bluuebunny/crossref_metadata_2025 huggingface dataset:
DC TRANSPORT PROPERTIES IN GdSr2RuCu2Oy COMPOUND
Authors: NIGRO A. , SAVO B. , VECCHIONE A. , GOMBOS M. , NOCE C. , PETTI S. , PACE S.
Published: April 2003

Dc transport properties of sintered samples of GdSr 2 RuCu 2 O y have been investigated in the superconducting state, at temperature ranging between 4.2K and 40K. To understand the origin of dissipation mechanism in these materials, the temperature dependence of the electrical resistivity has been analyzed at different bias currents. A thermally activated behavior has been clearly found in the Arrhenius plots of the data. The normalized critical current density as a function of the temperature has been also reported.
SYNTHESIS, MORPHOLOGY AND STRUCTURAL PROPERTIES OF (GD,ND)SR2RUCU2O8 SAMPLES
Authors: VECCHIONE A. , GOMBOS M. , TEDESCO C. , IMMIRZI A. , MARCHESE L. , FRACHE A. , NOCE C. , PACE S.
Published: April 2003

NdSr 2 RuCu 2 O x material has been prepared as polycrystalline powder by solid state reaction. The compound has been investigated by synchrotron x-ray powder diffraction and scanning electron microscopy. The experimental results show that the average crystal structure is a disordered cubic perovskite with Nd and Sr cations occupying the same site and the same substitution is found for Cu and Ru atoms. A comparison between the crystal structure and morphology of this compound and the superconducting tetragonal GdSr 2 RuCu 2 O 8 is also discussed.
POSSIBLE OBSERVATION OF TUNNELING CURRENTS IN NdBaCuO SUPERCONDUCTING THIN FILMS
Authors: NIGRO A. , ROMANO P. , SAVO B.
Published: April 2003

Phenomena resembling a tunneling behavior have been observed on dc sputtered Nd1+xBa2-xu3Oy c-axis oriented films. The current voltage characteristics at 4.2K give evidence of quasiparticle tunneling current as usually measured in superconductor-insulator-normal metal or superconductor-insulator-superconductor junctions, with normal resistance values of about 10Ω. In the conductance curves, peak at about +/-16mV are clearly visible. An analysis of these features is presented up to temperatures close to the sample critical temperature.
ANALYSIS OF AC TRANSPORT MEASUREMENTS ON GDSR2RUCU2O8
Authors: VECCHIONE A. , ZOLA D. , NOCE C. , CARAPELLA G. , GOMBOS M. , COSTABILE G. , PACE S.
Published: April 2003

Low frequency transport measurements have been performed on GdSr 2 RuCu 2 O 8 pellets. The current-voltage curves measured show an irreversible behavior in whole range of temperature explored. From these curve a Curie temperature TcM=133 K and a superconducting critical temperature TcS = 14 K , with an onset temperature TcO=33 K , have been deduced. A simple phenomenological model assuming a non-linear inductance in series with a resistance has been proposed to explain experimental current-voltage curves. Within this model, the temperature dependence of some physical quantities has been also investigated.
EFFECTS OF A MAGNETIC FIELD ON THE MICROWAVE SURFACE IMPEDANCE OF Bi2Sr2CaCu2O8-x SINGLE CRYSTALS
Authors: SILVA E. , ROGAI R. , MARCON R. , SARTI S. , FASTAMPA R. , GIURA M. , GU G. D.
Published: April 2003

We present measurements of the field-induced change of the microwave surface impedance in optimally doped Bi 2 Sr 2 CaCu 2 O 8-x crystals. Measurements are taken with microwave fields in the (a,b) planes. A moderate (< 0.7 T) dc magnetic field is applied normal to the (a,b) planes. Measurements are taken for temperatures above 70 K. At fixed temperature, with increasing field the surface resistance presents a sharp onset at low fields, a steep rise then a plateau or a peak, followed by a second, slower rise with the field. The surface reactance presents similarly a steep raise at low fields above the onset, then a sudden decrease. We discuss the applicability of commonly established vortex motion models to the observed response, and we find that substantial inconsistencies emerge. Possible influences of the layered nature on the vortex response are investigated.
MAGNETIC FIELD ORIENTATION DEPENDENCE OF THE MICROWAVE RESPONSE IN YBa2Cu3O7-δ
Authors: SILVA E. , MARCON R. , FASTAMPA R. , GIURA M. , SARTI S.
Published: April 2003

We present microwave resistivity measurements at 21 GHz in YBa 2 Cu 3 O 7-δ thin film as a function of the temperature and the magnetic field. Measurements are taken in various relative orientations of the microwave current, dc magnetic field and c axis. Attention is focussed on measurements taken with the dc field parallel to the (a, b) planes. In moderate magnetic field, we show that the microwave magnetic response is made up of a vortex motion contribution, which can be described by conventional models, and a noticeable magnetic field induced increase of the quasiparticle density, which exhibits features typical of the existence of lines of nodes in the superconducting gap. We estimate the effective vortex viscosity for vortex motion across the (a, b) planes.
CHARACTERISATION OF Al DEFECTS IN SmBa2Cu3-XAlXO6+δ SUPERCONDUCTOR
Authors: SCAVINI M. , MOLLICA L. , BIANCHI R. , COSTA G. A. , FERRETTI M. , MELE P. , UBALDINI A. , GHIGNA P. , MALAVASI L. , MUSTARELLI P.
Published: April 2003

We present here a study on the effect of Al doping on the stucture of SmBa 2 Cu 3-X Al X O 6+δ (Sm-123) superconductor. Electron MicroProbe Analysis (EMPA) and X-Ray Powder Diffraction (XRPD) have revealed that the limit of a aluminium solubility x is between 0.5 and 0.6. For further doping BaAl 2 O 4 appears besides the superconducting phase. XRPD analysis on samples annealed in both oxidising and reducing conditions have revealed that the Al doping inhibits the tetragonal to orthorhombic phase transition. Nuclear Magnetic Resonance (NMR) analysis has shown that almost all the Al ions are coordinated tetrahedrally. The comparison between oxygen non-stoichiometry in pure and Al doped SmBa 2 Cu 3-X Al X O 6+δ suggests that the Al ions are ordered in clusters. A model is proposed for short-range order around Al doping ions which allows us to interpret the phase transition inhibition.
STUDY OF THE ELECTRODYNAMIC RESPONSE OF SmBa2Cu3O7-δ THIN FILMS IN THE MICROWAVE REGION
Authors: LAMURA G. , DI GENNARO E. , ANDREONE A. , BOFFA M. , CUCOLO A. M.
Published: April 2003

We present some experimental results on the temperature dependence of the surface resistance Rs and magnetic penetration depth λ of thin films of SmBa 2 Cu 3 O 7-δ. The samples, 0.25 μm thick, were grown by a dc sputtering technique on (100) K LaAlO 3 single crystal substrates, with critical temperatures ranging between 87 and 88 K Accurate measurements af the surface impedance Zs were performed down to 4 K by means of a dielectrically loaded cavity operating in the microwave region (20 GHz). Both λ and Rs show a monotonic temperature behavior, with no evidence of low temperature up-turn characteristic of other rare earth based cuprates like GdBa 2 Cu 3 O 7-δ. At low temperatures, we observed am almost linear behavior of λ with a slope of ~ 0.3 nm/K up to 25 K, as expected in a d-wave pairing scenario. The real part of complex conductivity σ1, shows a bump at around 40 K, in agreement with previous reports.
CORRELATION OF CRITICAL TEMPERATURES AND ELECTRICAL PROPERTIES IN TITANIUM FILMS
Authors: GANDINI C. , LACQUANITI V. , MONTICONE E. , PORTESI C. , RAJTERI M. , RASTELLO M. L. , PASCA E. , VENTURA G.
Published: April 2003

Recently transition-edge sensors (TES) have obtained an increasing interest as light detectors due to their high energy resolution and broadband response. Titanium (Ti), with transition temperature up to 0.5 K, is among the suitable materials for TES application. In this work we investigate Ti films obtained from two materials of different purity deposited by e-gun on silicon nitride. Films with different thickness and deposition substrate temperature have been measured. Critical temperatures, electrical resistivities and structural properties obtained from x-ray are related to each other.
MICROSTRUCTURE AND THERMAL OXIDATION OF CUBE TEXTURED NiCrW METALLIC SUBSTRATE FOR HTS COATED CONDUCTORS
Authors: TUISSI A. , VILLA E. , ZAMBONI M.
Published: April 2003

The non-magnetic highly resistant to oxygenation Ni 88 Cr 8 W 4 tape demonstrated to be a good metallic substrate for the production high Tc coated conductors. In this work rhe rolling assisted biaxially textured substrates (RABiTS) method has been used to promote a sharp (100)[001] texture on NiCrW metallic tape. The influence of the critical processing parameters on the cube texture development of the tape is investigated Moreover thermal oxidation of the textured NiCrW substrate has been performed at several conditions to study the oxide growth on the surface. Electron BackScatter Diffraction (EBSD) analysis was used for high resolution crystal orientation mapping of the surfaces. The microstructure of the substrates has also been investigated by X-ray and SEM. Differential thermal analysis (TG/DTA) was used to study the oxidation behavior of the NiCrW tapes.
WETTING OF YBCO BY LIQUID SILVER
Authors: COSTA G. A. , MELE P. , LIONELLO A. , MORBELLI L.
Published: April 2003

The sessile drop technique was used to study the wettability behaviour of silver on sintered YBCO substrates. The temporal evolution of wetting angle at a temperature of 980°C is reported. SEM/EDS analysis on both surface and sectian of YBCO/Ag samples was performed: silver collects in particles, filling substrate pores in a layer of 200 microns under the silver drop. In this superficial region silver also induces partial melting of YBCO at a temperature highly lower than usual. The nature of this phenomenon is explained.
NELSON'S STOCHASTIC MECHANICS BY MEANS OF FEYNMAN PATH INTEGRALS
Authors: BOTELHO LUIZ C. L.
Published: April 2003

We show that Nelson's stochastic mechanics suitably formulated as a Hamilton–Jacobi first-order equation leads straightforwardly to the Feynman path integral formulation of quantum mechanics.
PREPARATION AND HOMOGENEITY OF LANTHANIDE-DOPED CERIA NANOCRYSTAL DISPERSIONS
Authors: HARTRIDGE A. , BHATTACHARYA A. K.
Published: April 2003

Aqueous sols of solid solutions of the general formula Ce 1-x Ln x O 2-x/2□x/2 (Ln=entire lanthanide range, x = 0–0.50 and =anion vacancy) were synthesized using inorganic materials. The sols contained single-phase nanocrystals with particle sizes between 7–20 nm from photon correlation spectroscopy and crystallite sizes around 5 nm from X-ray diffraction. The nanocrystals were dispersed on an amorphous silica support and individual crystals examined for composition and structure by high-resolution TEM/EDAX. High-resolution pictures showed the nanocrystals to be between 4–6 nm in size, in agreement with X-ray diffraction results. Conical dark field and bright field pictures of the same area highlighted nanocrystals to be analyzed and microdiffraction of these crystals showed spot patterns of various individual planes of the fcc fluorite lattice giving lattice parameters, depending on dopant, between 5.6–5.9 Å. EDAX analysis of individual crystals compared closely to each other, to that of an average over a large area and to that of the nominal composition.
RESONANCE FLUORESCENCE THEORY ANALYZED BY SUPERSYMMETRIC TRANSFORMATION
Authors: FAN HONG-YI , LIANG XIAN-TING
Published: April 2003

In this paper, use is made of supersymmetric transformation to discuss resonance fluorescence of two-level atom driven by a strong laser field and that of three-level atom driven by two single-mode laser fields. The supersymmetric derivation makes the analysis of the physical processes more accurate, clear and efficient. As a result, some new physical processes are revealed by this method.
THE ADHESION OF COPPER FILMS COATED ON SILICON AND GLASS SUBSTRATES
Authors: CHEN M. , GAO J.
Published: April 2003

A new method is developed to evaluate the adhesion properties of thin films. This method is based on a composite hardness model. In our experiments, Cu films which were deposited on Si and glass substrates by pulsed laser ablation were indented and scratched by a Vickers microhardness tester and a diamond cutter, respectively. It was found that adhesion influenced the micro-hardness of films for soft films deposited on hard substrates. This result was explained by the elastic–plastic deformation mode of indentation.
FOURIER-INTEGRAL DESCRIPTION OF SUPERLUMINAL PHOTON TUNNELING
Authors: CARDONE FABIO , MIGNANI ROBERTO , OLKHOVSKY VLADYSLAV S.
Published: April 2003

We give a general Fourier-integral description of photon tunneling which can be applied either to electromagnetic waveguides and to optical devices. Moreover, we extend to the case of frustrated total internal reflection our previous treatment of superluminal tunneling of evanescent waves in terms of a spacetime deformation.
PERIODIC HIERARCHICAL DEPOSITION
Authors: POSAZHENNIKOVA ANNA I. , INDEKEU JOSEPH O.
Published: April 2003

Surfaces that undergo random impact of fragments of debris obeying a hierarchy of decreasing sizes are investigated by numerical simulation and analytic solution. The previously introduced hierarchical model for random deposition of debris is extended to allow for periodically varying deposition probabilities P for hills, Q for holes, and spatial rescaling factors λ. The logarithmic fractal roughness of the surface is found to be robust with respect to these time-dependent perturbations and the model can be solved exactly. The fractal amplitudes, which replace the usual notion of fractal dimension, are periodic functions of the deposition time. Asymptotically, for long times, the amplitudes approach a limit cycle, which can be interpreted as the result of an interaction between the bare amplitudes associated with separate processes with constant deposition parameters. We distinguish amplitude repulsion, attraction, neutrality, coincidence and auto-repulsion. We also solve analytically the transient regime of exponential decay towards asymptotia.
THERMOELECTRIC PROPERTIES OF Ti-DOPED SiC/TiCx COMPOSITE SYNTHESIZED BY TPPP METHOD
Authors: CHEN HONG , YIN YUZHE , HE YUANJIN
Published: April 2003

To improve thermoelectric properties, we attempt to dope Ti into SiC-based composite by transient plastic phase process (TPPP) method. The final result is composed of the functional phase SiC and the reinforcement phases TiC x and TiSi 2. The process of doping is the diffusion of Ti in TiC x solid–solution into SiC grain at high temperature. When the initial SiC is α-type of 5 μm size, the Seebeck coefficient S is less than 10 μV/K at room temperature. SEM photograph shows the reason being that doping is very weak. We change the initial SiC to the β-type of 90 nm size to aid doping. It is observed that S can be significantly improved to 46.3 μV/K at room temperature. When the temperature rises, the improvement is even greater. Measurements of the lattice parameter of β- SiC show that the parameter parallel to the Si–C layer is almost unchanged and the parameter perpendicular to the Si–C layer increases by about 0.48%, which demonstrated that Ti has been successfully doped into the SiC grain and exists as interstitial impurities.
A DYNAMICAL METHOD FOR DETERMINING THE ELASTIC CONSTANTS AND RELAXATION PARAMETERS IN NEMATIC LIQUID CRYSTALS
Authors: PETRESCU EMIL , MOTOC CORNELIA , MANAILA DOINA
Published: April 2003

The theoretical model proposed by Pieranski et al.3 to describe the phenomena occurring in nematic liquid crystals when the magnetic field is suddenly varied was extended by considering higher powers of the distortion angle for the nematic director. Equations giving the time evolution of the number of extinctions in the light transmission were obtained. These equations depend on some relaxation parameters (the time constants τA and τB intervening when the magnetic field was switched "on" or "off", respectively) and on the ratio of elastic constants. The equations were solved numerically and good agreement with the experimental data was obtained for the nematic MBBA.
THE QUANTUM–CLASSICAL CORRESPONDENCE IN CHAOTIC DYNAMIC SYSTEMS
Authors: SU WEN YONG , LI QIAN SHU
Published: April 2003

The Wigner distribution function is computed for a particle in a double-well potential and an oscillatory driving force. The evolutions of the Wigner functions show clearly the relations with classical trajectories' characters: chaotic or regular. By choosing suitable parameters, we find the phenomena of localization and delocalization.
MINIMUM UNCERTAINTY SU(1,1) COHERENT STATES FOR NUMBER DIFFERENCE — TWO-MODE PHASE SQUEEZING
Authors: FAN HONG-YI , SUN ZHI-HU
Published: April 2003

For the two-mode photon number-difference operator D = a†a -b†b and the Noh, Fougers and Mandel (NFM) operational phase operator [Formula: see text], we introduce the concept of number-difference-phase squeezing. We then find a new minimum-uncertainty state for number-difference-phase squeezing, which turns out to be a special combination of generalized SU(1,1) coherent state. As a by-product, a new orthonormal and complete representation in two-mode Fock space made up of R†n|m, m> is found.
RELATION BETWEEN UNCERTAINTY EXPONENT AND MEAN LIFETIME OF CHAOTIC TRANSIENT FOR MAP ON ANNULUS
Authors: PAAR V. , PAVIN N.
Published: April 2003

For a map on the annulus, it is tested numerically that, within errors of the calculation of 0.4%, the inverse of the mean lifetime of chaotic transient is equal to the product of the uncertainty exponent and the Lyapunov exponent. The second-order term in the Taylor series expansion for inverse lifetime has no effect within the precision of the calculation.
DISORDER-INDUCED INSTABILITY OF THE QUANTUM CRITICAL BEHAVIOR OF BOSE FLUIDS
Authors: TAKOV I. P.
Published: April 2003

The one-loop renormalization-group equations for Bose fluids with randomly distributed impurities are derived and analyzed with the help of a double ∊-expansion. While the low temperature critical behavior is similar to that of classical systems with extended impurities, the proper quantum critical behavior of disordered Bose fluids at zero temperature is unstable with respect to randomly distributed impurities with short-range correlations.
TOPOLOGICAL TRANSPORT IN EDGE STATE OF HIERARCHIES
Authors: BANERJEE DIPTI
Published: April 2003

We have given here a topological approach of edge current flowing through one compressible state at the edge hierarchies. The shift quantum number visualized through deviation of the Berry phase has played a major role in realizing the edge transport theory.
A COMMENT ON THE "PEIERLS SUBSTITUTION"
Authors: FUNG M. K. , WANG Y. F.
Published: April 2003

We present a new way of doing perturbation theory of the Landau problem. We introduce two sets of raising and lowering operators. One set is for shifting the coordinates of the center of the cyclotron orbit. The other set is for shifting the energy levels. This method is compared to that of the Peierls substitution.
INTERACTION EFFECTS ON AC CONDUCTIVITY IN DISORDERED METALLIC THIN FILMS
Authors: YANG Y. H.
Published: April 2003

The interaction theory has been generalized to the case of anisotropic disordered electron systems. The interaction correction to ac conductivity in a disordered metallic thin film has been calculated in the weakly localized regime. The result turns out that the frequency dependence of this correction changes from three-dimensional (3D) to two-dimensional (2D) behavior with decreasing the film thickness d, and the dimensional crossover occurs at [Formula: see text], with Dz, and Ω being the perpendicular diffusion constant and the applied frequency, respectively.
HIGHER-ORDER SQUEEZING DEGREE IN MESOSCOPIC JOSEPHSON JUNCTION IN THE PRESENCE OF NONCLASSICAL RADIATION FIELD
Authors: POPESCU V. A.
Published: April 2003

Higher-order squeezing degree in mesoscopic Josephson junction of a circular superconducting ring can be improved if the electromagnetic field is initially in a successive squeezed vacuum state. We compare our method with the usual procedure for higher-order squeezing and consider the effect of different small inductances on the 2Nth-order squeezing degree for quantum current.
HIGHER-ORDER SUCCESSIVE SQUEEZED THERMAL STATES
Authors: POPESCU V. A.
Published: April 2003

The statistical properties of the higher-order squeezed thermal states can be improved by successive application of the squeeze operator. We compare our method with the usual procedure for higher-order squeezing.
OXYGEN INTERACTION WITH Rh(111) AND Ru(0001) SURFACES: BOND-FORMING DYNAMICS
Authors: SUN CHANG Q.
Published: April 2003

A new description of bonding and band-forming is presented for the nature and dynamics of O–Rh(111) and O–Ru(0001) surface bonding and its consequences on the behavior of atoms and electrons at the surfaces. The sp-orbital hybridization and electron transportation define that oxygen retains inside the hcp hollow site throughout the course of reaction in which O -1 forms and then O -2-hybrid follows with production of nonbonding lone pairs and the lone-pair induced antibonding dipoles. Consequently, the valence band and surface morphology are modified with the corresponding features, and the radial and pairing-row reconstruction arises in the corresponding phases.
UNIVERSAL BEHAVIOR OF BOSE-GLASS EXPONENTS IN 250 MeV Ag+17 ION IRRADIATED YBa2Cu3O7-δ MELT-TEXTURED SAMPLES
Authors: DIVAKAR UJJUAL , BHALLA G. L. , TRIGUNAYAT G. C.
Published: April 2003

Columnar defects along the c-axis in YBa 2 Cu 3 O 7-δ melt-textured samples have been created by 250 MeV Ag +17 ion irradiation. Angle-dependent magnetoresistance measurements have been carried out to examine the Bose-glass theory. The Bose-glass temperature "T BG " has been found to be maximum along the direction of the columnar defects. The value of the critical angle, θ cri , is found to be ~ 30°.
DRASTIC VIOLATION OF THE NORMALIZATION CONDITION BY THE CONVENTIONAL ON-SHELL RENORMALIZATION IN QED
Authors: SEKE JOSIP
Published: April 2003

It is proved that the conventional on-shell renormalization leads to a drastic violation of the initial normalization condition in both nonrelativistic and relativistic QED. Thus, in the case of the U-matrix and spectral line-shape renormalizations (where, because of the mentioned normalization violation, no conventional renormalization procedure can be used), the absolute necessity for the application of the author's recently developed new consistent, complete renormalization method is pointed out.
STRONG DEPENDENCE OF SUPERCONDUCTING TRANSITION TEMPERATURE (Tc) ON THE RARE EARTH IONIC SIZE IN REBaSrCu3O7 (RE = Y, Dy, Nd AND La) SERIES
Authors: AWANA V. P. S. , MALIK S. K. , CARDOSO CLAUDIO A. , DE LIMA O. F. , GUPTA ANURAG , SEDKY A. , YELON W. B. , PRASAD RAM , NARLIKAR A. V.
Published: April 2003

The REBaSrCu 3 O 7 compounds with RE = Y, Dy, Nd and La have been synthesized by the standard solid-state reaction route. Superconducting transition temperatures (T c ), as measured by ac susceptibility technique, are 81 K, 79 K, 62 K and 45 K for samples with RE = Y, Dy, Nd and La, respectively. The rare earth dependence of T c in the REBaSrCu 3 O 7 series is quite different from that observed in the REBa 2 Cu 3 O 7 (RE:123) series where T c is nearly independent of the choice of the RE (except when RE = Ce, Pr and Tb). Neutron diffraction studies have been carried out on the REBaSrCu 3 O 7 compounds and structural details have been obtained from the Rietveld analysis of the room-temperature neutron diffraction data. The compounds with RE = Y, Dy are found to crystallize in the orthorhombic RE:123 structure (space group Pmmm) with orthorhombicity considerably smaller than that of the RE:123 compounds. In fact, the orthorhombicity reduces so much that the REBaSrCu 3 O 7 compounds with light rare earths, RE = La and Nd, are tetragonal or almost tetragonal.
CHARGE DENSITY WAVE INSTABILITY IN TlMo6O17
Authors: XIONG RUI , XIAO QINGMING , SHI JING , LIU HAILIN , TANG WUFENG , TIAN DECHENG , TIAN MINGLIANG
Published: April 2003

The charge density wave instability in the quasi-two-dimensional conductor thallium purple molybdenum bronze TlMo 6 O 17 was carefully examined by studying the temperature dependence of resistivity, thermoelectric power (TEP) behavior and magnetic susceptibility. A metal-to-metal transition was confirmed near 110 K in TlMo 6 O 17 due to the partial opening of a gap at the Fermi surface and the driving of charge density wave.
APERIODIC SELF-REPLICATING INORGANIC STRUCTURES
Authors: BURSILL LESLIE A.
Published: April 2003

A prototype model is introduced for self-replicating octahedral shell structures. The structure is inherently aperiodic and unable to grow like a normal crystal. Conditions under which this growth mechanism may become favored energetically are discussed. High-resolution electron microscope images of the clay mineral allophane, an analog of the spheroidal fullerenes, are described. Kinetic equations are derived assuming an autocatalytic self-replicating growth mechanism for this model. More general mathematical treatments of self-replicating systems are also reviewed and discussed.
APPLYING THE 1/N APPROXIMATION TO THE DERIVATION OF THE BAND ENERGY OF THE HARPER EQUATION
Authors: PAPP E.
Published: April 2003

The 1/N approach to the Harper equation proposed previously is generalized towards performing the pertinent band-energy description. Leading forms and corrections proceeding to first order in the magnetic field are written down. The energy reflection symmetry has also been discussed.
COMPETITION BETWEEN SUPERCONDUCTIVITY AND CHARGE STRIPE ORDER IN HIGH-Tc CUPRATES
Authors: BASKARAN G.
Published: April 2003

Members of the high-T c cuprate family (with defect-free CuO 2 planes) are suggested to have an "Intrinsic single-layer superconductingT c ", larger than the experimentally observed T c , at a given hole concentration. This difference occurs to varying degrees among the different members due to an anomalous response of the d-wave superconducting state to self-generated charge perturbations. In particular, any quasielastic charge stripe order, arising from electron–electron and electron–lattice coupling, can suppress the large intrinsic superconducting T c . Existing experimental results on the wide T c variation in the single-layer cuprate families, such as the low T c (≈ 38 K, 33 K) of LSCO and Bi-2201 compared to the high-T c (≈ 95 K, 98 K) of Tl-2201 and Hg-1201, the strain-induced increase in T c (25 to 50 K) observed in LSCO are qualitatively explained by our mechanism. We predict that under proper epitaxial strain, the T c of LSCO and Bi-2201 should increase from the 30's all the way up to the intrinsic T c ~ 90 K at optimal doping.
AN EFFECTIVE FIELD MODEL TO HIGH TEMPERATURE SUPERCONDUCTORS: FITTING OF THE ENERGY GAP TO THE EXPERIMENTAL RESULTS OF THE Bi2Sr2CaCu2O8
Authors: BASTONE E. C. , SILVA P. R.
Published: April 2003

We use an effective field model (transverse Ising model) to describe the dependence on the temperature of the energy gap of some two-dimensional (2D) superconducting systems. The order parameter of this model is put in a direct correspondence with that of the Ising model. Then, we use the exact relations for the spontaneous magnetization of the Ising model in some 2D lattices as a means to fit the experimental results of Bi 2 Sr 2 CaCu 2 O 8 films obtained through reflectivity measurements by Brunel et al. [Phys. Rev. Lett.66, 1346 (1991)] and the argon-annealed Bi 2 Sr 2 CaCu 2 O 8 samples investigated by Staufer et al. [Phys. Rev. Lett.68, 1069 (1992)] through Raman scattering. The zero temperature energy gap Eg(0) relations were evaluated in various 2D lattices and also in the (3D) simple cubic lattice for comparison. In the square lattice case, we obtained Eg(0) = 3.52kT c , coincidentally the same number as the BCS result, and in the triangular lattice case, we get Eg(0) = 3.30kT c , in agreement with the experimental findings of Brunel et al.13
MEASUREMENT OF PRESSURE-BROADENING LINEWIDTHS OF NO FROM THE FITTING OF LMR SPECTRA WITH CORRECTIONS OF INSTRUMENTAL BROADENING
Authors: LIN JIE-LI , LIU YU-YAN , LIU HONG-PING , QUO YUAN-QING , LIU XIAO-YONG , LI FENG-YAN , LI JIN-RUI
Published: April 2003

For absorption lines, the distortion of spectral lines by experimental spectrometers must be considered in measuring linewidth which has been investigated by many authors. While in the derivative spectrum, we managed to give the corrections of instrumental broadening and distortion to obtain accurate linewidths. We developed a universal fitting program which was explored together with the method of correction in the fundamental band spectra of LMR of NO. The uncorrected halfwidths were compared with the corrected values, which were obtained from the program. The results of comparison are very satisfactory and demonstrate their useful application to analyze experimental spectra.
THERMOMETRY BETWEEN 10–300 K USING GaAlAs DIODE
Authors: OTA S. B. , OTA SMITA
Published: April 2003

The forward characteristics of a cryogenic GaAlAs temperature sensor diode (Lake Shore Cryotronics, Inc.) have been presented in the temperature range 10–300 K and for fixed current values between 10 nA and 500 μA. The upturn in the forward characteristic below 35 K was found to shift to lower temperatures by reducing the current. The sensitivity at low temperature was found to reduce with current (I) according to a power law. The sensitivity at high temperature was found to increase linearly with decrease in lg (I).
AC MAGNETIC SUSCEPTIBILITY INVESTIGATION OF THE INTERGRAIN VORTEX PINNING INVOLVING Er IONS IN BULK (Bi1.6Pb0.4)(Sr1.8Ba0.2)(Ca1-xErx)2Cu3Oy SUPERCONDUCTOR
Authors: POP A. V.
Published: April 2003

Bulk superconducting samples with composition ( Bi 1.6 Pb 0.4)( Sr 1.8 Ba 0.2)( Ca 1-x Er x)2 Cu 3 O y (0 ≤ x ≤ 0.02 Er ) were prepared by conventional solid-state reaction. X-ray diffraction confirmed that with increasing Er concentration, the volume fraction of 2223 phase decreases. The intergranular vortex dynamics (and the effective pinning barrier) of the bulk system have been investigated by ac susceptibility as a function of temperature, frequency and ac field amplitude. The effect of Er ion on the intergrain vortex pinning was characterized quantitatively by using a flux diffusion model in which the effective pinning barrier depends nonlinearly on the current density.
SOFT PHONON RESISTIVITY IN CONDUCTIVE SrTiO3
Authors: SUGAWARA K.
Published: April 2003

Electrical resistivity due to soft phonon (SPR) is proposed. To test SPR, resistivity measurements have been carried out for conductive single-crystal samples of the SrTiO 3 system; Sr 1-x La x TiO 3, SrTi 1-y Nb y O 3 and SrTiO 3 implanted with Fe, Cr or B. Experiments reveal a weak SPR for Sr 1-x La x TiO 3, but no noticeable SPR was found for SrTi 1-y Nb y O 3. Resistivity measurements on the ion-implanted specimens reveal rather profound SPR for low-dose (semiconducting) specimens but weak SPR for high-dose (metallic) specimens. These results indicate that the magnitude of SPR may be carrier-concentration dependent or crystallinity dependent. A possible profound SPR is proposed for SrTiO 3 under optical illumination and superlattices. Also proposed is a potential application of SPR to soft-phonon devices (SPD).
SPONTANEOUS SUPERCURRENTS IN MAGNETO-SUPERCONDUCTING SYSTEMS
Authors: LYUKSYUTOV I. F. , POKROVSKY V. L.
Published: April 2003

We predict the appearance of spontaneous superconducting currents in the ground states of the heterogeneous magneto-superconducting systems. These currents appear due to magnetic interaction between the supercurrent in the superconducting subsystem and the magnetic moment in the magnetic subsystem even if the magnetic field from the magnet does not penetrate into the superconductor. We propose several configurations in which spontaneous currents are expected.
JOSEPHSON COUPLING STRENGTHS AND OVERLAPPING OF DIMENSIONS IN THE CROSSOVER REGION IN IRRADIATED MULTIPERIODIC HIGH-Tc SUPERCONDUCTORS
Authors: GHOSH A. K. , BASU A. N.
Published: April 2003

We have bombarded (Bi,Pb)-2223 superconductors with 40 MeV α-particles to study the effect of irradiation on the dimensional crossover in fluctuation-induced conductivity. The pair-breaking parameter decreases with the irradiation and suppression of the critical temperature is obtained. The structural modification of the layer in the high-T c superconductors induced by irradiation affects the extent of the overlapping region in the process of dimensional crossover. The width of the overlapping regime is evaluated for the various doses of irradiation using the different possible relations for the normal state resistivity. The variation of the transition width (Δ T0) with the increase in dose of irradiation is discussed in terms of modifications of interlayer and intralayer Josephson coupling strengths.
ON Zr SUBSTITUTION IN T′-TYPE Nd–Ce–Cu–O SYSTEM
Authors: GUPTA SANJAY , MAZUMDAR CHANDAN , PADALIA B. D. , PRAKASH OM , NAGARAJAN R. , GUPTA L. C. , PATTANAIK ARUN K.
Published: April 2003

The effect of tetravalent Zr substitution (≤2 at%) at the Cu site in T′-type Nd 2-x Ce x CuO 4-δ (NCCO), x = 0.12, 0.14, 0.15, on the superconducting (SC) behavior is investigated. EDX analyses of the samples clearly reveal the presence of only ~0.5 at% Zr in the T′-phase. Irrespective of the Ce content (0.12 ≤ x ≤ 0.15), T c is found to depress with Zr. A fall in T c of ~2 K is observed due to 0.5 at% Zr 4+ in x = 0.14 samples, while the NCCO (x = 0.12) on substitution of Zr (expected to dope 2 electrons per Zr 4+ and induce superconductivity) remains non-SC. The reported conjecture regarding T c inducement due to the carrier addition of 0.03 (per formula unit) arising from 3 at% In 3+ (or Ga 3+) substitution for Cu in Nd 1.88 Ce 0.12 CuO 4-δ [Ayoub et al., PhysicaC170, 211 (1990); Felner et al., Phys. Rev.B40, 11366 (1989)] is not applicable for the Zr-substituted NCCO.
DIRECTED MOTION OF TWO-HEADED BROWNIAN MOTORS
Authors: LI YUXIAO , WU XIZHEN , ZHUO YIZHONG
Published: April 2003

Two-headed Brownian motors based on potential fluctuations are studied. Directed motion of the Brownian motor is induced by the shift transitions of the ratchet-like periodic potential. The Brownian motors with different lengths of necks can move in opposite directions. The efficiency of the Brownian motors to do work against external force is higher than the flashing thermal ratchet.
TEMPERATURE DEPENDENCE OF THE COMPLEX MAGNETIC SUSCEPTIBILITY FOR THE OXIDIC Y1-xZrxBa2Cu3O7-δ SUPERCONDUCTORS
Authors: DEAC I. G , REDAC R. , SBARCIOG C. , POP O. , POP I.
Published: April 2003

The thermal variation of the complex magnetic susceptibility χ(T) = χ′ (T) + iχ″ (T) for the oxidic superconducting compounds Y 1-x Zr x Ba 2 Cu 3 O 7-δ, x = 0.01, 0.05 and 0.10 was investigated. The real part of the complex magnetic susceptibility χ′ (T) below critical temperature T c (χ) is negative and is lost in two stages when the temperature decreases. The inflexion point on the χ′ (T) curve corresponds to the two peaks on the temperature dependence of the imaginary part, χ″ (T), of the complex magnetic susceptibility and represents the critical temperatures for the intergranular superconductivity [Formula: see text], i = 1, 2, 3 and for the intragranular superconductivity [Formula: see text], i = 1, 2, 3. The concentration dependence of the critical temperatures is almost linear for the investigated compounds Y 1-x Zr x Ba 2 Cu 3 O 7-δ, x = 0.01, 0.05 and 0.10. The presence of the second weak peak or its absence on the χ″ (T) curves at [Formula: see text]characterizes an intense intergranular coupling.
CORRECT ELECTRON-PROPAGATOR AND U-MATRIX RENORMALIZATION REPLACING THE INCONSISTENT ON-MASS-SHELL RENORMALIZATION AND THE RENORMALIZED NATURAL LINE SHAPE
Authors: SEKE JOSIP
Published: April 2003

After pointing out the drastic violation of the U-matrix boundary condition by the conventional quantum-field–theoretical on-mass-shell renormalization of the electron propagator, a new consistent renormalization concept (without mass and charge renormalization) is presented. From the correctly renormalized bound-electron propagator (respectively, U-matrix), the natural line shape is for the first time, after 50 years, correctly calculated in QFT.
NEW APPLICATIONS OF <η| REPRESENTATION IN THERMAL FIELD STATISTICS
Authors: FAN HONG-YI , WANG HUI
Published: April 2003

We derive <η| representation of density matrices ρ for radiation fields, where <η| is the newly established coherent thermal state [H.-Y. Fan and Y. Fan, Phys. Lett.A246, 242 (1998)] in thermal field dynamics. We then apply <η|ρ> to calculate thermal averages and develop the theory for the quantum phase space distributions. We also study the quantum master equations in the <η| representation and find it has similar evolving property to the coherent representation of a pure state.
ANOMALOUS HALL EFFECT NEAR Tc IN HIGH-Tc SUPERCONDUCTORS
Authors: CHANG P. H. , YANG H. C. , HORNG H. E.
Published: April 2003

A possible mechanism in the anomalous Hall coefficient in mixed state of high-T c superconductors was presented in this paper. The Hall voltage due to flux creep is the origin of the observed Hall anomaly. The calculated Hall coefficient exhibits a sign change as well as a re-entry behavior, which agree with experiments, qualitatively.
A COST EFFECTIVE X-RAY DETECTOR FOR PLASMA FOCUS DIAGNOSTICS
Authors: ZAKAULLAH M. , AKHTAR IJAZ , MEHMOOD S. F. , WAHEED A. , MURTAZA G.
Published: April 2003

A time-resolved rugged X-ray detector (XRD) which may be used in intense radiation environment is developed. The detector is used to study the X-ray emission from a low-energy (2.3 kJ) Mather-type plasma focus energized by a 32 μF single capacitor, using hydrogen and argon (3:2) mixture as gas filling. In the detector, the electron emitter is made of nickel and aluminum. The sensitivity of the detector with nickel cathode is found to be very low. No signal could be recorded by masking the detector with even the 2 μm thick Al foil. When Al cathode is used in the XRD, the sensitivity of the detector increases abruptly. To stop the optical/ultraviolet radiation from approaching the active area, it is masked with 6 μm Al filter. It is found that an XRD with nickel cathode is not useful for X-ray detection in a low-energy plasma focus. However, due to its excellent response to vacuum ultraviolet radiation (≤600 Å), it may find application in the study of the axial rundown of current sheath, and its velocity. The X-ray emission from focus plasma is the highest at 0.5 mbar. With increase in pressure, the emission is dropped. At filling pressures of 2.0–2.5 mbar, the X-ray emission increases again. High X-ray emission at 0.5 mbar is due to interaction of energetic electrons in the current sheath with the anode surface, whereas moderately high emission at 2.0–2.5 mbar is caused by an axially moving shockwave.
EPR OF Mn2+ AND Fe3+ IONS DOPED IN BISMUTH–BORATE GLASSES
Authors: STEFAN R. , SIMON S.
Published: April 2003

Experimental EPR results of 99.5%[x B2O3 (1-x) Bi2O3]0.5%MO glass samples (MO = MnO, Fe2O3 and 0.07 ≤ x ≤ 0.8) systems are presented. The resonance absorptions are centered at g ≈ 4.3 and g ≈ 2.0. For manganese-doped samples both lines show hyperfine structure for certain values of Bi/B ratio. In addition to these lines a well defined shoulder at g ≈ 9.8 is recorded from the samples doped with iron. The changes in matrix composition, corresponding to different values of x, induce changes in the surroundings of the resonance centers.

Structural data obtained from the EPR measurements indicate various sites for Mn2+ and Fe3+ ions in environments characterized by different crystalline field intensities. The EPR data also provides evidence that the redox effect of bismuth–borate matrices on the doped paramagnetic ions is a function of Bi/B ratio.
ENTANGLEMENT SWAPPING FOR TWO PAIRS OF EPR EIGENSTATES GENERATED VIA BELL MEASUREMENT
Authors: FAN HONG-YI
Published: April 2003

We demonstrate that a common eigenvector |η> (Einstein, Podolsky and Rosen, EPR states) of two particles' relatively coordinate and total momentum possesses a property that the projection (a Bell measurement) of two pairs of EPR states |η>1,2⊗| η'>3,4 onto the subspace spanned by 1,4<η″|, yields a EPR state |η″-η*-η′* >2,3 for particles 2 and 3. Entanglement swapping operator is also derived by virtue of the technique of integration within an ordered product of operators.
THEORY OF COMPLEX SCATTERING LENGTHS
Authors: HUSSEIN M. S.
Published: April 2003

We derive a generalized Low equation for the T-matrix appropriate for complex atom–molecule interaction. The properties of this new equation at very low energies are studied and the complex scattering length and effective range are derived.
NITROGENATION OF THE SAMARIUM–COBALT INTERMETALLIC, Sm2Co7
Authors: METHASIRI T. , THONGMEE S. , VARAMIT S. , TANG I. M.
Published: April 2003

The effects of nitrogenation on the 2:7 samarium–cobalt intermetallic, Sm2Co7 , are studied. The uptake of nitrogen by Sm2Co7 increases monotonically with the processing temperatures. The saturation magnetizations of Sm2Co7Nx are seen to increase initially with the nitrogen absorption, followed by decrease upon further nitriding. The behaviors of M s of the nitrides are explained within the framework of the simple Stoner picture of itinerant electron magnetism. The coercive force and maximum energy product increase with the nitrogen absorption.
SHORT-TIME DYNAMIC EXPONENTS OF AN ISING MODEL WITH COMPETING INTERACTIONS
Authors: ALVES NELSON , DRUGOWICH DE FELÍCIO JOSÉ ROBERTO
Published: April 2003

In this work the two-dimensional Ising model with nearest- and next-nearest-neighbor interactions is revisited. We obtain the dynamic critical exponents z and θ from short-time Monte Carlo simulations. The dynamic critical exponent z is obtained from the time behavior of the ratio [Formula: see text], whereas the non-universal exponent θ is estimated from the time correlation of the order parameter  ~ tθ, where M(t) is the order parameter at instant t, d is the dimension of the system and <(⋯)> is the average of the quantity (⋯) over different samples. We also obtain the static critical exponents β and ν by investigating the time behavior of the magnetization.
THE EFFECT OF 5% Sb DOPING ON HIGH Tc SUPERCONDUCTIVITY IN (Bi, Pb)2Sr2Ca2Cu3Oy COMPOUND
Authors: SIDDIQI SAADAT A. , AKHTAR BILQUEES , GHAURI IJAZ M.
Published: April 2003

The effect of a small amount of Sb doping (5%) on the formation of the high temperature superconducting phase has been investigated on the Bi 1.5 Pb 0.5 Sr 2 Ca 2 Cu 3 O y compound. It is observed that at 860°C the T c zero [Formula: see text] value depends on the sintering time. It first increases to a maximum value of 96 K and then decreases to a stable lowest value of 88 K. The samples have been characterized by X-ray diffraction (XRD), four probe electrical resistance and current density measurements. The XRD revealed the presence of two phases: an orthorhombic high-T c 2223 phases with lattice constants a = 5.395 Å, b = 5.508 Å, c = 37.0422 Å and another tetragonal low-T c 2212 phase with lattice constants a = b = 5.419 Å, c = 30.832 Å.
AC LOSSES OF SUPERCONDUCTING ACCELERATOR MAGNETS
Authors: KOVACHEV V.
Published: April 2003

We are focusing on the uncertainties of analytical and numerical analysis of AC losses in superconducting accelerator magnets working at a relatively high ramp rate. The loss experimental techniques are discussed as well as the source of error in the measurements. The correlation between the interstrand resistance of Rutherford cables and quench current behavior of superconducting magnets is addressed. The control of the critical current of full Rutherford cables by measuring the strands extracted from such cables is illustrated. The importance of cables curing temperature on microhardness and RRR of Cu-matrix of multifilamentary NbTi is pointed out.
IRON INFLUENCE ON OPTICAL AND MAGNETIC PROPERTIES OF LEAD-BISMUTHATE GLASSES
Authors: SIMON V. , POP R. , PUŞCAŞ N. N.
Published: April 2003

Results concerning the structural, optical and magnetic properties of x Fe 2 O 3 · (100 - x)[3 Bi 2 O 3 · 2 PbO ] glasses (0 = x = 20 mol%) are reported. The transparence in the infrared range was investigated. The homogeneous absorption cross section was determined from the optical absorption spectra using the density matrix formalism of the McCumber theoretical model. From the temperature dependence of reciprocal magnetic susceptibility, negative paramagnetic Curie temperatures have been found suggesting the antiferromagnetic nature of the magnetic interaction between the iron ions in the studied samples. The iron ions occur both in the (II) and (III) valence state. The Fe 2+/ Fe 3+ ratio was determined from the experimental values of the magnetic moments for all samples. The glass transition temperature with increasing Fe 2 O 3 content was also investigated.
PHOTON-BUNCHING, PHOTON-ANTIBUNCHING AND NONCLASSICAL PHOTON STATISTICS OF COHERENT LIGHT COUPLED TO A CUBIC NONLINEAR MEDIUM
Authors: PATHAK ANIRBAN , MANDAL SWAPAN
Published: April 2003

The quantum statistical properties of a single mode of the radiation field, prepared in the coherent state, interacting with a nonlinear medium of inversion symmetry are studied with the help of the usual two photon correlation function for zero time delay. We report the photon antibunching and sub-Poissonian photon statistics in addition to the usual photon bunching and the super-Poissonian photon statistics for an input vacuum field. The manipulation of the phase of input coherent light gives rise to the well known self induced transparency. The possible physical explanations for these events are presented.
DYNAMICS OF TWO ATOMS COUPLED TO A CAVITY FIELD
Authors: ROVERSI J. A. , VIDIELLA-BARRANCO A. , MOYA-CESSA H.
Published: April 2003

We investigate the interaction of two two-level atoms with a single mode cavity field. One of the atoms is exactly at resonance with the field, while the other is well far from resonance and hence is treated in the dispersive limit. We find that the presence of the non-resonant atom produces a shift in the Rabi frequency of the resonant atom, as if it was detuned from the field. We focus on the discussion of the evolution of the state purity of each atom.
HOW SIMPLE CAN THE PROTEINS BE: FROM THE PREDICTION OF THE CLASSES OF PROTEIN STRUCTURES
Authors: LI TANPING , WANG JUN , FAN KE , WANG WEI
Published: April 2003

The validity of complexity simplifications for proteins with different structural features may be different. In this paper, the simplification for proteins is studied using the ratios of successful prediction of structural class under a presumed amino-acid-grouping scheme with a composition-coupled method. It is found that for the α-class proteins, a two-letter alphabet may cover the degree of freedom to characterize the complexity of the class; for the β-class proteins, a 7-letter alphabet might indicate the minimal number of residue types to reconstruct the class feature of the natural proteins; for the α + β-class proteins and the α/β-class proteins, the redundancy of the compositions is weak and the simplification leads to a great loss of the information related to the corresponding structural classes.
AutoASC — A SYSTEM FOR AUTOMATIC ACQUISITION OF SENSE TAGGED CORPORA
Authors: MIHALCEA RADA , MOLDOVAN DAN I.
Published: April 2003

Many natural language processing tasks, such as word sense disambiguation, knowledge acquisition, information retrieval, use semantically tagged corpora. Till recently, these corpus-based systems relied on text manually annotated with semantic tags; but the massive human intervention in this process has become a serious impediment in building robust systems. In this paper, we present AutoASC, a system which automatically acquires sense tagged corpora. It is based on (1) the information provided in WordNet, particularly the word definitions found within the glosses and (2) the information gathered from Internet using existing search engines. The system was tested on a set of 46 concepts, for which 2071 example sentences have been acquired; for these, a precision of 87% was observed.