Teoria semi-clássica para super rede magnética formada por materiais ferromagnético e antiferromagnético

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Espectro das ondas de spin lineares e não-lineares em multicamadas magnéticas anisotrópicas

Conselho Nacional de Desenvolvimento Científico e Tecnológico

Ondas de spin em nanofilmes nagnéticos acoplados quasiperiodicamente

We studied the spin waves modes that can propagate in magnetic multilayers composed of ferromagnetic metallic films in the nanometer scale. The ferromagnetic films (iron) are separated and coupled through the nonmagnetic spacer films (chromium). The films that make up the multilayer are stacked in a quasiperiodic pattern, following the Fibonacci and double period sequences. We used a phenomenological theory taking into account: the Zeeman energy (between the ferromagnetic films and the external magnetic field), the energy of the magneto-crystalline anisotropy (present in the ferromagnetic films), the energy of the bilinear and biquadratic couplings (between the ferromagnetic films) and the energy of the dipole-dipole interaction (between the ferromagnetic films), to describe the system. The total magnetic energy of the system is numerically minimized and the equilibrium angles of the magnetization of each ferromagnetic film are determined. We solved the equation of motion of the multilayer to find the dispersion relation for the system and, as a consequence, the spin waves modes frequencies. Our theoretical results show that, in the case of trilayers (Fe/Cr/Fe), our model reproduces with excellent agreement experimental results of Brillouin light scattering, known from the literature, by adjusting the physical parameters of the nanofilms. Furthermore, we generalize the model to N ferromagnetic layers which allowed us to determine how complex these systems become when we increase the number of components. It is worth noting that our theoretical calculations generalize all the results known from the literature

Propriedades estáticas e dinâmicas de multicamadas magnéticas acopladas quasiperiodicamente

In this work we study, for two different growth directions, multilayers of nanometric magnetic metallic lms grown, using Fibonacci sequences, in such a way that the thickness of the non-magnetic spacer may vary from a pair of lms to another. We applied a phenomenological theory that uses the magnetic energy to describe the behavior of the system. After we found numerically the global minimum of the total energy, we used the equilibrium angles to obtain magnetization and magnetoresistance curves. Next, we solved the equation of motion of the multilayers to nd the dispersion relation for the system. The results show that, when spacers are used with thickness so that the biquadratic coupling is strong in comparison to the bilinear one, non usual behaviors for both magnetization and magnetoresistance are observed. For example, a dependence on the parity of the Fibonacci generation utilized for constructing the system, a low magnetoresistance step in low external magnetic fields and regions that show high sensibility to small variations of the applied field. Those behaviors are not present in quasiperiodic magnetic multilayers with constant spacer thickness

Buraco negros, correspondência AdS/BCFT e fluido/gravidade

Einstein’s equations with negative cosmological constant possess the so-called anti de Sitter space, AdSd+1, as one of its solutions. We will later refer to this space as to the "bulk". The holographic principle states that quantum gravity in the AdSd+1 space can be encoded by a d−dimensional quantum field theory on the boundary of AdSd+1 space, invariant under conformal transformations, a CFTd. In the most famous example, the precise statement is the duality of the type IIB string theory in the space AdS5 × S 5 and the 4−dimensional N = 4 supersymmetric Yang-Mills theory. Another example is provided by a relation between Einstein’s equations in the bulk and hydrodynamic equations describing the effective theory on the boundary, the so-called fluid/gravity correspondence. An extension of the "AdS/CFT duality"for the CFT’s with boundary was proposed by Takayanagi, which was dubbed the AdS/BCFT correspondence. The boundary of a CFT extends to the bulk and restricts a region of the AdSd+1. Neumann conditions imposed on the extension of the boundary yield a dynamic equation that determines the shape of the extension. From the perspective of fluid/gravity correspondence, the shape of the Neumann boundary, and the geometry of the bulk is sourced by the energy-momentum tensor Tµν of a fluid residing on this boundary. Clarifying the relation of the Takayanagi’s proposal to the fluid/gravity correspondence, we will study the consistence of the AdS/BCFT with finite temperature CFT’s, or equivalently black hole geometries in the bulk.

Anisotropia magnética em nanofilmes com assimetria cristalográfica

This Thesis comprises a theoretical study about the influence of the magnetocrystalline anisotropy on the static and dynamic magnetic properties of nanofilms: monolayers and trilayers coupled through the bilinear and biquadratic exchange fields, for situations in which the systems are grown in unusual [hkl] asymmetric directions. Using a theory based on a realistic phenomenological model for description of nanometric systems, we consider the total free magnetic energy including the Zeeman interaction, cubic and uniaxial anisotropies, demagnetizing and surface anysotropy energies, as well as the exchange terms. Numerical calculations are conducted by minimizing the total magnetic energy from the determination of equilibrium static configurations. We consider experimental parameters found in the literature to illustrate our results for Fe/Cr/Fe trilayer systems. In particular, a total of six different magnetic scenarios are analyzed for three regimens of exchange fields and the [211] and [321] asymmetric growth directions. After numerically minimize the total energy, we use the equilibrium configurations to calculate magnetization and magnetoresistance curves with the respective magnetic phases and corresponding critical fields. These results are also used to establish the boundary for occurrence of saturated states. Within the context of the spin waves, we solve the equation of motion for these systems in order to find the respective associated dispersion relations. The results show similar magnetization and magnetoresistance curves for both [211] and [321] growth scenarios, including an equivalent magnetic transition behavior. However, the combination of those peculiar symmetries and influence of the exchange energies results in attractive properties, including the generation of magnetic states as a function of the asymmetric degree imposed in the [hkl] growth orientations. There is also an increasing incompatibility between the values of saturation fields of magnetization and magnetoresistance for the cases in which a magnetic field acts along intermediate cubic anisotropic axes, particularly in the situations where the bilinear and biquadratic exchange fields are comparable. The dispersion relations and static results are consistent, the corresponding magnetic states are also present in both acoustic and optical modes. Furthermore, Goldstone excitations are also observed for that particular cases of a magnetic field acting in the intermediate axes, an effect related to transitions of second order and to the spontaneous symmetry breaking imposed by the combination of the biquadratic energy with the cubic and uniaxial anisotropies.

A esquina do povo de alt’lam: aprimoramento racial e moral no movimento espírita natalense

A partir de um conjunto de dados obtidos em pesquisa, o texto deseja salientar uma face pouco examinada pelos estudiosos do espiritismo no Brasil: aquela dos grupos espíritas que cultuam extraterrestres. Examina a narrativa Rebelião de Lúcifer, escrita pelo médium potiguar Jan Val Ellam. Sustenta que esta atualiza noções importantes em relação a narrativas de salvação anteriores construídas pelo espiritismo. Destaca em especial o aprimoramento racial e moral através da reencarnação em distintos corpos humanos e em diferentes planetas. Examina-os a partir das noções de exílio planetário e de evolução racializada. Argumenta que Jan Val Ellam as atualiza através da categoria nativa Povo de Alt’Lam e através de bricolagem com outros campos semânticos, notadamente a ufologia e a fi cção científica

Twitter e ciberativismo: o movimento social da hashtag #ForaMicarla em Natal-RN

The spatial and temporal fluidity conditioned by the technologies of social interaction online have been allowing that collective actions of protest and activism arise every day in cyberspace - the cyber-activism. If before these actions were located in geographical boundaries, today's demands and mobilizations extrapolate the location, connect to the global, and at the same time, return to the regional through digital virtuality. Within this context of the relationship between digital technology and global flow of sociability, emerges in October 2010 the social movement of the hashtag "#ForaMicarla", which means the dissatisfaction of cibernauts from Natal of Twitter with the current management of the municipality of Natal-RN, Micarla de Sousa (Green Party). We can find in the center of this movement and others who appeared in the world at the same time a technological condition of Twitter, with the hashtag "#". Given this scenario, this research seeks to analyze how the relationship of the agents of movement hashtag "ForaMicarla", based on the principle that it was formed in the Twitter network and is maintained on the platform on a daily basis, it can create a new kind of political culture. Thus, this study discusses theoretically the importance of Twitter and movements that emerge on the platform and through it to understand the social and political demands of the contemporary world and this public sphere, which now seems to include cyberspace

Avaliação das pressões respiratórias máximas em crianças e adolescentes da grande Natal: elaboração de uma equação preditiva

The human respiratory system was so designed that would allow efficient ventilation, regardless of variations in the external environment that may hinder the act of breathing, such an act involves dozens of variables, among them we find the respiratory depression, which is nothing more than respiratory muscle strength. The pressures are widely used in several cases: Neuro-muscular; evolution of pulmonary dysfunction and a predictor for discontinuation of mechanical ventilation. Therefore it was proposed to carry out evaluations of these respiratory pressures for children and adolescents aged 10 to 16 years and propose a predictive equation that involves the anthropometric variables age (A, years), body mass (BM, kilograms) and height (H, meters) with maximal respiratory pressures (maximum inspiratory and expiratory pressure). Evaluations were performed in this age group of students in public and private schools of the Grande Natal , measurements were performed using the analogue manometer, were children and adolescents and their parents gave informed consent. 517 samples were taken, and 250 for males (M), 255 for females (F) and 12 were excluded according to our exclusion criteria. The sample was subdivided into three age groups (10-11, 12-13 and 14 to 16 years old). It was found through the student s t test (p ≤ 0.05) for all variables studied, children and male adolescents had higher means than females, except for the MC. For the correlation between the variables found significant correlation (p <0.05) among all the variables when analyzed as pairs except between MIP and height for females. The development of predictive equations (for p ≤ 0.05) based on three types of strategies adopted were restricted to two association between anthropometric variables isolated, resulting in: for males: MIP = -32.29 + (-2.11*A) + (-0.52*BM), MIP = 9.99 + (-0.36*BM) + (-49.40*H); MEP = 18.54 + 3.53*A + 0, 42*BM, MEP = -33.37 + 2.78*A + 52.18* H, MEP = -17.39 + 0.33*BM + 55.04*H; and, for females we find: MEP = 24.32 + 2.59 * A + 0.24*BM

Juventude universitária nos anos 1980: as práticas culturais do movimento estudantil na UFRN

The 1980s, at UFRN represented a moment of resumption of student struggles. The major goals of the student movement in this period was the fight against the authoritarian regime and for the democracy within and outside the university. In this context, events, activities, artistic and cultural productions were organized in order to make a critical policy for the procedure, trying to establish a dialogue between the university community and the population. Our work has made a research on cultural practices of the student movement in the 1980s. We did an analysis on the process of democratic transition in Brazil, the political participation of youth, their cultural practices in the country, society and politics in the RN, the student movement at UFRN and its cultural practices. We also discussed the concept of culture and cultural practices, but also pointed each of the the main activities and cultural productions organized by students of UFRN in that period. As methodological resource, were used the oral sources, the academic literature on the subject and newspaper pieces, newsletters and advertisement material of the students

Organização e institucionalização política do movimento negro de Uberlândia(MG)

Este trabajo forma parte de una investigación cualitativa empírica que se ha realizado con el Movimiento Negro en Brasil, sobre todo en Uberlandia (MG), en busca de Políticas Públicas para la Promoción de la Igualdad Racial y sus conflictos históricos con la sociedad brasileña entre los años 1980 , 1990 y 2009. En cuanto a los objetivos generales destacan la variación en la forma de organización social y política de la comunidad Uberlandense negro, ya que es un ejemplo de los patrones de producción de la organización política y las correlaciones entre las múltiples formas de organización política de la población por la política pública Promoción de la Igualdad Racial, aprobada por el legislativo y constitucional

Escrever o movimento: o cinema itinerante como reinvenção de uma estética do viver

La tesis parte del presupuesto que el cine ofrece la imensa capacidad de entretejer de forma compleja realidad e imaginación. Con eso sugerimos que tal cual una "escuela de vida", según la definición de Edgar Morin (2003), el cine, por medio de sus producciones y exibiciones, pude ser capaz de operar un movimiento de reinvención de una estética del vivir en el espacio de lo improbable. De ahi surge la pregunta: ¿Cómo un fenómeno artístico, estético e imagético puede realizar tal movimiento? Tomando como referencia el guión de vida del personaje de la vida real José Isaias de Lucena Filho, más conocido por Zezeco, encontramos pistas de esa reinvención. Residente de una pequeña ciudad del interior de la província de Rio Grande do Norte, llamada Ouro Branco, en la década del 1960, se desplazó hacia el centro-sur de Brasil y retornó a su lugar de partida con la idea de trabajar proyectando peliculas. De manera singular y plural, este sujeto asumió el riesgo y la incertidumbre de enfrentar determinismos sociales, climáticos y culturales para proponer nuevas simbolizaciones por medio del cine itinerante. La presencia del séptimo arte en pequeñas ciudades de hábitos rurales marcadas por la miséria, el hambre, la negligéncia, el coronelismo político y los problemas climáticos, alteró escenários, actualizó mitos y proporcionó nuevas interacciones entre los sujetos. Zezeco entró en las cifras del éxodo rural y emigró hacia Rio de Janeiro, pero su éxodo fue cinematográfico, porque le sirvió como base para la inserción de efectos especiales fantásticos y poéticos en guiones de vidas inmersas en lo trivial y lo contingente. Tal cual un cinematógrafo vivo, capturó el escenário cultural efervescente de Rio de Janeiro y lo proyectó en la pequeña ciudad de Ouro Branco y en otras ciudades del interior de las províncias de Rio Grande do Norte y Paraiba. Con ello le atribuyó un nuevo uso a la vida de su lugar de partida y de retorno. Actuó en la ambiguedad, la ambivalencia y la complejidad entre el sapiens e el demens; real e imaginario; prosa y poesia de la vida; razón y pasión; racional y simbólico; lógico y mítico. El alcance de la investigación contempla entrevistas, memória, registros manuscritos y fotografías de colección particular de habitantes de la ciudad de Ouro Branco-RN. Como referenciales teóricos principales, tenemos las obras de Edgar Morin sobre el cine y de otros autores como Giorgio Agamben y Maria da Conceição de Almeida que expanden la comprensión sobre el entreejido de realidad e imaginación, vida e ideas

Bricolagem e magia das imagens em movimento: o cinema de Moustapha Alassane

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Estimativas de mortalidade para a região nordeste do Brasil em 2010: uma associação do método demográfico equação geral de balanceamento, com o estimador bayesiano empírico

One of the greatest challenges of demography, nowadays, is to obtain estimates of mortality, in a consistent manner, mainly in small areas. The lack of this information, hinders public health actions and leads to impairment of quality of classification of deaths, generating concern on the part of demographers and epidemiologists in obtaining reliable statistics of mortality in the country. In this context, the objective of this work is to obtain estimates of deaths adjustment factors for correction of adult mortality, by States, meso-regions and age groups in the northeastern region, in 2010. The proposal is based on two lines of observation: a demographic one and a statistical one, considering also two areas of coverage in the States of the Northeast region, the meso-regions, as larger areas and counties, as small areas. The methodological principle is to use the General Equation and Balancing demographic method or General Growth Balance to correct the observed deaths, in larger areas (meso-regions) of the states, since they are less prone to breakage of methodological assumptions. In the sequence, it will be applied the statistical empirical Bayesian estimator method, considering as sum of deaths in the meso-regions, the death value corrected by the demographic method, and as reference of observation of smaller area, the observed deaths in small areas (counties). As results of this combination, a smoothing effect on the degree of coverage of deaths is obtained, due to the association with the empirical Bayesian Estimator, and the possibility of evaluating the degree of coverage of deaths by age groups at counties, meso-regions and states levels, with the advantage of estimete adjustment factors, according to the desired level of aggregation. The results grouped by State, point to a significant improvement of the degree of coverage of deaths, according to the combination of the methods with values above 80%. Alagoas (0.88), Bahia (0.90), Ceará (0.90), Maranhão (0.84), Paraíba (0.88), Pernambuco (0.93), Piauí (0.85), Rio Grande do Norte (0.89) and Sergipe (0.92). Advances in the control of the registry information in the health system, linked to improvements in socioeconomic conditions and urbanization of the counties, in the last decade, provided a better quality of information registry of deaths in small areas

Movimento de borboletas frugívoras e conectividade funcional em uma paisagem de Mata Atlântica

An organisms movement within and between habitats is an essential trait of life history, one that shapes population dynamics, communities and ecosystems in space and time. Since the ability to perceive and react to specific conditions varies greatly between organisms, different movement patterns are generated. These, in turn, will reflect the way species persist in the original habitat and surrounding patches. This study evaluated patterns of movement of frugivorous butterflies in order to estimate the connectivity of a landscape mosaic in an area of Atlantic Forest. For this purpose, we used the capture-mark-recapture method on butterflies trapped with fermented fruit bait in three distinct habitats. The first represents a typical Atlantic forest fragment, while the other two represent man-made matrix habitats. One contains a coconut plantation and the other a plantation of the exotic Acacia mangium species. Five traps were randomly placed in each landscape unit in areas of 40 x 40m. Using recapture data and relating it to distance between captures and habitat structure, I found that movement frequencies, both within and between landscape units were different for the analyzed species, suggesting that they do not interpret and react to the landscape in the same way. Thus this study was able to measure landscape functional connectivity. For most species, the exchange between forest and coconut plantations occurred with low frequency compared to exchanges between the forest and acacia plantations, which share more structural similarities. This seems to indicate that a matrix that is more similar to patches of native vegetation can shelter species, permit their movement and, consequently, contribute to the landscape connectivity