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showing 10 items of 11436 documents
Etna and the perception of volcanic risk
2013
Sicily’s uneven geological structure is positioned within a system of tectonic plates, and its very active volcano has always made it prone to disasters. Many Sicilian cities have in fact been destroyed by natural events many times over the centuries. This can certainly be understood negatively as the destruction of entire towns, the emission of volcanic ash, and the mutation of landscapes by a terrifying force have instilled fearful memories in local populations. But from another point of view one must consider the positive elements of Etna. Its beautiful landscapes were a major attraction on the Grand Tour, and its inhabitants have long associated the volcano with the concept of rebirth a…
Sedimentary basins evolution and olistoliths formation: The case of Carpathian and Sicilian regions
2012
Abstract Comparative research carried out within two different basins, one in the Carpathians of Poland (Late Jurassic to Early Miocene) and another in the Apenninic-Maghrebian mountain chain of Sicily (Triassic-Miocene), indicate significant similarity not only in their evolution but also in the sedimentary features of horizons with olistoliths. The olistolith-bearing units are genetically related to stages of tectonic evolution and are independent of the size of the basins and of duration of these stages. However, the observed differences in composition and size of olistoliths suggested, among the others relationship with the size of source areas and thickness of their sedimentary cover.
Millennial-scale climate variability during the last 12.5 ka recorded in a Caribbean speleothem
2013
Abstract We present a speleothem stable oxygen isotope record for the last 12.5 ka based on two stalagmites from western Cuba. The δ18O signal is interpreted to represent past precipitation variability. Both stalagmites show a pronounced transition from higher δ18O values (indicating drier conditions) to more negative δ18O values (suggesting wetter conditions) between 10 and 6 ka. This transition is also visible in a planktonic δ18O record off Haiti. On orbital timescales, the δ18O value of Caribbean precipitation, thus, strongly resembles the oxygen isotope composition of Caribbean surface water. On millenial timescales, the speleothem δ18O record shows a high correlation to a North Atlant…
Comparative tests on different multi-electrode arrays using models in near-surface geophysics
2008
In this paper, the response of different synthetic models to geoelectrical multi-electrode surveys is studied. The models considered are related to two main problems, which are very common in geophysical research regarding hydrogeology and engineering. The first class of models represents buried walls, similar archaeological remains or remains of buried foundations; the other class corresponds to a sea-water intrusion of a fresh water aquifer, which is generally studied in hydrogeophysics. A set of 2D simulations, starting from the synthetic models, was carried out to compare the behaviour of the different arrays when acquiring measurements of electrical resistivity tomography. For each mod…
Models as Research Tools: Plücker, Klein, and Kummer Surfaces
2018
In the late summer of 1869, 20-year-old Felix Klein made his way to Berlin, where he planned to attend the renowned seminar founded by Ernst Eduard Kummer and Karl Weierstrass. Klein had already taken his doctorate in Bonn and he would soon be recognized as a leading expert on line geometry, a new approach to 3-space launched by his mentor in Bonn, Julius Plucker. Just before Plucker died in 1868, he entrusted Klein to complete the classic monograph, Neue Geometrie des Raumes gegrundet auf die Betrachtung der geraden Linie als Raumelement. Overall responsibility for this project fell to Alfred Clebsch in Gottingen, which was how Klein first came to the prestigious Georgia Augusta. There he …
A Methodology for Comparing the Surface Urban Heat Island in Selected Urban Agglomerations Around the World from Sentinel-3 SLSTR Data
2020
[EN] Retrieval of land surface temperature (LST) from satellite data allows to estimate the surface urban heat island (SUHI) as the difference between the LST obtained in the urban area and the LST of its surroundings. However, this definition depends on the selection of the urban and surroundings references, which translates into greater difficulty in comparing SUHI values in different urban agglomerations across the world. In order to avoid this problem, a methodology is proposed that allows reliable quantification of the SUHI. The urban reference is obtained from the European Space Agency Climate Change Initiative Land Cover and three surroundings references are considered; that is, the …
Ramification of lithic production and the search of small tools in Iberian Peninsula Middle Paleolithic
2015
The notion of recycling and it relationship with ramified productions and small tool production in Late Middle Paleolithic from the Iberian Peninsula are investigated. Results from Amalda, Axlor, Pen~a Miel, and Quebrada show that the production of small tools is one of the principal objectives of lithic provi- sioning in these sites. Whereas in Axlor and Amalda, this is achieved through the ramification of pro- duction, due to the remoteness of flint sources, in Quebrada, where raw material sources are closer, small flakes are obtained at the end of Levallois production. The implications for Neandertal society organi- zation of this small tool production is discussed, and its evolution is …
Evaporite karst in Italy: A review
2017
none 16 si Although outcropping rarely in Italy, evaporite (gypsum and anhydrite) karst has been described in detail since the early 20th century. Gypsum caves are now known from almost all Italian regions, but are mainly localised along the northern border of the Apennine chain (Emilia Romagna and Marche), Calabria, and Sicily, where the major outcrops occur. Recently, important caves have also been discovered in the underground gypsum mines in Piedmont. During the late 80s and 90s several multidisciplinary studies were carried out in many gypsum areas, resulting in a comprehensive overview, promoting further research in these special karst regions. More recent and detailed studies focused…
From Dupin cyclides to scaled cyclides
2003
Dupin cyclides are algebraic surfaces introduced for the first time in 1822 by the French mathematician Pierre-Charles Dupin. They have a low algebraic degree and have been proposed as a solution to a variety of geometric modeling problems. The circular curvature line’s property facilitates the construction of the cyclide (or the portion of a cyclide) that blends two circular quadric primitives. In this context of blending, the only drawback of cyclides is that they are not suitable for the blending of elliptic quadric primitives. This problem requires the use of non circular curvature blending surfaces. In this paper, we present another formulation of cyclides: Scaled cyclides. A scaled cy…
Pants complex, TQFT and hyperbolic geometry
2021
We present a coarse perspective on relations of the $SU(2)$-Witten-Reshetikhin-Turaev TQFT, the Weil-Petersson geometry of the Teichm\"uller space, and volumes of hyperbolic 3-manifolds. Using data from the asymptotic expansions of the curve operators in the skein theoretic version of the $SU(2)$-TQFT, as developed by Blanchet, Habegger, Masbaum and Vogel, we define the quantum intersection number between pants decompositions of a closed surface. We show that the quantum intersection number admits two sided bounds in terms of the geometric intersection number and we use it to obtain a metric on the pants graph of surfaces. Using work of Brock we show that the pants graph equipped with this …