Filtration coefficient

The transport of both solute and solvent can be described by an alternative approach that is based on the laws of irreversible thermodynamics. The fundamental concepts and equations for biological systems were described by Kedem and Katchalsky [6] and those for artificial membranes by Ginsburg and Katchal-sky [7], In this approach the transport process is defined in terms of three phenomenological coefficients, namely, the filtration coefficient LP, the reflection coefficient o, and the solute permeability coefficient to. 

Explain how the filtration coefficient and net filtration pressure determine glomerular filtration... 

The filtration coefficient is determined by the surface area and permeability of the filtration barrier. An increase in the filtration coefficient leads to an increase in GFR if the filtration coefficient decreases, then GFR decreases. However, this factor does not play a role in the daily regulation of GFR because its value is relatively constant under normal physiological conditions. On the other hand, chronic, uncontrolled hypertension and diabetes mellitus lead to gradual thickening of the basement membrane and therefore to a decrease in the filtration coefficient and GFR, and impaired renal function. 

Filtration coefficient The filtration coefficient, Lp, was measured under osmotic pressure utilizing thermostated glass cells ( 0.05°C) equipped with graduated cappillaries ( 0.001 cc). The cells had an effective membrane area of 1.77 cm and each compartment contained v25 cc of solution. One compartment was filled with deionized water and the second with a 1 or 2 molal solution of sucrose (depending upon lEC). 

If we consider a membrane having the same solute concentration on both sides, we have All 0 However, a hydrostatic pressure difference AP exists between the two sides, and we have a flow Jv that is a linear function of AP. The term Lp is called the mechanical filtration coefficient, which represents the velocity of the fluid per unit pressure difference between the two sides of the membrane. The cross-phenomenological coefficient Ldp is called the ultrafiltration coefficient, which is related to the coupled diffusion induced by a mechanical pressure of the solute with respect to the solvent. Osmotic pressure difference produces a diffusion flow characterized by the permeability coefficient, which indicates the movement of the solute with respect to the solvent due to the inequality of concentrations on both sides of the membrane. 

The local hydroconductivity (analogous to the filtration coefficient in Darcy s equation) represents the liquid volume flowing through all borders in unit time per unit area... 

The mass balance of the retained solid is described by Eq. (4.280). The Mint deterministic model results from the coupling of this relation vfith the definition of the filtration coefficient. The result is written in Eq. (4.281) for the start time of the filtration and in Eq. (4.282) for the remaining filtration time. Here a is the detachment coefficient of the retained particle its dimension is T h... 

In the Mint model, we have to take into account the following considerations (i) the initial filtration coefficient Xq, which is a parameter, presents a constant value after time and position (ii) the detachment coefficient, which is another constant parameter (iii) the quantity of the suspension treated by deep filtration depends on the quantity of the deposited solid in the bed this dependency is the result of the definition of the filtration coefficient (iv) the start of the deep bed filtration is not accompanied by an increase in the filtration efficiency. These considerations stress the inconsistencies of the Mint model 1. valid especially when the saturation with retained microparticles of the fixed bed is slow 2. unfeasible to explain the situations where the detachment depends on the retained solid concentration and /or on the flowing velocity 3. unfeasible when the velocity of the mobile phase inside the filtration bed, varies with time this occurrence is due to the solid deposition in the bed or to an increasing pressure when the filtration occurs with constant flow rate. Here below we come back to the development of the stochastic model for the deep filtration process. 

Delaunois, A., Gustin, P., Ansay, M. (1992). Altered capillary filtration coefficient in parathion- and paraoxon-induced edema in isolated and perfused rabbit lungs. Toxicol. Appl. Pharmacol. 116 161-9. 

Kf c = capUlary filtration coefficient for fluids (cannot be measured in the clinical setting)... 

Thus, a reduction in the glomerular filtration coefficient and the number and size of fenestrations in the glomerular endothelium have been observed. 

Some of the parameters used to evaluate membranes are the diffusion coefficient, D the permeability coefficient, P the solubility constant, S the filtration coefficient, L, the solute permeability coefficient, to and the reflection coefficient, o. The diffusion coefficient can be obtained by the time lag method illustrated in Figure 35-9. 

The filtration coefficient relates the water flux through a membrane to the applied pressure. AP... 

The diffusion coefficient, the permeability coefficient, the solubility constant, the filtration coefficient, the solute permeability coefficient, and the reflection coefficient. 

The filter coefficient, X, varies as deposited material changes the morphology of the porous medium and as conditions surrounding the collection sites change. It has been noted that the filtration coefficient increases as fines migrate through a clean filter bed the retained fines increase the specific surface area. This increase in X is short-lived, and the magnitude of the filter coefficient decreases as additional fines are retained. Since Iwasaki published his notes on filtration in 1937, numerous variations of the rate expression have been recorded (72). 

Unit Bed Element Modeling. The filter bed is divided into many cross-sectional elements along the axial direction of flow. If the number of elements is large, then it may be assumed that the filtration coefficient A is constant throughout each UBE, at an instant in time. The removal efficiency, rj, of each element, m, is based on the difference of the filtrate concentration entering and leaving the element. 

The removal efficiency can be related to the filtration coefficient by integrating equation 11. 

Seeger, W., Radinger, H. and Neuhof, H. (1984). Increase in the capillary filtration coefficient in isolated rabbit lungs due to non-cyclooxygenase pathway of arachidonic acid. Microcirc. Clin. Exp., 3, 351... 

Figure 8-6. Effects of subdiaphragmatic stimulation of the ventral vagus nerve (between panels A and B) on gastric blood flow and capillary filtration coefficient (CFC) in an anesthetized cat weighing 3.3 kg. (From Jansson G, Lundgren O, Martinson J. Neurohumoral control of gastric blood flow (comment). Gastroenterology 58 425-429, 1970.)...

F = function describing the effect of particle deposition on deep-bed filtration coefficient... 

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