The recovery of biological particles in high-speed continuous centrifuges with special reference to feed-zone break-up effects

In the first part of this thesis the means are described by which an industrial disc stack centrifuge may be scaled-down to process in a meaningful fashion small volumes of particle suspensions. The centrifuge separation characteristics so measured were suitable for direct scale-up predictions of centrifuge performance. Experiments with a dye tracer and a reduced number of discs indicated that the flow through the disc centrifuge is influenced by the position of the separating discs within the disc stack. This influence was also reflected in the separation performance of a particulate suspension. The results were shown to be in the range obtained using a full-scale industrial disc centrifuge. Experiments also showed a distinct trend that the flow rate and in particular the single passage throughput influenced the separation performance. Using a non-linear curve-fitting algorithm it was shown that the grade efficiency curve of a disc centrifuge may be approximated by a two-parameter model equation. In the second part of this thesis the means are described by which various feed zones designs may be examined in respect to particle breakup using small volumes of a diluted protein precipitate suspension. It has been shown that in the high shear fields which are present in the feed zones to centrifuges the precipitate particles are readily disrupted into smaller fragments, the fragment size depending on the strength of the shear field. Examination of three different feed zone types revealed that particle breakup increased in the following order: full-hermetic < hydro-hermetic < semi-hermetic It has also been demonstrated that the bowl speed and in particular the rotational velocity of the distributor ribs has a significant influence on the level of particle breakup in the hydro-hermetic feed zone, while the effects were less pronounced in the full-hermetic feed zone. Based on the results obtained during the above studies the major mechanism of particle breakup is thought to be due to a combination of turbulence and collision of the particle suspension with the rotating distributor ribs. It has been shown that the level of particle breakup is directly related to the circumferential velocity of the distributor ribs

Replica-Immunogold Technique Applied to Studies on Measles Virus Morphogenesis

The replica technique was applied to studies on the dynamic process of measles virus budding on infected HeLa cells. Virus structures were identified by labeling with anti-measles antibodies and protein A-gold. The combination of these two methods enabled us (1) to characterize the sequence of virus budding at the plasma membrane, (2) to localize virus structures on cytoskeletons of infected cells, and (3) to study the influence of Ca2+ ions on virus structures at the plasma membrane. Studies on platinum carbon surface replicas suggest that the process of virus budding is similar to the genesis of cellular microvilli. Replicas prepared from cytoskeletons of infected cells reveal a close association of budding virus with actin filaments composing the outer parts of the networks. Replicas of apical plasma membranes isolated from infected cells show the attachment of viral nucleocapsids to the protoplasmic membrane face of infected cells. These nucleocapsids are not present on membranes prepared from cells treated with calcium and the ionophore A23187. In addition viral cell surface antigens become randomly distributed on these cells. The data suggest that measles virus morphogenesis at the plasma membrane of cultured cells is dependent on the function of the cytoskeleton and may be influenced by Ca2+ ions

Plasma Membrane Antigens Detected by Replica Techniques

Methods are introduced for in situ preparation of cell cultures grown on glass coverslips using the replica technique. Special equipment and handling procedures enabled us to prepare large-sized and stable replicas suitable for ultrastructural and immunocytochemical analysis of the different faces of the plasma membrane (PM): the extraplasmic surface (ES), the complementary extraplasmic (EF) and protoplasmic (PF) fracture face, and the protoplasmic surface (PS). Colloidal gold markers in combination with protein A and monospecific/monoclonal antibodies were used to identify virus-specific antigens at the ES of infected cells. Stereo replicas show a coincident location of gold-labeled virus antigens at the ES and structures visible at the EF as well as at the PS. In addition, the association of these antigens with cytoskeletal elements is demonstrated

Effect of heating rate on the crack formation during baking in carbon anodes used in aluminum industry

The quality of carbon anodes used in aluminum industry depends on the raw material properties and the manufacturing process parameters. It is one of the key factors directly related to the aluminum production cost. The degradation in anode quality such as crack formation increases the energy consumption, the environmental emissions, and the smelter’s overall operating cost. The objective of this work is to investigate the formation of cracks in several industrial green anode samples during baking at different heating rates and to determine the influence of this baking parameter on the crack formation. The samples were characterized before and after baking by measuring a number of physical properties (electrical resistivity, density, etc.) which define the final quality of the anode samples. Also, techniques based on ultra-sound and scanning electron microscopy were used to determine the extent of cracking after baking

Feasibility studies for the measurement of time-like proton electromagnetic form factors from p¯ p→ μ+μ- at P ¯ ANDA at FAIR

This paper reports on Monte Carlo simulation results for future measurements of the moduli of time-like proton electromagnetic form factors, | GE| and | GM| , using the p¯ p→ μ+μ- reaction at P ¯ ANDA (FAIR). The electromagnetic form factors are fundamental quantities parameterizing the electric and magnetic structure of hadrons. This work estimates the statistical and total accuracy with which the form factors can be measured at P ¯ ANDA , using an analysis of simulated data within the PandaRoot software framework. The most crucial background channel is p¯ p→ π+π-, due to the very similar behavior of muons and pions in the detector. The suppression factors are evaluated for this and all other relevant background channels at different values of antiproton beam momentum. The signal/background separation is based on a multivariate analysis, using the Boosted Decision Trees method. An expected background subtraction is included in this study, based on realistic angular distributions of the background contribution. Systematic uncertainties are considered and the relative total uncertainties of the form factor measurements are presented

PANDA Phase One - PANDA collaboration

The Facility for Antiproton and Ion Research (FAIR) in Darmstadt, Germany, provides unique possibilities for a new generation of hadron-, nuclear- and atomic physics experiments. The future antiProton ANnihilations at DArmstadt (PANDA or P¯ANDA) experiment at FAIR will offer a broad physics programme, covering different aspects of the strong interaction. Understanding the latter in the non-perturbative regime remains one of the greatest challenges in contemporary physics. The antiproton–nucleon interaction studied with PANDA provides crucial tests in this area. Furthermore, the high-intensity, low-energy domain of PANDA allows for searches for physics beyond the Standard Model, e.g. through high precision symmetry tests. This paper takes into account a staged approach for the detector setup and for the delivered luminosity from the accelerator. The available detector setup at the time of the delivery of the first antiproton beams in the HESR storage ring is referred to as the Phase One setup. The physics programme that is achievable during Phase One is outlined in this paper