A physical interpretation of the discrete ambiguities in the optical potential for composite particles

It is shown that the appearance of discrete ambiguities in the optical potential of composite particles is caused by the existence of partly Pauli-forbidden states. The given interpretation is tested in the case ofα-⁵⁸Ni scattering atE _α=50.2 MeV where seven different optical potentials give satisfactory agreement with experiment.     

On asymptotic cones and quasi-isometry classes of fundamental groups of 3-manifolds

We apply the concept of asymptotic cone to distinguish quasi-isometry classes of fundamental groups of 3-manifolds. We prove that the existence of a Seifert component in a Haken manifold is a quasi-isometry invariant of its fundamental group.This research was partially supported by the grant SFB 256 Nichtlineare partielle Differentialgleichungen and the NSF grant DMS-9306140 (Kapovich).     

Goniodilactone and gomoheptenolactone,two novel cytotoxic styryllactones from the leaves of Goniothalamus cheliensis

Two novel styryllactones,goniodilactone（1） and gonioheptenolactone（2）,were isolated from the leaves of Goniothalamus cheliensis Hu.Their structures were determined on the basis of spectroscopic data as well as X-ray crystallography analysis. Compounds 1 and 2 exhibited significant cytotoxicities in a panel of human cancer cells,including DU-145,PC-3,MCF-7,A-549, KB and KBvin,with GI₅₀S in the range of 1.29-4.56μg/mL.     

Synthesis and novel reactivity of halomethyldimethylsulfonium salts

Iodomethyl-, chloromethyl-, and fluoromethyldimethylsulfonium salts, 4b-d, have been synthesized and are observed to be highly reactive molecules that exhibit extraordinary diversity with respect to the nature of their reactivity, undergoing facile direct substitution (S(N)2) reactions, but also being highly susceptible to electron-transfer reactions. Cyclic voltametry experiments indicated that the iodomethyldimethylsulfonium compound, 4b, is a potent electron acceptor, even surpassing the reactivity of perfluoro-n-alkyl iodides in that capacity. The iodo- and chloromethyldimethylsulfonium salts, 4b,c, as well as the analogous iodomethyltrimethylammonium salt, 3a, are shown to be reactive SET acceptors.     

A geometric characteristic splitting in all dimensions

We prove the existence of a geometric characteristic submanifold for non-positively curved manifolds of any dimension greater than or equal to three. In dimension three, our result is a geometric version of the topological characteristic submanifold theorem due to Jaco, Shalen and Johannson. Received: May 20, 1996     

Losses introduced by tilting intracavity etalons

An approximate analytical expression and numerical results for the on-resonance losses caused by tilting an intracavity etalon are given, when the laser operates in the zero-order Gaussian mode.     

A test of the fish bone optical model onα-16O scattering

The recently proposed fish bone optical model is tested on0α-¹⁶ O scattering. Using a microscopic interaction similar to that of resonating group calculations the characteristic rotational bands in²⁰Ne as well as the gross structure of the elastic differential cross section are reproduced. It is shown that the fish bone optical model can be extended by inclusion of a phenomenological imaginary part. A numerical comparison with the corresponding double folding model and with the Saito model confirms the theoretical prediction that the fish bone optical model is a further step towards inclusion of the effect of the Pauli principle in the optical model.