The impact of stellar rotation on the CNO abundance patterns in the Milky Way at low metallicities

We investigate the effect of new stellar models, which take rotation into account, computed for very low metallicities on the chemical evolution of the earliest phases of the Milky Way. We check the impact of these new stellar yields on a model for the halo of the Milky Way that can reproduce the observed halo metallicity distribution. In this way we try to better constrain the ISM enrichment timescale, which was not done in our previous work. The stellar models adopted in this work were computed under the assumption that the ratio of the initial rotation velocity to the critical velocity of stars is roughly constant with metallicity. This naturally leads to faster rotation at lower metallicity, as metal poor stars are more compact than metal rich ones. We find that the new Z = 10-8 stellar yields computed for large rotational velocities have a tremendous impact on the interstellar medium nitrogen enrichment for log(O/H)+12 < 7 (or [Fe/H]< -3). We show that upon the inclusion of the new stellar calculations in a chemical evolution model for the galactic halo with infall and outflow, both high N/O and C/O ratios are obtained in the very-metal poor metallicity range in agreement with observations. Our results give further support to the idea that stars at very low metallicities could have initial rotational velocities of the order of 600-800kms-1. An important contribution to N from AGB stars is still needed in order to explain the observations at intermediate metallicities. One possibility is that AGB stars at very low metallicities also rotate fast. This could be tested in the future, once stellar evolution models for fast rotating AGB stars will be available.Comment: Contribution to Nuclei in the Cosmos IX (Proceedings of Science - 9 pages, 4 figs., accepted) - Version 2: one reference added in the caption of Fig.

SPINSTARS at low metallicities

The main effect of axial rotation on the evolution of massive PopIII stars is to trigger internal mixing processes which allow stars to produce significant amounts of primary nitrogen 14 and carbon 13. Very metal poor massive stars produce much more primary nitrogen than PopIII stars for a given initial mass and rotation velocity. The very metal poor stars undergo strong mass loss induced by rotation. One can distinguish two types of rotationnaly enhanced stellar winds: 1) Rotationally mechanical winds occurs when the surface velocity reaches the critical velocity at the equator, {\it i.e.} the velocity at which the centrifugal acceleration is equal to the gravity; 2) Rotationally radiatively line driven winds are a consequence of strong internal mixing which brings large amounts of CNO elements at the surface. This enhances the opacity and may trigger strong line driven winds. These effects are important for an initial value of $\upsilon/\upsilon_{\rm crit}$ of 0.54 for a 60 M$_\odot$ at $Z=10^{-8}$, {\it i.e.} for initial values of $\upsilon/\upsilon_{\rm crit}$ higher than the one ($\sim$0.4) corresponding to observations at solar $Z$. These two effects, strong internal mixing leading to the synthesis of large amounts of primary nitrogen and important mass losses induced by rotation, occur for $Z$ between about 10$^{-8}$ and 0.001. For metallicities above 0.001 and for reasonable choice of the rotation velocities, internal mixing is no longer efficient enough to trigger these effects.Comment: 5 pages, 4 figures, to be published in the conference proceedings of First Stars III, Santa Fe, 200

Economic Impact of the Conservation Reserve Program in North Dakota

Environmental Economics and Policy, Land Economics/Use,

Financial, Managerial, and Attitudinal Characteristics of North Dakota Farm Families: Results of the 1986 Farm Survey

Agricultural Finance, Farm Management,

Can variability in the effect of opioids on refractory breathlessness be explained by genetic factors?

© 2015, BMJ Publishing Group. All rights reserved. Objectives: Opioids modulate the perception of breathlessness with a considerable variation in response, with poor correlation between the required opioid dose and symptom severity. The objective of this hypothesis-generating, secondary analysis was to identify candidate single nucleotide polymorphisms (SNP) from those associated with opioid receptors, signalling or pain modulation to identify any related to intensity of breathlessness while on opioids. This can help to inform prospective studies and potentially lead to better tailoring of opioid therapy for refractory breathlessness. Setting: 17 hospice/palliative care services (tertiary services) in 11 European countries. Participants: 2294 people over 18 years of age on regular opioids for pain related to cancer or its treatment. Primary outcome measures: The relationship between morphine dose, breathlessness intensity (European Organisation for Research and Treatment of Cancer Core Quality of Life Questionnaire; EORTCQLQC30 question 8) and 112 candidate SNPs from 25 genes (n=588). Secondary outcome measures: The same measures for people on oxycodone (n=402) or fentanyl (n=429). Results: SNPs not in Hardy-Weinberg equilibrium or with allele frequencies ( < 5%) were removed. Univariate associations between each SNP and breathlessness intensity were determined with Benjamini-Hochberg false discovery rate set at 20%. Multivariable ordinal logistic regression, clustering over country and adjusting for available confounders, was conducted with remaining SNPs. For univariate morphine associations, 1 variant on the 5-hydroxytryptamine type 3B (HTR3B) gene, and 4 on the β-2-arrestin gene (ARRB2) were associated with more intense breathlessness. 1 SNP remained significant in the multivariable model: people with rs7103572 SNP (HTR3B gene; present in 8.4% of the population) were three times more likely to have more intense breathlessness (OR 2.86; 95% CIs 1.46 to 5.62; p=0.002). No associations were seen with fentanyl nor with oxycodone. Conclusions: This large, exploratory study identified 1 biologically plausible SNP that warrants further study in the response of breathlessness to morphine therapy

One evidence base; three stories: do opioids relieve chronic breathlessness?

Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/. The efficacy of low-dose systemic opioids for chronic breathlessness was questioned by the recent Cochrane review by Barnes et al We examined the reasons for this conflicting finding and re-evaluated the efficacy of systemic opioids. Compared with previous meta-analyses, Barnes et al reported a smaller effect and lower precision, but did not account for matched data of crossover trials (11/12 included trials) and added a risk-of-bias criterion (sample size). When re-analysed to account for crossover data, opioids decreased breathlessness (standardised mean differences -0.32; -0.18 to -0.47; I2=44.8%) representing a clinically meaningful reduction of 0.8 points (0-10 numerical rating scale), consistent across meta-analyses

Massive Stars as Cosmic Engines through the Ages

Some useful developments in the model physics are briefly presented, followed by model results on chemical enrichments and WR stars. We discuss the expected rotation velocities of WR stars. We emphasize that the (C+O)/He ratio is a better chemical indicator of evolution for WC stars than the C/He ratios. With or without rotation, at a given luminosity the (C+O)/He ratios should be higher in regions of lower metallicity Z. Also, for a given (C+O)/He ratio the WC stars in lower Z regions have higher luminosities. The WO stars, which are likely the progenitors of supernovae SNIc and of some GRBs, should preferentially be found in regions of low Z and be the descendants of very high initial masses. Finally, we emphasize the physical reasons why massive rotating low Z stars may also experience heavy mass los

Rank-Ordering Statistics of Extreme Events: Application to the Distribution of Large Earthquakes

Rank-ordering statistics provides a perspective on the rare, largest elements of a population, whereas the statistics of cumulative distributions are dominated by the more numerous small events. The exponent of a power law distribution can be determined with good accuracy by rank-ordering statistics from the observation of only a few tens of the largest events. Using analytical results and synthetic tests, we quantify the systematic and the random errors. We also study the case of a distribution defined by two branches, each having a power law distribution, one defined for the largest events and the other for smaller events, with application to the World-Wide (Harvard) and Southern California earthquake catalogs. In the case of the Harvard moment catalog, we make more precise earlier claims of the existence of a transition of the earthquake magnitude distribution between small and large earthquakes; the $b$-values are $b_2 = 2.3 \pm 0.3$ for large shallow earthquakes and $b_1 = 1.00 \pm 0.02$ for smaller shallow earthquakes. However, the cross-over magnitude between the two distributions is ill-defined. The data available at present do not provide a strong constraint on the cross-over which has a $50\%$ probability of being between magnitudes $7.1$ and $7.6$ for shallow earthquakes; this interval may be too conservatively estimated. Thus, any influence of a universal geometry of rupture on the distribution of earthquakes world-wide is ill-defined at best. We caution that there is no direct evidence to confirm the hypothesis that the large-moment branch is indeed a power law. In fact, a gamma distribution fits the entire suite of earthquake moments from the smallest to the largest satisfactorily. There is no evidence that the earthquakes of the Southern California catalog have a distribution with tw

Close binary evolution. III. Impact of tides, wind magnetic braking, and internal angular momentum transport

Massive stars with solar metallicity lose important amounts of rotational angular momentum through their winds. When a magnetic field is present at the surface of a star, efficient angular momentum losses can still be achieved even when the mass-loss rate is very modest, at lower metallicities, or for lower-initial-mass stars. In a close binary system, the effect of wind magnetic braking also interacts with the influence of tides, resulting in a complex evolution of rotation. We study the interactions between the process of wind magnetic braking and tides in close binary systems. We discuss the evolution of a 10 M$_\odot$ star in a close binary system with a 7 M$_\odot$ companion using the Geneva stellar evolution code. The initial orbital period is 1.2 days. The 10 M$_\odot$ star has a surface magnetic field of 1 kG. Various initial rotations are considered. We use two different approaches for the internal angular momentum transport. In one of them, angular momentum is transported by shear and meridional currents. In the other, a strong internal magnetic field imposes nearly perfect solid-body rotation. The evolution of the primary is computed until the first mass-transfer episode occurs. The cases of different values for the magnetic fields and for various orbital periods and mass ratios are briefly discussed. We show that, independently of the initial rotation rate of the primary and the efficiency of the internal angular momentum transport, the surface rotation of the primary will converge, in a time that is short with respect to the main-sequence lifetime, towards a slowly evolving velocity that is different from the synchronization velocity. (abridged).Comment: 11 pages, 13 figures, accepted for publication in Astronomy and Astrophysic