Voracious planktonic hydroids: unexpected predatory impact on a coastal marine ecosystem     

Laurence P. Madin  Stephen M. Bollens  Erich Horgan  Mari Butler  Jeffrey Runge  Barbara K. Sullivan  Grace Klein-Macphee  Edward Durbin  Ann G. Durbin  Donna Van Keuren  Stphane Plourde  Ann Bucklin  M. Elizabeth Clarke 《Deep Sea Research Part II: Topical Studies in Oceanography》1996,43(7-8)

Hydroids are typically attached, benthic cnidarians that feed on a variety of small prey. During sampling on Georges Bank in spring 1994, we found huge numbers of hydroids suspended in the plankton. They fed on young stages of copepods that are an important prey for fish, as well as on young fish themselves. Two independent methods were used to estimate feeding rates of the hydroids; both indicate that the hydroids are capable of consuming from 50% to over 100% of the daily production of young copepods. These results suggest that hydroids can have a profound effect on the population dynamics of zooplankton and young fish on Georges Bank.  相似文献   

An example of visualization of the kinematic structure around a single building     

E. Mursch-Radlgruber 《Theoretical and Applied Climatology》1990,41(1-2):93-96

Summary The method of flow visualization with smoke allowed us to check the complexity of flow around an isolated building in a full-scale experiment. In the upstream zone the well established horseshoe vortex could be verified. Also the frontal separation point was clearly documented. Whether the flow reattaches to the sidewalls depends on the length of the building. Of special interest was the downstream region. In this region strong interaction of the different vortex structures was observed. The rising spiral vortices, which originated at the lateral edges, are important. Also an occasional breakdown and fast reorganization of the vortex is an interesting fact.This simple flow visualization experiment agrees well with the extensive laboratory experiments and topological criteria developed and used by Hunt (1978).NotesWith 6 Figures  相似文献   

Macropores as preferential flow paths in meander bends          下载免费PDF全文

Garrett T. Menichino  Adam S. Ward  Erich T. Hester 《水文研究》2014,28(3):482-495

Macropores are subsurface connected void spaces caused by processes such as fracture of soils, micro‐erosion, and fauna burrows. They are common near streams (e.g. hyporheic and riparian zones) and may act as preferential flow paths between surface and groundwaters, affecting hydrologic and biogeochemical processes. We tested the hydrologic function of macropores by constructing an artificial macropore within the saturated zone of a meander bend (open macropore, ‘OM’) and later filling its upstream end (partially filled macropore, ‘PFM’). For each treatment, we injected saline tracer at an upgradient monitoring well within the meander and monitored downgradient hydraulics and tracer transport. Pressure transducers in monitoring wells indicated hydraulic gradients within the meander were 32% higher perpendicular to and 6% higher parallel to the macropore for the OM than for the PFM. Additionally, hydraulic conductivities measured via falling head tests were 29 to 550 times higher along the macropore than in nearby sediment. We used electrical conductivity probes in wells and electrical resistivity imaging to track solute transport. Transport velocities through the meander were on average 9 and 21% higher (per temporal moment analysis and observed tracer peak, respectively) for the OM than for the PFM. Furthermore, temporal moments of tracer breakthrough analysis indicated downgradient longitudinal dispersion and breakthrough tracer curve tailing were on average 234% and 182% higher for the OM, respectively. This suggests the OM enabled solute transport at overall shorter timescales than the matrix but also increased tailing. Our results demonstrate the importance of macropores to meander bend hydrology and solute transport. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Electrical resistivity imaging of hydrologic flow through surface coal mine valley fills with comparison to other landforms          下载免费PDF全文

Breeyn M. Greer  Thomas J. Burbey  Carl E. Zipper  Erich T. Hester 《水文研究》2017,31(12):2244-2260

Surface coal mining has altered land cover, near‐surface geologic structure, and hydrologic processes of large areas in central Appalachia, USA. These alterations are associated with changes in water quality such as elevated total‐dissolved solids, which is usually measured via its surrogate, specific conductance (SC). The SC of valley fill effluent streams is a function of fill construction methods, materials, and age; yet hydrologic studies that relate these variables to water quality are sparse due to the difficulty of conducting traditional hydrologic studies in mined landscapes. We used electrical resistivity imaging (ERI) to visualize the subsurface geologic structure and hydrologic flow paths within a valley fill. ERI is a noninvasive geophysical technique that maps spatiotemporal changes in resistivity of the subsurface. We paired ERI with artificial rainfall experiments to track infiltrated water as it moved through the valley fill. Results indicate that ERI can be used to identify subsurface geologic structure and track advancing wetting fronts or preferential flow paths. Our results suggest that the upper portion of the fill contains significant fines, whereas the deeper profile is primarily large rocks and void spaces. Water tended to pond on the surface of compacted areas until it reached preferential flow paths, where it appeared to infiltrate quickly down to >15 m depth in 75 min. ERI applications can improve understanding of how fill construction techniques influence subsurface water movement, and in turn may aid in the development of valley fill construction methods to reduce water quality effects.  相似文献   

New harmonic tidal constants for some German North Sea stations     

Dr. Erich Pansch 《Ocean Dynamics》1989,42(1):27-39

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Transverse baroclinic oscillations in Lake Überlingen     

Erich Bäuerle 《Aquatic Sciences - Research Across Boundaries》1994,56(2):145-160

An episode of velocity measurements in the epilimnion at a midlake station in Lake Überlingen and taken from the campaign in October 1972 discloses a uni-nodal Poincaré-type baroclinic mode response with a 4 h period. We discuss the data and interpret it in terms of a two-layered linear wave model on the rotating Earth.

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Mean canopy flow in an oak forest and estimation of the foliage profile by a numerical model     

E. Mursch-Radlgruber  T. Kovacic 《Theoretical and Applied Climatology》1990,41(3):129-136

Summary The interaction of flow with the canopy structure is shown for an oak forest with hornbean trees (Carpinus betulus) as dense undergrowth using a large sample of 15 min mean profiles for the winter (without leaves) and the summer period (with leaves). The usefulness of the canopy flow index is analysed.To identify the processes involved in the momentum interaction a first-order closure model is interactively used. An approximation of the foliage area density from wind profile measurements is derived.With 7 Figures  相似文献   

4525282 Method of loading and/or transferring environmentally harmful materials in shallow-water and mudland regions and artificial Islands suitable therefor     

Erich O Bartsch  Gerald Vollstedt 《Marine pollution bulletin》1985,16(12):i-ii

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Tektonische Studien in Schiefer- und Phyllitgebieten Thüringens     

Dr. Peter Bankwitz  Dr. Erich Schroeder 《International Journal of Earth Sciences》1962,52(1):365-376

Zusammenfassung Schiefer- und Phyllitgebiete sind auch tektonisch voneinander verschieden. An Beispielen werden Charakteristika der beiden Einheiten erläutert. Im Schiefergebirge Ostthüringens sind die Beziehungen zwischen Faltung und Schieferung von besonderem Interesse. Im Schiefer- und Phyllitgebiet des Schwarzburger Sattels lassen sich mehreres-Flächensysteme und Achsen unterscheiden; zum Liegenden hin ist hier entsprechend den Vorstellungen einer Stockwerktektonik eine Änderung des tektonischen Stils zu beobachten.

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Tectonically, regions of shale and areas of phyllite are different. In the shale and phyllite area of the Schwarzburg Anticline several systems of s-surfaces and axes are represented. Toward the base a change in structural style can be observed in accordance with the concept of Stockwerk tectonics.

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Résumé Les domaines de schistes et de phyllites sont différents les uns des autres également du point de vue tectonique. Des exemples illustrent les caractéristiques des 2 unités. Dans le Massif schisteux de la Thuringe orientale, les relations entre le plissement et la schistosité sont particulièrement intéressantes. Dans le domaine des schistes et des phyllites de l'anticlinal de Schwarzburg, on peut distinguer plusieurs axes et plans de clivage; vers le bas on observe un changement du style tectonique conformément à une tectonique de Stockwerk.

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Die äquatoriale Beschleunigung bei Sonne,Jupiter und Saturn nebst Betrachtungen über die Form der Kontinente     

Prof. Dr. Erich Schoenberg 《Pure and Applied Geophysics》1959,43(1):1-11

Zusammenfassung Ausgehend von derEmden'schen Theorie der äquatorialen Beschleunigung der Sonne und einer früheren Anwendung derselben auf den Planeten Jupiter, wird auch die Beschleunigung bei Saturn hier erstmalig diskutiert und der Versuch gemacht, dieselbe Theorie zur Erklärung der Ostabweichung der Kontinente der Erde im äquatorialen Gebiet anzuwenden. Das ist nur möglich, wenn man 1.) auf die archaische Periode der Erdentwicklung zurückgreift, bei der aber die wesentlichen Höhenunterschiede der Erdoberfläche schon ausgebildet waren, 2.) der Pol im wesentlichen die jetzige Lage hatte und 3.) der Reibungskoeffizient der festen Erdkruste aber wesentlich geringer war: 10¹⁴ gegen etwa 10²⁰ c.g.s.

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Summary The hypothesis ofR. Emden to explain the equatorial acceleration of the sun has newly been discussed by the author and 11 years ago applied to the rotation ot the planet Jupiter. It is possible to apply her also to the planet Saturn and to the earth in the archaic period of evolution. The earth shows a striking eastern curvature of the continents in the equatorial zone, which possibly has originatet in times, when the earth crust was capable to yield to the same forces, which drive the equatorial zone forwards in rotating gaseous and liquid spheres, as the sun and the great planets. It is nenessary to suppose an invariable position of the pole and the principal height differences of the crust already developed. It is found, that the viscosity of the earth in that time has been small in comparison to its present value (10¹⁴ to 10²⁰ c.g.s.).

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