bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrode reactions of 3,4‐dihydroxyphenylacetic acid (DOPAC) at glassy carbon, graphite‐reinforcement carbon, and carbon fiber electrodes
Authors: Sujaritvanichpong Surasak , Aoki Koichi
Published: February 2006

The voltammetric behavior of 3,4‐dihydroxyphenylacetic acid (DOPAC) in a phosphate buffer solution (pH 7.4) was investigated at untreated and electrochemically treated glassy carbon (GC), graphite reinforcement carbon (GRC), and carbon fiber (CF) electrodes. Except for the pretreated GRC, all of the electrodes exhibit a well‐defined anodic wave (Aa) at approximately 0.25–0.5 V vs. SCE. The untreated and the pretreated GC electrodes yielded irreproducible behavior compared to the GRC electrode. Transfer coefficients and the charge transfer rate constant were evaluated from variations of the peak potential with the potential sweep rate. The peak current was controlled by both diffusion and the sluggish charge transfer process. Similar results were obtained at weakly pretreated CF electrodes. As the level of the pretreatment for the CF electrode was raised up by applying more anodic potential, wave Aa decreased and new anodic and cathodic waves, B and C, appeared at 0.1 and 0.27 V, respectively, versus SCE. Wave B was ascribed to the adsorption of DOPAC. Amounts of the adsorbed species increased with the time the electrode was immersed in the solution and then tended to the steady‐state value. They were subjected to the Langmuir adsorption isotherm. A value of the saturated adsorption was 0.89 × 10−9 mol/cm2 and the adsorption coefficient was 1.63/mmol/dm3.
Pretreatment of glassy carbon electrodes by anodic galvanostatic pulses with a large amplitude
Authors: Mattusch Jürgen , Hallmeier Karl‐Heinz , Štulík Karel , Pacáková Věra
Published: February 2006

Glassy carbon electrodes (GCEs) can be activated by the passage of large‐amplitude (for example, 20‐mA) anodic galvanostatic pulses with durations shorter than 1 second. The increased activity stems from an increase in the rate of charge‐transfer reactions and from the adsorption accumulation of the analytes on the electrode surface, which is demonstrated for catecholamines and ascorbic acid. As demonstrated by X‐ray photoelectron and fast‐atom‐bombardment mass spectrometry, the galvanostatic treatment leads to an increase in the amount of chemisorbed oxygen. Scanning electron microscopy shows very small mechanical changes of the electrode surface. The activation effect depends on the composition of the test solution and the character of the analytes. There is an optimal electric charge that produces the highest electrode activity and lowers the limits of determination for catecholamines by approximately two orders of magnitude; on further increase in the charge, the electrode activity decreases (due to the formation of a thick layer of graphite oxide). The activation effects are less pronounced in flow‐through measurements. The method can be readily implemented for the periodic, automated reactivation of glassy carbon electrodes, but the optimal conditions must be found experimentally for various systems.
Application of second harmonic alternating current anodic stripping voltammetry in the simultaneous trace and ultra trace metal determination of a multicomponent system
Authors: Fagioli Francesco , Locatelli Clinio , Landi Silvio , Vecchietti Roberto
Published: February 2006

Second harmonic alternating current voltammetry coupled with anodic stripping techniques has been used for the simultaneous determination of lead(II), tin(II), and thallium(I) (elements which, in common supporting electrolytes exhibit similar half‐wave potentials). The supporting electrolyte was 0.1 M HClO4 for the Pb‐Tl couple with the subsequent addition of EDTA (0.02 M) for measuring the tin ion. Once conditions for the experimental measurements were optimized, calculation was done for the various concentration ratios for which one could determine one element in the presence of the other two; the maximum experimental error was 5%. These concentration (c) ratios were as follows: CSn : CPb = 43:1; CSn : CTl = 32:1 (HClO40.1 M)and CTl:CSn = 45:1; Ctl:CPb = 156:1 (HClO4 0.1 M plus EDTA 0.02 M). Precision and accuracy data (3–5%) are also reported and expressed, respectively, as the relative standard deviation and relative error. The detection limit for each element proved to be around 10−8 M. The standard addition technique improved the resolution of the alteranting current voltammetric method, even in the case of very high concentration ratios.
Mn(III)—porphyrin‐based thiocyanate‐selective membrane electrodes: Characterization and application in flow injection determination of thiocyanate in saliva
Authors: Brown D. V. , Chaniotakis N. A. , Lee I. H. , Ma S. C. , Park S. B. , Meyerhoff M. E. , Nick R. J. , Groves J. T.
Published: February 2006

The response properties of a new thiocyanate‐selective solvent‐polymeric membrane electrode are reported. The membrane contains (5,10,15,20‐tetrakis(2,4,6‐triphenylphenyl)porphyrinato)manganese(III) chloride (Mn[TPPP]CI) in a plasticized polyvinyl chloride matrix. The electrode deviates from the Hofmeister selectivity pattern by responding to thiocyanate preferentially over inorganic anions (perchlorate, chloride, iodide, and bromide) and several organic anions often present in biological samples (ascorbate, citrate, urate, and salicylate). The performance of this electrode as an ion‐selective detector in a low‐dispersion, flow‐injection system is also evaluated. While selectivity in such a nonequilibrium flow arrangement is found to be somewhat different than that observed under equilibrium conditions, the electrode's response and selectivity is still adequate to allow for measurement of thiocyanate in biological samples. This application is demonstrated via the flow‐injection analysis (FIA) detection of thiocyanate in 22 human saliva samples with good correlation to a classical colorimetric method (r = 0.981).
Electrochemical speciation analysis of metals at membrane‐coated electrodes
Authors: Morrison Gregory M. P. , Florence T. Mark
Published: February 2006

Speciation of model Cu complexes on the basis of size and charge was achieved by anodic stripping voltammetry (ASV) at mercury film electrodes (MFE) coated with Nafion or cellulose acetate Nafion (CANMFE). The Nafion‐coated MFE effectively excludes negatively charged Cu complexes, and evidence for the containment of the diffusion layer beneath the Nafion coating is provided. The CANMFE excludes complexes with molecular weights greater than 200, including the Cu‐fulvic acid complex, which is of particular interest for speciation in natural waters. Complexation titrations of fulvic acid with Cu show the unsuitability of differential pulse ASV for providing a realistic estimate of the end point (complexation capacity). Differential pulse polarography, which provides results more comparable with bioassays, can be used for the determination of complexation capacity. Results for the speciation analysis of coastal seawater and polluted fresh water are presented. The CANMFE is insufficiently sensitive for seawater analysis, but in polluted fresh water its use indicates that organic and inorganic complexes with molecular weights greater than 200 dominate the speciation for Cd (72%), Pb (96%), and Cu (> 99.8%).
Electrocatalysis and determination of hydrazine compounds at glassy carbon electrodes coated with mixed‐valent ruthenium(III, II) cyanide films
Authors: Wang Joseph , Lu Ziling
Published: February 2006

Chemically modified electrodes, which were constructed by anodizing glassy carbon electrodes in a RuCl3/K4Ru(CN)6 solution, are shown to catalyze the electrooxidation of hydrazine compounds in acidic and neutral media. The mixed‐valent ruthenium cyanide film offers improved stability and a broader operational pH range compared to previously described phthalocyanine‐catalytic surfaces. The catalytic response of hydrazine, methylhydrazine, and dimethylhydrazine is evaluated with respect to the film preparation conditions, solution pH, potential scan rate, concentration dependence, and other variables. Highly stable and sensitive flow injection measurements [with a relative standard deviation (RSD) of 1.4% (n = 30) and a detection limit of 0.13 ng] are described. A composite film prepared by the codeposition of polyaniline offers additional advantages.
Cyclic voltammetry of metal/polyelectrolyte complexes: Complexes of cadmium and lead with deoxyribonucleic acid
Authors: Séquaris J.‐M. , Esteban M.
Published: February 2006

Cyclic voltammetry was used for the determination of the association constants of Pb2+and Cd2+with deoxyribonucleic acid. The adsorption of the biological polyelectrolyte at the mercury electrode surface was controlled by the alternating current voltammetric method, which permits corrective factors to be introduced in the evaluation of cyclic voltammetric responses. The results are based on the analysis of the labile complexation of the slow‐diffusing DNA by studying the current intensity peak as well as the peak potential shift of Pb2+and Cd2+. The association constants (β) obtained from the two treatments are in satisfactory agreement. The dependence of the conditional association constant (β1) for the Cd‐DNA system on the monovalent ion (Na+) concentration is also reported.
Electrochemical investigations of thiocinnamide
Authors: Bǎnicǎ F. G. , Florea M. , Diacu Elena
Published: February 2006

The electrochemical behavior of thiocinnamamide in aqueous solutions with 5% (v/v) ethanol was studied by dc and ac polarography and cyclic voltammetry. In acidic media, the reduction of thiocinna mamide occurs in the adsorbed state, giving a single dc wave. In alkaline solutions, the reduction starts at the negative limit of the adsorption potential range and produces two poorly separated dc waves. The first corresponds to the reduction of the adsorbed molecules with a strong dependence of the adsorption coefficient on the electrode potential. The second is due to the irreversible reduction of nonadsorbed molecules. This reaction involves a slow chemical step. The reduction results in the fission of the carbon‐sulfur bond. Another reaction is the hydrolysis of adsorbed molecules (in the absence of any charge‐transfer step), giving the nitrile of cinnamic acid. This compound is also formed in the range of the anodic wave of thiocinnamamide.
Enhanced voltammetric waves of iron(III)—EDTA at a chitin‐containing carbon paste electrode and its analytical application
Authors: Bai Zhu‐Ping , Nakamura Toshio , Izutsu Kosuke
Published: February 2006

A chitin‐containing carbon paste electrode was found to give highly sensitive voltammetric waves for Fe(III)‐EDTA chelate both in cyclic voltammetry (CV) and in differential pulse voltammetry (DPV). Various conditions for the determination of trace Fe(III) were studied. The optimum chitin content in the carbon paste (graphite powder: mineral oil = 2:1) was 6% (by weight). In a solution of 0.01 M KCl and 3 × 10−4 M EDTA (pH 3.0), the DPV peak potential for the reduction of Fe(III)‐EDTA was −0.05 V vs. Ag/AgCl. The peak current was proportional to the Fe(III) concentration between 2 × 10−7 and 6.5 × 10−6 M; the relative standard deviation for 2 × 10−6 M Fe(III) was 2.6%. The method was fairly free from interference and could be applied to the determination of iron in both river and tap water.
Photomicroscopic measurement of the diffusion layer around mercury drop electrodes: Part II, choice of the optimal conditions
Authors: Tercier M.‐L , Buffle J.
Published: February 2006

The special electrochemical system described in Part I was employed to determine the optimum conditions for the deposition step of anodic stripping voltammetric techniques with a sessile Hg drop electrode. Much care was taken to obtain a reproducible reduction flux that is predictable on sound theoretical grounds and, in particular, to minimize the screening effects of the capillary. This article illustrates how this can be achieved by coupling optical microscopy, photography, and video recording with computer‐controlled voltammetry. This set up allows to simultaneously observe the dynamic movement of the water flux around a Hg drop electrode, observe and determine the diffusion layer thickness during the reduction, and record the chronopotentiometric current‐time curves as a function of the stirring rate and geometric conditions of the cell. The best conditions for obtaining a reproducible reduction flux at the electrode are given for a sessile Hg drop. The system described here, however, can be applied for the determination of diffusion and hydrodynamic conditions around electrodes having other configurations.
Single‐sweep polarographic determination of ammonia by its reaction with 1‐naphthol and hypochlorite
Authors: Zhao Zaofan , Mo Jianwei
Published: February 2006

A polarographic procedure is described for the determination of ammonia at concentration levels below 10−4 M that is based on its reaction with 1‐naphthol and hypochlorite in a strongly alkaline medium whose (1,4‐indonapthol) product is polarographically active. The polarographic behavior of the compound and the electrode process has been studied by several electrochemical methods. The experimental results showed that it is an EC process involving the formation of a radical as the electrode product that is followed by a disproportionation reaction of the radical. The rate constant (kf) of the coupled following chemical reaction was found to be 0.228 s−1. The wave height at −0.47 V [versus the standard calomel electrode (SCE)] on the dropping mercury electrode (DME) is directly proportional to the concentration of ammonia from 1 × 10−7 to 5 ×−5 M, and the detection limit is 5 × 10−8 M. A mercury film electrode can also be used for the determination of ammonia. The method has been applied to the analysis of water and serum samples.
Theory of stationary current—potential curves at interdigitated microarray electrodes for quasi‐reversible and totally irreversible electrode reactions
Authors: Aoki Koichi
Published: February 2006

Analytical equations for steady‐state current‐potential curves at interdigitated microarray electrodes (IDA) were derived by the conformal mapping of the complex variable theory when the electrode reaction was quasi‐reversible and totally irreversible. In this technique, curved current lines in the IDA could be transformed into a set of parallel lines, as in a thin‐layer cell at a faced twin electrode. The current‐potential curves were a function of ko(we + wg)/D and were almost independent of the geometrical parameter, wg/(we + wg), where ko is the reaction rate constant, we is the common width of each microband anode or cathode, wg is the width of the gap between the anode and the cathode, and D is the diffusion coefficient. The quasi‐reversible domain was 0.2 < ko(we + wg)/D < 10. A polaro‐graphic log plot for the current‐potential curve did not fall on a straight line except for the reversible wave. A modified log‐plot method is presented in which the current‐potential curve can be transformed into a straight line. The transfer coefficient and ko can be evaluated from this technique.
An experimental study of phase‐sensitive ac voltammetry in continuous‐flow streams—reversible systems
Authors: Kingsley Edward D. , Curran David J.
Published: February 2006

Fundamental harmonic ac voltammetry at flow‐by wall electrodes was found experimentally to be independent of the flow rate for rates from 0 to 2.1 L/min. Measurements were made with phase‐sensitive instrumentation. The ac peak current dependence on the concentration, the frequency and amplitude of the applied ac voltage, and the dc scan rate was the same in flowing or stationary solutions. The shape of the ac voltammogram was also not influenced by the flow rate. These results are general for experimental conditions that produce unrestricted diffusion and that maintain simple, reversible electron‐transfer mechanisms.
HPLC separation and square‐wave adsorptive‐stripping detection of human immunoglobulin G and A
Authors: Zhang Li Qun , Sturrock Peter E.
Published: February 2006

Human immunoglobulin G and A (IgG and IgA) were studied with square‐wave voltammetry. For IgG, three reduction peaks (HIGG1, HIGG2, and HIGG3) were observed under different conditions. HIGG1 and HIGG3 are strongly related to the pH of the buffer solution. In pH 7.5 phosphate buffer, the peak potential of HIGG2 is −0.58 V (vs. Ag/AgCl). A linear response holds for human IgG below 3.3 × 10−8 M (5 ppm). As little as 1.1 × 10−10 M (16 ppb) of human IgG is detectable after only 20 seconds of adsorptive accumulation in static solution.

IgA has two flat adsorptive‐stripping responses (HIGA1 and HIGA2). The sensitivity of IgA is much poorer compared to IgG. HIGA2 at −0.44 V can be observed throughout the tested pH range with the maximum response between pH 6.0–6.2. In a static solution, a linear calibration graph can be obtained for 0.8–16.8 ppm IgA.

IgG and IgA can be separated from each other by using HPLC with an AB × column. The response of 32 ppb IgG can be observed clearly. This research indicates the possibility of direct separation and detection of immunoglobulins from a real sample (e.g., human serum) by simply applying HPLC‐adsorptive‐stripping analysis.
Mechanism of electrochemical oxidation of trimethoprim at pyrolytic graphite electrode
Authors: Goyal R. N. , Kumar Anoop
Published: February 2006

The electrochemical oxidation behavior of trimethoprim has been investigated at a pyrolytic graphite electrode over a wide pH range (1.35–10.71). Below pH 3.2, trimethoprim is electrooxidized in two well‐defined steps, each involving 4e, 4H+. Only one well‐defined oxidation peak was observed above pH 3.5 however. Products corresponding to each peak have been separated and characterized by thin‐layer chromatography (TLC), infra red (IR), and mass spectra. A tentative mechanism associated with the voltammetric oxidation has been proposed to account for the observed experimental behavior. The same product has also been observed during the metabolic oxidation of trimethoprim in albino rats.
Determination of food additive azo dyes at an HMDE with adsorptive stripping voltammetry
Authors: Castrillejo Yolanda , Pardo Rafael , Barrado Enrique , Batanero Pedro Sánchez
Published: February 2006

Controlled adsorptive accumulation of the food additives (azo dyes) ponceau 4R, Allura Red, and carmoisine at a hanging mercury drop electrode (HMDE) provided the basis for their determination by stripping voltammetry at nanomolar concentration levels. The adsorptive stripping response was evaluated with respect to experimental parameters such as accumulation potential, preconcentration time, pH, and bulk concentration. Best results were obtained using an ammonia buffer as the supporting electrolyte; depending on the dye, detection limits of 0.071, 0.076, and 0.043 nM were, respectively, achieved in pure dye solutions. The simultaneous determination was carried out by means of the generalized standard addition method.
Amperometric flow‐injection analysis of L‐glutamate using an immobilized enzyme reactor: Amplification by substrate recycling
Authors: Yao Toshio , Kobayashi Naokazu , Wasa Tamotsu
Published: February 2006

An amperometric flow injection system with an immobilized enzyme reactor that gives responses amplified by substrate recycling was employed for the highly sensitive determination of L‐glutamate. An L‐glutamate oxidase/glutamic‐pyruvic transaminase coimmobilized reactor was incorporated at fixed positions in a flow system. In the presence of sufficient amounts of L‐alanine and oxygen in the carrier solution, L‐glutamate was repeatedly converted to 2‐oxoglutarate by L‐glutamate oxidase, and the 2‐oxoglutarate produced was subsequently converted back to L‐glutamate by glutamic‐pyruvic transaminase during the passage through the enzyme reactor. As a result of this recycling reaction, a large amount of hydrogen peroxide was produced in the reactor and could be detected amperometrically at a downstream platinum detector. L‐Glutamate was determined with a 20‐ to 30‐fold increase in sensitivity compared to the unamplified responses. The detection limit was 1 pmol of L‐glutamate.
Charge transfer across a conducting polypyrrole membrane separated by two electrolyte solutions
Authors: Wang Erkang , Liu Yuqing , Samec Z. , Dvořák C.
Published: February 2006

This article describes anion transfer across a conducting polypyrrole membrane (PPM) using cyclic voltammetry with a four‐electrode system. The transfer process of both chloride and nitrate anions across the polypyrrole membrane used to separate two pools of electrolyte solutions has been studied. A wide potential window beyond 3 V was obtained, and well‐developed voltammograms for the transfer of nitrate and chloride anions appeared within this window. The transfer process depends on the ion size, the ion charge, and the surface characteristics of the polypyrrole membrane. The one‐way transfer phenomenon observed in different potential‐bias directions can be explained by the asymmetrical ion channel model of the polypyrrole membrane.
Climate and pre‐Columbian settlement at Anse à la Gourde, Guadeloupe, Northeastern Caribbean
Authors: Beets C.J. , Troelstra S.R. , Grootes P.M. , Nadeau M.‐J. , Borg K. van der , Jong A.F.M. de , Hofman C.L. , Hoogland M.L.P.
Published: February 2006

The authors present a reconstruction of precipitation, seasonality, and vegetation cover over the period from 200 cal yr B.C. to 1600 cal yr A.D. for the archaeological site of Anse à la Gourde, Guadeloupe, based on the oxygen and carbon isotope composition of accelerator mass spectrometry (AMS) 14C‐dated aragonitic shells of the landsnail Bulimulus guadaloupensis. The results show that the Late Cedrosan Saladoid population (˜400–800 cal yr A.D.) disappeared at the beginning of a dry and stormy period lasting from 800 to 1000 cal yr A.D. The Mamoran Troumassoid started to populate the site around 1000 cal yr A.D. when the climate became wetter, and remained until ˜1300 cal yr A.D. The snail‐shell carbon isotope values changed significantly around the period that the Late Cedrosan Saladoid occupation started. This indicates a vegetational response either to the wetter conditions, or because of the replacement of existing C4 plant vegetation by introduced C3 crops. © 2006 Wiley Periodicals, Inc.
Extracellular matrix deposition by fibroblasts is necessary to promote capillary‐like tube formation in vitro
Authors: Berthod François , Germain Lucie , Tremblay Nathalie , Auger François A.
Published: February 2006

The contribution of the cellular and fibrillar microenvironment to angiogenesis still remains unclear. Our purpose was to evaluate the effect of the extracellular matrix deposited by fibroblasts on the capacity of human endothelial cells to form capillaries in vitro. We have drastically decreased the amount of extracellular matrix surrounding fibroblasts in our model of endothelialized‐reconstructed connective tissue (ERCT) by culturing it without ascorbate. Under these conditions, the number of capillary‐like tubes (CLT) formed by endothelial cells was reduced by up to 10‐fold after 31 days of culture compared to controls. This decrease was due neither to a variation of MMP‐2 and MMP‐9 secretion, nor to a reduction in the number of fibroblasts and/or endothelial cells, or a diminution of fibroblast growth factor 2 (FGF2) synthesis. The secretion of vascular endothelial growth factor (VEGF) by fibroblasts accounted for 25–70% of the capillary‐like tube formation when tissues were cultured in the presence or absence of ascorbate, as demonstrated by VEGF‐blocking studies. The culture of endothelial cells on a similar extracellular matrix but in the absence of living fibroblasts did not promote the formation of CLT, even when tissues were fed with fibroblast‐conditioned medium. Thus, the deposition of a rich extracellular matrix by living fibroblasts appeared necessary, but not sufficient to promote capillary‐like formation. Fibroblasts seem to induce endothelial cells to spontaneously form CLT by secreting and organizing an abundant extracellular matrix, which creates a microenvironment around cells that could in turn trap growth factors produced by fibroblasts and promote three‐dimensional cell organization. J. Cell. Physiol. 207: 491–498, 2006. © 2006 Wiley‐Liss, Inc.
RepairNET: A bioinformatics toolbox for functional exploration of DNA damage response
Authors: Li Wei , Wen Liting , Feng Jin‐an
Published: February 2006

DNA damage response is one of the essential cellular mechanisms to maintaining the genomic integrity of the cell. Aberrations in the mechanism of DNA damage response often result in cancer. We describe here RepairNET, a protein–protein interaction network associated with the DNA damage response. RepairNET is assembled from the published literature by using a protocol that involved computational data mining of the MEDLINE and manual curation. This network represents the current knowledge on the intrinsic signaling pathways related to the DNA damage response process. RepairNET currently contains more than 1,200 proteins with over 2,300 functional interactions. A number of web‐interface tools have been implemented to facilitate a user‐friendly environment. The users can navigate through the cellular network associated with the DNA damage response via a Java‐based interactive graphical interface. In order to help users explore the functional relationships between the interacting proteins, we have assigned functional domains to the proteins in RepairNET based on their sequences. A total of 365 unique functional domains are assigned. RepairNET is available online at http://guanyin.chem.temple.edu/RepairNET.html. It could become an essential resource center for cancer research, providing clues to understanding the functional relationship between proteins in the network, and to building scientific models for the mechanism of DNA damage response and cancer proliferation. J. Cell. Physiol. 207: 293–299, 2006. © 2006 Wiley‐Liss, Inc.
Weak organic acids induce taurine release through an osmotic‐sensitive process in in vivo rat hippocampus
Authors: Solis J. M. , Herranz A. S. , Herreras O. , Menéndez N. , del Rio R. Martin
Published: February 2006

Isotonic media containing sodium salts from weak organic acids induce cell swelling in several experimental preparations (Grinstein et al., 1984; Jakubovicz et al., 1987). In vivo perfusion of rat dentate gyrus, using a microdialysis probe, with modified Krebs‐Ringer bicarbonate solutions in which 50 mM NaCl was isotonically substituted by the sodium salts from organic acids with a pKa value of >2 (acetate, propionate, or pyruvate), induced a reversible increase in the extracellular taurine concentration. By contrast, similar NaCl substitutions with sodium salts from the stronger organic acids isethionate and methanesulfonate did not change extracellular taurine levels. Extracellular taurine increases evoked by acetate, propionate, or pyruvate were almost completely abolished when the perfusion liquid was made hypertonic by adding sucrose (50 mM). A 30% reduction of the acetate‐induced extracellular taurine increase was observed both when amiloride was present or when the [Na+]0 was lowered. Both conditions are known to inhibit Na+/H+ exchange. These results are compatible with the hypothesis that acid load‐induced taurine release is stimulated by an osmotic sensitive mechanism, part of which is dependent on activation of the Na+/H+ exchange.
Brain regional distribution of physostigmine and its relation to cerebral blood flow following intravenous administration in rats
Authors: Scremin O. U. , Scremin A. M. E. , Somani S. M. , Giacobini E.
Published: February 2006

3H‐labeled physostigmine (50 μg·kg−1) was administered intravenously to rats, and its concentration in brain tissue and spinal cord was assessed by quantitative autoradiography. Regional cerebral blood flow (rCBF) was measured with iodo‐14C‐antipyrine auto‐radiography in control rats and in animals injected i.v. with a dose of physostigmine similar to that used for the distribution studies. Tissue concentration of 3H‐physostigmine was correlated with rCBF for 37 brain regions. A high degree of correlation was found at 0.5 min after drug injection, r (correlation coefficient) = 0.87. This association decreased at later times (5 min r = 0.73, 12 min r = 0.24). Structures with high cholinesterase activity (caudate‐putamen, amygdala, hippocampus) showed greater retention of physostigmine over time. The highest initial physostigmine concentrations were found in regions lacking a blood‐brain barrier (pineal gland, median eminence, choroid plexus) (range = 10.4–23.8 nCi/mg) and the lowest in white matter (corpus callosum, internal capsule, hippocampus commisure, spinal cord dorsal column) (range = 1.2–2.6 nCi/mg). Initial concentrations of the drug in the areas in which physostigmine induced vasodilatation (motor, sensory, temporal and occipital cortex, claustrum, and superior collicullus) were not different from concentrations in areas of comparable basal rCBF in which no such effect was observed. Variations in drug access to brain regions, then, do not explain the topographical variations of the cerebrovascular action of physostigmine.
Greffage d'acides aminés possédant une troisième fonction sur un polymère, 2. Fixation de tyrosine et de lysine sur un polymère α‐monofonctionnel. Model de réaction
Authors: Gueniffey Henri , Garnier Raymonde , Pinazzi Christian
Published: February 2006

La tyrosine et la lysine, sous forme de complexe cuivrique (1 et 5) ont été fixées respectivement par leur fonction phénol et amine sur des alcools primaires dont la chaine comprend 2, 8 et 16 atomes de carbone.
Stabilisation et caractérisation des polybutadiènes‐1,2 liquides cyanométhylés par réaction couplée à l'hydroboration
Authors: Pinazzi C. , Vassort J. , Jean F. , Reyx D.
Published: February 2006

L'existence de structures trialkylboranes résiduelles dans les polydiènes modifiés par réaction couplée à l'hydroboration confère aux produits obtenus une instabilité résultant de la réactivité de ces structures à l'air. Pour les polydiènes cyanométhylés par cette voie, une méthode d'élimination des structures trialkylboranes par une réaction sélective, spécifique et quantitative a été recherchée: l'optimisation de la réaction de cyanométhylation n'a pas permis une élimination quantitative; l'acétolyse est, selon les conditions, non quantitative ou non spécifique tandis que la réaction d'oxydation alcaline s'est révélée spécifique et quantitative mais non totalement sélective: elle provoque simultanément et à de faibles taux l'hydrolyse parasite des structures cyanométhylées. La caractérisation des produits obtenus par cette dernière methode a été réalisée par analyse spectrographique (IR et NMR) des produits eux‐měmes, de leurs dérivés acétylés et de leurs dérivés réduits.
Telechele Oligomere, 3. Oligoäthylene durch radikalische Polymerisation mit Diacylperoxiden als Initiator
Authors: Guth Werner , Heitz Walter
Published: February 2006

Die Möglichkeit der Bildung von telechelen Oligoäthylenen wurde durch die Analyse der Reaktionsprodukte von Dihexanoylperoxid und Äthylen studiert. Bei hohen Temperaturen (>200°C) erhält man vor allem unverzweigte Paraffine mit gerader C‐Atomanzahl (Kombinationsprodukt). Eine Reaktionstemperatur von 95°C führt dagegen fast ausschließlich zu Paraffinen mit ungerader C‐Atomzahl. Die Ursache dafür ist ein durch wachsende Alkylradikale ausgelöster, induzierter Zerfall des Dihexanoylperoxids, der unter H‐Abstraktion in β‐Position zur Carbonylgruppe erfolgt. Dieser induzierte Zerfall wird auch beim Zerfall von Dihexanoylperoxid in Abwesenheit von Äthylen beobachtet.
Studies on the copolymerization of acrylonitrile with butyl acrylate, vinylidene dichloride, and styrene
Authors: Tomescu Margareta , Simionescu Cristofor
Published: February 2006

Copolymer composition studies are reported, for different mole fractions of acrylonitrile (AN), butyl acrylate (BA), vinylidene dichloride (CV), and styrene (S) in the initial monomer mixture. A partial azeotropy of acrylonitrile was found.
Stereochemistry of copolymerization of optically active 3‐phenyl‐1,2‐epoxypropane with carbon dioxide
Authors: Hirano Takashi , Inoue Shohei , Tsuruta Teiji
Published: February 2006

The stereochemistry of alternating copolymerization of carbon dioxide with S‐(–)‐3‐phenyl‐1,2‐epoxypropane (5) using a diethylzinc/water system as catalyst was investigated. The optically active copolymer, poly[(oxycarbonyloxy)‐1‐benzylethylene] (6), was hydrolyzed and the epoxide unit was transformed into the form of 1,2‐bis(trimethylsilyloxy)‐3‐phenylpropane (8). From the determination of optical activity of this ether, it is concluded that the ring opening of 5 in the copolymerization takes place predominantly at the methylene‐oxygen linkage. The substituent effect on the ring opening mode of oxiranes is also discussed.
Comparative reactivities of electrogenerated radical cations in cationic polymerization
Authors: Glasel Arnold , Murray Kenneth , Funt B. Lionel
Published: February 2006

Persistent radical cations were produced electrochemically from the parent hydrocarbons 9,10‐diphenylanthracene (DPA), 9‐phenylanthracene (9‐PA), 9,10‐dimethylanthracene (DMA), rubrene (Ru), triphenylene (TP), 1,3,6,8‐tetraphenylpyrene (TPP), and perylene (P). The stabilities of these cations in the absence of monomer were

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The rates of decay of increased with the dielectric constant of the solvent and were 4 to 5 times greater in CH3CN than in CH2Cl2 or C6H5NO2.

The kinetics of the reaction of the radical cation with monomer were investigated for styrene and isobutyl vinyl ether. For styrene and or a first order dependence on the radical cation concentration was found. However, decay was unaffected by the addition of styrene and polymerization was not initiated. With and isobutyl vinyl ether a first order dependence on cation was observed and polymers were obtained.

Electropolymerizations were also conducted with the generation of radical cations in situ and the rates of monomer consumption and polymer production were measured. The passage of the same electric charge in Faradays (1 Faraday=96496 coulomb) resulted in the polymerization of different amounts of the monomer and generally paralleled the reactivities found for the various radical cations.
Gelation kinetics in aqueous solutions of syndiotactic‐rich poly(vinyl alcohol)
Authors: Ogasawara Kenji , Yuasa Kouji , Matsuzawa Shuji
Published: February 2006

Aqueous solutions of Syndiotactic‐rich poly(vinyl alcohol) (PVA) form thermally reversible gels. The volume of the solution decreases with gelling time on standing at isothermal condition. Assuming that the gelation is due to the crystallization of PVA, the kinetics of isothermal crystallization from 5 wt.‐% aqueous solutions of PVAs having 64,3 mol‐% syndiotactic diads was investigated as a function of temperature (45–90°C), using dilatometry. The maximum in the overall rate of crystallization appeared at 60°C, regardless of the degree of polymerization of PVA. Since the values of n in the Avrami equation vary from about 1 to 2, it was apparent that the crystallization from aqueous solution of the polymer proceeded in the fashion of one‐dimensional growth and heterogeneous, diffusion controlled nucleation. The phase diagram revealed that the syneresis of the gel was caused by the crystalline phase separation which supports the gelation accompanying crystallization.
Pair distribution function and pair potential of lattice model chains under theta conditions, 1. Numerical evaluation
Authors: Olaj Oskar Friedrich , Pelinka Kurt Heinz
Published: February 2006

Ensembles of unbranched non‐selfintersecting 4‐way cubic lattice chains consisting of 100 chains each occupying 50 lattice points have been developed for Θ‐conditions by a Metropolis‐Rosenbluth‐Monte‐Carlo technique using a kind of square well potential to describe the segment‐segment interaction. For these equilibrated ensembles the pair distribution function G(R) and the average pair potential U(R) have been estimated by calculating the intermolecular energy for all isolated pairs, which can be depicted from the ensemble, as a function of the distance of the centers of gravity R of the two chains. The resulting G(R) being less than one for small R and exceeding one for large R does not correspond to that of an ideal gas. This means that for thermodynamic reasons alone there can be no free interpenetration of chains at the Θ‐point. U(R) can be split into a repulsive and an attractive part both being approximately Gaussian in type. Thus, U(R) at the Θ‐point can be represented by the general expression.

with A>A′ and a>a′.
Product attributes for business markets: Implications for selling and sales management
Authors: Lichtenthal J. David , Goodwin Stephen A.
Published: February 2006

This article offers a conceptual framework for classifying attributes of offerings in a business‐marketing context. Typologies on the nature of product‐related attributes and classification of industrial products are synthesized for viewing levels of product meaning. Repertory grid procedures first developed in clinical psychology and recently adapted for use in business settings are presented as an approach for eliciting salient/determinant attributes. Enhanced effectiveness of the classic industrial selling process is demonstrated along with implications for managing the sales force. © 2006 Wiley Periodicals, Inc.
The capillary contact angle, II: The inclined plane
Authors: Finn Robert , Shinbrot Marvin
Published: February 2006

In an earlier paper an hypothesis on the nature of the forces resisting motion of a liquid drop on a support surface II was introduced and tested in the (rotationally symmetric) case for which ll is a horizontal plane. In the present work II is chosen as an inclined plane, so that rotational symmetry fails. The hypothesis leads to a formal series development; in a restricted case the result is verified by a perturbation analysis, which yields the identical series.

The series predictions are compared with results of computer calculations. A consequence of the analysis is an estimate for a Bohd number B0, such that a further increase in B would result in the fluid penetrating the support surface; thus an absolute upper bound B0, for stability of the envisaged configuration is obtained.
A non‐linearly stable implicit finite element algorithm for hypersonic aerodynamics
Authors: Iannelli G. S. , Baker A. J.
Published: February 2006

A generalized curvilinear co‐ordinate Taylor weak statement implicit finite element algorithm is developed for the two‐dimensional and axisymmetric compressible Navier‐Stokes equations for ideal and reacting gases. For accurate hypersonic simulation, air is modelled as a mixture of five perfect gases, i.e. molecular and atomic oxygen and nirogen as well as nitric oxide. The associated pressure is then determined via Newton solution of the classical chemical equilibrium equation system. The directional semi‐discretization is achieved using an optimal metric data Galerkin finite element weak statement, on a developed ‘companion conservation law system’, permitting classical test and trial space definitions. Utilizing an implicit Runge‐Kutta scheme, the terminal algorithm is then non‐linearly stable, and second‐order accurate in space and time on arbitrary curvilinear co‐ordinates. Subsequently, a matrix tensor product factorization procedure permits an efficient numerical linear algebra handling for large Courant numbers. For ideal‐ and real‐gas hypersonic flows, the algorithm generates essentially non‐oscillatory numerical solutions in the presence of strong detached shocks and boundary layer inviscid flow interactions.
Navier‐Stokes simulation of flow through a highly contoured subsonic diffuser
Authors: Chyu W. J. , Bencze D. P.
Published: February 2006

The flow through a highly offset subsonic diffuser with cross‐sectional profiles that varied from rectangular at the duct entrance to circular a t the engine face was numerically simulated. A multizonal approach combined with a two‐grid topology was used to represent both the internal and external flow fields, and an implicit, approximately‐factored, partially flux‐split finite‐difference algorithm was used to solve the three‐dimensional thin‐layer Navier‐Stokes equations. The computed static pressures along the inlet wall and total pressures on the engine face were compared with experimental data. In addition, the overall flow field within the duct was examined in detail. Good agreement is shown between experiment and computations, with the limiting factor being the lack of a reliable turbulence model for internal flow problems.
A staggered mesh finite difference scheme for the computation of compressible flows
Authors: Sanders Richard
Published: February 2006

A simple high resolution finite difference technique is presented to approximate weak solutions to hyperbolic systems of conservation laws. The method does not rely on Riemann problem solvers and is therefore easy to extend to a wide variety of problems. The overall performance (resolution and CPU requirements) is competitive with other state‐of‐the‐art techniques offering sharp non‐oscillatory shocks and contacts. Theoretical results confirm the reliability of the approach for linear systems and non‐linear scalar equations.
A preconditioning mass matrix to accelerate the convergence to the steady Euler solutions using explicit schemes
Authors: Storti M. A. , Baumann C. E. , Idelsohn S. R.
Published: February 2006

When explicit time marching algorithms are used to reach the steady state of problems governed by the Euler equations, the rate of convergence is strongly impaired both in the zones with low Mach number and in the zones with transonic flow, e.g. Mach ⩽ α and | Mach − 1| ⩽ α, with α ⩽ 0·2. The rate of convergence becomes slower as α diminishes.

We show in this paper, with analytical and numerical results, how the use of a preconditioning mass matrix accelerates the convergence in the aforementioned ranges of Mach numbers.

The preconditioning mass matrix (PMM) we advocate in this paper can be applied to any FEM/FVM that uses an explicit time marching scheme to find the steady state. The method's rate of convergence to the steady state is studied, and results for the one‐ and two‐dimiensional cases are presented.

In Sections 1‐3, using the one‐dimensional Euler equations, we first explain why there exists a slow rate of convergence when the plain lumping of mass is used. Then the convergence rate to steady solutions is analysed from its two constituents, that is, convergence by absorption at the boundaries and by damping in the domain. Next we give the natural solution to this problem, and with several examples we show the effectiveness of the proposed mass matrix when compared with the plain scheme.

In Sections 4‐8 we give the multidimensional version of the preconditioning mass matrix. We make a stability analysis and compare the group velocities and damping with and without the new mass matrix. To finish, we show the velocity of convergence for a common test problem.
Boundary element method of multi‐lobe hydrodynamic lubrication bearing for numerical analysis in lubrication theory
Authors: Dequan Yang
Published: February 2006

In the present paper, the hydrodynamic lubrication problems of multi‐lobe bearings are treated by the Boundary Element Method in lubrication theory. For example, we have made numerical calculations for elliptical bearings and three‐lobe bearings. The stress and pressure distributions on the bearings and the velocity fields of the lubricant are given. We also studied conditions for the occurrence of vortexes in the flow region. The numerical investigations have shown that the method is very effective in handling hydrodynamic lubrication problems and it can be used to study the vortex in arbitrary shape bearings. Furthermore, the method has some advantages of computational convenience and superior accuracy. Especially, the ending point of the oil film pressure can be ascertained when non‐linear terms are considered, and that is undoubtedly extremely important in studying hydrodynamic lubrication problems.
Alveolar epithelialisation in ovine pneumonia
Authors: Alley M. R. , Manktelow B. W.
Published: February 2006

PROLIFERATION of the alveolar epithelium, usually termed (epithelialisation) is a common feature of many mammalian pneumonias (Bell, 1943; Jarrett, 1954; Stamp and Nisbet, 1963). It occurs as a non‐specific reaction of the lung to injury by a wide variety of unrelated toxic and infective agents (Greever, Neubuerger and Davis, 1943; Omar, 1964).

Although changes resembling alveolar epithelialisation have been recognized since before the turn of the century (Colberg, 1866, cited by Miller, 1947) the exact origin of the cells involved in this reaction has remained uncertain.
Experimental respiratory distress induced by paraquat
Authors: Robertson B. , Enhörning G. , Ivemark B. , Malmqvist Eva , Modée J.
Published: February 2006

THE weed‐killer Paraquat (1,1′‐dimethyl‐4,4′‐dipyridyliurn dichloride, Gramoxone, ICI) is toxic not only to plants but also to animals including man. The predominant lesions induced by paraquat are found in the lungs and consist of collapse, hyaline membranes, haemorrhage, interstitial inflammation and proliferation of bronchiolar epithelium (Bullivant, 1966; Clark, McElligott and Hurst, 1966; Almog and Tal, 1967; Manktelow, 1967; Campbell, 1968; Matthew et al., 1968; Oreopoulos et al., 1968; Conning, Fletcher and Swan, 1969). The pathogenesis of these changes, which persist several days after the excretion of injected paraquat (Daniel and Cage, 1966), is obscure. However, the similarity between the pulmonary lesions in paraquat poisoning and those of newborn infants dying from idiopathic respiratory distress suggests some common pathogenic mechanism, possibly a derangement of surfactant (Manktelow).

The purpose of the present study is to analyse, by quantitative methods, the effect of paraquat on the surfactant system of the rat lung. In particular, we tried to find out whether experimental paraquat poisoning could be adopted as a model for the study of the idiopathic respiratory distress syndrome.
Alkaline phosphatase in craniopharyngiomas
Authors: Timperley W. R. , Turner P. , Davies S.
Published: February 2006

THE derivation of the epithelium from which craniopharyngiomas arise is in doubt. Willis (1953) and Russell and Rubinstein (1959) state that these tumours are not distinguishable from “epitheliomas” in which squamous and basal cells are both present. Timperley (1968a), in a histochemical investigation, showed that craniopharyngiomas differed from squamous epithelium and epidermal cyst epithelium in that they contained a high activity of alkaline phosphatase and in this respect they closely resembled the ameloblastoma of the jaw and the developing tooth bud. The present paper is a histochemical and chemical analysis comparing several more craniopharyngiomas with dental and dentigerous cysts.
Bending properties of compression molded three‐layer long fiber polypropylene composites
Authors: Hamada H. , Shonaike G. O. , Sato T. , Yamaguchi S. , Maekawa Z. , Koshimoto M.
Published: February 2006

The results of studies on bending properties of three‐layer long fiber polypropylene composites are presented. Thirteen samples with glass fibers of various lengths (i.e., 13, 25, 50 mm and continuous fiber length) in the laminates were prepared by stamping. Bending properties of shorter lengths exhibited a large scatter. On substitution of the middle layer with a continuous glass fiber the scatter was reduced. These results have been explained on the basis of flow models and X‐ray shadowgraphs, which showed that both slippage flow and orientation of the glass fiber during stamping are the major phenomena responsible for the scatter.