scholarly journals Empirical Studies in Alluvial Streams

2020 ◽  
Vol 3 (1) ◽  
Author(s):  
Levent Yilmaz
Keyword(s):  
Single Channel ◽  
Empirical Studies ◽  
Laboratory Data ◽  
Fine Sediments ◽  
Channel Interaction ◽  
Variable Curvature ◽  
Alluvial Channel ◽  
Channel Patterns ◽  
Bed Material ◽  
River Meandering

Meander flow takes place in one single channel which oscillates more orless regularly with amplitudes that tend to increase with time. Meandersare found in beds of fine sediments with gentle slopes. In this study, effortwill be made to investigate meanders’ turbulent boundary layer and toimprove the present knowledge about the river meandering phenomena. Itis assumed that the development of the perturbations which develop intomeanders or braids, is longer than the width of the channel. Interaction between the flow and mobile boundaries produces channel patterns which areclassified as meandering or braided. It is therefore long compared with theripples or dunes which cover the bed of such a channel and whose wavelength is shorter than the width of the channel. The variation of resistance toflow and rate of transport of bed material with velocity are discussed brieflyand taken into account. Meander flow and meander shear stress distribution of the channel are described. The basis is a steady, two-dimensionalmodel of flow in an alluvial channel with variable curvature. The meanderdevelopment is described by forcing a travelling, small-amplitude channelalignment wave on the system, and determining the growth characteristicsof the wave. Laboratory data are used to verify the formulas.

scholarly journals Is two-pole’s $$\varLambda (1405)$$ one state or two?

2021 ◽  
Vol 81 (9) ◽  
Author(s):  
Zhong-Yu Wang ◽  
Hiwa A. Ahmed ◽  
C. W. Xiao
Keyword(s):  
Single Channel ◽  
Wave Functions ◽  
Riemann Sheet ◽  
Lower Mass ◽  
Composite State ◽  
Channel Interaction ◽  
Quantum Numbers ◽  
Coupled Channels ◽  
Pole Structure

AbstractTo understand the nature of two poles for the $$\varLambda (1405)$$ Λ ( 1405 ) state, we revisit the interactions of $${\bar{K}}N$$ K ¯ N and $$\pi \Sigma $$ π Σ with their coupled channels, where two-pole structure is found in the second Riemann sheet. We also dynamically generate two poles in the single channel interaction of $${\bar{K}}N$$ K ¯ N and $$\pi \Sigma $$ π Σ , respectively. Moreover, we make a further study of two poles’ properties by evaluating the couplings, the compositeness, the wave functions, and the radii for the interactions of four coupled channels, two coupled channels and the single channel. Our results show that the nature of two poles is unique. The higher-mass pole is a pure $${\bar{K}} N$$ K ¯ N molecule, and the lower-mass one is a composite state of mainly $$\pi \Sigma $$ π Σ with tiny component $${\bar{K}} N$$ K ¯ N . From our results, one can conclude that the $$\varLambda (1405)$$ Λ ( 1405 ) state may be overlapped with two different states of the same quantum numbers.

ANG II blocks potassium currents in zona glomerulosa cells from rat, bovine, and human adrenals

1991 ◽  
Vol 260 (5) ◽  
pp. E772-E779 ◽  
Author(s):  
U. Brauneis ◽  
P. M. Vassilev ◽  
S. J. Quinn ◽  
G. H. Williams ◽  
D. L. Tillotson
Keyword(s):  
Single Channel ◽  
Calcium Influx ◽  
Membrane Resistance ◽  
Zona Glomerulosa ◽  
Ang Ii ◽  
K Channels ◽  
Channel Interaction ◽  
Whole Cell Patch Clamp ◽  
Outward Currents ◽  
K Currents

Angiotensin II (ANG II) is a principal secretagogue of adrenal zona glomerulosa (ZG) cells. The transduction process includes a depolarization of the plasma membrane and the activation of calcium influx. The ANG II-induced depolarization is associated with an increase in total membrane resistance. To directly address the mechanism underlying these observations, we examined the effect of ANG II on K+ currents of rat, bovine, and human ZG cells, using whole cell patch clamp. Although some differences were seen in the characteristics of K+ currents between species, ANG II consistently blocked outward currents in ZG cells [rat: 47.1 +/- 4.5% (SE), n = 17; bovine: 38.6 +/- 3.3%, n = 21; and human: 13-63%, n = 3]. With the use of the cell-attached mode, single-channel recordings in bovine ZG cells demonstrated K+ channels that were reversibly blocked when ANG II was added to the bath solution. This indicates that the block of K+ channels by ANG II involves a diffusible intracellular messenger rather than a direct receptor-channel interaction. The decreased conductance of K+ can account for the ANG II-induced membrane depolarization.

scholarly journals The Prediction of Fine Sediment Distribution in Gravel-Bed Rivers Using a Combination of DEM and FNN

Water ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 1515
Author(s):  
Van Hieu Bui ◽  
Minh Duc Bui ◽  
Peter Rutschmann
Keyword(s):  
Feedforward Neural Networks ◽  
Fine Sediment ◽  
Sediment Distribution ◽  
Gravel Bed ◽  
Fine Sediments ◽  
Porosity Variation ◽  
Sediment Sorting ◽  
Gravel Bed Rivers ◽  
Bed Material ◽  
The Relationship

Large amounts of fine sediment infiltration into void spaces of coarse bed material have the ability to alter the morphodynamics of rivers and their aquatic ecosystems. Modelling the mechanisms of fine sediment infiltration in gravel-bed is therefore of high significance. We proposed a framework for calculating the sediment exchange in two layers. On the basis of the conventional approaches, we derived a two-layer fine sediment sorting, which considers the transportation of fine sediment in the form of infiltration into the void spaces of the gravel-bed. The relationship between the fine sediment exchange and the affected factors was obtained by using the discrete element method (DEM) in combination with feedforward neural networks (FNN). The DEM model was validated and applied for gravel-bed flumes with different sizes of fine sediments. Further, we developed algorithms for extracting information in terms of gravel-bed packing, grain size distribution, and porosity variation. On the basis of the DEM results with this extracted information, we developed an FNN model for fine sediment sorting. Analyzing the calculated results and comparing them with the available measurements showed that our framework can successfully simulate the exchange of fine sediment in gravel-bed rivers.

scholarly journals ON THE GEOMETRY OF RIPPLES DUE TO WAVES

1978 ◽  
Vol 1 (16) ◽  
pp. 107 ◽  
Author(s):  
M.S. Yalin ◽  
E. Karahan
Keyword(s):  
Wind Waves ◽  
Laboratory Data ◽  
Specific Weight ◽  
Oscillatory Motion ◽  
Shallow Waters ◽  
Present Formulation ◽  
Unidirectional Flow ◽  
Single Curve ◽  
Bed Material

The present paper is an attempt to determine a single curve for the prediction of the length of ripples forming due to wind waves in shallow waters. The curve is revealed by normalising the field and laboratory data supplied by various authors. The concept of the unified plot embodied by the single curve mentioned is developed by using dimensional methods and by considering the fact that the specific weight and the density of the cohesionless bed material do not affect the length of ripples in a detectable manner. It is shown that the present formulation of the length of ripples due to waves satisfies the requirement of transition into the corresponding formulation of the unidirectional flow ripples when the period and the amplitude of the oscillatory motion increase indefinitely, while their ratio (implying "the velocity") remains finite.

scholarly journals A cusp catastrophe model for alluvial channel regime and classification of channel patterns

2014 ◽  
Vol 7 (1) ◽  
pp. 1477-1497
Author(s):  
Y. Xiao ◽  
X. J. Shao ◽  
Y. Yang
Keyword(s):  
Three Dimensional ◽  
Cusp Catastrophe ◽  
Channel Stability ◽  
Catastrophe Model ◽  
Cusp Catastrophe Model ◽  
Alluvial Channel ◽  
The Stability ◽  
Three Dimensional Coordinate ◽  
Channel Patterns ◽  
Natural Rivers

Abstract. A cusp catastrophe model for alluvial channel regime is established by selecting suitable parameters to reflect channel stability. An equation is obtained from the equilibrium state of channel regime, which is a cusp catastrophe surface in a translated three dimensional coordinate. The stability of channel patterns can be identified by such a model in a direct way, and the 2-D projection of the cusp catastrophe surface can be used to classify alluvial channel patterns. Predictions based on this model are consistent with field observations involving about 100 natural rivers. The results indicate that this method may be applied to study the regime of natural rivers and to assist decision making in river engineering.

Imaging and suppressing near-receiver scattered surface waves

Geophysics ◽  
2005 ◽  
Vol 70 (2) ◽  
pp. V21-V29 ◽  
Author(s):  
Xander H. Campman ◽  
Kasper van Wijk ◽  
John A. Scales ◽  
Gérard C. Herman
Keyword(s):  
Surface Waves ◽  
Single Channel ◽  
Laboratory Data ◽  
Body Waves ◽  
Surface Model ◽  
Imaging Method ◽  
Sampled Data ◽  
Impedance Function ◽  
Near Surface ◽  
Integral Equation Formulation

When traveling through a complex overburden, upcoming seismic body waves can be disturbed by scattering from local heterogeneities. Currently, surface-consistent static and amplitude corrections correct for rapid variations in arrival times and amplitudes of a reflector, but these methods impose strong assumptions on the near-surface model. Observations on synthetic and laboratory experiments of near-surface scattering with densely sampled data suggest that removing noise from near-receiver scattering requires multichannel approaches rather than single-channel, near-surface corrections. In this paper we develop a wavefield-based imaging method to suppress surface waves scattered directly beneath the receivers. Using an integral-equation formulation, we account for near-surface heterogeneities by a surface impedance function. This impedance function is used to model scattered surface waves, excited by upcoming wavefronts. The final step in our algorithm is to subtract the scattered surface waves. We successfully apply this method to laboratory data of scattered surface waves, excited and monitored with a noncontacting acquisition system.

Predicting changes in alluvial channel patterns in North-European Russia under conditions of global warming

Geomorphology ◽  
2008 ◽  
Vol 98 (3-4) ◽  
pp. 262-274 ◽  
Author(s):  
Oleg Anisimov ◽  
Jef Vandenberghe ◽  
Vladimir Lobanov ◽  
Alexander Kondratiev
Keyword(s):  
Global Warming ◽  
European Russia ◽  
Alluvial Channel ◽  
Channel Patterns

Resuspension processes and seston dynamics, southern North Sea

1993 ◽  
Vol 343 (1669) ◽  
pp. 475-491 ◽  
Keyword(s):  
Boundary Layer ◽  
Organic Carbon ◽  
North Sea ◽  
Sediment Resuspension ◽  
Metal Exchange ◽  
Pore Waters ◽  
Model Simulations ◽  
Fine Sediments ◽  
The North ◽  
Bed Material

Coupling of physical, biological and chemical processes associated with particle resuspension and seston flux was investigated at three sites in the North Sea with contrasting water column (mixed/stratified) and seabed (cohesive/non-cohesive) characteristics. Seston concentration was determined by a combination of local resuspension and advection of a regional horizontal concentration gradient. Model simulations of observations show that fair weather, the bed erosion rate was limited by the availability of suitable bed material. The resuspended particles were derived from a surficial veneer of material (fluff) that was relatively enriched in organic carbon. Sediment from the bed itself was therefore not resuspended by tidal currents even at a shallow water, sandy site. Bioturbation of the seabed by infauna significantly modified the properties of muddy sands at a deep water site in summer, but this was insufficient to cause tidal entrainment of the bed sediment. Resuspension increased under combined wave/current flows during storms. However, model simulations predict that self-stratification of the boundary layer by resuspended fine sediment during storms reduces bed stress and limits further resuspension, so that storm resuspension of fine sediments may be self-limiting. Seston was a mixture of: (1) particles relatively rich in organic carbon, with low settling velocities, in long-term suspension; (2) particles with less organic carbon (though still greater than that of the bed material), faster settling velocities, periodically resuspended; (3) particles that were very rich in organic carbon, with fast settling velocities, produced during plankton blooms. Particles in category 3 scavenged those in category 1 as they settled, so that seston concentrations diminished and deposition rates increased after blooms. In stratified waters during blooms, deposition of organic-rich detritus gave rise to seabed anoxia and efflux of trace metals (Fe and Mn) from pore waters. Differential rates of metal exchange altered the particulate Fe/Mn ratio below the thermocline. Settling, deposition, and resuspension of fluff were therefore important controls of metal exchanges in the boundary layer.

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