bluuebunny/crossref_metadata_2025 huggingface dataset:
Vibrational spectroscopic studies of aqueous solutions of tert-butyl alcohol and tert-butylamine
Authors: Kipkemboi Pius K , Easteal Allan J
Published: July 2002

Raman and FT-IR absorption spectra of aqueous tert-butyl alcohol (t-BuOH) and tert-butylamine (t-BuNH2) in the region of the OH and NH2 stretching and bending modes have been measured as a function of organic co-solvent concentration in the whole co-solvent mole fraction region. The major observed changes of the aqueous binary solution spectra compared with the solvent spectra are a loss or gain of band intensity. In particular, the observed changes in intensities and linewidths of some bands were significantly more pronounced at low concentrations of organic co-solvents in water, where t-BuOH and t-BuNH2 tend to integrate into the water structure. Clear evidence of structural enhancement of the network is obtained in dilute solutions as well as destruction of the network by hydrophobic interactions as the concentration is increased. Generally, the interpretation of the spectra is in agreement with the capacity of the hydrophobic co-solvent to break the structure of water in the more concentrated aqueous solutions and to enhance the structure in dilute solutions. Vibrational intensities and frequency shifts of some bands show definite trends with varying the concentration of the solutions. In the concentration-dependence study, unusual linewidth changes of certain bands were observed.Key words: infrared, Raman spectra, aqueous, tert-butanol, tert-butylamine.
Exploratory synthetic investigations related to 12a-deoxypillaromycinone
Authors: Wang Lan , Meegalla Sanath K , Fang Cheng-Lin , Taylor Nicholas , Rodrigo Russell
Published: July 2002

Furfural is converted to suitably substituted AB synthon 21 for 12a-deoxypillaromycinone in 10 steps by a sequence involving the following key steps: intramolecular Diels-Alder reaction of a furan, 5-endo-trig cleavage of the oxabicyclo adducts 18, and catalytic hydrogenation of the double bond of a tetrasubstituted enone to produce 19. Enones 21a and 21b obtained by dehydrogenation of 19a and 19b, respectively, are then annulated with ethyl 2-methoxy-6-methylbenzoate in a four-step procedure to generate tetracyclic products 25 in 14 steps from furfural.
Regiospecific synthesis of lactose analog Gal-(β 1,4)-Xyl by transgalactosylation
Authors: Fessner Wolf-Dieter , Juárez Ruiz Juan Manuel
Published: July 2002

A short enzymatic synthesis of disaccharide 4-O-β-D-galactopyranosyl-D-xylose (1) has been developed, which is of interest as a lactose analog for a non-invasive medicinal determination of lactose intolerance. The starting material, benzyl α-D-xyloside, was obtained by a Fischer-type glycosidation of D-xylose with benzyl alcohol, followed by anomeric differentiation of mixed glycosides using a glycosidase from Aspergillus oryzae. From several commercial β-galactosidases, which were screened for their transgalactosylation capacity, the enzyme from Escherichia coli was found to catalyze a virtually regio- and stereospecific galactosyl transfer from donor compounds o-nitrophenyl β-D-galactoside or lactose to the α-D-xyloside. Subsequent hydrogenolytic deprotection furnished desired disaccharide 1.Key words: oligosaccharide synthesis, β-galactosidase, lactose intolerance.
The determination of the stereochemistry of epoxides located at the 5,6-positions of decalinic systems: An empirical method based on 13C NMR chemical shifts
Authors: Cravero Raquel M , Labadie Guillermo R , Sierra Manuel González
Published: July 2002

The 13C NMR spectra of a series of 5,6-epoxides in decalinic systems were studied. The interpretation of the chemical shifts allowed us to formulate an empirical rule to predict the epoxide stereochemistry. A discussion of the scope and limitations of this method and its extension to larger carbon skeletons is also presented.Key words: epoxide stereochemistry, 13C NMR, NMR, decalinic systems, oxiranes.
Inhibition of endothelin-converting enzyme for protection against neointimal proliferation following balloon angioplasty of the rat carotid artery
Authors: Pham Dung , Jeng Arco Y , Plante Sylvain , Escher Emanuel , Battistini Bruno
Published: July 2002

Clinical success of percutaneous transluminal coronary angioplasty is limited by restenosis within months of the initial intervention. A number of vasoactive mediators and growth factors have been reported to participate in this process. The aim of the present experiments was to examine the effects of nonselective neutral endopeptidase (NEPi)/endothelin-converting enzyme (ECEi) inhibitors against neointimal proliferation (NIP) following balloon angioplasty of the left carotid artery of SpragueDawley rats with the right vessel serving as the uninjured control. The rats were divided in several groups: group 1, nontreated (vehicle); group 2, treated with a selective NEPi i.p.; groups 37, treated with nonselective NEPi/ECEi either i.p., s.c., i.v., or p.o. at various doses. After 2 weeks, cross-sectional histopathological and morphometrical examination of the left carotids revealed a severe NIP in vehicle-treated angioplastic rats compared with the control uninjured right carotid of the same rats. The selective NEPi CGS 24592 had no significant effect on restenosis, nor did the dual NEPi/ECEi CGS 26303 at 5 mg·kg1·day1i.p. Both s.c and i.v. NEPi/ECEi treatment (10 mg·kg1·day1b.i.d. s.c. or 10 mg·kg1·day1i.v.) reduced NIP by up to 35%. The prodrug CGS 26393 (p.o.) also attenuated NIP by 23%. Plasma concentrations of these compounds correlated with the degree of inhibition. These data support the participation of the endothelin system in the rat model of balloon angioplasty and suggest that selective ECEi may be effective.Key words: endothelin, endothelin-converting enzyme, neutral endopeptidase, neprilysin, inhibitors, balloon angioplasty, neointimal proliferation.
DISTRIBUTED PROCESSING IN AUTOMATA
Authors: KRITHIVASAN KAMALA , BALAN N. SAKTHI , HARSHA PRAHLADH
Published: July 2002

With distributed computing beginning to play a major role in modern Computer Science, the theory of grammar systems and distributed automata has been developed in order to model distributed computing. In this paper, we introduce the notion of distributed automata in the sequential sense. Distributed Automata are a group of automata working in unison to accept one language. We build the theory of distributed for FSA and PDA in different modes of acceptance like the t-mode, *-mode, =k-mode, ≤k-mode and ≥k-mode. We then analyze the acceptance power of each automata in all the above modes. We present proofs that distributed FSAs do not have any additional power over "centralized" FSAs in any of the modes, while distributed PDAs with only two components are as powerful as Turing Machines in all of the modes. We give proofs for the equivalence of all modes in the case of PDAs. We also study a restricted version of distributed PDA called k-turn distributed PDA.
A NOTE ON THE POLYNOMIAL REPRESENTATION OF BOOLEAN FUNCTIONS OVER GF(2)
Authors: BEIGEL RICHARD , BERNASCONI ANNA
Published: July 2002

We investigate the representation of Boolean functions as polynomials over the field GF(2), and prove an interesting characteriztion theorem: the degree of a Boolean function over GF(2) is equal to the size of its largest subfunction that takes the value 1 on an odd number of input strings. We then present some properties of odd functions, i.e., functions that take the value 1 on an odd number of strings, and analyze the connections between the problem of the existence of odd functions with very low maximal sensitivity and the long standing open problem of the relationship between the maximal sensitivity and the block sensitivity of Boolean functions.
PRIME IDEALS INVARIANT UNDER WINDING AUTOMORPHISMS IN QUANTUM MATRICES
Authors: GOODEARL K. R. , LENAGAN T. H.
Published: July 2002

The main goal of the paper is to establish the existence of tensor product decompositions for those prime ideals P of the algebra [Formula: see text] of quantum n × n matrices which are invariant under winding automorphisms of A, in the generic case (q not a root of unity). More specifically, every such P is the kernel of a map of the form [Formula: see text] where A → A ⊗ A is the comultiplication, A+ and A- are suitable localized factor algebras of A, and P± is a prime ideal of A± invariant under winding automorphisms. Further, the algebras A±, which vary with P, can be chosen so that the correspondence (P+, P-) ↦ P is a bijection. The main theorem is applied, in a sequel to this paper, to completely determine the winding-invariant prime ideals in the generic quantum 3 × 3 matrix algebra.
SMOOTH GROUP ACTIONS ON 4-MANIFOLDS AND SEIBERG–WITTEN INVARIANTS
Authors: FANG FUQUAN
Published: July 2002

In this paper we study the Seiberg–Witten invariants of 4-manifold acted on by a finite group (or a compact Lie group). Among other things, we have:

Let X be a smooth closed 4-dimensional ℤp-manifold, where p is a prime. Suppose H1(X,ℝ) = 0 and [Formula: see text] where [Formula: see text]. If ℤp acts trivially on the space [Formula: see text] of self dual harmonic 2-forms, then, for any ℤp-equivariant Spin c-structure [Formula: see text] on X, the Seiberg–Witten invariant satisfies [Formula: see text] provided [Formula: see text] for j = 0,1,…,p-1, where [Formula: see text], DA: Γ(W+) → Γ (W-) is the equivariant Dirac operator determined by [Formula: see text] for an equivariant connection A on det W+.
THE EFFECT OF FINITE LATTICE-SIZE IN LATTICE BOLTZMANN MODEL
Authors: IMRE ATTILA R. , HÁZI GÁBOR
Published: July 2002

In this paper, numerical results on two-dimensional vapor–liquid equilibrium calculated by lattice Boltzmann method have been presented. Artefacts resulted by the finite lattice-size have been reviewed. A set of criteria for minimal lattice-size to avoid lattice artefacts is given.
MONTE CARLO SIMULATION USING JOHNSON POTENTIAL ON Gd–Mg ALLOY FOR DEBYE–WALLER FACTOR AND DEBYE TEMPERATURE
Authors: CHITRA S. , RAMACHANDRAN K.
Published: July 2002

Monte Carlo simulation (MCS) on the thermal properties in Gd–Mg alloy becomes essential as there are only limited experiments available. A realistic Johnson potential is used to workout the specific heats for various temperatures and hence the Debye temperature. The results from the present simulation technique are very well compared with our shell model calculation. The need of better X-ray measurements for Debye–Waller factor and Debye temperature other than the measurements of Subadhra and Sirdeshmukh, is discussed in detail.
SPHERICALLY SYMMETRIC GRAVITATIONAL FIELDS: BLACK HOLES AND MIDISUPERSPACE QUANTIZATION NEAR THE APPARENT HORIZON
Authors: VARGAS MONIZ P.
Published: July 2002

The purpose of this paper is to investigate the quantum vacua directly implied by the wave function of a gravitational configuration characterized by the presence of an apparent horizon, namely the Vaidya space–time solution. Spherical symmetry is a main feature of this configuration, with a scalar field constituting a source [a Klein–Gordon geon or Berger–Chitre–Moncrief–Nutku (BCMN) type model]. The subsequent analysis requires solving a Wheeler–DeWitt equation near the apparent horizon (following the guidelinesintroduced by A. Tomimatsu,18; M. Pollock,19 and developed by A. Hosoya and I. Oda20,21) with the scalar field herein expanded in terms of S2 spherical harmonics: midisuperspace quantization. The main results present in this paper are as follows. It is found that the mass function characteristic of the Vaidya metric is positive definite within this quantum approach. Furthermore, the inhomogeneous matter sector determines a descrip-tion in terms of open quantum (sub)systems, namely in the form of an harmonic oscillator whose frequency depends on the mass function. For this open (sub)system, a twofold approach is employed. On the one hand, an exact invariant observable is obtained from the effective Hamiltonian for the inhomogeneous matter modes. It is shown that this invariant admits a set of discrete eigenvalues which depend on the mass function. The corresponding set of eigenstates is constructed from a particular vacuum state. On the other hand, exact solutions are found for the Schrädinger equation associated with the inhomogeneous matter modes. This paper is concluded with a discussion, where two other issues are raised: (i) the possible application to realistic black hole dynamics of the results obtained for a simplified (BCMN) model and (ii) whether such vacuum states could be related with others defined instead within scalar field theories constructed in classical backgrounds.
INTERACTION BETWEEN TWO FUZZY SPHERES
Authors: BAL SUBRATA , TAKATA HIROYUKI
Published: July 2002

We have calculated the interaction between two fuzzy spheres in three dimensions. It depends on the distance r between the spheres and the radii ρ1, ρ2. There is no force between the spheres when they are at infinite distance. We have also studied the interaction for the r = 0 case. We find that an attractive force exists between two fuzzy sphere surfaces for small and large distances. We have also studied an extension of this model in the ten-dimensional case.
ENTROPY OF OPERATOR-VALUED RANDOM VARIABLES: A VARIATIONAL PRINCIPLE FOR LARGE N MATRIX MODELS
Authors: AKANT L. , KRISHNASWAMI G. S. , RAJEEV S. G.
Published: July 2002

We show that, in 't Hooft's large N limit, matrix models can be formulated as a classical theory whose equations of motion are the factorized Schwinger–Dyson equations. We discover an action principle for this classical theory. This action contains a universal term describing the entropy of the noncommutative probability distributions. We show that this entropy is a nontrivial one-cocycle of the noncommutative analog of the diffeomorphism group and derive an explicit formula for it. The action principle allows us to solve matrix models using novel variational approximation methods; in the simple cases where comparisons with other methods are possible, we get reasonable agreement.
REVIEW ON PRECISION MEASUREMENTS OF HIGH ENERGY HADRONS
Authors: CASAUS J.
Published: July 2002

Precise measurements of high energy hadrons have been performed either on balloon-borne or space-borne experiments. The status of the present measurements on H and He, heavier nuclei, isotopes and antiprotons is separately reported. Implications of precise measurements within the framework of models for production and propagation of galactic cosmic rays is discussed. Near future experiments are expected to improve in a significant manner the collected statistics and the energy range covered by present experiments. The results thus obtained will validate current propagation models and accurately constrain their free parameters.
REVIEW OF PRECISION MEASUREMENTS OF HIGH ENERGY ELECTRONS
Authors: BERTUCCI BRUNA
Published: July 2002

An accurate measurement of the intensity and energy spectra of Cosmic Ray electrons and positrons represents a major experimental challenge. Long exposure times and excellent particle identification capabilities are needed in order to cope with the low intensity of the electron and positron fluxes and the overwhelming background from protons and nuclei in cosmic rays. The motivations for such an experimental effort will be briefly discussed and the most recent results revieweved together with the perspectives of future experiments.
PULSARS, BLAZARS AND DARK MATTER WITH AMS
Authors: POHL MARTIN
Published: July 2002

The detection potential of AMS for photon sources of different origin is assessed. In particular, galactic and extragalactic point sources detected by previous experiments are examined for their detectability at energies above a few GeV. In addition, gamma ray rates from a potential supersymmetric dark matter halo are estimated using different models. It is argued that the constant survey of the gamma ray sky by AMS with a high angular resolution will be an important complement to similar studies using other present and future instruments.
The Many Faces of the Chiral Potts Model
Authors: Au-Yang Helen , Perk Jacques H.H.
Published: July 2002

In this talk, we give a brief overview of several aspects of the theory of the chiral Potts model, including higher-genus solutions of the star–triangle and tetrahedron equations, cyclic representations of affine quantum groups, basic hypergeometric functions at root of unity, and possible applications.
Gibbs' States for Moser-Calogero Potentials
Authors: Vaninsky K. L.
Published: July 2002

We present two independent approaches for computing the thermodynamics for classical particles interacting via the Moser-Calogero potential Combining the results we conjecture the form of equation of state or, what is equivalent, the asymptotics of the Jacobian between volume elements corresponding to two symplectic structures on the phase space.
The Filterization Method to Calculate Eigenstates
Authors: Gögtas Fahrettin , Yildiz A. Kadir , Balint-Kurti Gabriel G.
Published: July 2002

We have proposed a new method to calculate low lying eigenstates of Hamiltonian operator for triatomic molecules. The method is a grid method based on continuously pumping flux onto the potential energy surface and gives the wave function overlapping with prechosen energy of interest. This energy may correspond to a bound state, a resonance or a continuum state. We have calculated several low lying bound state energies and corresponding bound state wave functions for HOCl with HO bond fixed at its equilibrium value.
Electron Interaction in a Quantum Dot with Hard Wall Confinement Potential
Authors: Matulis A. , Fjærestad J. O. , Chao K. A.
Published: July 2002

We have investigated the electron interaction energy in a circular quantum dot with hard confinement potential, using a renormalized perturbation series (RPS) approach which interpolates between the perturbation solutions in the weak interaction regime and the asymptotic solutions in the strong interaction regime. The RPS is based on the scaling property of the Hamiltonian, and the numerical procedure is not complicated even when the number of electrons in the dot is not very small. The accuracy of the RPS calculation has been tested with two electrons in a dot, where the RPS ground state energy agrees with the exact numerical solution within 1% relative error. We have performed the RPS calculation for three and four electrons in the dot, from which the Coulomb charging energy is derived. The results suggest the potential application of pillar-shaped quantum dots for single-electron tunneling transistors operating at higher temperatures.
Pulse Electrical Current Resonance: Classical and Quantum Echoes
Authors: Oliveira I. S.
Published: July 2002

We discuss the theoretical basis of a recent proposal for a new experimental technique in Solid State Physics: Electrical Current Resonance (ECR); continuous wave (CW) and pulsed. In the first part of the paper we show that the Bloch equations for magnetic moments in magnetic fields are formally identical to the Drude equation of motion for the electrical current in electric and magnetic fields. Then, applying a matrix method to solve the current equation of motion, we explore the consequences of this similarity. First we consider continuous magnetic fields; various examples of applications are worked out. In the pulsed case we deduce expressions for the current echoes and free current decays, transient effects similar to spin echoes and free induction decays in the magnetic case. We briefly discuss the application of the technique to the study of electron scattering rates and ECR spectroscopy.

On the second part we show that the quantum problem of a charged particle in a oscillating magnetic field has an exact solution, both for continuous and pulsed fields. In the continuous case we show that the particle energy states in the field (the Landau tubes) are turned by 90° as the resonance frequency is approached. In the pulsed case we calculate the expected value of the particle momentum [Formula: see text] after a sequence of one and two magnetic pulses, and show that this quantity corresponds to the free current decay and current echo, deduced classically.
Wigner's Problem and Alternative Commutation Relations for Quantum Mechanics
Authors: Man'ko V. I. , Marmo G. , Zaccaria F. , Sudarshan E. C. G.
Published: July 2002

It is shown that for quantum systems the vector field associated with the equations of motion may admit alternative Hamiltonian descriptions, both in the Schrödinger and Heisenberg picture. We illustrate these ambiguities in terms of simple examples.
Quantum Nondeterministic Computation based on Statistics Superselection Rules
Authors: Castagnoli G.
Published: July 2002

Quantum states which obey certain symmetry superselection rules under identical particles permutation can be interpreted as computational states satisfying corresponding Boolean predicates. Given the NP-complete problem of testing the satisfiability of a generic Boolean predicate P, we investigate the possibility of achieving quantum nondeterministic computation by deriving, from P, a physical situation in which the computational states satisfy Piff they satisfy a special fermion statistics.
Traveling Salesman Problem and Statistical Physics
Authors: Usami Yoshiyuki , Kitaoka Masatoshi
Published: July 2002

We introduce statistical physics approaches to the traveling salesman problem (TSP). TSP is a kind of combinatorial optimization problem which is known to be difficult to solve exactly for large size systems. We develop a new method for solving the TSP based on an idea of real space renormalization theory. It will be shown that the TSP has self similar characteristics, hence the renormalization frame works well for solving the problem. Statistical physics formalism is also presented on solving the TSP by simulated annealing (SA) algorithm. Analytic expression for temperature dependence of the path length is given and compared to numerical simulation. Throughout this work we will provide a new insight to this kind of optimization problem from a viewpoint of statistical physics.
Rigorous Bounds on the Free Energy of Electron–Phonon Models
Authors: De Raedt Hans , Michielsen Kristel , Van Dijk Luuk
Published: July 2002

We present a collection of rigorous upper and lower bounds to the free energy of electron–phonon models with linear electron–phonon interaction. These bounds are used to compare different variational approaches. It is shown rigorously that the ground states corresponding to the sharpest bounds do not exhibit Off-Diagonal Long-Range Order in the two-particle density matrix.
Continuum Approximations to the Hückel Spectrum of Fullerenes
Authors: Park Youngho , Pang Hanbin , Liang Shoudan
Published: July 2002

We discuss several continuum approximations to the tight-binding spectrum of fullerene molecules at the bottom, top and center of the spectrum. The bottom part of the spectrum can be well fit by spherical harmonics, whereas the top part can be understood as due to an electron moving in the magnetic field of a monopole. The center part of the spectrum is described by the theory of González et al. Comparison with the Hückel spectrum of fullerenes, with up to 2160 atoms, yields excellent agreement with the continuum approximations, especially for larger fullerenes.
Models for Assisted Phason Hopping and Phason Elasticity in Icosahedral Quasicrystals
Authors: Coddens G.
Published: July 2002

We present a simple model that allows to understand the essential features behind the mechanisms of assistance to phason hopping. We provide a discussion on the length scales in the phason dynamics and the relation between phason dynamics and phason elasticity. We propose an alternative explanation for the diffuse scattering observed in icosahedral quasicrystals that resembles more the explanations offered in decagonal systems, putting the phenomena on a footing of universality, and showing that the currently adopted interpretation for icosahedral systems is not exclusive.
Continuous Random Alloy Networks: Glass Transition and Elasticity
Authors: Theissen Oliver , Zippelius Annette , Goldbart Paul M.
Published: July 2002

Amorphous alloys can be modelled as random networks of atoms or molecules of differing valencies. A statistical-mechanical theory of such networks is presented for the case of binary amorphous alloys. The existence of a continuous equilibrium phase transition, from the liquid state to the amorphous solid state driven by increasing the density of permanent random covalent bonds, is demonstrated. The structural and elastic properties of the amorphous solid state are calculated through the use of a variational Ansatz, and a discussion is given of the dependence of these properties on the relative concentration of the constituent atoms or molecules and their valencies. Implications of the present results in the context of gelation are addressed, especially with regard to the (primarily entropic) elastic properties of gels.
Computer Simulation Evidence for Berezhinskiǐ–Kosterlitz–Thouless-Like Transitions in One Dimension
Authors: Romano S.
Published: July 2002

We have considered classical spin systems, consisting of n-component unit vectors (n=2,3), associated with a one-dimensional lattice {uk, k ∈ Z}, and interacting via translationally and rotationally invariant pair potentials, of the long-range and ferromagnetic form [Formula: see text] here ε is a positive constant setting energy and temperature scales (i.e. T*=k B T/ε). Available theorems entail the existence of an ordering transition at finite temperature when 0<σ<1, and its absence for σ≥1. When σ=1, spin-wave arguments and previous simulation results suggest the existence of a transition to a low-temperature phase with slow decay of correlations and infinite susceptibility, i.e. a Berezhinskiǐ–Kosterlitz–Thouless-like transition. We have reexamined this case by a more detailed simulation study, and especially addressed the sample-size dependence of calculated observables: simulation results suggest the existence of such a transition, and the proposed estimates for the transition temperatures are Θ2=0.775±0.025 and Θ3=0.500±0.025, when n=2 and n=3, respectively.
Tsallis-Statistical Approach to the Specific Heat of LIQUID 4HE: Comparison with Other Results
Authors: Curilef Sergio , Papa Andrés R. R.
Published: July 2002

A theoretical approach within a quantum-group formalism has recently been proposed and successfully compared to Greywall's high precision measurements of the liquid 4 He specific heat. We calculate here the specific heat for 4 He using Tsallis' non-extensive thermostatistics. A comparative analysis reveals that there is a temperature range where our theoretical results yield the best fitting to experimental data.
Coset Constructions of Conformal Blocks
Authors: Ikeda Takeshi
Published: July 2002

On the basis of the coset construction, we obtained canonical maps that relate the sheaf of conformal blocks of the Wess–Zumino–Witten model to those of the unitarizable Virasoro minimal model. We conjectured that the maps are isomorphisms. Making use of spinor realizations, we confirmed the conjecture for the case of the Ising model. We also discussed the coherency of the sheaf of conformal blocks for the Virasoro algebra.
EFFECTIVE THEORY FOR A QUANTUM SPIN SYSTEM IN LOW DIMENSIONS – BEYOND THE LONG WAVELENGTH LIMIT
Authors: CHAUDHURY RANJAN , PAUL SAMIR K.
Published: July 2002

An effective theory for a quantum spin system in low dimensions is constructed in the finite-q regime. It is shown that there are field configurations for which Wess–Zumino terms contribute to the partition functions as topological terms for ferromagnets as well as antiferromagnets in both one- and two-dimensional lattices. This is in sharp contrast to the absence of topological excitations in two-dimensional quantum antiferromagnets in the long wavelength limit.
SOFT X-RAY EMISSION IN THE (1.0–1.5 KEV) WINDOW WITH NITROGEN FILLING IN A LOW ENERGY PLASMA FOCUS
Authors: SHAFIQ M. , SARTAJ  , HUSSAIN S. , SHARIF M. , AHMAD S. , ZAKAULLAH M. , WAHEED A. , MURTAZA G. , AHMAD R.
Published: July 2002

A study of soft X-ray emission in the 1.0–1.5 keV energy range from a low energy (1.15 kJ) plasma focus has been conducted. X-rays are detected with the combination of Quantrad Si PIN-diodes masked with Al (50 μm), Mg (100 μm) and Ni (17.5 μm) filters and with a pinhole camera. The X-ray flux is found to be measurable within the pressure range of 0.1–1.0 mbar nitrogen. In the 1.0–1.3 keV and 1.0–1.5 keV windows, the X-ray yield in 4π-geometry is 1.03 J and 14.0-J, respectively, at a filling pressure of 0.25 mbar and the corresponding efficiencies are 0.04% and 1.22%. The total X-ray emission in 4π-geometry is 21.8 J, which corresponds to the system efficiency of about 1.9%. The X-ray emission is found dominantly as a result of the interaction of energetic electrons in the current sheath with the anode tip. Images recorded by the pinhole camera confirm the emission of X-rays from the tip of the anode.
CAR ACCIDENTS IN THE DETERMINISTIC AND NONDETERMINISTIC NAGEL–SCHRECKENBERG MODELS
Authors: YANG XIAN-QING , MA YU-QIANG
Published: July 2002

In this paper, we study further the probability for the occurrence of car accidents in the Nagel–Schreckenberg model. By considering the braking probability, the conditions for car accidents to occur are modified to obtain accurate results. A universal phenomenological theory will also be presented to describe the probability for car accidents to occur in the deterministic and nondeterministic models, respectively.
PAIRING STATE AND HIGH TEMPERATURE SUPERCONDUCTIVITY OF SEMI-LOCALIZED 2D ELECTRON SYSTEM WITH CIRCULAR MOLECULAR ORBITS
Authors: SUGAHARA MASANORI , BOGOLUBOV NIKOLAI N.
Published: July 2002

Recently, new types of high temperature superconductors have been found which are characterized by the existence of circular molecular orbits in each unit site of 2D s/p electron system. In view of the characteristic, a new model of superconductivity is studied based on the stability of the correlated state of electrons in the 2D interconnection of circular orbits. This model gives an estimation of the upper bound of superfluidity transition temperature: T c ~ 130-400 K for fcc C 60, and T c ~ 110-340 K for hole-doped MgB 2.
THE BAND STRUCTURE AND BULK MODULUS OF CUBIC (3C) AND HEXAGONAL (2H) POLYTYPES OF SILICON CARBIDE
Authors: MAHMOOD A. , SANSORESA L. ENRIQUE
Published: July 2002

Silicon carbide (SiC) is a high band-gap semiconductor material, which has very important and interesting characteristics for novel semiconductor applications. We have studied the cubic (3C) and hexagonal (2H) polytypes of this important material. For the band structure calculations of these polytypes, the density functional and total-energy technique have been applied in the generalized gradient approximation, which is the most powerful ab initio quantum-mechanica method. The important energy gaps have been determined and compared with the previous theoretical and experimental results. The density of state, charge density and bulk modulus have also been calculated.
SYNTHESIS AND STRUCTURE OF Ga2O3 NANOSHEETS
Authors: LI JIANYE , CHEN XIAOLONG , ZHANG GANG , LEE JEONG YONG
Published: July 2002

Monoclinic gallium oxide nanosheets were synthesized on a large scale through a simple gas reaction method. They were characterized by means of X-ray powder diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDS), high-resolution transmission electron microscopy (HRTEM), and Raman spectroscopy. FE-SEM images showed that the product was mainly composed of nanosheets. XRD, EDS and Raman spectra indicated the nanosheets were a monoclinic gallium oxide structure. An HRTEM lattice image revealed that the nanosheets are nearly uniform in structure and single crystalline.
LOCAL ACTIVITY CRITERIA FOR DISCRETE-MAP CNN
Authors: SBITNEV VALERY I. , CHUA LEON O.
Published: July 2002

Discrete-time CNN systems are studied in this paper by the application of Chua's local activity principle. These systems are locally active everywhere except for one isolated parameter value. As a result, nonhomogeneous spatiotemporal patterns may be induced by any initial setting of the CNN system when the strength of the system diffusion coupling exceeds a critical threshold. The critical coupling coefficient can be derived from the loaded cell impedance of the CNN system. Three well-known 1D map CNN's (namely, the logistic map CNN, the magnetic vortex pinning map CNN, and the spiral wave reproducing map CNN) are introduced to illustrate the applications of the local activity principle. In addition, we use the cell impedance to demonstrate the period-doubling scenario in the logistic and the magnetic vortex pinning maps.
FLOW OF A FOURTH GRADE FLUID
Authors: HAYAT T. , WANG Y. , HUTTER K.
Published: July 2002

The governing nonlinear equation for the unsteady flow of an incompressible fourth grade fluid is modelled. The fluid is also subjected to a magnetic field. In addition, we investigate steady flow between parallel plates with one plate at rest and the other moving parallel to it at constant speed with a suction velocity normal to the plates. Boundary conditions play a significant role. We construct the numerical solution to the sixth order nonlinear differential equation. It is found that the velocity increases with the increase in the material parameters of the fourth grade terms of the fluid.
SKEIN THEORY AND THE MURPHY OPERATORS
Authors: MORTON HUGH R.
Published: July 2002

The Murphy operators in the Hecke algebra Hn of type A are explicit commuting elements whose sum generates the centre. They can be represented by simple tangles in the Homfly skein theory version of Hn. In this paper I present a single tangle which represents their sum, and which is obviously central. As a consequence it is possible to identify a natural basis for the Homfly skein of the annulus, [Formula: see text].

Symmetric functions of the Murphy operators are also central in Hn. I define geometrically a homomorphism from [Formula: see text] to the centre of each algebra Hn, and find an element in [Formula: see text], independent of n, whose image is the mth power sum of the Murphy operators. Generating function techniques are used to describe images of other elements of [Formula: see text] in terms of the Murphy operators, and to demonstrate relations among other natural skein elements.
θ-CURVE POLYNOMIALS AND FINITE-TYPE INVARIANTS
Authors: HUH YOUNGSIK , JIN GYO TAEK
Published: July 2002

The normalized Yamada polynomial, [Formula: see text], is a polynomial invariant in variable A for θ-curves. In this work, we show that the coefficients of [Formula: see text] which is obtained by replacing A with ex = ∑ xn/n! are finite-type invariants for θ-curves although the coefficients of original [Formula: see text] are not finite-type. A similar result can be obtained in the case of Yokota polynomial for θ-curves.
TOWARDS AN IMPLEMENTATION OF THE B–H ALGORITHM FOR RECOGNIZING THE UNKNOT
Authors: BIRMAN JOAN S. , RAMPICHINI MARTA , BOLDI PAOLO , VIGNA SEBASTIANO
Published: July 2002

In the manuscript [2] the first author and Michael Hirsch presented a then-new algorithm for recognizing the unknot. The first part of the algorithm required the systematic enumeration of all discs which support a 'braid foliation' and are embeddable in 3-space. The boundaries of these 'foliated embeddable discs' (FED's) are the collection of all closed braid representatives of the unknot, up to conjugacy, and the second part of the algorithm produces a word in the generators of the braid group which represents the boundary of the previously listed FED's. The third part tests whether a given closed braid is conjugate to the boundary of a FED on the list. In this paper we describe implementations of the first and second parts of the algorithm. We also give some of the data which we obtained. The data suggests that FED's have unexplored and interesting structure. Open question are interspersed throughout the manuscript. The third part of the algorithm was studied in [3] and [4], and implemented by S. J. Lee [20]. At this writing his algorithm is polynomial for n ≤ 4 and exponential for n ≥ 5.
PREDICTABILITY OF MULTIPLICATIVE PROCESSES: A PRELIMINARY STUDY
Authors: VOJAK ROBERT , VÉHEL JACQUES LÉVY
Published: July 2002

We define a multifractal analysis for correlations. We present explicit results in the case of deterministic multinomial measures, and show that the multifractal formalism does not hold for correlations on binomial measures.
REAL TIME FRACTAL VIDEO FOR PERSONAL COMMUNICATIONS
Authors: MONRO DONALD M , NICHOLLS JEREMY A
Published: July 2002

Using a first order (bilinear) Bath Fractal Transform (BFT), we have obtained useful video sequences of talking heads with transmission rates as low as 40 KBits/sec. Previously, fractal image coding had been computationally asymmetric. In our work, 8 by 8 pixel blocks are coded in 250 µs and decoded in 200 µs on a 33 MHz i-486 based PC. This is of significance in consumer electronics, such as personal communications, where inexpensive coding systems will have an advantage over more expensive methods using DSP or custom chips to achieve the necessary speed. With a simple quantization and entropy coding scheme applied to standard QCIF frames, at 40 KBits/sec we achieve coding of 40% of each frame in a 25 Hz video sequence, equivalent to 100% at 10 Hz.
FRACTAL IMAGE COMPRESSION USING LOCALLY REFINED PARTITIONS
Authors: CAI D. , ARISAWA T. , ASAI N. , IKEBE Y. , ITOH T.
Published: July 2002

In the present report, we show a practical fractal image compression method using locally refined partition which is generated automatically and controlled by the values of gradients in images, The method is similar to the ones by Barnsley and Hurd. In our method, using the quad-tree scheme, before the compression processes of the image, we locally refine the domain regions recursively until the size of the regions become smaller than the scale lengths of the gradients in the image or until the predefined minimum refinement size is reached. Based on our method, it is possible to assess the optimum-like set of domain regions for the desired file size.
USING LINEAR FRACTAL INTERPOLATION FUNCTIONS TO COMPRESS VIDEO IMAGES
Authors: ALI MAARUF , CLARKSON TREVOR G.
Published: July 2002

This paper describes the novel application of using linear fractal interpolation functions (FIFs) to model video signals represented as single-valued discrete-time sequences to compress video images. The problem is data compression of full-motion broadband television signals. The viability of using FIFs to model video signals is shown by modelling test static image frames. Compression ratios, SNRs and compression-decompression times are reported. Extension of this work to compress motion video is described. Finally the images are analysed by calculating and plotting the fractal dimensions of each line in the frame against the line for that image.
THE APPLICATION OF DIFFUSIONAL TECHNIQUES IN TIME-SERIES ANALYSIS TO IDENTIFY COMPLEX FLUID DYNAMIC REGIMES
Authors: GIONA MASSIMILIANO , PAGLIANTI ALESSANDRO , SOLDATI ALFREDO
Published: July 2002

The diffusional analysis of time series is introduced and compared with corresponding results derived from rescaled-range (R/S) techniques. It is shown by means of simple examples that diffusional analysis is able to capture some details of the statistics of the time series which can become lost when other techniques (e.g. R/S) are applied. Examples of the application of this method to chaotic time series are briefly discussed. The problem of the identification of fluid dynamic regimes is investigated in detail by considering experimental time series derived from two-phase flow measurement in tubes. The results obtained confirm the validity of this method in dealing with time series derived from periodic or quasiperiodic phenomena with superimposed stochastic perturbations.
MEASURING HURST EXPONENTS WITH THE FIRST RETURN METHOD
Authors: HANSEN ALEX , ENGØY THOR , MÅLØY KNUT JØRGEN
Published: July 2002

The First Return method has proven to be an efficient method for determining the Hurst exponent, H, of self-affine surfaces. We discuss its foundations and some corrections to scaling which must be taken into account for an adequate estimation of H. Using this method, we analyze a set of artificially generated curves with known Hurst exponent and compare the result with Fourier analysis. We also discuss the case where the surface to be analyzed has a curved bias with a maximum or minimum. In this case, the relation between the scaling exponents associated with the first-return histograms and the Hurst exponent H is different from the unbiased case.
ON FAULT TOLERANCE OF HYPERCUBES USING SUBCUBES
Authors: SASAMA TOSHIHIKO , MASUYAMA HIROSHI , ICHIMORI TETSUO
Published: July 2002

A hypercube is an important interconnection topology in parallel and distributed processing. This paper treats fault tolerance of a hypercube. More precisely, it discusses relations between a faulty hypercube and its fault-free subcubes. First, this paper presents an upper bound on the minimum number of faults in an n-cube where no fault-free (n - m)-subcube can exist. Next, it is shown that the bound can be improved if m = 2. Finally, the paper discusses the number of faults when there are always at least two fault-free disjoint (n - 2)-subcubes.
STOCHASTIC PROCESSES ON GROUPS OF DIFFEOMORPHISMS AND VISCOUS HYDRODYNAMICS
Authors: BELOPOLSKAYA YA. I. , GLIKLIKH YU. E.
Published: July 2002

The viscous hydrodynamics is investigated via the studying diffusion processes on groups of Hs Sobolev diffeomorphisms of a flat n-dimensional torus (s > ½n + 1). A certain stochastic perturbation of the curve on the above groups, describing the motion of perfect incompressible fluid (or of the diffuse matter), is constructed such that it satisfies a certain stochastic analogue of the geodesic equation and the expectation of its "backward velocity" in the tangent space at identical diffeomorphism (algebra of the group) is a solution of Navier–Stokes (or Burgers, respectively) equations. In particular, the existence of solutions of those equations for lower s is proved. Some other approaches to stochastic presentation of viscous hydrodynamics, using the groups of diffeomorphisms, are also discussed.
GENERALIZED FEYNMAN–KAC FORMULA WITH STOCHASTIC POTENTIAL
Authors: OUERDIANE HABIB , SILVA JOSÉ LUIS
Published: July 2002

In this paper we study the solution of the stochastic heat equation where the potential V and the initial condition f are generalized stochastic processes. We construct explicitly the solution and we prove that it belongs to the generalized function space [Formula: see text].
Important Factors of Estimated Return and Risk: The Taiwan Evidence
Authors: Ku Kuang-Ping , Lin William T.
Published: July 2002

This paper seeks to identify which factors are important for estimating portfolio's expected return and standard deviation in the Taiwan stock market. We have summarized from the existing empirical literature a total of 26 factors that may have explanatory power. The results of our evaluation show that except for the trading volume, the remaining 25 factors do not seem to help explain the average stock returns during the July 1985–June 1999 period. However, the power of the trading volume to account for the expected returns on the stock is affected by any changes in the sample or by the use of a different evaluation model. We suggest three potential explanations of why all 26 factors show no stable power to explain average returns on Taiwan stocks: high volatility, selection bias, and market differences. Moreover, we find that all of the 26 factors are important in capturing the systematic covariation in stock returns.
On the Effect of Stock Stabilization Fund: A Case of Taiwan
Authors: Liu Yu-Jane , Yu Chih-Hsien
Published: July 2002

The purpose of this paper is to investigate the effect of Taiwan's stock stabilization fund on the stock market. Stabilization funds have long been used by many countries to achieve the goal of market stabilization. However, the actual impacts of the funds still remain a puzzle. This is the first paper that empirically examines the effect of the stabilization fund on the stock market. Taiwan's stock stabilization fund, which was inaugurated in February 1996 after the panic selling induced by the announcement of military exercise by mainland China, provides an experimental environment for investigating whether this alternative mechanism is effective in stabilizing the stock price when the market is in panic. By intervention analysis, we find that in the short run, the stabilization fund is statistically significant in preventing the market price from further declining after the announcement of the mainland China's military exercise. This evidence still holds after controlling the effects of the following two events: Morgan-Stanley's announcement to include Taiwan stock index into its worldwide equity market indices, and the event of U.S. aircraft carrier sent to Taiwan Strait to secure this area during the period of military exercise by mainland China.
A REVIEW OF PARRONDO'S PARADOX
Authors: HARMER GREGORY P. , ABBOTT DEREK
Published: July 2002

Inspired by the flashing Brownian ratchet, Parrondo's games present an apparently paradoxical situation. The games can be realized as coin tossing events. Game A uses a single biased coin while game B uses two biased coins and has a state dependent rule based on the player's current capital. Playing each of the games individually causes the player to lose. However, a winning expectation is produced when randomly mixing games A and B. This phenomenon is investigated and mathematically analyzed to give explanations on how such a process is possible.

The games are expanded to become dependent on other properties rather that the capital of the player. Some of the latest developments in Parrondian ratchet or discrete-time ratchet theory are briefly reviewed.
A PROBABILISTIC POWER DOMAIN ALGORITHM FOR FRACTAL IMAGE DECODING
Authors: DRAKOPOULOS V. , KAKOS A. , NIKOLAOU N.
Published: July 2002

A new algorithm, called herein the random power domain algorithm, is discussed; it generates the image corresponding to an iterated function system with probabilities, a technique used in fractal image decoding. A simple complexity analysis for the algorithm is also derived.
TRANSITIONS TO INTERMITTENCY AND COLLECTIVE BEHAVIOR IN RANDOMLY COUPLED MAP NETWORKS
Authors: VOLCHENKOV D. , SEQUEIRA S. , BLANCHARD Ph. , COSENZA M. G.
Published: July 2002

We study the transition to spatio-temporal intermittency in random network of coupled Chaté–Manneville maps. The relevant parameters are the network connectivity, coupling strength, and the local parameter of the map. We show that spatiotemporal intermittency occurs for some intervals or windows of the values of these parameters. Within the intermittency windows, the system exhibits periodic and other nontrivial collective behaviors. The detailed behavior depends crucially upon the topology of the random graph spanning the network. We present a detailed analysis of the results based on the thermodynamic formalism and random graph theory.
Understanding TCP Vegas
Authors: Low Steven H. , Peterson Larry L. , Wang Limin
Published: July 2002

We view congestion control as a distributed primal--dual algorithm carried out by sources and links over a network to solve a global optimization problem. We describe a multilink multisource model of the TCP Vegas congestion control mechanism. The model provides a fundamental understanding of delay, fairness and loss properties of TCP Vegas. It implies that Vegas stabilizes around a weighted proportionally fair allocation of network capacity when there is sufficient buffering in the network. It clarifies the mechanism through which persistent congestion may arise and its consequences, and suggests how we might use REM active queue management to prevent it. We present simulation results that validate our conclusions.
Designing the Internet for a networked society
Authors: Wellman Barry
Published: July 2002

Having moved out of confining local communities and work groups, people worldwide now involve themselves in far-flung, Internet-enhanced social relationships with friends, family, workmates, and neighbors.