It is important to quantify and analyze forest spatial patterns for studying biological characteristics,population interaction and the relationship between the population and environment.In this study,the forest spati...It is important to quantify and analyze forest spatial patterns for studying biological characteristics,population interaction and the relationship between the population and environment.In this study,the forest spatial structure unit was generated based on the Delaunay triangulation model(DTM),and the weights were generated using the comprehensive values of the tree diameter at breast height,total height and crown width.The distance between neighbors determined by the DTM was weighted to transform the original coordinates of trees into logical coordinates.Then,a weighted spatial pattern(WSP)was developed.After weighting,the neighboring trees were replaced,the replacement ratio was 38.3%,and there was 57.4%of the central tree.Correlation analysis showed that the uniform angle index of the WSP was significantly correlated with the tree size standard deviation under uniformity(r=0.932)and randomness(r=0.711).The DTM method not only considers the spatial distance between trees,but also considers the non-spatial attributes of trees.By changing the spatial topological relation between trees,this method further improves the spatial structure measurement of forest.展开更多
Detection of in vivo biodegradation is critical for development of next-generation medical devices such as bioresorbable stents or scaffolds(BRSs).In particular,it is urgent to establish a nondestructive approach to e...Detection of in vivo biodegradation is critical for development of next-generation medical devices such as bioresorbable stents or scaffolds(BRSs).In particular,it is urgent to establish a nondestructive approach to examine in vivo degradation of a new-generation coronary stent for interventional treatment based on mammal experiments;otherwise it is not available to semi-quantitatively monitor biodegradation in any clinical trial.Herein,we put forward a semi-quantitative approach to measure degradation of a sirolimus-eluting iron bioresorbable scaffold(IBS)based on optical coherence tomography(OCT)images;this approach was confirmed to be consistent with the present weight-loss measurements,which is,however,a destructive approach.The IBS was fabricated by a metal-polymer composite technique with a polylactide coating on an iron stent.The efficacy as a coronary stent of this new bioresorbable scaffold was compared with that of a permanent metal stent with the name of trade mark Xience,which has been widely used in clinic.The endothelial coverage on IBS was found to be greater than on Xience after implantation in a rabbit model;and our well-designed ultrathin stent exhibited less individual variation.We further examined degradation of the IBSs in both minipig coronary artery and rabbit abdominal aorta models.The present result indicated much faster iron degradation of IBS in the rabbit model than in the porcine model.The semi-quantitative approach to detect biodegradation of IBS and the finding of the species difference might be stimulating for fundamental investigation of biodegradable implants and clinical translation of the next-generation coronary stents.展开更多
Fully bioresorbable scaffolds have been designed to overcome the limitations of traditional drug-eluting stents(DESs),which permanently cage the native vessel wall and pose possible complications.The ultrathin-strut d...Fully bioresorbable scaffolds have been designed to overcome the limitations of traditional drug-eluting stents(DESs),which permanently cage the native vessel wall and pose possible complications.The ultrathin-strut designed sirolimus-eluting iron bioresorbable coronary scaffold system(IBS)shows comparable mechanical properties to traditional DESs and exhibits an adaptive degradation profile during target vessel healing,which makes it a promising candidate in all-comers patient population.For implanted medical devices,magnetic resonance(MR)imaging properties,including MR safety and compatibility,should be evaluated before its clinical use,especially for devices with intrinsic ferromagnetism.In this study,MR safety and compatibility of the IBS scaffold were evaluated based on a series of well-designed in-vitro,ex-vivo and in-vivo experiments,considering possible risks,including scaffold movement,over-heating,image artifact,and possible vessel injury,under typical MR condition.Traditional ASTM standards for MR safety and compatibility evaluation of intravascular devices were referred,but not only limited to that.The unique time-relevant MR properties of bioresorbable scaffolds were also discussed.Possible forces imposed on the scaffold during MR scanning and MR image artifacts gradually decreased along with scaffold degradation/absorption.Rigorous experiments designed based on a scientifically based rationale revealed that the IBS scaffold is MR conditional,though not MR compatible before complete absorption.The methodology used in the present study can give insight into the MR evaluation of magnetic scaffolds(bioresorbable)or stents(permanent).展开更多
This study aimed to investigate the long-term biocompatibility, safety, and degradation of the ultrathin nitrided iron bioresorbable scaffold (BRS) in vivo, encompassing the whole process of bioresorption in porcine c...This study aimed to investigate the long-term biocompatibility, safety, and degradation of the ultrathin nitrided iron bioresorbable scaffold (BRS) in vivo, encompassing the whole process of bioresorption in porcine coronary arteries. Fifty-two nitrided iron scaffolds (strut thickness of 70 μm) and 28 Vision Co–Cr stents were randomly implanted into coronary arteries of healthy mini-swine. The efficacy and safety of the nitrided iron scaffold were comparable with those of the Vision stentwithin 52 weeks after implantation. In addition, the long-term biocompatibility, safety, and bioresorption of the nitrided iron scaffold were evaluated by coronary angiog-raphy, optical coherence tomography, micro-computed tomography, scanning electron microscopy, energy dispersive spectrometry and histopathological evaluations at 4, 12, 26, 52 weeks and even at 7 years after im-plantation. In particular, a large number of struts were almost completely absorbed in situ at 7 years follow-up, which were first illustrated in this study. The lymphatic drainage pathway might serve as the potential clearance way of iron and its corrosion products.展开更多
基金funded by National Natural Science Foundation of China(31570627)Hunan Forestry Science and Technology Project(XLK201740)+1 种基金Hunan Science and Technology Innovation Platform and Talent Plan(2017TP1022)Hunan Science and Technology Plan Project(2015WK3017)。
文摘It is important to quantify and analyze forest spatial patterns for studying biological characteristics,population interaction and the relationship between the population and environment.In this study,the forest spatial structure unit was generated based on the Delaunay triangulation model(DTM),and the weights were generated using the comprehensive values of the tree diameter at breast height,total height and crown width.The distance between neighbors determined by the DTM was weighted to transform the original coordinates of trees into logical coordinates.Then,a weighted spatial pattern(WSP)was developed.After weighting,the neighboring trees were replaced,the replacement ratio was 38.3%,and there was 57.4%of the central tree.Correlation analysis showed that the uniform angle index of the WSP was significantly correlated with the tree size standard deviation under uniformity(r=0.932)and randomness(r=0.711).The DTM method not only considers the spatial distance between trees,but also considers the non-spatial attributes of trees.By changing the spatial topological relation between trees,this method further improves the spatial structure measurement of forest.
基金National Key R&D Program of China(grants number 2018YFC1106600 and 2016YFC1100300)Shenzhen Industrial and Information Technology Bureau(20180309174916657)+1 种基金Science,Technology and Innovation Commission of Shenzhen Municipality(grant number GJHZ20180418190517302)The authors thank Dr.Renu Virmani for her expert assistance on endothelialization and histopathology analysis.
文摘Detection of in vivo biodegradation is critical for development of next-generation medical devices such as bioresorbable stents or scaffolds(BRSs).In particular,it is urgent to establish a nondestructive approach to examine in vivo degradation of a new-generation coronary stent for interventional treatment based on mammal experiments;otherwise it is not available to semi-quantitatively monitor biodegradation in any clinical trial.Herein,we put forward a semi-quantitative approach to measure degradation of a sirolimus-eluting iron bioresorbable scaffold(IBS)based on optical coherence tomography(OCT)images;this approach was confirmed to be consistent with the present weight-loss measurements,which is,however,a destructive approach.The IBS was fabricated by a metal-polymer composite technique with a polylactide coating on an iron stent.The efficacy as a coronary stent of this new bioresorbable scaffold was compared with that of a permanent metal stent with the name of trade mark Xience,which has been widely used in clinic.The endothelial coverage on IBS was found to be greater than on Xience after implantation in a rabbit model;and our well-designed ultrathin stent exhibited less individual variation.We further examined degradation of the IBSs in both minipig coronary artery and rabbit abdominal aorta models.The present result indicated much faster iron degradation of IBS in the rabbit model than in the porcine model.The semi-quantitative approach to detect biodegradation of IBS and the finding of the species difference might be stimulating for fundamental investigation of biodegradable implants and clinical translation of the next-generation coronary stents.
基金supported by the National Key Research and Development Program of China(No.2018YFC1106600)the International Cooperation Research Project of Shenzhen No.GJHZ20180418190517302.
文摘Fully bioresorbable scaffolds have been designed to overcome the limitations of traditional drug-eluting stents(DESs),which permanently cage the native vessel wall and pose possible complications.The ultrathin-strut designed sirolimus-eluting iron bioresorbable coronary scaffold system(IBS)shows comparable mechanical properties to traditional DESs and exhibits an adaptive degradation profile during target vessel healing,which makes it a promising candidate in all-comers patient population.For implanted medical devices,magnetic resonance(MR)imaging properties,including MR safety and compatibility,should be evaluated before its clinical use,especially for devices with intrinsic ferromagnetism.In this study,MR safety and compatibility of the IBS scaffold were evaluated based on a series of well-designed in-vitro,ex-vivo and in-vivo experiments,considering possible risks,including scaffold movement,over-heating,image artifact,and possible vessel injury,under typical MR condition.Traditional ASTM standards for MR safety and compatibility evaluation of intravascular devices were referred,but not only limited to that.The unique time-relevant MR properties of bioresorbable scaffolds were also discussed.Possible forces imposed on the scaffold during MR scanning and MR image artifacts gradually decreased along with scaffold degradation/absorption.Rigorous experiments designed based on a scientifically based rationale revealed that the IBS scaffold is MR conditional,though not MR compatible before complete absorption.The methodology used in the present study can give insight into the MR evaluation of magnetic scaffolds(bioresorbable)or stents(permanent).
基金This study was supported by National Key R&D Program of China(grants number 2018YFC1106600)Shenzhen Industrial and Information Technology Bureau(20180309174916657)Science,Technology and Innova-tion Commission of Shenzhen Municipality(grant number GJHZ20180418190517302).
文摘This study aimed to investigate the long-term biocompatibility, safety, and degradation of the ultrathin nitrided iron bioresorbable scaffold (BRS) in vivo, encompassing the whole process of bioresorption in porcine coronary arteries. Fifty-two nitrided iron scaffolds (strut thickness of 70 μm) and 28 Vision Co–Cr stents were randomly implanted into coronary arteries of healthy mini-swine. The efficacy and safety of the nitrided iron scaffold were comparable with those of the Vision stentwithin 52 weeks after implantation. In addition, the long-term biocompatibility, safety, and bioresorption of the nitrided iron scaffold were evaluated by coronary angiog-raphy, optical coherence tomography, micro-computed tomography, scanning electron microscopy, energy dispersive spectrometry and histopathological evaluations at 4, 12, 26, 52 weeks and even at 7 years after im-plantation. In particular, a large number of struts were almost completely absorbed in situ at 7 years follow-up, which were first illustrated in this study. The lymphatic drainage pathway might serve as the potential clearance way of iron and its corrosion products.
