1,565 research outputs found
Optimal static and dynamic recycling of defective binary devices
The binary Defect Combination Problem consists in finding a fully working
subset from a given ensemble of imperfect binary components. We determine the
typical properties of the model using methods of statistical mechanics, in
particular, the region in the parameter space where there is almost surely at
least one fully-working subset. Dynamic recycling of a flux of imperfect binary
components leads to zero wastage.Comment: 14 pages, 15 figure
Cavity approach for real variables on diluted graphs and application to synchronization in small-world lattices
We study XY spin systems on small world lattices for a variety of graph
structures, e.g. Poisson and scale-free, superimposed upon a one dimensional
chain. In order to solve this model we extend the cavity method in the one
pure-state approximation to deal with real-valued dynamical variables. We find
that small-world architectures significantly enlarge the region in parameter
space where synchronization occurs. We contrast the results of population
dynamics performed on a truncated set of cavity fields with Monte Carlo
simulations and find excellent agreement. Further, we investigate the
appearance of replica symmetry breaking in the spin-glass phase by numerically
analyzing the proliferation of pure states in the message passing equations.Comment: 10 pages, 3 figure
Nematicidal activity of essential oils and organic amendments from Asteraceae against root-knot nematodes
The essential oil of Chrysanthemum coronarium flowerheads showed strong nematicidal activity in vitro and in growthchamber experiments. Essential oil concentrations of 2, 4, 8 and 16 ÎŒL mLâ1, significantly reduced hatch, J2 survival
(determined by final value and area under curves of cumulative percentage hatch or mortality) and reproduction rate of Meloidogyne artiellia in vitro, with the lowest values occurring at 16 ÎŒL mLâ1. In pot trials with chickpea cv. PV 61,
essential oil concentrations of 10â40 ÎŒL per 500 cm3 soil, applied on sterile cotton pellets, also significantly reduced the nematodeâs reproduction rate. The biological processes of mortality and hatching/reproduction were adequately described by the monomolecular and expanded negative exponential models, respectively. Effectiveness of soil amendment
with either flowers, leaves, roots or seeds of C. coronarium, and flowers from several species of Asteraceae (Chrysanthemum segetum, Calendula maritima, Calendula officinalis and Calendula suffruticosa) at 5 g per 500 cm3 soil was tested for suppression of M. artiellia and growth of chickpea cv. PV 61 under growth-chamber conditions. In these tests, flowers of all five Asteraceae species and various parts of C. coronarium significantly reduced reproduction rates of M. artiellia, by 83·0â95·9%, with the minimum rates occurring in infected chickpea plants amended with flowers of C. officinalis and C. suffruticosa. The in vitro and in planta results suggest that the essential oil of C. coronarium and organic amendments from Asteraceae species may serve as nematicides.This research, part of a PhD study by P.P., was supported by grant SC98-022 and a fellowship from the Instituto Nacional de TecnologĂas Agroalimentarias (INIA).Peer reviewe
DistribuciĂłn y estado del Jacamar Galbula ruficauda (Aves: Galbulidae) en Paraguay
Rufous-tailed Jacamar Galbula ruficauda is known from few records in Paraguay, all during the last 20 years. The species has been recorded in the northern Chaco and Paraguayan Pantanal, with all confirmed records from Alto Paraguay department. Here we summarise all reports and localities of the species in Paraguay to date. The species is categorized as Data Deficient at the national level, but may be more widely distributed than is currently recognised.Galbula ruficauda es una especie que cuenta con pocos registros a lo largo de 20 años en Paraguay. La especie ha sido observada en la zona norte del Chaco y Pantanal paraguayo, departamento Alto Paraguay. En este trabajo reportamos los registros y localidades de ocurrencia de la especie en el paĂs. Actualmente se encuentra en la categorĂa de Datos Insuficientes a nivel nacional, aunque puede ser que su distribuciĂłn sea mĂĄs amplia
Trading interactions for topology in scale-free networks
Scale-free networks with topology-dependent interactions are studied. It is
shown that the universality classes of critical behavior, which conventionally
depend only on topology, can also be explored by tuning the interactions. A
mapping, , describes how a shift of the
standard exponent of the degree distribution can absorb the
effect of degree-dependent pair interactions .
Replica technique, cavity method and Monte Carlo simulation support the
physical picture suggested by Landau theory for the critical exponents and by
the Bethe-Peierls approximation for the critical temperature. The equivalence
of topology and interaction holds for equilibrium and non-equilibrium systems,
and is illustrated with interdisciplinary applications.Comment: 4 pages, 5 figure
Spin models on random graphs with controlled topologies beyond degree constraints
We study Ising spin models on finitely connected random interaction graphs
which are drawn from an ensemble in which not only the degree distribution
can be chosen arbitrarily, but which allows for further fine-tuning of
the topology via preferential attachment of edges on the basis of an arbitrary
function Q(k,k') of the degrees of the vertices involved. We solve these models
using finite connectivity equilibrium replica theory, within the replica
symmetric ansatz. In our ensemble of graphs, phase diagrams of the spin system
are found to depend no longer only on the chosen degree distribution, but also
on the choice made for Q(k,k'). The increased ability to control interaction
topology in solvable models beyond prescribing only the degree distribution of
the interaction graph enables a more accurate modeling of real-world
interacting particle systems by spin systems on suitably defined random graphs.Comment: 21 pages, 4 figures, submitted to J Phys
Collyria seals in the Roman Empire
Roman seals associated with collyria (Latin expression for eye drops /washes and lotions for eye maintenance) provide valuable information about eye care in the antiquity. These small, usually stone-made pieces bore engravings with the names of eye doctors and also the collyria used to treat an eye disease. The collyria seals have been found all over the Roman empire and Celtic territories in particular and were usually associated with military camps. In Hispania (Iberian Peninsula), only three collyria seals have been found. These findings speak about eye care in this ancient Roman province as well as about of the life of the time. This article takes a look at the utility and social significance of the collyria seals and seeks to give an insight in the ophthalmological practice of in the Roman Empire
Hypothyroidism decreases the biogenesis in free mitochondria and neuronal oxygen consumption in the cerebral cortex of developing rats
Thyroid hormone plays a critical role in mitochondrial biogenesis in two areas of the developing brain, the cerebral cortex and the striatum. Here we analyzed, in the cerebral cortex of neonatal rats, the effect of hypothyroidism on the biogenesis in free and synaptosomal mitochondria by analyzing, in isolated mitochondria, the activity of respiratory complex I, oxidative phosphorylation, oxygen consumption, and the expression of mitochondrial genome. In addition, we studied the effect of thyroid hormone in oxygen consumption in vivo by determining metabolic flow through C-13 nuclear magnetic resonance spectroscopy. Our results clearly show that in vivo, hypothyroidism markedly reduces oxygen consumption in the neural population of the cerebral cortex. This effect correlates with decreased free mitochondria biogenesis. In contrast, no effect was observed in the biogenesis in synaptosomal mitochondria. The parameters analyzed were markedly improved after T-3 administration. These results suggest that a reduced biogenesis and the subsequent reduction of respiratory capacity in free mitochondria could be the underlying cause of decreased oxygen consumption in the neurons of the cerebral cortex of hypothyroid neonates.This work was supported by Ministerio de EducaciĂn y Ciencia Grants SAF2004-06263-CO2-02 (to A.S.), SAF2004-06263-CO2-01, and SAF2007-62811 and Comunidad de Madrid Grant GR/SAL/0033/2004 (to A.P.-C.). Centro de InvestigaciĂłn BiomĂ©dica en Red Sobre Enfermedades Neurodegenerativas is funded by the Instituto de Salud Carlos III. T.B.R. is a recipient of a fellowship from the Fundaçùo para a CiĂȘncia e Tecnologia, Portugal (SFRH/BPD/26881/2006).Peer reviewe
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