Dielectric constant of glasses: first observation of a two-dimensional behavior

The 1kHz real part $\chi'$ of the dielectric constant of a structural glass was measured at low temperature $T$ down to 14 mK. Reducing the sample thickness $h$ to 10 nm suppresses the usual minimum of $\chi'$ for measuring fields $E<.5$ MV/m. This contradicts the Two Level System (TLS) model but is well accounted for by including TLS-TLS interactions where excitations delocalize between TLS's through a $E$-induced mechanism recently designed: for small $h$'s this interaction is reduced, which explains the two-dimensional behavior of $\chi'(T)$. Hence, interactions play a key role in standard thick samples.Comment: latex finesse3.tex, 5 files, 4 figures, 4 pages [SPEC-S02/050], submitted to Phys. Rev. Let

The Central Regions of M31 in the 3 - 5 micron Wavelength Region

Images obtained with NIRI on the Gemini North telescope are used to investigate the photometric properties of the central regions of M31 in the 3 - 5 micron wavelength range. The light distribution in the central arcsecond differs from what is seen in the near-infrared in the sense that the difference in peak brigh tness between P1 and P2 is larger in M' than in K'; no obvious signature of P3 is dete cted in M'. These results can be explained if there is a source of emission that contributes ~ 20% of the peak M' light of P1 and has an effective temperature of no more than a few hundred K that is located between P1 and P2. Based on the red K-M' color of this source, it is suggested that the emission originates in a circumstellar dust shell surrounding a single bright AGB star. A similar bright source that is ~ 8 arcsec from the center of the galaxy is also detected in M'. Finally, the (L', K-L') color-magnitude diagram of unblended stars shows a domin ant AGB population with photometric characteristics that are similar to those of the most luminous M giants in the Galactic bulge.Comment: To appear in the Astronomical Journa

Lunar drill footplate and casing

To prevent hole collapse during lunar drilling operations, a casing has been devised of a graphite reinforced polyimide composite which will be able to withstand the lunar environment. Additionally, this casing will be inserted into the ground in segments two meters long which will penetrate the regolith simultaneously with the auger. The vertical action of the mobile platform will provide a downward force to the casing string through a special adaptor, giving the casing the needed impetus to sink the anticipated depth of ten meters. Casing segments will be connected with a simple snap arrangement. Excess casing will be cut off by a cylindrical cutting tool which will also transport the excess casing away from the hole. A footplate will be incorporated to grasp the auger rod string during rod segment additions or removals. The footplate grasping mechanism will consist of a set of vice-like arms, one end of each bearing threaded to a common power screw. The power screw will be threaded such that one end's thread pitch opposes that of the other end. The weight of the auger and rod string will be transmitted through the arms to the power screw and absorbed by a set of three ball bearing assemblies. The power screw will be driven by a one-half horsepower brushless motor actuated by radio control. The footplate will rest on four short legs and be anchored with pins that are an integral part of each leg

Inhibiting IL-1 signaling pathways to inhibit catabolic processes in disc degeneration

Intervertebral disc degeneration is characterized by an imbalance between catabolic and anabolic signaling, with an increase in catabolic cytokines particularly IL-1β, a key regulator of IVD degeneration. This study aimed to investigate intracellular signaling pathways activated by IL-1β, and GDF-5 in the degenerate IVD to identify potential new therapeutic targets. Human NP cells were cultured in alginate beads to regain in vivo phenotype prior to stimulation with IL-1β or GDF-5 for 30 min, a proteasome profiler array was initially utilized to screen activation status of 46 signaling proteins. Immunoflourescence was used to investigate activation of the NFκB pathway. Cell-based ELISAs were then deployed to confirm results for ERK1/2, p38 MAPK, c-jun, and IκB signaling. IHC was utilized to investigate native activation status within human IVD tissue between grades of degeneration. Finally, cells were stimulated with IL-1β in the absence or presence of p38 MAPK, c-jun, JNK, and NFκB inhibitors to investigate effects on MMP3, MMP13, IL-1β, IL-6, and IL-8 mRNA expression. This study demonstrated three key signaling pathways which were differentially activated by IL-1β but not GDF-5; namely p38 MAPK, c-jun, and NFκB. While ERK 1/2 was activated by both GDF-5 and IL-1. Immunohistochemistry demonstrated p38 MAPK, c-jun, and NFκB were activated during human IVD degeneration and inhibition of these pathways reduced or abrogated the catabolic effects of IL-1β, with inhibition of NFκB signaling demonstrating most widespread inhibition of IL-1β catabolic effect

Light storage protocols in Tm:YAG

We present two quantum memory protocols for solids: A stopped light approach based on spectral hole burning and the storage in an atomic frequency comb. These procedures are well adapted to the rare-earth ion doped crystals. We carefully clarify the critical steps of both. On one side, we show that the slowing-down due to hole-burning is sufficient to produce a complete mapping of field into the atomic system. On the other side, we explain the storage and retrieval mechanism of the Atomic Frequency Comb protocol. This two important stages are implemented experimentally in Tm$^{3+}$- doped yttrium-aluminum-garnet crystal

The flat phase of fixed-connectivity membranes

The statistical mechanics of flexible two-dimensional surfaces (membranes) appears in a wide variety of physical settings. In this talk we discuss the simplest case of fixed-connectivity surfaces. We first review the current theoretical understanding of the remarkable flat phase of such membranes. We then summarize the results of a recent large scale Monte Carlo simulation of the simplest conceivable discrete realization of this system \cite{BCFTA}. We verify the existence of long-range order, determine the associated critical exponents of the flat phase and compare the results to the predictions of various theoretical models.Comment: 7 pages, 5 figures, 3 tables. LaTeX w/epscrc2.sty, combined contribution of M. Falcioni and M. Bowick to LATTICE96(gravity), to appear in Nucl. Phys. B (proc. suppl.

Equivariant representable K-theory

We interpret certain equivariant Kasparov groups as equivariant representable K-theory groups. We compute these groups via a classifying space and as K-theory groups of suitable sigma-C*-algebras. We also relate equivariant vector bundles to these sigma-C*-algebras and provide sufficient conditions for equivariant vector bundles to generate representable K-theory. Mostly we work in the generality of locally compact groupoids with Haar system.Comment: Final version. Only minor corrections. 33 page

The Gattini cameras for optical sky brightness measurements at Dome C, Antarctica

The Gattini cameras are two site testing instruments for the measurement of optical sky brightness, large area cloud cover and auroral detection of the night sky above the high altitude Dome C site in Antarctica. The cameras have been operating since installation in January 2006 and are currently at the end of the first Antarctic winter season. The cameras are transit in nature and are virtually identical both adopting Apogee Alta CCD detectors. By taking frequent images of the night sky we obtain long term cloud cover statistics, measure the sky background intensity as a function of solar and lunar altitude and phase and directly measure the spatial extent of bright aurora if present and when they occur. The full data set will return in December 2006 however a limited amount of data has been transferred via the Iridium network enabling preliminary data reduction and system evaluation. An update of the project is presented together with preliminary results from data taken since commencement of the winter season