bluuebunny/crossref_metadata_2025 huggingface dataset:
The impacts of forest harvest and wildfire on soils and hydrology in temperate forests: A baseline to develop hypotheses for the Boreal Plain
Authors: Chanasyk D S , Whitson I R , Mapfumo E , Burke J M , Prepas E E
Published: October 2003

This component of the Forest Riparian and Watershed Disturbance (FORWARD) project evaluates soils in burned, harvested, and undisturbed watersheds to quantify effects of disturbance on forest soils in the Boreal Plain. The current knowledge of disturbance effects on soils is reviewed, with a focus on temperate ecosystems, to generate the following hypotheses to be tested in field studies. Harvest and fire should affect surface horizons more than mineral horizons. Forest harvest should affect soils most through compaction, the degree being mediated by soil texture, soil moisture, and harvest operations. Nutrient export will likely increase from logged watersheds, with changes in microbial processes being more strongly associated with nitrogen (N) losses and erosional processes more strongly linked to phosphorus (P) losses. Effects of fire on Boreal Plain soils will increase with fire severity. Coarser soils after fire should be subject to hydrophobicity, erosion, and low infiltration rates. Chemical changes should include increased solubility of oxidized cations. N losses should exceed P losses and be due to volatilization and leaching of mineralized N compounds. Particulate P should comprise P loss; although P availability may increase after fire, soluble P movement from the forest environment will be limited by P uptake by soils. Key words: watershed disturbance, forest soils, forest fire, forest harvest, soil properties, nutrient cycling.
Surface water chemistry of burned and undisturbed watersheds on the Boreal Plain: an ecoregion approach
Authors: Allen E W , Prepas E E , Gabos S , Strachan W , Chen W
Published: October 2003

The water chemistry of the euphotic zone in 12 lakes within burned and reference watersheds on Alberta's Boreal Plain was surveyed two years post-fire. Five burned and four reference lakes were located in the Boreal Foothills (mean elevation = 1048 m) and three reference lakes were situated at lower elevations in the Boreal Mixedwood ecoregion (748 m). Mean dissolved organic carbon (DOC) concentration in lake water from burned watersheds was 1.4-fold higher than in lake water from reference Foothills watersheds, whereas lake colour increased with the area of catchment burned divided by lake volume (r = 0.98). Reference Mixedwood lakes had higher mean total phosphorus (TP, 1.8-fold) and chlorophyll a (chl a; 4.4-fold) concentrations than reference Foothills lakes. Ten additional lakes from a previous study in boreal Alberta were used to further compare water chemistry between ecoregions. Boreal Mixedwood lakes (n = 13) had higher TP (2.3-fold), chl a (3-fold), and Ca2+ + Mg2+ (3.3-fold) concentrations than Boreal Foothills lakes (n = 9). Our data suggest an influence of forest fire on lake chemistry in the Boreal Foothills, and demonstrate the need for an ecoregion approach to detect the impacts of watershed disturbance on the Boreal Plain. Key words: watershed disturbance, forest fire, lake nutrients, lake elevation, phosphorus, chlorophyll a, anions, cations, dissolved organic carbon.
Ecologically-based forest planning and management for aquatic ecosystems in the Duck Mountains, Manitoba
Authors: Donnelly M
Published: October 2003

Current forest management guidelines require the extensive use of stand level approaches to minimize impacts on aquatic ecosystems. As forest management practices in Canada evolve from a sustained yield, timber-based focus to a more sustainable approach, the need has been recognized for the addition of landscape or watershed-based management strategies to address the cumulative effects of management practices on aquatic systems. Additional concerns expressed by regulatory agencies have resulted in the need to restrict cumulative harvest rates and monitor harvest levels for a forest management operation in Manitoba. Present riparian management practices and watershed analysis procedures are reviewed for the operations of Louisiana-Pacific Canada in Manitoba. Requirements are outlined for multi-scale indicators and research to support the development of a watershed-based planning approach for use in forest management planning and monitoring. The development of this watershed-based approach is linked to the Forest Watershed and Riparian Disturbance (FORWARD) project. Key words: riparian management, watershed management, natural disturbance, forest harvest.
Pilot-scale study of phosphorus recovery through struvite crystallization  examining the process feasibility
Authors: Adnan A , Mavinic D S , Koch F A
Published: October 2003

The suitability of a new pilot-scale reactor to recover phosphorus through struvite crystallization was examined. Based on the similar principles previously tested in bench-scale reactors and scaled up to overcome operating problems encountered in earlier work, the pilot-scale crystallizer was used to effectively removerecover phosphorus from synthetic wastewaters. Ortho-P removal rates as high as 90% were obtained for low (~5070 mg/L P) and medium (~70100 mg/L P) strength wastewaters. To achieve these removal rates, a relatively high pH value of 8.3 was required. Over 90% of the removed phosphates could be recovered in the form of harvestable struvite crystals with a mean size of 2.53.5 mm and sufficient mechanical strength to permit harvestingreuse. A new concept of crystal retention time (CRT) has been developed, which is used to make estimates of the struvite crystal age. Results of this study indicate that CRT is one of the main factors affecting the mean crystal size.Key words: crystallization, phosphorus removal, struvite, sustainability, wastewater.
Inactivation of Ascaris suum eggs in digested and dewatered biosolids with lime and fly ash at bench scale and full scale
Authors: Brewster J , Oleszkiewicz J , Bujoczek G , Reimers R S , Abu-Orf M , Bowman D , Fogarty E
Published: October 2003

The feasibility of inactivating Ascaris suum eggs spiked into digested and dewatered biosolids from Winnipeg, Manitoba to class A levels (as per USEPA 1993) by storing the biosolids treated with lime (CaO) and (or) fly ash under anoxic conditions was investigated. The study was comprised of two phases. The first phase involved mixing the biosolids with various quantities of lime and (or) fly ash in a Hobart mixer and storing the mixed product in 16 L buckets at 46 °C. Phase two involved full-scale mixing of lime and (or) fly ash using a Lödige mixer. The mixed product was buried in trenches and stored for 356 d at naturally occurring environmental temperatures that ranged from 1 to 33 °C in the trench. The lowest lime dose capable of inactivating Ascaris suum eggs to class A levels was 50 g of lime  amended with 1000 g of fly ash per kilogram of dry biosolids. Storage for 291 d at environmentally occurring temperatures was required to meet the class A criteria. Maintaining the higher temperatures for a longer duration would have reduced the time necessary to achieve the target inactivation. Key words: Ascaris suum, biosolids, eggs, fly ash, helminth, inactivation, lime.
Optimisation d'un procédé de lixiviation en milieu basique et acide pour la décontamination (Cd, Pb) d'un mélange de cendres de chaudières et d'électrofiltres d'incinérateur de déchets municipaux
Authors: Levasseur Béatrice , Blais Jean-Francois , Mercier Guy
Published: October 2003

The purpose of this research was to improve a process for the removal of Cd and Pb from municipal incinerator fly ashes (boiler and electrofilter ashes). The first part of this study was to evaluate the optimum conditions for Pb extraction using alkaline washing steps. The tests carried out with various ash solid concentrations (1050% (w/v)) have shown better Pb removal yields following the decrease of the solid concentrations. Nevertheless, by considering the economic aspect, a ratio of 30% (w/v) was retained as the optimal condition for alkaline leaching steps. A very short contact time (2 min) allows a maximum lead solubilization during alkaline washings. A series of two or three alkaline washing steps is necessary for sufficient lead removal. Once the alkaline leaching conditions have been optimized, research was applied to identify the optimum conditions of acid leaching. Best Pb and Cd removal yields of 25% and 85%, respectively, have been obtained by using two 30-min washing steps at pH 3 with a pulp density of 10% (w/v). The treated ashes respect the TCLP criteria. Finally, the adapted process of ash treatment presented in this study allows a substantial reduction of 57% of the chemical costs compared with the conventional procedure, and a significant reduction (83%) of water consumption. Key words: cadmium, lead, fly ash, alkaline leaching, acid leaching, removal, TCLP, decontamination.
Triple Loop Networks with Minimal Transmission Delay
Authors: Jia Xingde , Su Weidong
Published: October 2003

A multiloop network is a Cayley digraph of the additive group ℤm of integers modulo m generated by a set A of k ≥ 2 "steps". Because of their application to the computer network design, multiloop networks have been studied extensively. Given an integer d ≥ 2 and a real number r > 1, let m(d,3) be the maximum size of a triple loop network with transmission delay (diameter) less than or equal to d, and let m*(r,3) be the maximum size of a triple loop network with average transmission delay less than or equal to r. In this paper, the following lower bounds are proved: [Formula: see text]

which improve earlier lower bounds by Jia and Aguiló, Fiol and Garcia.
Current Methods of Speech Coding
Authors: Cox Richard V.
Published: October 2003

Digital speech coding is used in a wide variety of every day applications that the ordinary person takes for granted, such as network wireline and cellular telephony and telephone answering machines. This article reviews some of the most currently used methods of speech coding. This includes reviewing the basic attributes of these coders, the methods used for coding and some of the most important speech coding standards. It also reviews the methods used to realize digital speech coders, especially those for implementing these coders in a cost effective manner.
Image and Video Compression: A Review
Authors: Podilchuk Christine I. , Safranek Robert J.
Published: October 2003

The area of image and video compression has made tremendous progress over the last several decades. The successes in image compression are due to advances and better understanding of waveform coding methods which take advantage of the signal statistics, perceptual methods which take advantage of psychovisual properties of the human visual system (HVS) and object-based models especially for very low bit rate work. Recent years have produced several image coding standards—JPEG for still image compression and H.261, MPEG-I and MPEG-II for video compression. While we have devoted a special section in this paper to cover international coding standards because of their practical value, we have also covered a large class of nonstandard coding technology in the interest of completeness and potential future value. Very low bit rate video coding remains a challenging problem as does our understanding of the human visual system for perceptually optimum compression.

The wide range of applications and bit rates, from video telephony at rates as low as 9.6 kbps to HDTV at 20 Mbps and higher, has acted as a catalyst for generating new ideas in tackling the different challenges characterized by the particular application. The area of image compression will remain an interesting and fruitful area of research as we focus on combining source coding with channel coding and multimedia networking.
Micromachined Micro-Optic and Optoelectronic Devices
Authors: Tran A. T. T. D. , Christenson G. L. , Zhu Z. H. , Haronian D. , Lo Y.-H.
Published: October 2003

Rencent progress on micromachined micro-optic and optoelectronic devices is discussed. We describe a low temperature (240°C) surface micromachining process that can be used to fabricate a variety of micro-optic components on micromachined membranes integrated with microactuators. The devices discussed in this paper include Fabry-Pérot tunable filters with a 341 nm tuning range, wavelength tunable transmitters at 1.55 micron wavelength, high-sensitivity integrated sensors using optical Moiré patterns, and movable microlenses. Such devices represent a new class of micro-optic circuits that will find important applications in many areas including optical communication and sensing.
High Frequency Confinement Factor Modulation of Diode Lasers
Authors: Gurevich S. A. , Shatalov M. S. , Simin G. S.
Published: October 2003

In this paper we discuss the possibility of confinement factor and dual (confinement & pumping current) modulation of laser diodes. In the initial experiment, four-terminal Fabry–Pérot lasers of ridge guide type with two additional side electrodes were tested. The possibility of controlling the lateral part of the optical confinement factor by applying an external voltage to the side contacts was proved in this experiment. To analyze the dynamic behavior of the four-terminal laser under confinement factor and dual modulation, a simple model and a more accurate new model were developed, the last one based on the simultaneous solution of laser rate equations and matrix equation relating potentials and currents. The simulations carried out on the basis of the advanced model allowed us to propose an optimized four-terminal laser structure promising enhanced performance under dual modulation. It is shown that dual modulation may result in very efficient correction of output waveforms which leads to a much better opening of transmitted eye patterns at high bit rates as compared to direct modulation.
Dual Antiresonant Reflecting Optical Waveguide Devices
Authors: Huang Yang-Tung , Deng Jau-Jan , Chen Yeong-Her , Jang Chiou-Hung , Wang Chih-Lin
Published: October 2003

Basic theories to analyze and design dual antiresonant reflecting optical waveguide (ARROW) devices are discussed. These theories include modal analysis for all ARROW devices, coupling efficiency analysis between dual ARROW waveguides, and eigenmode expansion analysis with step discontinuities in the devices. Various dual ARROW devices of power dividers, hybrid, wavelength filters, polarization beamsplitters, and pressure sensors are introduced.
Consequences of Neutrinoless Double Beta Decay and WMAP
Authors: Klapdor-Kleingrothaus H. V. , Sarkar U.
Published: October 2003

Observation of the neutrinoless double beta decay (0νββ) has established that there is lepton number violation in nature and the neutrino masses are Majorana in nature. It also gives the absolute mass of the neutrinos and discriminates between different models of neutrino masses. The allowed amount of lepton number violation puts severe constraints on some possible new physics beyond the standard model. The recent results from WMAP are consistent with the consequences of the neutrinoless double beta decay. They improve some of these constraints very marginally, which we shall summarize here. We mention the new physics which is not affected by WMAP, and which could make the limits from the neutrinoless double beta decay even consistent with much tighter future cosmological limits.
Evolution of Elliptical Galaxies and Mechanism of Formation of Spiral Galaxies
Authors: Pavlov A. , Pavlova Y.
Published: October 2003

A mechanism of formation of a spiral galaxy is proposed. The galaxy is considered to be a cluster consisting of stars and gaseous clouds. Initially, the galaxy has elliptical geometry and slow rotational motion around one axis. The gravitational interaction between the stars has been modelled. The cluster contracted and transformed its geometry. The geometry of the initial cluster changes due to the change of the rotational velocities of the stars in accordance with the Kepler's second law and change of the relative positions of the stars. The computer simulation reveals that a spiral shaped galaxy is a result of the transformation of a cluster of non-spherical symmetry. An example of the gravitational contraction of an elliptically-shaped galaxy is presented in this paper.
Expected Improvement in the Determination of G Using an X Pendulum
Authors: Kuroda Kazuaki , Barton Mark A. , Onae Atsushi , Miki Yukinobu
Published: October 2003

We propose the application of a new technique, the X pendulum, to determine the Newtonian gravitational constant G. We evaluate the likely experimental errors for configurations realizable with existing technologies and show that improvement of the accuracy by an order of magnitude or more is possible.
SL(N + 1, R) Toda Solitons in Supergravities
Authors: LÜ H. , Pope C. N.
Published: October 2003

We construct (D - 3)-brane and instanton solutions using N ≤ 10 - D one-form field strengths in D dimensions, and show that the equations of motion can be cast into the form of the SL (N + 1, R) Toda equations. For generic values of the charges, the solutions are nonsupersymmetric; however, they reduce to the previously known multiple-charged supersymmetric solutions when appropriate charges vanish.
A Solvable Twisted One-Plaquette Model
Authors: Billó M. , D'Adda A.
Published: October 2003

We solve a hot twisted Eguchi-Kawai model with only timelike plaquettes in the deconfined phase, by computing the quadratic quantum fluctuations around the classical vacuum. The solution of the model has some novel features: the eigenvalues of the timelike link variable are separated in L bunches, if L is the number of links of the original lattice in the time direction, and each bunch obeys a Wigner semicircular distribution of eigenvalues. This solution becomes unstable at a critical value of the coupling constant, where it is argued that a condensation of classical solutions takes place. This can be inferred by comparison with the heat-kernel model in the Hamiltonian limit, and the related Douglas–Kazakov phase transition in QCD2. As a byproduct of our solution, we can reproduce the dependence of the coupling constant from the parameter describing the asymmetry of the lattice, and compare it to previous results by Karsch.
Trivariate Quasiprobability Distributions for Polarized Spin-1 Nuclei
Authors: Usha Devi A. R. , Sirsi Swarnamala , Ramachandran G. , Devi P.
Published: October 2003

Quasiprobability distributions are derived for arbitrarily polarized spin-1 nuclei using the Margenau–Hill and the Wigner–Weyl correspondence rules.
Perturbative-QCD Approach to Multiparticle Production
Authors: Khoze Valery A. , Ochs Wolfgang
Published: October 2003

In this review we discuss the analytical perturbative approach, based on perturbative QCD and local parton hadron duality (LPHD), and its application to multiparticle production in jets in the semisoft region. Analytical formulae are presented for various observables within the accuracy of the modified leading logarithmic approximation (MLLA), i.e. with terms of relative order [Formula: see text] taken into account systematically, and in some cases with even higher accuracy. These predictions are confronted with existing experimental data. Many details of the perturbative approach to multiple hadroproduction have been consolidated in recent years, and the overall picture is remarkably healthy. The prospects of future studies of the semisoft jet physics are also discussed.
Induced Quantum Fluctuations in the Spherically Symmetric Space–Time
Authors: Nandi Kamal K. , Islam Anwarul , Evans James
Published: October 2003

In the Schwarzschild field due to a mass moving with velocity v → c0, where c0 is the speed of light in vacuum, the source-induced quantum fluctuation in the light cone exhibits consistency with the Aichelburg–Sexl solution while that in the metric dynamical variable does not. At the horizon, none of the fluctuations is proportional to anything finite. However, in the nonrelativistic limit (v → 0), known expressions follow.
Small-Angle Scattering on a System of Magnetic and Electric Charges
Authors: Penttinen M.
Published: October 2003

The generalization of the conformal scattering method for small-angle scattering processes involving magnetic monopoles and ordinary charges is constructed. Using this generalization we show that the introduction of magnetic charges corresponds to analytical continuation of the eikonal amplitude in the complex charge plane (the imaginary part is proportional to the magnetic charge). We calculate explicitly the eikonal amplitude for scattering on a dyon and two monopoles in terms of confluent hypergeometric functions. The singularities of the corresponding amplitudes (focal points) are studied in detail.
Slavnov–Taylor Identities from the Causal Point of View
Authors: Dütsch Michael
Published: October 2003

We continue the investigation of quantized Yang–Mills theories coupled to matter fields in the framework of causal perturbation theory which goes back to Epstein and Glaser. In this approach gauge invariance is expressed by a simple commutator relation for the S matrix and the corresponding gauge transformations are simple transformations of the free fields only. In spite of this simplicity, gauge invariance implies the usual Slavnov–Taylor identities. The main purpose of this paper is to prove the latter statement. Since the Slavnov–Taylor identities are formulated in terms of Green functions, we investigate the agreement of two perturbative definitions of Green functions, namely Epstein and Glaser's definition with the Gell-Mann–Low series.
On the BRST Quantization of the Massless Bosonic Particle in Twistor-Like Formulation
Authors: Bandos Igor , Maznytsia Alexey , Rudychev Igor , Sorokin Dmitri
Published: October 2003

We study some features of bosonic-particle path-integral quantization in a twistor-like approach by the use of the BRST–BFV-quantization prescription. In the course of the Hamiltonian analysis we observe links between various formulations of the twistor-like particle by performing a conversion of the Hamiltonian constraints of one formulation to another. A particular feature of the conversion procedure applied to turn the second-class constraints into first-class constraints is that the simplest Lorentz-covariant way to do this is to convert a full mixed set of the initial first- and second-class constraints rather than explicitly extracting and converting only the second-class constraints. Another novel feature of the conversion procedure applied below is that in the case of the D = 4 and D = 6 twistor-like particle the number of new auxiliary Lorentz-covariant coordinates, which one introduces to get a system of first-class constraints in an extended phase space, exceeds the number of independent second-class constraints of the original dynamical system.

We calculate the twistor-like particle propagator in D = 3,4,6 space–time dimensions and show that it coincides with that of a conventional massless bosonic particle.
Deformed u(2) Algebra as the Symmetry Algebra of the Planar Anisotropic Quantum Harmonic Oscillator with Rational Ratio of Frequencies
Authors: Bonatsos Dennis , Kolokotronis P. , Lenis D. , Daskaloyannis C.
Published: October 2003

The symmetry algebra of the two-dimensional anisotropic quantum harmonic oscillator with rational ratio of frequencies is identified as a deformation of the u(2) algebra. The finite dimensional representation modules of this algebra are studied and the energy eigenvalues are determined using algebraic methods of general applicability to quantum superintegrable systems. For labelling the degenerate states an "angular momentum" operator is introduced, the eigenvalues of which are roots of appropriate generalized Hermite polynomials. The cases with frequency ratios 1:n correspond to generalized parafermionic oscillators, while in the special case with frequency ratio 2:1 the resulting algebra corresponds to the finite W algebra [Formula: see text].
Parametrization of U(N)-Monopoles on Black Holes by the Moduli Space of Holomorphic Vector Bundles Over Two-Sphere and Black Hole Entropy
Authors: Goncharov Yu. P.
Published: October 2003

We discuss how to describe U (N) monopoles on the Schwarzschild and Reissner–Nordström black holes by the parameters of the moduli space of holomorphic vector bundles over S2. For N = 2,3 we obtain such a description in an explicit form as well as the expressions for the corresponding monopole masses. This gives a possibility of adducing some reasonings in favor of existence of both a fine structure for black holes and the statistical ensemble tied with it which might generate the black hole entropy. Also, there arises an analogy with the famous K-theory in topology.
Anomalous Decay of Heavy Fermions by Electroweak Instanton
Authors: Yang Keyan
Published: October 2003

The presence of a heavy fermion doublet in the electroweak instanton probably leads to unsuppressed fermion number nonconservation. By calculating numerically the effective potential barrier of electroweak instanton with heavy fermion in Minkowski space by using semiclassical approximation, it is shown that, if the mass of heavy fermion exceeds a critical value [Formula: see text] TeV (for MH = MW), the tunneling by electroweak instanton should be unsuppressed and the heavy fermion decays with fermion number violation. The dependence of critical fermion mass on the Higgs mass is also presented.
Form Factors for Principal Chiral Field Model with Wess–Zumino–Novikov–Witten Term
Authors: Mejean P. , Smirnov F. A.
Published: October 2003

We construct the form factors of the trace of energy–momentum tensor for the massless model described by SU(2) principal chiral field model with WZNW term on level 1. We explain how this construction can be generalized to a class of integrable massless models including the flow from tricritical to critical Ising model.

From F. Smirnov. During several months I worked with Pierre Mejean. After his premature decease which deeply affected everybody who knew him I decided to collect and to publish the results which we obtained together.
Periods and Prepotential of N = 2 SU(2) Supersymmetric Yang–Mills Theory with Massive Hypermultiplets
Authors: Masuda Takahiro , Suzuki Hisao
Published: October 2003

We derive a simple formula for the periods associated with the low energy effective action of N = 2 supersymmetric SU(2) Yang–Mills theory with massive Nf ≤ 3 hypermultiplets. This is given by evaluating explicitly the integral associated to the elliptic curve using various identities of hypergeometric functions. Following this formalism, we can calculate the prepotential with massive hypermultiplets both in the weak coupling region and in the strong coupling region. In particular, we show how the Higgs field and its dual field are expressed as generalized hypergeometric functions when the theory has a conformal point.
Consistent Two-Dimensional Chiral Gravity
Authors: Smailagic A. , Spallucci E.
Published: October 2003

We study chiral induced gravity in the light-cone gauge and show that the theory is consistent for a particular choice of chiralities. The corresponding Kac–Moody central charge has no forbidden region of complex values. Generalized analysis of the critical exponents is given and their relation to the SL (2,R) vacuum states is elucidated. All the parameters containing information about the theory can be traced back to the characteristics of the residual symmetry group in the light-cone gauge.
Euclidean Thermal Green Functions of Photons in Generalized Euclidean Rindler Spaces for Any Feynman-Like Gauge
Authors: Moretti Valter
Published: October 2003

The thermal Euclidean Green functions for Photons propagating in the Rindler wedge are computed by employing an Euclidean approach within any covariant Feynman-like gauge. This is done by generalizing a formula which holds in the Minkowskian case. The coincidence of the found (β = 2π)-Green functions and the corresponding Minkowskian vacuum Green functions is discussed in relation to the remaining static gauge ambiguity already found in previous works. Further generalizations to more complicated manifolds are discussed. Ward identities are verified in the general case.
Precision Electroweak Data: Present Status and Future Prospects
Authors: Renton Peter B.
Published: October 2003

The present status of precision electroweak data is reviewed. These data include LEP measurements of the mass and width of the Z, together with various measurements on the Z-fermion couplings. These data are compared to, and combined with, data from the SLC on the left–right polarized asymmetry, A LR , and the left–right forward–backward asymmetries for b and c quarks.

These measurements are combined with hadron collider measurements from the Tevatron and CERN on the mass of the W boson, mW, as well as other electroweak data, in global electroweak fits in which various Standard Model parameters are determined. A comparison is made between the results of direct measurements of mW and the top-quark mass, mt, as determined from the Tevatron, with the indirect results coming from electroweak radiative corrections. Using all precision electroweak data, fits are also made to determine limits on the mass of the Higgs boson, mH. The influence on these limits of specific measurements, particularly those which are somewhat inconsistent with the Standard Model, is explored.

The data are also analyzed in terms of the quasi model independent ∊ variables.

Improvements in the determination of all of these quantities are expected when the Z data at LEP are fully analyzed, and further measurements on A LR and related asymmetries performed at the SLC. In addition, substantial improvements in the determination of mW are expected from measurements at the Tevatron and in the second phase of LEP. An estimate is made of the likely precision of these data, and the implications of the impact of these data on precision electroweak tests are discussed. This discussion is made both in terms of the Standard Model and also in the context of the quasi model independent ∊ variables.
Gauge-Invariant Differential Renormalization: The Abelian Case
Authors: Smirnov V. A.
Published: October 2003

A new version of differential renormalization is presented. It is based on pulling out certain differential operators and introducing a logarithmic dependence into diagrams. It can be defined either in coordinate or momentum space, the latter being more flexible for treating tadpoles and diagrams where insertion of counterterms generates tadpoles. Within this version, gauge invariance is automatically preserved to all orders in the Abelian case. Since differential renormalization is a strictly four-dimensional renormalization scheme it looks preferable for application in each situation when dimensional renormalization meets difficulties, especially, in theories with chiral and super symmetries. The calculation of the ABJ triangle anomaly is given as an example to demonstrate simplicity of calculations within the presented version of differential renormalization.
Minimal Models of CFT on ℤN-Surfaces
Authors: Apikyan S. A. , Efthimiou C. J.
Published: October 2003

The conformal field theory on a ℤN-surface is studied by mapping it on the branched sphere. Using a Coulomb gas formalism we construct the minimal models of the theory.
Casimir Effect in the Curved Background and the Black Hole in Three Dimensions
Authors: Nojiri Shin'ichi
Published: October 2003

We consider the quantum correction to the Lagrangian by the massless free boson in the curved background in three dimensions where one of the coordinates is periodic. The correction term is given by an expansion of the metric with respect to the derivative and the first term expresses to the usual Casimir energy. As an application, we investigate the change of the geometry in three dimensional black hole due to the quantum effect and we show that the geometry becomes like that of the Reissner–Nordstrøm solution.
Mixing Angle of Scalar Mesons and Kaon Polarizability in a Chiral Quark σ-Model
Authors: Ebert D. , Volkov M. K. , Feldmann T.
Published: October 2003

Using present data for the decays f0 → γγ, f0 → ππ, we determine the mixing angle of scalar mesons in a chiral quark σ-model. This value is employed for an analysis of the kaon polarizability. It is shown that pole diagrams from intermediate scalar mesons and their mixing angle significantly affect the electromagnetic polarizability of charged and neutral kaons. Our results are compared to other models and the results of the chiral symmetry limit.
BPS Monopoles
Authors: Sutcliffe Paul M.
Published: October 2003

We review classical BPS monopoles, their moduli spaces, twistor descriptions and dynamics. Particular emphasis is placed upon symmetric monopoles, where recent progress has been made. Some remarks on the role of monopoles in S duality and Seiberg–Witten theory are also made.
Manifest Duality in Born–Infeld Theory
Authors: Bengtsson Ingemar
Published: October 2003

Born–Infeld theory is formulated using an infinite set of gauge fields, along the lines of McClain, Wu and Yu. In this formulation electromagnetic duality is generated by a fully local functional. The resulting consistency problems are analyzed and the formulation is shown to be consistent.
Mirror Symmetry of Calabi–Yau Manifolds and Flat Coordinates
Authors: Noguchi Masayuki
Published: October 2003

We study mirror symmetry of Calabi–Yau manifolds within the framework of the Gauss–Manin system. Applying the flat coordinates to the Gauss–Manin system for the periods, we derive differential equations for the mirror map in addition to the ordinary Picard–Fuchs equations for the periods. These equations are obtained for a class of one-parameter models and a two-parameter model of Fermat type Calabi–Yau manifolds.
A Model of Affine Gravity in Two Dimensions and Plurality of Topology
Authors: Ferraris Marco , Francaviglia Mauro , Volovich Igor
Published: October 2003

A new model of two-dimensional gravity with an action depending only on a linear connection is suggested. This model is a topological one, in the sense that the classical action does not contain a metric or zweibein at all. A metric and an additional vector field are instead generated in the process of solving the equations of motion for the connection. The general solution of these equations of motion is given by an arbitrary Weyl connection which can be described by using the space of orbits under the action of the conformal group in the functional space containing all pairs formed by a metric and a vector field. By choosing a gauge one obtains a constant curvature equation. It is shown that this model admits an equivalent description by using a family of Lagrangians depending on the metric and the connection as independent variables. We show that nonlinear Lagrangians in the first order formalism lead to plurality of topology for the manifolds under consideration and give a simple general mechanism of governing topology change.
WW Physics at LEP2
Authors: Miquel Ramon
Published: October 2003

The LEP2 accelerator started producing WW pairs in June 1996. This article summarizes the first physics results obtained with the 1996 data sample and examines the prospects for the whole life of the accelerator, which will run until, at least, 1999. The two main topics on WW physics are discussed in detail: the determination of the W mass and the studies of the couplings among three gauge vector bosons.
Poisson Algebra of Differential Forms
Authors: Chu Chong-Sun , Ho Pei-Ming
Published: October 2003

We give a natural definition of a Poisson differential algebra. Consistency conditions are formulated in geometrical terms. It is found that one can often locally put the Poisson structure on the differential calculus in a simple canonical form by a coordinate trans-formation. This is in analogy with the standard Darboux's theorem for symplectic geometry. For certain cases there exists a realization of the exterior derivative through a certain canonical one-form. All the above are carried out similarly for the case of a complex Poisson differential algebra. The case of one complex dimension is treated in detail and interesting features are noted. Conclusions are made in the last section.
Modified Laplace Transformation Method and ITS Application to the Anharmonic Oscillator
Authors: Mizutani Naoki , Yamada Hirofumi
Published: October 2003

We apply a recently proposed approximation method to the evaluation of non-Gaussian integral and anharmonic oscillator. The method makes use of the truncated perturbation series by recasting it via the modified Laplace integral representation. The modification of the Laplace transformation is such that the upper limit of integration is cutoff and an extra term is added for the compensation. For the non-Gaussian integral, we find that the perturbation series can give an accurate result and the obtained approximation converges to the exact result in the N → ∞ limit (N denotes the order of perturbation expansion). In the case of the anharmonic oscillator, we show that several order result yields good approximation of the ground state energy over the entire parameter space. The large order aspect is also investigated for the anharmonic oscillator.
Construction of Free Energy of Calabi–Yau Manifold Embedded in CPN-1 via Torus Actions
Authors: Jinzenji Masao
Published: October 2003

We calculate correlation functions of topological sigma model (A-model) on Calabi–Yau hypersurfaces in CPN-1 using torus action method. We also obtain path-integral representation of free energy of the theory coupled to gravity.
A Class of N = 1 Dual String Pairs and Its Modular Superpotential
Authors: Curio Gottfried , Lüst Dieter
Published: October 2003

We compare the N = 1F theory compactification of Donagi, Grassi and Witten with modular superpotential — and some closely related models — to dual heterotic models. We read of the F theory spectrum from the cohomology of the fourfold and discuss on the heterotic side the gauge bundle moduli sector (including the spectral surface) and the necessary fivebranes. Then we consider the N = 1 superpotential and show how a heterotic superpotential matching the F theory computation is built up by world sheet instantons. Finally we discuss how the original modular superpotential should be corrected by an additional modular correction factor, which on the F theory side matches nicely with a "curve counting function" for the del Pezzo surface. On the heterotic side we derive the same factor demanding correct T duality transformation properties of the superpotential.
New Realization and Implementation of Fixed-Point IIR Digital Filters
Authors: Tawfik A. , El-Guibaly F. , Agathoklis P.
Published: October 2003

A new low-roundoff noise realization for narrow-band IIR digital filters with residue feedback and a block triangular system matrix is presented. The block triangular form of the system matrix allows a reduction in the number of arithmetic operations required for the implementation and leads also to a realization which is suitable for high speed implementation. Numerical comparison between the proposed structure and three other low-noise structures shows that the proposed structure provides excellent performance in terms of output roundoff noise and coefficient sensitivity. The output roundoff noise is slightly higher than that of the optimal residue feedback realization proposed by Williamson9 but lower than the optimal realization without residue feedback proposed by Mullis, Roberts and Hwang.6,7 Further an efficient (in terms of speed) VLSI processor array implementation of the proposed IIR structure is also presented. The proposed implementation has been obtained by taking advantage of both the parallel feature of the residue feedback and the block triangular structure of the system matrix of the proposed realization. A hardware comparison between the proposed implementation and another implementation which is based on direct form shows that the proposed implementation provides a higher sampling rate for any narrow-band filter.
Bifurcation of Homoclinic Orbits to a Saddle-Center in Reversible Systems
Authors: Klaus J. , Knobloch J.
Published: October 2003

We consider two-parameter families of reversible vector fields having (at the critical parameter value) a homoclinic orbit to a nonhyperbolic fixed point. The nonhyperbolicity is due to a pair of purely imaginary eigenvalues. We give a complete description of the bifurcating one-homoclinic orbits to the center manifold. For that purpose we adapt Lin's method.
Controlling the Chaotic n-Scroll Chua's Circuit
Authors: Zou Yan-Li , Luo Xiao-Shu , Jiang Pin-Qun , Wang Bing-Hong , Chen Guanrong , Fang Jin-Qing , Quan Hong-Jun
Published: October 2003

In this paper, controlling chaos in the chaotic n-scroll Chua's circuit is studied. The approach taken is to use feedback of a single state variable in a simple PD (proportional and differential) format. First, the unstable fixed points in the n-scroll Chua's circuit are classified into two different types according to the characteristics of the eigenvalues of the linearized system matrix at the fixed points. Then, the controllability of these two-types of fixed points is studied. Theoretical analysis shows that the first type of unstable fixed points can be stabilized, at which Hopf bifurcation can also be generated. Control results of the n-scroll Chua's circuit are then demonstrated. Both theoretical analysis and numerical simulation results show that the proposed chaos control method is indeed effective.
Nucleation from the Boundaries in Excitable Media
Authors: deCastro M. , Gómez-Gesteira M. , Lorenzo M. N. , Pérez-Muñuzuri V.
Published: October 2003

Nucleation from a boundary is experimentally and numerically studied in a one-dimensional array in two excitable media consisting of Chua's circuits and the Oregonator model, respectively. Forcing from a boundary with a pulse of constant amplitude and infinite duration gives rise to a periodic wave train propagating through the array. As the amplitude of the pulse increases, wave period evolves to chaos through a period doubling cascade.
Parallelizing an Algorithm for Visibility on Polyhedral Terrain
Authors: Teng Y. Ansel , Mount David , Puppo Enrico , Davis Larry S.
Published: October 2003

The best known output-sensitive sequential algorithm for computing the viewshed on a polyhedral terrain from a given viewpoint was proposed by Katz, Overmars, and Sharir,10 and achieves time complexity O((k + nα(n)) log n) where n and k are the input and output sizes respectively, and α() is the inverse Ackermann's function. In this paper, we present a parallel algorithm that is based on the work mentioned above, and achieves O( log 2n) time complexity, with work complexity O((k + nα(n)) log n) in a CREW PRAM model. This improves on previous parallel complexity while maintaining work efficiency with respect to the best sequential complexity known.
The Rectangle Enclosure and Point-Dominance Problems Revisited
Authors: Gupta Prosenjit , Janardan Ravi , Smid Michiel , Dasgupta Bhaskar
Published: October 2003

We consider the problem of reporting the pairwise enclosures in a set of n axes-parallel rectangles in ℝ 2, which is equivalent to reporting dominance pairs in a set of n points in ℝ 4. Over a decade ago, Lee and Preparata7 gave an O(n log n + k)-time and O(n)-space algorithm for these problems, where k is the number of reported pairs. Since that time, the question of whether there is a faster algorithm has remained an intriguing open problem.

In this paper, we give an algorithm which uses O(n + k) space and runs in O(n log n log log n + k log log n) time. Thus, although our result is not a strict improvement over the Lee-Preparata algorithm for the full range of k, it is, nevertheless, the first result since Ref. (6) to make any progress on this long-standing open problem. Our algorithm is based on the divide-and-conquer paradigm. The heart of the algorithm is the solution to a red-blue dominance reporting problem (the "merge" step). We give a novel solution for this problem which is based on the iterative application of a sequence of non-trivial sweep routines. This solution technique should be of independent interest. We also present another algorithm whose bounds match the bounds given in Ref. (6), but which is simpler. Finally, we consider the special case where the rectangles have a small number, α, of different aspect ratios, which is often the case in practice. For this problem, we give an algorithm which runs in O(α n log n + k) time and uses O(n) space.
Root Lattices are Efficiently Generated
Authors: Rajan Dayanand S. , Shende Anil M.
Published: October 2003

We show that root lattices are exactly those lattices whose relevant vectors are all equal in length. We define notions of "compatibility" between the euclidean metric and the shortest path metric in the infinite directed graph induced by a subset, G, of a lattice, i.e., the directed graph whose vertices are the points in the lattice, and whose arcs are the ordered pairs (x, x+g), with x a lattice point and g a point in G. We present some ("easy to check for") criteria that a lattice and a subset of it must satisfy to ensure "compatibility" between the corresponding graphical and the euclidean metrics. We use these criteria to characterize, in more than one way, a set of "economically and efficiently generated" lattices, including root lattices. Our results include a "graph theoretic" characterization of root lattices as well. We also discuss, in brief, certain algorithmic considerations in the simulation of macroscopic physical phenomena in massively parallel computers based on suitable discretizations of euclidean space that led us to our graphical treatment of lattices.
On the Semantics of Arbitration
Authors: Revesz Peter Z.
Published: October 2003

Revision and update operators add new information to some old information represented by a logical theory. Katsuno and Mendelzon show that both revision and update operators can be characterized as accomplishing a minimal change in the old information to accommodate the new information. Arbitration operators add two or more weighted informations together where the weights indicate the relative importance of the informations rather than a strict priority. This paper shows that arbitration operators can be also characterized as accomplishing a minimal change. The operator of model-fitting is also defined and analyzed in the paper.
Asphericity Tests
Authors: Klyachko Anton A.
Published: October 2003

In paper [5] the classical Kervaire-Laudenbach conjecture for torsion-free groups is proved. The proof is based on an amazing geometrical fact. Here we prove that this fact is a special case of a statement similar to the well-known Bogley-Pride weight test [2]. This article describes all analogous tests and demonstrates some of their applications to the theory of equations over groups.
Compactness of Systems of Equations in Semigroups
Authors: Harju T. , Karhumäki J. , Plandowski W.
Published: October 2003

We consider systems ui=vi(i∈I) of equations in semigroups over finite sets of variables. A semigroup (or a monoid) S is said to satisfy the compactness property (CP, for short), if each system of equations has an equivalent finite subsystem. We prove that all monoids in a variety [Formula: see text] satisfy CP if and only if the finitely generated monoids in [Formula: see text] satisfy the maximal condition on congruences. Consequently, all commutative monoids (and semigroups) satisfy CP. Also, if a finitely generated semigroup S satisfies CP, then S is necessarily hopfian and satisfies the chain condition on idempotents. It follows that the free inverse semigroups do not satisfy CP. Finally, we give two simple examples (the bicyclic monoid and the Baumslag-Solitar group) which do not satisfy CP, and show that the necessary conditions above are not sufficient.