The Evolution of Carbon and Oxygen in the Bulge and Disk of the Milky Way

The evolution of C and O abundances in the Milky Way can impose strong constraints on stellar nucleosynthesis and help understanding the formation and evolution of our Galaxy. The aim is to review the measured C and O abundances in the disk and bulge of the Galaxy and compare them with model predictions. We adopt two successful chemical evolution models for the bulge and the disk, which assume the same nucleosynthesis prescriptions but different histories of star formation. The data show a clear distinction between the trend of [C/O] in the thick and thin Galactic disks, while the thick disk and bulge trends are indistinguishable with a large (>0.5 dex) increase in the C/O ratio in the range from -0.1 to +0.4 dex for [O/H]. In our models we consider yields from massive stars with and without the inclusion of metallicity-dependent stellar winds. The observed increase in the [C/O] ratio with metallicity in the bulge and thick disk lies between the predictions utilizing the mass-loss rates of Maeder (1992) and those of Meynet & Maeder (2002). A model without metallicity-dependent yields completely fails to match the observations. Thus, the relative increase in carbon abundance at high metallicity appears to be due to metallicity-dependent stellar winds in massive stars. These results also explain the steep decline of the [O/Fe] ratio with [Fe/H] in the Galactic bulge, while the [Mg/Fe] ratio is enhanced at all [Fe/H]. (abridged)Comment: 18 pages, 6 figures, submitted to Astronomy & Astrophysic

Herbicide-resistant weeds : from research and knowledge to future needs

Synthetic herbicides have been used globally to control weeds in major field crops. This has imposed a strong selection for any trait that enables plant populations to survive and reproduce in the presence of the herbicide. Herbicide resistance in weeds must be minimized because it is a major limiting factor to food security in global agriculture. This represents a huge challenge that will require great research efforts to develop control strategies as alternatives to the dominant and almost exclusive practice of weed control by herbicides. Weed scientists, plant ecologists and evolutionary biologists should join forces and work towards an improved and more integrated understanding of resistance across all scales. This approach will likely facilitate the design of innovative solutions to the global herbicide resistance challenge

XMM-Newton Observation of Diffuse Gas and LMXBs in the Elliptical Galaxy NGC 4649 (M60)

(Abridged) We present an XMM-Newton X-ray observation of the X-ray bright E2 elliptical galaxy NGC 4649. In addition to bright diffuse emission, we resolve 158 discrete sources, ~50 of which are likely to be low-mass X-ray binaries (LMXBs) associated with NGC 4649. We find evidence for variability in three sources between this observation and a previous Chandra observation. Additionally, we detect five sources that were not detected with Chandra despite its better detection limit, suggesting that these sources have since brightened. The total X-ray spectrum of the resolved sources is well-fit by a hard power-law, while the diffuse spectrum requires a hard and a soft component, presumably due to the relatively soft diffuse gas and the harder unresolved sources. A deprojection of the diffuse emission revealed a radial temperature gradient that is hot in the center, drops to a minimum at about 20-50" (1.6-4.1 kpc), and rises again in the outer regions. The diffuse emission appears to require a two-temperature model with heavy element abundance ratios that differ from the solar values. We have verified the existence of faint radial features extending out from the core of NGC 4649 that had previously been seen with Chandra. The fingers are morphologically similar to radial features seen in hydrodynamic simulations of cooling flows in elliptical galaxies. We also find evidence for a longer, previously undetected filament that extends to the northeastern edge of NGC 4649. We conclude that the filament may be the result of a tidal interaction, possibly with NGC 4647, though more work is necessary to verify this conclusion.Comment: 23 pages, 4 tables, 10 figures, accepted for publication in Ap

The relationship between strategic control and conscious structural knowledge in artificial grammar learning

We address Jacoby’s (1991) proposal that strategic control over knowledge requires conscious awareness of that knowledge. In a two-grammar artificial grammar learning experiment all participants were trained on two grammars, consisting of a regularity in letter sequences, while two other dimensions (colours and fonts) varied randomly. Strategic control was measured as the ability to selectively apply the grammars during classification. For each classification, participants also made a combined judgement of (a) decision strategy and (b) relevant stimulus dimension. Strategic control was found for all types of decision strategy, including trials where participants claimed to lack conscious structural knowledge. However, strong evidence of strategic control only occurred when participants knew or guessed that the letter dimension was relevant, suggesting that strategic control might be associated with – or even causally requires – global awareness of the nature of the rules even though it does not require detailed knowledge of their content

Metabolism of 2,4-dichlorophenoxyacetic acid contributes to resistance in a common waterhemp (\u3ci\u3eAmaranthus tuberculatus\u3c/i\u3e) population

BACKGROUND: Synthetic auxins such as 2,4-D have been widely used for selective control of broadleaf weeds since the mid-1940s. In 2009, an Amaranthus tuberculatus (common waterhemp) population with 10-fold resistance to 2,4-D was found in Nebraska, USA. The 2,4-D resistance mechanism was examined by conducting [14C] 2,4-D absorption, translocation and metabolism experiments. RESULTS: No differences were found in 2,4-D absorption or translocation between the resistant and susceptible A. tuberculatus. Resistant plants metabolized [14C] 2,4-D more rapidly than did susceptible plants. The half-life of [14C] 2,4-D in susceptible plants was 105 h, compared to 22 h in resistant plants. Pre-treatment with the cytochrome P450 inhibitor malathion inhibited [14C] 2,4-D metabolism in resistant plants and reduced the 2,4-D dose required for 50% growth inhibition (GR50) of resistant plants by 7-fold to 27 g ha-1, similar to the GR50 for susceptible plants in the absence of malathion. CONCLUSIONS: Our results demonstrate that rapid 2,4-D metabolism is a contributing factor to resistance in A. tuberculatus, potentially mediated by cytochrome P450. Metabolism-based resistance to 2,4-D could pose a serious challenge for A. tuberculatus control due to the potential for cross-resistance to other herbicides

Fundamental Parameters and Abundances of Metal-Poor Stars: The SDSS Standard BD +17 4708

The atmospheric parameters and iron abundance of the Sloan Digital Sky Survey (SDSS) spectrophotometric standard star BD +17 4708 are critically examined using up-to-date Kurucz model atmospheres, LTE line formation calculations, and reliable atomic data. We find Teff = 6141+-50 K, log g = 3.87+-0.08, and [Fe/H]=-1.74+-0.09. The line-of-sight interstellar reddening, bolometric flux, limb-darkened angular diameter, stellar mass, and the abundances of Mg, Si, and Ca are also obtained. This star is a unique example of a moderately metal-poor star for which the effective temperature can be accurately constrained from the observed spectral energy distribution (corrected for reddening). Such analysis leads to a value that is higher than most spectroscopic results previously reported in the literature (~5950 K). We find that the ionization balance of Fe lines is satisfied only if a low Teff (~5950 K) is adopted. With our preferred Teff (6141 K), the mean iron abundance we obtain from the FeII lines is lower by about 0.15 dex than that from the FeI lines, and therefore, the discrepancy between the mean iron abundance from FeI and FeII lines cannot be explained by overionization by UV photons as the main non-LTE effect. We also comment on non-LTE effects and the importance of inelastic collisions with neutral H atoms in the determination of oxygen abundances in metal-poor stars from the 777 nm OI triplet. (Abridged)Comment: A&A in pres

Efficacy and tolerability of evolocumab vs. ezetimibe in patients with muscle-related statin intolerance: the GAUSS-3 randomized clinical trial

Importance: Muscle-related statin intolerance is reported by 5% to 20% of patients. Objective: To identify patients with muscle symptoms confirmed by statin rechallenge and compare lipid-lowering efficacy for 2 nonstatin therapies, ezetimibe and evolocumab. Design, Setting, and Participants: Two-stage randomized clinical trial including 511 adult patients with uncontrolled low-density lipoprotein cholesterol (LDL-C) levels and history of intolerance to 2 or more statins enrolled in 2013 and 2014 globally. Phase A used a 24-week crossover procedure with atorvastatin or placebo to identify patients having symptoms only with atorvastatin but not placebo. In phase B, after a 2-week washout, patients were randomized to ezetimibe or evolocumab for 24 weeks. Interventions: Phase A: atorvastatin (20 mg) vs placebo. Phase B: randomization 2:1 to subcutaneous evolocumab (420 mg monthly) or oral ezetimibe (10 mg daily). Main Outcome and Measures: Coprimary end points were the mean percent change in LDL-C level from baseline to the mean of weeks 22 and 24 levels and from baseline to week 24 levels. Results: Of the 491 patients who entered phase A (mean age, 60.7 [SD, 10.2] years; 246 women [50.1%]; 170 with coronary heart disease [34.6%]; entry mean LDL-C level, 212.3 [SD, 67.9] mg/dL), muscle symptoms occurred in 209 of 491 (42.6%) while taking atorvastatin but not while taking placebo. Of these, 199 entered phase B, along with 19 who proceeded directly to phase B for elevated creatine kinase (N = 218, with 73 randomized to ezetimibe and 145 to evolocumab; entry mean LDL-C level, 219.9 [SD, 72] mg/dL). For the mean of weeks 22 and 24, LDL-C level with ezetimibe was 183.0 mg/dL; mean percent LDL-C change, −16.7% (95% CI, −20.5% to −12.9%), absolute change, −31.0 mg/dL and with evolocumab was 103.6 mg/dL; mean percent change, −54.5% (95% CI, −57.2% to −51.8%); absolute change, −106.8 mg/dL (P < .001). LDL-C level at week 24 with ezetimibe was 181.5 mg/dL; mean percent change, −16.7% (95% CI, −20.8% to −12.5%); absolute change, −31.2 mg/dL and with evolocumab was 104.1 mg/dL; mean percent change, −52.8% (95% CI, −55.8% to −49.8%); absolute change, −102.9 mg/dL (P < .001). For the mean of weeks 22 and 24, between-group difference in LDL-C was −37.8%; absolute difference, −75.8 mg/dL. For week 24, between-group difference in LDL-C was −36.1%; absolute difference, –71.7 mg/dL. Muscle symptoms were reported in 28.8% of ezetimibe-treated patients and 20.7% of evolocumab-treated patients (log-rank P = .17). Active study drug was stopped for muscle symptoms in 5 of 73 ezetimibe-treated patients (6.8%) and 1 of 145 evolocumab-treated patients (0.7%). Conclusions and Relevance: Among patients with statin intolerance related to muscle-related adverse effects, the use of evolocumab compared with ezetimibe resulted in a significantly greater reduction in LDL-C levels after 24 weeks. Further studies are needed to assess long-term efficacy and safety

The nature of proximate damped Lyman alpha systems

We present high resolution echelle spectra of 7 proximate damped Lyman alpha (PDLA) systems whose relative velocity separation from the background quasar is Delta V < 3000 km/s. Combining our sample with a further 9 PDLAs from the literature we compare the chemical properties of the proximate systems with a control sample of intervening DLAs. Taken at face value, the sample of 16 PDLAs exhibits a wide range of metallicities, ranging from Z ~ 1/3 Z_sun down to Z ~ 1/1000 Z_sun, including the DLA with the lowest N(SiII)/N(HI) yet reported in the literature. We find several pieces of evidence that indicate enhanced ionization and the presence of a hard ionizing spectrum in PDLAs which lead to properties that contrast with the intervening DLAs, particularly when the N(HI) is low. The abundances of Zn, Si and S in PDLAs with log N(HI) > 21, where ionization corrections are minimized, are systematically higher than the intervening population by a factor of around 3. We also find possible evidence for a higher fraction of NV absorbers amongst the PDLAs, although the statistics are still modest. 6/7 of our echelle sample show high ionization species (SiIV, CIV, OVI or NV) offset by >100 km/s from the main low ion absorption. We analyse fine-structure transitions of CII* and SiII* to constrain the PDLA distance from the QSO. Lower limits range from tens of kpc up to >160 kpc for the most stringent limit. We conclude that (at least some) PDLAs do exhibit different characteristics relative to the intervening population out to 3000 km/s (and possibly beyond). Nonetheless, the PDLAs appear distinct from lower column density associated systems and the inferred QSO-absorber separations mean they are unlikely to be associated with the QSO host. We speculate that the PDLAs preferentially sample more massive galaxies in more highly clustered regions of the high redshift universe.Comment: Accepted for publication in MNRAS. Abstract abridged