5,466 research outputs found

    Percutaneous Endovascular Aortic Aneurysm Repair (PEVAR): Results From the First Prospective, Multicenter Randomized Trial

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    Development and Monitoring of Revegetation Methods: Connecting Students with Restoration Activities at Awcomin Marsh

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    Five classes in a local elementary school participated in an effort to grow and plant high marsh and upper border vegetation at a salt marsh restoration site in spring 2005. Seeds of six marsh upper edge species were successfully germinated and grown into seedlings by third graders. The seedlings were planted by the students in late spring 2005, but only switchgrass and quackgrass plants appeared to have established and survived after one year. Mature shoots of three high marsh species planted by the third graders (salt hay, salt grass and black grass) established successfully and continue to proliferate. In addition, we assessed an experiment of cordgrass plantings performed by community volunteers in 2002. The experiment was designed to test the effectiveness of three planting techniques at a salt marsh restored by the excavation of old dredge spoil that had been colonized by common reed. After four growing seasons, Plug, Bare Root Shoot, and Seed Head planting techniques exhibited greater cover of cordgrass and total cover of vascular plants when compared with unplanted areas. Cover of perennial plants (e.g., cordgrass), which contributes directly to belowground soil development in salt marshes, dominated the planted plots. Cover of annual species dominated the unplanted plots. Planting cordgrass in areas where dredge spoils and common reed had been excavated from a historic marsh accelerated the development of native vegetation compared with unplanted areas. Performance and evaluation of the two sets of plantings has provided information about appropriate planting techniques for our region and has involved and educated the local community about the values of salt marsh to promote stewardship. Recommendations included the use of bare root shoot and seed head planting techniques where cordgrass is desired. Outside plots or a greenhouse may be needed for successful propagation of upper edge marsh species from seed, and a planting program that includes mature plants as well as seedlings is recommended to ensure success

    Migration and Trade

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    Theoretical and empirical research in economics suggests that bilateral migration triggers bilateral trade through a number of channels. This paper assesses the functional form of the impact of migration on trade flows in a quasi-experimental setting. We provide evidence that the relationship is not log-linear. In particular, at small levels of migration (stocks) the elasticity of trade to migration is quite high, and it declines to zero at about 4,000 immigrants. If migration stocks exceed such a level, the evidence suggests that trade will not increase anymore. This suggests that cross-country network and other effects flowing from migration materialize at relatively low levels of migration, but there appears to be satiation as immigrant numbers increase by much.migration, bilateral trade, quasi-randomized experiment, generalized propensity score estimation

    The Vision Research Center of Kansas City

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    Neuroscience - Vision and Functional Brain Imaging Poster SessionThe Vision Research Center was founded as and is a well established collaboration of several of UMKC schools and Kansas City Medical Centers and thus offers an unprecedented interdisciplinary synergy with a unified goal: to better diagnose, prevent, and treat eye disease and vision disorders through translational research in order to make a difference in the lives of tens of millions of people. To this end, the center conducts federally and industry funded basic, translational and clinical research to develop new medical therapies and offers patient care in all subspecialties of ophthalmology. The center's nationally recognized excellence in research, patient care and medical education contribute to UMKC's strengths in the life sciences. Past, present and future objectives of the Vision Research Center: Provide a direct avenue for basic and translational research in eye and related diseases; Transfer basic science findings seamlessly into practical use with patients trough translational research; Develop new therapy approaches urgently needed by physicians in the US and worldwide; Provide educational excellence; Ensure patients receive the most advanced medical treatments available; Become national center of excellence for eye researc

    Note on paramoudra-like carbonate concretions in the Urenui Formation, North Taranaki: possible plumbing system for a Late Miocene methane seep field

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    A reconnaissance study of calcitic and dolomitic tubular concretions in upper slope mudstone of the Late Miocene Urenui Formation exposed along the north Taranaki coastline indicates that they have a complex diagenetic history involving different phases of carbonate cementation and likely hydrofracturing associated with build up of fluid/gas pressures. The concretions resemble classical paramoudra in the European chalk, but are not siliceous and do not have a trace fossil origin. Stable oxygen and carbon isotope data suggest that the micritic carbonate cements in the Urenui paramoudra were probably sourced primarily from ascending methane fluid/gases, and that they precipitated entirely within the host mudstone below the seafloor. We suggest the paramoudra may mark the subsurface plumbing networks of a Late Miocene cold seep system, in which case they have relevance to the evolution and migration of hydrocarbons in Taranaki Basin, at this site perhaps focussed along the Taranaki Fault. The presence of dislodged and mass-emplaced paramoudra in the axial conglomerate of channels within the Urenui mudstone suggests there could be a connection between the loci of seep field development and slope failure and canyon cutting on the Late Miocene Taranaki margin

    Undulation instability in a bilayer lipid membrane due to electric field interaction with lipid dipoles

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    Bilayer lipid membranes [BLMs] are an essential component of all biological systems, forming a functional barrier for cells and organelles from the surrounding environment. The lipid molecules that form membranes contain both permanent and induced dipoles, and an electric field can induce the formation of pores when the transverse field is sufficiently strong (electroporation). Here, a phenomenological free energy is constructed to model the response of a BLM to a transverse static electric field. The model contains a continuum description of the membrane dipoles and a coupling between the headgroup dipoles and the membrane tilt. The membrane is found to become unstable through buckling modes, which are weakly coupled to thickness fluctuations in the membrane. The thickness fluctuations, along with the increase in interfacial area produced by membrane buckling, increase the probability of localized membrane breakdown, which may lead to pore formation. The instability is found to depend strongly on the strength of the coupling between the dipolar headgroups and the membrane tilt as well as the degree of dipolar ordering in the membrane.Comment: 29 pages 8 fig

    Extracellular matrix proteins are potent agonists of human smooth muscle cell migration

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    AbstractPurpose: Extracellular matrix proteins can stimulate smooth muscle cell (SMC) migration by three distinct mechanisms: chemokinesis (nondirected migration in the presence of soluble protein), chemotaxis (directed migration toward soluble protein), and haptotaxis (directed migration toward insoluble, substrate-bound protein). This study investigates the effects of four prevalent extracellular matrix proteins (collagen types I and IV, fibronectin, and laminin), and platelet-derived growth factor (PDGF) on haptotaxis, chemotaxis, and chemokinesis of human SMCs. The role of large guanosine triphosphate-binding proteins (G-proteins) in the signaling mediating these effects is also evaluated.Methods: Human saphenous vein SMCs were used in all migration studies. Chemokinesis, chemotaxis, and haptotaxis to each of the matrix proteins were measured and compared with PDGF through the use of a 48-well microchemotaxis chamber. The role of G-proteins in matrix-induced SMC migration was studied with the modulators of G-protein function, cholera and pertussis toxins.Results: For all matrix proteins the relative strength of the various stimuli for migration was haptotaxis > chemotaxis > chemokinesis (p < 0.05). For all three stimuli collagen I and IV produced the most significant migration followed by fibronectin > PDGF-AB > laminin (p < 0.05). Pertussis toxin completely inhibited chemotaxis and partially inhibited haptotaxis by laminin but did not affect migration by other matrix proteins, whereas cholera toxin abolished migration in response to all four matrix proteins.Conclusion: Matrix proteins, with the exception of laminin, provide a more significant stimulus for SMC locomotion than does the prototypical agonist, PDGF-AB. Of the three mechanisms by which migration can be stimulated, haptotaxis elicits the most pro-found effect. The importance of G-proteins as second messengers for migration varies with each matrix protein and with the mechanism of stimulation. (J Vasc Surg 1996;24:25-33.

    Tubular carbonate concretions as hydrocarbon migration pathways? Examples from North Island, New Zealand

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    Cold seep carbonate deposits are associated with the development on the sea floor of distinctive chemosyn¬thetic animal communities and carbonate minerali¬sation as a consequence of microbially mediated anaerobic oxidation of methane. Several possible sources of the methane exist, identifiable from the carbon isotope values of the carbonate precipitates. In the modern, seep carbonates can occur on the sea floor above petroleum reservoirs where an important origin can be from ascending thermogenic hydrocar¬bons. The character of geological structures marking the ascent pathways from deep in the subsurface to shallow subsurface levels are poorly understood, but one such structure resulting from focused fluid flow may be tubular carbonate concretions. Several mudrock-dominated Cenozoic (especially Miocene) sedimentary formations in the North Island of New Zealand include carbonate concretions having a wide range of tubular morphologies. The concretions are typically oriented at high angles to bedding, and often have a central conduit that is either empty or filled with late stage cements. Stable isotope analyses (δ13C, δ18O) suggest that the carbonate cements in the concretions precipitated mainly from ascending methane, likely sourced from a mixture of deep thermogenic and shallow biogenic sources. A clear link between the tubular concretions and overlying paleo-sea floor seep-carbonate deposits exists at some sites. We suggest that the tubular carbonate concretions mark the subsurface plumbing network of cold seep systems. When exposed and accessible in outcrop, they afford an opportunity to investigate the geochemical evolution of cold seeps, and possibly also the nature of linkages between subsurface and surface portions of such a system. Seep field development has implications for the characterisation of fluid flow in sedimentary basins, for the global carbon cycle, for exerting a biogeochemical influence on the development of marine communities, and for the evaluation of future hydrocarbon resources, recovery, and drilling and production hazards. These matters remain to be fully assessed within a petroleum systems framework for New Zealand’s Cenozoic sedimentary basins

    Cosmology without inflation

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    We propose a new cosmological paradigm in which our observed expanding phase is originated from an initially large contracting Universe that subsequently experienced a bounce. This category of models, being geodesically complete, is non-singular and horizon-free, and can be made to prevent any relevant scale to ever have been smaller than the Planck length. In this scenario, one can find new ways to solve the standard cosmological puzzles. One can also obtain scale invariant spectra for both scalar and tensor perturbations: this will be the case, for instance, if the contracting Universe is dust-dominated at the time at which large wavelength perturbations get larger than the curvature scale. We present a particular example based on a dust fluid classically contracting model, where a bounce occurs due to quantum effects, in which these features are explicit.Comment: 8 pages, no figur

    Predicting wave-induced ripple equilibrium geometry

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    Author Posting. © American Geophysical Union, 2013. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 118 (2013): 3202–3220, doi:10.1002/jgrc.20241.A comprehensive database of existing (since 1954) field and laboratory measurements of ripple geometry is compiled and combined with newly collected field data to examine the performance of ripple equilibrium predictors. Reanalysis of this enlarged ripple geometry data set reveals that ripples formed from monochromatic waves scale differently than ripples formed from random waves for many existing ripple predictors. Our analysis indicates that ripple wavelengths from the two data sets collapse into a single scaling when the semiorbital excursion and sediment grain diameter are used as normalizing factors. Ripple steepness remains relatively constant for both regular and irregular wave conditions, and it only slightly increases for shorter ripple wavelengths. These findings allowed for the development of a new equilibrium ripple predictor suitable for application in a wide range of wave and sediment conditions.Financial support for this work was provided by the National Science Foundation (NSF awards OCE-0451989 and OCE-0535893) and by the South Carolina Coastal Erosion Project, a cooperative study supported by the U.S. Geological Survey and the South Carolina Sea Grant Consortium (Sea Grant Project R/CP-11).2013-12-2
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