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11.
Gerald Cecil 《New Astronomy Reviews》2006,49(10-12):553
An AO-assisted integral-field spectrograph is becoming the most efficient tool with which to explore ionized gas outflows. It maps faint spectral lines that diagnose cloud dust content, gas pressure, excitation mechanism, and chemical abundances. Coupled with recent improvements in photoionization models, the total mass hence flow energetics can be estimated. Establishing a consistent dynamical framework requires linking multi-frequency datasets to track the energy flow through its optimal-contrast emission in the various ISM phases. I show HST results on AGN, starburst nuclei, and Galactic Herbig-Haro Objects that need complementary 3D spectra at comparable spatial resolution to come soon from laser-guided AO + integral-field spectrographs at the William-Herschel and SOAR telescopes. 相似文献
12.
High levels of Cd and Zn in Jamaican soils observed in geochemical surveys are related to the presence of phosphorites of possible Late-Miocene or Pliocene age. The trace element and REE geochemistry of the phosphorites, together with SEM studies, indicate a guano origin for the phosphorites. No specific host minerals for Cd could be identified in the fossiliferous phosphorite which is characterized by uniquely high levels of Cd, Zn, Ag, Be, U and Y. However, in the soil Cd is present in lithiophorite and a complex history of pedological development is preserved in the aluminous–goethite present in the soil. The unique guano signature is preserved in the soil despite the fact that guanos themselves have either not been observed or have been destroyed by continuing karst and soil development. The phosphorite geochemical signature can be traced in the data of a 1988 island-wide soil geochemical survey, identifying areas where the Palaeo-environment that supported bird ‘rookeries’ existed in the Late-Miocene or Pliocene. 相似文献
13.
Cyclic sequences occur worldwide in nearly every stratigraphic sequence; they are particularly well-developed in fluvial and
deltaic sediments that have been influenced by high-frequency eustatic sea-level fluctuations. The large data base for this
study (including 471 deep foundation borings, thousands of line kilometers of high-resolution seismic, and sedimentological
and dating analyses) represents the most complete information on high-resolution chronostratigraphy and lithostratigraphy
that is available on any modern continental shelf/upper slope. These data are used to document sedimentological characteristics
and high-resolution seismic responses during three complete sea-level cycles over the entire continental shelf/upper slope
of offshore Louisiana.
Examination of high-resolution seismic records indicates that well-defined, high-amplitude, laterally continuous reflectors
correlate with rising and high stand condensed sedimentary sequences and that the deposits laid down during falling and low-stand
periods (expanded sections) are characterized by a wide range of acoustic responses. Discontinuous reflectors with high-amplitude
variability, continuous parallel reflectors, and chaotic and amorphous zones are common acoustic responses. The association
between a particular lithofacies and a specific acoustic response on 3.5-kHz records was found to be very poor. 相似文献
14.
The biological potency (relative to 2,3,7,8-tetrachlorodibenzo-p-dioxin. TCDD) of planar polychlorinated aromatic hydrocarbons (PCHs) in extracts of eggs and flesh from spawning female chinook salmon (Oncorhynchus tschawytscha) from Lake Michigan was determined by measuring the induction of 7-ethoxyresorufin O-deethylase activity in H-4-II-E rat hepatoma cells. TCDD-equivalents in flesh and egg samples ranged from 0 to 115·8 pg/g, and were approximately 5-fold greater in eggs than in flesh. These results suggest that the maternal transfer of PCHs may play a role in determining the reproductive success of Lake Michigan chinook salmon. 相似文献
15.
The influence of cyclic loading on the strength and deformation behavior of cemented marine clay has been studied. This marine clay is of recent Pleistocene origin and deposited in a shallow water marine environment. Open pits were dug in sheeted enclosures and from these pits, undisturbed samples were taken for strength testing. A series of standard triaxial shear tests and stress controlled one-way cyclic load tests were conducted at consolidation stress ranges below and above the preconsolidation pressure. For the stress levels below the preconsolidation pressure, the cyclic loading has brought about the collapse of the cementation bond through an increase in strains, and at higher pressure ranges, the soil behaves like typical soft clay. This experiment studied the rate of development of strain and pore water pressure and shows that rate is a function of number of cycles, applied stress, and stress history. In addition, soil degradation during cyclic loading is studied in terms of Degradation Index. Attempt has been made to predict stain, pore water pressure, and degradation index through an empirical model. 相似文献
16.
Alkalinity, dissolved inorganic carbon (DIC), and 13C profiles from seep sites on the northwestern Gulf of Mexico upper slope show anomalously negative 13C values of up to –4.5 PDB, increased levels of DIC of up to 2.45 mmole/liter, and slight alkalinity rises of up to 2.54 meq/liter, relative to water column profiles from a seep-free site (0.63, 2.04 mmole/liter, and 2.39 meq/liter). The observed DIC enrichments coupled with the13C-depletions are attributed to the release of CO2 by microbial oxidation of crude oil in the seep environment, and its migration into the water column. The 13C composition of the migrating CO2 is estimated to be –26.0 on the basis of dissolved carbon inventory. Manifestation of DIC and 13C anomalies in the water column caused by hydrocarbon seepage holds promise to be useful for hydrocarbon reconnaissance surveys over large offshore tracts on account of the simplicity of sampling acquisition, and rapidity of analytical techniques in the laboratory. 相似文献
17.
Limpets collected at three locations along the Turkish Mediterranean coast were analyzed for zinc, copper, cadmium, lead, chromium, nickel, iron, arsenic and strontium. Average metal concentrations in samples taken from busy harbor areas and near sewage outfalls differed little from those collected in primarily agricultural areas. Generally, an inverse relationship of metal concentration with size is seen. The average levels found in these samples are of the same order of magnitude as those in limpets from other regions of the world and thus should serve as a good indication of current background levels in this region. 相似文献
18.
Friedland Kevin D.; Chaput Gerald; MacLean Julian C. 《ICES Journal of Marine Science》2005,62(7):1338-1349
19.
20.
Wave run-up, and flow visualization experiments were conducted with a 1:2 sloped sea wall model. The visualization experiments gave an overview of flow fields in reflected, non-breaking conditions. Maximum particle velocities were found to be significantly smaller than suggested in the literature. Downrush produced a fast sheet flow, extending down to the toe of the sea wall. This created a ‘reverse’ breaker during the retreat of the initially non-breaking wave, which explains the high-energy dissipation rates for non-breaking waves reported in the literature. Embankments may therefore be exposed to wave impact pressures in areas up to 1.18H0 below MWL. 相似文献