Network interfacial

The NMR study by Wiithrich and coworkers has shown that there is a cavity between the protein and the DNA in the major groove of the Antennapedia complex. There are several water molecules in this cavity with a residence time with respect to exchange with bulk water in the millisecond to nanosecond range. These observations indicate that at least some of the specific protein-DNA interactions are short-lived and mediated by water molecules. In particular, the interactions between DNA and the highly conserved Gin 50 and the invariant Asn 51 are best rationalized as a fluctuating network of weak-bonding interactions involving interfacial hydration water molecules. 

Brown [46] continued the contact mechanics work on elastomers and interfacial chains in his studies on the effect of interfacial chains on friction. In these studies. Brown used a crosslinked PDMS spherical cap in contact with a layer of PDMS-PS block copolymer. The thickness, and hence the area density, of the PDMS-PS layer was varied. The thickness was varied from 1.2 nm (X = 0.007 chains per nm-) to 9.2 nm (X = 0.055 chains per nm-). It was found that the PDMS layer thickness was less than about 2.4 nm, the frictional force between the PDMS network and the flat surface layer was high, and it was also higher than the frictional force between the PDMS network and bare PS. When the PDMS layer thicknesses was 5.6 nm and above, the frictional force decreased dramatically well below the friction between PDMS and PS. Based on these data Brown [46] concluded that ... 

The study of acid-base interaction is an important branch of interfacial science. These interactions are widely exploited in several practical applications such as adhesion and adsorption processes. Most of the current studies in this area are based on calorimetric studies or wetting measurements or peel test measurements. While these studies have been instrumental in the understanding of these interfacial interactions, to a certain extent the interpretation of the results of these studies has been largely empirical. The recent advances in the theory and experiments of contact mechanics could be potentially employed to better understand and measure the molecular level acid-base interactions. One of the following two experimental procedures could be utilized (1) Polymers with different levels of acidic and basic chemical constitution can be coated on to elastomeric caps, as described in Section 4.2.1, and the adhesion between these layers can be measured using the JKR technique and Eqs. 11 or 30 as appropriate. For example, poly(p-amino styrene) and poly(p-hydroxy carbonyl styrene) can be coated on to PDMS-ox, and be used as acidic and basic surfaces, respectively, to study the acid-base interactions. (2) Another approach is to graft acidic or basic macromers onto a weakly crosslinked polyisoprene or polybutadiene elastomeric networks, and use these elastomeric networks in the JKR studies as described in Section 4.2.1. 

To prepare an interpenetrating polymer network (IPN) structure, PU networks having ACPA units were immersed with MMA and polymerized. PU-PMMA semi-lPN thus formed was given improved interfacial strength between PU and PMMA phases and showed flexibility with enforced tear strength [65,66]. 

Consequently, interpenetrating phase-separated D/A network composites, i.e. bulk heterojunction , would appear to be ideal photovoltaic materials [5]. By controlling the morphology of the phase separation into an interpenetrating network, one can achieve a high interfacial area within a bulk material. Since any point in the composite is within a few nanometers of a D/A interface, such a composite is a bulk D/A heterojunction material. If the network in a device is bicontinuous, as shown in Figure 15-26, the collection efficiency can be equally efficient. 

The restricted access principle is based on the concept of diffusion-based exclusion of matrix components and allows peptides, which are able to access the internal surface of the particle, to interact with a functionalized surface (Figure 9.2). The diffusion barrier can be accomplished in two ways (i) the porous adsorbent particles have a topochemically different surface functionalization between the outer particle surface and the internal surface. The diffusion barrier is then determined by an entropy controlled size exclusion mechanism of the particle depending on the pore size of adsorbent (Pinkerton, 1991) and (ii) the diffusion barrier is accomplished by a dense hydrophilic polymer layer with a given network size over the essentially functionalized surface. In other words, the diffusion barrier is moved as a layer to the interfacial... 

Variations of R with A suggest a two-step hydration process solvation and formation of disconnected water clusters centered on polar head groups, followed by the formation of a continuous hydrogen-bond network. At low A, Ri depends logarithmically on co, suggesting bidimensional diffusion of protons in the interfacial region between polymer and water. 

For typical catalyst layers impregnated with ionomer, sizes of hydrated ionomer domains that form during self-organization are of the order of 10 nm. The random distribution and tortuosity of ionomer domains and pores in catalyst layers require more complex approaches to account properly for bulk water transport and interfacial vaporization exchange. A useful approach for studying vaporization exchange in catalyst layers could be to exploit the analogy to electrical random resistor networks of... 

Molecular modeling of PT at dense interfacial arrays of protogenic surface groups in PEMs needs ab initio quantum mechanical calculations. In spite of fhe dramafic increase in computational capabilihes, it is still "but a dream" to perform full ab initio calculations of proton and water transport within realistic pores or even porous networks of PEMs. This venture faces two major obstacles structural complexity and the rarity of proton transfer events. The former defines a need for simplified model systems. The latter enforces the use of advanced compufahonal techniques that permit an efficient sampling of rare evenfs. ... 

Redman JA, Grant SB, Olson TM, Estes MK (2001) Pathogen filtration, heterogeneity, and the potable reuse of wastewater. Environ Sci Technol 35 1798-1805 Redman JA, Walker SL, Elimelech M (2004) Bacterial adhesion and transport in porous media Role of the secondary energy minimum. Environ Sci Technol 38 1777-1785 Reeves CP, CeUa MA (1996) A functional relationship between capillary pressure, saturation, and interfacial area as revealed by a pore-scale network model. Water Resour Res 32 2345-2358 Richards LA (1931) Capillary conduction of liquids through porous mediums. Physics 1 318-333... 

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