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Alkaline Solution (alkaline + solution)
Selected AbstractsApplication of Electrochemical Impedance Spectroscopy for Fuel Cell Characterization: PEFC and Oxygen Reduction Reaction in Alkaline Solution,FUEL CELLS, Issue 3 2009N. Wagner Abstract The most common method used to characterise the electrochemical performance of fuel cells is the recording of current/voltage U(i) curves. Separation of electrochemical and ohmic contributions to the U(i) characteristics requires additional experimental techniques like electrochemical impedance spectroscopy (EIS). The application of EIS is an approach to determine parameters which have proved to be indispensable for the characterisation and development of all types of fuel cell electrodes and electrolyte electrode assemblies [1]. In addition to EIS semi-empirical approaches based on simplified mathematical models can be used to fit experimental U(i) curves [2]. By varying the operating conditions of the fuel cell and by the simulation of the measured EIS with an appropriate equivalent circuit, it is possible to split the cell impedance into electrode impedances and electrolyte resistance. Integration in the current density domain of the individual impedance elements enables the calculation of the individual overpotentials in the fuel cell (PEFC) and the assignment of voltage loss to the different processes. In case of using a three electrode cell configuration with a reference electrode, one can directly determine the corresponding overvoltage. For the evaluation of the measured impedance spectra the porous electrode model of Göhr [3] was used. This porous electrode model includes different impedance contributions like impedance of the interface porous layer/pore, interface porous layer/electrolyte, interface porous layer/bulk, impedance of the porous layer and impedance of the pores filled by electrolyte. [source] A Convenient and Environmentally Benign Method of Reducing Aryl Ketones or Aldehydes by Zinc Powder in an Aqueous Alkaline Solution.CHEMINFORM, Issue 37 2007Chao-Zhi Zhang 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] A Convenient and Environmentally Benign Method of Reducing Aryl Ketones or Aldehydes by Zinc Powder in an Aqueous Alkaline SolutionCHINESE JOURNAL OF CHEMISTRY, Issue 5 2007Chao-Zhi Zhang Abstract A convenient and environmentally benign method for reducing the carbonyl group in hydroxy- and amino- 9,10-anthracenediones, ortho (or para) acyl phenols and acyl anilines to a methylene group by zinc powder in an aqueous sodium hydroxide solution was reported. Based on theoretical calculations using the density functional theory (DFT), the mechanism of these reduction reactions was postulated. This mechanism can be applied to help predicting the reduced products of aryl ketones (or aldehydes) in an alkaline solution. [source] Electrochemical Reduction of Oxygen on Carbon Supported Pt and Pt/Ru Fuel Cell Electrodes in Alkaline SolutionsFUEL CELLS, Issue 4 2003E.H. Yu Abstract A study of O2 reduction in 1 M NaOH solution at gas diffusion electrodes made from carbon supported Pt and Pt/Ru catalysts is reported. Two Tafel regions were observed for both the Pt and Pt/Ru electrodes. Although the same mechanism was suggested for oxygen reduction on both Pt and Pt/Ru catalysts, the O2 reduction activity was lower on Ru. Electrochemical Impedance Spectroscopy (EIS) analysis was carried out at different potentials and showed the significant contribution of diffusion on the reaction process and kinetics. The effect of methanol on O2 reduction was investigated in solutions containing various concentrations of methanol. The electrode performance deteriorated with increasing methanol concentration because of a mixed cathode potential. The methanol tolerance, i. e., the methanol concentration which polarises the O2 reduction reaction for O2 reduction, at the Pt/C electrode with a Pt loading of 1.2 mg cm,2 is 0.2 M methanol in 1 M NaOH. [source] Electrocatalytic Properties of Electropolymerized Ni(II)curcumin ComplexELECTROANALYSIS, Issue 5-6 2003Aleksander Ciszewski Abstract The voltammetric behavior in alkaline solution of a nickel-based chemically modified electrode (poly-Ni(II)curcumin) prepared by oxidative electropolymerization of nickel-curcumin complex for electrooxidation of aliphatic alcohols was investigated by cyclic voltammetry and rotating disk technique (curcumin=1,7-bis[4-hydroxy-3-methoxyphenyl]-1,6-heptadiene-3,5-dione). The dependence of the oxidation current on the alcohol concentration and on the number of redox centers Ni(II)/Ni(III) is discussed. From the fact that the oxidation current increases with the increase of film thickness it is evident that the electrocatalytic reaction occurs inside the polymer film. The system examined is a typical example of a redox polymer with 3D properties. It is also concluded that the reaction mechanism of alcohol oxidation is the case, according to the concept of Andrieux and Saveant, where the cross-exchange reaction is the limiting step. The mechanism of modifying the film formation has also been discussed. [source] Controlled Assembly of [Nb6,xWxO19](8,x), (x = 0,4) Lindqvist Ions with (Amine)copper ComplexesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 21 2008Travis M. Anderson Abstract The mixed addenda isopolyanion, [N(CH3)4]2Na2[cis -Nb2W4O19]·18H2O, reacts with Cu(NO3)2 in water and in the presence of NH2CH2CH2NH2 (en) or NH4OH at 60 °C to yield a phase that is decorated {[Cu(en)2(H2O)]2[Nb2W4O19]·2H2O (1)} or charge-balanced {[Cu(NH3)4(H2O)]2[Nb2W4O19]·8H2O (2)}, respectively, by (amine)copper complexes. The prolonged heating at 95 °C of [N(CH3)4]6[Nb10O28]·6H2O, [N(CH3)4]2Na2[cis -Nb2W4O19]·18H2O, or Na4K2[cis -Nb4W2O19]·12H2O and Cu(NO3)2 in a mixed water/amine [en or NH2CH2CH2CH2NH2 (dap)] solution results in the formation of two-dimensional materials with alternate layers of (amine)copper complexes linking Lindqvist [Nb6,xWxO19](8,x), (x = 0,4) clusters. These phasesinclude: [Cu(dap)2]3[Nb4W2O19]·7H2O (3), [Cu(dap)2]3[H2Nb6O19]·6H2O (4), [Cu(dap)2]3[Nb3W3O19]·Cl·6H2O (5), and [Cu(en)2]3[Nb4W2O19]·6H2O (6). Complexes 4 and 5 result from the decomposition of [Nb10O28]6, and [cis -Nb2W4O19]4, to [H2Nb6O19]6, and [fac -Nb3W3O19]5,, respectively, in alkaline solution. Complex 5 contains an extra-framework site that is occupied by Cl,, but this site is occupied by a water molecule in 3 and is vacant in structures 4 and 6. The results of this study suggest that charge density, cluster charge and symmetry, and cluster-cation pairing are all important parameters in the incorporation of d-electron metals onto the surfaces of [Nb6,xWxO19](8,x), (x = 0,4) clusters or into the frameworks of Lindqvist-based complex materials.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] A Fibronectin Peptide-Coupled Biopolymer Nanofibrous Matrix to Speed Up Initial Cellular EventsADVANCED ENGINEERING MATERIALS, Issue 4 2010Ji-Eun Kim Degradable polymer nanofibers produced by electrospinning are attractive for use in cell culture and tissue repair. However, the hydrophobicity and initial poor cell adhesion of synthetic polymers have limited their use in tissue regeneration. Herein, the surface of a poly(lactide-co-caprolactone) Arg-Gly-Asp sequence of nanofiber was tailored with a fibronectin peptide (FN10), which was designed to retain the central cell-binding domain. The electrospun nanofibers are first treated with an alkaline solution to reveal the carboxyl groups on the surface, which is followed by coupling with an FN10 solution in conjunction with a carbodiimide-based agent. Peptide coupling occurs effectively with saturation within 1,h, and the coupled peptide maintains its stability for several days. The peptide-coupled nanofibers show significant improvements in initial cell adhesion and spreading compared with the untreated one, confirming the role of the FN10 peptide in the initial cell events. This methodology may be useful in tailoring the surface of polymeric nanofibers with biomolecules targeted for specific tissue responses. [source] Determination of Transverse Dispersion Coefficients from Reactive Plume LengthsGROUND WATER, Issue 2 2006Olaf A. Cirpka With most existing methods, transverse dispersion coefficients are difficult to determine. We present a new, simple, and robust approach based on steady-state transport of a reacting agent, introduced over a certain height into the porous medium of interest. The agent reacts with compounds in the ambient water. In our application, we use an alkaline solution injected into acidic ambient water. Threshold values of pH are visualized by adding standard pH indicators. Since aqueous-phase acid-base reactions can be considered practically instantaneous and the only process leading to mixing of the reactants is transverse dispersion, the length of the plume is controlled by the ratio of transverse dispersion to advection. We use existing closed-form expressions for multidimensional steady-state transport of conservative compounds in order to evaluate the concentration distributions of the reacting compounds. Based on these results, we derive an easy-to-use expression for the length of the reactive plume; it is proportional to the injection height squared, times the velocity, and inversely proportional to the transverse dispersion coefficient. Solving this expression for the transverse dispersion coefficient, we can estimate its value from the length of the alkaline plume. We apply the method to two experimental setups of different dimension. The computed transverse dispersion coefficients are rather small. We conclude that at slow but realistic ground water velocities, the contribution of effective molecular diffusion to transverse dispersion cannot be neglected. This results in plume lengths that increase with increasing velocity. [source] Hydrothermal Synthesis and Characterization of KxNa(1,x)NbO3 PowdersINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 6 2007Jun-Hai Lv NaNbO3, KNbO3, and KxNa(1,x)NbO3 powders were successfully prepared by the hydrothermal method. The phase of the products was identified to be orthorhombic structure by X-ray diffraction (XRD) technique, and the XRD results revealed that the x value of the KxNa(1,x)NbO3 gradually increased with the increase in the ratio of K+ to Na+ in alkaline solution. The morphology and the microstructure were investigated by scanning electron microscopy, energy-dispersive spectroscopy, and transmission electron microscopy, and the results indicated that the ratio of K+ to Na+ in the solution had a great effect on the morphology and the size of products. Na0.5K0.5NbO3 with morphotropic phase boundary composition could be synthesized when the molar ratio of K+ to Na+ was between 4:1 and 6:1 in the solution. A possible formation mechanism of the KxNa(1,x)NbO3 crystal was also proposed based on the experimental results. [source] Kinetic evidence for the copper peroxide intermediate with two copper ions in proximityINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 7 2006S. Selvarani The decomposition of caroate (peroxomonosulfate, PMS) is catalyzed by Cu(II) ions even at 5 × 10,5 M in aqueous alkaline solution. The rate is second order in copper(II) ions concentrations and first order in [PMS]. The rate constant values are found to decrease with increase in hydroxide ion concentrations. The turnover number for the reaction is estimated as >1000. The experimental results suggest that the formation of peroxide type intermediate with two copper(II) ions is the rate-determining step. This peroxide intermediate reacts with another molecule of PMS to give the products oxygen, SO and copper ions. The overall entropy of activation is positive with a value of ,20 cals/mol/K. The very high turnover number suggests that Cu(II) ion is one of the best catalysts for the decomposition of caroate ions in alkaline medium. The reaction also represents a system in which metal ion catalyzed decomposition of caroate does not involve radical intermediates. © 2006 Wiley Periodicals, Inc. Int J Chem Kinet 38: 439,443, 2006 [source] Preparation and pH-sensitivity of polyacrylonitrile (PAN) based porous hollow gel fibersJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2008Xinyuan Shen Abstract Polyacrylonitrile based porous hollow gel fibers were prepared from PAN hollow fibers by oxidation and subsequent alkaline treatment. Fourier-transform infrared (FTIR), X-ray diffraction, and scanning electron microscope (SEM) analyses showed that the PAN porous hollow gel fiber was a kind of amphoteric fiber due to the combination of cationic groups of pyridyl and anionic groups of carboxyl; after gelation the hollow channel and finger-like pores on the fiber walls were conserved. The effects of cyclization reaction degree, alkaline solution concentration, and alkaline treatment time on the mechanical properties or pH-sensitive behavior of the porous hollow gel fibers were investigated. The elongation/contraction behavior was studied in detail. It was found that the gel fiber exhibited a large swelling in an alkaline solution and contracting in an acid solution; the swelling change in length was above 90%; the responsive time of elongation/contraction was less than 20 s; the maximum contraction force was 20 N/cm2; and pH-sensitivity was reversible. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Regulatory Mechanisms and Physiological Relevance of a Voltage-Gated H+ Channel in Murine Osteoclasts: Phorbol Myristate Acetate Induces Cell Acidosis and the Channel Activation,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 11 2003Hiroyuki Mori Abstract The voltage-gated H+ channel is a powerful H+ extruding mechanism of osteoclasts, but its functional roles and regulatory mechanisms remain unclear. Electrophysiological recordings revealed that the H+ channel operated on activation of protein kinase C together with cell acidosis. Introduction: H+ is a key signaling ion in bone resorption. In addition to H+ pumps and exchangers, osteoclasts are equipped with H+ conductive pathways to compensate rapidly for pH imbalance. The H+ channel is distinct in its strong H+ extrusion ability and voltage-dependent gatings. Methods: To investigate how and when the H+ channel is available in functional osteoclasts, the effects of phorbol 12-myristate 13-acetate (PMA), an activator for protein kinase C, on the H+ channel were examined in murine osteoclasts generated in the presence of soluble RANKL (sRANKL) and macrophage-colony stimulating factor (M-CSF). Results and Conclusions: Whole cell recordings clearly showed that the H+ current was enhanced by increasing the pH gradient across the plasma membrane (,pH), indicating that the H+ channel changed its activity by sensing ,pH. The reversal potential (Vrev) was a valuable tool for the real-time monitoring of ,pH in clamped cells. In the permeabilized patch, PMA (10 nM-1.6 ,M) increased the current density and the activation rate, slowed decay of tail currents, and shifted the threshold toward more negative voltages. In addition, PMA caused a negative shift of Vrev, suggesting that intracellular acidification occurred. The PMA-induced cell acidosis was confirmed using a fluorescent pH indicator (BCECF), which recovered quickly in a K+ -rich alkaline solution, probably through the activated H+ channel. Both cell acidosis and activation of the H+ channel by PMA were inhibited by staurosporine. In ,80% of cells, the PMA-induced augmentation in the current activity remained after compensating for the ,pH changes, implying that both ,pH-dependent and -independent mechanisms mediated the channel activation. Activation of the H+ channel shifted the membrane potential toward Vrev. These data suggest that the H+ channel may contribute to regulation of the pH environments and the membrane potential in osteoclasts activated by protein kinase C. [source] Extraction and recovery of gold from KAu(CN)2 using cetyltrimethylammonium bromide microemulsionsJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 11 2001Tian-Xi Zhang Abstract Extraction and stripping of KAu(CN)2 from alkaline solution by a w/o microemulsion formed with cetyltrimethylammonium bromide (CTAB) using 198Au(I) tracer has been investigated. Various parameters, such as the Au(I) concentration in aqueous phase, concentrations of halide ions, NH4SCN and thiodiethylene glycol in stripping solution as well as the relationship between water and Au(I) concentration in the organic phase in the extraction and stripping of Au(I) were studied. The results show that almost all of the Au(I) in the aqueous phase was extracted into the organic phase. The water content decreased significantly with an increase in Au(I) concentration in the organic phase, contrary to the results of a system with tributyl phosphate (TBP) as cosolvent. Almost all of the extracted Au(I) (,98%) can be recovered with pure thiodiethylene glycol as the stripping agent, and ,93% of the Au(I) is stripped with high concentrations of NH4SCN(>3.0,mol,dm,3) or KI (>2.0,mol,dm,3). © 2001 Society of Chemical Industry [source] Photoreaction of 1H -azepine-2,7-dione in alkaline solutionJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 2 2001Yoshihisa Fukai Photolysis of 1H -azepine-2,7-dione 2 proceeded with alkali as in the photoreaction of N -alkylimide to give 7-hydroxy-1H -azepine-2-one 13. [source] A new recovery process of carbon dioxide from alkaline carbonate solution via electrodialysisAICHE JOURNAL, Issue 12 2009Hiroki Nagasawa Abstract Bipolar membrane electrodialysis is applied to CO2 recovery from alkaline carbonate solution. CO2 in flue gas is captured by an alkaline hydroxide absorbing solution to form an alkaline carbonate solution. The captured CO2 is recovered from the alkaline carbonate solution via bipolar membrane electrodialysis, and the alkaline solution is regenerated simultaneously. To reduce the power requirement for CO2 recovery, this study considers optimal design and operation. Three membrane arrangements were compared, and the results indicate the membrane arrangement comprising a bipolar membrane and cation exchange membrane is the most energy saving. With further optimization of operation conditions, the minimum power requirement for CO2 recovery was reduced to 2.1 MJ/kg-CO2 (or 2.1 GJ/t-CO2). © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] INTERACTIONS OF THE MIX-LINKED ,-(1,3)/,-(1,4)- d -XYLANS IN THE CELL WALLS OF PALMARIA PALMATA (RHODOPHYTA),JOURNAL OF PHYCOLOGY, Issue 1 2003Estelle Deniaud Algal cell wall mechanical properties, crucial for biological functions and commercial applications, rely on interactions in macromolecular assemblies. In an effort to better understand the interactions of the matrix-phase ,-(1,3)/(1,4)- d -xylan in the edible seaweed Palmaria palmata ((L.) O. Kuntze, Rhodophyta, Palmariales), sequential extractions by saline, alkaline, and chaotropic solutions were done. The chemical composition and structure and the physicochemical properties of the isolated xylan revealed that it was partly acidic, probably due to the presence of sulfate (up to 5%) and phosphate groups (up to 4%). Although such acidity suggested ionic interactions of xylan in the cell walls, the high yields of polysaccharide extracted by alkali and particularly by 8 M urea and 4.5 M guanidium thiocyanate demonstrated that it was mainly hydrogen bonded in the cell wall. H-bonds did not appear to be related to the mean proportions of ,-(1,3) and ,-(1,4)- d -xylose linkages because these did not differ between extracts of increasing alkalinity. However, the decreasing molar weight and intrinsic viscosity of extracts obtained by alkaline solution containing a reducing agent used to prevent polysaccharide degradation suggested the presence of an alkali-labile component in the xylan. These results are discussed with regard to the role of potential wall proteins as a means of control of these interactions. [source] Identification of chemical species of fluorescein isothiocyanate isomer,I (FITC) monolayers on platinum by doubly resonant sum-frequency generation spectroscopyJOURNAL OF RAMAN SPECTROSCOPY, Issue 11 2008Toshiki Maeda Abstract Doubly resonant sum-frequency generation (DR-SFG) spectroscopy of fluorescein-4-isothiocyanate isomer-I (FITC) monolayers on platinum was performed. Vibrational spectra of the monolayers for the IR wavenumber of 1750,1450 cm,1 were measured with visible probes ranging from 431 to 582 nm. Two vibrational bands at 1643 and 1610 cm,1 were observed, and their DR-SFG excitation profiles displayed different shapes. By rinsing the monolayers with an alkaline solution, the smaller wavenumber band disappeared and the larger wavenumber band gained intensity. On the basis of the spectral response to the rinsing, we concluded that the FITC molecules existed on platinum as deprotonated and protonated forms; the former corresponds to the 1643 cm,1 band and the latter to the 1610 cm,1 band. The deprotonated form was assigned to an anionic surface species, and the protonated form to a neutral surface species by comparing the DR-SFG excitation profiles with electronic absorption spectra of the protolytic forms of fluorescein in an aqueous solution (Sjöback R et al., Spectrochimica Acta A 1995; 51: L7,L21). The results demonstrate that the measurement of DR-SFG excitation profiles is a useful technique to identify chemical species of monolayers on metal surfaces. Copyright © 2008 John Wiley & Sons, Ltd. [source] Polarization coherent anti-stokes Raman scattering using noisy lightJOURNAL OF RAMAN SPECTROSCOPY, Issue 1 2007Lindsay R. Weisel Abstract Several polarization studies on the noisy light version of coherent anti-Stokes Raman scattering (CARS) exist in the literature. However, the full advantages of polarization CARS (P-CARS), which are so useful in conventional and short-pulse CARS methods, have not yet been exploited in the noisy light version. This work presents experimental realization of fully functional P-CARS using noisy light. Several examples demonstrate the advantages brought by P-CARS. This includes the ,classic' example of benzene in carbon tetrachloride. Also presented are the carbon,carbon double bond stretches in acrylonitrile and 1-hexene. An interesting, and not fully understood, detection polarization angle dependence is discussed. Applications to an m -xylene/benzene mixture and an alkaline solution of the amino acid phenylalanine are presented. Copyright © 2006 John Wiley & Sons, Ltd. [source] Spherical ordered mesoporous silicas and silica monoliths as stationary phases for liquid chromatographyJOURNAL OF SEPARATION SCIENCE, JSS, Issue 6 2006Anne Galarneau Abstract Ordered mesoporous silicas such as micelle-templated silicas (MTS) feature unique textural properties in addition to their high surface area (,1000 m2/g): narrow mesopore size distributions and controlled pore connectivity. These characteristics are highly relevant to chromatographic applications for resistance to mass transfer, which has never been studied in chromatography because of the absence of model materials such as MTS. Their synthesis is based on unique self-assembly processes between surfactants and silica. In order to take advantage of the perfectly adjustable texture of MTS in chromatographic applications, their particle morphology has to be tailored at the micrometer scale. We developed a synthesis strategy to control the particle morphology of MTS using the concept of pseudomorphic transformation. Pseudomorphism was recognized in the mineral world to gain a mineral that presents a morphology not related to its crystallographic symmetry group. Pseudomorphic transformations have been applied to amorphous spherical silica particles usually used in chromatography as stationary phases to produce MTS with the same morphology, using alkaline solution to dissolve progressively and locally silica and reprecipitate it around surfactant micelles into ordered MTS structures. Spherical beads of MTS with hexagonal and cubic symmetries have been synthesized and successfully used in HPLC in fast separation processes. MTS with a highly connected structure (cubic symmetry), uniform pores with a diameter larger than 6 nm in the form of particles of 5 ,m could compete with monolithic silica columns. Monolithic columns are receiving strong interest and represent a milestone in the area of fast separation. Their synthesis is a sol-gel process based on phase separation between silica and water, which is assisted by the presence of polymers. The control of the synthesis of monolithic silica has been systematically explored. Because of unresolved yet cladding problems to evaluate the resulting macromonoliths in HPLC, micromonoliths were synthesized into fused-silica capillaries and evaluated by nano-LC and CEC. Only CEC allows to gain high column efficiencies in fast separation processes. Capillary silica monolithic columns represent attractive alternatives for miniaturization processes (lab-on-a chip) using CEC. [source] Investigation of the Structural Characterization of Mesoporous Molecular Sieves MCM-41 from SepioliteJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 3 2007Shengming Jin Mesoporous molecular sieves, MCM-41, were synthesized from sepiolite using acid leaching, followed by hydrothermal reconstruction and then calcinations at 540°C for 5 h. The structures and the porosity of MCM-41 were investigated by means of small-angle X-ray diffraction patterns, Brunaer-Emmett-Teller (BET), 29Si MAS NMR, Fourier transform infrared (FTIR), and high resolution transmission electron microscope (HRTEM) methods. The results showed that the hexagonal MCM-41 was formed in an alkaline solution of pH 12, when crystallization was carried out at 100°C for 24 h. The specific surface area, pore diameter, and pore volumes of MCM-41 from sepiolite were 1036 m2/g, 2.98 nm, and 1.06 cm3/g, respectively. 29Si MAS NMR results revealed that amorphous silica decomposed into Si,O chains consisting of two layers of Si atoms, with Q3 configurations resulting in an increase in the fraction of Q3 configuration during the crystallization of post-Mg-extraction sepiolite. The IR results illustrated that the complex of ,,SiO,,CTA+ was formed during the synthesis of MCM-41 from post-Mg-extraction sepiolite. [source] Chemiluminescent assay of alkaline phosphatase using dihydroxyacetone phosphate as substrate detected with lucigeninLUMINESCENCE: THE JOURNAL OF BIOLOGICAL AND CHEMICAL LUMINESCENCE, Issue 1 2002Amane Kokado Abstract A sensitive and simple chemiluminescent assay (CL) for alkaline phosphatase (ALP) using dihydroxyacetone phosphate or its ketal (DHAP or DHAP-ketal) was developed. New substrates were transformed to dihydroxyacetone (DHA) after they were hydrolysed by ALP, which reacts with lucigenin and produces strong chemiluminescence. Under the optimum assay condition, the detection limits were 3.8,×,10,19 and 1.5,×,10,18 moles of ALP, respectively. The coefficients of variation (CV) at each points on the standard curve were 0.8,5.4% and 1.8,7.1% (n,=,6), respectively. The mechanism of lucigenin CL with DHA was investigated by ESR spectrometry using the spin-trapping method. The mechanism was speculated as follows: the O2, generated by the reaction of DHA and O2 in alkaline solution reacts with lucigenin, and then emit light. The proposed CL assay was applied to the enzyme immunoassay of 17,-oestradiol, using ALP as a label enzyme. The measurable range of 17,-oestradiol was 15,4000,pg/mL, and the proposed method was four times more sensitive than the colorimetric assay for ALP by using 4-nitrophenyl phosphate as substrate. Copyright © 2002 John Wiley & Sons, Ltd. [source] Leaching characteristics of heavy metals in fly ash from a Chinese coal-fired power plantASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 2 2010Xun Gong Abstract China is the largest coal ash producer in the world. Hydraulic ash transport systems are used in most coal-fired power plants, which lead to serious water pollution due to leaching of trace elements. The investigation on the leaching behavior of trace contaminants from coal ash is critical to environmental risk assessments. Batch leaching tests have been performed on the fly ash collected from each field of the electrostatic precipitator (ESP) of a coal-fired power plant to study the leaching characteristics of Cd, Cr, Pb and V. Leaching solutions included HCl solution of initial pH = 4 and NaOH solution of pH = 10. The liquid/solid (L/S) ratio was about 4:1 in all leaching tests. Fourteen leaching time intervals were selected, ranging from 15 min to 7 days. The results show that under studied experimental conditions, Cr has a relatively higher leachability in the acid-leaching solution, while Pb has a higher leachability in the alkaline solution. With the increase of leaching time, the leachability of Cr in each ash sample increases obviously. Within the same time interval, Cr in the ash sample from the last field of ESP has the highest leachability. The concentration of Cd in FA3 is the highest, but the leachability of Cd for FA3 is not the highest among the three ash samples. The concentration of V in FA1 is the highest; no increased trend with leaching time has been found in the experiment. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Amelioration of Cyclosporine A-Induced Renal, Hepatic and Cardiac Damages by Ellagic Acid in Rats,BASIC AND CLINICAL PHARMACOLOGY & TOXICOLOGY, Issue 2 2008Abdurrauf Yüce Cyclosporine A also causes a dose-related decrease in body functions in experimental animals and human beings. The generation of reactive oxygen species has been implicated in cyclosporine A-induced dysfunctions. The aim of this study was to determine the effects of ellagic acid on cyclosporine A-induced alterations in the kidney, liver and heart oxidant/antioxidant system. The control group was treated with placebo and subcutaneous injection of 0.5 ml isotonic saline + 0.5 ml slightly alkaline solution for 21 days. The cyclosporine A group received a subcutaneous injection of cyclosporine A (15 mg/kg) + 0.5 ml slightly alkaline solution for 21 days. The ellagic acid group was treated with a subcutaneous injection of 0.5 ml isotonic saline + ellagic acid (10 mg/kg) for 21 days. The cyclosporine A plus ellagic acid group received a subcutaneous injection of cyclosporine A + ellagic acid for 21 days. Ellagic acid and slightly alkaline solution were administered by gavage. The rats were killed at the end of the treatment period. Malondialdehyde (MDA) and reduced glutathione (GSH) levels, glutathione peroxidase (GSH-Px) and catalase (CAT) activities were determined in kidney, liver and heart tissues. While administration of cyclosporine A increased the MDA levels in kidney, liver and heart tissues, it decreased the GSH, GSH-Px and CAT in these samples when compared to the control group. However, the simultaneously administration of ellagic acid markedly normalized the cyclosporine A-induced liver and heart MDA levels, liver CAT activities and GSH-Px activities of all samples. Cyclosporine A caused marked damages in the histopathological status of kidney, liver and heart tissues, which were partially ameliorated by ellagic acid administration. In conclusion, ellagic acid may be used in combination with cyclosporine A in transplantation treatment to improve the cyclosporine A-induced oxidative stress parameters and other adverse effects. [source] "Setting paint" analogy for the hydrophobic self-association of tropoelastin into elastin-like hydrogelBIOPOLYMERS, Issue 5 2009Christoph Naumann Abstract Alkaline tropoelastin solutions (pH 11) were optically clear at low temperatures, but a firm gel formed when the temperature was raised to 37°C. Reversion to a clear solution took place if the temperature was lowered to below 20°C within less than 2 h, but not if 37°C was maintained for several hours. The precipitated elastin-like hydrogel thus formed did not visually redissolve at low temperatures. Tropoelastin hydrogel was stable to subsequent washings with alkaline solution at 37°C, but at 4°C some hydrogel redissolved showing that association is at least partly reversible. Washing the hydrogel with neutral 8M urea solution at 4°C dissolved less than 10% of tropoelastin in 24 h. We characterized this phenomenon by combining temperature-controlled light microscopy analysis, 1H NMR spectroscopy (temperature, diffusion, and relaxation time studies), and UV-absorption-based concentration measurements. The self-association of tropoelastin at pH 11 is due to hydrophobic interactions in an emulsion-like system in which the spherules coalesce in a manner like a water-based latex paint that forms a durable hydrophobic sheet as water and the organic solvent evaporate. In the present case, the sedimentation and entanglement of the tropoelastin porous sheets means that reverse dissolution is a kinetically slow process. © 2009 Wiley Periodicals, Inc. Biopolymers 91: 321,330, 2009. This article was originally published online as an accepted preprint. The "Published Online" date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com [source] Intensification of Rate of Diffusion Controlled Reactions in a Parallel Plate Electrochemical Reactor Stirred by a Curtain of Electrochemically Generated Gas BubblesCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 10 2007G. H. Sedahmed Abstract Rates of mass transfer were measured at a vertical plate stirred by a rising curtain of oxygen bubbles generated electrochemically at an upstream plate by measuring the limiting current of the cathodic reduction of K3Fe(CN)6 in alkaline solution. The rate of mass transfer was found to increase over the natural convection value by a factor ranging from 2.4 to 25 compared to the previously reported range of 2,5 in the case of copper deposition from acidified solutions. The high tendency of oxygen bubbles to coalesce in alkaline solutions is believed to be responsible for the high rates of mass transfer in alkaline solutions. The rate of mass transfer at a plate stirred by a curtain of oxygen bubbles was found to decrease with increasing plate height and electrolyte concentration. Curtains of H2 bubbles were found to be less effective in enhancing the rate of mass transfer compared to that of oxygen. Practical application of the results in designing a modified parallel plate electrochemical reactor stirred by a counterelectrode gas curtain was highlighted. The suggested design has the potential of saving part or all of the mechanical stirring energy as well as floor space since it extends vertically. [source] Determination of Epinephrine by Flow Injection Analysis Coupled Ag(III) Complex-Luminol Chemiluminescence DetectionCHINESE JOURNAL OF CHEMISTRY, Issue 4 2009Jiangbo BAI Abstract A new Ag(III) complex-luminol chemiluminescent system which was applied to the determination of epinephrine is firstly reported. Based on the enhancing effect of epinephrine on the chemiluminescence reaction of luminol with [Ag(HIO6)2]5, in alkaline solution, a highly sensitive chemiluminescence (CL) detection by flow injection analysis (FIA) was developed for epinephrine. Under the optimum conditions, CL intensity was proportional to concentration of epinephrine in the 1.0×10,9,1.0×10,7 mol·L,1 range. The limit of detection was 8.0×10,10 mol·L,1 for epinephrine (3,), with a relative standard deviation (n=11) of 2.9% for 1.5×10,8 mol·L,1 epinephrine. The method validation was done with epinephrine determinations in commercial pharmaceutical products. The mechanism of the reactions was also discussed. [source] A Convenient and Environmentally Benign Method of Reducing Aryl Ketones or Aldehydes by Zinc Powder in an Aqueous Alkaline SolutionCHINESE JOURNAL OF CHEMISTRY, Issue 5 2007Chao-Zhi Zhang Abstract A convenient and environmentally benign method for reducing the carbonyl group in hydroxy- and amino- 9,10-anthracenediones, ortho (or para) acyl phenols and acyl anilines to a methylene group by zinc powder in an aqueous sodium hydroxide solution was reported. Based on theoretical calculations using the density functional theory (DFT), the mechanism of these reduction reactions was postulated. This mechanism can be applied to help predicting the reduced products of aryl ketones (or aldehydes) in an alkaline solution. [source] Synthesis and Electrochemical Properties of Semicrystalline Gyroidal Mesoporous MnO2CHINESE JOURNAL OF CHEMISTRY, Issue 7 2006Qin Zhou Abstract Mesoporous silica KIT-6 has novel three-dimensional gyroidal channel structure, space group of Ia-3d, and ordered tunable pores up to 10 nm. In this paper, such mesostructured silica was employed as hard template to prepare semicrystalline gyroidal mesoporous MnO2. The structure was investigated by XRD, TEM and HRTEM, and found to be of high quality Ia- 3d symmetry, in good accordance with the template structure. The material has a BET surface of 118 m2·g -1 and pore volume of 0.35 cm3·g,1 after eliminating template. Mesoporous MnO2 has shown good electrochemical property as supercapacitor material in 1 mol·L,1 Na2SO4 and 1 mol·L,1 LiClO4 solutions, but interesting pseudocapacitance behavior was observed in the case of 6 mol·L,1 KOH. It was found that mesoporous MnO2 performed stable reversible electrochemical behavior with capacitance of 220 F·g,1 in a potential range of ,0.1,0.55 V vs. Hg/HgO in alkaline solution, demonstrating that it is a promising novel electrode material for the fabrication of electrochemical capacitors. [source] The Determination of Methanol Using an Electrolytically Fabricated Nickel Microparticle Modified Boron Doped Diamond ElectrodeELECTROANALYSIS, Issue 5 2010Kathryn Abstract A nickel modified boron doped diamond (Ni-BDD) electrode and nickel foil electrode were used in the determination of methanol in alkaline solutions. The Ni-BDD electrode was electrodeposited from a 1,mM Ni(NO3)2 solution (pH,5), followed by repeat cycling in KOH. Subsequent analysis utilised the Ni(OH)2/NiOOH redox couple to electrocatalyse the oxidation of methanol. Methanol was determined to limits of 0.3,mM with a sensitivity of 110,nA/mM at the Ni-BDD electrode. The foil electrode was less sensitive achieving a limit of 1.6,mM and sensitivity of 27,nA/mM. SEM analysis of the electrodes found the Ni-BDD to be modified by a quasi-random microparticle array. [source] Electrocatalytic Oxidation of Sulfur Containing Amino Acids at Renewable Ni-Powder Doped Carbon Ceramic Electrode: Application to Amperometric Detection L -Cystine, L -Cysteine and L -MethionineELECTROANALYSIS, Issue 21 2006Abdollah Salimi Abstract A sol-gel technique was used here to prepare a renewable carbon ceramic electrode modified with nickel powder. Cyclic voltammograms of the resulting modified electrode show stable and a well defined redox couple due to Ni(II)/Ni(III) system with surface confined characteristics. The modified electrode shows excellent catalytic activity toward L -cystine, L -cysteine and L -methionine oxidation at reduced overpotential in alkaline solutions. In addition the antifouling properties at the modified electrode toward the above analytes and their oxidation products increases the reproducibility of results. L -cystine, L -cysteine and L -methionine were determined chronoamperometricaly at the surface of this modified electrode at pH range 9,13. Under the optimized conditions the calibration curves are linear in the concentration range 1,450,,M, 2,90,,M and 0.2,75,,M for L -cystine, L -methionine and L -cysteine determination, respectively. The detection limit and sensitivity were 0.64,,M, 3.8,nA/ ,M for L -cystine, 2,,M, 5.6,nA/ ,M for L -methionine and 0.2,,M and 8.1,nA/,M for L -cysteine. The advantageous of this modified electrode is high response, good stability and reproducibility, excellent catalytic activity for oxidation inert molecules at reduced overpotential and possibility of regeneration of the electrode surface by potential cycling for 5,minutes. Furthermore, the modified electrode has been prepared without using specific reagents. This sensor can be used as an amperometric detector for disulfides detection in chromatographic or flow systems. [source] | ||||||||||||||||||||||||||||||||||