The Experts below are selected from a list of 34635 Experts worldwide ranked by ideXlab platform
Joseba Zubia - One of the best experts on this subject based on the ideXlab platform.
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determination of the width of the output angular power distribution in step index multimode optical fibers
Journal of Optics, 2010Co-Authors: Svetislav Savovic, Joseba Zubia, Alexandar Djordjevich, Peter W Tse, Javier Mateo, Angeles M LosadaAbstract:Two functions for calculating the width of the output angular power distribution are tested for light launched centrally along the axis of a step-index plastic optical fiber. It is found that the more recent of the two agrees better with experimental measurements. The other function (Gloge’s) underestimates the output width for longer fiber lengths, which is attributed to it not accounting for an appropriate boundary condition at the critical Propagation Angle.
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frequency response in step index plastic optical fibers obtained from the generalized power flow equation
Optics Express, 2009Co-Authors: Javie Mateo, Miguel A. Losada, Joseba ZubiaAbstract:We present a method to obtain the frequency response of step index (SI) plastic optical fibers (POFs) based on the power flow equation generalized to incorporate the temporal dimension where the fibre diffusion and attenuation are functions of the Propagation Angle. To solve this equation we propose a fast implementation of the finite-difference method in matrix form. Our method is validated by comparing model predictions to experimental data. In addition, the model provides the space-time evolution of the angular power distribution when it is transmitted throughout the fibre which gives a detailed picture of the POFs capabilities for information transmission. Model predictions show that angular diffusion has a strong impact on temporal pulse widening with Propagation.
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global characterization of optical power Propagation in step index plastic optical fibers
Optics Express, 2006Co-Authors: Javie Mateo, I. Garces, Angel Miguel Diaz Losada, Joseba ZubiaAbstract:We propose to characterize optical power transmission in step-index plastic optical fibers by estimating fiber diffusion and attenuation as functions of the Propagation Angle. We assume that power flow is described by Glogeś differential equation and find a global solution that was fitted to experimental far field patterns registered using a CCD camera as a function of fiber length. The diffusion and attenuation functions obtained describe completely the fiber behavior and thus, along with the power flow equation, can be used to predict the optical power distribution for any condition.
David E Sosnovik - One of the best experts on this subject based on the ideXlab platform.
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myocardial scar delineation using diffusion tensor magnetic resonance tractography
Journal of the American Heart Association, 2018Co-Authors: Choukri Mekkaoui, Marcel P Jackowski, Aravinda Thiagalingam, William J Kostis, Jeremy N Ruskin, Timothy G Reese, Christian T Stoeck, Sebastian Kozerke, Vivek Y Reddy, David E SosnovikAbstract:BackgroundLate gadolinium enhancement (LGE) is the current standard for myocardial scar delineation. In this study, we introduce the tractographic Propagation Angle (PA), a metric of myofiber curva...
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infarct delineation in patients with acute myocardial infarction using the tractographic Propagation Angle and late gadolinium enhancement
Journal of Cardiovascular Magnetic Resonance, 2015Co-Authors: Choukri Mekkaoui, Marcel P Jackowski, William J Kostis, Christian T Stoeck, F Pereira, Sebastian Kozerke, David E SosnovikAbstract:Background Currently used techniques to quantify late gadolinium enhancement (LGE) include an intensity threshold 5 standard deviations (5-SD) above normal myocardium and the full width at half maximum (FWHM) of the histogram [1,2]. Validation of these segmentation schemes can be performed ex vivo using tetrazolium tetrachloride (TTC). However, no analogous gold standard metric exists in vivo. We recently introduced the tractographic Propagation Angle (PA) [3], and showed that a PA threshold of 4° in infarcted hearts produces a distribution that corresponds very closely to that of TTC staining [4]. Here, we use PA maps in patients with myocardial infarction (MI) to evaluate the standard FWHM and 5-SD metrics. In addition, we introduce a new metric based on a Gaussian fit of the LGE image histogram.
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correlation of dti tractography with electroanatomic mapping in normal and infarcted myocardium
Journal of Cardiovascular Magnetic Resonance, 2014Co-Authors: Choukri Mekkaoui, Marcel P Jackowski, Aravinda Thiagalingam, William J Kostis, Sonia Niellesvallespin, David N Firmin, Himanshu Bhat, Jeremy N Ruskin, Timothy G Reese, David E SosnovikAbstract:Background The tractographic Propagation Angle (PA) is a topographic measure of fiber architecture in the myocardium. We have previously shown in infarcted mice that a PA > 4° can be used to differentiate normal and infarcted myocardium [1]. Here, we extend these preliminary observations by 1) characterizing PA values in normal sheep and human hearts, and 2) correlating changes in PA with changes in myocardial voltage on electroanatomical maps of infarcted sheep hearts.
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myocardial infarct delineation in vivo using diffusion tensor mri and the tractographic Propagation Angle
Journal of Cardiovascular Magnetic Resonance, 2013Co-Authors: Choukri Mekkaoui, Marcel P Jackowski, Jeremy N Ruskin, Timothy G Reese, Shuning Huang, Guangping Dai, Udo Hoffmann, David E SosnovikAbstract:Background Delayed gadolinium enhancement (Gd-DE) is widely used to detect scar formation following myocardial infarction (MI) [1], but cannot be performed in patients with renal impairment. Here we use the tractographic Propagation Angle (PA), a novel index derived from 3D diffusion tensor MRI (DTI), to detect changes in myocardial fiber architecture post-MI [2]. We compare image segmentation based on the tractographic PA to infarct delineation with GdDE.
Javie Mateo - One of the best experts on this subject based on the ideXlab platform.
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frequency response in step index plastic optical fibers obtained from the generalized power flow equation
Optics Express, 2009Co-Authors: Javie Mateo, Miguel A. Losada, Joseba ZubiaAbstract:We present a method to obtain the frequency response of step index (SI) plastic optical fibers (POFs) based on the power flow equation generalized to incorporate the temporal dimension where the fibre diffusion and attenuation are functions of the Propagation Angle. To solve this equation we propose a fast implementation of the finite-difference method in matrix form. Our method is validated by comparing model predictions to experimental data. In addition, the model provides the space-time evolution of the angular power distribution when it is transmitted throughout the fibre which gives a detailed picture of the POFs capabilities for information transmission. Model predictions show that angular diffusion has a strong impact on temporal pulse widening with Propagation.
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global characterization of optical power Propagation in step index plastic optical fibers
Optics Express, 2006Co-Authors: Javie Mateo, I. Garces, Angel Miguel Diaz Losada, Joseba ZubiaAbstract:We propose to characterize optical power transmission in step-index plastic optical fibers by estimating fiber diffusion and attenuation as functions of the Propagation Angle. We assume that power flow is described by Glogeś differential equation and find a global solution that was fitted to experimental far field patterns registered using a CCD camera as a function of fiber length. The diffusion and attenuation functions obtained describe completely the fiber behavior and thus, along with the power flow equation, can be used to predict the optical power distribution for any condition.
I Dandouras - One of the best experts on this subject based on the ideXlab platform.
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slow magnetosonic waves detected in reconnection diffusion region in the earth s magnetotail
Journal of Geophysical Research, 2013Co-Authors: J B Cao, I Dandouras, Xun Wei, Aiying Duan, Tielong Zhang, H RemeAbstract:We studied the ULF waves with a period of 30s in the ion diffusion region of reconnection observed by Cluster satellites on 21 August 2002. The fast convective tailward ion flow accompanied with a large southward magnetic field component, a strong Hall magnetic field, and a Hall electric field demonstrates that the Cluster satellites are located in the ion diffusion region of reconnection. The analyses of wave properties using minimum variance analysis and timing method indicate that this wave is an obliquely propagating slow magnetosonic wave which is characterized by the anti phase relation between the magnitude of the magnetic field and the ion number density and by a Propagation Angle of around 130 degrees with respect to the ambient magnetic field. This wave is generated by periodic magnetic reconnection. The periodic oscillations in the By and Bx components are driven by the periodic Hall current system, while the oscillation in the Bz component is driven by quasiperiodic convective tailward ion flows. The slow magnetosonic wave significantly influences the frequency of whistler waves and low hybrid waves excited by magnetic reconnection by changing the magnitude of the local magnetic field and subsequently the electron cyclotron frequency.
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statistical phase Propagation and dispersion analysis of low frequency waves in the magnetosheath
Annales Geophysicae, 2005Co-Authors: S Schafer, K H Glassmeier, Yasuhito Narita, K H Fornacon, I Dandouras, M FranzAbstract:We present the results of a statistical analysis of low-frequency fluctuations in the high latitude regions of the dayside magnetosheath using CLUSTER as a wave telescope. Magnetic field observations are used to determine wave Propagation directions and wave numbers for selected frequencies. Using observations of the plasma flow velocity we correct for the Doppler shift, in order to calculate frequencies and phase velocities in the plasma rest frame. This provides us with the possibility to perform a statistical dispersion analysis and to investigate various wave properties, such as the phase velocity and the Propagation Angle between k and B . The analysis of dispersion distributions and Friedrichs diagrams results in the identification of different wave populations. We find a multiplicity of standing structures (mirror modes) convected with the plasma flow and a large number of Alfvenic waves. The results confirm previous magnetosheath wave studies, such as ISSE or AMPTE spacecraft observations, but we also find a small number of mirror mode-like waves that have Propagation speeds up to the local Alfven velocity, quasi-perpendicular to the magnetic field.
Choukri Mekkaoui - One of the best experts on this subject based on the ideXlab platform.
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myocardial scar delineation using diffusion tensor magnetic resonance tractography
Journal of the American Heart Association, 2018Co-Authors: Choukri Mekkaoui, Marcel P Jackowski, Aravinda Thiagalingam, William J Kostis, Jeremy N Ruskin, Timothy G Reese, Christian T Stoeck, Sebastian Kozerke, Vivek Y Reddy, David E SosnovikAbstract:BackgroundLate gadolinium enhancement (LGE) is the current standard for myocardial scar delineation. In this study, we introduce the tractographic Propagation Angle (PA), a metric of myofiber curva...
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infarct delineation in patients with acute myocardial infarction using the tractographic Propagation Angle and late gadolinium enhancement
Journal of Cardiovascular Magnetic Resonance, 2015Co-Authors: Choukri Mekkaoui, Marcel P Jackowski, William J Kostis, Christian T Stoeck, F Pereira, Sebastian Kozerke, David E SosnovikAbstract:Background Currently used techniques to quantify late gadolinium enhancement (LGE) include an intensity threshold 5 standard deviations (5-SD) above normal myocardium and the full width at half maximum (FWHM) of the histogram [1,2]. Validation of these segmentation schemes can be performed ex vivo using tetrazolium tetrachloride (TTC). However, no analogous gold standard metric exists in vivo. We recently introduced the tractographic Propagation Angle (PA) [3], and showed that a PA threshold of 4° in infarcted hearts produces a distribution that corresponds very closely to that of TTC staining [4]. Here, we use PA maps in patients with myocardial infarction (MI) to evaluate the standard FWHM and 5-SD metrics. In addition, we introduce a new metric based on a Gaussian fit of the LGE image histogram.
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correlation of dti tractography with electroanatomic mapping in normal and infarcted myocardium
Journal of Cardiovascular Magnetic Resonance, 2014Co-Authors: Choukri Mekkaoui, Marcel P Jackowski, Aravinda Thiagalingam, William J Kostis, Sonia Niellesvallespin, David N Firmin, Himanshu Bhat, Jeremy N Ruskin, Timothy G Reese, David E SosnovikAbstract:Background The tractographic Propagation Angle (PA) is a topographic measure of fiber architecture in the myocardium. We have previously shown in infarcted mice that a PA > 4° can be used to differentiate normal and infarcted myocardium [1]. Here, we extend these preliminary observations by 1) characterizing PA values in normal sheep and human hearts, and 2) correlating changes in PA with changes in myocardial voltage on electroanatomical maps of infarcted sheep hearts.
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myocardial infarct delineation in vivo using diffusion tensor mri and the tractographic Propagation Angle
Journal of Cardiovascular Magnetic Resonance, 2013Co-Authors: Choukri Mekkaoui, Marcel P Jackowski, Jeremy N Ruskin, Timothy G Reese, Shuning Huang, Guangping Dai, Udo Hoffmann, David E SosnovikAbstract:Background Delayed gadolinium enhancement (Gd-DE) is widely used to detect scar formation following myocardial infarction (MI) [1], but cannot be performed in patients with renal impairment. Here we use the tractographic Propagation Angle (PA), a novel index derived from 3D diffusion tensor MRI (DTI), to detect changes in myocardial fiber architecture post-MI [2]. We compare image segmentation based on the tractographic PA to infarct delineation with GdDE.
