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Air Atmosphere (air + atmosphere)
Selected AbstractsChemInform Abstract: Copper-Catalyzed Synthesis of Benzoxazoles via a Regioselective C,H Functionalization/C,O Bond Formation under an Air Atmosphere.CHEMINFORM, Issue 43 2009Satoshi Ueda 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 of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Simple Fabrication Method of Conductive Polymeric Arrays by Using Direct Laser Interference Micro-/Nanopatterning,ADVANCED MATERIALS, Issue 9 2007A. Acevedo Thin films of polyaniline (PANI) deposited onto different polymeric substrates are nanostructured by using "direct laser interference patterning" at room temperature and pressure in air atmosphere. Regular linelike arrays (see figure) with thicknesses up to 600,nm are fabricated and their activity is determined using different techniques. The structuring mechanisms of PANI supported in both polycarbonate and polyimide films are demonstrated using cross-sectional analyses performed with a dual-beam workstation. [source] Copper-Catalyzed N -Alkylation of Sulfonamides with Benzylic Alcohols: Catalysis and Mechanistic StudiesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 17 2009Xinjiang Cui Abstract The N -alkylation of sulfonamides with alcohols is efficiently performed in the presence of easily available copper catalysts via hydrogen borrowing methodology. Applying a copper acetate/potassium carbonate system the reaction of sulfonamides and alcohols gave the corresponding secondary amines in excellent yield. In situ HR-MS analysis indicated that bissulfonylated amines are formed under air atmosphere, which act as self-stabilizing ligands for the catalytic system. UV-visible measurements suggest the interaction between the copper centre and the bissulfonylated amine. Reactions of benzyl alcohol- d7 with p -toluenesulfonamide, N -benzyl- p -toluenesulfonamide or N -benzylidenetoluenesulfonamide revealed that the reaction proceeds via a transfer hydrogenation mechanism and the whole process is micro-reversible. Competitive reactions of benzyl alcohol and benzyl alcohol- d7 with p -toluenesulfonamide revealed a kinetic isotope effect (kH/kD) of 3.287 (0.192) for the dehydrogenation of benzyl alcohol and 0.611 (0.033) for the hydrogenation of the N -benzylidene- p -toluenesulfonamide intermediate, which suggests that dehydrogenation of the alcohol is the rate-determining step. [source] Catalytic performance of Brønsted acid sites during esterification of acetic acid with ethyl alcohol over phosphotungestic acid supported on silicaJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 6 2007Abd El-Aziz A Said Abstract Different ratios of phosphotungestic acid supported on silica gel were prepared by an impregnation method with PWA loadings ranging from 1 to 30% w/w and calcined at 350 and 500 °C for 4 h in a static air atmosphere. The catalysts were characterized by thermogravimety (TG), differential thermal analysis (DTA), X-ray diffraction, FT-IR spectroscopy and N2 adsorption measurements. The surface acidity and basicity of the catalyst were investigated by the dehydration,dehydrogenation of isopropanol and the adsorption of pyridine (PY) and 2,6-dimethyl pyridine (DMPY). The gas-phase estrification of acetic acid with ethanol was carried out at 185 °C in a conventional fixed-bed reactor at 1 atm using air as carrier gas. The results clearly revealed that the catalyst containing 10% w/w PWA/SiO2 is the most active and delivers reaction selectively to ester with 85% yield. The Brønsted acid site resulting from hydroxylation of tungsten oxide plays the main role in the formation of ester. Copyright © 2007 Society of Chemical Industry [source] ATPASE ACTIVITY, SURFACE HYDROPHOBICITY, SULFHYDRYL CONTENT AND PROTEIN DEGRADATION IN REFRIGERATED SEABASS MUSCLE IN MODIFIED ATMOSPHERE PACKAGINGJOURNAL OF FOOD BIOCHEMISTRY, Issue 1 2004PAYAP MASNIYOM The effect of modified atmosphere packaging (80% CO2, 10% O2, 10% N2) on ATPase activity, surface hydrophobicity, sulfhydryl content and degradation of proteins in seabass muscle during storage at 4C was investigated. No changes in Ca2+ -, Mg2+ -, Mg2+ -Ca2+ -ATPase activities of natural actomyosin (NAM) in seabass slices kept under MAP were observed throughout the storage for up to 21 days (P > 0.05). However, a slightly increased Mg2+ -EGTA-ATPase was found. For seabass slices stored under air atmosphere, Ca2+ -ATPase activity decreased, whereas Mg2+ -EGTA-ATPase activity increased (P < 0.05) with a concomitant loss in Ca2+ -sensitivity. Lower decreases in total sulfhydryl content but higher increases in surface hydrophobicity were observed in samples stored under MAP, compared to those kept under air atmosphere. No marked autolytic degradation in samples kept under MAP was observed throughout the storage as monitored by no changes in myosin heavy chain, free ,-amino acid and trichloroacetic acid soluble peptide. Conversely, a considerable degradation was found in samples kept under air atmosphere, especially after 9 days of storage. Therefore, MAP is a promising means to retard the changes in muscle proteins, especially degradation. [source] QUALITY OF ,ANJOU' PEARS AFTER DIFFERENT TYPES OF CONTROLLED ATMOSPHERE STORAGEJOURNAL OF FOOD QUALITY, Issue 1 2001S.R. DRAKE ABSTRACT ,Anjou' pears (Pyrus communis, L) were subjected to seven different controlled atmosphere (CA) storage practices and stored at 1C, for 90, 150 or 210 days plus 30 days at regular air atmosphere (RA). CA storage treatment conserved pear qualities to a certain extent regardless of storage treatment. Establishment of CA conditions (2% O2 and < 1 % CO2 on warm pears (20C), prior to cooling, resulted in reduced firmness, finish and color and increased amount of scald, shrivel and physiological disorders. Pears held in CA storage (2% O2 and < 1 % CO2) for 90 days and an additional 30 days in RA storage maintained good quality. When held for longer storage periods, firmness, finish and color decreased, and scald, shrivel and physiological disorders increased. [source] Extreme temperature 6H-SiC JFET integrated circuit technologyPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 10 2009Philip G. Neudeck Abstract Extreme temperature semiconductor integrated circuits (ICs) are being developed for use in the hot sections of aircraft engines and other harsh-environment applications well above the 300 °C effective limit of silicon-on-insulator IC technology. This paper reviews progress by the NASA Glenn Research Center and Case Western Reserve University (CWRU) in the development of extreme temperature (up to 500 °C) integrated circuit technology based on epitaxial 6H-SiC junction field effect transistors (JFETs). Simple analog amplifier and digital logic gate ICs fabricated and packaged by NASA have now demonstrated thousands of hours of continuous 500 °C operation in oxidizing air atmosphere with minimal changes in relevant electrical parameters. Design, modeling, and characterization of transistors and circuits at temperatures from 24 °C to 500 °C are also described. CWRU designs for improved extreme temperature SiC JFET differential amplifier circuits are demonstrated. Areas for further technology maturation, needed prior to beneficial system insertion, are discussed. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Studies on structural and optical properties of Cu-Sb-O thin filmsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 9 2010Nadia Chaglabou Abstract We report in this paper the structural and optical properties of Cu-Sb-O thin films systems. Samples were prepared via sequential thermal vacuum deposition of Cu and Sb or Sb and Cu (10 -5 Torr) on glass substrates after what they were heated in vacuum at 200 °C for 1 hour. So, the obtained intermetallic multilayer systems (Cu/Sb)j=1,2,3 and (Sb/Cu)j=1,2,3 were annealed in air atmosphere between 30°C and 400 °C for 3 h for j=1; for 6 h for j=2 and for 9 h for j=3. These films were characterized for their structural, surface morphological, compositional, and optical properties by using X-ray diffraction (XRD) and optical (transmittance and reflectance) measurement techniques. The X-ray diffraction (XRD) patterns revealed the presence of CuO, Sb2O3 and Sb2O4phases. The absorption coefficient of Cu-Sb-O thin films in all cases is in the range104 -105 cm -1. The films after annealing have two direct band gap energies in the ranges 1.48,1.50 eV and 2.20-2.95 eV. The electrical measurements show a conversion from a metallic phase to the semiconductor phase after annealing. The samples exhibit p-type conductivity after annealing in air of the intermetallic multilayer systems (Cu/Sb)j=3 and (Sb/Cu)j=3. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Effect of annealing temperature on the crystalline quality and phase transformation of Chemically Deposited CdSe filmsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 10 2005M. Zapata-Torres Abstract Polycrystalline CdSe thin films were grown on glass substrates by chemical bath deposition at 50 ºC. The samples were annealed in air atmosphere at different temperatures and characterized by X-ray diffraction and Raman spectroscopy. It was found that the as-grown films have cubic structure. These samples maintain their cubic structure for annealing temperatures between 60 ºC and 300 ºC. For annealing temperatures higher than 300 ºC we obtain a mixture of cubic and hexagonal phases. The analysis made by X-ray diffraction and Raman dispersion show that the samples annealed at temperatures under the phase-transition temperature increase their crystalline quality. In order to determinate the temperature for the complete transition of the cubic phase, we used the precipitated material obtained during the grown of the CdSe films. This material was annealed on air atmosphere between 300 °C and 500 °C with 50 ° intervals. The samples were measured by X-ray diffraction. The samples maintained the cubic structure if the annealing temperature is under 300 °C. For temperatures between 300 °C and 450 °C we found a mixture of cubic and hexagonal phase. For an annealing temperature of 500°C we obtain only the hexagonal phase. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Polydimethylsiloxane,cristobalite composite adhesive system for aerospace applicationsPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 5 2009Seema Ansari Abstract The effect of phase-pure cristobalite (a high temperature crystalline polymorph of silica) on the adhesive characteristics of hydroxyl terminated polydimethylsiloxane (PDMS) was studied. The potential advantages of PDMS/cristobalite composite system as an adhesive for aerospace applications are also discussed. A PDMS/cristobalite composite adhesive system containing different filler contents (0,46 volume percentage, vol%) was prepared. The filler material, phase-pure cristobalite, was synthesized by the pyrolysis of fused silica at 1400°C. The mechanical, rheological, and thermal characteristics of the composites were studied. A high yield stress (0.151,Pa), shear-thinning index (1.051), and fast recovery rate were observed for ,34,vol% cristobalite loading, which indicate that PDMS retains its excellent adhesive and flow characteristics even at high filler loading with enhanced mechanical characteristics. Thermal analysis shows the onset of degradation of PDMS shifts to higher temperatures, 372,438°C and 317,417°C in nitrogen and air atmosphere respectively, which shows excellent thermal stability. The residual component yields after thermal degradation of PDMS/cristobalite composite system in nitrogen and air atmosphere show different degradation mechanisms. Copyright © 2008 John Wiley & Sons, Ltd. [source] MCM-41-supported mercapto palladium(0) complex: an efficient and recyclable catalyst for the heterogeneous Stille coupling reactionAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 2 2010Hong Zhao Abstract The Stille cross-coupling reaction of organostannanes with aryl halides was achieved in the presence of a catalytic amount of MCM-41-supported mercapto palladium(0) complex (1 mol%) in DMFH2O (9:1) under air atmosphere in good to high yields. This MCM-41-supported palladium catalyst can be reused at least 10 times without any decrease in activity. Copyright © 2009 John Wiley & Sons, Ltd. [source] Experimental study on the comprehensive behavior of combustion for blended coalsASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 3 2010Yuangang Xu Abstract The combustion behaviors and kinetic parameters of two parent coals (lignite and bituminous) and their blends were evaluated to meet specifications of power plants. Nonisothermogravimetric experiments were conducted in air atmosphere. The flow rate was set at 100 ml/min within the temperature range from ambient temperature to 1100 °C and heating rate at 20 °C/min. The particle size used in the experiment was smaller than 0.09 mm. The combustion performance of blended coals, such as the ignition temperature and maximum weight loss rate, can be improved by the co-combustion of the blends. Thermal analysis, burnout and combustibility index S of the coal samples were used to demonstrate the impact of blending ratio on the combustion characteristic of blended coals; results of blends displayed the nonadditive effect of the parent coals. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Controlled Synthesis of Water-Dispersible Faceted Crystalline Copper Nanoparticles and Their Catalytic PropertiesCHEMISTRY - A EUROPEAN JOURNAL, Issue 35 2010Dr. Yanfei Wang Abstract We report a solution-phase synthetic route to copper nanoparticles with controllable size and shape. The synthesis of the nanoparticles is achieved by the reduction of copper(II) salt in aqueous solution with hydrazine under air atmosphere in the presence of poly(acrylic acid) (PAA) as capping agent. The results suggest that the pH plays a key role for the formation of pure copper nanoparticles, whereas the concentration of PAA is important for controlling the size and geometric shape of the nanoparticles. The average size of the copper nanoparticles can be varied from 30 to 80,nm, depending on the concentration of PAA. With a moderate amount of PAA, faceted crystalline copper nanoparticles are obtained. The as-synthesized copper nanoparticles appear red in color and are stable for weeks, as confirmed by UV/Vis and X-ray photoemission (XPS) spectroscopy. The faceted crystalline copper nanoparticles serve as an effective catalyst for N-arylation of heterocycles, such as the CN coupling reaction between p -nitrobenzyl chloride and morpholine producing 4-(4-nitrophenyl)morpholine in an excellent yield under mild reaction conditions. Furthermore, the nanoparticles are proven to be versatile as they also effectively catalyze the three-component, one-pot Mannich reaction between p -substituted benzaldehyde, aniline, and acetophenone affording a 100,% conversion of the limiting reactant (aniline). [source] Heterogeneous Palladium Chloride Catalyzed Ligand-free Suzuki-Miyaura Coupling Reactions at Ambient TemperatureCHINESE JOURNAL OF CHEMISTRY, Issue 9 2008Min WANG Abstract A mild and efficient ligand-free Suzuki-Miyaura coupling reaction catalyzed by heterogeneous palladium chloride was developed at room temperature in a short reaction time under air atmosphere. Various phenyl iodides, bromides and activated chlorides were coupled with sodium tetraphenylborate or phenylboronic acids efficiently to afford the corresponding cross-coupled products in good to excellent yields. Furthermore, the catalyst could be recycled up to four times without loss of its activity. [source] Synthesis and Thermal Decomposition Kinetics of the Complex of Samarium p -Methylbenzoate with 1,10-PhenanthrolineCHINESE JOURNAL OF CHEMISTRY, Issue 1 2007Jian-Jun Zhang Abstract The complex [Sm(p -MBA)3phen]2 (p -MBA, p -methylbenzoate; phen, 1,10-phenanthroline) was prepared and characterized by elemental analysis, IR and UV spectra. The thermal decomposition process of [Sm(p - MBA)3phen]2 was studied under a static air atmosphere by TG-DTG and IR techniques. Thermal decomposition kinetics was investigated employing a newly proposed method, together with the integral isoconversional non-linear method. Meanwhile, the thermodynamic parameters (,H,, ,G, and ,S,) were also calculated. The lifetime equation at mass-loss of 10% was deduced as ln ,=,24.7825+18070.43/T by isothermal thermogravimetric analysis. [source] A New Oxide Ion Conductor: La3GaMo2O12CHINESE JOURNAL OF CHEMISTRY, Issue 8 2006Tian Xia Abstract A new oxide ion conductor, La3GaMo2O12, with a bulk conductivity of 2.7×10,2 S·cm,1 at 800 °C in air atmosphere was prepared by the traditional solid-state reaction. The room temperature X-ray diffraction data could be indexed on a monoclinic cell with lattice parameters of a=0.5602(2) nm, b=0.3224(1) nm, c=1.5741(1) nm, ,=102.555(0)°, V=0.2775(2) nm3 and space group Pc(7). Ac impedance measurements in various atmospheres further support that it is an oxide ion conductor. This material was stable in various atmospheres with oxygen partial pressure p(O2) ranging from 1.0×105 to 1.0×10,7 Pa at 800 °C. A reversible polymorphic phase transition occurred at elevated temperatures as confirmed by the differential thermal analysis and dilatometric measurement. [source] Non-isothermal Decomposition Reaction Kinetics of the Magnesium Oxalate DihydrateCHINESE JOURNAL OF CHEMISTRY, Issue 3 2006Jian-Jun Zhang Abstract The thermal decomposition of the magnesium oxalate dihydrate in a static air atmosphere was investigated by TG-DTG techniques. The intermediate and residue of each decomposition were identified from their TG curve. The kinetic triplet, the activation energy E, the pre-exponential factor A and the mechanism functions f(,) were obtained from analysis of the TG-DTG curves of thermal decomposition of the first stage and the second stage by the Popescu method and the Flynn-Wall-Ozawa method. [source] The effect of overload on the fatigue crack growth behaviour of 304 stainless steel in hydrogenFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 1 2001M. H. Kelestemur Fatigue crack growth (FCG) behaviour and its characteristics following tensile overloads were investigated for AISI 304 stainless steel in three different atmospheres; namely dry argon, moist air and hydrogen. The FCG tests were performed by MTS 810 servohydraulic machine. CT specimens were used for the tests and crack closure measurements were made using an extensometer. FCG rates of 304 stainless steel at both dry argon and moist air atmospheres have shown almost the same behaviour. In other words, the effect of moisture on FCG of this material is very small. However, in a hydrogen atmosphere, the material showed considerably higher crack growth rate in all regimes. In general, for all environments, the initial effect of overloads was to accelerate the FCG rate for a short distance (less than a mm) after which retardation occurred for a considerable amount of time. The main causes for retardation were found as crack blunting and a long reinitiation period for the fatigue crack. Regarding the environmental effect, the overload retardation was lowest in a hydrogen atmosphere. This low degree of retardation was explained by a hydrogen embrittlement mechanism. In a general sense, hydrogen may cause a different crack closure mechanism and hydrogen induced crack closure has come in to the picture. Scanning electron microscope and light microscope examinations agreed well with the above results. [source] Poly(arylene sulfide)s by nucleophilic aromatic substitution polymerization of 2,7-difluorothianthreneJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 9 2009Maxwell J. Robb Abstract Poly(thianthrene phenylene sulfide) and poly(thianthrene sulfide) have been prepared by nucleophilic aromatic substitution polymerization of the activated monomer 2,7-difluorothianthrene with bis thiophenoxide and sulfide nucleophiles, respectively. The resulting polymers are thermally stable, amorphous materials that have been characterized by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), gel permeation chromatography (GPC), matrix-assisted laser desorption/ionization-time-of-flight (MALDI-TOF) mass spectrometry, UV-Vis spectroscopy, refractometry, and intrinsic viscosity (IV) measurements. The polymers produced exhibit 5% weight loss values approaching 500 °C in inert and air atmospheres and glass transition temperatures that range from 149 to 210 °C. Poly(thianthrene phenylene sulfide) with a number average molecular weight of 22,100 g/mol has been synthesized with an IV in DMPU of 0.62 dL/g at 30 °C. Creasable films of this polymer have been prepared by solvent casting and melt pressing at 250 °C. Films of poly(thianthrene phenylene sulfide) exhibit transparencies greater than 50% at wavelengths exceeding 400 nm and a high refractive index value of 1.692 at a wavelength of 633 nm, making the polymer interesting for optical applications. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2453,2461, 2009 [source] | |||||||||||||||||||||||||||||||