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481.
R. D. Kouznetsov V. F. Kramar M. A. Kallistratova 《Izvestiya Atmospheric and Oceanic Physics》2006,42(6):696-703
An acoustic locator—a sodar—is a unique instrument for getting the objective characteristics of the current state of the atmospheric boundary layer (ABL) owing to a combination of such properties as remoteness, mobility, resolution, and information content. This study demonstrates the capabilities of a sodar to obtain data on the second moments of the field of wind-velocity fluctuations, in particular, the profiles of momentum flux in the lower ABL, which are very important in practical applications. A corresponding method is described, and the results of its experimental verification and some examples of its application under the conditions of different ABL stratification are presented. 相似文献
482.
The ability of cultured zooxanthellae to use ammonium and nitrate was tested. The zooxanthellae were initially isolated from the anemone Aiptasia pulchella. The zooxanthellae were able to grow on media supplemented with either form of dissolved inorganic nitrogen (DIN) although ammonium was inhibitory above 300 μM. In accord with the intact symbiosis and freshly isolated algae, the cultured zooxanthellae took up ammonium. In contrast, the cultured algae demonstrated nitrate uptake and utilization. This was enhanced with DIN deprivation. Nitrate reductase was found in the algae and appeared to be inducible. Within the animal host, excretory ammonium may repress this induction. 相似文献
483.
Regoli F Gorbi S Frenzilli G Nigro M Corsi I Focardi S Winston GW 《Marine environmental research》2002,54(3-5):419-423
An integrate approach will be discussed for investigations on oxidative stress in xenobiotic toxicity. While the analysis of individual antioxidants is useful for their sensitivity and to understand the mode of action of a stressor, the integration with the analysis of the total antioxidant capacity provides a more holistic assessment of the overall biological significance of such variations. TOSC has a greater predictive value on the health condition of the organisms and allows to discriminate the different role of specific ROS in oxidative stress syndrome. 相似文献
484.
Distribution of trace and major elements in sediment and pore waters of the Lena Delta and Laptev Sea 总被引:1,自引:0,他引:1
Sediment cores collected during the SPASIBA expedition in 1991 were analysed for their trace- and major element concentrations. Leachable (0.1 N HCl) as well as residual concentrations were determined. Fe and Mn were measured in the interstitial waters to characterize redox conditions. Lateral distribution patterns of solid phase Cu, Cd, Ni, Pb and Zn show a small increase in concentration from the Lena Delta in seaward direction. In general concentrations of these metals are very low and similar to natural background values. With some exceptions, solid phase profiles with depth of all investigated elements do not show strong variations. No enrichment of Pb and Zn in surface layers was found. Remobilization processes and transport of particles enriched in Mn are responsible for Mn accumulation in a particular area. Pore-water concentrations of dissolved Mn in the latter sediments are very high (> 700 μM) and suggest strong Mn reduction directly below the sediment-water interface. In contrast to Mn, the depth profiles of Cd show a surface layer with lower concentrations and an increase deeper down the sediment. The C/N ratio in the sediment decreases from 13 in the Lena mouth to 9 in the more marine part of the Laptev Sea. Surface sediments in the Laptev Sea are very uniform and homogeneous and show only small concentration gradients. 相似文献
485.
X-band sea-clutter nonstationarity: influence of long waves 总被引:1,自引:0,他引:1
In this paper, we deal with the problem of modeling the backscattering from sea surface for low-grazing-angle and high-resolution radar systems. Based on the electromagnetic two-scale model, we analyzed both the amplitude and frequency modulations induced on the small-scale Bragg resonant waves by the large-scale surface tilt and advection due to the swell presence. Evidence of sea-clutter nonstationarity has been verified and the relationship between the variations of clutter spectral features, such as texture, Doppler centroid, and bandwidth, have been studied by processing real sea-clutter data recorded by the IPIX radar of McMaster University, Hamilton, ON, Canada. An autoregressive nonstationary process is proposed and validated to model the physical phenomenon. 相似文献
486.
Hydrodynamic and sediment transport measurements from instrumentation deployed during a 54-day winter period at two sites on the Louisiana inner shelf are presented. Strong extratropical storms, with wind speeds of 7.8 to 15.1 m s-1, were the dominant forcing mechanism during the study. These typically caused mean oscillatory flows and shear velocities about 33% higher than fair weather (averaging 12.3 and 3.2 cm s-1 at the landward site, and 11.4 and 2.7 cm s-1 at the seaward site, respectively). These responses were coupled with mean near-bottom currents more than twice as strong as during fair weather (10.3 and 7.5 cm s-1 at the landward and seaward sites, respectively). These flowed in approximately the same direction as the veering wind, causing a net offshore transport of fine sand. Weak storms were responsible for little sediment transport whereas during fair weather, onshore sand transport of approximately 25-75% of the storm values appears to have occurred. This contradicts previous predictions of negligible fair-weather sediment movement on this inner shelf. 相似文献
487.
The BIO Mark 8 thrust anemometer measures the drag of the wind on a perforated table tennis ball mounted on a vertical beam. The tri-axial displacement of the beam is sensed by eddy current proximity sensors. This anemometer has a flat frequency response from 0 to 10 Hz and can measure wind from 0 to 28 m s−1 at temperature from − 19 to + 28°C. It is designed for remote operation for extended periods of time such as on stable towers at sea. 相似文献
488.
Kazufumi Takayanagi George T. F. Wong Margaret J. Filardo 《Journal of Oceanography》1989,45(2):129-133
Nitrate reductase activity and the concentrations of selenite and selenate were monitored for six months at the mouth of Chesapeake Bay (USA). A positive correlation was found between nitrate reductase activity and the concentration of selenite, suggesting that selenite may be formed in coastal waters and nitrate reductase may be involved in the process. 相似文献
489.
A high-resolution seismic survey covering more than 2,000 km2 has revealed the processes responsible for the slope morphology and channel sedimentation across the forearc slope-basin
of the Kurile Arc–NE Japan Arc collision zone, offshore from Tokachi (Hokkaido, Japan). The dominant slope contours parallel
the trench but, in the middle and lower reaches of the southern slope, contours are convex-shaped with an offshore trend.
This sector of the slope is traversed diagonally by the Hiroo submarine channel. The offshore-trending convex contours and
the channel course have developed through the interplay of tectonic and sedimentary processes, including the development of
anticlines, anticline-induced lobe sedimentation and channel avulsion. In its upper reaches, the channel is restricted by
a topographic low associated with NNW–SSE-trending anticlines which developed within the upper and middle slope sectors during
late Miocene uplift. The uplift timing and trend of these anticlines indicate that they resulted from collision, the channel
sedimentology and slope morphology of the middle and lower slopes having been influenced by Pliocene uplift of NE–SW-trending
anticlines. The trends of these anticlines parallel those of the Kurile Trench. The Pliocene and early Pleistocene strata
of the middle and lower slopes consist of ponded lobe sediments deposited along the palaeo-Hiroo submarine channel on the
landward side of the anticlines. As a lobe pile accumulated, the channel thalweg shifted to the north of the stack, allowing
the channel to bypass the topographic high formed by the growing stack. Thick levee deposits built up along the channel course
during the late Pleistocene and Holocene. These levees, along with the Pliocene and early Pleistocene lobes, are reflected
in the present-day sigmoid-shaped, convex offshore-trending contours. Thus, the interplay of subduction- and collision-related
anticlines, tectonic-related channel ponding, and avulsion has contributed to the slope morphology of the southern Kurile
Trench. 相似文献
490.