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Complete relaxation map of polyethylene : filler-induced chemical modifications as dielectric probes
(2001)
We have recently reported the phenomenon of doubly stochastic resonance [Phys. Rev. Lett. 85, 227 (2000)], a synthesis of noise-induced transition and stochastic resonance. The essential feature of this phenomenon is that multiplicative noise induces a bimodality and additive noise causes stochastic resonance behavior in the induced structure. In the present paper we outline possible applications of this effect and design a simple lattice of electronic circuits for the experimental realization of doubly stochastic resonance.
We present a measure of quantum entanglement which is capable of quantifying the degree of entanglement of a multi-partite quantum system. This measure, which is based on a generalization of the Schmidt rank of a pure state, is defined on the full state space and is shown to be an entanglement monotone, that is, it cannot increase under local quantum operations with classical communication and under mixing. For a large class of mixed states this measure of entanglement can be calculated exactly, and it provides a detailed classification of mixed states.
The rescaling of geological data series to a geological reference time series is of major interest in many investigations. For example, geophysical borehole data should be correlated to a given data series whose time scale is known in order to achieve an age-depth function or the sedimentation rate for the borehole data. Usually this synchronization is performed visually and by hand. Instead of using this wiggle matching by eye, we present the application of cross recurrence plots for such tasks. Using this method, the synchronization and rescaling of geological data to a given time scale is much easier and faster than by hand.
The 300 year record of the yearly sunspot numbers and numerically generated trajectory of the solar inertial motion (SIM) were subjects of a synchronization analysis. Phase synchronization of the sunspot cycle and a fast component of the SIM have been found and confirmed with statistical significance in three epochs (1727-1757, 1802-1832 and 1863-1922) of the entire 1700-1997 record. This result can be considered as a quantitative support for the hypothesis that there is a weak interaction of gravity and solar activity.
We propose a technique to calculate large-scale dimension densities in both higher-dimensional spatio-temporal systems and low-dimensional systems from only a few data points, where known methods usually have an unsatisfactory scaling behavior. This is mainly due to boundary and finite size effects. With our rather simple method we normalize boundary effects and get a significant correction of the dimension estimate. This straightforward approach is basing on rather general assumptions. So even weak coherent structures obtained from small spatial couplings can be detected with this method, what is impossible by using the Lyapunov-dimension density. We demonstrate the efficiency of our technique for coupled logistic maps, coupled tent maps, the Lorenz-attractor and the Roessler-attractor.
So far, the evolution of post-AGB stars is not fully understood. In particular the formation of hydrogen- deficient and hydrogen-free Central Stars of Planetary Nebulae (CSPN) is unsettled. New evolution models, which allow for the consistent treatment of the physics of late thermal pulses, promise new insights to the formation of these stars. In this paper we summarize the results of non-LTE analyses of CSPN with wind. By comparing these results with the predictions of the new evolution models, open questions concerning the evolution of the stars might be answered. In addition we discuss the driving mechanism of the winds of Wolf-Rayet CSPN. New models, which account for millions of iron lines, support the assumptions that these winds are driven by radiation.
In the roughly 20 years of its existence as an observational science, gravitational lensing has established itself as a valuable tool in many astrophysical fields. In the introduction of this review we briefly present the basics of lensing. Then it is shown that the two propagation effects, lensing and scintillation, have a number of properties in common. In the main part various lensing phenomena are discussed with emphasis on recent observations.
Wachstum und Variabilität im Körperbau unter Berücksichtigung bei industriellen Größensystemen
(2001)
Phytoplankton dynamics in a shallow eutrophic lake were investigated over a 3-year period with respect to environmental forces which drive species composition and diversity. Diversity was calculated on the basis of species as well as on the basis of their functional properties (the C-R-S-concept). Stratification and water column mixing had a strong impact on phytoplankton composition. Application of a similarity-diversity model revealed that a high diversity was a transient non-stable state, whereas drastic changes or long-lasting stable environmental conditions are characterized by low diversity. This effect was more pronounced when the diversity was calculated on the basis of the phytoplankton species functional properties. Thus, this functional approach supports the intermediate disturbance hypothesis from field data.
alpha-Chymotrypsin was modified by covalent attachment of selected phenolic and related compounds (caffeic acid, chlorogenic acid, ferulic acid, gallic acid, quinic acid, m-/o-/p-dihydroxybenzene and p-benzoquinone) at pH 9. The derivatives formed were characterised in terms of their activity and selected physicochemical properties. In vitro experiments showed that the proteolytic digestion of food proteins with alpha-chymotrypsin derivatives was adversely affected. This decrease depended on the reactivity of the phenolic and related substances tested as well as on the kind of substrate applied. The derivatisation was accompanied by a reduction in the amount of free lysine and tryptophan residues. Moreover, the solubility of the derivatives decreased over a broad pH range, with a parallel increase in the hydrophobicity. The isoelectric point was shifted to a lower pH value, and formation of high-molecular-weight fractions was documented by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE).
Soya glycinin was derivatized with different phenolic substances (caffeic-, chlorogenic-, gallic acid and quercetin). The protein derivatives formed have been characterized in terms of their properties where they showed changes in the content of free epsilon-amino groups, tryptophan and thiol groups. The derivatives have also been characterized in terms of their solubility at different pH-values to document the influence on the functional properties. Another objective of this paper was to demonstrate the influence on the digestibility of the proteins with one of the main enzymes of the gastro-intestinal tract (pancreatin) on the basis of in vitro experiments after derivatization with phenolic substances. The enzymatic digestion of the derivatized proteins was promoted.
The transition from fully synchronized behavior to two-cluster dynamics is investigated for a system of N globally coupled chaotic oscillators by means of a model of two coupled logistic maps. An uneven distribution of oscillators between the two clusters causes an asymmetry to arise in the coupling of the model system. While the transverse period-doubling bifurcation remains essentially unaffected by this asymmetry, the transverse pitchfork bifurcation is turned into a saddle-node bifurcation followed by a transcritical riddling bifurcation in which a periodic orbit embedded in the synchronized chaotic state loses its transverse stability. We show that the transcritical riddling transition is always hard. For this, we study the sequence of bifurcations that the asynchronous point cycles produced in the saddle-node bifurcation undergo, and show how the manifolds of these cycles control the magnitude of asynchronous bursts. In the case where the system involves two subpopulations of oscillators with a small mismatch of the parameters, the transcritical riddling will be replaced by two subsequent saddle-node bifurcations, or the saddle cycle involved in the transverse destabilization of the synchronized chaotic state may smoothly shift away from the synchronization manifold. In this way, the transcritical riddling bifurcation is substituted by a symmetry-breaking bifurcation, which is accompanied by the destruction of a thin invariant region around the symmetrical chaotic state.
Hydrological modelling of a Pleistocene landslide-dammed lake in the Santa Maria Basin, NW Argentina
(2001)
The behavior of the Lyapunov exponents (LEs) of a disordered system consisting of mutually coupled chaotic maps with different parameters is studied. The LEs are demonstrated to exhibit avoided crossing and level repulsion, qualitatively similar to the behavior of energy levels in quantum chaos. Recent results for the coupling dependence of the LEs of two coupled chaotic systems are used to explain the phenomenon and to derive an approximate expression for the distribution functions of LE spacings. The depletion of the level spacing distribution is shown to be exponentially strong at small values. The results are interpreted in terms of the random matrix theory.
Ventricular tachycardia or fibrillation (VT) as fatal cardiac arrhythmias are the main factors triggering sudden cardiac death. The objective of this recurrence quantification analysis approach is to find early signs of sustained VT in patients with an implanted cardioverter-defibrillator (ICD). These devices are able to safeguard patients by returning their hearts to a normal rhythm via strong defibrillatory shocks; additionally, they are able to store at least 1000 beat-to-beat intervals immediately before the onset of a life-threatening arrhythmia. We study the
Chen et al. [Phys. Rev. E 61, 2559 (2000)] recently proposed an extension of the concept of phase for discrete chaotic systems. Using the newly introduced definition of phase they studied the dynamics of coupled map lattices and compared these dynamics with phase synchronization of coupled continuous-time chaotic systems. In this paper we illustrate by two simple counterexamples that the angle variable introduced by Chen et al. fails to satisfy the basic requirements to the proper phase. Furthermore, we argue that an extension of the notion of phase synchronization to generic discrete maps is doubtful.
We propose a method for experimental detection of directionality of weak coupling between two self-sustained oscillators from bivariate data. The technique is applicable to both noisy and chaotic systems that can be nonidentical or even structurally different. We introduce an index that quantifies the asymmetry in coupling.
Comment on "Simple approach to the creation of a strange nonchaotic attractor in any chaotic system"
(2001)
We address the problem of existence of strange nonchaotic attractors (SNAs) in quasiperiodically forced dynamical systems. Recently, Shuai and Wong [Phys. Rev. E 59, 5338 (1999)] suggested a universal method for constructing a SNA in an arbitrary system possessing chaos. We demonstrate here that, in general, this method fails. For arbitrary systems, it gives a SNA only in a vicinity of transition to chaos. We discuss also a special example, where the method by Shuai and Wong indeed produces a SNA.
Lai et al. [Phys. Rev. E 62, R29 (2000)] claim that the angular velocity of the phase point moving along the chaotic trajectory in a properly chosen projection (the instantaneous frequency) is intermittent. Using the same examples, namely the Rössler and the Lorenz systems, we show the absence of intermittency in the dynamics of the instantaneous frequency.This is confirmed by demonstrating that the phase dynamics exhibits normal diffusion. We argue that the nonintermittent behavior is generic.
Clustering in ensembles of globally coupled identical chaotic oscillators is reconsidered using a twofold approach. Stability of clusters towards "emanation" of the elements is described with the evaporation Lyapunov exponents. It appears that direct numerical simulations of ensembles often lead to spurious clusters that have positive evaporation exponents, due to a numerical trap. We propose a numerical method that surmounts the spurious clustering. We also demonstrate that clustering can be very sensitive to the number of elements in the ensemble.
Transition to Coherence in Populations of Coupled Chaotic Oscillators: A Linear Response Approach
(2001)
We consider the collective dynamics in an ensemble of globally coupled chaotic maps. The transition to the coherent state with a macroscopic mean field is analyzed in the framework of the linear response theory. The linear response function for the chaotic system is obtained using the perturbation approach to the Frobenius-Perron operator. The transition point is defined from this function by virtue of the self-excitation condition for the feedback loop. Analytical results for the coupled Bernoulli maps are confirmed by the numerics.
Noise-induced dynamics of a prototypical bistable system with delayed feedback is studied theoretically and numerically. For small noise and magnitude of the feedback, the problem is reduced to the analysis of the two-state model with transition rates depending on the earlier state of the system. Analytical solutions for the autocorrelation function and the power spectrum have been found. The power spectrum has a peak at the frequency corresponding to the inverse delay time, whose amplitude has a maximum at a certain noise level, thus demonstrating coherence resonance. The linear response to the external periodic force also has maxima at the frequencies corresponding to the inverse delay time and its harmonics.
The filtration rate of Daphnia galeata was determined in in situ experiments in Bautzen Reservoir and in laboratory experiments, where daphnids were exposed to filtrates that previously contained either natural phytoplankton or cultured eukaryotic algae (Scenedesmus obliquus or Asterionella formosa), respectively. Individual filtration rate (FR) was measured using fluorescent beads, taking into account ingested beads in the gut only. Compared to heated control treatments (100°C), dissolved compounds released by the nutritious cultured algae during the preconditioning phase or by the natural phytoplankton assemblages from Bautzen Reservoir strongly reduced the filtration rate of D. galeata (down to 60 %). Heating deactivated these dissolved compounds. A significant correlation was found between primary production measured in situ and the reduction of FR in the filtrate of reservoir water, indicating that extra- cellular products released during photosynthesis triggered the reduction of the filtration rate. The ratio of ingested to collected beads was used to quantify the proportion of food, which was not only collected but passed the mouth of D. galeata. The ratio of ingestion to collection was compared between filtered and unfiltered reservoir water both media identical with respect to the concentration of dissolved compounds, whereas other factors (e. g. food concentration, temperature, filtration rate) were different. The changes in this ratio between filtered and unfiltered reservoir water suggest that D. galeata is capable of a chemosensory control of the ingestion behaviour by detecting external metabolites.
1. After observing that juvenile roach fed intensively on cyanobacteria and that cyanobacteria were densely colonized by heterotrophic bacteria, we tested whether the bacteria are used by underyearling roach and the extent to which they contribute to the energy requirements of the fish. 2. We radiolabeled attached bacteria in a natural cyanobacterial suspension, fed the fish with these particles, and estimated their assimilation by roach. Biomass of attached bacteria on cyanobacteria increased with the proportion of the cyanobacterium Microcystis in total cyanobacteria. Biomass-specific thymidine incorporation of attached bacteria was higher than that of free bacteria. 3. In feeding experiments, we detected assimilation of bacterial biomass into muscle tissue of underyearling roach. Fish consumed Microcystis to a lesser extent compared to Aphanizomenon but assimilation of attached bacteria was higher when roach fed on Microcystis due to the higher biomass of epibacteria on this cyanobacterium. However, biomass of attached bacteria was too low to be an important food source for underyearling roach. 4. We conclude that assimilation of epibacteria from cyanobacteria cannot explain the success of roach in eutrophic lakes.
A transport theory for atomic matter waves in low-dimensional waveguides is outlined. The thermal fluctuation spectrum of magnetic near fields leaking out of metallic microstructures is estimated. The corresponding scattering rate for paramagnetic atoms turns out to be quite large in micrometer-sized waveguides (approx. 100/s). Analytical estimate for the heating and decoherence of a cold atom cloud are given. We finally discuss numerical and analytical results for the scattering from static potential imperfections and the ensuing spatial diffusion process.
Coherent transport
(2001)
We discuss the transport of matter waves in low-dimensional waveguides. Due to scattering from uncontrollable noise fields, the spatial coherence gets reduced and eventually lost. We develop a description of this decoherence process in terms of transport equations for the atomic Wigner function. We outline its derivation and discuss the special case of white noise where an analytical solution can be found.
We have obtained time-resolved observations of line-profile variations of the two Wolf-Rayet stars WR 135 and WR 111. The spectra, taken during two consecutive nights, cover a broad range from 4470 to 6590 Ang. The profile variability of the C iii emission line at 5696 Ang in WR 135 is shown in detail. The principal difficulties to constrain the velocity law from the frequency drift of discrete spectral features is discussed, emphasizing the crucial dependence on the adopted location of the line-emission region, and the possible necessity to distinguish between the motion of structures and the flow of the matter. - Full access to the observational data is provided via anonymous file transfer.
For several applications it is very useful to classify the linear or non-linear mappings by their summability properties. Absolutely summing operators and polynomials are prominent and classical examples of such setting. Here we are interested in the larger class of almost summing polynomials and we investigate their connections to other related notions of summability.
A model system of tanning of a protein matrix within a fibrous structure, such as most commonly found in insect cuticle, was developed, using the cellulose of paper in place of chitin. The paper was impregnated with a tripeptide, DOPA-Gly-Gly, or a protein (BSA) plus catechol and treated with tyrosinase to oxidize the catechol. The resulting material was waterproof and had very high wet strength. If the material was wetted and dried repeatedly its water retention decreased by a factor of at least two.
Industrieanthropologie
(2001)