Thèses : « CO2 density »

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Calabrese, Claudio. « Viscosity and density of reservoir fluids with dissolved CO2 ». Thesis, Imperial College London, 2017. http://hdl.handle.net/10044/1/61899.

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The viscosity and density of a range of aqueous and hydrocarbon reservoir fluids, with and without dissolved CO2, have been studied at high temperature and high pressure conditions. The findings of this research can be applied to the oil and gas industry, for instance to design and operate enhanced oil recovery (EOR) processes using CO2 and large-scale carbon storage in depleted hydrocarbon reservoirs or deep saline aquifers. In this work, the viscosity was measured by means of a vibrating-wire (VW) viscometer while the density was measured with a vibrating U-tube (VT) densimeter. The simultaneous measurements of viscosity and density were carried out in the single-phase compressed liquid region at temperatures between (273 and 466) K and pressures up to 100 MPa. In addition, density measurements were made for four hydraulic fluids up to a maximum pressure of 135 MPa. The viscosity and density measurements of NaCl(aq) and CaCl2(aq) brines under CO2 addition were made at salt molalities of 0.77 mol·kg-1 and 1.00 mol·kg-1, respectively. Additional density measurements were also made for the [CO2 + NaCl(aq) or CaCl2(aq)] systems at salt molalities of 2.50 mol·kg-1. To enable the viscosity measurements, a key contribution of this work was the development of a new modification of the working equation of the VW viscometer which takes into account the electrical conductivity of these brines, and hence expanded the use of this precise technique to an entire new class of conductive fluids. The results for the viscosity and density were correlated as functions of temperature, pressure and the mole fraction of dissolved CO2. For viscosity, a simple modification of the Vogel-Fulcher-Tamman equation was employed while, for density, an equation based on the partial molar volume of CO2(aq) and the molar volume of the CO2-free aqueous solution was used. The viscosity and density of two synthetic crude oil mixtures with dissolved CO2 were also measured. The synthetic dead oil contained a total of 17 components including linear and branched alkanes, cyclo-alkanes and aromatics. A live oil with a gas-to-oil ratio of 58 was obtained from this dead oil by adding solution gas (CH4 + C2H6 + C3H8). For the synthetic dead oil, the mole fractions of dissolved CO2 were x = (0.0, 0.1, 0.2, 0.4, 0.6 and 1.0). The investigated CO2 mole fractions for the synthetic live oil mixture were x = (0.0, 0.1, 0.2 and 0.4). The experimental viscosity and density data were correlated at each CO2 mole fraction as a function of temperature and pressure. A modified Tait equation was used to correlate the densities, while an empirical equation was used for modelling the viscosity of the (CO2 + synthetic crude oil) mixtures. Accurate viscosity and density data were then gathered for two synthetic paraffinic mixtures in order to validate the Vesovic-Wakeham (VW) predictive method for these complex mixtures over a wide range of temperature and pressure, at viscosities up to 2.5 mPa∙s. The two mixtures were referred to as oil #1 and oil #2 and contained a total of 10 and 5 liquid normal alkane components, respectively. The selection criteria for these components were based on the distribution of single carbon number (SCN) of a real light stock tank oil with a molecular weight of 184 g∙mol-1 and density of about 867 kg∙m-3. The mole fraction of C7+ in both mixtures was constrained to 0.9. n-alkane mixtures were chosen because they represent the simplest system to investigate for developing a generic predictive model applicable to more complex and heavy synthetic crude oils. The VW model was able to represent the viscosities of both mixtures with an absolute average deviation of 5 %. The positive results of this work on n-alkane mixtures is an essential precursor for the application of the VW model to more complex fluids encountered in the petrochemical industry. The density of four hydraulic fluids were also studied to test the correlative capability of the modified Tait equation over wide ranges of temperature and pressure. In this case, a correlative approach was preferred to a predictive model because the chemical composition of the above-mentioned fluids was unknown. The modified Tait equation fitted well the experimental density data and was successfully employed to extrapolate densities at 473.15 K, at pressures from (0.1 to 135) MPa. The accurate correlative power of the modified Tait equation over wide ranges of temperature and pressure can be exploited for improving the performance and design of motors and pumps which make use of hydraulic fluids. The results presented in this thesis were carried out as part of the Qatar Carbonates and Carbon Storage Research Centre (QCCSRC) program. The work extends the knowledge of the viscosity and density of reservoir fluids under CO2 addition at higher pressures and temperatures compared to the existing available data in the literature. In addition, it also provides purely empirical or semi-theoretical models which are able to determine the viscosity and density of reservoir fluids with dissolved CO2 with satisfactory accuracies for industrial applications. However, additional research is needed in this field, and for this reason, further experimental investigations have been identified and suggested.

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McBride-Wright, Mark. « Viscosity and density of aqueous fluids with dissolved CO2 ». Thesis, Imperial College London, 2014. http://hdl.handle.net/10044/1/19200.

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Carbon Capture and Storage (CCS) is considered a technology which can help ease the emissions associated with the use of fossil fuels for energy and industrial processes. In Qatar, rapid industrial expansion has established a need for CCS. Here, saline aquifers represent a potential sink for geologically storing the associated CO2 emissions. CCS is an important component of meeting carbon emission targets; CO2 storage in the carbonate reservoirs of the Middle East and elsewhere will become increasingly important. CO2 can also be used for enhanced oil recovery (EOR), which consequently brings an economic benefit. However, we know little about how CO2 behaves when it is mixed with reservoir fluids (hydrocarbons, water, brines) or with carbonate rocks; so we need more research in this area. In particular, the injection of CO2 into these reservoirs/aquifers depends crucially on the viscosity of the fluids involved. Hence the focus of this research has been on determining experimentally the viscosity and density of aqueous fluids with dissolved CO2. This thesis details the design, construction, testing and utilisation of a new experimental apparatus for performing measurements at high pressure and high temperature (HPHT). Measurements were made at temperatures between (274.15 and 448.15) K, and at pressures up to 100 MPa in the single-phase compressed liquid region. The vibrating-wire technique was used for viscosity determination, with simultaneous measurements of density by means of a vibrating-tube densimeter. Wetted parts were made from Hastelloy-C276 and Pt-Ir alloy, chosen to resist corrosion. Measurements were first performed on the system (water + CO2). Following this, mixtures of salt solutions with dissolved CO2 were measured and the results correlated in useful models which allowed for comparison with literature data where this was possible. Salts investigated include NaCl(aq), CaCl2(aq), each at two different concentrations, and lastly, a synthetic Qatari reservoir brine. A correlation based on the Vogel-Fulcher-Tammann (VFT) equation for viscosity is presented which represents all the data to within ±3%, including the pure Qatari brine and its modification by dissolved CO2. Density is correlated using the partial molar volume of CO2 and gives the densities of the mixtures to within ±0.1 %. The results presented in this thesis extend our knowledge of the viscosity of CO2-water-brine systems to significantly higher temperatures and pressures than are currently available in the literature. The effect of temperature on density and viscosity is significant whereas pressure effects are relatively small. Since rigorous theories for gas-saline mixtures are not yet available, semi-empirical correlations with some underlying physicochemical basis have been used to represent the new results. These are capable of estimating the density and viscosity of the fluid mixtures involved to an accuracy that is more than adequate for the design and control of CCS and EOR subsurface processes.

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Aleji, Amos. « Viscosity and density of crude oils and their mixtures with injected CO2 ». Thesis, Imperial College London, 2016. http://hdl.handle.net/10044/1/61829.

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With the increasing maturity of conventional oil resources and limited volumes of new conventional resources to replace production, attention has been focused on viscosity reduction to enhance oil production from brown-field reservoirs by the injection of light gases such as CO2. Also, viscosity plays a significant role in managing and controlling injection of CO2 into depleted oil reservoirs or saline aquifers for the purpose of carbon sequestration. In this study, experimental measurements on viscosity of crude oils and mixtures of crude oils injected with CO2 were performed using accurate technique including a vibrating-wire viscometer and a vibrating tube densimeter. However, for viscosity measurements involving crude oil using vibrating-wire viscometer, asphaltenes precipitation and deposition can be a problem making sensor to provide inaccurate and misleading results. To avoid this problem, the crude oil samples were carefully prepared using ASTM recommended procedure (ASTM2007-80) for separating asphaltenes. The performance and accuracy of a vibrating tube densimeter is critically dependent on the adopted calibration method. Two calibration methods were investigated: using vacuum and water; and using vacuum, water and toluene as standard fluids. The findings from subsequent validation procedures revealed that the method of calibration using vacuum, water and toluene lead to better performance of the density sensor. The percent average deviations remained within ± 0.2 % for density leading to percent average deviations within ± 5% for viscosity. In contrast, the percent average deviations of using vacuum and water method were above ± 0.2% for density and above ± 5% for viscosity. Consequently, the vacuum-water-toluene calibration of the densimeter was used. A vibrating-wire viscometer and a vibrating tube densimeter were used to measure the viscosity and density of crude oils Pi and NS. The temperatures studied were between (298.2 and 448.2) K and that of pressures were between (0.1 and 135) MPa. The experimental setup was further modified to measure the viscosity and density of mixtures of: Pi and CO2, and NS and CO2 for a range of compositions (0 ≤ wCO2 ≤ 0.11) at pressures between (0.1 and 70) MPa and temperatures between (298.2 and 448.2) K. The data were correlated with simple mathematical functions which express the viscosity and density in terms of pressure and temperature. The percent average deviations of the experimental data from the correlation equations were within ± 5 % for the viscosity and ± 0.2 % for density. The predictive capabilities of some physically-based viscosity models were tested using the experimental data. The models used were versions of the effective hard-sphere model for fluid mixture viscosity: (1) original model of Dymond and Assael, (2) an extended version by Caudwell et al, (3) and 1st and 2nd extended versions by Ciotta et al. The results obtained showed that the 2nd version of Ciotta et al model is capable of reproducing the viscosity prediction of crude oil within the limits of the percent average deviations of the experimental data, ± 5 %. For the mixtures of crude oil and CO2, the Caudwell et al model was able to predict the viscosity of both sets of mixtures (Pi and CO2 & NS and CO2) to within percent average deviations of ± 5 % from the experimental data. The injection of CO2 into the crude oils, markedly, reduced the viscosity of both crude oils.

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REMIGI, SAMANTHA. « On the application of Raman micro-spectroscopy to the characterization of Earth's CO2 fluids ». Doctoral thesis, Università degli Studi di Milano-Bicocca, 2021. http://hdl.handle.net/10281/325898.

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Questa tesi indaga l'applicabilità della micro-spettroscopia Raman per migliorare la caratterizzazione dei fluidi a CO2 terrestri, intrappolati come inclusioni fluide (FI) nelle peridotiti. Nello spettro Raman della CO2, la distanza delle due vibrazioni fondamentali è densità (d) dipendente, inoltre sono visibili le vibrazioni 13CO2 e 12CO2. Ciò permette alla micro-spettroscopia Raman di avere il potenziale per caratterizzare in situ FI a CO2, consentendo di comprendere meglio i meccanismi di trasporto del C all'interno della Terra. La proporzionalità tra le aree 13CO2 e 12CO2 con la loro concentrazione molare permette di calcolare il δ13CCO2 tramite micro-spettroscopia Raman. I rapporti delle aree richiedono precisione sulla 4° decimale per dare valori di δ13CCO2 rappresentativi dei serbatoi naturali terrestri. Gli spettri Raman sono influenzati da inevitabili effetti casuali che riducono la precisione dell'area. 42 FI a CO2 pura di alta d, provenienti dalla regione del Lago Tana e da El Hierro, sono state analizzate. Per ogni FI sono state acquisite due serie di spettri con tempi di acquisizione diversi. Di 84 serie di analisi, 23 avevano rapporti di area 13CO2/12CO2 diversi tra loro di più di un ordine di grandezza. Questi sono stati rimossi dal dataset. Il 95% dei restanti 61 set aveva riproducibilità dei rapporti di area <≈4‰, consentendo di calcolare valori di δ13CCO2 con precisione <±≈2‰. Solo poche analisi erano caratterizzate da una minore precisione. I valori di δ13CCO2 calcolati per FI nelle peridotiti dalla regione del Lago Tana hanno mostrato un’origine di mantello per la CO2, mentre quelli nelle peridotiti di El Hierro dai valori tipici di mantello. L'accuratezza delle misure è stata verificata tramite spettrometria di massa. Questa ha dimostrato che i valori di δ13CCO2 calcolati erano accurati, e consentivano di modellare la variazione isotopica a scala minerale. L’applicabilità della micro-spettroscopia Raman come densimetro per i fluidi a CO2 è stata precedentemente studiata. Molte equazioni di densimetro calcolano d differenti per gli stessi Δ, con distribuzione grafica bimodale, la cui origine non è stata ben compresa. L'origine di questa distribuzione è stata studiata nel presente lavoro calcolando la d di 40 FI a CO2 pura, provenienti da El Hierro, mediante microtermometria. I Δ sono stati misurati acquisendo spettri Raman con una procedura simile a quella adottata per altri densimetri, con risoluzione spettrale per px ≈1,50 cm-1/px. La distribuzione dei dati Δ-d è stata fittata al meglio con un'equazione polinomiale di III°, permettendo di calcolare le d della CO2 con un errore di ±0.015 g/cm3. L’equazione plottava con quelle ottenute mediante una risoluzione spettrale per px simile. Gli intervalli di confidenza al 95% della distribuzione Δ-d per tutte le equazioni sono stati calcolati mediante un algoritmo statistico. I CI hanno permesso di valutare l'accuratezza dei valori Δ-d e di definire un punto di cut-off al di sotto del quale la potenza di stima della d era bassa. Per tutti i densimetri, il punto di cut-off corrispondeva al punto in cui le distanze relative dei CI erano <7.5% (coincidenti con CO2 gassosa a P-T ambiente). Il confronto tra CI al 95% delle equazioni a bassa ed alta risoluzione spettrale per px ha mostrato che densimetri con risoluzione calcolano d statisticamente equivalente con una confidenza del 95%. Al contrario, densimetri con risoluzione diversa calcolano d non confrontabili. I risultati ottenuti hanno consentito di proporre un metodo preliminare per calcolare in situ i δ13CCO2 con una precisione ≈±2% per il 95% delle analisi. Inoltre, questi hanno migliorato la conoscenza della distribuzione Δ-d dei densimetri Raman, indicando che d di CO2 calcolate per mezzo di equazioni con risoluzione spettrale simile sono statisticamente equivalenti al 95% di confidenza per FI aventi d vicino e al di sopra del punto critico di CO2.
This thesis investigates the applicability of Raman micro-spectroscopy for CO2 density (d) and δ13CCO2 values calculations to improve characterisation of CO2 Earth’s fluid trapped as fluid inclusions (FI) in peridotites. Based on the properties of CO2 Raman spectrum, where the distance of two main vibrations is d-dependent and 13CO2 and 12CO2 vibrations are present, Raman micro-spectroscopy has the potential to become a complementary technique for in situ characterisation of CO2 FI, allowing to better understand the C transport mechanisms within Earth. The calculation of CCO2 isotopic composition by mean of Raman micro-spectroscopy is possible due to the proportionality between 13CO2 and 12CO2 areas with their molar concentration. Calculation of area ratios requires precision at 4th decimal place to obtain δ13CCO2 values representative of Earth’s natural reservoirs. Raman spectra are affected by unavoidable random effects that reduce area measurements’ precision. 42 high-d CO2-pure FI from Lake Tana region and El Hierro have been analysed. For each inclusion, two sets of spectra have been acquired by mean of different acquisition times. Among the 84 set of measurements, 23 were characterised by 13CO2/12CO2 area ratios differing more than one order of magnitude one another. These have been removed from dataset. 95% of remaining 61 sets were characterised by area ratios reproducibility <≈4‰, allowing to calculate FI δ13CCO2 values with precision <±≈2‰. Only few analyses were characterised by lower precision. Calculated δ13CCO2 values for FI trapped in peridotites from Lake Tana region showed CO2 mantle origin, while for those in peridotites from El Hierro differed from mantle isotopic signature. Accuracy of measurement has been checked by bulk measurements, proving that calculated δ13CCO2 values were accurate, and allowing to model δ13CCO2 variations at single mineral scale. The adoption of Raman micro-spectroscopy for calculating CO2 fluid d has been previously investigated. Many densimeter equations calculate different d for the same Δ values, with a bimodal graphic distribution, whose origin was not well understood. The origin of this distribution has been investigated in present work by calculating the d of 40 CO2-pure FI trapped in mantle xenoliths from El Hierro by mean of microthermometry. CO2 FI Δ values have been measured by acquiring Raman spectra applying analytical parameters common to those adopted for other densimeter equations, with spectral per px resolution ≈1.50 cm-1/px. A 3rd order polynomial equation best fitted obtained Δ-d data distribution. Equation calculates CO2 d with an error of ±0.015 g/cm3, and plots with those obtained by mean of a similar spectral per px resolution. The 95% confidence interval (CI) of Δ-d distribution for all the equations has been calculated by a bootstrapping statistical algorithm. CIs allowed to assess the accuracy of measured Δ-d values and define a cut-off point below which the CO2 d estimation power is low. For all the densimeters, cut-off point has been set where the relative distances of computed CIs were <7.5%, which corresponded for all the equations to gas-like CO2 at ambient conditions. The comparison of 95% CIs calculated for high and low spectral resolution per px equations showed that densimeters with similar spectral per px resolution calculate statistically equivalent CO2 d at 95% confidence. In contrast, densimeters with different resolution calculate incomparable CO2 d.Obtained results allowed to preliminarily propose an analytical procedure to calculate in situ δ13CCO2 with a precision of ≈±2% for 95% of the analyses. Moreover, these improved the knowledge about Δ-d distribution of Raman densimeters, indicating that CO2 d calculated by mean of equations having similar spectral resolution are statistically equivalent at 95% confidence for CO2 FI having d values near and above the CO2 critical point.

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Li, Hailong. « Thermodynamic Properties of CO2 Mixtures and Their Applications in Advanced Power Cycles with CO2 Capture Processes ». Doctoral thesis, KTH, Energiprocesser, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-9109.

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The thermodynamic properties of CO2-mixtures are essential for the design and operation of CO2 Capture and Storage (CCS) systems. A better understanding of the thermodynamic properties of CO2 mixtures could provide a scientific basis to define a proper guideline of CO2 purity and impure components for the CCS processes according to technical, safety and environmental requirements. However the available accurate experimental data cannot cover the whole operation conditions of CCS processes. In order to overcome the shortage of experimental data, theoretical estimation and modelling are used as a supplemental approach. In this thesis, the available experimental data on the thermodynamic properties of CO2 mixtures were first collected, and their applicability and gaps for theoretical model verification and calibration were also determined according to the required thermodynamic properties and operation conditions of CCS. Then in order to provide recommendations concerning calculation methods for engineering design of CCS, totally eight equations of state (EOS) were evaluated for the calculations about vapour liquid equilibrium (VLE) and density of CO2-mixtures, including N2, O2, SO2, Ar, H2S and CH4. With the identified equations of state, the preliminary assessment of impurity impacts was further conducted regarding the thermodynamic properties of CO2-mixtures and different processes involved in CCS system. Results show that the increment of the mole fraction of non-condensable gases would make purification, compression and condensation more difficult. Comparatively N2 can be separated more easily from the CO2-mixtures than O2 and Ar. And a lower CO2 recovery rate is expected for the physical separation of CO2/N2 under the same separation conditions. In addition, the evaluations about the acceptable concentration of non-condensable impurities show that the transport conditions in vessels are more sensitive to the non-condensable impurities and it requires very low concentration of non-condensable impurities in order to avoid two-phase problems. Meanwhile, the performances of evaporative gas turbine integrated with different CO2 capture technologies were investigated from both technical and economical aspects. It is concluded that the evaporative gas turbine (EvGT) cycle with chemical absorption capture has a smaller penalty on electrical efficiency, while a lower CO2 capture ratio than the EvGT cycle with O2/CO2 recycle combustion capture. Therefore, although EvGT + chemical absorption has a higher annual cost, it has a lower cost of electricity because of its higher efficiency. However considering its lower CO2 capture ratio, EvGT + chemical absorption has a higher cost to avoid 1 ton CO2. In addition the efficiency of EvGT + chemical absorption can be increased by optimizing Water/Air ratio, increasing the operating pressure of stripper and adding a flue gas condenser condensing out the excessive water.
QC 20100819

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Shukla, Ruchi. « An Experimental Study on a Density Driven Solar Water Heating System Using Supercritical CO2 as Working Fluid ». Thesis, North Dakota State University, 2013. https://hdl.handle.net/10365/26918.

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For supercritical carbon dioxide, a small change in temperature or pressure can result in large change in density, especially close to its critical point. At this pseudocritical region, density decreases rapidly with increase in temperature which aids the thermosyphon flow. Encouraged by this idea, an experimental investigation has been performed to investigate the feasibility and performance of thermosyphon solar water heating (SWH) system using R-744 (CO2) as the working fluid. Experimental results have shown that it is possible to induce the natural convective flow even during solar-adverse conditions. Although during winter this proposed density driven system was not possible to extract any useful heat gain, the system did show some promising results when operated during spring. The time-averaged collector and heat recovery efficiencies for summer were about 58% and 45%, respectively.

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Lourenço, Mirtha Alejandra de Oliveira. « Tuning functionalized periodic mesoporous organosilicas for CO2/CH ». Doctoral thesis, Universidade de Aveiro, 2016. http://hdl.handle.net/10773/21817.

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Doutoramento em Ciência e Engenharia de Materiais
Esta tese de doutoramento teve como principal objetivo a conceção de novas organossílicas mesoporosas periódicas (PMOs) para aplicação na separação de misturas gasosas de dióxido de carbono e metano. Materiais PMOs, com grupos fenileno e bifenileno bissililados, foram modificados por introdução de grupos funcionais amina, utilizando uma das seguintes metodologias: i) reação de co-condensação; ii) pós-modificação da ponte orgânica; iii) "grafting". O tamanho dos poros das PMOs funcionalizadas e não funcionalizadas foi definido pelo tamanho da cadeia alquilada da molécula molde (surfactante) utilizada na síntese do material poroso. Estudou-se o efeito do diâmetro dos poros na separação de CO2/CH4. Investigou-se também estratégias alternativas para modificar as propriedades físico-químicas dos materiais através de reações de superfície utilizando irradiação de micro-ondas; deposição de camada atómica (ALD) de óxido de alumínio; e carbonização dos materiais em atmosfera inerte. A investigação experimental foi efectuada em paralelo com estudos computacionais. Realizou-se um estudo de simulação molecular recorrendo ao método de DFT, e usando um arranjo regular de grupos fenileno-sílica, para determinar as características ideais dos materiais para promover a separação de metano do dióxido de carbono em misturas destes gases. Foi utilizado um modelo simples, obtido pela repetição de uma célula unitária com 3 anéis fenileno, para simular a parede dos materiais PMOs e desta forma selecionar e avaliar as interações entre os gases e os grupos funcionais presentes na superfície dos materiais. A tendência do rácio entre energias de interação entre a estrutura da parede do fenileno - PMO e as moléculas de CO2 e de CH4 foi concordante com os rácios das constantes de Henry obtidos pela técnica de adsorção. Demonstrou-se uma boa sinergia entre tarefas experimentais e computacionais, o que permite a otimização de recursos, evitando a síntese desnecessária de materiais que se antecipem serem pouco eficazes para o processo de separação de misturas gasosas CO2 e CH4. Assim, a abordagem seguida nesta tese para alcançar adsorventes eficazes foi baseada numa conjugação interdisciplinar envolvendo troca de informação entre as tarefas de síntese, modelação computacional e adsorção.
The main objective of this PhD Thesis was the design of periodic mesoporous organosilicas (PMOs) for applications in carbon dioxide and methane separation. Novel PMOs were prepared by the modification of phenylene and biphenylene PMO materials with different amine functionalities through one of the three following synthetic strategies: i) co-condensation reaction; ii) organic bridge post-modification; or/and iii) grafting. The pore size of both functionalized and non-functionalized phenylene PMOs was regulated by the size of the alkyl-chain in the surfactant template. Materials with different pore sizes were used to understand the influence of the pore diameter on the CO2/CH4 separation. Additionally, it was aimed to explore alternative strategies to modify the physical-chemical properties of the materials such as microwave-assisted functionalization; atomic layer deposition (ALD) of aluminum oxide at the PMO surfaces; and carbonization of the PMO materials. The experimental research was performed in parallel with computational studies. A molecular simulation study, using the DFT method and a regular arrangement of phenylene-silica groups, of the ideal characteristics of the adsorbent materials, for CO2/CH4 separation was performed. It was used a simple model of the wall of the PMO materials obtained by the repetition of a unit cell with 3 phenylene rings, to select and evaluate interactions between gases and functional groups in the surface of the materials. The tendency between the ratio of the interaction energies between the wall structure of the phenylene-PMO and the CO2 and CH4 molecules was in good agreement with the ratio of the Henry constants achieved by the adsorption technique. Therefore, a good synergy between experimental and computational tasks was implemented to optimize the resources, avoiding the synthesis of ineffective materials. Thus, the strategy of this PhD Thesis to achieve effective adsorbents was based on an interdisciplinary approach and on the ability to link and interchange information between synthetic, computer modeling and adsorption experiments

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Lowe, Alexander Rowland. « Alkyl pipéridine démixantes pour le captage du CO2 : approche thermodynamique ». Thesis, Clermont-Ferrand 2, 2016. http://www.theses.fr/2016CLF22772/document.

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L'augmentation de la concentration de dioxyde de carbone (CO2) dans l'atmosphère depuis la révolution industrielle a conduit à l'augmentation de la température moyenne du globe. Pour limiter l’accroissement des températures atmosphériques moyennes, la quantité de dioxyde de carbone émise dans l'atmosphère doit être réduite. Une des solutions envisagée sur les sources fixes est le captage et le stockage du CO2. Ce procédé d’absorption/désorption, bien connu dans le traitement du gaz naturel, est onéreux et peu efficace pour le traitement du gaz des sources fixes et doit être optimisé. La solution proposée s’appuie sur l’utilisation de solvants démixants, présentant une séparation de phase équilibre liquide-liquide (LLE) en solution aqueuse en fonction de la température. Ce manuscrit présente une étude réalisée pour la famille des alkyl-pipéridines connues pour ses séparations de phase. Cette étude permettra d’évaluer l’influence de la taille, de la positionet du nombre de substituants sur les propriétés thermodynamiques d’intérêt pour le procédé. Pour étudier les LLE des solutions aqueuses démixantes, en particulier dans le cas des solutions chargées en gaz, deux instruments ont été mis au point. Il a été possible de démontrer que les changements opérés sur les diagrammes de phase des amines sont liés aux réactions chimiques mises en jeu lors de la dissolution du CO2. Pour les alkyl-pipéridines tertiaire on observe la température de démixtion diminue avec l’addition de CO2, allant avec la formation de carbonates. Avec les alkyl-pipéridines secondaires la température de démixtion augmente, ce qui est lié à la présence en solution de carbamates qui stabilisent la solution aqueuse. Le comportement des amines secondaires très encombrées, qui ne peuvent donc pas formées de carbamates, est similaire à celui des amines tertiaires, ce qui est cohérent avec les conclusions précédentes. Une étude approfondies des propriétés thermodynamiques d’excès (VE, CpE et HE) des alkyl-pipéridines en solution aqueuse a également permis de démontrer des relations structure - propriétés. La position du substituant sur le cycle pipéridine a une influence considérable et prévisible sur l’intensité des propriétés d’excès, alors que la nature de l’amine (secondaire ou tertiaire) va influencer la position de l’extremum de cette propriété. Enfin, une modélisation thermodynamique rigoureuses des solubilités et des enthalpies de dissolution du CO2 dans les solutions aqueuses de pipéridines a permis de déterminer les constantes de formation des carbamates dans les solutions aqueuses de 3- et 4-méthylpipéridines
The increase of carbon dioxide (CO2) concentration in the atmosphere, since the industrial revolution has led to the rise in the average global climate temperature. To prevent the escalation of global climate temperatures the amount of CO2 emitted into the atmosphere must be reduced. One solution is carbon capture and sequestration which removes CO2 from fixed sources. The absorption/desorption cycle is well known for the treatment of acid gas, but is expensive and not as efficient for the treatment of gas from fixed/industrial sources. A solution to this problem is the use of aqueous demixing amine solvents which present a liquid-liquid phase equilibrium (LLE) as a function of temperature. This manuscript presents a study done to measure the LLE and thermodynamic properties of the alkyl piperidine family, which can be used for carbon capture processes. This work evaluates the effect of the size, position and number of alkyl substituents on the thermodynamic properties of interest in the carbon capture process. To study the LLE of aqueous demixing solutions, particularly gas loaded solutions, two novel apparatuses were developed. The results demonstrate that the changes in the amine phase diagrams are related to the chemical reactions involved with dissolution of CO2. The tertiary alkyl piperidines displayed reduced demixing temperature with the addition of CO2 due to the formation of carbonate species. The secondary alkyl piperidines display an increasing demixing temperature which is related to the formation of carbamate species which stabilizes the solution. Secondary alkyl piperidines that are severely sterically hindered, which cannot produce carbamates, behave similarly to the tertiary amine which is coherent with the preceding conclusion. The structure property relationship concerning the excess thermodynamic properties (VE, CpE et HE) of aqueous solutions were studied in depth. This revealed that the position of the substituents on the cyclic ring has a considerable and obvious influence on the intensity of the excess properties, along with the class of the amine, whether secondary or tertiary, will influence the positions of the extrema of the excess property. To conclude, a rigorous thermodynamic model based on the CO2 solubility and the enthalpy of solution for CO2 in aqueous solutions of alkyl piperidine, allowed for the determination of the carbamate formation constants of 3- and 4-methylpiperidine

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Gonzalez, Perez Alfonso. « Etudes expérimentales et modélisation du comportement de phase et des propriétés de transport des mélanges liés à la capture et au stockage du carbone ». Thesis, Paris Sciences et Lettres (ComUE), 2016. http://www.theses.fr/2016PSLEM059/document.

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L'objectif principal de ce travail est le développement d'une équation d’état précise pour la détermination des propriétés thermodynamique de mélange de gaz riche en gaz acides (CO2, H2S) contenant des hydrocarbures et autres gaz (impuretés) comme N2, O2, Ar, etc présente lors du stockage du CO2 (CCS). Après comparaisons avec des données expérimentales, nous avons retenu le modèle SAFT-VR Mie qui prédit de manière satisfaisante les masses volumiques pour les composés purs et les équilibres entre phases. Trois types de propriétés de transport ont également été prédites avec le modèle thermodynamique SAFT-VR Mie associé avec deux autres modèles de prédiction des propriétés de transport (TRAPP et DGT). La prédiction de ces propriétés de transport (viscosité et tension superficielle) repose sur une estimation la plus précise possible des masses volumiques. Pour compléter les banques données expérimentales, les équilibres liquide-vapeur concernant le système binaire H2S-Ar ont été déterminés à l'aide d'un dispositif de mesure dont la méthode technique repose sur la méthode "statique analytique" avec échantillonnage des phases (échantillonneur capillaire ROLI). Déplus, à l'aide d'un densimètre à tube vibrant, les masses volumiques de cinq systèmes binaires (H2S - hydrocarbures (méthane, éthane et propane) ont été mesurées. Les masses volumiques d'un système ternaire (CO2/CH4/H2S) et les masses volumiques et les viscosités d'un mélange multi-constituant riche en CO2 ont aussi été mesurées. Les données sont parfaitement représentées par les modèles développés au cours de cette thèse
The main aim of this research is to develop a thermodynamic model from an accurate equation of state (EoS) for CO2, hydrocarbons and other gases as N2, O2, Ar, etc. The SAFT-VR Mie EoS was selected to study the phase behaviour and transport properties of mixtures related to carbon capture and storage (CCS). In order to asses this new version of SAFT, several equations of state have been compared (PR, SRK and PC-SAFT). SAFT-VR Mie EoS provides very good density predictions for pure component and binary systems according to the comparative study carried out. Therefore, three transport properties were modelled with SAFT-VR Mie and two models based on density predictions from the EoS. Thus, density, viscosity and interfacial tension (IFT) of CO2-rich systems were calculated by this SAFT-EoS (density), TraPP model (viscosity) and DGT (IFT), in the framework of CCS. Some experimental work was done, in order to extend the available literature data. Isothermal vapor-liquid equilibrium of H2S-Ar binary system was determined at three temperatures from 258 to 288 K. Densities of five binary systems of H2S with methane, ethane and propane were measured continuously at 3 temperatures (253, 273 and 293K) and at pressures up to 30MPa. Following the same technique, the density of the ternary system 42%CO2, 40%CH4 and 18%H2S was measured at pressures ranging from 0.2 to 31.5MPa and at 6 temperatures between 253 and 353K. Densities and viscosities of a multicomponent CO2-rich with 50% of impurities were measured at 5 temperatures between 283 and 423 K and at pressures up to 150 MPa

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Marmitt, Sandro. « Investigação mecanística de ciclios orgânicos para fixação de CO2 na presença de líquidos iônicos : uma abordagem teórico-computacional ». reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2015. http://hdl.handle.net/10183/134192.

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A constante emissão de CO2 na atmosfera devido a fontes antropogênica despertou uma preocupação crescente em função da sua atuação no efeito estufa. Um número crescente de metodologias para redução da concentração deste gás na atmosfera vem sendo proposta e uma alternativa atrativa é a da inserção do CO2 em anéis epóxidos para formação de carbonatos cíclicos. Apesar de já existirem inúmeros trabalhos a respeito destas reações, o mecanismo pelo qual elas ocorrem não está completamente esclarecido. Neste trabalho é apresentado o estudo mecanístico da cicloadição de CO2 em diferentes epóxidos catalisada por líquidos iônicos haletos de alquil-imidazólios, CnMIm X (n = 1, 2, 3, 4 e X = Cl, Br, I), através da Teoria do Funcional da Densidade empregando-se o funcional !B97X-D e o conjunto de base 6-31G(d,p) e LanL2DZ (somente para o I). Propuseram-se duas rotas distintas para o mecanismo, uma composta por três etapas e outra composta por somente duas etapas. Ambas as rotas tiveram a primeira etapa como sendo a mais energética e correspondendo à abertura do anel epóxido e mostraram ser competitivas entre si energeticamente. Esta etapa mostrou depender de ambos cátion e ânion do catalisador para ocorrer, onde uma ligação de hidrogênio não clássica com o H2 do imidazólio aparece no estado de transição. Verificou-se que no geral a energia de ativação da reação diminui com o aumento da cadeia alquílica do cátion imidazólio assim como diminui com o aumento do caráter nucleofílico do haleto (Cl > Br > I). O substituinte do anel epóxido também exerce influência sobre a energia de ativação da reação, porém não há uma tendência bem definida. Constatou-se que o sítio mais favorável para ataque nucleofílico é o carbono não substituído do anel epóxido tanto pela diferença de energia quanto por análise de índices de reatividade de Fukui e de interações não covalentes. Uma análise de 14 funcionais da densidade e do método perturbativo de segunda ordem MP2 em comparação ao método composto G4MP2 revelaram a forte dependência das energias de ativação com o método empregado. Através de cálculos de dinâmica molecular clássica foi possível estudar dinamicamente o sistema brometo de 1-butil-3-metil imidazólio, o óxido de estireno e o CO2 e notou-se a formação de duas fases com a presença de uma interface. Adicionalmente, observou-se que a probabilidade da reação ocorrer no bulk do líquido iônico é maior, pois a proporção catalisador/substrato é maior nesta região. Por meio da dinâmica molecular de Born-Oppenheimer constatou-se que o anel epóxido também pode ser ativado através de interações com os hidrogênios H4 e H5 do anel imidazólio.
The constant emission of CO2 into the atmosphere due to anthropogenic sources has generated a growing concern regarding the greenhouse effect. Many methodologies to reduce the atmospheric CO2 concentration have been proposed and an alternative is the insertion of CO2 into epoxides to form cyclic carbonates. Although there are a lot of studies in this area, the reaction mechanism by which they occur is still unclear. In this work the cycloaddition mechanism of CO2 into different epoxides catalyzed by alkyl-imidazolium halide ionic liquids, CnMIm X (n = 1, 2, 3, 4 e X = Cl, Br, I), is presented. Density Functional Theory in conjunction with the functional !B97X-D and 6-31G(d,p) and LanL2DZ (for I atoms) basis sets were employed. Two distinct routes were proposed for the mechanism: one composed of three steps and another composed by only two steps. Both routes showed that the first step regarding the epoxide ring opening is the determined one and they are energetically competitive with each other. This step depends on both cation and anion from the catalyst to proceed through a non-classical hydrogen bond in the transition state. It was found that the activation energy decreases with the chain length of the alkyl group from the imidazolium ring as well as with the nucleophilic character of the halide (Cl > Br > I). The epoxide ring substituent also exerts influence on the activation energy of this reaction, but there is no well defined behaviour. The most favourable site for nucleophilic attack is the non-substituted epoxide ring carbon as was shown by the reaction energy difference and through reactive Fukui index and non-covalent interaction (NCI) analysis. 14 exchange-correlation density functionals were investigated and compared to the well established second order perturbation theory (MP2) method and G4MP2 composite method. One found out that the activation energies strongly depends on the chosen method. Through classical molecular dynamics it was possible to study the system 1-butyl-3-methyl-imidazolium bromide together with styrene oxide and CO2 e the formation of two phases with the presence of an interface was observed. Additionally, it was shown that the probability of the reaction to occur in the ionic liquid bulk is bigger because the catalyst/substrate proportion is bigger in this region. Born-Oppenheimer molecular dynamics was used to prove that the H4 and H5 hydrogen atoms from the imidazolium ring may interact with the oxygen atom from the epoxide and activate the C–O bond for the reaction to proceed.

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Yin, Wei. « Fundamental understanding of high-energy-density Li-ion batteries and beyond : structure-property relationships and reaction chemistries ». Electronic Thesis or Diss., Sorbonne université, 2019. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2019SORUS427.pdf.

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La recherche de dispositifs de stockage d'énergie plus denses en énergie pour les applications de transport et d'électronique portable a stimulé le développement de matériaux de cathode de grande capacité pour les batteries Li-ion. Les oxydes lamellaires riches en lithium figurent ainsi parmi les principaux candidats. Leur capacité importante résulte de la participation, en plus de la rédox cationique conventionnel, de la rédox anionique lors de l'insertion/désinsertion du lithium. Néanmoins, ils n'ont pas encore rencontré de succès commercial car la capacité supplémentaire offerte par la rédox anionique s'accompagne généralement d'une instabilité structurelle, ce qui entraîne une irréversibilité significative au premier cycle et une dégradation des performances lors du cyclage. Comprendre l'évolution structurelle de ces matériaux et son effet sur leurs propriétés électrochimiques revêt donc une importance vitale. Les travaux réalisés lors de cette thèse ont porté sur le phénomène de dégradation prédominant dans les oxydes lamellaires riches en lithium, à savoir la libération irréversible d'oxygène, en introduisant une technique de détection simple mais sensible à l'oxygène gazeux. Le couplage fort entre l'évolution de la structure et les comportements électrochimiques a été étudié plus en détail pour Li1.2Ni0.13Mn0.54Co0.13O2 qui présente un grand intérêt industriel. Afin de dépasser les limites de la technologie Li-ion, de nombreuses chimies alternatives font actuellement l'objet de recherches approfondies. Dans ce contexte, les aspects fondamentaux des batteries Li-CO2, qui incluent les mécanismes de réaction et la réduction catalytique de CO2, ont aussi été explorés
The increasing energy demands placed on energy storage devices for both transportation and mobile applications have stimulated the development of high-capacity positive materials for Li-ion batteries. Li-rich layered oxides are among the leading candidates provided their staggering capacities, owing to the participation of anionic redox in the charge compensation mechanism aside from the conventional transition metal redox. Nevertheless, Li-rich layered oxides are yet to reach commercial success since the extra capacities offered by oxygen anions generally come with structural instability, leading to significant first-cycle irreversibility and performance deterioration upon cycling. Understanding the structural evolution in these materials and its effect on their electrochemical properties are therefore of vital importance. This work addressed the major degradation phenomenon in Li-rich layered oxides, i.e., irreversible oxygen release, by introducing a simple while sensitive oxygen gas detection technique. The strong coupling between the structure evolution and the electrochemical behaviors was further investigated using a practically important Li1.2Ni0.13Mn0.54Co0.13O2 compound. Other than Li-ion batteries based on intercalation chemistry, numerous alternative battery chemistries are undergoing intensive research in the battery community to move beyond the limits of Li-ion technology. Within this context, the fundamental aspects of Li-CO2 batteries, which include the reaction mechanisms and the catalytic CO2 reduction, were explored in the second part of this work

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Iyemperumal, Satish Kumar. « Conversion of Carbon Dioxide to Fuels using Dispersed Atomic-Size Catalysts ». Digital WPI, 2018. https://digitalcommons.wpi.edu/etd-dissertations/505.

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Record high CO2 emissions in the atmosphere and the need to find alternative energy sources to fossil fuels are major global challenges. Conversion of CO2 into useful fuels like methanol and methane can in principle tackle both these environment and energy concerns. One of the routes to convert CO2 into useful fuels is by using supported metal catalyst. Specifically, metal atoms or clusters (few atoms large in size) supported on oxide materials are promising catalysts. Experiments have successfully converted CO2 to products like methanol, using TiO2 supported Cu atoms or clusters. How this catalyst works and how CO2 conversion could be improved is an area of much research. We used a quantum mechanical tool called density functional theory (DFT) to obtain atomic and electronic level insights in the CO2 reduction processes on TiO2 supported metal atoms and clusters. We modeled small Cu clusters on TiO2 surface, which are experimentally synthesizable. Our results show that the interfacial sites in TiO2 supported Cu are able to activate CO2 into a bent configuration that can be further reduced. The Cu dimer was found to be the most reactive for CO2 activation but were unstable catalysts. Following Cu, we also identified other potential metal atoms that can activate CO2. Compared to expensive and rare elements like Pt, Au, and Ir, we found several early and mid transition metals to be potentially active catalysts for CO2 reduction. Because the supported metal atom or cluster is a reactive catalyst, under reaction conditions they tend to undergo aggregation and/or oxidation to form larger less active catalysts. We chose Co, Ni, and Cu group elements to study their catalyst stability under oxidizing reaction conditions. Based on the thermodynamics of Cu oxidation and kinetics of O2 dissociation, we found that TiO2 supported Cu atom or a larger Cu tetramer cluster were the likely species observed in experiments. Our work provides valuable atomic-level insights into improving the CO2 reduction activities and predicts potential catalysts for CO2 reduction to valuable fuels.

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Kour, Gurpreet. « First principles investigations on transition metal based electrocatalysts for efficient clean energy conversion ». Thesis, Queensland University of Technology, 2022. https://eprints.qut.edu.au/232798/1/Gurpreet_Kour_Thesis.pdf.

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This dissertation relates to the application of density functional theory to the design of novel nanoelectrocatalysts for various electrochemical reduction reactions such as carbon dioxide reduction reactions, carbon monoxide reduction reactions and nitrogen reduction reactions. Many electrocatalysts with high activity, excellent selectivity and stability were designed and engineered using first principle calculations. These findings could potentially guide the experimentalists for creating clean and sustainable energy resources.

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Yang, Chi-Ta. « Interplays of CO₂, Subnanometer Metal Clusters, and TiO₂ : Implications for Catalysis and CO₂ Photoreduction ». Scholar Commons, 2015. http://scholarcommons.usf.edu/etd/5805.

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This research is motivated by two significant challenges facing the planet: reducing the emission of CO2 to the atmosphere and production of sustainable fuels by harnessing solar energy. The main objective of this work is the study of promising photocatalysts for CO2 reduction. DFT modeling of CO2, subnanometer Ag&Pt clusters, and anatase TiO2 (101) surface is employed to gain fundamental understanding of the catalytic process, followed by validation using a guided experimental endeavor. The binding mechanism of CO2 on the surface is investigated in detail to gain insights into the catalytic activity and to assist with characterizing the photocatalyst. For CO2 photoreduction, the cluster induced sub-bandgap and the preferred adsorbate in the first and key step of the CO2 photoreduction are explored. It is found that TiO2-supported Pt octamers offer key advantages for CO2 photoreduction: 1. by providing additional stable adsorption sites for favored CO2 species in the first step, and 2. by aiding in CO2- anion formation. Electronic structure analysis suggests these factors arise primarily from the hybridization of the bonding molecular orbitals of CO2 with d orbitals of the Pt atoms. Also, structural fluxionality is quantified to investigate geometry dependent (3D-2D) CO2 adsorption. Geometric information, electronic information, and C-O bond breaking tendency of adsorbed CO2 species are proposed to connect to experimental observables (IR frequency). The CO2 adsorption sites on supported Pt clusters are also identified using IR as the indicator. A cluster-induced CO2 dissociation to CO pathway is also discovered. Finally, experimental work including dendrimer-encapsulated technique, TPD, and UV-Vis is performed to validate the computational results, the availability of adsorption sites and CO2 binding strength on supported Pt clusters.

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Urban, Karel. « Studium vlivu výpalu na vlastnosti vápna ». Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2016. http://www.nusl.cz/ntk/nusl-240351.

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At the institute of technology of building materials and components at the fakulty of civil engineering in Brno was initiated research deal with study of the effect of limestone on the progress of decarbonization. This work is an introductory study into this problems. It focuses on describing the genesis and diagenesis of limestones, their crystallography, texture and requirements for burning. Further describes the extraction and treatment of limestones before burning. In very burning is focused on its mechanism and the used furnace systems. In the experimental part is focused on the analysis of samples of limestones of various world sites in terms of petrology, geological origin, chemical composition, the content of insoluble residues, density and porosity, and analysis of formed limes, burned at 900 °C in terms of density, CO2 content and crystal size.

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Karlsson, Joacim, et Oliwer Dysén. « Vindkraftsfundament i tungbetong : En dimensionerings-, miljö- och kostnadsanalys av tungbetong kontra konventionell betong ». Thesis, Uppsala universitet, Tillämpad mekanik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-448038.

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Det här examensarbete har genomförts i samarbete med Sweco Sverige AB på enheten för byggkonstruktion. Syftet med studien var att undersöka tungbetong som ett alternativ till konventionell konstruktionsbetong vid gjutning av vindkraftsfundament. I den här studien har ett vindkraftsfundament i konventionell konstruktionsbetong stått som grund för de dimensioneringsberäkningar som har utförts för att istället kunna använda tungbetong i fundamentet. Ett mål med studien var att med ett fundament i tungbetong minska dimensionerna och således minska klimatpåverkan och kostnaden. För att undersöka om målet kunde uppnås har beräkningar för fundamentets geometri, krav vid bruksgränstillståndet, ekonomiska data och klimatpåverkan utförts. Från studiens dimensioneringsberäkningar om fundamentets geometri framgår det att fundamentet behöver uppfylla vissa krav på mått och därav är fundamentets radie den parameter som kan minska volymen mest. Det ledde till att volymen på fundamentet i tungbetong blev mindre än den för konventionell konstruktionsbetong. Tungbetongens resultat blev ur vissa perspektiv bättre än konventionell konstruktionsbetong. Volymen för tungbetongsfundamentet kunde reduceras med 14 %. Detta resulterade i en minskning av koldioxidutsläpp med 7 %, priset ökade däremot med 65 %. Genom att i detta fall använda sig av tungbetong istället för konventionell betong kunde både volym och koldioxidutsläpp reduceras, däremot till ett väldigt högt pris.
The purpose of the study was to investigate an alternative to conventional construction concrete. In this study, a wind turbine foundation consisting of conventional construction concrete have been analysed and served as a basis for dimension calculations to the foundation of heavy weight concrete. A goal with the study was to decrease the dimensions of the foundation using heavy weight concrete instead of conventional and therefore also reduce the climate impact as well as the cost of the foundation. To investigate if the goal is achievable, calculations for the foundation geometry, the requirement of the service limit state, economic data and climate impact have been calculated. In the calculations about the foundation geometry, certain requirements regarding the dimensions needs to be achieved and therefore it is the radius of the foundations that can affect the volume the most. This resulted in a decrease of volume for the heavy weight concrete foundation. In some perspectives, the heavy weight concrete had better outcome than conventional construction concrete. The volume of the foundation could be reduced by 14 %. This led to a reduction in product emission by 7 %. The price of heavy weight concrete, per cubic meter, is almost five times more expensive than it is for conventional construction concrete and therefore the price was 65 % higher. This concludes in a possibility to reduce both the volume as well as the CO2-emissions but for a very high price.

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Han, Xiangmin. « CONTINUOUS PRODUCTION OF MICROCELLULAR FOAMS ». The Ohio State University, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=osu1041275301.

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Guedj, Annie. « Oxydation photo-assistee du silicium par laser au co2 continu et contribution a l'etude des couches de silice obtenues ». Toulouse, INSA, 1987. http://www.theses.fr/1987ISAT0011.

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Les caracteristiques de "l'oxyde laser" obtenu sont etudiees: 1)grace au controle de temperature par pyrometrie en ce qui concerne la cinetique de croissance. 2) a partir de mesures c(v) et i(v) en ce qui concerne les proprietes electriques. 3) par spectrometrie ir en ce qui concerne les proprietes physiques. Ces caracteristiques sont ensuite comparees a celles de l'oxyde thermique conventionnel. Enfin, par la realisation de transistors m. O. S. A "oxyde laser" (oxyde de grille), nous avons montre que ce mode d'oxydation assistee par laser peut etre utilise dans les technologies m. O. S.

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Hachmann, Tiago Luan. « Características agronômicas e índices de trocas gasosas do tomateiro em função de sistemas de condução em ambiente protegido ». Universidade Estadual do Oeste do Paraná, 2015. http://tede.unioeste.br:8080/tede/handle/tede/1263.

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This work was conducted in the period from April, 11th, 2014 until September, 9th, 2014 aiming studying the influence of the number of stems and the way of establishing these stems in productivity and quality characteristics of the tomato cultivars, and evaluate the daily course of gas exchange indexes of the tomato cultivars in the leaves exposed to solar radiation from the east (morning) or the west (afternoon). The experimental design used in the first experiment was a randomized block design with factorial 3 x 2 x 2, with four replications. Three numbers of stem per plant were tested (one, two and four steams) two forms of establishment (maintaining and removing the main stem) and two cultivars (Caniles and Rubi F1 hybrid). The total number of fruits, number of normal fruits, non-commercial and blossom-end rot was evaluated; percentage of unmarketable fruits and blossom end rot; average mass, longitudinal and transversal diameter of the normal fruits; fruit mass, transversal and longitudinal diameter, average fruit mass and productivity of the first four clusters; total mass of fruit and fruit normal mass; and was calculated productivity of normal fruits, non-commercial, with blossom end rot and total fruit yield. It was also evaluated pH, soluble solids, titratable acidity and soluble solids/titratable acidity ("ratio"). In the second experiment the experimental design was a randomized block design, factorial 2 x 2 x 6, with four replications. The first factor was composed of two evaluation positions in the plant (East and West), the second of two tomato cultivars (Caniles and Rubi) and finally six times evaluation throughout the day (8:00, 10:00, 12:00, 14:00, 16:00 and 18:00). It was measured the rate of CO2 net assimilation (A), leaf transpiration (E), stomatal conductance (gs), internal CO2 concentration (Ci) and leaf temperature (°C) and vapor pressure deficit. It was also calculated the water use efficiency (WUE) (A/E), intrinsic water use efficiency (WUEi) (A/gs) and the instantaneous efficiency of carboxylation (A/Ci). The conduction of plants with four steams is more favorable to productivity and the quality characteristics. The establishment of steams number keeping the main stem is best suited for providing greater productivity. The cultivar Caniles is the most suitable for driving on growing conditions, due to its higher yield and fruits with better "ratio". The values of net assimilation rate of CO2, leaf transpiration, stomatal conductance, leaf temperature, water use efficiency, intrinsic water use efficiency and instantaneous carboxylation efficiency on the east side are larger than on the west side. The cultivar Caniles has a higher net assimilation rate of CO2, leaf transpiration, leaf temperature and instantaneous carboxylation efficiency under conditions of high temperature and luminosity
Este trabalho foi conduzido no período de 11/04/2014 a 16/09/2014, tendo como objetivo estudar a influência do número de hastes e da forma de estabelecimento dessas hastes nas características produtivas e qualitativas de duas cultivares de tomateiro, e avaliar o curso diário dos índices de trocas gasosas de duas cultivares de tomateiro, em folhas expostas à radiação solar proveniente do quadrante leste (período da manhã) ou do quadrante oeste (período da tarde). O delineamento experimental utilizado no primeiro experimento foi de blocos casualizados, em esquema fatorial de 3 x 2 x 2, com quatro repetições. Foram testados três números de haste por planta (uma, duas e quatro hastes), duas formas de condução (mantendo a haste principal e retirando a haste principal) e duas cultivares (híbrido F1 Rubi e híbrido Caniles). Foi avaliado o número total de frutos, número de frutos normais, não comerciais e com podridão apical; porcentagem de frutos não comerciais e com podridão apical; massa média, diâmetro longitudinal e transversal dos frutos normais; massa de frutos, diâmetro transversal e longitudinal, massa média por fruto e produtividade dos quatro primeiros cachos; massa total de frutos e massa de frutos normais; e foi calculada a produtividade de frutos normais, não comerciais, com podridão apical e produtividade total de frutos. Também foi avaliado o pH, teor de sólidos solúveis, acidez titulável e a relação sólidos solúveis/acidez titulável ( ratio ). No segundo experimento o delineamento experimental utilizado foi de blocos ao acaso, em esquema fatorial 2 x 2 x 6, com quatro repetições. O primeiro fator foi composto de duas posições de avaliação na planta (Leste e Oeste), o segundo de duas cultivares de tomate (Caniles e Rubi) e por fim seis horários de avaliação ao longo do dia (8:00, 10:00, 12:00, 14:00, 16:00 e 18:00). Foi mensurada a taxa de assimilação líquida de CO2 (A), taxa de transpiração foliar (E), condutância estomática (gs), concentração interna de CO2 (Ci), temperatura foliar (°C) e déficit de pressão de vapor. Também foi calculada a eficiência no uso da água (WUE) (relação A/E), eficiência intrínseca no uso da água (WUEi) (relação A/gs) e a eficiência instantânea da carboxilação (A/Ci) (relação A/Ci). A condução das plantas com quatro hastes é mais favorável para a produtividade e para as características de qualidade. O estabelecimento do número de hastes mantendo a haste principal é mais adequado por proporcionar obtenção de maior produtividade. A cultivar Caniles é a mais adequada para a condução nas condições de cultivo, por apresentar maior produtividade e por apresentar frutos com maior ratio . Os valores de taxa de assimilação líquida de CO2, taxa de transpiração foliar, condutância estomática, temperatura foliar, eficiência no uso da água, eficiência intrínseca no uso da água e eficiência instantânea de carboxilação no quadrante leste são maiores que no quadrante oeste. A cultivar Caniles apresenta maior taxa de assimilação líquida de CO2, taxa de transpiração foliar, temperatura foliar e eficiência instantânea de carboxilação sob condições de temperatura e luminosidade elevadas

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LeBlanc, Denis R. « Density and recharge effects during the Cape Cod natural-gradient tracer test ». Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/84242.

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Guelzim, Abdelhalim. « Densité de déformation expérimentale et théorique dans des complexes organométalliques de formule générale Co2(Co)6 C2R2 ». Lille 1, 1985. http://www.theses.fr/1985LIL10039.

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Étude expérimentale par diffraction de rayons X avec analyse par la méthode X-XHO (affinement sur les réflexions d'ordre élevé) à l'aide du modèle de déformation de Hansen-Coppens. Étude théorique ab initio de la distribution de charge électronique. Interprétation de la liaison entre atome Co et coordinat acétylénique par donation et rétrodonation suivant le modèle de Dewar et Chatt.

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22

Bourgue, Emmanuelle. « Effets des volatils CO2 et H2O sur les propriétés rhéologiques des magmas ». Paris, Institut de physique du globe, 2003. http://www.theses.fr/2003GLOB0006.

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Les processus volcanologiques sont gouvernés par de nombreux paramètres physiques et chimiques (pression, température, composition chimique. . . ) qui exercent une grande influence sur les propriétés physiques des liquides silicatés (i. E. Magmatiques). Cependant, l'effet des volatils (gaz dissous) reste très mal connu. Leur présence dans les magmas joue pourtant un rôle primordial sur la fragmentation, le dégazage et le transport de ceux-ci. Les effets du CO2 et de H2O sur les propriétés rhéologiques (densité, viscosité, dilatation thermique) sont étudiés sur un liquide silicaté synthétique simple pour CO2, et sur un liquide basaltique pour H2O, le basalte étant la roche magmatique la plus répandue sur la surface de la Terre. L'ensemble des résultats obtenus permet une meilleure compréhension de l'interaction eau-magma en fonction de la chimie et apporte des résultats nouveaux quant à l'effet du CO2 dissous. Volcanological processes are governed by many physical and chemical parameters such as pressure, temperature and chemical composition, bubble and crystal content. . . These parameters are known for exerting a stong influence on the physical properties of silicate melts (i. E. Magmas). However, the effects of dissolved volatiles is still poorly understood, although their presence play an essential role in fragmentation, degassing and magma transport. The effects of CO2 and H2O, the two most abundant volatiles in magmas, are investigated, on the rheological properties (density and volume, viscosity, and thermal expansion) of a simple synthetic silicate melt for CO2, ans a basaltic melt for H2O, basalt being the most widely spread composition on the surface of the planet. The results allow a much better comprehension of the water/magma interactions depending on chemical composition, and bring new data regarding the effect of dissolved CO2

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Sasaki, K., H. Furukawa, K. Kadota et C. Suzuki. « Surface production of CF, CF_2 , and C_2 radicals in high-density CF_4/H_2 plasmas ». American Institute of Physics, 2000. http://hdl.handle.net/2237/7036.

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Methven, David Alan. « Density of juvenile cod in coastal Newfoundland habitats, multiscale analyses of spatial and temporal variation ». Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape16/PQDD_0005/NQ34247.pdf.

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Yang, Qigui. « Theoretical study of Gd2O3-CeO2 (111) interface ». Thesis, KTH, Materialvetenskap, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-234848.

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Atomistic modelling has widely been applied for studying structures and properties of materials. There are various methods to perform atomistic modelling. This master thesis presents a combined density functional theory (DFT) and cluster expansion (CE) study of Gd2O3 and Gd2O3-CeO2 interface (GCI) relevant for solid oxide fuel cells (SOFCs). The energy differences (ΔE) of Va-O exchanges in C-type Gd2O3 and at GCI are calculated using both DFT and CE methods. We also calculated the migration energy (Emig) of Va jumps in Gd2O3 and at GCI by DFT. The comparison between the CE and DFT results demonstrates that the CE method provides a relatively accurate estimation of ΔE while it requires less computational resources. Furthermore, the CE method is used to study the Va migration in the vicinity of the Gd2O3-CeO2 interface. The potential energy landscapes of different types of paths are studied.
Atomistisk modellering har i stor utsträckning använts för att studera strukturer och egenskaper hos material. Det finns många olika metoder för att utföra atomistisk modellering. Detta masterprojekt presenterar en kombinerad density functional theory (DFT) och cluster expansion (CE) studie av Gd2O3- och Gd2O3-CeO2 gränssnittet (GCI), relevant för fastoxidbränsleceller (SOFC). Energiskillnaderna (ΔE) för Va-O-utbytet i C-typ Gd2O3 och vid GCI beräknas med användning av både DFT- och CE-metoder. Vi beräknade också migrationsenergin (Emig) av Va-hopp i Gd2O3 och vid GCI med DFT. Jämförelsen mellan CE och DFT-resultaten visar att CE-metoden ger en relativt noggrann uppskattning av ΔE samt att den kräver mindre beräkningsresurser. Vidare används CE-metoden för att studera Va- migrering i närheten av Gd2O3-CeO2-gränssnittet. Det potentiella energilandskapet för olika vägar studeras.

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Huber, Florian. « Density Forecasting using Bayesian Global Vector Autoregressions with Common Stochastic Volatility ». WU Vienna University of Economics and Business, 2014. http://epub.wu.ac.at/4280/1/wp179.pdf.

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This paper puts forward a Bayesian Global Vector Autoregressive Model with Common Stochastic Volatility (B-GVAR-CSV). We assume that Country specific volatility is driven by a single latent stochastic process, which simplifies the analysis and implies significant computational gains. Apart from computational advantages, this is also justified on the ground that the volatility of most macroeconomic quantities considered in our application tends to follow a similar pattern. Furthermore, Minnesota priors are used to introduce shrinkage to cure the curse of dimensionality. Finally, this model is then used to produce predictive densities for a set of macroeconomic aggregates. The dataset employed consists of quarterly data spanning from 1995:Q1 to 2012:Q4 and includes 45 economies plus the Euro Area. Our results indicate that stochastic volatility specifications influences accuracy along two dimensions: First, it helps to increase the overall predictive fit of our model. This result can be seen for some variables under scrutiny, most notably for real GDP and short-term interest rates. Second, it helps to make the model more resilient with respect to outliers and economic crises. This implies that when evaluated over time, the log predictive scores tend to show significantly less variation as compared to homoscedastic models. (author's abstract)
Series: Department of Economics Working Paper Series

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Lugano, Roberta. « Low density lipoproteins, vascular smooth muscle cell function and vascular remodeling ». Doctoral thesis, Universitat Pompeu Fabra, 2013. http://hdl.handle.net/10803/283471.

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High levels of circulating low-density lipoproteins (LDL) are one of the major cardiovascular risk factors. Hypercholesterolemia induces endothelial dysfunction and chronic intimal inflammatory cell accumulation, hallmarks of the initiation of atherosclerosis. Additionally, growing human atherosclerotic plaques show proliferation and migration of vascular smooth muscle cells (VSMC) towards the intima producing remodeling of the vascular wall. However, those plaques that are most prone to rupture show a progressive loss of VSMC becoming soft and vulnerable and these lipid-rich high risk plaques cause clinical episodes resulting in morbid or fatal ischemic events. The mechanisms involved in the transformation of a plaque into a vulnerable VSMC-depleted atheroma have not been completely elucidated. Lipid-rich-VSMC have an impaired vascular repair function due to changes in cytoskeleton proteins. However, the effects of LDL on VSMC function during plaque remodeling and vascular repair are not fully understood. Thus, the aim of this thesis was to investigate early changes directly induced by LDL on VSMC phenotype and function and to identify the molecular mechanisms involved. This thesis demonstrates that the cardiovascular risk of hypercholesterolemia involves the interaction of LDL with VSMC and the regulation at a molecular level of different pathways that converge in the cell’s migratory capacity. Migratory function of lipid-loaded VSMC can be restored by inhibition of 3-hydroxy-methylglutaryl coenzyme A (HMG-CoA) through a Rho kinase and myosin light chain phosphatase dependent mechanism. In addition, the studies performed in this thesis show that LDL affect VSMC adhesion, migration and cytoskeleton dynamics through the abrogation of the urokinase-plasminogen activator (uPA)/uPA receptor (uPAR) system function and by modulation of HSP27 phosphorylation and subcellular localization.
El nivel elevado de lipoproteínas de baja densidad (LDL), uno de los principales factores de riesgo cardiovascular, conllevan a una disfunción endotelial y acumulación crónica de células inflamatorias en la íntima arterial en la etapa inicial de desarrollo de la arterosclerosis. Además, la progresión de las placas arterioscleróticas se caracteriza por un proceso de remodelado vascular consecuencia de la proliferación y migración de células musculares lisas vasculares (CML) en la íntima. Sin embargo, las placas ateroscleróticas con mayor susceptibilidad a la ruptura presentan una pérdida progresiva de CML, siendo estas placas ricas en lípidos y altamente vulnerables las que provocan eventos isquémicos mórbidos o fatales. Hoy día desconocemos todavía los mecanismos involucrados en la transformación de las placas en ateromas vulnerables. Las CML ricas en lípidos presentan alteraciones en su capacidad de reparación vascular debido a alteraciones en proteínas del citoesqueleto. Sin embargo, los efectos de las LDL en la función de las CML durante el remodelado de las placas y reparación vascular se desconocen en gran medida. Por ello, el objetivo de esta tesis ha sido investigar los cambios iniciales inducidos directamente por las LDL en el fenotipo y la función de las CML e identificar los mecanismos moleculares involucrados. Esta tesis demuestra que el riesgo cardiovascular de la hipercolesterolemia implica la interacción entre LDL y CML y la regulación a nivel molecular de diferentes vías de señalización que convergen en la migración celular. La capacidad de migración de CML cargadas de lípidos puede restituirse mediante la inhibición de la 3-hidroxi-3-metilglutaril coenzima-A (HMG-CoA), a través de un mecanismo dependiente de la quinasa Rho. Además, los estudios realizados en esta tesis demuestran que las LDL afectan la adhesión, migración y dinámica de formación del citoesqueleto de las CML a través de la alteración de la función del sistema del activador del plasminogeno tipo uroquinasa (uPA)/uPA receptor (uPAR) y mediante la modulación de la fosforilación y localización subcelular de la HSP27.

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Smith, Ross E. « Structural Bone Density of Pacific Cod (Gadus macrocephalus) and Halibut (Hippoglossus stenolepis) : Taphonomic and Archaeological Implications ». PDXScholar, 2008. https://pdxscholar.library.pdx.edu/open_access_etds/3355.

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Describing prehistoric human subsistence strategies and mobility patterns using archaeofaunal assemblages requires archaeologists to differentiate the effects of human behavior from natural taphonomic processes. Previous studies demonstrate that differences in bone density both within and between taxa contribute to variation in element representation in archaeofaunal assemblages. Measurements of contemporary Pacific Cod (Gadus macrocephalus) and Pacific Halibut (Hippoglossus stenolepis) skeletal elements using Dual Energy Absorptiometry (DEXA) and hydrostatic weighing revealed differences in bone volume density between elements and taxa. Density values were highest in Pacific cod and halibut jaw elements; the lowest bone volume densities were measured in Pacific cod and halibut basipterygia. While halibut and salmon often exhibited similar bone density values, the densities of Pacific cod elements were consistently higher than those from either salmon or halibut. These density data indicate that the remains of Pacific cod are more likely to persist in archaeological deposits. When combined with existing salmon bone density measurements, these data allow for the identification of density-mediated destruction in fish faunal assemblages from along the North Pacific rim. Analysis of cod, halibut and salmon faunal assemblages from the North Point, Cape Addington Rockshelter, Rice Ridge, Uyak and Amaknak Bridge sites revealed that density-mediated element attrition has not consistently affected cod, halibut and salmon element representation in these sites. Significant correlations identified in aggregate site assemblages were not present at finer scales of analysis; the effects of density-mediated element attrition varied between depositional contexts. This research demonstrates that bone density data can be used to differentiate the effects of density-mediated element attrition from the results of human decision-making. Once density-mediated element attrition is ruled out, archaeologists can examine the effects of human processing, transportation, preparation and disposal activities on the distribution of Pacific cod and halibut skeletal elements both within and between archaeological contexts.

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Ge, Jifeng. « Mesures simultanées de la constante diélectrique et de l'indice de réfraction à haute densité : applications sur des gaz non polaires : CH4, CO2 et SF6 supercritiques ». Thèse, Université du Québec à Trois-Rivières, 1992. http://depot-e.uqtr.ca/5420/1/000590773.pdf.

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30

Bousson, Valérie. « Microstructure et densité de l'os cortical fémoral : variations avec l'âge et la fracture du col ». Paris 12, 2001. http://www.theses.fr/2001PA120036.

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La fracture ostéoporotique de l'extrémité supérieure du fémur (FESF) est un problème de santé publique en raison de son énorme coût humain et financier. L'os cortical contribue pour 40 à 60 % de la résistance de l'ESF à la fracture, mais sa situation périphérique et sa faible épaisseur le rende difficile à étudier. Nous avons étudié la microstructure et la densité minérale osseuse (DM0) de l'os cortical de la mi-diaphyse fémorale de 163 fémurs d'une collection anthropologique récente, grâce respectivement à des microradiographies avec un système d'analyse d'image semi-automatisé et à un appareil de tomodensitométrie quantitative avec un protocole adapté à la haute résolution. Nous avons ainsi 1/ observé l'évolution de la taille, du nombre et de la répartition des pores avec l'âge, chez les hommes et les femmes, 2/ observé l'évolution de la DM0 avec l'âge, 3/ corrélé la porosité et la DM0. Nous avons également étudié, in vitro, la microstructure, la densité et le module d'élasticité de la corticale du col fémoral chez 16 patientes avec une fracture ostéoporotique du col et chez 16 femmes témoins de même âge, décédées sans fracture, afin de mesurer le lien entre ces paramètres et la fracture du col. Les moyens d'investigation ont été respectivement la microtomodensitométrie 3D par rayonnement synchrotron, la tomodensitométrie quantitative avec le même protocole que précédemment, et l'ultrasonographie. Nous n'avons pas observé de différence significative entre les deux groupes sur les paramètres mesurés, soit en raison d'un biais de sélection de la population témoin, soit en raison de l'absence réelle de différence. Les données obtenues améliorent la connaissance des phénomènes normaux de vieillissement de l'os cortical et des phénomènes liés à l'ostéoporose. Ces connaissances nouvelles pourraient prendre place dans la discussion des stratégies de prévention et de traitement de l'ostéoporose et du risque de fracture de l'extrémité supérieure du fémur.

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Roux, Sylvie Anne-Marie. « La fiabilité de la mesure de la densité minérale du col du fémur par absorptiométrie biphotonique : étude comparative multicentrique des différents dispositifs ». Bordeaux 2, 1991. http://www.theses.fr/1991BOR2M007.

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Lafargue, Véronique, et Christian Amathieux. « Absorptiométrie biphotonique du col du fémur : problèmes posés par la mesure de la densité minérale d'un site osseux à prédominance corticale ». Bordeaux 2, 1989. http://www.theses.fr/1989BOR25278.

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Righini, Alberto. « Densita con la proprieta di media per i sub-Laplaciani ». Master's thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amslaurea.unibo.it/12047/.

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Nella tesi studiamo le densità con la proprietà di media per i sub-Laplaciani. In particolare determiniamo un’espressione generale per una densità positiva con la proprietà di media, su un insieme Ω generico che soddisfi certe prorpietà di regolarità. Troviamo inoltre delle stime della funzione di Green e del nucleo di Poisson per un qualsiasi sub-Laplaciano su un generico gruppo di Carnot e tramite queste stime troviamo delle condizioni sufficienti affinchè, con la densità precedentemente trovata, si possa avere una struttura di Γ-tripla sull’insieme Ω. Studiamo infine un problema inverso per il quale sarà fondamentale avere una struttura di Γ-tripla.

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Christlmaier, Evelin Martine. « CC2 response method using local correlation and density fitting approximations for the calculation of the electronic g-tensor of extended open-shell molecules ». Doctoral thesis, Humboldt-Universität zu Berlin, 2021. http://dx.doi.org/10.18452/22835.

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In dieser Arbeit wird eine unrestricted Coupled-Cluster CC2 Response-Methode für die Berechnung von Eigenschaften erster und zweiter Ordnung, mit dem elektronischen g-Tensor als Schwerpunkt, präsentiert. Lokale Korrelations- und Dichtefittingnäherungen wurden verwendet. Die fundamentalen Konzepte notwendig für das Verständnis von Coupled-Cluster-Theorie, Dichtefitting, lokaler Korrelation, allgemeinen Coupled-Cluster Eigenschaften und dem elektronischen g-Tensor werden diskutiert. Die berechneten g-Tensoren werden mit denen durch Coupled-Cluster Singles and Doubles, Dichtefunktionaltheorie und Experiment erhaltenen verglichen. Effizienz und Genauigkeit der Näherung wird untersucht. Ein detailierter Anhang beschreibt die diagrammatische Coupled-Cluster-Theorie sowie ihre Anwendung zur Herleitung der verwendeten Arbeitsgleichungen. Die in dieser Arbeit entwickelte Methode ermöglicht es, den elektronischen g-Tensor von ausgedehnten Systemen mit einer Methode, die nicht auf Dichtefunktionaltheorie basiert, quantitativ vorherzusagen. Damit ist sie ein wichtiger Schritt hin zur Entwicklung von niedrig skalierenden Coupled-Cluster-Methoden höherer Ordnung für diese Art von Problem.
This work presents an unrestricted coupled-cluster CC2 response method using local correlation and density fitting approximations for the calculation of first and second order properties with particular focus on the electronic g-tensor. The fundamental concepts related to coupled-cluster theory, density fitting, local correlation, general coupled-cluster properties and the electronic g-tensor are discussed. The calculated g-tensors are benchmarked against those obtained from coupled-cluster singles and doubles, density functional theory and experiment. Efficiency and accuracy of the approximations is investigated. A detailed appendix covers the fundamentals of diagrammatic coupled-cluster and its application to the derivation of the working equations. The method presented in this thesis enables the quantitative prediction of the electronic g-tensor of extended systems with a method other than density functional theory. It represents an important step towards the development of low-scaling higher order coupled-cluster methods for this type of problem.

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Hotz-Behofsits, Christian, Florian Huber et Thomas Zörner. « Predicting crypto-currencies using sparse non-Gaussian state space models ». Wiley, 2018. http://dx.doi.org/10.1002/for.2524.

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In this paper we forecast daily returns of crypto-currencies using a wide variety of different econometric models. To capture salient features commonly observed in financial time series like rapid changes in the conditional variance, non-normality of the measurement errors and sharply increasing trends, we develop a time-varying parameter VAR with t-distributed measurement errors and stochastic volatility. To control for overparameterization, we rely on the Bayesian literature on shrinkage priors that enables us to shrink coefficients associated with irrelevant predictors and/or perform model specification in a flexible manner. Using around one year of daily data we perform a real-time forecasting exercise and investigate whether any of the proposed models is able to outperform the naive random walk benchmark. To assess the economic relevance of the forecasting gains produced by the proposed models we moreover run a simple trading exercise.

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Ahnadi, Charaf-Eddine. « Mécanismes de régulation du transfert des esters de cholestérol : effets d'un inhibiteur de l'HMG-CoA réductase et du diabète de type II ». Lyon 1, 1993. http://www.theses.fr/1993LYO1T048.

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Christlmaier, Evelin Martine [Verfasser]. « CC2 response method using local correlation and density fitting approximations for the calculation of the electronic g-tensor of extended open-shell molecules / Evelin Martine Christlmaier ». Berlin : Humboldt-Universität zu Berlin, 2021. http://d-nb.info/1235399281/34.

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Chebil, Mohamed Souheib. « Etude de films ultraminces de polystyrène par réflectivité des rayons X et ellipsométrie en fonction de leur exposition à du CO2 ». Thesis, Le Mans, 2013. http://www.theses.fr/2013LEMA1022/document.

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L’objectif principal de ce travail est d’étudier in-situ et ex-situ l’interaction du dioxyde de carbone (CO2) avec les films minces de polystyrène et les surfaces par deux techniques principales : la réflectivité des rayons X (RRX) et l’ellipsométrie.Dans cette thèse, nous abordons l’étude des propriétés physiques de films de polystyrène (PS) à l’état confiné (films minces) et leur évolution lors de leur exposition à du CO2 sous pression. Nous démontrons par RRX et par ellipsométrie sur les mêmes films que la densité et l’indice de réfraction augmentent quand l’épaisseur du film diminue. Nous confirmons la diminution de Tg pour des films de PS d’épaisseur inférieure à 70 nm selon la loi empirique de Keddie [1]. Ces deux résultats pourraient signifier que les films ultraminces présentent une certaine organisation des chaines.Nous abordons ensuite le comportement des films ultra minces de PS exposés à du CO2 en fonction de la pression de CO2 par réflectivité de rayons X (RRX) faite au rayonnement synchrotron (ESRF ligne ID10B). Nous suivons in-situ le gonflement et le dégonflement du film mince d’épaisseur 7 nm lors de la pressurisation et la dépressurisation du CO2. Par calcul de l’évolution de la densité électronique dans le film, nous mettons en évidence l’existence d’une pression de transition vitreuse Pg et d’un gonflement rémanent lié à la présence de molécules de CO2 piégées dans le film [2].Nous proposons par la suite une étude ex-situ par RRX du gonflement et de l’évolution au cours du temps des films de PS gonflés. Nous observons que les films minces présentent une plus grande capacité de gonflement et dégonflement au cours du temps par opposition aux films plus épais. Nous constatons que ce phénomène est fortement dépendant du taux de dépressurisation. En effet, nous constatons que la dépressurisation rapide renforce considérablement, non seulement le gonflement du film, mais aussi son dégonflement au cours du temps. Nous mettons alors en évidence que le taux de dépressurisation régit clairement l'état final des films gonflés, à savoir l’état métastable ou l’état vitreux.Finalement, nous étudions l’influence du gonflement du film par le CO2 sur l’évolution de la température de transition vitreuse. Cette étude est effectuée principalement par ellipsométrie. Nous montrons que ces films qui ne présentaient qu’une valeur unique de Tg avant exposition, présentent après exposition trois valeurs de Tg. En suivant l’évolution de l’épaisseur de ces films gonflés en fonction de la température, nous proposons des réponses qui peuvent expliquer les différentes Tg observées. En outre, nous mettons en évidence l’existence du CO2 stocké dans les films. Après un recuit au dessus de 150°C, les films reprennent le même comportement qu’avant exposition au CO2 qui est loin d’être l’état d’équilibre du polymère massique. Nous confirmons par ce fait l’existence de fortes forces de rappel dans les films ultraminces qui les ramènent vers leurs états initiaux de non équilibre. Ce résultat est à rapprocher de celui concernant l’évolution de la Tg due au confinement dans les films ultraminces avant exposition
The aim of this work is to study in-situ and ex-situ interaction of carbon dioxide (CO2) with thin films of polystyrene and surfaces by two main techniques: the X-ray reflectivity (XRR) and ellipsometry.In this thesis, we address the study of the physical properties of polystyrene films (PS) in the confined state (thin films) and their evolution when exposed to CO2 pressure. We demonstrate by XRR and ellipsometry in the same films that the density and the refractive index increase when the film thickness decreases. We confirm the decrease of Tg for PS films of thickness less than 70 nm according to the empirical law of Keddie [1]. Both results could mean that ultrathin films have a certain organization of channels.We then discuss the behavior of PS ultra thin films exposed to CO2 as a function of CO2 pressure by XRR made at synchrotron radiation (ESRF ID10B line). We monitor in situ the swelling and deswelling of the 7 nm thin film thickness upon pressurization and depressurization of CO2. By calculating the evolution of the electron density in the film, we highlight the existence of a glass transition pressure Pg and a residual swelling due to the presence of CO2 molecules trapped inside the film [2].We propose then an ex-situ XRR study of swelling and kinetic of deswelling for PS swollen films. We observe that the thin films have a higher swelling and deswelling capacity compare to the thicker films. We note that this phenomenon is highly dependent to the depressurization rate. Indeed, we find that the rapid depressurization greatly enhances not only the swelling of the film, but also its deswelling over time. We then highlight that the rate of depressurization clearly governs the final state of swolen films, to say the metastable state or glassy state.Finally, we study the effect of film swelling by CO2 on the evolution of the glass transition temperature. This study is carried out mainly by ellipsometry. We show that these films which showed only a single Tg value before exposure, after exposure has three values of Tg completely independent of film thickness. By following the thickness evolution of these swollen films as a function of temperature, we offer answers that can explain the different Tg values observed. In addition, we highlight the existence of CO2 stored in these films. After annealing above 150 ° C, the films show the same behavior as before exposure to CO2 which is far from the equilibrium state of the bulk polymer. We confirm therefore the existence of strong restoring forces in ultrathin films that bring them back to their initial states of non-equilibrium. This result presents similarities to that concerning the evolution of the Tg due to confinement in ultrathin films before exposure

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Kgasago, Hans. « Effect of planting dates and densities on yield and yield components of short and ultra-short growth period maize (Zea mays L.) ». Diss., University of Pretoria, 2007. http://hdl.handle.net/2263/28056.

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In general, yield reduction in most dryland maize growing areas of South Africa occur because seasonal rainfall distribution is erratic with annual variation that cannot be predicted accurately. Cultivar selection, planting date and plant density are other factors that consistently affect maize yield. Long growing season maize cultivars are higher yielding, particularly under conditions of good moisture and nutrient supply. However, as both moisture and nutrient availability becomes more limiting, yield tends to decline. Short growing season maize cultivars could yield more than long season counterparts because they can maximize the growing season and potentially reach the critical flowering stage before traditional midsummer droughts occur. The short growing season maize cultivars, which have only recently been developed, have traits, which can address the problem of reduced yield, which is ascribed to midsummer drought. There has been no previous effort to evaluate the effects of planting dates and plant densities on yield and yield components of these short and ultra-short growth period maize cultivars. This prompted research in the 2004/05 growing season. One field experiment was conducted at each of two selected areas (Bethlehem&Potchefstroom) in the “Maize Triangle” of South Africa. The aim was to evaluate the response of short and ultra-short growth period maize cultivars to planting dates and plant densities at two localities with distinct environmental conditions. The effects of planting date, plant density and cultivar on yield and yield components were investigated. Both yield and yield components were affected by planting date, plant density and cultivar at both localities. At both localities early and optimum planting dates as well as low and optimum plant densities promoted increases in yield components, which contributed to increased grain yield. As for the cultivars, PAN6017 proved to be the most consistent since it out-performed other cultivars in terms of both vegetative growth, yield components and grain yield at both localities. At both localities, plant height, leaf area index and dry matter yield were affected by both planting date and plant density, with optimum planting date and optimum plant density contributing to highest yield components and yield. PAN 6017 was superior to the other cultivars at all planting dates and plant densities at both localities. In order to make findings from a study such as this applicable to the “Maize Triangle”, more research on short and ultra-short growth period maize cultivars should be conducted over a wider range of locations and seasons.
Dissertation (M Inst Agrar (Agronomy))--University of Pretoria, 2007.
Plant Production and Soil Science
M Inst Agrar
unrestricted

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Poor, Kalhor Mahboubeh. « Étude DFT du mécanisme de formation du dimethyl carbonate à partir de CO2 et de CH3OH à l'aide de Me2Sn(OMe)2 ». Thesis, Lyon 1, 2009. http://www.theses.fr/2009LYO10325.

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Le dioxyde de carbone occupe une place particulière dans l'amplification anthropogénique de l'effet de serre. En particulier, son utilisation dans la synthèse de carbonates organiques à partir d'alcools constituerait une alternative à l'emploi actuel du phosgène ou du monoxyde de carbone. L'insertion de CO2 dans Sn-OCH3 liaison de dialkyldimethoxystannanes est reconnue comme la première étape pour la formation du carbonate de diméthyle (DMC) à partir du méthanol et CO2. L'identification des étapes ultérieures est cruciale pour améliorer l'activité et est encore l’objet de débats car les espèces étain ont la propension à l’oligomérisation. Nous avons utilisé des calculs basés sur la Théorie de la Fonctionnelle de la Densité pour donner un aperçu sur le mécanisme de réaction. L'insertion de CO2 est promue par l’interaction acide-base concertée de Lewis de CO2 avec l'étain et l'atome d'oxygène du ligand méthoxy. Le chemin principal de la réaction pour la formation de DMC est proposé selon un réarrangement intramoléculaire des espèces monomériques, Me2Sn[OC(O)OCH3]2. Le processus conduit à un transfert d'un groupe méthyle d'un carbonate de méthyle à l'autre via un anneau de 4 atomes ou 6 atomes formant un fragment Sn-CO3. Dans une deuxième étape, le méthanol réagit avec un intermédiaire et conduit à la formation de DMC et un complexe de trimère qui peut permettre la régénération des réactifs. Mais un complexe décanucléaire d’étain peut être aussi produit par une réaction latérale. Enfin, un cycle catalytique pour produire le DMC a pu être élaboré. Les calculs DFT sont en accord avec les données expérimentales et permettent une analyse comparative des chemins de réaction
Carbon dioxide occupies a special place in the amplification of the anthropogenic greenhouse effect. In particular, its use in the synthesis of organic carbonates from alcohols, constitute an alternative to the current application of phosgene or carbon monoxide. The insertion of CO2 into the Sn-OCH3 bond of dialkyldimethoxystannanes is recognized as the first step to dimethyl carbonate (DMC) formation from methanol and carbon dioxide. The identification of the subsequent steps is crucial for activity improvements and is still under debate as the tin species have the propensity for oligomerization. We have used density functional theory calculations to provide insight into the reaction mechanism. The CO2 insertion into the Sn-OCH3 bond is promoted by the concerted Lewis acid-base interaction of CO2 with tin and the oxygen atom of the methoxy ligand. The major reaction pathway to DMC is proposed to occur via an intramolecular rearrangement of the monomeric species, Me2Sn[OC(O)OCH3]2. The process results in the transfer of a methyl group from one methyl carbonate to the other via a 4-membered or 6-membered ring forming the Sn-CO3 moiety. In a second stage, methanol reacts with one intermediate and leads to DMC formation and a trimer compound which may allow the regeneration of the reactant. Also a decanuclear tin complex is produced due to the lateral reaction. Finally a catalytic cycle for DMC production in methanol can be elaborated. DFT calculations are in agreement with the experimental data and allow a comparative analysis of reaction channels

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Silveira, Douglas Severo. « Avaliação bioquímica e densitométrica dos efeitos do ultra-som terapêutico de 1 mhz, na dose de 0,5 OU 1 W/cm2, sobre o tecido ósseo de cães ». Universidade Federal de Santa Maria, 2007. http://repositorio.ufsm.br/handle/1/4139.

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Tendineous injuries on distal extremity of members are among the most frequent alterations of the locomotor system in both human and animal clinic-surgical routine and frequently adjuvant therapies are needed for the complete return of the physiological functions. The Therapeutic Ultrasound (TUS) is the most commonly used mode of treating tendineous injuries in rehabilitation clinics. However, due to the lack or the disagreements on specific studies about its effects on bone tissues, the use of TUS on distal regions of members, rich in bone protuberances and areas without muscular covering, always worries the professionals of the medical area. With the intention of clarifying the effects of TUS on bone tissue, 18 dogs were separated randomly into 3 groups, in which they received continuous ultrasonic treatment of 1 MHz for 5 minutes during 20 days on the cranium-distally region of the radio and ulna. According to the pre-determined groups, the frequency of TUS applied was of 0.5 or 1 W/cm2. The serum levels of total proteins, albumin, total calcium, ionic calcium, phosphates, alkaline phosphatase and bone alkaline phosphatase, were measured before the beginning of the therapy and after days 4, 7, 11, 14 and 20 of the treatment. The treated regions were also radiographed for analysis of bone densitometry in radiographic images before the therapy and at the end of the treatment. The laboratory exams detected normal serum levels for the main items researched, excepted for albumin which was inferior to the reference values. The statistic analysis of the results obtained show that the TUS caused alteration on the mineral bone metabolism and on the activity of the osteoblasts, especially on the first 7 days of the application, but did not alter the mineral bone density, no matter what dose was used (0.5 or 1 W/cm2). One can conclude that for the parameters in the experiment, TUS in regions of bone protuberances or deprived of muscular covering can be applied with safety.
As lesões tendíneas nas extremidades distais dos membros, estão entre as mais freqüentes alterações do aparelho locomotor da rotina clínico-cirúrgica humana e animal e, não raro, necessitam de terapias adjuvantes para seu completo retorno às funções fisiológicas. O ultra-som terapêutico (UST) é a modalidade mais utilizada nas clínicas de reabilitação para tratar lesões tendíneas, mas devido à falta ou a divergências de estudos específicos sobre seus efeitos no tecido ósseo, sua utilização sobre as regiões distais dos membros, ricas em protuberâncias ósseas e áreas desprovidas de cobertura muscular, sempre preocuparam os profissionais da área médica. No intuito de esclarecer os efeitos do UST sobre o tecido ósseo, 18 cães foram divididos aleatoriamente em três grupos, onde receberam tratamento ultra-sônico contínuo, de 1MHz, durante 5 minutos diários, por um período de 20 dias sobre a região crânio-distal do rádio e ulna. De acordo com os grupos prédeterminados, a freqüência do UST aplicada foi de 0,5 ou 1 W/cm2. Foram mensurados os níveis séricos de proteínas totais, albumina, cálcio total, cálcio iônico, fósforo, fosfatase alcalina e fosfatase alcalina óssea no momento anterior ao começo da terapia e após 4, 7, 11, 14 e 20 dias de tratamento. Também foram radiografadas as regiões tratadas, para análise de densitometria óssea em imagens radiográficas, antes da terapia e ao final do tratamento. Os exames laboratoriais detectaram níveis séricos normais para os principais itens pesquisados, apenas a albumina foi inferior aos valores de referência. As análises estatísticas dos resultados obtidos evidenciaram que o UST causou alterações no metabolismo mineral ósseo e na atividade dos osteoblastos, principalmente nos primeiros 7 dias de aplicação, porém não alteraram a densidade mineral óssea, não importando a dose utilizada (0,5 ou 1 W/cm2). Conclui-se que dentro dos parâmetros utilizados no experimento, a utilização do UST em regiões ósseas protuberantes ou desprovidas de cobertura muscular pode ser feita com segurança.

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Gérard, Pascale. « Contribution à l'étude magnétostatique des systèmes intermétalliques R(Co1-xNix)5 ». Grenoble 1, 1992. http://www.theses.fr/1992GRE10041.

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Une etude de l'evolution du magnetisme des electrons 3d dans le systeme y(co#1##xni#x)#5 (entre le fort ferromagnetisme itinerant associe au compose yco#3 et le paramagnetisme de pauli caracteristique du compose yni#5) est effectuee. On montre qu'aux fortes concentrations en nickel, les instabilites du magnetisme s'instaurent de maniere inhomogene, en fonction des environnements locaux. On precise ensuite les anisotropies associees a ce magnetisme. Elles revelent le caractere du magnetisme itinerant du sous-reseau (co#1##xni#x). Une etude de la coercivite magnetique, associee aux defauts d'echange et d'anisotropie introduits par la substitution du nickel au cobalt, est egalement menee sur les composes monocristallins du systeme riches en nickel. Cette coercivite est interpretee dans un modele de parois flexibles ancrees sur les clusters de faible densite d'aimantation. Nous considerons ensuite l'influence sur le magnetisme 3d, associe au sous-reseau (co#1##xni#x), d'une terre rare magnetique isotrope. Cette etude est realisee sur le systeme gd(co#1##xni)#5. Elle permet d'apprehender l'effet de champ d'echange, associe au gadolinium, sur la stabilite relative du magnetisme du sous-reseau 3d, et de mettre en evidence experimentalement une anisotropie des interactions d'echange entre les sous-reseaux 3d et 4f. Nous presentons enfin une etude par diffraction de neutrons polarises et non polarises du compose yco#3ni#2. Une determination fine de la structure cristallographique de ce compose est realisee. On met en evidence une repartition non aleatoire des atomes de cobalt et de nickel dans les deux types de sites qu'ils occupent. Une carte de la densite d'aimantation moyenne dans ce compose est etablie. Elle met en evidence l'existence d'une polarisation des electrons 5d, mediateurs des interactions d'echange 3d-4f, et permet en outre, d'evaluer la contribution orbitale au magnetisme du compose

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Tchéou, Jean-Marcel. « Analyse statistique multifractale en turbulence développée et application à la finance ». Cachan, Ecole normale supérieure, 1997. http://www.theses.fr/1997DENS0026.

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Cette thèse est consacrée à l'étude statistique (densité de probabilité et moments) des accroissements des variables d'état pour des systèmes présentant des lois d'échelle multifractales. A l'aide de la méthode du col, nous montrons qu'il existe dans ce cas une double relation asymptotique explicite et locale qui permet d'exprimer les densités de probabilité en fonction des moments et réciproquement. Les termes dominants (exponentiels) de la double asymptotique s'écrivent sous la forme d'une transformée de Legendre identique a celle du modèle de Parisi-Frisch. Cette asymptotique permet de reconstruire toute la famille de densités a partir du spectre des exposants multifractals et de la statistique des moments a grande échelle. Grace aux données de P. Tabeling en turbulence, nous avons pu montrer que les moments pouvaient être quantitativement représentés par des lois d'échelle multifractales et par une statistique quasi gaussienne a grande échelle. Cette grande échelle, déterminée a partir de données prises uniquement dans la zone inertielle, reste de l'ordre de l'échelle intégrale dans une gamme très large du nombre de Reynolds. Cette représentation des moments permet, a l'aide de la double relation asymptotique de reproduire quantitativement les distributions de probabilité. Nous avons également pu mettre à l'épreuve certaines expressions analytiques et théoriques de l'exposant multifractal. En utilisant les données financières du CAC 40 et du taux monétaire DEM/USD, nous avons pu montrer que ces données étaient susceptibles d'une modélisation semblable à celle effectuée en turbulence. En effet, les moments des accroissements présentent des lois d'échelle multifractales et une statistique gaussienne a grande échelle. La modélisation correspondante des densités de probabilité est en bien meilleur accord avec les données expérimentales que les modélisations usuelles monofractales du type gaussienne ou de Lévy.

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Klarbring, Johan. « A first-principles non-equilibrium molecular dynamicsstudy of oxygen diffusion in Sm-doped ceria ». Thesis, Linköpings universitet, Teoretisk Fysik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-118773.

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Solid oxide fuel cells are considered as one of the main alternatives for future sources of clean energy. To further improve their performance, theoretical methods able to describe the diffusion process in candidate electrolyte materials at finite temperatures are needed. The method of choice for simulating systems at finite temperature is molecular dynamics. However, if the forces are calculated directly from the Schrödinger equation (first-principles molecular dynamics) the computational expense is too high to allow long enough simulations to properly capture the diffusion process in most materials. This thesis introduces a method to deal with this problem using an external force field to speed up the diffusion process in the simulation. The method is applied to study the diffusion of oxygen ions in Sm-doped ceria, which has showed promise in its use as an electrolyte. Good agreement with experimental data is demonstrated, indicating high potential for future applications of the method.

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Bonganha, Valeria 1981. « Efeitos do treinamento com pesos sobre a densidade mineral ossea, força muscular e variaveis funcionais na menopausa ». [s.n.], 2009. http://repositorio.unicamp.br/jspui/handle/REPOSIP/274780.

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Orientador: Vera Aparecida Madruga
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Educação Fisica
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Resumo: O presente estudo analisou as respostas dos indicadores de força, densidade mineral óssea (DMO), taxa metabólica de repouso (TMR), composição corporal e capacidade aeróbia (O2 máximo e limiar anaeróbio) após intervenção de 16 semanas de treinamento com pesos (TP). Participaram desta pesquisa 22 voluntárias, na pós-menopausa (12 meses sem menstruações) subdivididas em dois grupos: grupo treinado (GT n=12) e grupo controle (GC n=10). O programa de TP teve freqüência de três sessões semanais em dias alternados, compreendendo 10 exercícios para membros superiores, inferiores e tronco, sendo realizado três séries de 10 repetições máximas (RM) na etapa 1 e três séries de 8 RM na etapa 2. Os níveis de força foram mensurados pelo teste de 1-RM, a composição corporal foi obtida pelo método de espessura de dobras cutâneas, a avaliação da DMO foi realizada por Densitometria Radiológica de Dupla Energia nas regiões da coluna lombar e colo do fêmur, a TMR e o O2 máximo foram obtidos por meio de calorimetria indireta, sendo a TMR calculada por meio da equação de Weir (1949). O O2 máximo foi obtido durante teste de esforço progressivo em esteira até a exaustão. Para análise dos dados foi utilizado o teste de Kruskal-Wallis, para avaliar os efeitos do TP intra e intergrupos e a correlação de Spearman nas correlações utilizadas. Os resultados encontrados mostraram aumentos com diferenças estatisticamente significantes para as cargas levantadas nos testes de 1-RM para supino e leg press no GT e nenhuma modificação foi encontrada para o GC. Não foram obtidas diferenças significantes para os valores de DMO, tanto da coluna quanto do fêmur, da TMR e do O2 pico e limiar anaeróbio em ambos os grupos. O treinamento com pesos foi eficaz para aumentar a força muscular, entretanto 16 semanas de intervenção não foram suficientes para provocar alterações significantes na DMO, na TMR e na capacidade aeróbia.
Abstract: This study examined the adaptive responses of indicators of strength, bone mineral density (BMD), the resting metabolic rate (RMR) and aerobic capacity (O2 max and anaerobic threshold ) after 16 weeks intervention resistance training program (RT). Participated 22 postmenopausal women (12 months without menstruation), subdivided in two groups: trained group (GT n = 12) and control group (GC n = 10). The RT period had frequency of three sessions per week on alternate days, with 10 exercises for upper limbs and lower limbs, and performed three sets of 10 repetitions maximum (RM) in step 1 and three sets of 8 RM in step 2. The levels of strength were measured by the 1-RM test, body composition was obtained by the method of skinfolds, the assessment of BMD was performed by densitometry of Radiological Dual Energy in the regions of lumbar spine and the femoral neck, and the RMR and O2 max were obtained by indirect calorimetry and the RMR calculated using equation of Weir (1949). The O2 max was obtained during progressive test on a treadmill until exhaustion. For statistical analysis we used the Kruskal-Wallis test to assess the effects of intra and inter RT and the Spearman correlation to the correlations used. The results showed statistically significant differences increase for the load being strength in the 1-RM tests and supine leg press for the GT and no change was found to GC. No significant differences were obtained for the BMD of the spine on both the femur, O2 peak and the TMR in both groups. RT was effective to increase muscle strength, but 16 weeks were not sufficient to cause changes in BMD, in TMR and aerobic capacity.
Mestrado
Atividade Fisica, Adaptação e Saude
Mestre em Educação Física

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BANDEIRA, Stanrley Wilker Trindade. « Estudo teórico de compostos de platina usados na terapia anti-câncer ». Universidade Federal do Maranhão, 2017. https://tedebc.ufma.br/jspui/handle/tede/tede/2029.

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FAPEMA
The present master's work was focused on quantum chemistry calculations and based on the Functional Density Theory (DFT) the interaction between platinum compounds used in anti-cancer therapy and DNA. Based on the analysis of the factors that influence the bonding process between the platinum complexes and the DNA. All the nitrogenous bases of the DNA were analyzed, in order to choose the one that would present better interaction with the studied complexes. The theoretical results showed that the different platinum compounds have binders that decrease toxicity, or increase membrane binding. The platinum compounds, Carboplatin, Iproplatin, Nedaplatin and Oxaliplatin, were structured through the GAUSS VIEW 5.0 software. Then, the optimization of these structures was performed using the GAUSSIAN 9.0 program. This optimization used bases extracted from the EMSL BASIS SET EXCHANGE database. As a result of these optimizations the HOMO-LUMO intervals were used to characterize the stability of the molecules, as well as the stability variations that occurred during the hydrolysis reactions, and their connections with the guanine base of the DNA. This observation, as well as the thermodynamic properties, served to describe the toxicities presented in the literature.
O presente trabalho de mestrado foi voltado a examinar por meio de cálculos de química quântica e com base na Teoria do Funcional Densidade (DFT) a interação entre compostos de platina usados na terapia anti-câncer e o DNA. Com base na análise dos fatores que influenciam o processo de ligação entre os complexos de platina e o DNA.Analisou-se todas as bases nitrogenadas do DNA, para a escolha da que apresentaria melhor facilidade de interação com os complexos estudados. os resultados teóricos mostraram que que os diferentes compostos de platina apresentam ligantes que diminuem a toxicidade, ou aumentam a ligação com membranas. Os compostos platínicos,Carboplatina, Iproplatina, Nedaplatina e Oxaliplatina, foram estruturados através do progarama GAUSS VIEW 5.0. Em seguida realizou-se a otimização dessas estruturas utilizando-se o programa GAUSSIAN 9.0. Essa otimização utilizou bases extraídas do banco de dados EMSL BASIS SET EXCHANGE. Como resultado dessas otimizações foram extraídos os intervalos HOMO-LUMO, utilizados para caracterizar a estabilidade das moléculas, bem como, as variações de estabilidade, que ocorriam durante as reações de hidrolise, e respectivas ligações com a base GUANINA do DNA. Essa observação,bem como as propriedades termodinâmicas serviu para descrever as toxicidades, apresentadas em literatura.

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Cadore, Ígor Renz. « Efeito das condições hidrodinâmicas no desempenho de um biorreator com membranas submersas em pressão constante ». reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2015. http://hdl.handle.net/10183/115548.

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O processo de Biorreatores com Membranas (BRM) foi desenvolvido no final da década de 1960, consistindo em um sistema que associa o tratamento biológico de efluentes com o mecanismo de separação por membranas, e apresenta vantagens com relação ao tratamento convencional, tais como maior eficiência de tratamento e um menor espaço físico de instalação para a mesma capacidade de tratamento. O fenômeno de incrustação das membranas (em inglês, fouling) representa a principal limitação desse processo, de modo que uma das condições operacionais mais importantes na prevenção da incrustação em um sistema BRM Submerso (BRMS) é a vazão de aeração. Diante desta situação, o objetivo do trabalho consiste em avaliar os efeitos das condições hidrodinâmicas no desempenho do processo, tais como vazão de aeração, densidade de empacotamento do módulo de membranas e geometria dos aeradores. O sistema utilizado no trabalho consistiu em um BRMS automatizado, operando em pressão constante e de forma contínua, durante um período de 4 dias. Os módulos foram construídos com membranas poliméricas de microfiltração do tipo fibra oca, cujo material foi a poli(éter)-imida (PEI). Três diferentes vazões de aeração foram estudadas (2, 5 e 8 L.min-1), mostrando, a partir dos resultados, que existe uma vazão de aeração limite benéfica ao sistema e que, acima deste valor, um melhor desempenho não pode ser atingido, inclusive, podendo prejudicá-lo. Para o sistema de estudo, a vazão de 5 L.min-1 apresentou o melhor desempenho, seguido de 8 e 2 L.min-1. O estudo da densidade de empacotamento do módulo mostrou que esta é uma variável que também exerce influência no desempenho do processo de BRMS. Módulos com dois diferentes diâmetros foram testados (2,54 cm e 1,91 cm); o melhor resultado foi observado no módulo de maior diâmetro. A menor densidade de empacotamento resulta em um maior espaçamento entre as fibras, provocando uma aeração mais homogênea no interior do feixe de membranas. As duas geometrias de aeração testadas (Modo 1 e Modo 2) apresentaram resultados semelhantes de fluxo permeado, indicando que o Modo 2 de aeração não melhorou o desempenho do processo como se esperava. A maior homogeneidade de aeração no interior de feixe, a partir de aeradores construídos com as próprias fibras, não foi atingida, mostrando que um novo projeto de aeradores deve ser estudado. Em todas as condições hidrodinâmicas testadas, a eficiência do tratamento foi verificada, uma vez que a remoção de matéria orgânica para COT e DQO foi de 96% e 93%, respectivamente. Propriedades do permeado, como condutividade elétrica, pH e turbidez foram mensuradas, apresentando variações menores que as medidas do efluente, revelando a capacidade que o sistema apresenta em suportar as variações na corrente de alimentação.
The Membrane Bioreactor (MBR) process was developed in the late 1960. The system consists in a combination of biological process and membrane separation mechanism, and the advantages with respect of conventional treatment are the higher treatment efficiency and a smaller area of installation for the same treatment capacity. The main limitation of this process is the membrane fouling, in a way that air flow rate represents an important operating condition to prevent the fouling formation in Submerged Membrane Bioreactors (SMBR). In this sense, the aim of this work is to evaluate the effects of hydrodynamic conditions on process performance, such as air flow rate, packing density of the membrane module and aeration geometry. The system used consists in a pilot-scale SMBR, which operates at constant pressure and continuous mode during a period of 4 days. The modules were built with hollow fiber polymeric microfiltration membrane and the material is poly(ether)imide (PEI). For the three different air flow rates studied (2, 5 and 8 L.min-1), results showed there is a limit value for this parameter, in which above this value a better performance will not be obtained, even can be worse. The air flow rate of 5 L.min-1 presented the best performance, followed by 8 and 2 L.min-1. The module packing density study for two diameters (0.75 and 1 inch), the best result was observed in the larger diameter module, because lower packing density causes more space between fibres, increasing the aeration homogeneity inside de fibre bundle. Both aeration geometry tested showed similar permeate flows, indicating the different geometry used did not affect the performance process. The aerators constructed with the hollow fibers did not promote aeration homogeneity inside the bundle, and new aeration geometry must be projected. For all hydrodynamics conditions, the system treatment was efficient in removing organical matter, since the removal for TOC and COD was 96% and 93%, respectively. Permeate properties such as electrical conductivity, pH and turbidity measurements presented minor variations than effluent properties measurements, showing the system capacity to withstand with feed stream variations.

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Berro, Abdel Jalil. « Déterminants de la santé osseuse chez des jeunes femmes en surpoids et obèses : exploration et influences de deux programmes d'entraînement physique (force vs. endurance) ». Thesis, Amiens, 2018. http://www.theses.fr/2018AMIE0024/document.

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Les buts de cette thèse étaient de définir les déterminants de la santé osseuse chez les jeunes femmes en surpoids et obèses et d'explorer les effets de deux programmes longitudinaux d'entraînement physique (force vs. endurance) sur les paramètres osseux chez les jeunes femmes en surpoids et obèses. Deux études préliminaires et six études principales ont été menées. La première étude préliminaire a montré que la VO2 max (L/mn) est un déterminant positif de la masse osseuse chez les enfants en surpoids. La deuxième étude préliminaire a démontré que l'IMC est un déterminant négatif du CSI, du BSI et de l'ISI chez les jeunes femmes. La première étude principale a montré que l'obésité est associée à de faibles valeurs de CSI, de BSI et d'ISI chez les jeunes femmes. La deuxième étude principale a montré que la VO2 max (ml/mn/kg) est positivement corrélée au CSI et à l'ISI chez les jeunes femmes. La troisième et la quatrième étude ont montré que la surcharge pondérale est associée à une augmentation du CMO et de la DMO mais pas du TBS et que le TBS est corrélé positivement à la VO2 max (L/mn). La cinquième étude principale chez 68 jeunes femmes en surpoids et obèses a montré que la détente verticale, la VO2 max (L/mn), la puissance maximale (watts) et la force maximale en demi-squat sont positivement corrélées aux paramètres osseux chez les jeunes femmes en surpoids et obèses. La sixième étude principale a montré que les deux types d'entrainement physique (force et endurance) sont efficaces pour augmenter le CMO CE et la DMO lombaire et diminuer le poids et la masse grasse. L'entrainement de force était aussi efficace pour l'augmentation du TBS et les indices de résistance osseuse du col fémoral (CSI, BSI et ISI)
The aims of this thesis were to define the determinants of bone health in young overweight and obese men and to explore the effects of two physical training programs (strength vs. endurance) on bone parameters in young overweight and obese women. Two preliminary studies and six main studies have been conducted. The first preliminary study has shown that VO2 max (L/mn) is a positive determinant of bone mass in overweight children. The second preliminary study has shown that BMI is a negative determinant of CSI, BSI and ISI in young women. The first main study has shown that obesity is associated with lower CSI, BSI and ISI values in young women. The second main study has shown that VO2 max (L/mn) is positively correlated to CSI and ISI in young women. The third and the fourth study have shown that being overweight is associated with higher BMC and BMD values but not with TBS values and that TBS is positively associated with VO2 max (L/mn). The fifth main study conducted on 68 young overweight and obese women has shown that vertical jump, VO2 max (L/min), maximal power (watts) and 1-RM half-squat are positively correlated with bone parameters in overweight and obese adult women. The sixth main study has shown that the two training programs (strength and endurance) are effective to increase whole body BMC and lumbar spine BMD, and to decrease body weight and fat mass. Strength training was also effective to increase TBS and composite indices of femoral neck strength (CSI, BSI and ISI)

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Pitocchi, Jonathan. « Quantitative assessment of bone quality after total hip replacement through medical images : 2D and 3D approaches ». Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amslaurea.unibo.it/13023/.

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La valutazione della qualità dell’osso è un passo importante nel campo clinico, sia in condizioni patologiche che non patologiche. In particolare, in pazienti sottoposti ad intervento di sostituzione totale d’anca, la presenza della protesi altera le condizioni di stress fisiologiche del femore, causando un processo di adattamento dell’osso che può avere conseguenze sulla stabilità dell’impianto e sulle condizioni dell’osso. Perciò, è evidente l’importanza di monitorare la qualità dell’osso che circonda lo stelo, sia nel breve che nel lungo termine. A partire da rilevazioni densitometriche effettuate su immagini TC, questa tesi affronta due argomenti principali: 1) miglioramento del protocollo corrente per la valutazione della variazione di densità minerale ossea (tridimensionalmente attorno alla protesi) dopo un anno dall’operazione e applicazione ad un ampio dataset (11 pazienti) per esaminare le differenze tra soggetti; 2) studio di fattibilità su 8 pazienti di nuovi approcci 2D basati su sezioni standard del femore, con lo scopo di ottenere uno strumento per la valutazione della qualità dell’osso che possa essere affidabile per i clinici, ma anche minimamente invasivo per i pazienti, riducendo la dose di radiazione. I risultati dell’approccio 3D suggeriscono che può essere usato come strumento di monitoraggio post-operatorio del paziente. Inoltre la tesi mostra la fattibilità di nuovi approcci 2D, sebbene alcuni limiti devono essere superati prima di poterli utilizzare in ambito clinico.

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Boucher, Philippe. « Régulation nutritionnelle de l'expression des principaux gènes qui contrôlent le métabolisme et la toxicité de l'alcool et du cholestérol alimentaire : CYP2E1, LDL récepteurs, HMG CoA réductase et LRP ». Lyon 1, 1999. http://www.theses.fr/1999LYO1T160.

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Thèses sur le sujet « CO2 density »

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