bluuebunny/crossref_metadata_2025 huggingface dataset:
Stable-isotope ratios of blood components from captive northern fur seals (Callorhinus ursinus) and their diet: applications for studying the foraging ecology of wild otariids
Authors: Kurle Carolyn M
Published: July 2002

Stable nitrogen and carbon isotope ratios (13C/12C and 15N/14N, respectively) of plasma, serum, clotted red blood cells, and unclotted red blood cells from six captive northern fur seals (Callorhinus ursinus) and two fish species in their diet, Atlantic herring (Clupea harengus) and Icelandic capelin (Mallotus villosus), were measured. The δ15N values from the fur seal blood components ranged from 15.5 ± 0.1 (mean ± SE; all RBCs) to 16.7 ± 0.1 (plasma), and δ13C values ranged from 18.3 ± 0.1 (serum) to 17.5 ± 0.1 (clotted RBCs). Fur seal blood components had higher δ15N and δ13C values than their diet. Mean enrichments of 15N between fur seal RBCs and plasma/serum and their prey were +4.1 and +5.2, respectively, while mean 13C enrichments were +0.6 (serum), +1.0 (plasma), and +1.3 to +1.4 (all RBCs). Fur seal blood components did not differ in δ15N or δ13C between the sexes. One female (Baabs) was pregnant at the time of sampling and was resampled 4 months later, when she was approximately 3 months post parturient. The δ15N values of the blood components taken from Baabs during pregnancy were all higher by 0.6 (unclotted RBCs) to 1.3 (plasma) than those of samples taken during lactation, while her δ13C values were nearly the same (RBCs) for the two time periods or lower during lactation by 0.5 (serum) and 0.7 (plasma). This study was the first to analyze isotope ratios of blood components from captive fur seals and their prey. The subsequent establishment of fractionation values between captive fur seals and their diet can be used to interpret trophic level and habitat usage of otariids feeding in the wild.
CLUSTER-BASED TASK SCHEDULING FOR THE LOGP MODEL
Authors: BOERES CRISTINA , NASCIMENTO ALINE , REBELLO VINOD E. F.
Published: July 2002

While the task scheduling problem under the delay model has been studied extensively, relatively little research exists for more realistic communication models such as the LogP model which considers, in addition to latency, the cost of sending and receiving messages, and the network or link capacity. The task scheduling problem is known to be NP-complete even under the delay model (a special case of the LogP model). This paper investigates the similarities and differences between task-clustering algorithms for the delay and LogP models, and describes task-scheduling algorithm for the allocation of arbitrary task graphs to fully connected networks of processors under the LogP model. The strategy exploits the replication and clustering of tasks to minimize the ill effects of communication overhead on the makespan. A number of restrictions are presented which are used to simplify the design of the new algorithm. The quality of the schedules produced by the algorithm compare favorably with two well-known delay model-based algorithms and a previously existing LogP strategy.
SIMPLE FLAT LANGUAGES: A LEARNABLE CLASS IN THE LIMIT FROM POSITIVE DATA
Authors: TAKESI OKADOME
Published: July 2002

The class of simple flat languages defined here is shonw to be learnable in the limit from positive data. In particular, its subclass named k-consecutive, which covers a part of the class of context-sensitive languages not belonging to the class of context-free languages, is polynomial-time learnable in the limit from positive data. The class of "disjunct" unions of simple flat languages is a nontrivial example which is learnable in the limit from positive data, but does not have Wright's finite elasticity. The learning algorithm presented here for identifying the subclasses of flat languages consists essentially of identifying an arithmetic progression in the limit from positive examples using Euclidean algorithm of mutual division.
INTERTEMPORAL DISTRIBUTIONS OF A RICE PILE MODEL
Authors: GLEISER PABLO M. , CANNAS SERGIO A. , TAMARIT FRANCISCO A.
Published: July 2002

In this work we study the distribution of time intervals between avalanches in a rice pile model. This model has shown that the crossover from power law to stretched exponential behaviors observed experimentally in the granular dynamics of rice piles can be well described as a long-range effect resulting from a change in the transport properties of individual grains. In this work we show that the change in the transport properties is also reflected in the behavior of the distribution of time intervals between avalanches.
EXACT RENORMALIZATION GROUP EQUATION IN THE PRESENCE OF RESCALING ANOMALY II
Authors: ARNONE STEFANO , FRANCIA DARIO , YOSHIDA KENSUKE
Published: July 2002

Exact renormalization group techniques are applied to the mass deformed [Formula: see text] super-symmetric Yang–Mills theory, viewed as a regularized [Formula: see text] model. The solution of the flow equation, in case of dominance of the potential term, reproduces the one-loop (perturbatively exact) expression for the effective action of [Formula: see text] supersymmetric Yang–Mills theory, when the regularizing mass, M, reaches the value of the dynamical cutoff Λ. One speculates about the way in which further nonperturbative contributions (instanton effects) may be accounted for.
GEOMETRICAL ORIGIN OF FERMION FAMILIES IN SU(2) × U(1) GAUGE THEORY
Authors: GUENDELMAN E. I. , KAGANOVICH A. B.
Published: July 2002

A spontaneously broken SU (2) × U (1) gauge theory with just one "primordial" generation of fermions is formulated in the context of generally covariant theory which contains two measures of integration in the action: the standard [Formula: see text] and a new Φd4x, where Φ is a density built out of degrees of freedom independent of the metric. Such type of models are known to produce a satisfactory answer to the cosmological constant problem. Global scale invariance is implemented. After SSB of scale invariance and gauge symmetry it is found that with the conditions appropriate to laboratory particle physics experiments, to each primordial fermion field corresponds three physical fermionic states. Two of them correspond to particles with different constant masses and they are identified with the first two generations of the electroweak theory. The third fermionic states at the classical level get nonpolynomial interactions which indicate the existence of fermionic condensate and fermionic mass generation.
INTERMEDIATE SYMMETRIES IN THE SPONTANEOUS BREAKING OF SUPERSYMMETRIC SO(10)
Authors: BUCCELLA F. , SAVOY C. A.
Published: July 2002

We study the supersymmetric spontaneous symmetry breaking of SO(10) into SU (3) ⊗ SU (2) ⊗ U (1) for the most physically interesting cases of SU(5) or flipped SU (5) ⊗ U (1) intermediate symmetries. The first case is more easily realized while the second one requires a fine-tuning condition on the parameters of the superpotential. This is because in the case of SU(5) symmetry there is at most one singlet of the residual symmetry in each SO(10) irreducible representation. We also point out on more general grounds in supersymmetric GUTs that some intermediate symmetries can be exactly realized and others can only be approximated by fine-tuning. In the first category, there could occur some tunneling between the vacua with exact and approximate intermediate symmetry. The flipped SU (5) ⊗ U (1) symmetry improves the unification of gauge couplings if (B-L) is broken by ‖(B-L)‖ =1 scalars yielding right-handed neutrino masses below 1014 GeV .
STRING THEORY EXTENSIONS OF EINSTEIN–MAXWELL FIELDS: THE STATIC CASE
Authors: HERRERA-AGUILAR ALFREDO , KECHKIN OLEG V.
Published: July 2002

We present a new approach for generating solutions in both the four–dimensional heterotic string theory with one vector field and the five–dimensional bosonic string theory, starting from static Einstein–Maxwell fields. Our approach allows one to construct classes of solutions which are invariant with respect to the total subgroup of three-dimensional charging symmetries of these string theories. The new solution-generating procedure leads to the extremal Israel–Wilson–Perjes subclass of string theory solutions in a special case and provides its natural continuous extension to the realm of nonextremal solutions. We explicitly calculate all string theory solutions related to three-dimensional gravity coupled to an effective dilaton field which arises after an appropriate charging symmetry invariant reduction of the static Einstein–Maxwell system.
A VARIATIONAL FOCK-SPACE TREATMENT OF QUARKONIUM
Authors: DI LEO L. , DAREWYCH J. W.
Published: July 2002

The variational method and the Hamiltonian formalism of QCD are used to derive relativistic, momentum space integral equations for a quark–antiquark system with an arbitrary number of gluons present. As a first step, the resulting infinite chain of coupled equations is solved in the nonrelativistic limit by an approximate decoupling method. Comparison with experiment allows us to fix the quark mass and coupling constant, allowing for the calculation of the spectra of massive systems such as charmonium and bottomonium. Studying the results with and without the non-Abelian terms, we find that the presence of the non-Abelian factors yields better agreement with the experimental spectra.
THE ALPHA MAGNETIC SPECTROMETER, A PARTICLE PHYSICS EXPERIMENT IN SPACE
Authors: BATTISTON ROBERTO
Published: July 2002

The Alpha Magnetic Spectrometer (AMS) is a state of the art detector for the extrater-restrial study of matter, antimatter and missing matter. During the STS-91 precursor flight in may 1998 AMS collected nearly 100 millions of Cosmic Rays on Low Earth Orbit, measuring with high accuracy their composition. We review the results on the flux of proton, electron, positron and helium. Analysis of the under cutoff spectra indicates the existence of a new type of belts of energetic trapped particles characterized by a dominance of positrons versus electrons. AMS is currently being refurbished for a three year mission on the International Space Station where the its sensitivity to rare events will be increased by three to four orders of magnitude.
DARK MATTER SEARCH WITH GAMMA RAYS: THE EXPERIMENTS EGRET AND GLAST
Authors: MORSELLI ALDO
Published: July 2002

The direct detection of annihilation products in cosmic rays offers an alternative way to search for supersymmetric dark matter particles candidates. The study of the spectrum of gamma-rays, antiprotons and positrons offers good possibilities to perform this search in a significant portion of the Minimal Supersymmetric Standard Model parameters space. In particular the EGRET team have seen a convincing signal for a strong excess of emission from the galactic center that have not easily explanation with standard processes. We will review the achievable limits with the experiment GLAST taking into accounts the LEP results and we will compare this method with the antiproton and positrons experiments, the direct underground detection and with future experiments at LHC.
Knot Theory and Statistical Mechanics
Authors: Kauffman Louis H.
Published: July 2002

This paper gives a self-contained exposition of the basic structure of quantum link invariants as state summations for a vacuum-vacuum scattering amplitude. Models of Vaughan Jones are expressed in this context. A simple proof is given that an important subset of these invariants are built from Vassiliev invariants of finite type.
The Thermodynamic Bethe Ansatz and a Connection with Painlevé Equations
Authors: Tracy Craig A. , Widom Harold
Published: July 2002

We summarize some recent connections between a class of nonlinear integral equations related to the thermodynamic Bethe Ansatz and a class of linear integral equations related to the Painlevé equations.
The Infinite-State Potts Model and Solid Partitions of an Integer
Authors: Huang H. Y. , Wu F. Y.
Published: July 2002

It has been established that the infinite-state Potts model in d dimensions generates restricted partitions of integers in d-1 dimensions, the latter a well-known intractable problem in number theory for d>3. Here we consider the d=4 problem. We consider a Potts model on an L × M × N × P hypercubic lattice whose partition function GLMNP(t) generates restricted solid partitions on an L × M × N lattice with each part no greater than P. Closed-form expressions are obtained for G222P(t) and we evaluated its zeroes in the complex t plane for different values of P. On the basis of our numerical results we conjecture that all zeroes of the enumeration generating function GLMNP(t) lie on the unit circle |t|=1 in the limit that any of the indices L, M, N, P becomes infinite.
Fully-Finite Two-Dimensional Critical Systems: Casimir Terms and Instabilities
Authors: Kleban Peter , Perchel Ingo
Published: July 2002

We review recent results for the universal part of the free energy of fully-finite two-dimensional regions at criticality. Their effect on the total free energy is considered. Including non-universal edge free energy terms leads to various Casimir instabilities toward elongation, sharp corners on the boundary, and other behavior. Universal features of certain matrix elements of the transfer matrix and corner transfer matrix are also obtained.
The Behavior of the Critical Magnetic Field and Correlation Functions in Finite-Size Hubbard-Like Models
Authors: Kocharian A.N.
Published: July 2002

We present exact analytical results for a critical field and correlations functions for N site ring and arbitrary size two dimensional coupled chains in a two component Hubbard model with a strong magnetic field and exactly at half-filling. The critical field near the Nagaoka instability with one spin and two spin flips is driven by Coulomb interaction, lattice geometry, dimensionality and crucially depends on the number of atomic sites N. Unsaturated ferromagnetism, reminiscent of Nagaoka-like behavior, and spin liquid state are examined in the structure of off-diagonal spin correlation at large U.
The One-Electron Energies of a Neutral Zinc Atom Evaluated Using Nonlinear Field Theoretical Methods: Comparison with Hartree–Fock Calculations
Authors: Dixon J. M. , Tuszyński J. A. , Nip M. L. A.
Published: July 2002

The Method of Coherent Structures (MCS) has been used, as an example of a sufficiently complex atomic system, to determine the one-electron eigenvalues of a neutral zinc atom. An ensemble procedure is used in MCS to properly account for spatial correlations even for a relatively small number of particles. The MCS is a semiclassical approach, but the essentially Fermionic character of the electrons emerges via physical boundary conditions on the choice of classical field. We interpret the classical field as a coherent state envelope which partly determines the effective potential in which quantum fluctuations take place. We find that three distinct régimes of behaviour of the classical field exist depending on the magnitude of the effective Coulomb repulsion, μ. When μ<μ0, a critical value, those classical fields which correspond to certain discrete values of μ are physically acceptable normalisable bound charge states. When μ<μ0 and does not correspond to the discrete values, classical solutions exhibit a damped oscillatory behaviour typical of charged "ring" waves. For μ>μ0, corresponding to an excess of electronic charge, only a small fraction of the charge, represented by a few oscillations about the nucleus, remains attracted to this centre while the remainder escapes from the nucleus. Parameters representing the repulsive energy strength and energy shifts agree well with trends in the Slater parameter F 0(2s,2p) as a function of atomic number Z and also Moseley's Law. Agreement is also obtained with the first-principles form of charge density at small distances from the nucleus as given by Kato's Theorem and also at large distances as outlined by March. The usefulness and validity of this approach has been shown by comparing such energies with those determined by a Hartree–Fock–Slater (HF) method which is well known to satisfactorily account for many specific details of the level structure of atoms. Good agreement with HF has been obtained for both shell positions and energy ordering of states within a shell.
Exact Results for Highly Correlated Electron Systems in One Dimension
Authors: Schlottmann P.
Published: July 2002

One-dimensional conductors are a long-standing topic of research with direct applications to organic conductors and mesoscopic rings. The discovery of the ceramic high-temperature superconductors has revitalized the interest in low-dimensional charge and spin fluctuations of highly correlated electron systems. Several mechanisms proposed to explain the high-T c superconductors invoke properties of the two-dimensional Hubbard model, but probably also some one-dimensional aspects are relevant. Numerous one-dimensional models for correlated electrons have been studied with various approximate, asymptotically exact and exact methods. These results lead to the concept of Luttinger liquid for interacting electron gases without excitation gaps (metallic systems). Characteristic of Luttinger liquids are the charge and spin separation, marginal Fermi liquid properties, e.g. the absence of quasiparticles in the vicinity of the Fermi surface, nonuniversal power-law singularities in the one-particle spectral function and the related absence of a discontinuity in the momentum distribution at the Fermi level, the power-law decay of correlation functions for long times and large distances, persistent currents in finite rings, etc.

Due to the peculiarities of the phase space in one dimension some of the models have sufficient conserved currents to be completely integrable. We review exact results derived within the framework of Bethe's ansatz for integrable one-dimensional models of correlated electrons. The Bethe-ansatz method is presented by explicitly showing the steps leading to the solution of the N-component electron gas interacting via a δ-function potential (repulsive and attractive interaction), which is probably the simplest model of correlated electrons. Emphasis is given to the procedure to extract the groundstate properties, the classification of states, the excitation spectrum, the thermodynamics and finite size effects, such as critical exponents of correlation functions and persistent currents. The method is then applied to numerous other models, e.g. (i) a two-band model involving attractive and repulsive potentials and crystalline fields splitting the bands, (ii) the traditional Hubbard chain with attractive and repulsive U, (iii) the degenerate Hubbard model with repulsive U, which displays a metal–insulator transition at a finite U, (iv) a two-band Hubbard model with repulsive U, (v) the traditional supersymmetric t–J model (vi) a two-band supersymmetric t–J model with band-splitting and (vii) the N-component supersymmetric t–J model. Finally, results for models with long-range interactions, in particular r-2 and sinh -2(r) potentials, are briefly reviewed.
A Microscopic Hierarchy Theory of the Fractional Quantum Hall Effect
Authors: Yang Jian , Su Wu-Pei
Published: July 2002

In this paper we present a microscopic hierarchy theory of the fractional quantum Hall effect. The wave functions of the ground state and the collective excitation states are obtained in terms of the electron coordinates. Working in the subspace spanned by the quasiparticles of the 1/m L Laughlin ground state, with m L an odd integer, it is shown that there exists a simple mapping between electron states in the quasiparticle subspace and states of an auxiliary boson system which is defined such that the number of the bosons is the same as that of the quasiparticles and the total magnetic flux quanta seen by the bosons equals the number of electrons. For the auxiliary boson system, one can write down the Laughlin state as well as the density wave states, analogous to the electron system at filling factor 1/m L . By mapping these states onto the quasiparticle subspace of the electrons, we find that the resulting wave functions provide a quite good description for the ground state and the collective excitations respectively of the original electron system at filling factor ν=1/(m L (± 1/2p)) with p a positive integer. This construction of the ground state and the collective excitation states can be repeated for higher filling factors. The theory presented in this paper can be viewed as a microscopic realization of Haldane's original hierarchy picture.
Band Degeneracy and the Mott Transition: Dynamical Mean Field Study
Authors: Kajueter Henrik , Kotliar Gabriel
Published: July 2002

We investigate the Mott transition in infinite dimensions in the orbitally degenerate Hubbard model. We find that the qualitative features of the Mott transition found in the one-band model are also present in the orbitally degenerate case. Surprisingly, the quantitative aspects of the density driven Mott transition around density one are not very sensitive to orbital degeneracy, justifying the quantitative success of the one-band model which was previously applied to orbitally degenerate systems. We contrast this with quantities that have a sizeable dependence on the orbital degeneracy and comment on the role of the intra-atomic exchange J.
The Behaviour of Individual Ultra-Small Capacitance Quantum Devices
Authors: Spiller T. P. , Ralph J. R. , Clark T. D. , Prance R. J. , Prance H.
Published: July 2002

We apply quantum state diffusion theory to an open angular system, such as a quantum capacitor or rotor. We consider various physically interesting Hamiltonian and environment terms, such as those which give rise to tunnelling, and dissipation. Quantum state diffusion (QSD) models the irreversible behaviour of an individual open system, underpinned by the statistics corresponding to a Bloch type of master equation evolution. Our work therefore provides examples of individual quantum device behaviour for cases where the ensemble evolution is Markovian. Since the Markovian approximation is decent for many experiments and since quantum device experiments usually address just one device, QSD should prove to be a useful tool for future device research.
Finite-Size Corrections in the Supersymmetric t–J Model with Boundary Fields
Authors: Asakawa Hitoshi , Suzuki Masuo
Published: July 2002

The supersymmetric t–J model with boundary fields is discussed. Using the exact solution of the present model, the finite-size corrections of the ground-state energy and the low-lying excitation energies are calculated. The partition functions are evaluated in the scaling limit to obtain the conformal weights of the primary fields in the present model. A surface critical exponent and the ground-state degeneracy are also derived.
Electron Subband Levels of n-Type δ-Doped Quantum Wells under In-Plane Magnetic Fields
Authors: Takahashi E. K. , Lino A. T. , Scolfaro L. M. R.
Published: July 2002

Self-consistent calculations of the electronic structure of center n-δ-doped GaAs/Al x Ga 1-x As quantum wells under in-plane magnetic fields are presented. The field B is varied up to 20 Tesla for different quantum well widths L w and sheet donor concentrations N D . The magnetic field produces noticeable changes in the energy dispersions along an in-plane direction perpendicular to B. The effects of B are more pronounced for higher electronic subbands. It is found that the diamagnetic shifts increase with increasing L w and/or N D . Contrarily to what has been observed in modulation-doped quantum wells, in these δ-doped systems the electron energy dispersions keep the single conduction band minimum at the center of the Brillouin zone even for intense magnetic fields.
On the Uniform Upper Bounds to the Ground State Energy of Quantum System
Authors: Kireev A. N.
Published: July 2002

We derive a set of improving uniform upper bounds to the ground state energy of a quantum system, which provides a natural generalization of the Ritz variational principle. The bounds have a general character, do not depend on the structure of Hamiltonian of a quantum system and converge to its exact ground state energy. As an illustration of the method proposed, we consider a simple example of the shifted harmonic oscillator.
Chern Numbers and Green's Functions in Solid State Physics
Authors: Wu-Morrow Xiao-Rong , Dewitt-Morette Cecile , Rozansky Lev
Published: July 2002

Using the energy Green's function formulation proposed by Niu 1 for particle densities, we construct and clarify the nature of the topological invariant assigned to the Hall conductance in the Hall system of 2-dimensional noninteracting electron gas; we identify this topological quantum number explicitly as the first Chern number of a complex vector bundle over a 2-torus parametrized by the magnetic potential (a1, a2); the fibres are finite dimensional spaces spanned by eigenfunctions of the system with energy eigenvalues below the Fermi energy. Other cases can be treated by a similar procedure, namely, by recognizing that some physical quantities are integrals of curvatures defined on a nontrivial finite dimensional complex bundle. Therefore, in suitable units, they take integer values. We treat, as an example, the electron density response to a dilation of a periodic potential. The integer in this case is the number of Bloch bands. The quantization of the Hall conductance and density response is also shown in the presence of disorder.
Finite Temperature Many-Particle Theory of Condensed Matter Systems in the Functional Schrödinger Picture
Authors: Sik Noh Hyun , Koo You Sang , Koo Kim Chul
Published: July 2002

A finite temperature many-particle theory of condensed matter systems is formulated using the functional Schrödinger picture. Using the interacting electron gas as a model system, we solve the equation of motion for the density matrix variationally with a Gaussian type trial density matrix. We show that the present formalism yields the finite temperature Hartree–Fock results both for the para- and ferromagnetic states in a simple and convenient fashion. Implications of the present results and future prospects are also discussed.
Magnetization Profile in the D= 2 Semi-Infinite Ising Model and Crossover Between Ordinary and Normal Transition
Authors: Czerner Peter , Ritschel Uwe
Published: July 2002

We study the two-dimensional semi-infinite Ising model with a free surface at or near bulk criticality. Special attention is paid to the influence of a boundary magnetic field h1 on the surface-near regime and the crossover between the fixed points at h1=0 and h1=∞. Near the surface, a smallh1 causes a steeply increasing magnetization m(z)~z3/8 log z as the distance z increases away from the surface. By means of a phenomenological scaling analysis, this phenomenon can be related to the well-known logarithmic dependence of the surface magnetization m1 on h1. Our analysis provides a deeper understanding of the existing exact results on m(z) and relates the short-distance phenomena in d=2 to those in higher dimensions. Both the results of the scaling analysis and the exact analytic profiles are corroborated by Monte Carlo simulations.
Generation and Detection of Linear Superpositions of Classically Distinguishable States of a Radiation Mode
Authors: Vitali D. , Tombesi P.
Published: July 2002

A full comprehension of the fuzzy boundary between the classical and the quantum world is still lacking. A deeper understanding of the problem can be obtained form the study of the so-called "Schrödinger cat states", i.e. the paradoxical states arising when the superposition principle of quantum mechanics is extended to the macroscopic world. Quantum optics is, up to now, the most studied field for the experimental realization of these states. A survey of all the proposals made for generating and detecting linear superpositions of classically distinguishable states in quantum optical systems is presented. Then, one of the most recent proposals [P. Tombesi and D. Vitali, Phys. Rev. Lett.77, 411 (1996)] is presented in detail and its experimental feasibility discussed.
INFRARED SPECTROSCOPIC STUDIES ON AMORPHOUS AND CRYSTALLINE LANTHANUM ALUMINOBORATES
Authors: SIMON S. , GRECU R. , SIMON V.
Published: July 2002

The development of lanthanum aluminoborate crystalline phase of LaAl 2.03 B 4 O 10.5 (124) composition from the amorphous xerogels prepared by sol-gel technique has been characterized by thermal analysis and infrared spectroscopy. Thermal analysis evidenced continuous weight losses up to 800°C as a result of nitrates decomposition, glycerol combustion and dehydroxylation. The crystallization of amorphous xerogels occurs between 760 and 860°C. The IR data indicate that the local structure dramatically modifies as crystalline phases are developed from the amorphous xerogels. The major changes occur in the boron surrounding where, from the most borons which are three-coordinated in amorphous xerogels, almost only tetra-coordinated species appear in the crystalline samples. While in amorphous xerogels, aluminum occurs as hexa-, penta- and tetra-coordinated by oxygen, in the crystalline samples obtained from lanthanum aluminoborates, amorphous precursors of composition corresponding to 124-lanthanum aluminoborate phase aluminum, it is preponderantly penta- and hexa-coordinated.
NONLINEAR SIGNAL CLASSIFICATION
Authors: RAPP P. E. , WATANABE T. A. A. , FAURE P. , CELLUCCI C. J.
Published: July 2002

In this contribution, we show that the incorporation of nonlinear dynamical measures into a multivariate discrimination provides a signal classification system that is robust to additive noise. The signal library was composed of nine groups of signals. Four groups were generated computationally from deterministic systems (van der Pol, Lorenz, Rössler and Hénon). Four groups were generated computationally from different stochastic systems. The ninth group contained inter-decay interval sequences from radioactive cobalt. Two classification criteria (minimum Mahalanobis distance and maximum Bayesian likelihood) were tested. In the absence of additive noise, no errors occurred in a within-library classification. Normally distributed random numbers were added to produce signal to noise ratios of 10, 5 and 0 dB. When the minimum Mahalanobis distance was used as the classification criterion, the corresponding error rates were 2.2%, 4.4% and 20% (Expected Error Rate = 89%). When Bayesian maximum likelihood was the criterion, the error rates were 1.1%, 4.4% and 21% respectively. Using nonlinear measures an effective discrimination can be achieved in cases where spectral measures are known to fail.

Most classification errors occurred at low signal to noise ratios when a stochastic signal was misclassified into a different group of stochastic signals. When the within-library classification exercise is limited to the four groups of deterministic signals, no classification errors occurred with clean data, at SNR = 10 dB, or at SNR = 5 dB. A single classification error (Observed Error Rate = 2.5%, Expected Error Rate = 75%) occurred with both classification criteria at SNR = 0 dB.
ABUNDANCE OF MOSAIC PATTERNS FOR CNN WITH SPATIALLY VARIANT TEMPLATES
Authors: HSU CHENG-HSIUNG , YANG TING-HUI
Published: July 2002

This work investigates the complexity of one-dimensional cellular neural network mosaic patterns with spatially variant templates on finite and infinite lattices. Various boundary conditions are considered for finite lattices and the exact number of mosaic patterns is computed precisely. The entropy of mosaic patterns with periodic templates can also be calculated for infinite lattices. Furthermore, we show the abundance of mosaic patterns with respect to template periods and, which differ greatly from cases with spatially invariant templates.
ON THE RELATIONSHIP BETWEEN PARAMETRIC VARIATION AND STATE FEEDBACK IN CHAOS CONTROL
Authors: LIU ZENGRONG , CHEN GUANRONG
Published: July 2002

In this Letter, we study the popular parametric variation chaos control and state-feedback methodologies in chaos control, and point out for the first time that they are actually equivalent in the sense that there exist diffeomorphisms that can convert one to the other for most smooth chaotic systems. Detailed conversions are worked out for typical discrete chaotic maps (logistic, Hénon) and continuous flows (Rösller, Lorenz) for illustration. This unifies the two seemingly different approaches from the physics and the engineering communities on chaos control. This new perspective reveals some new potential applications such as chaos synchronization and normal form analysis from a unified mathematical point of view.
TOPOLOGICAL CHAOS FOR BIRTH-AND-DEATH-TYPE MODELS WITH PROLIFERATION
Authors: BANASIAK JACEK , LACHOWICZ MIROSŁAW
Published: July 2002

In this paper we consider a class of infinite systems of linear ODEs. Each system corresponds to a process characterized by two components: the conservative one (birth-and-death process) and the proliferative one. A system of this type can describe the population of neoplastic cells divided into subpopulations characterized by different levels of cellular resistance to antineoplastic drugs. Under suitable assumptions on the "birth" (amplification) coefficients, the "death" (deamplification) coefficients and the averages of the life-spans we prove that this class of models is topologically chaotic.
A MATHEMATICAL MODEL FOR PHYTOPLANKTON
Authors: BOUSHABA KHALID , ARINO OVIDE , BOUSSOUAR AHMED
Published: July 2002

This paper introduces a model of growth and dispersion of the marine phytoplankton, focusing on the effects of the currents (3D) and vertical mixing. Our method consists of describing these effects as the product of the horizontal current, which is solved along the characteristic lines, and the coupled action of vertical current and vertical diffusion, restricted on each characteristic line of the horizontal current. We show that the trivial steady state loses its stability and a nontrivial (non-constant in space) steady state is created.
REMARKS ON Cn-MOVES FOR LINKS AND VASSILIEV INVARIANTS OF ORDER n
Authors: OHYAMA YOSHIYUKI
Published: July 2002

By the same way for knots, it can be proved that if a link L is transformed into L′ by a Cn-move, the difference of the Vassiliev invariants of order n between L and L′ is equal to the value of the one-branch tree diagram corresponding to the Cn-move. In this paper we show that a Cn-move for a link whose one-branch tree diagram has a cut edge cannot change the Vassiliev invariant of order n. And from this, we can give some examples of links that have the same Vassiliev invariants of order less than n and cannot be transformed into each other by Cn-moves.
CONTRIBUTIONS OF FRACTIONAL CALCULUS TO EARLY VISION
Authors: FALZON FRÉDÉRIC , GIRAUDON GÉRARD
Published: July 2002

As for almost all physical signals, useful information for image understanding is contained in the position and nature of singularities. Consequently, a set of early vision methods has been proposed for locating discontinuities of given derivatives with the aim of solving a large class of features extraction problems. Certain early vision tasks also require a more accurate knowledge of pointwise regularity, mainly for evaluating image roughness. We propose to take these requirements into account, by extending the usual singularity detection methods with the help of fractional calculus.
RATE/DISTORTION PERFORMANCE OF FRACTAL TRANSFORMS FOR IMAGE COMPRESSION
Authors: WOOLLEY STUART J , MONRO DONALD M
Published: July 2002

We study the fidelity/compression performance of fractal image coding, and evaluate the merits or otherwise of a number of complexity options. We can first of all choose a quantization scheme for the transmission of coefficients which limits the code alphabet, according to permissible degradations. This alphabet can then be entropy coded to eliminate redundancy so that the compression efficiency of a range of implementation options can be studied and related to objective and subjective measures of degradation. We find rotations and reflections of little value. A limited degree of searching may be of benefit within image regions of high edge value, but in general more is gained by using a higher order fractal function than by searching.
A SCALE-BASED MODEL OF REFLECTIVITY
Authors: SHIPULSKI E. MICHAEL , BROWN CHRISTOPHER A.
Published: July 2002

A computer simulation is described that models reflectivity as a set of discrete interactions, represented by perfectly reflecting, triangular mirrors fit to the surface using the patchwork method.1 The model is based on a premise that topographically dependent phenomena, such as reflectivity, interact with surfaces over certain scales and that these interaction scales can be used to characterize the interactions for use in the design evaluation of reflective topographies. The simulation is performed on a reflective topography and the results are discussed. Results from the simulation, plots of degree of specular reflection versus patch area, or scale, show that modeling the surface as a collection of mirrors of decreasing size results in less light reflected in the specular direction, or more scattering. Increased scattering from a reduction in patch size, or size of the interaction, models the increased scattering due to a reduction in wavelength of the incident light and reduced scattering due to an increase in incident angle, both shown experimentally in specular reflectance measurements.
UNIVERSAL MULTIFRACTALS IN SEISMICITY
Authors: HOOGE C. , LOVEJOY S. , PECKNOLD S. , MALOUIN J.-F. , SCHERTZER D.
Published: July 2002

Previous studies have examined the spatial, temporal or magnitude distributions of earthquakes. Moreover, others have shown that the spatial distribution of earthquakes is multiscaling. We extend these studies by incorporating the magnitude of the events when examining the scaling properties of the statistics of the earthquakes. We introduce seismic fields as deduced from the maximum ground motion of seismic events (i.e. earthquakes). We then show that these fields are multifractals. Moreover, using a technique called the double trace moment (DTM) analysis, we present here the estimates for the lower bound of the universal exponents of seismic fields: α = 1.1±0.1. We also estimate C1 = 1.35±0.05. It is suggested that while the value of C1 changes from year to year, the estimate of the Lévy index remains relatively constant.
URBAN PROPERTY VALUES, PERCOLATION THEORY AND FRACTAL GEOMETRY
Authors: FRIEDRICH ANNE , KAUFMAN SANDA , KAUFMAN MIRON
Published: July 2002

This project arose from the question: "Can fractal geometry be used to represent changes in urban property values?" In pursuit of an answer to this question, this paper reviews existing urban modeling techniques and their shortcomings in terms of their abilities to represent changes in property values. A percolation model will be used to model property value changes. Data sets of changes in property values over time in the Greater Cleveland area will be developed and mapped. The percolation model will be tested with these data.
RISK ASSESSMENT OF FISHING VESSELS USING FUZZY SET APPROACH
Authors: PILLAY A. , WANG J.
Published: July 2002

The data available from fishing vessels are scarce and often accompanied with a high degree of uncertainty. For this reason the use of conventional probabilistic risk assessment may not be well-suited. This paper proposes a method using fuzzy set theory (FST) to model the occurrence likelihood and consequences of failure for the identified hazards on a fishing vessel. The method uses fault tree analysis to calculate the fuzzy probability of the system failure. The consequences of failure for each basic event within the fault tree are considered for 4 different categories. The risk of the basic events is determined by combining the likelihood of occurrence and consequences of failure in linguistic terms and is further defuzzified to produce a risk ranking. The application of this method is demonstrated using a hydraulic winch operating system of a fishing vessel.
CANONICAL PROPERTY OF REPRESENTATIONS OF GAUSSIAN PROCESSES WITH SINGULAR VOLTERRA KERNELS
Authors: HIBINO YUJI , HITSUDA MASUYUKI
Published: July 2002

We consider the Gaussian process Xλ defined by parameterizing a singular kernel of Volterra-type introduced in Ref. 1. The kernel has a close connection with the noncanonical representation. The result is that the representation is canonical (resp. noncanonical) if λ < 1/2 (resp. λ > 1/2), being independent of the choice of g of a class of functions (Theorem 3).
MOTION DETECTION FROM TIME-VARIED BACKGROUND
Authors: REN YING , CHUA CHIN SENG , HO YEONG KHING
Published: July 2002

This paper proposes a new background subtraction method for detecting moving objects (foreground) from a time-varied background. While background subtraction has traditionally worked well for stationary backgrounds, for a non-stationary viewing sensor, motion compensation can be applied but is difficult to realize to sufficient pixel accuracy in practice, and the traditional background subtraction algorithm fails. The problem is further compounded when the moving target to be detected/tracked is small, since the pixel error in motion compensating the background will subsume the small target. A Spatial Distribution of Gaussians (SDG) model is proposed to deal with moving object detection under motion compensation that has been approximately carried out. The distribution of each background pixel is temporally and spatially modeled. Based on this statistical model, a pixel in the current frame is classified as belonging to the foreground or background. For this system to perform under lighting and environmental changes over an extended period of time, the background distribution must be updated with each incoming frame. A new background restoration and adaptation algorithm is developed for the time-varied background. Test cases involving the detection of small moving objects within a highly textured background and a pan-tilt tracking system based on a 2D background mosaic are demonstrated successfully.
REVERSE BIASED P-N JUNCTION NOISE IN GaAsP DIODES WITH AVALANCHE BREAKDOWN INDUCED MICROPLASMAS
Authors: KOKTAVÝ P. , ŠIKULA J.
Published: July 2002

Random two-level or multiple-level current impulses may occur in electronic devices containing reverse biased p-n junctions in a certain operating mode. These impulses are usually rectangular, featuring constant amplitude, random pulse width and pulse origin time points. This phenomenon is generally ascribed to local avalanche breakdowns originating in p-n junction defect regions called microplasma regions. Based on experiment results, a two-state model of stochastic generation-recombination process has been elaborated for the two-level impulse noise allowing to derive some statistical characteristics of this process. It can be shown that the distribution of the probability density w(τ0) of the impulse separation τ0 and the probability density w(τ1) of the impulse width τ1 have exponential courses. The power spectral density of the noise current is of a G-R process type and depends on the particular microplasma properties. From the viewpoint of noise diagnostics, the most important features are the spectral density Su and noise current I N versus reverse current I R plots, because each local extreme of these plots corresponds to an active microplasma region. Thus obtained results may be used for p-n junction non-destructive diagnostics and quality assessment.
NOISE PROPERTIES OF HIGH TEMPERATURE SUPERCONDUCTING BOLOMETERS
Authors: KHREBTOV I. A.
Published: July 2002

The review describes the noise properties of the high temperature superconducting (HTS) bolometers developed for the applications in the optical electronic devices of infrared and submillimeter wave-lengths. The principle of high-Tc transition edge bolometer operation and bolometer noise theory are considered, taking into account the peculiarities of constant bias current and constant bias voltage modes. The published results of bolometer noise modeling are discussed. Various sources of the excess 1/f-noise in HTS films as temperature sensitive element for bolometer are reviewed, including the experimental data and modern noise models. Comparative analysis of noise characteristics of the most developed HTS bolometers for application (antenna-coupled microbolometers and bolometers based on silicon micromachining technology) is reported.
THE ASYMPTOTIC BEHAVIOR OF SEMI-INVARIANTS FOR LINEAR STOCHASTIC SYSTEMS
Authors: MILSTEIN G. N.
Published: July 2002

The asymptotic behavior of semi-invariants of the random variable ln |X(t,x)|, where X(t,x) is a solution of a linear system of stochastic differential equations, is connected with the moment Lyapunov exponent g(p). Namely, it is obtained that the nth semi-invariant is asymptotically proportional to the time t with the coefficient of proportionality g(n)(0). The proof is based on the concept of analytic characteristic functions. It is also shown that the asymptotic behavior of the analytic characteristic function of ln |X(t,x)| in a neighborhood of the origin of the complex plane is controlled by the extension g(iz) of g(p).
Fast and secure distributed read-only file system
Authors: Fu Kevin , Kaashoek M. Frans , Mazières David
Published: July 2002

Internet users increasingly rely on publicly available data for everything from software installation to investment decisions. Unfortunately, the vast majority of public content on the Internet comes with no integrity or authenticity guarantees. This paper presents the self-certifying read-only file system, a content distribution system providing secure, scalable access to public, read-only data.The read-only file system makes the security of published content independent from that of the distribution infrastructure. In a secure area (perhaps off-line), a publisher creates a digitally signed database out of a file system's contents. The publisher then replicates the database on untrusted content-distribution servers, allowing for high availability.The read-only file system avoids performing any cryptographic operations on servers and keeps the overhead of cryptography low on clients, allowing servers to scale to a large number of clients. Measurements of an implementation show that an individual server running on a 550-Mhz Pentium III with FreeBSD can support 1,012 connections per second and 300 concurrent clients compiling a large software package.
On the closest string and substring problems
Authors: Li Ming , Ma Bin , Wang Lusheng
Published: July 2002

The problem of finding a center string that is "close" to every
given string arises in computational molecular biology and coding
theory. This problem has two versions: the Closest String problem
and the Closest Substring problem. Given a set of strings
S
= {
s
1
,
s
2
, ...,
s
n
}, each of length
m
, the Closest String
problem is to find the smallest
d
and a string s of length
m
which is within Hamming distance d to each
s
i
ε
S
. This problem comes from
coding theory when we are looking for a code not too far away from
a given set of codes. Closest Substring problem, with an additional
input integer
L
, asks for the smallest d and a string
s
, of length
L
, which is within Hamming distance d
away from a substring, of length
L
, of each si. This problem
is much more elusive than the Closest String problem. The Closest
Substring problem is formulated from applications in finding
conserved regions, identifying genetic drug targets and generating
genetic probes in molecular biology. Whether there are efficient
approximation algorithms for both problems are major open questions
in this area. We present two polynomial-time approximation
algorithms with approximation ratio 1 + ε for any small
ε to settle both questions.
Are intelligent e-commerce agents partners or predators?
Authors: Wagner Christian , Turban Efraim
Published: July 2002

Mobile agents are changing the face of e-business and reshaping business models. In the process these agents are also posing new concerns regarding who really owns information.
Adaptive interfaces for ubiquitous web access
Authors: Billsus Daniel , Brunk Clifford A. , Evans Craig , Gladish Brian , Pazzani Michael
Published: July 2002

Allowing mobile users to access any information at any time from any location.