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    • 3244121.PDF.jpg
    • Thesis

    • Authors: Lu, Carole Chih-Chen (2006)

    • The neural crest is a transient population of cells that migrate away from the dorsal neural tube in the vertebrate embryo. As the developing hindbrain constricts into rhombomeres, cranial neural crest cells migrate in three discrete streams adjacent to even-numbered rhombomeres, rhombomere 2 (r2), r4, and r6. To test the role of intrinsic versus extrinsic cues in influencing an individual cell's trajectory, we implanted physical barriers in the chick mesoderm, distal to emerging neural crest cells (NCCs). We analyzed spatio-temporal dynamics as NCCs encountered and responded to the barriers by using time-lapse confocal microscopy and cell tracking analysis. The majority of NCCs were...

    • 3197390.pdf.jpg
    • Thesis

    • Authors: Tobias, Alexander Vincent (2006)

    • Over the course of evolution, nature continually discovers new small molecules through the alteration of biosynthetic enzymes and pathways by mutation and gene transfer. Hundreds of these natural products have proven indispensable to medicine, culture, and technology, greatly contributing to increases in the length and quality of human lives. Chemists have found that the "chemical space" surrounding natural products is especially rich in functional molecules, and synthesis of natural product analogs has uncovered many with new or improved properties. Inspired by nature's search algorithm, we and others have conducted our own evolution of carotenoid biosynthetic pathways in the laborat...

    • 3235587.PDF.jpg
    • Thesis

    • Authors: Navilarekallu, Tejaswi (2006)

    • For a finite Galois extension K/Q of number fields with Galois group G and a motive M = M' h°(Spec(K))(O) with coefficients in Q[G], the equivariant Tamagawa number conjecture relates the special value L* (M, 0) of the motivic L-function to an element of Ko(Z[G];R) constucted via complexes associated to M. The conjecture for nonabelian groups G is very much unexplored. In this thesis, we will develop some techniques to verify the conjecture for Artin motives and motives attached to elliptic curves. In particular, we consider motives h°(Spec(K))(0) for an A4-extension K/Q and, hi (E x Spec(L))(1) for an S3-extension L/Q and an elliptic curve E/Q.

    • 3235586.PDF.jpg
    • Thesis

    • Authors: Michalak, David J. (2006)

    • Low interfacial electron-hole recombination rates are essential for low-noise electronic devices and high-efficiency solar energy converters. This recombination rate is dependent on both the surface electrical trap state density, NT,,, and the surface concentrations of electrons, ns, and holes, ps. A reduction in NT,, is often accomplished through surface chemistry, and lower recombination rates, through lower NT,., values, have been demonstrated in this work for surfaces chemically treated to produce methoxylated, Si-O-CH3, overlayers. The H-Si(111) surfaces can react with methanol quickly in the presence of an oxidant or slowly in neat anhydrous methanol. Mechanisms have been propos...

    • 3244113.PDF.jpg
    • Thesis

    • Authors: Forster, Robert (2006)

    • This thesis explores how natural selection acts on organisms such as viruses that have either highly error-prone reproduction or face variable environmental conditions or both. By modeling population dynamics under these conditions, we gain a better understanding of the selective forces at work, both in our simulations and hopefully also in real organisms. With an understanding of the important factors in natural selection we can forecast not only the immediate fate of an existing population but also in what directions such a population might evolve in the future. We demonstrate that the concept of a quasispecies is relevant to evolution in a neutral fitness landscape. Motivated by R...