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Showing papers on "Water flow published in 1978"


Journal ArticleDOI
01 Oct 1978-Nature
TL;DR: In this paper, the authors used 137Cs, a fallout product of nuclear testing, to measure sedimentation rates in a Louisiana coastal marsh, the first report of such use in coastal marshes.
Abstract: SEA-LEVEL records indicate that the coast of Louisiana and other parts of the Gulf Coast are rapidly subsiding1. Louisiana is now losing approximately 16 square miles of land per year, primarily to subsidence2; the rates of subsidence vary with location. Vertical marsh accretion is the process which counteracts subsidence and eustatic sea-level rise and prevents marsh deterioration, but, as in Louisiana's salt marshes, the pattern, rate and variability are sufficiently complicated to defy simple prediction. Conditions of marsh development vary throughout the coast, from the modern and Atchafalaya deltas through the abandoned deltas to the Chenier Plain3. In recent years, much of the coastal area such as Barataria Basin has been deprived of river-borne sediment through natural stream diversion and the construction of water-control embankments. In addition, dredging from petroleum operations has altered water flow and sedimentation patterns. The survival and productivity of Gulf Coast marshes depend on the influx and accumulation of sediment that offsets the effect of subsidence and maintains the marsh surface within the tidal range. To predict long-range trends in marsh stability, accurate measurements are needed of both subsidence and sedimentation rates. Information on subsidence is available from tide gauge measurements but no measurements have been made of sedimentation rates in marshland developed on Recent Mississippi alluvium. 137Cs, a fallout product of nuclear testing, has become a useful tool for dating recent sedimentary sequency in lakes4–8. We report here its use in the measurement of sedimentation rates in a Louisiana coastal marsh, the first report of such use in coastal marshes.

373 citations


Journal ArticleDOI
TL;DR: In this paper, the authors presented simulation analyses of heat and water flow during soil freezing using a modified form of a model presented by Harlan, and tested the model is tested in a simulated environment.
Abstract: The objective of this report is to present simulation analyses of heat and water flow during soil freezing. The analyses utilize a modified form of a model presented by Harlan. The model is tested ...

262 citations


Journal ArticleDOI
TL;DR: In this article, an ensemble average is fitted to a conical growth law by using data at three streamwise stations to determine the virtual origin in x and t and the two-dimensional unsteady stream function is expressed as ψ=U^2_∞tg(ξ,η) in conical similarity co-ordinates.
Abstract: Laser-Doppler velocity measurements in water are reported for the flow in the plane of symmetry of a turbulent spot. The unsteady mean flow, defined as an ensemble average, is fitted to a conical growth law by using data at three streamwise stations to determine the virtual origin in x and t. The two-dimensional unsteady stream function is expressed as ψ=U^2_∞tg(ξ,η) in conical similarity co-ordinates ζ = x/U_∞t and η = y/U_∞t. In these co-ordinates, the equations for the unsteady particle displacements reduce to an autonomous system. This system is integrated graphically to obtain particle trajectories in invariant form. Strong entrainment is found to occur along the outer part of the rear interface and also in front of the spot near the wall. The outer part of the forward interface is passive. In terms of particle trajectories in conical co-ordinates, the main vortex in the spot appears as a stable focus with celerity 0·77U_∞. A second stable focus with celerity 0·64U_∞ also appears near the wall at the rear of the spot. Some results obtained by flow visualization with a dense, nearly opaque suspension of aluminium flakes are also reported. Photographs of the sublayer flow viewed through a glass wall show the expected longitudinal streaks. These are tentatively interpreted as longitudinal vortices caused by an instability of Taylor-Gortler type in the sublayer.

245 citations


Journal ArticleDOI
TL;DR: Most calcite in speleothems is composed of columnar crystals (palisade calcite) and exhibits fabrics similar to those in some porefilling calcites interpreted to be replacive after acicular carbonate cements as discussed by the authors.
Abstract: Most calcite in speleothems is composed of columnar crystals (palisade calcite) and exhibits fabrics similar to those in some porefilling calcites interpreted to be replacive after acicular carbonate cements. The columnar crystals do not interfere with each other's growth (suggesting that they are secondary features) and this, together with the occurrence of layers of acicular calcite in some speleothems, leads to a conclusion that columnar crystals have replaced acicular carbonate. The evidence, however, is misleading. The same crystal fabrics can be explained by normal, but somewhat complex, growth processes. Inclusions (and patterns made by them) constitute the most important clues to the origin of the columnar crystals. Most inclusions are fluid-filled cavities and six types of growth layering are distinguished on the basis of variations in inclusion abundance, size and pattern. Growth layers defined by parallel, linear inclusions are interpreted to have formed during the incomplete lateral coalescence of numerous syntaxial overgrowth crystallites which grow upon the speleothem surface. The linear inclusions represent remnants of the former inter-crystallite spaces. Complete crystallite coalescence generates inclusion-free calcite, whereas inhibition of the lateral coalescence of the overgrowth crystallites generates layers of acicular calcite. During episodes of cave-flooding, however, he crystallites merge and overgrow each other and precipitation eventually occurs upon large, planar crystal faces. It is believed that the distinctive fabrics of palisade calcite are formed because precipitation usually occurs from thin water films that flow over the growing speleothem surfaces. Large crystal terminations do not form on the speleothem surface because they form projections that disturb the water flow away from the projections which, as a consequence, are gradually eliminated. Small crystal terminations (crystallites), on the other hand, do not disturb the water-flow and thus come to dominate the growth surfaces. Petrographic distinction columnar calcite crystals in speleothems (and other vadose calcites with similar fabrics) and mosaics of columnar crystals that have replaced earlier, acicular-carbonate cements is commonly difficult. Such distinctions are attempts to distinguish between calcite crystals that have grown penecontemporaneously from numerous syntaxial overgrowths (calcites in speleothems) and other calcites in which replacement occurs at a much later date, possibly accompanied by replacement of a metastable phase (replacement of acicular cements).

188 citations


Journal ArticleDOI
TL;DR: The need for and main elements of a strategy aimed at the abolition of absolute poverty within a short period of time are discussed in this paper, where the basic needs are defined as food, clothing, safe drinking water, and shelter.

177 citations


Journal ArticleDOI
TL;DR: In this paper, Nitrate-N concentration in tile water, loss from tile lines, and accumulation in soil profiles were determined following each of three annual applications of 20, 112, 224, and 448 kg N/ha to continuous corn (Zea mays L.) grown on a Webster clay loam (Typic Haplaquoll) in southern Minnesota.
Abstract: Nitrate-N concentration in tile water, loss from tile lines, and accumulation in soil profiles were determined following each of three annual applications of 20, 112, 224, and 448 kg N/ha to continuous corn (Zea mays L.) grown on a Webster clay loam (Typic Haplaquoll) in southern Minnesota. Plots were isolated to a depth of 1.8 m with plastic to allow an accurate assessment of the area drained. Water flow through the tile lines occurred annually for approximately 6 weeks in the period from mid-April through early July and constituted an equivalent from 20 to 46% of the precipitation during the flow periods and from 7 to 22% of the annual precipitation during the 3 years studied. There was relatively little increased NO₃-N accumulation in the soil profile or loss from tile lines at the recommended application rate of 112 kg N/ha compared to that for the check treatment. Nitrate-N losses through tile lines in 1975 (after 3 years treatment) were 19, 25, 59, and 120 kg/ha for the 20, 112, 224, and 448 kg N/ha applications, respectively, which had NO₃-N accumulations in the 0–3 m soil profiles of 54, 100, 426, and 770 kg NO₃-N/ha. Maximum NO₃-N accumulation in the soil profiles occurred at a depth of about 1 m with little evidence of movement below about 2.2 m.

161 citations


Journal ArticleDOI
01 Jul 1978-Ophelia
TL;DR: Dense Amphiura populations enlarge the water-sediment interface and thereby the oxydized layers and the microbial activity, which benefits Mysella which obtains protection from surface-hunting predators and additional supply of food.
Abstract: Mysella bidentata is a euryvalent species. Its distribution in the N. Oresund 3-4 months after settling is positively correlated with the density of adult Amphiura filiformis. In the laboratory, Mysella prefers to live in the oxydized layers around the burrow of Amphiura. Dense Amphiura populations enlarge the water-sediment interface and thereby the oxydized layers and the microbial activity. This benefits Mysella which obtains protection from surface-hunting predators and additional supply of food. In their second year the bivalves are functional males, and when three years old and 3 mm long they are hermaphrodites. Males produce fertile and oligopyrene sperm simultaneously. Sperm transfer involves sperm bags and receptacula seminis, and is thus time-independent of egg-spawning. Mysella reacts to gravitation by positive or negative taxes, and to direction of water flow by positive tropo-taxis or compass reactions. Chemical stimuli from a predator (Astropecten) evoke direct orthokinesis. Stimuli...

139 citations


Journal ArticleDOI
TL;DR: In this paper, a generalized correlation for burnout heat flux data, that is applied to either of water and freon-113, is successfully evolved, and it is shown that surface tension has an important role for the onset of burnout phenomenon, not only in the ordinary pool boiling, but also in the present boiling system with a forced flow.

131 citations


Journal ArticleDOI
TL;DR: The roots of tomato plants were exposed to low concentrations of oxygen by waterlogging the soil or by growing the plants in nutrient solution flushed with nitrogen gas and the rate of ethylene production by the petioles, main stem, and shoot apex was increased by 4-6-fold and thepetioles developed epinastic curvatures.
Abstract: The roots of tomato plants (Lycopersicon esculentum Mill., cv. Moneymaker) were exposed to low concentrations of oxygen by waterlogging the soil or by growing the plants in nutrient solution flushed with nitrogen gas. After 24 h, the rate of ethylene production by the petioles, main stem, and shoot apex was increased by 4-6-fold and the petioles developed epinastic curvatures. Removing the roots did not reproduce these responses. The amounts of ethylene produced by shoot tissues in response to physical wounding was greatly increased by waterlogging the soil. The production of ethylene by roots was suppressed by the absence of oxygen. When the roots were transferred back to an aerobic environment ethylene production quickly exceeded that observed in roots maintained continuously in aerobic conditions. The enhanced rate of ethylene production in the shoots occurred in the absence of increased water stress as measured with a leaf pressure chamber; leaf water potentials were increased rather than decreased by waterlogging for 30 h or more. This was associated with stomatal closure and reduced transpiration. Resistance to water flow through the plant increased as transpiration decreased in response to waterlogging. However, at similar rates of transpiration, resistance was normally lower in waterlogged plants than in controls.

129 citations


Journal ArticleDOI
TL;DR: In this article, a general model of trace element behavior is proposed for diagenetic processes in limestones, where the trace element/calcium ratio in a calcite being precipitated is always greater than the ratio in the solution.
Abstract: The partitioning behaviors of zinc and manganese can serve as important tracers of diageneticprocesses in limestones. A review of the literature indicates kcalciteZn2+, the trace element partition coefficient of zinc into calcite, equals 5.5 and kcalciteMn2+e 15, at the probable temperatures and solution compositions under which most limestone lithification is achieved. Since k is greater than unity for both these elements, the trace element/calcium ratio in a calcite being precipitated is always greater than the ratio in the solution. Thus in aragonite/calcite transformation by dissolution-reprecipitation in a closed system, the initial calcite is greatly enriched in e ther zinc or manganese relative to the parent aragonite. As closed system, homogeneous dissolution-reprecipitation progresses, the enrichment of the calcite falls exponentially until the ratio in the calcite being precipitated equals the ratio in the aragonite being dissolved. In an open system, dissolution-reprecipitation usually results in a calcite that is enriched in zinc or manganese. The more pure water that enters and leaves the diagenetic site, the greater excess loss of calcium occurs, since calcium preferentially remains in the liquid phase during calcite precipitation. In order to integrate the information provided by the distributions of manganese and zinc in calcites with that of strontium and magnesium, a general model of trace element behavior is proposed. Using the parameters of distribution coefficient, water flow relative to reaction rate (open or closed), and chemistry of the water before it enters the diagenetic site, it is possible to determine the enrichment or depletion of a calcite relative to its parent aragonite. Four distinct situations are noted. Autodepletion refers to the preferential loss of trace element from the diagenetic site due to a high water flow rate relative to reaction rate, where the trace element has a partition coefficient less than unity. A calcite depleted in trace element relative to the parent arag nite (or calcite) results. Autoenrichment is the preferential removal of calcium from the diagenetic site, with consequent enrichment of the calcite in trace element. This may occur for trace elements with k greater than unity. Alloenrichment is the result of calcite precipitation from a liquid that was enriched in trace element (a trace element/calcium ratio greater than that of the parent aragonite or calcite) before it entered the diagenetic site. It may occur for any value of k, but the trace element/calcium ratio of the liquid required for such enrichment increases with decreasing k. Allodepletion results when a liquid rich in calcium and poor in trace element flushes through the diagenetic site. For values of k close to one, each cycle of liquid may introduce s much calcium that after the liquid dissolves aragonite, its trace element/calcium ratio is still less than that of the aragonite. A depleted calcite is precipitated. Examination of the Zn2+, Mn2+, Mg2+, and Sr2+ content of Pleistocene corals from Barbados, West Indies, reveals an increase in Mn2+ and Mg2+ as a result of aragonite/calcite transformation. Sr2+ was lost in this process and Zn2+ remained approximately the same. Note that unlike kcalciteZn2+ and kcalciteMn2+, kcalciteSr2+ and kcalciteMg2+ are both < 1. Such changes denote an open diagenetic water system. Strong intercorrelations among these elements were found in corals altered under late vadose conditions. These suggest that liquid flow rate controlled the trace ele ent chemistry of these corals. Corals altered under phreatic conditions did not exhibit such systematic behavior; their chemistry was likely influenced by neighboring diagenetic events. The general trace element model gives a quantitative indication of the "openness" of these diagenetic systems. On average each liter of diagenetic liquid dissolved and reprecipitated between 10 and 20 millimoles of calcium carbonate. The trace element model can be applied to calcite/calcite recrystallization and cement precipitation later in the evolution of a limestone. Where there is no significant external source of these trace cations, later calcites should be depleted in strontium and magnesium, and enriched in zinc and manganese.

121 citations



Journal ArticleDOI
TL;DR: The sediment-water interface separates a mixture of solid sediment and interstitial water from an overlying body of water as mentioned in this paper, where sediment accumulation is achieved by sedimentation of solid particles and inclusion of water in the pore spaces among the particles.
Abstract: The sediment-water interface separates a mixture of solid sediment and interstitial water from an overlying body of water. Wherever sediment accumulates, growth of the sediment pile is achieved by sedimentation of solid particles and inclusion of water in the pore spaces among the particles. Growth or erosion of sediments on the bottom of a body of water results in a rise or fall of the sediment-water interface relative to an observer on shore. If, however, an imaginary observer were positioned at the sediment-water interface, he would observe the sediment particles and water moving downward past him when the sediment column grows, or moving upward when the sediment is being eroded. In considering various chemical, physical, and biological processes taking place near the sediment-water interface, it is often more convenient to regard the interface as a plane of reference, as if one were an imaginary observer who sees sediment particles and water flow by him while he balances him­ self on the interface. Arrival of sediment particles and inclusion of water in the interparticle pores space are the two major fluxes of materials across the sediment-water interface. The rates of sediment deposition vary from the low values of millimeters per 1000 years in the pelagic ocean up to 1 centimeter per 1 year in lakes and near-shore oceanic areas. Sediments near the interface commonly contain 70--90 vol % of water, but upon com­ paction the volume fraction of water (called the sediment porosity) usually decreases to 40-60% within a few tens of centimeters to a few meters below the interface. Representative values of the mass fluxes of solids and dissolved materials across the sediment-water interface can be estimated for areas of low and high deposition rates as follows. The slower sedimentation rates in the ocean are of the order of 5 x 10-4 cm yr-1 (5 mm 1000 yr-1), and the higher rates in lakes and coastal sections are

Journal ArticleDOI
TL;DR: In this article, the quantities of sediment moving as bed load in oscillatory flow over a flat bed were measured with an oscillating tray in still water but some were carried out in a wave flume.
Abstract: Measurements have been made of the quantities of sediment moving as bed load in oscillatory flow over a flat bed. Most of the measurements were made with an oscillating tray in still water but some were carried out in a wave flume. There is good agreement between the two sets of results. For sand and gravel the mean sediment transport rate is observed to vary during the course of the cycle like the fourth power of the velocity of oscillation but with a slight phase lead. For nylon pellets, however, the transport curve is not quite symmetrical about its maximum. Measurements were also made of the random fluctuations in transport rate and these are compared with Abou-Seida's theoretical model. An empirical relationship is derived for the sediment transport rate.

Book ChapterDOI
01 Jan 1978
TL;DR: A simulation model for abiotic variables influencing grassland ecosystems including water flow and temperature profile submodels is presented in this paper, which treats flow in the plant canopy and soil, while the temperature submodel includes solar radiation, canopy air temperature, and soil temperature.
Abstract: A simulation model for abiotic variables influencing grassland ecosystems including water flow and temperature profile submodels is presented. The water-flow submodel treats flow in the plant canopy and soil, while the temperature submodel includes solar radiation, canopy air temperature, and soil temperature. The atmospheric driving variables are either daily weather observations or stochastic weather-simulator results. A preliminary validation of the model has been performed.

Journal ArticleDOI
TL;DR: In this paper, an in-situ water circulator (ISWAC) was developed to allow accurate measurement of dissolution rates of various carbonate particles with minimal stagnation and mechanical weight loss.

Journal ArticleDOI
TL;DR: In this paper, the authors give solutions for instantaneous, continuous, and steady-state sources of pollution in uniform ground water flow, and then these solutions are used to determine how long a continuous source must be in place before steady state conditions are approached.
Abstract: Solutions are given for instantaneous, continuous, and steady-state sources of pollution in uniform ground water flow. Then these solutions are used to determine how long a continuous source must be in place before steady-state conditions are approached, to determine the effect of a finite aquifer depth upon solutions for an infinite aquifer depth, to calculate maximum concentrations for instantaneous sources, and to determine the time required for solutions for a point source and a source of finite size to approach each other.

Journal ArticleDOI
TL;DR: In this article, changes in permeability have been studied during the flow of water through granite for periods of time up to 17 days at temperatures of 100°, 200°, 300°, and 400°C with a constant confining pressure of 500 bars, differential stresses of 0-3500 bars, inlet pore pressure of 275 bars, and outlet pressure of 1 bar.
Abstract: Changes in permeability have been studied during the flow of water through granite for periods of time up to 17 days at temperatures of 100°, 200°, 300°, and 400°C with a constant confining pressure of 500 bars, differential stresses of 0–3500 bars, inlet pore pressure of 275 bars, and outlet pressure of 1 bar. In all cases the initial permeability at elevated temperatures was found to be higher by 1–2 orders of magnitude than the permeability at room temperature, perhaps because of thermal stress cracking. The high initial permeability did not persist with time and in nearly all cases decreased significantly during the first ½ day of water flow. Dissolution of plagioclase and quartz was concentrated near the inlet, where the pore pressure was highest. Precipitation occurred throughout the samples because of oversaturation as the pore pressure dropped, causing significant reduction in permeability. The final permeability after 10 days was less at 300°C than at lower temperatures, and measurable flow stopped in most of the 400°C samples.

Journal ArticleDOI
TL;DR: In this article, the authors measured the water potential field of a West Coast forested mountain soil during the wetting and drainage phases of simulated rainfall events and concluded that during a simulated rainfall event, water flow through the profile was partitioned between root channels and the soil matrix which is transversed by the channels.
Abstract: Inferences with respect to the hydrologic behavior of a West Coast forested mountain soil are based on measurement of the water potential field during the wetting and drainage phases of simulated rainfall events. The field was measured as a continuous function of time with an array of 13 tensiometers in combination with pressure transducers and a data collection system. Measurements were carried out with the forest floor intact, partly disturbed, and totally removed. Inferences were made by interpreting the water potential fields as ‘fingerprints of hydrologic behavior.’ It was concluded that during a simulated rainfall event, water flow through the profile was partitioned between root channels and the soil matrix which is transversed by the channels. The proportion of the flow conducted by the channels was at its maximum during the non-steady state phase of the event, decreasing to a minimum as steady state was approached. During the drainage phase of the event the channels did not contribute to downward flow. The process of internal infiltration is discussed. It causes the soil matrix to wet up both from the surface of the H horizon of the forest floor and from the wetted periphery of the root channels. Results indicated that simulated disturbance of the forest floor down to the mineral soil caused a shift in the water flow pathway from the channels to the soil matrix. It was speculated that this shift was due to closure of the channel openings. It was speculated that the flashy response of streams to rainfall events is related to rapid subsurface storm flow through root channels. Also, because water flow through the soil matrix is much slower than that through root channels, it is likely that forest floor disturbance on a watershed-wide scale would result in an increase in the time lag between the rainfall event and the corresponding streamflow event.

Journal ArticleDOI
TL;DR: The curves representing pumping and Filtration were clearly parallel, indicating that filtration efficiency did not vary greatly during the course of an experiment; the rates obtained were 65 to 87% (mean 76%) for C. intestinalis, 66 to 88% for P. mammillata, and 73 to 90% ( mean=80%) for S. plicata.
Abstract: A combination of a direct and an indirect method has been used for the first time in the study of filter-feeding in benthic invertebrates. Experiments over 12 h periods under constant temperature, pH, light and feeding conditions have been carried out with 3 species of ascidians: Ciona intestinalis (Linne, 1767); Phallusia mammillata (Cuvier, 1815) and Styela plicata (Lesueur, 1823). In C. intestinalis and P. mammillata, no pumping rhythm has been found; the water flow was constant for 12 h, except for some brief accidental interruptions. In S. plicata, the particular rhythm of spontaneous periodical contractions recorded during the experiment were related to gamete emission. The speed of water flow, which was fairly constant during recording, varied considerably during the 12 h period; these variations were generally related to modifications in the diameter of the cloacal siphon. The average speeds, in cm sec-1, lay between 5.7 and 9.5 for C. intestinalis, 5.2 and 19.4 for P. mammillata, and between 5.3 and 10.7 for S. plicata. Variations in the pumping-rate were small, oscillating around a mean value. In ml h-1 g-1 dry weight of organs these were 5,829 to 5,982 (mean=5,906) for C. intestinalis, 6,142 to 6,592 (mean=6,312) for P. mammillata, 1,0508 to 1,1505 (mean=1,0708) for S. plicata. Filtration was continuous without any particular rhythm; filtration rates in ml h-1 g-1 dry weight of organs varied between 4,244 and 4,418 (mean=4,331) for C. intestinalis, 4,620 and 4,960 (mean=4,779) for P. mammillata, 8,482 and 9,078 (mean=8,760) for S. plicata. The curves representing pumping and filtration were clearly parallel, indicating that filtration efficiency did not vary greatly during the course of an experiment; the rates obtained were 65 to 87% (mean=74%) for C. intestinalis, 66 to 88% (mean 76%) for P. mammillata, and 73 to 90% (mean=80%) for S. plicata. The slightly higher mean value in S. plicata is probably related to the higher complexity of the branchial apparatus of this species.

Journal ArticleDOI
TL;DR: Ultrasonic telemetry was used to follow the movements of two groups of smolts in the estuaries of two small Scottish rivers, finding that wild Smolts released into a typical wedge flow, partially mixed estuary had movements which were dominated by the influence of tide on the direction of water flow.
Abstract: Ultrasonic telemetry was used to follow the movements of two groups of smolts in the estuaries of two small Scottish rivers. Hatchery reared smolts released into a typical wedge flow, partially mixed estuary had movements which were dominated by the influence of tide on the direction of water flow. The net movements of wild native smolts in a two layer flow estuary, in which freshwater flow dominated, was downstream but were intermittent consisting of short steps and numerous long pauses. The hatchery reared smolts escaped from the estuary within a tidal cycle, moving out on an ebb tide. The wild smolts remained in the estuary for periods up to 108 h, none escaping within one tidal cycle.

Journal ArticleDOI
TL;DR: In this article, the authors investigated the effect of abscisic acid on both salt transport and the permeability of the roots to water, and found that salt transport increased in ABA and then fell, but was about the same as in control roots when transport was inhibited.
Abstract: Previous papers have shown that abscisic acid can inhibit transport of ions across the root to the xylem vessels, resulting in reduced exudation from excised roots or inhibiting guttation from intact plants. However, it has not been established whether the inhibition was due to a reduction in salt transport (Js) or in permeability of the roots to water (Lp). This paper investigates the effect of ABA on Lp and Js separately. It is shown that Lp increased in ABA and then fell, but was about the same as in control roots when transport was inhibited. The effect of ABA on exudation therefore appeared to be mainly due to reduction in Js. Inhibition of Js was also present in intact, transpiring plants and so was not due to reduced water flow. The inhibition of ion release to the xylem affected

Journal ArticleDOI
TL;DR: The results of a study on the comparative susceptibility of salmonid fishes to natural infections with M. margaritifera and on development of the parasites in these fish and the associated histopathology are reported.
Abstract: The comparative susceptibility of 4 species of salmonid fishes, 30.5 to 87.0 mm in fork length, to the glochidia of the freshwater mussel (Margaritifera margaritifera) was determined by examination of 594 caged and 178 uncaged (native) fish for infection. Of the caged fish, 99% of the chinook salmon (Oncorhynchus tshawytscha), 75% of the coho salmon (Oncorhynchus kisutch), 88% of the cutthroat trout (Salmo clarki), and 95% of the steelhead trout (Salmo gairdneri) were infected. There was a similar relationship in infection incidence in the native fish species. Mean infection intensities in the caged and native fish were: 446 and 399 for chinook salmon, 8 and 24 for coho salmon, and 72 and 88 for steelhead trout, respectively, and 212 for caged cutthroat trout (native juvenile trout were not captured). Glochidia completed development in mussels in the Siletz River, Oregon, in 13 days at an average water temperature of 12.8 C. They were released by these mussels from 13 May to 15 June 1971. During development in fish, the parasites increased in length by 500% from an initial size of 70 to 75 tum. Encysted parasites occurred in the gill filaments, arches, rakers, and occasionally in the pseudobranchs of all fish species; but most were in the lamellae of the filaments. Initially, the cyst walls were approximately 15 tLm in thickness, but as the parasites increased in size the exposed part of the wall became thinner. Up to 15 lamellae may be fused to the wall. Except for lamellae "grasped" by the parasites, blood apparently continued to flow through capillaries of the fused lamellae, but these lamellae, except the outermost ones, probably no longer functioned in respiration. Parasites encysted on the sides of gill filaments restricted blood flow by "pinching" the arterioles. Large encysted parasites on the lamellae increased the physiological dead space in the water flow. Clubbing of the filaments resulted when large parasites were located distally. These pathological changes in heavy infections may result in early death of fish by asphyxiation. In less heavy infections, the invading or exiting parasites may provide portals of entry for fungi, and delayed mortality may occur from secondary infection. The first two papers in this series reported on the comparative susceptibility of salmonid fishes to experimental infection with Margaritifera margaritifera (Meyers and Millemann, 1977) and on tissue reactions of coho (Oncorhynchus kisutch) and chinook salmon (Oncorhynchus tshawytscha) to experimental infections (Fustish and Millemann, 1977). This paper reports the results of a study on the comparative susceptibility of salmonid fishes to natural infections with M. margaritifera and on development of the parasites in these fish and the associated histopathology. Some observations on relationship of temperature and development of glochidia in mussels are also reported. Received for publication 13 May 1977. * Technical Paper No. 4558, Oregon Agricultural Experiment Station. t U.S. Environmental Protection Agency, Region X, 1200 6th Avenue, Seattle, Washington 98101. t Environmental Sciences Division, Oak Ridge National Laboratory, P.O. Box X, Oak Ridge, Tennessee 37830. MATERIALS AND METHODS

Journal ArticleDOI
01 Feb 1978-Botany
TL;DR: It can be shown that the total flux in a stem, calculated as the sum of the flux in single vessels, agrees quite well with the data reported in literature.
Abstract: We measured water flow in simple xylem vessels of Sechium edule at various pressures. We found a disagreement with Poiseuille's law, which changes from vessel to vessel and becomes abruptly pronounced in some cases. We discuss our data in terms of an 'impediment coefficient,' K. It can be shown that the total flux in a stem, calculated as the sum of the flux in single vessels, agrees quite well with the data reported in literature.

Journal ArticleDOI
TL;DR: In this article, a dual energy gamma scanning system was employed to locate the position of the growing ice lens relative to the freezing front, which is inconsistent with the location of the ice lenses predicted by the capillary theory.
Abstract: The flux of water and the resultant formation of discrete ice lenses were studied in samples of New Hampshire silt which were saturated and then frozen under different temperature gradients and overburden pressures A dual energy gamma scanning system was employed to locate the position of the growing ice lens relative to the freezing front Parameters controlling water flow and the location of the ice lenses were employed to evaluate theories that have been proposed to describe the mechanisms of ice lens formation The capillary theory was employed to locate the freezing front However, the ice lenses were found to be located 02–04 cm behind the freezing front, which is inconsistent with the location of the ice lenses predicted by the capillary theory Neither the hydrodynamic theory, nor the secondary frost heaving theory account for the redistribution of overburden pressure between soil particles, ice, and water These theories cannot be employed to predict the location of the ice lens relative to the freezing front until overburden pressure effects are incorporated into the theory

01 Jan 1978
TL;DR: In this paper, the authors presented measurements of film flow rates, pressure gradients, film thicknesses, wave frequencies and velocities, and burnout heat fluxes in one annular and two tubular geometries.
Abstract: Measurements are presented of film flow rates, pressure gradients, film thicknesses, wave frequencies and velocities, and burnout heat fluxes in one annular and two tubular geometries. The more than 250 experiments were performed with steam-water at 30 to 90 bar under both adiabatic and diabatic conditions. On the basis of these data a film-flow model for the prediction of burnout is set up. General film roughness and entrainment correlations are derived from the adiabatic, equilibrium data. The capability of the model is demonstrated by several comparisons between calculations and measurements. This report is submitted to the Technical University of Denmark in partial fulfilment of the requirements for obtaining the lie.tech. (Ph.D.) degree. ISBN 87-550-0593-4 ISSN 0418-6443

Journal ArticleDOI
TL;DR: Water flow has been studied in six tube-dwelling animals that have different pumping mechanism and layout of their tube systems and the characteristics of the pumping mechanisms and the resistance of the tube systems have been found.

Journal ArticleDOI
TL;DR: The characteristics of the neural responses to electrical stimulation as well as supporting data obtained from the studies of the effects of anoxia on the evoked responses indicate that the electrical stimulus acts on the hair cells or on the synapses, rather than directly on the nerve fibers.
Abstract: 1. The process of neural excitation in hair cell systems was studied in an in vitro preparation of the Xenopus laevis (African clawed toad) lateral line organ. A specially designed stimulus chamber was used to apply accurately controlled pressure, water movement, or electrical stimuli, and to record the neural responses of the two afferent fibers innervating each organ or stitch. The objective of the study was to determine the characteristics of the neural responses to these stimuli, and thus gain insight into the transduction process. 2. A sustained deflection of the hair cell cilia due to a constant flow of water past the capula resulted in a maintained change in the mean firing rate (MFR) of the afferent fibers. The data also demonstrated that the neural response was proportional to the velocity of the water flow and indicated that both deflection and movement of the cilia were the effective physiological stimuli for this hair cell system. 3. The preparations responded to sinusoidal water movements (past the capula) over the entire frequency range of the stimulus chamber, 0.1-130 Hz, and were most sensitive between 10 and 40 Hz. The variation of the MFR and the percent modulation indicated that the average dynamic range of each organ was 23.5 dB. 4. The thresholds, if any, for sustained pressure changes and for sinusoidal pressure variations in the absence of water movements were very high. Due to the limitations of the stimulus chamber it was not possible to generate pressure stimuli of sufficient magnitude to elicit a neural response without also generating suprathreshold water-movement stimuli. Sustained pressures had no detectable effect on the neural response to water-movement stimuli. 5. The preparations were very sensitive to electrical potentials applied across the toad skin on which the hair cells were located. Potentials which made the ciliated surfaces of the hair cells positive with respect to their bases increased the MFR of the fibers, whereas negative potentials decreased it. The responses to sinusoidal electrical stimuli were similar to responses to water-movement stimuli with respect to frequency and dynamic ranges. Thresholds as low as 100 muV peak to peak (p-p) for 16-Hz stimuli were found. 6. The characteristics of the neural responses to electrical stimulation as well as supporting data obtained from the studies of the effects of anoxia on the evoked responses indicate that the electrical stimulus acts on the hair cells or on the synapses, rather than directly on the nerve fibers. This finding suggests that receptor potentials or their associated currents play an important role in the process of neural excitation in hair cell systems.

Patent
18 Sep 1978
TL;DR: In this paper, a bentonite composition useful for preventing a flow of water through a structure is disclosed, which has substantially all of the bentonite in non-hydrated form by dispersing the bendonite throughout a nonaqueous gel formed from a non-aqueous liquid and a suitable gelling agent for the liquid to form a cohesive mass.
Abstract: A bentonite composition useful for preventing a flow of water through a structure is disclosed. The composition has substantially all of the bentonite in non-hydrated form by dispersing the bentonite throughout a non-aqueous gel formed from a non-aqueous liquid and a suitable gelling agent for the liquid to form a cohesive mass capable of adhering to a structure while maintaining a desired, cohesive form. The composition can be made into sheets, rods, tubes and the like. For example, the composition can be applied to one side of a water permeable cellulosic fiber containing sheet and the composition side of the sheet secured over an area of potential water flow.

Journal ArticleDOI
TL;DR: In this paper, a comparison of community respiration rates for the two beach populations excluding macrofaunal respiration shows that the tropical beach rates (which were constant over the period January-March) were about 9 times the winter rates of the temperate and about twice the summer rates.
Abstract: Investigation of a temperate and tropical beach has shown that, based on chlorophyll a analyses, an epipsammic diatom population present in the temperate beach is absent in the tropical beach. Comparison of community respiration rates for the two beach populations excluding macrofaunal respiration shows that the tropical beach rates (which were constant over the period January-March) were about 9 times the winter rates of the temperate beach and about twice the summer rates. Annual microbial production is estimated at 15 gC/m2 for the temperate beach and 72 gC/m2 for the tropical beach. The greatly increased rate of production in the tropical beach was considered to be a function of increased water flow into that beach. In comparison, meiofauna and macrofauna biomass are less in the tropical beach and their respective production likely to be at most no more than in the temperate beach. It is proposed from experimental studies that the failure of animal populations fully to utilise microbial production in sandy beaches is due to the relative degree of exposure stripping significant quantities of microbial growth from this system. This proposal is discussed as a means of explaining mechanisms of control of animal production in sandy beaches.

01 Oct 1978
TL;DR: In this article, the behavior of a water jet flowing into vacuum was investigated experimentally and theoretical interpretations of the flow phenomena which were found are given; the influence of parameters like the shape of the nozzle, the temperature and the gas content of water were studied.
Abstract: At certain intervals excess water has to be dumped into space overboard of the Spacelab cabin. For the development of a useful nozzle the behaviour of a water jet flowing into vacuum was investigated experimentally and theoretical interpretations of the flow phenomena which were found are given. The influence of parameters like the shape of the nozzle, the temperature and the gas content of water were studied. At certain test conditions, the jet leaves the nozzle exit in bundled form and ends abruptly bursting into droplets and ice-particles. The “bursting”-mechanism is explained by a sudden boiling of the water in the jet causing the growth of vapor bubbles decomposing the jet. The formation of vapor bubbles is initiated by a superheating of the water of the jet caused by a sudden pressure drop and a cooling at the surface of the jet. The expansion of vapor bubbles in the jet is retarded by surface tension forces which results in a relaxation time for the bursting of the jet. The vapor flow in radial directions of the jet is approximately described by a plane radial source flow. The measurement of the pitot-pressure radially to the jet proves that the vapor flow is supersonic.