101 research outputs found
Giotto in the Chapel of the Scrovegni: EDXRF analysis of the golden haloes with portable equipment
No full textEnergy-dispersive x-ray fluorescence (EDXRF) analysis is particularly suited to analyse paintings, because it does not significantly damage the sample and allows the measurement of several elements in a single measurement. The use of portable equipment allows a completely non-destructive analysis, although the interpretation of the measured spectra requires a more accurate approach.
EDXRF analysis of paintings generally gives the following information: identification of the elements, and therefore pigments, employed by the artist; possible presence of elements on the surface (sulphur, chlorine) due to pollution effects; identification of previous restoration areas, through the presence of 'modern' elements, such as titanium, zinc, cadmium and others.
Recently, the famous Chapel of the Scrovegni, painted by Giotto in Padua in 1303-05, was analysed in detail to obtain the above information and, more specifically, to analyse the golden haloes. In this paper the measurement of sulphur on the surface of the frescoes is described, together with the composition of the golden haloes
A portable apparatus for energy dispersive X-ray fluorescence analysis of sulfur and chlorine in frescoes and stone monuments
No full textElectronic structure of ScN
No full textThe optical reflectivity has been measured over more than four decades of photon energy on chemically well-defined single crystals of ScN, in addition to the electrical conductivity and the Hall effect. From a Kramers-Kronig analysis the dielectric functions have been derived. A plasmon-phonon coupling (plasmaron) has been observed in the far-infrared region which could be decomposed and the phonon part of which compared with a Raman measurement of the phonon density of states. The interpretation of the optical results in a two-band model together with other data confirms recent theoretical estimates of the electron and hole masses and of the charge-carrier density in this compound, which we find is a compensated semimetal
GROWTH AND OPTICAL STUDIES OF OPALS AS THREE-DIMENSIONAL PHOTONIC CRYSTALS
No full textThree-dimensional artificial opals showing photonic crystals properties are grown by self-assembly of polystyrene nanospheres. Atomic
force microscopy (AFM) images of opal surfaces show domains with regular triangular and squared packing of the spheres separated by
cracks whose relative fraction depends on the sample quality. The energy position of an optical pseudo gap in transmittance spectra is
observed by varying the angle of incidence and is accounted for by theoretical calculations of the photonic band structure based on a planewave
expansion method
Valutazione dei fenomeni corrosivi in corso sulla superficie della statua equestre dell'Imperatore Marco Aurelio
No full textIl monumento equestre in bronzo di Marco Aurelio ha recentemente subito un intervento di restauro che ne ha rimesso in luce la patina naturale e parte della doratura superficiale. In vista di una possibile ricollocazione della statua sulla Piazza del Campidoglio di Roma, è stato intrapreso uno studio sulle condizioni attuali di conservazione e sui più idonei metodi di protezione superficiale
Polarized optical and photoluminescence properties of highly oriented poly(p-phenylene-vinylene)
No full textWe report on the anisotropic reflectance (R), transmitlatice (T) and photoluminescence (PL) properties of stretch-oriented free standing films of poly(phenylene-vinylene) (PPV) at different temperatures. The PL quantum efficiency is strongly dependenl on the pumo polarization, being higher when pump is polarized perpendicular lo the polymer chain orientation. Independently of the pump polarization, we find that the PL emission spectra are mainly polarized along the polymer chain direction. The PL spectra have been corrected both for the number of absorbed photons and for self-absorption of the emitted light.
Frank-Condon analysis of the oscillator strengrh for absorption and corrected emission spectra suggest that two different "chromophores" contribute to the optical properties
Optical characterization of hierarchically self-assembled GaAs/AlGaAs quantum dots
No full textRecently, a simple method has been developed to obtain inverted GaAs/AlGaAs quantum dots (QDs) below a quantum well (QW) via multi-step (hierarchical) self-assembly [1]. Here we report on the optical characterization of a series of structures GaAs QDs with different size. The study is performed by means of reflectance (R) down to T=15 K, photo- and thermo-reflectance
(T>80 K) and by spectroscopic ellipsometry (at RT). Such measurements allow us to check the thickness and composition of the barrier layers and to complete the study of the electronic states involved in the emission properties of QDs and QW levels. QW states were well identified and their energies and shift with the size parameters well agree with the photoluminescence (PL)
data. The identification of QD states seems less straightforward in R measurements and deserves further investigation
EVOLUTION OF A METALLIC AND MAGNETIC STATE IN (Fe, Mn)Si AND Fe(Si, Ge)
No full textAn analysis of the pressure-dependent resistivity of FexMn1-xSi(1 less than or equal to x less than or equal to 0.82) and FeSixGe1-x (1 less than or equal to x less than or equal to 0.6) alloys in terms of a Kondo insulator description revealed a pressure-induced opening of the narrow gap. A negative magnetoresistance is observed for Fe-rich alloys of FexMn1-xSi at elevated temperatures
The golden altar of S. Ambrogio in Milan: non destructive XRF-analysis with a portable apparatus
No full text- …
