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Reduction Process (reduction + process)
Selected AbstractsTowards a Large-Scale Asymmetric Reduction Process with Isolated Enzymes: Expression of an (S)-Alcohol Dehydrogenase in E.,coli and Studies on the Synthetic Potential of this BiocatalystADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 3 2003Werner Hummel No abstract is available for this article. [source] Decorating Polypyrrole Nanotubes with Au Nanoparticles by an In Situ Reduction ProcessMACROMOLECULAR RAPID COMMUNICATIONS, Issue 11 2009Jingjing Xu Abstract Au nanoparticle-decorated polypyrrole nanotubes (defined as PPy/Au nanocomposites) are prepared by an in situ reduction process. Polypyrrole (PPy) nanotubes are prepared by a self-degraded template method, and Au nanoparticles are deposited in situ by the reduction of HAuCl4. The size and uniformity of the Au nanoparticles that decorate the PPy nanotubes can be controlled by adjusting the experimental conditions, such as the stabilizers used and the reaction temperature. The morphologies and optical properties of the nanocomposites have been characterized by scanning electron microscopy, transmission electron microscopy, UV-vis, and FT-IR spectroscopy. Conductivity measurements show that the conductivities of the nanocomposites decrease with a decrease of temperature, and the conductivity,temperature relationship obeys the quasi-one dimensional variable range hopping model. [source] Fast Tin-Free Hydrodehalogenation and Reductive Radical Cyclization Reactions: A New Reduction Process.CHEMINFORM, Issue 31 2004Santiago E. Vaillard Abstract For Abstract see ChemInform Abstract in Full Text. [source] Photostimulated Reduction Processes in a Titania Hybrid Metal,Organic FrameworkCHEMPHYSCHEM, Issue 11 2010Aron Walsh Dr. Lights, camera, action! A hybrid material derived from TiO2 is found to have remarkable defect chemistry: optical excitations larger than the band gap have sufficient energy to reduce titanium, accompanied by oxygen loss (see figure). New states introduced in the electronic gap are responsible for the material,s photochromicity. The future looks bright for photoactive metal,organic frameworks. [source] Synthesis of a Novel Oligoaniline: "Dumbbell-Shaped" Oligoaniline,MACROMOLECULAR RAPID COMMUNICATIONS, Issue 5 2004Youhai Yu Abstract Summary: A new kind of aniline oligomer with a "dumbbell" shape was synthesized through a simple oxidative coupling reaction with a new rigid aromatic amine as starting material. The oligomer was characterized with mass spectrometry, IR and NMR spectroscopies. Its redox property was checked by cyclic voltammetry and chemical oxidation/reduction process was monitored by UV spectroscopy. We found it has a reversible electrochemical property like common oligoanilines. Combined with its well-defined structure, it is expected to act as a model compound for a molecular electronic switch. The "dumbbell-shaped" oligoaniline compound synthesized here. [source] Photooxidation and Photoconductivity of Polyferrocenylsilane Thin FilmsMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 7 2003Paul W. Cyr Abstract Irradiation of thin films of poly(ferrocenylmethylphenylsilane) ([Fe(,5 -C5H4)2SiMePh]n) cast from chloroform solution with UV light leads to photooxidation of ferrocene centers in the polymer main chain. The extent of the polymer oxidation can be controlled in the range ca. 0,5% by the duration of the irradiation exposure and by the concentration of chloroform. The photooxidized polyferrocenylsilane material is conductive, with an increased conductivity of greater than three orders of magnitude relative to the unoxidized material. In addition, the photooxidized polymers have been found to be photoconductive. The photooxidation process can be reversed by means of chemical reduction using hydrazine or decamethylferrocene, leading to the regeneration of the neutral polymers. However, substantial molecular weight decline was detected during the photooxidation/reduction process, presumably as a result of chain cleavage reactions induced by the anionic or radical chlorinated photoproducts. Methylation of the cyclopentadienyl rings of the ferrocene moiety in the polymer was found to lead to materials which are significantly more stable. Time trace of the current at constant applied voltage of 100 V for a PFS film upon illumination. The ON and OFF states were created by using a mechanical shutter. [source] Chromate reduction in wastewater at different pH levels using thin iron wires,A laboratory studyENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 3 2005Li-Yang Chang Abstract The effectiveness of using thin zero-valent iron (Fe0) wires in the treatment of wastewater generated from a metal cleaning facility and with a pH in the range of 2 to 10 was examined. It was found that (1) when the sample containing low levels of total chromium (,14 mg/L) was mixed with iron wires at a pH of 3 to 8, 50 to 90% of the total chromium could be reduced in 4 h; (2) the initial reduction efficiency was pH-dependent: the lower the pH, the higher the reduction rate; (3) variations of solution pH, redox electrical potential, and electrical conductivity (EC) in samples were also pH-dependent; (4) the adsorption/reduction efficiency was limited by the diffusion of Cr(VI) from wastewater to the iron surface when the test duration was long; (5) when the initial pH = 3, iron corrosion and redox reaction dominated the reduction process; however, with pH = 8 or 10, corrosion, surface passivation, or metal precipitation could compete with reduction; (6) the used iron wires were still effective in chromium removal in new samples at pH = 3; and (7) some desorption of adsorbed chromium was observed in acidic samples when the test duration was long. Scanning electron microscope images and energy-dispersive X-ray spectra collected from iron samples also indicate that the efficiency of chromium adsorption/reduction is pH-dependent. Our results suggest that using zero-valent iron to polish acidic wastewater containing low contents of chromium and other heavy metals is feasible. © 2005 American Institute of Chemical Engineers Environ Prog, 2005 [source] Characterization of a nif-regulated flavoprotein (FprA) from Rhodobacter capsulatusFEBS JOURNAL, Issue 3 20002S] ferredoxin, Redox properties, molecular interaction with a [2Fe A flavoprotein from Rhodobacter capsulatus was purified as a recombinant (His)6 -tag fusion from an Escherichia coli clone over-expressing the fprA structural gene. The FprA protein is a homodimer containing one molecule of FMN per 48-kDa monomer. Reduction of the flavoprotein by dithionite showed biphasic kinetics, starting with a fast step of semiquinone (SQ) formation, and followed by a slow reduction of the SQ. This SQ was in the anionic form as shown by EPR and optical spectroscopies. Spectrophotometric titration gave a midpoint redox potential for the oxidized/SQ couple of Em1 = +20 mV (pH 8.0), whereas the SQ/hydroquinone couple could not be titrated due to the thermodynamic instability of SQ associated with its slow reduction process. The inability to detect the intermediate form, SQ, upon oxidative titration confirmed this instability and led to an estimate of Em2 , Em1 of > 80 mV. The reduction of SQ by dithionite was significantly accelerated when the [2Fe,2S] ferredoxin FdIV was used as redox mediator. The midpoint redox potential of this ferredoxin was determined to be ,275 ± 2 mV at pH 7.5, consistent with FdIV serving as electron donor to FprA in vivo. FdIV and FprA were found to cross-react when incubated together with the 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide, giving a covalent complex with an Mr of , 60 000. Formation of this complex was unaffected by the redox states of the two proteins. Other [2Fe,2S] ferredoxins, including FdV and FdVI from R. capsulatus, were ineffective as electron carriers to FprA, and cross-reacted poorly with the flavoprotein. The possible function of FprA with regard to nitrogen fixation was investigated using an fprA -deleted mutant. Although nitrogenase activity was significantly reduced in the mutant compared with the wild-type strain, nitrogen fixation was apparently unaffected by the fprA deletion even under iron limitation or microaerobic conditions. [source] Origin of quartz geodes from Laño and Tubilla del Agua sections (middle,upper Campanian, Basque-Cantabrian Basin, northern Spain): isotopic differences during diagenetic processesGEOLOGICAL JOURNAL, Issue 2 2002Juan J. Gómez-Alday Abstract Quartz geodes and nodular chert have been found within middle,upper Campanian carbonate sediments from the Laño and Tubilla del Agua sections of the Basque-Cantabrian Basin, northern Spain. The morphology of geodes together with the presence of anhydrite laths included in megaquartz crystals and spherulitic fibrous quartz (quartzine-lutecite), suggest an origin from previous anhydrite nodules. The anhydrite nodules at Laño were produced by the percolation of marine brines, during a period corresponding to a sedimentary gap, with ,34S and ,18O mean values of 18.8, and 13.6, respectively, consistent with Upper Cretaceous seawater sulphate values. Higher ,34S and ,18O mean values of 21.2, and 21.8, recorded in the Tubilla del Agua section are interpreted as being due to a partial bacterial sulphate reduction process in a more restricted marine environment. The idea that sulphates may have originated from the leaching of previously deposited Keuper sulphate evaporites with subsequent precipitation as anhydrite, is rejected because the ,34S, ,18O and 87Sr/86Sr values of anhydrite laths observed at both the Tubilla del Agua and Laño sections suggest an origin from younger marine brines. Later calcite replacement and precipitation of geode-filling calcite is recorded in both sections, with ,13C and ,18O values indicating the participation of meteoric waters. Synsedimentary activity of the Peñacerrada diapir, which lies close to the Laño section, played a significant role in the local shallowing of the basin and the formation of quartz geodes. In contrast, eustatic shallowing of the inner marine series of the Tubilla del Agua section led to the generation of morphologically similar quartz geodes. Copyright © 2002 John Wiley & Sons, Ltd. [source] Tetrakis-phthalocyanines bearing electron-withdrawing fluoro functionality: Synthesis, spectroscopy, and electrochemistryHETEROATOM CHEMISTRY, Issue 5 2009Ahmet T. Bilgiçli In this study, 2,9,16,23-tetrakis-4,-(2,3,5,6-tetrafluoro)-phenoxy-phthalocyaninatometalfree and metal(II) complexes, (H2PcBzF16, ZnPcOBzF16, CuPcOBzF16, and CoPcOBzF16) (Bz: Benzene) (2H, Zn, Cu, and Co), have been prepared directly from the corresponding 4,-(2,3,5,6-fluorophenylthio)-phthalonitrile compounds in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) in high boiling quinoline solvent. Tetrafluoro atoms on 2,3,5,6-position of benzene at the peripheral sites of phthalocyanines (Pcs) give rise interesting solubility to tetrakismetallophthalocyanines. Although all complexes were soluble in DCM, CHCl3, THF, DMF, and DMSO with increasing order, complexes synthesized, particularly H2PcBzF16, CuPcOBzF16, have very limited solubility in DMF and DMSO. The complexes have been characterized by elemental analysis, FTIR, 1H NMR, UV,vis, and MALDI,TOF mass spectral data. The cyclic voltammetry and differential pulsed voltammetry of the complexes show that while H2PcBzF16, CuPcOBzF16, and ZnPcOBzF16 give ligand-based reduction and oxidation processes, CoPcOBzF16 gives both ligand and metal-based redox processes, in harmony with the common metallophthalocyanine complexes. Redox processes due to both aggregated and disaggregated species were simultaneously observed during the first reduction process. The nature of the metal-based redox processes was confirmed using spectroelectrochemical measurements. © 2009 Wiley Periodicals, Inc. Heteroatom Chem 20:262,271, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20545 [source] Formation of Porous SiC Ceramics by Pyrolysis of Wood Impregnated with SilicaINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 6 2006Kateryna Vyshnyakova Biomorphous ,-SiC ceramics were produced at 1400°C from pine wood impregnated with silica. This one-step carbothermal reduction process decreases the cost of manufacturing of SiC ceramics compared with siliconization of carbonized wood in silicon vapor. The synthesized sample exhibits a 14 m2/g surface area and has a hybrid pore structure with large 5,20 ,m tubular macropores and small (<50 nm) slit-shaped mesopores. SiC whiskers of 20,400 nm in diameter and 5,20 ,m in length formed within the tubular pores. These whiskers are expected to improve the filtration by removing dust particles that could otherwise penetrate through large pores. After ultrasonic milling, the powdered sample showed an average particle size of ,30 nm. The SiC nanopowder produced in this process may be used for manufacturing SiC ceramics for structural, tribological, and other applications. [source] Identification of the effective distribution function for determination of the distributed activation energy models using the maximum likelihood method: Isothermal thermogravimetric dataINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 1 2009Bojan Jankovi The new procedure for identification of the effective distribution function for determination of the distributed activation energy models, which is based on use the maximum likelihood method (MLM), was established. The five different continuous probability functions (exponential, logistic, normal, gamma, and Weibull probability functions (the extended set of distributions)) were used for searching the best reactivity model for two heterogeneous processes: (a) the isothermal reduction process of nickel oxide under hydrogen atmosphere and (b) the isothermal degradation process of bisphenol-A polycarbonate (Lexan) under nitrogen atmosphere. The MLM showed that for both processes, the most suitable reactivity model represents the Weibull distribution model. It was concluded that the values of Arrhenius parameters (ln A and Ea), evaluated from the Weibull distribution model, represent the effective kinetic values for both considered processes. This procedure enables identification the suitable distribution model for considered process only from the experimental data (based on the shapes of obtained integral kinetic curves), and this fact represents the advantage of established analysis. The established mathematical procedure, which is based on the MLM, can be applied as the preliminary analysis for evaluating the distribution of activation energies for complex heterogeneous processes. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 41: 27,44, 2009 [source] Effects of NO2, CO, O2, and SO2 on oxidation kinetics of NO over Pt-WO3/TiO2 catalyst for fast selective catalytic reduction processINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 10 2006Muhammad Faisal Irfan The selective catalytic reduction rate of NO with N-containing reducing agents can be enhanced considerably by converting a part of NO into NO2. The enhanced reaction rate is more pronounced at lower temperatures by using an equimolar mixture of NO and NO2. The kinetics of NO oxidation over Pt-WO3/TiO2 catalyst has been determined in a fixed-bed reactor with different concentrations of oxygen, nitric oxide, and nitrogen dioxide in the presence of 8% water. It has been found that the reaction is second order with respect to nitric oxide, first order for oxygen with a third-order rate constant. Also, it is found that there is no effect on the reaction order with an addition of NO2, CO, or SO2. It follows the same second order but the reaction rate is found to be changed. It is observed that in the case of NO2 and SO2, the reaction rate tends to decrease, but it increases with the addition of CO into the feed. © 2006 Wiley Periodicals, Inc. Int J Chem Kinet 38: 613,620, 2006 [source] Enabling scalable multicast protocols using dynamic overlap tree pathINTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 4 2001Sheng Xu Abstract The scalability of a multicast protocol is a very critical issue when it is implemented on a global scale. The number of forwarding states that are maintained at each multicast router explodes when the number of multicast groups grows exponentially as in the case of global Internet. In this paper we describe a technique, called dynamic overlap tree path (DOTP), to reduce the forwarding states that need to be maintained in multicast routers and hence improve the scalability of existing multicast protocols. This technique, which can be incorporated in both the dense and sparse modes of multicast protocols, dynamically finds overlapped unbranched tree paths and merges their corresponding forwarding states to reduce the storage requirement in multicast routers. It does not introduce any additional control-message overheads through the reduction process. OPNET simulation results show that the overall average forwarding-state table size of the simulated networks can be reduced by about 30 per cent on the average. Copyright © 2001 John Wiley & Sons, Ltd. [source] Peat bog restoration by floating raft formation: the effects of groundwater and peat qualityJOURNAL OF APPLIED ECOLOGY, Issue 3 2002Alfons J. P. Smolders Summary 1,A prerequisite for the restoration of desiccated bog remnants is rewetting the peat surface. Frequently in Europe, extensive areas are flooded in order to maximize water retention, and growth of peat mosses is often observed in the shallow zones. In deeper waters, regeneration appears to depend on whether residual peat will become buoyant and form floating rafts. 2,In order to study the initial stages of peat bog regeneration, conditions required for peat buoyancy were studied on peat monoliths collected from three cut-over bog remnants in the Netherlands. The effects of different peat quality and water chemistry on buoyancy of the monoliths, as well as growth of Sphagnum cuspidatum and nutrient availability, were followed in a glasshouse experiment. 3,Both groundwater and peat quality affected the buoyancy of the monoliths and the growth of S. cuspidatum. When groundwater containing bicarbonate (1 mmol l,1 HCO3,, pH 6·0) was applied, the pH of peat monoliths increased from c. 3·5 to c. 4·5 due to acid buffering. As a result, two of the peat types became more buoyant and the concentration, production and emissions of methane (CH4) increased. It was concluded that the increase in CH4 production, induced by the increased pH, was responsible for the buoyancy. 4,When groundwater contained both HCO3, (1 mmol l,1) and sulphate (1 mmol l,1), pH was further increased to approximately pH 5·0 due to alkalinity generated by the SO42, reduction process. CH4 production, however, decreased because of interference from the SO42,, as confirmed in additional incubation experiments. Phosphate concentrations, however, greatly increased in the HCO3,/SO42, addition treatment due to the interaction between sulphide and iron phosphate precipitates. 5,In one of the peat types, treatments did not influence CH4 production and buoyancy, most probably because of its low decomposability. The chemical characteristics of the peat, notably the concentrations of lignin and soluble phenolics as well as C:N, C:P and C:K ratios, were all higher than in the other two peat types. 6,The increase of S. cuspidatum biomass during the experiment appeared to be strongly related to the N:P ratios of the capitula, which differed considerably among the three peat types. 7,We conclude that when bog remnants are inundated the prospects for bog regeneration are largely determined by peat quality and water chemistry. Peat mats with low concentration of lignin and phenolics and low C:N ratios are most likely to become buoyant in water with a higher pH, so providing suitable environments for Sphagnum species. When peat quality is inadequate, either shallow inundation or the addition of suitable peat from elsewhere is indicated. [source] Evaluation of the reduction of imidazophenazine dye derivatives under fast-atom-bombardment mass-spectrometric conditions,JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 1 2006Marina V. Kosevich Abstract Satellite [M + 2]+, and [M + 3]+ peaks accompanying the common peak of the protonated molecule [M + H]+ that are known to indicate the occurrence of a reduction process were observed in the fast atom bombardment (FAB) mass spectra of imidazophenazine dye derivatives in glycerol matrix. The distribution of the abundances in the [M + nH]+ peak group varied noticeably for different derivatives. This indicated different levels of the reduction depending on the different structure variations of the studied molecules. In the search for correlations between the mass spectral pattern and the structural features of the dyes, ab initio HF/6-31++G** quantum chemical calculations were performed. They revealed that the abundances of the [M + 2]+, and [M + 3]+ ions show growth proportional to the decrease of the energy of the lowest unoccupied molecular orbital, i.e. proportional to the increase of the electron affinity of the dye molecule. A method for rapid screening of reductive properties of sets of dye derivatives on the basis of the FAB mass spectral data is discussed. Copyright © 2005 John Wiley & Sons, Ltd. [source] Chemiluminescent picture of diphenyleneiodonium-inhibited NADPH oxidase: a bimodal process and its logistic,exponential model-based descriptionLUMINESCENCE: THE JOURNAL OF BIOLOGICAL AND CHEMICAL LUMINESCENCE, Issue 4 2007Bonawentura Kochel Abstract A chemiluminescence (CL) study of diphenyleneiodonium-inhibited NADPH oxidase was performed on a cellular system containing neutrophils stimulated by phorbol myristate acetate, indicating a complex bimodal structure of CL processes corresponding to different stages of the inhibition. The complex structure of these processes was described by a superposition of two logistic,exponential (LE) models, characterizing these processes as bimodal ones. To determine the mechanistic foundation of the LE model-described processes, a generalized form of the second-order dynamic system of CL reactions, the solution to which corresponds to the LE model, was constructed. The diphenyleneiodonium effects on neutrophil NADPH oxidase were separated from the total bimodal CL of the whole measurement system by the use of difference CL processes. These difference processes were also found to be bimodal; thus, inhibitor-induced reduction of CL could be described by a second-order dynamic system. The rate constants and initial concentrations in this dynamic system were determined by the least squares method applied to numerical solutions approximating the difference processes. Using interrelations between the parameters of the dynamic system, cooperative effects in the inhibitor reactions with NADPH oxidase were found and described quantitatively. Other evidences of cooperativity were obtained from integral characteristics of the CL reduction process, i.e. dose,response and progress curves, determined by numerical integration of the LE models constituting the superposition. On this basis, it was also possible to detect a specific binding of the inhibitor to the enzyme. Finally, putative reaction mechanisms suggested by the model obtained were considered and compared with those known at present. Copyright © 2007 John Wiley & Sons, Ltd. [source] Decorating Polypyrrole Nanotubes with Au Nanoparticles by an In Situ Reduction ProcessMACROMOLECULAR RAPID COMMUNICATIONS, Issue 11 2009Jingjing Xu Abstract Au nanoparticle-decorated polypyrrole nanotubes (defined as PPy/Au nanocomposites) are prepared by an in situ reduction process. Polypyrrole (PPy) nanotubes are prepared by a self-degraded template method, and Au nanoparticles are deposited in situ by the reduction of HAuCl4. The size and uniformity of the Au nanoparticles that decorate the PPy nanotubes can be controlled by adjusting the experimental conditions, such as the stabilizers used and the reaction temperature. The morphologies and optical properties of the nanocomposites have been characterized by scanning electron microscopy, transmission electron microscopy, UV-vis, and FT-IR spectroscopy. Conductivity measurements show that the conductivities of the nanocomposites decrease with a decrease of temperature, and the conductivity,temperature relationship obeys the quasi-one dimensional variable range hopping model. [source] Investigation of reduction of Cu(II) complexes in positive-ion mode electrospray mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 23 2001Luca Gianelli The electrospray ionization mass spectrometry (ESI-MS) behavior of seven Cu(II) complexes with tetradentate ligands has been studied. An unexpected reduction process, in positive ion mode, of the Cu oxidation state was observed, and shown to be due to charge transfer between the metal complex and the solvent molecules in the gas phase. Ion trap collision-induced dissociation experiments and deuterated solvents were used to support the proposed mechanism that is not a common electrochemical redox reaction at the ESI tip, but a gas-phase process. A series of solvents (acetonitrile, methanol, ethanol, propanol and iso -butanol) were tested, and a correlation between ionization energy (IE) and the amount of Cu(I) produced in ESI has been demonstrated for the alcohols, although some other solvent properties should also be taken into account. The electrochemical reduction potential of the complexes in solution is also an important parameter, since complexes more easily reduced in solution are also easier to reduce in the gas phase. Copyright © 2001 John Wiley & Sons, Ltd. [source] Applications of mulch biowalls,three case studiesREMEDIATION, Issue 1 2009Kevin A. Morris Mulch biowalls are proving to be an effective means of generating reducing conditions for the in situ anaerobic reduction of contaminants in groundwater that are amenable to the reduction process. Mulch is an inexpensive and readily available substrate that provides a long-lasting carbon and electron donor source for the stimulation of the anaerobic reduction process in groundwater. Examples of contaminants that are amenable to the biotic anaerobic reduction process include: chlorinated alkenes and alkanes, explosives, perchlorate, some metals, and petroleum hydrocarbons. The microbial degradation of cellulose fibers (mulch) is arguably the oldest reduction process known and is evident anywhere that plant material, soil, and water are present together. This article presents three case studies discussing three different uses of mulch biowalls to stimulate the anaerobic bioremediation of contaminants in shallow soils and groundwater. © 2009 Wiley Periodicals, Inc. [source] Long-chain silanes as reducing agents part 1: a facile, efficient and selective route to amine and phosphine-stabilized active Pd-nanoparticlesAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 3 2010Bhanu P. S. Chauhan Abstract Recently, metal nanoparticles have found applications in various fields, which have necessitated exploration of new avenues to obtain such materials. In this publication, a hydrosilane-based reduction and characterization of resulting palladium nanoparticles is achieved using palladium acetate as nanoparticle precursor and octadecylsilane as a reducing agent. The influence of phosphine and amine ligands in the stabilization of nanoparticles is also investigated. In addition, a brief mechanistic proposal of the reduction process is also discussed. Copyright © 2009 John Wiley & Sons, Ltd. [source] Automatic data reduction and archiving for STELLAASTRONOMISCHE NACHRICHTEN, Issue 6-8 2004Article first published online: 13 OCT 200, M. Weber Abstract The data is collected at the observatory, each data product is registered and a queue is set up to transfer the highest priority observations first. Optionally, lossy compression (e.g. White 1994) can be used to boost transfer speeds for time critical observations. Once the data has been transferred, the reduction process is started at the control-center in Potsdam. The type of reduction steps required can be specified by the user or a default pipeline setup can be used. The users can be notified about the status of their observations in any desired detail. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Expanded Pyridiniums: Bis-cyclization of Branched Pyridiniums into Their Fused Polycyclic and Positively Charged Derivatives,Assessing the Impact of Pericondensation on Structural, Electrochemical, Electronic, and Photophysical FeaturesCHEMISTRY - A EUROPEAN JOURNAL, Issue 36 2010Dr. Jérôme Fortage Abstract This study evaluates the impact of the extension of the ,-conjugated system of pyridiniums on their various properties. The molecular scaffold of aryl-substituted expanded pyridiniums (referred to as branched species) can be photochemically bis-cyclized into the corresponding fused polycyclic derivatives (referred to as pericondensed species). The representative 1,2,4,6-tetraphenylpyridinium (1H) and 1,2,3,5,6-pentaphenyl-4-(p -tolyl)pyridinium (2Me) tetra- and hexa-branched pyridiniums are herein compared with their corresponding pericondensed derivatives, the fully fused 9-phenylbenzo[1,2]quinolizino[3,4,5,6- def]phenanthridinium (1Hf) and the hitherto unknown hemifused 9-methyl-1,2,3-triphenylbenzo[h]phenanthro[9,10,1- def]isoquinolinium (2Mef). Combined solid-state X-ray crystallography and solution NMR experiments showed that stacking interactions are barely efficient when the pericondensed pyridiniums are not appropriately substituted. The electrochemical study revealed that the first reduction process of all the expanded pyridiniums occurs at around ,1,V vs. SCE, which indicates that the lowest unoccupied molecular orbital (LUMO) remains essentially localized on the pyridinium core regardless of pericondensation. In contrast, the electronic and photophysical properties are significantly affected on going from branched to pericondensed pyridiniums. Typically, the number of absorption bands increases with extended activity towards the visible region (down to ca. 450,nm in MeCN), whereas emission quantum yields are increased by three orders of magnitude (at ca. 0.25 on average). A relationship is established between the observed differential impact of the pericondensation and the importance of the localized LUMO on the properties considered: predominant for the first reduction process compared with secondary for the optical and photophysical properties. [source] High-Turnover Photochemical Hydrogen Production Catalyzed by a Model Complex of the [FeFe]-Hydrogenase Active SiteCHEMISTRY - A EUROPEAN JOURNAL, Issue 1 2010Daniel Streich Lifting the diiron curtain: 200,equivalents of H2 per catalyst at a maximum turnover rate of 3.7,H2 per minute can be obtained in a light-driven proton reduction process in near-neutral H2O/DMF (pH,5.5) by using an [FeFe]-hydrogenase active-site model complex as the catalyst (see scheme). [source] Effect of weight reduction process on printing properties of polyester fabricsCOLORATION TECHNOLOGY, Issue 5 2003Mehmet Kanik The weight reduction process used to improve the handle and appearance of polyester fabrics is used widely in industry. In this study, polyester fabrics, which had been subjected to this process in varying degrees, were printed using three disperse dyes under controlled printing conditions. The effect of weight reduction on the print paste add-on, colour strength, wash and crock fastness, and levelness and sharpness of the print were evaluated and the results discussed. [source] Engineering NADH metabolism in Saccharomyces cerevisiae: formate as an electron donor for glycerol production by anaerobic, glucose-limited chemostat culturesFEMS YEAST RESEARCH, Issue 8 2006Jan-Maarten A. Geertman Abstract Anaerobic Saccharomyces cerevisiae cultures reoxidize the excess NADH formed in biosynthesis via glycerol production. This study investigates whether cometabolism of formate, a well-known NADH-generating substrate in aerobic cultures, can increase glycerol production in anaerobic S. cerevisiae cultures. In anaerobic, glucose-limited chemostat sultures (D=0.10 h,1) with molar formate-to-glucose ratios of 0 to 0.5, only a small fraction of the formate added to the cultures was consumed. To investigate whether incomplete formate consumption was by the unfavourable kinetics of yeast formate dehydrogenase (high kM for formate at low intracellular NAD+ concentrations) strains were constructed in which the FDH1 and/or GPD2 genes, encoding formate dehydrogenase and glycerol-3-phosphate dehydrogenase, respectively, were overexpressed. The engineered strains consumed up to 70% of the formate added to the feed, thereby increasing glycerol yields to 0.3 mol mol,1 glucose at a formate-to-glucose ratio of 0.34. In all strains tested, the molar ratio between formate consumption and additional glycerol production relative to a reference culture equalled one. While demonstrating that that format can be use to enhance glycerol yields in anaerobic S. cerevisiae cultures, This study also reveals kinetic constraints of yeast formate dehydrogenase as an NADH-generating system in yeast mediated reduction processes. [source] Mineral Precipitation Upgradient from a Zero-Valent Iron Permeable Reactive BarrierGROUND WATER MONITORING & REMEDIATION, Issue 3 2008R.L. Johnson Core samples taken from a zero-valent iron permeable reactive barrier (ZVI PRB) at Cornhusker Army Ammunition Plant, Nebraska, were analyzed for physical and chemical characteristics. Precipitates containing iron and sulfide were present at much higher concentrations in native aquifer materials just upgradient of the PRB than in the PRB itself. Sulfur mass balance on core solids coupled with trends in ground water sulfate concentrations indicates that the average ground water flow after 20 months of PRB operation was approximately twenty fold less than the regional ground water velocity. Transport and reaction modeling of the aquifer PRB interface suggests that, at the calculated velocity, both iron and hydrogen could diffuse upgradient against ground water flow and thereby contribute to precipitation in the native aquifer materials. The initial hydraulic conductivity (K) of the native materials is less than that of the PRB and, given the observed precipitation in the upgradient native materials, it is likely that K reduction occurred upgradient to rather than within the PRB. Although not directly implicated, guar gum used during installation of the PRB is believed to have played a role in the precipitation and flow reduction processes by enhancing microbial activity. [source] Stress corrosion cracking susceptibility of stainless steels in pulp cooking processes,online capillary electrophoresis, potentiostatic and chromatographic studiesMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 8 2008H. Leinonen Abstract An online high temperature capillary electrophoresis instrument (HotUCE), a potentiometer and an ion chromatograph were used in studies on corrosive ions and changes in potential at normal pulping process temperatures in experimental liquors modelling pulp cooking processes at mills. The aim was to evaluate the stress corrosion cracking (SCC) susceptibility of stainless steels. The HotUCE instrument and the potentiometer were online coupled with an autoclave, where welded duplex stainless steel samples were immersed for 500 h in simulated high ionic strength hot black liquor (HBL), hot white liquor (HWL) or green liquor (GL) at 130, 150 or 170,°C, respectively. The results showed that only minor amounts of oxidized sulphur compounds were formed. The concentrations of corrosive sulphur anions were calculated against sulphur standards. Amounts of sulphur species in the liquor correlated with the changes in the potential of the duplex stainless steel specimens during the cooking experiments. The formation of sulphite during cooking was greater in HWL than in HBL. Changes in the potential showed that reduction processes occurred during the SCC tests. The results indicate that the SCC risk is enhanced at higher temperatures, probably, due to the increased formation of thiosulphate. [source] A comparison of DA white dwarf temperatures and gravities from Lyman and Balmer line studiesMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2001M.A. Barstow We present measurements of the effective temperatures and surface gravities for a sample of hot DA white dwarfs, using the Lyman line data available from the HUT, ORFEUS and FUSE FUV space missions. Comparing the results with those from the standard Balmer line technique, we find that there is a general good overall agreement between the two methods. However, significant differences are found for a number of stars, but not always of a consistent nature in that sometimes the Balmer temperature exceeds that derived from the Lyman lines and in other instances it is lower. We conclude that, with the latest model atmosphere calculations, these discrepancies probably do not arise from an inadequate theoretical treatment of the Lyman lines but rather from systematic effects in the observation and data reduction processes, which dominate the statistical errors in these spectra. If these systematic data reduction effects can be adequately controlled, the Lyman line temperature and gravity measurements are consistent with those obtained from the Balmer lines when allowance is made for reasonable observational uncertainties. [source] Petroleum Industry Effluents and Other Oxygen-Demanding Wastes in Niger Delta, NigeriaCHEMISTRY & BIODIVERSITY, Issue 7 2006Abstract In this article, we review the fundamental phenomenon of oxygenation within the overriding context of petroleum-industry effluents and the other oxygen demanding wastes in Niger Delta, Nigeria. Drill cuttings, drilling mud (fluids used to stimulate the production processes), and accidental discharges of crude petroleum constitute serious land and water pollution in the oil-bearing province. Effluents from other industrial establishments such as distilleries, pulp and paper mills, fertilizer plants, and breweries, as well as thermal effluents, plant nutrients (such as nitrates and phosphates), and eroded sediments have also contributed to the pollution of their surrounding environment. Since these wastes are oxygen-demanding in nature, their impact on the recipient environment can be reversed by the direct application of simple chemistry. The wastes can be reduced, particularly in natural bodies of water, by direct oxidation,reduction processes or simple chemical combinations, acid,base reactions, and solubility equilibria; these are pH- and temperature-dependent. A shift in pH and alkalinity affects the solubility equilibria of Na+, Cl,, SO2,, NO, HCO, and PO, and other ions and compounds. [source] | |||||||||||||||||||||||||||||||||||||