bluuebunny/crossref_metadata_2025 huggingface dataset:
Incidence of cancer among bookbinders, printers, photoengravers, and typesetters
Authors: Rafnsson V
Published: July 2002

OBJECTIVES

To to study the risk of cancer, particularly of lung cancer and bladder cancer, among workers in the printing industry according to different occupations.

METHODS

This is a population based retrospective cohort study. The cohort comprised 1332 men and 426 women employed in the printing industry in Iceland according to a published union registry. A computerised file of the cohort was record linked to the Cancer Registry by making use of personal identification numbers. Expected numbers of cases of cancer were calculated on the basis of number of person-years and specific incidences of cancer sites for men and women provided by the Cancer Registry.

RESULTS

Among the men (36 217.5 person-years at risk) there were 125 observed cancers versus 123.66 expected, standardised incidence ratio (SIR) 1.01, 95% confidence interval (95% CI) was 0.84 to 1.20. The SIR (95% CI) for liver cancer was 1.97 (0.55 to 5.20) and the SIR for non-Hodgkin's lymphoma was 2.26 (0.96 to 4.41). No excess risk for cancer was found among women (8631.0 person-years at risk). The SIR (95% CI) for liver cancer was 4.21 (0.47 to 15.20) and for non-Hodgkin's lymphoma it was 4.99 (1.61 to 11.63) among the typesetters. A survey on smoking habits among active and retired union members showed that they smoked less than a random sample of the general population.

CONCLUSION

The cancer site most often reported to show excess risk among printing industry workers has been the lung and the urinary bladder; however, this was not found in the present study. This may be explained by difference in smoking habits among union members compared with the general population. There is a high occurrence of non-Hodgkin's lymphoma, particularly among typesetters, which warrants further studies.
Bryophyte community structure in a boreal poor fen II: interspecific competition among five mosses
Authors: Mulligan Roisín C , Gignac L Dennis
Published: July 2002

A possible competitive hierarchy among five boreal bryophytes (Sphagnum angustifolium, Sphagnum fuscum, Sphagnum magellanicum, Ptilium crista-castrensis, and Pleurozium schreberi) was examined in a 2-year transplant experiment conducted in two habitats of a poor fen in northern Alberta, Canada, using a sixth moss (Aulacomnium palustre) as a phytometer. Change in relative growth rate in length and weight of A. palustre, measured as competitive effect, indicated the existence of a hierarchy in this peatland wherein the feather mosses are subordinates to the Sphagnum mosses. Relative competitive performance, which was calculated relative to the growth of the phytometer in monoculture, indicated that S. magellanicum exhibited the greatest competitive effect. Sphagnum magellanicum may be a strong competitor and partially inhibit S. fuscum from occupying its full fundamental niche. The competitive ability of S. fuscum and S. angustifolium in this peatland is low relative to that of the other study species. The feather mosses did not demonstrate competitive effect and may have facilitated growth of the phytometer.Key words: bryophyte, competition, feather moss, peatland, phytometer, Sphagnum.
Phyllosphere fungi on leaf litter of Fagus crenata: occurrence, colonization, and succession
Authors: Osono Takashi
Published: July 2002

Phyllosphere fungi occur on various litters, but the ecology of these fungi on leaf litter has received little attention. To investigate the occurrence, colonization, and succession of phyllosphere fungi on leaf litter of Fagus crenata Blume, fungi were isolated from living, senescent, freshly fallen, and decomposing leaves by surface sterilization and washing methods. A total of 18 and 47 fungal species were isolated from the interior and surface of living and senescent leaves, respectively, and 15 frequent species were regarded as phyllosphere fungi. These fungi were divided into three groups according to their frequency on freshly fallen and decomposing leaves. Nine species (Group I) occurred frequently on decomposing leaves, two species (Group II) on freshly fallen leaves only, and four species (Group III) were frequent on living or senescent leaves only. Colonization of sterilized, freshly fallen leaves by phyllosphere fungi was investigated to test their ability to infect litter directly after litter fall. Frequencies of four species were lower on sterilized leaves than on unsterilized leaves, whereas frequencies of other species did not differ between sterilized and unsterilized leaves. Successional trends of endophytes and epiphytes were observed during decomposition from freshly fallen to decomposing leaves. The sum of frequencies of endophytes decreased temporarily on freshly fallen leaves and increased on decomposing leaves. The sum of frequencies of epiphytes decreased from freshly fallen to decomposing leaves.Key words: beech, decomposition, endophyte, epiphyte, Xylariaceae.
A molecular phylogenetic study of two relict species of melanopline grasshoppers
Authors: Chapco W , Litzenberger G
Published: July 2002

Two species belonging to the large grasshopper genus Melanoplus, Melanoplus gaspesiensis and Melanoplus madeleineae, are thought to have survived in refugia in eastern Canada during the Wisconsin glaciation period and perhaps during earlier glacial episodes as well. It has been proposed that either Melanoplus borealis, which is widely distributed today, or its antecedent gave rise to the two relict species. Our research, based on standard phylogenetic analyses of mitochondrial sequences, examines this claim by establishing the positions of M. gaspesiensis and M. madeleineae within Melanoplus. There is a very close and strongly supported connection between M. madeleineae and M. borealis (d = 1.36%), whereas M. gaspesiensis is more distant from the latter (d = 2.08%) and appears closely aligned with two other species. Molecular clock estimates of the times of separation of M. madeleineae and M. gaspesiensis from M. borealis are 0.68 and 1.04 million years ago, respectively. Within-species diversities of 1.01 and 0.70% for M. madeleineae and M. gaspesiensis, respectively, are of comparable magnitudes to that of the continentally distributed Melanoplus sanguinipes (0.86%), clearly indicating that neither species endured bottleneck effects despite isolation.Key words: grasshopper, Melanoplus, relict species, mtDNA.
Distribution of moments in reinforced concrete slabs with continuous drop panels
Authors: Paultre Patrick , Moisan Caroline
Published: July 2002

Slabs with continuous drop panels between column lines facilitate formwork, make long spans possible in addition to increase punching shear resistance around supports and provide unobstructed spans with minimum structural floor depth resulting in lower floor-to-floor heights. The moment distribution in such slabs is different from that in conventional flat plates or slabs with drop panels systems. Dimensioning according to the current provisions in CSA A23.3-94 is problematic because the continuous drop panels are subject to moments exceeding the minimum values allowed by the Code for conventional slab systems. This analytical study presents the moment distribution in slabs with continuous drop panels in an attempt to provide more realistic transverse moment distribution factors.Key words: reinforced concrete, slab systems, slab design, drop panel, moment distribution.
Reaction of the tamoxifen cation and the bis-(4-methoxyphenyl)methyl cation in aqueous solutions containing 2'-deoxyguanosine
Authors: McClelland Robert A , Sanchez Cristina , Sauer Effiette , Vukovic Sinisa
Published: July 2002

The competition between 2'-deoxyguanosine (dG) and water has been quantitatively evaluated for the allylic carbocation derived from tamoxifen and for the stabilized diarylmethyl cation (bis-(4-methoxyphenyl)methyl). Both systems were examined by the competition kinetics method, in which the products were quantitatively analyzed after the SN1 solvolysis of the corresponding acetate esters in aqueous solutions containing the nucleoside. The principal product of the reaction of both cations with dG is the adduct at the NH2 group, a characteristic of delocalized carbocations. The tamoxifen cation was also examined by laser flash photolysis, with absolute rate constants for the reaction with dG and water being obtained and converted into rate constant ratios. The principal result of this study is that there is a three orders of magnitude difference in the reactivity of these cations towards the neutral form of dG and its conjugate base. Under acidic conditions where the reaction occurs with neutral dG, the guaninewater selectivity is low. Even at relatively high concentrations of dG, the majority of the product is alcohol derived from the water reaction. At pH 10 to 11, in contrast, dG is present as the anion and this is highly competitive. Yields of adduct as high as 90% can be attained. A consequence of the large difference in reactivities is that at neutral pH the majority of the reaction of the cation with dG is actually occurring via the small amount of conjugate base present. A further feature of the results is that the NH2 adduct is the predominant stable product from the anion. To explain the high rate constant for the reaction forming this product, a mechanism is proposed whereby one of the protons of the NH2 group is transferred to N1 as the N2-cation bond is forming.Key words: guanine, DNA adduct, carbocation, tamoxifen.
Estimating net primary production of forests in the Canadian Prairie Provinces using an inventory-based carbon budget model
Authors: Li Zhong , Apps Michael J , Banfield E , Kurz Werner A
Published: July 2002

The Carbon Budget Model of the Canadian Forest Sector (CBM-CFS2) is a forest inventory-based ecosystem simulation model. It has been used previously for both retrospective and projective analyses of the carbon pools and fluxes of the Canadian forest ecosystems at the national, regional, and stand level. The objective of this study was to determine and evaluate forest net primary production (NPP) in the three Prairie Provinces in west-central Canada, as estimated by the model. The model simulated an averaged aboveground NPP (NPPA) of 172 g C·m2·year1 for the regional forests, varying from 72 to 293 g C·m2·year1, depending on ecoclimatic province, forest type, age, and site productivity. Comparisons of NPPA estimates for the boreal forest (165179 g C·m2·year1) with results from direct measurements, modeling, and empirical calculations show that the CBM-CFS2 produced reasonable estimates of NPPA. The model incorporates different types of disturbances such as wildfire, harvesting, and insects and is able to evaluate NPP changes with stand age. However, belowground NPP may be overestimated, especially for young and unproductive stands. This can be explained by the current parameter estimates for the fine-root component of belowground biomass and for fine-root turnover rates.
RIGOROUS SEMICLASSICAL RESULTS FOR THE MAGNETIC RESPONSE OF AN ELECTRON GAS
Authors: COMBESCURE MONIQUE , ROBERT DIDIER
Published: July 2002

Consider a free electron gas in a confining potential and a magnetic field in arbitrary dimensions. If this gas is in thermal equilibrium with a reservoir at temperature T>0, one can study its orbital magnetic response (omitting the spin). One defines a conveniently "smeared out" magnetization M, and the corresponding magnetic susceptibility χ, which will be analyzed from a semiclassical point of view, namely when ℏ (the Planck constant) is small compared to classical actions characterizing the system. Then various regimes of temperature T are studied where M and χ can be obtained in the form of suitable asymptotic ℏ-expansions. In particular when T is of the order of ℏ, oscillations "à la de Haas-van Alphen" appear, that can be linked to the classical periodic orbits of the electronic motion.
INTERACTING QUANTUM FIELDS
Authors: JOHNSON GLENN ERIC
Published: July 2002

A wide class of quantum field theories (QFTs) describing interacting neutral scalar bosons are constructed. It is shown that a redefinition of the vacuum expectation values (VEV) of quantum fields as generalized functions leads to constructions of interacting fields that are operators in a Hilbert space and satisfy the physical requirements for a field theory. The field operators are constructed directly, without perturbation expansion, and constructed in spacetime of any number of dimensions. The corresponding scattering theory is developed. The limited function class underlying the QFT imposes a direction to time.
NON-COMMUTATIVE POLYNOMIAL RECIPROCITY FORMULAE
Authors: FUKUHARA SHINJI , MATSUMOTO YUKIO , YUI NORIKO
Published: July 2002

We prove non-commutative reciprocity formulae for certain polynomials using Fox's free differential calculus. The abelianizations of these reciprocity formulae rediscover the polynomial reciprocity formulae of Carlitz and Berndt–Dieter. Further, many other reciprocity formulae related to Dedekind sums are rederived from our polynomial reciprocity formulae; these include, for instance, generalizations of the classical Eisenstein reciprocity formula.
A SEMICONTINUOUS TRACE FOR ALMOST LOCAL OPERATORS ON AN OPEN MANIFOLD
Authors: GUIDO DANIELE , ISOLA TOMMASO
Published: July 2002

A semicontinuous semifinite trace is constructed on the C*-algebra generated by the finite propagation operators acting on the L2-sections of a Hermitian vector bundle on an amenable open manifold of bounded geometry. This trace is the semicontinuous regularization of a functional already considered by J. Roe. As an application, we show that, by means of this semicontinuous trace, Novikov–Shubin numbers for amenable manifolds can be defined.
UNIQUENESS POLYNOMIALS FOR ENTIRE FUNCTIONS
Authors: CHERRY WILLIAM , WANG JULIE TZU-YUEH
Published: July 2002

A polynomial P is called a strong uniqueness polynomial for the family of non-constant entire functions on the complex plane if one cannot find two distinct non-constant entire functions f and g and a non-zero constant c such that P(f)=cP(g). We give necessary and sufficient geometric conditions on the divisor of zeros of P that P be a strong uniqueness polynomial for the family of non-constant entire functions on the complex plane.
THE PHYSICAL SIGNIFICANCE OF CONFIDENCE INTERVALS
Authors: GIUNTI CARLO , LAVEDER MARCO
Published: July 2002

We define some appropriate statistical quantities that indicate the physical significance (reliability) of confidence intervals in the framework of both Frequentist and Bayesian statistical theories. We consider the expectation value of the upper limit in the absence of a signal (that we propose to call "exclusion potential", instead of "sensitivity" as done by Feldman and Cousins) and its standard deviation, we define the "Pull" of a null result, expressing the reliability of an experimental upper limit, and the "upper and lower detection functions", that give information on the possible outcome of an experiment if there is a signal. We also give a new appropriate definition of "sensitivity", that quantifies the capability of an experiment to reveal the signal that is searched for at the given confidence level.
CHAOS IN PIECEWISELY INTEGRABLE TRAIN MODEL FOR TWO BLOCKS
Authors: SZKUTNIK J. , KUŁAKOWSKI K.
Published: July 2002

The train model of two blocks with stick-slip dynamics (M. de Sousa Vieira, 1995) is believed to be the simplest spring-block system, which displays chaos. Here we simplify it even more by linearizing the velocity dependence of the friction force. In this way, the nonlinearity of the equations of motion is reduced to the time moments, when a block starts to move or stops, and when the analytical solutions are to be sewn together. We demonstrate, that for small values of the velocity of blocks, the character of motion is not changed. This is observed on the bifurcation diagrams, the Lyapunov exponents, the phase portraits and the power spectra.
A MODULAR DESCRIPTION OF THE GEOMETRY IN MONTE CARLO MODELING STUDIES FOR NUCLEAR MEDICINE
Authors: BOLLINI D. , CAMPANINI R. , LANCONELLI N. , RICCARDI A. , GOMBIA M.
Published: July 2002

EGS is a very popular Monte Carlo code, used in the simulation of Nuclear Medicine devices. Simulation techniques are particularly effective to optimize collimator configuration and camera design in Single Photon Emission studies. With the EGS code, users must define the geometry where particles are transported. This can be both a very hard task and a source of inefficiency, especially in the case of complex geometries as, for instance, hexagonal hole collimators or pixellated detectors. In this paper we present a modular description of such geometries. Our method allows the computation of the region a point belongs to in a few steps; thus we are able to calculate this region in a reduced number of operations, independently of the collimator and detector dimensions. With a modular description we can reduce the computational time by 30%, with respect to a "traditional" description of the geometry. We validated the modular description in the simulation of a Nuclear Medicine apparatus for scintimammography. Two different collimators have been considered: one with square holes and one with hexagonal holes. We accomplished their characterization and tested their performance in a torso–breast phantom. Outcomes of the two collimators are comparable, even if it seems that the hexagonal hole collimator, thanks to its greater septal penetration, could give slightly better results for small tumors located near the collimator.
AN IMPLICIT METHOD FOR DATA PREDICTION AND IMPULSE NOISE REMOVAL FROM CORRUPTED SIGNALS
Authors: ZHANG DE S. , WANG HAIXIANG , KOURI DONALD J. , HOFFMAN DAVID K.
Published: July 2002

A robust and reliable implicit method is proposed for application in data interpolation. The algorithm is based on a recently developed analytic approximation method, namely the distributed approximating functionals (DAFs), which is known to have the "well-tempered" property of UNIFORMLY approximating a function and its derivatives. In comparison with the conventionally used local explicit interpolation algorithms, the implicit method achieves much more accurate interpolation results because it couples all sample values (both known and unknown) in the domain of interest using a set of simultaneous linear algebraic equations. Due to the fact that the well-tempered DAFs also are very good low-pass filters, the performance of the DAF-based implicit method is not affected very much by the high frequency noise in the input signal. As an application, the proposed algorithm is applied to signals that are corrupted with impulse noise.
NOTE ON THE DUAL BRST SYMMETRY IN GAUGE THEORY
Authors: GAETE PATRICIO
Published: July 2002

We analyze the relation between the Lagrangian and Hamiltonian BRST symmetry generators for a recently proposed two-dimensional symmetry. In particular it is shown that this symmetry may be obtained from a canonical transformation in the ghost sector in a gauge-independent way.
ERG AND SCHWINGER-DYSON EQUATIONS – COMPARISON IN FORMULATIONS AND APPLICATIONS –
Authors: TERAO HARUHIKO
Published: July 2002

The advantageous points of ERG in applications to non-perturbative analyses of quantum field theories are discussed in comparison with the Schwinger-Dyson equations. First we consider the relation between these two formulations specially by examining the large N field theories. In the second part we study the phase structure of dynamical symmetry breaking in three dimensional QED as a typical example of the practical application.
TOWARDS STRING PREDICTIONS
Authors: CLEAVER G. B. , NANOPOULOS D. V. , FARAGGI A. E. , TER VELDHUIS T.
Published: July 2002

The aim of superstring phenomenology is to develop the tools and methodology needed to confront string theory with experimental data. The first mandatory task is to find string solutions which reproduce the observable data. The subsequent goal is to extract potential signatures beyond the observable data. Recently, by studying exact flat directions of non-Abelian singlet fields, we demonstrated the existence of free fermionic heterotic string models in which the SU(3) × SU(2) × U(1) Y-charged matter spectrum, just below the string scale, consists solely of the MSSM spectrum. In this paper we study the possibility that the exact flat directions leave a U(1) Z′ symmetry unbroken at the Planck scale. We demonstrate in a specific example that such unbroken U(1) Z′ is in general expected to be not of the GUT type but of intrinsic stringy origin. We study its phenomenological characteristics and the consequences in the case that U(1) Z′ remains unbroken down to low energies. We suggest that observation in forthcoming colliders of a Z′, with universal couplings for the two light generations but different couplings for the heavy generation may provide evidence for the Z2 × Z2 orbifold which underlies the free fermionic models.
CONDENSED MATTER PHYSICS — BIOLOGY RESONANCE
Authors: BASKARAN G.
Published: July 2002

The field of condensed matter physics had its genesis this century and it has had a remarkable evolution. A closer look at its growth reveals a hidden aim in the collective consciousness of the field — a part of the development this century is a kind of warm up exercise to underst and the nature of living condensed matter, namely the field of biology, by a growing new breed of scientists in the coming century. Through some examples the vitality of this interaction will be pointed out.
ERRATA: FERMIONIC AND BOSONIC SELF-ORGANIZED NETWORKS: A REPRESENTATION OF QUANTUM STATISTICS
Authors: BIANCONI GINESTRA
Published: July 2002

A new class of self organized networks is described that is relevant to understand the emerging order in a large number of complex systems such as biological systems, the web, and heterogeneous phases in high Tc superconductors. The Bose and Fermi quantum distributions are shown to be the right tool to describe the two extreme limit distributions, the scale-free and the Cayley-tree network respectively. The new class of self-organized networks is described by a 'mixed' quantum distribution. Here the bosonic and fermionic types of self organization coexists, maintaining the same 'ergodic' nature.
TWO-PHASE NUCLEI IN PARAELECTRIC PHASE OF Pb1-x(Li1/2La1/2)x(Zr1-yTiy)O3 SOLID SOLUTIONS
Authors: SOBOLEV V. L. , ISHCHUK V. M.
Published: July 2002

The phase transition from the paraelectric phase to ordered phases in Pb1-x(Li1/2La1/2)x(Zr1-yTiy)O3 with compositions close to the ferroelectric - antiferroelectric - paraelectric triple point in the Ti-content - temperature phase diagram is studied. X-ray diffraction is used to identify two - phase (antiferroelectric and ferroelectric) nuclei embeded in a paraelectric matrix. The relation between these two-phase nuclei in paraelectric phase and the diffuseness of the phase transition is discussed.
EXCITATION DYNAMICS AND ITS ELECTRIC FIELD DEPENDENCE OF MESO,MESO-LINKED PORPHYRIN ARRAYS IN A POLYMER FILM
Authors: OHTA N. , IWAKI Y. , OSUKA A. , ARATANI N.
Published: July 2002

External electric field effects both on absorption spectra and on fluorescence spectra of meso,meso-linked porphyrin arrays doped in a polymer film have been examined using electric field modulation spectroscopy with the number of linked porphyrins (N) from 1 to 48. The magnitudes of the change in electric dipole moment (Δμ) and in molecular polarizability (Δα) are evaluated for excitation into each of the exciton splitting components of the Soret band, and excitation dynamics has been discussed. Field-induced quenching of fluorescence occurs, as the number of N increases, suggesting that nonradiative process(es) at the emitting state is significantly enhanced by an electric field, as N increases.
EXCITONIC PHOTOLUMINESCENCE IN PENTACENE SINGLE CRYSTAL
Authors: AOKI-MATSUMOTO T. , FURUTA K. , YAMADA T. , MORIYA H. , MIZUNO K. , MATSUI A. H.
Published: July 2002

Photoluminescence of pentacene single crystals is studied in the temperature range of 7 K to 200 K under excitation with He-Ne laser light. Photoluminescence spectra consist of four broad bands, L1 to L4. The highest energy band, L1, located close to the lowest exciton absorption band mainly appears for //b-polarization. The intensity of the second one, L2, with Stokes-shift of about 1500 cm -1, decreases as temperature rises above 30 K and disappears at 100 K. The bands, L3 and L4, which are located at lower energy, are observed at higher temperatures up to 200 K. Based on their energy positions, the band L2 is assigned to a shallow self-trapped exciton luminescence band, and the bands L3 and L4 to deep self-trapped exciton luminescence bands. By comparing this result with reported result on tetracene crystals, self-trapped excitons are considered to be more stable in pentacene.
INTERFACIAL BEHAVIOR OF NICALON-FIBER-FEINFORCED GLASS-CERAMIC MATRIX COMPOSITE DUE TO CREEP-CONDITIONING
Authors: WIDJAJA S. , YIP T. H. , LIMARGA A. M. , LI S.
Published: July 2002

Creep-conditioning had been shown to be effective in inducing a compressive residual stress in the matrix of SiC-fiber-reinforced BMAS glass-ceramic matrix composite. The increase in the compressive stress in the matrix manifested in the increase in the proportional limit of the crept specimens, as compared to that of the as-received. The change of residual stresses in the composite due to creep-load transfer was evaluated through mechanical testing and X-ray diffraction. Microstructural studies on the fracture surfaces and fiber/matrix interface showed that no interfacial reaction or any significant change in the failure behavior of the composite was observed. Interfacial sliding stress at the interface, obtained from a fiber push-out test, revealed that essentially there was no change in the normal clamping stress. The results confirmed that creep-conditioning treatment, intended to increase the matrix cracking stress, could be successfully applied to composite materials without sacrificing the "composite-like" fracture behaviors.
CRYSTALLINE PHASE SEPARATION OF InGaN LAYER MATERIALS PREPARED BY METALORGANIC CHEMICAL VAPOR DEPOSITION
Authors: FENG ZHE CHUAN , YANG TZUEN RONG , LIU RONG , WEE ANDREW THYE SHEN
Published: July 2002

Zn -doped InGaN thin films were epitaxied on the top of 1-2 micron thick GaN grown on sapphire by metal organic chemical vapor deposition, and studied by a combination of high resolution X-ray diffraction (HR-XRD), micro-photoluminescence (PL) and secondary ion mass spectrometry (SIMS). HRXRD exhibits a GaN band and a single band from InGaN for samples without phase separation, but two or more InGaN bands corresponding to different x(In) for samples with phase separation. PL emissions from InGaN spread over a wider energy ranges and were modulated by the interference effects. Excitation power dependence measurements reveal 2-sets of PL emissions for samples with phase separation, but only 1-set for samples without phase separation. SIMS data showed that phase separated InGaN:Zn films possess a high Zn concentration near the InGaN-GaN interface and non-uniform distributions of In and Zn contents, which are in contrast with data from InGaN:Zn films with no In -phase separation. These interesting results are correlated to the growth process and microstructural properties.
ADSORPTION AND DIFFUSION OF Si ON THE Si(001): AN EMPIRICAL POTENTIAL CALCULATION
Authors: CAI JUN , WANG JIAN-SHENG
Published: July 2002

A recently developed potential function for covalent materials (Phys. Stat. Sol.B212, 9 (1999)) is used to simulate the surface adsorption, and diffusion of Si adtom and ad-dimer on the Si(001) surface. We calculate the formation energies and diffusion activation energies of several possible binding sites. The predicted stable and metastable configurations and diffusion paths of Si ad-atom and Si ad-dimer on Si(001)-(2×1) surface are in agreement with that from the first principle calculations or experiments.
ELECTRONIC AND DYNAMICAL PROPERTIES OF MgB2 AND RELATED COMPOUNDS
Authors: PROFETA G. , CONTINENZA A. , BERNARDINI F. , SATTA G. , MASSIDDA S.
Published: July 2002

We report a detailed study of the electronic and dynamical properties of MgB2 , BeB2 and of the AlMgB4 superlattice, within the local density approximation to the density functional theory. On the basis of our results we discuss the superconducting properties of these systems, and point to the high T c in MgB2 as a fortunate combination of events.
LOCAL STRUCTURE OF PHOTO-INDUCED PHASES PROBED BY X-RAY ABSORPTION SPECTROSCOPY: PHOTO-INDUCED ANISOTROPY IN CHALCOGENIDE GLASSES
Authors: OYANAGI H. , KOLOBOV A. , TANAKA K.
Published: July 2002

We describe X-ray absorption spectroscopy (XAS) technique to probe the local structure of photo-induced phase. Photo-induced melting of chalcogenide glass (amorphous selenium, a-Se) was investigated. A grazing-incidence fluorescence excitation and a high efficiency X-ray detector were used to detect a small change of coordination number due to photo-induced transformation. It was shown that photo-induced three-fold coordinated sites are formed upon light irradiation forming cross-linking between selenium chains (photo-induced melting). A simple model is proposed which describes the reorientation of selenium chain perpendicular to the polarization direction of excitation light leading to photo-induced dichroism (anisotropy). Potential of XAS as a local probe of nanoscale structural modifications induced by photo-excitation is clearly demonstrated.
Influence of the Deposition Techniques on the Quality of the Epitaxial Buffer Layers on Textured Ni Substrates
Authors: Fabbri F. , Boffa V. , Celentano G. , Ciontea L. , Galluzzi V. , Petrisor T. , Ceresara S. , Scardi P.
Published: July 2002

In order to fabricate high temperature superconducting tapes for power applications, we have analysed different buffer layer architectures grown on textured Ni substrates suitable for YBCO deposition. Due to its optimal lattice matching the studied structures present as top layer a CeO 2 film. The deposition of CeO 2 on Ni substrates was performed by pulsed laser ablation and by e-beam evaporation at different temperatures. The films obtained by the two deposition techniques have not optimal structural properties, having a polycrystalline component. The misorientation of CeO 2 is probably due to the formation of NiO at the interface between the film and the substrate during the deposition process even if no oxygen is introduced. In order to prevent Ni oxidation an intermediate 2000 Å Pd thick film was deposited by e-beam. Furthermore, the lattice mismatch between Pd and CeO 2 is smaller than that between Ni and CeO 2. The Pd layer inhibits nickel oxide formation and improves the CeO 2 epitaxial growth: the XRD pattern contains only the (001) peaks of Pd and CeO 2. SEM analysis on CeO 2/Pd/Ni shows a smooth surface free of cracks, contrary to that observed for CeO 2/Ni structure.
Experimental Results in Eddy Current Non Destructive Testing Based on Superconductive and Conventional Electromagnetic Probes
Authors: Valentino M. , Ruosi A. , Pepe G. , Mollo V. , D'Alto R. , Peluso G.
Published: July 2002

This paper deals with the electromagentic nondestructive testing performed by SQUID magnetometry on stratified aluminum alloy plates as those commonly encountered in the aircraft industry. The anomalous magnetic fields generated by flaws with know electromagnetic characteristics have been modeled by a three-dimensional specific code based on a finite element formulation. The numerical solution has correctly predicted the shape of the complicated magnetic field response due to the defect. Once accuracy and reliability of experimental data taken by superconductive probe have been tested, a benchmark-like problem has been faced. Measurements performed by conventional probes like fluxgate and inductive coil have been compared with the ones taken by innovative device based on superconductive materials.
Microwave Third Harmonic Emission by Ba0.6K0.4BiO3 Crystals
Authors: Gallitto A. Agliolo , Guccione M. , Vigni M. Li
Published: July 2002

We report a set of experimental results on microwave third-harmonic emission by Ba 0.6 K 0.4 BiO 3 crystals. Third-harmonic signals are investigated as a function of temperature, input power level and intensity of the static magnetic field. The experimental data are discussed in the framework of models previously reported in the literature.
d-Wave Tunnel Junctions
Authors: Cucolo A. M. , Cuoco M. , Noce C.
Published: July 2002

We study the tunneling spectra for superconductor-insulator-normal metal (S-I-N) tunnel junctions with an s -wave or a d -wave superconductor within the weak-coupling model. We deduce the temperature behavior of tunneling conductance and their peak positions as well as of the zero-bias conductance. The results obtained allow us to discriminate among the two singlet spin states.
Recent Development of Bi(2223)/Ag Tapes for Practical Applications
Authors: Grasso G. , Siri A. S. , Marti F. , Huang Y. , Flükiger R. , Caracino P. , Martini L.
Published: July 2002

In this paper we report about some of the major developments of Ag sheathed Bi(2223) tapes that are actually under study in view of a possible practical application of these conductors. Efforts on improving the tape behavior in presence of alternating currents and high magnetic fields have to be done together with a severe optimization of the Powder-In-Tube method. A clear reduction of the magnetic AC losses is observed by AC susceptibility measurements performed on twisted Bi(2223) tapes prepared at the University of Geneva, with a resistive barrier capable of reducing the coupling losses between filaments. Finally, we report on multifilamentary tapes developed with a special configuration that can be of great interest when a magnetic field is applied to the tape at a significant angle with respect to the a-b planes of the superconductor.
THERMODYNAMICS OF SUPERCONDUCTING LATTICE FERMIONS
Authors: OTNES E. , SUDBØ A.
Published: July 2002

We consider the Cooper-problem on a lattice model including onsite and near-neighbor interactions. Expanding the interaction in basis functions for the irreducible representations of the point group C4v yields a classification of the symmetry of the Cooper-pair wave function, which we calculate in real-space. A change of symmetry upon doping, from s-wave at low filling fractions, to dx2-y2 at higher filling fractions, is found. Fermi-surface details are thus important for the symmetry of the superconducting wave function. Symmetry forbids mixing of s-wave and d-wave symmetry in the Cooper-pair wave function on a square lattice, unless accidental degeneracies occur. This conclusion also holds for the selfconsistent treatment of the many-body problem, at the critical temperature T c . Below T c , we find temperatures which are not critical points, where new superconducting channels open up in the order parameter due to bifurcations in the solutions of the nonlinear gap-equation. We calculate the free energy, entropy, coherence length, critical magnetic fields and Ginzburg–Landau parameter κ. The model is of the extreme type-II variety. At the temperatures where subdominant channels condense, we find cusps in the internal energy and entropy, as well as BCS-like discontinuities in the specific heat. The specific heat anomalies are however weaker than at the true superconducting critical point and argued to be of a different nature.
DONOR 1s-2p± TRANSITIONS IN GaAs LOW-DIMENSIONAL SYSTEMS: EFFECTS OF MAGNETIC FIELDS
Authors: NICULESCU ECATERINA C.
Published: July 2002

An approach is presented for studying the effects of the axial magnetic field on the binding and 1s-2p± transition energies of shallow-donors in cylindrical pills of GaAs low-dimensional systems. Results for the infinite-barrier potential are obtained as a function of the structure geometry and the applied field. We have found that for certain values of the structure sizes and of the applied magnetic field the studied excited states are not bounded. In the two and three-dimensional limits the comparison with available infrared magnetospectroscopy measurements and with previous theoretical data shows that the present calculation is quite accurate.
ON THE CHARACTERIZATION OF METALLIC SUPERLATTICE STRUCTURES BY X-RAY DIFFRACTION
Authors: XU MING , YU WENXUE , LUO GUANGMING , CHAI CHUNLING , ZHAO TONG , CHEN FAN , MAI ZHENHONG , LAI WUYAN , WU ZHONGHUA , WANG DEWU
Published: July 2002

To solve the problem on the microstructural characterization of metallic superlattices, taking the NiFe/Cu superlattices as example, we show that the structures of metallic superlattices can be characterized exactly by combining low-angle X-ray diffraction with high-angle X-ray diffraction. First, we determine exactly the total film thickness by a straightforward and precise method based on a modified Bragg law from the subsidiary maxima around the low-angle X-ray diffraction peak. Then, by combining with the simulation of high-angle X-ray diffraction, we obtain the structural parameters such as the superlattice period, the sublayer and buffer thickness. This characterization procedure is also applicable to other types of metallic superlattices.
QUANTUM ABSORPTION IN SMALL METAL PARTICLES
Authors: SEROTA R. A. , GOODMAN B.
Published: July 2002

We evaluate the electric dipole absorption in small conducting particles in a longitudinal electric field, taking into account the Fermi–Thomas screening, and analyze the relationship between the classical and quantum limits.
STOCHASTIC AND HYDRODYNAMIC LATTICE GAS MODELS: MEAN-FIELD KINETIC APPROACHES
Authors: GOUYET JEAN-FRANÇOIS , APPERT CÉCILE
Published: July 2002

Fascinating tools to understand the link between microscopic and macroscopic dynamics in many systems, lattice gases have been developed into two important directions: thermodynamic phase transitions and hydrodynamics.

Here we present how mean-field approaches allow a more thorough analysis of these systems. The kinetic equations are nonlinear and allow to consider far from equilibrium systems. Another important advantage is to gain more flexibility for practical applications.
LOCAL REDUCTION OF FOLD BIFURCATION RELEVANT TO VOLTAGE COLLAPSE IN AN ELECTRIC POWER SYSTEM
Authors: CAO GUO-YUN , CHEN CHEN
Published: July 2002

In this paper, the reduction approach based on the center manifold theory for parameter-dependent nonlinear dynamical systems is applied to simplify the analysis of the fold bifurcation relevant to voltage collapse in a simple electric power system. This technique enables us to obtain a lower-dimensional and topologically equivalent system in the neighborhood of the bifurcation value, which is a subset in the state-parameter space. Explicit formulas are presented for the computation of quadratic coefficients of the Taylor approximations to the center manifold for the fold bifurcation in parameter-dependent dynamical systems. It is demonstrated that it is the fold bifurcation but not other static bifurcations that occurs in the reduced power system, via validating the nondegenerate conditions for the fold bifurcation. The dynamics of the reduced system are visualized by two- and three-dimensional plots, which show that the reduction method is applicable and accurate to analyze local bifurcations in the power system. Furthermore, time domain simulation and modal analysis technique for linear systems are applied to distinguish the voltage stability from the rotor (angle) stability in the electric power system.
VIBRATION ANALYSIS OF A SELF-EXCITED SYSTEM WITH PARAMETRIC FORCING AND NONLINEAR STIFFNESS
Authors: LITAK GRZEGORZ , SPUZ-SZPOS GRZEGORZ , SZABELSKI KAZIMIERZ , WARMIŃSKI JERZY
Published: July 2002

Vibrations of a self-excited oscillator under parametric excitation with nonlinear stiffness were investigated in this paper. Differential equation of motion includes van der Pol, Mathieu and Duffing terms. Vibrations synchronization, stability of solutions were examined by means of the multiple time scale method and Floquet theory. Chaotic solutions were found by means of Lyapunov exponent.
SYNCHRONIZATION OF CHAOTIC SYSTEMS DRIVEN BY IDENTICAL NOISE
Authors: KAULAKYS B. , IVANAUSKAS F. , MEŠKAUSKAS T.
Published: July 2002

An analysis of transition from chaotic to nonchaotic behavior and synchronization in an ensemble of systems driven by identical random forces is presented. The synchronization phenomenon is investigated in the ensemble of particles moving with friction in the time-dependent potential and driven by the identical noise. The threshold values of the parameters for transition from chaotic to nonchaotic behavior are obtained and dependencies of the Lyapunov exponents and power spectral density of the current of the ensemble of particles on the nonlinearity of the systems and intensity of the driven force are analyzed.
THREE-DIMENSIONAL ASPECTS OF RE-ENTRY IN EXPERIMENTAL AND NUMERICAL MODELS OF VENTRICULAR FIBRILLATION
Authors: BIKTASHEV V. N. , HOLDEN A. V. , MIRONOV S. F. , PERTSOV A. M. , ZAITSEV A. V.
Published: July 2002

Ventricular fibrillation is believed to be produced by the breakdown of re-entrant propagation waves of excitation into multiple re-entrant sources. These re-entrant waves may be idealized as spiral waves in two-dimensional, and scroll waves in three-dimensional excitable media. Optically monitored, simultaneously recorded endocardial and epicardial patterns of activation on the ventricular wall do not always show spiral waves. We show that numerical simulations, even with a simple homogeneous excitable medium, can reproduce the key features of the simultaneous endo- and epicardial visualizations of propagating activity, and so these recordings may be interpreted in terms of scroll waves within the ventricular wall.
PERTURBING TWO-DIMENSIONAL MAPS HAVING CRITICAL HOMOCLINIC ORBITS
Authors: BATTELLI FLAVIANO , LAZZARI CLAUDIO
Published: July 2002

Discrete planar maps such as xn+1=f(xn)+μ g(xn, μ), xn∈ℝ2, n∈ℤ, μ∈ℝ, are studied under the assumption that the unperturbed map xn+1=f(xn) has a critical homoclinic orbit to a hyperbolic fixed point. We give either necessary and sufficient conditions for a bifurcation from zero to two homoclinic orbits as the small parameter μ crosses zero. These conditions are stated in terms of geometrical objects such as critical lines, stable and unstable manifolds.
FEEDBACK RESONANCE IN SINGLE AND COUPLED 1-DOF OSCILLATORS
Authors: ANDRIEVSKY BORIS , FRADKOV ALEXANDER
Published: July 2002

The possibilities of studying nonlinear physical systems by feedback action are discussed. The feedback resonance phenomenon in nonlinear oscillators and the Speed–Gradient based method of creating feedback resonance are described. Examples of feedback resonance in 1-DOF system (controlled pendulum) and in 2-DOF system (two coupled pendulums) are studied by computer simulation.
NOISE-INDUCED FIRST-ORDER PHASE TRANSITIONS IN CHAOTIC BRAIN ACTIVITY
Authors: FREEMAN WALTER J.
Published: July 2002

Brain electrical activity in animals during normal behaviors has aperiodic wave forms suggesting its origin in chaotic dynamics. Attempts at finding experimental proofs using low-dimensional, deterministic chaotic models have not succeeded. The assumptions of autonomy, stationarity,and noise-free operation that are needed to define these at tractors and their embedding dimensions have been shown not to hold for brains, because numerical estimates of correlation dimensions and Lyapunov exponents have failed to converge to normative values. Analysis of EEGs from sensory cortices show that a very different model applies to brains, which is more closely related to lasers than models of twist–flip maps and reaction–diffusion systems. Neurons interact with each other through channels with nonlinear, amplitude-dependent gains, by which they form fields of white noise. When the strengths of interaction are increased by input from receptors, the neurons interact more strongly and lose their high degrees of freedom. The macroscopic constraint on their activity appears as an order parameter in the form of spatially coherent, indeterministic chaos.
SIGNAL DROPOUT RECONSTRUCTION IN COMMUNICATION WITH CHAOS
Authors: MARIÑO INES P. , ROSA EPAMINONDAS , GREBOGI CELSO
Published: July 2002

Recently, it has been demonstrated that chaotic signals can be used as carriers of information in communication systems. In this paper we propose a recovery method which, exploiting the determinism and redundancy of chaotic signals, allows us to reconstruct missing or distorted parts of a waveform that has been transmitted through a communication channel.
PREVENTING MISMATCH OF HOMOGENEOUS COMPONENTS IN THE DESIGN OF SOFTWARE ARCHITECTURE
Authors: ORLANDIC RATKO , PFALTZ JOHN L.
Published: July 2002

The objective of this work is to examine the feasibility of, as well as to learn about, a process of developing software architecture that prevents the possibility of mismatch between homogeneous components implemented according to the architectural specification. This paper shows how the architecture can be organized, which restrictions it can use and, provided that they are used, how elaborate it should be in order to ensure that independently-developed artifacts are structurally compatible. Two components are deemed structurally compatible as long as they have appropriate code to avoid mismatch. Since the focus of the paper is on the structural forms of mismatch, the results are derived under the assumption that no run-time environment can prevent a component from executing any path in its code. The paper develops a formal model of architecture that provides a minimal set of concepts in terms of which the designers can reason about incompatibility of components. The model is used to identify the causes of structural mismatch and examine alternative ways of eliminating these causes. Following that, the paper adopts a set of architectural restrictions and shows how these restrictions can be applied in the design of software architectures to prevent the possibility of structural mismatch.
LOWER BOUNDS ON THE GROWTH OF A GROUP ACTING ON THE BINARY ROOTED TREE
Authors: BARTHOLDI LAURENT
Published: July 2002

In 1980, Rostislav Grigorchuk constructed an infinite finitely generated torsion 2-group G, called the first Grigorchuk group, and in 1983 showed that it is of intermediate growth, with the following estimates on its growth function γ (See [6]): [Formula: see text] where β= log 32(31)≈ 0.991. He conjectured that the lower bound is actually tight.

In this paper we improve the lower bound to [Formula: see text] where α≈0.5157, and thus disproves the conjecture.
LOCAL GROUPS IN FREE GROUPOIDS SATISFYING CERTAIN MONOID IDENTITIES
Authors: DO LAGO ALAIR PEREIRA
Published: July 2002

Let G be a (possibly infinite) strongly connected graph and let [Formula: see text] be a set of monoid identities such that any monoid satisfying [Formula: see text] is also a group. Let ℬ be the free groupoid on G satisfying [Formula: see text]. Then, the local groups ℬv, for v ∈ V (G), are all isomorphic to a free group satisfying [Formula: see text]. Furthermore, it is free over a generating set which can be effectively characterized and whose cardinality is the cyclomatic number of the graph G.

We also show applications that establish an important connection between free Burnside groups and free Burnside semigroups.
THE GYROKINETIC APPROXIMATION FOR THE VLASOV–POISSON SYSTEM
Authors: SAINT-RAYMOND L.
Published: July 2002

Consider a plasma in a strong constant magnetic field with self-consistent electric field. We present here the formal derivation that leads to the so-called guiding center approximation, and justify it in the case of a well-prepared initial density of particles. More precisely, we prove that the motion of the particles can be approximatively decomposed as the sum of a fast rotation on Larmor circles, an advection along the magnetic lines and a small drift orthogonal to both electric and magnetic fields.