Extinction dynamics from meta-stable coexistences in an evolutionary game

Deterministic evolutionary game dynamics can lead to stable coexistences of different types. Stochasticity, however, drives the loss of such coexistences. This extinction is usually accompanied by population size fluctuations. We investigate the most probable extinction trajectory under such fluctuations by mapping a stochastic evolutionary model to a problem of classical mechanics using the Wentzel-Kramers-Brillouin (WKB) approximation. Our results show that more abundant types in a coexistence can be more likely to go extinct first well agreed with previous results, and also the distance between the coexistence and extinction point is not a good predictor of extinction. Instead, the WKB method correctly predicts the type going extinct first

Immune stimulatory activity of BRP-4, an acidic polysaccharide from an edible plant, Basella rubra L.

ABSTRACTObjectiveTo evaluated the immunomodulatory effect of BRP-4, an acidic polysaccharide from Basella rubra (B. rubra) L on the macrophage activity.MethodsPhagocytic activity was determined by the ingestion of Latex Beads-Rabbit IgG-FITC using the fluorescent microscopy and flow cytometry analysis and nitric oxide production was measured using Griess reaction assay.ResultsAn enhanced production of NO was observed at 10 and 100 μg/mL of BRP-4. The phagocytic activity of macrophage was enhanced in BRP-4 treated RAW264.7 cells. BRP-4 combined with concanavalin A (Con A) provided obvious promotion and strengthening of the proliferation of the splenocytes.ConclusionsBRP-4, polysaccharide isolated from B. rubra, is suggested to activate macrophage function and stimulate splenocyte proliferation. The strong immunomodulatory activity of BRP-4 confirmed its good potential as an immunotherapeutic adjuvant

Anomalous response in the vicinity of spontaneous symmetry breaking

We propose a mechanism to induce negative AC permittivity in the vicinity of a ferroelectric phase transition involved with spontaneous symmetry breaking. This mechanism makes use of responses at low frequency, yielding a high gain and a large phase delay, when the system jumps over the free-energy barrier with the aid of external fields. We illustrate the mechanism by analytically studying spin models with the Glauber-typed dynamics under periodic perturbations. Then, we show that the scenario is supported by numerical simulations of mean-field as well as two-dimensional spin systems.Comment: 6 pages, 5 figure

Analysis of Indirect Uses of Interrogative Sentences Carrying Anger

PACLIC 21 / Seoul National University, Seoul, Korea / November 1-3, 200

Enhancing Biodiversity through Self-Regulation in Large Ecosystems

The competitive exclusion principle (CEP) is a fundamental concept in the niche theory, which posits that the number of available resources constrains the coexistence of species. While the CEP offers an intuitive explanation for coexistence, it has been challenged by counterexamples observed in nature. One prominent counterexample is the phytoplankton community, known as the paradox of the plankton. Diverse phytoplankton species coexist in the ocean even though they demand a limited number of resources. To shed light on this remarkable biodiversity in large ecosystems quantitatively, we consider self-regulation into the generalized MacArthur's consumer-resource model and study the relative diversity, the number ratio between coexisting consumers and resource kinds. By employing the cavity method and generating functional analysis, we analytically show how the bounds of the relative diversity can exceed unity and its dependency on the strength of the self-regulation. We confirm the analysis with numerical simulations and reveal that the self-regulation suppresses the emergence of dominant species, thereby fostering high biodiversity. Furthermore, we study the effect of the self-regulation on different environments and show that the effect relies on the environmental condition. Our work presents a comprehensive framework within the niche theory that encompasses the CEP and its counterexamples by introducing the role of self-regulation.Comment: 34 pages (including supplementary material), 24 figures (4 figures in main, 20 figures in SM

Generalized gravity model for human migration

The gravity model (GM) analogous to Newton's law of universal gravitation has successfully described the flow between different spatial regions, such as human migration, traffic flows, international economic trades, etc. This simple but powerful approach relies only on the 'mass' factor represented by the scale of the regions and the 'geometrical' factor represented by the geographical distance. However, when the population has a subpopulation structure distinguished by different attributes, the estimation of the flow solely from the coarse-grained geographical factors in the GM causes the loss of differential geographical information for each attribute. To exploit the full information contained in the geographical information of subpopulation structure, we generalize the GM for population flow by explicitly harnessing the subpopulation properties characterized by both attributes and geography. As a concrete example, we examine the marriage patterns between the bride and the groom clans of Korea in the past. By exploiting more refined geographical and clan information, our generalized GM properly describes the real data, a part of which could not be explained by the conventional GM. Therefore, we would like to emphasize the necessity of using our generalized version of the GM, when the information on such nongeographical subpopulation structures is available.Comment: 14 pages, 6 figures, 2 table