Lithium abundance evolution in open clusters: Hyades, NGC752, and M67

Mixing mechanisms bring the Li from the base of the convective zone to deeper and warmer layers where it is destroyed. These mechanisms are investigated by comparing observations of Li abundances in stellar atmospheres to models of stellar evolution. Observations in open cluster are especially suitable for this comparison, since their age and metallicity are homogeneous among their members and better determined than in field stars. In this work, we compare the evolution of Li abundances in three different clusters: the Hyades, NGC752, and M67. Our models are calculated with microscopic diffusion and transport of chemicals by meridional circulation, and calibrated on the Sun. These comparisons allow us to follow the evolution of Li abundance as a function of stellar mass in each cluster and as a function of the age by comparing this evolution in each cluster. We evaluate the efficiency of the mixing mechanisms used in the models, and we try to identify the lacking mechanisms to reproduce the observed evolution of Li abundance.Comment: 6 pages, 4 figures, conference publication of "New advances in stellar physics: from microscopic to macroscopic processes

Weaning age effects on some growth and development characteristics of Nelore calves at pasture

O objetivo do presente trabalho foi o de acompanhar o desenvolvimento de bezerros, em regime exclusivo de pasto, submetidos a desmama precoce. Assim, bezerros e bezerras Nelore foram desmamados nas idades de três, cinco e sete meses. Nos bezerros, o desenvolvimento foi acompanhado até os doze meses, tendo a esta idade apresentado os pesos de 146 (D3), 155 (D5) e 172kg (D7), respectivamente. Não houve diferença significativa entre os pesos aos três e cinco meses e entre cinco e sete meses. No entanto, a elevada mortalidade, decorrente do estresse da desmama aos três meses desaconselha essa prática em condições semelhantes às do experimento. As fêmeas desmamadas nas mesmas idades, três, cinco e sete meses, não mostraram diferenças nos pesos aos 12 e 24 meses, peso à fecundação e idade ao primeiro parto, que foram, em media, de 152 kg, 252 kg, 318 kg e 1.279 dias, respectivamente. No entanto, as novilhas com segunda recria em campo limpo tiveram a primeira parição 2,8 meses mais tarde que as de segunda recria em Jaraguá, e isto, possivelmente por terem atingido o peso ideal pra a fecundação mais tardiamente. A idade ao primeiro parto pra novilhas que foram desmamadas aos três, cinco e sete meses foi de 1.274, 1.289 e 1.275 dias, respectivamente. Concluiu-se que a desmama aos cinco meses pode ser adotada sem afetar o crescimento e o bom desenvolvimento do bezerro.The objective of this experiment was to evaluate some growth characteristics of Nelore calves, raised at pastures and weaned at two early ages (three, five and seven months). Male yearling weights were 146 (W3), 155 (E5) and 172 kg (W7), for weaning at the, five and 7 months, respectively. There was no difference between W3 and W5 or between W5 and W7. A high mortality was observed in the first group. Female weights at 12 and 24 months and at conception, and the age at first parturition were not affected (P < 0.05) by weaning age. The mean squares for these characteristics were 152 kg, 252 kg, 318 kg and 1,279 days, respectively. Based on the results it is concluded that weaning at five months may be practiced without interfering with calf growth, and development

The effects of stellar winds on the magnetospheres and potential habitability of exoplanets

Context: The principle definition of habitability for exoplanets is whether they can sustain liquid water on their surfaces, i.e. that they orbit within the habitable zone. However, the planet's magnetosphere should also be considered, since without it, an exoplanet's atmosphere may be eroded away by stellar winds. Aims: The aim of this paper is to investigate magnetospheric protection of a planet from the effects of stellar winds from solar-mass stars. Methods: We study hypothetical Earth-like exoplanets orbiting in the host star's habitable zone for a sample of 124 solar-mass stars. These are targets that have been observed by the Bcool collaboration. Using two wind models, we calculate the magnetospheric extent of each exoplanet. These wind models are computationally inexpensive and allow the community to quickly estimate the magnetospheric size of magnetised Earth-analogues orbiting cool stars. Results: Most of the simulated planets in our sample can maintain a magnetosphere of ~5 Earth radii or larger. This suggests that magnetised Earth analogues in the habitable zones of solar analogues are able to protect their atmospheres and is in contrast to planets around young active M dwarfs. In general, we find that Earth-analogues around solar-type stars, of age 1.5 Gyr or older, can maintain at least a Paleoarchean Earth sized magnetosphere. Our results indicate that planets around 0.6 - 0.8 solar-mass stars on the low activity side of the Vaughan-Preston gap are the optimum observing targets for habitable Earth analogues.Comment: 8 pages, 3 figures, accepted to Astronomy and Astrophysic

Stellar Cycles in Fully Convective Stars and a New Interpretation of Dynamo Evolution

An $\alpha\Omega$ dynamo, combining shear and cyclonic convection in the tachocline, is believed to generate the solar cycle. However, this model cannot explain cycles in fast rotators (with minimal shear) or in fully convective stars (no tachocline); analysis of such stars could therefore provide key insights into how these cycles work. We reexamine ASAS data for 15 M dwarfs, 11 of which are presumed fully convective; the addition of newer ASAS-SN data confirms cycles in roughly a dozen of them, while presenting new or revised rotation periods for five. The amplitudes and periods of these cycles follow $A_{\rm cyc} \propto P_{\rm cyc}^{0.94 \pm 0.11}$, with $P_{\rm cyc}/P_{\rm rot} \propto {\rm Ro}^{-1.02 \pm 0.06}$ (where Ro is the Rossby number), very similar to $P_{\rm cyc}/P_{\rm rot} \propto {\rm Ro}^{-0.81 \pm 0.17}$ that we find for 40 previously studied FGK stars, although $P_{\rm cyc}/P_{\rm rot}$ and $\alpha$ are a factor of $\sim$20 smaller in the M stars. The very different $P_{\rm cyc}/P_{\rm rot}$-Ro relationship seen here compared to previous work suggests that two types of dynamo, with opposite Ro dependences, operate in cool stars. Initially, a (likely $\alpha^2$ or $\alpha^2\Omega$) dynamo operates throughout the convective zone in mid-late M and fast rotating FGK stars, but once magnetic breaking decouples the core and convective envelope, a tachocline $\alpha\Omega$ dynamo begins and eventually dominates in older FGK stars. A change in $\alpha$ in the tachocline dynamo generates the fundamentally different $P_{\rm cyc}/P_{\rm rot}$-Ro relationship.Comment: 26 pages, 18 figures, submitted to ApJ. Figure sets will be available in the final prin

Universo em descoberta: Palestras e noites de observação celeste no Campus Regional de Goioerê

Anais do 35º Seminário de Extensão Universitária da Região Sul - Área temática: ComunicaçãoO projeto busca através de visitas às escolas da região, e praças do município, para população em geral, divulgar e exemplificar o ensino da astronomia. O projeto de extensão Universo em Descoberta, vinculado ao Campus Regional da Universidade Estadual de Maringá em Goioerê/PR. tem como objetivos: estimular alunos e professores, de todos os níveis de ensino, a desenvolverem atividades que despertem o interesse pela busca do conhecimento científico; aproximar a universidade e a comunidade, fornecendo acesso a informações teóricas; e incentivar a participação em noites de observação celeste realizadas no Campus. Atualmente alunos da rede pública e particular de ensino são atendidos com palestras, participações em noite de observações celestes, feira de ciências e muitas outras atividades, além da divulgação das ciências e tecnologia. Dessa forma pretende-se compartilhar e evidenciar que atividades envolvendo as ciências e a Física em espaços diferentes do tradicionalismo de uma sala de aula são de fundamental importância, tanto para despertar interesse pela Ciência como para oportunizar a interação escola-universidade-comunidad

Inclusive education: choice and rejection among students

This work reports a research about inclusive education which objective was to verify if there are differences in preferences and rejections made by students considered as an inclusive status by the schools and their classmates, as well as the reasons for the preferences and rejections. A Proximity Scale has been built among the students and was applied in two classrooms: in a public school (one student considered in an inclusive status) and in a private school (three students considered in an inclusive status). It was observed that there was no difference among students, in both classes, regarding the frequency of choice or rejection and the reasons therefore. Reasons presented for choosing or not choosing classmates for school assignments denote an ideal of productivity and competitive relations. In social relations like playing or visiting classmates, being cool or friendly was appreciated.Este artigo relata pesquisa sobre educação inclusiva; teve como objetivos comparar escolhas e rejeições dos alunos considerados em situação de inclusão pelas escolas com seus colegas e os motivos para essas escolhas e rejeições. Construiu-se uma Escala de Proximidade entre alunos, que foi aplicada em duas classes: uma do ensino público (um aluno considerado em situação de inclusão) e outra do ensino particular (três alunos considerados em situação de inclusão). Observou-se que não houve diferenças entre os dois grupos de alunos, em ambas as classes, no que se refere à frequência de escolha ou rejeição e em relação aos motivos. Os motivos dados para escolher ou não colegas para a execução de tarefas escolares denotam um ideal de produtividade e relações de competição; quanto às relações sociais como brincar ou ir à casa do colega, valorizou-se ser legal e amigo.Universidade de São PauloUniversidade Federal de São Paulo (UNIFESP)Secretaria da Saúde do Estado de São PauloUNIFESPSciEL