7,503 research outputs found

    The Deforest Creek Landslide and Sediment Transport in Deer Creek, Skagit County, Washington

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    Unit stream power, stream power per unit channel length, and total boundary shear stress were used to assess probable zones of river-sediment transport and storage following a large landslide into the Deer Creek basin, Skagit County, Washington. Since an initial deep-seated failure in glacial deposits in 1983 and a larger failure in 1984, the DeForest Creek landslide has introduced fine (±75% finer than coarse sand) sediment into the main channel of Deer Creek. The influx of sediment has caused infilling of void space in channel gravel by sand and silt, increased bank erosion, and increased slump activity adjacent to the stream. Bankfull discharge (considered to be a channel-forming discharge) was calculated for each of 114 reaches in the 13.4 km study reach. The discharges were used in conjunction with thalweg slopes, bankfull widths, and active-channel depths to calculate unit stream power, stream power per unit channel length, and total boundary shear stress. Analysis of unit stream power for successive reaches of Deer Creek indicates that this variable is sensitive to the degree of bedrock control on channel morphology. In turn, unit stream power exerts a significant control on sites of bank erosion, channel aggradation, and degradation; and it appears to control, at least in part, sites of sediment storage. Thus, unit stream power can help locate reaches most likely to change as Deer Creek adjusts to the increased sediment load from the DeForest Creek landslide

    Neuroimaging Measures as Endophenotypes in Alzheimer's Disease

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    Late onset Alzheimer's disease (AD) is moderately to highly heritable. Apolipoprotein E allele ε4 (APOE4) has been replicated consistently as an AD risk factor over many studies, and recently confirmed variants in other genes such as CLU, CR1, and PICALM each increase the lifetime risk of AD. However, much of the heritability of AD remains unexplained. AD is a complex disease that is diagnosed largely through neuropsychological testing, though neuroimaging measures may be more sensitive for detecting the incipient disease stages. Difficulties in early diagnosis and variable environmental contributions to the disease can obscure genetic relationships in traditional case-control genetic studies. Neuroimaging measures may be used as endophenotypes for AD, offering a reliable, objective tool to search for possible genetic risk factors. Imaging measures might also clarify the specific mechanisms by which proposed risk factors influence the brain

    Spatial Morphometric Analysis Using Shape-Changing Rigid-Body Chains

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    Morphometry is the quantitative comparison of shapes, primarily curves. As an alternate to classical methods of spatial morphometry, this work investigates a kinematic synthesis methodology for designing a spatial chain of rigid-bodies to match arbitrary spatial curves. The goal is to find a single set of spatial bodies that can be moved to approximately align with any given set of spatial curves. Previous rigid-body shape-change morphometry work focused on mechanisms composed of rigid planar links connected by prismatic and revolute joints to approximate planar curves. Open space curves are the current focus of the research. The primary advantage of this method is its capacity to describe the difference in space curves with a limited number of parameters.https://ecommons.udayton.edu/stander_posters/2395/thumbnail.jp

    Natural Selection, Coevolution, and the Web of Life

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    Interactions of biotic and abiotic environmental factors in an ectomycorrhizal symbiosis, and the potential for selection mosaics

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    <p>Abstract</p> <p>Background</p> <p>Geographic selection mosaics, in which species exert different evolutionary impacts on each other in different environments, may drive diversification in coevolving species. We studied the potential for geographic selection mosaics in plant-mycorrhizal interactions by testing whether the interaction between bishop pine (<it>Pinus muricata </it>D. Don) and one of its common ectomycorrhizal fungi (<it>Rhizopogon occidentalis </it>Zeller and Dodge) varies in outcome, when different combinations of plant and fungal genotypes are tested under a range of different abiotic and biotic conditions.</p> <p>Results</p> <p>We used a 2 × 2 × 2 × 2 factorial experiment to test the main and interactive effects of plant lineage (two maternal seed families), fungal lineage (two spore collections), soil type (lab mix or field soil), and non-mycorrhizal microbes (with or without) on the performance of plants and fungi. Ecological outcomes, as assessed by plant and fungal performance, varied widely across experimental environments, including interactions between plant or fungal lineages and soil environmental factors.</p> <p>Conclusion</p> <p>These results show the potential for selection mosaics in plant-mycorrhizal interactions, and indicate that these interactions are likely to coevolve in different ways in different environments, even when initially the genotypes of the interacting species are the same across all environments. Hence, selection mosaics may be equally as effective as genetic differences among populations in driving divergent coevolution among populations of interacting species.</p

    Book Reviews

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    Below-ground plant-fungus network topology is not congruent with above-ground plant-animal network topology

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    植物を支える「共生ネットワーク」は地上と地下で構造が違う --見えてきた地下生物圏の構造--. 京都大学プレスリリース. 2015-10-26.In nature, plants and their pollinating and/or seed-dispersing animals form complex interaction networks. The commonly observed pattern of links between specialists and generalists in these networks has been predicted to promote species coexistence. Plants also build highly species-rich mutualistic networks below ground with root-associated fungi, and the structure of these plant–fungus networks may also affect terrestrial community processes. By compiling high-throughput DNA sequencing data sets of the symbiosis of plants and their root-associated fungi from three localities along a latitudinal gradient, we uncovered the entire network architecture of these interactions under contrasting environmental conditions. Each network included more than 30 plant species and hundreds of mycorrhizal and endophytic fungi belonging to diverse phylogenetic groups. The results were consistent with the notion that processes shaping host-plant specialization of fungal species generate a unique linkage pattern that strongly contrasts with the pattern of above-ground plant–partner networks. Specifically, plant–fungus networks lacked a “nested” architecture, which has been considered to promote species coexistence in plant–partner networks. Rather, the below-ground networks had a conspicuous “antinested” topology. Our findings lead to the working hypothesis that terrestrial plant community dynamics are likely determined by the balance between above-ground and below-ground webs of interspecific interactions

    The Next Step

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    In traditional radiology practice, reports are typically dictated and then transcribed.? While the free-text reports represent the semantic knowledge interpreted and conveyed by a physician, the information can be hard to access. The advantages of representing medical data in a structured format using standard terminology are clearly recognized. These include the ability to implement a standardized electronic medical record, automatically invoke medical guidelines when appropriate, and conduct outcomes research. Standard structured reports facilitate intelligent indexing, searching, and retrieval of documents from clinical databases. Recent attempts have been made in the industry to enable structured data entry using preformatted templates, but these have yet to gain widespread acceptance.1,2 These preformatted templates do not necessarily use standard nomenclature and tend to disturb a clinician’s normal workflow. This paper presents a prototype system that incorporates the benefits of both dictated free-text reports and standard, structured reports
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