The Experts below are selected from a list of 46605 Experts worldwide ranked by ideXlab platform
Mingxin Wang - One of the best experts on this subject based on the ideXlab platform.
-
nonlinear stability of traveling Wave Fronts for nonlocal delayed reaction diffusion equations
Journal of Mathematical Analysis and Applications, 2012Co-Authors: Mingxin WangAbstract:Abstract This paper is concerned with the nonlinear stability of traveling Wave Fronts for nonlocal delayed reaction–diffusion equation. We prove that these traveling Wave Fronts are exponentially stable to perturbation in some exponentially weighted L ∞ spaces, when the initial perturbation around the traveling Wave Fronts decays exponentially as x → − ∞ , but the initial perturbation can be arbitrary large in other locations. The time decay rate is also obtained by weighted energy estimates.
-
existence uniqueness and asymptotic behavior of traveling Wave Fronts for a vector disease model
Nonlinear Analysis-real World Applications, 2010Co-Authors: Mingxin WangAbstract:Abstract This paper is concerned with the existence, uniqueness and asymptotic behavior of traveling Wave Fronts for a vector disease model. We first establish the existence of traveling Wave Fronts by using geometric singular perturbation theory. Then the asymptotic behavior and uniqueness of traveling Wave Fronts are obtained by using the standard asymptotic theory and sliding method. In addition, our method is also suitable to establish the uniqueness and asymptotic behavior of traveling Wave Fronts for a cooperative system.
-
nonlinear stability of travelling Wave Fronts for delayed reaction diffusion equations
Nonlinearity, 2010Co-Authors: Mingxin WangAbstract:This paper deals with the nonlinear stability of travelling Wave Fronts for delayed reaction diffusion equations. We prove that the travelling Wave Fronts are exponentially stable to perturbations in some exponentially weighted L∞ spaces, and obtain the time decay rates of by the weighted energy estimate.
Yukio Sano - One of the best experts on this subject based on the ideXlab platform.
-
Equilibrium thermodynamic theory for the evaluation of temperature distributions in overdriven steady-plane Wave Fronts
Journal of Applied Physics, 2001Co-Authors: Tomokazu Sano, Yukio SanoAbstract:Temperature distributions in overdriven steady Wave Fronts in solid 2024 Al shocked up to 80 GPa, in which no melting occurred in the Wave Fronts, were evaluated using the equilibrium thermodynamic theory. The effective strain increments were sufficiently small and the effective temperature rise times were sufficiently long with respect to electron–phonon relaxation times to justify using equilibrium thermodynamics. In addition, the sufficiently large viscous-stress components supported the efficacy of the thermodynamic theory. The same is true of shocks up to 250 GPa in solid Pt and 230 GPa in solid Fe. Furthermore, the influence of viscous stress was examined by evaluating the temperature distributions for inviscid 2024 Al, Pt, and Fe solids using the equations for temperature derived from the Mie–Gruneisen equation. Finally, we demonstrate that there might be a solid–liquid–solid Hugoniot between the solid and liquid–solid Hugoniots for Fe and estimate the solid–liquid–solid and liquid–solid Hugoniots.
-
estimate of temperature distributions in steady plane Wave Fronts using a hugoniot function
Journal of Applied Physics, 2001Co-Authors: Yukio Sano, Akihisa AbeAbstract:The purpose of this study was to establish a method for estimating temperature distributions in steady-plane-Wave Fronts in a thermoviscous material using a Hugoniot function. To this end, under the fundamental assumption that the material in the Wave front is approximately in an equilibrium state, two irreversible thermodynamic equations for temperature in the Wave front were derived. In the first equation, heat transport was neglected, and in the second equation, the work done by thermal stress was offset by heat transport. The temperature distributions were evaluated qualitatively under the assumption of heat transport. This evaluation indicated that the second equation was effective if the effects of viscosity were large. These two equations were applied to the shock compressions up to 140 GPa of yttria-doped tetragonal zirconia. The second equation sufficiently predicted temperature behind the shock and also fairly accurately predicted temperatures in the shock front. The influence of heat transport on both temperatures was also examined.
-
UNSTEADY PLANE SMOOTH Wave Fronts OF COMBINED GROWING-ATTENUATING TYPE
Journal of Applied Physics, 1997Co-Authors: Yukio Sano, Isamu Miyamoto, Peter ArathoonAbstract:Unsteady plane smooth Wave Fronts of a combined growing-attenuating type, where the peak of each strain Wave is growing, are derived by a qualitative analysis. There are three different modes in this combined type: In mode I, the peak of a particle velocity Wave is growing, but that of a stress Wave is attenuating; in mode II, the former is attenuating, but the latter is growing; in mode III, both are attenuating. Three possible Wave Fronts belong to mode I, five to mode II, and three to mode III. Five new elementary Waves are found in these eleven Wave Fronts. The Wave Fronts near the impacted surface of sandstone detected by the previous quantitative analysis [Sano, J. Appl. Phys. 73, 118 (1993)] are identified with some of the eleven possible Wave Fronts. As a result, the theoretical existence of several new Wave Fronts and a new elementary Wave is verified. The equation for the stress at the impacted surface indicates that strain acceleration is responsible for the formation of the Wave Fronts of the ...
Hrayr S Karagueuzian - One of the best experts on this subject based on the ideXlab platform.
-
characteristics of Wave Fronts during ventricular fibrillation in human hearts with dilated cardiomyopathy role of increased fibrosis in the generation of reentry
Journal of the American College of Cardiology, 1998Co-Authors: James J C Ong, Michael C Fishbein, William J Mandel, John J Lee, Chun Hwang, L Czer, Alfredo Trento, Carlos Blanche, Robert M Kass, Hrayr S KaragueuzianAbstract:Abstract Objectives. We sought to evaluate the characteristics of Wave Fronts during ventricular fibrillation (VF) in human hearts with dilated cardiomyopathy (DCM) and to determine the role of increased fibrosis in the generation of reentry during VF. Background. The role of increased fibrosis in reentry formation during human VF is unclear. Methods. Five hearts from transplant recipients with DCM were supported by Langendorff perfusion and were mapped during VF. A plaque electrode array with 477 bipolar electrodes (1.6-mm resolution) was used for epicardial mapping. In heart no. 5, we also used 440 transmural bipolar recordings. Each mapped area was analyzed histologically. Results. Fifteen runs of VF (8 s/run) recorded from the epicardium were analyzed, and 55 episodes of reentry were observed. The life span of reentry was short (one to four cycles), and the mean cycle length was 172 ± 24 ms. In heart no. 5, transmural scroll Waves were demonstrated. The most common mode of initiation of reentry was epicardial breakthrough, followed by a line of conduction block parallel to the epicardial fiber orientation (34 [62%] of 55 episodes). In the areas with lines of block, histologic examination showed significant fibrosis separating the epicardial muscle fibers and bundles along the longitudinal axis of fiber orientation. The mean percent fibrous tissue in these areas (n = 20) was significantly higher than that in the areas without block (n = 28) (24 ± 7.5% vs. 10 ± 3.8%, p Conclusions. In human hearts with DCM, epicardial reentrant Wave Fronts and transmural scroll Waves were present during VF. Increased fibrosis provides a site for conduction block, leading to the continuous generation of reentry.
-
attachment of meandering reentrant Wave Fronts to anatomic obstacles in the atrium role of the obstacle size
Circulation Research, 1997Co-Authors: Takanori Ikeda, Takumi Uchida, Dustan Hough, Michael C Fishbein, William J Mandel, Peng Sheng Chen, Masaaki Yashima, Hrayr S KaragueuzianAbstract:Abstract Acetylcholine chloride (ACh) induces nonstationary meandering reentrant Wave Fronts in the atrium. We hypothesized that an anatomic obstacle of a suitable size prevents meandering by causing attachment of the reentrant Wave front tip to the obstacle. Eight isolated canine right atrial tissues (area, 3.8×3.2 cm) were mounted in a tissue bath and superfused with Tyrode’s solution containing 10 to 15 μmol/L ACh. Holes with 2- to 10-mm diameters were sequentially created in the center of the tissue with biopsy punches. Reentry was induced by a premature stimulus after eight regular stimuli at 400-ms cycle length. The endocardial activation maps and the motion of the induced reentry were visualized dynamically before and after each test lesion using 509 bipolar electrodes. In the absence of a lesion (n=8), the induced single reentrant Wave front, in the form of a spiral Wave, meandered irregularly from one site to another before terminating at the tissue border. Holes with 2- to 4-mm diameters (n=6) had no effect on meandering. However, when the hole diameters were increased to 6 mm (n=8), 8 mm (n=8), and 10 mm (n=6), the tip of the spiral Wave attached to the holes, and reentry became stationary. Transition from meandering to an attached state converted the irregular and polymorphic electrogram to a periodic and monomorphic activity with longer cycle lengths (101±11 versus 131±9 ms for no hole versus 10-mm hole, respectively; P <.001). Regression analysis showed a significant positive linear correlation between the cycle length of the reentry and the hole diameter ( r =.89, P <.01) and between the cycle length of the reentry and the excitable gap ( r =.89, P <.05). We conclude that a critically sized anatomic obstacle converts a nonstationary meandering reentrant Wave front to a stationary one. This transition converts an irregular “fibrillation-like” activity into regular monomorphic activity.
-
meandering and unstable reentrant Wave Fronts induced by acetylcholine in isolated canine right atrium
American Journal of Physiology-heart and Circulatory Physiology, 1997Co-Authors: Takanori Ikeda, Takumi Uchida, Dustan Hough, Michael C Fishbein, William J Mandel, Peng Sheng Chen, Hrayr S KaragueuzianAbstract:The mechanism(s) by which acetylcholine (ACh) increases atrial vulnerability to reentry and maintains its activity for longer durations remains poorly defined. In the present study we used high-resolution activation maps to test the hypothesis that ACh promotes meandering of atrial reentrant Wave Fronts, resulting in breakup and the generation of new Wave Fronts that sustain the activity. Reentry was induced in 11 isolated canine right atrial tissues (3.8 x 3.2 cm) by a premature point stimulus (S2) before and after superfusion with ACh (15 x 10(-6) M). Endocardial isochronal activation maps were constructed with the use of 509 bipolar electrodes (1.6-mm spatial resolution), and the dynamics of the activation Wave Fronts were visualized with animation. A vulnerable period was found during which an S2 current strength > 4.4 +/- 2.5 mA [lower limit of vulnerability (LLV)] and < 26 +/- 13 mA [upper limit of vulnerability (ULV)] induced a single stationary reentrant Wave front that lasted 3 +/- 2.5 s with a period of 159 +/- 17 ms (16 episodes). AC shortened the refractory period from 100 +/- 12 to 59 +/- 9 ms (P < 0.001) and increased vulnerability to reentry induction by simultaneous decrease in the LLV (0.7 +/- 0.2 mA, P < 0.001) and an increase in the ULV (82 +/- 24 mA, P < 0.01). ACh accelerated the rate (period of 110 +/- 16 ms, P < 0.001) and converted the stationary reentrant Wave front to a nonstationary (meandering) reentrant Wave front showing polymorphic electrograms, i.e., “fibrillation-like” activity (22 episodes). Rapid meandering of the reentry tip led to Wave front breakup (18 episodes) and the generation of new Wave Fronts (19 episodes). These Wave front dynamics also led to sustained (76 +/- 224 s, P < 0.001) fibrillation-like electrograms. We conclude that ACh increases the ULV and promotes meandering of a single reentrant Wave front, leading to breakup and the generation of new Wave Fronts. Single meandering and complex Wave front dynamics cause fibrillation-like activity and sustain the activity for longer duration.
-
reentrant Wave Fronts in wiggers stage ii ventricular fibrillation characteristics and mechanisms of termination and spontaneous regeneration
Circulation Research, 1996Co-Authors: John J Lee, Takanori Ikeda, Dustan Hough, Michael C Fishbein, Hrayr S Karagueuzian, Kamyar Kamjoo, Chun Hwang, Wei Fan, Claudio Bonometti, Peng Sheng ChenAbstract:The mechanisms of Wiggers' stage II ventricular fibrillation (VF) are poorly understood. Using computerized mapping techniques, we studied the patterns of activation during Wiggers' stage II VF in 13 open-chest dogs. In 7 of the 13 dogs, the right ventricular Purkinje fibers and adjacent subendocardial myocytes were ablated with Lugol solution. VF was induced electrically, and 3 to 5 seconds of data were obtained beginning approximately 2.5 seconds after the onset of VF. Dynamic displays of the activation patterns and isochronal maps revealed the presence of reentrant Wave Fronts in 17 of 33 runs of VF in ablated ventricles and in 12 of 45 runs of VF in intact ventricles. The incidence of reentry was not different between the subendocardium-ablated group versus the nonablated group (1.7 +/- 1.6 versus 1.2 +/- 1.6 rotations per episode of VF, P = .19). There were no differences in the core size (25 +/- 19 versus 29 +/- 18 mm2), life span (3.4 +/- 1.1 versus 3.2 +/- 1.2 rotations), or cycle length (111 +/- 12 versus 107 +/- 8 ms) in ablated ventricles versus intact ventricles, respectively. The core was unstable as it meandered within the mapped area displacing the entire reentrant Wave front. In all episodes, the reentrant Wave Fronts were spontaneously initiated by an interaction between two propagating Wave Fronts roughly perpendicular to each other. The second Wave front met the tail of the first Wave front 69 +/- 11 ms (range, 40 to 90 ms) after its latest activation, indicating that the interaction occurred during a vulnerable period. The reentrant Wave Fronts terminated spontaneously (n = 7), as the result of interference by an invading Wave front (n = 19 or meandered off the mapped region (n = 3). We conclude the following: (1) Reentrant activities with short life spans and meandering cores are present during Wiggers' stage II VF in dogs. (2) New reentrant Wave Fronts are generated when one Wave front interacts with another Wave front during its vulnerable period. (3) The reentrant Wave Fronts terminate spontaneously or as the result of interference. (4) Chemical subendocardial ablation does not affect the incidence, life span, cycle length, or core size of the reentrant Wave Fronts.
Guojian Lin - One of the best experts on this subject based on the ideXlab platform.
-
travelling Wave Fronts in a vector disease model with delay
Applied Mathematical Modelling, 2008Co-Authors: Guojian Lin, Yiguang HongAbstract:In this paper, we study the diffusive vector disease model with delay. This problem with strong biological background has attracted much research attention. We focus on the existence of traveling Wave Fronts, and find that there is a moving zone for the transition from the disease-free state to the infective state. To complete the theoretical analysis, we employ the mathematical tools including the monotone iteration technique as well as the upper and lower solution method.
Peng Sheng Chen - One of the best experts on this subject based on the ideXlab platform.
-
attachment of meandering reentrant Wave Fronts to anatomic obstacles in the atrium role of the obstacle size
Circulation Research, 1997Co-Authors: Takanori Ikeda, Takumi Uchida, Dustan Hough, Michael C Fishbein, William J Mandel, Peng Sheng Chen, Masaaki Yashima, Hrayr S KaragueuzianAbstract:Abstract Acetylcholine chloride (ACh) induces nonstationary meandering reentrant Wave Fronts in the atrium. We hypothesized that an anatomic obstacle of a suitable size prevents meandering by causing attachment of the reentrant Wave front tip to the obstacle. Eight isolated canine right atrial tissues (area, 3.8×3.2 cm) were mounted in a tissue bath and superfused with Tyrode’s solution containing 10 to 15 μmol/L ACh. Holes with 2- to 10-mm diameters were sequentially created in the center of the tissue with biopsy punches. Reentry was induced by a premature stimulus after eight regular stimuli at 400-ms cycle length. The endocardial activation maps and the motion of the induced reentry were visualized dynamically before and after each test lesion using 509 bipolar electrodes. In the absence of a lesion (n=8), the induced single reentrant Wave front, in the form of a spiral Wave, meandered irregularly from one site to another before terminating at the tissue border. Holes with 2- to 4-mm diameters (n=6) had no effect on meandering. However, when the hole diameters were increased to 6 mm (n=8), 8 mm (n=8), and 10 mm (n=6), the tip of the spiral Wave attached to the holes, and reentry became stationary. Transition from meandering to an attached state converted the irregular and polymorphic electrogram to a periodic and monomorphic activity with longer cycle lengths (101±11 versus 131±9 ms for no hole versus 10-mm hole, respectively; P <.001). Regression analysis showed a significant positive linear correlation between the cycle length of the reentry and the hole diameter ( r =.89, P <.01) and between the cycle length of the reentry and the excitable gap ( r =.89, P <.05). We conclude that a critically sized anatomic obstacle converts a nonstationary meandering reentrant Wave front to a stationary one. This transition converts an irregular “fibrillation-like” activity into regular monomorphic activity.
-
meandering and unstable reentrant Wave Fronts induced by acetylcholine in isolated canine right atrium
American Journal of Physiology-heart and Circulatory Physiology, 1997Co-Authors: Takanori Ikeda, Takumi Uchida, Dustan Hough, Michael C Fishbein, William J Mandel, Peng Sheng Chen, Hrayr S KaragueuzianAbstract:The mechanism(s) by which acetylcholine (ACh) increases atrial vulnerability to reentry and maintains its activity for longer durations remains poorly defined. In the present study we used high-resolution activation maps to test the hypothesis that ACh promotes meandering of atrial reentrant Wave Fronts, resulting in breakup and the generation of new Wave Fronts that sustain the activity. Reentry was induced in 11 isolated canine right atrial tissues (3.8 x 3.2 cm) by a premature point stimulus (S2) before and after superfusion with ACh (15 x 10(-6) M). Endocardial isochronal activation maps were constructed with the use of 509 bipolar electrodes (1.6-mm spatial resolution), and the dynamics of the activation Wave Fronts were visualized with animation. A vulnerable period was found during which an S2 current strength > 4.4 +/- 2.5 mA [lower limit of vulnerability (LLV)] and < 26 +/- 13 mA [upper limit of vulnerability (ULV)] induced a single stationary reentrant Wave front that lasted 3 +/- 2.5 s with a period of 159 +/- 17 ms (16 episodes). AC shortened the refractory period from 100 +/- 12 to 59 +/- 9 ms (P < 0.001) and increased vulnerability to reentry induction by simultaneous decrease in the LLV (0.7 +/- 0.2 mA, P < 0.001) and an increase in the ULV (82 +/- 24 mA, P < 0.01). ACh accelerated the rate (period of 110 +/- 16 ms, P < 0.001) and converted the stationary reentrant Wave front to a nonstationary (meandering) reentrant Wave front showing polymorphic electrograms, i.e., “fibrillation-like” activity (22 episodes). Rapid meandering of the reentry tip led to Wave front breakup (18 episodes) and the generation of new Wave Fronts (19 episodes). These Wave front dynamics also led to sustained (76 +/- 224 s, P < 0.001) fibrillation-like electrograms. We conclude that ACh increases the ULV and promotes meandering of a single reentrant Wave front, leading to breakup and the generation of new Wave Fronts. Single meandering and complex Wave front dynamics cause fibrillation-like activity and sustain the activity for longer duration.
-
reentrant Wave Fronts in wiggers stage ii ventricular fibrillation characteristics and mechanisms of termination and spontaneous regeneration
Circulation Research, 1996Co-Authors: John J Lee, Takanori Ikeda, Dustan Hough, Michael C Fishbein, Hrayr S Karagueuzian, Kamyar Kamjoo, Chun Hwang, Wei Fan, Claudio Bonometti, Peng Sheng ChenAbstract:The mechanisms of Wiggers' stage II ventricular fibrillation (VF) are poorly understood. Using computerized mapping techniques, we studied the patterns of activation during Wiggers' stage II VF in 13 open-chest dogs. In 7 of the 13 dogs, the right ventricular Purkinje fibers and adjacent subendocardial myocytes were ablated with Lugol solution. VF was induced electrically, and 3 to 5 seconds of data were obtained beginning approximately 2.5 seconds after the onset of VF. Dynamic displays of the activation patterns and isochronal maps revealed the presence of reentrant Wave Fronts in 17 of 33 runs of VF in ablated ventricles and in 12 of 45 runs of VF in intact ventricles. The incidence of reentry was not different between the subendocardium-ablated group versus the nonablated group (1.7 +/- 1.6 versus 1.2 +/- 1.6 rotations per episode of VF, P = .19). There were no differences in the core size (25 +/- 19 versus 29 +/- 18 mm2), life span (3.4 +/- 1.1 versus 3.2 +/- 1.2 rotations), or cycle length (111 +/- 12 versus 107 +/- 8 ms) in ablated ventricles versus intact ventricles, respectively. The core was unstable as it meandered within the mapped area displacing the entire reentrant Wave front. In all episodes, the reentrant Wave Fronts were spontaneously initiated by an interaction between two propagating Wave Fronts roughly perpendicular to each other. The second Wave front met the tail of the first Wave front 69 +/- 11 ms (range, 40 to 90 ms) after its latest activation, indicating that the interaction occurred during a vulnerable period. The reentrant Wave Fronts terminated spontaneously (n = 7), as the result of interference by an invading Wave front (n = 19 or meandered off the mapped region (n = 3). We conclude the following: (1) Reentrant activities with short life spans and meandering cores are present during Wiggers' stage II VF in dogs. (2) New reentrant Wave Fronts are generated when one Wave front interacts with another Wave front during its vulnerable period. (3) The reentrant Wave Fronts terminate spontaneously or as the result of interference. (4) Chemical subendocardial ablation does not affect the incidence, life span, cycle length, or core size of the reentrant Wave Fronts.
