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Search Results: 1 - 10 of 302554 matches for " Edward J. Moler "
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Comparison of Accuracy of Diabetes Risk Score and Components of the Metabolic Syndrome in Assessing Risk of Incident Type 2 Diabetes in Inter99 Cohort
Tracy B. Shafizadeh, Edward J. Moler, Janice A. Kolberg, Uyen Thao Nguyen, Torben Hansen, Torben Jorgensen, Oluf Pedersen, Knut Borch-Johnsen
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0022863
Abstract: Background Given the increasing worldwide incidence of diabetes, methods to assess diabetes risk which would identify those at highest risk are needed. We compared two risk-stratification approaches for incident type 2 diabetes mellitus (T2DM); factors of metabolic syndrome (MetS) and a previously developed diabetes risk score, PreDx? Diabetes Risk Score (DRS). DRS assesses 5 yr risk of incident T2DM based on the measurement of 7 biomarkers in fasting blood. Methodology/Principal Findings DRS was evaluated in baseline serum samples from 4,128 non-diabetic subjects in the Inter99 cohort (Danes aged 30–60) for whom diabetes outcomes at 5 years were known. Subjects were classified as having MetS based on the presence of at least 3 MetS risk factors in baseline clinical data. The sensitivity and false positive rate for predicting diabetes using MetS was compared to DRS. When the sensitivity was fixed to match MetS, DRS had a significantly lower false positive rate. Similarly, when the false positive rate was fixed to match MetS, DRS had a significantly higher specificity. In further analyses, subjects were classified by presence of 0–2, 3 or 4–5 risk factors with matching proportions of subjects distributed among three DRS groups. Comparison between the two risk stratification schemes, MetS risk factors and DRS, were evaluated using Net Reclassification Improvement (NRI). Comparing risk stratification by DRS to MetS factors in the total population, the NRI was 0.146 (p = 0.008) demonstrating DRS provides significantly improved stratification. Additionally, the relative risk of T2DM differed by 15 fold between the low and high DRS risk groups, but only 8-fold between the low and high risk MetS groups. Conclusions/Significance DRS provides a more accurate assessment of risk for diabetes than MetS. This improved performance may allow clinicians to focus preventive strategies on those most in need of urgent intervention.
Spontaneous Flux and Magnetic Interference Patterns in 0-pi Josephson Junctions
J. R. Kirtley,K. A. Moler,D. J. Scalapino
Physics , 1997, DOI: 10.1103/PhysRevB.56.886
Abstract: The spontaneous flux generation and magnetic field modulation of the critical current in a 0-pi Josephson junction are calculated for different ratios of the junction length to the Josephson penetration depth, and different ratios of the 0-junction length to the pi-junction length. These calculations apply to a Pb-YBCO c-axis oriented junction with one YBCO twin boundary, as well as other experimental systems. Measurements of such a junction can provide information on the nature of the c-axis Josephson coupling and the symmetry of the order parameter in YBCO. We find spontaneous flux even for very short symmetric 0-pi junctions, but asymmetric junctions have qualitatively different behavior.
Meissner response of a bulk superconductor with an embedded sheet of reduced penetration depth
J. R. Kirtley,B. Kalisky,L. Luan,K. A. Moler
Physics , 2009, DOI: 10.1103/PhysRevB.81.184514
Abstract: We calculate the change in susceptibility resulting from a thin sheet with reduced penetration depth embedded perpendicular to the surface of an isotropic superconductor, in a geometry applicable to scanning Superconducting QUantum Interference Device (SQUID) microscopy, by numerically solving Maxwell's and London's equations using the finite element method. The predicted stripes in susceptibility agree well in shape with the observations of Kalisky et al. of enhanced susceptibility above twin planes in the underdoped pnictide superconductor Ba(Fe1-xCox)2As2 (Ba-122). By comparing the predicted stripe amplitudes with experiment and using the London relation between penetration depth and superfluid density, we estimate the enhanced Cooper pair density on the twin planes, and the barrier force for a vortex to cross a twin plane. Fits to the observed temperature dependence of the stripe amplitude suggest that the twin planes have a higher critical temperature than the bulk, although stripes are not observed above the bulk critical temperature.
c-axis penetration depth of Hg-1201 single crystals
J. R. Kirtley,K. A. Moler,G. Villard,A. Maignan
Physics , 1998, DOI: 10.1103/PhysRevLett.81.2140
Abstract: We have magnetically imaged interlayer Josephson vortices emerging from an ac face of single crystals of the single layer cuprate high-Tc superconductor (Hg,Cu)Ba2CuO4+d. These images provide a direct measurement of the c-axis penetration depth of about 10 microns. This length is a factor of 10 longer than predicted by the interlayer tunneling model for the mechanism of superconductivity in layered compounds, indicating that the condensation energy available through this mechanism is 100 times smaller than is required for superconductivity.
Controlled Manipulation of Individual Vortices in a Superconductor
E. W. J. Straver,J. E. Hoffman,O. M. Auslaender,D. Rugar,Kathryn A. Moler
Physics , 2008, DOI: 10.1063/1.3000963
Abstract: We report controlled local manipulation of single vortices by low temperature magnetic force microscope (MFM) in a thin film of superconducting Nb. We are able to position the vortices in arbitrary configurations and to measure the distribution of local depinning forces. This technique opens up new possibilities for the characterization and use of vortices in superconductors.
Magnetic field of an in-plane vortex outside a layered superconductor
J. R. Kirtley,V. G. Kogan,J. R. Clem,K. A. Moler
Physics , 1998, DOI: 10.1103/PhysRevB.59.4343
Abstract: We present the solution to London's equations for the magnetic fields of a vortex oriented parallel to the plane, and normal to a crystal face, of a layered superconductor. These expressions account for flux spreading at the superconducting surface, which can change the apparent size of the vortex along the planes by as much as 30%. We compare these expressions with experimental results.
Specific Heat of YBa$_2$Cu$_3$O$_{7 - {\rm δ}}$ Single Crystals: Implications for the Vortex Structure
Kathryn A. Moler,David J. Baar,Ruixing Liang,Walter N. Hardy,Aharon Kapitulnik
Physics , 1995, DOI: 10.1016/0022-3697(95)00163-8
Abstract: The anisotropy of the magnetic field dependence of the specific heat of YBa$_2$Cu$_3$O$_{7 - {\rm \delta}}$ can be used to identify different low-energy excitations, which include phonons, spin-$ \frac{1}{2}$ particles, and electronic contributions. With a magnetic field H applied perpendicular to the copper oxide planes, we find that the specific heat includes a linear-T term proportional to $\sqrt{H}$. The nonlinear field dependence of the density of states at the Fermi level suggests that there are quasiparticle excitations throughout the entire vortex, not just in the vortex core. The $\sqrt{H} T$ term agrees quantitatively with G. Volovik's prediction for a superconductor with lines of nodes in the gap. A similar, but much smaller, effect is predicted for fields parallel to the planes, and sensitive measurements of the in-plane anisotropic magnetic field dependence of the specific heat could be used to map out the nodes.
Two-dimensional vortex behavior in highly underdoped YBa_2Cu_3O_{6+x} observed by scanning Hall probe microscopy
J. W. Guikema,Hendrik Bluhm,D. A. Bonn,Ruixing Liang,W. N. Hardy,K. A. Moler
Physics , 2008, DOI: 10.1103/PhysRevB.77.104515
Abstract: We report scanning Hall probe microscopy of highly underdoped superconducting YBa_2Cu_3O_{6+x} with T_c ranging from 5 to 15 K which showed distinct flux bundles with less than one superconducting flux quantum (Phi_0) through the sample surface. The sub-Phi_0 features occurred more frequently for lower T_c, were more mobile than conventional vortices, and occurred more readily when the sample was cooled with an in-plane field component. We show that these features are consistent with kinked stacks of pancake vortices.
Metal-coated carbon nanotube tips for Magnetic Force Microscopy
Zhifeng Deng,Erhan Yenilmez,Josh Leu,J. E. Hoffman,Eric Straver,Hongjie Dai,Kathryn A. Moler
Physics , 2004, DOI: 10.1063/1.1842374
Abstract: We fabricated cantilevers for magnetic force microscopy with carbon nanotube tips coated with magnetic material. Images of a custom hard drive demonstrated 20 nm lateral resolution, with prospects for further improvements.
Growth and Toxin Production by Microcystis Aeruginosa PCC 7806 (Kutzing) Lemmerman at Elevated Salt Concentrations  [PDF]
Ken Black, Mete Yilmaz, Edward J. Phlips
Journal of Environmental Protection (JEP) , 2011, DOI: 10.4236/jep.2011.26077
Abstract: One of the most common and widespread bloom-forming cyanobacteria associated with toxin production is Microcystis aeruginosa (Kutzing) Lemmerman. While normally associated with fresh water environments, this toxigenic species has been observed at bloom concentrations in a number of major estuaries worldwide. This study examined the effect of salinity on growth and toxin production by M. aeruginosa strain PCC 7806 under controlled laboratory conditions. Salt concentrations above 12.6 ppt resulted in total cessation of growth. Toxin production was similarly affected, with cultures grown in salt concentrations of 4.6 ppt and above yielding less toxin than the control after 20 days of culture. Toxin concentrations after 20 days of culture were 40% of the control at 4.6 ppt. The relative proportion of extracellular to intracellular toxin increased over time in cultures with salt concentrations greater than 4.6 ppt. Extracellular toxins persisted in the media long after the cessation of growth. The results suggest that the influence of M. aeruginosa and/or its toxins can extend well out into estuarine environments under the influence of significant freshwater inputs.
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