669 research outputs found

    Learning Theory and Differentiation in Flight Instruction: Perceptions from Certified Flight Instructors

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    The pilot shortage has reached critical levels. One strategy to minimize the loss of potentially skilled pilots is to focus attention on providing flight instructors with the background knowledge to understand student learning and support student pilots as they progress through flight training programs. Within flight instruction, little or no attention has been focused on the concept of Multiple Intelligences (MI) Theory and its impact on student learning and retention. Consequently, the purpose of this study was to determine if Certified Flight Instructors (CFI) who have been provided with information about MI Theory perceived a positive relationship between their new knowledge about multiple intelligences and their general instructional effectiveness. The study used CFI journals, observations, and individual interviews to determine if instructors perceived MI Theory to be valuable when applied to flight instruction. The results indicated that the participants believed knowledge regarding MI Theory added value to their flight instruction. Implications for practice and directions for future research are provided

    Sovereign debt restructuring : the judge, the vultures and creditor rights

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    What role did the US courts play in the Argentine debt swap of 2005? What implications does this have for the future of creditor rights in sovereign bond markets? The judge in the Argentine case has, it appears, deftly exploited creditor heterogeneity – between holdouts seeking capital gains and institutional investors wanting a settlement – to promote a swap with a supermajority of creditors. Our analysis of Argentine debt litigation reveals a ‘judge-mediated’ sovereign debt restructuring, which resolves the key issues of Transition and Aggregation - two of the tasks envisaged for the IMF’s still-born Sovereign Debt Restructuring Mechanism. For the future, we discuss how judge-mediated sovereign debt restructuring (together with creditor committees) could complement the alternative promoted by the US Treasury, namely collective action clauses in sovereign bond contracts

    The Acid Test of Fluoride: How pH Modulates Toxicity

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    Background: It is not known why the ameloblasts responsible for dental enamel formation are uniquely sensitive to fluoride (FF^−). Herein, we present a novel theory with supporting data to show that the low pH environment of maturating stage ameloblasts enhances their sensitivity to a given dose of FF^−. Enamel formation is initiated in a neutral pH environment (secretory stage); however, the pH can fall to below 6.0 as most of the mineral precipitates (maturation stage). Low pH can facilitate entry of FF^− into cells. Here, we asked if FF^− was more toxic at low pH, as measured by increased cell stress and decreased cell function. Methodology/Principal Findings: Treatment of ameloblast-derived LS8 cells with FF^− at low pH reduced the threshold dose of FF^− required to phosphorylate stress-related proteins, PERK, eIF2α, JNK and c-jun. To assess protein secretion, LS8 cells were stably transduced with a secreted reporter, Gaussia luciferase, and secretion was quantified as a function of FF^− dose and pH. Luciferase secretion significantly decreased within 2 hr of FF^− treatment at low pH versus neutral pH, indicating increased functional toxicity. Rats given 100 ppm FF^− in their drinking water exhibited increased stress-mediated phosphorylation of eIF2α in maturation stage ameloblasts (pH<6.0) as compared to secretory stage ameloblasts (pH∼7.2). Intriguingly, FF^−-treated rats demonstrated a striking decrease in transcripts expressed during the maturation stage of enamel development (Klk4 and Amtn). In contrast, the expression of secretory stage genes, AmelX, Ambn, Enam and Mmp20, was unaffected. Conclusions: The low pH environment of maturation stage ameloblasts facilitates the uptake of FF^−, causing increased cell stress that compromises ameloblast function, resulting in dental fluorosis

    Lunar Outgassing, Transient Phenomena and The Return to The Moon, I: Existing Data

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    Herein the transient lunar phenomena (TLP) report database is subjected to a discriminating statistical filter robust against sites of spurious reports, and produces a restricted sample that may be largely reliable. This subset is highly correlated geographically with the catalog of outgassing events seen by the Apollo 15, 16 and Lunar Prospector alpha-particle spectrometers for episodic Rn-222 gas release. Both this robust TLP sample and even the larger, unfiltered sample are highly correlated with the boundary between mare and highlands, as are both deep and shallow moonquakes, as well as Po-210, a long-lived product of Rn-222 decay and a further tracer of outgassing. This offers another significant correlation relating TLPs and outgassing, and may tie some of this activity to sagging mare basalt plains (perhaps mascons). Additionally, low-level but likely significant TLP activity is connected to recent, major impact craters (while moonquakes are not), which may indicate the effects of cracks caused by the impacts, or perhaps avalanches, allowing release of gas. The majority of TLP (and Rn-222) activity, however, is confined to one site that produced much of the basalt in the Procellarum Terrane, and it seems plausible that this TLP activity may be tied to residual outgassing from the formerly largest volcanic ffusion sites from the deep lunar interior. With the coming in the next few years of robotic spacecraft followed by human exploration, the study of TLPs and outgassing is both promising and imperiled. We will have an unprecedented pportunity to study lunar outgassing, but will also deal with a greater burden of anthropogenic lunar gas than ever produced. There is a pressing need to study lunar atmosphere and its sources while still pristine. [Abstract abridged.]Comment: 35 pages, 3 figures, submitted to Icarus. Other papers in series found at http://www.astro.columbia.edu/~arlin/TLP

    Tradeoffs in jet inlet design: a historical perspective

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    The design of the inlet(s) is one of the most demanding tasks of the development process of any gas turbine-powered aircraft. This is mainly due to the multi-objective and multidisciplinary nature of the exercise. The solution is generally a compromise between a number of conflicting goals and these conflicts are the subject of the present paper. We look into how these design tradeoffs have been reflected in the actual inlet designs over the years and how the emphasis has shifted from one driver to another. We also review some of the relevant developments of the jet age in aerodynamics and design and manufacturing technology and we examine how they have influenced and informed inlet design decision

    IRAS F02044+0957: radio source in interacting system of galaxies

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    The steep spectrum of IRAS F02044+0957 was obtained with the RATAN-600 radio telescope at four frequencies. Optical spectroscopy of the system components, was carried out with the 2.1m telescope of the Guillermo Haro Observatory. Observational data allow us to conclude that this object is a pair of interacting galaxies, a LINER and a HII galaxy, at z=0.093z=0.093.Comment: 2 pages, 2 EPS-figures, uses newpasp.sty. To appear in Proc. IAU Colloq. 184, AGN Surveys, ed. R. F. Green, E. Ye. Khachikian, & D. B. Sanders (San Francisco: ASP

    Soil surface temperatures reveal moderation of the urban heat island effect by trees and shrubs

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    Urban areas are major contributors to air pollution and climate change, causing impacts on human health that are amplified by the microclimatological effects of buildings and grey infrastructure through the urban heat island (UHI) effect. Urban greenspaces may be important in reducing surface temperature extremes, but their effects have not been investigated at a city-wide scale. Across a midsized UK city we buried temperature loggers at the surface of greenspace soils at 100 sites, stratified by proximity to city centre, vegetation cover and land-use. Mean daily soil surface temperature over 11 months increased by 0.6 °C over the 5 km from the city outskirts to the centre. Trees and shrubs in non-domestic greenspace reduced mean maximum daily soil surface temperatures in the summer by 5.7 °C compared to herbaceous vegetation, but tended to maintain slightly higher temperatures in winter. Trees in domestic gardens, which tend to be smaller, were less effective at reducing summer soil surface temperatures. Our findings reveal that the UHI effects soil temperatures at a city-wide scale, and that in their moderating urban soil surface temperature extremes, trees and shrubs may help to reduce the adverse impacts of urbanization on microclimate, soil processes and human health

    Influence of Olfactory Epithelium on Mitral/Tufted Cell Dendritic Outgrowth

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    Stereotypical connections between olfactory sensory neuron axons and mitral cell dendrites in the olfactory bulb establish the first synaptic relay for olfactory perception. While mechanisms of olfactory sensory axon targeting are reported, molecular regulation of mitral cell dendritic growth and refinement are unclear. During embryonic development, mitral cell dendritic distribution overlaps with olfactory sensory axon terminals in the olfactory bulb. In this study, we investigate whether olfactory sensory neurons in the olfactory epithelium influence mitral cell dendritic outgrowth in vitro. We report a soluble trophic activity in the olfactory epithelium conditioned medium which promotes mitral/tufted cell neurite outgrowth. While the trophic activity is present in both embryonic and postnatal olfactory epithelia, only embryonic but not postnatal mitral/tufted cells respond to this activity. We show that BMP2, 5 and 7 promote mitral/tufted cells neurite outgrowth. However, the BMP antagonist, Noggin, fails to neutralize the olfactory epithelium derived neurite growth promoting activity. We provide evidence that olfactory epithelium derived activity is a protein factor with molecular weight between 50–100 kD. We also observed that Follistatin can effectively neutralize the olfactory epithelium derived activity, suggesting that TGF-beta family proteins are involved to promote mitral/tufted dendritic elaboration
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