Senior Thesis Presentations - Philavanh and Swift

Time: 2 PM, Friday, May 8th, 2009

Place: P-148 (refreshments will be served at 1:45 PM in P145A)

Mechanical Properties of Simulated Temporary Cross-linked F-actin Polymer Networks

Rita Philavanh

Mechanical force plays an essential role in the physiology of the cell. The mechanical properties of the cell are predominantly determined by the properties of the polymeric (F) actin in the cytoplasm. The F-actin is cross-linked by actin binding proteins into reversible networks that make up the cytoskeleton. The Baljon lab has constructed code to model polymeric networks in which crosslinks are nonpermanent. The model has been employed to study the network microstructures at rest. This code will further be used to study the viscoelastic properties of these networks from their response to external stresses. The results will be compared with those observed in experiments of F actin networks. In particular we are interested in findings of the Weitz lab indicating that there is a strong increase in the elasticity of a stressed F-actin network compared to an unstressed one. An explanation for this type of non-linear response is still lacking. Investigations of the microstructure of our model networks might provide new insight, which is crucial to our understanding of the cell. Due to the presence of motor proteins, the cytoskeleton is believed to operate in this non-linear regime.

Generation of Optical Vortices with a Ti:Sapphire Femto-Second Laser

Stephen Swift

Femtosecond lasers produce extremely brief, high-energy light pulses that have a great deal of applications in industry, medicine and physics. In this paper we look at how the enormous power generated by a short pulse helps us to explore areas in physics that otherwise would be inaccessible. We begin with a brief description of the theory and operation of the Ti:Sapphire laser. We then examine the polarization equation and reveal how the higher order terms lead to interesting optical phenomena. Finally we discuss the theory of diffraction and the generation of optical vortices.

You can view other undergraduate thesis abstracts.
Or via the digital thesis archive.