bluuebunny/crossref_metadata_2025 huggingface dataset:
Phospholipase C-β1mediates α1-adrenergic receptor-stimulated activation of the sodium–hydrogen exchanger in Chinese hamster lung fibroblasts (CCL39)
Authors: Provost J J , Olmschenk S M , Metcalf A L , Korpi N , Thronson H , Liu M , Wallert M A
Published: April 2005

The activation of the Na+–H+exchanger 1 (NHE1) and extracellular-signal regulated kinase (ERK) phospho rylation in Chinese hamster lung fibroblasts (CCL39) was characterized in response to the specific α1-adrenergic agonist, phenylephrine (PE). Addition of 100 µmol PE/L increased the steady-state intracellular pH (pHi) by 0.16 ± 0.03 pH units, as well as increasing the phosphorylation of ERK. The response of NHE1 to PE in CCL39 cells was determined by the use of specific antagonists. Use of 2 specific chemical inhibitors of phosphoinositide-specific phospholipase C (PLC) reduced the ability of PE to activate either the exchanger or ERK. Studies were conducted in PLCβ-deficient cell lines derived from parental CCL39 cells. NHE1 activity in both mutant cell lines was increased in response to phorbal esters or lysophosphatidic acid, whereas the addition of PE only caused a minimal change in either pHior ERK phosphorylation. These results, combined with reconstitution experiments with exogenously expressed PLCβ1, PLCβ2, or PLCβ3, revealed that stimulation of NHE1 activity by PE in CCL39 cells is a PLCβ1-coupled event. Furthermore, the data indicate that α1-adrenergic signaling of PLCβ is upstream of ERK activation. These data demonstrate that PLCβ1is primarily involved in the activation of NHE1 in CCL39 fibroblasts.Key words: CCL39, sodium hydrogen exchanger, ERK, α1-adrenergic receptor, phospholipase Cβ.
Involvement of active oxygen species in protein and oligonucleotide degradation induced by nitrofurans
Authors: Zolla Lello , Timperio Anna Maria
Published: April 2005

It is of great interest to know how nitrofurans are mutagenic and clastogenic. In particular, the 3-amino-2-oxazolidone (AOZ) ring, deriving from a cleavage of furazolidone, is not further metabolized and has been found to be part of protein-bound residues in edible tissues of farm animals and these might be released in the stomach of the consumer. The data in this paper show that isoniazide as well as AOZ and 3-amino-5-morpholinomethyl-2-oxazolidinone (AMOZ), the latter deriving from furaltadone, cause irreversible damage to the prosthetic group of enzymes as well as degrade their polypeptide chain and cause fragmentation of the backbone chain of cellular or isolated DNA and RNA. Cellular DNA was degraded into small fragments of 2000 Mb, while rRNA was completely destroyed. Nitrofuran derivatives and hydrazides, in fact, share an N–N moiety, which is assumed to play an essential role in the irreversible damage observed. The key to the molecular mechanisms by which these compounds cause their irreversible effects may lie in oxygen consumption and electron spin resonance measurements, which reveal that both nitrofurans and isoniazide produce oxygen radicals at various degrees of efficiency. AOZ and AMOZ are not metabolized into more reactive metabolites, being themselves able to react with atmospheric oxygen and induce protein and oligonucleotide damage. The reaction does not require metal ions, although their presence will accelerate it.Key words: nitrofurans, active oxygen, furazolidone, DNA degradation, protein fragmentation.
Antioxidant status in J774A.1 macrophage cell line during chronic exposure to glycated serum
Authors: Bassi Anna Maria , Ledda Sabina , Pascale Maria Clara De , Penco Susanna , Rossi Simona , Odetti Patrizio , Cottalasso Damiano
Published: April 2005

Advanced glycation end-products (AGEs) are linked to aging and correlated diseases. The aim of present study was to evaluate oxidative stress related parameters in J774A.1 murine macrophage cells during chronic exposure to a subtoxic concentration of AGE (5% ribose-glycated serum (GS)) and subsequently for 48 h to a higher dose (10% GS). No effects on cell viability were evident in either experimental condition. During chronic treatment, glycative markers (free and bound pentosidine) increased significantly in intra- and extracellular environments, but the production and release of thiobarbituric acid reactive substances (TBARs), as an index of lipid peroxidation, underwent a time-dependent decrease. Exposure to 10% GS evidenced that glycative markers rose further, while TBARs elicited a cellular defence against oxidative stress. Nonadapted cultures showed an accumulation of AGEs, a marked oxidative stress, and a loss of viability. During 10% GS exposure, reduced glutathione levels in adapted cultures remained constant, as did the oxidized glutathione to reduced glutathione ratio, while nonadapted cells showed a markedly increased redox ratio. A constant increase of heat shock protein 70 (HSP70) mRNA was observed in all experimental conditions. On the contrary, HSP70 expression became undetectable for a longer exposure time; this could be due to the direct involvement of HSP70 in the refolding of damaged proteins. Our findings suggest an adaptive response of macrophages to subtoxic doses of AGE, which could constitute an important factor in the spread of damage to other cellular types during aging.Key words: in vitro cytotoxicity, AGE, pentosidine, glycoxidation, oxidative stress, TBARs.
Biochemical characterization of the human placental transcription factor GCMa/1
Authors: Lin Chenchen , Lin Meiyao , Chen Hungwen
Published: April 2005

Glial cells missing (GCM) proteins are a novel family of zinc-containing transcription factors. Human GCMa/1 is primarily expressed in placental trophoblast cells and regulates SYNCYTIN gene expression, which mediates fusion of cytotrophoblasts to form the syncytiotrophoblast layer of the human placenta. To biochemically characterize the transcriptional activity of GCMa/1, we set up an in vitro transcription system for human GCMa/1 (hGCMa/1). Using G-free reporter constructs carrying multiple copies of wild-type or mutant GCMa-binding site (GBS) in front of a synthetic TATA box, we observed specific transcriptional activities of recombinant hGCMa/1 proteins prepared from a baculovirus – insect cell or Escherichia coli expression system. We further characterized GCMa/1-mediated tran scriptional activation on the native syncytin promoter. Using G-free reporter constructs containing the native syncytin promoter, a TATA box downstream of the proximal GBS in the syncytin promoter was shown to be essential for the transcription activation directed by hGCMa/1. Therefore, our results demonstrate positive transcriptional activities of GCMa/1 in vitro and provide a better understanding of GCMa/1-mediated SYNCYTIN gene expression.Key words: syncytin, transcription factor, GCMa/1, placenta.
Electron-spin polarization in both magnetically and electrically modulated nanostructures
Authors: Lu Mao-Wang
Published: April 2005

We investigate theoretically the spin-dependent transport properties of electrons in realistic magnetic-electric-barrier (MEB) nanostructures produced by the deposition, onto a heterostructure, of a metallic ferromagnetic stripe. We find the degree of electron-spin polarization to be closely tied to the voltage applied to the stripe, despite the fact that this voltage in itself induces no spin-polarization effect. As a positive (negative) voltage is applied, the electron-spin polarization shifts in the low- (high-) energy direction and increases (decreases). Our results imply that the degree of electron-spin polarization can be tuned through the applied voltage. This implication might prove useful in the design and application of spintronic devices based on magnetic-barrier nanostructures. PACS Nos.: 73.40.Gk, 73.23.-b, 75.70.Cn
Many-body-QED perturbation theory: Connection to the two-electron BetheSalpeter equation
Authors: Lindgren I , Salomonson S , Hedendahl D
Published: April 2005

The connection between many-body perturbation theory (MBPT) and quantum electrodynamics (QED) is reviewed for systems of two fermions in an external field. The treatment is mainly based on the recently developed covariant-evolution-operator method for QED calculations (I. Lindgren, S. Salomonson, and B. Åsén. Phys. Rep. 389, 161 (2004)), which is quite similar in structure to MBPT. At the same time, this procedure is closely related to the S-matrix and Green's-function formalisms and can therefore serve as a bridge connecting various approaches. It is demonstrated that the MBPTQED scheme, when carried to all orders, leads to a Schrödinger-like equation, equivalent to the BetheSalpeter (BS) equation. A Bloch equation in commutator form that can be used for an "extended" or quasi-degenerate model space is derived. This is a multi-state equation that has the same relation to the single-state BS equation as the standard Bloch equation has to the ordinary Schrödinger equation. It can be used to generate a perturbation expansion compatible with the BS equation even in the case of a quasi-degenerate model PACS Nos.: 01.65.+g, 02.60.Cb, 03.65.Pm, 31.10+z, 31.15Md, 31.30Jv
DISORDER AND FRUSTRATION IN DILUTED MAGNETIC SEMICONDUCTORS AT LOW CARRIER DENSITIES
Authors: BHATT R. N. , ZHOU CHENGGANG , KENNETT MALCOLM , BERCIU MONA , WAN XIN
Published: April 2005

We examine the effects of positional disorder of the magnetic ion in III-V Diluted Magnetic Semiconductors such as ( Ga , Mn ) As at low carrier densities on the nature of the low-temperature ordered magnetic state, using numerical mean field and Monte Carlo methods. We find that positional disorder leads to a highly inhomogeneous ferromagnetic order in the low carrier density limit, with unusual thermodynamic and magnetic behavior. Spin-orbit coupling presented in the valence band leads to frustration in the hole-doped system, but does not significantly affect the low temperature magnetization.
AN APPLICATION OF THIRD FORMALISM OF QUANTUM STATISTICS AND A DIAGONALIZATION THEOREM IN ASYMPTOTIC EXACT THEORY OF SUPERCONDUCTIVITY
Authors: SUN LEI , YE JIPING , DAI XIANXI , DAI JIXIN
Published: April 2005

Starting from an electron-phonon interacting model, by means of the third formalism of quantum statistics, and with the aid of a diagonalization theorem, the Tc of superconductors from weak coupling to strong coupling cases are studied in a unified way. Our results are comparable with those of McMillan's theory, (which is valid up to the electron-phonon (e-ph) coupling parameter λ~1, a good agreement is shown for λ<1.3) and the Allen and Dynes's theory. Especially our results are very close to those of Hg spectrum with λ~2.0 and some strong coupling compounds. The theory is exact in the thermodynamic limit, without introducing variation method, the compensation of the dangerous diagrams in finite order in perturbation theory, abnormal green's function etc.
EFFECT OF PARTICLE-HOLE EXCITATIONS ON THE BCS GROUND STATE
Authors: FAN J. D. , MALOZOVSKY Y. M.
Published: April 2005

We show that the well-known BCS Hamiltonian in terms of the BCS ground state represents, in fact, the generator of the particle-hole pairs and that the BCS ground state describes both the particle-hole excitations and the pairing condensate. We calculate the contribution of particle-hole excitation to the ground state energy. We show that the particle-hole pairs in the case of attractive interaction significantly lower the ground state energy, which means that the BCS ground state is not really the superconducting ground state. In contrast, for the repulsive interaction the particle-hole excitations are just to renormalize the ground state energy. Thus, in the case of repulsive interaction the condensate of bound pairs would lead to the real superconducting ground state of the system as shown.
CHARGE TRANSPORT IN ELECTRON-DOPED CUPRATES
Authors: MA TIANXING , GUO HUAIMING , FENG SHIPING
Published: April 2005

Within the t-t'-J model, the charge transport in electron-doped cuprates is studied. The conductivity spectrum is characterized by a low-energy peak and unusual midinfrared band, while the resistivity exhibits a crossover from the high temperature metallic-like to low temperature insulating-like behavior in the relatively low doped regime, and a metallic-like behavior in the relatively high doped regime, which is qualitative agreement with experiments. Our results show that such unusual charge transport is closely related to a competition between the kinetic energy and the magnetic energy.
ISOTOPE EFFECT IN SUPERCONDUCTIVITY IN TERMS OF BETHE-SALPETER EQUATION
Authors: MALOZOVSKY Y. M. , FAN J. D.
Published: April 2005

We evaluate the temperature of superconducting phase transition in terms of the Bethe-Salpeter equation for a many-body system. We consider the case when both electron-phonon interaction and strong Coulomb interaction co-exist. To remove the artificial cutoff at high energy we solve the Bethe-Salpeter equation in terms of the two-particle vacuum scattering amplitude. We show that such an approach leads to the conclusion that the so-called Coulomb pseudopotential appears only due to the artificial cutoff and does not exists at all in terms of the Bethe-Salpeter equation.
UNUSUAL c-AXIS CHARGE DYNAMICS IN UNDERDOPED CUPRATES
Authors: MA TIANXING , FENG SHIPING
Published: April 2005

Within the t-J model, the c-axis charge dynamics of the underdoped cuprates has been studied based on the charge-spin separation fermion-spin theory. In contrast to the in-plane conductivity, the low energy peak of the c-axis conductivity is located at a finite energy, while the c-axis resistivity exhibits a crossover from the high temperature metallic-like behavior to the low temperature insulating-like behavior, in agreement with experiments.
MODEL OF SUPERCONDUCTING DOMAINS — A UNIFIED THEORY OF HIGH- AND LOW- TC SUPERCONDUCTORS (II)
Authors: PENG KUANGDING
Published: April 2005

The unified model of superconductivity has been discussed [1]. In the model the motion of phononic electron (PE) pairs is described by a non-linear schrödinger equation of PE pairs (SEPE). From SEPE the ideal conductivity in superconductors in external magnetic field has been derived. From wave property of motion of PE pairs, Josephson equations have been proven. From the formula of Tc, the relation of Tc to pressure p has been explained.
NUMERICAL STUDY OF THE ELECTRONIC STATES IN HOLE- AND ELECTRON-DOPED HIGH-TC CUPRATES
Authors: TOHYAMA TAKAMI
Published: April 2005

We examine the electronic states in the hole- and electron-doped cuprates by using the t-t′-t″-J model. Numerically exact diagonalization method is employed for a 20-site square lattice under twisted boundary conditions. The density of states in the underdoped region clearly shows a pseudogap behavior near the Fermi level in both hole and electron dopings. In hole doping, the edge of the pseudogap in the occupied side exhibits a large weight that comes from a flat band near k=(π,0). In contrast, the weight near the gap edge in electron doping is larger for the unoccupied side than for the occupied side.
PHASE–SENSITIVE ANDREEV CONDUCTANCE OF AN SNS SYSTEM WITH THE SUPPRESSED PROXIMITY EFFECT
Authors: CHIANG Yu. N. , SHEVCHENKO O. G.
Published: April 2005

A study is made of the dissipative component of the electron transport in a doubly connected Andreev SNS interferometer with elastic mean free paths lel in the metals of around 100μ m and a macroscopic phase–breaking length [Formula: see text] which is two or more orders of magnitude larger than [Formula: see text] in disordered nanostructures. At helium temperatures, the samples are found to exhibit new phase–sensitive effects of a quantum–interference nature. Below 2 K , the conductance of the macroscopic N region of the system has an oscillatory component of resonance shape which undergoes the phase inversion relative to the phase of the nonresonance oscillations. An explanation for the effects is suggested in terms of the contribution to the Josephson current from coherent quasiparticles with energies of order of the Thouless energy. The temperature behavior of the dissipative transport in a pure normal metal near an isolated NS point contact is studied.
ON THE MAXIMUM AND CHARACTERISTIC CURVATURE OF CURRENT DENSITY OF HIGH Tc SUPERCONDUCTOR YBCO IN FLUX RELAXATION
Authors: YE JIPING , SUN LEI , DAI XIANXI , DAI JIXIN
Published: April 2005

The flux relaxation is one of important topics in the studies of high Tc superconductivity, because it is related to the energy loss in practical applications. There are many mechanisms, theories and relaxation laws suggested in the literatures. It is very interesting to test them according to the characters and compare them with the experiments. Some people think that the characters of the famous theories are their negative curvature. According our inversion solution, the relaxation ArcG law and experimental data analysis, the relaxation law has both positive and negative signs. This prediction is hopeful to be checked by experiments in future. The current densities of many high Tc superconductors decrease very rapidly in the early time in the relaxation. People do not know what their maximums are. In this work, a theory to determine these maximums of the current densities is presented. The theory is concretely realized by inversion for some real data of the YBCO and their maximum current densities are obtained.
INFLUENCE OF FLUX CREEP ON AC SUSCEPTIBILITY OF SUPERCONDUCTORS
Authors: LIN J. W. , LIU G. , LENG X. , ZHANG L. , DING S. Y.
Published: April 2005

Influence of flux creep on ac susceptibility (acs) of a superconductor was examined by simulation. Comparing the acs with and without flux creep, it was found that frequency of ac field shifted the acs with flux creep but did not affect the acs of critical state model. In addition, the amplitude of ac field and dc field affect differently for the two models.
THERMAL CONDUCTIVITY OF YBa2Cu3O7: s-WAVE INTERPRETATION
Authors: HARSHMAN DALE R. , DOW JOHN D.
Published: April 2005

Previous interpretations of the thermal conductivity data of YBa 2 Cu 3 O 7 in terms of d-wave superconductivity have created the impression that this experiment can only be successfully explained in terms of a d-wave model. Here we show that thermal conductivity data can be (better) explained in terms of s-wave hole-pairing, which also handles some outstanding problems with the d-wave interpretation, namely, muon spectra that are s-wave and specific heat data that exhibit a zero-field linear-T term. The basic notion is that a high-temperature superconductor such as YBa 2 Cu 2 O 7 contains both superconducting and non-superconducting bands. The main superconducting bands are associated with BaO , and the CuO 2 bands are non-superconducting.
ELECTRON-PHONON INTERACTION IN TERNARY SILICIDES MGaSi (M=Ca, SrandBa)
Authors: HUANG G. Q. , CHEN L. F.
Published: April 2005

The electron-phonon (EP) interaction in ternary silicides M GaSi with M= Ca , Sr and Ba are calculated using the full potential, density-functional-based method. A striking feature of the phonon spectra is the existence of very soft " B 1g" mode, which is strong anharmonic and plays an important role in superconductivity of the M GaSi compounds. The superconducting transition temperatures Tc in these compounds have been evaluated. It is found that the variation trend in Tc can be explained from the strength of the electron-phonon coupling.
C-AXIS TWIST BICRYSTAL, ARTIFICIAL AND NATURAL CROSS-WHISKER Bi2212 JOSEPHSON JUNCTIONS
Authors: KLEMM RICHARD A.
Published: April 2005

We present the latest data of the c-axis bicrystal twist Josephson junctions experiments of Li et al. and of the artificial and recent natural cross-whisker junction experiments on Bi 2 Sr 2 CaCu 2 O 8+δ ( Bi 2212) of Takano et al. and Latyshev et al., respectively. These combined experiments provide strong evidence for a dominant s-wave order parameter and for strongly incoherent c-axis quasiparticle tunneling in Bi 2212 for T≤Tc.
USE OF THE ELECTROSTATIC POTENTIAL IN SUPERCONDUCTORS
Authors: KOLÁČEK JAN , LIPAVSKÝ PAVEL
Published: April 2005

The balance of forces on the superconducting condensate in the presence of currents is discussed. It is shown that the electrostatic potential known as the Bernoulli potential is a useful concept which allows one to establish conditions of a stationary motion.
SUB-BRANCH SPLITTING IN JOSEPHSON-VORTEX-FLOW CHARACTERISTICS OF A STACK OF Bi2Sr2CaCu2O8+x INTRINSIC JOSEPHSON JUNCTIONS
Authors: BAE MYUNG-HO , LEE HU-JONG
Published: April 2005

We observed subbranch splitting in the low-bias vortex-flow branch of a dense-Josephson-vortex state in current-voltage characteristics of Bi 2 Sr 2 CaCu 2 O 8+x intrinsic Josephson junctions in the long-junction limit. We suggest that each subbranch corresponds to a plasma mode in serially coupled Josephson junctions, manifested in the Josephson vortex-flow current-voltage characteristics resonating with the plasma modes.
TUNNELING SPECTROSCOPY OF TRILAYER HIGH-TC CUPRATE, TlBa2Ca2Cu2O10-δ
Authors: MIYAKAWA N. , TOKIWA K. , MIKUSU S. , WATANABE T. , IYO A. , ZASADZINSKI J. F. , KANEKO T.
Published: April 2005

We present point contact tunneling spectroscopy measured on TlBa 2 Ca 2 Cu 3 O 10-δ ( Tl 1223) with three CuO 2 planes in a unit cell. Our samples of Tl 1223 with Tc~91 K are heavily overdoped at the outer CuO 2 planes (OP), but slightly underdoped at the inner CuO 2 planes (IP). The tunneling conductances on Tl 1223 exhibit two kinds of gaps that originate from crystallographically inequivalent IP and OP. The overall spectral shape of tunneling conductance for Tl 1223 is consistent with that observed on a bilayer Bi 2 Sr 2 CaCu 2 O 8+δ, that is, unusual peak-dip-hump (PDH) structures are observed. The origin of PDH structures is controversial, but these results, especially, the observation of PDH for trilayer Tl 1223 in which interlayer effects should be quite different from that in bilayer, put severe constraints on any theoretical model for the origin of these structures.
STM/STS STUDY ON LOCAL ELECTRONIC STATES OF UNDERDOPED Bi2Sr2CaCu2O8+δ
Authors: MOMONO N. , HASHIMOTO A. , KOBATAKE Y. , NAKAMURA S. , ODA M. , IDO M.
Published: April 2005

Spatial variation of low temperature tunneling spectrum on atomic scale was examined on the slightly underdoped Bi 2212 sample (Tc~74 K , p~0.12) by using a STM/STS technique. We observed a V-shaped gap with sharp coherence peaks, which is expected for d-wave superconductors, over the distance of ~18 nm and no other kind of gap. The spatial variation of gap size Δ0 is small, ranging from 41 to 53 meV . These results indicate that the superconductivity takes place rather homogeneously in the slightly underdoped sample.
PRESSURE DEPENDENCE OF Tc FOR HIGH-TcCl-CONTEINED SUPERCONDUCTOR (Sr,Ca)3Cu2O4+δCl2-y
Authors: NISHIYAMA M. , SHIMIZU K. , LIU Q. Q. , JIN C. Q.
Published: April 2005

Chlorine-containing ( Sr , Ca )3 Cu 2 O 4+δ Cl 2-y (0212- Cl ) superconductor is the high-Tc Cu -oxide superconductor (HTSC) with Tc=80 K and was synthesized under high-pressure and high-temperature. The 0212- Cl has double [ CuO 2] planes and the apical oxygen are replaced by Chlorine. We measured the resistance of 0212- Cl under high pressure using a diamond-anvil cell up to 13.3 GPa and two-terminal ac-method to investigate the pressure dependence of Tc. Tc of 0212- Cl increases gently with increasing pressure.
THE SYNTHESIS OF INFINITE-LAYER CaCuO2 AND HYPOTHETICAL p-TYPE DOPING WITH Na UNDER HIGH-PRESSURE
Authors: QIN X. M. , WANG F. , YU Y. , LI F. Y. , YU R. C. , JIN C. Q.
Published: April 2005

The CaCuO 2 with infinite-layer structure (IL CaCuO 2) was synthesized under high-pressure. The p-type doped infinite layer compounds Ca 1-x Na x CuO 2 with the different carriers concentration ( x =0.05, 0.1) were also prepared from high temperature and high-pressure technique. The lattice parameter a decreases with increasing Na content x in the p-type doped Ca 1-x Na x CuO 2, suggesting that the hole like carriers enter into the CuO 2 plane, and Na is successfully doped into the infinite-layer CaCuO 2. This was confirmed by the systematic evolution of resistance with increasing the doping level. However, no superconductivity was observed in the samples.
CRYSTAL GROWTH OF MULTI-LAYERED Ba2Ca4Cu5O10(O,F)2 (F-0245) SUPERCONDUCTOR UNDER HIGH PRESSURE
Authors: TOKIWA K. , OKUMOTO H. , KONO S. , IGA S. , TAKEMURA K. , WATANABE T. , IYO A. , TANAKA Y.
Published: April 2005

Single crystals of multi-layered Ba 2 Ca 4 Cu 5 O 10( O , F )2 superconductor(F-0245) have been grown under a high pressure of 4.5 GPa . Single crystals with in-plane length of 500μm were typically obtained and flat shiny areas with more than 1 mm 2 were also observed on the surface of fractured samples. Tc values for these samples were determined by electrical resistivity measurements. These values were found to change from 70 K to 85 K by change of oxygen and fluorine contents in the starting mixture. The temperature dependence of resistivity showed characteristic of under-doped cuprate superconductors.
IMPURITY STATES IN SUPERCONDUCTING SYSTEMS WITH STRIPE LIKE MODULATION
Authors: XIA TIANLONG , HAN QIANG , CHEN YAN , WANG Z. D. , LI X.-G.
Published: April 2005

Based on the extended Hubbard model with the next nearest neighbor hopping term, we study the impurity states in a slightly underdoped (with 0.13 hole) system with competition between d-wave superconductivity and antiferromagnetism by solving the mean field Bogoliubov-de Gennes equations self-consistently. Nickel and Zinc impurities are studied respectively using the potential scattering impurity (PSI) model and the Anderson impurity (AI) model. The significant difference in their local density of states may be useful to predict the impurity states in the stripe phase of the superconductors in the slightly underdoped region.
MAGNETORESISTANCE AND HALL EFFECT OF TWO-DIMENSIONAL 2H-NbSe2
Authors: LI LINJUN , SHEN JINGQIN , XU ZHUAN , WANG HONGTAO
Published: April 2005

Single crystals of two-dimensional 2 H - NbSe 2, which undergo superconducting transition at Tc=7.1 K and charge-density wave (CDW) transition at TCDW=30 K , were synthesized. The resistance residual ratio (RRR=R(300 K )/R(8 K )) of the samples from different batches varies from 10 to 30, but the superconducting properties hardly change with RRR. The magneto-resistance (MR)is generally small and its temperature and field dependence of MR violate the Kohler's rule that holds for many conventional metals, indicating that the scattering times of charge carriers are no longer isotropic. The steep decrease of Hall coefficient RH below 50 K can be interpreted by the drastic increase of the mean-free-path of electron type charge carrier. The influence of CDW transition on the resistivity and Hall effect is discussed in a two-band model.
STUDY OF INVARIANT Tc IN HIGHER DOPING LEVEL Y1-xCaxBa2-xLaxCu3Oy
Authors: SUN X. F. , DU H. L. , RUI X. F. , ZHANG L. , WANG F. , ZHANG H.
Published: April 2005

The higher doping level Y 1-x Ca x Ba 2-x La x Cu 3 O y samples were synthesized with x from 0.25 to 0.55. Structure and superconductivity have been investigated. Comparing with the results of lower doping level, the Tc of these samples keeps almost constant when dopant increasing. While some structural characters, such as Cu (1)- O (4), Cu (2)- O (4) bond lengths change randomly in a narrow range. The relationship between Ba / La position and Tc is rather interesting. The results give another evidence that the influence of structural change on superconductivity is independent of carrier concentration.
MAGNETIZATION OF Ag-Y1.8Ba2.4Cu3.4O7-x
Authors: ZHANG L. , LIU G. , LENG X. , XU X. B. , DING S. Y. , JIAO Y. L. , XIAO L.
Published: April 2005

Three MTG Ag-Y1.8Ba2.4Cu3.4O7-x samples were fabricated to study the effect of doping Ag on magnetization. Magnetizations measured at various temperatures and fields show two peaks for all samples: the first peak in low field and second peak in middle field. We examined the effect of doping Ag and temperature on these peaks and discussed the origin of the peaks.
STRUCTURAL CHANGES OF Ni-DOPED YBCO AT DIFFERENT TEMPERATURE
Authors: ZHANG L. , DU H. L. , RUI X. F. , SUN X. F. , ZHANG H.
Published: April 2005

In YBa 2 Cu 3-x Ni x O y at about 480°C all the samples show a tetragonal phase. Comparing the structural changes at 480°C with those at room temperature, the bond lengths such as Cu (1)- O (4) and Cu (2)- O (4) vary regularly with Ni -content increasing at room temperature, but not at high temperature. It suggests that there is a close correlation between structural changes and superconductivity in this system. The difference of orthorhombic- tetragonal phase -transition is also discussed between undoped YBCO and Ni -doped YBCO at high temperature.
HIGH PRESSURE SYNTHESIS AND SUPERCONDUCTIVITY OF Sr2CuO2+δCl2-y BY APICAL OXYGEN DOPING
Authors: LIU Q. Q. , JIN C. Q. , YU Y. , LI F. Y. , LIU Z. X. , YU R. C.
Published: April 2005

Using the apical oxygen doping mechanism, i.e. a partial substitution of divalence O for the monovalence Cl , a p-type copper oxychloride superconductor, Sr 2 CuO 2+δ Cl 2-y, was synthesized at 1050°C under 6.0 GPa for 1h. The X-ray powder diffractions show that the main phase has a tetragonal structure with a=3.93Å, c=15.65 Å. The magnetic susceptibility as well as resistance measurements indicated that the bulk superconducting transition temperature of the sample is 30K.
ANGLE-RESOLVED PHOTOEMISSION SPECTROSCOPY (ARPES) OF Na0.7CoO2
Authors: KUPRIN ALEXANDER , HASAN ZAHID , CHUANG YI-DE , HUSSAIN ZAHID , QIAN DONG , FOO M. , CAVA R. J.
Published: April 2005

Detailed study of the electronic structure of the layered Na 0.7 CoO 2, doped Mott insulator with triangular Co lattice is performed by angle-resolved photoemission spectroscopy (ARPES). At low temperature Fermi surface is a centered hole pocket of hexagonal character shape in agreement with LDA. A broad valence band satellite at higher energies showing resonant enhancement at the 2p, 3p→3d excitations indicates large on-site Hubbard-U~5 eV . A momentum dependent quasiparticle band near Fermi level that is flat and vanished at energies already above 70 meV or 80 meV gives a value of the single particle hopping t<10 meV . This band is defined only in the region of non - Fermi liquid transport with linear growth of resistivity up to 120 K.
THE EFFECT OF La AND Sn DOPING ON THE STRUCTURAL AND MAGNETIC PROPERTIES OF RuSr2EuCeCu2Oz
Authors: LEE H. K. , Park H. M. , Williams G. V. M.
Published: April 2005

The crystal structure and magnetic properties of ( Ru 1-x Sn x) Sr 2 EuCeCu 2 O z and Ru ( Sr 2-x La x) EuCeCu 2 O z(0≤ x ≤0.1) samples have been investigated to shed light on the doping-induced changes in the magnetic properties of Ru -1222 system. We show that La substitution for Sr leads to an increase in the temperature where the ferromagnetic component is observed and a moderate suppression of the ferromagnetic component whereas Sn substitution for Ru results in a significant decrease of the volume fraction of the ferromagnetic phase as well as a decrease in the magnetic ordering temperature. The experimental results are discussed in connection with the structural data studied by Rietveld refinement of the x-ray diffraction data.
OCCURRENCE OF SUPERCONDUCTIVITY IN Ca-DOPED (Pb,Cu)Sr2PrCu2Oz
Authors: LEE H. K. , KIM Y. H. , HA D. H.
Published: April 2005

We have investigated the Ca -doping effects on the structural, electrical and magnetic properties of ( Pb 0.5 Cu 0.5) Sr 2( Pr 1-x Ca x Cu 2 O z( x =0-0.5) bulk ceramic samples. The electrical resistivity, thermoelectric power and magnetic susceptibility measurements reveal that the Ca doping introduces holes into the system and thereby superconductivity with onset T c, of about 36 K is induced for a phase with x =0.5. These results are discussed in conjunction with the roles of hole doping, structural changes and Pr - O hybridization in CuO 2 layers.
ANISOTROPIC SUPERCONDUCTING PROPERTIES OF CaAlSi AND CaGaSi
Authors: TAMEGAI T. , UOZATO K. , GHOSH A. K. , TOKUNAGA M.
Published: April 2005

Anisotropic superconducting properties of new layered intermetallic compounds CaAlSi and CaGaSi with AlB 2 structure are studied. These superconductors show moderate anisotropy with anisotropy parameter [Formula: see text] determined by both magnetic and transport measurements. Despite the small value of γ, angular dependence of Hc2 in CaAlSi shows cusp-like feature for fields parallel to the superconducting plane, suggesting the presence of two-dimensional superconducting units. By contrast, Hc2(θ) in CaGaSi can be reasonably well explained by the anisotropic GL-model. X-ray diffraction measurements reveal the presence of superstructure along the c-axis in CaAlSi but not in CaGaSi . These findings suggest a close relationship between the anomalous angular dependence of Hc2 and the superstructure. Possible origins of the two-dimensional superconducting units in CaAlSi are discussed.
THE EFFECTIVE BARRIER THICKNESS IN RAMP-TYPE JUNCTIONS WITH A CONTINUALLY GRADED BARRIER OF Y1-xPrxBa2Cu3Oy
Authors: GAO J. , SUN J. L.
Published: April 2005

Ramp junctions have been successfully synthesized utilizing an Y 1- x Pr x Ba 2 Cu 3 O y barrier with a continually graded concentration of Pr . The properties of these junctions are dominated by the barrier material rather than the boundary. Also, the damaged ramp surface is excluded from the weak link region so its influence is minimized. The Josephson coupling occurs at the naturally formed S/N interfaces within the Y 1- x Pr x Ba 2 Cu 3 O y layer. Thus it leads to a highly transparent S/N boundary and greatly enhances the performance of the junctions. The effective thickness of the barrier can be varied even post fabrication, depending on the measuring temperature and the concentration gradient. The temperature dependence of the barrier thickness and Josephson properties were investigated and compared with those junctions with a conventional single barrier. These unique features should motivate further studies on the nature of these junctions.
A COMPACT INTEGRATION OF HIGH-TEMPERATURE SUPERCONDUCTING BANDPASS AND BANDSTOP FILTERS
Authors: CHEN JING , SUN LIANG , HUANG JIANDONG , LI SHUNZHOU , HE AISHENG , ZHANG XUEQIANG , LI CHUNGUANG , LI HONG , LUO SHENG , HE YUSHENG
Published: April 2005

Integration of a high-temperature superconducting (HTS) narrowband bandpass filter and a HTS bandstop filter onto a single piece double-sided YBCO thin film with 0.5mm-thick LaAlO 3 substrate has been carried out. The 8-pole bandpass filter was designed with a fractional bandwidth about 0.8%. A pair of transmission zeros was implemented, showing typical quasi-elliptical function characteristics. The bandstop filter has a high stopband attenuation (~70 dB ) to fulfill the special requirement of potential application in communications. Integration of the two filters was successfully achieved.
EXPONENTIAL MODEL FOR LEVITATION FORCE OF YBa2Cu3O7-δ BULKS IN APPLIED FIELDS
Authors: SONG HONGHAI , REN ZHONGYOU , ZHENG JUN , WANG XINGZHI , WANG SUYU , WANG JIASU
Published: April 2005

The exponential model is proposed for levitation force calculations of high temperature superconductors in place of Bean model according to the Exponential relationship between the critical current density and applied field. The calculated results are larger than the experimental results in both symmetrical and unsymmetrical applied fields. The normalization curves agree well in the symmetrical applied field, however, they much differ in the unsymmetrical applied field.
MODULATION OF SUPERCONDUCTIVITY BY Si+ IMPLANTATION IN Bi2212 SINGLE CRYSTALS
Authors: WANG Z. H. , NIE Y. , DING S. Y. , LEE H. J. , SON Y. U. , BAE M. H. , NAKAJIMA K.
Published: April 2005

The multiple quasiparticle tunnelling branches with large hysteresis were measured on the mesas of Si + implanted Bi 2 Sr 2 CaCu 2 O 8+x single crystals. For given Si + dosage the tunnelling critical current I c, decreased for junctions located closer to the mesa surface; meanwhile the voltage interval between the neighboring quasiparticle branches decreased with increasing the Si + dosage.
APPLICATIONS IN THE ADVANCED TRANSPORTATION SYSTEM AND IMPACT ON SUPERCONDUCTIVITY INDUSTRY OF HTSM
Authors: ZHANG Y. P. , ZHAO Y.
Published: April 2005

As the information technology grows up and its application penetrates into every area of this world, how to faster and more efficiently transport people and goods is becoming the new social demand, which indicates a new revolution on advanced transportation technology being brewed. High-temperature Superconductivity Maglev (HTSM) is one with the best development potential among most transportation technologies. It could be used in many advanced transportation fields, overcoming the key contradiction and shortcoming of the current transportation patterns such as train, automobile and airplane. On the other hand, HTSM will promote theoretical study and technology exploitation on superconductivity. HTSM's applications in a large scale will bring up profound effect on the forming and development of the superconductivity industry.
SUPPRESSION OF MAGNETIZATION BY A SMALL TRANSVERSE AC MAGNETIC FIELD
Authors: KIM DONG HO , KIM HEON-JUNG , LEE SUNG-IK
Published: April 2005

One efficient method to investigate the vortex matter in the high-temperature superconductors is to measure the magnetization while shaking vortices by applying a transverse ac magnetic field, Hac. When a small transverse Hac is superposed with the dc magnetic field, the vortices will experience time-varying torque by ac field. This vortex shaking gives rise to effective reduction of pinning energy, which in turn gives rise to a rapid relaxation of the irreversible magnetization. This experimental approach has been used to study the nature of the anomalous magnetization peak in a N 2-annealed Tl 2 Ba 2 CuO single crystal. Shaking vortex unveiled the otherwise unobserved anomalous magnetization peak; when Hac=0, no noticeable structure in the magnetization loop was observed, but with vortex shaking by Hac, the magnetization loop deformed to exhibit the anomalous magnetization peak. The evolution of the anomalous peak with Hac can provide a clue to the understanding of the underlying mechanism for the occurrence of the peak.
QUANTUM PHASE TRANSITIONS IN DISSIPATIVE JOSEPHSON JUNCTION ARRAYS
Authors: MOON K.
Published: April 2005

Quantum phase slips can induce a phase transition in a single Josephson junction by varying coupling strength RS to the dissipative environment. We study the finite Josephson junction array with dissipations. For the infinite arrays with no dissipation, a quantum KT phase transition can occur by varying the ratio of the Josephson coupling strength EJ to the charging energy Ec due to the unbinding of instanton pairs. At finite temperature and array size, there will be a rich interplay between instantons and quantum phase slips.
ELASTIC-THEORY STUDY ON THE MELTING TRANSITION OF FLUX LINE LATTICE INDUCED BY MAGNETIC FIELDS PERPENDICULAR TO THE ANISOTROPIC AXIS
Authors: NIE QING-MIAO , LUO MENG-BO , CHEN QING-HU , HU XIAO
Published: April 2005

The melting transition in anisotropic type-II superconductors has been studied by the Lindemann criterion in the framework of elastic theory. Using two Lindemann numbers for two transverse directions, we find that the single melting transition can be obtained, when the ratio between the two Lindemann numbers reaches special value.
DISSIPATION OF THE Bi2.4-xPbxSr2CaCu2O8+y INTRINSIC ARRAY JOSEPHSON JUNCTIONS
Authors: NIE Y. , WANG Z. H. , QIU L. , DING S. Y. , GAO J.
Published: April 2005

We have fabricated a small-sized mesa on the surface of the Bi 2.4-x Pb x Sr 2 CaCu 2 O 8+y single crystals and measured the temperature dependence of the out-of-plane resistivity in different magnetic fields. The irreversibility line H irr( T ) follows different law in different temperature regions. But as a whole, the higher doping level x is, the irreversibility line locates in a higher field. The field dependence of activation energy follows U eff∝ H -m, m increases when doping level x improves.
ANALYSIS OF HEAT TRANSFER AND OPTIMAL DIMENSIONS OF THE SHUTTER FIN
Authors: LI K. N. , ZHAO J. G. , LUO H.
Published: April 2005

The author of this paper has conducted the experimental study and optimal computing for the condenser of automobile air conditioner. Especially studied and computed the properties of heat transfer and flow at the side of air when using louvered fin. Analyzed the influence of several combinations of fin's geometrical dimensions to heat transfer and pressure drop. Furthermore, designed a program to conduct optimal computing, and the computing results are basically consistent with experimental results.
EXERGO-ECONOMIC PERFORMANCE EVALUATION ON LOW TEMPERATURE HEAT EXCHANGER
Authors: WU S. Y. , LI Y. R. , ZENG D. L.
Published: April 2005

Based on the exergo-economic analysis of low temperature heat exchanger heat transfer and flow process, a new exergo-economic criterion which is defined as the net profit per unit heat flux for cryogenic exergy recovery low temperature heat exchangers is put forward. The application of criterion is illustrated by the evaluation of down-flow, counter-flow and cross-flow low temperature heat exchangers performance.
CRYSTALLINE SrTiO3 THIN FILMS ON SILICON BY PULSED LASER DEPOSITION
Authors: HAO J. H. , GAO J.
Published: April 2005

We have developed a process to grow SrTiO 3 ( STO ) thin films showing single (110) orientation directly on Si by means of pulsed laser deposition technique. The growth of STO films directly on Si has been described. The crystallinity of the grown STO films was characterized by X-ray diffraction analysis of θ-2θ scan and rocking curve. Our results may be of interest for better understanding of the growth based on the perovskite oxide thin films on silicon materials.
SYNTHESIS, STRUCTURAL AND MAGNETIC PROPERTIES OF DOUBLE PEROVSKITES Sr2CrWO6
Authors: CHAN T. S. , LIU R. S. , HUANG C. Y.
Published: April 2005

The double perovskite ( Sr 2 CrWO 6) has been prepared in polycrystalline state by solid state reaction. At room temperature, the crystal structure is cubic (space group: Fm3m) with lattice parameter of 7.8200(2) (Å). Both ρ( H =0) and ρ( H =5 T ) show a semiconductor-like behavior over the whole temperature range up to 5 K. The highest MR(magnetoresistance) value of 55% ( H =5 T ) was observed at 25 K. The valence state of Cr was determined by the X-ray absorption spectroscopy at Cr -L edge. The results, compared to the standard sample, show that the valence state of Cr is 3+.
STRUCTURE AND PROPERTIES OF (La2-xSrx)MnO4 COMPOUNDS
Authors: WU M. S. , KAO H.-C. I. , SHEU H. S. , CHIANG Y. P. , HORNG L. , HSUEH R. F. , YOUNG S. L. , PONG W. F. , HUANG J. H.
Published: April 2005

Polycrystalline single phase ( La 2-x Sr x) MnO 4 (1.10≤ x ≤1.40) samples were prepared by a citrate precursor method. They have tetragonal K 2 NiF 4 structure with a space group of 14/mmm, increasing x, unit-cell a-axis increases and c-axis decreases, which is a result of decreasing of the Jahn-Teller effect due to the increase of the Mn ( IV ) ion. Spin glass state exists at low temperature and a hump observed from the susceptibility (χ) measurement is probably caused by the interactions of several magnetic phases. Among them, ( La 0.6 Sr 1.4) MnO 4 has the largest magnetoresistance ratio ([ρ(H)-ρ(0)]/ρ(0)), which reaches to 78.4% at 48 K. It is not possible to obtain single phase materials with 0.60≤ x ≤1.00 in the heat treatment temperature range of 1000-1600°C. Impurities were easily observed under SEM and X-ray diffraction patterns. Increasing the heating period and decreasing the temperature, the amount of ABO3 perovskite phase increases. In order to extend the solubility range, of the SrO in the ( La 2-x Sr x) MnO 4, it probably needs a higher temperature (>1600°C) and a shorter heat treatment period (<1 h).
RESEARCH ON THE NANOMETER DENDRITIC FIBERS IN DORBEETLE CUTICLE
Authors: CHEN BIN , PENG XIANG-HE , FAN JING-HONG , WANG WAN-LU
Published: April 2005

The SEM observation on the cuticle of dorbeetle shows that the cuticle is composed of chitin fibers and protein matrix. The diameter of chitin fibers is from several to several-hundred nanometers. The observation also shows that there is a kind of dendritic fiber in the cuticle. The maximum pullout force of the dendritic fiber is analyzed based on its representative model. The analysis shows that the dendritic fibers can markedly increase the pullout force of the fibers and improve the fracture toughness of the cuticle.
RELATIONSHIP BETWEEN MICRO-STRUCTURE AND LASER DAMAGE THRESHOLD OF NANO-ZrO2 FILMS
Authors: DUAN L. H. , LIU A. P. , CHEN S. L. , WANG W. L. , MA P. , HU J. P. , LIAO K. J.
Published: April 2005

In this paper, the micro-structure and laser damage threshold of nano- ZrO 2 thin films were investigated. High-purity nano- ZrO 2 particles as the coating materials of samples were prepared by the electron beams evaporation. The micro-structure and crystallitic size of samples were analyzed by X-ray diffraction, a laser by 1064nm, 10ns, 3Hz Nd:YAG laser damage test each for nano- ZrO 2 films. The results showed that oxygen partial pressure has an important influence on the micro-structure of nano- ZrO 2 films, also found that the crystallitic size and different micro-structure influenced the laser damage threshold. The obtained results showed that laser damage threshold of polycrystalline structure is obviously higher than that of amorphous structure.
CARBON NANOTUBES USED IN ELECTROANALYSIS
Authors: HU C. G. , FENG B.
Published: April 2005

The fabrication of the carboxyl-modified CNT electrode was described. The electroanalytical investigation of sulfadiazine has been conducted in alkaline aqueous solution at the CNT electrode by voltammetry. Highly reproducible and well-defined cyclic voltammograms were obtained for sulfadiazine with a very good signal to background (S/B) ratio. However, no fouling of the electrode was observed at the CNT electrode within the experimental period of several hours, which illustrated that the CNT electrode was much better than traditional electrodes. Meanwhile, the detection of trace sulfadiazine in milk was also conducted by cyclic voltammetry with satisfactory ratio of recovery, indicating that the nanotube electrode can be used in routine monitoring of sulfadiazine residues in food.
EXPERIMENTAL STUDY ON PHASE CHANGING & MASS FLOW CHARACTERISTIC OF LIQUEFIED CO2 IN ADIABATIC CAPILLARY TUBES
Authors: TONG M. W. , YAN J.
Published: April 2005

This paper firstly presented a physical model, which is designed to study on the phase change of liquefied carbon dioxide in an adiabatic capillary tube. The study mainly gained corresponding temperature at a certain point of adiabatic capillary tubes, which external diameters were kinds of 3.0mm & 1.7mm, lengths were kinds of 4.0m & 3.3m, Based on the results, the author deduced the process of phase change and gas-liquid mixture of CO 2 in an adiabatic capillary tube. And also the author researched into the mass flow characteristic of liquefied CO 2 in adiabatic capillary tubes.
PREPARATION OF VANADIUM CATALYST CONTAINING NANO-V2O5 PARTICLES
Authors: WANG WEI , GAO JIACHENG , WANG YONG , ZHOU JIAN
Published: April 2005

A new preparation process of the vanadium catalyst with nano- V 2 O 5 particles was introduced in this paper. The inorganic sol-gel method is used to prepare the sols and gels with p nano- V 2 O 5 particles. The morphology, size and distribution of the nano- V 2 O 5 particles in the sols-gels and vanadium catalyst had been studied by TEM, SEM, XRD and DSC. The results show that with the w/v (the ratio of water and vanadium) declining, the morphology of the nano- V 2 O 5 particles varies from needle to near-ball then to sphere; the better process parameter to prepare the sols and gels with nano- V 2 O 5 particles is 800~860°C×10~15min; the sols and gels and catalyst with 30~60nm V 2 O 5 particles had been obtained by this process.