bluuebunny/crossref_metadata_2025 huggingface dataset:
Bis(1‐methylimidazol‐2‐yl)propionates and Bis(1‐methylbenzimidazol‐2‐yl)‐propionates: A New Family of Biomimetic N,N,O Ligands – Synthesis, Structures and CuII Coordination Complexes
Authors: Bruijnincx Pieter C. A. , Lutz Martin , Spek, Anthony L. , van Faassen Ernst E. , Weckhuysen Bert M. , van Koten Gerard , Klein Gebbink Robertus J. M.
Published: January 2005

A general synthetic route towards new tridentate, tripodal N,N,O ligands, bearing one carboxylate group and two of the biologically relevant imidazole moieties, is presented. The parent compounds of this new family of ligands, A[MIm2Pr] (1) and A[BenzMIm2Pr] (2) (A = H, K, Bu4N) were synthesized in two steps and high overall yield. The structures of HMIm2Pr (1a) and HBenzMIm2Pr (2a) were confirmed by X‐ray crystal structure determination, both molecules forming infinite one‐dimensional hydrogen bonded chains. The synthetic route allows for the fine‐tuning of the physical properties of both ligand systems, e.g., solubility and ease of crystallization. The capability of the two ligands to coordinate facially through all donor atoms was investigated and two isostructural mononuclear copper(II) complexes of the type [CuL2] were obtained. Both [Cu(MIm2Pr)2]·2H2O (3) and [Cu(BenzMIm2Pr)2]·3.12(H2O)·1.74(C2H5OH) (4) have been characterized by X‐ray crystallography, ESI‐MS, elemental analysis, UV/Vis, IR, and EPR spectroscopy. In both structures the copper atoms are on an inversion center, which results in a tetragonally distorted octahedral coordination geometry. The CuN4O2 chromophores consist of four equatorially coordinated imidazole nitrogen atoms and two axially coordinated carboxylate groups. The non‐coordinated water molecules of both crystal structures are involved in a one‐dimensional hydrogen‐bonded network. Two neighboring octahedrons are connected by two water molecules, each water molecule forming two hydrogen bonds with the non‐coordinated oxygen atoms of the carboxylate group. This results in the formation of infinite one‐dimensional chains. EPR spectroscopy and ESI‐MS measurements provide evidence for the integrity of the complexes in solution. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Determination of Amino Acids at a Silver Oxide/Silver Phosphate Electrode and the Analysis of Structure‐Response Relationships
Authors: DeMott James M. , Jahngen Edwin G. E.
Published: January 2005

When a silver electrode is conditioned in a solution of 0.5 M sodium hydroxide with added sodium phosphate and using a dual pulse (500 mV/750 mV vs. Ag/AgCl), a stable silver(I)/silver(II) oxide surface is formed. It has been previously shown that various moieties react with the silver(II) oxide in a chemical oxidation at the outer surface of the oxide layer. This is then followed by re‐oxidation of the silver with the generation of current at approximately 500 mV relative to the silver/silver chloride electrode. Previously we found the need to remove carbon dioxide from the base and condition the electrode in a solution containing phosphate ion in order to provide mechanical stability to the oxide layer. We have previously shown this electrode to be applicable to the detection of a variety of carbohydrates. The applicability of the silver oxide/silver phosphate electrode to the post‐chromatographic amperometric detection of amino acids was investigated. Calibration studies of amino acids representative of the various classes demonstrated good sensitivity and linearity in the 1–100 μM range. Responses of amino acids were measured using glucose as an external standard, in order to correct for variability of the oxide layer. Relative responses of the amino acids ranged from 3 down to 0.1. Correlation with structure suggested the importance of absorption in determining the rate of oxidation. Comparison of arginine with n‐benzoyl‐L‐arginine ethyl ester indicated that side chains as well as the backbone amino group can be oxidized. A Levitch plot of alanine was shown to be linear from approximately 30 to 300 radians per second spin rate at a scan rate of 50 mV per second. Application to post‐chromatographic detection was demonstrated.
A Nitric Oxide Biosensor Based on Myoglobin Adsorbed on Multi‐Walled Carbon Nanotubes
Authors: Zhang Li , Zhao Guang‐Chao , Wei Xian‐Wen , Yang Zhou‐Sheng
Published: January 2005

Myoglobin (Myb) of horse heart is incorporated on multi‐walled carbon nanotubes (MWNTs) and immobilized at a glassy carbon (GC) electrode surface. Its electrochemical behavior and enzyme activity are characterized by employing electrochemical methods. The results indicate that MWNTs can obviously promote the direct electron transfer between Myb and electrode, and that the Myb on MWNTs behaves as an enzyme‐like activity towards the electrochemical reduction of nitric oxide (NO). Accordingly, an unmediated NO biosensor is constructed. Experimental results reveal that the peak current related to NO is linearly proportional to its concentration in the range of 2.0×10−7–4.0×10−5 mol/L. The detection limit is estimated to be 8.0×10−8 mol/L. Considering a relative standard deviation of 2.1% in seven independent determinations of 1.0×10−5 mol/L NO, this biosensor shows a good reproducibility. The biosensor based on Myb/MWNTs modified electrode can be used for the rapid determination of trace NO in aqueous solution with a good stability, nice selectivity and easy construction.
Electrochemical Impedance Characterization of Nafion‐Coated Carbon Film Resistor Electrodes for Electroanalysis
Authors: Gouveia‐Caridade Carla , Brett Christopher M. A.
Published: January 2005

Carbon film disk electrodes with Nafion coatings have been characterized by electrochemical impedance spectroscopy (EIS) with a view to a better understanding of their advantages and limitations in electroanalysis, particularly in anodic stripping voltammetry of metal ions. After initial examination by cyclic voltammetry, spectra were recorded over the full potential range in acetate buffer solution at the bare electrodes, electrodes electrochemically pretreated in acid solution, and Nafion‐coated pretreated electrodes in the presence and absence of dissolved oxygen. EIS equivalent circuit analysis clearly demonstrated the changes between these electrode assemblies. In order to simulate anodic stripping voltammetry conditions, spectra were also obtained in the presence of cadmium and lead ions in solution at Nafion‐coated electrodes, both after metal ion deposition and following re‐oxidation. Permanent changes to the structure of the Nafion film occurred, which has implications for use of these electrode assemblies in anodic stripping voltammetry at relatively high trace metal ion concentrations.
Electrogenerated Chemiluminescence Determination of Dopamine and Epinephrine in the Presence of Ascorbic Acid at Carbon Nanotube/Nafion‐Ru(bpy)$\rm{ {_{3}^{2+}}}$ Composite Film Modified Glassy Carbon Electrode
Authors: Guo Zhihui , Dong Shaojun
Published: January 2005

Based on the inhibition effect of dopamine and epinephrine on Ru(bpy)$\rm{ {_{3}^{2+}}}$‐tripropylamine electrogenerated chemiluminescence system, the excellent properties of carbon nanotube, and the cation permselectivity of Nafion film, an electrogenerated chemiluminescence inhibition method for determination of dopamine and epinephrine in the presence of ascorbic acid at carbon nanotube/Nafion‐Ru(bpy)$\rm{ {_{3}^{2+}}}$ composite film modified glassy carbon electrode was described. The results showed that the proposed method was sensitive and selective for the determination of dopamine and epinephine. The linear calibration range was from 1.6×10−9 M to 3.2×10−5 M and 5×10−8 M to 6×10−5 M for dopamine and epinephrine, respectively. 200‐fold excess of ascorbic acid did not interfere with the determination of 1 μM dopamine and epinephrine.
Electroanalytical Studies of Biologically Active Azosalicylic Acid at a Hanging Mercury Drop Electrode
Authors: Nigović Biljana , Komorsky‐Lovrić Šebojka , Šimunić Branimir
Published: January 2005

The electrochemical behavior of disodium 3,3′‐azobis‐(6‐hydroxy‐)benzoate (olsalazine sodium), 2‐hydroxy‐5‐[(4‐sulfophenyl)azo]benzoic acid and 2‐hydroxy‐5‐azo‐benzoic acid was studied as a simple model of the metabolic reduction of azosalicylic acids using cyclic and square‐wave voltammetry. The stability of the hydrazo intermediate generated in the electroreduction process is strongly dependent on pH and the effect of different substituents in the aromatic ring adjacent to the azo bridge. The electrode mechanism of azosalicylic acids at hanging mercury drop electrode exhibits characteristic properties of a surface redox reaction. The kinetic parameters of azo/hydrazo reduction, such as the standard redox reaction rate constant and the electron transfer coefficient were estimated applying the methods of a split SW peak and a quasireversible maximum. A sensitive analytical method for the determination of trace level of biologically active azosalicylic acids by square‐wave voltammetry based on adsorptive stripping technique is described.
Amperometric Detection of Morphine at Preheated Glassy Carbon Electrode Modified with Multiwall Carbon Nanotubes
Authors: Salimi Abdollah , Hallaj Rahman , Khayatian Gholam‐Reza
Published: January 2005

A highly sensitive and fast responding sensor for the determination of morphine is described. The multiwall carbon nanotubes immobilize on preheated glassy carbon electrode (5 min at 50 °C) by gently rubbing of electrode surface on a filter paper supporting the carbon nanotubes.The results indicated that carbon nanotubes(CNTs) modified glassy carbon electrode exhibited efficiently electrocatalytic oxidation for morphine with relatively high sensitivity, stability and long life. Under conditions of cyclic voltammetry, the potential for oxidation of morphine is lowered by approximately 100 mV and the current is enhanced significantly (10 times) in comparison to the bare glassy carbon electrode at wide pH range (2–9). The electrocatalytic behavior is further exploited as a sensitive detection scheme for morphine determination by hydrodynamic amperometry. Under the optimized conditions the calibration plots are linear in the concentration range 0.5–150 μM with the calculated detection limit (S/N=3) of 0.2 μM and sensitivity of 10 nA/μM and a relative standard deviation (RSD) of 2.5% (n=10). The amperometric response is extremely stable, with no loss in sensitivity over a continual 30 min operation. Such attractive ability of multiwall carbon nanotubes (MWCNTs) modified GC electrode, suggests great promise for a morphine amperometric sensor. Finally the ability of the modified electrode was evaluated for simultaneous determination of morphine and codeine.
Adsorptive Stripping Voltammetric Determination of Amitrole at a Multi‐Wall Carbon Nanotubes Paste Electdrode
Authors: Chicharro M. , Bermejo E. , Moreno M. , Sánchez A. , Zapardiel A. , Rivas G.
Published: January 2005

This work reports the excellent electrocatalytic activity of carbon nanotubes paste electrodes (CNTPE) prepared by dispersion of multi‐wall carbon nanotubes (MWNT) within mineral oil toward the oxidation of 3‐amino‐1H‐1,2,4‐triazole (amitrole). The quantification is performed by adsorptive stripping voltammetry (AdSV). The influence of the paste composition and surface pretreatments as well as the amitrole accumulation conditions on the adsorption and further electrooxidation of this herbicide is described. After potentiodynamic pretreatment in 0.050 M phosphate buffer pH 7.4 the amitrole oxidation signal shifts 250 mV toward more negative potential and the sensitivity increases 29 fold, demonstrating that pretreated CNTPEs are extremely useful for a highly sensitive determination of amitrole down to the sub‐μM levels. The oxidation peak current is proportional to the amitrole concentration over the range from 0.8 to 7.0 μM (5 min accumulation), with a detection limit of 0.6 μM (48 μgL−1) and a precision of 4.3%, n=20. The proposed method was used for the determination of amitrole in spiked river water (Alberche River (Madrid, Spain)) and tap water samples (Madrid, Spain) at levels higher than 0.6 μM.
Improvement of Analytical Characteristic of Calcium Selective Electrode with Conducting Polymer Contact. The Role of Conducting Polymer Spontaneous Charge Transfer Processes and Their Galvanostatic Compensation
Authors: Michalska Agata
Published: January 2005

In this report processes affecting the analytical characteristic of all‐solid‐state, conducting polymer–polypyrrole based cation selective sensors are discussed on an example of a Ca‐electrode. It is shown that conditioning of the obtained electrode is coupled with transducer spontaneous discharge leading to accumulation of calcium cations in the polymer phase. As an ultimate result of this process, the sensor detection limit is close to 10−5 M, similarly as for traditional internal solution electrodes. The compensation of polypyrrole spontaneous charge transfer process over conditioning, by anodic galvanostatic polarization, prevents Ca2+ accumulation and results (in subsequent open circuit calibration) in linear responses within the activities range from 0.1 M to 10−10 M. In dilute solution, due to limited accessibility of cations in the solution and relatively high amount of cations present in the transducer phase, the spontaneous charging process of conducting polymer determines the accessible detection limit. It is also shown that in this case the linear range of responses can be extended to reach significantly lower activities under conditions of polarized electrode potentiometry, applying a cathodic current. The outstanding stability of the open circuit equilibrated all‐solid‐state sensor is attributed to accumulation of primary ions in the sensor transducer phase during conditioning.
Speciation of Inorganic Arsenic in Waters by Potentiometric Flow Analysis with On‐Line Preconcentration
Authors: Rodríguez J. A. , Barrado E. , Vega M. , Lima J. L. F. C.
Published: January 2005

A potentiometric flow system has been developed for the direct determination of arsenic(V) in water samples after on‐line preconcentration in a minicolumn packed with a new adsorbent material selective to As(V). Iron oxyhydroxide embedded in silica gel was synthesized and used simultaneously as adsorbent material in the minicolumn and as selective component in a tubular potentiometric electrode. In the first step, the sample solution is mixed on‐line with phosphate buffer of pH 7 and pumped through the minicolumn to adsorb As(V). The insertion of the minicolumn in the mobile section of a homemade injector‐commutator allows to relocate the minicolumn to desorb the retained As(V) in the second step. The desorption is maximum in the presence of 0.1 M phosphate of pH 12. Maximum response of the tubular selective membrane is achieved in phosphate buffer of pH 7. On‐line oxidation of As(III) to As(V) by iodine (I3−) in the presence of phosphate buffer of pH 7 allows the determination of total As as As(V) and then the speciation of inorganic arsenic, since As(III) can be estimated as the difference between total As and As(V). In the optimized experimental conditions, a linear range of 40–500 μg L−1 for As(V), and detection limits of 30.6 and 38.6 μg L−1 for As(V) and total As, respectively, were obtained.The flow system has been successfully applied to the determination of inorganic arsenic species in groundwater samples collected in areas affected by arsenic contamination. Relative standard deviation of replicated determinations of As in groundwater samples was always below 5%.
Anion Selective Potentiometric Sensor Based on Gallium Nitride Crystalline Membrane
Authors: Alifragis Yiannis , Konstantinidis Giorgos , Georgakilas Alexander , Chaniotakis Nikos
Published: January 2005

Gallium nitride (GaN) (0001) grown on sapphire has been used as a sensor element for the development of a potentiometric sensor. The GaN‐based ion‐selective electrode has pH sensitivity which originates from the direct interaction of the gallium with the hydroxide ions. At the same time the sensor shows very good selectivity towards the very hydrophilic anion of orthophosphate, over the very lipophilic ClO4−. Potentiometry and impedance spectroscopy suggest that the observed potentiometric sensitivity originates from the direct interaction of anions in solution with the acidic gallium(III) on the surface of the GaN (0001) crystal. This is also supported by the fact that the gallium atoms are electron deficient due to the induced polarity of the Ga to the N bond, enhancing the electrostatic interaction between the Lewis basic anions. The semiconductor properties of the GaN allow for its application as an all solid‐state semiconductor‐based anion potentiometric sensor, or alternatively as the transducer in composite cation sensitive potentiometric sensors. The latter has been demonstrated with the deposition of a potassium selective liquid polymeric membrane on top of the GaN surface.
Enantioselective Detection of D‐ and L‐Phenylalanine Using Optically Active Polyaniline
Authors: Sheridan Edel M. , Breslin Carmel B.
Published: January 2005

Chiral conducting polyaniline, which was prepared electrochemically from (+) and (−) camphorsulfonic acid, was utilized for the enantiomeric detection of phenylalanine in neutral phosphate buffer solution. Following electropolymerization the polymer films were dedoped in aqueous ammonia and subsequently shown to maintain their chiral character. The electrochemical window for this polymer was determined to be between 0.2 V and 0.8 V (vs. SCE) and enantiomeric discrimination between L‐ and D‐phenylalanine was seen with the application of differential pulse voltammetry. The (+) chiral polymer is shown to behave as an enantiomeric detector for the D enantiomer producing a peak in the voltammogram at ca. 0.7 V (vs. SCE) while the inverse is true for the (−) polymer, which detects the L enantiomer.
Well‐balanced finite volume evolution Galerkin methods for the shallow water equations with source terms
Authors: Lukáčová‐Medvid'ová M. , Vlk Z.
Published: January 2005

The goal of this paper is to present a new well‐balanced genuinely multi‐dimensional high‐resolution finite volume evolution Galerkin method for systems of balance laws. The derivation of the method will be illustrated for the shallow water equation with geometrical source term modelling the bottom topography. The results can be generalized to more complex systems of balance laws. Copyright © 2005 John Wiley & Sons, Ltd.
On the performance of discrete adjoint CFD codes using automatic differentiation
Authors: Müller J.‐D. , Cusdin P.
Published: January 2005

Adjoint methods are a computationally inexpensive way of deriving sensitivity information where there are fewer dependent (cost) variables than there are independent (input) variables. Automatic differentiation (AD) software makes it possible to create discrete adjoint codes with minimal human effort, an issue that had previously restricted acceptance of adjoint CFD codes. In terms of computational performance, automatic code is often assumed to be inferior to hand code. The structure of the underlying code is critical to the performance of the transformed code. This paper reviews the implementation of AD on Fortran CFD codes and gives details of how small rearrangements can be used to produce competitive tangent and adjoint code using source transformation AD. Copyright © 2005 John Wiley & Sons, Ltd.
Prediction of jet flows in the supersonic nozzle and diffuser
Authors: Liu Yi , Bellhouse Brain J.
Published: January 2005

The authors' recently‐developed code for a needle‐free powdered vaccine delivery device, the epidermal powdered inject system (EPI), is summarized in this paper. The behaviour of supersonic jet flows, which accelerate micron sized powdered vaccines to penetrate human skin or mucosal tissue, is therefore of great importance. A well‐established modified implicit flux vector splitting (MIFVS) solver for the Navier–Stokes equations is extended to study numerically the transient supersonic jet flows of interest. A low Reynolds number k–ε turbulence model, with the compressibility effect considered, is integrated into MIFVS solver to predict the turbulent structures and interactions with inherent shock systems. The results for the NASA validation case NPARC, Venturi and contoured shock tube (CST) of the EPI system are discussed. Copyright © 2005 John Wiley & Sons, Ltd.
Elimination AD applied to Jacobian assembly for an implicit compressible CFD solver
Authors: Tadjouddine Mohamed , Forth Shaun A. , Qin Ning
Published: January 2005

In CFD, Newton solvers have the attractive property of quadratic convergence but they require derivative information. An efficient way of computing derivatives is by algorithmic differentiation (AD) also known as automatic differentiation or computational differentiation. AD allows us to evaluate derivatives, usually at a cheap cost, without the truncation errors associated with finite‐differencing. Recently, efficient and reliable AD tools for evaluating derivatives have been published. In this paper, we use some of the best AD tools currently available to build up the system Jacobian involved in the solution of a finite‐volume parabolized Navier–Stokes (PNS) solver. Our aim is to direct scientists and engineers confronted with the calculation of derivatives to the use of AD and to highlight those AD tools that they should try. Moreover, we introduce an AD tool that produces Jacobian code that runs usually twice as fast as that from conventional AD tools. We further show that the use of AD increases the performance of a Newton‐like solver for the PNS equations. Copyright © 2005 John Wiley & Sons, Ltd.
Automated post‐hoc noise cancellation tool for audio recordings acquired in an MRI scanner
Authors: Cusack Rhodri , Cumming Nick , Bor Daniel , Norris Dennis , Lyzenga Johannes
Published: January 2005

There are several types of experiment in which it is useful to have subjects speak overtly in a magnetic resonance imaging (MRI) scanner, including those studying the articulatory apparatus and the neural basis of speech production, and fMRI experiments in which speech is used as a response modality. Although it is relatively easy to record sound from the bore, it can be difficult to hear the speech over the very loud acoustic noise from the scanner. This is particularly a problem during echo‐planar imaging, which is usually used for fMRI. We present a post‐hoc sound cancellation algorithm, and describe a Windows‐based tool that implements it. The tool is fast and operates with minimal user intervention. We evaluate cancellation performance in terms of the improvement in signal‐to‐noise ratio, and investigate the effect of the recording medium. A substantial improvement in audibility was obtained. Hum. Brain Mapping 24:299–304, 2005. © 2005 Crown Copyright
Brief breath holding may confound functional magnetic resonance imaging studies
Authors: Abbott David F. , Opdam Helen I. , Briellmann Regula S. , Jackson Graeme D.
Published: January 2005

We demonstrate that breath holding of short durations may confound functional magnetic resonance imaging (fMRI) studies. Some subjects may hold their breath for a short time during task performance, especially if the task is challenging. Breath holding may therefore need to be considered specifically when interpreting fMRI experiments. We studied the temporal and spatial characteristics of cerebral T2*‐weighted signal during short periods of breath holding by seven individuals in a 3‐tesla MR scanner. We demonstrate that breath‐holds as short as 3 s can result in regions of significant cerebral activation. More interestingly, we show that focal activation remains present when the data is analysed in a number of different ways, including analyses that correct for motion and model the task epoch as if it were 10 times longer than the actual breath‐hold length. These findings have potential relevance for many researchers carrying out fMRI studies. Hum. Brain Mapping 24:284–290, 2005. © 2005 Wiley‐Liss, Inc.
Visual evoked potentials may be recorded simultaneously with fMRI scanning: A validation study
Authors: Comi Eleonora , Annovazzi Pietro , Silva Ana Martins , Cursi Marco , Blasi Valeria , Cadioli Marcello , Inuggi Alberto , Falini Andrea , Comi Giancarlo , Leocani Letizia
Published: January 2005

Integrating electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) data may help to optimize anatomical and temporal resolution in the investigation of cortical function. Successful removal of fMRI scanning artifacts from continuous EEG in simultaneous recordings has been reported. We assessed the feasibility of recording reliable visual evoked potentials (VEPs) during fMRI scanning using available artifact removing procedures. EEG during administration of visual stimuli was recorded using MRI‐compatible 32‐channel equipment in nine normal subjects (mean age, 23.9 ± 2.5 years), with and without fMRI acquisition. fMRI scanning and cardioballistographic artifacts were removed after subtraction of averaged artifact waveforms. Consistency between VEPs waveforms and of P1 and N1 peak latencies and amplitudes in the two conditions was assessed. Good correlation was found between VEP waveforms (Pearson's correlation coefficient: rP between 0.76–0.94 across subjects; P < 0.0001) and between latency or amplitude of P1 and N1 peaks (latencies: r = 0.7, P < 0.035; amplitudes: r > 0.65, P < 0.05; Spearman rank correlation coefficient) in the two recording conditions. No significant differences were found between P1 and N1 parameters in the two conditions (Wilcoxon signed rank test). Consistent VEP waveforms, latencies, and amplitudes with and without fMRI scanning indicate that reliable VEPs may be obtained simultaneously with fMRI recording. This possibility might be helpful by shortening recording times and reducing variability from learning, habituation, and fatigue phenomena from separate recordings for the integration of event‐related EEG and fMRI data. Hum. Brain Mapping 24:291–298, 2005. © 2005 Wiley‐Liss, Inc.
Difference in somatosensory evoked fields elicited by mechanical and electrical stimulations: Elucidation of the human homunculus by a noninvasive method
Authors: Inoue Ken , Shirai Takushi , Nakanishi Kazuyoshi , Hashizume Akira , Harada Toshihide , Mimori Yasuyo , Matsumoto Masayasu
Published: January 2005

We recently recorded somatosensory evoked fields (SEFs) elicited by compressing the glabrous skin of the finger and decompressing it by using a photosensor trigger. In that study, the equivalent current dipoles (ECDs) for these evoked fields appeared to be physiologically similar to the ECDs of P30m in median nerve stimulation. We sought to determine the relations of evoked fields elicited by mechanically stimulating the glabrous skin of the great toe and those of electrically produced P40m. We studied SEFs elicited by mechanical and electrical stimulations from the median and tibial nerves. The orientations of dipoles from the mechanical stimulations were from anterior‐to‐posterior, similar to the orientations of dipoles for P30m. The direction of the dipole around the peak of N20m from median nerve electrical stimulation was opposite to these directions. The orientations of dipoles around the peak of P40m by tibial nerve stimulation were transverse, whereas those by the compression and decompression stimulation of the toe were directed from anterior‐to‐posterior. The concordance of the orientations in ECDs for evoked fields elicited by mechanical and electrical stimulations suggests that the ECDs of P40m are physiologically similar to those of P30m but not to those of N20m. The discrepancy in orientations in ECDs for evoked field elicited by these stimulations in the lower extremity suggests that electrical and compression stimulations elicit evoked fields responding to fast surface rubbing stimuli and/or stimuli to the muscle and joint. Hum. Brain Mapping 24:274–283, 2005. © 2005 Wiley‐Liss, Inc.
Measuring the equilibrium effects of unemployment benefits dispersion
Authors: Vuuren Aico Van , Van Den Berg Gerard J. , Ridder Geert
Published: January 2005

We analyse the impact of unemployment benefits and minimum wages using an equilibrium search model which allows for dispersion of benefits and productivity levels, job‐to‐job transitions, and structural and frictional unemployment. The estimation method uses readily available aggregate data on marginal distributions of unemployment durations as well as wages and benefit levels. Different causes of structural and frictional unemployment are investigated. We investigate the efficiency of the imposition of a single benefit level for all household types and the introduction of a tax credit on earned income. Copyright © 2000 John Wiley & Sons, Ltd.
Formation of viscoelastic protein layers on polymeric surfaces relevant to platelet adhesion
Authors: Weber Norbert , Wendel Hans Peter , Kohn Joachim
Published: January 2005

The hemocompatibility of biomaterials is highly dependent on the adhesion and activation of platelets. Surface‐adsorbed fibrinogen has a dominant role in promoting platelet adhesion to artificial surfaces by binding glycoprotein IIb‐IIIa (GPIIb‐IIIa), the major platelet membrane receptor. Using quartz crystal microbalance with dissipation monitoring (QCM‐D), we have investigated the material‐dependent binding kinetics of purified GPIIb‐IIIa to polymer‐adsorbed fibrinogen. The following ranking of polymer‐adsorbed mass (fibrinogen and GPIIb‐IIIa) to test polymers could be established: poly[desaminotyrosyl‐tyrosine ethyl (DTE) carbonate]/poly(lactide‐co‐glycolide) > poly[DTE co‐5% poly(ethylene glycol) carbonate]. The QCM‐D fibrinogen adsorption data were confirmed using an immunofluorescence assay. A synthetic RGD‐containing peptide, but not a control peptide, inhibited GPIIb‐IIIa binding to polymer‐adsorbed fibrinogen, demonstrating the specificity of binding. Importantly, the binding efficiency of purified GPIIb‐IIIa to polymer‐adsorbed fibrinogen correlated with increased platelet adhesion in an in vitro model. Theoretical simulations using a Voight‐based model provided quantitative data on the thickness and viscoelastic properties of the polymer‐adsorbed protein layers. The precision of the modeling technique was limited with respect to the shear moduli values, leading to large variations. However, the other modeling parameters showed reproducible results. The thickness of both protein layers was polymer‐dependent and ranged from 5 to 35 nm and the viscosity from 0.001 to 0.005 kg/ms, whereas the protein layer densities showed little differences between the test polymers. These results suggest that material‐dependent changes in the thickness and viscoelastic properties of adsorbed fibrinogen‐GPIIb‐IIIa layers are crucial factors in the binding behavior of platelets to biomaterials. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res 72A: 420–427, 2005
Nanoporous delivery system to treat osteomyelitis and regenerate bone: Gentamicin release kinetics and bactericidal effect
Authors: El‐Ghannam Ahmed , Ahmed Karima , Omran Maha
Published: January 2005

Conventional treatment of osteomyelitis involves the repeated surgical removal of dead bone tissue coupled with repeated irrigation of the wound and prolonged systemic administration of antibiotics. Therapy of bone infections could easily last the rest of the patient's life because of the poor accessibility of the infection site by common systemically administered antibiotics. The objective of the present study is to develop a novel bone bioactive resorbable nanocomposite that can serve as a delivery system for antibiotics. We synthesized three different samples of porous bioactive resorbable silica–calcium phosphate nanocomposite (C3S1, C1S1, and C1S3) that has the ability to provide a sustained release of effective dose of gentamicin for 28 days. Porosity measurements showed that the average pore diameter of C3S1, C1S1, and C1S3 samples is 44.8, 54.4, and 70.9 nm, respectively. Moreover, the silica‐rich composite (C1S3) is characterized by a significantly higher surface area (155.8 m2/g) than the silica‐poor samples (C3S1) (42.9 m2/g). For all samples, the release profile study showed initial burst release followed by a sustained release of gentamicin. The released gentamicin has a strong inhibitory effect on Staphylococcus aureus bacteria. In addition FTIR analysis showed the formation of a biological apatite layer on the material surface after 24 h of immersion in simulated body fluid. Results of the study suggest that the silica–calcium phosphate nanocomposite can serve as a delivery vehicle for gentamicin to treat osteomyelitis and regenerate bone. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater
Effect of acidic fluoride solution on β titanium alloy wire
Authors: Kwon Yong Hoon , Seol Hyo‐Joung , Kim Hyung‐Il , Hwang Ki‐Ju , Lee Sang‐Geul , Kim Kyo‐Han
Published: January 2005

The interaction between acidic fluoride solution and β titanium alloy was investigated to explore the changes that occur in β titanium alloy by fluoride‐containing acetic acid solutions. For this, alloy crystal structure, tensile strength, and elements released from the alloy wires were determined using four solutions (0.05%/pH 6, 0.05%/pH 4, 0.2%/pH 6, and 0.2%/pH 4) for 1 or 3 days. The immersed wire did not form any identifiable new crystal structure compared with the as‐received wire. The tensile strength of the immersed wires was significantly reduced compared to the as‐received wires in the test solutions if the period of immersion increased from as‐received to 3 days. The fractured area of the immersed wire was reduced compared to the as‐received one. The dimple pattern at the inner part and a cup–cone morphology at the outer part of the fractured wires were similar in both as‐received and immersed wires. After a 3‐day immersion, the amount of the released Ti and Mo has much increased for higher NaF concentration and lower pH value. During the long‐period orthodontic treatment, both patient and clinical doctor should carefully use the fluoride‐containing products to minimize unexpected damage on orthodontic wires. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater
Dental restorative composites containing 2,2‐bis‐[4‐(2‐hydroxy‐3‐methacryloyloxy propoxy) phenyl] propane derivatives and spiro orthocarbonates
Authors: Moon E.J. , Lee J.Y. , Kim C.K. , Cho B.H.
Published: January 2005

Various dental restorative composite resins containing 2,2‐bis‐[4‐(2‐hydroxy‐3‐methacryloyloxy propoxy) phenyl] propane (Bis‐GMA) derivatives and spiro orthocarbonates (SOCs) were explored for minimizing the volumetric shrinkage that generally occurs during polymerization. Previous reports suggested mixing Bis‐GMA with its derivative TMBis‐GMA (2,2‐bis[3,5‐dimethyl‐4‐(2‐hydroxy‐3‐methacryloyloxy propoxy) phenyl] propane) to obtain a dental composite with low volumetric shrinkage. It was hypothesized that spiro orthocarbonates would expand volumetrically during polymerization, because of their sophisticated ring‐opening reactions; therefore several of them were added to the mixture of Bis‐GMA and TMBis‐GMA to bring about further reductions in volumetric shrinkage. It was indeed possible to reduce the extent of volumetric shrinkage of dental composites containing SOCs, and to do so without compromising these resins' mechanical properties. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater
Endothelin‐1 modulates anterograde fast axonal transport in the central nervous system
Authors: Stokely Martha E. , Yorio Thomas , King Michael A.
Published: January 2005

Anterograde fast axonal transport (FAxT) maintains synaptic function and provides materials necessary for neuronal survival. Localized changes in FAxT are associated with a variety of central nervous system (CNS) neuropathies, where they may contribute to inappropriate remodeling, a process more appropriately involved in synaptic plasticity and development. In some cases, developmental remodeling is regulated by localized secretion of endothelins (ETs), neuroinflammatory peptides that are also pathologically elevated in cases of neurologic disease, CNS injury, or ischemia. To investigate the potential role of ETs in these processes, we decided to test whether locally elevated endothelin‐1 (ET‐1) modulates FAxT in adult CNS tissues. We used the established in vivo rat optic nerve model and a novel ex vivo rat hippocampal slice model to test this hypothesis. In vivo, exogenously elevated vitreal ET‐1 significantly affected protein composition of FAxT‐cargos as well as the abundance and peak delivery times for metabolically‐labeled proteins that were transported into the optic nerve. Proteins with molecular weights of 139, 118, 89, 80, 64, 59, 51, 45, 42, 37, and 25 kDa were evaluated at injection‐sacrifice intervals (ISIs) of 24, 28, 32, and 36 hr. In acute hippocampal slices maintained on nonvascular supplies of glucose and oxygen, ET‐1 significantly decreased the distance traveled along the Schaffer collateral tract by nonmetabolically‐labeled lipid rafts at 5 and 10 min after pulse‐labeling. In both models, ET‐1 significantly affected transport or targeted delivery of FaxT‐cargos, suggesting that ET‐1 has the potential to modulate FAxT in adult CNS tissues. © 2005 Wiley‐Liss, Inc.
A humanin derivative, S14G‐HN, prevents amyloid‐β‐induced memory impairment in mice
Authors: Tajima Hirohisa , Kawasumi Masaoki , Chiba Tomohiro , Yamada Marina , Yamashita Kaoru , Nawa Mikiro , Kita Yoshiko , Kouyama Keisuke , Aiso Sadakazu , Matsuoka Masaaki , Niikura Takako , Nishimoto Ikuo
Published: January 2005

Humanin (HN) is a 24‐amino acid peptide that protects neuronal cells from death caused by Alzheimer's disease (AD)‐related genes and amyloid‐β (Aβ). Multiple studies have revealed its biochemical and neuroprotective characteristics in vitro; however, little has been known regarding whether HN is effective in vivo in AD model systems. We examined the effect of S14G‐HN, a 1,000‐fold more potent derivative of HN in vitro, on amnesia induced by Aβ25–35 in mice. The Y‐maze test revealed that at least 50 pmol of S14G‐HN by intracerebroventricular injection prevented Aβ‐induced impairment of short‐term/spatial working memory; however, 5 nmol of S14A‐HN, a neuroprotection‐defective mutant in vitro, did not prevent Aβ‐induced amnesia. These results are in agreement with the structure–function correlation shown previously in vitro. In the water‐finding task, S14G‐HN prevented prolongation of finding latency (the time to find water) observed in Aβ‐amnesic mice, indicating that S14G‐HN also blocked Aβ‐induced impairment of latent learning. In accordance with these observations, immunohistochemical analysis showed that S14G‐HN sustained the number of cholinergic neurons in the basal forebrain and the striata nearly to the normal level. Furthermore, genistein, a specific inhibitor of tyrosine kinases, blocked recovery from scopolamine‐induced amnesia by S14G‐HN, suggesting that certain tyrosine kinase(s) are involved in the inhibitory function of S14G‐HN in vivo. Taking these findings together, we conclude that S14G‐HN has rescue activity against memory impairment caused by AD‐related insults in vivo by activating the same intracellular neuroprotective machinery as elucidated previously in vitro. © 2005 Wiley‐Liss, Inc.
γ‐glutamylcysteine ethyl ester‐induced up‐regulation of glutathione protects neurons against Aβ(1–42)‐mediated oxidative stress and neurotoxicity: Implications for Alzheimer's disease
Authors: Boyd‐Kimball Debra , Sultana Rukhsana , Abdul Hafiz Mohmmad , Butterfield D. Allan
Published: January 2005

Glutathione (GSH) is an important endogenous antioxidant found in millimolar concentrations in the brain. GSH levels have been shown to decrease with aging. Alzheimer's disease (AD) is a neurodegenerative disorder associated with aging and oxidative stress. Aβ(1–42) has been shown to induce oxidative stress and has been proposed to play a central role in the oxidative damage detected in AD brain. It has been shown that administration of γ‐glutamylcysteine ethyl ester (GCEE) increases cellular levels of GSH, circumventing the regulation of GSH biosynthesis by providing the limiting substrate. In this study, we evaluated the protective role of up‐regulation of GSH by GCEE against the oxidative and neurotoxic effects of Aβ(1–42) in primary neuronal culture. Addition of GCEE to neurons led to an elevated mean cellular GSH level compared with untreated control. Inhibition of γ‐glutamylcysteine synthetase by buthionine sulfoximine (BSO) led to a 98% decrease in total cellular GSH compared with control, which was returned to control levels by addition of GCEE. Taken together, these results suggest that GCEE up‐regulates cellular GSH levels which, in turn, protects neurons against protein oxidation, loss of mitochondrial function, and DNA fragmentation induced by Aβ(1–42). These results are consistent with the notion that up‐regulation of GSH by GCEE may play a viable protective role in the oxidative and neurotoxicity induced by Aβ(1–42) in AD brain. © 2005 Wiley‐Liss, Inc.
Subcellular localization of neural‐specific NPDC‐1 protein
Authors: Evrard C. , Rouget P.
Published: January 2005

NPDC‐1 is a gene specifically expressed in neural cells when they stop to divide and begin to differentiate. Immunocytochemical study analysis of differentiated PC12 cells transfected with NPDC‐tag vectors showed that NPDC‐1 is transported in vesicles from the Golgi apparatus to the cell membrane and is then likely internalized into endosomes. The protein colocalized, at least partially, with synaptic vesicle proteins: synaptophysin, synaptobrevin 2, and Rab3 GEP (Rab3 GTP/GDP exchange protein). Moreover, subcellular fractionation of rat brain showed that crude synaptic membrane and crude synaptic vesicle fractions were enriched in NPDC‐1. Although NPDC‐1 bound Rab3 GEP in vitro, it seems unlikely to be involved in Ca2+‐dependent exocytosis and, thus, in synaptic vesicle trafficking. © 2005 Wiley‐Liss, Inc.
Raman and pulse radiolysis studies of the antioxidant properties of quercetin: Cu(II) chelation and oxidizing radical scavenging
Authors: Torreggiani Armida , Trinchero Andrea , Tamba Maurizio , Taddei Paola
Published: January 2005

Quercetin (Querc), a pentahydroxyflavonol, is suggested to give protection to living organisms by both direct scavenging of free radicals and metal chelation. The scavenging ability of Querc towards oxidizing radicals, such as •OH, N3• and NO2•, was evaluated by pulse radiolysis studies in aqueous solutions at different pH. Phenoxyl radicals are the final transient products and are formed either by water elimination from •OH‐adducts or by one‐electron transfer from the deprotonated OH groups. Their formation rate is strongly affected by pH and reaches the maximum values in alkaline medium. The Raman and IR spectra were useful to assess the relevant interaction of Querc with Cu(II) ions, which play an important role in the metal‐catalysed generation of reactive oxygen species. Depending on pH and the metal‐to‐ligand ratio, the different chelating sites of Querc change their ability to complex copper ions. Under neutral conditions, the 5‐OH group of ring A and CO‐4 of ring C have a chelating power superior to that of the catechol group (ring B), whereas the complexation in alkaline medium occurs in the reverse order. In addition, experiments with Querc and Zn(II) ions, carried out at basic pH in order to verify the possible Cu(II)‐catalysed oxidation of the ligand, indicated the absence of the above process. Copyright © 2005 John Wiley & Sons, Ltd.
NMR Investigation of the Main‐Chain Orientation in Liquid‐Crystalline Side‐Chain Polymers
Authors: Hempel Günter , Schneider Horst
Published: January 2005

The main‐chain orientation in different groups of liquid‐crystalline side‐chain polymers was investigated using several NMR techniques. For two polyesters the average orientation of the main chain in dependence on the main‐chain spacer length could be found from 2D PASS experiments. In polysiloxanes with different mesogenic side groups and different spacer lengths this information could be received from chemical shift anisotropy measurements. Additionally, application of a modified β‐echo allowed the separation of the dipolar 29Si‐29Si interaction and to characterize the transversal anisotropy of the main‐chain segments. Comparison with small angle neutron scattering results gave good agreement, where the different length scale of both methods has to be taken into account.
NMR Microscopy of an “Anisotropic” Polymer
Authors: Canet D. , Malveau C. , Grandclaude D. , Tekely P. , Beaume F. , Germain Y.
Published: January 2005

Two different samples of high‐density polyethylene (HDPE) have been studied. One (isotropic) is extracted from the material core whereas the other (anisotropic) involves two sides which have been in contact with the injection mold. It is observed by NMR microscopy (using radiofrequency field gradients) that these two sides favor toluene penetration into the material. The distribution of toluene nuclear spin relaxation times (extracted from proton T1 and T2 images) exhibits likewise important differences between the two samples. These differences can be accounted for by partial molecular ordering at the vicinity of the “mold sides”. Finally, in investigating the anisotropic sample (without solvent), three different phases (two amorphous and one crystalline) are revealed by 13C chemical shift imaging experiments (performed with radiofrequency field gradients under CP/MAS conditions). Each amorphous component is preferentially present at one of the two “mold sides”.
Infrared Analysis of Elastomeric Composites under Uniaxial Extension
Authors: Bokobza Liliane
Published: January 2005

The orientational ordering taking place upon deforming uniaxially elastomeric networks is detected and quantified by infrared dichroism. The type of information gained from orientational measurements is discussed in the case of pure networks and also in rubber composites. This information, compared to that obtained from mechanical measurements, provided a better understanding of the molecular processes involved in rubber reinforcement.
Diffusion of Rod‐Like Polypeptides in the Liquid Crystalline and Isotropic Phases as Studied by High Field‐Gradient NMR Spectroscopy
Authors: Ando Isao , Yin Yige , Zhao Chenhua , Kanesaka Sho , Kuroki Shigeki
Published: January 2005

In this lecture the measurements and analyses of the isotropic and anisotropic diffusion coefficients(D) of rod‐like polypeptide such as poly(γ‐L‐glutamate)(PLG) with n‐alkyl side chains, of which the main chain takes the α‐helical conformation, as a function of the main chain length in the thermotropic and lyotropic liquid crystalline phases over a wide range of temperatures from 30 to 80°C by means of pulse high field‐gradient spin echo 1H NMR method have been introduced. In the anisotropic diffusion, the D∥ value in direction parallel to the α‐helical chain axis is found to be much larger than the D⊥ value in direction perpendicular to the α‐helical chain axis. The diffusion process is followed by the Kirkwood theory. Further, it is described that the diffusion in the nematic liquid crystalline phase is much slower than that in the isotropic phase.