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排序方式: 共有197条查询结果,搜索用时 46 毫秒
61.
Severe nonsuppurative meningoencephalitis associated with Aleutian mink disease parvovirus (ADV) infection was observed in adult ranch mink. Brain lesions included severe, locally extensive to coalescing lymphoplasmacytic meningoencephalitis with accompanying gliosis, satellitosis, and mild extension of inflammation into the leptomeninges. ADV was identified in mesenteric lymph node, spleen, brain, and liver of affected mink by polymerase chain reaction techniques. Sequences of the ADV isolate (TH5) revealed 2 unique residues in the region of the viral genome that determines pathogenicity. These findings suggest that certain strains of ADV may preferentially cause disease in the nervous system. ADV infection should be considered in the differential diagnosis of neurologic disorders in mink. 相似文献
62.
Edwards RL Beck JW Burr GS Donahue DJ Chappell JM Bloom AL Druffel ER Taylor FW 《Science (New York, N.Y.)》1993,260(5110):962-968
Paired carbon-14 ((14)C) and thorium-230((230)Th) ages were determined on fossil corals from the Huon Peninsula, Papua New Guinea. The ages were used to calibrate part of the (14)C time scale and to estimate rates of sea-level rise during the last deglaciation. An abrupt offset between the (14)C and (230)Th ages suggests that the atmospheric (14)C/(12)C ratio dropped by 15 percent during the latter part of and after the Younger Dryas (YD). This prominent drop coincides with greatly reduced rates of sea-level rise. Reduction of melting because of cooler conditions during the YD may have caused an increase in the rate of ocean ventilation, which caused the atmospheric (14)C/(12)C ratio to fall. The record of sea-level rise also shows that globally averaged rates of melting were relatively high at the beginning of the YD. Thus, these measurements satisfy one of the conditions required by the hypothesis that the diversion of meltwater from the Mississippi to the St. Lawrence River triggered the YD event. 相似文献
63.
The effect of magnesium pemoline on the synthesis of brain RNA in vivo was studied. No significant effect either on the concentration of RNA or on the uptake of H(3)-uridine into RNA was detected. 相似文献
64.
Levan AJ Tanvir NR Cenko SB Perley DA Wiersema K Bloom JS Fruchter AS Postigo Ade U O'Brien PT Butler N van der Horst AJ Leloudas G Morgan AN Misra K Bower GC Farihi J Tunnicliffe RL Modjaz M Silverman JM Hjorth J Thöne C Cucchiara A Cerón JM Castro-Tirado AJ Arnold JA Bremer M Brodie JP Carroll T Cooper MC Curran PA Cutri RM Ehle J Forbes D Fynbo J Gorosabel J Graham J Hoffman DI Guziy S Jakobsson P Kamble A Kerr T Kasliwal MM Kouveliotou C Kocevski D Law NM Nugent PE Ofek EO Poznanski D 《Science (New York, N.Y.)》2011,333(6039):199-202
Variable x-ray and γ-ray emission is characteristic of the most extreme physical processes in the universe. We present multiwavelength observations of a unique γ-ray-selected transient detected by the Swift satellite, accompanied by bright emission across the electromagnetic spectrum, and whose properties are unlike any previously observed source. We pinpoint the event to the center of a small, star-forming galaxy at redshift z = 0.3534. Its high-energy emission has lasted much longer than any γ-ray burst, whereas its peak luminosity was ~100 times higher than bright active galactic nuclei. The association of the outburst with the center of its host galaxy suggests that this phenomenon has its origin in a rare mechanism involving the massive black hole in the nucleus of that galaxy. 相似文献
65.
Mechanism of a reaction in vitro associated with delayed-type hypersensitivity 总被引:134,自引:0,他引:134
The cell type responsible for inhibition by antigen of migration in vitro of peritoneal exudate cells obtained from tuberculin-hypersensitive guinea pigs was studied. Exudate populations were separated into component cell types, the lymphocyte and the macrophage. Peritoneal lymphocytes from sensitive donors were the immunologically active cells in this system, the macrophages, being merely indicator cells which migrate. Sensitized peritoneal lymphocyte populations, upon interaction with specific antigen in vitro, elaborated into the medium a soluble material capable of inhibiting migration of normal exudate cells. 相似文献
66.
A second child with a ring D chromosome and anomalous inheritance of haptoglobin has been identified. Autoradiographic studies of peripheral lymphocytes from this child and of those from the previously described patient indicate that the ring in each is derived from chromosome No. 13. These findings are evidence that the locus for the haptoglobin alpha-chain is situated on one end of chromosome No. 13. 相似文献
67.
AE Pashitski A Gurevich AA Polyanskii DC Larbalestier A Goyal ED Specht DM Kroeger JA DeLuca JE Tkaczyk 《Science (New York, N.Y.)》1997,275(5298):367-369
Magneto-optical imaging was used to visualize the inhomogeneous penetration of magnetic flux into polycrystalline TlBa2Ca2Cu3Ox films with high critical current densities, to reconstruct the local two-dimensional supercurrent flow patterns and to correlate inhomogeneities in this flow with the local crystallographic misorientation. The films have almost perfect c-axis alignment and considerable local a- and b-axis texture because the grains tend to form colonies with only slightly misaligned a and b axes. Current flows freely over these low-angle grain boundaries but is strongly reduced at intermittent colony boundaries of high misorientation. The local (<10-micrometer scale) critical current density Jc varies widely, being up to 10 times as great as the transport Jc (scale of approximately 1 millimeter), which itself varies by a factor of about 5 in different sections of the film. The combined experiments show that the magnitude of the transport Jc is largely determined by a few high-angle boundaries. 相似文献
68.
Chemical speciation of mercury (Hg) in a wide variety of combustion flue gas matrices has been determined using the mercury speciation adsorption (MESA) method. The MESA sampling system for gas phase Hg species employs a series of heated, solid phase adsorbent traps. Flue gas oxidized Hg species (Hg(II) and MMHg) are adsorbed by a potassium chloride (KCl) impregnated soda lime sorbent. Elemental Hg (Hg0) is collected by an iodated carbon sorbent after passing through the KCl/soda lime sorbent. Total Hg (Hgt) is determined by summation of species. In the laboratory, cold vapor atomic fluorescence spectroscopy (CVAFS) is used for detection of Hg collected on the solid sorbents, after appropriate sample digestion and preparation. The MESA method has been evaluated for species stability, matrix effects, breakthrough, artifacts and precision. Based on eight duplicate samples a mean precision of 6.8% 11% and 4.5% (relative percent difference) has been calculated for Hg0, Hg(II) and Hgt respectively. Intercomparison of the MESA method with other methods shows very good agreement for Hgt. Mass balance calculations at 5 sites range from 75 to 140%, with a mean of 97±25%. Overall mean speciation results from 19 separate determinations suggest that Hg(II) has a 1 sigma range of 40 to 94% in coal combustion flue gas at, the inlet to pollution control devices. 相似文献
69.
70.