History of Polar Bears as Summer Residents on the St. Matthew Islands, Bering Sea

Polar bears were found as summer residents on the St. Matthew Islands in the northern Bering Sea from the time of their discovery in the mid-18th century until the late 19th century, when the last bears were presumably shot by crews from Canadian and American sealers and a U.S. revenue cutter. Historical documents suggest that the killing of the last summer-resident polar bears on the St. Matthew Islands was an indirect consequence of the controversy between the United States and Great Britain over management of the fur seal harvest and the associated pelagic hunting of these seals. Although polar bears have continued to be present near the St. Matthew Islands in winter, when sea ice is present, a metapopulation of summer-resident bears has not reestablished on these islands. In 1972, the State of Alaska considered a proposal to reestablish a summer-resident polar bear population on the St. Matthew Islands, and since 2008, when the United States listed the polar bear as a threatened species, such reestablishment has been suggested as a conservation strategy. However, given the observed changes in local Bering Sea ice conditions in recent decades, the lack of detailed information on the population ecology and habitat dependencies of the historical St. Matthew bears, and the unavailability of an analogous extant metapopulation of polar bears for comparison, it is highly unlikely that reestablishment of summer-resident polar bears on the St. Matthew Islands could be realized.Des ours polaires résidaient l’été sur les îles St. Matthew, dans le nord de la. mer de Béring, du moment où ils ont été découverts vers le milieu du XVIIIe siècle jusque vers la fin du XIXe siècle, lorsque les derniers ours auraient été tués par les équipages de phoquiers canadiens et américains ainsi que par des pataches de la douane américaine. Des documents historiques laissent entendre que la mise à mort des derniers ours polaires d’été sur les îles St. Matthew était une conséquence indirecte de la controverse entre les États-Unis et la Grande-Bretagne au sujet des récoltes d’otaries à fourrure et de la chasse pélagique connexe de ces otaries. Bien que la présence des ours polaires se soit poursuivie dans les environs des îles St. Matthew l’hiver, lorsqu’il y a de la glace de mer, une métapopulation d’ours d’été ne s’est pas réimplantée sur ces îles. En 1972, l’État de l’Alaska a considéré une proposition en vue du rétablissement de la population d’ours polaires résidant sur les îles St. Matthew l’été, et depuis 2008, lorsque les États-Unis ont ajouté les ours polaires à la liste des espèces menacées, ce rétablissement a été suggéré en guise de stratégie de conservation. Cependant, compte tenu des changements observés dans le régime des glaces de la mer de Béring ces dernières décennies, de l’absence de renseignements détaillés sur l’écologie de la population et sur les dépendances à l’habitat des ours historiques de St. Matthew, de même que de l’absence d’une métapopulation analogue historique à des fins de comparaison, il est peu vraisemblable que le rétablissement des ours polaires en résidence d’été sur les îles St. Matthew puisse se concrétiser

David Lucas

2013 Kentucky Folk Art Center exhibition catalog for artist David Lucas.https://scholarworks.moreheadstate.edu/kfac_exhibition_catalogs/1011/thumbnail.jp

Moment based estimation of stochastic Kronecker graph parameters

Stochastic Kronecker graphs supply a parsimonious model for large sparse real world graphs. They can specify the distribution of a large random graph using only three or four parameters. Those parameters have however proved difficult to choose in specific applications. This article looks at method of moments estimators that are computationally much simpler than maximum likelihood. The estimators are fast and in our examples, they typically yield Kronecker parameters with expected feature counts closer to a given graph than we get from KronFit. The improvement was especially prominent for the number of triangles in the graph.Comment: 22 pages, 4 figure

500 Years of Printmaking: Prints and Illustrated Books at Bowdoin College

Exhibition held Oct. 13-Dec. 31, 1978. Preface by Katherine J. Watson.https://digitalcommons.bowdoin.edu/art-museum-exhibition-catalogs/1042/thumbnail.jp

Broken-Symmetry Unrestricted Hybrid Density Functional Calculations on Nickel Dimer and Nickel Hydride

In the present work we investigate the adequacy of broken-symmetry unrestricted density functional theory (DFT) for constructing the potential energy curve of nickel dimer and nickel hydride, as a model for larger bare and hydrogenated nickel cluster calculations. We use three hybrid functionals: the popular B3LYP, Becke's newest optimized functional Becke98, and the simple FSLYP functional (50% Hartree-Fock and 50% Slater exchange and LYP gradient-corrected correlation functional) with two basis sets: all-electron (AE) Wachters+f basis set and Stuttgart RSC effective core potential (ECP) and basis set. We find that, overall, the best agreement with experiment, comparable to that of the high-level CASPT2, is obtained with B3LYP/AE, closely followed by Becke98/AE and Becke98/ECP. FSLYP/AE and B3LYP/ECP give slightly worse agreement with experiment, and FSLYP/ECP is the only method among the ones we studied that gives an unaceptably large error, underestimating the dissociation energy of nickel dimer by 28%, and being in the largest disagreement with the experiment and the other theoretical predictions.Comment: 17 pages, 7 tables, 7 figures; submitted to J. Chem. Phys.; Revtex4/LaTeX2e. v2 (8/5/04): New (and better) ECP results, without charge density fitting (which was found to give large errors). Subtracted the relativistic corrections from all experimental value

Old Master Drawings at Bowdoin College

Catalogue of an exhibition held at Bowdoin College Museum of Art, Brunswick Me., May 17-July 7 1985; Sterling and Francine Clark Art Institute, Williamstown Mass., Sept. 14-Oct. 27 1985; Helen Foresman Spencer Museum of Art, Uniersity of Kansas, Lawrence Kansas, Jan. 19-Mar. 2, 1986; Art Gallery of Ontario, Toronto Canada, May 17-June 29, 1986.https://digitalcommons.bowdoin.edu/art-museum-exhibition-catalogs/1065/thumbnail.jp

Biases in estimates of air pollution impacts: the role of omitted variables and measurement errors

Observational studies often use linear regression to assess the effect of ambient air pollution on outcomes of interest, such as human health outcomes or crop yields. Yet pollution datasets are typically noisy and include only a subset of potentially relevant pollutants, giving rise to both measurement error bias (MEB) and omitted variable bias (OVB). While it is well understood that these biases exist, less is understood about whether these biases tend to be positive or negative, even though it is sometimes falsely claimed that measurement error simply biases regression coefficient estimates towards zero. In this paper, we show that more can be said about the direction of these biases under the realistic assumptions that the concentrations of different types of air pollutants are positively correlated with each other and that each type of pollutant has a nonpositive association with the outcome variable. In particular, we demonstrate both theoretically and using simulations that under these two assumptions, the OVB will typically be negative and that more often than not the MEB for null pollutants or for pollutants that are perfectly measured will be negative. We also provide precise conditions, which are consistent with the assumptions, under which we prove that the biases are guaranteed to be negative. While the discussion in this paper is motivated by studies assessing the effect of air pollutants on crop yields, the findings are also relevant to regression-based studies assessing the effect of air pollutants on human health outcomes

The STP-2 Mission: Rideshare Lessons Learned from the Air Force’s First Falcon Heavy Launch

On 25 June 2019, the Department of Defense (DoD) Space Test Program (STP) launched the STP-2 mission from Kennedy Space Center’s Launch Complex 39A on a SpaceX Falcon Heavy. This groundbreaking mission carried twenty-four space vehicles to three different orbits and achieved many firsts. As might be expected in such a complex rideshare mission, there were many lessons learned. This paper discusses some of those lessons learned, particularly related to managing and working with multiple organizations, performing interface control, sorting through policy and compliance, and conducting mission assurance, fit checks, and launch integration. STP has a 50+ year history of providing access to space for research and development satellites, most of them small satellites. The STP-2 launch represents the latest in a long line of multi-manifest rideshare missions. Our hope is to enlighten similar mission teams attempting large rideshare efforts across the entire space system development and launch community