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Search Results: 1 - 10 of 339172 matches for " B. R. Johnson "
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Effect of Surgical Complications on Quality of Life after Thoracoscopic Lobectomy for Lung Cancer  [PDF]
Sayf Gazala, Jeffrey A. Johnson, James D. Kutsogiannias, Eric L. R. Bédard
World Journal of Cardiovascular Surgery (WJCS) , 2014, DOI: 10.4236/wjcs.2014.43005
Abstract: Background: Surgical resection is the main treatment for early stage lung cancer; the benefits of surgery, however, need to be weighed against possible complications and patients’ quality of life. Methods: We performed a cohort study following patients after video assisted thoracoscopic lobectomy at our tertiary care center. Before surgery, health related quality of life was assessed using the SF-36, the QLQ30, QLQ13 and EQ5D questionnaires. Post-operatively health related quality of life was assessed at regular intervals (2, 4, 8 and 12 weeks). A research team assessed post-operative complications on a daily basis during the patients’ hospital stay. Based on the Clavien classification system, the cohort was classified as experiencing high-grade (i.e., grade III or IV) complications or not. Changes in quality of life scores over the follow-up period were compared using linear regression with generalized estimating equations. Results: Between March and September 2011, 44 eligible patients were recruited into the study. The mean age was 65 (SD 8.7) years; 55% were male. The majority (n = 31; 71%) had no or low-grade complications. Patients experiencing high-grade complications reported significantly worse outcomes in the following domains of the SF-36: Global Health, Vitality, and Physical Functioning (p < 0.05 for all). On the QLQ 30 and QLQ 13, patients with high-grade complications had worse outcomes in the dyspnea, emotional function and cognitive function scales, as well as worse shoulder and chest pain, and financial difficulties (p < 0.05 for all). Conclusions: The severity of post-operative complications after video assisted thoracoscopic lobectomy negatively impacts patient centered outcomes post-operatively.

Stochastic Theory of Relativistic Particles Moving in a Quantum Field: I. Influence Functional and Langevin Equation
Philip R. Johnson,B. L. Hu
Physics , 2000,
Abstract: We treat a relativistically moving particle interacting with a quantum field from an open system viewpoint of quantum field theory by the method of influence functionals or closed-time-path coarse-grained effective actions. The particle trajectory is not prescribed but is determined by the backreaction of the quantum field in a self-consistent way. Coarse-graining the quantum field imparts stochastic behavior in the particle trajectory. The formalism is set up here as a precursor to a first principles derivation of the Abraham-Lorentz-Dirac (ALD) equation from quantum field theory as the correct equation of motion valid in the semiclassical limit. This approach also discerns classical radiation reaction from quantum dissipation in the motion of a charged particle; only the latter is related to vacuum fluctuations in the quantum field by a fluctuation-dissipation relation, which we show to exist for nonequilibrim processes under this type of nonlinear coupling. This formalism leads naturally to a set of Langevin equations associated with a generalized ALD equation. These multiparticle stochastic differential equations feature local dissipation (for massless quantum fields), nonlocal particle-particle interactions, multiplicative noise, and nonlocal particle-particle correlations, interrelated in ways characteristic of nonlinear theories, through generalized fluctuation-dissipation relations.
Stochastic Theory of Relativistic Particles Moving in a Quantum Field: II. Scalar Abraham-Lorentz-Dirac-Langevin Equation, Radiation Reaction and Vacuum Fluctuations
Philip R. Johnson,B. L. Hu
Physics , 2000, DOI: 10.1103/PhysRevD.65.065015
Abstract: We apply the open systems concept and the influence functional formalism introduced in Paper I to establish a stochastic theory of relativistic moving spinless particles in a quantum scalar field. The stochastic regime resting between the quantum and semi-classical captures the statistical mechanical attributes of the full theory. Applying the particle-centric world-line quantization formulation to the quantum field theory of scalar QED we derive a time-dependent (scalar) Abraham-Lorentz-Dirac (ALD) equation and show that it is the correct semiclassical limit for nonlinear particle-field systems without the need of making the dipole or non-relativistic approximations. Progressing to the stochastic regime, we derive multiparticle ALD-Langevin equations for nonlinearly coupled particle-field systems. With these equations we show how to address time-dependent dissipation/noise/renormalization in the semiclassical and stochastic limits of QED. We clarify the the relation of radiation reaction, quantum dissipation and vacuum fluctuations and the role that initial conditions may play in producing non-Lorentz invariant noise. We emphasize the fundamental role of decoherence in reaching the semiclassical limit, which also suggests the correct way to think about the issues of runaway solutions and preacceleration from the presence of third derivative terms in the ALD equation. We show that the semiclassical self-consistent solutions obtained in this way are ``paradox'' and pathology free both technically and conceptually. This self-consistent treatment serves as a new platform for investigations into problems related to relativistic moving charges.
Worldline Influence Functional: Abraham-Lorentz-Dirac-Langevin Equation from QED
Philip R. Johnson,B. L. Hu
Physics , 2000,
Abstract: We present a stochastic theory of charges moving in an electromagnetic field using nonequilibrium quantum field theory. We give a first principles' derivation of the Abraham-Lorentz-Dirac-Langevin equation which depicts the quantum expectation value for a particle's trajectory and its stochastic fluctuations by combining the worldline path integral quantization with the Feynman-Vernon influence functional or closed-time-path effective action methods. At lowest order, the equations of motion are approximated by a stochastic Lorentz-Dirac equation.
Beyond Unruh Effect: Nonequilibrium Quantum Dynamics of Moving Charges
B. L. Hu,Philip R. Johnson
Physics , 2000,
Abstract: We discuss some common misconceptions in Unruh effect and Unruh radiation for the cases of linear and circular uniform acceleration of a charged particle or detector moving in a quantum field. We point to the need to go beyond Unruh effect and develop a new theoretical framework for treating the stochastic dynamics of particles interacting with quantum fields under more general nonequilibrium conditions. This framework has been established in recent years using the influence functional formalism and applied to relativistically moving charged particles. Only with nonequilibrium concepts and methodology applied to particle-field interaction can one grasp the full complexity of the problems of beam physics under more realistic conditions, from electrons and heavy ions to coherent atoms.
Uniformly Accelerated Charge in a Quantum Field: From Radiation Reaction to Unruh Effect
Philip R. Johnson,B. L. Hu
Physics , 2005, DOI: 10.1007/s10701-005-6404-1
Abstract: We present a stochastic theory for the nonequilibrium dynamics of charges moving in a quantum scalar field based on the worldline influence functional and the close-time-path (CTP or in-in) coarse-grained effective action method. We summarize (1) the steps leading to a derivation of a modified Abraham-Lorentz-Dirac equation whose solutions describe a causal semiclassical theory free of runaway solutions and without pre-acceleration patholigies, and (2) the transformation to a stochastic effective action which generates Abraham-Lorentz-Dirac-Langevin equations depicting the fluctuations of a particle's worldline around its semiclassical trajectory. We point out the misconceptions in trying to directly relate radiation reaction to vacuum fluctuations, and discuss how, in the framework that we have developed, an array of phenomena, from classical radiation and radiation reaction to the Unruh effect, are interrelated to each other as manifestations at the classical, stochastic and quantum levels. Using this method we give a derivation of the Unruh effect for the spacetime worldline coordinates of an accelerating charge. Our stochastic particle-field model, which was inspired by earlier work in cosmological backreaction, can be used as an analog to the black hole backreaction problem describing the stochastic dynamics of a black hole event horizon.
Regime of a wideband phase-amplitude modulation in a CW magnetron transmitter with a phase control
G. Kazakevich,R. Johnson,B. Chase,R. Pasquinelli,V. Yakovlev
Physics , 2014,
Abstract: A model of the CW high-power transmitter, utilizing frequency-locked magnetrons with a phase control studied initially as a prototype of controllable in phase and power an RF source for intensity-frontier superconducting linacs, was considered for telecommunication as a model of magnetron source, acceptable for a wideband phase-amplitude modulation at a precisely stable carrier frequency. The R&D conducted with CW, 2.45 GHz, 1 kW, microwave oven magnetrons demonstrated that the frequency locking of the magnetrons by the phase-modulated signal provides wideband phase and amplitude modulation at the modulating frequency at least up to 3 MHz and large magnitude, keeping the carrier frequency precisely stable, without broadening of the spectral line width. Performed experiments with power combining verified applicability of the transmitter based on the frequency-locked magnetrons for wideband phase and amplitude modulation, which may be used for telecommunication. Results of the experiments are described in the presented work.
Moving Charges, Detectors, and Mirrors in a Quantum Field with Backreaction
Chad R. Galley,B. L. Hu,Philip R. Johnson
Physics , 2004,
Abstract: This is a progress report on our current work on moving charges, detectors, and moving mirrors in a quantum field treated in a fully relativistic way via the Feynman-Vernon influence functional method, which preserves maximal quantum coherence of the system with self-consistent back-reaction from the field.
A Statistical Framework for the Adaptive Management of Epidemiological Interventions
Daniel Merl, Leah R. Johnson, Robert B. Gramacy, Marc Mangel
PLOS ONE , 2009, DOI: 10.1371/journal.pone.0005807
Abstract: Background Epidemiological interventions aim to control the spread of infectious disease through various mechanisms, each carrying a different associated cost. Methodology We describe a flexible statistical framework for generating optimal epidemiological interventions that are designed to minimize the total expected cost of an emerging epidemic while simultaneously propagating uncertainty regarding the underlying disease model parameters through to the decision process. The strategies produced through this framework are adaptive: vaccination schedules are iteratively adjusted to reflect the anticipated trajectory of the epidemic given the current population state and updated parameter estimates. Conclusions Using simulation studies based on a classic influenza outbreak, we demonstrate the advantages of adaptive interventions over non-adaptive ones, in terms of cost and resource efficiency, and robustness to model misspecification.
Cellular Vacuoles Induced by Mycoplasma pneumoniae CARDS Toxin Originate from Rab9-Associated Compartments
Coreen Johnson, T. R. Kannan, Joel B. Baseman
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0022877
Abstract: Recently, we identified an ADP-ribosylating and vacuolating cytotoxin in Mycoplasma pneumoniae designated Community Acquired Respiratory Distress Syndrome (CARDS) toxin. In this study we show that vacuoles induced by recombinant CARDS (rCARDS) toxin are acidic and derive from the endocytic pathway as determined by the uptake of neutral red and the fluid-phase marker, Lucifer yellow, respectively. Also, we demonstrate that the formation of rCARDS toxin-associated cytoplasmic vacuoles is inhibited by the vacuolar ATPase inhibitor, bafilomycin A1, and the ionophore, monensin. To examine the ontogeny of these vacuoles, we analyzed the distribution of endosomal and lysosomal membrane markers during vacuole formation and observed the enrichment of the late endosomal GTPase, Rab9, around rCARDS toxin-induced vacuoles. Immunogold-labeled Rab9 and overexpression of green fluorescent-tagged Rab9 further confirmed vacuolar association. The late endosomal- and lysosomal-associated membrane proteins, LAMP1 and LAMP2, also localized to the vacuolar membranes, while the late endosomal protein, Rab7, and early endosomal markers, Rab5 and EEA1, were excluded. HeLa cells expressing dominant-negative (DN) Rab9 exhibited markedly reduced vacuole formation in the presence of rCARDS toxin, in contrast to cells expressing DN-Rab7, highlighting the importance of Rab9 function in rCARDS toxin-induced vacuolation. Our findings reveal the unique Rab9-association with rCARDS toxin-induced vacuoles and its possible relationship to the characteristic histopathology that accompanies M. pneumoniae infection.
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