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51.
The pyramid at La Venta, Tabasco, Mexico, was surveyed in May 1969 with a high-sensitivity difference magnetometer. The general pattern of the magnetic map is one of low (10-gamma) radial anomalies, which reflect the ridge and gully topography of the pyramid, with a larger magnetic high area (+30 gammas) centered 25 meters south and 10 meters east of the center of the pyramid. The anomalous region near the top has been interpreted with the aid of computer-calculated anomalies from three-dimensional rectangular blocks. The major high is probably associated with a basalt structure that rises to within 1 to 2 meters of the surface. A possible form for this structure was found to be a 10-meter-square horizontal platform with walls along its northern and eastern margin. 相似文献
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53.
Endocannabinoid hydrolysis generates brain prostaglandins that promote neuroinflammation 总被引:2,自引:0,他引:2
Nomura DK Morrison BE Blankman JL Long JZ Kinsey SG Marcondes MC Ward AM Hahn YK Lichtman AH Conti B Cravatt BF 《Science (New York, N.Y.)》2011,334(6057):809-813
Phospholipase A(2)(PLA(2)) enzymes are considered the primary source of arachidonic acid for cyclooxygenase (COX)-mediated biosynthesis of prostaglandins. Here, we show that a distinct pathway exists in brain, where monoacylglycerol lipase (MAGL) hydrolyzes the endocannabinoid 2-arachidonoylglycerol to generate a major arachidonate precursor pool for neuroinflammatory prostaglandins. MAGL-disrupted animals show neuroprotection in a parkinsonian mouse model. These animals are spared the hemorrhaging caused by COX inhibitors in the gut, where prostaglandins are instead regulated by cytosolic PLA(2). These findings identify MAGL as a distinct metabolic node that couples endocannabinoid to prostaglandin signaling networks in the nervous system and suggest that inhibition of this enzyme may be a new and potentially safer way to suppress the proinflammatory cascades that underlie neurodegenerative disorders. 相似文献
54.
Donnelly SE Birtcher RC Allen CW Morrison I Furuya K Song M Mitsuishi K Dahmen U 《Science (New York, N.Y.)》2002,296(5567):507-510
High-resolution transmission electron microscopy images of room-temperature fluid xenon in small faceted cavities in aluminum reveal the presence of three well-defined layers within the fluid at each facet. Such interfacial layering of simple liquids has been theoretically predicted, but observational evidence has been ambiguous. Molecular dynamics simulations indicate that the density variation induced by the layering will cause xenon, confined to an approximately cubic cavity of volume approximately 8 cubic nanometers, to condense into the body-centered cubic phase, differing from the face-centered cubic phase of both bulk solid xenon and solid xenon confined in somewhat larger (>/=20 cubic nanometer) tetradecahedral cavities in face-centered cubic metals. Layering at the liquid-solid interface plays an important role in determining physical properties as diverse as the rheological behavior of two-dimensionally confined liquids and the dynamics of crystal growth. 相似文献
55.
Advances in electronics and computers have enabled industries to attain better control of their processes with resulting increases in quality, productivity, profitability, and compliance with government regulations. With a hierarchy of computers, distributed data acquisition, and information processing and control, it is possible to achieve overall optimum performance of a plant. While further advances in microprocessors and large-scale integration will be useful to the process engineer, major improvements in process control await advances in sensor technology and software. 相似文献
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Smith BA Soderblom LA Beebe R Boyce J Briggs G Carr M Collins SA Cook AF Danielson GE Davies ME Hunt GE Ingersoll A Johnson TV Masursky H McCauley J Morrison D Owen T Sagan C Shoemaker EM Strom R Suomi VE Veverka J 《Science (New York, N.Y.)》1979,206(4421):927-950
Voyager 2, during its encounter with the Jupiter system, provided images that both complement and supplement in important ways the Voyager 1 images. While many changes have been observed in Jupiter's visual appearance, few, yet significant, changes have been detected in the principal atmospheric currents. Jupiter's ring system is strongly forward scattering at visual wavelengths and consists of a narrow annulus of highest particle density, within which is a broader region in which the density is lower. On Io, changes are observed in eruptive activity, plume structure, and surface albedo patterns. Europa's surface retains little or no record of intense meteorite bombardment, but does reveal a complex and, as yet, little-understood system of overlapping bright and dark linear features. Ganymede is found to have at least one unit of heavily cratered terrain on a surface that otherwise suggests widespread tectonism. Except for two large ringed basins, Callisto's entire surface is heavily cratered. 相似文献
58.
PC Sereno DB Dutheil M Iarochene HCE Larsson GH Lyon PM Magwene CA Sidor DJ Varricchio JA Wilson 《Science (New York, N.Y.)》1996,272(5264):986-991
Late Cretaceous (Cenomanian) fossils discovered in the Kem Kem region of Morocco include large predatory dinosaurs that inhabited Africa as it drifted into geographic isolation. One, represented by a skull approximately 1.6 meters in length, is an advanced allosauroid referable to the African genus Carcharodontosaurus. Another, represented by a partial skeleton with slender proportions, is a new basal coelurosaur closely resembling the Egyptian genus Bahariasaurus. Comparisons with Cretaceous theropods from other continents reveal a previously unrecognized global radiation of carcharodontosaurid predators. Substantial geographic differentiation of dinosaurian faunas in response to continental drift appears to have arisen abruptly at the beginning of the Late Cretaceous. 相似文献
59.
Prabhakar S Visel A Akiyama JA Shoukry M Lewis KD Holt A Plajzer-Frick I Morrison H Fitzpatrick DR Afzal V Pennacchio LA Rubin EM Noonan JP 《Science (New York, N.Y.)》2008,321(5894):1346-1350
Changes in gene regulation are thought to have contributed to the evolution of human development. However, in vivo evidence for uniquely human developmental regulatory function has remained elusive. In transgenic mice, a conserved noncoding sequence (HACNS1) that evolved extremely rapidly in humans acted as an enhancer of gene expression that has gained a strong limb expression domain relative to the orthologous elements from chimpanzee and rhesus macaque. This gain of function was consistent across two developmental stages in the mouse and included the presumptive anterior wrist and proximal thumb. In vivo analyses with synthetic enhancers, in which human-specific substitutions were introduced into the chimpanzee enhancer sequence or reverted in the human enhancer to the ancestral state, indicated that 13 substitutions clustered in an 81-base pair module otherwise highly constrained among terrestrial vertebrates were sufficient to confer the human-specific limb expression domain. 相似文献
60.
Holtkamp DJ Polson DD Torremorell M Morrison B Classen DM Becton L Henry S Rodibaugh MT Rowland RR Snelson H Straw B Yeske P Zimmerman J;American Association of Swine Veterinarians;United States Department of Agriculture PRRS-Coordinated Agricultural Project 《Tier?rztliche Praxis. Ausgabe G, Grosstiere/Nutztiere》2011,39(2):101-112
Standardized terminology for the porcine reproductive and respiratory syndrome virus (PRRSV) status of swine herds is necessary to facilitate communication between veterinarians, swine producers, genetic companies, and other industry participants. It is also required for implementation of regional and national efforts towards PRRSV control and elimination. The purpose of this paper is to provide a herd classification system for describing the PRRSV status of herds, based upon a set of definitions reflecting the biology and ecology of PRRSV. The herd classification system was developed by a definitions committee formed jointly by the American Association of Swine Veterinarians (AASV) and the United States Department of Agriculture PRRS-Coordinated Agricultural Project, and was approved by the AASV Board of Directors on March 9, 2010. The committee included veterinarians from private practice and industry, researchers, and representatives from AASV and the National Pork Board. Breeding herds, with or without growing pigs on the same premises, are categorized as Positive Unstable (Category I), Positive Stable (Category II), Provisional Negative (Category III), or Negative (Category IV) on the basis of herd shedding and exposure status. Growing-pig herds are categorized as Positive or Negative. Recommended testing procedures and decision rules for herd classification are detailed. 相似文献