Energy-momentum tensor of fields in the standard cosmology

With the use of the equations of motion of massless fields moving in a curved Friedmann-Robertson-Walker universe, we show, in some simple cases, that the energy-momentum tensor of a maximally 3-space symmetric distribution of the fields (i.e., an incoherent averaging over a complete set of modes of the field propagating in a Robertson-Walker background) has the standard perfect fluid form. As far as we know such an explicit demonstration, as well as the establishment of the compatibility of the equations of motion of the gravitational field with such an incoherently averaged source in the standard cosmology, has not previously been presented in the literature. Our results are found to hold for any value of the spatial curvature of the universe.     

Measurement of the normal-fluid velocity in superfluids

Numerical calculations of (finite temperature) superfluid vortex ring propagation against a particulate sheet show that the solid particle trajectories collapse to a very good approximation to the normal-fluid path lines. We propose an experiment in which, by measuring the solid particles' velocities, direct information about the instantaneous normal-fluid velocity values could be obtained.     

Strategies for the synthesis of novel indole alkaloid-based screening libraries for drug discovery

A series of diverse indole-based chemotypes were synthesized from -tetrahydrocarboline (-THC) scaffolds prepared from commercially and readily available tryptamines and -ketoesters. Diversity can be generated within these chemotypes through the following strategies: (a) appendage of substituents to the -THC scaffold, prepared in situ or as a template, through further elaboration and (b) skeletal modifications to the -THC scaffold via ring forming or ring breaking reactions. The strategies described here are amenable to high throughput solution-phase parallel synthesis, providing access to novel indole-based screening libraries for drug discovery.Dedicated to Professor Spyros P. Perlepes     

Reconnection of colliding vortex rings

We investigate numerically the Navier-Stokes dynamics of reconnecting vortex rings at small Reynolds number for a variety of configurations. We find that reconnections are dissipative due to the smoothing of vorticity gradients at reconnection kinks and to the formation of secondary structures of stretched antiparallel vorticity which transfer kinetic energy to small scales where it is subsequently dissipated efficiently. In addition, the relaxation of the reconnection kinks excites Kelvin waves which due to strong damping are of low wave number and affect directly only large scale properties of the flow.