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On compact splitting complex submanifolds of quotients of bounded symmetric domains

Science China Mathematics 2017年第6期60卷 1057-1076页

作者： MOK ngaiming ng SuiChung Department of Mathematics The University of Hong Kong Department of Mathematics Shanghai Key Laboratory of PMMPEast China Normal University

We study compact complex submanifolds S of quotient manifolds X =Ω/F of irreducible bounded symmetric domains by torsion free discrete lattices of automorphisms, and we are interested in the characterization of the totally geodesic submanifolds among compact splitting complex submanifolds S C X, i.e., under the assumption that the tangent sequence over S splits holomorphically. We prove results of two types. The first type of results concerns S C X which are characteristic complex submanifolds, i.e., embedding Ω as an open subset of its compact dual manifold M by means of the Borel embedding, the non-zero （1, 0）-vectors tangent to S lift under a local inverse of the universal covering map π → X to minimal rational tangents of M. We prove that a compact characteristic complex submanifold S C X is necessarily totally geodesic whenever S is a splitting complex submanifold. Our proof generalizes the case of the characterization of totally geodesic complex submanifolds of quotients of the complex unit ball B^n obtained by Mok （2005）. The proof given here is however new and it is based on a monotonic property of curvatures of Hermitian holomorphic vector subbundles of Hermitian holomorphic vector bundles and on exploiting the splitting of the tangent sequence to identify the holomorphic tangent bundle Ts as a quotient bundle rather than as a subbundle of the restriction of the holomorphic tangent bundle Tx to S. The second type of results concerns characterization of total geodesic submanifolds among compact splitting complex submanifolds S C X deduced from the results of Aubin （1978） and Yau （1978） which imply the existence of Kahler-Einstein metrics on S C X. We prove that compact s- plitting complex submanifolds S C X of sufticiently large dimension （depending on ） are necessarily totally geodesic. The proof relies on the Hermitian-Einstein property of holomorphic vector bundles associated to TS, which implies that endomorphisms of such bundles are parallel, and the co

关键词： bounded symmetric domains tangent sequence splitting complex submanifolds varieties of minimal rational tangents K/ihler-Einstein metrics

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Dysfunction of synaptic endocytic trafficking in Parkinson's disease

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Neural Regeneration Research 2024年第12期19卷 2649-2660页

作者： Xin Yi ng Mian Cao Programme in Neuroscience and Behavioural Disorders Duke-NUS Medical SchoolSingaporeSingapore Department of Physiology National University of SingaporeSingaporeSingapore

Parkinson's disease is characterized by the selective degeneration of dopamine neurons in the nigrostriatal pathway and dopamine deficiency in the *** precise reasons behind the specific degeneration of these dopamine neurons remain largely *** investigations have identified over 20 causative PARK genes and 90 genomic risk loci associated with both familial and sporadic Parkinson's ***,several of these genes are linked to the synaptic vesicle recycling process,particularly the clathrinmediated endocytosis *** suggests that impaired synaptic vesicle recycling might represent an early feature of Parkinson's disease,followed by axonal degeneration and the eventual loss of dopamine cell bodies in the midbrain via a"dying back"***,several new animal and cellular models with Parkinson's disease-linked mutations affecting the endocytic pathway have been created and extensively *** models faithfully recapitulate certain Parkinson's disease-like features at the animal,circuit,and cellular levels,and exhibit defects in synaptic membrane trafficking,further supporting the findings from human genetics and clinical *** this review,we will first summarize the cellular and molecular findings from the models of two Parkinson's disease-linked clathrin uncoating proteins:auxilin(DNAJC6/PARK19)and synaptojanin 1(SYNJ1/PARK20).The mouse models carrying these two PARK gene mutations phenocopy each other with specific dopamine terminal pathology and display a potent synergistic ***,we will delve into the involvement of several clathrin-mediated endocytosis-related proteins(GAK,endophilin A1,SAC2/INPP5 F,synaptotagmin-11),identified as Parkinson's disease risk factors through genome-wide association studies,in Parkinson's disease *** will also explore the direct or indirect roles of some common Parkinson's disease-linked proteins(alpha-synuclein(PARK1/4),Parkin(PARK2),and LRRK2(PARK

关键词： autophagy auxilin/PARK19 clathrin-mediated endocytosis dopamine neurons neurodegeneration nigrostriatal pathway Parkinson's disease synaptic vesicle recycling synaptojanin1/PARK20

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AN APPROACH TO ANALYSIS OF SIngLE PIER BASED ON THE VARIATIONAL PRINCIPLE IN MULTI-LAYERED SOIL

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Acta Mechanica Solida Sinica 2001年第3期14卷 275-282页

作者： ng Shiu Cho Department of Civil Enginddring The Hong Kong University of Science and TechnologyClearwaler BayHong Kong

In this study, a variational approach to the settlement analysisof an axially loaded pier em- bedded in a multi-layered soil profileis presented. In this method, the soil profile and the embedded pierare divided into a number of sub-layers according to the actualnumber o soil layers observed in the field. The displacement shapefunction of each soil layer is given as a product of an exponentialequation along the pier depth and the Bessel's solution in the radialdirection.

关键词： pier pile settlement

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Improved GaN grown on Si(111) substrate using ammonia flow modulation on SiN_x mask layer by MOCVD

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Science China(Technological Sciences) 2009年第9期52卷 2758-2761页

作者： ng KaiWei LAU KeiMay Department of Electrical and Electronic Engineering Hong Kong University of Science & Technology Clear Water BayKowloon Hong Kong China

In this paper,1 μm n-GaN was grown by using varied and fixed ammonia flow (NH3) on SiNx mask layer on Si(111) substrate using metal organic chemical vapor deposition (MOCVD). In-situ optical reflectivity traces of GaN growth show that the three-to two-dimensional process has been prolonged by using varied ammonia flow on SiNx mask layer method compared with that grown by fixing ammonia flow. Structural and optical properties were characterized by high-resolution X-ray diffraction and photolu-minescence,and compared with the sample grown by fixing ammonia flow,GaN grown using the varied ammonia flow on SiNx mask layer showed better structure and optical quality. It was assumed that the low NH3 flow in the initial growth stage considerably increased the GaN island density on the nano-porous SiNx layer by enhancing vertical growth. Lateral growth was significantly favored by high NH3 flow in the subsequent step. As a result,the improved crystal and optical quality was achieved utilizing NH3 flow modulation for GaN buffer growth on Si(111) substrate.

关键词： GaN epilayer MOCVD NH3 modulation

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ON INTEGRITY ASSESSMENT OF AXISYMMETRIC COMPONENTS OPERATIng WITHIN CREEP REGIME

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Chinese Journal of Mechanical Engineering 2006年第4期19卷 492-495页

作者： ZARRABI K LAWRENCE ng School of Mechanical and Manufacturing Engineering University of New South Wales Sydney NSW 2052 Australia

A multiaxial paradigm for predicting creep damage/lives of components is described. Although in principle the paradigm is general, it is verified using axisymmetric experimental data. It is shown that the proposed paradigm is capable of predicting creep lives with an error of less than 2%. It is also shown that the proposed paradigm is more accurate than the reference stress method.

关键词： Creep damage Creep life

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PSEUDO ALMOST PERIODIC SOLUTIONS OF DIFFERENTIAL EQUATIONS WITHPIECEWISE CONSTANT ARGUMENT

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Chinese Annals of Mathematics,Series B 1999年第4期20卷 489-494页

作者： PIAODAX10ng YUANROng SchoolofMathematicalSciences PekingUniversityBeijing100871China. DpaRmentofMathematics BeijingNormniUniversityBejLug100875China

The authors discuss the existence of pseudo almost periodic solutions of differential equations with piecewise constant argument by means of introducing new concept, pseudo almost periodic sequence.

关键词： Pseudo almost periodic functions Pseudo almost periodic sequences Piecewise constant arguments Ergodic perturbation

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Mechanical and hydraulic properties of carbonate rock:The critical role of porosity

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Journal of Rock Mechanics and Geotechnical Engineering 2023年第4期15卷 814-825页

作者： Kam ng J.Carlos Santamarina Department of Civil and Architectural Engineering and Construction Management University of WyomingLaramieWY82071USA Physical Science and Engineering Division King Abdullah University of Science and TechnologyThuwal23955-6900Saudi Arabia

Carbonate rocks are extensively used in civil infrastructure and play a critical role in geoenergy geoengineering,either as hydrocarbon reservoirs or potential repositories for CO_(2)geological *** genesis and diagenetic overprint determine the properties of carbonate *** study combines recent data gathered from Madison Limestone and an extensive dataset compiled from published sources to analyze the hydraulic and mechanical properties of limestone carbonate *** models and data analyses recognize the inherently granular genesis of carbonate rocks and explain the strong dependency of physical properties on *** asymptotically-correct power model in terms of(1-Ф/Ф*)a is a good approximation to global trends of unconfined stiffness E and unconfined compressive strength UCS,cohesive intercept in Mohr-Coulomb failure envelopes,and the brittle-toductile transition *** power model is the analytical solution for the mechanical properties of percolating granular *** adopted a limiting granular porosityФ*=0.5 for all models,which was consistent with the loosest packing of monosize *** fitted power model has exponent(α=2)in agreement with percolation theory and highlights the sensitivity of mechanical properties to *** and models confirm a porosity-independent ratio between unconfined stiffness and strength,and the ratio follows a log-normal distribution with mean(E/UCS)≈*** high angle of internal shear strength measured for carbonate rocks reflects delayed contact failure with increased confinement,and it is not sensitive to *** spans more than six orders of *** size controls pore size and determines the reference permeability k^(*)at the limiting porosityФ*=*** a given grain size from fine to coarse-grained dominant carbonates,permeability is very sensitive to changes in porosity,suggesting preferential changes in the internal pore network during compaction.

关键词： Rock porosity Carbonate permeability Rock unconfined stiffness Unconfined compressive strength(UCS)

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On Chiral Space Groups and Chiral Molecules

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Chinese Journal of Structural Chemistry 2003年第1期22卷 37-38页

作者： ng Seik Weng 胡盛志 Institute of Postgraduate Studies University of Malaya 50603 Kuala Lumpur Malaysia Department of Chemistry Xiamen University Xiamen 361005 China

This note explains the relationship (as well as the absence of a relationship) between chiral space groups and chiral molecules (which have absolute configurations). For a chiral molecule, which must crystallize in a chiral space group, the outcome of the absolute configuration determination must be linked to some other properties of the chiral crystal such as its optical activity for the observation to the relevant.

关键词：手性空间群手性分子手性化合物有机合成有机化合物晶体结构

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Preconditioned Iterative Methods for Algebraic Systems from Multiplicative Half-Quadratic Regularization Image Restorations

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Numerical Mathematics(Theory,Methods and Applications) 2010年第4期3卷 461-474页

作者： Michael K.ng Department of Mathematics Hong Kong Baptist UniversityKowloon TongHong Kong

Image restoration is often solved by minimizing an energy function consisting of a data-fidelity term and a regularization term.A regularized convex term can usually preserve the image edges well in the restored *** this paper,we consider a class of convex and edge-preserving regularization functions,i.e.,multiplicative half-quadratic regularizations,and we use the Newton method to solve the correspondingly reduced systems of nonlinear *** each Newton iterate,the preconditioned conjugate gradient method,incorporated with a constraint preconditioner,is employed to solve the structured Newton equation that has a symmetric positive definite coefficient matrix. The eigenvalue bounds of the preconditioned matrix are deliberately derived,which can be used to estimate the convergence speed of the preconditioned conjugate gradient *** use experimental results to demonstrate that this new approach is efficient, and the effect of image restoration is reasonably well.

关键词： Edge-preserving image restoration multiplicative half-quadratic regularization Newton method preconditioned conjugate gradient method constraint preconditioner eigenvalue bounds

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Production of rhamnolipids-producing enzymes of Pseudomonas in E. coli and structural characterization

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Frontiers of Chemical Science and Engineering 2017年第1期11卷 133-138页

作者： Kata Kiss Wei Ting ng Qingxin Li Institute of Chemical & Engineering Sciences Agency for Science Technology and Research Jurong Island 627833 Singapore

Rhamnolipids are a class ofbiosurfactants that have a great potential to be used in industries. Five proteins/enzymes, namely RhlA, RhlB, RhlC, RhlG and RhlI, are critical for the production of rhamnolipids in Pseudomonas aeruginosa. Four of the 5 proteins except RhlC were successfully over-expressed in E. coli and three of them （RhlA, RhlB and RhlI） were purified and obtained in milligram quantities. The purified proteins were shown to be folded in solution. Homology models were built for RhlA, RhlB and RhlI. These results lay a basis for further structural and functional characterization of these proteins in vitro to favor the construction of super strains for rhamnolipids production.

关键词： rhamnolipids Pseudomonas RhlA RhlB,RhlI protein folding

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