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Search Results: 1 - 10 of 10875 matches for " Scott Hansen "
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Uniform stabilization of a multilayer Rao-Nakra sandwich beam
Ahmet Ozkan Ozer,Scott W. Hansen
Mathematics , 2013, DOI: 10.3934/eect.2013.2.695
Abstract: We consider the problem of boundary feedback stabilization of a multilayer Rao-Nakra sandwich beam. We show that the eigenfunctions of the decoupled system form a Riesz basis. This allows us to deduce that the decoupled system is exponentially stable. Since the coupling terms are compact, the exponential stability of the coupled system follows from the strong stability of the coupled system, which is proved using a unique continuation result for the overdetermined homogenous system in the case of zero feedback.
Exact boundary controllability results for a multilayer Rao-Nakra sandwich beam
A. Ozkan Ozer,Scott W. Hansen
Mathematics , 2014, DOI: 10.1137/120892994
Abstract: We study the boundary controllability problem for a multilayer Rao-Nakra sandwich beam. This beam model consists of a Rayleigh beam coupled with a number of wave equations. We consider all combinations of clamped and hinged boundary conditions with the control applied to either the moment or the rotation angle at an end of the beam. We prove that exact controllability holds provided the damping parameter is sufficiently small. In the undamped case, exact controllability holds without any restriction on the parameters in the system. In each case, optimal control time is obtained in the space of optimal regularity for $L^2(0,T)$ controls. A key step in the proof of our main result is the proof of uniqueness of the zero solution of the eigensystem with the homogeneous boundary conditions together with zero boundary observation.
Modeling of a heat equation with a Dirac density
Scott W. Hansen,Jose de Jesus Martinez
Mathematics , 2015,
Abstract: We consider a linear hybrid system composed by two rods connected by a thin wall of length 2{\epsilon} and density 1/2{\epsilon}. By passing to a limit, we obtain a system describing heat flow of two rods connected by a singular point whose dynamics are governed by a partial differential equation. We prove that solutions of the approximate system converge weakly to solutions of the limiting system.
Null boundary controllability of a 1-dimensional heat equation with an internal point mass
Scott W. Hansen,Jose de Jesus Martinez
Mathematics , 2015,
Abstract: We consider a linear hybrid system composed by two rods of equal length connected by a point mass. We show that the system is null controllable with Dirichlet and Neumann controls. The results are based on a careful spectral spectral analysis together with the moment method.
Capstone Experiences: Lessons Learned in Mastering CS Competencies
Farid Hallouche,Scott James,John Hansen,Moe Bidgoli
Lecture Notes in Engineering and Computer Science , 2008,
Abstract:
Migrating Planets
Norm Murray,Brad Hansen,Matt Holman,Scott Tremaine
Physics , 1998, DOI: 10.1126/science.279.5347.69
Abstract: A planet orbiting in a disk of planetesimals can experience an instability in which it migrates to smaller orbital radii. Resonant interactions between the planet and planetesimals remove angular momentum from the planetesimals, increasing their eccentricities. Subsequently, the planetesimals either collide with or are ejected by the planet, reducing the semimajor axis of the planet. If the surface density of planetesimals exceeds a critical value, corresponding to 0.03 solar masses of gas inside the orbit of Jupiter, the planet will migrate inward a large distance. This instability may explain the presence of Jupiter-mass objects in small orbits around nearby stars.
A High-Performing and Cost-Effective SNP Genotyping Method Using rhPCR and Universal Reporters  [PDF]
Kristin Beltz, Daniel Tsang, Junzhou Wang, Scott Rose, Yun Bao, Yu Wang, Katelyn Larkin, Susan Rupp, Daniela Schrepfer, Krishnalekha Datta, Keith Gunderson, Chris Sailor, Scott Hansen, Joseph Dobosy, Lynette Lewis, Aurita Menezes, Joseph Walder, Mark Behlke, Caifu Chen
Advances in Bioscience and Biotechnology (ABB) , 2018, DOI: 10.4236/abb.2018.99034
Abstract: We have developed a novel dual enzyme chemistry called rhAmp® SNP genotyping based on RNase H2-dependent PCR (rhPCR) that provides high signal and specificity for SNP analysis. rhAmp SNP genotyping combines a unique two-enzyme system with 3’ end blocked DNA-RNA hybrid primers to interrogate SNP loci. Activation of the blocked primers occurs upon hybridization to its perfectly matched target, which eliminates or greatly reduces primer dimers. A thermostable hot-start RNase H2 cleaves the primer immediately 5’ of the ribose sugar, releasing the blocking group and allowing primer extension. PCR specificity is further improved with the use of a mutant Taq DNA polymerase, resulting in improved allelic discrimination. Signal generation is obtained using a universal reporter system which requires only two reporter probes for any bi-allelic SNP. 1000 randomly selected SNPs were chosen to validate the 95% design rate of the design pipeline. A subsampling of 130 human SNP targets was tested and achieved a 98% call rate, and 99% call accuracy. rhAmp SNP genotyping assays are compatible with various qPCR instruments including QuantStudioTM 7 Flex, CFX384TM, IntelliQube®, and Biomark HDTM. In comparison to TaqMan®, rhAmp SNP genotyping assays show higher signal (Rn) and greater cluster separation, resulting in more reliable SNP genotyping performance. The rhAmp SNP genotyping solution is suited for high-throughput SNP genotyping applications in humans and plants.
Dosage Regulation of the Active X Chromosome in Human Triploid Cells
Xinxian Deng,Di Kim Nguyen,R. Scott Hansen,Daniel L. Van Dyke,Stanley M. Gartler,Christine M. Disteche
PLOS Genetics , 2009, DOI: 10.1371/journal.pgen.1000751
Abstract: In mammals, dosage compensation is achieved by doubling expression of X-linked genes in both sexes, together with X inactivation in females. Up-regulation of the active X chromosome may be controlled by DNA sequence–based and/or epigenetic mechanisms that double the X output potentially in response to autosomal factor(s). To determine whether X expression is adjusted depending on ploidy, we used expression arrays to compare X-linked and autosomal gene expression in human triploid cells. While the average X:autosome expression ratio was about 1 in normal diploid cells, this ratio was lower (0.81–0.84) in triploid cells with one active X and higher (1.32–1.4) in triploid cells with two active X's. Thus, overall X-linked gene expression in triploid cells does not strictly respond to an autosomal factor, nor is it adjusted to achieve a perfect balance. The unbalanced X:autosome expression ratios that we observed could contribute to the abnormal phenotypes associated with triploidy. Absolute autosomal expression levels per gene copy were similar in triploid versus diploid cells, indicating no apparent global effect on autosomal expression. In triploid cells with two active X's our data support a basic doubling of X-linked gene expression. However, in triploid cells with a single active X, X-linked gene expression is adjusted upward presumably by an epigenetic mechanism that senses the ratio between the number of active X chromosomes and autosomal sets. Such a mechanism may act on a subset of genes whose expression dosage in relation to autosomal expression may be critical. Indeed, we found that there was a range of individual X-linked gene expression in relation to ploidy and that a small subset (~7%) of genes had expression levels apparently proportional to the number of autosomal sets.
Normal histone modifications on the inactive X chromosome in ICF and Rett syndrome cells: implications for methyl-CpG binding proteins
Stanley M Gartler, Kartik R Varadarajan, Ping Luo, Theresa K Canfield, Jeff Traynor, Uta Francke, R Scott Hansen
BMC Biology , 2004, DOI: 10.1186/1741-7007-2-21
Abstract: We show here that the inactive X in ICF cells, which appears to be hypomethylated at all CpG islands, exhibits normal histone modification patterns. In addition, in Rett cells with no functional MeCP2 methyl-CpG binding protein, the inactive X also exhibits normal histone modification patterns.These data suggest that DNA methylation and the associated methyl-DNA binding proteins may not play a critical role in determining histone modification patterns on the mammalian inactive X chromosome at the sites analyzed.Although it has been known for some time that histone modifications play a role in gene expression [1], it is only in the last several years that the details of these modifications have been more fully described. Acetylation and methylation of histone tails, for example, exhibit characteristic patterns for expressed and repressed genes in all eukaryotes studied [2]. This generality of histone modification and gene expression holds for eukaryotes with and without DNA methylation, indicating that DNA methylation is not required for histone modification. In organisms with DNA methylation, however, interactions between histone modification and DNA methylation do appear to exist.In Neurospora, histone methylation appears to determine DNA methylation patterns [3,4]. In Arabidopsis, non-CpG DNA methylation also appears to be determined by histone methyltransferases, whereas CpG methylation does not [5,6]. In mammals, there is considerable evidence suggesting that methyl-CpG binding proteins may play a significant role in histone modification through their association with histone deacetylases [7-11]. Mutations in the MeCP2 methyl-DNA binding protein, which are the cause of most Rett syndrome cases [12], support this model, because human male and female cells with MECP2 mutations exhibit histone hyperacetylation [10]. Histone hyperacetylation was also observed in mice with Mecp2 mutations [13]. Thus, DNA methylation is upstream of histone modification in this model o
Abnormal X : autosome ratio, but normal X chromosome inactivation in human triploid cultures
Stanley M Gartler, Kartik R Varadarajan, Ping Luo, Thomas H Norwood, Theresa K Canfield, R Scott Hansen
BMC Genetics , 2006, DOI: 10.1186/1471-2156-7-41
Abstract: Triploids provide a test of these ideas because the ratio of one Xa per diploid autosomal set cannot be achieved, yet this abnormal ratio should not necessarily affect the one-Xa choice mechanism for XCI. Previous studies of XCI patterns in murine triploids support the single-Xa model, but human triploids mostly have two-Xa cells, whether they are XXX or XXY. The XCI patterns we observe in fibroblast cultures from different XXX human triploids suggest that the two-Xa pattern of XCI is selected for, and may have resulted from rare segregation errors or Xi reactivation.The initial X inactivation pattern in human triploids, therefore, is likely to resemble the pattern that predominates in murine triploids, i.e., a single Xa, with the remaining X's inactive. Furthermore, our studies of XIST RNA accumulation and promoter methylation suggest that the basic features of XCI are normal in triploids despite the abnormal X:autosome ratio.Dosage compensation in mammals is normally achieved by the transcriptional silencing of one of the two X chromosomes (Xi) in females early in development (X chromosome inactivation; XCI). It is widely assumed that an early event in XCI is a counting mechanism that senses the X chromosome:autosome ratio, such that one X chromosome per diploid autosomal set remains active, with additional X's rendered inactive. [1-3]. In triploids, which occur in approximately 1% of human conceptions [4], this ratio of one active X (Xa) per diploid autosomal set cannot be achieved. If developmental steps are associated with checkpoints, it is likely that development in triploids would cease at this point. This is not the case, however, as development in triploids proceeds well beyond the X inactivation window, with some cases reaching term. A variety of XCI patterns have been observed in triploids; in XXX triploids, for example, single inactive X cells (XaXaXi) and double inactive X cells (XaXiXi) have been found in independent cultures as well as in the same (m
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