979 resultados para approximate calculation of sums
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Poster apresentado no Congresso O Norte da Anestesia, 19-21 Novembro 2015, Hotel Ipanema Park, Porto, Portugal.
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High-resolution records of carbon and oxygen isotopes and benthic foraminiferal accumulation rates for the Eocene-Oligocene section at Ocean Drilling Program Site 689 (Maud Rise, Weddell Sea; paleodepth about 1500 m) were used to infer variations in paleoproductivity in relation to changes in climate and ventilation of the deeper-water column. The benthic foraminiferal abundance and isotope records show short-term fluctuations at periodicities of 100 and 400 ka, implying orbitally driven climatic variations. Both records suggest that intermediate-depth water chemistry and primary productivity changed in response to climate. During the Eocene, productivity increased during cold periods and during cold-to-warm transitions, possibly as a result of increased upwelling of nutrient-rich waters. In the Oligocene, in contrast, productivity maxima occurred during intervals of low delta18O values (presumably warmer periods), when a proto-polar front moved to the south of the location of Site 689. This profound transition in climate-productivity patterns occurred around 37 Ma, coeval with rapid changes toward increasing variability of the oxygen and carbon isotope and benthic abundance records and toward larger-amplitude delta18O fluctuations. Therefore, we infer that, at this time, temperature fluctuations increased and a proto-polar front formed in conjunction with the first distinct pulsations in size of the Antarctic ice sheet. We speculate that this major change might have resulted from an initial opening of the Drake Passage at 37 Ma, at least for surface- and intermediate-water circulation.
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"April 1987."
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"October 2002."
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Mode of access: Internet.
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"August 20, 1965"
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Thesis--Illinois.
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"May 1982."
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"October 1964."
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"October 1980."
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"Contract No. AT 06-63380."
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"AFSWP no. 874. Office of Naval Research. Contract no. Nonr 266 (08) Technical report no. 14. CU-14-55-ONR-266 (08)-CE."
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"October 5, 1949."
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"Work performed for the Air Force Flight Dynamics Laboratory...by the Aerodynamics Research Department of the Northrup Corporation, Aircraft Division."
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Based on the 1947 Directory of Industrial Eestablishments prepared by the Virginia State Chamber of Commerce, and intended as an aid in the use of the annual directory. Transparent overlay map, in pocket.