Publications

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Selective methods for the functionalization of indoles and other nitrogen heterocycles would provide access to the core structures of many natural products and pharmaceuticals. Although there are many methods and strategies for the synthesis of substituted indoles or functionalization of the azole ring, strategies for the selective functionalization of the benzo-fused portion of the indole skeleton, particularly the 7-position, are less common. We report a one-pot, iridium-catalyzed, silyl-directed C-H borylation of indoles at the 7-position. This process occurs in high yield with a variety of substituted indoles, and conversions of the 7-borylindole products to 7-aryl-, 7-cinnamyl-, and 7-haloindoles are demonstrated. The Ir-catalyzed, silyl-directed C-H borylation also occurs with several other nitrogen heterocycles, including carbazole, phenothiazines, and tetrahydroquinoline. The utility of this methodology is highlighted by the one-pot synthesis of a member of the pyrrolophenanthridone class of alkaloid natural products.

A comparison of the physical properties of hyperbranched and dendritic macromolecules with linear polymers and the linear analogs of these 3-dimensional polymers is presented. It is found that thermal properties, such as glass transition temperature and degradation, are the same regardless of the macromolecular architecture but are very sensitive to the number and nature of chain end functional groups. However, other properties, such as solubility, melt viscosity, chemical reactivity, intrinsic viscosity were found to be very dependent on the macromolecular architecture.

Polyphosphate degradation and phosphate secretion were optimized in Escherichia coli strains overexpressing the E. coli polyphosphate kinase gene (ppk) and either the E. coli polyphosphatase gene (ppx) or the Saccharomyces cerevisiae polyphosphatase gene (scPPX1) from different inducible promoters on medium- and high-copy plasmids. The use of a host strain without functional ppk or ppx genes on the chromosome yielded the highest levels of polyphosphate, as well as the fastest degradation of polyphosphate when the gene for polyphosphatase was induced. The introduction of a hybrid metabolic pathway consisting of the E. coli ppk gene and the S. cerevisiae polyphosphatase gene resulted in lower polyphosphate concentrations than when using both the ppk and ppx genes from E. coli, and did not significantly improve the degradation rate. It was also found that the rate of polyphosphate degradation was highest when ppx was induced late in growth, most likely due to the high intracellular polyphosphate concentration. The phosphate released from polyphosphate allowed the growth of phosphate-starved cells; excess phosphate was secreted into the medium, leading to a down-regulation of the phosphate-starvation (Pho) response. The production of alkaline phosphatase, an indicator of the Pho response, can be precisely controlled by manipulating the degree of ppx induction. Copyright 1998 John Wiley & Sons, Inc.

The results of this study suggest that stressful life events are significantly more likely to occur in depressed children, particularly females, compared to anxious children, and that these events are predominantly characterized by independent events outside of the child's control. The results also suggest that loss events may be specific for depression in children. Interestingly, stress does not appear to impact the HPA axis in children, which is true for anxious, depressed, and normal control children. The temporal occurrence and severity, as well as the type of stressful life events as they relate to the onset and maintenance of anxiety and depression in children, need to be more fully explored.

There are billions of images with associated text available on the web. Some common areas where pictures and words are naturally linked include: web pages, captioned photographs, and video with speech or closed captioning. The central question that needs to be solved in order to organize these collections effectively is how to extract images in which specified objects are depicted from large pools of pictures with noisy text. This problem is challenging, because the relationship between words associated with an image and objects depicted within the image is often complex. This thesis demonstrates that, for many situations, collections of illustrated material can be exploited by using information from both the images themselves and from the associated text. The first project demonstrates that one can build a large collection of labeled face images by: identifying faces in images; identifying names in captions; then linking the faces and the names. The process of linking uses the fact that images of the same person tend to look more similar—in appropriate features—than images of different people. Furthermore, the structure of the language in a caption often supplies important cues as to which of the named people actually appear in the image. The second project shows that relations between words and images are strong, even when the text has a less formal structure than captions do. Images retrieved from the internet are classified as containing one of a set of animals or not, using both text that appears near the image and a set of simple image appearance descriptors. Animals are notoriously difficult to identify, because their appearance changes quite dramatically; however, this combination of words and weak appearance descriptors gives us a rather accurate classifier. The third project deals with the tendency of users to attach labels to images that do not belong there, typically because labels are attached to a whole set of images rather than to each image individually. This means that, for example, many images labeled with Chrysler building do not in fact depict that building. However, the ones that do tend to look similar in an appropriate sense, and it is possible to find images that are iconic representations of such a category using this cue.