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.

scholarly journals Reflection coefficients of homopore membranes: effect of molecular size and configuration.

1979 ◽  
Vol 73 (1) ◽  
pp. 49-60 ◽  
Author(s):  
J S Schultz ◽  
R Valentine ◽  
C Y Choi
Keyword(s):  
Hydrostatic Pressure ◽  
Pore Size ◽  
Osmotic Pressure ◽  
Water Flow ◽  
Molecular Size ◽  
Reflection Coefficients ◽  
Osmotic Water ◽  
Molecular Rigidity ◽  
Flow Through ◽  
Osmotic Water Flow

Osmotic water flow through membranes with uniform defined pores was measured for a variety of macromolecular solutes. Water flow increased linearly with applied hydrostatic pressure, allowing the effective osmotic pressure of the solutes to be estimated by extrapolation. Reflection coefficients for each solute-membrane combination were calculated and correlated with the ratio of solute size to pore size. For the same mean molecular size, proteins were found to have larger reflection coefficients than dextrans. Molecular rigidity may play a role in this difference in behavior.

scholarly journals Determination of cross-sectional void fraction in a two-phase water flow through a PVC pipe

2021 ◽  
Vol 655 (1) ◽  
pp. 012024
Author(s):  
O.H. Ajesi ◽  
M.B. Latif ◽  
S.T. Gbenu ◽  
C. A. Onumejor ◽  
M. K. Fasasi ◽  
...  
Keyword(s):  
Water Flow ◽  
Void Fraction ◽  
Two Phase ◽  
Cross Sectional ◽  
Flow Through ◽  
Pvc Pipe ◽  
Phase Water

On the Effects of Water Discharge Through Radial Gates at the Caruachi Dam

2010 ◽  
Author(s):  
Douglas Sanchez ◽  
Juan E. Salazar
Keyword(s):  
Water Flow ◽  
Water Discharge ◽  
Three Dimensional ◽  
Flow Induced Vibration ◽  
Discharge Flow ◽  
Cfd Models ◽  
Flow Through ◽  
Critical Velocities ◽  
Flow Effects

This paper presents numerical simulation of the water flow through the radial gates of the 2,280 MW Caruchi Dam, in southern Venezuela, and its relation to the vibration of the dam’s spillways and adjacent Control Building. The study is conducted as a contribution in determining the source of vibration of the fore mentioned structures in the case of gates opening above the normal values of up to 5 m, which occur when a larger water discharge is required in order to maintain an adequate level of the reservoir during the rainy season. The aim of the study was to find the pressure distribution and velocity profiles of the discharge flow through one of the dam’s radial gates and determine critical (reduced) velocities that may result in flow-induced vibration of the gates, as they were deemed to be the source of vibration of the whole set of structures in the first place. For this purpose, a commercially available FEM code was used. Three-dimensional CFD models were developed to simulate behavior of the flow when being released to the spillways, for opening values of 2, 5, 10 and 14 m, including the effect of the spillways’ deflectors. Modal analyses of the gate were performed, to take into account natural vibration frequencies in the determination of its critical velocities. After comparison of the gate’s critical velocities and velocity values from the CFD simulations, it is fair to say that the discharge flow does not directly induce vibration on the gates but rather on the spillways’ structure. This conclusion disregards flow through the gates as triggering the vibration phenomena which gave origin to this project, and puts the emphasis now on studying water flow effects on vibration in the spillway which, if not corrected on time, may ultimately lead to its catastrophic failure.

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.

Comparison Between Osmotic and Hydrostatic Water Flows in a Higher Plant Cell: Determination of Hydraulic Conductivities and Reflection Coefficients in Isolated Epidermis of Tradescantia virginiana

1982 ◽  
Vol 9 (4) ◽  
pp. 461 ◽  
Author(s):  
SD Tyerman ◽  
E Steudle
Keyword(s):  
Osmotic Pressure ◽  
Turgor Pressure ◽  
Water Volume ◽  
Pressure Probe ◽  
Reflection Coefficients ◽  
Higher Plant ◽  
Bathing Medium ◽  
Tradescantia Virginiana ◽  
Cell Turgor

Hydraulic conductivity (Lp), volumetric elastic modulus (ε) and reflection coefficients (δ) have been determined for cells from isolated strips of the lower epidermis of leaves of Tradescantia virginiana using the pressure probe. Lp was (6.4 � 4.5) × 10-8 ms-1 Mpa-1 [(6.4 � 4.5) × 10-7 cm s-1 bar-1; mean � s.d., n = 15 cells] and was independent of the cell turgor pressure (P) and of osmotic pressure of the bathing medium. P in Johnson's solution (π° = 0.09 MPa) was 0.42-0.67 MPa (4.2-6.7 bar), which was somewhat larger than in the intact tissue. ε increased linearly with increasing P in the pressure range from zero to full turgor. Reflection coefficients of some non-electrolytes were determined by measuring the ΔP in response to a change in external osmotic pressure (Δπ°) after the addition of the solutes. The data were corrected for solute flow. For sucrose, mannitol, urea, acetamide, formamide, glycerol and ethylene glycol, δ was close to unity and the cells behaved like ideal osmometers. For the monohydroxyalcohols n-propanol ( δ = -0.58), isopropanol (δ = 0.26), ethanol (δ = 0.25) and methanol (δ = 0.15), rather low reflection coefficients were found which were even negative for some solutes and cells. Values of δ obtained from measuring the inital water (volume) flow were in agreement with those determined from the ΔP/Δπ° ratios. For the rapidly permeating substances, the changes in turgor after the addition of solute were transient and the equilibration of solutes between cell and medium could be measured using the probe. Although unstirred layers may affect the equilibration of solute it should, in principle, be possible to use the technique for the determination of permeability coefficients of membranes of higher plant cells.

Asymmetrical transfer of inert hydrophilic solutes across rat placenta

1993 ◽  
Vol 265 (3) ◽  
pp. R670-R675
Author(s):  
J. Stulc ◽  
B. Stulcova
Keyword(s):  
Hydrostatic Pressure ◽  
Pressure Gradient ◽  
Osmotic Pressure ◽  
Active Transport ◽  
Free Water ◽  
Volume Flow ◽  
Placental Barrier ◽  
Pentobarbital Anesthesia ◽  
Hydrostatic Pressure Gradient ◽  
Hydrophilic Solutes

Transfer of [14C]mannitol, 51Cr-labeled EDTA, and [14C]-inulin from mother to fetus and from fetus to mother was measured in rats under pentobarbital anesthesia. The clearance of the three substances from the mother to fetus (Kmf) was 2.69 +/- 0.38, 1.93 +/- 0.73, and 0.47 +/- 0.14 microliter/min (means +/- SE), respectively, and the clearance from fetus to mother (Kfm) was 5.97, 6.66, and 4.95 microliters/min, respectively (the SE could not be estimated). Kfm appears to be consistently higher than Kmf by an almost constant value of approximately 4 microliters/min. To explain this a hypothesis was proposed according to which volume flow circulates across the placenta. Solute-free water is driven transcellularly across the placental barrier from the maternal to the fetal side by a difference of osmotic pressure created by active transport of some solutes (mainly Na+) to the fetus. Water together with all solutes dissolved returns from fetus to mother by filtration through wide extracellular channels in the placenta down a hydrostatic pressure gradient.

HEAT TRANSFER BURNOUT IN WATER FLOW THROUGH ROUND TUBES AND ANNULI

1970 ◽  
Author(s):  
B. A. Zenkevich ◽  
P. L. Kirillov ◽  
G. V. Alekseev ◽  
O. L. Peskov ◽  
O. A. Sudnitsyn
Keyword(s):  
Heat Transfer ◽  
Water Flow ◽  
Flow Through

Modeling of Reduced Water Flow through Concrete Caused by Crystallization Technology

2006 ◽  
Vol 9 (8) ◽  
pp. 723-730
Author(s):  
Abdelaziz Al-Khlaifat ◽  
Awni Al-Otoom
Keyword(s):  
Water Flow ◽  
Flow Through ◽  
Reduced Water
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