I. Colantoni

The chemical environment of iron in mineral fibres. A combined X-ray absorption and Mössbauer spectroscopic study

Although asbestos represents today one of the most harmful contaminant on Earth, in 72% of the countries worldwide only amphiboles are banned while controlled use of chrysotile is allowed. Uncertainty on the potential toxicity of chrysotile is due to the fact that the mechanisms by which mineral fibres induces cyto- and geno-toxic damage are still unclear. We have recently started a long term project aimed at the systematic investigation of the crystal-chemistry, bio-interaction and toxicity of the mineral fibres. This work presents a systematic structural investigation of iron in asbestos and erionite (considered the most relevant mineral fibres of social and/or economic-industrial importance) using synchrotron X-ray absorption and Mössbauer spectroscopy. In all investigated mineral fibres, iron in the bulk structure is found in octahedral sites and can be made available at the surface via fibre dissolution. We postulate that the amount of hydroxyl radicals released by the fibers depends, among other factors, upon their dissolution rate; in relation to this, a ranking of ability of asbestos fibres to generate hydroxyl radicals, resulting from available surface iron, is advanced: amosite > crocidolite ≈ chrysotile > anthophyllite > tremolite. Erionite, with a fairly high toxicity potential, contains only octahedrally coordinated Fe(3+). Although it needs further experimental evidence, such available surface iron may be present as oxide nanoparticles coating and can be a direct cause of generation of hydroxyl radicals when such coating dissolves.

Discoloration of the smalt pigment: experimental studies and ab initio calculations

Smalt is a blue pigment used by many European artists in mural and easel paintings, mainly in the period from the XV to XVIII century. It is a potassium glass where cobalt is added to the glassy matrix to get the blue hue. The pigment deteriorates with age, changing its colour from an intense blue to a grey-yellowish hue, causing severe problems in the conservation of the paintings. In this study a set of specimens of smalt dispersed in linseed oil was prepared and artificially aged to simulate the progressive deterioration of the pigment in a painting on canvas. The artificially aged smalt specimens were compared with some samples of naturally aged smalt taken from a banner painted at the end of XV century by Luca Signorelli, the “Baptism of Jesus”. A multi-technique approach, including SEM-EDX, spectro-colorimetry, X-ray absorption spectroscopy and ab initio calculations, was used to understand the progressive discoloration and to reveal its correlation with changes occurring in the pigment structure.

MOD Derived Pyrochlore Films as Buffer Layer for All-Chemical YBCO Coated Conductors

We report a detailed study performed on La2Zr2O7 pyrochlore material grown by the metal-organic decomposition method as buffer layers for YBa2Cu3O7-x (YBCO) coated conductors. High-quality epitaxial LZO thin films have been obtained on single crystal (SC) and Ni-5 %at.W substrates. In order to evaluate structural and morphological properties, films have been characterized by means of X-ray diffraction analyses, atomic force microscopy, and scanning electron microscopy. Precursor solutions and heat treatments have been studied by thermogravimetric analyses and infrared spectra with the aim of optimizing the annealing process. Thin films of YBCO have been deposited by pulsed laser ablation on this buffer layer. The best results obtained on SC showed YBCO films with critical temperature values above 90 K, high self-field critical current density values (Jc >; 1 MA/cm2) and high irreversibility field values (8.3 T) at 77 K together with a rather high depinning frequency νp (0.5 T, 77 K) >; 44 GHz as determined at microwaves. The best results on Ni-5% at.W has been obtained introducing in the heat treatment a pyrolysis process at low temperature in air in order to remove the residual organic part of the precursor solution.

High sensitivity phonon-mediated kinetic inductance detector with combined amplitude and phase read-out

Developing wide-area cryogenic light detectors with baseline resolution better than 20 eV is one of the priorities of next generation bolometric experiments searching for rare interactions, as the simultaneous read-out of the light and heat signals enables background suppression through particle identification. Among the proposed technological approaches for the phonon sensor, the naturally multiplexed Kinetic Inductance Detectors (KIDs) stand out for their excellent intrinsic energy resolution and reproducibility. The potential of this technique was proved by the CALDER project that reached a baseline resolution of 154 ± 7 eV RMS by sampling a 2 × 2 cm2 Silicon substrate with 4 Aluminum KIDs. In this paper, we present a prototype of Aluminum KID with improved geometry and quality factor. The design improvement, as well as the combined analysis of amplitude and phase signals, allowed to reach a baseline resolution of 82 ± 4 eV by sampling the same substrate with a single Aluminum KID.

Ultra high molecular weight polyethylene: Optical features at millimeter wavelengths

Abstract The next generation of experiments for the measurement of the Cosmic Microwave Background (CMB) requires more and more the use of advanced materials, with specific physical and structural properties. An example is the material used for receiver’s cryostat windows and internal lenses. The large throughput of current CMB experiments requires a large diameter (of the order of 0.5 m) of these parts, resulting in heavy structural and optical requirements on the material to be used. Ultra High Molecular Weight (UHMW) polyethylene (PE) features high resistance to traction and good transmissivity in the frequency range of interest. In this paper, we discuss the possibility of using UHMW PE for windows and lenses in experiments working at millimeter wavelengths, by measuring its optical properties: emissivity, transmission and refraction index. Our measurements show that the material is well suited to this purpose.

Development of Lumped Element Kinetic Inductance Detectors for the W-Band

We are developing a lumped element kinetic inductance detector (LEKID) array which can operate in the W-band (75

Al/Ti/Al phonon-mediated KIDs for UV–vis light detection over large areas

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Cryogenic Light Detectors for Background Suppression: The CALDER Project

-110 GHz) in order to perform ground-based cosmic microwave background (CMB) and mm-wave astronomical observations. The W-band is close to optimal in terms of contamination of the CMB from Galactic synchrotron, free-free, and thermal interstellar dust. In this band, the atmosphere has very good transparency, allowing interesting ground-based observations with large (