bluuebunny/crossref_metadata_2025 huggingface dataset:
Positive Magnetoresistance in Concentrated γ-CuMn Alloys — An Evidence for Electron–Electron Interaction
Authors: Chakraborty S. , Schnell B. , Thummes G. , Majumdar A. K.
Published: October 2003

High-resolution transverse magnetoresistance (TMR) data in γ- Cu 100-x Mn x alloys (x = 36, 60, 73, 76 and 83) are presented till 7.5 T at 4.2, 20.5 and 63 K and longitudinal (LMR) magnetoresistance at 4.2 K. They show positive magnetoresistance till 7.5 T in the Mn-rich (x≥60) alloys while an overall negative one in the alloy with x = 36 at all temperatures. However, the data at 4.2 K in x=36 clearly demonstrate a positive magnetoresistance till 3 T which becomes negative at higher fields. The data for the Mn-rich alloys (x ≥ 60) at 4.2 and 20.5 K are well described by the electron–electron interaction effects (EEI) along with localisation and normal magnetoresistance. In the two regions of high (4 to 7.5 T) and low (0 to 1 T) fields, distinctly dominant contribution of EEI effects compared to that of localisation has been observed. For x = 36, an additional term due to the cluster-glass (CG) phase (=-β CG H2) has to be considered in explaining its overall negative magnetoresistance. However, the EEI/localisation effects have hardly any significant contribution at 63 K. The contribution of the combined EEI and localisation effects has been separated convincingly from the normal magnetoresistance (C N ) and the cluster-glass (β CG ) terms. The temperature dependence of the normal magnetoresistance follows the Kohler's rule while the cluster-glass term shows a behavior similar to those of the dilute spin glasses. Moreover, the present interpretation of magnetoresistance is found to be very much consistent with that of the electrical resistivity (ρ(T)).
Study on Nonmagnetic Impurities in the Superconducting State of Two-Dimensional t-J Model
Authors: Tanaka Hideki , Kuboki Kazuhiro , Sigrist Manfred
Published: October 2003

We study the effect of nonmagnetic impurities in the superconducting state of the t–J model. The Bogoliubov de Gennes equation is derived using a slave-boson mean-field approximation, and we solve it numerically at T = 0. The dx2-y2-wave order parameter is suppressed near an impurity and the extended s-wave component is induced. We also find the local CDW-like feature due to the Friedel oscillations. This leads to the splitting of the expected zero-energy Andreev bound state. Therefore the system is unlikely introducing a localized state of other symmetry such as superconductivity with broken time reversal symmetry or antiferromagnetism.
Quantum Description of a Degenerate P-N Junction Coupled to an Electrical Circuit
Authors: Richardson W. H.
Published: October 2003

A theory of Coulomb blockade of tunneling in a degenerate p-n junction is presented. Perturbation theory and temperature Green's functions are used to obtain the current–voltage characteristics. The formulation extends the theory of Coulomb blockade in MIM junctions, to junctions in which the characteristics of the device, is partly determined by the many particle interaction in the electrodes. Exact analytical expressions for the I-V at zero temperature and approximate expressions at nonzero temperatures are obtained. Among the novel features observed are: an asymmetry in the current–voltage characteristics even for voltages on the scale of the Coulomb blockade threshold and threshold like behavior below (e/2C).
Dissipative Phase Fluctuations in a Superconductor in Proximity to an Electron Gas
Authors: Gaitonde D. M.
Published: October 2003

We study a two-dimensional superconductor in close proximity to a two-dimensional metallic sheet. The electrons in the superconducting sheet are coupled to those in the metallic sheet by the Coulomb interaction only. We obtain an effective phase-only action for the superconductor by integrating out all the electronic degrees of freedom in the problem. The Coulomb drag of the normal electrons in the metallic sheet is found to make the spectrum of phase-fluctuations in the superconductor, dissipative at long wavelengths. The dissipative co-efficient η is shown to be simply related to the normal state conductivities of the superconducting layer (σ S ) and the metallic sheet (σ E ) by the relation η∝σ S σ E /(σ S +σ E ).
Collective Charge Density Fluctuations in Superconducting Layered Systems with Bilayer Unit Cells
Authors: Hwang E. H. , Das Sarma S.
Published: October 2003

Collective modes of bilayered superconducting superlattices (e.g., YBCO) are investigated within the conserving gauge-invariant ladder diagram approximation including both the nearest interlayer single electron tunneling and the Josephson-type Cooper pair tunneling. By calculating the density–density response function including Coulomb and pairing interactions, we examine the two collective mode branches corresponding to the in-phase and out-of-phase charge fluctuations between the two layers in the unit cell. The out-of-phase collective mode develops a long wavelength plasmon gap whose magnitude depends on the tunneling strength with the mode dispersions being insensitive to the specific tunneling mechanism (i.e., single electron or Josephson). We also show that in the presence of tunneling the oscillator strength of the out-of-phase mode overwhelms that of the in-phase-mode at k‖ = 0 and finite kz, where kz and k‖ are respectively the mode wave vectors perpendicular and along the layer. We discuss the possible experimental observability of the phase fluctuation modes in the context of our theoretical results for the mode dispersion and spectral weight.
Disent to Pairing Mechanism
Authors: Cheng Kaijia , Cheng Shuyu
Published: October 2003

Up to now, the pairing mechanism is regarded as the rule of thumb criterion of an acceptable theory of superconductivity. It is generally held as a taboo for any theory which is not founded on this basis. However this is not true and it misleads the direction for the theoretical research for both the high and low temperature regions and eventually delays the progress in practice. It is now the time to clear up the situation.
The Solitary Wave Model of Superconductivity
Authors: Peng Kuangding
Published: October 2003

In metals and compounds there exist small regions in which the phases of electron-pair waves are coherent. These regions are called superconducting domains (SD). At temperatures lower than T c , these regions connect with each other and form a superconductor. The electron-pairs are partially bound pairs formed by electromagnetic interactions. Coherence gives rise to solitary waves and the Josephson effect. Ideal conductivity and the Meissner effect follow from these. The different effects of lattice vibrations on low and high-T c superconductors are explained as well.
Predicted Midgap States in Unconventional Superconductors and Their Numerous Implications for High-Tc Superconductors
Authors: Hu Chia-Ren
Published: October 2003

A fundamental topological consequence of the unconventional (i.e., non-s-wave) pairing symmetry of high-T c superconductors (HTSC's) is the existence of midgap (quasi-particle) states (MS's) bound to surfaces, interfaces and other locations. This prediction by the author has most-likely solved a decade-old puzzle, viz., the ubiquitous observation of a zero-bias conductance peak (ZBCP) in tunneling experiments performed on HTSC's. There are also numerous other novel consequences of these MS's, predicted by various researchers, including a new Josephson critical current term; an (already observed) low-temperature splitting of the ZBCP due possibly to a spontaneous breaking of the time-reversal symmetry at a sample surface; a new explanation of the paramagnetic Meissner effect; and a giant magnetic moment, etc. Here the author will review the physical origin of the MS's, the several extensions of the original idea and the many novel consequences of these MS's, some of which have been investigated quantitatively and some others only deduced in qualitative terms so far.
Pseudogap Regime in a BCS Bose–Einstein Crossover Scenario: Experimental Consequences and Tests
Authors: Jankó Boldizsár , Kosztin Ioan , Levin K.
Published: October 2003

We have argued that the pseudogap regime in the cuprates is characterized by the presence of metastable, long lived pairs which form the natural intermediate state between the free fermions of the BCS and bound pairs of the Bose Einstein limits. Here we investigate the experimental consequences associated with this resonant pair scattering in the normal state. The essential feature of these pair resonances is that they are dynamic pairing fluctuations. Of particular interest in distinguishing different scenarios for the cuprate pseudogap are probes which predominantly couple to the static and dynamic pair fluctuations, respectively. We therefore contrast the behavior of the diamagnetic susceptibility with the pair tunneling spectra of Superconductor-Pseudogapped cuprate junctions.
On the Origin of Zero-Bias Conductance Peak in High-Tc Superconductors
Authors: Nazarenko Alexander B. , Pashitskii Ernst A. , Pashitskii Alexander E.
Published: October 2003

We show that the zero-bias conductance peak observed in tunnel and point junctions of cuprates can be a consequence of "unitary" elastic scattering of the carriers by non-magnetic impurities in the vicinity of the junction interface and d-wave symmetry of the order parameter.
The Gap Function in YBa2Cu3O7
Authors: Zhao G. L. , Bagayoko D.
Published: October 2003

We have solved the four-dimensional anisotropic Eliashberg gap equation for YBa2Cu3O7 (YBCO) using the calculated electronic structure and the electron–phonon interaction matrix elements. The calculated T c for YBCO is about 89 K or μ*= 0.1. At or slightly above the transition temperature T c , the real part of the gap function Δ(k, 0), for all the k-points on the Fermi surface, becomes zero and the material is not superconducting. However, the energy gap function Δ(k,ω) is still nonzero for ω > 0 for some electronic states, leading to a pseudo-gap behavior in YBCO.
Evidence of Granular Superconductivity in Pr2<-zCezSr2Cu2NbO10
Authors: Blackstead Howard A. , Dow John D. , Felner Israel , Luo H. , Pulling David B. , Yelon W. B.
Published: October 2003

Pr 2-z Ce z Sr2Cu2NbO10 (Pr222Nb10), is widely believed to not superconduct, although its homologues in which Pr is replaced by Nd, Sm, Eu, or Gd do (with Tc ≈ 28 K). On the basis of bulk resistivity, bulk diamagnetism, electron spin resonance, and surface resistance measurements of Pr222Nb10, we conclude that it does exhibit granular superconductivity (as predicted) with a critical temperature in the range 25–28 K, but is not currently a bulk superconductor. Neutron diffraction studies show that our Pr222Nb10 is multi-phase, but does not contain significant amounts of any (known) superconducting phase other than Pr222Nb10. It does contain ~ 23% PrSr defects, but far fewer SrPr impurities (<2%), so that the predicted antistructure defect ( SrPr , PrSr ) is probably not responsible for breaking Cooper pairs and destroying superconductivity, but the important half of it, PrSr , almost certainly is.
How Could an Isotope Effect on TN Change the Physics of HTSC?
Authors: Bussmann-Holder A.
Published: October 2003

In a recent work it has been shown that if spin/charge phonon coupling is present in the underdoped parent compounds of high-T c superconductors, the Neel temperature could experience a substantial isotope effect. Consequences for superconductivity are discussed.
Forward Electron–Phonon Scattering in Normal and Superconducting States
Authors: Dolgov O. V. , Danylenko O. V. , Kulić M. L. , Oudovenko V.
Published: October 2003

The sharp forward electron–phonon (FEP) and impurity (FIS) scattering change the normal and superconducting properties significantly. The pseudo-gap like features are present in the density of states for ω<Ω, where Ω is the phonon frequency. The superconducting critical temperature T c , due to the FEP pairing, is linear with respect to the electron–phonon coupling constant. The FIS impurities are pair weakening for s- and d-wave pairing.
Anisotropic Order Parameter in Two-Band Superconductivity
Authors: Konsin P. , Kristoffel N. , Rubin P.
Published: October 2003

A two-overlapping band model of superconductivity with s+d interband scattering is investigated. The gap equation system has been solved numerically. Solutions of pure-d and -s, or of mixed s+d nature are possible. The pure Tcd(μ) or Tcs(μ) curves determine the onset of superconductivity with temperature lowering. In the under- and over-doped region pure-symmetry orderings are preferred. Mixed ordering can exist in a narrow region of μ, becoming narrower with T rising. The peculiarities of the and spectra are reflected in the behaviour of the order parameters. Order parameter symmetry can change with T and μ.
About the Influence of the Square-Root Van Hove Singularity on the Critical Temperature of Overdoped High-Temperature Superconductors
Authors: Pashitskii E. A. , Pentegov V. I.
Published: October 2003

It is shown that the square-root van Hove singularity in the density of states ν(E F )~ (E F -E0)-1/2, associated with the extended saddle-point singularities in the electron spectra of the cuprates, leads to a nonmonotonic dependence of the critical temperature T c on the position of the Fermi level E F with respect to the bottom E0 of the saddle. As a result of cancellation of the divergency of ν(E F ) in the electron–electron coupling constant, renormalized due to the account of the strong coupling effects, T c approaches zero in the limit E F → E0. This result contrasts that of the weak coupling approximation, which gives a finite value of T c for E F → E0. The T c on the concentration of doped holes, obtained in the strong coupling approximation, agrees qualitatively with the experimental data for the overdoped cuprate metal-oxides.
Hopping Motion of Small Polarons Versus Temperature and Dimensionality
Authors: Zoli Marco
Published: October 2003

The effects of dimensionality on the small polaron motion have been studied through a molecular crystal model in which the intermolecular forces are described by a first neighbors pair potential. The crossover temperature [Formula: see text] between band-like and hopping motion is sensibly reduced in low-dimensional systems due to the enhanced importance of the off-diagonal scattering processes. The dispersion in the phonon spectrum is essential for the validity of the model. The results may be of interest in order to understand the anomalous c-axis electrical transport in high-T c superconductors.
Metamagnetic Phases and Interplay with Superconductivity of Single Crystal DyNi2B2C
Authors: Naugle D. G. , Rathnayaka K. D. D. , Canfield P. C.
Published: October 2003

DyNi2B2C with T c ~ 6 K, less than the Neél temperature T N , is particularly interesting. Crystal electric field splitting locks the magnetic moments in the ab-plane at low temperature and a series of metamagnetic transitions is observed with increasing field below T N . Detailed measurments of in-plane magnetization, magnetic susceptibility and resistivity of DyNi2B2C single crystals have been carried out in order to investigate the anisotropic interplay between superconductivity and the magnetic phases.
Superconducting Gap in the Tunneling Spectra of High-Tc Cuprates
Authors: Oda M. , Hoya K. , Abe N. , Yokoyama M. , Momono N. , Nakano T. , Nagata T. , Ido M.
Published: October 2003

In Bi2212 and La214, the low-T(T ≪ T c ) superconducting gap magnitude 2Δ0 and the temperature dependence of in-plane resistivity ρ were examined over a wide carrier-doping range. In both systems, 2Δ0 increases with lowering doping level and ρ starts decreasing faster around a temperature T*, comparable to the mean-field T c or the onset temperature of a spin-channel singlet formation in the mean-field RVB thory, each of which is given by ~Δ0/2k B .
Out-of-Plane and in-Plane Conduction in Insulating and Strongly Underdoped Cuprates
Authors: Almasan C. C. , Levin G. A. , Cimpoiasu E. , Stein T. , Gajewski D. A. , Maple M. B. , Zheng Hong , Paulikas A. P. , Veal B. W.
Published: October 2003

We report measurements of out-of-plane (ρ c ) and in-plane (ρab) normal-state resistivities of single crystals of insulating PrBa2Cu3O 7-δ and strongly underdoped oxygen deficient YBa2Cu3O 6.41 using a flux transformer method. In the superconducting specimens, the onset of superconductivity was suppressed by a magnetic field of 9 T. We have found that the anisotropy ρc/ρab of these samples increases monotonically at low temperatures with no signs of saturation. The temperature dependence of ρc/ρab for YBa2Cu3O6.41 is well described by ρc/ρab=a +bT-2/3, but over a smaller temperature range than for insulating PrBa2Cu3O 7-δ. Both the absence of saturation of ρc/ρab and its T-2/3 dependence indicate two-dimensional conduction. This means that the average in-plane hopping distance of the localized charge carriers increases with decreasing T according to Mott's [Formula: see text] law, while the elementary step in the c-direction remains T independent, equal to the spacing between the bilayers.
Structural, Magnetic and Transport Properties of Li-Doped La2CuO4
Authors: Sarrao J. L.
Published: October 2003

We review recent work on La2Cu 1-x Li x O 4 for 0 < x < 0.5. Li substitutes for Cu in La2CuO4 , resulting in both the addition of a hole and the loss of a spin (because Li is monovalent and S = 0 while Cu is divalent and S = 1/2). Qualitatively, Li substitution has the same effect as the combined substitution of Sr and Zn. We explore the extent to which this analogy can be made quantitative and discuss how these results influence our understanding of the doped hole state in La2CuO4 .
The Use of New Stripline Structure in the Design of HTS Microwave Filters
Authors: Jakku Eino , Hagberg Juha , Rytivaara Martti , Leppävuori Seppo
Published: October 2003

The use of high temperature superconducting (HTS) materials in microwave filters makes it possible to realize smaller and higher performance filters compared to those that make use of conventional materials. This is generally true only at low and moderate power levels, but at normally used telecommunication transmitters power levels (20–50 W) the HTS filters do not work very well, if at all. There have been many attempts to demonstrate high power filters, but these have met with little success. We propose a new dual-stripline structure, where the current distributes into two equal current carrying layers. The consequence of this is that, with the same total current in one layer, the dual-line can carry twice as much current and four fold power.
Cluster Model Description of Polarized Cu K-Edge Spectra of Nd2-xCexCuO4-δ
Authors: Liang G. , Li M. , Markert J. T. , Wang L. V.
Published: October 2003

Single crystals Nd 2-x Ce x CuO 4-δ with x=0.0 and 0.2 are studied by polarized X-ray absorption measurements at Cu K-edge. The positions and intensities of the 1s→ 4pσ transition features in the K-edge spectra are analyzed with a modified cluster model and functional curve fitting procedure. All of the experimental results including the energies of the spectral features, the energy separations between features and the variation of feature intensities, can be well explained by the cluster model parameters obtained from the curve fitting. Particularly, it is found that the charge transfer energy gap Δ in the Nd 2-x Ce x CuO 4-δ system decreases from about 1.4 eV at x=0 to 0.5 eV at x = 0.2. Our analysis in this paper provides a method for quantitative X-ray absorption spectroscopy (XAS) study of the charge transfer gap for electron-doped cuprate superconductors and related materials.
Spin Fluctuations in Pressure-Induced Paramagnetic State of YMn2 — Comparison with High-Tc Cuprates —
Authors: Zheng G. -G. , Nishikido K. , Kitaoka Y. , Asayama K. , Hauser R.
Published: October 2003

From our NMR measurements, we compare the spin fluctuations spectrum in high-T c cuprates and the pressure-induced paramagnetic state of YMn 2. It is pointed out that the latter has a shorter magnetic correlation length and the bandwidth is smaller by one order in magnitude than the former.
Spin Dynamics of Magnetoresistive Oxides
Authors: Lynn J. W.
Published: October 2003

A review is given of the neutron scattering measurements of the spin dynamics of the magnetoresistive oxides. A number of anomalous features have been identified in the manganites, including very strong damping of the spin waves in the ground state and as a function of temperature, anomalous spin wave dispersion and the development of a strong spin-diffusion component to the fluctuation spectrum well below T C in the region of optimal doping. For the Tl2Mn2O7 pyrochlore, on the other hand, the behavior of the spin dynamics is conventional, which argues that the mechanism responsible for the magnetoresistive effect has a different origin in these two classes of materials.
Strain, Anisotropy and Low Field Magnetoresistance Effect in Ultrathin Manganite Films
Authors: Wang H. S. , Li Qi
Published: October 2003

We report low-field magnetoresistance (LFMR) of strained ultrathin Pr0.67Sr0.33MnO3 (PSMO) films. We observed very large LFMR, a factor of 7 of resistance change in zero-field-cooled sample at 80 K and 2000 Oe, in ultrathin PSMO films on LaAlO3 (LAO) (100). Samples with compressive (on (LAO), tensile (on SrTiO 3 (100)) and very small strain (on NdGaO 3 (110)) have been studied systematically and remarkable differences were observed. We also observed large LFMR anisotropy between magnetic fields applied parallel and perpendicular to the film surface. Our results demonstrated that strain and strain-induced spin scattering can result in large LFMR effect.
Effect of High-Energy Electron Irradiation on the Transport and Magnetoresistive Behavior in La0.64Ca0.36MnO3 Films
Authors: Parasiris A. , Rathnayaka K. D. D. , Naugle D. G. , Belevtsev B. I. , Krasovitsky V. B. , Bobkov V. V.
Published: October 2003

Defects introduced by irradiating LaCaMnO films with high-energy (≃ 6 MeV ) electrons produce a significant increase in film resistivity but have only a small effect on the colossal magnetoresistance and the temperature of the ferromagnetic phase transition. These results suggest that electron irradiation produces mainly point defects rather than a change in doping by oxygen depletion.
Ferromagnetism in Manganese Compounds
Authors: Zaitsev R. O.
Published: October 2003

The ferromagnetic instability in a system of manganese cations and oxygen, nitrogen and phosphorus anions on the basis of the strong electron–electron interaction is studied. The phase diagram for the existence of ferromagnetic ordering depending on the filling p6-shells of anions and dl0-shells of manganese is constructed.
q-Deformed Boson Oscillators and Zero Point Energy
Authors: Swamy P. Narayana
Published: October 2003

Just as for the ordinary quantum harmonic oscillators, we expect the zero-point energy to play a crucial role in the correct high temperature behavior. We accordingly reformulate the theory of the statistical distribution function for the q-deformed boson oscillators and develop an approximate theory incorporating the zero-point energy. We are then able to demonstrate that for small deformations, ln q≪1, the theory reproduces the correct limits both for very high temperatures and for very low temperatures. The deformed theory thus reduces to the undeformed theory in these extreme cases.
Monte Carlo Simulations of Short-Time Critical Dynamics
Authors: Zheng B.
Published: October 2003

Monte Carlo simulations of the short-time critical dynamics are reviewed. The short-time universal scaling behavior of the dynamic Ising model and Potts model are discussed in detail, while extension and application to more complex systems as the XY model, the fully frustrated XY model and other dynamic systems are also presented. The investigation of the universal behavior of the short-time dynamics not only enlarges the fundamental knowledge on critical phenomena but also, more interestingly, provides possible new ways to determine not only the new critical exponents θ and θ1, but also the traditional dynamic critical exponent z as well as all static critical exponents.
Exact Integrability of the su(n) Hubbard Model
Authors: Maassarani Z.
Published: October 2003

The bosonic su (n) Hubbard model was recently introduced. The model was shown to be integrable in one dimension by exhibiting the infinite set of conserved quantities. I derive the R-matrix and use it to show that the conserved charges commute among themselves. This new matrix is a nonadditive solution of the Yang–Baxter equation. Some properties of this matrix are derived.
Discrete Scale Invariance and the "Second Black Monday"
Authors: Feigenbaum James A. , Freund Peter G. O.
Published: October 2003

Evidence is offered for log-periodic (in time) fluctuations in the S&P 500 stock index during the three years prior to the October 27, 1997 "correction". These fluctuations were expected on the basis of a discretely scale invariant rupture phenomenology of stock market crashes proposed earlier.
Effect of Magnetic Field on the Lock-In Transition in Cupric Oxide
Authors: Rao T. V. Chandrasekhar , Ota S. B. , Sahni V. C.
Published: October 2003

We present magnetization measurements on polycrystalline CuO over the temperature range 5–300 K using a SQUID magnetometer. The change in sample magnetization at the lock-in transition temperature (212.6 K) as a function of the magnetic field has been found to scale with the field. The results are analyzed in terms of the magnetic analogue of the Clausius–Clapeyron equation.
X-, γ- and β-Irradiated Y-Ba-Cu-O Superconductor Studied by Thermostimulated Exoelectron Emission
Authors: Olszowski Z. , Duś-Sitek M. , Szymura S.
Published: October 2003

The results of measurements of the thermostimulated exoelectron emission (TSEE) from Y 1 Ba 2 Cu 3 O 7-δ superconductor are presented. They were recorded during heating in the temperature range 290–600 K superconductor previously irradiated with X-, γ- and β-radiation. Interaction between electromagnetic or corpuscular radiation and the sample cause the creation of defects which give TSEE maxima for other temperature. The size of maxima depend only on a dose of absorbed radiation. Heating the sample at a temperature T≥550 K completely removes electron traps which were created during irradiation.
Interference of "Coulomb Blockade"-Like and Persistent Current Mesoscopic Oscillations in Quantum Rings
Authors: Zvyagin A. A.
Published: October 2003

Persistent current and "Coulomb blockade" like oscillations of electrons in a mesoscopic quantum ring are analyzed within the framework of the exact Bethe ansatz solutions of two component Luttinger liquid (correlated electron systems and magnetic impurities models). Changes of the electron number and of the total magnetic moment governed by an external voltage and magnetic field produce the saw-tooth oscillations of the ground state mesoscopic energy, similar to the Coulomb blockade effect. The interference of these oscillations and the Aharonov–Bohm–Casher (ABC) persistent currents can be observed, e.g. as an initial phase shift of the persistent currents. The generalization for multichannel Luttinger liquid case is performed. The recent result of experiment on interference effects in mesoscopic semiconductor rings is explained.
Two-Dimensional Ising Model in an Annealed Random Field
Authors: Cordeiro C. E. , Gonçalves L. L.
Published: October 2003

The critical behavior of the two-dimensional Ising model (square lattice, exchange constant J) in an uniform field, and in an annealed random field is considered. The random field is generated by decorating the horizontal and vertical bonds of the lattice, and it satisfies an arbitrary distribution which is imposed by introducing a pseudo-chemical potential. By decimating the decorating variables the model can be mapped onto a homogeneous Ising model with effective exchange constant J′ and effective external field h′, dependent on the temperature. These parameters, which satisfy a set of coupled equations, depend on the spin average and nearest-neighbor two-spin correlation, and are obtained numerically. For the symmetric field distribution [Formula: see text] the mapping of the critical frontier on the (K′=βJ′,H′=βh′) plane onto the (K=β J,H=βh) plane is determined and, as in the model introduced by Essam and Place, there is a region on the (K, H) plane which cannot be reached from any real values of (K′, H′). The critical exponents are determined numerically, and it is shown that they do not satisfy renormalization relations obtained for their model.
X-Ray Photoelectron Spectroscopy Study of Oxygen and Argon Annealed YBa2Cu3O7-δ
Authors: Rajasekar P. , Chakraborty P. , Bandyopadhyay S. K. , Barat P. , Sen Pintu
Published: October 2003

X-ray Photoelectron Spectroscopy (XPS) measurements have been performed on oxygen- and argon-annealed YBa 2 Cu 3 O 7-δ (YBCO) and the results are compared with similar measurements performed on Y 2 O 3. The structural changes in oxygen- and argon-annealed YBCO are reflected in the shift of the Binding Energy (BE) peak positions for the various components existing in the YBCO lattice.
Uniaxial Pressure Effects on Lattice and Magnetic Transport Property inLa0.82Sr0.18MnO3
Authors: Zhang Ning , Ding Weiping , Zhong Wei , Xing Dingyu , Du Youwei
Published: October 2003

Using a 10~20 MPa uniaxial pressure, we have observed the giant changes of lattice parameters and cell volume in CMR perovskite La0.82Sr0.18MnO3. The experimental data for cell volume was found to be in good agreement with Bridman state equation. Meanwhile, the uniaxial pressure induced changes of electric and magnetic properties have also been observed. These effects suggest that the lattice of the manganese perovskite is flexible and its electric and magnetic properties are very structure-sensitive.
Properties of Sintered Al Substituted NdFeB Magnets
Authors: Szymura S. , Bala H. , Rabinovich Yu. M. , Wiechuła J.
Published: October 2003

The effect of partial substitution of Fe by Al (Al, Al 2 O 3) on the magnetic properties and the corrosion resistance of the sintered NdFeB magnet has been investigated. With the increasing amount of Al, the anisotropy field and the saturation magnetization decrease, but the coercivity increases up to 4 at.% Al and further alloying of Al leads to a decrease of the coercivity. Different substances like Al (metallic Al or Al 2 O 3) modify the microstructure to different increase in the coercivity and especially to changes in the remanence. Alloying Al via metallic Al decreases the remanence, whereas via Al 2 O 3) up to 4 at.%0 Al increases it. The Al additions inhibit atmospheric corrosion of the magnet. We have found that Al 2 O 3 in sintered NdFeB magnet substantially improves the coercivity and the corrosion resistance with the improved remanence.
Automatic Structures for Torus Link Groups
Authors: Picantin Matthieu
Published: October 2003

A general result of Epstein and Thurston implies that all link groups are automatic, but the proof provides no explicit automaton. Here we show that the groups of all torus links are groups of fractions of so-called Garside monoids, i.e., roughly speaking, monoids with a good theory of divisibility, which allows us to reprove that those groups are automatic, but, in addition, gives a completely explicit description of the involved automata, thus partially answering a question of D. F. Holt.
Extensions of Quandles and Cocycle Knot Invariants
Authors: Carter J. Scott , Elhamdadi Mohamed , Nikiforou Marina Appiou , Saito Masahico
Published: October 2003

Quandle cocycles are constructed from extensions of quandles. The theory is parallel to that of group cohomology and group extensions. An interpretation of quandle cocycle invariants as obstructions to extending knot colorings is given, and is extended to links component-wise.
Link Invariants Associated with Gauge Equivalent Solutions of the Yang–Baxter Equation: The One-Parameter Family of Minimal Typical Representations of Uq[gl(2|1)]
Authors: Links Jon R. , de Wit David
Published: October 2003

In this paper we investigate the construction of state models for link invariants using representations of the braid group obtained from various gauge choices for a solution of the trigonometric Yang–Baxter equation. Our results show that it is possible to obtain invariants of regular isotopy (as defined by Kauffman) which may not be ambient isotopic. We illustrate our results with explicit computations using solutions of the trigonometric Yang–Baxter equation associated with the one-parameter family of minimal typical representations of the quantum superalgebra Uq[gl(2|1)]. We have implemented MATHEMATICA code to evaluate the invariants for all prime knots up to 10 crossings.
Classical Invariants for Holomic Knots
Authors: Bergqvist Magnus
Published: October 2003

There are some well known indices of knots that give rise to classical knot invariants when minimized for a knot type. By classical knot invariants I mean the minimal number of crossing points, bridge number, braid index, genus and unknotting number. Considering these indices when restricting the minimum over holonomic knots, some of the minima stay the same while others differ. This supplies us with a new set of knot invariants: the holonomic counterparts of the classical knot invariants.
Detecting Non-Triviality of Virtual Links
Authors: Kadokami Teruhisa
Published: October 2003

J. S. Carter, S. Kamada and M. Saito showed that there is one to one correspondence between the virtual Reidemeister equivalence classes of virtual link diagrams and the stable equivalence classes of link diagrams on compact oriented surfaces. Using the result, we show how to obtain the supporting genus of a projected virtual link by a geometric method. From this result, we show that a certain virtual knot which cannot be judged to be non-trivial by known algebraic invariants is non-trivial, and we suggest to classify the equivalence classes of projected virtual links by using the supporting genus.
Sharp Bounds on Some Classical Knot Invariants
Authors: Kearton C. , Wilson S. M. J.
Published: October 2003

There are obvious inequalities relating the Nakanishi index of a knot, the bridge number, the degree 2n of the Alexander polynomial and the length of the chain of Alexander ideals. We give examples for every positive value of n to show that these bounds are sharp.
Isometries of Orbifolds Double-Covered by Lens Spaces
Authors: Jeevanjee Theresa L.
Published: October 2003

Let K be a two-bridge knot in S3. Then K is also denoted as the four-plat, b(p,q) to indicate its association with some rational number p/q.

The lens space L = L(p,q) admits an isometry, τ, of order 2, such that the quotient space L modulo the involution τ is an orbifold whose exceptional set is K.

In this paper, the isometries of these orbifolds are classified; this is equivalent to computing the isometries of (S3,K).
Hypergeometric Model of Evolution of Conserved Protein Coding Sequences in the Proteomes
Authors: Kuznetsov Vladimir A.
Published: October 2003

The diversity of protein sequences that exists today has probably evolved from antecedent evolutionarily- conserved domain-like sequences (i.e. motifs, repeats, structural domains) encoded by short ancient genes. We have studied the statistical distributions of the occurrences of the domain-like families within proteins in the proteomes. A generalized hypergeometric stochastic process is introduced in order to model the evolution dynamics of these conserved sequences. We found that the limiting probability function associated with this process fits the empirical distributions for the 90 fully-sequence bacterial, archaeal and eukaryotic organisms. For eukaryotes, our limiting distribution is reduced to Waring's distribution. However, for many archaeal and bacterial organisms the empirical distributions degenerate to the Yule-like distribution. Comparison of all of these distributions implies critical evolutionary events, which lead to the proportional growth of the number of new protein-coding genes and proteome complexity in the eukaryotic organisms and suggest that evolution of many archaeal and bacterial organisms are subject to external global (ecological) forces. Best-fit model data predicts that (1) there are only ~ 5500 or so of the distinct InterPro domains in a given higher eukaryotic organism and that (2) a general trend in eukaryotic proteome evolution is described by the increase in frequency of multi-domain proteins composed of already-existing (older) distinct domains as oppose to creating new ones. Our model can be applicable for analysis of the evolution of word distributions in the texts and be used in other large-scale evolutional systems like the Internet, the economy and the universe.
The Different Physical Origins of 1/f Noise and Superimposed RTS Noise in Light-Emitting Quantum Dot Diodes
Authors: Belyakov A. V. , Vandamme L. K. J. , Perov M. Yu. , Yakimov A. V.
Published: October 2003

Low frequency noise characteristics of light-emitting diodes with InAs quantum dots in GaInAs layer are investigated. Two noise components were found in experimental noise records: RTS, caused by burst noise, and 1/f Gaussian noise. Extraction of burst noise component from Gaussian noise background was performed using standard signal detection theory and advanced signal-processing techniques. It was found that Hooge's empirical relation applied to diodes by Kleinpenning is applicable to the electric 1/f noise in quantum dot diodes as well. Two different spectra decomposition techniques are used to obtain burst noise spectra. Bias dependences of burst and 1/f noise are compared. It is concluded that the RTS noise and 1/f noise have different physical origins in light-emitting diodes with quantum dots.
Probing a Noisy Oscillator System
Authors: Acebrón J. A. , Rappel W.-J. , Bulsara A. R.
Published: October 2003

We examine the effect of adding a sinusoidal signal to a system of coupled noisy nonlinear oscillators. When the frequency of this "probe" signal is close to the frequency of the unprobed system we observe a resonance behavior, enabling us to determine the underlying frequency of the noisy system. Furthermore, in the prototype SQUID system we consider here, we find that the frequency of the underlying solution decreases with increasing coupling strength. Combining this finding with the resonance phenomenon we discuss ways to enhance the sensitive of SQUIDs to weak low frequency signals.
Buried CMOS Structure with a Straddle-Gate Architecture for Low Noise-Analog Applications
Authors: Fantini Paolo , Riccardi Damiano , Croce Giuseppe
Published: October 2003

A new buried-channel CMOS structure with a straddle-gate architecture is proposed in the present work. It can be carried out within the standard CMOS VLSI technological platform giving rise to both N- and P-type MOSFETs with buried channel. The main electrical features of the novel N-MOS transistor have been experimentally investigated. A significant lowering in 1/f noise and higher carrier mobility have been observed coherently with a bulk-like carrier transport due to the buried channel. The novel device would be promising for both analog and RF circuitry design.
Time-Local Spectral Analysis for Non-Stationary Time Series: The S-Transform for Noisy Signals
Authors: Pinnegar C. R. , Mansinha L.
Published: October 2003

The S-transform is a method of time-local spectral analysis (also known as time-frequency analysis), a modified short-time Fourier Transform, in which the width of the analyzing window scales inversely with frequency, in analogy with continuous wavelet transforms. If the time series is non-stationary and consists of a mix of Gaussian white noise and a deterministic signal, though, this type of scaling leads to larger apparent noise amplitudes at higher frequencies. In this paper, we introduce a modified S-transform window with a different scaling function that addresses this undesirable characteristic.
Pseudoinversion of degenerate metrics
Authors: Atindogbe C. , Ezin J.-P. , Tossa Joël
Published: October 2003

Let (M, g) be a smooth manifold M endowed with a metric g. A
large class of differential operators in
differential geometry is intrinsically defined by means of the
dual metric g∗ on the dual bundle
TM∗ of 1‐forms on M. If the metric g is (semi)‐Riemannian,
the metric g∗ is just the inverse of g. This
paper studies the definition of the above‐mentioned geometric
differential operators in the case of manifolds
endowed with degenerate metrics for which g∗ is not
defined. We apply the theoretical results to Laplacian‐type
operator on a lightlike hypersurface to deduce a Takahashi‐like
theorem (Takahashi (1966)) for lightlike hypersurfaces in
Lorentzian space .
Identification of Novel Signaling Complexes by Functional Proteomics
Authors: Ping Peipei
Published: October 2003

The rapid development of proteomic technologies, combined with the completion of the Human Genome Map, has enabled the compiling of an unprecedented inventory of cellular proteins. Functional proteomics is an emerging field that aims to utilize the enormous amount of information provided by these proteomic technologies to understand the functions of cellular proteins. The utility of functional proteomics has been recently exploited to elucidate cellular mechanisms in numerous fields, of particular salience in the area of signal transduction. This review presents a functional proteomic approach for the study of cardiac cell signaling. It illustrates the strategies by which the subproteome of a targeted signaling system is characterized in an unbiased fashion, the manner in which the biochemical functions of this subproteome are assessed using established molecular and protein chemistry methods, and the challenges associated with these studies.
Ethics in Conflict Resolution: The Ties That Bind
Authors:   Barry,   Robinson
Published: October 2003

Ethical dilemmas are inevitable in negotiation and other conflict resolution situations as parties seek to guard self-interest while reconciling competing interests. There is a developing body of research on the psychology of ethics in conflict, but a relative dearth of scholarly attention to the wider field of ethics in conflict resolution. In this introductory essay, we describe and comment on the diversity of approaches and contexts featured in the articles that comprise this themed issue of International Negotiation. We identify the ethical dimensions of relationships among disputing parties and interveners as a common thematic element that may represent a fruitful avenue for thinking about the distinctive role of ethics in the resolution of conflict.
Relational Frames and Their Ethical Implications in International Negotiation: An Analysis Based on the Oslo II Negotiations
Authors:   Hoobler,   Donohue
Published: October 2003

In a recent set of papers, Donohue and colleagues used Relational Order theory to describe the relational context that evolved during the first Oslo negotiations held in 1992–1993. However, many relational shifts have developed between Palestinians and Israelis since Oslo. The question is have these shifts established a context that allows for the parties to bargain in good faith? Negotiations conducted to satisfy political agendas that are likely to fail because of stressed relationships between the parties make it difficult for parties to bargain in good faith. Relational Order Theory was used in the current article to better understand the relational context leading to the 1995 Oslo II accords and thus, the ethical sanction of the negotiations. Editorials and interviews from Palestinian and Israeli leaders leading up to the negotiations were analyzed to determine the extent to which the relational context was more affiliation-oriented or more focused on power and domination. The results indicate that the relational context leading up to Oslo II shifted dramatically over the course of several months as parties shaped their perspectives on the negotiations. However, the competition for power expressed by the exchanges suggested a less ethically defensible context for negotiations. The ethical implications of forcing negotiation in the face of a fairly aggressive relational context are discussed.
Moral Compromise: Owen and Holbrooke Mediating the Bosnia Conflict
Authors:   van Es
Published: October 2003

To analyze moral notions in conflict dynamics, several conceptions of negotiation, moral notions in conflict perspectives, and elements of moral compromise are examined. Together, these indicators provide a framework for analyzing the moral dimensions of the mediator's role in complex negotiations. These ideas are illustrated through a discussion of the actions of two mediators in the Bosnia conflict during the 1990s. The analysis considers why these mediators were so different in their effectiveness and capacity to reach compromise. It also becomes clear when moral compromise is feasible.
Lambs Among Lions? The Impact of Ethical Ideology on Negotiation Behaviors and Outcomes
Authors:   Parks,   Banas
Published: October 2003

Relationships between individuals' ethical orientations (classified on dimensions of idealism and relativism), their negotiation strategies, their views of ethically ``marginal'' tactics, and their outcomes in dyadic negotiation are examined. Results indicate a relationship between ethical orientation and negotiation strategy. Specifically, absolutists (high on idealism, low on relativism) tended to employ more assertive negotiation strategies than did those of other ethical orientations. Individuals in no one category of ethical ideology outperformed those in any other category in terms of integrativeness of agreements or outcomes. Absolutists viewed ethically questionable tactics as less acceptable, whereas subjectivists found them more acceptable. We found that individuals less accepting of questionable tactics (``lambs''), who negotiated against those more accepting of such tactics (``lions''), were able to achieve better outcomes and a greater percentage of joint outcomes.
Negotiating Global Change: Progressive Multilateralism in Trade in Telecommunications Talks
Authors: Ives Paula Murphy
Published: October 2003

This article provides an analysis of negotiated change within the global telecommunications regime. It examines how agreements are achieved in the area of trade and telecommunications, particularly within the aegis of the Geneva-based World Trade Organization (WTO). It argues that, in the negotiations examined, the interplay between unilateral action, bilateral, plurilateral and multilateral processes and the ensuing alchemy of coercion and concord led to an overall reframing of the central problem and thereby facilitated multilateral consensus. Drawing upon evidence from Japan-U.S. bilateral, Organization for Economic Cooperation and Development (OECD) and multilateral trade and telecom talks, this research tests the proposition that coercive pressure is the predominant factor in bringing about negotiated change. It also considers the alternate thesis that integrative reframing, involving the search for mutual gains, was paramount in facilitating change. Qualitative observations signal the phenomenon of progressive multilateralism, or the sequential interplay of unilateral action, bilateral, and multilateral processes, wherein undercurrents of coercion reorient perceptions of the outcome from uncertain gains towards loss avoidance. Together with information exchange and interaction, one observes position change. Understanding the dynamics at important impasse points facilitates a critical, political-economy reading of these international negotiations as well as more general conclusions about the nature of governance in this area.