Redistribution of emitting state population in conjugated polymers probed by single-molecule fluorescence polarization spectroscopy.

Fluctuations in the fluorescence polarization degree and direction are reported for the first time for single conjugated polymer molecules embedded in a polystyrene matrix at room temperature. The polymer molecule, a polythiophene derivative, clearly emits as a multi-chromophore ensemble showing that the energy does not funnel to any specific low-energy trap. The fluorescence instead originates from thermally populated exciton states with different relative orientations of the transition dipole moments. The fluctuations in the fluorescence polarization are explained in terms of changes in the relative contributions of the different exciton states to the signal due to conformational fluctuations of the molecule or selective exciton quenching by triplet states.

Acute alcohol intoxication and traumatic shock. An experimental study on circulating microaggregates and survival.

The reaction to a standardized soft tissue trauma was investigated in pigs pretreated with gastric administration of saline or 40% ethanol. Circulating microaggregates in vena cava, vena portae and aorta were determined with screen filtration pressure (SFP). Using Swan-Ganz thermistor catheters changes in central hemodynamics were recorded. 1 min after trauma, pulmonary capillary wedge pressure (PCW) increased over pretrauma values in alcohol-intoxicated pigs while cardiac output (CO) and mean arterial pressure (MAP) decreased. In control animals, CO and MAP were reduced. 30 min after trauma the control animals had restored their circulatory parameters while intoxicated animals had not. SFP increased in alcohol-intoxicated animals before trauma and more so after trauma except for in aorta. The standardized trauma was nonlethal to control animals while 6 out of 7 pigs, pretreated with alcohol, died within 65 min of the trauma. The data indicate that alcohol intoxication decreases survival after traumatic shock and that alcohol and trauma induced a significant increase in circulating microaggregates.