A photometric and spectroscopic survey of solar twin stars within 50 parsecs of the Sun: I. Atmospheric parameters and color similarity to the Sun

Solar twins and analogs are fundamental in the characterization of the Sun's place in the context of stellar measurements, as they are in understanding how typical the solar properties are in its neighborhood. They are also important for representing sunlight observable in the night sky for diverse photometric and spectroscopic tasks, besides being natural candidates for harboring planetary systems similar to ours and possibly even life-bearing environments. We report a photometric and spectroscopic survey of solar twin stars within 50 pc of the Sun. Hipparcos absolute magnitudes and (B-V)_Tycho colors were used to define a 2 sigma box around the solar values, where 133 stars were considered. Additional stars resembling the solar UBV colors in a broad sense, plus stars present in the lists of Hardorp, were also selected. All objects were ranked by a color-similarity index with respect to the Sun, defined by uvby and BV photometry. Moderately high-resolution, high-S/N spectra were used for a subsample of equatorial-southern stars to derive Teff, log g, and [Fe/H] with average internal errors better than 50 K, 0.20 dex, and 0.08 dex, respectively. Ages and masses were estimated from theoretical HR diagrams. The color-similarity index proved very successful. We identify and rank new excellent solar analogs, which are fit to represent the Sun in the night sky. Some of them are faint enough to be of interest for moderately large telescopes. We also identify two stars with near-UV spectra indistinguishable from the Sun's. We present five new "probable" solar twin stars, besides five new "possible" twins. Masses and ages for the best solar twin candidates lie very close to the solar values, but chromospheric activity levels range somewhat. We propose that the solar twins be emphasized in the ongoing searches for extra-solar planets and SETI searches.Comment: 25 pages, 15 figures, 14 table

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

Utilização do whiteside modificado e California Mastitis Test no diagnóstico da mastite subclínica em búfalas e sua relação com o exame microbiológico.

Foram avaliadas a sensibilidade e a especificidade dos testes California Mastitis Test (CMT) e Whiteside Modificado (WM) como métodos auxiliares no diagnóstico da mastite subclínica em búfalas do Estado de Pernambuco. Estabeleceu-se, também, uma relação entre o estágio e o número de lactações frente à infecção da glândula mamária e a participação dos agentes etiológicos na enfermidade. Foram analisadas 196 amostras de leite procedentes de 49 búfalas em cinco propriedades rurais da Zona da Mata Sul. Destas, 139 (70,9%) amostras foram positivas ao exame microbiológico, isolando-se 76 (55%) amostras de Staphylococcus spp, sendo 18 (13%) de Staphylococcus coagulase positiva e 58 (42%) Staphylococcus coagulase negativa. Isolaram-se também 25 amostras de bastonetes (18%) Gram negativos, oito de (6%) Streptococcus spp e três (2,2%) de Micrococcus spp em culturas puras ou em associação, além de 45 amostras (32,4%) de Bacillus spp. A análise dos testes CMT e WM demonstraram baixa sensibilidade e especificidade quando comparados ao isolamento bacteriano. O número e o estágio da lactação não influenciaram no aparecimento da infecção na glândula mamária desta espécie. ABSTRACT - One hundred and ninety six buffalo milk samples were analyzed from farms in the South region of Pernambuco State, Brazil. The sensibility and specificity of the California Mastitis Test (CMT) and the Modified Whiteside were studied as auxiliary methods in the diagnosis of subclinical mastitis. A relationship between the stage and the number of lactations regarding mammary infection was established. One hundred and thirty nine (70,9%) samples were positive in the microbiological exam, resulting in 76 samples of Staphylococcus spp. Fifty eight samples (42%) were classified as coagulase negative Staphylococcus. Other bacterias isolated were Bacillus spp (45/32,4%), Gram negative bacillus (25/18%), Streptococcus spp (8/6%) and Micrococcus spp (3/2,2%) in pure or mixed culture. The CMT and WM analysis showed low sensibility and specificity when compared to bacterial isolation. The number and stage of lactations did not influence on occurrence of the infection in the mammary gland of this species

Influência do tempo de exposição em ácido indol butírico no enraizamento de estacas de velame.

Suplemento. Edição dos Anais do 52 Congresso Brasileiro de Olericultura, Salvador, jul. 2012

Produção de mudas de marmeleiro em função do tipo, concentração e tempo de exposição em auxina.

Suplemento. Edição dos Anais do 52 Congresso Brasileiro de Olericultura, Salvador, jul. 2012

Manipulation of Magnetic Skyrmions by Superconducting Vortices in Ferromagnet-Superconductor Heterostructures

Dynamics of magnetic skyrmions in hybrid ferromagnetic films harbors novel physical phenomena and holds promise for technological applications. In this work, we discuss the behavior of magnetic skyrmions when coupled to superconducting vortices in a ferromagnet-superconductor heterostructure. We use numerical simulations and analytic arguments to reveal broader possibilities for manipulating the skyrmion-vortex dynamic correlations in the hybrid system, that are not possible in its separated constituents. We explore the thresholds of particular dynamic phases, and quantify the phase diagram as a function of the relevant material parameters, applied current and induced magnetic torques. Finally, we demonstrate the broad and precise tunability of the skyrmion Hall-angle in presence of vortices, with respect to currents applied to either or both the superconductor and the ferromagnet within the heterostructure

Avaliação da qualidade do efluente gerado pelas ETE do Estado de Pernambuco em relação aos contaminantes emergentes.

Existem alguns compostos orgânicos presentes na água que ainda não são investigados pelas legislações ambientais brasileiras, mas que estão presentes mesmo em baixas concentrações (?g.L-1 ou ng.L-1) e causam efeitos adversos à saúde humana e dos animais, denominados contaminantes emergentes. Estes compostos são introduzidos no meio ambiente através de esgoto doméstico e efluentes de ETE. As classes de substâncias que são consideradas persistentes são: fármacos, produtos de cuidado pessoal e limpeza, interferentes endócrinos e subprodutos da desinfecção de água potável. O derramamento de esgoto sem tratamento é um grave problema ambiental, pois ocasiona poluição em rios, águas represadas, abastecimento de cidades e irrigação de plantações, e mesmo que as ETE disponham de diversas formas de tratamento, estas são insuficientes para garantir a ausência de poluição. Neste trabalho foi realizado um monitoramento em quatro estações de tratamento de esgoto (ETE) da Região Metropolitana do Recife, a saber: Caçote, Mangueira, Jardim Paulista e Cabanga. Foram quantificados cinco contaminantes classificados como interferentes endócrinos, foram selecionados para quantificação: progesterona e 17?-etinilestradiol (hormônios), dibutilftalato e dietilfitalato (plastificantes) e nonilfenol (surfactantes). Para a identificação e quantificação foi empregado LC/MS-MS de alta resolução e os dados tratados por análise por componentes principais e constatado a ineficiência da remoção dos micropoluentes do tratamento empregado pelas estações de tratamento de esgoto estudadas