785 resultados para Mott criticality
Resumo:
BACKGROUND We describe the diversity of two kinds of mycobacteria isolates, environmental mycobacteria and Mycobacterium bovis collected from wild boar, fallow deer, red deer and cattle in Doñana National Park (DNP, Spain), analyzing their association with temporal, spatial and environmental factors. RESULTS High diversity of environmental mycobacteria species and M. bovis typing patterns (TPs) were found. When assessing the factors underlying the presence of the most common types of both environmental mycobacteria and M. bovis TPs in DNP, we evidenced (i) host species differences in the occurrence, (ii) spatial structuration and (iii) differences in the degree of spatial association of specific types between host species. Co-infection of a single host by two M. bovis TPs occurred in all three wild ungulate species. In wild boar and red deer, isolation of one group of mycobacteria occurred more frequently in individuals not infected by the other group. While only three TPs were detected in wildlife between 1998 and 2003, up to 8 different ones were found during 2006-2007. The opposite was observed in cattle. Belonging to an M. bovis-infected social group was a significant risk factor for mycobacterial infection in red deer and wild boar, but not for fallow deer. M. bovis TPs were usually found closer to water marshland than MOTT. CONCLUSIONS The diversity of mycobacteria described herein is indicative of multiple introduction events and a complex multi-host and multi-pathogen epidemiology in DNP. Significant changes in the mycobacterial isolate community may have taken place, even in a short time period (1998 to 2007). Aspects of host social organization should be taken into account in wildlife epidemiology. Wildlife in DNP is frequently exposed to different species of non-tuberculous, environmental mycobacteria, which could interact with the immune response to pathogenic mycobacteria, although the effects are unknown. This research highlights the suitability of molecular typing for surveys at small spatial and temporal scales.
Resumo:
Gene-on-gene regulations are key components of every living organism. Dynamical abstract models of genetic regulatory networks help explain the genome's evolvability and robustness. These properties can be attributed to the structural topology of the graph formed by genes, as vertices, and regulatory interactions, as edges. Moreover, the actual gene interaction of each gene is believed to play a key role in the stability of the structure. With advances in biology, some effort was deployed to develop update functions in Boolean models that include recent knowledge. We combine real-life gene interaction networks with novel update functions in a Boolean model. We use two sub-networks of biological organisms, the yeast cell-cycle and the mouse embryonic stem cell, as topological support for our system. On these structures, we substitute the original random update functions by a novel threshold-based dynamic function in which the promoting and repressing effect of each interaction is considered. We use a third real-life regulatory network, along with its inferred Boolean update functions to validate the proposed update function. Results of this validation hint to increased biological plausibility of the threshold-based function. To investigate the dynamical behavior of this new model, we visualized the phase transition between order and chaos into the critical regime using Derrida plots. We complement the qualitative nature of Derrida plots with an alternative measure, the criticality distance, that also allows to discriminate between regimes in a quantitative way. Simulation on both real-life genetic regulatory networks show that there exists a set of parameters that allows the systems to operate in the critical region. This new model includes experimentally derived biological information and recent discoveries, which makes it potentially useful to guide experimental research. The update function confers additional realism to the model, while reducing the complexity and solution space, thus making it easier to investigate.
Resumo:
Este artigo faz parte de uma pesquisa mais ampla realizada em nível de Pós-Doutuorado na Escola de Enfermagem da USP (1999-2000), intitulada «Caminhos Cruzados: os cursos para formação de parteiras e enfermeiras em São Paulo (1880-1971)» que teve por objetivo refletir sobre as atribuições de parteiras e enfermeiras obstétricas e a exclusão dessas profissionais na assistência ao parto no decorrer do século XX. O artigo se detém nos primeiros cursos para formação de parteiras e na fiscalização da profissão, apontando que no início do século XX, já se pode perceber uma associação entre parteiras e enfermeiras, não apenas em alguns cursos para formação profissional, como também no cotidiano de trabalho. Passa a existir a expectativa de que a parteira fosse também enfermeira.
Resumo:
Forest fire models have been widely studied from the context of self-organized criticality and from the ecological properties of the forest and combustion. On the other hand, reaction-diffusion equations have interesting applications in biology and physics. We propose here a model for fire propagation in a forest by using hyperbolic reaction-diffusion equations. The dynamical and thermodynamical aspects of the model are analyzed in detail
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This project focuses on studying and testing the benefits of the NX Remote Desktop technology in administrative use for Finnish Meteorological Institutes existing Linux Terminal Service Project environment. This was done due to the criticality of the system caused by growing number of users as the Linux Terminal Service Project system expands. Although many of the supporting tasks can be done via Secure Shell connection, testing graphical programs or desktop behaviour in such a way is impossible. At first basic technologies behind the NX Remote Desktop were studied, and after that started the testing of two possible programs, FreeNX and NoMachine NX server. Testing the functionality and bandwidth demands were first done in a closed local area network, and results were studied. The better candidate was then installed in a virtual server simulating actual Linux Terminal Service Project server at Finnish Meteorological Institute and connection from Internet was tested to see was there any problems with firewalls and security policies. The results are reported in this study. Studying and testing the two different candidates of NX Remote Desktop showed, that NoMachine NX Server provides better customer support and documentation. Security aspects of the Finnish Meteorological Institute had also to be considered, and since updates along with the new developing tools are announced in next version of the program, this version was the choice. Studies also show that even NoMachine promises a swift connection over an average of 20Kbit/s bandwidth, at least double of that is needed. This project gives an overview of available remote desktop products along their benefits. NX Remote Desktop technology is studied, and installation instructions are included. Testing is done in both, closed and the actual environment and problems and suggestions are studied and analyzed. The installation to the actual LTSP server is not yet made, but a virtual server is put up in the same place in the view of network topology. This ensures, that if the administrators are satisfied with the system, installation and setting up the system will go as described in this report.
Resumo:
Achieving a high degree of dependability in complex macro-systems is challenging. Because of the large number of components and numerous independent teams involved, an overview of the global system performance is usually lacking to support both design and operation adequately. A functional failure mode, effects and criticality analysis (FMECA) approach is proposed to address the dependability optimisation of large and complex systems. The basic inductive model FMECA has been enriched to include considerations such as operational procedures, alarm systems. environmental and human factors, as well as operation in degraded mode. Its implementation on a commercial software tool allows an active linking between the functional layers of the system and facilitates data processing and retrieval, which enables to contribute actively to the system optimisation. The proposed methodology has been applied to optimise dependability in a railway signalling system. Signalling systems are typical example of large complex systems made of multiple hierarchical layers. The proposed approach appears appropriate to assess the global risk- and availability-level of the system as well as to identify its vulnerabilities. This enriched-FMECA approach enables to overcome some of the limitations and pitfalls previously reported with classical FMECA approaches.
Resumo:
Elastic scattering of relativistic electrons and positrons by atoms is considered in the framework of the static field approximation. The scattering field is expressed as a sum of Yukawa terms to allow the use of various approximations. Accurate phase shifts have been computed by combining Bühring¿s power-series method with the WKB and Born approximations. This combined procedure allows the evaluation of differential cross sections for kinetic energies up to several tens of MeV. Numerical results are used to analyze the validity of several approximate methods, namely the first- and second-order Born approximations and the screened Mott formula, which are frequently adopted as the basis of multiple scattering theories and Monte Carlo simulations of electron and positron transport.
Resumo:
We analyze the collective behavior of a lattice model of pulse-coupled oscillators. By means of computer simulations we find the relation between the intrinsic dynamics of each member of the population and their mutual interactions that ensures, in a general context, the existence of a fully synchronized regime. This condition turns out to be the same as that obtained for the globally coupled population. When the condition is not completely satisfied we find different spatial structures. This also gives some hints about self-organized criticality.
Resumo:
We calculate noninteger moments ¿tq¿ of first passage time to trapping, at both ends of an interval (0,L), for some diffusion and dichotomous processes. We find the critical behavior of ¿tq¿, as a function of q, for free processes. We also show that the addition of a potential can destroy criticality.
Resumo:
Different microscopic models exhibiting self-organized criticality are studied numerically and analytically. Numerical simulations are performed to compute critical exponents, mainly the dynamical exponent, and to check universality classes. We find that various models lead to the same exponent, but this universality class is sensitive to disorder. From the dynamic microscopic rules we obtain continuum equations with different sources of noise, which we call internal and external. Different correlations of the noise give rise to different critical behavior. A model for external noise is proposed that makes the upper critical dimensionality equal to 4 and leads to the possible existence of a phase transition above d=4. Limitations of the approach of these models by a simple nonlinear equation are discussed.
Resumo:
The invaded cluster (IC) dynamics introduced by Machta et al. [Phys. Rev. Lett. 75, 2792 (1995)] is extended to the fully frustrated Ising model on a square lattice. The properties of the dynamics that exhibits numerical evidence of self-organized criticality are studied. The fluctuations in the IC dynamics are shown to be intrinsic of the algorithm and the fluctuation-dissipation theorem is no longer valid. The relaxation time is found to be very short and does not present a critical size dependence.
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Este artigo analisa os cursos para formação de parteiras no Brasil, no século XIX. A documentação pesquisada é extremamente rica e levanta importantes questões referentes à formação das parteiras, ao perfil de alunas desejado, à freqüência e ao número de alunas matriculadas, ao papel de médicos e parteiras no atendimento ao parto, à disputa profissional, como ainda, às relações de gênero e raciais, no período.
Resumo:
The magnetically induced splay Fréedericksz transition is reexamined to look for pattern forming phenomena slightly above or below criticality. By using our traditional scheme of stochastic nematodynamic equations, situations are, respectively, found of transient and permanent predominance of transversal periodicities (wave numbers) along the direction perpendicular to the initial orientation within the sample. The relevance of these predictions in relation with recent observations in the electrically driven splay Fréedericksz transition, and in general with other pattern forming phenomena, is stressed.
Resumo:
A part de l"ús del pretèrit perifràstic, format amb el verb ir + infinitiu (xistaví) o anar + infinitiu (català), els paral lelismes més interessants entre el xistaví i el català són de tipus lèxic. Tanmateix, sovint no resulta gens fàcil decidir si les formes compartides són préstecs directes o si constitueixen part d"un tresor comú. Determinades paraules com ara sep i boc, amb oclusiva final, i llesca, amb [ʎ] inicial, porten l"empremta d"identitat catalana, així com borde < bord, amb vocal de suport final en aragonès i en castellà, i cotón, sense l"article àrab aglutinat (però amb [n] final en aragonès). La forma mielsa és un catalanisme tan antic que presenta diftongació de la vocal radical en aragonès. A més a més, tancar, que és específic de l"Aragó oriental, sembla ser resultat de l"expansió del català a territoris dialectals veïns. En canvi, bachoca és tan generalitzat també es troba a Múrcia i València que no pot ésser considerat com el cas anterior. En aquest article intentem d"avaluar l"impacte del lèxic català en l"aragonès de Gistaín (xistaví).