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Search Results: 1 - 10 of 172881 matches for " Merle B Thomas "
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Genome wide signatures of positive selection: The comparison of independent samples and the identification of regions associated to traits
William Barendse, Blair E Harrison, Rowan J Bunch, Merle B Thomas, Lex B Turner
BMC Genomics , 2009, DOI: 10.1186/1471-2164-10-178
Abstract: In this study we compared the signals of selection, identified through population divergence in the Bovine HapMap project, to those found in an independent sample of cattle from Australia. Evidence for population differentiation across the genome, as measured by FST, was highly correlated in the two data sets. Nevertheless, 40% of the variance in FST between the two studies was attributed to the differences in breed composition. Seventy six percent of the variance in FST was attributed to differences in SNP composition and density when the same breeds were compared. The difference between FST of adjacent loci increased rapidly with the increase in distance between SNP, reaching an asymptote after 20 kb. Using 129 SNP that have highly divergent FST values in both data sets, we identified 12 regions that had additive effects on the traits residual feed intake, beef yield or intramuscular fatness measured in the Australian sample. Four of these regions had effects on more than one trait. One of these regions includes the R3HDM1 gene, which is under selection in European humans.Firstly, many different populations will be necessary for a full description of selective signatures across the genome, not just a small set of highly divergent populations. Secondly, it is necessary to use the same SNP when comparing the signatures of selection from one study to another. Thirdly, useful signatures of selection can be obtained where many of the groups have only minor genetic differences and may not be clearly separated in a principal component analysis. Fourthly, combining analyses of genome wide selection signatures and genome wide associations to traits helps to define the trait under selection or the population group in which the QTL is likely to be segregating. Finally, the FST difference between adjacent loci suggests that 150,000 evenly spaced SNP will be required to study selective signatures in all parts of the bovine genome.The goal of genome wide analyses of polymorphis
Variation at the Calpain 3 gene is associated with meat tenderness in zebu and composite breeds of cattle
William Barendse, Blair E Harrison, Rowan J Bunch, Merle B Thomas
BMC Genetics , 2008, DOI: 10.1186/1471-2156-9-41
Abstract: We identified single nucleotide polymorphisms (SNP) in the genomic sequence of the CAPN3 gene and tested three of these in a sample of 2189 cattle. Of the three SNP genotyped, the CAPN3:c.1538+225G>T had the largest significant additive effect, with an allele substitution effect in the Brahman of α = -0.144 kg, SE = 0.060, P = 0.016, and the polymorphism explained 1.7% of the residual phenotypic variance in that sample of the breed. Significant haplotype substitution effects were found for all three breeds, the Brahman, the Belmont Red, and the Santa Gertrudis. For the common haplotype, the haplotype substitution effect in the Brahman was α = 0.169 kg, SE = 0.056, P = 0.003. The effect of this gene was compared to Calpastatin in the same sample. The SNP show negligible frequencies in taurine breeds and low to moderate minor allele frequencies in zebu or composite animals.These associations confirm the location of a QTL for meat tenderness in this region of bovine chromosome 10. SNP in or near this gene may be responsible for part of the overall difference between taurine and zebu breeds in meat tenderness, and the greater variability in meat tenderness found in zebu and composite breeds. The evidence provided so far suggests that none of these tested SNP are causative mutations.The status of DNA tests for meat tenderness has been recently discussed [1] and so far there are only two genes identified that have consistent effects on meat tenderness reported in the literature, that for Calpastatin and Calpain 1 [2-5]. There are two polymorphisms in Calpain 1 (CAPN1), one appearing to be more useful in taurine breeds and one more useful in zebu breeds. On the other hand, although several possible causative mutations have been identified in Calpastatin (CAST), variation at this gene appears to affect all breed types.Quantitative trait loci (QTL) for meat tenderness were located to bovine chromosome 10 in a Charolais × Brahman experimental population [1]. The authors sugge
Dynamic of threshold solutions for energy-critical wave equation
Thomas Duyckaerts,Frank Merle
Mathematics , 2007,
Abstract: We consider the energy-critical non-linear focusing wave equation in dimension N=3,4,5. An explicit stationnary solution, $W$, of this equation is known. The energy E(W,0) has been shown by C. Kenig and F. Merle to be a threshold for the dynamical behavior of solutions of the equation. In the present article we study the dynamics at the critical level E(u_0,u_1)=E(W,0) and classify the corresponding solutions. We show in particular the existence of two special solutions, connecting different behaviors for negative and positive times. Our results are analoguous to our previous work on radial Schr\"odinger equation, but without any radial assumption on the data. We also refine the understanding of the dynamical behavior of the special solutions.
Dynamic of threshold solutions for energy-critical NLS
Thomas Duyckaerts,Frank Merle
Mathematics , 2007,
Abstract: We consider the radial energy-critical non-linear focusing Schr\"odinger equation in dimension N=3,4,5. An explicit stationnary solution, W, of this equation is known. In a previous work by C. Carlos and F. Merle, the energy E(W) has been shown to be a threshold for the dynamical behavior of solutions of the equation. In the present article, we study the dynamics at the critical level E(u)=E(W) and classify the corresponding solutions. This gives in particular a dynamical characterization of W.
Scattering norm estimate near the threshold for energy-critical focusing semilinear wave equation
Thomas Duyckaerts,Frank Merle
Mathematics , 2008,
Abstract: We consider the energy-critical semilinear focusing wave equation in dimension $N=3,4,5$. An explicit solution $W$ of this equation is known. By the work of C. Kenig and F. Merle, any solution of initial condition $(u_0,u_1)$ such that $E(u_0,u_1)
Effects of a Foliar Neem Formulation on Colonization and Mortality of Whiteflies (Hemiptera: Aleyrodidae) on Collard Plants  [PDF]
Dana Krzyzaniak, Alvin M. Simmons, B. Merle Shepard
Agricultural Sciences (AS) , 2016, DOI: 10.4236/as.2016.711071
A study was conducted to determine the effects of foliar sprays of a selected neem (Azadirachta indica A. Juss) product (GOS Neem 7-Way) on colonization and development by the Middle-East Asia Minor-1 (= B-biotype sweetpotato whitefly) Bemisia tabaci (Gennadius) on collard (Brassica oleracea variety acephala de Condolle) plants. GOS Neem 7-Way is marketed for use as an insecticide in organic and conventional crop production. Caged choice, caged no-choice, and Y-tube olfactometer assays were conducted on oviposition, survival and adult behavioral response to plant treatment with 1.25% azadiractin. In the caged choice experiment, colonization by the whiteflies was reduced and fewer eggs were deposited on neem-treated plants as compared with control plants (only treated with an adjuvant). Similarly, decreased numbers of adult whiteflies and reduced whitefly development were observed in no-choice assays for the neem-treatment, as compared with the untreated control. Both horizontal and vertical-orientated Y-tube olfactometer assays provided complementarily assessments that the neem had a repellency effect on the adult whiteflies. However, the repellency effect primarily dissipated within one day post treatment. Overall, the greatest benefit of the neem treatment appears to have been on whitefly mortality. The findings may be useful in providing a more ecologically sound way to manage populations of the B. tabaci whitefly in organic vegetable production.
Maximizers for the Strichartz norm for small solutions of mass-critical NLS
Thomas Duyckaerts,Frank Merle,Svetlana Roudenko
Mathematics , 2010,
Abstract: Consider the mass-critical nonlinear Schr\"odinger equations in both focusing and defocusing cases for initial data in $L^2$ in space dimension N. By Strichartz inequality, solutions to the corresponding linear problem belong to a global $L^p$ space in the time and space variables, where $p=2+4/N$. In 1D and 2D, the best constant for the Strichartz inequality was computed by D.~Foschi who has also shown that the maximizers are the solutions with Gaussian initial data. Solutions to the nonlinear problem with small initial data in $L^2$ are globally defined and belong to the same global $L^p$ space. In this work we show that the maximum of the $L^p$ norm is attained for a given small mass. In addition, in 1D and 2D, we show that the maximizer is unique and obtain a precise estimate of the maximum. In order to prove this we show that the maximum for the linear problem in 1D and 2D is nondegenerated.
Scattering for radial, bounded solutions of focusing supercritical wave equations
Thomas Duyckaerts,Carlos Kenig,Frank Merle
Mathematics , 2012,
Abstract: In this paper, we consider the wave equation in space dimension 3 with an energy-supercritical, focusing nonlinearity. We show that any radial solution of the equation which is bounded in the critical Sobolev space is globally defined and scatters to a linear solution. As a consequence, finite time blow-up solutions have critical Sobolev norm converging to infinity (along some sequence of times). The proof relies on the compactness/rigidity method, pointwise estimates on compact solutions obtained by the two last authors, and channels of energy arguments used by the authors in previous works on the energy-critical equation.
Profiles for bounded solutions of dispersive equations, with applications to energy-critical wave and Schr?dinger equations
Thomas Duyckaerts,Carlos E. Kenig,Frank Merle
Mathematics , 2013,
Abstract: Consider a bounded solution of the focusing, energy-critical wave equation that does not scatter to a linear solution. We prove that this solution converges in some weak sense, along a sequence of times and up to scaling and space translation, to a sum of solitary waves. This result is a consequence of a new general compactness/rigidity argument based on profile decomposition. We also give an application of this method to the energy-critical Schr\"odinger equation.
Concentration-compactness and universal profiles for the non-radial energy critical wave equation
Thomas Duyckaerts,Carlos Kenig,Frank Merle
Mathematics , 2015,
Abstract: In this paper, we give an overview of the authors' work on applications of the method of concentration-compactness to global well-posedness, scattering, blow-up and universal profiles for the energy critical wave equation in the non-radial setting. New results and proofs are also given.
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