12,072 research outputs found
Diversity, Stability, Recursivity, and Rule Generation in Biological System: Intra-inter Dynamics Approach
Basic problems for the construction of a scenario for the Life are discussed.
To study the problems in terms of dynamical systems theory, a scheme of
intra-inter dynamics is presented. It consists of internal dynamics of a unit,
interaction among the units, and the dynamics to change the dynamics itself,
for example by replication (and death) of units according to their internal
states. Applying the dynamics to cell differentiation, isologous
diversification theory is proposed. According to it, orbital instability leads
to diversified cell behaviors first. At the next stage, several cell types are
formed, first triggered by clustering of oscillations, and then as attracting
states of internal dynamics stabilized by the cell-to-cell interaction. At the
third stage, the differentiation is determined as a recursive state by cell
division. At the last stage, hierarchical differentiation proceeds, with the
emergence of stochastic rule for the differentiation to sub-groups, where
regulation of the probability for the differentiation provides the diversity
and stability of cell society. Relevance of the theory to cell biology is
discussed.Comment: 19 pages, Int.J. Mod. Phes. B (in press
Competition between isoscalar and isovector pairing correlations in N=Z nuclei
We study the isoscalar (T=0) and isovector (T=1) pairing correlations in N=Z
nuclei. They are estimated from the double difference of binding energies for
odd-odd N=Z nuclei and the odd-even mass difference for the neighboring
odd-mass nuclei, respectively. The empirical and BCS calculations based on a
T=0 and T=1 pairing model reproduce well the almost degeneracy of the lowest
T=0 and T=1 states over a wide range of even-even and odd-odd N=Z nuclei. It is
shown that this degeneracy is attributed to competition between the isoscalar
and isovector pairing correlations in N=Z nuclei. The calculations give an
interesting prediction that the odd-odd N=Z nucleus 82Nb has possibly the
ground state with T=0.Comment: 5 pages, 4 figures, to be published in Phys. Rev. C (R
Differentiation and Replication of Spots in a Reaction Diffusion System with Many Chemicals
The replication and differentiation of spots in reaction diffusion equations
are studied by extending the Gray-Scott model with self-replicating spots to
include many degrees of freedom needed to model systems with many chemicals. By
examining many possible reaction networks, the behavior of this model is
categorized into three types: replication of homogeneous fixed spots,
replication of oscillatory spots, and differentiation from `m ultipotent
spots'. These multipotent spots either replicate or differentiate into other
types of spots with different fixed-point dynamics, and as a result, an
inhomogeneous pattern of spots is formed. This differentiation process of spots
is analyzed in terms of the loss of chemical diversity and decrease of the
local Kolmogorov-Sinai entropy. The relevance of the results to developmental
cell biology and stem cells is also discussed.Comment: 8 pages, 12 figures, Submitted to EP
Inherent global stabilization of unstable local behavior in coupled map lattices
The behavior of two-dimensional coupled map lattices is studied with respect
to the global stabilization of unstable local fixed points without external
control. It is numerically shown under which circumstances such inherent global
stabilization can be achieved for both synchronous and asynchronous updating.
Two necessary conditions for inherent global stabilization are derived
analytically.Comment: 17 pages, 10 figures, accepted for publication in Int.J.Bif.Chao
Detailed Measurements of Characteristic Profiles of Magnetic Diffuse Scattering in ErBC
Detailed neutron diffraction measurements on a single crystalline
ErBC were performed. We observed magnetic diffuse scattering which
consists of three components just above the transition temperatures, which is
also observed in characteristic antiferroquadrupolar ordering compounds
HoBC and TbBC. The result of this experiments indicates that
the antiferroquadrupolar interaction is not dominantly important as a origin of
the magnetic diffuse scattering.Comment: 5 pages, 5 figures, submitted to J. Phys. Soc. Jp
An alternative understanding of mass formulas in terms of nuclear structure
A typical form of mass formula is re-explained in terms of nuclear structure.
For nuclei, we propose to start with the shell model picture
and to consider the T=0 (-like) correlations as the fundamental
concept, instead of the symmetry energy.
Subsequently, the symmetry energy is described on the basis of the
-like superfluidity caused by the T=0 correlations, in parallel
with the pairing energy described on the basis of the pairing superfluidity.
This re-explanation gives useful insight for understanding the nuclear mass
formula. The origin of the Wigner energy is also explained in an interacting
boson model for the Cooper pairs in the -like superfluid vacuum. Adding
a correction term due to the T=0 correlations, which determines the T=0
base level for nuclear masses, can improve the mass formulas in practice.Comment: to be published in Prog. Theor. Phys. Vol. 113, No.
Spontaneous structure formation in a network of chaotic units with variable connection strengths
As a model of temporally evolving networks, we consider a globally coupled
logistic map with variable connection weights. The model exhibits
self-organization of network structure, reflected by the collective behavior of
units. Structural order emerges even without any inter-unit synchronization of
dynamics. Within this structure, units spontaneously separate into two groups
whose distinguishing feature is that the first group possesses many
outwardly-directed connections to the second group, while the second group
possesses only few outwardly-directed connections to the first. The relevance
of the results to structure formation in neural networks is briefly discussed.Comment: 4 pages, 3 figures, REVTe
Dynamics of Coupling Functions in Globally Coupled Maps: Size, Periodicity and Stability of Clusters
It is shown how different globally coupled map systems can be analyzed under
a common framework by focusing on the dynamics of their respective global
coupling functions. We investigate how the functional form of the coupling
determines the formation of clusters in a globally coupled map system and the
resulting periodicity of the global interaction. The allowed distributions of
elements among periodic clusters is also found to depend on the functional form
of the coupling. Through the analogy between globally coupled maps and a single
driven map, the clustering behavior of the former systems can be characterized.
By using this analogy, the dynamics of periodic clusters in systems displaying
a constant global coupling are predicted; and for a particular family of
coupling functions, it is shown that the stability condition of these clustered
states can straightforwardly be derived.Comment: 12 pp, 5 figs, to appear in PR
Self-organized and driven phase synchronization in coupled maps
We study the phase synchronization and cluster formation in coupled maps on
different networks. We identify two different mechanisms of cluster formation;
(a) {\it Self-organized} phase synchronization which leads to clusters with
dominant intra-cluster couplings and (b) {\it driven} phase synchronization
which leads to clusters with dominant inter-cluster couplings. In the novel
driven synchronization the nodes of one cluster are driven by those of the
others. We also discuss the dynamical origin of these two mechanisms for small
networks with two and three nodes.Comment: 4 pages including 2 figure
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