Permeability factor

The permeability factor, K, has units of velocity and is inversely proportional to the viscosity of the gas. A permeabihty test is mn by passing air... 

To apply these package criteria to polymer properties, a conversion was made based on a 10-12 oz. container with a surface area-to-volume ratio of 4.0 (in.2/oz.) and an average wall thickness of 0.030 in. The oxygen, carbon dioxide, and water permeability rates needed to meet these high barrier criteria over a six month shelf life are shown in Table III. Larger container sizes—16, 32, 48 oz. etc.—would permit slightly higher permeability factors for the same bottle criteria, because of their lower ratio of surface-to-volume. 

We measure the permeation rate of liquids through bottles by filling them with the liquid of interest and placing them in a controlled atmosphere chamber. At intervals we remove the bottles, weigh them and return them to the chamber. We repeat this procedure over a period of days, or even weeks, until their rate of weight loss reaches a steady value. We calculate the permeability factor from Eq. 8.10. 

Pt = permeability factor R — mass loss per day T = average wall thickness of bottle A = surface area of bottle... 

Figure 5. Pressure drop per unit length versus permeability factor. (Mainwaring...

Figure 5 is a plot of permeability factor Kp versus (Ap/Ah)mf and contains the boundary Vmf = 50 mm S 1. Figure 6 is a plot of rcd/ps versus (Ap/Ah)mf-md contains the boundary X= 0.001 nf s kg-1. By using both Figs. 5 and 6, it is possible to propose the following three criteria relating to the potential modes of pneumatic conveying in conventional pipelines. 

Yeo KT, Wang HH, Nagy JA, et al. Vascular permeability factor (vascular endothelial growth factor) in guinea pig and human tumor and inflammatory effusions. Cancer Res 1993 53 2912-2918. 

Senger DR, Galli SJ, Dvorak AM, et al. Tumor cells secrete a vascular permeability factor that promotes accumulation of ascites fluid. Science 1983 219 983-985. 

Keck PJ, Hauser SD, Krivi G, et al. Vascular permeability factor, an endothelial cell mitogen related to PDGF. Science 1989 246 1309-1312. 

Cullumbine postulated the production of a "capillary permeability factor" caused by the reaction of H with tissues. Experiments that he and co-workers performed supported the appearance of such a factor. Figure 4-2 shows what he suggested occurs after H contaminates the skin. 

Equation (6.1.4) asserts that the volumetric flow rate is a superposition of two components. They are the electro-osmotic component proportional to the electric field intensity (voltage) with the proportionality factor u> and the filtrational Darcy s component proportional to —P with the hydraulic permeability factor i>. Teorell assumed both w and t> constant. Finally another equation, crucial for Teorell s model, was postulated for the dynamics of instantaneous electric resistance of the filter R(t). Teorell assumed a relaxation law of the type... 

Because mass flow bins have stable flow patterns that mimic the shape of the bin, permeability values can be used to calculate critical, steady-state discharge rates from mass flow hoppers. Permeability values can also be used to calculate the time required for fine powders to settle in bins and silos. In general, permeability is affected by particle size and shape, ie, permeability decreases as particle size decreases and the better the fit between individual particles, the lower the permeability moisture content, ie, as moisture content increases, many materials tend to agglomerate which increases permeability and temperature, ie, because the permeability factor, K, is inversely proportional to the viscosity of the air or gas in the void spaces, heating causes the gas to become more viscous, making the solid less permeable. 

Green, L.S., Jellinek, D., Bell, C., Beebe, L.A., Feistner, B.D., Gill, S.C., Jucker, F.M. and Janjic, N. (1995) Nuclease-resistant nucleic acid ligands to vascular permeability factor/vascular endothelial growth factor, Chem. Biol. 2, 683-695. 

Brown LF, Yeo KT, Berse B, Yeo TK, Senger DR, Dvorak HF, Van de Water L. 1992. Expression of vascular permeability factor (vascular endothelial growth factor) by epidermal keratinocytes during wound healing. J Exp Med 176 1375-1379. 

Dvorak, F., B. Lawrence, M. Detmar, and A. M. Dvorak. 1995. Vascular permeability factor/vascular endothelial growth factor, microvascular hyperpermeability, and angiogecteasJ. Pathol.146 1029-1039. 

Murohara, T., Horowitz, J.R., Silver, M., Tsurumi, Y., Chen, D., Sullivan, A. et al. (1998) Vascular endothelial growth factor/vascular permeability factor enhances vascular permeability via nitric oxide and prostacyclin. Circulation, 97, 99-107. 

Normal serum was recently demonstrated to contain substances inhibiting permeability factor(s). These inhibitors are not present in sera of patients with FSGS (Sll). Some of these inhibitors have been identified as apolipoproteins of the high-density lipoprotein (HDL) complex, for example, apo J, apo E2, and apo E4 (C2). Inhibitors of the permeability factors may be lost in urine in patients with nephrotic syndrome and their presence in urine has been documented (G5). FSGS may thus be caused not only by the (increased) production of permeability factors, but also by the urinary loss of their inhibitors. Bioassay (S5) is not able to differentiate between increased production of permeability factors and the loss of their inhibitors. Increased permeability was confirmed by this bioassay even in patients with FSGS and the documented mutation of the podocin gene, apparently without increased production of the permeability factors (G5). 

Sporadic forms of FSGS can be subdivided into three types FSGS with mutations of the genes for podocyte proteins (podocin, a-actinin, or others, yet unidentified), FSGS with increased production of the permeability factor(s), and FSGS... 

K20. Koyama, A., Fukisaki, M., Kobayashi, M., Igarashi, M., and Narita, M., A glomeular permeability factor produced by human T cell hybridomas. Kidney Int. 40,453-460 (1991). 

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