Epitaxial grain growth during surface modification of friction stir welded aerospace alloys by a pulsed laser system

The liquid film re-growth behaviour resulting from pulsed laser surface melting (LSM) has been investigated for typical 2xxx, and 7xxx aerospace alloys, both on parent plate and friction stir welded (FSW) joints. In Zr free alloys, as a result of the high growth rate and steep thermal gradient, the melted layer re-grew with a stable front, epitaxially, from the parent subsurface grains. This caused a thin coarse grained solidified layer to form over the parent material, thermomechanically affected zone (TMAZ) and heat affected zone (HAZ), and fine columnar grains to develop over the FSW nugget zone of the same order in width as the nugget grain size. In the case of the Zr containing alloys, a very fine columnar grain structure was found over the entire surface, independent of the subsurface grain structure. This has been shown to occur by growth selection from a band of nanoscale Al grains epitaxially nucleated on Al3Zr dispersoids, at the melt solid interface, that had not fully dissolved in the melt

Stereoselective Synthesis of Quaternary Carbons via the Dianionic Ireland-Claisen Rearrangement: An Approach to the Synthesis of Briarane Diterpenes

Investigation of the dianionic Ireland-Claisen rearrangement has led to the development of a simple method to enantioselectively access quaternary carbon stereocenters via a chelated transition state. This methodology was taken and applied to the synthesis of the core structure of Brianthein A. Peripheral modification of the core structure to complete the total synthesis proved quite challenging and ultimately was unsuccessful in forming the fused butenolide. This work represents the most advanced synthesis of brianthein A to date.Doctor of Philosoph

Agreement between bovine respiratory disease scoring systems for pre-weaned dairy calves.

Clinical scoring systems have been proposed for respiratory disease diagnosis in calves, including the Wisconsin (WI) system (McGuirk in 2008) which uses five clinical signs, each partitioned into four levels of severity. Recently, we developed the California (CA) bovine respiratory disease (BRD) scoring system requiring less calf handling and consisting of six clinical signs, each classified as normal or abnormal. The objective of this study was to estimate the on-farm agreement between the WI and the CA scoring systems. A total of 100 calves were enrolled on a CA dairy and assessed for BRD case status using the two scoring systems simultaneously. The Kappa coefficient of agreement between these two systems was estimated to be 0.85, which indicated excellent agreement beyond chance. The simpler design and reduced calf handling required by the CA BRD scoring system may make it advantageous for on-farm use

The Initial Configuration of Young Stellar Clusters: A K-band Number Counts Analysis of the Surface Density of Stars

We present an analysis of K-band stellar distributions for the young stellar clusters GGD 12-15, IRAS 20050+2720, and NGC 7129. We find that the two deeply embedded clusters, GGD 12-15 and IRAS 20050+2720, are not azimuthally symmetric and show a high degree of structure which traces filamentary structure observed in 850 micron emission maps. In contrast, the NGC 7129 cluster is circularly symmetric, less dense, and anti-correlated to 850 micron emission, suggesting recent gas expulsion and dynamical expansion have occured. We estimate stellar volume densities from nearest neighbor distances, and discuss the impact of these densities on the evolution of circumstellar disks and protostellar envelopes in these regions.Comment: 44 pages, 26 figures, Accepted to ApJ. Changes include extinction mapping, Monte Carlo field star modeling, and Nyquist sampled azimuthal stellar distributions. A version with full resolution figures is available at http://astro.pas.rochester.edu/~rguter/preprints/gutermuth_sd.tar.g