Anion-exchange membranes were evaluated for the capture of a small protein (α-lactalbumin, 3.5-nm diameter) and a large protein (thyroglobulin, 20-nm diameter). The static binding capacity equaled the dynamic binding capacity and increased with increasing protein size. This result was in agreement with calculations based on monolayer coverage on the membrane surface and an absence of mass-transfer limitations. In contrast, for anion-exchange beads, the static capacity was the same for both proteins, and the dynamic capacity decreased strikingly with increasing protein size. These observations were attributed to very slow intrapore diffusion for large proteins in the beads, resulting in surface binding only. This work has important applications in the selection of chromatography media for the purification of viruses and plasmid DNA. Specifically, membranes with a high capacity for large biomolecules (20−300 nm) and a low capacity for small host-cell proteins and endotoxin contaminants are preferable to beads for the purification of such biomolecules.
The flow structure of the dispersed gas phase within an aerated stirred tank reactor of pilot scale (600L) has been investigated by means of a new ultrasound reflection technique. A compact implementation of the new measuring technique is described in this article. It allows the investigation the flow structure of the dispersed gas phase in real multiphase flows within arbitrary large reaction vessels. Measurements have successfuly been performed even in complex biotechnological and chemical production systems. The measuring device exploits the Doppler-shift of ultrasound pulses upon reflections at the surfaces of moving bubbles. Only a single measuring probe needs to be introduced into the dispersion. Bubble velocity distributions can be obtained within a few minutes, even during production processes in highly viscous media. The device is simple to use, since it is fully automized by means of integrated microprocessors.On a CtudiC la structure de I'Ccoulement de la phase gazeuse disperste dans un rCacteur agitC aCrC ?i I'Cchelle pilote (600 L) au moyen d'une nouvelle technique de rkflexion B ultrasons. On dCcrit dans cet article la faqon dont a miniaturisi la technique de mesure. Cette technique permet l'btude de la structure de I'Ccoulement de la phase dans des Ccoulements multiphasiques reels ?i I'intCrieur de grands rkacteurs. On a m&me rCussi ?i effectuer des mesures dans des rkacteurs biochimiques et chimiques complexes. Le systbme de mesure exploite le dCcalage par effet Doppler de la frCquence de pulses ultrasonores causC par la rhflexion des ondes sur la surface de bulles en mouvement. II n'est nkcessaire d'introduire qu'une seule sonde de mesure dans la dispersion. Les distributions de vitesse des bulles peuvent &tre obtenues en quelques minutes, mCme durant les procCdCs de production dans des milieux trks visqueux. Le systbme est facile ?i utiliser du fait qu'il est complbtement automatis6 au moyen de microprocesseurs intCgrCs.
Bubble properties in stirred tank bioreactors equipped with standard radial flow Rushton turbines have been investigated. Bubble velocity patterns within a stirred tank reactor were derived from measured local bubble velocity distributions. Local information on specific interfacial areas, bubble number densities and bubble diameters together with local gas hold-ups, measured in a model medium at gas flow rates which are employed in practice, is presented. All measurements were performed with two new ultrasound pulse techniques which can be used in model media as well as during real cultivation processes.
The Formation Tester is a tool which is run in either open or cased holes on a conventional logging cable. Tests may be made rapidly and safely at various depths in the hole. The Formation Tester provides: a sample of the formation fluids, GORs, a means to determine accurate gas-oil, or oil-water contacts, bottom hole pressure data, an index to the permeability of the small zone adjacent to the tool. There are many formation testing problems peculiar to soft formations. Development of solutions has been very successful. The problems encountered and their solutions were:The percentage of successful tests was less than expected because unconsolidated sands would not support the packer. This problem was almost completely solved by the introduction of the shaped charge and snorkel testers.The number of fishing jobs needed to be reduced. This problem was overcome by keeping the cable in constant motion so that hydrostatic pressure could not seal the cable to the wall of the hole.Interpretation was confusing. It was found after many tests that the amount of oil or gas recovered was the factor which determined what the ultimate production would be. The water produced should not be used as an indicator of final production. The Wire Line Formation Tester has recently been used in cased holes with very good success. The operation and application are similar to those in open holes with the following additional applications: old wells may be tested, cement jobs can be evaluated for channeling, directional holes may be tested without wire line hazards. Introduction The Wire Line Formation Tester has, in the past year, become widely used and is now becoming a standard tool for formation evaluation in Southern Louisiana. During the first two years of testing the soft formations of these coastal regions, results were not as satisfactory as had been anticipated. Many problems were present. Many solutions were attempted. The purpose of this paper is to describe the equipment and techniques which have contributed to the recent success of the tester. In addition, the newly developed method of testing in cased holes will be discussed.
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