bluuebunny/crossref_metadata_2025 huggingface dataset:
Modeling of the Substrate and Product Transfer Coefficients for Ethanol Fermentation
Authors: Žerajić S. , Savković‐Stevanović J. , Grbavčić Ž.
Published: June 2008

The transfer phenomena of the substrate and product for ethanol fermentation with immobilized biocatalyst were investigated. Fermentation was carried out with a biocatalyst consisting of Ca‐alginate gel in the form of two‐layer spherical beads in anaerobic conditions. The determination of kinetic parameters was achieved by fitting bioreaction progress curves to the experimental data. The calculation of the diffusion coefficients was performed by numerical methods for experimental conditions. Finally, the glucose and ethanol transfer coefficients are defined and determined, using the effective diffusion coefficients.
Evaluation of an Entropy‐Based Combustion Model using Stochastic Reactors
Authors: Leicher J. , Wirtz S. , Scherer V.
Published: June 2008

The entropy transport concept (ETC) presented in this paper is a novel approach to describe reaction systems such that the dynamic behavior of a chemical system can be reproduced with a minimum in independent parameters. It is shown that, for adiabatic conditions, the mixture fraction and the reaction entropy are sufficient to describe combustion processes without significant loss of information. Entropy is used as a measure of the reaction progress in this context. In order to evaluate the applicability of the ETC for combustion modeling in turbulent systems, the entropy transport concept was implemented into a stochastic reactor model. For several test cases, the results of this ETC‐based reactor were compared with a reactor that directly integrates the species transport equations.
Flash Evaporation in Cyclones
Authors: Löffler M. K.
Published: June 2008

Flash processes have been investigated several times [1–4]. This study focuses on the flash process taking place in a cyclone. The separated and extracted steam expands directly into a cylinder of a piston engine. In contrast to known flash expanders, the pressure drops continuously within a short time. Of special interest is the efficiency of phase separation which is critical to the feasibility of the piston process with internal flash evaporation.
Particle Classification by Multishaft Disk Separator
Authors: Taamneh Y. , Steinke L. , Ripperger S.
Published: June 2008

Particle classification by sieving filtration using rotating disk filters mounted on single and double hollow shafts was investigated. The shaft and disks were enclosed in a stainless steel housing. Parameters such as particle concentration, feed flow rate and rotation speed of the filter disk were investigated to study their influence on the filtrate flux rate and particle classification. The filtrate flux rate was not affected by increasing the particle concentration. The analyzed particle size distributions were found to be narrow when the particle concentration increased. Increasing the rotation speed of the shaft produced a narrow particle size distribution. Increasing the feed flow rate (enhanced filtration pressure difference) resulted in a wider particle size distribution, but beyond a certain point a cake will form.
Cyclone Washer Adapted from an American‐Type Cyclone Separator
Authors: Majewski R. , Boulos Elias R. , Taqueda M. E. S.
Published: June 2008

A modified cyclone washer was designed, fabricated, and its collection efficiency evaluated. This equipment consists of an American‐type cyclone separator with a triple cone and a spray nozzle was introduced into its cylindrical body. The study consisted of an experimental evaluation of the operating conditions at ambient and higher than ambient temperatures, varying chimney height and water flow rate, with the purpose of humidifying the dust. The collection efficiency of the cyclone washer was evaluated particles of micronized quartz with an average diameter of 7.48 μm and a density of 2.650 g/cm3. The amount of particles varied from 20–100 mg/m3 of air. An average efficiency of 97.07 ± 1.03 % was obtained with four spray nozzles, a chimney height of 0.645 m and 0.358 m3/s of gas.
Dynamic Process Model for Nanoparticle Precipitation in Microemulsion Systems
Authors: Adityawarman D. , Niemann B. , Sundmacher K.
Published: June 2008

The controlled technical‐scale production of nanoparticles is a very important aspect in nanotechnology. The synthesis of nanoparticles by microemulsion precipitation is a laboratory‐scale technique which has to be scaled up to technical use. For a better understanding of this complex process, a numerically efficient process model was derived which is applicable to CFD studies, process control and the analysis of the scale‐up behavior. The model contains microemulsion specific nucleation kinetics allowing for the discrete character of the system on a molecular scale, and growth kinetics adopted from bulk phase approaches. The major output of this process model is the computationally efficient and reliable determination of the mean particle diameter as a function of time. A comparison with experimentally obtained data from barium sulfate precipitation showed a qualitatively good agreement.
Interrelation of Flooding and Complete Dispersion in Agitated Gas‐Liquid Contactors
Authors: Babalona E. , Markopoulos J.
Published: June 2008

Despite the fact that the complete dispersion characteristics in agitated gas‐liquid contactors are operationally important, the flooding‐loading transition is widely used as a design criterion, due to its experimental convenience and accuracy. Moreover, limited data are available in the literature on the interrelation of the flooding‐loading and the loading‐complete dispersion transitions, although several investigators have worked on these two transition stages. Thus, knowledge of the interrelation between these two stages would be of theoretical and practical importance. In this work, the dependence of the stirrer speed at complete dispersion,nCD, on the stirrer speed at flooding,nF, was experimentally studied, in coalescing and non‐coalescing systems, using Rushton turbines of two different diameters. The experimental results, having an accuracy of < 5 %, are given in the form of a dimensionless correlation.
Model Development for MEOR Process in Conventional Non‐Fractured Reservoirs and Investigation of Physico‐Chemical Parameter Effects
Authors: Behesht M. , Roostaazad R. , Farhadpour F. , Pishvaei M. R.
Published: June 2008

A three‐dimensional multi‐component transport model in a two‐phase oil‐water system was developed. The model includes separated terms to account for the dispersion, convection, injection, growth and death of microbes, and accumulation. For the first time, effects of both wettability alteration of reservoir rock from oil wet to water wet and reduction in interfacial tension (IFT) simultaneously on relative permeability and capillary pressure curves were included in a MEOR simulation model. Transport equations were considered for the bacteria, nutrients, and metabolite (bio‐surfactant) in the matrix, reduced interfacial tension on phase trapping, surfactant and polymer adsorption, and effect of polymer viscosity on mobility of the aqueous phase. The model was used to simulate effects of physico‐chemical parameters, namely flooding time schedules, washing water flowrate, substrate concentration, permeability, polymer and salinity concentration on Original Oil In Place (OOIP) in a hypothetical reservoir.
Precipitation and Characterization of Chelerythrine Microparticles by the Supercritical Antisolvent Process
Authors: Hong H. L. , Suo Q. L. , Li F. W. , Wei X. H. , Zhang J. B.
Published: June 2008

Chelerythrine was successfully micronized from methanol solution using Supercritical Carbon Dioxide (SC‐CO2) as an antisolvent via the Solution Enhanced Dispersion by Supercritical Fluids through the Prefilming Atomization (SEDS‐PA) process. The morphology and particle size of the chelerythrine microparticles were visually analyzed by scanning electron microscopy (SEM). For the purpose of the optimizing operating conditions of the SEDS‐PA process, the influences of the experimental variables, i.e., temperature, pressure, solution flow rate and initial solution concentration, on the particle size and morphology of chelerythrine microparticles are discussed in detail. The results show that the best process conditions for the micronization of chelerythrine are: T = 313 K, P = 20 MPa, C = 2.0 g/L and F = 2.0 mL/min. The precipitates obtained under the optimized experimental conditions are short rod‐like chelerythrine microparticles with a mean particle size of 0.1–1 μm in width.
Spiral waves in bio‐inspired oscillatory dissipative media
Authors: Corinto Fernando , Lanza Valentina , Gilli Marco
Published: June 2008

Spiral waves are the most universal form of patterns arising in dissipative media of oscillatory and excitable nature. By focusing on oscillatory networks, whose cells admit of a Lur'e description and are linearly connected through weak couplings, the occurrence of spiral waves has been studied. In particular, the global dynamic behavior of such networks is investigated through the phase deviation equation obtained by the joint application of the harmonic balance method and Malkin's theorem. Furthermore, a simple condition for verifying the occurrence of spiral waves is provided. Copyright © 2008 John Wiley & Sons, Ltd.
Implementation of embedded emulated‐digital CNN‐UM global analogic programming unit on FPGA and its application
Authors: Vörösházi Zsolt , Kiss András , Nagy Zoltán , Szolgay Péter
Published: June 2008

The paper addresses the issue of implementing an embedded global analogic programming unit (GAPU) on the reconfigurable emulated‐digital cellular neural/nonlinear networks universal machine (CNN‐UM) architecture that has been extended by a flexible Xilinx MicroBlaze soft processor core to take full advantage of the joint computing power of high‐speed distributed arithmetics and programmability. The implemented GAPU provides a stand‐alone operation, which is capable of controlling complex sophisticated CNN analogic algorithms similar to various visual microprocessors, such as the ACE4k, ACE16k, and Bi‐i vision systems. The quality of the embedded GAPU implementation is demonstrated by an analogic algorithm, in which sequences of template operations are required. Based on the experiments, several important issues relating to the acceleration efficiency, accuracy, cell size, and area consumption are discussed and compared with different CNN‐UM implementations. Copyright © 2008 John Wiley & Sons, Ltd.
A heat shock protein gene (Hsp70.1) is critically involved in the generation of the immune response to myelin antigen
Authors: Mycko Marcin P. , Cwiklinska Hanna , Walczak Agata , Libert Claude , Raine Cedric S. , Selmaj Krzysztof W.
Published: June 2008

Protracted inflammation has been associated with the generation of autoimmune responses. In this respect, increase in the chaperonin, heat shock protein 70 (hsp70) is an outcome of prolonged inflammatory stress. Previous experiments have shown that overexpression of inducible hsp70 in vitro enhanced myelin autoantigen recognition. To prove the role of hsp70 in myelin‐directed responses in vivo, we applied a mouse deficient in the major gene encoding inducible hsp70, hsp70.1. Hsp70.1–/– mice sensitized for experimental autoimmune encephalomyelitis (EAE) with myelin oligodendrocyte glycoprotein (MOG) peptide 35–55, displayed almost complete resistance to the disease. This correlated with the loss of T cell proliferation and IFN‐γ production in response to MOG35–55. T cell transfer experiments as well as antigen presentation assays in vitro demonstrated that hsp70 deficiency was associated with dysfunction in the activation of autoreactive T cells. Moreover, T cell responses to ovalbumin (OVA) peptide 323–339 were altered and CD4+ T cells were more prone to TCR‐induced apoptosis, suggesting broader spectrum of T cell defect in hsp70.1–/– mice. These results provide compelling evidence for generalized effect mediated by inducible hsp70 in the recognition of myelin self and non‐self antigens that influences the cytokine profile of the immune response affecting autoimmune demyelination.
Development of CTL memory despite arrested clonal expansion
Authors: van Stipdonk Marianne J. B. , Sluijter Marjolein , Han Wanda G. H. , Offringa Rienk
Published: June 2008

Activation of a cytotoxic T lymphocyte (CTL) response in an antigen‐exposed lymph node involves a great diversity of encounters between naive CTL and APC that differ in both duration and quality. This broad spectrum of priming events instigates a complex blend of CTL developmental pathways. Using an experimental system that allows tight control over CTL priming, we have singled out defined priming events and analyzed the impact of the resulting instructional program on the effector and memory phases of the CTL response. As expected, prolonged antigenic stimulation induces potent CTL expansion, effector function and CTL memory. In contrast, CTL that have received suboptimal stimulation fail to undergo extensive expansion. Nevertheless these arrested CTL persist long term and acquire memory function. Thus, our data demonstrate that CTL memory can develop as a result of a suboptimal stimulation that causes arrested clonal expansion.
Cover Picture: Clonally expanded plasma cells in the cerebrospinal fluid of MS patients produce myelin‐specific antibodies – Eur. J. Immunol. 7/2008
Authors: von Büdingen Hans‐Christian , Harrer Melanie D. , Kuenzle Sandra , Meier Mirjam , Goebels Norbert
Published: June 2008

The cover shows a confocal micrograph of myelinated nervous tissue at the rim of a demyelinating lesion in the brain white matter of a patient with multiple sclerosis (MS). Myelin surrounding the axon is stained by a monoclonal antibody obtained by recombinant expression of immunoglobulin genes from clonally expanded plasma cells as present in the cerebrospinal fluid of MS patients. The image was taken from the article by von Büdingen et al. (pp.

2014–2023)

in which the authors demonstrate that myelin specific antibodies result from antigen driven immune responses found in the cerebrospinal fluid of MS patients.
The Use of Liquid–Liquid Interface (Biphasic) for the Preparation of Benzenetricarboxylate Complexes of Cobalt and Nickel
Authors: Banerjee Abhishek , Mahata Partha , Natarajan Srinivasan
Published: June 2008

New metal–organic frameworks (MOFs) [Ni(C12N2H10)(H2O)][C6H3(COO)2(COOH)] (I), [Co2(H2O)6][C6H3(COO)3]2·(C4N2H12)(H2O)2(II), [Ni2(H2O)6][C6H3(COO)3]2·(C4N2H12)(H2O)2(III), [Ni(C13N2H14)(H2O)][C6H3(COO)2(COOH)] (IV), [Ni3(H2O)8][C6H3(COO)3] (V) and [Co(C4N2H4)(H2O)][C6H3(COO)3] (VI) {C6H3(COOH)3= trimesic acid, C12N2H10= 1,10‐phenanthroline, C4N2H12= piperazine dication, C13N2H14= 1,3‐bis(4‐pyridyl)propane and C4N2H4= pyrazine} have been synthesized by using an interface between two immiscible solvents, water and cyclohexanol. The compounds are constructed from the connectivity between the octahedral M2+(M = Ni, Co) ions coordinated by oxygen atoms of carboxylate groups and water molecules and/or by nitrogen atoms of the ligand amines and the carboxylate units to form a variety of structures of different dimensionality. Strong hydrogen bonds of the type O–H···O are present in all the compounds, which give rise to supramolecularly organized higher‐dimensional structures. In some cases π···π interactions are also observed. Magnetic studies indicate weak ferromagnetic interactions inI,IVandVand weak antiferromagnetic interactions in the other compounds (II,IIIandVI). All the compounds have been characterized by a variety of techniques.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Ruthenium Dihydrogen Complex for C–H Activation: Catalytic H/D Exchange under Mild Conditions
Authors: Prechtl Martin H. G. , Hölscher Markus , Ben‐David Yehoshoa , Theyssen Nils , Milstein David , Leitner Walter
Published: June 2008

Catalytic H/D‐exchange reactions were studied with [Ru(dtbpmp)(η2‐H2)(H)2] (1) as catalyst. Under mild reaction conditions (25–75 °C) a wide range of arenes and olefins undergo H/D exchange with [D6]benzene. A preference for protons at sp2 carbons was observed with conversions up to >90 % and significant regioselectivity in certain cases. For more reaction insights NMR‐based kinetic studies were performed with naphthalene as substrate, revealing an activation energy of 15.8 kcal mol–1 for the H/D exchange at the β‐position. Furthermore, the key steps of the reaction mechanism were investigated by means of DFT calculations for both model complexes (PMe2 donor sites) and real catalysts (PtBu2 donor sites). The calculations resulted in Gibb's free activation energies in the range of 10–16 kcal mol–1, indicating H/D exchange at the β‐position of naphthalene to be clearly favoured over the α‐position, which is in full accordance with the experimental observations.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
First Synthesis of Bi‐ and Tricyclic α,β‐Unsaturated δ‐Oxacaprolactams from Cyclic Imines via Ring‐Closing Metathesis
Authors: Watzke Martin , Schulz Knut , Johannes Katharina , Ullrich Pasqual , Martens Jürgen
Published: June 2008

A new class of α,β‐unsaturated δ‐oxacaprolactams was synthesized from imines as starting material. The synthetic procedure is based on an acyl chloride addition in the first step, followed by a ring‐closing metathesis using a ruthenium catalyst. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Synthesis of α2,2,β3‐Diamino Acids by Double Stereodifferentiation Aldol Addition of Oxazolidinone Enolates to N‐(tert‐Butylsulfinyl) Imines
Authors: Guerrini Andrea , Varchi Greta , Samorì Cristian , Battaglia Arturo
Published: June 2008

A novel application of Seebach's “SRS” synthetic principle works efficiently when conformationally restrained trisubstituted chiral α2,2,β3‐diamino acids are synthesized by double stereoinduction reactions of chiral oxazolidinone enolates with N‐sulfinyl aldimines. Two stereoisomers were isolated in a form of 1′‐(sulfinylamino)oxazolidinones and bicyclic 1H,3H‐imidazo[1,5‐c]oxazole‐1,5(6H)‐diones, from which the α2,2,β3‐diamino acids are obtained by selective deprotection methodologies. Among a variety of highly functionalized diamino acids, this highly diastereoselective protocol provides a synthetic route for yet unreported C‐glycosyl and α‐nucleoside diamino acids. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Regulatory focus systems and personal values
Authors: Leikas Sointu , Lönnqvist Jan‐Erik , Verkasalo Markku , Lindeman Marjaana
Published: June 2008

The present studies sought connections between two highly influential, but separate motivational systems: the regulatory foci and personal values. Study 1 (N = 173) showed that promotion focus was positively associated with Achievement and negatively with Tradition values, whereas prevention focus was positively associated with Conformity and Security values, and negatively with Self‐Direction and Stimulation values. Furthermore, interdependent self‐construal moderated trait prevention focus' associations with Power, Benevolence, Universalism, and Conformity values. Study 2 (N = 150) showed that a promotion‐framed message evoked more compliant behavior among those scoring high on Stimulation, Achievement, and Self‐Direction values, but that a prevention‐framed message evoked more compliance among those high in Conformity values. The results suggested that the regulatory foci are associated with certain values, and that these values may increase motivation in promotion‐ versus prevention‐relevant situations. Copyright © 2008 John Wiley & Sons, Ltd.
Antecedents and consequences of acculturation preferences of non‐indigenous Chileans in relation to an indigenous minority: longitudinal survey evidence
Authors: Zagefka Hanna , Brown Rupert , González Roberto
Published: June 2008

Two longitudinal survey studies were conducted with non‐indigenous majority Chilean participants (Ns = 755 cross‐sectional, 198 longitudinal in study 1; 390 cross‐sectional, 333 longitudinal in study 2). In contrast to most previous research, the longitudinal design allowed to test directly the hypothesised causal direction of effects. There were two broad research questions. Firstly, what is the relationship between acculturation preferences of non‐indigenous majority members and negative affect towards the indigenous Mapuche? More specifically, does a preference for integration lead to less negative affect than a preference for assimilation, separation or marginalisation? Related to this, do the dimensions of culture maintenance and contact taken singly predict negative affect and/or vice versa? Secondly, does knowledge about the Mapuche causally and indirectly influence acculturation preferences, partially mediated by sympathy with the Mapuche? Results confirmed that knowledge influenced acculturation preferences, and that sympathy was a partial mediator. Acculturation preferences, in turn, influenced negative affect. The contact dimension underlying the categorical acculturation strategies was a predictor of outcomes, while the culture maintenance dimension was not. Implications of the findings are discussed. Copyright © 2008 John Wiley & Sons, Ltd.
A Selective Film Based on Poly(3‐octylthiophene) Doped with Dihydroxyanthraquinone Sulfonate
Authors: Tamer Uğur , Ertaş Nusret , Ergüner Övgü , Gündoğdu Yusuf
Published: June 2008

A stable film of poly(3‐octylthiophene)–dihydroxyanthraquinone sulfonate has been synthesized electrochemically in non‐aqueous solution. The incorporation of dihydroxyanthraquinone sulfonate as an anionic complexing ligand into poly(3‐octylthiophene) film during electropolymerization was achieved and copper ions were accumulated by reduction on the electrode surface. The presence of dihydroxyanthraquinone sulfonate during the electrochemical polymerization of 3‐octylthiophene is shown to impact the sensitivity and the stability of the organic conducting film electrode response. The electroanalysis of copper(II) ions using conducting polymer electrode was achieved by differential pulse anodic stripping voltammetry with remarkable selectivity. The analytical performance was evaluated and linear calibration graphs were obtained in the concentration range of 50–400 ng mL−1 copper(II) ion for 240 seconds accumulation time and the limit of detection was found to be 7.8 ng mL−1. To check the selectivity of the proposed stripping voltammetric method for copper(II) ion, various metal ions as potential interferents were tested. The developed method was applied to copper(II) determination in certified reference material, NWRI‐TMDA‐61, trace elements in fortified water.
Electrochemical Polymerization of 3,4‐Ethylenedioxythiophene from Aqueous Solution Containing Hydroxypropyl‐β‐cyclodextrin and the Electrocatalytic Behavior of Modified Electrode Towards Oxidation of Sulfur Oxoanions and Nitrite
Authors: Vasantha V. S. , Thangamuthu R. , Chen Shen‐Ming
Published: June 2008

Poly(3,4‐ethylenedioxythiophene) (PEDOT) film was prepared on glassy carbon electrode from 0.1 M LiClO4 aqueous solution containing 3,4‐ethylenedioxythiophene (EDOT) monomer and hydroxypropyl‐β‐cyclodextrin (HP‐β‐CD), by multiple scan cyclic voltammetry. The effect of oxidation potentials on electropolymerization of EDOT was examined by chronoamperometry and cyclic voltammetric techniques. The results of potentiostatic experiments show that optimum potential range to obtain compact stable film was 0.9 to 1.05 V (vs. Ag/AgCl). At higher positive potential, i.e. above 1.05 V, polymer growth was hindered by passivation effect. The PEDOT film exhibited a strong absorption at 550 nm in the UV‐vis region and also a multicolor electrochromism in different buffer solutions (sky blue‐purple red). Cyclic voltammetric features of PEDOT‐coated electrode in pure supporting electrolyte suggested that charge transfer of the film resembles that of surface‐confined redox species. Finally, the electrocatalytic behavior of PEDOT‐modified electrode was tested towards oxidation of sulfur oxoanions and nitrite using cyclic voltammetry.
Heterogeneous Membrane and Coated Wire Type Electrode with Chitosan as Ionophore in the Potentiometric Determination of Glutamate: Comparative Study
Authors: Md Isa Illyas , Ab Ghani Sulaiman
Published: June 2008

This study reports on two types of glutamate sensors based on chitosan, i) heterogeneous membrane and ii) coated wire (CWE). The linearity ranges are: i) membrane, 1.0×10−5 to 1.0×10−1 M and ii) CWE, 1.0×10−5 to 1.0×10−3 M. The LODs, and pH ranges are i) membrane, 5.0×10−6 M and 4–8 and ii) CWE, 1.0×10−5 M and 3–5, respectively. The presence of ionic species normally found in foodstuffs did not interfere in both electrodes. Interference in CWE was minimized by prior dilution of the sample. The CWE was further investigated for on‐line analysis. The material for proposed electrodes was cheaper and environmental friendly. Hence, they were suggested as alternative tools for the analysis of glutamate.
High Sensitive Electrochemical Detection of Sequence‐Specific DNA Using Low Current Voltammetry
Authors: Lin Lingling , Zhou Jianzhang , Zhang Yan , Lin Zhonghua
Published: June 2008

In this article, we report on efforts to construct a high sensitive electrochemical sensor with immobilized sandwich‐type DNA borne ferrocene (Fc) head for sequence‐specific DNA detection using ultramicroelectrode and low current voltammetry. Based on the difference in deformability between the bending rigid complementary DNA double helix and its anomalous flexile mismatches, the fully complementary target can be distinguished from mismatched targets including the single‐base mismatched target. Detection limit estimated as the amount of DNA is observed to be 100 fM via low current voltammetry. The method offers great promise of high sensitivity and selectivity simultaneously for effective gene identification.
Some Properties of Sodium Dodecyl Sulfate Functionalized Multiwalled Carbon Nanotubes Electrode and Its Application on Detection of Dopamine in the Presence of Ascorbic Acid
Authors: Zheng Dan , Ye Jianshan , Zhang Weide
Published: June 2008

A sodium dodecyl sulfate (SDS) functionalized multiwalled carbon nanotubes (MWNTs) electrode (SDS/MWNTs) was successfully constructed in this study. The electrochemical property of the SDS/MWNTs electrode has been characterized by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Nyquist plots suggest that the immersion time of SDS affects the resistances of the MWNTs electrodes. The thickness of adsorbed SDS on MWNTs surface is estimated to be 1.23 nm, which is close to the value of SDS monolayer. CV results demonstrate a 5‐fold enhanced response for dopamine (DA) at the SDS/MWNTs electrode compared to the bare MWNTs one. DPV results illustrate that DA can be selectively determined in the presence of high concentration ascorbic acid (AA) with a linear range from 20 μM to 0.20 mM and a sensitivity of 0.024 μA μM−1 at the SDS/MWNTs electrode.
Protocol for Extraction and Determination of Cr(VI) in Solid Materials with a High Cr(III)/Cr(VI) Ratio Using EDDS as a Leaching Agent for Cr(VI) and a Masking Agent for Cr(III)
Authors: Grabarczyk Malgorzata
Published: June 2008

A sensitive and selective protocol for the extraction of all forms of Cr(VI) from solid materials followed by determination by catalytic adsorptive stripping voltammetry has been elaborated. Cr(VI) was leached to a solution with 0.2 mol L−1 (NH4)2SO4/NH4OH+0.1 mol L−1 EDDS (pH 9.5) and simultaneously Cr(III) was transferred to a nonactive electrochemical complex with EDDS. The method allows for Cr(VI) determination in solid samples containing even a 1000–2000 fold excess of extractable Cr(III) without its noticeable influence. The effects of several experimental variables such as the composition and pH of the extractant, the time and temperature of the solid sample mixing with the extractant were studied. At the optimized conditions more than 95% of total Cr(VI) recoveries from solid samples were achieved. The validation of the proposed procedure was carried out by Cr(VI) determination in certified reference material CRM 019 Ash, spiked and unspiked with Cr(III), and by comparing the obtained results with those obtained using other common extraction procedures.
Flow Injection Analysis of Iodate Reduction on PEDOT Modified Electrode
Authors: Balamurugan A. , Chen Shen‐Ming
Published: June 2008

Poly‐(3,4‐ethylenedioxythiophene) (PEDOT) films were electrodeposited by cyclic voltammetry on glassy carbon electrode at different anodic potentials in the range of 1.0–1.5 V (Ag/AgCl) and its electrocatalytic properties towards reduction of iodate were reported. The effect of the pH of the solution on the response of PEDOT electrode towards iodate also studied. The modified electrode was employed successfully as an amperometric sensor for iodate in a flow injection apparatus. The repeatability of the method for 14 injections of a μM iodate solution was 7%. Interference from other oxidant anions such as nitrate was not noticeable, whereas bromate, chlorate and nitrite interfere at slight levels.
Components of the Net Current in Differential Pulse Polarography
Authors: Zelić Marina , Jadreško Dijana
Published: June 2008

As the modern (voltammetric) software packages offer ‘resolution’ of each individual net signal in differential pulse polarography (DPP) to its components, an attempt was made to test such a possibility on several model systems. Reversible and nonreversible reduction processes of simple metal ions (Cd2+, Eu3+) were included, together with some examples of the anion induced adsorption (Cd2+‐I− and Pb2+‐Br− systems) under conditions of partly or fully covered electrode surface. Taking into account that so called ‘backward’ current is in fact DC wave, it could be said that one technique is hidden within the other. Consequently, DPP measurements together with following of the ‘backward’ signals could give more information and save the time. ‘Forward’ component offers additional possibilities in data treatment, especially when its relationship to the ‘backward’ current (with respect to the potential and height) is taken into account. Such an approach seems promising, even when applied on a purely qualitative level, because some effects which cannot be observed if only the net signals are followed become obvious when their components are taken into consideration.
Autooxidative Activity of Chlorogenic Acid and Damage to DNA
Authors: Yang Zhou‐sheng , Long Hai‐yan , Zhang Xiao‐yan , Wang Yong
Published: June 2008

The interaction of chlorogenic acid with double‐stranded calf thymus DNA was investigated in solution by cyclic voltammetry at a glassy carbon electrode (GCE). The different working electrodes were prepared by covering solution containing different components onto the surface of GCE. The autooxidative activity of chlorogenic acid and inducement of DNA damage were evaluated by employing the prepared working electrode in pH 5.0, 0.10 M acetate buffer solution with differential pulse voltammetry (DPV). The influences of temperature and metal ions (cupric ions) on the extent of DNA damage were examined. Chlorogenic acid possessed autooxidative activity and could induce DNA damage under certain conditions. The increasing temperature and existing cupric ions could enhance the autooxidative capability of chlorogenic acid and enlarge the extent of DNA damage. It was possible that the DNA damage induced by chlorogenic acid preferentially took place at guanosine‐containing segments, with the formation of 8‐oxo‐deoxyguanosine (a biomarker of DNA oxidative damage). A mechanism on the autooxidative activity of chlorogenic acid and inducing DNA damage was proposed.
Quantitative brain proton MR spectroscopy based on measurement of the relaxation time T1 of water
Authors: Bajzik Gábor , Auer Tibor , Bogner Péter , Aradi Miklós , Kotek Gyula , Repa Imre , Doczi Tamas , Schwarcz Attila
Published: June 2008

Purpose

To provide a straightforward method for metabolite quantitation in the brain. Tissue water concentration can be determined in a voxel by measuring T1 and it may provide an internal reference for the calculation of the metabolite concentrations.

Materials and Methods

Water‐suppressed stimulated echo acquisition mode spectra were obtained at 1.5T, and the tissue water content was calculated from T1.

Results

The calculated water content values demonstrated very good agreement with literature data. Metabolite concentrations (mmol/liter) in the gray and white matter: N‐acetyl‐aspartate = 14.02 ± 1.93, creatine = 9.98 ± 1.03, and choline = 1.14 ± 0.24; N‐acetyl‐aspartate = 11.08 ± 2.24, creatine = 7.83 ± 0.66, and choline = 2.05 ± 0.38, respectively.

Conclusion

The water content calculated from T1 can yield an internal reference in MR spectroscopy, and the accurate measurement of metabolite concentrations is feasible. The proposed method is simple and can readily be applied in any MR center without the need for complicated corrections or calibration procedures. J. Magn. Reson. Imaging 2008;28:34–38. © 2008 Wiley‐Liss, Inc.
Chronic hepatitis: Role of diffusion‐weighted imaging and diffusion tensor imaging for the diagnosis of liver fibrosis and inflammation
Authors: Taouli Bachir , Chouli Malik , Martin Alastair J. , Qayyum Aliya , Coakley Fergus V. , Vilgrain Valérie
Published: June 2008

Purpose

To determine the diagnostic performance of liver apparent diffusion coefficient (ADC) measured with conventional diffusion‐weighted imaging (CDI) and diffusion tensor imaging (DTI) for the diagnosis of liver fibrosis and inflammation.

Materials and Methods

Breathhold single‐shot echo‐planar imaging CDI and DTI with b‐values of 0 and 500 second/mm2 was performed in 31 patients with chronic liver disease and 13 normal volunteers. Liver biopsy was performed in all patients with liver disease with a median delay of two days from MRI. Fibrosis and inflammation were scored on a 5‐point scale (0–4). Liver ADCs obtained with CDI and DTI were compared between patients stratified by fibrosis stage and inflammation grade. Receiver operating characteristic (ROC) curve analyses were conducted to evaluate the utility of the ADC measures for prediction of fibrosis and inflammation.

Results

Patients with liver fibrosis and inflammation had significantly lower liver ADC than subjects without fibrosis or inflammation with CDI and DTI. For prediction of fibrosis stage ≥ 1 and stage ≥ 2, area under the ROC curve (AUC) of 0.848 and 0.783, sensitivity of 88.5% to 73.7%, and specificity of 73.3% to 72.7% were obtained, for ADC ≤1.40 × 10–3 mm2/second and ≤1.30 × 10–3 mm2/second (using CDI), respectively. For prediction of inflammation grade ≥ 1, AUC of 0.825, sensitivity of 75.0%, and specificity of 78.6% were obtained using ADC ≤ 1.30 × 10–3 mm2/second (using CDI). CDI performed better than DTI for diagnosis of fibrosis and inflammation.

Conclusion

Liver ADC can be used to predict liver fibrosis and inflammation with acceptable sensitivity and specificity. J. Magn. Reson. Imaging 2008;28:89–95. © 2008 Wiley‐Liss, Inc.
Automatic computation of left ventricular ejection fraction from spatiotemporal information in cine‐SSFP cardiac MR images
Authors: Pednekar Amol S. , Muthupillai Raja , Cheong Benjamin , Flamm Scott D.
Published: June 2008

Purpose

To clinically validate an algorithm that automatically computes left ventricular (LV) ejection fraction (LVEF) using a priori geometric and intrinsic spatiotemporal information from cine steady‐state free precession (SSFP) MR images.

Materials and Methods

The algorithm was evaluated in 64 subjects (21 healthy volunteers and 43 patients, LVEF 19–71%). Bland‐Altman analyses were performed on short‐axis slices subdivided into three sections (basal, midcavity, and apical) to assess the impact of morphologic variations on LVEF computation.

Results

The automated algorithm delineated the clinically applicable endocardial boundary in 1011 of 1078 short‐axis slices (94%). The bias (mean difference) values computed with clinically unusable contours replaced with hand‐drawn equivalents were small for the LV end‐diastolic volume (LVEDV, <11 mL/7%), end‐systolic volume (LVESV, <7 mL/11%), and LVEF (<1.2%). Moreover, these values were within the limits of interobserver and intraobserver variability of experienced observers (LVEDV, <13 mL/8%; LVESV, <12 mL/17%; and LVEF, <5%). In the end‐diastolic phase, the limits of agreement (bias ± 1.96 SD of difference) were small (<5% LVEDV) in all sections. However, in the end‐systolic phase, the limits of agreement were larger for the midcavity (<21% LVESV) and apical (<11% LVESV) slices.

Conclusion

This data‐driven algorithm can estimate LVEDV, LVESV, and LVEF with a bias that is comparable to the interobserver and intraobserver variability of experienced observers. J. Magn. Reson. Imaging 2008;28:39–50. © 2008 Wiley‐Liss, Inc.
Apparent wall thickening of cystic renal lesions on MRI
Authors: Gulani Vikas , Adusumilli Saroja , Hussain Hero K. , Vazquez Alberto L. , Francis Isaac R. , Noll Douglas C.
Published: June 2008

Purpose

To show that cystic renal lesions that would otherwise meet criteria for simple cysts can demonstrate perceptible walls or increased wall thickness on MRI, sometimes causing these lesions to be “upgraded.” It was hypothesized that thickening of cyst walls on MRI can be artifactual, due to data truncation, applied filtering, and low signal‐to‐noise ratio (SNR).

Materials and Methods

k‐Space data for a 4‐cm cyst were created in a 40‐cm field of view (FOV) (512 × 512 matrix). Additional data sets were created using the central 512 × 256 and 512 × 128 points. Noise was simulated so that the cyst SNR was approximately 7, 14, and 20, respectively. Actual wall thickness was set at 0.25 mm, and cyst:wall signal at 1:4. An inverse two‐dimensional (2D) fast Fourier transform (FFT) yielded simulated images. A Fermi filter was applied to reduce ringing. Images/projections were examined for wall thickening. Seven patients with initially thick‐walled cysts on fat‐saturated spoiled gradient‐echo (FS‐SPGR) images were scanned with increasing resolution (256 × 128 and 256 × 256; four patients were also scanned with 512 × 512). Average wall thickness at each resolution was compared using a two‐tailed paired Student's t‐test.

Results

Simulations showed apparent wall thickening at low resolution, improving with higher resolutions. Low SNR and application of the Fermi filter made it difficult to identify ringing as the cause of this thickening. The simulation results were confirmed on seven patients, whose cyst walls proved to be artifactually thickened (P < 0.01).

Conclusion

Thickening of cyst walls on MRI can be artifactual. Upon encountering thick‐walled cystic renal lesions, high‐resolution images can be acquired to exclude apparent thickening. J. Magn. Reson. Imaging 2008;28103–110. © 2008 Wiley‐Liss, Inc.
Depth‐dependent profiles of glycosaminoglycans in articular cartilage by μMRI and histochemistry
Authors: Xia Yang , Zheng ShaoKuan , Bidthanapally Aruna
Published: June 2008

Purpose

To quantify the distribution profile of glycosaminoglycans (GAGs) in articular cartilage with the magnetic resonance imaging (MRI) gadolinium (Gd) contrast method (the dGEMRIC procedure in clinical MRI) and correlate with histochemical results.

Materials and Methods

Fresh canine cartilage from seven humeral heads was harvested. Sixteen cartilage specimens were imaged at 13 μm pixel resolution using the μMRI T1‐Gd method to generate 2D GAG maps in cartilage. Nineteen cartilage specimens from adjacent locations on the same joints were papain‐digested to quantify the bulk GAG content in tissue. In addition, six cartilage specimens were microtomed into 40‐μm serial sections that were parallel with the articular surface. These sections were biochemically analyzed individually to determine the depth‐dependent profiles of GAG concentration.

Results

The GAG concentrations between the μMRI measurement and the bulk biochemical method have statistically significant agreement. The depth‐dependent GAG profiles from the histochemical method (40 μm depth resolution) have similar line shapes as that determined by μMRI at 13 μm resolution.

Conclusion

The GAG concentration as measured by μMRI T1‐Gd contrast method provides an accurate account of the macromolecular content in articular cartilage. J. Magn. Reson. Imaging 2008;28:151–157. © 2008 Wiley‐Liss, Inc.
Pelvic imaging using a t1w fat‐suppressed three‐dimensional dual echo dixon technique at 3T
Authors: Cornfeld Daniel M. , Israel Gary , McCarthy Shirley M. , Weinreb Jeffery C.
Published: June 2008

Purpose

To compare two T1‐weighted (T1W) fat‐suppressed sequences for 3D breath‐hold pre‐ and postcontrast fat‐suppressed T1W imaging of the female pelvis at 3T.

Materials and Methods

Pelvic MRI scans of 16 female patients were retrospectively identified who were scanned with two 3D breath‐hold sequences: 1) a fast spoiled gradient echo sequence with spectral inversion at lipids (SPECIAL) (called 3D FSPGR), and 2) a dual‐echo two‐point Dixon (DE Dixon) sequence. Contrast between soft tissue and fat, soft tissue and fluid, and fat and fluid was measured on pre‐ and postcontrast images. Additionally, two readers subjectively scored the images for degree and homogeneity of fat suppression plus presence and severity of artifacts.

Results

Contrast between muscle and myometrium to fat was improved with the Dixon technique (0.61 vs. 0.09 and 0.7 vs. 0.3, respectively, P < 0.001). Both readers agreed that fat suppression was stronger with the Dixon sequence (P < 0.001 and P = 0.06). Artifacts were equivalent (P = 0.53 and 0.65).

Conclusion

The 3D DE Dixon sequence achieved stronger fat suppression in the female pelvis when compared to a 3D FSPGR sequence with SPECIAL. J. Magn. Reson. Imaging 2008;28:121–127. © 2008 Wiley‐Liss, Inc.
Cardiac cine MRI: Quantification of the relationship between fast gradient echo and steady‐state free precession for determination of myocardial mass and volumes
Authors: Malayeri Ashkan Akhavan , Johnson W. Craig , Macedo Robson , Bathon Joan , Lima João A.C. , Bluemke David A.
Published: June 2008

Purpose

To determine the correlation function between the steady‐state free precession (SSFP) and fast gradient echo (FGRE) cine MRI pulse sequences for measuring the myocardial mass and volumes.

Materials and Methods

Cardiac cine MRI examinations were acquired in 50 individuals (female: 35, male: 15, mean age 64.1 ± 9.1 years, range 48–83) using SSFP and FGRE cardiac pulse sequences.

Results

The mean (standard deviation [SD]) left ventricular end diastolic volume measured by SSFP was significantly larger (4.5%) than by FGRE (P < 0.001); this was also the case for end systolic volume (15.0%, P < 0.001). The relationship between SSFP and FGRE measures were linear and highly correlated (P < 0.001) for both left ventricular end diastolic and end systolic volumes (r2 = 0.90 vs. 0.91, respectively). We determined linear regression models to estimate the SSFP values based on the FGRE measures. Slope (intercept) for ejection fraction, stroke volume, and cardiac output were 0.99 (−2.79), 0.77 (17.5), and 0.76 (1.29), respectively.

Conclusion

Linear relationships exist for key LV function parameters when comparing SSFP and FGRE cine MRI. These results indicate that existing databases and normal values for FGRE LV function may be converted to corresponding LV function values for SSFP MRI. J. Magn. Reson. Imaging 2008;28:60–66. © 2008 Wiley‐Liss, Inc.
Vascular space occupancy‐dependent functional MRI by tissue suppression
Authors: Wu Changwei W. , Chuang Kai‐Hsiang , Wai Yau‐Yau , Wan Yung‐Liang , Chen Jyh‐Horng , Liu Ho‐Ling
Published: June 2008

Purpose

To measure the cerebral blood volume (CBV) dynamics during neural activation, a novel technique named vascular space occupancy (VASO)‐based functional MRI (fMRI) was recently introduced for noninvasive CBV detection. However, its application is limited because of its low contrast‐to‐noise ratio (CNR) due to small signal change from the inverted blood.

Materials and Methods

In this study a new approach—VASO with tissue suppression (VAST)—is proposed to enhance CNR. This technique is compared with VASO and blood oxygenation level‐dependent (BOLD) fMRI in block‐design and event‐related visual experiments.

Results

Based on acquired T1 maps, 75.3% of the activated pixels detected by VAST are located in the cortical gray matter. Temporal characteristics of functional responses obtained by VAST were consistent with that of VASO. Although the baseline signal was decreased by the tissue suppression, the CNR of VAST was about 43% higher than VASO.

Conclusion

With the improved sensitivity, VAST fMRI provides a useful alternative for mapping the spatial/temporal features of regional CBV changes during brain activation. However, the technical imperfectness of VAST, such as the nonideal inversion efficiency and physiological contaminations, limits its application to precise CBV quantification. J. Magn. Reson. Imaging 2008;28:219–226. © 2008 Wiley‐Liss, Inc.
Detection of lymph node metastasis in cervical and uterine cancers by diffusion‐weighted magnetic resonance imaging at 3T
Authors: Lin Gigin , Ho Kung‐Chu , Wang Jiun‐Jie , Ng Koon‐Kwan , Wai Yau‐Yau , Chen Yen‐Ting , Chang Chee‐Jen , Ng Shu‐Hang , Lai Chyong‐Huey , Yen Tzu‐Chen
Published: June 2008

Purpose

To evaluate diffusion‐weighted imaging (DWI) for detection of pelvic lymph node metastasis in patients with cervical and uterine cancers.

Materials and Methods

Fifty patients scheduled for pelvic lymph node dissection were enrolled for 3T magnetic resonance imaging (MRI) using a single‐shot echo‐planar DWI technique, body‐phased array coil, b = 0, 1000 s/mm2. We measured short/long‐axis diameters, mean apparent diffusion coefficient (ADC) values of all identifiable nodes, relative ADC values between tumors and nodes, and utilized their cutoff values to validate the diagnostic accuracy internally. Histopathologic results served as the reference standard.

Results

The relative ADC values between tumor and nodes were significantly lower in metastatic than in benign nodes (0.06 vs. 0.21 × 10−3 mm2/s, P < 0.001; cutoff value 0.10 × 10−3 mm2/s). Compared to conventional MRI, the method combining size and relative ADC values resulted in better sensitivity (25% vs. 83%) and similar specificity (98% vs. 99%). The smallest metastatic lymph node detected by this method measured 5 mm on its short axis.

Conclusion

The combination of size and relative ADC values was useful in detecting pelvic lymph node metastasis in patients with cervical and uterine cancers. J. Magn. Reson. Imaging 2008. © 2008 Wiley‐Liss, Inc.
MRI and contrast‐enhanced ultrasound monitoring of prostate microwave focal thermal therapy: An in vivo canine study
Authors: Cheng Hai‐Ling Margaret , Haider Masoom A. , Dill‐Macky Marcus J. , Sweet Joan M. , Trachtenberg John , Gertner Mark R.
Published: June 2008

Purpose

To compare the value of diffusion‐weighted MRI (DWI), dynamic contrast‐enhanced (DCE) MRI, and microbubble contrast‐enhanced ultrasound (CEUS) for assessment of the thermal lesion created by interstitial microwave heating of the normal canine prostate.

Materials and Methods

A microwave antenna was inserted into each lobe of the prostate in seven dogs to induce coagulation necrosis. Immediately after therapy the lesion was assessed using CEUS, DCE‐MRI, and DWI. The prostates were excised, photographed, and prepared for hematoxylin and eosin staining. Results from posttreatment MRI and ultrasound were compared to histology.

Results

The apparent diffusion coefficient (ADC) was slightly lowered within the thermal lesion but was drastically reduced in a ring‐like region that corresponds to a grossly appearing red thermal damage zone immediately peripheral to the central coagulum. Both DCE‐MRI and CEUS delineated a smaller area of vascular damage, for which the borders lie within the red zone.

Conclusion

The red zone encompasses a range of vascular responses, including hyperemia and hemostasis, and is known to progress to necrosis and tissue nonviability. DWI clearly depicts this zone as a region of sharply reduced ADC, and may be better than contrast‐enhanced imaging for accurate assessment of the eventual full extent of thermal damage. J. Magn. Reson. Imaging 2008;28:136–143. © 2008 Wiley‐Liss, Inc.