A close encounter of the massive kind

We have used (a) HST ACS imaging and STIS spectroscopy, (b) ground-basedPIONIER/VLT long-baseline interferometry, and (c) ground-basedspectroscopy from different instruments to study the orbit of theextreme multiple system HD 93 129 Aa,Ab, which is composed of (at least)two very massive stars in a long-period orbit with e>0.92 that willpass through periastron in 2017/2018. In several ways, the system is aneta Car precursor. Around the time of periastron passage the two verystrong winds will collide and generate an outburst of non-thermal hardX-ray emission without precedent in an O+O binary since astronomers havebeen able to observe above Earth's atmosphere. A coordinatedmultiwavelength monitoring in the next two years will enable abreakthrough understanding of the wind interactions in such extremeclose encounters. Furthermore, we have found evidence that HD 93 129 Aamay be a binary system itself. In that case, we could witness athree-body interaction that may yield a runaway star or a stellarcollision close to or shortly after the periastron passage. Either ofthose outcomes would be unprecedented, as they are predicted to below-frequency events in the Milky Way.Instituto de Astrofísica de La Plat

A close encounter of the massive kind

We have used (a) HST ACS imaging and STIS spectroscopy, (b) ground-basedPIONIER/VLT long-baseline interferometry, and (c) ground-basedspectroscopy from different instruments to study the orbit of theextreme multiple system HD 93 129 Aa,Ab, which is composed of (at least)two very massive stars in a long-period orbit with e>0.92 that willpass through periastron in 2017/2018. In several ways, the system is aneta Car precursor. Around the time of periastron passage the two verystrong winds will collide and generate an outburst of non-thermal hardX-ray emission without precedent in an O+O binary since astronomers havebeen able to observe above Earth's atmosphere. A coordinatedmultiwavelength monitoring in the next two years will enable abreakthrough understanding of the wind interactions in such extremeclose encounters. Furthermore, we have found evidence that HD 93 129 Aamay be a binary system itself. In that case, we could witness athree-body interaction that may yield a runaway star or a stellarcollision close to or shortly after the periastron passage. Either ofthose outcomes would be unprecedented, as they are predicted to below-frequency events in the Milky Way.Instituto de Astrofísica de La Plat

Mid-infrared spectroscopic analysis of chemically bound metalcasting sands

Foundries around the world discard millions of tonnes of molding and core sand each year even though they can be beneficially used in manufactured soils and geotechnical applications. Despite their usefulness as an aggregate replacement, some environmental authorities are concerned over potential negative impacts associated with residual organic binders in waste foundry sands (WFSs). In this study, chemically bound molding and core sands were obtained from aluminum, bronze and iron foundries that used alkyd urethane, phenolic urethane, Novolac, and natural organic binders. The aim was to use mid-infrared (MIR) spectrometry to assess changes within the molding and core sands during the casting process, with a specific focus on proximity to the casting interface and casting temperature. In addition, the MIR spectra were compared to total carbon concentrations in the sands. Bands associated with C-H stretching were detected in most WFSs. The MIR spectra and total carbon data demonstrated that casting temperature and proximity of the sand to the molten metal contributed to various levels of thermal degradation of the organic binders. Our results also provided preliminary evidence that MIR spectroscopy could be used to identify WFSs with less residual binder

Informality, Inequality and ICT in Transition economies

In this paper, we examine the role of the quality of institutional infrastructure and information and communication technology (ICT) in the relationship between the size of the informal sector (IS) and income inequality. Following our results, the sign of the relationship between IS and income inequality depends on the quality of institutions. When institutions are weak, agents invest less human capital and ICT in the formal sector (FS), thereby reducing income inequality. Utilizing panel data for sixteen transition countries we show that the relationship between the size of the IS and the level of income inequality is ambiguous. Our findings highlight the problem of measuring the relative size of the IS which is a hidden entity. We control for robustness of our findings using alternative proxies of ICT, human capital, and institutional quality and some interaction terms among these variables

Weight change measurements of erosion/deposition at beryllium limiter tiles in ISX-B

The weight changes of Be tiles which functioned as a rail limiter in ISX-B for more than 3500 beam-heated discharges have been determined. The net weight loss for the limiter was 2.0 g, with the central tiles losing a total of 3.2 g and inboard tiles gaining 1.2 g. The weight loss is attributed primarily to the release of Be droplets as a result of limiter surface melting. The weight gains resulted from an inward flow of molten material along the limiter surface. The results indicate high erosion (melt loss) with incomplete and nonuniform redeposition (melt flow) of limiter material during periods of limiter melting

Black Rings in Taub-NUT and D0-D6 interactions

We analyze the dynamics of neutral black rings in Taub-NUT spaces and their relation to systems of D0 and D6 branes in the supergravity approximation. We employ several recent techniques, both perturbative and exact, to construct solutions in which thermal excitations of the D0-branes can be turned on or off, and the D6-brane can have $B$-fluxes turned on or off in its worldvolume. By explicit calculation of the interaction energy between the D0 and D6 branes, we can study equilibrium configurations and their stability. We find that although D0 and D6 branes (in the absence of $B$ fields, and at zero temperature) repeal each other at non-zero separation, as they get together they go over continuosly to an unstable bound state of an extremal singular Kaluza-Klein black hole. We also find that, for $B$-fields larger than a critical value, or sufficiently large thermal excitation, the D0 and D6 branes form stable bound states. The bound states with thermally excited D0 branes are black rings in Taub-NUT, and we provide an analysis of their phase diagram.Comment: 50 pages, 8 figures; v3: minor changes and references added; v4: improved figs. 7 and 8, matches with published versio

In vitro development of primordial follicles after long-term culture of goat ovarian tissue

This study aims to investigate the effects of follicle stimulating hormone (FSH) and fibroblast growth factor-2 (FGF-2) on the survival and growth of caprine preantral follicles. Ovarian tissues were cultured for 1, 7, 14, 21 or 28 days in medium supplemented with FSH (FSH-2d or FSH-7d, i.e., with replacement of the culture medium every 2 or 7 days, respectively) or FSH + FGF-2 (replacement of the medium every 2 days). Non-cultured (control) and cultured ovarian fragments were processed for histological and ultrastructural analysis. After 28 days of culture, the media supplemented with FSH-2d was the most effective in maintaining the percentage of normal follicles and in promoting follicular growth. Furthermore, both treatments with FSH increased the percentage of the primary follicles. However, ultrastructural studies did not confirm follicular integrity from 14 days of culture onward. In conclusion, culturing tissue for up to 7 days in medium containing FSH alone or combined with FGF-2 maintains caprine preantral follicle integrity and promotes their growth in vitro

Universality and scaling study of the critical behavior of the two-dimensional Blume-Capel model in short-time dynamics

In this paper we study the short-time behavior of the Blume-Capel model at the tricritical point as well as along the second order critical line. Dynamic and static exponents are estimated by exploring scaling relations for the magnetization and its moments at early stage of the dynamic evolution. Our estimates for the dynamic exponents, at the tricritical point, are $z= 2.215(2)$ and $\theta= -0.53(2)$.Comment: 12 pages, 9 figure