NATURALLY REDUCTIVE(α_(1),α_(2))METRICS

Letting F be a homogeneous(α_(1),α_(2))metric on the reductive homogeneous manifold G/H,we first characterize the natural reductiveness of F as a local f-product between naturally reductive Riemannian metrics.Second,we prove the equivalence among several properties of F for its mean Berwald curvature and S-curvature.Finally,we find an explicit flag curvature formula for G/H when F is naturally reductive.

双旋弹道修正弹弹体非对称载荷的数值研究

固定鸭舵双旋弹道修正弹的弹体受到鸭舵非对称尾流的影响,其载荷具有非对称特性。为了研究该非对称特性,通过计算流体力学(CFD)仿真和风洞实验的结果对比验证CFD方法的有效性。对0°舵偏、2°舵偏、4°舵偏的双旋弹道修正弹模型在多马赫数、多攻角下进行CFD仿真,并通过绘制鸭舵尾流的流线图和弹体压力系数云图对流场进行定性分析,通过对比弹体截面压力系数和弹体法向力、侧向力系数对弹体受力的非对称性进行定量分析。结果表明:0°舵偏模型的弹体压力系数呈面对称,2°舵偏模型、4°舵偏模型弹体压力系数呈非对称;在给定马赫数下,3种模型弹体法向力系数随攻角变化的曲线高度重合; 0°舵偏模型的弹体侧向力系数在0附近,2°舵偏模型、4°舵偏模型的弹体侧向力随攻角近似线性变化,随马赫数先增大、后减小;给定攻角时,4°舵偏模型对应曲线峰值约为2°舵偏模型的2倍。

基于地磁辅助的弹载两轴陀螺传感器校正方法研究

为解决弹载环境下两轴陀螺传感器难以实现三轴校正的问题,提出基于地磁辅助的两轴陀螺传感器校正方法。建立两轴陀螺传感器测量误差模型,由单轴地磁信号解算得到弹丸x轴角速率,解决了因陀螺传感器量程限制而无法测量低旋弹丸x轴滚转角速率的问题;研究线性最小二乘模型和卡尔曼滤波模型校正两轴陀螺传感器相关参数的方法,数值仿真分析弹丸x轴角速率解算误差和陀螺传感器测量噪声对校正结果的影响;半实物仿真模拟两轴陀螺传感器在工程中的应用,研究基于地磁辅助的两轴陀螺传感器校正方法校正效果。数值仿真结果表明:当弹丸x轴角速率解算误差在0. 261 8 rad/s以内且当陀螺传感器测量噪声在0. 001 6 rad/s以内时,经过校正后,弹丸y轴和z轴角速率校正误差在0. 01 rad/s以内。半实物仿真结果表明:当弹丸x轴角速率解算误差在0. 8 rad/s以内时,两种校正模型均能将陀螺传感器的测量误差从-0. 30～-0. 05 rad/s范围减小到-0. 02～0. 02 rad/s范围内。数值仿真和半实物仿真结果证明:基于地磁辅助的两轴陀螺传感器校正方法具有较好的校正效果。

The symmetric space,strong isotropy irreducibility and equigeodesic properties

A smooth curve on a homogeneous manifold G/H is called a Riemannian equigeodesic if it is a homogeneous geodesic for any G-invariant Riemannian metric.The homogeneous manifold G/H is called Riemannian equigeodesic,if for any x∈G/H and any nonzero y∈Tx(G/H),there exists a Riemannian equigeodesic c(t) with c(0)=x and ■(0)=y.These two notions can be naturally transferred to the Finsler setting,which provides the definitions for Finsler equigeodesics and Finsler equigeodesic spaces.We prove two classification theorems for Riemannian equigeodesic spaces and Finsler equigeodesic spaces,respectively.Firstly,a homogeneous manifold G/H with a connected simply connected quasi compact G and a connected H is Riemannian equigeodesic if and only if it can be decomposed as a product of Euclidean factors and compact strongly isotropy irreducible factors.Secondly,a homogeneous manifold G/H with a compact semisimple G is Finsler equigeodesic if and only if it can be locally decomposed as a product,in which each factor is Spin(7)/G2,G2/SU (3) or a symmetric space of compact type.These results imply that the symmetric space and the strongly isotropy irreducible space of compact type can be interpreted by equigeodesic properties.As an application,we classify the homogeneous manifold G/H with a compact semisimple G such that all the G-invariant Finsler metrics on G/H are Berwald.It suggests a new project in homogeneous Finsler geometry,i.e.,to systematically study the homogeneous manifold G/H on which all the G-invariant Finsler metrics satisfy a certain geometric property.

Isoparametric Hypersurfaces Induced by Navigation in Lorentz Finsler Geometry

Using a navigation process with the datum(F,V),in which F is a Finsler metric and the smooth tangent vector field V satisfies F(−V(x))>1 everywhere,a Lorentz Finsler metric F˜can be induced.Isoparametric functions and isoparametric hypersurfaces with or without involving a smooth measure can be defined for F˜.When the vector field V in the navigation datum is homothetic,we prove the local correspondences between isoparametric functions and isoparametric hypersurfaces before and after this navigation process.Using these correspondences,we provide some examples of isoparametric functions and isoparametric hypersurfaces on a Funk space of Lorentz Randers type.

Left-Invariant Minimal Unit Vector Fields on the Solvable Lie Group

Bozek(1980)has introduced a class of solvable Lie groups Gn with arbitrary odd dimension to construct irreducible generalized symmetric Riemannian space such that the identity component of its full isometry group is solvable.In this article,the authors provide the set of all left-invariant minimal unit vector fields on the solvable Lie group Gn,and give the relationships between the minimal unit vector fields and the geodesic vector fields,the strongly normal unit vectors respectively.

Preclinical evaluation of the safety and effectiveness of a new bioartificial cornea

Cross-linking agents are frequently used to restore corneal properties after decellularization,and it is especially important to select an appropriate method to avoid excessive cross-linking.In addition,how to promote wound healing and how to improve scar formation require further investigation.To ensure the safety and efficacy of animal-derived products,we designed bioartificial corneas(BACs)according to the criteria for Class III medical devices.Our BACs do not require cross-linking agents and increase mechanical strength via self-cross-linking of aldehyde-modified hyaluronic acid(AHA)and carboxymethyl chitosan(CMC)on the surface of decellularized porcine corneas(DPCs).The results showed that the BACs had good biocompatibility and transparency,and the modification enhanced their antibacterial and anti-inflammatory properties in vitro.Preclinical animal studies showed that the BACs can rapidly regenerate the epithelium and restore vision within a month.After 3 months,the BACs were gradually filled with epithelial,stromal,and neuronal cells,and after 6 months,their transparency and histology were almost normal.In addition,side effects such as corneal neovascularization,conjunctival hyperemia,and ciliary body hyperemia rarely occur in vivo.Therefore,these BACs show promise for clinical application for the treatment of infectious corneal ulcers and as a temporary covering for corneal perforations to achieve the more time.

Engineering hiPSC-CM and hiPSC-EC laden 3D nanofibrous splenic hydrogel for improving cardiac function through revascularization and remuscularization in infarcted heart

Cell therapy has been a promising strategy for cardiac repair after myocardial infarction(MI),but a poor ischemic environment and low cell delivery efficiency remain significant challenges.The spleen serves as a hematopoietic stem cell niche and secretes cardioprotective factors after MI,but it is unclear whether it could be used for human pluripotent stem cell(hiPSC)cultivation and provide a proper microenvironment for cell grafts against the ischemic environment.Herein,we developed a splenic extracellular matrix derived thermoresponsive hydrogel(SpGel).Proteomics analysis indicated that SpGel is enriched with proteins known to modulate the Wnt signaling pathway,cell-substrate adhesion,cardiac muscle contraction and oxidation-reduction processes.In vitro studies demonstrated that hiPSCs could be efficiently induced into endothelial cells(iECs)and cardiomyocytes(iCMs)with enhanced function on SpGel.The cytoprotective effect of SpGel on iECs/iCMs against oxidative stress damage was also proven.Furthermore,in vivo studies revealed that iEC/iCM-laden SpGel improved cardiac function and inhibited cardiac fibrosis of infarcted hearts by improving cell survival,revascularization and remuscularization.In conclusion,we successfully established a novel platform for the efficient generation and delivery of autologous cell grafts,which could be a promising clinical therapeutic strategy for cardiac repair and regeneration after MI.

Programming of Regulatory T Cells In Situ for Nerve Regeneration and Long-Term Patency of Vascular Grafts

Rapid integration into the host tissue is critical for long-term patency after small diameter tissue engineering vascular grafts(sdTEVGs)transplantation.Neural recognition may be required for host integration and functionalization of the graft.However,immune rejection and inflammation hinder nerve regeneration of sdTEVGs.Here,a CRISPR/dCas9-nanocarrier was used for targeted programming of regulatory T cells(Treg cells)in situ to promote nerve regeneration of sdTEVGs by preventing excessive inflammation.Treg cells and(C-C chemokine receptor)CCR2+macrophage recruitment occurred after transplantation.The nanodelivery system upregulated ten eleven translocation(TET2)in Treg cells in vitro.Reprogrammed Treg cells upregulated anti-inflammatory cytokines and decreased the proportion of CCR2+macrophages.IL-6 concentrations decreased to the levels required for nerve regeneration.Implantation of CRISPR/dCas9 nanodelivery system-modified sdTEVGs in rats resulted in Treg cell editing,control of excessive inflammation,and promoted nerve regeneration.After 3 months,nerve regeneration was similar to that observed in normal blood vessels;good immune homeostasis,consistency of hemodynamics,and matrix regeneration were observed.Neural recognition promotes further integration of the graft into the host,with unobstructed blood vessels without intimal hyperplasia.Our findings provide new insights into vascular implant functionalization by the host.

Programmable dual responsive system reconstructing nerve interaction with small-diameter tissue-engineered vascular grafts and inhibiting intimal hyperplasia in diabetes

Small-diameter tissue-engineered vascular grafts(sdTEVGs)with hyperglycemia resistance have not been constructed.The intimal hyperplasia caused by hyperglycemia remains problem to hinder the patency of sdTEVGs.Here,inspired by bionic regulation of nerve on vascular,we found the released neural exosomes could inhibit the abnormal phenotype transformation of vascular smooth muscle cells(VSMCs).The transformation was a prime culprit causing the intimal hyperplasia of sdTEVGs.To address this concern,sdTEVGs were modified with an on-demand programmable dual-responsive system of ultrathin hydrogels.An external primary Reactive Oxygen Species(ROS)-responsive Netrin-1 system was initially triggered by local inflammation to induce nerve remolding of the sdTEVGs overcoming the difficulty of nerve regeneration under hyperglycemia.Then,the internal secondary ATP-responsive DENND1A(guanine nucleotide exchange factor)system was turned on by the neurotransmitter ATP from the immigrated nerve fibers to stimulate effective release of neural exosomes.The results showed nerve fibers grow into the sdTEVGs in diabetic rats 30 days after transplantation.At day 90,the abnormal VSMCs phenotype was not detected in the sdTEVGs,which maintained long-time patency without intima hyperplasia.Our study provides new insights to construct vascular grafts resisting hyperglycemia damage.