scholarly journals Osmotic Flow of Water across Permeable Cellulose Membranes

1960 ◽  
Vol 44 (2) ◽  
pp. 315-326 ◽  
Author(s):  
Richard P. Durbin
Keyword(s):  
Hydrostatic Pressure ◽  
Biological Membrane ◽  
Volume Flow ◽  
Osmotic Gradient ◽  
Pressure Gradients ◽  
Deuterated Water ◽  
Direct Measurements ◽  
Flow Through ◽  
Cellulose Membranes ◽  
Effective Pore Radius

Direct measurements have been made of the net volume flow through cellulose membranes, due to a difference in concentration of solute across the membrane. The aqueous solutions used included solutes ranging in size from deuterated water to bovine serum albumin. For the semipermeable membrane (impermeable to the solute) the volume flow produced by the osmotic gradient is equal to the flow produced by the hydrostatic pressure RT ΔC, as given by the van't Hoff relationship. In the case in which the membrane is permeable to the solute, the net volume flow is reduced, as predicted by the theory of Staverman, based on the thermodynamics of the steady state. A means of establishing the amount of this reduction is given, depending on the size of the solute molecule and the effective pore radius of the membrane. With the help of these results, a hypothetical biological membrane moving water by osmotic and hydrostatic pressure gradients is discussed.

Bestimmung von Reflexionskoeffizienten an der Membran der Alge Valonia utricularis / Determination of Reflection Coefficients of the Membrane of the Algae Valonia utricularis

1970 ◽  
Vol 25 (5) ◽  
pp. 500-504 ◽  
Author(s):  
U. Zimmermann ◽  
E. Steudle
Keyword(s):  
Hydrostatic Pressure ◽  
Osmotic Pressure ◽  
Water Flow ◽  
Linear Dependence ◽  
Volume Flow ◽  
Reflection Coefficients ◽  
Valonia Utricularis ◽  
Flow Through ◽  
Zero Flow

A zero flow method of rapidly determining reflection coefficients of giant algae cells is described.Changes of the osmotic pressure in the outside medium caused a net volume flow through the cell membranes and consequently changes of the hydrostatic pressure inside the cell. By continously measuring the hydrostatic pressure it was possible, to determine the concentration outside the cell at which no volume flow occurs.The reflection coefficients of some non-electrolyts were determined on the membrane of the mediterranean algae Valonia utricularis with an error of 3 - 4% and are discussed on the basis of the pore model.The hydrostatic pressure inside Valonia cells decreased exponentially with time, when they were put into a hypertonic aequous solution. If a linear dependence of the volume (water) flow on the hydrostatic and osmotic pressure differences is supposed, it will be possible to calculate the volume (water) flow.

Nanoliter-volume flow-through fluorometer

1982 ◽  
Vol 54 (4) ◽  
pp. 840-842 ◽  
Author(s):  
Gerald G. Vurek
Keyword(s):  
Volume Flow ◽  
Flow Through

scholarly journals The structure and dynamics of patch-clamped membranes: a study using differential interference contrast light microscopy.

1990 ◽  
Vol 111 (2) ◽  
pp. 599-606 ◽  
Author(s):  
M Sokabe ◽  
F Sachs
Keyword(s):  
Cell Surface ◽  
Transmural Pressure ◽  
Positive Pressure ◽  
Radius Of Curvature ◽  
Pressure Gradients ◽  
Structure And Motion ◽  
Excised Patches ◽  
Glass Interface ◽  
Pipette Tip ◽  
Flow Through

We have developed techniques for micromanipulation under high power video microscopy. We have used these to study the structure and motion of patch-clamped membranes when driven by pressure steps. Patch-clamped membranes do not consist of just a membrane, but rather a plug of membrane-covered cytoplasm. There are organelles and vesicles within the cytoplasm in the pipette tip of both cell-attached and excised patches. The cytoplasm is capable of active contraction normal to the plane of the membrane. With suction applied before seal formation, vesicles may be swept from the cell surface by shear stress generated from the flow of saline over the cell surface. In this case, patch recordings are made from membrane that was not originally present under the tip. The vesicles may break, or fuse and break, to form the gigasealed patch. Patch membranes adhere strongly to the wall of the pipette so that at zero transmural pressure the membranes tend to be normal to the wall. With transmural pressure gradients, the membranes generally become spherical; the radius of curvature decreasing with increasing pressure. Some patches have nonuniform curvature demonstrating that forces normal to the membrane may be significant. Membranes often do not respond quickly to changes in pipette pressure, probably because viscoelastic cytoplasm reduces the rate of flow through the tip of the pipette. Inside-out patches may be peeled from the walls of the pipette, and even everted (with positive pressure), without losing the seal. This suggests that the gigaseal is a distributed property of the membrane-glass interface.

scholarly journals AN EXPERIMENTAL STUDY INTO THE CAUSE OF THE INCREASED PORTAL PRESSURE IN PORTAL CIRRHOSIS

1907 ◽  
Vol 9 (1) ◽  
pp. 93-104 ◽  
Author(s):  
Frederick C. Herrick
Keyword(s):  
Arterial Pressure ◽  
Portal Pressure ◽  
Normal Liver ◽  
Volume Flow ◽  
Cirrhotic Liver ◽  
Return Flow ◽  
Hepatic Veins ◽  
Portal Cirrhosis ◽  
Arterial Inflow ◽  
Flow Through

1. In the liver of portal cirrhosis there is a far freer communication between the arterial and portal currents than in the normal liver. 2. Factors contributing to the increased portal pressure in portal cirrhosis are (1) the direct communication of the arterial pressure to the portal vessels through dilated capillaries, (2) the larger volume-flow of the hepatic artery in proportion to the portal flow in cirrhosis as compared to that in the normal liver. 3. A portal cirrhotic liver gives passage to an amount of portal fluid proportionate to .its weight. There is no obstruction to the portal vessels from fibrosis in the large portal cirrhotic liver. 4. From an arterial inflow there is a free return flow through the portal as well as through the hepatic veins in both normal and cirrhotic livers. 5. From a portal inflow the return is through the hepatic vein only. The Gad's theory of valves and the arterial capillary network account for this fact. 6. The portal pressure has a decided influence on the arterial volume-flow and vice versa. This influence is more marked in the cirrhotic than in the normal liver. 7. The communication of the arterial pressure to the portal pressure is an important factor in an explanation of the increased portal pressure in portal cirrhosis.

scholarly journals Electromyography of the Respiratory Muscles and Gill Water Flow in the Dragonet

1968 ◽  
Vol 49 (3) ◽  
pp. 583-602
Author(s):  
G. M. HUGHES ◽  
C. M. BALLINTIJN
Keyword(s):  
Hydrostatic Pressure ◽  
Stroke Volume ◽  
Pressure Gradient ◽  
Time Course ◽  
Respiratory Muscles ◽  
Adverse Pressure Gradient ◽  
Pressure Head ◽  
Volume Flow ◽  
Frequency Change ◽  
Hydrostatic Pressure Gradient

1. An account is given of the main skeletal elements and muscles involved in the respiratory movements of the dragonet, Callionymus lyra. 2. Using electromyographic techniques it has been shown that the muscles chiefly involved in rapid ejection of water out of the opercular slit are the adductor mandibulae, protractor hyoideus, and hyohyoideus. During the expansion phase of the cycle, which is about six times the duration of the contraction phase, the levator hyomandibulae and sternohyoideus are active, though in some cases the latter only comes in at higher levels of pumping. 3. Changes in volume flow across the gills have been produced by either (a) altering the hydrostatic pressure gradient (Δp) across the system, or (b) altering the oxygen or carbon dioxide content of the water inspired by the fish. With (a), the volume flow decreases linearly at a rate of about 30 ml./min./cm. H2O static pressure head until an inflexion is reached in the curve at which rate of flow decreases and is normally when Δp is zero. That the relative increase in flow rate with negative Δp's is due to the activity of the fish pumping against the adverse pressure gradient has been confirmed by electromyogram recordings during such experiments. With (b), it was possible to demonstrate a clear relationship between stroke volume and the level of electrical activity as measured by the height of the integrated electromyogram. The integrated EMG increases more than linearly with increasing stroke volume during PO2 changes, but this relationship seems to be more nearly linear during changes in CO2 concentration. 4. The respiratory frequency is scarcely affected by changes in flow produced by altering the hydrostatic pressure gradient, but following a decrease in PO2 or an increase in CO2 there is a significant fall in frequency which accompanies the increased electromyogram. The time course of these changes during recovery from a decrease in PO2 or an increase in PCOCO2 suggests that the gas tensions of the inspired water are detected by receptors on the gills and thus influence the electromyogram activity, but the frequency change observed is due to a change in the blood affecting receptors in the brain.

A High Performance PFB System for Utility Application

1987 ◽  
Author(s):  
Paul A. Berman ◽  
Jeffrey A. Hynds
Keyword(s):  
Power System ◽  
High Performance ◽  
State Of The Art ◽  
Combustion Products ◽  
Volume Flow ◽  
Power Cycle ◽  
Turbine Inlet ◽  
Alkali Vapors ◽  
Fluid Bed ◽  
Flow Through

In the traditional pressurized fluid bed (PFB) power system, the PFB is located in the highest pressure portion of the power cycle, Figure 1. This results in the smallest volume flow through the PFB, but also requires the combustion products to flow through the entire expansion train. This is not expected to be a major problem when the PFB temperature is limited to 1600°F for effective sulfur capture and to avoid alkali vapors in the products of combustion. However, when topping combustion is added ahead of the turbine so as to reach state-of-the-art turbine inlet temperatures, a major risk for turbine corrosion and fouling develops.

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