scispace - formally typeset
Search or ask a question

Showing papers on "Water flow published in 1975"


Journal ArticleDOI
TL;DR: In this paper, the Manning n value is quantitatively evaluated for flow in heavily vegetated channels and the results show that the n value increases in proportion to two-thirds power of the hydraulic radius for conditions where the vegetation density is a constant over the flow depth.
Abstract: The Manning n value is quantitatively evaluated for flow in heavily vegetated channels. Momentum analysis shows that the composite n value as a function of flow depth is dependent on the bottom roughness and the density of vegetation. In some cases, the vegetation density can be evaluated directly from physical measurements of the vegetation. However, in most situations, it must be evaluated indirectly from limited field data. The results show that the n value increases in proportion to two-thirds power of the hydraulic radius for conditions where the vegetation density is a constant over the flow depth. Field application of the flow resistance model are described for projects concerned with flood routing, backwater computations, extension of rating curves, channel improvement work, and erosion control.

393 citations


Journal ArticleDOI
Edwin L. Fiscus1
TL;DR: This paper presents a general model for coupled solute and water flow through plant roots based on the thermodynamics of irreversible processes and shows that with a constant hydraulic conductivity the only features necessary to explain these phenomena are some type of membrane or membranelike structure and a mechanism for actively accumulating solutes.
Abstract: This paper presents a general model for coupled solute and water flow through plant roots based on the thermodynamics of irreversible processes. The model explains in a straight-forward manner such experimentally observed phenomena as changes in root resistance, increased solute flux, and apparent negative resistance, which have been reported for root systems under the influence of a hydrostatic pressure gradient. These apparent anomalies are explained on the basis of the interaction between the osmotic and hydrostatic driving forces and the well known "sweeping away" or dilution effect. We show that with a constant hydraulic conductivity the only features necessary to explain these phenomena are some type of membrane or membranelike structure and a mechanism for actively accumulating solutes.

254 citations


Journal ArticleDOI
TL;DR: In this article, the stability characteristics of a single-phase free convection loop are investigated and the contention made by previous workers that instabilities near the thermodynamic critical point can occur for ordinary fluids as well as those with unusual behavior in the near-critical region is confirmed.
Abstract: Experiments investigating the stability characteristics of a single-phase free convection loop are reported. Results of the study confirm the contention made by previous workers that instabilities near the thermodynamic critical point can occur for ordinary fluids as well as those with unusual behavior in the near-critical region. Such a claim runs counter to traditional beliefs, but it is supported by the observation of such instabilities for water at atmospheric pressure and moderate temperatures in the present work.

245 citations


Journal ArticleDOI
03 Oct 1975-Science
TL;DR: Freeze-fracture electron microscopy demonstrates that vasopressin stimulation of isolated toad bladder alters the structure of the luminal membrane of granular cells, and appears to be of functional significance, since the frequency of aggregation sites per area of membrane is closely correlated with vasopressive osmotic water flow.
Abstract: Freeze-fracture electron microscopy demonstrates that vasopressin stimulation of isolated toad bladder alters the structure of the luminal membrane of granular cells. This alteration consists of an ordered aggression of intramembranous particles, and appears to be of functional significance, since the frequency of aggregation sites per area of membrane is closely correlated with vasopressin-induced osmotic water flow.

209 citations


Journal ArticleDOI
TL;DR: The red cell membrane is a permeability barrier that limits the equilibration of a variety of solutes between red cell and plasma water as mentioned in this paper, and the effect of this barrier on the exchange in the liver of tracer substances that are not removed in net fashion from the hepatic circulation: thiourea, urea and chloride.
Abstract: The red cell membrane is a permeability barrier that limits the equilibration of a variety of solutes between red cell and plasma water. We utilized the multiple indicator dilution technique to investigate the effect of this barrier on the exchange in the liver of a group of tracer substances that are not removed in net fashion from the hepatic circulation: thiourea, urea, and chloride. We demonstrated that, after preequilibration of the label with red cells, a red cell carriage effect appeared (the trapping and translocation of label in the red cells), that this effect was most marked when the permeability of the red cell was relatively low for the substance under consideration (thiourea), and that the effect became small when the permeability of the red cells was large for the exchanging substance (urea and chloride). We developed a theoretical description of the retarding effect of the red cell permeability barrier on the extravascular exchange of label and were able to use this description to obtain estimates of the red cell permeability from the in vivo dilution curves. We examined the effect of plasma injection, of changing the input in such a fashion that the label was not preequilibrated with red cells, and found both experimentally and theoretically, that for substances of low permeability the transit time from these experiments, if multiplied by the total water flow or solute flux, gave an overestimate of both the apparent total volume of distribution and the mass of traced material in the system. This last effect is of great importance for the practical design of many biological experiments. Reliable volume and mass estimates can be made only when the labeled material has been preequilibrated with red cells.

105 citations


Journal ArticleDOI
TL;DR: In this paper, a natural snowpack with ice layers is described in terms of an equivalent anisotropic porous medium, represented as a diagonalized matrix whose principal values can be calculated from a small amount of information about the prototype snowpack.
Abstract: A natural snowpack with ice layers is described in terms of an equivalent anisotropic porous medium. The anisotropic permeability is represented as a diagonalized matrix whose principal values can be calculated from a small amount of information about the prototype snowpack. Ice layers increase the transit time for water movement by a factor equal to the ratio of the principal values of permeability. The flow path, volume flux, and wave speed are determined by the slope of the snowpack and principal values of permeability. When a snowpack is assumed to be isotropic, the error in calculating transit time increases with the difference between the principal values of permeability. Usual variations in slope introduce a small change in the transit time.

90 citations


Journal ArticleDOI
TL;DR: In this article, a single-phase simulation model was applied to the hot-water hydrothermal field at Wairakei, New Zealand, where a two-dimensional analysis was made of the production aquifer under steady state and transient flow conditions, allowing vertical flow of heat and fluid through an overlying confining bed.
Abstract: A single-phase simulation model was applied to the hot-water hydrothermal field at Wairakei, New Zealand. A two-dimensional areal analysis was made of the production aquifer under steady state and transient flow conditions, allowing vertical flow of heat and fluid through an overlying confining bed. Calculated temperature and pressure patterns correlate well with observed patterns until approximately 1963, when increasing quantities of steam in the production aquifer invalidated the assumption of single-phase flow. For further simulation of the Wairakei reservoir the numerical model will need to be extended to incorporate phase change and three-dimensional flow. Preliminary results, however, indicate that the response of hot-water hydrothermal systems to exploitation can be simulated by using a mathematical reservoir model based on a Galerkin-finite element approach.

89 citations


Patent
18 Jul 1975
TL;DR: In this paper, a heliothermal heating and cooling system using a heat transport fluid such as water is described, where the storage tank is stratified by means of baffles, and the strata are interconnected by a selector valve under the control of a differential temperature detector.
Abstract: A heliothermal heating and cooling system of the type using a heat transport fluid such as water is disclosed The energy collector comprises an assembly of individual solar collector panel modules in a series/parallel configuration and function to heat water flowing therethrough Each solar collector panel includes a pair of stepped headers respectively disposed at its input and output portions and which function to reduce water flow resistance therethrough The input and output headers communicate with an insulated water storage tank by way of return and supply lines, respectively A pump is provided in the return line to circulate the water through the system upon receipt of a command signal The storage tank communicates with a thermal energy utilization device and includes an integral, internal expansion chamber to accomodate expansion of the water The storage tank is stratified by means of baffles, and the strata are interconnected by a selector valve under the control of a differential temperature detector thereby to assure that the hottest available water is presented to the utilization deviceThe danger of freezing is avoided and the need for anti-freeze additives or solutions is eliminated by means of a vent line which connects the expansion chamber at the top of the storage tank to the top of the energy collector assembly and functions to drain the energy collector assembly of its water charge when the pump is de-energized

85 citations


Journal ArticleDOI
TL;DR: Evidence is presented in support of the standing gradient hypothesis as the structural basis of CSF secretion and the results suggest that transependymal water flow is secondary to the electrically silent pumping of sodium.
Abstract: v, After a brief summary of current views on the origin of cerebrospinal fluid (CSF) and the processes underlying its elaboration, the author discusses studies of isolated choroid plexus in extracorporeal perfusion systems and flux chambers. The results suggest that transependymal water flow is secondary to the electrically silent pumping of sodium. The author presents evidence in support of the standing gradient hypothesis as the structural basis of CSF secretion.

79 citations


Journal ArticleDOI
TL;DR: The cell wall becomes the rate-limiting barrier for water flow and the hydraulic conductivity of the cell membranes must be remarkable at low pressures, which indicates that for very large cells e has a saturation value equal to e*1, while for smaller volumes the influence of e*2 will become predominant.
Abstract: The hydraulic conductivities (L*p) and the volumetric elastic moduli (e) of N. flexilis, C. intermedia and C. fragilis were determined by means of direct cell turgor measurements. For large cell volumes (V) the function e = f(P), where P = pressure, is a hyperbola. For small cell volumes e is nearly independent of pressure and the absolute e values are smaller than those obtained for larger volumes. This volume dependence of the volumetric elastic modulus was also verified by measurements of the elastic properties of isolated cell walls of N. Jlexilis under conditions where the lengths of the cell wall tubes prepared from each cell were varied. The volume dependence of e, which is unexpected within the framework of Hooke's law, can be explained by assuming that two different intrinsic moduli e*1 and e*2 are applicable to different cell regions with volumes V*1 and V*2. The quantities e*1 and V*1 are related to the cylindrical part, and e*2 and V*2 to the small node or end regions of the internode. With this assumption the overall e is then given by: e = (e*1e*2V)/(e*2V*1 + e*1 V*2) ˜ e*1e*2 V /(e*2 V + e*1 V*2) . This indicates that for very large cells e has a saturation value equal to e*1, while for smaller volumes the influence of e*2 will become predominant. The value of e*1 was calculated to be about 7.5 x 10*7 Pa* and that of e*2 to be about 10*6 Pa. Since for small cells the overall volumetric elastic modulus e is mainly determined by e*2, the weak pressure dependence of e in such cells reflects a weak pressure dependence of e*2. On the other hand, the strong pressure dependence of e in large cells points to a strong pressure dependence of e*1. The direct determination of the elastic properties of the end regions of the internodes, which was not possible up to the present, is of great importance for growth and growth regulation. The hydraulic conductivity of Nitella and Chara spp. was found to be independent of cell volume, but dependent on the cell turgor pressure. The L*p values were constant at high pressures, but increased on approaching the plasmolytic points. In contrast, the L*p value of the isolated cell wall of N. flexilis was constant over the whole pressure range 0-8 x 10*5 Pa and amounted to (6.9 ± 1.3) x 10-*l2 ms-¹ Pa-¹. Since the L*p value in the living N. flexilis cell increased to 4 x 10-*12 ms-¹ Pa-¹ at a pressure of 5 x 10*4 Pa it can be concluded that the cell wall becomes the rate-limiting barrier for water flow and that the hydraulic conductivity of the cell membranes must be remarkable at low pressures. The increase in L, in the low pressure range is not caused by artificial leakages or by leakages through the plasmodesmata, since no water flow across plasmodesmata could be detected.

67 citations


Patent
27 Mar 1975
TL;DR: In this article, a conical paper brewing filter and its contents are supported by a rigid conical support, at least portions of which are spaced outwardly from the filter to allow flow of brewed beverages therefrom.
Abstract: A disposable one cup coffee brewer comprises a conical paper brewing filter having contained in the bottom thereof a quantity of loose coffee grounds, and having movably disposed therewithin, above the coffee grounds, a disc-shaped primary buoyant element for diverting water poured into the filter from falling directly upon the coffee grounds. Secondly, buoyant water flow diverting elements, disposed ouwardly from such primary buoyant element, may be provided to cover more of the water surface as the filter is filled. The filter and its contents are supported within a rigid conical support, at least portions of which are spaced outwardly from the filter to allow flow of brewed beverage therefrom. Two foldable tabs attached to the support have portions which rest upon the rim of a coffee mug or the like. A method for brewing coffee or the like is thereby provided.

Journal ArticleDOI
TL;DR: The results are compatible with the possibility that regulation by ADH and by cAMP of sodium transport in the toad bladder epithelium may be mediated through regulation of the amount of phosphate in a specific protein.
Abstract: It is well established that active sodium-ion transport and water flow across isolated toad bladder are increased by antidiuretic hormone (ADH) and by cAMP. These agents were also observed in previous studies to cause changes in the amount of radioactive phosphate in a specific protein in the toad bladder. This protein, found by SDS-polyacrylamide gel electrophoresis of toad bladder epithelial preparations, had an apparent molecular weight of 49,000 daltons. In the present study, a correlation was found between the ability of a variety of substances to affect the amount of radioactive phosphate in this 40,000-dalton protein and their ability to alter the rate of sodium transport. Thus several agents (ADH, cAMP, theophylline, adenine, prostaglandin E1, and Mn Cl-2) caused a decrease in the amount of radioactive phosphate in the 49,000-dalton protein and also stimulated active sodium transport across the bladder. Conversely, ZnCl-2 produced an increase in the amount of radioactive phosphate in this protein and an inhibition of sodium transport. With each of these agents, the time-course of change in phosphorylation of this protein was, in general, similar to that for sodium transport. A second phosphoprotein, with an apparent molecular weight of about 42,000 daltons, showed changes in parallel with, but less extensive than, those observed in the 49,000 dalton protein. There was no consistent relationship between changes in level of phosphorylation of either in the 49,000- or 42,000- dalton protein and changes in osmotic water permeability. The results are compatible with the possibility that regulation by ADH and by cAMP of sodium transport in the toad bladder epithelium may be mediated through regulation of the amount of phosphate in a specific protein.

Patent
30 Oct 1975
TL;DR: In this article, a unitary cylindrical member was inserted into the delivery end of a water supply line adjacent to a shower head connected to the sink, with a restrictive passage there through in the direction of the flow of water and the member being retained in position during operation of a shower.
Abstract: This invention relates to an improvement in a device which reduces the flow of water through a shower head. The invention consists of a unitary cylindrical member being inserted into the delivery end of a water supply line adjacent a shower head connected thereto, the cylindrical member having a restrictive passage therethrough in the direction of the flow of water and the member being retained in position during operation of a shower by water pressure.


Patent
12 Nov 1975
TL;DR: In this paper, rotatably adjustable elongated cylindrical solar collector plate cells, rotatable around the elongated axis thereof for adjusting angle of incidence of exterior light rays from the sun to the surface of the collector plate, are mounted upon a roof with water flow therefrom being channelled below an insulated ceiling downwardly for alternate flow as between parallel flow paths alternately selectively to and through concrete slab conduits having copper tubing directing heated water therethrough, and the parallel flow conduits through a layer of rocks beneath the concrete slab, where flow being directed dependent upon
Abstract: In a preferred embodiment of the invention, rotatably adjustable elongated cylindrical solar collector plate cells, rotatable around the elongated axis thereof for adjusting angle of incidence of exterior light rays from the sun to the surface of the collector plate, are mounted upon a roof with water flow therefrom being channelled below an insulated ceiling downwardly for alternate flow as between parallel flow paths alternately selectively to and through concrete slab conduits having copper tubing directing heated water therethrough, and the parallel flow conduits through a layer of rocks beneath the concrete slab, the concrete slab being a part of the floor structure of the dwelling and the layer of rocks being a reservoir sink therebeneath, flow being directed dependent upon differential temperature of the upper floor surface of the concrete slab, such that space within supporting wall room space defined between the ceiling and the floor is economically heated devoid of excessive room temperatures and with substantially level and constant ambient temperature ranges as desired and preset within the room space over extended periods of time for and throughout a heating season of the year, while being inoperative and non-functional when heat is not desired, and including further a hot-water heating provision embodied within an intermediate heat exchanger located between the solar cells fluid circuit and the concrete slab heating circuit, each circuit having its individual circulation pump controlled by its respective thermostat.

Journal ArticleDOI
TL;DR: A variety of experimentally observed phenomena such as changes in root resistance with flow rate, apparent negative resistance effects, xylem sap dilution, and apparent non-osmotic water transport can be adequately explained with this model.
Abstract: This paper presents a general model to describe coupled solute and water flow through plant roots when they are subjected to osmotic or hydrostatic pressure gradients, or both simultaneously. The model is based on well-established membrane transport equations derived from irreversible thermodynamic considerations. A variety of experimentally observed phenomena such as changes in root resistance with flow rate, apparent negative resistance effects, xylem sap dilution, and apparent non-osmotic water transport can be adequately explained with this model. The model also predicts that an exuding excised root system will be very insensitive to changes in the hydraulic conductivity coefficient. Previous work with a flat membrane of unit surface area and uniform properties is confirmed for a cylindrical coordinate system of nonuniform characteristics.

Journal ArticleDOI
TL;DR: All three ATPase enzymes were reduced in gill tissue sampled at the 266th day, with mitochondrial Mg2+ ATPase showing the greatest decline.
Abstract: Fat head minnows, 45-days old, were continuously exposed to DDT using continuous water flow and constant temperature conditions. Exposures were to 0.5 and 2.0 ppb of DDT in water, and combinations of the two concentrations with 50 ppm in food, and 50 ppm in food alone, using C14-DDT in food. Brain homogenates were analyzed for enzyme activity from fish treated for 56, 118, 225, and 266 days; and gill analysis was made at 225 and 226 days exposure. Enzyme reductions were greatest in oligomycin-sensitive (mitochondrial) Mg2+ ATPase, with pronounced effects (over 50% inhibition) at the 266th sampling day. In contrast, Na+-K+ ATPase and oligomycin-insensitive Mg2+ ATPase activities were activated by as much as 28% and 40%, respectively. Mitochondrial Mg2+ ATPase of fish brain has been inhibited to the greatest extent in previously reportedin vitro studies. All three ATPase enzymes were reduced in gill tissue sampled at the 266th day, with mitochondrial Mg2+ ATPase showing the greatest decline.

Patent
14 Feb 1975
TL;DR: In this paper, a method and apparatus for delivering constant water flow rates to the fire hose of a pumper truck at each of a plurality of selectable flow rate settings including the steps of transmitting a digital signal corresponding to a particular fire hose and pumper trucks, receiving and decoding the digital signal, activating a multi-position valve in response to the decoded signal to set a particular valve position, and maintaining a constant flow rate to a fire hose by automatically varying the valve position.
Abstract: A method and apparatus for delivering constant water flow rates to the fire hose of a pumper truck at each of a plurality of selectable flow rate settings including the steps of transmitting a digital signal corresponding to a particular fire hose and pumper truck, receiving and decoding the digital signal, activating a multi-position valve in response to the decoded signal to set a particular valve position, and maintaining a constant flow rate to the fire hose by automatically varying the valve position in response to changes in the output pressure of the pump and pressure drop in the fire hose.

Journal Article
TL;DR: In this article, the authors show that fine particle dispersion and the formation of a more continuous network of these particles at higher SAR values is related to the reduction in hydraulic conductivity of soils leached with mixed NaCl-CaCl2 solutions of low electrolyte concentrations.
Abstract: Direct SEM observations indicate that reduction in hydraulic conductivity of soils leached with mixed NaCl-CaCl2 solutions of low electrolyte concentrations are related to fine particle dispersion and the formation of a more continuous network of these particles at higher SAR values. This causes blockage of the larger pores in the soil and reduces the rate of water flow by increasing the proportion of small size pores. The changes in a sandy and in a clayey soil were quite similar. Dispersion of the fine particles seems to start at low SAR values (less than 8), but the formation of the network becomes apparent only at SAR greater than 16. /Author/

Patent
06 Nov 1975
TL;DR: In this article, a water purification apparatus capable of treating water having impurities producing substantial foaming includes a boiler tank having a water inlet and heater, and a stack portion there above containing contact surface means and a heater for heating the contact surface to a temperature above the vaporization temperature of water.
Abstract: A water purification apparatus capable of treating water having impurities producing substantial foaming includes a boiler tank having a water inlet and heater, and a stack portion thereabove containing contact surface means and a heater for heating the contact surface means to a temperature above the vaporization temperature of water. In this manner water droplets which may be carried by the steam vapors from the boiler and/or foam will be immediately vaporized as it comes in contact with the contact surface means. The steam vapors pass through a condenser assembly, and the condensate passes through a filter assembly before storage in a tank. The contact surface means desirably comprises screen members providing a tortuous path and high heat conductivity. Baffle members may be interposed in the flow path for vapors from the boiler tank to the stack. Valves and a control circuit are desirably included to automatically control the volume of water in the boiler, to cut off water flow to components and to drain the assembly upon shutdown.

Journal ArticleDOI
TL;DR: Water space, tritiated water flux, drinking and urine flow rates of the brown trout were decreased by increasing the environmental calcium concentration, which suggests that water flow across the gill occurs entirely by diffusion.
Abstract: Water space, tritiated water flux, drinking and urine flow rates of the brown trout were decreased by increasing the environmental calcium concentration. Diffusional and osmotic permeabilities were identical in fresh water. This suggests that water flow across the gill occurs entirely by diffusion. Previous suggestions of a discrepancy between the two permeabilities in freshwater teleosts could have been due to an overestimation of urine flow rate upon which the determination of osmotic permeability coefficient is based. The wide-ranging effects of calcium on hydro-mineral regulation suggests that the ion interacts with the gills.

Patent
29 Sep 1975
TL;DR: In this paper, an improvement in a water cooling system for an engine of the type that passes air and water through the radiator at relatively low flow rates whenever the engine was running in its low idle speed condition was described.
Abstract: The invention disclosed in this application relates to an improvement in a water cooling system for an engine of the type that passes air and water through the radiator at relatively low flow rates whenever the engine is running in its low idle speed condition. The radiator is disclosed as having upper and lower headers interconnected by a plurality of parallel extending rows of water tubes. A means responsive to the engine speed is provided for converting the water flow through the water tubes from a plurality of parallel paths to a single series path upon the engine speed dropping to its low idle speed condition.

Journal ArticleDOI
TL;DR: Anatomical examinations showed that fluid channels in the buccal chamber and gill raker sieve are complex and can be expected to vary spatially and temporally throughout the respiratory cycle.
Abstract: Simultaneous measurements of water velocity in the buccal chamber, and buccal and opercular hydrostatic pressure of carp have revealed surprisingly high water velocities. The high flow velocities mean that, at times, the kinetic energy of flow makes a substantial contribution to the total fluid energy. This suggests that there may be unequal distribution of hydrostatic pressures within the buccal chamber. Anatomical examinations showed that fluid channels in the buccal chamber and gill raker sieve are complex and can be expected to vary spatially and temporally throughout the respiratory cycle. It appears that there is a potential for error in many of the previous analyses of ‘gill resistance and energetics of fish breathing based solely on hydrostatic pressure measurements and the simplifying assumption of steady-state conditions.

Journal ArticleDOI
TL;DR: In this article, a theoretical model of statistically steady flow in a strongly stratified estuary is discussed, where a halocline is assumed to be present and the lower layer is taken to be deep and non-turbulent.
Abstract: The paper discusses a theoretical model of statistically steady flow in a strongly stratified estuary. A halocline is assumed to be present and the lower layer is taken to be deep and non-turbulent. The outflowing upper fluid mixes with the salty lower fluid and the flux of the brackish water increases with distance from the head of the estuary. The mixing is assumed to be similar to that in laboratory models of mixing across density interfaces.Two equations of mass conservation are used, one for the steady-state mass flux across a vertical section from top to bottom of the channel and one for the mass flux into a section of the upper fluid. A buoyancy conservation equation is used for the buoyancy flux across a vertical section. A final equation is obtained by integrating the horizontal equation of motion across a section of the upper fluid. The flow in this layer is assumed to be opposed by a frictional force proportional to the square of the velocity averaged over the layer. The pressure-gradient force arising from the slope of the free surface is solved for in terms of the thickness of the upper layer, the buoyancy difference across the interface, the slope of the interface and the horizontal density gradient in the upper layer. The derivation shows that the horizontal pressure-gradient force vanishes in the lower layer.The mathematical problem reduces to two ordinary differential equations for the flux in the upper layer and its thickness. Attention is confined to the solution for subcritical flow, in which the interface falls with distance from the head, reaching a maximum depth at a certain section of the estuary. Beyond this the interface rises. At the mouth, where, by definition, the width of the estuary increases rapidly, it is shown that there must be a transition from subcritical to supercritical flow. This condition, applied to the solution for uniform width, determines a remaining unknown related to the depth of the halocline at the head of the estuary and the complete solution is obtained as a function of the freshwater influx per unit width, the r.m.s. turbulent velocity, the estuary length and the buoyancy of sea water.The solution is complicated but has reasonable behaviour for variations of the given parameters of the problem. A basic feature for values of the constants appropriate to fjord-type estuaries is the dominance of friction, omitted in an earlier, incomplete investigation by Stommel. This is also revealed by the large drop in the free surface over the length of the estuary.A comparison with two estuaries, Oslofjord and Knight Inlet, British Columbia, indicates that the former is very different from the model of this paper but that the latter may have a similar nature.

Journal ArticleDOI
TL;DR: A model of NaCl and water flow through paracellular pathways of the proximal tubule and the principal conclusions are that system performance is indifferent to the distribution of active transport sites, to the numerical value of the compliance function, and to the relationship between lumen and cell pressures.
Abstract: To explain how hydrostatic pressure differences between tubule lumen and interstitium modulate isotonic reabsorption rates, we developed a model of NaCl and water flow through paracellular pathways of the proximal tubule. Structural elements of the model are a tight junction membrane, an intercellular channel whose walls transport NaCl actively at a constant rate, and a basement membrane. Equations of change were derived for the channel, boundary conditions were formulated from irreversible thermodynamics, and a pressure-area relationship typical of thin-walled tubing was assumed. The boundary value problem was solved numerically. The principal conclusions are: 1) channel NaCl concentration must remain within a few mOsm of isotonic values for reabsorption rates to be modulated by transtubular pressure differences known to affect this system; 2) basement membrane and channel wall parameters determine reabsorbate tonicity; tight junction parameters affect the sensitivity of reabsorption to transmural pressure; 3) channel NaCl concentration varies inversely with transmural pressure difference; this concentration variation controls NaCl diffusion through the tight junction; 4) modulation of NaCl diffusion through the tight junction controls the rate of isotonic reabsorption; modulation of water flow can increase sensitivity to transmural pressure; 5) no pressure-induced change in permeability of the tight junction or basement membrane is needed for pressure to modulate reabsorption; and 6) system performance is indifferent to the distribution of active transport sites, to the numerical value of the compliance function, and to the relationship between lumen and cell pressures.

Journal ArticleDOI
TL;DR: Evidence is discussed to suggest that most of the cyclic AMP generated in the tissue does not originate from the enzyme controlling sodium transport, and the stimulation of water flow by PGE1 in the presence of theophylline is thought to be caused by cyclicAMP spilling over from one compartment to the water flow compartment.
Abstract: The effect of prostaglandin E1 (PGE1) on osmotic water flow across toad bladder and cyclic AMP content of the mucosal epithelial cells has been determined under basal conditions and in the presence of either theophylline or antidiuretic hormone (ADH); Under basal conditions and with PGE1 concentrations from 10(-8) to 10(-5) M no evidence of stimulation of water flow was observed, and with 10(-7) M PGE1 a significant inhibition was foundmcyclic AMP content under control conditions was 8 pmol/mg protein. It was 9 at 10(-8) M PGE1, 13 at 10(-7) M, 16 at 10(-6) M, and 23 at 10(-5) M. In the presence of theophylline, 10(-8) and 10(-7) M PGE1 inhibited the theophylline-induced water flow as expected. In contrast, 10(-6) and 10(-5) M PGE1 enhanced the rate of water flow. Theophylline increased cyclic AMP content from 8 to 18 pmol/mg protein. PGE1 in the presence of theophylline caused marked increases in cyclic AMP content; The content was 23 at 10(-7) M, 41 at 10(-6) M, and 130 at 10(-5) M; Thus PGE1 stimulates theophylline-induced water flow at cyclic AMP concentrations somewhere between 23 and 41 pmol/mg. Further evidence along these lines was obtained from experiments in which the effects of PGE1 on ADH-induced water flow were studied. Inhibitory effects of PGE1 were not observed at concentrations of PGE1 which raised the level of intracellular cyclic AMP to 30 pmol/mg protein or higher. These results were obtained despite the fact that all four concentrations of PGE1 tested were found capable of inhibiting ADH-induced water flow under appropriate conditions or, in other words, were inhibiting the adenylate cyclase controlling water flow, Thus the increase in cyclic AMP content in response to PGE1 is not derived from this enzyme. Thus the stimulation of water flow by PGE1 in the presence of theophylline is thought to be caused by cyclic AMP spilling over from one compartment to the water flow compartment. No evidence was obtained to directly suggest spillover into the sodium transport compartment. Furthermore evidence is discussed to suggest that most of the cyclic AMP generated in the tissue does not originate from the enzyme controlling sodium transport. As cyclic AMP-stimulated water flow and sodium transport are thought to occur in one cell type, the granular cells, distinct pools of cyclic AMP are thought to be present in one and the same cell type. Thus one pool controls water flow and one controls sodium transport. With high concentrations of PGE1 in the presence of theophylline or high concentrations of ADH, the adenylate cyclase responsible for water flow is inhibited; However, PGE1 can stimulate a tissue adenylate cyclase to sufficiently high levels that cyclic AMP spills over into the "water flow compartment" and thus stimulates water flow.

Patent
12 Dec 1975
TL;DR: In this article, a fitting for installation in a water line to define a primary water flow path is presented, where a venturi tube is mounted in the fitting and positioned in the primary waterflow path.
Abstract: Apparatus for purifying water comprising a fitting for installation in a water line to define a primary water flow path. A Venturi tube is mounted in the fitting and positioned in the primary water flow path. A secondary water flow path is established between the fitting at either end of the Venturi tube and the inlet of a tank connected to the fitting. The tank houses a container having an outlet communicating with the primary water flow path which contains a bed of elemental iodine crystals. The Venturi creates a pressure differential forcing a small portion of the water in the water line to flow through the bed of iodine crystals in the container and then be returned to the water line.

Journal ArticleDOI
TL;DR: It is suggested that prolactin may combine its reproductive role in the mammals, with its hydromineral activity in fish, by acting on the water relationships of mammals during their “aquatic” period of fetal life.

Journal ArticleDOI
TL;DR: It was concluded that alcohol molecules interact with the membranes to make the equivalent pore radius of the membranes narrower without changing the nature of the water flow, which was nearly equal to that for the fluidity of water.
Abstract: Water permeability of theNitella internode was measured by means of transcellular osmosis. The internode was partitioned into two chambers, one filled with water or alcohol solution and the other with mannitol solution or mannitol-alcohol solution. In this experimental system, the osmotic driving force is equal to the osmotic pressure due to mannitol.