Huy Tài Hà

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Let G be a simple (i.e., no loops and no multiple edges) graph. We investigate the question of how to modify G combinatorially to obtain a sequentially Cohen-Macaulay graph. We focus on modifications given by adding configurations of whiskers to G, where to add a whisker one adds a new vertex and an edge connecting this vertex to an existing vertex in G. We(More)
Strains of Escherichia coli with mutations in the ubiE gene are not able to catalyze the carbon methylation reaction in the biosynthesis of ubiquinone (coenzyme Q) and menaquinone (vitamin K2), essential isoprenoid quinone components of the respiratory electron transport chain. This gene has been mapped to 86 min on the chromosome, a region where the(More)
It was recently discovered that the aarF gene in Providencia stuartii is required for coenzyme Q (CoQ) biosynthesis. Here we report that yigR, the Escherichia coli homologue of aarF, is ubiB, a gene required for the first monooxygenase step in CoQ biosynthesis. Both the P. stuartii aarF and E. coli ubiB (yigR) disruption mutant strains lack CoQ and(More)
I hereby declare that the materials and results in this thesis, unless accompanied by specific references, are original and have not been published elsewhere. Abstract This thesis attempts to investigate various embeddings of rational surfaces. Most of the attention is paid to those of the blowup of P 2 at a set of points. In Chapter 1, the notions of a(More)
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