On the aromatic character of some ten π-electron systems

The electronic structure of 1,4,5-triaza-cyclohepta-2,6-diene has been studied. The treatment accounts for the failure of detecting, by experiment, a cyclic conjugation in this and related seven membered ring systems.

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Zusammenfassung Die Elektronenstruktur des 1,4,5-triaza-cycloheptadien-2,6 wurde theoretisch untersucht. Das Ergebnis erklärt das Mißlingen von Versuchen, in diesem und verwandten Siebenringsystemen zyklische Konjugation aufzufinden.

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Résumé La structure électronique du 1,4,5-triaza-cycloheptadiène-2,6 a été étudiée. Le résultat explique pourquoi une conjugaison cyclique n'a pas été trouvée expérimentalement ni dans ce composé ni dans d'autres systèmes cycliques semblables à sept membres.

     

A rapid procedure for obtaining hydrodynamic voltammetry plots for electrochemical detectors in high-pressure liquid chromatography systems

The construction of relatively simple and inexpensive apparatus for the determination of the operating conditions for electrochemical detectors in high-pressure liquid chromatography systems is described. A procedure has been developed for the characterization of electrochemically active compounds.     

On the Dirac–Kepler problem: The Johnson–Lippmann operator,supersymmetry, and normal-mode representations

The relativistic Kepler problem is discussed, with emphasis on the exact supersymmetry of the problem. It is shown that the supersymmetry is generated by the Johnson–Lippmann operator. Two related operators are found to generate new supersymmetries in an extended function space. Each of these supersymmetries may be disguised as radial supersymmetries. The radial supersymmetries are discussed and it is shown that each of them defines a normal-mode representation of the hydrogen-atom radial functions. Thus, one obtains two different, but equivalent, analytical expressions for these functions. The expressions are well known, but are rederived here in the light of the new understanding. Finally, the nonrelativistic image of the relativistic supersymmetry is constructed and its generators shown to be identical with those recently presented in the literature. © 1995 John Wiley & Sons, Inc.     

Proper holomorphic embeddings of finitely and some infinitely connected subsets of into

We show that any finitely connected domain can be properly embedded into . For some sequences can also be properly embedded into .     

Improved synthesis of oligonucleotides with an allylic backbone. Oligonucleotides containing acyclic, achiral nucleoside analogues: N-1 or N-9-[3-hydroxy-2-(hydroxymethyl)prop-1-enyl]nucleobases

An improved phosphoramidite method is described to prepare oligonucleotides modified with the acyclic, achiral monomers 1. Examination of dimers, prepared on solid support or in solution, showed that phosphortriester dimers containing the allylic unit 1 were unstable towards bases, whereas phosphordiester dimers were stable. Phosphordiester dimers were obtained by replacing cyanoethyl phosphoramidites 2 with phosphoramidites 3, which gave phosphordiesters directly upon oxidation. The phosphordiester dimers were found to be stable towards capping and oxidation, but were somewhat labile towards acids. By reducing the contact time to acids during detritylation it was possible to prepare oligonucleotides containing 4 or 8 modified A, G or T units. The modified oligonucleotides hybridized to complementary DNA and RNA, although with reduced affinity (DeltaT(m) per modification -1 to -5 degrees C).     

A long ℂ<Superscript>2</Superscript> which is not Stein

We construct a 2-dimensional complex manifold X which is the increasing union of proper subdomains that are biholomorphic to ℂ², but X is not Stein.