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Gaseous Mixture (gaseous + mixture)
Selected AbstractsChemInform Abstract: Catalytic Systems Based on Platinum and Heteropoly Compounds for Oxidation of Hydrocarbons with a Dioxygen,Dihydrogen Gaseous Mixture.CHEMINFORM, Issue 49 2002N. V. Kirillova 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] The piloted transition to flaming in smoldering fire retarded and non-fire retarded polyurethane foamFIRE AND MATERIALS, Issue 8 2008Olivier M. Putzeys Abstract The piloted transition from smoldering to flaming, though a significant fire safety concern, has not been previously extensively studied. Experimental results are presented on the piloted transition from smoldering to flaming in non-fire retarded (NFR) polyurethane foam and the fire retarded polyurethane foam Pyrell®. The samples are small blocks, vertically placed in the wall of an upward wind tunnel. The free surface is exposed to an oxidizer flow and a radiant heat flux. The smolder product gases pass upwards through a pilot. The experiments on NFR foam show that the smolder velocity and peak smolder temperature, which increase with the oxygen concentration and heat flux, are strongly correlated to the transition to flaming event, in that there are minimum values of these parameters for transition to occur. The existence of a minimum smolder velocity for ignition supports the concept of a gaseous mixture reaching a lean flammability limit as the criterion for the transition to flaming. To compensate for the solid- and gas-phase effects of the fire retardants on the piloted transition in Pyrell, it was necessary to increase the oxygen concentration and the power supplied to the smolder igniter and the pilot. The piloted transition is observed in oxygen concentrations above 17% in NFR foam and above 23% in Pyrell. The results show that although Pyrell is less flammable than NFR foam, it is still susceptible to smoldering and the piloted transition to flaming in oxygen-enriched environments, which is of interest for special applications such as future space missions. Copyright © 2008 John Wiley & Sons, Ltd. [source] THE EFFECT of MODIFIED ATMOSPHERE PACKAGING ON the MICROBIAL ECOLOGY IN REQUEIJÃO, A PORTUGUESE WHEY CHEESEJOURNAL OF FOOD PROCESSING AND PRESERVATION, Issue 2 2000MANUELA E. PINTADO The effects of modified atmosphere packaging on growth of adventitious microorganisms in Portuguese whey cheese (Requeijão) were studied following a response surface methodology using storage time (2, 6, 10 and 15 days), storage temperature (4, 12 and 18C) and fraction of CO2 in the overhead gaseous mixture also containing nitrogen (0, 50 and 100%) as manipulated variables. the viable numbers of Enterobacteriacea, staphylococci, yeasts and spore-forming bacteria in the experimental whey cheeses did not increase within 15 days when storage was at 4C under 100% CO2; those of enterococci increased significantly after 6 days under similar conditions, and a similar inhibiting effect was observed against Bacillus, pseudomonads, lactobacilli and streptococci. It was observed that 100% N2 at 4C was able to completely inhibit growth of staphylococci, lactobacilli and Bacillus for 2 days. the loci (and the nature) of the optima in terms of manipulated variables were obtained for all microbial groups studied. No true overall minimum was found, but storage conditions preset at 4C and 100% CO2 led to a 15 day extension of the shelf-life of Requeijão. [source] Performance Evaluation of the Scent Transfer UnitÔ (STU-100) for Organic Compound Collection and ReleaseJOURNAL OF FORENSIC SCIENCES, Issue 4 2006Brian A. Eckenrode Ph.D. ABSTRACT: The Scent Transfer UnitÔ (STU-100) is a portable vacuum that uses airflow through a sterile gauze pad to capture a volatiles profile over evidentiary items for subsequent canine presentation to assist law enforcement personnel. This device was evaluated to determine its ability to trap and release organic compounds at ambient temperature under controlled laboratory conditions. Gas chromatography-mass spectrometry (GC-MS) analyses using a five-component volatiles mixture in methanol injected directly into a capture pad indicated that compound release could be detected initially and 3 days after the time of collection. Additionally, 15 compounds of a 39-component toxic organic gaseous mixture (10,1000 parts per billion by volume [p.p.b.v]) were trapped, released, and detected in the headspace of a volatiles capture pad after being exposed to this mixture using the STU-100 with analysis via GC-MS. Component release efficiencies at ambient temperature varied with the analyte; however, typical values of c. 10% were obtained. Desorption at elevated temperatures of reported human odor/scent chemicals and colognes trapped by the STU-100 pads was measured and indicated that the STU-100 has a significant trapping efficiency at ambient temperature. Multivariate statistical analysis of subsequent mass spectral patterns was also performed. [source] CO2 Plasticization of polyethersulfone/polyimide gas-separation membranesAICHE JOURNAL, Issue 7 2003G. C. Kapantaidakis This work reports the CO2 plasticization of gas-separation hollow-fiber membranes based on polyimide and polyethersulfone blends. The feed pressure effect on the permeance of pure gases (CO2, N2) and the separation performance of a gaseous mixture (CO2/N2, 55/45%) is examined. Contrary to dense membranes, the permeance of CO2 through ultrathin asymmetric fibers increases immediately with pressure resulting in pronounced apparent plasticization and reduction of the ideal CO2/N2 selectivity. However, no evidence of plasticization was observed when a CO2/N2, 55/45% mixture was fed to the hollow-fiber membranes. In all cases, CO2 permeance decreased with pressure, while that of N2 remained constant. Experimental results were validated by means of mathematical modeling. Membrane-separation performance was overestimated when pressure-independent permeabilities were used in the model, while pressure-dependent permeabilities, due to the overall effect of plasticization and competition phenomena, explained excellently, the obtained stage-cut and permeate purity. [source] UV Laser-Induced Gas-Phase Copolymerization of Carbon Disulfide and EtheneMACROMOLECULAR RAPID COMMUNICATIONS, Issue 4 2004Radmila Tomovska Abstract Summary: The laser irradiation at 193 nm of a gaseous mixture of carbon disulfide and ethene induces the copolymerization of both compounds and affords the chemical vapour deposition of a C/S/H polymer, the composition of which indicates the reaction between two to three CS2 molecules and one C2H4 molecule. Polymer structure is interpreted on the basis of X-ray photoelectron and FT-IR spectra as consisting of >CS, >CC<, CH2CH2, (CC)SnC4,,,n, C(CS)S, S(CS)S, and CSSC configurations. The gas-phase copolymerization of carbon disulfide and ethene represents the first example of such a reaction between carbon disulfide and a common monomer. Scheme showing the expected reaction of excited CS2 molecules with other CS2 molecules to form dimers, which then react with another CS2 molecule or add to ethene. [source] Development of graphene layers by reduction of graphite fluoride C2F surfacePHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 11-12 2009A. V. Okotrub Abstract We studied a possibility of reduction of the surface of graphite fluoride obtained by fluorination of highly oriented pyrolytic graphite (HOPG) by a gaseous mixture of BrF3 and Br2. X-ray diffraction (XRD) revealed a layered structure of the fluorinated product being a second-stage intercalate due to a presence of bromine molecules between the fluorinated graphite layers. Scanning tunneling microscopy and spectroscopy showed that the "old" surface of graphite fluoride (exposed to the ambient air) has the graphite-like structure, while the fresh cleaved surface is non-conductive. Therefore, the outer layers of graphite fluoride can be reduced by water present in the laboratory atmosphere. The sample was treated by H2O vapor to confirm that. The reduction was controlled by Raman spectroscopy using intensity of the 1360 and 1580,cm,1 bands. The energy dependent photoelectron spectroscopy was used for estimation of thickness of the reduction layer, which was found, does not exceed 2,3 graphite layers. The obtained results indicate the possibility of synthesis of graphene layers on dielectric fluorinated graphite matrix. [source] Study of metal-oxide-semiconductor capacitors with r.f. magnetron sputtering TiOxNy films dielectric layerPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 3-4 2010Katia Franklin Albertin Abstract A set of MOS capacitors with TiOxNy films as gate dielectric layer was fabricated and characterized. The TiOxNy films were deposited by reactive r.f. magnetron sputtering varying the nitrogen and oxygen partial pressure in a Ar/N2/O2 gaseous mixture. The TiOxNy films were characterized by, Rutherford Backscattering (RBS), X-ray absorption near edge spectroscopy (XANES) in oxygen K-edge (O-K), optical absorption and High Resolution Transmission Electron Microscopy (HRTEM). Capacitance-voltage (1MHz) and current-voltage measurements were performed to obtain the effective dielectric constant, the effective oxide thickness (EOT), the leakage current density, and the interface quality. MOS capacitors results show that the TiOxNyfilms dielectric constant varies from 28 to 80, present a good interface quality with silicon, and the leakage current density values are in the order of 0.25 mA/cm2 for VG = ,2V, which is acceptable for high performance logic circuits and low power circuits fabrication. The leakage current density is reduced in 2 orders of magnitude for increasing nitrogen concentration (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Pilot-scale evaluation of in situ cometabolic bioremediation of TCE in groundwater using PHOSter® technologyREMEDIATION, Issue 2 2008Karl W. Eggers A study was conducted to evaluate the efficacy of PHOSter® technology for treating groundwater contaminated with trichloroethene (TCE) at Edwards Air Force Base, California. The technology consists of injecting a gaseous mixture of air, methane, and nutrients into groundwater with the objective of stimulating the growth of methanotrophs, a naturally occurring microbial group that is capable of catalyzing the aerobic degradation of chlorinated solvents into nontoxic products. Injection operations were performed at one well for a period of three months. Six monitoring wells were utilized for groundwater and wellhead vapor monitoring and for groundwater and microbial sampling. In the five monitoring wells located within 44 feet of the injection well, the following results were observed: dissolved oxygen concentrations increased to a range between 6 and 8 milligrams per liter (,g/L); the biomass of target microbial groups increased by one to five orders of magnitude; and TCE concentrations decreased by an average of 92 percent, and to below the California primary maximum contaminant level (MCL; 5 micrograms per liter [µg/L]) in the well closest to the injection well. © 2008 Wiley Periodicals, Inc., [source] Initiated CVD of Poly(methyl methacrylate) Thin Films,CHEMICAL VAPOR DEPOSITION, Issue 10 2005K. Chan Abstract Initiated CVD (iCVD), a dry method, is able to produce poly(methyl methacrylate) (PMMA) thin films by utilizing a reactive gaseous mixture of the monomer methyl methacrylate and the initiator triethylamine. The deposition rate is twenty times faster with the use of the initiator. Fourier-transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) show high structural resemblance between iCVD PMMA and conventional PMMA, and the degree of functionality retention increases with decreasing residence time in the vacuum chamber. XPS detection of nitrogen incorporation is consistent with the incorporation of the initiator into the polymer chains. NMR spectroscopy on completely dissolved films shows that the tacticity of iCVD PMMA resembles that of conventional, radically polymerized PMMA. Altogether these observations support the hypothesis that, for iCVD PMMA, the polymerization is by a free-radical mechanism. [source] Ion chemistry in germane/fluorocompounds gaseous mixtures: a mass spectrometric and theoretical studyJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 10 2008Paola Antoniotti Abstract The ion,molecule reactions occurring in GeH4/NF3, GeH4/SF6, and GeH4/SiF4 gaseous mixtures have been investigated by ion trap mass spectrometry and ab initio calculations. While the NFx+ (x = 1,3) react with GeH4 mainly by the exothermic charge transfer, the open-shell Ge+ and GeH2+ undergo the efficient F-atom abstraction from NF3 and form GeF+ and FGeH2+ as the only ionic products. The mechanisms of these two processes are quite similar and involve the formation of the fluorine-coordinated complexes GeFNF2+ and H2GeFNF2+, their subsequent crossing to the significantly more stable isomers FGeNF2+ and FGeH2NF2+, and the eventual dissociation of these ions into GeF+ (or FGeH2+) and NF2. The closed-shell GeH+ and GeH3+ are instead much less reactive towards NF3, and the only observed process is the less efficient formation of GeF+ from GeH+. The theoretical investigation of this unusual H/F exchange reaction suggests the involvement of vibrationally-hot GeH+. Passing from NF3 to SF6 and SiF4, the average strength of the MF bond increases from 70 to 79 and 142 kcal mol,1, and in fact the only process observed by reacting GeHn+ (n = 0,3) with SF6 and SiF4 is the little efficient F-atom abstraction from SF6 by Ge+. Irrespective of the experimental conditions, we did not observe any ionic product of GeN, GeS, or GeSi connectivity. This is in line with the previously observed exclusive formation of GeF+ from the reaction between Ge+ and CF compounds such as CH3F. Additionally observed processes include in particular the conceivable formation of the elusive thiohypofluorous acid FSH from the reaction between SF+ and GeH4. Copyright © 2008 John Wiley & Sons, Ltd. [source] Gas-phase ion chemistry in the ternary SiH4,C3H6,PH3 systemJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 2 2002Stefania Calderan Abstract Propene,phosphine and the silane,propene,phosphine gaseous mixtures were studied by ion trap mass spectrometry. For the binary mixture the variation of ion abundances under different partial pressures and the mechanisms of ion,molecule reactions are reported. Moreover, the rate constants of the main processes were measured and compared with the collisional rate constants to determine the reaction efficiencies. In the ternary silane,propene,phosphine mixture the mechanisms of formation of ion clusters were elucidated, but the complexity of the system and the low abundances of the ions usually isolated by successive steps prevented the determination of rate constants. The hydrogenated ternary ions are mainly formed by reactions of ions with propene, whereas a minor contribution comes from reactions of ions with phosphine. The ions show very low reactivity with silane. The formation processes of these species are discussed in relation to their possible role as precursors of amorphous silicon carbides doped with phosphorus obtained by deposition from properly activated silane,propene,phosphine mixtures. Copyright © 2001 John Wiley & Sons, Ltd. [source] UV Laser Deposition of SiS/Poly(thiacarbosilane) Composites and their Conversion to SiO/Poly(thiacarbosiloxane) CompositesMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 16 2007Radmila Tomovska Abstract ArF laser irradiation of gaseous mixtures of carbon disulfide and silane allows efficient deposition of SiS bond-containing poly(thiacarbosilanes) incorporating SiS bodies. These SiS/poly(thiacarbosilane) composites are the first example of silicon sulfide/polymer composites. Composite formation is analyzed by GC/MS analysis of volatile products and the structure of the composite as determined by electron microscopy and FT-IR spectra. The composites undergo reaction with air moisture and methanol vapor, evolve H2S and evolve to nano-sized poly(thiacarbosiloxane)s and poly(methoxythiacarbosiloxane)s. [source] A Pressure-controlled Rat Ventilator With Electronically Preset RespirationsARTIFICIAL ORGANS, Issue 12 2006Valentin L. Ordodi Abstract:, Major experimental surgery on laboratory animals requires adequate anesthesia and ventilation to keep the animal alive throughout the procedure. A ventilator is a machine that helps the anesthesized animal breathe through an endotracheal tube by pumping a volume of gas (oxygen, air, or other gaseous mixtures), comparable with the normal tidal volume, into the animal's lungs. There are two main categories of ventilators for small laboratory rodents: volume-controlled and pressure-controlled ones. The volume-controlled ventilator injects a preset volume into the animal's lungs, no matter the airways' resistance (with the peak inspiratory pressure allowed to vary), while the pressure ventilator controls the inspiratory pressure and allows the inspiratory volume to vary. Here we show a rat pressure ventilator with a simple expiratory valve that allows gas delivery through electronic expiration control and offers easy pressure monitoring and frequency change during ventilation. [source] | ||||||||||||||||