bluuebunny/crossref_metadata_2025 huggingface dataset:
Notch signaling is activated by TLR stimulation and regulates macrophage functions
Authors: Palaga Tanapat , Buranaruk Chayanit , Rengpipat Sirirat , Fauq Abdul H. , Golde Todd E. , Kaufmann Stefan H. E. , Osborne Barbara A.
Published: December 2007

Notch signaling is a well‐conserved pathway involved in cell fate decisions, proliferation and apoptosis. We report on the involvement of Notch signaling in regulating gene expression in activated macrophages. Toll‐like receptors (TLR) agonists such as bacterial lipopeptide, polyI:C, lipopolysaccharide and unmethylated CpG DNA all induced up‐regulation of Notch1 in primary and macrophage‐like cell lines. Notch1 up‐regulation was dependent on the MyD88 pathway when stimulated through TLR2, but not TLR4. Activated Notch1 and expression of the Notch target genes, Hes1 and Deltex, were detected in activated macrophages, suggesting that Notch signaling was activated upon stimulation. Inhibiting processing of Notch receptor by γ‐secretase using a γ‐secretase inhibitor (GSI), the expression of Notch1 was down‐regulated to basal levels. This treatment significantly modulated expression of TNF‐α, IL‐6, and IL‐10. In addition, the amount of nitric oxide produced was significantly lower and the expression of MHC class II was up‐regulated in GSI‐treated cells. Treatment with GSI or silencing Notch1 resulted in decreased translocation of NF‐κBp50 into nucleus upon stimulation. Taken together, stimulation of macrophages through the TLR signaling cascade triggered activation of Notch signaling, which in turn regulated gene expression patterns involved in pro‐inflammatory responses, through activation of NF‐κB.
Levels of autoantibodies, unlike antibodies to all extrinsic antigen groups, fall following B cell depletion with Rituximab
Authors: Ferraro Alastair J. , Drayson Mark T. , Savage Caroline O. S. , MacLennan Ian C. M.
Published: December 2007

Many autoantibodies have variable‐region sequences indicating their production in an affinity‐matured antibody response involving germinal centers (GC). Plasma cells from GC can be long‐lived, do not express CD20 and thus should not be depleted by a therapeutic monoclonal Ab against human CD20 ‐ Rituximab. Nevertheless, autoantibody titers often fall following Rituximab treatment. To test if this reflects exclusive production by short‐lived plasma cells in extrafollicular Ab responses, we monitored, after Rituximab treatment, levels of natural Ab and Ab against extrinsic antigens that do not induce productive GC. Eleven patients with active vasculitis and anti‐proteinase‐3 (PR3) Ab were assessed before and during 5 months after Rituximab therapy. Blood B cells were undetectable within 2 wk, and all patients achieved clinical remission. Levels of natural Ab – isohemagglutinins and anti‐phosphorylcholine Ab – and Ab levels against thymus‐independent and thymus‐dependent extrinsic antigens were little affected. By contrast, 5 months after Rituximab, IgG autoantibody against PR3 had fallen to a median of 22% of pretreatment values. While the kinetics of this fall do not suggest an intrinsically short lifespan of autoantibody‐producing cells, the data are consistent with Rituximab causing loss of sites within inflammatory tissues that selectively sustain autoantibody‐producing cells.
Regression with spatially misaligned data
Authors: Madsen L. , Ruppert D. , Altman N. S.
Published: December 2007

We present a simple approach to the problem of estimating the regression slope parameter from spatially misaligned point data. We assume a linear regression model with errors and covariates from two independent Gaussian spatial processes where covariate and response are observed at different locations. Correlation in the covariate is exploited to predict unobserved covariates via kriging. Kriged values are used to find weighted least squares estimates of regression parameters in a ‘krige‐and‐regress’ (KR) procedure. The variance of this estimator is calculated, and a variance estimator is proposed. Because the model and assumptions make it possible to write down the joint likelihood of the data, a maximum likelihood (ML) estimator can be found. Under regularity conditions, this estimator is asymptotically normal with asymptotic variance given by the inverse information matrix, which yields a variance estimator for the ML estimator of the regression parameters. The KR and ML estimators are compared in an example using Environmental Protection Agency data and a simulation study is conducted. While the ML estimator of the slope parameter has a smaller variance than the KR estimator, the ML variance estimator is too small to be used for inference whereas the KR variance estimator gives approximately correct inference. Copyright © 2007 John Wiley & Sons, Ltd.
Raviart–Thomas and Brezzi–Douglas–Marini finite‐element approximations of the shallow‐water equations
Authors: Rostand V. , Le Roux D. Y.
Published: December 2007

An analysis of the discrete shallow‐water equations using the Raviart–Thomas and Brezzi–Douglas–Marini finite elements is presented. For inertia–gravity waves, the discrete formulations are obtained and the dispersion relations are computed in order to quantify the dispersive nature of the schemes on two meshes made up of equilateral and biased triangles. A linear algebra approach is also used to ascertain the possible presence of spurious modes arising from the discretization. The geostrophic balance is examined and the smallest representable vortices are characterized on both structured and unstructured meshes. Numerical solutions of two test problems to simulate gravity and Rossby modes are in good agreement with the analytical results. Copyright © 2007 John Wiley & Sons, Ltd.
On restraining convective subgrid‐scale production in Burgers' equation
Authors: Helder Joop , Verstappen Roel
Published: December 2007

Since most turbulent flows cannot be computed directly from the (incompressible) Navier–Stokes equations, a dynamically less complex mathematical formulation is sought. In the quest for such a formulation, we consider nonlinear approximations of the convective term that preserve the symmetry and conservation properties. The underlying idea is to restrain the convective production of small scales in an unconditionally stable manner, meaning that the approximate solution cannot blow up in the energy norm. In this paper, the method is worked out and tested successfully for Burgers' equation. Copyright © 2007 John Wiley & Sons, Ltd.
Novel biostable and biocompatible amphiphilic membranes
Authors: Jewrajka Suresh K. , Erdodi Gabor , Kennedy Joseph P. , Ely Daniel , Dunphy Gail , Boehme Shannon , Popescu Flavius
Published: December 2007

We determined the biostability and biocompatibility of two types of amphiphilic conetworks (APCNs): (1) hydrophilic poly(N,N‐dimethyl acrylamide) (PDMAAm) and hydrophobic polydimethylsiloxane (PDMS) microdomains co‐crosslinked with polymethylhydrosiloxane (PMHS) clusters (PDMAAm/PMHS/PDMS), and (2) poly(ethylene glycol) (PEG) and PDMS microdomains co‐crosslinked with two specially designed small‐molecule crosslinking agents SiC6H5(SiH)2OEt (Y) and polypentamethylhydrocyclosiloxane (PD5) (PEG/Y or PD5/PDMS). Negative standards for comparing biocompatibility and biostability were crosslinked PDMS. Biostability was assessed by quantitatively determining extractables, equilibrium water swelling, mechanical properties (stress‐strain response) of polymer samples before and after implantation in rats for up to 8 weeks, and oxidative accelerated degradation test. Biocompatibility was assessed by determining body weight, fibrous tissue encapsulation, fluid accumulation, and by histological evaluation of lymphocyte infiltration, fibrous tissue accumulation and collagen deposition. According to these stringent metrics PDMAAm/PMHS/PDMS is both biostable and biocompatible, whereas PEG/Y or PD5/PDMS degrades in living tissue but is biocompatible. Surprisingly, the overall biocompatibility scores of these APCNs were superior to those of the PDMS negative standard. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2008
The relationship between femoral periprosthetic cortical bone geometry and porosity after total hip arthroplasty
Authors: Rosenbaum Chou Teri G. , Child Jeremy R. , Naughtin Ryan J. , Rigdon Ryan R. , Schumann Craig , Bloebaum Roy D.
Published: December 2007

Stress shielding from the presence of a femoral component can cause adverse changes to cortical bone geometry and porosity leading to increased fracture risk in the periprosthetic cortical bone. The objectives of this study were to determine if porosity increased after total hip arthroplasty along the principal axes, and to determine if a relationship existed between cortical bone porosity and geometry. Ten postmortem donors allowed comparisons of implanted femurs to the contralateral nonimplanted femurs. Transverse cross‐sections of the femur were taken at 25, 45, 65, and 85% along the length of the femoral component. The cortical bone principal axes' location (degrees) and rigidity values (mm4) were based on cortical bone geometry by using digitized images of the cortical bone cross‐sections. Percent porosity was measured along the principal axes using backscatter electron imaging. Cortical bone porosity increased in the more distal sections of the implanted femurs by ∼3%, but did not preferentially increase along a particular principal axis. No correlation was found between changes in porosity and rigidity values. In conclusion, the porosity increases in the implanted femurs may have regionally reduced cortical bone strength. The locations of higher porosity did not appear related to the cortical bone geometry. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2008
Biocompatibility of atomic layer‐deposited alumina thin films
Authors: Finch Dudley S. , Oreskovic Tammy , Ramadurai Krishna , Herrmann Cari F. , George Steven M. , Mahajan Roop L.
Published: December 2007

Presented in this paper is a study of the biocompatibility of an atomic layer‐deposited (ALD) alumina (Al2O3) thin film and an ALD hydrophobic coating on standard glass cover slips. The pure ALD alumina coating exhibited a water contact angle of 55° ± 5° attributed, in part, to a high concentration of OH groups on the surface. In contrast, the hydrophobic coating (tridecafluoro‐1,1,2,2‐tetrahydro‐octyl‐methyl‐bis(dimethylamino)silane) had a water contact angle of 108° ± 2°. Observations using differential interference contrast microscopy on human coronary artery smooth muscle cells showed normal cell proliferation on both the ALD alumina and hydrophobic coatings when compared to cells grown on control substrates. These observations suggested good biocompatibility over a period of 7 days in vitro. Using a colorimetric assay technique to assess cell viability, the cellular response between the three substrates can be differentiated to show that the ALD alumina coating is more biocompatible and that the hydrophobic coating is less biocompatible when compared to the control. These results suggest that patterning a substrate with hydrophilic and hydrophobic groups can control cell growth. This patterning can further enhance the known advantages of ALD alumina, such as conformality and excellent dielectric properties for bio‐micro electro mechanical systems (Bio‐MEMS) in sensors, actuators, and microfluidics devices. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2008
Biomimetic fabrication of fibrin/apatite composite material
Authors: Yoh Rui , Matsumoto Takuya , Sasaki Jun‐ichi , Sohmura Taiji
Published: December 2007

Bidirectional diffusion of the Ca and PO4 solutions into the fibrin gel was performed at various pH conditions and fluoride concentrations to generate organic/inorganic composite materials mimicking biomineralization. The minerals produced in this system had a higher crystallinity than those generated by the solution mineralization system. The minerals generated in fibrin gel varied depending on the pH conditions as follows: Dicalcium phosphate dihydrate (DCPD) in the noncontrolled pH solution, the DCPD and octacalcium phosphate (OCP) mixture at pH 7.4, and the OCP and hydroxyapatite (HAp) mixture at pH 9.0. When fluoride ions were added in the range of 2–500 ppm, the minerals produced at pH 7.4 altered from OCP/HAp to HAp/fluorapatite (FAp). In addition, the crystallinity of the obtained minerals increased with an increase in fluoride ion concentration, and the solubility was inversely correlated to crystallinity. In conclusion, we established a novel fabrication method for synthesizing organic/inorganic composite materials composed of fibrin and calcium phosphate and revealed that the characteristics of the minerals in the synthesized material can be controlled by the fabrication condition. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2008
Claisen rearrangement induced by low‐energy collision of ESI‐generated, protonated benzyloxy indoles
Authors: Crotti Sara , Stella Laura , Munari Ilaria , Massaccesi Franco , Cotarca Livius , Forcato Massimiliano , Traldi Pietro
Published: December 2007

The Claisen rearrangement is a well‐known process occurring in condensed phase. In the gas‐phase protonated allyl phenyl ethers, propargyl phenyl ethers, and N‐allyl aniline produced by positive ion chemical ionization undergo Claisen rearrangement. This reaction has been observed even in the case of odd‐electron molecular ions. Phenyl allenyl ether molecular ions actually undergo Claisen rearrangement, producing intense [M − CO]+• ions. In this investigation, the behavior of protonated benzyloxy indole and some of its derivatives, obtained in electrospray conditions, is described. Low‐energy MS/MS experiments carried out on [M + H]+ species show CO loss and an unexpected water loss: both can be justified only by the occurrence of Claisen rearrangement. Deuterium labeling experiments confirm this mechanism. The influence of different substituents in the indole moiety is discussed. Copyright © 2007 John Wiley & Sons, Ltd.
GC‐MS analysis of organic compounds in wastewater and sewage sludge
Authors: Ligon Axel Patrick , Zuehlke Sebastian , Spiteller Michael
Published: December 2007

A multimethod based on liquid–liquid extraction and solid–liquid extraction for the analysis of persistent organic pollutants in water and sludge from sewage treatment plants has been established. Traces of 22 organic compounds used in industry and personal care products (PCPs) were analyzed by GC/MS. The LODs for the analytes were less than 2.3 ng/L for wastewater and 31 μg/kg (dry weight matter) for sewage sludge. Satisfactory recoveries (70–130%) were achieved. The validated method permits the analysis of water and sludge samples at various stages of the treatment from different sewage treatment plants. Thus, the distribution between water and sludge as well as the dissipation of the compounds analyzed were balanced. By this means, the efficiency of different wastewater treatment plants (WWTPs) can be evaluated and measures can be taken to optimize the treatment process at different stages.
Inverse scattering for planar cracks via nonlinear integral equations
Authors: Ivanyshyn O. , Kress R.
Published: December 2007

We present a Newton‐type method for reconstructing planar sound‐soft or perfectly conducting cracks from far‐field measurements for one time‐harmonic scattering with plane wave incidence. Our approach arises from a method suggested by Kress and Rundell (Inv. Probl. 2005; 21(4):1207–1223) for an inverse boundary value problem for the Laplace equation. It was extended to inverse scattering problems for sound‐soft obstacles (Mathematical Methods in Scattering Theory and Biomedical Engineering. World Scientific: Singapore, 2006; 39–50) and for sound‐hard cracks (Inv. Probl. 2006; 22(6)). In both cases it was shown that the method gives accurate reconstructions with reasonable stability against noisy data. The approach is based on a pair of nonlinear and ill‐posed integral equations for the unknown boundary. The integral equations are solved by linearization, i.e. by regularized Newton iterations. Numerical reconstructions illustrate the feasibility of the method. Copyright © 2007 John Wiley & Sons, Ltd.
Does more solvent in bore liquid create more open inner surface in hollow fiber membranes?
Authors: Li Xue‐Mei , He Tao
Published: December 2007

The solvent content in the bore liquid controls the inner structure of a hollow fiber membrane. Based on the theory of liquid–liquid phase separation, at a higher solvent concentration, the inner surface is more open and the transport resistance is lower. However, the theory does not describe clearly the membrane structure formation at a very high solvent concentration. A logic deduction is that more solvent in the bore liquid results in more open inner structure. In this report, a polymer solution, polysulfone (PSf)/N‐methylpyrrolidone (NMP)/diethylene glycol (DegOH) was used to investigate the relationship between the membrane resistance and solvent content in the bore liquid. A triple orifice spinneret was used to prepare an open outer surface, minimizing the transport resistance in the membrane outer layer. Bore liquid solutions with NMP concentration close to the critical solvent concentration (CSC) were used. The membranes were characterized by scanning electron microscopy (SEM), pore size and pore size distribution, nitrogen and pure water permeability. The results indicated that at a concentration far below the CSC, a higher NMP content corresponds to a more open inner surface, but the aggressive addition of solvent to a concentration close to CSC tends to form closed cells; thus water and gas permeability significantly decreases. This phenomenon was explained by nuclei formation and growth, followed by the formation of a dense skin and closed cell structure in a mild coagulant. Copyright © 2007 John Wiley & Sons, Ltd.
Highly elevated ferritin levels and the diagnosis of hemophagocytic lymphohistiocytosis
Authors: Allen Carl E. , Yu Xiaoying , Kozinetz Claudia A. , McClain Kenneth L.
Published: December 2007

Background

Hemophagocytic lymphohistiocytosis (HLH) is a potentially lethal condition characterized by a pathologic inflammation. The diagnostic criteria for HLH include fever, splenomegaly, cytopenias, hypertriglyceridemia, hypofibrinogenemia, abnormal natural killer cell (NK cell) functional assay, elevated soluble IL‐2Rα level, and elevated ferritin level (>500 µg/L). Institution of timely therapy in these critically ill patients may be delayed by difficulties establishing the diagnosis. NK cell functional assay and soluble IL‐2Rα level may require send‐out to a specialized lab. However, ferritin level is available on a same‐day basis at most institutions. In this study, we examined the utility of quantitative ferritin levels in diagnosing HLH.

Procedure

All patients with ferritin values >500 µg/L obtained at Texas Children's Hospital between January 10, 2003 and January 10, 2005 were identified. Patient charts were reviewed for ferritin levels and hospital course.

Results

During the study interval, 330 patients had ferritin levels >500 µg/L. Ten of the 330 patients were diagnosed with HLH. A ferritin level over 10,000 µg/L was 90% sensitive and 96% specific for HLH. Another diagnostic category with significantly elevated ferritin level was illness of unknown cause (n = 10), and only two of these patients were fully evaluated for HLH.

Conclusions

Ferritin levels above 10,000 µg/L appear to be specific and sensitive for HLH. In patients without a significant medical history and a new onset of febrile illness with highly elevated ferritin levels, the diagnosis of HLH should be evaluated. Pediatr Blood Cancer 2008;50:1227–1235. © 2007 Wiley‐Liss, Inc.
The dipeptidyl‐peptidase‐4 (DPP‐4) inhibitors: a new class of oral therapy for patients with type 2 diabetes mellitus
Authors: Elrishi MA , Khunti K , Jarvis J , Davies MJ
Published: December 2007

The observation that an oral glucose load is more effective at releasing insulin, compared with the same amount of glucose given intravenously, has been called the incretin effect, and is due to the augmentation of glucose‐stimulated insulin secretion by intestinally derived peptides.

Glucagon‐like peptide‐1 (GLP‐1), in particular, has been shown to stimulate insulin release in a glucose‐dependent manner in humans, but it is rapidly metabolised by dipeptidyl‐peptidase‐4 (DPP‐4). Inhibition of DPP‐4 activity enhances fasting and post‐prandial GLP‐1 which, in turn, improves glycaemic control by increasing glucose‐dependent insulin secretion and by decreasing glucagon concentration.

Current oral antidiabetic drugs (OADs) for type 2 diabetes are limited by adverse effects such as gastrointestinal problems, weight gain, oedema, or hypoglycaemia. In addition, there are recent concerns about rosiglitazone and cardiovascular outcomes, and with the thiazolidinediones in general regarding excess fracture rate in women and increased risk of heart failure. Thus the introduction of a new class of OADs, the DPP‐4 inhibitors, is welcome.

This review article discusses the most clinically relevant data published on DPP‐4 inhibitors based on Medline literature searches (1966 to August 2007) and posters and oral presentations from the American Diabetes Association Scientific Sessions in 2006 and 2007. We have concentrated our review on two DPP‐4 inhibitors: sitagliptin (Januvia) and vildagliptin (Galvus). Copyright © 2007 John Wiley & Sons.
Highly selective and rapid enrichment of phosphorylated peptides using gallium oxide‐coated magnetic microspheres for MALDI‐TOF‐MS and nano‐LC‐ESI‐MS/MS/MS analysis
Authors: Li Yan , Lin Huaqing , Deng Chunhui , Yang Pengyuan , Zhang Xiangmin
Published: December 2007

In this work, we present, to our knowledge, the first demonstration of the utility of iron oxide magnetic microspheres coated with gallium oxide for the highly selective enrichment of phosphopeptide prior to mass spectrometric analysis. These microspheres that we prepared not only have a shell of gallium oxide, giving them a high‐trapping capacity for the phosphopeptides, but also their magnetic property enables easy isolation by positioning an external magnetic field. Tryptic digest products of phosphoproteins including β‐casein, ovalbumin, casein, as well as five protein mixtures were used as the samples to exemplify the feasibility of this approach. In very short time (only 0.5 min), phosphopeptides sufficient for characterization by MALDI‐TOF‐MS were selectively enriched by the Ga2O3‐coated Fe3O4 microspheres. The performance of the Ga2O3‐coated Fe3O4 microspheres were further compared with Fe3+‐immobilized magnetic silica microspheres, commercial Fe3+‐IMAC resin, and TiO2 beads for enrichment of peptides originating from tryptic digestion of β‐casein and BSA with a molar ratio of 1:50, and the results proved a stronger selective ability of Ga2O3‐coated Fe3O4 microspheres over the other materials. Finally, the Ga2O3‐coated Fe3O4 microspheres were successfully utilized for enrichment of phosphopeptides from digestion products of rat liver extract. All results show that Ga2O3‐coated Fe3O4 microsphere is an effective material for selective isolation and concentration of phosphopeptides.
A new standardizexd treadmill walking test requiring low motor skills in children aged 4–10 years
Authors: Wäffler‐Kammermann Nathalie , Lacorcia Ruth Stauffer , Wettstein Markus , Radlinger Lorenz , Frey Urs
Published: December 2007

Exercise intolerance may be reported by parents of young children with respiratory diseases. There is, however, a lack of standardized exercise protocols which allow verification of these reports especially in younger children. Consequently the aims of this pilot study were to develop a standardized treadmill walking test for children aged 4–10 years demanding low sensorimotor skills and achieving high physical exhaustion. In a prospective experimental cross sectional pilot study, 33 healthy Caucasian children were separated into three groups: G1 (4–6 years, n = 10), G2 (7–8 years, n = 12), and G3 (9–10 years, n = 11). Children performed the treadmill walking test with increasing exercise levels up to peak condition with maximal exhaustion. Gas exchange, heart rate, and lactate were measured during the test, spirometry before and after. Parameters were statistically calculated at all exercise levels as well as at 2 and 4 mmol/L lactate level for group differences (Kruskal–Wallis H‐test, α = 0.05; post hoc: Mann–Whitney U‐test with Bonferroni correction α = 0.05/n) and test–retest differences (Wilcoxon‐rank‐sum test) with SPSS. The treadmill walking test could be demonstrated to be feasible with a good repeatability within groups for most of the parameters. All children achieved a high exhaustion level. At peak level under exhaustion condition only the absolute VO2 and VCO2 differed significantly between age groups. In conclusion this newly designed treadmill walking test indicates a good feasibility, safety, and repeatability. It suggests the potential usefulness of exercise capacity monitoring for children aged from early 4 to 10 years. Various applications and test modifications will be investigated in further studies. Pediatr Pulmonol. 2008; 43:187–195. © 2007 Wiley‐Liss, Inc.
Numerical simulation of spin accumulation and tunnel magnetoresistance in single electron tunnelling junctions with a nonmagnetic nanoparticle
Authors: Wang H. , Mitani S. , Takanashi K. , Imamura H.
Published: December 2007

For the device designs showing a large tunnel magnetoresistance (TMR) due to spin accumulation, spin dependent single electron tunnelling in double tunnel junctions with a nonmagnetic nanoparticle is investigated by numerical simulations in the sequential tunnelling regime. We show that the bias voltage dependecnce of TMR ratio takes a maximum value just above the Coulomb threshold voltage and the optimal junction parameters for a large TMR ratio are obtained. We also show that the maximum value of the TMR ratio almost agrees with 2P2/(1+P2) where P is the spin polarization of ferromagnetic electrodes. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Spin accumulation and magnetoresistance of a CPP‐GMR system with a current confined path
Authors: Imamura Hiroshi
Published: December 2007

We theoretically studied the spin accumulation and magnetoresistance of the CPP‐GMR system with a current confined path (CCP) by starting with the Boltzmann equation. We numerically solved the continuity equations for charge and spin currents and showed that the MR ratio is enhanced for the system with a narrow contact. We discussed the origin why the MR ratio is enhanced due to the CPP structure. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Nonequilibrium process of magnetization switching influenced by thermal spin fluctuations
Authors: Choi B. C. , Hong Y. K. , Rudge J. , Girgis E. , Kolthammer J. , Donohoe G. W.
Published: December 2007

We present a systematic study of the dynamic behavior of nonequilibrium magnetization configurations with time‐resolved scanning Kerr microscope and micromagnetic modeling. The magnetization switching dynamics enters a fully dynamic regime when the external field conditions are changed much faster than the magnetization in the elements is able to respond. We observe that the dynamic pathway develops a complexity not seen in quasi‐static reversal, but still retains a high level of order with well‐developed dynamic domain patterns formed in response to sub‐nanosecond transitions of the external applied magnetic field pulse. An increasing complexity in the spatial structure of the evolution is found to accompany the increasing switching speed, when a ferromagnetic element is driven by progressively faster reversing fields applied anti‐parallel to the initial magnetization direction. The sensitive dependence of the nonequilibrium magnetization configurations on switching speed can be understood in terms of a dynamic exchange interaction of thermally excited spins; the coherent modulation of the spins is strongly dependent on the rise time of switching magnetic field pulses. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Mössbauer study of iron ordering in mixed valence system LuFe2O4
Authors: Bang Bong Kyu , Kim Sung Baek , Cheong S‐W. , Kim Chul Sung
Published: December 2007

Single crystalline LuFe2O4 was grown by the floating zone method. The crystallographic and magnetic properties of the sample were measured using x‐ray diffractometer (XRD), Mössbauer spectroscopy, and vibrating sample magnetometer (VSM). The crystal structure was found to be a two‐dimensional layered‐type rhombohedral with space group R3‐mh. The magnetic Curie temperature (TC) was determined to be 250 K from the M ‐T curve and Mössbauer spectra. Just below TC, the magnetic moment has large value and shows a abrupt change in M ‐T curve. The Mössbauer spectra have been taken at various temperatures ranging from 4.2 to 370 K. We confirmed that the charge ordering of Fe3+ and Fe2+ ions was begun below 350 K, magnetic superstructure of the different ionic state was formed around 320 K. The isomer shift value of Fe2+ doublet increases with decreasing temperature from 320 to 235 K. At low temperature, Mössbauer spectra consisted of four sextets with magnetic ordering. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Direct observation of saw‐tooth typed domain wall jumps in epitaxial ferromagnetic MnAs film on GaAs(001)
Authors: Ryu Kwang‐Su , Akinaga Hiro , Shin Sung‐Chul
Published: December 2007

We report the direct observation of saw‐tooth domain wall jumps in epitaxial ferromagnetic MnAs film on GaAs(001) via a magneto‐optical Kerr effect microscope. Interestingly, it is found that the saw‐tooth domain wall jumps are generated along an easy axis orientation and the saw‐tooth angle is nearly constant irrespective of the applied field direction. These observations can be understood on the basis of strong uniaxial anisotropy on the sample plane. The analytical study reveals that the saw‐tooth domain wall structure results from competition between the domain wall energy and the dipolar energy. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Domain wall pinning by alternating materials in current‐induced domain wall motion
Authors: Kim W. J. , Lee T. D. , Lee K. J.
Published: December 2007

For the application of current‐induced domain wall motion, the pinning position of a domain wall must be precisely defined with a low depinning current density. A conventional way of pinning a domain wall is to use a notch which is patterned on an edge of nanostrip. As an alternative scheme of domain wall pinning, we performed micromagnetic investigation of the current‐induced domain wall motion in a nanostrip with alternating materials. A segment with different magnetic parameters such as saturation magnetization, exchange constant or crystalline anisotropy can effectively pin a domain wall. It is because the segment acts as an energy barrier in the domain wall motion. Threshold current densities to depin the domain wall in nanostrips with alternating materials were of the order of 108 A/cm2, and can be modulated by changing the material parameters and the length of the segment. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Enhancement of ordering temperatures of La0.67Ca0.33MnO3 thin films by adding Ho atoms
Authors: Hsu Jen‐Hwa , Hung S. H. , Biswas Subhayan , Sharma Puneet , Lin J. G.
Published: December 2007

A series of Hox‐La0.67Ca0.33MnO3 thin films with x = 0.0, 0.2, 04, 0.6, and 1.0 mol percent have been deposited on SrTiO3(100) substrates with the substrate temperature controlled at 600 oC by dc magnetron sputtering. The magnetic ordering (Tc) and metal‐insulator transition temperature (TMI) were enhanced about 25∼60 K for Hox‐La0.67Ca0.33MnO3 films. At x = 0.4 the ordering temperature has been increased above 280 K. The variation of the ordering temperature is simply ascribed to the presence of Ho. The results of magnetoresistance measurements indicated that the samples exhibited colossal magnetoresistance effect (CMR) and a maximum was observed at a temperature TP. It was noted that the variation of TP with x displayed the same trend as that of TMI. Although the CMR was suppressed with the addition of Ho, a sizeable CMR ≈ 20% was still detected at 270 K in the sample with 0.4 mol% Ho due to much higher TP. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Magnetoresistance and Hall effect in spin‐polarized two‐dimensional electron gas with spin‐orbit interaction
Authors: Kato T. , Ishikawa Y. , Itoh H. , Inoue J.
Published: December 2007

We study the effect of disorder on the intrinsic anomalous Hall (AH) conductivity and anisotropic magnetoresistance (AMR) in a spin‐polarized two‐dimensional electron gas with a Rashba‐type spin‐orbit interaction. We find that both AH conductivity and AMR vanish unless the lifetime is spin‐dependent, similar to the spin Hall (SH) conductivity in the non‐magnetic system. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Depth sensitive exchange coupling in top and bottom pinned spin valve structures
Authors: Parvatheeswara Rao B. , Ananda Kumar S. , Noh Y. O. , Kim CheolGi
Published: December 2007

Top and bottom pinned spin valve structures have been fabricated using rf magnetron sputtering to study the depth sensitive exchange coupling. M‐H curves of both the configurations in as‐deposited and annealed forms have been measured by vibration sample magnetometry (VSM) and transverse Kerr effect spectrometry (TKE) using DC and AC magnetic fields, respectively. The TKE signal was also examined as a function of wavelength in the range from 300‐800 nm, to obtain data from the full length of the bottom NiFe free layer covering either side of the interface. Annealing of the samples brings in higher values of exchange bias field compared to as‐deposited samples perhaps due to improved uniformity in exchange conditions. The TKE data at 500 nm wavelength point towards energetically favourable spin structure at the pinned interface. Wavelength dependence of the TKE data shows an anamolous trend close to the NiFe‐Cu (seed layer) inteface, which was attributed to a periodic Cu diffusion assisted non‐specular reflection (diffraction) component. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
55Mn NMR study of the A‐type antiferromagnetic and metallic manganites La1–xSrxMnO3 (0.5 ≤ x ≤ 0.6)
Authors: Shim Jung Hyun , Lee Soonchil , Dho Joonghoe
Published: December 2007

The microscopic magnetic and electronic properties of La1‐xSrxMnO3 (0.5 ≤ x ≤ 0.6) were investigated using 55Mn nuclear magnetic resonance (NMR). The NMR spectral intensity showed a large decrement as x increases above the boundary (x ∼ 0.52) of ferromagnetic (FM) and A‐type antiferromagnetic (AFM) phases. The spectrum of the samples shows a coexistence of two different phases, i.e., a metallic major phase and an insulating minor phase. The spin‐spin relaxation time strongly depends on the resonance frequency, indicating that the Shul‐Nakamura process by spin‐wave excitation is the dominant relaxation mechanism. This type of frequency dependence of the spin‐spin relaxation time was not observed in the CE‐type AFM manganite Nd0.5Sr0.5MnO3. The A‐type AFM spin structure and the Shul‐Nakamura relaxation process appears to be a unique characteristics of La1‐xSrxMnO3 (0.54 ≤ x ≤ 0.6) that is related to the 2D‐like spin coupling in a nearly tetragonal crystal structure. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Exchange bias and uncompensated spins in a Fe/Cr(100) bilayer
Authors: Kim Ki‐Yeon , Hwang Yo‐Sun , Park J.‐G. , Torikai N. , Takeda M. , Han S. W. , Shin Sung‐Chul
Published: December 2007

We have investigated the effect of the field cooling on the exchange bias and the coercivity in an exchange‐biased Fe/Cr(100) bilayer using SQUID magnetometer. After the field cooling, magnetization shifted upwards, indicative of surplus magnetic moments, which could be interpreted as an evidence of pinned and uncompensated Cr magnetic moments induced by the cooling field. Interestingly enough, we also discovered that not all the pinned and uncompensated spins seem to be involved in producing the exchange bias, although they contribute to increasing the coercivity and inducing the surplus magnetization. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Influence of the nano‐oxide layer position on magnetoresistance ratio and magnetic properties in spin valves
Authors: Suh Jeong Dae , Ross C. A.
Published: December 2007

We have investigated the influence of nano‐oxide layer position on magnetoresistance of the NiFe/Cu/Co/Cu spin valves. We found that the giant magnetoresistance (GMR) ratio, magnetic coercivity and surface roughness were strongly dependent on the nano‐oxide layer positions. For nano‐oxide layer positions from the bottom to top part of spin valve, the GMR ratio varied from 2.8% to 0.15% depending on the position of the nano‐oxide layer within the spin valves. It was also found that the nano‐ oxide layer(NOL) position affect the surface roughness and magnetic coercivity significantly. Variation of the GMR ratio with nano‐oxide layer position can be explained well by the variation of the spin electron transport confinement due to the specular reflection effect of the nano‐oxide layer. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The electronic structure and magnetism of a rocksalt FeN(001) surface: A density functional study
Authors: Lee J. I. , Bialek B. , Kim I. G.
Published: December 2007

We investigated the electronic structure and magnetism of the rocksalt FeN(001) surface. We considered both the ferromagnetic and antiferromagnetic configurations. We calculated the electronic structure using the full‐potential linearized augmented plane wave method within generalized gradient approximation. We found that the antiferromagnetic phase is more stable than the ferromagnetic one, as in bulk, with an energy difference of 0.14 eV per the considered slab. The magnetic moments of the Fe atoms in the antiferromagnetic phase slab are 2.90 μB, −2.26 μB and 2.37 μB for the surface, subsurface, and center layers, respectively, while the values for the ferromagnetic one are 2.85 μB, 1.81 μB, and 2.37 μB, respectively. The detailed electronic structures for ferromagnetic and antiferromagnetic phases are compared and discussed with the calculated spin‐densities and density of states. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A theoretical study of an amorphous aluminium oxide layer used as a tunnel barrier in a magnetic tunnel junction
Authors: Noh E. S. , Ulloa S. E. , Lee H. M.
Published: December 2007

An amorphous aluminium oxide layer is assumed to be a condensed gas phase composed of (AlOx)N molecules. The total energy and the electron affinity of (AlOx)N molecules is calculated by using a DFT program. The effective tunnel barrier height in the MTJ is presumed from a difference between the work function of the ferromagnetic metal and the electron affinity of (AlOx)N molecules. By using a quantum‐mechanical free electron model the TMR and the R×A product are calculated as a function of the thickness of an amorphous aluminium oxide layer in the F/I/F tunnel junction. It is inferred that the tunnel barrier width determined by subtracting 6 Å from the thickness of an amorphous aluminium oxide layer is more suitable to explain an experimental report qualitatively than the tunnel barrier width equivalent to the thickness of an amorphous aluminium oxide layer. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Magnetic inhomogeneities in crystalline bulk and nanometer sized La0.7Ca0.3MnO3: ESR probing
Authors: Rozenberg E. , Shames A. I. , Jung G. , Mukovskii Ya. M. , Sominski E. , Gedanken A. , Lee Cheol Eui
Published: December 2007

Electron spin resonance was studied on three (two bulk and one nanometer sized) samples of the same La0.7Ca0.3MnO3 manganite compound aiming to compare their magnetic homogeneities. The results obtained show that both ceramic and single crystalline bulk samples are less homogeneous than nano‐crystalline one. Except for higher homogeneity, the nano sample demonstrates also a weaker magnetic anisotropy. As a result, well pronounced coexistence of different magnetic phases (coexistence of ferromagnetic and paramagnetic resonance signals) is observed in bulk samples, while it is absent in nano. It is suggested that such strong difference is directly connected to the difference in structural state of the samples. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Structural and magnetic properties of electron‐doped manganites La0.85Te0.15Mn1–xCuxO3 (0 ≤ x ≤ 0.20)
Authors: Yang J. , Li Y. , Lee Y. P.
Published: December 2007

The effects of Cu doping at the Mn site on the structural and the magnetic properties of electron‐doped manganites La0.85Te0.15Mn1–xCuxO3 (0 ≤ x ≤ 0.20) have been studied. The structural parameters were obtained by fitting the XRD data with space group $ R \bar 3 c $ by the Rietveld method. Upon cooling, all the samples undergo the paramagnetic‐ferromagnetic phase transition. The magnetization measurements under an applied field of 0.1 and 4.5 T show that the Curie temperature TC decreases with increasing the Cu‐doping level, whereas the magnitude of magnetization at low temperatures increases as the Cu content increases from x = 0 to 0.10 but decreases when x > 0.10. We consider that these interesting phenomena are intrinsic. The results can be understood by the opening of new double‐exchange channel between Mn3+‐O‐Mn4+ due to the introduction of Mn4+ ion caused by the substitution of Cu2+ for Mn3+. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Gate‐Current Model for Advanced MOSFET Technologies Implemented into HiSIM2
Authors: Inagaki Ryosuke , Sadachika Norio , Navarro Dondee , Miura‐Mattausch Mitiko , Inoue Yasuaki
Published: December 2007

A gate leakage current model for advanced MOSFETs has been developed and implemented into the Hiroshima‐university STARC IGFET Model (HiSIM), the first complete surface‐potential‐based model. The model consists of four tunneling mechanisms, the gate to channel/bulk/source/drain, and requires totally 15 model parameters covering all bias conditions. Simulation results reproduce measurement for any device size and temperature without binning. Validity of the model has been tested with circuits that are sensitive to the change of stored charge due to tunneling current. Copyright © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.
Investigation of Electrical Resistivity Changes of Human Blood during Dynamic Exercise
Authors: Yamagata Tomohisa , Fujisaki Hirohisa
Published: December 2007

The purpose of this paper is to clarify the main cause of blood resistivity changes during exercise. Hematocrit and blood resistivity were measured during dynamic bicycle exercise, and plasma resistivity was estimated from those measurements. Further, this paper presents an investigation on the effects of hematocrit and plasma on the blood resistivity changes: The mixture function, which is a mixture factor of red blood cells was not correlated with the blood resistivity, but the plasma resistivity was correlated significantly with the blood resistivity. This shows that the plasma resistivity changes strongly and influences the behavior of blood resistivity changes. Copyright © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.
Applications of Sinusoidal Neural Network and Momentum Genetic Algorithm to Two‐wheel Vehicle Regulating Problem
Authors: Chau Sam Duong , Kinjo Hiroshi , Uezato Eiho , Yamamoto Tetsuhiko
Published: December 2007

In an attempt to enhance the performance of neural network (NN), we propose a sinusoidal activation function for NN and apply a fast genetic algorithm (GA) with uses of momentum offspring (MOS) and constant‐range mutation (CRM) for training the NN. The proposed methods are aimed at designing a neurocontroller (NC) for regulating a two‐wheel vehicle system, known as nonholonomic system, in the viewpoint that it is necessary to improve the control process of the system even though several control methods, including applications of NN and GAs, have been developed.

The learning performances of NCs are evaluated through the successful evolutionary rates of the control process based on the values of the squared errors. In order to compare the conventional methods with our proposed approaches and verify the effects of momentum GA on NC training, various numerical simulations will be carried out with different numbers of generations in GAs and different activation functions of NCs. Finally, the controllability of NC is investigated with certain sets of initial states. The simulations show that sinusoidal NC trained by momentum GA has a good performance regardless of the small values of population size and generations in GA. Copyright © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.
Evaluation of Humidity Correction Factor of Disruptive Discharge Voltage of Standard Sphere Air Gaps
Authors: Fujii Osamu , Hayakawa Student Takahiro , Mizuno Yukio , Naito Katsuhiko
Published: December 2007

The humidity correction method prescribed in the existing IEC standard is based on experimental data obtained under absolute humidity between 5 and 12 g/m3. A discussion on the humidity correction method is needed for higher absolute humidity regions, which is experienced during summer in Japan, and also throughout the year in tropical countries. The effect of absolute humidity on disruptive discharge voltages of standard sphere air gaps has been studied experimentally for several years under conditions of natural humidity, between 2 and 22 g/m3. In the cases of a.c. and lightning impulse voltage application, it was found that the existing IEC humidity correction method seems to be proper for most of the gap spacings studied under absolute humidity up to 22 g/m3. Copyright © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.
A Low‐Loss Medium‐Voltage Inverter Applying Series Connected General Purpose 1.2 kV Insulated Gate Bipolar Transistors with Accurate Voltage Balancing Techniques
Authors: Abe Yasushi , Matsubara Kunio , Sasagawa Kiyoaki , Matsuse Kouki
Published: December 2007

This paper presents a medium‐voltage inverter applying series connected general‐purpose 1.2 kV insulated gate bipolar transistors (IGBTs) as a switching device to achieve low switching losses compared to inverters applying high‐voltage IGBTs with over 3 kV rating. Gate signal synchronization, which is essential to keep the balance of collector‐emitter voltages across the IGBTs, is achieved by magnetically coupling all gate lines using a simple two‐windings transformer. In order to obtain better voltage balancing, influence of stray capacitance distribution associated with an insulating substrate in a two‐in‐one IGBT module on the voltage sharing is investigated, and an optimized layout of heat sinks for the IGBT modules is proposed. To validate some performances concerning the device losses and the voltage sharing, a 170 kVA inverter based on three 1.2 kV IGBTs connected in series is built and evaluated. The experimental results are shown. Copyright © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.