Two-neutron knockout from neutron-deficient 34^{34}Ar, 30^{30}S, and 26^{26}Si

Two-neutron knockout reactions from nuclei in the proximity of the proton dripline have been studied using intermediate-energy beams of neutron-deficient $^{34}$Ar, $^{30}$S, and $^{26}$Si. The inclusive cross sections, and also the partial cross sections for the population of individual bound final states of the $^{32}$Ar, $^{28}$S and $^{24}$Si knockout residues, have been determined using the combination of particle and $\gamma$-ray spectroscopy. Similar to the two-proton knockout mechanism on the neutron-rich side of the nuclear chart, these two-neutron removal reactions from already neutron-deficient nuclei are also shown to be consistent with a direct reaction mechanism.Comment: Phys. Rev. C, rapid communication, in pres

Low Mate Encounter Rate Increases Male Risk Taking in a Sexually Cannibalistic Praying Mantis

Male praying mantises are forced into the ultimate trade-off of mating versus complete loss of future reproduction if they fall prey to a female. The balance of this trade-off will depend both on (1) the level of predatory risk imposed by females and (2) the frequency of mating opportunities for males. We report the results of a set of experiments that examine the effects of these two variables on male risk-taking behavior and the frequency of sexual cannibalism in the praying mantis Tenodera sinensis. We experimentally altered the rate at which males encountered females and measured male approach and courtship behavior under conditions of high and low risk of being attacked by females. We show that male risk taking depends on prior access to females. Males with restricted access to females showed greater risk-taking behavior. When males were given daily female encounters, they responded to greater female-imposed risk by slowing their rate of approach and remained a greater distance from a potential mate. In contrast, males without recent access to mates were greater risk-takers; they approached females more rapidly and to closer proximity, regardless of risk. In a second experiment, we altered male encounter rate with females and measured rates of sexual cannibalism when paired with hungry or well-fed females. Greater risk-taking behavior by males with low mate encounter rates resulted in high rates of sexual cannibalism when these males were paired with hungry females

Estimativa do estado de saúde de baterias chumbo-ácido seladas aplicadas em sistemas de emergência de elevadores

O presente trabalho tem como objetivo estimar o estado de saúde de baterias chumboácido seladas de 1,3 Ah, as quais são utilizadas em sistemas de emergência de elevadores. O projeto é feito por meio do levantamento do comportamento da tensão da bateria quando submetida a descarga e também por parâmetros que afetem sua vida útil. O estudo é dividido em duas partes: a primeira trata do levantamento do modelo de descarga da bateria; a segunda etapa, por sua vez, refere-se ao desenvolvimento do circuito que é conectado à bateria, tendo como função estimar e exibir o estado de saúde atual da bateria. O circuito também dispõe de um sistema de segurança a fim de garantir que a bateria esteja disponível quando ocorrer uma falha no sistema de distribuição de energia.This study focuses on the state of health estimation of 1,3 Ah sealed lead acid batteries, employed in elevators’ emergency systems. The project will be developed by gathering data regarding the battery’s voltage behavior when subjected to discharge, as well as additional parameters that have an impact in the battery’s lifespan. There are two main stages to this study: The first one encompasses the acquisition of the battery’s discharge model. The second one, in turn, accounts for the development of the circuit which will be connected to the battery, aiming to estimate and then to show the battery’s current state of health. Additionally the circuit must include a security system in order to ensure the availability of the battery in the moment when a failure in the power distribution system occurs

Direct radiative proton capture Al(p,γ) Si studied via one-proton nuclear breakup of Si

We present the results of an experimental work that studied the direct component of the radiative proton capture reaction Al(p,γ) Si for its relevance in X-ray burst nucleosynthesis. The experiment was performed at GANIL using one-proton nuclear breakup reaction at intermediate energies to determine the Asymptotic Normalization Coefficient (ANC) of the system Si→ Al + p. Using the ANC, we evaluated the corresponding astrophysical S factor and reaction rate

β-Delayed proton-decay study of 20Mg and its implications for the Ne19(p,γ)Na20 breakout reaction in X-ray bursts

Under astrophysical conditions of high temperature and density, such as for example found in X-ray bursts, breakout can occur from the hot CNO cycles into the rapid proton capture process. A key breakout route is via the sequence O15(α,γ)Ne19(p,γ)Na20. The Ne19(p,γ)Na20 reaction rate is expected to be dominated by a single resonance at 457(3) keV. The identity of the resonance has been under discussion for a long time, with J π=1 + and 3 + assignments suggested. In this study of the β-delayed proton decay of 20Mg we report a new, significantly more stringent, upper limit on the β-decay branch to this state of 0.02% with a confidence level of 90%. This makes a 1 + assignment highly unlikely and favours a 3 + assignment for which no branch is expected to be observed. The 3 + state is predicted to have a significantly higher resonance strength, and to produce a proportionately higher Ne19(p,γ)Na20 reaction rate in X-ray burst conditions. © 2012 Elsevier B.V

β-Delayed proton-decay study of 20Mg and its implications for the Ne19(p,γ)Na20 breakout reaction in X-ray bursts

Under astrophysical conditions of high temperature and density, such as for example found in X-ray bursts, breakout can occur from the hot CNO cycles into the rapid proton capture process. A key breakout route is via the sequence O15(α,γ)Ne19(p,γ)Na20. The Ne19(p,γ)Na20 reaction rate is expected to be dominated by a single resonance at 457(3) keV. The identity of the resonance has been under discussion for a long time, with J π=1 + and 3 + assignments suggested. In this study of the β-delayed proton decay of 20Mg we report a new, significantly more stringent, upper limit on the β-decay branch to this state of 0.02% with a confidence level of 90%. This makes a 1 + assignment highly unlikely and favours a 3 + assignment for which no branch is expected to be observed. The 3 + state is predicted to have a significantly higher resonance strength, and to produce a proportionately higher Ne19(p,γ)Na20 reaction rate in X-ray burst conditions. © 2012 Elsevier B.V