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291.
The oxidation of S(IV) by ozone in aqueous solution has been studied in highly dispersed droplets in a laboratory could chamber at 20°C. Urban air was used. Ozone concentrations ranged from 15 to 120 ppb, orders of magnitude lower than most previous works. Rate constants were derived from differential product determination, rather than from rates of decay of bulk reactants. Comparison of the results obtained here with those from previous work indicates that the reaction rate is indeed first order with respect to ozone. The second-order reaction rate constants found in this work lay between, or close to, other recent results, and could be represented by:k=1.23×104 [H+]–0.51 M–1 s–1. 相似文献
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293.
The active volcano, Oldoinyo Lengai in the Eastern Rift in northern Tanganyika consists mainly of yellow ijolitic pyroclasts with interbedded relatively thin phonolite and nephelinite lavas, overlain by nephelinitic pyroclasts and younger ashes with marked unconformity. Ejected blocks in the pyroclasts are of rocks of the urtite-jacupirangite series with or without wollastonite, wollastonitite, fenite, carbonite, biotite pyroxenite and various lavas. Observations were made of minor activity during September–October 1960 when it was noted that soda-rich carbonate lava was extruded on the crater-floor in addition to minor emissions of ash. From examination of the rock sequence it appears that the volcano is waning and there has been a change from earlier dominantly gas eruptions to the more recent minor emissions of lava. 相似文献
294.
Pb, Nd and Sr isotope analyses together with U, Pb, Sm, Nd, Rb and Sr concentrations have been obtained for separated phases of lherzolite and bulk rock mafic granulite xenoliths in Recent volcanics from Tanzania. A garnet lherzolite from the Lashaine vent has yielded the least radiogenicPb(206Pb/204Pb= 15.55) and Nd(143Nd/144Nd= 0.51127; ?Nd0 = ?26.7) isotope compositions recorded so far for an ultramafic xenolith, and 87Sr/86Sr= 0.83604. The Pb isotope compositions of the mafic granulites are variable 15.77<206Pb/204Pb<17.50 and some show evidence for depletion of U relative to Pb up to 2.0 Ga ago. Overall the isotope results suggest that the mantle part of the continental lithosphere beneath Tanzania has components that have undergone a complex history that includes major chemical fractionations ca. 2.0 Ga ago. A phlogopite-amphibole vein from the Pello Hill sample has Sr, Nd and Pb isotope compositions similar to those of mid-ocean ridge basalts, indicating both a young emplacement age for the vein material and a source which had an isotopic signature characteristic of depleted mantle.The Sr, Nd and Pb isotope systematics of ultramafic xenoliths do not conform with those of MORB, particularly in terms of their PbSr, and NdPb relationships. In this regard they are similar to some ocean islands and could be a viable source material for some ocean island basalts at least. The mantle part of the continental lithosphere is as likely to contain recycled components derived from the continental crust as are other regions of mantle. If the mantle part of continental lithosphere is invoked as a source for ocean islands, it does not negate the possibility that substantial recycled components are involved. 相似文献
295.
Two experimental populations of Gammarus duebeni have been found to contain high levels of what appeared to be pollutants in their gill neutral lipids. Detailed analysis, involving capillary gas chromatography-mass spectrometry, confirmed the presence of hydrocarbons, a plasticizer and silicone compounds. Such a localized concentration of lipophilic pollutants in a tissue such as the gills might be sufficient to influence the metabolism of the whole organism even though the total body burden is low. 相似文献
296.
The fatty acid composition of the gill lipids from Gammarus duebeni have been compared in relation to the degree of contamination of the gills by lipophilic materials. The results indicate that at higher levels of gill contamination a greater proportion of polyunsaturated 20:5 fatty acid occurs in the gill phospholipids. We suggest this may be a response to a change in the physical state of the gill membranes resulting from the contamination. 相似文献
297.
Electron microprobe analyses yielded mean values of for primary-textured phlogopites in coarse, depleted garnet-lherzolite xenoliths from kimberlites. Most secondary-textured phlogopites have too low Cl (0.01–0.08 wt.%) to be metamorphic precursors of primary-textured phlogopites. MARID-suite phlogopites and many megacrysts in kimberlites have low Cl (), and some but not necessarily all secondary micas may result from infiltration of kimberlite into peridotite xenoliths. A good correlation between P and F in some oceanic basalts and gabbros might suggest that these elements are derived mainly from F-rich apatite inthe mantle, and that whitlockite is not present in the source region. Mantle-derived mica and amphibole have such low Cl that it is necessary to attribute Cl in oceanic basalts and gabbros either to substantial Cl in the source apatite, or to Cl from invading solutions, or both: three apatites from the mantle contain 0.8–1.0 wt.% Cl, and others contain lower amounts. The halogen contents of kimberlitic magmas can be explained by incorporation of Cl-bearing mica and F-rich apatite during melting of peridotites, but compositional constraints are weak. 相似文献
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In this paper, we show how to couple the local discontinuous Galerkin method and the Raviart–Thomas mixed finite element method for elliptic equations modeling flow problems. We then show that the approximation of the velocity converges with the optimal order of k when we take the local discontinuous Galerkin that uses polynomials of degree k and the Raviart–Thomas space of polynomials of degree k?1. 相似文献