Research on the aromas. On the aroma of coffee. I

The analysis of a coffee concentrate is described: 202 constituents have been identified, 154 of which for the first time. Some of these compounds are new chemicals; their synthesis is described. Most identifications are based upon mass spectrometry combined in many cases with IR. spectrometry and comparison with reference compounds. MS. and IR. data are given in detail. The analysis shows that a large number of minor constituents is present, many of which could not be identified.     

Undulation instability in two-dimensional foams of magnetic fluid

Two-dimensional magnetic fluid foams are cellular structures whose framework is made of magnetic fluid. The features of these equilibrated patterns are driven by a control parameter: the amplitude of the applied magnetic field. When the latter is rapidly increased, an instability occurs: the walls between cells undulate. Such an instability has also been observed in other 2D cellular structures, which exist for instance in Langmuir monolayers or in magnetic garnets thin films. In this paper we give a theoretical analysis of this instability, the issues of which are shown to be well confirmed by experiments and numerical simulations. Received: 13 October 1997 / Received in final form: 28 January 1998 / Accepted: 9 March 1998     

Activite optique de la methyl-3 cyclopentenanone; un calcul ab initio

Ab initio calculations for two conformers of 3-methyl cyclopentanone, with and without 3d orbitals, show that inclusion of d orbitals on the carbonyl group lower energies and is thus necessary, as follows from the variation principle; it also markedly affects rotatory strengths of the n→π^* and π→π^* transitions, but conformational equilibria of the cyclic skeleton and the methyl group are almost independent of the basis chosen. Internal rotation of the methyl group exerts a negligible influence on the rotatory strength of the n→π^* transition, so that this group can be considered as a sphere in this respect.     

Synthese de diterpenes tetracycliques du type hibane

Hibaone has been synthesized from manool through a photochemical cycloaddition of Δ⁸⁽¹⁴⁾ podocarpene-13-one to ethylene or 1,2 dichloroethylene.     

Determination of contracted atomic basis sets for the study of CN; application to the MCSCF calculations of its spectroscopic constants

Contracted atomic basis sets have been constructed from ANOs in order to describe the ground and excited states of C and N and their anions. Application is given with the MCSCF calculation of the vibration frequency of CN⁻ and of other spectroscopic constants. A procedure is proposed to do MCSCF calculations when some problems of convergence arise.     

Perturbative solution of the RPA equation. An application to the calculation of rotational strengths

The RPA equation is solved by perturbation in Møller-Plesset (MP) and Epstein-Nesbet (EN) partitions, which are first compared on a specific example. To still accelerate the faster one (EN), a third scheme is proposed, which involves preliminary diagonalization within a limited subset , followed by usual EN perturbation between and the rest of the whole configuration space. Criteria for the choice of are given.     

Recherches sur les arǒmes, 18e communication Sur l'arǒme de viande de boeuf grillée,I. Pyrazines

A combined gas chromatography-mass spectrometry analysis of roasted meat flavor prepared by pyrolysis of water-soluble components of fresh beef has yielded 17 alkylpyrazines (5 already found in heated beef fat), one being a new flavor compound. The mass spectrum of this compound is given.     

Conductivity of irradiated Kapton in relation to energy loss of ions and electrons

Abstract

We have studied the effects of 2.5 MeV electron irradiation and ion (C, N, F, Si and Kr) bombardment on the electrical conductivity of a polyimide (Kapton-H) with ion energies ranging between 320 keV (N) and 1.25 GeV (Kr). In this wide range of situations we have tried to sort out the respective effects of nuclear and electronic excitation energy losses.

For all ion irradiation the conductivity is found to scale with the electronic excitation absorbed dose: i.e. a power law of conductivity versus absorbed dose with an exponent around 9 is observed. At a given absorbed dose (in Gray units) the efficiency of each ion to enhance conductivity is found to be proportional to the electronic energy loss; electrons are much less efficient than ions and thus collective excitations are required to achieve this process.

The nuclear energy loss can perhaps play some role at conductivities higher than 100 Ω^?1 m^?1, but its effects are negligible in the range explored here.     

ChemInform Abstract: An ab initio Theoretical Study of the Electronic Structure of UO2+ and [UO2(CO3)3]5‐.

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