|Ph.D Student||Daphne Weihs|
|Subject||Dynamics and Microstructure of Complex Liquids|
|Department||Department of Chemical Engineering||Supervisors||Professor Emeritus Talmon Yeshayahu|
|Full Professor Fred M Konikoff|
|Full Professor L.e Scriven|
In the two main directions of research we studied the initial stages of cholesterol gallstone crystallization, and in a qualitative project we examined the effects of forces and defects on surfactant microstructures and structural transitions between them.
We combined cryogenic transmission electron microscopy (cryo-TEM) with digital light microscopy to visualize microstructures. We also used cryo-electron diffraction to characterize single crystals growing in solution. We used rheometry to obtain the flow and deformation response of solutions to an applied shear strain.
Comparing pairs of gallbladder bile and hepatic bile, i.e., bile withdrawn from the hepatic bile ducts, showed that the relative resistance of hepatic bile to crystal nucleation cannot be attributed to any specific microstructures different from those seen in nucleating gallbladder bile. Additionally, we asserted that the stable cholesterol crystal in model and native bile is cholesterol monohydrate. However, in a relatively dilute bile model we observed a new unstable cholesterol monohydrate polymorph, which eventually transformed to the stable cholesterol monohydrate. We also examined the effects of adding a crystallization inhibitor on model bile. It induced formation of cholesterol monohydrate crystals at shorter times than in the pure model, but crystal size and growth were limited, and aggregation of those crystals was inhibited.
In the second part of the work we examined microstructural transitions and their intermediates. Forces applied to microstructures can form defects and alter their topology. We compiled an extensive list of possible defects and examined their effects on surfactant structures. We examined two shear-induced transitions in detail.