Bestimmung des specifischen Gewichtes

Ohne Zusammenfassung     

A parametric analysis of the performances of a linear collectors' network of a solar power plant

Summary The influence of some design parameters on the performances of a linear collectors' solar power plant has been evaluated. An analysis of the results can suggest some technical solutions in the plant's design. This work has been performed in the framework of activities of the ?Progetto Finalizzato Energetica?, supported by the C.N.R.     

Sensible improvements induced by ionic liquids in the reaction of modified carbasugars with bases for the building of constrained carbanucleosides

Starting from racemic 4-hydroxy-4-methyl-2-cyclopentenone, a family of enantiopure carbanucleosides locked in the northern conformation has been synthesized. The use of ionic liquids was determinant in the last step resulting in a tangible increase of the yields and dramatic reduction of reaction times and volumes of organic solvents. To our knowledge, this is the first example of the use of ionic liquids in the coupling of carbasugars with heterocyclic bases.     

Overriding Intrinsic Reactivity in Aliphatic C−H Oxidation: Preferential C3/C4 Oxidation of Aliphatic Ammonium Substrates

The site‐selective C?H oxidation of unactivated positions in aliphatic ammonium chains poses a tremendous synthetic challenge, for which a solution has not yet been found. Here, we report the preferential oxidation of the strongly deactivated C3/C4 positions of aliphatic ammonium substrates by employing a novel supramolecular catalyst. This chimeric catalyst was synthesized by linking the well‐explored catalytic moiety Fe(pdp) to an alkyl ammonium binding molecular tweezer. The results highlight the vast potential of overriding the intrinsic reactivity in chemical reactions by guiding catalysis using supramolecular host structures that enable a precise orientation of the substrates.     

Vanadin-Bestimmungsmethoden

Ohne Zusammenfassung     

Optical and electrical properties of tin-dioxide films

Summary The electro-optical properties of thin SnO₂ films are analysed in relation to different experimental deposition conditions. Heating tests have been performed on the samples; the results are discussed.

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Riassunto Si analizza l'influenza di differenti condizioni sperimentali di deposizione sulle proprietà elettro-ottiche di film sottili di SnO₂. Si riportano i risultati di prove di invecchiamento condotte mediante cicli termici.

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Резюме Анализируется влияние различных экслериментальных условий напыления на электрические и оптические свойства тонких пленок диоксида олова. Проводятся испытания с использованием темических циклов. Обосуждаются полученные резльтаты.

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This work has been performed in the framework of activities of the ?Progetto Finalizzato Energetica? supported by the C.N.R.     

Ab Initio Calculation of Rate Constants for Molecule–Surface Reactions with Chemical Accuracy

The ab initio prediction of reaction rate constants for systems with hundreds of atoms with an accuracy that is comparable to experiment is a challenge for computational quantum chemistry. We present a divide‐and‐conquer strategy that departs from the potential energy surfaces obtained by standard density functional theory with inclusion of dispersion. The energies of the reactant and transition structures are refined by wavefunction‐type calculations for the reaction site. Thermal effects and entropies are calculated from vibrational partition functions, and the anharmonic frequencies are calculated separately for each vibrational mode. This method is applied to a key reaction of an industrially relevant catalytic process, the methylation of small alkenes over zeolites. The calculated reaction rate constants (free energies), pre‐exponential factors (entropies), and enthalpy barriers show that our computational strategy yields results that agree with experiment within chemical accuracy limits (less than one order of magnitude).     

EPR and IR spectra of Ni(ClO4)2)·6H2O between 98 and 298 K

EPR measurements between 98 and 298 K on single crystal of Ni(ClO₄)₂·6H₂O have indicated the appearance of a rhombic component in the axial crystal field at Ni²⁺ sites at T_c = 224 K, confirming a phase transition first reported by Chaudhuri from magnetic susceptibility measurements. Temperature variations of g, D and E parameters were determined. IR spectra at room and liquid nitrogen temperatures are consistent with our EPR results.