Ab initio free energy of vacancy formation and mass-action kinetics in vis-active TiO2

Recent reports have identified bulk defects such as oxygen vacancies as key players in visible-light photoactive TiO2. This would imply greater visible light absorption rates may be possible provided effective defect engineering can be achieved. To further this we have developed methods to simulate vacancy formation in bulk TiO2 using ab initio techniques. Initial results of these methods show an entropic reduction in the free energy of vacancy formation of 2.3 eV over a range of 266 K. The use of this result is illustrated by a 'toy' mass-action kinetics model which offers insight into vacancy concentration, rate constants, and enthalpy of reaction

Demographic Differences, Self-esteem and Sexual Assertiveness among Black Women

There is a high HIV prevalence rate for Black women in Virginia; however, few scholars have examined how sexual assertiveness and self-esteem against HIV vary within this group. Black women who have low levels of self-esteem may increase their risk for HIV. The purpose of this quantitative cross-sectional study was to determine if four aspects of sexual assertiveness (sexual initiation, sexual refusal, HIV/AIDS/STD communication, and contraception/STD prevention) differed across demographic categories and were associated with self-esteem in a diversified group of Black women living in Virginia. A cross-sectional survey was conducted with a community-based sample of 117 adult Black women. The social cognitive theory was the framework that guided this study. ANOVAs were used to determine differences in means of the four sexual assertiveness subscales across the demographic categories (age, sexual orientation, income, education, and relationship status. HIV, AIDS, and sexual transmitted disease communication assertiveness mean scores were significantly higher among higher income Black women (padj=.016) and Black women with a college versus a high school degree (padj=.047). Moreover, Pearson bivariate correlation results showed self-esteem was significantly positively associated with all but one measure (sexual initiation) of sexual assertiveness. Health educators can use the findings of this study to create education initiatives that focus on building self-esteem and sexual assertiveness behaviors among Black women as an HIV/AIDS prevention method

Screen-printed platinum electrodes for measuring crevice corrosion: Nickel aluminium bronze as an example

Screen-printed platinum electrodes were used to monitor crevice corrosion processes. The electrodes, printed on an inert alumina substrate, formed the bottom of an artificial crevice when mechanically clamped to a rectangular block of nickel-aluminium bronze (NAB). Cyclic differential pulse voltammetry was used to detect corrosion products over time whilst the assembly was immersed in a 3.5% by weight aqueous solution of sodium chloride. Cupric (Cu2+), ferric (Fe3+) and ferrous (Fe2+) ions were detected with evolution profiles indicative of selective phase corrosion

Lifetime performance characteristics of screen-printed potentiometric Ag/AgCl chloride sensors

Ag/AgCl chloride sensors were fabricated using thick-film technology. A number of different formulations were prepared and chloride responses were investigated over time. Near Nernstian, identical responses were observed over the first 160 days with an average chloride sensitivity of -51.8 ± 0.4 mV per decade change in chloride concentration (pCl), irrespective of paste formulation. After 6- months continuous immersion in tap water, pastes formulated with a glass binder began to exhibit a loss in sensitivity whilst those formulated from a commercial thickfilm dielectric paste remained functional for the best part of a year. The difference is attributed to the inclusion of proprietary additives in the commercial paste aiding adhesion and minimising AgCl leaching

Screen-printed platinum electrodes for the detection of cupric and ferric ions in high chloride backgrounds

Screen-printed platinum electrodes developed for use in corrosion monitoring applications have been used to detect cupric and ferric ions both individually and as mixtures in a background of 3.5% by weight sodium chloride and in the presence of dissolved oxygen. In single species detection linear responses for the Fe3+/Fe2+ couple were observed over the concentration range 0.3 to 100mM. By contrast, the small size of the working electrode caused a current limiting response for cupric ions over the same concentration range. In mixtures of these ions, the sensors show good differentiation and are able to separate the individual metal ion responses