bluuebunny/crossref_metadata_2025 huggingface dataset:
Soleus accessorius, an anomalous muscle in a young athlete: case report and analysis of the literature
Authors: Christodoulou A , Terzidis I , Natsis K , Gigis I , Pournaras J
Published: November 2004

The soleus accessory muscle is a rare anatomical variation. It usually appears as a soft tissue mass and may be mistaken for a tumour or an inflammatory lesion. The differential diagnoses include ganglion, lipoma, haemangioma, synovioma, and sarcoma. This is a report of such a muscle mass in the leg of a young athlete with 16 years follow up. A review of the English literature on this subject is also presented.
Fatal pulmonary embolism in hospitalised patients: a necropsy review
Authors: Alikhan R , Peters F , Wilmott R , Cohen A T
Published: November 2004

Aims:To carry out a retrospective review of all postmortem reports during the period 1991 to 2000 at King’s College Hospital, London, as an extension of a previous analysis performed for the period 1965 to 1990.

Methods:The number of deaths resulting from necropsy confirmed fatal pulmonary embolism in hospitalised patients was determined, and a limited analysis of the clinical characteristics of those patients who died was performed.

Results:During the 10 year period, 16 104 deaths occurred and 6833 (42.4%) necropsies were performed. The outcome measure, fatal pulmonary embolism, was recorded as cause of death in 265 cases (3.9% of all necropsies; 5.2% of adult cases). No deaths from pulmonary embolism occurred in patients under 18 years of age; 80.0% occurred in patients older than 60 years. Of the fatal emboli, 214 of 265 (80.8%) occurred in patients who had not undergone recent surgery. Of these patients, 110 (51.4%) had suffered an acute medical illness in the six weeks before death, most often an acute infectious episode (26 cases).

Conclusions:Thromboembolic events remain a relatively common cause of death in hospitalised patients and appear to occur more frequently in non-surgical than in surgical patients.
Role of p53, apoptosis, and cell proliferation in early stage Epstein-Barr virus positive and negative gastric carcinomas
Authors: Ishii H H , Gobe G C , Yoneyama J , Mukaide M , Ebihara Y
Published: November 2004

Aims:Mechanisms of Epstein-Barr virus (EBV) associated gastric tumour development are incompletely understood. The interrelations between EBV infection, apoptosis, cell proliferation, and the expression of the tumour suppressor gene p53 was investigated in 133 early stage gastric carcinomas.

Methods:Tumour tissue was compared with paired non-tumour tissue. EBV encoded small RNAs (EBERs) determined EBV status. The apoptotic index (AI) was determined by morphology and verified biochemically. p53 and Ki-67 expression (cell proliferation) was assessed using immunohistochemistry.

Results:EBV was detected in 14.3% of the cases. Cell proliferation did not differ significantly between EBV positive and negative cancers. However, within both these groups, the p53 positive and negative subsets differed significantly (EBV positive group: 76.8% and 55.3% were p53 positive or negative cancers, respectively; p<0.05; EBV negative group: 65.2% and 51.7% were p53 positive or negative, respectively; p<0.005). The numbers of p53 expressing EBV positive and negative cases were significantly different (57.9% and 82.5%, respectively; p<0.05). Compared with cell proliferation, apoptosis was significantly lower in EBV positive versus negative cancers (AI of 4.36 and 6.50, respectively; p<0.01). The p53 positive and negative subsets also differed significantly in AI (EBV positive group: AI of 5.13 and 3.30 for p53 positive and negative cancers, respectively; p<0.05: EBV negative group: AI of 6.84 and 4.90 for p53 positive and negative cancers, respectively; p<0.05).

Conclusions:These factors probably combine to promote development and progression of early stage gastric carcinomas and, at the same time, ensure the survival of EBV itself.
The perforin mediated apoptotic pathway in lung injury and fibrosis
Authors: Miyazaki H , Kuwano K , Yoshida K , Maeyama T , Yoshimi M , Fujita M , Hagimoto N , Yoshida R , Nakanishi Y
Published: November 2004

Aims:The perforin mediated pathway is the major pathway of cytotoxicity induced by activated T cells and natural killer cells, and may be involved in the development of pulmonary fibrosis.

Methods:Perforin and granzyme B expression were examined in idiopathic pulmonary fibrosis by means of immunohistochemistry, and perforin knockout mice were used to examine whether or not perforin mediated cytotoxicity participates in the pathophysiology of bleomycin induced pneumopathy.

Results:Perforin and granzyme B expression were upregulated in infiltrating lymphocytes in lung tissue from patients with idiopathic pulmonary fibrosis compared with normal lung parenchyma. Perforin and granzyme B expression were upregulated predominantly in infiltrating mononuclear cells after bleomycin instillation in wild-type mice. Although the development of bleomycin induced pneumopathy was not completely prevented, the pathological grade of inflammation and fibrosis, and the number of apoptotic cells in lung tissue, were significantly decreased in perforin knockout mice compared with wild-type mice.

Conclusions:These results suggest that perforin mediated apoptosis may be associated with the pathophysiology of lung injury and fibrosis.
Clonal B cell populations in a minority of patients with Hashimoto’s thyroiditis
Authors: Saxena A , Alport E C , Moshynska O , Kanthan R , Boctor M A
Published: November 2004

Background:Hashimoto’s thyroiditis (HT) is a risk factor for thyroid lymphoma, and clonal B cell populations in HT support this link. The literature on B cell clonality in HT is controversial.

Aims:To identify clonal B cell populations in HT and to assess their usefulness in differentiating HT from mucosa associated lymphoid tissue (MALT) lymphoma and predicting future development of lymphoma.

Methods:DNA from formalin fixed, paraffin wax embedded blocks of thyroid specimens from 10 patients with HT and two thyroid MALT lymphomas was analysed for B cell clonality by seminested polymerase chain reaction (PCR) using FRIII/LJH and FRIII/VLJH primers to amplify the IgH gene VDJ region. In one case, PCR products were sequenced. Immunohistochemistry was performed by labelled streptavidin–biotin technique using antibodies to: CD45, CD45RO, CD3, CD20, and cytokeratin.

Results:The histopathological and clinical findings were characteristic of HT. Clonal bands were seen in three and a polyclonal smear pattern was seen in seven cases. The clonal bands in HT were associated with a background smear, and could not be reproduced from other blocks from the same case or from deeper sections of the same block. The clonal bands in thyroid lymphomas were not associated with a background smear and were reproducible. None of the patients with clonal B cells has developed malignant lymphoma during a follow up of 10–13 years.

Conclusions:B cell clonal bands in HT have different features from those in lymphoma (non-pure and non-reproducible) and do not predict future development of lymphoma.
Impact of positive legionella urinary antigen test on patient management and improvement of antibiotic use: Table 1
Authors: Garbino J , Bornand J-E , Uçkay I , Fonseca S , Sax H
Published: November 2004

Aim:To assess the incidence of legionella infection over a 27 month period at a large university hospital.

Material and Methods:The present retrospective cohort study enrolled patients with legionellosis, defined as those presenting a positive urinary antigen for legionella together with a medical history, clinical findings, and radiological findings consistent with pneumonia. These patients were evaluated to determine the relation between their test results and changes in treatment modalities. A control group of patients with pneumonia but a negative urinary antigen test for legionella were also analysed.

Results:Twenty seven of 792 assessed patients tested positive for legionella. In 22 of these patients, legionella active antibiotics were administered empirically. In seven patients, the test results prompted a legionella specific treatment, whereas in 12 cases, non-specific antibiotics were stopped within 24 hours. Overall, treatment was altered in more than half of the patients as a result of the test results.

Conclusions:The urinary antigen may have a direct impact on clinical management of pulmonary legionellosis. However, patient comorbidities and individual clinical judgment are still important for determining the best treatment to be given in each individual case.
The case of the floating gel: Figure 1
Authors: Srivastava R , Murphy M J , Card J , Severn A , Fraser C G
Published: November 2004

In patients with chronic renal failure, blood samples for laboratory analysis are often taken via dialysis catheters. This report describes a case of gross spurious hypernatraemia in a blood sample collected from a patient undergoing haemodialysis. After centrifugation of the blood sample in question, the separator gel formed the topmost layer, with the serum in the middle and the clot at the bottom. Subsequent analysis of the serum showed severe hypernatraemia (serum sodium, 744 mmol/litre). It was established that the blood sample had been taken from the patient’s dialysis catheter into which 3 ml of Citra-Lock™ (46.7% trisodium citrate) had been instilled previously as a “catheter locking” solution. The hypernatraemia seen in this case was recognised immediately as an artefact, but it was found that even minimal contamination of blood samples with Citra-Lock may significantly affect sodium concentrations. This contamination may be missed, with potentially adverse consequences for patient management.
PUSHDOWN AUTOMATA ON INFINITE TREES AND NONDETERMINISTIC CONTEXT-FREE PROGRAMS
Authors: SAOUDI A.
Published: November 2004

We introduce various types of top-down pushdown infinite tree automata. We extend the Landweber-Staiger-Wagner hierarchy to pushdown infinite tree automata. We prove that the extension of Kleene’s theorem to pushdown infinite tree automata is not possible. We characterize recognizable (i.e. regular) infinite trees and extend Eilenberg’s theorem to ω-tree pushdown automata. We give some characterizations of infinite computations of nondeterministic context-free program schemes. We show that the equivalence problem for nondeterministic context-free program schemes is unsolvable.
A CALCULUS OF TIMED COMMUNICATING SYSTEMS
Authors: KRISHNAN PADMANABHAN
Published: November 2004

In this paper we define an operational semantics for a timed version of a Calculus of Communicating Systems (CCS) [1], We also consider timing constraints that a process needs to satisfy and develop preorder relations induced by the temporal constraints.
A GOAL PROGRAMMING NETWORK FOR MIXED INTEGER LINEAR PROGRAMMING: A CASE STUDY FOR THE JOB-SHOP SCHEDULING PROBLEM
Authors: Van Hulle M.M.
Published: November 2004

Job-shop scheduling is an np-complete optimization problem subject to precedence and resource constraints. Recently, Foo and Takefuji have introduced a network-based solution procedure for solving job-shop problems formulated as mixed integer linear programming problems. To obtain the solution, the Tank and Hopfield linear programming network was repeatedly used. However, since such a network frequently produces constraint-violating solutions, the reliability of Foo and Takefuji’s approach is doubtful. In this article, it is shown that reliability of the network approach can be greatly improved, by guaranteeing constraint-satisfying solutions, if the original job-shop problem is reformulated as a goal programming problem, before it is mapped onto a goal programming network.
USE OF NEURAL NETS TO MEASURE THE τ POLARIZATION AND ITS BAYESIAN INTERPRETATION
Authors: Garrido Lluís , Gaitan Vicens
Published: November 2004

We have tested a neural network (NN) technique as a method to determine the helicity of the τ particles in the process: e+e−→(Z0, γ*)→τ+τ−→(ρν)(ρν). It takes into account in a natural way the fact that both taus have different helicity and gives efficiencies comparable to the Bayesian method. We have found this “academic” example a nice way to introduce the analytical interpretation of the net output, showing that these neural nets techniques are equivalent to a Bayesian Decision Rule.
POPULATION OSCILLATIONS IN NEURONAL GROUPS
Authors: Menon V. , Tang D.S.
Published: November 2004

We study nonlinear oscillations in localized populations (neuronal groups) of excitatory and inhibitory neurons. In particular, we investigate the role of delay in inhibition and slowly decaying inhibition in inducing robust population oscillations. It is found that an arbitrarily small delay in the inhibitory signal can induce oscillations by destroying the stability of the fixed points. A phase shift between the excitatory and inhibitory components underlies the generation of oscillations. Delay in inhibition and slowly decaying inhibitory signals readily result in such phase shift. Linear theory is found to be inadequate to study these oscillations. A nonlinear theory of the relations between the frequency, amplitude, and phase of the oscillations is described. With these relations, some aspects of the origin and characteristics of the oscillations—in particular, the effect of delay in the inhibitory signal, disparate excitatory and inhibitory activity decay time periods, refractoriness in the excitatory neurons, and the mean synaptic strengths between the excitatory and inhibitory subpopulations—are studied. It is suggested that (realistic) excitatory time courses of the alpha form, [Formula: see text], and inhibitory time courses of the form [Formula: see text], with τe<τi can generate robust oscillations. The generation of harmonics, which can be strong when the frequency is low, the refractory period is large, or the net population activity is high, is analyzed.
TRAINING RECURRENT NETS OF HARDWARE REALISABLE SIGMA-PI UNITS
Authors: GURNEY KEVIN N.
Published: November 2004

The dynamics and training of recurrent nets which make use of probabilistic nodes based on Boolean functions are explored. These are shown to be equivalent to sigma-pi units when using binary inputs and have the advantage of an immediate implementation in readily available digital hardware. The underlying hypercube structure of the Boolean address space is used to describe the process of generalisation and also sheds light on the role of hidden units. This is made more precise with the aid of the concept of hypercube order statistics. Training algorithms are described which make use of a node time-integration apparatus to promote near optimal cube structures in a natural way.
WIS-ART: UNSUPERVISED CLUSTERING WITH RAM DISCRIMINATORS
Authors: Fulcher Eamon P.
Published: November 2004

WIS-ART merges the self-organising properties of Adaptive Resonance Theory (ART) with the operation of WISARD, an adaptive pattern recognition machine which uses discriminators of conventional Random Access Memories (RAMs). The result is an unsupervised pattern clustering system operating at near real-time that implements the leader algorithm. ART’s clustering is highly dependent upon the value of a “vigilance” parameter, which is set prior to training. However, for WIS-ART hierarchical clustering is performed automatically by the partitioning of discriminators into “multi-vigilance modules”. Thus, clustering may be controlled during the test phase according to the degree of discrimination (hierarchical level) required. Methods for improving the clustering characteristics of WIS-ART whilst still retaining stability are discussed.
ANALOG CMOS NEURAL CIRCUITS — IN SITU LEARNING
Authors: Card H.C. , Schneider C.R.
Published: November 2004

This paper presents a tutorial review of artificial neurons and synapses which are implemented as analog CMOS circuits and which employ in situ learning of the synaptic weights. In situ learning implies that circuits local to the synapses perform computation of the weight updates according to built-in learning rules. This makes these synapses less flexible than those with external learning which do not commit to predetermined rules. On the other hand, in situ learning has potential advantages in increased learning rates in compensating for component inaccuracies and in adapting to nonstationary tasks. Both supervised and unsupervised learning rules and their implementations are described. The discussion focusses on synapses whose weights are stored on capacitors or in binary registers but also includes EEPROMs and CCDs. The emphasis is on synapses implemented using analog multipliers but other circuit techniques such as pulse streams are also briefly mentioned.
A MACROSCOPIC MODEL OF NEURAL ENSEMBLES: LEARNING-INDUCED OSCILLATIONS IN A CELL ASSEMBLY
Authors: Chang Hung-Jen , Ghosh Joydeep , Liano Kadir
Published: November 2004

A mathematical model is developed to characterize the aggregate behavior of large neural networks in which each individual neuron can be described by the general Hodgkin-Huxley format. Equations relating the average input activation and connection strength of the neurons to other ensemble parameters are derived using only the first and second order statistics of the system. The model describes the global effects of weight changes brought about by a local Hebb-type adaptation rule. In particular, such adaptation can lead to rhythmic behavior of ensemble activity even in an isolated cell assembly of homogeneous cells. Conditions that make such oscillatory behavior possible are identified and the frequency of oscillation is quantitatively related to the network parameters. Results from computer simulation support the mathematical analysis.
A NEURAL NETWORK IMPLEMENTATION FOR THE TRAFFIC CONTROL PROBLEM ON CROSSBAR SWITCH NETWORKS
Authors: Sun K.T. , Fu H.C.
Published: November 2004

In this paper, we propose a neural network for the traffic control problem on crossbar switch networks. First, we represent this problem by an energy function, then apply the proposed neural network to update the state of the energy function until a stable state is reached. Within O(n) iteration steps, where n is the size of an n×n network, the energy function reaches a stable state which corresponds to a feasible solution of the traffic control problem. Also, the simulation results show that our neural network generates either optimal or near optimal solutions. Based on our neural network approach, many problems of applying neural networks to optimization problems are overcome, for example, the unpredictable converging time to reach a stable state, the probability of converging to a local minimum which corresponds to an invalid solution and the selecting of proper parameters of an energy function for obtaining a good (near optimal) solution, etc.
INFORMATION PROCESSING BY A PERCEPTRON
Authors: Nadal J.-P. , Parga N.
Published: November 2004

The information coming into a module, which is part of a global system, will in general require pre-processing that consists in building a representation — expressing it in a new code — convenient to the task to be performed by this particular module. This information, coming either from the environment or from another module in the system, will undergo this operation in what we can call an encoder. In this work we describe our results for a perceptron architecture viewed as an encoder, using encoding principles based on Information Theory. In particular we show how to evaluate the information capacity and the typical mutual information, quantities which are relevant to analize the different criteria used to code the information. Techniques taken from statistical mechanics of disordered systems will be shown to be useful for these calculations.
LOCAL NEOCORTICAL PROCESSING: A TIME FOR RECOGNITION
Authors: Treves Alessandro
Published: November 2004

The experimentally observed rapid processing of information in visual cortex has led to the suggestion that it may be primarily carried out through feedforward, as opposed to lateral, connections. A novel analytical approach allows studying the dynamics of networks of integrate-and-fire model neurons, reciprocally connected through synaptically activated conductances. This yields the attractor states of the network and the full spectrum of time constants of the transients. The results indicate that, unexpectedly, a substantial amount of lateral processing may contribute, already very early on, to the information contained in single-cell responses.
THE MODELLING OF CHEMICAL MODULATION IN NEURAL NETWORKS
Authors: Coolen A.C.C. , Noest A.J. , de Vries G.B.
Published: November 2004

We analyse the effect of chemical neuro-modulation on collective processes in Ising spin neural networks with separable Hebbian type synaptic interactions. Neuro-modulation is taken into account in the most simple way: a modulator-specific subset of neurons is prevented from transmitting signals. However, the presence of neuro-modulators is taken into account also during the learning stage, which leads to non-symmetric interaction matrices. We derive (in the limit of an infinite system size) the macroscopic laws that determine the system’s evolution in time on the level of order parameters. These laws are very transparant and show that, within the proposed framework, one can understand the functioning of neuro-modulators as follows: their role is to choose from the repertoire of learned behaviour a particular mode of operation. By considering specific examples of learning stages we indicate how neuro-modulation might be used by the brain as an extra degree of freedom for (a) performing selective pattern reconstruction, (b) controlling the reproduction speed of stored pattern sequences or (c) for choosing a particular path from a set of partially overlapping stored trajectories through state space (at points where the trajectories separate).
ON THE MEAN FIELD THEORY OF RANDOM HETEROPOLYMERS
Authors: FRANZ SILVIO , MÉZARD MARC , PARISI GIORGIO
Published: November 2004

We discuss some of the problems appearing in the Mean Field Theory of Random Heteropolymers. We show how an hypothesis of replica symmetry maps this problem onto a directed polymer in a random potential, and explain how this hypothesis can be checked through numerical simulations on directed polymers. The approach of Shaknovitch and Gutin is also reviewed in light of these findings.
Ar K-SHELL IONIZATION CROSS SECTIONS FOR PROTONS FROM 100 keV DOWN TO 40 keV
Authors: HSU C.C. , CHU T.C. , CHANG Y.C.
Published: November 2004

The K-shell ionization cross sections for Ar gas were measured from 100 keV down to 40 keV of H ions. The results are compared with theoretical calculations of PWBABC, CPSSR, and ECPSSR. They indicate that the discrepancy between experimental results and theoretical calculation increases as the H+ energy decreases in the range below ~50 keV. This is consistent with previous results on K-shell X-rays for Si.
PRODUCTION OF HYDROGEN RYDBERG STATES AND QUANTUM BEATS IN COLLISIONS OF PROTONS WITH ARGON
Authors: DEPAOLA B.D. , CHANG Y.C. , HSU C.C.
Published: November 2004

We describe a new experiment setup, designed to measure Stark quantum beats, following charge capture to high n states by protons incident on argon. The experiment makes use of state selective field ionization followed by zero degree electron energy analysis. Preliminary data are presented and discussed. Future directions are indicated.
TOXIC CHROMIUM ANALYSED BY PIXE
Authors: FOLKMANN FINN
Published: November 2004

Exciting different Cr-containing chemical compounds with heavy ions, e.g. 1.4 MeV/u 12C16O and 35Cl K x rays from Cr were measured with high resolution by diffraction in a curved crystal and with a position sensitive detector. Small differences are seen for different compounds and valancy states 3 and 6 of Cr (6 is toxic).
PIXE ANALYSIS OF CARTILAGE SAMPLES
Authors: VOGT J. , OTTO G. , Dannhauer K.H.
Published: November 2004

Despite intensive investigation, normal and abnormal calcification mechanisms are still poorly understood.

In our study we measured the change of main and trace element concentrations across the calcification area of the mandibular cartilage of domestic pigs of different age.

The PIXE method was employed for the analysis of the cartilage samples, using a proton beam with an energy of 1700 keV.

Concentration values of the elements P, S, Cl, K, Fe, Ni, Cu, Zn, Br, Rb, and Sr were evaluated from the measured spectra.

Significant changes of elemental contents across the calcification area could be observed.
HISTORY AND FUTURE TRENDS IN THE DEVELOPMENT OF HDTV TECHNOLOGY IN JAPAN
Authors: HORI KENJI , NUMAKURA TOSHIHIKO
Published: November 2004

This paper covers the historical development of HDTV technology in Japan, the results obtained to date, and the future outlook from the viewpoint of consumer-oriented HDTV product development.
ON THE STRUCTURE OF CONTINUOUS SPATIAL SEMIGROUPS OF *-ENDOMORPHISMS OF ${\mathfrak B} ({\mathfrak h})$
Authors: POWERS ROBERT T.
Published: November 2004

This paper concerns the structure of continuous spatial semigroups of *-endomorphisms of [Formula: see text]. These are semigroups of *-endomorphisms of [Formula: see text] for which there exist a strongly continuous one parameter semigroup of intertwining isometries. The nature of the intertwining semigroups and the associated boundary representation is analyzed.
GENERALIZED WEYL-VON NEUMANN THEOREMS
Authors: LIN HUAXIN
Published: November 2004

The conjecture that the real rank of multiplier algebra of every AF-algebra is zero was formally made by L. G. Brown and G. K. Pedersen in [4]. The main purpose of this note is to prove the conjecture. However, we also show that this Weyl-von Neumann type theorem holds for C*-algebras with stable (FU) and stable rank one. In particular, this Weyl-von Neumann type theorem holds for C*-algebras of inductive limits of finite direct sums of basic building blocks with real rank zero and trivial K1-groups considered by George A. Elliott recently.
SUPER KRICHEVER FUNCTOR
Authors: MULASE MOTOHICO , RABIN JEFFREY M.
Published: November 2004

A supersymmetric generalization of the Krichever map is proposed. This map assigns injectively a point of an infinite dimensional super Grassmannian to a set of geometric data consisting of an arbitrary algebraic super manifold of dimension 1|1 defined over a field of any characteristic and a line bundle on it. The naturality of this map comes from the fact that it is obtained as the restriction of a contravariant functor to certain special objects. This functor gives an antiequivalence between the category of infinite dimensional super vector spaces satisfying the Fredholm condition together with their stabilizers, and the category of algebraic super curves and certain sheaves on them including all even vector bundles of arbitrary rank.
Collocation Method to Solve Analytically Nonseparable Boundary Problems
Authors: CAP F.
Published: November 2004

Boundary problems in which the boundary does not coincide with coordinate lines or surfaces of coordinate systems in which the pertinent partial differential equation is not separable into ordinary differential equations are usually called nonseparable [1]. In these days such problems are mainly solved numerically by the finite elements method. However, the general solution of a partial differential equation contains one or more arbitrary functions. Since an arbitrary function is equivalent to an infinite set of coefficients (partial amplitudes of modes) one has an infinite number of constants available to satisfy arbitrary boundary conditions on arbitrary boundaries. In practice, a finite number of these coefficients is used to satisfy the boundary condition exactly in a finite number of given collocation points chosen on the boundary. A plot of the boundary given by the collocation points check the satisfaction of the boundary condition not only in the collocation points but also in other points. A theorem of Courant [2] guarantees smoothness and analyticity of the solution between the collocation points.
Random-Number Generation
Authors: COMPAGNER A.
Published: November 2004

In large-scale Monte Carlo simulations, reliable random numbers will soon be needed at bit rates of 1 GHz or more. Therefore, existing recipes for the generation of random numbers have to be improved. This is not easy, due to the many unrelated and laborious statistical tests needed to compensate for the lack of an accepted and operational definition of randomness. When however the notion of randomness as a complete absence of all correlations is made precise, a practical approach results.
Parallelisation of a 2-D Fast Fourier Transform Algorithm
Authors: HAMMERSLEY ANDREW
Published: November 2004

The calculation of two and higher-dimension Fast Fourier Transforms (FFT’s) are of great importance in many areas of data analysis and computational physics. The two-dimensional FFT is implemented for a parallel network using a master-slave approach. In-place performance is good, but the use of this technique as an “accelerator” is limited by the communications time between the host and the network. The total time is reduced by performing the host-master communications in parallel with the master-slave communications. Results for the calculation of the two-dimensional FFT of real-valued datasets are presented.
A Molecular Dynamics Study of SF6
Authors: HUA LU , PAWLEY G.S.
Published: November 2004

The stress-free molecular dynamics method has been used to study the phases of sulphur hexafluoride (SF6). The low-temperature structure was found to be monoclinic of space group C2/m, and this is consistent with neutron diffraction experiments.
AN EFFICIENT METHOD TO CALCULATE FIELD THEORIES WITH DYNAMICAL FERMIONS
Authors: DO AMARAL MARCIA G. , KISCHINHEVSKY M. , DE CARVALHO C. ARAGÃO , TEIXEIRA F.L.
Published: November 2004

We discuss the application of the Hybrid Monte Carlo method for models that describe conducting polymers, namely the Su-Schrieffer-Heeger and the Krive-Rozhavskii models. We use a fourth order Leap Frog algorithm, in order to decrease the number of Monte Carlo rejections. We also make a detailed study of which solver has the best performance in each phase of the theory as well as the dependence of the acceptance probability as a function of the time step size and other parameters.
QUANTUM MONTE CARLO SIMULATIONS FOR THE THREE-BAND HUBBARD MODEL
Authors: DOPF GEORG , MURAMATSU ALEJANDRO , HANKE WERNER
Published: November 2004

We present in this article results of Quantum Monte Carlo simulations for the three-band Hubbard model obtained both with the grand canonical approach as well as with the T =0 formalism. A direct comparison of Quantum Monte Carlo results with experimental values for the charge-transfer gap leads to a set of parameters for the three-band Hubbard model that consistently describes salient features of the high- T c superconductors. We find long-range antiferromagnetic order in the undoped case as well as an incommensurate structure for a doping concentration of δ≈0.20. Moreover the magnetic susceptibility as a function of doping δ is in a qualitative agreement with experiments. Concerning dynamical properties, we have evaluated the spectral density [Formula: see text]. The dispersion of the state with the lowest excitation energy is in very good agreement with experimental photoemission and inverse photoemission experiments for a doping concentration of δ=0.25. In the superconducting regime, we find that the interaction vertex for the pairing correlation function in the extended s-channel shows a maximum for δ~0.20, resembling the dependence of T c on doping. This feature is not present for other symmetries of the order parameter or in other parameter regions.
AN EFFICIENT ALGORITHM FOR CLUSTER UPDATES IN Z(2) LATTICE GAUGE THEORIES
Authors: BUNK B.
Published: November 2004

An efficient algorithm for identifying the independent cluster flips in a Z(2) lattice gauge theory with stochastic percolation is presented. It applies Gaussian elimination to the incidence matrix, with special attention payed to the pivoting strategy and appropriate linked list structures. At the critical point of the 3-dimensional pure gauge model, storage and cpu-time scale like L3 and L3 log L, respectively. The algorithm is also applied to the 3-D Z(2) gauge-Higgs model along the self-dual line. A second order critical line is found, endpoints and critical indices are determined. The cluster update is superior to the heat bath in the region near the triple point.
BOOLEAN DERIVATIVES AND COMPUTATION OF CELLULAR AUTOMATA
Authors: BAGNOLI FRANCO
Published: November 2004

The derivatives of a Boolean function are defined up to any order. The Taylor and MacLaurin expansions of a Boolean function are thus obtained. The last corresponds to the ring sum expansion (RSE) of a Boolean function, and is a more compact form than the usual canonical disjunctive form. For totalistic functions the RSE allows the saving of a large number of Boolean operations. The algorithm has natural applications to the simulations of cellular automata using the multi-site coding technique. Several already published algorithms are analyzed, and expressions with fewer terms are generally found.
SCIENTIFIC TEXT PROCESSING
Authors: GOOSSENS MICHEL , HERWIJNEN ERIC VAN
Published: November 2004

Aspects of text processing important for the scientific community are discussed, and an overview of currently available software is presented. Progress on standardization efforts in the area of document exchange (SGML), document formatting (DSSSL), document presentation (SPDL), fonts (ISO 9541) and character codes (Unicode and ISO 10646) is described. An elementary particle naming scheme for use with LATEX and SGML is proposed. LATEX, PostScript, SGML and desk-top publishing allow electronic submission of articles to publishers, and printing on demand. Advantages of standardization are illustrated by the description of a system which can exchange documents between different word processors and automatically extract bibliographic data for a library database.
ON THE KINETICS OF THE ELECTROWEAK PHASE TRANSITION
Authors: BUCHMÜLLER W. , HELBIG T.
Published: November 2004

We discuss several aspects of the electroweak phase transition, which is generally believed to be first order. Starting from Langer’s theory of metastable states we derive an approximate formula for the decay rate. We then investigate the uncertainties in present evaluations of size and surface tension of critical bubbles and comment on the stumbling blocks on the way towards a quantitative description of the electroweak phase transition.
CHIRAL SYMMETRY RESTORATION IN THE LINEAR SIGMA MODEL
Authors: MEYER-ORTMANNS H. , PIRNER H.-J. , PATKÓS A.
Published: November 2004

We report on results about the mass sensitivity of chiral symmetry restoration in the linear sigma model. For masses of the pseudoscalar meson octet which are close to the experimental values, we observed only a gradual change in the order parameters, when the temperature was changed. To estimate the size of the first order transition region around the chiral limit, we have varied the mass input for the tree level parametrization in several ways. The point with realistic meson masses turned out to lie well inside the crossover region.
INVESTIGATION OF THE 3-STATE, 2-D POTTS MODEL WITH ONE DEFECT LINE OF COUPLINGS BY DENSITY OF STATES MONTE CARLO METHOD
Authors: ÓDOR GÉZA
Published: November 2004

The critical 3-state two-dimensional Potts model with one line of defect couplings has been studied. Interpolating the coupling strength between the free and periodic boundary conditions renormalization group arguments suggest that the algebraic content should change discontinuously. Monte Carlo data on different sized and shaped lattice systems have been collected. Predictions for the surface-free energy density, the central charge and the magnetization two-point correlation scaling dimension are given.
SWENDSEN-WANG DYNAMICS ON LARGE 2D CRITICAL ISING MODELS
Authors: KERTÉSZ J. , STAUFFER D.
Published: November 2004

Lattices up to size 6400*6400 are simulated on a 32-processor Intel Hypercube parallel computer. At the critical temperature of the square-lattice Ising model, the magnetization decays roughly exponentially with time if we start with all spins parallel and if the lattice is large enough. This result is consistent with those of Heermann and Burkitt.
DARK MATTER PREDICTION FROM CANONICAL QUANTUM GRAVITY WITH FRAME FIXING
Authors: CORVINO GIOVANNI , MONTANI GIOVANNI
Published: November 2004

We show how, in canonical quantum cosmology, the frame fixing induces a new energy density contribution having features compatible with the (actual) cold dark matter component of the Universe. First we quantize the closed Friedmann–Robertson–Walker (FRW) model in a synchronous reference and determine the spectrum of the super-Hamiltonian in the presence of ultra-relativistic matter and a perfect gas contribution. Then we include in this model small inhomogeneous (spherical) perturbations in the spirit of the Lemaitre–Tolman cosmology. The main issue of our analysis consists in outlining that, in the classical limit, the nonzero eigenvalue of the super-Hamiltonian can account for the present value of the dark matter critical parameter. Furthermore we obtain a direct correlation between the inhomogeneities in our dark matter candidate and those that appear in the ultra-relativistic matter.
TOPOLOGICAL FIELD THEORIES AND THE SPACE-TIME SINGULARITY
Authors: EGUCHI TOHRU
Published: November 2004

Based on a study of recently proposed solution of two-dimensional black hole we argue that the space-time singularities of general relativity may be described by topological field theories (TFTs). We also argue that in general TFT is a field theory which describes singular configurations of a reduced holonomy in its field space.
VIABLE SU(5) GUT WITH LIGHT LEPTOQUARK BOSONS
Authors: MURAYAMA H. , YANAGIDA T.
Published: November 2004

It is shown that the standard SU(5) GUT survives all experimental constraints if one introduces a pair of leptoquark bosons at the Fermi scale ~ O(100) GeV. This model predicts τ(p→e+π0)=7×1029−7×1032 yr which is marginally allowed by the present proton decay experiments and lies in the range testable at the super-Kamiokande.
TESTS OF PERTURBATIVE QCD USING R, $\Gamma _h^Z $ AND EVENT TOPOLOGY MEASUREMENTS IN HADRONIC Z-DECAYS
Authors: FIELD J.H.
Published: November 2004

The world data on R and [Formula: see text] is used to derive a value of the QCD scale parameter, free of hadronization and renormalization scale uncertainties, of [Formula: see text]. This value is then used to investigate the convergence of the QCD perturbation expansions for several different jet topology measures, with the choice [Formula: see text] of the renormalization scale. In most cases satisfactory convergence is observed. The overall consistency of all measurements of [Formula: see text] is also discussed. Although [Formula: see text] seems high, present data is consistent (17% C.L.) with a global world average value of [Formula: see text], [Formula: see text].
A TESTABLE MODEL OF A 17 keV TAU NEUTRINO
Authors: NG DANIEL
Published: November 2004

We discuss an extension of the standard model with a local symmetry of Le−Lμ and a global symmetry of Lτ to incorporate a 17 keV Dirac tau neutrino. A massive neutral gauge boson (AX) and a majoron (J) are present by breaking the symmetries spontaneously. The tau neutrino, with a life-time of the order 10−3 s, will decay by emitting an electron and a majoron. Tau will also decay into an electron and a majoron with a branching ratio as large as 10−4. The breaking scale of Le−Lμ symmetry can be as low as 700 GeV. Hence, AX can be produced in LEP II in the near future.
K FACTOR FOR HIGGS BOSON PRODUCTION VIA GLUON FUSION PROCESS AT HADRON COLLIDERS
Authors: TANAKA HIDEKAZU
Published: November 2004

Soft gluon corrections for Higgs boson production at hadron colliders are calculated. It is found that the soft gluon contributions for the Higgs boson production via gluon fusion process is large and it cannot be neglected even at SSC energy. Some qualitative discussions for the QCD corrections to the Higgs boson production at hadron colliders and their background processes are presented for various Higgs boson mass cases.
CRITERIA TO FIX THE DIMENSIONALITY CORRESPONDING TO SOME HIGHER DERIVATIVE LAGRANGIANS
Authors: BOLLINI C.G. , GIAMBIAGI J.J. , OBREGON O.
Published: November 2004

Newtonian potential and Huygens’ principle can be simultaneously satisfied by means of a D’Alambertian (Laplacian) to a certain power for one specific dimension of the space. This can be of relevance for some physical higher derivative Lagrangians.
WARD IDENTITIES IN TWO-DIMENSIONAL STRING THEORY
Authors: KLEBANOV IGOR R.
Published: November 2004

I study the Ward identities of the w∞ symmetry of the two-dimensional string theory. It is found that, not just an isolated vertex operator, but also a number of vertex operators colliding at a point can produce local charge non-conservation. The structure of all such contact terms is determined. As an application, I calculate all the non-vanishing bulk tachyon amplitudes directly through the Ward identities for a Virasoro subalgebra of the w∞.
CLEAN PRECISION TESTS OF THE ELECTROWEAK THEORY
Authors: HIOKI ZENRŌ
Published: November 2004

Present status of electroweak precision tests via the weak boson masses is reviewed, emphasizing that the standard SU(2) × U(1) theory is phenomenologically very successful also at quantum correction level. In particular, it is shown that the latest experimental data indicate the existence not only of the whole one-loop corrections but also of the non-decoupling top-quark effects, independent of the Higgs mass, which are a characteristic feature of theories with masses generated by spontaneous symmetry breakdown plus large Yukawa couplings.
DISCRETE AND CONTINUOUS AMBIGUITIES IN THE ISOSPIN ANALYSIS OF THE B→πK DECAYS
Authors: LAVOURA L.
Published: November 2004

A polynomial equation of the fifth degree, which solves completely the theoretical problem of the isospin analysis of the B→πK decays, is derived. It is shown that the problem has in general an even number (two or four) of non-trivially-related solutions. There are six particular cases of null measure, but which might be relevant due to the experimental errors, in which the problem has a continuous set of solutions. It is concluded that the isospin analysis, even if experimentally feasible, has a large probability of being inconclusive.
ON CERTAIN TOPOLOGICAL ASPECTS OF THE FAMILY PROBLEM
Authors: BATAKIS NIKOLAOS A. , KEHAGIAS ALEXANDROS A.
Published: November 2004

Certain topological aspects of potential significance to the problem of family formation are investigated. Specifically, it is shown that the conventional vacuum state for gauge theories with non-trivial topology and fermions in the fundamental representation of the universal covering group of the gauge group, is not, in general, gauge invariant. The true gauge invariant vacuum, as well as the corresponding generating functionals are constructed. As a result, for the particular case of an SO(10) gauge symmetry over R3×S1 which is explicitly considered here, gauge and Lorentz invariance requires the existence of four-fermion generations.
ARE NARROW POSITRON-ELECTRON LINES CREATED BY DECAY OF EXCITED VACUUM-LIKE SYSTEMS FORMED FROM A COHERENT PIONIC PHASE PRESENT IN HEAVY-ION COLLISIONS?
Authors: BARSHAY SAUL
Published: November 2004

A novel description of several narrow, correlated electron-positron lines observed in heavy-ion collisions, arises from a physical picture involving the decay of a group of related, excited coherent bosonic states, which resemble an excited, chira σ vacuum-condensate. These systems are formed in the collision of a coherent pionic phase present in the heavy ions. Further experimental tests of the idea, involve the specific form of the opening angle correlation between the positron-electron pair, and possibly, the nature of the charge states of the final-state ions.
3D MANIFOLDS, GRAPH INVARIANTS AND CHERN-SIMONS THEORY
Authors: RAMA S. KALYANA , SEN SIDDHARTHA
Published: November 2004

We show how the Turaev-Viro invariant, which is closely related to the partition function of three-dimensional gravity, can be understood within the framework of SU(2) Chern-Simons theory. We also show that, for S3 and RP3, this invariant is equal to the absolute value square of their respective partition functions in SU(2) Chern-Simons theory and give a method of evaluating the latter in a closed form for a class of 3D manifolds, thus in effect obtaining the partition function of three-dimensional gravity for these manifolds. By interpreting the triangulation of a manifold as a graph consisting of crossings and vertices with three lines we also describe a new invariant for certain class of graphs.
NON-PERTURBATIVE GAUGE THEORETIC TREATMENT OF TWO-PARTICLE SCATTERING IN (2 + 1)-DIMENSIONAL GRAVITY
Authors: FALBO-KENKEL M. K. , MANSOURI F.
Published: November 2004

By a suitable choice of phase space variables, which is natural for the reduction of a two-body problem, we couple two sources to the Chern-Simons-Witten action and obtain the exact two-body Hamiltonian. For particles of (nearly) equal mass and of small momenta, the Hamiltonian reduces to that of 't Hooft. In the corresponding geometry, when viewed from a particular frame, the relative coordinate moves on a cone of deficit angle equal to the classical Hamiltonian.
RENORMALIZATION PROPERTIES OF TWO-DIMENSIONAL HOMOGENEOUS SYMPLECTIC σ-MODELS
Authors: BRATCHIKOV A. V.
Published: November 2004

The structure of renormalization of the two-dimensional σ-model, built on an arbitrary homogeneous symplectic manifold, is found within a convenient parametrization of the fields. Solution of the Ward-Takahashi (WT) identities determines the renormalized action up to a finite number of renormalization constants. All the infinities can be absorbed in a coupling constants renormalization and in a renormalization of an auxiliary constant finite-dimensional matrix.
EQUIVALENCE OF LIGHT-CONE AND CONFORMAL GAUGES IN TWO-DIMENSIONAL QUANTUM GRAVITY
Authors: AHN CHANG-JUN , KIM WON-TAE , PARK YOUNG-JAI , KIM KEE YONG , KIM YONGDUK
Published: November 2004

We show that the light-cone and conformal gauges are equivalent in the sense that the well known SL (2, ℝ) current structure in the light-cone gauge is obtained from the results in the conformal one under a proper coordinate transformation. This result is due to the residual symmetry of the scalar field Φ.
DECONFINEMENT IN (2 + 1)-DIMENSIONAL NON-ABELIAN GAUGE THEORIES WITH FUNDAMENTAL FERMIONS
Authors: KOVNER A. , ROSENSTEIN B.
Published: November 2004

Non-Abelian gauge theories with fundamental fermions are analyzed using dual Lagrangian approach. It is found that in certain range of parameters the baryon number symmetry is spontaneously broken and one of the gauge bosons is identified as the corresponding Goldstone boson. It therefore remains massless beyond perturbation theory. All the other gauge bosons acquire a mass due to one-loop and monopole effects. Correspondingly, unlike in theories with bosonic matter only, one type of charged particles is not linearly confined.
GENERALIZED QUANTUM STATISTICS
Authors: CHOU CHIHONG
Published: November 2004

In this letter, a non-anyonic generalization of quantum statistics is presented, in which Fermi-Dirac statistics (FDS) and Bose-Einstein statistics (BES) appear as two special cases. This new quantum statistics, which is characterized by the dimension of its single particle Fock space, contains three consistent parts, namely the generalized bilinear quantization, the generalized quantum mechanical description and the corresponding statistical mechanics.
QUANTUM GROUP GENERALIZATION OF THE CLASSICAL SUPERSYMMETRIC POINT PARTICLE
Authors: MATHEUS-VALLE J.L. , MONTEIRO MARCO A.R.
Published: November 2004

Following the generalization of the Grassmann Algebra provided by Quantum Groups, we introduce an extension of fermionic coordinates and an action for the classical point particle mechanics which has a symmetry that resembles a supersymmetric transformation.