1,721,603 research outputs found
Carry-over of water and suspension of fines by coarser particulate solids - its influence on the design of DMS regeneration circuits
No full textIn dense medium separation (DMS) systems, a particulate (ore or coal) is treated in a suspension of fine particles in water having a density intermediate between the densities of the mineral phases to be separated. During the process the water and the fine particles constituting the medium adhere to the coarse particles and are carried over from the draining to the washing screen, so that they are extracted from the medium circuit. This extraction is selective, i.e., it is different for water and solids particles; it depends on the size of the particulate and on the viscosity and density of the medium stream considered. For a correct design of the medium regenerationcircuit it is important to know all the above mentioned data. Therefore laboratory research was performed in order to determine the carry-over of fine particles and water due to a particulate. The paper reports the results of this research and gives information useful for the analysis and the design of medium circuits of dense medium separation plants
VIRAL ION CHANNEL PRODUCTION FOR STRUCTURAL STUDIES
Full text linkCrystallization of ion channel proteins is a difficult task for several reasons related to the hydrophobic nature of these proteins, and still is a matter of trials and errors.
In this work I will present an experimental approach to the crystallization of a group of small potassium channels: the viral Kcv channels.
The first part deals with the expression of MA-1D Kcv in the heterologous system Pichia pastoris and its purification by detergent solubilization. Attempts to increase the yield of the protein by modification of the construct at the DNA level are discussed.
In parallel the production of Fab fragments from monoclonal antibodies that recognized the tetrameric form of the protein has been established in order to make protein-antibody complexes that can promote an ordered crystallization process by increasing the polar contacts within the crystals.
In the second part of this thesis, the planar lipid bilayer technique is applied to study the functional properties of several Kcv channels at the single channel level. In particular I have analyzed the block by barium of the wt PBCV-1 Kcv and of its mutants in the 4th site of the selectivity filter, residue Threonine 63. This mutation affects protein sensitivity to barium, but also alters the open probability and the number of subconductance levels. The mutation of an adjacent aminoacid, Serine 62, recovers the wt functions. The T63 mutation was then moved also to another Kcv channel, MA-1D Kcv, to check if the behavior related to the mutation is conserved.
The third part deals with Kesv, a Kcv-like channel founding a related class of viruses, ESV that, differently to Kcv, shows a mitochondrial localization when expressed in heterologous systems. Due to the difficulties encountered in measuring from mitochondria of transfected cells, we have not been able to record currents from this channel in the past. It was therefore decided to produce and purify recombinant protein for functional studies in artificial lipid bilayer. Since all attempts to express it in Pichia pastoris failed, it was decided to express it in a cell-free system in collaboration with the lab of Dr. Bernhard, at the University of Frankfurt. Functional studies on the reconstituted protein channel have revealed that the protein forms a functional, selective K+ channel with overall features of the Kcv-like channels
Influence of contamination and type of ferrosilicon on viscosity and stability of dense medium
No full textParticle segregation in hydrocyclones
No full textHydrocyclones and other dynamic separators are normally fed with pulps consisting of water and solid particles. The solids usually consist of particles of different sizes, shapes and densities. Except in the special case of monocharacteristic particles, the particles are segregated by these differences in size, shape and density. Segregation is magnified by the high values of centrifugal acceleration in the hydrocyclones. This paper develops a segregation theory that indicates the major variables involved. Experimental data on segregation under different operating conditions for mixtures of magnetite and/or ferrosilicon and nonmagnetic minerals are reported
Valutazione con l'ausilio dei fuzzy sets di un indicatore di rischio sismico e degli interventi volti a mitigarlo
No full textRelationship between apparent and actual partition curves of gravity separation processes
No full textThe paper discusses the problem of accuracy in the determination of the partition curve of gravity separation processes, which is strongly affected by both the sharpness of separation of the density analysis system used and the width of the density range selected. The problem is important when the density analysis of the separation products cannot be performed using heavy liquids, but has to be performed using heavy suspensions or using other systems such magnetogravimetric separation. The imperfect separation given by these systems and the use of large density ranges lead to the determination of apparent partition curves instead of actual partition curves for the process. In the paper the relation between apparent and actual partition curves is studied under different conditions through a simulation program. For different input data, special diagrams are given which, once the apparent partition curves and the sharpness of the density cuts are known, allow calculation of the actual partition curves and the related parameters
- …
