Comparing cardiovascular responses during exercise between head-down tilt pedaling with lower body negative pressure and upright cycling in man

If lower body negative pressure (LBNP) loaded on exercise in weightlessness environment is able to derive a comparable cardiovascular responses to these in the ground, it should be identified as an optimal LBNP for exercise in space. To investigate the LBNP, 7 young subjects were exercised 4 work rates stepping up every 50 watts from 50 watts to 200 watts every 5 minutes in the upright position or 6 degree head down tilt position with each LBNP of 20, 40, 60, 80, and 100 mmHg. Oxygen uptake during tilt exercise with over 60 mmHg LBNP was not different from it in upright exercise. Heart rate and systolic arterial pressure responses to exercise were very similar between tilt exercise with 60 mmHg LBNP and upright exercise. In conclusion, the optimal LBNP loaded on exercise in space should be around 60 mmHg.     

Zipf's law in phonograms and Weibull distribution in ideograms: comparison of English with Japanese

Frequency distribution of word usage in a word sequence generated by capping is estimated in terms of the number of "hits" in retrieval of web-pages, to evaluate structure of semantics proper not to a particular text but to a language. Especially we compare distribution of English sequences with Japanese ones and obtain that, for English and Japanese phonogram, frequency of word usage against rank follows power-law function with exponent 1 and, for Japanese ideogram, it follows stretched exponential (Weibull distribution) function. We also discuss that such a difference can result from difference of phonogram based- (English) and ideogram-based language (Japanese).     

Temporal criterion for behavior: orientation of the young Japanese flounder Paralichthys olivaceus

When considering a behavioral pattern as a specific type of mechanism, an inherent problem is that it is difficult to determine to what extent the mechanism is programmed to behave selectively in individual situations. To probe this question further, we investigated the orientation of the body axis of the young Japanese flounder Paralichthys olivaceus. The pattern of the substrate and the orientation of neighboring fish were recognized as the determining factors for orientation in P. olivaceus. It was expected, therefore, that a group of individuals would exhibit a definite orientation pattern with respect to the striped pattern. However, the global orientation patterns on the striped substrate based on ten individuals could be classified into two categories: perpendicular and cross to the stripe pattern. This suggests that the substrate pattern and the surrounding individuals operated as distinct temporal criteria as stimuli for orientation. Analysis based on the local and global viewpoints reveals the temporality quantitatively.     

Ongoing Processes in a Fitness Network Model under Restricted Resources

In real networks, the resources that make up the nodes and edges are finite. This constraint poses a serious problem for network modeling, namely, the compatibility between robustness and efficiency. However, these concepts are generally in conflict with each other. In this study, we propose a new fitness-driven network model for finite resources. In our model, each individual has its own fitness, which it tries to increase. The main assumption in fitness-driven networks is that incomplete estimation of fitness results in a dynamical growing network. By taking into account these internal dynamics, nodes and edges emerge as a result of exchanges between finite resources. We show that our network model exhibits exponential distributions in the in- and out-degree distributions and a power law distribution of edge weights. Furthermore, our network model resolves the trade-off relationship between robustness and efficiency. Our result suggests that growing and anti-growing networks are the result of resolving the trade-off problem itself.     

Minimal model of a cell connecting amoebic motion and adaptive transport networks

A cell is a minimal self-sustaining system that can move and compute. Previous work has shown that a unicellular slime mold, Physarum, can be utilized as a biological computer based on cytoplasmic flow encapsulated by a membrane. Although the interplay between the modification of the boundary of a cell and the cytoplasmic flow surrounded by the boundary plays a key role in Physarum computing, no model of a cell has been developed to describe this interplay. Here we propose a toy model of a cell that shows amoebic motion and can solve a maze, Steiner minimum tree problem and a spanning tree problem. Only by assuming that cytoplasm is hardened after passing external matter (or softened part) through a cell, the shape of the cell and the cytoplasmic flow can be changed. Without cytoplasm hardening, a cell is easily destroyed. This suggests that cytoplasmic hardening and/or sol-gel transformation caused by external perturbation can keep a cell in a critical state leading to a wide variety of shapes and motion.     

Imbalance and balancing: Development of ecological flow networks

In this paper we address balancing process of ecological flow networks. In existing approaches, macroscopic objectives to which systems organize are assumed. Flow balance provides only constraints for the optimization. Since flow balance and objectives are separated from each other, it is impossible to address how the appearance of objectives is related to flow balance. Therefore, we take an alternative approach, in which we directly describe a dynamics of balancing process. We propose a simple mathematical formula for local balancing dynamics and show that it can generate a self-organizing property, which could be seen as a primitive objective.     

Crosstalk of prolyl isomerases, Pin1/Ess1, and cyclophilin A.

Previous studies have indicated that Ess1/Pin1, a gene in the parvulin family of peptidyl-prolyl isomerases (PPIases), plays an important role in regulating the G(2)/M transition of the cell cycle by binding cell-cycle-regulating proteins in eukaryotic cells. Although the ess1 gene has been considered to be essential in yeast, we have isolated viable ess1 deletion mutants and demonstrated, via analysis of yeast gene expression profiles using microarray techniques, a novel regulatory role for ESS1 in the G(1) phase. Although the overall expression profiles in the tested strains (C110-1, W303, S288c, and RAY-3AD) were similar, marked changes were detected for a number of genes involved in the molecular action of ESS1. Among these, the expression levels of a cyclophilin A gene, also a member of the PPIase family, increased in the ess1 null mutant derived from C110-1. Subsequent treatment with cyclosporin A significantly retarded growth, which suggests that ESS1 and cyclophilin A are functionally linked in yeast cells and play important roles at the G(1) phase of the cell cycle.     

Emergent Runaway into an Avoidance Area in a Swarm of Soldier Crabs

Emergent behavior that arises from a mass effect is one of the most striking aspects of collective animal groups. Investigating such behavior would be important in order to understand how individuals interact with their neighbors. Although there are many experiments that have used collective animals to investigate social learning or conflict between individuals and society such as that between a fish and a school, reports on mass effects are rare. In this study, we show that a swarm of soldier crabs could spontaneously enter a water pool, which are usually avoided, by forming densely populated part of a swarm at the edge of the water pool. Moreover, we show that the observed behavior can be explained by the model of collective behavior based on inherent noise that is individuals’ different velocities in a directed group. Our results suggest that inherent noise, which is widely seen in collective animals, can contribute to formation and/or maintenance of a swarm and that the dense swarm can enter the pool by means of enhanced inherent noise.