Differential chemical abundance analysis of a 47 Tuc AGB star with respect to Arcturus

This study resolves a discrepancy in the abundance of Zr in the 47 Tucanae asymptotic giant branch star Lee 2525. This star was observed using the echelle spectrograph on the 2.3 m telescope at Siding Spring Observatory. The analysis was undertaken by calibrating Lee 2525 with respect to the standard giant star Arcturus. This work emphasises the importance of using a standard star with stellar parameters comparable to the star under analysis rather than a calibration with respect to the Sun (Koch & McWilliam 2008). Systematic errors in the analysis process are then minimised due to the similarity in atmospheric structure between the standard and programme stars. The abundances derived for Lee 2525 were found to be in general agreement with the Brown & Wallerstein (1992) values except for Zr. In this study Zr has a similar enhancement ([Zr/Fe] = +0.51 dex) to another light s-process element, Y ([Y/Fe] = +0.53 dex), which reflects current theory regarding the enrichment of s-process elements by nuclear processes within AGB stars (Busso et al. 2001). This is contrary to the results of Brown & Wallerstein (1992) where Zr was under-abundant ([Zr/Fe] = +0.51 dex) and Y was over-abundant ([Y/Fe] = +0.50 dex) with respect to Fe.Comment: 11 pages, 5 figures Accepted for publication in MNRA

Ab initio parametrised model of strain-dependent solubility of H in alpha-iron

The calculated effects of interstitial hydrogen on the elastic properties of alpha-iron from our earlier work are used to describe the H interactions with homogeneous strain fields using ab initio methods. In particular we calculate the H solublility in Fe subject to hydrostatic, uniaxial, and shear strain. For comparison, these interactions are parametrised successfully using a simple model with parameters entirely derived from ab initio methods. The results are used to predict the solubility of H in spatially-varying elastic strain fields, representative of realistic dislocations outside their core. We find a strong directional dependence of the H-dislocation interaction, leading to strong attraction of H by the axial strain components of edge dislocations and by screw dislocations oriented along the critical slip direction. We further find a H concentration enhancement around dislocation cores, consistent with experimental observations.Comment: part 2/2 from splitting of 1009.3784 (first part was 1102.0187), minor changes from previous version

Recommendations for riparian ecosystem management based on the general frame defined in EUFORGEN and results from EUROPOP

International audienc

Variations in Fe\u3csup\u3e3+\u3c/sup\u3e/∑Fe of Mariana Arc Basalts and Mantle Wedge \u3cem\u3ef\u3c/em\u3eO\u3csub\u3e2\u3c/sub\u3e

Arc basalts are more oxidized than mid-ocean ridge basalts, but it is unclear whether this difference is due to differentiation processes in the Earth’s crust or to a fundamental difference in the oxygen fugacity of their mantle sources. Distinguishing between these two hypotheses is important for understanding redox-sensitive processes related to arc magmatism, and thus more broadly how Earth materials cycle globally. We present major, volatile, and trace element concentrations in combination with Fe3+/∑Fe ratios determined in olivine-hosted glass inclusions and submarine glasses from five Mariana arc volcanoes and two regions of the Mariana Trough. For single eruptions, Fe3+/∑Fe ratios vary along liquid lines of descent that are either slightly oxidizing (olivine + clinopyroxene + plagioclase fractionation, CO2 ± H2O degassing) or reducing (olivine + clinopyroxene + plagioclase ± magnetite fractionation, CO2 + H2O + S degassing). Mariana samples are consistent with a global relationship between calc-alkaline affinity and both magmatic H2O and magmatic oxygen fugacity, where wetter, higher oxygen fugacity magmas display greater affinity for calc-alkaline differentiation. We find, however, that low-pressure differentiation cannot explain the majority of variations observed in Fe3+/∑Fe ratios for Mariana arc basalts, requiring primary differences in magmatic oxygen fugacity. Calculated oxygen fugacities of primary mantle melts at the pressures and temperatures of melt segregation are significantly oxidized relative to mid-ocean ridge basalts (∼QFM, where QFM is quartz–fayalite–magnetite buffer), ranging from QFM + 1·0 to QFM + 1·6 for Mariana arc basalts, whereas back-arc related samples record primary oxygen fugacities that range from QFM + 0·1 to QFM + 0·5. This Mariana arc sample suite includes a diversity of subduction influences, from lesser influence of a homogeneous H2O-rich component in the back-arc, to sediment melt- and fluid-dominated influences along the arc. Primary melt oxygen fugacity does not correlate significantly with sediment melt contributions (e.g. Th/La), nor can it be attributed to previous melt extraction in the back-arc. Primary melt oxygen fugacity correlates strongly with indices of slab fluids (e.g. Ba/La) from the Mariana Trough through the Mariana arc, increasing by 1·5 orders of magnitude as Ba/La increases by a factor of 10 relative to mid-ocean ridge basalts. These results suggest that contributions from the slab to the mantle wedge may be responsible for the elevated oxygen fugacity recorded by Mariana arc basalts and that slab fluids are potentially very oxidized

Changes in Self Concept and Perception Concerning Marriage of Students Enrolled in a Junior College Marriage Education Course with Implications for Teaching

Home Economics Educatio

Characterization of aerosol associated with enhanced small particle number concentrations in a suburban forested environment

Two elevated particle number/mass growth events associated with Aitken‐mode particles were observed during a sampling campaign (13–29 September 2004) at the Duke University Free‐Air CO2 Enrichment facility, a forested field site located in suburban central North Carolina. Aerosol growth rates between 1.2 and 4.9 nm hr−1 were observed, resulting in net increases in geometric mean diameter of 21 and 37 nm during events. Growth was dominated by addition of oxidized organic compounds. Campaign‐average aerosol mass concentrations measured by an Aerodyne quadrupole aerosol mass spectrometer (Q‐AMS) were 1.9 ± 1.6 (σ), 1.6 ± 1.9, 0.1 ± 0.1, and 0.4 ± 0.4 μg m−3 for organic mass (OM), sulfate, nitrate, and ammonium, respectively. These values represent 47%, 40%, 3%, and 10%, respectively, of the measured submicron aerosol mass. Based on Q‐AMS spectra, OM was apportioned to hydrocarbon‐like organic aerosol (HOA, likely representing primary organic aerosol) and two types of oxidized organic aerosol (OOA‐1 and OOA‐2), which constituted on average 6%, 58%, and 36%, respectively, of the apportioned OM. OOA‐1 probably represents aged, regional secondary organic aerosol (SOA), while OOA‐2 likely reflects less aged SOA. Organic aerosol characteristics associated with the events are compared to the campaign averages. Particularly in one event, the contribution of OOA‐2 to overall OM levels was enhanced, indicating the likelihood of less aged SOA formation. Statistical analyses investigate the relationships between HOA, OOA‐1, OOA‐2, other aerosol components, gas‐phase species, and meteorological data during the campaign and individual events. No single variable clearly controls the occurrence of a particle growth event

Density hardening plasticity and mechanical aging of silica glass under pressure: A Raman spectroscopic study

In addition of a flow, plastic deformation of structural glasses (in particular amorphous silica) is characterized by a permanent densification. Raman spectroscopic estimators are shown to give a full account of the plastic behavior of silica under pressure. While the permanent densification of silica has been widely discussed in terms of amorphous-amorphous transition, from a plasticity point of view, the evolution of the residual densification with the maximum pressure of a pressure cycle can be discussed as a density hardening phenomenon. In the framework of such a mechanical aging effect, we propose that the glass structure could be labelled by the maximum pressure experienced by the glass and that the saturation of densification could be associated with the densest packing of tetrahedra only linked by their vertices

The classification of frequencies in the {\gamma} Doradus / {\delta} Scuti hybrid star HD 49434

Hybrid stars of the {\gamma} Doradus and {\delta} Scuti pulsation types have great potential for asteroseismic analysis to explore their interior structure. To achieve this, mode identi- fications of pulsational frequencies observed in the stars must be made, a task which is far from simple. In this work we begin the analysis by scrutinizing the frequencies found in the CoRoT photometric satellite measurements and ground-based high-resolution spectroscopy of the hybrid star HD 49434. The results show almost no consistency between the frequencies found using the two techniques and no characteristic period spacings or couplings were identified in either dataset. The spectroscopic data additionally show no evidence for any long term (5 year) variation in the dominant frequency. The 31 spectroscopic frequencies identified have standard deviation profiles suggesting multiple modes sharing (l, m) in the {\delta} Scuti frequency region and several skewed modes sharing the same (l, m) in the {\gamma} Doradus frequency region. In addition, there is a clear frequency in the {\gamma} Doradus frequency region that appears to be unrelated to the others. We conclude HD 49434 remains a {\delta} Scuti/ {\gamma} Doradus candidate hybrid star but more sophisticated models dealing with rotation are sought to obtain a clear picture of the pulsational behaviour of this star.Comment: Accepted for publication in MNRAS December 201