Search results for "stone"
showing 10 items of 1137 documents
Using mechanical experiments to study ground stone tool use: Exploring the formation of percussive and grinding wear traces on limestone tools
2021
Ground Stone Tools (GST) have been identified in several Levantine archaeological sites dating to the Middle Paleolithic. These tools, frequently made of limestone, are often interpreted based on their morphology and damage as having been used for knapping flint, and sometimes for breaking animal bones or processing vegetal materials as well. However, the lack of experimental referential collections on limestone is a major obstacle for the identification of diagnostic traces on these types of tools and raw material. In this sense, the understanding of the specific function of these GST and the association between tool types and activity often remains unknown or merely speculative. Recent di…
Documenting carved stones from 3D models. Part II - Ambient occlusion to reveal carved parts.
2021
10 pages; International audience; Revealing carved parts in rock art is of primary importance and remains a major challenge for archaeological documentation. Computational geometry applied to 3D imaging provides a unique opportunity to document rock art. This study evaluates five algorithms and derivatives used to compute ambient occlusion and sky visibility on 3D models of Mongolian stelae, also known as deer stones. By contrast with the previous companion work, models are processed directly in 3D, without preliminary projection. Volumetric obscurance gives the best results for the identification of carved figures. The effects of model resolution and parameters specific to ambient occlusio…
Antiguas excavaciones, nuevas respuestas. El yacimiento epimagdaleniense de la Cova del Clot de l'Hospital (Roquetes, Baix Ebre)
2015
El objetivo de este trabajo ha sido estudiar los materiales obtenidos con las excavaciones de Francesc Esteve Gálvez en la Cova del Clot de l’Hospital (Bajo Ebro), yacimiento de finales del Pleistoceno-inicios del Holoceno, descubierto por él mismo el año 1945. La representación de raspadores, truncaduras, buriles y laminitas de dorso, entre otros tipos, permite atribuirlo al Epimagdaleniense, atribución corroborada por dos fechas radiocarbónicas sobre huesos de fauna: 11.115 y 10.045 BP. De esta forma, este yacimiento se suma a un numeroso conjunto de yacimientos del período citado, conocidos en las provincias de Tarragona y de Castellón de la Plana. Así mismo, el estudio de los restos fau…
Spazio artistico ed espressione di libertà: volti spazi e creatività nell'opera di Filippo Bentivegna
2018
In this essay the author investigates the life and the work of F. Bentivegna, a sicilian migrants who had the power to translate the failure of a dream in an artistic expression form, thus becoming one of the exponents of the european Art Brut's artistic movement.
Astrophysical bound on the majoron-Higgs-boson coupling
1989
Abstract We show that the coupling of the “standard” Higgs boson to majorons, that could lead to a very fast decay of the neutral Higgs scalar to invisible modes, can be bounded using astrophysical arguments. We discuss the relevance of this bound for low-energy phenomenology related to majoron production. The bound so obtained may also jeopardize the stability of the VEV hierarchy in the doublet and triplet majoron models if the mass of the top quark is less than the W mass. A similar analysis may be applied to other models which exhibit Goldstone-or pseudo-Goldstone-bosons in the spectrum.
Thinking outside the box: effects of modes larger than the survey on matter power spectrum covariance
2012
Considering the matter power spectrum covariance matrix, it has recently been found that there is a potentially dominant effect on mildly non-linear scales due to power in modes of size equal to and larger than the survey volume. This {\it beat coupling} effect has been derived analytically in perturbation theory and while it has been tested with simulations, some questions remain unanswered. Moreover, there is an additional effect of these large modes, which has so far not been included in analytic studies, namely the effect on the estimated {\it average} density which enters the power spectrum estimate. In this article, we work out analytic, perturbation theory based expressions including…
Conditions of a Philosophical Discussion
2020
As its method, philosophy uses argumentative discussion. Philosophy does not often appeal directly to observations or experiences, although they have a place in argumentation as well. Because philosophy is discursive, it delves in the realms of language and the use of language. Defining concepts is a central theme. The rules and argumentation principles of rational discussion are another cornerstone of philosophy. I defend two things that are seen to be conflicting: philosophical relativity and common core rationality. Both are necessary in order to balance each other out. I argue that a certain intuitive and common conception of truth and reality is necessary in order to conduct philosophi…
I Barrai, picapedrers cagliaritani della seconda metà del Cinquecento. Stato degli studi e nuove ipotesi
2014
This essay is focused on the Barrai family, a group of stonecutters operating in Cagliari between 15th and 16th centuries. The family played a leading role in the construction and diffusion of star-shaped rib vaults in the late Sardinian 16th centuries religious architecture. The study attempts to systematize available evidence and information about the Barrai family in order to provide a starting point for further investigation. New hypotheses about the family’s genealogy and activity during the second half of the 16th century are also explored.
Petrogenetic evolution of metabasalts and metakomatiites of the lower Onverwacht Group, Barberton Greenstone Belt (South Africa)
2019
A well-preserved sequence, by Archean standards, of mantle-derived metabasalts and metakomatiites forms large parts of the lower Onverwacht Group of the Barberton Greenstone Belt (South Africa). To elucidate the origin of mafic and ultramafic rocks from this 3.55 to 3.45 Ga sequence, we present a comprehensive geochemical dataset including major and trace elements as well as Lu-Hf and Sm-Nd isotope compositions for a variety of metavolcanic rocks. These include metabasalts of the amphibolite-facies Sandspruit and Theespruit Formations as well as metabasalts and metakomatiites of the lower greenschist-facies Komati Formation. Based on their incompatible trace element patterns, the basalts of…
Coupled silicon-oxygen isotope fractionation traces Archaean silicification
2011
International audience; Silica alteration zones and cherts are a conspicuous feature of Archaean greenstone belts worldwide and provide evidence of extensive mobilisation of silica in the marine environment of the early Earth. In order to understand the process(es) of silicification we measured the silicon and oxygen isotope composition of sections of variably silicified basalts and overlying bedded cherts from the Theespruit, Hooggenoeg and Kromberg Formations of the Barberton Greenstone Belt, South Africa.The δ30Si and δ18O values of bulk rock increase with increasing amount of silicification from unsilicified basalts (-0.64‰ 30Si 18O 30Si and δ18O values as high as + 0.81‰ and + 15.6‰, r…