Four-wave mixing using polarization grating induced thermal grating in liquids exhibiting circular dichroism

A novel four-wave mixing technique for the detection of circular dichroism in optically active liquid samples is demonstrated. When two cross-polarized laser beams are crossed at a small angle in a circular dichroic liquid a weak thermal grating is produced with a phase depending on the sign of the circular dichroism. The authors show that the polarization of one of the beams can be modified to allow coherent interference with an intensity-grating induced thermal grating. A probe beam scattering from the composite grating results in a signal that reveals the sign and magnitude of the circular dichroism. The use of this technique to optimize the signal-to-noise ratio in the presence of scattered light and laser intensity noise is discussed

Characterizing the HIV care continuum among a community sample of black men who have sex with men in the United States

Black men who have sex with men (BMSM) have the highest HIV incidence rates among all men who have sex with men (MSM) and have been less likely than other MSM to be diagnosed, linked or retained in care for HIV. The Promoting Our Worth, Equality, and Resilience (POWER) study administered a behavioral health survey and HIV test to BMSM to estimate the HIV continuum of care among a community-derived sample. Of the N = 1,680 BMSM living with HIV, n = 956 (56.9%) were aware of their HIV-positive status. BMSM who had been previously diagnosed reported progression through the care continuum at greater than 80% for linkage to medical care (97.6%), retention in medical care (97.3%), prescription of antiretroviral therapy (93.6%) and viral suppression (86.4%). Results of this analysis reveal the urgent need to ensure BMSM are being screened and diagnosed. Additionally, community-driven samples are a promising method offering the opportunity to build on the resilience of BMSM progressing though the continuum as well as engage BMSM not yet in care. Lastly, such methods can assist in communicating with those lost to retention

Black Men Who Have Sex with Men and Lifetime HIV Testing: Characterizing the Reasons and Consequences of Having Never Tested for HIV

HIV testing remains a critical point of entry to HIV treatment services and now biomedical prevention as well. Yet despite the high HIV prevalence among Black men who have sex with men (MSM), insufficient attention has been given to factors associated with those Black MSM in the United States who have never received an HIV test in their lifetime. Promoting Our Worth, Equality, & Resilience (POWER) is a cross-sectional observational study that recruited Black MSM at Black Pride events across six cities in the United States from 2014 to 2017. Participants completed an anonymous questionnaire and were offered free, confidential HIV testing. Of the 4174 Black MSM without a prior HIV diagnosis, 404 (9.68%) had never tested for HIV (mean age = 31.03 years). Lower education and greater internalized homophobia were associated with never having tested for HIV. Higher age (AOR = 1.05, 95%, 1.02–1.07) and assumption of HIV-positivity (AOR = 3.24, 95% CI 1.53–6.84) were both associated with increased odds of an HIV-positive test result (n = 119; 36%). To compare, HIV prevalence among Black MSM who had received at least one HIV test before study participation was 23%. While a minority of Black MSM had never received an HIV test, this group had a significantly higher likelihood of HIV infection. Alternative HIV testing strategies are needed to facilitate HIV testing initiation among Black MSM for whom conventional HIV testing modalities are insufficient

Syndemic Health Disparities and Sexually Transmitted Infection Burden Among Black Men Who Have Sex with Men Engaged in Sex Work in the U.S.

Black men who have sex with men (MSM) engaged in sex work (BMSM-SW) experience elevated HIV and sexually transmitted infection (STI) prevalence. Further, BMSM-SW have been shown to have higher rates of syndemic psychosocial health conditions which contribute to HIV risk behavior and incidence, and poorer care outcomes than other groups of men who have sex with men. However, syndemic perspectives have not been applied to understanding past-year STI burden among BMSM-SW in the U.S. Sexually active Black MSM ≥ 18 years old were recruited from Black Pride events in six U.S. cities (n = 4421) between 2014 and 2017. Multivariable logistic regressions assessed correlates of past-year sex work engagement; whether BMSM-SW had higher odds of syndemic conditions; and whether BMSM-SW had higher odds of self-reported, past-year STI diagnoses. Structural equation models assessed relationships between sex work engagement, syndemic conditions, and STI controlled for sociodemographics and number of sexual partners. A total of 254 (5.7%) Black MSM reported past-year sex work, of whom 45.3% were HIV positive. BMSM-SW were significantly more likely to be Hispanic, to report past-year bisexual behavior, and to report annual income < $10,000. In multivariable models, BMSM-SW were significantly more likely to report intimate partner violence, assault victimization, polydrug use, and depression symptoms; they were also more likely to report past-year gonorrhea, chlamydia, and syphilis. Syndemic conditions mediated the relationship between past-year sex work and past-year STI burden, constituting a significant indirect effect. BMSM-SW in the U.S. face severe biopsychosocial health disparities. Interventions developed for BMSM engaged in sex work are lacking. Our results suggest that interventions containing safer sex work education and sex-positive biobehavioral HIV/STI prevention alongside substance use, mental health, employment, and education components will be most effective

Prevalence and Correlates of PrEP Awareness and Use Among Black Men Who Have Sex with Men and Women (MSMW) in the United States

Men who have sex with men and women (MSMW), including those who are Black, experience HIV-related disparities compared to men who have sex with men only (MSMO). Few studies have assessed the prevalence and correlates of pre-exposure prophylaxis (PrEP) awareness and use among Black MSMW. We recruited MSM ≥ 18 attending Black Gay Pride events between 2014–2017. We conducted multivariable logistic regressions to assess differences in PrEP awareness and use among HIV-negative Black MSM (n = 2398) and within Black MSMW (n = 419). MSMW were less likely than MSMO to report PrEP awareness (p < 0.001). Among PrEP-aware MSM, MSMW were more likely than MSMO to report PrEP use (p < 0.05). MSMW receiving gay community support were more likely to be PrEP-aware (p < 0.01). MSMW reporting any past-year STI diagnoses were more likely to report PrEP use (p < 0.01). Findings suggest that PrEP awareness campaigns tailored for Black MSMW, concomitant with STI-to-PrEP interventions, will facilitate greater PrEP uptake in this population

Wavenumber-explicit continuity and coercivity estimates in acoustic scattering by planar screens

We study the classical first-kind boundary integral equation reformulations of time-harmonic acoustic scattering by planar sound-soft (Dirichlet) and sound-hard (Neumann) screens. We prove continuity and coercivity of the relevant boundary integral operators (the acoustic single-layer and hypersingular operators respectively) in appropriate fractional Sobolev spaces, with wavenumber-explicit bounds on the continuity and coercivity constants. Our analysis is based on spectral representations for the boundary integral operators, and builds on results of Ha-Duong (Jpn J Ind Appl Math 7:489--513 (1990) and Integr Equat Oper Th 15:427--453 (1992)).Comment: v2 has minor corrections compared to v1. arXiv admin note: substantial text overlap with arXiv:1401.280

Understanding the impact of a syndemic on the use of pre-exposure prophylaxis in a community-based sample of behaviorally PrEP-eligible BMSM in the United States

HIV Pre-Exposure Prophylaxis (PrEP) has shown great promise in reducing HIV transmission among affected populations; however, PrEP uptake among Black men who have sex with men (BMSM) has stalled. This study compares BMSM using PrEP and BMSM at risk for HIV not using PrEP based on differences in behavior, psychosocial conditions and the presence of a syndemic (n = 1,411). BMSM reporting PrEP use were significantly more likely to report three of five HIV risk behaviors and three of four psychosocial conditions. Odds of reporting PrEP use increased as the number of psychosocial conditions increased such that BMSM with three psychosocial conditions (AOR= 5.65, 95% CI: 3.17, 10.08) and four conditions (AOR = 18.34, 95% CI: 5.01, 67.20) demonstrated significantly greater odds of PrEP use compared to BMSM reporting one or less conditions. While BMSM at greatest risk are using PrEP, strategies are still needed for men at varying risk levels

Examining the Impact of a Psychosocial Syndemic on Past Six-Month HIV Screening Behavior of Black Men who have Sex with Men in the United States: Results from the POWER Study

Syndemic production theory has been used to explore HIV transmission risk or infections but has not been used to investigate prevention behavior, or with large samples of non-Whites. This analysis is the first to explore the impact of syndemic factors on previous six-month HIV screening behavior among US Black MSM. Data from Promoting Our Worth, Equality and Resilience (POWER) were analyzed from 3294 participants using syndemic variable counts and measures of interaction/synergy. Syndemic variables included: past three-month poly-drug use, depression, last year intimate partner violence, HIV risk and problematic binge drinking. BMSM reporting two syndemic factors were more likely to report screening (AOR = 1.37, 95% CI 1.04–1.80; p = 0.028) with no significant associations for three or more conditions. Measures of joint effect revealed that there were synergies among depression, problematic binge drinking and poly-drug use but these psychosocial factors cannot entirely explain testing patterns and excess disease burden among BMSM

PDGF-B gene therapy accelerates bone engineering and oral implant osseointegration

Platelet-derived growth factor-BB (PDGF-BB) stimulates repair of healing-impaired chronic wounds such as diabetic ulcers and periodontal lesions. However, limitations in predictability of tissue regeneration occur due, in part, to transient growth factor bioavailability in vivo. Here, we report that gene delivery of PDGF-B stimulates repair of oral implant extraction socket defects. Alveolar ridge defects were created in rats and were treated at the time of titanium implant installation with a collagen matrix containing an adenoviral (Ad) vector encoding PDGF-B (5.5 x 10(8) or 5.5 x 10(9) pfu ml(-1)), Ad encoding luciferase (Ad-Luc; 5.5 x 10(9) pfu ml(-1); control) or recombinant human PDGF-BB protein (rhPDGF-BB, 0.3 mg ml(-1)). Bone repair and osseointegration were measured through backscattered scanning electron microscopy, histomorphometry, micro-computed tomography and biomechanical assessments. Furthermore, a panel of local and systemic safety assessments was performed. Results indicated that bone repair was accelerated by Ad-PDGF-B and rhPDGF-BB delivery compared with Ad-Luc, with the high dose of Ad-PDGF-B more effective than the low dose. No significant dissemination of the vector construct or alteration of systemic parameters was noted. In summary, gene delivery of Ad-PDGF-B shows regenerative and safety capabilities for bone tissue engineering and osseointegration in alveolar bone defects comparable with rhPDGF-BB protein delivery in vivo