Coupling of inverse gas chromatography at infinite dilution (IGC-ID) with a controlled modification of a solid surface

This paper presents a new method for studying the surface of a heterogeneous solid by inverse gas chromatography at infinite dilution (IGC-ID). After saturating the high-energy sites by impregnation with a suitable polymer, the chromatographic probes visit the low energy sites, which are not visible by conventional IGC-ID. This method has been used to study the two types of surface of talc: lateral and basal surfaces. In the second part of the paper the influence of the structure of the polymer on the impregnation is examined. In particular it is shown that a polymer with a linear structure is more able to fit a rough surface than is a branched or a cyclic polymer.     

In situ formation of allyl ketones via Hiyama-Nozaki reactions followed by a chromium-mediated Oppenauer oxidation

In Hiyama-Nozaki reactions of allylchromium with aldehydes the expected products are homoallylalcohols. However, oxidation products derived from these, predominantly allyl ketones, can be common side products. This can be explained by an Oppenauer-(Meerwein-Ponndorf-Verley)-type mechanism (OMPV-reaction). The amount of oxidation is strongly dependent on the substitution pattern of the reaction partners and the reaction conditions. An appropriate choice of these can lead to preferential formation of ketones instead of the alcohols. In addition to its synthetic usefulness, the oxidation-reduction equilibrium is of the utmost importance for the design of enantioselective Hiyama-Nozaki reactions because it is also a potential racemization pathway.     

Bis(isoquinoline N-oxide) pincers as a new type of metal cation dual channel fluorosensor

[structure: see text] A new type of donor-spacer-acceptor podand system has been synthesized and proved as an efficient dual channel fluorosensor for Li+, Mg2+, and Ca2+. The known ability for the N-oxide function to bind Lewis acids is the key step in the appearance of a new emitting charge-transfer (CT) excited state. The occurrence of this CT state for alkaline earth (Mg2+ and Ca2+) and not for alkaline metals (Li+) provided a new type of dual channel fluorosensors.     

Milliwatt-peak-power pulse characterization at 1.55 microm by wavelength-conversion frequency-resolved optical gating

A novel wavelength-conversion configuration based on four-wave mixing in an optical fiber has been used to generate a frequency-resolved optical gating (FROG) trace identical to that obtained from second-harmonic generation (SHG). The use of an optical fiber waveguide permits enhanced measurement sensitivity compared with that of conventional SHG-FROG and has been used for complete characterization of 1-mW peak-power picosecond pulses at 1.55 microm from an unamplified semiconductor laser diode gain switched at 10 GHz.     

Hamilton's Principle and Rankine–Hugoniot Conditions for General Motions of Mixtures

In previous papers [1, 2], we presented hyperbolic governing equations and jump conditions for barotropic fluid mixtures. Now we extend our results to the most general case of twocomponent media. We obtain governing equations for each component. This is not a system of conservation laws. Nevertheless, using Hamilton's principle we are able to obtain a complete set of Rankine–Hugoniot conditions. For the twofluid case, the jump relations do not involve the conservation of the total momentum and the total energy.Sommario. In precedenti lavori [1, 2] sono state dedotte equazioni di governo iperboliche e condizioni di salto per miscele fluide barotropiche. I risultati sono estesi al caso più generale di mezzi a due componenti, ottenendo le equazioni di governo per ciascun componente. Questo sistema non è derivabile dalle leggi di conservazione. Nondimeno, usando il principio di Hamilton è possibile ottenere un insieme completo di condizioni di Rankine–Hugoniot. Nel caso dei due fluidi, le condizioni di salto non coinvolgono la conservazione del momento e dell'energia totali.     

Completeness and Admissibility for General Heuristic Search Algorithms—A Theoretical Study: Basic Concepts and Proofs

We propose a formal generalization for various works dealing with Heuristic Search in State Graphs. This generalization focuses on the properties of the evaluation functions, on the characteristics of the state graphs, on the notion of path length, on the procedures that control the node expansions, on the rules that govern the update operations. Consequently, we present the algorithm family and the sub-family Ã, which include Nilsson's A or A_* and many of their successors such as HPA, B, A ^* , A, C, BF^*, B, IDA^*, D, A^**, SDW. We prove general theorems about the completeness and the sub-admissibility that widely extend the previous results and provide a theoretical support for using diverse kinds of Heuristic Search algorithms in enlarged contexts, specially when the state graphs and the evaluation functions are less constrained than ordinarily.     

Chemoenzymatic synthesis of α-halogeno-3-octanol and 4- or 5-nonanols. Application to the preparation of chiral epoxides

A study of the microbiological reduction of different α-halogenoketones (4-chloro-3-octanone, 4-chloro-5-nonanone, 5-bromo-4-nonanone and 5-chloro-4-nonanone) with several strains of microorganism showed great difficulty in reducing ketone functions located in the middle of carbon chains. However, by choosing the appropriate microorganism, several enantiomerically pure diastereoisomers of the corresponding halohydrins have been obtained and were transformed into chiral epoxides.     

Étude des restes pour les suites de Van Der Corput généralisées

We get the asymptotic behaviour of the remainder function with respect to the Van Der Corput generalized sequences construted in a previous paper (in Bulletin de la S.M.F, n^o 109, 1981). As a consequence, we obtain the intervals [0, a] for which the remainder is bounded. Moreover, we give an explicit formula for the remainder with respect to the Van Der Corput sequence in the r-adic system.