887 resultados para Col·lapse gravitacional
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Mode of access: Internet.
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"A complete revision and expansion of an essay ... first published as a brief account in one of the Howard University studies in history."--Pref.
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Includes bibliographical references.
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Includes indexes.
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Errata sheet at end.
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Mode of access: Internet.
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A much-revised Quaternary stratigraphy is presented for ignimbrites and pumice fall deposits of the Bandas del Sur, in southern Tenerife. New Ar-41/Ar-39 data obtained for the Arico, Granadilla, Fasnia, Poris, La Caleta and Abrigo formations are presented, allowing correlation with previously dated offshore marine ashfall layers and volcaniclastic sediments. We also provide a minimum age of 287 +/- 7 ka for a major sector collapse event at the Gaimar valley. The Bandas del Sur succession includes more than seven widespread ignimbrite sheets that have similar characteristics, including widespread basal Plinian layers, predominantly phonolite composition, ignimbrites with similar extensive geographic distributions, thin condensed veneers with abundant diffuse bedding and complex lateral and vertical grading patterns, lateral gradations into localized massive facies within palaeo-wadis, and widespread lithic breccia layers that probably record caldera-forming eruptions. Each ignimbrite sheet records substantial bypassing of pyroclastic material into the ocean. The succession indicates that Las Canadas volcano underwent a series of major explosive eruptions, each starting with a Plinian phase followed by emplacement of ignimbrites and thin ash layers, some of coignimbrite origin. Several of the ignimbrite sheets are compositionally zoned and contain subordinate mafic pumices and banded pumices indicative of magma mingling immediately prior to eruption. Because passage of each pyroclastic density current was characterized by phases of non-deposition and erosion, the entire course of each eruption is incompletely recorded at any one location, accounting for some previously perceived differences between the units. Because each current passed into the ocean, estimating eruption volumes is virtually impossible. Nevertheless, the consistent widespread distributions and the presence of lithic breccias within most of the ignimbrite sheets suggest that at least seven caldera collapse eruptions are recorded in the Bandas del Sur succession and probably formed a complex, nested collapse structure. Detailed field relationships show that extensive ignimbrite sheets (e.g. the Arico, Poris and La Caleta formations) relate to previously unrecognized caldera collapse events. We envisage that the evolution of the nested Las Cahadas caldera is more complex than previously thought and involved a protracted history of successive ignimbrite-related caldera collapse events, and large sector collapse events, interspersed with edifice-building phases.
An ultrasonic instrumentation system for the study of vapour bubble formation and collapse in sodium
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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.