We present constraints on the progenitor metallicities of core-collapse supernovae. To date, nearly all metallicity constraints have been inferred from indirect methods such as metallicity gradients ...in host galaxies, luminosities of host galaxies or derived global galaxy metallicities. Here, progenitor metallicities are derived from optical spectra taken at the sites of nearby supernovae, from the ratio of strong emission lines found in their host H ii regions. We present results from the spectra of 74 host H ii regions and discuss the implications that these have on the nature of core-collapse supernova progenitors. Overall, while we find that the mean metallicity of Type Ibc environments is higher than that of Type II events, this difference is smaller than observed in previous studies. There is only a 0.06 dex difference in the mean metallicity values, at a statistical significance of ∼1.5σ, while using a Kolmogorov–Smirnov test we find that the two metallicity distributions are marginally consistent with being drawn from the same parent population (probability >10 per cent). This argues that progenitor metallicity is not a dominant parameter in deciding supernovae type, with progenitor mass and/or binarity playing a much more significant role. The mean derived oxygen metallicities 12+log(O/H) for the different supernova types, on the Pettini & Pagel scale, are 8.580 (standard error on the mean of 0.027) for the 46 Type II supernovae (dominated by Type II plateau), 8.616 (0.040) for 10 Type Ib and 8.626 (0.039) for 14 Type Ic. Overall, the Type Ibc supernovae have a mean metallicity of 8.635 (0.026, 27 supernovae). Hence, we find a slight suggestion of a metallicity sequence, in terms of increasing progenitor metallicity going from Type II through Ib and finally Ic supernovae arising from the highest metallicity progenitors. Finally we discuss these results in the context of all current literature progenitor metallicity measurements, and discuss biases and selection effects that may affect the current sample compared to overall supernova and galaxy samples.
We present DES13S2cmm, the first spectroscopically-confirmed superluminous supernova (SLSN) from the Dark Energy Survey (DES). We briefly discuss the data and search algorithm used to find this event ...in the first year of DES operations, and outline the spectroscopic data obtained from the European Southern Observatory (ESO) Very Large Telescope to confirm its redshift (z = 0.663 ± 0.001 based on the host-galaxy emission lines) and likely spectral type (Type I). Using this redshift, we find
$M^{\rm peak}_U=-21.05^{+0.10}_{-0.09}$
for the peak, rest-frame U-band absolute magnitude, and find DES13S2cmm to be located in a faint, low-metallicity (sub-solar), low stellar-mass host galaxy (log (M/M⊙) = 9.3 ± 0.3), consistent with what is seen for other SLSNe-I. We compare the bolometric light curve of DES13S2cmm to 14 similarly well-observed SLSNe-I in the literature and find that it possesses one of the slowest declining tails (beyond +30 d rest-frame past peak), and is the faintest at peak. Moreover, we find the bolometric light curves of all SLSNe-I studied herein possess a dispersion of only 0.2–0.3 mag between +25 and +30 d after peak (rest frame) depending on redshift range studied; this could be important for ‘standardizing’ such supernovae, as is done with the more common Type Ia. We fit the bolometric light curve of DES13S2cmm with two competing models for SLSNe-I – the radioactive decay of 56Ni, and a magnetar – and find that while the magnetar is formally a better fit, neither model provides a compelling match to the data. Although we are unable to conclusively differentiate between these two physical models for this particular SLSN-I, further DES observations of more SLSNe-I should break this degeneracy, especially if the light curves of SLSNe-I can be observed beyond 100 d in the rest frame of the supernova.
Characterizing the nature and spatial distribution of the lensing objects that produce the previously measured microlensing optical depth toward the Large Magellanic Cloud (LMC) remains an open ...problem. We present an appraisal of the ability of the SuperMACHO Project, a next-generation microlensing survey directed toward the LMC, to discriminate between various proposed lensing populations. We consider two scenarios: lensing by a uniform foreground screen of objects and self-lensing by LMC stars. The optical depth for "screen lensing" is essentially constant across the face of the LMC, whereas the optical depth for self-lensing shows a strong spatial dependence. We have carried out extensive simulations, based on data obtained during the first year of the project, to assess the SuperMACHO survey's ability to discriminate between these two scenarios. In our simulations we predict the expected number of observed microlensing events for various LMC models for each of our fields by adding artificial stars to the images and estimating the spatial and temporal efficiency of detecting microlensing events using Monte Carlo methods. We find that the event rate itself shows significant sensitivity to the choice of the LMC luminosity function, limiting the conclusions that can be drawn from the absolute rate. If instead we determine the differential event rate across the LMC, we will decrease the impact of these systematic biases and render our conclusions more robust. With this approach the SuperMACHO Project should be able to distinguish between the two categories of lens populations. This will provide important constraints on the nature of the lensing objects and their contributions to the Galactic dark matter halo.
ABSTRACT The ESSENCE survey discovered 213 Type Ia supernovae at redshifts between 2002 and 2008. We present their R- and I-band photometry, measured from images obtained using the MOSAIC II camera ...at the CTIO Blanco, along with rapid-response spectroscopy for each object. We use our spectroscopic follow-up observations to determine an accurate, quantitative classification, and precise redshift. Through an extensive calibration program we have improved the precision of the CTIO Blanco natural photometric system. We use several empirical metrics to measure our internal photometric consistency and our absolute calibration of the survey. We assess the effect of various potential sources of systematic bias on our measured fluxes, and estimate the dominant term in the systematic error budget from the photometric calibration on our absolute fluxes is ∼1%.
We report the successful identification of the type of the supernova (SN) responsible for the supernova remnant SNR 0509-675 in the Large Magellanic Cloud (LMC) using Gemini spectra of surrounding ...light echoes. The ability to classify outbursts associated with centuries-old remnants provides a new window into several aspects of SN research and is likely to be successful in providing new constraints on additional LMC SNe, as well as their historical counterparts in the Milky Way (MW). The combined spectrum of echo light from SNR 0509-675 shows broad emission and absorption lines consistent with a SN spectrum. We create a spectral library consisting of 28 SNe Ia and 6 SNe Ib/c that are time-integrated, dust-scattered by LMC dust, and reddened by the LMC and MW. We fit these SN templates to the observed light echo spectrum using image minimization, as well as correlation techniques, and we find that overluminous 1991T-like SNe Ia with image match the observed spectrum best.
During childhood growth, bone undergoes modelling involving separate osteoblastic and osteoclastic processes. Markers of bone turnover circulate at high concentrations, parallel the childhood growth ...curve and correlate with height velocity. The aim of this study was to compare serum markers of bone turnover in children with haemophilia and normal bone mineral density (BMD) vs. those with low BMD. In a cross‐sectional study, 69 children with haemophilia were evaluated, 45 children with normal spine BMD vs. 24 with low BMD. Lumbar spine BMD was determined using dual X‐ray absorptiometry and Z‐scores were calculated. Serum samples of markers of bone turnover, osteocalcin (bone formation) and C‐telopeptide of type I collagen (bone resorption) were measured using ELISA. The mean BMD (g cm−2) in the normal group was 0.656 ± 0.15 vs. 0.558 ± 0.12 in those with low BMD (P = 0.007), osteocalcin levels in children with normal BMD were 9.29 ± 4.97 vs. 7.06 ± 2.17 ng μL−1 in the low BMD group (P = 0.012). C‐telopeptide levels in the normal group were 1.06 ± 1.4 vs. 0.74 ± 0.3 ng mL−1 in the low BMD group (P = 0.169). Our results showed that low osteocalcin levels predominated in the group with low BMD, which indicates a diminished osteoblastic bone formation activity while there were no differences with regard to bone resorption markers. Moreover, osteocalcin levels explain 10% of the variation of lumbar spine Z‐score.
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•Mini-bioreactors managed to remove benzo(a)anthracene and benzo(a)pyrene together.•The shape and the mode of operation of the bioreactor markedly influenced the efficiency of ...removal.•Stirring speed, flow, contact time, number of cells/bead and cell species ratio were studied.•The results obtained may be useful for scaling and future applications in bioremediation.
Polycyclic aromatic hydrocarbons (PAHs), especially those having four or more rings, are abundant and toxic environmental contaminants that are highly persistent and difficult to remove from contaminated ecosystems. Bioreactors with microalgae have been used to remove some low-molecular-weight PAHs. Immobilization is a good choice for the recovery of biomass from reactors once its function of removing contaminants is fulfilled. Alginate is a natural material that is transparent, is permeable and acts as a protective barrier against other microorganisms and harmful particulates suspended in water. Therefore, in this study, we designed and evaluated four mini-bioreactors packed with alginate beads that contain two microalgal species, Selenastrum capricornutum and Scenedesmus acutus which are capable of removing the high-molecular-weight PAHs benzo(a)anthracene and benzo(a)pyrene. One of the bioreactors was a batch reactor with a continuous magnetic stirring tank, and the other bioreactors were enclosed tubular bioreactors operating in semi-continuous mode with two cycles. The influence of parameters such as the reactor shape, stirring speed, flow, number of alginate beads, number of cells and cell species ratio, as well as the time of contact and the use of two operation cycles were studied. The amounts of the remaining PAHs after exposure tests with microalgae were determined. It was found that the shape and the mode of operation of the bioreactor markedly influenced the efficiency of removal. The removal capacity of these mini-bioreactors and the advantages and the disadvantages of using these mini-bioreactors were analyzed.
Increased production capacity is one of the most important priorities for seasonal and pandemic influenza vaccines. In the present study, we used a baculovirus-insect larvae system (considered small, ...living biofactories) to improve the production of recombinant influenza virus H1N1 hemagglutinin (HA). Insect larvae produced four-fold more HA protein than insect cells per biomass unit (1
g of fresh larvae weight). A single infected
Trichoplusia ni larva produced up to 113
μg of soluble and easily purified recombinant HA, an amount similar to that produced by 1.2
×
10
8 Sf21 insect cells infected by the same baculovirus. The use of the KDEL endoplasmic reticulum retention signal fused to the HA protein further increased recombinant protein production. Larvae-derived HA was immunogenically functional in vaccinated mice, inducing the generation of hemagglutination inhibition antibodies and a protective immune response against a lethal challenge with a highly virulent virus. The productivity, scalability and cost efficiency of small, living biofactories based on insect larvae suggest a broad-based strategy for the production of recombinant subunit vaccines against seasonal or pandemic influenza as an alternative to fermentation technologies.
Objective:To evaluate genotoxicity of anabolic androgenic steroids (AAS) in male bodybuilders by a micronucleus assay in buccal mucosa cells.Methods:11 male bodybuilders volunteered to participate in ...this study and two groups were formed: group 1 (n = 6), without AAS consumption and group 2 (n = 5), with AAS consumption. A sample of buccal epithelium was taken from each participant once a week for 6 weeks. Samples were fixed, stained and analysed by a light microscope, and 2000 cells were counted from each slide. Results are expressed as micronucleated cells (MNC) per 1000 cells and were analysed by the Mann–Whitney U test and Wilcoxon’s test.Results:A marked increased in MNC was seen in bodybuilders with AAS consumption compared with those without AAS consumption (mean (SD) 4.1 (2.4) MNC/1000 cells vs 0.4 (0.4) MNC/1000 cells, respectively; p<0.004). Intragroup comparisons showed no differences in the MNC frequencies during the sampling time in group 1, whereas the MNC frequency in group 2 varied significantly, reaching the highest MNC frequencies in the third and fourth week of sampling (5.9 (2.4) MNC/1000 cells; 5.8 (1.8) MNC/1000 cells, respectively); frequency in the first sampled week was 1.1 (0.1) MNC/1000 cells. Significant differences in all sampled weeks were found between the two groups.Conclusion:AAS consumption increased the frequency of MNC from buccal mucosa in bodybuilders.
We present analytic models for a photoionized region in pressure equilibrium with the surrounding, neutral material. The models are based on the assumption of a linear relation between the H ...ionization fraction and the square of the sound speed of the gas. We show that under these assumptions the "grey" radiative transfer equation has analytic solutions that provide the ionization structure and the density of the nebula as a function of radius.
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