912 resultados para GENERALIZED-GRADIENT-APPROXIMATION


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In this paper, we proposed a flexible cure rate survival model by assuming the number of competing causes of the event of interest following the Conway-Maxwell distribution and the time for the event to follow the generalized gamma distribution. This distribution can be used to model survival data when the hazard rate function is increasing, decreasing, bathtub and unimodal-shaped including some distributions commonly used in lifetime analysis as particular cases. Some appropriate matrices are derived in order to evaluate local influence on the estimates of the parameters by considering different perturbations, and some global influence measurements are also investigated. Finally, data set from the medical area is analysed.

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After sintering advanced ceramics, there are invariably distortions, caused in large part by the heterogeneous distribution of density gradients along the compacted piece. To correct distortions, machining is generally used to manufacture pieces within dimensional and geometric tolerances. Hence, narrow material removal limit conditions are applied, which minimize the generation of damage. Another alternative is machining the compacted piece before sintering, called the green ceramic stage, which allows machining without damage to mechanical strength. Since the greatest concentration of density gradients is located in the outer-most layers of the compacted piece, this study investigated the removal of different allowance values by means of green machining. The output variables are distortion after sintering, tool wear, cutting force, and the surface roughness of the green ceramics and the sintered ones. The following results have been noted: less distortion is verified in the sintered piece after 1mm allowance removal; and the higher the tool wear the worse the surface roughness of both green and sintered pieces.

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In this work we present nonlinear models in two-dimensional space-time of two interacting scalar fields in the Lorentz and CPT violating scenarios. We discuss the soliton solutions for these models as well as the question of stability for them. This is done by generalizing a model recently published by Barreto and collaborators and also by getting new solutions for the model introduced by them.

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The existence of an interpolating master action does not guarantee the same spectrum for the interpolated dual theories. In the specific case of a generalized self-dual (GSD) model defined as the addition of the Maxwell term to the self-dual model in D = 2 + 1, previous master actions have furnished a dual gauge theory which is either nonlocal or contains a ghost mode. Here we show that by reducing the Maxwell term to first order by means of an auxiliary field we are able to define a master action which interpolates between the GSD model and a couple of non-interacting Maxwell-Chern-Simons theories of opposite helicities. The presence of an auxiliary field explains the doubling of fields in the dual gauge theory. A generalized duality transformation is defined and both models can be interpreted as self-dual models. Furthermore, it is shown how to obtain the gauge invariant correlators of the non-interacting MCS theories from the correlators of the self-dual field in the GSD model and vice-versa. The derivation of the non-interacting MCS theories from the GSD model, as presented here, works in the opposite direction of the soldering approach.

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In this work we solve the Dirac equation by constructing the exact bound state solutions for a mixing of vector and scalar generalized Hartmann potentials. This is done provided the vector potential is equal to or minus the scalar potential. The cases of some quasi-exactly solvable and Morse-like potentials are briefly commented. (c) 2006 Elsevier B.V. All rights reserved.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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In this work, are discussed two formulations of the boundary element method - BEM to perform linear bending analysis of plates reinforced by beams. Both formulations are based on the Kirchhoffs hypothesis and they are obtained from the reciprocity theorem applied to zoned plates, where each sub-region defines a beam or a stab. In the first model the problem values are defined along the interfaces and the external boundary. Then, in order to reduce the number of degrees of freedom kinematics hypothesis are assumed along the beam cross section, leading to a second formulation where the collocation points are defined along the beam skeleton, instead of being placed on interfaces. on these formulations no approximation of the generalized forces along the interface is required. Moreover, compatibility and equilibrium conditions along the interface are automatically imposed by the integral equation. Thus, these formulations require less approximation and the total number of the degrees of freedom is reduced. In the numerical examples are discussed the differences between these two BEM formulations, comparing as well the results to a well-known finite element code.

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The purpose of the work is to study the existence and nonexistence of shock wave solutions for the Burger equations. The study is developed in the context of Colombeau's theory of generalized functions (GFs). This study uses the equality in the strict sense and the weak equality of GFs. The shock wave solutions are given in terms of GFs that have the Heaviside function, in x and ( x, t) variables, as macroscopic aspect. This means that solutions are sought in the form of sequences of regularizations to the Heaviside function, in R-n and R-n x R, in the distributional limit sense.

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In this work we define the composite function for a special class of generalized mappings and we study the invertibility for a certain class of generalized functions with real values.

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Paracoccidioidomycosis (PCM) is a severe systemic mycosis, endemic in Latin America and highly prevalent in Brazil, where it ranks eighth as a mortality cause among infectious and parasitic diseases in humans. The disease in animals has been little explored. It is observed that armadillos can harbor the fungus at high frequencies, although the active disease has not been well documented in this wild mammal. Dogs are susceptible to experimental infection, and the naturally acquired PCM-disease was reported only recently in a dog from Brazil. The present work reports the second case of naturally acquired PCM in a 6-year-old female dog that presented emaciation, lymphadenomegaly, and hepatosplenomegaly. Biochemical and pulmonary radiographic evaluation did not reveal any abnormalities. PCM was diagnosed by clinical findings, culturing, immunohistochemistry, and histopathology of popliteal lymph node. The fungus was recovered from popliteal lymph node, and the molecular analysis showed respective sequencing similarities of 99 and 100% for 803 nucleotides of the Gp43 gene and 592 nucleotides from the ITS-5.8S region of Paracoccidioides brasiliensis. Immunohistochemistry revealed severe lymphadenitis and presented numerous yeasts, which reacted against the gp43 antibody. Histopathology revealed a severe granulomatous lymphadenitis associated with numerous single or multiple budding yeasts. After diagnosis, the dog was successfully treated with itraconazol for 2 years. Veterinarians should be aware of the importance of considering PCM for differential diagnosis, especially in dogs from PCM-endemic areas, whose monophagocytic system involvement is evident.

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Sarcoidosis is a rare equine skin disease characterized primarily by an exfoliative and granulomatous dermatitis but also presenting granulomatous inflammation of multiple systems. The current report presents the clinical and histopathological findings of sarcoidosis in a 16-year-old American Quarter Horse gelding with nested polymerase chain reaction Mycobacterium spp. DNA detection within hepatic and skin samples. Mycobacterium spp. may play a role in the pathogenesis of equine sarcoidosis as has been proposed for human sarcoidosis.

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International Journal of Paediatric Dentistry 2012; 22: 310316 Background. Generalized aggressive periodontitis (GAP) in primary teeth is a rare periodontal disease that occurs during or soon after eruption of the primary teeth. An association with systemic diseases is a possibility. Case Report. A 4-year-old Brazilian girl presented with GAP involving the entire primary dentition. The patient and her parents and sister were subjected to microbiological testing to identify the microorganisms involved in the disease. The patient underwent tooth extraction to eradicate the disease and received a prosthesis for the restoration of masticatory function. After the permanent teeth erupted, fixed orthodontic appliances were place to restore dental arch form and occlusion. Conclusions. The results show the importance of an early diagnosis of GAP and of a multidisciplinary approach involving laboratory and clinical management to treat the disease and to restore masticatory function, providing a better quality of life for patients.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)