bluuebunny/crossref_metadata_2025 huggingface dataset:
MÖSSBAUER EFFECT STUDIES ON LITHIUM FERRITE SUBSTITUTED WITH CHROMIUM AND ANTIMONY
Authors: LAISHRAM RADHAPIYARI , PRAKASH CHANDRA , PHANJOUBAM SUMITRA , SARMA H. N. K.
Published: February 2003

The effect of Cr 3+ concentration on the various hyperfine interactions for the ferrite system Li 0.5+t Cr x Sb t Fe 2.5-2t-x O 4, 0.0 ≤ x ≤ 1.0, x in steps of 0.2 and t = 0.1, have been studied at room temperature using Mössbauer spectroscopy. The isomershift and the quadrupole splitting are almost negligibly influenced by the change in chromium level. The internal nuclear magnetic field, as determined from the Mössbauer spectra and the linewidth are also studied with the variation of composition. The results have been explained on the basis of various models and a cation distribution has been worked out.
INFLUENCE OF PHOTODEGRADATION ON THE OPTICAL LIMITING PROCESS OF CHLOROPHYLL A
Authors: BARBOSA NETO N. M. , CORRÊA D. S. , DOS SANTOS D. S. , MISOGUTI L. , OLIVEIRA O. N. , ZILIO S. C. , MENDONÇA C. R.
Published: February 2003

The influence of photodegradation on the optical limiting process of chloroform solutions of chlorophyll A is investigated. Optical limitation experiments were carried out with a frequency-doubled, 10 ns Nd:YAG laser at a 5 Hz repetition rate, as a function of sample degradation. Optical limitation becomes less effective in photodegraded samples, which may be explained by the decrease in the concentration of chlorophyll A molecules. It is concluded that the optical limiting process is mainly related to the reverse saturated absorption mechanism, and contributions from light scattering due to photodegradation and the cavity bubbles appear irrelevant.
STRUCTURAL ANALYSIS AND LIFETIME DISTRIBUTION OF ELECTRIC CARRIERS IN CdSe EPITAXIAL LAYERS
Authors: CERBANIC G. , BURDA I. , BORODI Gh. , CHICINAS I. , VIDA SIMITTI I. , SIMON S.
Published: February 2003

X-ray diffraction and scanning microscopy were used to analyze the structure of CdSe epitaxial layers. The structural data indicate the growth from CdSe layers of crystallites corresponding to the hexagonal modification. The lifetime distribution of electric carriers investigated by photoconductive frequency-resolved spectroscopy allows for the appreciation of the carrier kinetics in the studied semiconducting layers.
EFFECTS OF MAGNETIC FIELD ON FRACTURE TOUGHNESS OF MANGANESE–ZINC FERRITE CERAMICS
Authors: WAN Y. P. , FANG D. N. , SOH A. K.
Published: February 2003

Effects of magnetic field on the fracture toughness of magnetic ceramics were experimentally investigated by the use of the single-edge-notch-beam (SENB) specimens of three kinds of manganese–zinc ferrite ceramics with different permeability. Results indicate that there is no significant change in the measured fracture toughness of the Manganese-Zinc Ferrite ceramics in the presence of the magnetic field. Furthermore, the crack lengths caused by the Vickers' indentation on the manganese–zinc ferrite ceramics show that the fracture toughness in the magnetic field direction is almost identical to that in the direction perpendicular to the magnetic field. This reveals that the polycrystalline ceramic still exhibits isotropic fracture behavior after magnetization. Finally, a qualitative explanation is given in terms of a small-scale magnetic saturation model.
ELASTIC PROPERTIES OF THE Zn SUBSTITUTED ErBa2Cu3O7-δ SUPERCONDUCTOR
Authors: CHONG T. V. , ABD-SHUKOR R.
Published: February 2003

Ultrasonic longitudinal and shear velocity in superconducting ErBa 2( Cu 3-x Zn x) O 7-δ (x = 0, 0.01 and 0.05) have been measured using the pulse-echo-overlap method at frequency 5–10 MHz in the temperature range 80–300 K. Longitudinal velocity hysteresis and elastic anomaly were observed in the x = 0 sample. Similar hysteresis was not observed in the x = 0.01 and 0.05 samples. The characteristic Debye temperature and electron–phonon coupling constant were calculated. The absence of hysteresis for longitudinal velocity in the x = 0.01 and 0.05 samples may be due to the spin correlation at the CuO 2 planes which affects the electron–phonon interaction.
HILBERT'S 16TH PROBLEM AND BIFURCATIONS OF PLANAR POLYNOMIAL VECTOR FIELDS
Authors: LI JIBIN
Published: February 2003

The original Hilbert's 16th problem can be split into four parts consisting of Problems A–D. In this paper, the progress of study on Hilbert's 16th problem is presented, and the relationship between Hilbert's 16th problem and bifurcations of planar vector fields is discussed. The material is presented in eight sections.

Section 1: Introduction: what is Hilbert's 16th problem?

Section 2: The first part of Hilbert's 16th problem.

Section 3: The second part of Hilbert's 16th problem: introduction.

Section 4: Focal values, saddle values and finite cyclicity in a fine focus, closed orbit and homoclinic loop.

Section 5: Finiteness problem.

Section 6: The weakened Hilbert's 16th problem.

Section 7: Global and local bifurcations of Zq–equivariant vector fields.

Section 8: The rate of growth of Hilbert number H(n) with n.
BIFURCATIONS OF THE COMMON LEVEL SETS OF ATOMIC HYDROGEN IN VAN DER WAALS POTENTIAL
Authors: KHARBACH J. , DEKKAKI S. , OUAZZANI A. T.-H. , OUAZZANI-JAMIL M.
Published: February 2003

The classical dynamics of a hydrogen atom in a generalized van der Waals potential is investigated. In order to carry out the analytical and numerical investigations for a range of parametric values, we removed the singularity of the problem using Levi–Civita regularization and converted the problem into that of two coupled sextic anharmonic oscillators. We give a complete description of the real phase space structure of the converted system and give also an explicit periodic solution for singular common-level sets of the first integrals. All generic bifurcations of Liouville tori were determined theoretically. Numerical investigations are carried out for all generic bifurcations and we observe chaos-order-chaos transition when one of the system parameters is varied.
DEVIL'S STAIRCASE OF GAP MAPS
Authors: BAN JUNG-CHAO , HSU CHENG-HSIUNG , LIN SONG-SUN
Published: February 2003

This study demonstrates the devil's staircase structure of topological entropy functions for one-dimensional symmetric unimodal maps with a gap inside. The results are obtained by using kneading theory and are helpful in investigating the communication of chaos.
VOLTERRA FUNCTIONAL SECURE COMMUNICATION SYSTEMS
Authors: IRVING A. D. , DEWSON T.
Published: February 2003

Two methods, based on nonlinear dynamics, are described for broad- and narrow-band communication systems. The first approach employs hyperchaotic discrete time series carrier sequences generated with mixed linear–nonlinear coupled differential equations [Irving & Dewson, 1997]. In this first approach it is assumed that the solution of the coupled ordinary differential equations can be represented as a multichannel Volterra functional expansion. Identification, synchronization and the potential unmasking of hyperchaotic communications systems, are achieved by generating a tractable hierarchy of ascending order time series moment equations by operating on a suitably truncated Volterra functional expansion. The estimated moment hierarchy facilitates the calculation of the coefficients of the coupled differential equations that generate the multichannel carrier that is to be modulated by the message. Due to its ability to easily and accurately estimate the coefficients of the governing differential equations the method is applied to the multichannel carrier sequences of data generated by a set of hyperchaotic equations. The inherent problem of resynchronization in chaotic communication systems cannot be avoided in general because of the evolutionary, time dependent, nature of the time series carriers used. This time dependence problem that results in repeated resynchronization can be avoided by considering an alternative and innovative approach that employs time series carrier sequences generated by an input–output multichannel Volterra kernel expansion [Dewson & Irving, 1996]. In this second method, mixed order multichannel Volterra kernel functions are used to generate the carrier sequence that is then modulated by the message. The Volterra kernel function values used to generate the carrier can be identified with the moment hierarchy method [Dewson & Irving, 1996] enabling the message to be deconvolved from the transmitted signal. The modulated nonlinear multichannel signal is transmitted to the receiver. The effect of transmission is to distort and corrupt the signal. In this work it is assumed that the distortions to the transmitted signal remain small, with the case where they become significant being treated elsewhere. First, the case where the signal is received free from both noise and distortion, for example the decryption of an encrypted e-mail, is first considered. Then signal reception in the presence of additive noise is considered. Each of the two proposed methods has been investigated to determine their accuracy and robustness in the presence of additive noise.
WHEN TWO COUPLED PENDULUMS EQUAL ONE: A SYNCHRONIZATION MACHINE
Authors: SMITH H. J. T. , BLACKBURN JAMES A. , BAKER GREGORY L.
Published: February 2003

We show that two coupled pendulums that are coupled and can synchronize, are mathematically equivalent to one "horizontal" parametrically driven pendulum. We have fabricated a horizontal pendulum and present data from this horizontal pendulum which we believe to be the first physical realization of such a mechanical "synchronization machine." A description of intermittent synchronization that can occur when two coupled pendulums are in a chaotic state is given in terms of the data from the horizontal pendulum. We discuss the relationship between the modes of the horizontal pendulum and the corresponding synchronization of the two coupled pendulums. Finally, we show that when a horizontal pendulum is driven by any random source, not necessarily chaotic, intermittent synchronization can occur.
ON SYNCHRONIZATION AND CONTROL OF COUPLED WILSON–COWAN NEURAL OSCILLATORS
Authors: UETA TETSUSHI , CHEN GUANRONG
Published: February 2003

This paper investigates the complex dynamics, synchronization and control of chaos in a system of strongly connected Wilson–Cowan neural oscillators. Some typical synchronized periodic solutions are analyzed by using the Poincaré mapping method, for which bifurcation diagrams are obtained. It is shown that topological change of the synchronization mode is mainly caused and carried out by the Neimark–Sacker bifurcation. Finally, a simple feedback control method is presented for stabilizing an in-phase synchronizing periodic solution embedded in the chaotic attractor of a higher-dimensional model of such coupled neural oscillators.
AN EFFICIENT METHOD FOR COMPUTING THE SIMPLEST NORMAL FORMS OF VECTOR FIELDS
Authors: YU P. , YUAN Y.
Published: February 2003

A computationally efficient method is proposed for computing the simplest normal forms of vector fields. A simple, explicit recursive formula is obtained for general differential equations. The most important feature of the approach is to obtain the "simplest" formula which reduces the computation demand to minimum. At each order of the normal form computation, the formula generates a set of algebraic equations for computing the normal form and nonlinear transformation. Moreover, the new recursive method is not required for solving large matrix equations, instead it solves linear algebraic equations one by one. Thus the new method is computationally efficient. In addition, unlike the conventional normal form theory which uses separate nonlinear transformations at each order, this approach uses a consistent nonlinear transformation through all order computations. This enables one to obtain a convenient, one step transformation between the original system and the simplest normal form. The new method can treat general differential equations which are not necessarily assumed in a conventional normal form. The method is applied to consider Hopf and Bogdanov–Takens singularities, with examples to show the computation efficiency. Maple programs have been developed to provide an "automatic" procedure for applications.
TIME-DELAYED FEEDBACK CONTROL OF TIME-DELAY CHAOTIC SYSTEMS
Authors: GUAN XINPING , CHEN CAILIAN , PENG HAIPENG , FAN ZHENGPING
Published: February 2003

This paper addresses time-delayed feedback control (DFC) of time-delay chaotic systems. To extend the DFC approach to time-delay chaotic system, alter having been successfully used in chaotic systems without time-delays, the standard feedback control (SFC) method is firstly employed to show the main control technique in this paper based on one error control system. Then sufficient conditions for stabilization and tracking problems via DFC are derived from the results based on SFC. Also, the systematic and analytic controller design method can be obtained to stabilize the system to an unstable fixed point and to tracking an unstable periodic orbit, respectively. Some numerical examples are provided to demonstrate the effectiveness of the presented method.
THE MALKUS–ROBBINS DYNAMO WITH A LINEAR SERIES MOTOR
Authors: MOROZ IRENE M.
Published: February 2003

Hide [1997] has introduced a number of different nonlinear models to describe the behavior of n-coupled self-exciting Faraday disk homopolar dynamos. The hierarchy of dynamos based upon the Hide et al. [1996] study has already received much attention in the literature (see [Moroz, 2001] for a review). In this paper we focus upon the remaining dynamo, namely Case 3 of [Hide, 1997] for the particular limit in which the Malkus–Robbins dynamo [Malkus, 1972; Robbins, 1997] obtains, but now modified by the presence of a linear series motor. We compare and contrast the linear and the nonlinear behaviors of the two types of dynamo.
FEEDBACK SYNCHRONIZATION OF CHAOTIC SYSTEMS
Authors: SARASOLA C. , TORREALDEA F. J. , D'ANJOU A. , MOUJAHID A. , GRAÑA M.
Published: February 2003

Feedback coupling through an interaction term proportional to the difference in the value of some behavioral characteristics of two systems is a very common structural setting that leads to synchronization of the behavior of both systems. The degree of synchronization attained depends on the strength of the interaction term and on the mutual interdependency of the structures of both systems. In this paper, we show that two chaotic systems linked through a feedback coupling interaction term of gain parameter k reach a synchronized regime characterized by a vector of variable errors which tends towards zero with parameter k while the interaction term tends towards a finite nonzero permanent regime. This means that maintaining a certain degree of synchronization has a cost. In the limit, complete synchronization occurs at a finite limit cost. We show that feedback coupling in itself brings about conditions permitting that systems with a degree of structural parameter flexibility evolve close towards each other structures in order to facilitate the maintenance of the synchronized regime. In this paper, we deduce parameter adaptive laws for any family of homochaotic systems provided they are previously forced to work, via feedback coupling, within an appropriate degree of synchronization. The laws are global in the space of parameters and lead eventually to identical synchronization at no interaction cost. We illustrate this point with homochaotic systems from the Lorenz, Rössler and Chua families.
CHAOS SYNCHRONIZATION OF GENERAL LUR'E SYSTEMS VIA TIME-DELAY FEEDBACK CONTROL
Authors: LIAO XIAOXIN , CHEN GUANRONG
Published: February 2003

This paper studies a master-slave type of chaos synchronization problem for a general form of Lur'e systems by a time-delay feedback control technique, improving some results of Yalçin et al. [2001]. Some fairly simple algebraic conditions are derived for easier verification, facilitating the design and applications of such chaos synchronization systems.
FUZZY MODEL-BASED APPROACH TO CHAOTIC ENCRYPTION USING SYNCHRONIZATION
Authors: LIAN KUANG-YOW , LIU PETER , CHIU CHIAN-SONG , CHIANG TUNG-SHENG
Published: February 2003

This paper proposes a fuzzy model-based chaotic encryption approach using synchronization. The cryptosystem uses T–S fuzzy models to exactly represent discrete-time chaotic systems into separate linear systems. Then the synchronization problem is solved using linear matrix inequalities. The advantages of this approach are: the general and systematic T–S fuzzy model design methodology suitable for well-known Luré type discrete-time chaotic systems; flexibility in selection of chaotic signals for cryptosystem secure key generator; and multiuser capabilities. Especially taking a chaotic superincreasing sequence as an encryption key enhances the chaotic communication structure to a higher-level of security compared to traditional masking methods. In addition, numerical simulations and DSP-based experiments are carried out to verify the validity of theoretical results.
A ROBUST DEMODULATION APPROACH TO COMMUNICATIONS USING CHAOTIC SIGNALS
Authors: WANG XIAO FAN , WANG ZHI QUAN
Published: February 2003

In this Letter, a new demodulation approach to communication using chaotic signals is presented. Information signal is modulated by applying it as an input to a chaotic system. At the receiver, a synchronous subsystem is constructed for estimates on the states of the chaotic system. The key innovation in our communication system is a new robust filter that recovers the information signal from the scalar transmitted signal.
DIGITAL INFORMATION RECEIVER BASED ON STOCHASTIC RESONANCE
Authors: MORFU S. , BILBAULT J. M. , COMTE J. C.
Published: February 2003

An electronic receiver based on stochastic resonance is presented to rescue subthreshold modulated digital data. In real experiment, it is shown that a complete data restoration is achieved for both uniform and Gaussian white noise.
AN APPLICATION OF THE HIGHLY OPTIMIZED TOLERANCE MODEL TO ELECTRICAL BLACKOUTS
Authors: STUBNA M. D. , FOWLER J.
Published: February 2003

The recently proposed Highly Optimized Tolerance (H.O.T.) model [Carlson & Doyle, 1999, 2000], which aims to describe the statistics of robust complex systems in uncertain environments, is compared with data from the Western United States (W.S.C.C.) power distribution system. We use for comparison a 15-year record of all power outages occurring on the grid, measured in the size of megawatts lost and the number of customers without service. In applying the model to the power grid data, we find that the problem of determining how the resources in the system scale with event size is nontrivial given the assumptions of the model and the information about how the power grid actually operates. Further, we observe that the model agrees closely with the W.S.C.C. data for the megawatts but not the customers, and consequently propose that the assumption in the model of optimal resource distribution is not valid in general when more than one measure of event size is used. A modified H.O.T. model which allows for resource misallocation is introduced and we find that this model can be made to fit both data sets reasonably well.
A NEW CHAOTIC SYSTEM AND ITS GENERATION
Authors: LIU WENBO , CHEN GUANRONG
Published: February 2003

This Letter introduces a relatively simple three-dimensional continuous autonomous chaotic system, which can display complex 2- and 4-scroll attractors in simulations. Its generation and basic dynamical behaviors are briefly described.
STRANGE NONCHAOTIC ATTRACTOR IN HIGH-DIMENSIONAL NEURAL SYSTEM
Authors: SHUAI J. W. , DURAND D. M.
Published: February 2003

A general method for the creation of strange nonchaotic attractor is proposed. As an example, the strange nonchaotic attractor in a high-dimensional globally coupled neural system is studied numerically. For such an attractor, the time interval of continuously positive finite-time Lyapunov exponent must be smaller than the period of the driving stimulus, although it has a long-time positive tail. The intermittency between laminar and burst behavior is a characteristic dynamic of the strange nonchaotic attractors. Simulation results show that the chaotic phase occurs only within a small region around the origin in the parameter space. More than half of the large nonchaotic region is the strange nonchaotic phase. The chaotic phase is typically surrounded by strange nonchaotic attractors. This result also suggests that some biological signals that have a strange structure may be nonchaotic rather than chaotic.
THE SAME DISTRIBUTION OF LIMIT CYCLES IN FIVE PERTURBED CUBIC HAMILTONIAN SYSTEMS
Authors: LIU ZHENGRONG , YANG ZHIYAN , JIANG TAO
Published: February 2003

Using the method of qualitative analysis we show that five perturbed cubic Hamiltonian systems have the same distribution of limit cycles and have 11 limit cycles for some parameters. The accurate location of each limit cycle is given by numerical exploration. In other words, we demonstrate the existence of 11 limit cycles and their distribution in five perturbed systems in two ways, the results obtained from both ways are the same.
CELLULAR NEURAL NETWORKS AND VISUAL COMPUTING
Authors: MAINZER KLAUS
Published: February 2003

Brain-like information processing has become a challenge to modern computer science and chip technology. The CNN (Cellular Neural Network) Universal Chip is the first fully programmable industrial-sized brain-like stored-program dynamic array computer which dates back to an invention of Leon O. Chua and Lin Yang in Berkeley in 1988. Since then, many papers have been written on the mathematical foundations and technical applications of CNN chips. They are already used to model artificial, physical, chemical, as well as living biological systems. CNN is now a new computing paradigm of interdisciplinary interest. In this state of development a textbook is needed in order to recruit new generations of students and researchers from different fields of research. Thus, Chua's and Roska's textbook is a timely and historic publication. On the background of their teaching experience, they have aimed at undergraduate students from engineering, physics, chemistry, as well as biology departments. But, actually, it offers more. It is a brilliant introduction to the foundations and applications of CNN which is distinguished with conceptual and mathematical precision as well as with detailed explanations of applications in visual computing.
Synchronization in Networks of Excitatory and Inhibitory Neurons with Sparse, Random Connectivity
Authors: Börgers Christoph , Kopell Nancy
Published: February 2003

In model networks of E-cells and I-cells (excitatory and inhibitory neurons, respectively), synchronous rhythmic spiking often comes about from the interplay between the two cell groups: the E-cells synchronize the I-cells and vice versa. Under ideal conditions—homogeneity in relevant network parameters and all-to-all connectivity, for instance—this mechanism can yield perfect synchronization. We find that approximate, imperfect synchronization is possible even with very sparse, random connectivity. The crucial quantity is the expected number of inputs per cell. As long as it is large enough (more precisely, as long as the variance of the total number of synaptic inputs per cell is small enough), tight synchronization is possible. The desynchronizing effect of random connectivity can be reduced by strengthening the E→I synapses. More surprising, it cannot be reduced by strengthening the I→E synapses. However, the decay time constant of inhibition plays an important role. Faster decay yields tighter synchrony. In particular, in models in which the inhibitory synapses are assumed to be instantaneous, the effects of sparse, random connectivity cannot be seen.
A Theoretical Model of Axon Guidance by the Robo Code
Authors: Goodhill Geoffrey J.
Published: February 2003

After crossing the midline, different populations of commissural axons in Drosophila target specific longitudinal pathways at different distances from the midline. It has recently been shown that this choice of lateral position is governed by the particular combination of Robo receptors expressed by these axons, presumably in response to a gradient of Slit released by the midline. Here we propose a simple theoretical model of this combinatorial coding scheme. The principal results of the model are that purely quantitative rather than qualitative differences between the different Robo receptors are sufficient to account for the effects observed following removal or ectopic expression of specific Robo receptors, and that the steepness of the Slit gradient in vivo must exceed a certain minimum for the results observed experimentally to be consistent.
Spike-Driven Synaptic Dynamics Generating Working Memory States
Authors: Amit Daniel J. , Mongillo Gianluigi
Published: February 2003

The collective behavior of a network, modeling a cortical module of spiking neurons connected by plastic synapses is studied. A detailed spike-driven synaptic dynamics is simulated in a large network of spiking neurons, implementing the full double dynamics of neurons and synapses. The repeated presentation of a set of external stimuli is shown to structure the network to the point of sustaining working memory (selective delay activity). When the synaptic dynamics is analyzed as a function of pre- and postsynaptic spike rates in functionally defined populations, it reveals a novel variation of the Hebbian plasticity paradigm: in any functional set of synapses between pairs of neurons (e.g., stimulated—stimulated, stimulated—delay, stimulated—spontaneous), there is a finite probability of potentiation as well as of depression. This leads to a saturation of potentiation or depression at the level of the ratio of the two probabilities. When one of the two probabilities is very high relative to the other, the familiar Hebbian mechanism is recovered. But where correlated working memory is formed, it prevents overlearning. Constraints relevant to the stability of the acquired synaptic structure and the regimes of global activity allowing for structuring are expressed in terms of the parameters describing the single-synapse dynamics. The synaptic dynamics is discussed in the light of experiments observing precise spike timing effects and related issues of biological plausibility.
A Stochastic Method to Predict the Consequence of Arbitrary Forms of Spike-Timing-Dependent Plasticity
Authors: Câteau Hideyuki , Fukai Tomoki
Published: February 2003

Synapses in various neural preparations exhibit spike-timing-dependent plasticity (STDP) with a variety of learning window functions. The window functions determine the magnitude and the polarity of synaptic change according to the time difference of pre- and postsynaptic spikes. Numerical experiments revealed that STDP learning with a single-expo nential window function resulted in a bimodal distribution of synaptic conductances as a consequence of competition between synapses. A slightly modified window function, however, resulted in a unimodal distribution rather than a bimodal distribution. Since various window functions have been observed in neural preparations, we develop a rigorous mathematical method to calculate the conductance distribution for any given window function. Our method is based on the Fokker-Planck equation to determine the conductance distribution and on the Ornstein-Uhlenbeck process to characterize the membrane potential fluctuations. Demonstrating that our method reproduces the known quantitative results of STDP learning, we apply the method to the type of STDP learning found recently in the CA1 region of the rat hippocampus. We find that this learning can result in nearly optimized competition between synapses. Meanwhile, we find that the type of STDP learning found in the cerebellum-like structure of electric fish can result in all-or-none synapses: either all the synaptic conductances are maximized, or none of them becomes significantly large. Our method also determines the window function that optimizes synaptic competition.
Elements of a Semiotic Theory of Religion
Authors: Murphy Tim
Published: February 2003

This work is a synopsis of an argument for a semiotic approach to theorizing religion. The central argument combines Jonathan Z. Smith's notion of "sacred persistence" as the dynamic relationship between a canon and a hermeneute with the work of Roland Barthes, Michel Foucault, Friedrich Nietzsche, and Mikhail Bakhtin. The argument is that religion is a process of on-going semiotic construction and displacement wherein heremeneutes select paradigmatic elements to form syntagmatic combinations. One of the aspects of this process of selection and combination is what Bakhtin refers to as "the speech of the other". Often, though not always, this element of religious semiotica takes the form of an agon, or contest. This work draws upon Foucault and Nietzsche to supplement Smith's and Bakhtin's notion of the production of religious speech/interpretations by further theorizing the concept of the agon. It is argued that this approach is an advance upon both essentialist phenomenological approaches and inductive, explanatory approaches. Religion, it is claimed, is best understood on the model of language, and by means of analogous approaches used in the study of language and language behaviors.
Religion after Religion, History after History: Postmodern Historiography and the Study of Religions
Authors: Rennie Bryan
Published: February 2003

The following essay reviews Steven Wasserstrom's Religion after Religion— a partial history of the History of Religions—and three theoretical works on historiography: Hayden White's Metahistory, Peter Novick's That Noble Dream, and Robert F. Berkhofer Jr.'s Beyond the Great Story. As well as introducing readers to the argument of these works, the essay uses Wasserstrom's book as an example of a "monovocal" style of the narration of the phenomenal past in opposition to the polyvocal style called for by the historiographers. The purpose of the essay is to indicate the degree to which monovocal representations can apparently justify singular viewpoints by concealing various agendas and lending authority to dubious conclusions. The essay challenges the elevation of a single authorial voice over the plurality of voices representing the plurality of phenomenal pasts and calls for a greater engagement with the pluralism and polyvocality of postmodern historiography.
Cellular response to hypoxia involves signaling via Smad proteins
Authors: Zhang Hong , Akman Hasan O. , Smith Eric L. P. , Zhao Jin , Murphy-Ullrich Joanne E. , Batuman Olcay A.
Published: February 2003

The transforming growth factor-β (TGF-β) family of cytokines regulates vascular development and inflammatory responses. We have recently shown that exposure of human umbilical vein endothelial cells (HUVECs) to hypoxia (1% O2) increases gene expression and bioactivation of TGF-β2 and induces its downstream effectors, Smad proteins (Smads), to associate with DNA. In the present study, we show that hypoxia-induced TGF-β2 gene expression is dependent on thrombospondin-1–mediated bioactivation of latent TGF-β. Blocking TGF-β2 but not TGF-β1 in hypoxic endothelial cell cultures inhibited induction of the TGF-β2 gene, indicating that an autocrine mechanism driven by bioactivation of TGF-β2 leads to its gene expression in hypoxic HUVECs. Exposure of HUVECs to hypoxia resulted in phosphorylation and nuclear transportation of Smad2 and Smad3 proteins as well as stimulation of transcriptional activities of Smad3 and the transcription factor hypoxia-inducible factor-1α and culminated in up-regulation of TGF-β2 gene expression. Autocrine regulation of TGF-β2 production in hypoxia may involve cross-talk between Smad3 and HIF-1α signaling pathways, and could be an important mechanism by which endothelial cells respond to hypoxic stress.
The function of the bcl-x promoter in erythroid progenitor cells
Authors: Tian Cuixia , Gregoli Paul , Bondurant Maurice
Published: February 2003

The protein Bcl-xL is essential for survival of erythroid progenitor cells, and it increases substantially during late erythrocyte differentiation due to an increase of mRNA. We mapped the transcription start sites of bcl-x mRNA in mouse and human erythroblasts, and we analyzed the function of the mousebcl-x promoter by transient and stable transfection assays in a mouse erythroid cell line using plasmids containing thebcl-x promoter fused to a luciferase reporter gene. In mouse erythroblasts, a cluster of start sites at positions −664, −655, and −644 relative to the ATG initiation codon account for almost all transcripts. Human erythroblasts exhibit a start site at −654 that is homologous to the triplet in the mouse. A short sequence element in the mouse bcl-x promoter that includes nucleotides −1804 through −1734 was identified as very important for transcription. This element also showed strong enhancerlike activity in concert with the SV40 promoter in an enhancer test vector. Analyses of mutations indicated that 2 short sequences within the element, about 15 base pair apart, are necessary for full enhancer activity. Gel shift experiments with oligonucleotides representing these sequences revealed specific binding of nuclear proteins from erythroblasts. Some of these proteins are regulated during the late erythroid differentiation.
Amount of spontaneous apoptosis detected by Bax/Bcl-2 ratio predicts outcome in acute myeloid leukemia (AML)
Authors: Del Poeta Giovanni , Venditti Adriano , Del Principe Maria Ilaria , Maurillo Luca , Buccisano Francesco , Tamburini Anna , Cox Maria Christina , Franchi Annibale , Bruno Antonio , Mazzone Carla , Panetta Paola , Suppo Giovanna , Masi Mario , Amadori Sergio
Published: February 2003

The inability to undergo apoptosis is a crucial mechanism of multidrug resistance in acute myeloid leukemia (AML), and the analysis of mitochondrial apoptotic proteins may represent a significant prognostic tool to predict outcome. Bcl-2 and Bax oncoproteins were evaluated in 255 de novo AML patients (pts) by flow cytometry using an anti–bcl-2 monoclonal antibody (MoAb) and an anti-bax MoAb. The results were expressed as an index (bax/bcl-2) obtained by dividing bax mean fluorescence intensity (MFI) and bcl-2 MFI. Lower bax/bcl-2 ratio was associated with French-American-British (FAB) M0-M1 classes (P = .000 01) and CD34 more than 20% (P < .000 01). There were striking inverse correlations between CD34 or CD117 MFI and bax/bcl-2 values (r = −.40, P < .000 001 andr = −.29, P = .000 002), confirming that immaturity is consistent with this index. Moreover, lower bax/bcl-2 levels were correlated with poor-risk cytogenetics (P = .0002). A significant higher complete remission (CR) rate was found in pts with higher bax/bcl-2 levels (79% versus 45%; P = .000 01). Also, both a longer overall survival (OS) and disease-free survival (DFS) were observed in pts with higher bax/bcl-2 levels (P = .000 01 and = .019). Noteworthy, bax/bcl-2 levels accurately predicted the clinical response and outcome of pts with normal or unknown cytogenetics. Indeed, within this subset of 147 pts, higher bax/bcl-2 ratio was significantly associated both with a higher CR rate (86% versus 42%;P < .000 01) and a longer OS (P = .0016). The independent prognostic value of bax/bcl-2 ratio was confirmed in multivariate analysis. Therefore, mitochondrial oncoproteins, such as bcl-2 and bax, represent both sensitive indicators of clinical outcome and potential targets of novel proapoptotic molecules in order to circumvent chemoresistance.
Pre- and postjunctional inhibitory effects of fenspiride on guinea-pig bronchi
Authors: Girard V , Naline E , Crambes O , Malbezin M , Malmstrom RE , Lundberg JM , Advenier C
Published: February 2003

Fenspiride is a drug with potential benefits in the treatment of obstructive airways disease. It has antibronchoconstriction and anti-inflammatory properties. The aim of this study was to investigate the effect of this drug on the contractions induced in the guinea-pig isolated main bronchus and perfused lung by electrical field stimulation (EFS) or exogenously added agents. Bronchi were stimulated transmurally in the presence of indomethacin 10(-6) M and propranolol 10(-6) M, and isometric tension was measured. In the perfused lung model calcitonin gene-related peptide (CGRP) release was determined in the perfusate fractions as a measure of neuropeptide production. Two successive contractile responses were observed: a rapid cholinergic contraction, followed by a long-lasting contraction due to local release of neuropeptides from C-fibre endings. Fenspiride (10(-6) to 10(-4) M) inhibited the nonadrenergic, noncholinergic (NANC) component of the contraction of the guinea-pig isolated main bronchus induced by EFS. Fenspiride significantly affected contractions induced by exogenously added substance P or [Nle10]-NKA(4-10) only at concentrations higher than 10(-3) M. In the guinea-pig perfused lung, fenspiride inhibited low pH- but not capsaicin-evoked release of CGRP. At higher concentrations (10(-4) M to 3x10(-4) M) fenspiride exhibited a significant inhibitory effect both on the cholinergic component of contractile response induced by EFS in the guinea-pig isolated main bronchus and on exogenously added acetylcholine. In conclusion, the result of this study suggests that fenspiride, in moderate concentrations, reduces the release of neuropeptides, including tachykinins, from sensory nerve endings at a prejunctional level. At higher concentrations, postjunctional actions on bronchial smooth muscle are also present.
Is nitric oxide in exhaled air produced at airway or alveolar level?
Authors: Byrnes CA , Dinarevic S , Busst C , Bush A , Shinebourne EA
Published: February 2003

The aim of this study was to determine whether the nitric oxide (NO) measured in exhaled air is produced at airway or alveolar level. Exhaled NO was measured using a chemiluminescence analyser, and carbon dioxide (CO2 concentration using a Morgan capnograph in single exhalations in 12 healthy subjects (mean age 32 yrs; 6 males and 6 females). For each subject, five exhalations were made directly into the NO analyser and five were made through a T-piece system, which allowed measurement of expiratory flow rate. The peak NO levels measured via the T-piece system were 41.2 (SEM 10.8) parts per billion (ppb), significantly lower than direct levels 84.8 (14.0) ppb (p<0.001). The levels of NO tended to rise to an early peak and plateau, while the CO2 levels continued to rise to peak late in the exhalation. The mean times to reach peak NO levels were 32.2 s (direct) and 23.1 s (T-piece), which were significantly different from that of peak CO2 levels 50.5 s (direct) and 51.4 s (T-piece) (p<0.001). At peak NO level, the simultaneous CO2 level mean 4.9% (SEM 0.14)%, was significantly lower than the peak CO2 reached, 5.8 (0.21)% (p<0.001). We conclude that peak nitric oxide levels are dependent on measurement conditions. There are significant differences between the time to peak of carbon dioxide and nitric oxide. Therefore, most nitric oxide, unlike carbon dioxide, is produced in airways and not at alveolar level.
Atopy, lung function and bronchial responsiveness in symptom-free paediatric asthma patients
Authors: Gruber W , Eber E , Steinbrugger B , Modl M , Weinhandl E , Zach MS
Published: February 2003

In adolescence, some paediatric asthma patients will become symptom-free and require no further treatment. There is little information on the atopic status, lung function and bronchial responsiveness of these patients. Symptom-free asthma patients (n=118) aged 7.7-19.2 yrs, were evaluated 1 year after termination of therapy. Bronchial asthma had previously been diagnosed on the basis of recurrent wheezing episodes. Atopic status was assessed by skin-prick testing. Baseline lung function was measured by spirometry, flow-volume curve and plethysmography. Bronchial responsiveness was assessed nonpharmacologically by cold dry air challenge. Eighty one patients had at least one positive skin test result, and the remaining 37 were defined as nonatopic. In atopic subjects, the prevalence of bronchial hyperresponsiveness was significantly higher than in nonatopic patients (41 out of 81 versus 7 out of 37; p=0.001). Atopic subjects showed a significantly lower maximal expiratory flow at 25% remaining vital capacity (p<0.05) and a higher residual volume (p<0.05) than nonatopic subjects. Nonatopic subjects were significantly younger than atopic patients (p<0.01). These symptom- and medication-free paediatric and adolescent asthma patients could, thus, be divided into two groups: 1) atopic subjects with a tendency towards bronchial hyperresponsiveness; and 2) nonatopic subjects with better lung function and normal bronchial responsiveness In view of the increased understanding of the epidemiology of early childhood wheezing, these findings support the concept of different pathogenic mechanisms underlying wheezing episodes in early childhood.
Airway obstruction and rheumatoid arthritis
Authors: Vergnenegre A , Pugnere N , Antonini MT , Arnaud M , Melloni B , Treves R , Bonnaud F
Published: February 2003

The aim of this study was to assess the percentage of respiratory disorders and airway obstruction in patients with rheumatoid arthritis by comparing lung function test results between patients with rheumatoid arthritis and control subjects with other rheumatological conditions. A prospective case-control study of respiratory symptoms and lung function abnormalities was performed in a series of 100 patients with rheumatoid arthritis. Eighty eight patients with other rheumatological diseases served as controls. Diagnosis of respiratory disorders was based on clinical, radiological and spirometric findings. Airway obstruction was determined from predicted values. The results were compared using Student's t-test and Chi-squared tests. An explanatory analysis was carried out by linear regression. The number of symptoms, respiratory disorders (including bronchiectasis) and lung function abnormalities was higher in patients with rheumatoid arthritis than in controls. After exclusion of smokers, the proportion of airway obstruction in patients with rheumatoid arthritis was 16% (versus 0% in controls), although the patients with rheumatoid arthritis still had more symptoms and respiratory disorders. The Chi-squared test did not identify any relationship between airway obstruction, duration of rheumatoid arthritis and type of treatment and occurrence of Sjogren's syndrome. In the nonsmokers, different explanatory models for the patients with and without a history of cardiac and respiratory disease emerged from multivariate analysis of indices of obstruction. These models included variables characterizing the severity and course of the rheumatoid arthritis. Respiratory disorders (including bronchiectasis) and airway obstruction are more frequent among patients with rheumatoid arthritis than in rheumatological controls. Although the exact pathophysiology of the link between bronchial obstruction and rheumatoid arthritis is still a matter of debate, explanatory factors for obstruction included variables characterizing the rheumatoid arthritis.
Effects of inhaled versus intravenous vasodilators in experimental pulmonary hypertension
Authors: Walmrath D , Schermuly R , Pilch J , Grimminger F , Seeger W
Published: February 2003

Inhaled nitric oxide (NO) causes selective pulmonary vasodilation and improves gas exchange in acute lung failure. In experimental pulmonary hypertension, we compared the influence of the aerosolized vasodilatory prostaglandins (PG) PGI2 and PGE1 on vascular tone and gas exchange to that of infused prostanoids (PGI2, PGE1) and inhaled NO. An increase of pulmonary artery pressure (Ppa) from 8 to approximately 34 mmHg was provoked by continuous infusion of U-46619 (thromboxane A2 (TxA2) analogue) in blood-free perfused rabbit lungs. This was accompanied by formation of moderate lung oedema and severe ventilation-perfusion (V'/Q') mismatch, with predominance of shunt flow (>50%, assessed by the multiple inert gas elimination technique). When standardized to reduce the Pps by approximately 10 mmHg, inhaled NO (200 ppm), aerosolized PGI2 (4 ng x kg(-1) x min(-1)) and nebulized PGE1 (8 ng x kg(-1) x min(-1)) all reduced both pre- and postcapillary vascular resistance, but did not affect formation of lung oedema. All inhalative agents improved the V'/Q' mismatch and reduced shunt flow, the rank order of this capacity being NO > PGI2 > PGE1. In contrast, lowering of Ppa by intravascular administration of PGI2 and PGE1 did not improve gas exchange. "Supratherapeutic" doses of inhaled vasodilators in control lungs (400 ppm NO, 30 ng x kg(-1) x min(-1) of PGI2 or PGE1) did not provoke vascular leakage or affect the physiological V'/Q' matching. We conclude that aerosolization of prostaglandins I2 and E1 is as effective as inhalation of nitric oxide in relieving pulmonary hypertension. When administered via this route instead of being infused intravascularly, the prostanoids are capable of improving ventilation-perfusion matching, suggesting selective vasodilation in well-ventilated lung areas.
Chlorine gas induced acute lung injury in isolated rabbit lung
Authors: Menaouar A , Anglade D , Baussand P , Pelloux A , Corboz M , Lantuejoul S , Benchetrit G , Grimbert FA
Published: February 2003

This study was designed to investigate the pathogenesis of chlorine gas (Cl2) induced acute lung injury and oedema. Isolated blood-perfused rabbit lungs were ventilated either with air (n=7) or air plus 500 parts per million (ppm) of Cl2 (n=7) for 10 min. Capillary pressure, measured by analysing the pressure/time transients of pulmonary arterial, venous and double (both arterial and venous) occlusions, was unchanged in both groups. In Cl2-exposed lungs, the fluid filtration rate increased from -0.228+/-0.25 to 1.823+/-1.23 mL min(-1) x 100 g(-1) (p<0.001) and the filtration coefficient increased from 0.091+/-0.01 to 0.259+/-0.07 mL x min(-1) x cmH2O(-1) x 100 g(-1) (p<0.001). No changes were observed in the control lungs. The extravascular lung water/blood-free dry weight ratio was 8.6+/-1.6 in the Cl2 group and 4.0+/-0.5 in the control group (p<0.001), confirming that the increase in lung weight was related to accumulation of extravascular fluid. Although the alveolar flooding by oedema is explained, in part, by the Cl2-induced epithelial injury, our results suggest that Cl2 exposure induces acute lung injury and oedema due to an increased microvascular permeability.
A longitudinal analysis of pulmonary function in rats during a 12 month cigarette smoke exposure
Authors: Wright JL , Sun JP , Vedal S
Published: February 2003

We wanted to examine the longitudinal effects of chronic cigarette smoke exposure, and to determine whether the chronic alterations in pulmonary function induced by long-term cigarette smoke exposure in an animal model could be predicted by initial or early alterations in function. A group of Sprague Dawley rats was exposed to the smoke of 7 cigarettes x day(-1) for 5 days x week(-1) during a total period of 12 months. Lung volume, flow-volume curves and pressure-volume curves were recorded at baseline, and after 2, 4, 8 and 12 months of smoke exposure. A control group of rats was subjected to the same regimen of testing, but was not exposed to smoke. Thirteen rats completed the study in the smoke-exposed group and seven rats in the control group. We found that chronic exposure to cigarette smoke produced early abnormalities in pulmonary function, with the forced expiratory volume in one second/forced vital capacity (FEV1/FVC) ratio showing an acceleration of ageing effect, particularly between 4 and 8 months of exposure. In this model, although the two groups had significantly different airflow after 12 months, the initial values in each group were remarkably similar, and we could not identify any pulmonary function test which had predictive value. We conclude that longitudinal studies of cigarette smoke exposure in this rat model allow better characterization of the nature and time course of the effects of smoking on the lung.