bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electroanalysis of Bromate, Iodate and Chlorate at Tungsten Oxide Modified Platinum Microelectrode Arrays
Authors: Ordeig Olga , Banks Craig E. , Del Campo Fco. Javier , Muñoz Francesc Xavier , Compton Richard G. 
Published: August 2006

AbstractThis article describes the direct detection of Bromate, but also of chlorate and iodate, using modified arrays of platinum ultramicroelectrodes. The detection limits for these ions are IO$\rm{ {_{3}^{-}}}$=0.76 μM; BrO$\rm{ {_{3}^{-}}}$=2.34 μM and ClO$\rm{ {_{3}^{-}}}$=133.2 μM. The formation of a suitable tungsten oxide layer and the optimum analytical conditions are described. These oxide layers are formed electrochemically from hydrogen peroxide‐tungstanate solutions in acid conditions. Although film stability may be an issue, particularly at pH>3, these modified arrays of microelectrodes can be used for analytical purposes. After the analysis, the modifying oxide is easily removed and the Pt microelectrode array recovers its original properties.
Enantioselective, Potentiometric Memberane Electrodes Based on Different Cyclodextrins as Chiral Selectors for the Assay of S‐Flurbiprofen
Authors: Stefan‐van Staden Raluca‐Ioana , Bokretsion Rahel Girmai , Ozoemena Kenneth I , van Staden Jacobus Frederick , Aboul‐Enein Hassan Y. 
Published: August 2006

AbstractFour enantioselective, potentiometric membrane electrodes (EPMEs) based on carbon paste impregnated with α‐, β‐, 2‐hydroxyl‐3‐trimethylammoniopropyl‐β‐(as chloride salt) and γ‐cyclodextrins, were proposed as a chiral selectors for assay of S‐flurbiprofen raw materials and in its pharmaceutical formulation Froben 100 tablets. The best response was obtained when β‐cyclodextrin was used for the electrode design. The four EPMEs showed very low detection limits (of 10−8 to 10−9 mol/L magnitude orders). The surfaces of the electrodes are easily renewable by simply polishing on an alumina paper.
A Bipartite Expression for the Transient Amperometric Current at a Membrane Covered Planar Electrode to Characterize Solute Diffusion Through the Membrane
Authors: Rong Zimei , Rashid Sarah , Vadgama Pankaj 
Published: August 2006

AbstractA simple bipartite expression for transient amperometric currents at a membrane covered planar electrode has been derived. This expression is uniquely applicable across the entire measurement time frame and enables a rapid, comprehensive dynamic simulation of solute diffusion through the membrane barrier. The effective diffusion coefficient through the membrane for an electrochemically active solute can be readily obtained by employing the simple curve fitting routine. The diffusion coefficients for 4‐acetaminophenol through 0.05 and 0.025 μm pore diameter mixed cellulose esters membranes were determined to be 1.96×10−7 and 1.21×10−7 cm2/s, respectively. For catechol respective values were 1.55×10−7 and 1.15×10−7 cm2/s. Diffusion coefficients were reduced following membrane exposure to bovine serum albumin and this change provided a functional counterpart to conventional structural measures of surface biofouling. The approach has relevance to both sensors and membrane separation systems in biomedicine, and has the potential to offer a rapid assessment of membrane surface biofouling.
A Peroxidase‐Based Biosensor Supported by Nanoporous Magnetic Silica Microparticles for Acetaminophen Biotransformation and Inhibition Studies
Authors: Yu Donghui , Renedo Olga Dominguez , Blankert Bertrand , Sima Veronica , Sandulescu Robert , Arcos J. , Kauffmann Jean‐Michel 
Published: August 2006

AbstractMagnetized nanoporous silica based microparticles (MMPs) were used for horseradish peroxidase (HRP) immobilization and applied for amperometric peroxidase‐based biosensor development. A magnetized carbon paste electrode permitted the MMPs attraction. The biosensor was applied to the investigation of the enzymatic oxidation of acetaminophen (paracetamol). The biosensor operated at low applied potential and the signal corresponded to the electroreduction of N‐acetylbenzoquinoneimine (NAPQI) generated by the enzyme HRP in the presence of hydrogen peroxide. The biosensor allowed performing the quantitation of acetaminophen in the micromolar concentration range and the comparative study of thiols which inhibited the biosensor response. Distinct inhibition results were observed for HRP entrapped in the silica microparticles compared to the soluble HRP.
Amperometric Electronic Tongue for the Evaluation of the Tea Astringency
Authors: Scampicchio Matteo , Benedetti Simona , Brunetti Barbara , Mannino Saverio 
Published: August 2006

AbstractA new multi‐flow‐through amperometric detectors design was employed as a sensors array system for the detection of flavor related phenols. Relevant parameters of the amperometric detection were examined and optimized. The multivariate analytical signal was processed with chemometric analysis for exploring and classifying the tea beverages. Multivariate regression was used to correlate the astringency value of several tea beverages, obtained by the UNI (Italian Organization for Standardization) sensory profile test, with the signals collected by this amperometric electronic tongue.
Morphology of the Itapeva to Tramandai transgressive dunefield barrier system and mid‐ to late Holocene sea level change
Authors: Hesp Patrick A. , Dillenburg Sergio Rebello , Barboza Eduardo Guimaraes , Clerot Luiz C. P. , Tomazelli Luiz J. , Norberto Ayup Zouain Ricardo 
Published: August 2006

AbstractThe surface morphology of the transgressive dunefield barrier extending from Itapeva to Tramandai along the northern littoral of Rio Grande do Sul, is examined and an attempt is presented to link morphological changes across the barrier to Holocene sea level changes. The 4·5 km wide Holocene barrier displays two typical morphologies: an inner part dominated by large‐scale, continuous alongshore, overlapping dunefield phases comprising sand sheets, dunes, deflation plains and precipitation ridges; and an outer part dominated by discontinuous, medium‐ to small‐scale, triangular to lobate transgressive dunefield phases, cut by both active and relict (palaeo‐) creeks or washouts. Holocene sea level in the region rose to c. +1 to +3 m above present reaching a maximum around 5100 years bp and then progressively fell to the present level. We argue that the effect on barrier development was to suppress the development of a drainage system during the rising and maximum stages, and encourage the development of an organized drainage system in the form of regularly spaced washouts during the falling period, and that this change in sea level from rising to falling therefore produced the large‐scale differences in barrier morphology. Copyright © 2006 John Wiley & Sons, Ltd.
Temperature Dependence of Oxygen Reduction Catalyzed by Cobalt Fluoro‐Phthalocyanine Adsorbed on a Graphite Electrode
Authors: Song C. , Zhang L. , Zhang J. , Wilkinson D. P. , Baker R. 
Published: August 2006

AbstractThe graphite electrode surface onto which cobalt(II) 1,2,3,4,8,9,10,11,15,16,17,18,22,23,24,25‐hexadecafluoro‐29H,31H‐phthalo‐cyanine (abbreviated as CoIIHFPC) is adsorbed displays a strong electrocatalytic activity toward O2 reduction. The electrochemical response of surface adsorbed CoIIHFPC is investigated at different pHs and temperatures by cyclic voltammetry. The kinetics of the catalyzed O2 reduction at different temperatures, measured by cyclic voltammetric and rotating disk electrode methods, is analyzed and a corresponding reaction mechanism is proposed. A two‐electron/two‐proton process is found to be the dominating pathway for CoIIHFPC catalyzed O2 reduction. The increase in temperature, from 20 to 70 °C, enhances the reduction rate significantly. The presence of methanol has no effect on its catalytic activity towards O2 reduction. The implications of using this non‐noble electrocatalyst for the cathode reaction in low temperature fuel cells, including direct organic, metal‐air fuel cells, etc., are discussed in this paper.
Tubular Cathode Prepared by a Dip‐Coating Method for Low Temperature DMFC
Authors: Shao Z.‐G. , Lin W.‐F. , Zhu F. , Christensen P. A. , Zhang H. 
Published: August 2006

AbstractA novel tubular cathode for the direct methanol fuel cell (DMFC) is proposed, based on a tubular titanium mesh. A dip‐coating method has been developed for its fabrication. The tubular cathode is composed of titanium mesh, a cathode diffusion layer, a catalyst layer, and a recast Nafion® film. The titanium mesh is present at the inner circumference of the diffusion layer, while the recast Nafion® film is at the outer circumference of the catalyst layer. A DMFC single cell with a 3.5 mgPt cm–2 tubular cathode was able to perform as well, in terms of power density, as a conventional planar DMFC. A peak power density of 9 mW cm–2 was reached under atmospheric air at 25 °C.
Accurate evaluation of the absorption maxima of retinal proteins based on a hybrid QM/MM method
Authors: Matsuura Azuma , Sato Hiroyuki , Houjou Hirohiko , Saito Shino , Hayashi Tomohiko , Sakurai Minoru 
Published: August 2006

AbstractHere we improved our hybrid QM/MM methodology (Houjou et al. J Phys Chem B 2001, 105, 867) for evaluating the absorption maxima of photoreceptor proteins. The renewed method was applied to evaluation of the absorption maxima of several retinal proteins and photoactive yellow protein. The calculated absorption maxima were in good agreement with the corresponding experimental data with a computational error of <10 nm. In addition, our calculations reproduced the experimental gas‐phase absorption maxima of model chromophores (protonated all‐trans retinal Schiff base and deprotonated thiophenyl‐p‐coumarate) with the same accuracy. It is expected that our methodology allows for definitive interpretation of the spectral tuning mechanism of retinal proteins. © 2006 Wiley Periodicals, Inc. J Comput Chem, 2006
Computational study of the process of hydrogen bond breaking: The case of the formamide–formic acid complex
Authors: Pacios Luis F. 
Published: August 2006

AbstractMP2/6‐311++G(d,p) and B3LYP/6‐311++G(d,p) quantum calculations are used to study the formamide–formic acid complex (FFAC), a system bound by two hydrogen bonds, NH···O and OH···O, that forms a bond ring at equilibrium. When the intermolecular separation between monomersRincreases, this ring opens at a distance for which the weaker NH···O bond breaks remaining the stronger OH···O bond. The computational study characterizes that process addressing changes of interaction energy ΔE, structure and properties of the electron density ρ(r) as well as spatial distributions of ρ(r), the electrostatic potentialU(r), and the electron localization function η(r). It is shown that the spatial derivatives of ΔE, the topology of ρ(r), and qualitative changes noticed inU(r) = 0 isocontours allow to identify a precise distanceRfor which one can say the NH···O hydrogen bond has broken. Both levels of theory predict essentially the same changes of structure and electron properties associated to the process of breaking and virtually identical distances at which it takes place. © 2006 Wiley Periodicals, Inc. J Comput Chem, 2006
Variation of atomic charges on proton transfer in strong hydrogen bonds: The case of anionic and neutral imidazole–acetate complexes
Authors: Pacios Luis F. , Gómez Pedro C. , Gálvez Oscar 
Published: August 2006

AbstractThe variation of atomic charges upon proton transfer in hydrogen bonding complexes of 4‐methylimidazole, in both neutral and protonated cationic forms, and acetate anion, is investigated. These complexes model the histidine (neutral and protonated)–aspartate pair present in active sites of proteases where strong NH···O hydrogen bonds are formed. Three procedures (Merz–Kollman scheme, Natural Population Analysis, and Atoms in Molecules Method) are used to compute atomic charges and explore their variation upon H‐transfer in the gas phase and in the presence of two continuum media with dielectric constants 5 (protein interiors) and 78.39 (water). The effect of electron correlation was also studied by comparing Hartree–Fock and MP2 results for both complexes in the gas phase. Greater net charge interchanged upon H‐transfer is observed in the anionic complex with respect to the neutral complex. Raising the polarity of the medium increases the amount of net charge transfer in both complexes, although the neutral system exhibits a larger sensitivity to the presence of solvent. Charge transfer associated to NH···O and N···HO bonds reveal the ionic contribution to the interaction depending on the number of charged subunits but the presence of solvent affects little this quantity. The lack of electron correlation overestimates all the charges as well as their variations and so uncorrelated calculations should be avoided. © 2006 Wiley Periodicals, Inc. J Comput Chem, 2006
The effect of the time and mode of application of gibberellic acid on the growth and yield of potato plants derived from true potato seed
Authors: Alexopoulos Alexios A , Akoumianakis Konstantinos A , Passam Harold C 
Published: August 2006

AbstractThe effect of the time and mode of treatment (single or repeated applications) of gibberellic acid (GA3) on the growth and tuberisation of plants grown from true seed (TPS) of potato Chacasina F1 was studied. Plant height, fresh and dry weight of stems and leaf dry weight increased in response to single or repeated GA3 applications. Leaf colour was not affected by single applications of GA3, whereas repeated applications caused a reduction in colour intensity. The numbers of secondary shoots and leaves per plant as well as total leaf area were largely unaffected by GA3, although repeated applications from early in the growth cycle increased these parameters under conditions of decreasing photoperiod. When applied as a single dose during spring, GA3 caused an increase in the number of tubers per plant, with a concomitant decrease in tuber dry matter content, irrespective of application date. In autumn the number of tubers per plant increased following single applications of GA3 up to 50 days after transplantation, whereas tuber dry matter decreased. By contrast, repeated applications of GA3 in both seasons increased tuber number only when initiated early in the growth cycle. The mean weight of tubers per plant was variably affected by GA3 application, depending on the season, time and mode of application. It is suggested that the foliar application of GA3 to plants from TPS at an early stage of vegetative development may be of value for seed tuber or micro‐tuber production, primarily by increasing the number of tubers produced per plant. Copyright © 2006 Society of Chemical Industry
Positive solutions and multiple solutions for periodic problems driven by scalar p ‐Laplacian
Authors: Hu Shouchuan , Papageorgiou N. S. 
Published: August 2006

AbstractIn this paper we study a nonlinear second order periodic problem driven by a scalar p ‐Laplacian and with a nonsmooth, locally Lipschitz potential function. Using a variational approach based on the nonsmooth critical point theory for locally Lipschitz functions, we first prove the existence of nontrivial positive solutions and then establish the existence of a second distinct solution (multiplicity theorem) by strengthening further the hypotheses. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical algorithms for cyclic phase transformation hysteresis in a shape memory plate subject to axisymmetric plane stress
Authors: Chi Yuwei , Pence Thomas J. , Tsai Hungyu 
Published: August 2006

AbstractWe present numerical algorithms for calculating stress fields in an annulus composed of a shape memory material under conditions of quasi‐static edge loading at constant temperature. The algorithms track the material microstructure in terms of the volume fraction of austenite (A) and martensite (M), the latter of which provides a transformation strain. The dependence on load path imparts significant hysteresis in the stress induced transformation between A and M. A previous study that was restricted to proportional loading in the direction of forward transformation (J. Appl. Mech. 2005; 72:44–53) is here generalized to consider arbitrary loadings. The shooting algorithm that was robust for the previously considered proportional loadings is found to be subject to numerical instability for the most general transformation possibilities considered here. This motivates the development of an alternative iterated mapping algorithm that is found to generate a robust semi‐analytical finite difference procedure. The algorithm efficiently determines the operative transformation type, as is illustrated in cases where forward and reverse loading are occurring simultaneously at different plate locations. At those locations where phase transformation is inactive, the algorithm continues to account for martensite reorientation that alters the local transformation strain. Copyright © 2006 John Wiley & Sons, Ltd.
A generalization of the method of incompatible modes
Authors: Bischoff Manfred , Romero Ignacio 
Published: August 2006

AbstractA generalization of the classical method of incompatible modes is presented, containing the original formulation as a special case. The method constitutes a class of finite elements which is equivalent to the class of enhanced assumed strain elements, yet based on a pure displacement formulation. Copyright © 2006 John Wiley & Sons, Ltd.
Finite element formulations for transient dynamic analysis in structural systems with viscoelastic treatments containing fractional derivative models
Authors: Cortés Fernando , Elejabarrieta María Jesús 
Published: August 2006

AbstractThis paper presents finite element formulations for transient dynamic analysis in structural systems with damping treatments in which viscoelastic materials are characterized by means of fractional derivative models. In contrast to other formulations, such as that of Padovan employing the principle of virtual work, the proposed formulations begin from the local equation of linear momentum and make use of the weighted residual method, providing a matrix equation of motion involving fractional operators. The numerical approximations of these are developed through the Grünwald–Letnikov definition, which allows to formulate explicit and implicit numerical schemes.The principal advantage of the proposed formulations is that the history of the displacements and external forces must be stored, but not that of the stress, which reduces computational time and storage needs.Numerical applications are presented for a cantilever beam, where a viscoelastic treatment has been applied using damping material modelled by a five‐parameter fractional derivative model. The results of the proposed formulation are compared among them and with those of Padovan for different damping values and for different load cases. The influence of the truncation of Grünwald coefficients and of the integration time‐step is also investigated. Copyright © 2006 John Wiley & Sons, Ltd.
Organic ion exchangers as beads. Synthesis, characterization and applications
Authors: Dragan E. S. , Avram E. , Dinu M. V. 
Published: August 2006

AbstractTwo less explored strategies in the preparation of porous organic ion exchangers in bead form are presented in this paper: the preparation of macroporous strong base anion exchangers with N,N‐diethyl‐2‐hydroxyethyl benzylammonium chloride units, a less explored chloromethylation reagent of the styrene‐divinylbenzene copolymers being used, and the preparation of anion exchangers with primary amine groups by the aminolysis‐hydrolysis reaction with 1,2‐diaminoethane of the nitrile groups, contained in some porous copolymers of acrylonitrile‐divinylbenzene, followed by the carboxymethylation of the primary amine groups to prepare chelating ion exchangers. The influence of porogen nature, monomers dilution and crosslinking degree on the properties of the ion exchangers was examined. Structural characterization, functionalization‐morphology correlations, the ion exchange properties, and potential applications for the ion exchangers thus prepared have been discussed. Copyright © 2006 John Wiley & Sons, Ltd.
Preparation of a highly luminescent nanocomposite by chelating copolymer
Authors: Wang Cheng‐Chien , Chen An‐Liu , Chen I‐Han 
Published: August 2006

AbstractHighly luminescent hybrid CdS (diameter = 3–6 nm)/copolymer nanocomposites are prepared by using the soap‐free emulsion polymerization with chemical precipitation methods in this investigation. The core/shell type of ZnS/CdS nanoparticle on the shell layer of the copolymer microsphere can be obtained via the ion‐exchange method. The luminescent intensity and energy of the hybrid CdS/copolymer nanocomposite not only can be improved by increasing the pH value due to the surface passivated by the iminodiacetic acid sodium salt of the polymer side chain, but also can be enhanced by the higher band gap inorganic materials ZnS shell layer. In addition, the CdS nanoparticle passivated by inorganic shell ZnS is more robust than when organically passivation. Furthermore, these hybrid nanoparticles are easily employed to manufacture the transparent copolymer membrane at the film formation temperature (60°C), and they still keep their high luminescent property. Copyright © 2006 John Wiley & Sons, Ltd.
Synthesis and characterization of a π‐conjugated hybrid of oligothiophene and porphyrin
Authors: Oyaizu Kenichi , Hoshino Manabu , Ishikawa Masuhide , Imai Takuya , Yuasa Makoto 
Published: August 2006

Abstract5‐(3‐Thienyl)‐10,15,20‐triethyl‐21H,23H‐porphine (H2(ttep)) was synthesized and characterized. Oxidative polymerization of H2(ttep) gave a novel oligomeric porphyrin linked at the 2,5‐positions of the thienyl group. Electric conductivity of 4 × 10−1 S/cm after I2 doping indicated that the oligomer had a π‐conjugated structure with a delocalization of π electrons over the thienylene backbone. PM3 calculations revealed a low HOCO‐LUCO gap, which was consistent with the relatively high electric conductivity. Regioregular (head‐to‐tail) structure was inferred from spectroscopic and calculational results. The pendant porphyrin groups formed a regular J‐type array along the thienylene backbone, which was indicated by a significant red shift of the Soret band maximum. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5403–5412, 2006
Electroluminescence from a conjugated polymer grafted with CdSe/ZnS: High brightness and improved efficiency
Authors: Chen Kuei‐Bai , Chen Ming‐Hwey , Yang Sheng‐Hsiung , Hsieh Chao‐Hsiang , Hsu Chain‐Shu , Chen Chia‐Chun , Chien Hsiao‐Ju 
Published: August 2006

AbstractA new series of sulfide‐substituted poly(1,4‐phenylene vinylene) derivatives (S1PPV–S3PPV) with different composition ratios were successfully synthesized via the Gilch route. The CdSe/ZnS were grafted to the sulfur atoms by ligand exchange reaction. The grafted CdSe/ZnS contents were determined from TGA analysis to be from 4.6 to 37.8%. A new peak at 1151 cm−1 formed in FT‐IR after ligand exchange, which is attributed to the force formation between sulfur and CdSe. The GPC results show that the molecular weights of final polymers became higher after ligand exchange. Thin films of obtained polymers emitted bright green and yellow light with the max emission peak located from 546 to 556 nm. Double‐layer LEDs with an ITO/PEDOT/polymer/Ca/Al configuration were fabricated to evaluate the potential use of these polymers. The turn‐on voltages of the devices were about 4–5 V. As the CdSe/ZnS content increased in grafted polymers, the device performance was significantly enhanced as compared to pristine polymers. In the case of S3PPV, the double‐layer device showed a maximum luminance of 6073 cd/m2 with a current yield of 0.82 cd/A. The maximum luminance and current yield was enhanced to 13,390 cd/m2 and 2.25 cd/A by grafting CdSe/ZnS onto polymers. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5378–5390, 2006