Ferreira A.S.,Federal University of Pernambuco |
Raposo E.P.,Federal University of Pernambuco |
Viswanathan G.M.,Federal University of Rio Grande do Norte |
Viswanathan G.M.,Federal University of Alagoas |
Da Luz M.G.E.,University Federal Do Paran
Physica A: Statistical Mechanics and its Applications | Year: 2012
An open problem in the field of random searches relates to optimizing the search efficiency in fractal environments. Here we address this issue through a systematic study of Lvy searches in landscapes encompassing several degrees of target aggregation and fractality. For scarce resources, non-destructive searches with unrestricted revisits to targets are shown to present universal optimal behavior irrespective of the general scaling properties of the spatial distribution of targets. In contrast, no such universal behavior occurs in the destructive case with forbidden revisits, in which the optimal strategy strongly depends on the degree of target aggregation. We also investigate how the presence of memory and learning skills of the searcher affect the search efficiency. By considering a limiting model in which the searcher learns through recent experience to recognize food-rich areas, we find that a statistical memory of previous encounters does not necessarily increase the rate of target findings in random searches. Instead, there is an optimal extent of memory, dependent on specific details of the search space and stochastic dynamics, which maximizes the search efficiency. This finding suggests a more general result, namely that in some instances there are actual advantages to ignoring certain pieces of partial information while searching for objects. © 2012 Elsevier B.V. All rights reserved.
Rouhan G.,French National Center for Scientific Research |
Labiak P.H.,University Federal Do Paran |
Randrianjohany E.,Laboratoire Of Microbiologie Of Lenvironnement |
Rakotondrainibe F.,French National Center for Scientific Research
Systematic Botany | Year: 2012
Based on morphological and molecular evidence (DNA sequences from six plastid regions: atp, rbcL, trnG-trnR, trnL-trnF, atp-rbcL, and rps4-trnS), the new fern species Leucotrichum madagascariense is described from Madagascar, where it is found in the North (Marojejy), Centre (Andringitra), and South (Andohahela) regions. Leucotrichum madagascariense has long, whitish laminar hairs, among the other distinguishing characters of the genus: arching fronds, laminar apices subconform to the lateral pinnae, dark sclerenchyma covered by the green laminar tissue, and laterally marginate petioles. Its most remarkable feature is the lack of rhizome scales, a character that is shared with the Neotropical L. pseudomitchelliae. However, our phylogenetic results suggest that this character has evolved twice independently within the genus. In contrast, the sister relationship between the new Madagascan species and the group composed of L. schenckii and L. mortonii is morphologically supported by linear and deeply pinnatifid laminae, incised 2/33/4 of the way to the rachis along its length. Leucotrichum madagascariense is the only representative of the genus known from the Old World. Because it is nested within a clade of five Neotropical species, we hypothesize that its occurrence outside the Neotropics results from one long-distance dispersal event from America, likely southeastern Brazil, to Madagascar. © Copyright 2012 by the American Society of Plant Taxonomists.
Fiore C.E.,University Federal Do Paran
Journal of Chemical Physics | Year: 2011
Parallel tempering Monte Carlo simulations have been applied to a variety of systems presenting rugged free-energy landscapes. Despite this, its efficiency depends strongly on the temperature set. With this query in mind, we present a comparative study among different temperature selection schemes in three lattice-gas models. We focus our attention in the constant entropy method (CEM), proposed by Sabo In the CEM, the temperature is chosen by the fixed difference of entropy between adjacent replicas. We consider a method to determine the entropy which avoids numerical integrations of the specific heat and other thermodynamic quantities. Different analyses for first-and second-order phase transitions have been undertaken, revealing that the CEM may be an useful criterion for selecting the temperatures in the parallel tempering. © 2011 American Institute of Physics.
Fiore C.E.,University Federal Do Paran |
Da Luz M.G.E.,University Federal Do Paran
Journal of Chemical Physics | Year: 2010
The simulated tempering (ST) is an important method to deal with systems whose phase spaces are hard to sample ergodically. However, it uses accepting probabilities weights, which often demand involving and time consuming calculations. Here it is shown that such weights are quite accurately obtained from the largest eigenvalue of the transfer matrix-a quantity straightforward to compute from direct Monte Carlo simulations-thus simplifying the algorithm implementation. As tests, different systems are considered, namely, Ising, Blume-Capel, Blume-Emery-Griffiths, and Bell-Lavis liquid water models. In particular, we address first-order phase transition at low temperatures, a regime notoriously difficulty to simulate because the large free-energy barriers. The good results found (when compared with other well established approaches) suggest that the ST can be a valuable tool to address strong first-order phase transitions, a possibility still not well explored in the literature. © 2010 American Institute of Physics.
Dal-Forno M.,University Federal Do Paran |
Eliasaro S.,University Federal Do Paran
Lichenologist | Year: 2010
Four species of the genus Graphis Adans. are described as new to science, namely G. archeri, G. invisibilis, G. lueckingii and G. paranaensis. These new species were found growing in restinga forest in southern Brazil. © 2009 British Lichen Society.
Caddah M.K.,University of Campinas |
Goldenberg R.,University Federal Do Paran
Systematic Botany | Year: 2012
During the preparation of a monographic treatment for a group of Miconia from the Atlantic Forest, Brazil, a new species was detected and is presented here. Miconia ruschiana can be recognized among other species of Miconia sect. Glossocentrum by the terete branches, shortly plinerved leaves abaxially covered by non-lepidote stellate trichomes, panicles with glomerulate ending branches, large flowers with the calyx bearing long, caducous, external lobes, and ovaries that are densely covered by trichomes at the apex. The new species is known from the mountains of the state of Espírito Santo in eastearn Brazil. © Copyright 2012 by the American Society of Plant Taxonomists.
Mancinelli W.S.,University Federal Do Paran |
Blum C.T.,University Federal Do Paran |
Smidt E.D.C.,University Federal Do Paran
Systematic Botany | Year: 2012
A new Thismiaceae species, Thismia prataensis , from the Brazilian Atlantic Rain Forest is described and illustrated. This species was found growing in the "Serra da Prata" mountain range, Morretes, Paran State, southeastern Brazil, and is distinguished from the other species in the genus by the presence of six bracts in two whorls, free interstaminal lobes, six depressions that surround the throat, double longitudinal lamellae on the outside of the floral tube and stigma with papillose surface. This is the most southerly record for the group in the Neotropical region. A key of the Thismia species inhabiting the Atlantic Rain Forest is also provided. © Copyright 2012 by the American Society of Plant Taxonomists.
Kremer G.M.,University Federal Do Paran
Physica A: Statistical Mechanics and its Applications | Year: 2010
The aim of this work is to analyze the entropy, entropy flux and entropy rate of granular materials within the frameworks of the Boltzmann equation and continuum thermodynamics. It is shown that the entropy inequality for a granular gas that follows from the Boltzmann equation differs from the one of a simple fluid due to the presence of a term which can be identified as the entropy density rate. From the knowledge of a non-equilibrium distribution functionvalid for processes closed to equilibriumit is obtained that the entropy density rate is proportional to the internal energy density rate divided by the temperature, while the entropy flux is equal to the heat flux vector divided by the temperature. A thermodynamic theory of a granular material is also developed whose objective is the determination of the basic fields of mass density, momentum density and internal energy density. The constitutive laws are restricted by the principle of material frame indifference and by the entropy principle. Through the exploitation of the entropy principle with Lagrange multipliers, it is shown that the results obtained from the kinetic theory for granular gases concerning the entropy density rate and entropy flux are valid in general for processes close to equilibrium of granular materials, where linearized constitutive equations hold. © 2010 Elsevier B.V. All rights reserved.
Fujimotoa M.M.,University Federal do Paran |
Brigg W.J.,University College London |
Tennysonb J.,University College London
European Physical Journal D | Year: 2012
Electron collisions with C2H5OH are studied up to impact energies of 10 eV using several theoretical models. Calculated differential cross sections suggest that the extrapolation to low angles used to extend experimental data and hence give integral cross sections significantly underestimates the large, dipole-driven forward scattering cross section. An improved set of values for the rotationally-unresolved elastic cross section is proposed; the corresponding rotationally resolved cross sections are also presented. Static exchange plus polarisation calculations find a very broad shape resonance in each of the 2A' and 2A'' symmetries in the 7 eV collision region however no resonance at lower energies, in qualitative agreement with the interpretation of some but not all dissociative electron attachment measurements. © EDP Sciences, Societ́ Italiana di Fisica, Springer-Verlag 2012.
Huergo L.F.,National University of Costa Rica |
Huergo L.F.,University Federal Do Paran |
Dixon R.,John Innes Center
Microbiology and Molecular Biology Reviews | Year: 2015
The metabolite 2-oxoglutarate (also known as ketoglutarate, 2-ketoglutaric acid, or oxoglutaric acid) lies at the intersection between the carbon and nitrogen metabolic pathways. This compound is a key intermediate of one of the most fundamental biochemical pathways in carbon metabolism, the tricarboxylic acid (TCA) cycle. In addition, 2-oxoglutarate also acts as the major carbon skeleton for nitrogen-assimilatory reactions. Experimental data support the conclusion that intracellular levels of 2-oxoglutarate fluctuate according to nitrogen and carbon availability. This review summarizes how nature has capitalized on the ability of 2-oxoglutarate to reflect cellular nutritional status through evolution of a variety of 2-oxoglutarate-sensing regulatory proteins. The number of metabolic pathways known to be regulated by 2-oxoglutarate levels has increased significantly in recent years. The signaling properties of 2-oxoglutarate are highlighted by the fact that this metabolite regulates the synthesis of the well-established master signaling molecule, cyclic AMP (cAMP), in Escherichia coli. © 2015, American Society for Microbiology. All Rights Reserved.