The formation of nerve bundles,which is partially regulated by neural cell adhesion molecule 1(NCAM1),is important for neural network organization during peripheral nerve regeneration.However,little is known about how...The formation of nerve bundles,which is partially regulated by neural cell adhesion molecule 1(NCAM1),is important for neural network organization during peripheral nerve regeneration.However,little is known about how the extracellular matrix(ECM)microenvironment affects this process.Here,we seeded dorsal root ganglion tissue blocks on different ECM substrates of peripheral nerve ECM-derived matrixgel,Matrigel,laminin 521,collagen I,and collagen IV,and observed well-aligned axon bundles growing in the peripheral nerve ECM-derived environment.We confirmed that NCAM1 is necessary but not sufficient to trigger this phenomenon.A protein interaction assay identified collagen VI as an extracellular partner of NCAM1 in the regulation of axonal fasciculation.Collagen VI interacted with NCAM1 by directly binding to the FNIII domain,thereby increasing the stability of NCAM1 at the axolemma.Our in vivo experiments on a rat sciatic nerve defect model also demonstrated orderly nerve bundle regeneration with improved projection accuracy and functional recovery after treatment with 10 mg/m L Matrigel and 20μg/m L collagen VI.These findings suggest that the collagen VI-NCAM1 pathway plays a regulatory role in nerve bundle formation.This study was approved by the Animal Ethics Committee of Guangzhou Medical University(approval No.GY2019048)on April 30,2019.展开更多
A 3D motion and geometric information system of single-antenna radar is proposed,which can be supported by spotlight synthetic aperture radar（SAR） system and inverse SAR（ISAR） system involving relative 3D motion o...A 3D motion and geometric information system of single-antenna radar is proposed,which can be supported by spotlight synthetic aperture radar（SAR） system and inverse SAR（ISAR） system involving relative 3D motion of the rigid target.In this system,applying the geometry invariance of the rigid target,the unknown 3D shape and motion of the radar target can be reconstructed from the 1D range data of some scatterers extracted from the high-resolution range image.Compared with the current 1D-to-3D algorithm,in the proposed algorithm,the requirement of the 1D range data is expanded to incomplete formation involving large angular motion of the target and hence,the quantity of the scatterers and the abundance of 3D motion are enriched.Furthermore,with the three selected affine coordinates fixed,the multi-solution problem of the reconstruction is solved and the technique of nonlinear optimization can be successfully utilized in the system.Two simulations are implemented which verify the higher robustness of the system and the better performance of the 3D reconstruction for the radar target with unknown relative motion.展开更多
Segal’s chronometric theory is based on a space-time D, which might be viewed as a Lie group with a causal structure defined by an invariant Lorentzian form on the Lie algebra u(2). Similarly, the space-time F is rea...Segal’s chronometric theory is based on a space-time D, which might be viewed as a Lie group with a causal structure defined by an invariant Lorentzian form on the Lie algebra u(2). Similarly, the space-time F is realized as the Lie group with a causal structure defined by an invariant Lorentzian form on u(1,1). Two Lie groups G, GF are introduced as representations of SU(2,2): they are related via conjugation by a certain matrix Win Gl(4). The linear-fractional action of G on D is well-known to be global, conformal, and it plays a crucial role in the analysis on space-time bundles carried out by Paneitz and Segal in the 1980’s. This analysis was based on the parallelizing group U(2). In the paper, singularities’ general (“geometric”) description of the linear-fractional conformal GF-action on F is given and specific examples are presented. The results call for the analysis of space-time bundles based on U(1,1) as the parallelizing group. Certain key stages of such an analysis are suggested.展开更多
基金supported by the National Natural Science Foundation of China,No.31800892(to JLZ)the Natural Science Foundation of Guangdong Province of China,No.2018A030310254(to YY)a grant from Guangzhou Medical University Start-up Project of China,No.B195002002048(to JLZ)。
文摘The formation of nerve bundles,which is partially regulated by neural cell adhesion molecule 1(NCAM1),is important for neural network organization during peripheral nerve regeneration.However,little is known about how the extracellular matrix(ECM)microenvironment affects this process.Here,we seeded dorsal root ganglion tissue blocks on different ECM substrates of peripheral nerve ECM-derived matrixgel,Matrigel,laminin 521,collagen I,and collagen IV,and observed well-aligned axon bundles growing in the peripheral nerve ECM-derived environment.We confirmed that NCAM1 is necessary but not sufficient to trigger this phenomenon.A protein interaction assay identified collagen VI as an extracellular partner of NCAM1 in the regulation of axonal fasciculation.Collagen VI interacted with NCAM1 by directly binding to the FNIII domain,thereby increasing the stability of NCAM1 at the axolemma.Our in vivo experiments on a rat sciatic nerve defect model also demonstrated orderly nerve bundle regeneration with improved projection accuracy and functional recovery after treatment with 10 mg/m L Matrigel and 20μg/m L collagen VI.These findings suggest that the collagen VI-NCAM1 pathway plays a regulatory role in nerve bundle formation.This study was approved by the Animal Ethics Committee of Guangzhou Medical University(approval No.GY2019048)on April 30,2019.
基金supported by the National Natural Science Foundation of China (60572093)the Doctoral Program of Higher Education(20050004016)the Outstanding Doctoral Science Innovation Foundation of Beijing Jiaotong University (141095522)
文摘A 3D motion and geometric information system of single-antenna radar is proposed,which can be supported by spotlight synthetic aperture radar（SAR） system and inverse SAR（ISAR） system involving relative 3D motion of the rigid target.In this system,applying the geometry invariance of the rigid target,the unknown 3D shape and motion of the radar target can be reconstructed from the 1D range data of some scatterers extracted from the high-resolution range image.Compared with the current 1D-to-3D algorithm,in the proposed algorithm,the requirement of the 1D range data is expanded to incomplete formation involving large angular motion of the target and hence,the quantity of the scatterers and the abundance of 3D motion are enriched.Furthermore,with the three selected affine coordinates fixed,the multi-solution problem of the reconstruction is solved and the technique of nonlinear optimization can be successfully utilized in the system.Two simulations are implemented which verify the higher robustness of the system and the better performance of the 3D reconstruction for the radar target with unknown relative motion.
文摘Segal’s chronometric theory is based on a space-time D, which might be viewed as a Lie group with a causal structure defined by an invariant Lorentzian form on the Lie algebra u(2). Similarly, the space-time F is realized as the Lie group with a causal structure defined by an invariant Lorentzian form on u(1,1). Two Lie groups G, GF are introduced as representations of SU(2,2): they are related via conjugation by a certain matrix Win Gl(4). The linear-fractional action of G on D is well-known to be global, conformal, and it plays a crucial role in the analysis on space-time bundles carried out by Paneitz and Segal in the 1980’s. This analysis was based on the parallelizing group U(2). In the paper, singularities’ general (“geometric”) description of the linear-fractional conformal GF-action on F is given and specific examples are presented. The results call for the analysis of space-time bundles based on U(1,1) as the parallelizing group. Certain key stages of such an analysis are suggested.
文摘国产高空间分辨率卫星影像的几何定位精度一直是人们关注的热点问题。以GF-1和ZY-3卫星影像为研究对象,在分析检验有理多项式参数(rational polynomial coefficients,RPCs)存在的系统误差后,采用基于像面仿射变换的有理函数模型(rational function model,RFM)区域网平差方法消除单颗卫星立体影像对的定位系统误差;全面分析并评价了影像的几何定位精度,包括单景影像的定位精度、单颗卫星立体影像对的定位精度以及多星联合的定位精度;初步探讨了影响国产高空间分辨率卫星影像几何定位精度的主要因素,为实现国产卫星联合高精度对地观测提供参考。
