420 research outputs found
Nucleosynthesis in Advective Accretion Disks Around Galactic and Extra-Galactic Black Holes
We compute the nucleosynthesis of materials inside advective disks around
black holes. We show that composition of incoming matter can change
significantly depending on the accretion rate and accretion disks. These works
are improvements on the earlier works in thick accretion disks of Chakrabarti,
Jin & Arnett (1987) in presence of advection in the flow.Comment: Latex pages including figures. Kluwer Style files included. Appearing
in `Observational Evidence for Black Holes in the Universe', ed. Sandip K.
Chakrabarti, Kluwer Academic Publishers (DORDRECHT: Holland
Racial/ethnic differences in job loss for women with breast cancer
IntroductionWe examined race/ethnic differences in treatment-related job loss and the financial impact of treatment-related job loss, in a population-based sample of women diagnosed with breast cancer.MethodsThree thousand two hundred fifty two women with non-metastatic breast cancer diagnosed (August 2005-February 2007) within the Los Angeles County and Detroit Metropolitan Surveillance Epidemiology and End Results registries, were identified and asked to complete a survey (mean time from diagnosis = 8.9 months). Latina and African American women were over-sampled (n = 2268, eligible response rate 72.1%).ResultsOne thousand one hundred eleven women (69.6%) of working age (<65 years) were working for pay at time of diagnosis. Of these women, 10.4% (24.1% Latina, 10.1% African American, 6.9% White, p < 0.001) reported that they lost or quit their job since diagnosis due to breast cancer or its treatment (defined as job loss). Latina women were more likely to experience job loss compared to White women (OR = 2.0, p = 0.013)), independent of sociodemographic factors. There were no significant differences in job loss between African American and White women, independent of sociodemographic factors. Additional adjustments for clinical and treatment factors revealed a significant interaction between race/ethnicity and chemotherapy (p = 0.007). Among women who received chemotherapy, Latina women were more likely to lose their job compared to White women (OR = 3.2, p < 0.001), however, there were no significant differences between Latina and White women among those who did not receive chemotherapy. Women who lost their job were more likely to experience financial strain (e.g. difficulty paying bills 27% vs. 11%, p < 0.001).ConclusionJob loss is a serious consequence of treatment for women with breast cancer. Clinicians and staff need to be aware of aspects of treatment course that place women at higher risk for job loss, especially ethnic minorities receiving chemotherapy
Theory of disk accretion onto supermassive black holes
Accretion onto supermassive black holes produces both the dramatic phenomena
associated with active galactic nuclei and the underwhelming displays seen in
the Galactic Center and most other nearby galaxies. I review selected aspects
of the current theoretical understanding of black hole accretion, emphasizing
the role of magnetohydrodynamic turbulence and gravitational instabilities in
driving the actual accretion and the importance of the efficacy of cooling in
determining the structure and observational appearance of the accretion flow.
Ongoing investigations into the dynamics of the plunging region, the origin of
variability in the accretion process, and the evolution of warped, twisted, or
eccentric disks are summarized.Comment: Mostly introductory review, to appear in "Supermassive black holes in
the distant Universe", ed. A.J. Barger, Kluwer Academic Publishers, in pres
Exercise in type 2 diabetes: to resist or to endure?
There is now evidence that a single bout of endurance (aerobic) or resistance exercise reduces 24 h post-exercise subcutaneous glucose profiles to the same extent in insulin-resistant humans with or without type 2 diabetes. However, it remains to be determined which group would benefit most from specific exercise protocols, particularly with regard to long-term glycaemic control. Acute aerobic exercise first accelerates translocation of myocellular glucose transporters via AMP-activated protein kinase, calcium release and mitogen-activated protein kinase, but also improves insulin-dependent glucose transport/phosphorylation via distal components of insulin signalling (phosphoinositide-dependent kinase 1, TBC1 domain family, members 1 and 4, Rac1, protein kinase C). Post-exercise effects involve peroxisome-proliferator activated receptor-γ coactivator 1α and lead to ATP synthesis, which may be modulated by variants in genes such as NDUFB6. While mechanisms of acute resistance-type exercise are less clear, chronic resistance training activates the mammalian target of rapamycin/serine kinase 6 pathway, ultimately increasing protein synthesis and muscle mass. Over the long term, adherence to rather than differences in metabolic variables between specific modes of regular exercise might ultimately determine their efficacy. Taken together, studies are now needed to address the variability of individual responses to long-term resistance and endurance training in real life
Promoter prediction and annotation of microbial genomes based on DNA sequence and structural responses to superhelical stress
BACKGROUND: In our previous studies, we found that the sites in prokaryotic genomes which are most susceptible to duplex destabilization under the negative superhelical stresses that occur in vivo are statistically highly significantly associated with intergenic regions that are known or inferred to contain promoters. In this report we investigate how this structural property, either alone or together with other structural and sequence attributes, may be used to search prokaryotic genomes for promoters. RESULTS: We show that the propensity for stress-induced DNA duplex destabilization (SIDD) is closely associated with specific promoter regions. The extent of destabilization in promoter-containing regions is found to be bimodally distributed. When compared with DNA curvature, deformability, thermostability or sequence motif scores within the -10 region, SIDD is found to be the most informative DNA property regarding promoter locations in the E. coli K12 genome. SIDD properties alone perform better at detecting promoter regions than other programs trained on this genome. Because this approach has a very low false positive rate, it can be used to predict with high confidence the subset of promoters that are strongly destabilized. When SIDD properties are combined with -10 motif scores in a linear classification function, they predict promoter regions with better than 80% accuracy. When these methods were tested with promoter and non-promoter sequences from Bacillus subtilis, they achieved similar or higher accuracies. We also present a strictly SIDD-based predictor for annotating promoter sequences in complete microbial genomes. CONCLUSION: In this report we show that the propensity to undergo stress-induced duplex destabilization (SIDD) is a distinctive structural attribute of many prokaryotic promoter sequences. We have developed methods to identify promoter sequences in prokaryotic genomes that use SIDD either as a sole predictor or in combination with other DNA structural and sequence properties. Although these methods cannot predict all the promoter-containing regions in a genome, they do find large sets of potential regions that have high probabilities of being true positives. This approach could be especially valuable for annotating those genomes about which there is limited experimental data
Salt-inducible kinases (SIKs) regulate TGFβ-mediated transcriptional and apoptotic responses
Leucine-enriched protein feeding does not impair exercise-induced free fatty acid availability and lipid oxidation: beneficial implications for training in carbohydrate-restricted states
Given that the enhanced oxidative adaptations observed when training in carbohydrate (CHO) restricted states are potentially regulated through free fatty acid (FFA) mediated signalling and that leucine rich protein elevates muscle protein synthesis, the present study aimed to test the hypothesis that leucine enriched protein feeding enhances circulating leucine concentration but does not impair FFA availability nor whole body lipid oxidation 56 during exercise. Nine males cycled for 2 h at 70% VO2peak when fasted (PLACEBO) or having consumed a whey protein solution (WHEY) or a leucine enriched whey protein gel (GEL), administered as 22 g 1 hour pre-exercise, 11 g/h during and 22 g thirty minutes post-exercise. Total leucine administration was 14.4 g and 6.3 in GEL and WHEY, respectively. Mean plasma leucine concentrations were elevated in GEL (P= 0.001) compared 60 with WHEY and PLACEBO (375 ± 100, 272 ± 51, 146 ± 14 μmol.L-1 respectively). No differences (P= 0.153) in plasma FFA (WHEY 0.53 ± 0.30, GEL 0.45 ± 0.25, PLACEBO 0.65 ± 0.30, mmol.L-1) or whole body lipid oxidation during exercise (WHEY 0.37 ± 0.26, GEL 0.36 ± 0.24, PLACEBO 0.34 ± 0.24 g/min) were apparent between trials, despite elevated (P= 0.001) insulin in WHEY and GEL compared with PLACEBO (38 ± 16, 35 ± 16, 22 ± 11 pmol.L-1 respectively). We conclude that leucine enriched protein feeding does not impair FFA availability nor whole body lipid oxidation during exercise, thus having practical applications for athletes who deliberately train in CHO restricted states to promote skeletal muscle adaptations
X-Ray Spectroscopy of Stars
(abridged) Non-degenerate stars of essentially all spectral classes are soft
X-ray sources. Low-mass stars on the cooler part of the main sequence and their
pre-main sequence predecessors define the dominant stellar population in the
galaxy by number. Their X-ray spectra are reminiscent, in the broadest sense,
of X-ray spectra from the solar corona. X-ray emission from cool stars is
indeed ascribed to magnetically trapped hot gas analogous to the solar coronal
plasma. Coronal structure, its thermal stratification and geometric extent can
be interpreted based on various spectral diagnostics. New features have been
identified in pre-main sequence stars; some of these may be related to
accretion shocks on the stellar surface, fluorescence on circumstellar disks
due to X-ray irradiation, or shock heating in stellar outflows. Massive, hot
stars clearly dominate the interaction with the galactic interstellar medium:
they are the main sources of ionizing radiation, mechanical energy and chemical
enrichment in galaxies. High-energy emission permits to probe some of the most
important processes at work in these stars, and put constraints on their most
peculiar feature: the stellar wind. Here, we review recent advances in our
understanding of cool and hot stars through the study of X-ray spectra, in
particular high-resolution spectra now available from XMM-Newton and Chandra.
We address issues related to coronal structure, flares, the composition of
coronal plasma, X-ray production in accretion streams and outflows, X-rays from
single OB-type stars, massive binaries, magnetic hot objects and evolved WR
stars.Comment: accepted for Astron. Astrophys. Rev., 98 journal pages, 30 figures
(partly multiple); some corrections made after proof stag
The Formation of the First Massive Black Holes
Supermassive black holes (SMBHs) are common in local galactic nuclei, and
SMBHs as massive as several billion solar masses already exist at redshift z=6.
These earliest SMBHs may grow by the combination of radiation-pressure-limited
accretion and mergers of stellar-mass seed BHs, left behind by the first
generation of metal-free stars, or may be formed by more rapid direct collapse
of gas in rare special environments where dense gas can accumulate without
first fragmenting into stars. This chapter offers a review of these two
competing scenarios, as well as some more exotic alternative ideas. It also
briefly discusses how the different models may be distinguished in the future
by observations with JWST, (e)LISA and other instruments.Comment: 47 pages with 306 references; this review is a chapter in "The First
Galaxies - Theoretical Predictions and Observational Clues", Springer
Astrophysics and Space Science Library, Eds. T. Wiklind, V. Bromm & B.
Mobasher, in pres
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