1,149 research outputs found

    Technology transfer and other public policy implications of multi-national arrangements for the production of commercial airframes

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    A study to examine the question of technology transfer through international arrangements for production of commercial transport aircraft is presented. The likelihood of such transfer under various representative conditions was determined and an understanding of the economic motivations for, effects of, joint venture arrangements was developed. Relevant public policy implications were also assessed. Multinational consortia with U.S. participation were focused upon because they generate the full range of pertinent public issues (including especially technology transfer), and also because of recognized trends toward such arrangements. An extensive search and analysis of existing literature to identify the key issues, and in-person interviews with executives of U.S. and European commercial airframe producers was reviewed. Distinctions were drawn among product-embodied, process, and management technologies in terms of their relative possibilities of transfer and the significance of such transfer. Also included are observations on related issues such as the implications of U.S. antitrust policy with respect to the formation of consortia and the competitive viability of the U.S. aircraft manufacturing industry

    Economic analysis of aeronautical research and technology

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    The appropriateness of government intervention in the civilian market for aeronautics research and technology (R&T) is examined. The economic rationale for government intervention is examined. The conclusion is that the institutional role played by NASA in civilian aeronautics R&T markets is economically justified

    WTC2005-64353 ACTIVATION OF SIC SURFACES FOR VAPOR PHASE LUBRICATION BY CHEMICAL VAPOR DEPOSITION OF FE

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    ABSTRACT Vapor phase lubrication (VPL) has been proposed as a method for lubricating high temperature engines. During VPL, lubricants are delivered through the vapor phase to high temperature engine parts and react on their surfaces to deposit a thin, solid, lubricating film. Although ceramics such as SiC are desirable materials for high temperature applications, their surfaces are unreactive for the decomposition of TCP and thus not amenable to vapor phase lubrication. As a means of activating the SiC surface for TCP decomposition we have used chemical vapor deposition of Fe from Fe(CO) 5 . Modification of the SiC surface with adsorbed Fe accelerates subsequent decomposition of TCP and deposition of P and C onto the surface. In the temperature range 500 -800 K, m-TCP decomposes more readily on Fe-coated SiC surfaces than on SiC surfaces. The C and P deposition rates depend on the thickness of the Fe film and are further enhanced by oxidation of the Fe. This work provides a proof-of-concept demonstration of the feasibility of using vapor phase lubrication for ceramics

    Effective action and density functional theory

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    The effective action for the charge density and the photon field is proposed as a generalization of the density functional. A simple definition is given for the density functional, as the functional Legendre transform of the generator functional of connected Green functions for the density and the photon field, offering systematic approximation schemes. The leading order of the perturbation expansion reproduces the Hartree-Fock equation. A renormalization group motivated method is introduced to turn on the Coulomb interaction gradually and to find corrections to the Hartree-Fock and the Kohn-Sham schemes.Comment: New references and a numerical algorithm added, to appear in Phys. Rev. B. 30 pages, no figure

    Structural and functional diversity among agonist-bound states of the GLP-1 receptor

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    Recent advances in G-protein-coupled receptor (GPCR) structural elucidation have strengthened previous hypotheses that multidimensional signal propagation mediated by these receptors depends, in part, on their conformational mobility; however, the relationship between receptor function and static structures is inherently uncertain. Here, we examine the contribution of peptide agonist conformational plasticity to activation of the glucagon-like peptide 1 receptor (GLP-1R), an important clinical target. We use variants of the peptides GLP-1 and exendin-4 (Ex4) to explore the interplay between helical propensity near the agonist N terminus and the ability to bind to and activate the receptor. Cryo-EM analysis of a complex involving an Ex4 analog, the GLP-1R and Gs heterotrimer revealed two receptor conformers with distinct modes of peptide-receptor engagement. Our functional and structural data, along with molecular dynamics (MD) simulations, suggest that receptor conformational dynamics associated with flexibility of the peptide N-terminal activation domain may be a key determinant of agonist efficacy.</p

    Toward a soluble model system for the amyloid state

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    The formation and deposition of amyloids is associated with many diseases. β-Sheet secondary structure is a common feature of amyloids, but the packing of sheets against one another is distinctive relative to soluble proteins. Standard methods that rely on perturbing a polypeptide’s sequence and evaluating impact on folding can be problematic for amyloid aggregates because a single sequence can adopt multiple conformations and diverse packing arrangements. We describe initial steps toward a minimum-sized, soluble model system for the amyloid state that supports comparisons among sequence variants. Critical to this goal is development of a new linking strategy to enable intersheet association mediated by side chain interactions, which is characteristic of the amyloid state. The linker design we identified should ultimately support exploration of relationships between sequence and amyloid state stability for specific strand-association modes

    Association of self-reported physical activity with obstructive sleep apnea: Results from the Hispanic Community Health Study/Study of Latinos (HCHS/SOL)

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    We examined associations of mild and moderate to severe obstructive sleep apnea (OSA; apnea-hypopnea index ≥5 and ≥15, respectively) with recommended amounts of moderate-vigorous physical activity (MVPA) or vigorous physical activity (VPA) and by type of activity (i.e., recreational, transportation, and work activity). The Hispanic Community Health Study/Study of Latinos (HCHS/SOL), a multicenter population-based study, enrolled individuals from 2008 to 2011 from four U.S. metropolitan areas (Bronx, New York; Chicago, Illinois; Miami, Florida; San Diego, California). Participants in this study included 14,206 self-identified Hispanic/Latino ages 18 to 74 years from theHCHS/SOL. Survey logistic regression analysis was used to compute odds ratios [OR] and 95% confidence intervals [CI], adjusting for sociodemographics, smoking status, and body mass index (BMI). Relative to being inactive, performing some MVPA (>0 to <150 minutes/week) or meeting the recommended MVPA (≥150 minutes/week) were associated with lower odds of mild OSA (ORs and 95% CIs 0.70 [0.61-0.82] and 0.76 [0.63-0.91], respectively), as well as moderate to severe OSA (ORs and 95% CIs 0.76 [0.62-0.93] and 0.76 [0.59-0.98], respectively). Associations of VPA with OSA were not significant. Engaging in medium or high levels of transportation activity was associated with lower odds of mild OSA (OR: 0.84, 95% CI: 0.74-0.96; OR: 0.64, 95% CI: 0.43-0.95, respectively). Performing some recreational MVPA was associated with lower likelihood of mild and moderate to severe OSA (OR: 0.82, 95% CI: 0.71-0.93; OR: 0.79, 95% CI: 0.64-0.97, respectively). Health promotion and OSA prevention efforts should encourage individuals to engage in at least some MVPA
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