Bimodal crystallization at polymer-fullerene interfaces

The growth-kinetics of [6,6]-phenyl C61-butyric acid methyl ester (PCBM) crystals, on two different length-scales, is shown to be controlled by the thickness of the polymer layer within a PCBM-polymer bilayer. Using a model amorphous polymer we present evidence, from in situ optical microscopy and grazing-incidence X-ray diffraction (GIXD), that an increased growth-rate of nanoscale crystals impedes the growth of micron-sized, needle-like PCBM crystals. A combination of neutron reflectivity and GIXD measurements, also allows us to observe the establishment of a liquid-liquid equilibrium composition-profile between the PCBM layer and a polymer-rich layer, before crystallization occurs. While the interfacial composition-profile is independent of polymer-film-thickness, the growth-rate of nanoscale PCBM crystals is significantly larger for thinner polymer films. A similar thickness-dependent behavior is observed for different molecular weights of entangled polymer. We suggest that the behavior may be related to enhanced local-polymer-chain-mobility in nanocomposite thin-films

Near infrared spectroscopy measurement of sacral tissue oxygenation saturation (StO2) in healthy volunteers immobilized on spine boards

Paper presented to the 5th Annual Symposium on Graduate Research and Scholarly Projects (GRASP) held at the Hughes Metropolitan Complex, Wichita State University, May 1, 2009.Research completed at the Department of Physician Assistant, College of Health Professions, and University of Kansas School of Medicine-WichitaImmobilization of patients utilizing rigid spine boards (RSB) is standard practice in the management of trauma patients. Pressure ulcers (PU) have been associated with prolonged immobilization. The possibility exists that PU formation may begin when the patient is initially immobilized, the effects not fully recognized because of limited research on the direct tissue effects of prolonged immobilization. Near-infrared spectroscopy is an emerging tool to measure peripheral tissue oxygenation (StO2). The purpose of this pilot study was to study the effects of prolonged spinal immobilization on sacral tissue oxygenation of healthy volunteers. This cross-sectional study measured tissue oxygenation (StO2) in 73 volunteers at baseline and then after 30 minutes of immobilization on a RSB at two sites, the sacrum and a control site not subjected to direct pressure. Data were analyzed utilizing within-subjects analysis of variance. There was a significant increase in the StO2 percentage at the sacral (intervention) area following immobilization, p < .001, rpb = .48. No significant change in oxygenation was noted at the control site. An increase in oxygenation of sacral tissue following immobilization was an unexpected finding and may be a result of initial, rapid tissue reperfusion at the time of pressure release and the inability of this methodology to detect hypoperfusion during tissue compression

Relaxation and intermediate asymptotics of a rectangular trench in a viscous film

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