Calculation of electric fields induced by body and head motion in high-field MRI

In modern magnetic resonance imaging (MRI), patients are exposed to strong, nonuniform static magnetic fields outside the central imaging region, in which the movement of the body may be able to induce electric currents in tissues which could be possibly harmful. This paper presents theoretical investigations into the spatial distribution of induced electric fields and currents in the patient when moving into the MRI scanner and also for head motion at various positions in the magnet. The numerical calculations are based on an efficient, quasi-static, finite-difference scheme and an anatomically realistic, full-body, male model. 3D field profiles from an actively shielded 4T magnet system are used and the body model projected through the field profile with a range of velocities. The simulation shows that it possible to induce electric fields/currents near the level of physiological significance under some circumstances and provides insight into the spatial characteristics of the induced fields. The results are extrapolated to very high field strengths and tabulated data shows the expected induced currents and fields with both movement velocity and field strength. (C) 2003 Elsevier Science (USA). All rights reserved.

Influence of magnetically-induced E-fields on cardiac electric activity during MRI: A modeling study

In modern magnetic resonance imaging (MRI), patients are exposed to strong, time-varying gradient magnetic fields that may be able to induce electric fields (E-fields)/currents in tissues approaching the level of physiological significance. In this work we present theoretical investigations into induced E-fields in the thorax, and evaluate their potential influence on cardiac electric activity under the assumption that the sites of maximum E-field correspond to the myocardial stimulation threshold (an abnormal circumstance). Whole-body cylindrical and planar gradient coils were included in the model. The calculations of the induced fields are based on an efficient, quasi-static, finite-difference scheme and an anatomically realistic, whole-body model. The potential for cardiac stimulation was evaluated using an electrical model of the heart. Twelve-lead electrocardiogram (ECG) signals were simulated and inspected for arrhythmias caused by the applied fields for both healthy and diseased hearts. The simulations show that the shape of the thorax and the conductive paths significantly influence induced E-fields. In healthy patients, these fields are not sufficient to elicit serious arrhythmias with the use of contemporary gradient sets. However, raising the strength and number of repeated switching episodes of gradients, as is certainly possible in local chest gradient sets, could expose patients to increased risk. For patients with cardiac disease, the risk factors are elevated. By the use of this model, the sensitivity of cardiac pathologies, such as abnormal conductive pathways, to the induced fields generated by an MRI sequence can be investigated. (C) 2003 Wiley-Liss, Inc.

Applied physiology and game analysis of rugby union

Increased professionalism in rugby has elicited rapid changes in the fitness profile of elite players. Recent research, focusing on the physiological and anthropometrical characteristics of rugby players, and the demands of competition are reviewed. The paucity of research on contemporary elite rugby players is highlighted, along with the need for standardised testing protocols. Recent data reinforce the pronounced differences in the anthropometric and physical characteristics of the forwards and backs. Forwards are typically heavier, taller, and have a greater proportion of body fat than backs. These characteristics are changing, with forwards developing greater total mass and higher muscularity. The forwards demonstrate superior absolute aerobic and anaerobic power, and Muscular strength. Results favour the backs when body mass is taken into account. The scaling of results to body mass can be problematic and future investigations should present results using power function ratios. Recommended tests for elite players include body mass and skinfolds, vertical jump, speed, and the multi-stage shuttle run. Repeat sprint testing is a possible avenue for more specific evaluation of players. During competition, high-intensity efforts are often followed by periods of incomplete recovery. The total work over the duration of a game is lower in the backs compared with the forwards; forwards spend greater time in physical contact with the opposition while the backs spend more time in free running, allowing them to cover greater distances. The intense efforts undertaken by rugby players place considerable stress on anaerobic energy sources, while the aerobic system provides energy during repeated efforts and for recovery. Training should focus on repeated brief high-intensity efforts with short rest intervals to condition players to the demands of the game. Training for the forwards should emphasise the higher work rates of the game, while extended rest periods can be provided to the backs. Players should not only be prepared for the demands of competition, but also the stress of travel and extreme environmental conditions. The greater professionalism of rugby union has increased scientific research in the sport; however, there is scope for significant refinement of investigations on the physiological demands of the game, and sports-specific testing procedures.

A comparison of the whole-body and segmental methodologies of bioimpedance analysis

Theory supports the use of a segmental methodology (SM) for bioimpedance analysis (BIA) of body water (BW). However, previous studies have generally failed to show a significant improvement when the SM is used in place of a whole-body methodology. A pilot study was conducted to compare the two methodologies in control and overweight subjects. BW of each subject was measured by D2O dilution and also estimated from BIA measurements. Bland and Altman analysis was used to compare the two values of BW. The SM resulted in a small but not significantly improved limits of agreement of measured and BIA estimated BW (psimilar to0.3). This and the results of previous studies suggest that improvements in prediction of BW obtained from application of the SM may be intrinsically small and may not justify the additional effort in application.

Performing race, culture, and gender in an Indigenous Australian women's music and dance classroom

One perpetual concern among Indigenous Australian peoples is authenticity of voice. Who has the right to speak for, and to make representations about, the knowledges and cultures of Indigenous Australian peoples? Whose voice is more authentic, and what happens to these ways of knowing when they make the journey into mainstream Western academic classrooms? In this paper, I examine these questions within the politics of “doing” Indigenous Australian studies by focusing on my own experiences as a lecturer in the Aboriginal and Torres Strait Islander Studies Unit at the University of Queensland. My findings suggest that representation is a matter of problematizing positionality and, from a pedagogical standpoint, being aware of, and willing to address, the ways in which power, authority, and voice are performed and negotiated as teachers and learners of Indigenous Australian studies.

Para além do arco-íris : a construção social da mulher e as experiências da transexualidade

O objetivo central desta pesquisa é propor uma abordagem socioantropológica do fenômeno da transexualidade, na sociedade ocidental contemporânea, a partir da análise das “trajetórias de vida” de quatro mulheres que vivenciam a transexualidade, residentes na Grande Vitória - ES, com o intuito de compreendermos as suas visões de mundo e projetos de vida, constituídos em meio a uma heteronormatividade pungente. A metodologia utilizada foi a História de Vida, tendo como objetivo primeiro a percepção dos elementos que são recorrentes na construção social dessa mulher. Os meus contatos com essas mulheres se deram a partir de 2012 até os primeiros meses de 2014. Além das histórias de vida, utilizei algumas entrevistas e dados jornalísticos de mulheres na transexualidade, que ganharam notoriedade na sociedade brasileira nos últimos anos. Inicialmente, foi realizada uma revisão bibliográfica sobre as noções de gênero e seus impactos na sociedade ocidental, assim como o do fenômeno da transexualidade. A partir das histórias de vida e dos dados jornalísticos busquei interpretar os elementos que são invocados para a construção social da mulher nas experiências da transexualidade, analisando os eventos que são recorrentes em suas vidas, tendo como pressuposto a noção de que essa experiência, em nossa sociedade, é entendida como “comportamento desviante”.As análises das histórias de vida tiveram como referência primeira o conceito de projeto proposto por Alfred Schutz e revistado por Gilberto Velho.Outro foco de análise dessa pesquisa é a produção da “feminilidade”, a partir do corpo, levando em consideração que essa é uma dimensão muito importante nesse processo de tornar-se mulher,buscando a compreensão das representações de corpo e gênero na produção dessa identidade. De forma geral, pretende-se desvelar o processo de construção social da pessoa pelo qual essas mulheres passam e o modo como se percebem nas relações sociais que estabelecem em sua vida cotidiana, como também o lugar social que elas tendem a ocupar na sociedade ocidental, principalmente na brasileira.

Pectus Excavatum postsurgical outcome based on preoperative soft body dynamics simulation

Pectus excavatum is the most common congenital deformity of the anterior chest wall, in which an abnormal formation of the rib cage gives the chest a caved-in or sunken appearance. Today, the surgical correction of this deformity is carried out in children and adults through Nuss technic, which consists in the placement of a prosthetic bar under the sternum and over the ribs. Although this technique has been shown to be safe and reliable, not all patients have achieved adequate cosmetic outcome. This often leads to psychological problems and social stress, before and after the surgical correction. This paper targets this particular problem by presenting a method to predict the patient surgical outcome based on pre-surgical imagiologic information and chest skin dynamic modulation. The proposed approach uses the patient pre-surgical thoracic CT scan and anatomical-surgical references to perform a 3D segmentation of the left ribs, right ribs, sternum and skin. The technique encompasses three steps: a) approximation of the cartilages, between the ribs and the sternum, trough b-spline interpolation; b) a volumetric mass spring model that connects two layers - inner skin layer based on the outer pleura contour and the outer surface skin; and c) displacement of the sternum according to the prosthetic bar position. A dynamic model of the skin around the chest wall region was generated, capable of simulating the effect of the movement of the prosthetic bar along the sternum. The results were compared and validated with patient postsurgical skin surface acquired with Polhemus FastSCAN system

Effects of Age-Related Cognitive Deficits on EEG Phase Coherence

Body and brain undergo several changes with aging. One of these changes is the loss of neuroplasticity, which leads to the decrease of cognitive abilities. Hence the necessity of stopping or reversing these changes is of utmost importance to contemporary society. In the present work, electroencephalogram (EEG) markers of cognitive decline are sought whilst the subjects perform the Wisconsin Card Sorting Test (WCST). Considering the expected age-related cognitive deficits, WCST was applied to young and elder participants. The results suggest that coherence on theta and alpha EEG rhythms decrease with aging and increase with performance. Additionally, theta phase coherence seems more sensitive to performance, while alpha synchronization appears as a potential ageing marker.

Contemporary issues in the government and administration of Latin American megacities

This paper is the first to systematically analyze and compare the structures of city governance and administration for seven major cities in Latin America, four of which are megacities (population of over 10 million), and three others are large national capitals. U.S. and U. K. models of city administration are reviewed as baseline models against which differences in Latin American may be explored. Structures of Government in Latin America show several important features and trends: 1) the lack of metropolitan (cross jurisdictional) authority; 2) the existence of strong mayors and weak councils"; 3) high levels of partisanship; 4) overlapping rather than interlocking bureaucracies; 5) pressures towards the privatization of city services, but continuing tension over the desirability of public versus private control; 6) greater fiscal responsibility and autonomy; and 7), a continuing marginalization of public participation in megacity governance.In spite of these features, many cities throughout the region (regardless of whether they are megacity size or national capitals), are actively intensifying their efforts to develop more effective, accountable and democratic governance structures.

Recensao de: I. K. Healy, Social Work Practices: Contemporary Perspectives on Change, London, Sage, 2000.

Revista Lusófona de Ciências Sociais

The process of implementing answerability in contemporary Brazil

Abstract: The aim of this study was to characterize the trajectory of answerability in Brazil. In the light of studies based on the historical neo-institutionalism approach, formal institutional changes adopted at federal level between 1985 and 2014, and which favor the typical requirements of answerability - information and justification - were identified and analyzed through the content analysis technique. The conclusion is that the trajectory of answerability in contemporary Brazil can be characterized as continuous, primarily occurring through the layering strategy, and whose leitmotif, since its origin, has consisted of matters of financial and budgetary nature. Nevertheless, a recent influence of deeper democratic subjects on it has been observed.