Determination of 30 elements in colorectal biopsies by sector field inductively coupled plasma mass spectrometry: method development and preliminary baseline levels

An analytical procedure applicable to restricted sample sizes was developed and applied to the analysis of 30 chemical elements in colorectal biopsies of healthy patients. Acidic microwave digestion processed 相似文献   

Water/polymer interactions in poly(amidoamine) hydrogels by 1H nuclear magnetic resonance relaxation and magnetization transfer

Hydrated cross-linked polymers belonging to the family of poly(amidoamine)s were investigated by high and low resolution (1)H nuclear magnetic resonance techniques in order to obtain information on water/polymer interactions in the swollen state. (1)H spin-spin and spin-lattice relaxation time analysis, as well as magnetization transfer experiments, indicated that water and polymer proton pools are essentially uncoupled, with water molecules diffusing fast within the hydrogel structure and exchanging between "bound" and free sites. For the polymer characterized by the highest cross-linking degree, there is strong evidence of a beadlike structure resulting in higher network rigidity and hydrogel micrometric heterogeneity.     

Bond-order correlation energies for small Si-containing molecules compared with ab initio results from low-order Møller–Plesset perturbation theory

The present study of small molecules containing silicon was motivated by (a) the considerable interest currently being shown in the kinetics and reactivity of such molecules, and (b) the biotechnological potential of silicon-derivate surfaces as substrates for the adsorption of, for instance, amino acids and proteins. Therefore, we have studied by (i) a semi-empirical approach and (ii) an ab initio procedure employing low-order Møller–Plesset perturbation theory, the molecular correlation energies of some neutral closed and open shell silicon-containing molecules in the series SiX _n Y _m . Procedure (i) is shown to have particular merit for the correlation of the ionic members studied in the above series, while the ab initio procedures employed come into their own for neutral species.     

Densities and refractive indices of imidazolium- and phosphonium-based ionic liquids: Effect of temperature,alkyl chain length,and anion

A systematic study of densities and refractive indices of 17 room temperature ionic liquids is presented at four different temperatures ranging from 293 K to 333 K. The ionic liquids are grouped into four families: 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide, [C_nmim][Ntf₂], ionic liquids (with n = 2, 4, 6, 8, 10, 12, and 14); 1-alkyl-3-methylimidazolium hexafluorophosphate, [C_nmim][PF₆], ionic liquids (with n = 4, 6, 8); ionic liquids based on the trihexyl(tetradecyl)phosphonium cation, [P_{6 6 6 14}], combined with the anions bis(trifluoromethylsulfonyl)amide, [Ntf₂], acetate, [OAc], and triflate, [OTf]; and [C₄mim]-based ionic liquids combined with the anions [OAc], [OTf], methylsulfate [MeSO₄], and tetrafluoroborate [BF₄]. The data obtained were analysed to determine the effect of (i) temperature, (ii) the alkyl chain length of the 1-alkyl-3-methylimidazolium cation, and (iii) the nature of the anion. Different empirical models for the calculation of the densities of the ionic liquids were tested. Molar refractions were also calculated from the volumetric and refractive index data and the values were discussed with the aim of checking their utility in obtaining insights on the intermolecular forces and behaviour in solution of the different ionic liquids.     

Abiotic and biotic degradation of oxo-biodegradable polyethylenes

Conventional polymeric materials accumulate in the environment due to their low biodegradability. However, an increase in the biodegradation rate of these polymers may be obtained with the addition of pro-degrading substances. This study aimed to evaluate abiotic and biotic degradation of polyethylenes (PEs) using plastic bags of high-density polyethylene (HDPE) and linear low-density polyethylene (LLDPE) formulated with pro-oxidant additives as test materials. These packaging materials were exposed to natural weathering and periodically analyzed with respect to changes in mechanical and structural properties. After a year of exposure, residue samples of the bags were incubated in substrates (compost of urban solid waste, perlite and soil) at 58 °C and at 50% humidity. The biodegradation of the materials was estimated by their mineralization to CO₂. The molar mass of the pro-oxidant-activated PE decreased and oxygen incorporation into the chains increased significantly during natural weathering. These samples showed a mineralization level of 12.4% after three months of incubation with compost. Higher extents of mineralization were obtained for saturated humidity than for natural humidity. The growth of fungi of the genera Aspergillus and Penicillium was observed on PE films containing pro-oxidant additives exposed to natural weathering for one year or longer. Conventional PE films exposed to natural weathering showed small biodegradation.     

CP MAS 13C spectral editing and relative quantitation of a soil sample

A hydrofluoric acid (HF)-treated soil sample was studied by 13C NMR spectroscopy. Cross polarization (CP) Magic Angle Spinning (MAS) 13C spectral editing and relative CP peak quantitation, obtained through variable-contact-time experiments, were used to aid the interpretation of the spectrum. The combination of these two types of experiment allowed to obtain a higher degree of detail on the composition of the sample with respect to a standard CP MAS experiment.     

Sulle pseudo-probabilita’ associate all’informazione

Sommario Si definiscono pseudo-probabilità quelle funzioni di evento associate alla funzione di informazione quando si postula per l’informazione della unione di due eventi una legge di carattere universale. Si studiano le principali proprietà delle pseudo-probabilità e si dimostra che esse sono caratterizzate da una classe particolare di soluzioni di una equazione funzionale.

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Résumé On définit pseudo-probabilité les fonctions d’événement associées à la fonction d’information quand on postule que l’information de deux événements suit une loi à caractère universel. On étudie les principales propriétés des pseudo-probabilités et l’on démontre qu’elles sont caractérisées par une classe particulière de solutions d’une équation fonctionelle.

     

Entropies with the branching property

Summary It is proved that every entropy with the property of branching has the form , where J is a compositive information measure under a regular binary operation. In particular all the classical entropies with the branching property such as that of Shannon have the form .

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Sunto Si dimostra che ogni entropia che goda della proprietà di diramazione ha necessariamente la forma dove J è una misura di informazione compositiva con una operazione binaria regolare. In particolare tutte le entropie classiche che godono della proprietà di diramazione quale quella di Shannon hanno la forma .

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Entrata in Redazione il 9 aprile 1973.     

A characterization of the entropy functionals for grand canonical ensembles. The discrete case

Summary ? Natural ? properties lead to a representation theorem for the entropy functional of a grand canonical ensemble. In addition to the classical Boltzmann term, the representation contains three more terms that seem to be meaningful in statistical mechanics.

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Sunto Da proprietà ? naturali ? imposte al funzionale entropia di un insieme gran canonico si deduce un teorema di rappresentazione per esso. In aggiunta al termine classico di Boltzmann, la rappresentazione mette in luce tre ulteriori termini che sembrano significativi in meccanica statistica.

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A Dario Graffi per il suo 70° compleanno

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Entrata in Redazione il 17 marzo 1976.

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While on sabbatical leave of absence from the University of Waterloo, Canada, Department of Applied Mathematics.

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Research supported in part by National Research Council of Canada, grant A-7677 and IBM-Italia.