Face Value

There is growing evidence of systematic heterogeneity in behavior by observable characteristics, such as what one would see in a face. We ask, is there informational value in knowing these characteristics in a strategic interaction? Subjects are given the opportunity to purchase a photograph of their partner in the play of a trust game. Not everyone purchases the photo, even at prices as low as $0.20. Senders (first movers in the game) have a more inelastic demand for pictures than responders (second movers). White senders have a substantially higher demand than nonwhite senders or responders. For responders, there is no difference in demand for pictures across ethnicity or sex. White senders who pay to see the picture of their partner use the information to discriminate, sending significantly less to black responders than to white responders. Overall, responders return a higher percentage of the amount received as offers go up, but they do differentiate that percentage when they see the picture of the sender, returning more to a member of the same ethnicity. A face, it appears, has strategic value, especially for those who will use the information to differentiate their decisions.

Nonlithographic epitaxial Sn_xGe_(1–x) dense nanowire arrays grown on Ge(001)

We have grown 1-µm-thick Sn_xGe_(1–x)/Ge(001) epitaxial films with 0 < x < 0.085 by molecular-beam epitaxy. These films evolve during growth into a dense array of Sn_xGe_(1–x) nanowires oriented along [001], as confirmed by composition contrast observed in scanning transmission electron microscopy in planar view. The Sn-rich regions in these films dominate optical absorption at low energy; phase-separated Sn_xGe_(1–x) alloys have a lower-energy band gap than homogeneous alloys with the same average Sn composition

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

Remote sensing as an aid for marsh management: Lafouche parish, Louisiana

NASA aerial photography, primarily color infrared and color positive transparencies, was used in a study of marsh management practices and in comparing managed and unmanaged marsh areas. Weir locations for tidal control are recommended

Evidence that widespread star formation may be underway in G0.253+016, "The Brick"

Image cubes of differential column density as a function of dust temperature are constructed for Galactic Centre molecular cloud G0.253+0.016 ("The Brick") using the recently described PPMAP procedure. The input data consist of continuum images from the Herschel Space Telescope in the wavelength range 70-500 $\mu$m, supplemented by previously published interferometric data at 1.3 mm wavelength. While the bulk of the dust in the molecular cloud is consistent with being heated externally by the local interstellar radiation field, our image cube shows the presence, near one edge of the cloud, of a filamentary structure whose temperature profile suggests internal heating. The structure appears as a cool ($\sim 14$ K) tadpole-like feature, $\sim 6$ pc in length, in which is embedded a thin spine of much hotter ($\sim$ 40-50 K) material. We interpret these findings in terms of a cool filament whose hot central region is undergoing gravitational collapse and fragmentation to form a line of protostars. If confirmed, this would represent the first evidence of widespread star formation having started within this cloud.Comment: 5 pages, 4 figures; accepted for publication in MNRAS Letter

Metal Ions in Neuroscience

Metal ions are believed to participate in many neurodegenerative conditions. In excitotoxic cell death there is convincing evidence for the participation of Ca2+ and Zn2+ ions although the exact molecular mechanisms by which these metals exert their effects are unclear. Only in one instance has the metal binding site of metalloenzymes been exploited for therapeutic purposes and this is the use of Li+ in the treatment of bipolar affective disorder. Again the exact molecular target is not clear but is likely to involve a Mg2+-dependent enzyme of an intracellular signalling pathway. In Parkinson's disease, the selective loss of dopaminergic neurones in the substantia nigra may be caused by radical-mediated damage and there is good evidence to suggest that Fe2+ or 3+ is important in promoting formation of radical species. The evidence that free radicals are important in mediating other neurodegenerative conditions is less strong but still substantial enough to suggest that removal of reactive oxygen species or preventing their formation may be a valid approach to therapy

On the temperature structure of the Galactic Centre cloud G0.253+0.016

We present a series of smoothed particle hydrodynamical models of G0.253+0.016 (also known as 'The Brick'), a very dense molecular cloud that lies close to the Galactic Centre. We explore how its gas and dust temperatures react as we vary the strength of both the interstellar radiation field (ISRF) and the cosmic ray ionisation rate (CRIR). As the physical extent of G0.253+0.016 along our line-of-sight is unknown, we consider two possibilities: one in which the longest axis is that measured in the plane of the sky (9.4 pc in length), and one in which it is along the line of sight, in which case we take it to be 17 pc. To recover the observed gas and dust temperatures, we find find that the ISRF must be around 1000 times the solar neighbourhood value, and the CRIR must be roughly 1E-14 /s, regardless of the geometries studied. For such high values of the CRIR, we find that cooling in the cloud's interior is dominated by neutral oxygen, in contrast to standard molecular clouds, which at the same densities are mainly cooled via CO. Our results suggest that the conditions near G0.253+0.016 are more extreme than those generally accepted for the inner 500 pc of the galaxy.Comment: 6 pages, 4 figures, 1 table, accepted for publication in ApJ Letter