Short-range ordering in face-centered-cubic Ni3Al

Films of fcc Ni3Al with suppressed short-range order (SRO) were prepared by physical vapor deposition of Ni3Al onto room-temperature substrates. Extended electron energy-loss fine-structure spectra were obtained from both Al K and Ni L23 edges. After the samples were annealed for various times at 150 °C, a moderate growth of SRO was observed in the first-nearest-neighbor environments of both the Al and Ni atoms. As prepared, these fcc Ni3Al materials, and presumably others having similar heat evolutions as measured by differential scanning calorimetry, have a high degree of chemical disorder

A prior history of binge-drinking increases sensitivity to the motivational valence of methamphetamine in female C57BL/6J mice.

Methamphetamine (MA) and alcohol use disorders exhibit a high degree of co-morbidity and sequential alcohol-MA mixing increases risk for co-abuse. Recently, we reported greater MA-conditioned reward in male C57BL/6J mice with a prior history of binge alcohol-drinking (14 days of 2-hour access to 5, 10, 20 and 40% alcohol). As female mice tend to binge-drink more alcohol than males and females tend to be more sensitive than males to the psychomotor-activating properties of MA, we first characterized the effects of binge-drinking upon MA-induced place-conditioning (four pairings of 0.25, 0.5, 1, 2, or 4 mg/kg IP) in females and then incorporated our prior data to analyze for sex differences in MA-conditioned reward. Prior binge-drinking history did not significantly affect locomotor hyperactivity or its sensitization in female mice. However, the dose-response function for place-conditioning was shifted to the left of water-drinking controls, indicating an increase in sensitivity to MA-conditioned reward. The examination of sex differences revealed no sex differences in alcohol intake, although females exhibited greater MA-induced locomotor stimulation than males, irrespective of their prior drinking history. No statistically significant sex difference was apparent for the potentiation of MA-conditioned reward produced by prior binge-drinking history. If relevant to humans, these data argue that both males and females with a prior binge-drinking history are similarly vulnerable to MA abuse and it remains to be determined whether or not the neural substrates underpinning this increased vulnerability reflect common or sex-specific adaptations in reward-related brain regions

Ekman layers and the damping of inertial r-modes in a spherical shell: application to neutron stars

Recently, eigenmodes of rotating fluids, namely inertial modes, have received much attention in relation to their destabilization when coupled to gravitational radiation within neutron stars. However, these modes have been known for a long time by fluid dynamicists. We give a short account of their history and review our present understanding of their properties. Considering the case of a spherical container, we then give the exact solution of the boundary (Ekman) layer flow associated with inertial r-modes and show that previous estimations all underestimated the dissipation by these layers. We also show that the presence of an inner core has little influence on this dissipation. As a conclusion, we compute the window of instability in the Temperature/rotation plane for a crusted neutron star when it is modeled by an incompressible fluid.Comment: 7 pages, 2 figures, revised version to appear in ApJ, March 1

Hydrogen adsorption and cohesive energy of single-walled carbon nanotubes

Hydrogen adsorption on crystalline ropes of carbon single-walled nanotubes (SWNT) was found to exceed 8 wt.%, which is the highest capacity of any carbon material. Hydrogen is first adsorbed on the outer surfaces of the crystalline ropes. At pressures higher than about 40 bar at 80 K, however, a phase transition occurs where there is a separation of the individual SWNTs, and hydrogen is physisorbed on their exposed surfaces. The pressure of this phase transition provides a tube-tube cohesive energy for much of the material of 5 meV/C atom. This small cohesive energy is affected strongly by the quality of crystalline order in the ropes

Methamphetamine-alcohol interactions in murine models of sequential and simultaneous oral drug-taking

BackgroundA high degree of co-morbidity exists between methamphetamine (MA) addiction and alcohol use disorders and both sequential and simultaneous MA-alcohol mixing increases risk for co-abuse. As little preclinical work has focused on the biobehavioral interactions between MA and alcohol within the context of drug-taking behavior, we employed simple murine models of voluntary oral drug consumption to examine how prior histories of either MA- or alcohol-taking influence the intake of the other drug.MethodsIn one study, mice with a 10-day history of binge alcohol-drinking [5,10, 20 and 40% (v/v); 2h/day] were trained to self-administer oral MA in an operant-conditioning paradigm (10-40mg/L). In a second study, mice with a 10-day history of limited-access oral MA-drinking (5, 10, 20 and 40mg/L; 2h/day) were presented with alcohol (5-40% v/v; 2h/day) and then a choice between solutions of 20% alcohol, 10mg/L MA or their mix.ResultsUnder operant-conditioning procedures, alcohol-drinking mice exhibited less MA reinforcement overall, than water controls. However, when drug availability was not behaviorally-contingent, alcohol-drinking mice consumed more MA and exhibited greater preference for the 10mg/L MA solution than drug-naïve and combination drug-experienced mice. Conversely, prior MA-drinking history increased alcohol intake across a range of alcohol concentrations.DiscussionThese exploratory studies indicate the feasibility of employing procedurally simple murine models of sequential and simultaneous oral MA-alcohol mixing of relevance to advancing our biobehavioral understanding of MA-alcohol co-abuse

Metal hydrides as electrode/catalyst materials for oxygen evolution/reduction in electrochemical devices

An at least ternary metal alloy of the formula, AB.sub.(5-Y)X(.sub.y), is claimed. In this formula, A is selected from the rare earth elements, B is selected from the elements of groups 8, 9, and 10 of the periodic table of the elements, and X includes at least one of the following: antimony, arsenic, and bismuth. Ternary or higher-order substitutions, to the base AB.sub.5 alloys, that form strong kinetic interactions with the predominant metals in the base metal hydride are used to form metal alloys with high structural integrity after multiple cycles of hydrogen sorption

Statistics of Microstructure Formation in Martensitic Transitions Studied by a Random-Field Potts Model with Dipolar-like Interactions

We have developed a simple model for the study of a cubic to tetragonal martensitic transition, under athermal conditions, in systems with a certain amount of disorder. We have performed numerical simulations that allow for a statistical study of the dynamics of the transition when the system is driven from the high-temperature cubic phase to the low-temperature degenerate tetragonal phase. Our goal is to reveal the existence of kinetic constraints that arise from competition between the equivalent variants of the martensitic phase, and which prevent the system from reaching optimal final microstructures.Comment: 11 pages, 14 figure

Vibrational entropy of ordered and disordered Ni3Al

We have measured the difference in vibrational entropy of Ni3Al in two states of chemical order: as a disordered fcc solid solution, and as the equilibrium L12 ordered structure. Data were obtained from three independent methods: low-temperature calorimetry, temperature-dependent x-ray diffractometry, and temperature-dependent extended electron energy loss fine structure spectrometry. We estimate that at high temperatures, the vibrational entropy of chemically disordered Ni3Al is 0.3kB/atom greater than for ordered Ni3Al

Optical Spectral Variability of the Very-High-Energy Gamma-Ray Blazar 1ES 1011+496

We present results of five years of optical (UBVRI) observations of the very-high-energy gamma-ray blazar 1ES 1011+496 at the MDM Observatory. We calibrated UBVRI magnitudes of five comparison stars in the field of the object. Most of our observations were done during moderately faint states of 1ES 1011+496 with R > 15.0. The light curves exhibit moderate, closely correlated variability in all optical wavebands on time scales of a few days. A cross-correlation analysis between optical bands does not show significant evidence for time lags. We find a positive correlation (Pearson's r = 0.57; probability of non-correlation P(>r) ~ 4e-8) between the R-band magnitude and the B - R color index, indicating a bluer-when-brighter trend. Snap-shot optical spectral energy distributions (SEDs) exhibit a peak within the optical regime, typically between the V and B bands. We find a strong (r = 0.78; probability of non-correlation P (>r) ~ 1e-15) positive correlation between the peak flux and the peak frequency, best fit by a relation $\nu F_{\nu}^{\rm pk} \propto \nu_{\rm pk}^k$ with k = 2.05 +/- 0.17. Such a correlation is consistent with the optical (synchrotron) variability of 1ES 1011+496 being primarily driven by changes in the magnetic field.Comment: Accepted for publication in ApJ. 16 pages, including 7 figure

A ^(119)Sn Mössbauer Spectrometry Study of Li-SnO Anode Materials for Li-Ion Cells

Anodes of SnO were charged reversibly with Li to capacities greater than 600 mAh/g, The anode materials were characterized by 119Sn Mössbauer spectrometry at 11 and 300 K, and by X-ray diffractometry at 300 K. Trends in the valence of Sn were as expected when the Sn oxides are reduced in the presence of Li. At low Li capacities the SnO is reduced to small particles of β-Sn, and with increasing Li capacity an alloy of Li_(22)Sn_5 is formed. Although the Li_(22)Sn_5 develops over a range of Li concentrations in the anode material, the Li_(22)Sn_5 that forms at low Li insertions is not typical of bulk Li_(22)Sn_5 in either its structural or electrochemical properties. The recoil-free fraction of the Sn oxide (and perhaps the metallic Sn) in the anode materials showed an anomalously large temperature dependence. This is indicative of nanoparticles or a severely defective structure. We monitored the changes in the Li-SnO and Li-Sn materials during atmospheric exposure over times up to 2 months. This oxidation process of Sn was very much the reverse of the Sn reduction during the Li insertion, although it occurred over a much longer time scale. We also report the temperature dependencies of recoil-free fractions for standard samples of β-Sn, SnO_2, and the alloy Li_(22)Sn_5