1,408 research outputs found

    GPS based tectonic analysis of the Aleutian arc and Bering plate

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    Thesis (M.S.) University of Alaska Fairbanks, 2007Global Positioning System (GPS) measurements enable a quantitative analysis of tectonic deformation in the Aleutian Islands, Alaska. We construct elastic deformation models to calculate coupling on the subduction interface and the interseismic strain recorded at stations throughout the Aleutian arc. Using a grid-search inversion procedure, we determine an arc translation velocity for each region of the arc, revealing south to southwest motions of 4 to 14 mm/yr. In the central Aleutians, there is good agreement between areas of high coupling and areas of large moment release in major seismogenic events. We have combined modeling results from the Aleutians with direct measurements of station velocities of sites in western Alaska and the Bering Sea islands to test the hypothesis of a clockwise rotating Bering plate. The Bering Sea area including the Aleutian arc and western Alaska is fit by an Euler pole located at 42.5°N, 121.3°E with an angular velocity of 6.0°/my, relative to stable North America. The Bering plate's eastern boundary appears to be related to left lateral faulting in interior Alaska as clockwise rotation of the plate results in south-southwest motion relative to the North American plate. The Bering plate's interaction with a counter-clockwise rotating southcentral Alaska block may be responsible for the decreased slip-rate on the western Denali fault. Thrust earthquake slip azimuths expose a systematic discrepancy with Pacific-Bering plate convergence direction. A simple model of slip partitioning and GPS measurements reveal that slip partitioning is present in the forearc throughout the arc but only develops in the back arc west of Amchitka Pass.1. Introduction -- 2. Plate coupling variation and block translation in the Andreanof segment of the Aleutian arc determined by subduction zone modeling using GPS data -- 3. Evidence for and implications of a Bering plate based on geodetic measurements from the Aleutians and Western Alaska -- 4. Conclusions

    LoCoH: nonparameteric kernel methods for constructing home ranges and utilization distributions.

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    Parametric kernel methods currently dominate the literature regarding the construction of animal home ranges (HRs) and utilization distributions (UDs). These methods frequently fail to capture the kinds of hard boundaries common to many natural systems. Recently a local convex hull (LoCoH) nonparametric kernel method, which generalizes the minimum convex polygon (MCP) method, was shown to be more appropriate than parametric kernel methods for constructing HRs and UDs, because of its ability to identify hard boundaries (e.g., rivers, cliff edges) and convergence to the true distribution as sample size increases. Here we extend the LoCoH in two ways: "fixed sphere-of-influence," or r-LoCoH (kernels constructed from all points within a fixed radius r of each reference point), and an "adaptive sphere-of-influence," or a-LoCoH (kernels constructed from all points within a radius a such that the distances of all points within the radius to the reference point sum to a value less than or equal to a), and compare them to the original "fixed-number-of-points," or k-LoCoH (all kernels constructed from k-1 nearest neighbors of root points). We also compare these nonparametric LoCoH to parametric kernel methods using manufactured data and data collected from GPS collars on African buffalo in the Kruger National Park, South Africa. Our results demonstrate that LoCoH methods are superior to parametric kernel methods in estimating areas used by animals, excluding unused areas (holes) and, generally, in constructing UDs and HRs arising from the movement of animals influenced by hard boundaries and irregular structures (e.g., rocky outcrops). We also demonstrate that a-LoCoH is generally superior to k- and r-LoCoH (with software for all three methods available at http://locoh.cnr.berkeley.edu)

    Poly-arginine peptide R18D reduces neuroinflammation and functional deficits following traumatic brain injury in the Long-Evans rat

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    We have previously demonstrated that the poly-arginine peptide R18 can improve histological and functional outcomes following traumatic brain injury (TBI) in the Sprague–Dawley rat. Since D-enantiomer peptides are often exploited in pharmacology for their increased stability and potency, the present study compared the effects of R18 and its D-enantiomer, R18D, following TBI in the Long-Evans rat. Following a closed-head impact delivered via a weight-drop apparatus, peptide was administered at a dose of 1000 nmol/kg at 30 min after TBI. Treatment with R18D, but not R18 resulted in significant reductions in sensorimotor (p = 0.026) and vestibulomotor (p = 0.049) deficits as measured by the adhesive tape removal and rotarod tests. Furthermore, treatment with R18 and R18D resulted in a significant reduction in brain protein levels of the astrocytic marker, glial fibrillary acidic protein (p = 0.019 and 0.048, respectively). These results further highlight the beneficial effects of poly-arginine peptides in TBI, however additional studies are required to confirm these positive effects

    En busca del aguacate perfecto : La ciudad como poema sonoro

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    El pregonero, vendedor ambulante quien utiliza la proyección de su voz, es un fenómeno común en el mundo en desarrollo latinoamericano, caso particular de Colombia y en este caso Pereira, lugar de la investigación. Esta investigación pretende sintetizar el proyecto de investigación-creación en busca del aguacate perfecto: La ciudad como poema sonoro, llevado a cabo dentro de la maestría en Estética y Creación en la Universidad Tecnológica de Pereira, Colombia. A través de la categoría estética prosaica desarrollada por Kayta Mandoki, y la estética cotidiana, se muestra cómo las experiencias cotidianas generan estesis, y funcionan para expandir el análisis estético hacia todos los rincones del mundo

    How Student Written Communication Skills Benefit During Participation in an Industry-Sponsored Civil Engineering Capstone Course

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    Because many engineering programs use capstone design courses and value strong communication abilities, authors sought to identify how student written communication skills changed because of industry-sponsored capstone design projects. A student exit survey was collected at the end of the capstone design course during faculty-led projects and projects led by practicing engineers in industry. These results led the researchers to subsequently evaluate two semesters of before-andafter writing samples using a rubric. Student surveys suggested a statistically significant increase in learning about professional issues, problem solving, and written/oral communication. Evaluation of student writing samples suggests that the students significantly improved their grammar/spelling and their organization of content during the course. These findings suggest that industry-sponsored projects help students recognize the relation between professionalism and correspondence that is organized and void of grammar and spelling errors

    In Vitro Reconstituted Biotransformation of 4-Fluorothreonine from Fluoride Ion: Application of the Fluorinase

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    SummaryIn this paper, we report that fluoride ion is converted to the amino acid/antibiotic 4-fluorothreonine 2 in a biotransformation involving five (steps a–e) overexpressed enzymes. The biotransformation validates the biosynthetic pathway to 4-fluorothreonine in the bacterium Streptomyces cattleya (Schaffrath et al., 2002). To achieve an in vitro biotransformation, the fluorinase and the purine nucleoside phosphorylase (PNP) enzymes (steps a and b), which are coded for by the flA and flB genes of the fluorometabolite gene cluster in S. cattleya, were overexpressed. Also, an isomerase gene product that can convert 5-FDRP 6 to 5-FDRibulP 7 (step c) was identified in S. cattleya, and the enzyme was overexpressed for the biotransformation. A fuculose aldolase gene from S. coelicolor was overexpressed in E. coli and was used as a surrogate aldolase (step d) in these experiments. To complete the complement of enzymes, an ORF coding the PLP-dependent transaldolase, the final enzyme of the fluorometabolite pathway, was identified in genomic DNA by a reverse genetics approach, and the S. cattleya gene/enzyme was then overexpressed in S. lividans. This latter enzyme is an unusual PLP-dependent catalyst with some homology to both bacterial serine hydroxymethyl transferases (SHMT) and C5 sugar isomerases/epimerases. The biotransformation demonstrates the power of the fluorinase to initiate C-F bond formation for organo-fluorine synthesis

    Histopathological Analysis of Quails in the Trans-Pecos Ecoregion of Texas

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    Quail populations in Texas, USA, have declined over the past few decades due primarily to habitat loss. The role that parasites may play in such declines has been a recent topic of concern. To help address this question, we collected 12 scaled quail (Callipepla squamata), 8 Gambel’s quail (Callipepla gambelii), and 3 Montezuma quail (Cyrtonyx montezumae) from across the Trans-Pecos ecoregion of Texas via hunter harvest, funnel traps, and night netting. Quail samples were necropsied to determine the abundance of eyeworms (Oxyspirura petrowi). Histopathological analyses were conducted on quail eyeballs and periocular tissues to gain information on parasite-related tissue damage and document other pathogenic factors. We calculated mean abundances of Oxyspirura petrowi for sampled scaled (x̄ = 5.5, standard deviation [SD] = 2.5, x̃ = 3, n = 12), Gambel’s (x̄ = 6.4, SD = 4.2, x̃ = 1.5, n = 8), and Montezuma quail (x̄ = 13, SD = 1.5, x̃ = 13, n = 3). Host tissues exhibited immune responses (i.e., lymphocytic conjunctivitis and plasmacytic adenitis) to O. petrowi. The observed immune responses indicated relatively mild irritation within the ocular tissues. It has been speculated that such irritation to ocular tissues could negatively impact quail vision. This potential impact is worth noting because quails rely on keen vision to detect predators. Future research should focus on measuring the effects of O. petrowi infections on quail survival
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