Supernova (SN) 2016bdu is an unusual transient resembling SN 2009ip. SN 2009ip-like events are characterized by a long-lasting phase of erratic variability that ends with two luminous outbursts a few weeks apart. The second outburst is significantly more luminous (about 3 mag) than the first. In the case of SN 2016bdu, the first outburst (Event A) reached an absolute magnitude M-r approximate to -15.3 mag, while the second one (Event B) occurred over one month later and reached M-r approximate to -18 mag. By inspecting archival data, a faint source at the position of SN 2016bdu is several times in the past few years. We interpret these detections as signatures of a phase of erratic variability, similar to that experienced by SN 2009ip between 2008 and mid-2012, and resembling the currently observed variability of the luminous blue variable SN 2000ch in NGC 3432. Spectroscopic monitoring of SN 2016bdu during the second peak initially shows features typical of an SN IIn. One month after the Event B maximum, the spectra develop broad Balmer lines with P Cygni profiles and broad metal features. At these late phases, the spectra resemble those of a typical Type II SN. All members of this SN 2009ip-like group are remarkably similar to the Type IIn SN 2005gl. For this object, the claim of a terminal SN explosion is supported by the disappearance of the progenitor star. While the similarity with SN 2005gl supports a genuine SN explosion scenario for SN 2009ip-like events, the unequivocal detection of nucleosynthesized elements in their nebular spectra is still missing.

We present a systematic study of mid-infrared emission from 141 nearby supernovae (SNe). observed with Spitzer/IRAC as part of the ongoing SPIRITS survey. We detect 8 Type Ia and 36 core-collapse SNe. All Type. Ia/Ibc SNe. become undetectable within three. years of explosion, whereas 22 +/- 11% of Type. II SNe. continue to be detected. Five Type. II SNe are detected even two decades after discovery (SN 1974E, 1979C, 1980K, 1986J, and 1993J). Warm dust luminosity, temperature, and a lower limit on mass are obtained by fitting the two IRAC bands, assuming an optically thin dust shell. We derive warm dust masses between 10(-6) and 10(-2) M-circle dot and dust color temperatures between 200 and 1280 K. This observed warm dust could be pre-existing or newly created, but in either case represents a lower limit to the dust mass because cooler dust may be present. We present three case studies of extreme SNe.. SN 2011ja (II-P) was over-luminous ([4.5] = -15.6 mag) at 900 days post explosion with increasing hot dust mass, suggesting either an episode of dust formation or intensifying circumstellar material (CSM) interactions heating up pre-existing dust. SN 2014bi (II-P) showed a factor of 10 decrease in dust mass over one month, suggesting either dust destruction or reduced dust heating. The IR luminosity of SN 2014C (Ib) stayed. constant over 800 days, possibly due to strong CSM interaction with an. H-rich shell, which is rare among stripped-envelope SNe. The observations suggest that this CSM shell originated from an LBV-like eruption roughly 100 years pre-explosion. The observed diversity demonstrates the power of mid-IR observations of a large sample of SNe.

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We present multi-wavelength observations of SN 2014C during the first 500 days. These observations represent the first solid detection of a young extragalactic stripped-envelope SN out to high-energy X-rays similar to 40 keV. SN 2014C shows ordinary explosion parameters (E-k similar to 1.8 x 10(51) erg and M-ej similar to 1.7M circle dot). However, over an similar to 1 year timescale, SN 2014C evolved from an ordinary hydrogen-poor supernova into a strongly interacting, hydrogen-rich supernova, violating the traditional classification scheme of type-I versus type-II SNe. Signatures of the SN shock interaction with a dense medium are observed across the spectrum, from radio to hard X-rays, and revealed the presence of a massive shell of similar to 1Me of hydrogen-rich material at similar to 6. x. 10(16) cm. The shell was ejected by the progenitor star in the decades to centuries before collapse. This result challenges current theories of massive star evolution, as it requires a physical mechanism responsible for the ejection of the deepest hydrogen layer of H-poor SN progenitors synchronized with the onset of stellar collapse. Theoretical investigations point at binary interactions and/or instabilities during the last nuclear burning stages as potential triggers of the highly time-dependent mass loss. We constrain these scenarios utilizing the sample of 183 SNe Ib/c with public radio observations. Our analysis identifies SN 2014C-like signatures in similar to 10% of SNe. This fraction is reasonably consistent with the expectation from the theory of recent envelope ejection due to binary evolution if the ejected material can survive in the close environment for 10(3)-10(4) years. Alternatively, nuclear burning instabilities extending to core C-burning might play a critical role.

We construct some new spaces determined by SN functions based on the classical SN theory.Also we have some new result in the densness of algebraic elements in a C* algebra.

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No description available.

Eletrocatalisadores de Pt-Sn suportados em carbono de elevada área superficial foram preparados por redução química de precursores metálicosm em solução usando como agente redutor o ácido fórmico. Esse método mostrou-se muito eficiente sendo possível obter tanto catalisadores com baixos teores de Sn (razão atômica Pt:Sn de 9:1) como com altos teores de Sn (razão atômica Pt:Sn de 1:3). Entretanto, apesar de ser o Sn reduzido e ancorado sobre o substrato de carbono apenas parte deste Sn é inserido na rede cristalina da Pt sendo necessário um tratamento térmico em atmosfera redutora para aumentar o grau de liga. Foram realizados tratamentos térmicos entre 100 e 500 ºC e o melhor desempenho na célula a combustível foi obtido com o material Pt3Sn tratado a 200 ºC. O tratamento térmico a 200ºC permitiu um incremento no grau de liga dos metais Pt e Sn sem modificar a estrutura cúbica de face centrada da Pt e sem promover a coalescência das nanopartículas ancoradas no suporte de carbono. Os materiais de Pt-Sn foram caracterizados através de difração de raios-X, absorção de raios-X e microscopia eletrônica de transmissão. A atividade para a eletro-oxidação de etanol foi avaliada através de técnicas eletroquímicas e experimentos em células a combustível unitárias. Para complementar o estudo da eletro-oxidação de etanol foram realizados estudos fundamentais usando monocristais de Pt com baixos e altos índices de Miller. / Carbon supported Pt-Sn catalysts were prepared by reduction of Pt and Sn precursors with formic acid. The method allowed the efficient preparation of catalysts with low Sn contents (Pt:Sn ratio 9:1) and with high Sn contents (Pt:Sn ratio 1:3. In spite of the fact that Sn was anchored in the material, only part of the Sn is inserted in the fcc structure of Pt. Therefore, a thermal treatment in a reducing atmosphere was necessary to increase the degree of alloy. Thermal treatments were done between 100 and 500 oC and the Pt3Sn material treated at 200 oC showed the best performance in a direct ethanol fuel cell. The thermal treatment at 200 oC allowed an increase of the degree of alloy without modifying the face centered cubic Pt structure and without promoting the coalescence of the nanoparticles anchored on the carbon support. The Pt-Sn catalysts were characterized by X-ray diffraction, X-ray absorption and transmission electron microscopy. The activity for the electro-oxidation of ethanol was evaluated with electrochemical techniques and experiments in a single direct ethanol fuel cell. Studies with Pt single crystals with low and high Miller indices were done to complement the study of the ethanol electro-oxidation.

Eletrocatalisadores de Pt-Sn suportados em carbono de elevada área superficial foram preparados por redução química de precursores metálicosm em solução usando como agente redutor o ácido fórmico. Esse método mostrou-se muito eficiente sendo possível obter tanto catalisadores com baixos teores de Sn (razão atômica Pt:Sn de 9:1) como com altos teores de Sn (razão atômica Pt:Sn de 1:3). Entretanto, apesar de ser o Sn reduzido e ancorado sobre o substrato de carbono apenas parte deste Sn é inserido na rede cristalina da Pt sendo necessário um tratamento térmico em atmosfera redutora para aumentar o grau de liga. Foram realizados tratamentos térmicos entre 100 e 500 ºC e o melhor desempenho na célula a combustível foi obtido com o material Pt3Sn tratado a 200 ºC. O tratamento térmico a 200ºC permitiu um incremento no grau de liga dos metais Pt e Sn sem modificar a estrutura cúbica de face centrada da Pt e sem promover a coalescência das nanopartículas ancoradas no suporte de carbono. Os materiais de Pt-Sn foram caracterizados através de difração de raios-X, absorção de raios-X e microscopia eletrônica de transmissão. A atividade para a eletro-oxidação de etanol foi avaliada através de técnicas eletroquímicas e experimentos em células a combustível unitárias. Para complementar o estudo da eletro-oxidação de etanol foram realizados estudos fundamentais usando monocristais de Pt com baixos e altos índices de Miller. / Carbon supported Pt-Sn catalysts were prepared by reduction of Pt and Sn precursors with formic acid. The method allowed the efficient preparation of catalysts with low Sn contents (Pt:Sn ratio 9:1) and with high Sn contents (Pt:Sn ratio 1:3. In spite of the fact that Sn was anchored in the material, only part of the Sn is inserted in the fcc structure of Pt. Therefore, a thermal treatment in a reducing atmosphere was necessary to increase the degree of alloy. Thermal treatments were done between 100 and 500 oC and the Pt3Sn material treated at 200 oC showed the best performance in a direct ethanol fuel cell. The thermal treatment at 200 oC allowed an increase of the degree of alloy without modifying the face centered cubic Pt structure and without promoting the coalescence of the nanoparticles anchored on the carbon support. The Pt-Sn catalysts were characterized by X-ray diffraction, X-ray absorption and transmission electron microscopy. The activity for the electro-oxidation of ethanol was evaluated with electrochemical techniques and experiments in a single direct ethanol fuel cell. Studies with Pt single crystals with low and high Miller indices were done to complement the study of the ethanol electro-oxidation.

In this study the effects of Sn content and isothermal transformation temperature on the ultimate tensile strength (UTS), elongation and hardness of austempered ductile cast iron (ADI) was investigated. To determine the possible effect of Sn on these properties the Sn content of standard GGG30, GGG40 and GGG50 materials were taken as reference, whose chemical compositions vary from 0,016 to 0,050% in terms of Sn. However the Sn content was increased to a maximum of 0,26% for investigating the effect of Sn on mechanical properties. The test specimens were obtained from standard 1-in Y-blocks and austenitized at 925oC for 1 hour and austempered at 350oC,375oC, 400oC and 420oC for 60 minutes in a salt bath. Microstructural examination of the specimens were also done. To determine the amount of retained austenite of the specimens X-Ray analyses were used. As a result of the study The UTS increases up to 0,1% Sn and then levels off. A similar behavior is observed in the variation of hardness. Percent elongation decreases and falls to a minimum around 0,1% Sn, from this point on, a slight increase is observed. Strength and hardness increase while percent elongation decreases with decreasing temperatures.