732 research outputs found

    Chandra Observation of the Interaction of the Radio Source and Cooling Core in Abell 2063

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    We present the results of a Chandra observation of the cooling core cluster Abell 2063. Spectral analysis shows that there is cool gas (2 keV) associated with the cluster core, which is more than a factor of 2 cooler than the outer cluster gas (4.1 keV). There also is spectral evidence for a weak cooling flow, Mdot ~ 20 Msun/yr. The cluster exhibits a complex structure in the center that consists of several bright knots of emission, a depression in the emission to the north of the center of the cluster, and a shell of emission surrounding it. The depression in the X-ray emission is coincident with the position of the north-eastern radio lobe of the radio source associated with the cluster-central galaxy. The shell surrounding this region appears to be hotter, which may be the result of a shock that has been driven into the gas by the radio source. The power output of the radio source appears to be sufficient to offset the cooling flow, and heating of the gas through shocks is a possible explanation of how the energy transfer is established.Comment: Astrophysical Jounal, in press, 26 page with 9 figures, some in color. Uses AASTEX late

    Alloying of Surface Layers of the Fuel Claddings from Sponge Based E110 Alloy to Increase High Temperature Oxidation Resistance

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    The results of experiments of parts of cladding tubes from sponge based zirconium E110 alloy near-surface layers doping by means of ion-plasma technologies are presented in this paper. Alloying of material by method of pre-deposited Fe, Y, Mo, Al, Mg, Cr films ion mixing is performed on installation ILUR-03 by means of radialAr+ion beam 3-4 keV average energy. State of modified material layer and oxides, grown on the modified samples in argon-water steam mixture at 1200 ∘C studied by scanning electron and ion microscopy methods, X-ray analysis and secondary ion mass spectroscopy. It is shown that treating modes defined contribute to the barrier for oxygen penetration and material oxidation formation near ion-doped surface

    The deep human prehistory of global tropical forests and its relevance for modern conservation

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    Significant human impacts on tropical forests have been considered the preserve of recent societies, linked to large-scale deforestation, resource mining, livestock grazing, and plantation industries. Cumulative archaeological evidence now demonstrates, however, that Homo sapiens has actively manipulated tropical forest ecologies for at least 45,000 years. It is clear that these millennia of impacts need to be taken into account when studying and conserving tropical forest ecosystems today. Nevertheless, archaeology has so far provided minimal practical insight into contemporary human-tropical forest interactions. Here, we review significant archaeological evidence for impacts of prehistoric hunter-gatherers, agriculturalists, and urban settlements on global tropical forests. We compare the challenges faced, as well as the solutions adopted, by these groups with those confronting present-day societies, which rely on tropical forests for ecosystem services, ranging from the maintenance of global carbon sinks to bioprospection for medicinal plants. We emphasise archaeology’s importance in not only promoting natural and cultural heritage in tropical forests, but also taking an active role in informing modern conservation and policy-making

    Behaviour of Ion-modified Cladding Tubes from E110 Alloy in High-temperature Water Steam

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    Beryllium materials are widely used in science and technology. They are of importance both for nuclear and thermonuclear energy applications. Additionally, metallic beryllium is transparent to x-ray radiation and used in the manufacture of X-ray windows and refractive x-ray lenses. SC “VNIINM” has developed beryllium materialsfor various purposes: for coating of the ITER’s first wall, for focusing and controlling X-ray radiation. Porous beryllium is of particular interest as it is an upcoming trend as a temper and neutron multiplier in blankets of thermonuclear facilities. A unique combination of X-ray optical properties also makes it possible to use porous beryllium in imaging devices in a synchrotron radiation beam (speckle suppressor)

    Thyroglossal duct cyst carcinoma

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    Not required for Clinical Vignette

    Origin and residence time of groundwater in the shallow coastal aquifer of eastern Dahomey Basin, Southwestern Nigeria, using δ18O and δD isotopes

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    This study employed stable isotopes of δ18O and δ2H in conjunction with other hydrological parameters to understand the origin, inferred residence time, and seasonal effect of groundwater in the shallow aquifers of the eastern Dahomey Basin. A total of 230 groundwater samples (97 in the wet season and 133 in the dry season) were collected from the borehole and shallow aquifer between May 2017 and April 2018. Groundwater analysis included major ions and δ18O and δ2H, isotopes data in precipitation from three selected Global Network of Isotope in Precipitation (GNIP) stations across West Africa, Douala in Cameroon, Cotonou in Republic of Benin, and Kano in Nigeria were used in comparative analysis. Results of the hydrochemical model revealed Ca-HCO3 and Na-Cl as dominant water types with other mixing water types such as Ca–SO4, Ca–Cl, Na–SO4, and K–Mg–HCO3, which characterised early stage of groundwater transformation as it infiltrates through vadose zone into the aquifer. δ18O and δ2H precipitation data from the three stations plotted along with the groundwater samples indicate recent meteoric water origin, with little effect of evaporation during the dry season. The plot of Total Dissolved Solids (TDS) against δ18O showed clustering of the water samples between the recharge and the evaporation zone with dry season samples trending towards increased TDS, which is an indication of the subtle effect of evaporation during this period. Tracing groundwater types along the flow paths within the basin is problematic and attributed to the heterogeneity of the aquifer with anthropogenic influences. Moreover, a comparison of the δ18O and δ2H isotopic compositions of groundwater and precipitation in the three selected stations, with their respective deuterium excess (D-excess) values established low evapotranspiration induced isotope enrichment, which could be due to higher precipitation and humidity in the region resulting in low isotope fractionation; hence, little effect of seasonal variations. The study, therefore, suggested groundwater recharge in the shallow aquifer in the eastern Dahomey Basin is of meteoric origin with a short residence time of water flows from soils through the vadose zone to the aquifers

    A study of algal establishment and growth in acid mine drainage (AMD) seeps and precipitation ponds : final report

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    Algae can frequently be found in acid mine drainage seeps. Their distribution in the waste water stream, however, is patchy. If present in high densities, and in the entire waste stream, algae could be utilized as polishing agents. In order to develop biological polishing systems, it is necessary to understand the factors controlling algal distributions

    Algal biopolishing of zinc : final report

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    Report examines the relationship between periphytic algae and the removal of zinc from waste water

    Alternans in Genetically Modified Langendorff-Perfused Murine Hearts Modeling Catecholaminergic Polymorphic Ventricular Tachycardia

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    The relationship between alternans and arrhythmogenicity was studied in genetically modified murine hearts modeling catecholaminergic polymorphic ventricular tachycardia (CPVT) during Langendorff perfusion, before and after treatment with catecholamines and a β-adrenergic antagonist. Heterozygous (RyR2p/s) and homozygous (RyR2s/s) RyR2-P2328S hearts, and wild-type (WT) controls, were studied before and after treatment with epinephrine (100 nM and 1 μM) and propranolol (100 nM). Monophasic action potential recordings demonstrated significantly greater incidences of arrhythmia in RyR2p/s and RyR2s/s hearts as compared to WTs. Arrhythmogenicity in RyR2s/s hearts was associated with alternans, particularly at short baseline cycle lengths. Both phenomena were significantly accentuated by treatment with epinephrine and significantly diminished by treatment with propranolol, in full agreement with clinical expectations. These changes took place, however, despite an absence of changes in mean action potential durations, ventricular effective refractory periods or restitution curve characteristics. Furthermore pooled data from all hearts in which arrhythmia occurred demonstrated significantly greater alternans magnitudes, but similar restitution curve slopes, to hearts that did not demonstrate arrhythmia. These findings thus further validate the RyR2-P2328S murine heart as a model for human CPVT, confirming an alternans phenotype in common with murine genetic models of the Brugada syndrome and the congenital long-QT syndrome type 3. In contrast to these latter similarities, however, this report demonstrates the dissociation of alternans from changes in the properties of restitution curves for the first time in a murine model of a human arrhythmic syndrome
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