Apex Section Research Articles

Flow simulation in curved compound channels: Effect of changing the sinuosity of the main channel and width of floodplain

In this research, the effect of different sinuosity (s) and width of floodplain on the flow structures in curved compound channels was investigated numerically. Six different sinuosities of main channel (s = 1, 1.026, 1.096, 1.209, 1.381, and 1.641) and three different relative depths (Dr = 0.26, 0.35, and 0.45) have been used. The findings revealed that with the increase in sinuosity from 1 to 1.641 (64% increase), the maximum flow velocity in the apex section (CS1) and the middle crossover section (CS4) decreases by 23% and 62%, respectively. In the relative depth (Dr) of 0.26, 0.35, and 0.45 with the increase in sinuosity from 1 to 1.641 (with the corresponding decrease in width of floodplain), the ratio of main channel discharge to total discharge (Qmc/Q) is reduced by 40%, 45%, and 45%, respectively. Also, with the increase in relative depth (Dr), the main channel discharge is reduced, and the majority of the flows discharge through floodplain, so that with the increase in the relative depth from 0.26 to 0.45, the amount of Qmc/Q in the channel with maximum sinuosity (s = 1.641) and straight channel (s = 1) decreases by 30% and 14%, respectively. With the increase in sinuosity, the changes of v/u and the angle of flow deviation are more noticeable in the middle sections and above the bankfull level, so that in the most critical state, with an increase in the sinuosity from 1 to 1.641, the relative intensity of secondary flow (v/u) increases from 0 to 3.6, and along a meander, the size of the secondary flow cell in each section becomes larger with increasing sinuosity.

Bed shear stress distribution across a meander path

ABSTRACT Laboratory experimentation for bed shear stress distribution has been carried out in two sets of meandering channels. The channels have crossover angles of 110° and 60° constructed by ‘sine-generated’ curves over a flume of 4 m width. Variations in bed roughness were studied for the meandering main channel. Bed shear stress distribution across a meandering length for the 110° and 60° channels was examined for different sinuosities and roughnesses. The boundary shear stress study illustrated the position of maximum shear along the apex section and across the meandering path. These variations were observed for different flow depths. A comparison of the bed shear among the three experimental channels was conducted, and the results were analyzed.

Experimental assessment of velocity and bed shear stress in the main channel of a meandering compound channel with one-sided blocks in floodplain

Meandering rivers have an important role in transporting runoff from rainfall, especially during floods. With many cities and villages along rivers and the construction of water-management structures in floodplains, the flow pattern of the meandering rivers changes in time of floods. Here the flow behaviors in meandering compound channels with smooth floodplains and one-sided building floodplains are investigated using laboratory experiments. The experiments have been performed at three relative depths of 0.29, 0.39 and 0.49 and the corresponding discharges. The results show that the block density in a floodplain has a significant effect on flow behavior in the main channel. So that, with the increase of the relative depth, the ratios of main channel discharge compared to the total discharge (Qmc/Q) decreases in the bends with minimal extension of blocks floodplain, the crossover areas and the bends with maximal extension of blocks floodplain. For a given Dr, the significant increase in the Manning's n values as the density of the blocks increases (approximately 30%). With increasing the blocks density from zero to 23.7%, the maximum Darcy–Weisbach friction factor in sections CS1 and CS7 increases by 110% and 2%, respectively, which shows that increasing the density of blocks does not have a great effect on f in the section CS7. Under one-sided blocked floodplain conditions, the maximum longitudinal velocity in the main channel in the section with maximal extension of the blocks in the floodplain (CS7) is greater than the section with minimal extension of blocks in the floodplain (CS1). At the relative depth of 0.49, the maximum value of depth-averaged velocity in sections CS1-4 decreased by an average of 52% compared to the smooth floodplain. The maximum shear stress on the bed at the apex section for all channels occurs near the convex side and the bed shear stress at all sections decreases with decreasing relative depth and in the section with minimal extension of blocks floodplain (CS1) and cross-over sections. The maximum shear stress of the bed decreases with increasing the block density and these changes are more near the convex side than the concave side.

The impacts of near-bed flow characteristics on river bed sediment transport under ice-covered conditions in 2016–2021

Global climate change has been projected to affect hydrology, the ice-covered flow period and river morphology (including changed sediment transport conditions) in northern high-latitude regions. To understand the impact of the expected shortening of the ice-covered period on bedload transport, one needs to understand the present sediment transport in these high-latitude rivers with annually occurring ice cover. Thus, the aims are (1) to define the impacts of ice cover on near-bed flow characteristics during hydrologically varying years, and (2) to analyse the impacts of these mid-winter flow characteristics on the bed sediment transport potential. The analyses are based on Acoustic Doppler Current Profiler (ADCP: 2016–21) and Acoustic Doppler Velocimeter (ADV: 2020–21) measurements performed in mid-winter ice-covered conditions of the sandy and small (circa 20 m wide) Pulmanki River in northern Finnish Lapland.Despite the ice-covered river conditions in winter, sediment transport occurs even during these harshest mid-winter conditions. The critical velocities and shear velocities of mid-winter conditions were exceeded in winters 2016–2021, and bedload transport occurred according to bedload measurements. Three different situations occurred regarding the bed sediment transport and near-bed velocity conditions: (1) high measured mid-winter discharges indicate high velocities throughout the meander bend; (2) low measured mid-winter discharges cause low near-bed velocities throughout the meander bend; (3) winters having intermediate discharges indicate near-bed velocities and sediment transport potential being higher at the upstream inlet and apex sections of the meander bend but clearly lower downstream of the apex. The confinement by the river ice cover, i.e. bottom-fast ice, explains the velocity variation. The near-bed velocities were the highest at the upstream inlet section of a symmetrical meander bend, where the measurement cross-sections were narrower and shallower. The velocities were the lowest downstream of the apex, where the channel changed from relatively narrow to wider and deeper.

An experimental evaluation of the blocks in floodplain on hydraulic characteristics of flow in a meandering compound channel

• Flow behavior in meandering channels with 2-sided blocks in floodplains examined experimentally. • The presence of blocks in floodplains significantly enhances Q mc / Q ). • In cases with blocks densities of 6.2% and less, the values of Manning's n decrease by increasing Dr. • For all cases of blocks densities, the maximum bed shear stress occures near the convex side of CS1. • With high blocks density, apparent lateral velocity gradients seen in central region of CS3-CS5. In this research, the main flow behaviors in the meandering compound channels with different densities of two side blocks on the floodplains were investigated by using laboratory experiments at the three relative depths of 0.29, 0.39 and 0.49 and the corresponding discharges. The results show that the blocks density on the floodplain has a significant effect on the flow behavior in the main channel. So that the smooth channel efficiently conveys 100% more water on average than that conveyed in the case with maximum blocks density. For the case with smooth floodplains, the Q mc /Q ratios of main channel discharge to total discharge increases continuously by reducing the flow depth, reaching 47% for Dr = 0.29 (Dr is the relative depth). By contrast, Q mc /Q in the channel with maximum blocks density peaks at 70% (>50%), showing that the main channel controls the capacity of compound channel conveyance because the blocks occupy most of the cross-sectional area of the floodplain when Dr = 0.29. In cases with blocks densities of 6.2% and less in floodplain, the Manning n decreases by increasing the relative depth (Dr). In cases with blocks densities of 9.7% and 23.7%, the Manning n increases by increment the relative depth. In addition, in cross-over sections of the case with smooth floodplains, a steep gradient of velocity in the vertical direction appears from the dense contour lines around the bankfull level near the right-hand sidewall indicating that a considerable effect occurs from the upstream flow. Instead, for channel with maximum blocks density, an apparent lateral velocity gradient was located in the central region in cross-over sections. The maximum shear stress of the bed at the apex section for all channels occurs near the convex side and the amount of bed shear stress at all sections decreases with reducing the relative depth. In the cross-over sections, due to the increase of the flow angle between the main channel and the floodplain, the effect of the secondary flow is stronger and the flow velocity decreases more, so the Darcy–Weisbach coefficient increases more in this area.

Effects of discharge on the velocity distribution and riverbed evolution in a meandering channel

To discuss the effects of discharge on the velocity distribution and riverbed evolution in a meandering river, a generalized meandering channel model was designed, and the instantaneous velocities and water levels in thirteen cross-sections and the digital elevations of the bed surfaces were measured. The results show that for the same discharge, the transverse water surface gradients are large at the downstream positions adjacent to the apex sections and small near the middle positions of the crossover areas. With increasing discharge, the transverse water surface gradients in the curved segments increase, the transverse underflows strengthen, and the transverse surface flows exhibit no obvious changes. If the curvature of a meandering channel is large and there are a large number of sediment particles whose incipient velocities are smaller than the transverse underflow velocities near the apex sections, then the regions between the apex-sectional convex sides and the outlets of the adjacent downstream crossover areas are prone to sediment deposition, and the frequency distributions of the bed surface elevations are positively skewed. For the same cross-section, the cross-sectional average velocity increases with increasing discharge. For the same discharge, the cross-sectional average velocities are large near the middle positions of the crossover areas and small near the apex sections. The thalweg swings randomly along the channel, but its overall trend is approximately the same as that of the flow dynamic axis. In a cross-section, the positions with large turbulent kinetic energy are located in the mainstream area, and the average turbulent kinetic energy increases with increasing discharge.

Flow-induced vegetation uprooting in a meandering bend: Experimental investigation

Vegetation uprooting is a complex process which depends on many interrelated factors. In this paper, attention is focused on the flow-induced uprooting in river bends, where the flow characteristics vary as effected by the channel's curvature and its continuous changing in the downstream direction. Results are presented by an experimental work done in a high-amplitude meandering flume with mature herbaceous vegetation on the bed. In the first part of the paper, the variation along the bend of the geometrical (length, thickness, and radical architecture) and the mechanical (resistance force) characteristics of the roots are analyzed. In the second part of the paper, the transition from the condition of vegetation distributed on the bed to the condition of vegetation uprooted by the flow is experimentally examined. The results show that the flow-induced uprooting varies along the bend depending on the roots' geometrical and mechanical characteristics which are, in turn, influenced by the variation of the water surface elevation along the bend itself. It has been found that lower values of the resistance force occur at the apex section where the roots are characterized by higher values of length and lower values of thickness and have radical apparatuses characterized by limited encumbrance, a high number of roots, and low bushyness. The flow-induced uprooting especially develops close to the outer bank along the channel reach between the bend entrance and the apex section, where the root resistance force and the water surface slope tend to decrease in value.

Evaluating the role of left ventricle global longitudinal strain in myocardial perfusion defect assessment.

Myocardial perfusion defect, assessed with single photon emission computed tomography (SPECT), is useful for patient management and risk stratification. Left ventricle Global Longitudinal Strain (LV GLS) has gained interest for observing subclinical LV dysfunction. We aimed to investigate the utility of LV GLS in evaluating myocardial perfusion defect. A retrospective study of all patients who underwent SPECT and LV GLS at Tel Aviv Sourasky medical center. Overall, 86 patients were included. LV GLS and SPECT correlated in the base and apex sections for infraction, and in the apex only for ischemia. Adjusted analysis showed a significant correlation between LV GLS of both the mid and apical section and infarction by SPECT, but no association with ischemia. No associations were found by arterial supply territory. A sub-analysis of patients without left bundle branch block (LBBB) strengthened the correlations, with a 58-70% higher chance of both fixed and reversible defects for every 1-unit decrease LV GLS in the mid and apical sections. LV GLS effectively evaluated the presence of infarction by SPECT in the mid and apical sections, particularly in patients without LBBB. Due to its high availability, LV GLS may have a role in evaluating myocardial perfusion defect.

Forensic Autopsies can Determine Latent Prostate Cancer Prevalence.

To evaluate the usefulness of forensic autopsies in determining latent prostate cancer (PC) prevalence, we examined latent PC prevalence from autopsies and compared our findings between decedents with and without cancer. Data from forensic autopsies performed in Japan from 2004 to 2014 were obtained. For each prostate, histopathological examinations were performed in both the base and the apex sections. Three hundred and seventeen Japanese decedents were selected for analysis. The mean age of decedents was 56.4 ± 17.8 years (range, 14-94 years). Among this population, 39.4% died suddenly of disease and 60.6% died of external causes. Latent PC was identified in 45 (14.2%) decedents, who ranged from 27 to 93 years old (mean, 71.1 ± 12.9 years). The prevalence of clinically significant PC with a Gleason score of 7 or more was 8.8%, and the rate increased with age. Fifteen males had cancers other than PC. The prevalence of overall latent PC was significantly higher for those with cancer compared with those without (40.0% vs. 12.9%; P = 0.003). In this study, the use of forensic autopsy materials provided the opportunity to obtain a more accurate natural history of PC, as the decedents in this situation would have been more likely to have died suddenly while behaving as normal prior to death, and less likely to have been impacted by long-term medical interventions.

The Plasma Compression Fusion Device—Enabling Nuclear Fusion Ignition

The plasma compression fusion device (PCFD) generates the energy gain by plasma compression-induced nuclear fusion. This concept has the capability of maximizing the product of plasma pressure and energy confinement time to maximize the energy gain, and thus give rise to fusion ignition conditions. The preferred embodiment of this original concept uses a hollow cross-duct configuration of circular cross section in which the concentrated magnetic energy flux from two pairs of opposing curved-headed counter-spinning conical structures (possibly made from an alloy of tungsten with high capacitance) whose outer surfaces are electrically charged compresses a gaseous mixture of fusion fuel into a plasma, heated to extreme temperatures and pressures. The generated high-intensity electromagnetic (EM) radiation heats the plasma and the produced magnetic fields confine it in between the counter-spinning conical structures, named the dynamic fusors (four of them-smoothly curved apex sections opposing each other in pairs). The dynamic fusors can be assemblies of electrified grids and toroidal magnetic coils, arranged within a conical structure whose outer surface is electrically charged. The cross-duct inner surface surrounding the plasma core region is also electrically charged and vibrated in an accelerated mode to minimize the flux of plasma particles (including neutrals) from impacting the PCFD surfaces and initiating a plasma quench. The fusion fuel (preferably deuterium gas) is introduced into the plasma core through the counterspinning conical structures, namely, injected through orifices in the dynamic fusor heads. There is envisioned another even more compact version of this concept, which uses accelerated vibration in a linear-duct configuration (using two counterspinning dynamic fusors only) and would best be suited for fusion power generation on aircraft, or main battle tanks. The concept uses controlled motion of electrically charged matter through accelerated vibration and/or accelerated spin subjected to smooth, yet rapid acceleration transients, to generate extremely high-energy/high-intensity EM radiation (fields of high-energy photons) which not only confines the plasma but also greatly compresses itso as to produce a high power density plasma burn, leading to ignition. The PCFD concept can produce power in the gigawatt to terawatt range (and higher) with input power in the kilowatt to megawatt range and can possibly lead to ignition (selfsustained) plasma burn. Several important practical engineering and operational issues with operating a device such as the PCFD are discussed.

Discharge Estimation at the Apex of Compound Meandering Channels

A new method is proposed to calculate flow in a compound meandering channel by considering the momentum transfer between different zones. Vertical momentum transfer, at the horizontal interface of the lower main channel and the meander belt; and the horizontal momentum transfer, at the vertical interfaces between the meander belt and the adjoining outer floodplains. Modelling of this analytical method for the bend apex section is carried out, for a control volume of unit length. Calibration has been carried out for different laboratory channels and a natural river, demonstrating that the present model is capable of providing an adequate prediction of discharge in experimental as well as in field study. A constant value of 0.01 as the momentum transfer coefficient is verified to act at the interacting interfaces for the meandering channels. The zonal velocity for each subsection is determined, which facilitates prediction of discharge distribution.

Experimental study of the effects of apex section internals and conical section length on the performance of solid–liquid hydrocyclone

Several new type hydrocyclones were designed for fine particles removal from the liquid by adding internals to the underflow section of the typical solid–liquid hydrocyclone. Both separation efficiency and energy consumption of these hydrocyclones were verified experimentally, aiming to determine whether adding internals could make the hydrocyclone more compact and energy-saving. The results indicated that adding an inner cylinder to the underflow pipe can reduce the Euler number remarkably and has little influence on the separation efficiency. The fixing method of the inner cylinder on the underflow pipe could influence the performance of hydrocyclones in some specific feed flow rates, and it is better to fix the inner cylinder using two crossed thin rods. When the conical section length was reduced by about 1/3, the separation efficiency of the hydrocyclone with an inner cylinder decreased only 1.1%–2.0% and was similar to the traditional one under high feed flow rates. Under low feed flow rates, the separation efficiency of this shortened hydrocyclone decreased as high as 5.8%. Meanwhile, both the overflow and underflow Euler number decreased significantly when the conical section length was shortened. In addition, it is shown that the separation efficiency under low feed flow rates can be enhanced by adding a short inner cone at the bottom of the hydrocyclone’s conical section. New conceptions proposed in this work can be used to design compact industrial hydrocyclones for fine particles separation under low inlet pressure.

Experimental Analysis of the Source and Sink Relationship in a Meandering Bend

The source-sink-relationships in natural rivers are compound results of various influencing factors, and correlated fitted equations are kind of qualitative description. Experiment analyses was conducted in a laboratory flume to reach a quantitative description, whose center line follows a sine-generated curve with deflection angle of 30 degree. Three-dimensional velocities, bed deformation and composition of the pool-bar complexes in the meander bend are analyzed. The comparison of deformed bed and the depth-averaged velocities founds that, the maximum depth-averaged velocities of sections around the transition reach occurred at the edge of pool with smaller transverse slope, and the maximum depth-averaged velocities for sections around the apex section occurred at the edge of pool with larger transverse slope. Quantitative analysis of the composition of pool-bar complexes revealed the source-sink relation of moved particles. It shows that, moved particles sourced from the concave bank are mainly come from area down the apex section, and moved particles sourced from the convex bank are mainly come from area upper the apex section. Besides, there exit an area with strong sediment exchange, namely the bar around the convex-side of the apex section.

Turbulence structure and implications in exchange processes in high-amplitude vegetated meanders: Experimental investigation

Abstract Aquatic plants in rivers interact with flow and exert an important role in maintaining suitable habitat and ecological equilibrium. Understanding turbulence structure in the presence of vegetation is important with respect to environmental processes, such as sediment transport and mixing of transported quantities. Literature indicates that mass and momentum exchanges in the presence of vegetation are strongly influenced by the sequence of coherent structures which form between vegetated and non-vegetated zones. In the present paper we investigate turbulence structure and coherent motion in high-curvature channels with submerged vegetation. The analysis is performed with the aid of detailed experimental data collected in a meandering flume of large amplitude. Results essentially highlight that the contribution of turbulence to lateral diffusion and to streamwise and vertical transport may be significantly influenced by the relative submergence h/kv. The dominant mechanism of exchange obtained for h/kv 2. Quadrant analysis has been also applied to investigate the occurrence of turbulent events and the associated exchange mechanism. In particular, at the apex section, it has been found that ejection events dominate in the outer bank region and, as literature indicates, this could cause the suspension of sediment in the flow that is transported downstream. In the central region the motion is especially characterized by high-speed fluid directed towards the bed, influencing the transport process significantly.

Estimation of flow direction in meandering compound channels

The flow in the main channel of a meandering compound channel does not occur in the ridge direction because of the effect of the upstream floodplain flows. This study proposes a model for estimating the flow direction in the depth-averaged two-dimensional domain (depth-averaged flow angles) between the entrance and the apex sections. Detailed velocity measurements were performed in the region between the meander entrance section and apex section in a large-scale meandering compound channel. The vertical size of the secondary current cell is highly related to the depth-averaged flow angle; thus, the means of the local flow angles above the secondary current cell and within the cell are separately discussed. The experimental measurements indicate that the mean local flow angle above the cell is equal to the section angle, whereas the mean local flow angle within the cell is equal to zero. The proposed model is validated using published data from five sources. Good agreement is obtained between the predictions and measurements, indicating that the proposed model can accurately estimate the depth-averaged flow direction in the meandering compound channels. Finally, the limitations and application ranges of the model are discussed.

Abscission zone development in Setaria viridis and its domesticated relative, Setaria italica.

Development of an abscission zone (AZ) is needed for dispersal of seeds, and AZ loss was a critical early step in plant domestication. The AZ forms in different tissues in different species of plants, but whether the AZ is developmentally similar wherever it occurs is unknown. AZ development in Setaria viridis was studied as a representative of the previously uncharacterized subfamily Panicoideae. One accession of the wild species S. viridis and two of its domesticate, S. italica, were studied. Strength of the AZ was measured with a force gauge. Anatomy of the AZ was studied throughout development using bright field and confocal microscopy. The force required to remove a spikelet of S. viridis from the parent plant dropped steadily during development, whereas that required to remove spikelets of S. italica increased initially before stabilizing at a high level. Despite the clear difference in tensile strength of the AZ, anatomical differences between S. viridis and S. italica were subtle, and the position of the AZ was not easy to determine in cross sections of pedicel apices. Staining with DAPI showed that nuclei were present up to and presumably through abscission in S. viridis, and acridine orange staining showed much less lignification than in other cereals. The AZ in Setaria is developmentally and anatomically different from that characterized in rice, barley, and many eudicots. In particular, no set of small, densely cytoplasmic cells is obvious. This difference in anatomy could point to differential genetic control of the structure.

Dark-chilling of Seedlings Affects Initiation and Morphology of Broccoli Inflorescence

The constant supply of broccoli heads for a vegetable market can be kept by the differentiation of sowing time and the age of seedlings. Dark-chilling of young seedlings can also modify the time of transplanting, subsequent plant development, yield and inflorescence quality. The aim of the present study was to analyze the influence of seedling dark-chilling on the inflorescence initiation and the morphological quality of broccoli heads. The experiment was carried out at the University of Agriculture in Krakow (South Poland) in the years 2009 and 2010, with broccoli (Brassica oleracea L. var. italica Plenck) medium late cultivar ‘Monaco’ F1. The examined factors were the age of seedlings (4-, 6-, 8-, and 10-week-old) and dark-chilling (2°C/2 weeks and non-chilled control). Microscopic analysis of the apex sections was performed to determine the time of the inflorescence differentiation in chilled and non-chilled seedlings of different age. Chosen morphological features of the mature heads were also described as depended on age and chilling of seedlings. The inflorescence initiation was observed between 4 and 6 week of the plant ontogeny. Especially 4-week-old seedlings, chilled by two weeks, were more advanced in the generative development in comparison to non-chilled control. Low temperature applied in the seedling stage did not cause the head buttoning. Inflorescences developed by broccoli planted from 4 and 6-week-old seedlings, both chilled and control, were characterized by the best visual quality, determined by a convex head shape, tight branching angle, small and uniform size and regular form of flower buds. Chilling of oldest, 8- and 10-week-old seedlings negatively affected the inflorescence quality, through planed and spread shape of heads and non-uniform shape of flower buds.

Experimental analysis of cross‐sectional flow motion in a large amplitude meandering bend

AbstractFlow in meandering bends is characterized by the formation of a large cross‐sectional central‐region circulation cell. The width‐to‐depth ratio is one of the most important parameters affecting the entity of the cross‐circulation motion. In steep outside bends, beside the central‐region cell, a counter‐rotating circulation cell often forms in the upper part of the outer‐bank. In spite of its practical importance, the evolving mechanisms of both the circulation cells and their role on boundary shear stress distribution in bends are not yet fully understood. The aim of the present paper is to gain some insight into how cross‐sectional flow motion evolves along meandering bends. Experiments have been carried out in a laboratory meandering channel of large amplitude, over a deformed‐rigid bed, for two values of the width‐to‐depth ratio. The three‐dimensional flow velocity field has been measured in detail at five cross‐sections, almost equally spaced along the channel reach between two consecutive apex sections. The measurements have been carried out on a fine grid by an acoustic Doppler velocity profiler. The distributions of the cross‐sectional flow (e.g. cross‐sectional flow velocity, net transversal flux) and turbulent kinetic energy are analyzed in each investigated section. Measurements show that the counter‐rotating circulation cell is evident only in the case of ‘small’ width‐to‐depth ratio. Such circulation cell begins at the bend entrance and it is fully developed at the bend apex; then it decays. At the bend apex, the core of maximum velocity is found near the bed at about the separation between the central and the outer‐bank circulation cells. Moreover, the presence of the counter‐rotating circulation cell allows the bank shear stress to maintain low values in the outer‐side of the bend. Copyright © 2010 John Wiley & Sons, Ltd.

Width variations and mid-channel bar inception in meanders: River Bollin (UK)

The extent and pattern of width variations along a meandering channel and its association with variation in bed topography and development of mid-channel bars have been examined through field survey evidence for a reach of the River Bollin in NW England. The wet width has been quantified along the reach by applying a hydraulic model to surveyed cross sections under a range of discharges between low flow and defined bankfull conditions. This approach allows an objective, modelling-based method to compute channel width. The high spatial resolution of the topographical survey allows capture of significant variations in the cross-sectional morphology at the meander wavelength scale. Results disclose some features of longitudinal and stage-dependent width variability in meanders. Width variation is shown to be highly correlated with curvature: at bankfull conditions width peaks in bend apex sections exceed those at inflection sections and can be up to twice greater. The width-curvature behavior is correlated with the pattern of bed and banks morphology, which is different in bend apices and in meander inflections. The survey shows that the bedform morphology can be characterized by a mid-channel bar pattern that is initiated at the inflection section and that the bedform dynamics can be closely associated with channel width variations.

Correlation between Dose of Ethacrynic Acid and Weight of Cat in the Cat Deafening Procedure

Background and Objectives : Co-administration of kanamycin (KM) with the loop diuretic ethacrynic acid (EA) has been known to produce a rapid and profound hearing loss in adult animals. The objective of this study was to see if monitoring the hearing status during intravenous infusion of EA could minimalize individual variability and to evaluate the correlation between the dose of EA and the body weight (wt). Materials and Method : Twenty cats with the mean age of 24 weeks3.7 (range, 20.6-28.3 weeks) and the mean weight of 3.27 kg0.75 (range 2.4-4.75 kg) received a subcutaneous injection of KM (300 mg/kg) followed by an intravenous infusion of EA (1 mg/min). Click evoked auditory brainstem responses (ABRs) were recorded to monitor the hearing during the infusion. When the ABR thresholds rose to levels in excess of 90 dB SPL, the infusion of EA was stopped. The histopathologies for sections of apex, middle, base of cochlea were examined after 6 months. Results : There was a significant positive correlation (p=.583) between the EA dose and body weight. Cochlear histopathology showed an absence of organ of Corti and decrease of spiral ganglion cells in the majority of cochleas, especially in the basal turn. The extent of loss of spiral ganglion cells was dependent on their distance from the round window. Conclusion : Monitoring the animal's hearing status during the procedure ensured that the dose of EA was optimized for individual animals. Thus, the positive correlation between the EA dose and body weight should be considered should in designing the animal models of controlled high frequency hearing loss.