Star formation history in the solar neighborhood: the link between stars and cosmology

Using a cosmological galactic evolutionary approach to model the Milky Way, we calculate the star formation history (SFH) of the solar neighborhood. The good agreement we obtain with the observational inferences suggests that our physical model describes accurately the long term/large spatial trends of the local and global Milky Way SFH. In this model, star formation is triggered by disk gravitational instabilities and self-regulated by an energy balance in the ISM. The drivers of the SFH are the cosmological gas infall rate and the gas surface density determined by the primordial spin parameter. A LambdaCDM cosmology was used throughout.Comment: 8 pages, uses kluwer.cls. Invited talk, to appear in "New Quests in Stellar Astrophysics: The link between Stars and Cosmology", eds. M. Chavez, A. Bressan, A. Buzzoni & D. Mayya, Kluwer Academic Publisher

Corós associados ao sistema plantio direto no Estado de Mato Grosso do Sul.

Os sistemas de produção de grãos têm sido bastante modificados nos últimos anos, especialmente na Região Oeste do Brasil. Diversos eventos têm concorrido para isto, dentre os quais destacam-se a expansão das culturas para regiões antes inexploradas e a adoção de novas práticas de cultivo como o sistema plantio direto. No Estado de Mato Grosso do Sul tem sido constatado um aumento significativo na abundância e riqueza de espécies de insetos com hábitos subterrâneos, em especial os corós. Esses insetos são larvas de melolontídeos ou de escarabeídeos, que passam toda a fase imatura no solo emergindo somente na fase adulta para a reprodução. Neste documento são apresentadas as principais espécies de corós que ocorrem no sistema plantio direto de Mato Grosso do Sul. As espécies Liogenys suturalis, Phyllophaga cuyabana e Anomala testaceipennis podem causar danos severos nas culturas dependendo das condições climáticas, do estádio de desenvolvimento da cultura e da sua densidade populacional na área, enquanto outras espécies, como Cyclocephala spp. e Bothynus medon, mesmo em alta densidade populacional, não prejudicam a capacidade produtiva e o vigor das plantas. As diferentes espécies de corós geralmente apresentam os ciclos biológicos sincronizado com as épocas de cultivo das culturas na região. Quando o segundo e/ou terceiro ínstar de desenvolvimento dos corós-praga coincide com o estádio inicial de desenvolvimento das plantas, as perdas na produtividade são normalmente intensificadas.bitstream/CPAO-2010/31935/1/DOC2009101.pdfDocumento on-line

Pulsed x-rays dose measurements from a hundred joules plasma focus device

Indexación: Scopus.Present work is aimed to perform dosimetric measurements to characterize dosis obtained from pulsed x-rays emitted from a hundred joules plasma focus device PF-400J using thermoluminescent dosimeters (TLD-100). Two dosimeter arrays (containing 21 dosimeters in each) were used. One of the arrays was kept inside the PF-400J vacuum chamber and other outside the vacuum chamber, simultaneously. It was found that dosis obtained from the inside array (∼200.7 mGy) were hundred times larger than the outside array (∼1.1 mGy) for hundred pulses of x-rays. Later, the vacuum window of PF-400J, which was made of 1 mm aluminum, was replaced by a plastic window and a similar dosimeter array was kept outside the chamber over the plastic window. With this arrangement, the obtained doses (100 pulses of x-rays) were of the same order of magnitude (∼106 mGy) as it was inside the vacuum chamber. Later, a lead piece was inserted inside the hollow anode of PF-400J, which increased dose (∼250 mGy) per hundred pulses of x-ray outside the vacuum chamber using plastic vacuum window. Our results suggest that PF-400J could be a useful device to study low dose pulsed radiation effects on cancer cell lines in in vitro experiments. © Published under licence by IOP Publishing Ltd.The work is supported by grant ACT-1115, CONICYT, Chile.https://iopscience.iop.org/article/10.1088/1742-6596/1043/1/01204