Synthesis of cananodine by intramolecular epoxide opening

Cananodine is a guaipyridine alkaloid with activity against liver cancer. Cananodine was synthesized using a remarkable intramolecular opening of a trisubstituted epoxide as the key step in construction of the seven-membered carbocycle of the target. The epoxide opening strategy allows all four stereoisomers of cananodine to be prepared.     

The diffraction of elastic waves by an imperfect fusion bond

We consider diffraction by a semi-infinite crack located alonga fusion interface between two differing elastic media. Twotypes of crack, namely open and partially closed cracks, areinvestigated. An open crack is modelled by a stress-free contactboundary condition and a partially closed crack is modelledby a spring contact boundary condition. For the latter, thejump in the stress across the crack is assumed to be proportionalto the jump in the displacement across the crack. This situationarises in, for example, a K-weld where the fine grain of theparent material (for example, ferritic or forged austeniticsteel) is in stark contrast with the coarse-grained weld metal(for example, austenitic weld metal). In the metal weld thedirection of the grain axis varies through the metal. However,diffraction is a local phenomenon and so the austenitic steelis assumed to have a zonal axis so that it may be modelled bya transversely isotropic composite. The ferritic or forged austeniticsteel will be modelled as an isotropic material.     

Inelastic mean free paths for electrons in bulk jellium

Bulk inelastic mean free paths, λ, of electrons in jellium are given in graphical form as a function of the electron spacing parameter r_s and the electron energy E, based on self-energy results of Lundqvist. The results are suggested as a useful guide to the dependence of λ on the material in the energy range near the minimum of λ.     

RAPID: Randomized pharmacophore identification for drug design

This paper describes a randomized approach for finding invariants in a set of flexible and chemically distinct ligands (drug molecules) that underlies an integrated software system called RAPID currently under development. An invariant is a collection of features embedded in ³ which is present in one or more of the possible low-energy conformations of each ligand. Such invariants are called pharmacophores and contain the parts of the ligand that are primarily responsible for its binding with a receptor. The identification of pharmacophores is crucial in drug design since frequently the structure of targeted receptor is unknown but a number of molecules that interact with it have been discovered by experiments. In these cases the pharmacophore is used as a template for building more effective drugs. It is expected that our techniques and results will prove useful in other applications such as molecular database screening and comparative molecular field analysis.     

A perturbation scheme for spherical arrangements with application to molecular modeling

We describe a software package for computing and manipulating the subdivision of a sphere by a collection of (not necessarily great) circles and for computing the boundary surface of the union of spheres. We present problems that arise in the implementation of the software and the solutions that we have found for them. At the core of the paper is a novel perturbation scheme to overcome degeneracies and precision problems in computing spherical arrangements while using floating point arithmetic. The scheme is relatively simple, it balances between the efficiency of computation and the magnitude of the perturbation, and it performs well in practice. In one O(n) time pass through the data, it perturbs the inputs necessary to insure no potential degeneracies and then passes the perturbed inputs on to the geometric algorithm. We report and discuss experimental results. Our package is a major component in a larger package aimed to support geometric queries on molecular models; it is currently employed by chemists working in “rational drug design”. The spherical subdivisions are used to construct a geometric model of a molecule where each sphere represents an atom.     

Raman spectrographic system for quantitative analysis of isotopic hydrogen mixtures for muon catalysis experiments

We show that Raman spectral lines from H₂, D₂, T₂, HD, HT and DT are readily resolved, permitting an effective means to analyze isotopic hydrogen mixtures used in muon-catalyzed fusion experiments. We propose a Raman spectrographic system to allow for real-time analysis of targets involving all three isotopes of hydrogen.     

Molecular frame distortion and molecular pair polarizability

The contribution of frame distortion to the collision-induced polarizability of the isotropic molecules CH₄, CF₄, CCl₄ and SF₆ is estimated and found to be negligible