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Search Results: 1 - 10 of 332177 matches for " R. K. Keeler "
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Propagation of Errors for Matrix Inversion
M. Lefebvre,R. K. Keeler,R. Sobie,J. White
Physics , 1999, DOI: 10.1016/S0168-9002(00)00323-5
Abstract: A formula is given for the propagation of errors during matrix inversion. An explicit calculation for a 2 by 2 matrix using both the formula and a Monte Carlo calculation are compared. A prescription is given to determine when a matrix with uncertain elements is sufficiently nonsingular for the calculation of the covariances of the inverted matrix elements to be reliable.
Persistent Spin Dynamics in the $S=1/2$ V$_{15}$ Molecular Nano-Magnet
Z. Salman,R. F. Kiefl,K. H. Chow,W. A. MacFarlane,T. Keeler,T. Parolin,S. Tabbara,D. Wang
Physics , 2008, DOI: 10.1103/PhysRevB.77.214415
Abstract: We present muon spin lattice relaxation measurements in the V15 spin 1/2 molecular nano-magnet. We find that the relaxation rate in low magnetic fields (<5 kG) is temperature independent below ~10 K, implying that the molecular spin is dynamically fluctuating down to 12 mK. These measurements show that the fluctuation time increases as the temperature is decreased and saturates at a value of ~6 nsec at low temperatures. The fluctuations are attributed to V15 molecular spin dynamics perpendicular to the applied magnetic field direction, induced by coupling between the molecular spin and nuclear spin bath in the system.
Muon spin relaxation study of the magnetism in unilluminated Prussian Blue analogue photomagnets
Z. Salman,T. J. Parolin,K. H. Chow,T. A. Keeler,R. I. Miller,D. Wang,W. A. MacFarlane
Physics , 2005, DOI: 10.1016/j.physb.2005.11.033
Abstract: We present longitudinal field muon spin relaxation ($\mu$SR) measurements in the unilluminated state of the photo-sensitive molecular magnetic Co-Fe Prussian blue analogues M$_{1-2x}$Co$_{1+x}$[Fe(CN)$_6$]$\cdot z$ H$_2$O, where M=K and Rb with $x=0.4$ and $\simeq 0.17$, respectively. These results are compared to those obtained in the $x=0.5$ stoichiometric limit, Co$_{1.5}$[Fe(CN)$_6$]$\cdot 6$ H$_2$O, which is not photo-sensitive. We find evidence for correlation between the range of magnetic ordering and the value of $x$ in the unilluminated state which can be explained using a site percolation model.
Noncommutative ampleness from finite endomorphisms
D. S. Keeler,K. Retert
Mathematics , 2015, DOI: 10.1016/j.jalgebra.2015.01.025
Abstract: Let $X$ be a projective integral scheme with endomorphism $\sigma$, where $\sigma$ is finite, but not an automorphism. We examine noncommutative ampleness of bimodules defined by $\sigma$. In contrast to the automorphism case, one-sided ampleness is possible. We also find that rings and bimodule algebras associated with $\sigma$ are not noetherian.
Development of Tracking Detectors with industrially produced GEM Foils
F. Simon,B. Azmoun,U. Becker,L. Burns,D. Crary,K. Kearney,G. Keeler,R. Majka,K. Paton,G. Saini,N. Smirnov,B. Surrow,C. Woody
Physics , 2007, DOI: 10.1109/TNS.2007.909912
Abstract: The planned tracking upgrade of the STAR experiment at RHIC includes a large-area GEM tracker used to determine the charge sign of electrons and positrons produced from W+(-) decays. For such a large-scale project commercial availability of GEM foils is necessary. We report first results obtained with a triple GEM detector using GEM foils produced by Tech-Etch Inc. of Plymouth, MA, USA. Measurements of gain uniformity, long-term stability as well as measurements of the energy resolution for X-Rays are compared to results obtained with an identical detector using GEM foils produced at CERN. A quality assurance procedure based on optical tests using an automated high-resolution scanner has been established, allowing a study of the correlation of the observed behavior of the detector and the geometrical properties of the GEM foils. Detectors based on Tech-Etch and CERN produced foils both show good uniformity of the gain over the active area and stable gain after an initial charge-up period, making them well suited for precision tracking applications.
Liberation Health and the Role of the Public Health Leader  [PDF]
Courtney Keeler
Open Journal of Leadership (OJL) , 2013, DOI: 10.4236/ojl.2013.24012

The following short report lays the groundwork for rethinking the practice and implications of public health leadership in the context of liberation health. Liberation health reduces to a universal idea:health is freedom. In short, everyone holds a subjective notion of health and, within certain bounds, has the right to promote and maintain that health. This report briefly describes liberation health, discusses the implications of liberation health for public health leadership, and outlines two needed transformations in moving towards a liberation health model of leadership. The report details areas for future research on this topic among public health leaders and within public health curricula.

Clinical Leadership and Asymmetric Information: The Impact of Physician Advice on Smoking Cessation  [PDF]
Courtney Keeler
Open Journal of Leadership (OJL) , 2014, DOI: 10.4236/ojl.2014.32002

A knowledge gradient exists between experts in a given field and consumers of that knowledge. When the need arises, not knowing the best path, an average individual typically relies on the advice of an expert. Given the steep knowledge gradient between patient and provider, clinicians play an essential role in the clinical setting, acting as both a health leader and a health facilitator; however, this asymmetric information implies that clinical providers face an acute pressure not only to advise but to advise correctly. This paper explores the importance of physician advice within the context of smoking cessation, addressing two specific research questions: (1) among current smokers, do patients have a higher probability of any quit attempts in the last twelve months if a physician advised them to quit over the same period? and, (2) among current smokers who were advised to quit, do patients have a higher probability of any quit attempts in the past twelve months based, at least in part, on the specific quitting strategy suggested by the physician? The results suggest that physicians play a crucial role in promoting smoking cessation efforts. The findings further highlight a significant association between the advised cessation strategy and any quit attempts, although the direction of this relationship varies by the cessation strategy suggested.

Matter Under Extreme Conditions: The Early Years
R. Norris Keeler,Carl H. Gibson
Physics , 2010,
Abstract: Extreme conditions in natural flows are examined, starting with a turbulent big bang. A hydro-gravitational-dynamics cosmology model is adopted. Planck-Kerr turbulence instability causes Planck-particle turbulent combustion. Inertial-vortex forces induce a non-turbulent kinetic energy cascade to Planck-Kolmogorov scales where vorticity is produced, overcoming 10^113 Pa Planck-Fortov pressures. The spinning, expanding fireball has a slight deficit of Planck antiparticles. Space and mass-energy powered by gluon viscous stresses expand exponentially at speeds >10^25 c. Turbulent temperature and spin fluctuations fossilize at scales larger than ct, where c is light speed and t is time. Because "dark-energy" antigravity forces vanish when inflation ceases, and because turbulence produces entropy, the universe is closed and will collapse and rebound. Density and spin fossils of big bang turbulent mixing trigger structure formation in the plasma epoch. Fragmenting protosuperclustervoids and protoclustervoids produce weak turbulence until the plasma-gas transition give chains of protogalaxies with the morphology of turbulence. Chain galaxy clusters observed at large redshifts ~8.6 support this interpretation. Protogalaxies fragment into clumps, each with a trillion Earth-mass H-He gas planets. These make stars, supernovae, the first chemicals, the first oceans and the first life soon after the cosmological event.
Hyperfine Fields in an Ag/Fe Multilayer Film Investigated with 8Li beta-Detected Nuclear Magnetic Resonance
T. A. Keeler,Z. Salman,K. H. Chow,B. Heinrich,M. D. Hossian,B. Kardasz,R. F. Kiefl,S. R. Kreitzman,C. D. P. Levy,W. A. MacFarlane,O. Mosendz,T. J. Parolin,M. R. Pearson,D. Wang
Physics , 2008, DOI: 10.1103/PhysRevB.77.144429
Abstract: Low energy $\beta$-detected nuclear magnetic resonance ($\beta$-NMR) was used to investigate the spatial dependence of the hyperfine magnetic fields induced by Fe in the nonmagnetic Ag of an Au(40 \AA)/Ag(200 \AA)/Fe(140 \AA) (001) magnetic multilayer (MML) grown on GaAs. The resonance lineshape in the Ag layer shows dramatic broadening compared to intrinsic Ag. This broadening is attributed to large induced magnetic fields in this layer by the magnetic Fe layer. We find that the induced hyperfine field in the Ag follows a power law decay away from the Ag/Fe interface with power $-1.93(8)$, and a field extrapolated to $0.23(5)$ T at the interface.
Giant Vortices Below the Surface of NbSe$_2$ Detected Using Low Energy $β$-NMR
Z. Salman,D. Wang,K. H. Chow,M. D. Hossain,S. R. Kreitzman,T. A. Keeler,C. D. P. Levy,W. A. MacFarlane,R. I. Miller,G. D. Morris,T. J. Parolin,H. Saadaoui,M. Smadella,R. F. Kiefl
Physics , 2007, DOI: 10.1103/PhysRevLett.98.167001
Abstract: A low energy radioactive beam of polarized $^8$Li has been used to observe the vortex lattice near the surface of superconducting NbSe$_2$. The inhomogeneous magnetic field distribution associated with the vortex lattice was measured using depth-resolved $\beta$-detected NMR. Below $T_c$ one observes the characteristic lineshape for a triangular vortex lattice which depends on the magnetic penetration depth and vortex core radius. The size of the vortex core varies strongly with magnetic field. In particular in a low field of 10.8 mT the core radius is much larger than the coherence length. The possible origin of these giant vortices is discussed.
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