Laboratory cooling techniques

The possibility of overcoming encrustation problems by applying direct contact cooling techniques (section 8.4.1) has been explored for the separation of organic eutectic systems by suspension melt erystallization (Kim and Mers-mann, 1997 Bartosch and Mersmann, 1999). These laboratory studies, whieh utilized both gas (air) and liquid (water) as eoolants were aimed at measuring heat transfer and kinetic data and observing the erystal produet eharaeteristies. Eventual industrial application (section 8.2.3) appears possible. 

The polymer/additive system in combination with the proposed extraction technique determines the preferred solvent. In ASE the solvent must swell but not dissolve the polymer, whereas MAE requires a high dielectric solvent or solvent component. This makes solvent selection for MAE more problematical than for ASE . Therefore, MAE may be the preferred method for a plant laboratory analysing large numbers of similar samples (e.g. nonpolar or polar additives in polyolefins [210]). At variance to ASE , in MAE dissolution of the polymer will not block any transfer lines. Complete dissolution of the sample leads to rapid extractions, the polymer precipitating when the solvent cools. However, partial dissolution and softening of the polymer will result in agglomeration of particles and a reduction in extraction rate. 

The Ba.C) N, nanotubes and fullerene-like structures have been synthesized by various laboratories in recent years. The most popular method is the plasma arc technique. The first report on the synthesis of BN nanotubes was by Zettl and coworkers (55). Since BN is an insulator, a composite anode was prepared from a tungsten rod with an empty bore in the center, which was stuffed with a pressed hexagonal BN powder. For the cathode, a water-cooled Cu rod was used. The collected gray soot contained limited amount of multi wall BN nanotubes. It is possible that in this case, the tungsten serves also as a catalyst. By perfecting this method, macroscopic amounts of double-wall BN nanotubes of a uniform diameter (2 nm)... 

The unsaturated zone, where most of the low-level waste is buried, could probably be used for high-level waste after cooling but it does not lend itself to the regional approach to defining permeability. Additionally, the laboratory methods of evaluating permeability of unsaturated material are extremely difficult to perform consistently. However, an air permeability technique that may prove useful in evaluating the zone between the surface and the water table was developed by Weeks W. The technique uses normal barometric fluctuations measured at different depths in the formation to determine permeability to air which can be used to determine permeability to water. 

Filter Particulate Analysis. In the laboratory, the filters were immediately placed in a desiccator for 24 hrs and then weighed. The particulate concentration was calculated from this weight and the previously determined tare weight of the filter. The filters were analyzed for mercury by a procedure previously reported by the author (11) consisting of boiling the filters in concentrated nitric acid. After being cooled, aliquots of these solutions were pipetted into the interchangeable sample tubes and analyzed by the direct aeration technique. 

In 1991. a research team tEcole Normal Superieure. Parist reported the cooling of a sample of cesium atoms to 2.5 pK. At about the same lime, a research group (.hunt Institute for Laboratory Astrophysics. Boulder. Coloiado) inputted the achievement ol 5 iK The aforementioned "optical molasses" technique was used in both eases. 

Rocketborne Field-Widened Interferometer-Spectrometer. The rocket-borne field-widened interferometer-spectrometer (RBFWI) is an example of an instrument that uses emission techniques to make broad-band spectral measurements in the 2 - 7.5 pm spectral region in the upper atmosphere. Figure 10 illustrates the concept of this cryogenically-cooled instrument developed at Utah State University under an Air Force Geophysics Laboratory contract. 

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