Pions as spin waves: Chiral symmetry breaking in lattice gauge theory

In hamiltonian lattice gauge theory, the fermion vacuum at lowest order in 1/g² can be determined from degenerate perturbation theory plus mean field-spin wave techniques. Using compact QED as an example, we show that: (i) chiral symmetry is spontaneously broken; and (ii) $\text{m}{}_{\mathrm{<mtext>pseudoGoldstone</mtext>}}{}^2\text{∝ m}{}_{\mathrm{<mtext>fermion</mtext>}}\text{〈}\text{ψ}\text{ψ〉}$. The pseudoscalar pseudoGoldstone particles—the “pions” of this abelian theory—correspond to antiferromagnetic spin wave excitations of the fermion vacuum.     

Mimicking dihydroxy acetone phosphate-utilizing aldolases through organocatalysis: a facile route to carbohydrates and aminosugars

[reaction: see text] A practical and environmentally friendly organocatalytic strategy designed to mimic the DHAP aldolases has been developed and shown to be effective in the preparation of carbohydrates and aminosugars. (S)-Proline and (S)-2-pyrrolidine-tetrazole catalyzed the aldol reaction between dihydroxy acetone variants such as 1,3-dioxan-5-one and 2,2-dimethyl-1,3-dioxan-5-one with aldehydes to give the corresponding polyols in good yields with very high ees.     

Ultrasonic wave propagation across a thin nonlinear anisotropic layer between two half-spaces

Boundary conditions and perturbation theory are combined to create a set of equations which, when solved, yield the reflected and transmitted wave forms in the case of a thin layer of material that is perfectly bonded between two isotropic half-spaces. The set of perturbed boundary conditions is created by first using the fully bonded boundary conditions at each of the two interfaces between the thin layer and the half-spaces. Then, by restricting the layer's thickness to be much smaller than an acoustic wavelength, perturbation theory can be used on these two sets of boundary equations, producing a set of equations which effectively treat the thin layer as a single interface via a perturbation term. With this set of equations, the full range of incident and polar angles can be considered, with results general enough to use with a layer that is anisotropic, nonlinear, or both anisotropic and nonlinear. Finally the validity of these equations is discussed, comparing the computer simulation results of this theory to results from standard methods, and looking at cases where the results (or various properties of the results) are known or can be predicted.     

A new method for the stereoselective synthesis of alpha- and beta-glycosylamines using the Burgess reagent

Although glycosylamines constitute an important group of carbohydrates from the standpoint of biology and medicine, methods for their synthesis typically lack substrate generality and/or result in variable stereoselectivity, especially in complex contexts. In this communication, we report an operationally simple method for the synthesis of both alpha- and beta-glycosylamines using the Burgess reagent that overcomes many of these limitations in a bare minimum of synthetic steps.     

Choosing an equivalent replacement column for a reversed-phase liquid chromatographic assay procedure

The column selectivity parameters (H, S*, A, B and C) described in the preceding paper [L.R. Snyder, A. Maule, A. Heebsch, R. Cuellar, S. Paulson, J. Carrano, L. Wrisley C.C. Chan, N. Pearson, J.W. Dolan, J.J. Gilroy, J. Chromatogr. A 1057 (2004) 49-57] can be used to compare columns in terms of selectivity. A detailed procedure for such column comparisons is presented here, and evaluated by its use in finding suitable replacement columns for 12 different routine separations performed in five different pharmaceutical analysis laboratories.     

Novel porphyrin-fullerene assemblies: from rotaxanes to catenanes

[reaction: see text] Titration of porphyrin-fullerene rotaxanes with DABCO or 4,4'-bipyridine led to photo- and redoxactive catenanic architectures, which upon photoexcitation undergo a sequence of short-range energy and electron transfer events to give a long-lived charge-separated radical-pair state.