An examination of the process and magnitude of ionospheric plasma supply to the magnetosphere.

The contribution of ionospheric plasma to the Earth’s magnetosphere has beenrecognized for more than 3 decades. The magnitude of this contribution has become moreevident over that same time period with the observed magnitude of the low-energyionospheric supply increasing as the measurement techniques improved. Estimates basedon Dynamics Explorer measurements in the mid-1980s suggested that the ionosphericplasma supply is sufficient to populate the plasmasphere, plasma trough, plasma sheet, andmagnetotail lobes. Recent measurements from the Thermal Ion Dynamics Experiment onthe Polar spacecraft have been used in conjunction with an ion trajectory model toreexamine the process and magnitude of the ionospheric supply of magnetosphericplasma. These measurements reveal the energy, pitch angle, and flux characteristics of theupward flowing polar wind over broad regions of the high-latitude ionosphere. Onboardmeasurement of spacecraft potential is found to be a fundamental element ininterpreting the measured ion outflow. Newly derived polar wind fluxes are determined tobe near 6.0 107 ions cm2 s1 at 5000 km altitude during local winter and magneticallyquiet conditions. Using the measured ionospheric source characteristics incombination with the trajectory code reveals the nature of the ionospheric/magnetospherefilling process and shows that the ionospheric source is sufficient to supply the observeddensities and energies of the plasma sheet and magnetotail lobes. Many of theionospheric particles are further transformed to ring current energies and locations aftercirculation through the plasma sheet. This measurement/calculation approach is ableto show which regions of the high-latitude ionosphere are important for plasma sheet/ringcurrent filling. The ionospheric sources used in the calculations include thedominant polar wind, the cleft ion fountain, and the auroral zone

Seed research for improved technologies Pesquisa para o aprimoramento de tecnologia de sementes

The production of high-quality seed is the basis for a durable a profitable agriculture. After production, seed is processed, conditioned, stored, shipped and germinated. For quality assurance, seed quality has to be controlled at all steps of the production chain. Seed functioning is accompanied by programmed transitions from cell proliferation to quiescence upon maturation and from quiescence to reinitiation of cellular metabolism upon imbibition. Despite the obvious importance of these control mechanisms, very little information is available at the molecular level concerning those elements that regulate seed germination. In the present study, the induction of cell cycle activity and the regulation of ß-tubulin expression is related to the water content and other physical properties of the seed.<br>A produção de sementes de alta qualidade é a base para uma agricultura produtiva. Após a colheita, a semente é beneficiada, embalada, armazenada, transportada e semeada. Para maior segurança, tanto dos produtores como dos consumidores, a qualidade da semente deve ser mantida sob controle em todas as fases do processo de produção. O desempenho da semente é resultado de transições programadas desde a divisão celular até a quiescência, durante a maturação, e da quiescência até o reinicio do metabolismo celular, durante a embebição. Apesar da importância destes mecanismos de controle, há pouca informação disponível, a nível molecular, no que diz respeito aos elementos que regulam a germinação da semente. No presente trabalho, a indução do ciclo de atividade celular e a regulação da expressão de ß-tubulina são relacionadas ao grau de umidade e a outras propriedades físicas da semente