Spin dependent fragmentation functions for heavy flavor baryons and single heavy hyperon polarization

Spin dependent fragmentation functions for heavy flavor quarks to fragment into heavy baryons are carculated in a quark-diquark model. The production of intermediate spin 1/2 and 3/2 excited states is explicity included. Λ _b , Λ_c and Ξ _c production rate and polarization at LEP energies are calculated and, where possible, compared with experiment. A different approach, also relying on a heavy quark-diquark model, is proposed for the small momentum transfer inclusive production of polarized heavy flavor hyperons. The predicted Λ_c polarization is roughly in agreement with experiment.     

Chiral self-propulsion of growing bacterial macrofibers on a solid surface

Supercoiling motions that accompany the growth of bacterial macrofibers (multicellular filamentous structures formed in B. subtilis by cell division without separation) are responsible for rolling, pivoting, and walking of fibers on a surface. Fibers possess a fulcrum about which they pivot and step in a chiral manner; forces and torques associated with cell growth, when blocked by friction, result in self-propulsion. The elastic engine that drives macrofiber motions generates torques estimated as microdyn cm and femtowatts of power; optical trapping studies yield a first direct measurement of the Young's modulus of the bacterial cell wall, the engine's "working fluid," of ca. 0.05 GPa.     

Chemoselective 1,3-dipolar cycloadditions of azomethine ylide with conjugated dienes

Methods are described of synthesizing various 3-carboxy-4-vinyl pyrrolidines, versatile building blocks for our drug discovery efforts. The 1,3-dipolar cycloaddition between activated olefins and nonstabilized azomethine ylide is a known method for synthesizing pyrrolidines in a stereospecific manner. Steric and electronic effects on the chemoselectivity of the 1,3-dipolar cycloaddition between azomethine ylide and α,β,γ,δ-unsaturated carboxylates have been explored.     

Michael J. Moravcsik: A biographical sketch

A brief biography of Michael J. Moravcsik is presented, concentrating on the chronology of his contributions to theoretical high- and intermediateenergy physics. The evolution of his interest in science development in the third world, scientific methodology, and scientometrics are indicated. A personal reminiscence is included.     

Mathematics of Philosophy or Philosophy of Mathematics?

This article examines recent attempts to gain insight into philosophical paradoxes through using NDS models employing iterated difference equations and resulting phase portraits and escape time diagrams. The temporal nature of such models is contrasted with an alternative approach based on the a-temporal and non-dynamical construct of a lattice. Finally, there is a discussion of how such strategies for understanding paradox transcend the realm of empirical research and enter territory in the philosophy of mathematics.     

Notiz über das Diäthoxychinon

Ohne Zusammenfassung