Membranes models for

A fundamental difference exists between the assumptions of the homogeneous and porous membrane models. For the homogeneous models, it is assumed that the membrane is nonporous, that is, transport takes place between the interstitial spaces of the polymer chains or polymer nodules, usually by diffusion. For the porous models, it is assumed that transport takes place through pores that mn the length of the membrane barrier layer. As a result, transport can occur by both diffusion and convection through the pores. Whereas both conceptual models have had some success in predicting RO separations, the question of whether an RO membrane is truly homogeneous, ie, has no pores, or is porous, is still a point of debate. No available technique can definitively answer this question. Two models, one nonporous and diffusion-based, the other pore-based, are discussed herein. 

Fig. 2 Mechanically oriented bilayer samples as a membrane model for ssNMR. (a) Illustration of the hydrated lipid bilayers with MAPs embedded, the glass supports, and the insulating wrapping, (b) A real sample consists of 15 stacked glass slides, (c) Schematic solid-state 19F-NMR lineshapes from an oriented CF3-labelled peptide (red), and the corresponding powder lineshape from a non-oriented sample (grey), (d) Illustration of typical orientational defects in real samples - the sources of powder contribution in the spectra...

Fig. 5 Membrane models for NMR structure analysis, (a) An isotropic detergent micelle (left) is compared to the dimensions of lipid bilayers (right), (b) Macroscopically oriented membrane samples can be prepared on solid support, as nanodiscs, or as magnetically oriented bicelles. (c) Nomenclature and variability of liposomes small (SUV, 20-40 nm), intermediate (IUV, 40-60 nm), large (LUV, 100-400 nm), and giant unilamellar vesicles (GUV, 1 pm) multi-lamellar (MLV), oligo-lamellar (OLV) and highly heterogeneous multi-oligo-lamellar vesicles (MOLV)...

Chatterjee SN, Agarwal S. Liposomes as membrane model for study of lipid peroxidation. Eree Radic Biol Med 1988 4 51. 

Figure 9.4 Membrane model for electron transfer reaction in photosynthetic cycle with acceptor A and donor D on either side of the membrane (a) P, P. P+ are respectively normal state electronically excited state and oxidised form of pigment molecule, (b) Illustrating energy levels of ground and excited states of pigment molecule in the membrane and acceptor and donor molecules in solution. tk.G=riFE is theoretically available electrochemical free energy e=electron, +=positive hole.

Maler, L., and Graslund, A. (2008) Artificial membrane models for the study of macromolecular delivery, in Macromolecular drag delivery (Belting, M., ed.), Humana Press, pp. 129-139. 

Artificial Membrane Models for the Study of Macromolecular Delivery... 

The ability of crown ethers to bind selectively to particular Group IA and Group IIA metal ions, because of the relationship between hole size and metal ion radius, has led to considerable interest in them in relation to membranes (models for selective ion transport), antibiotics (similar polyether structure), organic synthesis [solubilization of inorganic reagents leading to milder routes for oxidation (122), nucleophilic substitution (123), fluoridation (90)] and extraction of alkali... 

Eugster R, Spichiger UE, Simon W, Membrane model for neutral-camer-based membrane electrodes containing ionic sites. Anal. Chem. 1993 65, 689-695. 

R.A. Arcus, A membrane model for positive photoresist development, Proc. SPIE 631, 124 (1986). 

FIGURE 19.2 Cardiac action potential. Computed with the DiFrancesco-Noble membrane model for the cardiac conduction system (membrane patch). B, baseline E, excitation R, recovery (repolarization). 

AE in the above model can be solved using the generalized Newton method. The model output (that is, predictions) should be verified against the experimental results to validate the model and values of Qi,..., Q used. The above membrane model is already validated in the literature, and hence model validation is not discussed here. Interested readers are referred to Chapter 10 in ihis book, where a gas separation model is validated, and Ahmad et al. (2015) for experimental validation of a hollow fiber membrane model for a gas separation system. 

Ahmad, R, Lau, K.K., Lock, S.S.M., et al. (2015) Hollow fiber membrane model for gas separation systems experimental validation, process simulation and module characteristics study. Journal of Industrial and Engineering Chemistry, 21,1246-1257. 

In their theoretical studies, Bogen et al (1980) assumed an initially spherical membrane model for the infarcted LV. Employing a finite element method, it was possible to obtain end diastolic and end systolic pressure-volume curves. From these P-V curves, the effects of infarct size and infarct stiffness on the... 

Monolayer systems are composed of only a monomolecnlar lipid film on water surface. The aim in these systems is to study the properties of a monomolecnlar thin lipid film spread on the surface of water, which is not possible by any other techniqne. Lately, it has been shown that such lipid films are useful membrane models for biological membranes strnctnre and function studies. The modem methods have allowed one to measure the monolayer properties in mnch detail than earlier. No other method exists through which one can obtain any direct information about the molecular packing or interactions (forces acting in two dimensions). 

L. Maeler and A. Graeslund, Artificial Membrane Models for the Study of Macromolecular Delivery , in Methods in Molecular Biology (Totowa, NJ, United States), ed. M. Belting, 2009, vol. 480, Macromolecular Drug Delivery, p. 129. 

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