The role of sediment on the energy availability for fishes in the upper Paraná river floodplain / O papel do sedimento na disponibilidade de energia para peixes da planície de inundação do alto rio Paraná

This study aimed to identify potential sources of organic matter in sediment, using stable isotopes of carbon (δ13C) and nitrogen (δ15N). Sediment samples were gathered from the margin and in center of three subsystems: Ivinheima, Paraná and Baia, in August/2001. The samples were fractionated granulometrically and separated by size (< 200 µm; 70-200 µm; > 70 µm), prepared and sent to CENA / USP, for identifying the isotopes proportions. Significant differences were detected in the isotopic ratios of the sediment only between sampling stations. The Baía channel presented the lowest δ13C values, while the highest ones were recorded in Paraná river. At this last, δ15N values were negative (-14.41‰). We did not verify significant difference in isotopic composition between the particle sizes of sediment, and between the sampling points. The main sources of carbon for the sediment were C3 macrophytes, periphyton and particulate organic carbon (POC).

O presente trabalho teve por objetivo identificar as fontes potenciais de matéria orgânica do sedimento, utilizando isótopos estáveis de carbono (δ13C) e nitrogênio (δ15N). Foram coletadas amostras de sedimento das margens e do centro de três subsistemas: Ivinheima, Paraná e Baía, em agosto/2001. As amostras foram fracionadas granulometricamente e <200 µm; 70-200 µm; >70 µm, e enviadas ao CENA/USP para identificação das proporções dos isótopos. Foram verificadas diferenças significativas nas razões isotópicas do sedimento apenas entre as estações de coleta. O canal Baía, exibiu s baixos valores de δ13C, enquanto altos valores foram registrados no rio Paraná. Nesta última estação, os valores de δ15N foram negativos (-14.41‰). Não foram registradas diferenças significativas na composição isotópica entre os tamanhos de partículas do sedimento e nem entre os pontos de coleta. As principais fontes de carbono para o sedimento foram as macrófitas C3, perifíton e carbono orgânico particulado (COP).

A Three-dimensional analysis on mechanical energy flows of torso and arm segments in baseball throw / 体力科学

Twenty-four male university baseball players were each requested to throw a baseball, and filmed using the direct linear transformation method of three-dimensional (3D) videography. 3 D coordinates of landmarks were obtained. Resultant joint forces and resultant joint torques in the wrists, elbows, shoulders, neck, and upper torso joints were calculated using the inverse dynamics method. The mechanical powers caused by the resultant joint forces (joint force power) and by the resultant joint torques (joint torque power) of each segment were calculated, and the mechanical work was also obtained by integrating the joint torque powers with time. Peak values of energies of the upper torso, upper arm, forearm, hand, and ball appeared in sequence from the proximal segment to the distal segment. The joint force powers in any segment were markedly larger than the joint torque powers. Little joint torque power was produced in the wrist throughout the throwing motion. The negative joint force power and joint torque power at the proximal end of the upper torso were rapidly increased immediately after the foot contact stride. It was clarified that the appearance of the large energies in the distal throwing arm segments during the final phase of throwing motion were caused mainly by transfer of the energies produced by the motions of the torso and shoulder joints. This paper discusses the mechanical energy flows of the upper torso and upper limb segments during the motion of baseball throwing.