6,564 research outputs found

    Development of a turbojet combustor with a segmentally constructed liner Final summary report

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    Axial and circumferential segmented combustor liners for turbojet engin

    Thyroid-hormone therapy and thyroid cancer: a reassessment.

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    Experimental studies and clinical data have demonstrated that thyroid-cell proliferation is dependent on thyroid-stimulating hormone (TSH), thereby providing the rationale for TSH suppression as a treatment for differentiated thyroid cancer. Several reports have shown that hormone-suppressive treatment with the L-enantiomer of tetraiodothyronine (L-T(4)) benefits high-risk thyroid cancer patients by decreasing progression and recurrence rates, and cancer-related mortality. Evidence suggests, however, that complex regulatory mechanisms (including both TSH-dependent and TSH-independent pathways) are involved in thyroid-cell regulation. Indeed, no significant improvement has been obtained by suppressing TSH in patients with low-risk thyroid cancer. Moreover, TSH suppression implies a state of subclinical thyrotoxicosis. In low-risk patients, the goal of L-T(4) treatment is therefore to obtain a TSH level in the normal range (0.5-2.5 mU/l). Only selected patients with high-risk papillary and follicular thyroid cancer require long-term TSH-suppressive doses of L-T(4). In these patients, careful monitoring is necessary to avoid undesirable effects on bone and heart

    Nonequilibrium gas-liquid transition in the driven-dissipative photonic lattice

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    We study the nonequilibrium steady state of the driven-dissipative Bose-Hubbard model with Kerr nonlinearity. Employing a mean-field decoupling for the intercavity hopping JJ, we find that the steep crossover between low and high photon-density states inherited from the single cavity transforms into a gas−-liquid bistability at large cavity-coupling JJ. We formulate a van der Waals like gas−-liquid phenomenology for this nonequilibrium situation and determine the relevant phase diagrams, including a new type of diagram where a lobe-shaped boundary separates smooth crossovers from sharp, hysteretic transitions. Calculating quantum trajectories for a one-dimensional system, we provide insights into the microscopic origin of the bistability.Comment: 5 pages, 4 figures + Supplemental Material (2 pages, 2 figures

    Plant communities of Italy. The vegetation prodrome

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    The Vegetation Prodrome of Italy was promoted in 2012 by the Italian "Ministry of Environment, Land and Sea Protection", in collaboration with the "Italian Society of Botany", to provide a comprehensive and systematic catalogue and description of Italian plant communities. The Prodrome that is presented in this paper is the first full organic synthesis of the vegetation of Italy at the alliance syntaxonomic level. It fulfils several needs, the main one being a unified and comprehensive national framework that may make an important contribution to the definition of the European Vegetation Prodrome. Syntaxonomy, as well as taxonomy, is sometimes based on considerations that may in part diverge: several authors tend to favour models that are divisive or aggregative to a greater or lesser extent in terms of flora, biogeography and ecology. These different points of view stimulate the scientific debate and allow the adoption of a framework that is more widely supported. The Prodrome includes 75 classes, 2 subclasses, 175 orders, 6 suborders and 393 alliances. The classes were grouped into nine broad categories according to structural, physiognomic and synecological elements rather than to syntaxonomic criteria. The rank, full valid name, any synonymies and incorrect names are provided for each syntaxon. The short declaration highlights the physiognomy, synecology, syndynamics and distribution of the plant communities that belong to the syntaxon. The Prodrome of the Italian Vegetation is linked to the European Strategy for Biodiversity, the European Habitats Directive and the European Working Groups related to the ecosystems and their services. In addition to basic applications, the Prodrome can be used as a framework for scientific research related to the investigation of the relationships between plant communities and the environmental factors that influence their composition and distribution

    Much ado about making money: The impact of disclosure, news and rumors over the formation of security market prices over time

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    This article develops an agent-based model of security market pricing process, capable to capture main stylised facts. It features a collective market pricing mechanism based upon evolving heterogenous expectations that incorporate signals of security issuer fundamental performance over time. Distinctive signaling sources on this performance correspond to institutional mechanisms of information diffusion. These sources differ by duration effect (temporary, persistent, and permanent), confidence, and diffusion degree among investors over space and time. Under full and immediate diffusion and balanced reaction by all the investors, the value of these sources should be consistently and timely integrated by the market price process, implying efficient pricing. By relaxing these quite heroic conditions, we assess the impact of distinctive information sources over market price dynamics, through financial systemic properties such as market price volatility, exuberance and errancy, as well as market liquidity. Our simulation analysis shows that transient information shocks can have permanent effects through mismatching reactions and self-reinforcing feedbacks, involving mispricing in both value and timing relative to the efficient market price series. This mispricing depends on both the information diffusion process and the ongoing information confidence mood among investors over space and time. We illustrate our results through paradigmatic cases of stochastic news, before generalising them to autocorrelated news. Our results are further corroborated by robustness checks over the parameter space

    Abandoned Railroads in Maine: Their Potential for Trail Use

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    Abandoned railroads in Maine : their potential for trail use / prepared by Arnold S. Biondi, Frederick W. Lyman for the Maine Department of Parks & Recreation, Planning & Research Division This report, conceived as part of an in-depth analysis of existing and potential trail facilities in Maine, attempts to provide some concrete information and recommendations as the first step in the realization of a Statewide railroad right-of- way trail system.https://digitalcommons.usm.maine.edu/me_collection/1014/thumbnail.jp

    Causal inference on the impact of nutrition policies using observational data

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    We discuss the state-of-the-art in the application of quasi-experimental methods to estimate the impact of nutrition policies based on observational data. This field of application is less mature compared to other settings, especially labour and health policy, as food economists have started to implement widely counterfactual methods only over the last decade. We review the underlying assumptions behind the most prominent methods, when they can be regarded as credible and if/when they can be tested. We especially focus on the problem of dealing with unobserved confounding factors, emphasizing recent evidence on the limitations of propensity score methods, and the hard task of convincing reviewers about the quality of instrumental variables. We discuss the application of Difference-in-Difference, with an emphasis on its potential in consumer panel data applications, and how results from Regression Discontinuity Design studies should be interpreted. Finally, we cover the estimation of counterfactual outcomes using structural methods and provide an overview of recent developments and current gaps

    Design and test of a parallel kinematic solar tracker

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    This article proposes a parallel kinematic solar tracker designed for driving high-concentration photovoltaic modules. This kind of module produces energy only if they are oriented with misalignment errors lower than 0.4°. Generally, a parallel kinematic structure provides high stiffness and precision in positioning, so these features make this mechanism fit for the purpose. This article describes the work carried out to design a suitable parallel machine: an already existing architecture was chosen, and the geometrical parameters of the system were defined in order to obtain a workspace consistent with the requirements for sun tracking. Besides, an analysis of the singularities of the system was carried out. The method used for the singularity analysis revealed the existence of singularities which had not been previously identified for this kind of mechanism. From the analysis of the mechanism developed, very low nominal energy consumption and elevated stiffness were found. A small-scale prototype of the system was constructed for the first time. A control algorithm was also developed, implemented, and tested. Finally, experimental tests were carried out in order to verify the capability of the system of ensuring precise pointing. The tests have been considered passed as the system showed an orientation error lower than 0.4° during sun tracking
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