SUBJECTS membrane

While use of thin membranes, subject to bowing, has so far not been successful for use in brackish water demineralizers operating near polarization, such membranes offer more promise in treating solutions of high concentration such as sea water where polarization is less likely to be encountered. 

A later publication from the same group [153] reporting on 31P- and 2H-NMR and DSC studies on zwitterionic and anionic phospholipids in the absence and presence of doxombicin (adriamycin) described different results [152], Doxorubicin had a stronger disordering effect on the membrane of lipid mixtures enriched with anionic lipids. However, extensive segregation of DOPE and DOPA or DPS was not observed even under conditions of Hlrphase formation . According to the authors, the reason for this discrepancy was that in the earlier paper the phase separation was obtained with membranes subject to gel-liquid crystalline phase transition , which was, however, discounted in the first paper. 

In the present paper, we will argue that the experimental results of Sentenac and Benattar,19 which apparently contradict sharply the DLVO theory, can be explained in terms of the traditional theory, when the thermal undulations of the film interfaces are also taken into account. The interface will be treated as a membrane subjected to thermal undulations, which can take place at either constant or nonconstant surface area. In the first case the fluctuations generate bending, while in the second they can produce bothbending and change of area. 

Zundel reports on the hydration of thin polyelectrolyte ion-exchange membranes subject to progressive increases in water sorption. Spectroscopic observations of these systems reflect the hydration of polyion charge centers in the membranes but in the presence of associated counterions, which in turn are progressively hydrated. Zundel worked with polysulfonates and found the spectra of unhydrated polymer salts the cation is attached unsymmetrically to the SOj groups. This mode of attachment leads to a loss of degeneracy in the antisymmetric vibrations. 

Not usable where absolute purification is necessary monovalent radioactive ions pass through the membrane Membranes subjected to fouling... 

Fouling-need for chemical cleaning or backflushing Organic membranes subject to radiation damage... 

Figure 6 Function of a bilayer membrane subjected to a large gradient of oxygen chemical potential. The protective coating diminishes the gradient across the delicate MIEC substrate, which would decompose below lM02)cnt...

The stability of the membranes obtained against various solvents was investigated by Immersing the membranes in the solvent concerned at 40°C for about three weeks. After that their mechanical and osmotic properties were tested again and compared with their properties before the treatment. The results of the experiments are shown in table I. The stability of the membranes subjected to cross-linking by an organic reagent is very satisfactory. Additional treatment with Cr(III) solutions... 

Figure 20.4. Capacitance current measured with monensin-impregnated, black lipid membrane subjected to pulse protonation of one side of the membrane. The traces represent the charge flux, already expressed in molar units as function of time. The signals...

The present review deals with calcium transport and the accompanying enzymatic reactions displayed by the sarcoplasmic reticulum membranes. Subjects such as the molecular organization of the membranes, transport energetics, activity modulation, the development of the calcium transport system and its role in the regulation of muscular activity could not be considered. These problems have been partially reviewed previously (cf. [1-6]). 

The high proton conductivity of hydrated Nafion is the main reason of its wide use in PEM fuel cells. Many studies were devoted to determine this property under different conditions of temperature and water uptake (from vapor and liquid phase) on membranes subjected to different pretreatments, using AC impedance and DC techniques. Slade et al. [305] reviewed the conductivity of Nafion membranes measured tUl 2002, and recently Yadav and Fedkiw [306] have updated the information collected during the last decade. 

Kusoglu A, Karlsson AM, Santare MH, Cleghom S, Johnson WB (2006) Mechanical response of fuel cell membranes subjected to hydro-thermal loading. J Power Sources 161 987—996... 

Hyder et al. (2006) studied the surface and bulk properties of hydrophilic PVA membranes subjected to PV. The PVA membranes were cross-linked in two ways by heating at 125°C or by chemical reaction with glutaraldehyde at room temperature. These membranes were used for the dehydration of EtOH-water mixtures over a range of EtOH concentrations (10%-70%) in feed solution and at varied temperatures (from 25°C to 50°C). The PV results showed that the thermally cross-linked membrane was more hydrophilic than the chemically cross-linked membranes, and this helped transport water at a higher flux through the membrane. However, the selectivity of the thermally cross-linked membrane was lower and water flux through the membrane became higher when compared with the chemically cross-linked membranes. The dehydration results were correlated with the results of the physiochemical measurements of the membranes. 

Superiority of PI membranes subjected to PV over other polymeric membranes has been highlighted by Jiang et al. (2009). Membranes prepared from soluble Pis derived from 4,4 -diamino-3,3 -dimethyldiphenylmethane was used as a PV membrane for EtOH-water mixture (Wang et al.2006). The average value of the separation factor and total permeation flux were 46-108 and 660-1380 g/m h, respectively. Yanagishita et al. (1995) used asymmetric PI (aromatic) membranes (flat sheet) prepared by a phase inversion process, for the separation of alcohol solution by PV. The membrane exhibited separation factors of afHjO/EtOH) = 900 and a(H20/2-Pr0H) = 11,000 with a flux of 0.45 kg/m h for 95 vol% alcohol aqueous solution at 60°C. The membrane showed stable performance for 3 months. 

Wang et al. (2002) demonstrated a composite membrane (subjected to PV) of an asymmetric poly(4-methyl-l-pentene) (TPX) membrane dip-coated with poly(acrylic acid) (PAA). To improve the interface peeling of the PA A/TPX composite membranes, the surfaces of TPX membranes were modified by residual air plasma in a tubular-type reactor. The plasma treatments were effective in rendering the asymmetric TPX membrane hydrophilic. Optimal results were obtained with PAA/TPX composite membrane prepared from the PAA/ethylene glycol (EG)/aluminum nitrate = 1/2/0.05 coating solution at 5 W/30 s plasma treatment condition. Concentration of the water in the permeate was nearly 100%, and a permeate flux of 960 g/m h was obtained with a 3 wt% feed acetic acid concentration. 

Oxygen separation by using a membrane is expected to be a real possibility, thanks to developments in mixed ionic and electronic conductors (MIECs). With mixed ionic and electronic conduction, oxide-ion conductors selectively permeate oxygen as a form of oxide ion. The mixed oxide-ion and electronic conductors used for this purpose are referred to as oxygen-permeable membranes. An oxygen-permeable membrane subjected to an oxygen potential gradient at elevated temperatures of around 700—1000 °C leads to the ambipolar conduction of oxide ions and electrons, as shown... 

On mechanical behavior and in-plane modeling of constrained PEM fuel cell membranes subjected to hydration and temperature cycles. J. Power Sources,... 

Janz et al. (1980) developed a mathematical model for the finite deformation of a prolate spheroidal membrane subjected to a hydrostatic pressure and unconstrained with respect to eccentricity. Figure 1 displays the deformed and undeformed geometry of this membrane model. This deformed geometry is determined by solving a system of differential equations for the stretch ratios and... 

The membranes subjected to FT were further investigated by SEM to see to what extent the membrane surfaces were corroded by the... 

The permanent proton conductivity of the PA-PBI-based membranes was investigated on membranes subjected to accelerated leaching in order to completely remove the fraction of the free acid. Such tests were carried out by means of washing steps of the doped membranes in water-methanol mixtures at 80 °C for several days. Quantitative determinations of H3PO4 released in the water baths were carried out by inductively coupled plasma (ICP) analyses and/or proper titration procedures. 

In one of the first papers dealing with dielectric elastomers, Pelrine et al. (1998) proposed a widely used model to analyze stresses and strains in a thin elastomeric membrane subjected to a transverse electric field. The notion of Maxwell s pressure Pel = eE is well known among the EAP research community. How does this concept match with the theory developed here This can be easily explained recalling that fire stress measure adopted by Pelrine et al. (1998) corresponds to our and their model is valid only for incompressible materials. 

The H2 permeation rate, P (H2), and the permeation rate ratio P (H2>/P (CH ) are also given in the figure. The membrane subjected to the oxidative treatment showed lower P (H2) and higher P (H2>/P (CH ) ratio than the untreated precursor membrane. As for the pyrolyzed membranes, P (H2) kept decreasing with an increase in pyrolysis temperature, while the P (CH ) ratio showed a maximum at about 800°C. More specifically, P (H2>= 1.0 x lo- cm fSTPj/fcm s cmHg) and P (H2)/P (CH ) ratio = 132 at the pyrolysis temperature of 700°C while they... 

It is evident fi-om Eq. (13.3.12) that a measurement of the steady-state flux alone does not yield D, but instead gives the product DS, called the permeability. To obtain the diffiisivity, we have to know the value of the solubility or make one additional measurement this is usually the time lag before a steady state is reached in the permeation experiment [26]. The time lag can be related to D by solving Eq. (13.2.11) for one-dimensional transient diffusion through the initially solute-fi ee membrane, subject to the boundary conditions (see Fig. 13.4) ... 

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