Permeability increasing factor

Individuals with hereditary angioneurotic oedema lack serum CT-esterase inhibitor, the inhibitor of the activated first component of hemolytic complement. During an acute episode of this disorder circulating CT-esterase, which is a permeability-increasing factor in human skin, is markedly increased [57, 97, 140, 142, 219, 332]. It is unlikely that a similar mechanism is involved in the anaphylactoid reaction in rats as reactivity is not an absolute phenomenon [32-34, 274]. The final inflammatory mediator(s) of the reaction is, therefore, available for release in both reactor and non-reactor rats. This implies that the trigger mechanism or some intermediary step in the reaction is different in the two types of rat. 

Du 1986). This reflects the importance of smaU pores in order to apply effectively capillary condensation as a separation mechanism. Uhlhom (1990) demonstrated the effect of multilayer diffusion of propylene through a modified y-alumina membrane at 0°C. The separation factor for the N2/CjHg mixture was 27, where propylene is the preferentially permeating component, while the permeability increased to 7 times the Knudsen diffusion permeability. Although this mechanism appears to be very effective because of a high separation factor and a high permeability, it is limited by the obvious need for a condensable component. This in turn restricts the applicability range, due to limits set by temperature and pressure, needed for formation of multilayers or capillary condensation. 

Finally the synthesis of inorganic-polymer composite membranes should be mentioned. Several attempts have been made to combine the high permeability of inorganic membranes with the good selectivity of polymer membranes. Furneaux and Davidson (1987) coated a anodized alumina with polymer films. The permeability increased by a factor of 100, as compared to that in the polymer fiber, but the selectivities were low (H2/O2 = 4). Ansorge (1985) made a supported polymer film and coated this film with a thin silica layer. Surprisingly, the silica layer was found to be selective for the separation mixture He-CH4 with a separation factor of 5 towards CH4. The function of the polymer film is only to increase the permeability. No further data are given. 

Not only can absorption alter the aroma and flavor of a product, it can also change the mechanical properties of the polymer. Swelling and gas permeability are factors that effect the physical properties of a polymer (Robertson, 2006 Sadler and Braddock, 1991 Safa and Bourelle, 1999). Swelling occurs when compounds are absorbed into the polymer and distort the shape of the package. As absorption increases there is also a subsequent increase in gas permeability. This increase in gas permeability can affect the shelf-life and sensory quality of a food by, for example, increasing oxidation. In very severe cases, absorption can affect package integrity. 

Weiss, J., Elsbach, P., Shu, C., Castillo, J., Grinna, L., Horwitz, A., Theofan, G. Human bactericidal/permeability-increasing protein and a recombinant NH2-terminal fragment cause killing of serum-resistant gram-negative bacteria in whole blood and inhibit tumor necrosis factor release induced by the bacteria. J Clin Invest 90 (1992) 1122-1130. 

Ohuchi, K., Watanabe, M., Hirasawa, N., Yoshizaki, S., Mue, S. and Tsurufuji, S. (1990). Suppression by adrenoceptor 0-agonists of vascular permeability increase and edema formation induced by arachidonate metabolites, plateletactivating factor, and tumor-promoting phorbol ester TPA. Immunopharmacology 20, 81-88. 

Crosslinked polymer-like bulk gel used in water shut-off has very poor flowability the viscosity is very high (>10,000 mPa s). Uncrosslinked polymer is used to increase water viscosity. A movable gel is used in between it has the intermediate viscosity, and more importantly, it can flow under some pressure gradient. Colloidal dispersion gel (CDG) is a typical gel used in these situations. The mechanisms of a movable gel are (1) it has high viscosity to improve mobility ratio like an uncrosslinked polymer solution (2) it has a high resistance factor and high residual permeability reduction factor and (3) it has viscoelasticity so that the remaining oil in the rocks can be further reduced. 

Figure 5.49 shows the polymer concentration effect on the permeability reduction factor, F, predicted from Eq. 5.36. This figure shows that F is a weak function of polymer concentration, and it increases shghtly within a low concentration range. Concentration quickly reaches a plateau. This effect is consistent with the polymer adsorption shown in Figure 5.43. 

Resistance is related to mobility, which includes the effects of both permeability reduction and viscosity increase. Obviously, the viscosity effect is not included in the residual resistance factor defined in Eq. 5.41 because water viscosity is used before and after polymer flow. Such a name convention is confusing. Therefore, we suggest the terms permeability reduction factor and residual permeability reduction factor be used. If the process were considered reversible, there would be no need for the term of residual permeability reduction factor. To include both permeability reduction and viscosity increase, we define another parameter, resistance factor (F,) ... 

For adsorbing polymers and weak gels, permeability reduction factors and residual permeability reduction factors increase with decreased permeability (Seright, 2006). 

Dentener MA, Franco GJ, Hiemstra PS, Tool AT, Verhoeven AJ, Vandenabeele P, Buurman WA Bactericidal/permeability-increasing protein release in whole blood ex vivo Strong induction by lipopolysaccharide and tumor necrosis factor-alpha. J Infect Dis 1997 175 108-117. 

Another method relies on thermal properties of lipid membranes. Every lipid bilayer is characterized by a phase transition, from solid-like to liquid-like states. It is known that at the transition temperature (called melting temperature, r ), the bilayer permeability is maximal. It is then possible to exploit this higher permeability to allow solutes pass through the membrane (Figure 17.5.4). It has been reported, for example, that ATP permeability increase by a factor -100 in dimyristoyl phosphatidylcholine vesicles, and that such vesicles can therefore be fed with ATP by keeping them at the (23.3 °C). It... 

The porosity and pores structure will be of special importance for liquids transport in concrete. These both properties relate directly to w/c ratio and the degree of hydration, because porosity of concrete is affected mainly by cement paste the porosity of aggregate is generally very low. Continuous pores volume is increasing with w/c ratio and decreases with degree of cement hydration. There ate the permeability controlling factor, because the transport of liqitids in concrete composite occurs principally in continuous pores. 

Generalized oedema of the face, body and extremities was a complication seen in one 41-year-old patient 24 h following UAE [94]. In this case, a transient spike in vascular endothelial growth factor (VEGF) level was seen to coincide with the oedema. VEGF has permeability-increasing activity for vascular endothelial cells [46] and was hypothesized to have been released by the hypoxic fibroids. 

It should be borne in mind that protective clothing is not universal for all chemieal materials. For this reason, protection against one penetrant does not suggest that the glove has protecting qualities against the other materials. Mixtures of solvents behave in a different manner than do pure components. The temperature at which exposure occurs is also an important factor. Generally as temperature increases, permeability increases. 

Gas permeability depends on chain mobility and intermolecular distances (free volume). Both properties can be modified by plasticizers. Figure 10.84 shows that by increasing the amount of the plasticizer or increasing the temperature, water permeability is increased. This is a simple illustration of the influence of flee volume on permeability. Replacement of a low molecular weight plasticizer (DOP) by polyolefin flexibilizer decreased oxygen permeability by factor 2.5. " ... 

It has been observed [24] that for PEG (200g/mol) modified Pebax membrane for CO2 separation the CO2 permeability increased by a factor of about 2 (from 73 to 151 Barrer) and the separation factor CO2/H2 also increased by PEG addition (50 wt.%). This enhancement was attributed to the appearance of additional ethylene oxide (EO) units and free volume increase. Higher content of EO units results in an increase in the solubility of CO2. Later, the total free volume increase and hence the increase of the permeability was demonstrated by measurements of density and by positron annihilation lifetime spectroscopy (PALS) analysis [75]. 

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