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Effects of cosmological constant on motion of UHECR particles

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Science china(Physics,Mechanics & Astronomy) 2005年第1期48卷 44-56页

作者： CHEN Shaoxia & CHANG Zhe Institute of High Energy Physics, Chinese Academy of Sciences, beijing 100039, china Graduate School of Chinese Academy of Sciences, beijing 100039, china Institute of High Energy Physics Chinese Academy of Sciences Beijing 100039 China Graduate School Chinese Academy of Sciences Beijing 100039 China

Recent astronomical observations manifest that about two-thirds of the whole energy in the Universe is contributed by a small positive cosmological constant A (> 0). Then, an asymptotically de Sitter spacetime is premised naturally. However, physics in the de Sitter spacetime is very different from that in the Minkowski spacetime. As the first step, a covariant formalism of the kinematics in the de Sitter spacetime is presented here. By solving exactly the equations of motion for a field, we obtain the dispersion relation of a free particle. It is noticed that the dispersion relation is dependent on the degree of freedom of angular momentum of the particle. We show the threshold anomaly of the ultra high energy cosmic ray disappears naturally in the framework of the de Sitter kinematics.

关键词： ultrahigh energy cosmic ray, cosmological constant, curved spacetime.

Multiplicity of periodic solutions to Birkhoff's billiard ball problem

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Chinese Science Bulletin 1997年第5期42卷 353-355页

作者： Jl MinGraduate School, University of Science and Technology of china, beijing 100039, china Graduate School University of Science and Technology of Chine Beijing China

THE motion of a perfectly elastic billiard ball upon a convex billiard table is a highly typical system of dynamical systems. Let Γ be the boundary of a billiard table, strictly convex and C^1 smooth. The ball is assumed to roll on the table. It goes straight until it hits the boundary Γ where the ball bounces off according to the law that the angle of incidence is equal to the angle of reflection. Its path will be a closed n-sided polygon inscribed in Γ having no coincident sides, if and only if the motion is periodic with the positive number n as its minimal period. This is called n-bounce periodic orbit. If an n-bounce periodic orbit makes κ circuits of Γ

关键词： n-bounce stationary point periodic orbit incomplete space perimeter function.

Prescribing symmetric scalar curvature on S^2

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Chinese Science Bulletin 1999年第6期44卷 514-517页

作者： Jl MinGraduate School, University of Science and Technology of china, beijing 100039, china Graduate School University of Science and Technology of China Bajing China

The problem of prescribing scalar curvature in S^2 is discussed, and the solvability of the equation - ΔU + 2-Re^U= 0 on S^2, is given, where R ∈ C^0 (S^2). It is known that there are some obstructions. Some new results are given by seeking a solution of the minimax type. For example, supposing that R is G symmetric and is constant on the set of fixed points on S^2 under G ( where G is a subgroup of O (3)), it is proved that the equation is solvable if and only if R is positive somewhere.

关键词： scalar curvature critical point symmetric function minimax solution transformation group.

Twistor bundle theory and its application

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Science china Mathematics 2004年第4期47卷 605-616页

作者： PENG Chia-Kuei & TANG ZizhouDepartment of Mathematics, Graduate School of Chinese Academy of Sciences, beijing 100039, china Department of Mathematical Sciences, Tsinghua University, beijing 100084, china 1. Department of Mathematics Graduate School of Chinese Academy of Sciences 100039 Beijing China 2. Department of Mathematical Sciences Tsinghua University 100084 Beijing China

Over an oriented even dimensional Riemannian manifold(M 2m ,ds2 ), in terms of the Levi-Civita connection form Ω and the canonical form Θ on the bundle of positive orthonormal frames, we give a detailed description of the twistor bundle Гm = SO(2m)/U(m)? J +(@#@ M,ds2 ) →M. The integrability on an almost complex structureJ compatible with the metric and the orientation, is shown to be equivalent to the fact that the corresponding cross section of the twistor bundle is holomorphic with respect toJ and the canonical almost complex structureJ 1 onJ +(M,ds2 ), by using moving frame theory. Moreover, for various metrics and a fixed orientation onM, a canonical bundle isomorphism is established. As a consequence, we generalize a celebrated theorem of LeBrun.

关键词： almost complex structure, integrability, twistor bundle.

Recent advances in the data analysis method of functional magnetic resonance imaging and its applications in neuroimaging

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Progress in Natural Science:Materials International 2006年第8期16卷 785-795页

作者： TIAN Jie, YANG Lei and HU Jin (Institute of Automation, Chinese Academy of Sciences, beijing 100080, china Graduate School of Chinese Academy of Sciences, beijing 100039, china) [a]Chinese Academy of Sciences Institute of Automation Beijing China [b]Graduate School of Chinese Academy of Sciences Beijing China

Functional magnetic resonance imaging (fMRI) has opened a new area to explore the human brain. The fMRI can reveal the deep insights of spatial and temporal changes underlying a broad range of brain function, such as motor, vision, memory and emotion, all of which are helpful in the clinical investigation. In this paper, we introduce some recent-developed algorithms for fMRI signal detection such as model-driven method (general linear model, deconvolution model, non-linear model, etc. ) and data-driven method (principle component analysis, independent component analysis, self-organization mapping, clustered constrained non-negative matrix factorization, etc. ). We also propose several important applications of neuroimaging and point out their shortcomings and future perspectives.

关键词： fMR1 data analysis neuroimaging.

Plasmacytoid Dendritic Cells Act as the Most Competent Cell Type in Linking Antiviral Innate and Adaptive Immune Responses

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Cellular & Molecular Immunology 2005年第6期2卷 411-417页

作者： Zheng Zhang~1 Fu-Sheng Wang~(1,2) ~1Research Center of Biological Therapy,beijing 302 Hospital,beijing 100039,china ~2Research Centre of Biological Therapy,beijing Institute of Infectious Diseases,beijing 302 Hospital,100 Xi Si Huan Middle Road,beijing 100039,china. Research Center of Biological Therapy Beijing 302 Hospital Beijing 100039 China.

Appropriate in vivo control of plasmacytoid dendritic cell (pDC) recruitment and activation is a fundamentalrequirement for defense against viral *** this process,a pivotal event that influences the outcome ofviral infection is the production of high levels of type I interferon by *** particular,recent research findingsshowed that pDCs not only shape the nature of innate resistance,but are also responsible for the successfultransition from innate to adaptive immunity for viral *** addition,pDCs can differentiate into antigenpresenting cells that may regulate tolerance to a given ***,in a series of recent clinical studies,pDCs appeared to be defective in number and function in conditions of chronic viral diseases such as infected withHIV-1,HBV or ***-associated clinical antiviral therapy is also *** review describes researchfindings examining the functional and antiviral properties of in vivo pDC *** & MolecularImmunology.2005;2(6):411-417.

关键词： virus plasmacytoid dendritic cell innate immunity adaptive immunity

Comment on “Evolution model of the earth's limited expanding” from comparative planetology

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Chinese Science Bulletin 2001年第17期46卷 1495-1496页

作者： SHI YaolinGraduate School, University of Science and Technology of china, Chinese Academy of Sciences, beijing 100039, china Graduate School University of Science and Technology of China Chinese Academy of Sciences Beijing China

In the article 'Evolution Model of the Earth’s Limited Expanding' published in Volume 45 Number (4) of Chinese Science Bulletin[1], the author suggests that the earth expands according to a law R(t) = R0+A(1 -exp(β(t-ts))) (remark: this formula was mistakenly printed as R(t) = R0 + Aexp(β(t-ts)) in the and formula (12) of the text of ref. [1]). According to ref. [1], the earth was formed 4.6 billion years ago. After 0.3 billion years from its birth (ts), it started expansion from an initial radius R0 of 4651 km, and may reach a final maximum radius of R0+A = 6511 km. In the 4.6 billion years history, the radius of the earch has increased by 1720 km, or the density decreased from 14200 km/m3 (2.57 times the present density) to 5520 kg/m3 within the latest 4.3 billion years.

关键词： from comparative planetology Evolution model of the earth’s limited expanding

Evolution of terraces Ⅰ–Ⅲ along the Anning River, western Sichuan, based on pollen records and terrace structure

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Science china Earth Sciences 2011年第1期54卷 127-135页

作者： CHENG JianWu1,2 1 Institute of Geology, china Earthquake Administration, beijing 100039, china 2 Earthquake Administration of Gansu Province, Lanzhou 730000, china Institute of Geology China Earthquake Administration Beijing China Earthquake Administration of Gansu Province Lanzhou China

This study reconstructs the long-term evolution of river terraces over large spatial scales along the Anning River, western Sichuan, and identifies external factors controlling terrace formation. Pollen record analysis and terrace structure indicate that formation of the middle section of terraces I-III resulted from the interaction of changing climates and uplift of the margins of the Qinghai-Tibet Plateau. The relative influence of climate and uplift in terrace formation changes in different periods. The terraces reveal multiple, gradual uplift events on the eastern Qinghai-Tibet Plateau, which is of great significance for determining uplift mechanisms across the entire plateau.

关键词： Anning River in western Sichuan terrace formation pollen paleoclimate

ON SYMMETRIC SCALAR CURVAURE ON S^2

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Chinese Annals of Mathematics,Series B 1999年第3期20卷 325-330页

作者： JI MIN(Graduate School at beijing, University of Science and Technology of china, beijing 100039, china.)(Project supported by the National Natural Science Foundation of china (No.19631050, No.19725102)and the Foundation of the Ministry of Education of Ch Univ Sci & Technol china Grad Sch Beijing 100039 Peoples R China

Some new results are obtained for the problem of prescribing scalar curvature R on S2 when R possesses some kinds of symmetries.

关键词： Scalar curvature Symmetry Critical point Minimax method