RESUMO
We describe a measurement of the angular power spectrum of anisotropies in the cosmic microwave background (CMB) at scales of 0&fdg;3 to 5 degrees from the North American test flight of the Boomerang experiment. Boomerang is a balloon-borne telescope with a bolometric receiver designed to map CMB anisotropies on a long-duration balloon flight. During a 6 hr test flight of a prototype system in 1997, we mapped more than 200 deg(2) at high Galactic latitudes in two bands centered at 90 and 150 GHz with a resolution of 26&arcmin; and 16&farcm;5 FWHM, respectively. Analysis of the maps gives a power spectrum with a peak at angular scales of 1 degrees with an amplitude 70 µK(CMB).
RESUMO
Studies of the helix-to-coil transition in dilute solutions of poly-L-lysine, dissolved in mixtures of water and methanol (MeOH), have been carried under shear flow using flow birefringence and modulated polarimetry. The fraction of helical conformations in a given solution remains independent of shear rate for MeOH concentrations above and below the critical value for the helix-coil transition (i.e., 87.5% MeOH). For the 87.5% MeOH solutions, a shear-induced helix-to-"stretched" coil transition occurs above a critical shear rate. Induction times for the transition show a temperature and shear rate dependence that can be described in terms of an activated jump process. Measurements of circular birefringence on cessation of flow also show that the transition is reversible, with the stretched coil reverting to the helical state on a time scale of several seconds. The activation energy for the jump process is found to be 16.2 kJ/mole. Copyright 1999 John Wiley & Sons, Inc.