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O2 Atmosphere (o2 + atmosphere)
Selected AbstractsPhotocatalytic Oxidation of Primary and Secondary Benzylic Alcohols to Carbonyl Compounds Catalyzed by H3PW12O40/SiO2 under an O2 Atmosphere.CHEMINFORM, Issue 12 2006Saeid Farhadi Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Internal atmosphere, quality attributes and sensory evaluation of MAP packaged fresh-cut Conference pearsINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 2 2007Robert Soliva-Fortuny Summary Conference pear cubes processed at partially ripe maturity could preserve an acceptable sensory quality during 3-week storage. A processing treatment consisting of a dip in 10 g L,1 ascorbic acid and 5 g L,1 calcium chloride and a packaging atmosphere of 2.5 kPa O2 + 7% CO2 preserved the overall sensory shelf life without significant changes in relation to untreated freshly prepared samples. However, high CO2 conditions were responsible for a rapid degradation of the product during the following days. Under 0 kPa O2 atmosphere, the product underwent a progressive but slight loss of flavour; but colour and firmness variations were not detected through sensory tests. [source] EFFECT OF OXYGEN CONCENTRATION ON THE BIOCHEMICAL AND CHEMICAL CHANGES OF STORED LONGAN FRUITJOURNAL OF FOOD QUALITY, Issue 1 2009G. CHENG ABSTRACT Longan fruits were stored for 6 days in atmosphere of 5, 21 (air) or 60% O2 (balance N2) at 28C and 90,95% relative humidity to examine effects of low and high O2 concentration on enzymatic browning and quality attributes of the fruit. Changes in pericarp browning, pulp breakdown, disease development, total phenol content, activities of phenol metabolism-associated enzymes, relative leakage rate, ,,, -diphenyl- , -picrylhydrazy (DPPH) radical scavenging activity, and contents of total soluble solids, titratable acidity and ascorbic acid were evaluated. Storage of fruit in a 5% O2 atmosphere markedly delayed pericarp browning in association with maintenance of high total phenolic content and reduced activities of polyphenol oxidase (PPO), peroxidase (POD) and phenylalanine ammonia lyase. Moreover, the fruit stored in a 5% O2 atmosphere exhibited a lower relative leakage rate and higher DPPH radical scavenging activity than fruit stored in air. This presumably was beneficial in maintaining compartmentation of enzymes and substrates, and thus, reducing pericarp browning. Pulp breakdown and disease development were also reduced by exposure to a 5% oxygenatmosphere. On the contrary, exposure of longan fruit to a 60% O2 atmosphere accelerated pericarp browning, pulp breakdown and decay development. PPO and POD activities and relative leakage rate were similar for control and 60% O2 -treated fruit after 4 and 6 days of storage. Furthermore, treatment with 60% O2 significantly decreased the phenolic content and DPPH scavenging activity of fruit. In addition, exposure to 5 or 60% O2 resulted in a higher level of total soluble solids, but a lower level of ascorbic acid of longan fruit flesh. In conclusion, exposure to a 5% O2 atmosphere showed great potential to reduce pericarp browning and extend shelf life of longan fruit. PRACTICAL APPLICATIONS Pericarp browning and pulp breakdown are the major causes of deterioration in postharvest longan. Conventional controlled atmosphere with low O2 and high CO2 is effective in maintaining quality and extending shelf life of fruits and vegetables, including inhibition of tissue browning. In this study, 5%-controlled atmosphere reduced significantly pericarp browning, pulp breakdown and rot development. It could potentially be useful as a postharvest technology of longan fruit for reducing or replacing the use of chemicals such as SO2 and fungicides, but it requires further investigation. [source] Synthesis of hyperbranched polymer having binaphthol units via oxidative cross-coupling polymerizationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 3 2008Tomohisa Temma Abstract The oxidative coupling polymerization of triphenylamine derivatives having 2-naphthol moieties with a CuCl-2,2,-isopropylidenebis(4-phenyl-2-oxazoline) catalyst under an O2 atmosphere was carried out. The polymerization of the monomer bearing both the hydroxynaphthoate and naphthol units afforded a hyperbranched polymer with a high cross-coupling selectivity of > 99%, which showed a number-average molecular weight of 20.3 × 103. In addition, the obtained polymer was quite soluble in THF. The photoluminescence and electrochemical properties of the obtained polymers were also examined. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1034,1041, 2008 [source] Revisit to the Origin of Grain Growth Anomaly in Yttria-Doped Barium TitanateJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2001Jung-Kun Lee In this study, the effect of atmosphere during calcining and sintering of Y2O3 -doped BaTiO3 was investigated to reveal the origin of the anomaly of grain growth and conductivity as a function of Y2O3 content. Samples with various atmospheric histories were prepared. Microstructural and electrical variations were observed using SEM, dielectric (,r vs T) and thermopower measuring techniques, and impedance spectroscopy. An abrupt decrease in grain growth and a transition from semiconducting to insulating behavior were observed when the Y2O3 concentration exceeded 0.3 mol% and the samples were heat-treated in an O2 atmosphere. In contrast, the samples treated under N2+ 5% H2 atmosphere revealed neither grain growth anomaly nor conductivity anomaly even though the Y2O3 concentration was much greater than 3 mol%. The undoped BaTiO3 samples also demonstrated increased average grain size with increased oxygen partial pressure. Therefore, it was suggested that the grain growth anomaly did not result from the formation of cation vacancies V,Ba or V,,Ti. To investigate the origin of the grain growth anomaly, the Curie temperature, concentration of free electrons, and impedance spectra were measured. The grain growth anomaly and conductivity anomaly were associated with abrupt changes in all the measurements. These abrupt changes could be explained by the partial incorporation of donor dopants. Consequently, the origin of the anomaly in the microstructure and electrical properties are discussed in terms of grain-boundary segregation of the donor dopant. [source] Transparent ohmic contacts to GaSb/In(Al)GaAsSb photovoltaic cellsPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 4 2007K. Golaszewska Abstract In this paper we present the results of study of thin oxide films: CdO, ZnO and RuSiO4 used as transparent ohmic contacts to GaSb/InGaAsSb/AlGaAsSb photodiodes. Thin oxide films with thickness of 50 nm were deposited by magnetron sputtering. CdO and RuSiO4 were formed in a reactive process in Ar,O2 atmosphere, from Cd and Ru1Si1 targets, respectively. ZnO films were deposited directly from ZnO target by rf sputtering. We have shown that application of CdO, ZnO and RuSiO4 transparent films instead of conventional metal-based contacts enables to improve of photodiode properties. As a result, GaSb/InGaAsSb/AlGaAsSb photodiodes with detectivity D * increased by factor of 2 and reduced by factor of 3 the series resistance were obtained. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] MOCVD of Hafnium Silicate Films Obtained from a Single-Source Precusor on Silicon and Germanium for Gate-Dielectric Applications,CHEMICAL VAPOR DEPOSITION, Issue 2-3 2007M. Lemberger Abstract In this work, hafnium silicate layers on Si and Ge wafers for gate dielectric application in metal,oxide,semiconductor devices are investigated. Films are deposited by metal,organic (MO)CVD using the single-source precursor Hf(acac)2(OSitBuMe2)2. This precursor exhibits good properties in terms of hydrolysis stability, volatility, and deposition. However, precursor decomposition is affected by surface conditions. Films deposited on Si wafers reveal high C contamination (up to 20,at,%) and low Si content (up to 20,at,%). In contrast, for film deposition on Ge wafers, no C contamination can be detected and Si incorporation is delayed until after about 15,nm HfO2 dielectric growth. Post-deposition rapid thermal annealing in an O2 atmosphere causes crystallization of deposited films, Si and Ge redistribution in the dielectric, respectively, and interfacial layer growth. However, oxygen annealing was also found to reduce effective oxide thickness (EOT) significantly compared to as-deposited films, which is attributed to crystallization effects. However, scaling of EOT is limited by that interfacial layer growth. Leakage currents are mainly caused by trap-related conduction mechanisms. Energy levels of involved traps decrease with increasing crystallization and/or Hf content, and values of 0.5,eV and 1,eV related to Hf and Si bonds, respectively, are obtained. [source] Effect of Nitrogen Atmosphere on the Densification of a 3-mol%-Yttria-Doped ZirconiaJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 6 2002Yeong-Kyeun Paek The densification behavior of a 3-mol%-Y2O3 -doped ZrO2 (3Y-ZrO2) has been investigated under N2 and O2 atmospheres. Powder compacts have been sintered at 1550° and 1400°C for various times. The density of the specimen sintered at 1550°C is higher in N2 than in O2, while the contrary result is obtained in the case of the specimen sintered at 1400°C. Such results can be explained in terms of nitrogen solubility and oxygen vacancy in a ZrO2 matrix. Because nitrogen solubility into the ZrO2 increases with an increase in heat-treatment temperature, leading to the formation of oxygen vacancy, the densification rate becomes higher. The present study thus shows evidence of nitrogen solubility into the ZrO2 and its role on the densification behavior of 3Y-ZrO2. [source] Non-isothermal thermogravimetric analysis of plywood wastes under N2, CO2 and O2 atmospheresASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 5 2008A. T. Harris Abstract The rates of (1) devolatilisation, (2) char combustion and (3) char gasification with CO2 of plywood sawdust (Australian Standard 2207 ,Interior Grade') was measured using non-isothermal thermogravimetric analysis (TGA). The influence of heating rate (, = 5, 10, 20, 50 and 100 °C/min) and reaction atmosphere (N2, Air, CO2) was investigated. Irrespective of the reaction atmosphere, devolatilisation typically occurred at the same rate. Weight loss attributed to char oxidation was observed at temperatures > 400 °C, while weight loss due to CO2 gasification of char was observed at temperatures > 800 °C. There was uncertainty about the fate of some of the constituents of the plywood sawdust, i.e. urea-formaldehyde binders, which could not be fully evaluated using a TGA system without evolved-gas analysis. These components appeared to volatilise around 380 °C on the differential mass loss profiles in the presence of N2 and CO2 and around 490 °C in the presence of air. A simple first-order reaction model was used to interpret the experimental observations. The kinetic parameters for the main components of plywood sawdust were consistent with those reported previously for other biomass materials. This information is potentially useful for the design of large-scale equipment to recover energy from discarded wood wastes. Copyright © 2008 Curtin University of Technology and John Wiley & Sons, Ltd. [source] | |||||||||||||