1,339 research outputs found

    Who Manages The Money? How Foundations Should Help Democratize Capital

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    For the past twenty-five years or more there has been a groundswell of activity among investment managers institutional investors, consultants and diversity advocates to democratize capital -- that is, to create more opportunities for diverse investment professionals and the firms they lead, to manage institutional capital This effort, grounded in both fiduciary and equity principles, has led to the growth of many diverse investment management firms like Progress Investment Management Company LLC ("Progress") and others. A range of stakeholders now recognizes that democratization of capital brings a range of positive benefits to our industry and society at larg

    Application of high-precision two-way ranging to Galileo Earth-1 encounter navigation

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    The application of precision two-way ranging to orbit determination with relatively short data arcs is investigated for the Galileo spacecraft's approach to its first Earth encounter (December 8, 1990). Analysis of previous S-band (2.3-GHz) ranging data acquired from Galileo indicated that under good signal conditions submeter precision and 10-m ranging accuracy were achieved. It is shown that ranging data of sufficient accuracy, when acquired from multiple stations, can sense the geocentric angular position of a distant spacecraft. A range data filtering technique, in which explicit modeling of range measurement bias parameters for each station pass is utilized, is shown to largely remove the systematic ground system calibration errors and transmission media effects from the Galileo range measurements, which would otherwise corrupt the angle-finding capabilities of the data. The accuracy of the Galileo orbit solutions obtained with S-band Doppler and precision ranging were found to be consistent with simple theoretical calculations, which predicted that angular accuracies of 0.26-0.34 microrad were achievable. In addition, the navigation accuracy achieved with precision ranging was marginally better than that obtained using delta-differenced one-way range (delta DOR), the principal data type that was previously used to obtain spacecraft angular position measurements operationally

    How Changes in Plant Community Structure Affect Terrestrial Invertebrate Food Webs

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    We investigated how change in plant community composition and vegetative structure brought about by annual grass-specific herbicide application affects terrestrial arthropod communities, with special emphasis on the potential mutualists and predators of the endangered Fender’s blue butterfly, Plebejus icarioides fenderi (Family: Lycaenidae). Larvae of this species form facultative protective mutualisms with ants, and they may be preyed upon by numerous invertebrate predators. We used pitfall trapping to compare terrestrial invertebrate community structure between control and herbicide-treated plots through time. The extent to which major changes in plant community composition affect the rest of the invertebrate community may have relevance for management decisions if the focus of the conservation effort has strong ecological interactions with greatly affected non-target species

    Observation of Coherently-Enhanced Tunable Narrow-Band Terahertz Transition Radiation from a Relativistic Sub-Picosecond Electron Bunch Train

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    We experimentally demonstrate the production of narrow-band (δf/f20\delta f/f \simeq20% at f0.5f\simeq 0.5 THz) THz transition radiation with tunable frequency over [0.37, 0.86] THz. The radiation is produced as a train of sub-picosecond relativistic electron bunches transits at the vacuum-aluminum interface of an aluminum converter screen. We also show a possible application of modulated beams to extend the dynamical range of a popular bunch length diagnostic technique based on the spectral analysis of coherent radiation.Comment: 3 pages, 6 figure

    Initial beam-profiling tests with the NML prototype station at the Fermilab A0 Photoinjector

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    The beam-profile diagnostics station prototype for the superconducting rf electron linac being constructed at Fermilab at the New Muon Lab has been tested. The station uses intercepting radiation converter screens for the low-power beam mode: either a 100-\mu m thick YAG:Ce single crystal scintillator or a 1-\mu m thin Al optical transition radiation (OTR) foil. The screens are oriented with the surface perpendicular to the beam direction. A downstream mirror with its surface at 45 degrees to the beam direction is used to direct the radiation into the optical transport. The optical system has better than 20 (10) \mu m rms spatial resolution when covering a vertical field of view of 18 (5) mm. The initial tests were performed at the A0 Photoinjector at a beam energy of ~15 MeV and with micropulse charges from 25 to 500 pC for beam sizes of 45 to 250 microns. Example results will be presented.Comment: 3 pp. Particle Accelerator, 24th Conference (PAC'11) 2011. 28 Mar - 1 Apr 2011. New York, US

    Acute tubular necrosis is characterized by activation of the alternative pathway of complement

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    Acute tubular necrosis is characterized by activation of the alternative pathway of complement.BackgroundStudies in animal models have shown that the alternative pathway of complement is activated in the kidney after ischemia/reperfusion. In addition, mice deficient in complement factor B, a necessary component of the alternative pathway, are protected from ischemic acute renal failure. The purpose of this study was to determine whether alternative pathway activation also occurs during the development of ischemic acute tubular necrosis in the human kidney.MethodsBiopsies were identified from nine patients with morphologically normal kidneys and seven patients with evidence of acute tubular necrosis by light microscopy. Immunofluorescence microscopy was used to quantify and localize the complement activation products C3d and C4d. The results were correlated with available clinical data.ResultsSimilar to mice, small amounts of activated C3d were present along the tubular basement membrane in normal kidneys. However, kidneys from patients with acute tubular necrosis had C3d complement deposition along a significantly greater number of tubules, and many of the tubules were completely circumscribed. In contrast, C4d was not detectable, indicating that complement activation occurred primarily via alternative pathway activation.ConclusionComplement activation occurs in human ischemic acute tubular necrosis. As in rodents, complement activation along the tubular basement membrane after ischemia appears to occur principally via the alternative complement pathway. Because of this, an inhibitor of the alternative pathway might limit complement activation and inflammation after ischemia/reperfusion, thereby protecting the kidney from ischemic acute renal failure

    The ocean's saltiness and its overturning

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    Here we explore the relationship between the mean salinity urn:x-wiley:grl:media:grl55555:grl55555-math-0001 of the ocean and the strength of its Atlantic and Pacific Meridional Overturning Circulations (AMOC and PMOC). We compare simulations performed with a realistically configured coarse‐grained ocean model, spanning a range of mean salinities. We find that the AMOC strength increases approximately linearly with urn:x-wiley:grl:media:grl55555:grl55555-math-0002. In contrast, the PMOC strength declines approximately linearly with urn:x-wiley:grl:media:grl55555:grl55555-math-0003 until it reaches a small background value similar to the present‐day ocean. Well‐established scaling laws for the overturning circulation explain both of these dependencies on urn:x-wiley:grl:media:grl55555:grl55555-math-0004

    Beam instrumentation for the Tevatron Collider

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    The Tevatron in Collider Run II (2001-present) is operating with six times more bunches and many times higher beam intensities and luminosities than in Run I (1992-1995). Beam diagnostics were crucial for the machine start-up and the never-ending luminosity upgrade campaign. We present the overall picture of the Tevatron diagnostics development for Run II, outline machine needs for new instrumentation, present several notable examples that led to Tevatron performance improvements, and discuss the lessons for future colliders

    Complement activation induces dysregulation of angiogenic factors and causes fetal rejection and growth restriction

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    Immune mechanisms have been implicated in placental dysfunction in patients with recurrent miscarriages and intrauterine growth restriction (IUGR), but the mediators are undefined. Here we show that complement activation, particularly C5a, is a required intermediary event in the pathogenesis of placental and fetal injury in an antibody-independent mouse model of spontaneous miscarriage and IUGR, and that complement activation causes dysregulation of the angiogenic factors required for normal placental development. Pregnancies complicated by miscarriage or growth restriction were characterized by inflammatory infiltrates in placentas, functional deficiency of free vascular endothelial growth factor (VEGF), elevated levels of soluble VEGF receptor 1 (sVEGFR-1, also known as sFlt-1; a potent anti-angiogenic molecule), and defective placental development. Inhibition of complement activation in vivo blocked the increase in sVEGFR-1 and rescued pregnancies. In vitro stimulation of monocytes with products of the complement cascade directly triggered release of sVEGFR-1, which sequesters VEGF. These studies provide the first evidence linking the complement system to angiogenic factor imbalance associated with placental dysfunction, and identify a new effector of immune-triggered pregnancy complications
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