Spin Diffusion in Trapped Gases: Anisotropy in Dipole and Quadrupole Modes

Recent experiments in a mixture of two hyperfine states of trapped Bose gases show behavior analogous to a spin-1/2 system, including transverse spin waves and other familiar Leggett-Rice-type effects. We have derived the kinetic equations applicable to these systems, including the spin dependence of interparticle interactions in the collision integral, and have solved for spin-wave frequencies and longitudinal and transverse diffusion constants in the Boltzmann limit. We find that, while the transverse and longitudinal collision times for trapped Fermi gases are identical, the Bose gas shows unusual diffusion anisotropy in both dipole and quadrupole modes. Moreover, the lack of spin isotropy in the interactions leads to the non-conservation of transverse spin, which in turn has novel effects on the hydrodynamic modes.Comment: 18 pages, 9 figure

Absence of Fragmentation in Two-Dimensional Bose-Einstein Condensation

We investigate the possibility that the BEC-like phenomena recently detected on two-dimensional finite trapped systems consist of fragmented condensates. We derive and diagonalize the one-body density matrix of a two-dimensional isotropically trapped Bose gas at finite temperature. For the ideal gas, the procedure reproduces the exact harmonic-oscillator eigenfunctions and the Bose distribution. We use a new collocation-minimization method to study the interacting gas in the Hartree-Fock approximation and obtain a ground-state wavefunction and condensate fraction consistent with those obtained by other methods. The populations of the next few eigenstates increase at the expense of the ground state but continue to be negligible; this supports the conclusion that two-dimensional BEC is into a single state.Comment: 6 pages, 1 figur

#Comparison: An Examination of Social Comparison Orientation on Instagram as It Relates to Self-Esteem and State Anxiety

The purpose of this study was to examine social comparison orientation on Instagram as it relates to self-esteem and state anxiety. One hundred and ninety-six young adults (ages 18-30) who use Instagram at least once a week completed scales measuring social comparison orientation, self-esteem, and state anxiety before being randomly assigned to one of two Instagram feed conditions—one that displayed non-celebrity photos and the other that displayed celebrity photos. Participants were then post-tested using the same self-esteem and state anxiety scales. Information about Instagram use, information about participants’ feelings toward the feeds, and demographic characteristics were also collected. It was expected that participants with high social comparison orientations (SCOs) would experience greater decreases in self-esteem and greater increases in state anxiety than participants with low SCOs across both conditions. Additionally, it was expected that all participants, regardless of SCO, would experience a greater decrease in self-esteem and a greater increase in state anxiety after looking at photos of non-celebrities in comparison to looking at photos of celebrities. Findings were insignificant, indicating that using Instagram may not be detrimental to mental wellbeing. A second follow-up experiment found a relationship between SCO and state anxiety, with higher SCO being related to a greater decrease in anxiety

The NASA photovoltaic technology program

The NASA Office of Aeronautical and Space Technology OAST Program in space photovoltaics is reviewed. From the perspective of national landmark mission requirements and five year and 25-year long range plans, the texture of the program is revealed. Planar silicon and concentrator GaAs array technology advances are discussed. Advances in lightweight (50 micro cell) arrays and radiation tolerance research are presented. Recent progress in cascade cells and ultralightweight GaAs planar cells is noted. Progress in raising silicon cell voltage to its theoretical maximum is detailed. Advanced concepts such as plasmon converters and the Long Duration Exposure Facility LDEF flight experiments pertaining to solar cell and array technology are also shown

Effects of magnesium treatment in a model of internal capsule lesion in spontaneously hypertensive rats

<p><b>Background and Purpose:</b> The study aim was to assess the effects of magnesium sulfate (MgSO4) administration on white matter damage in vivo in spontaneously hypertensive rats.</p> <p><b>Methods:</b> The left internal capsule was lesioned by a local injection of endothelin-1 (ET-1; 200 pmol) in adult spontaneously hypertensive rats. MgSO4 was administered (300 mg/kg SC) 30 minutes before injection of ET-1, plus 200 mg/kg every hour thereafter for 4 hours. Infarct size was measured by T2-weighted magnetic resonance imaging (day 2) and histology (day 11), and functional recovery was assessed on days 3 and 10 by the cylinder and walking-ladder tests.</p> <p><b>Results:</b> ET-1 application induced a small, localized lesion within the internal capsule. Despite reducing blood pressure, MgSO4 did not significantly influence infarct volume (by magnetic resonance imaging: median, 2.1 mm3; interquartile range, 1.3 to 3.8, vs 1.6 mm3 and 1.2 to 2.1, for the vehicle-treated group; by histology: 0.3 mm3 and 0.2 to 0.9 vs 0.3 mm3 and 0.2 to 0.5, respectively). Significant forelimb and hindlimb motor deficits were evident in the vehicle-treated group as late as day 10. These impairments were significantly ameliorated by MgSO4 in both cylinder (left forelimb use, P<0.01 and both-forelimb use, P<0.03 vs vehicle) and walking-ladder (right hindlimb score, P<0.02 vs vehicle) tests.</p> <p><b>Conclusions:</b> ET-1–induced internal capsule ischemia in spontaneously hypertensive rats represents a good model of lacunar infarct with small lesion size, minimal adverse effects, and a measurable motor deficit. Despite inducing mild hypotension, MgSO4 did not significantly influence infarct size but reduced motor deficits, supporting its potential utility for the treatment of lacunar infarct.</p&gt

Magnetically levitated mesenchymal stem cell spheroids cultured with a collagen gel maintain phenotype and quiescence

Multicellular spheroids are an established system for three-dimensional cell culture. Spheroids are typically generated using hanging drop or non-adherent culture; however, an emerging technique is to use magnetic levitation. Herein, mesenchymal stem cell spheroids were generated using magnetic nanoparticles and subsequently cultured within a type I collagen gel, with a view towards developing a bone marrow niche environment. Cells were loaded with magnetic nanoparticles, and suspended beneath an external magnet, inducing self-assembly of multicellular spheroids. Cells in spheroids were viable and compared to corresponding monolayer controls, maintained stem cell phenotype and were quiescent. Interestingly, core spheroid necrosis was not observed, even with increasing spheroid size, in contrast to other commonly used spheroid systems. This mesenchymal stem cell spheroid culture presents a potential platform for modelling in vitro bone marrow stem cell niches, elucidating interactions between cells, as well as a useful model for drug delivery studies

Quantum-limited mass flow of liquid 3^{3}He

We consider theoretically the possibility of observing unusual quantum fluid behavior in liquid $^{3}$He and solutions of $^{3}$He in $^{4}$He systems confined to nano-channels. In the case of pure ballistic flow at very low temperature conductance will be quantized in units of $2m^{2}/h$. We show that these steps should be sensitive to increases in temperature. We also use of a random scattering matrix simulation to study flow with diffusive wall scattering. Universal conductance fluctuations analogous to those seen in electron systems should then be observable. Finally we consider the possibility of the cross-over to a one-dimensional system at sufficiently low temperature where the system could form a Luttinger liquid

Thermoregulation of Male Elaphe Spiloides in an Agriculturally-Fragmented Forest in Illinois

Anthropogenic forest fragmentation increases the amount of edge habitat. Although edges are harsh environments for many native species, ratsnakes often prefer this habitat. We examined thermoregulatory effectiveness of Central Ratsnakes (Elaphe spiloides) using forest edges preferentially to determine if edge preference is driven by increased thermoregulatory efficiencies. Six male subjects were located every 1-2 days using radio-telemetry and temperature sensitive transmitters. Subjects did not thermoregulate more efficiently in edges than in forest. Snakes were thermoconformers in both habitat types suggesting edge preference might be driven by other factors