Dissertations / Theses on the topic 'Thermodynamics studies'
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Kjellqvist, Lina. "Studies of Steel/Slag Equilibria using Computational Thermodynamics." Licentiate thesis, Stockholm Stockholm : Materialvetenskap, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3914.
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Willson, Richard James. "Isothermal microcalorimetry : theoretical development and experimental studies." Thesis, University of Kent, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.283265.
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Zanchetta, Marcantony. "Kinetic heating and transition studies at hypersonic speeds." Thesis, Imperial College London, 1996. http://hdl.handle.net/10044/1/37124.
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The thesis reports on an experimental and computational study of kinetic heating at hypersonic speeds. Of particular interest is the transition of the laminar boundary layer to a state of turbulent motion. The experiments are performed in a Mach 9 Gun tunnel with a 5° semi-angle cone geometry. Twelve hemispherically blunted nose radii are tested at three unit Reynolds numbers. Testing has indicated that as the nose is progressively blunted, the transition region moves downstream. Further amounts of bluntness enhance other instability mechanisms and transition events are witnessed in the near nose regions. There are clearly two transitional regimes, denoted the "small bluntness" and "transition reversal" regime, respectively. This study investigates the structure of the transitional boundary layer in both regimes using thin film heat transfer rate gauges and liquid crystal surface thermography. The heat transfer measurements indicate that the small bluntness transition regime is governed by the rapid formation, growth and merging of turbulent events. Transition occurs over hundreds of boundary layer lengths. The reversal regime transition process is characterised by the birth of turbulent events in the nose and near nose regions. The temporal formation rate of the events is governed by roughness. In a low roughness environment, transition occurs over many model lengths. Increasing the roughness level, increases the spot formation rate, and transition is witnessed immediately downstream of the spherical nose region. The role of roughness is further explored using boundary layer trips. The trip causes a laminar wake which rapidly undergoes transition and forms a turbulent wedge. Event circumferential spreading angles are found for a variety of trip geometries and locations. The heat transfer distribution in the wedge is mapped using the thin film gauges. Computational work is used to perform laminar flow field predictions. Of interest is the entropy layer caused by the presence of the bow shock, and its interaction with the boundary layer. Heat transfer predictions in the transitional region are also performed aided with the experimentally obtained intermittency information.
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Burgess, Sarah Elisabeth. "Membrane transport studies : novel methods, model systems and thermodynamics." Thesis, University of Greenwich, 2005. http://gala.gre.ac.uk/6121/.
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The work in this thesis shows that it is possible to design a diffusion cell which will allow access to the flux and lag time of a permeant without the need for invasive sampling and that this novel cell is both sensitive and reproducible. It was also shown that the cell could be used in conjunction with both simple model membranes and more complex biological membranes, namely the epidermis. From the data achieved from the cell it was possible to derive a series of equations which allowed access to thermodynamic parameters such as ?H, ?G and ?S. An extension of this calculational approach revealed that manipulation of the van’t Hoff isochore, under the condition where enthalpy is constant over the temperature range, it should be possible to calculate the partition coefficient. Ultimately these parameters can be used in the description of structure activity relationships. The systems described in this thesis are of a complex biological nature consequently the returned data reflect this complexity. In order to utilise the data to their full potential some method for dealing with this complexity was sought. One approach widely discussed in the literature is that of chemometric analysis or soft modelling. Initial studies into the use of chemometric analysis proved positive for the data presented in this thesis, and suggested that formulation contributions from components with close absorbance maxima could be separated.
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Fletcher, P. "Studies on the thermodynamics of association of drug molecules." Thesis, University of Manchester, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.375062.
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Tindall, A. T. R. "Experimental and theoretical studies of convective heat transfer from fin arrays." Thesis, University of Lincoln, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.354881.
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Allan, William D. E. "Heat transfer and instrumentation studies on rotating turbine blades in a transient facility." Thesis, University of Oxford, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.257952.
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Olsen, Katherine Anna. "NMR studies reveal the kinetics and thermodynamics of hairpin formation /." Thesis, Connect to this title online; UW restricted, 2006. http://hdl.handle.net/1773/8611.
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Williamson, Mark Allen. "Thermodynamic and kinetic studies of sulfur geochemistry." Diss., Virginia Tech, 1992. http://hdl.handle.net/10919/38485.
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Rennie, Timothy J. "Numerical and experimental studies of a double-pipe helical heat exchanger." Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=85642.
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A double-pipe helical heat exchanger was studied numerically and experimentally for both heat transfer and hydrodynamic characteristics.Results from the numerical trials show that the inner Nusselt numbers in the heat exchanger were similar to literature data, despite the different boundary conditions. Nusselt numbers in the annulus were correlated to a modified Dean number. It was shown that the thermal resistance in the annulus to be the greatest limiting factor for the heat transfer, and heat transfer rates could be increased by increasing the inner tube diameter.
The Prandtl number was shown to affect the inner Nusselt number; however the effects were much greater at low Dean numbers. These differences were attributed to the difference in the developing thermal and hydrodynamic boundary layers. The studies with the thermally dependent thermal conductivities showed that the Nusselt number correlated well with a modified Graetz number.
Thermally dependent viscosity had little effect on the heat transfer; however it affected the pressure drop. Furthermore, it was shown that by keeping the flow rate in the inner tube or the annulus constant, the pressure drop in that section can be affected by changes in the flow rate in the opposite section, due to the change in the heat transfer rate and hence the average temperature and viscosity of the fluid. Non-Newtonian fluids showed little effect on the heat transfer rates, though they significantly affected the pressure drop relations.
The uniformity of the residence time and the temperature distribution were both increased in the inner tube with increasing flow rates. It was shown that a smaller gap size in the annulus resulted in more uniform residence times. Temperature distributions in the inner tube and the annulus were affected by changes in the flow velocity in the opposite section, with lower flow rates resulting in more uniform temperature distributions. Implications of using parallel flow versus counterflow, heating versus cooling, and flow rate are discussed.
Overall heat transfer coefficients and Nusselt numbers were calculated for the experimental data. The inner and annulus heat transfer coefficients were determined using Wilson plots. The results were compared to the numerical data and literature values and showed reasonable agreement. (Abstract shortened by UMI.)
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Frederiksen, Joorgen Segerlund. "Theoretical studies in high energy physics and atmospheric dynamics /." Title page, introduction and contents only, 1987. http://web4.library.adelaide.edu.au/theses/09SD/09sdf852.pdf.
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Bhuiyan, Golam Mohammed. "Theoretical studies of the liquid structure and thermodynamics of transition metals." Thesis, University of East Anglia, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.357163.
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Mokdad, Audrey. "Time-resolved thermodynamics studies of heme signaling proteins and model systems." [Tampa, Fla] : University of South Florida, 2009. http://purl.fcla.edu/usf/dc/et/SFE0003063.
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Davidson, James Prentice. "Calorimetric and structural studies of 1,2,3-trisubstituted cyclopropanes as conformationally constrained peptide mimics /." Full text (PDF) from UMI/Dissertation Abstracts International, 2001. http://wwwlib.umi.com/cr/utexas/fullcit?p3008309.
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Lewis, Amanda. "Fundamental studies of the chemical vapour deposition of graphene on copper." Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/fundamental-studies-of-the-chemical-vapour-deposition-of-graphene-on-copper(f85feb54-5994-4201-b400-c622f4d7b216).html.
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The chemical vapour deposition (CVD) of graphene is the most promising route for production of large-area graphene films. However there are still major challenges faced by the field, including control of the graphene coverage, quality, and the number of layers. These challenges can be overcome by developing a fundamental understanding of the graphene growth process. This thesis contributes to the growing body of work on graphene CVD by uniquely exploring the gas phase chemistry and fluid flow in the hot-wall graphene CVD reactor. Firstly the reported parameter space for the hot-wall CVD of graphene on copper was mapped, informing the subsequent work and providing a resource for the wider community. A CVD reactor was constructed to extend this parameter space to lower pressures using methane as a carbon source, and the films were categorised using scanning electron microscopy, Raman spectroscopy and optical dark field microscopy. The latter showed particular promise as a rapid and non-destructive characterization technique for identifying graphene films on the deposition substrate. The gas phase equilibrium compositions were calculated across the parameter space, and correlations between the stabilities of various chemical species and the types of deposition were drawn. This laid a foundation for the remainder of the experimental work, which explored the effect of diluent gases and different feedstocks on the growth to understand the importance of the identified correlations. Diluent gases (argon and nitrogen) were added to the experimental conditions and the thermodynamic model, and were found to reduce the degree of coverage of the graphene films. This result shows that the CVD of graphene is sensitive to factors other than the thermodynamic state parameters, such as the fluid flow profile in the reactor and inelastic collisions between the higher mass diluent gases and the methane/hydrogen/copper system. Using a nitrogen diluent raises the equilibrium carbon vapour pressure and seems to allow larger graphene grains to form. This suggests that thermodynamic factors can contribute to the nucleation of graphene films. Varying the hydrocarbon feedstock and the process conditions indicated that the structure of the deposited carbon is closely related to the nucleation kinetics. Three nucleation regimes are associated with different types of deposition: homogeneous nucleation with amorphous carbon or soot; uncatalysed nucleation with multilayer deposition; and nucleation processes controlled by the copper substrate withpredominantly monolayer deposition. Changing the feedstock from methane to acetylene resulted in poorer graphene coverage, showing that thermodynamic control does not apply in the portion of the parameter space at the high temperatures and lowpressures most successfully used for the deposition of continuous graphene monolayers.
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Smit, Reneé. "The nature of engineering and science knowledge in curriculum: a case study in thermodynamics." Doctoral thesis, University of Cape Town, 2017. http://hdl.handle.net/11427/25532.
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Abstract The study explores the nature of disciplinary knowledge differences and similarities between the sciences and the engineering sciences as these appear in curriculum texts. The work is presented as a case study of curriculum knowledge in thermodynamics, and the epistemic properties are investigated in four sub-cases in mechanical engineering, chemical engineering, physics and chemistry. Data was collected from prescribed undergraduate textbooks in the four disciplinary fields. The work is theoretically informed by two fields of scholarly work: the sociology of educational knowledge (in particular the work of Basil Bernstein) and the applied philosophies of science and engineering science, in order to develop a theoretical framework for analysis of the data. The framework allows the study to move beyond the typical binary classification of the sciences as 'hard-pure' and engineering sciences as 'hard-applied' disciplines. Starting from broad teleological considerations, the philosophical concepts of specialisation, idealisation and normativity are explored and developed into modalities and modal continua of variance to allow investigation of the epistemic differences and similarities in the recontextualised disciplinary knowledge from these contiguous conceptual fields. The empirical study identifies important differences in thermodynamics curriculum knowledge in terms of specialisation, normativity and idealisation across the broad disciplinary fields, rendering more complex Bernstein's notions of singulars and regions. The epistemic modalities and modes provide a way to conceive in more detail how the professional engineering science knowledge is orientated towards its field of practice. Curriculum knowledge in the engineering sciences is shown to be remarkably different from the knowledge in the sciences: both mechanical and chemical engineering knowledge emphasise particulars, rather than universals, have stronger normative aspects, and employ a limited form of idealisation in their commitment to physical realisability. By contrast, knowledge in the sciences is more universal, normativity is incidental, and idealisation is used expansively. In addition, the research findings suggest a negative correlation between idealisation and normativity as epistemic modalities: a commitment to normative concerns in the engineering sciences constrains the extent to which knowledge idealisation is pursued, compared to what is observed in the bodies of science curriculum knowledge. Furthermore, over and above differences in curriculum knowledge between the broad fields of science and engineering science, discernible variation exists between the engineering sciences investigated, raising cautions against a monolithic view of curricular epistemic properties across broad disciplinary areas.
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Monga, Zinki. "THERMODYNAMIC STUDIES ON THE SYNTHESIS OF NITRIDES AND EPITAXIAL GROWTH OF INGAN." Master's thesis, University of Central Florida, 2007. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3881.
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Nitride semiconductor materials have been used in a variety of applications, such as LEDs, lasers, photovoltaic cells and medical applications. If incandescent bulbs could be replaced by white GaN LEDs, they would not only provide compactness and longer lifetime, but this would also result in huge energy savings. A renewed interest in InGaN emerged recently after it was discovered that the band gap for InN is 0.7eV, instead of the previously published value of 1.9eV. Thus InGaN solid solutions cover almost the whole visible spectrum, from a band gap of 3.34eV for GaN and 0.7eV for InN. Hence, InGaN can have excellent applications for photovoltaic cells. The objective of this work was to investigate and search for new ways of synthesis of nitrides. We studied the thermodynamics and evaluated chemical compatibilities for the growth of AlN, GaN, InN and their solid solutions from metallic solvents. The compatibility between potential substrate, crucible and solvent materials and various growth atmospheres was evaluated from Gibbs free energy calculations. Most of the nitride synthesis experiments performed by other groups were at higher temperatures (around 2,000C) and pressures up to 1GPa using different growth methods. Therefore, their results could not be extrapolated to our growth system, as their growth conditions were significantly different from ours Moreover, to the best of our knowledge; no-one has ever evaluated such compatibilities by thermodynamic calculations. We used those calculations to design our experiments for further studies on nitrides. Experimentally, we encountered fewer issues such as corrosion problems than others observed with their growth procedures, because near-atmospheric pressures and temperatures not exceeding 1,000C could be used. Preliminary experiments were performed to confirm the thermodynamic computations and test the behavior of the chosen system. A suitable configuration was found that allowed to nucleate films of InGaN on the templates. Nitride templates or 'Buffer layers' were used to saturate the solution and grow the films. A relatively simpler configuration, to create a temperature gradient in the solution was used. Two templates were placed in the crucible, one at the top and the other one at the bottom. The temperature was raised to 950C and they were soaked there for 15-20hrs. After the growth the surface morphology was analyzed using an optical microscope and it was found to be entirely different for both the templates. The atoms from the top template dissolved and attached at the bottom template. This can be explained by the thermal gradient between the two templates: one at the bottom was at lower temperature than the top template, so there was diffusion from the top substrate towards the bottom one. AFM studies were carried out on the film to study the surface morphology of the top and the bottom templates. Growth hillocks having step height typically between 15 and 50 nm were observed. Such hillocks were not present on the templates before the experiment.M.S.M.S.E.
Department of Mechanical, Materials and Aerospace Engineering;
Engineering and Computer Science
Materials Science & Engr MSMSE
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Skorobogatiy, Maksim. "Theoretical studies of the thermodynamics and kinetics of proteins : application to protein folding." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ44280.pdf.
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Abyzov, Anton. "Nuclear Magnetic Resonance Studies of the Dynamics and Thermodynamics of Intrinsically Disordered Proteins." Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAY026/document.
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Les protéines intrinsèquement désordonnées sont des hétéropolymères très flexibles, impliqués dans des activités cellulaires importantes (transduction du signal, reconnaissance moléculaire, traduction etc.), représentant des cibles potentielles de médicaments contre les maladies neurodégénératives et cancers, et dont les modes dynamiques définissent leur fonction biologique. Même si les états conformationnels qu'elles échantillonnent sont relativement bien connus, ce n'est pas le cas des échelles de temps de la dynamique associée. Dans ce travail nous étudions le comportement conformationnel du domaine C-terminal intrinsèquement désordonné de la nucléoprotéine de virus de Sendai (NTAIL), qui interagit avec le domaine PX de la phosphoprotéine. Des études précédentes montrent que le site d'interaction échantillonne un équilibre entre trois hélices discrètes dans l’état libre, et que l’interaction avec PX passe d’abord par la formation d'un pré-complexe, où l’une des conformation hélicoïdales de NTAIL est stabilisée, puis par sa diffusion sur la surface de PX, et enfin sa rétention sur le site de liaison. Cependant, aucun renseignement n'existe sur les échelles de temps de mouvements de la chaine de NTAIL, qui influencent certainement la cinétique de cette interaction, en particulier sa constante de vitesse d’association. Cette protéine de 124 acides aminés représente aussi un système modèle pertinent contenant à la fois de longs domaines dépliés et des régions de structure résiduelle. La mesure d’un vaste et cohérent ensemble de taux de relaxation à différents champs magnétiques et différentes températures nous a permis de caractériser la dynamique de NTAIL à un niveau de détail sans précèdent. A l’aide d’analyse « model-free » étendu, nous avons montré que les composants rapides de la fonction de corrélation nous informent sur les librations. Le mode dominant se situe à des échelles de temps autour d’une nanoseconde et est lié à l’échantillonnage de l’espace de Ramachandran par le squelette peptidique. Enfin, le composant lent (5-25 ns) nous informe sur les mouvements de segments de la chaine peptidique. La description des mouvements intrinsèques des protéines désordonnées et leurs échelles de temps contribuera à notre compréhension du comportement et des fonctions de ces protéinesIntrinsically disordered proteins (IDPs) are highly flexible heteropolymers, implicated in important cellular activities (signal transduction, molecular recognition, transcription, translation, etc.) and representing potential drug targets against cancer and neurodegenerative diseases, whose dynamic modes define their biological function. Although the conformational states sampled by IDPs are relatively well understood, essentially nothing is known about the associated dynamic timescales. In this study we investigate the conformational behavior of the intrinsically disordered C-terminal domain of the nucleoprotein of Sendai virus (NTAIL), which interacts with the PX domain of the phosphoprotein. The interaction site has been shown to sample an equilibrium of discrete helices in the free state, which forms an encounter complex implicating the stabilization of one of the helical conformers upon interaction with PX, prior to diffusing on the surface of PX and engaging in the actual binding site. However, very little is known about the timescales of chain motions, which surely play a role in the interaction kinetics, in particular in terms of the on-rate of the interaction. This 124 amino acid protein also provides a good model system, containing long unfolded domains with chain-like dynamics and regions with residual structure. The measurement of extensive set of coherent relaxation rates at multiple magnetic fields, multiple temperatures and in three different length constructs of the same IDP has allowed us to characterize the dynamic nature of NTAIL in unprecedented detail. By analyzing the relaxation data using extended model-free approach, we show that fast (≤ 50 ps) components of the correlation function report on librational motions. A dominant mode occurs on timescales around one nanosecond, apparently reporting on backbone sampling within Ramachandran sub-states, while a slower component (5-25 ns) reports on segmental dynamics dominated by the chain-like nature of the protein. The ability to delineate intrinsic modes and timescales will improve our understanding of the behavior and function of IDPs
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Abdel, Aziz May. "Kinetic and Thermodynamic Studies of Thrombin Inhibitors." VCU Scholars Compass, 2013. http://scholarscompass.vcu.edu/etd/2956.
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Sulfated low molecular weight lignins (LMWLs), CDSO3 and FDSO3, designed recently as macromolecular mimetics of heparin, were found to exhibit potent anticoagulant activity. Small molecules based on the same scaffold, SBD and SBT, showed promising thrombin inhibition. We were able to address the mechanism of the inhibition using Michaelis-Menten kinetics. All the molecules were found to be allosterically impairing thrombin activity using either noncompetitive or uncompetitive mechanism. Absence of competition with hirugen, an exosite 1 ligand, and competition with polymeric heparin points to exosite 2 as the site of interaction for these inhibitors. Yet mixed competition results with other exosite 2 ligands indicated that the molecules utilize different sub-sites within exosite 2 for interaction. Site-directed mutagenesis was used to pin point the key residues important for inhibition. All of all positively charged exosite 2 residues were mutated one at a time to alanine to abolish its charge. The data showed that Arg93 and Arg175 are the major residues involved in CDSO3 binding. FDSO3 showed a progressively greater defect in inhibition with double point mutations, the triple mutant Arg93,97,101Ala displayed a 50 fold drop in inhibition. A single mutant, Arg173Ala, displayed 22-fold reduction in IC50 of SBD, while Arg233Ala was the only mutation that impaired SBT inhibition. This proves the fact that inspite of the structural similarity between the two polymers and the two small molecules, thtey do not share the same binding space in exosite 2. To understand the types of interactions involved in thrombin interaction with the polymers, we resorted to salt-dependence studies. This showed that CDSO3 had fewer ionic contacts with thrombin, with most of its binding energy derived from non-ionic interactions. FDSO3 on the other hand had a balanced contribution of ionic and non-ionic forces. Thermodynamic studies showed that both polymers have a positive ΔCp of binding, which proves the involvement of electrostatic forces and signals the burial of the polar residues on thrombin exosite 2. These molecules offer a rare chance to study thrombin allostery. Little is known about the interplay between exosite 2, active site and sodium binding site. The allosteric nature of inhibition indicated that, for the first time, a link is proven to exist between exosite 2 and the active site that could be used to inhibit the enzyme. The presence of sodium was found to enhance the binding of FDSO3 at exosite 2, which establish the energetic coupling between exosite 2 and sodium binding site. The results identify novel binding sub-sites within exosite 2 that are energetically coupled to thrombin’s catalytic function and linked to the sodium binding site. The design of high affinity small molecules based on LMWLs scaffold presents major opportunities for developing clinically relevant, allosteric modulators of thrombin.
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Packwood, Daniel Miles. "Theoretical and Experimental Studies of the Gas-Liquid Interface." Thesis, University of Canterbury. Department of Chemistry, 2010. http://hdl.handle.net/10092/4618.
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A theoretical model describing the motion of a small, fast rare gas atom as it passes over a liquid surface is developed and discussed in detail. A key feature of the model is its reliance on coarse-grained capillary wave and local mode descriptions of the liquid surface. Mathematically, the model is constructed with several concepts from probability and stochastic analysis. The model makes predictions that are quantitative agreement with neon-liquid surface scattering data collected by other research groups. These predictions include the dominance of single, rather than multiple, neon-liquid surface collision dynamics, an average of 60 % energy transfer from a neon atom upon colliding with a non-metallic surface, and an average of 25 % energy transfer upon colliding with a metallic surface. In addition to this work, two other investigations into the gas-liquid interface are discussed. The results of an experimental investigation into the thermodynamics of a gas flux through an aqueous surface are presented, and it is shown that a nitrous oxide flux is mostly due to the presence of a temperature gradient in the gas-liquid interface. Evidence for a reaction between a carbon dioxide flux and an ammonia monolayer on an aqueous surface to produce ammonium carbamate is also found. The second of these is an investigation into the mechanism of bromine production from deliquesced sodium bromide aerosol in the presence of ozone, and involves a sensitivity and uncertainty analysis of the computer aerosol kinetics model MAGIC. It is shown that under dark, non-photolytic conditions, bromine production can be accounted for almost exclusively by a reaction between gas-phase ozone and surface-bound bromide ions. Under photolytic conditions, bromine production instead involves a complicated interplay between various gas-phase and aqueous-phase reactions.
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Small, Meagan. "Photothermal Studies of Carboxymyoglobin." Scholar Commons, 2010. https://scholarcommons.usf.edu/etd/1775.
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Small ligand diffusion in heme proteins is not fully understood. To help better understand CO diffusion, three systems were investigated: L29H/F43H site-directed sperm whale myoglobin, horse heart myoglobin in a heavy water buffer, and calix[4]resorcinarene. Binding of copper to calix[4]resorcinarene was photophysically characterized to unravel transient binding of small molecules in heme-copper proteins. Copper binding was found to have a low dissociation constant of approximately 8.6 micrometers.. Reaction profiles using photoacoustic calorimetry were constructed for the myoglobin systems. In deuterium oxide, ligand escape is not rate limited by water entry. Large enthalpy differences arise from the thermodynamic properties of deuterium oxide and the extensive hydrogen bonding network in myoglobin. In the mutant, CO rebinds primarily to the heme and is exothermic with a large volume contraction because of altered electrostatics within the binding pocket and higher water occupancy.
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Bhagan, Salome. "REACTIVITY AND EQUILIBRIUM THERMODYNAMIC STUDIES OF IRIDIUM PORPHYRINS IN WATER AND ALCOHOL." Diss., Temple University Libraries, 2012. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/213129.
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ChemistryPh.D.
Environmental and energy issues have stimulated renewed interest in utilizing both water and methanol as reagents and reaction mediums. Our current interest is to evaluate the scope of group nine organometallics and establish thermodynamic parameters for their reactivity in aqueous solvent. A comprehensive thermodynamic database for a wide scope of organo-rhodium transformations in a range of reaction media including benzene, water, and methanol has been well established by our group. Aqueous solutions of rhodium porphyrin have been determined to manifest an exceptional range of substrate reactions with carbon monoxide, dihydrogen, olefins, methanol and aldehydes. This study will focus on expansion of the thermodynamic database to all the group nine metals, particularly the iridium porphyrin systems in both water and methanol. Substrate reactivity and development of new mechanistic strategies for the conversion of carbon monoxide, alkanes, and alkenes to organic oxygenates are central objectives. Water/Methanol soluble porphyrin iridium complexes including iridium tetrakis(p-sulfonatophenyl)porphyrin ((TSPP)Ir) and iridium tetrakis(3,5-sulfonatomesityl)porphyrin ((TMPS)Ir) derivatives can be prepared by sulfonation of tetra phenyl porphyrin (H2TPP) and tetra mesityl porphyrin (H2TMP). The reactivity of dihydrogen with aqueous solutions of iridium(III) tetrakis(p-sulfonatophenyl)porphyrin ((TSPP)Ir(III)) complexes produce equilibrium distributions between six iridium species including iridium hydride ([(TSPP)Ir-D(D2O)]-4), iridium(I) ([(TSPP)IrI(D2O)]-5), and iridium (II) dimer ([(TSPP)IrII(D2O)]2-8) complexes. Each of these types of iridium porphyrin species including Ir(I), Ir(II), Ir(III), Ir-H, and Ir-OH function as precursors for a range of organometallic substrate reactions. A primary objective is to define the quantitative relationships pertaining to the distribution of species in aqueous solution as a function of the dihydrogen and hydrogen ion concentrations through direct measurement of five equilibrium constants along with free energy changes of coordinated water and free energy changes of reactions of dihydrogen in water. Reactivity, kinetics and evaluation of equilibrium thermodynamics, including the reactions of iridium hydroxide and methoxide with olefins to produce beta-hydroxyalkyl and beta-methoxyalkyl complexes, reactions of iridium hydride and olefins to produce iridium alkyl complexes, and reactions of iridium hydride with carbon monoxide to produce iridium formyl [Ir-CHO] complexes are also objectives of this research. Another research goal is the design and synthesis of diporphyrin ligands that form dimetal complexes capable of preorganizing transition states for substrate reactions that involve two metal centers. Dirhodium dimetalloradical complexes are observed to manifest large rate increases over mono-metalloradical activation reactions of hydrogen, methane, and other small molecule substrates. In this study, synthesis of diporphyrin (bisporphyrin) ligands and other ligands which will permit dimetallo complexes like anti-aromatic [14]annulene and low steric porphine ligands will be also be examined.
Temple University--Theses
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Shough, Anne Marie. "Quantum chemistry studies of catalytic and photocatalytic materials transition metal substitution, active sites, thermodynamics and reaction mechanisms /." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 260 p, 2008. http://proquest.umi.com/pqdweb?did=1597619031&sid=2&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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Imler, Gregory H. "Reactivity, Characterization, Equilibrium Thermodynamics and Hetero-bimetallic Studies of Tridentate and Tetradentate Complexes Relevant to Syngas Catalysis." Diss., Temple University Libraries, 2014. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/302256.
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ChemistryPh.D.
The unifying objective of this work is the study of model systems that will assist in the development of new metal catalysts capable of converting carbon monoxide and hydrogen (syngas) into organic oxygenates at mild temperature and pressure. The selective catalytic transformation of carbon monoxide and hydrogen to liquid fuels and chemical feedstocks represents a major "Grand Challenge" of catalysis science. A core objective is the study of a macrocycle that is related to a porphyrin ligand in order to circumvent some of the disadvantages of utilizing porphyrins in catalysis. The rhodium complex of the macrocycle dibenzotetramethylaza[14]annulene ([(tmtaa)Rh]2]) was reacted with a series of small molecules relevant to CO reduction and hydrogenation. Several complexes were formed that demonstrated the ability to partially reduce and hydrogenate carbon monoxide, including the dirhodium ketone (Rh-C(O)-Rh) and an example of a thermodynamically favorable metal formyl complex ((tmtaa)Rh-C(O)H). An important feature of this work is the measurement of thermodynamic data to provide experimental benchmarks for obtaining key species in CO reduction and hydrogenation. A thorough study of the (tmtaa)Rh system will help in identifying structural features that assist or hinder CO hydrogenation. All reactions are monitored by 1H NMR which permits determination of solution thermodynamics from equilibrium constants obtained by NMR peak integrations. DFT calculations have supplemented experimental results by providing estimates to compare with the experimentally determined thermodynamic data. These computations also provide insight into the structures and thermodynamics of species that cannot be observed directly such as short lived intermediates and thermodynamically unfavorable products. Heterobimetallic complexes of (tmtaa)Rh* with a second metal radical have been utilized to attempt to convert CO to organic products. Reactivity with CO and H2 has been accomplished, with most of these metal systems providing (tmtaa)Rh-C(O)H and M-H as final products. These systems are now ideally set up for catalysis in which M-H can deliver hydrogen to reduce and hydrogenate the rhodium formyl unit. Performing these reactions at high pressures of CO/H2 or with a more sterically hindered analog of tmtaa may provide the conditions necessary for catalysis. Reactivity, thermodynamic and computational studies have been used to analyze and compare bond energies in this current work with previous studies accomplished in the Wayland group. These comparisons permit further understanding into the factors that control bond strength, guiding future studies and allowing tuning of bond strengths based on choice of conditions for a catalytic process. This research has resulted in a more complete understanding of the factors that control the favorability of various intermediates in CO reduction and hydrogenation and the application of these results can be used to guide the next generation of metal ligand systems that will yield organic oxygenates at mild conditions.
Temple University--Theses
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Deegan, Brian J. "Biophysical Studies of the Binding of ERα Nuclear Receptor to DNA." Scholarly Repository, 2011. http://scholarlyrepository.miami.edu/oa_dissertations/579.
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Estrogen receptor α (ERα) is a member of a family of ligand-modulated transcription factors that have come to be known as nuclear receptors. ERα mediates the action of estrogens and plays an integral role in a wide range of physiological processes ranging from embryonic development and morphogenesis to reproduction to cardiovascular health. Not surprisingly, malfunction of the estrogen system is associated with a host of pathological conditions such as osteoporosis, heart disease and most notably breast cancer. Essential to its functioning as a transcription factor are specific protein-DNA interactions which are mediated by the binding of the DNA-binding (DB) domain of ERα to particular DNA sequences located within target gene promoters called estrogen response elements (EREs). Here, using a diverse array of biophysical techniques, including in particular isothermal titration calorimetry coupled with molecular modeling and semi-empirical analysis, I provide new insights into the ERα-DNA interaction in thermodynamic and structural terms. My data show that the binding of the DB domain of ERα to DNA is coupled to protonation at two specific amino acids, H196 and E203. Protonation of these residues is non-trivial and is required for high affinity binding. Amino acid sequence alignment of the DB domains of the NR family suggests that this may be a hallmark feature common to the functioning of all nuclear receptors. Furthermore, I demonstrate that the DB domain can tolerate all single nucleotide substitutions within the ERE and bind in the physiologically relevant nanomolar to micromolar range. Comparative thermodynamic analysis reveals that the DB domain binds to these ERE sequences utilizing a considerable range of energetic signatures such that any one thermodynamic component of binding is not predictive of associated affinity. In addition, it is shown that nucleotide substitution results in significant changes in secondary and three-dimensional features of the oligonucleotides and may impact binding affinity. Finally, I demonstrate that the zinc-finger of the DB domain of ERα is relatively promiscuous and can accommodate several heavy-metal divalent cations. Other than zinc, only DB domains reconstituted with cobalt, cadmium and mercury were capable of binding DNA. Incorporation of the metals resulted in a wide range of CD spectroscopic features which were found not to be predictive of DNA binding capacity. Thus, isostructure does not equate to isofunction in the case of metal reconstituted DB domain of ERα. This analysis suggests that metal coordination is not likely to be required for domain folding, but rather is required to bind DNA. Taken together, this thesis provides novel insights into the physicochemical basis of a key protein-DNA interaction essential to human health and disease. My studies bear the potential to impact the development of novel therapies harboring greater efficacy coupled with lower toxicity for the treatment of disease.
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GUPTA, VINEET K. "EXPERIMENTAL AND THEORETICAL STUDIES IN REVERSE OSMOSIS AND NANOFILTRATION." University of Cincinnati / OhioLINK, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1061233200.
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Fabbri, Marco. "Neutronics analysis and thermodynamics studies of several DEMO breeding blankets for the development of the AINA safety code." Doctoral thesis, Universitat Politècnica de Catalunya, 2018. http://hdl.handle.net/10803/552957.
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By 2050 the energy consumption is expected to increase considerably.The production might be mostly based on renewable energy mix driven by the nuclear fusion which could potentially deliver continuous, large-scale power for the long-term without harming the environment. Regrettably, the nuclear fusion still requires numerous developments, which are undergoing around the word, to prove the design feasibility and to evaluate the safety relatad aspects which are to sorne extent embraced this thesis. In light of this, during the last ten years the Nuclear Engineering Research Group (NERG-UPC) has being developing a safety code callad AJNA (acron of Analyses of IN-vessel Accidents) to evaluate the magnetic fusion reactor plasma-wall transients in case of ex-vessel LOCA and overfuelling , determining thermal wall profiles as well as checking the integrity of in-vessel components (melting). Considering the e'v'Olution of technologies and related methodologies, a substantial renewal/improvement plan for AJNA were established. Two specific development tasks are part of this PhD
thesis. (i) The definition, standardization and validation of an enhanced methodology to develop new AJNA versions in order to obtain robust models, estimating as accurately as possible the behaviour of the studied systems. (ii) The re-design, generalization and optimization of thermal-hydraulics routines for the determination of the AJNA thermal-wall distributions both in normal and accident scenarios in substitution of the former unverified/unqualified ones. In addition, the thermal hydraulic routines have been validated against commercial software as ANSYS Fluent.
Consequently, the code has been almost rewritten, improved and consolidated giving special attention on document, comment and V&Vaccording to the current software standard requirements . lndeed, severa! novel features have been introduced to extend the modelling capacity of the AJNA application solver and to estimate the errors .
Afterward, two specific AJNA blanket thermal-wall models have been developed: the Water Cooled Pebble Sed JAPANESE DEMO and the Helium Cooled Pebble Bed EUROPEAN-DEMO. According to the established methodology, the complete process of design, improvement and validation has included the complete set of compulsory radiation transport analyses , thermal-hydraulic studies and AJNA thermal-wall model tuning. Furthermore, preliminary assessments of the transient accident scenarios and sensibility studies haw been also performed. So, starting from fully detailed neutronics and thermal hydraulic results, a simplified and conservatiw wall model has been implemented in AJNA obtaining reliable results in a short calculation time validating the approach proposed. lndeed, simplified models haw been iteratiwly built and adjusted, achieving a good agreement with the fully detailed simulation and yielding a maximum absolute temperature differences around 10%. The determination and coherence of the temperature distribution obtained using independenttool s and approaches, ANSYS® Fluent® vs AJNA thermal-hydraulic routines, supports the proposed methodology, hence validating the whole results obtained. Newrtheless, the 1D non-conservatiw temperature field, where present, could be compensated by the application of scaling functions , obtaining a perfect match with the most conservative 30 distribution. In this innovative approach, the scaling functions correspond to the ratios between the most conservatiw radial distribution in the fully detailed and the 10 simulations . Moreowr, thanks to the simplified and endorsed model, sensitivities and screening assessment can be easily perforrned showing how the system reacts as consequences of loads, boundary conditions and perturbations. In light of this, the detailed number of study can be extensively reduced.
To conclude, this multidisciplinary activity has requested the establishment of a specific framework , including skills and tools.En el año 2050 la producción de energía podría estar distribuida principalmente entre fuentes renovables lideradas por la fusión nuclear que potencialmente puede proveer grande cantidades de energías para largos tiempos, sin afectar considerablemente el ambiente. Desafortunadamente, la fusión nuclear requiere aun numerosos desarrollos para demostrar entre otros la validez del diseño y la seguridad nuclear, argumentos que son tratados en esta tesis doctoral. Durante los últimos diez años, el Nuclear Engineering Research Group (NERG-UPC) ha estado desarrollando un código de seguridad nuclear denominado AINA (Analyses of IN-vessel Accidents) para evaluar los transitorios de plasma-pared en los TOKAMAK, reactores de fusión nuclear a confinamiento magnético, en caso LOCA ex-vessel y accidentes de combustible. El programa determina las consecuencias en componentes in-vessel como la temperatura de los mismos y su integridad. Teniendo en cuenta la ewlución de las tecnologías, un plan de renovación para AINA ha sido puesto en marcha incluyendo dos tareas específicas en esta tesis.(i) La definición, estandarización y validación de una metodología para el desarrollo de nuevas versiones de AINA para obtener modelos simplificados y fiables que puedan estimar de manera precisa el comportamiento de los componentes estudiados. (ii) El rediseño, generalización y optimización de las rutinas termo-hidráulicas para la determinación de los perfiles de temperatura evaluados por AINA, en caso estacionario o transitorios con el fin de remplazar las anteriores. Así mismo, dichas funciones han sido evaluadas y verificadas a través de comparaciones directas a software comerciales como ANSYS Fluent. De esta manera, AINA ha sido casi completamente replanteado, mejorado y consolidado con especial atención a la documentación, comentarios y verificación en línea con los estándares de software actuales. Novedosas técnicas han sido introducidas para añadir la capacidad de modelación y su capacidad.
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Wang, Zhengrong Burnett Donald S. "Oxygen isotope studies of the petrogenesis of Hawaiian lavas and a theoretical study on equilibrium thermodynamics of multiply-substituted isotopologues /." Diss., Pasadena, Calif. : California Institute of Technology, 2005. http://resolver.caltech.edu/CaltechETD:etd-05192005-000025.
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Fredriksson, Patrik. "Thermodynamic Studies of the Fe-Pt System and “FeO”-Containing Slags for Application Towards Ladle Refining." Doctoral thesis, KTH, Materials Science and Engineering, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3630.
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In the present work, the thermodynamic activites of ironoxide, denoted as "FeO" in the slag systems Al2O3-"FeO", CaO-"FeO", "FeO"-SiO2, Al2O3-"FeO"-SiO2, CaO-"FeO"-SiO2and "FeO"-MgO-SiO2were investigated by employing the gasequilibration technique at steelmaking temperatures. Thestrategy was to expose the molten slag mixtures kept inplatinum crucibles for an oxygen potential, determined by aCO/CO2-ratio. A part of the iron reduced from the "FeO"in the slag phase was dissolved into the Pt crucible.
In order to obtain the activites of "FeO", chemical analysisof the quenched slag samples together with thermodynamicinformation of the binary metallic system Fe-Pt is required.Careful experimental work was carried out by employing asolid-state galvanic cell technique as well as calorimetricmeasurements in the temperature ranges of 1073-1273 K and300-1988 K respectively. The outcome of these experiments wasincorporated along with previous studies into a CALPHAD-type ofthermodynamic assessment performed with the Thermo-Calcsoftware. The proposed equilibrium diagram enabledextrapolation to higher temperatures.
The experimentally obtained activites of "FeO" in thepresent work, along with earlier investigations were assessedwith the KTH slag model, THERMOSLAG©. New binaryparameters were evolved and incorporated in THERMOSLAG©.The present model calculations are compared with othercommercially available software such as F*A*C*TandThermo-Calc. The validity of the modified model wasinvestigated by measurements carried out in case of Al2O3-"FeO"-SiO2, CaO-"FeO"-SiO2and "FeO"-MgO-SiO2ternary slags. The potential of the model tocompute the activities in the case of multicomponent slags wasdemonstrated.
A correlation between the activity of a metallic oxide in aternary slag system and the sulphide capacity of the slag wasinvestigated by using the solubility of sulphur in the binarysystems CaO-SiO2and Al2O3-CaO along with the sulphide capacity of the Al2O3-CaO-SiO2system. The estimated values of the activitieswere found to be in good agreement with the measured values.This correlation also gives the possibility to elucidate theapplicability of Henry's law to the activity of a metallicsulphide and to determine the order in the affinity of a cationto sulphur between two metallic oxides in a slag.
Model calculations were performed with THERMOSLAG©, by using plant data from the ladle refiningprocess at OVAKO Steel, Hofors, Sweden. It was found thatoxygen estimations in the metal from the "FeO" analyses ofslags, obtained by conventional sampling and analysis methodwere less reliable. Reliable estimation of the oxygen levelsutilising the sulphur partition between the slag and the metalwere carried out using THERMOSLAG© software.
Keywords:Thermodynamics, Activity, Galvanic cell,Calorimetry, Gas equilibration technique, Iron-platinum alloys,FeO, Slags, Modelling, Ladle
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Isaksson, Johan. "Studies on Nucleic Acids – Structure and Dynamics." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-5867.
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Chen, Yiqiang. "High-resolution microstructural and microanalysis studies to better understand the thermodynamics and diffusion kinetics in an advanced Ni-based superalloy RR1000." Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/highresolution-microstructural-and-microanalysis-studies-to-better-understand-the-thermodynamics-and-diffusion-kinetics-in-an-advanced-nibased-superalloy-rr1000(1d4e96e0-b362-484e-82cb-bec18cab850b).html.
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The commercial polycrystalline superalloy RR1000 developed for turbine disc applications contains a large number of alloying elements. This complex alloy chemistry is required in order to produce appropriate microstructures and the required mechanical properties, such that the most important strengthener γʹ displays complex alloy chemistry. The broad aim of this project is to develop an approach to measuring the composition of γʹ precipitates at a broad range of length scales from nanometres to hundreds of nanometres, and subsequently develop a better understanding of the role of thermodynamics and diffusion kinetics on γʹ phase separation and precipitate growth. A solution of the absorption-corrected EDX spectroscopy to spherical particles was developed in our work, therefore enabling the quantitative analysis of precipitates' composition using an absorption-corrected Cliff-Lorimer approach. By performing this quantification, size-dependent precipitate compositional variations were obtained. Examination of this quantitative approach was compared to thermodynamic calculations of primary γ' precipitates possessing equilibrium compositions. Given the development of semi-quantitative compositional measurements for spherical γʹ precipitates and that cooling is one of the most common and critical regimes in physical metallurgy of Ni-based superalloys, this approach was then applied to study the local compositional variations that are induced in γ' precipitates when the alloy RR1000 undergoes different cooling rates. These measured compositions have been compared to detailed thermodynamic calculations and provide new experimental evidence of the importance of the dominant role of aluminium antisite diffusion in determining the low-temperature growth kinetics of fine-scale γ' precipitates. We have applied a similar analysis approach to study the compositional variations of γʹ cores within the class of secondary precipitates upon cyclic coarsening and reversal coarsening. It was shown that supersaturated Co in secondary γʹ exhibits an overall trend towards the equilibrium but Co content can significantly increase as γʹ coarsens. It was demonstrated that the limited elemental diffusivity in γ and γʹ compared to the observed coarsening rate in the coarsening regime results in the long-lasting Co supersaturation in γʹ and builds up elemental enhancements or depletions. These inhomogeneous elemental distributions produce compressive elastic constraints on large-scale secondary γʹ, therefore inducing morphological instability of these γʹ and causing the reversal coarsening. These results enable us to better understand the role that both thermodynamics and limited diffusion kinetics plays in controlling the complex microstructures of γ' precipitates.
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Mishima, Hirokazu. "Studies Based on Statistical Mechanics for Mechanism of Multidrug Efflux of AcrA/AcrB/TolC." Kyoto University, 2015. http://hdl.handle.net/2433/199416.
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Wicky, Basile Isidore Martin. "Biophysical studies of protein assemblies." Thesis, University of Cambridge, 2019. https://www.repository.cam.ac.uk/handle/1810/288004.
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Proteins are synthesised as linear polymeric chains. The subtle energetic interplay of interatomic interactions results in chain folding, through which proteins may acquire defined structures. This spatial organisation is encoded by the protein sequence itself; the so-called thermodynamic hypothesis formulated by Anfinsen in 1961. A defined structure is often considered a pre-requisite to protein function, but widespread existence of intrinsically disordered proteins (IDPs) has prompted a re- evaluation of the ways biological function may be encoded into polypeptide chains. Furthermore, proteins often exist as part of multi-component entities, where regulation of assembly is integral to their properties. The interplay between disorder, oligomerisation and function is the focus of this thesis. Some IDPs fold conditionally upon interacting with a partner protein; a process known as coupled folding and binding. What are the biophysical advantages and consequences of disorder in the context of these interactions? A common feature of IDPs is their sequence composition bias, with charged residues being often over-represented. It is therefore tempting to speculate that electrostatic interactions may play a major role in coupled folding and binding reactions. Surprisingly, the opposite was found to be true. Charge-charge interactions only contributed about an order of magnitude to the association rate constants of two contrasting model systems. The lack of pre-formed binding interfaces-a consequence of disorder-might preclude electrostatic acceleration from complementary patches. By looking at the role of the sequence, many studies have taken a protein-centric approach to understanding disorder. Yet there is paucity of data about the effect of extrinsic factors on interactions involving disordered partners. Investigating the role of co-solutes, it was discovered that the kinetic and thermodynamic profiles of coupled folding and binding reactions were sensitive to ion-types. This effect followed the Hofmeister series, and occurred at physiological concentrations of salt. The sensitivity of coupled folding and binding reactions-a consequence of the lack of stability of IDPs-might be advantageous. Given the role of ions in biology, this 'biophysical sensing' could be a mechanism of physiological relevance, allowing modulation of protein-protein interactions involving disordered partners in response to changes in their environments. In cells, signalling networks are often multi-layered, and involve competing protein-protein interactions. The interplay between the biophysical characteristics of the components, and the behaviour of the network were investigated in a model tripartite system composed of folded and disordered proteins. The BCL-2 family regulates the intrinsic pathway of apoptosis through control of mitochondrial outer-membrane permeabilisation; a result of BAK and BAX oligomerisation. Through a shared homology motif (termed BH3), the subtle balance of their interactions determines cellular fate at the molecular level. Characterisation of the model under simple biochemical conditions revealed large differences in affinities among binary interactions; the consequence of the lifetime of the complexes, not their speed of association. A membrane-like environment, re-created using detergents, allows the oligomerisation of BAK and BAX in vitro. Furthermore, investigation of the tripartite system under detergent conditions showed that regulation of the network was the result of competing hetero- and homo-oligomerisation events. Relationships to their biophysical properties were gained by probing their energy landscapes using protein folding techniques. The connection between the biophysical properties of the components of the network and their interactions provides a molecular explanation for the regulation of apoptosis. This thesis offers insights into the ways structured assemblies and environmentally responsive disorder elements may encode functions into proteins.
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Maximo, Guilherme José 1982. "Lipid thermodynamics = new perspectives on phase studies for applications in engineering = Termodinâmica de lipídios: novas perspectivas em estudos de fases para aplicações em engenharia." [s.n.], 2014. http://repositorio.unicamp.br/jspui/handle/REPOSIP/255144.
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Orientadores: Antonio José de Almeida Meirelles, Mariana Conceição CostaTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos
Made available in DSpace on 2018-08-24T10:06:55Z (GMT). No. of bitstreams: 1 Maximo_GuilhermeJose_D.pdf: 6364914 bytes, checksum: 716122d30b63141c35ee3d3c3305de17 (MD5) Previous issue date: 2014
Resumo: Para o desenvolvimento de chocolates, manteigas, molhos para salada, cremes cosméticos, medicamentos ou biocombustíveis, assim como na otimização de processos de extração, refino, fracionamento, cristalização e produção de energia, os fenômenos de transição de fases dos sistemas lipídicos são temas, há muito tempo, de diversos trabalhos na literatura. O objetivo desses trabalhos tem sido avaliar como a composição dos produtos altera as suas propriedades físico-químicas e em especial aquelas relacionadas aos processos de fusão. De fato, alterações na temperatura exercem um grande impacto na estrutura cristalina da fase sólida dos sistemas graxos e, consequentemente, nas propriedades sensoriais e reológicas dos produtos. Essas alterações produzem comportamentos termodinâmicos tão variados que a determinação do equilíbrio de fases sólido-líquido desses sistemas representa um grande desafio. Não obstante, quanto maior a complexidade do sistema, menor é a compreensão do seu comportamento. Ou seja, apesar do grande número de trabalhos presentes na literatura envolvidos na investigação dos fenômenos de fusão de sistemas lipídicos, novos dados experimentais e abordagens teóricas para a modelagem dos diagramas são necessários para sua compreensão. Neste contexto, este trabalho teve dois objetivos principais. O primeiro relacionado à determinação e análise de diagramas de fases sólido-líquido de sistemas lipídicos binários de interesse para a indústria. O segundo foi desenvolver alternativas teóricas para aprimorar a representação dos diagramas de fases baseado em abordagens termodinâmicas clássicas. Portanto, onze sistemas binários compostos por triacilgliceróis, ácidos graxos e álcoois graxos foram avaliados. Esses sistemas são potenciais agentes de estruturação, formação de organogéis, produção e armazenamento de energia na indústria de alimentos, farmacêutica e de materiais. Os diagramas de equilíbrio sólido-líquido dessas misturas apresentaram comportamentos distintos, dependentes da formação de fases sólidas miscíveis ou imiscíveis e da não-idealidade do sistema. Além disso, foram estudados quatro sistemas formados a partir da reação ácido-base de Brønsted entre ácidos graxos e etanolaminas. Neste caso, a formação de líquidos iônicos próticos cristalinos com grande habilidade para auto-organização e comportamento não-Newtoniano singular podem atuar como auxiliares em diversas aplicações químicas e farmacêuticas. O problema imposto pela miscibilidade da fase sólida na construção dos diagramas de fases foi superado pela implementação de um algoritmo para a resolução de um sistema de equações não-lineares baseado nas equações fundamentais do equilíbrio sólido-líquido. O objetivo do algoritmo "Crystal-T" foi determinar a temperatura em que o primeiro e o último cristal se fundem durante o aquecimento do sistema. Para isso, a não-idealidade de ambas as fases líquida e sólida foi avaliada utilizando equações baseadas na energia de Gibbs em excesso, incluindo o método de contribuição de grupos UNIFAC, para o cálculo dos coeficientes de atividade. Considerando o aumento da produção mundial e do consumo de óleos e gorduras, este trabalho, a partir de demandas emergentes da indústria e da pesquisa científica, contribuiu na superação de alguns obstáculos relacionados à compreensão do equilíbrio de fases sólido-líquido de sistemas lipídicos para a engenharia de produtos e processos
Abstract: The phase transition phenomena of lipidic systems have long since been evaluated by several works in literature for developing chocolate, butters, dressings, spreads, cosmetic creams, medicines or biofuels as well as for optimizing processes such as extraction, refining, fractionation, crystallization or energy production. The aim of such works has been to answer how the products¿ composition can affect their physicochemical characteristics especially that related to the melting processes. In fact, changes in temperature highly impact the crystalline structure of fatty systems¿ solid phase and, consequently, in the sensorial and rheological properties of the products. These changes led to so many thermodynamic behaviors that the determination of the solid-liquid equilibrium of these systems can configure a particular challenge. However, the greater the complexity of the system the lower the understanding of its behavior. In other words, despite the number of works in literature involved in the investigation of the melting phenomena of lipidic systems, there is still a lack of experimental data and modeling approaches for their understanding. In this context, this work was conducted with two main goals. The first was focused on the measurement and comprehension of the solid-liquid equilibrium phase diagrams of lipidic binary systems of industrial interest. The second was aimed at the development of theoretical alternatives to improve the phase diagram description based on classical thermodynamic approaches. Thus, eleven binary systems composed by triacylglycerols, fatty alcohols and fatty acids were evaluated. Such mixtures are potential structuring, organogelating and energy storing agents for food, pharmaceutical and materials industry. The solid-liquid phase diagrams of these mixtures presented distinct behaviors depending on the formation of immiscible or miscible solid phases and the non-ideality of the system. Also, four systems built through a Brønsted acid-base reaction between fatty acids and ethanolamines were also evaluated. In this case, the formation of protic ionic liquid crystals with high self-assembling ability and marked non-Newtonian behavior are promising for pharmaceutical and chemical applications. The problem imposed by the partial miscibility of the solid phase in the construction of the phase diagrams was overtaken by the implementation of an algorithm based on the resolution of a non-linear equations system built by the solid-liquid equilibrium fundamental equations. The "Crystal-T" algorithm was aimed at the determination of the temperature at which the first and last crystal melts during the heating process. For this, the non-ideality of both liquid and solid phases was evaluated using excess Gibbs energy equations, including the group-contribution UNIFAC model, for the calculation of the activity coefficients. Taking into account the growing increase of the world production and consumption of fat and oils, this work, from industrial and academic emerging demands, contributed to overtake some barriers on the understanding of the solid-liquid phase equilibrium of lipidic mixtures for products and process engineering
Doutorado
Engenharia de Alimentos
Doutor em Engenharia de Alimentos
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Farooqi, Mohammed Junaid. "METHODS FOR IN SITU PIEZOPHYSIOLOGICAL STUDIES: OPTICAL SECTIONING VIA STRUCTURED ILLUMINATION AND FLUORESCENCE BASED CHARACTERIZATION OF NADH CONFORMATION." Oxford, Ohio : Miami University, 2009. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=miami1249225952.
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Lorenzo, Ros Sara de. "Single molecule studies in a temperature-jump optical trap." Doctoral thesis, Universitat de Barcelona, 2015. http://hdl.handle.net/10803/286174.
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In the field of biophysics, the study of the thermodynamic characteristics of biomolecules, such as DNA, RNA or proteins, allows us to understand more about the building blocks of life. The thermodynamic characterization of the biomolecule gives us clues as to their functions and capabilities inside every living organism.
The thermodynamic characterization of nucleic acids describes how temperature affects the stability and the structure of double stranded DNA. The melting temperature of DNA (T(M)) is defined as the temperature at which half of the DNA strands in a bulk solution experiment are in the double stranded DNA (dsDNA) or random coil configuration and half of the DNA are in the single-stranded DNA (ssDNA) configuration. Using T(M), it has been possible to experimentally determine the thermodynamic parameters of Delta-G, Delta-H and Delta-S. Viceversa, when the thermodynamic parameters of a given nucleic acid sequence are known, the TM can be predicted. This effect has important applications for biomolecule techniques such as PCR (Polymerase chain reaction) or sequencing.
Traditionally thermodynamic properties of DNA have been determined using bulk techniques such as calorimetry or UV absorbance. In both cases the melting temperature has been determined by changing the temperature or pH of the entire sample.
Over the past two decades single molecule force spectroscopy has been established as a powerful, accurate and bulk-complementary method of characterizing the thermodynamics of nucleic acids. Optical trapping is an experimental technique which allows force to be exerted on a micrometric particle by using the radiation pressure of light. The miniTweezers (mT) is the newest generation of optical tweezers instruments. This instrument can be used to exert and measure forces in a range between 1-200 pN and has unprecedented resolution (0.1 pN in force an around 1 nm in distance) with very high thermal and noise stability. Optical trapping is very useful in the field of molecular biology because it allows forces to be exerted on single biomolecules bonded to the micrometric particle.
This technique is used to carry out pulling experiments on single molecules allowing us to study the mechanical, thermodynamic and kinetic properties of the molecule. Mechanical melting or unzipping is a process that consists of pulling apart the two strands of the dsDNA until the base pairs are disrupted and the molecule converts into ssDNA. In this case, and in contrast to other techniques, force, rather than temperature or pH, is used to open the molecule.
Past experiments have shown that better resolution can be obtained using single molecule techniques than can be obtained using bulk experiments. Although force unzipping provides a direct estimation of Delta-G at room temperature, extracting the value of TM always requires the determination of the Delta-H and Delta-S contributions and until now has not been reliable accomplished.En el campo de la biofísica, el estudio de las características termodinámicas de las biomoléculas, como ADN, ARN o proteínas, permite conocer más sobre los componentes básicos de la vida. La caracterización termodinámica de las biomoléculas nos proporciona pistas sobre sus funciones y capacidades dentro de un organismo vivo. La caracterización termodinámica de los ácidos nucleicos describe como la temperatura afecta la estabilidad y la estructura de la doble cadena de ADN. La temperatura de melting del ADN (TM) se define como la temperatura a la cual la mitad de las moléculas de ADN disueltas en una solución se encuentran en configuración de doble cadena (dsDNA) y la otra mitad se encuentra en la configuración de cadena individual (ssDNA). Conociendo el valor de la TM es posible determinar experimentalmente los parámetros termodinámicos: Delta-G, Delta-H y Delta-S. Viceversa, cuando los parámetros termodinámicos de la secuencia de un ácido nucleico es conocido, la TM puede ser predecida. Este efecto tiene importantes aplicaciones en técnicas de biología molecular como PCR (en inglés Polymerase chain reaction) o secuenciación. Tradicionalmente las propiedades termodinámicas del ADN han sido medidas utilizando técnicas de volumen como calorimetría o absorbancia de UV. En ambos casos la TM ha sido calculada modificando la temperatura o el pH de toda la muestra. En las pasadas dos décadas, las técnicas de espectroscopía de fuerzas sobre moléculas individuales, han sido reconocidas como técnicas de un gran valor y precisión cuyos resultados en el estudio de la caracterización termodinámica pueden ser considerados perfectamente complementarios a los medidos en técnicas de volumen. La técnica de atrapamiento óptico es una técnica experimental la cual permite ejercer fuerza sobre una partícula micrométrica utilizando la presión de radiación de la luz. Las minipinzas (en inglés minitweezers) es una nueva generación a los instrumentos de pinzas ópticas. Este instrumento puede ser usado para ejercer y medir fuerzas en un rango de entre 1-200pN y con una resolución en fuerza y distancia sin precedentes. El atrapamiento óptico es muy útil en el campo de la biología molecular permitiendo ejercer fuerzas sobre biomoléculas individuales enganchadas. Esta técnica es usada para llevar a cabo experimentos de estiramiento sobre moléculas individuales permitiendo el estudio de las propiedades mecánicas, termodinámicas y cinéticas de la molécula bajo estudio. El experimento de unzipping o melting mecánico es un proceso que consiste en separar las dos hebras de la dsDNA hasta que los enlaces entre los pares de bases complementarios son deshechos y la molécula se convierte en ssDNA. En este caso la fuerza es usada como medio para abrir la molécula, en vez de la temperatura o el pH como en otras técnicas. Pasados experimentos han mostrado que podemos obtener mejor resolución utilizando técnicas de moléculas individuales que utilizando técnicas en volumen. Aunque la fuerza de unzipping nos proporciona una estimación directa de Delta-G a temperatura ambiente, para poder extraer el valor de TM requiere conocer las contribuciones de Delta-H y Delta-S y hasta ahora no ha sido posible. Para llevar a cabo una completa caracterización termodinámica de ácidos nucleicos es importante conocer ambas magnitudes (Fuerza y Temperatura). El mejor camino para hacer este análisis es llevar a cabo experimentos de unzipping sobre moléculas individuales de ADN a diferentes temperaturas. Por ello hemos desarrollado un novedoso instrumento de pinzas ópticas con un controlador de temperatura que nos permite modificar y cambiar la temperatura de manera local y rápida. Se ha usado un específico láser calentador con una longitud de onda con una alta absorción en agua que permite cubrir un amplio rango de temperaturas. Este instrumento nos permite grabar diversas curvas de fuerza/extensión para una molécula individual a varias temperaturas con una buena estabilidad térmica y mecánica. Este diseño tiene ciertas mejoras para reducir la convección, el cual ha sido un grave problema en previos equipos calentados a través de un láser. Este equipo ha sido usado para hacer experimentos de ADN, lo que nos ha permitido hacer un análisis promediado de Delta-G, Delta-S y Delta-H entre pares de bases en un rango de temperatura entre 5ºC y 50ºC.
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Strach, Michal. "In situ studies of uranium-plutonium mixed oxides : Influence of composition on phase equilibria and thermodynamic properties." Thesis, Aix-Marseille, 2015. http://www.theses.fr/2015AIXM4044.
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En raison de leurs propriétés chimiques et physiques, les oxydes mixtes d'uranium et de plutonium sont considérés comme combustibles pour les réacteurs nucléaires de quatrième génération. Dans ce cadre, des études expérimentales complémentaires sont nécessaire, notamment pour mieux comprendre les phénomènes mis en jeu lors de la fabrication ou sous irradiation. L'objet de ce travail est d'étudier le diagramme de phase U-Pu-O dans une large gamme de composition et de températures afin d'améliorer notre connaissance de ce système. La plupart des expériences ont été réalisées par diffraction des rayons X en fonction de la température. La contrôle in situ de la pression partielle en oxygène a permis de faire varier la stœchiométrie en oxygène dans le matériau. L'approche expérimentale a été couplée avec la modélisation thermodynamique par la méthode CALPHAD afin de mieux dimensionner les expériences et interpréter les résultats. Cette méthodologie a permis d'améliorer notre connaissance des équilibres de phase dans le système U-Pu-ODue to their physical and chemical properties, mixed uranium-plutonium oxides are considered for fuel in 4th generation nuclear reactors. In this frame, complementary experimental studies are necessary to develop a better understanding of the phenomena that take place during fabrication and operation in the reactor. The focus of this work was to study the U Pu–O phase diagram in a wide range of compositions and temperatures to ameliorate our knowledge of the phase equilibria in this system. Most of experiments were done using in situ X-ray diffraction at elevated temperatures. The control of the oxygen partial pressure during the treatments made it possible to change the oxygen stoichiometry of the sample, which gave us an opportunity to study rapidly different compositions and the processes involved. The experimental approach was coupled with thermodynamic modeling using the CALPHAD method, to precisely plan the experiments and interpret the obtained results. This approach enabled us to enhance the knowledge of phase equilibria in the U–Pu–O system
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Choudhury, Pabitra. "Theoretical and experimental study of solid state complex borohydride hydrogen storage materials." [Tampa, Fla] : University of South Florida, 2009. http://purl.fcla.edu/usf/dc/et/SFE0003164.
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Prilliman, Gerald Stephen. "Synchrotron X-ray diffraction studies of phase transitions and mechanical properties of nanocrystalline materials at high pressure." Berkeley, Calif. : Oak Ridge, Tenn. : Lawrence Berkeley National Laboratory ; distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy, 2003. http://www.osti.gov/servlets/purl/825137-DcNEaM/native/.
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Thesis (Ph.D.); Submitted to The University of California at Berkeley, Berkeley, CA (US); 1 Sep 2003.Published through the Information Bridge: DOE Scientific and Technical Information. "LBNL--55022" Prilliman, Gerald Stephen. USDOE Director. Office of Science. Office of Basic Energy Sciences (US) 09/01/2003. Report is also available in paper and microfiche from NTIS.
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Shelton, John. "Thermophysical Characterization of Nanofluids Through Molecular Dynamic Simulations." Scholar Commons, 2011. http://scholarcommons.usf.edu/etd/3343.
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Using equilibrium molecular dynamics simulations, an analysis of the key thermophysical properties critical to heat transfer processes is performed. Replication of thermal conductivity and shear viscosity observations found in experimental investigations were performed using a theoretical nanopthesis-fluid system and a novel colloid-fluid interaction potential to investigate the key nanofluid parameters. Analysis of both the heat current (thermal conductivity) and stress (shear viscosity) autocorrelation functions have suggested that the dominant physical mechanisms for thermal and momentum transport arises from enhancements to the longitudinal and transverse acoustic modes energy transfer brought about by the increased mass ratio of the nanopthesis to the fluid. This conclusion was further supported by analysis of the local density fluctuations surrounding increasing nanopthesis diameters where the longitudinal acoustic mode characteristics for density fluxes were seen to be enhanced by the presence of the heavier platinum nanopthesiss. It is then concluded that the key macroscopic characteristic in obtaining the largest thermal energy transfer enhancement is through the mass of the nanopthesis relative to the base fluid. Also, the small local density effects in the nanofluid are greatly affects the viscosity calculations. These conclusions provide the theoretical framework for many of the experimental results obtained.
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Rendell, Benjamin William Spiby. "Thermodynamic studies of glass refining." Thesis, University of Cambridge, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.619563.
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Butt, Michael David. "Macromolecular thermodynamics studied by titration calorimetry." Thesis, University of Leicester, 1994. http://hdl.handle.net/2381/34042.
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This thesis is centred on the use of an isothermal titration microcalori-meter which can measure heat changes of the order of a few microcalories. The calorimeter provides a rapid and convenient method, incorporating a thermodynamic analysis, for estimating enthalpic pairwise interaction parameters, hjj, for solute-j in aqueous solution. Estimates of hjj for three solutes; urea, monoethylurea and hexamethylenetetramine are reported. Comparisons with published estimates of hjj show good agreement, and confirm the importance of the new technology in calorimetry. The critical micellar concentrations (cmc's) of a series of l-alkyl-4-alkylpyridinium halide and bisquaternary ammonium bromide surfactants are reported, using q, heat change on injection, as the reporter. The standard enthalpy of micelle formation is also obtained, directly, from titration experiments. An equation is derived for the standard Gibbs energy of micelle formation, for these compounds. Thus, the standard entropy is calculated and the driving force (enthalpy or entropy) for micellisation, of these surfactants, is identified. Injection of small aliquots of fusogenic agents (the dianions of dipicolinic acid and sodium sulphate) into aqueous solutions of dioctadecyldimethyl-ammonium bromide (DOAB) vesicles is endothermic at 50 Celsius. For solutions containing greater than equimolar ratios of DOAB and fusogenic agent, the injection process is effectively athermal. The patterns of enthalpy change are attributed to vesicle-dianion interaction (exothermic) and headgroup dehydration (endothermic). Other effects such as the presence of buffer and the interaction of DOAB with halide monoanions are also discussed. Binding of the substrate, chloramphenicol (CM), to the enzyme, chloramphenicol acetyltransferase (CAT), is exothermic. Calorimetric measurements of a series of injections of CM into CAT, and subsequent analysis, yield the binding constant, number of binding sites per macromolecule (enzyme) and the standard enthalpy of binding for the interaction. These three parameters are presented, together with the standard entropy and standard Gibbs energy of binding.
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Conn, Graeme Leslie. "Structural and thermodynamic studies of RNA." Thesis, University of Edinburgh, 1996. http://hdl.handle.net/1842/12169.
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The nucleic acids, RNA in particular, are conformationally complex biomolecules. The structures that they can form and the subtle sequence dependent modifications of conformation are of pivotal importance to their function in vivo. The advent of solid phase chemical synthesis methodologies for DNA and, more recently RNA, has fuelled the rapid growth in our knowledge of nucleic acid structure. The work described here is concerned with the development of rapid and reliable synthesis and purification protocols for the automated chemical synthesis of RNA. The use of RNA phosphoramidite monomers incorporating two different 2'-hydroxyl protecting groups is described, along with ion-exchange and reversed phase HPLC protocols for the purification of oligoribonucleotides. The quality of the material obtained by these methods has allowed detailed biophysical investigations by UV melting, high field NMR and X-ray crystallography.
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Amezawa, Koji. "Irreversible Thermodynamic Studies on Electrochemical Systems." Kyoto University, 1998. http://hdl.handle.net/2433/77878.
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Whiteway, Clare Ann. "Structural and thermodynamic studies on retinal proteins." Thesis, University of Oxford, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240487.
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Jackson, Philip R. "Thermodynamic studies of binary mixtures involving aromatic fluorocarbons." Thesis, University of Leicester, 1986. http://hdl.handle.net/2381/33750.
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Solid-liquid phase diagrams have been determined for binary systems of hexafluorobenzene + naphthalene-type compounds, and indicate strong 1:1 congruently melting point complexes. Hexafluorobenzene + cis- and + trans-deca1in were found to give simple eutectic phase diagrams. Excess enthalpies, excess volumes and excess Gibbs functions have been measured for the same hexaf1uorobenzene + naphthalene-type compound mixtures and are large and negative, which is characteristic of systems where specific interactions take place. This contrasts with the large positive excess functions found with hexafluorobenzene + decalin systems, where only dispersion forces are assumed present. The excess Gibbs function for hexafluorobenzene + trans- and cis-decalin have been determined theoretically from freezing point data as well as directly from vapour pressure measurements. A batch calorimeter, besides being used for excess enthalpy measurememts, has been employed in determining heats of solution, which lead to a value for the enthalpy change for the process, solid + solid ? complex. The possibility of charge-transfer interactions occuring in hexafluorobenzene + naphthalene-type compound systems has been discussed in terms of HOMO/LUMO overlap considerations and is supported by the observation that pentafluorocyanobenzene forms stronger (higher melting point) complexes with 1- and 2-methylnaphthalene, than hexafluorobenzene does.
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Ding, Shu. "Thermodynamic studies on iron-sulfur cluster assembly proteins." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1316472363.
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Boclair, Joseph W. (Joseph Walter). "Thermodynamic and Structural Studies of Layered Double Hydroxides." Thesis, University of North Texas, 1998. https://digital.library.unt.edu/ark:/67531/metadc278144/.
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The preparation of layered double hydroxides via titration with sodium hydroxide was thoroughly investigated for a number of M(II)/M(III) combinations. These titration curves were examined and used to calculate nominal solubility product constants and other thermodynamic quantities for the various LDH chloride systems.
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Massis, Sameer. "Biophysical studies and thermodynamic analysis of cathepsin B interactions." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape7/PQDD_0026/MQ50833.pdf.
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