Bis- and tetrakis(organosilyl) decatungstosilicate,

The high propensity of organosilanes towards polycondensation and reaction with nucleophilic moieties has facilitated the formation of new organic-inorganic hybrids based on the lacunary divacant heteropolyanion [gamma-SiW10O36]8-. Depending on the experimental conditions two different types of derivatives were obtained with the general formula [gamma-SiW10O36(RSi)2O]4- (1) (>90% yield) and [gamma-SiW10O36(RSiO)4]4- (2) (>85% yield) (R = H (1a, 2a), vinyl (1b), -C3H6OC(O)C-(Me)=CH2 (1c, 2c), phenyl (1d, 2d)). The structures of the hybrid anions have been inferred from spectroscopic data, in particular from multinuclear (29Si and 183W) NMR solution studies and from MALDI-TOF mass spectrometry. Both species correspond to the grafting of an oxo-bridged siloxane unit onto the surface of the lacunary polyoxoanion.     

Die Raman-Spektren der Orthovanadate der Seltenen Erden

Raman Spectra of the Rare Earth Orthovanadate The laser-Raman spectra of the tetragonal rare earth orthovanadates of the type LnVO₄ (Ln = Pr to Lu) as well as those of ScVO₄ and YVO₄ has been recorded and interpreted with the aid of both, the site symmetry and the factor group analysis, using also IR data reported previously. The influence of the cations on the internal vibrations of the anion are discussed in detail.     

Isomorphismes d'hypergraphes par intersections équicardinales d'arêtes et configurations exclues

In this note we characterize isomorphism between two hypergraphs by means of equicardinality of certain edge intersections and the exclusion of certain pairs of subhypergraphs. Our result is slightly stronger than Theorem 3 of C. Berge and R. Rado (J. Combinatorial Theory Ser. B13 (1972), 226–241) in particular in that isolated vertices are admitted. As a corollary we obtain a result due to J.-L. Paillet.     

Tetraazamacrocycles lipophiles : synthese et application a l'extraction de Cu (II), Cd (II) et Pb (II)

The synthesis of three lipophilic n-dodecyl tetraazacycloalkanes is described. Extraction of Cu(II), Cd(II) and Pb(II) is related.     

Simple enantiospecific syntheses of the C(2)-diastereomers of omuralide and 3-methylomuralide

[reaction: see text] Syntheses of two novel omuralide derivatives are described.     

Monte carlo estimates of domain-deformation sensitivities

It is shown that, when a Monte Carlo algorithm is used for estimation of any physical quantity A, a simple and fast additional procedure can be implemented that simultaneously estimates the sensitivity of A to any problem parameter. The proposed approach is general and systematic in the sense that: (i) it includes domain-deformation sensitivities, i.e., cases where a change in the parameter modifies the domain over which the sampled random variables are defined and (ii) a simple generic procedure is presented to address all remaining free choices in terms of variance minimization.     

Measurement of the generalized polarizabilities of the proton in virtual Compton scattering at Q2=0.92 and 1.76 GeV2

We report a virtual Compton scattering study of the proton at low c.m. energies. We have determined the structure functions P(LL)-P(TT)/epsilon and P(LT), and the electric and magnetic generalized polarizabilities (GPs) alpha(E)(Q2) and beta(M)(Q2) at momentum transfer Q(2)=0.92 and 1.76 GeV2. The electric GP shows a strong falloff with Q2, and its global behavior does not follow a simple dipole form. The magnetic GP shows a rise and then a falloff; this can be interpreted as the dominance of a long-distance diamagnetic pion cloud at low Q2, compensated at higher Q2 by a paramagnetic contribution from piN intermediate states.