Turbulent superfluid profiles in a counterflow channel

We have developed a two-dimensional model of quantised vortices in helium II moving under the influence of applied normal fluid and superfluid in a counterflow channel. We predict superfluid and vortex-line density profiles which could be experimentally tested using recently developed visualization techniques.Comment: 3 double figures, 9 page

SELF-PRESERVING STRUCTURES IN HOMOGENEOUS SUPERFLUID TURBULENCE

La force de frottement mutuel dans le contrecourant thermique d'He II a été expliquée par Vinen dans un modèle de la turbulence superfluide. Ce modèle a été appliqué avec succès à plusieurs phénomènes de contrecourant. Nous avons essayé d'examiner l'homogéneité de la turbulence en faisant des comparaisons entre ces gradients de température et les vitesses critiques dans des canaux de contrecourant circulaires et rectangulaires. Les résultats suggèrent que la turbulence est homogène mais que chaque configuration géométrique possède sa propre structure self-entraînante.The mutual friction force in He II thermal counterflow has been accounted for by Vinen in a model for superfluid turbulence. The model has been successfully applied to a number of counterflow phenomena. We have attempted to examine the homogeneity of the turbulence by comparing temperature gradients and critical velocities from circular and rectangular counterflow channels. The data suggest the turbulence is homogeneous, but that each geometry possesses a different self-sustaining structure

Correlation between three-dimensional structure and chemical reactivity of transfer RNA

The bases of yeast tRNA(Phe) which react with carbodiimide and methoxyamine have been determined and this information has been combined with chemical modification studies of other workers to produce a composite picture of base accessibility in this tRNA. The results are compared with the three-dimensional structure which we have recently determined. The bases which react chemically lie in exposed positions in the three-dimensional model and those which do not are either in the double helical stem regions or else are involved in maintaining the tertiary structure through pairing or stacking interactions

Finding Reductions Automatically

Abstract. We describe our progress building the program Reduction-Finder, which uses off-the-shelf SAT solvers together with the Cmodels system to automatically search for reductions between decision problems described in logic