Estudo das propriedades críticas do processo de contato por par para diferentes atualizações

We study the critical behavior of the one-dimensional pair contact process (PCP), using the Monte Carlo method for several lattice sizes and three different updating: random, sequential and parallel. We also added a small modification to the model, called Monte Carlo com Ressucitamento" (MCR), which consists of resuscitating one particle when the order parameter goes to zero. This was done because it is difficult to accurately determine the critical point of the model, since the order parameter(particle pair density) rapidly goes to zero using the traditional approach. With the MCR, the order parameter becomes null in a softer way, allowing us to use finite-size scaling to determine the critical point and the critical exponents β, ν and z. Our results are consistent with the ones already found in literature for this model, showing that not only the process of resuscitating one particle does not change the critical behavior of the system, it also makes it easier to determine the critical point and critical exponents of the model. This extension to the Monte Carlo method has already been used in other contact process models, leading us to believe its usefulness to study several others non-equilibrium models

Parâmetros físico-químicos de estrelas nos campos de exoplanetas do satélite corot

A rotação estelar é um dos mais importantes observáveis da evolução estelar. Neste sentido, o satélite CoRoT representa uma oportunidade única de medir os períodos rotacionais para uma amostra de estrelas estatisticamente robusta, oferecendo dados absolutamente necessários para o estudo da rotação e seu papel na evolução estelar. Para conseguir isto, um passo fundamental é a caracterização física e química das estrelas observadas pelo CoRoT, especificamente devido ao fato de que o cálculo de períodos rotacionais confiáveis é um trabalho difícil sem a ajuda dos parâmetros estelares. Desta forma, foi elaborado um importante seguimento observacional das estrelas nos campos do CoRoT do anticentro LRa01 e do centro LRc01, permitindo a correta identificação dos períodos que reflitam a modulação rotacional. Nesta tese de doutorado são apresentados os resultados de tal seguimento. Parâmetros físicos e químicos, tais como temperatura efetiva Teff , gravidade superficial log(g), velocidade de microturbulência Vmic, abundância de ferro [Fe/H], velocidade de rotação projetada Vsin(i), e abundância de lítio A(Li) são apresentados para uma amostra de 116 estrelas dos campos CoRoT. Elas se encontram em diferentes estágios evolutivos, desde a sequência principal (SP) até o ramo das gigantes vermelhas (GV). As observações foram feitas utilizando os espectrógrafos UVES (VLT) e HYDRA (CTIO). Para a derivação de tais parâmetros foram utilizados o programa TurboSpectrum e os modelos de atmosfera de MARCS. Paralelamente, velocidades rotacionais Vsin(i) foram obtidas a partir do ajuste dos perfis observados e sintéticos das linhas de ferro e por meio de uma calibração de função de correlação cruzada (CCF). Períodos rotacionais Prot para 77 estrelas da amostra foram obtidos a partir das curvas de luz do satélite CoRoT. Extensas tabelas destes parâmetros e seus respectivos erros são apresentadas. Foram encontradas diferenças nas distribuições de Teff , [Fe/H] e estágios evolutivos entre os diferentes campos do CoRoT, indicando possíveis efeitos de seleção na amostra, assim como a existência de diferentes populações estelares do disco Galáctico. Por outro lado, o comportamento rotacional e as abundâncias de lítio não apresentam diferenças entre estrelas de parâmetros físicos similares, mas que pertencem a diferentes campos do CoRoT. A partir da análise de temperaturas, foi encontrada uma maior extinção por avermelhamento para estrelas do CoRoT localizadas no campo LRc01, assim como um gradiente deste valor em função da distância. Os resultados mostram que as abundâncias de lítio, as velocidades de rotação e os períodos rotacionais apresentam o mesmo comportamento descrito na literatura. Por outro lado, é apresentada pela primeira vez a relação que existe entre o lítio e o período de rotação em diferentes estágios evolutivos, mostrando, tal como era esperado, que ambas as grandezas possuem uma anticorrelação. Também é apresentada a evolução simultânea da rotação e do lítio, e foram calculadas relações que permitem obter valores médios de A(Li) como função da temperatura efetiva e do período rotacional. Os dados apresentados nesta tese de doutorado representam um importante ponto de partida para serem utilizados como uma amostra de calibração para diferentes programas no contexto da missão do satélite CoRoT, uma vez que a lista de estrelas aqui analisadas são parte das mais brilhantes que compõem o campo Exo do CoRoT

Formação estelar desencadeada pela colisão entre nuvens moleculares magnetizadas

We use a finite diference eulerian numerical code, called ZEUS 3D, to do simulations involving the collision between two magnetized molecular clouds, aiming to evaluate the rate of star formation triggered by the collision and to analyse how that rate varies depending on the relative orientations between the cloud magnetic fields before the shock. The ZEUS 3D code is not an easy code to handle. We had to create two subroutines, one to study the cloud-cloud collision and the other for the data output. ZEUS is a modular code. Its hierarchical way of working is explained as well as the way our subroutines work. We adopt two sets of different initial values for density, temperature and magnetic field of the clouds and of the external medium in order to study the collision between two molecular clouds. For each set, we analyse in detail six cases with different directions and orientations of the cloud magnetic field relative to direction of motion of the clouds. The analysis of these twelve cases allowed us to conform analytical-theoretical proposals found in the literature, and to obtain several original results. Previous works indicate that, if the cloud magnetic fields before the collision are orthogonal to the direction of motion, then a strong inhibition of star formation will occur during a cloud-cloud shock, whereas if those magnetic fields are parallel to the direction of motion, star formation will be stimulated. Our treatment of the problem confirmed numerically those results, and further allowed us to quantify the relative star forming efficiencies in each case. Moreover, we propose and analyse an intermediate case where the field of one of the clouds is orthogonal to the motion and the field of the other one is parallel to the motion. We conclude that, in this case, the rate at which the star formation occurs has a value also intermediate between the two extreme cases we mentioned above. Besides that we study the case in which the fields are orthogonal to the direction of the motion but, instead of being parallel to each other, they are anti-parallel, and we obtained for this case the corresponding variation of the star formation rate due to this alteration of the field configuration. This last case has not been studied in the literature before. Our study allows us to obtain, from the simulations, the rate of star formation in each case, as well as the temporal dependence of that rate as each collision evolves, what we do in detail for one of the cases in particular. The values we obtain for the rate of star formation are in accordance with those expected from the presently existing observational data

Efeitos interfaciais em heteroestruturas quânticas nô-abruptas: GaAs/ALxGa1-xAs

Um minuncioso estudo das propriedades de confinamento em heterostructuras bidimensionais(poços quânticos) GaAs/AlxGa1_xAs, com interfaces graduais é realizado. Um modelo teórico que represente bem a variação da fração molar do alumínio nas interfaces, resultante do aparecimento de micro-rugosidades e ilhas durante os processos de crescimento e recozimento pós-crescimento da amostra, é elaborado. Vários perfis desta fração molar de alumínio nas interfaces são considerados. Soluções analíticas da equação de Schrodinger, na aproximação da massa efetiva constatne nas interfaces, resultando em equações transcendentais, que possibilitam a obtenção dos níveis de energia dos portadores, decorrentes do seu confinamento quântico, são apresentadas. Energias de ligação e de confinamento de excitons 2D, utilizando-se um método analítico e numerérico e a aproximação do potencial efetivo, são também calculadas. Resultados numéricos para os níveis de energia dos portadores e para as energias de ligação e de confinamento dos excitons 2D, em poços quânticos GaAs/Al0.35Ga0.65As não-abruptos, sem e com a presença de campo elétrico aplicado para vários perfis interfaciais da fração de molar, são mostrados. Para a obtenção desses resultados, faz-se uso do método dos degraus múltiplos e da técnica da matriz de transferência, e adota-se, como operador de energia cinética, o de Ben-Daniel e Duque para uma massa efetiva dependente da posição. Conclui-se que um modelo que leva em conta a existência de interfaces não-abruptas e seus diversos perfis é indispensável para uma melhor descrição das propriedades opto-eletrônicas de poços quânticos GaAs/AlxGa1-xAs, enquanto que a aproximação das interfaces abruptas apresenta-se bastante limitada

Testes cinemáticos em cosmologia com decaimento do vácuo

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Formação estelar desencadeada pela colisão entre nuvens moleculares magnetizadas

Conselho Nacional de Desenvolvimento Científico e Tecnológico

Um estudo da rotação em estrelas da seqüência principal

Conselho Nacional de Desenvolvimento Científico e Tecnológico

Evolução da atividade cromosférica, abundância de lítio e rotação das estrelas análogas e gêmeas solares

The study of solar-type stars also includes the familiar solar analogs and twins. These objects have been one of the major research subjects in astrophysics nowadays. A direct comparison of solar activity with chromospheric activity indices for a set of stars very similar to the Sun (twins and analogs) provides an excellent opportunity to study the evolution of stellar activity on timescales of the order of the lifetime on the main sequence. This work deals with the relationship between the abundance of lithium, chromospheric activity, X-ray emission and rotation period in terms of stellar ages. We explore the influence of stellar evolution in the global properties of the stars and the aspects linked to its coronal, chromospheric and magnetic activity. Our main objective is to probe the law of decay of each of these parameters based on a sample of stars classified as well-connected as analogs stars and solar twins.

O papel das relações sociais e da atenção social durante tarefas cooperativas em Callithrix jacchus

Several studies on nonhuman primates show that the relationships between individuals strongly influence the expression of cooperative behavior, both in natural environment and in captivity settings. Recent studies suggest that cooperative breeders present outstanding performance in tasks involving social cognition, such as cooperative tasks with experimental apparatuses. In experimental research on this subject it is crucial to differentiate between real cooperation (or communicative cooperation, mediated by social attention) and by-product cooperation that results from simultaneous actions of individuals. The present study assessed, in Callithrix jacchus, a cooperative breeder species, if social relationships and social attention between subjects are important factors during performance in cooperative tasks. During the experimental procedure the animals participated in three different cooperative tasks: cooperation task, prosocial task and control task. Diverging from the literature, matrix correlation tests revealed no significant relationship between grooming or proximity and the execution of the tasks, suggesting that other factors such as age or hierarchy may have an effect on the performance in cooperative tasks in this species. There was also no relationship between the execution of the cooperative tasks and social glances, suggesting that there was no social attention during the tasks. Moreover, there were lower rates of social glances in the cooperative tasks as opposed to the control tasks. However, the small number of pulls in prosocial tasks suggests that the animals distinguished between tasks that benefited only a partner and tasks that generated benefits to themselves, choosing the latter. We conclude that, for the tasks presented in this study, we could neither detect the role of social relationships on the cooperative tasks nor assert that there were true cooperation and prosocial behavior

Relações sociais de callithrix jacchus machos: competição ou cooperação?

The group Callithrichidae is characterized by the flexibility in its mating system. This fact generates questions about the mechanisms that Callithrix jacchus males reach the breeding position in a group and how they prevent the subordinates reproduction, since the competition apparently happens with less intensity when compared to the females. Studies have shown the importance of social interactions and kinship among individuals in the distribution of mating opportunities in a group. This work aimed to evaluate if dyads of Callithrix jacchus males acted socially different due to kinship. We observed the agonistic and affiliative behaviours made by the males when associated in dyads (Phase 1) and when these dyads received a female (Phase 2), which was introduced in the pair`s cage for 45 minutes. In the phase 2, we also accounted for the sexual interactions between males and female in each trio. We used 16 males, 8 related (brothers-R) and 8 nonrelated (NR), as well as 8 females. Each phase lasted 4 weeks, with 3 observations/week, during 15 min/male in phase 1 and 2. In the first phase, two pairs of R males had a contested dominance and the other two, just like in the NR males, had an uncontested dominance. The NR dominant males were more aggressive than the subordinates. With the female`s entrance in the cage, all male pairs began to have an uncontested dominance. The NR males aggression frequency rose along with the subordinates` submission. In the R males, the frequency of grooming and physical contact was higher than in the NR males. So, we conclude that the low levels of agonism presented by the R males, along with the higher tolerance shown amongst them, lead us to believe that kinship attenuate the competition among these males

Adolescentes e jovens e suas bases de apoio :relações de amizade como suporte social no enfrentamento à violência

The purpose of this work is to map the family and community social supports for adolescents and young students from Bom Pastor Distric, West Zone of Natal/RN, as well as to describe how such resources are used by these individuaIs in that community. Social support refers not only to formal activities or organizations, but also to spontaneous or informal forms of support - friendship and solidarity nets available in the community, affective relations that are meaningful in the lives of children and young people. Our discussion is based on a research performed with 382 adolescents and young students from Jean Mermoz Public School (students from 5th to 11th grades, aged 13 to 14). We emphasized the situations of violence derived from family or community spheres faced by these students. In relation to this specific aspect, we observed the participants more frequently look for help from the informal social supports, mostly from their friends, which indicates that the formal ones are not considered to be effective instruments for social assistance. The search for informal social supports shows the relations informally established in the streets (for instance when they look for help from friends, rei atives or neighbors) have more effect and play an important role in which there are values and affections exchange. Thinking the strengthening of these social links is of extreme importance and leads to the weakening of the hegemonic logics focused on the production of subjects as private identities, and to the amplification of an ethics committed to the disassembly of a sociability anchored to fear, impotence, intolerance, discrimination, and reduction of spaces for circulating and confronting mechanisms of social exclusion. It is crucial that we concentrate our attention to building friendship as a system of reciprocity and affective exchanges, as a space for political actions and production of forms of lives that are potent against social anesthesia

Praça: lugar de lazer: relações entre características ambientais e comportamentais na Praça Kalina Maia Natal RN

Nowadays, the urban chaos brings some problems to the citizens such as mental fatigue, irritability and lack of attention, emphasizing the need for open urban spaces, capable to contribute to the restoration of physical and mental balance of people. By the variety of alternative uses available, many of them related to the stimulus of entertainment activities, the squares have been identified as restorative environments, especially by its potential as a place of leisure. In this context, the objective of this dissertation is to understand the use of the square as leisure environment, by a square in Natal RN, establishing the relationship between environmental and behavioral characteristics. More specifically, I attempt to identify the major activities that happen there, the people that develop them and the spatial and temporal configurations of this occupation. Among the 290 squares available in the city, the Kalina Maia Square was selected, which is located in the district of Lagoa Nova. The case study chosen was based on criteria relating to scale, shape, location on the urban environment, variability of uses and conservation status. In the study were used behavioral mapping place-centered and people-centered, behavior trace analysis and 14 interviews. The results show that the square is used by people from different ages and social classes, subdivided into groups with specific days and times. These users are usually engaged in activities related to various types of leisure, with sports predominance. The relationship between spatial configuration and behavior shows that there is a sectorization of uses, being possible to identify the environmental characteristics that most favor observed activities, especially in relation to shading and presence of furniture and equipment. Moreover, throughout the day it appears that the affordances inherent to the various fixed objects on the square are decoded differently by various categories of users, by giving them insights that help the development of leisure activities that characterize each group

Humanização hospitalar, ambiente físico e relações assistenciais :a percepção de arquitetos especialistas

The creation of the Humanization Program of Hospital Care and the increasing number of academic works and journal articles that discuss more humane practices in the health care services express the emphasis given to the theme in Brazil. In these discussions, however, it is not usual to find reference to architecture as a relevant factor in the humanization of hospitals, even though it is known that the physical structure of the building may help the recovering of the patients; elements such as gardens, the use of colors and open spaces may soften the impact caused by the hospital routine on patients. Considering the contribution the architectural project may bring to the humanization of hospitals, the aim of this study was to verify how the architects perceive the hospital humanization process. Besides having searched for subsides in informal interviews with health professionals, in visits to hospitals and in related seminars, the study was based on semi-structured interviews with architects of Natal, Rio Grande do Norte, who are specialists in this kind of projects. The content analysis of the interviews showed that physical space and attendance are essential to the humanization process. Those professionals see two humanization tendencies: while private hospitals have the structural physical appearance considered as humanized, public hospitals emphasize the humanization in attendance, fact that illustrates the contradictions in Brazilian health system. The interviewees consider the post-occupancy evaluation of the building as a learning exercise that contributes to new projects, but surprisingly they do not mention the patients opinion as part of it. Two annoying facts have emerged from the interviews, as also seen in preliminary stages of the study: rare are the works that focus on the person-environment relationship, and the definition of humanized hospital environments is still broad and inaccurate. This suggests the need of new studies in order to better understand how the two factors shown in this study attendance and physical space interact towards a true hospital humanization

Avaliação do comportamento termoanalítico e oxidativo do biodiesel de mamona

In this work biodiesel was gotten through the transesterification reaction using the oil of castor as source of triglycerides and using the methylic route for obtaining of esters. For the characterization of biodiesel and its mixtures with mineral diesel oil, physical chemical parameters and several analytical techniques had been used, as well as: gas chromatography (GC), nuclear magnetic resonance of proton (1H NMR), infrared spectroscopy (IR) and thermal analysis. The chromatography confirmed the complete reaction of esters in biodiesel presenting a 97,08% conversion. The 1H - NMR presented singlet in 3,6 ppm corresponding to the hydrogen of the group ester RCOO CH3. The infrared presented a strong band in 1741 cm-1 referring to stretching C=O of ester and an average band in 1175 cm-1 referring C O deformation. With the data of thermal analysis it was possible to observe the thermal and oxidative stability of the samples changing the atmospheres of synthetic air and nitrogen, where stages of the thermal decomposition had been verified and had been attributed to the volatilization and/or decomposition of the triacylglycerides. The thermal degradation of the samples was carried through 150 and 210°C during 1, 12, 24 and 48 hours and was observed change in the thermogravimetric profile, therefore an increase in the number of stages of the thermal decomposition also occurred indicating characteristic intermediate composites of polymerization, being this confirmed through the rheological study that presented brusque increase of viscosity. The kinetic study showed that the activation energy has the following order: biodiesel > mineral diesel oil > mixtures biodiesel/diesel

efeito da aplicação de uma solução salina no crescimento e na composição química da atriplex nummularia

This study aimed to analyze the effect of a saline solution on growth and chemical composition of Atriplex nummularia, shrubby plant, absorbing salts used in the diet of animals and the management of water and saline soils. These plant seedlings were planted and grown in a reserved area at the Federal University of Rio Grande do Norte. The plantation was divided into two blocks, in which one of them was irrigated with saline solution with a concentration of 2840 mgL-1 of NaCl and the second group was irrigated with drinking water. After six months, the plants were collected, harvested and divided into three parts: leaf, thin and thick stem. Monthly, dimension measurements were carried out for cataloging the growth of Atriplex. Ion Chromatography (IC) and Optical Emission Spectroscopy Inductively Coupled Plasma (ICP-OES) were used to analyze the chemical composition of the partition plant parts. The results of these analyses revealed that an absorption process of anions and cations by Atriplex nummularia plant during its growth was achieved, in particular by a higher concentration of sodium and chloride ions. Scanning electron microscopy images showed and confirmed the presence of small crystals on the leaf surface. Electrical conductivity and pH measurements of the aerial parts of the plant were carried out and these results showed that the leaf is the plant part where there is a largest concentration of ions. In addition, measurements of specific surface were obtained from irrigated plants with saline solution, achieving higher surface area, in all cases. Plant dimensions obtained monthly showed that the plants irrigated with water grew 5% more than those plants irrigated with saline solution. Based on results obtained, Atriplex plant showed a higher potential to survive and adapt to environments (aquatic or geological) with high levels of salinity and this property can be used as a tool for removing salts/metals from industrial contaminated soils and effluents.