bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of vitamin A deficiency on cardiovascular function in the rat
Authors: Wright G L , Wang S , Fultz M E , Arif I , Matthews K , Chertow B S
Published: July 2002

Selected parameters of cardiovascular function were evaluated in vitamin A-deficient rats at 70 days of age. Resting heart rate was increased by an average of 100 bpm (21.4 ± 2.7%), whereas resting systolic blood pressure was normal in vitamin A-deficient animals. The maximal contractile force developed per milligram weight of tissue by aortic rings excised from vitamin A-deficient animals was reduced in response to high potassium (25.0 ± 8.7%) and phorbol 12,13-dibutyrate (36.8 ± 8.4%) but was only slightly reduced in response to norepinephrine (17.8 ± 11.1%). Intimal rubbing to remove the endothelium had no effect on the loss in contractile responsiveness, and the relaxant response to acetylcholine was similar between control and vitamin A-deficient tissue groups. This suggests that the decrease in contractility of vascular smooth muscle from the vitamin A-deficient rats did not involve altered release of endothelium-derived vasoactive factors. Western blot analysis suggested a reduction in the protein levels of several differentiation markers including α-actin (22%), calponin (37%), desmin (37%), and vinculin (40%), whereas the level of PKCα was unchanged from control values. Our findings indicate a significant decrease in contractile responsiveness of aortic smooth muscle of the vitamin A-deficient rat that may be associated with a down regulation in the expression of contractile-related proteins.Key words: vitamin A, retinoids, in vivo, cardiovascular, contractility, blood pressure.
Human placental trophoblast as an in vitro model for tumor progression
Authors: Lala P K , Lee B P , Xu G , Chakraborty C
Published: July 2002

The human placenta is a highly invasive tumor-like structure in which a subpopulation of placental trophoblast cells known as the "extravillous trophoblast" (EVT) invades the uterine decidua and its vasculature to establish adequate fetalmaternal exchange of molecules. By utilizing in vitro-propagated short-lived EVT cell lines we found that molecular mechanisms responsible for their invasiveness are identical to those of cancer cells; however, unlike cancer cells, their proliferation, migration, and invasiveness in situ are stringently controlled by decidua-derived transforming growth factor (TGF)-β. By SV40T antigen transfection of normal EVT cells followed by a forced crisis regimen in culture we produced an immortalized premalignant derivative that is hyperproliferative, hyperinvasive, and deficient in gap-junctional intercellular communication. Both premalignant and malignant EVT (JAR and JEG-3 choriocarcinoma) cell lines were found to be TGF-β-resistant. Using these cell lines, we investigated genetic changes responsible for transition of the normal EVT cells to premalignant and malignant phenotype. Hyperinvasiveness in both cases resulted from a downregulation of tissue inhibitor of metalloprotease (TIMP)-1 and plasminogen activator inhibitor (PAI)-1 genes. In contrast to normal EVT cells, both cell types failed to upregulate these genes in response to TGF-β. Loss of TGF-β response in malignant EVT cells was explained by the loss of expression of Smad3 gene. Differential mRNA display of normal and premalignant EVT cells identified up- and down-regulation of numerous known or novel genes in premalignant EVT cells, with potential oncogenic and (or) tumor-suppressor functions, e.g., loss of fibronectin and insulin-like growth factor binding protein (IGFBP-5). Premalignant EVT cells also lost IGF receptor type 2 (IGFR-II). IGFBP-5 was shown to be a negative regulator of IGF-1-induced proliferation of premalignant EVT cells, so that loss of IGFBP-5 as well as IGFR-II permitted their unrestricted proliferation in an IGF-I-rich microenvironment of the fetalmaternal interface. The present model may be a good prototype for identifying genetic changes underlying epithelial tumor progression.Key words: trophoblast, TGF-β, IGFBP-5, fibronectin, choriocarcinoma.
The milliped genus Oriulus Chamberlin (Julida: Parajulidae)
Authors: Shelley Rowland M
Published: July 2002

The milliped genus Oriulus Chamberlin is composed of one anatomically uniform species for which venustus Wood, 1864, is the oldest available name. The species has the greatest distribution of any known North American diplopod, covering three-fourths of the continental United States and adjacent southern Canada. The following binomials are placed in synonymy under O. venustus, all constituting new synonymies: Parajulus rugosus Bollman; O. medianus, O. delus, O. eutypus, O. notus, and O. georgicolens, all authored by Chamberlin; O. grayi Causey; and O. grandiceps Loomis. A neotype is designated for Iulus venustus from West Frankfort, Franklin County, Illinois.
ON THE HARDNESS OF RECOGNIZING BUNDLES IN TIME TABLE GRAPHS
Authors: LIEBERS ANNEGRET , WAGNER DOROTHEA , WEIHE KARSTEN
Published: July 2002

In a cooperation with the national German railway company, we construct a directed graph from a set of train time tables where train stations correspond to vertices, and where pairs of consecutive stops of trains correspond to edges. We consider the problem of locating vertices of this time table graph that intuitively correspond to train stations where the underlying railroad network branches into several directions, and that induce a partition of the edge set into bundles.

We formulate this problem as a graph theoretic optimization problem, and show for two versions of the problem that they are NP-hard. For the first version we show that it is even NP-complete to decide whether any other solution besides the trival one exists.
ON THE LEFTMOST DERVIATION IN MATRIX GRAMMARS
Authors: DASSOW JÜRGEN , FERNAU HENNING , PĂUN GHEORGHE
Published: July 2002

Matrix grammars are one of the classical topics of formal languages, more specifically, regulated rewriting. Although this type of control on the work of context-free grammars is one of the earliest, matrix grammars still raise interesting questions (not to speak about old open problems in this area). One such class of problems concerns the leftmost derivation (in grammars without appearance checking). The main point of this paper is the systematic study of all possibilities of defining leftmost derivation in matrix grammars. Twelve types of such a restriction are defined, only four of which being discussed in literature. For seven of them, we find a proof of a characterization of recursively enumerable languages (by matrix grammars with arbitrary context-free rules but without appearance checking). Other three cases characterize the recursively enumerable languages modulo a morphism and an intersection with a regular language. In this way, we solve nearly all problems listed as open on page 67 of the monograph [7], which can be seen as the main contribution of this paper.

Moreover, we find a characterization of the recursively enumerable languages for matrix grammars with the leftmost restriction defined on classes of a given partition of the nonterminal alphabet.
ON THE PROBLEM OF THE RIGHT HAMILTONIAN UNDER SINGULAR FORM-SUM PERTURBATIONS
Authors: ALBEVERIO SERGIO , KOSHMANENKO VOLODYMYR
Published: July 2002

Let a perturbation of the self-adjoint operator H0>0 in the Hilbert space ℋ be given by an operator V (or by a quadratic form ν) which is possibly singular and in general nonpositive, so H0+V on [Formula: see text] is only a symmetric operator with nontrivial deficiency indices. The definition of the sum [Formula: see text] in the sense of quadratic forms is extended to cases which are not covered by the well-known KLMN-theorem and conditions are found which ensure the unique self-adjoint realization of H in ℋ. It is also shown that ℋ coincides with the strong resolvent limit of the approximating sequence Hn = H0+Vn, where Vn are bounded self-adjoint operators such that Vn → V in a suitable sense. Essentially that operator V might be strongly singular and acts in the H0-scale of spaces, V:ℋ+→ℋ-.
STOCHASTIC ADAMS THEOREM FOR A GENERAL COMPACT MANIFOLD
Authors: LÉANDRE RÉMI
Published: July 2002

We give a stochastic analoguous of the theorem of Adams, which says that the Hochschild cohomology is equal to the cohomology of the based smooth loop space. The key tools are the stochastic Chen iterated integrals as well as Driver's flow.
SEMICLASSICAL MOTION OF DRESSED ELECTRONS
Authors: TEUFEL STEFAN , SPOHN HERBERT
Published: July 2002

We consider an electron coupled to the quantized radiation field and subject to a slowly varying electrostatic potential. We establish that over sufficiently long times radiation effects are negligible and the dressed electron is governed by an effective one-particle Hamiltonian. In the proof only a few generic properties of the full Pauli–Fierz Hamiltonian H PF enter. Most importantly, H PF must have an isolated ground state band for |p|<p c ≤∞ with p the total momentum and p c indicating that the ground state band may terminate. This structure demands a local approximation theorem, in the sense that the one-particle approximation holds until the semiclassical dynamics violates |p|<p c . Within this framework we prove an abstract Hilbert space theorem which uses no additional information on the Hamiltonian away from the band of interest. Our result is applicable to other time-dependent semiclassical problems. We discuss semiclassical distributions for the effective one-particle dynamics and show how they can be translated to the full dynamics by our results.
UNIVERSAL CENTRAL EXTENSIONS
Authors: RAGHUNATHAN M. S.
Published: July 2002

The following is an account, self-contained and essentially expository, of the general theory of universal central extensions of groups with applications to some important classes of groups: perfect groups, abelian groups and connected Lie groups. The notation is occasionally different from that in the text — this should not cause any confusion.
TWISTLESS KAM TORI, QUASI FLAT HOMOCLINIC INTERSECTIONS, AND OTHER CANCELLATIONS IN THE PERTURBATION SERIES OF CERTAIN COMPLETELY INTEGRABLE HAMILTONIAN SYSTEMS: A REVIEW
Authors: GALLAVOTTI GIOVANNI
Published: July 2002

Rotators interacting with a pendulum via small, velocity independent, potentials are considered. If the interaction potential does not depend on the pendulum position then the pendulum and the rotators are decoupled and we study the invariant tori of the rotators system at fixed rotation numbers: we exhibit cancellations, to all orders of perturbation theory, that allow proving the stability and analyticity of the diophantine tori. We find in this way a proof of the KAM theorem by direct bounds of the k-th order coefficient of the perturbation expansion of the parametric equations of the tori in terms of their average anomalies: this extends Siegel's approach, from the linearization of analytic maps to the KAM theory; the convergence radius does not depend, in this case, on the twist strength, which could even vanish ("twistless KAM tori"). The same ideas apply to the case in which the potential couples the pendulum and the rotators: in this case the invariant tori with diophantine rotation numbers are unstable and have stable and unstable manifolds ("whiskers"): instead of studying the perturbation theory of the invariant tori we look for the cancellations that must be present because the homoclinic intersections of the whiskers are "quasi flat", if the rotation velocity of the quasi periodic motion on the tori is large. We rederive in this way the result that, under suitable conditions, the homoclinic splitting is smaller than any power in the period of the forcing and find the exact asymptotics in the two dimensional cases (e.g. in the case of a periodically forced pendulum). The technique can be applied to study other quantities: we mention, as another example, the homoclinic scattering phase shifts.
UPPER BOUND ON THE TRUNCATED CONNECTIVITY IN ONE-DIMENSIONAL β/|x–y|2 PERCOLATION MODELS AT β>1
Authors: MARCHETTI DOMINGOS H.U.
Published: July 2002

We consider one-dimensional Fortuin-Kasteleyn percolation models generated by the bond occupation probabilities [Formula: see text] and weighting factor κ. For any β>1 and κ≥1 the percolation density M is known to be strictly positive provided p is sufficiently close to 1. We prove that, under these assumptions, the following upper bound for the truncated connectivity [Formula: see text] holds with [Formula: see text] where [Formula: see text] as [Formula: see text]. This result extends Imbrie-Newman’s upper bound to independent percolation models (κ=1) and random-cluster models with non-integer values of κ.
Exponential Decay of Truncated Correlation Functions Via the Generating Function: A Direct Method
Authors: Braga Gastão A. , Lima Paulo C. , O'Carroll Michael L.
Published: July 2002

We consider statistical mechanics lattice models where the external field dependent partition function can be represented as a standard polymer system. Using this polymer representation and elementary complex analytic arguments, we obtain upper bounds and give a simple proof on the uniform (in n) exponential decay of the n-point truncated correlation function. We illustrate the method by applying it to the high and low temperature Ising model and to contour models.
LOOP VARIABLES AND GAUGE-INVARIANT INTERACTIONS — II
Authors: SATHIAPALAN B.
Published: July 2002

We continue the discussion of our previous paper on writing down gauge-invariant interacting equations for a bosonic string using the loop variable approach. In the earlier paper the equations were written down in one higher dimension where the fields are massless. In this paper we describe a procedure for dimensional reduction that gives interacting equations for fields with the same spectrum as in bosonic string theory. We also argue that the on-shell scattering amplitudes implied by these equations for the physical modes are the same as for the bosonic string. We check this explicitly for some of the simpler equations. The gauge transformation of space–time fields induced by gauge transformations of the loop variables are discussed in some detail. The unintegrated (i.e. before the Koba–Nielsen integration), regularized version of the equations, are gauge invariant off-shell (i.e. off the free mass shell).
AdS/CFT CORRESPONDENCE, CONFORMAL ANOMALY AND QUANTUM CORRECTED ENTROPY BOUNDS
Authors: NOJIRI SHIN'ICHI , ODINTSOV SERGEI D.
Published: July 2002

The role of conformal anomaly in AdS/CFT and related issues is clarified. The comparison of holographic and QFT conformal anomalies (with the account of brane quantum gravity contribution) indicates the possibility for brane quantum gravity to occur within the AdS/CFT setup. Three-dimensional quantum induced inflationary (or hyperbolic) brane-world is shown to be realized in the frames of AdS3/CFT2 correspondence where the role of 2d brane cosmological constant is played by effective tension due to two-dimensional conformal anomaly. The dynamical equations to describe 4d FRW universe with the account of quantum effects produced by conformal anomaly are obtained. The quantum corrected energy, pressure and entropy are found. The dynamical evolution of entropy bounds in the inflationary universe is estimated and its comparison with quantum corrected entropy is done. It is demonstrated that entropy bounds for quantum corrected entropy are getting the approximate ones and occur for some limited periods of evolution of the inflationary universe.
PHYSICAL PROJECTIONS IN BRST TREATMENTS OF REPARAMETRIZATION INVARIANT THEORIES
Authors: MARNELIUS ROBERT , SANDSTRÖM NICLAS
Published: July 2002

Any regular quantum mechanical system may be cast into an Abelian gauge theory by simply reformulating it as a reparametrization invariant theory. We present a detailed study of the BRST quantization of such reparametrization invariant theories within a precise operator version of BRST which is related to the conventional BFV path integral formulation. Our treatments lead us to propose general rules for how physical wave functions and physical propagators are to be projected from the BRST singlets and propagators in the ghost extended BRST theory. These projections are performed by boundary conditions which are specified by the ingredients of BRST charge and precisely determined by the operator BRST. We demonstrate explicitly the validity of these rules for the considered class of models.
CURVATURE VACUUM CORRELATIONS IN FOUR-DERIVATIVE GRAVITY
Authors: SHAO D. , NODA H. , SHAO L. , SHAO C. G.
Published: July 2002

Under the flat Minkowski space–time background, in the harmonic coordinate system, we calculate the expressions of the leading terms of several two-point curvature vacuum correlation functions in n dimensional four-derivative gravity, resulting in that the two-point curvature vacuum correlation functions are not zero, and discuss the relations between the four-derivative gravity and the R-gravity for the graviton propagator and the curvature correlation functions.
GAUGING YANG–MILLS SYMMETRIES IN (1+1)-DIMENSIONAL SPACE–TIME
Authors: ALMUKAHHAL RAJA Q. , HÜBSCH TRISTAN
Published: July 2002

We present a systematic and "from the ground up" analysis of the "minimal coupling" type of gauging of Yang–Mills symmetries in (2, 2)-supersymmetric (1+1)-dimensional space–time. Unlike in the familiar (3+1)-dimensional N=1 supersymmetric case, we find several distinct types of minimal coupling symmetry gauging, and so several distinct types of gauge (super)fields, some of which entirely novel. Also, we find that certain (quartoid) constrained superfields can couple to no gauge superfield at all, others (haploid ones) can couple only very selectively, while still others (nonminimal, i.e. linear ones) couple universally to all gauge superfields.
EXTRA DIMENSIONS AND THEIR IMPLICATIONS FOR NEUTRINO PHYSICS
Authors: DIENES KEITH R.
Published: July 2002

In this talk, I discuss recent developments concerning the possibility of large extra space-ime dimensions and their relation to neutrino physics. After briefly reviewing how such dimensions can lower the fundamental GUT, Planck, and string scales, I then outline how these scenarios lead to a new higher-dimensional seesaw mechanism for generating neutrino oscillations — perhaps even without neutrino masses. I also discuss how neutrino flavor oscillations can occur in a higher-dimensional theory even if the Standard Model on the brane is flavor-diagonal, the bulk theory is flavor-neutral, and the brane/bulk couplings are flavor-blind. This talk reports on work done in collaboration with Emilian Dudas, Tony Gherghetta, and Ina Sarcevic.
BOSE OPERATOR HAMILTONIAN MODEL FOR ROTATING ELECTRIC DIPOLE AND GENERALIZED EHRENFEST'S THEOREM
Authors: FAN HONGYI
Published: July 2002

We present a Bose operator Hamiltonian model for totally quantum mechanically describing energy and eigenfunctions of a rotating dipole in the presence of electric field. The corresponding Heisenberg equations of motion are derived which leads us to the generalized Ehrenfest theorem for rotating system. Remarkably, a zero-point angular momentum ℏ/2 appears in the generalized Ehrenfest theorem corresponding to the classical equation Iω=L.
CASIMIR ENERGY OF A DIELECTRIC-DIAMAGNETIC MEDIA
Authors: KLICH ISRAEL
Published: July 2002

We study the density of Casimir energy in dielectric and magnetic media. To do so we derive Born series for the Green's function of the electromagnetic field in a medium with arbitrary ∊ and μ. Within this framework the case of uniform velocity of light (∊μ = const ) is studied. As an application we consider the Casimir energy of a thick dielectric-diamagnetic shell, as a function of the radii and the permeabilities. We show that there is a range of parameters in which the stress on the outer shell is inward, and a range where the stress on the outer shell is outward.
BEC IN NONEXTENSIVE STATISTICAL MECHANICS
Authors: SALASNICH LUCA
Published: July 2002

We discuss the Bose–Einstein condensation (BEC) for an ideal gas of bosons in the framework of Tsallis's nonextensive statistical mechanics. We study the corrections to the st and ard BEC formulas due to a weak nonextensivity of the system. In particular, we consider three cases in the D-dimensional space: the homogeneous gas, the gas in a harmonic trap and the relativistic homogenous gas. The results show that small deviations from the extensive Bose statistics produce remarkably large changes in the BEC transition temperature.
ANOMALOUS INFRARED PROPERTIES OF THE OXYGEN DEFICIENT CUPRATE La8-xSrxCu8O20
Authors: LUCARELLI A. , LUPI S. , CALVANI P. , MASELLI P. , BIANCONI A. , SAINI N. L. , DE MARZI G. , ROY P. , ITO T. , OKA K.
Published: July 2002

We present the first infrared conductivity spectra on single crystals of oxygen deficient cuprate La 8- x Sr x Cu 8 O 20. The infrared conductivity for a sample with x = 2.24 behaves as a function of temperature according to a conventional Drude model. On the other hand, the low energy excitations for a sample with x =1.56 are itinerant polarons. Below T =100 K , polarons localize and this effect can be related to the anomalies present in the transport and magnetic properties around this temperature.
INFLUENCE OF SQUEEZING OPERATOR ON THE QUANTUM PROPERTIES OF VARIOUS BINOMIAL STATES
Authors: EL-ORANY FAISAL A. A. , ABDALLA M. SEBAWE , OBADA A-.S. F. , ABD AL-KADER G. M.
Published: July 2002

In this communication we investigate the action of a single-mode squeeze operator on the statistical behaviour of different binomial states. For the resulting states (squeezed generalized binomial states) normalized second-order correlation function, quasiprobability distribution functions and the distribution function P(x) associated with the quadrature x are studied both analytically and numerically. Furthermore, the quadrature phase distribution as well as the phase distribution in the framework of Pegg–Barnett formalism are discussed.
PROPERTIES AND TURNING OF INTRABAND OPTICAL ABSORPTION IN InxGa1-xAs/GaAs SELF-ASSEMBLED QUANTUM DOT SUPERLATTICE
Authors: LIU B. , ZHUANG Q. D. , YOON S. F. , DAI J. H. , KONG M. Y. , ZENG Y. P. , LI J. M. , LIN L. Y. , ZHANG H. J.
Published: July 2002

We investigated properties of intraband absorption in In x Ga 1-x As quantum dots (QDs) superlattice. Energy levels in conduction band in QDs were calculated for a cone-shaped quantum dot associated with coupling between QDs in the framework of the effective-mass envelope-function theory. Theoretical results demonstrated that energy levels in conduction band were greatly affected by the vertical coupling between quantum dots, which can be used to modify transition wavelength by adjusting the space layer thickness. Intraband transition is really sensitive to normal incidence and the absorption peak intensity is dependent on the polarization. A satisfying agreement is found between theoretical and experimental values. This result opens up prospects for the fabrication of QDs infrared detectors, which work at atmospheric windows.
A MICROSCOPIC LOOK AT LIQUID HELIUM: THE 3He IMPURITY CASE
Authors: POLLS A. , FABROCINI A.
Published: July 2002

The description of the properties of liquid Helium is a challenge for any microscopic many-body theory. In this context, we study the ground state and the excitation spectrum of one 3 He impurity in liquid 4 He at T=0 with the aim of illustrating the power of the correlated basis function formalism in describing heavily correlated systems. The strong interatomic interaction and the large density require the theory to be pushed to a high degree of sophistication. A many-body correlation operator containing explicit two- and three-particle correlation functions is needed to obtain a realistic ground state wave function, whereas a perturbative expansion including up to two phonon correlated states must be enforced to study the impurity excitation energies. The theory describes accurately the experimental spectrum along all the available momentum range. As empirically shown by the experiments, a marked deviation from the quadratic Landau-Pomeranchuck behavior is found and the momentum dependent effective mass of the impurity increases of ~50% at q~1.7 Å-1 with respect to its q=0 value. Although the main emphasis is given to the correlated basis function theory, we present also comparisons with other methods, as diffusion Monte Carlo, variational Monte Carlo with shadow wave functions and time dependent correlations.
SIMPLE APPROXIMATIONS FOR THE PSEUDO-JAHN-TELLER HAMILTONIAN USING THE COUPLED CLUSTER METHOD
Authors: BISHOP RAYMOND F. , CARTER (QUICK) RACHEL M. , DAVIDSON NEIL J. , VAN DER WALT DAVID M.
Published: July 2002

The normal coupled cluster method has been used to obtain simple accurate approximations to the ground and first excited state energies of the linear e⊗E pseudo-Jahn-Teller Hamiltonian.
LOCALIZATION IN THIN FILMS: CROSS-OVER FROM TWO DIMENSIONS TO THREE DIMENSIONS
Authors: SINGH R. K. BROJEN , KUMAR DEEPAK
Published: July 2002

We have examined the localization of electronic states in disordered thin films as a function of film thickness. The study is motivated by the following consideration. According to the present understanding, in two-dimensions all electronic states are localized for any strength of disorder, however weak. Whereas in three-dimensions, there is a threshold disorder W3c, only above which all the band states are localized. We consider a film of thickness b, with a disorder strength smaller than W3c. With increasing thickness, one might expect a dimensional cross-over, so that film becomes conducting. We have examined questions that arise in this context by two techniques. The first is a finite size scaling technique due to Pichard and Sarma, in which the localization length is calculated numerically for strips and bars as a function of their lateral dimensions. Using this technique we study the delocalization of states at the band centre, as the thickness of the film is increased for moderate to strong disorders. The second technique involves the incorporation of quantum corrections to conductivity by extending the weak scattering methods to films of finite thickness. The two techniques complement each other, as the first one is more suitable for strong disorder, while the latter for weak disorder.
ON THE CORRESPONDENCE BETWEEN CLASSICAL AND QUANTUM MECHANICS IN DEFINING ATOMS AND MOLECULES IN CONDENSED SYSTEMS
Authors: SITE L. DELLE
Published: July 2002

We analyze and discuss the concept of "proper quantum subsystem" (PQS). In particular we focus the attention on the theory of "quantum mechanics of a subspace" developed by R. F. W. Bader and coworkers whose definition of a PQS is based on the Schwinger's Quantum Action Principle; we illustrate some properties of this definition and propose a problem whose solution could be relevant in formulating a correct physical interpretation of the concept above.
BOSE–EINSTEIN CONDENSATION OF PARTICLES TRAPPED IN A BOUNDED HARMONIC POTENTIAL
Authors: LUMB SHALINI , MUTHU S. K.
Published: July 2002

The behavior of a finite number of bosons trapped in a bounded harmonic potential is investigated. The eigenvalue spectrum is worked out numerically for three different sizes of the trap. The condensate fraction is determined and is found to increase suddenly below a certain temperature which is a characteristic signature of BEC. The specific heat-temperature curve also shows a peak, with the maximum shifting to lower values and occurring at higher temperatures, as the size of the assembly is reduced.
A PREISACH ANALYSIS OF IRREVERSIBILITY IN A PARTICULATE THIN FILM: Fe-Al2O3
Authors: HARDER C. , SONG T. , ROSHKO R. M. , GE SHIHUI , GAO MEIZHEN
Published: July 2002

We present measurements of some of the principal response functions of a thin film of nanodimensional Fe particles embedded in A l2 O 3, specifically the temperature dependence of the moment measured under field cooled and zero field cooled conditions at temperatures between 5 K ≤ T ≤ 300 K in a low applied field ha =10 Oe , and the major hysteresis loop measured at T =5 K in applied fields between -2000 Oe ≤ h a ≤ + 2000 Oe . The data were analyzed within the framework of a generalized version of the Preisach model of hysteresis, which treats all magnetic systems as ensembles of interacting bistable Barkhausen elements, and which includes both thermal barrier relaxation effects and critical effects. Numerical simulations based on the model are able to replicate the principal structural features of the experimental data, and allow us to extract the characteristics of the bistable elements, specifically their moments μ, their coercive fields h c and their interaction fields h i .
MAGNETIC ORDERING IN ISING MAGNET CsDy(MoO4)2
Authors: Knigavko A. , Cherny A. S. , Khatsko E. N. , Paulsen C.
Published: July 2002

We propose a model for equilibrium magnetic configuration of CsDy(MoO4)2 which is based on the new space group established in recent neutron scattering experiments. These results are complimented by measurements of magnetization below magnetic critical temperature.
TRICOMI COHERENT STATES
Authors: SIXDENIERS J.-M. , PENSON K. A , KLAUDER J. R.
Published: July 2002

We construct explicit families of coherent states whose parametrization permits an arbitrarily small deviation from conventional coherent states. They possess the resolution of unity with a positive weight function given as the solution of a Stieltjes power-moment problem, with moments analytically expressible through Tricomi's confluent hypergeometric function. These states are in general squeezed, can be either sub- or super-Poissonian in nature, and induce a deformation of the metric of the complex plane.
INFLUENCES OF PREPARATION CONDITIONS ON CNx THIN FILM STRUCTURE AND CHARACTERISTICS
Authors: WU XIANCHENG , WANG BO , CHEN GUANGHUA , LI HULIN
Published: July 2002

Carbon nitride (CNx) thin films have been synthesized by hot filament assisted r.f. plasma-enhanced chemical vapor deposition with negative bias methods on Si (100) substrates. The influences on the thin film structure and hardness characteristics of r.f. power and substrate negative bias have been emphatically investigated. The optimal preparation parameters have been summarized as follows: r.f. power of 200W, substrate negative bias of -200V, substrate temperature of about 600°C, total reactive gas pressure of about 110Pa, flow ratio of CH4 to N2 of 1 : 5.5.
EXOTIC GALILEAN SYMMETRY AND THE HALL EFFECT
Authors: DUVAL C. , HORVÁTHY P. A.
Published: July 2002

The "Laughlin" picture of the Fractional Quantum Hall effect can be derived using the "exotic" model based on the two-fold centrally-extended planar Galilei group. When coupled to a planar magnetic field of critical strength determined by the extension parameters, the system becomes singular, and "Faddeev-Jackiw" reduction yields the "Chern-Simons" mechanics of Dunne, Jackiw, and Trugenberger. The reduced system moves according to the Hall law.
RECENT DEVELOPMENTS IN THE NUCLEAR MANY-BODY PROBLEM
Authors: PANDHARIPANDE V. R.
Published: July 2002

We review recent developments in a few selected areas of the many-body theory of nuclei and neutron stars. The chosen topics are (i) femtometer toroidal structures in nuclei; (ii) modern models of nuclear forces; (iii) advances in the application of quantum Monte Carlo methods to nuclei; (iv) relativistic boost corrections to nuclear forces; (v) dense nucleon matter; (vi) kaon condensation in neutron star matter; and (vii) the nature of the transition from nucleon to quark matter at high density.
SPATIAL- AND SPATIO-TEMPORAL PATTERN FORMATION IN OPTICALLY DRIVEN DISCRETE SYSTEMS
Authors: BURLAKOV VICTOR M.
Published: July 2002

Dynamical coherent structure (pattern) formation in the Klein–Gordon lattice excited by periodic external field near the optical resonance is studied. It is shown that the patterns involve spatial or spatio-temporal modulation of particles vibration amplitude in the lattice and can be generated in rather broad region of excitation parameters. An influence of cubic anharmonicity in the lattice potential and that of random noise on the pattern formation is examined.
Effect of CuO Chains Ordering on the Opening of the Spin-Gap in YBa2Cu3O6+x
Authors: Carretta P. , Manca P. , Sanna S.
Published: July 2002

The authors report on 63 Cu NMR relaxation measurements in YBa 2 Cu 3 O 6+x samples having similar T c's but a different structural ordering of the Cu(1)O chains. It is found that the gap in the spin excitations estimated from 63 Cu (2) nuclear spin-lattice relaxation rate 1/T1, varies from 110 K up to 190 K depending on the sample. This observation suggests that there is not a one to one relationship between the hole concentration and the amplitude of the spin-gap in the normal state of YBa 2 Cu 3 O 6+x. The sizeable variation in the gap, related to the different ordering of the Cu(1)O chains, is tentatively explained in the framework of a phase separation scenario where Cu(1)O chains act as pinning wells for the stripes.
Pair Symmetry and Degree of Gap Depression at S-I Interfaces in HTS Josephson Junctions
Authors: Ummarino G. A. , Gonnelli R. S. , Bravi C. , Inoue Masumi
Published: July 2002

A new possible indirect way of testing pair symmetry in high-Tc superconductors has been set up. The degree of intrinsic gap depression at Superconductor-Insulator [S-I] interfaces required to match Ic(T)Rn(T) data in HTS Josephson junctions depends on the pair symmetry of the material itself, so that an higher fraction of d-wave symmetry for the order parameter requires less gap depression, while an higher fraction of s-wave corresponds to a larger degree of gap depression. In order to obtain a general reference value for the intrinsic amount of gap depression at S-I interfaces the de Gennes condition has been used, and resulting reduced Ic(T)Rn(T) data have been calculated in the framework of a mixed (s+id)-wave pair symmetry for the depressed order parameter ranging from pure s to pure d-wave. This model has been tentatively applied to two junctions' made of very different HTSs: YBCO and BKBO, yielding a result of almost pure d-wave for YBCO and of pure s-wave for BKBO.
Optimized Magnetic Design of a High Temperature Micro-SMES
Authors: Fabbri M. , Negrini F. , Ribani P. L.
Published: July 2002

The optimal design of the high temperature superconducting coils of a micro-SMES is described. Two formulations of the problem are considered which minimize the overall dimensions of the device or the volume of the superconducting coils. Out of the device the stray field is lower than the desired value. The coils are solenoids which can be arranged in an axial symmetric or toroidal configuration. The results in correspondence to different values of the stored energy and other parameters of the design are reported and discussed.
Some Inverse Problems in the Studies of High Tc Superconductivity
Authors: XianXi Dai , Tao Wen , GuiCun Ma , Dai JiXin
Published: July 2002

Two topics are reviewed or studied in this paper: 1. The specific heat-photon spectrum inversion problem; 2. The inverse relaxation problem in high Tc superconductors and finding its maximum current density problem.
STRIPE STRUCTURES AND THE BERRY-PHASE CONNECTION: CONCEPT OF GEOMETRIC ENERGY
Authors: TAKADA YASUTAMI , HOTTA TAKASHI , KOIZUMI HIROYASU
Published: July 2002

Electronic states of an eg electron are calculated in the system composed of two MnO 6 octahedra with the inclusion of the Berry phase acquired by parallel transport. Based on this calculation, a comment is made on the controversy between "Wigner-crystal" and "paired-stripe" models for the the insulatIng charge-ordered manganese oxides.
CATHODOLUMINESCENCE AND PHOTOLUMINESCENCE CHARACTERISTICS OF RUBY
Authors: SANCHEZ E. MARTINEZ , GARCIA M. , BRITO F. RAMOS , ALVAREZ-FREGOSO O. , AZORIN J. , RIVERA T. , FALCONY CIRO
Published: July 2002

The ruby samples were grown by the Czochralski technique. We used as starter materials Al 2 O 3 powder of 99.99% doped with 1% of Cr 2 O 3. The monocrystals obtained were clived to form samples of 5× 5× 2 mm3 size. The X-ray diffraction pattern shows a rhombohedral structure type. The elemental composition was determined by EDS. The samples were irradiated with a power from 0 to 15 KV to observe the different impurities levels of emission and the saturation power. The photoluminescence spectra showed two band at 697 and 772 nm, respectively.
BLUE PHOTOLUMINESCENCE IN GaAs(N) NANOWHISKERS
Authors: POZOS S. ADRIAN CANALES , JARA DAVID RIOS , ALVAREZ-FREGOSO OCTAVIO , ALVAREZ-PEREZ M. A. , GARCIA MANUEL , SANCHEZ ENRIQUE MARTINEZ , JUAREZ-ISLAS JULIO A. , ZELAYA - ANGEL ORLANDO , MENDOZA-ALVAREZ JULIO G. , FALCONY C.
Published: July 2002

GaAs(N) nanostructured thin films have been deposited using the radio frequency sputtering technique. Films are formed by filament-like nanocrystallites with a sharp grain size distribution. The measured nanowhisker average diameter range about 3.9 to 4.1 nm. The film structure was cubic with a preferential (1,1,1) orientation. Particle size effects were observed in the photoluminescence emission spectra. The blue emission (λ = 425-432 nm) was due to the quantum confinement effect with a effective band gap of 2.92 eV and a quantum yield of about 92% of efficiency.
STRAIHGHTFORWARD REPRESENTATION OF A THICK NONLINEAR OPTICAL MATERIAL, WITH LINEAR AND NONLINEAR ABSORPTION
Authors: QUINTERO-TORRES R. , CARRETO-PARRA F. , NAVARRETE-MEZA Z. , ZAMBRANO-VALENCIA L.
Published: July 2002

Z-scan is a technique where a thin sample with good optical quality is scanned through the focus of a gaussian laser beam. A sensor is placed behind a finite aperture in the far field to monitor the output from the sample. A further simplification is obtained measuring transmission only when the sample is close to the focal point, and the aperture is small.

In this work. z-scan like results are obtained when a nonlinear optical material is modeled as a set of spherical lenses using geometric optics. Here we discus the thick sample case; sample thicker than the confocal length (defined by the external lens) or samples with nonlinear phase change appreciably different from zero. An absorbent material with instantaneous nonlinear response will be used.

With this procedure, an explanation for the distortion in the z-scan is obtained with the increase in the aperture, the nonlinear refractive index and the sample thickness as well as with the presence of nonlinear absorption.
THEORY OF BUOYANCY IN TURBULENT SHEAR FLOW
Authors: DEKKER H.
Published: July 2002

Given the inertial range energy spectrum, a novel theory of 3D turbulent shear flow allows one to analytically calculate the 4D cospectrum of Reynolds fluxes and stresses. In this paper, we consider the Kolmogorov spectrum of lateral heat flow, i.e. of buoyant turbulence production.
ON THE GROUND STATE STRUCTURE OF P AND NP-COMPLETE RANDOM DECISION PROBLEMS
Authors: GLIOZZI ANTONIO S. , ZECCHINA RICCARDO
Published: July 2002

The structure of the space of solutions of a prototype model of complexity theory and random structures is analyzed. Depending on a single control parameter, the model interpolates between different complexity classes and is known to undergo continuous as well as discontinuous phase transitions. Some geometrical aspects of such a symmetry breaking phenomena are studied analytically and numerically, and a simple conjecture for the onset of exponential regimes in recursive search algorithms is discussed.
SYMMETRIES OF THE LANDAU PROBLEM
Authors: FUNG M. K. , WANG Y. F.
Published: July 2002

We find that three constants of motion of the Landau problem form an algebra of the Euclidean group in the plane with a cocycle extension. We succeed in expressing the Hamiltonian in terms of these constants of motion in a gauge independent way and solve the problem by algebraic methods.
ENERGY TRANSFER BETWEEN LIGHT WAVES IN NONLINEAR MEDIA WITH TWO DIFFERENT RESPONSE TIMES
Authors: PASCHOAL C. W. A. , PENAFORTE J. C. , GUEDES I.
Published: July 2002

In this work we extend the conventional theory of the two-wave mixing in Kerr-like media, in order to take into account two different contributions to nonlinear gain. To this end, we use a modified Debye relaxation relation to obtain the dynamical behavior of the nonlinearity and consequently, derive the expressions for pump and probe wave intensities. The two-wave mixing gain coefficient Γ1 is calculated as a function of several parameters.
ELASTIC BEHAVIOR OF SOME SUBSTITUTED Sr–Zn W-TYPE HEXAGONAL FERRITES
Authors: PURUSHOTHAM Y. , REDDY P. VENUGOPAL
Published: July 2002

In the present work, we investigate the elastic behavior of monovalent and divalent doped Sr–Zn W-type hexagonal ferrites at room temperature by measuring their longitudinal and shear wave velocities using a pulse transmission technique. The values of Young (E) and rigidity (G) moduli have been corrected to the theoretical density. The zero porosity values of both the elastic moduli are found to increase with increasing dopant concentration. Further, a linear relationship between the Debye temperature and the average sound velocity has also been observed and the behavior is explained qualitatively.
DATA-DRIVEN DESIGN OF HMM TOPOLOGY FOR ONLINE HANDWRITING RECOGNITION
Authors: LEE JAY J. , KIM JAHWAN , KIM JIN H.
Published: July 2002

Although HMM is widely used for online handwriting recognition, there is no simple and well-established method of designing the HMM topology. We propose a data-driven systematic method to design HMM topology. Data samples in a single pattern class are structurally simplified into a sequence of straight-line segments, and then these simplified representations of the samples are clustered. An HMM is constructed for each of these clusters, by assigning a state to each straight-line segments. Then the resulting multiple models of the class are combined to form an architecture of a multiple parallel-path HMM, which behaves as a single HMM. To avoid excessive growing of the number of the states, parameter tying is applied such that structural similarity among patterns is reflected. Experiments on online Hangul recognition showed about 19% of error reductions, compared to the intuitive design method.
CHAOS AND COMPLEXITY
Authors: BROWN RAY , BEREZDIVIN ROBERT , CHUA LEON O.
Published: July 2002

In this paper we show how to relate a form of high-dimensional complexity to chaotic and other types of dynamical systems. The derivation shows how "near-chaotic" complexity can arise without the presence of homoclinic tangles or positive Lyapunov exponents. The relationship we derive follows from the observation that the elements of invariant finite integer lattices of high-dimensional dynamical systems can, themselves, be viewed as single integers rather than coordinates of a point in n-space. From this observation it is possible to construct high-dimensional dynamical systems which have properties of shifts but for which there is no conventional topological conjugacy to a shift. The particular manner in which the shift appears in high-dimensional dynamical systems suggests that some forms of complexity arise from the presence of chaotic dynamics which are obscured by the large dimensionality of the system domain.
ANIMATION OF CHAOTIC MIXING BY A BACKWARD POINCARE CELL-MAP METHOD
Authors: WANG LINXIANG , FAN YURUN , CHEN YING
Published: July 2002

A Backward Poincare cell-mapping (BPCM) method has been developed for animating chaotic fluid mixing. The chaotic mixing field considered is induced by periodically rotating the secondary flow of incompressible fluids in a curved pipe. The pipe's cross-section is transformed into a cell space where each cell is initially assigned with a color code and mapped by integrating the velocity field forward in time. The mixing process is thus animated efficiently with each cell being painted with its color on a computer screen. We propose the backward Poincare cell-mapping instead of direct Poincare cell-mapping as a useful tool for probing the chaotic fluid mixing and for animating the phase deformation of nonlinear dynamical systems.
CHAOTIFYING A CONTINUOUS-TIME SYSTEM VIA IMPULSIVE INPUT
Authors: YANG LING , LIU ZENGRONG , CHEN GUANRONG
Published: July 2002

This paper studies the chaotification problem of driving a continuous-time system to a chaotic state by using an impulsive control input. The controller is designed to ensure the controlled orbit be bounded and, meanwhile, have positive Lyapunov exponents. This is proved to be not only possible but also implementable near a stable limit cycle of the given system. Two numerical examples are given to illustrate the effectiveness of the proposed chaotification method.
CHAOTIC BEHAVIOR INDUCED BY THERMAL MODULATION IN A MODEL OF THE CONVECTIVE FLOW OF A FLUID MIXTURE IN A POROUS MEDIUM
Authors: MALASOMA J.-M. , WERNY P. , LAMARQUE C.-H.
Published: July 2002

Numerical investigations of the global behavior of a model of the convective flow of a binary mixture in a porous medium are reported. We find a complex behavior characterized by the presence of coexisting periodic, quasiperiodic and chaotic attractors. Bifurcations of periodic solutions and routes to chaos via type-I intermittency and period-doubling bifurcations are described. Boundary crises and band merging crises have also been observed.
PREIMAGE ENTROPY FOR MAPPINGS
Authors: NITECKI ZBIGNIEW , PRZYTYCKI FELIKS
Published: July 2002

Several entropy-like invariants have been defined for noninvertible maps, based on various ways of measuring the dispersion of preimages and preimage sets in the past. We investigate basic properties of four such invariants, finding that their behavior in some ways differs sharply from the analogous behavior for topological entropy.
CONJUGATION IN TREE AUTOMORPHISM GROUPS
Authors: GAWRON PIOTR W. , NEKRASHEVYCH VOLODYMYR V. , SUSHCHANSKY VITALY I.
Published: July 2002

It is given a full description of conjugacy classes in the automorphism group of the locally finite tree and of a rooted tree. They are characterized by their types (a labeled rooted trees) similar to the cyclical types of permutations. We discuss separately the case of a level homogenous tree, i.e. conjugality in wreath products of infinite sequences of symmetric groups. It is proved those automorphism groups of rooted and homogenous non-rooted trees are ambivalent.
ON A PROPERTY OF THE FACTORIZING CODES
Authors: DE FELICE CLELIA
Published: July 2002

In this paper we consider factorizing codesC over A, i.e. codes verifying the factorization conjecture by Schützenberger. We give a description of the structure of the words in C∩a*(A\a)a*, a being a letter in A, by using a class of factorizations of the cyclic groups discovered by Hajós.
DYNAMIC CONTACT PROBLEMS WITH SMALL COULOMB FRICTION FOR VISCOELASTIC BODIES: EXISTENCE OF SOLUTIONS
Authors: JARUŠEK J. , ECK C.
Published: July 2002

The existence of solutions to the dynamic contact problem with Coulomb friction for viscoelastic bodies is proved with the use of penalization and regularization methods. The contact condition, which describes the nonpenetrability of mass, is formulated in velocities. The coefficient of friction may depend on the solution but is assumed to be bounded by a certain constant.