Calorimetric investigation of the antiferromagnetic transition in NiCl2·6H2O

Measurements of the heat capacity of NiCl2·6H2O were made in the vicinity of the antiferromagnetic transition using calorimetric techniques of sufficient resolution so that the observed behavior was intrinsic to the samples studied. Two crystals of different origins were investigated in zero field, and one crystal was investigated with external fields applied parallel to the easy axis. The temperature of the heat-capacity maximum Tmax differed by approximately 3 mK between the two crystals, but the heat-capacity anomalies of each were best described with the same value of TN, 5.348 K. This value of TN was 9 and 12 mK above the temperatures at which the maximum heat capacity occurred. The data implied critical exponents of 0.20 ± 0.03 above the transition and 0.00 ± 0.01 below. An analysis of the data in terms of the imaginary temperature described the rounding of the calorimetric anomaly which occurred below Tmax. The analysis yielded best values for the imaginary part of the temperature comparable to the shift between TN and Tmax. The application of an external field caused a slow monotonic decrease in the amplitude and an increase in the width of the calorimetric anomaly. The width could be described by Δ^2=Δ0^2+aH, suggesting that the broadening of the transition could be described by two independent mechanisms, one intrinsic to the sample and the second field dependent. The shift of the Tmax with field was proportional to H^2

Behavior of a sandy clay under vertical impact of geometric shapes

Sandy clay response under vertical impact of cone, plate, and plane geometric shape

Tethers in space handbook

The handbook provides a list and description of ongoing tether programs. This includes the joint U.S.-Italy demonstration project, and individual U.S. and Italian studies and demonstration programs. An overview of the current activity level and areas of emphasis in this emerging field is provided. The fundamental physical principles behind the proposed tether applications are addressed. Four basic concepts of gravity gradient, rotation, momentum exchange, and electrodynamics are discussed. Information extracted from literature, which supplements and enhances the tether applications is also presented. A bibliography is appended

Self-trapping at the liquid vapor critical point

Experiments suggest that localization via self-trapping plays a central role in the behavior of equilibrated low mass particles in both liquids and in supercritical fluids. In the latter case, the behavior is dominated by the liquid-vapor critical point which is difficult to probe, both experimentally and theoretically. Here, for the first time, we present the results of path-integral computations of the characteristics of a self-trapped particle at the critical point of a Lennard-Jones fluid for a positive particle-atom scattering length. We investigate the influence of the range of the particle-atom interaction on trapping properties, and the pick-off decay rate for the case where the particle is ortho-positronium.Comment: 12 pages, 3 figures, revtex4 preprin

Imaging the Sunyaev-Zel'dovich Effect

We report on results of interferometric imaging of the Sunyaev-Zel'dovich Effect (SZE) with the OVRO and BIMA mm-arrays. Using low-noise cm-wave receivers on the arrays, we have obtained high quality images for 27 distant galaxy clusters. We review the use of the SZE as a cosmological tool. Gas mass fractions derived from the SZE data are given for 18 of the clusters, as well as the implied constraint on the matter density of the universe, $\Omega_M$. We find $\Omega_M h_{100} \le 0.22 ^{+0.05}_{-0.03}$. A best guess for the matter density obtained by assuming a reasonable value for the Hubble constant and also by attempting to account for the baryons contained in the galaxies as well as those lost during the cluster formation process gives $\Omega_M \sim 0.25$. We also give preliminary results for the Hubble constant. Lastly, the power for investigating the high redshift universe with a non-targeted high sensitivity SZE survey is discussed and an interferometric survey is proposed.Comment: 14 pages, 7 figures, latex, contribution to Nobel Symposium "Particle Physics and the Universe" to appear in Physica Scripta and World Scientific, eds L. Bergstrom, P. Carlson and C. Fransso

Low-temperature specific heat of ruthenium

Measurements of the specific heat of Ru have been performed in the temperature range 2-11.5 K. Values for the Sommerfeld γ and the Debye Θ of 3.10 ± 0.02 mJ/mole K2 and 555±6 K were obtained. Deviations of Θ from its limiting value were observed above 9 K. This value of Θ is in good agreement with the acoustically determined value, thus removing the discrepancy between calorimetric determinations of Θ and the acoustic results

A Sunyaev-Zel'dovich Effect Survey for High Redshift Clusters

Interferometric observations of the Sunyaev-Zel'dovich Effect (SZE) toward clusters of galaxies provide sensitive cosmological probes. We present results from 1 cm observations (at BIMA and OVRO) of a large, intermediate redshift cluster sample. In addition, we describe a proposed, higher sensitivity array which will enable us to survey large portions of the sky. Simulated observations indicate that we will be able to survey one square degree of sky per month to sufficient depth that we will detect all galaxy clusters more massive than 2x10^{14} h^{-1}_{50}M_\odot, regardless of their redshift. We describe the cluster yield and resulting cosmological constraints from such a survey.Comment: 7 pages, 6 figures, latex, contribution to VLT Opening Symposiu

Limits on Arcminute Scale Cosmic Microwave Background Anisotropy with the BIMA Array

We have used the Berkeley-Illinois-Maryland-Association (BIMA) millimeter array outfitted with sensitive cm-wave receivers to search for Cosmic Microwave Background (CMB) anisotropies on arcminute scales. The interferometer was placed in a compact configuration which produces high brightness sensitivity, while providing discrimination against point sources. Operating at a frequency of 28.5 GHz, the FWHM primary beam of the instrument is 6.6 arcminutes. We have made sensitive images of seven fields, five of which where chosen specifically to have low IR dust contrast and be free of bright radio sources. Additional observations with the Owens Valley Radio Observatory (OVRO) millimeter array were used to assist in the location and removal of radio point sources. Applying a Bayesian analysis to the raw visibility data, we place limits on CMB anisotropy flat-band power Q_flat = 5.6 (+3.0 -5.6) uK and Q_flat < 14.1 uK at 68% and 95% confidence. The sensitivity of this experiment to flat band power peaks at a multipole of l = 5470, which corresponds to an angular scale of approximately 2 arcminutes. The most likely value of Q_flat is similar to the level of the expected secondary anisotropies.Comment: 15 pages, 5 figures, LaTex, aas2pp4.sty, ApJ submitte