bluuebunny/crossref_metadata_2025 huggingface dataset:
Bi-Based Superconducting Multilayers Obtained by Molecular Beam Epitaxy
Authors: Salvato M. , Attanasio C. , Carbone G. , Di Luccio T. , Prischepa S. L. , Russo R. , Maritato L.
Published: July 2002

High temperature superconducting multilayers have been obtained depositing Bi2Sr2CuO6+δ(2201) and ACuO2 layers, where A is Ca or Sr, by Molecular Beam Epitaxy (MBE) on MgO and SrTiO3 substrates. The samples, formed by a sequence of 2201/ACuO2 bilayers, have different thickness of ACuO2 layers while the thickness of the 2201 layers is kept constant. The surface structure of each layer has been monitored by in situ Reflection High Energy Electron Diffraction (RHEED) analysis which has confirmed a 2D nucleation growth. X-ray diffraction (XRD) analysis has been used to confirm that the layered structure has been obtained. Moreover, one-dimensional X-ray kinematic diffraction model has been developed to interpret the experimental data and to estimate the period of the multilayers. Resistive measurements have shown that the electrical properties of the samples strongly depend on the thickness of the ACuO2 layers.
Growth and Superconducting Properties of Sm1Ba2Cu3O7-δ Thin Films
Authors: Di Trolio A. , Morone A. , Orlando S. , Gambardella U.
Published: July 2002

We successfully used the pulsed laser ablation and deposition to prepare superconducting thin films of SmBaCuO under different growth parameters. The films were grown on both MgO (100) and SrTiO 3 (100) substrates. The best samples showed a good degree of orientation, having the θ-scan around the 005 reflection an FWHM ≈ 0.2°. We report the critical temperature as a function of the deposition parameters, comparing the results between the two substrates. We also estimate the critical current density at 60 K from the magnetization curve.
Vibrational Pseudo-Diffusive Motion of the Oxygen Octahedra in La2CuO4 and Sr Doped La2CuO4 from Anelastic and 139La NQR Relaxation
Authors: Cordero F. , Campana A. , Corti M. , Rigamonti A. , Cantelli R. , Ferretti M.
Published: July 2002

The vibrational dynamics in nearly stoichiometric La 2 CuO 4+δ has been studied by means of anelastic relaxation and by 139 La NQR relaxation. Evidence of dynamical tilting of the octahedra in a double well local potential is obtained with both the experimental techniques. Anelastic relaxation shows a peak at T ~ 150 K for a measuring frequency in the kHz region, while the peak in the NQR relaxation at the quadrupole frequency ν Q ~ 19 MHz occurs at T ~ 330 K. The data are analyzed in terms of a model of pseudo-diffusive cooperative motion. The measured effective barrier is 2800 K, higher than the one of the local potential becuase of the cooperative character of the motion. Upon Sr doping the 139 La relaxation is still dominated by the octahedra tilting waves for T >100 K, while allow temperatures the magnetic relaxation mechanism related to Cu 2+ spin fluctuation dominates. It is argued how the freezing of the tilts (occurring below 100 K in the undoped La 2 CuO 4) might correspond to the formation of static stripes.
High Frequency Resistivity in YBa2Cu3O7-δ: Effects of Anisotropic Renormalized Fluctuations
Authors: Neri D. , Marcon R. , Silva E. , Fastampa R. , Iacobucci L. , Sarti S.
Published: July 2002

We discuss the excess conductivity above Tc due to renormalized order-parameter fluctuation in YBCO at microwave frequencies. We show that a phenomenological cut-off in the fluctuative spectrum can extend the results of the anisotropic theory of renormalized fluctuations up to the high temperature region. Measurements of the real part of the microwave resistivity at 24 GHz are performed on two YBCO films. The onset of the superconducting transition and the deviation from the linear temperature behavior can be fully accounted for by the extended theory. Very consistent values of the fundamental parameters (critical temperature, coherence lenghts, penetration depth) of the superconducting state are obtained.
Macroscopic Quantum Tunneling in Josephson Junctions and Squids
Authors: Granata C. , Esposito E. , Ruggiero B. , Russo M. , Silvestrini P.
Published: July 2002

We report experiments on energy level quantization in Nb/AlOx/Nb Josephson junctions while measurements on SQUIDs are in progress. Data on the presence of energy level quantization are shown at temperatures above the classical-quantum regime crossover temperature. This has been possible by extending the measurements of the rate of the escape from the zero-voltage state at higher sweep bias rate in order to induce non-stationary conditions in the energy potential describing the junction dynamics. Data are compatible with extremely low "effective" dissipation in our system. Theoretical predictions on quantum effects related to the presence of non-stationary conditions in the potential associated to a rf SQUID are reported in view of new possible experiments.
X-RAY PHOTOELECTRON STUDY OF Bi2Sr2CaCu2-xCoxO~8
Authors: MAN N. K. , KUMARI KAMLESH , VENKATESH S. , HIEN T. D. , SINH N. K. , PHUC N. X. , GARG K. B.
Published: July 2002

An X-ray photoelectron spectroscopy study has been performed on well characterized Bi 2 Sr 2 CaCu 2-x Co x O ~8 (x=0, 0.02 and 0.1) samples. There is a shift in the Sr binding energy with Co concentration, which is related to the change in T c . This relationship can be understood by the change of hole concentration in the CuO 2 planes as a result of Cobalt doping. The results of Bi 4f and Co 2p core level spectra are also discussed in detail.
Physicochemical Aspects of Forming Electrorheological Fluids
Authors: Korobko E.V.
Published: July 2002

Based on the experimental results and physical representations fo ER-fluids as a "poor" dielectric, a physical model of the ER-effect is elaborated and the main approaches to creation of electrosensitive fluids with desired properties are determined.
ELECTRICAL TRANSPORT IN MAGNETIC SANDWICH WITH INTERFACE INTER-DIFFUSIONAL ROUGHNESS AND/OR ALLOYING
Authors: XU HUI-YING , YU WEN-XUE , MAI ZHEN-HONG
Published: July 2002

A thin transition sublayer with its own spin-dependent lattice potentials and relaxation times of the conduction electrons is introduced to describe the interface inter-diffusional roughness and/or alloying. Within the real-space Kubo formalism, the contribution of the spin-dependent lattice potentials to the giant magnetoresistance (GMR) effect, the dependence of the GMR effect on the spin asymmetry ratio and the spin-down relaxation time of the transition sublayers, the GMR effect versus the thicknesses of the ferromagnetic (FM) and nonmagnetic (NM) layers are discussed based on the jellium model with step-like and spin-dependent lattice potentials. The interesting results emerging in our calculations are that (1) the contribution of the spin-dependent lattice potentials to the GMR effect may be positive or negative, it is decided by the thicknesses of the FM and NM layers; (2) the contribution of spin-dependent lattice potentials to the GMR effect is much weaker than that of the spin-dependent relaxation times; (3) the increase or decrease of the GMR effect is not simply decided by the increased or decreased interface disorder but decided by the increased or decreased spin asymmetry ratio of the interface structure, which is caused by the change of the interface disorder; (4) for the case of the spin asymmetry ratio of the transition sublayers smaller than that of the FM layers, there exists a critical thickness d c for the thickness d F of the FM layers, when d F >d c , the existence of the interface inter-diffusional roughness and/or alloying increases the GMR effect, however, when d F <d c , it is on the contrary.
VIOLATION OF LUTTINGER'S THEOREM IN STRONGLY CORRELATED ELECTRONIC SYSTEMS WITHIN A 1/N EXPANSION
Authors: CAPPELLUTI EMMANUELE , ZEYHER ROLAND
Published: July 2002

We study the 1/N expansion of a generic, strongly correlated electron model ( SU (N) symmetric Hubbard model with U=∞ and N degrees of freedom per lattice site) in terms of X operators. The leading order of the expansion describes a usual Fermi liquid with renormalized, stable particles. The next-to-leading order violates Luttinger's theorem if a finite convergence radius for the 1/N expansion for a fixed and non-vanishing doping away from half-filling is assumed. We find that the volume enclosed by the Fermi surface, is at large, but finite N's and small dopings larger than at N=∞. As a by-product an explicit expression for the electronic self-energy in O(1/N) is given which cannot be obtained by factorization or mode-coupling assumptions but contains rather sophisticated vertex corrections.
STUDY OF SITE GEOMETRY OF THE Sn CATIONS IN THE Sn-ADDED Tl-Pb(1223) SUPERCONDUCTING SYSTEM USING MÖSSBAUER AND AUGER EMISSION TECHNIQUES
Authors: KUMARI KAMLESH , SINGHAL R. K. , GARG K. B. , BAGGIO-SAITOVICH E. M. , AZAVEDO SOUZA , GOMEZ J. , HEINONEN M. , LEIRO J. , HERMANN A. M. , WANG Y. T.
Published: July 2002

The addition of Sn in Tl,Pb(1223) ( Tl 0.5 Pb 0.5 Sn x Sr 1.6 Ca 2.4 Cu 3 O y) has been investigated using AES and Mössbauer Emission techniques to probe the valence and site geometry of Sn cations. It was found that Sn is present in tetravalent state in the compound at two sites with differing weights. The major part of the tin resides inside the grain and a minor part (weak doublet line in Mossbauer spectra) represents the contribution from the tin at the grain boundary.
PHASE FLUCTUATIONS AND NON-FERMI LIQUID PROPERTIES OF 2D FERMI-SYSTEM WITH ATTRACTION
Authors: GUSYNIN VALERY P. , LOKTEV VADIM M. , QUICK RACHEL M. , SHARAPOV SERGEI G.
Published: July 2002

The effect of static fluctuations in the phase of the order parameter on the normal and superconducting properties of a 2D system with attractive four-fermion interaction has been studied. Analytic expressions for the fermion Green function, its spectral density and the density of states are derived. The resultant single-particle Green function clearly demonstrates non-Fermi liquid behavior. The results show that as the temperature increases through the 2D critical temperature the width of the quasiparticle peaks broadens significantly. At the same time one retains the gap in quasiparticle spectrum. The spectral density for the dynamical fluctuations can also be obtained. Clearly the dynamical fluctuations fill the gap giving the observed pseudogap behaviour.
ARE THERE ANY n-TYPE HIGH-TEMPERATURE CUPRATE SUPERCONDUCTORS?
Authors: Blackstead Howard A. , Dow John D. , Lehmann Martin
Published: July 2002

Based (i) on data for the Pb 2 Sr 2 YCu 3 O 8 (PSYCO) homologues with Y replaced by R = Ce or R = Am, and (ii) on experimental facts for Nd 2-z Ce z CuO 4, we conclude that all the main high-temperature cuprate superconductors are p-type, and that very likely none are n-type.
A NEW INTEGRABLE MODEL OF STRONGLY CORRELATED ELECTRONS WITH HUBBARD-LIKE INTERACTION
Authors: GE XIANG-YU
Published: July 2002

A new completely integrable model of strongly correlated electrons is proposed which describes two competitive interactions: one is the correlated one-particle hopping, the other is the Hubbard-like interaction. The integrability follows from the fact that the Hamiltonian is derivable from a one-parameter family of commuting transfer matrices. The Bethe ansatz equations are derived by algebraic Bethe ansatz method.
SIZE VARIATION OF Tb-DOPED Gd2O3 NANOPARTICLES STUDIED BY X-RAY EXCITED LUMINESCENCE AND DIFFRACTION
Authors: SOO Y. L. , HUANG S. W. , KAO Y. H. , YANG Y. W. , LAI L. J. , CHHABRA V. , KULKAMI B. , VELIADIS J. V. D. , BHARGAVA R. N.
Published: July 2002

Post-fabrication heat treatment has been found as an effective means for controlling the size distribution of Tb-doped Gd 2 O 3 nanoparticles. Variations in the electronic structure and structural order of these doped quantum dots are investigated by using the techniques of X-ray excited luminiscence and diffraction. From room temperature to 1000°C X-ray powder diffraction of this nanoparticle system shows a three-stage transition from featureless data to that of the bulk crystalline structure with increasing particle size. However, substantial changes found in the X-ray excited luminescence are not directly related to the crystalline structure of the nanoparticles. These observations also indicate that bulk-like crystalline phase of the quantum dot material is not a necessary condition for generating the X-ray induced optical effects which are useful for some technological applications.
DYNAMIC CRITICAL EXPONENTS OF THE ISING MODEL WITH MULTISPIN INTERACTIONS
Authors: SIMÕES C. S. , DRUGOWICH DE FELÍCIO J. R.
Published: July 2002

We revisit the short-time dynamics of 2D Ising model with three spin interactions in one direction and estimate the critical exponents z, θ, β and ν. Taking properly into account the symmetry of the Hamiltonian, we obtain results completely different from those obtained by Wang et al.10 For the dynamic exponent z our result coincides with that of the 4-state Potts model in two dimensions. In addition, results for the static exponents ν and β agree with previous estimates obtained from finite size scaling combined with conformal invariance. Finally, for the new dynamic exponent θ we find a negative and close to zero value, a result also expected for the 4-state Potts model according to Okano et al.
CdTe and Si SOLAR CELL PERFORMANCE COMPARISON IN A NEW SYSTEM FOR SOLAR ENERGY CONVERSION AND STORAGE
Authors: MORALES-SÁNCHEZ E. , GONZÁLEZ-HERNÁNDEZ J. , RAMÍREZ-BON R. , ESPINOZA-BELTRÁN F. , VOROBIEV Y. , MORALES-ACEVEDO A. , GORLEY PETRO , KOVALYUK Z. , HORLEY PAUL
Published: July 2002

A new system for the effective conversion and storage of solar energy using CdTe and Si based photovoltaic solar cells and the Li- Bi 2 Se 3 rechargable batteries was created and studied. PV Solar Cells with the different types of structure and barrier were studied (Shottky. MIS with thin insulating layer, and p-n junction), employing low-temperature and high-temperature technological cycles. The influence of the technological details upon the electrical parameters as well as the efficiency and stability of their performance were analyzed, and also the condition for improving the efficiency were found. In particular, it was established that Zn-doping of CdTe and the Al alloying to Si at 800°C have a profound effect upon the PV cell characteristics. The influence of the recombination in different parts of the cell upon the cell's efficiency and the recombination dependence upon the technological features were investigated.

A comparison of the performance and fabrication cost of the new systems for solar energy conversion and storage with others using conventional cells and batteries is made. It is shown that newly developed systems could provide a global efficiency close to that for traditional ones, with simpler and cheaper technology. With some modifications of the technology, we expect to get even higher efficiencies and a wider system operation temperature range. The possibilities are discussed for the creation of a hybrid energy conversion system on the basis of our cells and batteries, with an overall efficiency of transformation of solar-to-electric energy around 40%.
USE OF IBA TECHNIQUES FOR THE MEASUREMENT OF OXIDATION PROCESSES IN SIALON CERAMICS
Authors: BROWN I. W. M. , BARRIS G. C. , SHEPPARD C. M. , TROMPETTER W. J. , VICKRIDGE I. C.
Published: July 2002

Sialon ceramics (Si-Al-O-N) are high performance engineering materials used as cutting tools and wear parts whose performance may be compromised by high temperature oxidation. Ion Beam Analysis (IBA) techniques, coupled with X-ray Diffraction, have been used to monitor oxidation processes in dense bodies of α/β-sialon, X-sialon and O-sialon subjected to heat treatment schedules in air to induce surface oxidation. This has permitted depth profiling of Si, Al, Y, O, & N in the sialon bodies, enabling direct comparison of oxidation resistance to be made between the different sialon compositions.
ELECTRICAL CHARACTERIZATION OF EPITAXIAL BI:2201
Authors: POP A. V. , ILONCA G. , POP MARIANA , DELTOUR R.
Published: July 2002

Bi2.1Sr1.9CuOy thin films (Bi:2201) were deposited onto heated single crystal (100) MgO substrates using inverted cylindrical DC magnetron sputtering with different partial pressures of oxygen in a sputtering gas. The behavior of the normal state resistivity function of temperature is strongly influenced by the composition of sputtering gas used in thin films synthesis. Near the transition to the superconducting state, electrical resistivity changes strongly from "metallic" to insulator (MI). The origin for the increase of electrical resistance was analyzed using some models for the localization of mobile carriers. A good linearity is obtained for ln R as a function of Tα for α = 1/10 and for R as a function of ln T. The last behavior agrees with the pinning and fragmentation of 1D stripes in CuO2 planes.
U(1)×SU(2) Gauge Theory of Underdoped Cuprate Superconductors
Authors: Marchetti P. A. , Su Zhao-Bin , Yu Lu
Published: July 2002

The U(1)×SU(2) Chern–Simons gauge theory is applied to study the 2D t–J model describing the normal state of underdoped cuprate superconductors. The U(1) field produces a flux phase for holons converting them into Dirac-like fermions, while the SU(2) field, due to the coupling to holons gives rise to a gap for spinons. An effective low-energy action involving holons, spinons and a self-generated U(1) gauge field is derived. The Fermi surface and electron spectral function obtained are consistent with photoemission experiments. The theory predicts a minimal gap proportional to doping concentration. It also explains anomalous transport properties.
Exact Finite Size Results for the Ising Model on the Tetrahedron
Authors: González J. , Martín-Delgado M. A.
Published: July 2002

We propose an approach to statistical systems on lattices with sphere-like topology. Focusing on the Ising model, we consider the thermodynamic limit along a sequence of lattices with a finite number of defects approaching the large scale geometry of a tetrahedron. The hypothesis of scaling appears to hold at criticality, pointing at a sensible definition of the continuum limit of the model in the polyhedron. Finite size scaling is shown to produce, however, an anomalous exponent for the critical behavior of the correlation length, which we determine alternatively by looking at the temperature dependence of the gap at large lattice size.
INTEGRABILITY OF A t–J MODEL WITH BOUNDARY IMPURITY COUPLING
Authors: CHEN SHU , WANG YUPENG , HU ZHANNING , PU FU-CHO
Published: July 2002

In this paper, we present a t–J model with a boundary impurity coupling term. By selecting the boundary matrix appropriately, the corresponding Hamiltonians are derived in the framework of quantum inverse scattering method and thus the integrability is guaranteed.
THE CRITICAL EXPONENT θ′ IN SPIN GLASSES
Authors: LUO H. J. , SCHÜLKE L. , ZHENG B.
Published: July 2002

Short-time dynamic scaling behavior of the 3D ± J Ising spin glass is studied by Monte Carlo methods. Starting the replicas with independent initial configurations with a small pseudo-magnetization, the dynamic evolution of the overlap q(t) between two replicas is measured. The initial increase of the overlap q(t) is observed and the corresponding exponent θ′ is obtained. From the scaling relation λ= d/z-θ′, the dynamic exponent z is estimated.
ELECTRON MOMENTUM DENSITIES IN GaxIn1-xAsySb1-y PROBED BY POSITRONS
Authors: BOUARISSA N.
Published: July 2002

Momentum densities of electron–positron pairs in cubic Ga x In 1-x As y Sb 1-y lattice matched to GaSb and InAs are studied for the first time to the best of our knowledge, with the aim of investigating the disorder and substrate effects on these quantities in the materials for interest. The electron wavefunction is calculated using the pseudopotential band model under the virtual crystal approximation with and without incorporating the effects of compositional variations. The calculations of the positron wavefunction is made in an identical manner, employing the point-core approximation for the ionic potential. It is found that while the electron–positron momentum densities in Ga x In 1-x As y Sb 1-y at x=0.50 are sensitive to the compositional disorder, they are not altered by the change of substrate.
A MODEL FOR OPTICAL ABSORPTION OF AMORPHOUS GaAs IN THE FAR-INFRARED RANGE BY USING AN OPERATIONAL TECHNIQUE
Authors: GRADO-CAFFARO M. A. , GRADO-CAFFARO M.
Published: July 2002

By considering a sample of amorphous GaAs with a small zone of dynamical disorder, an expression for the optical absorption coefficient and phonon density of states in the low region of the far-infrared range is obtained. To get to this end, absorption corresponding to structural disorder is neglected.
CAN PULLING CAUSE RIGHT- TO LEFT-HANDED STRUCTURAL TRANSITIONS IN NEGATIVELY SUPERCOILED DNA DOUBLE-HELIX?
Authors: ZHOU HAIJUN , OU-YANG ZHONG-CAN
Published: July 2002

The folding angle distribution of stretched and negatively supercoiled DNA double-helix is investigated based on a previously proposed model of double-stranded biopolymers [H. Zhou et al., Phys. Rev. Lett.82, 4560 (1999)]. It is shown that pulling can cause transition of a negatively supercoiled DNA double-helix from the right-handed B-form to a left-handed configuration which resembles DNA Z-form in some important aspects. The energetics of this possible transition is calculated and a comparison with recent experimental observations is qualitatively discussed.
SHORT-TIME CRITICAL DYNAMICS OF MULTISPIN INTERACTION ISING MODEL IN TWO DIMENSIONS
Authors: WANG L. , ZHANG J. B. , YING H. P. , JI D. R.
Published: July 2002

We investigated the short-time dynamics of a multispin model in two dimensions. A dynamical Monte Carlo simulation which avoids the critical slowing down is performed at critical temperature and the short-time dynamic scaling behavior is found. By using the universal power-law scaling features, the critical exponents θ, z and 2β/ν are estimated in our calculations.
MARGINAL FERMI LIQUID WITH A TWO-DIMENSIONAL PATCHED FERMI SURFACE
Authors: FERRAZ A. , SAIKAWA T. , WENG Z. Y.
Published: July 2002

We consider a model composed of Landau quasiparticle states with patched Fermi surfaces (FS) sandwiched by states with flat FS to simulate the "cold" spot regions in cuprates. We calculate the one-particle irreducible function and the self-energy up to two-loop order. Using renormalization group arguments, we show that in the forward scattering channel, the renormalized coupling constant is never infrared stable due to the flat FS sectors. Furthemore, we show that the self-energy scales with energy as Re ∑~ω ln ω as ω→0, and thus the Fermi liquid state within each FS patch is turned into a marginal Fermi liquid.
MCE-BASED FACE RECOGNITION
Authors: CHEN LIANG-HUA , DENG SHAO-HUA , LIAO HONG-YUAN
Published: July 2002

This paper proposes a complete procedure for the extraction and recognition of human faces in complex scenes. The morphology-based face detection algorithm can locate multiple faces oriented in any direction. The recognition algorithm is based on the minimum classification error (MCE) criterion. In our work, the minimum classification error formulation is incorporated into a multilayer perceptron neural network. Experimental results show that our system is robust to noisy images and complex background.
DARBOUX INTEGRABILITY FOR THE RÖSSLER SYSTEM
Authors: LLIBRE JAUME , ZHANG XIANG
Published: July 2002

In this note we characterize all generators of Darboux polynomials of the Rössler system by using weight homogeneous polynomials and the method of characteristic curves for solving linear partial differential equations. As a corollary we prove that the Rössler system is not algebraically integrable, and that every rational first integral is a rational function in the variable x2+y2+2z. Moreover, we characterize the topological phase portrait of the Darboux integrable Rössler system.
ANALYSIS OF A QUANTIZED CHAOTIC SYSTEM
Authors: TORIKAI HIROYUKI , SAITO TOSHIMICHI , KAWASAKI YOSHINOBU
Published: July 2002

We consider quantized chaotic dynamics for a spiking oscillator with two periodic inputs. As the first input is applied, the oscillator generates various periodic and chaotic pulse-trains governed by a pulse position map. As the second input is added, the oscillator produces pulse positions restricted on a lattice, and the pulse position map is quantized. Then the oscillator generates a set of super-stable periodic pulse-trains (SSPTs). The oscillator has various coexisting SSPTs and generates one of them depending on the initial state condition. In order to characterize the set of SSPTs, we elucidate the number and the minimum pulse interval of the SSPTs theoretically. By presenting a simple test circuit, we then verify some typical phenomena in the laboratory environment.
RADIAL BASIS FUNCTION NETWORKS AS CHAOTIC GENERATORS FOR SECURE COMMUNICATION SYSTEMS
Authors: PAPADIMITRIOU S. , BEZERIANOS A. , BOUNTIS T.
Published: July 2002

This paper improves upon a new class of discrete chaotic systems (i.e. chaotic maps) recently introduced for effective information encryption. The nonlinearity and adaptability of these systems are achieved by designing proper radial basis function networks. The potential for automatic synchronization, the lack of periodicity and the extremely large parameter spaces of these chaotic maps offer robust transmission security. The Radial Basis Function (RBF) networks offer a large number of parameters (i.e. the centers and spreads of the RBF kernels and the weights of the linear layer) while at the same time as universal approximators they have the flexibility to implement any function. The RBF networks can learn the dynamics of chaotic systems (maps or flows) and mimic them accurately by using many more parameters than the original dynamical recurrence. Since the parameter space size increases exponentially with respect to the number of parameters, the RBF based systems greatly outperform previous designs in terms of encryption security. Moreover, the learning of the dynamics from data generated by chaotic systems guarantees the chaoticity of the dynamics of the RBF networks and offers a convenient method of implementing any desirable chaotic dynamics. Since each sequence of training data gives rise to a distinct RBF configuration, theoretically there exists an infinity of possible configurations.
LINEAR STABILITY ANALYSIS GENERALIZED TO A THERMALLY-DRIVEN FLOW
Authors: CORNET JEAN-MICHEL , LAMARQUE CLAUDE-HENRI
Published: July 2002

We intend to establish a methodology suited to the search of the first bifurcations of convective flows using a linear stability analysis so that it permits us to define a relationship between amplitude and frequency of the perturbation. We use a particular combination of various numerical methods to compute on one hand the basic solution. On the other hand the perturbation is applied to the search for the bifurcations in a thermally-driven cavity.
CHECKERBOARD SPIRAL WAVES IN A 2D COUPLED MAP LATTICE: SCALING EVIDENCE
Authors: SBITNEV VALERY I. , DUDKIN ALEX. O.
Published: July 2002

Checkerboard spiral waves in a 2D CML under consideration are generic solutions in a narrow parameter layer located adjacent to the saddle-node bifurcation boundary in the spatiotemporal chaos region. The spiral wave self-organization is in close agreement with the Haken's slaving principle. Scaling correspondence between sizes of the spiral waves and the diffusion length that is a natural unit of length in the CML is established.
"SPIRAL WAVE–TRAVELING CLUSTERING" INTERMITTENCY AND 1/f-NOISE IN A 2D COUPLED MAP LATTICE
Authors: PUSTOVOIT MARK A. , SBITNEV VALERY I.
Published: July 2002

Intermittency of checkerboard spiral waves and traveling clusterings originating from sudden shrinking of the strange attractor of the 2D CML in the neighborhood of the saddle-node bifurcation boundary is found. A power-law probability density for lifetimes in the spiral wave (laminar) phase is observed, while in the checkerboard clusterings (bursting) phase the above quantity exhibits an exponential decay. This difference can be interpreted through the self-organized behavior of the spiral waves, and the passive relaxation of the disordered checkerboard clusterings.
COMPUTER TOOLS FOR BIFURCATION ANALYSIS: GENERAL APPROACH WITH APPLICATION TO DYNAMICAL AND DISTRIBUTED SYSTEMS
Authors: PISMEN LEONID M. , RUBINSTEIN BORIS Y.
Published: July 2002

A general approach of the automated algorithms for derivation of amplitude equations for dynamical and distributed systems is presented. A brief description of the Mathematica functions designed using this approach is given. Application of the functions is illustrated by several examples dealing with dynamical and distributed systems.
ON THE ROLE OF RANDOM TRANSVERSAL UNCOUPLING ON RE-ENTRY FORMATION
Authors: GÓMEZ-GESTEIRA M. , DECASTRO M. , PÉREZ-VILLAR V.
Published: July 2002

The effect of randomly distributed connections among cells on spiral initiation by vulnerability is studied into the framework of active electronic circuits. We have observed the increase of the vulnerable region due to the transversal uncoupling among adjacent cells.
ARCHITECTURE-LEVEL DEPENDENCE ANALYSIS FOR SOFTWARE SYSTEMS
Authors: STAFFORD JUDITH A. , WOLF ALEXANDER L.
Published: July 2002

The emergence of formal software architecture description languages provides an opportunity to perform analyses at high levels of abstraction, as well as early in the development process. Previous research has primarily focused on developing techniques such as algebraic and transition-system analysis to detect component mismatches or global behavioral incorrectness. In this paper we motivate the utility and describe the challenges in developing a different kind of analysis for use at the architectural level, namely dependence analysis. Various kinds of dependence analyses have been used widely at the implementation level to aid program optimization, anomaly checking, program understanding, testing, and debugging. However, the languages used for architectural description offer quite different features than the languages for which traditional dependence analysis techniques have been developed. We describe our initial approach to architecture-level dependence analysis and illustrate that approach through a prototype tool we have built, called Aladdin, to automatically perform the analysis.
SIMULTANEOUS REPRESENTATIONS OF SEMILATTICES BY LATTICES WITH PERMUTABLE CONGRUENCES
Authors: TŮMA JIŘÍ , WEHRUNG FRIEDRICH
Published: July 2002

The Congruence Lattice Problem (CLP), stated by R. P. Dilworth in the forties, asks whether every distributive {∨, 0}-semilattice S is isomorphic to the semilattice Con c L of compact congruences of a lattice L.

While this problem is still open, many partial solutions have been obtained, positive and negative as well. The solution to CLP is known to be positive for all S such that |S|≤ℵ1. Furthermore, one can then take Lwith permutable congruences. This contrasts with the case where |S|≥ℵ2, where there are counterexamples S for which Lcannot be, for example, sectionally complemented. We prove in this paper that the lattices of these counterexamples cannot have permutable congruences as well.

We also isolate finite, combinatorial analogues of these results. All the "finite" statements that we obtain are amalgamation properties of the Con c functor. The strongest known positive results, which originate in earlier work by the first author, imply that many diagrams of semilattices indexed by the square22 can be lifted with respect to the Con c functor.

We prove that the latter results cannot be extended to the cube, 23. In particular, we give an example of a cube diagram of finite Boolean semilattices and semilattice embeddings that cannot be lifted, with respect to the Con c functor, by lattices with permutable congruences.

We also extend many of our results to lattices with almost permutable congruences, that is, α∨β=αβ ∪βα, for all congruences α and β.

We conclude the paper with a very short proof that no functor from finite Boolean semilattices to lattices can lift the Con c functor on finite Boolean semilattices.
MONOIDS WITH IDEMPOTENT CROSS-SECTIONS
Authors: PUTCHA MOHAN S.
Published: July 2002

In this paper we consider monoids M with an idempotent cross-section Λ of regular [Formula: see text]-classes such that for all idempotents e, f of M with e≥f, there exists x in the unit group such that x-1ex, x-1fx∈Λ. Such monoids arise frequently in connection with group representations. We show that Λ is then necessarily a semilattice and that the idempotent structure of M can for the most part, be determined within the unit group.

We identify a particular class of "canonical monoids" inspired by some projective compactifications of algebraic groups. We show that these canonical monoids are 0-semilattice unions of completely 0-simple semigroups.
QUANTUM SCHUBERT POLYNOMIALS AND QUANTUM SCHUR FUNCTIONS
Authors: KIRILLOV ANATOL N.
Published: July 2002

We introduce the quantum multi–Schur functions, quantum factorial Schur functions and quantum Macdonald polynomials. We prove that for restricted vexillary permutations, the quantum double Schubert polynomial coincides with some quantum multi-Schur function and prove a quantum analog of the Nägelsbach–Kostka and Jacobi–Trudi formulae for the quantum double Schubert polynomials in the case of Grassmannian permutations. We prove also an analog of the Giambelli and the Billey–Jockusch–Stanley formula for quantum Schubert polynomials. Finally we formulate two conjectures about the structure of quantum double and quantum Schubert polynomials for 321–avoiding permutations.
THE ALPERIN AND DADE CONJECTURES FOR THE FISCHER SIMPLE GROUP Fi23
Authors: AN JIANBEI , O'BRIEN E. A.
Published: July 2002

We modify the local strategy of [2] and use it to classify the radical subgroups and chains of the Fischer simple group Fi 23. We verify the Alperin weight conjecture and the Dade final conjecture for this group.
EVOLUTION OF GRAIN BOUNDARIES
Authors: KINDERLEHRER DAVID , LIU CHUN
Published: July 2002

Evolution and trend to equilibrium of a (planar) network of grain boundaries subject to curvature driven growth is established under the assumption that the system is initially close to some equilibrium configuration. Curvature driven growth is the primary mechanism in processing polycrystalline materials to achieve desired texture, ductility, toughness, strength, and other properties. Imposition of the Herring condition at triple junctions ensures that this system is dissipative and that the complementing conditions hold. We introduce a new way to employ the known Solonnikov-type estimates, which are only local in time, to obtain solutions that are global in time with controlled norm. These issues were raised as part of the Mesoscale Interface Mapping Project.
HIGH-FIELD LIMIT OF THE VLASOV–POISSON–FOKKER–PLANCK SYSTEM: A COMPARISON OF DIFFERENT PERTURBATION METHODS
Authors: BONILLA LUIS L. , SOLER JUAN S.
Published: July 2002

A reduced drift-diffusion (Smoluchowski–Poisson) equation is found for the electric charge in the high-field limit of the Vlasov–Poisson–Fokker–Planck system, both in one and three dimensions. The corresponding electric field satisfies a Burgers equation. Three methods are compared in the one-dimensional case: Hilbert expansion, Chapman–Enskog procedure and closure of the hierarchy of equations for the moments of the probability density. Of these methods, only the Chapman–Enskog method is able to systematically yield reduced equations containing terms of different order.
EXTENSION OF THE MORTAR FINITE ELEMENT METHOD TO A VARIATIONAL INEQUALITY MODELING UNILATERAL CONTACT
Authors: BELGACEM FAKER BEN , HILD PATRICK , LABORDE PATRICK
Published: July 2002

The purpose of this paper is to extend the mortar finite element method to handle the unilateral contact model between two deformable bodies. The corresponding variational inequality is approximated using finite element meshes which do not fit on the contact zone. The mortar technique allows one to match these independent discretizations of each solid and takes into account the unilateral contact conditions in a convenient way. By using an adaptation of Falk's lemma and a bootstrap argument, we give an upper bound of the convergence rate similar to the one already obtained for compatible meshes.
A MINIMAL LINK ON THE CUBIC LATTICE
Authors: ERNST C. , PHIPPS M.
Published: July 2002

The main theorem in this article shows that the link [Formula: see text] cannot be realized with fewer than 28 steps on the cubical lattice. There are at least two very different 28-step realizations of [Formula: see text] on the cubical lattice in which the length of the components of the link differs. The two 28-step realizations of [Formula: see text] do not have minimal curvature. A realization with a minimal curvature of 6.5 π of the link [Formula: see text] with 30 steps is also shown.
BIANCHI TYPE I UNIVERSES WITH CAUSAL BULK VISCOUS COSMOLOGICAL FLUID
Authors: MAK M. K. , HARKO T.
Published: July 2002

We consider the dynamics of a causal bulk viscous cosmological fluid filled flat constantly decelerating Bianchi type I spacetime. The matter component of the Universe is assumed to satisfy a linear barotropic equation of state and the state equation of the small temperature Boltzmann gas. The resulting cosmological models satisfy the condition of smallness of the viscous stress. The time evolution of the relaxation time, temperature, bulk viscosity coefficient and comoving entropy of the dissipative cosmological fluid is also obtained.
MULTI-BLACK HOLES AND INSTANTONS IN EFFECTIVE STRING THEORY
Authors: DEMELIO S. , MIGNEMI S.
Published: July 2002

The effective four-dimensional action for string theory contains non-minimal couplings of the dilaton and the moduli arising from the compactification of higher dimensions. We show that the resulting field equations admit multi-black hole solutions. The Euclidean continuation of these solutions can be interpreted as an instanton mediating the splitting and recombination of the throat of extremal magnetically charged black holes.
SAMPLE VARIANCE IN LARGE-SCALE COSMIC MICROWAVE BACKGROUND ANISOTROPY MEASUREMENTS
Authors: NG KIN-WANG
Published: July 2002

The effects of limited sky coverage in large-angle cosmic microwave background anisotropy experiments are investigated by computing the variance of the angular two-point correlation function with an incomplete sphere. We find that, assuming a power spectrum of density fluctuations with spectral index n = 1, the Galactic cut of half-width 20° (40°) about the Equator made by the COBE DMR experiment would induce a sample variance on the rms temperature fluctuation [(ΔT/T) rms ]2 (or equivalently, the correlation function at zero lag), which is 12% (38%) greater than the cosmic variance with a whole sky coverage. This result is about two times smaller than the naive expectation that the cosmic variance is enhanced by a factor of [Formula: see text], where A is the solid angle sampled by the experiment. We also find that the sample variance of the correlation function at nonzero lag can approach the cosmic variance limit. Our approach provides an analytic way of finding a theoretical error to the theoretical prediction for a particular experiment (either large- or small-scale), without having recourse to computationally intensive Monte Carlo or maximum likelihood methods.
THE MORPHOGENESIS OF HIGH SYMMETRY: THE SYMMETRIZATION THEOREM
Authors: MARZEC CHRISTOPHER J.
Published: July 2002

A multi-part theorem is presented concerning the morphogenesis of high-symmetry structures made of three-dimensional morphological units (MU's) free to move on the surface of a sphere. All parts of each MU interact non-specifically with the remainder of the structure, via an isotropic function of distance. Summing all interactions gives a net figure of merit, ℐ, that depends upon MU positions and orientations. The structure evolves via gradient dynamics, each MU moving down the local gradient of ℐ. The analysis is reresented with generality in Fourier space, which eases the expression of symmetry.

Structures near symmetry, but far from a local minimum of ℐ, are analyzed. For each, a symmetrical configuration can be found, for which ℐ is an extremum with respect to symmetry-breaking perturbations. Under gradient dynamics, a quadratic measure of such deviations from symmetry decreases monotonically, anywhere in the large basin of attraction of a local minimum. Thus: high symmetry is an attractor.

Application is made to icosahedral virus capsids. The Symmetrization Theorem shows that a stable capsid, maintained by non-specific interactions among its capsomeres, could arise generically in a "bottom-up" process. For animated evolutions that self-assemble into high symmetry, visit
GENERALIZATION OF BARENBLATT'S COHESIVE FRACTURE THEORY FOR FRACTAL CRACKS
Authors: YAVARI ARASH
Published: July 2002

In this paper, we generalize Barenblatt's cohesive fracture theory for fractal cracks. We discuss the difficulties of generalizing the concept of traction on a fractal surface. Borodich's modification of Griffith's theory for fractal cracks is reviewed. Irwin's driving force is generalized for fractal cracks and a fractal driving force (Gf) is defined. It is shown that to generalize Barenblatt's theory for fractal cracks it is necessary to introduce a new quantity, D-fractal cohesive pseudo-stress. This new quantity is cohesive force per unit of a fractal measure. Fractal modulus of cohesion is seen to be a function of both the material and the fractal dimension of the crack. Equivalence of fractal Barenblatt's and Griffith's theories is discussed. It is seen that the order of stress singularity at the tip of a fractal crack cannot be obtained using modified Barenblatt's theory because this theory is a local theory and assumes the order of stress singularity a priori.
UNIFORMLY ASYMPTOTIC SOLUTIONS FOR PSEUDODIFFERENTIAL EQUATIONS WITH SINGULAR INTEGRAL OPERATORS
Authors: HANYGA A. , SEREDYŃSKA M.
Published: July 2002

Uniformly asymptotic frequency-domain solutions for a class of hyperbolic equations with singular convolution operators are derived. Asymptotic solutions for this class of equations involve additional parameters — called attenuation parameters — which control the smoothing of the wavefield at the wavefront. At caustics the ray amplitudes have a singularity associated with vanishing of ray spreading and with divergence of an integral controlling the rate of exponential amplitude decay. Both problems are resolved by applying a generalized Kravtsov–Ludwig formula derived in this paper. A different asymptotic solution is constructed in the case of separation of dispersion and focusing effects.
BOND STRETCHING AND DISTORTION IN LARGE ORGANIC MOLECULES ON Ag(111) DETERMINED BY SURFACE X-RAY DIFFRACTION
Authors: MEYERHEIM H. L. , GLOEGE TH. , MALTOR H. , SOKOLOWSKI M. , UMBACH E. , BÄUERLE P.
Published: July 2002

The geometric structure of large organic molecules (end-capped quaterthiophene and 2-thiouracil) adsorbed on Ag(111) was analyzed in detail by surface X-ray diffraction. In both cases our data give direct evidence for significant stretching of the C–S and the C–C bonds by up to 0.16 Å and — in the case of EC4T — for a distortion of the thiophene rings. This is in contrast to the common belief that such molecules remain undistorted upon adsorption on a weakly interacting substrate. Our results provide the basis for a deeper understanding of large organic adsorbates and have important implications for a deeper insight into organic/inorganic interfaces in general.
Endoscopic Carpal Tunnel Release: A Retrospective Study of the Modified Okutsu Technique Using Glass Tubes
Authors: Tsai TM , Favetto M. , Elluru R.
Published: July 2002

We evaluated 108 endoscopically assisted carpal tunnel releases in 90 patients in a retrospective study to determine the efficiency and safety of a modified Okutsu endoscopic carpal tunnel release (ECTR) technique. The modification consisted of the use of glass tubes 5, 7, and 9 mm in diameter and a sharp tipped hook knife. The results were evaluated using a patient questionnaire, time off from work, grip strength, and two point discrimination. Symptoms were resolved in 71% of the patients, improved in 19.4%, and not improved in 9.3%. In this series, 59 patients were gainfully employed: 84.7% returned to work, half within 2 weeks of surgery. Severe complications included one laceration of the ulnar nerve, and one neuroma in continuity of the median nerve. ECTR using this modification of Okutsu's technique is effective in the relief of symptoms and returning patients to work quickly.
TRIGGERING CAUSED BY COMPLETE TRANSECTION OF ONE SLIP OF THE FLEXOR DIGITORUM SUPERFICIALIS TENDON: A CASE REPORT
Authors: Koger Kim Edward , Schmidt Stephen , Somia Naveen N. , Gupta Amit
Published: July 2002

Trigger finger was observed in a patient with a healed laceration at the palmar-digital crease of the left long finger. Examination revealed complete transection of the ulnar slip of the FDS tendon. The proximal ulnar slip was excised and the cut edge tapered, which restored a full range of motion without triggering.
NEW TARGETS FOR THE STUDIES OF BIOMECHANICAL, ENDOCRINOLOGIC, GENETIC AND PHARMACEUTICAL EFFECTS ON BONES: BONE'S "NEPHRON EQUIVALENTS", MUSCLE, NEUROMUSCULAR PHYSIOLOGY
Authors: Frost Harold M.
Published: July 2002

As age, experience and common sense look at biomechanical, hormonal, genetic and other roles in bone physiology and its disorders, two questions can arise: (a) How did we fail? (b) How could we make it better? The acerbic Sam Johnson said that to teach new things, we should use examples of already known ones. If so, an analogy might help to clarify this article's message for people who work with bones and their disorders.

Assume this: (a) Mythical physiologists were taught that renal physiology depends on "kidney cells" but were taught nothing about nephrons; (b) so they explained renal health and disorders in those terms. (c) For many decades, they "knew" that view was correct (as the ancients "knew" the world was flat). (d) But then others described nephrons and some errors their properties revealed in those views about renal physiology; (e) so controversies began.

Today, an analogous situation confronts real biomechanicians and physiologists. (i) Most of them were taught that osteoblasts and osteoclasts (bone's "effector cells") explain bone physiology without "nephron-equivalent" input, so they explained bone disorders and mechanical effects in those terms. (ii) Yet nephron-equivalent mechanisms and functions, including biomechanical ones, in bones have the same operational relationship to their cells, health and disorders as nephrons and their functions do to renal cells, health and disorders. (iii) Adding that knowledge to former views led to the Utah paradigm of skeletal physiology. It also revealed errors in many former views about bone physiology; (iv) so real controversies have begun.

Biomechanicians, physiologists, clinicians and pharmacologists from whom poor interdisciplinary communication hid that paradigm could think the view in (i) above remains valid, and keep analyzing data and designing studies within its constraints.

Like Wegner's idea of plate tectonics in geology, the Utah paradigm came before its field was ready, so others fought it. But while the plate-tectonics war was won, it has just begun for the Utah paradigm. This article reviews how such things could apply to bone and some of their implications. Its conclusion offers succinct answers to the italicized questions above.
MARKET SEGMENTATION AND NOISE TRADER RISK
Authors: ERRUNZA VIHANG , HOGAN KED , HUNG MAO-WEI
Published: July 2002

A simple asset pricing model is developed to take into account two important characteristics in global investments: market segmentation and noise trader risk. Our results show the removal of international investment barriers and cross-border listings have not led to a fully integrated international capital market. We also show that different degree of investor rationality across borders induces an additional component of risk premium which is related to the "noise spill-over effect".