Membranes overview

I. Pinnau and B. D. Freeman, Formation and modification of polymeric membranes overview. In Membrane Formation and Modification, I. Pinnau and B. D. Freeman (eds.), American Chemical Society, Washington, DC, pp. 1-22 (2000). 

FIGURE 2-11 Covalent and noncovalent linkage of monomers to form biopolymers and membranes. Overview of the cell s chemical building blocks and the macrostructures formed from them, (fop) The three major types of biological macromolecules are each assembled by the polymerization of multiple small molecules (monomers) of a particular type proteins from amino acids (Chapter 3), nucleic acids from... 

Palladium-based Membranes Overview and Potential for Hydrogen Purification... 

IV. MOLECULAR DYNAMICS IN MEMBRANES A. Overview of Dynamic Processes in Membranes... 

This chapter has given an overview of the structure and dynamics of lipid and water molecules in membrane systems, viewed with atomic resolution by molecular dynamics simulations of fully hydrated phospholipid bilayers. The calculations have permitted a detailed picture of the solvation of the lipid polar groups to be developed, and this picture has been used to elucidate the molecular origins of the dipole potential. The solvation structure has been discussed in terms of a somewhat arbitrary, but useful, definition of bound and bulk water molecules. 

By the time the next overview of electrical properties of polymers was published (Blythe 1979), besides a detailed treatment of dielectric properties it included a chapter on conduction, both ionic and electronic. To take ionic conduction first, ion-exchange membranes as separation tools for electrolytes go back a long way historically, to the beginning of the twentieth century a polymeric membrane semipermeable to ions was first used in 1950 for the desalination of water (Jusa and McRae 1950). This kind of membrane is surveyed in detail by Strathmann (1994). Much more recently, highly developed polymeric membranes began to be used as electrolytes for experimental rechargeable batteries and, with particular success, for fuel cells. This important use is further discussed in Chapter 11. 

The so-called El-emission class describes a wood panel presenting formaldehyde emission which is low enough to prevent any danger, irritation or inflammation of the eyes, nose and mouth mucous membranes. However, it is important that not only the boards themselves, but also the veneering and carpenter s adhesive resins, laquers, varnishes and other sources of formaldehyde are under control, since they also might contribute to the mixture steady state formaldehyde concentration [9]. Table 3 gives an overview on some European regulations. However, it is necessary here to introduce the principal types of composite wood products, especially panels, that are produced in this industry ... 

Paulson, David J., "An Overview of and Definitions for Membrane Fouling," Osmonics, Inc. Presented at 5th Annual Membrane Technology/Planning Conference, October 1987, Cambridge, MA. 

In this chapter we will provide an overview of the application of membrane separations for chiral resolutions. As we will focus on physical separations, the use of membranes in kinetic (bio)resolutions will not be discussed. This chapter is intended to provide an impression, though not exhaustive, of the status of the development of membrane processes for chiral separations. The different options will be discussed on the basis of their applicability on a large scale. 

Armstrong and Jin [15] reported the separation of several hydrophobic isomers (including (l-ferrocenylethyl)thiophenol, 1 -benzylnornicotine, mephenytoin and disopyramide) by cyclodextrins as chiral selectors. A wide variety of crown ethers have been synthesized for application in enantioselective liquid membrane separation, such as binaphthyl-, biphenanthryl-, helicene-, tetrahydrofuran and cyclohex-anediol-based crown ethers [16-20]. Brice and Pirkle [7] give a comprehensive overview of the characteristics and performance of the various crown ethers used as chiral selectors in liquid membrane separation. 

Although blood pressure control follows Ohm s law and seems to be simple, it underlies a complex circuit of interrelated systems. Hence, numerous physiologic systems that have pleiotropic effects and interact in complex fashion have been found to modulate blood pressure. Because of their number and complexity it is beyond the scope of the current account to cover all mechanisms and feedback circuits involved in blood pressure control. Rather, an overview of the clinically most relevant ones is presented. These systems include the heart, the blood vessels, the extracellular volume, the kidneys, the nervous system, a variety of humoral factors, and molecular events at the cellular level. They are intertwined to maintain adequate tissue perfusion and nutrition. Normal blood pressure control can be related to cardiac output and the total peripheral resistance. The stroke volume and the heart rate determine cardiac output. Each cycle of cardiac contraction propels a bolus of about 70 ml blood into the systemic arterial system. As one example of the interaction of these multiple systems, the stroke volume is dependent in part on intravascular volume regulated by the kidneys as well as on myocardial contractility. The latter is, in turn, a complex function involving sympathetic and parasympathetic control of heart rate intrinsic activity of the cardiac conduction system complex membrane transport and cellular events requiring influx of calcium, which lead to myocardial fibre shortening and relaxation and affects the humoral substances (e.g., catecholamines) in stimulation heart rate and myocardial fibre tension. 

Sol-gel techniques have been widely used to prepare ceramic or glass materials with controlled microstructures. Applications of the sol-gel method in fabrication of high-temperature fuel cells are steadily reported. Modification of electrodes, electrolytes or electrolyte/electrode interface of the fuel cell has been also performed to produce components with improved microstructures. Recently, the sol-gel method has expanded into inorganic-organic hybrid membranes for low-temperature fuel cells. This paper presents an overview concerning current applications of sol-gel techniques in fabrication of fuel cell components. 

The first two volumes in the series New Comprehensive Biochemistry appeared in 1981. Volume 1 dealt with membrane structure and Volume 2 with membrane transport. The editors of the last volume (the present editor being one of them) tried to provide an overview of the state of the art of the research in that field. Most of the chapters dealt with kinetic approaches aiming to understand the mechanism of the various types of transport of ions and metabolites across biological membranes. Although these methods have not lost their significance, the development of molecular biological techniques and their application in this field has given to the area of membrane transport such a new dimension that the appearance of a volume in the series New Comprehensive Biochemistry devoted to molecular aspects of membrane proteins is warranted. 

General anesthetics are usually small solutes with relatively simple molecular structure. As overviewed before, Meyer and Overton have proposed that the potency of general anesthetics correlates with their solubility in organic solvents (the Meyer-Overton theory) almost a century ago. On the other hand, local anesthetics widely used are positively charged amphiphiles in solution and reversibly block the nerve conduction. We expect that the partition of both general and local anesthetics into lipid bilayer membranes plays a key role in controlling the anesthetic potency. Bilayer interfaces are crucial for the delivery of the anesthetics. 

Electric field sensitive dyes respond to changes in electrical membrane potential by a variety of different mechanisms with widely varying response times depending on their chemical structure and their interaction with the membrane. An understanding of the mechanisms of dye response and their response mechanisms is important for an appropriate choice of a probe for a particular application. The purpose of this chapter is, therefore, to provide an overview of the dyes presently available, how they respond to voltage changes, and give some examples of how they have been applied. Finally, because there is still scope for the development of new dyes with improved properties, some directions for future research will be discussed. 

This volume gives an overview of the current status and an outlook to future more reliable predictive approaches. It is subdivided in five sections dealing with studies of membrane permeability and oral absorption, drug dissolution and solubility, the role of transporters and metabolism in oral absorption, computational approaches to drug absorption and bioavailability, and finally with certain drug development issues. 

Fig. 8.9 Condensed overview of the interaction of Ca2+ with intracellular proteins (after S. Forsen). The extracellular systems are equally important. The connections between the Ca2+ input and linked signalling from the membrane are shown.

Ghosal, K. and B.D. Freeman, Gas separation using polymer membranes an overview, Polym. Advan. Technol., 5,673-697,1994. 

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