1,273 research outputs found

    1.3 mm Polarized emission in the circumstellar disk of a massive protostar

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    We present the first resolved observations of the 1.3 mm polarized emission from the disk-like structure surrounding the high-mass protostar Cepheus A HW2. These CARMA data partially resolve the dust polarization, suggesting a uniform morphology of polarization vectors with an average position angle of 57° ± 6° and an average polarization fraction of 2.0% ± 0.4%. The distribution of the polarization vectors can be attributed to (1) the direct emission of magnetically aligned grains of dust by a uniform magnetic field, or (2) the pattern produced by the scattering of an inclined disk. We show that both models can explain the observations, and perhaps a combination of the two mechanisms produces the polarized emission. A third model including a toroidal magnetic field does not match the observations. Assuming scattering is the polarization mechanism, these observations suggest that during the first few 104 years of high-mass star formation, grain sizes can grow from1 mm to several 10s μm.Fil: Fernandez Lopez, Manuel. Provincia de Buenos Aires. Gobernación. Comision de Investigaciones Científicas. Instituto Argentino de Radioastronomía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Argentino de Radioastronomia; ArgentinaFil: Stephens, I. W.. Harvard-Smithsonian Center for Astrophysics; Estados Unidos. Boston University; Estados Unidos. University of Illinois; Estados UnidosFil: Girart, J. M.. Harvard-Smithsonian Center for Astrophysics; Estados Unidos. Institut de Ciències de l’Espai; EspañaFil: Looney, L.. University of Illinois; Estados UnidosFil: Curiel, S.. Universidad Nacional Autónoma de México; MéxicoFil: Segura Cox, D.. University of Illinois; Estados UnidosFil: Eswaraiah, C.. National Tsing Hua University; República de ChinaFil: Lai, S. P.. National Tsing Hua University; República de Chin

    Multi-filter transit observations of WASP-39b and WASP-43b with three San Pedro M\'artir telescopes

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    Three optical telescopes located at the San Pedro M\'artir National Observatory were used for the first time to obtain multi-filter defocused photometry of the transiting extrasolar planets WASP-39b and WASP-43b. We observed WASP-39b with the 2.12m telescope in the U filter for the first time, and additional observations were carried out in the R and I filters using the 0.84m telescope. WASP-43b was observed in VRI with the same instrument, and in the i filter with the robotic 1.50m telescope. We reduced the data using different pipelines and performed aperture photometry with the help of custom routines, in order to obtain the light curves. The fit of the light curves (1.5--2.5mmag rms), and of the period analysis, allowed a revision of the orbital and physical parameters, revealing for WASP-39b a period (4.0552947±9.65×1074.0552947 \pm 9.65 \times 10^{-7} days) which is 3.084±0.7743.084 \pm 0.774 seconds larger than previously reported. Moreover, we find for WASP-43b a planet/star radius (0.1738±0.00330.1738 \pm 0.0033) which is 0.01637±0.003710.01637 \pm 0.00371 larger in the i filter with respect to previous works, and that should be confirmed with additional observations. Finally, we confirm no evidence of constant period variations in WASP-43b.Comment: 13 pages, 7 figures, accepted in PASP, scheduled for the February 1, 2015 issu

    Multiple Sources toward the High-mass Young Star S140 IRS1

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    S140 IRS1 is a remarkable source where the radio source at the center of the main bipolar molecular outflow in the region is elongated perpendicular to the axis of the outflow, an orientation opposite to that expected if the radio source is a thermal jet exciting the outflow. We present results of 1.3 cm continuum and H2O maser emission observations made with the VLA in its A configuration toward this region. In addition, we also present results of continuum observations at 7 mm and re-analyse observations at 2, 3.5 and 6 cm (previously published). IRS 1A is detected at all wavelengths, showing an elongated structure. Three water maser spots are detected along the major axis of the radio source IRS 1A. We have also detected a new continuum source at 3.5 cm (IRS 1C) located ~0.6'' northeast of IRS 1A. The presence of these two YSOs (IRS 1A and 1C) could explain the existence of the two bipolar molecular outflows observed in the region. In addition, we have also detected three continuum clumps (IRS 1B, 1D and 1E) located along the major axis of IRS 1A. We discuss two possible models to explain the nature of IRS 1A: a thermal jet and an equatorial wind.Comment: 17 pages, 4 figures, to be published in A

    Isomeric carbazolocarbazoles: synthesis, characterization and comparative study in Organic Field Effect Transistors

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    We report here the synthesis and characterization of a new family of isomeric carbazolocarbazole derivatives, namely carbazolo[1,2-a]carbazole, carbazolo[3,2-b]carbazoleand carbazolo[4,3-c]carbazole. Thermal, optical, electrochemical, morphological and semiconducting properties have been studied to understand the influence of geometrical isomerism on the optoelectronic properties of these compounds. Different packing patterns have been observed by single crystal X-ray diffraction (XRD) which then correlate with the different morphologies of the evaporated thin films studied by XRD and Atomic Force Microscopy (AFM). The effect of N-substituents has also been evaluated for one of the isomers revealing a noticeable influence on the performance as organic semiconductors in Organic Field Effect Transistors (OFETs). A good p-channel field effect has been determined for N,N′-dioctylcarbazolo[4,3-c]carbazole with a mobility of 0.02 cm2 V−1 s−1 and Ion/Ioff ratio of 106 in air. These preliminary results demonstrate the promising properties of molecular carbazolocarbazole systems which should be further explored in the area of organic semiconducting materials

    Cascading effects associated with climate-change-induced conifer mortality in mountain temperate forests result in hot-spots of soil CO 2 emissions

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    Climate change-induced tree mortality is occurring worldwide, at increasingly larger scales and with increasing frequency. How climate change-induced tree mortality could affect the ecology and carbon (C) sink capacity of soils remains unknown. This study investigated regional-scale drought-induced tree mortality, based on events that occurred after a very dry year (2012) in the Carpathians mountain range (Romania), which caused mortality in three common conifer species: Scots pine, Black pine, and Silver fir. This resulted in hot-spots of biogenic soil CO 2 emissions (soil respiration; Rs). Four to five years after the main mortality event, Rs-related soil CO 2 emissions under dead trees were, on average, 21% (ranging from 18 to 35%) higher than CO 2 emissions under living trees. Total (Rs) and heterotrophic (R H )-related soil CO 2 emissions were strongly related to alterations in the soil environment following tree mortality (e.g. changes in quantity and quality of soil organic matter, microclimate, pH or fine root demography). Moreover, the massive mortality event of 2012 resulted in greater presence of successional vegetation (broadleaf seedlings, shrubland and grasses), which may control the environmental factors that either directly or indirectly affected biotic soil fluxes (Rs and R H ). Besides the well-known direct effects of climate change on soil CO 2 emissions, the cascading effects triggered by climate change-induced tree mortality could also exert a strong indirect impact on soil CO 2 emissions. Overall, climate change-induced tree mortality alters the magnitude of environmental controls on Rs and hence determines how the ecosystem C budget responds to climate change. © 2019 Elsevier LtdThis work was supported by the Spanish Ministry of Economy and Competitiveness (MINECO) with the projects VERONICA ( CGL2013-42271-P ) and the project IBERYCA ( CGL2017-84723-P ), and by the Romanian Ministry of Education and Scientific Research through UEFISCDI with the projects TREEMORIS ( PN-II-RU-TE-2014-4-0791 ), NATIvE ( PN-III-P1-1.1-PD-2016-0583 ), and BIOCARB ( PN-III-P1-1.1-TE-2016-1508 ). This research was also supported by the Basque Government through the BERC 2018-2021 program, and by the Spanish Ministry of Economy and Competitiveness (MINECO) through the BC3 María de Maeztu excellence accreditation ( MDM-2017-0714 ). I.C. Petritan was partially funded by the H2020/ERA-NET/ERA-GAS (Project 82/2017, Mobilizing and monitoring climate positive efforts in forests and forestry, FORCLIMIT ). Many thanks to Cosmin Zgremtia, Ionela Medrea, Andrei Apafaian, Raluca Enescu and Marta Ramos for their valuable help during field campaigns and laboratory work

    High resolution AMI Large Array imaging of spinning dust sources: spatially correlated 8 micron emission and evidence of a stellar wind in L675

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    We present 25 arcsecond resolution radio images of five Lynds Dark Nebulae (L675, L944, L1103, L1111 & L1246) at 16 GHz made with the Arcminute Microkelvin Imager (AMI) Large Array. These objects were previously observed with the AMI Small Array to have an excess of emission at microwave frequencies relative to lower frequency radio data. In L675 we find a flat spectrum compact radio counterpart to the 850 micron emission seen with SCUBA and suggest that it is cm-wave emission from a previously unknown deeply embedded young protostar. In the case of L1246 the cm-wave emission is spatially correlated with 8 micron emission seen with Spitzer. Since the MIR emission is present only in Spitzer band 4 we suggest that it arises from a population of PAH molecules, which also give rise to the cm-wave emission through spinning dust emission.Comment: accepted MNRA

    Peculiarities of the function of cardiomyocytes in patients with ischemic heart disease associated with diabetes mellitus type 2

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    The functional activity of myocardium in patients with type 2 diabetes mellitus(T2DM) and coronary heart disease (CAD) was studied. The study included patients with CAD with T2DM as representatives of the main group, the comparison group consisted of patients with univariant course of ischemic heart disease without violation of carbohydrate metabolism. Contractile activity of the myocardium was evaluated by the inotroic reaction of isolated trabeculae of patients according to the Protocol tests "Post-rest" and "Ekstrasistoliei test". As a result, it was found that rhythm-inotropic myocardial response in patients with comorbid pathology persists to a greater extent than in the one-dimensional flow of CAD

    Effects of Supersymmetric Threshold Corrections on High-Scale Flavor Textures

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    Integration of superpartners out of the spectrum induces potentially large contributions to Yukawa couplings. These corrections, the supersymmetric threshold corrections, therefore influence the CKM matrix prediction in a non-trivial way. We study effects of threshold corrections on high-scale flavor structures specified at the gauge coupling unification scale in supersymmetry. In our analysis, we first consider high-scale Yukawa textures which qualify phenomenologically viable at tree level, and find that they get completely disqualified after incorporating the threshold corrections. Next, we consider Yukawa couplings, such as those with five texture zeroes, which are incapable of explaining flavor-changing proceses. Incorporation of threshold corrections, however, makes them phenomenologically viable textures. Therefore, supersymmetric threshold corrections are found to leave observable impact on Yukawa couplings of quarks, and any confrontation of high-scale textures with experiments at the weak scale must take into account such corrections.Comment: 25 pages, submitted to JHE
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