Shape oscillations in non-degenerate Bose gases - transition from the collisionless to the hydrodynamic regime

We investigate collective oscillations of non-degenerate clouds of Rb-87 atoms as a function of density in an elongated magnetic trap. For the low-lying M=0 monopole-quadrupole shape oscillation we measure the oscillation frequencies and damping rates. At the highest densities the mean-free-path is smaller than the axial dimension of the sample, which corresponds to collisionally hydrodynamic conditions. This allows us to cover the cross-over from the collisionless to the hydrodynamic regime. The experimental results show good agreement with theory. We also analyze the influence of trap anharmonicities on the oscillations in relation to observed temperature dependencies of the dipole and quadrupole oscillation frequencies. We present convenient expressions to quantify these effects.Comment: 10 pages, 5 figure

Lunar resources: Oxygen from rocks and soil

The first set of hydrogen reduction experiments to use actual lunar material was recently completed. The sample, 70035, is a coarse-grained vesicular basalt containing 18.46 wt. percent FeO and 12.97 wt. percent TiO2. The mineralogy includes pyroxene, ilmenite, plagioclase, and minor olivine. The sample was crushed to a grain size of less than 500 microns. The crushed basalt was reduced with hydrogen in seven tests at temperatures of 900-1050 C and pressures of 1-10 atm for 30-60 minutes. A capacitance probe, measuring the dew point of the gas stream, was used to follow reaction progress. Experiments were also conducted using a terrestrial basalt similar to some lunar mare samples. Minnesota Lunar Simulant (MLS-1) contains 13.29 wt. percent FeO, 2.96 wt. percent Fe2O3, and 6.56 wt. percent TiO2. The major minerals include plagioclase, pyroxene, olivine, ilmenite, and magnetite. The rock was ground and seived, and experiments were run on the less than 74- and 500-1168-micron fractions. Experiments were also conducted on less than 74-micron powders of olivine, pyroxene, synthetic ilmenite, and TiO2. The terrestrial rock and mineral samples were reduced with flowing hydrogen at 1100 C in a microbalance furnace, with reaction progress monitored by weight loss. Experiments were run at atmospheric pressure for durations of 3-4 hr. Solid samples from both sets of experiments were analyzed by Mossbauer spectroscopy, petrographic microscopy, scanning electron microscopy, tunneling electron microscopy, and x-ray diffraction. Apollo 17 soil 78221 was examined for evidence of natural reduction in the lunar environment. This sample was chosen based on its high maturity level (I sub s/FeO = 93.0). The FeO content is 11.68 wt. percent and the TiO2 content is 3.84 wt. percent. A polished thin section of the 90-150 micron size fraction was analyzed by petrographic microscopy and scanning electron microscopy

Exploring the environment, magnetic fields, and feedback effects of massive high-redshift galaxies with [CII]

Massive galaxies are expected to grow through different transformative evolutionary phases where high-redshift starburst galaxies and quasars are examples of such phases. The physical mechanisms driving these phases include companion galaxy interactions, active galactic nuclei feedback, and magnetic fields. Our aim is to characterize the physical properties and the environment of the submillimeter galaxy AzTEC-3 at z = 5.3 and the lensed quasar BRI 0952-0115 at z = 4.4, to set a limit on the polarization properties, as well as placing both in the broader context of galaxy evolution. We used full polarization, sub-arcsecond-resolution, ALMA band-7 observations of both BRI 0952-0115 and AzTEC-3 and detect [CII] line emission towards both galaxies, along with companions in each field. We present an updated gravitational lensing model for BRI 0952-0115. We present infrared luminosities, star-formation rates, and [CII] line to infrared luminosity ratios for each source. The [CII] emission line profile for both BRI 0952-0115 and AzTEC-3 exhibit a broad, complex morphology, indicating the possible presence of outflows. We present evidence of a 'gas bridge' between AzTEC-3 and a companion source. Using a simple dynamical mass estimate for the sources, we suggest that both systems are undergoing minor or major mergers. No polarization is detected for the [CII], placing an upper limit below that of theoretical predictions. Our results show that high-velocity wings are detected, indicating possible signs of massive outflows; however, the presence of companion galaxies can affect the final interpretation. Furthermore, the results provide additional evidence in support of the hypothesis that massive galaxies form in overdense regions, growing through interactions. Finally, strong, ordered magnetic fields are unlikely to exist at the kiloparsec scale in the two studied sources

Diamagnetic Susceptibility and Current Distributions in Granular Superconductors at Percolation

Comments: 4 pages RevTeX, 4 Postscript figures. References added. We study a two-dimensional granular superconducting network at the percolation threshold under the influence of an external perpendicular magnetic field. By numerical simulations on the full nonlinear problem, we determine the scaling exponent for the magnetic susceptibility. Further, we report on the scaling properties of the current distribution. The scaling of the current is found to be independent of the value of the magnetic field. Our results are in contradiction with previous numerical results based on linearized equations. We find a value for the susceptibility exponent which does not agree with existing theoretical suggestions, but agrees perfectly with renormalization group calculations

Intercalation-enhanced electric polarization and chain formation of nano-layered particles

Microscopy observations show that suspensions of synthetic and natural nano-layered smectite clay particles submitted to a strong external electric field undergo a fast and extended structuring. This structuring results from the interaction between induced electric dipoles, and is only possible for particles with suitable polarization properties. Smectite clay colloids are observed to be particularly suitable, in contrast to similar suspensions of a non-swelling clay. Synchrotron X-ray scattering experiments provide the orientation distributions for the particles. These distributions are understood in terms of competing (i) homogenizing entropy and (ii) interaction between the particles and the local electric field; they show that clay particles polarize along their silica sheet. Furthermore, a change in the platelet separation inside nano-layered particles occurs under application of the electric field, indicating that intercalated ions and water molecules play a role in their electric polarization. The resulting induced dipole is structurally attached to the particle, and this causes particles to reorient and interact, resulting in the observed macroscopic structuring. The macroscopic properties of these electro-rheological smectite suspensions may be tuned by controlling the nature and quantity of the intercalated species, at the nanoscale.Comment: 7 pages, 5 figure

MyChemise: A 2D drawing program that uses morphing for visualisation purposes

MyChemise (My Chemical Structure Editor) is a new 2D structure editor. It is designed as a Java applet that enables the direct creation of structures in the Internet using a web browser. MyChemise saves files in a digital format (.cse) and the import and export of .mol files using the appropriate connection tables is also possible

Classic and spatial shift-share analysis of state-level employment change in Brazil

This paper combines classic and spatial shift-share decompositions of 1981 to 2006 employment change across the 27 states of Brazil. The classic shift-share method shows higher employment growth rates for underdeveloped regions that are due to an advantageous industry-mix and also due to additional job creation, commonly referred to as the competitive effect. Alternative decompositions proposed in the literature do not change this broad conclusion. Further examination employing exploratory spatial data analysis (ESDA) shows spatial correlation of both the industry-mix and the competitive effects. Considering that until the 1960s economic activities were more concentrated in southern regions of Brazil than they are nowadays, these results support beta convergence theories but also find evidence of agglomeration effects. Additionally, a very simple spatial decomposition is proposed that accounts for the spatially-weighted growth of surrounding states. Favourable growth in northern and centre-western states is basically associated with those states’ strengths in potential spatial spillover effect and in spatial competitive effect

Neutron Resonance Spectroscopy of 106Pd, and 108Pd from 20–2000 eV

Parity nonconserving asymmetries have been measured in p-wave resonances of 106Pd and 108Pd. The data analysis requires knowledge of the neutron resonance parameters. Transmission and capture γ-ray yields were measured for En=20–2000 eV with the time-of-flight method at the Los Alamos Neutron Science Center (LANSCE). A total of 28 resonances in 106Pd and 32 resonances in 108Pd were studied. The resonance parameters for 106Pd are new for all except one resonance. In 108Pd six new resonances were observed and the precision improved for many of the resonance parameters. A Bayesian analysis was used to assign orbital angular momentum for the resonances studied

Evidence for unusually high densities of plasma in the Venusian ionosheath

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/94972/1/grl5268.pd