Ancient silver extraction in the Montevecchio mine basin (Sardinia, Italy): micro-chemical study of pyrometallurgical materials

Different pyrometallurgical materials such as slags, refractory materials and thermally treated lead ores likely related to smelting and extractive processes and chronologically related to Punic and Roman periods (IV–III BC) have been found at Bocche di Sciria and Conca e Mosu in the Montevecchio mine basin (south western Sardinia, Italy), where archaeological findings and classical authors locate extractive metallurgy activities since pre-Roman times. By means of the combined use of X-ray diffraction (XRD), scanning electron microscopy (SEM) combined with energy-dispersive X-ray spectrometry (EDS), selected-area X-ray photoelectron spectroscopy (XPS) and optical microscopy (OM), micro-chemical and micro-structural investigations have been carried out in order to identify the nature of the pyrometallurgical materials, to decipher the processes carried out there and their technological steps and to determine the technological level of competence reached by the ancient metallurgists. The results confirm that the findings can be associated with smelting and extractive processes carried out close to the metal ore deposits first for the argentiferous lead production and, then, for the silver recovery via a cupellation process. Finally, the results disclose the high level of technological competence of the ancient metallurgists able to carry out complex high-temperature processes to treat the argentiferous lead ores and to recover low amounts of silver via high-temperature lead-selective oxidation.     

Experimental NMR and MS study of benzoylguanidines. Investigation of E/Z isomerism

Molecules containing the guanidinic nuclei possess several pharmacological applications, and knowing the preferred isomers of a potential drug is important to understand the way it operates pharmacologically. Benzoylguanidines were synthesized in satisfactory to good yields and characterized by NMR, Electrospray Ionization Mass Spectrometry (ESI‐MS) and Fourrier Transform InfraRed Spectroscopy techniques (FTIR). E/Z isomerism of the guanidines was studied and confirmed by NMR analysis in solution (¹H‐¹³C Heteronuclear Single Quantum Coherence (HSQC) and Heteronuclear Multiple‐Bond Correlation (HMBC), ¹H‐¹⁵N HMBC, ¹H‐¹H Correlation Spectroscopy (COSY) and Nuclear Overhauser Effect Spectroscopy (NOESY) experiments) at low temperatures. Compounds with p‐Cl and p‐Br aniline moiety exist mainly as Z isomer with a small proportion of E isomer, whereas compounds with p‐NO2 moiety showed a decrease in proportion of isomer Z. The results are important for the application of these molecules as enzymatic inhibitors. Copyright © 2013 John Wiley & Sons, Ltd.     

Hiv-1 Specific Reverse Transcriptase Inhibitors: why are Tsao-Nucleosides so Unique?

1. INTRODUCTION

AIDS will still be one of the most important challenges for the Scientific Community in the approaching new century. Since the identification, in 1983-84,^1,2 of human immunodeficiency virus (HIV) as the etiological agent of AIDS, significant progress has been made in the treatment of HIV-infected patients. This has been in part due to the discovery and clinical use of an increasing number of anti-HIV drugs. However, while highly active antiretroviral therapy (HAART)³ approaches have reduced the morbidity and mortality, the intertwined problems of drug induced viral resistance, poor compliance with complex regimens and therapy failure continue. Therefore, there remains a pressing need for the development of new antiviral agents that can be used not only as first line therapeutic candidates, but also in the antiretroviral-experienced patient population.     

A theoretical NMR study of the structure of benzynes and some of their carbocyclic and heterocyclic analogs

This work reports the theoretical study of the aromaticity of a series of carbocycles (benzene, cyclohexane, bent and planar cyclooctatetraene) and heterocycles (pyridine, furan, thiophene, pyrrole) and their didehydro forms (arynes and hetarynes). As aromaticity probe Schleyer's NICS were used and represented in two 3D isosurfaces of the electron density. The spatial 3D representation of the NICS is shown to be a powerful tool to visualize the aromaticity (or its absence) of different molecules.     

[1,3‐Bis(2,6‐diisopropylphenyl)imidazol‐2‐ylidene]chloridogold(I)

The molecule of the title compound, [AuCl(C₂₇H₃₆N₂)], which belongs to a class of potentially catalytically active N‐heterocyclic carbene complexes, has crystallographic C₂ symmetry and approximate C_2v symmetry. The structure is isostructural with the Cu^I and Ag^I analogues. A previous report of the structure of the title compound as its toluene solvate [Fructos et al. (2005). Angew. Chem. Int. Ed. 44 , 5284–5288] has inaccurate geometry for the complex molecule as a consequence of probable incorrect refinement in the space group Cc, instead of C2/c [Marsh (2009). Acta Cryst. B 65 , 782–783]. The Au—C bond length of 1.998 (4) Å in the title compound is more consistent with the mean distance of 1.979 (14) Å found in 52 other reported [AuCl(carbene)] complexes than with the shorter distance of 1.942 (3) Å given for the refinement in the space group Cc for the toluene solvate and the value of 1.939 Å obtained from the recalculation of that structure in C2/c.     

On the effective potential in higher-derivatives superfield theories

We study the one-loop quantum corrections for higher-derivative superfield theories, generalizing the approach for calculating the superfield effective potential. In particular, we calculate the effective potential for two versions of higher-derivative chiral superfield models. We point out that the equivalence of the higher-derivative theory for the chiral superfield and the one without higher derivatives but with an extended number of chiral superfields occurs only when the mass term is contained in the general Lagrangian. The presence of divergences can be taken as an indication of that equivalence.     

Straightforward Method for the Preparation of Lysine-Based Double-Chained Anionic Surfactants

Double-chained surfactants with potential biocompatibility have been prepared in high yields by lysine acylation with four natural saturated fatty acids (C₆ to C₁₂) and with cis-undec-5-enoic acid. The surfactants were found to assemble into nanotubules in aqueous medium and, when mixed with a commercial cationic surfactant, to spontaneously form liposomes.     

Toward a Raman/FORS discrimination between Art Nouveau and contemporary stained glasses from CdSxSe1 − x nanoparticles signatures

CdS_xSe_{1 − x} quantum dots received considerable attention in academic studies and as cut‐off filters and indirect‐gap semiconductors. These later compounds have also been used for artistic purposes to produce colored glass since the 1920s thanks to their bright colors. Because non‐invasive conditions are now mandatory when considering objects belonging to the cultural heritage, the use of Raman and fiber optics reflectance spectroscopy has been identified as potential ones to obtain information about the nanostructure of six samples of historical glass produced between the late 1920s and modern days. The average elemental composition of the nanocrystals has been deduced processing both optical and vibrational data, and the result arising has been compared taking into account the several factors affecting the experimental results. The diffusion of zinc inside the nanocrystals has also been questioned by the shift caused on the CdS‐ and CdSe‐like phonon band wavenumber and on the absorption edge wavelength. An investigation of the size distribution and crystallinity of CdS_xSe_{1 − x} nanoparticles has been also performed considering those parameters that are mainly influenced by the disorder of the system, such as the extent of the Urbach tail and the Raman bandwidth. Thanks to the results obtained, discrimination between the more recent glass and the older Art Nouveau ones has been verified, leading to the identification of a useful analytical protocol for conservation purposes. Copyright © 2015 John Wiley & Sons, Ltd.     

Pyrolysis of the hybrid energy cane: thermal decomposition and kinetic modeling using non-isothermal thermogravimetric analysis

Journal of Thermal Analysis and Calorimetry - This work aims to investigate the thermal decomposition and reaction kinetics of the hybrid energy cane, as well as its thermochemical properties....