Multiplicity of Limit Cycle Attractors in Coupled Heteroclinic Cycles

A square lattice distribution of coupled oscillators that have heteroclinic cycle attractors is studied. In this system, we find a novel type of patterns that is spatially disordered and periodic in time. These patterns are limit cycle attractors in the ambient phase space (i.e. not chaotic) and many limit cycles exist dividing the phase space as their basins. The patterns are constructed with a local law of difference of phases between the oscillators. The number of patterns grows exponentially with increasing of the number of oscillators.Comment: 10 pages, 6 figure

FOOD POLICY COUNCIL AS CIVIC ENGAGEMENT FOR FOOD ISSUES

The purpose of this paper is to elucidate the nature of food issue in our society and propose a forum to discuss multi-facet issues of food based on the North American experience, such as food policy council (FPC). Contemporary food system in Japan is full of problems, such as low level self-sufficiency, food loss, problem of food access, large food miles, declining food culture under globalization, and so on. After reviewing these food related issues, the paper refers to the US and Canadian experiences on food policy council as a model to provide a forum for various stakeholders with different or even conflicting interests. Based on observations on the FPCs, such as Knoxville (US) and Toronto (Canada), author emphasized public aspect of food issues and draw attentions to differences in structural aspects of food between North America and Japan. The paper also tries to draw attention to differences between North America and Japan in terms of food issues. In particular, the demographic and geographical differences would exist of a major structural aspect when considering food issue in Japan.

WHAT CONSTITUTES “GOODNESS” IN FARMING? FARMING AND LOCAL COMMUNITY IN NEOLIBERAL CONTEXT IN JAPAN

Japanese agriculture has been going through a drastic change especially in terms of the number of farmers today. Modernization of agricultural structure, which had been pursued for many years by the government, seems to be suddenly realized through a large scale retirement of elder farmers. The advancing structural change in farming, especially consolidation of farming into fewer agricultural entities, raises a concern that rural community people are completely detached from farming per se. This concern leads our study to analyze the relationship between large-scale farming entities and local communities, which were once closely tied. In order to understand the nature and change of the relationship, we have focused on a Japanese farm competition and try to elucidate how the “desirability” of farms have evolved over time, and try to draw implications for the above-mentioned relationship. Our examinations of selection criteria of agricultural competitions, where advanced farmers seek to be awarded as the “best” farmers, reveal that the criteria have evolved from simpler ones to highly complex ones. More specifically, in an early era (the 1960s), farmers competing there are expected to have almost solely technical skills, whereas more recent criteria dictate that farmers should make social contribution to local communities. This indicates that goodness or “desirability” for advanced farmers has also gone through substantial changes. Farming entities are now not only to survive market competitions, but also to confront and deal with complex local demands to play roles that used to be fulfilled by local governments faced with declining budgets from the state government. The fact that Japanese cutting-edge farmers are expected to play substantial roles to sustain local communities seems to resonate with discourses extolled by neoliberalism penetrating into rural areas across the world. That is, rural actors are supposed to be entrepreneurial, efficient, and competitive in market principles, and simultaneously required to make contradictory commitments to sustain local communities

Modeling membrane morphological change during autophagosome formation

Autophagy is an intracellular degradation process that is mediated by de novo formation of autophagosomes. Autophagosome formation involves dynamic morphological changes; a disk-shaped membrane cisterna grows, bends to become a cup-shaped structure, and finally develops into a spherical autophagosome. We have constructed a theoretical model that integrates the membrane morphological change and entropic partitioning of putative curvature generators, which we have used to investigate the autophagosome formation process quantitatively. We show that the membrane curvature and the distribution of the curvature generators stabilize disk- and cup-shaped intermediate structures during autophagosome formation, which is quantitatively consistent with in vivo observations. These results suggest that various autophagy proteins with membrane curvature-sensing properties control morphological change by stabilizing these intermediate structures. Our model provides a framework for understanding autophagosome formation.Comment: 33 pages, 8 figure

Fluctuation induces evolutionary branching in a modeled microbial ecosystem

The impact of environmental fluctuation on species diversity is studied with a model of the evolutionary ecology of microorganisms. We show that environmental fluctuation induces evolutionary branching and assures the consequential coexistence of multiple species. Pairwise invasibility analysis is applied to illustrate the speciation process. We also discuss how fluctuation affects species diversity.Comment: 4 pages, 4 figures. Submitted to Physical Review Letter

Evolutionary process with bi-periodic fluctuation.

<p>Evolutionary branching and the resulting three quasi-species coexistence induced by a bi-periodic fluctuation in environment. We choose resource supplying function <i>c</i>′(<i>t</i>) which is constructed by two different periodic function with periods 5.9 and 50, <i>c</i>′(<i>t</i>) = 0.03+0.4Σ<i>δ</i>(<i>t</i>−5.9<i>n</i>)+500Σ<i>δ</i>(<i>t</i>−50<i>n</i>). The fluctuation starts at <i>t</i> = 5000. After that and the system shows transient branching dynamics and reaches the three quasi-species coexistence state.</p