Papers by Andreas Karydas
ABSTRACT In contrast to other 16th and 17th century painters whose work has been extensively stud... more ABSTRACT In contrast to other 16th and 17th century painters whose work has been extensively studied, information regarding Theotokopoulos works is very scarce technical and poorly documented. The restoration of El Greco’s Baptism of Christ, by the Conservation Department of the Benaki Museum, Athens, provided a unique opportunity to examine, analyze and document the materials and other technical aspects of the painting by use of non-destructive physicochemical techniques A series of such non destructive analytical techniques were applied prior to the conservation procedure , X-ray radiography, computer aided tomography (CAT), multi-spectral (UV-Visible-IR) imaging, optical microscopy and X-ray fluorescence spectroscopy (XRF). Following completion of the restoration works, the painting was analyzed by use of near infrared (FT-NIR) and laser induced breakdown spectroscopy (LIBS). In addition, scanning electron microscopy combined with energy dispersive X-ray analysis (SEM/EDXA) was applied on selected micro-samples obtained during the conservation process . The conclusions obtained from the above mentioned analyses provided solid ground for the safe characterisation of the materials, the collection of technical information regarding the creation of the work, but also the accurate definition of various alterations of the work during previous restoration attempts. The “Baptism of Christ”, dating from 1567 , as established by the present analysis, was painted by El Greco soon after his arrival in Venice, where it is believed that he joined Titian’s workshop and became acquainted with the works of Tintoretto and of the Venetian School. Recent studies of the material and technical aspects of late 16th - early 17th century Venetian paintings have brought to light specific information relating to individual masters such as Titian, Tintoretto, Bellini, Lotto and others. Such specific information is lacking for El Greco of this period and the results presented here are discussed in the light of these recent analyses of other Renaissance Venetian painters. The examination of the painting by use of various wave lengths (UV, Visible, IR, X-ray) has lead us to the conclusion that Theotokopoulos has applied an imprimatura, rich in lead white and used a brush for the underdrawing, to which he made several alterations. The extent of recent overpaintings as well as the partially destroyed date MDLXVII (1567) under these was also revealed. The pigments used fort the blue were lapis lazuli (LIBS technique); smalt -cobalt rich glass (XRF) for the light blue; and well crystalised azurite (XRF) for the dark blue of the sky (center of panel) and Christ’s loincloth. Gold paint has been used for the details of Christ’s loincloth and the date. Umber, possibly mixed with organic black has been used, for the brown and black. Arsenic sulfides (orpiment and/or realgar) mixed with umber and yellow ochre for the orange garment of the right angel and most probably verdigris (basic copper acetate) for the foliage of the trees and the green garment of the right angel which in an oil medium forms a copper glaze. Organic red (lake) has been identified in St John’s garment, the towel held by the angel and the red tints in the sky. Cinnabar has been used for the miniature orange-red figure which stands out in the crowd on the bank of the river Jordan (between St John and Christ); cinnabar, possibly in thin underlying layers, has also been used for the flesh of Christ while the shadows are rendered with umber. Lead tin yellow type II (mixed with lead-tin type I) has been used selectively for the yellow leaves of the trees and the yellow highlights of the sky around the Holy Spirit. Poorly crystallized azurite, ochre and gypsum have been used for the coloring of the wooden substrate (on both sides of the arch) into which the panel was laid after its separation from the original triptych. Ti¬tanium oxide and a blue that is non-identifiable by XRF were used for an extended retouching on the sky in an attempt to cover cracks and craquelure, clearly visible under UV imaging. Titanium oxide has also been used for the most recent retouching of the painting, either before or on the oc¬casion of the appearance of the panel on the market.
Fine-particle pollution in large populated Asian cities can be very high compared with internatio... more Fine-particle pollution in large populated Asian cities can be very high compared with internationally accepted health goals. Much of this fine-particle pollution is produced by motor vehicles, fossil-fuel combustion, industrial processes and even windblown soils from desert regions. As part of a long term project in the Asian region with support from the IAEA, ANSTO has been using nuclear techniques not only to characterize fine-particle pollution, but also to quantify their sources and origins within Vietnam. Fine particles in ambient air are defined as those particles with aerodynamic diameters less than 2.5 μm in diameter. Particles in this size range can be directly absorbed into the blood stream from the lungs, are most efficient at absorbing and scattering visible light and can travel thousands of kilometres from their original source emission points. A full characterisation of these particles, their sources and their origins will help regulators better understand and hence c...
Nanomaterials, 2021
Polymer nanocomposites have emerged as a new powerful class of materials because of their versati... more Polymer nanocomposites have emerged as a new powerful class of materials because of their versatility, adaptability and wide applicability to a variety of fields. In this work, a facile and cost-effective method to develop poly(methyl methacrylate) (PMMA)-based polymer nanocomposites with copper oxide (CuO) nanofillers is presented. The study concentrates on finding an appropriate methodology to realize CuO/PMMA nanocomposites that could be used as resist materials for e-beam lithography (EBL) with the intention of being integrated into nanodevices. The CuO nanofillers were synthesized via a low-cost chemical synthesis, while several loadings, spin coating conditions and two solvents (acetone and methyl ethyl ketone) were explored and assessed with regards to their effect on producing CuO/PMMA nanocomposites. The nanocomposite films were patterned with EBL and contrast curve data and resolution analysis were used to evaluate their performance and suitability as a resist material. Mi...
Thirteen glasses from the Byzantine Church of Transfiguration of the Saviour in Metamorfosis in M... more Thirteen glasses from the Byzantine Church of Transfiguration of the Saviour in Metamorfosis in Messinia, Peloponnese, dating back to the Middle Byzantine Period (12 th century A.D.), have been analyzed. The methodology adopted aimed to identify the chemical properties of the glasses and the methods used were the following complementary techniques: Optical Microscopy (OM) for preliminary morphological observations, Scanning Electron Microscopy coupled with Energy-Dispersive X-ray Spectrometry (SEM-EDS) for high-resolution morphological examination and qualitative chemical analyses and Micro X-ray Fluorescence Spectrometry (μ-XRF) for the detection of trace elements. The chemical characterization of the glasses allowed the discrimination between different glass groups and the identification of raw materials and technological traditions of their production. Fundamental changes in the production processes occurred from the 8 th-9 th century A.D. onwards, when mineral soda was gradually replaced by organic plant ash. These changes in the raw materials are reflected in the chemical composition of the glasses. The major components of the glasses are silicon dioxide (SiO 2) , sodium oxide (Na 2 O), and calcium oxide (CaO) and the samples can be classified as soda-limesilica glass. Most of the fragments revealed an intermediate composition a combination of natron and plant ash glass. Among the samples a glass composition with a certain amount of plant ash was also identified, an indication of a new glass composition introduced after several centuries in which natron glass was dominating glass production. Micro X-ray Fluorescence Spectrometry (μ-XRF) results highlighted the elements responsible for coloring and indicate the possibility for the glasses to be obtained through recycling processes, clarifying production technology issues. Finally, it is possible to assume as the source of the raw glass to have been the Middle East.
Technè, 2014
Un microcosme de couleur et d'éclat. La polychromie des lits de banquets chryséléphantins de la M... more Un microcosme de couleur et d'éclat. La polychromie des lits de banquets chryséléphantins de la Macédoine antique
Analytical chemistry, Jan 7, 2018
This work presents a state-of the-art analytical methodology, by which chemical state information... more This work presents a state-of the-art analytical methodology, by which chemical state information of metallic elements is obtained for liquid samples in a fast and simple manner. This method overcomes limitations of conventional x-ray techniques, such as x-ray absorption spectroscopy, by applying Resonant Inelastic X-Ray Scattering under Total Reflection geometry (TRIXS). TRIXS is particularly applicable for the analysis of small quantity of liquid samples deposited on polished reflectors. This feature is relevant for the chemical speciation of metallic trace elements contained in water samples, since the degree of their toxicity depends crucially on the concentration of specific chemical species included. The analytical merits of the proposed methodology were studied at Elettra Sincrotrone Trieste and at the Brazilian Synchrotron Light Laboratory. Contaminated water samples with low concentration of different chromium and manganese compounds were measured. Results prove the analyti...
Journal of synchrotron radiation, 2018
The International Atomic Energy Agency (IAEA) jointly with the Elettra Sincrotrone Trieste (EST) ... more The International Atomic Energy Agency (IAEA) jointly with the Elettra Sincrotrone Trieste (EST) operates a multipurpose X-ray spectrometry endstation at the X-ray Fluorescence beamline (10.1L). The facility has been available to external users since the beginning of 2015 through the peer-review process of EST. Using this collaboration framework, the IAEA supports and promotes synchrotron-radiation-based research and training activities for various research groups from the IAEA Member States, especially those who have limited previous experience and resources to access a synchrotron radiation facility. This paper aims to provide a broad overview about various analytical capabilities, intrinsic features and performance figures of the IAEA X-ray spectrometry endstation through the measured results. The IAEA-EST endstation works with monochromatic X-rays in the energy range 3.7-14 keV for the Elettra storage ring operating at 2.0 or 2.4 GeV electron energy. It offers a combination of d...
AIP Conference Proceedings, 1999
... 1.414 Rba - .~[JK,s(EI/E2)nj +1 ] where JK,s is the absorption jump of the mass absorption co... more ... 1.414 Rba - .~[JK,s(EI/E2)nj +1 ] where JK,s is the absorption jump of the mass absorption coefficient in the sample at the K-edge of the j element. ... CuK~ copper 7.10 940 Co 716 2.3 254 CoK~ iron 6.20 187 Mn 680 8.6 999 FeK~ iron 5.70 712 Cr 725 2.2 240 462 Page 4. ...
AIP Conference Proceedings, 1999
ABSTRACT
1999 IEEE Nuclear Science Symposium. Conference Record. 1999 Nuclear Science Symposium and Medical Imaging Conference (Cat. No.99CH37019)
A charge sensitive readout chain has been designed for pixel applications with small die area and... more A charge sensitive readout chain has been designed for pixel applications with small die area and low power dissipation. The tests in an X-ray environment have been performed with a detector integrated on the same substrate with the electronics. It consists of a 20 μm×20 μm diode, which is DC coupled to the input of the readout chain. The system
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2004
The proton induced Kα X-ray emission spectra of pure and some compound targets of sulfur were mea... more The proton induced Kα X-ray emission spectra of pure and some compound targets of sulfur were measured with a crystal spectrometer in Johansson geometry, which enables energy resolution below the natural linewidth of the measured Kα line. From these measurements the absolute energies of the S-Kα1,2 lines were experimentally determined. In addition, the energies of the KαL1 X-ray satellite lines, appearing in these spectra as a result of the radiative decay of atomic states with one hole in the K shell and one in the L subshells, were also measured. The measured Kα diagram and satellite line energies depend crucially on the S chemical state. The measured diagram line energies, as well as their relative intensity ratios obtained from the X-ray spectra of different S compounds, allow the deconvolution of X-ray spectra of mixed targets containing two different S compounds and the accurate determination of their mass ratio. Finally, the proton induced S-Kα X-ray spectrum from an aerosol sample was collected and the measured energies of the Kα1,2 lines were used to specify the chemical state of S in the aerosol as a sulfate ([SO4]2−). In conclusion, the results of the present paper demonstrate that the S-Kα1,2 emission energies depend on the S chemical state and, therefore, their determination allows the chemical state speciation of S in a given sample.
Spectrochimica Acta Part B: Atomic Spectroscopy, 2001
Uranium has been classified as a toxic chemical. It affects the kidneys, with nephritis being the... more Uranium has been classified as a toxic chemical. It affects the kidneys, with nephritis being the primarily chemically-induced effect in animals and humans. Intermediate-term studies on animals indicate that increased uranium doses are positively correlated with various biochemical effects and histopathological changes. Since the kidneys efficiently excrete in urine the major portion of solubilized uranium circulating in blood, an increased urinary uranium excretion can provide a sensitive quantitative measure of exposure, especially in the case of acute exposure. In the present work a method was developed for the quantitative determination of uranium in human urine. It combines the chemical treatment of urine, which results in a significant pre-concentration of uranium, with its Ž. subsequent detection by means of total reflection X-ray fluorescence TXRF. The method has been proven to be relatively fast, offering detection limits that allow for monitoring uranium intake above normal levels.
Spectrochimica Acta Part B: Atomic Spectroscopy, 2001
Ž. Total Reflection X-Ray Fluorescence TXRF is a well-established method, mainly applied in the a... more Ž. Total Reflection X-Ray Fluorescence TXRF is a well-established method, mainly applied in the analysis of liquid samples, offering very low detection limits in most of the cases. Direct application of the TXRF method is not so efficient in blood serum analysis, since the high content of the organic matrix increases significantly the background due to Compton scattering. Chemical treatment of the blood serum samples and related preconcentration techniques have been suggested in the literature, but they are time consuming and increase the possibility of adding contaminants in the sample. In this paper, the applicability of direct TXRF analysis in blood serum samples is examined. The insertion of a Mo filter, after the cutoff reflector, has been found to improve significantly the peak-to-background ratio, especially for the elements of interest such as Cu, Zn, Se and Br. The influence of self-absorption phenomena in the quantification procedure was also investigated with respect to the internal standard used and the sample mass analyzed. Precision and accuracy in the analysis was found to be approximately 4% over the whole atomic number range.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2002
Ion Beam Analysis (IBA) techniques are established as an indispensable tool for material analysis... more Ion Beam Analysis (IBA) techniques are established as an indispensable tool for material analysis. They are very powerful when applied to the examination of uniform layers. In recent years they have been also used for the quality control of implanted layers, which improve the mechanical or chemical properties of common materials. The use of IBA techniques for the study of corrosion is impeded by the non-uniformity of such layers, which renders the analysis difficult. In the Material Analysis Laboratory of the Institute of Nuclear Physics, a combination of experimental techniques and analytical algorithms has been developed, which allows the non-destructive examination of corrosion layers on cultural artifacts. Ancient glass fragments from Kenchreai, Greece, were analyzed with ion beam techniques, in order to examine the applicability of the latter to the characterization of the surface. The relative distribution of heavy components was determined by X-Ray Fluorescence (XRF). Nuclear reactions were used to determine the depth distribution of H, O, C and Si. The Hydrogen distribution rises sharply from the surface, reaching a maximum of 9xl0 22 at/cm 3 at 0.5 μπι and then decays smoothly to a depth of approximately 2 μπα. Examination of the same samples with aparticles, indicates a depletion of Silicon in the same surface region, while the Oxygen distribution is uniform. A detailed analysis, using the 28 Si(p, p) reaction, which resonates at 2.095 MeV, confirms the depletion and other non-uniformities in the Silicon distribution.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2000
A new method has recently been proposed for the simulation and analysis of channeling spectra in ... more A new method has recently been proposed for the simulation and analysis of channeling spectra in the backscattering geometry [1], based on reaction cross sections and the assumption that beam particles escape from the aligned direction at an exponential rate. The success of the method in the system p+ 28 Si cut along the <100> plane [2] led to the investigation of more complicated crystal structures and beam-target combinations, namely a+MgO and a+A^Oa, which revealed the prospects as well as the limitations of the method [3]. In the present work channeling spectra of protons in a 28 Si crystal cut along the <111> plane, in the energy region E p = 1.7-2.4 MeV are studied and analyzed. The measured backscattering spectra are reproduced by computer simulations and an attempt is made to describe the differences between the <100> and the <111> axis in the silicon crystal and their subsequent effect on the stopping power of channeled protons. The results are compared with those of methods reported in the past at different energy regions of the incoming protons [4,5].
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Papers by Andreas Karydas