Stoichiometric hydrogenation of the heterobimetallic (α-alkynyl) complex [μ(1σ, 23η3H2CC  CCH3)] [(CO)3FeCo(CO)3]

The title compound reacts with molecular hydrogen at 60°C giving rise to the homometallic complexes Fe(CO)₅ and Co₂(CO)₈, and a very rich mixture of gaseous hydrocarbons (e.g. butenes from partial hydrogenation, butane from total hydrogenation and methane and propene from selective hydrogenolysis of the organic chain).The influence of concentration of the title complex, and partial pressure of hydrogen or carbon monoxide on the hydrogenation rate have been investigated. Although an unequivocal mechanism cannot be ascertained from the kinetic data owing to the complexity of the reaction, the pattern of products strongly indicates that the σ-interaction between the iron atom and the organic chain is preserved in the transition state.     

Synthesis of cavity extended cyclotriveratrylenes

Aromatic nucleophilic substitution reaction of cyclotriguaiacylene 1 with fluorobenzene derivatives bearing electron-withdrawing groups X (CHO, COCH(3), CN, NO(2)) in the para position gives a series of cyclotriveratrylene derivatives (3a-d), where the X substituents can be transformed to hydrogen-bond donor groups to afford new CTV-based heteroditopic receptors. The substituents of compounds 3a-d favor the facile demethylation reaction of the CTV derivatives. Attempts to perform alkylation reactions on derivatives (8c,d) evidenced the formation of a stereoisomeric mixture of symmetrical and unsymmetrical compounds.     

Direct resolution of racemic compounds on chiral microbore columns by sub- and supercritical fluid chromatography

Fast resolutions of racemic compounds (sulfoxides, amino alcohols, and α-methylarylacetic acids derivatives) were achieved on a chiral microbore column using carbon dioxide and a polar methanol/dioxane modifier. The stationary phase used in this study contains the 3,5-dinitrobenzoyl derivative of R,R(?)-1,2-diaminocyclohexane (DACH-DNB) as the chiral moiety, anchored to a silica gel surface by covalent bonds. Both thermodynamic and kinetic separation performances were improved by using a super- or subcritical carbon dioxide mobile phase (SFC, SubFC).     

The behaviour of 2-nitrothiophene and of 3-nitrothiophene with some nucleophiles

The reactivity of 2-nitrothiophene (1) and of 3-nitrothiophene (II) with some nucleophiles has been studied. According to calculated electronic densities I can receive nucleophilic attack at C₃ and C₅ depending on the nucleophile used, but II only at C₂. With N-lithium piperidine both I and II also give coupling products (VII and XI respectively) of the hithienyl type.     

Identification of polymers by library search of pyrolysis mass spectra and pattern recognition analysis

A library of mass spectra of polymers containing about 200 entries is described. These spectra were obtained by direct pyrolysis-electron-impact mass spectrometry, i.e., by heating the polymers in the direct insertion probe for solid samples at a constant heating rate and recording repetitive mass spectra during the temperature rise. The library can be used both as a data base for library searches and as a training set for a pattern recognition analysis. The algorithm used to generate and search the files and a few applications of the library search and pattern recognition analysis are presented.     

Silicon oxycarbide glasses from gels

Silicon-oxycarbide glasses can be synthesized from modified silica gels through a pyrolysis process in inert atmosphere. A critical analysis of the literature suggests a close relationship between oxygen content in the gel precursors and the amount of carbon atoms covalently bonded to silicon atoms in the corresponding silicon-oxycarbide phase. The problem of the formation of a free carbon phase will be discussed and related to the amount of carbon in the starting gel. An example of successful synthesis of an almost pure carbon-rich oxycarbide phase will also be presented.     

Isolation of an urate-binding protein by affinity chromatography

This paper describes an affinity chromatography procedure to purify an urate binding protein from human serum. The specific ligand was 8-amino-2,6-dihydroxypurine bound to Sepharose through the amino group. The specific elution was obtained with an uric acid or allopurinol solution. Electrophoretic analysis of the eluted protein shows a single sharp band with an α₂-globulin mobility. Molecular weight, determined by gel filtration, is approximately 70,000 daltons.     

Light-induced fluorescence spectroscopy of adenomas, adenocarcinomas and non-neoplastic mucosa in human colon. I. In vitro measurements.

In an attempt to evaluate whether induced fluorescence could be exploited to discriminate neoplastic from non-neoplastic tissue, fluorescence spectroscopy was performed at 450-800 nm on 83 biopsy specimens of colonic mucosa. Measurements showed that fluorescence spectra of adenoma, adenocarcinoma and non-neoplastic mucosa manifest dissimilar patterns. Nine variables, whose photophysical and/or biological bases need further investigation, were derived from the spectra. Discriminant functions between the groups of lesions were determined by using a stepwise discriminant analysis. The diagnostic test had a sensitivity of 80.6% and 88.2%, and a specificity of 90.5% and 95.2% in discriminating neoplastic from non-neoplastic mucosa and adenoma from non-neoplastic mucosa respectively. These results suggest that fluorescence spectroscopy has the potential to improve endoscopic diagnosis of premalignant and malignant lesions of colonic mucosa.     

Characterization of three types of planar spaces with invisible planes

In this paper we characterize a class of finite planar spaces whose planes have two sizes.Dedicato alla memoria dell'amico e Maestro Giuseppe TalliniWork supported by G.N.S.A.G.A. of C.N.R. and the projects M.U.R.S.T. 40 %     

Approximation in area of continuous graphs

Summary We prove that graphs of continuous maps with finite area can be approximated weakly as currents and in area by graphs of smooth maps.This article was processed by the author using the style filepljour1m from Springer-Verlag.