排序方式: 共有16条查询结果,搜索用时 31 毫秒
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B Dilday DA Howell SB Cenko JM Silverman PE Nugent M Sullivan S Ben-Ami L Bildsten M Bolte M Endl AV Filippenko O Gnat A Horesh E Hsiao MM Kasliwal D Kirkman K Maguire GW Marcy K Moore Y Pan JT Parrent P Podsiadlowski RM Quimby A Sternberg N Suzuki DR Tytler D Xu JS Bloom A Gal-Yam IM Hook SR Kulkarni NM Law EO Ofek D Polishook D Poznanski 《Science (New York, N.Y.)》2012,337(6097):942-945
There is a consensus that type Ia supernovae (SNe Ia) arise from the thermonuclear explosion of white dwarf stars that accrete matter from a binary companion. However, direct observation of SN Ia progenitors is lacking, and the precise nature of the binary companion remains uncertain. A temporal series of high-resolution optical spectra of the SN Ia PTF 11kx reveals a complex circumstellar environment that provides an unprecedentedly detailed view of the progenitor system. Multiple shells of circumstellar material are detected, and the SN ejecta are seen to interact with circumstellar material starting 59 days after the explosion. These features are best described by a symbiotic nova progenitor, similar to RS Ophiuchi. 相似文献
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AV Pereira SA Pereira IDF Gremião MP Campos AMR Ferreira 《Australian veterinary journal》2012,90(11):448-450
This study compared the sensitivity of acetate tape impression and skin squeezing with that of deep skin scraping for the diagnosis of demodicosis in dogs. Demodex canis was detected in 100% of acetate tape impressions obtained after skin squeezing and in 90% of deep skin scrapings. There was a significant difference (P < 0.001) between the techniques in the total number of mites detected. Acetate tape impression with skin squeezing was found to be more sensitive than deep skin scraping and is an alternative diagnostic method for canine demodicosis. 相似文献
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Maeda K Kawabata K Mazzali PA Tanaka M Valenti S Nomoto K Hattori T Deng J Pian E Taubenberger S Iye M Matheson T Filippenko AV Aoki K Kosugi G Ohyama Y Sasaki T Takata T 《Science (New York, N.Y.)》2008,319(5867):1220-1223
Core-collapse supernovae (CC-SNe) are the explosions that announce the death of massive stars. Some CC-SNe are linked to long-duration gamma-ray bursts (GRBs) and are highly aspherical. One important question is to what extent asphericity is common to all CC-SNe. Here we present late-time spectra for a number of CC-SNe from stripped-envelope stars and use them to explore any asphericity generated in the inner part of the exploding star, near the site of collapse. A range of oxygen emission-line profiles is observed, including a high incidence of double-peaked profiles, a distinct signature of an aspherical explosion. Our results suggest that all CC-SNe from stripped-envelope stars are aspherical explosions and that SNe accompanied by GRBs exhibit the highest degree of asphericity. 相似文献
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Objective To determine the usefulness of a snake venom detection kit (SVDK) in the management of envenomed cats.
Design A clinical study.
Twenty-two cats were investigated.
Procedure Cats injected subcutaneously with approximately 0.25 or 1.0 lethal dose (LD) of tiger snake venom or 1 or 4 LD of brown snake venom were observed for clinical symptoms of envenomation at intervals over the ensuring 24 to 48 hours(h). Blood and urine samples were taken at regular intervals and assayed in a quantitative laboratory assay for snake venoms. Selected samples were assayed in parallel in a rapid, semi-quantitative SVDK.
Results The studies showed that it was important to estimate the elapsed time from envenomation to presentation. If this time was less than 8 h, blood was the most appropriate sample and a negative result should exclude serious envenomation. If the elapsed time exceeded 8 h, it was essential that urine be sampled. Venom levels in urine were high at 8 h and approached the level of test sensitivity over 24 to 48 h; however by this time clinical signs were obvious in endangered cats.
Careful use of the SVDK is a valuable aid in the management of a potentially envenomed cat. 相似文献
Design A clinical study.
Animals
Twenty-two cats were investigated.
Procedure Cats injected subcutaneously with approximately 0.25 or 1.0 lethal dose (LD) of tiger snake venom or 1 or 4 LD of brown snake venom were observed for clinical symptoms of envenomation at intervals over the ensuring 24 to 48 hours(h). Blood and urine samples were taken at regular intervals and assayed in a quantitative laboratory assay for snake venoms. Selected samples were assayed in parallel in a rapid, semi-quantitative SVDK.
Results The studies showed that it was important to estimate the elapsed time from envenomation to presentation. If this time was less than 8 h, blood was the most appropriate sample and a negative result should exclude serious envenomation. If the elapsed time exceeded 8 h, it was essential that urine be sampled. Venom levels in urine were high at 8 h and approached the level of test sensitivity over 24 to 48 h; however by this time clinical signs were obvious in endangered cats.
Conclusions
Careful use of the SVDK is a valuable aid in the management of a potentially envenomed cat. 相似文献
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Sternberg A Gal-Yam A Simon JD Leonard DC Quimby RM Phillips MM Morrell N Thompson IB Ivans I Marshall JL Filippenko AV Marcy GW Bloom JS Patat F Foley RJ Yong D Penprase BE Beeler DJ Allende Prieto C Stringfellow GS 《Science (New York, N.Y.)》2011,333(6044):856-859
Type Ia supernovae are key tools for measuring distances on a cosmic scale. They are generally thought to be the thermonuclear explosion of an accreting white dwarf in a close binary system. The nature of the mass donor is still uncertain. In the single-degenerate model it is a main-sequence star or an evolved star, whereas in the double-degenerate model it is another white dwarf. We show that the velocity structure of absorbing material along the line of sight to 35 type Ia supernovae tends to be blueshifted. These structures are likely signatures of gas outflows from the supernova progenitor systems. Thus, many type Ia supernovae in nearby spiral galaxies may originate in single-degenerate systems. 相似文献