bluuebunny/crossref_metadata_2025 huggingface dataset:
Host Range of Chlamydiaphages φCPAR39 and Chp3
Authors: Everson J. S. , Garner S. A. , Lambden P. R. , Fane B. A , Clarke I. N.
Published: October 2003

The host range of φCPAR39 is limited to four
Chlamydophila
species:
C. abortus
,
C. caviae
,
C. pecorum
, and
C. pneumoniae
. Chp3 (a newly discovered bacteriophage isolated from
C. pecorum
) shares three of these hosts (
C. abortus
,
C. caviae
, and
C. pecorum
) but can additionally infect
Chlamydophila felis
. The ability to support replication was directly correlated with the binding properties of the respective bacteriophages with their host species. Binding studies also show that φCPAR39 and Chp3 use different host receptors to infect the same host cells: cell binding is sensitive to proteinase K treatment, confirming that the chlamydiaphage receptors are proteinaceous in nature.
Comparison of supported liquid membranes and solid-phase extraction for quantitative removal of lead from aqueous solutions
Authors: Yourd Emily R , Tyson Julian F
Published: October 2003

The selective transport of a target metal ion across a membrane from a donor to an acceptor solution is an attractive concept for preconcentration or separation in a flow injection (FI) system. However, we found that the transport of lead across a supported liquid membrane consisting of dicyclohexano-18-crown-6 in decanol embedded in Celgard 2400 was too slow to be practical for an FI atomic spectrometry system. On the other hand, the same chemistry in an on-line, solid-phase reactor (a mini-column containing Pb-Spec resin) gave a satisfactory performance. In an attempt to understand the kinetics of the system, we have calculated the rate of transport across the membrane. As flux is proportional to concentration on the donor side  which decreases with time  we performed a series of numerical simulations involving fixed time intervals of decreasing values. These calculations show that for the sizes of membranes in a typical FI system, transport is very slow compared with the adsorption of lead by the Pb-Spec resin: it takes about 100 min for the concentration in a 0.06 mL donor solution to decrease by a factor of 1000. The time required for the same decrease in concentration for a membrane having the same surface area and ligand concentration as the Pb-Spec column was calculated as approximately 9 s.Key words: supported liquid membrane, solid-phase extraction, flow-injection, lead.
Syntheses, characterization, and X-ray crystal structures of diorganotin(IV) derivatives of 2-pyridinethiolato-N-oxide
Authors: Ma Chunlin , Zhang Junhong , Zhang Rufen
Published: October 2003

The diorganotin(IV) dichloride reacts with sodium 2-pyridinethiolato-N-oxide in a 1:1 ratio to produce [Me2SnCl(2-SpyO)] (1), [Et2SnCl(2-SpyO)] (2), [Bu2SnCl(2-SpyO)] (3), [Ph2SnCl(2-SpyO)] (4), and [(PhCH2)2SnCl(2- SpyO)] (5). The new complexes have been characterized by elemental analysis and IR and NMR (1H, 119Sn, and 13C) spectroscopy. On the basis of 119Sn NMR data the effective coordination number in solution is five. The structures 1 and 4 have been confirmed by X-ray crystallography. Crystals of 1 are triclinic with space group P[Formula: see text] and those of 4 are monoclinic, P21/n. The tin environment is a distorted trigonal bipyramid with the Cl and oxygen atoms in apical positions. Both complexes exhibit strong ππ stacking interactions. Key words: diorganotin, ππ stacking interaction, 2-pyridinethiolato-N-oxide, crystal structure.
Synthesis, characterization, and optical properties of a novel azo-dye bearing an oligo(ethylene glycol) methyl ether side chain in solution and in the solid state
Authors: Rivera Ernesto , Belletête Michel , Natansohn Almeria , Durocher Gilles
Published: October 2003

A novel azobenzene compound bearing a short poly(ethylene glycol) methyl ether side chain, N-methyl-N-{4-[(E)-(4-nitrophenyl)diazenyl]phenyl}-N-(3,6,9,12,15,18,21,24-octaoxapentacos-1-yl)amine (RED-PEGM-8) was synthesized and characterized. RED-PEGM-8 exhibits a thermal behavior similar to that of Disperse Red-1; however, its thermal stability, as well as its Tg and Tm values, are lower because of the presence of the PEGM segment. The optical properties of this compound in solution and in the solid state were studied by UVvis spectroscopy. The appearance of a blue-shifted band in aqueous solutions at high concentrations of the chromophore reveals the existence of H-type aggregates, resulting from ππ intermolecular interactions between the azobenzene units. Strong intermolecular interactions were also confirmed by 1H NMR measurements. Optical properties of RED-PEGM-8 in the solid state (thin film) also suggest the presence of H aggregates. However, a tail is also detected in the red region of the absorption spectrum, which could be because of the formation of J-type aggregates in the thin film.Key words: aggregation, azo-dye, poly(ethylene glycol) methyl ether.
Electroreduction of 1-methyl 5-nitroindole, 5-nitrobenzofurane, and 5-nitrobenzothiophene in acidic and basic hydroorganic media: Generation and trapping of iminoquinone-type intermediates and electrosynthesis of ring-substituted amino derivatives
Authors: Bouchard Luc , Marcotte Ian , Chapuzet Jean Marc , Lessard Jean
Published: October 2003

Preparative electrolysis of 1-methyl-5-nitroindole (1b, X = NCH3), 5-nitrobenzofurane (1c, X = O), and 5-nitrobenzothiophene (1d, X = S) at Hg, in acidic hydromethanolic media, leads to the formation of the corresponding 4-substituted amino derivatives 5, which result from the 100% regioselective addition to iminoquinone-type intermediate 4 of methanol or of any other good nucleophile present in the electrolytic solution. In acidic medium, the iminoquinonium intermediates 4b and 4c were trapped in a cycloaddition reaction with cyclopentadiene added to the electrolysis medium. The regiochemistry of the nucleophilic addition is discussed in light of AM1 calculations. Key words: 1-methyl-5-nitroindole, 5-nitrobenzofurane, 5-nitrobenzothiophene, iminoquinone, electrosynthesis.
Orthogonene: A computational study of a strongly twisted alkene
Authors: Lewars E
Published: October 2003

The strongly twisted (calculated dihedral angle 84°) alkene orthogonene (tetracyclo[8,2,2,02,7,03,10]tetradecene-2(3)) was studied at the DFT (B3LYP/6-31G*) and ab initio (HF/6-31G* and MP2(fc)/6-31G*) levels with a view to exploring the question of how realistic a synthetic objective it is, particularly in view of the fact that an attempt was made to synthesize it. Orthogonene is a relative minimum on the potential energy surface at the B3LYP/6-31G* and MP2(fc)/6-31G* levels, but is predicted to have a very low barrier (1.2 kJ mol1 from the B3LYP calculations) to rearrangement by a 1,2-carbon shift to a carbene, which in turn isomerizes to a cyclopropane and (or) an alkene (the carbene is perhaps not a stationary point on the potential energy surface). Thus, very likely orthogonene could be observed only at temperatures approaching absolute zero, if at all.Key words: orthogonene, tetracyclo[8,2,2,02,7,03,10]tetradecene-2(3), twisted double bond, orthogonal double bond, carbene-strained alkene isomerization, ab initio, DFT.
Geometric Transformations of Language Families: The Power of Symmetry
Authors: Mateescu Alexandru , Rozenberg Grzegorz , Salomaa Arto
Published: October 2003

We consider certain isomorphisms between language families. When viewed as a group, the isomorphisms reduce to well-known geometric transformations. We obtain new characterizations for linear, simple matrix, simple contextual and trace languages. Our results make it possible to transfer results concerning languages in one family into results concerning languages in another family.
Complexity of Task Graph Scheduling with Fixed Communication Capacity
Authors: Finta Lucian , Liu Zhen
Published: October 2003

Consider a scheduling problem of parallel computations in multiprocessor systems. Let a parallel program be modeled by a task graph, where vertices represent tasks and arcs the communications between tasks. An interprocessor communication time incurs when two tasks assigned to two different processors have to communicate. Such a scheduling problem has recently been studied in the literature, mostly for the case where interprocessor communication times are fully determined. In this paper, we consider the scheduling problem with communication resource constraints. More specifically, we consider the case where all interprocessor communications take place on a network of bounded capacity. We consider two variants of the problem: communications with independent-data semantics and common-data semantics. We show that even for very specific subproblems, viz. scheduling of general graphs on two processors and scheduling of binary trees on an infinite number of processors, the minimization of the makespan of parallel programs in such a multiprocessor system is strongly [Formula: see text]-hard. We first establish the results for the case of capacity 1, referred to as the single-bus system. We then extend the results to the more general case of fixed communication capacities. As a consequence, the general scheduling problem of parallel programs with communication resource constraints is strongly [Formula: see text]-hard. These results are to be contrasted with the corresponding scheduling problems without contraint on the communication capacity, where the two-processor case has unknown time complexity and the infinite-processor case is polynomial. Our results are also extended to the case of broadcasting communications, and can be applied to multiprocessor systems with shared memory.
Pattern Languages Versus Parallel Communicating Grammar Systems
Authors: Dumitrescu Sorina , Păun Gheorghe , Salomaa Arto
Published: October 2003

We compare the power of two (fairly different) recently investigated language identifying devices: patterns and parallel communicating (PC) grammar systems. The simulation of multi-patterns by context-free PC grammar systems is rather obvious, but, unexpectedly, this can be realized also by (non-centralized) PC grammar systems with right-linear components. Moreover, infinite multi-patterns forming a regular set can also be simulated by PC grammar systems with right-linear components, whereas PC grammar systems with context-free components can simulate context-free multi-patterns with context-free domains for variables.
Logspace Reducibility: Models and Equivalences
Authors: Hemaspaandra Lane A. , Jiang Zhigen
Published: October 2003

We study the relative computational power of logspace reduction models. In particular, we study the relationships between one-way and two-way oracle tapes, resetting of the oracle head, and blanking of the oracle tape. We show that oracle models letting information persist between queries can be quite powerful, even if the information is not readable by the querying machine. We show that logspace f(n)-Turing reductions are stronger than polynomial-time f(n)-Turing reductions when f(n) = ω(log n), and that this is optimal if P = L.
Design and Analysis of the Symmetric Banyan Network (SBN): A Min with High Performance and High Fault Tolerance
Authors: Keum Young Wook , Rim Hwakyung
Published: October 2003

A new MIN called the Symmetric Banyan Network (SBM) is presented in this paper. In the SBN, 4 × 4 switching elements are used and they are connected symmetrically between the upper and lower parts of the network. There are 2N paths for every source-destination pair. The SBN is basically single-fault tolerant, but can tolerate up to three faults, with more elegant routing, except in the first and last stages which are still single-fault tolerant. And full accessibility is preserved even in some instances when half of the network is in fault. The routing of the SBN is self-adaptive in the presence of a fault. The throughput analysis of the SBN is done using computer simulations and shows that the SBN performs better than the Itoh's network, the ASEN (Augmented Shuffle Exchange Network) and the crossbar network. We analyze the cost/performance of the SBN against the MINs with multiple banyan networks such as MBSF (Multi Banyan Switching Fabric) and the PBSF (Piled Banyan Switching Fabric) and the analysis shows that the SBN is also attractive in terms of the cost.
Web Technologies and the Potential for Innovation in Distance Education
Authors: Fox Geoffrey , Mills Kim
Published: October 2003

Web-based distance education technologies may improve education and support totally new educational systems. Web technologies present new opportunities for delivering multimedia information and interacting with physical simulations. This paper describes some infrastructure and human interaction issues, a text-indexed video, and a Web-based image storage and presentation system, and three on-going distance education projects.
Another Look at Neural Multigrid
Authors: Bäker Martin
Published: October 2003

We present a new multigrid method called neural multigrid which is based on joining multigrid ideas with concepts from neural nets. The main idea is to use the Greenbaum criterion as a cost functional for the neural net. The algorithm is able to learn efficient interpolation operators in the case of the ordered Laplace equation with only a very small critical slowing down and with a surprisingly small amount of work comparable to that of a Conjugate Gradient solver

In the case of the two-dimensional Laplace equation with SU(2) gauge fields at β = 0 the learning exhibits critical slowing down with an exponent of about z≈0.4. The algorithm is able to find quite good interpolation operators in this case as well. Thereby it is proven that a practical true multigrid algorithm exists even for a gauge theory. An improved algorithm using dynamical blocks that will hopefully overcome the critical slowing down completely is sketched.
Search of Molecular Ground State Via Genetic Algorithm: Implementation on a Hybrid Simd–Mimd Platform
Authors: Pucello N. , Rosati M. , D'Agostino G. , Pisacane F. , Rosato V. , Celino M.
Published: October 2003

A genetic algorithm for the optimization of the ground-state structure of a metallic cluster has been developed and ported on a SIMD–MIMD parallel platform. The SIMD part of the parallel platform is represented by a Quadrics/APE100 consisting of 512 floating point units, while the MIMD part is formed by a cluster of workstations. The proposed algorithm is composed by a part where the genetic operators are applied to the elements of the population and a part which performs a further local relaxation and the fitness calculation via Molecular Dynamics. These parts have been implemented on the MIMD and on the SIMD part, respectively. Results have been compared to those generated by using Simulated Annealing.
Boundary Integral Method for Stationary States of Two-Dimensional Quantum Systems
Authors: Kosztin Ioan , Schulten Klaus
Published: October 2003

The boundary integral method for calculating the stationary states of a quantum particle in nano-devices and quantum billiards is presented in detail at an elementary level. According to the method, wave functions inside the domain of the device or billiard are expressed in terms of line integrals of the wavefunction and its normal derivative along the domain's boundary; the respective energy eigenvalues are obtained as the roots of Fredholm determinants. Numerical implementations of the method are described and applied to determine the energy level statistics of billiards with circular and stadium shapes and demonstrate the quantum mechanical characteristics of chaotic motion. The treatment of other examples as well as the advantages and limitations of the boundary integral method are discussed.
Genetic Algorithms in a Distributed Computing Environment Using PVM
Authors: Cronje G. A. , Steeb W.-H.
Published: October 2003

The Parallel Virtual Machine (PVM) is a software system that enables a collection of heterogeneous computer systems to be used as a coherent and flexible concurrent computation resource. We show that genetic algorithms can be implemented using a Parallel Virtual Machine and C++. Problems with constraints are also discussed.
Liquid Crystal Lattice Models on Quadrics Supercomputers
Authors: Boschi Sigismondo , Brunelli Marco P. , Zannoni Claudio , Chiccoli Cesare , Pasini Paolo
Published: October 2003

The implementation of a Monte Carlo code for simulations of liquid crystal lattice models on the Quadrics massively parallel SIMD supercomputer is described. The use of a Quadrics with 512 processors is proving essential in studying the nematic–isotropic phase transition to an unprecedented level of accuracy using more than 106 particles. Here some tests on the Lebwohl–Lasher model with and without an applied field are presented.
Entropy and Correlations in Lattice-Gas Automata Without Detailed Balance
Authors: Tribel Olivier , Boon Jean Pierre
Published: October 2003

We consider lattice-gas automata where the lack of semi-detailed balance results from node occupation redistribution ruled by distant configurations; such models with nonlocal interactions are interesting because they exhibit non-ideal gas properties and can undergo phase transitions. For this class of automata, mean-field theory provides a correct evaluation of properties such as compressibility and viscosity (away from the phase transition), despite the fact that no H-theorem strictly holds. We introduce the notion of locality — necessary to define quantities accessible to measurements — by treating the coupling between nonlocal bits as a perturbation. Then if we define operationally "local" states of the automaton — whether the system is in a homogeneous or in an inhomogeneous state — we can compute an estimator of the entropy and measure the local channel occupation correlations. These considerations are applied to a simple model with nonlocal interactions.
Digital Physics Simulation of Lid-Driven Cavity Flow
Authors: Teixeira Christopher M.
Published: October 2003

Digital Physics is a new extension of the lattice-gas concept for the simulation of fluid flow which removes disadvantages that prevented practical application of the original method. The extensions are summarized. Simulation results for a three-speed model demonstrate the absence of artifacts and significant reduction in viscosity. Also, simulation results for 2D and 3D lid-driven cavities for a range of Reynolds numbers and geometries are compared with experiment, CFD and the lattice-Boltzmann BGK method. Accurate results are obtained with the new method.
A Lattice-Boltzmann Model for Visco-Elasticity
Authors: Giraud Laurent , d'HumièRes Dominique , Lallemand Pierre
Published: October 2003

The classical lattice-Boltzmann scheme is extended in an attempt to represent visco-elastic fluids in two dimensions. At each lattice site, two new quantities are added. A suitable coupling of these quantities with the viscous stress tensor leads to a nonzero shear modulus and visco-elastic effects. A Chapman–Enskog expansion gives us the equilibrium populations and conditions for isotropy of the model. A finite wave vector analysis is needed to study the relaxation of sound waves and to determine the dependence of the transport coefficients upon the frequency.
Using the FHP-BGK-Model to Get Effective Dispersion Constants for Spatially Periodic Model Geometries
Authors: Grubert Dietmar
Published: October 2003

Tracer dispersion is governed by the velocity fluctuations that the particles are subjected to during their movement. The fluctuation of particle velocity is due to deviations from the mean velocity in the flow field and also to the change of the streamline caused by diffusion. The lattice-BGK method is a good tool to investigate the interaction of both of them, because it models the flow field in detail with even small flow structures. A serious drawback of direct simulations are the requirements in computer time and memory. For spatially periodic media, this can be overcome by using the generalized Taylor-dispersion method to calculate the asymptotic effective dispersion from a solution in an elementary cell. This solution is obtained by simulations with an FHP-BGK-lattice gas. Joining the two methods yields a tool to study the effective dispersion constant of a given periodic geometry.
A Thermal LBGK Model for Large Density and Temperature Differences
Authors: Huang Jian , Xu Feng , Vallières Michel , Feng Da Hsuan , Qian Yue-Hong , Fryxell Bruce , Strayer Mike R.
Published: October 2003

We present a new lattice-Boltzmann method for hydrodynamic simulations, which is capable of handling very large density and temperature gradients. Unlike other LBGK models, the discrete velocities we used center at the local mean flow velocity, and their values vary according to the local temperature. The adiabatic index of the gas can be easily controlled by a parameter.
Symmetry Breaking of Flow in 2D Symmetric Channels: Simulations by Lattice-Boltzmann Method
Authors: Luo Li-Shi
Published: October 2003

In this paper, a numerical study of nonlinear flow phenomena in two-dimensional symmetric channels using the lattice-Boltzmann equation method is presented. The results are compared with both experimental results and other numerical results using some traditional methods. Comparisons are found to be quantitatively accurate.
Lattice-Boltzmann Scheme for Natural Convection in Porous Media
Authors: Van Der Sman R. G. M.
Published: October 2003

A lattice-Boltzmann scheme for natural convection in porous media is developed and applied to the heat transfer problem of a 1000 kg potato packaging. The scheme has features new to the field of LB schemes. It is mapped on a orthorhombic lattice instead of the traditional cubic lattice. Furthermore the boundary conditions are formulated with a single paradigm based upon the particle fluxes. Our scheme is well able to reproduce (1) the analytical solutions of simple model problems and (2) the results from cooling down experiments with potato packagings.
Clustering Instability in Granular Gases: A Mesoscopic Investigation
Authors: Succi Sauro , Wang Jane , Qian Yue-Hong
Published: October 2003

We present a numerical study of the density fluctuations in granular flows in the hydrodynamic limit. By simulating the continuum equations posed for granular flows,1,2 we study the onset of the density-cluster formation. Clusters are observed when the restitution coefficient of granular collision is sufficiently small. However, unlike the clusters seen in molecular dynamics simulations,3,4 these macroscopic clusters appear to be transient. In the long time limit, they are damped by the viscous dissipation.
Microscopic Simulation of Urban Traffic Based on Cellular Automata
Authors: Esser J. , Schreckenberg M.
Published: October 2003

Saturated capacities in traffic systems evoke increasing interest in simulations of complex networks serving as laboratory environment for developing management strategies. Especially for urban areas questions concerning overall traffic control have to be considered with regard to their impacts on the whole network. Modeling traffic flow dynamics using cellular automata allows us to run large network traffic simulations with only comparatively low computational efforts. We present a traffic simulation tool for urban road networks which is based on the Nagel–Schreckenberg Model. Arbitrary kinds of roads and crossings are modeled as combinations of only a few basic elements. Furthermore parking capacities are considered as well as circulations of public transports. The vehicles are driven corresponding to route plans or at random depending on the available data. The application of this network simulation covers investigations on the field of traffic planning as well as online simulations based on real-time traffic data as basis for dynamic traffic management systems.
A New Look at the 2D Ising Model from Exact Partition Function Zeros for Large Lattice Sizes
Authors: Alves Nelson A. , Drugowich de Felicio J. R. , Hansmann Ulrich H. E.
Published: October 2003

A general numerical method is presented to locate the partition function zeros in the complex β plane for large lattice sizes. We apply this method to the 2D Ising model and results are reported for square lattice sizes up to L = 64. We also propose an alternative method to evaluate corrections to scaling which relies only on the leading zeros. This method is illustrated with our data.
Molecular Orbitals Calculation on LiH with Algebraic Treatment of the Integrals
Authors: Righi A. F. M. , Kuhnen C. A.
Published: October 2003

In this work we employ an algebraic computational method to solve the integrals which arise in the study of diatomic molecules. Using the Slater-type orbitals (STO), we obtain analytical solutions for the one-center and two-center hybrid and Coulomb integrals. The exchange integrals are considered, as much as possible, in a similar manner. These results are used to calculate the electronic properties of the ground state of the LiH molecule, by means of a variational calculation using a basis of molecular orbitals. The behavior of the Slater exponents of the atomic orbitals are studied as functions of internuclear distance. We show that the STO undergo a lengthening of their shape when the nuclear separation increases.
Specific Heat Singularity in Two-Dimensional Random Ising Ferromagnets
Authors: Stauffer D. , Aarão Reis F. D. A. , de Queiroz S. L. A. , dos Santos R. R.
Published: October 2003

We use transfer-matrix methods to calculate free energies and specific heats on long, finite-width strips of Ising spins with randomly distributed ferromagnetic couplings. By implementation of our code on a highly parallel computer, we have managed to generate high-quality data for strip widths up to L = 18 sites. An unequivocal trend towards a divergency of the specific heat in the thermodynamic limit can be discerned. Finite-size data appear to behave halfway between a single- ( ln L) and double- ( ln ln L) logarithmic dependence on strip width. This is in line with a crossover within the Dotsenko-Shalaev picture of logarithmic corrections to pure-system singularities.
The Energy Spectra of the Relativistic Rotating Oscillators
Authors: Ardelean Gheorghe , Cotăescu Ion I.
Published: October 2003

We study, by using numerical computation methods, the structure of the energy spectra of the quantum relativistic rotating oscillators we have recently proposed, starting with a set of one-parameter deformations of the static (3+1) de Sitter or anti-de Sitter metrics.1
Critical 2D and 3D Dynamics of Q2R Cellular Automata
Authors: Stauffer D.
Published: October 2003

Simulation of critical relaxation of the magnetization in a microcanonical Ising model agrees with the expected exponent z ≃2 after very long times on the square lattice, while on the simple cubic lattice z≃3.3 seems different.
Non-Universal Gauge Bosons Z′ and Rare Top Decays
Authors: Yue Chongxing , Zong Hongjie , Liu Lanjun
Published: October 2003

We study a new method for detecting non-universal gauge bosons Z′ via considering their effects on rare top decays. We calculate the contributions of the non-universal gauge bosons Z′ predicted by topcolor-assisted technicolor (TC2) models and flavor-universal TC2 models on the rare top decays t → cV (V = g,γ,Z) and t → clilj (li,lj = τ,μ, or e). We show that the branching ratios of these processes can be significantly enhanced. Over a sizeable region of the parameter space, we have Br (t → cg) ~ 10-5 and Br (t → cττ) ~ 10-7, which may approach the observable threshold of near future experiments. Non-universal gauge bosons Z′ may be detected via the rare top decay processes at the top-quark factories such as the CERN LHC.
Nonlocal Regularization and Renormalization of Sp(2) Symmetric BRST Theories
Authors: Calian V. , Stoenescu G.
Published: October 2003

An extension of the nonlocal regularization scheme is formulated for the Sp(2) symmetric Lagrangian BRST quantization. It provides a systematic treatment of the anomalous quantum master equations and allows to subtract the divergences as well as to calculate genuine higher loop BRST and anti-BRST anomalies.
Magnetic Properties of the U1-xYxNiAl System
Authors: Lucaci P. , Lupsa Ileana
Published: October 2003

The magnetic properties of the U 1-x Y x NiAl system were studied in the 4–600 K temperature range fields up to 7 T. The systems with x≤0.8 were analyzed in terms of the spin fluctuations theory. The system presents a Curie–Weiss type behavior over a certain temperature T*. The paramagnetic Curie temperatures are negative and decrease in absolute magnitude as yttrium content increases. The effective magnetic moment per uranium atom is composition independent (≈3.1 μB) proving the presence of temperature induced spin fluctuations.
Kinetic Energy Driven Charge Pairing and Superconductivity in the t–J Model
Authors: Feng Shiping
Published: October 2003

The superconducting mechanism of doped cuprates is studied within the t–J model. It is shown that dressed holons interact directly through the kinetic energy by exchanging dressed spinon excitations. This interaction leads to a net attractive force between dressed holons, and the electron Cooper pairs originating from the dressed holon pairing state are due to the charge-spin recombination, and their condensation reveals the superconducting ground state. The superconducting transition temperature is determined by the dressed holon pair transition temperature, and is proportional to the hole doping concentration in the underdoped regime, in qualitative agreement with experiments.
Basis Matrix Representation of Morphological Filters with N-Dimensional Structuring Elements
Authors: Choi Byung-Tae , Lee Kyung-Hoon , Ko Sung-Jea , Morales Aldo
Published: October 2003

In this paper, we present a basis matrix representation of grayscale morphological filters in N-dimensions. A procedure is proposed to derive the basis matrix and the block basis matrix (BBM) from an N-dimensional grayscale structuring element (GSE). It is shown that both opening and closing with arbitrary N-dimensional GSE can be accomplished by a local matrix operation using the basis matrix. Furthermore, these basis matrix representations are extended to the efficient implementation of open-closing (OC) and close-opening (CO) using the BBM.
A Collision-Free Reservation Protocol for WDM Optical Star Networks
Authors: Kim Young-Chon , Lee Ho-Sook
Published: October 2003

WDM single-hop networks allow a pair of nodes to exchange data packets directly and require an efficient protocol that coordinates the process of data transmission. However, the network performance with such protocols can be deteriorated by collisions that occur on control channel, data channel, destination node and source node. We present a Collision-Free Reservation Protocol (CFRP) for WDM single-hop networks with a passive optical star coupler. To eliminate all causes of collision, the CFRP properly distributes the transmission schedule both in time (position of data channel on the time axis) and space (wavelength of data channel to be used). Compared with the previous reservation-based protocols, the proposed CFRP enhances the overall network performance. This improvement in terms of network throughput and delay is verified by simulation.
Performance Study of Time Delay Estimation in a Multi-Path Environment
Authors: Jian Ming , Kot Alex C. , Er Meng H.
Published: October 2003

A theoretical analysis of the performance of the maximum likelihood (ML) time delay estimate in a multi-path propagation is proposed. An expression for the probability of anomaly of the ML time delay estimate is obtained. Percentages of anomalous time delay estimates obtained through Monte Carlo simulation are shown to be in close agreement with theoretically predicted values.
Radial Basis Function Networks for Analog Circuit Fault Isolation
Authors: Babu N. S. C. , Prasad V. C.
Published: October 2003

The application of a radial basis function neural network (RBFN) for analog circuit fault isolation is presented. In this method the RBFN replaces the fault dictionary of analog circuits. The proposed method for analog circuit fault isolation takes the advantage of extremely fast training of RBFN compared to earlier neural network methods. A method is suggested to select centers and widths of RBF units. This selection procedure accounts for the component tolerances. The effectiveness of the RBFN for the fault isolation problem is demonstrated with an illustrative example. RBFN performed well even when the input patterns are drawn directly from the test node voltages of the analog circuit under consideration. A method is suggested to modify the RBF network in the event of occurrence of a new fault. The suggested modifications do not affect the previous training.
Sampling the SU(N) Invariants of Three-Manifolds
Authors: Lickorish W. B. R.
Published: October 2003

The SU(N) quantum invariants for three-manifolds have been established in a combinatorial way by Yokota starting from the skein theory associated with the HOMFLY polynomial invariant of knot theory. Using Yokota's formulation it is here noted that there are distinct three-manifolds that are not distinguished by these invariants and that there are manifolds distinguished by the SU(N) invariants for N ≥ 3 that have the same SU(2) invariants. A by-product of the investigation is a reversing result for the HOMFLY polynomial.
A Computation of the Basic Invariant J+ for Closed 2-Vertex Curves
Authors: Umehara Masaaki
Published: October 2003

In this paper, we will give an explicit and simple formula for J+-invariant of closed 2-vertex curves. As an application, we give an affirmative answer to a problem conjectured by Arnold [A2], related to Legendrian knots in R2 × S1.
The Rank of the Trip Matrix of a Positive Knot Diagram
Authors: Zulli Louis
Published: October 2003

In this note we show that the rank of the trip matrix of a positive knot diagram is exactly twice the genus of the associated positive knot. From this, we give a quick proof of the following result of Murasugi: The term of lowest degree in the Jones polynomial of a positive knot is 1 · tg, where g is the genus of the knot.
The Third Derivative of the Jones Polynomial
Authors: Miyazawa Yasuyuki
Published: October 2003

Let L be an oriented n-component link and let VL (t) be the Jones polynomial of L. A relationship between [Formula: see text] (1) and the coefficients of the Conway polynomials of L is given.
Renormalization and Knot Theory
Authors: Kreimer Dirk
Published: October 2003

We investigate to what extent renormalization can be understood as an algebraic manipulation on concatenated one-loop integrals. We find that the resulting algebra indicates a useful connection to knot theory as well as number theory and report on recent results in support of this connection.
Knot Enumeration Through Flypes and Twisted Splices
Authors: Calvo Jorge Alberto
Published: October 2003

I propose a method to enumerate prime alternating knots. The algorithm is both combinatorial and geometrical in nature; it rests on a particular splicing of knot projections (on the sphere [Formula: see text]) which is guaranteed to produce every prime knot projection when repeatedly applied (starting on the trivial unknot projection). By exploring the behavior of the flype structure of alternating knots (as in Tait's Flyping Theorem), I prove not only completeness of the enumerator, but also some useful "shortcuts" to producing a full dictionary of prime alternating knots.
The Potts Model with a Reflecting Boundary
Authors: Häring-Oldenburg Reinhard
Published: October 2003

A Potts model with a reflecting boundary is introduced and it is shown that its partition function can be expressed as a Markov trace on the Temperley-Lieb Algebra of Coxeter type B.
On Conway Algebras and the Homflypt Polynomial
Authors: Sikora Adam S.
Published: October 2003

In 1984 J. H. Przytycki and P. Traczyk introduced the notion of Conway algebras. They had proved that for every Conway algebra there exists an invariant of links in ℝ3, which takes values in that algebra. In this paper we show that any link invariant obtained in this way is not better than the Homflypt (Jones-Conway) polynomial.
Vacuum Structure, Chiral Symmetry Breaking and Radiative Decays of Vector Mesons
Authors: Panda A. R. , Roy K. C.
Published: October 2003

The radiative decay widths of vector mesons were considered in a model involving chiral symmetry breaking through a nontrivial vacuum structure where the pion and kaon being treating consistently yield the constituent quark wave functions, approximately the same as that obtained from the gap equations and thus in a way determine the constituent quark field operators. Like its earlier success to some low energy hadronic phenomena, here also the model calculations of radiative decay widths of mesons are in reasonable agreements with other theoretical estimations as well as experimental measurements.
Target-Associated Particles Production in the Interactions of 3.7 and 200A GeV Sulphur Projectiles with Nuclear Emulsion
Authors: El-Nadi M. , Salam A. Abdel , Hussein A. , Shaat E. A. , Ali-Mousa N. , Abou-Mousa Z. , Kamel S. , Abdel-Waged Kh. , El-Falaky E.
Published: October 2003

The characteristics of the associated particles produced in 3.7 and 200A GeV 32 S -emulsion inelastic interactions are reported. The experimental data at 3.7 A GeV are compared with the predictions of the standard cascading evaporation model. For explaining the results at higher energy (200A GeV), a simple model which includes the nucleon sub-structure (Reggeon model) is introduced. This model is found to be capable of producing the mean features of the data obtained for the two used exposures.
On the Effect of Transmission-Coefficients Approximations in Sub-Barrier Fusion
Authors: Marta H. D. , Canto L. F. , Donangelo R.
Published: October 2003

The constant-coupling and parabolic approximations to calculate the fusion cross section in coupled-channels problems are investigated in a simple two-channel problem. A comparison with the results of a full quantum mechanics calculation indicates that these frequently used approximations considerably overestimate the sub-barrier fusion cross sections. The discrepancy is traced back to the treatment of the transmission coefficient and we show that a very accurate cross section at all energies can be obtained with the use of WKB transmission coefficients.
Identification of the $\nu_{\frac 32}-[521]$ Band in 153Nd and the γ-Transitions in 149Nd
Authors: Hwang J. K. , Ramayya A. V. , Hamilton J. H. , Kormicki J. , Peker L. K. , Babu B. R. S. , Ginter T. N. , Ter–Akopian G. M. , Oganessian Yu. Ts. , Daniel A. V. , Ma W. C. , Varmette P. G. , Asztalos S. J. , Chu S. Y. , Gregorich K. E. , Lee I. Y. , Macchiavelli A. O. , Macleod R. W. , Rasmussen J. O. , Cole J. D. , Aryaeinejad R. , Butler-Moore K. , Dardenne Y. X. , Drigert M. W. , Stoyer M. A. , Wild J. F. , Becker J. A. , Bernstein L. A. , Lougheed R. W. , Moody K. J. , Donangelo R. , Prussin S. G. , Griffin H. C.
Published: October 2003

From an experiment with Gammasphere and a 252 C spontaneous fission source, two bands with signatures -i and +i are identified in 153 Nd Also several new transitions in 149 Nd are observed for the first time. The band with signature -i in 153 Nd shows no back bending, similar to the one observed in 161 Er . The signature splitting observed in the ground band of 153 Nd is similar to the ones observed in N=93 isotones in this mass region. In 149 Nd the new transitions are placed into a band with a proposed configuration of [Formula: see text].
On the Strong Consistency of the Maximum-Likelihood Estimators from Randomly-Censored Samples
Authors: Wang Jin , Chen Jiading
Published: October 2003

In the randomly-censored model, we define Y = min (X, T) and Z = I{X < T}, where X is the life length, and T is the random censoring time which is independent of X. Couple (Y, Z) is observed. Sufficient conditions are found to ensure that the Maximum-Likelihood Estimators (MLE) are strongly consistent. Application is made to usual life distributions.
Markovian Availability Measurement and Assessement for Hardware-Software System
Authors: Tokuno Koichi , Yamada Shigeru
Published: October 2003

It is important to take into account the trade-off between hardware and software systems when total computer-system reliability/performance are evaluated and assessed. We develop an availability model for a hardware-software system. The system treated here consists of one hardware subsystem and one software subsystem and it is assumed that the system is down and restored whenever a hardware or a software failure occurs. Especially, for the software subsystem, it is supposed that (i) the restoration actions are not always performed perfectly, (ii) the restoration times for later software failures become longer and (iii) reliability growth occurs in the perfect restoration action. The hardware and the software failure-occurrence phenomena are respectively described by constant and geometrically decreasing hazard rates. The time-dependent behavior of the system, which alternately repeats the operational state that a system is operating without failures and the restoration state that a system is inoperable and restored, is described by a Markov process. Useful expressions for several quantitative measures of system performance are derived from this model. Finally, numerical examples are presented for illustration of system availability measurement and assessment.
Geometrical Interpretations of Repair-Cost Limit Replacement Policies
Authors: Dohi T. , Koshimae H. , Kaio N. , Osaki S.
Published: October 2003

The 'total time on test' (TTT) concept has proven to be a very useful tool in many reliability applications. The graphical method based on this concept gives geometrical interpretations to solutions of stochastic maintenance problems as well as estimates of the optimal policies directly from empirical failure or repair data. In fact, some renewal type of maintenance models such as age replacement and burn-in problems have been analyzed by applying the TTT concept. In this paper, we discuss a repair limit replacement problem with a cost constraint for determining the optimal cost–limit to stop repairing a unit after it fails. Two solution methods for the problem are proposed: one is a straightforward/algebraic method and the other is a geometrical one based on the TTT concept. Also, we develop a computer software to calculate numerically the optimal repair-cost limit policies or its estimates by using the function of computer graphics, and refer to its educational effect throughout numerical examples.
The Optimal Lot Sizing for Unreliable Economic Manufacturing Model
Authors: Dohi Tadashi , Yamada Yasunori , Kaio Naoto , Osaki Shunji
Published: October 2003

This paper considers the optimal policy for an economic manufacturing model with stochastic machine breakdown and repair. The expected cost function is formulated and the optimal age replacement-like policy which minimizes it is derived analytically. The detailed properties on the resulting optimal lot size are examined for some special cases. Finally, numerical examples are devoted to show that the effect of corrective maintenance operation in the production process is remarkable.
On the Formal Specification and Verification of Multi-Agent Systems
Authors: Fisher Michael , Wooldridge Michael
Published: October 2003

This article describes first steps towards the formal specification and verification of multi-agent systems, through the use of temporal belief logics. The article first describes Concurrent METATEM, a multi-agent programming language, and then develops a logic that may be used to reason about Concurrent METATEM systems. The utility of this logic for specifying and verifying Concurrent METATEM systems is demonstrated through a number of examples. The article concludes with a brief discussion on the wider implications of the work, and in particular on the use of similar logics for reasoning about multi-agent systems in general.
Desire: Modelling Multi-Agent Systems in a Compositional Formal Framework
Authors: Brazier Frances M. T. , Dunin-Keplicz Barbara M. , Jennings Nick R. , Treur Jan
Published: October 2003

This paper discusses an example of the application of a high-level modelling framework which supports both the specification and implementation of a system's conceptual design. This framework, DESIRE (framework for DEsign and Specification of Interacting REasoning components), explicitly models the knowledge, interaction, and coordination of complex tasks and reasoning capabilities in agent systems. For the application domain addressed in this paper, an operational multi-agent system which manages an electricity transportation network for a Spanish electricity utility, a comprehensible specification is presented.
Loosely-Specified Query Processing in Large-Scale Information Systems
Authors: Nica Anisoara , Rundensteiner Elke A.
Published: October 2003

Challenging issues for processing queries specified over large-scale information spaces (for example, Digital Libraries or the World Wide Web) include the diversity of the information sources in terms of their structures, query interfaces and search capabilities, as well as the dynamics of sources continuously being added, removed or upgraded. In this paper, we give an innovative solution for query planning in such environments. The foundation of our solution is the Dynamic Information Integration Model (DIIM) which supports the specification of not only content but also capabilities of resources without requiring the establishment of a uniform integration schema. Besides the development of the DIIM model, contributions of this paper include:

(1) the introduction of the notion of fully specified queries that are semantically equivalent to a loosely-specified query;

(2) a translation algorithm of a loosely-specified query into a set of semantically equivalent feasible query plans that are consistent with the binding patterns of query templates of the individual sources (capability descriptions in DIIM) and with interrelationships between information sources (expressed as join constraints in DIIM); and

(3) a search restriction algorithm for optimizing query processing by pruning the search space into the relevant subspace of a query. The plans obtained by the proposed query planning process which is composed of the search restriction and translation algorithms can be shown to correspond to query plans semantically equivalent to the initial loosely-specified input query.
Single Mode Wave Guide with a Liquid Crystalline Core
Authors: Reyes J. A. , Rodriguez R. F.
Published: October 2003

A model for a planar single mode waveguide with a thermotropic nematic core is discussed. In previous work we have shown that in the optical limit this guide is multimodal and that a waveguide effect exists and concentrates the ray trajectories in the central part of the cell. In this work we show that for the WKB limit the same waveguide model may become single modal. To derive the conditions under which this regime may be attained, we first calculate the propagating transverse magnetic (TM) modes, their cut off frequency and the maximum number of modes for a given frequency of the incident optical field. From these results we then derive the condition to have a unimodal waveguide and calculate the spatial distribution of the electromagnetic energy density within the cell. We show that the waveguide effect may still exist for the strong regime only, by exhibiting that this energy is concentrated between two caustics in the central part of the cell. Finally, we discuss the limitations and possible generalizations of our model and give some concluding remarks.
Low-Coherence Reflectometry Through Scattering Media with Degenerate Four-Wave Mixing in a Thin Nonlinear Optical Layer
Authors: Fleurov V. , Brown D. , Lawson C.
Published: October 2003

We have demonstrated the coherence filtering operation for optical low-coherence reflectometry via degenerate four-wave mixing (DFWM) in a thin nonlinear optical layer. To perform proof-of-principle DFWM experiments, we use a thin dye solution with a thermally-induced optical nonlinearity. In contrast to previous works, which used c.w. light-emitting diodes or Fourier-transform limited ultra-short laser pulses, we have used broad-band nanosecond laser pulses for depth resolved measurements through scattering media.