303 research outputs found
Tracking the Equator Into the Paleogene (abstract of paper presented at AGU Fall Meeting, San Francisco, 8-12 Dec 2003)
Stratigraphy has been compiled for 63 tropical Pacific drill sites that sample lower Neogene and Paleogene sediments. These Sites derive from drilling on DSDP Leg 5 through ODP Leg 199. All Sites have been put on the biostratigraphic and paleomagnetic timescale refined by Leg 199 scientists. Sediment accumulation rates have been calculated for ten intervals ranging in age from 10 Ma to 56 Ma. A simple fixed hotspot model was used for Pacific lithospheric plate rotation in reconstructing the position of the selected sites for each of these ten intervals. The reconstruction of all intervals show the development of a tongue of relatively high accumulation rates associated with the oceanographic divergence at the geographic equator. The estimated position of the geographic equator based on these reconstructions lies consistently south of the position of the equator based on the rotation model used. However, the southward displacement is generally 2 degrees of latitude or less. We believe that this relatively small disagreement between the two estimates of equatorial position back to 56 Ma indicates: 1) Whatever hotspot movement that may have occurred in the interval between 40 and 56 Ma did not affect the motion of the Pacific plate; its motion after 40 Ma appears to have been approximately the same as before 40 Ma. 2) The estimated rate of true polar wander during the interval of 40 - 56 Ma must be very small (~0.125/m.y.) and is probably not significant (i.e., well within the error of these reconstructions)
Posterior variant of alien limb syndrome with sudden clinical onset as self-hitting associated with thalamic stroke
We present a case of sudden postischaemic onset of alien limb syndrome, with unintentional self-injury. Alien limb syndrome is an uncommon neurological disorder featured by uncontrolled and involuntary movements of a limb. Three variants of alien limb syndrome have been described: the anterior, featured by grasping of surrounding objects, the callosal, presenting with intermanual conflict, and the posterior, associated with involuntary levitation of the limb. Our patient suffered from an acute presentation of the posterior variant of the alien limb syndrome, resulting from an isolated thalamic stroke which was documented using 24-h computed tomography brain scan. Only one previous case of alien limb syndrome after thalamic infarct has been reported. Our case enhances the possibility that pure thalamic injury may represent a trigger for this condition
Problems Associated With the Assessment of Local Site Effects Through a Multidisciplinary Integrated Study: The Case of Fivizzano’s Town (Italy)
The evaluation of local site effects, by means of ground response analyses, is a very complex and difficult task, which requires a multidisciplinary approach. This is operative philosophy expressed by VEL Project (Valutazione degli Effetti Locali), sponsored by Tuscany Region, to the aim to seismic risk characterization in the main seismic areas (i.e. Garfagnana, Lunigiana, Amiata, Valtiberina and Mugello). One of the most important urban centres, involved in the multidisciplinary activity of the VEL project, is certainly the town of Fivizzano located nearby the city of Massa, which was strongly damaged during the earthquake of September 1920 (the strongest seismic event occurred in Northern Apennines in the latest centuries). Remarkably good macroseismic information is available about the destructive impact yielded at Fivizzano by this earthquake (e.g. number of casualties, level of damage of buildings, etc). The main objective of this paper is to identify the occurrence of possible local site effects in the Fivizzano’s area following the 1920 earthquake and to quantify them by means of one and two-dimensional site response analysis. The input data required for study were obtained through a comprehensive geological survey and a multi disciplinary underground exploration of the area
The Role of Commerce in the Main Urban Area of Abruzzo: an Intra-Urban Reading
Since the 1950s, the urban structure of Abruzzo has gradually polarized on the area of Pescara-Chieti, as the expression of a series of location and settlement advantages. There, the trade sector, favoured by a period of expansion of large-scale commercial distribution, represented a powerful vehicle for territorial convergence and cohesion, contributing to the progressive process of marginalization of urban proximity trade. The aim of this work is to go beyond the opposition between suburban shopping center/central urban trade and to propose an interpretation at intra-urban scale that starts from peripheral neighbourhoods and peculiar spaces: They are able, in some cases, to better represent urban identity, but, above all, to provide a favourable observation point from which to promote a balanced and sustainable reorganization of the city
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