Synthesis of novel rod-shaped and star-shaped fluorescent phosphane oxides--nonlinear optical properties and photophysical properties

The design of a new class of fluorophores is presented. Some push-pull chromophores (D-pi-A) containing polyphenylethynyl units and a phosphane oxide moiety were efficiently prepared from common intermediates. Straightforward syntheses gave novel one-armed, rod-shaped and three-armed, star-shaped fluorophores. The optical properties of the resulting star-shaped derivatives were evaluated, showed high fluorescence quantum yields, and their excitation induces very efficient charge redistribution. Moreover, thanks to their push-pull character, the molecules exhibited significant second-order NLO properties with good transparency, up to 67x10(-30) esu at 1907 nm, with an absorption lambdamax at 369 nm. The effect of the donor group and of the number of phenylethynyl arms have been studied in this work.     

Crystal structure of mixed rubidium–ammonium hydrogen sulfate Rb0.7(NH4)0.3HSO4 at room temperature

The structure of Rb_0.7(NH₄)_0.3HSO₄ has been determined by X-ray analysis. The mixed compound crystallizes in the monoclinic space group P2₁/n with unit cell parameters a = 14.374(6) Å, b = 4.618(6) Å, c = 14.412(2) Å, = 118.03(2)°, V = 844.4(4) ų, and D _cal = 1.536 g cm^–3 for Z = 8. The mixed compound Rb_0.7(NH₄)_0.3HSO₄ is a chain-based structure. The Rb⁺ and NH₄ ⁺ cations are intercalated between chains, formed of HSO₄ ^- groups linked with OHO hydrogen-bonding. Rb_0.7(NH₄)_0.3HSO₄ presents a new type of structural arrangement different from those of pure RbHSO₄ and NH₄HSO₄.     

On the subordinate killed B.M in bounded domains and existence results for nonlinear fractional Dirichlet problems

We take up in this paper the existence of positive continuous solutions for some nonlinear boundary value problems with fractional differential equation based on the fractional Laplacian (-D_|D)^\fraca2{(-\Delta _{|D})^{\frac{\alpha }{2}}} associated to the subordinate killed Brownian motion process Z_a^D{Z_{\alpha }^{D}} in a bounded C ^1,1 domain D. Our arguments are based on potential theory tools on Z_a^D{Z_{\alpha }^{D}} and properties of an appropriate Kato class of functions K _α (D).     

<Superscript>29</Superscript>Si MAS-NMR study of oxide conductors derived from the apatite-type La<Subscript>9.33</Subscript>Si<Subscript>6</Subscript>O<Subscript>26</Subscript> compound

The preparation of (La_9.33−2x/3Sr _x □_0.67−x/3)Si₆O₂₄O₂ (0 ≤ x ≤ 2) samples with different amounts of cation vacancies is reported. Structure and unit-cell parameters were deduced by Rietveld analysis of XRD patterns. Structural features that enhance oxygen conductivity in Sr-doped apatites are discussed. Up to three components were detected in ²⁹Si MAS-NMR spectra which change with the amount and distribution of cation vacancies. In general, oxygen conductivity increases with the amount of vacancies at La1 (6h) sites, passing through a maximum for x = 0.4. In the case of activation energy, a minimum is detected near x = 1.2, indicating that entropic and enthalpic change in different ways. The presence of cation vacancies should enhance oxygen hopping along c-axis; however, the analysis of the frequency dependence of conductivity suggests that oxygen motions are produced along three axes.     

Mass spectrometric behavior of functionalized calix[4]arenes: the screening ability of host�Cguest complex formation with amino acid methyl esters

The ESI?CMS and MS/MS behavior of functionalized calix[4]arenes (1?C5) has been studied in both positive and negative-ion mode. Liquid chromatography coupled to ESI?CMS has been successfully used for separation of the byproducts issuing from the functionalization pathways, through the application of a simple reversed phase mechanism. The ability of (1?C5) to host methyl esters of amino acids, tyrosine, tryptophan, phenylalanine, cysteine, valine, serine, leucine, isoleucine, and threonine has been evaluated by means of MS identification of the host?Cguest resulting in protonated molecular ions. The direct infusion within the ESI source of the solutions containing the two partners (i.e., calixarene and amino acid derivative) could act as a fast screening means for the evaluation of hosting capability. Only positive ionization may offer information about the host?Cguest complexes being formed. The influence of the excess of a partner in the infused solution strongly alters ionization yields, making quantitative approaches meaningless. Attempts to chromatographically isolate the host?Cguest complexes failed, probably due to the fact that interactions of the partners with the mobile and stationary phases are higher than the inclusion interactions. Structures consisting of combined fragments of the host?Cguest partners resulting from the collisional induced dissociation have not been observed.     

Directive metamaterial-based subwavelength resonant cavity antennas – Applications for beam steering

This article presents the use of composite resonant metamaterials for the design of highly directive subwavelength cavity antennas. These metamaterials, composed of planar metallic patterns periodically organized on dielectric substrates, exhibit frequency dispersive phase characteristics. Different models of metamaterial-based surfaces (metasurfaces), introducing a zero degree reflection phase shift to incident waves, are firstly studied where the bandwidth and operation frequency are predicted. These surfaces are then applied in a resonant Fabry–Perot type cavity and a ray optics analysis is used to design different models of ultra-compact high-gain microstrip printed antennas. Another surface presenting a variable reflection phase by the use of a non-periodic metamaterial-based metallic strips array is designed for a passive low-profile steering beam antenna application. Finally, the incorporation of active electronic components on the metasurfaces, allowing an electronic control of the phase responses, is applied to an operation frequency reconfigurable cavity and a beam steering cavity. All these cavity antennas operate on subwavelength modes, the smallest cavity thickness being of the order of λ/60. To cite this article: A. Ourir et al., C. R. Physique 10 (2009).     

Solving multi-criteria scheduling flow shop problem through compromise programming and satisfaction functions

The multi-criteria scheduling problem is one of the main research subjects in the field of multiple objectives programming. Several procedures have been developed to deal with this type of problem where some conflicting criteria have to be optimized simultaneously. The aim of our paper is to propose an aggregation procedure that integrates three different criteria to find the best sequence in a flow shop production environment. The compromise programming model and the concept of satisfaction functions will be utilized to integrate explicitly the manager’s preferences according to the deviations between the achievement and the aspiration levels of the following criteria: Makespan, total flow time and total tardiness.     

Asymptotic behavior of ground state radial solutions for problems involving the $$\Phi $$ Φ -Laplacian

Positivity - We are concerned with the existence of positive solutions to the following boundary value problem in $$(0,\infty ),$$ $$\begin{aligned} \frac{1}{A}\left( A\phi \left( \left| u^{\prime...     

Nanostructure and mechanical properties of polybutylacrylate filled with grafted silica particles

We investigate the nanostructure and the linear rheological properties of polybutylacrylate (PBA) filled with St?ber silica particles grafted with PBA chains. The silica volume fractions range from 1.8 to 4.7%. The nanostructure of these suspensions is investigated by small-angle neutron scattering (SANS), and we determine their spectromechanical behavior in the linear region. SANS measurements performed on low volume fraction composites show that the grafted silica particles are spherical, slightly polydisperse, and do not form aggregates during the synthesis process. These composites thus constitute model filled polymers. The rheological results show that introducing grafted silica particles in a polymer matrix results in the appearance of a secondary process at low frequency: for the lowest volume fractions, we observe a secondary relaxation that we attribute to the diffusion of the particles in the polymeric matrix. By increasing the silica volume fraction up to a critical value, we obtain gellike behavior at low frequency as well as the appearance of a structure factor on the scattering intensity curves obtained by SANS. Further increasing the silica particle concentration leads to composites exhibiting solidlike low-frequency behavior and to an enhanced structure peak on the SANS diagrams. This quantitative correlation between the progressive appearance of a solidlike rheological behavior, on one hand, and a structure factor, on the other hand, supports the idea that the viscoelastic behavior of filled polymers is governed by the spatial organization of the fillers in the matrix.     

Selective reduction of imonium salts by sodium hydrogen telluride

Sodium hydrogen telluride reduces imonium salts effeciently at room temperature in ethanol. The products of the reaction depend upon the pH. Under alkaline pH only dihydro-derivatives are formed. Under acid pH (6-7) the products depend on the structure of the salt. The tellurium con be recovered quantitatively.