Evidence for chain molecules enriched in carbon, hydrogen, and oxygen in comet halley     

Mitchell DL  Lin RP  Anderson KA  Carlson CW  Curtis DW  Korth A  Rème H  Sauvaud JA  D'Uston C  Mendis DA 《Science (New York, N.Y.)》1987,237(4815):626-628

In situ measurements of the composition and spatial distribution of heavy thermal positive ions in the coma of comet Halley were made with the heavy-ion analyzer RPA2-PICCA aboard the Giotto spacecraft. Above 50 atomic mass units an ordered series of mass peaks centered at 61, 75, 91, and 105 atomic mass units were observed. Each peak appears to be composed of three or more closely spaced masses. The abundances decrease and the dissociation rates increase smoothly with increasing mass. These observations suggest the presence of chain molecules that are enriched in carbon, oxygen, and hydrogen, such as polyoxymethylene (polymerized formaldehyde), in comet Halley.  相似文献   

Site-directed neovessel formation in vivo   总被引：20，自引：0，他引：20  

J A Thompson  K D Anderson  J M DiPietro  J A Zwiebel  M Zametta  W F Anderson  T Maciag 《Science (New York, N.Y.)》1988,241(4871):1349-1352

Angiogenesis is an important component of organogenesis and wound repair and occurs during the pathology of oncogenesis, atherogenesis, and other disease processes. Thus, it is important to understand the physiological mechanisms that control neovascularization, especially with methods that permit the molecular dissection of the phenomenon in vivo. Heparin-binding growth factor-1 was shown to bind to collagen type I and type IV. When complexed with gelatin, heparin-binding growth factor-1 can induce neovascularization at polypeptide concentrations that are consistent with the biological activity of the mitogen in vitro. The adsorption strategy induces rapid blood vessel formation at and between organ- and tissue-specific sites and permits recovery of the site-specific implant for examination and manipulation by molecular methods.  相似文献   

c-axis electrodynamics as evidence for the interlayer theory of high-temperature superconductivity     

PW Anderson 《Science (New York, N.Y.)》1998,279(5354):1196-1198

In the interlayer theory of high-temperature superconductivity, the interlayer pair tunneling energy (similar to the Josephson or Lawrence-Doniach energy) is the motivation for superconductivity. This connection requires two experimentally verifiable identities: the coherent normal-state conductance must be smaller than the "Josephson" coupling energy, and the Josephson coupling energy must be equal to the condensation energy of the superconductor. The first condition is well satisfied in the only case that is relevant, (La, Sr)2CuO4, but the second condition has been questioned. It is satisfied for all dopings in (La,Sr)2CuO4 and also in optimally doped Hg(Ba)2CuO5, which was measured recently, but seems to be strongly violated in measurements on single crystals of Tl2Ba2CuO6.  相似文献   

A Fluted Point from the Uptar Site, Northeastern Siberia     

ML King  SB Slobodin 《Science (New York, N.Y.)》1996,273(5275):634-636

Lanceolate bifacial points, including one fluted specimen, have been collected from beneath an early Holocene tephra at the Uptar site, northeastern Siberia. Thus, the technology associated with the well-known Paleoindian tradition was not confined to the Americas. The Uptar collection does not compare readily with other Beringian complexes and demonstrates that there is greater diversity in the archaeological record of northeastern Siberia than traditional colonization models imply.  相似文献   

Electron Plasma Oscillations Associated with Type III Radio Bursts     

Gurnett DA  Anderson RR 《Science (New York, N.Y.)》1976,194(4270):1159-1162

Plasma wave electric field measurements with the solar orbiting Helios spacecraft have shown that intense (approximately 10 millivolts per meter) electron plasma oscillations occur in association with type III solar radio bursts. These observations confirm the basic mechanism, proposed in 1958, that type III radio emissions are produced by intense electron plasma oscillations excited in the solor corona by electrons ejected from a solar flare.  相似文献   

High-Resolution Imaging by Fourier Transform X-ray Holography     

McNulty I  Kirz J  Jacobsen C  Anderson EH  Howells MR  Kern DP 《Science (New York, N.Y.)》1992,256(5059):1009-1012

Fourier transform x-ray holography has been used to image gold test objects with submicrometer structure, resolving features as small as 60 nanometers. The hologram-recording instrument uses coherent 3.4-nanometer radiation from the soft x-ray undulator beamline X1A at the National Synchrotron Light Source. The specimen to be imaged is placed near the first-order focal spot produced by a Fresnel zone plate; the other orders, chiefly the zeroth, illuminate the specimen. The wave scattered by the specimen interferes with the spherical reference wave from the focal spot, forming a hologram with fringes of low spatial frequency. The hologram is recorded in digital form by a charge-coupled device camera, and the specimen image is obtained by numerical reconstruction.  相似文献   

Gravity field of jupiter from pioneer 11 tracking data     

Null GW  Anderson JD  Wong SK 《Science (New York, N.Y.)》1975,188(4187):476-477

Significantly improved values of the zonal gravity harmonic coefficients J(39) J(4), and J(6) of Jupiter have been obtained from a preliminary analysis of Pioneer 11 spacecraft Doppler data taken while the spacecraft was near Jupiter. The new results, which will have an important application as boundary conditions for theoretical models of Jupiter's interior. are consistent with a planet in hydrostatic equilibrium.  相似文献   

Burnsi and Kandiyohi Genes in the Leopard Frog Rana pipiens     

Anderson SC  Volpe EP 《Science (New York, N.Y.)》1958,127(3305):1048-1050

  相似文献   

NATIONAL ARCHEOLOGICAL RESOURCES     

Seeley HW  Anderson EO  Plastridge WN  Pearson P 《Science (New York, N.Y.)》1945,102(2637):44-45

  相似文献   

NUTRITIVE VALUE OF THE MEXICAN TORTILLA     

Cravioto RO  Anderson RK  Lockhart EE  DE P Miranda F  Harris RS 《Science (New York, N.Y.)》1945,102(2639):91-93

  相似文献