Stereoselective preparation of a cyclopentane-based NK1 receptor antagonist bearing an unsymmetrically substituted sec-sec ether

A highly efficient synthesis of the potent and selective NK-1 receptor antagonist 1 is described. The key transformation involved the etherification reaction between cyclopentanol 12 and chiral imidate 30 which was catalyzed by HBF4 to initially give ether 14 as a 17:1 mixture of diastereomers and in 75% combined yield. The diastereoselectivity was upgraded to 109:1 by crystallization of the triethylamine solvate 44 which was isolated in 54% yield from 12. Mechanistic studies confirmed that the etherification reaction proceeds through an unprecedented S(N)2 reaction pathway under typical S(N)1 reaction conditions.     

Nanostructured substrates for portable and miniature SPR biosensors

Surface plasmon resonance (SPR) biosensing has matured into a valuable analytical technique for measurements related to biomolecules, environmental contaminants, and the food industry. Contemporary SPR instruments are mainly suitable for laboratory-based measurements. However, several point-of-measurement applications would benefit from simple, small, portable and inexpensive sensors to assess the health condition of a patient, potential environmental contamination, or food safety issues. This Trend article explores nanostructured substrates for improving the sensitivity of classical SPR instruments and nanoparticle (NP)-based colorimetric substrates that may provide a solution to the development of point-of-measurement SPR techniques. Novel nanomaterials and methodology capable of enhancing the sensitivity of classical SPR sensors are destined to improve the limits of detection of miniature SPR instruments to the level required for most applications. In a different approach, paper or substrate-based SPR assays based on NPs, are a highly promising topic of research that may facilitate the widespread use of a novel class of miniature and portable SPR instruments.     

EOT or Kretschmann configuration? Comparative study of the plasmonic modes in gold nanohole arrays

The debate is still ongoing on the optimal mode of interrogation for surface plasmon resonance (SPR) sensors. Comparative studies previously demonstrated that nanoparticles exhibiting a localized SPR (LSPR) have superior sensitivity to molecular adsorption processes while thin Au film-based propagating SPR is more sensitive to bulk refractive index. In this paper, it is demonstrated that nanohole arrays (1000 nm periodicity, 600 nm diameter and 125 nm depth), which support both LSPR and propagating SPR modes, exhibited superior sensitivity to bulk refractive index and improved detection limits for IgG sensing by using the Kretschmann configuration. The greater sensitivity to IgG detection in the Kretschmann configuration was obtained despite the shorter penetration depth of nanohole arrays excited in the enhanced optical transmission (EOT) configuration. The decay length of the electromagnetic field in EOT mode was estimated to be approximately 140 nm using a layer-by-layer deposition technique of polyelectrolytes (PAH and PSS) and was confirmed with 3D FDTD simulations, which was lengthen by almost a factor of two in the Kretschmann configuration. Spectroscopic data and field depth were correlated with RCWA and FDTD simulations, which were in good agreement with the experimental results. Considering these analytical parameters, it is advantageous to develop sensors based on nanohole arrays in the Kretschmann configuration of SPR.     

Stabilization of non-premixed flames in supersonic reactive flows

A Lagrangian framework is set out to describe turbulent non-premixed combustion in high speed coflowing jet flows. The final aim is to provide a robust computational methodology to simulate, in various conditions, the underexpanded GH2/GO2 torch jet that is used to initiate combustion in an expander cycle engine. The proposed approach relies on an early modelling proposal of Borghi and his coworkers. The model is well suited to describe finite rate chemistry effects and its recent extension to high speed flows allows one to take the influence of viscous dissipation phenomena into account. Indeed, since the chemical source terms are highly temperature sensitive, the influence of viscous phenomena on the thermal runaway is likely to be all the more pronounced since the Mach number values are high. The validation of the extended model has been recently performed through the numerical simulation of two distinct well-documented experimental databases. Only a brief summary of this preliminary validation step is provided here. The main purpose of the present work is to proceed with the numerical simulation of geometries that bring together the essential peculiarities of the underexpanded GH2/GO2 torch. The behavior of the corresponding supersonic coflowing jet flames for various conditions is discussed in the light of computational results. To cite this article: J.-F. Izard, A. Mura, C. R. Mecanique 337 (2009).     

A proximal point algorithm for control approximation problems

We consider the optimization problem $$f(x): = (c,x) + \sum\limits_{i = 1}^n {\alpha _i \parallel A^i x - a^i \parallel ^{\beta _i } \to \mathop {\min }\limits_{x \in D} ,} $$ which is an extension of a problem studied by Idrissi, Lefebvre and Michelot [7]. This class of problems contains many practically important special cases so as approximation, location and optimal control problems, perturbed linear programming problems and surrogate problems for linear programming. Necessary and sufficient optimality conditions are derived using the sub-differential calculus. A proximal point algorithm is modified by the method of partial inverse [13] in order to solve the optimality conditions.     

Mesure de la duree de vie de niveaux d'energie d'ions par transfert de coherence dans une collision de penning: Application aux niveaux 4f 2F72 et 2F52 de Mg+

Metastable 2³S₁ He atoms are optically oriented and their orientation is transferred to metallic ions produced by Penning collisions $\text{[He (2}{}^3\text{S}{}_1\text{)}\text{+ M →}\text{He (}{}^1\text{S}{}_0\text{)}\text{+ M}{}^{\mathrm{+}}\text{+}\text{e}$. If r.f. transitions are induced in the 2³S₁ He level, the circularly polarized light emitted by the ions in a direction perpendicular to the static magnetic field is modulated at the r.f. frequency. The variation of the modulation amplitude with frequency depends on the lifetime of the level of the excited ion.We describe an experimental apparatus with which we measure the modulation amplitude from 1 MHz to 110 MHz. In this way the lifetime of the 4f²F_{$\text{7}\text{2}$} and ²F_{$\text{5}\text{2}$} Mg⁺ levels has been determined.     

Set-valued average value at risk and its computation

New versions of the set-valued average value at risk for multivariate risks are introduced by generalizing the well-known certainty equivalent representation to the set-valued case. The first ’regulator’ version is independent from any market model whereas the second version, called the market extension, takes trading opportunities into account. Essential properties of both versions are proven and an algorithmic approach is provided which admits to compute the values of both versions over finite probability spaces. Several examples illustrate various features of the theoretical constructions.     

Complete Duality for Quasiconvex and Convex Set-Valued Functions

This paper provides a unique dual representation of set-valued lower semi-continuous quasiconvex and convex functions. The results are based on a duality result for increasing set-valued functions.     

Composition analysis of an ethylene–propylene block copolymer by fractionation and turbidity measurements at the lower critical solubility gap

The composition of an ethylene-propylene block copolymer with a nominal 15% content of ethylene by weight (EP?B15%) has been investigated through fractionation near the lower critical solution temperature (LCST). Observation of the solution heated above the boiling point of the solvent indicated that some polymer was phase separating, apparently continuously, between the LCSTs of polyethylene (PE) an polypropylene (PP) of similar molecular weight. IR and DSC analysis of three fractions obtained by twice separating the concentrated phase from the dilute phase gave the following result: EP?B15% consists of an ethylene-rich block copolymer (93% E), an EP copolymer of intermediate composition, and a propylene-rich copolymer (94% P). The three fractions constitute respectively 12%, 12%, and 76% of the total weights. In order to choose a suitable temperature for fractionation, a turbidity analysis of the solution of the initial polymer is made continuously during phase separation. The trace of turbidity against temperature shows three peaks of turbidity at temperatures T₀, T₁ and T₂, which can be associated with the above fractions. A mixture of PE, PP, and a 33% E random copolymer gives a turbidity trace with characteristic temperatures very similar to that of EP-B15% in the same solvent. Fractionation from several solvents or mixtures of solvents indicated that the composition of the fractions did not depend significantly on the nature of the solvent. Conditions for obtaining a quantitative analysis of a mixture from a thermogram are discussed. Turbidity analysis during phase separation and fractionation at the LCST can be a useful tool in analyzing and separating complex mixtures before use of powerful analytical techniques such as NMR or IR spectroscopy.