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991.
CHENZhe HUJie ZHOUChuanming XlAOShuhai YUANXunlai 《科学通报(英文版)》2004,49(15):1625-1628
Abundant well-preserved large articulated sponge fossils and isolated spicules have been reported from the Early Cambrian Hetang Formation, southern Anhui Province. This unique epifaunal fossil assemblage dominated by articulated sponge fossils is called the Xidi Sponge Fauna. The sponge fauna lived in a quiet oxygenic environment below the storm wave base. Bloom of phytoplankton and rapid sedimentation rate resulted in the deposition of the black shales. Sufficient food supply, lack of other competitors, abundant ecological niches, and demand for oxygen during early Cambrian were in favor of the diversification and evolution of large sponges in the Early Cambrian. 相似文献
992.
SONGCheng CHENYaqing WEIShuai YOUXiaozeng XIAOShoujun 《科学通报(英文版)》2004,49(9):879-882
Self-assembly of synthetic oligonucleotides into two-dimensional lattices presents a 慴ottom-up?approach to the fabrication of devices on nanometer scale. We report the design and observation of two-dimensional crystalline forms of DNAs that are composed of twenty-one plane oligonucleo-tides and one phosphate-modified oligonucleotide. These synthetic sequences are designed to self-assemble into four double-crossover (DX) DNA tiles. The 憇ticky ends?of these tiles that associate according to WatsonCrick抯 base pairing are programmed to build up specific periodic patterns upto tens of microns. The patterned crystals are visualized by the transmission electron microscopy. 相似文献
993.
XUJin LISanping DONGYafei WEIXiaopeng 《科学通报(英文版)》2004,49(9):863-871
Sticker model is one of the basic models in the DNA computer models. This model is coded with sin-gle-double stranded DNA molecules. It has the following advantages that the operations require no strands extension and use no enzymes; What抯 more, the materials are reusable. Therefore, it arouses attention and interest of scientists in many fields. In this paper, we extend and improve the sticker model, which will be definitely beneficial to the construction of DNA computer. This paper is the second part of our series paper, which mainly focuses on the application of sticker model. It mainly consists of the following three sections: the matrix representation of sticker model is first presented; then a brief review of the past research on graph and com-binatorial optimization, such as the minimal set covering problem, the vertex covering problem, Hamiltonian path or cycle problem, the maximal clique problem, the maximal independent problem and the Steiner spanning tree problem, is described; Finally a DNA algorithm for the graph iso-morphic problem based on the sticker model is given. 相似文献
994.
Zircon U-Pb SHRIMP ages of eclogites from the North Qilian Mountains in NW China and their tectonic implication 总被引:9,自引:5,他引:4
SONG Shuguang ZHANG Lifei NIU Yaoling SONG Biao ZHANG Guibing & WANG Qianjie . MOE Key Laboratory of Orogenic Belts Crustal Evolution De-partment of Geology Peking University Beijing China . Department of Geology University of Houston Houston TX USA . Beijing SHRIMP Centre Institute of Geology CAGS Beijing China Correspondence should be addressed to Zhang Lifei 《科学通报(英文版)》2004,49(8):848-852
TheNorthQilianMountainsattheboundarybe-tweenGansuandQinghaiProvincesareafamousCaledo-nianplatesuturezoneinthenorthwesternChina.Thissuturezoneis80to100kmwideandextendsintheNWdirectionparalleltotheNorthQaidamUHPbeltinthesouth[1,2].Itconsistspredominantlyofophiolite,island-arccomplexandhigh-presuremetamorphicrocks[38],andshowstypicalfeaturesofPacific-type[9](orB-type)sub-ductionzone.Spatially,thehigh-pressurerockscanbesubdividedintohigh-gradeblueschistbeltandlow-gradeblueschistbelt[5,6].Th… 相似文献
995.
Abnormal austenite-ferrite transformation behavior in pure iron 总被引:1,自引:0,他引:1
LIUYongchang F.Sommer E.J.Mittemeijer 《科学通报(英文版)》2004,49(9):972-975
The austenite → ferrite transformation is themost important reaction route in the manufacture ofFe-based materials. Here the austenite (γ) → ferrite (α)transformation of pure iron was systematically explored byhigh-resolution dilatometry. Abnormal transformation ki-netics, multi-peak discontinuous reaction, was recognized inpure iron according to the variation of the ferrite-formationrate. The occurrence the one or the other type of γ→∝ trans-formation strongly depends on the grain size: the transfor-mation type changes from abnormal to normal (single-peakcontinuous reaction) with decreasing grain size. The inherentreason for the occurrence of abnormal transformation couldbe attributed to the repeated nucleation in front of the mov-ing γ/α interface induced by the accumulation of elastic andplastic accommodation energy. 相似文献
996.
XlAOShuhai 《科学通报(英文版)》2004,49(10):983-984
The Sphinx is an enigmatic monster in Greek my-thology that had the body of a lion, wings of a bird, and head and bust of a woman. As the myth goes, the Sphinx guarded the gate to Thebes and would kill anyone unableto answer her riddle. The Sphinx riddle was eventuallycorrectly solved by Oedipus who later became the king of Thebes. 相似文献
997.
Indonesian Throughflow in an eddy-permitting oceanic GCM 总被引:4,自引:0,他引:4
LIWei LIUHailong ZHANGXuehong 《科学通报(英文版)》2004,49(21):2305-2310
An eddy-permitting quasi-global oceanic GCM was driven by wind stresses from reanalysis data for the period of 1958-2001 to get the time series of the upper circulation in the Indonesian Sea. The model represents a reasonable pathway of Indonesian Throughflow (ITF) with Makassar Strait making the major passage transfer the North Pacific water southward. The simulated annual mean ITF transport is 14.5 Sv, with 13.2 Sv in the upper 700 m. Annual cycle is the dominant signal for the seasonal climatology of the upper layer transport. Both the annual mean and seasonal cycle agree well with the observation. The overall correlation between the interannual anomaly of the ITF transport and Nino 3.4 index reaches -0.65 in the simulation,which indicates that ENSO-related interannual variability in the Pacific is dominant in controlling the ITF transport. The relationship between the interannual anomalies of ITF and sea surface temperature in the Pacific, the Indian Ocean is not fixed in the simulation. In 1994, for instance, the intensive Indian Ocean sea surface temperature anomaly plays a dominant role in the formation of an impressive large transport of ITF. 相似文献
998.
Radiative forcing due to dust aerosol over east Asia-north Pacific region during spring, 2001 总被引:6,自引:0,他引:6
Hong?WangEmail author Guangyu?Shi Aoki?Teruo Biao?Wang Tianliang?Zhao 《科学通报(英文版)》2004,49(20):2212-2219
Atmosphericaerosolsinfluencetheradiationbudgetoftheatmosphere-terrestrialsystem,andthereforeinflu-encetheclimate.Dustaerosolisconsideredtobeacriticalfactortoclimateforcingamongotherkindsofaerosols,whichaccountsfor30percentofaerosolloadingandop-ticaldepth[1].Therearelargeuncertaintiesinthequantita-tiveassessmentsoftheradiativeeffectofdustatthepre-sentday,involvingvariousfactors:refractiveindices,par-ticlesizedistribution,atmosphericaerosolloading,parti-cleshape,etc.[2].Dustaerosolgenerallyorigi… 相似文献
999.
KANGJiancheng LIULeibao QINDahe WANGDali WENJiahong TANDejun LIZhongqin LIJun ZHANGXiaowei 《科学通报(英文版)》2004,49(20):2205-2211
The surface-snow geochemical characteristics are discussed on the East Antarctic Ice Sheet, depending on the stable isotopes ratios of oxygen and hydrogen, concentration of impurities (soluble-ions and insoluble micro-particle) in surface snow collected on the ice sheet. The purpose is to study geochemical zones on the East Antarctic Ice Sheet and to research sources and transportation route of the water vapor and the impurities in surface snow. It has been found that the ratio coefficients, as S1, d1 in the equation δD =S1δ^18O d1, are changed near the elevation 2000 m on the ice sheet. The weight ratio of Cl^-/Na^ at the area below the elevation of 2000 m is close to the ratio in the sea salt; but it is about 2 times that of the sea salt, at the inland area up to the elevation of 2000 m. The concentrations of non-sea-salt Ca^2 ion (nssCa^2 ) and fine-particle increase at the interior up to the elevation 2000 m. At the region below the elevation of 2000 m, the impurity concentration is decreasing with the elevation increasing. Near coastal region, the surface snow has a high concentration of impurity, where the elevation is below 800 m. Combining the translating processes of water.vapor and impurities, it suggests that the region up to the elevation 2000 m is affected by large-scale circulation with longitude-direction, and that water-vapor and impurities in surface snow come from long sources. The region below the elevation 2000 m is affected by some strong cyclones acting at peripheral region of the ice sheet, and the sources of water and impurities could be at high latitude sea and coast. The area below elevation 800 m is affected by local coastal cyclones. 相似文献
1000.