1,925 research outputs found
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
Emerging Ionic Soft Materials based on Deep Eutectic Solvents
PostprintIn the last five years, the use of deep eutectic solvents (DES) have been opening new perspectives towards the creation of novel ionic soft materials as alternatives to expensive ionic liquids. This Mini-Review highlights the progress and advances in soft ionic materials or gels, mostly composed by a DES immobilized within difference matrices, such as linear polymers, polymer networks, biopolymers, supramolecular compounds or organosilane networks. By taking advantage of the DES characteristics and properties in the solid state, this building system delivers a variety of tailor-made materials showing different functionalities (ionic conductivity, self-healing, stretchability and pH-responsiveness) and offers a way to circumvent drawbacks related to shaping and risk of leakage in many technological applications. In this context, we provide a judicious analysis of these emerging ionic soft materials, their properties and applications open in energy, (bio)electronics, drug delivery, analytical chemistry, and wastewater treatment. Perspectives and opportunities for future research directions on this blossoming field are also discussed.Liliana C. Tomé has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement no. 745734. This work was supported by Marie Sklodowska-Curie Research and Innovation Staff Exchanges (RISE) project under the grant agreement No 823989 “IONBIKE”
O CD-ROM "Vamos fazer jornais escolares " : um contributo para a inserção da literacia dos media e das TIC nos currículos
Este texto apresenta uma investigação realizada em Portugal, cujos resultados apontam para o facto da produção de jornais escolares, por alunos do 2º e 3º Ciclo, contribuir para desenvolver a Literacia dos Media e a Educação para a Cidadania, bem como para promover a utilização da Tecnologias de Informação e Comunicação na sala de aula
cLFV processes and suppression of non-unitary mixing effects in low scale seesaw models
We examine the parameter space region of the inverse seesaw model that is
consistent with neutrino oscillation data. We focus on the correlation between
the current limits from the search of the lepton flavour
violating decay and the non-standard effects associated with the presence of
new heavy neutrino states. Unlike what we would expect from an inverse seesaw
model, we have found a parametrization for the mass matrices in which the rates
of charged lepton flavour-violating processes are negligible. Additionally, we
provide a model where the inverse seesaw is obtained naturally, and the mass
matrices get this structure with negligible violation of the lepton flavour.Comment: 20 pages, 3 figures and 3 table
Dynamic critical exponents of the Ising model with multispin interactions
We revisit the short-time dynamics of 2D Ising model with three spin
interactions in one direction and estimate the critical exponents
and . Taking properly into account the symmetry of the
Hamiltonian we obtain results completely different from those obtained by Wang
et al.. For the dynamic exponent our result coincides with that of the
4-state Potts model in two dimensions. In addition, results for the static
exponents and agree with previous estimates obtained from finite
size scaling combined with conformal invariance. Finally, for the new dynamic
exponent we find a negative and close to zero value, a result also
expected for the 4-state Potts model according to Okano et al.Comment: 12 pages, 9 figures, corrected Abstract mistypes, corrected equation
on page 4 (Parameter Q
Mean-field analysis of the majority-vote model broken-ergodicity steady state
We study analytically a variant of the one-dimensional majority-vote model in
which the individual retains its opinion in case there is a tie among the
neighbors' opinions. The individuals are fixed in the sites of a ring of size
and can interact with their nearest neighbors only. The interesting feature
of this model is that it exhibits an infinity of spatially heterogeneous
absorbing configurations for whose statistical properties we
probe analytically using a mean-field framework based on the decomposition of
the -site joint probability distribution into the -contiguous-site joint
distributions, the so-called -site approximation. To describe the
broken-ergodicity steady state of the model we solve analytically the
mean-field dynamic equations for arbitrary time in the cases n=3 and 4. The
asymptotic limit reveals the mapping between the statistical
properties of the random initial configurations and those of the final
absorbing configurations. For the pair approximation () we derive that
mapping using a trick that avoids solving the full dynamics. Most remarkably,
we find that the predictions of the 4-site approximation reduce to those of the
3-site in the case of expectations involving three contiguous sites. In
addition, those expectations fit the Monte Carlo data perfectly and so we
conjecture that they are in fact the exact expectations for the one-dimensional
majority-vote model
Neonatal Diagnosis of Prader-Willi Syndrome
A síndrome de Prader-Willi tem uma prevalência aproximada de 1:25000 nascimentos. No período neonatal há
hipotonia severa, atraso de crescimento e dificuldade alimentar que persistem durante o primeiro ano de vida. O quadro clínico inicial contrasta com a bulimia que se evidencia mais tarde e que, não controlada, pode conduzir à obesidade mórbida.
Descrevem-se as características clínicas, o diagnóstico genético e os cuidados específicos a ter na promoção da saúde a propósito de cinco crianças com síndrome de
Prader Willi, cujo diagnóstico foi feito no período neonatal
- …