9,172 research outputs found

    Water-Column Variability Assessment for Underway Profilers to Improve Efficiency and Accuracy of Multibeam Surveys

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    With the advent of underway profilers, sampling the water-column to obtain sound speed corrections is no longer a detriment to hydrographic survey efficiency. Instead, the challenge has become deciding how many casts are necessary to maintain a desired level of multibeam sounding accuracy, while not needlessly overworking the profiler. Ray tracing uncertainty analysis can determine in hindsight whether a particular sampling interval is adequate or not. Based on this methodology, an algorithm was developed to generate recommended sampling intervals based on successively acquired sound speed profiles, allowing the MVP to run in a ā€œcruise-controlā€ mode where the sampling interval is altered in response to changing oceanographic conditions. In collaboration with Rolls Royce, the algorithm was implemented in Python and loosely couples with the MVP controller software such that the recommended sampling interval can be adjusted without operator intervention. Integration of the software with the MVP controller was successfully tested aboard the NOAA Ship Ferdinand R. Hassler in September of 2012. Initial results from field trials and from analysis of existing data sets are presented

    Geochemical support for a climbing habit within the Paleozoic seed fern genus Medullosa

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    A long-standing problem in paleobotany is the accurate identification of the growth habits and statures of fossil plants. Tissue-specific analysis of stable carbon isotope ratios in plant fossils can provide an independent perspective on this issue. Lignin, a fundamental biopolymer providing structural support in plant tissues and the second most abundant organic material in plants, is ^(13)C depleted by several parts per thousand, averaging 4.1ā€°, relative to other plant constructional materials (e.g. cellulose). With this isotopic difference, the biochemical structural composition of ancient plants (and inferred stature) can be interrogated using microscale in situ isotope analysis between different tissues in fossils. We applied this technique to a well-preserved specimen of the Late Paleozoic seed plant Medullosa, an extinct genus with a variety of growth habits that includes several enigmatic yet abundant small-stemmed species widely found in calcium carbonate concretions (ā€œcoal ballsā€) in the Pennsylvanian coal beds of Iowa, USA. It remains unclear which of the medullosans were freestanding, and recent analysis of the medullosan vascular system has shown that this system provided little structural support to the whole plant. The leading hypothesis for small-stemmed medullosan specimens predicts that cortical tissues could have provided additional structural support, but only if they were lignified. The expected isotopic difference between lignified tissue and unlignified tissue is smaller than that expected from pure extracts, for the simple reason that even woody tissues maximally contain 40% lignin (by mass). This reduces the expected maximum difference between weakly and heavily lignified tissues by 60%, down to ~0.5ā€°ā€“2ā€°. Analysis of the medullosan stem reveals a consistent difference in isotope ratios of 0.7ā€°ā€“1.0ā€° between lignified xylem and cortical tissues. This implies low abundances of lignin (between 0% and 11%) within the cortex. This inferred structural biochemistry supports hypotheses that the peripheral portions of these medullosan stems were not biomechanically reinforced to permit the plants to grow as freestanding, arborescent trees. A number of climbing or scandent medullosans have been identified in the fossil record, and this mode of growth has been suggested to be common within the group on the basis of observations from comparative biomechanics, hydraulics, and development. Finally, this mode of growth is common in several clades of stem group seed plants, including Lyginopteris and Callistophyton, along with Medullosa. This study provides further support for ideas that place a great portion of early seed plant diversity under the canopy, rather than forming it

    A Case Report of Case Report Pursuit by Medical Student

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    Medical students often seek case reports as vehicles for academic writing opportunities, conference presentation avenues, and residency/fellowship application highlights. Here we review a case where, due to unfortunate circumstances, a student made a unique diagnosis central to proper patient clinical care, wished to write up the case subsequently, but was ultimately excluded from the final work stemming from the patient case. We review the pitfalls that occurred in the process of pursuing publication of an interesting case, the educational value of pursuing case reports for students, the necessity for strong mentorship in this process, and general principles that medical students can follow regarding case report creation to avoid being burned

    Protein crystallization in vivo

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    Protein crystallization in vivo provides some fascinating examples of biological self-assembly. Here, we provide a selective survey to show the diversity of functions for which protein crystals are used, and the physical properties of the crystals thatare exploited. Where known, we emphasize how the nature of the protein-protein interactions leads to control of the crystallization behaviour.Comment: 17 pages, 1 figur

    Making Voting Easier: Election Day Registration in New York

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    As policymakers, election officials, and the public consider whether New York should change the way in which voters are allowed to register to participate in elections, and bring New York State election law into compliance with the Help America Vote Act, the following report provides an analysis of the potential impact of election day registration (EDR) in New York. EDR in New York has the potential to increase voter participation for New Yorkers by as much as: Over 12 percentage point increase in turnout by 18-to-25-year-olds. Nearly 10 percentage point increase in turnout by thosewith a grade school education or less.An 11 point increase in turnout by Latinos and nearly 9 percentage point increase in turnout by African Americans.Over 10 percentage point increase in turnout by those who have lived at their current address for less than six months.Over 12 percentage point increase in turnout by naturalized citizens
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