Giant Magnetic Moments of Nitrogen Stabilized Mn Clusters and Their Relevance to Ferromagnetism in Mn Doped GaN

Using first principles calculations based on density functional theory, we show that the stability and magnetic properties of small Mn clusters can be fundamentally altered by the presence of nitrogen. Not only are their binding energies substantially enhanced, but also the coupling between the magnetic moments at Mn sites remains ferromagnetic irrespective of their size or shape. In addition, these nitrogen stabilized Mn clusters carry giant magnetic moments ranging from 4 Bohr magnetons in MnN to 22 Bohr magnetons in Mn_5N. It is suggested that the giant magnetic moments of Mn_xN clusters may play a key role in the ferromagnetism of Mn doped GaN which exhibit a wide range (10K - 940K) of Curie temperatures

Total Infrared Luminosity Estimation of Resolved and Unresolved Galaxies

The total infrared (TIR) luminosity from galaxies can be used to examine both star formation and dust physics. We provide here new relations to estimate the TIR luminosity from various Spitzer bands, in particular from the 8 micron and 24 micron bands. To do so, we use 45" subregions within a subsample of nearby face-on spiral galaxies from the Spitzer Infrared Nearby Galaxies Survey (SINGS) that have known oxygen abundances as well as integrated galaxy data from the SINGS, the Local Volume Legacy Survey (LVL) and Engelbracht et al. (2008) samples. Taking into account the oxygen abundances of the subregions, the star formation rate intensity, and the relative emission of the polycyclic aromatic hydrocarbons at 8 micron, the warm dust at 24 micron and the cold dust at 70 micron and 160 micron we derive new relations to estimate the TIR luminosity from just one or two of the Spitzer bands. We also show that the metallicity and the star formation intensity must be taken into account when estimating the TIR luminosity from two wave bands, especially when data longward of 24 micron are not available.Comment: 11 pages, 10 figures, accepted for publication in Ap

Re-examining High Abundance SDSS Mass-Metallicity Outliers: High N/O, Evolved Wolf-Rayet Galaxies?

We present new MMT spectroscopic observations of four dwarf galaxies representative of a larger sample observed by the Sloan Digital Sky Survey (SDSS) and identified by Peeples et al. (2008) as low-mass, high oxygen abundance outliers from the mass-metallicity relation. Peeples et al. (2008) showed that these four objects (with metallicity estimates of 8.5 =< 12 + log(O/H) =< 8.8) have oxygen abundance offsets of 0.4-0.6 dex from the M_B luminosity-metallicity relation. Our new observations extend the wavelength coverage to include the [OII] 3726,3729 doublet, which adds leverage in oxygen abundance estimates and allows measurements of N/O ratios. All four spectra are low excitation, with relatively high N/O ratios (N/O >~ 0.10), each of which tend to bias estimates based on strong emission lines toward high oxygen abundances. These spectra all fall in a regime where the "standard" strong line methods for metallicity determinations are not well calibrated either empirically or by photoionization modeling. By comparing our spectra directly to photoionization models, we estimate oxygen abundances in the range of 7.9 =< 12 + log(O/H) =< 8.4, consistent with the scatter of the mass-metallicity relation. We discuss the physical nature of these galaxies that leads to their unusual spectra (and previous classification as outliers), finding their low excitation, elevated N/O, and strong Balmer absorption are consistent with the properties expected from galaxies evolving past the "Wolf-Rayet galaxy" phase. We compare our results to the "main" sample of Peeples et al. (2008) and conclude that they are outliers primarily due to enrichment of nitrogen relative to oxygen, and not due to unusually high oxygen abundances for their masses or luminosities.Comment: 38 pages, 10 figures, accepted to Ap

FUSE observations of the HI interstellar gas of IZw18

We present the analysis of FUSE observations of the metal-deficient dwarf galaxy IZw18. We measured column densities of HI, NI, OI, ArI, SiII, and FeII. The OI/HI ratio (log(OI/HI)=-4.7^{+0.8}_{-0.6}) is consistent with the O/H ratio observed in the HII regions (all uncertainties are 2-sigma). If the oxygen is depleted in the HI region compared to the HII regions, the depletion is at most 0.5dex. This is also consistent with the log(O/H) ratios ~-5 measured with FUSE in the HI regions of other blue compact dwarf galaxies. With log(NI/OI)=-2.4^{+0.6}_{-0.8}, the measured NI/OI ratio is lower than expected for primary nitrogen. The determination of the NII column density is needed to discriminate between a large ionization of NI or a possible nitrogen deficiency. The neutral argon is also apparently underabundant, indicating that ionization into ArII is likely important. The column densities of the other alpha-chain elements SiII and ArI favor the lower edge of the permitted range of OI column density, log(N(OI))~16.3.Comment: Accepted for publication in A&

Phenotype standardization for statin-induced myotoxicity

Statins are widely used lipid-lowering drugs that are effective in reducing cardiovascular disease risk. Although they are generally well tolerated, they can cause muscle toxicity, which can lead to severe rhabdomyolysis. Research in this area has been hampered to some extent by the lack of standardized nomenclature and phenotypic definitions. We have used numerical and descriptive classifications and developed an algorithm to define statin-related myotoxicity phenotypes, including myalgia, myopathy, rhabdomyolysis, and necrotizing autoimmune myopathy.</p

An Aromatic Inventory of the Local Volume

Using infrared photometry from the Spitzer Space Telescope, we perform the first inventory of aromatic feature emission (AFE, but also commonly referred to as PAH emission) for a statistically complete sample of star-forming galaxies in the local volume. The photometric methodology involved is calibrated and demonstrated to recover the aromatic fraction of the IRAC 8 micron flux with a standard deviation of 6% for a training set of 40 SINGS galaxies (ranging from stellar to dust dominated) with both suitable mid-infrared Spitzer IRS spectra and equivalent photometry. A potential factor of two improvement could be realized with suitable 5.5 and 10 micron photometry, such as what may be provided in the future by JWST. The resulting technique is then applied to mid-infrared photometry for the 258 galaxies from the Local Volume Legacy (LVL) survey, a large sample dominated in number by low-luminosity dwarf galaxies for which obtaining comparable mid-infrared spectroscopy is not feasible. We find the total LVL luminosity due to five strong aromatic features in the 8 micron complex to be 2.47E10 solar luminosities with a mean volume density of 8.8E6 solar luminosities per cubic Megaparsec. Twenty-four of the LVL galaxies, corresponding to a luminosity cut at M = -18.22 in the B band, account for 90% of the aromatic luminosity. Using oxygen abundances compiled from the literature for 129 of the 258 LVL galaxies, we find a correlation between metallicity and the aromatic to total infrared emission ratio but not the aromatic to total 8 micron dust emission ratio. A possible explanation is that metallicity plays a role in the abundance of aromatic molecules relative to the total dust content, but other factors such as star formation and/or the local radiation field affect the excitation of those molecules.Comment: ApJ in press; 29 pages, 14 figures, 3 tables; emulateapj forma

Results of international standardised beekeeper surveys of colony losses for winter 2012-2013 : analysis of winter loss rates and mixed effects modelling of risk factors for winter loss.

This article presents results of an analysis of winter losses of honey bee colonies from 19 mainly European countries, most of which implemented the standardised 2013 COLOSS questionnaire. Generalised linear mixed effects models (GLMMs) were used to investigate the effects of several factors on the risk of colony loss, including different treatments for Varroa destructor, allowing for random effects of beekeeper and region. Both winter and summer treatments were considered, and the most common combinations of treatment and timing were used to define treatment factor levels. Overall and within country colony loss rates are presented. Significant factors in the model were found to be: percentage of young queens in the colonies before winter, extent of queen problems in summer, treatment of the varroa mite, and access by foraging honey bees to oilseed rape and maize. Spatial variation at the beekeeper level is shown across geographical regions using random effects from the fitted models, both before and after allowing for the effect of the significant terms in the model. This spatial variation is considerable

Chemical Properties of Star-Forming Emission Line Galaxies at z=0.1 - 0.5

We measure oxygen and nitrogen abundances for 14 star-forming emission line galaxies (ELGs) at 0.11<z<0.5 using Keck/LRIS optical spectroscopy. The targets exhibit a range of metallicities from slightly metal-poor like the LMC to super-solar. Oxygen abundances of the sample correlate strongly with rest-frame blue luminosities. The metallicity-luminosity relation based on these 14 objects is indistinguishable from the one obeyed by local galaxies, although there is marginal evidence (1.1sigma) that the sample is slightly more metal-deficient than local galaxies of the same luminosity. The observed galaxies exhibit smaller emission linewidths than local galaxies of similar metallicity, but proper corrections for inclination angle and other systematic effects are unknown. For 8 of the 14 objects we measure nitrogen-to-oxygen ratios. Seven of 8 systems show evidence for secondary nitrogen production, with log(N/O)> -1.4 like local spirals. These chemical properties are inconsistent with unevolved objects undergoing a first burst of star formation. The majority of the ELGs are presently ~4 magnitudes brighter and ~0.5 dex more metal-rich than the bulk of the stars in well-known metal-poor dwarf spheroidals such as NGC 205 and NGC 185, making an evolution between some ELGs and metal-poor dwarf spheroidals improbable. However, the data are consistent with the hypothesis that more luminous and metal-rich spheroidal galaxies like NGC 3605 may become the evolutionary endpoints of some ELGs. [abridged]Comment: 41 pages, w/12 figures, uses AASTeX aaspp4.sty, psfig.sty; To appear in The Astrophysical Journa