Takuji Kume

butterfly light scattering pattern in shear-enhanced concentration fluctuations in polymer solutions and anomaly at high shear rates

The effects of simple shear flow on concentration fluctuations in semidilute solutions of high molecular weight polystyrene are investigated by the flow light scattering method. The shear-rate (\(\dot{\gamma}\) ) dependence of scattering was found to fall into four regimes: Regime I at \(\dot{\gamma} \dot{\gamma}_{c}\), \(\dot{\gamma}_{c}\) being the critical shear rate for the shear-enhanced concentration fluctuations. In Regime II, a unique butterfly-type scattering pattern with a dark streak perpendicular to the flow direction appears. The intensity parallel to the flow increases by about 100 times with increasing \(\dot{\gamma}\) . In Regime III at higher shear rates, the intensity increase with \(\dot{\gamma}\) tends to saturate, and finally in Regime IV at even higher shear rates, the intensity further increases and the butterfly pattern changes into a two-point pattern elong...

Photophysical characteristics of two model antenna systems: a fucoxanthin–pyropheoporbide dyad and its peridinin analogue

Abstract Photophysical investigations of a fucoxanthin–pheophorbide- a dyad and its peridinin analogue have revealed that the efficiency of carotenoid-to-pheophorbide transfer of singlet excitation and of pheophorbide-to-carotenoid transfer of triplet excitation depend markedly both on the solvent and on the dyad. Furthermore, the carotenoid moiety, whose first excited singlet state lies higher than that of its pheophorbide partner, is able to quench the fluorescence of the latter; such indirect quenching, which must entail a process other than the transfer of electronic excitation, might provide a channel for the dissipation of excess energy in some natural antenna systems.

Fucoxanthin and peridininpheophorbide-α molecules as a new light-harvesting model

Abstract In fucoxanthinpheophorbide-α and peridininpheophorbide-α dyads prepared by trans-esterification at the 13 2 methoxycarbonyl group of methyl pheophorbide-α, singlet-singlet energy transfer from the carotenoid to the pheophorbide occurs with 23 and 54% efficiencies, respectively.