bluuebunny/crossref_metadata_2025 huggingface dataset:
PROBABILISTIC ORDER LEVEL SYSTEM WHEN ITEMS IN INVENTORY DETERIORATE AND DELAY IN PAYMENTS IS PERMISSIBLE
Authors: SHAH NITA H.
Published: August 2004

An order level inventory model is developed for deteriorating items with a constant rate of deterioration and vendor offering delay in payments. The model is developed under probabilistic demand. It is shown that the model derived can be related to the existing model for non-deteriorating items and when delay in payments is not permissible. The model is supported by a probability distribution function.
OPTIMAL ALLOCATION OF TESTING RESOURCE FOR A MODULAR SOFTWARE
Authors: KAPUR P. K. , JHA P. C. , BARDHAN A. K.
Published: August 2004

Several Software Reliability Growth Models (SRGMs) have been developed in the literature to account for exponential and S-shaped growth curves. There are others, which can account for both depending on the testing environment. Such models are termed as flexible models. Most of the models use calendar/execution time as the testing time. Very few SRGMs have been developed which define explicitly the testing effort functions into the modeling. Testing effort/resource may be computer time and manpower needed during testing. The aim of this paper is twofold.

1. Develop an SRGM with testing efforts which is also flexible

2. Use model in (1) to allocate optimally the testing resource to a modular software subject to different constraints.

Model developed in (1) is validated on different data sets and predictive validity is established. Optimization problems in (2) are mathematical programming problems having the sum of fractional functions as the common objective. These are solved using a dynamic programming approach and closed form solutions have been obtained. Finally, numerical illustrations are provided for two optimization problems.
EDUCING INCONSISTENCY IN FUZZY AHP BY MATHEMATICAL PROGRAMMING MODELS
Authors: GHAZANFARI MEHDI , NOJAVAN MAJID
Published: August 2004

The inconsistency of judgments in the fuzzy Analytic Hierarchy Process (AHP) is a crucial issue. To make the appropriate decision, the inconsistency in decision maker's (DM) judgments needs to be eliminated or reduced. This paper proposes two mathematical models to deal with inconsistency in fuzzy AHP. In the first model, the DM's judgments are modified where the preference order of the DM's judgments remained unchanged. The second model allows reversing the preference orders of judgments. The proposed models aim to eliminate or reduce the inconsistency of fuzzy AHP by changing judgments. The models cause fewer changes for the high certain judgments. Two examples solved by the proposed models are included for purposes of illustration.
BOOTSTRAP CONFIDENCE INTERVALS FOR STEADY-STATE AVAILABILITY
Authors: LIM JAE-HAK , SHIN SANG WOOK , KIM DAE KYUNG , PARK DONG HO
Published: August 2004

Steady-state availability, denoted by A, has been widely used as a measure to evaluate the reliability of a repairable system. In this paper, we develop new confidence intervals for steady-state availability based on four bootstrap methods; standard bootstrap confidence interval, percentile bootstrap confidence interval, bootstrap-t confidence interval, and bias-corrected and accelerated confidence interval. We also investigate the accuracy of these bootstrap confidence intervals by calculating the coverage probability and the average length of intervals.
WORLD VOLUME SOLITONS OF THE D3-BRANE IN THE BACKGROUND OF (p, q) FIVE-BRANES
Authors: LLATAS P. M. , RAMALLO A. V. , SÁNCHEZ DE SANTOS J. M.
Published: August 2004

We analyze the world volume solitons of a D3-brane probe in the background of parallel (p, q) five-branes. The D3-brane is embedded along the directions transverse to the five-branes of the background. By using the S duality invariance of the D3-brane, we find a first-order differential equation whose solutions saturate an energy bound. The SO(3) invariant solutions of this equation are found analytically. They represent world volume solitons which can be interpreted as formed by parallel (-q, p) strings emanating from the D3-brane world volume. It is shown that these configurations are 1/4 supersymmetric and provide a world volume realization of the Hanany–Witten effect.
BOUNDARY OPERATORS IN QUANTUM FIELD THEORY
Authors: ESPOSITO GIAMPIERO
Published: August 2004

The fundamental laws of physics can be derived from the requirement of invariance under suitable classes of transformations on the one hand, and from the need for a well-posed mathematical theory on the other hand. As a part of this programme, the present paper shows under which conditions the introduction of pseudodifferential boundary operators in one-loop Euclidean quantum gravity is compatible both with their invariance under infinitesimal diffeomorphisms and with the requirement of a strongly elliptic theory. Suitable assumptions on the kernel of the boundary operator make it therefore possible to overcome problems resulting from the choice of purely local boundary conditions.
A UNIFORM MODEL OF THE MASSIVE SPINNING PARTICLE IN ANY DIMENSION
Authors: LYAKHOVICH S. L. , SHARAPOV A. A. , SHEKHTER K. M.
Published: August 2004

The general model of an arbitrary spin massive particle in any dimensional space–time is derived on the basis of Kirillov–Kostant–Souriau approach. It is shown that the model allows consistent coupling to an arbitrary background of electromagnetic and gravitational fields.
ON THE CONSISTENCY OF THE EXACT RENORMALIZATION GROUP APPROACH APPLIED TO GAUGE THEORIES IN ALGEBRAIC NONCOVARIANT GAUGES
Authors: SIMIONATO M.
Published: August 2004

We study a class of Wilsonian formulations of non-Abelian gauge theories in algebraic noncovariant gauges where the Wilsonian infrared cutoff Λ is inserted as a mass term for the propagating fields. In this way the Ward–Takahashi identities are preserved to all scales. Nevertheless BRST-invariance in broken and the theory is gauge-dependent and unphysical at Λ≠0. Then we discuss the infrared limit Λ→0. We show that the singularities of the axial gauge choice are avoided in planar gauge and light-cone gauge. In addition the issue of on-shell divergences is addressed in some explicit example. Finally the rectangular Wilson loop of size 2L×2T is evaluated at lowest order in perturbation theory and a noncommutativity between the limits Λ→0 and T→∞ is pointed out.
INTEGRABILITY OF THE N-BODY PROBLEM IN (2+1)-AdS GRAVITY
Authors: VALTANCOLI P.
Published: August 2004

We derive a first order formalism for solving the scattering of point sources in (2+1) gravity with negative cosmological constant. We show that their physical motion can be mapped, with a polydromic coordinate transformation, to a trivial motion, in such a way that the point sources move as timelike geodesics (in the case of particles) or as spacelike geodesics (in the case of BTZ black holes) of a three-dimensional hypersurface immersed in a four-dimensional Minkowskian space–time, and that the two-body dynamics is solved by two invariant masses, whose difference is simply related to the total angular momentum of the system.
THE EFFECTIVE POTENTIAL AND ADDITIONAL LARGE RADIUS COMPACTIFIED SPACE–TIME DIMENSIONS
Authors: CLARK T. E. , LOVE S. T.
Published: August 2004

The consequences of large radius extra space–time compactified dimensions on the four-dimensional one-loop effective potential are investigated for a model which includes scalar self interactions and Yukawa coupling to fermions. The Kaluza–Klein tower of states associated with the extra compact dimensions shifts the location of the effective potential minimum and modifies its curvature. The dependence of these effects on the radius of the extra dimension is illustrated for various choices of coupling constants and masses. For large radii, the consequence of twisting the fermion boundary condition on the compactified dimensions is numerically found to produce but a negligible effect on the effective potential.
TOPOLOGY CLASSES OF FLAT U(1) BUNDLES AND DIFFEOMORPHIC COVARIANT REPRESENTATIONS OF THE HEISENBERG ALGEBRA
Authors: GOVAERTS Jan , VILLANUEVA VICTOR M.
Published: August 2004

The general construction of self-adjoint configuration space representations of the Heisenberg algebra over an arbitrary manifold is considered. All such inequivalent representations are parametrized in terms of the topology classes modulo integer holonomies of flat U(1) bundles over the configuration space manifold. In the case of Riemannian manifolds, these representations are also manifestly diffeomorphic covariant. The general discussion, illustrated by some simple examples in nonrelativistic quantum mechanics, is of particular relevance to systems whose configuration space is parametrized by curvilinear coordinates or is not simply connected, which thus include for instance the modular spaces of theories of non-Abelian gauge fields and gravity.
RESULTS FROM THE BES
Authors: ZHENG ZHI-PENG
Published: August 2004

Results from the BES for the past decade, such as τ mass measurement, measurements of fDs and fD, studies of ξ(2230) and ψ(2s) physics, R scan, and so on, are summarized.
ON SOME MATHEMATICAL TOPICS IN CLASSICAL SYNCHRONIZATION.: A TUTORIAL
Authors: SHILNIKOV ANDREY , SHILNIKOV LEONID , TURAEV DMITRY
Published: August 2004

A few mathematical problems arising in the classical synchronization theory are discussed; especially those relating to complex dynamics. The roots of the theory originate in the pioneering experiments by van der Pol and van der Mark, followed by the theoretical studies by Cartwright and Littlewood. Today, we focus specifically on the problem on a periodically forced stable limit cycle emerging from a homoclinic loop to a saddle point. Its analysis allows us to single out the regions of simple and complex dynamics, as well as to yield a comprehensive description of bifurcational phenomena in the two-parameter case. Of a particular value is the global bifurcation of a saddle-node periodic orbit. For this bifurcation, we prove a number of theorems on birth and breakdown of nonsmooth invariant tori.
CHAOTIC BEHAVIOR OF INTERVAL MAPS AND TOTAL VARIATIONS OF ITERATES
Authors: CHEN GOONG , HUANG TINGWEN , HUANG YU
Published: August 2004

Interval maps reveal precious information about the chaotic behavior of general nonlinear systems. If an interval map f:I→I is chaotic, then its iterates fnwill display heightened oscillatory behavior or profiles as n→∞. This manifestation is quite intuitive and is, here in this paper, studied analytically in terms of the total variations of fnon subintervals. There are four distinctive cases of the growth of total variations of fnas n→∞:

(i) the total variations of fnon I remain bounded;

(ii) they grow unbounded, but not exponentially with respect to n;

(iii) they grow with an exponential rate with respect to n;

(iv) they grow unbounded on every subinterval of I.

We study in detail these four cases in relations to the well-known notions such as sensitive dependence on initial data, topological entropy, homoclinic orbits, nonwandering sets, etc. This paper is divided into three parts. There are eight main theorems, which show that when the oscillatory profiles of the graphs of fnare more extreme, the more complex is the behavior of the system.
LOCAL ACTIVITY OF THE VAN DER POL CNN
Authors: MIN LEQUAN , CHEN GUANRONG
Published: August 2004

This paper studies a class of coupled Van der Pol (CVDP) cellular neural networks (CNNs) that can be realized via a coupled fourth-order circuit with two synaptic currents. The local activity theory, developed by Chua in 1997, is applied to study the CVDP CNN, thereby revealing that the bifurcation diagram of the CVDP CNN has a local activity domain with an edge of chaos, as well as a one-dimensional locally passive domain. Although no chaotic phenomena have been identified in simulations, many complex dynamical behaviors have been observed, such as the co-existence of one-periodic, divergent, and convergent orbits, at the edge of chaos.
THE FOLD-FLIP BIFURCATION
Authors: YU. A. KUZNETSOV  , MEIJER H. G. E. , VAN VEEN L.
Published: August 2004

The fold-flip bifurcation occurs if a map has a fixed point with multipliers +1 and -1 simultaneously. In this paper the normal form of this singularity is calculated explicitly. Both local and global bifurcations of the unfolding are analyzed by exploring a close relationship between the derived normal form and the truncated amplitude system for the fold-Hopf bifurcation of ODEs. Two examples are presented, the generalized Hénon map and an extension of the Lorenz-84 model. In the latter example the first-, second- and third-order derivatives of the Poincaré map are computed using variational equations to find the normal form coefficients.
ALFVÉN INTERIOR CRISIS
Authors: BOROTTO F. A. , CHIAN A. C.-L. , REMPEL E. L.
Published: August 2004

A numerical study of an interior crisis of a large-amplitude Alfvén wave described by the driven-dissipative derivative nonlinear Schrödinger equation, in the low-dimensional limit, is reported. An example of Alfvén interior crisis is characterized using the unstable periodic orbits and their associated invariant stable and unstable manifolds in the Poincaré plane. We suggest that this type of chaotic transition can be observed in space and laboratory plasmas.
BASINS OF ATTRACTION OF THE TWO-DIMENSIONAL "POOR MAN'S NAVIER–STOKES EQUATION"
Authors: BIBLE S. A. , MCDONOUGH J. M.
Published: August 2004

This research is part of an ongoing effort to construct "synthetic velocity" subgrid-scale (SGS) models using discrete dynamical systems (DDSs) for use in large-eddy simulations of turbulent flows. Here we will outline the derivation of the two-dimensional (2-D) "Poor Man's Navier–Stokes" (PMNS) equation from the 2-D, incompressible Navier–Stokes equation to be used in such models and report results from subsequent numerical investigations. In our results emphasis is placed on the effects of initial conditions on the dynamics of the 2-D PMNS equation, using such modes of investigation as regime maps, basins of attraction diagrams, phase portraits, time series and power spectra. The most important findings of this investigation concern applicable ranges of bifurcation parameters, causes and effects of symmetries seen in solutions of the PMNS equation, and the suitability of the methods of investigation used here.
APPLICATION OF MONODISPERSIVE FOAMS AS A SPATIALLY STRUCTURED TWO-PHASE MEDIUM FOR CHEMICAL GAS/LIQUID-REACTIONS
Authors: MATHES HENDRIK , PLATH P. J.
Published: August 2004

Nonideal mixed yet structured chemical reaction systems tend to exhibit spatial inhomogeneities in their conversion kinetics. Reactive two-phase systems invariably involve coupling phenomena between transport processes and the chemical reaction, at least in the phase boundary region. The spatiotemporal structure of the dispersion determines the contact area as well as contact times, local penetration depths, thus setting the boundary conditions for chemical conversion kinetics and mass transport processes. A monodispersive foam is a system of reduced complexity for investigating spatial and temporal reaction kinetics in conjunction with transport processes.

Producing a well-defined foam with equally sized bubbles is a difficult task. After solving this problem, we introduce chemical reactive species into the foams and observe their physicochemical behavior.
MESOSCOPIC DESCRIPTION OF CHEMICAL SUPERCRITICAL HOPF BIFURCATION
Authors: LI QIAN SHU , ZHU RUI
Published: August 2004

The mesoscopic dynamic behavior of the Oregonator model of the Belousov–Zhabotinsky chemical reaction is investigated as the model system experiences a supercritical Hopf bifurcation from focus to limit cycle oscillation. The study is performed by stochastically simulating the corresponding chemical master equation. Comparing the mesoscopic dynamic results with those obtained by the macroscopic dynamics, we find in the mesoscopic description a new type of oscillating state, in which large-amplitude oscillations and small-amplitude oscillations appear randomly alternately. This new state comes out spontaneously within a certain region called Hopf bifurcation range by us. In the mesoscopic description, the Hopf bifurcation point cannot be shown, being replaced by a Hopf bifurcation range. Furthermore, the applications of this new oscillating state to internal signal stochastic resonance are pointed out.
FLUCTUATION-INDUCED SYMMETRY BREAKING IN A BISTABLE SYSTEM: A GENERIC MECHANISM OF SELECTION BETWEEN COMPETING OPTIONS
Authors: NICOLIS S. C.
Published: August 2004

A two-variable bistable system modeling the selection between competing options is considered in the presence of additive white noise, representing environmental or internal variability. It is shown that when the strengths of the noises acting on the evolution equations of the two variables are different a symmetry-breaking process takes place, whereby the state in which the excess variable is perturbed by the strongest noise becomes predominant.
DESIGNING HOPF BIFURCATIONS INTO NONLINEAR DISCRETE-TIME SYSTEMS VIA FEEDBACK CONTROL
Authors: WEN GUILIN , XU DAOLIN
Published: August 2004

Hopf bifurcations lead to limit circles that exhibit oscillatory behaviors in nonlinear dynamical systems. Building a specified limit circle into nonlinear systems by control enables us to achieve preferred dynamical performance in the systems. This paper reports a general control method for generating a variety of specified Hopf bifurcations at a desired parameter location. The proposed control law is applicable to nonresonance, weak resonance, strong resonance, or degenerate cases. It allows us to flexibly operate and manipulate the control of Hopf bifurcations. The discrete washout filters are used for the feedback controller. The feedback control gains are derived from the critical conditions and stability conditions of Hopf bifurcations by means of the center manifold method and normal form technique. Numerical experiments indicate that the control method is effective.
LOGISTIC MAPPING WITH A TIME-DEPENDENT SYSTEM-PARAMETER AND ITS ATTRACTOR BASINS WITH SELF-SIMILAR STRUCTURE
Authors: KUROIWA JOUSUKE , MIKI TAKAFUMI
Published: August 2004

In this paper, logistic mapping with a time-dependent system-parameter (referred as "LMTD") is proposed. In various choices of time dependence, the periodic one has been tried in order to investigate the dynamical properties of LMTD. In certain parameter regions, two different attractors coexist depending on the initial values, for instances, two different chaotic attractors, two different periodic attractors, or two periodic/chaotic attractors. In addition, the whole configuration space of the initial values forms basins of attractions of which structures indicate self-similarity.
THE ABELIAN INTEGRALS OF A ONE-PARAMETER HAMILTONIAN SYSTEM UNDER POLYNOMIAL PERTURBATIONS
Authors: ZHANG TONGHUA , CHEN WENCHENG , HAN MAOAN , ZANG HONG
Published: August 2004

An upper bound Z(2,n)≤[n/2]+6[(n-1)/2]+5 is derived for the number of zeros of Abelian integrals Ĩ(h)=∮γ(h)g(x,y)dx-f(x,y)dy on the open interval (0,1/6), where γ(h) is an oval lying on the algebraic curve Hλ=(1/3)x3+(1/2)x2+λy3-y2=h, f(x,y), g(x,y) are polynomials of x and y, and n= max { deg f(x,y), deg g(x,y)}. The proof exploits the expansion of [Formula: see text] near λ=0.
CHAOTIC BEHAVIORS OF A DIGITAL FILTER WITH TWO'S COMPLEMENT ARITHMETIC AND ARBITRARY INITIAL CONDITIONS AND ORDER
Authors: LING BINGO WING-KUEN , HUNG WAI-FUNG , TAM PETER KWONG-SHUM
Published: August 2004

This letter shows some counter-intuitive simulation results that the symbolic sequences and the state variables of a digital filter with two's complement arithmetic and arbitrary initial conditions and order will be eventually zero when all the filter parameters are even numbers, no matter the system matrix of the filter is stable or not.
MODEL OF CARDIAC TISSUE AS A CONDUCTIVE SYSTEM WITH INTERACTING PACEMAKERS AND REFRACTORY TIME
Authors: LOSKUTOV ALEXANDER , RYBALKO SERGEI , ZHUCHKOVA EKATERINA
Published: August 2004

The model of the cardiac tissue as a conductive system with two interacting pacemakers and a refractory time is proposed. In the parametric space of the model the phase locking areas are investigated in detail. The obtained results make possible to predict the behavior of excitable systems with two pacemakers, depending on the type and intensity of their interaction and the initial phase. Comparison of the described phenomena with intrinsic pathologies of cardiac rhythms is given.
EMERGENCIES AS A MANIFESTATION OF THE EFFECT OF BIFURCATION MEMORY IN CONTROLLED UNSTABLE SYSTEMS
Authors: FEIGIN M. I. , KAGAN M. A.
Published: August 2004

Unusual behavior of dynamic systems with a control parameter is analyzed. Bifurcation induced qualitative changes in phase portraits of such systems are quite routine and ensure efficient operation. This class of systems includes ships with high maneuvering capabilities, aircraft and controlled underwater vehicles designed to be unstable in steady-state motion that are interesting in terms of applications.

Bifurcations may generate tracks of bifurcation memory that are "indicators" of regions of reduced controllability referred to as phase spots. The transition process in the phase spot is estimated qualitatively as a universal dependence of the index of loss of controllability on the control parameter.

The proposed approach has allowed us to predict and investigate emergency manifestations of the bifurcation memory effect occurring during routine maneuvering.
A NEW SYNCHRONIZATION PRINCIPLE FOR A CLASS OF LUR'E SYSTEMS WITH APPLICATIONS IN SECURE COMMUNICATION
Authors: BOWONG SAMUEL , KAKMENI F. M. MOUKAM , KOINA RODOUMTA
Published: August 2004

In this Letter, we propose a new synchronization principle for a class of Lur'e systems. We design, using only a single scalar output, a possible class of observers to detect whether two dynamical systems exhibit identical oscillations. The proposed method is then applied to suggest a means to secure communications. The transmitter contains a chaotic oscillator with an input that is modulated by the information signal. The receiver is a copy of the transmitter driven by a synchronization signal. The advantage of this method over the existing one is that the synchronization time is explicitly computed. An illustrative example of the cubic Chua's circuit is given to show the effectiveness of the proposed approach.
SYNCHRONIZATION OF CHAOTIC SYSTEMS WITH PARAMETRIC UNCERTAINTIES USING SLIDING OBSERVERS
Authors: FEKI MOEZ
Published: August 2004

This paper is concerned with synchronization of chaotic systems. We consider a drive-response type of synchronization via a scalar transmitted signal. Given some structural conditions of chaotic systems, a sliding observer-based response system is constructed to synchronize with the drive system within a finite time. Moreover, if the observer gain is judiciously chosen, robustness with respect to bounded parameter variations is guaranteed. To improve furthermore the performance of the response system, unknown parameters are adaptively estimated in conjunction with the sliding observer. To demonstrate the efficiency of the proposed approach numerical simulation results are presented.
A RECEIVER DESIGN APPROACH TO GENERALIZED SYNCHRONIZATION ON A LINEAR MANIFOLD
Authors: CINCOTTI SILVANO , TEGLIO ANDREA
Published: August 2004

In this paper, generalized synchronization (GS) on a linear manifold between two algebraic nonlinear systems is considered. In particular, conditions for generalized synchronization on a linear manifold are derived and a general approach to the design of a nonlinear receiver that operates under GS conditions is presented. The coupling signal is unidirectional and depends on the state variables of the drive. Moreover, a method that ensures the occurrence of linear GS is discussed and applied to standard chaotic systems (i.e. Lorenz system and Chua's circuit).
SIMPLE CHAOTIC CIRCUIT USING CMOS RING OSCILLATORS
Authors: HOSOKAWA YASUTERU , NISHIO YOSHIFUMI
Published: August 2004

In this study, a chaotic circuit suitable for an integrated circuit is proposed. The circuit consists of two CMOS ring oscillators and a pair of diodes. By using a simplified model of the circuit, the mechanism of generating chaos is explained and the exact solutions are derived. The exact expressions of the Poincaré map and its Jacobian matrix make those possible to confirm the generation of chaos using the Lyapunov exponents and to investigate the related bifurcation phenomena.
CHAOTIFYING DISCONTINUOUS DYNAMICAL SYSTEMS VIA TIME-DELAY FEEDBACK ALGORITHM
Authors: DANCA MARIUS-F.
Published: August 2004

In this paper the anti-control technique of chaos to systems continuous with respect to the state variable using a time-delay feedback technique introduced by Wang, Chen and Yu, is adapted to a class of dynamical systems discontinuous with respect to the state variable. The considered discontinuous initial value problem is transformed into a differential inclusion using the Filippov regularization. Then, certain results on existence and uniqueness of solutions to differential inclusions are used to define our class of discontinuous dynamical systems. Afterwards, introducing an adequate concept of derivative for the considered discontinuous functions, we show that the algorithm for continuous dynamical systems can be adapted to our class of discontinuous problems. Three examples are given.
PERIODICITY AND RECURRENCE IN PIECEWISE ROTATIONS OF EUCLIDEAN SPACES
Authors: MENDES MIGUEL , NICOL MATTHEW
Published: August 2004

We consider the behavior of piecewise isometries in Euclidean spaces. We show that if n is odd and the system contains no orientation reversing isometries then recurrent orbits with rational coding are not expected. More precisely, a prevalent set of piecewise isometries do not have recurrent points having rational coding. This implies that when all atoms are convex no periodic points exist for almost every piecewise isometry.

By contrast, if n≥2 is even then periodic points are stable for almost every piecewise isometry whose set of defining isometries are not orientation reversing. If, in addition, the defining isometries satisfy an incommensurability condition then all unbounded orbits must be irrationally coded.
BREATHER COMPETITION AND PULSE ORBITS IN THE DAMPED DRIVEN SINE–GORDON EQUATION
Authors: HUANG DEBIN
Published: August 2004

The generalized asymptotic inertial manifold (GAIM) of the damped driven Sine–Gordon equation is put forward to govern the long-term behavior of the full partial differential equation (PDE). We then study qualitatively the ordinary differential equation (ODE) by the singular perturbation-theory, which results from restricting the damped driven Sine–Gordon equation to its GAIM. Firstly an analytical criterion for the existence of the homoclinic orbit resulting in chaos is given. Further, the existence of the pulse orbits is showed under the same parametric values as those used in the previous numerical experiments. In our viewpoint these results reflect just the breather competition behavior observed numerically in the Sine–Gordon equation. By comparing with the earlier results obtained in the two-mode Fourier truncation system of the damped driven Sine–Gordon equation, we think that a reasonable discretization reduction from PDE to ODE is very important in the study of dynamics in the infinite dimensional dynamical systems.
GLOBAL SPREAD OF INFECTIOUS DISEASES
Authors: HSU S. , ZEE A.
Published: August 2004

We develop simple models for the global spread of infectious diseases, emphasizing human mobility via air travel and the variation of public health infrastructure from region to region. We derive formulas relating the total and peak number of infections in two countries to the rate of travel between them and their respective epidemiological parameters.
MANAGEMENT OF A PREY-PREDATOR FISHERY BASED ON CONTINUOUS FISHING EFFORT
Authors: KAR T. K. , PAHARI U. K. , CHAUDHURI K. S.
Published: August 2004

This paper deals with the problem of selective harvesting in a hybrid type of prey-predator model. Here we have taken the fishing effort as a dynamic variable and tax as a control instrument. The existence of the possible steady states along with their local stability is discussed. The optimal tax policy is also discussed with the help of Pontryagin's maximum principle. Finally, two numerical examples are taken to illustrate some of the key results.
STABILITY ANALYSIS OF A CONTINUOUS AGE-STRUCTURED MODEL WITH SPECIFIC REFERENCE TO NORTH SEA COD
Authors: ANDREWS J. M. , BLYTHE S. P. , GURNEY W. S. C.
Published: August 2004

We examine the stability of a class of continuous age-structured models. Stability borders are established for the different parameters in the model, including levels required for viability. Two examples are then given, the first is a simple model for which the analysis is straightforward. An example is then shown of the cod population in the North Sea, which involves more complicated life history structures making stability analysis more difficult. The model predicts that the North Sea population will go extinct if fishing levels remain high. We show, however, that if mortality was lowered it would eventually be possible for the population to reach a point where it was stable and within safe biological limits.
Fourier transform and distributional representation of the gamma function leading to some new identities
Authors: Chaudhry M. Aslam , Qadir Asghar
Published: August 2004

We present a Fourier transform representation of the gamma functions, which leads naturally to a distributional representation for them. Both of these representations lead to new identities for the integrals of gamma functions multiplied by other functions, which are also presented here.
Twin positive solutions for three‐point boundary value problems of higher‐order differential equations
Authors: Liu Yuji , Ge Weigao
Published: August 2004

A new fixed point theorem on cones is applied to obtain the existence of at least two positive solutions of a higher‐order three‐point boundary value problem for the differential equation subject to a class ofboundary value conditions. The associated Green′s function is given. Some results obtained recently are generalized.
Association between C-Reactive Protein Levels and N-Terminal Pro-B-Type Natriuretic Peptide in Pre-Dialysis Patients
Authors: Ortega Olimpia , Gallar Paloma , Muñoz Mar , Rodríguez Isabel , Carreño Agustín , Ortiz Milagros , Molina Alvaro , Oliet Aniana , Lozano Luz , Vigil Ana
Published: August 2004

Background: The prevalence of inflammation is high among patients with chronic renal failure but the reason of inflammation is unclear. We test the hypothesis that inflammation in chronic renal failure could be the consequence of an increased left-ventricular wall tension related to ventricular dysfunction, hypervolemia or both. Methods: For assessing left-ventricular filling pressure, plasma level of N-terminal pro-B-type natriuretic peptide (N-BNP) was used, as B-type natriuretic peptide is secreted from the cardiac ventricles in response to increased wall tension. N-BNP levels and C-reactive protein (CRP) were measured on the same day in 75 pre-dialysis patients. A previous history of cardiomiopathy with systolic dysfunction was present in 27 (36%) of them. Results: The levels of N-BNP were not normally distributed (mean: 2,589 ± 4,514 pg/ml; median: 789 pg/ml). The distribution of CRP levels was also not normal (mean: 15 ± 27 mg/l; median: 5 mg/l). Both parameters correlated significantly (r: 0.41; p < 0.005). N-BNP was higher (p < 0.001) in patients with known ventricular dysfunction. Excluding these patients, the correlation between N-BNP and CRP was stronger (r: 0.88; p < 0.001). Univariate analysis in these patients without known cardiomyopathy showed that N-BNP levels also correlated with systolic and diastolic blood pressure (r: 0.54; p < 0.005) and inversely with creatinine clearance (r: –0.43; p < 0.01), serum albumin (r: 0.6; p < 0.001) and hemoglobin levels (r: 0.37; p < 0.05). CRP levels correlated significantly (p < 0.01) with the same parameters as N-BNP in univariate analysis. However, in multiple stepwise regression analysis in which CRP was the dependent variable, only the association with N-BNP remained significant (r: 0.87; p < 0.001). Conclusions: Our results suggest a link between left-ventricular filling pressure and inflammation in patients with advanced renal insufficiency. The importance of strict volume control in these patients, in order to reduce left-ventricular pressure and therefore inflammation, should be considered.
Levamisole in Steroid-Sensitive Nephrotic Syndrome Children with Frequent Relapses and/or Steroid Dependency: Comparison of Daily and Every-Other-Day Usage
Authors: Fu Lin-Shien , Shien Chao-Yan , Chi Ching-Shiang
Published: August 2004

Steroid dependency (SD) and frequent relapses (FR) are common with steroid-sensitive nephrotic syndrome (SSNS). We assessed the effectiveness of daily levamisole in 36 children with SSNS with FR and/or SD. Twenty patients (group 1) were given levamisole 2–3 mg/kg q.o.d. for 4–24 months. Sixteen (group 2) had relapses within 3 months: 5 received levamisole q.d. for 3–18 months, and 11 q.d. for 6 months and then q.o.d. for 4–18 months. Follow-up was 4–36 (mean 20.4 ± 9.2) months. After therapy, relapses (4.82 ± 3.15 vs. 2.01 ± 2.5 in group 1; 5.97 ± 3.38 vs. 1.34 ± 2.1 in group 2; p < 0.05) and prednisolone doses (0.57 ± 0.37 vs. 0.15 ± 0.33 mg/kg/day in group 1; 0.61 ± 0.42 vs. 0.19 ± 0.35 mg/kg/day in group 2; p < 0.05) decreased. Relapse frequency, prednisolone dose, response percentage, and survival curves for remission did not differ between groups. Group 1 had five episodes of leukopenia, and group 2 had four. White blood cell counts normalized after levamisole was discontinued. Serum blood urea nitrogen/creatinine and alanine aminotransferase/aspartate aminotransferase levels were normal. Levamisole is effective in maintaining remission in children with SSNS and FR and/or SD. Daily levamisole can be considered when responses to q.o.d. usage are unsatisfactory.
Fluvastatin Reduces Renal Fibroblast Proliferation and Production of Type III Collagen: Therapeutic Implications for Tubulointerstitial Fibrosis
Authors: Ikeuchi Hidekazu , Kuroiwa Takashi , Yamashita Shin , Hiramatsu Noriyuki , Maeshima Akito , Kaneko Yoriaki , Hiromura Keiju , Ueki Kazue , Nojima Yoshihisa
Published: August 2004

Background: Accumulating evidence suggests that hydroxymethylglutaryl-CoA reductase inhibitors have many biological effects beyond reducing cholesterol synthesis. In a mouse model of renal interstitial fibrosis induced by unilateral ureteral obstruction, fluvastatin, one of the lipophilic hydroxymethylglutaryl-CoA reductase inhibitors, was shown to ameliorate fibrosis. Methods: In the present study, we examined the direct effects of fluvastatin on proliferation, matrix and growth factor production by rat kidney fibroblasts (NRK-49F cells). Results: Treatment with fluvastatin reduced proliferation of NRK-49F cells in a dose-dependent manner. The addition of mevalonate or geranylgeranyl pyrophosphate but not farnesyl pyrophosphate to the culture medium almost completely abolished the effect of fluvastatin. Moreover, fluvastatin treatment decreased the expression of activated Rho in NRK-49F cells suggesting that fluvastatin may decrease cell growth through blocking the activation of Rho. The majority of fluvastatin-treated cells were arrested at the G1 phase, associated with down-regulation of cyclin A and up-regulation of cyclin-dependent kinase inhibitor p27kip1, indicating that cell cycle modulation is an important mechanism. Fluvastatin significantly decreased messenger RNA expression of type III collagen and connective tissue growth factor. Conclusions: Taken together, it is suggested that fluvastatin may prevent tubulointerstitial fibrosis in a variety of progressive renal diseases by inhibiting proliferation of interstitial fibroblasts and their matrix synthesis.
Exogenous Bone Morphogenetic Protein-7 Fails to Attenuate Renal Fibrosis in Rats with Overload Proteinuria
Authors: Ikeda Yukiko , Jung Young Ok , Kim Heungsoo , Oda Takashi , López-Guisa Jesús , Maruvada Ravi , Diamond Deborah L. , Martin Kevin J. , Wing Diane , Cai Xiaohe , Eddy Allison A.
Published: August 2004

Background: Bone morphogenetic protein-7 (BMP-7) plays a critical role in renal development, accelerates recovery from acute renal injury, and more recently it has been shown to delay progressive renal disease. The present study was designed to investigate the effect of BMP-7 on interstitial fibrosis in the rat protein-overloaded model. Methods: Renal disease was induced in 26 rats by daily intraperitoneal injections of bovine serum albumin (BSA); controls (n = 28) were injected with saline. Half of the rats in each group were treated with human recombinant BMP-7 (300 µg/kg i.p. 3 times weekly) and half with placebo. Animals were killed after 3 or 6 weeks. Results: Compared to the saline control groups, the BSA groups had evidence of chronic renal disease: significantly increased urinary protein excretion rates; total kidney collagen content, and increased fibronectin and collagen III interstitial areas. By 6 weeks the BSA + BMP-7 group compared to the BSA + placebo group had a nonsignificant decrease in blood urea nitrogen (40 ± 13 vs. 46 ± 11 mg/dl), total kidney collagen (10.8 ± 2.1 vs. 12.2 ± 3.5 µg/kidney), fibronectin interstitial area (23 ± 4 vs. 25 ± 8%) and collagen III interstitial area (22 ± 6 vs. 28 ± 7%). Despite these results, renal gene expression profiles actually predicted worse fibrosis in the BSA + BMP-7 group with significantly higher total kidney mRNA levels for α1(III) procollagen (2.8 ± 0.5 vs. 1.6 ± 0.6, p < 0.05) and fibronectin at 6 weeks (1.9 ± 0.3 vs. 1.2 ± 0.5, p < 0.05). Renal BMP-7 mRNA levels at 6 weeks were significantly increased in the BSA + placebo group compared to the saline + placebo group with no difference between the BSA + BMP-7 and the BSA + placebo groups. Both cortical and medullary tubules expressed BMP-7 protein but BMP-7 was only detected in the tubular lumina and urine of proteinuric animals. Conclusions: In rats with protein-overload proteinuria, renal tubules continue to express BMP-7 but some of the endogenous protein is secreted into the urinary space. Administration of exogenous recombinant BMP-7 had no effect on proteinuria but was associated with a nonsignificant trend towards less interstitial fibrosis at 6 weeks despite significantly higher kidney extracellular matrix gene mRNA levels. These findings suggest that BMP-7 treatment may have anti-fibrotic effects through enhancement of matrix turnover, although overall these effects are modest in proteinuric states in the absence of significant tubular epithelial cell apoptosis and epithelial-mesenchymal transition.
N-Acetyl Functions and Acetate Detected by Nuclear Magnetic Resonance Spectroscopy of Urine to Detect Renal Dysfunction following Aminoglycoside and/or Glycopeptide Antibiotic Therapy
Authors: Racine S.X. , Le Toumelin P. , Adnet F. , Cohen Y. , Cupa M. , Hantz E. , Le Moyec L.
Published: August 2004

Background/Aims: N-acetylneuraminidine (NeuNAc), N-acetylglutamine (GIcNAc) and acetate are metabolites present in normal urine. In patients treated with aminoglycosides and/or glycopeptides, elevation of these metabolites in urine suggests renal tubular injury. NeuNAc, GIcNAc and acetate are easily detected by magnetic resonance spectroscopy (MRS), in contrast to other bioanalytical methods. In the present study, these urinary metabolites were detected using MRS and compared with standard biochemical markers of renal injury in intensive care unit patients treated with aminoglycosides and/or glycopeptides. Methods: 16 patients with clinical and biochemical signs of renal dysfunction were included in the study. Proton magnetic resonance spectra were obtained from 134 urine samples. The resonance intensity of NeuNAc, GIcNAc and acetate were reported relative to the resonance intensity of creatinine (ct). These ratios were compared with classical parameters of renal dysfunction, such as plasma creatinine and urea concentration, and 24-hour urine volume, by logistic regression and general linear models. Results: Statistical analysis showed that changes in plasma creatinine and urea concentration were reliably reflected in changes in the NeuNAc/ct ratio, and that plasma urea concentration changes also correlated with the acetate/ct ratio; however, the GIcNAc/ct ratio was not related to these measures of overall renal function. Conclusions: NeuNAc/ct may be a useful marker of renal dysfunction in patients treated with aminoglycosides and glycopeptides; by MRS it can be both straightforward and informative to follow the renal function of patients treated with these antibiotics.
Combined Therapy of Cilazapril and Losartan Has No Additive Effects in Ameliorating Adriamycin-Induced Glomerulopathy
Authors: Kim Ho-Jung , Ryu Jun-Ho , Han Sang-Woong , Park Ile Kyu , Paik Seung Sam , Park Moon Hyang , Paik Doo Jin , Chung Ho-Sam , Kim Soo Wan , Lee Jong Un
Published: August 2004

Aims: Effects of the blockade of renin-angiotensin system (RAS), by angiotensin-converting enzyme inhibitor (ACEi), type 1 angiotensin II receptor blocker (ARB), or a combination of both, were evaluated in Adriamycin (ADR)-induced glomerulopathy. Methods: Male Sprague-Dawley rats (180–250 g) were induced of glomerulopathy by treatment with ADR (2 mg/kg, i.v.). Six weeks later, they were treated with cilazapril (1 mg/kg/day) and/or losartan (10 mg/kg/day) for an additional 6 weeks. Results: The urinary excretion of protein progressively increased following the treatment with ADR, which was prevented by ACEi, ARB, and a combination of both. Similarly, the glomerulopathy assessed by glomerulosclerosis index was also ameliorated by ACEi or ARB. However, combined therapy of both ACEi and ARB was without an additional effect (Control 1.4 ± 0.4%, ADR 10.7 ± 2.7%**, ACEi 0.8 ± 0.4%, ARB 2.6 ± 1.0%, ACEi+ARB 1.7 ± 1.5%, ** p < 0.01 vs. Control). The expression of transforming growth factor-β1 was increased following the treatment with ADR (1.4 ± 0.07-fold, p < 0.05 vs. Control), however, the degree of which was similarly blunted by either ACEi, ARB, or the combination of both. The expression of type 1 angiotensin II receptor mRNA increased following the treatment with ADR, the degree of which was further upregulated by ACEi and decreased by ARB to the control level (ADR 1.3 ± 0.06-fold*, ACEi 1.8 ± 0.05-fold***, ARB 1.0 ± 0.04-fold, * p < 0.05 and *** p < 0.001 vs. Control). The combined therapy of ACEi and ARB still showed an upregulation of type 1 angiotensin II receptor mRNA, however, of which degree was mitigated compared with that induced by ACEi alone (ACEi+ARB 1.5 ± 0.04-fold, ** p < 0.01 vs. Control). On the contrary, the expression of type 2 angiotensin II receptor mRNA was downregulated following the treatment with ADR, which was similarly restored to the control level by ACEi, ARB, and a combination of both (ADR 0.5 ± 0.08-fold**, ACEi 1.0 ± 0.06-fold, ARB 1.0 ± 0.05-fold, ACEi+ARB 1.0 ± 0.05-fold, ** p < 0.01 vs. Control). Conclusion: It is suggested that combined therapy of ACEi and ARB with relatively high or maximal doses of each drug has no additive or synergistic benefits on the progression of ADR-induced glomerulopathy. Effects of RAS blockade may in part be related to differential regulation of type 1 and type 2 angiotensin II receptors.
Nystagmus Measured with Video-Oculography: Methodological Aspects and Normative Data
Authors: Levo Hilla , Aalto Heikki , Petteri Hirvonen Timo
Published: August 2004

Detailed analysis of eye movements is essential in order to understand the pathophysiology underlying vestibular disturbances. We applied a commercial video-oculography (VOG) to measure spontaneous and provoked nystagmus in 20 healthy subjects. The slow-phase velocity (SPV) of the nystagmus was calculated. We also simultaneously recorded the eye movements on a standard VHS videotape to be able to confirm the results derived from the VOG paper charts. The nystagmus results derived from the VOG charts and the simultaneous videotaping agreed well. Nystagmus was found in 17 subjects. Spontaneous nystagmus was seen in 20%, positional nystagmus in 55%, and head-shaking nystagmus in 35% of the participants. Although nystagmus was frequent (85%), the mean SPV for nystagmus was low (1.7°/s). The VOG is a modern and sensitive method to record eye movements, but visual inspection of the videotape may be needed in selected cases to confirm occurrence of nystagmus.
Use of Morphological Indicators to Predict Outcomes of Palatopharyngeal Surgery in Patients with Obstructive Sleep Apnea
Authors: Li Hsueh-Yu , Chen Ning-Hung , Lee Li-Ang , Shu Yu-Hsiang , Fang Tuan-Jen , Wang Pa-Chun
Published: August 2004

There is no consensus on how to quantify the abnormality of upper airway structures in patients with obstructive sleep apnea (OSA). This research aimed to use morphological indicators as clinical predictors to correlate morphological stage and surgical results in OSA patients. One hundred and five patients with OSA received palatopharyngeal surgery, i.e. extended uvulopalatal flap (EUPF). Morphological indicators including modified Mallampati grade (MMP), tonsil size, and body mass index were used to stage OSA patients preoperatively. Change of respiratory disturbance index (RDI) was used to monitor change of sleep apnea events. Success rates were compared among patients of different morphological stages. One year after EUPF, the success rates of EUPF in stage I, II, and III patients were 100, 92.9 and 61.4%, respectively. Change of RDI was significantly correlated with MMP and tonsil size. MMP and tonsil size were predictive of the change of RDI (R2 = 0.29). Morphological stage may serve as a reliable selection criterion for patients undergoing EUPF surgery and can significantly predict the change of sleep apnea events following EUPF surgery.
Effects of Alcohol and Noise on Temporary Threshold Shift in Guinea Pigs
Authors: Liu Tien-Chen , Hsu Chuan-Jen , Hwang Juen-Haur , Tseng Fen-Yu , Chen Yuh-Shyang
Published: August 2004

The purpose of this study was to investigate the effects of concomitant exposure to noise and alcohol on the auditory thresholds. Twenty-four guinea pigs were equally divided into three groups: the acute intoxication group, the chronic intoxication group and the control group. Animals in the acute group received single intraperitoneal injections of ethanol (2 g/kg). In the chronic group, alcohol was administered via drinking water (10%, v/v) over a 60-day period. All animals were exposed to a white noise at the intensity of 105 dB A for 30 min. Auditory brainstem response (ABR) thresholds and distortion product otoacoustic emission (DPOAE) levels were measured before, immediately after noise exposure and also 1, 2, and 7 days following exposure. The results showed: first, acute alcohol injection caused a significant, temporary elevation of ABR threshold (4.8 dB in average), while chronic alcohol treatment did not change auditory threshold significantly. Second, noise exposure induced a mean threshold shift of 15.4– 19.7 dB. ABR threshold returned to normal 2 days after exposure. Both acute and chronic alcohol treatment did not alter the magnitude and time course of recovery of the temporary threshold shift (TTS). Third, the mean DPOAE amplitudes decreased at most frequencies following acute injection of alcohol. However, the differences did not reach statistical significance. Fourth, the mean DPOAE levels dropped 3.4–9.6 dB in all groups after noise exposure and returned to normal 1 day to 2 days after noise. There were no significant differences in the amount of DPOAE suppression after noise between the three groups. In summary, we have found that acute and chronic treatment of alcohol in combination with noise did not significantly exacerbate TTS or decrease DPOAE amplitudes relative to noise exposure alone.