To the Editor: Tetralogy of Fallot (TOF) was first surgically repaired in 1955. Initial TOF repairs were performed using a trans-annular right ventricular outflow tract patch to relieve the obstruction. However, this ...To the Editor: Tetralogy of Fallot (TOF) was first surgically repaired in 1955. Initial TOF repairs were performed using a trans-annular right ventricular outflow tract patch to relieve the obstruction. However, this procedure resulted in long-standing pulmonary valve regurgitation and increased right ventricular (RV) volume, causing arrhythmias and sudden death.[1] Thus, pulmonary annulus preservation became the most prevalent surgical strategy for TOF repair, possibly causing a mix of pulmonary stenosis and pulmonary valve regurgitation. Currently, clinicians concerned with RV function decrease during the long-term follow-up use of cardiac magnetic resonance imaging (CMR) to predict the appropriate timing of interventions for valve sparing. Although CMR techniques have evolved as the reference standard for assessing RV volumes and function during the last two decades, routinely monitoring the progression of repaired tetralogy of Fallot (rTOF) RV dysfunction remains difficult.展开更多
In the fast growing field of scaffold-based tissue engineering, improvement on the mechanical properties of newly formed tissues, e.g. the repaired cartilage, has always been one of the core issues. Studies on the cor...In the fast growing field of scaffold-based tissue engineering, improvement on the mechanical properties of newly formed tissues, e.g. the repaired cartilage, has always been one of the core issues. Studies on the correlations among scaffold composition, in vivo morphological changes of the construct, and the finite deformation behaviors of new tissues （e.g. creep and stress-relaxation, and equilibrium response）, have attracted increasing interests. In this paper, the correlations between the compressive biphasic mechanical properties （i.e., equilibrium elastic modulus E and permeability coefficient k） of 3D printing scaffold （consisting of collagen and fl-tricalcium phosphate） and the proteoglycans （PGs） concentration of the repaired carti- lages after 24 weeks, 36 weeks and 52 weeks of scaffold implantation were investigated. Results indicated that the repaired cartilage covered the entire cartilage surface of large cylindrical osteochondral defects （10 mm in diameter ~ 15 mm in depth） on the canine trochlea grooves after 24 weeks. The equilibrium elastic modulus of the repaired cartilage reached 22.4% at 24 weeks, 70.3% at 36 weeks, and 93.4% at 52 weeks of the native cartilage, respectively. Meanwhile, the permeability coefficient decreased with time and at 52 weeks was still inferior to that of the native cartilage in one order of magnitude. In addition, the amount of glycosaminoglycans （GAGs） of repaired cartilage increased constantly with time, which at 52 weeks approached to nearly 60% of that of native cartilage. 3D printed scaffolds have potential applications in repairing large-scale cartilage defects.展开更多
One of the main factors of laser induced damage is the modulation to incident laser which is caused by the defect in the subsurface of the fused silica. In this work, the repaired damage site irradiated by CO2 laser i...One of the main factors of laser induced damage is the modulation to incident laser which is caused by the defect in the subsurface of the fused silica. In this work, the repaired damage site irradiated by CO2 laser is simplified to a Gaussian rotation according to the corresponding experimental results. Then, the three-dimensional finite-difference time-domain method is employed to simulate the electric field intensity distribution in the vicinity of this kind of defect in fused silica front subsurface. The simulated results show that the modulation is notable, the Emax is about 2.6 times the irradiated electric field intensity in the fused silica with the damage site （the width is 1.5 μm and depth is 2.3 μm） though the damage site is repaired by CO2 laser. The phenomenon and the theoretical result of the annular laser enhancement existed on the rear surface are first verified effectively, which agrees well with the corresponding experimental results. The relations between the maximal electric field intensity in fused silica with defect depth and width are given respectively. Meanwhile, the corresponding physical mechanism is analysed theoretically in detail.展开更多
The threat of cascading damage to downstream components caused by the light modulation intensification of laser repaired morphology on the surface of fused silica optics cannot be ignored in high-power laser systems.T...The threat of cascading damage to downstream components caused by the light modulation intensification of laser repaired morphology on the surface of fused silica optics cannot be ignored in high-power laser systems.This paper uses the angular spectrum diffraction theory based on the analysis of repaired surface morphology of CO_(2)laser rapid ablation mitigation to study the influence of different repaired morphologies on the downstream 355 nm laser transmission.Studies show that the arc-shaped laser processing lines on the repaired surface are formed by the residual height superposition of the material after laser scanning of two adjacent layers,and the short-pulse laser can substantially suppress the heat-affected zone of the repaired area.The offaxis ring caustic and on-axis hotspot are sequentially generated in the downstream modulated light fields of the conical repaired sites with different diameters.A secondary peak with modulation larger than 3 emerges downstream of the modulation curve.Meanwhile,the maximum modulation and the secondary peak increase with the diameter and cone angle of the repaired site,and the position of the secondary peak appears farther away from the rear surface.The modulations of three repaired sites with cone angles of 15°,20°,and 25°can finally be stabilized below 3.Overall,the downstream optics should be installed far away from the positions where the maximum modulation and the secondary peak emerge.Additionally,the maximum value and the secondary peak of the downstream light modulation of double repaired sites are larger than that of the single repaired site,and both rise as the repaired sizes increase.Thus,large-scale and large-size repairing of multiple surface damages in the same area should be avoided in the laser repairing of fused silica.展开更多
The mechanical properties of 316L stainless steel repaired with Fe314 under different temperatures and humidities without inert gas protection were studied. Results indicated favorable compatibility between Fe314 and ...The mechanical properties of 316L stainless steel repaired with Fe314 under different temperatures and humidities without inert gas protection were studied. Results indicated favorable compatibility between Fe314 and 316L stainless steel. The average yield strength, tensile strength, and sectional contraction percentage were higher in repaired samples than in 316L stainless steel, whereas the elongation rate was slightly lower. The different conditions of humiture environment on the repair sample exerted minimal influence on tensile and yield strengths. The Fe314 cladding layer was mainly composed of equiaxed grains and mixed with randomly oriented columnar crystal and tiny pores or impurities in the tissue. Results indicated that the hardness value of Fe314 cladding layer under different humiture environments ranged within 419-451.1 HVo.2. The field humimre environment also showed minimal impact on the average hardness of Fe314 cladding layers. Furthermore, 316L stainless steel can be repaired through laser cladding by using Fe314 powder without inert gas protection under different temperatures and humidity environments.展开更多
KH2PO4 （KDP） crystal with excellent optical properties is a very important element of inertial confinement fusion （ICF） device. However, KDP crystal surface micro-defects severely reduce the crystal laser damage t...KH2PO4 （KDP） crystal with excellent optical properties is a very important element of inertial confinement fusion （ICF） device. However, KDP crystal surface micro-defects severely reduce the crystal laser damage threshold, affecting the crystal service life. In this paper, Gaussian repaired pit is used to replace the crystal surface micro-defects, in order to improve the laser damage resistance of the KDP crystal with surface micro-defects. At first, the physical model of Gaussian repaired pit is built by Fourier model method, and the accuracy of the method is analyzed. It is found that the calculation error can be reduced by increasing the product of the width-period ratio and the truncation constant of the repaired pit. The calculation results about the physical model of Gaussian repaired pit show that the light intensity distribution within the crystal is symmetrical, and there are evidently enhanced light intensity regions in the crystal. Meanwhile, the maximum relative intensity inside the KDP crystal decreases gradually with the increase of the width of the Gaussian repaired pit. Secondly, the Gaussian repaired pits with different widths and the same depth of 20 μm are processed by micro-milling. Their surfaces are very smooth and present the ductile cutting state under the microscope. Finally, the laser damage threshold of the Gaussian repaired pits on the surface of the KDP crystal sample is measured by a 3 ω, 6-ns laser. The results showthat the maximum threshold of the Gaussian repaired pits is 3.12 J/cm2, which is 60% higher than the threshold of initial damage point, and the laser damage threshold increases with the increase of the width of the Gaussian repaired pit.展开更多
CO2 laser rapid ablation mitigation(RAM)of fused silica has been used in high-power laser systems owing to its advantages of high efficiency,and ease of implementing batch and automated repairing.In order to study the...CO2 laser rapid ablation mitigation(RAM)of fused silica has been used in high-power laser systems owing to its advantages of high efficiency,and ease of implementing batch and automated repairing.In order to study the effect of repaired morphology of RAM on laser modulation and to improve laser damage threshold of optics,an finite element method(FEM)mathematical model of 351 nm laser irradiating fused silica optics is developed based on Maxwell electromagnetic field equations,to explore the 3D near-field light intensity distribution inside optics with repaired site on its surface.The influences of the cone angle and the size of the repaired site on incident laser modulation are studied as well.The results have shown that for the repaired site with a cone angle of 73.3°,the light intensity distribution has obvious three-dimensional characteristics.The relative light intensity on z-section has a circularly distribution,and the radius of the annular intensification zone increases with the decrease of z.While the distribution of maximum relative light intensity on y-section is parabolical with the increase of y.As the cone angle of the repaired site decreases,the effect of the repaired surface on light modulation becomes stronger,leading to a weak resistance to laser damage.Moreover,the large size repaired site would also reduce the laser damage threshold.Therefore,a repaired site with a larger cone angle and smaller size is preferred in practical CO2 laser repairing of surface damage.This work will provide theoretical guidance for the design of repaired surface topography,as well as the improvement of RAM process.展开更多
Appropriate heart rate in a failing pulmonary ventricle remains unknown, particularly in congenital heart diseasewith unique hemodynamics. A 71-year-old male with repaired tetralogy of Fallot and a pacemaker for a sin...Appropriate heart rate in a failing pulmonary ventricle remains unknown, particularly in congenital heart diseasewith unique hemodynamics. A 71-year-old male with repaired tetralogy of Fallot and a pacemaker for a sinusnode dysfunction suffered from heart failure symptoms with preserved left ventricular function. Simply changingthe pacemaker’s lower rate from 60 to 75 bpm, New York Heart Association classification improved from III to II,and hemodynamic parameters drastically improved. We regarded this case as informative. Appropriate heart ratecould be higher in congenital patients with failing right and non-failing left ventricles than in adults with malfunctioningLV.展开更多
文摘To the Editor: Tetralogy of Fallot (TOF) was first surgically repaired in 1955. Initial TOF repairs were performed using a trans-annular right ventricular outflow tract patch to relieve the obstruction. However, this procedure resulted in long-standing pulmonary valve regurgitation and increased right ventricular (RV) volume, causing arrhythmias and sudden death.[1] Thus, pulmonary annulus preservation became the most prevalent surgical strategy for TOF repair, possibly causing a mix of pulmonary stenosis and pulmonary valve regurgitation. Currently, clinicians concerned with RV function decrease during the long-term follow-up use of cardiac magnetic resonance imaging (CMR) to predict the appropriate timing of interventions for valve sparing. Although CMR techniques have evolved as the reference standard for assessing RV volumes and function during the last two decades, routinely monitoring the progression of repaired tetralogy of Fallot (rTOF) RV dysfunction remains difficult.
基金This work was supported by grants from the Native Science Foundation of China （Nos. 51323007, 51375371 and 51075320）, the National High Technology Research and Development Program of China （No. 2015AA020303） and the Fundamental Research Funds for the Central Universities. The authors would like to acknowledge the contributions of Dichen Li, Manyi Wang, Yongmei Chen and Yusheng Qiu of Xi＇an Jiaotong University.
文摘In the fast growing field of scaffold-based tissue engineering, improvement on the mechanical properties of newly formed tissues, e.g. the repaired cartilage, has always been one of the core issues. Studies on the correlations among scaffold composition, in vivo morphological changes of the construct, and the finite deformation behaviors of new tissues （e.g. creep and stress-relaxation, and equilibrium response）, have attracted increasing interests. In this paper, the correlations between the compressive biphasic mechanical properties （i.e., equilibrium elastic modulus E and permeability coefficient k） of 3D printing scaffold （consisting of collagen and fl-tricalcium phosphate） and the proteoglycans （PGs） concentration of the repaired carti- lages after 24 weeks, 36 weeks and 52 weeks of scaffold implantation were investigated. Results indicated that the repaired cartilage covered the entire cartilage surface of large cylindrical osteochondral defects （10 mm in diameter ~ 15 mm in depth） on the canine trochlea grooves after 24 weeks. The equilibrium elastic modulus of the repaired cartilage reached 22.4% at 24 weeks, 70.3% at 36 weeks, and 93.4% at 52 weeks of the native cartilage, respectively. Meanwhile, the permeability coefficient decreased with time and at 52 weeks was still inferior to that of the native cartilage in one order of magnitude. In addition, the amount of glycosaminoglycans （GAGs） of repaired cartilage increased constantly with time, which at 52 weeks approached to nearly 60% of that of native cartilage. 3D printed scaffolds have potential applications in repairing large-scale cartilage defects.
基金Project supported by the National High Technology Research and Development Program of China (Grant No.2008AA8040508)the Youth Foundation of University of Science and Technology of China (Grant Nos.L08010401JX0834 and L08010401JX0806)the Fundamental Research Funds for the Central Universities of China
文摘One of the main factors of laser induced damage is the modulation to incident laser which is caused by the defect in the subsurface of the fused silica. In this work, the repaired damage site irradiated by CO2 laser is simplified to a Gaussian rotation according to the corresponding experimental results. Then, the three-dimensional finite-difference time-domain method is employed to simulate the electric field intensity distribution in the vicinity of this kind of defect in fused silica front subsurface. The simulated results show that the modulation is notable, the Emax is about 2.6 times the irradiated electric field intensity in the fused silica with the damage site （the width is 1.5 μm and depth is 2.3 μm） though the damage site is repaired by CO2 laser. The phenomenon and the theoretical result of the annular laser enhancement existed on the rear surface are first verified effectively, which agrees well with the corresponding experimental results. The relations between the maximal electric field intensity in fused silica with defect depth and width are given respectively. Meanwhile, the corresponding physical mechanism is analysed theoretically in detail.
基金supported by the National Natural Science Foundation of China(Grant Nos.51775147 and 52175389)the Consolidation Program for Fundamental Research(Grant No.2019JCJQZDXX00)+6 种基金the Science Challenge Project(Grant No.TZ2016006-0503-01)the Young Elite Scientists Sponsorship Program by CAST(Grant No.2018QNRC001)the Natural Science Foundation of Heilongjiang Province(Grant No.YQ2021E021)the China Postdoctoral Science Foundation(Grant No.2018T110288)the Self-Planned Task of State Key Laboratory of Robotics and System(HIT)of China(Grant Nos.SKLRS201718A and SKLRS201803B)the Science and Technology Research Program of Chongqing Municipal Education Commission(Grant No.KJQN201800623)the China Scholarship Council(Grant No.202006120158)。
文摘The threat of cascading damage to downstream components caused by the light modulation intensification of laser repaired morphology on the surface of fused silica optics cannot be ignored in high-power laser systems.This paper uses the angular spectrum diffraction theory based on the analysis of repaired surface morphology of CO_(2)laser rapid ablation mitigation to study the influence of different repaired morphologies on the downstream 355 nm laser transmission.Studies show that the arc-shaped laser processing lines on the repaired surface are formed by the residual height superposition of the material after laser scanning of two adjacent layers,and the short-pulse laser can substantially suppress the heat-affected zone of the repaired area.The offaxis ring caustic and on-axis hotspot are sequentially generated in the downstream modulated light fields of the conical repaired sites with different diameters.A secondary peak with modulation larger than 3 emerges downstream of the modulation curve.Meanwhile,the maximum modulation and the secondary peak increase with the diameter and cone angle of the repaired site,and the position of the secondary peak appears farther away from the rear surface.The modulations of three repaired sites with cone angles of 15°,20°,and 25°can finally be stabilized below 3.Overall,the downstream optics should be installed far away from the positions where the maximum modulation and the secondary peak emerge.Additionally,the maximum value and the secondary peak of the downstream light modulation of double repaired sites are larger than that of the single repaired site,and both rise as the repaired sizes increase.Thus,large-scale and large-size repairing of multiple surface damages in the same area should be avoided in the laser repairing of fused silica.
文摘The mechanical properties of 316L stainless steel repaired with Fe314 under different temperatures and humidities without inert gas protection were studied. Results indicated favorable compatibility between Fe314 and 316L stainless steel. The average yield strength, tensile strength, and sectional contraction percentage were higher in repaired samples than in 316L stainless steel, whereas the elongation rate was slightly lower. The different conditions of humiture environment on the repair sample exerted minimal influence on tensile and yield strengths. The Fe314 cladding layer was mainly composed of equiaxed grains and mixed with randomly oriented columnar crystal and tiny pores or impurities in the tissue. Results indicated that the hardness value of Fe314 cladding layer under different humiture environments ranged within 419-451.1 HVo.2. The field humimre environment also showed minimal impact on the average hardness of Fe314 cladding layers. Furthermore, 316L stainless steel can be repaired through laser cladding by using Fe314 powder without inert gas protection under different temperatures and humidity environments.
基金Project support by the National Natural Science Foundation of China(Grant No.51275113)the National Science and Technology Major Project of China(Grant No.2013ZX04006011-215)
文摘KH2PO4 （KDP） crystal with excellent optical properties is a very important element of inertial confinement fusion （ICF） device. However, KDP crystal surface micro-defects severely reduce the crystal laser damage threshold, affecting the crystal service life. In this paper, Gaussian repaired pit is used to replace the crystal surface micro-defects, in order to improve the laser damage resistance of the KDP crystal with surface micro-defects. At first, the physical model of Gaussian repaired pit is built by Fourier model method, and the accuracy of the method is analyzed. It is found that the calculation error can be reduced by increasing the product of the width-period ratio and the truncation constant of the repaired pit. The calculation results about the physical model of Gaussian repaired pit show that the light intensity distribution within the crystal is symmetrical, and there are evidently enhanced light intensity regions in the crystal. Meanwhile, the maximum relative intensity inside the KDP crystal decreases gradually with the increase of the width of the Gaussian repaired pit. Secondly, the Gaussian repaired pits with different widths and the same depth of 20 μm are processed by micro-milling. Their surfaces are very smooth and present the ductile cutting state under the microscope. Finally, the laser damage threshold of the Gaussian repaired pits on the surface of the KDP crystal sample is measured by a 3 ω, 6-ns laser. The results showthat the maximum threshold of the Gaussian repaired pits is 3.12 J/cm2, which is 60% higher than the threshold of initial damage point, and the laser damage threshold increases with the increase of the width of the Gaussian repaired pit.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51775147 and 51705105)the Science Challenge Project of China(Grant No.TZ2016006-0503-01)+2 种基金the Young Elite Scientists Sponsorship Program by CAST(Grant No.2018QNRC001)the China Postdoctoral Science Foundation funded project(Grant Nos.2018T110288 and 2017M621260)the Self-Planned Task of State Key Laboratory of Robotics and System(HIT)(Grant Nos.SKLRS201718A and SKLRS201803B).
文摘CO2 laser rapid ablation mitigation(RAM)of fused silica has been used in high-power laser systems owing to its advantages of high efficiency,and ease of implementing batch and automated repairing.In order to study the effect of repaired morphology of RAM on laser modulation and to improve laser damage threshold of optics,an finite element method(FEM)mathematical model of 351 nm laser irradiating fused silica optics is developed based on Maxwell electromagnetic field equations,to explore the 3D near-field light intensity distribution inside optics with repaired site on its surface.The influences of the cone angle and the size of the repaired site on incident laser modulation are studied as well.The results have shown that for the repaired site with a cone angle of 73.3°,the light intensity distribution has obvious three-dimensional characteristics.The relative light intensity on z-section has a circularly distribution,and the radius of the annular intensification zone increases with the decrease of z.While the distribution of maximum relative light intensity on y-section is parabolical with the increase of y.As the cone angle of the repaired site decreases,the effect of the repaired surface on light modulation becomes stronger,leading to a weak resistance to laser damage.Moreover,the large size repaired site would also reduce the laser damage threshold.Therefore,a repaired site with a larger cone angle and smaller size is preferred in practical CO2 laser repairing of surface damage.This work will provide theoretical guidance for the design of repaired surface topography,as well as the improvement of RAM process.
文摘Appropriate heart rate in a failing pulmonary ventricle remains unknown, particularly in congenital heart diseasewith unique hemodynamics. A 71-year-old male with repaired tetralogy of Fallot and a pacemaker for a sinusnode dysfunction suffered from heart failure symptoms with preserved left ventricular function. Simply changingthe pacemaker’s lower rate from 60 to 75 bpm, New York Heart Association classification improved from III to II,and hemodynamic parameters drastically improved. We regarded this case as informative. Appropriate heart ratecould be higher in congenital patients with failing right and non-failing left ventricles than in adults with malfunctioningLV.
