Drought is the most important factor limiting rice yields in the rainfed areas of Asia. To overcome the problem, we developed a new strategy 'designed QTL pyramiding' to more effi ciently develop drought toler...Drought is the most important factor limiting rice yields in the rainfed areas of Asia. To overcome the problem, we developed a new strategy 'designed QTL pyramiding' to more effi ciently develop drought tolerant (DT)展开更多
For the two-dimensional Navier-Stokes equations of isentropic magnetohydrodynamics （MHD） with γ-law gas equation of state, γ≥ 1, and infinite electrical resistivity, we carry out a global analysis categorizing al...For the two-dimensional Navier-Stokes equations of isentropic magnetohydrodynamics （MHD） with γ-law gas equation of state, γ≥ 1, and infinite electrical resistivity, we carry out a global analysis categorizing all possible viscous shock profiles. Precisely, we show that the phase portrait of the traveling-wave ODE generically consists of either two rest points connected by a viscous Lax profile, or else four rest points, two saddles and two nodes. In the latter configuration, which rest points are connected by profiles depends on the ratio of viscosities, and can involve Lax, overcompressive, or undercompressive shock profiles. Considered as three-dimensional solutions, undercompressive shocks axe Lax-type （Alfven） waves. For the monatomic and diatomic cases γ= 5/3 and γ=7/5, with standard viscosity ratio for a nonmagnetic gas, we find numerically that the the nodes are connected by a family of overcompressive profiles bounded by Lax profiles connecting saddles to nodes, with no undercompressive shocks occurring. We carry out a systematic numerical Evans function analysis indicating that all of these two-dimensional shock pro- files are linearly and nonlinearly stable, both with respect to two- and three-dimensional perturbations. For the same gas constants, but different viscosity ratios, we investigate also cases for which undercompressive shocks appear; these are seen numerically to be stable as well, both with respect to two-dimensional and （in the neutral sense of convergence to nearby Riemann solutions） three-dimensional perturbations.展开更多
The killing of tumor cells by ionizing radiation beams in cancer radiotherapy is currently based on a rather empirical understanding of the basic mechanisms and effectiveness of DNA damage by radiation.By contrast,the...The killing of tumor cells by ionizing radiation beams in cancer radiotherapy is currently based on a rather empirical understanding of the basic mechanisms and effectiveness of DNA damage by radiation.By contrast,the mechanical behaviour of DNA encompassing sequence sensitivity and elastic transitions to plastic responses is much better understood.A novel approach is proposed here based on a micromechanical Silicon Nanotweezers device.This instrument allows the detailed biomechanical characterization of a DNA bundle exposed to an ionizing radiation beam delivered here by a therapeutic linear particle accelerator(LINAC).The micromechanical device endures the harsh environment of radiation beams and still retains molecular-level detection accuracy.In this study,the first real-time observation of DNA damage by ionizing radiation is demonstrated.The DNA bundle degradation is detected by the micromechanical device as a reduction of the bundle stiffness,and a theoretical model provides an interpretation of the results.These first real-time observations pave the way for both fundamental and clinical studies of DNA degradation mechanisms under ionizing radiation for improved tumor treatment.展开更多
This article is devoted to the construction of a numerical scheme to solve the equations of radiative hydrodynamics.We use this numerical procedure to compute shock profiles and illustrate some earlier theoretical res...This article is devoted to the construction of a numerical scheme to solve the equations of radiative hydrodynamics.We use this numerical procedure to compute shock profiles and illustrate some earlier theoretical results about their smoothness and monotonicity properties.We first consider a scalar toy model,then we extend our analysis to a more realistic system for the radiative hydrodynamics that couples the Euler equations and an elliptic equation.展开更多
OBJECTIVES: Recently, a novel method to measure strain from standard two-dimensional images has been developed. Our goal was to characterize global and regional systolic function abnormalities using this technique in ...OBJECTIVES: Recently, a novel method to measure strain from standard two-dimensional images has been developed. Our goal was to characterize global and regional systolic function abnormalities using this technique in patients with hypertrophic cardiomyopathy(HCM). BACKGROUND: Strain has been proposed as a sensitive tool to detect early systolic function abnormalities in HCM. However, the clinical application of conventional Doppler-derived strain has been limited by poor reproducibility and angle dependency. METHODS: Echocardiographic examinations were performed in 26 patients with nonobstructive HCM and 45 healthy subjects. Using a dedicated software package, bidimensional acquisitions were analyzed to measure longitudinal and transverse strain in apical views and circumferential and radial strain in parasternal short-axis view. RESULTS: Despite apparently normal left ventricular systolic function, all components of strain were significantly reduced in HCM. Average longitudinal, transverse, circumferential, and radial strain in patients with HCM and controls were -15.1± 6.2% versus -20.3± 5.6% , 23.3± 17.0% versus 27.2± 14.9% ,-16.8± 7.1% versus 19.6± 5.2% , and 25.2± 13.9% versus 36.8± 17.2% , respectively(all p< 0.001). In patients with asymmetrical HCM, longitudinal septal strain was significantly lower than for other left ventricular segments combined:-9.2± 4.7% versus-12.7± 7.1% (p=0.001). Average interobserver and intraobserver variabilities were 11% and 11.3% , respectively. CONCLUSIONS: Two-dimensional strain is a new simple, rapid, and reproducible method to measure different components of systolic strain. This technique identified early abnormalities in patients with HCM that have apparently normal left ventricular systolic function.展开更多
Quantitative coronary angiography(QCA) is routinely performed before valve surgery for severe acquired valvular disease. This technique is relatively invasive, especially in a population with an average risk for signi...Quantitative coronary angiography(QCA) is routinely performed before valve surgery for severe acquired valvular disease. This technique is relatively invasive, especially in a population with an average risk for significant coronary stenosis. Multidetector computed tomography(MDCT) coronary angiography allows the noninvasive evaluation of the coronary anatomy. The aim of this prospective study was to evaluate the predictive values of 16-slice MDCT in the detection of significant coronary stenosis(≥50%) before valve surgery in patients with severe valvular disease without known coronary artery disease and average risk, in comparison with conventional QCA. Forty patients with severe acquired valvular disease(mean age 70±8.6 years; 20 women; 27 with severe aortic stenosis) underwent coronary MDCT 2 days before cardiac catheterization with QCA. The mean heart rate was 64.7±8.8 beats/min(range 41 to 78). Four hundred fifty-eight of 600 coronary artery segments(77.3%) were considered assessable by MDCT. In a per-segment analysis, the sensitivity of MDCT for the detection of significant coronary lesions ≥50%was 77.7%, the specificity was 98%, the positive predictive value was 42.4%, and the negative predictive value was 99%. The main cause of false-positive or false-negative results or nonassessable evaluations was severe coronary calcification. In a per-patient analysis, in comparison with QCA, MDCT correctly classified 33 of 40 patients(82.5%). In conclusion, in patients with an average risk for coronary stenosis before valve surgery, MDCT coronary angiography detected significant obstructive coronary artery disease, with a 99%NPV.展开更多
文摘Drought is the most important factor limiting rice yields in the rainfed areas of Asia. To overcome the problem, we developed a new strategy 'designed QTL pyramiding' to more effi ciently develop drought tolerant (DT)
基金supported in part by the National Science Foundation award numbers DMS-0607721the National Science Foundation award numbers DMS-0300487
文摘For the two-dimensional Navier-Stokes equations of isentropic magnetohydrodynamics （MHD） with γ-law gas equation of state, γ≥ 1, and infinite electrical resistivity, we carry out a global analysis categorizing all possible viscous shock profiles. Precisely, we show that the phase portrait of the traveling-wave ODE generically consists of either two rest points connected by a viscous Lax profile, or else four rest points, two saddles and two nodes. In the latter configuration, which rest points are connected by profiles depends on the ratio of viscosities, and can involve Lax, overcompressive, or undercompressive shock profiles. Considered as three-dimensional solutions, undercompressive shocks axe Lax-type （Alfven） waves. For the monatomic and diatomic cases γ= 5/3 and γ=7/5, with standard viscosity ratio for a nonmagnetic gas, we find numerically that the the nodes are connected by a family of overcompressive profiles bounded by Lax profiles connecting saddles to nodes, with no undercompressive shocks occurring. We carry out a systematic numerical Evans function analysis indicating that all of these two-dimensional shock pro- files are linearly and nonlinearly stable, both with respect to two- and three-dimensional perturbations. For the same gas constants, but different viscosity ratios, we investigate also cases for which undercompressive shocks appear; these are seen numerically to be stable as well, both with respect to two-dimensional and （in the neutral sense of convergence to nearby Riemann solutions） three-dimensional perturbations.
基金G.P.received a Doctoral Scholarship from the Institut National du Cancer and additional financial support provided by CNRS.
文摘The killing of tumor cells by ionizing radiation beams in cancer radiotherapy is currently based on a rather empirical understanding of the basic mechanisms and effectiveness of DNA damage by radiation.By contrast,the mechanical behaviour of DNA encompassing sequence sensitivity and elastic transitions to plastic responses is much better understood.A novel approach is proposed here based on a micromechanical Silicon Nanotweezers device.This instrument allows the detailed biomechanical characterization of a DNA bundle exposed to an ionizing radiation beam delivered here by a therapeutic linear particle accelerator(LINAC).The micromechanical device endures the harsh environment of radiation beams and still retains molecular-level detection accuracy.In this study,the first real-time observation of DNA damage by ionizing radiation is demonstrated.The DNA bundle degradation is detected by the micromechanical device as a reduction of the bundle stiffness,and a theoretical model provides an interpretation of the results.These first real-time observations pave the way for both fundamental and clinical studies of DNA degradation mechanisms under ionizing radiation for improved tumor treatment.
文摘This article is devoted to the construction of a numerical scheme to solve the equations of radiative hydrodynamics.We use this numerical procedure to compute shock profiles and illustrate some earlier theoretical results about their smoothness and monotonicity properties.We first consider a scalar toy model,then we extend our analysis to a more realistic system for the radiative hydrodynamics that couples the Euler equations and an elliptic equation.
文摘OBJECTIVES: Recently, a novel method to measure strain from standard two-dimensional images has been developed. Our goal was to characterize global and regional systolic function abnormalities using this technique in patients with hypertrophic cardiomyopathy(HCM). BACKGROUND: Strain has been proposed as a sensitive tool to detect early systolic function abnormalities in HCM. However, the clinical application of conventional Doppler-derived strain has been limited by poor reproducibility and angle dependency. METHODS: Echocardiographic examinations were performed in 26 patients with nonobstructive HCM and 45 healthy subjects. Using a dedicated software package, bidimensional acquisitions were analyzed to measure longitudinal and transverse strain in apical views and circumferential and radial strain in parasternal short-axis view. RESULTS: Despite apparently normal left ventricular systolic function, all components of strain were significantly reduced in HCM. Average longitudinal, transverse, circumferential, and radial strain in patients with HCM and controls were -15.1± 6.2% versus -20.3± 5.6% , 23.3± 17.0% versus 27.2± 14.9% ,-16.8± 7.1% versus 19.6± 5.2% , and 25.2± 13.9% versus 36.8± 17.2% , respectively(all p< 0.001). In patients with asymmetrical HCM, longitudinal septal strain was significantly lower than for other left ventricular segments combined:-9.2± 4.7% versus-12.7± 7.1% (p=0.001). Average interobserver and intraobserver variabilities were 11% and 11.3% , respectively. CONCLUSIONS: Two-dimensional strain is a new simple, rapid, and reproducible method to measure different components of systolic strain. This technique identified early abnormalities in patients with HCM that have apparently normal left ventricular systolic function.
文摘Quantitative coronary angiography(QCA) is routinely performed before valve surgery for severe acquired valvular disease. This technique is relatively invasive, especially in a population with an average risk for significant coronary stenosis. Multidetector computed tomography(MDCT) coronary angiography allows the noninvasive evaluation of the coronary anatomy. The aim of this prospective study was to evaluate the predictive values of 16-slice MDCT in the detection of significant coronary stenosis(≥50%) before valve surgery in patients with severe valvular disease without known coronary artery disease and average risk, in comparison with conventional QCA. Forty patients with severe acquired valvular disease(mean age 70±8.6 years; 20 women; 27 with severe aortic stenosis) underwent coronary MDCT 2 days before cardiac catheterization with QCA. The mean heart rate was 64.7±8.8 beats/min(range 41 to 78). Four hundred fifty-eight of 600 coronary artery segments(77.3%) were considered assessable by MDCT. In a per-segment analysis, the sensitivity of MDCT for the detection of significant coronary lesions ≥50%was 77.7%, the specificity was 98%, the positive predictive value was 42.4%, and the negative predictive value was 99%. The main cause of false-positive or false-negative results or nonassessable evaluations was severe coronary calcification. In a per-patient analysis, in comparison with QCA, MDCT correctly classified 33 of 40 patients(82.5%). In conclusion, in patients with an average risk for coronary stenosis before valve surgery, MDCT coronary angiography detected significant obstructive coronary artery disease, with a 99%NPV.
