12,425 research outputs found
Potencial da soja na produção de biodiesel.
Disponível em .bitstream/item/128055/1/SP-15547.pd
Stellar equilibrium configurations of white dwarfs in the gravity
In this work we investigate the equilibrium configurations of white dwarfs in
a modified gravity theory, na\-mely, gravity, for which and
stand for the Ricci scalar and trace of the energy-momentum tensor,
respectively. Considering the functional form , with
being a constant, we obtain the hydrostatic equilibrium equation for
the theory. Some physical properties of white dwarfs, such as: mass, radius,
pressure and energy density, as well as their dependence on the parameter
are derived. More massive and larger white dwarfs are found for
negative values of when it decreases. The equilibrium configurations
predict a maximum mass limit for white dwarfs slightly above the Chandrasekhar
limit, with larger radii and lower central densities when compared to standard
gravity outcomes. The most important effect of theory for massive
white dwarfs is the increase of the radius in comparison with GR and also
results. By comparing our results with some observational data of
massive white dwarfs we also find a lower limit for , namely, .Comment: To be published in EPJ
Vibratory signals of four neotropical stink bug species.
The stink bugs Acrosternum impicticorne, Euschistus heros, Piezodorus guildinii and Thyanta perditor (Heteroptera: Pentatomidae) feed and mate on the same host plants and constitute major components of the soybean pest complex in Brazil. During mating, they communicate with species and sex-specific vibratory signals whose spectral properties are characteristic of the subfamily Pentatominae. Songs differ between species in the time structure and amplitude modulation of their units. The repertoire of A. impicticorne, E. heros and T. perditor fits into the scheme described for most investigated stink bugs: females call with a sequence of pulses that differ between species in their duration and repetition rate, and males respond with courtship songs of species-specific temporal structure and amplitude modulation of complex pulse trains. Female calling and male courtship songs are the main constituents of vibratory communication between sexes in the mating period. The other vibratory emissions appear to represent either transitional songs, support recognition during close-range courtship, or are involved in male rivalry. The first recorded vibratory emissions of P. guildinii confirm that the genus Piezodorus represents an exception within the Pentatominae. Irregularly repeated female vibratory signals of P. guildinii do not trigger typical male courtship responses as they would in the small stink bugs Holcostethus strictus and Murgantia histrionica. On the other hand, complex rivalry with extensive frequency modulation of pulses, as also described in Piezodorus lituratus, opens a new insight into the role of vibratory communication in stink bug
Vibratory communication and its relevance to reproductive isolation in two sympatric stink bug species (Hemiptera: Pentatomidae: Pentatominae).
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Electrostatic self-force in (2+1)-dimensional cosmological gravity
Point sources in (2+1)-dimensional gravity are conical singularities that
modify the global curvature of the space giving rise to self-interaction
effects on classical fields. In this work we study the electrostatic
self-interaction of a point charge in the presence of point masses in
(2+1)-dimensional gravity with a cosmological constant.Comment: 9 pages, Late
Exploitation of insect and plant semiochemicals as tools for real-time control and detection of pests in crops.
Attractant Pheromone of the Neotropical Species Neomegalotomus parvus (Westwood) (Heteroptera: Alydidae).
The Neotropical broad-headed bug, Neomegalotomus parvus (Westwood), is adapted to various leguminous crops and is considered a pest in common bean and soybean. The chemical communication of this species was studied in order to identify an attractant pheromone. Males and females of N. parvus produce several short-chain esters and acids, and their antennae showed electrophysiological responses to ?ve of these compounds, three common to both sexes (hexyl butanoate, 4-methylhexyl butanoate, and hexyl hexanoate), and two female-speci?c compounds (4-methylhexyl pentanoate and hexyl pentanoate). Both aeration extracts of females and a solution containing ?ve synthetic compounds mimicking the natural blend were attractive to males and females N. parvus in a laboratory bioassay. Aspects of the chemical ecology of the broad-headed bugs and the possibility to use pheromone-baited traps in the ?eld for monitoring are discussed
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