Self-organized patterns of coexistence out of a predator-prey cellular automaton

We present a stochastic approach to modeling the dynamics of coexistence of prey and predator populations. It is assumed that the space of coexistence is explicitly subdivided in a grid of cells. Each cell can be occupied by only one individual of each species or can be empty. The system evolves in time according to a probabilistic cellular automaton composed by a set of local rules which describe interactions between species individuals and mimic the process of birth, death and predation. By performing computational simulations, we found that, depending on the values of the parameters of the model, the following states can be reached: a prey absorbing state and active states of two types. In one of them both species coexist in a stationary regime with population densities constant in time. The other kind of active state is characterized by local coupled time oscillations of prey and predator populations. We focus on the self-organized structures arising from spatio-temporal dynamics of the coexistence. We identify distinct spatial patterns of prey and predators and verify that they are intimally connected to the time coexistence behavior of the species. The occurrence of a prey percolating cluster on the spatial patterns of the active states is also examined.Comment: 19 pages, 11 figure

The influence of differential rotation on the detectability of gravitational waves from the r-mode instability

Recently, it was shown that differential rotation is an unavoidable feature of nonlinear r-modes. We investigate the influence of this differential rotation on the detectability of gravitational waves emitted by a newly born, hot, rapidly-rotating neutron star, as it spins down due to the r-mode instability. We conclude that gravitational radiation may be detected by the advanced laser interferometer detector LIGO if the amount of differential rotation at the time the r-mode instability becomes active is not very high.Comment: 8 pages, 6 figures, revtex

Topological phase transition driven by magnetic field and topological Hall effect in an antiferromagnetic skyrmion lattice

The topological Hall effect (THE), given by a composite of electric and topologically non-trivial spin texture is commonly observed in magnetic skyrmion crystals. Here we present a study of the THE of electrons coupled to antiferromagnetic Skyrmion lattices (AF-SkX). We show that, in the strong Hund coupling limit, topologically non-trivial phases emerge at specific fillings. Interestingly, at low filling an external field controlling the magnetic texture, drives the system from a conventional insulator phase to a phase exhibiting THE. Such behavior suggests the occurrence of a topological transition which is confirmed by a closing of the bulk-gap that is followed by its reopening, appearing simultaneously with a single pair of helical edge states. This transition is further verified by the calculation of the the Chern numbers and Berry curvature. We also compute a variety of observables in order to quantify the THE, namely: Hall conductivity and the orbital magnetization of electrons moving in the AF-SkX texture.Comment: 6 pages, 5 figure

Changes in the diet and body size of a small herbivorous mammal (hispid cotton rat, \u3ci\u3eSigmodon hispidus\u3c/i\u3e) following the late Pleistocene megafauna extinction

The catastrophic loss of large-bodied mammals during the terminal Pleistocene likely led to cascading effects within communities. While the extinction of the top consumers probably expanded the resources available to survivors of all body sizes, little work has focused on the responses of the smallest mammals. Here, we use a detailed fossil record from the southwestern United States to examine the response of the hispid cotton rat Sigmodon hispidus to biodiversity loss and climatic change over the late Quaternary. In particular, we focus on changes in diet and body size. We characterize diet through carbon (δ13C) and nitrogen (δ15N) isotope analysis of bone collagen in fossil jaws and body size through measurement of fossil teeth; the abundance of material allows us to examine population level responses at millennial scale for the past 16 ka. Sigmodon was not present at the cave during the full glacial, first appearing at ~16 ka after ice sheets were in retreat. It remained relatively rare until ~12 ka when warming tempera­tures allowed it to expand its species range northward. We find variation in both diet and body size of Sigmodon hispidus over time: the average body size of the population varied by ~20% (90–110 g) and mean δ13C and δ15N values ranged between −13.5 to −16.5‰ and 5.5 to 7.4‰ respectively. A state–space model suggested changes in mass were influenced by diet, maximum temperature and community structure, while the modest changes in diet were most influenced by community structure. Sigmodon maintained a fairly similar dietary niche over time despite contemporaneous changes in climate and herbivore community composition that followed the megafauna extinc­tion. Broadly, our results suggest that small mammals may be as sensitive to shifts in local biotic interactions within their ecosystem as they are to changes in climate and large-scale biodiversity loss

Hearing evaluation of Portuguese school communities: School-based Audiology versus Hearing Screening

Objectivo: Estudo da incidência da perda auditiva e de problemas otológicos em comunidades escolares do Norte do país de um total de 2550 participantes, entre os 3 e os 17 anos de idade. Desenho do Estudo: Levantamento estatístico nas próprias instituições de ensino sendo realizado um protocolo de avaliação auditiva de rastreio. Material e Métodos: A todos os participantes foi realizado o mesmo protocolo de avaliação que consistiu numa anamnese audiológica, otoscopia e exame audiométrico de rastreio, sendo considerado como critério de inclusão a autorização prévia por parte do encarregado de educação. Resultados: Foram identificados diversos problemas otológicos e a audiometria tonal de rastreio contabilizou limiares auditivos indicativos de hipoacusia, uni e bilateralmente, em cerca de 5,7% dos casos. Conclusões: O rastreio auditivo deve ser realizado o mais precocemente possível e fazer parte integral dos cuidados de saúde primários, de modo a orientar a criança para uma educação e acompanhamento apropriados.info:eu-repo/semantics/publishedVersio

Proposta de um modelo de utilização sustentável do solo para a instalação de novas culturas na Beira Baixa, Portugal: o caso do pistácio (Pistacia vera L.)

É consensual que a escolha dos usos mais adequados às aptidões edafo-climáticas, complementada com critérios socioeconómicos, promove uma utilização sustentável dos espaços rurais. Existem diferentes metodologias que permitem determinar a aptidão do solo para usos agroflorestais ou para a manutenção de ecossistemas seminaturais, nomeadamente culturas agrícolas, povoamentos florestais, territórios agro-silvo-pastoris e áreas críticas em termos de riscos de erosão hídrica ou outro risco natural. Neste estudo pretendeu-se determinar os diferentes níveis de aptidão para o cultivo do Pistácio (Pistacia vera L.), no território da Beira Baixa, delimitando as áreas que apresentam aptidão com base na análise dos fatores limitantes, nomeadamente: tipo de solo, precipitação, geadas na primavera (temperaturas mínimas nos meses de março, abril e maio), horas de frio, humidade relativa nos meses de verão e horas de calor. Para o efeito procedeu-se à identificação dos parâmetros biofísicos determinantes para o cultivo de Pistácio, bem como das condicionantes recorrendo à integração de um conjunto de fatores com recurso a um Sistema de Informação Geográfica. A avaliação da aptidão foi efetuada com recurso ao método de análise multicritério Analytical Hierachy Process (AHP). A metodologia utilizada divide o problema em níveis hierárquicos de tomada de decisão. Após a hierarquização do problema, em cada nível, os critérios que condicionam a tomada de decisão são comparados dois a dois (pairwise comparation) numa matriz de decisão quadrada, baseada numa escala de importância de nove valores numéricos. Para esta análise foi utilizada a extensão AHP. O processo AHP é concluído pela determinação da importância relativa de cada critério/subcritério e pela validação da consistência destas operações. A AHP mostrou-se adequada na avaliação da aptidão da área de estudo, por permitir a integração dos vários critérios estudados, sendo uma ferramenta interativa muito útil na análise do território, que possibilita a tomada de decisão e a resolução de problemas.info:eu-repo/semantics/publishedVersio

Effect of a hyper-protein diet on Wistar rats development and intestinal function

This study was designed to investigate the long-term effects of a high-protein diet on the functional and histological structure of the intestinal epithelium. Sixteen adult male Wistar rats (180 ± 2.27 g) were divided into two groups: 1) the control group, (n = 30) were fed a normal diet of 14% protein; 2) the P50- group (n = 30) were fed a 50% protein diet. The effects of a high-protein diet were studied over a periodof 2 months. Functional and morphological differences between the high-protein and control groups were compared. Internal organs (liver, stomach, lungs, heart, kidneys, spleen, intestine, skin, surrenalglands, white and brown adipose tissues) were removed from each sacrificed animal. The organs were weighed, and histological studies were performed on jejunal fragments. The weight of the P50 grouprats increased 79%, while the weight of the control-group increased 98% (p< 0.01 0.05). The weight of the white adipose tissue, the skeleton and the skin were significantly greater in control-group rats (p< 0.01). An important modification of the epithelial structure in the intestine was observed in rats of the P50 group. The average length of their villi was significantly reduced and there was a significantincrease in their IEL (p< 0.01). Our results indicate that ingestion of a protein-rich diet over a long period leads to modification of the histological structure of the intestinal epithelium, as indicated by;pronounced atrophy of mucosa; marked inflammatory infiltration of lymphocytes in the chorion; and many intra-epithelial lymphocytes

Partial Differential Equation-Constrained Diffeomorphic Registration from Sum of Squared Differences to Normalized Cross-Correlation, Normalized Gradient Fields, and Mutual Information: A Unifying Framework; 35632143

This work proposes a unifying framework for extending PDE-constrained Large Deformation Diffeomorphic Metric Mapping (PDE-LDDMM) with the sum of squared differences (SSD) to PDE-LDDMM with different image similarity metrics. We focused on the two best-performing variants of PDE-LDDMM with the spatial and band-limited parameterizations of diffeomorphisms. We derived the equations for gradient-descent and Gauss-Newton-Krylov (GNK) optimization with Normalized Cross-Correlation (NCC), its local version (lNCC), Normalized Gradient Fields (NGFs), and Mutual Information (MI). PDE-LDDMM with GNK was successfully implemented for NCC and lNCC, substantially improving the registration results of SSD. For these metrics, GNK optimization outperformed gradient-descent. However, for NGFs, GNK optimization was not able to overpass the performance of gradient-descent. For MI, GNK optimization involved the product of huge dense matrices, requesting an unaffordable memory load. The extensive evaluation reported the band-limited version of PDE-LDDMM based on the deformation state equation with NCC and lNCC image similarities among the best performing PDE-LDDMM methods. In comparison with benchmark deep learning-based methods, our proposal reached or surpassed the accuracy of the best-performing models. In NIREP16, several configurations of PDE-LDDMM outperformed ANTS-lNCC, the best benchmark method. Although NGFs and MI usually underperformed the other metrics in our evaluation, these metrics showed potentially competitive results in a multimodal deformable experiment. We believe that our proposed image similarity extension over PDE-LDDMM will promote the use of physically meaningful diffeomorphisms in a wide variety of clinical applications depending on deformable image registration