<p>To improve the adsorption capacity of polyacrylonitrile (PAN) fibres, hydrophilic amidoxime fibres were prepared by subsequent conversion of the cyano groups to an amidoxime group by reacting with hydroxylamine at 80&deg / C at an optimum amidoximation time of 2 hrs. The amidoxime fibre was hydrolyzed/alkali treated in a solution of sodium hydroxide to enhance or improve the adsorption properties. This was followed by characterization of the amidoxime and hydrolyzed fibres using Scanning electron microscopy (SEM) / Fourier transform Infrared Spectroscopy (FTIR) and exchange capacity (cationic and anionic). SEM showed that the hydrolysis process made the surface of Amidoxime fibre rougher than that of Polyacrylonitrile fibre. FTIR revealed that the hydrolyzed Amidoxime fibres contained conjugated imine (-C=N-) sequences. Functionalization enhanced the sorption of amidoxime fibres by an increase of 20 % in the cationic exchange capacity. This was achieved by the part conversion of the cyano groups into the carboxylic acid groups. The fibres showed faster kinetics largely due the available exchange sites on the surface of the fibres hence the equilibration was achieved much quicker.</p>

The development of modern information technology has enabled collecting data of unprecedented size and complexity. Examples include web text data, microarray & proteomics, and data from scientific domains (e.g., meteorology). To learn from these high dimensional and complex data, traditional machine learning techniques often suffer from the curse of dimensionality and unaffordable computational cost. However, learning from large-scale high-dimensional data promises big payoffs in text mining, gene analysis, and numerous other consequential tasks. Recently developed sparse learning techniques provide us a suite of tools for understanding and exploring high dimensional data from many areas in science and engineering. By exploring sparsity, we can always learn a parsimonious and compact model which is more interpretable and computationally tractable at application time. When it is known that the underlying model is indeed sparse, sparse learning methods can provide us a more consistent model and much improved prediction performance. However, the existing methods are still insufficient for modeling complex or dynamic structures of the data, such as those evidenced in pathways of genomic data, gene regulatory network, and synonyms in text data. This thesis develops structured sparse learning methods along with scalable optimization algorithms to explore and predict high dimensional data with complex structures. In particular, we address three aspects of structured sparse learning: 1. Efficient and scalable optimization methods with fast convergence guarantees for a wide spectrum of high-dimensional learning tasks, including single or multi-task structured regression, canonical correlation analysis as well as online sparse learning. 2. Learning dynamic structures of different types of undirected graphical models, e.g., conditional Gaussian or conditional forest graphical models. 3. Demonstrating the usefulness of the proposed methods in various applications, e.g., computational genomics and spatial-temporal climatological data. In addition, we also design specialized sparse learning methods for text mining applications, including ranking and latent semantic analysis. In the last part of the thesis, we also present the future direction of the high-dimensional structured sparse learning from both computational and statistical aspects.

Malaria affects about forty percent of the world’s population. Annually more than 1.5 million fatalities due to malaria occur and parasite resistance to existing antimalarial drugs such as mefloquine has already reached disturbingly high levels in South-East Asia and on the African continent. Consequently, there is a dire need for new drugs or formulations in the prophylaxis and treatment of malaria. Artesunate, an artemisinin derivative, represents a new category of antimalarials that is effective against drug-resistant Plasmodium falciparum strains and is of significance in the current antimalarial campaign. As formulating an ACT double fixed-dose combination is technically difficult, it is essential that fixed-dose combinations are shown to have satisfactory ingredient compatibility, stability, and dissolution rates similar to the separate oral dosage forms. Since the general deployment of a combination of artesunate and mefloquine in 1994, the cure rate increased again to almost 100% from 1998 onwards, and there has been a sustained decline in the incidence of Plasmodium falciparum malaria in the experimental studies (Nosten et al., 2000:297; WHO, 2010:17). However, the successful formulation of a solid oral dosage form and fixed dosage combination of artesunate and mefloquine remains both a market opportunity and a challenge. Artesunate and mefloquine both exhibited poor flow properties. Furthermore, different elimination half-lives, treatment dosages as well as solubility properties of artesunate and mefloquine required different formulation approaches. To substantiate the FDA’s pharmaceutical quality by design concept, the double fixed-dose combination of artesunate and mefloquine required strict preliminary formulation considerations regarding compatibility between excipients and between the APIs. Materials and process methods were only considered if theoretically and experimentally proved safe. Infrared absorption spectroscopy (IR) and X-ray powder diffraction (XRPD) data proved compatibility between ingredients and stability during the complete manufacturing process by a peak by peak correlation. Scanning Electron Micrographs (SEM) provided explanations for the inferior flow properties exhibited by the investigated APIs. Particle size analysis and SEM micrographs confirmed that the larger, rounder and more consistently sized particles of the granulated APIs contributed to improved flow under the specified testing conditions. A compressible mixture containing 615 mg of the APIs in accordance with the WHO recommendation of 25 mg/kg of mefloquine taken in two or three divided dosages, and 4 mg/kg/day for 3 days of artesunate for uncomplicated falciparum malaria was developed. Mini-tablets of artesunate and mefloquine were compressed separately and successfully with the required therapeutic dosages and complied with pharmacopoeial standards. Preformulation studies eventually led to a formula for a double fixed-dose combination and with the specific aim of delaying the release of artesunate due to its short half-life. A factorial design revealed the predominant factors contributing to the successful wet granulation of artesunate and mefloquine. A fractional factorial design identified the optimum factors and factor levels. The application of the granulation fluid (20% w/w) proved to be sufficient by a spraying method for both artesunate and mefloquine. A compatible acrylic polymer and coating agent for artesunate, Eudragit® L100 was employed to delay the release of approximately half of the artesunate dose from the double fixed-dose combination tablet until a pH of 6.8. A compressible mixture was identified and formulated to contain 200 mg of artesunate and 415 mg of mefloquine per tablet. The physical properties of the tablets complied with BP standards. An HPLC method from available literature was adapted and validated for analytical procedures. Dissolution studies according to a USP method were conducted to verify and quantify the release of the APIs in the double fixed-dose combination. The initial dissolution rate (DRi) of artesunate and mefloquine in the acidic dissolution medium was rapid as required. The enteric coated fraction of the artesunate exhibited no release in an acidic environment after 2 hours, but rapid release in a medium with a pH of 6.8. The structure of the granulated particles of mefloquine may have contributed to its first order release profile in the dissolution mediums. A linear correlation was present between the rate of mefloquine release and the percentage of mefloquine dissolved (R2 = 0.9484). Additionally, a linear relationship was found between the logarithm of the percentage mefloquine remaining against time (R2 = 0.9908). First order drug release is the dominant release profile found in the pharmaceutical industry today and is coherent with the kinetics of release obtained for mefloquine. A concept pre-clinical phase, double fixed-dose combination solid oral dosage form for artesunate and mefloquine was developed. The double fixed-dose combination was designed in accordance with the WHO’s recommendation for an oral dosage regimen of artesunate and mefloquine for the treatment of uncomplicated falciparum malaria. The specifications of the double fixed-dose combination were developed in close accordance with the FDA’s quality by design concept and WHO recommendations. An HPLC analytical procedure was developed to verify the presence of artesunate and mefloquine. The dissolution profiles of artesunate and mefloquine were investigated during the dissolution studies. / PhD (Pharmaceutics), North-West University, Potchefstroom Campus, 2014

Ce travail se place dans le contexte des recherches sur les mémoires quantiques pour la lumière. L'information quantique est stockée dans un état de superposition atomique, dont la durée de vie détermine le temps maximum de stockage.On s'intéresse particulièrement aux matériaux capables de capturer la lumière par excitation résonnante d'une raie d'absorption, puis de conserver l'information quantique dans un état de superposition du fondamental électronique.Dans Tm3+:YAG, l'information est enregistrée dans un état de spin nucléaire. Cependant le champ magnétique qui lève la dégénérescence nucléaire entraîne les différents spins à des vitesses de précession différentes, ce qui tend à détruire l'aimantation initiale, porteuse de l'information.Une étude quantique du cristal est réalisée lors du premier chapitre de ce manuscrit. Les trois chapitres suivants traitent des différents mécanismes conduisant au déphasage des spins nucléaires. On y trouvera différente analyses théoriques qui seront confirmées par un ensemble de résultats expérimentaux, ainsi qu'une description détaillée du dispositif expérimental. Enfin le dernier chapitre, prospectif, exploite les outils développés au cours de la thèse pour préserver les cohérences optiques. Il présente quelques résultats expérimentaux prometteurs sur l'allongement du temps de vie de ces cohérences optiques.

In this thesis, we study advanced reasoning about dynamical systems in a logical framework -- the situation calculus. In particular, we consider promoting the efficiency of reasoning about action in the situation calculus from three different aspects. First, we propose a modified situation calculus based on the two-variable predicate logic with counting quantifiers. We show that solving the projection and executability problems via regression in such language are decidable. We prove that generally these two problems are co-NExpTime-complete in the modified language. We also consider restricting the format of regressable formulas and basic action theories (BATs) further to gain better computational complexity for reasoning about action via regression. We mention possible applications to formalization of Semantic Web services. Then, we propose a hierarchical representation of actions based on the situation calculus to facilitate development, maintenance and elaboration of very large taxonomies of actions. We show that our axioms can be more succinct, while still using an extended regression operator to solve the projection problem. Moreover, such representation has significant computational advantages. For taxonomies of actions that can be represented as finitely branching trees, the regression operator can sometimes work exponentially faster with our theories than it works with the BATs current situation calculus. We also propose a general guideline on how a taxonomy of actions can be constructed from the given set of effect axioms. Finally, we extend the current situation calculus with the order-sorted logic. In the new formalism, we add sort theories to the usual initial theories to describe taxonomies of objects. We then investigate what is the well-sortness for BATs under such framework. We consider extending the current regression operator with well-sortness checking and unification techniques. With the modified regression, we gain computational efficiency by terminating the regression earlier when reasoning tasks are ill-sorted and by reducing the search spaces for well-sorted objects. We also study that the connection between the order-sorted situation calculus and the current situation calculus.

This thesis deals with the problem of estimating the velocity of a mobile station (MS)in a mobile communication system using the instantaneous frequency (IF) of the received signal at the MS antenna. This estimate is essential for satisfactory handover performance, effective dynamic channel assignment, and optimisation of adaptive multiple access wireless receivers. Conventional methods for estimating the MS velocity are based either on the statistics of the envelope or quadrature components of the received signal. In chapter 4 of the thesis, we show that their performance deteriorates in the presence of shadowing. Other velocity estimators have also been proposed which require prior estimation of the channel or the average received power. These are generally difficult to obtain due to the non-stationary nature of the received signal. An appropriate window which depends on the unknown MS velocity must first be applied in order to accurately estimate the required quantities. Using the statistics of the IF of the received signal at the MS antenna given in chapter 3, new velocity estimators are proposed in chapter 4 of this thesis. The proposed estimators are based on the moments, zero-crossing rate, and covariance of the received IF. Since the IF of the received signal is not affected by any amplitude distortion, the proposed IF-based estimators are robust to shadowing and propagation path-loss. The estimators for the MS velocity in a macro- and micro-cellular system are presented separately. A macro-cell system can be considered as a special case of a micro-cell in which there is no line-of-sight component at the receiver antenna. It follows that those estimators which are derived for micro-cells can be used in a macro-cell as well. In chapter 4, we analyse the performance of the proposed velocity estimators in the presence of additive noise, non-isotropic scattering, and shadowing. We also prove analytically that the proposed velocity estimators outperform the existing methods in the presence of shadowing and additive noise. The proposed IF-based estimators need prior estimation of both the IF of the received signal and Ricean K-factor. The IF estimation in a typical wireless environment, can be considered as a special case of a general problem of IF estimation in the presence of multiplicative and additive noise. In chapter 5, we show that current time-frequency approaches to this problem which are based on the peak of a time-frequency distribution (TFD) of the signal, fail because of the special shape of the power spectral density of the multiplicative noise in a wireless environment. To overcome this drawback, the use of the first-order moment of a TFD is studied in chapter 5. Theoretical analysis and simulations show that the IF estimator based on the first-order moment of a TFD exhibits negligible bias when the signal-to-additive noise ratio is more than 10 dB. The Ricean K-factor is not only necessary for velocity estimation in micro-cells, but also is a measure of the severity of fading and a good indicator of the channel quality. Two new methods for estimating the Ricean K-factor based on the first two moments of the envelope of the received signal, are proposed in chapter 6. Performance analysis presented in chapter 6, prove that the proposed K estimators are robust to non-isotropic scattering. Theoretical analysis and simulations which are presented in chapters 4 and 7 of this thesis, prove that the proposed velocity and K estimators outperform existing estimators in the presence of shadowing and additive noise.

Nous considérons le problème de débruitage d'un signal ou d'une image observés dans le bruit gaussien. Dans ce problème les estimateurs linéaires classiques sont quasi-optimaux quand l'ensemble des signaux, qui doit être convexe et compact, est connu a priori. Si cet ensemble n'est pas spécifié, la conception d'un estimateur adaptatif qui ``ne connait pas'' la structure cachée du signal reste un problème difficile. Dans cette thèse, nous étudions une nouvelle famille d'estimateurs des signaux satisfaisant certains propriétés d'invariance dans le temps. De tels signaux sont caractérisés par leur structure harmonique, qui est généralement inconnu dans la pratique.Nous proposons des nouveaux estimateurs capables d'exploiter la structure harmonique inconnue du signal è reconstruire. Nous démontrons que ces estimateurs obéissent aux divers "inégalités d'oracle," et nous proposons une implémentation algorithmique numériquement efficace de ces estimateurs basée sur des algorithmes d'optimisation de "premier ordre." Nous évaluons ces estimateurs sur des données synthétiques et sur des signaux et images réelles. / We consider the problem of denoising a signal observed in Gaussian noise.In this problem, classical linear estimators are quasi-optimal provided that the set of possible signals is convex, compact, and known a priori. However, when the set is unspecified, designing an estimator which does not ``know'' the underlying structure of a signal yet has favorable theoretical guarantees of statistical performance remains a challenging problem. In this thesis, we study a new family of estimators for statistical recovery of signals satisfying certain time-invariance properties. Such signals are characterized by their harmonic structure, which is usually unknown in practice. We propose new estimators which are capable to exploit the unknown harmonic structure of a signal to reconstruct. We demonstrate that these estimators admit theoretical performance guarantees, in the form of oracle inequalities, in a variety of settings.We provide efficient algorithmic implementations of these estimators via first-order optimization algorithm with non-Euclidean geometry, and evaluate them on synthetic data, as well as some real-world signals and images.

The FT-Raman techniques were developed to quantify reactions that follow on mixing aqueous solutions of bis-(1,3-diaminopropane)diaquacobalt( III) ion ([Co(tn)2(0H)(H20)]2+) and p-nitrophenylphosphate (PNPP). For the development and validation of the kinetic modelling technique, the well-studied inversion of sucrose was utilized. Rate constants and concentrations could be estimated using calibration solutions and modelling methods. It was found that the results obtained are comparable to literature values. Hence this technique could be further used for the [Co(tn)2(0H)(H20)]2+ assisted hydrolysis of PNPP. It was found that rate constants where the pH is maintained at 7.30 give results which differ from those where the pH is started at 7.30 and allowed to change during the reaction. The average rate constant for 2:1 ([Co(tn)2(0H)(H20)]2+:PNPP reactions was found to be approximately 3 x 104 times the unassisted PNPP hydrolysis rate. / Chemistry / M. Sc. (Chemistry)

Network Direct Selling Organisations (NDSOs) exist in more than 50 countries and have more than 74 million members. The most recent statistical information reveals that the vast majority of members do not earn significant income. Criticism of these organisations revolves around the ethicality of consumption, the commercialisation of personal relationships, and the exploitation of unrealistic expectations. This study aims to explore how communication creates networks that sustain an industry of this kind despite the improbability of its existence. The study commences with a description of NDSOs from historical, operational, tactical, and strategic perspectives. Given the broader context created by the global presence of this industry, cybernetics has been selected as a meta-theoretical perspective for the study of communication. The more recent development of second-order cybernetics and social autopoiesis are introduced to communication theory as a field. Niklas Luhmann‟s new social theory of communication is assessed and applied in relation to existing communication theory. New conceptual models are developed to explore communication as the unity of the synthesis of information, utterance, understanding, and expectations as selections that occur both consciously and unconsciously, intentionally and unintentionally. These models indicate the multiplexity of individual and social operationally closed, yet informationally open systems, and they are used here to provide a systemic and coherent alternative to orthodox communication approaches to the study of organisations. The study adopts a constructivist epistemological stance and propounds throughout the necessity of further interdisciplinary collaboration. The study concludes that individuals are composite unities of self-creating systems, and they co-create social systems by self-creating and co-creating meaning. Meaning is described as the continuous virtualisation and actualisation of potentialities that in turn coordinate individual and social systems‟ actions. A communication process flow model is created to provide a theoretical explanation for the existence of NDSOs as self-creating systems. The study aims to show that communication has arguably become the most pervasive discipline as a result of the globally interactive era. It is shown that second-order cybernetics and social autopoiesis raise several further questions to be explored within communication theory as a field. / Communication, first-order cybernetics, second-order cybernetics, Complexity and complex systems, autopoiesis, self-reference, recursivity, operational closure, system boundaries, Network Direct Selling Organisations / Communication / D. Litt. et Phil. (Communication)

La marche est définie par des séquences de gestes cycliques et répétées. Il a été déjà montré que la vitesse et la variabilité de ces séquences peuvent révéler des aptitudes ou des défaillances motrices. L’originalité de ce travail est alors d’analyser et de caractériser les foulées de sujets âgés à partir des signaux de pression issus de semelles instrumentées lors de la marche, au moyen d’outils de traitement du signal. Une étude préliminaire, sur les signaux de pression générés lors de la marche, nous a permis de mettre en évidence le caractère cyclo-stationnaire de ces signaux. Ces paramètres sont testées sur une population de 47 sujets. Tout d'abord, nous avons commencé par un prétraitement des signaux et nous avons montré dans la première de cette thèse que le filtrage peut éliminer une partie vitale du signal. C’est pourquoi un filtre adaptatif basé sur la décomposition en mode empirique a été conçu. Les points de retournement ont été filtrés ensuite en utilisant une technique temps-fréquence appelée «synochronosqueezing». Nous avons également montré que le contenu des signaux de force de marche est fortement affecté par des paramètres inquantifiables tels que les tâches cognitives qui les rendent difficiles à normaliser. C’est pourquoi les paramètres extraits de nos signaux sont tous dérivées par une comparaison inter-sujet. Par exemple, nous avons assimilé la différence dans la répartition de poids entre les pieds. Il est également recommandé dans ce travail de choisir le centre des capteurs plutôt que de compter sur la somme des forces issues du réseau de capteurs pour la classification. Ensuite, on a montré que l’hypothèse de la marche équilibrée et déséquilibrée peut améliorer les résultats de la classification. Le potentiel de cette hypothèse est montré à l'aide de la répartition du poids ainsi que le produit de l'âge × vitesse dans le premier classificateur et la corrélation dans le second classificateur. Une simulation de la série temporelle de VGRF basé sur une version modifiée du modèle de Markov non stationnaire, du premier ordre est ensuite dérivée. Ce modèle prédit les allures chez les sujets normaux et suffisamment pour les allures des sujets de Parkinson. On a trouvé que les trois modes: temps, fréquence et espace sont très utiles pour l’analyse des signaux de force, c’est pourquoi l’analyse de facteurs parallèles est introduite comme étant une méthode de tenseur qui peut être utilisée dans le futur / Walking is defined as sequences of repetitive cyclic gestures. It was already shown that the speed and the variability of these sequences can reveal abilities or motorskill failures. The originality of this work is to analyze and characterize the steps of elderly persons by using pressure signals. In a preliminary study, we showed that pressure signals are characterized by cyclostationarity. In this study, we intend to exploit the nonstationarity of the signals in a search for new indicators that can help in gait signal classification between normal and Parkinson subjects in the elderly population. These parameters are tested on a population of 47 subjects. First, we started with preprocessing the vertical ground reaction force (VGRF) signals and showed in this first part of the thesis that filtering can remove a vital part of the signal. That is why an adaptive filter based on empirical mode decomposition (EMD) was built. Turning points are filtered using synochronosqueezing of time-frequency representations of the signal. We also showed that the content of gait force signals is highly affected by unquantifiable parameter such as cognitive tasks which make them hard to be normalized. That is why features being extracted are derived from inter-subject comparison. For example we equated the difference in the load distribution between feet. It is also recommended in this work to choose the mid-sensor rather than relying on summation of forces from array of sensors for classification purposes. A hypothesis of balanced and unbalanced gait is verified to be potential in improving the classification accuracy. The power of this hypothesis is shown by using the load distribution and Age×Speed in the first classifier and the correlation in the second classifier. A time series simulation of VGRF based on a modified version of nonstationary- Markov model of first order is derived. This model successfully predict gaits in normal subjects and fairly did in Parkinson’s gait. We found out that the three modes: time, frequency and space are helpful in analyzing force signals that is why parallel factor analysis is introduced as a tensor method to be used in a future work