Enantioselective synthesis of 3-demethoxyaranciamycinone via asymmetric epoxidation

The tetracyclic olefin 1 was enantioselectively epoxidized using a molybdenum(VI)- oxodiperoxo complex containing a chiral lactamide. Conversion to the glycosides 8 and 9 showed the epoxide 2 to be the predominant (3 : 1) enantiomer.     

Calorimetric relaxation and glass transition in poly(propylene glycols) and its monomer

The glass transition temperature T_g of propylene glycol (PG) and poly(propylene glycols) (PPGs) of molecular weight up to 4000 has been measured by differential scanning calorimetry, and the activation energy and change in heat capacity ΔC_p have been determined in the glass transition range. The activation energy increases with an increase in the molecular weight of the polymer, and ΔC_p measured at a fixed heating rate decreases. The increase in T_g with molecular weight is remarkably more rapid for poly(propylene glycols) than for other polymers, and a limiting value of T_g is reached for a chain containing 20 monomer units. These results are discussed in terms of the Fox-Flory and the entropy theories. The calorimetric relaxation times are comparable with the extrapolated dielectric relaxation times. The initial increase of ΔC_p from PG to PPG 200 is attributed to the decrease of H-bonding sites from 12 in 3 monomers to 4 on polymerization to PPG 200 and further decrease with increase in molecular weight to an increasingly large amplitude of the β-process at T < T_g.     

Inequalities for Mean Circumscribing Simplices

The aim of this note is to strengthen and generalize an inequality of Sangwine–Yager regarding means of various quantities associated with the simplices circumscribing a convex body.     

On a generalization of Wick-powers for generalized free-fields in terms of Jacobi-fields

Within the frame of Jacobi-fields a generalization of Wick-powers of generalized free fields is proposed. The key notion is that of a (generalized) contraction map. Those contraction maps F which yield a relativistic quantum field A^F are characterized. Using some simplifying assumptions the general form of a contraction map F which yields a relativistic quantum field A^F is determined. Furthermore, those contraction maps F are characterized for which A^F is in the Borchers class of the generalized free field A we start with. The Wick-product of generalized free fields appears as a particular example of this construction.     

Untersuchung von Stossvorgängen mittels eines Laser-Interferometers

Zusammenfassung Während sich die experimentellen Untersuchungen des Stosses deformierbarer Körper bisher im wesentlichen auf den Anfangs- und den Endzustand beschränkten, untersucht die vorliegende Arbeit den zeitlichen Verlauf der Bewegung während des Stosses bei zwei zentral aufeinander treffenden Kugeln. Als Messgerät diente ein Laser-Interferometer, das räumliche Messpunktabstände von weniger als 200 Å und eine zeitliche Auflösung von weit unter einer Mikrosekunde zulässt, Es wurden als Beispiele ein elastischer und ein unelastischer Stoss vermessen, wobei der elastische Übereinstimmung mit der Hertzschen Theorie zeigte.

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Summary Hitherto, experimental studies of the collision process between deformable bodies mainly concerned the difference between the initial and the final state of the shape at the beginning and at the end of the contact interval. In comparison with this method, the present note deals with an experimental analysis of the deformation process itself during the contact period. The measuring device consists essentially of an optical Michelson type interferometer fed by a He-Ne-gas Laser. It allows a spatial resolution of the timedisplacement history of the event of less than 200 Å, whereas the time resolution is much better than one microsecond. Typical experimental results of elastic and non-elastic collision processes between spheres are discussed, leading in the former case to the conclusion of a good agreement with the classical theory of Hertz.

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Résumé Les études expérimentales de la mécanique des chocs entre des corps déformables visaient jusqu'ici à connaître essentiellement les différences entre leurs états au début et à la fin du phénomène. Par contre, la présente note concerne les variations dans le temps de la déformation de deux sphères pendant leur phase de contact lors d'un choc droit. L'installation de mesure comprenant un interféromètre du type Michelson associée à un laser à gaz fournit une solution meilleure que 200 Å dans la courbe espace-temps du déplacement relatif des deux objets. Ceci co rrespond à une solution dans le temps très inférieure à la microseconde. Comme exemple type de cette méthode, on discute les résultats obtenus pour des chocs droits élastiques et non-élastiques. Il en résulte dans le premier cas une bonne concordance avec la theorie classique de Hertz.

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Vom Ernst-Mach-Institut, Weil am Rhein, gemeinnütziges Institut der Fraunhofergesellschaft, zum ISL abgeordnet.