bluuebunny/crossref_metadata_2025 huggingface dataset:
Liquid chromatography and electrochemical detection of alditols and acidic sugars at a cobalt phthalocyanine‐containing chemically modified electrode
Authors: Tolbert Andre M. , Baldwin Richard P.
Published: February 2006

Chemically modified carbon paste electrodes containing incorporated cobalt phthalocyanine (CoPC) were shown to exhibit an electrocatalytic response for the oxidation of carbohydrate derivatives from the alditol and aldonic, uronic, and aldaric acid families. The electrocatalysis, which is similar to that previously seen for simple carbohydrates, resulted in the electrolysis of these compounds between +0.4 and +0.6 V vs. Ag/AgCl where Co(II)PC is oxidized to Co(III)PC. The response was greatest for the alditols and decreased from the aldonic to the aldaric acids. When used to quantify these compounds following anion exchange chromatography, detection limits at +0.42 V ranged from 10 pmol for the alditols to the nanomole level for some of the aldaric acids.
Amperometric determination of lactose in human and cow's milk using a flow‐injection system with some immobilized enzyme reactors
Authors: Yao Toshio , Akasaka Reina , Wasa Tamotsu
Published: February 2006

A bioelectrochemical flow‐injection system is proposed for the determination of lactose in milk from humans and cows. The system includes an amperometric flow‐through platinum electrode to measure hydrogen peroxide, which was enzymatically generated by injecting a 10‐μL sample into the packed‐bed reactors of immobilized β‐galactosidase and glucose oxidase that are incorporated in series in the flow line. Because the presence of glucose interfered with the measurement of lactose, a precolumn packed with coimmobilized glucose oxidase and catalase was positioned just before the two immobilized enzyme reactors to remove the glucose from the milk. The peak current was linearly related to the lactose concentration between 0.01 and 2.0 mM. The determinations of lactose in milk could be performed at a rate of 60 samples/h with satisfactory precision (less than 0.8% RSD) and no pretreatment except for the sample dilution.
Mediated enzyme/wall‐jet amperometric electrode in flow‐injection monitoring of glucose
Authors: Gunasingham Hari , Tan Chin‐Huat
Published: February 2006

Tetrathiafulvalene serves as a useful mediator for glucose oxidase in its application in second‐generation enzyme electrodes for monitoring glucose. Among its useful characteristics are a low redox potential, fast homogeneous electron exchange kinetics with glucose oxidase, high stability, and low solubility in aqueous solutions. The fabrication and characterization of tetrathiafulvalene‐glucose oxidase enzyme electrodes in flow‐injected and stopped‐flow analysis is described. One of the conclusions is that the homogeneous rate constant for tetrathiafulvalene is higher than that of dimethyl ferrocene. Tetrathiafulvalene is, however, more susceptible to pH variations. The characteristics and advantages of the mediated enzyme/wall‐jet amperometric detection are described.
Optimization of parameters for differential pulse voltammetry at the hanging mercury drop electrode
Authors: Pelzer Jürgen , Scholz Fritz , Henrion Günter , Nitschke Lutz
Published: February 2006

The detection limit of differential pulse voltammetry at a hanging mercury drop electrode is investigated. The most important result of this study is that very small pulse amplitudes considerably improve the signal‐to‐background ratio and lead to lower detection limits. Due to the fact that (in practice) the background current does not originate only from capacitive properties of the electrode, an optimal pulse duration also exists, which guarantees the highest signal‐to‐background ratio. It is shown that the background current consists of the capacitive current and a very noisy but, on average, constant component, presumably of a faradaic nature that originates from impurities. The effects of the prepulse time, the pulse amplitude, the pulse duration, the step height of the staircase ramp, and the duration of the current sampling time on the signal and background intensity and noise are described.
Ion transfer of barium and strontium across the liquid‐liquid interface facilitated by polyethylene glycol 400
Authors: Sun Zhisheng , Wang Erkang
Published: February 2006

A mechanism of metal ion transfer for Ba2+ and Sr2+ at the liquid‐liquid interface, facilitated by polyethylene glycol 400 and based on complexation in aqueous and organic phases, is proposed. The interfacial half‐wave potential equations are deduced in terms both of the mechanism proposed and of the equilibria of distribution and dissociation in two phases and are verified experimentally. The effect of the polyoxyethylene structure on the selectivity of the facilitated transfer is discussed, and a useful way of improving the selectivity by selecting neutral carriers for practical analysis is suggested.
Preconcentration and determination of promethazine at lipid‐modified carbon paste electrodes
Authors: Khodari Mahmoud , Kauffmann Jean‐Michel , Patriarche Gaston J. , Ghandour Mahmoud A.
Published: February 2006

Lipid‐modified carbon paste electrodes were electrochemically characterized and their potential for drug analysis was compared with conventional carbon paste electrodes. The presence of lipids (phospholipids, fatty acids) in the paste matrix provided enhanced current responses with improved reproducibility. With 5 minutes of accumulation, phenothiazines exhibit a 40‐fold enhancement of the response compared to that obtained without accumulation. As a result, a detection limit of 1 × 10−9 M was attained. The response was characterized with respect to pH, preconcentration potential, accumulation time, paste composition, possible interferences, and other variables. The determination of the tranquilizer in serum and urine required no preliminary treatment other than dilution with phosphate buffer and medium exchange. Detection limits are 5 × 10−8 M in urine and 2 × 10−7 M in serum.
Electrochemical oxidation of dacarbazine and its major metabolite (AIC) on carbon electrodes
Authors: Rodriguez José R. Barreíra , Garcia Agustin Costa , Ordieres Arturo J. Miranda , Blanco Paulino Tuñón
Published: February 2006

The electrochemical behavior of the antitumor agent dacarbazine (DTIC) and its major metabolite, 5‐aminoimidazole‐4‐carboxamide (AIC), on carbon paste electrodes has been studied. Linear sweep voltammetry (LSV) and differential pulse voltammetry (DPV) have been applied, showing that both molecules are active in oxidation. Both compounds are oxidized in a two‐electron process, presenting a charge transfer coefficients (β) of 0.44 ± 0.03 and 0.48 ± 0.03 for DTIC and AIC, respectively, which indicate slow processes. The oxidation mechanisms proposed for each of these compounds seem to yield the same final product, the 5‐hydroxyimidazol‐4‐carboxamide. DPV proved to be a valuable analytical technique that is suitable for distinguishing and analyzing both compounds when the most adequate medium (0.1 M HCIO4) and operating conditions are chosen.
UV‐visible and ESR spectroelectrochemical study of xylenol orange
Authors: Dong Shaojun , Song Shihua
Published: February 2006

The proposed first step in the electroreduction of xylenol orange (XO), a reversible electrode process coupled with a chemical reaction, is based on ultraviolet (UV)‐visible spectroelectrochemistry. Electrochemical excitation‐electron spin resonance (ESR) in situ measurements are used to observe the radical signal produced by the first step reduction of XO. The ESR spectra of the radical in solution at pH 4.0, 4.5, and 5.0 have the same characteristics: no observed hyperfine structure, a line width of 10.5 G, and a g value of 2.0034. The structure of the XO radical and its disproportionation reaction are elucidated.
The importance of adsorption in anodic surface‐catalyzed oxygen‐transfer reactions at gold electrodes
Authors: Vitt Joseph E. , Larew Larry A. , Johnson Dennis C.
Published: February 2006

A large number of anodic oxygen‐transfer reactions were studied at Au electrodes in both acidic and alkaline media. Results of competitive adsorption studies are interpreted and support the conclusion that adsorption is a prerequisite to subsequent oxygen‐ and electron‐transfer steps. Many of these oxidation reactions gave the voltammetric appearance of reversible waves, even though the observed half‐wave potential values were shifted hundreds of millivolts positive of the thermodynamic potentials. A catalytic mechanism is proposed in which adsorbed hydroxyl radicals (AuOH) participate in the oxygen‐transfer step. The absence of pH effects on half‐wave potentials for several inorganic compounds suggests that the electron transfer precedes the deprotonation step for these reactants.
Linear sweep polarographic studies of trace gold in an N‐allyl‐N′‐(sodium‐p‐phenylsulphonate)thiourea medium
Authors: Zhao Zaofan , Jiang Mian , Liu Qing
Published: February 2006

Using linear sweep polarography (LSP) in an acidic solution (pH 2.8) containing Au(III) ions and N‐allyl‐N′‐(sodium‐p‐phenylsufonate)thiourea (NTu), the product of the reaction between Au(III) and NTu (NDF) is reducible at the mercury electrode with two waves at about −0.40 and −0.95 V [versus the saturated calomel electrode (SCE)]. In the presence of excess chloride, the potential of the first wave shifts positively to −0.35 V. This forms the basis of a highly selective and sensitive method for gold. The linear range for gold is from 1 × 10−7 to 3 × 10−M, and the detection limit is 5 × 10−8 M (9 ppb). This method has been used for the determination of gold in ore samples, and the results agree well with values obtained by accepted procedures. Various electrochemical techniques were used to study the mechanism of the redox process. The reaction mainly involves the formation of C,C′‐di‐N‐allyl‐N′‐ (sodium‐p‐phenysulfonate)dithiodiformamidine (NDF). Unlike some explanations reported in the literature about the reduction of formamidine derivatives (containing an SS bond) on an Hg electuode, the electrode process for the first wave (−0.40 V) is ascribed to the reduction of the HgS film, which is caused by the reaction of Hg with adsorbed NDF. In the presence of excess Cl‐ ions, the mixed precipitation film of HgS·xHg2Cl2 may be formed on the electrode surface and make the first wave shift to −0.35 V. The second wave (−0.95 V) is caused by the irreversible reduction of NDF.
Photomicroscopic measurement of the diffusion layer around mercury drop electrodes: Part I, description of the electrochemical system
Authors: Tercier M.‐L. , Bernard C. , Bujard F. , Rodak S. , Buffle J.
Published: February 2006

A special electrochemical system has been developed to determine the optimum conditions for the stirred deposition step of anodic stripping voltammetric techniques with the sessile mercury drop electrode (SMDE) in order to get a reproducible flux that is predictable on sound theoretical grounds. The sessile Hg drop is formed at the upper part of a vertical capillary, which is placed coaxially below a rotating disc electrode that serves as both an auxilliary electrode and a stirrer. This system permits the visualization of the hydrodynamic flux, diffusion layer, and screening effects of the capillary around the mercury drop.
New bromide‐selective membrane electrodes based on a methyl methacrylate matrix and their use in drug analysis
Authors: Pastor Tibor J. , Pastor Milka M. , Kalajdžievski Krume
Published: February 2006

A new, simple procedure for the preparation of methyl methacrylate‐based bromide ion‐selective membrane electrodes with an internal solid contact is described. The stability, response range, and slope as well as the selectivity and interference‐free pH range of these electrodes were found to be satisfactory. The electrodes were applied to the determination of low bromine levels in biologically active substances with direct potentiometry and potentiometric titration after their combustion in an oxygen atmosphere. The results obtained are accurate and reproducible.
Brucine, part 1: Electrochemistry of brucine
Authors: Nyasulu Frazier W.
Published: February 2006

Cyclic voltammetry and chronocoulometry were used to study the electrochemistry of brucine. The oxidation of brucine 0.9 V versus a saturated calomel electrode at a carbon paste electrode produces a compound that undergoes reversible electrochemical behavior at Eo′ = 0.47 V. The product formed on the oxidation of brucine undergoes a slow chemical reaction to produce a compound that shows reversible behavior at Eo′ = 0.27 V. The hexadecane content of the carbon paste plays an important role in the observed behavior. Electrodes with low hexadecane did show oxidation of brucine, but irreversible waves occurred at Eo′ = 0.47 and 0.27 V. These features were also displayed by a platinum electrode. Calcium oxalate incorporated into the carbon paste catalyzes the oxidation of brucine. Chronocoulometry was used to estimate the heterogenous rate constant for the oxidation of brucine at calcium oxalate‐modified and unmodified electrodes. The values found were 21.4 × 10−3 cm/s for the modified electrode and 6.1 × 10−3 cm/s for the unmodified electrode. Preliminary results on the use of brucine as a reagent for the determination of nitrate are given.
Amperometric determination of carbon dioxide using a gold electrode modified by the underpotential‐deposited cadmium
Authors: Shao Mei‐Jun , Xing Xue‐Kun , Liu Chung‐Chiun
Published: February 2006

An underpotential‐deposited cadmium layer formed on a gold electrode was used to amperometrically determine PCO2 in an aqueous medium. This electrode reduces nitrate anions in an aqueous solution. The reduction current produced can be related to the proton concentration. Thus, when dissolved CO2 is present in a nitrate solution it alters the proton concentration, which can then be measured amperometrically. Experimental investigation of this system and a Nafion coated gold electrode were both carried out. The effect of oxygen present in the system is also discussed.
Chemically modified carbon paste electrodes in voltammetric analysis
Authors: Kalcher Kurt
Published: February 2006

A review of chemically modified carbon paste electrodes (CMCPEs) and their use in voltammetric analysis is presented. The different methods of modification as well as the types of interaction between substrate and modifier are discussed. In addition to a survey of the literature (173 references), the scope of and prospects in this field of electroanalysis are discussed briefly.
Dynamic response characteristics of an impinging‐jet amperometric detector
Authors: Powell Francis E. , Fogg Arnold G.
Published: February 2006

A dynamic response experiment at an impinging‐jet detector indicated that laminar flow in the straight delivery tube was modified by mixing stages in the electrode channel and its connections. The response obtained, resulting from this final dispersion, defines an effective detection volume of 7 μL. In a practical flow injection line made from a number of connectors, coils, and so on, this small volume ensured that the detector described here, which incorporated a well‐activated glassy carbon electrode, would not be expected to contribute significantly to the overall dispersion.
Determination of the pesticide guthion by flow‐injection analysis with amperometric detection
Authors: Méndez J. Hernández , Martínez R. Carabias , Gonzalo E. Rodríguez , Trancon J. Pérez
Published: February 2006

Guthion, a pesticide, was determined by flow‐injection analysis using single‐ and three‐channel systems with and without a chemical reaction. The experimental variables involved in each case were investigated and optimized, and the analytical features of the two procedures were compared. A method based on the oxidation of anthranilic acid yielded in the alkaline hydrolysis of the pesticide at a glassy carbon electrode is proposed for its determination. The detection limit is 4.1 × 10−7 M, and the relative standard deviation is 2.2% (n = 10) when the hydrolysis reaction takes place within the threeenamel manifold.
Electroanalytical study of pirimicarb by anodic voltammetry at a glassy carbon electrode in aqueous and acetonitrile media
Authors: Pingarrón José M. , González Araceli , Polo Luis M.
Published: February 2006

An electroanalytical study of the oxidation process of pirimicarb at a glassy carbon electrode using different voltammetric techniques was carried out. Two media were used: aqueous Britton‐Robinson buffer and acetonitrile (0.1 mol L−1 Bu4NClO4). Studies using linear sweep voltammetry (LSV) at a rotating disk electrode show that the limiting current becomes nondiffusion controlled at concentrations higher than 6.0 × 10−5 mol L−1. Cyclic voltammetry showed an irreversible electrode process. The best detection and determination limits were obtained by differential pulse voltammetry at a stationary electrode in an acetonitrile medium. The differential pulse mode in an aqueous medium was used to determine pirimicab in soil samples.
Composite electrodes for electroanalysis: Principles and applications
Authors: Tallman Dennis E. , Petersen Steven L.
Published: February 2006

A composite electrode has a surface that consists of an ordered arrangement (array) or a random arrangement (ensemble) of conductor regions, typically micrometers in dimension, separated from one another by an insulator. These active regions (or microelectrodes) may themselves be of regular geometry and confined primarily to the surface, as with most array electrodes, or of irregular geometry and permeate the bulk of the material, as with most ensemble electrodes. In this review, we classify composite electrodes according to the distribution of a conductor and insulator within the material (or on the surface), survey a number of the fabrication schemes used to construct composite electrodes, discuss percolation theory as it applies to certain composite electrodes, examine the surface morphology of selected composite materials, discuss the origins of the enhancement in current density observed at many composite electrodes in both quiescent and flowing solutions, and provide a few examples illustrating the applications of composite electrodes to real analytical problems.
Pineapple‐tissue based bioelectrode for the determination of hydrogen peroxide
Authors: Lin Meng Shan , Tham Sock Ying , Rechnitz Garry A.
Published: February 2006

A flow‐injection analysis (FIA) system for the determination of hydrogen peroxide was developed by utilizing a pineapple‐tissue‐based modified carbon paste electrode. Pineapple stem core tissue contains peroxidase, which is not available commercially in the pure isolated form. Hydrogen peroxide concentrations were determined in the presence of O‐phenylenediamine as a hydrogen donor at a potential of −200 mV. The detection limit (S/N = 3) for hydrogen peroxide using this tissue electrode is 2.1 μM with a relative standard deviation of 0.44% (n = 12). The tissue‐modified carbon paste electrode is stable for up to 20 days with no significant activity changes.
Amperometric amino acid electrodes
Authors: Pfeiffer Dorothea , Wollenberger Ulla , Makower Alexander , Scheller Frieder , Risinger Lars , Johansson Gillis
Published: February 2006

Substrate specificity, the linear measurement range, and the lifetime of monoenzyme electrodes were determined using L‐glutamate oxidase, L‐lysine oxidase, and tyrosinase immobilized in gelatin. These sensors were applied to the analysis of protein hydrolyzates. By coimmobilizing the three enzymes, an electrode responding to a group of amino acids was obtained. Its analytical performance was compared with that of an L‐amino acid oxidase sensor. The net charge of the immobilization matrix influenced the relative sensitivities of the amino acids.
Determination of the catalytic reaction rate constant of the ferrocyanide—aniline system using spectroelectrochemistry
Authors: Dong Shaojun , Xie Yuanwu
Published: February 2006

This work develops the theoretical equations for a single potential step—open circuit relaxation chronoabsorptometry for use in cases when the other species also displays absorption at the wavelength being observed for oxidation. A data analysis method is proposed to determine the rate constant of the catalytic reaction. The rate constants of ferrocyanide—aniline and ferrocyanide—antipyrine systems are determined by an optically transparent spectroelectrochemical method. The result coincides with the value determined by the electrochemical method.
Direct determination of bentazepam in a biological sample with a sepiolite‐modified carbon paste electrode
Authors: Hernandez L. , Hernandez P. , Lorenzo E.
Published: February 2006

Carbon paste electrodes (CPEs) modified with sepiolite are employed for adsorptive accumulation and voltammetric determination of the drug bentazepam. Response variables are explored, and measurements in urine samples are illustrated.
Electroosmotic flow in a rectangular channel with variable wall zeta‐potential: Comparison of numerical simulation with asymptotic theory
Authors: Datta Subhra , Ghosal Sandip , Patankar Neelesh A.
Published: February 2006

Electroosmotic flow in a straight micro‐channel of rectangular cross‐section is computed numerically for several situations where the wall zeta‐potential is not constant but has a specified spatial variation. The results of the computation are compared with an earlier published asymptotic theory based on the lubrication approximation: the assumption that any axial variations take place on a long length scale compared to a characteristic channel width. The computational results are found to be in excellent agreement with the theory even when the scale of axial variations is comparable to the channel width. In the opposite limit when the wavelength of fluctuations is much shorter than the channel width, the lubrication theory fails to describe the solution either qualitatively or quantitatively. In this short wave limit the solution is well described by Ajdari's theory for electroosmotic flow between infinite parallel plates (Ajdari, A., Phys. Rev. E 1996, 53, 4996–5005.) The infinitely thin electric double layer limit is assumed in the theory as well as in the simulation.
Capillary electrophoresis for thermodynamic and kinetic studies of peptidyl‐proline isomerization by the theoretical plate height model
Authors: Newman Carl I. D. , McGuffin Victoria L.
Published: February 2006

The theoretical plate height model, extended to include reactive CE, is used to calculate equilibrium constants and rate constants for the reversible, first‐order isomerization of proline dipeptides. This model is consistent with chromatographic theory and enables calculation of equilibrium constants from velocity and calculation of rate constants from plate height. Thermodynamic and kinetic parameters for isomerization of Ala‐Pro and Phe‐Pro are calculated by using the plate height model, and are shown to be in good agreement with literature values. Additionally, the efficacy of the plate height model is compared to ChromWin, an existing simulation method for calculating rate constants from zone profiles. It is shown that ChromWin and the plate height model are complementary methods. ChromWin is best used for calculating rate constants for reactions that are far from steady state, where the zone profiles exhibit plateau formation. On the other hand, the plate height model is best used for calculating rate constants for reactions that are at or near steady state, where the zone profiles exhibit a single zone containing both reacting species.
Fundamentals of Electrophoresis 2006
Authors: Gaš Bohuslav
Published: February 2006

No abstracts.
Modeling environmental influences on the locations of Irish early medieval ringforts
Authors: Legg Robert J. , Taylor David
Published: February 2006

For the past two decades, archaeologists have been constructing predictive archaeological models to determine the occurrence probability of archaeological sites. Here, the technique has been used to explore the environmental factors that may have had an influence on the distribution of ringforts in Ireland. In the Inny River catchment of the Irish midlands, locational information, together with corresponding environmental variables, were assembled in a geographic information system. The analysis showed that ringfort sites have a distinctive locational pattern and cluster on moderately fertile, well‐drained soils on gently sloping land surfaces (slopes of 4–9%) between 80 and 150 m above mean sea level. To test the practical applicability of the model, the results were extended to two separate areas adjoining the Inny River catchment (Blackwater valley and Lough Ramor catchment) in the form of a probability surface. The model predicts relatively low densities of ringforts in the Blackwater valley and much higher probabilities of occurrence in the Lough Ramor catchment. These predictions are broadly consistent with recorded site distributions. © 2006 Wiley Periodicals, Inc.
Modified calculations of hydrocarbon thermodynamic properties
Authors: Liu Min Hsien , Chen Cheng
Published: February 2006

A test set of 65 hydrocarbons was examined to elucidate theoretically their thermodynamic properties by performing the density‐functional theory (DFT) and ab initio calculations. All the calculated data were modified using a three‐parameter calibration equation and the least‐squares approach, to determine accurately enthalpies of formation (ΔHf), entropies (S), and heat capacities (Cp). Calculation results demonstrated that the atomization energies of all compounds exhibited an average absolute relative error ranging between 0.11– 0.13%, and an ΔHf of formation with a mean absolute absolute error (M.|A.E.|) ranging from only 5.7–6.8 kJ/mol (1.3–1.6 kcal/mol) (i.e., those results correlated with those of Dr. Herndon's 1.1 kcal/mol). Additionally, the entropy ranged from 3.5–4.2 J/mol K (0.8–1.0 cal/mol K) M.|A.E.|; a heat capacity between 2.3–2.9 J/mol K (0.5–0.7 cal/mol K) M.|A.E.| was obtained as well. © 2006 Wiley Periodicals, Inc. J Comput Chem 27: 537–544, 2006
In vivo serial diffusion tensor imaging of experimental spinal cord injury
Authors: Deo Aparna A. , Grill Raymond J. , Hasan Khader M. , Narayana Ponnada A.
Published: February 2006

In vivo longitudinal diffusion tensor imaging (DTI) of rodent spinal cord injury (SCI) was carried out over a period of eight weeks post‐injury. A balanced, rotationally invariant, alternating gradient polarity icosahedral diffusion encoding scheme was used for an unbiased estimation of the DTI metrics. The fractional anisotropy (FA), diffusivities along (longitudinal), and perpendicular (transverse) to the fiber tracts, were estimated for the ventral, dorsal, and lateral white matter. In all the three regions, the DTI metrics were observed to be significantly different in injured cords relative to the uninjured controls close to the epicenter of the injury. However, these differences gradually disappeared away from the epicenter. The spatio‐temporal changes in the DTI metrics showed a recovery pattern that is region specific. Although the temporal trends in the tissue recovery in rostral and caudal sections seem to be similar, overall the DTI metrics were observed to be closer to the normal tissue values in the caudal relative to the rostral sections (rostral–caudal asymmetry). © 2006 Wiley‐Liss, Inc.
Open brain gene product Rab23: Expression pattern in the adult mouse brain and functional characterization
Authors: Guo Anchen , Wang Ting , Ng Ee Ling , Aulia Selina , Chong Kooi Hoong , Teng Felicia Yu Hsuan , Wang Ya , Tang Bor Luen
Published: February 2006

The gene mutated in the mouse open brain (opb) phenotype antagonizes sonic hedgehog‐mediated signaling and encodes a small GTPase of the Rab family, Rab23. To date, the brain expression profile and exact mechanism of function of the Rab23 protein has remained unknown. Specific antibodies generated against Rab23 showed that the protein is highly enriched in the adult rodent brain and present in low levels in multiple tissues of the adult rodent. Rab23 is found in the cytosol as well as being associated with the plasma and endosomal membranes. In the adult mouse brain, Rab23 is found in βIII tubulin (TuJ) positive neuronal cell bodies and are most prominent in the cortex, hypothalamus and the cerebellum. It is, however, absent from glial fibrillary acidic protein (GFAP) positive astrocytes or CNPase positive oligodendrocytes. Despite the plasma membrane/endosomal membrane localization of Rab23, neither overexpression of the GTP‐restricted nor the GDP‐bound mutant forms affect internalization of transferrin or epidermal growth factor. Exogenous overexpression of Rab23 or its mutants also did not affect the morphological differentiation of thalamic neurons in culture. Expression of Rab23 in the adult brain is suggestive, however, of having a postnatal function beyond its role in embryonic development. © 2006 Wiley‐Liss, Inc.
Pharmacological and molecular properties of opioid binding sites synthesized in a cell‐free translation system
Authors: Cabon F. , Cupo A. , Ruiz‐Gayo M. , Baumann N. A. , Zalc B.
Published: February 2006

Cell‐free translation of mRNA, extracted from NG108‐15 cells, was used to examine some properties of the opioid binding sites synthesized in vitro. A monoclonal antiidiotype antibody directed against the δ opioid receptor immunoprecipitated a major band of Mr 51,000. Translational immunoassays of poly‐[A]+RNA, size fractionated by methylmercury agarose gel electrophoresis, demonstrated that the 51,000 Mr protein specifically immunoprecipitated by the anti‐opioid receptor antiidiotype antibodies was coded by a transcript which length was in the 6 to 8 kb range. Displacement binding studies of tritiated ligands (either bremazocine or δ or μ selective peptides) with type selective opioid ligands showed that only one type of opioid binding site was synthesized in vitro. Although the pharmacological profiles of ligands binding to NG 108‐15 cells were characteristic of the δ receptor type, the de novo synthesized opioid binding site had lost its δ selectivity and showed equal affinity for both the μ and δ but not for the K ligands. Similar to our finding using the immunoprecipitation system, size fractionation of the NG108‐15 poly [A]+RNA demonstrated that the transcript coding for the “μ‐δ” binding site had a length of 6,500 to 7,500 nucleotides.
Endogenous levels of nerve growth factor (NGF) are altered in experimental diabetes mellitus: A possible role for NGF in the pathogenesis of diabetic neuropathy
Authors: Hellweg R. , Hartung H.‐D.
Published: February 2006

Sympathetic and neural‐crest derived sensory neurons consisting of unmyelinated and small myelinated fibers are known to be affected at an early stage in diabetes mellitus (DM). Since these peripheral neurons need nerve growth factor (NGF) for their development and maintenance of function in adulthood, changes in endogenous NGF levels could be of relevance for the pathogenesis of diabetic neuropathy (DNP). Using an improved two‐site enzyme immunoassay for NGF, we have investigated whether endogenous NGF levels are altered in Sprague‐Dawley rats with DM induced by a single injection of streptozotocin (STZ). STZ‐treated rats are known to develop in many respects equivalents to neuropathic complications observed in human DM. We found in some sympathetically innervated target organs decreased NGF contents by maximally 56%: transiently in the iris 2 weeks and in the ventricle 12‐24 weeks after DM induction and permanently in the submandibular gland already 3 days after DM induction. Several weeks after onset of DM, NGF content was increased by maximally 145‐300% in most peripheral targets investigated, such as in iris, cardiac atrium and ventricle, spleen, prostate gland, and vas deferens. This is suggestive for an impaired NGF removal by NGF‐sensitive neurons in diabetic rats. Moreover, NGF levels were decreased to minimally 42.6 ± 4% of control in the NGF‐transporting sciatic nerve. NGF levels began to decrease not before 3 weeks after DM induction and remained decreased with 54.0 ± 5% of control even after 6 months duration of DM. About the same time (i.e., 2 weeks after induction of DM) NGF levels began to decrease in the superior cervical ganglion (where the sympathetic perikarya are located) to minimally 53.2 ± 4% of control 12 weeks after DM induction. No altered NGF levels were observed during a 3‐month duration of DM in the terminal ileum and sensory trigeminal ganglion. Since NGF exerts its neurotrophic action in the perikarya after its retrograde transport from the NGF‐producing periphery, our results are consistent with the hypothesis that an alteration in NGF levels may play a role in the pathogenesis of DNP as far as sympathetic neurons are concerned. Thus, our results suggest that DM influences the production and/or transport of endogenous NGF and consequently, that a deprivation of this neurotrophic factor may account for some of the functional deficits known to occur in DNP, such as impaired catecholaminergic transmitter synthesis. This hypothesis possibly opens the way for new concepts in the therapy of DNP.
Defoliation and Plasmid Delivery with Layer‐by‐Layer Coated Colloids
Authors: Reibetanz Uta , Claus Claudia , Typlt Elke , Hofmann Jörg , Donath Edwin
Published: February 2006

Summary: The uptake of polyelectrolyte multilayer coated colloids into cells, subsequent defoliation and plasmid delivery was studied by means of confocal microscopy and flow cytometry. Silica particles coated layer‐wise with protamine and dextran sulfate were given to HEK 293T cells. Optimum uptake was found with protamine as the top layer. The particle uptake likely follows an non‐receptor‐mediated endocytotic pathway. Defoliation of polyelectrolyte multilayer coated particles within cells was demonstrated by the release of incorporated plasmids as indicated by the expression of plasmid encoded proteins using the enhanced green fluorescence proteine (pEGFP‐C1) plasmid and a red fluorescence protein (pDsRed1‐N1) plasmid. This proves, together with the direct observation of fluorescent layer debris, the defoliation of coated particles and the release of layer components into the cytoplasm.

Particle uptake and GFP expression.

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Particle uptake and GFP expression.
Novel Functional Hyperbranched Polyether Polyols as Prospective Drug Delivery Systems
Authors: Tziveleka Leto‐Aikaterini , Kontoyianni Christina , Sideratou Zili , Tsiourvas Dimitris , Paleos Constantinos M.
Published: February 2006

Summary: Multifunctional hyperbranched polyether polyols bearing protective poly(ethylene glycol) (PEG) chains with or without the folate targeting ligand at their end have been prepared. Solubilization in these polymers of a fluorescent probe, pyrene, and an anticancer drug, tamoxifen, was physicochemically investigated. It was found that PEG chains attached at the surface of these hyperbranched polymers, in addition to their well‐established protective role, enhance the encapsulation efficiency of the polymers. The release of pyrene and tamoxifen observed upon addition of sodium chloride is, in most of the cases, significant only at concentrations exceeding the physiological extracellular concentration. Thus, a significant amount of the probe or drug remains solubilized inside the carriers, which is an encouraging result if the polymers are to be used for drug delivery.

Schematic representation of the multifunctional hyperbranched polyether polyol bearing protective poly(ethylene glycol) (PEG) chains with folate targeting ligand.

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Schematic representation of the multifunctional hyperbranched polyether polyol bearing protective poly(ethylene glycol) (PEG) chains with folate targeting ligand.
Reducing superheater corrosion in wood‐fired boilers
Authors: Henderson P. , Szakálos P. , Pettersson R. , Andersson C. , Högberg J.
Published: February 2006

One of the major drawbacks to the combustion of 100% biomass in power station boilers is the increase in the fouling and corrosion of superheaters. Experience shows that conventional superheater steels last no more than 20 000 h or four operating years before they must be replaced, if 100% wood‐based fuel is used and the steam temperature is higher than 480°C. Rapid corrosion of superheaters leads to increased maintenance costs while widespread deposit formation gives rise to a decrease in efficiency of the turbine and an increase in unplanned outages. This paper reports on measures taken to reduce superheater corrosion.

Most biomass fuels have a high content of alkali metals and chlorine, but they contain very little sulphur compared to fossil fuels. Potassium chloride, KCl, is found in the gas phase, condenses on the superheater tubes and forms complex alkali salts with iron and other elements in the steels. These salts have low melting points and are very corrosive. The corrosion can be mitigated by use of an instrument for in‐situ measurement of alkali chlorides in the flue gases, in combination with the addition of ammonium sulphate. An ammonium sulphate solution, specially developed for the reduction of corrosion was sprayed into the flue gases and effectively converted KCl into potassium sulphate, K2SO4, much less corrosive than KCl.

Deposit probe tests and long‐term corrosion probe tests have been performed in‐situ in two biomass‐fired fluidised bed boilers. One boiler, 105 MWtot, 540 °C steam, is the CHP plant in Nyköping, Sweden. The other producing 98 MWtot, 480 °C steam, is a bark‐fired boiler at a pulp and paper mill in Munksund, also in Sweden. Tests have been performed with a range of steel types, ferritic and austenitic, with ammonium sulphate additive and under normal conditions (no additive). Corrosion rates have been measured, deposit chemistry analysed and flue gas chemistry and KCl content measured. The structure and composition of the oxide with and without ammonium sulphate has been investigated. The results show that ammonium sulphate reduced the KCl levels in the flue gases, removed the chlorides from the deposits and the metal/oxide interface, greatly reduced the deposition rates and halved the corrosion rates for superheater materials. The alkali chloride measuring system and the use of ammonium sulphate for the reduction of corrosion have now been patented.
Local reactions of KCl particles with iron, nickel and chromium surfaces
Authors: Cha S. C. , Spiegel M.
Published: February 2006

Corrosion of superheaters caused by the deposition and subsequent reaction of alkali chloride containing ashes is one of the main material problems by combustion of biomass for energy conversion. The alkali chloride particles are formed during combustion and transported as aerosol or in the vapor phase within the combustion gas, subsequently sticking on the surface of the metallic tube. The initial reaction between the tube surface and the salt particle plays a major role in the initiation of the corrosion process and, therefore, are studied in detail in this work. The salt particles were locally deposited by means of thermophoresis within an aerosol generator, available at MPIE. Studies on the reaction of KCl particles with iron surfaces showed that a reaction takes place already at 300 °C. In N2‐O2 atmospheres, the attack was very local, whereas the addition of 0.05 vol.% HCl to the reaction gas led to complete coverage of the iron surface with chloride. In contrast, reactions of KCl with nickel and chromium surfaces start to be significant only at 500 °C and higher. The paper summarizes the reaction behavior of Fe, Ni and Cr after thermophoretic deposition of KCl particles and subsequent reaction at elevated temperatures.
The effect of ash deposition on corrosion behaviour of boiler steels in simulated combustion atmospheres containing carbon dioxide (CORBI PROJECT)
Authors: Środa S. , Mäkipää M. , Cha S. , Spiegel M.
Published: February 2006

This study is a part of the FP5 Project entitled “Mitigation of Formation of Chlorine Rich Deposits Affecting Superheater Corrosion under Co‐Combustion Conditions” (CORBI) which is aimed to improve the understanding of corrosion mechanisms in cases of biomass and waste combustion.

The laboratory experiments, made at the JRC Plant Simulation Test Laboratory, are focused mainly on common ferritic and austenitic materials (X10, X20, 2.25Cr1Mo, AC66, Sanicro28, Esshette 1250, etc.), which are usually used in energy conversion systems. The experiments were carried out in multi‐sample autoclaves at an isothermal temperature of 535 °C in various simulated combustion atmospheres (22% H2O + 5% O2 + xCO2 + N 2 with different CO2 content varying from 0 to 25 vol.%) on samples with and without filter/cyclone ash deposition. The results obtained show that the corrosion rate of the studied materials increases with increasing CO2 content in the atmosphere. Such behaviour was observed for samples with and without ash deposit.

The detailed analysis and thermodynamic calculations of cyclone and filter ash behaviour were performed at MPIE in Duesseldorf. The ashes were exposed to 13% CO2 + 5% O2 + xH2O + y HCl + N2 atmospheres with different H2O content varying from 5–22% and HCl content varying from 0–200 ppm at 535 °C. The results obtained show that in an HCl‐containing atmosphere the alkali chloride formed from alkali carbonate, as well as hydroxides and oxides, can additionally accelerate the oxidation process. In the HCl free atmosphere at increased H2O content, alkali carbonates and hydroxides can form, so enhanced alkali chloride induced oxidation will not occur.
The use of the 18O2‐exposure + SIMS‐based approach to investigate the spallation mechanisms of alumina scales
Authors: Jedlinski J.
Published: February 2006

Spallation of the protective alumina scale accelerates the oxidation‐induced degradation of ‚alumina formers’︁. Despite of the vast evidence of this process its mechanism has not been elucidated, so far.

This paper reports the results of the scale spallation mechanism investigation using a novel 18O2‐exposure + SIMS‐based approach. The FeCrAl‐type alumina‐forming alloys, without and with Zr additions, were subjected to high temperature exposure at 1473 K in 18O2‐rich atmosphere and, subsequently, cooled down in air. The surfaces exposed after spallation were observed using SEM, while high resolution SIMS was used to determine the elemental distributions.

The obtained results indicate that: (i) in all cases the spallation occurs according to the adhesive‐mode; (ii) for reactive‐element‐free alloys the scales spalls away at temperatures high enough to enable the re‐oxidation of the exposed surface already during cooling; (iii) for the Zr‐containing alloys the spallation occurs at fairly low temperatures.

Two practical implications of the obtained results should be noted: (i) oxide layers and not ‘bare substrate’ result from the scale spallation process during cooling; (ii) the formation of oxide layers during cooling may affect the behaviour of the system during subsequent heating to the reaction temperature.
High temperature corrosion of metallic materials in simulated waste incineration environments at 300–600 °C
Authors: Sánchez Pastén M. , Spiegel M.
Published: February 2006

The durability of the materials employed in waste incineration plants is affected by different factors that together result in severe degradation of the materials. The effects of alloying elements, as well as deposit composition and temperature range are investigated in this work. Different alloys were exposed in laboratory experiments to a specifically simulated waste incineration atmosphere N2 – 8 vol.% O2 – 2000 vppm HCl – 15 vol.% H2O – 200 vppm SO2 at 300–600 °C. The samples are covered with different salt mixtures especially chlorides and sulphates. Experiments with PbCl2‐KCl‐ZnCl2 at 450 °C, which is molten, showed catastrophic corrosion, but this was not observed in the case with KCl, which is solid. Mixtures of five different sulphates did not cause significant mass losses at 600 °C, but sulphate‐chlorided mixtures caused bigger mass losses. The presence of Al and Si in the alloys decreased mass change effects, the presence of Mo in alloys tested showed a negative effect.
Radikalische Polymerisation von Vinylmonomeren in Gegenwart von Disulfiden, 1. Substanzpolymerisation von Styrol in Gegenwart linearer Disulfide
Authors: Hallensleben Manfred L.
Published: February 2006

Die SS‐Bindung in Disulfiden wird beim Angriff eines Kohlenstoffradikals unter Bildung einer CS‐Bindung und eines Thiylradikals gespalten; Disulfide können daher als Regler bei der radikalischen Vinylpolymerisation verwendet werden. Während aliphatische Disulfide die Polymerisationsgeschwindigkeit nicht beeinflussen, wird diese durch aromatische Disulfide leicht herabgesetzt.
Radikalische Polymerisation von Vinylmonomeren in Gegenwart von Disulfiden, 2. Polymerisation von Styrol bzw. Methylmethacrylat in Gegenwart von Polydisulfiden
Authors: Hallensleben Manfred L.
Published: February 2006

Durch radikalische Substanz‐ oder Lösungspolymerisation von Styrol oder Methylmethacrylat in Gegenwart polymerer Disulfide werden Copolymere gebildet, deren Zusammensetzung stark vom Umsatz abhängt. Die Copolymerbildung erfolgt durch eine Übertragung der wachsenden Vinylpolymerketten mit den polymeren Disulfiden unter SS Spaltung. Mit zunehmendem Umsatz entstehen daneben zunehmend reine Vinylpolymere.
Meromorphic symbolic structures for boundary value problems on manifolds with edges
Authors: De Donno G. , Schulze B.‐W.
Published: February 2006

We investigate the ideal of Green and Mellin operators with asymptotics for a manifold with edge‐corner singularities and boundary which belongs to the structure of parametrices of elliptic boundary value problems on a configuration with corners whose base manifolds have edges. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Equivalence of weak Dirichlet's principle, the method of weak solutions and Perron's method towards classical solutions of Dirichlet's problem for harmonic functions
Authors: Simader Christian G.
Published: February 2006

For boundary data ϕ ∈ W 1,2(G ) (where G ⊂ ℝN is a bounded domain) it is an easy exercise to prove the existence of weak L 2‐solutions to the Dirichlet problem “Δu = 0 in G, u |∂G = ϕ |∂G ”. By means of Weyl's Lemma it is readily seen that there is ũ ∈ C ∞(G ), Δũ = 0 and ũ = u a.e. in G . On the contrary it seems to be a complicated task even for this simple equation to prove continuity of ũ up to the boundary in a suitable domain if ϕ ∈ W 1,2(G ) ∩ C 0($ {\overline {G} } $). The purpose of this paper is to present an elementary proof of that fact in (classical) Dirichlet domains. Here the method of weak solutions (resp. Dirichlet's principle) is equivalent to the classical approaches (Poincaré's “sweeping‐out method”, Perron's method). (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Monte Carlo Simulations of the Morphologies and Conformations of Triblock Copolymer Thin Films
Authors: Huang Yongmin , Liu Honglai , Hu Ying
Published: February 2006

Summary: The morphologies and conformations of triblock copolymer (ABA and ABC) thin films confined between two identical walls were investigated by Monte Carlo simulation using bond length fluctuation and cavity diffusion algorithm on cubic lattice. Effects of the wall‐block interactions, copolymer chain composition and film thickness on morphologies, as well as on the fraction of chain “bridge” conformation fbridge are presented in detail. In ABA thin film, column, parallel, perforated and perpendicular lamellas were discriminated, furthermore, the transition of morphology and the variation of fbridge of ABA film along with the increase of thickness were revealed. In ABC thin film, lamella especially perpendicular lamella morphologies are predominant in varying the wall‐block interactions and the thickness. The results are consistent with some theoretical predictions such as DDFT and simulations reported in literature.

Isodensity profile of A5B5A5 thin film.

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Isodensity profile of A5B5A5 thin film.