RESUMO
We investigate the effects of external dielectric screening on the electronic dispersion and the band gap in the atomically thin, quasi-two-dimensional (2D) semiconductor WS_{2} using angle-resolved photoemission and optical spectroscopies, along with first-principles calculations. We find the main effect of increased external dielectric screening to be a reduction of the quasiparticle band gap, with rigid shifts to the bands themselves. Specifically, the band gap of monolayer WS_{2} is decreased by about 140 meV on a graphite substrate as compared to a hexagonal boron nitride substrate, while the electronic dispersion of WS_{2} remains unchanged within our experimental precision of 17 meV. These essentially rigid shifts of the valence and conduction bands result from the special spatial structure of the changes in the Coulomb potential induced by the dielectric environment of the monolayer.
RESUMO
Despite improvements in medical treatment and numerous public health campaigns stigmatization remains a potent stressor for people living with HIV/ AIDS. This study provides an initial German adaptation of the HIV Stigma Scale (HSS-D). Participants were 167 HIV-positive homosexual men aged 22-74 years. Exploratory factor analysis replicated the original four-factor structure (subscales: enacted stigma, disclosure concerns, negative self-image, concern with public attitudes). Further psychometric analysis led to a revised version comprising 21 items (HSS-D21). The scale showed high reliability (α=0.90). Significant associations with anxiety, depres-sion, life satisfaction and perceived social support confirmed for construct validity. The majority of the respondents expressed high acceptance of the stigma measure. In order to eslish a thorough German adaptation further research with diverse samples is needed.