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351.
352.
Nanyao Lu Edward T. Polehampton Bruce M. Swinyard Dominique Benielli Trevor Fulton Rosalind Hopwood Peter Imhof Tanya Lim Nicola Marchili David A. Naylor Bernhard Schulz Sunil Sidher Ivan Valtchanov 《Experimental Astronomy》2014,37(2):239-252
The Fourier Transform Spectrometer (FTS) of the Spectral and Photometric Imaging REceiver (SPIRE) on board the ESA Herschel Space Observatory has two detector setting modes: (a) a nominal mode, which is optimized for observing moderately bright to faint astronomical targets, and (b) a bright-source mode recommended for sources significantly brighter than 500 Jy, within the SPIRE FTS bandwidth of 446.7–1544 GHz (or 194–671 microns in wavelength), which employs a reduced detector responsivity and out-of-phase analog signal amplifier/demodulator. We address in detail the calibration issues unique to the bright-source mode, describe the integration of the bright-mode data processing into the existing pipeline for the nominal mode, and show that the flux calibration accuracy of the bright-source mode is generally within 2 % of that of the nominal mode, and that the bright-source mode is 3 to 4 times less sensitive than the nominal mode. 相似文献
353.
354.
Jonas Mota e Silva Cesar Fonseca Ferreira Filho Bernhard Bühn Elton Luiz Dantas 《Mineralium Deposita》2011,46(1):57-90
The “Americano do Brasil” Complex (ABC) is part of a cluster of coeval synorogenic mafic–ultramafic intrusions emplaced during
the Brasiliano/Pan-African Orogenic Cycle in Brazil. The medium-sized ABC consists of interlayered dunite, peridotite, websterite,
and gabbronorite. High Fo values of olivine (up to Fo88) and the crystallization sequence of the ABC (Ol + Chr ≥ Ol + Opx + Chr ≥ Cpx + Opx ≥ Opx + Pl + Cpx ≥ Opx + Pl + Cpx + Ilm + Mag)
suggest crystallization from tholeiitic high-MgO parental magmas. Light rare earth element (REE)-enriched mantle-normalized
REE profiles and εNd(T) values of +2.4 for cumulate rocks from the ABC suggest a depleted mantle source for the parental magma.
The ABC Ni–Cu sulfide deposit (3.1 Mt at 1.12 wt.% Ni and 1.02 wt.% Cu) consists of three distinctively different orebodies
(S1, S2, and G2). The S2 orebody, an unusual occurrence of stratiform massive sulfide hosted by dunite and peridotite in the
interior of a layered intrusion, results from sulfides accumulated at the transient base of the magma chamber following a
new influx of parental magma. The G2 orebody has an irregular and roughly cylindrical shape, consisting mainly of net-textured
sulfides. The G2 orebody is hosted by peridotite and pyroxenite and located stratigraphically below the S1 orebody. S2 and
G2 orebodies are characterized by low Cu/Cu + Ni ratios (mainly below 0.4). The S1 orebody, hosted by websterite and gabbronorite
in the more fractionated sequence of the ABC, is a cluster of several irregular discontinuous orebodies of Ni–Cu disseminated
sulfides. The sulfides of the S1 orebody have high Cu/Cu + Ni ratios (mainly between 0.5 and 0.8) and are highly depleted
in PGE. The S1 orebody is interpreted to result from a later event of sulfide segregation in the magma chamber, possibly following
the event that originated the G2 orebody. The bulk of δ34S values for sulfides of the ABC orebodies and their host rocks fall in the range of 0 ± 2‰. Higher δ34S values (between 3‰ and 5‰) are restricted to pyrite from xenoliths of gneiss located close to the S1 orebody and sulfides
from the S1 orebody. Crustal xenoliths and chemical data (lithogeochemistry and sulfur isotope composition) provide evidence
of crustal contamination of the igneous rocks hosting the S1 orebody, suggesting that sulfur saturation was induced by contamination
with sulfide-bearing crustal rocks. The ABC deposit is an example of Ni–Cu sulfide mineralization hosted by synorogenic mafic–ultramafic
intrusions. The S2 orebody is the first documented example of an economic stratiform massive sulfide orebody located within
layered intrusions, expanding the opportunities for exploration of Ni–Cu sulfides in orogenic regions worldwide. 相似文献
355.
The effect of nutrient enrichments on natural phytoplankton assemblages was examined in six experiments conducted from June to October 1992. Short-term (4 d to 7 d) nutrient enrichment bioassays were incubated in situ in Padilla Bay, a slough-fed estuary in northern Puget Sound, Washington. Ammonium additions (15 μM) significantly (p<0.001) stimulated phytoplankton biomass accumulation during all six experiments. In two experiments, nitrate additions (15 μM) significantly stimulated accumulation of phytoplankton biomass during October, but not September. Addition of phosphate (1.0 μM) or silicate (15 μM) alone did not stimulate phytoplankton biomass accumulation during any of the experiments. In most experiments, phytoplankton response was greatest in combination treatments of ammonium and phosphate. Dissolved inorganic nutrient concentrations in the containers decreased during all incubations, but showed the greatest reduction in treatments receiving nitrogen. Dissolved inorganic nitrogen (DIN) to phosphate (PO4 3?) ratios were below 16∶1 during all experiments, suggesting the potential for nitrogen limitation. In three experiments, the response of photosynthetic nanoplankton (<20 μm) to ammonium additions was compared to that of the total phytoplankton assemblages. Accumulation of nanoplankton biomass exceeded that of the total phytoplankton during two experiments in August but showed no significant response to ammonium additions in October. Results from the bioassays, the low DIN∶PO4 3? ratios, and the reduction in nutrient concentrations in the containers provide evidence for potential nitrogen limitation of phytoplankton production during summer in Padilla Bay. 相似文献