Methylaluminium compounds

The S.C.M.O. methods has been employed to study the valence electronic structures of some isomers of the methylboron and methylaluminium hydrides. Basis sets including 3s, 3p and diffuse and contracted 3d orbitals were used for the aluminium atoms. For both boron and aluminium compounds hydrogen is energetically favoured over methyl as a bridging group. This stems mainly from the different nuclear repulsion energies of the isomers. Participation of the 3d orbitals is quite marked, particularly in the metal-metal cross-ring interactions.

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Zusammenfassung Mittels der SCMO Methode wurde die Valenzelektronenstruktur einiger Isomere der Methylborund Methylaluminiumhydride untersucht. Die Basis enthielt für Aluminiumatome 3s, 3p und kontrahierte und nicht kontrahierte 3d Zustände. Sowohl bei den Bor- als auch den Aluminiumverbindungen sind Wasserstoffatome als Brücke gegenüber Methylgruppen energetisch begünstigt. Das rührt hauptsächlich von den unterschiedlichen Kernabstoßungsenergien her. Die Beteiligung der 3d Orbitale ist deutlich, besonders in der (transannularen) Metall-Wechselwirkung.

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Résumé La méthode S.C.M.O. a été utilisée pour étudier les structures électroniques de valence de certains isomères des hydrures de méthylbore et de methylaluminium. Pour les atomes d'aluminium on a utilisé des bases contenant des orbitales 3s, 3p et des orbitales 3d diffuses et contractées. Tant pour les composés du bore que ceux de l'aluminium l'hydrogène est favorisé énergétiquement par rapport au méthyl en tant que groupement de pont. Ceci provient essentiellement des différences d'énergie de répulsion nucléaire. La participation des orbitales 3d est nettement marquée, particulièrement dans les interactions métal-métal à travers le cycle.

     

Uniform measure results for the image of subsets under Brownian motion

Summary The paper obtains bounds on the Hausdorff and packing measures of the imageX(E) of a Borel setE by a transient strictly stable processX _t which a.s. hold for allE and for every measure function . In some cases examples are constructed to show that the bounds are sharp.While preparing this paper, the author was partially supported by NSERC and by NSF on contract #DMS-8317815     

The polarographic determination of aluminium* : General introduction polarography of solochrome violet r.s. in the presence of aluminium

A survay is made of the methods available for the determination of microgram quantities of aluminium, together with techniques for its separation from interfering ion species. The polarography of aluminium is briefly discussed and a. study is reported of a method involving the modification, by this element, of the polarographic characteristics of a diortho-hydroxy azo dye. Interferences other elements are given in detail and discussed. Means for their removal are suggested     

Advantages of deuterium modification of nitroxide spin labels for biological epr studies

The spin label, perdeuterio-N-(1-oxy 1-2,2,6,6-tetramenthyl-4-piperidinyl)maleimide (DMSL) was synthesized and its EPR and saturation transfer EPR spectra were compared to those of the hydrogen analogue, HMSL- The labels were studied as freely tumbling entities and also bound to bovine serum albumin (BSA). Significant gains in spectral resolution and detectability were observed for DMSL relative to HMSL.     

Spin dynamics in the generalized ferromagnetic Kondo model for manganites

We calculate the dynamic spin susceptibility in the generalized Kondo model describing the interaction between the band e_g electrons and the localized t_2g electrons coupled via the antiferromagnetic exchange. We show that the spin-wave spectrum in the ferromagnetic phase has acoustic and optical branches in the mean-field approximation. We evaluate the self-energy corrections to the spectrum and estimate the damping of acoustic magnons. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 120, No. 3, pp. 438–450 September, 1999.