Fases magnéticas de sistemas nanoestruturados de terras-raras

There is presently a worldwide interest in artificial magnetic systems which guide research activities in universities and companies. Thin films and multilayers have a central role, revealing new magnetic phases which often lead to breakthroughs and new technology standards, never thought otherwise. Surface and confinement effects cause large impact in the magnetic phases of magnetic materials with bulk spatially periodic patterns. New magnetic phases are expected to form in thin film thicknesses comparable to the length of the intrinsic bulk magnetic unit cell. Helimagnetic materials are prototypes in this respect, since the bulk magnetic phases consist in periodic patterns with the length of the helical pitch. In this thesis we study the magnetic phases of thin rare-earth films, with surfaces oriented along the (002) direction. The thesis includes the investigation of the magnetic phases of thin Dy and Ho films, as well as the thermal hysteresis cycles of Dy thin films. The investigation of the thermal hysteresis cycles of thin Dy films has been done in collaboration with the Laboratory of Magnetic Materials of the University of Texas, at Arlington. The theoretical modeling is based on a self-consistent theory developed by the Group of Magnetism of UFRN. Contributions from the first and second neighbors exchange energy, from the anisotropy energy and the Zeeman energy are calculated in a set of nonequivalent magnetic ions, and the equilibrium magnetic phases, from the Curie temperature up to the Nèel temperature, are determined in a self-consistent manner, resulting in a vanishing torque in the magnetic ions at all planes across the thin film. Our results reproduce the known isothermal and iso-field curves of bulk Dy and Ho, and the known spin-slip phases of Ho, and indicate that: (i) the confinement in thin films leads to a new magnetic phase, with alternate helicity, which leads to the measured thermal hysteresis of Dy ultrathin films, with thicknesses ranging from 4 nm to 16 nm; (ii) thin Dy films have anisotropy dominated surface lock-in phases, with alignment of surface spins along the anisotropy easy axis directions, similar to the known spin-slip phases of Ho ( which form in the bulk and are commensurate to the crystal lattice); and (iii) the confinement in thin films change considerably the spin-slip patterns of Ho.

Propriedades magnéticas de nanopartículas de ferro em substratos antiferromagnéticos

The effect of finite size on the magnetic properties of ferromagnetic particles systems is a recurrent subject. One of the aspects wide investigated is the superparamagnetic limit where the temperature destroys the magnetic order of ferromagnetic small particles. Above the block temperature the thermal value of the magnetic moment of the particle vanishes, due to thermal fluctuations. The value of the blocking temperature diminishes when the size of the particle is reduced, reflecting the reduction of the anisotropy energy barrier between the uniform states along the uniaxial axis. The increasing demand for high density magnetic media has recently attracted great research interest in periodic arrangements of nanometric ferromagnetics particles, approach in the superparamagnetic limit. An interesting conjecture is the possibility of stabilization of the magnetic order of small ferromagnetic particles (F) by interface coupling with antiferromagnetic (AF) substrate. These F/AF systems may also help to elucidate some details of the effect of exchange bias, because the effect of interface roughness and the paper of domain walls, either in the substrate or the particle, are significantly reduced. We investigate the magnetic phases of small ferromagnetic particles on a antiferromagnetic substrate. We use a self-consistent local field method, incorporating the interface field and the dipole interaction between the spins of the ferromagnetic particle. Our results indicate that increasing the area of the interface favors the formation of the uniform state. Howere above a critical height value appears a state non-uniform is formed where the spins of in the particle s free surface are rotated with respect to the interface spins direction. We discuss the impact of the competition between the dipolar and interface field on the magnetic charge, that controls the field of flux leakage of the particle, and on the format of the hysteresis curves. Our results indicate that the liquid magnetic charge is not a monotonically increasing function of the height of the particle. The exchange bias may display anomalous features, induced for the dipolar field of the spins near the F/AF interface

New developmental stages for common marmosets (Callithrix jacchus) using mass and age variables obtained by K-means algorithm and self-organizing maps (SOM)

LEÃO, Adriano de Castro; DÓRIA NETO, Adrião Duarte; SOUSA, Maria Bernardete Cordeiro de. New developmental stages for common marmosets (Callithrix jacchus) using mass and age variables obtained by K-means algorithm and self-organizing maps (SOM). Computers in Biology and Medicine, v. 39, p. 853-859, 2009

A coordenação pedagógica e o processo de inclusão do aluno com necessidade educacionais especiais:Um estudo de caso

The school inclusion presents a number of challenges that has been mobilizing initiatives and studies about its effectiveness. If on one hand in such studies and initiatives it becomes important to emphasize on the role and training of teachers, on the other, there is few studies about the role (and performance) of the pedagogical coordination in face of this process. In this sense, this research focuses on the role of educational coordination in face of the school inclusion of students with Special Educational Needs (SEN) and it undertakes the following study s questions: has the action by the coordinator contributed to the process of including students with Special Educational Needs? How is it presented in the process of inclusion of students with SEN in regular education? And it aims to: investigate the role of the pedagogical coordinator in the process of inclusion of students with Special Educational Needs of Primary Education at regular schools; and to analyze the limits and possibilities of the coordinator actions in the process of inclusion of students with SEN. For the effectiveness of the research, a state school of Elementary School located at the city of Natal/RN was taken as an empiric field. It was selected as research subjects 4 coordinators, 2 teachers of the Multifunctional Resources Room and 2 teachers of 6th to 9th grades. The methodological approach that was used in this research is consistent with the qualitative approach, and it is configured as a case study, as it is understood that this type of research responds to the objective of the study, assuming the observation of everyday school life, the educational document analysis and interviews with the subjects as procedures and tools to build data. The construction and analysis of the data were followed by a dialogue with the literature dedicated to coordinating education and school enrollment. Considering the responsibilities of the contemporary pedagogical coordination due to the challenges and possibilities of schooling for all students, specially regarding to what is referred as collaborative work and ongoing training of teachers, this study points out to the lack of an articulated action related to the school inclusion process, considering the monitoring of the teaching activity and its dialogue with the Multifunctional Resources Room. Moreover, the emphasis on meeting the daily school routines and the compliance with bureaucratic procedures, put it into second, restructuring of the Political-Pedagogical and the possibility of mobilization of school around the problematization and systematization of an inclusive school project. The effectiveness of school s inclusion, therefore, implies the scaling of the functions of the pedagogical coordination, as well as the reorganization of the school it self, to ensure the mediation of collaborative actions, contemplating the teachers continuing education, having as a landmark difficulties, problems and experiences constructed in the school context

A constituição da identidade em crianças vítimas de abuso sexual

Subject s identity is constituted in the relation with the other, which is characterized by dialeticity, and is configured as an identification and/or recognize movement, and strangeness and/or distance. In social interactions, people with whom subject relates himself assign meanings to him and, from these, the subject will ressignify, producing sense about himself. In other words, is through these interactions that subjects organizes themselves, recognize what is yours, and acquire the sense about themselves. It can be highlighted, too, the social-historic context s importance in the self-constitution process, whereas, from this, the subject produces particular forms of perception about reality charged with cultural meaning. Thus, the self-conception, the manners of thinking, of being, of relates, of take position against experiences, coming from values internalization, roles and related, are permeated by the manner witch the others relates themselves with the subject. However, when the relation with the other happens to be in a violent way, like in children sexual abuse, there are implications in the subjects constitution, whereas violates his physical and psychological integrities, as well as the rights of dignity, respect and even healthy physical, psychological and sexual developments. Therefore, this work aims to investigate how the identity process is constituted in children victims of sexual abuse. As specific aims the research proposes: 1) to characterize the relations between child and abuser, before and after the abuse act; 2) to identify images that the subjects, abuse victims, have about themselves and; 3) to identify the features of subject s relation with their own body. Toward this aims, procedures involving drawings, painting, collage, photography, activities with cardboard, colored pens, glue and tissue snips. The research took place at the Social Assistance Specialized Reference Center, where there is the treatment of children who suffered of rights violation, which includes sexual abuse. The research subjects were 3 girl children, between 6 and 10 years old, victims of sexual abuse. The corpus analyses was done through Thematic Content Analysis, structured in three meaning nucleus: 1) self-reference without the explicit attendance of other s discourse; 2) self-reference with the explicit attendance of other s discourse; 3) The other abuser. The analysis indicates that children, research subjects, have deteriorated images about themselves, about their bodies, which is consistent with the studies in the children and adolescents sexual violence field. In the other hand, were identified, too, self-references with positive values in the cases with mention about their way-of-being, which can be read as important to subject s development. About the other s discourse towards the subjects, were identified positive observations and found that these can contribute to subject s self-image reorganization. The contribution of negative comments, on the other hand, was showed in a more clear and incisive form in subject s constitution. There is, yet, an overvaluation of the other s discourse, so the meanings attributed toward them by the other are internalized, overshadowing the self-appreciation. To conclude, it can be highlighted that the need of psychological accompaniment of the children victims of sexual abuse, based on the possibility of this trauma experience elaboration, trying to overcome, as well as can be expected that this research s results contributes to the practices of professionals who work with subjects who have their rights violated

Estudo geológico e geofísico da falha de carnaubais, Bacia Potiguar-RN, e implicações neotectônicas

The segment of Carnaubais Fault located in the southeasthern portion of Guamaré Graben (Potiguar Basin) was studied. Several structures were detected and some of them strongly suggest that the last movements in Carnaubais Fault are of Neotectonic age. The study comprises an integrated interpretation of geologic, geomorphologic and geophysical data (gravimetry, magnetometry, resistivity, and self potential methods). According to the size of the studied areas, two approaches were used in this research. The first approach is of a regional nature and was conducted in an area, hereafter named Regional Area, having approximately 6,000 km2 and localized in the northern portion of Rio Grande do Norte state, around Macau city. The second approach comprises detailled studies of two small areas inside the Regional Area: the Camurupim and São Bento areas. Gravimetric and topographic data were used in the Regional Area. A separation into regional and residual components were conducted both on gravimetric and topographic data. The interpretation of the residual component of the gravimetric data allows a precise mapping of the borders of the Guamaré Graben. The regional component features of the topographic data are controlled by the pair of conjugate faults composed by the Carnaubais Fault (NE direction) and the Afonso Bezerra Fault (NW direction). On the other hand, the residual component of the topographic data shows that river valleis of NW direction are sharply interrupted where they intersect Carnaubais Fault. This fact is interpreted as an evidency that the last significant moviments occured in the Carnaubais Fault. Geologic, geomorphologic and geophysical data (magnetometry, resistivity, and self potential methods) were used in the Camurupim Area. The geologic mapping allows to identify five lithophacies unities. The first two unities (from base to top) were interpreted as composing a marine (or transitional) depositional sequency while the other were interpreted is composing a continental depositional sequence. The two sequences are clearly separated of an erosional discordance. The unities grouped in the marine sequence are composed by calcarenites (Unity A) and mudstones (Unity B). Unity A was deposited in a shalow plataform while Unity B, in a tidal flat. The unities grouped in the continental sequence are composed of conglomerate (Unity C) and sandstones (Unities D and E). Unities C and D are fluvial deposits while unity E is an eolian deposit. Unities A and B can be stratigraphycally correlated with Guamaré Formation. Unities C and D present three possible correlations. They may be correlated with Tibau Formation; or with Barreiras Formation; or with a clastic sediment deposit, commonly found in some rivers of Rio Grande do Norte state, and statigraphycally positioned above Barreiras Formation. Based on the decrease of the grain sizes from base to top both on unities C and D, it is proposed that these unities are correlated with the clastic sediment above mentioned. In this case, these unities would have, at least, Pleistocenic age. Finally, it is proposed that Unity E represent an eolian deposit that sufferred recent changes (at least in the Quaternary). The integrated interpretation of hydrographic, morphologic and geophysical data from Camurupim Area shows that Carnaubais Fault is locally composed by a system of several paralel subvertical faults. The fault presenting the larger vertical slip controls the valley of Camurupim river and separates the area in two blocks; in the nothern block the top of the Jandaira limestone is deeper than in the southern block. In addition, at least one of the faults in the northern block is cutting the whole sedimentary section. Because unities C , D, and/or E may be of Quaternary age, tectonic moviments possibly occured in Carnaubais Fault during this period. Detailled geologic mapping were conducted in beachrocks found in São Bento Area. This area is located at the intersection of the coast line with the Carnaubais Fault. The detected structures in the beachrocks are very similar to those caused by fragile deformations. The structures mapped in the beachrocks are consistent with a stress field with maximun compressional stress in E-W direction and extensional stress in the N-S direction. Since the Carnaubais Fault has a NE direction, it is optimally positioned to suffer tectonic movements under the action of such stress field. In addition, the shape of the coastal line appear to be controlled by the Carnaubais Fault. Furthemore, the observed structures in Camurupim Área are consistent with this stress field. These facts are interpreted as evidences that Carnaubais Fault and beachrocks suffered coupled tectonic movements. These moviments are of Neotectonic age because the beachrocks present ages less than 16,000 years

New developmental stages for common marmosets (Callithrix jacchus) using mass and age variables obtained by K-means algorithm and self-organizing maps (SOM)

LEÃO, Adriano de Castro; DÓRIA NETO, Adrião Duarte; SOUSA, Maria Bernardete Cordeiro de. New developmental stages for common marmosets (Callithrix jacchus) using mass and age variables obtained by K-means algorithm and self-organizing maps (SOM). Computers in Biology and Medicine, v. 39, p. 853-859, 2009