A Model of the Optical Properties of a Non-absorbing Media with Application to Thermotropic Materials for Overheat Protection

AbstractThermotropic materials offer the potential to provide overheat protection for polymer absorbers. These materials are composed of a matrix material in which a second material, referred to as the scattering domain, is dispersed. Temperature control is accomplished by a reduction in transmittance at a desired temperature corresponding to the phase change temperature of the scattering domain. The phase change is accompanied by a change in refractive index. This paper describes a numerical model to predict the transmittance and reflectance of a polymer based thermotropic material as a function of the relative index of refraction m between the matrix and scattering domains, the scattering domain size and volume fraction fv, and the sheet thickness. The thermotropic material is modelled as a non-absorbing sheet comprised of discrete anisotropic scattering spherical particles embedded in a matrix material. Under the assumption that the particles scatter incident radiation independently, the direction of scattered radiation is determined by Mie theory. A Monte Carlo numerical technique is used to predict the transmittance and reflectance for thermotropic materials in which the matrix index of refraction is 1.5 (representative of polymers) and the incident wavelength is 550nm. Model results are validated by comparison to measured transmittance for 0.3mm thick polymer samples containing particles with 200nm radius at m ranging from 0.97 to 1.09 and fv ranging from 5 to 18.2%. As the mismatch in refractive indices and volume fraction increase, the transmittance is reduced. For example, the transmittance is reduced from 83% for m=1.02 and fv = 9.6 to approximately 50% for m=1.09 and fv =13.5% (200nm radius and 0.3mm thick)

Mother Centriole Distal Appendages Mediate Centrosome Docking at the Immunological Synapse and Reveal Mechanistic Parallels with Ciliogenesis.

Cytotoxic T lymphocytes (CTLs) are highly effective serial killers capable of destroying virally infected and cancerous targets by polarized release from secretory lysosomes. Upon target contact, the CTL centrosome rapidly moves to the immunological synapse, focusing microtubule-directed release at this point [1-3]. Striking similarities have been noted between centrosome polarization at the synapse and basal body docking during ciliogenesis [1, 4-8], suggesting that CTL centrosomes might dock with the plasma membrane during killing, in a manner analogous to primary cilia formation [1, 4]. However, questions remain regarding the extent and function of centrosome polarization at the synapse, and recent reports have challenged its role [9, 10]. Here, we use high-resolution transmission electron microscopy (TEM) tomography analysis to show that, as in ciliogenesis, the distal appendages of the CTL mother centriole contact the plasma membrane directly during synapse formation. This is functionally important as small interfering RNA (siRNA) targeting of the distal appendage protein, Cep83, required for membrane contact during ciliogenesis [11], impairs CTL secretion. Furthermore, the regulatory proteins CP110 and Cep97, which must dissociate from the mother centriole to allow cilia formation [12], remain associated with the mother centriole in CTLs, and neither axoneme nor transition zone ciliary structures form. Moreover, complete centrosome docking can occur in proliferating CTLs with multiple centriole pairs. Thus, in CTLs, centrosomes dock transiently with the membrane, within the cell cycle and without progression into ciliogenesis. We propose that this transient centrosome docking without cilia formation is important for CTLs to deliver rapid, repeated polarized secretion directed by the centrosome.We thank the Wellcome Trust for funding to GMG (075880) and CIMR (100140).This is the final version of the article. It was first available from Elsevier via http://dx.doi.org/10.1016/j.cub.2015.10.02

Infectious bronchitis virus nonstructural protein 4 alone induces membrane pairing

Positive-strand RNA viruses, such as coronaviruses, induce cellular membrane rearrangements during replication to form replication organelles allowing for efficient viral RNA synthesis. Infectious bronchitis virus (IBV), a pathogenic avian of significant importance to the global poultry industry, has been shown to induce the formation of double membrane vesicles (DMVs), zippered endoplasmic reticulum (zER) and tethered vesicles, known as spherules. These membrane rearrangements are virally induced; however, it remains unclear which viral proteins are responsible. In this study, membrane rearrangements induced when expressing viral non-structural proteins (nsps) from two different strains of IBV were compared. Three non-structural transmembrane proteins, nsp3, nsp4, and nsp6, were expressed in cells singularly or in combination and the effects on cellular membranes investigated using electron microscopy and electron tomography. In contrast to previously studied coronaviruses, IBV nsp4 alone is necessary and sufficient to induce membrane pairing; however, expression of the transmembrane proteins together was not sufficient to fully recapitulate DMVs. This indicates that although nsp4 is able to singularly induce membrane pairing, further viral or host factors are required in order to fully assemble IBV replicative structures. This study highlights further differences in the mechanism of membrane rearrangements between members of the coronavirus family

Young women's use of a microbicide surrogate: The complex influence of relationship characteristics and perceived male partners' evaluations

This is the post-print version of the article. The official published version can be found at the link below.Currently in clinical trials, vaginal microbicides are proposed as a female-initiated method of sexually transmitted infection prevention. Much of microbicide acceptability research has been conducted outside of the United States and frequently without consideration of the social interaction between sex partners, ignoring the complex gender and power structures often inherent in young women’s (heterosexual) relationships. Accordingly, the purpose of this study was to build on existing microbicide research by exploring the role of male partners and relationship characteristics on young women’s use of a microbicide surrogate, an inert vaginal moisturizer (VM), in a large city in the United States. Individual semi-structured interviews were conducted with 40 young women (18–23 years old; 85% African American; 47.5% mothers) following use of the VM during coital events for a 4 week period. Overall, the results indicated that relationship dynamics and perceptions of male partners influenced VM evaluation. These two factors suggest that relationship context will need to be considered in the promotion of vaginal microbicides. The findings offer insights into how future acceptability and use of microbicides will be influenced by gendered power dynamics. The results also underscore the importance of incorporating men into microbicide promotion efforts while encouraging a dialogue that focuses attention on power inequities that can exist in heterosexual relationships. Detailed understanding of these issues is essential for successful microbicide acceptability, social marketing, education, and use.This study was funded by a grant from National Institutes of Health (NIHU19AI 31494) as well as research awards to the first author: Friends of the Kinsey Institute Research Grant Award, Indiana University’s School of HPER Graduate Student Grant-in-Aid of Research Award, William L. Yarber Sexual Health Fellowship, and the Indiana University Graduate and Professional Student Organization Research Grant

Predictors of antiretroviral therapy initiation in eThekwini (Durban), South Africa: Findings from a prospective cohort study

Despite expanded antiretroviral therapy (ART) eligibility in South Africa, many people diagnosed with HIV do not initiate ART promptly, yet understanding of the reasons is limited. Using data from an 8-month prospective cohort interview study of women and men newly-diagnosed with HIV in three public-sector primary care clinics in the eThekwini (Durban) region, South Africa, 2010–2014, we examined if theoretically-relevant social-structural, social-cognitive, psychosocial, and health status indicators were associated with time to ART initiation. Of 459 diagnosed, 350 returned to the clinic for their CD4+ test results (linkage); 153 (33.3%) were ART-eligible according to treatment criteria at the time; 115 (75.2% of those eligible) initiated ART (median = 12.86 weeks [95% CI: 9.75, 15.97] after linkage). In adjusted Cox proportional hazard models, internalized stigma was associated with a 65% decrease in the rate of ART initiation (Adjusted hazard ratio [AHR] 0.35, 95% CI: 0.19–0.80) during the period less than four weeks after linkage to care, but not four or more weeks after linkage to care, suggesting that stigma-reduction interventions implemented shortly after diagnosis may accelerate ART uptake. As reported by others, older age was associated with more rapid ART initiation (AHR for 1-year age increase: 1.04, 95% CI: 1.01–1.07) and higher CD4+ cell count (≥300μL vs. <150μL) was associated with a lower rate of initiation (AHR 0.38, 95% CI: 0.19–0.80). Several other factors that were assessed prior to diagnosis, including stronger belief in traditional medicine, higher endorsement of stigma toward people living with HIV, food insecurity, and higher psychological distress, were found to be in the expected direction of association with ART initiation, but confidence intervals were wide and could not exclude a null finding

The African Women's Protocol: Bringing Attention to Reproductive Rights and the MDGs

Andrew Gibbs and colleagues discuss the African Women's Protocol, a framework for ensuring reproductive rights are supported throughout the continent and for supporting interventions to improve women's reproductive health, including the MDGs