排序方式: 共有13条查询结果,搜索用时 10 毫秒
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Kaneko H Dridi S Tarallo V Gelfand BD Fowler BJ Cho WG Kleinman ME Ponicsan SL Hauswirth WW Chiodo VA Karikó K Yoo JW Lee DK Hadziahmetovic M Song Y Misra S Chaudhuri G Buaas FW Braun RE Hinton DR Zhang Q Grossniklaus HE Provis JM Madigan MC Milam AH Justice NL Albuquerque RJ Blandford AD Bogdanovich S Hirano Y Witta J Fuchs E Littman DR Ambati BK Rudin CM Chong MM Provost P Kugel JF Goodrich JA Dunaief JL Baffi JZ Ambati J 《Nature》2011,471(7338):325-330
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山西省地处我国中西部经济不发达地区,科技水平和经济发展相对滞后。因此,经济转轨过程中,引进国外智力显得更加必要和迫切。 相似文献
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Ambati BK Nozaki M Singh N Takeda A Jani PD Suthar T Albuquerque RJ Richter E Sakurai E Newcomb MT Kleinman ME Caldwell RB Lin Q Ogura Y Orecchia A Samuelson DA Agnew DW St Leger J Green WR Mahasreshti PJ Curiel DT Kwan D Marsh H Ikeda S Leiper LJ Collinson JM Bogdanovich S Khurana TS Shibuya M Baldwin ME Ferrara N Gerber HP De Falco S Witta J Baffi JZ Raisler BJ Ambati J 《Nature》2006,443(7114):993-997
Corneal avascularity-the absence of blood vessels in the cornea-is required for optical clarity and optimal vision, and has led to the cornea being widely used for validating pro- and anti-angiogenic therapeutic strategies for many disorders. But the molecular underpinnings of the avascular phenotype have until now remained obscure and are all the more remarkable given the presence in the cornea of vascular endothelial growth factor (VEGF)-A, a potent stimulator of angiogenesis, and the proximity of the cornea to vascularized tissues. Here we show that the cornea expresses soluble VEGF receptor-1 (sVEGFR-1; also known as sflt-1) and that suppression of this endogenous VEGF-A trap by neutralizing antibodies, RNA interference or Cre-lox-mediated gene disruption abolishes corneal avascularity in mice. The spontaneously vascularized corneas of corn1 and Pax6+/- mice and Pax6+/- patients with aniridia are deficient in sflt-1, and recombinant sflt-1 administration restores corneal avascularity in corn1 and Pax6+/- mice. Manatees, the only known creatures uniformly to have vascularized corneas, do not express sflt-1, whereas the avascular corneas of dugongs, also members of the order Sirenia, elephants, the closest extant terrestrial phylogenetic relatives of manatees, and other marine mammals (dolphins and whales) contain sflt-1, indicating that it has a crucial, evolutionarily conserved role. The recognition that sflt-1 is essential for preserving the avascular ambit of the cornea can rationally guide its use as a platform for angiogenic modulators, supports its use in treating neovascular diseases, and might provide insight into the immunological privilege of the cornea. 相似文献
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A. Joshua Leffler Michael S. Peek Larry Hipps Sasha Ivans Ronald J. Ryel Martyn M. Caldwell 《西北部美国博物学家》2011,67(1)
Disturbance events can significantly influence net CO 2 exchange (NCE) in ecosystems. High densities of Anabrus simplex (Mormon crickets) periodically afflict large areas of the western USA; their sheer numbers could make them a significant source of CO 2 . We modeled cricket respiration at the ecosystem level using air and body temperatures and insect gas exchange measurements. Cricket CO 2 efflux values were compared to ecosystem CO 2 flux from eddy covariance measurements in 3 Great Basin ecosystems: a juniper woodland, a sagebrush shrubland, and a crested wheatgrass pasture. Mean respiration from Mormon crickets was 0.96 g CO 2 ? m –2 d –1 . Since Mormon crickets are present when NCE is otherwise near 0, they can potentially alter NCE between 20% (juniper woodland) and 60% (crested wheatgrass pasture). Transient pests such as Mormon crickets can be an important component of NCE. 相似文献
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Graphene-based composite materials 总被引:31,自引:0,他引:31
Stankovich S Dikin DA Dommett GH Kohlhaas KM Zimney EJ Stach EA Piner RD Nguyen ST Ruoff RS 《Nature》2006,442(7100):282-286
Graphene sheets--one-atom-thick two-dimensional layers of sp2-bonded carbon--are predicted to have a range of unusual properties. Their thermal conductivity and mechanical stiffness may rival the remarkable in-plane values for graphite (approximately 3,000 W m(-1) K(-1) and 1,060 GPa, respectively); their fracture strength should be comparable to that of carbon nanotubes for similar types of defects; and recent studies have shown that individual graphene sheets have extraordinary electronic transport properties. One possible route to harnessing these properties for applications would be to incorporate graphene sheets in a composite material. The manufacturing of such composites requires not only that graphene sheets be produced on a sufficient scale but that they also be incorporated, and homogeneously distributed, into various matrices. Graphite, inexpensive and available in large quantity, unfortunately does not readily exfoliate to yield individual graphene sheets. Here we present a general approach for the preparation of graphene-polymer composites via complete exfoliation of graphite and molecular-level dispersion of individual, chemically modified graphene sheets within polymer hosts. A polystyrene-graphene composite formed by this route exhibits a percolation threshold of approximately 0.1 volume per cent for room-temperature electrical conductivity, the lowest reported value for any carbon-based composite except for those involving carbon nanotubes; at only 1 volume per cent, this composite has a conductivity of approximately 0.1 S m(-1), sufficient for many electrical applications. Our bottom-up chemical approach of tuning the graphene sheet properties provides a path to a broad new class of graphene-based materials and their use in a variety of applications. 相似文献
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刘萨沙 《科技情报开发与经济》1997,(3)
保护知识产权制度是保护科学技术和文化艺术成果的重要法律制度。本文针对我国目前知识产权保护方面存在的问题,提出了在对外科技合作交流中正确处理知识产权问题的一些具体措施 相似文献
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Functional improvement of dystrophic muscle by myostatin blockade 总被引:42,自引:0,他引:42
Bogdanovich S Krag TO Barton ER Morris LD Whittemore LA Ahima RS Khurana TS 《Nature》2002,420(6914):418-421
Mice and cattle with mutations in the myostatin (GDF8) gene show a marked increase in body weight and muscle mass, indicating that this new member of the TGF-beta superfamily is a negative regulator of skeletal muscle growth. Inhibition of the myostatin gene product is predicted to increase muscle mass and improve the disease phenotype in a variety of primary and secondary myopathies. We tested the ability of inhibition of myostatin in vivo to ameliorate the dystrophic phenotype in the mdx mouse model of Duchenne muscular dystrophy (DMD). Blockade of endogenous myostatin by using intraperitoneal injections of blocking antibodies for three months resulted in an increase in body weight, muscle mass, muscle size and absolute muscle strength in mdx mouse muscle along with a significant decrease in muscle degeneration and concentrations of serum creatine kinase. The functional improvement of dystrophic muscle by myostatin blockade provides a novel, pharmacological strategy for treatment of diseases associated with muscle wasting such as DMD, and circumvents the major problems associated with conventional gene therapy in these disorders. 相似文献
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Preparation and characterization of graphene oxide paper 总被引:7,自引:0,他引:7
Dikin DA Stankovich S Zimney EJ Piner RD Dommett GH Evmenenko G Nguyen ST Ruoff RS 《Nature》2007,448(7152):457-460
Free-standing paper-like or foil-like materials are an integral part of our technological society. Their uses include protective layers, chemical filters, components of electrical batteries or supercapacitors, adhesive layers, electronic or optoelectronic components, and molecular storage. Inorganic 'paper-like' materials based on nanoscale components such as exfoliated vermiculite or mica platelets have been intensively studied and commercialized as protective coatings, high-temperature binders, dielectric barriers and gas-impermeable membranes. Carbon-based flexible graphite foils composed of stacked platelets of expanded graphite have long been used in packing and gasketing applications because of their chemical resistivity against most media, superior sealability over a wide temperature range, and impermeability to fluids. The discovery of carbon nanotubes brought about bucky paper, which displays excellent mechanical and electrical properties that make it potentially suitable for fuel cell and structural composite applications. Here we report the preparation and characterization of graphene oxide paper, a free-standing carbon-based membrane material made by flow-directed assembly of individual graphene oxide sheets. This new material outperforms many other paper-like materials in stiffness and strength. Its combination of macroscopic flexibility and stiffness is a result of a unique interlocking-tile arrangement of the nanoscale graphene oxide sheets. 相似文献
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