighten during the late spring and darken during the summer, possibly as fine-grained water ice that was cold trapped onto the ice during late spring sintered into larger grains or finally sublimated, exposing larger-grained ice. CRISM spectra first show evidence of widespread ice during the night at solar longitude (Ls) ∼ 109°, ∼9 sols before Phoenix’s Surface Stereo Imager detected it. CRISM spectra first show evidence of afternoon surface ice and water ice clouds after Ls ∼ 155°, after Phoenix operations ended

Statistical Mechanics of Membrane Protein Conformation: A Homopolymer Model

The conformation and the phase diagram of a membrane protein are investigated via grand canonical ensemble approach using a homopolymer model. We discuss the nature and pathway of $\alpha$-helix integration into the membrane that results depending upon membrane permeability and polymer adsorptivity. For a membrane with the permeability larger than a critical value, the integration becomes the second order transition that occurs at the same temperature as that of the adsorption transition. For a nonadsorbing membrane, the integration is of the first order due to the aggregation of $\alpha$-helices.Comment: RevTeX with 5 postscript figure

Generalized conductance sum rule in atomic break junctions

When an atomic-size break junction is mechanically stretched, the total conductance of the contact remains approximately constant over a wide range of elongations, although at the same time the transmissions of the individual channels (valence orbitals of the junction atom) undergo strong variations. We propose a microscopic explanation of this phenomenon, based on Coulomb correlation effects between electrons in valence orbitals of the junction atom. The resulting approximate conductance quantization is closely related to the Friedel sum rule.Comment: 4 pages, 1 figure, appears in Proceedings of the NATO Advanced Research Workshop ``Size dependent magnetic scattering'', Pecs, Hungary, May 28 - June 1, 200

Genetic variation for adaptive traits is associated with polymorphic inversions in Littorina saxatilis

Chromosomal inversions have long been recognized for their role in local adaptation. By suppressing recombination in heterozygous individuals, they can maintain coadapted gene complexes and protect them from homogenizing effects of gene flow. However, to fully understand their importance for local adaptation we need to know their influence on phenotypes under divergent selection. For this, the marine snail Littorina saxatilis provides an ideal study system. Divergent ecotypes adapted to wave action and crab predation occur in close proximity on intertidal shores with gene flow between them. Here, we used F2 individuals obtained from crosses between the ecotypes to test for associations between genomic regions and traits distinguishing the Crab-/Wave-adapted ecotypes including size, shape, shell thickness, and behavior. We show that most of these traits are influenced by two previously detected inversion regions that are divergent between ecotypes. We thus gain a better understanding of one important underlying mechanism responsible for the rapid and repeated formation of ecotypes: divergent selection acting on inversions. We also found that some inversions contributed to more than one trait suggesting that they may contain several loci involved in adaptation, consistent with the hypothesis that suppression of recombination within inversions facilitates differentiation in the presence of gene flow