On the X-ray Properties of OH Megamaser Sources: Chandra Snapshot Observations

We present Chandra snapshot observations for a sample of 7 sources selected from the Arecibo OH megamaser (OHM) survey at z~0.13-0.22 and with far-infrared luminosities in excess of 10^{11} L_sun. In contrast with the known H2O megamasers, which are mostly associated with powerful Active Galactic Nuclei (AGN), the situation is far less clear for OHMs, which have been poorly studied in the X-ray band thus far. All of the observed sources are X-ray weak, with only one OHM, IRAS FSC 03521+0028 (z=0.15), being detected by Chandra (with 5 counts). The results from this pilot program indicate that the X-ray emission, with luminosities of less than ~10^{42} erg/s, is consistent with that from star formation (as also suggested in some cases by the optical spectra) and low-luminosity AGN emission. If an AGN is present, its contribution to the broad-band emission of OHM galaxies is likely modest. Under reasonable assumptions about the intrinsic X-ray spectral shape, the observed count distribution from stacking analysis suggests absorption of ~10^{22} cm^{-2}.Comment: 8 pages, 3 figures, accepted for publication in MNRA

Invoice from Thomas N. Darling to Robert Goelet

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Race in the Life Sciences: An Empirical Assessment, 1950-2000

The mainstream narrative regarding the evolution of race as an idea in the scientific community is that biological understandings of race dominated throughout the nineteenth and twentieth centuries up until World War II, after which a social constructionist approach is thought to have taken hold. Many believe that the horrific outcomes of the most notorious applications of biological race—eugenics and the Holocaust—moved scientists away from thinking that race reflects inherent differences and toward an understanding that race is a largely social, cultural, and political phenomenon. This understanding of the evolution of race as a scientific idea informed the way that many areas of law conceptualize human equality, including civil rights, human rights, and constitutional law. This Article provides one of the first large-scale empirical assessments of publications in peer-reviewed biomedical and life science journals to examine whether biological theories of race actually lost credibility in the life sciences after World War II. We find that biological theories of race transformed yet persisted in the dominant academic discourse up through modern times—a finding that contradicts the central narrative that the life sciences became “color-blind” or “post-racial” several decades ago. The continued salience of biological race in the life sciences suggests that more attention needs to be paid to the questionable assumptions driving this research on biological race and its potential spillover effects, i.e., how persisting claims of biological race in the scientific literature might reconstitute its significance in law and society in a manner that may be harmful to racial minorities

A Laboratory for Constraining Cosmic Evolution of the Fine Structure Constant: Conjugate 18 cm OH Lines Toward PKS 1413+135 at z=0.2467

We report the detection of the satellite 18 cm OH lines at 1612 and 1720 MHz in the z=0.2467 molecular absorption system toward the radio source PKS 1413+135. The two OH lines are conjugate; the 1612 MHz line is seen in absorption while the 1720 MHz line is seen in weak maser emission of equal, but negative, optical depth. We do not detect the main 18 cm OH lines at 1667 and 1665 MHz down to 1.1 mJy rms in 4.0 km/s channels. The detected and undetected 18 cm OH lines support a scenario of radiatively pumped stimulated absorption and emission with pumping dominated by the intraladder 119 micron line of OH, suggesting a column density N(OH) ~= 10^15 to 10^16 cm^-2. Combined with simultaneous HI 21 cm observations and published CO data, we apply the OH redshifts to measurements of cosmic evolution of the fine structure constant alpha = e^2/(hbar c). We obtain highly significant (~25 sigma) velocity offsets between the OH and HI lines and the OH and CO lines, but measurements of alpha-independent systematics demonstrate that the observed velocity differences are entirely attributable to physical velocity offsets between species rather than a change in alpha. The OH alone, in which conjugate line profiles guarantee that both lines originate in the same molecular gas, provides a weak constraint of Delta alpha/alpha_o = (+0.51 +/- 1.26) x 10^-5 at z=0.2467. Higher frequency OH line detections can provide a larger lever arm on Delta alpha and can increase precision by an order of magnitude. The OH molecule can thus provide precise measurements of the cosmic evolution of alpha that include quantitative constraints on systematic errors. Application of this technique is limited only by the detectability of |tau|~0.01 OH lines toward radio continuum sources and may be possible to z~5.Comment: AASTeX, 11 pages, 2 figures, accepted by Astrophysical Journa

Patient and doctor perspectives on HIV screening in the emergency department: A prospective cross-sectional study.

The emergency department (ED) is mentioned specifically in the Swiss HIV testing recommendations as a site at which patients can benefit from expanded HIV testing to optimise early HIV diagnosis. At our centre, where local HIV seroprevalence is 0.2-0.4%, 1% of all patients presenting to the ED are tested for HIV. Barriers to HIV testing, from the patient and doctor perspective, and patient acceptability of rapid HIV testing were examined in this study. Between October 2014 and May 2015, 100 discrete patient-doctor encounter pairs undertook a survey in the ED of Lausanne University Hospital, Switzerland. Patients completed a questionnaire on HIV risk factors and were offered free rapid HIV testing (INSTI™). For every patient included, the treating doctor was asked if HIV testing had 1) been indicated according to the national testing recommendations, 2) mentioned, and 3) offered during the consultation. Of 100 patients, 30 had indications for HIV testing through risk factors or a suggestive presenting complaint (PC). Fifty patients accepted rapid testing; no test was reactive. Of 50 patients declining testing, 82% considered themselves not at risk or had recently tested negative and 16% wished to focus on their PC. ED doctors identified 20 patients with testing indications, mentioned testing to nine and offered testing to six. The main reason for doctors not mentioning or not offering testing was the wish to focus on the PC. Patients and doctors at our ED share the testing barrier of wishing to focus on the PC. Rapid HIV testing offered in parallel to the patient-doctor consultation increased the testing rate from 6% (offered by doctors) to 50%. Introducing this service would enable testing of patients not offered tests by their doctors and reduce missed opportunities for early HIV diagnosis

Relaxation at late stages in an entropy barrier model for glassy systems

The ground state dynamics of an entropy barrier model proposed recently for describing relaxation of glassy systems is considered. At stages of evolution the dynamics can be described by a simple variant of the Ehrenfest urn model. Analytical expression for the relaxation times from an arbitrary state to the ground state is derived. Upper and lower bounds for the relaxation times as a function of system size are obtained.Comment: 9 pages no figures. to appear in J.Phys. A: Math. and Ge

Electrostatic Patch Effect in Cylindrical Geometry. III. Torques

We continue to study the effect of uneven voltage distribution on two close cylindrical conductors with parallel axes started in our papers [1] and [2], now to find the electrostatic torques. We calculate the electrostatic potential and energy to lowest order in the gap to cylinder radius ratio for an arbitrary relative rotation of the cylinders about their symmetry axis. By energy conservation, the axial torque, independent of the uniform voltage difference, is found as a derivative of the energy in the rotation angle. We also derive both the axial and slanting torques by the surface integration method: the torque vector is the integral over the cylinder surface of the cross product of the electrostatic force on a surface element and its position vector. The slanting torque consists of two parts: one coming from the interaction between the patch and the uniform voltages, and the other due to the patch interaction. General properties of the torques are described. A convenient model of a localized patch suggested in [2] is used to calculate the torques explicitly in terms of elementary functions. Based on this, we analyze in detail patch interaction for one pair of patches, namely, the torque dependence on the patch parameters (width and strength) and their mutual positions. The effect of the axial torque is then studied for the experimental conditions of the STEP mission.Comment: 28 pages, 6 Figures. Submitted to Classical Quantum Gravit

Chiral segregation driven by a dynamical response of the adsorption footprint to the local adsorption environment: Bitartrate on Cu(110)

Local or global ordering of chiral molecules at a surface is a key step in both chiral separation and heterogeneous enantioselective catalysis. Using density functional theory and scanning probe microscopy results, we find that the accepted structural model for the well known bitartrate on Cu(110) chiral system cannot account for the chiral segregation observed. Instead, we show that this strongly bound, chiral adsorbate changes its adsorption footprint in response to the local environment. The flexible adsorption geometry allows bitartrate to form stable homochiral trimer chains in which the central molecule restructures from a rectangular to an oblique footprint, breaking its internal hydrogen bonds in order to form strong intermolecular hydrogen bonds to neighbouring adsorbates. Racemic structures containing mixed enantiomers do not form strong hydrogen bonds, providing the thermodynamic driving force for the chiral separation that is observed experimentally. This result shows the importance of considering the dynamical response of molecular adsorption footprints at the surface in directing chiral assembly and segregation. The ability of strongly-chemisorbed enantiomers to change footprint depending on the local adsorption environment indicates that supramolecular assemblies at surfaces may exhibit more complex dynamical behaviour than hitherto suspected, which, ultimately, could be tailored to lead to environment and stimuli-responsive chiral surfaces