检索结果-南通市图书馆

Evolution of desertification in a two-dimensional energy balance model coupled with thermodynamics and dynamics

Science china Earth sciences 2010年第11期53卷 1726-1733页

作者： CHAO JiPing1,2 & LI YaoKun3,4 1National Marine Environmental Forecasting Center, beijing 100081, china 2First institute of Oceanography, State Oceanic Administration, Qingdao 266061, china 3State key laboratory of Numerical Modeling for Atmospheric sciences and Geophysical Fluid Dynamics, institute of Atmospheric physics, chinese academy of sciences, beijing 100029, china 4Graduate University of chinese academy of sciences, beijing 100049, china National Marine Environmental Forecasting Center Beijing China First institute of Oceanography State Oceanic Administration Qingdao China State key laboratory of Numerical Modeling for Atmospheric sciences and Geophysical Fluid Dynamics Institute of Atmospheric Physics Chinese Academy of Sciences Beijing China Graduate University of chinese academy of sciences Beijing China

The relationship between desert evolution and change in albedo has been investigated quasi-analytically using a zonal mean two-dimensional energy balance model which considers the radiation transmission process due to thermodynamics and bound- ary layer movement caused by kinetics. A climate state including temperature, zonal wind, meridional wind and vertical wind can be simulated according to the current zonal distribution of albedo. Given desert distribution, characterized by the value and distribution of albedo, the response of climate on albedo has been studied to analyze the evolution of desert climate. One significant result is that the simple model can reproduce mean meridional circulation. Another result indicates that climate corresponds to two equilibria. This happens when the junction temperature between vegetation and desert is higher than a certain critical value. As for the first equilibrium, the desert belt is predicted to move southward in the northern hemisphere with the increasing values of albedo, which corresponds to the current trend of climate change. For the second equilibrium, vegetation will expand northward with increasing values of albedo, which would indicate a narrowing of the desert belt. In order to determine if the two equilibria exist, new physical models are needed.

关键词： two-dimensional energy balance model desertification two equilibria

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

A puzzle of the radio-quiet quasar PG 1407+265:Are optical and X-ray emissions produced from a relativistic jet?

引用

Science china(physics,Mechanics & Astronomy) 2011年第1期54卷 183-186页

作者： CHEN Liang 1,2,3 & BAI JinMing 1,2 1 National Astronomical Observatories/Yunnan Observatory,chinese academy of sciences,Kunming 650011,china 2.key laboratory for the Structure and Evolution of Celestial Objects,chinese academy of sciences,Kunming 650011,china 3 Graduate University of chinese academy of sciences,beijing 100049,china National Astronomical Observatories/Yunnan Observatory Chinese Academy of Sciences Kunming China key laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming China Graduate University of chinese academy of sciences Beijing China

PG 1407+265 is a radio quiet quasar that has a relativistic *** this report,we show some peculiar properties of its optical and X-ray emissions,which indicate possible non-thermal origins produced from the *** use a simple synchrotron + synchrotron self Compton (SSC) model to fit the emissions with different ratios of energy densities between the magnetic field and electrons (η≡U B/U e),which predicts a different γ-ray *** First LAT AGN Catalog (1LAC) did not include PG 1407+265,which indicates an upper limit of γ-ray *** upper limit constrains the ratio to be unreasonably large (η≥10 4-5).This inversely indicates that the optical and X-ray emissions may not be produced from the beaming *** discuss the physical implications of these results.

关键词： active galactic nuclei jet non-thermal emission PG 1407+265

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Effects of diatoms on reproduction and growth of marine copepods

引用

Progress in Natural Science:Materials International 2004年第10期14卷 1-7页

作者： ZHANG Guangtao 1,2 and SUN Song 1 (1.key laboratory of Marine Ecology&Environment sciences,institute of Oceanology,chinese academy of sciences,Qingdao266071,china 2.Graduate School,chinese academy of sciences,beijing100039,china) Lab. of Marine Ecology Inst. of Oceanology Chinese Acad. of Sci. Qingdao 266071 China Graduate Sch. Chinese Acad. of Sci. Beijing 100039 China

Two hot spots in marine ecology,deleterious effects of diatoms and feeding selectivity of copepods,as well as new progress on these two issues achieved in the recent ten years,are *** two issues are considered correlated *** and their metabolites can induce deleterious effects on growth,reproduction and development of copepods,including increase of mortality and decrease of egg production,hatching and growth *** negative effects,resulting from either chemical toxin or nutritional defi-ciency,can be conquered in natural environments by diverse *** is therefore concluded that deleterious effects of diatoms observed in laboratory or during blooming period are only a special case that accommodation of feeding strategy of copepods is *** under-stand their feeding strategy in natural environments is a prerequisite to explaining the mechanisms of deleterious effects caused by diatoms,and makes it possible to re-evaluate the energy flow in marine ecosystems.

关键词： diatoms copepod feeding strategy reproduction deleterious effects

来源：

同方期刊数据库评论

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Study on the atmospheric photochemical reaction of CF_3 radicals using ultraviolet photoelectron and photoionization mass spectrometer

引用

Science china Chemistry 2008年第4期51卷 316-321页

作者： YAO Li1,2, DU Lin1,2, YIN Shi1,2 & GE MaoFa1 1 beijing National laboratory for Molecular sciences (BNLMS), State key laboratory for Structural Chemistry of Unstable and Stable Species, institute of Chemistry, chinese academy of sciences, beijing 100080, china 2 Graduate University of chinese academy of sciences, beijing 100080, china beijing National laboratory for Molecular sciences (BNLMS) State Key Laboratory for Structural Chemistry of Unstable and Stable Species Institute of Chemistry Chinese Academy of Sciences Beijing China Graduate University of chinese academy of sciences Beijing China

A study of the atmospheric photochemical reaction of CF3 radical with CO and O2 was performed by using a homemade ultraviolet photoelectron spectrometer-photoionization mass spectrometer (PES- PIMS). The electronic structures and mechanism of ionization and dissociation of CF3OC(O)OOC(O)- OCF3 were investigated. It was indicated that the two bands on the photoelectron spectrum of CF3OC(O)OOC(O)OCF3 are the result of ionization of an electron from a lone pair of oxygen and a fluo- rine lone pair of CF3 group. The outermost electrons reside in the oxygen lone pair. The experimental and theoretical first vertical ionization energy is 13.21 and 13.178 eV, respectively, with the PES and OVGF method. They are in good agreement. The photo ionization and dissociation processes were discussed with the help of theoretical calculations and PES-PIMS experiment. After ionization, the parent ions prefer the dissociation of the C-O bond and giving the fragments CF3OCO+ and CF3+. It demonstrated that the ultraviolet photoelectron and photoionization mass spectrometer could be ap- plied widely in the study of atmospheric photochemical reaction.

关键词： photochemical reaction CF3 radical ultraviolet photoelectron and photoionization mass spectroscopy transient species

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Bioreducible crosslinked low molecular weight branched PEI-PBLG as an efficient gene carrier

引用

Science china Chemistry 2010年第12期53卷 2490-2496页

作者： GUO ZhaoPei 1,TIAN HuaYu 1,XIA JiaLiang 1,2,CHEN Jie 1,LIN Lin 1 & CHEN XueSi 1 1 key laboratory of Polymer Ecomaterials Changchun institute of Applied Chemistry,chinese academy of sciences,Changchun 130022,china 2 Graduate University of chinese academy of sciences,beijing 100049,china key laboratory of Polymer Ecomaterials Changchun institute of Applied Chemistry Chinese Academy of Sciences Changchun China Graduate University of chinese academy of sciences Beijing China

Low molecular weight polyethylenimine-poly(gamma-benzyl L-glutamate) (PEI-PBLG) was crosslinked by N,N'-cystaminebisacrylamide (CBA) to get the polymer named as CBA-PEI-PBLG (CPP).CPP not only inherits PEI-PBLG's amphiphilic advantages,but also possesses reducible *** can complex with DNA to form ***/DNA complex particles were characterized by particle size and zeta potential *** result showed that the complex particles have suitable size and surface charges for gene *** gel retardation assay also prove CBA-PEI-PBLG has proper condensing ability for *** has good reducible property,and also has good biocompatibility because of introducing PBLG *** cytotoxicity of CPP was evaluated using MTT assay,and the results showed CPP has lower cytotoxicity compared with PEI 25 *** transfection properties were characterized in different cells by using plasmid DNA as a *** showed higher transfection efficiencies and lower cytotoxicity in HeLa *** was attributed to bioreducible and biocompatibility properties of the *** results suggested that CPP is a promising low-toxic,highly effective non-viral gene carrier.

关键词： gene carrier transfection cytotoxicity crosslinked

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Anomalous magnetotransport in LaMn_(1-x)Te_xO_3

引用

Science china(physics,Mechanics & Astronomy) 2009年第7期52卷 987-992页

作者： TAN GuoTai1,2, CHEN ZhengHao3 & ZHANG XiaoZhong4,5 1 key laboratory of Beam Technology & Materials Modification of the Ministry of Education, institute of Low energy Nuclear physics, beijing Normal University, beijing 100875, china 2 beijing Radiation Center, beijing 100875, china 3 laboratory of Optical physics, institute of physics, chinese academy of sciences, beijing 100080, china 4 key laboratory of Advanced Materials of the Ministry of Education, Department of Materials Science and Engineering, Tsinghua University, beijing 100084, china 5 beijing National Center for Electron Microscopy, Tsinghua University, beijing 100084, china key laboratory of Beam Technology & Materials Modification of the Ministry of Education Institute of Low Energy Nuclear Physics Beijing Normal University Beijing China beijing Radiation Center Beijing China laboratory of Optical physics Institute of Physics Chinese Academy of Sciences Beijing China key laboratory of Advanced Materials of the Ministry of Education Department of Materials Science and Engineering Tsinghua University Beijing China beijing National Center for Electron Microscopy Tsinghua University Beijing China

The LaMn1-xTexO3+δ (x=0.1, 0.2, 0.3) were synthesized using solid-state reaction method for the first time. X-ray photoemission spectrum (XPS) shows that in the samples the Te ions have a valence of Te4+, and Mn3+ ions are partly converted into Mn2+ and Mn4+ due to the excess oxygen and Te doping. The magnetotransport associated with Mn2+, Mn3+ and Mn4+ was investigated. The experimental results show that the samples are insulator at 0 T when the amount of Mn3+ is much larger or less than the sum of Mn2+ and Mn4+; by contrast, the samples display metal to insulator transition with increasing temperature when the amount of Mn3+ is close to the sum of Mn2+ and Mn4+. These anomalous magnetotransport behaviors were analyzed in the frame of the double-exchange (DE) mechanism.

关键词： colossal magnetoresistance La-Te-Mn-O magnetotransport

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

fMRI time series analysis based on stationary wavelet and spectrum analysis

引用

Progress in Natural Science:Materials International 2006年第11期16卷 1171-1176页

作者： ZHI Lianhe~ 1,2,3 , ZHAO Xia~4, SHAN Baoci~1**, PENG Silong~5, YAN Qiang~1, YUAN Xiuli~1 and TANG Xiaowei~ 1,6 (1. key laboratory of Nuclear Analysis Techniques, institute of high energy physics, chinese academy of sciences, beijing 100049, china 2. Graduate School of chinese academy of sciences, beijing 100049, china 3. Department of physics, Zhoukou Normal University, Zhoukou 466100, china 4. Research Imaging Center, University of Texas Health Science Center, San Antonio, Texas 78229, USA 5. National ASIC Design and Engineering Center, institute of Automation, chinese academy of sciences, beijing 100049, china 6. Department of physics, Zhejiang University, Hangzhou 310027, china) key laboratory of Nuclear Analysis Techniques Institute of High Energy Physics Chinese Academy of Sciences Beijing 100049 China Graduate School of chinese academy of sciences Beijing 100049 China Department of physics Zhoukou Normal University Zhoukou 466100 China Research Imaging Center University of Texas Health Science Center San Antonio TX 78229 United States National ASIC Design and Engineering Center Institute of Automation Chinese Academy of Sciences Beijing 100049 China Department of physics Zhejiang University Hangzhou 310027 China

The low signal to noise ratio (SNR) of functional MRI (fMRI) prefers more sensitive data analysis methods. Based on stationary wavelet transform and spectrum analysis, a new method with high detective sensitivity was developed for analyzing fMRI time series, which does not require any prior assumption of the characteristics of noises. In the proposed method, every component of fMRI time series in the different time-frequency scales of stationary wavelet transform was discerned by the spectrum analysis, then the components from noises were removed using the stationary wavelet transform, finally the components of real brain activation were detected by cross-correlation analysis. The results obtained from both simulated and in vivo visual experiments illustrated that the proposed method has much higher sensitivity than the traditional cross-correlation method.

关键词： fMRI stationary wavelet transform spectrum analysis data analysis.

来源：

同方期刊数据库评论

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Zircon and apatite fission track analyses on mineralization ages and tectonic activities of Tuwu-Yandong porphyry copper deposit in northern Xinjiang, china

引用

Science china Earth sciences 2007年第12期50卷 1787-1795页

作者： YUAN WanMing1,BAO ZengKuan2,DONG JinQuan2,GUO ZhaoJie3 & DENG Jun1 1 State key laboratory of Geological Processes and Mineral Resources,china University of Geosciences,beijing100083,china 2 laboratory of Nuclear Analysis Techniques,institute of high energy physics,chinese academy of sciences,beijing 100039,china 3 Department of Geology,Peking University,beijing 100871,china State key laboratory of Geological Processes and Mineral Resources China University of Geosciences Beijing China laboratory of Nuclear Analysis Techniques Institute of High Energy Physics Chinese Academy of Sciences Beijing China Department of Geology Peking University Beijing China

The mineralization ages reported in the past in the Tuwu-Yandong copper district not only are different,but also fall into the Hercynian *** study has achieved 9 zircon and 7 apatite fission track analysis *** zircon fission track ages range from 158 Ma to 289 Ma and the apatite ages are between 64 Ma and 140 *** mineralization accords with the regional tectonics in the copper *** consider that the zircon fission track age could reveal the mineralization age based on annealing zone temperature of 140―300℃ and retention temperature of ～250℃ for zircon fission track,and metallogenetic temperature of 120―350℃ in this ore *** three mineralization epochs have been identified,i.e.,289―276 Ma,232―200 Ma and 165―158 Ma,and indicate occurrence of the min-eralization in the Indosinian and Yanshan *** to apatite fission track ages,the three tectonic-mineralizing epochs are 140―132 Ma,109―97 Ma and 64 Ma,which means age at about 100℃ after the *** three epochs lasted 146 Ma,108 Ma and about 100 Ma from ～250℃ to ～100℃ and trend decrease from early to *** is shown by the fission track modeling that this district underwent three stages of geological thermal histories,stable in Cretaceous and cooling both before Cretaceous and after 20 Ma.

关键词： mineralization age, tectonic epoch, fission track, zircon, apatite, Tuwu-Yandong, Xinjiang

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Spectroscopic evidence for triplet excitation energy transfer among carotenoids in the LH2 complex from photosynthetic bacterium Rhodopseudomonas palustris

引用

Science china Chemistry 2004年第1期47卷 80-90页

作者： FENG Juan, WANG Qian, ZHANG Xujia, HUANG Youguo, Al Xicheng, ZHANG Xingkang & ZHANG JianpingState key laboratory for Structural Chemistry of Unstable and Stable Species, institute of Chemistry, chinese academy of sciences, beijing 100080, china National laboratory of Biomacromolecules, institute of Biophysics, chinese academy of sciences, beijing 100101, china State key laboratory for Structural Chemistry of Unstable and Stable Species institute of Chemistry Chinese Academy of Sciences Beijing China National laboratory of Biomacromolecules institute of Biophysics Chinese Academy of Sciences Beijing China

The LH2 complex from Rhodopsudomonas (Rps.) palustris is unique in the heterogeneous carotenoid compositions. The dynamics of triplet excited state Carotenoids (3Car* has been investigated by means of sub-microsecond time-resolved absorption spectroscopy both at physiological temperature (295 K) and at cryogenic temperature (77K). Broad and asymmetric T n ←T 1 transient absorption was observed at room temperature following the photo-excitation of Car at 532 nm, which suggests the contribution from various carotenoid compositions having different numbers of conjugated C=C double bonds (Nc=c). The triplet absorption bands of different carotenoids, which superimposed at room temperature, could be clearly distinguished upon decreasing the temperature down to 77 K. At room temperature the shorter-wavelength side of the main Tn04T1 absorption band decayed rapidly to reach a spectral equilibration with a characteristic time constant of ∽1 μs, the same spectral dynamics, however, was not observed at 77 K. The aforementioned spectral dynamics can be explained in terms of the triplet-excitation transfer among heterogeneous carotenoid compositions. Global spectral analysis was applied to the time-resolved spectra at room temperature, which revealed two spectral components peaked at 545 and 565 nm, and assignable to the Tn04 T1 absorption of Cars with Nc=c=11 and Nc=c=13, respectively. Surprisingly, the decay time constant of a shorter-conjugated Car, i.e. 0.72 ?s (aerobic) and 1.36 ?s (anaerobic), is smaller than that of a longer-conjugated Car, i.e. 2.12 us (aerobic) and 3.75 ?s (anaerobic), which is contradictory to the general rule of carotenoids and relative polyenes. The results are explained in terms of triplet-excitation transfer among different types of Cars. It is postulated that two Cars with different conjugation lengths coexist in an α, β-subunit in the LH2 complex.

关键词： purple photosynthetic bacteria, carotenoid, excited-state, time-resolved spectroscopy.

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

TRANSIENT EFFECT OF A BOGER FLUID FLOWING AROUND A CONFINED CYLINDER

引用

chinese Journal of Polymer Science 2001年第4期19卷 377-384页

作者： Xian-feng Li Huai-tian Bu De-lu Zhao State key laboratory of Polymer physics and Chemistry Center for Molecular Science,institute of Chemistry, chinese academy of sciences, beijing 100080, china 中科院化学所高分子物理与化学国家重点实验室北京

This paper is concerned with the numerical simulation of the transient effect of an inertialess Boger flow past a confined circular cylinder and the comparison of predictions with particle image velocimetry (PIV) measurements given by Shiang et al.. Dynamic simulation based on the Oldroyd-B constitutive model was carried out using a Lagrangian-Eulerian algorithm. The evolution of velocity field was obtained for the flow at two Deborah (De) numbers, i.e. De = 1.2 and 3.0. At low De, the flow reached steady state rapidly, and showed a symmetric flow regime. However, at high De, the time required to reach steady flow behind the cylinder increased significantly, and the distribution of the velocity field appears to be asymmetric with respect to the stagnation line. Fairly good agreement between the numerical results and the experimental observations is reported. It can be concluded that both the experimental measurements and the present simulations indicate that the elasticity of the polymeric flow strongly affect the flow regime of viscoelastic flow around a confined cylinder.

关键词： transient effect flow around a cylinder Lagrangian-Eulerian algorithm Oldroyd-B model

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

欢迎您,

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案：

请选择收藏分类：

通借通还

欢迎您,

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：