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Saleemi, Ali Nauman. "Strategic feedback control of pharmaceutical crystallization systems." Thesis, Loughborough University, 2011. https://dspace.lboro.ac.uk/2134/8530.
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Crystallization is a widely used purification and separation technique in the pharmaceutical industry. More than 90 % of the active pharmaceutical ingredients are produced in the crystalline form. The quality of the crystalline product greatly affects the downstream processing and bioavailability of the drug. The Food and Drug Administration (FDA) initiated in 2004 the use and implementation of process analytical technology (PAT) in the pharmaceutical development and production and encourages the pharmaceutical industry to adopt quality by design (QBD) approaches. The prime objective of this initiative has been to optimize the drug development and manufacturing process by reducing cost, improving product quality and reducing the number of failed batches. The work presented in this thesis focuses on expanding the use of two PAT tools, namely attenuated total reflection ultra violet/visible spectroscopy (ATR-UV/Vis spectroscopy) and focused beam reflectance measurement (FBRM). ATR-UV/Vis spectroscopy and FRBM are mostly used for process monitoring. The aim here was to develop sophisticated control approaches using these in situ tools for enhancing the product quality. Chemometrics is an integral part of PAT, and can provide valuable information about the system. This tool has also been used in this study for calibration model development and monitoring the cooling and antisolvent crystallization processes for single and muticomponent crystallisations. The development of an accurate and robust calibration model is necessary for qualitative and quantitative analysis of a system using spectroscopy. A systematic methodology was therefore presented for the selection of a suitable calibration model for ATR-UV/Vis spectroscopy. The developed model was then used as part of supersaturation control approach (SSC). SSC uses information from ATR-UV/Vis spectroscopy in a feedback control loop to keep the system at desired supersaturation. The developed approach resulted in the production of crystals of uniform size and can represent the bases for a model-free direct design approach for crystallization systems.
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Sheikh, Ahmad Yahya. "Synthesis, optimisation and control of crystallization systems." Thesis, University College London (University of London), 1997. http://discovery.ucl.ac.uk/1317664/.
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Process systems engineering has provided with a range of powerful tools to chemical engineers for synthesis, optimisation and control using thorough understanding of the processes enhanced with the aid of sophisticated and accurate multi-faceted mathematical models. Crystallization processes have rarely benefited from these new techniques, for they lack in models that could be used to bridge the gaps in their perception before utilising the resulting insight for the three above mentioned tasks. In the present work, first a consistent and sufficiently complex models for unit operations including MSMPR crystallizer, hydrocyclone and fines dissolver are developed to enhance the understanding of systems comprising these units. This insight is then utilised for devising innovative techniques to synthesise, optimise and control such processes. A constructive targeting approach is developed for innovative synthesis of stage-wise crystallization processes. The resulting solution surpasses the performance obtained from conventional design procedure not only because optimal temperature profiles are used along the crystallizers but also the distribution of feed and product removal is optimally determined through non-linear programming. The revised Machine Learning methodology presented here for continual process improvement by analysing process data and representing the findings as zone of best average performance, has directly utilised the models to generate the data in the absence of real plant data. The methodology which is demonstrated through KNO₃ crystallization process flowsheet quickly identifies three opportunities each representing an increase of 12% on nominal operation. An optimal multi-variable controller has been designed for a one litre continuous recycle crystallizer to indirectly control total number and average size of crystals from secondary process measurements. The system identification is solely based on experimental findings. Linear Quadratic Gaussian method based design procedure is developed to design the controller which not only shows excellent set-point tracking capabilities but also effectively rejects disturbance in the simulated closed loop runs.
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Montenegro, Rivelino V. D. "Crystallization, biomimetics and semiconducting polymers in confined systems." Phd thesis, Universität Potsdam, 2003. http://opus.kobv.de/ubp/volltexte/2005/76/.
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populärwissenschaftlicher Abstract:Kristallisation, Biomimetik und halbleitende Polymere in räumlich begrenzten Systemen:
Öl und Wasser mischen sich nicht, man kann aber aus beiden Flüssigkeiten Emulsionen herstellen, bei denen Tröpfchen der einen Flüssigkeit in der anderen Flüssigkeit vorliegen. Das heißt, es können entweder Öltröpfchen in Wasser oder Wassertröpfchen in Öl erzeugt werden. Aus täglichen Erfahrungen, z.B. beim Kochen weiß man jedoch, dass sich eine Emulsion durch Schütteln oder Rühren herstellen lässt, diese jedoch nicht besonders stabil ist. Mit Hilfe von hohen Scherenergien kann man nun sehr kleine, in ihrer Größe sehr einheitliche und außerdem sehr stabile Tröpfchen von 1/10000 mm erhalten. Eine solche Emulsion wird Miniemulsion genannt.
In der Dissertation wurden nun z.B. Miniemulsionen untersucht, die aus kleinen Wassertröpfchen in einem Öl bestehen. Es konnte gezeigt werden, dass das Wasser in diesen Tröpfchen, also in den räumlich begrenzten Systemen, nicht bei 0 °C, sondern bei -22 °C kristallisierte. Wie lässt sich das erklären? Wenn man einen Eimer Wasser hat, dann bildet sich normalerweise bei 0 °C Eis, da nämlich in dem Wasser einige (manchmal ganz wenige) Keime (z.B. Schutzteilchen, ein Fussel etc.) vorhanden sind, an denen sich die ersten Kristalle bilden. Wenn sich dann einmal ein Kristall gebildet hat, kann das Wasser im gesamten Eimer schnell zu Eis werden. Ultrareines Wasser würde bei -22 °C kristallisieren. Wenn man jetzt die Menge Wasser aus dem Eimer in kleine Tröpfchen bringt, dann hat man eine sehr, sehr große Zahl, nämlich 1017 Tröpfchen, in einem Liter Emulsion vorliegen. Die wenigen Schmutzpartikel verteilen auf sehr wenige Tröpfchen, die anderen Tröpfchen sind ultrarein. Daher kristallisieren sie erst bei -22 °C.
Im Rahmen der Arbeit konnte auch gezeigt werden, dass die Miniemulsionen genutzt werden können, um kleine Gelatine-Partikel, also Nanogummibärchen, herzustellen. Diese Nanogummibärchen quellen bei Erhöhung der Temperatur auf ca. 38 °C an. Das kann ausgenutzt werden, um zum Beispiel Medikamente zunächst in den Partikeln im menschlichen Körper zu transportieren, die Medikamente werden dann an einer gewünschten Stelle freigelassen. In der Arbeit wurde auch gezeigt, dass die Gelatine-Partikel genutzt werden können, um die Natur nachzuahnen (Biomimetik). Innerhalb der Partikel kann nämlich gezielt Knochenmaterial aufgebaut werden kann. Die Gelatine-Knochen-Partikel können dazu genutzt werden, um schwer heilende oder komplizierte Knochenbrüche zu beheben. Gelatine wird nämlich nach einigen Tagen abgebaut, das Knochenmaterial kann in den Knochen eingebaut werden.
LEDs werden heute bereits vielfältig verwendet. LEDs bestehen aus Halbleitern, wie z.B. Silizium. Neuerdings werden dazu auch halbleitende Polymere eingesetzt. Das große Problem bei diesen Materialien ist, dass sie aus Lösungsmitteln aufgebracht werden. Im Rahmen der Doktorarbeit wurde gezeigt, dass der Prozess der Miniemulsionen genutzt werden kann, um umweltfreundlich diese LEDs herzustellen. Man stellt dazu nun wässrige Dispersionen mit den Polymerpartikeln her. Damit hat man nicht nur das Lösungsmittel vermieden, das hat nun noch einen weiteren Vorteil: man kann nämlich diese Dispersion auf sehr einfache Art verdrucken, im einfachsten Fall verwendet man einfach einen handelsüblichen Tintenstrahldrucker.
The colloidal systems are present everywhere in many varieties such as emulsions (liquid droplets dispersed in liquid), aerosols (liquid dispersed in gas), foam (gas in liquid), etc. Among several new methods for the preparation of colloids, the so-called miniemulsion technique has been shown to be one of the most promising. Miniemulsions are defined as stable emulsions consisting of droplets with a size of 50-500 nm by shearing a system containing oil, water, a surfactant, and a highly water insoluble compound, the so-called hydrophobe
1. In the first part of this work, dynamic crystallization and melting experiments are described which were performed in small, stable and narrowly distributed nanodroplets (confined systems) of miniemulsions. Both regular and inverse systems were examined, characterizing, first, the crystallization of hexadecane, secondly, the crystallization of ice. It was shown for both cases that the temperature of crystallization in such droplets is significantly decreased (or the required undercooling is increased) as compared to the bulk material. This was attributed to a very effective suppression of heterogeneous nucleation. It was also found that the required undercooling depends on the nanodroplet size: with decreasing droplet size the undercooling increases.
2. It is shown that the temperature of crystallization of other n-alkanes in nanodroplets is also significantly decreased as compared to the bulk material due to a very effective suppression of heterogeneous nucleation. A very different behavior was detected between odd and even alkanes. In even alkanes, the confinement in small droplets changes the crystal structure from a triclinic (as seen in bulk) to an orthorhombic structure, which is attributed to finite size effects inside the droplets. An intermediate metastable rotator phase is of less relevance for the miniemulsion droplets than in the bulk. For odd alkanes, only a strong temperature shift compared to the bulk system is observed, but no structure change. A triclinic structure is formed both in bulk and in miniemulsion droplets.
3. In the next part of the thesis it is shown how miniemulsions could be successfully applied in the development of materials with potential application in pharmaceutical and medical fields. The production of cross-linked gelatin nanoparticles is feasible. Starting from an inverse miniemulsion, the softness of the particles can be controlled by varying the initial concentration, amount of cross-link agent, time of cross-linking, among other parameters. Such particles show a thermo-reversible effect, e.g. the particles swell in water above 37 °C and shrink below this temperature. Above 37 °C the chains loose the physical cross-linking, however the particles do not loose their integrity, because of the chemical cross-linking. Those particles have potential use as drug carriers, since gelatin is a natural polymer derived from collagen.
4. The cross-linked gelatin nanoparticles have been used for the biomineralization of hydroxyapatite (HAP), a biomineral, which is the major constituent of our bones. The biomineralization of HAP crystals within the gelatin nanoparticles results in a hybrid material, which has potential use as a bone repair material.
5. In the last part of this work we have shown that layers of conjugated semiconducting polymers can be deposited from aqueous dispersion prepared by the miniemulsion process. Dispersions of particles of different conjugated semiconducting polymers such as a ladder-type poly(para-phenylene) and several soluble derivatives of polyfluorene could be prepared with well-controlled particle sizes ranging between 70 - 250 nm. Layers of polymer blends were prepared with controlled lateral dimensions of phase separation on sub-micrometer scales, utilizing either a mixture of single component nanoparticles or nanoparticles containing two polymers. From the results of energy transfer it is demonstrated that blending two polymers in the same particle leads to a higher efficiency due to the better contact between the polymers. Such an effect is of great interest for the fabrication of opto-electronic devices such as light emitting diodes with nanometer size emitting points and solar cells comprising of blends of electron donating and electron accepting polymers.
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Succaw, Gary Lee. "Dynamics of crystal growth of self-assembling systems /." view abstract or download file of text, 2004. http://wwwlib.umi.com/cr/uoregon/fullcit?p3136448.
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Thesis (Ph. D.)--University of Oregon, 2004.Typescript. Includes vita and abstract. Includes bibliographical references (leaves 209-215). Also available for download via the World Wide Web; free to University of Oregon users.
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Sultana, Mahmooda. "Microfluidic systems for continuous crystallization of small organic molecules." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/59879.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2010.Cataloged from PDF version of thesis.
Includes bibliographical references.
This thesis presents one of the first demonstrations of continuous crystallization in microfluidic devices, and illustrates their use for various applications related to crystallization of small organic molecules. Crystallization is an important process in a number of industries, including specialty chemicals, food, cosmetics, nutraceuticals and, most importantly, pharmaceuticals. Most small molecule pharmaceuticals are isolated in crystalline form, and more than ninety percent of all pharmaceutical products are formulated in particulate, mainly crystalline form. However, crystallization is not a completely understood process. The sensitivity of the process to synthesis conditions gives rise to serious reproducibility issues. The traditional batch crystallizers suffer from non-uniform process conditions across the reactor, and chaotic, poorly controlled mixing of the reagents, often resulting in polydisperse crystal size distribution and impure polymorphs. This makes it difficult to obtain reliable information on the process kinetics that can be used for scale-up, as well as to study the fundamentals of the process. Microfluidic systems offer a unique toolset for crystallization because of well-defined laminar flow profiles, enhanced heat and mass transfer, better control over the contact mode of the reagents, and optical access for in situ characterization. The better control over the synthesis conditions gives rise to the potential for controlling the crystal size, as well as the polymorphic form. In addition, low consumption of reagents makes it an attractive research tool for expensive pharmaceutical compounds. Some of the advantages of microfluidics have been demonstrated for crystallization in micro-batches, but so far not in continuous devices. Continuous crystallization is difficult to achieve in microchannels as uncontrolled nucleation, crystal growth, agglomeration and sedimentation of crystals easily clog the small channels. The interaction of crystals with channel walls may also contribute to channel plugging in these devices. This thesis has developed microfluidic devices for continuous crystallization of small organic molecules for the first time. We have decoupled nucleation and growth, the two key steps of crystallization, using reaction engineering principles, and have developed two separate continuous devices, one for each of these two processes. We have used seeded crystallization and reactor design to achieve controlled growth, as well as to suppress secondary nucleation, agglomeration and sedimentation of crystals. In addition, we have eliminated any significant interaction of crystals with channel walls by controlling the properties of channel surfaces. We have also integrated microscopy and spectroscopy tools with the device for in-situ characterization of crystal size and polymorphic form. We have illustrated the use of these devices to extract growth kinetics data for crystals of various shapes, including high aspect ratio systems such as that with acicular or plate-like habits. The reproducibility and control in our devices have allowed us to elucidate the growth mechanism and fundamentals of the growth process for difficult crystal systems. In addition, we have demonstrated that continuous microfluidic devices offer a unique advantage over the current state-of-the art technology to measure the size, size distribution and growth kinetics of high aspect ratio crystal systems more accurately. Moreover, we have demonstrated the use of microfluidic devices for understanding crystal habit modification in the presence of impurities. We take advantage of the high spatiotemporal resolution of microfluidic devices to study the evolution of crystal habit over time, and to obtain information on the kinetics of habit modification in the presence of different impurities. We have developed an understanding of the habit modification mechanism for alpha glycine in the presence of alpha amino acids. Such information may not only provide insights into impurity-crystal interactions, but also serve as a powerful tool for the design of impurities that can be deliberately added to improve the crystallization process. Furthermore, we have designed and developed a second microfluidic device for continuous supercritical crystallization for the first time. Using supercritical fluid as an antisolvent, we have demonstrated continuous spontaneous nucleation of acetaminophen. We have shown the ability to produce micron-sized crystals, which may be useful for increasing the bioavailability of drugs with lower solubility, as well as for inhalable and highly potent drugs with stringent size requirements. The developed platform can also be used as a high-throughput device for safely screening crystallization conditions in the supercritical domain. We have demonstrated such use by screening the effects of pressure and various solvents on the habit, size and polymorphic form of acetaminophen crystals.
by Mahmooda Sultana.
Ph.D.
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Chavez, Krystle J. "Crystallization of pseudopolymorphic forms of sodium naproxen in mixed solvent systems." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/29759.
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Thesis (Ph.D)--Chemical Engineering, Georgia Institute of Technology, 2009.Committee Chair: Rousseau, Ronald; Committee Member: Meredith, Carson; Committee Member: Prausnitz, Mark; Committee Member: Teja, Amyn; Committee Member: Wilkinson, Angus. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Antonello, Alice [Verfasser]. "Crystallization of complex inorganic systems within the confinement of miniemulsion droplets / Alice Antonello." Mainz : Universitätsbibliothek Mainz, 2017. http://d-nb.info/1136638776/34.
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Shank, Dale. "Evaluating carbon dioxide as a causative agent of otolith crystallization in recirculating aquaculture systems." Bowling Green State University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1603716784275007.
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Böbel, Alexander [Verfasser], and Gregor [Akademischer Betreuer] Morfill. "Crystallization and demixing: morphological structure analysis in many-body systems / Alexander Böbel ; Betreuer: Gregor Morfill." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2018. http://d-nb.info/1173616233/34.
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Carr, Joel Matthew. "CONFINED LAYERED POLYMERIC SYSTEMS FOR PACKAGING ANDCAPACITOR APPLICATIONS." Case Western Reserve University School of Graduate Studies / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=case1363104386.
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Simone, Elena. "Application of process analytical technology (PAT) tools for the better understanding and control of the crystallization of polymorphic and impure systems." Thesis, Loughborough University, 2015. https://dspace.lboro.ac.uk/2134/20098.
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This work presents a comprehensive study on the application of PAT tools to study, monitor and control polymorphism during batch cooling crystallization processes. For the first time, the same techniques were used to control and adjust polymorphic purity of the solid phase but also to investigate the relation between chemical equilibrium in solution and polymorphic outcome of cooling crystallization. Crystallization is an important unit operation used as separation and purification technique. It is widely employed in the pharmaceutical, chemical, agrochemical, food and cosmetics industries but also in the electronic, metallurgic and material industries. More than 90% of the APIs on the market are produced by crystallization, therefore, monitoring and control this process is fundamental to ensure the quality of the final product. The implementation of process analytical technology (PAT) tools during the development stage of APIs has largely helped in better understanding and optimizing both batch and, more recently, continuous crystallization. Polymorphism is the capacity of a compound to crystallize in more than one different crystalline structure, which can have different properties such as density, melting point, bioavailability and solubility. The choice of solvent, pH, kinetic conditions and presence of impurities has very strong effect on the polymorphic outcome of a cooling crystallization in solution. Understanding this phenomenon as well as being able to monitor and control it during industrial crystallization is one the biggest challenges for pharmaceutical industries.
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Hu, Yushan. "OXYGEN TRANSPORT AS A STRUCTURE PROBE FOR HETEROGENEOUS POLYMERIC SYSTEMS." Case Western Reserve University School of Graduate Studies / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=case1112902488.
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Erdiller, Emrah Salim. "Investigation Of Solidification And Crystallization Of Iron Based Bulk Amorphous Alloys." Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/3/1096585/index.pdf.
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The aim of this study is to form a theoretical model for simulation of glass forming ability of Fe �
Based bulk amorphous alloys, to synthesize Fe &
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based multicomponent glassy alloys by using the predictions of the theoretical study, and to analyze the influence of crystallization and solidification kinetics on the microstructural features of this amorphous alloys. For this purpose, first, glass forming ability of Fe &
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(Mo, B, Cr, Nb, C) &
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X ( X = various alloying elements, selected from the periodic table) ternary alloy systems were simulated for twenty different alloy compositions by using the electronic theory of alloys in pseudopotential approximation and regular solution theory. Then, by using the results of the theoretical study, systematic casting experiments were performed by using centrifugal casting method. The alloying elements were melted with induction under argon atmosphere in alumina crucibles and casted into copper molds of different shapes. Characterization of the cast specimens were performed by using DSC, XRD, SEM, and optical microscopy. Comparison of equilibrium and nonequilibrium solidification structures of cast specimens were also performed so as to verify the existence of the amorphous phase. Good agreement of the results of experimental work, with the predictions of the theoretical study, and the related literature was obtained.
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Lundin, Josefin. "Investigation of How Different Fat Systems and Other Ingredients Affect the Properties of Whipping Creams Based on Vegetable Fat." Thesis, Linnéuniversitetet, Institutionen för kemi och biomedicin (KOB), 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-27209.
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Whipping creams are oil-in-water emulsion which by whipping can be formed to a foam by the incorporation of air into the system. Traditionally whipping creams are made out of milk but today imitation whipping creams based on vegetable fat has gained a large share of the marked due to their many benefits compared to traditionally whipping creams. Imitation whipping creams are both cheaper and more flexible than traditionally creams. By vary the characteristics of the fat system and the cream recipe the properties of the imitation creams can be adapted to fit the purpose of a specific product. The aim of this thesis was to increase the understanding of how different types of fat systems and other ingredients affect the properties of imitation whipping creams based on vegetable fat. This was done by studying three vegetable fat systems with different physicochemical properties. The properties of the fat systems were characterized and the three fat systems were then used for making different imitation whipping creams. The properties of the creams were characterized and the properties of the fat systems and the creams were assessed and compared with each other. The study showed that the fat characteristics that generally seem to have the highest impact on the properties of whipping creams are the structure, the solid fat content and the crystallization temperature of the fat. A fat solution with a hard structure, a high crystallization temperature and a high solid fat content at a wide range of temperatures overall seem to provide the whipping creams with the best properties. This as these fat properties provide the creams with a high foam stability, a high overrun and a short whipping time. This study has also shown that other ingredients than the fat systems provide the creams with diverging properties. This is best shown by the results of the freeze-thaw stability which indicate that a recipe with a high amount of sugar seem to provide the whipping creams with good freeze-thaw stability. Other properties of the whipping creams also seem to be very much influenced by other ingredients than the fat systems but further studies are needed to provide clarity to the complexity of the interplay of the ingredients in whipped creams.
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Clogston, Jeffrey. "Applications of the lipidic cubic phase from controlled release and uptake to in meso crystallization of membrane proteins /." Connect to resource, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1117564268.
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Thesis (Ph.D.)--Ohio State University, 2005.Title from first page of PDF file. Document formatted into pages; contains xxii, 352 p.; also includes graphics. Includes bibliographical references (p. 346-352). Available online via OhioLINK's ETD Center
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Vialetto, Jacopo. "Interface-driven soft matter systems : from 2D particle crystallization and light-responsive assemblies to magnet-guided fluid transport." Thesis, Sorbonne université, 2018. http://www.theses.fr/2018SORUS358.
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Les matériaux mous impliquant des interfaces liquides présentent un grand intérêt scientifique en raison des multiples forces faibles en jeu qui dictent leur disposition et leur comportement, souvent surprenants. Dans cette thèse, nous avons étudié de nouveaux phénomènes et principes d'actuation pour le contrôle de la structure (organisation) et de la dynamique (mouvement) des systèmes de matière molle aux interfaces liquides, de l'assemblage dirigé de particules solides à la manipulation de gouttes flottantes. Nous avons établi une méthode pour adsorber et cristalliser des particules, de taille micro- ou nanométrique, à l'interface air/eau, mettant en évidence un nouveau rôle des tensioactifs pour contrôler l'organisation bidimensionnelle (2D) des particules à une concentration de tensioactif extraordinairement faible. Nous avons ensuite programmé ces assemblages en 2D afin de contrôler l'organisation des particules avec la lumière, en élaborant deux stratégies innovantes. L'utilisation de particules absorbant la lumière nous a permis de construire des structures ordonnées reconfigurables. Avec des particules ordinaires et des surfactant photosensibles, nous avons démontré un nouveau type de cristaux 2D dissipatifs (organisation induite par la lumière grâce à un apport constant en énergie). En parallèle, nous avons conçu une nouvelle méthode d'actuation magnétique pour la manipulation de petites entités liquides (gouttes, billes liquides) au moyen de substrats liquides paramagnétiques déformables, permettant de diriger, à l'aide de simples aimants permanents, le mouvement de gouttes d'huile ou d'eauSoft materials interacting at/with liquid interfaces are of great scientific interest because of the multiple weak forces at play that dictate their, often surprising, arrangement and behaviour. In this thesis, we studied novel phenomena and actuating principles for the control of the structure (organization) and dynamics (motion) of soft matter systems at liquid interfaces, from the directed assembly of thousands of solid particles, to the manipulation of small floating drops. We established the first method to both adsorb and crystallise nm- to µm-sized particles at air/water interface, evidencing a new role of surfactants to control two-dimensional (2D) particle organization at extremely low surfactant concentration. We then programmed such 2D assemblies in order to control particle organization with light stimulation, devising two innovative strategies. Using light-absorbing particles allowed us to construct reconfigurable ordered structures (light-controlled inter-particle distance and disassembly). With ordinary particles and photosensitive surfactant, we demonstrated a new kind of dissipative 2D crystals (light-induced organization through continuous consumption of energy). In parallel, we conceived a novel magnetic actuation method for the manipulation of small liquid entities (drops, liquid marbles) by means of deformable paramagnetic liquid substrates, shaping the liquid surface with small permanent magnets and in turn directing the motion of water and oil drops in a user-defined fashion
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Esposito, Rosario. "Studies of volatile evolution in magmatic systems using melt inclusions." Diss., Virginia Tech, 2012. http://hdl.handle.net/10919/28287.
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Understanding volatile evolution associated with active volcanic magmatic systems is of paramount importance because volatiles control and determine the magnitude of an eruption owing to the large change in molar volume that volatile species show depending on their physical state (volatiles dissolved in silicate melts vs. volatiles exsolved as vapor). For active volcanic systems studying the volatile evolution can help to assess the potential hazard associated to a certain locality. Also, volatile evolution in magmatic system controls the formation of certain ore deposits.
Despite the importance of understanding volatile evolution of magmatic systems, concentrations of volatiles of evolving magmas are not easily available especially for magmas originated in the deep crust. Fortunately, sample of melts can be entrapped as melt inclusion (MI) into growing igneous minerals in crystalizing magma chamber. After the entrapment, the crystal works as an insulating capsule from the external magmatic environment.
Researchers have started to use MI because they provide some advantages in respect to the classical whole rock approach to petrological studies. One of the most important advantages is that MI often represent sample of a deep and non-degassed melt (glass) available at Earth's surface. In fact, with the exception of deep ocean basalts, igneous whole rocks found at the Earth's surface are degassed magmas.
This dissertation is a compilation of four publications produced during six years of research and is addressed to give a contribution in understanding the volatile evolution in magmatic systems and also to improve the present understanding of information that can be obtained using the melt inclusions technique.
In the first chapter, I present an alternative interpretation of H₂O-CO₂ trends obtained from MI. In this study, we demonstrate that these trends can be due to post entrapment crystallization on the wall of the MI and not to magma ascent. This alternative view is more realistic especially for cases where in the same phenocrysts MI show strongly different CO₂ concentrations.
In the second chapter, I present a study to test for the MI reliability in recording volatile concentrations. We used the approach of the melt inclusion assemblage (MIA) that consists of analyzing groups of MI presumably entrapped at the same time and, thus, at same chemical and physical conditions. The results show that most of the MIA studied show consistent volatile concentrations corroborating the reliability of the MI technique. CO₂ shows the highest degrees of variability and we have assessed this behavior mostly to C-contamination in the surface of the sample.
The third chapter is a study case (the Solchiaro eruption in Southern Italy) that shows the potential uses of MI to understanding the volatile evolution. I present a model showing the dynamic of the magma based on MI. This study also discusses the origin of anomalous MI and which MI provide the best information.
The final chapter is dedicated to test the applicability of the new Linkam TS1400XY heating stage. I was able to show how this new microthermometric tool is capable of homogenizing MI at high temperature and to quench MI to a homogeneous glass state.Ph. D.
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Sharma, Satyajeet. "AMORPHOUS PHASE FORMATION IN MECHANICALLY ALLOYED FE-BASED SYSTEMS." Doctoral diss., University of Central Florida, 2008. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2484.
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ABSTRACT Bulk metallic glasses have interesting combination of physical, chemical, mechanical, and magnetic properties which make them attractive for a variety of applications. Consequently there has been a lot of interest in understanding the structure and properties of these materials. More varied applications can be sought if one understands the reasons for glass formation and the methods to control them. The glass-forming ability (GFA) of alloys can be substantially increased by a proper selection of alloying elements and the chemical composition of the alloy. High GFA will enable in obtaining large section thickness of amorphous alloys. Ability to produce glassy alloys in larger section thicknesses enables exploitation of these advanced materials for a variety of different applications. The technique of mechanical alloying (MA) is a powerful non-equilibrium processing technique and is known to produce glassy (or amorphous) alloys in several alloy systems. Metallic amorphous alloys have been produced by MA starting from either blended elemental metal powders or pre-alloyed powders. Subsequently, these amorphous alloy powders could be consolidated to full density in the temperature range between the glass transition and crystallization temperatures, where the amorphous phase has a very low viscosity. This Dissertation focuses on identifying the various Fe-based multicomponent alloy systems that can be amorphized using the MA technique, studying the GFA of alloys with emphasis on improving it, and also on analyzing the effect of extended milling time on the constitution of the amorphous alloy powder produced at earlier times. The Dissertation contains seven chapters, where the lead chapter deals with the background, history and introduction to bulk metallic glasses. The following four chapters are the published/to be published work, where the criterion for predicting glass formation, effect of Niobium addition on glass-forming ability (GFA), lattice contraction on amorphization, effect of Carbon addition on GFA, and observation of mechanical crystallization in Fe-based systems have been discussed. The subsequent chapter briefly mentions about the consolidation of amorphous powders and presents results of hot pressing and spark plasma sintering on one of the alloy systems. The final chapter summarizes the Dissertation and suggests some prospective research work that can be taken up in future. The Dissertation emphasizes the glass-forming ability, i.e., the ease with which amorphization can occur. In this work the milling time required for amorphization was the indicator/measure of GFA. Although the ultimate aim of this work was to consolidate the Fe-based amorphous alloy powders into bulk so as to undertake mechanical characterization, however, it was first necessary to study the glass forming aspect in the different alloy systems. By doing this a stage has been reached, where different options are available with respect to amorphous phase-forming compositions and the knowledge to improve glass-forming ability via the mechanical alloying technique. This will be ultimately useful in the powder compaction process into various shapes and sizes at optimum pressure and temperature. The study on mechanical crystallization indicates, or in a way defines, a limit to the process of amorphization, and it was also demonstrated that this phenomenon is more common in occurrence than and not as restricted as it was earlier reported to be.Ph.D.
Department of Mechanical, Materials and Aerospace Engineering
Engineering and Computer Science
Materials Science & Engr PhD
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Lucas, Bruce. "Fundamental Modeling of Solid-State Polymerization Process Systems for Polyesters and Polyamides." Diss., Virginia Tech, 2005. http://hdl.handle.net/10919/29378.
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The dissertation describes and assembles the building blocks for sound and accurate models for solid-state polymerization process systems of condensation polymers, particularly poly(ethylene terephthalate) and nylon-6. The work centers on an approach for modeling commercial-scale, as opposed to laboratory-scale, systems. The focus is not solely on coupled polymerization and diffusion, but extends to crystallization, physical properties, and phase equilibrium, which all enhance the robustness of the complete model.
There are three applications demonstrating the utility of the model for a variety of real, industrial plant operations. One of the validated simulation models is for commercial production of three different grades of solid-state PET. There are also validated simulation models for the industrial leaching and solid-state polymerization of nylon-6 covering a range of operating conditions. The results of these studies justify our mixing-cell modeling approach as well as the inclusion of all relevant fundamental concepts.
The first several chapters discuss in detail the engineering fundamentals that we must consider for modeling these polymerization process systems. These include physical properties, phase equilibrium, crystallization, diffusion, polymerization, and additional modeling considerations. The last two chapters cover the modeling applications.Ph. D.
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Shah, Zulfiqar Hussain. "Synthesis and Characterizations of Fe-based Metallic Glassy Systems." Thesis, KTH, Materialvetenskap, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-37395.
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This thesis is a study of tailoring amorphous Fe-B-Si based alloy to produce bulk glassy rods by adding Nb. We have prepared rapid quenched thin ribbons (thickness ~12 µm) by melt spinning, and glassy rods of diameter ~1mm by Cu-mold casting based on compositions (Fe0.78B0.13Si0.9)100-xNbx (x=0, 4, 8, 12), and studied their different physical properties. The melt-spun ribbons are found to be X-ray amorphous, whereas some nano-crystallinity is observed in the case of rods. All the ribbons show high saturation magnetization and low coercivity, which are the desirable characteristics of a soft ferromagnet. These ribbons are thus suitable for designing high frequency transformers, and sensors from an applications point of view. With increasing Nb content their saturation magnetization, ferromagnetic Curie temperature, and resistivity are found to decrease as expected. The temperature dependence of electrical resistivity shows small positive temperature co-efficient that is expected for a metallic disordered material. We have also studied the modification of the properties on thermal annealing the (Fe0.78B0.13Si0.9)96 Nb4 ribbon at different temperatures in a neutral atmosphere.
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Tam, Le Minh [Verfasser]. "Designing crystallization based-enantiomeric separation for chiral compound-forming systems in consideration of polymorphism and solvate formation / Le Minh Tam." München : Verlag Dr. Hut, 2014. http://d-nb.info/1052374735/34.
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[Verfasser], Le-Minh-Tam. "Designing crystallization based-enantiomeric separation for chiral compound-forming systems in consideration of polymorphism and solvate formation / Le Minh Tam." München : Verlag Dr. Hut, 2014. http://nbn-resolving.de/urn:nbn:de:101:1-2014062022375.
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Hernandez, Lindsey Danielle. "Magma Plumbing Systems along the Juan de Fuca Ridge." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1587630136962186.
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Querniard, Florian. "Thermodynamic study of organic heterogeneous systems : improvement of discontinuous isoperibolic thermal analysis, and use of phase diagrams to design enantiomeric resolutions by crystallization." Rouen, 2010. http://www.theses.fr/2010ROUES026.
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Ce travail de thèse traite de l'étude thermodynamique des systèmes hétérogènes organiques. L'analyse thermique isopéribolique discontinues (DITA), une technique expérimentale permettant l'étude des diagrammes de phases a été améliorée dans trois de ses aspects. Tout d'abord, il a été montré que le signe des ruptures de pente, qui sont caractéristiques du franchissement des limites de domaines, indique le comportement direct ou rétrograde de ces limites. Ensuite, l'incertitude des résultats fournis par la DITA a été estimée grâce à un inventaire des sources d'erreur et à des tests de répétabilité. Enfin, un nouveau logiciel d'automatisation et d'exploitation des résultats a été mis au point pour rendre la technique plus accessible. L'influence de la quantité d'agent dédoublant sur la résolution d'énantiomères par sels diastéréomériques a été étudiée sur la base des diagrammes de phase. Il a été montré que, dans les cas favorables, la quantité d'agent dédoublant peut-être diminuée en dessous d'un demi équivalent sans perte d'efficacité. Cela s'accompagne d'une économie en solvant et d'une réduction de la taille du réacteur pour un résultat équivalent. La résolution de la CF361H par l'αMBA dans l'éthanol est donnée en exemple expérimental. Un nouveau procédé de résolution du phencyphos a été mis au point. La cristallisation préférentielle de son monohydrate a été développée et optimisée à l'aide de diagrammes de phase. Ce procédé a été porté avec succès à l'échelle de 35 litres et 30kg de chaque énantiomère ont été produitsThe work presented consists of thermodynamic study of organic heterogeneous systems. Discontinuous Isoperibolic Thermal Analysis (DITA), an experimental technique dedicated to phase diagram investigation has been improved in three aspects. First, it has been demonstrated that the sign of slope breaks, which are characteristic of phase domain boundary crossing, indicates the direct or retrograde behaviour of these boundaries. Then, the uncertainty of DITA results has been estimated through an inventory of error sources and repeatability tests. Finally, a new automation and processing software has been developed to make the technique more accessible. The influence of resolving agent amount on enantiomer resolution by diastereomeric salts has been studied based on phase diagrams. It has been demonstrated that on favourable cases, the amount of resolving agent can be reduced to less than a half equivalent without efficiency loss. This reduction comes with an economy of solvent and reactor size. The resolution of (±)-CF361H by various amount of αMBA in ethanol is given as experimental example. A new resolution route for phencyphos has been found through preferential crystallization of its monohydrate. This new process has been designed and optimized with the help of phase diagram knowledge. It has been upscaled successfully to 35 litres. 30kg of each enantiomer have been produced
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[Verfasser], Le-Minh-Tam, and Andreas [Akademischer Betreuer] Seidel-Morgenstern. "Designing crystallization based-enantiomeric separation for chiral compound-forming systems in consideration of polymorphism and solvate formation / Tam Le Minh. Betreuer: Andreas Seidel-Morgenstern." Magdeburg : Universitätsbibliothek, 2014. http://d-nb.info/105791391X/34.
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Bai, Xianming. "Thermodynamics and Kinetics of Phase Transitions during Supercooling and Superheating: A Theoretical and Computational Investigation in Model Lennard-Jones Systems." Diss., Available online, Georgia Institute of Technology, 2006, 2006. http://etd.gatech.edu/theses/available/etd-11132006-110828/.
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Thesis (Ph. D.)--Materials Science and Engineering, Georgia Institute of Technology, 2007.Martha A. Gallivan, Committee Member ; Andrei G. Fedorov, Committee Member ; Christopher Summers, Committee Member ; Thomas H. Sanders, Jr., Committee Member ; Mo Li, Committee Chair.
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Zago, Gustavo Pereira. "Estudo da co-cristalização em sistema ternário NaCI-CaSO4-H2O para dessalinização de água." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/3/3137/tde-15012018-132007/.
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O crescimento acelerado da população mundial e o consequente aumento da produção de bens de consumo tem impulsionado uma crise na disponibilidade de recursos naturais, principalmente os hídricos. Diante da escassez de recursos hídricos, processos de tratamento de efluentes industriais e domésticos que visam o descarte zero de líquido (ZLD - Zero Liquid Discharge) vêm sendo cada vez mais estudados. Atualmente, diversos processos têm sido empregados com este propósito. No entanto, ainda há a geração, juntamente com a água recuperada, de uma corrente composta por uma solução salina concentrada, cuja composição normalmente é constituída por diferentes tipos de sais inorgânicos. Uma das formas de alcançar o descarte zero de líquidos é por meio da implementação de um processo adicional de separação, sendo a cristalização evaporativa considerada viável para essa finalidade. O emprego deste processo é limitado ao controle das características morfológicas das partículas obtidas, visto que estas influenciam diretamente na efetividade de separação dos processos subsequentes à cristalização (filtração, centrifugação). Além disso, efluentes industriais são soluções complexas, e a utilização da cristalização envolve a presença de mais de um sal em solução (co-cristalização). Este processo é pouco investigado na literatura científica, logo, a determinação de condições de processos visando controlar a características destas partículas não é trivial. Neste trabalho, foram estudados o efeito da taxa de evaporação e da presença de sementes na morfologia, composição, tamanho e hábito de partículas de cloreto de sódio e sulfato de cálcio obtidas por co-cristalização evaporativa em bateladas. Os resultados serviram para a determinação de parâmetros de operação para a co-cristalização visando a obtenção de partículas com elevado tamanho médio e baixa dispersão de tamanhos. Taxas de evaporação elevadas favoreceram a obtenção de aglomerados de partículas. A presença de sulfato de cálcio em solução resultou em partículas maiores, menos polidispersas e com menor grau de aglomeração. Tal resultado foi considerado positivo, visto que, estas características são desejáveis para a separação dos cristais da solução mãe. Foi também observado que as sementes de hemihidrato atuam inibindo a aglomeração dos cristais de NaCl. O aumento da quantidade de sementes destes sais culminou na obtenção de partículas menos aglomeradas, porém houve um alargamento das distribuições de tamanho de partículas. Nos experimentos em que foram utilizadas sementes de ambos os sais, o mesmo efeito na aglomeração foi observado. Em todos os experimentos com semeadura de hemihidrato, foi observada a aglomeração deste sal com o NaCl, que foi intensificada com o aumento da taxa de evaporação e com o aumento da concentração de sementes. Foi identificada a possibilidade de recuperação de ambos os sais e obtenção - em determinadas condições - de mais de 90% do NaCl com até 99,50% de pureza.The accelerated growth of the world population and the consequent increase in the production of consumer goods, has driven to a crisis in the availability of natural resources, especially water. Due to the scarcity of water resources, industrial and domestic wastewater treatment processes that aim the Zero Liquid Discharge (ZLD) have been increasingly studied. Nowadays, several processes have been used for this purpose. However, in all of them, there is still the generation of a brine composed of a concentrated salt solution, concomitantly with the recovered water, whose composition is normally constituted by different types of inorganic salts. One way to achieve the ZLD is through the implementation of an additional separation process, for which the evaporative crystallization is considered technically viable for this purpose. The use of this process is limited to the control of the morphological characteristics of the particles obtained, since this influences directly the separation effectiveness of the downstream processes to crystallization (filtration, centrifugation). Besides, industrial effluents are complex solutions and its crystallization involves the presence of more than one salt in solution (cocrystallization). This process is still not well investigated on scientific literature, thus, the determination of process conditions aiming to control the characteristics of these particles is not trivial. In this work, the effect of the evaporation rate and the presence of seeds on the morphology, composition, size and habit of sodium chloride and calcium sulfate particles obtained by batch evaporative co-crystallization were studied. The results were used to determine the operating parameters for the cocrystallization in order to obtain particles with high average size and narrow dispersion of sizes. High evaporation rates favored the obtaining of agglomerated particles. The presence of calcium sulfate in solution resulted in larger particles, less polydisperse and with less degree of agglomeration. Such result was considered positive, since, these characteristics are desirable for the separation of the crystals from the solution. Seeds of hemihydrate inhibited the agglomeration of the NaCl crystals. The increase in seed load of hemihydrate culminated in obtaining less agglomerated particles, but there was an increase in particle size distributions. In the experiments in which seeds of both salts were used, the same effect in the agglomeration was observed. In all experiments with seeds of hemihydrate, agglomeration of this salt with NaCl was observed, which was intensified with increasing evaporation rate and increasing seed amount. It was identified the possibility of recovery of both salts and, for certain conditions, obtaining more than 90% of NaCl with up to 99.50% purity.
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Angelin, Marcus. "Discovery-Oriented Screening of Dynamic Systems: Combinatorial and Synthetic Applications." Doctoral thesis, KTH, Organisk kemi, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-12524.
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This thesis is divided into six parts, all centered around the development of dynamic (i.e., reversibly interacting) systems of molecules and their applications in dynamic combinatorial chemistry (DCC) and organic synthesis. Part one offers a general introduction, as well as a more detailed description of DCC, being the central concept of this thesis. Part two explores the potential of the nitroaldol reaction as a tool for constructing dynamic systems, employing benzaldehyde derivatives and nitroalkanes. This reaction is then applied in part three where a dynamic nitroaldol system is resolved by lipase-catalyzed transacylation, selecting two out of 16 components. In part four, reaction and crystallization driven DCC protocols are developed and demonstrated. The discovery of unexpected crystalline properties of certain pyridine β-nitroalcohols is used to resolve a dynamic system and further expanded into asynthetic procedure. Furthermore, a previously unexplored tandem nitroaldol-iminolactone rearrangement reaction between 2-cyanobenzaldehyde and primarynitroalkanes is used for the resolution of dynamic systems. It is also coupled with diastereoselective crystallization to demonstrate the possibility to combine several selection processes. The mechanism of this reaction is investigated and a synthetic protocol is developed for asymmetric synthesis of 3-substituted isoindolinones. Part five continues the exploration of tandem reactions by combining dynamic hemithioacetal or cyanohydrin formation with intramolecular cyclization to synthesize a wide range of 3-functionalized phthalides. Finally, part six deals with the construction of a laboratory experiment to facilitate the introduction of DCC in undergraduate chemistry education. The experiment is based on previous work in our group and features an acetylcholinesterase-catalyzed resolution of a dynamic transthioacylation system.QC 20100628
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Lin, JiaCheng, and HaoRan Teng. "Influence of Nucleation Techniques on the Degree of Supercooling and Duration of Crystallization for Sugar Alcohol as Phase Change Material : Investigation on erythritol-based additiveenhanced Composites." Thesis, KTH, Energiteknik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-257758.
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Utilizing Phase Change Materials (PCM) for Latent Thermal Energy Storage (LTES) applications have previously been extensively researched as a measure to reduce greenhouse gas emissions from energy consumption. In order to make use of the waste heat from industrial processes for LTES purposes, a new demand emerged for PCMs capable of phase change in mid-temperature ranges of 100 °C - 200 °C. This higher temperature requirement made most of the previously studied material inapplicable as they had much lower melting and solidification temperatures. With this in mind, a new generation of PCMs consisting of Sugar Alcohols (SA) has been proposed. Erythritol is seen as an especially promising SA with good thermophysical properties for LTES purposes. However, it has been shown to suffer from severe supercooling, which makes it unreliable in real applications. To eradicate this issue, two additives, Graphene Oxide (GO) and Polyvinylpyrrolidone (PVP) at varying mass fractions were mixed with pure erythritol to form a composite which was studied using the Temperature-history (T-history) method to determine its effectiveness in reducing supercooling. Results show that at its most effective mass fraction, GO reduces supercooling by 28 o C and a 31 o C reduction is seen by the addition of PVP. The impacts on the duration of crystallization was also documented and analyzed using the same method. It was observed that the duration of crystallization was increased with increasing mass fractions of the additives. Other important properties of the composites were also studied in order to determine the overall feasibility for industrial applications. It includes analysis of the storage capacity through latent heat, changes in viscosity along with impacts on thermal diffusivity of the composites.Att använda fasändringsmaterial (PCM) för termisk energilagring i form av latent värme (LTES) har tidigare extensivt forskats och undersökts som en lösning för att minska utsläppen av växthusgaser från energiförbrukning. För att utnyttja spillvärme från industriella processer för LTES-ändamål uppstod en efterfrågan på PCM som ändrar fas i temperaturer mellan 100 °C - 200 °C. Detta krav på högre temperatur gjorde att de flesta av de tidigare aktuella materialen inte kunde tillämpas eftersom de hade mycket lägre smält- och kristalliseringstemperaturer. Med detta i åtanke har en ny generation av PCM bestående av sockeralkoholer (SA) föreslagits. Erytritol ses som ett särskilt lovande SA med goda egenskaper för LTES-ändamål. Den har dock visat sig drabbas av svår underkylning, vilket gör den opålitligt i verkliga tillämpningar. För att utrota detta problem blandades två tillsatser, Graphene Oxide (GO) och Polyvinylpyrrolidone (PVP) vid olika massfraktioner med ren erytritol för att bilda en komposit som studerades med metoden Temperature-history (T-history) för att bestämma dess effektivitet på att minska underkylningen. Resultaten visar att GO på sin mest effektiva massfraktion minskar underkylningen med 28 o C och tillsats av PVP lyckats minska den med som mest 31 o C. Påverkningarna på varaktighet av kristallisering dokumenterades och analyserades med samma metod. Det var observerad att varaktigheten av kristallisering ökades med ökande massfraktioner av tillsatserna. Även andra viktiga egenskaper hos kompositerna studerades för att avgöra rimligheten att använda dessa för industriella tillämpningar. Det inkluderar analys av lagringskapaciteten genom latent värme, förändringar i viskositet tillsammans med påverkan på kompositernas termiska diffusivitet.
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Oak, Milind Prabhakar. "Virtual customer driven product design crystallization." Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/91722.
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Álvarez, Marimón Mª Elena. "Structural studies of Heteromeric Amino acid Transporters (HATs): Validation of the first 3D structural model of a HAT (human 4F2hc/LAT2) and identification of new HAT targets for 3D‐crystallization." Doctoral thesis, Universitat de Barcelona, 2014. http://hdl.handle.net/10803/284082.
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Heteromeric amino acid transporters (HATs) mediate the transport of amino acids through the plasma membrane. They are composed of two subunits (a heavy and a light one) linked by a conserved disulfide bridge. Genetic defects in the genes coding these HATs may affect its functionality or expression, leading to inherited aminoacidurias. Thus, solving the structure of the Eukaryotic HATs has become of great importance. However structural information about interactions between the heavy and light subunits of HATs is scarce.
In this work, human 4F2hc/L-type amino acid transporter 2 (LAT2) first low resolution 3D model obtained by single particle negative-staining transmission electron microscopy (TEM) was validated. In order to assess the interaction between both subunits of the heterodimer, crosslinking experiments between cysteine residues in both moieties was tried. Namely, two chemical spacers of different length (10.5 and 14.3 Å) were tested and crosslinking was observed for those mutants with pairing positions between 8 and 17.5 Å. Indeed, specific residues that crosslinked 4F2hc and LAT2 nearly completely (>80%). As a result of the positive results (as compared to the appropriate controls) the idea that 4F2hc-ED almost completely covers the extracellular surface of the transporter subunit LAT2 is reasonable. Moreover, further varied evidences (TEM, SPA and docking experiments) were in line with the obtained results, revealing that the extracellular domain of 4F2hc interacts with LAT2, almost completely covering the extracellular face of the transporter. The interaction of 4F2hc with LAT2 gives insights into the structural bases for light subunit recognition and the stabilizing role of the ancillary protein in HATs. In addition, it has been demonstrated that the ectodomain of 4F2hc suffices the stabilization of the light subunit.
The second goal of the thesis was to find a suitable HAT candidate to perform crystallization trials and posterior structure elucidation, since human 4F2h/LAT2 was not stable enough for this aim. Until now, only the human 4F2hc ectodomain atomic structure has been solved (Fort et al., 2007), and some low sequence amino acid identity prokaryotic homologues of LATs.
In order to identify putative good eukaryotic light subunits for 3D crystallization the adopted GFP‐based Saccharomyces cerevisiae protocol for our transporters resulted successful since it allowed to find three putative good candidate eukaryotic light subunits for 3D crystallization studies. GFP technology allowed quick expression screening, membrane protein-detergent solubilization screening and finally another screening step including assessment of the stability by ultracentrifugation dispersity sedimentation.
Once the candidates selected in the best conditions, further purification was required (size exclusion chromatography) before attempting crystallization. In this sense, further efforts were delivered in order to try to enhance the stability (and minimize aggregation). Thus, addition of lipids in the solubilization step and during protein purification was used to mimic the protein membrane environment and reduce the aggregation. Really interesting is the stabilizing effect that cholesterol has on almost all light subunits tested. This is in concordance with the fact that 4F2hc has been found located in lipid rafts where membrane are rich in cholesterol. Removal of reactive cysteine and generation of truncated versions of the protein in the C and N terminal were introduced to increase the crystallization probability. This work ended with the finding of 3 good candidates for crystallization screenings, and the best candidate was optimized in terms of stability and protein flexibility for crystallization studies. Just preliminary crystallization trials were done.Los transportadores heteroméricos de aminoácidos (HAT) median el transporte de aminoácidos a través de la membrana plasmática. Representan el único ejemplo de transportadores de solutos formado por dos subunidades distintas unidas por un puente disulfuro. Debido a su gran relevancia en fisiología (asociados a aminoacidurias, infección por virus, cáncer,…) el estudio de su estructura-función resulta clave. Debido a su naturaleza, son proteínas difíciles de cristalizar, de las que sólo se conoce la estructura atómica del ectodominio de 4F2hc humano. En este escenario la tesis se centró en la validación del primer modelo 3D a baja resolución de un HAT humano (4F2hc/LAT2), mediante experimentos de crosslinking entre subunidades, e identificación de nuevos candidatos para cristalización 3D. Para ello se seleccionaron 24 subunidades ligeras de distintas especies eucariotas y se testaron en un proceso de selección para determinar el/los mejores candidatos. El primer objetivo de la tesis concluyó con la determinación de residuos concretos en 4F2hc y LAT2 cercanos a una distancia de 3-14 Å mediante la utilización de crosslinkings de cisteínas. Finalmente, tres líneas distintas: el modelo 3D obtenido por microscopía electrónica de transmisión y tinción negativa de partículas individuales (en colaboración con Dr. Fotiadis), los experimentos de crosslinking, y el docking generado en colaboración con Dr. Fdz-Recio, demostraron que 4F2hc-ED cubre, casi completamente, la superficie extracelular de LAT2. Además, se demostró que el ectodominio de 4F2hc es suficiente para estabilizar LAT2. Como resultados del segundo objetivo, tres subunidades ligeras fueron seleccionadas, tras adaptar el protocolo desarrollado por Drew et al.,2008, como mejores candidatas para estudios de cristalización 3D. Posteriormente, distintas estrategias se siguieron para mejorar la estabilidad de la mejor candidata: eliminación de la cisteína reactiva, adición de lípidos a la muestra, cambio de sistema de expresión para aumentar su expresión a células de insecto Sf9. Además, se generaron mutantes delecionados en N y C terminal para reducir su flexibilidad y aumentar la probabilidad de cristalización. Se concluyó en encontrar un buen candidato para estudios de cristalización.
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PINHEIRO, LUCAS B. "Síntese e caracterização de compósitos de NiO-YSZ-CeOsub(2) com tratamento hidrotermal assistido por micro-ondas." reponame:Repositório Institucional do IPEN, 2013. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10574.
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Made available in DSpace on 2014-10-09T12:42:08Z (GMT). No. of bitstreams: 0Made available in DSpace on 2014-10-09T14:04:41Z (GMT). No. of bitstreams: 0
Dissertação (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Ibrahim, Mohamed Asim Y. "Co-processing of drugs and co-crystal formers and its effect on pharmaceutical dosage-form performance. Co-crystallization of urea/ 2-methoxybenzamide, caffeine/ malonic acid, caffeine/ oxalic acid and theophylline/ malonic acid systems: Solid-state characterization including imaging, thermal, X-ray and Raman spectroscopic techniques with subsequent evaluation of tableting behaviour." Thesis, University of Bradford, 2008. http://hdl.handle.net/10454/12760.
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This dissertation has focused on the solid-state characterization of different co-crystal system as well as the effect of co-crystallization of these systems on pharmaceutical dosage form performance. Urea/ 2-MB, caffeine/ malonic acid, caffeine/ oxalic acid and theophylline/ malonic acid co-crystals were prepared using co-grinding- and co-precipitation techniques. In addition, the synthesis of co-crystals through two novel methods has been demonstrated. This includes compaction and convection mixing. The solid-state characterization of the co-crystals has been carried out using XRPD, Raman spectroscopy, DSC, TGA, hot-stage microscopy and SEM. After preparation of co-crystals, tablets have been produced from co-ground-, co-precipitated-, and physical mixtures using Compaction Studies Press (Kaleva), and the data were recorded to compare between the different mixtures, regarding compactibilty, compressibility and deformational properties. The DSC results showed that the physical mixtures of all systems, formed co-crystals during heating process. For systems of urea/ 2-MB, caffeine/ malonic acid and theophylline/ malonic acid, the co-ground mixture produced tablets with higher tensile strength compared with either co-precipitated or physical mixture. However, for caffeine/ oxalic acid system, the tensile strengths of compacts produced from the physical mixture were greater than those obtained from either co-ground or co-precipitated mixtures. The Heckel data suggested that urea/ 2-MB, caffeine/ malonic acid and theophylline/ malonic acid systems are Type 1 materials, as an extensive linearity during compression was indicative of a plastic deformation mechanism, while the caffeine/ oxalic acid system was Type 2 materials. However, the co-precipitated mixture of urea/ 2-MB system was the least compressible, as it possessed the greatest value of yield pressure (85 MPa) and the highest elastic recovery (7.42%). The co-precipitated mixture of both of caffeine/ malonic acid and theophylline/ malonic acid systems was the most compressible with small yield pressure values of (44 & 80 MPa) and elastic recovery of (7.2% & 6.56%), respectively. The co-ground mixture of caffeine/ oxalic acid possessed the highest value of yield pressure (166 MPa) and thus the lowest compressibility among other mixtures. Furthermore, the addition of microcrystalline cellulose and α-lactose monohydrate has affected the crystallinity as well as the tableting properties of the co-crystals. After the addition of excipients, the tensile strength of compacts was about 2 times higher than any other mixture. Finally, urea/ 2-MB and caffeine/ malonic acid co-crystals were successfully synthesized through convection mixing and compaction.Islamic University of Omdurman and the Ministry of Higher Education in Sudan
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Ibrahim, Mohamed Asim Yousif. "Co-processing of drugs and co-crystal formers and its effect on pharmaceutical dosage-form performance : co-crystallization of urea/2-methoxybenzamide, caffeine/malonic acid, caffeine/oxalic acid and theophylline/malonic acid systems : solid-state characterization including imaging, thermal, X-ray and Raman spectroscopic techniques with subsequent evaluation of tableting behaviour." Thesis, University of Bradford, 2008. http://hdl.handle.net/10454/12760.
Full textAbstract:
This dissertation has focused on the solid-state characterization of different co-crystal system as well as the effect of co-crystallization of these systems on pharmaceutical dosage form performance. Urea/ 2-MB, caffeine/ malonic acid, caffeine/ oxalic acid and theophylline/ malonic acid co-crystals were prepared using co-grinding- and co-precipitation techniques. In addition, the synthesis of co-crystals through two novel methods has been demonstrated. This includes compaction and convection mixing. The solid-state characterization of the co-crystals has been carried out using XRPD, Raman spectroscopy, DSC, TGA, hot-stage microscopy and SEM. After preparation of co-crystals, tablets have been produced from co-ground-, co-precipitated-, and physical mixtures using Compaction Studies Press (Kaleva), and the data were recorded to compare between the different mixtures, regarding compactibilty, compressibility and deformational properties. The DSC results showed that the physical mixtures of all systems, formed co-crystals during heating process. For systems of urea/ 2-MB, caffeine/ malonic acid and theophylline/ malonic acid, the co-ground mixture produced tablets with higher tensile strength compared with either co-precipitated or physical mixture. However, for caffeine/ oxalic acid system, the tensile strengths of compacts produced from the physical mixture were greater than those obtained from either co-ground or co-precipitated mixtures. The Heckel data suggested that urea/ 2-MB, caffeine/ malonic acid and theophylline/ malonic acid systems are Type 1 materials, as an extensive linearity during compression was indicative of a plastic deformation mechanism, while the caffeine/ oxalic acid system was Type 2 materials. However, the co-precipitated mixture of urea/ 2-MB system was the least compressible, as it possessed the greatest value of yield pressure (85 MPa) and the highest elastic recovery (7.42%). The co-precipitated mixture of both of caffeine/ malonic acid and theophylline/ malonic acid systems was the most compressible with small yield pressure values of (44 & 80 MPa) and elastic recovery of (7.2% & 6.56%), respectively. The co-ground mixture of caffeine/ oxalic acid possessed the highest value of yield pressure (166 MPa) and thus the lowest compressibility among other mixtures. Furthermore, the addition of microcrystalline cellulose and α-lactose monohydrate has affected the crystallinity as well as the tableting properties of the co-crystals. After the addition of excipients, the tensile strength of compacts was about 2 times higher than any other mixture. Finally, urea/ 2-MB and caffeine/ malonic acid co-crystals were successfully synthesized through convection mixing and compaction.
35
Wollmann, Georgia. "Crystallization Fields of Polyhalite and its Heavy Metal Analogues." Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2010. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-32906.
Full textAbstract:
Polyhalite is an abundant distributed mineral in rock salt formations, and considered to respond as a natural heavy metal sink because the Mg2+ ion can be substituted by other bivalent metal ions like Mn2+, Co2+, Ni2+, Cu2+ and Zn2+.
One of the quantities needed to predict mineral solubilities in multi-electrolyte solutions is the solubility constant Ksol. Since polyhalite forms slowly over months or years at 298 K, the solid-liquid phase equilibria experiments were accomplished at 313 K. Enthalpies of dissolution were measured and used to extrapolate lnKsol from 313 K to 298 K. Pitzer’s equations have been applied to describe activities of solute and water, with Pitzer parameters estimated from experimental data.
The solubility constants for the polyhalites were applied to calculate the solubility equilibria in the quaternary systems K+, M2+, Ca2+ / SO42- // H2O (M = Mg, Mn, Co, Cu, Zn) at 298 K and 313 K, and in case of Mg-polyhalite also in the hexary system Na+, K+, Mg2+, Ca2+ / Cl-, SO42- // H2O.
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Boulay, Emilie. "Amorphous phase separation and crystallization in the BaO-TiO2-SiO2 system: experimental approach and thermodynamic study." Doctoral thesis, Universite Libre de Bruxelles, 2015. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209133.
Full textAbstract:
Glass-ceramics are of growing interest due to their enhanced properties compared to the base glasses. More specifically, the control of microstructures is a major challenge as the properties of glass-ceramics are the direct consequences of microstructures. Microstructures can be modified by forming specific crystal phases or by using a prior amorphous phase separation before crystallization. The PhD thesis objectives are to demonstrate that the properties of silicate glasses can be enhanced by controlling their microstructure genesis with composition and thermal process parameters. More specifically, two systems were studied and compared: the BaO-TiO2-SiO2 system and the soda-lime silica Na2O-CaO-SiO2 used industrially. Both systems exhibit a large zone of immiscibility allowing the study of the influence of phase separation on crystallization.The first system BaO-TiO2-SiO2 has gathered interest from the interesting properties of fresnoite (Ba2TiSi2O8): piezo and pyroelectricity, second harmonic generation and blue/white photoluminescence. Many studies on the stoichiometric composition were conducted to understand and improve those promising properties. However, it was recently suggested that the photoluminescence can be improved with composition exhibiting phase separation. This indicates that the photoluminescence intensity can be improved through a microstructural control. The possible role of a prior amorphous phase separation on the subsequent crystallization has been however the topic of vigorous debates over the last decades and has not yet been clarified, especially regarding the role of the interfaces created by the phase separation. In this PhD, the effect of phase separation on fresnoite crystallization was studied. This had to pass through the calculation of the liquid-liquid immiscibility in the phase diagram in order to select suitable compositions to compare in a systematic study. The systematic study concludes to a surface crystallization mechanism for all non- stoichiometric compositions and shows no influence between amorphous droplets and matrix crystallization. This study was also completed with the investigation of the effect of composition (i.e. SiO2-excess), annealing temperature and prior heat treatment, i.e. heating rate, cooling rate or a prior isothermal step before annealing. It is shown that specific microstructures are obtained depending on the process parameters. Finally, selected compositions and heat treatment show how photoluminescence intensity can be improved by a microstructural control. The highest intensity is obtained with a high crystallization fraction and a maximization of the number of interfaces.
The results obtained in the study of the BaO-TiO2-SiO2 system are extended to the soda-lime-silica system in order to study the effect of phase separation on crystallization. It is shown that cristobalite forma- tion from the surface cannot be avoided and that the involved composition shift inhibits phase separation. It is consequently difficult to observe an interplay. Those studies lead to a general discussion about the criteria allowing to observe an interplay between phase separation and crystallization in oxide glasses.
Doctorat en Sciences de l'ingénieur
info:eu-repo/semantics/nonPublished
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Zeng, Jianming. "Constrained crystallization and depletion in the polymer medium for transdermal drug delivery system." Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/5102.
Full textAbstract:
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.
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Kim, Seong-Jin. "Directional crystallization in the bismuth-strontium-calcium-copper-oxygen system: Effect of phase separation." Diss., The University of Arizona, 1992. http://hdl.handle.net/10150/186040.
Full textAbstract:
Novel unidirectional crystallization was tested in glasses of the Bi-Sr-Ca-Cu-O system to produce highly oriented microstructures. Some evidence of liquid-liquid phase separations on cooling melts of Bi₂Sr₂Ca₁Cu₂Oₓ and Pb₀ͺ₃₂Bi₁ͺ₆₈Sr₁ͺ₇₅Ca₂Cu₃Oₓ is found for the first time from Differential Thermal Analysis (DTA), X-ray Diffraction (XRD), and Transmission Electron Microscope (TEM). This made it difficult to produce highly oriented microstructures through the present route because one of the phases in the phase separated structure is likely close to "R"-phase composition and lead to copious nucleation of "R"-phase on heating. This also resulted in sequential crystallization of the current liquids, first to "R"-phase and then to the Bi₂Sr₂Ca₁Cu₂Oₓ phase. Theoretical modelling was performed to understand general questions in the present route. The model suggests that a liquid with high interfacial energy is a good candidate for the present route to produce highly oriented microstructures. The model was tested in lithium diborate glass and showed a highly oriented microstructure. Thus, unidirectional crystallization is generally an attractive processing option for a liquid free of phase separation.
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Taylor, Donald Fulton. "Measurement of binary phase equilibria and ternary/quaternary gas antisolvent (GAS) system measurement and analysis." Thesis, Available online, Georgia Institute of Technology, 2004:, 2004. http://etd.gatech.edu/theses/available/etd-07112004-194307/unrestricted/taylor%5Fonald%5Ff%5F200407%5FMS.pdf.
Full textAbstract:
Thesis (M.S.)--School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, 2005. Directed by Charles Eckert.Charles Eckert, Committee Chair ; Amyn Teja, Committee Member ; Pete Ludovice, Committee Member. Includes bibliographical references.
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Getson, Jacqueline. "Effect of plagioclase crystallization on liquid and magma viscosity in the Anorthite-diopside-dorsterite-quartz system." Diss., Columbia, Mo. : University of Missouri-Columbia, 2006. http://hdl.handle.net/10355/4628.
Full textAbstract:
Thesis (M.S.) University of Missouri-Columbia, 2006.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (June 25, 2007) Includes bibliographical references.
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Liu, Lei. "The link between convection and crystallization in a sub-axial magma chamber and heat output in a seafloor hydrothermal system." Thesis, Available online, Georgia Institute of Technology, 2007, 2007. http://etd.gatech.edu/theses/available/etd-07072007-142506/.
Full text
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Rowland-Smith, Andrea. "The 1630 AD eruption of Furnas Volcano, São Miguel, Azores (Portugal): chemical variations and magmatic processes." Miami University / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=miami1186143145.
Full text
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Stanojevic, Sanja [Verfasser], and Ralf [Akademischer Betreuer] Busch. "Processing, crystallization and oxidation of the Ni-Nb(-Sn) refractory alloy glass system / Sanja Stanojevic. Betreuer: Ralf Busch." Saarbrücken : Saarländische Universitäts- und Landesbibliothek, 2013. http://d-nb.info/1053681666/34.
Full text
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Xiao, Yi. "Structural study of ExsA, the regulator of Type III Secretion System of Pseudomonas aeruginosa." Thesis, Virginia Tech, 2013. http://hdl.handle.net/10919/50944.
Full textAbstract:
The Type III secretion system (T3SS) of Pseudomonas aeruginosa uses a needle-like protein apparatus to detect eukaryotic host cells and translocate effectors directly into the host cell. The effectors are also known as cytotoxins, which cause disruption of a series of signaling events in the host cell, facilitating the infection by P. aeruginosa. As the T3SS is antigenic and the expression of T3SS is energy-consuming, it is highly regulated where several regulatory proteins interact with each other and control the expression of T3SS genes. Among these proteins, ExsA, the master regulator of T3SS in P. aeruginosa, is of great importance as it is a transcriptional activator that activates the expression of all T3SS genes. Also, as ExsA belongs to the AraC protein family which only exists in bacteria and fungi, it makes an excellent potential target for drugs against P. aeruginosa related infections. With a combination of molecular biology tools and structural biology methods, we solved the N-terminal domain structure of the ExsA protein in P. aeruginosa. The model of the ExsA N-terminal domain has enriched our knowledge about ExsA dimerization and can serve as the base for mapping the interaction interfaces on ExsA and ExsD. Further, we have found two homologues of ExsA by structural alignment, which share a lot of similarities and have conserved amino acid residues that are important for ligand binding. The fact that both of these two proteins are regulated by small ligands rather than proteins also raises the possibility that ExsA may have a second regulatory mechanism under which ExsA is regulated by a small ligand, which so far has not been observed or reported by researchers. In order to map the binding site of ExsA on its anti-activator ExsD, we removed the coiled-coil region (amino acid residue 138-202, the potential binding site) of ExsD, based on the structure of ExsD. We surprisingly found that the ExsD variant without the coiled-coil region readily inhibits ExsA-dependent in vitro transcription. This result rules out other possibilities and makes us focus on the N-terminus and adjacent regions of ExsD for the interface with ExsA. Moreover, in order to gain a comprehensive understanding of the dynamics of the regulation of T3SS in P. aeruginosa, we have begun to build a mathematical model of the T3SS regulatory pathways. We are measuring the cellular concentrations of T3SS regulatory proteins with quantitative molecular biology methods such as quantitative western blot, quantitative PCR and quantitative mass spectrometry. We have determined the cellular level of ExsA and ExsD proteins under different physiological conditions, and found that some factors such as temperature have a significant impact on the levels of ExsA and ExsD. This study has thus unveiled some unknown features of the T3SS of P. aeruginosa and its related infections. Master of Science
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Mina-Mankarios, George. "Crystallization kinetics of sodium sulphate in a salting out MSMPR crystallizer system Na₂SO₄/H₂S0₄/H₂O/MeOH /." Thesis, University of British Columbia, 1988. http://hdl.handle.net/2429/42007.
Full textAbstract:
The growth and nucleation rates of sodium sulfate
crystals salted out from their solution in a 38% w/w
sulfuric acid solvent by the addition of an 80:20 w/w
methanol : water solution, were determined from measurements
of the steady-state crystal size distribution (CSD)
generated in a continuous mixed-suspension, mixed-product-removal
(MSMPR) salting out crystallizer, and the effect of
the supersaturation, the crystal suspension density and the
temperature on these rates was investigated. The effect of
the Cr+ + + impurity was also briefly studied.
For the pure system, the power-law kinetic rate
equations of crystal growth (G = KGSg ) and crystal
nucleation (B = KBSb ) were fitted to the experimental data
and the fitting parameters were determined at each of 25, 30
and 35°C. In addition, the nucleation and growth rate data
were fitted to the relative kinetic equation (B = KbGi) to
provide a basis for comparison between i and b/g.
Secondary nucleation effects were investigated by testing,
in parallel with the primary nucleation rate equation
B = KBSb, the rate equation B = KNMTJSu which includes a
nucleation dependence on the crystal suspension density.
The relative kinetic equation B = KnMJTGv was also tested for
comparison (v compared with u/g).
No evidence of secondary nucleation could be shown.
The fitted estimates of j were non-positive at all
temperatures and statistically non-different from zero at 35
and 30°C, just approaching significance at 25°C with a
negative point estimate for j. Primary nucleation was shown
to be the dominant nucleating mechanism for this system.
The growth rate kinetic order g was determined to be
essentially unity (G = KGS0.97 ) and was statistically non-changing
with temperature. The nucleation rate kinetic
order b was similarly temperature independent and was
determined as 2.1 (B = KBS2.1). The kinetic rate constants
KG and KB were both a function of temperature and
were fitted to an Arrhenius type temperature dependence to
give
KG = 43960 exp(-24600/RT)
and
KB = 0.064 exp(70870/RT)
where R is in kJ/kmole-K.
The activation energy for growth was positive at 24600
kJ/kmole. The nucleation activation energy was negative and
larger in magnitude at -70870 kJ/kmole. In the presence of the chromium impurity, the kinetic
parameters KG , g, KB , Kb, and i were determined at three
levels of the concentration of the impurity in the
crystallizer feed. An increase in the impurity
concentration was shown to cause an increase in the growth
rate constant KG but had no significant effect on the
nucleation kinetics. The result was a decrease in the
relative rate constant and therefore a larger crystal
size.
The kinetics of crystallization as determined for this
system would indicate that a high temperature, high crystal
suspension density and long residence time are conditions
which are favourable for the production of a large sodium
sulfate crystal.Applied Science, Faculty of
Chemical and Biological Engineering, Department of
Graduate
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Zheltonozhskaya, T. B., S. V. Partsevskaya, D. O. Klymchuk, and V. F. Gorchev. "Specific Interactions and Crystallization of Drug-Loaded Micelles in the System: Prednisolon/PAAm-b-PEO-b-PAAm Micellar Solutions." Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35235.
Full textAbstract:
Encapsulaton of poorly soluble crystallizing drug prednisolone (PS) in micellar solutions of PAAm-b-
PEO-b-PAAm triblock copolymer (TBC) based on chemically complementary poly(ethylene oxide) and polyacrylamide
(MnPEO = 6 kDa, MnPAAm = 116 kDa) was studied by dynamic light scattering and transmission
electron microscopy. The equilibrium mechanism of the encapsulation process and the effect of specific aggregation
of PS-loaded micelles by their “coronas” that promoted the drug crystallization were established.
The question about the presence of TBC micelles inside crystalline space was discussed.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35235
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Gallo, Leonardo Sant'ana. "Microstructure and mechanical properties of glass-ceramics from the MgO-Al₂O₃-SiO₂ system for ballistic protection." Thesis, Rennes 1, 2016. http://www.theses.fr/2016REN1S063/document.
Full textAbstract:
Afin d'examiner les effets de la cristallisation sur certaines propriétés mécaniques, l'évolution du module de Young (E), du module de cisaillement (G) et du coefficient de Poisson, ainsi que la séquence des phases cristallines formées au cours d'un traitement thermique en deux étapes ont été accompagnées sur un verre baptisé 75-25, du système MgO-Al2O3-SiO2 (MAS), en utilisant TiO2 comme le principal agent de nucléation. L'évolution de la dureté et de la résistance à la rupture a aussi été examinée. La diffractométrie de Rayons X à haute température a révélé, après cristallisation, la présence de spinelle (MgO.Al2O3) rutile (TiO2), karooite (MgO.2TiO2), sillimanite (Al2O3.SiO2) et la saphirine (4MgO.5Al2O3.2SiO2). Les modules élastiques et de cisaillement des vitrocéramiques (VC) se sont montré environ 20% plus élevés que ceux du verre précurseur. Les valeurs de dureté obtenues sont proches de 10 GPa et KIC proche de 1,2 MPa.m1/2. Dans le but de fabriquer des VCs transparentes et incolores, de nouvelles formulations, dénommées ZT1B4, 75-25/ZT et 75-25/25TI, avec des teneurs en TiO2 réduites et des teneurs en ZrO2 plus élevées, ont été proposées et cristallisées. La formulation ZT1B4 a produit une VC transparente avec une dureté maximale de 8GPa et une ténacité à la fracture (TF) à peu près 40% plus élevée que celle du verre de base. Les formulations 75-25 ZT et 75-25/25Ti ont produit des VC transparentes avec des valeurs de dureté allant jusqu'à 9GPa et une ténacité à la fracture jusqu'à 35% plus élevée que celle du verre de base. Une série de verres ont été fondus en utilisant Ag métallique, au lieu de ZrO2 et TiO2, en tant qu'agent de nucléation. Les traitements thermiques appliqués ont produit des VCs non-homogènes, qui perdent la forme en raison des températures de cristallisation élevées. Ces nouveaux verres précurseurs ont donc été écartés. La transmittance dans la région de l'ultraviolet et visible a été mesurée dans les échantillons de verre et VCs de formulation 75-25, 75-25 / ZT et 75-25 / 25TI. La formulation 75-25 / ZT a présenté la plus haute transmittance soit à l'état vitreux ou en forme de vitrocéramique. En conclusion, parmi les nouvelles compositions, la formulation 75-25 / ZT est la plus adéquate pour une utilisation en tant que protection balistique, lorsque la transparence à la lumière visible est nécessaireIn situ experiments were conducted on a glass dubbed 75-25, of the MgO-Al2O3-SiO2 (MAS) system, using TiO2 as the main nucleating agent, in order to examine the evolution of Young’s modulus (E), shear modulus (G) and Poisson's ratio, and the sequence of the crystalline phases formed during a double-stage heat treatment. The effects of crystallization on hardness and fracture toughness were also examined. High temperature X-ray diffraction experiments revealed the presence of spinel (MgO.Al2O3), rutile (TiO2), karooite (MgO.2TiO2), sillimanite (Al2O3.SiO2) and sapphirine (4MgO.5Al2O3.2SiO2) after crystallization. The elastic and shear moduli of the glass-ceramics (GC) were approximately 20% larger than those of the parent glass. Hardness values were close to 10 GPa and KIC close to 1.2 MPa.m1/2. Aiming to obtain transparent and colorless GC, new formulations, dubbed ZT1B4, 75-25/ZT and 75-25/25Ti, with lower titania content and higher zirconia content, were proposed and crystallized. Formulation ZT1B4 yielded a transparent GC with hardness of up to 8 GPa and an indentation fracture toughness (IFT) about 40% higher than that of the parent glass. Formulations 75-25/ZT and 75-25/25Ti yielded transparent GC with hardness values of up to 9 GPa and an IFT up to 35% higher than that of the parent glass. A series of glasses were also melted using metallic Ag as nucleating agent instead of ZrO2 and TiO2. The applied heat treatments generated non-homogeneous GC, which became warped due to the high crystallization temperatures. These new precursor glasses were therefore discarded. Transmittance in the ultraviolet to visible range was measured in the glass and GC samples of formulations 75-25, 75-25/ZT and 75-25/25Ti. Formulation 75-25/ZT presented the highest transmittance in both glass and GC states. It was concluded that among the new compositions, formulation 75-25/ZT is the most suitable one for use as ballistic protection when transparency to visible light is required
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Araújo, Hugo Valença 1988. "Simulação e análise do desempenho termodinâmico de sistemas de refrigeração por absorção com diferentes configurações." [s.n.], 2013. http://repositorio.unicamp.br/jspui/handle/REPOSIP/266566.
Full textAbstract:
Orientador: José Vicente Hallak d'AngeloDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química
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Resumo: A refrigeração e o condicionamento de ar representam um campo tecnológico em potencial para a adoção de medidas de economia de eletricidade. Nesse sentido, Sistemas de Refrigeração por Absorção (SRAs) figuram como uma opção interessante por serem adequados à produção de frio mediante um gasto significativamente menor de energia elétrica em comparação a Sistemas de Refrigeração por Compressão Mecânica (SRCMs) de vapor. Com a finalidade de gerar o efeito de refrigeração, o SRCM realiza uma compressão mecânica de vapor à custa do consumo de trabalho elétrico em um compressor; em contrapartida, a compressão no SRA é de natureza termofísica/química e promovida por energia térmica. No segmento de açúcar e álcool brasileiro, a etapa determinante da produção de etanol a partir da cana consiste na fermentação alcoólica do mosto em dornas. Tal etapa é exotérmica e, uma vez que a elevação descontrolada da temperatura desfavorece a produção de álcool, há a necessidade de remover o calor gerado por meio do resfriamento do meio em fermentação. Dessa forma, o objetivo geral do presente trabalho foi simular e analisar o desempenho termodinâmico (energético, COP, e exergético, ?ex) de SRAs com diferentes configurações, trabalhando com o par água/brometo de lítio (H2O/LiBr) e que satisfaçam a carga de refrigeração demandada por um processo fermentativo. Adicionalmente, um dos objetivos específicos foi investigar o risco de ocorrência da cristalização do LiBr, a qual resulta em depósitos, com o auxílio da curva de equilíbrio sólido-líquido (solubilidade) do par H2O/LiBr. As análises dos efeitos de variáveis de projeto e operação (realizadas no software Engineering Equation Solver - EES) demonstraram que os valores de COP das configurações de SRAs de duplo efeito são significativamente maiores do que aquele da configuração de simples efeito; no entanto, as eficiências exergéticas de todas as configurações são equiparáveis, o que pode ser atribuído à quantidade e à qualidade da energia térmica consumida nos respectivos geradores de primeiro efeito. Baixos desempenhos de Segunda Lei são devidos principalmente ao absorvedor, pois esse equipamento apresenta os maiores defeitos de eficiência em todos os SRAs estudados. Adicionalmente, avaliou-se a dependência do desempenho termodinâmico quanto às efetividades de trocadores de calor intermediários, a diferenças de pressão operacional e à cessão direta de calor externo a geradores de segundo efeito. Entre outros resultados, observou-se a existência de máximos do COP e da ?ex em função da temperatura no gerador de primeiro efeito. No que se refere à possibilidade de precipitação do LiBr, verificou-se menor iminência no SRA de duplo efeito com fluxo em paralelo. Em particular, observou-se que aumentos excessivos da temperatura no gerador de primeiro efeito, além de não favorecerem o desempenho termodinâmico, tornam o risco de cristalização do LiBr mais significativo
Abstract: Refrigeration and air conditioning represent a potential technological field for the adoption of measures to save electricity. In this way, Absorption Refrigeration Systems (ARSs) are an interesting option because they are suitable for the production of cold utilities with a significantly lower cost of electric power compared to Mechanical Compression Refrigeration Systems (MCRSs). In order to generate the cooling effect, the MCRS performs a mechanical vapor compression at the expense of the consumption of electrical work in a compressor. On the other side, the nature of the compression in ARSs is thermo physical/chemical and this process is promoted by thermal energy. In the Brazilian sugar and ethanol industry, the main stage of ethanol production from sugarcane is the alcoholic fermentation in vats. This stage is exothermic and since the uncontrolled elevation of temperature results in disadvantages to the ethanol production, it is necessary to remove the heat generated by the cooling of the fermentation medium. Thus, the general objective of this study was to simulate and analyze the thermodynamic performance (energy, COP, and exergy, ?ex) of ARSs with different configurations, working with the water/lithium bromide (H2O/LiBr) mixture, and satisfying the cooling load demanded by a fermentation process. Additionally, one of the specific objectives was to investigate the risk of LiBr crystallization, resulting in deposits, with the aid of the solid-liquid equilibrium (solubility) curve of the H2O/LiBr mixture. Analyses of the effects of design and operating variables (executed in the software Engineering Equation Solver - EES) have shown that the values of COP of the double effect configurations are significantly greater than that of the simple effect configuration; however, the exergetic efficiencies of all configurations are comparable, which can be attributed to the quantity and the quality of the energy consumed in the respective first effect generators. Low Second Law performances are mainly due to the absorber because this equipment has the highest efficiency defects in all ARSs studied. Additionally, it was evaluated the dependence of the thermodynamic performance regarding to the effectivenesses of intermediate heat exchangers, the differences in operating pressures and the direct supply of external heat to second effect generators. Among other findings, it was observed the existence of maximums of COP and ?ex as functions of the temperature in the first effect generator. With regard to the possibility of LiBr precipitation, it was verified lower imminence in the double effect ARS with parallel flow. In particular, it was observed that excessive rises in the temperature in the first effect generator, besides not favor the thermodynamic performance, makes the risk of LiBr crystallization more significant
Mestrado
Sistemas de Processos Quimicos e Informatica
Mestre em Engenharia Química
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Vicard, Céline. "Étude et modélisation de la synthèse du polyamide 6 pour la mise en œuvre de composites thermoplastiques par voie liquide réactive." Thesis, Ecole nationale des Mines d'Albi-Carmaux, 2018. http://www.theses.fr/2018EMAC0001/document.
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L’utilisation de procédés de type voie liquide (RTM, LRI) pour l’élaboration de composites thermoplastiques est une des voies prometteuses pour pallier les limitations liées à la haute viscosité des polymères thermoplastiques. Pour cela, la matrice est obtenue par polymérisation in situ de son monomère de faible viscosité après l’imprégnation du renfort fibreux. Cette étude s’est focalisée sur le polyamide 6 (PA6) obtenu par polymérisation anionique par ouverture de cycle de l'ε-caprolactame. La particularité de cette synthèse réside dans le couplage entre la polymérisation des chaînes et leur cristallisation, qui sont des phénomènes tous deux thermodépendants, exothermiques et régissant la viscosité du milieu réactif. La caractérisation cinétique par DSC de ce couplage a permis une meilleure compréhension de l'interaction des phénomènes, en révélant notamment une cinétique de cristallisation particulière à basse température. Cette base de données, complétée par l’étude des propriétés physico-chimiques du PA6 synthétisé, a permis d'alimenter la modélisation des phénomènes. Un nouveau couplage a ainsi été proposé pour rendre compte de la dépendance de la cristallisation à la cinétique de polymérisation et a permis d'éditer des diagrammes Temps-Température-Transformation (TTT) de la synthèse du PA6. En vue de la mise en œuvre de composites thermoplastiques, la simulation du couplage thermocinétique avec un terme source a été réalisée afin de mesurer l’impact de ces phénomènes exothermiques sur les gradients thermiques et cinétiques dans l’épaisseur d’une pièce. Les cinétiques ont de plus été étudiées en présence de fibres de verre et en rhéologie. La présence de fibres engendre un ralentissement de la cinétique de synthèse et le comportement rhéocinétique révèle l’existence d’un point de gel. Ces observations restent à considérer pour simuler l’écoulement du système réactif dans un renfortLiquid type processes (RTM, LRI) for thermoplastic composites manufacturing is one of the most promising routes to overcome the limitations due to the high viscosity of thermoplastic polymers. In this process, the matrix is obtained via in situ polymerization of its low-viscosity monomer after impregnation of the fibrous reinforcement. This study focused on polyamide 6 (PA6) obtained by anionic ring-opening polymerization of ε-caprolactam. The distinctive aspect of this reaction resides in the coupling between chains polymerization and their crystallization, both thermo-dependent, exothermic and driving the viscosity of the reactive mixture.The kinetic characterization of this coupling by DSC allowed for a better understanding of phenomena interaction, revealing notably a specific crystallization kinetic at low temperature. This database, complemented by a study of physicochemical properties of synthesized PA6, has been used to model the underlying phenomena. A new coupling equation has been proposed to take into account the crystallization dependence on the polymerization kinetic, allowing to edit Time-Temperature-Transformation (TTT) diagrams of the PA6 synthesis. Simulations of the thermokinetic coupling with a source term have been performed, highlighting the impact of these exothermic phenomena on thermal and kinetic gradient in the thickness of a part. To reproduce the conditions of the composite manufacturing process, kinetics have also been studied in the presence of glass fibers and in a rheometer. The presence of fibers leads to slower kinetics and the rheokinetic behavior revealed gelation. These observations have to be considered to simulate the reactive system flow in a reinforcement
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Zhang, Kun. "Contrôle de l'évolution d'un procédé de cristallisation en batch gouverné par des équations aux dérivées partielles." Phd thesis, Université Claude Bernard - Lyon I, 2011. http://tel.archives-ouvertes.fr/tel-00965757.
Full textAbstract:
L'objectif principal de ce travail de recherche est de contrôler l'évolution de la distribution des tailles de cristaux (DTC) dans un procédé de cristallisation en batch. Nous avons été amenés à chercher une résolution numérique du bilan de population et à proposer un algorithme rapide et précis. La méthode numérique a été étendue au cas de la taille des cristaux multidimensionnels en utilisant un maillage mouvant. Nous avons étudié le problème de la commandabilité du système à partir de son modèle discrétisé et puis à partir du modèle continu. Nous avons conçu une loi de commande en boucle fermée pour atteindre la DTC désirée à partir de la condition initiale. Pour compenser l'incertitude des paramètres du modèle, nous avons ajouté un second contrôle par retour d'état afin d'assurer la poursuite de la DTC désirée en présence de l'incertitude des paramètres. Nous avons construit un observateur qui nous permet d'avoir en ligne l'estimation des variables d'états. Ces variables d'état estimées sont utilisées dans la synthèse de la loi du contrôle