Study of Late Roman and Byzantine glass by the combined use of analytical techniques

In the present work, we report on a detailed characterization of Late Roman and Byzantine (from 2nd to 8th century A.D.) glass specimen found in Catania (Sicily, Southern Italy) by the employment of two complementary techniques, namely scanning electron microscopy coupled with energy-dispersive spectrometry (SEM–EDS) and Fourier transform infrared (FT-IR) absorbance spectroscopy. The glass fragments come from archaeological excavations in the courtyard of St. Agata la Vetere's church in Catania. In particular, compositional data were obtained by scanning SEM–EDS measurements and the investigation of the degradation on the surface of the glass specimen was made combining the SEM–EDS observations with those performed through FT-IR absorbance. The whole set of results contributed to define the provenance of the specimens. Furthermore, the data furnished new evidences of the technical development of glass production in Late Roman and Byzantine period in Catania.     

Conformational studies of Phe-rich foldamers by VCD spectroscopy and ab initio calculations

Employing VCD spectroscopy, we demonstrate that the structural behavior of the oligomers Boc-(L-Phe-L-Oxd)(n)-OBn is similar from n = 2 to n = 6; ab initio calculations for the n = 1 case provide physical insight into the conformational properties. Further information is gained by IR, (1)H NMR, and ECD spectroscopies. ECD spectra suggest the presence of different conformations between n = 1 on one side and longer chain foldamers on the other side. VCD and absorption IR spectra in methanol solutions can be interpreted as indicative of a PPII structure. In the case of Boc-L-Phe-L-Oxd-OBn, VCD spectra in CCl(4) and detailed DFT computational analysis allow one to demonstrate that the most populated conformers exhibit backbone dihedral angles similar to those of a PPII geometry. This is a remarkable outcome, as we had previously demonstrated that the Boc-(L-Ala-D-Oxd)(n)-OBn series folds in a β-band ribbon spiral that is a subtype of the 3(10) helix.     

Stereoselective synthesis of pseudotripeptides incorporating uncommon bis-α-aminoacid derivatives and X-ray analysis. Part 3

Stereoselective synthesis of pseudotripeptides 4, 5, 6, 8, 9, 13 and 14, incorporating an uncommon bis(α-aminoacid) derivative, has been accomplished starting from the L-valine derived chiral synthon 1. The configuration of the introduced stereogenic centres has been assigned on the basis of ¹H NMR spectroscopic data. The geometry of the tripeptides, deduced on the basis of ¹H NMR parameters and IR spectra, was confirmed by X-ray crystal structure analysis of 6.     

Temperature sensing with thermochromic liquid crystals

A review of the most recent developments in the application of thermochromic liquid crystals to fluid flow temperature measurement is presented. The experimental aspects including application, illumination, recording, and calibration of liquid crystals on solid surfaces, as well as in fluid suspensions, are discussed. Because of the anisotropic optical properties of liquid crystals, on-axis lighting/viewing arrangements, combined with in-situ calibration techniques, generally provide the most accurate temperature assessments. However, where on-axis viewing is not possible, calibration techniques can be employed, which reduce the uncertainty associated with off-axis viewing and lighting arrangements. It has been determined that the use of hue definitions that display a linear trend across the color spectrum yield the most accurate correlation with temperature. The uncertainty of both wide-band and narrow-band thermochromic liquid crystal calibration techniques can be increased due to hysteresis effects, which occur when the temperature of the liquid crystals exceeds their maximum activation temperature. Although liquid crystals are commonly used to provide time-mean temperature measurements, techniques are available which allow the monitoring of temporal changes. Selected examples illustrating the use of thermochromic liquid crystals are shown, and a survey of reported temperature measurement uncertainties is presented. Received: 3 February 1999/Accepted: 30 March 2000     

Pigments characterization of polychrome vases production at Lipára: New insights by noninvasive spectroscopic methods

One of the most impressive Sicilian pottery production is attributed to the so‐called Lipari Painter and his followers, whose vessels—found in the archeological site of Lipari (Aeolian Island, Sicily)—are decorated with characteristic blue, red, and white figures. From the archeological point of view, these artworks keep open many questions concerning dating, production technique, and cultural background. In this context, new data on the manufacture procedures and on the raw materials used for the pigments may contribute to a deeper comprehension of this early Hellenistic vase tradition. The preciousness of the vessels, exhibited at the Archeological Museum of Lipari, imposed the use of in situ nondestructive methods to address new insights on the nature of the colored layers. Thus, analyses by Raman and X‐ray fluorescence spectroscopy have been performed with portable instruments on a selection of vessels certainly attributed to Lipari Painter and to some others of his followers. The results of this study testify the use of different pigments: kaolin and gypsum, probably supplied locally, for white layers; Egyptian blue for blue hues; red ochre for brown‐reddish hues; and cinnabar for pink and red‐purple nuances. The identification of both Egyptian blue and cinnabar opens an interesting discussion about dating and circulation of the raw materials.     

HPLC/PDA/ESI-MS evaluation of saffron (Crocus sativus L.) adulteration

The present study evaluated the reliability of the ISO/TS 3632-2 UV-Vis spectrometric method for saffron classification, making experiments on saffron samples to which were added increasing concentrations of common saffron spice adulterants (safflower, marigold and turmeric). The results showed that the ISO/TS 3632-2 method is not able to detect addition of up to 10-20%, w/w, of saffron adulterants. For additions from 20 to 50%, w/w, of the three adulterants, saffron was classified in a wrong category; addition of higher than 50%, w/w, determined variations in the investigated parameters that did not allow identification of the product as "saffron". In all cases, the method did not permit the recognition of the nature of the adulterant. On the contrary, the specificity of the HPLC/PDA/MS technique allowed the unequivocal identification of adulterant characteristic marker molecules that could be recognized by the values of absorbance and mass. The selection of characteristic ions of each marker molecule has revealed concentrations of up to 5%, w/w, for safflower and marigold and up to 2% for turmeric. In addition, the high dyeing power of turmeric allowed the determination of 2%, w/w, addition using exclusively the HPLC/PDA technique.     

A high-accuracy calibration technique for thermochromic liquid crystal temperature measurements

There are a variety of phenomena which may impact the accuracy of wide-band thermochromic liquid crystal temperature measurements, including: irregularities in liquid crystal and black paint layers, reflective components from light sources, and variations in the lighting/viewing angle across the surface. A wide-band calibration technique has been developed which inherently accounts for these and other sources of uncertainty by employing a point-wise calibration of the entire test surface. Both on and off-axis lighting arrangements are assessed for ease of implementation and accuracy of color displayed under uniform temperature conditions. The technique employs a series of uniform-temperature images to construct calibration curves relating the local hue component to temperature in a point-wise manner for the entire test surface. An off-axis lighting/viewing arrangement is found to be most practical for typical experimental setups. Hysteresis effects are quantified for excursions beyond both the lower and upper clearing point of the liquid crystals. Finally, the total uncertainty of the measured temperature is determined to vary from ±1.2% to ±7.2% across the bandwidth of the liquid crystals. Received: 21 October 1998/Accepted: 7 August 1999