Onset of fluidization in vertically shaken granular material

When granular material is shaken vertically one observes convection, surface fluidization, spontaneous heap formation and other effects. There is a controversial discussion in literature whether there exists a threshold for the Froude number $\Gamma=A_0\omega_0^2/g$ below which these effects cannot be observed anymore. By means of theoretical analysis and computer simulation we find that there is no such single threshold. Instead we propose a modified criterion which coincides with critical Froude number $\Gamma_c=1$ for small driving frequency $\omega_0$.Comment: 7 pages, 5 figure

Studies of Mass and Size Effects in Three-Dimensional Vibrofluidized Granular Mixtures

We examine the steady state properties of binary systems of driven inelastic hard spheres. The spheres, which move under the influence of gravity, are contained in a vertical cylinder with a vibrating base. We computed the trajectories of the spheres using an event-driven molecular dynamics algorithm. In the first part of the study, we chose simulation parameters that match those of experiments performed by Wildman and Parker. Various properties computed from the simulation including the density profile, granular temperature and circulation pattern are in good qualitative agreement with the experiments. We then studied the effect of varying the mass ratio and the size ratio independently while holding the other parameters constant. The mass and size ratio are shown to affect the distribution of the energy. The changes in the energy distributions affect the packing fraction and temperature of each component. The temperature of the heavier component has a non-linear dependence on the mass of the lighter component, while the temperature of the lighter component is approximately proportional to its mass. The temperature of both components is inversely dependent on the size of the smaller component.Comment: 14 Pages, 12 Figures, RevTeX

Bifurcations of a driven granular system under gravity

Molecular dynamics study on the granular bifurcation in a simple model is presented. The model consists of hard disks, which undergo inelastic collisions; the system is under the uniform external gravity and is driven by the heat bath. The competition between the two effects, namely, the gravitational force and the heat bath, is carefully studied. We found that the system shows three phases, namely, the condensed phase, locally fluidized phase, and granular turbulent phase, upon increasing the external control parameter. We conclude that the transition from the condensed phase to the locally fluidized phase is distinguished by the existence of fluidized holes, and the transition from the locally fluidized phase to the granular turbulent phase is understood by the destabilization transition of the fluidized holes due to mutual interference.Comment: 35 pages, 17 figures, to be published in PR

Bipartição escrotal associada à má formação prepucial em ovino Morada Nova: relato de caso

As alterações anatômicas do aparelho reprodutor masculino de ovinos são pouco relatadas, especialmente a condição de bipartição escrotal. Devido à importância do esclarecimento sobre esta alteração anatômica, objetivou-se relatar o caso de um ovino da raça Morada Nova que apresentava bipartição escrotal associada à má formação prepucial. Observou-se que essa alteração pode ocorrer como condição de adaptabilidade a climas tropicais

Antidepressant-like effect of Hoodia gordonii in a forced swimming test in mice: evidence for involvement of the monoaminergic system

Hoodia gordonii is a plant species used traditionally in southern Africa to suppress appetite. Recently, it has been associated with a significant increase in blood pressure and pulse rate in women, suggesting sympathomimetic activity. The present study investigated the possible antidepressant-like effects of acute and repeated (15 days) administration of H. gordonii extract (25 and 50 mg/kg, po) to mice exposed to a forced swimming test (FST). Neurochemical analysis of brain monoamines was also carried out to determine the involvement of the monoaminergic system on these effects. Acute administration of H. gordonii decreased the immobility of mice in the FST without accompanying changes in general activity in the open-field test during acute treatment, suggesting an antidepressant-like effect. The anti-immobility effect of H. gordonii was prevented by pretreatment of mice with PCPA [an inhibitor of serotonin (5-HT) synthesis], NAN-190 (a 5-HT1A antagonist), ritanserin (a 5-HT2A/2C antagonist), ondansetron (a 5-HT3A antagonist), prazosin (an α1-adrenoceptor antagonist), SCH23390 (a D1 receptor antagonist), yohimbine (an α2-adrenoceptor antagonist), and sulpiride (a D2 receptor antagonist). A significant increase in 5-HT levels in the striatum was detected after acute administration, while 5-HT, norepinephrine and dopamine were significantly elevated after chronic treatment. Results indicated that H. gordonii possesses antidepressant-like activity in the FST by altering the dopaminergic, serotonergic, and noradrenergic systems

Percepções do médico-chefe a respeito de atividades educativas em Postos de Assistência Médica Perceptions of head doctors regarding the educational activities undertaken in Municipal Health Services

Realizou-se pesquisa com médicos-chefe dos Postos de Assistência Médica (PAMs) da Prefeitura Municipal de São Paulo, Brasil, com o objetivo de investigar seus conhecimentos, expectativas e predisposições em participar e incentivar as programações educativas nos PAMs. Utilizou-se questionário, com questões abertas e fechadas que foi respondido por 88,6% dos médicos-chefe dos PAMs. Os resultados demonstraram que o conceito de saúde da maioria dos médicos-chefe dos PAMS (66,3%) coincide com o emitido pela Organização Mundial da Saúde. Apenas 2,9% consideram que saúde está relacionada a qualidade de vida. Educação em saúde foi considerada por 70,0% como transmissão de informação; somente 6,7% reconheceram sua responsabilidade no processo de transformação social e de saúde. Na visão de 68,2% as ações educativas são reconhecidas como úteis para conscientizar o usuário sobre a importância do tratamento de doenças. Essas ações, seu planejamento, execução e avaliação são reconhecidas como responsabilidade de todos que trabalham nos PAMs mas, especialmente, das enfermeiras, assistentes sociais e educadores de saúde pública. Dificuldades foram mencionadas na execução de atividades educativas, referentes à falta de material suficiente e local adequado para sua realização, falta do educador de saúde pública e, principalmente, falta de motivação de funcionários e da própria população. A maioria dos médicos-chefe reconhece a importância das ações educativas, reconhece que são desenvolvidas por pelo menos parte de sua equipe embora, muitas vezes, precariamente, com dificuldades técnicas e administrativas.<br>The results of a research project carried out along with head-physicians of the Municipal Health Services (PAMs) of the city of S. Paulo in order to survey their knowledge, expectations and willingness to participate in and incentivate educational programs in the various PAMs, are reported on. An open-ended questionnaire was answered by 88.6% of the head-physicians. Results showed that the concept of health of the majority of the PAMs' head-physicians (66.3%) was coincidental with that adopted by the WHO. Only 2.9% considered that health is related to quality of life. Health education was seen as the provision of information by 70.0%; only 6.7% recognized their responsibility for the process of social and health change. According to 68.2% of them, health actions were acknowledged to be useful tools for making the users aware of the importance of having the diseases treated. Health actions, their planing, implementation and evaluation were considered to be the responsibility of all who work at the PAMs, but mainly of nurses, social workers and the health educator. Some difficulties in implementing educational activities were indicated; among them being lack of sufficient material and adequate space for their implementation, lack of professional Public Health Educators and, mainly, a lack of motivation on the part of both staff and population. The majority of the head-physicians recognized that educational activities are important, that they are carried out at least by part of their staffs, although frequently hampered by technical and operational difficulties