1,381 research outputs found

    Trading on Preconceptions: Why World War I Was Not a Failure of Economic Interdependence

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    World War I is generally viewed by both advocates and critics of commercial liberal theory as the quintessential example of a failure of economic integration to maintain peace. Yet this consensus relies on both methodologically flawed inference and an incomplete accounting of the antecedents to the war. Crucially, World War I began in a weakly integrated portion of Europe with which highly integrated powers were entangled through the alliance system. Crises among the highly interdependent European powers in the decades leading up to the war were generally resolved without bloodshed. Among the less interdependent powers in Eastern Europe, however, crises regularly escalated to militarized violence. Moreover, the crises leading to the war created increased incentives for the integrated powers to strengthen commitments to their less interdependent partners. In attempting to make these alliances more credible, Western powers shifted foreign policy discretion to the very states that lacked strong economic disincentives to fight. Had globalization pervaded Eastern Europe, or if the rest of Europe had been less locked into events in the east, Europe might have avoided a “Great War.” </jats:p

    Wind speed vertical distribution at Mt. Graham

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    The characterization of the wind speed vertical distribution V(h) is fundamental for an astronomical site for many different reasons: (1) the wind speed shear contributes to trigger optical turbulence in the whole troposphere, (2) a few of the astroclimatic parameters such as the wavefront coherence time (tau_0) depends directly on V(h), (3) the equivalent velocity V_0, controlling the frequency at which the adaptive optics systems have to run to work properly, depends on the vertical distribution of the wind speed and optical turbulence. Also, a too strong wind speed near the ground can introduce vibrations in the telescope structures. The wind speed at a precise pressure (200 hPa) has frequently been used to retrieve indications concerning the tau_0 and the frequency limits imposed to all instrumentation based on adaptive optics systems, but more recently it has been proved that V_200 (wind speed at 200 hPa) alone is not sufficient to provide exhaustive elements concerning this topic and that the vertical distribution of the wind speed is necessary. In this paper a complete characterization of the vertical distribution of wind speed strength is done above Mt.Graham (Arizona, US), site of the Large Binocular Telescope. We provide a climatological study extended over 10 years using the operational analyses from the European Centre for Medium-Range Weather Forecasts (ECMWF), we prove that this is representative of the wind speed vertical distribution at Mt. Graham with exception of the boundary layer and we prove that a mesoscale model can provide reliable nightly estimates of V(h) above this astronomical site from the ground up to the top of the atmosphere (~ 20 km).Comment: 12 pages, 9 figures (whereof 3 colour), accepted by MNRAS May 27, 201

    Optical turbulence simulations at Mt Graham using the Meso-NH mode

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    The mesoscale model Meso-NH is used to simulate the optical turbulence at Mt Graham (Arizona, USA), site of the Large Binocular Telescope. Measurements of the CN2-profiles obtained with a generalized scidar from 41 nights are used to calibrate and quantify the model's ability to reconstruct the optical turbulence. The measurements are distributed over different periods of the year, permitting us to study the model's performance in different seasons. A statistical analysis of the simulations is performed for all the most important astroclimatic parameters: the CN2-profiles, the seeing {\epsilon}, the isoplanatic angle {\theta}0 and the wavefront coherence time {\tau}0. The model shows a general good ability in reconstructing the morphology of the optical turbulence (the shape of the vertical distribution of CN2) as well as the strength of all the integrated astroclimatic parameters. The relative error (with respect to measurements) of the averaged seeing on the whole atmosphere for the whole sample of 41 nights is within 9.0 %. The median value of the relative error night by night is equal to 18.7 %, so that the model still maintains very good performances. Comparable percentages are observed in partial vertical slabs (free atmosphere and boundary layer) and in different seasons (summer and winter). We prove that the most urgent problem, at present, is to increase the ability of the model in reconstructing very weak and very strong turbulence conditions in the high atmosphere. This mainly affects the model's performances for the isoplanatic angle predictions, for which the median value of the relative error night by night is equal to 35.1 %. No major problems are observed for the other astroclimatic parameters. A variant to the standard calibration method is tested but we find that it does not provide better results, confirming the solid base of the standard method.Comment: 12 pages, 12 figures. The definitive version can be found at: http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2966.2010.18097.x/abstrac

    The Saharan heat low and moisture transport pathways in the central Sahara-multiaircraft observations and Africa-LAM evaluation

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    We present a characterization of the Saharan heat low (SHL) based on dropsonde observations made on 22 June 2011 by two simultaneously flying aircraft during the Fennec project. The observations are used to identify moisture transport pathways and to validate the UK Met Office limited area model for northern Africa (Africa-LAM). The observations capture the SHL, harmattan, and monsoon surge. The SHL has a northeast-southwest orientated elongated shape centered over northern Mauritania. The SHL core is associated with a 950 hPa temperature minimum (36.4°C) in the morning caused by the monsoon surge and a maximum (42.6°C) in the afternoon. The monsoon surge east of the SHL core splits into two transport pathways: (a) curving around the SHL core in the north, especially pronounced in a morning near-surface layer, and (b) northeastward transport within the ~2km deep monsoon surge (afternoon observations only). In the morning the model forecasts the harmattan, monsoon surge, and the SHL geographic location and northeast-southwest orientation well but the model represents the SHL flatter and more spatially extended and overestimates the convective boundary layer (CBL) by up to ~0.3 km. The simulated afternoon SHL location appears shifted westward by up to ~1°. The model overestimates the shallow afternoon monsoon surge CBL depth of ~1.8km by >2kmresulting in southwestward transport of vertically mixed moisture above ~2.5km contrasting observed northeastward-only transport at lower levels. This moisture distribution model error is likely to have consequences for simulations of Saharan thermodynamics and dust emissions caused by convection-driven cold pools

    American Classic

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    Teaching Solidarity: Popular Education in Grassroots U.S. Social Movements

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    Fifty years after he wrote Pedagogy of the Oppressed (1970), Brazilian educator Paulo Freire’s work is as relevant as ever. But while many of Freire’s ideas are well known in the United States, there is limited research on their application in social movement settings, a practice commonly known as popular education. This comparative case study draws on Freire’s theory of popular education to analyze two U.S.-based grassroots education programs, one with low-income residents in the Tenderloin neighborhood of San Francisco and one with front-line hospital and public school employees on the East Coast. Through six months of participant observation and over 50 interviews with facilitators and participants, the study finds that the two programs carved out spaces that were relatively independent from union and non-profit hierarchies, which enabled them to apply popular education’s radically democratic principles within their organizing work and larger social struggles. These findings point to the possibility that popular education can offer participants not only knowledge and skills but also–and perhaps more importantly–strengthened connections across divisions, confidence that they can make change, and the courage to organize. The dissertation also expands on commonly understood meanings of “critical consciousness,” arguing that what moves people to action may be not only their intellectual understanding of power, but also an increased solidarity that gives them an awareness of their collective historical agency. Finally, the study identifies tensions in the programs, for example related to funding constraints, that at times interfered with facilitators’ abilities to apply the radical principles of popular education. These findings speak to the value of a reflective practice on the part of practitioners, and highlight the ongoing significance of Freirean popular education in U.S. social movement contexts

    Export of Asian pollution during two cold front episodes of the TRACE-P experiment

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    Two cold front episodes were sampled during the two flights out of Yokota, Japan, during the Transport and Chemical Evolution Over the Pacific (TRACE-P) experiment during March 2001. The data from these two flights are examined using a mesoscale three-dimensional model. We show how these cyclonic systems have impacted the export of pollution out of the Asian continent. We contrast the relative role of convection and ascent in the warm conveyor belts associated with the cyclone during these two episodes. Although the necessary meteorological conditions for an efficient export of pollution are met during flight 13 (i.e., the occurrences of the warm conveyor belt near the source regions), no significant pollution is simulated in the mid-Pacific in the lower and middle troposphere. The efficient ventilation of the WCB by convection near the coast, the advection by the anticyclonical flow above 700 hPa, and the downward motion associated with the Pacific high in the remote ocean significantly prevent any long-range transport of undiluted pollution in the WCB. During flight 15 the conveyor belts have already moved to the remote ocean. The polluted plume is split by the rising air in the warm conveyor belt which transports CO-poor air northward and by the oceanic convection which transports clean air masses upward. These mechanisms lead to the dilution of Asian pollution in WCB en route to North America and add to the episodic nature of the Asian outflow by fragmenting the pollution plume

    Fennec dust forecast intercomparison over the Sahara in June 2011

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    International audienceIn the framework of the Fennec international programme , a field campaign was conducted in June 2011 over the western Sahara. It led to the first observational data set ever obtained that documents the dynamics, thermodynam-ics and composition of the Saharan atmospheric boundary layer (SABL) under the influence of the heat low. In support to the aircraft operation, four dust forecasts were run daily at low and high resolutions with convection-parameterizing and convection-permitting models, respectively. The unique airborne and ground-based data sets allowed the first ever intercomparison of dust forecasts over the western Sahara. At monthly scale, large aerosol optical depths (AODs) were forecast over the Sahara, a feature observed by satellite retrievals but with different magnitudes. The AOD intensity was correctly predicted by the high-resolution models, while it was underestimated by the low-resolution models. This was partly because of the generation of strong near-surface wind associated with thunderstorm-related density currents that could only be reproduced by models representing con-vection explicitly. Such models yield emissions mainly in the afternoon that dominate the total emission over the western fringes of the Adrar des Iforas and the Aïr Mountains in the high-resolution forecasts. Over the western Sahara, where the harmattan contributes up to 80 % of dust emission, all the models were successful in forecasting the deep well-mixed SABL. Some of them, however, missed the large near-surface dust concentration generated by density currents and low-level winds. This feature, observed repeatedly by the airborne lidar, was partly forecast by one high-resolution model only

    First observations of polarized scattering over ice clouds at close-to-millimeter wavelengths (157 GHz) with MADRAS on board the Megha-Tropiques mission

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    Polarized scattering by frozen hydrometeors is investigated for the first time up to 157 GHz, based on the passive microwave observations of the Microwave Analysis and Detection of Rain and Atmospheric Structures (MADRAS) instrument on board the Indo-French Megha-Tropiques satellite mission. A comparison with time-coincident Tropical Rainfall Measurement Mission Microwave Imager records confirms the consistency of the coincident observations collected independently by the two instruments up to 89 GHz. The MADRAS noise levels of 1.2 K at 89 GHz and of 2.5 K at 157 GHz are in agreement with the required specifications of the mission. Compared to the 89 GHz polarized channels that mainly sense large ice particles (snow and graupel), the 157 GHz polarized channel is sensitive to smaller particles and provides additional information on the cloud systems. The analysis of the radiometric signal at 157 GHz reveals that the ice scattering can induce a polarization difference of the order of 10 K at that frequency. Based on radiative transfer modeling the specific signature is interpreted as the effect of mainly horizontally oriented ice cloud particles. This suggests that the effects of the cloud particle orientation should be considered in rain and cloud retrievals using passive radiometry at microwave and millimeter wavelengths.Fil: Defer, Eric. Centre National de la Recherche Scientifique. Observatoire de Paris; FranciaFil: Galligani, Victoria Sol. Centre National de la Recherche Scientifique. Observatoire de Paris; Francia. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Prigent, Catherine. Centre National de la Recherche Scientifique. Observatoire de Paris; FranciaFil: Jimenez, Carlos. Centre National de la Recherche Scientifique. Observatoire de Paris; Franci

    An eddy permitting coupled physical-biological model of the North Atlantic. Part I: Sensitivity to advection numerics and mixed layer physics

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    Physical influences on biological primary production in the North Atlantic are investigated by coupling a four-component pelagic ecosystem model with a high-resolution numerical circulation model. A series of sensitivity experiments demonstrates the important role of an accurate formulation of upper ocean turbulence and advection numerics. The unrealistically large diffusivity implicit in upstream advection approximately doubles primary production when compared with a less diffusive, higher-order, positive-definite advection scheme.This is of particular concern in the equatorial upwelling region where upstream advection leads to a considerable increase of upper ocean nitrate concentrations. Counteracting this effect of unrealistically large implicit diffusion by changes in the biological model could easily lead to misconceptions in the interpretation of ecosystem dynamics. Subgrid-scale diapycnal diffusion strongly controls biological production in the subtropical gyre where winter mixing does not reach the nutricline. The parameterization of vertical viscosity is important mainly in the equatorial region where friction becomes an important agent in the momentum balance
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