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Reduced Temperature (reduced + temperature)
Selected AbstractsChemInform Abstract: High Performance Anodes for SOFCs Operating in Methane-Air Mixture at Reduced Temperatures.CHEMINFORM, Issue 20 2002Takashi Hibino Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Investigation of semi-insulating InP co-doped with Ti and various acceptors for use in X-ray detectionCRYSTAL RESEARCH AND TECHNOLOGY, Issue 4-5 2005K. Zdansky Abstract Semi-insulating InP single crystals co-doped with Zn and Ti and co-doped with Ti and Mn were grown by Czochralski technique. Wafers of these crystals were annealed for a long time at a high temperature and cooled slowly. The samples were characterized by temperature dependent resistivity and Hall coefficient measurements. The binding energies of Ti in semi-insulating InP co-doped with Ti and Zn and co-doped with Ti and Mn were found to differ which shows that Ti may occupy different sites in InP. The curves of Hall coefficient vs. reciprocal temperature deviate from straight lines at low temperatures due to electron and hole mixed conductance. The value of resistivity of the annealed semi-insulating InP co-doped with Ti and Mn reaches high resistivity at a reduced temperature easily achievable by thermo-electric devices which could make this material useable in X-ray detection. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] The atmospheric oxidation of ethyl formate and ethyl acetate over a range of temperatures and oxygen partial pressuresINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 7 2010John J. Orlando The Cl-atom-initiated oxidation of two esters, ethyl formate [HC(O)OCH2CH3] and ethyl acetate [CH3C(O)OCH2CH3], has been studied at pressures close to 1 atm as a function of temperature (249,325 K) and O2 partial pressure (50,700 Torr), using an environmental chamber technique. In both cases, Cl-atom attack at the CH2 group is most important, leading in part to the formation of radicals of the type RC(O)OCH(O,)CH3 [R = H, CH3]. The atmospheric fate of these radicals involves competition between reaction with O2 to produce an anhydride compound, RC(O)OC(O)CH3, and the so-called ,-ester rearrangement that produces an organic acid, RC(O)OH, and an acetyl radical, CH3C(O). For both species studied, the ,-ester rearrangement is found to dominate in air at 1 atm and 298 K. Barriers to the rearrangement of 7.7 ± 1.5 and 8.4 ± 1.5 kcal/mole are estimated for CH3C(O)OCH(O,)CH3 and HC(O)OCH(O,)CH3, respectively, leading to increased occurrence of the O2 reaction at reduced temperature. The data are combined with those obtained from similar studies of other simple esters to provide a correlation between the rate of occurrence of the ,-ester rearrangement and the structure of the reacting radical. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 397,413, 2010 [source] Employment of stressful conditions during culture production to enhance subsequent cold- and acid-tolerance of bifidobacteriaJOURNAL OF APPLIED MICROBIOLOGY, Issue 1 2003J.E. Maus Abstract Aims: This study examined whether exposure of early stationary phase Bifidobacterium longum and B. lactis cells to various combinations of reduced temperature, reduced pH and starvation would enhance the cells' subsequent cold- and/or acid-tolerance. Methods and Results: Survival of B. longum in growth medium at 6°C significantly (P < 0·05) increased as a result of starving cells for 30 or 60 min without any simultaneous decrease in temperature or pH. Acid-tolerance of B. lactis (at pH 3·5 in synthetic gastric fluid) increased significantly when the growth medium pH was decreased from 6·0 to 5·2 and cells experienced 30 or 60 min of starvation. Enhanced B. lactis acid-tolerance persisted through 8,11 weeks of ,80°C storage in the pH 5·2 growth medium. Upon addition to milk during yogurt manufacture, these cells initially had enhanced acid-tolerance relative to untreated cells but untreated cells became equally acid-tolerant during the first 2·5 h of yogurt manufacture. Conclusions: The cold- and acid-tolerance of bifidobacteria vary widely, but may be significantly increased by application of sub-lethal stress to early stationary phase cells during culture production. Significance and Impact of the Study: The enhancement of B. lactis acid-tolerance observed in this study may be of potential importance in the production of effective ready-to-consume probiotic dietary supplements. [source] The influence of thermal parameters on the acclimation responses of pinfish Lagodon rhomboides exposed to static and decreasing low temperaturesJOURNAL OF FISH BIOLOGY, Issue 3 2007C. M. Reber Pinfish Lagodon rhomboides acclimation rates were determined by modelling changes in critical thermal minimum (Tcrit min, ° C) estimates at set intervals following a temperature decrease of 3,4° C. The results showed that pinfish gained a total of 3·7° C of cold tolerance over a range of acclimation temperatures (Tacc, ° C) from (23,12° C), that cold tolerance increased with exposure time to the reduced temperature at all Tacc, but that the rate of cold tolerance accruement (mean 0·14° C day,1) was independent of Tacc. A highly significant (P < 0·001) multivariate predictive model was generated that described the acclimation rates and thermal tolerance of pinfish exposed to reduction in water temperature: log10Tcrit min= 0·41597 , 0·01704Tacc+ 0·04320Tplunge, 0·08376[log10 (t+ 1)], where Tplunge is plunge temperature (° C) and t is the time (days). A comparison of the present data, with acclimation rate data for other species, suggests that factors such as latitude or geographic range may play a more important role than ambient temperature in determining cold acclimation rates in fishes. [source] Simulated Annealing Study of Self-Assembly of Symmetric ABA Triblock Copolymers Confined in Cylindrical NanoporesMACROMOLECULAR THEORY AND SIMULATIONS, Issue 2-3 2008Zheng Wang Abstract We report a simulated annealing study of the self-assembly of symmetric lamella-forming ABA triblock copolymers confined in cylindrical nanopores. We systematically examine the dependence of the self-assembled morphologies and structural parameters on the degree of confinement and the strength of the surface preference. We find that the confined morphologies for the symmetric ABA triblocks with fA,=,1/2 are similar to those for the symmetric or nearly symmetric AB diblock copolymers under the same confinement. We also find that different structural parameters can reflect different information. The predicted bridging fraction value for the bulk phase is in good agreement with previously established values, whereas the predicted values for the confined morphologies change with both the degree of confinement and the strength of the surface preference. We further explore the self-assembling process by examining the morphology and various ensemble-averaged thermodynamic quantities and structure parameters as a function of the reduced temperature. [source] Temperature Effects on Survival and DNA Repair in Four Freshwater Cladoceran Daphnia Species Exposed to UV RadiationPHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 1 2009Sandra J. Connelly The biological responses of four freshwater daphniid species, Daphnia middendorffiana, D. pulicaria, D. pulex and D. parvula, to a single acute dose of ultraviolet B radiation (UVB) were compared. In addition to survival, we compared the induction of DNA damage (i.e. cyclobutane pyrimidine dimers) between species as well as the ability to repair this damage in the presence or absence of photoreactivating light. All four species showed high levels of shielding against DNA damage when compared to damage induced in purified DNA dosimeters at the same time and dose. Significant variation in survival was observed between species depending on temperature and light conditions. Contrary to our expectations, all species showed significantly higher survival and light-dependent DNA damage removal rates at 10°C compared to 20°C, suggesting that the enhanced rate of photoenzymatic repair (PER) at the lower temperature contributed significantly to the recovery of these organisms from UVB. PER was highly effective in promoting survival of three of the four species at 10°C, but at 20°C it was only partially effective in two species, and ineffective in two others. None of the species showed significant dark repair at 20°C and only D. pulicaria showed a significant capacity at 10°C. Two species, D. middendorffiana and D. pulex, showed some short-term survival at 10°C in absence of PER despite their inability to repair any appreciable amount of DNA damage in the dark. All species died rapidly at 20°C in absence of PER, as predicted from complete or near-absence of nucleotide excision repair (NER). Overall, the protective effects of tissue structure and pigmentation were similar in all Daphnia species tested and greatly mitigated the absorption of UVB by DNA and its damaging effects. Surprisingly, the visibly melanotic D. middendorffiana was not better shielded from DNA damage than the three non-melanotic species, and in fact suffered the highest damage rates. Melanin content in this species was not temperature dependent under the experimental growth conditions, and so did not contribute to temperature-dependent responses. It is evident that different species within the same genus have developed diverse biological responses to UVB. Our data strongly suggest that DNA damage is lethal to Daphnia and that photoenzymatic repair is the primary mechanism for removing these lesions. In the absence of light, few species are capable of removing any DNA damage. Surprisingly, the single species in which significant excision repair was detected did so only at reduced temperature. This temperature-dependence of excision repair is striking and may reflect adaptations of certain organisms to stress in a complex and changing environment. [source] Fluctuation conductivity analysis on the Bi-based superconductors processed under same conditionsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 9 2006F. Ben Azzouz Abstract We report electrical conductivity fluctuation measurements on different Bismuth-based granular samples synthesized under same processing conditions.Using the fluctuation conductivity ,, as a function of the reduced temperature , in the range ,7 < ln , < 1, we identified Gaussian and critical fluctuation conductivity in (Bi,Pb)-2223 and Bi-2212 samples. Within the mean field region, samples show predominately two dimensional (2D) behaviour with exponent , = ,1. Closer to critical temperature TC, we have observed a crossover of , from ,2/3 to ,1/3 in the critical region. The obtained exponents are consistent with 3D-XY model predictions. The regime with the critical exponent ,2/3 is dominate in the case of (Bi,Pb)-2223 sample. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] A novel equation of state (EOS) for prediction of solute solubility in supercritical carbon dioxide: Experimental determination and correlationTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 6 2009Sh. Jafari Nejad Abstract Solubility data of organophosphorous metal extractants in supercritical fluids (SCF) are crucial for designing metal extraction processes. We have developed a new equation of state (EOS) based on virial equation including an untypical parameter as BP/RT, reduced temperature and pressure for prediction of solute solubility in supercritical carbon dioxide (SC CO2). Solubility experimental data (solubility of tributylphosphate in SC CO2) were correlated with the two cubic equations of state (EOS) models, namely the Peng,Robinson EOS (PR-EOS) and the Soave,Redlich,Kwong EOS (SRK-EOS), together with two adjustable parameter van der Waals mixing and combining rules and our proposed EOS. The AARD of our EOS is significantly lower than that obtained from the other EOS models. The proposed EOS presented more accurate correlation for solubility data in SC CO2. It can be employed to speed up the process of SCF applications in industry. Les données de solubilité d'extractants de métaux organo-phosphorés dans des fluides supercritiques (FSC) sont cruciales pour concevoir des processus d'extraction des métaux. Nous avons développé une nouvelle équation d'état (ÉÉ) basée sur une équation d'état du viriel comprenant un paramètre atypique tel que la température et la pression réduite pour la prédiction de la solubilité du soluté dans du dioxyde de carbone supercritique. Les données expérimentales de solubilité (solubilité du phosphate de tributyle dans CO2 SC) ont été corrélées avec les deux modèles d'équations d'état cubiques, soit l'ÉÉ Peng,Robinson (ÉÉ-PR) et l'ÉÉ Soave,Redlich,Kwong (ÉÉ-SRK), avec deux paramètres ajustables, les règles de mélange et de combinaison van der Waals et notre ÉÉ proposée. L'AARD de notre ÉÉ est significativement plus faible que celui obtenu à partir des autres modèles d'ÉÉ. L'ÉÉ proposée présentait une corrélation plus exacte pour les données de solubilité dans le CO2 SC. Elle peut être employée pour accélérer les processus des applications de FSC dans l'industrie. [source] Ternary single-source precursors for polycrystalline thin-film solar cellsAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 11 2002Kulbinder K. Banger The development of thin-film solar cells on flexible, lightweight, space-qualified substrates provides an attractive cost solution for fabricating solar arrays with high specific power (W kg,1). The use of a polycrystalline chalcopyrite absorber layer for thin-film solar cells is considered as the next generation in photovoltaic devices. At NASA GRC we have focused on the development of new single-source precursors (SSPs) and their utility to deposit the chalcopyrite semiconducting layer (CIS) onto flexible substrates for solar-cell fabrication. The syntheses and thermal modulation of SSPs via molecular engineering are described. Thin-film fabrication studies demonstrate that the SSPs can be used in a spray chemical vapor deposition process for depositing CIS at reduced temperatures, and result in electrical properties that are suitable for photovoltaic devices. Copyright © 2002 John Wiley & Sons, Ltd. [source] | ||||||||||||||||