Delamination membranes

However, in interphase delaminating neuroblasts, which are known to have completed S-phase and are at the G2 stage of the cell cycle, this codependence of Baz/Insc/Pins seen in mitotic neuroblasts does not apply. Delaminating neuroblasts possess an apical membrane stalk which retains contact with the epithelial surface and this is where apical cortical localization of Insc is initially seen (see Fig. 2). This initial localization of Insc to the apical stalk occurs... 

The above test provides a basis for evaluating a seal material s capability at the desired operating temperature. However, in realistic stack conditions, a seal material is under a shear stress. A double tube arrangement can be used to study the seal behavior. A disc can be sealed on both sides, and both tube enclosures can be pressurized to the same level. Such condition will eliminate the flexing of the membrane causing the seal to delaminate at a fairly low pressure when tested above Tg. In fact, a repeat test of the above seal with a double-tube arrangement showed that the seal could withstand 20 psi pressure before a small leak developed. 

Mench et al. developed a technique to embed microthermocouples in a multilayered membrane of an operating PEM fuel cell so that the membrane temperature can be measured in situ. These microthermocouples can be embedded inside two thin layers of the membrane without causing delamination or leakage. An array of up to 10 thermocouples can be instrumented into a single membrane for temperature distribution measurements. Figure 32 shows the deviation of the membrane temperature in an operating fuel cell from its open-circuit state as a function of the current density. This new data in conjunction with a parallel modeling effort of Ju et al. helped to probe the thermal environment of PEM fuel cells. 

At the microscopic scale, mechanical stress can also develop due to the property-mismatch of the electrode and the membrane. The porous electrode is typically much weaker than the membrane and has lower hygrothermal expansion coefficient than the membrane hence it can develop mud-cracks and delaminates from the membrane after RH cycling. This will perturb the local electrochemical processes and results in non-uniform decay of membranes. 

Film Delamination Most sensors have a film or membrane used as a sensing layer and/or a biocompatible layer. When this film is not attached properly or degrades, it can fail and delaminated from the electrode surface, causing the sensor to lose function through increased mass transfer resistance, diminished electron transfer, and/or its ability to deter the foreign body reaction.31... 

This structure (Fig. 7.14) has received much attention due to the role it plays in the hatching process (see below). It is not a typical unit membrane but resembles a membranous lamina and consists of a layer of regularly arranged granules bounded on both sides by a number of lamina (442). Its chemical composition has not been determined but, in taeniid cestodes, there is some histochemical evidence that it may be a lipoprotein (442). It is apparently formed by the delamination of the inner part of the inner envelope, detaching from it as a thin, separate layer. 

This layer appears to be unique to H. nana. It forms a layer between the oncospheral membrane and the oncosphere (Fig. 7.11). It is apparently formed by the delamination of the epithelial covering of the oncosphere into two layers, separated from each other by membranes - the outer polar filament layer and the inner embryonic epithelium. It has been suggested that the polar filaments in H. nana are reminiscent of the tendrils of the egg cases of elasmobranchs and may serve to delay expulsion of the oncosphere from the mammalian intestine by becoming entangled amongst the intestinal villi or mucous lining of the gut. This may further serve to bring the oncosphere into close contact with the gut wall for successful penetration to take place (204). 

Somewhat surprisingly, however, only a very limited amount of literature is available on hydrothermal stability of even the most commonly applied mesoporous membrane type, namely y-alumina membranes on OC-AI2O3 supports. These mesoporous y-alumina membranes are the common supports for the microporous silica membranes to be used in membrane steam reformers. In the investigations that finally led to the present study, delamination of the y-alumina membrane from the OC-AI2O3 supports in hot steam was found to be a major compli-... 

The surface area of the membrane materials was measured before and after SASRA treatment by a single point BET instrument with a TC-detector. Three samples were run in parallel and the amount of adsorbed nitrogen on the sample surface was measured and used for calculating the surface area. The phase composition was characterised by XRD. After SASRA treatment the adherence of the membranes to the support was tested by the Scotch Tape Test [26], In this test, a piece of Scotch Tape was applied firmly with the sticky side onto the membrane surface and torn off rapidly. If the membrane layer was torn off together with the tape, it was concluded that delamination had occurred. For membranes that showed no sign of delamination, the pore-size was measured with permporometry for a second time. 

Figure la SEM micrograph of a delaminated conventional mesoporous y-alumina membrane after SASRA... 

Standard y-alumina membrane-layers on CX-AI2O3 supports not treated with MAP and prepared as described in [10] always came off in the Scotch Tape Test after SASRA treatment. As shown in Figure 1 (a and b), in these membranes a crack is formed in the membrane-support interface leading to delamination. When the support was treated with MAP, however, after steam treatment no delamination was observed. 

Some vendors place both passes on a single skid, thereby eliminating the RO feed pump to the second pass RO. The backpressure from the first pass is sufficient to provide the applied pressure required of the second pass. Care must be taken so that permeate backpressure does not exceed the applied influent pressure to the first pass, or osmosis rather than reverse osmosis will occur. Additionally, high back pressure can lead to delamination of the membranes (see Chapter 12.1.2.1 and Figure 12.1)... 

Figure 13.1 Membrane delamination caused by high permeate pressure.

Hollow fiber membrane modules can be backwashed to remove foulants whereas tubular and most spiral configurations cannot be backwashed. Backwashing of traditional spiral-wound modules would break the glue lines holding the membrane leaves together or cause blistering and delamination of the membrane from the backing in both spiral and tubular modules (TriSep Corporation has recently developed a back-washable, spiral-wound module (SpiraSep—US patent 6,755,970), that is used in immersed systems see below). 

Other types of commercial coatings and membranes were also evaluated in the test facility at that time, and analysis indicated the performance of the sulfur composite was superior to all the others tested. At the conclusion of the test, all the other systems were in various stages of failure because of cracking, crazing, delamination, or tearing. 

Delamlnation. As was mentioned earlier, specimen L-l in Figure 10 had areas where delamination apparently had occurred. This observation suggested that the metal wrapping might be a membrane covered... 

The first applications of CMRs have concerned high temperature reactions. The employed inorganic membranes, characterized by higher chemical and thermal stability with respect to polymeric membranes, still today suffer from some important drawbacks high cost, limited lifetime, difficulties in reactor manufacturing (delamination of the membrane top-layer from the support due to the different thermal expansion coefficients). 

Zeolites are currently manu ctured as micron size crystals and compacted into millimeter size pellets for applications as packed beds. In many catalytic and adsorptive applications, mass and heat transfer properties could potentially be improved by structuring the zeolite in a different way. Research in this area led already to significant achievements. Alternatively structured zeolite matter are e.g. delaminated zeolites [1], supported zeolite films and membranes [2], hybrid structures with microporosity in walls of ordered mesoporous materials [3-6] and nanosized zeolites such as those synthesized in confined space [7]. The common property of these alternative zeolites is that at least in one direction, the zeolite framework has a dimension of around a nanometer. 

Fortunately, hollow fibers may be cleaned by back-washing which tends to compensate for their propensity to foul. Manufacturers of tubes, plate and frame units, and spiral wound modules do not recommend back-washing due to problems with membrane delamination and glue line seal rupture. Because hollow fibers are self-supporting and hold up well under the compression force of a reverse transmembrane pressure drop, they can easily withstand back-wash pressures of 15 to 20 psi. However, the back-wash fluid should be filtered to remove any particles which would tend to lodge in the porous wall of the fiber. 

Figure 5.5 Cross section and surface of a microporous polysulfone sheet used in composite reverse osmosis membranes (a) total cross section of a polysulfone sheet cast on a nonwoven polyester fabric, then delaminated prior to freeze-fracture for SEM (note fiber trecks on backside of the sheet) (b) backside of sheet showing cellular structure, which extends through 85% of the sheet thickness (c) transition region from cellular to nodular structure near film surface (d) dense nodular structure at the surface (e) high magnification of the extreme top surface cross section (f) high magnification view of the surface structure showing tha texture of the top surface.

A SEM micrograph of a co-sintered multilayer reactor is presented in Fig. 6.8 no delamination or interfacial reaction can be observed on the membrane. These co-sintered multilayer reactors, only based on perovskite materials, present higher oxygen flux than dense 1 mm thick membranes in an air/argon gradient. 

As will be shown later, during cathodic delamination of a polymer from a metal surface due to ingress of an electrolyte into the metal/polymer interface, an additional liquid phase could be formed between the substrate and the organic layer. In this case, the metal/electrolyte interface can be treated as a conventional electrochemical interface, but an additional Galvani potential difference ADonnan potential or membrane potential [24—26]) has to be taken into account at the electrolyte/polymer interface. The latter is directly correlated with the incorporation of ions into the polymer membrane according to Eq. (14). 

---