bluuebunny/crossref_metadata_2025 huggingface dataset:
Climate and the prevalence of symptoms of asthma, allergic rhinitis, and atopic eczema in children
Authors: Weiland S K , Hüsing A , Strachan D P , Rzehak P , Pearce N
Published: June 2004

Aims:To investigate the association between climate and atopic diseases using worldwide data from 146 centres of the International Study of Asthma and Allergies in Childhood (ISAAC).

Methods:Between 1992 and 1996, each centre studied random samples of children aged 13–14 and 6–7 years (approx. 3000 per age group and centre) using standardised written and video questionnaires on symptoms of asthma, allergic rhinoconjunctivitis, and atopic eczema during the past 12 months. Data on long term climatic conditions in the centres were abstracted from one standardised source, and mixed linear regression models calculated to take the clustering of centres within countries into account.

Results:In Western Europe (57 centres in 12 countries), the prevalence of asthma symptoms, assessed by written questionnaire, increased by 2.7% (95% CI 1.0% to 4.5%) with an increase in the estimated annual mean of indoor relative humidity of 10%. Similar associations were seen for the video questionnaire and the younger age group. Altitude and the annual variation of temperature and relative humidity outdoors were negatively associated with asthma symptoms. The prevalence of eczema symptoms correlated with latitude (positively) and mean annual outdoor temperature (negatively).

Conclusions:Results suggest that climate may affect the prevalence of asthma and atopic eczema in children.
Assessing individual employee risk factors for occupational asthma in primary aluminium smelting
Authors: Barnard C G , McBride D I , Firth H M , Herbison G P
Published: June 2004

Aims:To assess the significance of individual risk factors in the development of occupational asthma of aluminium smelting (OAAS).

Methods:A matched case-control study nested in a cohort of 545 workers employed in areas with moderate to high levels of smelting dust and fume. The cohort comprised those who had their first pre-employment medical examination between 1 July 1982 and 1 July 1995; follow up was until 31 December 2000. Forty five cases diagnosed with OAAS and four controls per case were matched for the same year of pre-employment and age within ±5 years. The pre-employment medical questionnaires were examined, blinded as to case-control status, and information obtained on demographics and details of allergic symptoms, respiratory risk factors, respiratory symptoms, and spirometry. Data from the subsequent medical notes yielded subsequent history of hay fever, family history of asthma, full work history, date of termination or diagnosis, and tobacco smoking history at the end-point.

Results:There was a significant positive association between hay fever diagnosed either at or during employment and OAAS (adjusted OR 3.58, 95% CI 1.57 to 8.21). A higher forced expiratory ratio (FEV1/FVC%) at employment reduced the risk of developing OAAS (adjusted OR 0.93, 95% CI 0.88 to 0.99). The risk of OAAS was more than three times higher in individuals with an FER of 70.0–74.9% than in individuals with an FER ⩾80.0% (adjusted OR 3.46, 95% CI 1.01 to 11.89).

Conclusions:Individuals with hay fever may be more susceptible to occupational asthma when exposed to airborne irritants in aluminium smelting. The pathological basis may be reduced nasal filtration and increased bronchial hyperresponsiveness.
Erosion of nails following thallium poisoning: a case report
Authors: Saha A , Sadhu H G , Karnik A B , Patel T S , Sinha S N , Saiyed H N
Published: June 2004

This case report describes a patient with thallium poisoning caused by repeated exposure to low doses of thallium. Alopecia and nail changes were the most prominent features of this case. There was dystrophy of nails in the form of whitish lunular stripes. This is the first report of complete erosion of proximal parts of nails following thallium poisoning. This case is the first report of thallium poisoning from India occurring from repeated low dose exposure.
Deindustrialisation and the long term decline in fatal occupational injuries
Authors: Loomis D , Richardson D B , Bena J F , Bailer A J
Published: June 2004

Aims:To examine the extent to which deindustrialisation accounts for long term trends in occupational injury risk in the United States.

Methods:Rates of fatal unintentional occupational injury were computed using data from death certificates and the population census. Trends were estimated using Poisson regression. Standardisation and regression methods were used to adjust for the potential effect of structural change in the labour market.

Results:The fatal occupational injury rate for all industries declined 45% from 1980 to 1996 (RR (rate ratio) 0.55, 95% CI 0.52 to 0.57). Adjustment for structural changes in the workforce shifted the RR to 0.62 (95% CI 0.60 to 0.65). Expanding industries enjoyed more rapid reduction in risk (−3.43% per year, 95% CI −3.62 to −3.24) than those that contracted (−2.65% per year, 95% CI −2.88 to −2.42).

Conclusions:Deindustrialisation contributed to the decline of fatal occupational injury rates in the United States, but explained only 10–15% of the total change.
Point-of-sale glass bottle recycling: indoor airborne exposures and symptoms among employees
Authors: Kennedy S M , Copes R , Bartlett K H , Brauer M
Published: June 2004

Aims:To assess the impact of newly introduced point-of-sale glass bottle recycling on indoor air quality and employee health.

Methods:Airborne exposures and both chronic and acute respiratory and somatic symptoms were surveyed among 226 employees at 36 randomly selected liquor stores with bottle recycling and in-house glass breaking. Each store was visited twice; between visits glass breaking was discontinued for one month in half the stores (selected at random), although bottles were still collected and stored on site. Rates of chronic symptoms were compared to an external, unexposed control population.

Results:Geometric mean exposure levels were 0.18 mg/m3for inhalable particulate matter and 3.6 EU/m3for endotoxin (270 personal samples); 1064 CFU/m3for viable fungi (648 area samples). Fungal levels were associated with visibly mouldy bottles being broken, outdoor fungal counts, and uncovered glass bins. Exposures were not altered by the intervention of shutting down glass breaking machinery. Compared to controls, employees reported more work related chronic chest tightness and chronic nasal symptoms. Acute chest symptoms were associated with breaking visibly mouldy bottles, but not with measured fungal counts. Inhalable particulate matter levels >0.2 mg/m3were associated with acute upper airway irritation. Somatic symptoms were associated with measures of psychosocial job strain.

Conclusion:Results suggest that this type of recycling programme may generate fungal exposures sufficient to elicit upper airway and chest symptoms.
Using a representative sample of workers for constructing the SUMEX French general population based job-exposure matrix
Authors: Guéguen A , Goldberg M , Bonenfant S , Martin J C
Published: June 2004

Background:Job-exposure matrices (JEMs) applicable to the general population are usually constructed by using only the expertise of specialists.

Aims:To construct a population based JEM for chemical agents from data based on a sample of French workers for surveillance purposes.

Methods:The SUMEX job-exposure matrix was constructed from data collected via a cross-sectional survey of a sample of French workers representative of the main economic sectors through the SUMER-94 survey: 1205 occupational physicians questioned 48 156 workers, and inventoried exposure to 102 chemicals. The companies’ economic activities and the workers’ occupations were coded according to the official French nomenclatures. A segmentation method was used to construct job groups that were homogeneous for exposure prevalence to chemical agents. The matrix was constructed in two stages: consolidation of occupations according to exposure prevalence; and establishment of exposure indices based on individual data from all the subjects in the sample.

Results:An agent specific matrix could be constructed for 80 of the chemicals. The quality of the classification obtained for each was variable: globally, the performance of the method was better for less specific and therefore more easy to assess agents, and for exposures specific to certain occupations.

Conclusions:Software has been developed to enable the SUMEX matrix to be used by occupational physicians and other prevention professionals responsible for surveillance of the health of the workforce in France.
Biomonitoring of traffic police officers exposed to airborne platinum
Authors: Iavicoli I , Bocca B , Petrucci F , Senofonte O , Carelli G , Alimonti A , Caroli S
Published: June 2004

Background:Over the past two decades there has been a substantial increase in environmental levels of palladium, platinum, and rhodium, the platinum group elements (PGEs), due to the widespread use of catalytic converters for automotive traction.

Aim:To evaluate urinary platinum levels in occupationally exposed subjects.

Methods:A total of 161 employees from the Rome City Police Force were studied; 103 were traffic police involved in controlling streets with an average flow of vehicles, while the remaining 58 were control subjects engaged only in office work. Platinum quantification in the urine samples of these subjects was carried out by sector field inductively coupled plasma mass spectrometry.

Results:There were no statistically significant differences between platinum levels in the group of subjects engaged in traffic control and the control group (4.45 (2.42) ng/lv4.56 (2.84) ng/l, respectively).

Conclusions:Urinary levels were found to be higher than those reported for other urban populations, thus showing a progressive increase in human exposure to Pt.
A SIMPLE MODEL FOR DYNAMIC HETEROGENEITIES IN A SUPERCOOLED LIQUID
Authors: HARBOLA UPENDRA , DAS SHANKAR P.
Published: June 2004

The self-consistent mode-coupling theory (MCT) has been used to analyze the heterogeneous dynamical nature of a binary supercooled liquid. The non-Gaussian behavior is studied by analyzing the self part of the Van Hove correlation function, Gs(r, t). From the analysis of the single particle dynamics we identify a fraction (ϕM) of particles which are dynamically more active and find that ϕM increases as the temperature is decreased. This behavior is qualitatively similar to the computer simulation studies of the same system.
ON THE OPTICAL CHARACTERISTICS OF CdS THIN FILMS DEPOSITED BY QUASI-CLOSED VOLUME TECHNIQUE
Authors: RUSU MIHAELA , SALAORU IULIA , POPA M. E. , RUSU G. I.
Published: June 2004

Cadmium sulfide (CdS) thin films (d=0.15–1.15 μ m ) were deposited onto glass substrates by the quasi-closed volume technique under vacuum. The investigations shown that the films are polycrystalline and have a hexagonal structure. It was experimentally established that the films with stable structure can be obtained if they are submitted to a heat treatment, consisting of several succesive heating/cooling cycles within a given temperature range (ΔT=300–600 K ), the temperature dependence of the electrical conductivity becomes reversible. For heat-treated samples, the values of thermal activation energy calculated from the temperature dependence of the electrical conductivity, ranged between 2.30–2.45 eV. The spectral dependences of the transmission and absorption coefficients were studied in the range 500–1400 nm. The influence of heat treatment on the shape of the absorption spectra and dispersion index of refraction is studied for samples with different thickness. Optical energy gap, calculated from the absorption spectra was in the range 2.30–2.5 eV.
THE STRUCTURE OF BETHE ANSATZ SOLUTIONS FOR THE CHAIN N=8, r=4
Authors: CASPERS W. J. , LULEK B. , LULEK T. , KUZMA M. , WAL A.
Published: June 2004

The Bethe Ansatz can be treated using two approaches: The Co-ordinate Bethe Ansatz (CBA) and The Algebraic Bethe Ansatz (ABA). In this paper the relation between the solutions given by these two methods is addressed. The considerations are based on the finite Heisenberg magnet with N=8 nodes and for r=4 reversed spins s=1/2. Both methods provide consistent solutions in the entire Brillouin zone (BZ). Moreover there is a special point — a border of the BZ — for both approaches, in which the solutions are not well-defined.
NEW PATH-INTEGRAL QUANTIZATION APPROACH FOR A LAGRANGIAN MODEL IN TERMS OF HUBBARD OPERATORS
Authors: FOUSSATS A. , REPETTO C. , ZANDRON O. P. , ZANDRON O. S.
Published: June 2004

In the present work the renormalized field theory for the Lagrangian formalism in terms of Hubbard operators is given. It is shown that starting from our path-integral representation found recently, it is possible to contruct the perturbative formalism and the standard Feynman diagram approach for operators verifying the Hubbard algebra. We show that by means of the introduction of proper ghost variables, propagators and vertices can be renormalized to each order. Our Lagrangian approach is checked using the Heisenberg ferromagnet and the antiferromagnet simpler models. In particular, the renormalized ferromagnetic magnon propagator coming from our formalism is studied in details, and it is shown how the softening of the magnon frequency is predicted by the model.
QUANTUM STATES OF A GENERALIZED TIME-DEPENDENT INVERTED HARMONIC OSCILLATOR
Authors: PEDROSA I. A. , GUEDES I.
Published: June 2004

We discuss the extension of the Lewis and Riesenfeld method of solving the time-dependent Schrödinger equation to cases where the invariant has continuous eigenvalues and apply it to the case of a generalized time-dependent inverted harmonic oscillator. As a special case, we consider a generalized inverted oscillator with constant frequency and exponentially increasing mass.
STRUCTURAL STUDIES ON GALLIUM–BISMUTHATE GLASSES CONTAINING IRON
Authors: SIMON S.
Published: June 2004

Glasses belonging to x Fe2O3·(80-x) Bi2O3·20 Ga2O3system (0≤x≤20 mol %) were prepared using the melt quenching technique. Local order changes were investigated as a function of iron content using electron paramagnetic resonance and infrared spectroscopy results. The glass network mainly consist of [ BiO6] octahedral units. Iron ions enter the glass network by breaking up Bi - O - Bi bonds. Gallium ions also behave as glass network modifier.
ON THE EFFECT OF NEURON ACTIVATION GAIN ON ROBUSTNESS OF COMPLETE STABILITY
Authors: DI MARCO M. , FORTI M. , NISTRI P. , TESI A.
Published: June 2004

The paper addresses robustness of complete stability with respect to perturbations of the interconnections of nominal symmetric neural networks. The influence of the maximum neuron activation gain on complete stability robustness is discussed for a class of third-order neural networks. It is shown that high values of the gain lead to an extremely small complete stability margin of all nominal symmetric neural networks, thus allowing to conclude that complete stability robustness cannot be, in general, guaranteed.
EXISTENCE OF HORSESHOE IN A FOODWEB MODEL
Authors: YANG XIAO-SONG , LI QINGDU
Published: June 2004

This paper studies a foodweb model concerning hare–lynx-vegetation, and presents a computer assisted proof for existence of horseshoe for Poincaré map derived from this model.
BI-SPIRALING HOMOCLINIC CURVES AROUND A T-POINT IN CHUA'S EQUATION
Authors: FERNÁNDEZ-SÁNCHEZ FERNANDO , FREIRE EMILIO , RODRÍGUEZ-LUIS ALEJANDRO J.
Published: June 2004

In this work, the existence of curves of homoclinic connections that bi-spiral around a T-point between two saddle-focus equilibria is detected in Chua's equation. That is, the homoclinic curve emerges spiraling from a T-point in a parameter bifurcation plane and ends, by a different spiral, at the same T-point. This new phenomenon is related to the existence of more than one intersection between the two-dimensional manifolds of the involved equilibria at the T-point.
NONPERIODIC OSCILLATIONS OF PRESSURE IN A SPARK IGNITION COMBUSTION ENGINE
Authors: WENDEKER M. , LITAK G. , CZARNIGOWSKI J. , SZABELSKI K.
Published: June 2004

We report our results on nonperiodic experimental time series of pressure in a spark ignition engine. The experiments were performed for a low rotational velocity of a crankshaft and a relatively large spark advance angle. We show that the combustion process has many chaotic features. Surprisingly, the reconstructed attractor has a characteristic butterfly shape similar to a chaotic attractor of Lorentz type. The suitable recurrence plot shows that the dynamics of the combustion is a nonlinear multidimensional process mediated by stochastic noise.
NUMERICAL AND ANALYTIC DISSIPATIVITY OF THE θ-METHOD FOR DELAY DIFFERENTIAL EQUATIONS WITH A BOUNDED VARIABLE LAG
Authors: TIAN HONGJIONG
Published: June 2004

This paper focuses on the analytic and numerical dissipativity of θ-method for delay differential equations with a bounded variable lag. A generalized Halanay inequality is derived, and a sufficient condition is presented to ensure that delay differential equations with a bounded variable lag are dissipative. We then apply θ-method to such delay differential equations, and investigate the numerical dissipativity of the θ-method.
A SERIES OF BIFURCATION SCENARIOS IN THE FIRING PATTERN TRANSITIONS IN AN EXPERIMENTAL NEURAL PACEMAKER
Authors: LI LI , GU HUAGUANG , YANG MINGHAO , LIU ZHIQIANG , REN WEI
Published: June 2004

Various bifurcation scenarios from period-1 bursting to period-1 spiking via a complex procedure were simulated in previous theoretical studies on neuronal models. The results revealed a general principle of neuronal firing pattern transitions. In this letter, three types of bifurcation scenarios with respect to extracellar calcium concentration ([ Ca ++]o) were discovered in experiments on neural pacemakers. Such a series of bifurcation scenarios implied complex structure of bifurcations in the firing pattern transitions of neurons. In the two-dimensional parameter space of Chay model, three classical kinds of bifurcation scenarios with respect to the bifurcation parameter vc (the reverse potential of calcium concentration) were simulated. By the variation of the conditional parameter, λn, the relationship among the three bifurcation scenarios was revealed. The results not only verified the existence of different bifurcation scenarios in real neuronal system, but also indicated that the differences among the bifurcation scenarios were caused by the different configuration of parameters. The physiological significance of such bifurcation structures to a deeper understanding of neural coding mechanism was also discussed.
MODELING THE CUMULATIVE DISTRIBUTION FUNCTION OF SPIKES IN NEURAL NETWORKS
Authors: HOPPENSTEADT FRANK
Published: June 2004

Important components of neural networks are input synapses, action potential generators and output synapses. Rather than modeling a whole neuron in terms of a few ionic channels or as having Hodgkin–Huxley, Morris–Lecar or FitzHugh–Nagumo dynamics, we describe a neuron's action potential generator (APG). An APG may be at the hillock region at the base of an axon or another specific region of a cell. We model it using bifurcation theory based on observations by A. F. Hodgkin about membrane excitability. The result is a simplified model that leads us to view a neural network as comprising input and output synapses (electrical or chemical) that network APGs. These centers of activity are coupled by transfer functions from input synapses to an APG and from an APG to output synapses. The transfer functions account for time delays and signal attenuation that result from input and output structures. While this falls far short of a complete biophysical model of specific neurons in a network, it is consistent with empirical data, it is easily formulated, it is analytically tractable, and computer simulations based on it are straightforward. One outcome is a precise description of the cumulative distribution function (CDF) of action potentials. Since records of cell firing amount to collections of CDFs, the model is for a variable that is accessible to experimental observation. This methodology is applied here to describe bursting neural circuits and embedded loop networks similar to those occurring in basal ganglia.
A NEW CHAOTIC SYSTEM AND BEYOND: THE GENERALIZED LORENZ-LIKE SYSTEM
Authors: LÜ JINHU , CHEN GUANRONG , CHENG DAIZHAN
Published: June 2004

This article introduces a new chaotic system of three-dimensional quadratic autonomous ordinary differential equations, which can display (i) two 1-scroll chaotic attractors simultaneously, with only three equilibria, and (ii) two 2-scroll chaotic attractors simultaneously, with five equilibria. Several issues such as some basic dynamical behaviors, routes to chaos, bifurcations, periodic windows, and the compound structure of the new chaotic system are then investigated, either analytically or numerically. Of particular interest is the fact that this chaotic system can generate a complex 4-scroll chaotic attractor or confine two attractors to a 2-scroll chaotic attractor under the control of a simple constant input. Furthermore, the concept of generalized Lorenz system is extended to a new class of generalized Lorenz-like systems in a canonical form. Finally, the important problems of classification and normal form of three-dimensional quadratic autonomous chaotic systems are formulated and discussed.
EXPERIMENTAL PROPAGATION FAILURE IN A NONLINEAR ELECTRICAL LATTICE
Authors: BINCZAK S. , BILBAULT J. M.
Published: June 2004

We consider an experimental setup, modeling the FitzHugh–Nagumo equation without recovery term and composed of a nonlinear electrical network made up of discrete bistable cells, resistively coupled. In the first place, we study experimentally the propagation of topological fronts in the continuum limit where the analytical solution can be obtained. We show that experimental results match the theoretical predictions. The discrete case is then investigated theoretically and in the lattice, emphasizing the pinning of traveling waves.
ON THE INTEGRABILITY, BÄCKLUND TRANSFORMATION AND SYMMETRY ASPECTS OF A GENERALIZED FISHER TYPE NONLINEAR REACTION–DIFFUSION EQUATION
Authors: BINDU P. S. , LAKSHMANAN M. , SENTHILVELAN M.
Published: June 2004

The dynamics of nonlinear reaction–diffusion systems is dominated by the onset of patterns, and Fisher equation is considered to be a prototype of such diffusive equations. Here we investigate the integrability properties of a generalized Fisher equation in both (1+1) and (2+1) dimensions. A Painlevé singularity structure analysis singles out a special case (m=2) as integrable. More interestingly, a Bäcklund transformation is shown to give rise to a linearizing transformation for the integrable case. A Lie symmetry analysis again separates out the same m=2 case as the integrable one and hence we report several physically interesting solutions via similarity reductions. Thus we give a group theoretical interpretation for the system under study. Explicit and numerical solutions for specific cases of nonintegrable systems are also given. In particular, the system is found to exhibit different types of traveling wave solutions and patterns, static structures and localized structures. Besides the Lie symmetry analysis, nonclassical and generalized conditional symmetry analysis are also carried out.
ALGORITHM FOR ESTIMATION OF THE STABLE BASIN IN CONTROLLING CHAOTIC DISCRETE DYNAMICS
Authors: GU EN-GUO , RUAN JIONG , LIN WEI
Published: June 2004

In this paper, we apply OPCL control to discrete system, and based on relative nonlinear measure, give an algorithm for estimating the radius of stable basin. We rigorously prove that this basin is bound to be of existence for nonlinear discrete system, whose goal dynamics is either periodic orbits or fixed point. We also, in particular, investigate the stable basin in a quadratic polynomial map system, and present that the stable basin is irrelevant to the goal orbits with a negative Jacobian gain matrix. Furthermore, we take the well-known Hénon system and Ikeda system as examples to illustrate the implementation of our theory, and give the corresponding simulations to reinforce our method.
CONTROLLING UNCERTAIN VAN DER POL OSCILLATOR VIA ROBUST NONLINEAR FEEDBACK CONTROL
Authors: CHEN MAO-YIN , HAN ZHENG-ZHI , SHANG YUN , ZONG GUANG-DENG
Published: June 2004

Combining the backstepping design and the variable structure control, we propose a robust nonlinear feedback control method to control an uncertain van der Pol oscillator even if there exist system uncertainties and external disturbances in this oscillator. If system uncertainties are estimated and some parameters are chosen suitably, the output of van der Pol osicllator can track arbitrary smooth reference signal. Theoretical analysis and numerical simulations verify the effectiveness of this method.
ON A PARTICULAR FOLIATION ASSOCIATED WITH A POLYNOMIAL FAMILY OF NONINVERTIBLE MAPS OF THE PLANE
Authors: GARDINI LAURA , FORONI ILARIA , MIRA CHRISTIAN
Published: June 2004

The present work describes a family of polynomial noninvertible maps of the plane shared within two open regions: (i) (denoted by Z0) each point having no real preimage, and (ii) (denoted by Z2) each point having two real preimages. The regions Z0, Z2 are separated by the critical curve LC, locus of points having two coincident preimages. Z2 is made up of two sheets (giving rise to a plane foliation) joining on LC, each being associated with a well-defined inverse of the map. The considered maps family is structurally unstable. For a wide choice of the parameter space it generates a singular foliation in the sense that the region Z2 is separated into two zones, Z'2 and [Formula: see text], inside which the two preimages do not have the same qualitative behavior. Moreover, the boundary between Z'2 and [Formula: see text] is made up of points having only one real preimage at finite distance, the second one being at infinity. This situation gives rise to a nonclassical homoclinic bifurcation. The maps of the family have another important feature: their inverses present a denominator which vanish along a line of the plane. This has a great consequence on a chaotic attractor structure, when it exists. The imbedding of the map into a wider structurally stable family, generating regions Zk (k=1,3 being the number of real preimages), permits to understand the foliation nature when the imbedding parameter cancels leading to the structurally unstable map.
STUDY OF DEGENERATE BIFURCATIONS IN MAPS: A FEEDBACK SYSTEMS APPROACH
Authors: D'AMICO MARÍA BELÉN , MOIOLA JORGE L. , PAOLINI EDUARDO E.
Published: June 2004

The dynamical behavior of nonlinear maps undergoing degenerate period doubling or degenerate Hopf bifurcations is studied via a frequency-domain approach. The technique is based on a discrete-time feedback representation of the system and the application of the well-known engineering tools of harmonic balance to approximate the emerging solutions. More specifically, the results are a higher-order extension of the previous developments obtained by the authors for nondegenerate bifurcations. Two examples are included for illustration.
MODE-LOCKING IN QUASIPERIODICALLY FORCED SYSTEMS WITH VERY SMALL DRIVING FREQUENCY
Authors: VASYLENKO ANNA , MAISTRENKO YURI , FEELY ORLA , FEUDEL ULRIKE
Published: June 2004

In this paper we consider the dynamics of the sine circle map with quasiperiodic forcing and very small forcing frequency. One of our goals is to compare the dynamics of our system with those of the system with larger values of the frequency. In particular we discovered an unusual fine structure of the mode-locking regions which disappears with increase in the forcing frequency. We investigated how this fine structure depends on the system parameters and described the bifurcations which occur on the boundaries of the mode-locking regions.
HOPF BIFURCATION CONTROL USING NONLINEAR FEEDBACK WITH POLYNOMIAL FUNCTIONS
Authors: YU PEI , CHEN GUANRONG
Published: June 2004

A general explicit formula is derived for controlling bifurcations using nonlinear state feedback. This method does not increase the dimension of the system, and can be used to either delay (or eliminate) existing bifurcations or change the stability of bifurcation solutions. The method is then employed for Hopf bifurcation control. The Lorenz equation and Rössler system are used to illustrate the application of the approach. It is shown that a simple control can be obtained to simultaneously stabilize two symmetrical equilibria of the Lorenz system, and keep the symmetry of Hopf bifurcations from the equilibria. For the Rössler system, a control is also obtained to simultaneously stabilize two nonsymmetric equilibria and meanwhile stabilize possible Hopf bifurcations from the equilibria. Computer simulation results are presented to confirm the analytical predictions.
STAR CELLULAR NEURAL NETWORKS FOR ASSOCIATIVE AND DYNAMIC MEMORIES
Authors: ITOH MAKOTO , CHUA LEON O.
Published: June 2004

In this paper, we propose a Star cellular neural network (Star CNN) for associative and dynamic memories. A Star CNN consists of local oscillators and a central system. All oscillators are connected to a central system in the shape of a Star, and communicate with each other through a central system. A Star CNN can store and retrieve given patterns in the form of synchronized chaotic states with appropriate phase relations between the oscillators (associative memories). Furthermore, the output pattern can occasionally travel around the stored patterns, their reverse patterns, and new relevant patterns which are called spurious patterns (dynamic memories).
BOUNDARY FEEDBACK ANTICONTROL OF SPATIOTEMPORAL CHAOS FOR 1D HYPERBOLIC DYNAMICAL SYSTEMS
Authors: HUANG YU
Published: June 2004

In this paper, boundary anticontrol of spatiotemporal chaos for 1D hyperbolic equations is studied. Firstly, a new definition of chaotic vibrations for PDEs is given in terms of the growth rate of the total variations of the solutions with respect to the spatial variable as t→∞. Then, a boundary feedback controller is designed as composing with a sawtooth function, which can drive the originally nonchaotic linear or nonlinear dynamical system chaotic. Finally, as applications, anticontrol of chaos for 1D linear wave equations with linear or nonlinear boundary conditions is discussed.
QSPR CALCULATION OF AROMATICITY IN SOME FIVE-MEMBERED HETEROAROMATIC COMPOUNDS
Authors: DUCHOWICZ PABLO R. , CASTRO EDUARDO A.
Published: June 2004

Aromatic stabilization energies (ASE) for a set of 29 five-membered heteroaromatic compounds are calculated using molecular descriptors such as magnetic susceptibility exaltation (Λ), nucleus-independent chemical shifts (NICS), and electrotopological indices (EI) via linear, quadratic and cubic fitting polynomials. Theoretical estimations compare fairly well with experimental data when three variables multilinear regression equations are employed.
A MONTE CARLO SIMULATION OF MAGNETIC ORDERING IN ISING CUBIC FERROSPINELS
Authors: STANICA N. , CIMPOESU F. , DOBRESCU GIANINA , CHIHAIA V. , PATRON LUMINITA , MUNTEANU G. , BOSTAN C. G.
Published: June 2004

This work signifies the next step in our way in the magnetic properties simulation of spin clusters and extended networks containing quantum spins, by original FORTRAN codes based on Heisenberg–Dirac–VanVleck (HDVV) or Ising approaches, using Full Diagonalization Heisenberg Matrix (FDHM) or Monte Carlo–Metropolis (MCM) procedure, respectively.

We present the results of magnetic Monte Carlo studies on a magnetite type lattice, Ising model ferrimagnet that provide insight into the exchange interactions involved in Cubic Ferrospinels. We have demonstrated that a comparatively simple model can reproduce ferrimagnetic behavior of ferrospinels, particularly for magnetite.
THEORETICALLY EXPLORING METHYLATION EFFECTS ON SOLVATED MULTI-HYDROGEN BONDING AMMONIUM PERCHLORATE SYSTEMS
Authors: LIU MIN-HSIEN , CHEN CHENG , HONG YAW-SHUN
Published: June 2004

Methyl substituents are introduced into solvated ammonium perchlorate (AP) systems to explicate the effects of methylation on localized hydrogen-bonding. Methylation systems are modeled using density functional theory (DFT) B3LYP type with 4-31G(d, p), 6-311+(2d, p) basis set methods, indicating that whichever methyl group is substituted at the proton site in an ammonium ion or solvent, both methyl groups cease to H-bond, as evidence by elongation of the neighboring bond and characteristic red-shifts in the frequency of vibration. The energy barriers to the conversion from reactants to products in solvated AP systems are also discussed herein to help to elucidate the relationship solubility and H-bonding.
A THEORETICAL STUDY OF THE SUBSTITUENT EFFECT ON THE STABILITY OF COLLAGEN
Authors: QUAN JUN-MIN , Wu YUN-DONG
Published: June 2004

Theoretical calculations have been carried out to investigate the effect of the 4(R)-substituents ( OH , F , NH2, and [Formula: see text]) in proline on the stability of the collagen triple helix. A series of substituted proline models were studied first with density functional (B3LYP/6-31+G*) calculations. The solvent effect was studied using the SCIPCM method. While the F , OH and NH2groups increase the stability of the trans-up conformation with respect to the trans-down conformation, [Formula: see text] appears to favor the trans-down conformation in an aqueous solution. Second, the triple helices of the tripeptide models, Ac – Pro – Pro(X) – Gly – H with the two proline residues in the down/down and down/up puckering conformations, were optimized with a repeating unit approach using the HF/6-31G* method. For the Ac – Pro – Pro – Gly – H model peptide, the calculated binding energies of the two triple helices with the different puckering modes are similar. All four substituents, F , OH , NH2, and [Formula: see text], considerably increased the binding energy of the down/up helix, but only [Formula: see text] stabilizes the down/down triple helix. Our calculations indicate that the inter-chain electrostatic interactions involving the 4(R)-substituents play an important role in stabilizing triple helical collagen models and allow the rationalization of all available experimental observations. Further model studies indicate that the substituent effects by the F , OH and NH2substituents are local while the effect of [Formula: see text] is long-range in nature.
Monocyte chemotactic protein-1 regulates leukocyte recruitment during gastric ulcer recurrence induced by tumor necrosis factor-α
Authors: Watanabe Toshio , Higuchi Kazuhide , Hamaguchi Masaki , Shiba Masatsugu , Tominaga Kazunari , Fujiwara Yasuhiro , Matsumoto Takayuki , Arakawa Tetsuo
Published: June 2004

TNF-α has numerous biological activities, including the induction of chemokine expression, and is involved in many gastric injuries. C-C chemokines [monocyte chemotactic protein (MCP)-1 and macrophage inflammatory protein (MIP)-1α] and C-X-C chemokines [MIP-2 and cytokine-induced neutrophil chemoattractant (CINC)-2α] mediate chemotaxis of monocytes and neutrophils, respectively. We examined the roles of TNF-α and dynamics of chemokine expression in gastric ulceration including ulcer recurrence and indomethacin-induced injury. Rats with healed chronic gastric ulcers received intraperitoneal TNF-α to induce ulcer recurrence. Some rats were given neutralizing antibodies against neutrophils or MCP-1 together with TNF-α. In a separate experiment, rats were orally administered 20 mg/kg indomethacin with or without pretreatment with pentoxifylline (an inhibitor of TNF-α synthesis) or anti-MCP-1 antibody. TNF-α (1 μg/kg) induced gastric ulcer recurrence after 48 h, which was completely prevented by anti-neutrophil antibody. TNF-α increased the number of macrophages and MCP-1 mRNA expression in scarred mucosa from 4 h, whereas it increased MPO activities (marker of neutrophil infiltration) and mRNA expression of MIP-2 and CINC-2α from 24 h. Anti-MCP-1 antibody inhibited leukocyte infiltration with reduction of the levels of C-X-C chemokines and prevented ulcer recurrence. Indomethacin treatment increased TNF-α/chemokine mRNA expression from 30 min and induced macroscopic erosions after 4 h. Pentoxifylline inhibited the indomethacin-induced gastric injury with reduction of neutrophil infiltration and expression of chemokine (MCP-1, MIP-2, and CINC-2α). Anti-MCP-1 antibody also inhibited the injury and these inflammatory responses but did not affect TNF-α mRNA expression. In conclusion, increased MCP-1 triggered by TNF-α may play a key role in gastric ulceration by regulating leukocyte recruitment and chemokine expression.
Growth factors associated with gastric mucosal hypertrophy in autoimmune gastritis
Authors: Franic Teo V. , Judd Louise M. , Nguyen Nhung V. , Samuelson Linda C. , Loveland Kate L. , Giraud Andy S. , Gleeson Paul A. , van Driel Ian R.
Published: June 2004

A prominent pathological feature of murine autoimmune gastritis is a pronounced mucosal hypertrophy. Here, we examined factors that may be responsible for inducing this hypertrophy. Because gastrin is known to be both an inducer of gastric mucosal cell proliferation and is elevated in autoimmune gastritis, mice deficient in gastrin were thymectomised at day 3 and assessed for autoimmune gastritis. Gastrin-deficient mice showed all the characteristic features of murine autoimmune gastritis, including gastric unit hypertrophy due to hyperproliferation and accumulation of immature epithelial cells, decreases in the number of zymogenic and parietal cells, and autoantibodies to the gastric H+/K+-ATPase. Hence, gastrin is not required for either the establishment of chronic gastritis or development of the typical pathological features of this disease. We also examined mRNA levels of a number of gastric mucosal growth factors in RNA samples from mice with hypertrophic autoimmune gastritis. Members of the Reg family, RegIIIβ and RegIIIγ, were greatly elevated in mice with hypertrophic gastritis, whereas RegI and amphiregulin (an EGF receptor ligand) were more modestly and/or inconsistently induced. These data demonstrate that induction of gastric mitogenic factors, such as members of the Reg family, can be achieved in inflammatory situations by gastrin-independent pathways. Members of the Reg family, in particular RegIIIβ and RegIIIγ, are good candidates to be involved in inducing the mucosal hyperproliferation in autoimmune gastritis. These findings are likely to be of relevance to other gastric inflammatory conditions.
In vivo TNF-α inhibition ameliorates cardiac mitochondrial dysfunction, oxidative stress, and apoptosis in experimental heart failure
Authors: Moe Gordon W. , Marin-Garcia Jose , Konig Andrea , Goldenthal Michael , Lu Xiangru , Feng Qingping
Published: June 2004

Heart failure is associated with increased myocardial expression of TNF-α. However, the role of TNF-α in the development of heart failure is not fully understood. In the present study, we investigated the contribution of TNF-α to myocardial mitochondrial dysfunction, oxidative stress, and apoptosis in a unique dog model of heart failure characterized by an activation of all of these pathological processes. Male mongrel dogs were randomly assigned ( n = 10 each) to 1) normal controls; 2) chronic pacing (250 beats/min for 4 wk) with concomitant administration of etanercept, a soluble p75 TNF receptor fusion protein, 0.5 mg/kg subcutaneously twice weekly; 3) chronic pacing with administration of saline vehicle. Mitochondrial function was assessed by left ventricular (LV) tissue mitochondrial respiratory enzyme activities. Oxidative stress was assessed with aldehyde levels, and apoptosis was quantified by photometric enzyme immunoassay for cytoplasmic histone-associated DNA fragments and terminal deoxynucleotide transferase-mediated nick-end labeling (TUNEL) assays. LV activity levels of mitochondrial respiratory chain enzyme complex III and V were reduced in the saline-treated dogs and restored either partially (complex III) or completely (complex V) in the etanercept-treated dogs. Aldehyde levels, DNA fragments, and TUNEL-positive cells were increased in the saline-treated dogs and normalized in etanercept-treated dogs. These changes were accompanied by an attenuation of LV dilatation and partial restoration of ejection fraction. Our data demonstrate that TNF-α contributes to progressive LV dysfunction in pacing-induced heart failure, mediated in part by a local impairment in mitochondrial function and increase in oxidative stress and myocyte apoptosis.
Contribution of mitral annular excursion and shape dynamics to total left ventricular volume change
Authors: Carlhäll C. , Wigström L. , Heiberg E. , Karlsson M. , Bolger A. F. , Nylander E.
Published: June 2004

The mitral annulus (MA) has a complex shape and motion, and its excursion has been correlated to left ventricular (LV) function. During the cardiac cycle the annulus’ excursion encompasses a volume that is part of the total LV volume change during both filling and emptying. Our objective was to evaluate the contribution of MA excursion and shape variation to total LV volume change. Nine healthy subjects aged 56 ± 11 (means ± SD) years underwent transesophageal echocardiography (TEE). The MA was outlined in all time frames, and a four-dimensional (4-D) Fourier series was fitted to the MA coordinates (3-D+time) and divided into segments. The annular excursion volume (AEV) was calculated based on the temporally integrated product of the segments’ area and their incremental excursion. The 3-D LV volumes were calculated by tracing the endocardial border in six coaxial planes. The AEV (10 ± 2 ml) represented 19 ± 3% of the total LV stroke volume (52 ± 12 ml). The AEV correlated strongly with LV stroke volume ( r = 0.73; P < 0.05). Peak MA area occurred during middiastole, and 91 ± 7% of reduction in area from peak to minimum occurred before the onset of LV systole. The excursion of the MA accounts for an important portion of the total LV filling and emptying in humans. These data suggest an atriogenic influence on MA physiology and also a sphincter-like action of the MA that may facilitate ventricular filling and aid competent valve closure. This 4-D TEE method is the first to allow noninvasive measurement of AEV and may be used to investigate the impact of physiological and pathological conditions on this important aspect of LV performance.
Age-dependent biochemical and contractile properties in atrium of transgenic mice overexpressing junctin
Authors: Kirchhefer Uwe , Baba Hideo A. , Hanske Gabriela , Jones Larry R. , Kirchhof Paulus , Schmitz Wilhelm , Neumann Joachim
Published: June 2004

Junctin is a transmembrane protein of the cardiac junctional sarcoplasmic reticulum (SR) that binds to the ryanodine receptor, calsequestrin, and triadin 1. This quaternary protein complex is thought to facilitate SR Ca2+release. To improve our understanding of the contribution of junctin to the regulation of SR function, we examined the age-dependent effects of junctin overexpression in the atrium of 3-, 6-, and 18-wk-old transgenic mice. The ratio of atrial weight and body weight was unchanged between junctin-overexpressing (JCN) and wild-type (WT) mice at all ages investigated ( n = 6–8). The protein expression of triadin 1 was decreased starting in 3-wk-old JCN atria (by 69%), whereas the expression of the ryanodine receptor was diminished in 6- (by 48%) and 18-wk-old (by 57%) JCN atria compared with age-matched WT atria. Force of contraction was decreased by 35% in 18-wk-old JCN compared with age-matched WT left atrial muscle strips, which was accompanied by a prolonged time of relaxation (48.1 ± 0.9 vs. 44.2 ± 0.8 ms, respectively, n = 6–8, P < 0.05). The spontaneous beating rate of isolated right atria was higher in 18-wk-old JCN mice compared with age-matched WT mice (389 ± 10 vs. 357 ± 6 beats/min, respectively, n = 6–8, P < 0.05). Heart rate was lower by 9% in telemetric ECG recordings in 18-wk-old JCN mice during stress tests. Three-week-old JCN atria exhibited a higher potentiation of force of contraction at rest pauses of 30 s (by 13%) and of 300 s (by 35%), suggesting increased SR Ca2+content. This was consistent with the higher force of contraction in 3-wk-old JCN atria (by 29%) compared with age-matched WT atria (by 10%) under the administration of caffeine. We conclude that in 3-wk-old atria, junctin overexpression was associated with a reduced expression of triadin 1 resulting in a higher SR Ca2+load without changes in contractility or heart rate. In 6-wk-old JCN atria, the compensatory downregulation of the ryanodine receptor may offset the effects of junctin overexpression. Finally, the progressive decrease in ryanodine receptor density may contribute to the decreased atrial contractility and lower heart rate during stress in 18-wk-old JCN mice.
Redox active hemoglobin enhances lipopolysaccharide-induced injury to cultured bovine endothelial cells
Authors: D'Agnillo Felice
Published: June 2004

The interaction of cell-free hemoglobin with lipopolysaccharide (LPS) is thought to aggravate the pathophysiology of sepsis and/or septic shock. This study examines the possible modulatory role of cell-free hemoglobin on LPS-induced apoptosis of cultured bovine aortic endothelial cells. Experiments were performed with or without fetal bovine serum, a source of LPS-binding protein and soluble CD14. In the absence of serum, LPS alone or coincubated with purified bovine hemoglobin (BvHb), human hemoglobin (Hb), or α-cross-linked Hb (ααHb) did not induce apoptosis. In the presence of serum, LPS induced significant apoptosis. LPS combined with BvHb, Hb, or ααHb produced the same extent of apoptosis as LPS alone. To examine whether the H2O2-driven redox activity of hemoglobin alters LPS-induced apoptosis, glucose oxidase was added to the system to generate a subtoxic flux of H2O2. The combined treatment of LPS, glucose oxidase, and BvHb, Hb, or ααHb enhanced apoptosis compared with LPS alone. These findings support a possible mechanism whereby the redox cycling of hemoglobin, and not its direct interaction with LPS, contributes to the hemoglobin-mediated enhancement of LPS-related pathophysiology.
Protein kinase Cε and the antiadrenergic action of adenosine in rat ventricular myocytes
Authors: Miyazaki Koji , Komatsu Satoshi , Ikebe Mitsuo , Fenton Richard A. , Dobson James G.
Published: June 2004

Adenosine-induced antiadrenergic effects in the heart are mediated by adenosine A1receptors (A1R). The role of PKCε in the antiadrenergic action of adenosine was explored with adult rat ventricular myocytes in which PKCε was overexpressed. Myocytes were transfected with a pEGFP-N1 vector in the presence or absence of a PKCε construct and compared with normal myocytes. The extent of myocyte shortening elicited by electrical stimulation of quiescent normal and transfected myocytes was recorded with video imaging. PKCε was found localized primarily in transverse tubules. The A1R agonist chlorocyclopentyladenosine (CCPA) at 1 μM rendered an enhanced localization of PKCε in the t-tubular system. The β-adrenergic agonist isoproterenol (Iso; 0.4 μM) elicited a 29–36% increase in myocyte shortening in all three groups. Although CCPA significantly reduced the Iso-produced increase in shortening in all three groups, the reduction caused by CCPA was greatest with PKCε overexpression. The CCPA reduction of the Iso-elicited shortening was eliminated in the presence of a PKCε inhibitory peptide. These results suggest that the translocation of PKCε to the t-tubular system plays an important role in A1R-mediated antiadrenergic actions in the heart.