bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermal radiation effects on magnetohydrodynamic flow past a semi-infinite vertical plate in the presence of mass diffusion
Authors: Aboeldahab Emad M , Azzam Gamal El-Din A
Published: April 2005

Magnetohydrodynamic (MHD) mixed freeforced heat and mass convective steady incompressible laminar boundary layer flow of a gray optically thick electrically conducting viscous fluid past a semi-infinite vertical plate for high temperature and concentration differences is studied. A uniform magnetic field is applied perpendicular to the plate. The density of the fluid is assumed to reduce exponentially with temperature and concentration. The usual Boussinesq approximation is neglected because of the high temperature and concentration differences between the plate and the ambient fluid. The Rosseland approximation is used to describe the radiative heat flux in the energy equation. The boundary layer equations governing the flow are reduced to ordinary differential equations, which are numerically solved by applying an efficient technique. The effects of the densitytemperature parameter n, the densityconcentration parameter m, the local magnetic parameter Mx, and the radiation parameter R are examined on the velocity, temperature, and con- centration distributions as well as the coefficients of skin-friction, heat flux, and mass flux.PACS No.: 44.27+g
Some differences between Dirac's hole theory and quantum field theory
Authors: Solomon Dan
Published: April 2005

Dirac's hole theory (HT) and quantum field theory (QFT) are generally considered equivalent. However, it was recently shown by several investigators that this is not necessarily the case because when the change in the vacuum energy was calculated for a time-independent perturbation, HT and QFT yielded different results. In this paper, we extend this discussion to include a time-dependent perturbation for which the exact solution to the Dirac equation is known. We show that for this case also, HT and QFT yield different results. In addition, we offer some discussion of the problem of anomalies in QFT. PACS Nos.: 03.65w, 11.10z
A "FLAT/STEEP BAND" MODEL FOR SUPERCONDUCTIVITY
Authors: DENG S. , SIMON A. , KÖHLER J.
Published: April 2005

Based on a viewpoint of chemical pairwise interactions between electrons, a Hamiltonian was proposed for the "flat/steep band" scenario. This model has been studied analytically, and numerically with the first-principles method. With Hg and MgB 2 as examples, we have explained the characteristics of this model and observed peak-like structures of the electron-phonon coupling constants λ(q) in q space. The strong coupling of the "flat band" electrons with phonons has been corroborated by developing a new functional Psib(Φ), through which we can quantitatively compare different electronic states in coupling to a specific phonon. The relevance of our model to an electronic inhomogeneity is also discussed. Investigations on experimental and theoretical low-energy electronic structures of superconductors support our flat/steep scenario.
SUPERCONDUCTIVITY IN NaxCoO2·yH2O DRIVEN BY THE KINETIC ENERGY
Authors: LIU BIN , LIANG YING , FENG SHIPING
Published: April 2005

Within the charge-spin separation fermion-spin theory, the mechanism of superconductivity in Na x CoO 2·y H 2 O is studied. It is shown that dressed fermions interact occurring directly through the kinetic energy by exchanging magnetic excitations. This interaction leads to a net attractive force between dressed fermions(then the electron Cooper pairs), and their condensation reveals the superconducting ground state. The optimal superconducting transition temperature occurs in the electron doping concentration δ≈0.29, and then decreases for both underdoped and overdoped regimes, in qualitative agreement with the experimental results.
SUPERCONDUCTIVITY FROM SPIN-WAVE EXCITATIONS NEAR THE FERROMAGNETIC AND ANTIFERROMAGNETIC INSTABILITIES
Authors: MALOZOVSKY Y. M. , FAN J. D.
Published: April 2005

We study pairing by the exchange of spin-wave excitations near the ferromagnetic or antiferromagnetic instability in terms of the effective two-particles T-matrix. We show that near the ferromagnetic instability the paring due to the exchange of the paramagnetic excitations can occur in the p-wave state (ℓ=1) and m=±1. We show that near the antiferromagnetic instability the pairing due to the exchange by the paramagnetic excitations occurs also in the p-wave state (ℓ=1) but with m=0 and that there is no pairing in d-wave state.
PrBa2[Cu1-xMx]3O7 AS I-LAYER MATERIALS FOR JOSEPHSON SIS JUNCTIONS
Authors: CHEN T.-P. , TIPZARACH U. , YANG X. , ZHOU A. , CHEN B. , CHEN Q. Y. , CHU W. K. , CHEN J. C. J. , WANG J. T.
Published: April 2005

Metal (M) doped PrBa 2 Cu 3 O 7, i.e. PrBa 2( Cu 1-x M x)3 O 7 for M = Al , Co , Fe , Ga , Ni and Zn , and x =0.05, 0.10, 0.15, and 0.20 were fabricated. No significant second phase was found for the Al , Co , Fe and Ga doped samples up to 20% doping level. Impurity phases, however, were detected for Ni and Zn doped samples when doping concentration reached 15% and higher. At 77 K the electrical resistivity for most of these compounds is several orders in magnitude higher than that of the PrBa 2 Cu 3 O 7-δ. Although the lattice parameters in the doped samples changes toward tetragonal structure, all sample remained in orthorhombic structure and the parameters remain very close to those of the undoped one and YBa 2 Cu 3 O 7-δ. For this reason these compounds may serve as improved I-layer materials for making YBa 2 Cu 3 O 7-δ SIS Josephson junction.
CALCULATION OF EPR PARAMETERSgFACTORS FORCe3+ION INYBa2Cu3O6+xSUPERCONDUCTOR
Authors: DONG HUI-NING , DU HUI-PING , DUAN CHANG-KUI , LUO XIAO-BING
Published: April 2005

The perturbation formulae of EPR parameters g factors gx, gyand gzfor the lowest Kramers doublet of 4f1ion in orthorhombic symmetry are established. In these formulae, the contributions of the covalency effects, the admixture between J=7/2 and J=5/2 states as well as the second-order perturbation (which is not considered in the previous works) via crystal-field and orbital angular momentum interactions are all included. According to these formulae, and by using the superposition model, the g-factors gx, gyand gzfor Ce3+center in YBa2Cu3O6+ xsuperconductor are calculated. The results are discussed.
ORIGIN OF ORDERING OSCILLATION OF LOCAL COMPOSITION IN MELT-PROCESSED REBa2Cu3O7-δ SUPERCONDUCTORS (RE: Sm, Eu, Gd)
Authors: HU A. , SAKAI N. , HIRABAYASHI I. , WINTER M. , KOBLISCHKA M. R. , ZHOU H.
Published: April 2005

High quality melt-processed ( Sm 0.33 Eu 0.33 Gd 0.33) Ba 2 Cu 3 O 7-δ superconductors were grown and microstructural origin of their distinguished superconducting performance was investigated by atomic force microscopy (AFM), transmission electron microscopy (TEM) and the field dependent superconducting transition performed with SQUID. A nanoscopic periodic array of chemical composition was unveiled. This novel structure acted as δTc-style pinning centers.
PHASE-SLIPS AND FILAMENTS IN HTSC
Authors: JUNG J. , ABDELHADI M. , DARHMAOUI H. , YAN H.
Published: April 2005

The presence of nano-structures, i.e. static or dynamic stripe-like features or nano-domains in HTSC, can cause a quasi-1D flow of a transport current through these materials. We present the experimental results, which reveal the effect of a filamentary flow of the current on the normal and superconducting transport properties of HTSC.
PRESSURE-INDUCED SUPERCONDUCTIVITY IN SYMPLE METALS
Authors: SHIMIZU KATSUYA
Published: April 2005

Experimental results in search for pressure-induced superconductivity are reviewed. Typical examples are simple inorganic and organic molecular crystals, magnetic metals, and elements. We have developed complex extreme condition of very low temperature down to 30 mK and ultra high pressure exceeding 200 GPa by assembling compact diamond-anvil cell (DAC) on a powerful 3 He /4 He dilution refrigerator. Using the newly developed apparatus and techniques, we have studied superconductivity in various materials in various pressure range. In this paper, we will shortly review our newly developed experimental apparatus and techniques and discuss about examples of pressure-induced superconductivity in simple metals.
TWO-DIMENSIONAL CORRELATION ANALYSIS OF SUPERCONDUCTING YNi2B2C RAMAN SPECTRA
Authors: YANG IN-SANG , JUNG YOUNG MEE , KIM SEUNG BIN , KLEIN M. V.
Published: April 2005

Two-dimensional (2D) correlation analysis is applied to the temperature dependence on the Raman spectra of superconducting YNi 2 B 2 C single crystal. 2D correlation analysis on the temperature dependence of the B 1g superconducting gap peak shows strong correlation with the Ni B 1g phonon peak near 200 cm -1. The analysis on the B 1g phonon peak itself shows that the peak is composed of essentially two peaks at 197 and 203 cm -1, and only the weight of the two peaks changes as the temperature changes. The result suggests that there are two distinctive environments of the Ni - B bonds in YNi 2 B 2 C system at the superconducting state.
PHASE SEPARATION IN THE TWO-DIMENSIONAL HUBBARD MODEL
Authors: YU M. , LIN H. Q.
Published: April 2005

In this paper, we study phase separation in the two-dimensional single-band Hubbard model with the unrestricted Hartree-Fock(UHF) method and the restricted Hartree-Fock (RHF) method. We perform the calculation for square lattices and rectangle lattices. It is observed that the stripe phase exists and it depends on three aspects: geometry of the lattice, Coulomb interaction U and band filling n. To gain more physical insights, we consider the Hubbard model with spin dependent hoppings: t↑ and t↓, and study the effect of varying [Formula: see text] on the phase separation.
POINT CONTACT STUDY OF THE SUPERCONDUCTING ORDER PARAMETER IN RuSr2GdCu2O8
Authors: PIANO S. , BOBBA F. , GIUBILEO F. , CUCOLO A. M. , VECCHIONE A.
Published: April 2005

We have performed a detailed study of the conductance characteristics obtained by point contact junctions realized between a normal Pt / Ir tip and syntered RuSr 2 GdCu 2 O 8 ( Ru -1212) samples. Indeed, this compound is subject of great interest due to the coexistence of both magnetic order and bulk superconductivity. In our experiments, the low temperature tunneling spectra reproducibly show a zero bias conductance peak that can be well reproduced by a generalized BTK model in the case of d-wave symmetry of the superconducting order parameter.
FLUX PINNING MECHANISM IN NEW MgCNi3 SUPERCONDUCTOR
Authors: FANG M. H. , YANG J. H. , WAN H. Y. , ZHANG W. , KATO M. , YOSHIMURA K.
Published: April 2005

The measurements of lower-critical-field Hc1(T), upper-critical-field Hc2(T) and the bulk pinning force Fp(H) were carried out for a superconductor MgCNi 3 sample with Tc=7.5K prepared under high pressure. The sample has a good extensibility. We conclude that the flux pinning at lower fields results from the intra-granular structural defects, such as dislocations, and the enhancement of bulk pinning force near the irreversibility field Hirr is due to the softening of the flux lattice.
AN HTS FILTER SUBSYSTEM FOR 800MHz MOBILE COMMUNICATION SYSTEM
Authors: YIN Z. S. , WEI B. , CAO B. S. , GUO X. B. , ZHANG X. P. , HE W. J. , HE S. , GAO L. M. , ZHU M. H. , GAO B. X.
Published: April 2005

In this paper, we present a high temperature superconducting (HTS) Filter subsystem, which consists of a 14-pole HTS filter, a low noise amplifier (LNA), a Stirling Cooler and an electronic control system. The HTS filter has a 2.1% fractional bandwidth at 814MHz. It was fabricated on MgO substrate which was double sides coated with YBCO thin films. The insertion loss of the HTS filter is less than 0.2 dB , the gain of the subsystem is 22 dB at 60K . In this subsystem, the out-of-band rejection is better than 70 dB and the steepness of the band-edges is larger than 25 dB/MHz at 60K .
YBa2CU3O7-x THICK FILMS DEPOSITED BY PHOTO-ASSISTED METAL-ORGANIC CHEMICAL VAPOR DEPOSITION
Authors: ZENG JIANMING , RUSAKOVA IRENE , TANG ZHONGJIA , ZHANG XIN , SANCHEZ DALBER , MOLODYK ALEXANDER , WU NAIJUAN , IGNATIEV ALEX
Published: April 2005

High-quality YBa2Cu3O7-x ( YBCO ) thick films with thickness over 4.0μm were deposited by photo-assisted metal-organic chemical vapor deposition (PhA-MOCVD) technique with high growth rates. Microstructures of YBCO thick films have been systematically investigated by scanning electron microscopy, high-resolution transmission electron microscopy, and selected area electron diffraction techniques. The fabricated YBCO thick films are very dense and single-crystal like with no visible grain boundaries or voids. The high quality of the prepared YBCO thick films was confirmed further by the results of X-ray diffraction analyses and Jc measurements. Thus, these thick YBCO films prepared by PhA-MOCVD technique have promising application potential in fields such as coated conductors.
THE VORTEX LATTICE IN SUPERCONDUCTORS: PHENOMENOLOGICAL THEORIES
Authors: BRANDT ERNST HELMUT
Published: April 2005

Some properties of the ideal and pinned vortex lattice in superconductors are outlined.
IN-PLANE CURRENT DRIVEN JOSEPHSON-VORTEX LATTICE IN HIGH-Tc CUPRATES
Authors: CHEN QING-HU , HU XIAO
Published: April 2005

We performed simulations on in-plane current driven Josephson vortex systems in high- T c cuprates at weak parallel magnetic fields and /or low anisotropies. It is found that the in-plane resistivity is Lorentz-force dependent at small current regime below the melting transition. As the current increases, the Josephson vortex lattice melts dynamically, the Lorentz-force independence of resistivity reappears. These results are possibly related to the experiments on YBCO.
TRANSPORT CHARACTERISTICS IN c-AXIS La2-xSrxCuO4 (LSCO) SINGLE CRYSTALS
Authors: KIM SANG-JAE , HATANO TAKESHI
Published: April 2005

c-axis micro-bridges of La 2-x Sr x CuO 4 ( LSCO ) single crystals were fabricated by the focused-ion-beam (FIB) etching method. Small rectangular LSCO pieces were fabricated by cutting and grinding single crystals of underdoped LSCO of x=0.09. The size of LSCO single crystals between electrodes was cut to 20×40μm2 in ab-plane by using the FIB etching method. Superconductor-insulator-superconductor (SIS) like-branch structures on I-V curves of the LSCO stacks were observed for the first time. The branch structures exhibited voltage jumps of several tens mV in the range of from 1.7 K to 5 K with temperature dependence. When the temperature is changed from 5 K to 1.7 K , the critical current and the next branch split into a few of small voltage jumps with the intervals of several mV in the range of from 0.1 mV and 2.0 mV .
DEPINNING TRANSITION IN FLUX-LINE SYSTEM OF TYPE-II SUPERCONDUCTORS
Authors: LUO MENG-BO , HU XIAO
Published: April 2005

Zero temperature velocity-force curve of a flux-line system driven by Lorentz force in the presence of quenched random point-like disorders is simulated. The velocity shows a sudden increase at the depinning force Fc for both systems with Bragg glass (BG) annealed ground state and vortex glass (VG) one. At driving force slightly above Fc all flux lines move forward incoherently with large fluctuations in velocity as well as in the transverse direction, resulting in winding flow paths and no channel.
STUDY ON VORTEX DYNAMICS OF Tl2Ba2CaCu2O10 THIN FILM IN TILTED MAGNETIC FIELDS
Authors: ZHANG GUOHUA , LUO SHENG , LI CHUNGUANG , HUANG SAIJUN , HE YUSHENG , LU RONGTAO , YAN SHAOLIN , FANG LAN
Published: April 2005

Tl 2 Ba 2 CaCu 2 O 10 ( Tl :2212) thin films were prepared on LaAlO 3 substrates with (0 0 1) direction normal to their surface, and the logR-logH characteristics were measured using the in-plane resistivity measurements in magnetic fields tilted away from c axis to the ab-plane. The H *c- H ab phase diagram was obtained by defining a resistance criterion below the vortex phase melting transition resistance. The linear dependence of H *c on H ab in most angular range shows that the crossing-lattice structure in the tilted fields exists in Tl :2212. A perpendicular line was observed in the H *c- H ab diagram at the range of θ ¡ 0.4 ° at 88K, which was attributed to the lock-in transition.
EXCHANGE FIELD EFFECT ON THE ANDREEV BOUND STATE STUDIED BY FERROMAGNET/HIGH Tc SUPERCONDUCTOR INTERFACE
Authors: NG K.-W. , FREAMAT MARIO
Published: April 2005

We have prepared Ag / BSCCO and Fe / Ag / BSCCO planar junctions to study the effect of Fe exchange field on the tunneling spectra. The junctions were constructed so that the tunneling direction is within the ab-plane, either along the maximum or minimum gap direction. Andreev bound states were observed as zero energy peak in the minimum gap direction. The exchange field caused major splitting of the zero energy peak, which did not occur in Ag / BSCCO junctions. We had detected a few percent (6 to 7%) of s-wave subcomponent at the interface in many of these junctions. This s-wave subcomponent had a Tc of about 20K.
FERROELECTRIC/PIEZOELECTRIC MATERIALS AND THEIR APPLICATIONS IN ADVANCED SCIENCES AND TECHNOLOGIES
Authors: WANG J. T. , ZHANG C. , FU Y. S.
Published: April 2005

This paper is a brief introduction to the ferroelectric materials and their applications. Ferroelectric materials are very intriguing materials to both fundamental science and technologies. Ferroelectricity is an important critical phenomenon in physics. Ferroelectrics possess unique physical properties which make them very useful in electronics, computer memory unit and micro-electro-mechanic devices. The author proposed some interesting possible applications for the near future.
INFLUENCE OF ELECTROLYTIC PULSE FREQUENCY ON THE PROPERTY OF NANO CARBON FILM DEPOSITED IN MOLTEN SALT
Authors: FANG L. , XIAO F. , YANG L. C. , ZHANG J. , LIU G. B.
Published: April 2005

Nano carbon film was synthesized on a nickel substrate in molten LiCl - KCl - K 2 CO 3 salt by an electrolytic deposition method. The influence of pulse frequency on the property of the carbon films was studied. Over the carbonate ion concentration range of 0.10–0.20 mol%, the mass of carbon film on unit area increases with increasing pulse frequency over the range of 0.05–33Hz or 33–166Hz, whereas, it decreases with increasing pulse frequency over the range of 33-166Hz. It means that a critical pulse frequency exists, which can be thought to correspond to the natural vibration frequency of the film. When the electrolytic pulse frequency is equal to the natural vibration frequency of film, a resonance maybe happen, and the film exfoliates.
SIMULTANEOUS MEASUREMENT OF DOPAMINE AND ASCORBIC ACID AT CNT ELECTRODE
Authors: HU C. G. , WANG W. L. , FENG B. , WANG H.
Published: April 2005

Electrochemical behaviors of dopamine and ascorbic acid have been studied at the carbon nanotube electrode using cyclic voltammetry. Electrocatalysis has been found for dopamine redox reactions at the carbon nanotube electrode in comparison with the glassy carbon electrode. A well-defined oxidative peak for ascorbic acid was observed at the carbon nanotube electrode with the peak potential negative shift versus the glassy carbon electrode. The important discover was that the carbon nanotube electrode can be used to detect low level of dopamine selectively with high sensitivity in the presence of a large excess of ascorbic acid in the acidic media and in the physiological pH buffer solution as well.
STRAIN-INDUCED RESISTANCE CHANGES OF CARBON NANOTUBE FILMS
Authors: LU J. W. , WANG W. L. , LIAO K. J. , WAN B. Y.
Published: April 2005

The strain-induced resistance changes of both SWNT and MWNT films have been studied. Carbon nanotubes in this study were synthesized by hot filament chemical vapor deposition. Experimental results showed that there is a striking piezoresistive effect in carbon nanotube films. The relative change in resistance of carbon nanotube films was increased with the increasing strain. In the same strain, the resistance changes of SWNT films exceed that of MWNT films. The origin of the resistance change in the films may be caused by strain-induced change in the bandgap and intertube contact resistance.
PREFERRED ORIENTATION OF NANOCRYSTALLINE ZnO FILMS PREPARED BY THERMAL OXIDATION OF THE METALLIC Zn FILMS
Authors: MA Y. , KONG C. Y. , YANG X. H. , XU J.
Published: April 2005

Nanocrystalline ZnO films were prepared by thermally oxidizing the Zn films deposited on mirror-polished quartz substrates by thermal evaporation of Zn granule. The structure of the films was studied by X-ray diffraction (XRD). The results showed that highly preferred (002) orientation of the ZnO films has been achieved. The oxidation temperature has an important effect on preferred orientation of ZnO films.
PREPARATION OF SICP/6066AL COMPOSITE AS SHEATH OF HIGH-TC SUPERCONDUCTING CABLE FOR TRANSMITTING ELECTRICITY
Authors: WANG WENMING
Published: April 2005

High- T C Superconducting Cable for transmitting electricity will scale up application extension before long. Superconducting Cable consists of cable core made up of superconducting material and cladding argentine and structure-functional material complying with cable requirement for transmitting electricity. As a kind of composite with high tensile strength, high elastic module, moderate elongation and high heat-exchange, low thermal expansion, SiCp /6066 Al composite will have extensive application as sheath of high- T C superconducting cable for transmitting electricity. Thus the advance in high- T C superconducting cable has been referred .The detailed experiment on preparation of SiCp /6066 Al composite as sheath of high- T C superconducting cable for transmitting electricity by new-style powder metallurgy technology—sheathed hot extrusion. Mechanical, damping and thermal characteristics have been tested. Even microstructure and clean interface between SiCp and Al alloy matrix have been found via OM, SEM, TEM, etc. The authors explained internal relations between characteristics and microstructure. The characteristics of the composite reach to established characteristic requirement for high- T C superconducting cable for transmitting electricity.
STUDY OF CONDUCTION MECHANISM AND SCANNING TUNNELING SPECTRUM OF NANO-CaCO3
Authors: WANG Y. F. , YANG X. H. , WANG S. F. , XIN H. Z. , LIU A. P.
Published: April 2005

We have experimentally found out that an obvious tunnel current begins to appear between nano- CaCO 3 film and tip of STM when the bias voltage reaches 0.6V, above which there is a non-linear rise quickly. We further measure the scanning tunneling spectrum (STS) of nano- CaCO 3 and analyze it compared to that of Au and Silicon. The results show that CaCO 3, an insulating material, after nanometer processing presents a characteristic similarly to a metal, and the constraint to electrons is even smaller than a semiconductor. STS has not only well explained the spectroscopic mechanism of conducting performances of nano- CaCO 3, but also expanded applications of STM to one of the most important research areas. Moreover, the method can be applied to the study of the structure of superconductive materials and energy spectrum characterization.
STUDIES ON THE TiO2 THIN FILMS DOPED WITH Fe3+
Authors: XIAO PENG , WANG WANLU
Published: April 2005

The Fe 3+- TiO 2 thin films obtained through sol-gel method were characterized by x-ray diffraction, AFM and Raman spectroscopy. It was found that TiO 2 films consisted of nanometer particles. The experimental results shows that the nanometer TiO 2 thin films doped with Fe 3+ were greatly improved in the activity aspect. This may be ascribed to change their structure and electrical properties after doping with Fe 3+. The results were discussed theoretically in detail.
NANO-MODIFICATION INSIDE TRANSPARENT MATERIALS BY FEMTOSECOND LASER SINGLE BEAM
Authors: SHIMOTSUMA YASUHIKO , HIRAO KAZUYUKI , QIU JIARONG , KAZANSKY PETER G.
Published: April 2005

Periodic nanostructures along the polarization direction of light are observed inside silica glasses and tellurium dioxide single crystal after irradiation by a focused single femtosecond laser beam. Backscattering electron images of the irradiated spot inside silica glass reveal a periodic structure of stripe-like regions of ~20 nm width with a low oxygen concentration. In the case of the tellurium dioxide single crystal, secondary electron images within the focal spot show the formation of a periodic structure of voids with ~30 nm width. Oxygen defects in a silica glass and voids in a tellurium dioxide single crystal are aligned perpendicular to the laser polarization direction. These are the smallest nanostructures below the diffraction limit of light, which are formed inside transparent materials. The phenomenon is interpreted in terms of interference between the incident light field and the electric field of electron plasma wave generated in the bulk of material.
ABSCISIC ACID BIOSYNTHESIS AND CATABOLISM
Authors: Nambara Eiji , Marion-Poll Annie
Published: April 2005

The level of abscisic acid ( ABA abscisic acid ) in any particular tissue in a plant is determined by the rate of biosynthesis and catabolism of the hormone. Therefore, identifying all the genes involved in the metabolism is essential for a complete understanding of how this hormone directs plant growth and development. To date, almost all the biosynthetic genes have been identified through the isolation of auxotrophic mutants. On the other hand, among several ABA catabolic pathways, current genomic approaches revealed that Arabidopsis CYP707A genes encode ABA 8′-hydroxylases, which catalyze the first committed step in the predominant ABA catabolic pathway. Identification of ABA metabolic genes has revealed that multiple metabolic steps are differentially regulated to fine-tune the ABA level at both transcriptional and post-transcriptional levels. Furthermore, recent ongoing studies have given new insights into the regulation and site of ABA metabolism in relation to its physiological roles.
Depolarization induces Rho-Rho kinase-mediated myosin light chain phosphorylation in kidney tubular cells
Authors: Szászi Katalin , Sirokmány Gábor , Ciano-Oliveira Caterina Di , Rotstein Ori D. , Kapus András
Published: April 2005

Myosin-based contractility plays important roles in the regulation of epithelial functions, particularly paracellular permeability. However, the triggering factors and the signaling pathways that control epithelial myosin light chain (MLC) phosphorylation have not been elucidated. Herein we show that plasma membrane depolarization provoked by distinct means, including high extracellular K+, the lipophilic cation tetraphenylphosphonium, or the ionophore nystatin, induced strong diphosphorylation of MLC in kidney epithelial cells. In sharp contrast to smooth muscle, depolarization of epithelial cells did not provoke a Ca2+ signal, and removal of external Ca2+ promoted rather than inhibited MLC phosphorylation. Moreover, elevation of intracellular Ca2+ did not induce significant MLC phosphorylation, and the myosin light chain kinase (MLCK) inhibitor ML-7 did not prevent the depolarization-induced MLC response, suggesting that MLCK is not a regulated element in this process. Instead, the Rho-Rho kinase (ROK) pathway is the key mediator because 1) depolarization stimulated Rho and induced its peripheral translocation, 2) inhibition of Rho by Clostridium difficile toxin B or C3 transferase abolished MLC phosphorylation, and 3) the ROK inhibitor Y-27632 suppressed the effect. Importantly, physiological depolarizing stimuli were able to activate the same pathway: l-alanine, the substrate of the electrogenic Na+-alanine cotransporter, stimulated Rho and induced Y-27632-sensitive MLC phosphorylation in a Na+-dependent manner. Together, our results define a novel mode of the regulation of MLC phosphorylation in epithelial cells, which is depolarization triggered and Rho-ROK-mediated but Ca2+ signal independent. This pathway may be a central mechanism whereby electrogenic transmembrane transport processes control myosin phosphorylation and thereby regulate paracellular transport.
Mitral tetrahedron as a geometrical surrogate for chronic ischemic mitral regurgitation
Authors: Yu Hsi-Yu , Su Mao-Yuan , Chen Yih-Sharng , Lin Fang-Yue , Tseng Wen-Yih Isaac
Published: April 2005

The present study tests the hypothesis that a mitral tetrahedron (MT) is a useful geometrical surrogate for assessment of chronic ischemic mitral regurgitation (CIMR). Fifty-eight subjects were divided into three groups on the basis of left ventricular ejection fraction (LVEF) and the presence or absence of CIMR: LVEF ≥0.5 and negative CIMR ( group 1, n = 28), LVEF <0.5 and negative CIMR ( group 2, n = 12), and LVEF <0.5 and positive CIMR ( group 3, n = 18). MT was defined by its four vertices at the anterior annulus, posterior annulus, and medial and lateral papillary muscle roots, determined by MRI at peak systole. The results showed no clear cutoff values of MT parameters between groups 2 and 1. In contrast, all MT indexes were significantly different between groups 3 and 2 ( P < 0.05), and significant cutoff values differentiated the two groups. A scoring system employing parameters of the whole MT confirmed the absence of CIMR with total edge length index <268 mm/BSA1/3, total surface area index <2,528 mm2/BSA2/3, and volume index <5,089 mm3/BSA (where BSA is body surface area). The sensitivity, specificity, and positive and negative predictive values were 1.00. This preliminary study demonstrates that MT might serve as a good geometrical surrogate for assessing CIMR. The derived geometrical criteria of MT may be useful in surgical correction of CIMR.
Autoregulation of CCL26 synthesis and secretion in A549 cells: a possible mechanism by which alveolar epithelial cells modulate airway inflammation
Authors: Abonyo B. O. , Alexander M. S. , Heiman A. S.
Published: April 2005

Eotaxins (CCL11, CCL24, CCL26) originating from airway epithelial cells and leukocytes have been detected in bronchoalveolar lavage of asthmatics. Although the alveolar epithelium is the destination of uncleared allergens and other inflammatory products, scanty information exists on their contribution to the generation and regulation of the eotaxins. We envisioned a state whereby alveolar type II cells, a known source of other inflammatory proteins, could be involved in both the production and regulation of CCL24 and CCL26. Herein, we demonstrated that all three eotaxins are constitutively expressed in A549 cells. IL-4 and IL-13 stimulated a concentration-dependent secretion of CCL24 and CCL26. The cytokines did not act synergistically. Cycloheximide and actinomycin D abrogated IL-4- and IL-13-dependent CCL26 but not CCL24 secretion. Both IL-13 and IL-4 stimulated CCL26 synthesis that was inhibited in a concentration-dependent manner by CCL26 but not CCL24. Only CCL26 reduced expression of CCR3 receptors by 30–40%. On the other hand, anti-CCR3 pretreatment reduced IL-4+IL-13-dependent CCL26 secretion, implying autoregulation. A CCR3-specific antagonist (SB-328437) significantly decreased IL-4-dependent synthesis and release of CCL26. Eosinophils treated with medium from IL-4-stimulated A549 cells preincubated with anti-CCL26 showed a marked decrease of superoxide anion production compared with anti-CCL24 treated. These results suggest that CCL26 is a major eotaxin synthesized and released by alveolar epithelial cells and is involved in autoregulation of CCR3 receptors and other eotaxins. This CCL26-CCR3 ligand-receptor system may be an attractive target for development of therapeutics that limits progress of inflammation in airway disease.
Persistence of sleep-temperature coupling after suprachiasmatic nuclei lesions in rats
Authors: Baker F. C. , Angara C. , Szymusiak R. , McGinty D.
Published: April 2005

The suprachiasmatic nucleus (SCN) regulates the circadian rhythms of body temperature (Tb) and vigilance states in mammals. We studied rats in which circadian rhythmicity was abolished after SCN lesions (SCNx rats) to investigate the association between the ultradian rhythms of sleep-wake states and brain temperature (Tbr), which are exposed after lesions. Ultradian rhythms of Tbr (mean period: 3.6 h) and sleep were closely associated in SCNx rats. Within each ultradian cycle, nonrapid eye movement (NREM) sleep was initiated 5 ± 1 min after Tbr peaks, after which temperature continued a slow decline (0.02 ± 0.006°C/min) until it reached a minimum. Sleep and slow wave activity (SWA), an index of sleep intensity, were associated with declining temperature. Cross-correlation analysis revealed that the rhythm of Tbr preceded that of SWA by 2–10 min. We also investigated the thermoregulatory and sleep-wake responses of SCNx rats and controls to mild ambient cooling (18°C) and warming (30°C) over 24-h periods. SCNx rats and controls responded similarly to changes in ambient temperature. Cooling decreased REM sleep and increased wake. Warming increased Tbr, blunted the amplitude of ultradian Tbr rhythms, and increased the number of transitions into NREM sleep. SCNx rats and controls had similar percentages of NREM sleep, REM sleep, and wake, as well as the same average Tb within each 24-h period. Our results suggest that, in rats, the SCN modulates the timing but not the amount of sleep or the homeostatic control of sleep-wake states or Tb during deviations in ambient temperature.
HIV protein, transactivator of transcription, alters circadian rhythms through the light entrainment pathway
Authors: Clark J. P. , Sampair Christopher S. , Kofuji Paulo , Nath Avindra , Ding Jian. M.
Published: April 2005

Patients infected with the human immunodeficiency virus (HIV), and other mammals infected with related lentiviruses, exhibit fatigue, altered sleep patterns, and abnormal circadian rhythms. A circadian clock in the hypothalamic suprachiasmatic nucleus (SCN) temporally regulates these functions in mammals. We found that a secretary HIV transcription factor, transactivator of transcription (Tat), resets the murine circadian clock, in vitro and in vivo, at clinically relevant concentrations (EC50= 0.31 nM). This effect of Tat occurs only during the subjective night, when N-methyl-d-aspartate (NMDA) receptor [d-2-amino-5-phosphonovaleric acid (0.1 mM)] and nitric oxide synthase ( NG-nitro-l-arginine methyl ester, 0.1 mM) inhibitors block Tat-induced phase shifts. Whole cell recordings of SCN neurons within the brain slice revealed that Tat did not activate NMDA receptors directly but potentiated NMDA receptor currents through the enhancement of glutamate release. Consistent with this presynaptic mechanism, inhibitors of neurotransmission block Tat-induced phase shifts, such as tetrodotoxin (1 μM), tetanus toxin (1 μM), P/Q/N type-calcium channel blockers (1 μM ω-agatoxin IVA and 1 μM ω-conotoxin GIVA) and bafilomycin A1(1 μM). Thus the effect of Tat on the SCN may underlie lentiviral circadian rhythm dysfunction by operating as a disease-dependent modulator of light entrainment through the enhancement of excitatory neurotransmission.
Day- and nighttime injection of a nitric oxide synthase inhibitor elicits opposite sleep responses in rats
Authors: Ribeiro Ana C. , Kapás Levente
Published: April 2005

Previous studies suggest that nitric oxide (NO) may play a role in sleep regulation, particularly in the homeostatic process. The present studies were undertaken to compare the sleep effects of injecting a NO synthase (NOS) inhibitor when homeostatic sleep pressure is naturally highest (light onset) or when it is at its nadir (dark onset) in rats. Sleep, electroencephalogram delta-wave activity during nonrapid eye movement sleep (NREMS), also known as slow-wave activity (SWA), and brain temperature responses to three doses of the NOS inhibitor Nω-nitro-l-arginine methyl ester (l-NAME; 5, 50, and 100 mg/kg) injected intraperitoneally at light or dark onset were examined in rats ( n = 6 to 8). The effects of 5 mg/kg l-NAME were determined in both normal and vagotomized (VX) rats. Light onset administration of 50 mg/kg l-NAME decreased NREMS amounts and suppressed SWA and increased rapid eye movement sleep (REMS) amounts. At dark onset, l-NAME injection also dose dependently suppressed SWA; however, unlike light onset injections, both NREMS and REMS amounts were increased after all three doses. Sleep responses to 5 mg/kg l-NAME were not different in control and VX rats, suggesting that the sleep effects of l-NAME are not mediated through the activation of sensory vagal mechanisms. The present findings suggest that timing of the injection is a major determinant of the sleep responses observed after systemic l-NAME injection in rats.
Muscle performance during maximal isometric and dynamic contractions is influenced by the stiffness of the tendinous structures
Authors: Bojsen-Møller Jens , Magnusson S. Peter , Rasmussen Lars Raundahl , Kjaer Michael , Aagaard Per
Published: April 2005

Contractile force is transmitted to the skeleton through tendons and aponeuroses, and, although it is appreciated that the mechanocharacteristics of these tissues play an important role for movement performance with respect to energy storage, the association between tendon mechanical properties and the contractile muscle output during high-force movement tasks remains elusive. The purpose of the study was to investigate the relation between the mechanical properties of the connective tissue and muscle performance in maximal isometric and dynamic muscle actions. Sixteen trained men participated in the study. The mechanical properties of the vastus lateralis tendon-aponeurosis complex were assessed by ultrasonography. Maximal isometric knee extensor force and rate of torque development (RTD) were determined. Dynamic performance was assessed by maximal squat jumps and countermovement jumps on a force plate. From the vertical ground reaction force, maximal jump height, jump power, and force-/velocity-related determinants of jump performance were obtained. RTD was positively related to the stiffness of the tendinous structures ( r = 0.55, P < 0.05), indicating that tendon mechanical properties may account for up to 30% of the variance in RTD. A correlation was observed between stiffness and maximal jump height in squat jumps and countermovement jumps ( r = 0.64, P < 0.05 and r = 0.55, P < 0.05). Power, force, and velocity parameters obtained during the jumps were significantly correlated to tendon stiffness. These data indicate that muscle output in high-force isometric and dynamic muscle actions is positively related to the stiffness of the tendinous structures, possibly by means of a more effective force transmission from the contractile elements to the bone.
Blow‐up of solutions of a semilinear heat equation with amemory term
Authors: Messaoudi Salim A.
Published: April 2005

We consider an initial
boundary value problem related to the equation and prove, under suitable conditions on g and p,
a blow‐up result for certain solutions with positive initial energy.
A Leray-Schauder alternative for weakly-strongly sequentially continuous weakly compact maps
Authors: Agarwal Ravi P , O'Regan Donal , Liu Xinzhi
Published: April 2005

A new applicable Leray-Schauder alternative is presented for weakly-strongly sequentially continuous maps. This result is then used to establish a general existence principle for operator equations.
Toxoplasma gondii Antigens GRA1 (p24) and SAG1 (p30): A Comparison of Their Stimulatory Influence on T-Cell Activation and Cytokine Expression in in vitro Cultures
Authors: Kato M. , Claveria F.G. , Maki Y. , Tanaka T. , Suzuki N. , Nagasawa H.
Published: April 2005

The influence of recombinant cell surface SAG1 (rp30) and secretory GRA1 (rp24) antigens (Ag) on T-cell activation and cytokine induction in vitro was compared. T-cell activity and the level of IFN-γ, IL-10 and IL-12 expression in rp30-immunized T cells were considerably increased in the presence of rp30 Ags. IgG2a and IgG1 antibodies (Ab) were detected in sera of rp24- and rp30-immunized mice, with the secretory rp24 Ag having induced significantly higher titer of IgG1 Ab. In vitro, the greater antigenicity of surface rp30 Ag was notable based on the level of T-cell activation, and cytokine synthesis suggestive of the participation of Th1 cells. Although, IFN-γ expression by rp24 Ag was lower compared to rp30 Ag, the synthesis of both IgG2a and IgG1 Abs reflects the protective nature of rp24 Ag. We have generated two recombinant Toxoplasma gondii Ags that demonstrated differences in antigenicity in vitro. It would be interesting to evaluate the mechanism(s) of immunity induced by SAG1 (p30) and GRA1 (p24) Ags against infection with T. gondii in vivo.
Thwaites’ Diagnostic Scoring and the Prediction of Tuberculous Meningitis
Authors: Sunbul Mustafa , Atilla Aynur , Esen Saban , Eroglu Cafer , Leblebicioglu Hakan
Published: April 2005

Objective: This study was conducted to investigate the applicability of Thwaites’ diagnostic criteria in order to differentiate tuberculous from bacterial meningitis. Material and Methods: The study was done retrospectively in HIV-negative patients (n = 126) with meningitis. Of the 126 patients, 103 had bacterial meningitis and 23 patients had tuberculous meningitis. The diagnosis was confirmed microbiologically in 59 and 12 patients with bacterial and tuberculous meningitis, respectively. The prediction of tuberculous meningitis was determined by Thwaites’ diagnostic scoring using parameters such as age, history of illness, white blood cell count, total cerebrospinal fluid (CSF) white cell count and the percent of neutrophils in CSF. The diagnostic value of the model was assessed by calculating the area under the receiver operating characteristic (ROC) curves. Results: The sensitivity and the specificity of Thwaites’ diagnostic scoring were 95.6% (22/23) and 70.8% (73/103), respectively. In microbiologically proven cases the sensitivity and the specificity were 91.7% (11/12), 79.7% (57/59), respectively. The area under the ROC curve value for the diagnostic scoring was 0.92. Conclusions: Thwaites’ diagnostic score was found to be helpful in differential diagnosis of tuberculous meningitis, however, the usefulness of diagnostic scoring should be validated in large series especially in patients with viral meningitis and low CSF glucose levels.
Postmortem Biopsies: The Experience in Kuwait
Authors: El-Reshaid Wael , El-Reshaid Kamel , Madda John
Published: April 2005

Objective: To report our 4-year experience in postmortem needle biopsy of liver, heart, kidney and lung tissues when formal autopsy could not be performed. Subjects and Methods: In the period from January 2000 to December 2003, postmortem biopsies were done at Al-Amiri Hospital, Kuwait, in 19 cases where the original diagnosis or cause of death was not clear. The procedure was performed by a dedicated trained medical team using a biopsy needle or limited incisions guided by the knowledge of the clinical presentation and results of laboratory and radiological investigations. Results: The actual diagnosis was established in 8 cases by postmortem histological findings and corrected in another 9 cases. In the remaining 2 cases with systemic sepsis, autopsy only confirmed the antemortem clinical diagnosis. Conclusion: Our study shows that needle biopsy is an adequate technique for postmortem examination and should be considered as the minimum alternative to conventional autopsy.
Utilization of the Pulmonary Function Test Laboratory in the Evaluation of Respiratory Disorders in the Al-Amiri Hospital: A Secondary Medical Center
Authors: Al-Mutairi S.S. , Sugathan T.N.
Published: April 2005

Objective: The aim of this study was to describe the current use of pulmonary function tests (PFT) and the degree of matching between the diagnoses at referral and after the test. Subjects and Methods: A pre-test questionnaire was administered to 464 (5–88 years) patients referred to the PFT laboratory followed by a complete PFT test. The results of the patients’ tests were analyzed in terms of the diagnosis before the test, its relation to symptoms, and the rate of concordance between the diagnoses before and after the test. Results: The most referrals were from the medical Outpatient Department; 61%) and the most frequent diagnosis before the test was asthma (31.8%). Of the 464 patients, 34% were currently smoking cigarettes, and the most common symptoms were chronic dyspnea (30.2%) and chronic cough (19.6%). The chronicity of symptoms showed some association with the diagnosis before PFT in the case of chronic obstructive pulmonary disease (COPD) showing the symptom of dyspnea (p = 0.05), and COPD and restrictive lung disease with cough (p < 0.05). The overall rate of concordance in matching diagnoses before and after the test was 60.4% by consultant physicians and 51.9% by non-consultants, with an overall rate of 55% by all physicians. Conclusion: Our findings show that there should be better utilization of the PFT laboratory by physicians in all sub-specialities and there is a need to facilitate its use to make a better functional diagnosis.
Surgical Management Strategies in Patients with Primary Hyperparathyroidism: Which Technique in Which Patients?
Authors: Koyuncu Ayhan , Dökmetaş Hatice Sebila , Aydın Cengiz , Turan Mustafa , Erselcan Taner , Sözeri Selçuk , Şen Metin
Published: April 2005

Objective: This study was planned to investigate the efficacy of either 99mTc-sestamibi scan or ultrasonography in predicting the operative treatment in patients with primary hyperparathyroidism (PHPT). Subjects and Method: Thirty patients (25 female, 5 male; mean age: 53 years) being operated for symptomatic primary PHPT were included in this study. Ultrasonography was used in 29 patients while 99mTc-sestamibi scintigraphy was done in 28 patients to localize the hyperfunctioning gland(s). Standard bilateral neck exploration was done in 6 patients. Although unilateral intervention had been planned for 24 patients, bilateral intervention was performed in 9 of them. Results: Sensitivity of 99mTc-sestamibi was 81%, while that of ultrasonography was 42%. 99mTc-sestamibi localization method led to misleading results in 10/28 (35.7%) patients. False-positive localization and accompanying thyroid pathologies played an important role in determining transition from unilateral to bilateral intervention. Conclusion: Our findings indicate that bilateral intervention remains a successful management option without prior localization in patients with PHPT especially in an endemic goiter region.
Biophysical and Physiological Properties of Porcine Surfactant Enriched with Polymyxin B
Authors: Calkovska A. , Some M. , Linderholm B. , Johansson J. , Curstedt T. , Robertson B.
Published: April 2005

Objective: We examined whether the biophysical and physiological properties of Curosurf® were improved by the cyclic amphipathic decapeptide polymyxin B (PxB). Methods: Curosurf was diluted to 1–5 mg/ml with PxB added at 1, 2 or 3% (w/w). Albumin was added at 40 mg/ml. Minimum surface tension (γmin) during surface compression was determined for each mixture with pulsating bubble. Immature newborn rabbits were treated with 2.5 ml/kg of Curosurf 80 mg/ml, or Curosurf 32 mg/ml with or without 2% PxB and ventilated for up to 5 h. Results: At surfactant concentration 2 mg/ml, γmin was high (17 ± 8.9 mN/m) but remained low (2.7 ± 0.8 mN/m) when PxB was added. Albumin inactivated Curosurf at both 2 and 3.5 mg/ml; this inactivation was prevented by 2% PxB. Treatment of newborn rabbits with Curosurf 80 mg/kg + 2% PxB significantly decreased incidence of pneumothorax in comparison with controls but had no significant effect on lung-thorax compliance or alveolar expansion. Conclusion: Addition of 2% PxB improves surface activity of Curosurf at low concentration, increases its resistance to inactivation by albumin, and reduces the incidence of pneumothorax in immature newborn rabbits undergoing prolonged ventilation.