bluuebunny/crossref_metadata_2025 huggingface dataset:
Identification of a Novel
Anaplasma marginale
Appendage-Associated Protein That Localizes with Actin Filaments during Intraerythrocytic Infection
Authors: Stich Roger W. , Olah Glenn A. , Brayton Kelly A. , Brown Wendy C. , Fechheimer Marcus , Green-Church Kari , Jittapalapong Sathaporn , Kocan Katherine M. , McGuire Travis C. , Rurangirwa Fred R. , Palmer Guy H.
Published: November 2004

The rickettsial pathogen
Anaplasma marginale
assembles an actin filament bundle during intracellular infection. Unlike other bacterial pathogens that generate actin filament tails,
A. marginale
infects mature erythrocytes, and the F-actin appendages are assembled on the cytoplasmic surface of a vacuole containing several organisms. To identify
A. marginale
molecules associated with these filaments, two complementary approaches were used: matrix-assisted laser desorption ionization-time-of-flight mass spectrometry and tandem mass spectrometry of
A. marginale
proteins identified with an appendage-specific monoclonal antibody and expression screening of an
A. marginale
phage library. Amino acid and nucleotide sequences were mapped to a full-length gene in the genome of the St. Maries strain of
A. marginale
; the correct identification was confirmed by expression of full-length recombinant protein and its reactivity with appendage-specific antibodies. Interestingly, there is marked variation in the abilities of diverse
A. marginale
strains to assemble the F-actin appendages. Comparison of four strains, the Florida, Illinois, St. Maries, and Virginia strains, revealed substantial polymorphism in the gene encoding the appendage-associated protein, with amino acid sequence identity of as low as 34% among strains. However, this variation does not underlie the differences in expression, as there is no specific polymorphism associated with loss of ability to assemble actin appendages. In contrast, the ability to assemble an actin filament bundle reflected dramatic strain-specific differences in the expression level of the appendage-associated protein. Understanding how this protein influences the cycle of invasion, replication, and egress in the host cell may provide new insights into pathogen-host interactions.
Mannose-Resistant
Proteus
-Like Fimbriae Are Produced by Most
Proteus mirabilis
Strains Infecting the Urinary Tract, Dictate the In Vivo Localization of Bacteria, and Contribute to Biofilm Formation
Authors: Jansen Angela M. , Lockatell Virginia , Johnson David E. , Mobley Harry L. T.
Published: November 2004

Proteus mirabilis
, an etiologic agent of complicated urinary tract infections, expresses mannose-resistant
Proteus
-like (MR/P) fimbriae whose expression is phase variable. Here we examine the role of these fimbriae in biofilm formation and colonization of the urinary tract. The majority of wild-type
P. mirabilis
cells in transurethrally infected mice produced MR/P fimbriae. Mutants that were phase-locked for either constitutive expression (MR/P ON) or the inability to express MR/P fimbriae (MR/P OFF) were phenotypically distinct and swarmed at different rates. The number of
P. mirabilis
cells adhering to bladder tissue did not appear to be affected by MR/P fimbriation. However, the pattern of adherence to the bladder surface was strikingly different. MR/P OFF colonized the lamina propria underlying exfoliated uroepithelium, while MR/P ON colonized the luminal surfaces of bladder umbrella cells and not the exfoliated regions. Wild-type
P. mirabilis
was usually found colonizing intact uroepithelium, but it occasionally adhered to exfoliated areas. MR/P ON formed significantly more biofilm than either
P. mirabilis
HI4320 (
P
= 0.03) or MR/P OFF (
P
= 0.05). MR/P OFF was able to form a biofilm similar to that of the wild type. MR/P ON formed a three-dimensional biofilm structure as early as 18 h after the initiation of the biofilm, while MR/P OFF and the wild type did not. After 7 days, however,
P. mirabilis
HI4320 formed a 65-μm-thick biofilm, while the thickest MR/P ON and MR/P OFF biofilms were only 12 μm thick. We concluded that MR/P fimbriae are expressed by most
P. mirabilis
cells infecting the urinary tract, dictate the localization of bacteria in the bladder, and contribute to biofilm formation.
Use of Translational Fusion of the MrpH Fimbrial Adhesin-Binding Domain with the Cholera Toxin A2 Domain, Coexpressed with the Cholera Toxin B Subunit, as an Intranasal Vaccine To Prevent Experimental Urinary Tract Infection byProteus mirabilis
Authors: Li Xin , Erbe Jarrod L. , Lockatell C. Virginia , Johnson David E. , Jobling Michael G. , Holmes Randall K. , Mobley Harry L. T.
Published: November 2004

This is a follow-up to our previous study using an intranasal vaccine composed of MrpH, the tip adhesin of the MR/P fimbria, and cholera toxin to prevent urinary tract infection byProteus mirabilis(X. Li, C. V. Lockatell, D. E. Johnson, M. C. Lane, J. W. Warren, and H. L. Mobley, Infect. Immun. 72:66-75, 2004). Here, we have expressed a cholera toxin-like chimera in which the MrpH adhesin-binding domain (residues 23 to 157) replaces the cholera toxin A1 ADP-ribosyltransferase domain. This chimera, when administered intranasally without additional adjuvant, is sufficient to induce protective immunity in mice.
Absorption spectroscopy of trapped rubidium atoms
Authors: Cauchi S , Vorozcovs A , Weel M , Beattie S , Gagnon O , Kumarakrishnan A
Published: November 2004

We determine the absolute density of a sample of laser-cooled atoms in a two-level system by recording the absorption spectrum of the 85Rb 5S1/2 (F = 3, mf = 3) → 5P3/2 (F′ = 4, m′f = 4) transition. Trapped atoms were prepared in the (F = 3, mf = 3) ground state through optical-pumping techniques. We compare our results with an independent measure of the density that relies on a direct measurement of the number of atoms and size of the atomic sample. We also study the contributions of power broadening, laser line width, and Doppler broadening to the measured absorption spectrum. Our studies suggest that the natural line width (~6 MHz) can be measured to a precision of less than ~50 kHz if the laser line width is measured in real-time with a high-finesse Fabry–Perot cavity. PACS Nos.: 32.70.Cs, 32.70.Jz, 32.80.Pj, 42.62.Fi, 32.70.–n, 32.30.–r
Movement behaviour and dynamics of an aquatic insect in a stream benthic landscape
Authors: Olden Julian D , Hoffman Aaron L , Monroe Jeremy B , Poff N LeRoy
Published: November 2004

Understanding not just where organisms move but how they move is an important step towards integrating animal behaviour into landscape ecology. The three-dimensional landscape of a streambed provides an ideal setting for forging this integration because of the persuasive effects of flowing water. In this study, we experimentally examine the larval movement of the case-building caddisfly Agapetus boulderensis Milne, 1936 in response to two current velocities in each of five levels of contrasting habitat types (i.e., smooth patches that facilitate movement and thick algal patches that constrain movement). Detailed behavioural observations showed that larvae employed two distinctly different strategies of movement in different current velocities: faster crawling and slower pivoting. Our results suggest that individual decision-making between crawling and pivoting is related to the magnitude of current velocity across the streambed, and the frequency at which larvae employ these behaviours translates into differential movement rates and directions. Strong concordance between a conceptual model and our results supports the notion that the presence of structural "nonhabitat" patches at high current velocities may create areas of local flow interruption and refugia. This, in turn, plays an important role in eliciting either crawling or pivoting and in shaping patterns and directions of larval movement, and by extension resource acquisition.
TIME-ORIENTED HIERARCHICAL METHOD FOR COMPUTATION OF PRINCIPAL COMPONENTS USING SUBSPACE LEARNING ALGORITHM
Authors: JANKOVIC MARKO , OGAWA HIDEMITSU
Published: November 2004

Principal Component Analysis (PCA) and Principal Subspace Analysis (PSA) are classic techniques in statistical data analysis, feature extraction and data compression. Given a set of multivariate measurements, PCA and PSA provide a smaller set of "basis vectors" with less redundancy, and a subspace spanned by them, respectively. Artificial neurons and neural networks have been shown to perform PSA and PCA when gradient ascent (descent) learning rules are used, which is related to the constrained maximization (minimization) of statistical objective functions. Due to their low complexity, such algorithms and their implementation in neural networks are potentially useful in cases of tracking slow changes of correlations in the input data or in updating eigenvectors with new samples. In this paper we propose PCA learning algorithm that is fully homogeneous with respect to neurons. The algorithm is obtained by modification of one of the most famous PSA learning algorithms — Subspace Learning Algorithm (SLA). Modification of the algorithm is based on Time-Oriented Hierarchical Method (TOHM). The method uses two distinct time scales. On a faster time scale PSA algorithm is responsible for the "behavior" of all output neurons. On a slower scale, output neurons will compete for fulfilment of their "own interests". On this scale, basis vectors in the principal subspace are rotated toward the principal eigenvectors. At the end of the paper it will be briefly analyzed how (or why) time-oriented hierarchical method can be used for transformation of any of the existing neural network PSA method, into PCA method.
LEARNING THE RULE OF A TIME SERIES
Authors: Ginzberg I. , Horn D.
Published: November 2004

Neural networks can be trained to predict the next value of a time series on the basis of its preceding values. We try to find out how well such a network approximates the rule which underlies the series. For this purpose, we study the net-sequence, which is a long time series generated iteratively by the network. We introduce a new measure: the difference between the distributions of function values in the data and the net-sequence. We demonstrate its usefulness on the problem of the chaotic quadratic map. Adding random noise to the series we find, by using this tool, that the networks can approximate well the correct rule only if the noise amplitude is very small. Applying the new measure as a weak constraint in the problem of sunspot data, we see that it correlates well with the ability of the network to predict several time steps into the future.
EXERCISING MULTI-LAYERED NETWORKS ON PROTEIN SECONDARY STRUCTURE
Authors: Rost Burkhard , Sander Chris
Published: November 2004

The quality of a multi-layered network predicting the secondary structure of proteins is improved substantially by: (i) using information about evolutionarily conserved amino acids (increase of overall accuracy by six percentage points), (ii) balancing the training dynamics (increase of accuracy for strand), and (iii) combining uncorrelated networks in a jury (increase two percentage points). In addition, appending a second level structure-to-structure network results in better reproduction of the length of secondary structure segments.
QUARK FLAVOR SENSITIVITY OF THE MAMMALIAN CORTEX
Authors: Denby Bruce
Published: November 2004

Most applications of Neural Networks in High Energy Physics have involved the use of simple backpropagation or learning vector quantization networks on offline data sets with relatively low dimensionality. In the present work we raise the question of whether ideas drawn from the current understanding of animal nervous systems can be used to build trigger systems for use on raw high energy physics data of high dimensionality. The problem of a secondary vertex trigger is chosen as an illustrative example.
STUDY OF TRACE ELEMENT ABNORMALITIES IN BLOOD OF CHRONIC RENAL FAILURE (CRF) PATIENTS BY PROTON-INDUCED X-RAY EMISSION (PIXE)
Authors: LAL MADAN , BAJPAI H.N. , JOSEPH DAISY , PATRA P.K. , KHOKHAWALA M.Y. , ALMEIDA A.F. , ACHARYA V.N.
Published: November 2004

A study of trace element abnormalities in serum of uremic patients has been carried out by Proton-induced X-ray emission (PIXE) in the case of non-dialysed, hemodialysed and post-transplantation. Forty two patients and eight healthy controls selected for this study were grouped on the basis of their Serum Creatinine (SC) levels. Serum samples of these subjects were converted into solution by acid digestion and the solutions were micropippetted and dried on a thin mylar sheet to be mounted on a sample holder of the PIXE chamber. Proton beam from Van de Graaff accelerator (Trombay, India) of 2.5 Mev energy was employed for exciting the characteristic X-rays of the elements present in the samples and their X-rays were detected by a Si(Li) detector. The results obtained showed significant abnormalities in the concentration levels of Ni, Cu, Br, SrandPb amongst various groups. Ni was found to be significantly higher in all the groups compared to controls. Concentration of Cu was also found to be high in the sera of patients on hemodialysis as compared to controls and non-dialysed uremics. Cu levels returned to normal after transplantation. Br was lower in patients undergoing hemodialysis which returned to normal after transplantation. Sr was found to be higher in all groups of renal failure as compared to controls. Patients on hemodialysis accumulated significant quantities of Pb which was found to decrease after transplantation. No significant abnormalities were observed in the case of the elements Zn, Se and Rb.
PIXE ANALYSIS OF OTOLITHS FROM REARED RED SEA BREAM, Pagrus major(Temminck et Schlegl)
Authors: ARAI NOBUAKI , SAKAMOTO WATARU
Published: November 2004

PIXE analysis was applied to estimate mineral concentration in red sea bream otoliths without cutting or polishing. Detected elements include Sr, Fe, Mn and Zn, which are commonly found in the otoliths in marine fishes. Strontium-Calcium concentration ratio is calculated by means of combined X-ray yields. The ratio doesn’t indicate dear correlaion with mean reared seawater temperature. It is caused by the diffraction error induced by rough topographies of the otoliths surface.
JOSEPHSON DEVICES FOR COMPUTER APPLICATIONS
Authors: HASUO SHINYA
Published: November 2004

Josephson integrated circuit technology has progressed remarkably since the introduction of the reliable niobium junction. Josephson microprocessors and memory circuits that were once considered impracticable have been demonstrated. All the functions required for a Josephson computer can now be fabricated, although integration densities are still much lower than those achievable with semiconductor devices. The next step is to demonstrate a small-scale special-purpose Josephson computer system.
DIVIDER ARCHITECTURES FOR VLSI IMPLEMENTATION
Authors: MOES E. A. J. , NOUTA R. , HEKSTRA G. J.
Published: November 2004

For the mapping on VLSI of digital signal processing algorithms, fast implementations of the basic arithmetical operations are of great importance. Fast parallel addition and multiplication has received much attention. In this contribution we propose new parallel binary divider structures with favorable properties, such as efficient pipelining, compared with the classical parallel divider architectures.
PARALLEL, LOCALLY CONNECTED ALGORITHMS FOR NONLINEAR ADAPTIVE FILTERING
Authors: AHMED HASSAN M. , RAUF FAWAD
Published: November 2004

A new adaptive modular realization for nonlinear filters is presented whereby construction is both computationally efficient and readily implemented. The proposed layered structure consists of locally connected, locally adapted linear filters. Modularity and local connectivity make efficient VLSI layout easy and amenable to automation. The layered structure is based on "state dependent embedding", a new approach to the design of series based nonlinear adaptive filters.
GRADIENT BASED SUBSPACE TRACKING ALGORITHMS AND SYSTOLIC IMPLEMENTATION
Authors: YANG BIN
Published: November 2004

A variety of modern signal processing applications like high resolution temporal/spatial spectral analysis and eigenvalue decomposition based data compression requires subspace estimation. In an unknown and possibly changing environment, adaptive algorithms which are computationally efficient, numerically stable, and easy to implement in hardware are highly desirable. In this paper, we first review some gradient-based adaptive algorithms for subspace tracking. We show that these algorithms, in comparison to other classical techniques, are not only competitive in tracking performance but also advantageous in both computational complexity and robustness. Then we present a novel systolic architecture for implementing these algorithms with a high processor utilization.
PRACTICAL METHODS FOR WORST-CASE AND YIELD ANALYSIS OF ANALOG INTEGRATED CIRCUITS
Authors: ANTREICH KURT J. , GRAEB HELMUT E. , WIESER CLAUDIA U.
Published: November 2004

Worst-case analysis is commonly used in integrated circuit design to verify a satisfactory circuit performance with regard to changes in the manufacturing conditions. However, worst-case analysis is often carried out using approximate worst-case parameter sets. This paper presents a new approach to the worst-case design of integrated circuits that takes account of fluctuations in the operating conditions. It provides exact and unique worst-case manufacturing conditions and worst-case operating conditions for given circuit specifications. These specifications may be either performance limits or minimum yield requirements. The method is illustrated with the parametric design of integrated CMOS bias stages.
SELF-CONSISTENT FIELD THEORY OF GENERAL PERIODIC CIRCUITS FOR TRAVELING WAVE TUBES
Authors: WESSEL-BERG TORE
Published: November 2004

A general method for exact analysis of cylindrical periodic circuits for traveling wave tubes without initial assumptions of field or current distributions is described. The procedure is based on transforming the stationary periodic circuit to Fourier space, in the same manner as one does the ordinary RF fields. By this approach the circuit is represented in Fourier space by an infinite number of harmonic circuit components. The interaction, or coupling, between the field harmonics and the stationary circuit harmonics is conceptually a convolution process. The mathematical description of this process involves the intermediary of a convoluting circuit matrix formed from the harmonics of the stationary metallic circuit. For any circuit this matrix is Hermitian and therefore guaranteed a full set of orthogonal eigenvectors and corresponding real eigenvalues. This complete set of vectors serves as a basis for expansions of the RF electric and magnetic harmonic fields. Due to the general nature of the metallic circuit, with surface areas that are partly metallic and partly open, the eigenvectors separate into two distinct sets, one set having eigenvalues equal or close to unity, and the other set eigenvalues equal or close to zero. The first set is associated directly with the metallic parts of the circuit and describes localized surface modes, including surface currents on the two circuit boundaries. The second set, which essentially is a nullset, does not "see" the metallic parts of the circuit, and describes the fields in the open areas of the circuit. Similar expansions are made in the dielectric rod support system exterior to the circuit itself. The paper provides a systematic and general analysis of the entire periodic configuration, based on a conversion of the field equations to a set of first order differential equations in the tangential components of the RF electric and magnetic field harmonics. In all regions the solutions are expressed in terms of transmission matrices which combine through simple boundary conditions to form an overall homogeneous set of equations. Its numerical solution provides all relevant data for the entire periodic configuration, comprising the finite thickness circuit itself, the dielectric support rods, and the enclosing metallic shield. The paper provides explicit formulae for numerical calculations of circuit characteristics, such as omega-beta diagram, interaction impedance, loss due to finite circuit conductivity, and detailed field and current distributions. Throughout the paper emphasis is placed on generality, so that the results are applicable to any kind of periodic cylindrical circuits. Application of the theory to a tape helix circuit is discussed briefly.
STRONGLY FREE ACTIONS ON SUBFACTORS
Authors: WINSLØW CARL
Published: November 2004

For actions on arbitrary inclusions of factors with finite index, we define an algebraic property called "strong freeness". In the case of strongly amenable subfactors of type II∞ or IIIλ (0 < λ < 1), this property is shown to be a characterization of centrally free actions.

We then classify strongly free actions of discrete amenable groups on strongly amenable subfactors of type II∞, and strongly free actions of a class of discrete amenable groups (which include ℤn, n ∈ ℕ) on strongly amenable subfactors of type IIIλ. Namely, we show that the (generalized) fundamental homomorphism is a complete invariant for cocycle conjugacy in both cases.
HYBRID MONTE CARLO ALGORITHM ON THE CONNECTION MACHINE
Authors: KENNEDY A.D.
Published: November 2004

This paper is divided into three parts: an introduction to the Hybrid Monte Carlo (HMC) algorithm; a detailed discussion of its implementation for Quantum Chromodynamics (QCD) in CMIS on the Connection Machine (CM-2); and a summary of recent analytic results on the behavior of HMC for free field theory. We present a detailed description of the architecture of the CM-2 and explain how it can execute the Conjugate Gradient (CG) solver for HMC at 6.35 GFlops/s.
OFF-DIAGONAL LONG RANGE ORDER IN AN ELECTRON-PHONON MODEL FOR HIGH-Tc SUPERCONDUCTORS
Authors: Frick M. , Morgenstern I. , Linden W.von der
Published: November 2004

We study a model for high- T c superconductors describing both the strong electronic correlations and a coupling of the carriers to anharmonic phonons. The Projector Quantum Monte Carlo Scheme has been employed to investigate ground state properties. We analyze the superconducting properties of the model by directly addressing to the existence of Off-Diagonal Long Range Order (ODLRO). We review the numerical algorithm and discuss the possibility to observe ODLRO. In the presented model, we find ODLRO pointing towards superconductivity instead of the presence of strong electronic correlations. We discuss several features of the superconducting condensate.
CLUSTER SIMULATIONS OF THE ISING MODEL ON DYNAMICALLY TRIANGULATED LATTICE
Authors: BEN-AV R. , KINAR J. , SOLOMON S.
Published: November 2004

We have performed high precision finite size scaling measurements of the critical behavior of the Ising model on dynamically triangulated surfaces of genus 0.

The results are in perfect agreement with the matrix model predictions.1,2 Values of the critical exponents equal to the regular lattice 2D Ising model are excluded by our error bars.

In order to accumulate sufficient statistics we used cluster methods which eliminated critical slowing down to a great extent.
PHASE DIAGRAM OF A DILUTE BINARY SYSTEM
Authors: SADIQ A. , YALDRAM K. , DAD M.
Published: November 2004

Phase diagram of a binary system with quenched impurities has been studied with Monte Carlo computer simulation technique. Use of Swendsen-Wang algorithm makes it possi-ble to explore the vicinity of percolation transition which was difficult to explore with the traditional Metropolis method. For small vacancy concentration υ(υ=1−p, where p is the spin concentration) the critical temperature, Tc, decreases linearly with υ consistent with earlier results on this system. For larger values of v departure from linearity is observed with Tc decreasing to zero sharply near the percolation threshold. An estimate of the critical exponent describing this sharp drop of Tc is also given.
DYNAMIC LOAD-BALANCING STRATEGIES FOR DATA PARALLEL IMPLEMENTATIONS OF REACTION-EVOLUTION-MIGRATION SYSTEMS
Authors: SMITH MARK
Published: November 2004

We introduce Reaction-Evolution-Migration Systems and explain their importance in the scientific field. Details are given of data parallel implementations of such systems, and how a naïve attempt can give very poor performance for stochastic simulations. Thus details are given of a number of dynamic load-balancing strategies to counter this problem, along with comparisons of the performance and ease of implementation of these strategies.
PARALLEL COMPUTING AT THE UNIVERSITY OF GENEVA
Authors: CHOPARD BASTIEN
Published: November 2004

This short paper reviews the activities in parallel computing at the University of Geneva. The current hardware configuration of the CM-2a installed at this site is given. The main applications running on this machine are outlined.
ON THE USE OF THE SYMBOLIC LANGUAGE MAPLE IN PHYSICS AND CHEMISTRY: SEVERAL EXAMPLES
Authors: Čížek J. , Vinette F. , Weniger E. J.
Published: November 2004

The purpose of this paper is to present several physical and chemical applications of the symbolic computation language Maple which has been developed by the Symbolic Computation Group at the University of Waterloo. The paper will highlight the activity of the Quantum Theory Group of the Department of Applied Mathematics at the University of Waterloo during the years 1985–1992, which has already led to more than 20 articles on applications of Maple. Special attention will be given to examples from quantum mechanics and quantum chemistry: the application of the inner projection technique to anharmonic oscillators yielding explicit expressions for Löwdin's approximants as well as to simple many-electron problem, the use of hypervirial and Hellmann-Feynman theorems for the computation of perturbation series coefficients in rational arithmetics, the creation of coupled-cluster equations by the computer, the use of several techniques including the method of Weniger for the summation of divergent series as they occur in perturbation expansions for anharmonic oscillators or in heat conduction with nonlinear boundary conditions. In all these examples, the symbolic computation language Maple proved to be very useful, and in many cases, it was actually indispensable for obtaining a solution or for keeping control of the accuracy.
MOLECULAR DYNAMICS SIMULATIONS OF GRANULAR MATERIALS
Authors: HERRMANN HANS J.
Published: November 2004

When sand or other granular materials are shaken, poured or sheared many intriguing phenomena can be observed. We will model the granular medium by a packing of elastic spheres and simulate it via Molecular Dynamics. Dissipation of energy and shear friction at collisions are included. The onset of fluidization can be determined and is in good agreement with experiments. On a vibrating plate we observe the formation of convection cells due to walls or amplitude modulations. Density and velocity profiles on conveyor belts are measured and the influence of an obstacle discussed. We mention various types of rheology for flow down an inclined chute or through a pipe and outflowing containers.
WHAT CAN WE LEARN FROM QMC SIMULATIONS
Authors: VON DER LINDEN WOLFGANG
Published: November 2004

A brief review will be given about the state of the art of Quantum Monte Carlo (QMC) simulations in solid state physics. Particularly in this field, QMC has become very popular during the last couple of years due to the growing interest in reliable results for strongly correlated electronic systems. It will be demonstrated how QMC schemes cope with typical many many-body problems. Representative applications will be discussed. Present algorithms suffer, however, from various problems, restricting the practicableness of QMC. An exposition of the difficulties will be given which have to be overcome to make QMC studies applicable to a much wider range of physical problems.
HIGH-DIMENSIONAL AND VERY LARGE CELLULAR AUTOMATA FOR IMMUNOLOGICAL SHAPE SPACE
Authors: Stauffer Dietrich , Sahimi Muhammad
Published: November 2004

Simulations with 109 cells are made on an iPSC Hypercube with 32 parallel i860 processors, updating more than a million sites per second and per processor. This size reaches into the size range of natural immune systems. Smaller sizes are simulated in higher dimensions up to ten. These cellular automata due to de Boer. van der Laan, and Hogeweg model the idiotypic shape space and differ from usual Ising models through interactions with the mirror sites of the lattice. For majority rules (voter rules) we find Ising-like behavior with a spontaneous magnetization vanishing at some critical temperature which approaches its mean field value for high dimensions. The previously observed self-organization in the form of domain formation is thus explained as spinodal decomposition.
DEDICATED COMPUTERS FOR LATTICE GAUGE THEORY SIMULATIONS
Authors: TRIPICCIONE RAFFAELE
Published: November 2004

I discuss several features of lattice gauge theory simulations that have been exploited by dedicated processors to achieve extremely high computing speed. I describe in some details APE100, one such machine, and discuss the possible use of dedicated processors in other areas of computational physics.
ON EFFICIENT BOX COUNTING ALGORITHMS
Authors: GRASSBERGER PETER
Published: November 2004

We present two variants of a fast and storage efficient algorithm for box counting of fractals and fractal measures. In contrast to recently proposed algorithms, no sorting of the data is done. With comparable storage demands, CPU times are between 1 and 2 orders of magnitude lower than those needed with the latter algorithms.
NUMERICAL RELATIVITY: EVOLVING SPACETIME
Authors: BONA C. , MASSÓ J.
Published: November 2004

The construction of numerical solutions of Einstein's General Relativity equations is formulated as an initial-value problem. The space-plus-time (3 + 1) decomposition of the spacetime metric tensor is used to discuss the structure of the field equations. The resulting evolution system is shown to depend in a crucial way on the coordinate gauge. The mandatory use of singularity avoiding coordinate conditions (like maximal slicing or similar gauges) is explained. A brief historical review of Numerical Relativity is included, showing the enormous effort in constructing codes based in these gauges, which lead to non-hyperbolic evolution systems, using "ad hoc" numerical techniques. A new family of first order hyperbolic evolution systems for the vacuum Einstein field equations in the harmonic slicing gauge is presented. This family depends on a symmetric 3 × 3 array of parameters which can be used to scale the dynamical variables in future numerical applications.
LBE SIMULATIONS OF RAYLEIGH-BÉNARD CONVECTION ON THE APE100 PARALLEL PROCESSOR
Authors: BARTOLONI A. , BATTISTA C. , CABASINO S. , PAOLUCCI P. S. , PECH J. , SARNO R. , TODESCO G. M. , TORELLI M. , TROSS W. , VICINI P. , BENZI R. , CABIBBO N. , MASSAIOLI F. , TRIPICCIONE R.
Published: November 2004

In this paper we describe an implementation of the Lattice Boltzmann Equation method for fluid-dynamics simulations on the APE100 parallel computer. We have performed a simulation of a two-dimensional Rayleigh-Bénard convection cell. We have tested the theory proposed by Shraiman and Siggia for the scaling of the Nusselt number vs. Rayleigh number.
PARALLELIZATION OF THE 2D SWENDSEN–WANG ALGORITHM
Authors: HACKL R. , MATUTTIS H.-G. , SINGER J. M. , HUSSLEIN TH. , MORGENSTERN I.
Published: November 2004

We implemented a parallel Swendsen–Wang algorithm for a 2D Ising system without magnetization in a host–node programming model. The simulations were performed on the Intel Hypercube IPSC/860. Our maximum number of updates/s on 32 nodes ist three times as high as in the implementation by Stauffer and Kertész on the same machine. With 32 processors we reach half the speed of the simulations by Tamayo and Flanigan on 256 nodes of a CM5. We discuss the non–equilibrium relaxation for the energy and the magnetization.
CONSTRUCTION OF LARGE PACKET RADIO NETWORKS
Authors: BERMOND JEAN-CLAUDE , HELL PAVOL , QUISQUATER JEAN-JACQUES
Published: November 2004

We outline constructions of packet radio networks (with time division multiplexing) that achieve much better parameters than those previously proposed. Given the desired diameter and number of slots per time frame, our networks seek to maximize the possible number of users. We model this as a problem of constructing large graphs or digraphs with given diameter and chromatic index, and relate it to extant work on large graphs with given diameter and maximum degree.
SYNTHESIZING LINEAR SYSTOLIC ARRAYS FOR DYNAMIC PROGRAMMING PROBLEMS
Authors: MYOUPO JEAN FRÉDÉRIC
Published: November 2004

In this paper we design modular linear systolic arrays for the solutions of dynamic programming problems using geometric considerations. Our results show that solving a dynamic programming problem of size n requires (n - 1) ⌈( n/α)⌉ + 1 cells and (n - 1) ((α + 3) ⌈(n/α)⌉ + 2) + 1 time steps, where each cell has a local memory of constant size α and the time delay between two consecutive cells of the array is assumed to be constant.
DTML IS LOGSPACE HARD UNDER NC1 REDUCTIONS
Authors: SARNATH R.
Published: November 2004

The Different Than Majority Labeling (DTML) problem has a simple polynomial time algorithm, but is not known to be in NC. In this paper, we show that the DTML problem is extremely unlikely to have an NC1 algorithm.
PERIODIC SORTING ON TWO-DIMENSIONAL MESHES
Authors: KUTYLOWSKI MIROSLAW , WANKA ROLF
Published: November 2004

We consider the following periodic sorting procedure on two-dimensional meshes of processors: Initially, each node contains one number. We proceed in rounds each round consisting of sorting the columns of the grid, and, in the second phase, of sorting the rows according to the snake-like ordering. We exactly characterize the number of rounds necessary to sort on an l × m-grid in the worst case, where l is the number of the rows and m the number of the columns. An upper bound of ⌈ log l⌉ + 1was known before. This bound is tight for the case that m is not a power of 2. Surprisingly, it turns out that far fewer rounds are necessary if m is a power of 2 (and m ≪ l) in this case, exactly min { log m + 1, ⌈ log l⌉ + 1} rounds are needed in the worst case.
A SIMPLE OPTIMAL SYSTOLIC ALGORITHM FOR GENERATING PERMUTATIONS
Authors: AKL SELIM G. , STOJMENOVIĆ IVAN
Published: November 2004

We describe a simple parallel algorithm for generating all permutations of n elements. The algorithm is designed to be executed on a linear array of n processors, each having constant size memory and each being responsible for producing one element of a given permutation. There is a constant delay per permutation, leading to an O (n!) time solution. The algorithm is cost-optimal, assuming the time to output the permutations is counted.
A MODEL OF SPECULATIVE PARALLELISM
Authors: WONG W. F. , YUEN C. K.
Published: November 2004

Speculative parallelism is the parallelism that one finds when parallel tasks are spawned in the hope that they will later be of use. While this aggressive form of parallelism promises high levels of parallelism, there are numerous problems involved. In this letter, we propose a model of handling speculative parallelism in Lisp. Some properties of the model, related issues in parallelism and implementation considerations are also discussed. The model described is already incorporated into BaLinda Lisp and the techniques used in its simulation were first used in writing the prototype interpreter on an IBM PC.
ON UPDATE-LAST SCHEMES
Authors: TROMP JOHN
Published: November 2004

We introduce the notion of Update-Last scheme as a distributed method of storing an index, and derive exact bounds on their space complexity.
THE TIME COMPLEXITY OF SCHEDULING INTERVAL ORDERS WITH COMMUNICATION IS POLYNOMIAL
Authors: ALI HESHAM H. , EL-REWINI HESHAM
Published: November 2004

Papadimitrjou and Yannakakis showed that unit execution time tasks in interval orders can be scheduled in linear time on N processors when communication cost is ignored. The objective function was to minimize the schedule length. They have also shown that the generalization of this problem to arbitrary execution times is NP- complete . In this paper, we study the problem of scheduling task graphs with communication on N processors when the task graph is an interval order. We prove that this scheduling problem can be solved in polynomial time when the execution cost of the system tasks is identical and equal to the communication cost between any pair of processors. We introduce an algorithm of O(Ne) to minimize the schedule length, where e is the number of arcs in the interval order.
PROBLEM HEAPS AND THEIR EVALUATION
Authors: SCHMECK H. , SCHRÖDER H. , STAUNSTRUP J. , MIDDENDORF M.
Published: November 2004

Problem heaps provide a means of asynchronous communication in multiprocessor systems: Processors put problems (subtasks, messages) on the heap and retrieve problems from it. In this paper we present an abstract model of problem heaps, analyse their hardware complexity and present realizations meeting the derived lower bounds.
DATA REPLICATION IN DENSE MATRIX FACTORIZATION
Authors: MALARD J. , PAIGE C.C.
Published: November 2004

Gossiping is proposed as the preferred communication primitive for replicating pivot data in dense matrix factorization on message passing multicomputer. Performance gains are demonstrated on a hypercube for LU factorization algorithms based on gossiping as opposed to broadcasting. This finding has consequences for the design of numerical software libraries.
ABELIAN CHERN–SIMONS THEORY WITH MATTER FIELDS
Authors: CHO KYUNG-HYUN , RIM CHAIHO
Published: November 2004

It is shown that in the Abelian Chern–Simons plus Maxwell theory in 1 + 2 dimensions there is a unitary transformation such that massless modes of the gauge field are eliminated completely in the Hilbert space and a nonlocal interaction between matter fields (fermions or scalars) remains instead. The nonlocal interaction is given in terms of an effective gauge field satisfying the Gauss constraint. It is also pointed out that it is the nonlocal interaction that changes the statistics of pointlike particles and that makes a vortex charged.
PHASE STRUCTURE OF THE THREE-DIMENSIONAL $g (\vec {\bf \phi}^2)^2$ FIELD THEORY
Authors: EFIMOV G. V. , NEDELKO S. N.
Published: November 2004

The phase structure of the three-dimensional superrenormalizable scalar-field model with the O (N)-invariant interaction g(ϕ2)2 is considered. By the method of canonical transformations, it is shown that this model describes the O (N)-symmetric system at both the small and the large coupling constant g. At the same time, phase transitions accompanied by symmetry rearrangement are possible at intermediate values of g. Comparison with the case of two dimensions shows a crucial influence of higher-order renormalization on the phase structure of the model.
2D SIGMA MODEL APPROACH TO 4D INSTANTONS
Authors: PARK Q-HAN
Published: November 2004

4D self-dual theories are proposed to generalize 2D conformal field theory. We identify 4D self-dual gravity as well as self-dual Yang-Mills theory with 2D sigma models valued in infinite-dimensional gauge groups. It is shown that these models possess infinite-dimensional symmetries with associated algebras—“CP1 extensions” of respective gauge algebras of 2D sigma models—which generalize the Kac-Moody algebra as well as W∞. We address various issues concerning 2D sigma models, twistors and sheaf cohomology. An attempt to connect 4D self-dual theories with 2D conformal field theory is made through sl (∞) Toda field theory.
TOPOLOGICAL CONFORMAL FIELD THEORIES AND THE FLAT COORDINATES
Authors: BLOK B. , VARCHENKO A.
Published: November 2004

We discuss the relation between topological conformal field theories and singularity theory. We argue that the problem of the explicit solution of these theories is equivalent to that of finding the flat-coordinate basis in the space of couplings. The latter problem is the well-known problem of singularity theory. It has especially simple solutions in the case of minimal models.
A THOUGHTFUL STUDY OF LORENTZ TRANSFORMATIONS BY CLIFFORD ALGEBRAS
Authors: ZENI J. RICARDO , RODRIGUES WALDYR A.
Published: November 2004

We give a thoughtful presentation of proper orthocronous Lorentz transformations using the space-time (ℝ1,3) and the Pauli (ℝ3,0) algebras. We present in a closed finite form, a generic [Formula: see text] written as the exponential of elements of the associated Lie Algebra, together with a physical interpretation of the parameters. We call the result obtained the master equation and it is used to study several important topics of Special Relativity, e.g. exact product of two boosts and the Thomas precession. We also derive other results necessary for a dynamic interpretation of Lorentz transformations.
THE NEXT STEP IN LEPTONIC DECAYS OF ETA AND KL BOUND STATES
Authors: KOZLOV G.A.
Published: November 2004

A systematic discussion of the probability of eta and KL bound-state decays—[Formula: see text] and [Formula: see text](l=e, μ)—within a three-dimensional reduction to the two-body quantum field theory is presented. The bound-state vertex function depends on the relative momentum of constituent-like particles. A structure-transition form factor is defined by a confinement-type quark-antiquark wave function. The phenomenology of this kind of decays is analyzed.
PARTICLE PRODUCTION DURING INFLATIONARY REHEATING
Authors: BASLER M. , KÄMPFER B.
Published: November 2004

A possible reheating mechanism in inflationary universe models is studied in some detail. Results are presented of numerical investigations of particle creation and corresponding reheating within a self-coupled scalar field model. By using the method of Hamiltonian diagonalization attention is devoted to the time development of the process and its parameter dependence. The effect of particle production is found to depend strongly on the anharmonicity of the potential around its minimum and on the amplitude of the oscillations of the scalar background field.
FINE STRUCTURE OF THE MVW CORRESPONDENCE
Authors: KAWAI TOSHIYA
Published: November 2004

A correspondence observed by Martinec, Vafa and Warner (MVW) between the singularity theory and the N = 2 super conformal field theory is reviewed by using N = 2 SUSY quantum mechanics.
QUANTUM DISCRETE GAUGE MODELS WITH BOSONIC AND FERMIONIC DEGREES OF FREEDOM
Authors: FILIPPOV A. T. , GANGOPADHYAY D. , ISAEV A. P.
Published: November 2004

A general approach to quantizing discrete models (i.e. having a finite number of coordinates) with quadratic first-class constraints is presented in the framework of gauging linear canonical symmetries. Also, it is proposed how a natural superextension of matrix field theories (viz. orthosymplectic "zero-dimensional" matrix field theories) might emerge in this approach.
PATH INTEGRAL DERIVATION OF THE U(1) KAC–MOODY CHARACTERS AND OF THE WEYL–KAC DENOMINATOR
Authors: BAAQUIE B. E.
Published: November 2004

The U(1) Kac–Moody character functions are derived from a path integral expression. It is shown that point-split regularization of the Virasoro generator also exactly regularizes the path integral. An exact derivation of the Weyl–Kac denominator is then given for an arbitrary Lie group using the semiclassical approximation and the results of the U(1) calculation.
A NEW METHOD TO MEASURE THE ELECTROMAGNETIC PROPERTY OF THE W BOSON IN e+e− COLLISIONS
Authors: IWASAKI HIROTOMO
Published: November 2004

With the effective WW γ couplings incorporating the magnetic dipole, electric dipole, magnetic quadrupole and electric quadrupole moments of the W boson, the cross-section of e+e− → e±νe W ∓ is evaluated exactly and its sensitivity to these moments is investigated. The background elimination is discussed for the measurement of the WW γ couplings, and the resulting event rate of the single-W production is evaluated at [Formula: see text] and 500 GeV. Also, a new method for the precision measurement of the WW γ coupling is proposed: it utilizes the distinction of the W boson energy distributions of the annihilation and nonannihilation contributions and reduces the systematic errors.
TWO-BODY FINAL STATE INTERACTIONS WITH EXAMPLES
Authors: KAMAL A. N.
Published: November 2004

Two-body multichannel scattering is discussed using, for pedagogical reasons, a field-theoretical model. Methods for unitarizing two-body hadronic weak decay amplitudes are considered. For illustrative purposes detailed studies are carried out for the following three cases: (i) [Formula: see text], ωρ+, ϕρ+, (ii) D0 → ππ, [Formula: see text], and (iii) [Formula: see text], [Formula: see text].
STRING FRAGMENTATION MODEL AND INCLUSIVE PRODUCTION OF K MESONS
Authors: SALEEM MOHAMMAD , RAFIQUE MUHAMMAD
Published: November 2004

An account of the inclusive production of K mesons in electron-positron annihilation is given. The most recent measurements on the cross section are exhibited and compared with the predictions of the Lund model. The model gives a satisfactory agreement with the experimental data. The results from different experiments on cross section, the mean multiplicity per multihadronic event and various other characteristics are found to be consistent.
PARASTATISTICAL SYSTEMS AT FINITE TEMPERATURES IN THERMOFIELD DYNAMICS
Authors: SHANTA P. , CHATURVEDI S. , KAPOOR A.K. , SRINIVASAN V.
Published: November 2004

We consider para-Bose and para-Fermi oscillators within the framework of thermofield dynamics. For these systems, we construct the transformation relating the thermal vacuum state to the zero temperature vacuum. This construction makes use of a nonlinear realization of the single mode para-Bose (para-Fermi) algebra in terms of a single boson.
QUANTUM HAMILTONIAN REDUCTION AND WB ALGEBRA
Authors: ITO KATSUSHI
Published: November 2004

We study the quantum Hamiltonian reduction of affine Lie algebras and the free field realization of the associated W algebra. For the nonsimply laced case this reduction does not agree with the usual coset construction of the W minimal model. In particular, we find that the coset model [Formula: see text] can be obtained through the quantum Hamiltonian reduction of the affine Lie superalgebra B(0, n)(1). To show this we also construct the Feigin-Fuchs representation of affine Lie superalgebras.
A SUPERSTRING MODEL WITH R SYMMETRIES AND LOW B−L BREAKING
Authors: ANANTHANARAYAN B.
Published: November 2004

The phenomenology of a three-generation superstring model arising from the compactification of the ten-dimensional heterotic superstring theory on the Tian-Yau manifold with a discrete Z2×Z3 symmetry is discussed. The Z2 is used to define a matter parity and the Z3 generates an R symmetry. Presence of the discrete R symmetry enforces the existence of exactly flat directions in the superpotential that motivate us to break the SU(3) 3 to SU(3) × SU(2) L× SU(2) R× U(1) B−L at a scale M X closely associated with the compactification scale MC~1018 GeV , since the R symmetry and B−L breaking need to arise from unknown string physics and for the successful suppression of proton decay rate due to certain dimension-five operators. When the R symmetry is broken at a scale MR~1014 GeV , the matter parity is broken spontaneously as well, guiding us to the scale of the breaking to the standard model, MB−L~103 GeV , making the additional Z boson accessible at accelerator energies. When the spectrum of particles is derived from the mass matrices, the model emerges as the first model with known particles having nonstandard Z2 matter-parity assignments. The transformation properties of the standard model fermions under the discrete symmetries of the theory give rise to an extremely interesting pattern for their mass generation. The model has acceptable properties vis à vis proton decay lifetime considerations and renormalization group considerations. This is a superstring model where the lightest supersymmetric particle, favored to be the photino, decays with a cosmologically interesting lifetime.