3,130 research outputs found
Evolutionary game of coalition building under external pressure
We study the fragmentation-coagulation (or merging and splitting)
evolutionary control model as introduced recently by one of the authors, where
small players can form coalitions to resist to the pressure exerted by the
principal. It is a Markov chain in continuous time and the players have a
common reward to optimize. We study the behavior as grows and show that the
problem converges to a (one player) deterministic optimization problem in
continuous time, in the infinite dimensional state space
Hamiltonian dynamics and geometry of phase transitions in classical XY models
The Hamiltonian dynamics associated to classical, planar, Heisenberg XY
models is investigated for two- and three-dimensional lattices. Besides the
conventional signatures of phase transitions, here obtained through time
averages of thermodynamical observables in place of ensemble averages,
qualitatively new information is derived from the temperature dependence of
Lyapunov exponents. A Riemannian geometrization of newtonian dynamics suggests
to consider other observables of geometric meaning tightly related with the
largest Lyapunov exponent. The numerical computation of these observables -
unusual in the study of phase transitions - sheds a new light on the
microscopic dynamical counterpart of thermodynamics also pointing to the
existence of some major change in the geometry of the mechanical manifolds at
the thermodynamical transition. Through the microcanonical definition of the
entropy, a relationship between thermodynamics and the extrinsic geometry of
the constant energy surfaces of phase space can be naturally
established. In this framework, an approximate formula is worked out,
determining a highly non-trivial relationship between temperature and topology
of the . Whence it can be understood that the appearance of a phase
transition must be tightly related to a suitable major topology change of the
. This contributes to the understanding of the origin of phase
transitions in the microcanonical ensemble.Comment: in press on Physical Review E, 43 pages, LaTeX (uses revtex), 22
PostScript figure
Geometry of dynamics, Lyapunov exponents and phase transitions
The Hamiltonian dynamics of classical planar Heisenberg model is numerically
investigated in two and three dimensions. By considering the dynamics as a
geodesic flow on a suitable Riemannian manifold, it is possible to analytically
estimate the largest Lyapunov exponent in terms of some curvature fluctuations.
The agreement between numerical and analytical values for Lyapunov exponents is
very good in a wide range of temperatures. Moreover, in the three dimensional
case, in correspondence with the second order phase transition, the curvature
fluctuations exibit a singular behaviour which is reproduced in an abstract
geometric model suggesting that the phase transition might correspond to a
change in the topology of the manifold whose geodesics are the motions of the
system.Comment: REVTeX, 10 pages, 5 PostScript figures, published versio
Thermal conductivity of nonlinear waves in disordered chains
We present computational data on the thermal conductivity of nonlinear waves
in disordered chains. Disorder induces Anderson localization for linear waves
and results in a vanishing conductivity. Cubic nonlinearity restores normal
conductivity, but with a strongly temperature-dependent conductivity
. We find indications for an asymptotic low-temperature and intermediate temperature laws. These findings are in
accord with theoretical studies of wave packet spreading, where a regime of
strong chaos is found to be intermediate, followed by an asymptotic regime of
weak chaos (EPL 91 (2010) 30001).Comment: 8 pages, 3 figure
Why Some Interfaces Cannot be Sharp
A central goal of modern materials physics and nanoscience is control of
materials and their interfaces to atomic dimensions. For interfaces between
polar and non-polar layers, this goal is thwarted by a polar catastrophe that
forces an interfacial reconstruction. In traditional semiconductors this
reconstruction is achieved by an atomic disordering and stoichiometry change at
the interface, but in multivalent oxides a new option is available: if the
electrons can move, the atoms don`t have to. Using atomic-scale electron energy
loss spectroscopy we find that there is a fundamental asymmetry between
ionically and electronically compensated interfaces, both in interfacial
sharpness and carrier density. This suggests a general strategy to design sharp
interfaces, remove interfacial screening charges, control the band offset, and
hence dramatically improving the performance of oxide devices.Comment: 12 pages of text, 6 figure
Rare coding SNP in DZIP1 gene associated with late-onset sporadic Parkinson's disease
We present the first application of the hypothesis-rich mathematical theory
to genome-wide association data. The Hamza et al. late-onset sporadic
Parkinson's disease genome-wide association study dataset was analyzed. We
found a rare, coding, non-synonymous SNP variant in the gene DZIP1 that confers
increased susceptibility to Parkinson's disease. The association of DZIP1 with
Parkinson's disease is consistent with a Parkinson's disease stem-cell ageing
theory.Comment: 14 page
Costs of Reproduction and Terminal Investment by Females in a Semelparous Marsupial
Evolutionary explanations for life history diversity are based on the idea of costs of reproduction, particularly on the concept of a trade-off between age-specific reproduction and parental survival, and between expenditure on current and future offspring. Such trade-offs are often difficult to detect in population studies of wild mammals. Terminal investment theory predicts that reproductive effort by older parents should increase, because individual offspring become more valuable to parents as the conflict between current versus potential future offspring declines with age. In order to demonstrate this phenomenon in females, there must be an increase in maternal expenditure on offspring with age, imposing a fitness cost on the mother. Clear evidence of both the expenditure and fitness cost components has rarely been found. In this study, we quantify costs of reproduction throughout the lifespan of female antechinuses. Antechinuses are nocturnal, insectivorous, forest-dwelling small (20–40 g) marsupials, which nest in tree hollows. They have a single synchronized mating season of around three weeks, which occurs on predictable dates each year in a population. Females produce only one litter per year. Unlike almost all other mammals, all males, and in the smaller species, most females are semelparous. We show that increased allocation to current reproduction reduces maternal survival, and that offspring growth and survival in the first breeding season is traded-off with performance of the second litter in iteroparous females. In iteroparous females, increased allocation to second litters is associated with severe weight loss in late lactation and post-lactation death of mothers, but increased offspring growth in late lactation and survival to weaning. These findings are consistent with terminal investment. Iteroparity did not increase lifetime reproductive success, indicating that terminal investment in the first breeding season at the expense of maternal survival (i.e. semelparity) is likely to be advantageous for females
STUDY OF SPATIAL AND TEMPORAL VARIABILITY OF ARSENIC IN GROUNDWATER DUE TO DRAIN BY USING GIS
Industrial activity is one of the major reason of groundwater contamination. Arsenic is one, which is responsible
for the contamination of the groundwater. Its testing in groundwater is considered as an important activity due
to its serious effects on human health. Arsenic problem in Pakistan has been identified recently as a result of field
testing. In Faisalabad, arsenic has been found in groundwater within permissible limit. But due to increasing
industrial activities the concentration of arsenic is increasing day by day. Drain passing through the city is one of
the sources of arsenic in groundwater. The research work was conducted at Syedabbad, Faisalabad. Samples were
taken from the selected drain portion and from the groundwater by the help of water pumps. The sampling points
were drawn on GIS map by the help of GPS receiver to study the spatial variability of arsenic contamination The
results shows that there 10109.9 mg per second intake of arsenic due to drain. Results show that there is no
temporal variability of arsenic within the research period but they have spatial variabilit
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