Phase change and the regulation of developmental timing in plants     

Poethig RS 《Science (New York, N.Y.)》2003,301(5631):334-336

Plants produce different types of organs at different times in shoot development. Along with the major changes in organ morphology that take place during developmental transitions, more gradual patterns of variation occur. The identity of organs produced at a particular position on the shoot is determined by interactions between several independently regulated, temporally coordinated processes. Two of these processes are organ production and the specification of organ identity. Coordination of these processes is accomplished in part by a thermal clock and by signal transduction pathways that mediate the response of plants to light.  相似文献   

An Argonaute transports siRNAs from the cytoplasm to the nucleus     

Guang S  Bochner AF  Pavelec DM  Burkhart KB  Harding S  Lachowiec J  Kennedy S 《Science (New York, N.Y.)》2008,321(5888):537-541

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THE EDENTATA OF THE SANTA CRUZ BEDS     

Scott WB 《Science (New York, N.Y.)》1903,17(440):900-904

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A rational chemical synthesis of C60     

Scott LT  Boorum MM  McMahon BJ  Hagen S  Mack J  Blank J  Wegner H  de Meijere A 《Science (New York, N.Y.)》2002,295(5559):1500-1503

Isolable quantities of C60, the smallest stable fullerene, have been synthesized in 12 steps from commercially available starting materials by rational chemical methods. A molecular polycyclic aromatic precursor bearing chlorine substituents at key positions forms C60 when subjected to flash vacuum pyrolysis at 1100 degrees C. No other fullerenes are formed as by-products. The methods we have developed for the target-specific synthesis of fullerenes, applied here to a synthesis of C60, should make possible the directed laboratory preparation of other fullerenes as well, including those not accessible by graphite vaporization.  相似文献   

THE ATOMIC WEIGHT OF BORON     

Baxter GP  Scott AF 《Science (New York, N.Y.)》1921,54(1404):524-525

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Optical frequency synthesis and comparison with uncertainty at the 10(-19) level     

Ma LS  Bi Z  Bartels A  Robertsson L  Zucco M  Windeler RS  Wilpers G  Oates C  Hollberg L  Diddams SA 《Science (New York, N.Y.)》2004,303(5665):1843-1845

A femtosecond laser-based optical frequency synthesizer is referenced to an optical standard, and we use it to demonstrate the generation and control of the frequency of electromagnetic fields over 100 terahertz of bandwidth with fractional uncertainties approaching 1 part in 10(19). The reproducibility of this performance is verified by comparison of different types of femtosecond laser-based frequency synthesizers from three laboratories.  相似文献   

The IkappaB-NF-kappaB signaling module: temporal control and selective gene activation     

Hoffmann A  Levchenko A  Scott ML  Baltimore D 《Science (New York, N.Y.)》2002,298(5596):1241-1245

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Carbon in Amazon forests: unexpected seasonal fluxes and disturbance-induced losses   总被引：1，自引：0，他引：1  

Saleska SR  Miller SD  Matross DM  Goulden ML  Wofsy SC  da Rocha HR  de Camargo PB  Crill P  Daube BC  de Freitas HC  Hutyra L  Keller M  Kirchhoff V  Menton M  Munger JW  Pyle EH  Rice AH  Silva H 《Science (New York, N.Y.)》2003,302(5650):1554-1557

The net ecosystem exchange of carbon dioxide was measured by eddy covariance methods for 3 years in two old-growth forest sites near Santarém, Brazil. Carbon was lost in the wet season and gained in the dry season, which was opposite to the seasonal cycles of both tree growth and model predictions. The 3-year average carbon loss was 1.3 (confidence interval: 0.0 to 2.0) megagrams of carbon per hectare per year. Biometric observations confirmed the net loss but imply that it is a transient effect of recent disturbance superimposed on long-term balance. Given that episodic disturbances are characteristic of old-growth forests, it is likely that carbon sequestration is lower than has been inferred from recent eddy covariance studies at undisturbed sites.  相似文献   

Itokawa dust particles: a direct link between S-type asteroids and ordinary chondrites     

Nakamura T  Noguchi T  Tanaka M  Zolensky ME  Kimura M  Tsuchiyama A  Nakato A  Ogami T  Ishida H  Uesugi M  Yada T  Shirai K  Fujimura A  Okazaki R  Sandford SA  Ishibashi Y  Abe M  Okada T  Ueno M  Mukai T  Yoshikawa M  Kawaguchi J 《Science (New York, N.Y.)》2011,333(6046):1113-1116

The Hayabusa spacecraft successfully recovered dust particles from the surface of near-Earth asteroid 25143 Itokawa. Synchrotron-radiation x-ray diffraction and transmission and scanning electron microscope analyses indicate that the mineralogy and mineral chemistry of the Itokawa dust particles are identical to those of thermally metamorphosed LL chondrites, consistent with spectroscopic observations made from Earth and by the Hayabusa spacecraft. Our results directly demonstrate that ordinary chondrites, the most abundant meteorites found on Earth, come from S-type asteroids. Mineral chemistry indicates that the majority of regolith surface particles suffered long-term thermal annealing and subsequent impact shock, suggesting that Itokawa is an asteroid made of reassembled pieces of the interior portions of a once larger asteroid.  相似文献   

Human PAD4 regulates histone arginine methylation levels via demethylimination   总被引：1，自引：0，他引：1  

Wang Y  Wysocka J  Sayegh J  Lee YH  Perlin JR  Leonelli L  Sonbuchner LS  McDonald CH  Cook RG  Dou Y  Roeder RG  Clarke S  Stallcup MR  Allis CD  Coonrod SA 《Science (New York, N.Y.)》2004,306(5694):279-283

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