bluuebunny/crossref_metadata_2025 huggingface dataset:
Species relationships between antifungal chitinase and nuclear rDNA (internal transcribed spacer) sequences in the genusHordeum
Authors: Bustos Alfredo De , Loarce Yolanda , Jouve Nicolás
Published: July 2002

The sequences of the chitinase gene (Chi-26) and the internal transcribed spacer of 18S  5.8S  26S rDNA (ITS1) were determined to analyze the phylogenetic relationships among species representing the four basic genomes of the genus Hordeum. Grouping analysis based on data for Chi-26 gene sequences placed Hordeum secalinum (H genome) near the Hordeum murinum complex (Xu genome), and Hordeum bulbosum distant from the other species that carried the I genome. ITS sequence data showed the expected grouping based on the genome classification of the species studied. Different sequences of ITS were detected even in the genomes of the diploid species. The results are interpreted in terms of defective or unfinished concerted evolution processes in each taxon.Key words: ITS, Hordeum, phylogeny, chitinase, concerted evolution.
Travel time, speed, and delay analysis using an integrated GIS/GPS system
Authors: Faghri Ardeshir , Hamad Khaled
Published: July 2002

The backbone of any successful Integrated Traffic Management System (ITMS) for a metropolis is reliable, accurate, and real-time data. Travel time, speed, and delay are three of the most important factors used in ITMS for quantifying, monitoring, and controlling congestion. Global Positioning Systems (GPS) have recently become available for civil applications. As it provides real-time spatial and time measurements, it has an increasing use in conducting different transportation studies. This paper presents the application of GPS in collecting travel time, speed, and delay information on 64 major roads throughout the State of Delaware. A comparative statistical analysis was performed on data collected by GPS method, with data collected simultaneously by the conventional method. The GPS data proved to be at least as accurate as the data collected by conventional methods and was 50% more efficient in terms of manpower. Moreover, the sample-size requirement was determined to maintain 95% confidence level throughout the controlled test. Statistical trend analyses for the data collected from 1997 to 2000 are also presented and applications in the overall ITMS area are discussed.Key words: global positioning system, geographic information system, travel time and delay studies.
Substitution reactions at the Ni(III) cation in macrobicyclic complexes  Reaction of metal ion complexes prepared from ligands L1 (17-oxa-1,4,8,11-tetraazabicyclo[6.5.6]nonadecane) and L2 (17-oxa-1,4,8,11-tetraazabicyclo[10.5.2]nonadecane) with chloride ion
Authors: Ingham Alison M , Xu Chao , Whitcombe T W , Xu Chengtian , Bridson J N , McAuley Alexander
Published: July 2002

The potentially penta-coordinating ligand L1 has been synthesized by reaction of the bridge bis-(2-(methylsulfonyl)oxyethyl)ether with the tetraazamacrocycle cyclam (cyclam = 1,4,8,11-tetraazatetradecane). The copper(II) complex was characterized initially and subsequent demetallation provided pure L1. Electrochemical and chemical oxidation of the nickel(II) species yields a Ni(III) ion (low-spin d7, rhombic, gxx 2.195, gyy 2.189, gzz 2.027) of sufficient stability in acidic solutions for kinetic measurements to be undertaken of substitution reactions at the sixth site. The isomeric ligand L2, has been synthesized previously, and reactions of the [Ni(L1)(solv)]3+ and [Ni(L2)(solv)]3+ ions with chloride have also been investigated. In both reactions, an unusually high acid dissociation constant is observed, associated with the proposed replacement of the apical ether oxygen by a water molecule that is bound both to the metal centre and hydrogen bonded to the ether. The structure [Ni(L2)](PF6)2 (monoclinic, P21/c, a = 10.699(2), b = 13.244(4), c = 16.603(2) Å, β = 92.10(1)°) converged at R = 0.055 (R' = 0.057) for 325 parameters using 3293 reflections with I > 2σ(I). In this complex, the detachment of the ether O donor to yield a square-planar complex is confirmed. Comparisons are made with substitution rates at other Ni(III) macrocyclic ions.Key words: nickel(III), substitution, macrobicyclic ligand, synthesis, kinetics.
Kinetics of glycoluril template-directed Claisen condensations and mechanistic implications
Authors: Rahimizadeh Mohammad , Kam Karen , Jenkins Stephen I , McDonald Robert S , Harrison Paul HM
Published: July 2002

Eight N-acetyl-N-aroyl-glycolurils were prepared and found to undergo efficient tert-butoxide-promoted Claisen-like condensation between the two acyl moieties. The kinetics for formation of each of the N-(aroylacetyl)gly coluril products were monitored by UV spectroscopy. The reaction exhibited pseudo-first-order kinetics in substrate in the presence of excess base. For the parent benzoyl compound the observed first-order rate constant (kobs) was linearly dependent on the concentration of the base, tert-butoxide. A Hammett plot of the resulting apparent second-order rate constants (kapp) vs. σ for each of the eight aroyl derivatives was linear and had a positive ρ value 1.04 ± 0.04), demonstrating that the substituent on the aromatic ring exerts a significant effect upon the condensation reaction. The corresponding plot for three [D3]acetyl analogues was also linear, but the slope was reduced by 20% relative to the protonated compounds. The isotope effect (kHapp/kDapp) thus increased from 1.4 (benzoyl) to 2.6 (p-nitrobenzoyl). The results are consistent with a three-step mechanism in which both deprotonation of the acetyl entity and the ensuing nucleophilic attack of the resulting enolate on the benzoyl group are partially rate-determining steps. The tetrahedral intermediate thus produced rapidly collapses to the product. For the [D3]acetyl benzoyl derivative, exchange of substrate deuterium with solvent hydrogen due to reprotonation of the enolate intermediate occurs at a rate that is similar to that of condensation, but the enolate partitions towards the product when electron withdrawing groups are present in the aroyl ring. Thus, despite the presence of a large excess of co-solvent tert-butanol, the efficiency with which the enolate undergoes condensation remains high. The clean kinetics observed allows further exploration of the details of this intramolecular Claisen-like condensation process.Key words: Claisen condensation, glycoluril, kinetics, Hammett, mechanism.
Thermal ecology of male tarantulas (Aphonopelma anax) during the mating season
Authors: Shillington C
Published: July 2002

During the mating season, male tarantulas abandon their burrows and actively search for widely distributed females, which remain fossorial. As a result, males are exposed to larger fluctuations in environmental conditions without the protection of a permanent retreat. Body temperatures (Tb) of active male tarantulas (Aphonopelma anax) encountered fortuitously in the field ranged from 24.7 to 35.1°C and preferred Tb's measured in a laboratory thermal gradient ranged from 22.1 to 31.3°C. The thermal options available to males at random points in their environment varied substantially throughout the day but temperatures typically exceeded 40°C. In comparison, temperatures within burrows remained below 40°C. Indices calculated from these temperature data suggested that males thermoregulated effectively during the day, while environmental temperatures were within their preferred Tbrange at night and so active regulation of Tbwas unnecessary. In addition, I determined the exact times that males ceased locomotory activity in the morning (retreat) and when they started activity in the evening (emergence). Data from 23 radio-tagged males indicated that they retreated into temporary burrows between 06:47 and 10:53 CST. Activity commenced again between 16:36 and 20:53 CST as temperatures approached their preferred or selected Tbrange.
LOSSLESS SUBDIVISION-BASED MULTIRESOLUTION REPRESENTATION OF ARBITRARY TRIANGLE MESHES USING KITE TREES
Authors: XU WEI , HAMMERSLEY RICHARD , LU KAREN , FUSSELL DONALD
Published: July 2002

We introduce a new type of subdivision-based multiresolution representation for triangle meshes, kite trees, which has the flexibility to represent arbitrary triangle meshes losslessly. We also develop an algorithm for extracting a balanced kite tree representation of an arbitrary input mesh that preserves mesh topology and regularities in the subdivision structure. Our scheme allows us to combine surface information automatically extracted from input data with algorithmically-generated information in a single multiresolution representation and to represent the results of adaptive refinement of regular subdivision surfaces.
CONNES–LOTT MODEL BUILDING ON THE TWO-SPHERE
Authors: MIGNACO J. A. , SIGAUD C. , VANHECKE F. J. , DA SILVA A. R.
Published: July 2002

In this work we examine generalized Connes–Lott models, with C⊕C as finite algebra, over the two-sphere. The Hilbert space of the continuum spectral triple is taken as the space of sections of a twisted spinor bundle, allowing for nontrivial topological structure (magnetic monopoles). The finitely generated projective module over the full algebra is also taken as topologically non-trivial, which is possible over S2. We also construct a real spectral triple enlarging this Hilbert space to include "particle" and "anti-particle" fields.
SOME MATHEMATICAL RESULTS ON THE ASYMPTOTIC BEHAVIOUR OF THE SOLUTIONS TO THE INITIAL VALUE PROBLEM FOR THE ENSKOG EQUATION
Authors: BELLOMO N. , LACHOWICZ M.
Published: July 2002

This paper deals with the analysis of some mathematical results on the asymptotic behaviour of the solutions to the initial value problem for the Enskog equation when the radius of the gas particles and the Knudsen number tend to zero, that is, respectively, analysis of the asymptotic equivalence with the Boltzmann equation and hydrodynamic limit.
ON THE WEAK COUPLING LIMIT FOR A FERMI GAS IN A RANDOM POTENTIAL
Authors: HO T. G. , LANDAU L. J. , WILKINS A. J.
Published: July 2002

General conditions are derived for the essential self-adjointness of –∆ + V, where V is a translation-invariant random potential, and for the existence of the perturbation expansion. A sequence of graphs is exhibited violating Dell'Antonio's bound for skeleton graphs. For a translation-invariant and clustering Gaussian random potential V, and a translation-invariant and clustering initial state S of the Fermi gas, uncorrelated with the random potential, the weak coupling limit (Van Hove limit) yields increase of entropy, propagation of chaos, convergence of the state for sufficiently small values of the parameter τ to a gauge-invariant and quasi-free asymptotic state, and the semigroup describing the evolution of the two-point function. The asymptotic system is Bernoulli. Results are obtained not only for the average over the random potential but also with probability one. If the random potential V′ is absolutely continuous with respect to V, and if the state S′ is given by a density matrix in the GNS representation for S, then the weak coupling limit is the same as for V and S.
Localization and Analytic Properties of the Solutions of the Simplest Quantum Filtering Equation
Authors: Kolokol'tsov Vassili N.
Published: July 2002

The paper deals with the quantum Langevin equation describing a quantum particle with continuously observed position. Special Banach spaces of entire analytic functions are introduced and studied (including a theorem of Paley–Wiener type for them), which comprise all solutions of this equation and in which the uniform convergence (as time tends to infinity) of the solutions to the Gaussian function with a fixed dispersion (selflocalisation or continuous collapse) is proved. The asymptotic behavior at infinity of the mean position and momentum of the limit Gaussian wave packet (which satisfy classical Langevin equations) is also investigated.
ON THE LOWER BOUND ESTIMATES OF SECTIONS OF THE CANONICAL BUNDLES OVER A RIEMANN SURFACE
Authors: LU ZHIQIN
Published: July 2002

We give a lower bound estimate of the sum of the square norm of the sections of the pluricanonical bundles over a Riemann surface of genus greater than 2 and Gauss curvature -1. Such an estimate must depend on the injective radius of the Riemann surface. However, using this estimate, we give a uniform estimate of the corona problem on Riemann surface. Here "uniform" means that the estimate depends only on the genus of Rieman surface, not on the injective radius.
DEFORMATION QUANTIZATION OF CERTAIN NONLINEAR POISSON STRUCTURES
Authors: KAHNG BYUNG-JAY
Published: July 2002

As a generalization of the linear Poisson bracket on the dual space of a Lie algebra, we introduce certain nonlinear Poisson brackets which are "cocycle perturbations" of the linear Poisson bracket. We show that these special Poisson brackets are equivalent to Poisson brackets of central extension type, which resemble the central extensions of an ordinary Lie bracket via Lie algebra cocycles. We are able to formulate (strict) deformation quantizations of these Poisson brackets by means of twisted group C*-algebras. We also indicate that these deformation quantizations can be used to construct some specific non-compact quantum groups.
ARE THE STRING AND EINSTEIN FRAMES EQUIVALENT?
Authors: ÁLVAREZ ENRIQUE , CONDE JORGE
Published: July 2002

The low energy physics as predicted by strings can be expressed in two (conformally related) different variables, usually called frames. The problem is raised as to whether it is physically possible in some situations to differentiate one from the other.
POWER SCALING RULES FOR CHARMONIA PRODUCTION AND HQEFT
Authors: SANCHIS-LOZANO MIGUEL-ANGEL
Published: July 2002

We discuss the power scaling rules along the lines of a complete heavy quark effective field theory (HQEFT) for the description of heavy quarkonium production through a color-octet mechanism. To this end, we firstly derive a tree-level heavy quark effective Lagrangian keeping both particle–antiparticle mixed sectors allowing for heavy quark–antiquark pair annihilation and creation, but describing only low-energy modes around the heavy quark mass. Then we show the consistency of using HQEFT fields in constructing four-fermion local operators à la NRQCD, to be identified with standard color-octet matrix elements. We analyze some numerical values extracted from charmonia production by different authors and their hierarchy in the light of HQEFT.
EXTENDED OBSERVABLES IN HAMILTONIAN THEORIES WITH CONSTRAINTS
Authors: LYAKHOVICH SIMON L. , MARNELIUS ROBERT
Published: July 2002

In a classical Hamiltonian theory with second-class constraints the phase space functions on the constraint surface are observables. We give general formulas for extended observables, which are expressions representing the observables in the enveloping unconstrained phase space. These expressions satisfy in the unconstrained phase space a Poisson algebra of the same form as the Dirac bracket algebra of the observables on the constraint surface. The general formulas involve new differential operators that differentiate the Dirac bracket. Similar extended observables are also constructed for theories with first-class constraints which, however, are gauge-dependent. For such theories one may also construct gauge-invariant extensions with similar properties. Whenever extended observables exist the theory is expected to allow for a covariant quantization. A mapping procedure is proposed for covariant quantization of theories with second-class constraints.
SOLVABILITY OF THE F4 INTEGRABLE SYSTEM
Authors: BORESKOV KONSTANTIN G. , VIEYRA JUAN CARLOS LOPEZ , TURBINER ALEXANDER V.
Published: July 2002

It is shown that the F4 rational and trigonometric integrable systems are exactly-solvable for arbitrary values of the coupling constants. Their spectra are found explicitly while eigenfunctions are by pure algebraic means. For both systems new variables are introduced in which the Hamiltonian has an algebraic form being also (block)-triangular. These variables are invariant with respect to the Weyl group of F4 root system and can be obtained by averaging over an orbit of the Weyl group. An alternative way of finding these variables exploiting a property of duality of the F4 model is presented. It is demonstrated that in these variables the Hamiltonian of each model can be expressed as a quadratic polynomial in the generators of some infinite-dimensional Lie algebra of differential operators in a finite-dimensional representation. Both Hamiltonians preserve the same flag of spaces of polynomials and each subspace of the flag coincides with the finite-dimensional representation space of this algebra. Quasi-exactly-solvable generalization of the rational F4 model depending on two continuous and one discrete parameters is found.
GEOMETRY OF MIXED STATES AND DEGENERACY STRUCTURE OF GEOMETRIC PHASES FOR MULTI-LEVEL QUANTUM SYSTEMS: A UNITARY GROUP APPROACH
Authors: ERCOLESSI E. , MARMO G. , MORANDI G. , MUKUNDA N.
Published: July 2002

We analyze the geometric aspects of unitary evolution of general states for a multilevel quantum system by exploiting the structure of coadjoint orbits in the unitary group Lie algebra. Using the same methods in the case of SU(3) we study the effect of degeneracies on geometric phases for three-level systems. This is shown to lead to a highly nontrivial generalization of the result for two-level systems in which degeneracy results in a "monopole" structure in parameter space. The rich structures that arise are related to the geometry of adjoint orbits in SU(3). The limiting case of a two-level degeneracy in a three-level system is shown to lead to the known monopole structure.
THE BRANE-WORLD FROM SUPERSYMMETRIC DOMAIN WALLS
Authors: LIU JAMES T.
Published: July 2002

We show that the Randall-Sundrum brane-world may be realized in terms of a doubled D3-brane configuration of type IIB theory. We demonstrate the supersymmetry of this realization and indicate how it overcomes previous supersymmetric no-go theorems.
STATUS OF THE CDF II ONLINE TRIGGER
Authors: WINER BRIAN L.
Published: July 2002

Run II at the Tevatron is scheduled to start in March 2001. The accelerator complex and collider detectors are undergoing substantial upgrades. This has motivated a complete redesign of the online-trigger system for the Collider Detector at Fermilab (CDF). The CDF trigger system has a three-level architecture that will reduce the 7.6 MHz crossing rate to 50 Hz written to tape. Using a pipelined and buffered system, the trigger is designed to be "deadtimeless". The structure of the trigger will be flexible and programmable in order to respond to changing beam conditions or physics goals. This paper will review the structure of the CDF trigger system and give a status report on construction and commissioning of the system.
REGULAR AND STOCHASTIC CONFIGURATIONS OF GAUGE FIELDS WITH NONTRIVIAL TOPOLOGY
Authors: ZHUKOVSKY V. C.
Published: July 2002

Time-dependent solution of field equations for the 3-d gauge field model with a Chern-Simons (CS) topological mass is found. After Lorentz boost, this solution describes a massive nonlinear non-abelian plane wave. The CS-massive gauge fields interacting with Higgs fields are demonstrated to display stochastic character. Effective action for an SU(2) 4-d gauge model with a vortex is calculated in the 1-loop approximation. The minimum of the effective potential is found.
COMMENSURATE VERSUS INCOMMENSURATE SPIN-ORDERING IN THE TRIANGULAR HUBBARD MODEL
Authors: CAPRARA SERGIO , CAPONE MASSIMO , CAPRIOTTI LUCA , BECCA FEDERICO
Published: July 2002

The presence of incommensurate spin structures in the half-filled triangular Hubbard model, where frustration leads to a competition among different magnetic phases, is investigated using both the slave-boson technique, and exact diagonalization of finite clusters. We also investigate the metal-insulator transition which, due to the lack of perfect nesting, takes place at a finite value of U. Within the slave-boson approach, as the interaction grows the paramagnetic metal turns into a metallic phase with incommensurate spiral ordering. Increasing further the interaction, a linear spin-density-wave is stabilized, and finally for strong coupling the latter phase undergoes a first-order transition towards an antiferromagnetic insulator. No trace of the intermediate phases is instead found in the exact diagonalization results.
NODAL SPECTRAL WEIGHT AND FERMI SURFACE INLa2-xSrxCuO4
Authors: YOSHIDA T. , NAKAMURA M. , INO A. , MIZOKAWA T. , FUJIMORI A. , ZHOU X. J. , KELLAR S. A. , BOGDANOV P. V. , LU E. D. , LANZARA A. , EISAKI H. , HUSSAIN Z. , SHEN Z.-X. , KAKESHITA T. , UCHIDA S.
Published: July 2002

We present spectral weight mapping in the momentum space for La2-xSrxCuO4using angle-resolved photemission spectroscopy. The spectral weight of the nodal states, which shows suppression in previous results, is enhanced and shows sharp peaks in the second Brillouin zone for the overdoped sample due to matrix element effects, although they remain much weaker than the other cuprates.
COORDINATION AND STRUCTURAL ENERGETICS OF VARIOUS PHASES OF Ni
Authors: KHAJIL T. M. A. , RAHMAN S. M. MUJIBUR , BHUIYAN G. M.
Published: July 2002

Nickel is one of the most versatile metals in the transition series of the periodic table. We have investigated the coordination and the cohesion of Ni corresponding to its various phases. The neighboring distances and the coordination numbers are estimated from the observed and simulated pair distribution functions (PDF) g(r) relevant to the various phases. Since the profiles of these functions are not symmetric, we have used the concept of minimum-to-minimum positions of the PDFs to estimate the successive coordination numbers for the solid amorphous and microcrystalline phases. The approximate values of the pseudo-lattice vectors estimated from the peak positions of the PDFs are employed to calculate the total energies for the amorphous and the microcrystalline phases of Ni in terms of the pseudopotential theory. The roles of the s- and d-electrons in the cohesion of Ni have been investigated by calculating the free energies for the relevant phases. The calculated energetics reveal the relative stability of the various phases in a qualitative manner. It is noted that the d-electrons play the dominant role in predicting the stability of the various phases; the s-electrons merely supplement the d-electron trend. Since the formalism corresponds to very low temperature, the lattice vibrations [Einstein model] do not seem to play any visible role in the prediction.
ANOMALOUS SPECTRAL SHIFTS OF INDIRECT EXCITONS IN COUPLED GaAs QUANTUM WELLS
Authors: SNOKE D. W. , NEGOITA V. , HACKWORTH D. , EBERL K.
Published: July 2002

We have studied the energy shifts of indirect excitons consisting of an electron in one quantum well and a hole in an adjacent quantum well. Several surprising effects occur: (1) a very strong blue shift with increasing intensity of resonant laser excitation, (2) a very strong red shift with weak magnetic field, and (3) very low-frequency (sub-Hz) fluctuations of the spectral position at high excitation density. We discuss the effect of screening by carriers excited in the substrate material.
OHMIC CONTACTS ON DIAMOND BY R. F. SPUTTERING AND Ti-Au METALLIZATION
Authors: WANG Y. Y. , ZHEN C. M. , YAN Z. J. , GUO Q. F. , CHEN G. H.
Published: July 2002

Low resistance ohmic contacts were fabricated on diamond films. A high boron concentration (~1020 cm -3) was obtained on the surface by ion implantation. The initial film of Ti (20nm) followed by Au (100nm) was deposited by r. f. sputtering. I-V measurements showed that the as-deposited contacts were ohmic. Upon annealing, the ohmic characteristics of the contacts were improved significantly. The specific contacts resistivity decreased from 6.2 × 10-3 to 1.2 × 10-6Ω cm 2 as a result of post-deposition annealing. The X-ray photoelectron spectroscopy analysis indicated the formation of titanium carbide at the Ti/diamond interface in the as-deposited and annealed states. A low oxygen concentration was observed.
ICP ETCHING OF RF SPUTTERED AND PECVD SILICON CARBIDE FILMS
Authors: SHI J. , CHOR E. F. , CHOI W. K.
Published: July 2002

In this paper, we report the Inductive Coupled Plasma (ICP) etching of RF sputtered unhydrogenated amorphous silicon carbide film (a-Si0.5C0.5) , and plasma enhanced chemical vapour deposited (PECVD) hydrogenated amorphous silicon carbide films (a-Si0.3C0.7:H and a-Si0.7C0.3:H) , asprepared and annealed, using CF4/O2 chemistry. The etch rate of amorphous SiC is observed to be closely related to the hydrogen content. The mechanism of etching is studied by varying the RIE power, ICP power and pressure. It has been suggested that the removal of surface polymers (CFx) is a key factor in the etching process. In order to study the difference in etch rate between sputtered and PECVD SiC and the effects of changing Si/C ratio, IR spectra are used to reveal the bonds density in the samples.
Dynamic Viscoelasticity in Oscillatory Slit Flow of an ER Suspension Containing Sulfonated Polymer Particles
Authors: Nakano Masami , Ito Kouya , Konno Makoto , Aizawa Ryuji
Published: July 2002

An oscillatory slit flow type rheometer has been developed to measure the dynamic viscoelasticity in an oscillatory slit flow of an ER fluid. Using the rheometer, an ER suspension of numerously sulfonated polymer particles in an insulating oil is evaluated. The results are compared with those for the oscillatory shear flow. In the slit flow, the dynamic viscoelasticity of the ER suspension mainly depends on the fluid strain amplitude and the applied electric field strength. In the fluid strain amplitude of less than about 50% the viscoelastic property becomes dominant, while in the fluid strain amplitude of more than that the viscoelastic plastic property dominates. As the applied field strength increases, the dynamic viscoelasticity changes from viscoelastic plastic to linear viscoelastic. In an oscillatory shear flow, on the other hand, the dynamic viscoelasticity of the ER suspension largely depends on the fluid strain and hardly on the applied field strength. The differences between the dynamic viscoelasticity in the two flow modes can be explained based on the formation and deformation of ER particle clusters which span the electrodes.
A FORMALISM BASED ON THE INPUT IMPEDANCE TO DESIGN OPTICAL STRUCTURES WITH SPECIFIC PROPERTIES
Authors: LEHMAN M.
Published: July 2002

A method to obtain the optical characteristics of new materials is devoloped, based on a simple mathematil formalism. This method can be used in the design of new materials, using the contour plots which permits such characterization, using the input impedance function.
FEW-ELECTRON DOUBLE-LAYER QUANTUM DOTS IN MAGNETIC FIELDS: ENERGY SPECTRUM OF AN ARTIFICIAL MOLECULE
Authors: XIE WENFANG , CHEN CHUANYU , LIN D. L.
Published: July 2002

An exact method is proposed to diagonalize the Hamiltonian of a double-layer quantum dot containing N electrons in arbitrary magnetic fields. For N = 3 and 4, energy spectra of the dot are calculated as a function of the applied magnetic field. As a result of the electron–electron interaction, complete sets of "magic numbers" are found to characterize the total orbital angular momentum of the N-electron dot in the ground state for both the polarized and unpolarized spins. It is shown that discrete transitions of the ground state between magic numbers takes place when the external magnetic field changes. The origin of the magic numbers is completely explained in terms of the underlying symmetry.
A NOVEL PROBABILISTIC MODEL FOR OBJECT RECOGNITION AND POSE ESTIMATION
Authors: HORNEGGER J. , NIEMANN H.
Published: July 2002

In this paper we consider the problem of object recognition and localization in a probabilistic framework. An object is represented by a parametric probability density, and the computation of pose parameters is implemented as a nonlinear parameter estimation problem. The presence of a probabilistic model allows for recognition according to Bayes rule. The introduced probabilistic model requires no prior segmentation but characterizes the statistical properties of observed intensity values in the image plane. A detailed discussion of the applied theoretical framework is followed by a concise experimental evaluation which demonstrates the benefit of the proposed approach.
A NEW INTEGRATED CLUSTERING ALGORITHM GFC AND SWITCHING REGRESSIONS
Authors: WANG SHITONG , JIANG HAIFENG , LU HONGJUN
Published: July 2002

The switching regression problems are attracting more and more attention in a variety of disciplines such as pattern recognition, economics and databases. To solve switching regression problems, many approaches have been investigated. In this paper, we present a new integrated clustering algorithm GFC that combines gravity-based clustering algorithm GC with fuzzy clustering. GC, as a new hard clustering algorithm presented here, is based on the well-known Newton's Gravity Law. Our theoretic analysis shows that GFC can converge to a local minimum of the object function. Our experimental results illustrate that GFC for switching regression problems has better performance than standard fuzzy clustering algorithms, especially in terms of convergence speed. Hence GFC is a new more efficient algorithm for switching regression problems.
TOPOLOGICAL STRUCTURE OF CHAOS IN DISCRETE-TIME NEURAL NETWORKS WITH GENERALIZED INPUT–OUTPUT FUNCTION
Authors: WANG JINLIANG , JING ZHUJUN
Published: July 2002

By analogue of [Chen & Aihara, 1995, 1997, 1999], we theoretically investigate the topologically chaotic structure, attracting set and global searching ability of discrete-time recurrent neural networks with the form of [Formula: see text] where the input–output function is defined as a generalized sigmoid function, such as vi= tanh (μiui), [Formula: see text] and [Formula: see text], etc. We first derive sufficient conditions of existence for a fixed point, and then prove that this fixed point eventually evolves into a snap-back repeller which generates chaotic structure when certain conditions are satisfied. Furthermore we prove that there exists an attracting set which includes not only the homoclinic orbit but also the globally unstable set of fixed points, thereby ensuring the neural networks to have global searching ability.

Numerical simulations are also provided to demonstrate the theoretical results. The results indicated in this paper can be viewed as an extension of the works of [Chen & Aihara, 1997, 1999] and others [Gopalsamy & He, 1994; Wang & Smith, 1998].
MULTISTABILITY AND NONSMOOTH BIFURCATIONS IN THE QUASIPERIODICALLY FORCED CIRCLE MAP
Authors: OSINGA HINKE , WIERSIG JAN , GLENDINNING PAUL , FEUDEL ULRIKE
Published: July 2002

It is well known that the dynamics of the Arnol'd circle map is phase locked in regions of the parameter space called Arnol'd tongues. If the map is invertible, the only possible dynamics is either quasiperiodic motion, or phase-locked behavior with a unique attracting periodic orbit. Under the influence of quasiperiodic forcing the dynamics of the map changes dramatically. Inside the Arnol'd tongues open regions of multistability exist, and the parameter dependency of the dynamics becomes rather complex. This paper discusses the bifurcation structure inside the Arnol'd tongue with zero rotation number and includes a study of nonsmooth bifurcations that occur for large nonlinearity in the region with strange nonchaotic attractors.
FURTHER INVESTIGATION OF HYSTERESIS IN CHUA'S CIRCUIT
Authors: BORRESEN J. , LYNCH S.
Published: July 2002

For a system to display bistable behavior (or hysteresis), it is well known that there needs to be a nonlinear component and a feedback mechanism. In the Chua circuit, nonlinearity is supplied by the Chua diode (nonlinear resistor) and in the physical medium, feedback would be inherently present, however, with standard computer models this feedback is omitted. Using Poincaré first return maps, bifurcations for a varying parameter in the Chua circuit equations are investigated for both increasing and decreasing parameter values. Evidence for the existence of a small bistable region is shown and numerical methods are applied to determine the behavior of the solutions within this bistable region.
PERIODIC ORBITS IN THE NEWTON–LEIPNIK SYSTEM
Authors: MARLIN BENJAMIN A.
Published: July 2002

This paper considers an autonomous nonlinear system of differential equations derived in [Leipnik, 1979]. A criterion for the existence of closed orbits in similar systems is presented. Numerical results are made rigorous by the use of interval analytic techniques in establishing the existence of a periodic solution which is not asymptotically stable. The limitations of the method of locating orbits are considered when a promising candidate for a closed orbit is shown not to intersect itself.
COMPLETE STABILITY FOR STANDARD CELLULAR NEURAL NETWORKS
Authors: LIN SONG-SUN , SHIH CHIH-WEN
Published: July 2002

We consider cellular neural networks with symmetric space-variant feedback template. The complete stability is proved via detailed analysis on the energy function. The proof is presented for the two-dimensional case with Dirichlet boundary condition. It can be extended to other dimensions with minor adjustments. Modifications to the cases of Neumann and periodic boundary conditions are also mentioned.
SYNCHRONIZATION IN COUPLED MAP LATTICES WITH PERIODIC BOUNDARY CONDITION
Authors: LIN WEN-WEI , PENG CHEN-CHANG , WANG CHERN-SHUH
Published: July 2002

We consider a lattice of coupled logistic maps with periodic boundary condition. We prove that synchronization and almost synchronization occur for the case of 1D lattice with lattice size n=2, 3, 4 provided the coupling strength c is chosen in a suitable open interval contained in [Formula: see text]. For the case of lattice size n≥4, we also show the numerical results of (almost) synchronized chaotic behavior of the coupled map lattice. For each fixed parameter γ∈ [3.57, 4] of the logistic maps, the lattice sizes and the ranges of the coupling strengths c so that the coupled map lattice is synchronized, are given.
LOW-DIMENSIONAL COMBINATORIAL DYNAMICS
Authors: ALSEDÀ LLUÍS , LLIBRE JAUME , MISIUREWICZ MICHAŁ
Published: July 2002

The aim of this paper is to give an account of some of the progress made in these last years in the combinatorial low-dimensional dynamics and to suggest some research directions and open problems.
ON GROWTH OF GRIGORCHUK GROUPS
Authors: MUCHNIK ROMAN , PAK IGOR
Published: July 2002

We present an analytic technique for estimating the growth for groups of intermediate growth. We apply our technique to Grigorchuk groups, which are the only known examples of such groups. Our estimates generalize and improve various bounds by Grigorchuk, Bartholdi and others.
RECENT RESULTS ON EXTENSIONS OF STURMIAN WORDS
Authors: BERSTEL JEAN
Published: July 2002

Sturmian words are infinite words over a two-letter alphabet that admit a great number of equivalent definitions. Most of them have been given in the past ten years. Among several extensions of Sturmian words to larger alphabets, the Arnoux–Rauzy words appear to share many of the properties of Sturmian words. In this survey, combinatorial properties of these two families are considered and compared.
NUMERICAL CONTINUATION OF EQUILIBRIA OF PHYSIOLOGICALLY STRUCTURED POPULATION MODELS I: THEORY
Authors: KIRKILIONIS MARKUS A. , DIEKMANN ODO , LISSER BERT , NOOL MARGREET , SOMMEIJER BEN , DE ROOS ANDRE M.
Published: July 2002

The paper introduces a new numerical method for continuation of equilibria of models describing physiologically structured populations. To describe such populations, we use integral equations coupled with each other via interaction (or feedback) variables. Additionally we allow interaction with unstructured populations, described by ordinary differential equations. The interaction variables are chosen such that if they are given functions of time, each of the resulting decoupled equations becomes linear. Our numerical procedure to approximate an equilibrium which will use this special form of the underlying equations extensively. We also establish a method for local stability analysis of equilibria in dependence on parameters.
SOLUTION OF FUZZY DYNAMIC OPTIMIZATION PROBLEMS BY ADAPTIVE STOCHASTIC ALGORITHM
Authors: CHEN CHENG-LIANG , SUN DAIM-YUANG
Published: July 2002

This article proposes a novel algorithm for optimizing a nonlinear dynamic system subjected to flexible path constraints. Each flexible constraint is fuzzified by using the concept of degree-of-acceptability, and the fuzzy degree-of-satisfaction for the objective is then derived. The numerical method of Integrated Controlled Random Search for Dynamic System (ICRS/DS) is applied here for solving the resulting fuzzy decision problem. One numerical example is supplied, demonstrating the applicability of the proposed algorithm.
HEEGAARD SPLITTINGS OF TRIVIAL ARCS IN COMPRESSION BODIES
Authors: HAYASHI CHUICHIRO , SHIMOKAWA KOYA
Published: July 2002

We show that any Heegaard splitting of trivial arcs in a compression body is standard.
Irreducibility of spatial graphs
Authors: TANIYAMA KOUKI
Published: July 2002

A graph embedded in the 3-sphere is called irreducible if it is non-splittable and for any 2-sphere embedded in the 3-sphere that intersects the graph at one point the graph is contained in one of the 3-balls bounded by the 2-sphere. We show that irreducibility is preserved under certain deformations of embedded graphs. We show that certain embedded graphs are irreducible.
PREDICTION AND ANALYSIS OF VACCINATION POSSIBILITIES IN AUTOIMMUNE DISEASES: AN APPLICATION OF ARTIFICIAL IMMUNE SYSTEM
Authors: JOSHI RAJANI R. , NATARAJAN BHUVANESWARAN
Published: July 2002

We present an adaptive machine learning model of the humoral immune response. Antigens (epitopes/ids) and antibodies (paratopes/anti-ids) are represented here as sequences of single letter amino acid codes. The model effectively simulates dynamic affinity maturation, memory and associativity. Specific age-function is derived here based on recent experimental findings and is used to incorporate self and non-self antigens. Computational experiments using real data on Type-1 Diabetes and Systemic Lupus Erythematosus offer quantitative elucidation of autoimmunity. The results also provide applications towards vaccine design and possible solution to the therapeutic difficulties in the autoimmune diseases and disorders of the above kind.
ATTRACTORS WITH FLARES
Authors: ROSSLER OTTO E. , HARTMANN GEORG C.
Published: July 2002

When a chaotic signal is used to force a switching-type variable which dependent on the momentary magnitude of the chaotic stimulus either shows a damped or an autocatalytic response, a new dynamical phenomenon arises. It is reminiscent of the “flares” observed in astrophysical situations. Several numerical simulations of both continuous and discrete examples are presented. The phenomenon was first observed in the simulation of an Ott-Sommerer-Yorke map. The latter possesses not only a “riddled” basin in phase space but also a nongeneric (unbounded) flare attractor. Unlike riddledness, the flare property persists after the introduction of a growth limiting term. Flares occur readily in realistic continuous systems like abstract reaction systems. Search for the new qualitative behavior in experimental situations may be justified. Its potential uses range from signal analysis to economic modelling. From a mathematical point of view, the existence of an automatic “symbolic-dynamics evaluator” is the most surprising.
A MODIFIED INFINITE ELEMENT METHOD FOR ACOUSTIC RADIATION
Authors: LI L.-X. , SUN J.-S. , SAKAMOTO H.
Published: July 2002

An infinite element method is proposed to help solve practical problems in engineering and extend the applicability of infinite element. Based on the Helmholtz's equation, a novel governing equation is derived in terms of the modified sound pressure. The relative boundary conditions are established and the system matrices in using the combination of conventional finite element and new infinite element are subsequently formed. As a result, the use of coarser finite element meshes is permitted for a given frequency. The effectiveness and accuracy of this method are demonstrated in application to two typical examples.
IONIZATION AND EXCITATION PROCESSES IN SPUTTERING IN THE LIGHT OF THE EXPERIMENTAL EVIDENCE
Authors: ŠROUBEK ZDENĚK , LÖRINČÍK JAN
Published: July 2002

So far only one type of theoretical approach for the description of ion formation during sputtering of solids has been developed in detail: the nonadiabatic approach, which uses an unperturbed solid state substrate and which is characterized by the exponential dependence of the ionization probability on the inverse velocity of the sputtered particle. For example, the well-established electron tunneling model belongs to this group of ionization theories. It turns out, however, that the nonadiabatic theories cannot fully explain many experimental observations on ion formation in sputtering. In order to interpret these experiments the assumption of an electronically unexcited substrate must be dropped and a generalizing concept of localization of electronic excitations around the emission spot must be taken into account. Typical consequences of this more general approach are a weaker dependence of the ionization probability on the emission velocity (compared to the nonadiabatic theories) and the dependence of the ionization probability on bombarding conditions. To document the idea several characteristic experiments are presented in this paper and are interpreted within the concept of excitation localization.
STRUCTURE OF Ag{410}
Authors: JONA F. , MARCUS P. M. , ZANAZZI E. , MAGLIETTA M.
Published: July 2002

A quantitative low-energy electron diffraction (QLEED) analysis of data collected from a clean Ag{410} surface finds no relaxation of the first interlayer spacing, 36% compression of the second interlayer spacing and 18% expansion of the third interlayer spacing with respect to the bulk value (0.496 Å). The Ag{410} surface is a stepped surface with the smallest interlayer spacing analyzed so far by QLEED with the computer program CHANGE. Some difficulties in the analysis are discussed.
MEASUREMENTS OF AUGER ELECTRON DIFFRACTION USING A 180° DEFLECTION TOROIDAL ANALYZER
Authors: SHIRAKI SUSUMU , ISHII HIDESHI , NIHEI YOSHIMASA , OWARI MASANORI
Published: July 2002

A 180° deflection toroidal analyzer is a novel electron spectrometer, which allows the simultaneous registration of the wide range of polar angles in a given azimuth of the sample. Therefore, measurements of photo- and Auger electron intensities over π steradians can be performed rapidly by azimuthal rotation of the sample. Using this analyzer, two-dimensional patterns of electron-beam-excited O KVV and Mg KVV Auger electron diffraction (AED) from a MgO(001) surface were measured in short acquisition times. The AED patterns obtained were compared with theoretical ones calculated by the multiple-scattering scheme. The agreement between experimental and theoretical data was good for both O KVV and Mg KVV transitions.
THE SIMULATED ANNEALING GLOBAL SEARCH ALGORITHM APPLIED TO THE CRYSTALLOGRAPHY OF SURFACES BY LEED
Authors: NASCIMENTO V. B. , DE CARVALHO V. E. , DE CASTILHO C. M. C. , SOARES E. A. , BITTENCOURT C. , WOODRUFF D. P.
Published: July 2002

Surface structure determination by Low Energy Electron Diffraction (LEED) is based on a comparison between experimentally measured and theoretically calculated intensity versus energy I(V) curves for the diffracted beams. The level of agreement between these, for different structural models, is quantified using a correlation function, the so-called R factor. Minimizing this factor allows one to choose the best structure for which the theoretical simulations are computed. Surface structure determination thus requires an exhaustive search of structural parameter space in order to minimize the R factor. This minimization is usually performed by the use of directed search methods, although they have serious limitations, most notably their inability to distinguish between false and real structures corresponding to local and global R factor minima. In this work we present the implementation of a global search method based on the simulated annealing algorithm, as suggested earlier by Rous, using the Van Hove and Tong standard LEED code and the results of its application to the determination of the structure of the Ag(111) and CdTe(110) surfaces. Two different R factors, RP and R1, have been employed in the structural searches, and the statistical topographies of these two factors were studied. We have also implemented a variation of the simulated annealing algorithm (Fast Simulated Annealing) and applied it to these same two systems. Some preliminary results obtained with this algorithm were used to compare its performance with the original algorithm proposed by Rous.
XPD STUDY OF VANADIUM OXIDE FILMS GROWN ON THE SnO2(110) SURFACE
Authors: ATREI A. , BARDIB U. , CORTIGIANI B. , ROVIDA G.
Published: July 2002

The oxide phases formed upon annealing at 800 K of ultrathin vanadium films deposited on the SnO 2(110) surface have been investigated by XPD and other techniques. We found that the annealing in vacuum of vanadium layers results in the oxidation of the metal carried out by lattice oxygen diffusing from the bulk of SnO 2. The vanadium oxide phase formed in this way is epitaxially oriented with respect to the substrate and is covered by disordered layers of tin oxide. The XPD results rule out the formation of V–Sn mixed oxides. The simulation of the experimental XPD curves with SSC calculations performed for various structural models indicates that the product of the oxidation is a VO x ≈ 2 phase with a structure close to that of the rutile VO 2(110) surface.
A COMPARISON OF SILICONE REPLACEMENT AND TENDON ARTHROPLASTY FOR BASAL THUMB ARTHRITIS
Authors: Cumming W. J. , Parker G. A.
Published: July 2002

This paper presents a retrospective review of 39 patients having 52 procedures for first carpometacarpal joint arthritis. Swanson silicone replacement arthroplasty is compared with tendon suspension arthroplasty. There were 34 silicone replacement arthroplasties with an average follow-up of 8.9 years, and 18 suspension arthroplasties with an average follow-up of 6.1 years.

There was no statistically significant difference between the two groups. We continue to use silicone for first carpometacarpal joint replacement in elderly patients with low demands.
SALMONELLASPONDYLITIS IN NON-SICKLE CELL PATIENTS
Authors: CHEN PO-QUANG , YANG SHU-HUA , YEN CHANG-CHOU , CHEN WEN-JER , SHIH TIFFANY T. F.
Published: July 2002

This article was a retrospective study of Salmonella spondylitis in seven non-sickle cell anemic patients. The objective of this study was to clarify the clinical manifestations of spinal infection by Salmonella, and to select the proper method of treatment. Comparison with the reported 25 cases in the literature was also attempted.

The clinical symptoms and signs, laboratory data, bony images, treatment modalities and outcomes were documented, and compared with the 25 cases in the English literatures. The patients all suffered from insidious onset of low back pain, with progressive increasing intensity. Leucocytosis (>9000) and body temperature elevation (>37°C) were noted in four cases. Positive cultures were mainly obtained from blood (5 cases) and surgical specimens (one case) before treatment. One patient also had positive culture in the stool and urine. Six patients underwent surgical debridement of the infected foci, while one patient received antibiotic treatment only. The outcome was good in the uncomplicated cases. One patient with concurrent aortic aneurysm died of sepsis. We stress that Salmonella infection can be found in the apparently healthy persons. In the endemic region, high suspicion is needed. Surgical debridement, bone grafting and two months of antibiotic treatment are recommended.