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Physics Seminar 02-20-2009

 

Dynamic Light Scattering in Ultraphosphate Glass-forming Liquids
 
Roberto Fabian Jr
 Department of Physics
Creighton University
 
 
We report results of an extensive study of the viscoelastic response of several compositions of sodium ultraphosphate liquids. The study covers a wide compositional range from pure P2 O5 whose bridging oxygens form a three dimensional network to the sodium metaphosphate, NaPO3, which form two dimensional chains. Spectra of the time-dependent structure factor were obtained using photon correlation spectroscopy and values of the glass transition, fragility, and the heterogeneity parameter have been determined. A decrease in fragility was observed with alklai addition which is shown to parallel changes in fragility occurring in alklai-free chalcogenide glass forming materials.
 
 

 
Diffusion Measurements of Fluorescent Lipophilic Neurotracers
 
Jeff Tonniges
Physics Department
Creighton University
 

Lipophilic fluorescent molecules have been used to trace neuronal connections because of their ability to diffuse laterally along nerve cell membranes. A set of five spectrally distinct neurotracer molecules have been developed with fluorescence emissions ranging from blue to the near-infrared. When labeling with multiple neurotracers, it is desirable for the set to have similar lateral diffusion rates. Given the distance the typical neuron extends its processes, a fast lateral diffusion rate for the neurotracer molecules is desirable. However, because the neuron’s processes come into contact with other cell membranes on its way to its targets, it is undesirable for the neurotracer to diffuse intercellularly. Preliminary data was collected on the intercellular diffusion of neurotracer molecules of varying hydrocarbon tails. This will be compared to recent data on the lateral diffusion of neurotracers with varying hydrocarbon tails measured with fluorescence recovery after photobleaching (FRAP).

 

 

Date of Event: 
Friday, February 20, 2009 - 12:30
Location: 
Hixson Lied G59
Contact info: 
Dr. Patricia Soto

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