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131.
132.
Dr. Hans Ulrich Roll 《Pure and Applied Geophysics》1952,21(1):110-126
Zusammenfassung Eineabsolute «kritische Windgeschwindigkeit» für Prozesse an der Grenzfläche Wasser-Luft scheint nicht zu existieren. Unsere Beobachtungen liefern jedoch Anzeichen für das Vorhandenseinrelativer «kritischer Windgeschwindigkeiten, die vom Ueberströmungsweg, bzw. von der Wellenlaufstrecke abzuhängen scheinen. Diese relativen «kritischen Windgeschwindigkeiten» sind durch folgende-Merkmale gekennzeichnet: Aenderung der Struktur der Meeresoberfläche (glatt-rauh); Umschlag der laminaren Wassergrenzschicht zur Turbulenz; Ueberbrechen der Schwerewellen; Minimum des Widerstandskoeffizienten der Meeresoberfläche.
Summary It seems that there is no absolute «critical wind speed» for air-sea boundary processes. From our observations it may, however, be referred that there are relative values of the «critical wind speed» which seem to depend on the fetch. These relative values of the «critical wind speed» are characterized by the following marks: The sea surface pattern is changed (smooth-rough);, the boundary layer in water turns from laminar to turbulent flow; the gravity waves break; the resistance coefficient of the sea surface has a minimum.相似文献
133.
134.
Summary The aminoacids in hydrolysates (HCl) of the scales of six different fish-species have been determined by partition paper chromatography
(Consden andDent). The scales contain considerable amounts of protein besides hydroxyl apatit and guanin, but none or only minute quantities
of carbohydrates. Some of the aminoacids in the liver, air-bladder, kidney and the body muscles of two fish species were investigated.
相似文献
135.
R. Signer F. v. Beust Ulrich A. Corti 《Aquatic Sciences - Research Across Boundaries》1951,13(1):31-35
Summary The investigation with an electron-microscope of the scales of the fresh water fish,Leuciscus rutilus L., showed that their ventral “smooth” surface scems to be formed like a corrugated plate with a distance between the ridges
of 1–2 μ. The dorsal “rough” side of the scales shows a very fine roughness. It is interrupted by pointed combs of the same
structure in a regular distance of 16–27 μ. The thickness of these combs is of about 1 μ at their base, their height of about
5–10 μ. It seems probable that the surface of scales is partially covered with laminas of hyalodentine or guanine.
13. Mitteilung siehe diese Zeitschrift,13, 29–30 (1951). 相似文献
13. Mitteilung siehe diese Zeitschrift,13, 29–30 (1951). 相似文献
136.
137.
Evidence from over 200 sediment cores, numerous submersible dives, and bottom photographs prove that bioturbation and bioerosion are ongoing processes affecting northeastern U.S. continental slope and rise sedimentation. Evidence of biological activity was found in greater than 95% of the cores examined. Submersible dive observations reveal that the results of biological activity often dominate sea-floor microtopography. Bioturbation can disturb sediments several centimeters deep in a matter of seconds and is in some areas the primary sediment transport mechanism. Many cores with sandy intervals were profoundly disturbed by bioturbation. Biologically camouflaged sand-rich intervals can easily be missed by visual observation. 相似文献
138.
Jason M. Dortch Lewis A. Owen William C. Haneberg Marc W. Caffee Craig Dietsch Ulrich Kamp 《Quaternary Science Reviews》2009,28(11-12):1037-1054
Four large landslides, each with a debris volume >106 m3, in the Himalaya and Transhimalaya of northern India were examined, mapped, and dated using 10Be terrestrial cosmogenic radionuclide surface exposure dating. The landslides date to 7.7±1.0 ka (Darcha), 7.9±0.8 ka (Patseo), 6.6±0.4 ka (Kelang Serai), and 8.5±0.5 ka (Chilam). Comparison of slip surface dips and physically reasonable angles of internal friction suggests that the landslides may have been triggered by increased pore water pressure, seismic shaking, or a combination of these two processes. However, the steepness of discontinuities in the Darcha rock-slope, suggests that it was more likely to have started as a consequence of gravitationally-induced buckling of planar slabs. Deglaciation of the region occurred more than 2000 years before the Darcha, Patseo, and Kelang Serai landslides; it is unlikely that glacial debuttressing was responsible for triggering the landslides. The four landslides, their causes, potential triggers and mechanisms, and their ages are compared to 12 previously dated large landslides in the region. Fourteen of the 16 dated landslides occurred during periods of intensified monsoons. Seismic shaking, however, cannot be ruled out as a mechanism for landslide initiation, because the Himalaya has experienced great earthquakes on centennial to millennial timescales. The average Holocene landscape lowering due to large landslides for the Lahul region, which contains the Darcha, Patseo, and Kelang Serai landslides, is ~0.12 mm/yr. Previously published large-landslide landscape-lowering rates for the Himalaya differ significantly. Furthermore, regional glacial and fluvial denudation rates for the Himalaya are more than an order of magnitude greater. This difference highlights the lack of large-landslide data, lack of chronology, problems associated with single catchment/large landslide-based calculations, and the need for regional landscape-lowering determinations over a standardized time period. 相似文献
139.
Molecular characterization of uranium(VI) sorption complexes on iron(III)-rich acid mine water colloids 总被引:1,自引:0,他引:1
Kai-Uwe Ulrich André Rossberg Harald Foerstendorf Andreas C. Scheinost 《Geochimica et cosmochimica acta》2006,70(22):5469-5487
A mixing of metal-loaded acid mine drainage with shallow groundwater or surface waters usually initiates oxidation and/or hydrolysis of dissolved metals such as iron (Fe) and aluminum (Al). Colloidal particles may appear and agglomerate with increasing pH. Likewise chemical conditions may occur while flooding abandoned uranium mines. Here, the risk assessment of hazards requires reliable knowledge on the mobility of uranium (U). A flooding process was simulated at mesocosm scale by mixing U-contaminated acid mine water with near-neutral groundwater under oxic conditions. The mechanism of U-uptake by fresh precipitates and the molecular structure of U bonding were determined to estimate the mobility of U(VI). Analytical and spectroscopic methods such as Extended X-ray Absorption Fine-Structure (EXAFS) spectroscopy at the Fe K-edge and the U LIII-edge, and Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) spectroscopy were employed. The freshly formed precipitate was identified as colloidal two-line ferrihydrite. It removed U(VI) from solution by sorption processes, while surface precipitation or structural incorporation of U was not observed. EXAFS data suggest a mononuclear inner-sphere, edge-sharing complex of U(VI) with ferrihydrite in the absence of dissolved carbonate. By employing a novel EXAFS analysis method, Monte Carlo Target Transformation Factor Analysis, we could for the first time ascertain a 3-D configuration of this sorption complex without the necessity to invoke formation of a ternary complex. The configuration suggests a slightly tilted position of the adsorbed unit relative to the edge-sharing Fe(O, OH)6 octahedra. In the presence of dissolved carbonate and at pH ∼8.0, a distal carbonate O-atom at ∼4.3 Å supports formation of ternary U(VI)-carbonato surface complexes. The occurrence of these complexes was also confirmed by ATR-FTIR. However, in slightly acidic conditions (pH 5-6) in equilibrium with atmospheric CO2, the U(VI) sorption on ferrihydrite was dominated by the binary complex species Fe(O)2UO2, whereas ternary U(VI)-carbonato surface complexes were of minor relevance. While sulfate and silicate were also present in the mine water, they had no detectable influence on U(VI) surface complexation. Our experiments demonstrate that U(VI) forms stable inner-sphere sorption complexes even in the presence of carbonate and at slightly alkaline pH, conditions which previously have been assumed to greatly accelerate the mobility of U(VI) in aqueous environments. Depending on the concentrations of U(VI) and carbonate, the type of surface complexes may change from binary uranyl-ferrihydrite to ternary carbonato-uranyl-ferrihydrite complexes. These different binding mechanisms are likely to influence the binding stability and retention of U(VI) at the macroscopic level. 相似文献
140.
T. Appourchaux P. Liewer M. Watt D. Alexander V. Andretta F. Auchère P. D’Arrigo J. Ayon T. Corbard S. Fineschi W. Finsterle L. Floyd G. Garbe L. Gizon D. Hassler L. Harra A. Kosovichev J. Leibacher M. Leipold N. Murphy M. Maksimovic V. Martinez-Pillet B. S. A. Matthews R. Mewaldt D. Moses J. Newmark S. Régnier W. Schmutz D. Socker D. Spadaro M. Stuttard C. Trosseille R. Ulrich M. Velli A. Vourlidas C. R. Wimmer-Schweingruber T. Zurbuchen 《Experimental Astronomy》2009,23(3):1079-1117
The POLAR Investigation of the Sun (POLARIS) mission uses a combination of a gravity assist and solar sail propulsion to place
a spacecraft in a 0.48 AU circular orbit around the Sun with an inclination of 75° with respect to solar equator. This challenging
orbit is made possible by the challenging development of solar sail propulsion. This first extended view of the high-latitude
regions of the Sun will enable crucial observations not possible from the ecliptic viewpoint or from Solar Orbiter. While
Solar Orbiter would give the first glimpse of the high latitude magnetic field and flows to probe the solar dynamo, it does
not have sufficient viewing of the polar regions to achieve POLARIS’s primary objective: determining the relation between
the magnetism and dynamics of the Sun’s polar regions and the solar cycle.
相似文献
T. AppourchauxEmail: |