The crystal structure of urea oxalic acid (2:1)

The crystal structure of urea oxalic acid, 2[CO(NH2)2].(COOH)2 has been determined using three-dimensional X-ray data, collected on an automatic diffractometer. The space group is P21/c. The lattice constants are: a = 5.058 (3), b = 12.400 (3), c = 6.964 (2) A, fl= 98"13 (7) °. The number of molecules in the unit cell is two. The structure consists of layers of urea and oxalic acid molecules held together by hydrogen bonds. The positions of all hydrogen atoms have been found. The compound is not a uronium salt

25 Innovative Ideas

PreLaw Magazine names GGU Law among the top 20 most innovative law programs for our 1st STEP Trial and Evidence program

25 Innovative Ideas

PreLaw Magazine names GGU Law among the top 20 most innovative law programs for our 1st STEP Trial and Evidence program

STATISTICS IN THE BILLERA-HOLMES-VOGTMANN TREESPACE

This dissertation is an effort to adapt two classical non-parametric statistical techniques, kernel density estimation (KDE) and principal components analysis (PCA), to the Billera-Holmes-Vogtmann (BHV) metric space for phylogenetic trees. This adaption gives a more general framework for developing and testing various hypotheses about apparent differences or similarities between sets of phylogenetic trees than currently exists. For example, while the majority of gene histories found in a clade of organisms are expected to be generated by a common evolutionary process, numerous other coexisting processes (e.g. horizontal gene transfers, gene duplication and subsequent neofunctionalization) will cause some genes to exhibit a history quite distinct from the histories of the majority of genes. Such “outlying” gene trees are considered to be biologically interesting and identifying these genes has become an important problem in phylogenetics. The R sofware package kdetrees, developed in Chapter 2, contains an implementation of the kernel density estimation method. The primary theoretical difficulty involved in this adaptation concerns the normalizion of the kernel functions in the BHV metric space. This problem is addressed in Chapter 3. In both chapters, the software package is applied to both simulated and empirical datasets to demonstrate the properties of the method. A few first theoretical steps in adaption of principal components analysis to the BHV space are presented in Chapter 4. It becomes necessary to generalize the notion of a set of perpendicular vectors in Euclidean space to the BHV metric space, but there some ambiguity about how to best proceed. We show that convex hulls are one reasonable approach to the problem. The Nye-PCA- algorithm provides a method of projecting onto arbitrary convex hulls in BHV space, providing the core of a modified PCA-type method

Depositional and Diagenetic History of the Middle Ordovician Carbonates of the Shenandoah Valley, Northern Virginia

An examination of the Middle Ordovician carbonates in northwest Virginia has revealed a particularly sensitive record of deposition and subsidence. Two-hundred acetate peels from six measured stratigraphic sections in Shenandoah County, Virginia were examined to interpret the depositional and diagenetic history. Two major lithofacies have been recognized within the New Market Limestone and three have been recognized in the Lincolnshire Formation. These five lithofacies represent an overall transgressive sequence. This transgression was not uniform but paused several times to allow carbonate deposition to reach sea-level. These shoaling events suggest a slowly subsiding basin in this region. The carbonate rocks within the study area have been compared to the sediments of the modern Andros Island, Bahamas to establish a depositional and diagenetic model. The models proposed for the study area are in agreement with models proposed for adjacent areas along strike

Hemorrhagic Gastropathy

AbstractHemorrhagic gastropathy is the term used to describe multifocal gastric mucosal hemorrhage. The most frequently observed causes for this condition are the use of nonsteroidal anti-inflammatory drugs and the ingestion of large amounts of alcohol. In addition to patients exposed to these chemical causes, hemorrhagic gastropathy can also be observed in the critically ill. This article is part of an expert video encyclopedia

Grading the Quality of Bowel Preparation

AbstractIn colonoscopy, even a complete examination has little diagnostic accuracy when the endoscopic view of the mucosa was impaired by residual stool. Therefore, an assessment of the visibility of the mucosa is important, in order to be able to judge the reliability of positive, but even more importantly, negative findings during colonoscopy.Insufficient visualization can result in lesions, especially small or flat ones, being missed. Poor bowel preparation may also result in difficult progression, an increased risk of complications, prolonged procedure duration and an increase in the amount of sedatives and analgetics required. Poor bowel preparation is also a frequent cause for incomplete procedures.The optimal grading scale uses objective terminology, is validated, and informs both on segmental as overall bowel preparation quality. The Boston bowel preparation scale fulfils all these criteria, making it the most uses bowel preparation scale in colorectal cancer screening programs