bluuebunny/crossref_metadata_2025 huggingface dataset:
Parametric Adaptive Control in Nonlinear Dynamical Systems
Authors: Wang Jie , Wang Xiaohong
Published: September 2003

The paper is concerned with parametric adaptive control of continuous time chaotic systems. A method of parametric adaptive control is presented for a nonlinear chaotic system with multi-parameters. First, the system parameters are considered to be linear form in the adaptive control. Secondly, the Lyapunov method is used to prove parametric control equations are global asymptotically stable. Finally, the nonlinear form of the system parameter with uncertain noise is considered. It has been shown that the method in this paper is a very effective one to analyze parametric adaptive control for chaotic systems.
Synchronization of Chaotic Maps by Feedback Control and Application to Secure Communications Using Chaotic Neural Networks
Authors: de Oliveira Ana Guedes , Jones Antonia J.
Published: September 2003

In this paper we propose a method to synchronize chaotic maps by feedback control. This approach is particularly attractive, if it can be made to work on a wide variety of chaotic systems, because it requires very little computational overhead and so is extremely easy to implement in fast hardware. In general the control feedback used here makes use of a diagonal matrix with experimentally determined components. However, for this particular application, synchronization is achieved by using only one element of the feedback matrix. To demonstrate the method we first apply it to the Hénon map and study the local stability properties. We next apply the method to a neural network approximation of the Ikeda system and show that two identical copies of this network approximations of a given chaotic system has potentially interesting applications in secure communications. In the final section we demonstrate how message can be encoded, transmitted and decoded using the Ikeda neural network in combination with the feedback control method.
A CNN Approach to Brian-Like Chaos-Periodicity Transitions
Authors: Muñuzuri Alberto P. , Suykens Johan A. K. , Chua Leon O.
Published: September 2003

Chaos-periodicity transitions are studied within the framework of a one-dimensional CNN which are qualitatively similar to some brian-like transitions described in the literature. The nonlinearity of each cell is designed such that chaotic and periodic regimes coexist at the cell level. When a coupling between cells is considered, transition waves from chaotic behavior into a periodic one are observed to propagate along the one-dimensional array. The signals measured are qualitatively similar to some EEG measurements in biology. Here we present the study of these transitions for different types of couplings and parameters.
Chaos Structure and Spiral Wave Self-Organization in 2D Coupled Map Lattice
Authors: Sbitnev Valery I.
Published: September 2003

Methods borrowed from nonequilibrium thermodynamics and statistical physics have been employed in the quantitative analysis of spatiotemporal chaos in a 2D coupled map lattice (CML). Emphasis is made on entropy, entropy variation and entropy production. These quantities manifest peculiar changes in a region where spiral waves emerge. The spiral waves observed in the 2D CML are found to be dissipative objects with an elevated entropy production.
Synchronization in a Lattice of Coupled van der Pol Systems
Authors: Chiu Chuang-Hsiung , Lin Wen-Wei , Wang Chern-Shuh
Published: September 2003

We consider a lattice of coupled van der Pol systems with external periodic forces and Dirichlet boundary conditions. Under the assumption of bounded dissipativeness, we prove that the asymptotic synchronization occurs provided that the coupling coefficients are sufficiently large. Furthermore, we demonstrate from numerical simulations that asymptotic synchronization is affected by the coupling coefficients and the size of lattice.
Extending the Concept of Isochrons from Oscillatory to Excitable Systems for Modeling an Excitable Neuron
Authors: Ichinose Natsuhiro , Aihara Kazuyuki , Judd Kevin
Published: September 2003

In this paper, we study an excitable and nonoscillating neuron on the basis of a technique of extending the concept of isochrons from oscillatory to excitable systems. The extended isochrons allow reduction of an excitable system described by possibly high dimensional differential equations to a simpler system. We analytically derive a one-dimensional model of an excitable neuron stimulated by instantaneous pulses with the technique of the extended isochrons and show its similarity to an isochronal map numerically obtained from the FitzHugh–Nagumo model. Response characteristics of the one-dimensional model to periodic impulsive stimulations are also analyzed numerically.
Controlling Nonlinear Dynamics in a Two-Well Impact System.
Authors: Lenci Stefano , Rega Giuseppe
Published: September 2003

A method for controlling nonlinear dynamics based on avoiding homoclinic intersection is systematically implemented to perform a numerical analysis of the control induced modifications of the steady attractors and bifurcation scenario of a two-well impact system. The work is divided into two parts. This paper (Part I) deals with the analysis of the harmonic (reference) and global optimal excitations, which are both symmetric. The bifurcation diagrams obtained for increasing values of the excitation amplitude show there exist a "basic" attractor and other "complementary" solutions. The range of stability of the principal complementary attractors is numerically established, and the mechanisms leading to their disapperance are identified. The role of classical and nonclassical local bifurcations in determining the system response is emphasized. Chaotic attractors are seen to appear and disappear both by classical period doubling route to chaos and by sudden changes. Subductions, boundary and interior crises are repeatedly observed. By comparison of the system response under different excitations we obtain information on the performances of global control, which furnishes relatively low gain in terms of regularization but succeeds in controlling the whole phase space.
Controlling Nonlinear Dynamics in a Two-Well Impact System.
Authors: Lenci Stefano , Rega Giuseppe
Published: September 2003

To exploit all potentialities of the optimal control procedure, the analysis initiated in Part I focuses on the system response under one-side control, an excitation which furnishes high gain though, roughly, controlling only one part of the phase space. Many bifurcational and control items related to the unsymmetric and pulsed nature of the excitation are deeply investigated. A nonclassical kind of homoclinic bifurcation is identified and it is discussed how it may lead to major regularity. The system response is very rich, and the main local and global phenomena of the dynamics are analyzed in detail through combined use of bifurcation diagrams and attractor-basin phase portraits. Both the confinement of steady dynamics in the controlled potential well and their successive transition from confined to scattered are studied, and it is discussed how they are obtained through comparison with the case of harmonic excitation. It is shown that the two investigated optimal excitations permit to increase the amplitude level for confined to scattered dynamics and to regularize the steady dynamics, although in a different manner. The analysis shows the effectiveness — in "average" sense — of the proposed method for controlling nonlinear dynamics.
Analytical Approximation of the Solution of the Dissipative Standard Map
Authors: Celletti Alessandra , Penna Gabriella Della , Froeschlé Claude
Published: September 2003

We consider a dissipative mapping derived from a modification of the Chirikov standard mapping. For simplicity, we assume that the dissipative strength is of the order of the square of the perturbing parameter of the conservative model. Under this assumption, we derive an analytical approximation of the solution associated to the dissipative mapping. The equations are explicitly solved up to the order 7 in the perturbing parameter.

Having fixed a frequency ω, a comparison of the associated to the dissipative solutions shows that the two curves coincide for low values of the perturbing parameter, while in most cases they diverge as the breakdown threshold of the invariant curve with rotation number ω is approached.
Bifurcation and Controlling of Chaotic Delayed Cellular Neural Networks
Authors: Thangavel P. , Murali K. , Lakshmanan M.
Published: September 2003

Bifurcation and chaos in one-cell cellular neural network with delay is investigated. Further controlling of chaotic behavior with suitable additional parameter is studied. Later, the study has been extended by adding one additional cell without delay. Further the dynamics of two coupled homogeneous and hetrogeneous cells with delay is also investigated. The numerical global bifurcaiton analysis for all the systems have also been performed.
Shortest-Path-Finder Algorithm in a Two-Dimensional Array of Nonlinear Electronic Circuits
Authors: Muñuzuri Alberto P. , Chua Leon O.
Published: September 2003

A two-dimensional array of diffusively-coupled nonlinear electronic circuits, Chua's cells, operating in a bistable regime, is used to find the shortest path connecting two points of a given image. Images are previously stored in the system by modulating the diffusion coefficients. Different types of images were considered, from black and white pictures (where 0 means no propagation and 1 propagation), to analog figures (with many intermediate states) and, in all cases, the algorithm used for such calculations succeeded to find the shortest path. The full description of the algorithm is here described and applied to nontrivial cases where the shortest path strongly differs from the straight line.
Solution of Semi-Inverse Buckling Problems Yields a Flexural Rigidity as a Rational Function
Authors: Baruch Menahem , Elishakoff Isaac , Catellani Giulia
Published: September 2003

Novel closed-form solutions for buckling of inhomogeneous columns are reported in this study, utilizing the integral formulation of the problem. Whereas previous closed-form solutions were confined solely to polynomial mode shapes, here the rational functions are postulated as candidate mode shapes. Inhomogeneous column's flexural rigidities are derived as to have the column with specified buckling modes.
Improved Secant Matrices for the Postbuckling Analysis of Thin Composite Plates
Authors: Jayachandran S. Arul , Gopalakrishnan S. , Narayanan R.
Published: September 2003

To study the postbuckling behavior of imperfect laminated composite plates, improved incremental or secant matrices are presented in this paper using what is called additional displacement formulation (ADF). These secant matrices are derived using the Marguerre's shell theory and they can be used in combination with any thin plate finite element. The advantage of the present formulation is that it involves no numerical approximation in forming the initial imperfection matrices as opposed to earlier secant matrices published in the literature using total displacement formulation. With the addition of shear stiffness matrix and little modification, the present incremental matrices could be extended to model postbuckling behavior of plates using the first-order shear deformation theory. The secant matrices presented in this study are shown to be very accurate in tracing the postbuckling behavior of thin isotropic and laminated composite plates with general initial imperfections.
Free Vibration Analysis of Parabolic Arches in Cartesian Coordinates
Authors: Lee Byoung Koo , Oh Sang Jin , Li Guangfan , Choi Kou Moon
Published: September 2003

The differential equations governing free vibrations of the elastic, parabolic arches with unsymmetric axes are derived in Cartesian coordinates rather than in polar coordinates. The formulation includes the effects of axial extension, shear deformation and rotatory inertia. Frequencies and mode shapes are computed numerically for arches with clamped-clamped, clamped-hinged, hinged-clamped and hinged-hinged ends. The convergent efficiency is highly improved under the newly derived differential equations in Cartesian coordinates. The lowest four natural frequency parameters are reported as functions of four non-dimensional system parameters: the rise to chord length ratio, the span length to chord length ratio, the slenderness ratio and the shear parameter. Typical mode shapes of vibrating arches are also presented.
Optimization for Harmonics Reduction and Path Generation of Linkage Mechanisms
Authors: Yuan Zhongfan , Wu Yi Min
Published: September 2003

The optimal design of linkage mechanisms for path generation and motions with reduced harmonic content is investigated. The designs are carried out using a two-objective optimizer based on the fuzzy theory. As an illustration, the present approach is applied to the optimization of a five-bar hybrid mechanism driven by a constant speed motor and a servo motor. The dynamic characteristics of the servo motor are improved, as the harmonics in the servo motion are reduced.
Blending Functions for Vibration Analysis of a Cylindrical Shell with an Oblique End
Authors: Hu X. J. , Redekop D.
Published: September 2003

The free vibration problem of a cylindrical shell with an oblique end is considered. A theoretical solution based on the Sanders–Budiansky linear shell theory, and the differential quadrature method, is presented. The surface of the shell is first developed onto a plane, and the resulting irregular domain is then mapped, using blending functions, onto a square parent domain. The analysis is finally carried out in the parent domain. Two solutions are derived, using either trigonometric or polynomial trial functions in the circumferential direction of the domain. Convergence, validation and parametric studies are carried out. Results from the two solutions are compared with each other and with finite element results. The paper ends with an appropriate set of conclusions.
Bursting Dynamics of a Model Neuron Induced by Intrinsic Channel Noise
Authors: Ginzburg Saul L. , Pustovoit Mark A.
Published: September 2003

Irregular switching of ion channels is an inherent source of noise in real neurons. Taking into account the stochastic nature of calcium and fast potassium channel currents in the Plant model of a bursting neuron, we found noise-induced coherent bursting even in the case when the deterministic neuron is silent. The bursts keep their regularity in a wide range of membrane sizes. The measure of this coherence, the coefficient of variation of interspike intervals, passes through a minimum at the membrane area near 150 μ m 2. The degree of coherence obtained from power spectra of spike trains increases monotonously with decrease of membrane size.
Rhythmic Activity of Noisy Neural Circuits
Authors: Postnov Dmitry , Sosnovtseva Olga , Setsinsky Dmitry
Published: September 2003

Dynamical features of neural circuits generating different patterns of spike trains in the presence of noise are investigated: (i) We explore noise-induced multimode dynamics in excitable functional units. Multiple gain of regularity is found to be related to different frequency entrainments and to the appearance of additional time scales; (ii) We develop stochastic implementation of central pattern generator to show that excitable units can successfully replace pacemakers at the appropriate level of noise; (iii) We study the coexistence of beta and gamma rhythms in a local network of nerve cells. It is found that noise can cause coherent switchings between different oscillatory states.
Competition Noise in DBR Tunable Lasers
Authors: Myara M. , Signoret P. , Tourrenc J. P. , Perez J. P. , Orsal B. , Alabedra R. , Jacquet J.
Published: September 2003

Tunable Lasers are key-components for Wavelength Division Multiplexing optical communication applications at 1.55μ m . In this paper, we report the study of low to mid frequency noise power spectral densities and correlation factors in various spectral purity configurations, using the Bragg section tunability around a mode-hopping situation.
Roles of Systemic Intermediaries in Transition Processes
Authors: van Lente Harro , Hekkert Marko , Smits Ruud , van Waveren Bas
Published: September 2003

We note the emergence of a new type of intermediary organization, which functions at system or network level, in contrast to traditional intermediary organizations that operate mainly bilaterally. These "systemic intermediaries" are important in long-term and complex changes, such as "transitions" to sustainable development, which require the coordinated effort of industry, policy makers, research institutes and others. We use the Systems of Innovation approach to characterize the roles of traditional and systemic intermediary organizations. A review of recent changes in innovation systems points to the need of more systemic efforts, such as the articulation of needs and options, the alignment of relevant actors and the support of learning processes. In a phase model of transitions additional roles of systemic intermediaries are identified. A case study of the Californian Fuel Cell Partnership shows how the efforts of systemic intermediaries in encompassing systemic innovations are useful and necessary, but not sufficient.
Standard-Setting Strategies in the Multimedia Sector
Authors: Chiesa Vittorio , Toletti Giovanni
Published: September 2003

In many hi-tech sectors one of the most important competitive weapons is standardisation. It is particularly true in network markets where users would like to buy products compatible with those bought by others. Different processes may lead to standard setting. Sometimes there are fierce standardisation wars, whereas in other cases competitors are able to agree on a common standard before the introduction of a new technology on the market. Quite often a single firm is not able to adequately sponsor the adoption of its technology as a standard. Therefore, partners supporting the standard-setting process have to be found and collaborations have to be formed. In this paper, the reasons that may lead firms to co-operate or not co-operate are first analysed and then the different typologies of collaborations are described together with their motivations and critical success factors. Finally, the dynamic of the standard-setting process will be investigated and discussed. The paper is based on the study of ten cases in the multimedia sector.
Success and Failure of Innovation: A Literature Review
Authors: van der Panne Gerben , van Beers Cees , Kleinknecht Alfred
Published: September 2003

This review examines 43 recent papers about factors behind success and failure of innovative projects. Nine out of the 43 papers report a larger number of possible causes for success or failure and provide some rank ordering. Analyzing these rankings we find that the nine studies have a significant degree of similarity among the ten highest-ranking success factors; however, there is little similarity among lower ranking factors. The various studies remain either inconsistent or inconclusive with respect to factors such as strength of competition, R&D intensity, the degree to which a project is "innovative" or "technologically advanced" and top management support. Agreement exists, however, about the positive impact on innovative success of factors such as firm culture, experience with innovation, the multidisciplinary character of the R&D team and explicit recognition of the collective character of the innovation process or the advantages of the matrix organization.
Building the Concept of Learning by Decomposing: Case of Numerical Control Architecture
Authors: Shibata Tomoatsu , Yano Masaharu
Published: September 2003

The industries that arose in the 20th century characteristically involve complex systems. We try to build a concept of "Learning by Decomposing". A product as a system can be designed through the integration and combination of several subsystems, based on the interaction between subsystems. Important in designing a system is how it should be decomposed into subsystems, and how the interface between subsystems should be designed. To find the best way of decomposing the whole product as a system, abundant knowledge, experience, and know-how is indispensable. Thus, there must be some process of learning through decomposition.
Simultaneous Involvement in Service Product Development: A Strategic Contingency Approach
Authors: Hull Frank M.
Published: September 2003

This paper analyzes how simultaneous involvement by multiple functions in the development of service products affects performance. Early simultaneous involvement entails input from the outset by all relevant functions, especially those representing downstream competencies. Given that cross-functional involvement is time consuming and costly, one may hypothesize that its best for high performance only to the extent needed, such as at early stages of development or under the condition of novelty.

The impact of simultaneous involvement on performance is measured as time compression and cost reduction. The contributions of ten functions are examined at three stages of a development cycle: (1) product concept; (2) product release; and (3) after sale. How product innovation strategy moderates the impact of simultaneous influence on performance, measured as time compression and cost reduction, is examined for three product innovation strategies: new, major modifications, and minor modifications.

Results from analyzing 62 service enterprises in New York show that simultaneous involvement by multiple functions has the strongest main effects on performance at the earliest stage of the product concept. But, it also has weaker effects after initial sale. If the product innovation strategy is one of novelty, simultaneous involvement by multiple functions has interactions with performance throughout the development cycle. Some functions appear to be a kind of core team that is involved throughout. Others play more stage specific roles.

If the product innovation strategy involves a lesser magnitude of innovation, levels of simultaneous involvement are either lower and/or do not have positive interactions with performance. These results are generally consistent with contingency theory that suggests the level of coordination and integration is affected by the novelty and uncertainty of the task environment.

These results parallel those observed studies of goods industries. However, the level of augmentation of service products after initial sale, especially those involving interpersonal exchanges and transactions, appears higher than for more tangible goods.
Barriers to Deliberative Participation in EIA: Learning from Waste Policies, Plans and Projects
Authors: Petts Judith
Published: September 2003

Despite increased legislative, political and social support for extended public engagement in environmental assessment, questions remain over the best means to integrate more analytic-deliberative processes within extended and fragmented decision-making frameworks. Using evidence from waste management decision-making in Britain this paper discusses institutional, cultural and technical barriers to effective integration of analysis and deliberation. The barriers are seen to limit effective participation intra decisions but particularly inter-decisions and hence to limit public impact on assessments and achievement of consensus on the optimum integrated waste management strategies. Institutional, technical and cultural barriers to effective process are discussed that compound the problems of enhancing public participation and promote maintenance of the status quo. Thus, environmental assessment still largely proceeds in advance of discussion with the public rather than through discussion with them.
Introduction to the Environmental Impact Assessment System and Public Participation in the Russian Federation
Authors: Kovalev Nicole , Koeppel Johann
Published: September 2003

The Environmental Impact Assessment (EIA) system in the Russian Federation has an extensive set of rules, the main ones are the Assessment of the Environmental Impact (OVOS) of a project and the State Environmental Review (SER). The SER is designed as an investigation of both a project and of its OVOS by an independent expert commission, which is appointed by the federal and regional environmental bodies. The decision of the commission is binding. In addition, a Public Environmental Review (PER) can be conducted by NGOs and recognised by the state.

A mandatory component of the EIA in Russia is public participation. The process of public participation is regulated by Russian legislation (for example the Land Code, the OVOS guidelines and autonomous regional laws) and can take various forms. All these opportunities are established on paper; in reality, they are not always taken into account. There are a number of case studies used to observe the extent to which the public has an impact on environmental decision-making. Selected cases include examples in which the public was passive, in which it undertook limited activities, and in which participation was strong and projects were improved or stopped.
Participatory Modelling in Environmental Decision-Making: The Ria Formosa Natural Park Case Study
Authors: Videira Nuno , Antunes Paula , Santos Rui , Gamito Sofia
Published: September 2003

Environmental decision-making generally involves issues of complexity, uncertainty and information feedback. The complexity of environmental problems calls for integrated and multi-disciplinary approaches, which include civil society and stakeholder groups affected by or affecting environmental decisions. This paper presents a participatory modelling framework to facilitate public and stakeholder involvement in environmental decision-making. Results from a case study in the Ria Formosa Natural Park in Portugal illustrate the process of participatory modelling. The use of the System Dynamics modelling methodology facilitates the identification of the fundamental structure underlying the processing of information flows in order to achieve the desired behaviour of environmental decisions. It sets up a collaborative environment for the involvement of stakeholders in the development and experimentation of alternative policy scenarios. Along with the achievement of a simulation model, this approach is likely to foster trust in institutions, promote team learning and increase commitment towards actions.
ICT Tools to Support Public Participation in Water Resources Governance & Planning: Experiences from the Design and Testing of a Multi-Media Platform
Authors: Pereira Ângela Guimarães , Rinaudo Jean-Daniel , Jeffrey Paul , Blasques João , Quintana Serafin Corral , Courtois Nathalie , Funtowicz Silvio , Petit Vincent
Published: September 2003

Whilst the drivers for public participation in water resources management have been firmly established by the Water Framework Directive, guidance on the design, implementation and management of appropriate tools, particularly Information & Communication Technology (ICT) based tools, and processes to support such participation remains sparse. This paper begins by reviewing the motivations for stakeholder participation in water resources planning & governance and highlighting some of the methodological and technical problems associated with the design and deployment of suitable ICT platforms. It then goes on to report the design and field testing of a specific Multi-Media based ICT platform for use in stakeholder debates, drawing on case study material from a catchment in Southern France. Specifically, we focus our comments on the issues of content structuring, information presentation, knowledge quality and tool functionality, seen as the major determinants of the tool's ability to support dialogue among non-scientific stakeholders. Finally, we draw conclusions about the experimental deployment of the tool, draw out lessons for future design and implementation activities, and comment on some of the limitations emergent from the use of the tool.
Promoting Public Participation for Integrating Sustainability Issues in Environmental Decision-Making: The Indian Experience
Authors: Rajvanshi Asha
Published: September 2003

In most regions of the world, consultative approaches involving "open door" model of public involvement are already being adopted in EIA process for ensuring sustainability of environmental and biodiversity resources and the security of the livelihoods of local communities. In India too, legislative provisions for public involvement in EIA were made mandatory by the enactment of Public Hearing Notification in April 1997 with an objective to strengthen public involvement in EIA process. The paper has drawn extensively from the case studies and proceedings of the public hearing to highlight the inherent weaknesses and process constraints that have undermined the benefits of public hearing in influencing the environmental decisions. To overcome some of the existing pitfalls of the consultative process, the paper emphasises the merit of initiating public involvement fairly early in EIA to make it an integral feature of the assessment procedures. The paper also stresses the significant need for a more proactive participation by adequately represented stakeholders in bringing about a positive tilt in the existing ceremonial nature of public hearing process to enhance its effectiveness as a participatory tool for consensus building and decision-making.
Achieving Effectiveness in Stakeholder Participation Using the GIS-Based Collaborative Spatial Delphi Methodology
Authors: Balram Shivanand , Dragicevic Suzana , Meredith Thomas
Published: September 2003

Environmental problems have spatial origins and consequences. Hence, effective stakeholder participation demands the integration of comprehensive facilities for understanding the spatial components that affect environmental change. This study develops the Collaborative Spatial Delphi (CSD) methodology to embed spatial thinking, conceptualise the dynamic mechanisms, and assess the effectiveness of the resulting participatory process. The CSD uses a collaborative geographic information system (GIS) and the Delphi procedure in a descriptive decision-making framework that integrates diverse stakeholder knowledge for spatial awareness, understanding, and negotiated outcomes. The CSD synthesises relevant theories to conceptualise the participation mechanisms, and an application of the methodology to urban green spaces planning in Montreal, Canada is presented. The results suggest that a deficiency in technical background is not a barrier to effective use of spatial technology in participatory planning. The methodology enhanced many spatial facets of the participation process and was evaluated as effective in achieving negotiated outcomes.
Hyaluronan in the Human Neonatal Lung: Association with Gestational Age and Other Perinatal Factors
Authors: Johnsson Hans , Eriksson Lars , Gerdin Bengt , Hällgren Roger , Sedin Gunnar
Published: September 2003

The aim of this study was to determine the influence of gestational age at birth, postnatal age, specific complications and methods of treatment on the lung hyaluronan concentration in infants. Lung samples and clinical records from 117 infants who died 0–228 days (32 weeks) after preterm or term birth were studied. The lung hyaluronan concentration at death was most strongly associated with the gestational age at birth, an association best described by an exponential function with a negative power coefficient. After adjustments for gestational age, the lung hyaluronan concentration also correlated significantly with birth weight, weight at death, the wet-to-dry lung weight ratio and specific staining for hyaluronan in the pleura. Intrauterine infection was also associated with a significantly higher lung hyaluronan concentration.
Plasma Transforming Growth Factor β1 Levels in Thrombocytopenic and Nonthrombocytopenic Neonates
Authors: Duman Murat , İrken Gülersu , Ören Hale , Uçar Canan , Atabay Berna , Yilmaz Şebnem , Yüksel Faize , Özkan Hasan
Published: September 2003

In this study, we determined the plasma TGF-β1 levels in healthy and thrombocytopenic and nonthrombocytopenic neonates who had perinatal risk factors and examined the association between plasma TGF-β1 levels and platelet counts in these newborns to investigate the role of TGF-β1 in the pathogenesis of neonatal thrombocytopenia. Three groups were defined in this prospective study: group 1, thrombocytopenic neonates (n = 22) who had perinatal risk factors; group 2, nonthrombocytopenic neonates who had similar perinatal risk factors for thrombocytopenia (n = 20); group 3, healthy and nonthrombocytopenic neonates without any risk factors (n = 20). Plasma TGF-β1 levels were measured with ELISA. Plasma TGF-β1 levels of the thrombocytopenic neonates were significantly lower than those of healthy nonthrombocytopenic neonates but did not differ significantly from nonthrombocytopenic neonates who had similar perinatal risk factors for thrombocytopenia. There was a significant positive correlation between plasma TGF-β1 levels and platelet counts. Further studies are needed to determine the cause of low plasma TGF-β1 levels in thrombocytopenic neonates and to investigate the role of plasma TGF-β1 levels in the pathogenesis of neonatal thrombocytopenia.
Chaotic Analysis Approach in Neonatal Magneto-Encephalography
Authors: Kotini A. , Koutlaki N. , Anninos P. , Adamopoulos A. , Liberis V. , Anastasiadis P.
Published: September 2003

The aim of this study was to investigate the presence of any non-linearity in the magneto-encephalographic recordings (MEG) in neonates born to pre-eclamptic mothers in comparison with the ones born to mothers having uncomplicated pregnancies, in order to find out differences in the mechanisms underlying their brain waves. Our study population consisted of 40 term neonates who were delivered normally, without any clinical signs of brain damage. Thirty of them had a normal pregnancy and labour with normal Apgar scores, umbilical cord pH, and birth weight, while 10 neonates had suffered a pre-eclamptic pregnancy. The above analysis of the MEG in the neonatal pre-eclamptic brain showed a lower dimension complexity as compared with the normal neonatal brain and a lower first Lyapunov exponent which means lower information processing. The non-linear analysis of the MEG activities in neonates may offer important perspectives to understand significant features of their brain function.
Differential Changes in Dopamine D2- and D1-Receptor mRNA Levels Induced by Hypoxia in the Arterial Chemoreflex Pathway Organs in One-Day-Old and Adult Rabbits
Authors: Bairam Aida , Carroll John L. , Labelle Yves , Khandjian Edouard W.
Published: September 2003

This study determined: (1) whether dopamine (DA) D2-receptor (R) and D1-R mRNA levels in the carotid body (CB), petrosal ganglion (PG) and superior cervical ganglion (SCG) are modulated by hypoxia; (2) the role of hypoxia intensity and exposure duration, and (3) whether the pattern of modulation differs between newborn (1-day-old) and adult rabbits. Rabbits were exposed to five FiO2 conditions: 21% (control); 15%/6 h; 15%/24 h; 8%/6 h and 8%/24 h. D2- and D1-R mRNA expression levels were calculated for each hypoxia condition relative to control using RT-PCR analysis. In the CB of 1-day-old rabbits, D2- and D1-R transcript levels increased and decreased after exposure to 15 and 8% O2, respectively. In the adult CB, D2- and D1-R transcript levels decreased independently of hypoxia intensities. Only changes in D1-R mRNA levels were dependent on exposure time. In the PG, both hypoxia intensities decreased the D2-R transcript levels in 1-day-old and adult rabbits; but for the D1-R mRNA levels, hypoxia decreased its level in 1-day-old rabbits and increased it in adults regardless of exposure duration. In the SCG, hypoxia had no determinant effect on the D2-R mRNA levels either in newborn or adult rabbits while it induced a decrease of D1-R transcript levels in 1-day-old rabbits and an increase in adult rabbits. It is concluded that hypoxia affects DA D2- or D1-R mRNA levels in the chemoreflex pathway in an age-dependent and site-specific manner.
Long-Term Tidal Liquid Ventilation in Premature Lambs: Physiologic, Biochemical and Histological Correlates
Authors: Cox Cynthia , Stavis Robert L. , Wolfson Marla R. , Shaffer Thomas H.
Published: September 2003

Chronic lung disease in infants continues to be problematic. Tidal liquid ventilation (TLV) improves lung mechanics and provides effective gas exchange. We hypothesized that premature lambs could be supported safely with TLV and evaluated 9 preterm lambs (132 days gestation) on TLV up to 72 h. Results (mean ± SEM): pH 7.36 ± 0.003, PaCO2 44 ± 0.34 mm Hg, PaO2 170 ± 4.8 mm Hg, compliance = 1.65 ± 0.24 ml/cm H2O/kg, mean arterial blood pressure = 53 ± 0.08 mm Hg, heart rate = 189 ± 1.5 bpm. Blood perflubron levels were 6.0 ± 0.24 µg/ml over 24 h. Tissue perflubron levels increased from 81 ± 7.0 µg/g at 24 h to 108 ± 15 µg/g at 72 h (p < 0.05). There was a difference in perflubron concentrations as a function of tissue (p < 0.001) that correlated to lipid levels (r2 = 0.93, p < 0.01). These data demonstrate that TLV is both safe and effective up to 72 h in premature lambs.
Differential Branching of the Sphingolipid Metabolic Pathways with the Stage of Development
Authors: Facchinetti Maria M. , Beuret Cecilia , Marquez Maria G. , Sterin-Speziale Norma
Published: September 2003

We have studied sphingomyelin metabolism in the papillae of neonatal (10-day-old) and adult (70-day-old) kidneys of male Wistar rats because sphingolipid second messengers generated by sphingomyelin metabolism are involved in cellular processes such as proliferation, differentiation and apoptosis. We showed that sphingomyelin and ceramide concentrations in homogenized rat papilla tissue increase with the time whereas sphingosine-1-phosphate content decreases. This is consistent with the finding of a higher biosynthesis of the latter sphingolipid in neonatal than in adult rat papillae. De novo synthetized ceramide was, however, higher in adult than in neonatal papilla homogenates probably accounting for the high ceramide content of the adult rat papilla. These results suggest an active de novo pathway not ending in sphingomyelin but instead arresting at ceramide in adult rat papilla tissue, partially metabolized into sphingosine-1-phosphate in neonatal rat papillae. The activity and the expression of sphingosine kinase, one of the enzymes involved in ceramide metabolism, was found to be higher in neonatal than adult rat kidney tissue. The intracellular distribution of sphingosine kinase was also different; in neonatal rat tissue the enzyme was predominantly associated with plasma membranes but it was cytosolic in adult rat papilla tissue. These findings seem to indicate that, in rat renal papillae, the developmental regulation of sphingosine kinase expression and activity addresses the sphingolipid metabolism to the formation of the proliferative metabolite sphingosine-1-phosphate in the neonatal period, and ceramide, which is associated with cell arrest and differentiation in the adult tissue. These data are consistent with the proliferative state necessary for tubular elongation during the neonatal period and the maintenance of the differentiated state in the adult tissue.
C-Reactive Protein Levels and Arterial Abnormalities in the Offspring of Patients with Premature Myocardial Infarction
Authors: Magadle R. , Merlon H. , Weiner P. , Mohammedi I. , Robert D.
Published: September 2003

Aims: To determine whether high C-reactive protein (CRP) levels and increased intima-media thickness of the common carotid arteries are coexistent in adolescents and young adults with a family history (FH) of premature myocardial infarction (MI). Methods: 50 healthy young subjects whose parents had had premature MI and 50 control matched subjects were enrolled in the study. CRP levels and the intima-media thickness of the distal common carotid arteries were evaluated in all subjects. Results: As compared with the control subjects, the offspring of patients with premature MI had a higher CRP concentration (mean ± SD 8.8 ± 2.6 versus 3.9 ± 0.6 mg/l, p < 0.02) and greater intima-media thickness of the common carotid arteries (values for combined sides, mean ± SD 0.48 ± 0.02 versus 0.43 ± 0.02 mm, p < 0.03). Conclusion: High serum levels of CRP and arterial structural changes are coexistent at an early age in subjects with an FH of premature MI.
Does Chronic ST Segment Elevation following Q Wave Myocardial Infarction Exclude Tissue Viability?
Authors: Saber Walid , Nishime Erna Obenza , Brunken Richard C. , Apperson-Hansen Carolyn , Mills Roger M.
Published: September 2003

Purpose: Electrocardiographic (ECG) ST segment elevation lasting 2 or more weeks following Q wave myocardial infarction has been associated with ‘ventricular aneurysm’ and absence of tissue viability. Regional systolic dysfunction may reflect either viable myocardium or scar. Positron emission-tomographic (PET) imaging can distinguish viable from nonviable tissue. We hypothesized that patients with chronic ST segment elevation after Q wave infarction might demonstrate salvageable myocardium in the infarct region. Methods: The ECGs of 1,229 sequential patients undergoing PET scans for viability assessment were reviewed by an electrocardiographer to identify individuals with chronic anteroseptal Q wave infarctions with persistent ST segment elevation exceeding 1 mV. Patients with QRS duration longer than 0.14 ms or rhythm other than sinus were excluded. Viability was considered present if either a reversible stress-induced perfusion defect (ischemia) or a resting perfusion-metabolism mismatch (hibernation) was identified. Results: Anteroseptal ECG Q wave infarction was identified in 132 subjects (74% male, age 61 ± 12 years). Chronic ST segment elevation was present in 84 subjects (64%) and absent in 48. Baseline clinical characteristics and left ventricular systolic function were similar in both groups. 63% of those with and 56% of those without chronic ST elevation had viable myocardium. No relationship was noted between chronic ST segment elevation and the presence or absence of myocardial viability. Conclusions: Chronic ST segment elevation after anteroseptal Q wave myocardial infarction does not exclude myocardial viability in the ‘infarct zone’. Evaluation of residual tissue viability is indicated to assess the benefit of revascularization in patients with Q wave infarction and chronic ST segment elevation.
Mechanical Unloading of the Failing Human Heart Fails to Activate the Protein Kinase B/Akt/Glycogen Synthase Kinase-3β Survival Pathway
Authors: Razeghi Peter , Bruckner Brian A. , Sharma Saumya , Youker Keith A. , Frazier O.H. , Taegtmeyer Heinrich
Published: September 2003

Background: Left ventricular assist device (LVAD) support of the failing human heart improves myocyte function and increases cell survival. One potential mechanism underlying this phenomenon is activation of the protein kinase B (PKB)/Akt/glycogen synthase kinase-3beta (GSK-3β) survival pathway. Methods and Results: Left ventricular tissue was obtained both at the time of implantation and explantation of the LVAD (n = 11). Six patients were diagnosed with idiopathic dilated cardiomyopathy, 4 patients with ischemic cardiomyopathy and 1 patient with peripartum cardiomyopathy. The mean duration of LVAD support was 205 ± 35 days. Myocyte diameter and phosphorylation of ERK were used as indices for reverse remodeling. Transcript levels of genes required for the activation of PKB/Akt (insulin-like growth factor-1, insulin receptor substrate-1) were measured by quantitative RT-PCR. In addition, we measured the relative activity of PKB/Akt and GSK-3β, and assayed for molecular and histological indices of PKB/Akt activation (cyclooxygenase mRNA levels and glycogen levels). Myocyte diameter and phosphorylation of ERK decreased with LVAD support. In contrast, none of the components of the PKB/Akt/GSK-3β pathway changed significantly with mechanical unloading. Conclusion: The PKB/Akt/GSK-3β pathway is not activated during LVAD support. Other signaling pathways must be responsible for the improvement of cellular function and cell survival during LVAD support.
Clinical Usefulness of a Functional Test of Neutralising Streptokinase Antibodies for the Prediction of the Thrombolytic Effect of Streptokinase in Acute Myocardial Infarction
Authors: Gill Sabine , Kristensen Søren Risom , Haastrup Benedikte , Haghfelt Torben
Published: September 2003

We investigated whether the occurrence of neutralising streptokinase (SK) antibodies, as assessed by a new bedside test, was related to the effect of SK in acute myocardial infarction (AMI), assessed with continuous vectorcardiography (VCG). Twenty-eight patients with ST elevation, admitted ≤ 6 h after the onset of symptoms, treated with 1.5 MIU SK were included. The level of SK antibodies was assessed by the TAS Streptokinase Test Panel, measuring the lysis time of clotted fibrin in the sample. Clot lysis time was negatively correlated to ST vector magnitude (ST-VM) recovery at 90 min (rS = –0.40, p = 0.03), and clot lysis time was positively correlated to time to reperfusion, (rS = 0.42, p = 0.03). The predictive values of the test, however, were low. In conclusion, as the prediction of reperfusion in AMI after SK by the new test was poor, we cannot recommend it for clinical decision-making prior to the choice of the thrombolytic agent.
Colour Tissue Doppler Echocardiographic Evaluation of Right Ventricular Function in Patients with Right Ventricular Infarction
Authors: Oguzhan Abdurrahman , Abaci Adnan , Eryol Namik Kemal , Topsakal Ramazan , Seyfeli Ergün
Published: September 2003

Objective: This study was undertaken to determine right ventricular (RV) function as assessed by colour Doppler tissue imaging (DTI) in patients with RV infarction. Methods: During the study period, 35 patients were evaluated: 14 patients had an inferior myocardial infarction (MI) with RV infarction and 21 patients had an inferior MI without RV involvement. Twenty age-matched healthy subjects served as controls. The diagnosis of RV infarction was defined by ST segment elevation >0.1 mV in lead V4R. Systolic and early and late diastolic velocities were acquired from the apical four-chamber view at the lateral tricuspid annulus, the septal side of the tricuspid annulus and the RV free mid-wall using colour DTI. Results: Systolic and early diastolic velocities at the lateral tricuspid annulus were significantly reduced in patients with inferior MI with RV infarction compared with those in healthy individuals (7.8 ± 1 vs. 11 ± 2 cm/s, p < 0.002) and patients with inferior MI without RV infarction (7.8 ± 1 vs. 10 ± 1 cm/s, p < 0.002). The late diastolic lateral annular velocity did not differ between the groups. Systolic and early diastolic RV free wall velocities were also significantly decreased in patients with RV infarction compared with those in healthy individuals (7 ± 1 vs. 8.7 ± 1 cm/s, p < 0.01; 6.3 ± 2 vs. 8.7 ± 2 cm/s, p < 0.05, respectively) and patients with inferior MI without RV infarction (7 ± 1 vs. 9 ± 2 cm/s, p < 0.01; 6.3 ± 2 vs. 8.3 ± 2 cm/s, p < 0.05, respectively). Conclusion: The evaluation of tricuspid annular and RV free wall velocities using colour DTI provides a rapid and noninvasive tool for assessing RV function in patients with RV infarction.