63,461 research outputs found

    Chaos in the thermal regime for pinned manifolds via functional RG

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    The statistical correlations of two copies of a d-dimensional elastic manifold embedded in slightly different frozen disorder are studied using the Functional Renormalization Group to one-loop accuracy, order O(eps = 4-d). Determining the initial (short scale) growth of mutual correlations, i.e. chaos exponents, requires control of a system of coupled differential (FRG) equations (for the renormalized mutual and self disorder correlators) in a very delicate boundary layer regime. Some progress is achieved at non-zero temperature, where linear analysis can be used. A growth exponent a is defined from center of mass fluctuations in a quadratic potential. In the case where temperature is marginal, e.g. a periodic manifold in d=2, we demonstrate analytically and numerically that a = eps (1/3 - 1/(2 log(1/T)) with interesting and unexpected logarithmic corrections at low T. For short range (random bond) disorder our analysis indicates that a = 0.083346(6) eps, with large finite size corrections.Comment: 14 pages, 3 figure

    Study of thermometers for measuring a microcanonical phase transition in nuclear fragmentation

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    The aim of this work is to study how the thermodynamic temperature is related to the known thermometers for nuclei especially in view of studying the microcanonical phase transition. We find within the MMMC-model that the "S-shape" of the caloric equation of state e^*(T) which is the signal of a phase transition in a system with conserved energy, can be seen in the experimentally accessible slope temperatures T_slope for different particle types and also in the isotopic temperatures T_He-Li. The isotopic temperatures T_H-He are weaker correlated to the shape of the thermodynamic temperature and therefore are less favorable to study the signal of a microcanonical phase transition. We also show that the signal is very sensitive to variations in mass of the source

    Neuronal plasticity: cell-based strategy for target identification and validation

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    While growing neurites are relatively plastic during development, their plasticity levels drop rapidly as neurons mature and become integrated into neuronal networks. As a consequence, the central nervous system ability to reorganize itself in response to injury or disease is insufficient. One of the main limitations for the design of therapeutic strategies to enhance neurite sprouting following neurological diseases is our poor understanding of the mechanisms underlying neurite structural plasticity. 

To overcome this limitation, we have implemented a strategy to identify, characterize and validate the most therapeutically relevant drug targets to modulate neuronal plasticity. This strategy is based on the hypothesis that the molecular regulation of the neurite shaft (controlling its ability to sprout) shares similarities with other cell systems. In an initial selection step (1), candidate targets are identified from the literature based on predetermined criteria (e.g. involvement in cell migration and growth cone collapse). (2) Compounds acting on those targets are tested in a neuronal cell-based assay for their effects on neurite sprouting as well as for early detection of undesired effects. (3) The selected targets are further analyzed during a verification step where their subcellular expression and activity is assessed. The regulation of the activity of the potential targets by branching factors is also determined at this point. (4) Once the biological relevance has been established, the signalling pathway in which the potential targets operates within neurons is mapped using activity reporters to uncover additional potential targets. 

This candidate approach, combined with the use of primary neurons, is designed to increase the probability of identifying suitable targets at the same time that it minimizes costs and time to validation. By using this strategy, we have been able to identify a set of proteins controlling neuronal sprouting together with an unsuspected mechanism of regulation of structural plasticity in neurons

    Empirical Comparison of Chirp and Multitones on Experimental UWB Software Defined Radar Prototype

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    This paper proposes and tests an approach for an unbiased study of radar waveforms' performances. Using the ultrawide band software defined radar prototype, the performances of Chirp and Multitones are compared in range profile and detection range. The architecture was implemented and has performances comparable to the state of the art in software defined radar prototypes. The experimental results are consistent with the simulations

    Observing the sky at extremely high energies with the Cherenkov Telescope Array: Status of the GCT project

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    The Cherenkov Telescope Array is the main global project of ground-based gamma-ray astronomy for the coming decades. Performance will be significantly improved relative to present instruments, allowing a new insight into the high-energy Universe [1]. The nominal CTA southern array will include a sub-array of seventy 4 m telescopes spread over a few square kilometers to study the sky at extremely high energies, with the opening of a new window in the multi-TeV energy range. The Gamma-ray Cherenkov Telescope (GCT) is one of the proposed telescope designs for that sub-array. The GCT prototype recorded its first Cherenkov light on sky in 2015. After an assessment phase in 2016, new observations have been performed successfully in 2017. The GCT collaboration plans to install its first telescopes and cameras on the CTA site in Chile in 2018-2019 and to contribute a number of telescopes to the subsequent CTA production phase.Comment: 8 pages, 7 figures, ICRC201

    Contribution of simulation and gaming to natural resource management issues: An introduction

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    Nowadays, computer-mediated simulations and games are widely used in the field of natural resource management (NRM). They have proved to be useful for various purposes such as supporting decisionmaking processes and training. First, the specificities of the NRM research field are highlighted. Then, based on the analysis of the articles presented in this special issue of Simulation & Gaming, some key features related to the implementation of gaming in such a context are introduced. Finally, after reviewing the benefits of using simulation games in NRM, the authors stress the ethical issue of changing social relationships among stakeholders by playing a game with some of themGESTION DE L'ENVIRONNEMENT;RESSOURCE NATURELLE;SIMULATION;SOCIOLOGIE;JEU DE ROLE;BENEFITS;CONTEXT;COLLECTIVE POLICY DESIGN;DECISION MAKING;ETHICAL ISSUES;IMPLEMENTATION;NATURAL RESOURCE MANAGEMENT (NRM);SIMULATION GAMES;SOCIAL EMPOWERMENT;SOCIAL RELATIONSHIPS;SOCIOECOLOGICAL SYSTEMS;STAKEHOLDERS

    Low-wage employment in Portugal: Social dimension and recent evolution

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    Low-wage employment is one of the main origins of poverty and social exclusion in Portugal, along with low pensions granted to elder citizens. In this paper our aim is to provide a first approach of the social dimension of low-wage employment in Portugal, analysing its incidence and profile among regions, sectors, professions, skill levels and gender. This decomposition analysis will stress the most important factors underlying the phenomenon. At a first stage we shall study wage structure and wage inequality evolution in the last decade. The incidence and evolution of low wages and minimum legal wages will be compared whith average wages, in order to evaluate the situation of the low payed vis a vis the other better paid workers. We proceed analysing low-wage decomposition by the criteria mentioned above, taken separately and in interaction, to identify the main determinants and the cumulative effects of these factors in the explanation and evolution of low wages. The main data set available is "Quadros de Pessoal" (Data base of worker characteristics provided by firms) from the MESS ( Employment and Social Security Ministry). In this study we will use directly this data base. Other statistical sources will also be used for complementary aspects. We must say that the data on these area of research are still insufficiently developed in Portugal, and that, in consequence, socio-economic knowledge on low-wage employment as a mechanism of social exclusion is still incipient. Low-wage are but one of the dimensions of social exclusion, closely related with poverty as insufficient economic resources, and is often associated with other dimensions of social exclusion in the labour market, such as unemployment vulnerability and job instability. The crucial role in this triad - low-pay, unemployment, job instability - is played by skill levels, which are particularly low in our country, as we?ll try to demonstrate. Social exclusion must however be analysed at the family unit. As long as income is concerned, wages are far the most important source, particularly for low income active families, and the ?low skills - low pay - low income? chain seems to be the major determinant of social exclusion. The evidence about this mechanism can be found in recent data on Family Budgets.
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