Hydrogenated amorphous semiconductors

Solar cells based on hydrogenated amorphous silicon are now made from a variety of materials including alloys and microcrystalline films. Research aimed at improving cell efficiency should emphasize studies of alloys and metastable defects. We discuss several research topics related to the growth, structure, and electronic properties of these materials, which should lead to improved photovoltaic devices.     

CW laser operation with new F+2-type color centers in NaF

In NaF doped with divalent alkaline earth impurities, thermally stabilized F+2* centers were found. Compared to the corresponding centers in transition-metal-doped crystals, they show improved properties (slope efficiency, output power, reduced fading) as active media in CW color center lasers.     

The effect of hypoxia on the regional distribution of cardiac output in the dog

Twenty-one dogs were studied under conditions of normal oxygenation and hypoxia with the microsphere distribution method to determine the effect of arterial oxygen saturation on the regional distribution of cardiac output. The dogs were anesthetized and artifically ventilated. Cannulas were placed in the left ventricle to administer microspheres and in a peripheral artery to determine cardiac output. Each dog received two microsphere injections: (1) while normally oxygenated (room air), and (2) under hypoxia (10% oxygen-90% nitrogen in 10 dogs and 5% oxygen-95% nitrogen in 11 dogs). Absolute cardiac output increased from 87 +/- 15 ml/min per kg to 101 +/- 14 ml/min per kg during mild hypoxia (10% oxygen) (P less than 0.05), and from 73 +/- 17 ml/min per kg to 120 +/- 24 ml/min per kg during severe hypoxia (5% oxygen) (P less than 0.01). Absolute blood flows increased to all organs except skin and muscle during hypoxia, although there were decreases in the fractional distribution of cardiac output to the splanchnic bed and kidney. Striking changes were found in coronary, hepatic, and cerebral circulation, and the organ with, greatest response to hypoxia was the heart, with increased coronary flow of 37% and 285% during exposure to 10% and 5% oxygen, respectively. Hence, low oxygen levels in blood cause redistribution of cardiac output and arterial content plays an important role in blood flow regulation.     

Factors affecting the uptake of 99mTc-sulfur colloid by the lung and kidney

Occasionally patients injected with 99mTc-sulfur colloid (TSC) for liver--spleen imaging show increased uptake by the lungs or kidneys. In animals, increased lung uptake of TSC can be produced by injecting endotoxin intraperitoneally. Using an intraperitoneal endotoxin model, we studied the effect of heparin on dose-response curves for TSC uptake by the lungs and kidneys. Over a dose range of 1 mug to 10 mg of endotoxin, TSC uptake by the lungs increased progressively; heparin had no effect. In the kidneys, endotoxin in doses from 1 mug to 1 mg resulted in an increased TSC uptake which was less marked than that in the lungs and which was also unaffected by heparin. However, at a dose of 10 mg of endotoxin, a marked increase occurred in TSC uptake by the kidneys, and this could be prevented by heparin. Although the increased TSC uptake by the kidneys at lower doses of endotoxin and by the lungs at all doses is probably not related to intraavascular coagulation, the marked increase in TSC uptake by the kidneys at 10 mg of intraperitoneal endotoxin probably is related to intravascular coagulation, possibly by entrapment in fibrin deposits in the renal capillaries.     

Microviscosity of togavirus membranes studied by fluorescence depolarization: influence of envelope proteins and the host cell

The microviscosities of the hydrophobic regions of the membranes of intact Semliki forest and Sindbis viruses grown on BHK-21 cells, of liposomes derived from the extracted viral lipids, and of protease-treated virions were measured by fluorescence depolorization using the fluorescence probe 1, 6-diphenyl-1,3,5-hexatriene. The intact virus membranes were found to have a higher microviscosity than did virus-derived liposomes, indicating the viral envelope proteins contribute to microviscosity. However, protease-treated virus, devoid of protruding spikes but with residual lipophilic peptide tails, was found to have a microviscosity more similar to that of the intact virus than to that of protein-free liposomes. Sindbis virus grown in BHK-21 cells at 37 C had a much higher microviscosity than did Sindbis virus grown on Aedes albopicuts cells at 22 C. Sindbis virus grwon in A. albopictus and BHK-21 cells also gave higher microviscosity values than did the intact host cells. These data indicate that both the virion proteins and the cellular lipids selected during viral growth and maturation contribute to the increased microviscosity of togavirus membranes.     

Development of a Risk-Ranking Framework to Evaluate Potential High-Threat Microorganisms, Toxins, and Chemicals in Food

ABSTRACT:  Through a cooperative agreement with the U.S. Food and Drug Administration, the Institute of Food Technologists developed a risk-ranking framework prototype to enable comparison of microbiological and chemical hazards in foods and to assist policy makers, risk managers, risk analysts, and others in determining the relative public health impact of specific hazard–food combinations. The prototype is a bottom-up system based on assumptions that incorporate expert opinion/insight with a number of exposure and hazard-related risk criteria variables, which are propagated forward with food intake data to produce risk-ranking determinations. The prototype produces a semi-quantitative comparative assessment of food safety hazards and the impacts of hazard control measures. For a specific hazard–food combination the prototype can produce a single metric: a final risk value expressed as annual pseudo-disability adjusted life years (pDALY). The pDALY is a harmonization of the very different dose–response relationships observed for chemicals and microbes. The prototype was developed on 2 platforms, a web-based user interface and an Analytica® model (Lumina Decision Systems, Los Gatos, Calif., U.S.A.). Comprising visual basic language, the web-based platform facilitates data input and allows use concurrently from multiple locations. The Analytica model facilitates visualization of the logic flow, interrelationship of input and output variables, and calculations/algorithms comprising the prototype. A variety of sortable risk-ranking reports and summary information can be generated for hazard–food pairs, showing hazard and dose–response assumptions and data, per capita consumption by population group, and annual p-DALY.     

Prebiotic fibre‐incorporated whey protein crisps processed by supercritical fluid extrusion

Prebiotic soluble fibre (fructooligosaccharides)‐incorporated whey protein crisps were produced by low‐shear supercritical fluid extrusion (SCFX), which utilises supercritical CO₂ as an expansion agent instead of steam. Protein crisps with desirable qualities were obtained with a formulation containing 8% prebiotic fibre and 60% whey protein concentrate (WPC‐80), which gave the final product with a protein content of 49.6% (w/w). A maximum of 70% WPC‐80 and 8% prebiotic fibre could be incorporated to produce expanded protein crisps; however, increasing WPC‐80 from 50% to 70% decreased the end‐product expansion ratio from 3.1 to 1.2 and increased the product hardness and piece density from 1.3 to 2.8 kN and 0.63 to 0.75 g mL^?1, respectively. Addition of 8% prebiotic fibre did not affect the textural qualities of final products. The process produced an expanded protein matrix with unique internal microstructure of uniformly distributed closed cells. Amino acid analysis indicated that 90% of the total lysine and 92% of the total essential amino acids were retained after SCFX processing and oven‐drying, indicating the preservation of protein nutritional quality during the process.