Effects of impurities on silicon solar-cell performance

Model analyses indicate that sophisticated solar cell designs (back surface fields, optical reflectors, surface passivation, and double layer antireflective coatings) can produce devices with conversion efficiencies above 20%. To realize this potential, the quality of the silicon from which the cells are made must be improved; and these excellent electrical properties must be maintained during device processing. As the cell efficiency rises, the sensitivity to trace contaminants also increases. For example, the threshold Ti impurity concentraion at which cell performance degrades is more than an order of magnitude lower for an 18% cell than for a 16% cell. Similar behavior occurs for numerous other metal species which introduce deep level traps that stimulate the recombination of photogenerated carriers in silicon. Purification via crystal growth in conjunction with gettering steps to preserve the large diffusion length of the as grown material can lead to the production of devices with efficiencies above 18%, as verified experimentally

Inorganic solid film lubricants Patent

Preparation of inorganic solid film lubricants with long wear life and stability in aerospace environment

Research study on materials processing in space, experiment M512

Gallium arsenide, a commercially valuable semiconductor, has been prepared from the melt (M.P. 1237C), by vapor growth, and by growth from metallic solutions. It has been established that growth from metallic solution can produce material with high, and perhaps with the highest possible, chemical homogeneity and crystalline perfection. Growth of GaAs from metallic solution can be performed at relatively low temperatures (about 600C) and is relatively insensitive to temperature fluctuations. However, this type of crystal growth is subject to the decided disadvantage that density induced convection currents may produce variations in rates of growth at a growing surface. This problem would be minimized under reduced gravity conditions

Coxsackie B2 Virus Infection Causing Multiorgan Failure and Cardiogenic Shock in a 42-Year-Old Man

Infections from coxsackie B2 viruses often cause viral myocarditis and, only rarely, multisystem organ impairment. We present the unusual case of a 42-year-old man in whom coxsackie B2 virus infection caused multiorgan infection, necessitating distal pancreatectomy, splenectomy, renal dialysis, and venoarterial extracorporeal membrane oxygenation with mechanical ventilation. In addition, the patient had a rapid-eye-movement sleep-related conduction abnormality that caused frequent sinus pauses of longer than 10 s, presumably due to myocarditis from the coxsackievirus infection. He recovered after permanent pacemaker placement and was discharged from the hospital. We discuss our aggressive supportive care and the few other reports of multiorgan impairment from coxsackieviruses

Vanishing lines in generalized Adams spectral sequences are generic

We show that in a generalized Adams spectral sequence, the presence of a vanishing line of fixed slope (at some term of the spectral sequence, with some intercept) is a generic property.Comment: 11 pages. Published copy, also available at http://www.maths.warwick.ac.uk/gt/GTVol3/paper7.abs.htm

Validation of scramjet exhaust simulation technique at Mach 6

Current design philosophy for hydrogen-fueled, scramjet-powered hypersonic aircraft results in configurations with strong couplings between the engine plume and vehicle aerodynamics. The experimental verification of the scramjet exhaust simulation is described. The scramjet exhaust was reproduced for the Mach 6 flight condition by the detonation tube simulator. The exhaust flow pressure profiles, and to a large extent the heat transfer rate profiles, were then duplicated by cool gas mixtures of Argon and Freon 13B1 or Freon 12. The results of these experiments indicate that a cool gas simulation of the hot scramjet exhaust is a viable simulation technique except for phenomena which are dependent on the wall temperature relative to flow temperature

Validation of scramjet exhaust simulation technique

Scramjet/airframe integration design philosophy for hypersonic aircraft results in configurations having lower aft surfaces that serve as exhaust nozzles. There is a strong coupling between the exhaust plume and the aerodynamics of the vehicle, making accurate simulation of the engine exhaust mandatory. The experimental verification of the simulation procedure is described. The detonation tube simulator was used to produce an exact simulation of the scramjet exhaust for a Mach 8 flight condition. The pressure distributions produced by the exact exhaust flow were then duplicated by a cool mixture Argon and Freon 13B1. Such a substitute gas mixture validated by the detonation tube technique could be used in conventional wind tunnel tests. The results presented show the substitute gas simulation technique to be valid for shockless expansions

A wild web: The tangled history of attitudes toward wildlife in a dynamic New England culture, 1945--1985

Attitudes toward wildlife are considerably more complex than one might suspect. This dissertation started with a hypothesis that population growth would correlate with increasing negative attitudes toward wildlife, but historical evidence only partially supports this hypothesis. Information about the frequency and types of wildlife references appearing in newspapers between 1945 and 1985 was gathered from a systematic sampling of six New Hampshire newspapers that represented towns with differing growth trends. While analysis of quantitative data minimized any correlation between growth and negative attitudes, qualitative data from newspaper articles, archival sources, government reports, books and articles, and other sources provided evidence that growth-related changes did have some effect on attitudes toward wildlife. Therefore, this research evolved to look more carefully at the effects of growth, and to identify what additional cultural elements played a role in shaping attitudes toward wildlife. Elements identified and explored include: growth, changes in agriculture, environmentalism, trends in outdoor recreation, and relationships with domestic companion animals. The general finding was that the history of local attitudes toward wildlife is a complicated web of intersecting cultural elements that have affected attitudes in diverse ways