Muscular thin films for building actuators and powering devices     

Feinberg AW  Feigel A  Shevkoplyas SS  Sheehy S  Whitesides GM  Parker KK 《Science (New York, N.Y.)》2007,317(5843):1366-1370

We demonstrate the assembly of biohybrid materials from engineered tissues and synthetic polymer thin films. The constructs were built by culturing neonatal rat ventricular cardiomyocytes on polydimethylsiloxane thin films micropatterned with extracellular matrix proteins to promote spatially ordered, two-dimensional myogenesis. The constructs, termed muscular thin films, adopted functional, three-dimensional conformations when released from a thermally sensitive polymer substrate and were designed to perform biomimetic tasks by varying tissue architecture, thin-film shape, and electrical-pacing protocol. These centimeter-scale constructs perform functions as diverse as gripping, pumping, walking, and swimming with fine spatial and temporal control and generating specific forces as high as 4 millinewtons per square millimeter.  相似文献   

Two-dimensional nanosheets produced by liquid exfoliation of layered materials   总被引：1，自引：0，他引：1  

Coleman JN  Lotya M  O'Neill A  Bergin SD  King PJ  Khan U  Young K  Gaucher A  De S  Smith RJ  Shvets IV  Arora SK  Stanton G  Kim HY  Lee K  Kim GT  Duesberg GS  Hallam T  Boland JJ  Wang JJ  Donegan JF  Grunlan JC  Moriarty G  Shmeliov A  Nicholls RJ  Perkins JM  Grieveson EM  Theuwissen K  McComb DW  Nellist PD  Nicolosi V 《Science (New York, N.Y.)》2011,331(6017):568-571

If they could be easily exfoliated, layered materials would become a diverse source of two-dimensional crystals whose properties would be useful in applications ranging from electronics to energy storage. We show that layered compounds such as MoS(2), WS(2), MoSe(2), MoTe(2), TaSe(2), NbSe(2), NiTe(2), BN, and Bi(2)Te(3) can be efficiently dispersed in common solvents and can be deposited as individual flakes or formed into films. Electron microscopy strongly suggests that the material is exfoliated into individual layers. By blending this material with suspensions of other nanomaterials or polymer solutions, we can prepare hybrid dispersions or composites, which can be cast into films. We show that WS(2) and MoS(2) effectively reinforce polymers, whereas WS(2)/carbon nanotube hybrid films have high conductivity, leading to promising thermoelectric properties.  相似文献   

Retraction     

Ricaurte GA  Yuan J  Hatzidimitriou G  Cord BJ  McCann UD 《Science (New York, N.Y.)》2003,301(5639):1479

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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   

Infrared echoes near the supernova remnant Cassiopeia A     

Krause O  Rieke GH  Birkmann SM  Le Floc'h E  Gordon KD  Egami E  Bieging J  Hughes JP  Young ET  Hinz JL  Quanz SP  Hines DC 《Science (New York, N.Y.)》2005,308(5728):1604-1606

Two images of Cassiopeia A obtained at 24 micrometers with the Spitzer Space Telescope over a 1-year time interval show moving structures outside the shell of the supernova remnant to a distance of more than 20 arc minutes. Individual features exhibit apparent motions of 10 to 20 arc seconds per year, independently confirmed by near-infrared observations. The observed tangential velocities are at roughly the speed of light. It is likely that the moving structures are infrared echoes, in which interstellar dust is heated by the explosion and by flares from the compact object near the center of the remnant.  相似文献   

Growth of SiO2 at room temperature with the use of catalyzed sequential half-reactions     

JW Klaus  O Sneh  SM George 《Science (New York, N.Y.)》1997,278(5345):1934-1936

Films of silicon dioxide (SiO2) were deposited at room temperature by means of catalyzed binary reaction sequence chemistry. The binary reaction SiCl4 + 2H2O --> SiO2 + 4HCl was separated into SiCl4 and H2O half-reactions, and the half-reactions were then performed in an ABAB ellipsis sequence and catalyzed with pyridine. The pyridine catalyst lowered the deposition temperature from >600 to 300 kelvin and reduced the reactant flux required for complete reactions from approximately 10(9) to approximately 10(4) Langmuirs. Growth rates of approximately 2.1 angstroms per AB reaction cycle were obtained at room temperature for reactant pressures of 15 millitorr and 60-second exposure times with 200 millitorr of pyridine. This catalytic technique may be general and should facilitate the chemical vapor deposition of other oxide and nitride materials.  相似文献   

Quantitative morphological signatures define local signaling networks regulating cell morphology     

Bakal C  Aach J  Church G  Perrimon N 《Science (New York, N.Y.)》2007,316(5832):1753-1756

Although classical genetic and biochemical approaches have identified hundreds of proteins that function in the dynamic remodeling of cell shape in response to upstream signals, there is currently little systems-level understanding of the organization and composition of signaling networks that regulate cell morphology. We have developed quantitative morphological profiling methods to systematically investigate the role of individual genes in the regulation of cell morphology in a fast, robust, and cost-efficient manner. We analyzed a compendium of quantitative morphological signatures and described the existence of local signaling networks that act to regulate cell protrusion, adhesion, and tension.  相似文献   

Biomarkers of caloric restriction may predict longevity in humans     

Roth GS  Lane MA  Ingram DK  Mattison JA  Elahi D  Tobin JD  Muller D  Metter EJ 《Science (New York, N.Y.)》2002,297(5582):811

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Multi-party responses to environmental problems. A case of contaminated dairy cattle     

George E. B. Morren Jr. 《Agriculture and Human Values》1989,6(4):30-39

This paper presents a framework for exploring the temporal and behavioral aspects of the responses of various involved parties that may lead to governmental intervention in situations involving exposure of the public to hazardous substances. The activities of key individuals are closely scrutinized. Relevance of the framework to agricultural and food concerns is also indicated. The exemplary case is the contamination of livestock in Michigan that began in 1973, but other cases are discussed that conform closely to the pattern described by the framework.George Morren is Associate Professor of Anthropology and Ecology in the Department of Human Ecology at Cook College, Rutgers, the State University of New Jersey, where he coordinates the International Environmental Studies Program. His areas of interest include tropical human ecology and social responses to hazards. He has done field research in Papua, New Guinea, northern Europe, and the U. S. and is currently studying public participation in environmental affairs in New Jersey and long term forest change in Papua, New Guinea. He is co-author (with Kathleen Wilson) ofSystems Approaches for Improvement in Agriculture and Resource Management, MacMillan, 1990.  相似文献   

Spatial regulation of an E3 ubiquitin ligase directs selective synapse elimination     

Ding M  Chao D  Wang G  Shen K 《Science (New York, N.Y.)》2007,317(5840):947-951

Stereotyped synaptic connectivity can arise both by precise recognition between appropriate partners during synaptogenesis and by selective synapse elimination. The molecular mechanisms that underlie selective synapse removal are largely unknown. We found that stereotyped developmental elimination of synapses in the Caenorhabditis elegans hermaphrodite-specific motor neuron (HSNL) was mediated by an E3 ubiquitin ligase, a Skp1-cullin-F-box (SCF) complex composed of SKR-1 and the F-box protein SEL-10. SYG-1, a synaptic adhesion molecule, bound to SKR-1 and inhibited assembly of the SCF complex, thereby protecting nearby synapses. Thus, subcellular regulation of ubiquitin-mediated protein degradation contributes to precise synaptic connectivity through selective synapse elimination.  相似文献