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981.
W. L. F. Brinkmann Dr. H. Hahn H. Schick J. W. Fachbereich Geowissenschaften 《GeoJournal》1987,14(3):331-338
Two lakes, Lake Gänseweiher (LGW) and Lake Fechenheimer Weiher (LFW) occupy groundwater filled abandoned gravel pits which serve as fishing grounds and are part of recreational areas, respectively.Both lakes are cut into a near-surface groundwater aquifer, which is located in the pleistocene River Main gravel terrace t6. They are sealed at the base by miocene clays and above by overlying flood deposits of the River Main. The latter provide protection from pollutants derived from wet and dry deposition of atmospheric contaminants.Groundwater chemistry determines the pool of dissolved constituents in lake water. The temporal and spatial distribution patterns of chemical compounds in lake water are brought about by endo-biogenic processes, of which the indicators are nitrate-nitrogen and dissolved silica. The latter illustrates an instantaneous response to pulses of diatom blooms.Both lakes are eutrophic (polytrophic) according to the classification guidelines presented in literature. 相似文献
982.
The accuracy of differential scanning calorimetry (DSC) on a heat capacity measurement was evaluated using MgO. The result indicated that the deviation of the result in comparison to literature values was less than 0.4% at temperatures above 300 K and 2.1% below this temperature. Since this experiment proved the reliability of DSC, heat capacity, compressibility, and thermal expansion of ilmenite-type MgGeO3 were measured by means of DSC, a diamond anvil high pressure device, and a high-temperature X-ray camera, respectively. The heat capacity was approximated by C p = a + b·T + c·T ?2 at high temperatures and by the Debye function at low temperatures. The compressibility was well-represented by the Murnaghan-Birch equation of 2nd order. The thermal expansion coefficient was constant up to 1073 K. 相似文献
983.
984.
985.
Zagidullin A. A. Usanin V. S. Petrova N. K. Nefedyev Yu. A. Andreev A. O. Gudkova T. V. 《Astronomy Reports》2020,64(12):1093-1106
Astronomy Reports - The work is devoted to the study of the physical libration of the Moon. Interest in the traditional topic related to the rotation of the Moon is stirred up by the activity of... 相似文献
986.
M.A. Janssen R.D. Lorenz F. Paganelli R.L. Kirk S.D. Wall Y. Anderson P. Callahan G.A. Hamilton L. Roth A. Le Gall the Cassini Radar Team 《Icarus》2009,200(1):222-239
The first comprehensive calibration and mapping of the thermal microwave emission from Titan's surface is reported based on radiometric data obtained at 2.2-cm wavelength by the passive radiometer included in the Cassini Radar instrument. The data reported were accumulated from 69 separate observational segments in Titan passes from Ta (October 2004) through T30 (May 2007) and include emission from 94% of Titan's surface. They are diverse in the key observing parameters of emission angle, polarization, and spatial resolution, and their reduction into calibrated global mosaic maps involved several steps. Analysis of the polarimetry obtained at low to moderate resolution (50+ km) enabled integration of the radiometry into a single mosaic of the equivalent brightness temperature at normal incidence with a relative precision of about 1 K. The Huygens probe measurement of Titan's surface temperature and radiometry obtained on Titan's dune fields allowed us to infer an absolute calibration estimated to be accurate to a level approaching 1 K. The results provide evidence for a surface that is complex and varied on large scales. The radiometry primarily constrains physical properties of the surface, where we see strong evidence for subsurface (volume) scattering as a dominant mechanism that determines the emissivity, with the possibility of a fluffy or graded-density surface layer in many regions. The results are consistent with, but not necessarily definitive of a surface composition resulting from the slow deposition and processing of organic compounds from the atmosphere. 相似文献
987.
988.
We solve a plane problem of linear baroclinic seiches in closed rotating basins of variable depth with two-layer density stratification.
In the long-wave approximation, we get a boundary-value problem for a system of ordinary differential equations and propose
a numerical procedure for finding internal seiches. The analytic solutions of the problem are obtained for a basin of constant
depth. The numerical analysis of seiches is performed for the distributions of depth corresponding to the zonal and meridional
sections of the Black Sea and model basins including the cases of a shelf zone and an underwater ridge. It is shown that the
baroclinic seiches become more intense in shallow-water regions and that the intense longshore currents caused by Earth’s
rotation are formed in the shelf zones and over the underwater ridges. 相似文献
989.
Wind erosion of soil is an appreciable but unstudied event following fires in cold desert. We examined aeolian transport of sediment for 1 year following fire in semi-arid shrub steppe on loess soils in southern Idaho, USA. Sediment collectors were used to determine horizontal mass transport of soil and saltation sensors and anemometers were used to determine saltation activity (fraction of time having saltation) and threshold wind speed in an area burned in August and an unburned control site. Horizontal mass transport (per 30-day period) was negligible in the unburned area, but in the burned area was 5.40 kg m?1 in October and decreased to 2.80 kg m?1 in November and 0.32 kg m?1 in December. Saltation activity was high enough to determine threshold wind speeds only in the burn site during fall, when values ranged from 10.0 to 10.6 m s?1. Sediment flux and saltation activity in the burned site became much less pronounced following the emergence of herbaceous vegetation in the spring. Post-fire sediment flux in the shrub steppe we examined was of greater magnitude but shorter duration than post-fire fluxes in warm deserts or sandier regions that experience more frequent wind erosion. 相似文献
990.
Although methane is the dominant absorber in Titan's reflection spectrum, the amount of methane in the atmosphere has only been determined to an order of magnitude. We analyzed spectra from the Space Telescope Imaging Spectrograph, looking at both a bright surface region (700-km radius) and a dark surface region. The difference between the spectra of the two regions is attributed to light that has scattered off the surface, and therefore made a round-trip through all of Titan's methane. Considering only absorption, the shape of the difference spectrum provides an upper limit on methane abundance of 3.5 km-am. Modeling the multiple scattering in the atmosphere further constrains the methane abundance to 2.63±0.17 km-am. In the absence of supersaturation and with a simplified methane vertical profile, this corresponds to a surface methane-mole fraction near 3.8% and a relative humidity of 0.32. With supersaturation near the tropopause, the surface methane mole fraction could be as low as 3%. 相似文献