Improved performance of microbial fuel cells using a gradient porous air cathode: An experiment and simulation study.

High carbon catalyst loadings are commonly used for the catalyst layer (CL) in air-cathodes to obtain a performance comparable with that using platinum. This results in a much thicker CL, which severely limits mass transfer. In this study, we developed a porosity-gradient CL to passively enhance mass transfer in the air-cathode of microbial fuel cells (MFCs) for the first time. Computational results demonstrated that a cathode CL with increasing porosity (CL-IP) and decreasing porosity (CL-DP) from the water to the air-facing side exhibited improved transport of oxygen and OH-, respectively, alleviating concentration overpotentials in the CL. Experimental results also showed that an MFC that included a cathode with CL-IP achieved a maximum power density of 1781 ±â€¯92 mW m-2, which was higher than that achieved with CL-DP and a homogeneous CL (1614 ±â€¯72 and 1183 ±â€¯205 mW m-2).

Assessment of Tablet Surface Hardness by Laser Ablation and Its Correlation With the Erosion Tendency of Core Tablets.

Surface erosion of uncoated tablets results in processing problems such as dusting and defects during coating and is governed by the strength of particle bonding on tablet surface. In this study, the correlation between dusting tendency of tablets in a coating pan with friability and laser ablation surface hardness was assessed using tablets containing different concentrations of magnesium stearate and tartaric acid. Surface erosion propensity of different batches was evaluated by assessing their dusting tendency in the coating pan. In addition, all tablets were analyzed for crushing strength, friability, modified friability test using baffles in the friability apparatus, and weight loss after laser ablation. Tablets with similar crushing strength showed differences in their surface erosion and dusting tendency when rotated in a coating pan. These differences did not correlate well with tablet crushing strength or friability but did show reasonably good correlation with mass loss after laser ablation. These results suggest that tablet surface mass loss by laser ablation can be used as a minipiloting (small-scale) tool to assess tablet surface properties during early stages of drug product development to assess the risk of potential large-scale manufacturing issues.

HIV prevention among street-based sex workers (SSWs) in Chongqing, China: interviews with SSWs, clients and healthcare providers.

Street-based female sex workers (SSWs) are subjected to a relatively high risk of HIV transmission, even higher than establishment-based female sex workers in China. However, very few HIV intervention programmes have targeted this particular group to date. Based in Southwest China, this study aims to identify perceived barriers, demands and suggestions on HIV prevention from the perspectives of SSWs, clients and healthcare providers in Chongqing. Face-to-face, in-depth interviews were conducted in July 2008 with 23 participants. They were recruited by purposive, convenience sampling and included 12 SSWs, 5 male clients, 4 government healthcare providers and 2 outreach workers from a community-based non-governmental organisation. Thematic analysis was used. SSWs were largely rural-to-urban migrants with a low socioeconomic status. Most of their clients shared a similar background. Both SSWs and their clients demonstrated a low awareness of HIV infection and a lack of understanding of effective preventive strategies. Financial hardships, lack of family support, fear of police arrest and stigma in relation to sex work were identified as SSWs' major barriers for accessing healthcare services. Both SSWs and their clients indicated an urgent demand for accessing adequate HIV prevention and care programmes. On the other hand, government organisations trying to provide services to this group have also encountered obstacles, specifically their limited ability to establish mutual trust. Programmes provided by community-based non-governmental organisation, however, were perceived to be more attractive. In conclusion, there remains a substantial gap between the need of adequate HIV prevention services for SSWs and their clients and what is currently available. Strengthening inter-sectoral collaboration, providing specifically tailored health services, actively involving SSW peers and their clients, and reducing stigma in the society are keys to meet this urgent demand by SSWs in China.

Investigation of carbon dioxide emission in China by primary component analysis.

Principal component analysis (PCA) is employed to investigate the relationship between CO2 emissions (COEs) stemming from fossil fuel burning and cement manufacturing and their affecting factors. Eight affecting factors, namely, Population (P), Urban Population (UP); the Output Values of Primary Industry (PIOV), Secondary Industry (SIOV), and Tertiary Industry (TIOV); and the Proportions of Primary Industry's Output Value (PPIOV), Secondary Industry's Output Value (PSIOV), and Tertiary Industry's Output Value (PTIOV), are chosen. PCA is employed to eliminate the multicollinearity of the affecting factors. Two principal components, which can explain 92.86% of the variance of the eight affecting factors, are chosen as variables in the regression analysis. Ordinary least square regression is used to estimate multiple linear regression models, in which COEs and the principal components serve as dependent and independent variables, respectively. The results are given in the following. (1) Theoretically, the carbon intensities of PIOV, SIOV, and TIOV are 2573.4693, 552.7036, and 606.0791 kt per one billion $, respectively. The incomplete statistical data, the different statistical standards, and the ideology of self sufficiency and peasantry appear to show that the carbon intensity of PIOV is higher than those of SIOV and TIOV in China. (2) PPIOV, PSIOV, and PTIOV influence the fluctuations of COE. The parameters of PPIOV, PSIOV, and PTIOV are -2706946.7564, 2557300.5450, and 3924767.9807 kt, respectively. As the economic structure of China is strongly tied to technology level, the period when PIOV plays the leading position is characterized by lagging technology and economic developing. Thus, the influence of PPIOV has a negative value. As the increase of PSIOV and PTIOV is always followed by technological innovation and economic development, PSIOV and PTIOV have the opposite influence. (3) The carbon intensities of P and UP are 1.1029 and 1.7862 kt per thousand people, respectively. The carbon intensity of the rural population can be inferred to be lower than 1.1029 kt per thousand people. The characteristics of poverty and the use of bio-energy in rural areas result in a carbon intensity of the rural population that is lower than that of P.