Stress-related hydrogen degradation of 0.1-/spl mu/m InP HEMTs and GaAs PHEMTs

Hydrogen degradation of III-V field-effect transistors (FETs) is a serious reliability concern. Previous work has shown that threshold-voltage shifts induced by H/sub 2/ exposure in 1-/spl mu/m-channel InP high-electron mobility transitors (HEMTs) can be attributed to compressive stress in the gate due to the formation of TiH/sub x/ in Ti/Pt/Au gates. The compressive stress affects the device characteristics through the piezoelectric effect. This paper examined the H/sub 2/ sensitivity of 0.1-/spl mu/m strained-channel InP HEMTs and GaAs pseudomorphic HEMTs. After exposure to H/sub 2/, the threshold voltage V/sub T/ of both types of devices shifted positive. This positive shift in V/sub T/ is predicted by a model for hydrogen-induced piezoelectric effect. In situ V/sub T/ measurements reveal distinct time dependences of the V/sub T/ shifts, which are also consistent with stress-related phenomena.     

Impacts of lindane usage in the Canadian Prairies on the Great Lakes ecosystem. 2. Modeled fluxes and loadings to the Great Lakes

Atmospheric loadings of gamma-hexachlorocyclohexane (gamma-HCH) from May 1, 1998, to April 30, 1999, to the Great Lakes simulated by a coupled soil-air and water-air atmospheric transport model are presented. Modeling results on an annual basis indicate that Lake Superior received the highest dry deposition load of 2.17 kg yr(-1). Dry deposition to the lower Great Lakes (Lakes Erie and Ontario) was 2-6 times lower as compared to the upper Great Lakes. Greater deposition in the upper Great Lakes is due mainly to their larger surface area and greater proximity to sources of gamma-HCH. Dry deposition fluxes (pg m(-2)) to lake surfaces were much lower than to land as a result of lower deposition velocities and lower air concentrations of gamma-HCH over the lakes. The highest gamma-HCH loading (kg yr(-1), in 1998-99) due to wet deposition occurred for Lake Ontario. This was mainly attributed to greater annual rainfall over Lake Ontario. An investigation of average seasonal fluxes predicted by the model shows that deposition fluxes to the Great Lakes are considerably higher in the summer than that in the autumn and winter seasons. The net direction of gas exchange also exhibits a seasonal dependence. Lakes Michigan, Huron, and Ontario show net absorption in the summer 1998 whereas at all other times net outgassing occurred at all of the lakes. Overall, gas exchange was the dominant process affecting loadings to the Great Lakes. Model-derived loadings and total deposition flows across the Great Lakes basin due to dry and wet depositions and net gas exchange agree reasonably well with the summer estimates compiled by the Integrated Atmospheric Deposition Network whereas autumn values show greater discrepancies. Better agreement was also observed for dry deposition as compared to wet deposition. Specifically, to improve short-term loading estimates (e.g., over days to months), the model results indicate the need for better spatially and temporally resolved information on concentrations in air and surface water and better estimates of precipitation and deposition velocities over the lakes.     

Integral equation analysis of artificial media

This paper presents an integral equation and method of moments (MM) solution to determine the effective permittivity and permeability of an artificial medium. The artificial medium is modeled as a triple infinite periodic array of identical scattering elements. A plane wave of unknown phase constant is assumed to propagate in the periodic medium in a given direction, and the periodic moment method (PMM) is used to set up a matrix equation for the currents on the center element of the periodic array. By setting the determinant of the PMM impedance matrix to zero, one can determine the phase constant of the plane wave, and then the effective permittivity and permeability of the artificial medium     

Nitric oxide acutely inhibits neuronal energy production. The Committees on Neurobiology and Cell Physiology

Disruption of mitochondrial respiration has been proposed as an action of nitric oxide (NO) responsible for its toxicity, but the effects of NO on the energetics of intact central neurons have not been reported. We examined the effects of NO on mitochondrial function and energy metabolism in cultured hippocampal neurons. The application of NO from NO donors or from dissolved gas produced a rapid, reversible depolarization of mitochondrial membrane potential, as detected by rhodamine-123 fluorescence. NO also produced a progressive concentration-dependent depletion of cellular ATP over 20 min exposures. The energy depletion produced by higher levels of NO (2 microM or more) was profound and irreversible and proceeded to subsequent neuronal death. In contrast to the effects of NO, mitochondrial protonophores produced complete depolarizations of mitochondrial membrane potential but depleted the neuronal ATP stores only partially. Inhibitors of mitochondrial oxidative phosphorylation (rotenone or 3-nitropropionic acid) or of glycolysis (iodoacetate plus pyruvate) also produced only partial ATP depletion, suggesting that either process alone could partially maintain ATP stores. Only by combining the inhibition of glycolytic energy production with the inhibition of mitochondria could the effects of NO in depleting energy and inducing delayed toxicity be duplicated. These results show that NO has rapid inhibitory actions on mitochondrial metabolism in living neurons. However, the severe ATP-depleting effects of high concentrations of NO are not fully explained by the direct effects on mitochondrial activity alone but must involve the inhibition of glycolysis as well. These inhibitory effects on energy production may contribute to the delayed toxicity of NO in vitro and in ischemic stroke.     

Ontogeny of estrogen receptor-beta expression in rat testis

The recently discovered estrogen receptor-beta (ERbeta) is expressed in rodent and human testes. To obtain insight in the physiological role of ERbeta we have investigated the cell type-specific expression pattern of ERbeta messenger RNA (mRNA) and protein in the testis of rats of various ages by in situ hybridization and immunohistochemistry. In fetal testes of rats 16 days postcoitum and testes of 4-day-old animals, fetal germ cells (gonocytes) reveal the ERbeta mRNA in their cytoplasm and the ERbeta protein in their nucleus. In testes of 11- and 15-day-old rats, ERbeta mRNA and protein were detected in Sertoli cells and type A spermatogonia. No signal was found in other types of germ cells. In the adult testes, expression of ERbeta mRNA as well as ERbeta protein was found in pachytene spermatocytes from epithelial stages VII-XIV and in round spermatids from stages I-VIII. Low ERbeta expression was observed in all type A spermatogonia, including undifferentiated A spermatogonia, whereas no expression was found in In and type B spermatogonia and early spermatocytes. At all ages, Sertoli cells showed a weak hybridization signal as well as weak immunoreactivity for ERbeta. In adult testes, no ERbeta mRNA or protein was detected in the interstitial tissue, indicating that Leydig cells and peritubular myoid cells do not express ERbeta. The expression of ERbeta in fetal and late male germ cells as well as in Sertoli cells suggests that estrogens directly affect germ cells during testicular development and spermatogenesis.     

Hedonic capacity and schizotypy revisited: A taxometric analysis of social anhedonia.

P. E. Meehl (1962) originally conjectured that hedonic capacity was an indicator of the latent class or taxon of schizotypy. However, P. E. Meehl (1989, 1990) subsequently diminished the role of hedonic capacity in his theory, indicating that hypohedonia is one of a dozen normal-range (nontaxonic) individual-differences factors that may potentiate the expression of schizophrenia. This dimensional-only view of hedonic capacity was tested by applying taxometric procedures to the Revised Social Anhedonia Scale (RSAS; M. L. Eckblad, L. J. Chapman, J. P. Chapman, & M. Mishlove, 1982) in a sample of college students (N?=?1,526). Analyses indicated that the construct measured by the RSAS is taxonic in nature with a base rate approximating .10. These data are interpreted in the context of other findings suggesting that social anhedonia is an indicator of schizotypy. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The implications of the relevant legislation for printing ink formulation, manfacture and supply

Conclusion  The implications of legislation on the activities of the ink industry are far reaching and complex. This paper has described the major influences on formulation (food safety and VOC control), manufacture (solid waste and health and safety) and supply (packaging). There is little doubt that further legislation will be implemented, and that existing legislation will become more stringent. Directly or indirectly, this will have increasing cost implications for the industry and its customers, and awareness and proper management at all levels is required to maintain control with legislative compliance.     

Titanium hydride formation in Ti/Pt/Au-gated InP HEMTs

Ti/Pt metal layers are an integral part of the gate stack of many GaAs PHEMTs and InP HEMTs. These devices are known to be affected by H ₂ exposure. In this study, Auger Electron Spectroscopy (AES) measurements of Ti/Pt bilayers are correlated with electrical measurements of InP HEMTs fabricated with Ti/Pt/Au gates. The FET measurements show that H₂ exposure shifts the device threshold voltage through the piezoelectric effect. AES reveals the formation of titanium hydride (TiH_x) in Ti/Pt bilayers after identical H₂ exposures. These results indicate that the volume expansion associated with TiH_x formation causes compressive stress in Ti/Pt/Au gates, leading to the piezoelectric effect. After a subsequent recovery anneal in N₂, the FET measurements show that V_T recovers. AES measurements confirm that the TiH_x in hydrogenated Ti/Pt bilayers also decreases after further annealing in N₂     

An inter-laboratory ring trial for the detection and isolation of Mycobacterium avium subsp. paratuberculosis from raw milk artificially contaminated with naturally infected faeces

There is a need for standardised, robust, reproducible molecular and culture methods to achieve clarification of the inactivation of Mycobacterium avium subsp. paratuberculosis (Map), the causative microbial agent of Johne's disease, in (faecally) contaminated milk and other food products such as meat. This study assessed the performance of a commercially available Map DNA extraction kit for milk Adiapure and accompanying PCR detection kit Adiavet alongside 'in-house' molecular and culture methods in an inter-laboratory ring trial using raw milk spiked with Map-infected faeces. The combined Adiapure-Adiavet Map DNA extraction and detection kit consistently detected 30 copies of IS900 (equivalent to approximately 2 cells) ml(-1) raw milk, when used in four different laboratories. Improvements in sensitivity and ease of use for 'in-house' Map detection were observed when the Adiapure extraction kit was combined with 'in-house' detection assays. Detection by real-time PCR methods, using the commercial extraction and detection systems, resulted in an overall detection rate of 100%, 90%, 85% and 25% for respective Map concentrations of 300, 30, 3 and 0.3 copies of IS900ml(-1) raw milk. Map, at 300 copies of IS900 (equivalent to approximately 20 Map cells) ml(-1) raw milk, was recovered from all samples cultured in mycobacteria growth indicator tube (MGIT) medium, from 10 of 12 samples on Herrold's egg yolk medium (HEYM) and not recovered from any samples using BACTEC medium. In conclusion, the Adiapure DNA extraction kit allows for sensitive and easy detection of Map in raw milk. The extraction method can form a candidate part of essential methodology and real-time PCR can further increase the sensitivity of the detection method. Moreover, MGIT medium is promising for culture-dependent detection of Map from raw milk.