Membrane coaxial

Figure 3.4. Membrane-type breakup mode of round liquid jets in coaxial air flow. (Reprinted with permission from Ref. 210.)...

Farago and Chigier 2l() found that at similar aerodynamic Weber numbers, the disintegration modes of a thin liquid sheet in air streams are similar to those of a round liquid jet in a coaxial air stream (Table 3.2). At high aerodynamic Weber numbers, Membrane-Type or Fiber-Type breakup mode may set in. 

The first factor, especially important with ion-selective microelectrodes, can be eliminated by a suitable modification of the measuring instrument, notably by the use of a coaxial microelectrode (see [167] and section 4.2). If an inter-ferent is present in the solution at a concentration at which it does not affect the ISE potential, factors 4 and 6 are not operative. Penetration of the deter-minand into the membrane, factor 5, is very important for the response times of ISEs with ionophores in their membranes, provided that no hydrophobic anion is present in the membrane solution, as has been theoretically treated by Morf et aL [114]. As shown in section 3.3, the presence of a hydrophobic anion stabilizes the conditions in the membrane, with a marked effect on the shortening of the response time [93]. 

The concept of these systems comprises a coaxial fiber. In this fiber, a drug is dispersed or dissolved in a core polymer. The release of the drug from these coaxial fibers is proportional to the concentration gradient in the fiber. If the drug is present in a concentration that exceeds solubility in the membrane, on the adjacent surface the saturated concentration is established. This stationary concentration is responsible for the gradient. 

Get a coaxial cable of 5-10 cm length. Strip the plastic cover of its end in order to leave exposed approximately 2 cm of the Cu wire. The wire exposed will be used as the substrate for the sensor membrane. In the same way, strip approximately 1 cm of the other end s cover. This will offer a mean for the sensor s external electric connection. 

Cover with an epoxy resin (Araldit) the portion of the exposed wire not covered with membrane. Apply epoxy resin around a short portion of the coaxial cable near the exposed wire. This step assures that only the coated wire is in contact with the analyte s solution. Leave the epoxy resin to cure for 24 h at 40°C. 

Thompson, A.J., A.S. Creba, R.M. Ferguson, E.T. Krogh, and C.G. Gill. 2006. A coaxially heated membrane introduction mass spectrometry interface for the rapid and sensitive on-line measurement of volatile and semi-volatile organic contaminants in air and water at parts-per-trillion levels. Rapid Commun. Mass Spectrom. 20 2000-2008. 

Pbres of anodic alumina have been used for the growth of coaxial nanotubes of Ti02 sheathed SiO 92 Electrochemical deposition in the pores of a polymeric alumina membrane generates arrays of Ti02 nanotubes. R>r the coaxial nanotubes, the SiOj nanotubes are first grown inside the pores of the anodic alumina membrane The Ti02 nanotubes are then grown inside the SiOj nanotubes. The existence of Ti-O-Si bonds in the amorphous sheaths is believed to play a role in the formation of these composite nanotubes... 

Figure 5.12. Open-ended coaxial probe for conductivity measurement a geometry, b equivalent circuit [12]. (Reprinted from Journal of Electroanalytical Chemistry, 395, Gardner CL, Anantaraman AV. Measurement of membrane conductivities using an open-ended coaxial probe, 67-73, 1995, with permission from Elsevier.)...

A coaxial probe can also be used to measure the through-plane conductivity of membranes. Figure 5.15 shows the schematic for a coaxial conductivity measurement cell. In this method, the membrane is cut to the same size as the inner conductor, and the measured resistance is the through-plane resistance. The resulting conductivity, 2.4 x 10 2 S/cm, is close to that reported in the literature. 

Gardner CL, Anantaraman AV (1995) Measurement of membrane conductivities using an open-ended coaxial probe. J Electroanal Chem 395 67-73... 

Careful control of the surfactant-water content and the rate of condensation of silica at high alkalinity resulted in hollow tubules 0.3 to 3 pm in diameter.[292] The wall of the tubules consisted of coaxial cylindrical pores, nanometers in size, that are characteristic of those of MCM-41. The formation of this higher-order structure may take place through a liquid-crystal-phase transformation mechanism involving an anisotropic membrane-to-tubule phase change. 

When the size of the pore is comparable to the molecular size, the effect of solvent water on membrane transport cannot be ignored. In a pore there is an area into which the center of water molecule cannot enter due to its collision onto the pore wall. This area is illustrated in Figure 5 as the area surrounded by coaxial circles of radii R-j and R2. The quantity R2-R1 corresponds to the molecular radius of water (D,atej- =... 

The way membranes (in various forms, i.e., cylindrical, coaxial, flat-sheet, spiral-wound, and hollow fiber, etc.) couple with the bioreactor depends on the role the membrane performs. As with catalytic and pervaporation membrane reactors, the simplest configuration consists of two separate but coupled units, one being the bioreactor the other the membrane module. The biocatalyst (e.g., enzymes, bacteria, yeasts, mammalian cells) could, in this case, be suspended in a solution and continuously circulated through the... 

The modelling of enzymatic membrane reactors follows, in general, the same approach as described previously. In enzymatic membrane reactors the catalyst is a macromolecule (enzyme). It can be found either in a free form in the reactor or supported on the membrane surface, or inside the membrane porous structure by grafting it or in the form of a gel obtained by ultrafiltration. As in the case of the whole-cell membrane bioreactors discussed above, the proper calculation of the mass transfer characteristics is of great importance for the modelling of this type of reactor. One of the earliest models of enzymatic membrane bioreactors is by Salmon and Robertson [5.108]. These authors modelled an enzymatic membrane bioreactor, which was made of four coaxial compartments the enzyme is confined within one of the compartments, and one of the substrates is fed in a gaseous form. 

The spinning of asymmetric hollow fibers with the skin on the inside closely resembles the procedure used in casting flat-sheet membranes. Figure 3.1510 is a schematic diagram of a spinneret used to spin these fibers. The degassed and filtered polymer solution is forced under pressure into a coaxial tube spinneret. The liquid is extruded through an annular orifice and the hollow fiber (still liquid) is stabilized and precipitated by an internal coagulating fluid (usually water) which flows out the center tube. 

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