Non-perturbative effects in two-dimensional lattice O(N) models

Non-abelian analogues of Kosterlitz-Thouless vortices may have important effects in two-dimensional lattice spin systems with O(N) symmetries. Renormalization group equations which include these effects are developed in two ways. The first set of equations extends the renormalization group equations of Kosterlitz to O(N) spin systems, in a form suggested by Cardy and Hamber. The second is derived from a Villain-type O(N) model using Migdal's recursion relations. Using these equations, the part played by topological excitations in the crossover from weak to strong coupling behavior is studied. Another effect which influences crossover behavior is also discussed: irrelevant operators which occur naturally in lattice theories can make important contributions to the renormalization group flow in the crossover region. When combined with conventional perturbative results, these two effects may explain the observed crossover behavior of these models.     

On the Ricatti equation for eigenvalue problems

The Riccati equation is shown to be suitable for obtaining implicit approximate analytic expressions for the eigenvalues of quantum-mechanical systems. The Hamiltonian operator H = (1/2)p² – (Z/r) + λr² is used as a test example, and the resulting formulae are modified to deal with the Zeeman effect in hydrogen.     

Nitrate ion as catalyst for selective silylations of nucleosides

Nitrate ion has been found to have a remarkable effect on the selectivity of silylation of ribonucleosides using the $\text{t}$-butyldimethylsilyl group.     

Necessary protection of the O6-position of guanine during the solid phase synthesis of oligonucleotides by the phosphoramidite approach

It has been observed that the use of O⁶-protected deoxyguanosine phosphoramidites leads to a significant improvement in the automated synthesis of oligonucleotides on an insoluble support.     

Chemical synthesis of branched RNA: novel trinucleoside diphosphates containing vicinal 2′–5′ and 3′–5′ phosphodiester linkages

The phosphite-triester synthesis of four triribonucleotides containing novel vicinal 2′–5′ and 3′–5′ phosphodiester linkages is described.     

The Conformation of a Peptidyl Methyl Ketone Inhibitor Bound to the Human Cytomegalovirus Protease

A weak inhibitor means faster exchange! Since the methyl ketone MK2 is a weak noncovalent peptidyl inhibitor of the human cytomegalovirus protease, exchange between the free and enzyme-bound forms is rapid. This allows for the use of transferred NOE NMR methods and molecular modeling, which show that the bound conformation of MK2 is an extended peptide. This is confirmed by the results of an X-ray crystallographic analysis of a related enzyme–inhibitor complex.     

Is a molecular orbital measurable by means of tomographic imaging?

Interpretation of experiments involving use of vacuum ultraviolet radiation to effect ionization of N₂ in terms of measurements of a molecular orbital is erroneous.     

News Release

The forms of the dependences on the vibrational and rotational quantum numbers in the series representation of the vibration-rotational energies of diatomic molecules are discussed. It is concluded that the most convenient forms for diatomic molecules in ^lσ electronic states are (v+1/2) and (J+1/2)² respectively.     

Derivation,properties and application of Coulomb Sturmians defined in spheroidal coordinates

Coulomb Sturmian amplitude functions are derived in prolate spheroidal coordinates and are presented in a closed algebraic form. Spheroidal Sturnian functions are revealed to be related to the polynomial solutions of Heun's confluent equation. A reduction of symmetry from spherical to axial leads to the coupling of spherical polar orbitals and the formation of hybrid orbitals. The contribution of each spherical orbital into a hybrid orbital depends strongly on distance R from a nucleus to the dummy centre, and substantially alters when R varies. At two limiting cases R = 0 and R → ∞ spheroidal Sturmians are purely atomic orbitals, whereas at intermediate R they contain many features intrinsic to diatomic molecular orbitals. Applications of spheroidal Sturmian basis are discussed; Coulomb spheroidal Sturmians are asserted to be the most appropriate basis functions for diatomic molecular calculations.