bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermodynamic and Kinetic Description of the Second Order Phase Transitions
Authors: Klimontovich Yu. L. 
Published: September 2003

A thermodynamic and kinetic description of phase transitions for the model of ferroelectrics on the basis of kinetic equations for the distribution function of values of the "order parameter", coordinates and time is discussed. For one-domain ferroelectrics the self-consistent approximation for the first moment is used. The kinetic equation is reduced to the relaxation Ginsburg–Landau equation. The susceptibility is governed by the Curie law and there is an increase in heat capacity. Calculations are carried out for one-domain and polydomain ferroelectrics. In the first case the self-consistent approximation for the first moment is used. In the second one the self-consistent approximation for the second moment is carried out. In the last case there is a jump in susceptibility. The heat capacity is governed by the Curie law. It is shown also that the Ornstein–Zernike formula is valid not for the space correlator of fluctuations, but only for the temporal spectral density of the space correlator at zero frequency. In the kinetic theory of the phase transition all physical characteristics at the critical point have finite values. Thus, the problem of "infinities" is absent.
Climate Dynamics as a Nonlinear Brownian Motion
Authors: Sonechkin D. M. 
Published: September 2003

Based on the heat balance equation of the global climate system the well-known surface air temperature time series of the Northern and Southern hemispheres were analyzed as realizations of a fractional Brownian motion. The technique of the so-called wavelet transform was used for this purpose. The technique easily admits splitting time series of interest to statistically stationary oscillations and a trend. Such temperature oscillations were extracted which include within themselves almost all differences between both hemispheric time series. As a result of subtraction of the oscillations from the primary hemispheric series a residual trend-like component was evaluated. The latter evidences a single warming trend of the global climate system that was started from the early 20th century.
Game of Morphogenesis: What Can We Learn from the Pattern-Form Interplay Models?
Authors: Spirov A. V. 
Published: September 2003

We approach the problem of how the information encoded in linear DNA molecule becomes translated into a three-dimensional form from position of Pattern-Form Interplay Models. The characteristic feature of these models is the existence of feedback loops from (bio)chemical pattern formation to modeling embryo form changes. In accordance with the model the system is open and changes in a pattern give rise to changes in form and these changes in form (surface geometry) cause further pattern changes, and so on.Spontaneous pattern formation takes place in the model as primary and secondary bifurcations of nonlinear parabolic PDEs describing reaction-diffusion systems with imposed gradient. We briefly review the main results of previous works and consider the phenomenon of axis tilting as a case of symmetry breaking via secondary bifurcations. The axis tilting bifurcation occurs as a consequence of position-dependency of diffusion coefficients. The explicit demonstration of this phenomenon in Pattern-Form Interplay Models is believed to be new.
Global Bifurcation Approximation in Controlling Chaotic Systems
Authors: Lee Byoung-Cheon , Kim Bong-Gyun , Wang Bo-Hyeun 
Published: September 2003

In our previous research [Lee et al., 1995], we demonstrated that return map control and adaptive tracking method can be used together to locate, stabilize and track unstable periodic orbits (UPO) automatically. Our adaptive tracking method is based on the control bifurcation (CB) phenomenon which is another route to chaos generated by feedback control. Along the CB route, there are numerous driven periodic orbits (DPOs), and they can be good control targets if small system modification is allowed. In this paper, we introduce a new control concept of global bifurcation approximation (GBA) which is quite different from the traditional local linear approximation (LLA). Based on this approach, we also demonstrate that chaotic attractor can be induced from a periodic orbit. If feedback control is applied along the direction to chaos, small erratic fluctuations of a periodic orbit is magnified and the chaotic attractor is induced. One of the special features of CB is the existence of irreversible orbit (IO) which is generated at the strong extreme of feedback control and has irreversible property. We show that IO induces a hysteresis phenomenon in CB, and we discuss how to keep away from IO.
Nonlinear Resonance in Basin Portraits of Two Coupled Swings Under Periodic Forcing
Authors: Ueda Yoshisuke , Ueda Yoshinori , Stewart H. Bruce , Abraham Ralph H. 
Published: September 2003

A model of a simple electric power supply network involving two generators connected by a transmission network to a bus is studied by numerical simulation. In this model, the bus is supposed to maintain a voltage of fixed amplitude, but with a small periodic fluctuation in the phase angle. In such a case, traditional analysis using direct methods is not applicable. The frequency of the periodic fluctuation is varied over a range of values near a nonlinear resonance of the two-generator network. When the bus fluctuation frequency is away from resonance, the system has several attractors; one is a small-amplitude periodic oscillation corresponding to synchronized, quasi-normal operation (slightly swinging), while others are large amplitude periodic oscillations which, if realized, would correspond to one or both generators operating in a desynchronized steady state. When the bus fluctuation frequency approaches resonance, a new periodic attractor with large amplitude oscillations appears. Although it does correspond to a synchronized steady state, this attractor has a disastrously large amplitude of oscillation, and represents an unacceptable condition for the network. Basin portraits show that this resonant attractor erodes large, complicated regions of the basin of the safe operating condition. Under conditions of small periodic fluctuation in bus voltage, this basin erosion would not be detected by traditional analysis using direct methods. Further understanding of such complicated basin structures will be essential to correctly predict the stability of electric power supply systems.
Chaos: An Ecological Reality?
Authors: Upadhyay Ranjit Kumar , Iyengar S. R. K. , Rai Vikas 
Published: September 2003

Deterministic chaos has been studied extensively in various fields. Some of the ideas emerging out of these studies have been put to novel applications. However, it is unknown whether natural ecological systems support chaotic dynamics. There is no concrete evidence which suggests that ecosystem evolution is chaotic in certain situations. This is very intriguing because ecosystems do possess all the necessary qualifications to be able to support such a dynamical behavior. The present paper attempts to answer the above question with the help of a few systems modeling different but very common ecological situations. A new methodology for the analysis of a class of model ecological systems is presented. Simulation experiments suggest that natural terrestrial systems are not suitable candidates where one should look for chaos. Additionally, our study also points out that the failure of attempts to observe chaos in natural populations might have resulted because biological interactions are not conducive for such a behavior to be supported. The cause of these failures may not be the poor data quality or demerits in the analysis techniques.
Applications of Chaotic Digital Code-Division Multiple Access (CDMA) to Cable Communication Systems
Authors: Yang Tao , Chua Leon O. 
Published: September 2003

In this paper the technical details of chaotic digital code-division multiple access ((CD)2MA) communication systems used in cable communication systems are presented. The cable communication system may be a pure coaxial RF cable network, a hybrid fiber-coax network, or a pure optical fibre network for high-capacity data link. As an example of its many potential applications in cable communication systems, (CD)2MA is used to support the upstream digital data communications in cable TV systems occupying the very noisy 5–40 MHz portion of spectrum. Although the (CD)2MA proposed in this paper is only used to support current Internet services via cable TV networks, it can also be used to support the high-speed data-link provided in the 550–750 MHz band in hybrid fiber-coax networks. (CD)2MA is a new communication framework which uses band-limited chaotic carriers insted of linear ones. For the purpose of generality, in this paper the band-limited chaotic carriers are approximated by groups of linear sub-carriers, which distribute within the same bandwidth with a fixed amplitude, random phases and uniformly distributed frequencies. The theoretical result of the performance of (CD)2MA is given. We also provide the simulation results of the bit-error-rate (BER) performances of a synchronous (CD)2MA used in cable communication systems. The results show that the (CD)2MA system has a better performance than the synchronous CDMA system proposed for the same cable communication system. Technical details of (CD)2MA are also presented for the future design of prototype systems. We present the framework of the whole (CD)2MA system including carrier syncronization, timing recovery and the details of nonlinear carrier generators.
Controlling Chaos with Parametric Perturbations
Authors: Fronzoni Leone , Giocondo Michele 
Published: September 2003

We consider the effects of parametric perturbation on the onset of chaos in different dynamical systems. Favoring or suppression of chaos was observed depending on the phase or the frequency of the periodic perturbation. A lowering of the threshold of chaos was observed in an electronic device simulating a Josephson-Junction model and the suppression of chaos was obtained in a bistable mechanical device. We showed that in case of spatial instability in a sample of liquid crystal, the action of the parametric perturbation is to modify the velocity and the onset of the defects. Considering that the emergence of defects precedes the threshold of spatio-temporal chaos, we infer that parametric perturbation can modify the threshold of chaos in this spatial dynamical system.
Simulation of Heartbeat Dynamics: A Nonlinear Model
Authors: Signorini Maria G. , di Bernardo Diego 
Published: September 2003

The mathematical modeling of biological systems has proven to be a valuable tool by allowing experiments which would otherwise be unfeasible in a real situation. In this work we propose a system of nonlinear differential equations describing the macroscopic behavior of the cardiac conduction system. The model describes the interactoin between the SinoAtrial and AtrioVentricular node. Its very simple structure consists of two nonlinear oscillators resistively coupled. The numerical analysis detects different kinds of bifurcations whose pathophysiological meanings are discussed. Moreover, the model is able to classify different pathologies, such as several classes of arrhythmic events, as well as to suggest hypothesis on the mechanisms that induce them. These results also show that the mechanisms generating the heartbeat obey complex laws. The model provides a wuite complete description of different pathological phenomena and its simplicity can be exploited for further studies on the control of cardiac dynamics.
Slow-Fast Autonomous Dynamical Systems
Authors: Rossetto Bruno , Lenzini Thierry , Ramdani Sofiane , Suchey Gilles 
Published: September 2003

In this paper, we consider a class of slow-fast autonomous dynamical systems, i.e. systems having a small parameter ∊ multiplying a component of velocity. At first, the singular perturbation method (∊ = 0+) is recalled. Then we consider the case ∊ ≠ 0. Starting from a working hypothesis and particularly in the case of a singular approximation, our purpose is to show that there exists slow manifolds which can be defined as the slow manifolds of a so-called tangent linear system. The method allowed us to plot the slow manifold and to go further into the qualitative study and the geometric characterization of attractors. As an example, we give the explicit slow manifold equation of the van der Pol limit cycle. The value of the parameter corresponding to bifurcations is computed. Other third order systems are also treated. The method is extended to dynamical systems with no small parameter, and, therefore, which have no singular approximations, but have at least one real and negative eigenvalue in a large domain. It is numerically shown from the Lorenz model and from a laser model that there exists slow manifolds which can be defined as the slow manifods of a so-called tangent linear system, as in the previous cases. The implicit equation of these slow manifolds has been calculated too.
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.
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.
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.
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

<i>Aims:</i> 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). <i>Methods:</i> 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. <i>Results:</i> 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). <i>Conclusion:</i> High serum levels of CRP and arterial structural changes are coexistent at an early age in subjects with an FH of premature MI.
Synthesis, Structural Analysis and Antibacterial Activity of a Butyl Ester Derivative of Ampicillin
Authors: Bartzatt Ronald , Malesa Cynthia 
Published: September 2003

<i>Background:</i> Ester groups placed on medicinal agents have been found to increase lipophilicity (more positive log p value). Alterations in a partition coefficient may affect medicinal activity. Formation of an ester group such as -C(O)OCH<sub>2</sub>CH<sub>2</sub>CH<sub>2</sub>CH<sub>3</sub> from a carboxyl group [-C(O)OH] can be efficiently accomplished utilizing diazoalkanes and produces a prodrug-like structure of ampicillin (a bipartate drug carrier). Formation of an ester group may produce beneficial changes in medicinal parameters such as log P, log BB, and molecular polar surface area (TPSA). <i>Methods:</i> An ester of ampicillin was synthesized by replacing the carboxyl group with a butyl ester group. The ester formed was synthesized utilizing diazobutane, which is a gas at room temperature and reacts with the acidic hydrogen of the carboxylic acid. The ampicillin ester was dissolved into LB agarose media at levels of 0.228 and 0.180 mg/ml, and its antibacterial activity was compared to that of normal ampicillin. Medicinal parameters such as log P, solubility, polar surface area, log BB, molecular dipole, Clog P, intestinal absorption and the ‘Rule of 5’ were determined. <i>Results:</i> The ampicillin ester consisted of yellow crystals that were stable for >12 weeks at 0°C. The ester has reduced hydrogen bonding capacity and increased lipophilic character (by log P) compared to the parent structure. Each concentration of the ester tested induced 100% growth inhibition of ampicillin-susceptible but streptomycin-resistant <i>Escherichia coli</i> bacteria, and >30% growth inhibition of an ampicillin-resistant <i>E. coli.</i> This ester compound of ampicillin showed zero violations of the ‘Rule of 5’, which indicates good bioavailability and good bioactivity. Intestinal absorption indicated by TPSA value showed moderate absorption activity for both parent and ester compounds. The lipophilic substituent constant for the butyl ester is +0.941, which indicates increased lipophilicity. The ester group improves log BB and dermal permeability of ampicillin. <i>Conclusion:</i> The butyl ester of ampicillin inhibited the growth of susceptible and resistant <i>E. coli.</i> Favorable values for parameters such as TPSA, log P, log BB, and zero violations of the ‘Rule of 5’ suggest good bioavailability and good bioactivity.
Brief Exposure to Antimycotics Reduces the Extracellular Phospholipase Activity of <i>Candida albicans</i> and <i>Candida tropicalis</i>
Authors: Anil S. , Samaranayake L.P. 
Published: September 2003

<i>Background:</i> Although the phospholipase activity is considered a potential virulence determinant of the pathogenic <i>Candida</i> species, the effect of antimycotics on this attribute is not known. Hence we evaluated the phospholipase activity in 10 isolates each of <i>Candida albicans</i> and <i>Candida tropicalis,</i> after their exposure to antifungals. <i>Methods:</i> The impact of antimycotics on phospholipase activity was also assessed after exposure of the isolates to sub-minimum inhibitory concentrations of nystatin, amphotericin B and fluconazole. <i>Results:</i> All <i>Candida</i> isolates investigated exhibited phospholipase activity (Pz). In general <i>C. albicans</i> showed relatively higher P<sub>z</sub> activity than <i>C. tropicalis,</i> and exposure of the isolates to antimycotics led to a significant (p < 0.05) reduction in the phospholipase activity. Nystatin and amphotericin B, but not fluconazole, significantly reduced the phospholipase activity of both <i>Candida</i> species. <i>Conclusion:</i> These observations, while confirming the higher virulence of <i>C. albicans</i> relative to <i>C. tropicalis,</i> demonstrate for the first time the effect of antifungal agents on extracellular phospholipases of these common opportunistic pathogens.