Multi-conformational compounds with two absorbing groups

Two methods are proposed for dealing with a three-membered ring which is incorporated into a large molecule. The first, an all-valence electron approach, is an iterative CNDO/2 which provides, through bond indices, self-consistent hybridizations and valency angles. The second is compatible with -electron approaches and aims at the study of conjugation and transmission of conjugation. The methods are illustrated by application to the unsubstituted cyclopropane molecule.

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Zusammenfassung Es werden zwei Methoden zur Behandlung von Molekülen, die einen Dreiring enthalten, vorgeschlagen. Die eine besteht in der iterativen Anwendung des CNDO/2-Verfahrens mit selbst-konsistenten Hybridisierungen und Valenzwinkeln. Die zweite entspricht etwa einem -Elektronenverfahren und dient besonders dem Studium von Konjugationseffekten. Illustriert werden beide am Beispiel des einfachen Cyclopropan.

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Résumé On propose deux méthodes pour étudier les molécules contenant une composante cyclopropanique. La première, qui tient compte de tous les électrons de valence, est une CNDO/2 itérative qui fournit — par l'intermédiaire des indices carrés de liaison — des valeurs auto-cohérentes pour l'hybridation et les angles de valence. L'autre, compatible avec les techniques -électroniques, a pour but l'étude de la conjugaison et de la transmission de conjugaison. Les méthodes sont illustrées par application au cyclopropane non-substitué.

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For Part V, see Ref. [1].     

Total synthesis of the marine alkaloid halitulin

The structure of the strongly cytotoxic marine alkaloid halitulin (1) has been confirmed by total synthesis and its absolute configuration determined as (15S). The synthesis follows a strategy previously reported by one of us and uses an efficient preparation of the quinoline-7,8-diol unit by modified Baeyer-Villiger and Skraup reactions. The O-benzyl protecting groups were removed in the last step of the synthesis by transfer hydrogenolysis without concomitant reduction of the quinoline ring. The method can be applied for the synthesis of halitulin analogues.     

Longitudinal nuclear relaxation measurements in hcp H2

Measurements of T₁ in the hep phase of H₂, over the temperature range 2°–12°K and the ortho concentration range between 0.5 and 0.97 are presented. At temperatures below 10°K, the thermally activated self-diffusion is negligible and the mechanism for nuclear relaxation is that attributed by Moryia and Motizuki and by Harris to intramolecular dipolar interaction, modulated by intennolecular electric quadrupole-quadrupole (EQQ) interaction. The gaussian approximation for the correlation function was used by these authors to predict T₁. From the comparison between experiment and theory, we determine the EQQ parameter Γ/k_B to be 0.67°K. Above 10°K the effect of diffusion influences T₁, and the experimental results for an 88 per cent ortho H₂ sample up to the melting point suggest that the relaxation mechanisms resulting from EQQ interaction and diffusion are not independent of one another.     

Determination of the atmospheric neutrino spectra with the Fréjus detector

The combined analysis of the final event set of data on neutrino interactions inside the detector, upward going stopping muons and horizontal muons recorded in the Fréjus experiment is presented. The absolute atmospheric neutrino spectra in the energy range for electron neutrinos and for muon neutrinos are determined. Based on the parameterization of Volkova for thev ^µ a spectral index of =2.66±0.05 is obtained from the ratio of horizontal muons over upward going stopping muons and from the measurement of the energy loss of horizontal muons inside the detector. The neutrino spectra are compared with various flux calculations. They do not show any evidence for neutrino oscillations in agreement with earlier analyses of the Fréjus data.Now atUniversity of Michigan, Ann Arbor, USA     

Wave equations onq-Minkowski space

We give a systematic account of a component approach to the algebra of forms onq-Minkowski space, introducing the corresponding exterior derivative, Hodge star operator, coderivative, Laplace-Beltrami operator and Lie-derivative. Using this (braided) differential geometry, we then give a detailed exposition of theq-d'Alembert andq-Maxwell equation and discuss some of their non-trivial properties, such as for instance, plane wave solutions. For theq-Maxwell field, we also give aq-spinor analysis of theq-field strength tensor.