Capillaries resistance

Thomson-Freundlich equation relates the solubility of a particle to its curvature radius (e.g., Swalin, 1962). Using this equation, Kirkaldy and Young (1987) show how periodic precipitation may result from the capillary resistance of the matrix to grow small precipitates. Formally, the conditions read... 

Sophora japonica L. Huai Hua (Japanese pagoda tree) (flower bud) Rutin, sophoradiol, genisteine, sophoricoside, sophorabioside, sophoraflavonoloside, isorhammetin.33 252 Antihemostatic, increase capillary resistance and decreasing capillary fragility and permeability. 

The effects of pycnogenol on circulation can be seen as the outcome of two different activities — relaxation of arterial walls and increase of capillary resistance. The combination of these effects results in an increase of peripheral blood flow and a facilitation of microcirculation. Early studies suggested a strong vasoactivity of procyanidins extracted from sources such as wine and grape seed, which have recently been confirmed for pycnogenol. 

Pycnogenol enhances microcirculation and reduces capillary resistance in spontaneous hypertensive animals. 

A constricted tube model is used to analyze viscous and capillary effects associated with foam flow in porous media. The foam moves through the pore structure as single layer, continuous bubble trains. Capillary resistance stems from the drainage and imbibition surfaces as well as the internal lamellae structure. 

During this cascading displacement process, the maximum capillary resistance will generally occur when the drainage surface... 

In order to obtain an estimate of such effects, the pressure associated with the capillary resistance of the internal lamellae structure was calculated for different sets of bubbles, with different numbers and sizes. The specific pore geometry chosen was that shown in Figure 3. The pressure is the pressure in the front bubble and pressure Pn is that of the Nth bubble Pn - Po then gives the capillary resistance associated with the internal... 

Additional trials suggest that the expected value of the pressure difference over a series of lamellae due to capillary resistance can be approximated by... 

It should be noted that an upper bound for the capillary resistance occurs when all lamellae are simultaneously at the minimum constrictions (exit side of constricted pore bodies). For this case. 

In this relationship the capillary resistance is directly proportional to the number of lamellae in the flow path and the average pressure drop across a single lamella. 

As a final point in this section, we should mention that as the bubble trains advance through the constricted channels, the capillary resistance will assume its maximum value (the mobilization pressure) only when the lamellae in the train assume their most unfavorable positions with respect to displacement. At other times, the capillary resistance will be below this maximum value with the result that the actual work required to maintain foam flow at a given rate will be below that which would be required if the mobilization pressure was operative at all times. This is easily understood if one pushes a bubble through a single constriction in a tube and notes that the pressure in the train builds up to the mobilization pressure as the drainage surface advances into the constriction and then rapidly falls as the front bubble experiences a Haines jump. To account for such effects in the present model, the Km term in Equation 63 would vary with time as the bubble train moved through the constricted channels. 

A somewhat different interpretation of such phenomena has been given recently by Falls et al. (14). These investigators use energy arguments to account for the work associated with moving lamellae into the constrictions along the bubble train path. Such an approach is attractive from a mechanistic standpoint however, it predicts that the capillary resistance increases with the length of the porous medium, which has not been observed experimentally. Obviously, more extensive analysis and experimentation are required before such pore constriction effects are fully understood and accurately represented. 

Re-entrainment of liquid droplets that are captured can also occur as a result of squeezing when the local pressure drop is increased to overcome the capillary resistance force. The shape of the liquid droplets depends on the wettability of the rock. On the basis of this physical picture, Soo and Radke 12) proposed a model to describe the flow of dilute, stable emulsion flow in a porous medium. The flow redistribution phenomenon and permeability reduction are included in the model. Both low and high interfacial tension were considered. 

Pycnogenol was shown to improve capillary resistance and reduce leakages into the retina. 

Sevin R, Cuendet JF. Resistance capillaire et retinopathie dia-betique. Effect de I etamsylate (Cyclonamine ou Dicynone). [Capillary resistance and diabetic retinopathy. Effect of etamsylate (Cyclonamine or Dicynone).] Ophthalmologica 1968 155(3) 186-93. 

Swan HT, Nutt AB, Jowett GH, Ferguson WJ, Blackburn EK. Monosemicarbazone of adrenochrome (Adrenoxyl) and cataract surgery. Effect on capillary resistance and incidence of hyphaema. Br J Ophthalmol 1961 45 415. 

In a subsequent experiment (5), intraperitoneal injection of Myrtocyan ameliorated histamine-induced capillary permeability measured by permeability to Evans blue. The minimum effective dose was 50 mg/kg (p <0.01 compared to control, Dunnett /-test). At a dose of200 mg/kg Myrtocyan was effective in improving capillary resistance to vacuum-induced petechiae in rats fed a flavonoid deficient diet (p < 0.01 compared to baseline, Dunnett /-test). 

We use the term deformation seal to denote seals which rely on the capillary resistance of the products of shearing. The are a large number of conceivable... 

Capillary sealing effects take place at the interface between the non-wetting phase in a reservoir and the wetting phase within a top seal. The capillary forces exerted at this interface are in no way related to the thickness of the seal above. Therefore the existence of a relationship between top seal thickness and sealing capacity is not expected in the field. Thicker seals may be better equipped to resist breaching by faults, but will not retain greater columns by capillary resistance. 

The capillary pressure equation (Berg, 1975) predicts that capillary leakage will occur when the upward pressure of the hydrocarbon column is greater than the capillary resistance of the seal. The magnitude of upward reservoir pressure is determined by hydrocarbon buoyancy pressure plus any overpressure in the reservoir relative to the seal. The capillary resistance of the seal is determined by the size of interconnected pore throats and the interfacial tension between hydrocarbon (gas or oil) and formation water. The relationship between these factors can be expressed as follows if the angle of contact of the hydrocabon-water interface is assumed to be 0° (Clayton and Hay, 1994) ... 

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