Analisa os objetivos e propostas de organização da informação desenvolvidos pelo Movimento Bibliográfico e indica sua influência na Ciência da Informação. Esta pesquisa de natureza exploratória, realizada através de levantamento, revisão e análise bibliográficos, investiga o pensamento de Paul Otlet, Wilhelm Ostwald, H. G. Wells, John Cotton Dana e Watson Davis, expoentes do Movimento Bibliográfico, no contexto da modernidade. O Movimento Bibliográfico caracterizava-se por sua pluralidade e buscava responder às alterações no mundo informacional decorrentes da modernidade. O movimento atribuía à informação a potencialidade de transformação dos indivíduos e, portanto, transformou o foco dos serviços de informação da preservação para o acesso, procurando organizar acervos em função de seus conteúdos. O desenvolvimento tecnológico contemporâneo ao movimento fez com que seus expoentes enfatizassem a aplicação de novas tecnologias ao processo de disseminação da informação, pois entendiam que este seria facilitado e agilizado. A Ciência da Informação herdou seu papel social parcialmente do Movimento Bibliográfico, objetivando a organização da informação para seu acesso, e compartilha com o movimento a perspectiva de emprego de alta tecnologia na disseminação da informação. O espírito do tempo no qual se originou o Movimento Bibliográfico levou ao aparecimento de um ideário comum que permitiu a elaboração de propostas similares, entretanto, não se descarta a influência mútua entre os indivíduos analisados na pesquisa. Apesar de sua especificidade histórica, o Movimento Bibliográfico compartilha com a Ciência da Informação o ideário informacional moderno e a relação deste com a cultura. Conclui-se que a cultura da informação contemporânea e aquela do movimento pesquisado apresentam diferenças, porém são culturas que se entrelaçam; muitos de seus problemas sendo semelhantes e necessitando soluções similares. / Analyses the objectives and proposals of information organisation developed by the Bibliographic Movement, and indicates its influence in Information Science. This exploratory research, accomplished through bibliographic survey, literature review, and analysis, investigates in the context of modernity the ideas of Bibliographic Movement exponents Paul Otlet, Wilhelm Ostwald, H. G. Wells, John Cotton Dana, and Watson Davis. The Bibliographic Movement was characterized by its plurality, and aimed to respond to modernity\'s effects in the information world. The movement attributed to information the potentiality of individual transformation. Therefore, it changed the focus of information services from preservation to access, and pursued the organisation of collections according to its contents. The development of technology made the Bibliographic Movement exponents emphasise the application of new technologies to the process of information dissemination in order to facilitate and accelerate it. Information Science inherited its social role partially from the Bibliographic Movement, and aims at organising information so that it can be accessed. Information Science also shares with the movement the perspective of employing high technology to disseminate information. The Zeitgeist that gave rise to the Bibliographic Movement led to a common set of ideas and allowed the elaboration of similar proposals for the organisation of information. However, it is not discarded the probability of mutual influence between the individuals analysed. Despite its historical specificity the Bibliographic Movement shares with Information Science modern ideas and its relation to culture. It is concluded that the current information culture and the information culture of the Bibliographic Movement have differences, notwithstanding, they are entwined cultures and many of their problems are similar and need similar solutions

Ausgehend von einem thermodynamisch konsistenten Modell von Dreyer und Duderstadt für Tropfenbildung in Galliumarsenid-Kristallen, das Oberflächenspannung und Spannungen im Kristall berücksichtigt, stellen wir zwei mathematische Modelle zur Evolution der Größe flüssiger Tropfen in Kristallen auf. Das erste Modell behandelt das Regime diffusionskontrollierter Interface-Bewegung, während das zweite Modell das Regime Interface-kontrollierter Bewegung des Interface behandelt. Unsere Modellierung berücksichtigt die Erhaltung von Masse und Substanz. Diese Modelle verallgemeinern das wohlbekannte Mullins-Sekerka-Modell für die Ostwald-Reifung. Wir konzentrieren uns auf arsenreiche kugelförmige Tropfen in einem Galliumarsenid-Kristall. Tropfen können mit der Zeit schrumpfen bzw. wachsen, die Tropfenmittelpunkte sind jedoch fixiert. Die Flüssigkeit wird als homogen im Raum angenommen. Aufgrund verschiedener Skalen für typische Distanzen zwischen Tropfen und typischen Radien der flüssigen Tropfen können wir formal so genannte Mean-Field-Modelle herleiten. Für ein Modell im diffusionskontrollierten Regime beweisen wir den Grenzübergang mit Homogenisierungstechniken unter plausiblen Annahmen. Diese Mean-Field-Modelle verallgemeinern das Lifshitz-Slyozov-Wagner-Modell, welches rigoros aus dem Mullins-Sekerka-Modell hergeleitet werden kann, siehe Niethammer et al., und gut verstanden ist. Mean-Field-Modelle beschreiben die wichtigsten Eigenschaften unseres Systems und sind gut für Numerik und für weitere Analysis geeignet. Wir bestimmen mögliche Gleichgewichte und diskutieren deren Stabilität. Numerische Resultate legen nahe, wann welches der beiden Regimes gut zur experimentellen Situation passen könnte. / Based on a thermodynamically consistent model for precipitation in gallium arsenide crystals including surface tension and bulk stresses by Dreyer and Duderstadt, we propose two different mathematical models to describe the size evolution of liquid droplets in a crystalline solid. The first model treats the diffusion-controlled regime of interface motion, while the second model is concerned with the interface-controlled regime of interface motion. Our models take care of conservation of mass and substance. These models generalise the well-known Mullins-Sekerka model for Ostwald ripening. We concentrate on arsenic-rich liquid spherical droplets in a gallium arsenide crystal. Droplets can shrink or grow with time but the centres of droplets remain fixed. The liquid is assumed to be homogeneous in space. Due to different scales for typical distances between droplets and typical radii of liquid droplets we can derive formally so-called mean field models. For a model in the diffusion-controlled regime we prove this limit by homogenisation techniques under plausible assumptions. These mean field models generalise the Lifshitz-Slyozov-Wagner model, which can be derived from the Mullins-Sekerka model rigorously, see Niethammer et al., and is well-understood. Mean field models capture the main properties of our system and are well adapted for numerics and further analysis. We determine possible equilibria and discuss their stability. Numerical evidence suggests in which case which one of the two regimes might be appropriate to the experimental situation.

Analisa os objetivos e propostas de organização da informação desenvolvidos pelo Movimento Bibliográfico e indica sua influência na Ciência da Informação. Esta pesquisa de natureza exploratória, realizada através de levantamento, revisão e análise bibliográficos, investiga o pensamento de Paul Otlet, Wilhelm Ostwald, H. G. Wells, John Cotton Dana e Watson Davis, expoentes do Movimento Bibliográfico, no contexto da modernidade. O Movimento Bibliográfico caracterizava-se por sua pluralidade e buscava responder às alterações no mundo informacional decorrentes da modernidade. O movimento atribuía à informação a potencialidade de transformação dos indivíduos e, portanto, transformou o foco dos serviços de informação da preservação para o acesso, procurando organizar acervos em função de seus conteúdos. O desenvolvimento tecnológico contemporâneo ao movimento fez com que seus expoentes enfatizassem a aplicação de novas tecnologias ao processo de disseminação da informação, pois entendiam que este seria facilitado e agilizado. A Ciência da Informação herdou seu papel social parcialmente do Movimento Bibliográfico, objetivando a organização da informação para seu acesso, e compartilha com o movimento a perspectiva de emprego de alta tecnologia na disseminação da informação. O espírito do tempo no qual se originou o Movimento Bibliográfico levou ao aparecimento de um ideário comum que permitiu a elaboração de propostas similares, entretanto, não se descarta a influência mútua entre os indivíduos analisados na pesquisa. Apesar de sua especificidade histórica, o Movimento Bibliográfico compartilha com a Ciência da Informação o ideário informacional moderno e a relação deste com a cultura. Conclui-se que a cultura da informação contemporânea e aquela do movimento pesquisado apresentam diferenças, porém são culturas que se entrelaçam; muitos de seus problemas sendo semelhantes e necessitando soluções similares. / Analyses the objectives and proposals of information organisation developed by the Bibliographic Movement, and indicates its influence in Information Science. This exploratory research, accomplished through bibliographic survey, literature review, and analysis, investigates in the context of modernity the ideas of Bibliographic Movement exponents Paul Otlet, Wilhelm Ostwald, H. G. Wells, John Cotton Dana, and Watson Davis. The Bibliographic Movement was characterized by its plurality, and aimed to respond to modernity\'s effects in the information world. The movement attributed to information the potentiality of individual transformation. Therefore, it changed the focus of information services from preservation to access, and pursued the organisation of collections according to its contents. The development of technology made the Bibliographic Movement exponents emphasise the application of new technologies to the process of information dissemination in order to facilitate and accelerate it. Information Science inherited its social role partially from the Bibliographic Movement, and aims at organising information so that it can be accessed. Information Science also shares with the movement the perspective of employing high technology to disseminate information. The Zeitgeist that gave rise to the Bibliographic Movement led to a common set of ideas and allowed the elaboration of similar proposals for the organisation of information. However, it is not discarded the probability of mutual influence between the individuals analysed. Despite its historical specificity the Bibliographic Movement shares with Information Science modern ideas and its relation to culture. It is concluded that the current information culture and the information culture of the Bibliographic Movement have differences, notwithstanding, they are entwined cultures and many of their problems are similar and need similar solutions

Biological cells consist of many subunits that form distinct compartments and work together to allow for life. These compartments are clearly separated from each other and their sizes are often strongly correlated with cell size. Examples for those structures are centrosomes, which we consider in this thesis. Centrosomes are essential for many processes inside cells, most importantly for organizing cell division, and they provide an interesting example of cellular compartments without a membrane. Experiments suggest that such compartments can be described as liquid-like droplets. In this thesis, we suggest a theoretical description of the growth phase of centrosomes. We identify a possible mechanism based on phase separation by which the centrosome may be organized. Specifically, we propose that the centrosome material exists in a soluble and in a phase separating form. Chemical reactions controlling the transitions between these forms then determine the temporal evolution of the system. We investigate various possible reaction schemes and generally find that droplet sizes and nucleation properties deviate from the known equilibrium results. Additionally, the non-equilibrium effects of the chemical reactions can stabilize multiple droplets and thus counteract the destabilizing effect of surface tension. Interestingly, only a reaction scheme with autocatalytic growth can account for the experimental data of centrosomes. Here, it is important that the centrioles found at the center of all centrosomes also catalyze the production of droplet material. This catalytic activity allows the centrioles to control the onset of centrosome growth, to stabilize multiple centrosomes, and to center themselves inside the centrosome. We also investigate a stochastic version of the model, where we find that the autocatalytic growth amplifies noise. Our theory explains the growth dynamics of the centrosomes of the round worm Caenorhabditis elegans for all embryonic cells down to the eight-cell stage. It also accounts for data acquired in experiments with aberrant numbers of centrosomes and altered cell volumes. Furthermore, the model can describe unequal centrosome sizes observed in cells with disturbed centrioles. Our example thus suggests a general picture of the organization of membrane-less organelles. / Biologische Zellen bestehen aus vielen Unterstrukturen, die zusammen arbeiten um Leben zu ermöglichen. Die Größe dieser meist klar voneinander abgegrenzten Strukturen korreliert oft mit der Zellgröße. In der vorliegenden Arbeit werden als Beispiel für solche Strukturen Zentrosomen untersucht. Zentrosomen sind für viele Prozesse innerhalb der Zelle, insbesondere für die Zellteilung, unverzichtbar und sie besitzen keine Membran, welche ihnen eine feste Struktur verleihen könnte. Experimentelle Untersuchungen legen nahe, dass solche membranlose Strukturen als Flüssigkeitstropfen beschrieben werden können. In dieser Arbeit wird eine theoretische Beschreibung der Wachstumsphase von Zentrosomen hergeleitet, welche auf Phasenseparation beruht. Im Modell wird angenommen, dass das Zentrosomenmaterial in einer löslichen und einer phasenseparierenden Form existiert, wobei der Übergang zwischen diesen Formen durch chemische Reaktionen gesteuert wird. Die drei verschiedenen in dieser Arbeit untersuchten Reaktionen führen unter anderem zu Tropfengrößen und Nukleationseigenschaften, welche von den bekannten Ergebnissen im thermodynamischen Gleichgewicht abweichen. Insbesondere verursachen die chemischen Reaktionen ein thermisches Nichtgleichgewicht, in dem mehrere Tropfen stabil sein können und der destabilisierende Effekt der Oberflächenspannung unterdrückt wird. Konkret kann die Wachstumsdynamik der Zentrosomen nur durch eine selbstverstärkende Produktion der phasenseparierenden Form des Zentrosomenmaterials erklärt werden. Hierbei ist zusätzlich wichtig, dass die Zentriolen, die im Inneren jedes Zentrosoms vorhanden sind, ebenfalls diese Produktion katalysieren. Dadurch können die Zentriolen den Beginn des Zentrosomwachstums kontrollieren, mehrere Zentrosomen stabilisieren und sich selbst im Zentrosom zentrieren. Des Weiteren führt das selbstverstärkende Wachstum zu einer Verstärkung von Fluktuationen der Zentrosomgröße. Unsere Theorie erklärt die Wachstumsdynamik der Zentrosomen des Fadenwurms Caenorhabditis elegans für alle Embryonalzellen bis zum Achtzellstadium und deckt dabei auch Fälle mit anormaler Zentrosomenanzahl und veränderter Zellgröße ab. Das Modell kann auch Situationen mit unterschiedlich großen Zentrosomen erklären, welche auftreten, wenn die Struktur der Zentriolen verändert wird. Unser Beispiel beschreibt damit eine generelle Möglichkeit, wie membranlose Zellstrukturen organisiert sein können.

Biological cells consist of many subunits that form distinct compartments and work together to allow for life. These compartments are clearly separated from each other and their sizes are often strongly correlated with cell size. Examples for those structures are centrosomes, which we consider in this thesis. Centrosomes are essential for many processes inside cells, most importantly for organizing cell division, and they provide an interesting example of cellular compartments without a membrane. Experiments suggest that such compartments can be described as liquid-like droplets. In this thesis, we suggest a theoretical description of the growth phase of centrosomes. We identify a possible mechanism based on phase separation by which the centrosome may be organized. Specifically, we propose that the centrosome material exists in a soluble and in a phase separating form. Chemical reactions controlling the transitions between these forms then determine the temporal evolution of the system. We investigate various possible reaction schemes and generally find that droplet sizes and nucleation properties deviate from the known equilibrium results. Additionally, the non-equilibrium effects of the chemical reactions can stabilize multiple droplets and thus counteract the destabilizing effect of surface tension. Interestingly, only a reaction scheme with autocatalytic growth can account for the experimental data of centrosomes. Here, it is important that the centrioles found at the center of all centrosomes also catalyze the production of droplet material. This catalytic activity allows the centrioles to control the onset of centrosome growth, to stabilize multiple centrosomes, and to center themselves inside the centrosome. We also investigate a stochastic version of the model, where we find that the autocatalytic growth amplifies noise. Our theory explains the growth dynamics of the centrosomes of the round worm Caenorhabditis elegans for all embryonic cells down to the eight-cell stage. It also accounts for data acquired in experiments with aberrant numbers of centrosomes and altered cell volumes. Furthermore, the model can describe unequal centrosome sizes observed in cells with disturbed centrioles. Our example thus suggests a general picture of the organization of membrane-less organelles.:1 Introduction 1.1 Organization of the cell interior 1.2 Biology of centrosomes 1.2.1 The model organism Caenorhabditis elegans 1.2.2 Cellular functions of centrosomes 1.2.3 The centriole pair is the core structure of a centrosome 1.2.4 Pericentriolar material accumulates around the centrioles 1.3 Other membrane-less organelles and their organization 1.4 Phase separation as an organization principle 1.5 Equilibrium physics of liquid-liquid phase separation 1.5.1 Spinodal decomposition and droplet formation 1.5.2 Formation of a single droplet 1.5.3 Ostwald ripening destabilizes multiple droplets 1.6 Non-equilibrium phase separation caused by chemical reactions 1.7 Overview of this thesis 2 Physical Description of Centrosomes as Active Droplets 2.1 Physical description of centrosomes as liquid-like droplets 2.1.1 Pericentriolar material as a complex fluid 2.1.2 Reaction-diffusion kinetics of the components 2.1.3 Centrioles described as catalytic active cores 2.1.4 Droplet formation and growth kinetics 2.1.5 Complete set of the dynamical equations 2.2 Three simple growth scenarios 2.2.1 Scenario A: First-order kinetics 2.2.2 Scenario B: Autocatalytic growth 2.2.3 Scenario C: Incorporation at the centrioles 2.3 Diffusion-limited droplet growth 2.4 Discussion 3 Isolated Active Droplets 3.1 Compositional fluxes in the stationary state 3.2 Critical droplet size: Instability of small droplets 3.3 Droplet nucleation facilitated by the active core 3.4 Interplay of critical droplet size and nucleation 3.5 Perturbations of the spherical droplet shape 3.5.1 Linear stability analysis of the spherical droplet shape 3.5.2 Active cores can center themselves in droplets 3.5.3 Surface tension stabilizes the spherical shape 3.5.4 First-order kinetics destabilize large droplets 3.6 Discussion 4 Multiple Interacting Active Droplets 4.1 Approximate description of multiple droplets 4.2 Linear stability analysis of the symmetric state 4.3 Late stage droplet dynamics and Ostwald ripening 4.4 Active droplets can suppress Ostwald ripening 4.4.1 Perturbation growth rate in the simple growth scenarios 4.4.2 Parameter dependence of the stability of multiple droplets 4.4.3 Stability of more than two droplets 4.5 Discussion 5 Active Droplets with Fluctuations 5.1 Stochastic version of the active droplet model 5.1.1 Comparison with the deterministic model 5.1.2 Ensemble statistics and ergodicity 5.1.3 Quantification of fluctuations by the standard deviation 5.2 Noise amplification by the autocatalytic reaction 5.3 Transient growth regime of multiple droplets 5.4 Influence of the system geometry on the droplet growth 5.5 Discussion 6 Comparison Between Theory and Experiment 6.1 Summary of the experimental observations 6.2 Estimation of key model parameters 6.3 Fits to experimental data 6.4 Dependence of centrosome size on cell volume and centrosome count 6.5 Nucleation and stability of centrosomes 6.6 Multiple centrosomes with unequal sizes 6.7 Disintegration phase of centrosomes 7 Summary and Outlook Appendix A Coexistence conditions in a ternary fluid B Instability of multiple equilibrium droplets C Numerical solution of the droplet growth D Diffusion-limited growth of a single droplet E Approximate efflux of droplet material F Determining stationary states of single droplets G Droplet size including surface tension effects H Distortions of the spherical droplet shape H.1 Harmonic distortions of a sphere H.2 Physical description of the perturbed droplet H.3 Volume fraction profiles in the perturbed droplet H.4 Perturbation growth rates I Multiple droplets with gradients inside droplets J Numerical stability analysis of multiple droplets K Numerical implementation of the stochastic model / Biologische Zellen bestehen aus vielen Unterstrukturen, die zusammen arbeiten um Leben zu ermöglichen. Die Größe dieser meist klar voneinander abgegrenzten Strukturen korreliert oft mit der Zellgröße. In der vorliegenden Arbeit werden als Beispiel für solche Strukturen Zentrosomen untersucht. Zentrosomen sind für viele Prozesse innerhalb der Zelle, insbesondere für die Zellteilung, unverzichtbar und sie besitzen keine Membran, welche ihnen eine feste Struktur verleihen könnte. Experimentelle Untersuchungen legen nahe, dass solche membranlose Strukturen als Flüssigkeitstropfen beschrieben werden können. In dieser Arbeit wird eine theoretische Beschreibung der Wachstumsphase von Zentrosomen hergeleitet, welche auf Phasenseparation beruht. Im Modell wird angenommen, dass das Zentrosomenmaterial in einer löslichen und einer phasenseparierenden Form existiert, wobei der Übergang zwischen diesen Formen durch chemische Reaktionen gesteuert wird. Die drei verschiedenen in dieser Arbeit untersuchten Reaktionen führen unter anderem zu Tropfengrößen und Nukleationseigenschaften, welche von den bekannten Ergebnissen im thermodynamischen Gleichgewicht abweichen. Insbesondere verursachen die chemischen Reaktionen ein thermisches Nichtgleichgewicht, in dem mehrere Tropfen stabil sein können und der destabilisierende Effekt der Oberflächenspannung unterdrückt wird. Konkret kann die Wachstumsdynamik der Zentrosomen nur durch eine selbstverstärkende Produktion der phasenseparierenden Form des Zentrosomenmaterials erklärt werden. Hierbei ist zusätzlich wichtig, dass die Zentriolen, die im Inneren jedes Zentrosoms vorhanden sind, ebenfalls diese Produktion katalysieren. Dadurch können die Zentriolen den Beginn des Zentrosomwachstums kontrollieren, mehrere Zentrosomen stabilisieren und sich selbst im Zentrosom zentrieren. Des Weiteren führt das selbstverstärkende Wachstum zu einer Verstärkung von Fluktuationen der Zentrosomgröße. Unsere Theorie erklärt die Wachstumsdynamik der Zentrosomen des Fadenwurms Caenorhabditis elegans für alle Embryonalzellen bis zum Achtzellstadium und deckt dabei auch Fälle mit anormaler Zentrosomenanzahl und veränderter Zellgröße ab. Das Modell kann auch Situationen mit unterschiedlich großen Zentrosomen erklären, welche auftreten, wenn die Struktur der Zentriolen verändert wird. Unser Beispiel beschreibt damit eine generelle Möglichkeit, wie membranlose Zellstrukturen organisiert sein können.:1 Introduction 1.1 Organization of the cell interior 1.2 Biology of centrosomes 1.2.1 The model organism Caenorhabditis elegans 1.2.2 Cellular functions of centrosomes 1.2.3 The centriole pair is the core structure of a centrosome 1.2.4 Pericentriolar material accumulates around the centrioles 1.3 Other membrane-less organelles and their organization 1.4 Phase separation as an organization principle 1.5 Equilibrium physics of liquid-liquid phase separation 1.5.1 Spinodal decomposition and droplet formation 1.5.2 Formation of a single droplet 1.5.3 Ostwald ripening destabilizes multiple droplets 1.6 Non-equilibrium phase separation caused by chemical reactions 1.7 Overview of this thesis 2 Physical Description of Centrosomes as Active Droplets 2.1 Physical description of centrosomes as liquid-like droplets 2.1.1 Pericentriolar material as a complex fluid 2.1.2 Reaction-diffusion kinetics of the components 2.1.3 Centrioles described as catalytic active cores 2.1.4 Droplet formation and growth kinetics 2.1.5 Complete set of the dynamical equations 2.2 Three simple growth scenarios 2.2.1 Scenario A: First-order kinetics 2.2.2 Scenario B: Autocatalytic growth 2.2.3 Scenario C: Incorporation at the centrioles 2.3 Diffusion-limited droplet growth 2.4 Discussion 3 Isolated Active Droplets 3.1 Compositional fluxes in the stationary state 3.2 Critical droplet size: Instability of small droplets 3.3 Droplet nucleation facilitated by the active core 3.4 Interplay of critical droplet size and nucleation 3.5 Perturbations of the spherical droplet shape 3.5.1 Linear stability analysis of the spherical droplet shape 3.5.2 Active cores can center themselves in droplets 3.5.3 Surface tension stabilizes the spherical shape 3.5.4 First-order kinetics destabilize large droplets 3.6 Discussion 4 Multiple Interacting Active Droplets 4.1 Approximate description of multiple droplets 4.2 Linear stability analysis of the symmetric state 4.3 Late stage droplet dynamics and Ostwald ripening 4.4 Active droplets can suppress Ostwald ripening 4.4.1 Perturbation growth rate in the simple growth scenarios 4.4.2 Parameter dependence of the stability of multiple droplets 4.4.3 Stability of more than two droplets 4.5 Discussion 5 Active Droplets with Fluctuations 5.1 Stochastic version of the active droplet model 5.1.1 Comparison with the deterministic model 5.1.2 Ensemble statistics and ergodicity 5.1.3 Quantification of fluctuations by the standard deviation 5.2 Noise amplification by the autocatalytic reaction 5.3 Transient growth regime of multiple droplets 5.4 Influence of the system geometry on the droplet growth 5.5 Discussion 6 Comparison Between Theory and Experiment 6.1 Summary of the experimental observations 6.2 Estimation of key model parameters 6.3 Fits to experimental data 6.4 Dependence of centrosome size on cell volume and centrosome count 6.5 Nucleation and stability of centrosomes 6.6 Multiple centrosomes with unequal sizes 6.7 Disintegration phase of centrosomes 7 Summary and Outlook Appendix A Coexistence conditions in a ternary fluid B Instability of multiple equilibrium droplets C Numerical solution of the droplet growth D Diffusion-limited growth of a single droplet E Approximate efflux of droplet material F Determining stationary states of single droplets G Droplet size including surface tension effects H Distortions of the spherical droplet shape H.1 Harmonic distortions of a sphere H.2 Physical description of the perturbed droplet H.3 Volume fraction profiles in the perturbed droplet H.4 Perturbation growth rates I Multiple droplets with gradients inside droplets J Numerical stability analysis of multiple droplets K Numerical implementation of the stochastic model

Transdermal drug delivery systems (TDS) are pharmaceutical devices that are designed to deliver specific drugs to the human body by diffusion through skin. The TDS effectiveness suffers from crystallization in the patch when they are kept in storage for more than two years. It has been reported that there are two types of crystals in the patch: needle and aggregate, and growth of drug crystals in TDS generally occurs only in the middle third of the polymer layer. In our study, fluorescence microscopy, EDS (SEM) and Raman microspectroscopy were used to further characterize the crystals. The results show that the needle crystals most probably contain estradiol and acrylic resin conjugate. The FTIR spectrum of the model sample proved the occurrence of a reaction between estradiol and acrylic resin. Crystal growth in an unstressed matrix of a dissolved crystallizable drug component was simulated using a kinetic Monte Carlo model. Simulation using Potts model with proper boundary condition gives the crystals in the middle of matrix in the higher temperature. Bond fluctuation model is also being implemented to study representative dense TDS polymer matrix. This model can account for the size effect of polymer chain on the crystal growth. The drug release profile from TDS was also studied by simulating the diffusion of drug molecules using Monte Carlo techniques for different initial TDS microstructure. The release rate and profile of TDS depend on the dissolution process of the crystal. At low storage temperature, the grains are evenly distributed throughout the thickness of the TDS patch, thus the release rate and profile is similar to the randomly initiated system. Further work on stress induced crystallization is currently under development. Although the study was specifically done for drug in a polymer medium, the techniques developed in this investigation is in general applicable to any constrained crystallization in a polymer medium.

The phase separation of mixed Langmuir-Blodgett (LB) monolayers was investigated using a combination of atomic force microscopy (AFM), X-ray photoelectron emission microscopy (X-PEEM) and confocal fluorescent microscopy measurements. Shapes of phase-separated domains that formed on solid substrate surfaces depended on a competition between line tension and dipole-dipole interactions. In the mixed LB film of arachidic acid (C19H39COOH) (C20) and perfluorotetradecanoic acid (C13F27COOH) (F14), the components phase separated into elevated hexagonal domains of C20 surrounded by a continuous domain primarily consisting of F14. The underlying molecular arrangement of C20 was found to be an oblique packing. The domains in this system grew via Ostwald ripening and the kinetics of their growth was modeled by twodimensional LifshitzSlyozov equation. In the stearic acid (C17H35COOH) (C18) and F14 mixed films, the C18 domains formed a linear pattern where the F14 molecules filled the areas in between the lines occupied by C18. For the mixed film of palmitic acid (C15H31COOH) (C16) and perfluorooctadecanoic acid (C17F35COOH) (F18), the surfactants phaseseparated into elevated hexagonal domains with hairy extensions radiating from them. These domains were composed of F18 and surrounded by C16. Ostwald ripening was found to be the mechanism of domain growth. Phase separation was controlled by different forces such as line tension and dipole interactions, as well as the diffusion of the molecules, solubility of the surfactant in the sub-phase, temperature and surface pressure. Simple mechanisms regarding phase separation and pattern formation were discussed in these mixed systems. It was observed that all fatty acid / F14 systems in this study were immiscible at all molar fractions examined. The fatty acid / F18 systems were immiscible at short chains of fatty acids (myristic acid (C13H27COOH) C14, C16, C18), whereas at longer fatty acid chains (C20, C22 behenic acid (C21H43COOH)) the components of the mixed system became miscible. When perfluorocarboxylic acid chain combined with fatty acids, the domains changed from large hexagonal domains into narrow lines as the fatty acid chain decreased in length.

The phase separation of mixed Langmuir-Blodgett (LB) monolayers was investigated using a combination of atomic force microscopy (AFM), X-ray photoelectron emission microscopy (X-PEEM) and confocal fluorescent microscopy measurements. Shapes of phase-separated domains that formed on solid substrate surfaces depended on a competition between line tension and dipole-dipole interactions. In the mixed LB film of arachidic acid (C19H39COOH) (C20) and perfluorotetradecanoic acid (C13F27COOH) (F14), the components phase separated into elevated hexagonal domains of C20 surrounded by a continuous domain primarily consisting of F14. The underlying molecular arrangement of C20 was found to be an oblique packing. The domains in this system grew via Ostwald ripening and the kinetics of their growth was modeled by twodimensional LifshitzSlyozov equation. In the stearic acid (C17H35COOH) (C18) and F14 mixed films, the C18 domains formed a linear pattern where the F14 molecules filled the areas in between the lines occupied by C18. For the mixed film of palmitic acid (C15H31COOH) (C16) and perfluorooctadecanoic acid (C17F35COOH) (F18), the surfactants phaseseparated into elevated hexagonal domains with hairy extensions radiating from them. These domains were composed of F18 and surrounded by C16. Ostwald ripening was found to be the mechanism of domain growth. Phase separation was controlled by different forces such as line tension and dipole interactions, as well as the diffusion of the molecules, solubility of the surfactant in the sub-phase, temperature and surface pressure. Simple mechanisms regarding phase separation and pattern formation were discussed in these mixed systems. It was observed that all fatty acid / F14 systems in this study were immiscible at all molar fractions examined. The fatty acid / F18 systems were immiscible at short chains of fatty acids (myristic acid (C13H27COOH) C14, C16, C18), whereas at longer fatty acid chains (C20, C22 behenic acid (C21H43COOH)) the components of the mixed system became miscible. When perfluorocarboxylic acid chain combined with fatty acids, the domains changed from large hexagonal domains into narrow lines as the fatty acid chain decreased in length.

<div>Metal-zeolites are promising materials for passive adsorber technologies for the abatement of nitrogen oxides (NOx, x = 1,2) and aldehydes during low-temperature operation in automotive exhaust aftertreatment systems. The aqueous-phase exchange processes used commonly to prepare metal-zeolites typically require mononuclear, transition metal complexes to diffuse within intrazeolite pore networks with their solvation shells and replace extra framework cations of higher chemical potential. When metal complexes are larger than the zeolite pore-limiting diameter, this imposes intracrystalline transport restrictions; thus, complexes and agglomerates tend to preferentially deposit near the surfaces of crystallites, requiring post-synthetic treatments to disperse metal species more uniformly throughout zeolite crystallites via solid-state ion-exchange processes. Here, we address the influence of post-synthetic gas treatments and zeolite material properties on the structural interconversion and exchange of extra framework Pd in CHA zeolites with a focus on the thermodynamic, kinetic, and mechanistic factors that dictate the Pd site structures and spatial distributions that form.<br></div><div><br></div><div>Pd-amine complexes introduced via incipient wetness impregnation on CHA zeolites were found to preferentially site near crystallite surfaces. Post-synthetic treatments in flowing air results in Pd-amine decomposition and agglomeration to metallic Pd0and supersequent oxidation to PdO, before converting to mononuclear Pd²⁺cations through an Ostwald ripening mechanism at high temperatures (>550 K). Progressively higher air treatment temperatures (up to 1023 K) were found to (1) thermodynamically favor the formation of mononu-clear Pd²⁺cations relative to agglomerated PdO particles, (2) increase the apparent rate of structural interconversion to mononuclear Pd²⁺, and (3) facilitate longer-range mobility of molecular intermediates involved in Ostwald ripening processes that allow Pd cations to form deeper within zeolite crystallites to form more uniformly dispersed Pd-zeolite materials. Additionally, the controlled synthetic variation of the atomic arrangement of 1 or 2Al sites in the 6-membered ring of CHA was used to show a thermodynamic preference to form mononuclear Pd2+cations charge-compensated by 2 Al sites over [PdOH]⁺complexes at 1 Al site. Colloidal Pd nanoparticle syntheses and deposition methods were used to prepare monodisperse Pd-CHA materials to isolate the effects of Pd particle size on structuralinterconversion to mononuclear Pd²⁺under a range of external environments. Consistent with computational thermodynamic predictions, smaller Pd particle sizes favor structural interconversion to mononuclear Pd²⁺under high-temperature air treatments (598–973 K),while adding H2O to the air stream inhibits the thermodynamics but not the kinetics of mononuclear Pd²⁺formation, demonstrating that water vapor in exhaust streams may be deleterious to the long-term stability of Pd-zeolite materials for passive NOx adsorption.<br></div><div><br></div><div>The influence of metal-zeolite material properties on the adsorption, desorption, and conversion of formaldehyde, a government-regulated automotive pollutant, under realistic conditions was investigated to identify beneficial material properties for this emerging application in mobile engine pollution abatement. A suite of Beta zeolite materials was synthesized with varied adsorption site identity (Brønsted acid, Lewis acid, silanol groups, and extra framework metal oxide) and bulk site densities. All materials stored formaldehyde and converted a large fraction of formaldehyde to more environmentally benign CO and CO₂, demonstrating the efficacy of silanol defects and zeolitic supports for the storage of formaldehyde. Sn-containing zeotypes, containing either Lewis acidic framework Sn sites or extra framework SnO_x particles, resulted in the greatest selectivity to CO and CO₂ formed during formaldehyde desorption, suggests that Sn species are a beneficial component in metal-zeolite formulations for the abatement of formaldehyde in automotive exhaust streams.<br></div><div><br></div><div>This work demonstrates how combining precise synthesis of metal-zeolites of varied bulk and atomic properties with site-specific characterization and titration methods enables systematically disentangling the influence of separate material properties (e.g., Pd particle size, zeolite framework Al arrangement, silanol density, heteroatom identify) and external environment on changes to metal structure, speciation, and oxidation state. This approach provides thermodynamic, kinetic, and mechanistic insights into the factors that influence metal re-structuring under the practical conditions encountered in automotive exhaust after treatment applications and guidance for materials design and treatment strategies to form desired metal structures during synthesis and after regeneration protocols.<br></div>

M. Tech. (Department of Chemistry, Faculty of Applied and Computer Sciences), Vaal University of Technology. / The ligand 2, 2-dithiobisbenzothiazole and it metal complexes have been a subject of interest in various fields but they have found to exhibit remarkable and prevalent biological and pharmacological activities. The ligand tends to coordinate to complexes through the sulfur atom and hence the metal-sulphide bond are good precursor to generate metal sulfide nanoparticles using single-source precursor route. The complexes are generally prepared by reflux for 1 to 2 hours depending on the solvent used to produce very stable solid products and some form in crystalline form. All the prepared nickel and cadmium complexes were characterized using techniques such as elemental analyzer, IR, 13C NMR spectroscopy and thermogravimatric analysis. The data obtained from the spectroscopic analysis was consistent of the coordination of the ligand with the metal ions through the sulphur atoms of the 2,2-dithiobisbenzothiazole moiety. The thermal analysis of the prepared complexes gave a final residue of metal sulphide for both metal complexes. Characterization techniques showed the formation of bidentate complexes for both nickel complex and cadmium complex. The prepared complexes were then used to synthesize metal sulphide nanoparticles .The nanoparticles were prepared by thermal decomposition method of the single source precursor in a solution of oleylamine (OLA). Two different parameters were investigated temperature and time to study their effect on the size and shape of the nanoparticles. The synthesized nanoparticles were characterized using techniques such as UV-Vis spectroscopy, photoluminescence spectroscopy, and X-ray diffraction analysis and transmission electron microscopy. The temperatures of the reaction have a significant effect on the rate of the reaction that will affect the size and shape of the nanoparticles. This effect was confirmed by the optical properties of the synthesized nanoparticles prepared at different reaction temperatures. The spectra shows that absorption maximum and band edge shift to lower wavelength as the temperature of reaction was progressively increased. This trend is associated to the decrease in particles size of the prepared nanoparticles. TEM images further confirmed that the particles size of the prepared nanoparticles was progressively decreased as the temperature was increased. The time of the reaction is one of the most significant factors in the synthesis of the nanoparticles. The investigation of the time of the reaction yield results that depicted that with increase in time of the reaction, the band edge increases, but relatively at short wavelength to the bulk. Hence, the band edges of the nanoparticles were blue shifted significantly to the bulk. The results show that with an increase in the time of the reaction, the nanoparticles increases in their size due to Ostwald ripening. The optimum complexes and optimum nanoparticles were used to further study their electrochemical properties using cyclic voltammetry and electrochemical impedance spectroscopy (EIS) graphs were fitted using the randles circuit and they confirm that the NiS nanoparticles GCE greatly increase the electron transfer rate, probably due to the nanostructured surface property of the NiS nanoparticles. Differential pulse voltammetry (DPV) was used to study the electrochemical behavior and the DPV showed that the current response of Rhb was higher for the optimum temperature NiS nanoparticles compared to all the materials used. There was an increase in the Rhb current response with an increase in pH and pH 7 was used as the optimum pH when Ni- complex was used as a modifier and pH 8 was used as optimum when NiS nanoparticles were used as a modifier. Effect of concentration showed that the NiS nanoparticles for the optimum temperature had a wide linear range and a low detection limit. The method has good accuracy, acceptable precision, and reproducibility. This method provides a novel electrochemical method for determination of RhB.