bluuebunny/crossref_metadata_2025 huggingface dataset:
Candidate testis‐determining gene, Maestro (Mro), encodes a novel HEAT repeat protein
Authors: Smith Lee , Van Hateren Nick , Willan John , Romero Rosario , Blanco Gonzalo , Siggers Pam , Walsh James , Banerjee Ruby , Denny Paul , Ponting Chris , Greenfield Andy
Published: July 2003

Mammalian sex determination depends on the presence or absence of SRY transcripts in the embryonic gonad. Expression of SRY initiates a pathway of gene expression resulting in testis development. Here, we describe a novel gene potentially functioning in this pathway using a cDNA microarray screen for genes exhibiting sexually dimorphic expression during murine gonad development. Maestro (Mro) transcripts are first detected in the developing male gonad before overt testis differentiation. By 12.5 days postcoitus (dpc), Mro transcription is restricted to the developing testis cords and its expression is not germ cell‐dependent. No expression is observed in female gonads between 10.5 and 14.5 dpc. Maestro encodes a protein containing HEAT‐like repeats that localizes to the nucleolus in cell transfection assays. Maestro maps to a region of mouse chromosome 18 containing a genetic modifier of XX sex reversal. We discuss the possible function of Maestro in light of these data. Developmental Dynamics 227:600–607, 2003. © 2003 Wiley‐Liss, Inc.
Expression of the Wdr9 gene and protein products during mouse development
Authors: Huang He , Rambaldi Isabel , Daniels Eugene , Featherstone Mark
Published: July 2003

Human WDR9 has been mapped to chromosome 21, within one of the Down syndrome (DS) critical regions. Here, we study the expression pattern of the murine Wdr9 gene and its protein product. We show that Wdr9 is broadly expressed in the mouse embryo by means of in situ hybridization and immunohistochemistry. Wdr9 expression levels are dynamic during embryonic development as revealed by Northern blot analysis. We further show that WDR9 is a nuclear protein associated with BRG1, a SWI/SNF complex component. We also demonstrate that a polyglutamine‐containing region of the protein functions as a transcriptional activation domain. We propose that WDR9 is a transcriptional regulator involved in chromatin remodeling through the action of two bromodomains and contacts to the SWI/SNF complex. These results may provide a molecular basis for the association of WDR9 with DS. Developmental Dynamics 227:608–614, 2003. © 2003 Wiley‐Liss, Inc.
Intercalary and supernumerary regeneration in the limbs of the frog, Xenopus laevis
Authors: Shimizu‐Nishikawa Keiko , Takahashi Jun , Nishikawa Akio
Published: July 2003

Anuran amphibians, such as Xenopus laevis, can regenerate their limbs only when they are young tadpoles, whereas urodele amphibians have a regenerative ability throughout their lives. It is still unclear whether anuran and urodele use the same mechanism during regeneration. In the present study, we analyzed intercalary and supernumerary regeneration in Xenopus. In contrast to urodele blastema that induces intercalary regeneration along the proximodistal (PD) axis, intercalation did not occur in the Xenopus limb bud when the presumptive zeugopodium (fibula and tibia) was removed. However, when the limb bud tip (presumptive autopodium) was transplanted to the presumptive stylopodium (femur) with a 180‐degree rotation at stage 52, the complete zeugopodium was regenerated. These results were similar to the results of urodele mature limbs, suggesting that Xenopus limb buds are equivalent to the urodele mature limbs but not to the urodele blastemas. We hypothesized that the ability for intercalation depends on the expression pattern of fibroblast growth factor (fgf)‐8, because the expression of fgf‐8 in the urodele spreads over the whole blastema and is close enough to activate the growth of the stump. To test this hypothesis, an FGF‐8–soaked bead was implanted at the boundary between the stump and tip of a Xenopus limb bud. Intercalary regeneration was induced at stages 52 and 53. These results suggest that the Xenopus limb bud possesses the potential for intercalation, but endogenous FGF‐8 in the apical ectodermal ridge (AER) does not induce intercalation to the stump because of the long distance between the AER and stump. Developmental Dynamics 227:563–572, 2003. © 2003 Wiley‐Liss, Inc.
Occupation choices of adults with and without symptoms of dyslexia
Authors: Taylor Kathleen E. , Walter Janet
Published: July 2003

People with the learning disability developmental dyslexia characteristically have difficulties in processing written language. There is some evidence that they may also have talents in other areas such as visuospatial processing. This pattern of strengths and weaknesses may predispose people who have dyslexia towards adopting certain occupations and away from others. Although there is literature on career choice in learning disabled adults in general, relatively little work has been done specifically for dyslexia. We therefore compared the occupations of adults with and without symptoms of developmental dyslexia. Results were analysed using non‐parametric statistics and are illustrated with a case study. We found significant differences in the distribution of our samples. Adults with symptoms of dyslexia were much less likely than adults not reporting such symptoms to be involved in professions such as science/computing, management and finance. They were more likely to be involved in people‐oriented professions such as nursing or sales. While preliminary, these results suggest that people with dyslexia may indeed show significantly different patterns of occupation choice. Copyright © 2003 John Wiley & Sons, Ltd.
Reading intervention: A ‘conventional’ and successful approach to helping dyslexic children acquire literacy
Authors: Hatcher Peter J.
Published: July 2003

The effectiveness of the ‘conventional’ approach to helping children with dyslexia to acquire literacy has been questioned by Reynolds et al. (Dyslexia 2003). Data are presented in this reply to support the effectiveness of Reading Intervention, a conventional approach to teaching reading delayed children. Copyright © 2003 John Wiley & Sons, Ltd.
Measurement mischief: A critique of Reynolds, Nicolson and Hambly (2003)
Authors: Singleton Chris , Stuart Morag
Published: July 2003

Reynolds, Nicolson and Hambly (2003) report an intervention study of the effects of exercise‐based training on literacy development, using literacy measures from the Dyslexia Screening Test (DST), the NFER‐Nelson Group Reading Test, and the Standard Assessment Tasks (SATs). Investigation of the nature and psychometric characteristics of these measures casts serious doubt on their appropriateness in a study of this nature. Consideration of the findings obtained using these measures does not support the authors' conclusion that reading was improved by the intervention. The study by Reynolds et al. does not demonstrate that exercise‐based treatment improves literacy skills and the use of its purported findings as evidence that exercise‐based treatment would be beneficial for children with literacy difficulties is scientifically untenable. Copyright © 2003 John Wiley & Sons, Ltd.
Science, sense and synergy: Response to commentators
Authors: Nicolson Roderick I. , Reynolds David
Published: July 2003

The commentaries on our evaluation of the DDAT exercise treatment raise several common themes and several individual themes. We rebut criticisms in terms of research design, consider the comments made, and conclude that our evidence is indeed solid. We conclude by advocating ‘science, sense and synergy’ as the key to making further progress. Copyright © 2003 John Wiley & Sons, Ltd.
Measurements of electron density profile characteristics in various kinds of plasma configurations in the TS‐3 plasma merging device
Authors: Hayashiya Hitoshi , Katsurai Makoto
Published: July 2003

Measurements and a comparative study have been performed on electron density profiles, focusing on the electron density gradient near the magnetic separatrix in various kinds of plasma confinements such as the ST, spheromak, and RFP in the TS‐3 device. A CO2 laser interferometer using a glass tube to clear the path for the laser was introduced in order to measure the electron density profile with time resolution. It was shown that ST with a high q value at the plasma edge (q: safety factor) has a larger electron density gradient than low‐q plasma confinements such as the spheromak and RFP. In particular, the ST with edge q value greater than about 2 showed a large electron density gradient at the edge. The idea that the j×B force profile of the higher‐q ST could sustain the higher thermal pressure supports these results. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 145(2): 35–41, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10158
Dynamical movements of electron density profiles in spherical tokamak merging processes
Authors: Hayashiya Hitoshi , Katsurai Makoto
Published: July 2003

Plasma merging is a promising, innovative method of initial heating for spherical tokamak (ST) plasmas. Detailed measurements of the temporal evolution of electron density profiles during plasma merging processes in a TS‐3 device was studied using a CO2 laser interferometer with temporal and spatial resolution. The experimental observations show that the electrons are confined securely inside the magnetic separatrix in the moving plasma during the merging process. It has been found that the plasma particles are not ejected from the confinement region during the magnetic reconnection event, even though the magnetic structure of the plasma is changed drastically. Furthermore, it is shown that the electron density profile becomes hollow after plasma merging. These results indicate that plasma merging is effective not only as a method of initial heating of the ST, but also as a means of particle supply to the ST. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 145(2): 42–49, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10159
Numerical analysis and experimental investigation of discharge characteristics in a ring dielectric line surface‐wave processing plasma apparatus
Authors: Kim Jaeho , Itagaki Toshifumi , Katsurai Makoto
Published: July 2003

Discharge characteristics in ring dielectric line surface‐wave processing plasma (RDL‐SWP) apparatus are studied both numerically and experimentally. To numerically simulate electromagnetic waves in SWP apparatus with a cylindrical discharge chamber such as RDL‐SWP apparatus, a three‐dimensional computer code is developed, employing Cartesian coordinates to allow simulation of both the plasma and rectangular waveguide connected to the chamber. The finite difference time domain (FDTD) method is the basis of the numerical code. Electron density and temperature profiles are measured experimentally in Ar plasma using a movable single probe and the optical emission patterns are studied. It is found that peaks in the electron density profiles coincide with intense optical emissions. For profiles across bulk plasmas with densities higher than cut‐off, diffusion effects are found to be more dominant than localized plasma effects produced by surface waves. In particular, by comparison of numerical and experimental results, the applicability and limitations of a plasma model in which uniform electron density is assumed are evaluated. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 145(2): 10–20, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10174
Conduction of water clusters in modified aged oil
Authors: Ota Koji , Miura Masaki , Sone Mototaka , Mitsui Hideo
Published: July 2003

Dissolved water in insulating liquids has been regarded as a kind of impurity that degrades electrical properties. Recently, the state and the behavior of water molecules in liquid have been measured by infrared methods, making it possible to analyze where water molecules are bound to dielectric molecules and how many molecules gather around polar radicals on the alkyl chain.

In the case of transformer oil, which consists almost entirely of saturated hydrocarbons, the content of oxidation products is gradually increased by aging during use. These oxidation products include polar radicals such as carbonyl and ketone radicals. When water dissolves in such oil, water molecules interact with these polar radicals to form water clusters, which can make the conductivity increase. In the research reported here, partially oxidized hydrocarbon was mixed with saturated hydrocarbon and the effect of water clusters around ketone radicals on the conductivity was investigated. When the content of oxidation products was less than 10%, the conductivity did not increase with an increase in the amount of water. But when the ratio exceeded 10%, specific kinds of water clusters increased the conductivity. It appears that these clusters consist of water molecules gathered around one ketone radical. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 145(2): 21–27, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10178
Electric field measurement just beneath a surface discharge by optical‐waveguide pockels sensors
Authors: Takahashi Tsuguhiro
Published: July 2003

Although surface discharges are one of the principal kinds of phenomena associated with faults in electrical apparatus, they have not yet been fully elucidated. Electric field measurements in and around a corona streamer during the creeping advance of a surface discharge are very helpful in analyzing discharges. Pockels crystals have been used in the optical measurement of electric fields, and an optical waveguide technique has been successfully used to miniaturize the sensors. Electric field measurements are made just beneath a surface discharge with an optical waveguide Pockels sensor installed on a PMMA plate and output signals expressing the development of the discharge are obtained. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 145(2): 28–34, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10185
Electric field of surface discharge inception by electrification charge
Authors: Tashiro Shinichi , Endo Masao
Published: July 2003

It is well known that a surface discharge is significantly affected by the electrification charge on the surface of an insulator. However, only limited information is available concerning the electric field strength of a surface discharge produced by the charge itself. This paper describes the relationship between the surface discharge inception field caused by the charge itself and the pressure. After electrification of the surface of a film covering a plane electrode by a corona discharge produced with a needle electrode, this electrode system was placed in a vacuum chamber and the pressure was lowered. A weak discharge momentarily occurred at a critical pressure around the center of the electrification charge. We obtained the relation between the maximum field strength and the critical pressure in the range of about 50 to 1000 hPa. It should be emphasized that the inception electric field was 6 to 8 kV/mm at atmospheric pressure and 0.5 kV/mm at 50 hPa. Finally, these results are discussed, comparing the flashover voltage of the uniform field and the electric field of discharge inception obtained by experiments at various altitudes in lightning clouds. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 145(2): 1–9, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10192
Trial design of a 6.6‐kV magnetic shielding type of superconducting fault current limiter and performance analysis based on a finite element method
Authors: Kado Hiroyuki , Ichikawa Michiharu , Ueda Hiroshi , Ishiyama Atsushi
Published: July 2003

Superconducting fault current limiter (SCFCL) is expected to be a first application of high‐TC superconductors to electric power systems. We have been developing a magnetic shielding type of SCFCL. In this paper, we propose a design method for the magnetic shield SCFCL. The method is based on a newly developed computer program which can evaluate the dynamic thermal and electromagnetic behaviors of high‐TC superconducting cylinder in fault current limiter operation. As an example, the trial design of a model system, which is 6.6 kV (rms) in rated voltage, 400 A(rms) in rated current, and 12.5 kA(rms) in maximum prospective short‐circuit current, is shown. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 145(2): 50–57, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10197
Load‐following control for dispersed generators using a PI controller
Authors: Senjyu Tomonobu , Takara Hitoshi , Uezato Katsumi , Funabashi Toshihisa , Ito Takamitsu
Published: July 2003

Recently, there has been growing interest in utilizing dispersed generation systems, which are grouped into micro turbine systems, co‐generation systems, and so on, as a substitute for fuel oil energy and a technology to prevent global warming. Since start‐up time of dispersed generation systems is short, it is possible to operate systems to supply load power corresponding to a demand. Moreover, PPSs (Power Producers and Suppliers) can participate in a power retail sales company, since deregulation of electric utilities was instituted in March 2000. However, PPSs have to keep instantaneous generating power commissioning rule, to maintain supply‐and‐demand balance between customer and supplier. Therefore, in this paper, we examine instantaneous generating power commissioning for dispersed generators where start‐up time is short and it is possible to operate systems to supply a power load corresponding to a demand. We adopt a PI controller as a controller. The system is composed of double control loop in inner loop and in outer loop. In inner loop electric power is controlled and in outer loop electric energy is controlled. The controller parameters are designed using the pole‐placement technique. The effectiveness of the proposed control system is confirmed by simulations. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 145(2): 58–66, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10200
A novel method for active filter current regulation using deadbeat control
Authors: Hamasaki Shin‐Ichi , Kawamura Atsuo
Published: July 2003

The shunt‐type active filter (AF), which is widely used due to its protection capability, is installed in parallel to the load. It is considered as an ideal current source and it compensates the harmonic current of the load. However, the AF is practically realized by a current regulator using a voltage source‐type inverter, and it is very difficult to realize the AF current as an ideal current source, especially when it is controlled by digital equipment.

A new control scheme for a line current detection AF is proposed to improve the current regulation capability based on digital deadbeat control. The current control scheme is achieved by controlling the intermediate voltage of the inverter output filter so that the AF output current is regulated, using the dead‐beat control law for the calculation of the pulse width of the PWM inverter. In the proposed scheme, the current regulation performance is much better than in the conventional one.

The control method, mathematical analysis, simulation results, and experimental results are presented in this paper. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 145(2): 67–77, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10201
Recent Updates of Chemically Modified Electrodes in Analytical Chemistry
Authors: Zen Jyh‐Myng , Senthil Kumar Annamalai , Tsai Dong‐Mung
Published: July 2003

This review article updates recent developments in chemically modified electrodes (CMEs) towards analytical applications for the year of 2000–2002 with 179 references. The broad topics are subdivided into four main categories: i) physisorption/chemisorption, ii) covalently linked, iii) homogenous (uniform) multilayer and iv) heterogeneous (non‐uniform) multilayer CMEs. The criteria for the preparation of CMEs in elecrocatalytic systems are clearly described in Section 1. Some of the encouraging results related to Au‐nanoparticles for DNA detection and new ceramic carbon, carbon nanotubes, copper‐plated screen‐printed and Nafion/lead ruthenate pyrochlore CMEs for catalytic application were especially discussed in this review.
Biosensors Based on Aligned Carbon Nanotubes Coated with Inherently Conducting Polymers
Authors: Gao Mei , Dai Liming , Wallace Gordon G.
Published: July 2003

The use of multiwalled aligned carbon nanotubes provides a novel electrode platform for inherently conducting polymer based biosensors. The example used here to highlight the usefulness of such a platform is the polypyrrole based glucose oxidase system for detection of glucose. The use of these three dimensional electrodes offers advantages in that large accessible enzyme loadings can be obtained within an ultrathin layer. It has also been found that the detection of H2O2 at these new electrode structures containing iron loaded nanotube tips can be achieved at low anodic potentials. The result is a sensitive and selective glucose sensor.
New Strategy for Dehydrogenase Amperometric Biosensors Using Surfactant to Enhance the Sensitivity of Diaphorase/Ferrocene Modified Carbon Paste Electrodes for Electrocatalytic Oxidation of NADH
Authors: Ramírez‐Molina César , Boujtita Mohammed , El Murr Nabil
Published: July 2003

A carbon paste electrode (CPE) modified with diaphorase (DAP) and ferrocene (FcH) has been developed for determination of NADH at low working potential. The sensitivity and operational stability, towards the detection of the reduced form of the nicotinamide adenine dinucleotide (NADH) in flow injection analysis (FIA), were greatly improved (5 times) upon adding Tween 20 into the electrode matrix. The magnitude of the amperometric signal was dependent on DAP, FcH and surfactant loading, into the modified carbon paste electrode. A rapid and repeatable response was observed to the variation of NADH concentration in the vicinity of the electrode surface. Such advantages of the DAP/FcH/Tween 20 modified carbon paste were successfully used in the construction of L‐lactate dehydrogenase modified electrodes. The use of this new approach can be generalized to other dehydrogenases and represents a decisive step for a versatile preparation method of amperometric biosensors.
The Voltammetric Behavior of Superoxide Dismutase/Catalase Mimics
Authors: O'Hare Danny , Fucassi Flavia , Cragg Peter J. , Green Michael H. L.
Published: July 2003

The voltammetric behavior of the superoxide dismutase/catalase mimics [(N,N′‐bis(salicylidene)ethylenediamine)Mn(III)]Cl (or salenMn(III) chloride) 1 and [(N,N′‐bis(3‐methoxysalicylidene)ethylenediamine)Mn(III)]Cl (or 3,3′‐methoxysalenMn(III) chloride) 2 in acetonitrile is described. Both compounds show quasi‐reversible one‐electron reductions to the Mn(II) compound. Electroanalytical techniques are used to follow the reaction between superoxide and 1 and 2 and it is shown that it is the reduced Mn(II) compounds which scavenge superoxide. It is also shown that both compounds electrocatalytically generate superoxide in the presence of dissolved dioxygen. The rate constant for this reaction was determined for both compounds using microelectrode steady state voltammetry. A general reaction scheme for interactions between these compounds and both dissolved dioxygen and superoxide is proposed.
A Siloxane Homopolymer with Interacting Ferrocenes as a New Material for the Preparation of Sensors Based on the Detection of Hydrogen Peroxide
Authors: Garcí Armada M. Pilar , Losada José , Cuadrado Isabel , Alonso Beatriz , González Blanca , Casado Carmen M.
Published: July 2003

The electrochemical characterization of a hydrogen peroxide sensor based on a ferrocene‐containing polymer electrochemically deposited onto a platinum electrode is described. The redox polymer consists of a siloxane‐based homopolymer, with pendant electronically communicated ferrocenyl moieties. The electrodes were used as the transducer for glucose and lactate‐sensing enzyme sensors. Amperometric biosensors were prepared by immobilization of glucose oxidase (Gox) or lactate oxidase (Lox) onto these modified electrodes. The steady‐state amperometric response of the sensors is investigated as a function of the applied potential and substrate concentration. Interferences, sensitivity and stability of the sensors were also studied.
TTF‐TCNQ Functionalized Ormosil Based Electrocatalytic Biosensor: A comparative study on Bioelectrocatalysis
Authors: Pandey P. C. , Upadhyay S. , Sharma S.
Published: July 2003

A novel electrocatalytic biosensor for glucose is reported that incorporate encapsulation of tetrathifulvalene‐tetracyanoquinodimethane (TTF‐TCNQ) functionalized organically modified sol gel glass (ormosil). The new ormosil is made using palladium‐linked glycidoxypropyltrimethoxysilane precursor, trimethoxysilane, HCl and TTF‐TCNQ powder at 25 °C. The ormosil is converted into fine powder and incorporated within graphite paste electrode along with glucose oxidase. The bioelectrochemistry of GOD and TTF‐TCNQ functionalized ormosil is examined based on cyclic voltammetry and amperometric measurements. A large electrocatalytic current to the order of 8000 μA/cm2 is recorded on the addition of 300 mM glucose. Typical responses of new biosensor are reported. The sensitivity of glucose analysis is found relatively much better as compared to earlier reported glucose biosensors. The role of palladium and TTF‐TCNQ introduction within ormosil and its advantages on bioelectrocatalysis are discussed.
Determination of Melatonin Hormone in Bulk Form, Tablets and Human Serum by Square‐Wave Cathodic Adsorptive Stripping Voltammetry
Authors: Beltagi A. M. , Khashaba P. Y. , Ghoneim M. M.
Published: July 2003

Melatonin hormone plays an important role in many distinct physiological functions. A fully validated, sensitive and reproducible square‐wave cathodic adsorptive stripping voltammetric procedure was described for determination of melatonin in bulk form, tablets and human serum. The procedure was based on the reduction of the adsorptive hormone onto a hanging mercury drop electrode. Reduction behavior of melatonin was studied in both Britton‐Robinson (pH 2–11) and acetate (4.5–5.5) buffers. Acetate buffer of pH 5.0 was found reasonable as a supporting electrolyte for assay of the drug. The square‐wave cathodic adsorptive stripping voltammogram of melatonin showed a single well‐defined peak at −1.45 V (vs. Ag/AgCl/KCls) using an accumulation potential of −0.65 V. This peak may be attributed to the reduction of CO double bond of the amide functional group of the reactant molecule. A mean recovery for 1×10−8 M melatonin in bulk form followed 30 s accumulation of 98.87%±0.78 and a detection limit of 3.13×10−10 M were achieved. The proposed procedure was successfully applied for the determination of the drug in tablets and human serum with mean recoveries of 97.68%±0.57 and 101.67%±0.85, respectively. A detection limit of 8.80×10−10 M was achieved for the determination of the drug in human serum. Results of the proposed method were comparable and coincided with those obtained by reported method. Vitamin B6 and common excipients, which are co‐formulated with melatonin, did not interfere. Also the effect of some interfering compounds such as serotonin, tryptophan and 5‐hydroxytryptophan on the determination of melatonin in human serum was studied, and all have no significant effect on the assay recovery.
The Electrocatalytic Oxidation of Thymine at α‐Cyclodextrin Incorporated Carbon Nanotube‐Coated Electrode
Authors: Wang Zonghua , Wang Yiming , Luo Guoan
Published: July 2003

Electrocatalytic oxidation of thymine at α‐cyclodextrin (α‐CD) incorporated carbon nanotube‐coated electrode (CNT/CE) was thoroughly studied in alkaline media. CNT showed an electrocatalytic effect on the oxidation of thymine, formation of a supramolecular inclusion complex between α‐CD and thymine at CNT/CE further enhanced the sensitivity to thymine. The electrocatalytic behavior was further developed as a sensitive detection scheme for thymine by differential pulse voltammetry. A linear calibration over the concentration range from 2.5×10−5 to 1.8×10−3 mol/L in pH 10.8 NaHCO3‐Na2CO3 buffer solution was obtained with a detection limit of 5×10−6 mol/L.
Evaluation of the Conductivity of the Polypyrrole Film via Its CC Bonds Stretching on Surface‐Enhanced Raman Spectrum
Authors: Liu Yu‐Chuan
Published: July 2003

In this study, the conductivities of various polypyrrole (PPy) films were evaluated via the corresponding surface‐enhanced Raman scattering (SERS) spectrum and X‐ray photoelectron spectroscopy (XPS). The results indicate that the peak position of CC bonds stretching of PPy obtained from the SERS spectrum shows more exactly both qualitatively and quantitatively representing the conductivity of PPy than the N+/N ratio or the doping level obtained from the XPS analysis does. Namely the peak position of CC bonds stretching of PPy monotone decreases to a lower frequency side with the increase of the conductivity of PPy. Furthermore, a satisfactory correlated equation between them was obtained. On the contrary, neither the N+/N ratio nor the doping level can be qualitatively reflective on the corresponding conductivity of PPy.
Polyelectrolyte Multilayer Films Containing Ferrocene: Effects of Polyelectrolyte Type and Ferrocene Contents in the Film on the Redox Properties
Authors: Liu Aihua , Kashiwagi Yoshitomo , Anzai Jun‐ichi
Published: July 2003

Electrochemical properties of Fc‐PEM films have been studied by changing the chemical structure of the polymer chains and the content of Fc moiety in the film systematically. We have prepared a series of PEM films by a layer‐by‐layer deposition of polycations, Fc‐modified poly(allylamine) (Fc‐PAA) and poly(ethyleneimine) (Fc‐PEI), and polyanionic poly(vinyl sulfate) (PVS) on the surface of a gold electrode. The redox properties of the Fc‐PAA/PVS and Fc‐PEI/PVS films depended significantly on the content of Fc moiety in the polymer chains and on the polymer type. Fc‐ PAA and Fc‐PEI polymer chains can penetrate 3 or 4 PAA/PVS bilayers inserted between the redox polymers and electrode. The Fc‐PAA film‐modified electrode can be used for electrocatalytic oxidation of ascorbic acid.
Flow reversal over a natural pool–riffle sequence: a computational study
Authors: Cao Zhixian , Carling Paul , Oakey Rob
Published: July 2003

A computational study is presented on the hydraulics of a natural pool–rifﬂe sequence composed of mixed cobbles, pebbles and sand in the River Lune, northern England. A depth‐averaged two‐dimensional numerical model is employed, calibrated with observed data at the ﬁeld site. From the computational outputs, the occurrence of longitudinally double peak zones of bed shear stress and velocity is found. In particular, at low discharge there exists a primary peak zone of bed shear stress and velocity at the rifﬂe tail in line with the local maximum energy slope, in addition to a secondary peak at the pool head. As discharge increases, the primary peak at the rifﬂe tail at low ﬂow moves toward the upstream side of the rifﬂe along with the maximum energy slope, showing progressive equalization to the surrounding hydraulic proﬁles. Concurrently, the secondary peak, due to channel constriction, appears to stand at the pool head, with its value increasing with discharge and approaching or exceeding the primary peak over the rifﬂe. The existence of ﬂow reversal is demonstrated for this speciﬁc case, which is attributable to channel constriction at the pool head. A dynamic equilibrium model is presented to reconstruct the pool–rifﬂe morphology. A series of numerical modelling exercises demonstrates that the pool–rifﬂe morphology is more likely produced by shallow ﬂows concentrated with coarse sediments than deep ﬂows laden with low concentrations of ﬁne sediments. It is concluded that channel constriction can, but may not necessarily, lead to competence reversal, depending on channel geometry, ﬂow discharge and sediment properties. Copyright © 2003 John Wiley & Sons, Ltd.
An optical tachometer for short‐path measurement of flow speeds in shallow overland flows: improved alternative to dye timing
Authors: Dunkerley David L.
Published: July 2003

Tracers, such as ﬂuorescein dye, are widely employed to measure overland ﬂow speeds by time‐of‐travel along measured ﬂow paths. Among several disadvantages of this method are the involvement of human reaction time when using stop‐watches, and the relatively long travel path that is consequently needed for reliable timing. Long ﬂow paths mean that local variability along the ﬂow path cannot be detected.

This paper describes a new optical tachometer that overcomes these limitations, as well as offering other advantages. It is based on the use of a small ﬂoating reﬂector target that is carried on the surface tension ﬁlm, and which passes between two reﬂective sensors mounted above the ﬂow. The new device allows virtual ‘spot’ measurements of surface ﬂow speed over a path as short as 1 cm, and eliminates the inﬂuence of human reaction time. The new device is battery powered and portable, and provides an improved alternative to dye timing in many ﬁeld and laboratory applications. Its use will allow the collection of more reﬁned data than have hitherto been easily achievable. Copyright © 2003 John Wiley & Sons, Ltd.
Hydrologic and geomorphic effects of temporary ice‐dammed lake formation during jökulhlaups
Authors: Roberts Matthew J. , Tweed Fiona S. , Russell Andrew J. , Knudsen Óskar , Harris Timothy D.
Published: July 2003

Glacial outburst ﬂoods (jökulhlaups) occur frequently in glaciated environments, and the resultant ﬂooding causes geomorphic change and, in some instances, damage to local infrastructure. During some jökulhlaups, ﬂoodwater is stored temporarily in ice‐marginal locations. In July 1999, a linearly rising jökulhlaup burst from Sólheimajökull, Iceland. During this remarkable event, subglacial ﬂoodwater pooled transiently in two relict ice‐dammed lake basins, before draining suddenly back into Sólheimajökull. The signiﬁcance of such rapid formation and attendant drainage of temporary ice‐dammed lakes during jökulhlaups has not been addressed. Consequently, this paper: (i) assesses the hydrologic and geomorphic effects of temporary ice‐dammed lake formation caused by lake‐basin ‘retro‐ﬁlling’; and (ii) discusses the impact and signiﬁcance of transient retro‐ﬁlling under jökulhlaup conditions. Pre‐ and post‐ﬂood ﬁeldwork at Sólheimajökull enabled the impact and signiﬁcance of lake‐basin retro‐ﬁlling to be assessed. Field evidence demonstrates that the July 1999 jökulhlaup had an unusually rapid rise to peak discharge, resulting in subglacial ﬂoodwater being purged to ice‐marginal locations. The propensity for temporary retro‐ﬁlling was controlled by rapid expulsion of ﬂoodwater from Sólheimajökull, coincident with locations suitable for ﬂoodwater storage. Floodwater inundated both ice‐marginal lake basins, permitting signiﬁcant volumes of sediment deposition. Coarse‐grained deltas prograding from the ice margin and boulders perched on scoured bedrock provide geomorphic records of sudden retro‐ﬁlling. The depositional characteristics of lake‐basin deposits at Sólheimajökull are similar to jökulhlaup sediments documented in proglacial settings elsewhere; however, their depositional setting and association with ice‐marginal landforms is distinctive. Findings suggest that temporary ice‐dammed lake formation and drainage has the capacity to alter the shape of the ﬂood hydrograph, especially if drainage of a temporary lake is superimposed on the original jökulhlaup. Deposits associated with lake‐basin retro‐ﬁlling have a long‐term preservation potential that could help to identify temporary ice‐dammed lake formation in modern and ancient glacial environments. Copyright © 2003 John Wiley & Sons, Ltd.
Spatial and temporal factors controlling short‐term sedimentation in a salt and freshwater tidal marsh, Scheldt estuary, Belgium, SW Netherlands
Authors: Temmerman S. , Govers G. , Wartel S. , Meire P.
Published: July 2003

During a one‐year period temporal and spatial variations in suspended sediment concentration (SSC) and deposition were studied on a salt and freshwater tidal marsh in the Scheldt estuary (Belgium, SW Netherlands) using automatic water sampling stations and sediment traps. Temporal variations were found to be controlled by tidal inundation. The initial SSC, measured above the marsh surface at the beginning of inundation events, increases linearly with inundation height at high tide. In accordance with this an exponential relationship is observed between inundation time and sedimentation rates, measured over 25 spring–neap cycles. In addition both SSC and sedimentation rates are higher during winter than during summer for the same inundation height or time. Although spatial differences in vegetation characteristics are large between and within the studied salt and freshwater marsh, they do not affect the spatial sedimentation pattern. Sedimentation rates however strongly decrease with increasing (1) surface elevation, (2) distance from the nearest creek or marsh edge and (3) distance from the marsh edge measured along the nearest creek. Based on these three morphometric parameters, the spatio‐temporal sedimentation pattern can be modelled very well using a single multiple regression model for both the salt and freshwater marsh. A method is presented to compute two‐dimensional sedimentation patterns, based on spatial implementation of this regression model. Copyright © 2003 John Wiley & Sons, Ltd.
Nucleotide‐mediated calcium signaling in rat cortical astrocytes: Role of P2X and P2Y receptors
Authors: Fumagalli Marta , Brambilla Roberta , D'Ambrosi Nadia , Volonté Cinzia , Matteoli Michela , Verderio Claudia , Abbracchio Maria P.
Published: July 2003

ATP is the dominant messenger for astrocyte‐to‐astrocyte calcium‐mediated communication. Definition of the exact ATP/P2 receptors in astrocytes and of their coupling to intracellular calcium ([Ca2+]i) has important implications for brain physiology and pathology. We show that, with the only exception of the P2X6 receptor, primary rat cortical astrocytes express all cloned ligand‐gated P2X (i.e., P2X1–5 and P2X7) and G‐protein‐coupled P2Y receptors (i.e., P2Y1, P2Y2, P2Y4, P2Y6, and P2Y12). These cells also express the P2Y‐like UDP‐glucose receptor, which has been recently recognized as the P2Y14 receptor. Single‐cell image analysis showed that only some of these receptors are coupled to [Ca2+]i. While ATP induced rapid and transient [Ca2+]i increases (counteracted by the P2 antagonists suramin, pyridoxal‐phosphate‐6‐azophenyl‐2′‐4′‐disulfonic acid and oxidized ATP), the P2X1/P2X3 agonist αβmeATP produced no changes. Conversely, the P2X7 agonist BzATP markedly increased [Ca2+]i; the presence and function of the P2X7 receptor was also confirmed by the formation of the P2X7 pore. ADP and 2meSADP also produced [Ca2+]i increases antagonized by the P2Y1 antagonist MRS2179. Some cells also responded to UTP but not to UDP. Significant responses to sugar‐nucleotides were also detected, which represents the first functional response reported for the putative P2Y14 receptor in a native system. Based on agonist preference of known P2 receptors, we conclude that, in rat astrocytes, ATP‐induced calcium rises are at least mediated by P2X7 and P2Y1 receptors; additional receptors (i.e., P2X2, P2X4, P2X5, P2Y2, P2Y4, and P2Y14) may also contribute. © 2003 Wiley‐Liss, Inc.
Expression and regulation of L‐cystine transporter, system xc−, in the newly developed rat retinal Müller cell line (TR‐MUL)
Authors: Tomi Masatoshi , Funaki Takeshi , Abukawa Hayato , Katayama Kazunori , Kondo Tetsu , Ohtsuki Sumio , Ueda Masatsugu , Obinata Masuo , Terasaki Tetsuya , Hosoya Ken‐Ichi
Published: July 2003

The purpose of the present study was to elucidate the expression and regulation of the L‐cystine transporter, system xc−, in Müller cells. In this study, newly developed conditionally immortalized rat Müller cell lines (TR‐MUL) from transgenic rats harboring the temperature‐sensitive SV 40 large T‐antigen gene were used as an in vitro model. TR‐MUL cells express large T‐antigen and grow well at 33°C with a doubling time of 30 h, but do not grow at 39°C. TR‐MUL cells express typical Müller cell markers such as S‐100, glutamine synthetase, and EAAT1/GLAST, whereas EAAT2/GLT‐1 and EAAT5 are not detected. TR‐MUL cells also exhibit little or no expression of glial fibrillary acidic protein. We found that TR‐MUL5 cells exhibited [14C]L‐cystine uptake activity and expressed xCT and 4F2hc, which involve system xc−. The uptake of [14C]L‐cystine was significantly inhibited by L‐glutamic acid and L‐aspartic acid, whereas L‐leucine had no effect. Following diethyl maleate (DEM) treatment, the glutathione concentration in TR‐MUL5 cells was reduced in the first 24 h, then gradually recovered for more than 24 h. The L‐cystine uptake rate and the xCT expression level in TR‐MUL5 cells were enhanced by DEM treatment. In contrast, the 4F2hc expression level was unchanged. In conclusion, TR‐MUL cells have the properties of Müller cells and exhibit system xc−‐mediated L‐cystine uptake activity. The oxidative stress conditions following DEM treatment activate L‐cystine transport in TR‐MUL cells due to the enhanced transcription of the xCT gene. GLIA 9999:000–000, 2003. © 2003 Wiley‐Liss, Inc.
Evidence for astrocyte heterogeneity: A distinct subpopulation of protoplasmic‐like glial cells is detected in transgenic mice expressing Lmo1‐lacZ
Authors: Scotti Campos Lia
Published: July 2003

The adult mammalian central nervous system (CNS) contains a large number of different cell types, which arise from the ventricular (VZ) and subventricular zones during embryonic development. In this study, we used a transgenic mouse expressing Lmo1‐LacZ from a randomly inserted promoter/reporter gene construct to identify a glial subpopulation. LMO1 is an LIM domain‐containing protein, thought to act in protein‐protein interactions. We found first that in the adult transgenic CNS, β‐galactosidase (β‐gal) was expressed in a specific subpopulation of protoplasmic‐like cells, which did not express detectable levels of glial fibrilary acidic protein unless a lesion was produced. Secondly, during development, β‐gal+ cells were found arising from discrete regions of the VZ. Taken together, these results identify a subpopulation of protoplasmic glial cells in the adult CNS and suggest that they arise from a restricted VZ region during CNS development. © 2003 Wiley‐Liss, Inc.
Essential role for ERK mitogen‐activated protein kinase in matrix metalloproteinase‐9 regulation in rat cortical astrocytes
Authors: Arai Ken , Lee Sun‐Ryung , Lo Eng H.
Published: July 2003

Matrix metalloproteinases (MMPs) contribute to the pathophysiology of brain injury and inflammation but little is known about their regulatory signaling pathways in brain cells. Here we examine the role of mitogen‐activated protein (MAP) kinase pathways in MMP‐9 regulation in cortical rat astrocytes. The protein kinase C (PKC) activator phorbol 12‐myristate 13‐acetate (PMA) induced MMP‐9 but not MMP‐2 secretion as measured by gelatin zymography. Northern blot and RT‐PCR analysis showed that MMP‐9 responses occurred at the mRNA level. Although PMA increased phosphorylation in all three major MAP kinase pathways (ERK, p38 MAP kinase, and JNK), only inhibition of the ERK pathway by the MEK/ERK inhibitor U0126 (0.1–10 μM) significantly reduced MMP‐9 upregulation, even when treatment was delayed for 4 h after PMA exposure. Inhibitors of p38 MAP kinase (SB203580) and JNK (SP600125) had no effect. This PKC pathway was compared to a cytokine response by exposing astrocytes to TNFα, which also activated MAP kinase and induced MMP‐9 upregulation. But in this case, all three MAP kinase inhibitors (U0126, SB203580, and SP600125) reduced TNFα‐induced MMP‐9 upregulation. Taken together, these results suggest that the ERK MAP kinase is essential for MMP‐9 upregulation via PKC and cytokine pathways in astrocytes. © 2003 Wiley‐Liss, Inc.
Cultured astrocytes express toll‐like receptors for bacterial products
Authors: Bowman Christal C. , Rasley Amy , Tranguch Susanne L. , Marriott Ian
Published: July 2003

It has become apparent that astrocytes may be important contributors to inflammatory immune responses within the brain in response to microbial challenges. To date, the mechanisms that underlie activation of this major glial cell type by such challenges have not been investigated. In the present study, we present evidence for members of a recently discovered family of receptors for highly conserved microbial components, the Toll‐like receptors (TLRs), in isolated cultures of primary murine astrocytes. We describe the low‐level constitutive expression of messenger RNA‐encoding TLR2, TLR4, TLR5, and TLR9 in resting cultures of these cells. Importantly, the level of expression of messenger RNA for each of these receptors is markedly elevated following exposure to specific bacteria‐derived ligands for these receptors. The functional expression of these receptor proteins is further supported by the ability of known ligands for each TLR to induce both message expression and protein secretion of the proinflammatory cytokine, interleukin‐6. In addition, the recent availability of antibodies to TLR2 and TLR4 has enabled us to demonstrate directly the presence of these receptors on astrocytes by Western blot and immunofluorescence analysis, respectively. Furthermore, we have confirmed the sensitivity of such receptor expression to ligand stimulation. The present demonstration of Toll‐like microbial pattern‐recognition receptors on primary astrocytes provides a mechanistic link between bacterial challenge and inflammatory immune responses that may be an important component of the pathologies of bacterially induced inflammatory CNS disorders. © 2003 Wiley‐Liss, Inc.
Modulation of intercellular calcium signaling in astrocytes by extracellular calcium and magnesium
Authors: Stout Charles , Charles Andrew
Published: July 2003

The extracellular concentrations of Ca2+ and Mg2+ are well known to play important roles in the function of the central nervous system. We examined the effects of extracellular Ca2+ and Mg2+ on ATP release and intercellular signaling in astrocytes. The extent of propagation of intercellular Ca2+ waves evoked by mechanical stimulation was increased by reduction of extracellular Ca2+ ([Ca2+]o) or Mg2+ concentration ([Mg2+]o) and was decreased by elevated [Mg2+]o. Reduction of extracellular Ca2+ concentration ([Ca2+]o) evokes intercellular Ca2+ signaling in astrocytes; a similar effect was observed in response to change from 5 mM [Mg2+]o to 0 [Mg2+]o. Release of low‐molecular‐weight dyes and ATP was also activated by low [Ca2+]o or [Mg2+]o and inhibited by high [Ca2+]o or [Mg2+]o. Astrocytes showed low [Ca2+]o–activated whole cell currents consistent with currents through connexin hemichannels. These currents were inhibited by extracellular Mg2+. We conclude that extracellular divalent cations modulate intercellular Ca2+ signaling in astrocytes by modulating the release of ATP, possibly via connexin hemichannels. © 2003 Wiley‐Liss, Inc.