Evaluation of an automatic sampling gas chromatographic–mass spectrometric instrument for continuous monitoring of trace anthropogenic gases

Continuous monitoring of the atmospheric volatile halogenated hydrocarbons is needed in light of the role played by these compounds in global climate change phenomena. The analytical methodology described in the following implies the use of a gas chromatographic–mass spectrometric system equipped with a sampling/pre-concentration unit, for the simultaneous and continuous analysis of a number of halogenated hydrocarbons present in the atmosphere at concentration levels ranging from a few to hundreds of part per trillion by volume. The optimization of the analytical procedure in terms of efficiency, linearity, and reproducibility is reported together with some of the results obtained in the frame of a monitoring activity carried out on a remote mountain station in central Italy.     

Compensated compactness for differential forms in Carnot groups and applications

In this paper we prove a compensated compactness theorem for differential forms of the intrinsic complex of a Carnot group. The proof relies on an Ls-Hodge decomposition for these forms. Because of the lack of homogeneity of the intrinsic exterior differential, Hodge decomposition is proved using the parametrix of a suitable 0-order Laplacian on forms.     

Synthesis, structural characterization, solution behavior, and in vitro antiproliferative properties of a series of gold complexes with 2-(2'-pyridyl)benzimidazole as ligand: comparisons of gold(III) versus gold(I) and mononuclear versus binuclear derivatives

A variety of gold(III) and gold(I) derivatives of 2-(2'-pyridyl)benzimidazole (pbiH) were synthesized and fully characterized and their antiproliferative properties evaluated in a representative ovarian cancer cell line. The complexes include the mononuclear species [(pbi)AuX(2)] (X = Cl, 1; OAc, 2), [(pbiH)AuCl] (3), [(pbiH)Au(PPh(3))][PF(6)] (4-PF(6)), and [(pbi)Au(L)] (L = PPh(3), 5; TPA, 6), and the binuclear gold(I)/gold(I) and gold(I)/gold(III) derivatives [(PPh(3))(2)Au(2)(μ(2)-pbi)][PF(6)] (10-PF(6)), [ClAu(μ(3)-pbi)AuCl(2)] (7),and [(PPh(3))Au(μ(3)-pbi)AuX(2)][PF(6)] (X = Cl, 8-PF(6); OAc, 9-PF(6)). The molecular structures of 6, 7, and 10-PF(6) were determined by X-ray diffraction analysis. The chemical behavior of these compounds in solution was analyzed both by cyclic voltammetry in DMF and absorption UV-vis spectroscopy in an aqueous buffer. Overall, the stability of these gold compounds was found to be acceptable for the cellular studies. For all complexes, relevant antiproliferative activities in vitro were documented against A2780 human ovarian carcinoma cells, either resistant or sensitive to cisplatin, with IC(50) values falling in the low micromolar or even in the nanomolar range. The investigated gold compounds were found to overcome resistance to cisplatin to a large degree. Results are interpreted and discussed in the frame of current knowledge on cytotoxic and antitumor gold compounds.     

Combinatorics of angular momentum recoupling theory: spin networks,their asymptotics and applications

The quantum theory of angular momentum and the associated Racah–Wigner algebra of the Lie group SU(2) have been widely used in many branches of theoretical and applied physics, chemical physics, and mathematical physics. This paper starts with an account of the basics of such a theory, which represents the most exhaustive framework in dealing with interacting many-angular momenta quantum systems. We then outline the essential features of this algebra, that can be encoded, for each fixed number N = (n + 1) of angular momentum variables, into a combinatorial object, the spin network graph, where vertices are associated with finite-dimensional, binary coupled Hilbert spaces while edges correspond to either phase or Racah transforms (implemented by 6j symbols) acting on states in such a way that the quantum transition amplitude between any pair of vertices is provided by a suitable 3nj symbol. Applications of such a combinatorial setting—both in fully quantum and in semiclassical regimes—are briefly discussed providing evidence of a unifying background structure.     

Efficacious N-protection of O-aryl sulfamates with 2,4-dimethoxybenzyl groups

Sulfamates are important functional groups in certain areas of current medicinal chemistry and drug development. Alcohols and phenols are generally converted into the corresponding primary sulfamates (ROSO(2)NH(2) and ArOSO(2)NH(2), respectively) by reaction with sulfamoyl chloride (H(2)NSO(2)Cl). The lability of the O-sulfamate group, especially to basic conditions, usually restricts this method to a later stage of a synthesis. To enable a more flexible approach to the synthesis of phenolic O-sulfamates, a protecting group strategy for sulfamates has been developed. Both sulfamate NH protons were replaced with either 4-methoxybenzyl or 2,4-dimethoxybenzyl. These N-protected sulfamates were stable to oxidising and reducing agents, as well as bases and nucleophiles, thus rendering such masked sulfamates suitable for multi-step synthesis. The protected sulfamates were synthesised by microwave heating of 1,1'-sulfonylbis(2-methyl-1H-imidazole) with a substituted phenol to give an aryl 2-methyl-1H-imidazole-1-sulfonate. This imidazole-sulfonate was N-methylated by reaction with trimethyloxonium tetrafluoroborate, which enabled subsequent displacement of 1,2-dimethylimidazole by a dibenzylamine (e.g. bis-2,4-dimethoxybenzylamine). The resulting N-diprotected, ring-substituted phenol O-sulfamates were further manipulated through reactions at the aryl substituent and finally deprotected with trifluoroacetic acid to afford a phenol O-sulfamate. The use of 2,4-dimethoxybenzyl was particularly attractive because deprotection occurred quantitatively within 2 h at room temperature with 10% trifluoroacetic acid in dichloromethane. The four key steps in the protocol described [reaction of 1,1'-sulfonylbis(2-methyl-1H-imidazole) with a phenol, methylation, displacement with a dibenzylamine and deprotection] all proceeded in very high yields.     

Three-dimensional molecular reconstruction of rat heart with mass spectrometry imaging

Cardiovascular diseases are the world’s number one cause of death, accounting for 17.1 million deaths a year. New high-resolution molecular and structural imaging strategies are needed to understand underlying pathophysiological mechanism. The aim of our study is (1) to provide a molecular basis of the heart animal model through the local identification of biomolecules by mass spectrometry imaging (MSI) (three-dimensional (3D) molecular reconstruction), (2) to perform a cross-species validation of secondary ion mass spectrometry (SIMS)-based cardiovascular molecular imaging, and (3) to demonstrate potential clinical relevance by the application of this innovative methodology to human heart specimens. We investigated a MSI approach using SIMS on the major areas of a rat and mouse heart: the pericardium, the myocardium, the endocardium, valves, and the great vessels. While several structures of the heart can be observed in individual two-dimensional sections analyzed by metal-assisted SIMS imaging, a full view of these structures in the total heart volume can be achieved only through the construction of the 3D heart model. The images of 3D reconstruction of the rat heart show a highly complementary localization between Na⁺, K⁺, and two ions at m/z 145 and 667. Principal component analysis of the MSI data clearly identified different morphology of the heart by their distinct correlated molecular signatures. The results reported here represent the first 3D molecular reconstruction of rat heart by SIMS imaging.

On the redox behaviour of glycerol at TiO2 electrodes

An experimental work is presented in which alkaline solutions of glycerol are electrochemically treated at TiO₂ electrodes obtained by electrochemical oxidation of Ti foils annealed a 400 °C and 600 °C. The semiconductor properties of the material, strictly correlated to the presence of structural defects, and their different concentration and distribution originated by the different annealing temperature are investigated. In order to derive useful indications for possible application on reduction or photo-oxidation of glycerol, particular attention is paid on the working mechanism of the electrodes in a wide range of potential at which the semiconductor may be under accumulation or depletion regime.     

Fast H-vacancy dynamics during alanate decomposition by anelastic spectroscopy. proposition of a model for Ti-enhanced hydrogen transport

A systematic study of the dehydrogenation process of undoped and of catalyzed NaAlH4 by means of anelastic spectroscopy is presented. Evidence is reported of the formation of a highly mobile species during decomposition, which has been identified in off-stoichiometric AlH6-x units, giving rise to fast H vacancy local dynamics. The formation of such stoichiometry defects starts at temperatures much lower in Ti doped than in undoped samples, and concomitantly with the decomposition reaction. The catalyst atoms decrease the energy barrier to be overcome by H to break the bond, thus enhancing the kinetics of the chemical reactions and decreasing the temperature at which the dehydrogenation processes take place. The experimental data show that not all the hydrogen released by the formula units during the evolution of decomposition evolves out of the sample, but part of it remains in the lattice and migrates on a long-range scale within the sample. We identify, in this H mobilized population, the species which induces the fast tetragonal to monoclinic phase transformation accompanying decomposition. A partial spontaneous thermally activated regression of decomposition has also been observed by aging experiments. A model is proposed which accounts for the action of the Ti catalyst and for the atomistic mechanism of decomposition.