We investigate the effect of early chemical freeze-out on radial flow, elliptic flow and HBT radii by using a fully three dimensional hydrodynamic model. When we take account of the early chemical freeze-out, the space-time evolution of temperature in the hadron phase is considerably different from the conventional model in which chemical equilibrium is always assumed. As a result, we find that radial and elliptic flows are suppressed and that the lifetime and the spatial size of the fluid are reduced. We analyze the p t spectrum, the differential elliptic flow, and the HBT radii at the RHIC energy by using hydrodynamics with chemically non-equilibrium equation of state.

Higher generations of poly(propylene imine) dendrimers functionalized with aliphatic chains form large micrometer-sized spherical objects in aqueous solution below pH 8. These spheres are giant vesicles with a multilaminar onion-like structure. The size distribution and the structure of the vesicles depend on the pH of the solution and the endgroups at the periphery of the dendrimer. The vesicles containing azobenzene units (2 and 3) fluoresce with a maximum at λ max ) 600 nm. This emission can be attributed to the dense and ordered arrangement of the azobenzene chromophores in the bilayer structure. Laser irradiation of a small area of giant vesicles of 2 or 3 with 1064 and/or 420 nm light leads to changes in the morphology of the vesicles. Infrared light induces a rearrangement, whereas the azobenzene units isomerize under the influence of 420 nm light. Both irradiations lead to a change in refractive index in the illuminated area. Irradiation using 420 nm light is accompanied by an increase in the emission intensity. In aqueous solutions at pH 1, the increase in fluorescence intensity is concurrent with a blue shift of the emission maximum to 540 nm. This blue shift is not observed when the experiment is performed in Milli Q water (pH 5.5). The enhanced fluorescence can be attributed to reorganization of the chromophores within the giant vesicle. The increase in emission proves that the giant vesicle is a kinetically formed system that reaches a thermodynamically more relaxed state after light-induced isomerization.

The differences in the fluorescence behavior of a polyphenylene dendrimer with eight peryleneimides chromophores (1) and a single hexaphenylperyleneimide chromophore have been investigated at a single‐molecule level through the combination of ultrasensitive fluorescence detection and microscopy.

Diese Arbeit wurde von der FWO, dem flämischen Ministerium für Bildung (GOA/1/96), der Europäischen Union (TMR-Projekte ¹Sisitomasª und ¹Marie Curieª), der Volkswagen-Stiftung und der DWTC (Belgien; IUAP-IV-11) gefördert. J.H. dankt der FWO für ein Graduiertenstipendium.

We investigate the effect of early chemical freeze-out on hydrodynamic flow and HBT radii at the RHIC energy with a genuinely three dimensional hydrodynamic model. It is found that the property of early chemical freeze out reduces radial flow, elliptic flow, R out and R long .

Optical trapping was combined with transmission microscopy (TM), confocal and nonconfocal fluorescence scanning microscopy (CFSM and FSM, respectively), and confocal and nonconfocal time-resolved fluorescence spectroscopy (CTRFS and TRFS, respectively) to study latex particles and block copolymer micelles. Dye-labeled latex particles of various size, in polymer composite films as well as optically trapped in solution, were studied with CFSM to characterize the limits of the setup. CFSM revealed that the resolution in the x- and y-directions was near the theoretical limit, i.e., 200−250 nm. CTRFS on the labeled latex particles revealed that the decay time of the label was not influenced by the polymer matrix nor the optical trap. Poly(tert-butylstyrene-block-sodium methacrylate) micelles (diameter approximately 30−40 nm) in deuterated aqueous solutions could be optically trapped, this region of high copolymer micelle concentration being referred to as a trapped cluster. In the transmission images, trapped clusters of 1.5−2 μm diameter were detected. Fluorescence images were obtained using perylene as a fluorophore that is specifically dissolved within the block copolymer micelles. The size of the trapped cluster, estimated from TM and FSM images, increases with increasing irradiation time and power, respectively. In the TM images, the trapped cluster appears as a dark spot (low transmission) with a bright (high transmission) corona-like ring around it. The appearance of the corona is explained as a light deflection phenomenon; i.e., the trapped cluster acts as lens due to a lateral refractive index gradient. When the corona is taken into account when the diameter of the trapped clusters is calculated, a very good agreement is found between TM and FSM. Long irradiation times lead to the formation of large trapped clusters, which are stable for about 10 s, with diameters of several hundred nanometers, while, for short irradiation times, the trapped cluster is smaller and disappears within a time less than 1 s. With CFSM it could be shown that the trapped particle has a spot size of approximately 1.7 μm in the region of the IR laser focus, while the diameter extends up to 5 μm without using the confocal imaging capability. The reason for this is that the conditions for optical trapping are fulfilled not only in but also above and below the focal region. Due to the high numerical aperture, a dumbbell-like shape of the trapped cluster results.

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A fifth-generation poly(propylene imine) dendrimer decorated with palmitoyl-and azobenzene-containing alkyl groups forms giant vesicles in aqueous solutions with diameters from 50 nm up to 20 µm and a multilaminar onion-like structure. Dense and ordered arrangement of the azobenzene chromophores in the bilayer structure leads to fluorescence with λ max = 600 nm. The fluorescence intensity can be increased by irradiation with blue light, and at low pH a distinctive blue shift of the spectrum is observed. With the aid of a single-beam optical tweezers it is possible to trap vesicles and direct them in a billiard-like fashion against each other using forces in the range of several pN. In collision experiments, the vesicles behave like hard spheres, and merging is not observed.