Diamagnetism as a structure and bonding related property in semiconductors

The reformulation of the quantum mechanical expression of the diamagnetic susceptibility, in terms of bond and band related parameters, leads us to evaluate separately the Langevin and the Van Vleck components of the lattice magnetic susceptibility of semiconductors. Its validity, checked for a number of semiconductors covering seven different structures and almost the entire range of variability of Suchet's ionicity parameter, confirms that a definite link exists between the diamagnetism of semiconductors and dielectrics and the nature of their interatomic bonds.     

Synthesis of regiospecifically substituted quinolines from anilines

A protocol for the synthesis of quinolines substituted on both pyridine and benzo-fused rings is reported. The method is based on the formylation of a substituted N-(tert-butoxycarbonyl)aniline followed by direct cyclisation and aromatisation of the intermediate product obtained by condensation of the formed N-Boc o-aminobenzaldehyde with an enolisable carbonyl compound. Yields up to 88% have been obtained.     

Coordination of metal ions by indolic acids. Complexes of indole-3-carboxylic,indole-3-acetic,indole-3-β-acrylic,indole-N-acetic and indole-N-methyl-2-carboxylic acids with some divalent metal ions

Complexes of formula M(L)₂·nH₂O [M=Co or Ni; L=indole-3-carboxylic (I3CH), indole-3-acetic (I3AH), indole-N-acetic (INAH), indole-N-methyl-2-carboxylic (INMH) and M=Co or Ni and Cu, L=indole-3-β-acrylic acids (I3βH)] were pepared and characaterized by i.r. and electronic spectroscopy and by susceptibility measurements and e.s.r. at room and low temperature. The cobalt and nickel complexes exhibit a distorted octahedral coordination except the Co(I3C)₂ complex for which a tetrahedral coordination was suggested. The Cu(I3β)₂·H₂O shows e.p.r. features that can be interpreted if the triplet state, S=1, depending on the temperature, is able to migrate through the crystal lattice of carboxylate dimers such as the copper(II) acetate monohydrate.     

Superhydrophobicity due to the hierarchical scale roughness of PDMS surfaces

Wettability control has been widely investigated in the last decades for technological applications such as microfluidic devices and self-cleaning surfaces by modifying both the chemical composition and the geometric structure of the surfaces. Inspired by the typical morphology of superhydrophobic leaves (such as lotus leaves), we have developed a dual-scale roughness, micro- and nanosized, on polydimethylsiloxane (PDMS) surfaces. By combining different geometric parameters and plasma treatment conditions, the structures were controlled hierarchically, at different independent length scales. Both the microsized replicated pillars and the nanosized etched posts tuned the wettability of the PDMS surfaces in a very simple way, up to contact angles of 170 degrees . Furthermore, changes in the influence of micro- and nanoscale geometrical structures were investigated. Hysteresis and contact angles of water droplets are evaluated as a combined effect of micropillars and a superimposed roughness, resulting in high advancing contact angles and low sliding angles.     

Release of rifampicin from chitosan, PLGA and chitosan-coated PLGA microparticles

Recently three groups of rifampicin (RIF)-loaded microparticles (MPs), consisting of chitosan (CHT), PLGA and PLGA/CHT mixtures, were assessed in terms of RIF-loading and retention during nebulisation. The CHT-coated PLGA MPs were found to exhibit high RIF-loading ability together with nebulisation ability, stability, and mucoadhesive properties. All MP types had comparable toxicity towards alveolar cells which was significantly lower than that of the free drug. Herein, we study the release of RIF from all MP-types, during incubation in buffer with pH values: 4.40 and 7.40. Results show that CHT particles exhibit a higher burst release compared to PLGA MPs; at pH 4.40, which is explained by the higher solubility of CHT in acidic media. At pH 7.40 burst release from CHT MP's is significantly lower when CHT is crosslinked with glutaraldehyde, which is consistent with their - previously observed - increased stability during nebulization. From PLGA MPs, RIF release was pH independent under the conditions applied, while the amount of PVA (stabilizer) considerably affected drug release. When PLGA MP's were coated with CHT, at pH 7.40 the retention of RIF increased further (compared to non-coated MPs), while at pH 4.40 the release was faster from the CHT-coated particles. Concluding, it is proven that when PLGA MPs are coated with CHT, in addition to increased particle mucoadhesive properties, the release kinetics of RIF are modified.     

PLGA, chitosan or chitosan-coated PLGA microparticles for alveolar delivery? A comparative study of particle stability during nebulization

Various types of rifampicin (RIF)-loaded microparticles were compared for their stability during nebulization. Poly(lactide-co-glycolide) (PLGA), chitosan (CHT) and PLGA/CHT microparticles (MPs) were prepared by emulsion or precipitation techniques. MPs ability to be nebulized (NE%) as well as stability during freeze-drying or/and nebulization (NEED%), were evaluated after RIF extraction from MPs and determination by light spectroscopy. MP mean diameters and ζ-potential values were measured by dynamic light scattering, morphology was assessed by SEM, cytotoxicity by MTT method and mucoadhesive properties by mucin association.

In all cases, freeze-drying prior to nebulization did not affect EE%, NE or NEED%. In CHT, MPs RIF encapsulation efficiency (EE%) decreased with increasing CHT concentration (viscosity) and CHT-MP NEED% was higher when the polymer was crosslinked by glutaraldehyde. PLGA MPs, exhibited both higher RIF EE% and also higher nebulization ability and NEED%, compared to CHT ones, but also higher cytotoxicity. However, when the two polymers were combined in the PLGA/CHT MPs, EE%, NE% and NEED% increased with increasing MP CHT-content. PLGA/CHT MPs with 0.50% or 0.75% CHT exhibited highest EE% for RIF and also best nebulization ability and stability, compared to all other MP formulations studied. Additionally they had good mucoadhesive properties and comparably low cytotoxicity.     

DSC study of YaBabCucO72212;δ homogeneity in the region 1050–1300 K

Phase transitions of the compositions Y_1±xBa_2±yCu_3±zO_72212; (x,y=0–0.2;z=0–0.5; step 0.1) were studied by DSC in argon atmosphere in the temperature range 1050–1300 K. The formation of three polymorphous modifications of the 123 phase was observed. The solubilities of yttrium, barium and copper oxides in every modification were determined. TheT-x-y phase microdiagram for the 123 phase was mapped out.     

Exploring excited-state hydrogen atom transfer along an ammonia wire cluster: competitive reaction paths and vibrational mode selectivity

The excited-state hydrogen-atom transfer (ESHAT) reaction of the 7-hydroxyquinoline(NH(3))(3) cluster involves a crossing from the initially excited (1)pipi(*) to a (1)pisigma(*) state. The nonadiabatic coupling between these states induces homolytic dissociation of the O-H bond and H-atom transfer to the closest NH(3) molecule, forming a biradical structure denoted HT1, followed by two more Grotthus-type translocation steps along the ammonia wire. We investigate this reaction at the configuration interaction singles level, using a basis set with diffuse orbitals. Intrinsic reaction coordinate calculations of the enol-->HT1 step predict that the H-atom transfer is preceded and followed by extensive twisting and bending of the ammonia wire, as well as large O-H...NH(3) hydrogen bond contraction and expansion. The calculations also predict an excited-state proton transfer path involving synchronous proton motions; however, it lies 20-25 kcal/mol above the ESHAT path. Higher singlet and triplet potential curves are calculated along the ESHAT reaction coordinate: Two singlet-triplet curve crossings occur within the HT1 product well and intersystem crossing to these T(n) states branches the reaction back to the enol reactant side, decreasing the ESHAT yield. In fact, a product yield of approximately 40% 7-ketoquinoline.(NH(3))(3) is experimentally observed. The vibrational mode selectivity of the enol-->HT1 reaction step [C. Manca, C. Tanner, S. Coussan, A. Bach, and S. Leutwyler, J. Chem. Phys. 121, 2578 (2004)] is shown to be due to the large sensitivity of the diffuse pisigma(*) state to vibrational displacements along the intermolecular coordinates.     

On the Dynamic Programming Approach for the 3<Emphasis Type="Italic">D</Emphasis> Navier–Stokes Equations

The dynamic programming approach for the control of a 3D flow governed by the stochastic Navier–Stokes equations for incompressible fluid in a bounded domain is studied. By a compactness argument, existence of solutions for the associated Hamilton–Jacobi–Bellman equation is proved. Finally, existence of an optimal control through the feedback formula and of an optimal state is discussed. This paper has been written at Scuola Normale Superiore di Pisa and at école Normale Supérieure de Cachan, Antenne de Bretagne.