Quark- and Gluon-Condensate Contributions to Penguin Four-Fermi Operators

The nonperturbative content of the QCD vacuum permits the occurrence of QCD-vaccum condensate contributions to penguin amplitudes. We calculate the dimension-4 $$and$$ contributions to the effective Wilson coefficients for penguin four-Fermi operators, and discuss how such contributions may contribute to nonleptonic B decays.Comment: 7 pages, latex uses aipproc, 3 postscript figures included, Talk given at 21st Annual MRST Conference: High Energy Physics at the Millenium (MRST 99 and the Sundarfest), Ottawa, Ontario, Canada, 10-12 May 199

Continuous growth of vimentin filaments in mouse fibroblasts

We have investigated the dynamics of intermediate filament assembly in vivo by following the fate of heterologous chicken vimentin subunits expressed under the control of an inducible promoter in transfected mouse fibroblasts. Using RNase protection, metabolic protein pulse-chase and immunofluorescence microscopy, we have examined the fate of newly assembled subunits under physiological conditions in situ. Following induction and subsequent removal of inducer, chicken vimentin mRNA had a half-life of approximately 6 h while both chicken and mouse vimentin protein polymer had long half-lives--roughly equivalent to the cell generation time. Moreover, following deinduction, chicken vimentin immunolocalization progressed from a continuous (8-10 h chase) to a discontinuous (> or = 20 h chase) pattern. The continuous chicken vimentin staining reflects the uniform incorporation of chicken vimentin throughout the endogenous mouse vimentin network while the discontinuous or punctate chicken vimentin staining represents short interspersed segments of assembled chicken vimentin superimposed on the endogenous polymer. This punctate staining pattern of chicken vimentin was present throughout the entire array of intermediate filaments, with no bias toward the perinuclear region. These results are consistent with a continuous growth model of intermediate filament assembly, wherein subunit addition occurs at discrete sites located throughout the cytoskeleton