Numerical Simulations and Analysis of Thermally Excited Waves in Plasma Crystals

A numerical model for a 2D-monolayer plasma crystal was established using the Box_tree code. Box_tree is a Barnes_Hut tree code which has proven effective in modeling systems composed of large numbers of particles. Thermally excited waves in this plasma crystal were numerically simulated and dispersion relations for both the longitudinal and transverse wave modes were found. These were compared with the dispersion relations extrapolated from experiment as well as a theory based on harmonic approximation. The results were found to agree with theoretical dispersion relations under different wave propagation directions with different particle charges and over a range of 0.9<k<5.Comment: 7 pages, Presented at COSPAR '0

Uma Alternativa de Conteúdo para um Programa de Iniciação à Ginástica Artística: A Experiência do Canadá

Existem alguns programas de iniciação à Ginástica Artística nos quais técnicos e professores poderiam se basear para organizar o conteúdo do seu programa. Entre eles poderíamos destacar os trabalhos de MAGAKIAN (1978), CARRASCO (1977), RUSSELL & KINSMAN (1986) e LEGUET (1987). Entretanto, por desconhecimento ou por resistência às mudanças e novas abordagens, ainda continuam a definir o conteúdo de seus programas em uma série de habilidades no solo, na barra e no salto. Não podemos afirmar que a literatura referente à Ginástica Artística seja ampla e acessível a todos os técnicos e professores do Brasil. Uma possível justificativa para essa escassez seria a pouca popularidade desta modalidade se comparada a outros esportes como o futebol, voleibol, basquetebol, natação, etc. Mas, segundo DIANNO (1988), o número reduzido de pessoas envolvidas na modalidade seria um problema de “aparelhagem inadequada e escassa” e “material humano desqualificado”. Ainda segundo o mesmo autor, o pouco incentivo dos órgãos governamentais e dos clubes privados é que condicionou a Ginástica Artística do Brasil a esta situação precária. Entretanto, em nenhum momento o autor discutiu a competência e conhecimento das pessoas que orientam esse esporte ou fez menção à pouca literatura referente a esta área

Driven transverse shear waves in a strongly coupled dusty plasma

The linear dispersion properties of transverse shear waves in a strongly coupled dusty plasma are experimentally studied by exciting them in a controlled manner with a variable frequency external source. The dusty plasma is maintained in the strongly coupled fluid regime with (1 < Gamma << Gamma_c) where Gamma is the Coulomb coupling parameter and Gamma_c is the crystallization limit. A dispersion relation for the transverse waves is experimentally obtained over a frequency range of 0.1 Hz to 2 Hz and found to show good agreement with viscoelastic theoretical results.Comment: The manuscripts contains five pages and 6 figure

Gymnastics in higher education: reflections on assessment

Assessment procedures were based on the traditional educational paradigms of linearity and sequence, whose aim was to categorize and select individuals. With the advancement of Social and Human Sciences, assessments gained both a reflexive and an analytical characteristic and now they constitute a system of support and guidance for individual and group learning, all without losing sight of building character in the students. Supported by qualitative research, this study identified and discussed the assessments used by 14 university lecturers in the state of São Paulo who teach Gymnastics in the Physical Education undergraduate courses. The results showed different formats of assessment, namely: theoretical; debates; practical/experience; research; self-assessment and peer-review. None of the evaluated lecturers clearly stated the assessment criteria, becoming it, mainly, subjective. Four lecturers gave indication of using the assessment tools in the formative conception and only one lecturer guides its practice during the teaching-learning process after analyzing what has been detected in assessments.Os processos de avaliação tradicionais pautavam-se nos paradigmas educativos de linearidade e encadeamento, cujo objetivo era classificar e selecionar os indivíduos. Com o avanço do discurso das Ciências Humanas e Sociais, a avaliação ganhou um caráter reflexivo e analítico, e passou a se constituir em um sistema de apoio e orientação para as aprendizagens individuais e coletivas, e sem perder de vista a formação pessoal dos alunos. Apoiado na pesquisa qualitativa, o presente estudo identificou e discutiu as avaliações utilizadas por 14 docentes universitários do Estado de São Paulo que ministram as disciplinas de ginástica nos cursos de licenciatura em Educação Física. Os resultados evidenciaram diferentes formatos de avaliação, quais sejam: teórica; debates; prática/vivência pesquisa; autoavaliação e avaliação entre pares . Nenhum dos docentes esclareceram claramente os critérios de avaliação, ficando a mesma, sobretudo, subjetiva, quatro docente apontaram indícios de utilização dos instrumentos avaliativos na concepção formativa e apenas um docente orienta sua prática durante o processo de ensino-aprendizagem, após analisar o que foi detectado nas avaliações

Fine-Tuning of Mast Cell Activation by FcεRIβ Chain

Mast cells play a key role in allergic reaction and disorders through the high affinity receptor for IgE (FcεRI) which is primarily activated by IgE and antigen complex. In humans, mast cells express two types of FcεRI on the cell surface, tetrameric αβγ2 and trimeric αγ2, whereas in mice, the tetrameric αβγ2 type is exclusively expressed. In human allergic inflammation lesions, mast cells increase in number and preferentially express the αβγ2 type FcεRI. By contrast, in the lesion of non-allergic inflammation, mast cells mainly express the αγ2type. Since the β chain amplifies the expression and signaling of FcεRI, mast cell effector functions and allergic reaction in vivo are enhanced in the presence of the β chain. In contrast, a truncated β chain-isoform (βT) inhibits FcεRI surface expression. The human FcεRIβ gene contains seven exons and a repressor element located in the forth intron, through which FcεRIβ transcription is repressed in the presence of GM-CSF. Regarding the additional signal regulatory function of the β chain, the β chain ITAM has dual (positive and negative) functions in the regulation of the mast cell activation. Namely, the FcεRIβ chain ITAM enhances the mast cell activation signal triggered by a low-intensity (weak) stimulation whereas it suppresses the signal triggered by high-intensity (strong) stimulation. In an oxazolone-induced mouse CHS model, IgE-mediated mast cell activation is required and the β chain ITAM is crucially involved. Adenosine receptor, one of the GPCRs, triggers a synergistic degranulation response with FcεRI in mast cells, for which the β chain ITAM critically plays positive role, possibly reflecting the in vivo allergic response. These regulatory functions of the FcεRIβ ITAM finely tune FcεRI-induced mast cell activation depending on the stimulation strength, enabling the FcεRIβ chain to become a potential molecular target for the development of new strategies for therapeutic interventions for allergies

Investigating transport of dust particles in plasmas

An algorithm has been developped, which makes it possible to automatically extract trajectories of a large number of particles from fast imaging data, allowing a statistical analysis of particles trajectories under various plasma conditions, a better understanding of their influence on plasma properties, and a better characterization of the plasma itself. In this contribution, we focus on results obtained in a radiofrequency parallel plate reactor, where a large amount of micron-sized carbon dust is produced in situ. The use of the rescaled range analysis (R/S analysis) applied to dust particles displacements allows decomposing dust dynamic on different time scales. It is shown that dust displacement is dominated by collisions on short time scales whereas long term behaviour is strongly influenced by large scale plasma fluctuations.Comment: This version contains 8 pages and 5 figures. This work has been presented in the 1st Int. Conf. on Plasma Diagnostics, O8, April 12-16 2010, Pont-\`a-Mousson, France (2010). It has been submitted to Contribution to Plasma Physic

Detection of superoxide anion radical in phospholipid liposomal membrane by fluorescence quenching method using 1,3-diphenylisobenzofuran

AbstractUtilization of a fluorescence dye, 1,3-diphenylisobenzofuran (DPBF) as a detector of superoxide anion radical (O⋅−2) was examined. The fluorescence intensity of DPBF incorporated in phospholipid liposomes consisting of phosphatidylcholine (PC) and phosphatidylserine (PS) is effectively quenched by incubation with xanthine/xanthine oxidase system. On the other hand, xanthine or xanthine oxidase alone did not induce quenching of the DPBF fluorescence in the liposomes. Xanthine/xanthine oxidase-induced fluorescence quenching of DPBF-labeled liposomes was almost completely protected by the addition of superoxide dismutase (SOD, 1 U/ml), but not by heat-denatured SOD (10 min boiling) at the same concentration. On the other hand, catalase (1 U/ml), and hydroxyl radical and singlet oxygen scavengers (10 mM sodium benzoate, 300 mM mannitol, 1 mM tryptophan and 1 mM sodium azide) did not protect xanthine/xanthine oxidase-induced fluorescence quenching of DPBF-labeled liposomes. The concentration dependence profiles of xanthine oxidase on the DPBF fluorescence quenching and O⋅−2 generation showed that there is a good correlation between these parameters. Under the present experimental conditions, approximately 7 μM H2O2/30 min were produced, but the addition of H2O2 (1 mM) to DPBF-labeled liposomes did not quench the dye fluorescence in the liposomes. Temperature dependence profiles of the DPBF fluorescence quenching induced by xanthine/xanthine oxidase treatment and the excimer fluorescence formation of pyrene molecules embedded in the liposomal membrane suggested that the quenching efficiency of the DPBF fluorescence is largely dependent on their lipid dynamics. Based on these results, we proposed the possibility that DPBF fluorescence quenching method is able to be used as a simple method for detecting O⋅−2 inside the membrane lipid layer and that DPBF fluorescence quenching by O⋅−2 is controlled by the physical state of membrane lipids

Insights into the Function of the Unstructured N-Terminal Domain of Proteins 4.1R and 4.1G in Erythropoiesis

Membrane skeletal protein 4.1R is the prototypical member of a family of four highly paralogous proteins that include 4.1G, 4.1N, and 4.1B. Two isoforms of 4.1R (4.1R135 and 4.1R80), as well as 4.1G, are expressed in erythroblasts during terminal differentiation, but only 4.1R80 is present in mature erythrocytes. One goal in the field is to better understand the complex regulation of cell type and isoform-specific expression of 4.1 proteins. To start answering these questions, we are studying in depth the important functions of 4.1 proteins in the organization and function of the membrane skeleton in erythrocytes. We have previously reported that the binding profiles of 4.1R80 and 4.1R135 to membrane proteins and calmodulin are very different despite the similar structure of the membrane-binding domain of 4.1G and 4.1R135. We have accumulated evidence for those differences being caused by the N-terminal 209 amino acids headpiece region (HP). Interestingly, the HP region is an unstructured domain. Here we present an overview of the differences and similarities between 4.1 isoforms and paralogs. We also discuss the biological significance of unstructured domains

Dispersion Relations for Thermally Excited Waves in Plasma Crystals

Thermally excited waves in a Plasma crystal were numerically simulated using a Box_Tree code. The code is a Barnes_Hut tree code proven effective in modeling systems composed of large numbers of particles. Interaction between individual particles was assumed to conform to a Yukawa potential. Particle charge, mass, density, Debye length and output data intervals are all adjustable parameters in the code. Employing a Fourier transform on the output data, dispersion relations for both longitudinal and transverse wave modes were determined. These were compared with the dispersion relations obtained from experiment as well as a theory based on a harmonic approximation to the potential. They were found to agree over a range of 0.9<k<5, where k is the shielding parameter, defined by the ratio between interparticle distance a and dust Debye length lD. This is an improvement over experimental data as current experiments can only verify the theory up to k = 1.5.Comment: 8 pages, Presented at COSPAR '0

Segurança na Ginástica Olímpica.

a Ginástica Olímpica, o praticante desafia as leis da física, buscando o domínio do corpo nas mais variadas situações: em posições invertidas, em rotações, em diferentes alturas e equipamentos, utilizando diferentes partes do corpo, assumindo formas diferentes, etc. Este fato poderia levar alguns professores a considerarem a Ginástica Olímpica como uma atividade perigosa, desencorajando a sua prática em muitos ambientes. Porém, o risco de lesões e acidentes ocorre em qualquer forma de atividade física. Mais particularmente na Ginástica Olímpica, a causa de muitos acidentes é proveniente da falta de conhecimento e bom senso dos próprios professores e não da atividade em si. Por meio de uma orientação adequada aos alunos, associada ao bom senso e conhecimento, pode-se criar um ambiente seguro, sem prejudicar o prazer e a obtenção dos benefícios proporcionados pela prática da Ginástica Olímpica. Os principais fatores relacionados à segurança na Ginástica Olímpica serão apresentados neste artigo, destacando-se a importância do ensino das aterrissagens. Como muitos estudos têm revelado que a causa da maioria dos acidentes e lesões nesta atividade ocorrem em aterrissagens mal sucedidas, seria coerente enfatizar o seu aprendizado e domínio completo