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Comparison of dark energy models:A perspective from the latest observational data

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中国科学：物理学、力学、天文学英文版 2010年第9期53卷 1631-1645页

作者： LI Miao1,2,LI XiaoDong2,3.& ZHANG Xin1,4 1Kavli Institute for Theoretical Physics china,chinese academy of sciences,Beijing 100190,china 2Key Laboratory of Frontiers in Theoretical Physics,Institute of Theoretical Physics,chinese academy of sciences,Beijing 100190,china 3.7} center for Theoretical Study,University of Science and Technology of china,Hefei 23.026,china 4Department of Physics,College of sciences,Northeastern University,Shenyang 110004,china 1. Kavli Institute for Theoretical Physics china Chinese Academy of Sciences Beijing 100190 China2. Key Laboratory of Frontiers in Theoretical Physics Institute of Theoretical Physics Chinese Academy of Sciences Beijing 100190 China3. Interdisciplinary Center for Theoretical Study University of Science and Technology of China Hefei 230026 China4. Department of Physics College of Sciences Northeastern University Shenyang 110004 China

We compare some popular dark energy models under the assumption of a flat universe by using the latest observational data including the type Ia supernovae Constitution compilation,the baryon acoustic oscillation measurement from the Sloan Digital Sky Survey,the cosmic microwave background measurement given by the seven-year Wilkinson Microwave Anisotropy Probe observations and the determination of H0 from the Hubble Space *** comparison statistics such as the Bayesian and Akaike information criteria are applied to assess the worth of the *** statistics favor models that give a good fit with fewer *** on this analysis,we find that the simplest cosmological constant model that has only one free parameter is still preferred by the current *** other dynamical dark energy models,we find that some of them,such as the αdark energy,constant w,generalized Chaplygin gas,Chevalliear-Polarski-Linder parametrization,and holographic dark energy models,can provide good fits to the current data,and three of them,namely,the Ricci dark energy,agegraphic dark energy,and Dvali-Gabadadze-Porrati models,are clearly disfavored by the data.

关键词： dark energy models observational constraints model comparison information criteria

Carbon Dioxide Fluxes and Concentrations in a Cotton Field in Northwestern china:Effects of Plastic Mulching and Drip Irrigation

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Pedosphere 2011年第2期21卷 178-185页

作者： LI Zhi-Guo Key Laboratory of Oasis Ecology and Desert Environment Xinjiang Institute of Ecology and Geography Chinese Academy ofSciences Urumqi 830011 (China) Graduate University of chinese academy of sciences Beijing 100049 (China) Institute of Soil Science Chinese Academy of Sciences Nanjing 210008 (China) Earth System Science interdisciplinary center University of Maryland College Park MD 20740 (USA)

In northwestern china, there has been a change from traditional cultivation system （TC） with no mulching and flood irrigation to a more modern cultivation system （MC） using plastic film mulching with drip irrigation. A field study was conducted to compare soil ＇C02 concentrations and soil surface COs fluxes between TC and MC systems during a cotton growing season. CO2 concentrations in the soil profile were higher in the MC system （3.07-9212μL L-1） than in the TC system （1 275-8994 μL L-1） but the rate of CO2 flux was lower in the MC system. Possible reasons for this included decreased gas diffusion and higher soil moisture due to the mulching cover in the MC system, and the consumption of soil CO2 by weathering reactions. Over the whole cotton growing season, accumulated rates of CO2 flux were 3.0 and 3.4 g C m-2 for the MC and TC systems, respectively. When agricultural practices were converted from traditional cultivation to a plastic film mulching system, soil CO2 emissions could be reduced by approximately 100 g C m-2 year-1 in agricultural lands in arid and/or semi-arid areas of northern and northwestern china.

关键词： agricultural practice carbon cycle greenhouse gas emission soil respiration weathering reaction

Ab-initio molecular dynamics simulation on nano-system under external pressure

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Science china mathematics 2004年第z1期47卷 92-100页

作者： Jl Min, SUN Deyan & GONG XingaoSurface Physics Laboratory and Department of Physics, Fudan University, Shanghai 20043., china Institute of Solid State Physics, chinese academy of sciences, Hefei 23.03., china Interdisciplary {3. for Theoretical studies, chinese academy of sciences, Beijing 100080, china Fudan Univ Surface Phys Lab Shanghai 200433 Peoples R China Fudan Univ Dept Phys Shanghai 200433 Peoples R China chinese Acad Sci Inst Solid State Phys Hefei 230031 Peoples R China chinese Acad Sci Interdisciplinary Ctr Theoret Studies Beijing 100080 Peoples R China

A new constant-pressure molecular dynamics (MD) method is developed to simulate the dynamic behavior and structure transition of finite system under external pressure. In this method, no artificial parameter is introduced and the computation overheads are very small. As an application, a hard-soft transition of single wall carbon nanotube (SWCNT) under external pressure is found, which is in agreement with the experiments.

关键词： phase transition, simulation, nano-particles

Theoretical study on S_1(~1B_(3.)) state electronic structure and absorption spectrum of pyrazine

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Science china Chemistry 2008年第12期51卷 1166-1173页

作者： HE RongXing1, ZHU ChaoYuan 2, CHIN Chih-Hao3.& LIN Sheng-Hsien2,3.1 College of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715, china 2 Department of Applied Chemistry, Institute of Molecular Science and center for interdisciplinary Molecular Science, National Chiao-Tung University, Hsinchu 3.0, china 3.Institute of Atomic and Molecular sciences, Academia Sinica, Taipei 106, china 1. College of Chemistry and Chemical Engineering Southwest University Chongqing 400715 China 2. Department of Applied Chemistry Institute of Molecular Science and Center for Interdisciplinary Molecular Science National Chiao-Tung University Hsinchu 300 China 3. Institute of Atomic and Molecular sciences Academia Sinica Taipei 106 China

Making use of a set of quantum chemistry methods, the harmonic potential surfaces of the ground state (S0(1Ag)) and the first (S1(1B3.)) excited state of pyrazine are investigated, and the electronic structures of the two states are characterized. In the present study, the conventional quantum mechanical method, taking account of the Born-Oppenheimer adiabatic approximation, is adopted to simulate the absorp-tion spectrum of S1(1B3.) state of pyrazine. The assignment of main vibronic transitions is made for S1(1B3.) state. It is found that the spectral profile is mainly described by the Franck-Condon progression of totally symmetric mode ν6a. For the five totally symmetric modes, the present calculations show that the frequency differences between the ground and the S1(1B3.) state are small. Therefore the displaced harmonic oscillator approximation along with Franck-Condon transition is used to simulate S1(1B3.) absorption spectra. The distortion effect due to the so-called quadratic coupling is demonstrated to be unimportant for the absorption spectrum, except the coupling mode ν10a. The calculated S1(1B3.) ab-sorption spectrum is in reasonable agreement with the experimental spectra.

关键词： pyrazine absorption spectrum quantum mechanical method electronic structure

Anomalous boundary deformation induced by enclosed active particles

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chinese Physics B 2017年第10期26卷 82-88页

作者：田文得顾燕郭永坤陈康 center for Soft Condensed Matter Physics & interdisciplinary Research College of Physics Optoelectronics and EnergySoochow University Kavli Institute for Theoretical Physics china Chinese Academy of Sciences

We simulate a two-dimensional model of a round soft boundary enclosed with self-propelled particles. Persistent motion drives these particles to accumulate near the boundary, thereby dramatically deforming the boundary shape through collisions. Quantitative analyses of the boundary shape and the particle distribution show that there are two typical regimes in the variation of the morphology with the increase of self-propulsion of particles. One is under small forces, characterized by the radially inhomogeneous distribution of particles and the suppression of local fluctuations of the almost round boundary, and the other is under large forces, featured by the angularly inhomogeneous distribution of particles and the global shape deformation of the boundary. These two features are strongly cooperative. We also find different mechanisms in the particle relocation at low and high particle concentrations.

关键词： self-propelled particles boundary active matter confinement

Hamiltonian Formalism of de-Sitter Invariant Special Relativity

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Communications in Theoretical Physics 2007年第7期48卷 27-36页

作者： YAN Mu-Lin XIAO Neng-Chao HUANG Wei interdisciplinary center for Theoretical Study,University of Science and Technology of china,Hefei 23.026,chinaLI Si Department of mathematics,University of Science and Technology of china,Hefei 23.026,china interdisciplinary center for Theoretical Study University of Science and Technology of China Hefei 230026 China Department of mathematics University of Science and Technology of China Hefei 230026 China

The Lagrangian of Einstein's special relativity with universal parameter c(SR_c)is invariant under Poincarétransformation,which preserves Lorentz metric η_μν.The SR_c has been extended to be one which is invariant underde Sitter transformation that preserves so-called Beltrami metric B_(μv).There are two universal parameters,c and R,inthis Special Relativity(denoted as SR_(cR)).The Lagrangian-Hamiltonian formulism of SR_(cR) is formulated in this *** canonic energy,canonic momenta,and 10 Noether charges corresponding to the space-time's,de Sitter symmetryare *** canonical quantization of the mechanics for SR_(CR)-free particle is *** physics related to itis discussed.

关键词： de-Sitter invariance special relativity canonic energy and canonic momenta Beltrami metric

Grouping of amino acids and recognition of protein structurally conserved regions by reduced alphabets of amino acids

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Science china(Life sciences) 2007年第3期50卷 392-402页

作者： LI Jing1 & WANG Wei1,2 1 National Laboratory of Solid State Microstructure and Department of Physics, Nanjing University, Nanjing 210093. china 2 interdisciplinary center of Theoretical Studies, {3., Beijing 100080, china 1. National Laboratory of Solid State Microstructure and Department of Physics Nanjing University Nanjing 210093 China 2. interdisciplinary center of Theoretical Studies Chinese Academy of Sciences Beijing 100080 China

Sequence alignment is a common method for finding protein structurally conserved/similar regions. However, sequence alignment is often not accurate if sequence identities between to-be-aligned se- quences are less than 3.%. This is because that for these sequences, different residues may play similar structural roles and they are incorrectly aligned during the sequence alignment using substitu- tion matrix consisting of 20 types of residues. Based on the similarity of physicochemical features, residues can be clustered into a few groups. Using such simplified alphabets, the complexity of protein sequences is reduced and at the same time the key information encoded in the sequences remains. As a result, the accuracy of sequence alignment might be improved if the residues are properly clustered. Here, by using a database of aligned protein structures (DAPS), a new clustering method based on the substitution scores is proposed for the grouping of residues, and substitution matrices of residues at different levels of simplification are constructed. The validity of the reduced alphabets is confirmed by relative entropy analysis. The reduced alphabets are applied to recognition of protein structurally conserved/similar regions by sequence alignment. The results indicate that the accuracy or efficiency of sequence alignment can be improved with the optimal reduced alphabet with N around 9.

关键词： Grouping of amino acids and recognition of protein structurally conserved regions by reduced alphabets of amino acids

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耦合量子阱中激子凝聚的研究进展

物理 2004年第11期33卷 809-815页

作者：刘承师向涛中国科学院理论物理研究所

近年来 ,半导体量子阱中激子的玻色 -爱因斯坦凝聚研究取得了很大进展 .实验上利用耦合量子阱间接激子中电子和空穴在空间上的分离 ,显著提高了激子的冷却速度和寿命 ,成功地把激子冷却到 1K以下 ,观察到了激子的准凝聚状态 ,并且在强... 详细信息

近年来 ,半导体量子阱中激子的玻色 -爱因斯坦凝聚研究取得了很大进展 .实验上利用耦合量子阱间接激子中电子和空穴在空间上的分离 ,显著提高了激子的冷却速度和寿命 ,成功地把激子冷却到 1K以下 ,观察到了激子的准凝聚状态 ,并且在强激光照射下 ,发现了随光照强度增强而增大的激子发光环和环上形成的有规则斑点图案 ,引起了广泛的兴趣和重视 .理论研究表明 ,发光环的出现是电子和空穴在量子阱中的反常输运行为造成的 ,但环上形成规则斑点的物理机理目前尚不清楚 .文章介绍了这方面的实验背景和形成激子环的物理图像 ,指出了理论研究中存在的问题 ,并对解决问题的方案进行了讨论 .

关键词：激子发光半导体量子阱子环空穴电子凝聚强激光耦合物理机理

Glacial-Interglacial Atmospheric CO_2 Change——The Glacial Burial Hypothesis

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Advances in Atmospheric sciences 2003年第5期20卷 677-693页

作者： Ning ZENG Department of Meteorology and Earth System Science interdisciplinary center, University of Maryland, USA Department of Meteorology and Earth System Science interdisciplinary center University of Maryland USA

Organic carbon buried under the great ice sheets of the Northern Hemisphere is suggested to be the missing link in the atmospheric CO2 change over the glacial-interglacial cycles. At glaciation, the advancement of continental ice sheets buries vegetation and soil carbon accumulated during warmer periods. At deglaciation, this burial carbon is released back into the atmosphere. In a simulation over two glacial-interglacial cycles using a synchronously coupled atmosphere-land-ocean carbon model forced by reconstructed climate change, it is found that there is a 547-Gt terrestrial carbon release from glacial maximum to interglacial, resulting in a 60-Gt (about 3.-ppmv) increase in the atmospheric CO2, with the remainder absorbed by the ocean in a scenario in which ocean acts as a passive buffer. This is in contrast to previous estimates of a land uptake at deglaciation. This carbon source originates from glacial burial, continental shelf, and other land areas in response to changes in ice cover, sea level, and climate. The input of light isotope enriched terrestrial carbon causes atmospheric δ13./SUP>C to drop by about 0.3. at deglaciation, followed by a rapid rise towards a high interglacial value in response to oceanic warming and regrowth on land. Together with other ocean based mechanisms such as change in ocean temperature, the glacial burial hypothesis may offer a full explanation of the observed 80–100-ppmv atmospheric CO2 change.

关键词： atmospheric CO2 ice age glacial burial hypothesis climate