Pregnant women as a reservoir of undetected sexually transmitted diseases in rural South Africa: implications for disease control

OBJECTIVES: This study was undertaken to determine the prevalence of sexually transmitted diseases (STDs) in pregnant women in rural South Africa and to determine the value of using abnormal urogenital symptoms to identify infected women. METHODS: This was a cross-sectional study of 327 patients attending prenatal clinics. RESULTS: Of the 271 women with complete data, 141 (52%) had at least 1 STD and 49 (18%) had more than 1. Abnormal symptoms were common (n = 225; 83%), but associations were weak, and the positive predictive value of different symptoms for infection ranged from 2% to 54%. CONCLUSIONS: Most STDs in rural South African women remain undetected and untreated. As the scope for laboratory diagnosis in resource-poor settings is limited, presumptive treatment of pregnant women and their partners may be a cost-effective option to reduce transmission of STDs and HIV infection.     

Effect of Sediment pH on Resuspension of Kaolinite Sediments

The resuspension of contaminated cohesive sediments can impact water quality by mobilizing sediment particles and adsorbed contaminants. Changes in psysicochemical and electrochemical environments, around resuspended sediment particles, may cause some contaminants to desorb into the water column. The contribution of contaminated sediments to degradation of water quality depends on an estimate of sediment resuspension rates. In this study, the resuspension of Georgia kaolinite sediments under varying pH conditions was investigated in laboratory flume experiments. Because the edge charge of kaolinite particles is pH dependent, kaolinite particles exhibit different modes of particle associations under varying pH conditions. The paper characterizes these particle associations and relates them to the resuspension of kaolinite sediments for varying pH values. Variations in sediment water content, changes from a stratified to a uniform sediment bed, changes in rheological properties, and variations in the electrophoretic mobility of kaolinite particles were all indicative of the changes in particle associations that resulted from changes in sediment pH. The critical shear stress and the erosion rate coefficient were evaluated for varying pH values and explained by particle associations. A rheometer was used to measure rheological properties of the settled sediment bed; the measured yield stresses had a direct correlation with critical shear stresses.     

Integrated amorphous and polycrystalline silicon thin-filmtransistors in a single silicon layer

Using a masked hydrogen plasma treatment to spatially control the crystallization of amorphous silicon to polycrystalline silicon in desired areas, amorphous and polycrystalline silicon thin-film transistors (TFTs) with good performance have been integrated in a single film of silicon without laser processing. Both transistors are top gate and shared all process steps. The polycrystalline silicon transistors have an electron mobility in the linear regime of ~15 cm²/Vs, the amorphous silicon transistors have a linear mobility of ~0.7 cm²/Vs and both have an ON/OFF current ratios of >10⁵. Rehydrogenation of amorphous silicon after the 600°C crystallization anneal using another hydrogen plasma is the critical process step for the amorphous silicon transistor performance. The rehydrogenation power, time, and reactor history are the crucial details that are discussed in this paper     

Computational simulations and optimization of flow and temperature distributions in a large-scale power plant building

For reduced carbon dioxide and pollutant emission, it is often as effective, if not more, to minimize energy use on the consumption side, as to maximize the efficiency on the power supply side. In this study, we seek to fully characterize and optimize the heating, ventilation, and air conditioning (HVAC) electrical energy use in a large-scale structure: a power-plant building that houses boilers, turbines and other operating equipment. We use a fully three-dimensional computational fluid dynamics (CFD) model of this building, measuring 80 m in width, 120 m in length and 60 m in height, replicating the complex internal and external geometries, in order to simulate the flow and temperature distributions under a wide range of ambient and HVAC operating conditions. The flow patterns and temperature distributions in this building structure are computationally simulated in detail, wherein the computed temperatures are validated through spot measurements. The detailed understanding of the flow patterns and temperature distributions then allows for optimization of the HVAC configuration. Identification of the problematic flow patterns and temperature mis-distributions, leads to some corrective measures, for optimization of the temperature distributions. The basic principles of fluid mechanics and heat transfer, applied in conjunction with CFD simulation results, can result in substantial improvements under both hot- and cold-weather conditions, in most cases with relatively simple, implementable modifications.     

Role of majority and minority carrier barriers silicon/organic hybrid heterojunction solar cells

A hybrid approach to solar cells is demonstrated in which a silicon p-n junction, used in conventional silicon-based photovoltaics, is replaced by a room-temperature fabricated silicon/organic heterojunction. The unique advantage of silicon/organic heterojunction is that it exploits the cost advantage of organic semiconductors and the performance advantages of silicon to enable potentially low-cost, efficient solar cells.