Universal Power-law Decay in Hamiltonian Systems?

The understanding of the asymptotic decay of correlations and of the distribution of Poincar\'e recurrence times $P(t)$ has been a major challenge in the field of Hamiltonian chaos for more than two decades. In a recent Letter, Chirikov and Shepelyansky claimed the universal decay $P(t) \sim t^{-3}$ for Hamiltonian systems. Their reasoning is based on renormalization arguments and numerical findings for the sticking of chaotic trajectories near a critical golden torus in the standard map. We performed extensive numerics and find clear deviations from the predicted asymptotic exponent of the decay of $P(t)$. We thereby demonstrate that even in the supposedly simple case, when a critical golden torus is present, the fundamental question of asymptotic statistics in Hamiltonian systems remains unsolved.Comment: Phys. Rev. Lett., in pres

Modeling Infection with Multi-agent Dynamics

Developing the ability to comprehensively study infections in small populations enables us to improve epidemic models and better advise individuals about potential risks to their health. We currently have a limited understanding of how infections spread within a small population because it has been difficult to closely track an infection within a complete community. The paper presents data closely tracking the spread of an infection centered on a student dormitory, collected by leveraging the residents' use of cellular phones. The data are based on daily symptom surveys taken over a period of four months and proximity tracking through cellular phones. We demonstrate that using a Bayesian, discrete-time multi-agent model of infection to model real-world symptom reports and proximity tracking records gives us important insights about infec-tions in small populations

Fractal Conductance Fluctuations of Classical Origin

In mesoscopic systems conductance fluctuations are a sensitive probe of electron dynamics and chaotic phenomena. We show that the conductance of a purely classical chaotic system with either fully chaotic or mixed phase space generically exhibits fractal conductance fluctuations unrelated to quantum interference. This might explain the unexpected dependence of the fractal dimension of the conductance curves on the (quantum) phase breaking length observed in experiments on semiconductor quantum dots.Comment: 5 pages, 4 figures, to appear in PR

Isolated resonances in conductance fluctuations in ballistic billiards

We study numerically quantum transport through a billiard with a classically mixed phase space. In particular, we calculate the conductance and Wigner delay time by employing a recursive Green's function method. We find sharp, isolated resonances with a broad distribution of resonance widths in both the conductance and the Wigner time, in contrast to the well-known smooth conductance fluctuations of completely chaotic billiards. In order to elucidate the origin of the isolated resonances, we calculate the associated scattering states as well as the eigenstates of the corresponding closed system. As a result, we find a one-to-one correspondence between the resonant scattering states and eigenstates of the closed system. The broad distribution of resonance widths is traced to the structure of the classical phase space. Husimi representations of the resonant scattering states show a strong overlap either with the regular regions in phase space or with the hierarchical parts surrounding the regular regions. We are thus lead to a classification of the resonant states into regular and hierarchical, depending on their phase space portrait.Comment: 2 pages, 5 figures, to be published in J. Phys. Soc. Jpn., proceedings Localisation 2002 (Tokyo, Japan

Temporal-spatial Patterns of Noctuinae Communities (Lep. Noctuidae) in Hungarian Apple Orchards (Apple Ecosystem Research)

In our present study we aimed to recognize the temporal and spatial patterns of Noctuinae communities (Lep.Noctuidae) of four differently managed apple orchards laying in different localities of Hungary. Data were obtained by light trap collection. The quantitative data resulting from our investigations were analyzed by multivariate methods and were also analyzed by their diversity characteristics.As a result connections were found regarding the diversities of species and individuals, the patterns of occurrence and phenological properties. The studies were based on 8497 individuals of 39 species

Textural Properties and Structure of Starch-Reinforced Surimi Gels as Affected by Heat-Setting

The gel forming behavior of red hake (Urophycis chuss) surimi with and without starch and its relationship to the structure of the gel matrix were studied. For surimi gels without starch, a combination of preheat- setting at 40 C and cooking at 90 C resulted in significantly greater gel strength than cooking alone. However, preheat - setting of gels containing wheat or potato starch had no significant effect on gel strength demonstrating an opposite trend in gel strength due to the differences in swelling power, water holding ability and gelatinization temperature between potato and wheat starches. This difference in gel forming behavior due to the sources of starch and heat- setting prior to cooking correlated with changes in the structure of the matrix as evidenced by the results of image analysis. An examination of the microstructure of the gel matrix by light and electron microscopy showed that the structural differences may be due to the different protein matrix density as reflected in the increased gel strength

Textural and Microstructural Properties of Frozen Fish Mince as Affected by the Addition of Nonfish Proteins and Sorbitol

Changes in textural and microstructural properties of washed and unwashed frozen fish mince were studied as affected by the addition of non fish proteins (soy protein isolate, milk protein isolate, egg white, and wheat gluten at 2 , 4 or 6%) and 6% crystalline sorbitol. Soy and milk proteins and sorbitol reduced the hardness of frozen fish mince, while egg white and wheat gluten made the texture firmer without rubberiness developing after frozen storage. All nonfish proteins and sorbitol stabilized the myofibrillar organization by reducing freeze-induced contraction of myofibrils. The mechanisms of reducing texture hardening appear to be different between sorbitol and nonfish proteins. Water binding properties and dispersibility made the difference among nonfish proteins in reducing freeze-contraction of myofibrils. Nonfish proteins not only reduced texture hardening during frozen storage, but also modified texture during cooki ng as they underwent thermal gelation specific to each protein used