117,613 research outputs found
Scienze dell’uomo e romanzo: prospettive di studio nella storia letteraria del “tournant des Lumières” francese
No full text
Archeologie del quotidiano. Così lontano, così vicino
No full textLa quotidianità delle rovine urbane che per secoli hanno abitato come presenze familiari l'ambiente di vita dei cittadini e dei viaggiatori, nel corso del Novecento è andata perduta: soltanto artisti, poeti e paesaggisti hanno continuato a interagire con le archeologie, facendole vivere come catalizzatori di energie narrative, per svelarne presenza e poesia, o per immaginare nuove dimensioni del tempo e diverse idee di bellezza.
L’uso pubblico della storia e le rovine strumentali dei regimi totalitari, l’ oggettività delle indagini scientifiche e l’abuso iconografico hanno contribuito ad allontanarci da quei frammenti che, ricomposti nel quadro di un paesaggio storico, oppure nel nostro immaginario, possono ancora raccontarci innumerevoli storie
THE THREE-DIMENSIONAL EVOLUTION OF ION-SCALE CURRENT SHEETS: TEARING AND DRIFT-KINK INSTABILITIES IN THE PRESENCE OF PROTON TEMPERATURE ANISOTROPY
No full textWe present the first three-dimensional (3D) hybrid simulations of the evolution of ion-scale current sheets, with an investigation of the role of temperature anisotropy and associated kinetic instabilities on the growth of the tearing instability and particle heating. We confirm the ability of the ion cyclotron and firehose instabilities to enhance or suppress reconnection, respectively. The simulations demonstrate the emergence of persistent 3D structures, including patchy reconnection sites and the fast growth of a narrow-band drift-kink instability, which suppresses reconnection for thin current sheets with weak guide fields. Potential observational signatures of the 3D evolution of solar wind current sheets are also discussed. We conclude that kinetic instabilities, arising from non-Maxwellian ion populations, are significant to the evolution of 3D current sheets, and two-dimensional studies of heating rates by reconnection may therefore over-estimate the ability of thin, ion-scale current sheets to heat the solar wind by reconnection
MULTIPLE CURRENT SHEET SYSTEMS IN THE OUTER HELIOSPHERE: ENERGY RELEASE AND TURBULENCE
No full textAccepted for publication in The Astrophysical Journal, March 21, 201
L'ipogeo dei Volumni. 170 anni dalla scoperta. I documenti
No full textresponsabile scientifico del progetto di allestimento e ordinamento della mostr
Non-explosive magma–water interaction in a continental setting: Miocene examples from the Eastern Cordillera (central Andes; NW Argentina)
No full text
Effects of atmospheric NOx on biocalcarenite coated with different conservation products
No full textOne of the most important factors of calcareous stone decay is the chemical attack caused by atmospheric pollutants dissolved in water, in particular acidic gases such as SOx, NOx and CO2. The treatment of stone artefacts with hydrophobic products reduces the water uptake of the rock and is, therefore, considered a "protective treatment". The aims of the present study were the observation of the effects of NOx on a biocalcarenite (Lecce stone) and the evaluation of the performance of protective products (Paraloid B72 and a fluoroelastomer) normally used in stone conservation. A system for the simulation of accelerated ageing has been assembled and the Lecce stone samples, treated with polymeric products, have been exposed to NO2 (nearly 1 ppm) during thermo hygrometric cycles. The nitrite and nitrate salts formed on the specimens have been determined by ion chromatography. Both the polymeric products tested have given high hydrophobic properties to the stone, even if they do not assure satisfactory protection toward NO2 exposure. Actually, their protective efficacy, or ability to reduce the acidic attack of NO2, quickly decreases when the ageing period increases. Paraloid B72 seems more effective than fluoroelastomer because, on the samples treated with the latter, higher amounts of nitrites and nitrates have always been detected. In contrast, non-treated samples - used as reference - have shown a constant increase in the amount of nitrates and nitrites during ageing. However, the surface analyses of the stone samples, by environmental SEM and μ-laser profilometry, did not show any change in superficial morphology after the ageing, suggesting that NO2 acts inside the pores
- …
