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Search Results: 1 - 10 of 231457 matches for " Stephen C Harris "
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Design of bi-tortuous, anisotropic graphite anodes for fast ion-transport in Li-ion batteries
V. Pavan Nemani,Stephen J. Harris,Kyle C. Smith
Physics , 2015, DOI: 10.1149/2.0151508jes
Abstract: Thick Li-ion battery electrodes with high ion transport rates could enable batteries that cost less and that have higher gravimetric and volumetric energy density, because they require fewer inactive cell-components. Finding ways to increase ion transport rates in thick electrodes would be especially valuable for electrodes made with graphite platelets, which have been shown to have tortuosities in the thru-plane direction about 3 times higher than in the in-plane direction. Here, we predict that bi-tortuous electrode structures (containing electrolyte-filled macro-pores embedded in micro-porous graphite) can enhance ion transport and can achieve double the discharge capacity compared to an unstructured electrode at the same average porosity. We introduce a new two-dimensional version of porous-electrode theory with anisotropic ion transport to investigate these effects and to interpret the mechanisms by which performance enhancements arise. From this analysis we determine criteria for the design of bi-tortuous graphite anodes, including the particular volume fraction of macro-pores that maximizes discharge capacity (approximately 20 vol.%) and a threshold spacing interval (half the electrode's thickness) below which only marginal enhancement in discharge capacity is obtained. We also report the sensitivity of performance with respect to cycling rate, electrode thickness, and average porosity/electroactive-material loading.
Numerical Experiments Using MATLAB: Superconvergence of Conforming Finite, Element Approximation for Second Order, Elliptic Problems  [PDF]
Anna Harris, Stephen Harris, Camille Gardner, Tyrone Brock
Applied Mathematics (AM) , 2018, DOI: 10.4236/am.2018.96047
The superconvergence in the finite element method is a phenomenon in which the finite element approximation converges to the exact solution at a rate higher than the optimal order error estimate. Wang proposed and analyzed superconvergence of the conforming finite element method by L2-projections. The goal of this paper is to perform numerical experiments using MATLAB to support and to verify the theoretical results in Wang for the superconvergence of the conforming finite element method (CFEM) for the second order elliptic problems by L2-projection methods. MATLAB codes are published at https://github.com/annaleeharris/Superconvergence-CFEM for anyone to use and to study.
Polymorphism Interaction Analysis (PIA): a method for investigating complex gene-gene interactions
Leah E Mechanic, Brian T Luke, Julie E Goodman, Stephen J Chanock, Curtis C Harris
BMC Bioinformatics , 2008, DOI: 10.1186/1471-2105-9-146
Abstract: We developed the Polymorphism Interaction Analysis tool (PIA version 2.0) to include different approaches for ranking and scoring SNP combinations, to account for imbalances between case and control ratios, stratify on particular factors, and examine associations of user-defined pathways (based on SNP or gene) with case status. PIA v. 2.0 detected 2-SNP interactions as the highest ranking model 77% of the time, using simulated data sets of genetic models of interaction (minor allele frequency = 0.2; heritability = 0.01; N = 1600) generated previously [Velez DR, White BC, Motsinger AA, Bush WS, Ritchie MD, Williams SM, Moore JH: A balanced accuracy function for epistasis modeling in imbalanced datasets using multifactor dimensionality reduction. Genet Epidemiol 2007, 31:306–315.]. Interacting SNPs were detected in both balanced (20 SNPs) and imbalanced data (case:control 1:2 and 1:4, 10 SNPs) in the context of non-interacting SNPs.PIA v. 2.0 is a useful tool for exploring gene*gene or gene*environment interactions and identifying a small number of putative associations which may be investigated further using other statistical methods and in replication study populations.In the absence of highly penetrant, rare, genetic mutations, the risk of common diseases, such as cancer, is likely determined by a complex interplay between several genetic and environmental factors. Common genetic variation, in the form of single nucleotide polymorphisms (SNPs), are believed to modulate cancer susceptibility [1,2]. However, only a fraction of association studies examining single loci have replicated [3,4]. One reason for the lack of replication of SNP studies, in particular when considering the complexity of pathways of carcinogenesis, may include a failure to consider complex gene*gene or gene*environment interactions [5,6]. Others include chance, poor design, insufficient power, or population stratification [7,8].With the advent of high-density SNP arrays and genome-wide associati
Carrying Gold in Supercritical CO2
Jeremy D Glennon,Stephen J Harris,Andrew Walker,Conor C McSweeney,Mark O’Connell
Gold Bulletin , 1999, DOI: 10.1007/BF03214791
Abstract: A series of fluorinated calixarene derivatives, with lower rim sulfur-donor atoms, were synthesized and studied for the sequestration of gold using supercritical fluid extraction. Following temperature and pressure optimization and using extracts collected in methyliso-butyl ketone, analysis by flame atomic absorption spectrometry reveals that Au(III) can be efficiently complexed and extracted by a novel calix[4]arene thiourea reagent in supercritical CO2.
Constraints on Intervening Stellar Populations Toward the Large Magellanic Cloud
Dennis Zaritsky,Stephen A. Shectman,Ian Thompson,Jason Harris,D. N. C. Lin
Physics , 1999, DOI: 10.1086/300841
Abstract: The suggestion by Zaritsky & Lin that a vertical extension of the red clump feature in color-magnitude diagrams of the Large Magellanic Cloud (LMC) is consistent with a significant population of foreground stars to the LMC that could account for the observed microlensing optical depth has been challenged by various investigators. We respond by (1) examining each of the challenges presented and (2) presenting new photometric and spectroscopic data. We conclude that although the CMD data do not mandate the existence of a foreground population, they are entirely consistent with a foreground population associated with the LMC that contributes significantly (~ 50%) to the observed microlensing optical depth. From our new data, we conclude that <~ 40% of the VRC stars are young, massive red clump stars because (1) synthetic color-magnitude diagrams created using the star formation history derived indepdently from HST data suggest that < 50% of the VRC stars are young, massive red clump stars, (2) the angular distribution of the VRC stars is more uniform than that of the young (age < 1 Gyr) main sequence stars, and (3) the velocity dispersion of the VRC stars in the region of the LMC examined by ZL is inconsistent with the expectation for a young disk population. Each of these arguments is predicated on assumptions and the conclusions are uncertain. Therefore, an exact determination of the contribution to the microlensing optical depth by the various hypothesized foreground populations, and the subsequent conclusions regarding the existence of halo MACHOs, requires a detailed knowledge of many complex astrophysical issues, such as the IMF, star formation history, and post-main sequence stellar evolution. (abridged)
The Assessment of Animal Welfare in British Zoos by Government-Appointed Inspectors
Chris Draper,Stephen Harris
Animals , 2012, DOI: 10.3390/ani2040507
Abstract: We analysed the reports of government-appointed inspectors from 192 zoos between 2005–2008 to provide the first review of how animal welfare was assessed in British zoos since the enactment of the Zoo Licensing Act 1981. We examined the effects of whether or not a veterinarian was included in the inspection team, type of inspection, licence status of the zoo and membership of a zoo association on the inspectors’ assessments of animal welfare standards in five areas that approximate to the Five Freedoms. At least 11% of full licence inspections did not comply with the legal requirement for two inspectors. The inspectors’ reports were unclear as to how animal welfare was assessed, whether all animals or only a sub-sample had been inspected, and were based predominantly on welfare inputs rather than outcomes. Of 9,024 animal welfare assessments across the 192 zoos, 7,511 (83%) were graded as meeting the standards, 782 (9%) as substandard and the rest were not graded. Of the 192 zoos, 47 (24%) were assessed as meeting all the animal welfare standards. Membership of a zoo association was not associated with a higher overall assessment of animal welfare standards, and specialist collections such as Farm Parks and Other Bird collections performed least well. We recommend a number of changes to the inspection process that should lead to greater clarity in the assessment of animal welfare in British zoos.
Cytoplasmic location of factor-inhibiting hypoxia-inducible factor is associated with an enhanced hypoxic response and a shorter survival in invasive breast cancer
Ern Tan, Leticia Campo, Cheng Han, Helen Turley, Francesco Pezzella, Kevin C Gatter, Adrian L Harris, Stephen B Fox
Breast Cancer Research , 2007, DOI: 10.1186/bcr1838
Abstract: Microarrayed tissue cores from 295 invasive carcinomas were stained for FIH-1, for HIF-1α and for carbonic anhydrase 9. FIH-1 expression was correlated with standard clinicopathological parameters and with the expression of the surrogate hypoxic markers HIF-1α and carbonic anhydrase 9.FIH-1 was positive in 239/295 (81%) tumours, 42/295 (14%) exclusively in the nucleus and 54/295 (18%) exclusively in the cytoplasm. Exclusive nuclear FIH-1 expression was significantly inversely associated with tumour grade (P = 0.02) and risk of recurrence (P = 0.04), whereas exclusive cytoplasmic FIH-1 was significantly positively associated with tumour grade (P = 0.004) and carbonic anhydrase 9 expression (P = 0.02). Patients with tumours that excluded FIH-1 from the nucleus had a significantly shorter survival compared with those with exclusive nuclear expression (P = 0.02). Cytoplasmic FIH-1 expression was also an independent poor prognostic factor for disease-free survival.FIH-1 is widely expressed in invasive breast carcinoma. As with other HIF regulators, its association between cellular compartmentalization and the hypoxic response and survival suggests that tumour regulation of FIH-1 is an additional important mechanism for HIF pathway activation.Regions of hypoxia are common in breast carcinoma [1,2] as the rate of nutrient and oxygen delivery is often insufficient to meet the high metabolic demands of neoplastic cells. The neoplastic cells can adapt to this hostile microenvironment using the activation of hypoxia-induced genes for angiogenesis, glycolysis and other processes advantageous to cell proliferation and survival. The activation of these hypoxia-induced genes centres on the levels of hypoxia-inducible factor (HIF) 1 within the tumour cell [3]. HIF-1 is a heterodimer, consisting of a HIF-1α subunit and a HIF-1β subunit. While HIF-1β is constitutively expressed, HIF-1α levels are tightly regulated with rapid upregulation and degradation [4].It is therefore not surpri
SNPTrackTM : an integrated bioinformatics system for genetic association studies
Joshua Xu, Reagan Kelly, Guangxu Zhou, Steven A Turner, Don Ding, Stephen C Harris, Huixiao Hong, Hong Fang, Weida Tong
Human Genomics , 2012, DOI: 10.1186/1479-7364-6-5
Numerical Experiments Using MATLAB: Superconvergence of Nonconforming Finite Element Approximation for Second-Order Elliptic Problems  [PDF]
Anna Harris, Stephen Harris, Danielle Rauls
Applied Mathematics (AM) , 2016, DOI: 10.4236/am.2016.717173
Abstract: The superconvergence in the finite element method is a phenomenon in which the fi-nite element approximation converges to the exact solution at a rate higher than the optimal order error estimate. Wang proposed and analyzed superconvergence of the conforming finite element method by L2-projections. However, since the conforming finite element method (CFEM) requires a strong continuity, it is not easy to construct such finite elements for the complex partial differential equations. Thus, the nonconforming finite element method (NCFEM) is more appealing computationally due to better stability and flexibility properties compared to CFEM. The objective of this paper is to establish a general superconvergence result for the nonconforming finite element approximations for second-order elliptic problems by L2-projection methods by applying the idea presented in Wang. MATLAB codes are published at https://github.com/annaleeharris/Superconvergence-NCFEM for anyone to use and to study. The results of numerical experiments show great promise for the robustness, reliability, flexibility and accuracy of superconvergence in NCFEM by L2- projections.
Genome Wide Analysis Indicates Genes for Basement Membrane and Cartilage Matrix Proteins as Candidates for Hip Dysplasia in Labrador Retrievers
Ineke C. M. Lavrijsen, Peter A. J. Leegwater, Alan J. Martin, Stephen J. Harris, Marianna A. Tryfonidou, Henri C. M. Heuven, Herman A. W. Hazewinkel
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0087735
Abstract: Hip dysplasia, an abnormal laxity of the hip joint, is seen in humans as well as dogs and is one of the most common skeletal disorders in dogs. Canine hip dysplasia is considered multifactorial and polygenic, and a variety of chromosomal regions have been associated with the disorder. We performed a genome-wide association study in Dutch Labrador Retrievers, comparing data of nearly 18,000 single nucleotide polymorphisms (SNPs) in 48 cases and 30 controls using two different statistical methods. An individual SNP analysis based on comparison of allele frequencies with a χ2 statistic was used, as well as a simultaneous SNP analysis based on Bayesian variable selection. Significant association with canine hip dysplasia was observed on chromosome 8, as well as suggestive association on chromosomes 1, 5, 15, 20, 25 and 32. Next-generation DNA sequencing of the exons of genes of seven regions identified multiple associated alleles on chromosome 1, 5, 8, 20, 25 and 32 (p<0.001). Candidate genes located in the associated regions on chromosomes 1, 8 and 25 included LAMA2, LRR1 and COL6A3, respectively. The associated region on CFA20 contained candidate genes GDF15, COMP and CILP2. In conclusion, our study identified candidate genes that might affect susceptibility to canine hip dysplasia. These genes are involved in hypertrophic differentiation of chondrocytes and extracellular matrix integrity of basement membrane and cartilage. The functions of the genes are in agreement with the notion that disruptions in endochondral bone formation in combination with soft tissue defects are involved in the etiology of hip dysplasia.
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