13,449 research outputs found
As abelhas Irapuá (Trigona spinipes) podem contribuir com a polinização da romãzeira (Punica granatum)?.
O objetivo deste trabalho foram avaliar se ocorre autopolinização na romãzeira e se estas abelhas podem contribuir efetivamente para a sua polinização
Vacuum fluctuations of a scalar field near a reflecting boundary and their effects on the motion of a test particle
The contribution from quantum vacuum fluctuations of a real massless scalar
field to the motion of a test particle that interacts with the field in the
presence of a perfectly reflecting flat boundary is here investigated. There is
no quantum induced dispersions on the motion of the particle when it is alone
in the empty space. However, when a reflecting wall is introduced, dispersions
occur with magnitude dependent on how fast the system evolves between the two
scenarios. A possible way of implementing this process would be by means of an
idealized sudden switching, for which the transition occurs instantaneously.
Although the sudden process is a simple and mathematically convenient
idealization it brings some divergences to the results, particularly at a time
corresponding to a round trip of a light signal between the particle and the
wall. It is shown that the use of smooth switching functions, besides
regularizing such divergences, enables us to better understand the behavior of
the quantum dispersions induced on the motion of the particle. Furthermore, the
action of modifying the vacuum state of the system leads to a change in the
particle energy that depends on how fast the transition between these states is
implemented. Possible implications of these results to the similar case of an
electric charge near a perfectly conducting wall are discussed.Comment: 17 pages, 8 figure
Relation between high at nest entrance and diameter of trees which serve as nesting sites for Melipona mandacaia (Apidae, Meliponini).
The aim of this study was to investigate details on natural nesting sites as the high of the nests' entrance and relation of this and the Diameter at Breast Height (DBH)
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