bluuebunny/crossref_metadata_2025 huggingface dataset:
ONLINE SECURE CHATTING SYSTEM USING DISCRETE CHAOTIC MAP
Authors: KWOK H. S. , TANG WALLACE K. S. , MAN K. F.
Published: March 2004

In this paper, an online chatting system with an embedded real-time chaotic encryption/decryption method is designed for the Internet. Such system not only provides a real-time communication platform, but also ensures a secure channel for communication. By the use of cipher feedback and the skew tent map, the input text can be real-time encoded and the cipher text is sent via TCP/IP. With the properties of randomness of the map, and its sensitivity on system parameters and the initial conditions, the encrypted transmitting messages are difficult to be eavesdropped. The implemented method is simple and can be easily embedded in any existing systems.
NEW RESULTS ABOUT ROUTE TO CHAOS IN ROSSLER SYSTEM
Authors: NIKOLOV SVETOSLAV , PETROV VALKO
Published: March 2004

In this paper, the theory of Lyapunov–Andronov is applied to investigate the route to chaos in Rossler system. On the base of a new analytical formula for the first Lyapunov value at the boundary of stability region, we make a detailed bifurcation analysis of this system. From the obtained results the following new conclusions are made: Transition to chaos in the Rossler's system takes place at soft stability loss in the form of a cascade of periodic self-oscillations. Then the occurrence of chaotic self-oscillations in this system takes place under hard stability loss.
GENERAL SYNCHRONIZATION OF GENESIO–TESI SYSTEMS
Authors: CHEN MAO-YIN , HAN ZHENG-ZHI , SHANG YUN
Published: March 2004

In this paper we develop a new approach to generally synchronize Genesio–Tesi systems. A suitable scalar signal of the master, Genesio–Tesi system, is transmitted to the slaver, which is derived from an iteration transformation of a Genesio–Tesi system. If a parameter is chosen properly, the stability of synchronization manifold becomes Hurwitz stability. Numerical simulation verifies the effectiveness of this method.
NONLINEAR DYNAMICS TEXT MINING USING BIBLIOMETRICS AND DATABASE TOMOGRAPHY
Authors: KOSTOFF RONALD N. , SHLESINGER MICHAEL F. , TSHITEYA RENE
Published: March 2004

Database Tomography (DT) is a textual database analysis system consisting of two major components: (1) algorithms for extracting multiword phrase frequencies and phrase proximities (physical closeness of the multiword technical phrases) from any type of large textual database, to augment (2) interpretative capabilities of the expert human analyst. DT was used to derive technical intelligence from a Nonlinear Dynamics database derived from the Science Citation Index/Social Science Citation Index (SCI). Phrase frequency analysis by the technical domain experts provided the pervasive technical themes of the Nonlinear Dynamics database, and the phrase proximity analysis provided the relationships among the pervasive technical themes. Bibliometric analysis of the Nonlinear Dynamics literature supplemented the DT results with author/journal/institution publication and citation data.
AN INTEGRATED CHUA'S CELL FOR THE IMPLEMENTATION OF A CHUA'S ARRAY
Authors: ARENA PAOLO , CASTORINA SALVATORE , FORTUNA LUIGI , FRASCA MATTIA , RIZZO ALESSANDRO
Published: March 2004

In this paper a new integrated Chua's circuit is implemented through switched-capacitor techniques. Recent studies on complex systems made of vast arrays or matrices of Chua's cells motivate the need for experimental verifications which could be easily accomplished by an integrated version of the array. Design efforts have been devoted to the reduction of the chip area consumption. The cell layout, realized in CMOS technology, is presented and experimental results confirm the validity of our chip implementation. The implementation presented allows the user to generate a wide gallery of complex behaviors. The system is in fact programmable: both the chaotic attractor generated by the single cell and the frequency range of the chaotic oscillations can be easily set via external control pins.
HEXAGONAL PATTERNS IN A MODEL FOR ROTATING CONVECTION
Authors: MADRUGA S. , PÉREZ-GARCÍA C.
Published: March 2004

We study a model equation that mimics convection under rotation in a fluid with temperature-dependent properties (non-Boussinesq (NB)), high Prandtl number and idealized boundary conditions. It is based on a model equation proposed by Segel [1965] by adding rotation terms that lead to a Küppers–Lortz instability [Küppers & Lortz, 1969] and can develop into oscillating hexagons. We perform a weakly nonlinear analysis to find out explicitly the coefficients in the amplitude equation as functions of the rotation rate. These equations describe hexagons and oscillating hexagons quite well, and include the Busse–Heikes (BH) model [Busse & Heikes, 1980] as a particular case. The sideband instabilities as well as short wavelength instabilities of such hexagonal patterns are discussed and the threshold for oscillating hexagons is determined.
HYPERCHAOS IN A MODIFIED CANONICAL CHUA'S CIRCUIT
Authors: THAMILMARAN K. , LAKSHMANAN M. , VENKATESAN A.
Published: March 2004

In this paper, we present the hyperchaos dynamics of a modified canonical Chua's electrical circuit. This circuit, which is capable of realizing the behavior of every member of the Chua's family, consists of just five linear elements (resistors, inductors and capacitors), a negative conductor and a piecewise linear resistor. The route followed is a transition from regular behavior to chaos and then to hyperchaos through border-collision bifurcation, as the system parameter is varied. The hyperchaos dynamics, characterized by two positive Lyapunov exponents, is described by a set of four coupled first-order ordinary differential equations. This has been investigated extensively using laboratory experiments, Pspice simulation and numerical analysis.
A SC–CNN-BASED CHAOTIC MASKING SYSTEM WITH FEEDBACK
Authors: KILIÇ RECAI , ALÇI MUSTAFA , GÜNAY ENIS
Published: March 2004

A secure transmission application of the State Controlled Cellular Neural Network (SC–CNN)-based circuit is presented. Since the SC–CNN-based circuit has feedback connections between the cells, it is potentially very suitable for realizing a chaotic masking system with feedback algorithm. So, we have constructed a chaotic masking system with feedback using the SC–CNN-based circuit. PSpice simulation experiments verify that the proposed SC–CNN-based secure communication system exhibits a good performance for a wide range of amplitude and spectral characteristics of the information signal.
DYNAMICS OF LINEAR MULTISTEP METHODS FOR DELAY DIFFERENTIAL EQUATIONS
Authors: TIAN HONGJIONG , GUO QIAN
Published: March 2004

In this paper we study the relationship between the asymptotic behavior of a numerical simulation by linear multistep method and that of the true solution itself for fixed step sizes. The numerical method is viewed as a dynamical system in which the step size acts as a parameter. Numerical stability of linear multistep method for nonlinear delay differential equation is investigated and we prove that A-stable linear multistep methods are NP-stable. It is shown that a consistent zero-stable linear multistep method does not admit spurious fixed points. The existence of spurious period-two solutions in the time-step is also studied. Finally we give a simple example to illustrate instability of the spurious period-two solutions.
PINNING OF A KINK IN A NONLINEAR DIFFUSIVE MEDIUM WITH A GEOMETRICAL BIFURCATION: THEORY AND EXPERIMENTS
Authors: MORFU S. , MARQUIÉ P. , BILBAULT J. M.
Published: March 2004

We study the dynamics of a kink propagating in a Nagumo chain presenting a geometrical bifurcation. In the case of weak couplings, we define analytically and numerically the coupling conditions leading to the pinning of the kink at the bifurcation site. Moreover, real experiments using a nonlinear electrical lattice confirm the theoretical and numerical predictions.
COMPUTATIONAL MODEL OF OBSESSIVE–COMPULSIVE DISORDER: A UNIFIED EXPLANATION OF THE TREATMENTS
Authors: KUBOTA SHIGERU , AIHARA KAZUYUKI
Published: March 2004

We propose a computational model explaining the pharmacological, behavioral, and neurosurgical treatments of obsessive–compulsive disorder (OCD) in a unified framework. On the basis of the concept that the striatum stores information linked to OCD symptoms, we analyze dynamical changes of a chaotic neural network modeling the striatum. The effect of pharmacological treatment is explained by the increase in refractoriness induced by the neurotransmitter serotonin. The effect of behavior therapy is explained by the time-variant input stimulus weakening neural interconnections according to the covariance rule concerning synaptic plasticity. The effect of neurosurgical treatment is explained by the lesions to the cortical-striatal-thalamic-cortical loop decreasing the feedback of the closed loop. These treatments have a common property that they decrease the stability of stored information in the striatum.
SINGLE STATE-FEEDBACK CHAOTIFICATION OF DISCRETE DYNAMICAL SYSTEMS
Authors: ZHENG YONGAI , CHEN GUANRONG
Published: March 2004

In this paper, the problem of making a nonlinear system chaotic by using state-feedback control is studied, where the feedback controller uses a simple sine function of the system state with only one single component in each dimension. It is proved that the designed control system generates chaos in the sense of Li and Yorke.
SYNCHRONIZATION OF THE REGULAR AND CHAOTIC STATES OF ELECTROMECHANICAL DEVICES WITH AND WITHOUT DELAY
Authors: YAMAPI R. , CHABI OROU J. B. , WOAFO P.
Published: March 2004

We consider in this paper the problem of stability and duration of the synchronization process between two electromechanical devices, both in their regular and chaotic states. Stability boundaries are derived through Floquet theory. The influence of the precision on the synchronization time is also analyzed using numerical simulation of the equations of motion.
AN APPROACH TO CALCULATE THE BIT ERROR RATES OF MULTIPLE ACCESS CHAOTIC-SEQUENCE SPREAD-SPECTRUM COMMUNICATION SYSTEMS EMPLOYING MULTI-USER DETECTORS
Authors: TAM WAI MAN , LAU FRANCIS C. M. , TSE CHI K.
Published: March 2004

In a multiple access spread-spectrum communication system, the bit error performance is usually limited by the mutual interference between users. The use of multi-user detection is an effective method to reduce such interference. In this paper, we consider two linear multi-user detectors, namely, decorrelating detector and minimum mean-square-error detector, applied to a multiple access chaotic-sequence spread-spectrum communication system. An approach to calculate the bit error rate (BER) for such systems is presented. The calculated BERs are compared with those obtained using brute-force computer simulations which give the true system performance.
COARSE BIFURCATION DIAGRAMS VIA MICROSCOPIC SIMULATORS: A STATE-FEEDBACK CONTROL-BASED APPROACH
Authors: SIETTOS CONSTANTINOS I. , KEVREKIDIS IOANNIS G. , MAROUDAS DIMITRIOS
Published: March 2004

We present and illustrate a feedback control-based framework that enables microscopic/stochastic simulators to trace their "coarse" bifurcation diagrams, characterizing the dependence of their expected dynamical behavior on parameters. The framework combines the so-called "coarse time stepper" and arc-length continuation ideas from numerical bifurcation theory with linear dynamic feedback control. An augmented dynamical system is formulated, in which the bifurcation parameter evolution is linked with the microscopic simulation dynamics through feedback laws. The augmentation stably steers the system along both stable and unstable portions of the open-loop bifurcation diagram. The framework is illustrated using kinetic Monte Carlo simulations of simple surface reaction schemes that exhibit both coarse regular turning points and coarse Hopf bifurcations.
ON THE SPATIAL ENTROPY OF TWO-DIMENSIONAL GOLDEN MEAN
Authors: JUANG JONQ , SHIEH SHIH-FENG
Published: March 2004

The aim of this paper is to derive a sharper lower bound for the spatial entropy of two-dimensional golden mean.
A PANORAMIC VIEW OF SOME PERTURBED NONLINEAR WAVE EQUATIONS
Authors: JIMÉNEZ S. , PASCUAL P. , AGUIRRE C. , VÁZQUEZ L.
Published: March 2004

In this paper we present a panoramic view of numerical simulations associated with nonlinear wave equations which appear in different experimental contexts. Mainly, we deal with scalar wave equations, but also the Maxwell equations in nonlinear media are studied. A basic part of this work is devoted to the construction and verification of numerical schemes on a physical basis. The stochastic perturbations of scalar wave equations are especially analyzed by analytical and numerical approaches. Also, other kinds of perturbations are considered, like nonlocal ones. Finally, a summary of promising experimental results from the numerical simulations of the Maxwell system in a nonlinear media is presented.
DYNAMICS OF A TWO DEGREE OF FREEDOM VIBRO-IMPACT SYSTEM WITH MULTIPLE MOTION LIMITING CONSTRAINTS
Authors: WAGG D. J. , BISHOP S. R.
Published: March 2004

We consider the dynamics of impact oscillators with multiple degrees of freedom subject to more than one motion limiting constraint or stop. A mathematical formulation for modeling such systems is developed using a modal approach including a modal form of the coefficient of restitution rule. The possible impact configurations for an N degree of freedom system are considered, along with definitions of the impact map for multiply constrained systems. We consider sticking motions that occur when a single mass in the system becomes stuck to an impact stop, and discuss the computational issues related to computing such solutions. Then using the example of a two degree of freedom system with two constraints we describe exact modal solutions for the free flight and sticking motions which occur in this system. Numerical examples of sticking orbits for this system are shown and we discuss identifying the region, S in phase space where these orbits exist. We use bifurcation diagrams to indicate differing regimes of vibro-impacting motion for two different cases; firstly when the stops are both equal and on the same side (i.e. the same sign) and secondly when the stops are unequal and of opposing sign. For these two different constraint configurations we observe qualitatively different dynamical behavior, which is interpreted using impact mappings and two-dimensional parameter space.
FRACTAL SPECTROSCOPY BY NOISE-FREE STOCHASTIC MULTIRESONANCE AT HIGHER HARMONICS
Authors: KRAWIECKI A. , MATYJAŚKIEWICZ S. , HOŁYST J. A. , KACPERSKI K.
Published: March 2004

Noise-free stochastic resonance is investigated in two chaotic maps with periodically modulated control parameter close to a boundary crisis: the Hénon map and the kicked spin model. Response of the maps to the periodic signal at the fundamental frequency and its higher harmonics is examined. The systems show noise-free stochastic multiresonance, i.e. multiple maxima of the signal-to-noise ratio at the fundamental frequency as a function of the control parameter. The maxima are directly related to the fractal structure of the attractors and basins of attraction colliding at the crisis point. The signal-to-noise ratios at higher harmonics show more maxima, as well as dips where the signal-to-noise ratio is zero. This opens a way to use noise-free stochastic resonance to probe the fractal structure of colliding sets by a method which can be called "fractal spectroscopy". Using stochastic resonance at higher harmonics can reveal smaller details of the fractal structures, but the interpretation of results becomes more difficult. Quantitative theory based on a model of a colliding fractal attractor and a fractal basin of attraction is derived which agrees with numerical results for the signal-to-noise ratio at the fundamental frequency and at the first two harmonics, quantitatively for the Hénon map, and qualitatively for the kicked spin model. It is also argued that the maps under study belong to a more general class of threshold-crossing stochastic resonators with a modulated control parameter, and qualitative discussion of conditions under which stochastic multiresonance appears in such systems is given.
A STUDY ON THE EXISTENCE OF LIMIT CYCLES OF A PLANAR SYSTEM WITH THIRD-DEGREE POLYNOMIALS
Authors: HAN M. , LIN Y. , YU P.
Published: March 2004

The focus of the paper is mainly on the existence of limit cycles of a planar system with third-degree polynomial functions. A previously developed perturbation technique for computing normal forms of differential equations is employed to calculate the focus values of the system near equilibrium points. Detailed studies have been provided for a number of cases with certain restrictions on system parameters, giving rise to a complete classification for the local dynamical behavior of the system. In particular, a sufficient condition is established for the existence of k small amplitude limit cycles in the neighborhood of a high degenerate critical point. The condition is then used to show that the system can have eight and ten small amplitude (local) limit cycles for a set of particular parameter values.
SINGULAR PERTURBATIONS OF QUADRATIC MAPS
Authors: DEVANEY ROBERT L. , JOSIĆ KREŠIMIR , SHAPIRO YAKOV
Published: March 2004

We give a complete description of the dynamics of the mapping fε(z)=z2+(ε/z) for positive real values of ε. We then consider two generalizations: the case of complex ε and the mapping z→zn+(ε/zm), where ε is positive and real. In both cases we provide a full characterization of the map for a certain set of parameters, and give observations based on numerical evidence for all other parameter values. The dynamics of all maps that we consider bears striking resemblance to that of complex quadratic maps.
PEER-TO-PEER INFORMATION WORKSPACES IN INFOTOP
Authors: MAIER RONALD , SAMETINGER JOHANNES
Published: March 2004

Knowledge workers collaborate in teams, networks and communities in order to accomplish knowledge processes. They have to be supported with adequate organizational as well as information and communication technological (ICT) infrastructures. From an ICT perspective, requirements have changed when compared to more traditional (office) work due to the considerably higher complexity of data, the focus on communication across the boundaries of corporate ICT infrastructures and the mobility of knowledge workers. This requires the systematic handling of context and substantially extended functionality for collaboration in the knowledge workers' personal workspaces.

In this paper, we outline typical knowledge processes and discuss ICT support for the personal management of information, of web content, of collaboration and of knowledge. We present Infotop, a tool that supports the creation and management of shared-context information workspaces and organizes knowledge resources in a peer-to-peer (p2p) architecture. We show how Infotop can be used to support typical knowledge work processes and discuss its dimensions, its user interface, its shared context workspaces, its architecture, and some thoughts on a prototype implementation currently under development.
ISOSPIN AND DENSITY DEPENDENCIES OF NUCLEAR MATTER SYMMETRY ENERGY COEFFICIENTS
Authors: BRAGHIN FÁBIO L.
Published: March 2004

Symmetry energy coefficients of explicitly isospin asymmetric nuclear matter at variable densities (from 0.5ρ0 up to 2ρ0) are studied as generalized screening functions. An extended stability condition for asymmetric nuclear matter is proposed. We find the possibility of obtaining stable asymmetric nuclear matter even in some cases for which the symmetric nuclear matter limit is unstable. Skyrme-type forces are extensively used in analytical expressions of the symmetry energy coefficients derived as generalized screening functions in the four channels of the particle hole interaction producing alternative behaviors at different ρ and b (respectively, the density and the asymmetry coefficient). The spin and spin-isospin coefficients, with corrections to the usual Landau Migdal parameters, indicate the possibility of occurring instabilities with common features depending on the nuclear density and n–p asymmetry. Possible relevance for high energy heavy ions collisions and astrophysical objects is discussed.
INTERFERENCE OF DIFFRACTIVE, REFRACTIVE AND COULOMB EFFECTS IN LIGHT NUCLEUS–NUCLEUS ELASTIC SCATTERING CROSS-SECTIONS AT INTERMEDIATE ENERGIES
Authors: BEREZHNOY YU. A. , MOLEV A. S.
Published: March 2004

The patterns typical of Fraunhofer and Fresnel diffraction scattering and refraction (rainbow) scattering are discussed. We extract different interference contributions responsible for the characteristic structural features of the analyzed scattering patterns by means of the S-matrix approach.
KAON PSEUDORAPIDITY DISTRIBUTION IN pA AND AA COLLISIONS AT AGS AND SPS ENERGIES
Authors: LIU FU-HU , ZHANG DONG-HAI , DUAN MAI-YING , ABD ALLAH NABIL N.
Published: March 2004

We study systematically the kaon pseudorapidity distribution in proton-nucleus and nucleus-nucleus collisions at AGS and SPS energies within the cylinder model. The calculated results are compared and shown to be in agreement with the available experimental data.
THE HIDDEN SYMMETRY FOR A QUANTUM SYSTEM WITH A PÖSCHL–TELLER-LIKE POTENTIAL
Authors: DONG SHI-HAI , SUN GUO-HUA , TANG YU
Published: March 2004

The eigenvalues and eigenfunctions of the Schrödinger equation with a Pöschl–Teller (PT)-like potential are presented. A realization of the creation and annihilation operators for the wave functions is carried out. It is shown that these operators satisfy the commutation relations of an SU(1,1) group. Closed analytical expressions are evaluated for the matrix elements of different functions, sin (ρ) and [Formula: see text] with ρ=πx/L.
RELATIVISTIC QUARK MODEL AND PENTAQUARK SPECTROSCOPY
Authors: GERASYUTA S. M. , KOCHKIN V. I.
Published: March 2004

Relativistic five-quark equations are found in the framework of the dispersion relation technique. The solutions of these equations using the method based on the extraction of the leading singularities of the amplitudes are obtained. The five-quark amplitudes for the low-lying pentaquarks are calculated under the condition that flavor SU(3) symmetry holds. The poles of the five-quark amplitudes determine the masses of the lowest pentaquarks. The mass spectra of pentaquarks which contain only light quarks are calculated. The calculation of pentaquark amplitudes estimates the contributions of three subamplitudes: molecular subamplitude BM, Mqqq subamplitude and [Formula: see text] subamplitude. The main contributions to the pentaquark amplitude are determined by the subamplitudes, which include the meson states M.
THE APPLICATION OF THE MODIFIED GLAUBER MODEL II FOR THE DESCRIPTION PROTON-NUCLEUS SCATTERING: EFFECT OF RELATIVISTIC AND NON-RELATIVISTIC OPTICAL POTENTIALS
Authors: AHMED HUSSEIN M. A. , ESMAEL E. H.
Published: March 2004

Calculations of total reaction cross-sections and differential cross-sections using the modified Glauber model II for p –16 O scattering in the energy range 100–497.5 MeV are compared with experimental data. The real parts of the nuclear central potential and spin-orbit potential were used to calculate the modified Glauber model II. The nuclear potential was constructed using two approaches: the Dirac-equation-based optical potential and the non-relativistic treatment. The phenomenological and analytical methods are used to calculate these two approaches. The strength of the real parts of central and spin-orbit potentials are normalized to the best fit to the data. The best values were obtained close to unity. Most of the calculations derived from the Dirac-equation-based optical potentials were more comparable with the experimental data than the non-relativistic calculations. This may be attributed to the delicate cancellation between the short-range repulsive and the long-range attractive contributions. The present investigation indicated that a good choice of the potential at given energy offers a reliable determination of the impact parameter estimated according to the modified Glauber model II.
INFLUENCE OF ISOSPIN ON PRESCISSION PARTICLE EMISSION OF LIGHT FISSIONING SYSTEMS
Authors: YE W.
Published: March 2004

The isospin effect on particle emission for fissioning isobaric sources of 110Tc, 110Pd, 110In and for isotopic sources of 110,117,124In is explored in the framework of the Smoluchowski equation. A statistical model including dissipation is employed to study particle emission in asymmetric and symmetric fission of the In nucleus with different isospins. Calculations show that for a fissioning nucleus which has a larger isospin, charged particle multiplicities are no longer sensitive to dissipation strength or the fission time scale. Hence, for those systems with very high isospins, protons and α particles cannot be used as probes of the dissipation in the fission of hot nuclei. This conclusion does not depend on the mass asymmetry of the fission process.
THE EFFECTIVE ELECTRON-NUCLEUS HAMILTONIAN WITH DISTORTED ELECTRON WAVES
Authors: KEZERASHVILI R. Ya.
Published: March 2004

The interaction of non-relativistic nucleons with relativistic electrons is expressed by the Hamiltonian expanded in a power series of the inverse nucleon mass keeping interaction terms up to second order in the coupling constant e and retaining up through terms of order M-3. The effective Hamiltonian, describing the interaction of the electron wave distorted by the nucleus with the nucleon is obtained. This Hamiltonian describes the distortion of electron waves and allows one to calculate its effect. Using this Hamiltonian for the description of (e,e′p) and (e,e′NN) reactions for medium and heavy nuclei, the off-shell transition matrix elements can be calculated.
COMMENT ON "PROXIMITY POTENTIAL FOR DEFORMED, ORIENTED COLLISIONS AND ITS APPLICATIONS TO 238U+238U" AND "NECK FORMATION EFFECTS IN A PREFORMED CLUSTER MODEL FOR EXOTIC CLUSTER DECAYS"
Authors: ABDUL-LATEEF ALADDIN M.
Published: March 2004

Two papers (N. Malhorta and R. K. Gupta, Phys. Rev.C31, 1179 (1985)) and (S. Kumar and R. K. Gupta, Phys. Rev.C55, 218 (1997)) introduce calculations of the interaction potential between two deformed and pole-to-pole oriented nuclei forming a necked configuration in the overlap region. These calculations have been carried out by using the nuclear proximity approach and utilizing the two-center model for the parameterization of the nuclear shapes. In the first paper the proximity potential for the non-overlapping as well as for the overlapping necked symmetric configuration have been derived. The results obtained for the overlapping necked symmetric configuration is generalized to the asymmetric configuration in the second paper. We have found that the obtained formulas for the proximity energy for the overlapping necked configuration in these previous works are to be corrected as they are obtained with an unrealistic parameterization of the nuclear shape in the neck region.
EFFECT OF THE ADIABATIC VIBRATIONAL COUPLING ON THE FUSION OF THE 16O-238U INTERACTION
Authors: ISMAIL M. , OSMAN M. , RAMADAN KH. A. , SEIF W.
Published: March 2004

The effect of both rotation and vibration of a deformed target nucleus on the fusion cross-section and barrier distributions was studied. This was done in the framework of the microscopically derived heavy-ion (HI) potential. Moreover, the effect of target deformation up to β6 and the density dependence of the NN force on the fusion process was studied in the presence of vibrational excitations of the target. The results obtained were compared with experimental data.
AZIMUTHAL CORRELATION OF SECONDARY PARTICLES FROM 24Mg-NUCLEI COLLISIONS WITH EMULSION AT 4.5A GeV/c
Authors: ABD ALLAH N. N. , ABOU-STEIT S. A. H. , MOHERY M. , LIU FU-HU
Published: March 2004

A systematic study and statistically significant results of the different types of correlations, for angles, rapidity and rapidity intervals, between various charged secondary particles and projectile fragments produced in the inelastic interactions of 24 Mg with emulsion at 4.5 A GeV/c have been investigated. All types of particles are found to be emitted asymmetrically in the azimuthal plane. This asymmetry increases with decreasing the impact parameter. The two-particle correlation function is found to be positive except in the extreme projectile fragmentation region. It has also been observed that the particles belonging to the different kinematical regions of the nucleus-nucleus interactions (intergroup correlation) have a tendency to be emitted from opposite sides of the azimuthal plane. The azimuthal angle correlations for pairs of charged secondary particles are also studied.
THE STABILITY AND DYNAMICS OF HOT-SPOT SOLUTIONS TO TWO ONE-DIMENSIONAL MICROWAVE HEATING MODELS
Authors: IRON DAVID , WARD MICHAEL J.
Published: March 2004

The stability and dynamics of hot-spot solutions to two different classes of scalar, nonlocal, singularly perturbed reaction-diffusion equations is analyzed. These problems arise in the modeling of the microwave heating of a ceramic material placed in a single-mode resonant cavity. For the first model, where the coefficients in the differential operator are spatially homogeneous, an explicit characterization of metastable hot-spot behavior is given in the limit of small thermal diffusivity ε. For the second model, where the differential operator has a spatially inhomogeneous term resulting from the variation in the electric field along the ceramic sample, a hot-spot solution is shown to propagate on an algebraically long time-scale of order O(ε-2) towards the point of maximum field strength. The electrical conductivity of the sample is taken to have either an exponential or a polynomial dependence on the temperature. For the polynomial form, the stability of a hot-spot profile is determined from the eigenvalues of a non-self-adjoint eigenvalue problem. It is proved that a general class of eigenvalue problems of this type may have complex conjugate eigenvalues in the limit ε→0. A careful proof of the stability of the hot-spot profile is given for this delicate case.
FORMATION OF SELF-ASSEMBLED MONOLAYERS ON GOLD SURFACES BY LUMINESCENT OLIGO (PARA-PHENYLENE-VINYLENE)-METHANETHIOL
Authors: LIANG TIEN-TZU , AZEHARA HIROAKI , ISHIDA TAKAO , MIZUTANI WATARU , TOKUMOTO HIROSHI
Published: March 2004

Oligo(para-phenylene-vinylene)-methanethiol of trimer and dimer have been synthesized to prepare monolayers onto Au(111). The trimer diluted in dichloromethane glows with a brilliant blue fluorescence when excited with UV light (365 nm). The absorption and emission spectra of the dimer diluted in CH 2 Cl 2 show a blue shift. The molecular level morphologies of the monolayers prepared on gold surfaces were probed by scanning tunneling microscopy or atomic force microscopy (AFM). The dimer is entire trans isomer, which formed highly ordered self-assembled monolayers (SAMs) on Au. The trimer is a mixture of cis–trans isomers, and did not form ordered monolayers on Au. However, the trimer molecules could be embedded in dodecanethiol SAM, and showed higher conductance than oligo(para-phenylene) molecules characterized using a conductive AFM.
ELECTRO-DISCHARGE METHOD TO MANUFACTURE SUPERPARAMAGNETIC IRON OXIDE NANOPARTICLES
Authors: LEE W. H. , CHUNG C. H. , CHUNG C. L.
Published: March 2004

Functional nanocrystalline metallic iron powder is produced by the method of electro-discharge in the low oxygen environment of water. In order to obtain superparamagnetic iron oxide Fe 3 O 4, the manufacturing Fe particles were oxidized in the oxygen-rich water to continue oxidation process. Besides, the nanocrystalline Fe particle will be oxidized at temperatures of 200° C , 250° C , 300° C , 350° C , 400° C , 500° C and 600° C for 1 h in air to produce iron oxide α- Fe 2 O 3. The X-ray diffraction, SEM and transmission electron microscope (TEM) were used to analyze the crystal structure and the powder morphologies. The results showed that pure Fe and FeO with a pretty narrow particle size distribution ranges from 1 nm to 10 nm were obtained by the method of electro-discharge. After oxygen-rich oxidation treatment the γ- Fe 2 O 3 and Fe 3 O 4 were obtained at room temperature in 10 days. Thereafter, no more transformation was found in water environment. This result proves that Fe 3 O 4 can be a stable superparamagnetic iron oxide. However, for the Fe particles heat-treated at temperatures of 200 to 600° C , α- Fe 2O3 was formed at temperatures above 300° C for 1 h treating time. Further application studies of this material will be presented in our future research works.
DETERMINE THE SIZE AND OXIDIZATION OF SILICON QUANTUM DOTS PREPARED BY THERMAL EVAPORATION METHOD
Authors: CHIEN T. Y. , CHIA C. T. , LIN T. C. , LEE S. C.
Published: March 2004

Raman spectrum has been used to analyze the size of Silicon (Si) quantum dots (QDs) prepared by thermal evaporation. Si QDs were grown in thermal evaporation chamber with Ar gas presented. We determined the average size of the Si QDs by analyzing the optical phonon of Si QDs in Raman spectra. We found that the higher the Ar gas pressure in the chamber, the larger the average size of Si QDs grown by thermal evaporation. We found the Si dot size reaches a maximum, about 7.5 nm in diameter, when Ar gas pressure is about 2–3 torr. The oxidization of Si QDs is also observed by Raman spectra. The life time of oxidized process was about 46 days.
FABRICATION AND MODELING OF MICROCHANNEL MILLING USING FOCUSED ION BEAM
Authors: TSENG A. A. , LEELADHARAN B. , LI B. , INSUA I. , CHEN C. D.
Published: March 2004

The capability of using Focused Ion Beam (FIB) for milling microchannels is experimentally and theoretically investigated. Microchannel structures are fabricated by a NanoFab 150 FIB machine, using an Arsenic (As2+) ion source. A beam current of 5 pA at 90 keV accelerating energy is used. Several microchannel patternings are milled at various dwell times at pixel spacing of 14.5 nm on top of a 60 nm gold-coated silicon wafer. An analytical/numerical model is developed to predict the FIB milling behavior. By comparing with the experimental measurements, the model predictions have been demonstrated to be reliable for guiding and controlling the milling processes.
Pattern differences between distributions of microregional myocardial flows in crystalloid- and blood-perfused rat hearts
Authors: Matsumoto Takeshi , Tachibana Hiroyuki , Asano Takahisa , Takemoto Mami , Ogasawara Yasuo , Umetani Keiji , Kajiya Fumihiko
Published: March 2004

Regional myocardial flow distributions in Langendorff rat hearts under Tyrode and blood perfusion were assessed by tracer digital radiography (100-μm resolution). Flow distributions during baseline and maximal hyperemia following a 60-s flow cessation were evaluated by the coefficient of variation of regional flows (CV; related to global flow heterogeneity) and the correlation between adjacent regional flows (CA; inversely related to local flow randomness). These values were obtained for the original images (642 pixels) and for coarse-grained images (322, 162, and 82 blocks of nearby pixels). At a given point in time during baseline, both CV and CA were higher in blood ( n = 7) than in Tyrode perfusion ( n = 7) over all pixel aggregates ( P < 0.05, two-way ANOVA). During the maximal hyperemia, CV and CA were still significantly higher in blood ( n = 7) than in Tyrode perfusion ( n = 7); however, these values decreased substantially in blood perfusion and the CV and CA differences became smaller than those at baseline accordingly. During basal blood perfusion, the 60-s average flow distribution ( n = 7) showed a smaller CV and CA than those at a given point in time ( P < 0.05, two-way ANOVA). Coronary flow reserve was significantly higher in blood than in Tyrode perfusion. In conclusion, the flow heterogeneity and the local flow similarity are both higher in blood than in Tyrode perfusion, probably due to the different degree of coronary tone preservation and the presence or absence of blood corpuscles. Under blood perfusion, temporal flow fluctuations over 60-s order are largely involved in shaping microregional flow distributions.
Inhibition of cyclooxygenase-2 improves cardiac function after myocardial infarction in the mouse
Authors: LaPointe Margot C. , Mendez Mariela , Leung Alicia , Tao Zhenyin , Yang Xiao-Ping
Published: March 2004

Cyclooxygenase (COX)-2 is expressed in the heart in animal models of ischemic injury. Recent studies have suggested that COX-2 products are involved in inflammatory cell infiltration and fibroblast proliferation in the heart. Using a mouse model, we questioned whether 1) myocardial infarction (MI) in vivo induces COX-2 expression chronically, and 2) COX-2 inhibition reduces collagen content and improves cardiac function in mice with MI. MI was produced by ligation of the left anterior descending coronary artery in mice. Two days later, mice were treated with 3 mg/kg NS-398, a selective COX-2 inhibitor, or vehicle in drinking water for 2 wk. After the treatment period, mice were subjected to two-dimensional M-mode echocardiography to determine cardiac function. Hearts were then analyzed for determination of infarct size, interstitial collagen content, brain natriuretic peptide (BNP) mRNA, myocyte cross-sectional area, and immunohistochemical staining for transforming growth factor (TGF)-β and COX-2. COX-2 protein, detected by immunohistochemistry, was increased in MI versus sham hearts. MI resulted in increased left ventricular systolic and diastolic dimension and decreased ejection fraction, fractional shortening, and cardiac output. NS-398 treatment partly reversed these detrimental changes. Myocyte cross-sectional area, a measure of hypertrophy, was decreased by 30% in the NS-398 versus vehicle group, but there was no effect on BNP mRNA. The interstitial collagen fraction increased from 5.4 ± 0.4% in sham hearts to 10.4 ± 0.9% in MI hearts and was decreased to 7.9 ± 0.6% in NS-398-treated hearts. A second COX-2 inhibitor, rofecoxib (MK-0966), also decreased myocyte cross-sectional area and interstitial collagen fraction. TGF-β, a key regulator of collagen synthesis, was increased in MI hearts. NS-398 treatment reduced TGF-β immunostaining by 40%. NS-398 treatment had no effect on infarct size. These results suggest that COX-2 products contribute to cardiac remodeling and functional deficits after MI. Thus selected inhibition of COX-2 may be a therapeutic target for reducing myocyte damage after MI.
ET-1 induces cortical spreading depression via activation of the ETAreceptor/phospholipase C pathway in vivo
Authors: Kleeberg Jörg , Petzold Gabor C. , Major Sebastian , Dirnagl Ulrich , Dreier Jens P.
Published: March 2004

Recently, it has been shown that brain topical superfusion of endothelin (ET)-1 at concentrations around 100 nM induces repetitive cortical spreading depressions (CSDs) in vivo. It has remained unclear whether this effect of ET-1 is related to a primary neuronal/astroglial effect, such as an increase in neuronal excitability or induction of interastroglial calcium waves, or a penumbra-like condition after vasoconstriction. In vitro, ET-1 regulates interastroglial communication via combined activation of ETAand ETBreceptors, whereas it induces vasoconstriction via single activation of ETAreceptors. We have determined the ET receptor profile and intracellular signaling pathway of ET-1-induced CSDs in vivo. In contrast to the ETBreceptor antagonist BQ-788 and concentration dependently, the ETAreceptor antagonist BQ-123 completely blocked the occurrence of ET-1-induced CSDs. The ETBreceptor antagonist did not increase the efficacy of the ETAreceptor antagonist. Direct stimulation of ETBreceptors with the selective ETBagonist BQ-3020 did not trigger CSDs. The phospholipase C (PLC) antagonist U-73122 inhibited CSD occurrence in contrast to the protein kinase C inhibitor Gö-6983. Our findings indicate that ET-1 induces CSDs through ETAreceptor and PLC activation. We conclude that the induction of interastroglial calcium waves is unlikely the primary cause of ET-1-induced CSDs. On the basis of the receptor profile, likely primary targets of ET-1 mediating CSD are either neurons or vascular smooth muscle cells.
NMDA receptors in nucleus tractus solitarii are linked to soluble guanylate cyclase
Authors: Chianca Deoclecio A. , Lin Li-Hsien , Dragon Deidre Nitschke , Talman William T.
Published: March 2004

We sought to test the hypothesis that cardiovascular responses to activation of ionotropic, but not metabotropic, glutamate receptors in the nucleus tractus solitarii (NTS) depend on soluble guanylate cyclase (sGC) and that inhibition of sGC would attenuate baroreflex responses to changes in arterial pressure. In adult male Sprague-Dawley rats anesthetized with chloralose, the ionotropic receptor agonists N-methyl-d-aspartate (NMDA) and dl-α-amino-3-hydroxy-5-methylisoxazole-propionic acid (AMPA) and the metabotropic receptor agonist trans-dl-amino-1,3-cyclopentane-dicarboxylic acid (ACPD) were microinjected into the NTS before and after microinjection of sGC inhibitors at the same site. Inhibition of sGC produced significant dose-dependent attenuation of cardiovascular responses to NMDA but did not alter responses produced by injection of AMPA or ACPD. Bilateral inhibition of sGC did not alter arterial pressure, nor did it attenuate baroreflex responses to pharmacologically induced changes in arterial pressure. This study links sGC with NMDA, but not AMPA or metabotropic, receptors in cardiovascular signal transduction through NTS.
Impairment of endothelial function in women with a history of preeclampsia: an indicator of cardiovascular risk
Authors: Agatisa Patricia K. , Ness Roberta B. , Roberts James M. , Costantino Joseph P. , Kuller Lewis H. , McLaughlin Margaret K.
Published: March 2004

Preeclampsia is a disorder of pregnancy diagnosed by gestational hypertension and proteinuria. Epidemiological evidence suggests that women who experience preeclampsia are at a greater risk of hypertension and heart disease later in life compared with women who had normal pregnancies. Our objective was to determine whether endothelial function is impaired in postpartum women with a history of preeclampsia in their first pregnancy. We measured forearm blood flow (FBF) by venous occlusion plethysmography in 50 healthy women: 16 with prior preeclampsia, 14 with a prior normotensive pregnancy, and 20 never pregnant controls. The postpartum women participated 6–12 mo after delivery. Heart rate (HR) and blood pressure (BP) were concurrently monitored on the contralateral arm. Hemodynamic variables were assessed at baseline and during a mental stress test known to elicit endothelium-dependent vasodilatation. We found that baseline FBF, HR, systolic BP, and diastolic BP did not significantly differ among the groups, whereas mean arterial pressure in the preeclamptic group was greater than that of the normal pregnancy group ( P = 0.03). Stress-induced FBF (percent change over baseline) was reduced in the preeclamptic group compared with both the normal pregnancy and never pregnant groups ( P = 0.06) and was significantly attenuated compared with women with prior normal pregnancies (91% vs. 147%, P = 0.006). These data demonstrate that women with a history of preeclampsia exhibit impaired endothelial function up to 1 yr postpartum. This observation may explain their increased risk for hypertension and cardiovascular disease.
Subcellular localization of the delayed rectifier K+channels KCNQ1 and ERG1 in the rat heart
Authors: Rasmussen Hanne Borger , Møller Morten , Knaus Hans-Günther , Jensen Bo Skaaning , Olesen Søren-Peter , Jørgensen Nanna Koschmieder
Published: March 2004

In the heart, several K+channels are responsible for the repolarization of the cardiac action potential, including transient outward and delayed rectifier K+currents. In the present study, the cellular and subcellular localization of the two delayed rectifier K+channels, KCNQ1 and ether- a- go- go-related gene-1 (ERG1), was investigated in the adult rat heart. Confocal immunofluorescence microscopy of atrial and ventricular cells revealed that whereas KCNQ1 labeling was detected in both the peripheral sarcolemma and a structure transversing the myocytes, ERG1 immunoreactivity was confined to the latter. Immunoelectron microscopy of atrial and ventricular myocytes showed that the ERG1 channel was primarily expressed in the transverse tubular system and its entrance, whereas KCNQ1 was detected in both the peripheral sarcolemma and in the T tubules. Thus, whereas ERG1 displays a very restricted subcellular localization pattern, KCNQ1 is more widely distributed within the cardiac cells. The localization of these K+channels to the transverse tubular system close to the Ca2+channels renders them with maximal repolarizing effect.
Heart rate reduction by zatebradine reduces infarct size and mortality but promotes remodeling in rats with experimental myocardial infarction
Authors: Hu Kai , Naumann Anne , Fraccarollo Daniela , Gaudron Peter , Kaden Jens J. , Neubauer Stefan , Ertl Georg
Published: March 2004

The importance of heart rate for left ventricular remodeling and prognosis after myocardial infarction is not known. We examined the contribution of heart rate reduction by zatebradine, a direct sinus node inhibitor without negative inotropic effects on left ventricular function and dilatation, on mortality, energy metabolism, and neurohormonal changes in rats with experimental myocardial infarction (MI). Thirty minutes after left coronary artery ligation or sham operation, the rats were randomized to receive either placebo or zatebradine (100 mg·kg–1·day–1per gavage) continued for 8 wk. Mortality during 8 wk was 33.3% in the placebo and 23.0% in the zatebradine group ( P < 0.05); MI size was 36 ± 2% and 30 ± 1% (means ± SE, P < 0.05), respectively. Zatebradine improved stroke volume index in all treated rats but increased left ventricular volume in rats with small MI (2.43 ± 0.10 vs. 1.81 ± 0.10 ml/kg, P < 0.05) but not in rats with large MI (2.34 ± 0.09 vs. 2.35 ± 0.11 ml/kg, not significant). Zatebradine reduced left and right ventricular norepinephrine and increased left and right ventricular 3,4-dihydroxyphenyl ethylene glycol-to-norepinephrine ratio suggesting aggravation of cardiac sympathetic activation by zatebradine after MI. Creatine kinase and lactate dehydrogenase isoenzymes in rats with MI remained unchanged by zatebradine. Lowering heart rate per se reduces mortality and MI size in this model but induces adverse effects on left ventricular remodeling in rats with small MI.