Approaches toward the synthesis of 2,5-disubstituted-1,3-thiazolidines

Synthetic approaches for new 2,5-disubstituted-1,3-thiazolidines are described. Steric and electronic effects of the N-substituent of the thiazolidine ring represent the major parameter in the rearrangement process. The nmr studies demonstrate that N-unsubstituted 2,5-disubstituted-1,3-thiazolidines exist as epimeric mixture, while the corresponding N-acetylated analogues exist as a conformer mixture.     

A far infrared scanning plane Fabry-Perot spectro interferometer

We describe a mounting fitted to select a narrow frequency band between 20 and 100 cm^–1 in the far infrared; it consists of a coupling of a grating monochromator with a plane scanning Fabry-Perot interferometer (F. P.).This apparatus is intended for the fine study of profiles, pure rotation line broadening and shifting of simple dipolar molecules perturbed under low pressure.     

Orbits of triples in the Shilov boundary of a bounded symmetric domain

Let be a bounded symmetric domain of tube-type, S its Shilov boundary, and G the neutral component of its group of biholomorphic transforms. We classify the orbits of G in the set      

Galactose Oxidase models: 19F NMR as a powerful tool to study the solution chemistry of tripodal ligands in the presence of copper(II)

In copper(ii) complexes of tripodal ligands, the protonation state of the phenol moiety, and its position (axial vs. equatorial), are easily assessed by (19)F NMR.     

Doing arithmetic with nonlinear acoustic vortices

Phase singularities of wave-front-like screw dislocations or vortices possess a well-defined quantity that can only take integer value: the topological charge. In the nonlinear regime, it has been demonstrated that optical or acoustical vortices interact and the topological charge follows a conservation law. Here this facility is used in nonlinear parametric interaction of two vortices shifted in frequency to perform sums and subtractions of the topological charge. Thus, we experimentally demonstrate a new technique to perform wave computation in the group of integer Z. When the two vortices have commensurable frequencies, different combinations give the same frequencies but different tolopological charges may occur. We show that an energy criterion can be used to predict the outcome. A corollary is that a modulation of amplitude of the vortices switches from one result to the other.     

On the influence of spatial correlations on sound propagation in concentrated solutions of rigid particles

In a previous paper [J. Acoust. Soc. Am. 121, 3386-3387 (2007)], a self-consistent effective medium theory has been used to account for hydrodynamic interactions between neighboring rigid particles, which considerably affect the sound propagation in concentrated solutions. However, spatial correlations were completely left out in this model. They correspond to the fact that the presence of one particle at a given position locally affects the location of the other ones. In the present work, the importance of such correlations is demonstrated within a certain frequency range and particle concentration. For that purpose, spatial correlations are integrated in our two-phase formulation by using a closure scheme similar to the one introduced by Spelt et al. ['Attenuation of sound in concentrated suspensions theory and experiments," J. Fluid Mech. 430, 51-86 (2001)]. Then, the effect is shown through a careful comparison of the results obtained with this model, the ones obtained with different self-consistent approximations and the experiments performed by Hipp et al. ["Acoustical characterization of concentrated suspensions and emulsions. 2. Experimental validation," Langmuir, 18, 391-404 (2002)]. With the present formulation, an excellent agreement is reached for all frequencies (within the limit of the long wavelength regime) and for concentrations up to 30% without any adjustable parameter.     

Excimer laser crystallization of microcrystalline silicon for TFTs on flexible substrate

Microcrystalline silicon (μc-Si) films have been deposited on PDMS as well as on PEN substrate. Excimer laser annealing was used to improve the crystalline structure and so to obtain high mobility TFTs. The effect of the laser annealing on the crystalline structure of silicon films is studied using different characterization techniques and discussed. Mobility values of 60 cm²/V s with PDMS and 46 cm²/V s with PEN are obtained.     

Fluorescent P-Hydroxyphosphole for Peptide Labeling through P-N Bond Formation

Synthesis of fluorescent P-hydroxybinaphtylphosphole-oxide or -sulfide was achieved by trapping a binaphtyl dianion with methyl dichlorophosphite or P-(N,N-diethylamino)dichlorophosphine, followed by oxidation or sulfuration of the P-center. After saponification or acid hydrolysis, the P-hydroxyphospholes were coupled to peptides using the coupling agent BOP, under the conditions required for the synthesis in solution or on a solid support. This new method was illustrated by the labeling of the JMV2959, a potent antagonist of the Growth Hormone Secretagogue Receptor type 1a (GHS−R1a). The labeled conjugates were used to characterize GHSR ligands by competition assays, based on Fluorescence Resonance Energy Transfer (FRET). Such P-hydroxyphosphole-oxide or -sulfide constitute a promising new class of compact fluorophores with large Stokes shift, for labeling biomolecules by grafting through the phosphorus atom.     

Acetylcholinesterase-based biosensors for quantification of carbofuran, carbaryl, methylparaoxon, and dichlorvos in 5% acetonitrile

Amperometric acetylcholinesterase biosensors have been developed for quantification of the pesticides carbofuran, carbaryl, methylparaoxon, and dichlorvos in phosphate buffer containing 5% acetonitrile. Three different biosensors were built using three different acetylcholinesterase (AChE) enzymes—AChE from electric eel, and genetically engineered (B394) and wild-type (B1) AChE from Drosophila melanogaster. Enzymes were immobilized on cobalt(II) phthalocyanine-modified electrodes by entrapment in a photocrosslinkable polymer (PVA-AWP). Each biosensor was tested against the four pesticides. Good operational stability, immobilisation reproducibility, and storage stability were obtained for each biosensor. The best detection limits were obtained with the B394 enzyme for dichlorvos and methylparaoxon (9.6 × 10⁻¹¹ and 2.7 × 10⁻⁹ mol L⁻¹, respectively), the B1 enzyme for carbofuran (4.5 × 10⁻⁹ mol L⁻¹), and both the B1 enzyme and the AChE from electric eel for carbaryl (1.6 × 10⁻⁷ mol L⁻¹). Finally, the biosensors were used for the direct detection of the pesticides in spiked apple samples.