838 research outputs found
Spatial distribution of radionuclides in 3D models of SN 1987A and Cas A
Fostered by the possibilities of multi-dimensional computational modeling, in
particular the advent of three-dimensional (3D) simulations, our understanding
of the neutrino-driven explosion mechanism of core-collapse supernovae (SNe)
has experienced remarkable progress over the past decade. First
self-consistent, first-principle models have shown successful explosions in 3D,
and even failed cases may be cured by moderate changes of the microphysics
inside the neutron star (NS), better grid resolution, or more detailed
progenitor conditions at the onset of core collapse, in particular large-scale
perturbations in the convective Si and O burning shells. 3D simulations have
also achieved to follow neutrino-driven explosions continuously from the
initiation of the blast wave, through the shock breakout from the progenitor
surface, into the radioactively powered evolution of the SN, and towards the
free expansion phase of the emerging remnant. Here we present results from such
simulations, which form the basis for direct comparisons with observations of
SNe and SN remnants in order to derive constraints on the still disputed
explosion mechanism. It is shown that predictions based on hydrodynamic
instabilities and mixing processes associated with neutrino-driven explosions
yield good agreement with measured NS kicks, light-curve properties of SN
1987A, and asymmetries of iron and 44Ti distributions observed in SN 1987A and
Cassiopeia A.Comment: 9 pages, 6 figures; submitted to: "SN 1987A, 30 years later",
Proceedings IAU Symposium No. 331, 2017; eds. M. Renaud et a
Scholarly Communication and Publishing Lunch and Learn Talks
This series of talks focuses on issues in scholarly communication and publishing presented to University Library System (ULS), University of Pittsburgh colleagues by staff members of the ULS Office of Scholarly Communication and Publishing. Many of these talks feature "toolbox" tips on how to apply knowledge gained from the talks. Links to recordings of the talks are provided when available. For topics and presentations, see the record for each talk
Ertragsentwicklung von Erbsen sowie Sommergerste in Reinsaat und in Mischung mit Leindotter oder Koriander im Ă–kologischen Landbau
Mischkulturen können unterschiedliche Wachstumsbedingungen besser ausschöpfen als Monokulturen. Im Gemenge mit Leguminosen können Nicht-Leguminosen überschüssigen Stickstoff aus der Bodenlösung aufnehmen. Ein ökonomischer Zusatzertrag wird bei einer Beimengung von Leindotter zu Erbsen oder Sommergerste diskutiert. Erbsenreinsaaten erreichten im Vergleich zu beiden Leindotter-Varianten gesichert höhere Erträge; Erbsen mit resp. ohne Koriander unterschieden sich nicht. Sommergerste – Reinsaaten waren bezüglich dem Ertrag den Mischungen mit Leindotter überlegen; Koriander wurde von der Sommergerste vollständig unterdrückt. Abschließend kann festgehalten werden, dass unter limitierenden Niederschlägen im pannonischen Klimaraum dem Mischkulturanbau enge Grenzen gesetzt sind
Dietary oil composition differentially modulates intestinal endotoxin transport and postprandial endotoxemia
Background: Intestinal derived endotoxin and the subsequent endotoxemia can be considered major predisposing factors for diseases such as atherosclerosis, sepsis, obesity and diabetes. Dietary fat has been shown to increase postprandial endotoxemia. Therefore, the aim of this study was to assess the effects of different dietary oils on intestinal endotoxin transport and postprandial endotoxemia using swine as a model. We hypothesized that oils rich in saturated fatty acids (SFA) would augment, while oils rich in n-3 polyunsaturated fatty acids (PUFA) would attenuate intestinal endotoxin transport and circulating concentrations.
Methods: Postprandial endotoxemia was measured in twenty four pigs following a porridge meal made with either water (Control), fish oil (FO), vegetable oil (VO) or coconut oil (CO). Blood was collected at 0, 1, 2, 3 and 5 hours postprandial and measured for endotoxin. Furthermore, ex vivo ileum endotoxin transport was assessed using modified Ussing chambers and intestines were treated with either no oil or 12.5% (v/v) VO, FO, cod liver oil (CLO), CO or olive oil (OO). Ex vivo mucosal to serosal endotoxin transport permeability (Papp) was then measured by the addition of fluorescent labeled-lipopolysaccharide.
Results: Postprandial serum endotoxin concentrations were increased after a meal rich in saturated fatty acids and decreased with higher n-3 PUFA intake. Compared to the no oil control, fish oil and CLO which are rich in n-3 fatty acids reduced ex vivo endotoxin Papp by 50% (P \u3c 0.05). Contrarily, saturated fatty acids increased the Papp by 60% (P = 0.008). Olive and vegetable oils did not alter intestinal endotoxin Papp.
Conclusion: Overall, these results indicate that saturated and n-3 PUFA differentially regulate intestinal epithelial endotoxin transport. This may be associated with fatty acid regulation of intestinal membrane lipid raft mediated permeability
Synthetic spectra of H Balmer and HeI absorption lines. I: Stellar library
We present a grid of synthetic profiles of stellar H Balmer and HeI lines at
optical wavelengths with a sampling of 0.3 A. The grid spans a range of
effective temperature 4000 K < Teff < 50000 K, and gravity 0.0 < log g < 5.0 at
solar metallicity. For Teff > 25000 K, NLTE stellar atmosphere models are
computed using the code TLUSTY (Hubeny 1988). For cooler stars, Kurucz (1993)
LTE models are used to compute thesynthetic spectra. The grid includes the
profiles of the high-order hydrogen Balmer series and HeI lines for effective
temperatures and gravities that have not been previously synthesized. The
behavior of H8 to H13 and HeI 3819 with effective temperature and gravity is
very similar to that of the lower terms of the series (e.g. Hb) and the other
HeI lines at longer wavelengths; therefore, they are suited for the
determination of the atmospheric parameters of stars. These lines are
potentially important to make predictions for these stellar absorption features
in galaxies with active star formation. Evolutionary synthesis models of these
lines for starburst and post-starburst galaxies are presented in a companion
paper. The full set of the synthetic stellar spectra is available for retrieval
at our website http://www.iaa.es/ae/e2.html and
http://www.stsci.edu/science/starburst/ or on request from the authors at
[email protected]: To be published in ApJS. 28 pages and 12 figure
Postprandial serum endotoxin in healthy humans is modulated by dietary fat in a randomized, controlled, cross-over study
Background: High-fat diets may contribute to metabolic disease via postprandial changes in serum endotoxin and inflammation. It is unclear how dietary fat composition may alter these parameters. We hypothesized that a meal rich in n-3 (ω3) fatty acids would reduce endotoxemia and associated inflammation but a saturated or n-6 (ω6) fatty acid-rich meal would increase postprandial serum endotoxin concentrations and systemic inflammation in healthy adults. Methods: Healthy adults (n = 20; mean age 25 ± 3.2 S.D. years) were enrolled in this single-blind, randomized, cross-over study. Participants were randomized to treatment and reported to the laboratory, after an overnight fast, on four occasions separated by at least one week. Participants were blinded to treatment meal and consumed one of four isoenergetic meals that provided: 1) 20 % fat (control; olive oil) or 35 % fat provided from 2) n-3 (ω3) (DHA = 500 mg; fish oil); 3) n-6 (ω6) (7.4 g; grapeseed oil) or 4) saturated fat (16 g; coconut oil). Baseline and postprandial blood samples were collected. Primary outcome was defined as the effect of treatment meal on postprandial endotoxemia. Serum was analyzed for metabolites, inflammatory markers, and endotoxin. Data from all 20 participants were analyzed using repeated-measures ANCOVA. Results: Participant serum endotoxin concentration was increased during the postprandial period after the consumption of the saturated fat meal but decreased after the n-3 meal (p  0.05). There was no treatment meal effect on participant postprandial serum biomarkers of inflammation. Postprandial serum triacylglycerols were significantly elevated following the n-6 meal compared to the n-3 meal. Non-esterified fatty acids were significantly increased after consumption of the saturated fat meal compared to other treatment meals. Conclusions: Meal fatty acid composition modulates postprandial serum endotoxin concentration in healthy adults. However, postprandial endotoxin was not associated with systemic inflammation in vivo. Trial registration: This study was retrospectively registered at clinicaltrials.gov as NCT02521779 on July 28, 2015
Effects of Heat Stress and Plane of Nutrition on Production and Metabolism in Growing Pigs
We heat-stressed growing pigs and evaluated the differential effects of environmental hyperthermia and reduced feed intake. Our results indicate that hyperthermia directly effects production and metabolism and many of these are independent of reduced nutrient intake. Identifying how and why heat stress alters metabolism and physiology are prerequisites in developing ameliorating strategies to prevent the reduction in performance and lost income typically observed during the warm summer months
Scholarly Communication and Publishing Lunch and Learn Talk #12: Kickstarting Open Access Week 2014
For the June 2014 talk, we discussed plans for Open Access Week 2014, the 7th Open Access Week commemorated internationally and the 4th at Pitt. We began with a report on the recent SPARC-sponsored 2014 Open Access Week Planning Kickoff Webcast. Featuring speakers from California, Kansas, and Kenya, the webcast offered many good ideas on how to engage faculty, students, and library colleagues in Open Access Week activities and scholarly communications issues. Then we continued with some brainstorming to generate ideas on how we can use Open Access Week to get our message out about the open sharing of knowledge and how we can all deliver that message in a way that resonates with Pitt faculty and students. We also discussed some of our ideas for this year's Open Access Week, scheduled for October 20-26, 2014
Three-dimensional Models of Core-collapse Supernovae From Low-mass Progenitors With Implications for Crab
We present 3D full-sphere supernova simulations of non-rotating low-mass (~9
Msun) progenitors, covering the entire evolution from core collapse through
bounce and shock revival, through shock breakout from the stellar surface,
until fallback is completed several days later. We obtain low-energy explosions
[~(0.5-1.0)x 10^{50} erg] of iron-core progenitors at the low-mass end of the
core-collapse supernova (LMCCSN) domain and compare to a super-AGB (sAGB)
progenitor with an oxygen-neon-magnesium core that collapses and explodes as
electron-capture supernova (ECSN). The onset of the explosion in the LMCCSN
models is modelled self-consistently using the Vertex-Prometheus code, whereas
the ECSN explosion is modelled using parametric neutrino transport in the
Prometheus-HOTB code, choosing different explosion energies in the range of
previous self-consistent models. The sAGB and LMCCSN progenitors that share
structural similarities have almost spherical explosions with little metal
mixing into the hydrogen envelope. A LMCCSN with less 2nd dredge-up results in
a highly asymmetric explosion. It shows efficient mixing and dramatic shock
deceleration in the extended hydrogen envelope. Both properties allow fast
nickel plumes to catch up with the shock, leading to extreme shock deformation
and aspherical shock breakout. Fallback masses of <~5x10^{-3} Msun have no
significant effects on the neutron star (NS) masses and kicks. The anisotropic
fallback carries considerable angular momentum, however, and determines the
spin of the newly-born NS. The LMCCSNe model with less 2nd dredge-up results in
a hydrodynamic and neutrino-induced NS kick of >40 km/s and a NS spin period of
~30 ms, both not largely different from those of the Crab pulsar at birth.Comment: 47 pages, 27 figures, 6 tables; minor revisions, accepted by MNRA
Scholarly Communication and Publishing Lunch and Learn Talk #1: ULS Journal Publishing -- Why We Do It
This series of talks focuses on issues in scholarly communication and publishing presented to University Library System (ULS), University of Pittsburgh colleagues by staff members of the ULS Office of Scholarly Communication and Publishing. Many of these talks feature "toolbox" tips on how to apply knowledge gained from the talks. Links to recordings of the talks are provided when available. For topics and presentations, see the record for each talk
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