Sky Variability in the y Band at the LSST Site

We have measured spatial and temporal variability in the y band sky brightness over the course of four nights above Cerro Tololo near Cerro Pachon, Chile, the planned site for the Large Synoptic Survey Telescope (LSST). Our wide-angle camera lens provided a 41 deg field of view and a 145 arcsec pixel scale. We minimized potential system throughput differences by deploying a deep depletion CCD and a filter that matches the proposed LSST y_3 band (970 nm-1030 nm). Images of the sky exhibited coherent wave structure, attributable to atmospheric gravity waves at 90 km altitude, creating 3%-4% rms spatial sky flux variability on scales of about 2 degrees and larger. Over the course of a full night the y_3 band additionally showed highly coherent temporal variability of up to a factor of 2 in flux. We estimate the mean absolute sky level to be approximately y_3 = 17.8 mag (Vega), or y_3 = 18.3 mag (AB). While our observations were made through a y_3 filter, the relative sky brightness variability should hold for all proposed y bands, whereas the absolute levels should more strongly depend on spectral response. The spatial variability presents a challenge to wide-field cameras that require illumination correction strategies that make use of stacked sky flats. The temporal variability may warrant an adaptive y band imaging strategy for LSST, to take advantage of times when the sky is darkest.Comment: 8 pages, 5 figures, accepted to PASP. Minor changes from referee report and editor's revisions

Feeding Two Birds With One Scone? The Relationship Between Teaching and Research for Graduate Students Across the Disciplines

We surveyed over 300 graduate students at a Southeastern research university to increase our understanding of their perceptions of (a) the connection between teaching and research, (b) the means by which integration occurs, and (c) the extent to which teaching and research contribute to a shared skill set that is of value in both contexts. We also examined differences across disciplines in the perception of this teaching-research nexus. Overall, findings indicate that graduate students perceive important relationships between teaching and research, and they point toward opportunities for administrators to promote teaching and research integration

Accelerated return to sport after osteochondral autograft plug transfer

Background:Previous studies have reported varying return-to-sport protocols after knee cartilage restoration procedures.Purpose:To (1) evaluate the time for return to sport in athletes with an isolated chondral injury who underwent an accelerated return-to-sport protocol after osteochondral autograft plug transfer (OAT) and (2) evaluate clinical outcomes to assess for any consequences from the accelerated return to sport.Study Design:Case series; Level of evidence, 4.Methods:An institutional cohort of 152 OAT procedures was reviewed, of which 20 competitive athletes met inclusion and exclusion criteria. All patients underwent a physician-directed accelerated rehabilitation program after their procedure. Return to sport was determined for all athletes. Clinical outcomes were assessed using International Knee Documentation Committee (IKDC) and Tegner scores as well as assessment of level of participation on return to sport.Results:Return-to-sport data were available for all 20 athletes; 13 of 20 athletes (65%) were available for clinical evaluation at a mean 4.4-year follow-up. The mean time for return to sport for all 20 athletes was 82.9 ± 25 days (range, 38-134 days). All athletes were able to return to sport at their previous level and reported that they were satisfied or very satisfied with their surgical outcome and ability to return to sport. The mean postoperative IKDC score was 84.5 ± 9.5. The mean Tegner score prior to injury was 8.9 ± 1.7; it was 7.7 ± 1.9 at final follow-up.Conclusion:Competitive athletes with traumatic chondral defects treated with OAT managed using this protocol had reduced time to preinjury activity levels compared with what is currently reported, with excellent clinical outcomes and no serious long-term sequelae.</jats:sec

Cognitive Apprenticeship and the Supervision of Science and Engineering Research Assistants

We explore and critically reflect on the process of science and engineering research assistant skill development both within laboratory-based research teams and, when no team is present, within the faculty supervisor-research assistant interactions. Using a performance-based measure of research skill development, we identify research assistants who, over the course of an academic year of service as a researcher, markedly developed, modestly developed, or failed to develop their research skills. Interviews with these research assistants and their faculty supervisors, seen through the lens of cognitive apprenticeship, provide insight into this variation. We found that within the contours of supervisory relationships and research teams, research skill development is indelibly shaped, for better or worse, by supervisor influence and abundant trial-and-error

Elemental abundances and their implications for the chemical enrichment of the boötes i ultrafaint galaxy

We present a double-blind analysis of high-dispersion spectra of seven red giant members of the Boötes I ultrafaint dwarf spheroidal galaxy, complemented with re-analysis of a similar spectrum of an eighth-member star. The stars cover [Fe/H] from -3.7 t

Graduate students\u27 teaching experiences improve their methodological research skills

Science, technology, engineering, and mathematics (STEM) graduate students are often encouraged to maximize their engagement with supervised research and minimize teaching obligations. However, the process of teaching students engaged in inquiry provides practice in the application of important research skills. Using a performance rubric, we compared the quality of methodological skills demonstrated in written research proposals for two groups of early career graduate students (those with both teaching and research responsibilities and those with only research responsibilities) at the beginning and end of an academic year. After statistically controlling for preexisting differences between groups, students who both taught and conducted research demonstrate significantly greater improvement in their abilities to generate testable hypotheses and design valid experiments. These results indicate that teaching experience can contribute substantially to the improvement of essential research skills

Boo-1137 - An Extremely Metal-Poor Star in the Ultra-Faint Dwarf Spheroidal Galaxy Bo\"{o}tes I

We present high-resolution, high-S/N spectra of an extremely metal- poor giant star Boo-1137 in the "ultra-faint" dwarf spheroidal galaxy (dSph) Bootes I (absolute magnitude Mv ~ -6.3). With [Fe/H] = -3.7, this the most metal-poor star yet identified in an ultra-faint dSph. Comparison of relative abundances, [X/Fe], for some 15 elements with those of the extremely metal-poor giants of the Galactic halo shows Boo-1137 is "normal" with respect to C and N, the odd-Z elements Na and Al, the Fe-peak elements, and the n-capture elements Sr and Ba, in comparison with the bulk of the halo with [Fe/H] < -3.0. The alpha- elements Mg, Si, Ca, and Ti are all higher by Delta[X/Fe] ~ 0.2 than average halo values. Monte-Carlo analysis indicates Delta[alpha/Fe] values this large are expected with probability ~ 0.02. The abundance pattern in Boo-1137 suggests inhomogeneous chemical evolution, consistent with the wide internal spread in Fe abundances we reported earlier. The similarity of most of the Boo-1137 relative abundances with respect to halo values, and the fact that the alpha-elements are all offset by a similar small amount from the halo averages, points to the same underlying galaxy-scale stellar initial mass function, but that Boo-1137 likely originated in a star-forming region where the abundances reflect either poor mixing of supernova (SN) ejecta, or poor sampling of the SN progenitor mass range, or both.Comment: 33 pages, 6 figures, submitted to Astrophysical Journa

IACT observations of gamma-ray bursts: prospects for the Cherenkov Telescope Array

Gamma rays at rest frame energies as high as 90 GeV have been reported from gamma-ray bursts (GRBs) by the Fermi Large Area Telescope (LAT). There is considerable hope that a confirmed GRB detection will be possible with the upcoming Cherenkov Telescope Array (CTA), which will have a larger effective area and better low-energy sensitivity than current-generation imaging atmospheric Cherenkov telescopes (IACTs). To estimate the likelihood of such a detection, we have developed a phenomenological model for GRB emission between 1 GeV and 1 TeV that is motivated by the high-energy GRB detections of Fermi-LAT, and allows us to extrapolate the statistics of GRBs seen by lower energy instruments such as the Swift-BAT and BATSE on the Compton Gamma-ray Observatory. We show a number of statistics for detected GRBs, and describe how the detectability of GRBs with CTA could vary based on a number of parameters, such as the typical observation delay between the burst onset and the start of ground observations. We also consider the possibility of using GBM on Fermi as a finder of GRBs for rapid ground follow-up. While the uncertainty of GBM localization is problematic, the small field-of-view for IACTs can potentially be overcome by scanning over the GBM error region. Overall, our results indicate that CTA should be able to detect one GRB every 20 to 30 months with our baseline instrument model, assuming consistently rapid pursuit of GRB alerts, and provided that spectral breaks below 100 GeV are not a common feature of the bright GRB population. With a more optimistic instrument model, the detection rate can be as high as 1 to 2 GRBs per year.Comment: 28 pages, 24 figures, 4 tables, submitted to Experimental Astronom

Gendered endings: Narratives of male and female suicides in the South African Lowveld

This is the author's accepted manuscript. The final publication is available at Springer via http://dx.doi.org/10.1007/s11013-012-9258-y. Copyright @ Springer Science+Business Media, LLC 2012.Durkheim’s classical theory of suicide rates being a negative index of social solidarity downplays the salience of gendered concerns in suicide. But gendered inequalities have had a negative impact: worldwide significantly more men than women perpetrate fatal suicides. Drawing on narratives of 52 fatal suicides in Bushbuckridge, South Africa, this article suggests that Bourdieu’s concepts of ‘symbolic violence’ and ‘masculine domination’ provide a more appropriate framework for understanding this paradox. I show that the thwarting of investments in dominant masculine positions have been the major precursor to suicides by men. Men tended to take their own lives as a means of escape. By contrast, women perpetrated suicide to protest against the miserable consequences of being dominated by men. However, contra the assumption of Bourdieu’s concept of ‘habitus’, the narrators of suicide stories did reflect critically upon gender constructs