Classification of ancient proteinaceous painting media by the joint use of pattern recognition and factor analysis on GC/MS data

Reference proteinaceous binding media of the kinds historically used in painting (specially prepared for this study) and samples collected from ancient polychrome works of art were analysed by gas chromatography – mass spectrometry. The data have been processed by several multivariate chemometric techniques, such as cluster analysis, principal component analysis, factor analysis and SIMCA technique in order to classify the binding media of the ancient works of art on the basis of the proteinaceous material used. The characterisation of ancient samples was possible by the joint use of SIMCA technique and factor analysis. The latter, in particular, has made it possible to point into evidence the presence of at least two latent factors. The first factor seems to be connected with the chemical composition of the painting media, while the second factor is likely to be connected with ageing processes. Received: 14 October 1998 / Revised: 23 April 1999 / Accepted: 20 May 1999     

Convenient Synthesis of N-Benzyl-N′-acyl-piperazines

The importance of N,N′ asymmetrically disubstituted piperazines in pharmaceutical and medicinal chemistry does not need to be emphasized. Such a basic moiety is present in a number of drugs belonging to different classes, and especially in those of the central and peripheral nervous system. In recent times the interest connected with piperazines appears to be a fast growing topic in drug research.     

Properties of L-phenylalanine tetraamides as chiral selectors for D,L-amino acids by capillary gas chromatography

Summary A wide series of L-phenylalanine tetraamide selectors (Phe-n-O-TA) have been synthesized and used as stationary phases for chiral resolution of D,L-amino acids by capillary gas chromatography. The influence of length and polarity of the oxaalkanoyl bridge spacing the diamide chains of the selectors and the effects of steric hindrance on separating power were investigated. The characteristics of the chiral columns and the separation factors of D,L-n-butyl-N-trifluoroacetyl amino esters are reported.     

The effect of topical anesthesia on vocal fold motion

The objective of this study was to determine if topical anesthesia to the larynx and pharynx affects vocal fold motion during dynamic voice evaluation with transnasal flexible endoscopy. Transnasal dynamic laryngeal examinations of 10 patients with no voice complaints were evaluated by five blinded fellowship-trained laryngologists. Each patient was examined before and after application of topical anesthetic. Reviewers rated briskness of right and left vocal fold movement and longitudinal tension on a visual analogue scale. Statistical comparisons were made between individual subject scores before and after anesthetic application. Inter-rater reliability was also assessed. No statistical difference was observed between subject scores before and after anesthetic application. Average intraclass correlation coefficients were 0.643 and 0.591 for pre- and postanesthesia scores, respectively. Application of topical anesthesia to the larynx and pharynx does not affect vocal fold motion.     

Quantitative 2H NMR spectroscopy with 1H lock extender

An inexpensive external unit that allows the use of the commercial high-resolution NMR spectrometer for (2)H observation with an (1)H lock system is described. The external unit does not require any tuning, is extremely easy to use, and could be a cheaper and more straightforward alternative to the more expensive (19)F lock configuration. An application for the quantitative determination of the natural isotopic ratio (2)H/(1)H of ethanol and acetic acid is reported.     

Synthesis of 2-alkylthio (or trifluoromethylthio)-2-halogenoethenyl derivatives by means of wittig (under phase transfer conditions) or wittig-horner reactions. Application in the field of pyrethroids

A mixture of RSCHCl₂, Ph₃P and $\text{trans}$-caronaldehyde ethyl ester, treated with aq.NaOH under phase transfer conditions, gave the corresponding 2-alkylthio,2-chloroethenyl derivative, the product of the Wittig reaction of a phosphorane formed 'in situ'. The analogous derivative of the $\text{cis}$- and the 2-methylthio, 2-bromoethenyl derivative of the $\text{trans}$-caronaldehyde ethyl ester were synthesized also by means of Wittig-Horner reactions. The 2-trifluoromethylthio, 2-chloro-ethenyl derivative of the caronaldehyde ethyl ester ($\text{cis}$-$\text{trans}$ mixture) was also obtained through the phosphonate prepared from CF₃Cl + N₂CHP(OET)₂→ CF₃SCHClP(O)(OEt) The new derivatives prepared were converted to final pyrethroids by esterification with cyano(m-phenoxyphenyl)methanol.     

Presence and racemisation of amino acids in calcium oxalate patinas. A case study from the Baptistery in Parma,Italy

The organic material present in oxalate patinas, collected from the stone external surfaces of the Baptistery in Parma (Italy), was analysed by GC-MS. The high racemisation levels determined for several specific amino acids indicate that microbial activity could contribute to the formation and modification of the organic material leading to the calcium oxalate patinas.     

Solvent effect in free radical reactions on protonated heteroaromatic bases

The influence of reaction medium on the relative reactivity of various carbon radicals towards 4-CH₃-and 4-CN- quinolines has been investigated. A relevant solvent effect for α-amidoalkyl and α-oxyalkyl radicals has been demonstrated and a solvent-radical interaction is proposed to explain the phenomenon.