Thermoanalytical and spectroscopic characterization ofβ-cyclodextrin/ketoprofen inclusion complexes

A method to determine the composition and hydration state of the complexes formed in aqueous solution by cyclodextrins (CD) is presented and applied to the -CD/ketoprofen system; it is based on a combination of spectroscopic, calorimetric, and thermogravimetric analyses. The complexes have, on average and per -CD mole, more than eleven water molecules, which are present in completely different bound states.     

Sobolev inequalities on homogeneous spaces

We consider a homogeneous spaceX=(X, d, m) of dimension 1 and a local regular Dirichlet forma inL ² (X, m). We prove that if a Poincaré inequality of exponent 1p< holds on every pseudo-ballB(x, R) ofX, then Sobolev and Nash inequalities of any exponentq[p, ), as well as Poincaré inequalities of any exponentq[p, +), also hold onB(x, R).Lavoro eseguito nell'ambito del Contratto CNR Strutture variazionali irregolari.     

Stereoselective reduction with sodium dithionite of conjugated enones in the presence ofβ-cyclodextrin and its heptakis(2,6-di-O-methyl) derivative as host compounds or phase transfer agents

The reduction with sodium dithionite in aqueous alkaline solution of the conjugated carbon-carbon double bond of carbonyl compounds1–5 as inclusion compounds in-cyclodextrin (CD) and its heptakis(2,6-di-O-methyl) derivative (DMCD) has been investigated. These results are compared with those obtained under phase transfer conditions (1 : 1 water-toluene) using methyltrioctylammonium chloride or DMCD as transfer agents. Remarkable kinetic effects as well as regio-and stereoselectivities were observed, depending on the nature of the host molecule and of the substrate.     

Characterization of low temperature protonic conductivity in bulk nanocrystalline fully stabilized zirconia

We investigated the conductivity of samples of bulk nanometric cubic yttria stabilized zirconia (YSZ 8%) with a grain size of about 16 nm and a relative density above 98%. In an oxygen atmosphere the material showed a large grain boundary resistivity. However, when exposed to a moist atmosphere at temperatures below 150 °C it showed a high conductivity, several orders of magnitude higher than the corresponding extrapolated ionic conductivity. A fairly high conductivity was measured even at room temperature. The conductivity was strongly dependent on the water partial pressure and showed a distinct isotopic effect, suggesting a protonic conductivity mechanism. This effect was not observed in samples with grain size above 50 nm, suggesting the possibility that nanostructure can induce drastic modification in the conduction mechanism of ceramic electrolytes.     

Facile synthesis of core‐shell organic–inorganic hybrid nanoparticles with amphiphilic polymer shell by one‐step sol–gel reactions

Organic–inorganic hybrid core‐shell nanoparticles with diameters ranging from 100 to 1000 nm were prepared by a one‐pot synthesis based on base catalyzed sol–gel reactions using tetraethoxysilane and a triethoxysilane‐terminated polyethylene‐b‐poly(ethylene glycol) as reactants. Data from TEM, TGA, and solid‐state NMR analysis are in agreement with the formation of core‐shell nanoparticles with an inorganic‐rich core and an external shell consisting of an amphiphilic block copolymer monolayer. The influence of the organic–inorganic ratio, solution concentration, and postcuring temperature on core and shell dimensions of the nanospheres were investigated by TEM microscopy. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1699–1709, 2008     

Janssen's law and stress fluctuations in confined dry granular materials

In order to clarify the mechanisms which determine the Janssen's law for the pressure distribution at the bottom of a silo we reconsider the so-called q-model describing an assembly of granular particles on a lattice, confined between vertical walls. We find that the expected macroscopic behavior with the correct scaling is obtained whenever a mechanism able to transfer the weight from the interior of the silo to the walls in an efficient way is present, i.e., in mean field regime. Deviations from the Janssen law's found in lattice models are due to the absence of this efficient mechanism. We investigate the scaling properties of a stick-slip model recently introduced, and find that relative fluctuations do not disappear for large systems and are of the order of average values. Finally we observe that an exponential local weight distribution at the bottom of the silo is independent of the model considered.     

On Sums of Roots of Unity

 Suppose that for some root of unity ζ of order Q with and all coefficients a _i belonging to a number field L. We bound Q in terms of k and . This generalizes a result of Conway and Jones for the case of rational coefficients. Moreover, we give an application to linear relations among characteristic functions of arithmetical progressions.