On semi-classical weight functions on the unit circle

We consider orthogonal polynomials on the unit circle associated with certain semi-classical weight functions. This means that the Pearson-type differential equations satisfied by these weight functions involve two polynomials of degree at most 2. We determine all such semi-classical weight functions and this also includes an extension of the Jacobi weight function on the unit circle. General structure relations for the orthogonal polynomials and non-linear difference equations for the associated complex Verblunsky coefficients are established. As application, we present several new structure relations and non-linear difference equations associated with some of these semi-classical weight functions.Comment: 26 page

Clasificación de los revoques multiestratificados del claustro de S. Abbondio en Como (Italia): un instrumento analítico para la arqueología de la arquitectura

S. Abbondio (Como, Italia) es una de las mas extraordinariasbasilicas romanicas presentes en el norte de Italia.El edificio entero y en particular el claustro ha sido expuestoa varias intervenciones durante los ultimos siglos, enparticular los ultimos trabajos de conservacion ejecutadosentre los anos 2000 y 2003. En esta ocasion se ha efectuadouna vasta campana diagnostica sobre los revoquestanto internos como externos, destinada a clasificarlosdesde el punto de vista compositivo-morfologico y paradescubrir la historia sobre la conservacion del claustro.Revoques representativos de las diferentes fases constructivashan sido identificados con la utilizacion de metodoscomo el analisis de difraccion de rayos X en polvo,porosimetria por intrusion de mercurio, microscopia opticapara secciones finas y espectrometria atomica. Losresultados han permitido agrupar las muestras que presentabancaracteristicas similares, confirmando hipotesishistoricas sobre la secuencia de las intervenciones en eledificio, sugiriendo un metodo analitico que podria serusado como un instrumento valido en caso de estudiossobre la arqueologia de la arquitectura

Unveiling the complexity of japanese metallic threads

In the framework of an extensive survey campaign on a collection of Japanese samurai armors, metallic threads from different parts of the traditional equipment were studied by several analytical techniques. The collection of armors belongs to Museo delle Culture (Lugano, Switzerland) and it is composed of ten elements, which date back from the 15th to 20th century. Metallic threads under study come from six of ten elements of the collection and represent a complex and unique multimaterial, which shows specific characteristics in Japanese tradition (kinran). The multianalytical approach based on ATR-FTIR spectroscopy and SEM-EDX analysis, together with a careful observation with optical and digital microscopy, permitted to obtain a complete characterization of materials, which have shown a great variability in metal foils and in organic adhesives (urushi, animal glue, starch). Gold and silver turned out to be not so largely used as scholars thought, while aluminum showed a great diffusion. Within the collection of analyzed armors, the obtained results allowed us for the first time to get a complete comprehension of materials and techniques used by Japanese craftsmen, and to observe differences in the quality of the materials and in manufacture technology over the centuries

Differentiating between Natural and Modified Cellulosic Fibres Using ATR-FTIR Spectroscopy

This paper presents the limitations and potential of ATR-FTIR spectroscopy applied to the study of cellulosic textile collections The technique helps to differentiate natural fibres according to the content of lignin, pectin, hemicellulose, and wax, although some problematic issues should be considered. The spectral differences derived from the environmental humidity uptake and the plant composition are reviewed and discussed in the light of new experimental data. Diagnostic bands are proposed that can discriminate between different fibres from different plants. The contribution of ageing is also considered, demonstrating that sometimes aged fibres cannot be reliably recognised. In contrast, the potential of ATR-FTIR spectroscopy to discriminate between natural and modified fibres is discussed and proven. The best results were obtained when microinvasive ATR-FTIR spectroscopy was coupled with SEM observations. The proposed protocol was tested on microsamples of various cellulosic materials from traditional Japanese samurai armours dating from the 16th to the 20th centuries (Morigi Collection, Museo delle Culture, Lugano, Switzerland). The results facilitated a complete characterisation of the materials and demonstrated that the protocol can be used to study a wide variety of cellulosic materials, including both natural and man-modified fibres, and paper

How to clean and safely remove HF from acid digestion solutions for ultra-trace analysis: a microwave-assisted vessel-inside-vessel protocol

The complete dissolution of silicate-containing materials, often necessary for elemental determination, is generally performed by microwave-assisted digestion involving the forced use of hydrofluoric acid (HF). Although highly efficient in dissolving silicates, this acid exhibits many detrimental effects (e.g., formation of precipitates, corrosiveness to glassware) that make its removal after digestion essential. The displacement of HF is normally achieved by evaporation in open-vessel systems: atmospheric contamination or loss of analytes can occur when fuming-off HF owing to the non-ultraclean conditions necessarily adopted for safety reasons. This aspect strongly hinders determination at the ultra-trace level. To overcome this issue, we propose a clean and safe microwaveassisted procedure to induce the evaporative migration of HF inside a sealed \u201cvessel-inside-vessel\u201d system: up to 99.9% of HF can be removed by performing two additional microwave cycles after sample dissolution. HF migrates from the digestion solution to a scavenger (ultrapure H2O) via a simple physical mechanism, and then, it can be safely dismissed/recycled. The procedure was validated by a soil reference material (NIST 2710), and no external or cross-contamination was observed for the 27 trace elements studied. The results demonstrate the suitability of this protocol for ultra-trace analysis when the utilization of HF is mandatory

Historical silk: a novel method to evaluate degumming with non-invasive infrared spectroscopy and spectral deconvolution

: To correctly manage a collection of historical silks, it is important to detect if the yarn has been originally subjected to degumming. This process is generally applied to eliminate sericin; the obtained fiber is named soft silk, in contrast with hard silk which is unprocessed. The distinction between hard and soft silk gives both historical information and useful indications for informed conservation. With this aim, 32 samples of silk textiles from traditional Japanese samurai armors (15th-20th century) were characterized in a non-invasive way. ATR-FTIR spectroscopy has been previously used to detect hard silk, but data interpretation is challenging. To overcome this difficulty, an innovative analytical protocol based on external reflection FTIR (ER-FTIR) spectroscopy was employed, coupled with spectral deconvolution and multivariate data analysis. The ER-FTIR technique is rapid, portable, and widely employed in the cultural heritage field, but rarely applied to the study of textiles. The ER-FTIR band assignment for silk was discussed for the first time. Then, the evaluation of the OH stretching signals allowed for a reliable distinction between hard and soft silk. Such an innovative point of view, which exploits a "weakness" of FTIR spectroscopy-the strong absorption from water molecules-to indirectly obtain the results, can have industrial applications too

Understanding the microstructure of mortars for cultural heritage using X-ray CT and MIP

In this study, the microstructure of mock-up mortar specimens for a historic environment, composed of different mixtures, was studied using mercury intrusion porosity (MIP) and micro-computed tomography (\ub5CT), highlighting the advantages and drawbacks of both techniques. Po-rosity, sphericity, and pores size distribution were studied, evaluating changes according to mortar composition (aerial and hydraulic binders, quartz sand, and crushed limestone aggregate). The \ub5CT results were rendered using 3D visualization software, which provides complementary information for the interpretation of the data obtained using 3D data-analysis software. Moreover, \ub5CT contrib-utes to the interpretation of MIP results of mortars. On the other hand, MIP showed significant ink-bottle effects in lime and cement mortars samples that should be taken into account when interpret-ing the results. Moreover, the MIP results highlighted how gypsum mortar samples display a porosity distribution that is best studied using this technique. This multi-analytical approach provides important insights into the interpretation of the porosimetric data obtained. This is crucial in the characterization of mortars and provides key information for the study of building materials and cultural heritage conservation

Digitatio and Scientific Exploitation of the Italian and Vatican Astronomical Plate Archives

There is a widespread interest to digitize the precious information contained in the astronomical plate archives, both for the preservation of their content and for its fast distribution to all interested researchers in order to achieve their better scientific exploitation. This paper presents the first results of our large-scale project to digitize the archive of plates of the Italian Astronomical Observatories and of the Specola Vaticana. Similar systems, composed by commercial flat-bed retro-illuminated scanners plus dedicated personal computers and acquisition and analysis software, have been installed in all participating Institutes. Ad-hoc codes have been developed to acquire the data, to test the suitability of the machines to our scientific needs, and to reduce the digital data in order to extract the astrometric, photometric and spectroscopic content. Two more elements complete the overall project: the provision of high quality BVRI CCD sequences in selected fields with the Campo Imperatore telescopes, and the distribution of the digitized information to all interested researchers via the Web. The methods we have derived in the course of this project have been already applied successfully to plates taken by other Observatories, for instance at Byurakan and at Hamburg.Comment: To appear in Experimental Astronom

Two-step analytical procedure for the characterization and quantification of metal soaps and resinates in paint samples

Metal soaps and resinates are known to be spontaneously formed in artistic paintings, as a product of the reaction between aliphatic and terpenoid acids released by hydrolysis and oxidation of the organic media and certain cations contained in some inorganic pigments. In this paper we present an optimization and the validation of a GC/MS method for the qualitative and quantitative analysis of mixtures of terpenoid acids and aliphatic mono and dicarboxylic acids and metal carboxylates of terpenoid and aliphatic mono and dicarboxylic acids in the same paint microsample. This is based on a two-step analytical approach entailing the subsequent use of two silylating agents, N,O-bis(trimethylsilyl)trifluoroacetamide for the analysis of free acids and metal carboxylates, and 1,1,1,3,3,3-hexamethyldisilazane for the analysis of free acids. The application of this approach is possible because of the good stability at room temperature of the TMS derivatives of aliphatic and terpenoid species, characterized by high boiling points and relatively low vapour pressures. The method was then applied to the characterization of samples collected from two reference paint layers aged for 20 years, a paint sample taken from a pulpit, and sample of the varnish coating of a wooden writing desk, both from the second half of the seventeenth century