883 resultados para EXTENSIONAL COLLAPSE
An ultrasonic instrumentation system for the study of vapour bubble formation and collapse in sodium
Resumo:
The presidential and legislative elections of 2007 are widely seen to have marked the end of the far right as a major political force in France. How could this occur only five years after Le Pen’s qualification for the presidential run-off, and with his party seemingly in the ascendant? This article discusses recent fluctuations in far-right electoral performance in France. It focuses largely on the presidential elections of 2002 and 2007, re-examining the (supposed) upswell of far-right support in 2002 and its (supposed) subsidence in 2007. Both elections require nuanced interpretation. Both confounded poll predictions, which in 2007 failed to measure the effect of Sarkozy’s hard-right campaign and, crucially, the extent to which the border between “mainstream right” and “far right” had shifted since 2002. This allowed Sarkozy to drain part of Le Pen’s electorate, and raises questions over the longer-term impact of Le Pen and the FN on the political agenda in France.
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This paper explores the nature of the co-called ‘private equity business model’ (PEBM) and assesses its shortcomings, using the illustrative example of the role of private equity in structuring the finance and subsequent collapse of MG Rover, as the automotive industry has been a significant destination for private equity financing. The paper outlines the nature of the PEBM. It then details how the PEBM extracts value, before stressing how this can affect workers in a portfolio business. We argue that the emergence of the PEBM changes the basis of competitive rules in organizations and the running of erstwhile going concerns, necessitating a need for further regulation—particularly, how to secure wider stakeholder oversight without reducing the efficiency of PEBM concerns.
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We have used neutron reflectometry to characterize the swelling behaviour of brushes of poly[2-(diethyl amino)ethyl methacrylate], a polybase, as a function of pH. The brushes, synthesized by the "grafting from" method of atom transfer radical polymerization, were observed to approximately double their thickness in low pH solutions, although the pK is shifted to a lower pH than in dilute solution. The composition-depth profile obtained from the reflectometry experiments for the swollen brushes reveals a region depleted in polymer between the substrate and the extended part of the brush.
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Scholarship on how to rebuild failed or collapsed states provides scant theoretical guidance in the search for specific warning signs or mechanisms of collapsing states. This thesis argues that state collapse is a societal response to an identity crisis politicized by the state apparatus in response to a legitimation crisis. As regime legitimacy deteriorates, identity politics are deployed to build support for the regime, but typically at the cost of increasing other forces of internal conflict. Absent a mediating force to suppress internal conflict, the state collapses once the regime has been removed. Somalia and Sudan proceeded through this trajectory during their civil wars, though with different outcomes. Somalia fragmented into clan and subclan groups that continued their inimical relationship perpetuating the war following Siyad Barre's coup. Sudan maintained two core identity groups separated by the implementation of sharia that survived each state legitimation crisis, though the state's physical solidity endured.
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The purpose of my dissertation was to examine the competition between the U.S.-led Western bloc and the Soviet bloc in the less developed world during Détente. I assessed whether or not the Soviet bloc pushed for strategic gains in the less developed world in the middle-to-late 1970's and whether this contributed to the U.S. decision to abandon Détente in 1979. I made the attempt to test the international relations theory of balance of threat realism (Walt, 1992). I accomplished the test in two ways. First, I measured the foreign aid allocations (military and economic) made by each respective bloc towards the Third World by using a quantitative approach. Second, I examined U.S. archives using the process-tracing/historical method. The U.S. archives gave me the ability to evaluate how U.S. decision-makers and U.S. intelligence agencies interpreted the actions of the Soviet bloc. They also gave me the chance to examine the U.S. response as we evaluated the policies that were pushed by key U.S. decision-makers and intelligence agencies. On the question of whether or not the Soviet bloc was aggressive, the quantitative evidence suggested that it was not. Instead, the evidence found the Western-bloc to have been more aggressive in the less developed world. The U.S. archives also showed Soviet actions to have been defensive. Key U.S. decision-makers and intelligence agencies attested to this. Finally, the archives show that U.S. officials pushed for aggressive actions against the Third World during the final years of Détente. Thus, balance of threat realism produced an incorrect assessment that U.S. aggression in the late 1970's was a response to Soviet aggression during Détente. The evidence suggests structural Marxism and domestic politics can better explain U.S./Western actions. The aggressive foreign aid allocations of the West, coupled with evidence of U.S. decision-makers/agencies vehemently concerned about the long-term prospects of the West, strengthened structural Marxism. Domestic politics can also claim to explain the actions of U.S. decision-makers. I found extensive archival evidence of bureaucratic inter-agency conflict between the State Department and other intelligence agencies in areas of strategic concern to the U.S.
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C.-W.W. is supported by a studentship funded by the College of Physical Sciences, University of Aberdeen. M.S.B. acknowledges EPSRC grant NO. EP/I032606/1.
Processes of social flourishing and their liminal collapse: elements to a genealogy of globalization
Resumo:
This article aims at exploring a long-term historical perspective on which contemporary globalization can be more meaningfully situated. A central problem with established approaches to globalization is that they are even more presentist than the literature on modernization was. Presentism not only means the ignoring of history, but also the unreflective application to history of concepts taken from the study of the modern world. In contrast, it is argued that contemporary globalization is not a unique development, but rather is a concrete case of a historical type. Taking as its point of departure the spirit, rather than the word, of Max Weber, this article extends the scope of sociological investigation into archaeological evidence. Having a genealogical design and introducing the concept of ‘liminality’, the article approaches the modern process of globalization through reconstructing the internal dynamics of another type of historical change called ‘social flourishing’. Taking up the Weberian approach continued by Eisenstadt in his writings on ‘axial age’, it moves away from situations of crisis as reference point, shifting attention to periods of revival by introducing the term ‘epiphany’. Through the case of early Mesopotamia, it shows how social flourishing can be transmogrified into globalizing growth, gaining a new perspective concerning the kind of ‘animating spirit’ that might have driven the shift from Renaissance to Reformation, the rise of modern colonialism, or contemporary globalization. More generally, it will retrieve the long-term historical background of the axial age and demonstrate the usefulness and importance of archaeological evidence for sociology.
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We propose a mechanism for testing the theory of collapse models such as continuous spontaneous localization (CSL) by examining the parametric heating rate of a trapped nanosphere. The random localizations of the center-of-mass for a given particle predicted by the CSL model can be understood as a stochastic force embodying a source of heating for the nanosphere. We show that by utilising a Paul trap to levitate the particle and optical cooling, it is possible to reduce environmental decoher- ence to such a level that CSL dominates the dynamics and contributes the main source of heating. We show that this approach allows measurements to be made on the timescale of seconds, and that the free parameter λcsl which characterises the model ought to be testable to values as low as 10^{−12} Hz.
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We present self-consistent, axisymmetric core-collapse supernova simulations performed with the Prometheus-Vertex code for 18 pre-supernova models in the range of 11–28 M ⊙, including progenitors recently investigated by other groups. All models develop explosions, but depending on the progenitor structure, they can be divided into two classes. With a steep density decline at the Si/Si–O interface, the arrival of this interface at the shock front leads to a sudden drop of the mass-accretion rate, triggering a rapid approach to explosion. With a more gradually decreasing accretion rate, it takes longer for the neutrino heating to overcome the accretion ram pressure and explosions set in later. Early explosions are facilitated by high mass-accretion rates after bounce and correspondingly high neutrino luminosities combined with a pronounced drop of the accretion rate and ram pressure at the Si/Si–O interface. Because of rapidly shrinking neutron star radii and receding shock fronts after the passage through their maxima, our models exhibit short advection timescales, which favor the efficient growth of the standing accretion-shock instability. The latter plays a supportive role at least for the initiation of the re-expansion of the stalled shock before runaway. Taking into account the effects of turbulent pressure in the gain layer, we derive a generalized condition for the critical neutrino luminosity that captures the explosion behavior of all models very well. We validate the robustness of our findings by testing the influence of stochasticity, numerical resolution, and approximations in some aspects of the microphysics.
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Since core-collapse supernova simulations still struggle to produce robust neutrino-driven explosions in 3D, it has been proposed that asphericities caused by convection in the progenitor might facilitate shock revival by boosting the activity of non-radial hydrodynamic instabilities in the post-shock region. We investigate this scenario in depth using 42 relativistic 2D simulations with multigroup neutrino transport to examine the effects of velocity and density perturbations in the progenitor for different perturbation geometries that obey fundamental physical constraints (like the anelastic condition). As a framework for analysing our results, we introduce semi-empirical scaling laws relating neutrino heating, average turbulent velocities in the gain region, and the shock deformation in the saturation limit of non-radial instabilities. The squared turbulent Mach number, 〈Ma2〉, reflects the violence of aspherical motions in the gain layer, and explosive runaway occurs for 〈Ma2〉 ≳ 0.3, corresponding to a reduction of the critical neutrino luminosity by ∼25∼25 per cent compared to 1D. In the light of this theory, progenitor asphericities aid shock revival mainly by creating anisotropic mass flux on to the shock: differential infall efficiently converts velocity perturbations in the progenitor into density perturbations δρ/ρ at the shock of the order of the initial convective Mach number Maprog. The anisotropic mass flux and ram pressure deform the shock and thereby amplify post-shock turbulence. Large-scale (ℓ = 2, ℓ = 1) modes prove most conducive to shock revival, whereas small-scale perturbations require unrealistically high convective Mach numbers. Initial density perturbations in the progenitor are only of the order of Ma2progMaprog2 and therefore play a subdominant role.
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Models of neutrino-driven core-collapse supernova explosions have matured considerably in recent years. Explosions of low-mass progenitors can routinely be simulated in 1D, 2D, and 3D. Nucleosynthesis calculations indicate that these supernovae could be contributors of some lighter neutron-rich elements beyond iron. The explosion mechanism of more massive stars remains under investigation, although first 3D models of neutrino-driven explosions employing multi-group neutrino transport have become available. Together with earlier 2D models and more simplified 3D simulations, these have elucidated the interplay between neutrino heating and hydrodynamic instabilities in the post-shock region that is essential for shock revival. However, some physical ingredients may still need to be added/improved before simulations can robustly explain supernova explosions over a wide range of progenitors. Solutions recently suggested in the literature include uncertainties in the neutrino rates, rotation, and seed perturbations from convective shell burning. We review the implications of 3D simulations of shell burning in supernova progenitors for the ‘perturbations-aided neutrino-driven mechanism,’ whose efficacy is illustrated by the first successful multi-group neutrino hydrodynamics simulation of an 18 solar mass progenitor with 3D initial conditions. We conclude with speculations about the impact of 3D effects on the structure of massive stars through convective boundary mixing.
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This thesis argues that Cassius Dio used his speeches of his Late Republican and Augustan narratives as a means of historical explanation. I suggest that the interpretative framework which the historian applied to the causes and success of constitutional change can be most clearly identified in the speeches. The discussion is divided into eight chapters over two sections. Chapter 1 (Introduction) sets out the historical, paideutic, and compositional issues which have traditionally served as a basis for rejecting the explanatory and interpretative value of the speeches in Dio’s work and for criticising his Roman History more generally. Section 1 consists of three methodological chapters which respond to these issues. In Chapter 2 (Speeches and Sources) I argue that Dio’s prosopopoeiai approximate more closely with the political oratory of that period than has traditionally been recognised. Chapter 3 (Dio and the Sophistic) argues that Cassius Dio viewed the artifice of rhetoric as a particular danger in his own time. I demonstrate that this preoccupation informed, credibly, his presentation of political oratory in the Late Republic and of its destructive consequences. Chapter 4 (Dio and the Progymnasmata) argues that although the texts of the progymnasmata in which Dio will have been educated clearly encouraged invention with a strongly moralising focus, it is precisely his reliance on these aspects of rhetorical education which would have rendered his interpretations persuasive to a contemporary audience. Section 2 is formed of three case-studies. In Chapter 5 (The Defence of the Republic) I explore how Dio placed speeches-in-character at three Republican constitutional crises to set out an imagined case for the preservation of that system. This case, I argue, is deliberately unconvincing: the historian uses these to elaborate the problems of the distribution of power and the noxious influence of φθόνος and φιλοτιμία. Chapter 6 (The Enemies of the Republic) examines the explanatory role of Dio’s speeches from the opposite perspective. It investigates Dio’s placement of dishonest speech into the mouths of military figures to make his own distinctive argument about the role of imperialism in the fragmentation of the res publica. Chapter 7 (Speech after the Settlement) argues that Cassius Dio used his three speeches of the Augustan age to demonstrate how a distinctive combination of Augustan virtues directly counteracted the negative aspects of Republican political and rhetorical culture which the previous two case-studies had explored. Indeed, in Dio’s account of Augustus the failures of the res publica are reinvented as positive forces which work in concert with Augustan ἀρετή to secure beneficial constitutional change.
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The continual eruptive activity, occurrence of an ancestral catastrophic collapse, and inherent geologic features of Pacaya volcano (Guatemala) demands an evaluation of potential collapse hazards. This thesis merges techniques in the field and laboratory for a better rock mass characterization of volcanic slopes and slope stability evaluation. New field geological, structural, rock mechanical and geotechnical data on Pacaya is reported and is integrated with laboratory tests to better define the physical-mechanical rock mass properties. Additionally, this data is used in numerical models for the quantitative evaluation of lateral instability of large sector collapses and shallow landslides. Regional tectonics and local structures indicate that the local stress regime is transtensional, with an ENE-WSW sigma 3 stress component. Aligned features trending NNW-SSE can be considered as an expression of this weakness zone that favors magma upwelling to the surface. Numerical modeling suggests that a large-scale collapse could be triggered by reasonable ranges of magma pressure (greater than or equal to 7.7 MPa if constant along a central dyke) and seismic acceleration (greater than or equal to 460 cm/s2), and that a layer of pyroclastic deposits beneath the edifice could have been a factor which controlled the ancestral collapse. Finally, the formation of shear cracks within zones of maximum shear strain could provide conduits for lateral flow, which would account for long lava flows erupted at lower elevations.