A Chandra Search for Coronal X Rays from the Cool White Dwarf GD 356

We report observations with the Chandra X-ray Observatory of the single, cool, magnetic white dwarf GD 356. For consistent comparison with other X-ray observations of single white dwarfs, we also re-analyzed archival ROSAT data for GD 356 (GJ 1205), G 99-47 (GR 290 = V1201 Ori), GD 90, G 195-19 (EG250 = GJ 339.1), and WD 2316+123 and archival Chandra data for LHS 1038 (GJ 1004) and GD 358 (V777 Her). Our Chandra observation detected no X rays from GD 356, setting the most restrictive upper limit to the X-ray luminosity from any cool white dwarf -- L_{X} < 6.0 x 10^{25} ergs/s, at 99.7% confidence, for a 1-keV thermal-bremsstrahlung spectrum. The corresponding limit to the electron density is n_{0} < 4.4 x 10^{11} cm^{-3}. Our re-analysis of the archival data confirmed the non-detections reported by the original investigators. We discuss the implications of our and prior observations on models for coronal emission from white dwarfs. For magnetic white dwarfs, we emphasize the more stringent constraints imposed by cyclotron radiation. In addition, we describe (in an appendix) a statistical methodology for detecting a source and for constraining the strength of a source, which applies even when the number of source or background events is small.Comment: 27 pages, 4 figures, submitted to the Astrophysical Journa

The Disconnect between China's Public Health and Public Security Responses to Injection Drug Use, and the Consequences for Human Rights

Stephen Koester discusses a research article by Elizabeth Cohen and Joseph Amon that illustrates how injection drug users are caught between China's conflicting policies and practices toward drug use and HIV prevention and care

Sunyaev Zel'dovich Effect Observations of Strong Lensing Galaxy Clusters: Probing the Over-Concentration Problem

We have measured the Sunyaev Zel'dovich (SZ) effect for a sample of ten strong lensing selected galaxy clusters using the Sunyaev Zel'dovich Array (SZA). The SZA is sensitive to structures on spatial scales of a few arcminutes, while the strong lensing mass modeling constrains the mass at small scales (typically < 30"). Combining the two provides information about the projected concentrations of the strong lensing clusters. The Einstein radii we measure are twice as large as expected given the masses inferred from SZ scaling relations. A Monte Carlo simulation indicates that a sample randomly drawn from the expected distribution would have a larger median Einstein radius than the observed clusters about 3% of the time. The implied overconcentration has been noted in previous studies with smaller samples of lensing clusters. It persists for this sample, with the caveat that this could result from a systematic effect such as if the gas fractions of the strong lensing clusters are substantially below what is expected.Comment: submitte

Interventions Delivered in Clinical Settings are Effective in Reducing Risk of HIV Transmission Among People Living with HIV: Results from the Health Resources and Services Administration (HRSA)’s Special Projects of National Significance Initiative

To support expanded prevention services for people living with HIV, the US Health Resources and Services Administration (HRSA) sponsored a 5-year initiative to test whether interventions delivered in clinical settings were effective in reducing HIV transmission risk among HIV-infected patients. Across 13 demonstration sites, patients were randomized to one of four conditions. All interventions were associated with reduced unprotected vaginal and/or anal intercourse with persons of HIV-uninfected or unknown status among the 3,556 participating patients. Compared to the standard of care, patients assigned to receive interventions from medical care providers reported a significant decrease in risk after 12 months of participation. Patients receiving prevention services from health educators, social workers or paraprofessional HIV-infected peers reported significant reduction in risk at 6 months, but not at 12 months. While clinics have a choice of effective models for implementing prevention programs for their HIV-infected patients, medical provider-delivered methods are comparatively robust

A comparative evaluation of the process of developing and implementing an emergency department HIV testing program

<p>Abstract</p> <p>Background</p> <p>The 2006 Centers for Disease Control and Prevention (CDC) HIV testing guidelines recommend screening for HIV infection in all healthcare settings, including the emergency department (ED). In urban areas with a high background prevalence of HIV, the ED has become an increasingly important site for identifying HIV infection. However, this public health policy has been operationalized using different models. We sought to describe the development and implementation of HIV testing programs in three EDs, assess factors shaping the adoption and evolution of specific program elements, and identify barriers and facilitators to testing.</p> <p>Methods</p> <p>We performed a qualitative evaluation using in-depth interviews with fifteen 'key informants' involved in the development and implementation of HIV testing in three urban EDs serving sizable racial/ethnic minority and socioeconomically disadvantaged populations. Testing program HIV prevalence ranged from 0.4% to 3.0%.</p> <p>Results</p> <p>Three testing models were identified, reflecting differences in the use of existing ED staff to offer and perform the test and disclose results. Factors influencing the adoption of a particular model included: whether program developers were ED providers, HIV providers, or both; whether programs took a targeted or non-targeted approach to patient selection; and the extent to which linkage to care was viewed as the responsibility of the ED. A common barrier was discomfort among ED providers about disclosing a positive HIV test result. Common facilitators were a commitment to underserved populations, the perception that testing was an opportunity to re-engage previously HIV-infected patients in care, and the support and resources offered by the medical setting for HIV-infected patients.</p> <p>Conclusions</p> <p>ED HIV testing is occurring under a range of models that emerge from local realities and are tailored to institutional strengths to optimize implementation and overcome provider barriers.</p

Understanding patient acceptance and refusal of HIV testing in the emergency department

<p>ABSTRACT</p> <p>Background</p> <p>Despite high rates of patient satisfaction with emergency department (ED) HIV testing, acceptance varies widely. It is thought that patients who decline may be at higher risk for HIV infection, thus we sought to better understand patient acceptance and refusal of ED HIV testing.</p> <p>Methods</p> <p>In-depth interviews with fifty ED patients (28 accepters and 22 decliners of HIV testing) in three ED HIV testing programs that serve vulnerable urban populations in northern California.</p> <p>Results</p> <p>Many factors influenced the decision to accept ED HIV testing, including curiosity, reassurance of negative status, convenience, and opportunity. Similarly, a number of factors influenced the decision to decline HIV testing, including having been tested recently, the perception of being at low risk for HIV infection due to monogamy, abstinence or condom use, and wanting to focus on the medical reason for the ED visit. Both accepters and decliners viewed ED HIV testing favorably and nearly all participants felt comfortable with the testing experience, including the absence of counseling. While many participants who declined an ED HIV test had logical reasons, some participants also made clear that they would prefer not to know their HIV status rather than face psychosocial consequences such as loss of trust in a relationship or disclosure of status in hospital or public health records.</p> <p>Conclusions</p> <p>Testing for HIV in the ED as for any other health problem reduces barriers to testing for some but not all patients. Patients who decline ED HIV testing may have rational reasons, but there are some patients who avoid HIV testing because of psychosocial ramifications. While ED HIV testing is generally acceptable, more targeted approaches to testing are necessary for this subgroup.</p

Specificity of Synaptic Connectivity between Layer 1 Inhibitory Interneurons and Layer 2/3 Pyramidal Neurons in the Rat Neocortex

Understanding the structure and function of the neocortical microcircuit requires a description of the synaptic connectivity between identified neuronal populations. Here, we investigate the electrophysiological properties of layer 1 (L1) neurons of the rat somatosensory neocortex (postnatal day 24–36) and their synaptic connectivity with supragranular pyramidal neurons. The active and passive properties of visually identified L1 neurons (n = 266) suggested division into 4 groups according to the Petilla classification scheme with characteristics of neurogliaform cells (NGFCs) (n = 72), classical-accommodating (n = 137), fast-spiking (n = 23), and burst-spiking neurons (n = 34). Anatomical reconstructions of L1 neurons supported the existence of 4 major neuronal groups. Multiparameter unsupervised cluster analysis confirmed the existence of 4 groups, revealing a high degree of similarity with the Petilla scheme. Simultaneous recordings between synaptically connected L1 neurons and L2/3 pyramidal neurons (n = 384) demonstrated neuronal class specificity in both excitatory and inhibitory connectivity and the properties of synaptic potentials. Notably, all groups of L1 neurons received monosynaptic excitatory input from L2/3 pyramidal neurons (n = 33), with the exception of NGFCs (n = 68 pairs tested). In contrast, NGFCs strongly inhibited L2/3 pyramidal neurons (n = 12 out 27 pairs tested). These data reveal a high specificity of excitatory and inhibitory connections in the superficial layers of the neocortex

Genetic effects on gene expression across human tissues

Characterization of the molecular function of the human genome and its variation across individuals is essential for identifying the cellular mechanisms that underlie human genetic traits and diseases. The Genotype-Tissue Expression (GTEx) project aims to characterize variation in gene expression levels across individuals and diverse tissues of the human body, many of which are not easily accessible. Here we describe genetic effects on gene expression levels across 44 human tissues. We find that local genetic variation affects gene expression levels for the majority of genes, and we further identify inter-chromosomal genetic effects for 93 genes and 112 loci. On the basis of the identified genetic effects, we characterize patterns of tissue specificity, compare local and distal effects, and evaluate the functional properties of the genetic effects. We also demonstrate that multi-tissue, multi-individual data can be used to identify genes and pathways affected by human disease-associated variation, enabling a mechanistic interpretation of gene regulation and the genetic basis of diseas