707 resultados para Integrable hierarchies
Resumo:
The A(n-1) Gaudin model with integrable boundaries specified by non-diagonal K-matrices is studied. The commuting families of Gaudin operators are diagonalized by the algebraic Bethe ansatz method. The eigenvalues and the corresponding Bethe ansatz equations are obtained. (c) 2005 Elsevier B.V. All rights reserved.
Resumo:
Several behavioral studies of large, gregarious, and sexually dimorphic macropods have shown that males form dominance hierarchies and large males have the highest reproductive success. The bridled nailtail wallaby (Onychogalea fraenata) is a smaller and strongly sexually dimorphic macropod, but is also highly solitary and males do not form dominance hierarchies that are maintained temporally or spatially. Genetic studies of paternity have shown that large males are the most reproductively successful and only one-quarter of males sire offspring at any one time. The aim of this study was to investigate the tactics that males adopt to secure access to females at the time of estrus and to investigate whether females can influence which males have access to them. This study was conducted using 2 wild, free-ranging populations of bridled nailtail wallabies. Females in estrus were located and observed. and the total number of males present, the relative weight rank of each mate, and interactions between individuals were recorded. Females showed a preference for large males and incited male-male competition when the group of males present was large. Unlike other dimorphic macropods, fights among males were rare and were restricted to males of similar size. Large males gained access to females by guarding and following them closely and threatening other males who attempted to gain access. Smaller males spent less time with females, suggesting that small males may leave multimale groups in an attempt to locate unguarded females. Given the solitary nature of this species and the lack of a stable dominance hierarchy to influence male reproductive success. mate searching and mate guarding may be important male reproductive tactics in this species.
Resumo:
We propose that the Baxter's Q-operator for the quantum XYZ spin chain with open boundary conditions is given by the j -> infinity limit of the corresponding transfer matrix with spin-j (i.e., (2j + I)-dimensional) auxiliary space. The associated T-Q relation is derived from the fusion hierarchy of the model. We use this relation to determine the Bethe Ansatz solution of the eigenvalues of the fundamental transfer matrix. The solution yields the complete spectrum of the Hamiltonian. (c) 2006 Elsevier B.V. All rights reserved.
Resumo:
We introduce a general Hamiltonian describing coherent superpositions of Cooper pairs and condensed molecular bosons. For particular choices of the coupling parameters, the model is integrable. One integrable manifold, as well as the Bethe ansatz solution, was found by Dukelsky et al. [J. Dukelsky, G.G. Dussel, C. Esebbag, S. Pittel, Phys. Rev. Lett. 93 (2004) 050403]. Here we show that there is a second integrable manifold, established using the boundary quantum inverse scattering method. In this manner we obtain the exact solution by means of the algebraic Bethe ansatz. In the case where the Cooper pair energies are degenerate we examine the relationship between the spectrum of these integrable Hamiltonians and the quasi-exactly solvable spectrum of particular Schrodinger operators. For the solution we derive here the potential of the Schrodinger operator is given in terms of hyperbolic functions. For the solution derived by Dukelsky et al., loc. cit. the potential is sextic and the wavefunctions obey PT-symmetric boundary conditions. This latter case provides a novel example of an integrable Hermitian Hamiltonian acting on a Fock space whose states map into a Hilbert space of PE-symmetric wavefunctions defined on a contour in the complex plane. (c) 2006 Elsevier B.V. All rights reserved.
Resumo:
Time-course experiments with microarrays are often used to study dynamic biological systems and genetic regulatory networks (GRNs) that model how genes influence each other in cell-level development of organisms. The inference for GRNs provides important insights into the fundamental biological processes such as growth and is useful in disease diagnosis and genomic drug design. Due to the experimental design, multilevel data hierarchies are often present in time-course gene expression data. Most existing methods, however, ignore the dependency of the expression measurements over time and the correlation among gene expression profiles. Such independence assumptions violate regulatory interactions and can result in overlooking certain important subject effects and lead to spurious inference for regulatory networks or mechanisms. In this paper, a multilevel mixed-effects model is adopted to incorporate data hierarchies in the analysis of time-course data, where temporal and subject effects are both assumed to be random. The method starts with the clustering of genes by fitting the mixture model within the multilevel random-effects model framework using the expectation-maximization (EM) algorithm. The network of regulatory interactions is then determined by searching for regulatory control elements (activators and inhibitors) shared by the clusters of co-expressed genes, based on a time-lagged correlation coefficients measurement. The method is applied to two real time-course datasets from the budding yeast (Saccharomyces cerevisiae) genome. It is shown that the proposed method provides clusters of cell-cycle regulated genes that are supported by existing gene function annotations, and hence enables inference on regulatory interactions for the genetic network.
Resumo:
Os movimentos de contestação social que tiveram lugar nos anos 60 trouxeram novas perspectivas para as mulheres, verificando-se crescente inserção destas no mercado de trabalho. No entanto, a persistência do trabalho doméstico sob responsabilidade dominante das mulheres, mesmo nesse contexto em que os índices de participação feminina no mercado de trabalho se elevam, tem chamado a atenção para os constrangimentos de ordem subjetiva e sócio-cultural como elementos decisivos dentre os que cooperam para a manutenção desse quadro. Ou seja, a desigualdade persiste em face da persistência de hierarquias de gênero que continuam a delimitar o lugar das mulheres e que encontram nas religiões o seu lócus privilegiado de produção e reprodução. É no contexto da economia simbólica batista, em que as representações tradicionais do homem como cabeça e da mulher como auxiliadora significam o homem como provedor e a mulher como esposa e mãe, responsável pelos afazeres domésticos, que abordamos aqui a problemática da divisão sexual do trabalho, enquanto e a partir da representação e prática de sujeitos religiosos batistas paulistanos. Ao mesmo tempo em que o discurso religioso batista afirma e ratifica a divisão sexual do trabalho, está sujeito às solicitações sociais por mudanças nas relações de gênero, favorecendo a mobilização de doutrinas religiosas igualitárias presentes entre os batistas. É, portanto, numa perspectiva dinâmica de tensões entre os avanços e permanências nas práticas de gênero ao nível da sociedade mais ampla, e que se colocam tanto a partir dos valores culturais desta, quanto a partir das condições materiais e estruturais encontradas aí, e de tensões entre o processo de secularização e compromisso ético que as representações e práticas de gênero entre os batistas pesquisados permanecem enquanto se transformam e avançam enquanto se mantêm.
Resumo:
Esta dissertação propõe uma interface entre duas áreas de conhecimento, a educação e a teologia, a partir de um novo paradigma educacional: a inclusão. Tomamos a perspectiva das pessoas com deficiência e perguntamos pela contribuição da educação inclusiva para os discursos teológicos, bem como dos discursos teológicos para a inclusão social e educacional das pessoas com deficiência. A antropologia dará a nuance desta interface, posto que, historicamente, este tema esteve envolto em antropologias religiosas dicotômicas e excludentes. propomos, portanto, a superação dos paradigmas exclusivamente cartesianos que marcam a sociedade contemporânea, sociedade esta acostumada a classificar as pessoas, hierarquizando as suas diferenças. Nestes termos, a sociologia das ausências nos auxilia na compreensão dos mecanismos de segregação e exclusão das pessoas com deficiência (tanto na educação quanto na teologia) e aponta para a necessária valorização das experiências sociais das pessoas com deficiência - respeitando a diversidade e valorizando a diferença. O movimento se dá, portanto, no sentido da visibilidade das pessoas com deficiência nos discursos teológicos, bem como nos espaços eclesiais (dada à dimensão dialética desta rela-ção). Entendemos que este é um movimento inadiável, já iniciado por alguns teólogos, quando os mesmos falam do necessário reconhecimento recíproco, da digna vulnerabilidade humana e do desafio ético que a inclusão nos coloca no sentido do reconhecimento da interdependência e da necessária operacionalização da solidariedade nos espaços sociais (acessibilidade). Todavia, estas categorias são como frestas entreabertas na porta teológica, pois, em sua maioria, nem os discursos teológicos e nem os espaços eclesiais ainda não dão visibilidade às pessoas com deficiência.
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The use of ontologies as representations of knowledge is widespread but their construction, until recently, has been entirely manual. We argue in this paper for the use of text corpora and automated natural language processing methods for the construction of ontologies. We delineate the challenges and present criteria for the selection of appropriate methods. We distinguish three ma jor steps in ontology building: associating terms, constructing hierarchies and labelling relations. A number of methods are presented for these purposes but we conclude that the issue of data-sparsity still is a ma jor challenge. We argue for the use of resources external tot he domain specific corpus.
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We consider return-to-zero (RZ) pulses with random phase modulation propagating in a nonlinear channel (modelled by the integrable nonlinear Schrödinger equation, NLSE). We suggest two different models for the phase fluctuations of the optical field: (i) Gaussian short-correlated fluctuations and (ii) generalized telegraph process. Using the rectangular-shaped pulse form we demonstrate that the presence of phase fluctuations of both types strongly influences the number of solitons generated in the channel. It is also shown that increasing the correlation time for the random phase fluctuations affects the coherent content of a pulse in a non-trivial way. The result obtained has potential consequences for all-optical processing and design of optical decision elements.
Resumo:
By transforming the optical fiber span into an ultralong cavity laser, we experimentally demonstrate quasilossless transmission over long (up to 75 km) distances and virtually zero signal power variation over shorter (up to 20 km) spans, opening the way for the practical implementation of integrable nonlinear systems in optical fiber. As a by-product of our technique, the longest ever laser (to the best of our knowledge) has been implemented, with a cavity length of 75 km. A simple theory of the lossless fiber span, in excellent agreement with the observed results, is presented.
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A key objective of autonomic computing is to reduce the cost and expertise required for the management of complex IT systems. As a growing number of these systems are implemented as hierarchies or federations of lower-level systems, techniques that support the development of autonomic systems of systems are required. This article introduces one such technique, which involves the run-time synthesis of autonomic system connectors. These connectors are specified by means of a new type of autonomic computing policy termed a resource definition policy, and enable the dynamic realisation of collections of collaborating autonomic systems, as envisaged by the original vision of autonomic computing. We propose a framework for the formal specification of autonomic computing policies, and use it to define the new policy type and to describe its application to the development of autonomic system of systems. To validate the approach, we present a sample data-centre application that was built using connectors synthesised from resource-definition policies.
Resumo:
This thesis presents a new approach to designing large organizational databases. The approach emphasizes the need for a holistic approach to the design process. The development of the proposed approach was based on a comprehensive examination of the issues of relevance to the design and utilization of databases. Such issues include conceptual modelling, organization theory, and semantic theory. The conceptual modelling approach presented in this thesis is developed over three design stages, or model perspectives. In the semantic perspective, concept definitions were developed based on established semantic principles. Such definitions rely on meaning - provided by intension and extension - to determine intrinsic conceptual definitions. A tool, called meaning-based classification (MBC), is devised to classify concepts based on meaning. Concept classes are then integrated using concept definitions and a set of semantic relations which rely on concept content and form. In the application perspective, relationships are semantically defined according to the application environment. Relationship definitions include explicit relationship properties and constraints. The organization perspective introduces a new set of relations specifically developed to maintain conformity of conceptual abstractions with the nature of information abstractions implied by user requirements throughout the organization. Such relations are based on the stratification of work hierarchies, defined elsewhere in the thesis. Finally, an example of an application of the proposed approach is presented to illustrate the applicability and practicality of the modelling approach.
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It is widely accepted that the Thatcher years and their immediate aftermath were associated with substantive social and organizational change. The privatisation programme, 'the rolling back of the State', prosecuted by the successive Conservative Governments from 1979-1997 was a central pillar of Governmental policy. This thesis seeks to engage with privatization through the of CoastElectric, a newly privatised Regional Electricity Company. This thesis contributes to the extant understanding of the dynamics of organizational change in four major ways. Firstly, the study into CoastElectric addresses the senior management decision making within the organization: in particular, it will attempt to make sense of 'why' particular decisions were made. The theoretical backdrop to this concern will draw on the concepts of normalization, cultural capital and corporate fashion. The argument presented in this thesis is that the decision-making broadly corresponded with that which could be considered to be at the vanguard of mangerialist thought. However, a detailed analysis suggested that at different junctures in CoastElectric's history there were differences in the approach to decision making that warranted further analysis. The most notable finding was that the relative levels of new managerialist cultural capital possessed by the decision-making elite had an important bearing upon whether the decision was formulated either endogenously or exogenously, with the assistance of cultural intermediaries such as management consultants. The thesis demonstrates the importance of the broader discourse of new managerialism in terms of shaping what is considered to be a 'commonsensical, rational' strategy. The second concern of this thesis is that of the process of organizational change. The study of CoastElectric attempts to provide a rich account of the dynamics of organizational change. This is realized through, first, examining the pre-existing context of the organization; second, through analyzing the power politics of change interventions. The master concepts utilised in this endeavour are that of: dividing practices, the establishment of violent hierarchies between competing discourses; symbolic violence; critical turning points; recursiveness; creative destruction; legitimation strategies and the reconstitution of subjects in the workplace.
Resumo:
We consider the random input problem for a nonlinear system modeled by the integrable one-dimensional self-focusing nonlinear Schrödinger equation (NLSE). We concentrate on the properties obtained from the direct scattering problem associated with the NLSE. We discuss some general issues regarding soliton creation from random input. We also study the averaged spectral density of random quasilinear waves generated in the NLSE channel for two models of the disordered input field profile. The first model is symmetric complex Gaussian white noise and the second one is a real dichotomous (telegraph) process. For the former model, the closed-form expression for the averaged spectral density is obtained, while for the dichotomous real input we present the small noise perturbative expansion for the same quantity. In the case of the dichotomous input, we also obtain the distribution of minimal pulse width required for a soliton generation. The obtained results can be applied to a multitude of problems including random nonlinear Fraunhoffer diffraction, transmission properties of randomly apodized long period Fiber Bragg gratings, and the propagation of incoherent pulses in optical fibers.
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The intellectual project of using whiteness as an explicit tool of analysis is not one that has taken root in Britain. However, there are a number of empirical studies that investigate the racialization of white identities. In this article, I look at some empirical sociological fieldwork carried out on white identities in Britain since the early 1990s and identify the key themes arising. These themes are (in)visibility, norms and values, cultural capital and integration, contingent hierarchies and Empire in the present. In Britain, a pertinent distinction is between rural and urban settings for the enactment of white identities vis-a`-vis those of minorities, and there is an exploration of some of the contingency that draws the boundary between ‘white’ and ‘Other’ in different places. Areas of commonality and distinctiveness are noted in terms of the American work. In the last section, I argue that there are a number of issues to resolve around continuing such studies, including linking the micro-level to the macro-level analysis, and expanding to international comparative work.