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Notes: A series of samples was deposited by very high frequency glow discharge in a plasma of silane diluted in hydrogen in concentrations SiH4/(SiH4+H2) varying from 100% to 1.25%. For silane concentrations below 8.4%, a phase transition between amorphous and microcrystalline silicon occurs. Microcrystalline silicon has been characterized by transmission electron microscopy (TEM) and x-ray diffraction. The medium-resolution TEM observations show that below the transition, the microstructure of microcrystalline silicon varies in a complex way, showing a large variety of different growth structures. For the sample close to the phase transition, one observes elongated nanocrystals of silicon embedded in an amorphous matrix followed at intermediate dilution by dendritic growth, and, finally, at very high dilution level, one observes columnar growth. X-ray diffraction data evidence a (220) crystallographic texture; the comparison of the grain sizes as evaluated from TEM observations and those determined using Scherrer's equation illustrates the known limitations of the latter method for grain size determination in complex microstructures. © 2000 American Institute of Physics.

Notes: A simple in vitro test system was established to determine the degradation of hyaluronic acid induced by reactive oxygen species (ROS). ROS were selectively generated by exogenic and endogenic factors and the effects of directly and indirectly acting antioxidants with different modes of action were systematically examined. The proposed experimental strategy, simulating specific stress conditions, can be used for an easy and fast screening of putative antioxidant activity of water soluble compounds. Under the chosen test conditions, the antioxidant enzymes catalase and Cu/Zn-superoxide dismutase revealed the most effective protection against the ROS-induced depolymerization of hyaluronic acid, whereas individual tested compounds acted as prooxidants under certain circumstances.〈section xml:id="abs1-2"〉〈title type="main"〉RésuméUn système expérimental simple a été mis au point in vitro pour déterminer la dégradation de l'acide hyaluronique induite par des espèces d'oxygène réactives (ROS, de l'anglais ‘reactive oxygen species’). On sait que les ROS influencent la viscosité de l'acide hyaluronique in vivo, ce qui explique le grand nombre de systèmes expérimentaux in vitro basés sur ce changement de viscosité. La combinaison des méthodes présentées pour la première fois dans cet article représente une approche pour l'étude comparative et systématique d'anti-oxydants agissant différemment de manière directe et indirecte dans des systèmes produisant diverses ROS. Les anti-oxydants peuvent capter ou éliminer les ROS de façon spécifique ou non, empêcher directement ou indirectement la formation de ROS ou même réparer les dommages causés par les ROS. Ainsi, il n'est pas surprenant qu'un anti-oxydant dans un systéme agisse de manière entièrement différente dans un autre. Ceci n'est pas uniquement démontré dans nos modèles in vitro mais est également mentionné pour certains effets négatifs in vivo, révélant qu'il existe une cascade complexe de réactions dépendant des ROS et qu'il n'existe pas d'anti-oxydant parfait. Ainsi, seule une action synergique de différents anti-oxydants peut fournir une protection efficace. Ceci reflète la situation physiologique et doit être pris en compte lors du développement de tout concept topique contre les ROS. La stratégie expérimentale proposée, simulant des conditions de stress spécifiques, peut être utilisée pour évaluer aisément et rapidement l'activité anti-oxydante putative de composés hydrosolubles. Dans les conditions de test choisies, ce sont les enzymes anti-oxydantes catalase et Cu/Zn-superoxyde dismutase qui ont assuré la meilleure protection contre la dépolymérisation de l'acide hyaluronique induite par les ROS, alors que des composés testés séparément ont agi comme des pro-oxydants dans certaines circonstances.

Notes: Complete μc-Si:H p-i-n solar cells have been prepared by the very high frequency glow discharge method. Up to now, intrinsic μc-Si:H has never attracted much attention as a photovoltaic active material. However, an efficiency of 4.6% and remarkably high short circuit current densities of up to 21.9 mA/cm2 due to an enhanced absorption in the near-infrared could be obtained. First light-soaking experiments indicate no degradation for the entirely μc-Si:H cells. Voltage-dependent spectral response measurements suggest that the carrier transport in complete μc-Si:H p-i-n cells may possibly be cosupported by diffusion (in addition to drift).

Notes: A new technique is required which enables tailoring of the morphology of a metallic nanostructured material down to the 10 nm length scale. Using nanoporous nuclear track etched membranes as templates for electrodeposition, an assembly of wires with diameters as low as 30 nm could be obtained. Alternating the electrodeposition of two metals resulted in multilayers grown perpendicular to the wire axis. Layer thicknesses as low as 2 nm could be reached. Application is demonstrated by making wires 6 μm long, 80 nm in diameter, having a succession of either Co and Cu layers or of (Ni,Fe) and Cu layers. Wires containing layers of 5–10 nm in thickness exhibited a giant magnetoresistance. The current was naturally perpendicular to the layers. At ambient temperature, a magnetoresistance of 14% for Co/Cu and of 10% for (Fe,Ni)/Cu was observed. © 1994 American Institute of Physics.

Notes: We tested the hypothesis that exposure to an aroma through a food or beverage in the first part of a meal (preload) would reduce the consumption of a food with the same aroma in the second portion of the meal, because of olfactory-specific satiety. In a first experiment, 35 young, normal-weight adults participated in 2 lunch sessions during which they consumed a fixed preload of either ranch-flavored or plain potato chips and sparkling water, followed by ad libitum consumption of a pasta salad with ranch dressing and sparkling water. In the second experiment, 33 subjects consumed a fixed preload of either lemon-flavored or plain sparkling water and pasta salad with ranch dressing, followed by ad libitum consumption of lemon-flavored yogurt and plain sparkling water. No difference was observed in the amount of food consumed (corrected for session order effects) as a function of prior exposure to ranch flavor in the chips or lemon flavor in the water. We conclude that exposure to a preload aroma may not have a significant effect on subsequent intake of a food with the same aroma.

Notes: Laser-based cavity ringdown techniques have demonstrated ultrahigh sensitivities for trace gas detection in the optical and infrared wavelength regions. We have investigated the applicability of the cavity ringdown technique in the millimeter wave region, which is rich in the rotational spectra of molecules. The millimeter-wave system uses a tunable Fabry–Perot cavity that is excited by a continuous-wave, phase-locked source at the W band; a fast PIN diode switch that turns off the excitation after the cavity is tuned to resonance; and a diode detector that records the resonance decay. Proof of concept has been established by measuring the ringdown times with absorbing materials in the cavity and comparing them with theoretical prediction. © 2002 American Institute of Physics.

Notes: Besprechungen

Notes: Abstract. Given an improper action (= cell stabilizers are infinite) of a group G on a CW-complex $ {\cal X} $ , we present criteria, based on connectivity at infinity properties of the cell stabilizers under the action of G that imply connectivity at infinity properties for G. A refinement of this idea yields information on the topology at infinity of Artin groups, and it gives significant progress on the question of which Artin groups are duality groups.

Notes: BOOK REVIEWS

Notes: Abstract Previous work revealed substantial levels of mutagenicity in effluents from certain municipal wastewater treatment plants. One of these treatment plants was selected for further study to track the effluent mutagenicity to its sources, to chemically characterize the mutagenicity, and to assess the treatability of the mutagens. Mutagenicity testing using the Salmonella/microsome assay was performed on methylene chloride extracts of influent and effluent samples from the municipal wastewater treatment plant, as well as on four selected industrial effluents entering the plant. The mutagenicity of the influent samples was detected only in the presence of a microsomal metabolic activation system and was highest in Salmonella strain TA98. About two-thirds of the mutagenicity passed through the treatment plant, suggesting that the mutagenic compounds were refractory to conventional biological treatment. No significant mutagenic activity was detected in three of the industrial waste streams, all paper products plant discharges. However, a high level of mutagenicity (1.2 million TA98 revertants/liter) was detected in the effluent from a coke oven plant. This source could account for all of the mutagenicity entering the wastewater treatment plant. After fractionation of the coke oven effluent by sequential extraction at neutral, acidic and basic pH with methylene chloride, 93% of the TA98 (+S9) mutagenicity was found in the neutral fraction. A C18 column fractionation scheme using a methanol/water elution gradient revealed that 92% of the mutagenicity eluted with the 75% and the 80% methanol in water fractions. The C18 fractionation also provided good separation of mutagenicity from toxicity to fathead minnows. This study has demonstrated the potential of toxicity reduction evaluation (TRE) methodology for tracing effluent toxicity to its source, using genotoxicity as an endpoint.