Water-glass interface, sample

Electron Microscopy. A modified Langmuir-Blodgett method was used to transfer monolayer samples to electron microscope screens that were sandwiched between Formvar and a glass plate (5, 6). A motor drive raised the plate slowly through the water-air interface, and a variable-speed motor drive moved the compressing barrier at a rate that maintained constant surface pressure during the transfer. Many samples were transferred at low surface pressures because the lipids in membranes are undoubtedly subjected to relatively small horizontal or surface pressures. 

Containers selected to transport fuel or the fuel/water bottom to a laboratory should be impervious to the fuel. If possible, sterile glass or plastic (i.e., high density polyethylene or polypropylene) containers are suggested. The Institute of Petroleum (1996) recommends using silicone rubber stoppers or plastic screw caps with inserts to cap these bottles. All samples should be properly labeled with the company name, the location of the tank, the location within the tank where the sample was taken, the type of sample collected (either fuel, water bottom or fuel/water bottom interface) and the date and time the sample was collected. 

The situation is more complex when various other ingredients are added to PBT. Glass fibers, for instance, may lose adhesion from the resin due to the action of water on the glass-PBT interface, independent of the PBT-matrix reaction. This action will depend on specific contact conditions such as time, temperature and pH. In some instances, fiber-to-matrix adhesion can be recovered when the sample is dried, resulting in the recovery of some mechanical properties (if the PBT matrix is not too severely degraded). Other additives can introduce additional complications. 

A sample of the fuel is shaken, using a standardized technique, at room temperature with a phosphate buffer solution in very clean glassware. The cleanliness of the glass cylinder is tested. The change in volume of the aqueous layer and the appearance of the interface define the water reaction of the fuel. 

Figure 9.29 Membrane formation by meteoritic amphiphilic compounds (courtesy of David Deamer). A sample of the Murchison meteorite was extracted with the chloroform-methanol-water solvent described by Deamer and Pashley, 1989. Amphiphilic compounds were isolated chromatographically on thin-layer chromatography plates (fraction 1), and a small aliquot ( 1 p,g) was dried on a glass microscope slide. Alkaline carbonate buffer (15 p,l, 10 mM, pH 9.0) was added to the dried sample, followed by a cover slip, and the interaction of the aqueous phase with the sample was followed by phase-contrast and fluorescence microscopy, (a) The sample-buffer interface was 1 min. The aqueous phase penetrated the viscous sample, causing spherical structures to appear at the interface and fall away into the medium, (b) After 30 min, large numbers of vesicular structures are produced as the buffer further penetrates the sample, (c) The vesicular nature of the structures in (b) is clearly demonstrated by fluorescence microscopy. Original magnification in (a) is x 160 in (b) and (c) x 400.

It follows from the fit presented in Fig. 46 that Eb energies for all porous glass samples are about the same value of 33 kJ mol-1. However, for sample B the value of Eh is about 10% less than those for samples A and C. This fact can most likely be explained by the additional chemical treatment of sample B with KOH, which removes the silica gel from the inner surfaces of the pore networks. It is reasonable to assume that the defects generally form at the water interfaces, and only then penetrate into the water layer. Thus, it seems that the KOH treatment decreases the interaction between the water and inner pore surfaces and, consequently, decreases the defect formation energy Eb. 

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