1,721,065 research outputs found
METODO E DISPOSITIVO PER LA IDENTIFICAZIONE AUTOMATICA DI UNA ROCCIA" (inventore: ARMIENTI Pietro)
No full textLa presente invenzione è relativa a un metodo e a un dispositivo per la identificazione automatica di una roccia.
In particolare, la presente invenzione trova vantaggiosa, ma non esclusiva applicazione nel settore lapideo per la identificazione automatica e non distruttiva di rocce granitoidi a grana grossa, per esempio quelle impiegate come pietre ornamentali, sulla base delle loro caratteristiche cromatiche
Telaio Portacampione per sezioni sottili di rocce
No full textIl dispositivo, di cui si è realizzato un prototipo, è stato messo a punto nell'ambito di un progetto di ricerca co-finaziato dal MURST nel 1998 (Materiali terrestri ed analoghi sintetici ad alta pressione ed alta temperatura: proprieta' fisiche, chimiche e reologiche) ed utilizzato per l'esecuzione di numerose misure. La slitta portacampioni di cui si propone il brevetto si è rivelato un potente strumento per facilitare l'acquisizione a basso costo di dati per l'elaborazione di immagini di rocce. Per le potenzialità del dispositivo si veda l'articolo pubblicato dagli autori:Tarquini, S., Armienti, P. (2001) Slide color scanner as a new and cheap tool for image anlysis in petrology. Image analysis and stereology. Vol 20 suppl 1 - Proceedings of the 8th European Congress for Stereology and Image Analysis. 567-57
The medieval roots of modern scientific thought. A Fibonacci abacus on the facade of the church of San Nicola in Pisa
No full textA marble intarsia on the main entrance of the church of San Nicola in Pisa provides the opportunity to appreciate the level of cultural excellence achieved by the Maritime Republic at the height of its power during the twelfth and thirteenth centuries. The intarsia reveals the direct influence of the great Pisan mathematician Leonardo Fibonacci due to the presence of circles whose radii represent the first nine elements of the Fibonacci's sequence and which were arranged to depict some properties of the sequence. Moreover, the tiles can be used as an abacus to draw sequences of regular polygons inscribed in a circle of given radius. This construction is a novelty that has resurfaced after eight hundred years of neglect and its implications, in themselves, are worthy of special examination. The presence of so many symbolic references makes the intarsia an icon of medieval philosophical thought and reveals aspects that pave the way to modern scientific thought
Flank cones at Mount Etna volcano: Do they have a power-law distribution?
No full textMount Etna is currently characterised by intense effusive and explosive activity of its summit vents, whereas 319 non-active Holocene flank cones are spread across its flanks at altitudes of between 2990 and 475 m. In volcanic areas the relationships between fracture occurrence and cone growth/location are well established. With this in mind, the spatial distribution of the Mount Etna flank cones was analysed in order to make some inferences about the fracture systems that feed the cones. The positions of the flank cones were acquired by the use of a digital elevation model of the volcano with a geometric resolution of 10x10 m. Spatial distribution of the cones was analysed through counting-box and sand-box methods, checking for fractal or multifractal behaviours. The four data sets analysed consist of the whole number of parasitic cones (319), and cones located on the NE (50), south (143) and west (61) rifts, respectively. The cones have a non-trivial power-law distribution. The sand-box method gave the best results with a fractal exponent D-f for all cones of 1.41+/-0.02 over the length range 0.2-10 km. The same analysis was performed on the other data sets: South Rift (1.42+/-0.02); West Rift (1.39+/-0.02); and NE Rift (1.43+/-0.02), The cones do not have a multifractal distribution, as suggested also by the strong similarity between fractal exponents of the different data sets. Data suggest a strong control over flank cone distribution by fracture length and density. These two characteristics are, in turn, expressions of highly connected fractures activated as magma feeders by the volcano's present stress field. We interpret the rifts as inherited structures that represent preferential sites of fracture connectivity
Power law olivine crystal size distributions in lithospheric mantle xenoliths
No full textOlivine crystal size distributions (CSDs) have been measured in three suites of spinel- and garnet-bearing harzburgites and lherzolites found as xenoliths in alkaline basalts from Canary Islands, Africa; Victoria Land, Antarctica; and Pali Aike, South America. The xenoliths derive from lithospheric mantle, from depths ranging from 80 to 20 km. Their textures vary from coarse to porphyroclastic and mosaic-porphyroclastic up to cataclastic. Data have been collected by processing digital images acquired optically from standard petrographic thin sections. The acquisition method is based on a high-resolution colour scanner that allows image capturing of a whole thin section. Image processing was performed using the VISILOG 5.2 package, resolving crystals larger than about 150 gm and applying stereological corrections based on the Schwartz-Saltykov algorithm. Taking account of truncation effects due to resolution limits and thin section size, all samples show scale invariance of crystal size distributions over almost three orders of magnitude (0.2-25 mm). Power law relations show fractal dimensions varying between 2.4 and 3.8, a range of values observed for distributions of fragment sizes in a variety of other geological contexts. A fragmentation model can reproduce the fractal dimensions around 2.6, which correspond to well-equilibrated granoblastic textures. Fractal dimensions >3 are typical of porphyroclastic and cataclastic samples. Slight bends in some linear arrays suggest selective tectonic crushing of crystals with size larger than I mm. The scale invariance shown by lithospheric mantle xenoliths in a variety of tectonic settings forms distant geographic regions, which indicate that this is a common characteristic of the upper mantle and should be taken into account in theological models and evaluation of metasomatic models. (C) 2002 Elsevier Science B.V. All rights reserved
Slide color scanner as a new and cheap tool for image analysis in petrology
No full textAn acquisition and analysis method based on a commercial, low-cost, high-resolution film scanner is
presented. It allows to collect data from standard rock thin sections with a resolution up to 9.4 μm per pixel.
Common and general purpose facilities (scanner + PC + image analysis software) may thus be transformed
in an appropriate tool for quantitative textural analysis of rocks. The procedure implies the acquisition of
four images with crossed polarizers and one parallel light image. Crystal boundaries are extracted from
fields in crossed polarizers, while markers for mineral recognition are obtained thresholding the parallel
light image. The method is tested for fresh rocks with simple mineralogy (harzburgites and marbles) with no
more than three phases, all exhibiting well distinct optical properties. Image processing is performed
developing procedures with VISILOG 5.2 package. 2-D size data from binary images are converted to 3-D
size data applying stereological corrections. 3-D data are reported in bi-logarithmic diagrams, plotting the
crystal number density versus characteristic lengths. The harzburgite samples show a scale invariance of
size distributions of olivine while mosaic equant marbles exhibit a different size distribution pattern, without
scale invariance and a relative maximum
Cenozoic thermal evolution of lithospheric mantle in northern Victoria Land (Antarctica): Evidences from mantle xenoliths
No full textThermobarometry of spinel peridotites collected in northern Victoria Land in Cenozoic basalts of the Mt Melbourne Volcanic Province, reveals warming of local lithospheric mantle, marked by a shift of geothermal gradient from 0.5. °C/km to ̃3. °C/km during the development of Cenozoic magmatism related to the opening of the Ross Sea rift system. We suggest that a significant uplift fraction of the rift shoulder on the West Antarctic margin is due to the change in olivine molar volume induced by mantle heating. The heat source is provided by enhancement of asthenospheric convection induced by an "edge effect" in the mantle circulation, following the opening phase of the Ross Sea. Besides explaining the asymmetric uplift of the rift shoulder corresponding to the Transantarctic Mountains, this mechanism satisfactorily accounts for the time scale (̃10. Ma) and most of total uplift (̃3000m) of the western border of the Ross Sea in northern Victoria Land. © 2010 Elsevier B.V
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