The Nature of the Variable Galactic Center Source IRS16SW

We report measurements of the light curve of the variable Galactic Center source IRS16SW. The light curve is not consistent with an eclipsing binary or any other obvious variable star. The source may be an example of a high mass variable predicted theoretically but not observed previously.Comment: 11 pages, 2 figures. Accepted by Ap

Characterization of Lubricants on Ball Bearings by FT-IR Using an Integrating Sphere

Fourier Transform-Infrared reflectance microspectroscopy has been used extensively for the examination of coatings on nonplanar surfaces such as ball bearings. While this technique offers considerable advantages, practical application has many drawbacks, some of which are easily overcome by the use of integrating sphere technology. This paper describes the use of an integrating sphere for the quantification of thin layers of lubricant on the surface of ball bearings and the parameters which require optimization in order to obtain reliable data. Several applications of the technique are discussed including determination of lubricant load on 12.7 mm steel ball bearings and the examination of degraded lubricant on post mortem specimens

Incipient Formation of an Electron Lattice in a Weakly Confined Quantum Wire

We study the low-temperature transport properties of 1D quantum wires as the confinement strength V-conf and the carrier density n(1D) are varied using a combination of split gates and a top gate in GaAs/AlGaAs heterostructures. At intermediate V-conf and n(1D), we observe a jump in conductance to 4e(2)/h, suggesting a double wire. On further reducing n(1D), plateau at 2e(2)/h returns. Our results show beginnings of the formation of an electron lattice in an interacting quasi-1D quantum wire. In the presence of an in-plane magnetic field, mixing of spin-aligned levels of the two wires gives rise to more complex states

Macroscopic superpositions via nested interferometry: finite temperature and decoherence considerations

Recently there has been much interest in optomechanical devices for the production of macroscopic quantum states. Here we focus on a proposed scheme for achieving macroscopic superpositions via nested interferometry. We consider the effects of finite temperature on the superposition produced. We also investigate in detail the scheme's feasibility for probing various novel decoherence mechanisms.Comment: 12 pages, 2 figure

A Photometric Survey for Variables and Transits in the Field of Praesepe with KELT

The Kilodegree Extremely Little Telescope (KELT) project is a small aperture, wide-angle search for planetary transits of solar-type stars. In this paper, we present the results of a commissioning campaign with the KELT telescope to observe the open cluster Praesepe for 34 nights in early 2005. Lightcurves were obtained for 69,337 stars, out of which we identify 58 long period variables and 152 periodic variables. Sixteen of these are previously known as variable, yielding 194 newly discovered variable stars for which we provide properties and lightcurves. We also searched for planetary-like transits, finding four transit candidates. Follow-up observations indicate that two of the candidates are astrophysical false positives, with two candidates remaining as potential planetary transits.Comment: 45 pages, 16 figures. Submitted to AJ. PDF version with full resolution figures located at http://www.astronomy.ohio-state.edu/~pepper/kelt.pd

Spin-incoherent transport in quantum wires

When a quantum wire is weakly confined, a conductance plateau appears at e(2)/h with decreasing carrier density in zero magnetic field accompanied by a gradual suppression of the 2e(2)/h plateau. Applying an in-plane magnetic field B-parallel to does not alter the value of this quantization; however, the e(2)/h plateau weakens with increasing B-parallel to up to 9 T, and then strengthens on further increasing B-parallel to, which also restores the 2e(2)/h plateau. Our results are consistent with spin-incoherent transport in a one-dimensional wire

Unusual conductance collapse in one-dimensional quantum structures

We report an unusual insulating state in one-dimensional quantum wires with a non-uniform confinement potential. The wires consist of a series of closely spaced split gates in high mobility GaAs/AlGaAs heterostructures. At certain combinations of wire widths, the conductance abruptly drops over three orders of magnitude, to zero on a linear scale. Two types of collapse are observed, one occurring in multi-subband wires in zero magnetic field and one in single subband wires in an in-plane field. The conductance of the wire in the collapse region is thermally activated with an energy of the order of 1 K. At low temperatures, the conductance shows a steep rise beyond a threshold DC source-drain voltage of order 1 mV, indicative of a gap in the density of states. Magnetic depopulation measurements show a decrease in the carrier density with lowering temperature. We discuss these results in the context of many-body effects such as charge density waves and Wigner crystallization in quantum wires.Comment: 5 pages, 5 eps figures, revte

Editorial: The Mammary Stroma in Normal Development and Function

The mammary gland can no longer be simply viewed as an organ composed of epithelial cells within a passive stromal microenvironment. Many lines of evidence have evolved to reinforce the notion that mammary epithelial cell growth, differentiation, lactation and progression to cancer involves bidirectional interactions between the epithelial population and its surrounding stroma. Within this stroma are numerous systems that are all capable of modulating epithelial function. In this context, the mammary stroma is not simply a depot of adipose tissue in which mammary epithelial cells undertake a unique growth and differentiation process, although adipocytes can impart numerous modulatory signals to epithelial cells, and vice versa. Rather, the stromal environment constitutes and supports a critical vasculature that supplies nutrients and endocrine cues, a lymphatic system that not only removes metabolites but also provides an intimate interface with the immune system, and an extracellular matrix scaffold in which epithelial cells grow, differentiate and regress. Ultimately all of these components play a critical role in directing the epithelial phenotype during normal mammary gland growth and function. An increasing appreciation for these different systems demands a view of mammary epithelial cells in a much different light, and further necessitates the development of model systems that incorporate and integrate increasing complexity