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151.
We describe observations of the generation and propagation of coastally trapped waves in the laboratory and their comparison with theory, over a range of values of several experimental parameters. The topography and stratification used consisted of a sloping continental shelf and vertical continental slope with three-layer stratification that could be approximated by an extended version of the Gill and Clarke model [Gill, A.E., Clarke, A., 1974. Wind-induced upwelling, coastal currents and sea level changes. Deep Sea Res. 21, 325–345]. The latter was modified to accommodate a central mixed layer, curved geometry, and friction on the shelf. This configuration represents coastal geometry with large Burger number. The experiments were successful in realizing coastally trapped waves that were consistent with the theoretical expectations. However, the waves propagated more slowly, and for narrow shelves were damped more rapidly than predicted by the theory. The first was attributed to: (i) the effect of stratification on fluid on the shelf, reducing the topographic Rossby wave effect; (ii) the parameterization of the viscosity. The second difference was attributed to the mechanism of generation: the paddle used did not always generate sinusoidal waves, and the subsequent dispersion resulted in a net loss of amplitude. 相似文献
152.
O. Don Hermes 《Contributions to Mineralogy and Petrology》1968,18(3):270-294
The Mecklenburg complex, which crops out in the Carolina Piedmont, consists of older metagabbro and metafelsic rocks of upper amphibolite grade, and a younger postmetamorphic gabbro. On the evidence of field data and gravity measurements, the younger gabbro appears to be a plug-like body with steeply dipping contacts that may converge inward at relatively shallow depth; the pluton may extend only 8,000–15,000 feet into the subsurface.Gabbroic rocks contain plagioclase, olivine, orthopyroxene, clinopyroxene, hornblende, and biotite, and display hypidiomorphic textures characterized by numerous reaction relations among the mafic phases; hydrous minerals are commonly abundant, comprising up to 37% of the rock, and indicate the fugacity of H2O was relatively high during primary crystallization. In contrast metagabbro lacks olivine and exhibits textures that range from relict igneous varieties to crystalloblastic types that appear to represent equilibrium assemblages. A less common metagabbro type, associated with local zones of deformation, is characterized by faint banding and only trace amounts of anhydrous mafics. Varieties of metagabbro are complexly intermingled in the field, and resultant assemblages and textures largely reflect whole-rock composition and differences in initial H2O contents, slightly modified locally by addition of fluid along favorable channelways.In general metagabbro is slightly higher in TiO2, Na2O, and K2O, and lower in MgO relative to gabbro; regardless of the degree of recrystallization, the chemistry of the various metagabbro types is nearly identical, thus indicating metamorphism was essentially isochemical. 相似文献
153.
Nguyen Cao Don 《中国海洋工程》2018,32(3):1-1
正Introduction The International Conference on Asian and Pacific Coasts(APAC)is an international conference to promote academic and technical exchange on coastal related studies that include coastal engineering and coastal environmental problems,among the Asian and Pacific countries/regions.APAC 相似文献
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156.
This study was performed in order to assess whether bisphenol (BPA) and diethylstilbestrol (DES) had agonistic or antagonistic effects on oocyte maturation using marine fish. We tested the effects of these chemicals on in vitro maturation, germinal vesicle breakdown (GVBD), assay using oocytes from the longchin goby, Chasmichthys dolichognathus. During the maturation process, low concentrations of BPA and DES triggered GVBD depending on the stage of oocyte development; BPA at 0.044 nM and DES at 0.037, 0.37, and 3.73 nM induced GVBD in 0.82-0.88 mm diameter oocytes (germinal vesicle located near the center of oocytes). In 0.76-0.80 mm diameter oocytes (fully vitellogenic oocytes), BPA induced GVBD at relatively higher concentrations (4.38, 43.8, and 438 nM). In 0.86-0.90 mm diameter oocytes, BPA and DES had no observable effect on GVBD at the concentrations tested. Oocytes with diameters between 0.82 and 0.88 mm appeared to be more sensitive to these chemicals. Moreover, our results showed that BPA and DES did not inhibit GVBD. 相似文献
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158.
The distribution of neodymium isotopes in Arctic Ocean basins 总被引:1,自引:0,他引:1
Don Porcelli Per S. Andersson Martin Frank Igor Semiletov 《Geochimica et cosmochimica acta》2009,73(9):2645-5950
Nd concentration and isotope data have been obtained for the Canada, Amundsen, and Makarov Basins of the Arctic Ocean. A pattern of high Nd concentrations (up to 58 pM) at shallow depths is seen throughout the Arctic, and is distinct from that generally seen in other oceans where surface waters are relatively depleted. A range of isotopic variations across the Arctic and within individual depth profiles reflects the different sources of waters. The dominant source of water, and so Nd, is the Atlantic Ocean, with lesser contributions from the Pacific and Arctic Rivers. Radiogenic isotope Nd signatures (up to εNd = −6.5) can be traced in Pacific water flowing into the Canada Basin. Waters from rivers draining older terrains provide very unradiogenic Nd (down to εNd = −14.2) that can be traced in surface waters across much of the Eurasian Basin. A distinct feature of the Arctic is the general influence of the shelves on the Nd concentrations of waters flowing into the basins, either from the Pacific across the Chukchi Sea, or from across the extensive Siberian shelves. Water-shelf interaction results in an increase in Nd concentration without significant changes in salinity in essentially all waters in the Arctic, through processes that are not yet well understood. In estuarine regions other processes modify the Nd signal of freshwater components supplied into the Arctic Basin, and possibly also contribute to sedimentary Nd that may be subsequently involved in sediment-water interactions. Mixing relationships indicate that in estuaries, Nd is removed from major river waters to different degrees. Deep waters in the Arctic are higher in Nd than the inflowing Atlantic waters, apparently through enrichments of waters on the shelves that are involved in ventilating the deep basins. These enrichments generally have not resulted in major shifts in the isotopic compositions of the deep waters in the Makarov Basin (εNd ∼ −10.5), but have created distinctive Nd isotope signatures that were found near the margin of the Canada Basin (with εNd ∼ −9.0). The deep waters of the Amundsen Basin are also distinct from the Atlantic waters (with εNd = −12.3), indicating that there has been limited inflow from the adjacent Makarov Basin through the Lomonosov Ridge. 相似文献
159.
Gregory J. Holk T. Kurtis Kyser Don Chipley Eric E. Hiatt Jim Marlatt 《Journal of Geochemical Exploration》2003,80(2-3):297-320
Lead isotope ratios and associated trace element concentrations (U, Th and Pb) extracted by partial-leaching with 2% nitric acid from Proterozoic sandstones and basement rocks reveal much about the fluid evolution of sedimentary basins hosting unconformity-type uranium deposits. In addition, these techniques have great potential as a guide for exploration of uranium and other types of deposits in basins of any age. Isotope ratios of Pb in Proterozoic sandstones from basins known to contain high-grade uranium deposits are radiogenic at key geological localities and settings distal to known mineralization and particularly in altered zones proximal to mineralization. Sandstones completely cemented by quartz overgrowths typically have non-radiogenic Pb isotope ratios, indicating early closure of porosity and isolation of these rocks from later fluid events. Alternatively, the unconformity served as both a source of uranium and radiogenic Pb as well as an avenue for late-stage (<250–900 Ma) fluid flow. The mafic volcanic units, which are relatively reducing lithologies and therefore have removed uranium from basinal brines, have uranium-supported radiogenic Pb isotope ratios. Comparison of 238U/206Pb and 206Pb/204Pb ratios is useful in determining the timing and nature of U and Pb migration before, during and after mineralization in these basins. This comparison can be used to delineate the presence of radiogenic Pb isotope ratios that are not internally supported by uranium and thorium in rocks, eventually providing the explorationist with geochemical vectors that point toward sites of high potential for economic uranium mineralization. 相似文献
160.