Single Be stars as binary ejecta? Rinehart, S. A.
Monthly notices of the Royal Astronomical Society,
02/2000, Letnik:
312, Številka:
2
Journal Article
Recenzirano
Among the mechanisms suggested for the creation of discs around Be stars is interaction with binary companions. This idea has largely been dismissed, because the majority of Be stars have no observed ...companion. This difficulty can be circumvented if single Be stars are actually ejected from binary systems (owing, for instance, to the supernova of the companion). Using Hipparcos data, we show that this explanation is not likely, by comparing the velocity distributions of Be stars with those of normal B stars. We find that the distributions are consistent to within 1σ uncertainties, and thus do not support the formation of single Be stars through binary breakup.
Glutaminyl-tRNA synthetase is thought to be absent from organelles. Instead, Gln-tRNA is formed via the transamidation pathway, the other route to this essential compound in protein biosynthesis. ...However, it was previously shown that glutaminyl-tRNA synthetase activity is present in Leishmania mitochondria. This work identifies genes encoding glutaminyl- and glutamyl-tRNA synthetase in the closely related organism Trypanosoma brucei. Down-regulation of their respective gene products by RNA interference showed that (i) they are essential for the growth of insect stage T. brucei and (ii) they are responsible for essentially all of the glutaminyl- and glutamyl-tRNA synthetase activity detected in both the cytosol and the mitochondria. In vitro aminoacylation experiments with the recombinant T. brucei enzymes and total tRNA confirmed the identity of the two aminoacyl-tRNA synthetases. Interestingly, T. brucei uses the same eukaryotic-type glutaminyl-tRNA synthetase to form mitochondrial and cytosolic Gln-tRNA. The formation of Glu-tRNA in mitochondria and the cytoplasm is catalyzed by a single eukaryotic-type discriminating glutamyl-tRNA synthetase. T. brucei, similar to Leishmania, imports all of its mitochondrial tRNAs from the cytosol. The use of these two eukaryotic-type enzymes in mitochondria may therefore reflect an adaptation to the situation in which the cytosol and mitochondria use the same set of tRNAs.
We present medium-resolution (R∼ 600), mid-infrared (7.5–14 μm) spectra of 15 young planetary nebulae. Linestrengths for observed forbidden transitions are presented, and numerous broad emission ...features from silicates, polyaromatic hydrocarbons (PAHs) and silicon carbide (SiC) are observed.
Abstract Background Gun violence is a controversial public health issue plagued by a lack of recent research. We sought to provide a 13-year overview of firearm hospitalizations in Pennsylvania, ...analyzing trends in mode, intent, and outcome. We hypothesized that no adjusted change in mortality or functional status at discharge (FSD) would be observed for gunshot wound (GSW) victims over the study period. Methods All admissions to the Pennsylvania Trauma Outcome Study database from 2003-2015 were queried. GSWs were identified by external cause-of-injury codes. Collected variables included patient demographics, firearm type, intent (assault, attempted suicide), FSD, and mortality. Multilevel mixed-effects logistic regression models and ordinal regression analyses using generalized linear mixed models assessed the impact of admission year (continuous) on adjusted mortality and FSD score, respectively. Significance was set at p <0.05. Results Of the 462,081 patients presenting to Pennsylvania trauma centers from 2003-2015, 19,342 (4.2%) were GSWs. Handguns were the most common weapon of injury (n=7,007; 86.7%) among cases with specified firearm type. The majority of GSWs were coded as assaults (n=15,415; 79.7%), with suicide attempts accounting 1,866 hospitalizations (9.2%). Suicide attempts were most prevalent among young and middle-aged white males, while assaults were more common in young black males. Rates of firearm hospitalizations decreased over time (test of trend p=0.001), however admission year was not associated with improved adjusted survival (AOR: 0.99, 95% CI: 0.97-1.01; p=0.353) or FSD (AOR: 0.99, 95% CI: 0.98-1.00; p=0.089) while controlling for demographic and injury severity covariates. Conclusion Temporal trends in outcomes suggest rates of firearm hospitalizations are declining in Pennsylvania, however outcomes remain unchanged. To combat this epidemic, a multidisciplinary, demographic-specific approach to prevention should be the focus of future scientific pursuits.
We present observations that were carried out with the Two HUndred Micron PhotometER (THUMPER) mounted on the James Clerk Maxwell Telescope (JCMT) in Hawaii, at a wavelength of 200 μm (frequency 1.5 ...THz). The observations utilize a small atmospheric window that opens up at this wavelength under very dry conditions at high-altitude observing sites. The atmosphere was calibrated using the sky-dipping method and a relation was established between the optical depth, τ, at 1.5 THz and that at 225 GHz: τ1.5 THz= (95 ± 10) ×τ225 GHz. Mars and Jupiter were mapped from the ground at this wavelength for the first time, and the system characteristics measured. A noise-equivalent flux density (NEFD) of ∼ 65 ± 10 Jy (1σ 1s) was measured for the THUMPER-JCMT combination, consistent with predictions based upon our laboratory measurements. The main beam resolution of 14 arcsec was confirmed and an extended error beam detected at roughly two-thirds of the magnitude of the main beam. Measurements of the Sun allow us to estimate that the fraction of the power in the main beam is ∼15 per cent, consistent with predictions based on modelling the dish surface accuracy. It is therefore shown that the sky over Mauna Kea is suitable for astronomy at this wavelength under the best conditions. However, higher or drier sites should have a larger number of useable nights per year.
One hundred sixty-five patients were randomized to receive either interferon alfa-n1 (Wellferon; Burroughs Wellcome Co, Research Triangle Park, NC) alone or with vinblastine. An initial six-cycle ...induction treatment consisted of interferon given at daily doses of 3, 5, 20, 20, and 20 x 10(6) U/m2 every 2 weeks. Vinblastine at a dose of 10 mg/m2 (later decreased to 5 mg/m2) was given on day 1 of alternate cycles. Toxicities were generally well tolerated. The overall response rate was 10% with no significant difference between treatment arms. Survival was also not significantly different for the arms. A small subset of patients (16) with metastases only to the lungs had a high complete response (CR) and partial response (PR) rate of 44%. Responses were durable, and overall survival of this group was much better than that of the other patients.
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