Formation of X-ray emitting stationary shocks in magnetized protostellar jets

X-ray observations of protostellar jets show evidence of strong shocks heating the plasma up to temperatures of a few million degrees. In some cases, the shocked features appear to be stationary. They are interpreted as shock diamonds. We aim at investigating the physics that guides the formation of X-ray emitting stationary shocks in protostellar jets, the role of the magnetic field in determining the location, stability, and detectability in X-rays of these shocks, and the physical properties of the shocked plasma. We performed a set of 2.5-dimensional magnetohydrodynamic numerical simulations modelling supersonic jets ramming into a magnetized medium and explored different configurations of the magnetic field. The model takes into account the most relevant physical effects, namely thermal conduction and radiative losses. We compared the model results with observations, via the emission measure and the X-ray luminosity synthesized from the simulations. Our model explains the formation of X-ray emitting stationary shocks in a natural way. The magnetic field collimates the plasma at the base of the jet and forms there a magnetic nozzle. After an initial transient, the nozzle leads to the formation of a shock diamond at its exit which is stationary over the time covered by the simulations (~ 40 - 60 yr; comparable with time scales of the observations). The shock generates a point-like X-ray source located close to the base of the jet with luminosity comparable with that inferred from X-ray observations of protostellar jets. For the range of parameters explored, the evolution of the post-shock plasma is dominated by the radiative cooling, whereas the thermal conduction slightly affects the structure of the shock.Comment: Accepted for publication in Astronomy and Astrophysic

Pathway Weathering in Granitoid Rocks from Central Region of Angola: Geochemical and Mineralogical Data

The Central Region of Angola is characterized by the abundance of granitoid rocks, whose weathering “in situ” originated the so-called residual soils. The textural, geochemical and mineralogical properties of these soils depend not only on the chemical composition of parent rock, but mainly on the local climatic and geomorphological characteristics. In the study area, sampling sites were selected, which extend from the region of Kwanza- Norte (Kassenda, Dondo) through Kwanza-Sul (Cangulo, Quibala and Waco Kungo) until the plateau of Huambo, where samples of fresh rock, weathered rock and its residual soil were collected along each weathering profile. Chemical analytical data were determined using X-ray fluorescence (XRF) analysis of the major and minor elements, whereas mineralogical data were determined using X-ray diffraction (XRD), on the samples of rock and on the respective residual soil. The results obtained and their comparative analysis between the sampling sites, as well as along each weathering profile is presented. This paper allows contributing to the knowledge of the geochemical weathering in tropical areas, as is the case of Angola

Quality of board members’ training and bank financial performance : evidence from Portugal

This study examines the impact of the quality of board members’ training on the financial performance of Portuguese banks. The study employs a sample of 276 board members. Financial ratios such as return on average assets (ROAA) and return on average equity (ROAE) are used as measures for gauging banks’ financial performance. Three indexes are used as proxies for board members’ educational qualifications, specifically: Eduindex, for all academic qualifications obtained in areas such as business or economics; EduindexDP, for all qualifications obtained in prestigious domestic business schools; and EduindexFP, for all qualifications obtained in prestigious foreign business schools. The study findings have important policy implications, specifically a positive and significant impact on the bank’s financial performance from having board members holding degrees from prestigious foreign business schools. In particular, the findings suggest that the prudential supervision developed by Banco de Portugal in cooperation with the European Central Bank should include a more rigorous process in the selection of board members. The present study is one of the first attempts in the literature emphasizing all these aspects simultaneously, that is, the banking sector, quality of board members’ training, and Eduniversal Rankings, in the context in which all the banks of a specific country are analysed.peer-reviewe

Quality of board members’ training and bank financial performance: evidence from Portugal

This study examines the impact of the quality of board members’ training on the financial performance of Portuguese banks. The study employs a sample of 276 board members. Financial ratios such as return on average assets (ROAA) and return on average equity (ROAE) are used as measures for gauging banks’ financial performance. Three indexes are used as proxies for board members’ educational qualifications, specifically: Eduindex, for all academic qualifications obtained in areas such as business or economics; EduindexDP, for all qualifications obtained in prestigious domestic business schools; and EduindexFP, for all qualifications obtained in prestigious foreign business schools. The study findings have important policy implications, specifically a positive and significant impact on the bank’s financial performance from having board members holding degrees from prestigious foreign business schools. In particular, the findings suggest that the prudential supervision developed by Banco de Portugal in cooperation with the European Central Bank should include a more rigorous process in the selection of board members. The present study is one of the first attempts in the literature emphasizing all these aspects simultaneously, that is, the banking sector, quality of board members’ training, and Eduniversal Rankings, in the context in which all the banks of a specific country are analysed. © 2018 International Strategic Management Association.info:eu-repo/semantics/publishedVersio

Fungal Endophytes of Populus trichocarpa Alter Host Phenotype, Gene Expression, and Rhizobiome Composition.

Mortierella and Ilyonectria genera include common species of soil fungi that are frequently detected as root endophytes in many plants, including Populus spp. However, the ecological roles of these and other endophytic fungi with respect to plant growth and function are still not well understood. The functional ecology of two key taxa from the P. trichocarpa rhizobiome, M. elongata PMI93 and I. europaea PMI82, was studied by coupling forest soil bioassays with environmental metatranscriptomics. Using soil bioassay experiments amended with fungal inoculants, M. elongata was observed to promote the growth of P. trichocarpa. This response was cultivar independent. In contrast, I. europaea had no visible effect on P. trichocarpa growth. Metatranscriptomic studies revealed that these fungi impacted rhizophytic and endophytic activities in P. trichocarpa and induced shifts in soil and root microbial communities. Differential expression of core genes in P. trichocarpa roots was observed in response to both fungal species. Expression of P. trichocarpa genes for lipid signaling and nutrient uptake were upregulated, and expression of genes associated with gibberellin signaling were altered in plants inoculated with M. elongata, but not I. europaea. Upregulation of genes for growth promotion, downregulation of genes for several leucine-rich repeat receptor kinases, and alteration of expression of genes associated with plant defense responses (e.g., jasmonic acid, salicylic acid, and ethylene signal pathways) also suggest that M. elongata manipulates plant defenses while promoting plant growth

Positive approximations of the inverse of fractional powers of SPD M-matrices

This study is motivated by the recent development in the fractional calculus and its applications. During last few years, several different techniques are proposed to localize the nonlocal fractional diffusion operator. They are based on transformation of the original problem to a local elliptic or pseudoparabolic problem, or to an integral representation of the solution, thus increasing the dimension of the computational domain. More recently, an alternative approach aimed at reducing the computational complexity was developed. The linear algebraic system $\cal A^\alpha \bf u=\bf f$, $0< \alpha <1$ is considered, where $\cal A$ is a properly normalized (scalded) symmetric and positive definite matrix obtained from finite element or finite difference approximation of second order elliptic problems in $\Omega\subset\mathbb{R}^d$, $d=1,2,3$. The method is based on best uniform rational approximations (BURA) of the function $t^{\beta-\alpha}$ for $0 < t \le 1$ and natural $\beta$. The maximum principles are among the major qualitative properties of linear elliptic operators/PDEs. In many studies and applications, it is important that such properties are preserved by the selected numerical solution method. In this paper we present and analyze the properties of positive approximations of $\cal A^{-\alpha}$ obtained by the BURA technique. Sufficient conditions for positiveness are proven, complemented by sharp error estimates. The theoretical results are supported by representative numerical tests

Alteração de Rochas Granitóides em Angola.

A Região Central de Angola caracteriza-se pela abundância de rochas granitóides, cuja alteração “in-situ” originou os denominados solos residuais. As propriedades texturais, geoquímicas e mineralógicas destes solos dependem não só da composição química da rocha mãe, mas principalmente das características geomorfológicas e climatéricas locais. Na região em estudo, seleccionaram-se locais de amostragem, que se estendem desde a província do Kwanza-Norte (Kassenda, no Alto Dondo), passando pela província do Kwanza-Sul (Cangulo, Quibala e Waco Kungo), até ao Planalto do Huambo, onde se colheram amostras de rocha sã, rocha alterada e respectivo solo residual, ao longo de cada perfil de alteração. Realizaram-se análises de caracterização geoquímica por Fluorescência de Raios-X dos elementos maiores e menores, e de caracterização mineralógica por Difracção de Raios–X, tanto nas amostras de rocha sã, como no respectivo solo residual. Apresentam-se os resultados obtidos e a sua análise comparativa entre os diferentes locais de amostragem, assim como ao longo de cada perfil de alteração. Os resultados obtidos permitem contribuir para o conhecimento dos fenómenos de alteração geoquímica em zonas tropicais, como é o caso de Angola

Importância dos Dispositivos Eletrónicos Cardíacos Implantáveis no Diagnóstico da Síndrome da Apneia do Sono

Introduction: Sleep Apnea Syndrome (SAS) is a prevalent respiratory disease with marked expression in the population with cardiovascular disease. The diagnosis is based on polysomnography. In patients with cardiac implantable electronic devices (CIED), the prevalence of SAS may reach 60%. The objective of this study was to evaluate the value of DEC in the SAS screening. Methods: Prospective study that included patients with CIED with sleep apnea algorithm. The frequency response function was activated and simplified polygraphy was performed. The data of the device were collected on the day of the polygraph. Results: The sample included 29 patients, with a mean age of 76.1 years, 71.4% of the male gender. The prevalence of SAS was 77%. For SAS, the agreement between polysomnography and the Pacemaker was Kappa = 0.54 (p = 0.001), 95% CI (0.28, 0.81) (moderate agreement); for moderate to severe SAS, the agreement was Kappa = 0.73 (p <0.001), 95% CI (0.49, 0.976) (substantial agreement). Severe SAS was obtained: sensitivity 60%, specificity 100%, positive predictive value 100%, negative predictive value 60% and diagnostic accuracy 75%; for moderate to severe SAS: sensitivity of 90%, specificity of 83%, positive predictive values of 90% and negative of 87.5%, with a diagnostic accuracy of 87.5%. Conclusion: SAS is highly prevalent in patients with CIED. The values obtained through these devices have a strong positive correlation with the Apnea-Hypopnea Índex, which makes them a good tool for the screening of severe SAS.info:eu-repo/semantics/publishedVersio

The Gaia-ESO Survey: membership and Initial Mass Function of the Gamma Velorum cluster

Understanding the properties of young open clusters, such as the Initial Mass Function (IMF), star formation history and dynamic evolution, is crucial to obtain reliable theoretical predictions of the mechanisms involved in the star formation process. We want to obtain a list, as complete as possible, of confirmed members of the young open cluster Gamma Velorum, with the aim of deriving general cluster properties such as the IMF. We used all available spectroscopic membership indicators within the Gaia-ESO public archive together with literature photometry and X-ray data and, for each method, we derived the most complete list of candidate cluster members. Then, we considered photometry, gravity and radial velocities as necessary conditions to select a subsample of candidates whose membership was confirmed by using the lithium and H$\alpha$ lines and X-rays as youth indicators. We found 242 confirmed and 4 possible cluster members for which we derived masses using very recent stellar evolutionary models. The cluster IMF in the mass range investigated in this study shows a slope of $\alpha=2.6\pm0.5$ for $0.5<M/M_\odot <1.3$ and $\alpha=1.1\pm0.4$ for $0.16<M/M_\odot <0.5$ and is consistent with a standard IMF. The similarity of the IMF of the young population around $\gamma^2$Vel to that in other star forming regions and the field suggests it may have formed through very similar processes.Comment: Accepted for publication in A&A; 18 pages, 11 figures, 5 table

The Gaia-ESO Survey: Chromospheric Emission, Accretion Properties, and Rotation in γ\gamma Velorum and Chamaeleon I

We use the fundamental parameters delivered by the GES consortium in the first internal data release to select the members of $\gamma$ Vel and Cha I among the UVES and GIRAFFE spectroscopic observations. A total of 140 $\gamma$ Vel members and 74 Cha I members were studied. We calculated stellar luminosities through spectral energy distributions, while stellar masses were derived by comparison with evolutionary tracks. The spectral subtraction of low-activity and slowly rotating templates, which are rotationally broadened to match the $v\sin i$ of the targets, enabled us to measure the equivalent widths (EWs) and the fluxes in the H$\alpha$ and H$\beta$ lines. The H$\alpha$ line was also used for identifying accreting objects and for evaluating the mass accretion rate ($\dot M_{\rm acc}$). The distribution of $v\sin i$ for the members of $\gamma$ Vel displays a peak at about 10 km s$^{-1}$ with a tail toward faster rotators. There is also some indication of a different $v\sin i$ distribution for the members of its two kinematical populations. Only a handful of stars in $\gamma$ Vel display signatures of accretion, while many more accretors were detected in the younger Cha~I. Accreting and active stars occupy two different regions in a $T_{\rm eff}$-flux diagram and we propose a criterion for distinguishing them. We derive $\dot M_{\rm acc}$ in the ranges $10^{-11}$-$10^{-9} M_\odot$yr$^{-1}$ and $10^{-10}$-$10^{-7} M_\odot$yr$^{-1}$ for $\gamma$ Vel and Cha I accretors, respectively. We find less scatter in the $\dot M_{\rm acc}-M_\star$ relation derived through the H$\alpha$ EWs, when compared to the H$\alpha$ $10\%W$ diagnostics, in agreement with other authors