The Experts below are selected from a list of 318 Experts worldwide ranked by ideXlab platform
P Entel - One of the best experts on this subject based on the ideXlab platform.
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calculation of current induced torque from spin Continuity Equation
Physical Review B, 2008Co-Authors: Gen Tatara, P EntelAbstract:Current-induced torque is formulated based on the spin Continuity Equation. The formulation does not rely on the assumption of separation of local spin and charge degrees of freedom, in contrast to approaches based on the $s$-$d$ model or mean-field approximation of itinerant ferromagnetism. This new method would be thus useful for the estimation of torques in actual materials by first-principles calculations. As an example, the formalism is applied to the adiabatic limit of the $s$-$d$ model in order to obtain the analytical expression for torques and corresponding $\beta$ terms arising from spin relaxation due to spin-flip scattering and spin-orbit interaction.
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calculation of current induced torque from spin Continuity Equation
Physical Review B, 2008Co-Authors: Gen Tatara, P EntelAbstract:Current-induced torque is formulated based on the spin Continuity Equation. The formulation does not rely on the assumption of separation of local spin and charge degrees of freedom, in contrast to approaches based on the $s\text{\ensuremath{-}}d$ model or mean-field approximation of itinerant ferromagnetism. This method would be thus useful for the estimation of torques in actual materials by first-principles calculations. As an example, the formalism is applied to the adiabatic limit of the $s\text{\ensuremath{-}}d$ model in order to obtain the analytical expression for torques and the corresponding $\ensuremath{\beta}$ terms arising from spin relaxation due to spin-flip scattering and spin-orbit interaction.
C A Young - One of the best experts on this subject based on the ideXlab platform.
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A comparison of two forms of the Continuity Equation in the Trifecta bovine pericardial aortic valve
Echo research and practice, 2016Co-Authors: John C. Chambers, Denise Parkin, James Roxburgh, Vinayak Bapat, C A YoungAbstract:AIM To compare the classical and simplified form of the Continuity Equation in small Trifecta valves. METHODS This is a retrospective analysis of post-operative echocardiograms performed for clinical reasons after implantation of Trifecta bioprosthetic valves. RESULTS There were 60 patients aged 74 (range 38-89) years. For the valves of size 19, 21 and 23mm, the mean gradient was 11.3, 10.7 and 9.7mmHg, respectively. The effective orifice areas by the classical form of the Continuity Equation were 1.4, 1.7 and 1.9cm(2), respectively. There was a good correlation between the two forms of the Continuity Equation, but they were significantly different using a t-test (P
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a comparison of two forms of the Continuity Equation in the trifecta bovine pericardial aortic valve
Echo research and practice, 2016Co-Authors: John C. Chambers, Denise Parkin, James Roxburgh, Vinayak Bapat, C A YoungAbstract:AIM To compare the classical and simplified form of the Continuity Equation in small Trifecta valves. METHODS This is a retrospective analysis of post-operative echocardiograms performed for clinical reasons after implantation of Trifecta bioprosthetic valves. RESULTS There were 60 patients aged 74 (range 38-89) years. For the valves of size 19, 21 and 23mm, the mean gradient was 11.3, 10.7 and 9.7mmHg, respectively. The effective orifice areas by the classical form of the Continuity Equation were 1.4, 1.7 and 1.9cm(2), respectively. There was a good correlation between the two forms of the Continuity Equation, but they were significantly different using a t-test (P<0.00001). Results using the classical form were a mean 0.11 (s.d. 0.18)cm(2) larger than those using the simple formula. CONCLUSION Haemodynamic function of the Trifecta valve in the small aortic root is good. There are significant differences between the classical and simplified forms of the Continuity Equation.
John C. Chambers - One of the best experts on this subject based on the ideXlab platform.
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A comparison of two forms of the Continuity Equation in the Trifecta bovine pericardial aortic valve
Echo research and practice, 2016Co-Authors: John C. Chambers, Denise Parkin, James Roxburgh, Vinayak Bapat, C A YoungAbstract:AIM To compare the classical and simplified form of the Continuity Equation in small Trifecta valves. METHODS This is a retrospective analysis of post-operative echocardiograms performed for clinical reasons after implantation of Trifecta bioprosthetic valves. RESULTS There were 60 patients aged 74 (range 38-89) years. For the valves of size 19, 21 and 23mm, the mean gradient was 11.3, 10.7 and 9.7mmHg, respectively. The effective orifice areas by the classical form of the Continuity Equation were 1.4, 1.7 and 1.9cm(2), respectively. There was a good correlation between the two forms of the Continuity Equation, but they were significantly different using a t-test (P
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a comparison of two forms of the Continuity Equation in the trifecta bovine pericardial aortic valve
Echo research and practice, 2016Co-Authors: John C. Chambers, Denise Parkin, James Roxburgh, Vinayak Bapat, C A YoungAbstract:AIM To compare the classical and simplified form of the Continuity Equation in small Trifecta valves. METHODS This is a retrospective analysis of post-operative echocardiograms performed for clinical reasons after implantation of Trifecta bioprosthetic valves. RESULTS There were 60 patients aged 74 (range 38-89) years. For the valves of size 19, 21 and 23mm, the mean gradient was 11.3, 10.7 and 9.7mmHg, respectively. The effective orifice areas by the classical form of the Continuity Equation were 1.4, 1.7 and 1.9cm(2), respectively. There was a good correlation between the two forms of the Continuity Equation, but they were significantly different using a t-test (P<0.00001). Results using the classical form were a mean 0.11 (s.d. 0.18)cm(2) larger than those using the simple formula. CONCLUSION Haemodynamic function of the Trifecta valve in the small aortic root is good. There are significant differences between the classical and simplified forms of the Continuity Equation.
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The Continuity Equation tested in a bileaflet aortic prosthesis.
International journal of cardiology, 1991Co-Authors: John C. Chambers, Fiona Coppack, Philip B. Deverall, Graham Jackson, Edgar SowtonAbstract:Abstract The Continuity Equation is valid for a population of aortic valves, but its accuracy in individual valves is uncertain. In bileaflet prostheses, obstruction to forward flow is small and individual variability in opening behaviour is minimal. In these valves, the area of the effective orifice should be close to that measured by the manufacturer. A total of 57 patients aged 58 ± 11 years were studied at a mean of 3.6 months after implantation with a CarboMedics aortic prosthesis. Nine had additional implants in the mitral position and all prostheses were clinically normal. Peak subaortic and transaortic velocities were averaged over 5 beats. The area of the effective orifice was significantly different between the four diameters ( P r s = 0.73, P 2 . Discrepancies probably arose in the estimation of subaortic cross-sectional area and subaortic velocity. Thus, the Continuity Equation may be inaccurate in an individual prosthetic valve when functioning normally.
William A Zoghbi - One of the best experts on this subject based on the ideXlab platform.
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doppler echocardiographic assessment with the Continuity Equation of st jude medical mechanical prostheses in the mitral valve position
American Journal of Cardiology, 1995Co-Authors: Jamil N Bitar, Marcel E Lechin, Gabriel Salazar, William A ZoghbiAbstract:Evaluation of the St. Jude Medical (SJM) valve in the mitral position with Doppler echocardiography has usually involved the use of gradients across the valve and the application of the pressure half-time (PHT) method to derive a mitral valve area. The purpose of this study was, first, to determine the normal values of effective orifice areas for the SJM valve in the mural position using the Continuity Equation, and second, to evaluate whether this parameter provides an improved assessment of valve function. Accordingly, Doppler echocardiography was performed in 40 patients within 6 weeks after valve replacement. All patients were clinically stable, without evidence of valvular dysfunction or aortic insufficiency. Valve size ranged from 23 to 33 mm and ventricular ejection fraction averaged 54 ± 13%. Effective orifice area was derived by the Continuity Equation using stroke volume measured in the ventricular outflow tract, divided by the time-velocity integral of the SJM valve jet, and by PHT. Doppler-derived SJM valve mean gradient averaged 4 ± 2 mm Hg. Effective area by the Continuity Equation averaged 1.82 ± 0.36 cm2 (range 1.03 cm2 for a 23 mm valve to 2.63 cm2 for a 31 mm valve) and was smaller than by PHT (mean 3.10 ± 0.65 cm2, p = 0.0001; range 1.38 to 4.78 cm2). Areas by both methods were smaller than the actual valve orifice area provided b the manufacturer (4.53 ± 0.80 cm2, p = 0.0001). With use of analysis of variance, effective SJM valve area by the Continuity Equation differentiated various valve sizes (p = 0.0002) better than did mean gradient (p = 0.013) or PHT (p = NS). Effective area by the Continuity Equation also correlated better with actual valve orifice area (r = 0.68, p <0.0001) than the area derived by PHT (r = 0.31, p = 0.06). Derivation of effective orifice area of SJM valves in the mitral position with the Continuity Equation allows better differentiation among valve sizes than mean gradients and PHT, and provides an additional index for assessing prosthetic mitral valve function.
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doppler echocardiographic assessment of the st jude medical prosthetic valve in the aortic position using the Continuity Equation
Circulation, 1991Co-Authors: Edward R Chafizadeh, William A ZoghbiAbstract:To test whether the Continuity Equation can be applied to the noninvasive assessment of prosthetic aortic valve function, Doppler echocardiography was performed in 67 patients (mean age, 58 +/- 14 years) within 10 +/- 6 days after valve replacement with St. Jude Medical valves. All patients were clinically stable and without evidence of valve dysfunction. Valve size ranged from 19 to 31 mm, and ejection fraction ranged from 30% to 75%. With the parasternal long-axis view, the left ventricular outflow diameter measured just proximal to the prosthetic valve correlated well with valve size (r = 0.92). Doppler-derived maximal gradients ranged from 9 to 71 mm Hg. Effective prosthetic aortic valve area by the Continuity Equation ranged between 0.73 cm2 for a 19-mm valve and 4.23 cm2 for a 31-mm valve. With analysis of variance, effective orifice area differentiated various valve sizes (p less than 10(-14)) better than did gradients alone (p = 0.003) and correlated better with actual valve orifice area (r = 0.83 versus - 0.40). A Doppler velocity index, the ratio of peak velocity in the left ventricular outflow to that of the aortic jet, averaged 0.41 +/- 0.09 and was less dependent on valve size (r = 0.43). Thus, the Continuity Equation can be applied to the assessment of prosthetic St. Jude valves in the aortic position. By accounting for flow through the valve, it provides an improved assessment over the sole use of gradients in the evaluation of prosthetic valve function.
Gen Tatara - One of the best experts on this subject based on the ideXlab platform.
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calculation of current induced torque from spin Continuity Equation
Physical Review B, 2008Co-Authors: Gen Tatara, P EntelAbstract:Current-induced torque is formulated based on the spin Continuity Equation. The formulation does not rely on the assumption of separation of local spin and charge degrees of freedom, in contrast to approaches based on the $s$-$d$ model or mean-field approximation of itinerant ferromagnetism. This new method would be thus useful for the estimation of torques in actual materials by first-principles calculations. As an example, the formalism is applied to the adiabatic limit of the $s$-$d$ model in order to obtain the analytical expression for torques and corresponding $\beta$ terms arising from spin relaxation due to spin-flip scattering and spin-orbit interaction.
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calculation of current induced torque from spin Continuity Equation
Physical Review B, 2008Co-Authors: Gen Tatara, P EntelAbstract:Current-induced torque is formulated based on the spin Continuity Equation. The formulation does not rely on the assumption of separation of local spin and charge degrees of freedom, in contrast to approaches based on the $s\text{\ensuremath{-}}d$ model or mean-field approximation of itinerant ferromagnetism. This method would be thus useful for the estimation of torques in actual materials by first-principles calculations. As an example, the formalism is applied to the adiabatic limit of the $s\text{\ensuremath{-}}d$ model in order to obtain the analytical expression for torques and the corresponding $\ensuremath{\beta}$ terms arising from spin relaxation due to spin-flip scattering and spin-orbit interaction.