3 resultados para Many-body models

em Universidade Federal do Rio Grande do Norte(UFRN)


Relevância:

80.00% 80.00%

Publicador:

Resumo:

In the first part of this work our concern was to investigate the thermal effects in organic crystals using the theory of the polarons. To analyse such effect, we used the Fröhlich s Hamiltonian, that describes the dynamics of the polarons, using a treatment based on the quantum mechanics, to elucidate the electron-phonon interaction. Many are the forms to analyzing the polaronic phenomenon. However, the measure of the dielectric function can supply important information about the small polarons hopping process. Besides, the dielectric function measures the answer to an applied external electric field, and it is an important tool for the understanding of the many-body effects in the normal state of a polaronic system. We calculate the dielectric function and its dependence on temperature using the Hartree-Fock decoupling method. The dieletric function s dependence on the temperature is depicted by through a 3D graph. We also analyzed the so called Arrhenius resistivity, as a functionof the temperature, which is an important tool to characterize the conductivity of an organic molecule. In the second part we analyzed two perovskita type crystalline oxides, namely the cadmium silicate triclinic (CdSiO3) and the calcium plumbate orthorhombic (CaPbO3), respectively. These materials are normally denominated ABO3 and they have been especially investigated for displaying ferroelectric, piezoelectric, dielectrics, semiconductors and superconductors properties. We found our results through ab initio method within the functional density theory (DFT) in the GGA-PBE and LDA-CAPZ approximations. After the geometry optimization for the two structure using the in two approximations, we found the structure parameters and compared them with the experimental data. We still determined further the angles of connection for the two analyzed cases. Soon after the convergence of the energy, we determined their band structures, fundamental information to characterize the nature of the material, as well as their dielectrics functions, optical absorption, partial density of states and effective masses of electrons and holes

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Ulcerative colitis comprising an inflammatory bowel disease, whose most severe consequence is the development of intestinal neoplasia. The drugs currently used to treat the disease trigger a variety of serious adverse effects and are not effective in many cases. Recent studies demonstrated the effectiveness of natural products for the treatment of inflammatory processes. Seaweed extracts and their purified products have shown protective effects in models of inflammation and the association of traditional therapies with probiotics has significantly improved the clinical symptoms of ulcerative colitis. Therefore, the aims of this study include evaluating the potential effects of the use of probiotic strain Enterococcus faecium 32 (Ef32), the methanolic extract of the green seaweed Caulerpa mexicana (M.E.) and their concomitant administration in a murine model of colitis induced by dextran sodium sulfate (DSS). Accordingly, C57BL /6 mice were pretreated orally with Ef32 (109 CFU/ml) for seven days. In the seven days following, the colitis was induced by administration of 3% DSS (w/v) diluted in the animals drinking water. During this period, animals were treated daily with Ef32 and the M.E. (2.0 mg/kg) every other day by intravenous route. The development of colitis was monitored by the disease activity index (DAI), which takes into account the loss of body weight, consistency and presence of blood in stools. After euthanasia, the colon was removed, its length measured and tissue samples were destined for histological analysis and culture for cytokine quantification. The levels of cytokines in the culture supernatant of the colon were measured by ELISA. The treatments with the probiotic Ef32 or the M.E. alone or the combination of these two substances provoked significant improvement as to weight loss and DAI, and prevented the shortening of the colon in response to DSS. The isolated treatments triggered a slight improvement in intestinal mucosal tissue damage. However, their combination was able to completely repair the injury triggered by DSS. The association was also able to reduce the levels of all the cytokines analyzed (IFN-γ, IL-4, IL-6, IL-12, IL-17A and TNF-α). On the other hand, the treatment with Ef32 did not interfere with the levels of TNF-α, whereas treatment with M.E. did not alter the levels of IL-6. Moreover, the treatment with Ef32 not interferes in TNF-α levels, whereas treatment with M.E. did not alter the levels of IL-6. Therefore, the potential probiotic Ef32 and M.E. and especially when these samples were associated proved promising alternatives in the treatment of ulcerative colitis as demonstrated in an experimental model because of its beneficial effects on morphological and clinical parameters, and by reducing the production of proinflammatory cytokines of Th1, Th2 and Th17

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Talking about body and beauty seems fairly familiar to physical education. We understand that the body language in the area provides many meanings over the appearance, beauty and aesthetics, thus requiring the need of criticism and the need to interrogate her to realize how physical education has been re-signified. For this purpose, considering the multiplicity of meanings that surround the body and beauty, we discussed the implications that this brings to the area of Physical Education, analyzing the conception of body and beauty in the studies in this area, at the masters level, from some questions: What conceptions of body and beauty have been discussed in the studies of physical education at the masters level? What is the relationship between the meanings of body and beauty products analyzed and identified in the models of beauty outlined in Physical Education? We understand the importance of this research and its contribution to the epistemological analysis of existing studies. And, mainly because there is a lack of studies that discuss these productions. For construction of this text and for our reflections, we rely on thoughts like David Le Breton, Claude Levi- Strauss, Michel Foucault, Maurice Merleau-Ponty, Ana Marcia Silva, Carmen Smith, Isabel Mendes, Karenin Porpino Nobrega and flounder. The present study is characterized as a qualitative research, and content analysis proposed by Laurence Bardin (1977) for data processing. The corpus was composed of eight essays in the area of Physical Education, published in the CAPES Theses Database for the period 2004 to 2008, selected from the subject and body beauty. The initial reading allowed us to select meaningful units and guide our discussions on two main themes, which make up the two chapters of the work. In the first chapter, entitled Body, beauty and culture, as evidenced understandings of body, nature and culture that are present in the work is considered. In the second chapter, Standard Body Transformations and beauty, we present the concepts of body and beauty found in the dissertation, focusing on the mutability of representations of the models of beauty in body singularities in the relations of power-knowledge and the importance given the body in society, especially with regard to physical education professionals. We have thus found that, considering the dissertations analyzed, the understanding of body and beauty has been resignified, when dealing with other aesthetic conceptions that consider the uniqueness expressed in the human body and the culture of which the individual belongs