238 research outputs found
Optimal diffusion in ecological dynamics with Allee effect in a metapopulation
How diffusion impacts on ecological dynamics under the Allee effect and
spatial constraints? That is the question we address. Employing a microscopic
minimal model in a metapopulation (without imposing nonlinear birth and death
rates) we evince --- both numerically and analitically --- the emergence of an
optimal diffusion that maximises the survival probability. Even though, at
first such result seems counter-intuitive, it has empirical support from recent
experiments with engineered bacteria. Moreover, we show that this optimal
diffusion disappears for loose spatial constraints.Comment: 16 pages; 6 figure
Phase transition in the Galam's majority-rule model with information-mediated independence
We study the Galam's majority-rule model in the presence of an independent
behavior that can be driven intrinsically or can be mediated by information
regarding the collective opinion of the whole population. We first apply the
mean-field approach where we obtained an explicit time-dependent solution for
the order parameter of the model. We complement our results with Monte Carlo
simulations where our findings indicate that independent opinion leads to
order-disorder continuous nonequilibrium phase transitions. Finite-size scaling
analysis show that the model belongs to the mean-field Ising model universality
class. Moreover, results from an approach with the Kramers-Moyal coefficients
provide insights about the social volatility.Comment: Invited paper for the special issue "In honor of professor Serge
Galam for his 70th birthday and forty years of sociophysics" (special issue
editors: A. Martins, T. Cheon, X.Tang, B. Chopard, S. Biswas), to appear in
Physic
Genetic determinants and absence of breast cancer in Xavante Indians in Sangradouro Reserve, Brazil
Genetic compositions of distinct human populations are different. How genomic variants influence many common and rare genetic diseases is always of great medical and anthropological interest, and understanding of genetic architectures of population groups in relation to diseases can advance our knowledge of medicine. Here, we have studied the genomic architecture of a group of Xavante Indians, an indigenous population in Brazil, and compared them with normal populations from the 1000 Genomes Projects. Principal component analysis (PCA) indicates that the Xavante Indians are genetically distinctive when compared to other ethnic groups. No incidence of breast cancer cases has ever been reported in the population, and polygenic risk analysis indicates extremely low breast cancer risk in this population when compared with germline TCGA (The Cancer Genome Atlas) breast cancer normal control samples. Low germinal mutation burden among this population is also observed. Our findings will help to deepen the understanding of breast cancer and might also provide new approaches to study the disease.publishersversionpublishe
Quantum walks with spatiotemporal fractal disorder
We investigate the transport and entanglement properties exhibited by quantum
walks with coin operators concatenated in a space-time fractal structure.
Inspired by recent developments in photonics, we choose the paradigmatic
Sierpinski gasket. The 0-1 pattern of the fractal is mapped into an alternation
of the generalized Hadamard-Fourier operators. In fulfilling the blank space on
the analysis of the impact of disorder in quantum walk properties --
specifically, fractal deterministic disorder --, our results show a robust
effect of entanglement enhancement as well as an interesting novel road to
superdiffusive spreading with a tunable scaling exponent attaining effective
ballistic diffusion. Namely, with this fractal approach it is possible to
obtain an increase in quantum entanglement without jeopardizing spreading.
Alongside those features, we analyze further properties such as the degree of
interference and visibility. The present model corresponds to a new application
of fractals in an experimentally feasible setting, namely the building block
for the construction of photonic patterned structures.Comment: 16 pages, 9 figure
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