Ultrafast bond softening in bismuth: mapping a solid's interatomic potential with X-rays     

Fritz DM  Reis DA  Adams B  Akre RA  Arthur J  Blome C  Bucksbaum PH  Cavalieri AL  Engemann S  Fahy S  Falcone RW  Fuoss PH  Gaffney KJ  George MJ  Hajdu J  Hertlein MP  Hillyard PB  Horn-von Hoegen M  Kammler M  Kaspar J  Kienberger R  Krejcik P  Lee SH  Lindenberg AM  McFarland B  Meyer D  Montagne T  Murray ED  Nelson AJ  Nicoul M  Pahl R  Rudati J  Schlarb H  Siddons DP  Sokolowski-Tinten K  Tschentscher T  von der Linde D  Hastings JB 《Science (New York, N.Y.)》2007,315(5812):633-636

Intense femtosecond laser excitation can produce transient states of matter that would otherwise be inaccessible to laboratory investigation. At high excitation densities, the interatomic forces that bind solids and determine many of their properties can be substantially altered. Here, we present the detailed mapping of the carrier density-dependent interatomic potential of bismuth approaching a solid-solid phase transition. Our experiments combine stroboscopic techniques that use a high-brightness linear electron accelerator-based x-ray source with pulse-by-pulse timing reconstruction for femtosecond resolution, allowing quantitative characterization of the interatomic potential energy surface of the highly excited solid.  相似文献   

Submarine thermal sprirngs on the galapagos rift   总被引：2，自引：0，他引：2  

Corliss JB  Dymond J  Gordon LI  Edmond JM  von Herzen RP  Ballard RD  Green K  Williams D  Bainbridge A  Crane K  van Andel TH 《Science (New York, N.Y.)》1979,203(4385):1073-1083

The submarine hydrothermal activity on and near the Galápagos Rift has been explored with the aid of the deep submersible Alvin. Analyses of water samples from hydrothermal vents reveal that hydrothermal activity provides significant or dominant sources and sinks for several components of seawater; studies of conductive and convective heat transfer suggest that two-thirds of the heat lost from new oceanic lithosphere at the Galápagos Rift in the first million years may be vented from thermal springs, predominantly along the axial ridge within the rift valley. The vent areas are populated by animal communities. They appear to utilize chemosynthesis by sulfur-oxidizing bacteria to derive their entire energy supply from reactions between the seawater and the rocks at high temperatures, rather than photosynthesis.  相似文献   

Controlling chemical turbulence by global delayed feedback: pattern formation in catalytic CO oxidation on Pt(110)     

Kim M  Bertram M  Pollmann M  von Oertzen A  Mikhailov AS  Rotermund HH  Ertl G 《Science (New York, N.Y.)》2001,292(5520):1357-1360

Control of spatiotemporal chaos is one of the central problems of nonlinear dynamics. We report on suppression of chemical turbulence by global delayed feedback using, as an example, catalytic carbon monoxide oxidation on a platinum (110) single-crystal surface and carbon monoxide partial pressure as the controlled feedback variable. When feedback intensity was increased, spiral-wave turbulence was transformed into new intermittent chaotic regimes with cascades of reproducing and annihilating local structures on the background of uniform oscillations. The global feedback further led to the development of cluster patterns and standing waves and to the stabilization of uniform oscillations. These findings are reproduced by theoretical simulations.  相似文献   

Bat flight generates complex aerodynamic tracks     

Hedenström A  Johansson LC  Wolf M  von Busse R  Winter Y  Spedding GR 《Science (New York, N.Y.)》2007,316(5826):894-897

The flapping flight of animals generates an aerodynamic footprint as a time-varying vortex wake in which the rate of momentum change represents the aerodynamic force. We showed that the wakes of a small bat species differ from those of birds in some important respects. In our bats, each wing generated its own vortex loop. Also, at moderate and high flight speeds, the circulation on the outer (hand) wing and the arm wing differed in sign during the upstroke, resulting in negative lift on the hand wing and positive lift on the arm wing. Our interpretations of the unsteady aerodynamic performance and function of membranous-winged, flapping flight should change modeling strategies for the study of equivalent natural and engineered flying devices.  相似文献   

Comment on "Reactions at interfaces as a source of sulfate formation in sea-salt particles" (II)     

Sander R  Crutzen PJ  von Glasow R 《Science (New York, N.Y.)》2004,303(5658):628; author reply 628

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Immunology. T cell activation in six dimensions     

von Andrian UH 《Science (New York, N.Y.)》2002,296(5574):1815-1817

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Chemistry. The chlorine dilemma     

Sedlak DL  von Gunten U 《Science (New York, N.Y.)》2011,331(6013):42-43

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Wheat Leaf Rust: Control by 4-n-Butyl-1,2,4-triazole, a Systemic Fungicide     

von Meyer WC  Greenfield SA  Seidel MC 《Science (New York, N.Y.)》1970,169(3949):997-998

Compound 4-n-butyl-1,2,4-triazole was demonstrated as an enduring and selective systemic fungicide for the control of wheat leaf rust by foliar and soil applications. Among several species of rust fungi treated, only wheat leaf rust (Puccinia recondita Rob.) was controlled. Wheat stem rust, for example, was unaffected by either soil or foliar applications.  相似文献   

Spreading of the ocean floor: undeformed sediments in the peru-chile trench     

Scholl DW  von Huene R  Ridlon JB 《Science (New York, N.Y.)》1968,159(3817):869-871

None of the expected stratigraphic and structural effects of a spreading sea floor have been imposed on the sedimentary fill of the Peru-Chile Trench. During at least the last several million years, and perhaps during much of the Cenozoic, the trench has not been affected by an oceanic crust thrusting under the continent.  相似文献   

Dynamic visualization of thrombopoiesis within bone marrow     

Junt T  Schulze H  Chen Z  Massberg S  Goerge T  Krueger A  Wagner DD  Graf T  Italiano JE  Shivdasani RA  von Andrian UH 《Science (New York, N.Y.)》2007,317(5845):1767-1770

Platelets are generated from megakaryocytes (MKs) in mammalian bone marrow (BM) by mechanisms that remain poorly understood. Here we describe the use of multiphoton intravital microscopy in intact BM to visualize platelet generation in mice. MKs were observed as sessile cells that extended dynamic proplatelet-like protrusions into microvessels. These intravascular extensions appeared to be sheared from their transendothelial stems by flowing blood, resulting in the appearance of proplatelets in peripheral blood. In vitro, proplatelet production from differentiating MKs was enhanced by fluid shear. These results confirm the concept of proplatelet formation in vivo and are consistent with the possibility that blood flow-induced hydrodynamic shear stress is a biophysical determinant of thrombopoiesis.  相似文献