Phase conversion in a weakly first-order quark-hadron transition

We investigate the process of phase conversion in a thermally-driven {\it weakly} first-order quark-hadron transition. This scenario is physically appealing even if the nature of this transition in equilibrium proves to be a smooth crossover for vanishing baryonic chemical potential. We construct an effective potential by combining the equation of state obtained within Lattice QCD for the partonic sector with that of a gas of resonances in the hadronic phase, and present numerical results on bubble profiles, nucleation rates and time evolution, including the effects from reheating on the dynamics for different expansion scenarios. Our findings confirm the standard picture of a cosmological first-order transition, in which the process of phase conversion is entirely dominated by nucleation, also in the case of a weakly first-order transition. On the other hand, we show that, even for expansion rates much lower than those expected in high-energy heavy ion collisions, nucleation is very unlikely, indicating that the main mechanism of phase conversion is spinodal decomposition. Our results are compared to those obtained for a strongly first-order transition, as the one provided by the MIT bag model.Comment: 12 pages, 10 figures; v2: 1 reference added, minor modifications, matches published versio

The sdA problem - II. Photometric and Spectroscopic Follow-up

Subdwarf A star (sdA) is a spectral classification given to objects showing H-rich spectra and sub-main sequence surface gravities, but effective temperature lower than the zero-age horizontal branch. Their evolutionary origin is an enigma. In this work, we discuss the results of follow-up observations of selected sdAs. We obtained time resolved spectroscopy for 24 objects, and time-series photometry for another 19 objects. For two targets, we report both spectroscopy and photometry observations. We confirm seven objects to be new extremely-low mass white dwarfs (ELMs), one of which is a known eclipsing star. We also find the eighth member of the pulsating ELM class.Comment: Accepted for publication in MNRAS. 19 pages, 30 figures, 6 table

Nitrogen fluorescence in air for observing extensive air showers

Extensive air showers initiate the fluorescence emissions from nitrogen molecules in air. The UV-light is emitted isotropically and can be used for observing the longitudinal development of extensive air showers in the atmosphere over tenth of kilometers. This measurement technique is well-established since it is exploited for many decades by several cosmic ray experiments. However, a fundamental aspect of the air shower analyses is the description of the fluorescence emission in dependence on varying atmospheric conditions. Different fluorescence yields affect directly the energy scaling of air shower reconstruction. In order to explore the various details of the nitrogen fluorescence emission in air, a few experimental groups have been performing dedicated measurements over the last decade. Most of the measurements are now finished. These experimental groups have been discussing their techniques and results in a series of Air Fluorescence Workshops commenced in 2002. At the 8$^{\rm{th}}$ Air Fluorescence Workshop 2011, it was suggested to develop a common way of describing the nitrogen fluorescence for application to air shower observations. Here, first analyses for a common treatment of the major dependences of the emission procedure are presented. Aspects like the contributions at different wavelengths, the dependence on pressure as it is decreasing with increasing altitude in the atmosphere, the temperature dependence, in particular that of the collisional cross sections between molecules involved, and the collisional de-excitation by water vapor are discussed.Comment: 12 pages, 17 figures, 2 tables, International Symposium on Future Directions in UHECR Physics, 13-16 February 2012, CERN, Geneva (Switzerland); the updated version corrects for a typo in Eq. (1

From QCD lattice calculations to the equation of state of quark matter

We describe two-flavor QCD lattice data for the pressure at finite temperature and zero chemical potential within a quasiparticle model. Relying only on thermodynamic selfconsistency, the model is extended to nonzero chemical potential. The results agree with lattice calculations in the region of small chemical potential.Comment: 5 eps figure

Social Capital in Transition(s) to Early Adulthood: A Longitudinal and Mixed-Methods Approach

Social capital captures the value of relationships. Although research has examined social capital among adults, comparatively little attention has been paid to social capital among young adults—particularly from a longitudinal and mixed-methods perspective. As social capital predicts educational achievement, employment, and psychosocial well-being, it is an important construct to study alongside youth transition(s). Following a Bourdieusian approach, we define social capital as the resources potentially available in our ties that can be mobilized when necessary. To examine social capital in transition to adulthood, we draw on survey (n = 1,650, at ages 17 and 21) and interview (n = 70, at age 24) data from a cohort of Portuguese youth. We study the two main dimensions of social capital: bonding and bridging. Survey data were analyzed with latent class modeling, logistic regressions, and Wilcoxon signed-rank tests, and interviews with thematic analysis. Findings show that respondents reported receiving more emotional support than financial support from their networks, but that both types of support increased over time. Perceived bonding and bridging also changed positively in transition to adulthood. In addition, gender and parental education predicted bonding and bridging. We contextualize these results with qualitative meanings and experiences of social capital.The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This study was funded by the Portuguese Foundation for Science and Technology (2013-2015), Grant No. PTDC/IVCSOC/4943/2012

Recuperação de atributos físicos de um argissolo em função do seu revolvimento e do tempo de semeadura direta.

A melhoria da qualidade estrutural do solo pelo uso continuado do sistema semeadura direta ocorre junto com o processo de sua (re)acidificação. Em algumas circunstâncias, ocorre também compactação superficial devido ao tráfego de máquinas, que necessita ser corrigida pela mobilização do solo. Assim, em experimento conduzido há 12 anos sob diferentes sistemas de manejo do solo, avaliou-se o tempo necessário para o solo readquirir os atributos físicos iniciais, alterados no processo de revolvimento do solo, por ocasião da reaplicação de calcário. O experimento foi realizado na Estação Experimental Agronômica da UFRGS, em Eldorado do Sul - RS, em um Argissolo Vermelho distrófico típico. Os sistemas de manejo avaliados foram: (a) preparo convencional durante 12 anos, (b) sistema semeadura direta com revolvimento do solo para incorporar calcário a cada quatro anos, (c) sistema semeadura direta durante oito anos e (d) sistema semeadura direta durante 12 anos. Determinaram-se, imediatamente antes e 6, 12, 24, 36 e 48 meses depois da terceira reaplicação de calcário, a densidade, a porosidade total, a macroporosidade, a microporosidade, a estabilidade de agregados e o teor de C orgânico em três camadas (0,0-2,5; 2,5-7,5 e 7,5-15,0 cm) de solo. O revolvimento do solo para incorporação do calcário no sistema semeadura direta de quatro anos propiciou condições mais favoráveis de densidade e porosidade do solo, mas diminuiu a estabilidade de agregados. Houve necessidade de um período de quatro anos de cultivo do solo no sistema semeadura direta para o retorno da estabilidade de agregados à condição original. Os atributos físicos do solo foram mais uniformes no perfil no preparo convencional, porém com menor estabilidade de agregados na camada superficial, que foi relacionada ao teor de C orgânico

Formation of ions by high energy photons

We calculate the electron energy spectrum of ionization by a high energy photon, accompanied by creation of electron-positron pair. The total cross section of the process is also obtained. The asymptotics of the cross section does not depend on the photon energies. At the photon energies exceeding a certain value $\omega_0$ this appeares to to be the dominant mechanism of formation of the ions. The dependence of $\omega_0$ on the value of nuclear charge is obtained. Our results are consistent with experimental data.Comment: 16 pages, 6 figure

Diversidade genética entre acessos de Jatropha sp.

Uma das formas de identificação rápida de genótipos para composição de um banco de germoplasma é por meio da técnica de marcadores isoenzimáticos e moleculares. Com o objetivo de avaliar a variabilidade genética de acessos de Jatropha sp. Utilizou-se a técnica de marcadores isoenzimáticos e moleculares tipo RAPD. Foram utilizados 14 acessos de pinhão manso de diferentes origens, coletadas folhas jovens e procedido a extração (Isoenzimas) e purificação do DNA (RAPD). Para as isoenzimas a revelação foi feita para os sistemas enzimáticos álcool desidrogenase (ADH), esterase (EST), glutamato oxaloacetato transaminase (GOT) e peroxidase (PO), e na amplificação do DNA foram utilizados 14 oligonucleotídeos, sendo os produtos de amplificação separados em gel de agarose 0,8%, corados com brometo de etídio (0,5 µg/mL) e visualizados sob luz UV. As estimativas das similaridades genéticas (Sgij) entre cada par de genótipos foram calculadas pelo coeficiente de Jaccard usando o programa NTSYS-pc versão 2.1. Na análise de isoenzimas, os acessos mais similares foram 1 e 3, com 89% e o mais divergente foi o acesso 13 com 71%. No RAPD houve formação de grupos da espécie Jatropha curcas L. E do gênero Jatropha sp. O acesso 109 obteve 90% de divergência com os demais acessos. Os grupamentos formados apresentaram origens diversas, sendo possível um estudo de melhoramento visando características agronômicas desejáveis. Com os marcadores utilizados é possível a caracerização do banco de germoplasm