Dais membranes

Dais membranes are reported to be much less expensive to produce than Nation they are also reported to exhibit a rich array of microphase-separated morphologies because of the ability to tailor the block length and composition of the unsulfonated starting polymer. The main drawback of employing hydrocarbon-based materials is their much... 

The first type of hydrocarbon membrane for fuel cell applications was the sulfonated polystyrene-divinylbenzene co-polymer membranes equipped for the power source in NASA s Gemini space flights, but the sulfonated polystyrene had low chemical stability for long-term applications, because the proton on the tertiary carbons and benzylic bonds are easily dissociated in an oxygen environment forming hydroperoxide radicals. Since a styrene monomer is easily co-polymerized with other vinyl monomers via radical polymerization methods, various styrenic polymers were researched intensively. Two commercial polystyrene-based/related membranes are available BAM (Ballard), and Dais Analytic s sulfonated styrene-ethylene-butylene-styrene (SEBS) membrane. Dais membranes are produced using... 

Dai J, Baker GL, Bruening ML (2006) Use of porous membranes modified with polyelectrolyte multilayers as substrates for protein arrays with low nonspecific binding. Anal Chem 78 135-140... 

Basura, V. I., Chuy, C., Beattie, P. D. and Holdcroft, S. 2001. Effect of equivalent weight on electrochemical mass transport properties of oxygen in proton exchange membranes based on sulfonated a,j3,j3-trifluorostyrene (BAM) and sulfonated-styrene-(ethylene-butylene)-styrene triblock (DAIS-analytical) copolymers. Journal ofElectroanalytical Chemistry 501 77-88. 

Presently, two commercial (or semicommercial) PEMs are based on styrene or styrene-like monomers BAM from Ballard, and Dais Analytic s sul-fonated styrene—ethylene—butylene—styrene (SEBS) membrane. Ballard Advanced Materials Corporation introduced a styrenic membrane based on a novel family of sulfonated copolymers incorporating a,/3,l3-trifluorostyrene and substituted a,y3, -trifluoro-styrene comonomers. These are registered as BAM membranes, and their general formula is given in Figure 3. 

Dai, R., Pincus, M. R., and Friedman, F. K. (1998) Molecular modeling of cytochrome P450 2B1 mode of membrane insertion and substrate specificity. J. Protein Chem. 17, 120-129. 

Even a cursory review of the pertinent literature leaves the reader in little doubt that cestodes can subvert host immune responses by mechanisms that vary from membrane fluidity (i.e. membrane turnover) (Taylor et al., 1997) to active immunomodulation thatfavours development of immunosuppressive/immunoregula-tory cells (Dai and Gottstein, 1999) and/or an immune-suppressed environment. In this respect the cestode is no different than other helminth parasites. However, the data are fragmented, often quite vague and confused by the specificity of the host-parasite interaction. Therefore we have opted to provide the reader with tabulated data on some of the main findings illustrating cestode manipulation of their... 

H. Yu, F. Yan, Z. Dai and H.X. Ju, A disposable amperometric immunosensor for alpha-1-fetoprotein based on enzyme-labeled antibody/chito-san-membrane-modified screen-printed carbon electrodes, Anal. Biochem., 331 (2004) 98-105. 

Dai, X.P., Yang, Z.F., Luo, R.G. and Sirkar, K.K. (2000) Lipase-facilitated separation of organic-acids in a hollow-fiber contained liquid membrane module. Journal of Membrane Science, 171, 183. 

Liu B., Dai W., Wu G., Deng J.-F. Amorphous alloy/ceramic composite membrane preparation, characterization and reaction studies. Catalysis Letters 1997 49 181-188. 

Bonifacino IS, Lippincott-Schwartz J. Coat proteins shaping membrane transport. Nat. Rev. Mol. Cell Biol. 2003 4 409 14. LaPlante JM, Sun M, Falardeau J, Dai D, Brown EM, Slau-genhaupt SA, Vassilev PM. Lysosomal exocytosis is unpaired in mucolipidosis type IV. Mol. Genet. Metab. 2006 89 339-348. 

Huang Y, Anderle P, Bussey KJ, Barbacioru C, Shankavaram U, Dai Z, Reinhold WC, Papp A, Weinstein JN, Sadfe W. Membrane transporters and channels Role of the transportome in cancer chemosensitivity and chemoresistance. Cancer Res 2004 64 4294-301. 

A numerical integration technique is applied to calculate the aluminum ion concentration at intermediate times. The input parameters are (1) initial concentration of the ions in the feed and the sweep solutions, CAi,feed> Cai,sweep Cn.feed CH,sweep (2) volume of the two solutions, Vfeed and Vsweep (3) area of exchange A, (4) self-diffusion coefficient Dai and Dai/Dh determined from Step 4, and (5) wet membrane thickness, L. Two sets of equations are generated from the isotherm plot for... 

Experiments were carried out with Ionac MC 3470 to determine the self-diffusion coefficient values for H+ and Al + in the coupled transport. Data points were used from the experiment involving 2N acid sweep solution in Figure 34.24b, presented later. These values formed the basis for aluminum transport rate or flux (7ai) calculation at different time intervals. The equilibrium data generated in Figure 34.20b were used in conjunction with Equation 34.25 to determine the interdiffusion coefficient values. Local equilibrium was assumed at the membrane-water interface. Eigure 34.24a shows computed Dai,h values for this membrane. When compared with Dai,h values for Nafion 117, it was noticed that the drop in interdiffusion coefficient values was not so steep, indicative of slow kinetics. The model discussed earlier was applied to determine the self-diffusion coefficient values of aluminum and hydrogen ions in Ionac MC 3470 membrane. A notable point was that the osmosis effect was not taken into account in this case, as no significant osmosis was observed in a separate experiment. 

Even for lonac MC 3470, it was the H" " ion that was the trace species. A comparison of the diffusion coefficient values for the two membranes is presented in Table 34.3. From this table, it can be observed that the self-diffusion coefficient values for aluminum and hydrogen ions are similarly lowered as the experimental interdiffusion coefficient value. This lowering is about one order for both the cases. Explanation for low Dai,h values in the heterogeneous membrane is desired, as it explains the slow transport kinetics in heterogeneous membrane. 

Huang, Y Anderle, P., Bussey, K.J., Barbacioru, C., Shankavaram, U., Dai, Z., Reinhold, W.C., Papp, A., Weinstein, J.N. and Sadee, W. (2004) Membrane transporters and channels role of the transportome in cancer chemosensitivity and chemoresistance. Cancer Research,... 

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