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The aim of the thesis was to optimise the separation and purify an amino acid solution consisting of mono-valent amino acids. Amino acids have historically been separated by chromatographic separation for analytical requirements but separation commercially has not been possible due to the close physical and chemical properties of the amino acids. The study looks at two amino acids, isoleucine and alpha amino butyric acid and used operating and process variables to conclude whether a commercial application is possible. A 3m glass column operating at atmospheric conditions was set up in the development laboratory at SA Bioproducts for test work. Pulse tests were carried out to evaluate the separation of the individual amino acids and the samples were analysed using HPLC. The column incorporated a jacket which allowed for constant temperature during the experiments. Experiments started initially with the column being tested for hydraulic consistency and this was done using resin in the Na+ ionic form and passing a NaCI feed stream over the resin as a pulse. A base case was chosen and this using a feed volume of 0.1 bed volume, an eluant flow of 1 bed volume per hour, feed concentrations of 2% and an operating temperature of 75°C. The resin was used in the Na+ ionic form, with a particle size of 320llm, and a height of 1.5m. Results of the base case indicated a low resolution of 38%, and low recoveries at 11.85% at purities of 86%. Evident from the chromatogram was that isoleucine was held more strongly than AABA by the resin as isoleucine was eluted last. Increasing the concentration of the feed to 4% moved the peaks closer and caused more overlapping thereby decreasing the recovery. Decreasing the concentration resulted in better separation. From the results it was concluded that the separation was dependant on concentration. The next variable which was studied was the effects of changing the feed pulse volume. For this the feed volume was increased to 0.2BV and this ended up shifting the chromatogram to the right, with lower separation efficiency being measured. The effects of eluant flowrate were studied next. Decreasing the eluant flowrate to O.SBVIh resulted in sharper peaks and less overlapping. The conclusion reached was that the higher the contact time between the amino acids and the resin, the greater would be the separation efficiency. Increasing the flowrate of the eluant reduced the contact time and more overlapping was observed. The effects of temperature were also investigated. The experiment carried out at 90°C, showed very similar separation to the base case with higher recoveries. Decreasing the temperature to 30°C decreased the separation efficiency drastically. The experiments proved that an increase in temperature increased the kinetics, and allowed the amino acids to enter and exit the bead quicker. Once operating conditions have been evaluated, the resin was converted to the Ca2+ ionic form, and all other conditions were run according to the base case. ' From the chromatogram it was obvious that the amino acids were held more strongly by the resin and the retention time was increased thereby increasing the recovery. Changing the particle size of the resin from 320~m to 220~m increased the separation efficiency due to the faster kinetics. Increasing the height of the resin was attempted by adding more resin to the column. The separation efficiency was increased. Finally a optimised experiment was attempted where a 2% feed solution was used, feed volume was 0.1 BV, temperature of 90°C, eluate flow of O.SBV Ih, resin in the Ca2+ ionic form, with a particle size range of. 21 0-230~m, and resin height of 1.8m. The chromatogram indicated high peak separation efficiencies and high recoveries. The results indicated that the study was feasible. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2005.

The chemical and process industries rely largely on filtration processes to separate solid-liquid process / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2010.

No description available.

Dans cette thèse, nous nous sommes intéressés aux méthodes de séparation de mélanges convolutifs de signaux cyclostationnaires, et particulièrement de signaux issus de systèmes de communications numériques. Les résultats de ces travaux concernent principalement les méthodes de séparation basées sur la minimisation d'un critère du type CMA avec une approche par déflation. Dans la première partie de ce manuscrit nous nous sommes concentrés sur les mélanges de sources non-circulaires à l'ordre 2, notamment des sources BPSK ou CPM d'indice 1/2. Nous avons montré que dans le cas où les sources ont des caractéristiques différentes (en terme de débit et de résidu de porteuse) la minimisation du critère du module constant couplée avec une approche par déflation permet d'extraire les sources du mélange sans connaître leurs fréquences cycliques ni leurs fréquences cycliques non conjuguées. Dans le cas opposé, où les sources partagent les mêmes fréquences cycliques et les mêmes fréquences cycliques non conjuguées, nous avons prouvé l'existence de minima locaux non-séparants du critère du CMA. Nous avons aussi montré que le critère du CMA converge dans un grand nombre de cas vers ces points et que par conséquent la séparation de sources n'est pas toujours réalisée pour ce type de mélanges. Nous avons ensuite proposé un nouveau critère basé sur le critère du CMA qui, couplé avec une approche par déflation, assure l'extraction des sources dans ces situations. Ce nouveau critère ne nécessite pas la connaissance des fréquences cycliques des signaux mais nécessite quand même la connaissance des fréquences cycliques non-conjuguées les plus significatives. Nous avons proposé une méthode assez grossière d'estimation de ces fréquences et nous avons montré que, avec les fréquences cycliques non-conjuguées significatives ainsi estimées, l'algorithme proposé fonctionne correctement et qu'il est capable d'extraire les sources des mélanges pour lesquels le critère du CMA échoue. Dans la deuxième partie de ce manuscript, nous nous sommes intéressés aux séparateurs dérivés du principe du maximum de vraisemblance. Nous avons d'abord étudié des mélanges instantanés des signaux cyclostationnaires et circulaires à l'ordre 2. Dans ce contexte, nous avons mis en évidence des estimateurs basés sur le principe du maximum de vraisemblance et nous avons présenté une méthode pour les implanter. Nous avons ensuite étudié les propriétés asymptotiques de ces estimateurs et nous avons montré que, dans des conditions idéales (absence du bruit), ces estimateurs permettent d'améliorer les performances du critère du CMA. Toujours dans ces conditions, nous avons montré que les estimateurs dérivés du critère du maximum de vraisemblance permettent dans certains cas d'estimer la source ayant la bande passante la plus petite avec une erreur plus petite que les méthodes usuelles. Ces résultats ne sont malheureusement plus vrais dans un context plus réaliste comme en présence de bruit. Nous avons généralisé les idées développées dans le cas de mélanges instantanés au cas de mélanges convolutifs mais pour ce type de mélanges, nous n'avons pas constaté d'amélioration des performances du critère du CMA même dans le cas non-bruité. Bien qu'en pratique cette étude n'apporte pas de grandes contributions, elle a néanmoins un intérêt théorique certain / This thesis addresses the problem of blind separation of convolutive mixtures of cyclostationnary, linearly modulated signals. We mainly focus on signals issued from digital communications systems. Our work involves separating methods based on the minimisation of a criterion (like the constant modulus) combined with a deflation approach. In the first part of the manuscript we considered convolutive mixtures of non second order circular signals such as BPSK and $1/2$ index CPM modulations. We have proven that if the transmission sources all have different baud rates and offset frequencies, minimizing the constant modulus criterion and using a deflation approach successfully achieves the extraction of the original signals from the mixture without prior knowledge of the signal cyclic and non conjugate cyclic frequencies. This result is no longer obtained if all the transmission sources have the same baud rate and frequency offset. We have proven that in this case the CMA criterion has non separating local minima and that the minimisation algorithm very often converges to these spurious points. This means that in a non-negligible number of cases separation is not achieved for this type of mixtures. We therefore propose a new criterion based on the CMA which combined with a deflation approach ensures the extraction of source signals from this particular type of mixtures. This new criterion does not need prior knowledge of the cyclic frequencies but does need information on the most significant non conjugate cyclic frequencies of the signals. We also propose an estimation method for these frequencies and we show that our new algorithm works correctly with the estimated non conjugate cyclic frequencies and that it is capable to extract all the source signals from those types of mixtures for which the CMA fails.The second part of this manuscript focuses on a class of Maximum Likelihood derived separators. We are only considering second order circularly modulated signals. We first studied the case of instantaneous mixtures and then extended our results to convolutive mixtures. For the instantaneous mixtures, we have developed Maximum Likelihood based estimators and presented an implementation method for them. We have then studied their asymptotic properties and we have shown that, in the absence of noise, these estimators improve the performance of the CMA algorithm. Under the same assumptions we have shown that the Maximum Likelihood based estimators allow, in some cases, to extract the signal with the largest bandwidth with a lower error than the one obtained when using other well known separating methods. This results however are no longer true in more realistic contexts such as the presence of noise. We have extended this study to the convolutive mixtures of signals but in this case we have not seen an important improvement on the performances achieved by the CMA algorithm, not even in the absence of noise. Even though this study does not have practical applications, it has nevertheless a certain theoretical significance

När barn skolas in på förskolan bryts relationen mellan barnet och de personer som är viktigast i deras liv – de som de under sina första år fått anknytning till. Nu är det dags att barnet får lära sig att lita på och känna trygghet med andra – pedagogerna på förskolan. Vilken inskolningsmetod som anses som mest lämplig att använda motiveras säkert med att det är ”bäst för barnen” men att synen på hur brytningen från föräldern sker för att ersättas av annan anknytningsperson är olika. Utifrån begreppen trygg bas, anknytningsperson och separation från John Bowlbys anknytningsteori samt från tidigare forskning inom området har jag analyserat och jämfört fyra förskollärares uppfattningar om anknytning och separation i samband med inskolning på förskolan och deras egen roll i denna. Resultatet visar att förskollärarnas svar skiljer sig när det gäller vilken inskolningsmetod de valt, men samtidigt är samtliga förskollärare nöjda med sina inskolningsmetoder. Endast en förskollärare nämner vikten av ansvarspedagog och anknytning under inskolningen då hon ansåg att det underlättar för barnet. En annan menade att nackdelen med ansvarspedagog var att barnet kunde bli för hårt anknutna till en pedagog samt att det inte ger barnet en sann bild av verksamheten. Trots olika inskolningsmetoder visade resultaten ändå flera lika uppfattningar hos förskollärarna. Alla förskollärarna ansåg att syftet med inskolningen var att barnet skulle bli tryggt men samtidigt var alla fyra överens om att det är minst lika viktigt att få föräldern trygg. Hur förskollärarens såg på sin roll i separationsprocessen och som kompletterande anknytningsperson var också lika men de hade olika syn på förälderns roll. Det Bowlby nämner som Trygg bas är det bara en förskollärare som nämner. Istället menar de andra att föräldern ska vara aktiv tillsammans med barnet under inskolningen.

In this paper the Cartesian product topology for an arbitrary family of topological spaces and some of its basic properties are defined. The space is investigated to determine which of the separation properties of the component spaces are invariant.

A new column, Dionex AS4A, (polystyrenedivinylbenzene matrix) used for the separation of ribonucleotides and deoxyribonucleotides for the first time, and previously used for ion analysis was found superior to conventional silica columns because it separates ribonucleotides and deoxyribonucleotides. Resolution of dGTP was not possible with the Dionex column and CTP and GDP often co-eluted. Using conventional silica columns, monophosphates separated from diphosphates and diphosphates from triphosphates. Using the new Dionex column resolves all three simultaneously. The Dionex column resolved nucleotides with sharper peaks than silica columns, and the longer its retention time the better was the resolution. This Dionex column is stable, with 80 runs possible without cleaning while resolving ribonucleotides and deoxyribonucleotides to the picomole level.