Zonal flows and long-distance correlations during the formation of the edge shear layer in the TJ-II stellarator

A theoretical interpretation is given for the observed long-distance correlations in potential fluctuations in TJ-II. The value of the correlation increases above the critical point of the transition for the emergence of the plasma edge shear flow layer. Mean (i.e. surface averaged, zero-frequency) sheared flows cannot account for the experimental results. A model consisting of four envelope equations for the fluctuation level, the mean flow shear, the zonal flow amplitude shear, and the averaged pressure gradient is proposed. It is shown that the presence of zonal flows is essential to reproduce the main features of the experimental observations.Comment: 19 pages, 7 figure

Different ventilatory responses to progressive maximal exercise test performed with either the arms or legs

OBJECTIVE: This study aimed to compare respiratory responses, focusing on the time-domain variability of ventilatory components during progressive cardiopulmonary exercise tests performed on cycle or arm ergometers. METHODS: The cardiopulmonary exercise tests were conducted on twelve healthy volunteers on either a cycle ergometer or an arm ergometer following a ramp protocol. The time-domain variabilities (the standard deviations and root mean squares of the successive differences) of the minute ventilation, tidal volume and respiratory rate were calculated and normalized to the number of breaths. RESULTS: There were no significant differences in the timing of breathing throughout the exercise when the cycle and arm ergometer measurements were compared. However, the arm exercise time-domain variabilities for the minute ventilation, tidal volume and respiratory rate were significantly greater than the equivalent values obtained during leg exercise. CONCLUSION: Although the type of exercise does not influence the timing of breathing when dynamic arm and leg exercises are compared, it does influence time-domain ventilatory variability of young, healthy individuals. The mechanisms that influence ventilatory variability during exercise remain to be studied

Dynamics of zonal flow-like structures in the edge of the TJ-II stellarator

The dynamics of fluctuating electric field structures in the edge of the TJ-II stellarator, that display zonal flow-like traits, is studied. These structures have been shown to be global and affect particle transport dynamically [J.A. Alonso et al., Nucl. Fus. 52 063010 (2012)]. In this article we discuss possible drive (Reynolds stress) and damping (Neoclassical viscosity, geodesic transfer) mechanisms for the associated ExB velocity. We show that: (a) while the observed turbulence-driven forces can provide the necessary perpendicular acceleration, a causal relation could not be firmly established, possibly because of the locality of the Reynolds stress measurements, (b) the calculated neoclassical viscosity and damping times are comparable to the observed zonal flow relaxation times, and (c) although an accompanying density modulation is observed to be associated to the zonal flow, it is not consistent with the excitation of pressure side-bands, like those present in geodesic acoustic oscillations, caused by the compression of the ExB flow field

Desempenho de cultivares de tomate em sistema orgânico de produção.

O experimento foi conduzido na fazenda experimental Santa Rita da EPAMIG, em Prudente de Morais - MG, no período de maio a novembro de 2010, com o objetivo de avaliar a adaptabilidade de quatro genótipos de tomate ao sistema orgânico de produção. O delineamento experimental foi o de blocos casualizados com quatro repetições, os dados foram submetidos à analise de viariância e as médias comparadas pelo texte de Tukey a 55 de probalilidade.CD-ROM. Suplemento. Trabalho apresentado no 51. Congresso Brasileiro de Olericultura, Viçosa, MG

Produtividade econômica e componentes da produção de espigas verdes de milho em função da adubação nitrogenada.

Foi avaliado, durante dois anos, o efeito de doses de nitrogênio (N) na produtividade de espigas verdes de milho e em componentes da sua produção. Cinco doses de N (0, 60, 120, 180 e 240 kg ha-1) aplicadas em cobertura foram testadas num delineamento experimental de blocos casualizados, com quatro repetições. Foram avaliadas a produção e o número de espigas comerciais com palha por hectare, peso das espigas com e sem palha, comprimento e diâmetro de espigas sem palha e relação espiga com palha/palha. Aumentos na produtividade de espigas comerciais com palha com a aplicação de N foram encontrados, sendo estimadas as máximas produtividades de 13,52 t ha-1 com a dose de 157 kg ha-1 de N (primeiro ano) e de 14,86 t ha-1 com a dose de 177 kg ha-1 de N (segundo ano). Os aumentos na produtividade de espigas não foram devido aos aumentos do número de espigas por área e do comprimento destas, que não foram afetados pela adubação nitrogenada. Diferentemente da relação espiga/palha, o peso e o diâmetro das espigas foram influenciados pela elevação das doses de N. Foi proposta uma tabela de recomendação de adubação nitrogenada nos moldes de preços preestabelecidos de N e de espigas

Tillering of ‘Marandu’ \u3ci\u3eBrachiaria\u3c/i\u3e Under Different Nitrogen Rates in The Brazilian Savannah

The tiller is the basic unit of grass growth and tiller density determines the horizontal ground cover, leaves production and pastures perennially. The objective in this study was to quantify the number of aerial and basal tillers and basal:aerial tillers ratio in Urochloa brizantha cv. Marandu, established in Brazilian savannah, submitted to nitrogen doses (0, 50, 100 and 150 kg N/ha). The experiment was carried out in the Forage and Pasture Sector of Jataí Federal University (UFJ) and after soil correction and fertilization, plots were established with Marandu palisade grass in a randomized block design, with four replications and four N doses. Tiller count was performed after the uniformity cut and at the end of each cycle, when the average height of the forage canopy reached average 30 cm. Tillers were identified with colored wires (one color/generation), in a total of six generations (cycles). The highest ratio of basal:aerial tiller was 1.36 and occurred at dose of 100 kg N/ha as an answer to the highest tiller survival and lowest tiller mortality. Highest percentage of basal tiller and the lowest percentage of aerial tiller occurs at dose of 100 kg N/ha. Nitrogen fertilization is an important strategy to obtain more production of high quality mass, highest ground cover by highest survival rate, less mortality and a better proportion between basal and aerial tillers in Marandu palisade grass, favoring their perennity when is used 100 kg N/ha