Analysis of quaternary ammonium and phosphonium ionic liquids by reversed-phase high-performance liquid chromatography with charged aerosol detection and unified calibration

Several hydrophobic ionic liquids (ILs) based on long-chain aliphatic ammonium- and phosphonium cations and selected aromatic anions were analyzed by reversed-phase high-performance liquid chromatography (RP-HPLC) employing trifluoroacetic acid as ion-pairing additive to the acetonitrile-containing mobile phase and adopting a step-gradient elution mode. The coupling of charged aerosol detection (CAD) for the non-chromophoric aliphatic cations with diode array detection (DAD) for the aromatic anions allowed their simultaneous analysis in a set of new ILs derived from either tricaprylmethylammonium chloride (Aliquat 336) and trihexyltetradecylphosphonium chloride as precursors. Aliquat 336 is a mix of ammonium cations with distinct aliphatic chain lengths. In the course of the studies it turned out that CAD generates an identical detection response for all the distinct aliphatic cations. Due to lack of single component standards of the individual Aliquat 336 cation species, a unified calibration function was established for the quantitative analysis of the quaternary ammonium cations of the ILs. The developed method was validated according to ICH guidelines, which confirmed the validity of the unified calibration. The application of the method revealed molar ratios of cation to anion close to 1 indicating a quantitative exchange of the chloride ions of the precursors by the various aromatic anions in the course of the synthesis of new ILs. Anomalies of CAD observed for the detection of some aromatic anions (thiosalicylate and benzoate) are discussed.     

Physical Science in Bologna

We provide a guide to Bologna, Italy, focusing particularly on sites of interest to physicists. Our first tour is in the city center; it begins in the Piazza Maggiore at the Palazzo d’Accursio, the Basilica di San Petronio, and the Archiginnasio (Old University) and then proceeds to the Two Towers and the Palazzo Poggi, which houses the Astronomical Observatory Museum and other important instrument and art collections; it concludes at the Physics Museum, Department of Physics and Astronomy. Our second tour again begins in the Piazza Maggiore but goes to sites beyond the city center where famous Bolognese physicists and other scientists were born, lived, and are buried. Finally, we point out important museums and other institutions on the outskirts of Bologna.     

A Structure–Activity Study of Nickel NNN Pincer Complexes for Alkyl‐Alkyl Kumada and Suzuki–Miyaura Coupling Reactions

A new series of Ni NNN pincer complexes were synthesized and characterized. The main difference among these complexes is the substituents on the side arm amino group(s). No major structural difference was found except for the C–N–C angle of the various substituents and the ‘pseudo bite angle’ of the complexes. Four new complexes were efficient for the alkyl‐alkyl Kumada reaction of primary alkyl halides, and among them, one complex was also efficient with secondary alkyl halides. The influence of the substituents on the catalytic performance of the Ni complexes in alkyl‐alkyl Kumada and Suzuki–Miyaura cross‐coupling reactions was systematically investigated. No correlation was found between the catalytic activity and the key structural parameters (C–N–C angle and ‘pseudo bite angle’), redox properties or Lewis acidity of the complexes.     

Risk premium and fair option prices under stochastic volatility: the HARA solution

We have solved the problem of finding (HARA) fair option price under a general stochastic volatility model. For a given HARA utility, the ‘risk premium’, i.e., the ‘market price of volatility risk’ is determined via a solution of a certain nonlinear PDE. Equivalently, the fair option price is determined as a solution of an uncoupled system of a non-linear PDE and a Black–Scholes type PDE. To cite this article: S.D. Stojanovic, C. R. Acad. Sci. Paris, Ser. I 340 (2005).     

Universality in Orthogonal and Symplectic Invariant Matrix Models with Quartic Potential

In this work, we develop an orthogonal-polynomials approach for random matrices with orthogonal or symplectic invariant laws, called one-matrix models with polynomial potential in theoretical physics, which are a generalization of Gaussian random matrices. The representation of the correlation functions in these matrix models, via the technique of quaternion determinants, makes use of matrix kernels. We get new formulas for matrix kernels, generalizing the known formulas for Gaussian random matrices, which essentially express them in terms of the reproducing kernel of the theory of orthogonal polynomials. Finally, these formulas allow us to prove the universality of the local statistics of eigenvalues, both in the bulk and at the edge of the spectrum, for matrix models with two-band quartic potential by using the asymptotics given by Bleher and Its for the corresponding orthogonal polynomials.     

Compressed sensing in random access networks with applications to underwater monitoring

For networks that are deployed for long-term monitoring of environmental phenomena, it is of crucial importance to design an efficient data gathering scheme that prolongs the life-time of the network. To this end, we consider a Random Access Compressed Sensing (RACS) scheme that considerably reduces the power and bandwidth usage of a large network. Motivated by underwater applications, we propose a continuous-time RACS that eliminates the need for synchronization and scheduling which are difficult to achieve in a distributed acoustic network. We provide an analytical framework for system design that ensures fast recovery and power-efficiency. Through analysis and examples, we demonstrate that recovery of the field can be attained using only a fraction of the resources used by a conventional TDMA network, while employing a scheme which is simple to implement.     

Aptamer-based folding fluorescent sensor for cocaine.

We adapted in two steps a deoxyribonucleotide-based aptamer to signal the recognition of cocaine: an instability was engineered in one stem of a three-way junction that forms the cocaine-binding pocket and the resulting short stem was end labeled with a fluorophore and a quencher. In the absence of cocaine, two stems are open, but in its presence they close and the three-way junction forms. This major structural change brings fluorophore and quencher together thereby signaling the presence and concentration of ligand. The sensor is selective for cocaine over its metabolites, can operate in serum, and is useful for the screening of cocaine hydrolases.     

Photoluminescence spectroscopy of CdSe nanoparticles embedded in transparent glass

In this paper we present photoluminescence measurements of CdSe nanoparticles embedded in transparent glass. Sample is prepared using an original technique, which combines both heat treatment and ultraviolet laser irradiation. Photoluminescence spectra displayed one main emission band at 2.14 eV. We identify this bands energy as basic interband transition in CdSe nanoparticle. We calculated energy of basic (1s_h–1s_e) transition in spherical CdSe quantum dot (QD), within infinite potential barrier, in effective-mass approximation. On the basis of this model, average radius of synthesized CdSe QDs is about 3 nm, which is in consistence with AFM measurements and UV–VIS absorption measurements.