Showing papers by "Wheaton College (Massachusetts) published in 2002"
TL;DR: In this article, the atmospheric deposition of mercury (Hg) over the last 800-1000 years in both hemispheres was reconstructed using two different natural archiving media from remote locations.
Abstract: [1] Using two different natural archiving media from remote locations, we have reconstructed the atmospheric deposition of mercury (Hg) over the last 800–1000 years in both hemispheres. This effort was designed (1) to quantify the historical variation and distributional patterns of atmospheric Hg fluxes in the midlatitudes of North America at Nova Scotia (N.S.) and at a comparable midlatitude region in the Southern Hemisphere at New Zealand (N.S.), (2) to identify and quantify the influence of anthropogenic and natural Hg contributions to atmospheric Hg fluxes, (3) to further investigate the suitability and comparability of our two selected media (lake sediments and ombrotrophic peat) for Hg depositional reconstructions, and (4) to assess the relative importance of wet and dry deposition to the study areas. Significant findings from the study include the following: (1) The lake sediments examined appear to faithfully record the contemporary flux of Hg from the atmosphere (e.g., 1997: N.S. Lakes: approximately 8 ± 3 μg m−2 yr−1; N.S. Rain: 8 μg m−2 yr−1). The upper 10 cm (approximately 10 yr) of ombrotrophic peat cores from Nova Scotia were dated using a biological chronometer (Polytrichum) and were also consistent with the flux data provided by current direct sampling of precipitation. These observations place limits on the contribution of dry deposition (40 ± 50% of wet flux). Unfortunately, the peat samples could not be dated below 10 cm. This was due to the apparent diagenetic mobility of the geochronological tracer (210Pb). (2) There is no evidence of a significant enhancement in the atmospheric Hg flux as a result of preindustrial (<1900 c.e. (Common Era)) activities such as the extensive Au and Ag mining in the Americas. (3) A factor of 3 and 5x increase in the deposition of Hg to the lake sediment archives was observed since the advent of the industrial revolution in New Zealand and Nova Scotia respectively, suggesting a worldwide increase in the atmospheric deposition of Hg. Furthermore, this increase is synchronous with increases in the release of CO2 from combustion of fossil fuels on a global scale. The magnitude of increase since industrialization appears larger in Nova Scotia than in New Zealand. This may be due to enhanced deposition of Hg as a result of either regional emission of Hg or enhanced regional oxidation of Hg°.
257 citations
TL;DR: In this paper, it was shown that the winner from Dodgson's method can occur at any position in the ranking obtained from the Borda Count, the plurality method, or any other positional voting procedure.
Abstract: In an election without a Condorcet winner, Dodgson's Method is designed to find the candidate that is “closest” to being a Condorcet winner. In this paper, we show that the winner from Dodgson's Method can occur at any position in the ranking obtained from the Borda Count, the plurality method, or any other positional voting procedure. In addition, we demonstrate that Dodgson's Method does not satisfy the Independence of Irrelevant Alternatives axiom.
49 citations
TL;DR: Very high-resolution imaging and stereo topographic data obtained during the Galileo G28 encounter with Ganymede show evidence for Europa-like, crustal spreading and resurfacing to form portions of the bright terrain, and bright terrain that appears smooth at Voyager resolution but instead is tectonically deformed and lacks embayment relationships when viewed at high resolution as discussed by the authors.
Abstract: [1] Very high-resolution imaging and stereo topographic data obtained during the Galileo G28 encounter with Ganymede show 1) evidence for Europa-like, crustal spreading and resurfacing to form portions of the bright terrain, and 2) bright terrain that appears smooth at Voyager resolution (and thus a strong candidate for cryovolcanism) but instead is tectonically deformed and lacks embayment relationships when viewed at high resolution. In contrast to previous views, these new data show that tectonism has been the dominant process in shaping some very smooth areas and that Ganymede appears to have experienced Europa-like crustal spreading during its previous history.
43 citations
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37 citations
18 citations
TL;DR: The distribution and properties of enzymes of the catabolic pathway of pyrimidine nucleotides in Riftia pachyptila, a tubeworm living around deep-sea hydrothermal vents and known to be involved in a highly specialized symbiotic association with a bacterium, suggest that the production of nucleosides in the trophosome may represent an alternative source of carbon and nitrogen for R. pachyPTila.
TL;DR: This initial workshop began a dialogue between colleagues and uncovered issues and questions that the authors must address together so that they can design labs, collaborations, and programs to meet the needs of the next generation of students.
Abstract: In short, participants ranked the workshop a huge success toward helping them develop ideas for incorporating genomics into undergraduate curricula. Bioinformatics and genomics are new fields of research, and teaching in these areas is newer still. In many ways, this initial workshop began a dialogue between colleagues and uncovered issues and questions that we must address together so that we can design labs, collaborations, and programs to meet the needs of the next generation of students. These open questions include the following five:
What are the right courses or tracks for students in bioinformatics/genomics?
What concepts in computing and in particular what types of algorithms do biologists really need to know?
What are the biological concepts that computer science students need to learn for them to be effective players?
What are the differences in language between biology and computer science and what can we do pedagogically to educate our students to work with these differences?
What are the different ways biologists and computer scientists solve problems (e.g., the scientific method vs. decomposition/encapsulation)?
The pursuit of answers to these and other emerging questions is part of our relentless effort to bring genomics to undergraduate biology and computer science students.
TL;DR: In this paper, the hyperbolic Coxeter n-simplex reflection groups up to widecommensurability for all n 3 were classified up to a wide range of subgroups.