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Search Results: 1 - 10 of 8268 matches for " Kevin Morgan "
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TV Computes the Flat Norm for Boundaries
Simon P. Morgan,Kevin R. Vixie
Abstract and Applied Analysis , 2007, DOI: 10.1155/2007/45153
Abstract: We show that the recently introduced L1TV functional can be used to explicitly compute the flat norm for codimension one boundaries. Furthermore, using L1TV, we also obtain the flat norm decomposition. Conversely, using the flat norm as the precise generalization of L1TV functional, we obtain a method for denoising nonboundary or higher codimension sets. The flat norm decomposition of differences can made to depend on scale using the flat norm with scale which we define in direct analogy to the L1TV functional. We illustrate the results and implications with examples and figures.
Cane River: the archaeology of “free people of colour” in colonial Louisiana
Kevin MacDonald,David Morgan,Fiona Handley
Archaeology International , 2002, DOI: 10.5334/ai.0615
Abstract: The overseas dispersal and subsequent history of people of African descent – the African diaspora – has attracted much interest in recent decades from anthropologists, archaeologists and historians, particularly in the USA. But such studies have seldom been undertaken by archaeologists with experience of West Africa and its material culture. In a new project on the African heritage in colonial Louisiana, members of the Institute are collaborating with American colleagues to combine expertise on cultural contacts in the Americas between Native Americans,Africans and European colonists.
Extreme Measures of Agricultural Financial Risk
John Cotter,Kevin Dowd,Wyn Morgan
Quantitative Finance , 2011,
Abstract: Risk is an inherent feature of agricultural production and marketing and accurate measurement of it helps inform more efficient use of resources. This paper examines three tail quantile-based risk measures applied to the estimation of extreme agricultural financial risk for corn and soybean production in the US: Value at Risk (VaR), Expected Shortfall (ES) and Spectral Risk Measures (SRMs). We use Extreme Value Theory (EVT) to model the tail returns and present results for these three different risk measures using agricultural futures market data. We compare the estimated risk measures in terms of their size and precision, and find that they are all considerably higher than normal estimates; they are also quite uncertain, and become more uncertain as the risks involved become more extreme.
Normalization and analysis of DNA microarray data by self-consistency and local regression
Thomas B Kepler, Lynn Crosby, Kevin T Morgan
Genome Biology , 2002, DOI: 10.1186/gb-2002-3-7-research0037
Abstract: We have developed a robust semi-parametric normalization technique based on the assumption that the large majority of genes will not have their relative expression levels changed from one treatment group to the next, and on the assumption that departures of the response from linearity are small and slowly varying. We use local regression to estimate the normalized expression levels as well as the expression level-dependent error variance.We illustrate the use of this technique in a comparison of the expression profiles of cultured rat mesothelioma cells under control and under treatment with potassium bromate, validated using quantitative PCR on a selected set of genes. We tested the method using data simulated under various error models and find that it performs well.Among the most fascinating open questions in biology today are those associated with the global regulation of gene expression, itself the basis for the unfolding of the developmental program, the cellular response to insult and changes in the environment, and many other biological phenomena. The answers to some of these questions have been moved a few steps closer to realization with the advent of DNA hybridization microarrays [1,2,3,4,5,6]. These tools allow the simultaneous monitoring of the expression levels of hundreds to tens of thousands of genes - sufficient numbers to measure the expression of all of the genes in many organisms, as is now being done in the eukaryote Saccharomyces cerevisiae [7,8].If we designate the intensity of a given spot in the microarray as I and the abundance of the corresponding mRNA in the target solution as A, we have, under ideal circumstances,I = NA + error ??? (1)where N is a constant, unknown normalization factor. When comparing two different sets of intensities, these factors (or at least their relative sizes) must be determined in order to make a relative comparison of the abundances A.The simple normalization techniques commonly used at this time assume Equation
Transepithelial leak in Barrett's esophagus patients: The role of proton pump inhibitors
Christopher Farrell,Melissa Morgan,Owen Tully,Kevin Wolov
World Journal of Gastroenterology , 2012, DOI: 10.3748/wjg.v18.i22.2793
Abstract: AIM: To determine if the observed paracellular sucrose leak in Barrett’s esophagus patients is due to their proton pump inhibitor (PPI) use. METHODS: The in vivo sucrose permeability test was administered to healthy controls, to Barrett’s patients and to non-Barrett’s patients on continuous PPI therapy. Degree of leak was tested for correlation with presence of Barrett’s, use of PPIs, and length of Barrett’s segment and duration of PPI use. RESULTS: Barrett’s patients manifested a near 3-fold greater, upper gastrointestinal sucrose leak than healthy controls. A decrease of sucrose leak was observed in Barrett’s patients who ceased PPI use for 7 d. Although initial introduction of PPI use (in a PPI-na ve population) results in dramatic increase in sucrose leak, long-term, continuous PPI use manifested a slow spontaneous decline in leak. The sucrose leak observed in Barrett’s patients showed no correlation to the amount of Barrett’s tissue present in the esophagus. CONCLUSION: Although future research is needed to determine the degree of paracellular leak in actual Barrett’s mucosa, the relatively high degree of leak observed with in vivo sucrose permeability measurement of Barrett’s patients reflects their PPI use and not their Barrett’s tissue per se.
Kevin Morgan,Robin L. Jones,David Gilbourne,David Llewellyn
Nuances : Estudos sobre Educa??o , 2013,
Abstract: ABSTRACT: We know that coach education programmes continue to be criticized for their largely didactic methods of delivery and rather superficial engagement with the complex reality of practice and we understand that innovative approaches in coach education pedagogy means moving somewhat away from the competencies based approach and it has been increasingly argued that the aim of coach education should be to develop in practitioners a ‘quality of mind’ so that they are better equipped to deal with the problematic and dynamic nature of their work. The skills of coach educators in facilitating the learning of student coaches are crucial to the effectiveness of the pedagogies. Coach educators, therefore, must be committed to the approaches outlined in this article and invest the time and work necessary to learning new skills if they are to be successfully implemented. We found that teaching in this way resulted in a raised degree of responsibility on behalf of the tutors, not so much in relation to their content delivery, but for the subsequent student interaction and learning (JONES et al., 2011). In this sense tutors took greater care to listen and react to group interactions, recognising that their (non) interventions at (in) appropriate times could genuinely affect and frame ensuing students’ discussions and perceptions. A further area of research, therefore, could be to explore the issues surrounding the training and support of coach educators in implementing such pedagogical innovative approaches to coach education. RESUMO: Sabemos que os trabalhos de orienta o de técnicos/professores s o muito criticados por seus métodos pouco se aproximarem de práticas inovadoras. No entanto, práticas pedagógicas inovadoras devem se aproximar da realidade prática e avan ar aos métodos tradicionais, considerando que uma pedagogia inovadora deve mover alguém do lugar onde se encontra para conhecer novas possibilidades. As habilidades dos técnicos/professores devem ser trabalhadas no sentido dos mesmos se constituírem facilitadores do processo de aprendizagem dos estudantes para se pensar numa pedagogia inovadora. Entendemos que uma concep o pedagógica construída nessa dire o possibilita o desenvolvimento tanto de técnicos/professores, assim como os estudantes e pesquisas educacionais devem caminhar nessa dire o, tendo em vista a necessidade de transforma o qualitativa dessa área de atua o.
Probing the GnRH receptor agonist binding site identifies methylated triptorelin as a new anti-proliferative agent
Kevin Morgan,Samuel P Leighton,Robert P Millar
Journal of Molecular Biochemistry , 2012,
Abstract: D-amino acid substitutions at Glycine postion-6 in GnRH-I decapeptide can possess super-agonist activity and enhanced in vivo pharmacokinetics. Agonists elicit growth-inhibition in tumorigenic cells expressing the GnRH receptor above threshold levels. However, new agonists with modified properties are required to improve the anti-proliferative range. Effects of residue substitutions and methylations on tumourigenic HEK293[SCL60] and WPE-1-NB26-3 prostate cells expressing the rat GnRH receptor were compared. Peptides were ranked according to receptor binding affinity, induction of inositol phosphate production and cell growth-inhibition. Analogues possessing D-Trp6 (including Triptorelin), D-Leu6 (including Leuprolide), D-Ala6, D-Lys6, or D-Arg6 exhibited agonist and anti-proliferative activity. Residues His5 or His5,Trp7,Tyr8, corresponding to residues found in GnRH-II , were tolerated, with retention of sub-nanomolar/low nanomolar binding affinities and EC50s for receptor activation and IC50s for cell growth-inhibition. His5D-Arg6-GnRH-I exhibited reduced binding affinity and potency, effective in the mid-nanomolar range. However, all GnRH-II-like analogues were less potent than Triptorelin. By comparison, three methylated-Trp6 Triptorelin variants showed differential binding, receptor activation and anti-proliferation potency. Significantly, 5-Methyl-DL-Trp6-Triptorelin was equipotent to triptorelin. Subsequent studies should determine whether pharmacologically enhanced derivatives of Triptorelin can be developed by further alkylations, without substitutions or cleavable cytotoxic adducts, to improve the extent of growth-inhibition of tumour cells expressing the GnRH receptor.
Gamma Ray Burst as Sources of Exotic Particles
Ian Morgan,Ted Tao,Erin De Pree,Kevin Tennyson
Physics , 2015,
Abstract: We consider the possible production of stable lightest first level KK particle (LKP) in baryonic gamma ray bursts (GRB) out flows. We numerically computed the energy-dependent cross-sections of Kaluza-Klein (KK) excitations for the Standard Model gauge bosons, photon and Z. Next, we determined the feasibility of producing these KK excitations in gamma-ray emitting regions of GRBs. We found that a GRB fireball that accelerates baryons to energies greater than 10^14 eV could produce KK excitations out to approximately 10^12 cm from the central engine, indicating that GRBs may be a significant source of the LKP. Finally, we explore the potential observational consequences of our results.
A Matlab Implementation of a Flat Norm Motivated Polygonal Edge Matching Method using a Decomposition of Boundary into Four 1-Dimensional Currents
Simon P. Morgan,Wotao Yin,Kevin R. Vixie
Computer Science , 2008,
Abstract: We describe and provide code and examples for a polygonal edge matching method.
A Whole-Body Model for Glycogen Regulation Reveals a Critical Role for Substrate Cycling in Maintaining Blood Glucose Homeostasis
Ke Xu,Kevin T. Morgan,Abby Todd Gehris,Timothy C. Elston ,Shawn M. Gomez
PLOS Computational Biology , 2011, DOI: 10.1371/journal.pcbi.1002272
Abstract: Timely, and sometimes rapid, metabolic adaptation to changes in food supply is critical for survival as an organism moves from the fasted to the fed state, and vice versa. These transitions necessitate major metabolic changes to maintain energy homeostasis as the source of blood glucose moves away from ingested carbohydrates, through hepatic glycogen stores, towards gluconeogenesis. The integration of hepatic glycogen regulation with extra-hepatic energetics is a key aspect of these adaptive mechanisms. Here we use computational modeling to explore hepatic glycogen regulation under fed and fasting conditions in the context of a whole-body model. The model was validated against previous experimental results concerning glycogen phosphorylase a (active) and glycogen synthase a dynamics. The model qualitatively reproduced physiological changes that occur during transition from the fed to the fasted state. Analysis of the model reveals a critical role for the inhibition of glycogen synthase phosphatase by glycogen phosphorylase a. This negative regulation leads to high levels of glycogen synthase activity during fasting conditions, which in turn increases substrate (futile) cycling, priming the system for a rapid response once an external source of glucose is restored. This work demonstrates that a mechanistic understanding of the design principles used by metabolic control circuits to maintain homeostasis can benefit from the incorporation of mathematical descriptions of these networks into “whole-body” contextual models that mimic in vivo conditions.
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