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排序方式: 共有266条查询结果,搜索用时 31 毫秒
191.
Sung Hwan Hong Jeong Tae Kim Jin Man Park Gian Song Wei-Min Wang Ki Buem Kim 《自然科学进展(英文版)》2018,28(6):704-710
Ti_(45)Cu_(40)Ni_7Zr_5Sn_(2.5)Si_(0.5) alloys were prepared under various cooling rate conditions during solidification.The alloys exhibited different volume fractions of B2 particles with 0~40 vol%in an amorphous matrix.Monolithic bulk metallic glass of 1 mm diameter showed no macroscopic plasticity and exhibited the typical vein patterns in a maximum shear stress plane on the fracture surface.However,a bulk metallic glass composite containing the B2 particles revealed obvious plasticity(~5.6%)with a remarkable work-hardening behavior that resulted from a stress-induced martensitic transformation of the B2 particles.Moreover,the composite displayed the complicated fracture morphologies containing of three types of fracture features.Through detailed investigations on the microstructural evolution,mechanical,deformation and fracture characteristics,the influence of B2 particle on overall behavior of the TiCu-based bulk metallic glass composites was elucidated. 相似文献
192.
Blain S Quéguiner B Armand L Belviso S Bombled B Bopp L Bowie A Brunet C Brussaard C Carlotti F Christaki U Corbière A Durand I Ebersbach F Fuda JL Garcia N Gerringa L Griffiths B Guigue C Guillerm C Jacquet S Jeandel C Laan P Lefèvre D Lo Monaco C Malits A Mosseri J Obernosterer I Park YH Picheral M Pondaven P Remenyi T Sandroni V Sarthou G Savoye N Scouarnec L Souhaut M Thuiller D Timmermans K Trull T Uitz J van Beek P Veldhuis M Vincent D Viollier E Vong L Wagener T 《Nature》2007,446(7139):1070-1074
The availability of iron limits primary productivity and the associated uptake of carbon over large areas of the ocean. Iron thus plays an important role in the carbon cycle, and changes in its supply to the surface ocean may have had a significant effect on atmospheric carbon dioxide concentrations over glacial-interglacial cycles. To date, the role of iron in carbon cycling has largely been assessed using short-term iron-addition experiments. It is difficult, however, to reliably assess the magnitude of carbon export to the ocean interior using such methods, and the short observational periods preclude extrapolation of the results to longer timescales. Here we report observations of a phytoplankton bloom induced by natural iron fertilization--an approach that offers the opportunity to overcome some of the limitations of short-term experiments. We found that a large phytoplankton bloom over the Kerguelen plateau in the Southern Ocean was sustained by the supply of iron and major nutrients to surface waters from iron-rich deep water below. The efficiency of fertilization, defined as the ratio of the carbon export to the amount of iron supplied, was at least ten times higher than previous estimates from short-term blooms induced by iron-addition experiments. This result sheds new light on the effect of long-term fertilization by iron and macronutrients on carbon sequestration, suggesting that changes in iron supply from below--as invoked in some palaeoclimatic and future climate change scenarios--may have a more significant effect on atmospheric carbon dioxide concentrations than previously thought. 相似文献
193.
Akimov AV Mukherjee A Yu CL Chang DE Zibrov AS Hemmer PR Park H Lukin MD 《Nature》2007,450(7168):402-406
Control over the interaction between single photons and individual optical emitters is an outstanding problem in quantum science and engineering. It is of interest for ultimate control over light quanta, as well as for potential applications such as efficient photon collection, single-photon switching and transistors, and long-range optical coupling of quantum bits. Recently, substantial advances have been made towards these goals, based on modifying photon fields around an emitter using high-finesse optical cavities. Here we demonstrate a cavity-free, broadband approach for engineering photon-emitter interactions via subwavelength confinement of optical fields near metallic nanostructures. When a single CdSe quantum dot is optically excited in close proximity to a silver nanowire, emission from the quantum dot couples directly to guided surface plasmons in the nanowire, causing the wire's ends to light up. Non-classical photon correlations between the emission from the quantum dot and the ends of the nanowire demonstrate that the latter stems from the generation of single, quantized plasmons. Results from a large number of devices show that efficient coupling is accompanied by more than 2.5-fold enhancement of the quantum dot spontaneous emission, in good agreement with theoretical predictions. 相似文献
194.
Seung-Jae Lee In Hwan Lee Jeong Hun Park So-Jung Gwak Jong-Won Rhie Dong-Woo Cho Tae Jo Ko Dong Sung Kim 《科学通报(英文版)》2009,54(19):3608-3612
We developed a hybrid scaffold and a bioreactor for cartilage regeneration. The hybrid scaffold was developed as combination of two components: a biodegradable framework and hydrogel-containing chondrocytes. We performed the MTT cell proliferation assay to compare the proliferation and viability of chondrocytes on three types of scaffolds: an aiginate gel, the hybrid scaffold, and an alginate sponge. Cells were encapsulated in 2% agarose gel. The bioreactor consisted of a circulation system and a compression system. We performed dynamic cell culture on these agarose gels in the bioreactor for 3 days. 相似文献
195.
196.
Hye-Kyoung Jeon Jung-Hyun Lee Kee-Wook Rim Yang-Jae Park 《重庆邮电大学学报(自然科学版)》2007,19(3):392-396
This paper presents a system to alert of dangerous a child situation of a child by applying context information collected from a home network to ontology that is capable of inference. Radio frequency Identification (RFID) and sensors were used for the configuration of a home network, to obtain the raw data to convert into context information. To express the ontology, web ontology language (OWL) was used to provide the inference of context information. Then, simple object access protocol (SOAP) messages were used to notify of the dangerous situations that a child may be involved in via mobile devices. The proposed system consists of Context Manager, Service Manager, and Notification Manager. The child's safety management system can proactively detect the context data of a child on the basis of context awareness. In the experiment, the Jena 2.0 by ontology reasoner and the OSGi(Open Service Gateway initiative) Gateway developed using open source software Knopflerfish 1.3.3 were used to implement the service frame work. 相似文献
197.
Park S Park SH Baek JY Jy YJ Kim KS Roth J Cho JW Choe KM 《Cellular and molecular life sciences : CMLS》2011,68(20):3377-3384
Modification of nuclear and cytosolic proteins by O-linked N-acetylglucosamine (O-GlcNAcylation) is ubiquitous in cells. The in vivo function of the protein O-GlcNAcylation, however, is not well understood. Here, we manipulated the cellular O-GlcNAcylation level in Drosophila and found that it promotes developmental growth by enhancing insulin signaling. This increase in growth is due mainly to
cell growth and not to cell proliferation. Our data suggest that the increase in the insulin signaling activity is mediated,
at least in part, through O-GlcNAcylation of Akt. These results indicate that O-GlcNAcylation is one of the crucial mechanisms involved in control of insulin signaling during Drosophila development. 相似文献
198.
Eight new species of Promalactis were discovered from Indonesia: Promalactis diazomatis sp. nov., Promalactis hamatella sp. nov., Promalactis ingenticula sp. nov., Promalactis laetusella sp. nov., Promalactis latifundus sp. nov., Promalactis minutispina sp. nov., Promalactis mooatana sp. nov. and Promalactis trigonilancis sp. nov. Illustrations of adults and genitalia of the new species and taxonomic information for the six previously known species from Indonesia are provided. A checklist of the genus in Indonesia is given.
www.zoobank.org/urn:lsid:zoobank.org:pub:E25224C7-2D41-4F5A-A4BB-41AA1307E0C0 相似文献
199.
Seungbae Park 《Foundations of Science》2017,22(3):613-625
The pessimistic induction over scientific theories (Poincaré in Science and hypothesis, Dover, New York, 1905/1952) holds that present theories will be overthrown as were past theories. The pessimistic induction over scientists (Stanford in Exceeding our grasp: science, history, and the problem of unconceived alternatives, Oxford University Press, Oxford, 2006) holds that present scientists cannot conceive of future theories just as past scientists could not conceive of present theories. The pessimistic induction over realists (Wray in Synthese 190(18):4321–4330, 2013) holds that present realists are wrong about present theories just as past realists were wrong about past theories. The pessimistic induction over antirealist theories (Park in Organon F 21(1):3–21, 2014) holds that the latest antirealist explanation of the success of science (Lyons in Philos Sci 70(5):891–901, 2003) has hidden problems just as its eight predecessors did. In this paper, I (1) criticize the pessimistic inductions over scientific theories, scientists, and realists, (2) introduce a pessimistic induction over antirealist theories, and then (3) construct two new pessimistic inductions. One is a pessimistic induction over antirealists according to which the author of the latest antirealist proposal cannot see hidden problems with his proposal just as his antirealist predecessors could not see hidden problems with their proposals. The other is the pessimistic induction over pessimists according to which since past pessimists have been wrong about their present scientific theories from the early twentieth century to the early twenty-first century, future pessimists will also be wrong about their present scientific theories from the early twenty-first century to the early twenty-second century. 相似文献
200.
Barbieri CE Baca SC Lawrence MS Demichelis F Blattner M Theurillat JP White TA Stojanov P Van Allen E Stransky N Nickerson E Chae SS Boysen G Auclair D Onofrio RC Park K Kitabayashi N MacDonald TY Sheikh K Vuong T Guiducci C Cibulskis K Sivachenko A Carter SL Saksena G Voet D Hussain WM Ramos AH Winckler W Redman MC Ardlie K Tewari AK Mosquera JM Rupp N Wild PJ Moch H Morrissey C Nelson PS Kantoff PW Gabriel SB Golub TR Meyerson M Lander ES Getz G Rubin MA Garraway LA 《Nature genetics》2012,44(6):685-689