Dissertations / Theses on the topic 'Acidity'
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1
Crowhurst, Lorna. "Acidity in ionic liquids." Thesis, Imperial College London, 2006. http://hdl.handle.net/10044/1/11301.
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Xu, Xiaohan. "Acidity of Lanthanide Clusters." University of Akron / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=akron1619532111562154.
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Smallbone, Kieran. "The role of acidity in tumour development." Thesis, University of Oxford, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.442910.
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Acidic pH is a common characteristic of human tumours. It has a significant impact on tumour progression and response to therapies. In this thesis, we utilise mathematical modelling to examine the role of acidosis in the interaction between normal and tumour cell populations. In the first section we investigate the cell–microenvironmental interactions that mediate somatic evolution of cancer cells. The model predicts that selective forces in premalignant lesions act to favour cells whose metabolism is best suited to respond to local changes in oxygen, glucose and pH levels. In particular the emergent cellular phenotype, displaying increased acid production and resistance to acid-induced toxicity, has a significant proliferative advantage because it will consistently acidify the local environment in a way that is toxic to its competitors but harmless to itself. In the second section we analyse the role of acidity in tumour growth. Both vascular and avascular tumour dynamics are investigated, and a number of different behaviours are observed. Whilst an avascular tumour always proceeds to a benign steady state, a vascular tumour may display either benign or invasive dynamics, depending on the value of a critical parameter. Extensions of the model show that cellular quiescence, or non-proliferation, may provide an explanation for experimentally observed cycles of acidity within tumour tissue. Analysis of both models allows assessment of novel therapies directed towards changing the level of acidity within the tumour. Finally we undertake a comparison between experimental tumour pH images and the models of acid dynamics set out in previous chapters. This analysis will allow us to assess and verify the previous modelling work, giving the mathematics a firm biological foundation. Moreover, it provides a methodology of calculating important diagnostic parameters from pH images.
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Ceciliani, Francesco. "Taster responses to acidity in white wines." Master's thesis, ISA-UL, 2017. http://hdl.handle.net/10400.5/13344.
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Mestrado Vinifera Euromaster - Instituto Superior de Agronomia - UL / Universitá degli Studi di UdineThe aim of this study was to evaluate the responses of a panel of tasters trained to acidity in white wines. The training of tastes and sensations of the mouth was performed in relation to the acidity, sweetness, bitterness and astringency. Next, the tasters were segmented according to vinotype, sensitivity to PROP (6-n-propylthiouracil) and saliva flow. This panel was used to determine the detection and recognition thresholds of tartaric, malic and lactic acids in white wine with 4.2 g / L of total acidity. The detection and recognition thresholds were 1.05 g/L and 1.32 g/L for tartaric acid, 0.85 g/L and 1.06 g/L for malic acid and 1.12 g/L and 1.30 g/L for lactic acid, respectively. These acids were added to an Arinto wine at concentrations 1.5 times higher than the recognition threshold, obtaining responses regarding the flavor effect considering intensity, persistence, salinity and appreciation. There were no differences (p<0.05) in relation to the first 3 parameters, while the appreciation was higher in relation to lactic and malic acids. The statistical treatment of the responses according to the segmentation revealed relationships (p<0.05) between saliva flow and sensitivity to PROP, and between saliva flow and the tartaric acid recognition threshold. The acidity appreciation was higher in men than in women. The results obtained can be used by the wine industry in the sense of adapting the white wines to the preference of the consumers, taking into account the recent trend towards the consumption of cold climate wines.
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Jacob, Daniel J. Hoffmann Michael R. "The origins of inorganic acidity in fogs /." Diss., Pasadena, Calif. : California Institute of Technology, 1985. http://resolver.caltech.edu/CaltechETD:etd-01112005-133508.
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Doherty, Sean Kevin. "Control of pH in chemical processes using artificial neural networks." Thesis, Liverpool John Moores University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.247329.
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Kidd, Petra Susan. "Aspects of soil acidity and their effect on plant growth." Thesis, University of Stirling, 1998. http://hdl.handle.net/1893/28841.
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The effects of low pH, AI, organic and phenolic acids on the growth of naturally occurring plant species were determined. The amelioration of Al toxicity by Si and organic acids was also investigated. Plants were grown from seeds in nutrient solutions simulating the ionic composition of soil solutions from five soil types ranging from acidic peat to calcareous soil. Soil solutions were extracted and analysed using centrifugation, with and without an immiscible displacent (1,1, I-trichloroethane), at both low (4000 rpm) and high speed (12000 rpm). Races of Holcus lanatus L. and Betula pendula Roth. from acidic soils (FM and SMM) grew better in low pH solutions (pH< 4.0). In acid-sensitive races Ca absorption was inhibited at low pH. Races of B.pendula from strongly to moderately acidic soils (FM, SMM, KP) were AI-tolerant and effectively excluded Al from shoots. Root elongation and leaf expansion were inhibited by all Al concentrations in races from calcareous soils (KR). Low concentrations of Al stimulated growth in some races of B.pendula (2 and 5 mg Al lˉ¹) and Anthoxanthum odoratum L. (1.3 and 2.7 mg Al lˉ¹). Al (25 and 35 mg lˉ¹) inhibited root and shoot growth in H.lanatus. Si (1500 and 2500 µM Si(OH)₄) addition to nutrient solutions alleviated AI-damage and restored nutrient uptake to values similar to those in plants grown with neither Al or Si. The ameliorative effects of Si were possibly achieved through AI/Si co-deposition in the root cell walls and maintenance of Golgi activity. Si at 1500 µM was beneficial but inhibited growth at 2500 µM. Al and hydroxyaluminosilicates at pH 5.6 were not toxic. Formic and tartaric acid ameliorated Al toxicity by reducing its availability. These organic acids on their own stimulated growth in H.lanatus and Deschampsia flexuosa (L.) Trin. Phenolic acids stimulated growth of H.lanatus in acidic solutions (pH 4.0) but not near-neutral solutions, particularly in races from soils high in phenolics. Addition of plant residue to acidic peats increased the growth of races from calcareous and acidic mineral soils.
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Shoghi, Kalkhoran Elham. "Physico-Chemical Characterization of Drugs: Acidity and Solubility." Doctoral thesis, Universitat de Barcelona, 2013. http://hdl.handle.net/10803/98463.
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The aim of the present work was to contribute to establish robust and high throughput methodology of interest in the "Drug Discovery" step commonly done in pharmaceutical laboratories. This purpose involves the exploration of the possibilities of the potentiometric Sirius methodology to determine both acidity constants and solubilities of drugs and other bioactive compounds and also to do a study about how to improve bioavailability of a model drug, Amphotericine 8, by increasing its dissolution rate. In the first part of this project, the acidic dissociation enthalpies and constants of anilinium, protonated tris (hydroxymethyl)- aminomethane (HTris+), benzoic and acetic acids, have been determined at several temperatures in pure water and in methanol/water mixtures by potentiometry method. The pK(a) values determined by this technique are in accordance with those values determined by ITC method in our laboratory and also with those other values from literature. Also dissociation enthalpies can be obtained from potentiometric pK(a) values by means of the Van't Hoff approach and these obtained values are in agreement with those ones determined directly by calorimetry in our laboratory. In the second part, we focused on studying about solubility. The Chasing Equilibrium method offers an alternative to the classical procedures to measure the solubility of compounds with acid-base properties. The method is fast and yields accurate results. In this work, the solubility of several compounds including acids and bases was determined through the Chasing Equilibrium approach. A study of experimental conditions in terms of sample weight was performed to measure solubilities. The study shows that only a limited range of weights, depending on the nature and solubility of the compounds, is adequate to obtain reliable results. In the third part of this work, the solubility vs. pH profiles of five ionizable drugs of different nature (a monoprotic acid, a monoprotic base, a diprotic base and two amphoteric compounds showing a zwitterionic species each one) have been determined through two different methodologies: the classical Shake-Flask (S-F) and the potentiometric Cheqsol methods using in both instances the appropriate Henderson-Hasselbalch (H-H) or derived relationships. The results obtained independently from both approaches are consistent. A critical revision about the influence of the electrolyte used as buffering agent in the S-F method on the obtained solubility values is also performed. Thus, some deviations of the experimental points with respect the H-H profiles can be attributed to specific interactions between the buffering electrolyte and the drug due to the hydrotrophic character of citric and lactic acids. In other cases, the observed deviations are independent of the buffers used since they are caused by the formation of new species such as drug aggregates (cefadroxil) or the precipitation of a salt from a cationic species of the analysed compound (quetiapine). In the forth part, the objective was to compare the dissolution behavior of tablets prepared from solid dispersions prepared in DMSO dissolvent with and without drug-carrier and also with and without surfactants in aqueous and acidic solutions. Amphotericine B was used as a model drug. Two types of carriers were used; mannitol, inulin. Solid dispersions with two different drug loads were prepared by freeze drying method. It was found that the drug dissolution rate in aqueous and acidic solutions was significantly increased in the presence of drug-carrier and surfactants. X-ray powder diffraction revealed that all solid dispersions were fully amorphous.El objetivo del presente trabajo ha sido contribuir a establecer metodología robusta y de high throughput de interés en la etapa conocida como "Drug Discovery" que tiene lugar en los laboratorios farmacéuticos al inicio del proceso de desarrollo de nuevos fármacos. Este objetivo ha implicado la exploración de las posibilidades de la metodología potenciométrica establecida y comercializada por Sirius Analytical Ltd. para la determinación de las constantes de acidez y de la solubilidad de compuestos bioactivos y también un estudio sobre la mejora de la biodisponibilidad de un fármaco muy insoluble tomado como modelo mediante el aumento de su velocidad de disolución. En la primera parte de esta Tesis se han determinado potenciométricamente las constantes de disociación ácida y la variación de entalpía asociada de dos bases y dos ácidos tomados como modelo en agua pura y en mezclas de metanol/agua (0-60% w/w) a varias temperaturas (25-55°C). Esto ha implicado la puesta a punto de la estandarización del sistema potenciométrico en las condiciones de trabajo. Los valores de pK(a) determinados son concordantes con los que ofrece la literatura. Se han calculado también las entalpias de disociación en los distintos solventes binarios estudiados mediante la ecuación de Van't Hoff a partir de los valores experimentales de pK(a). La consistencia de los resultados obtenidos con los de la literatura, obtenidos directamente por calorimetría, confirma la robustez de la metodología. En la segunda parte de este trabajo, el estudio se centró sobre la determinación potenciométrica de la solubilidad de ácidos y bases mediante el método conocido como Chasing Equilibrium, como alternativa a los procedimientos clásicos de equilibración. El método es rápido y produce resultados precisos. Se ha realizado un estudio sobre las condiciones experimentales óptimas en términos de peso de la muestra para medir eficazmente la solubilidad. El estudio muestra que, en función de la naturaleza y solubilidad de los compuestos, existe un intervalo limitado de peso de muestra adecuado para obtener resultados fiables. En la tercera parte de la presente memoria, se estudian los perfiles de solubilidad en función del pH de cinco fármacos ionizables de naturaleza diferente, un ácido y una base monopróticos, una base diprótica y dos compuestos anfóteros que muestran una especie zwitteriónica cada uno. Se han determinado los perfiles de solubilidad mediante el método clásico de equilibración (Shake-Flak, S-F) y el potenciómétrico y, en ambos casos, se han utilizado las relaciones apropiadas de Henderson-Hasselbalch (H-H) o derivadas. Los resultados obtenidos de forma independiente por ambos métodos son consistentes. Se ha hecho un estudio crítico acerca de la influencia del electrolito utilizado como agente tampón en el método S-F en los valores de solubilidad obtenidos y se han observado algunas desviaciones de los puntos experimentales con respecto a los perfiles esperados que pueden ser debidas a interacciones específicas entre el electrolito tampón y el fármaco. En otros casos, las desviaciones observadas son independientes de los tampones utilizados y se pueden atribuir a la formación de nuevas especies tales como agregados iónicos del fármaco en estudio o la precipitación de una sal a partir de una especie catiónica del compuesto analizado. En la cuarta parte de esta memoria el objetivo ha sido estudiar la velocidad de disolución de comprimidos preparados a partir de dispersiones sólidas de un fármaco modelo con y sin portador del fármaco y también en presencia y en ausencia de tensioactivo en soluciones acuosas neutras y ácidas. Como fármaco modelo se estudió la Anfotericina B y se utilizaron como portadores manitol e inulina y como tensioactivos se ensayaron el deoxicolato de sodio (SDC) y el laurilsulfato de sodio (SLS). La difracción de rayos X reveló que el fármaco en estudio se hallaba en estado amorfo en todas las dispersiones sólidas estudiadas. Se puede concluir que la velocidad de disolución del fármaco se incrementa significativamente en presencia de portador y tensioactivo.
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Godsey, Chad B. "Managing soil acidity in no-till production systems /." Search for this dissertation online, 2005. http://wwwlib.umi.com/cr/ksu/main.
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Halldin, Stenlid Karl Joakim. "Quantum chemical predictions of localelectrophilicity (and Lewis acidity)." Thesis, KTH, Skolan för kemivetenskap (CHE), 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-146040.
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Solaiman, Abu Rayhan Mohammad. "Influence of soil acidity factors on Lotus rhizobia." Thesis, Queen's University Belfast, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.356972.
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Meredith, Will. "Geochemical controls on the acidity of crude oils." Thesis, University of Newcastle Upon Tyne, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.394720.
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McGillen, Jessica Buono. "Mathematical modelling of metabolism and acidity in cancer." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:552f9ea8-ac6c-4413-9535-0318e855d85c.
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Human cancers exhibit the common phenotype of elevated glycolytic metabolism, which causes acidification of the tissue microenvironment and may facilitate tumour invasion. In this thesis, we use mathematical models to address a series of open problems underlying the glycolytic tumour phenotype and its attendant acidity. We first explore tissue-scale consequences of metabolically-derived acid. Incorporating more biological detail into a canonical model of acidity at the tumour-host interface, we extend the range of tumour behaviours captured by the modelling framework. We then carry out an asymptotic travelling wave analysis to express invasive tumour properties in terms of fundamental parameters, and find that interstitial gaps between an advancing tumour and retreating healthy tissue, characteristic of aggressive invasion and comprising a controversial feature of the original model, are less significant under our generalised formulation. Subsequently, we evaluate a potential role of lactate---historically assumed to be a passive byproduct of glycolytic metabolism---in a perfusion-dependent metabolic symbiosis that was recently proposed as a beneficial tumour behaviour. Upon developing a minimal model of dual glucose-lactate consumption in vivo and employing a multidimensional sensitivity analysis, we find that symbiosis may not be straightforwardly beneficial for our model tumour. Moreover, new in vitro experiments, carried out by an experimental collaborator, place U87 glioblastoma tumours in a weakly symbiotic parameter regime despite their clinical malignancy. These results suggest that intratumoural metabolic cooperation is unlikely to be an important role for lactate. Finally, we examine the complex pH regulation system that governs expulsion of metabolically derived acid loads across tumour cell membranes. This system differs from the healthy system by expression of only a few key proteins, yet its dynamics are non-intuitive in the crowded and poorly perfused in vivo environment. We systematically develop a model of tumour pH regulation, beginning with a single-cell scenario and progressing to a spheroid, within a Bayesian framework that incorporates information from in vitro data contributed by a second experimental collaborator. We predict that a net effect of pH regulation is a straightforward transmembrane pH gradient, but also that existing treatments are unable to disrupt the system strongly enough to cause tumour cell death. Taken together, our models help to elucidate previously unresolved features of glycolytic tumour metabolism, and illustrate the utility of a combined mathematical, statistical, and experimental approach for testing biological hypotheses. Opportunities for further investigation are discussed.
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Sun, Xiaojiao. "Single molecule studies of acidity in heterogeneous catalysts." Diss., Kansas State University, 2013. http://hdl.handle.net/2097/16423.
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Doctor of PhilosophyDepartment of Chemical Engineering
Keith L. Hohn
Amorphous silica-alumina is widely used as a solid acid catalyst for various reactions in oil refining and the petrochemical industry. The strength and the number of the acid sites in the material are most often believed to arise from the alumina atoms inserted into the silica lattice. The existence of the acidity distribution across the framework is a result of the local composition or the short-range interactions on the silica-alumina surface. Conventional techniques used to characterize silica-alumina provide effective information on the average acidity, but may not reflect the heterogeneity of surface acidity within the material. Recently, it is possible to study individual catalytic sites on solid catalysts by single molecule fluorescence microscopy with high time and space resolution. Fluorophores can be chosen that emit at different wavelengths depending on the properties of the local environment. By doping these fluorophores into a solid matrix at nanomolar concentrations, individual probe molecules can be imaged. Valuable information can be extracted by analyzing changes in the fluorescence spectrum of the guest molecules within a host matrix. In this research, silica-alumina thin films were studied with single molecule fluorescence microscopy. The samples were prepared by a sol-gel method and a wide-field fluorescence microscope was used to locate and characterize the fluorescent behaviors of pH sensitive probes. In mesoporous thin films, the ratio of the dye emission at two wavelengths provides an effective means to sense the effective pH of the microenvironment in which each molecule resides. The goal of this work was to develop methods to quantify the acidity of individual micro-environments in heterogeneous networks. Pure silica films treated with external phosphate solutions of different pH values were used to provide references of the fluorescence signals from individual dye molecules. SM emission data were obtained from mesoporous Al-Si films as a function of Al content in films ranging from 0% to 20% alumina. Histograms of the emission ratio revealed that films became more acidic with increasing Al content. The acidity on interior surfaces in zeolite pores was also of interest in this work. A microfluidic device was built to isolate the interior surface from the exterior surface. Some preliminary results showed the potential of using SM fluorescence method to study the acidic properties inside the pores of zeolite crystals.
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Soleimani, Mostafa. "Thick film sensors for engine oil acidity detection." Thesis, University of Southampton, 2014. https://eprints.soton.ac.uk/364525/.
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Engine oil condition monitoring has attracted considerable interests from industries and general public over the years due to its critical role in maintaining the performance and longevity of cars and industrial engines. Lubricants degrade during the course of operation and can be costly or detrimental to the engine if oil change intervals are not optimised. However, on-line robust monitoring for oils has been very challenging since oil degradation process is often complicated and influenced by a number of parameters, such as the operating temperature and contamination. Due to the complexity of the oil chemistry and their degradation processes, there have not been any commercially available on-line sensors for oil chemical property monitoring reported. Oil acidity is traditionally measured through potentiometric or photometric/colorimetric titration methods. Recent attempts at miniaturising infrared (IR) and chronopotentiometric (CP) sensors based on solid-state devices for acidity/alkalinity determination of oil have not been very successful since the CP technology suffers from sensitivity and stability issues and IR sensors are still bulky and adversely susceptible to the engine‟s harsh environment. This project, sponsored by Shell Global Solutions, aims to develop robust chemical sensors that can detect oil acidity due to oil degradation. The initial comprehensive literature review has identified that thick film (TF) sensor technology offers compact and low cost mass production solutions and have been proved to be robust with good reproducibility for aqueous solutions acidity measurements. Their feasibility in detecting oil acidity was thus investigated in this study and experimental work has been carried out to fabricate TF electrodes and evaluate them in a range of oils to explain their performance in detecting acid content. Based on their performance in aqueous solutions in previous studies, this study has investigated the performance of one type of TF working electrode (Ruthenium Oxide (RuO2)) combined with various TF reference electrodes in order to develop the most suitable electrodes for oils. To simulate oil ageing, a fully formulated engine oil and a base oil were oxidised under controlled conditions. Also, different amount of nitric acid was added to a fully formulated oil to simulate the oil acidity changes. Acid number (AN) of the oil samples was obtained using conventional titration methods and viscosity and conductivity of the oil samples were measured using laboratory-based equipment in order to validate TF sensor measurements and establish a relationship between different properties of oil samples during their degradation process. Temperature effects on thick film electrodes as well as their long-term stability and repeatability were also investigated. The results show that, for the first time, TF sensors respond to the acidity changes in all oil types tested and linear correlation between the TF responses and the AN was found in the oxidised oils within certain ranges at the tested temperatures (50 °C and 80 °C). TF sensors can detect oil acidity up to AN of 28 mgKOH/g. Although oil conductivity and viscosity were affected by the oil oxidation process, but no direct relationship was found between them and the TF responses. Based on the experimental results, sensing mechanisms of the TF electrodes in oils are proposed.
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Sood, Dhiraj S. "The role of strongly acidic media on the formylation of toluene." Diss., Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/10090.
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Kitto, Abdul-Massih N. "Physico-chemical investigation of acidic and basic gaseous and particulate pollutants in the troposphere." Thesis, University of Essex, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.292093.
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Moore, Jonathan D. "Synthetic studies on the Lewis acidity of diboron compounds." Thesis, University of Bristol, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.396640.
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Hadjifilippou, Irineos. "Characterizing the determinants of berry acidity in the grapevine." Master's thesis, ISA/UL, 2018. http://hdl.handle.net/10400.5/17938.
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Mestrado Vinifera Euromaster - Viticulture and Enology - Instituto Superior de AgronomiaGlobal warming is expected to be a major issue for grapevine productivity and sustainability in the long-term future. Major grapevine characteristics at berry level (physiological development and com-position) but also at the whole plant level (e.g. sugar accumulation, malic acid respiration, photosyn-thesis rate etc) are expected to be changed by elevated temperatures. In order to further decipher major berry physiology and development traits, data from two different experimental conditions and V.vinifera genotypes were used. The data set from experiment 1 was obtained from three genotypes (Merlot, G7 and G14 which are interspecific crossings of V. vinifera x V. rotundifolia, (macrovine) and possess the trait VDQA – “Vins de qualité à teneur réduite en alcool”, which produce wines with lower alcohol content. Plants were grown in open field conditions and berry development was mon-itored every week since early stages to over-ripeness providing a full berry development curve. In a second trial,76 genotypes were tested at two key stages, at green stage (just before ripening onset) and at ripe stage (maximum berry volume) to explore the diversity of primary metabolites and cations that exist in a progeny of microvine deriving from a cross. The progeny derived from a crossing of V3 microvine (female dwarf plant) with G14. Data analysis provided important information on berry development at limited number (8 berries maximum) and at large number (hundreds) scale for all parameters (glucose + fructose, tartartic acid,malic acid,potassium). In addition, complex berry pa-rameters such as titratable acidity were calculated on the basis of simple parameters (e.g. anions and cations). Finally, our results showed that the genetic variability of V. vinifera is potentially inter-esting to identify QTLs that can be used in breeding programs to develop new grapevine genotypes more suitable to climate change conditions
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Pathak, Ravi Kant. "Acidity and sampling artifacts of PM2.5 in Hong Kong /." View abstract or full-text, 2004. http://library.ust.hk/cgi/db/thesis.pl?CENG%202004%20PATHAK.
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Thesis (Ph. D.)--Hong Kong University of Science and Technology, 2004.Includes bibliographical references (leaves 122-135). Also available in electronic version. Access restricted to campus users.
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Leonardelli, Lorena. "Grapevine acidity: SVM tool development and NGS data analyses." Doctoral thesis, Università degli studi di Trento, 2014. https://hdl.handle.net/11572/368613.
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Single Nucleotide Polymorphisms (SNPs) represent the most abundant type of genetic variation and they are a valuable tool for several biological applications like linkage mapping, integration of genetic and physical maps, population genetics as well as evolutionary and protein structure-function studies. SNP genotyping by mapping DNA reads produced via Next generation sequencing (NGS) technologies on a reference genome is a very common and convenient approach in our days, but still prone to a significant error rate. The need of defining in silico true genetic variants in genomic and transcriptomic sequences is prompted by the high costs of the experimental validation through re-sequencing or SNP arrays, not only in terms of money but also time and sample availability. Several open-source tools have been recently developed to identify small variants in whole-genome data, but still the candidate variants, provided in the VCF output format, present a high false positive calling rate. Goal of this thesis work is the development of a bioinformatic method that classifies variant calling outputs in order to reduce the number of false positive calls. With the aim to dissect the molecular bases of grape acidity (Vitis vinifera L.), this tool has been then used to select SNPs in two grapevine varieties, which show very different content of organic acids in the berry. The VCF parameters have been used to train a Support Vector Machine (SVM) that classifies the VCF records in true and false positive variants, cleaning the output from the most likely false positive results. The SVM approach has been implemented in a new software, called VerySNP, and applied to model and non-model organisms. In both cases, the machine learning method efficiently recognized true positive from false positive variants in both genomic and transcriptomic sequences. In the second part of the thesis, VerySNP was applied to identify true SNPs in RNA-seq data of the grapevine variety Gora Chirine, characterized by low acidity, and Sultanine, a normal acidity variety closely related to Gora. The comparative transcriptomic analysis crossed with the SNP information lead to discover non-synonymous polymorphisms inside coding regions and, thus, provided a list of candidate genes potentially affecting acidity in grapevine.
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Leonardelli, Lorena. "Grapevine acidity: SVM tool development and NGS data analyses." Doctoral thesis, country:IT, 2014. http://hdl.handle.net/10449/24467.
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Single Nucleotide Polymorphisms (SNPs) represent the most abundant type of genetic variation and they are a valuable tool for several biological applications like linkage mapping, integration of genetic and physical maps, population genetics as well as evolutionary and protein structure-function studies. SNP genotyping by mapping DNA reads produced via Next generation sequencing (NGS) technologies on a reference genome is a very common and convenient approach in our days, but still prone to a significant error rate. The need of defining in silico true genetic variants in genomic and transcriptomic sequences is prompted by the high costs of the experimental validation through re-sequencing or SNP arrays, not only in terms of money but also time and sample availability. Several open-source tools have been recently developed to identify small variants in whole-genome data, but still the candidate variants, provided in the VCF output format, present a high false positive calling rate.
Goal of this thesis work is the development of a bioinformatic method that classifies variant calling outputs in order to reduce the number of false positive calls. With the aim to dissect the molecular bases of grape acidity (Vitis vinifera L.), this tool has been then used to select SNPs in two grapevine varieties, which show very different content of organic acids in the berry. The VCF parameters have been used to train a Support Vector Machine (SVM) that classifies the VCF records in true and false positive variants, cleaning the output from the most likely false positive results. The SVM approach has been implemented in a new software, called VerySNP, and applied to model and non-model organisms. In both cases, the machine learning method efficiently recognized true positive from false positive variants in both genomic and transcriptomic sequences.
In the second part of the thesis, VerySNP was applied to identify true SNPs in RNA-seq data of the grapevine variety Gora Chirine, characterized by low acidity, and Sultanine, a normal acidity variety closely related to Gora. The comparative transcriptomic analysis crossed with the SNP information lead to discover non-synonymous polymorphisms inside coding regions and, thus, provided a list of candidate genes potentially affecting acidity in grapevine
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Leonardelli, Lorena. "Grapevine acidity: SVM tool development and NGS data analyses." Doctoral thesis, University of Trento, 2014. http://eprints-phd.biblio.unitn.it/1350/1/PhD-Thesis.pdf.
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Single Nucleotide Polymorphisms (SNPs) represent the most abundant type of genetic variation and they are a valuable tool for several biological applications like linkage mapping, integration of genetic and physical maps, population genetics as well as evolutionary and protein structure-function studies. SNP genotyping by mapping DNA reads produced via Next generation sequencing (NGS) technologies on a reference genome is a very common and convenient approach in our days, but still prone to a significant error rate. The need of defining in silico true genetic variants in genomic and transcriptomic sequences is prompted by the high costs of the experimental validation through re-sequencing or SNP arrays, not only in terms of money but also time and sample availability. Several open-source tools have been recently developed to identify small variants in whole-genome data, but still the candidate variants, provided in the VCF output format, present a high false positive calling rate. Goal of this thesis work is the development of a bioinformatic method that classifies variant calling outputs in order to reduce the number of false positive calls. With the aim to dissect the molecular bases of grape acidity (Vitis vinifera L.), this tool has been then used to select SNPs in two grapevine varieties, which show very different content of organic acids in the berry. The VCF parameters have been used to train a Support Vector Machine (SVM) that classifies the VCF records in true and false positive variants, cleaning the output from the most likely false positive results. The SVM approach has been implemented in a new software, called VerySNP, and applied to model and non-model organisms. In both cases, the machine learning method efficiently recognized true positive from false positive variants in both genomic and transcriptomic sequences. In the second part of the thesis, VerySNP was applied to identify true SNPs in RNA-seq data of the grapevine variety Gora Chirine, characterized by low acidity, and Sultanine, a normal acidity variety closely related to Gora. The comparative transcriptomic analysis crossed with the SNP information lead to discover non-synonymous polymorphisms inside coding regions and, thus, provided a list of candidate genes potentially affecting acidity in grapevine.
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Lee, Sze Chung. "The acidity and basicity of the atmosphere in Hong Kong /." access abstract and table of contents access full-text, 2006. http://libweb.cityu.edu.hk/cgi-bin/ezdb/thesis.pl?phd-bch-b21471411a.pdf.
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Thesis (Ph.D.)--City University of Hong Kong, 2006."Submitted to Department of Biology and Chemistry in partial fulfillment of the requirements for the degree of Doctor of Philosophy" Includes bibliographical references.
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Li, Yue. "Analysis of acidity in oil-based matrices by infrared spectroscopy." Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=86906.
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The feasibility of employing a portable variable filter array (VFA) infrared spectrometer equipped with a transmission flow cell to quantitatively analyze edible oils for free fatty acids (FFA) was evaluated. The approach to FFA determination was based on a previously reported FTIR method that involves the extraction of FFAs into methanol containing the base sodium hydrogen cyanamide (NaHNCN), which converts the FFAs to their salts, followed by measurement of the carboxylate absorbance at 1571 cm-1 in the spectrum of the methanol phase. The VFA IR spectrometer, which had a relatively weak pulsed IR source, was found to provide insufficient energy for accurate measurement of the carboxylate absorption superimposed on the strong methanol absorption at 1450 cm-1. By changing the extraction solvent to ethanol, good spectra and calibrations having an overall SD of ±0.07% FFA could be obtained. This work in turn led to the investigation of an ethanol solution of NaHNCN as a signal transduction reagent for Acid Number (AN) analysis in mineral-based lubricants, whereby total acidity would be measured by monitoring the decrease of the νC≡N absorption of NaHNCN at 2109 cm-1 as a result of the acid/base reaction. The equivalent response of the νC≡N band to strong inorganic acids and oleic acid demonstrated that NaHNCN, a somewhat weaker base than KOH, fully ionizes organic acids. Calibration standards were prepared by direct addition of oleic acid to the NaHNCN/ethanol solution, and a calibration equation for the determination of AN was obtained by a quadratic fit of the concentration data to the FTIR νC≡N absorbance data. The AN values obtained for ethanolic NaHNCN extracts of used oils by the FTIR method correlated well with those produced by titration of these extracts. Comparison between FTIR and titrimetric AN values (obtained by ASTM Standard Method D664-89) for a set of used oils spanning an AN range of 0.3-5 mg KOH/g showed a reasonably good linear relatiLa praticabilité d'utiliser un spectromètre infrarouge portatif comportant un filtre variable superposé à une barrette de détecteurs (dénommé un spectromètre VFA IR) et équipé d'une cellule d'écoulement de transmission pour analyser quantitativement les huiles de table pour leur teneur en acide gras libre (AGL) a été évaluée. L'approche à la détermination de la teneur en AGL a été basée sur une méthode précédemment élaborée sur un spectromètre infrarouge à transformée de Fourier (IRTF) qui implique l'extraction des AGL dans le méthanol contenant le cyanamide d'hydrogène de sodium, qui convertit les AGL en leurs sels, suivie de la mesure de l'absorbance de carboxylate à 1571 cm-1 dans le spectre de la phase de méthanol. L'Énergie fournie par la source pulsée relativement faible du spectromètre VFA IR s'est avérée insuffisante pour la mesure précise de l'absorption de carboxylate superposée à l'absorption forte de méthanol à 1450 cm-1. En changeant le dissolvant d'extraction en éthanol, de bons spectres et des courbes d'étalonnage ayant un écart-type global de ±0.07% AGL ont pu être obtenus. Ce travail a à son tour mené à la recherche sur l'utilisation d'une solution d'éthanol et de NaHNCN comme réactif de transduction de signal pour une analyse de nombre acide (NA) en huiles lubrifiantes à base minérale, par lequel l'acidité totale soit mesurée par la diminution de l'absorption νC≡N du NaHNCN à 2109 cm-1 comme résultat de la réaction acide-base. La réponse équivalente de l'absorption νC≡N aux acides inorganiques forts et à l'acide oléique a démontré que le NaHNCN, une base légèrement plus faible que le KOH, ionise entièrement les acides organiques. Des solutions étalons ont été préparées par l'addition directe de l'acide oléique à la solution de NaHNCN/éthanol, et une équation de calibrage pour la détermination de NA a été obtenue par un ajustement quadratique des données de co
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Martin, Natasha Kaleta. "Mathematical modelling of tumour acidity : buffer therapy and stromal effects." Thesis, University of Oxford, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.526083.
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Mohd, Saupi Hanim Salami Binti. "Investigation of the acidity of Brønsted acids in ionic liquids." Thesis, Imperial College London, 2018. http://hdl.handle.net/10044/1/58941.
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The Hammett acidity functions (H0) of mixtures of Brønsted acids-ionic liquids were measured using a 13C NMR probe and several UV-Vis probes. Successful measurements for all of the systems were demonstrated using the UV-Vis probes. A suitable probe was chosen and used to measure each mixture with the estimation of H0 values from the 13C NMR probe. The 13C NMR probe can be used to calculate the acidity of the mixtures approximately while the UV-Vis probe gave more precise results. The H0 of Brønsted acids-ionic liquids systems with different acids were successfully measured using the 13C NMR probe. Additional measurements were done using the UV-Vis probe to get a full acidity measurements for each system that cannot be measured using the 13C NMR probe. Finally, the effect on acidity of the cation of the ionic liquid was found to depend on the strength of the acid mixed with ionic liquids. There is no difference in the acidity of mixtures with a weak acid.
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Gao, Xiangming. "Novel electrochemical methods for acidity monitoring : theory, design and application." Thesis, University of Cambridge, 2019. https://www.repository.cam.ac.uk/handle/1810/289710.
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This thesis reports the design and development of novel voltammetric pH sensors for buffered, low-buffered and unbuffered media. pH sensors in stagnant and hydrodynamic environments were designed and developed for performing measurements using square wave voltammetry. Chapter 1 introduces the motivation of this project, the current development of electrochemical sensors, and the basic theory and techniques of electrochemistry concerned within the thesis. The existing development of carbon-based electrochemical sensors and the application of screen-printing technology in sensor fabrication are highlighted. Chapter 2 introduces the screen-printing technology and the fundamental methods of numerical simulation. In addition, reagents, equipment and software packages used in the thesis are listed in this chapter. In Chapter 3, a novel design of quinone derivative-based pH probes is presented for the application in stagnant weakly buffered media (< 1mM), based on previous studies of quinone compounds in buffered media. The results from the weakly buffered system is consistent with the results in buffered systems. To further extend the application of this design in unbuffered media, a numerical model of a pH-sensitive redox particle immobilised on an electrode was developed, which predicted that the accumulation of hydrogen ions near the electrode is the possible limiting factor for the performance of this design in unbuffered media. To develop a pH-monitoring technology for unbuffered media, Chapter 4 reports on the design, fabrication and testing of different electropolymerised-phenol derivative modified electrodes, which overcome the limitation of hydrogen ions accumulation. The results revealed that 2-(methylthio)phenol graphite resin electrodes have high accuracy (ca. 1% error) in unbuffered media, benchmarked by a commercial glass pH meter. This is the first detailed study on the v application of the economical and scalable technology in pH sensing in unbuffered environment. Chapter 5 presents a unique design of electrochemical pH sensors, free from the need to use a glass reference electrode. This design integrates a pH indicator and an internal reference electrode. Different designs of ferrocene screen-printed electrodes were tested as the internal reference electrode. The nafion-coated ferrocene screen-printed electrode showed stable peak potential in a wide pH range (pH 1 - 12) with good durability (stable in 500+ cycles of test). It was then cross connected with an alizarin electrode, forming the pH sensor free from a glass reference electrode. Chapter 6 describes novel designs of hydrodynamic pH sensors. The design of a microfluidic pH sensor modified by poly-sodium salicylate was firstly demonstrated. The sensor showed a Nernstian response in a wide pH range and, in hydrodynamic conditions, provided improved accuracy in unbuffered media compared to the stagnant state. For more convenient measurements, a novel rocking disc electrode was studied for pH sensing, modified with alizarin and poly-salicylic acid as pH indicators. The electrodes modified by both chemicals showed a Nernstian response in buffered media and the highest accuracy in unbuffered media was reached at 50 rpm.
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Lemishko, Tetiana. "Inelastic neutron scattering study of Brønsted acidity in LTA zeolite." Doctoral thesis, Universitat Politècnica de València, 2019. http://hdl.handle.net/10251/119966.
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[ES] En esta tesis se realiza un estudio de acidez de zeolita LTA con la relación Si/Al 5 y 40 utilizando la técnica de dispersión inelástica de neutrones (INS) en combinación con otras tecnicas como la modelización computacional y la espectroscopía de resonancia magnética nuclear (RMN).
Las zeolitas son aluminosilicatos altamente cristalinos que forman parte de un grupo importante de los materiales funcionales. Las zeolitas son extremadamente útiles como catalizadores para muchas reacciones importantes con moléculas orgánicas. Las más importantes son craqueo, isomerización y síntesis de hidrocarburos.
Las propiedades catalíticas de una zeolita dependen principalmente de su acidez y ésta depende de tres factores: el número totál de los sitios ácidos, sus fuerzas individuales y su localización individual, estando estos tres factores relacionados. Los parámetros geométricos definidos por localización de los sitios ácidos (es decir, la longitud y los ángulos de enlaces entre los átomos alrededor del sitio ácido) contribuyen de una manera importante a la fuerza ácida.
En la literatura hay muchos trabajos de estudios de acidez en zeolita utilizando la espectrometría infrarroja (IR), sin embargo, con esta técnica es imposible medir las vibraciones de flexión (bending modes, 200-1200 cm-1), las bandas más sensibles al entorno local de los centros ácidos, ya que estas bandas se superponen con las bandas de vibración de la red de zeolite (300-1800 cm-1).
En esta tesis se realiza un estudio de acidez utilizando la tecnica de INS, que nos permite medir principalmente los modos de vibración de los átomos de H y también nos permite medir todas las bandas de vibración (incluido el bending).
Este estudio muestra que la combinación de la alta calidad de las muestras y la sensibilidad del instrumento utilizado permite detectar con alta precisión los sitios ácidos y obtener la información sobre su posición que a su vez nos perimte obtener la posición de los átomos de Al. Con el fin de interpretar los espectros INS se ha realizado un estudio computacional (cálculos ab-initio) con el objetivo de comparar los espectros cálculados con los resultados experimentales y definir el modelo que reproduce la posición mas probable de los centros ácidos en la muestra.[CAT] En aquesta tesi es realitza un estudi d'acidesa de zeolita LTA amb la relació Si / Al 5 i 40 utilitzant la tècnica de dispersió inelastica de neutrons (INS) en combinació d'altres tècniques com la modelització computacional i la espectroscòpia de ressonància magnètica nuclear (RMN ). Les zeolites són aluminosilicats altament cristal·lins que formen part d'un grup important dels materials funcionals. Les zeolites són extremadament útils com a catalitzadors per a moltes reaccions importants amb molècules orgàniques. Les més importants són craqueig, isomerització i síntesi d'hidrocarburs. Les propietats catalítiques d'una zeolita depenen principalment de la seva acidesa i aquesta depèn de tres factors: el nombre total dels llocs àcids, les seves forces individuals i la seva localització individual, estant aquests tres factors relacionats. Els paràmetres geomètrics definits per localització dels llocs àcids (és a dir, la longitud i els angles d'enllaços entre els àtoms al voltant del lloc àcid) contribueixen d'una manera important a la força àcida. En literatura hi ha molts treballs d'estudis d'acidesa en zeolita utilitzant l'espectrometria infraroja (IR), però és impossible mesurar les vibracions de flexió (bending modes, 200-1200 cm-1) amb aquesta tècnica ja que aquestes bandes es superposen amb les bandes de vibració de la xarxa de zeolita (300-1800 cm-1). La tècnica de dispersió inelastica de neutrons (Inelastic neutron scattering) ha estat utilitzada per estudiar l'acidesa de la zeolita LTA amb diferents relacions Si / Al (per tant diferents c.ontinguts de H en la zeolita). En aquesta tesi es realitza un estudi d'acidesa utilitzant la tècnica de INS, que ens permet mesurar principalment els modes de vibració dels àtoms d'H i també ens permet mesurar totes les bandes de vibració (inclòs el bending). Aquest estudi mostra que la combinació de l'alta qualitat de les mostres i la sensibilitat del instrument utilitzat permet detectar amb alta precisió els llocs àcids i obtenir la informació sobre la seva posició que en el seu lloc ens perimte obtenir la posició d'Al. Per tal de interpretar els espectres INS s'ha realitzat un estudi computacional (càlculs ab-initio) amb la comparació dels espectres calculats amb els resultats experimentals.
[EN] This thesis is dedicated to the study of acidity of LTA zeolites with Si/Al ratios 5 and 40 by using the technique of inelastic neutron scattering (INS) in combination with other techniques such as computational modeling and nuclear magnetic resonance (NMR) spectroscopy. Zeolites are crystalline and microporous aluminosilicates which form one of the most important groups of functional materials. Zeolites are widely used as solid acid catalysts for the wide range of important processes regarding organic molecules. The most important are cracking, isomerization reaction and synthesis of hydrocarbons. The catalytic properties of a zeolite depend strongly on its acidity, and this in turns depends on: the total number of acid sites, their individual strength, and their individual location. These three factors are strongly correlated. Geometric parameters that are defined by the location of the acid site (i.e., bond angles and lengths around the acid site) make a remarkable contribution to the acid strength. There are several studies, found in literatures, typically done by Infrared (IR) or Nuclear magnetic resonance (NMR) technique and dedicated to acidity of zeolites. However, the hydrogen bending modes (200-1200 cm-1), which are found to be more sensitive to local environment, cannot be observed by this technique, since these bands overlap with strong bands of the vibrations of zeolitic framework (300-1800 cm-1). INS technique used in this study allows to detect the bands of vibrations of hydrogen atoms in zeolites (including bending modes). Moreover, this study shows that the combination of an extremely high quality of the samples and the sensitivity of the instrument allows to detect with high precision the acid sites of both high-silica and low-silica zeolites and obtain information about their position. This in its turn gives us the possibility to obtain the aluminium location in zeolites. In order to fully understand the INS spectra we performed ab-initio calculations that allow to interpret the experimental bands and choose a structural model that reproduces the probable location of acid sites in the sample.
Lemishko, T. (2019). Inelastic neutron scattering study of Brønsted acidity in LTA zeolite [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/119966
TESIS
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Binti, Shafiee @. Ismail Nor Sahida. "Carboxylic acid composition and acidity in crude oils and bitumen." Thesis, University of Newcastle upon Tyne, 2014. http://hdl.handle.net/10443/2763.
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As the world’s demand for crude oil increases and the amount of conventional reserves decline, the proportion of high acidity oils being produced is increasing, but this acidity can cause corrosion problems during production and refining. Total Acid Number (TAN) values are often used to predict whether a crude oil may cause corrosion problems and thus affect the value of the oil, although the relationship between TAN and the organic acid composition of oils is not fully understood. This thesis investigate the types of acidic compounds that contribute to acidity in crude oils and the geochemical factors that influence the compositions and concentrations of these compound classes in a suite of oils and bitumens from a variety of different locations, including the North Sea, Venezuela, Canada and California. This work in this thesis includes the development of a modified ASTM D664 titrimetric assay method for measuring acid numbers on small samples of heavy crude oil, core extracts and also isolated maltene and asphaltene fractions. The TAN values in the crude oils and their fractions analysed ranges from 0.04 to 21.24 (mg KOH/g). The results show that in general, the maltene fraction contributes most to the acidity in crude oils, however in some samples a large proportion of the oil TAN is contributed by the asphaltenes, even though they are quantitatively a small percentage of the oil. The geological reasons for the occurrence of oils with these highly acidic asphaltenes are not currently known. The analysis of isolated carboxylic acid fractions from ten oils of different origins, including those from different source depositional environments, levels of biodegradation and thermal maturity, using a gas chromatographic method, showed that the concentrations of total carboxylic acids corresponded well with TAN and biodegradation, indicating that these acidic compounds may be a major control on the acidity in crude oils and that the concentration of these were in turn controlled by the extent of biodegradation. ii Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR MS) was used to characterise a set of North Sea crude oils with TAN values ranging from 0.11 to 7.58 (mg KOH/g oil). This showed that the O2 compound class (assumed to be mainly carboxylic acid “COOH” species) appeared as the dominant compound class under the analytical conditions used, with a strong correlation (r2 = 0.989) of the O2/N ratio with the TAN values of the oils, indicating that these compounds may control the TAN in these samples. This observation also applied to their maltene and asphaltene fractions. The dominant acid species in the high acidity North Sea oils, maltenes and asphaltenes were three and four ringed naphthenic acids. As the TAN of the oils increased, the double bond equivalent (DBE) distributions shifted to higher values indicating that their molecular structures became more highly aromatic. Fourier Transform Infrared (FTIR) spectroscopy potentially offers a much more rapid analysis of acids in oils compared to the ASTM D664 method. This study included the development of a rapid method for the determination of TAN by FTIR spectroscopy of conventional and heavy crude oils using single bounce attenuated total reflectance (ATR) and multi bounce horizontal HATR accessories. Using multivariate data analysis software, a multivariate model that correlates infrared spectra with the TAN value was developed using carbonyl (C=O) absorption bands ranging from 1770 to1650 cm-1. It was found that the correlation of FTIR measured TAN versus ASTM D664 measurements, obtained by multi bounce HATR (r2 = 0.943) were better than correlations produced by single bounce ATR (r2 = 0.812). Based on these findings, the measurement of oil acidity and TAN using FTIR is simpler and faster and also allows the analysis of small sample sizes and avoids other problematic issues such as the fouling of electrodes that can be experienced using the ASTM D664 standard method.
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Wade, Andrew John. "Assessment and modelling of water chemistry in a large catchment, River Dee, NE Scotland." Thesis, University of Aberdeen, 1999. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU133417.
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This thesis describes the water chemistry of the River Dee and its tributaries, and the potential water chemistry changes that may occur under acid deposition and land use change scenarios. Historic water quality and flow records were collated and supplemented with new water chemistry data. These data were analysed in relation to catchment geography and river flow using both mathematical modelling and novel, GIS based techniques. This analysis established the importance of diffuse inputs and highlighted differences between upland and lowland regions in the catchment. In headwater streams, different geological types create hydrochemical source areas that strongly influence stream chemistry whilst in lowland tributaries, agricultural sources are particularly important. In the upland region most major ions were diluted as flows increased, further emphasizing the influence of deeper geological sources on baseflow chemistry, but showing soilwater controls on stormflow composition. The headwaters, which drain predominantly acid rocks, are presently oligotrophic but threatened by the impact of acid deposition and land use change (re-afforestation). In some of the lowland tributaries, increased NO3-N concentrations have resulted from more intensive land management. The potential impacts of acid deposition and land use change were simulated in both upland and lowland catchments by considering existing and new models within a Functional Unit Network. For upland regions this consisted of developing a new, two component hydrochemical mixing model to simulate the spatial and flow-related variations in streamwater acidity. The mixing model was based on End Member Mixing Analysis (EMMA), and site specific end members (alkalinity and Ca) could be predicted from emergent catchment characteristics (soil and land use) using linear regression.
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Ling, Huajuan. "Development of Novel Nanocatalysts for Green Chemical Processes." Thesis, The University of Sydney, 2017. http://hdl.handle.net/2123/17708.
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The key aim of this thesis was to develop titanium-containing mesoporous catalysts (Ti-MCM-41) and supported Pt catalysts on mesoporous materials (Pt/Al-MCM-41) with specific functionality to direct the target reactions by a green method. Both catalysts have high surface area and size-confined nano-pore to enhance the activity for oxidation reactions. A one-pot room-temperature direct synthesis method was developed for a series of amorphous Ti-MCM-41 with and without Brønsted acid sites (BAS). The investigation was focused on the relationship between the acidity and the formation of surface active sites for cyclohexene oxidation using hydrogen peroxide. The formation of intermediates peroxo-titanium and superoxo-titanium was confirmed by diffuse reflectance UV-visible spectroscopy and electron paramagnetic resonance (EPR) spectroscopic studies. The relationships between Ti precursors and the local coordination structure of Ti-MCM-41 were investigated and evaluated in cyclohexene oxidation. DRUV-visible and EPR spectroscopies investigation have provided evidence that the nature of the oxo intermediates formed on contact with H2O2 depends on the intrinsic local structure and environment of the Ti ions. Well dispersed and size-confined Pt nanoparticles into Al-MCM-41 were successfully prepared and evaluated in benzyl alcohol oxidation. With a small amount of acidic OH groups covered by Pt particles over Pt/Al-MCM-41 exhibited excellent conversion and selectivity due to the electron transfer between Pt and the supports. The influence of the alkali-treatment of Pt/Al-MCM-41 on the mesoporous structure for benzyl alcohol oxidation was investigated. Alkali-treatment apparently influenced the pore properties and the surface area of the catalysts. The catalysts prepared with acidic supports had higher conversion than those with alkali-treated catalysts.
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Bigard, Antoine. "Varietal differences in solute accumulation and grape development." Thesis, Montpellier, SupAgro, 2018. http://www.theses.fr/2018NSAM0063.
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Jusqu'à récemment, les variétés destinées à la production de vin (majoritairement V. vinifera) ont été sélectionnées pour forte accumulation en sucres et composés du métabolisme secondaire (arômes, tanins, anthocyanes). Certains paramètres du changement climatique (températures, CO2) accentuent la tendance à l'augmentation des teneurs en sucres à la récolte donnant des vins plus alcooleux. L'augmentation de la teneur en alcool des vins est un phénomène planétaire, avec des augmentations annuelles de 0,16%. Cela altérant le profil qualitatif notamment en impactant l'équilibre alcool/acidité et pose un problème vis-à-vis de la santé des consommateurs.Le raisin est un fruit pulpeux non-climactérique se développant en deux phases. La première est la phase herbacée durant laquelle s’accumule majoritairement les acides maliques et tartriques. Durant cette phase, la baie grossit par mitose et expansion vacuolaire. La deuxième phase de croissance est associée à l'importation massive d'hexoses, d’eau et de potassium. A la fin de la deuxième phase de croissance, le phloème arrête son déchargement et la baie concentre ses principaux métabolites par évaporation. Certaines pratiques œnologiques permettent de réduire les teneurs en sucres des moûts ou en alcool des vins (CEE-606/2009 et CEE-53/2011), mais sont partielles ou coûteuses et peuvent impacter la qualité des vins. Les pratiques culturales ne modifient pas suffisamment le développement du raisin pour être efficaces, sauf à dégrader le potentiel qualitatif de la vendange. Sur le long terme, l'approche la plus prometteuse est la sélection variétale.Ce dernier aspect fut abordé dans le projet de thèse. En premier lieu, de nouvelles stratégies/outils de phénotypage permettant la caractérisation du développement du raisin furent développés. Ensuite, la diversité pour l'accumulation des métabolites primaires dans le raisin (V. vinifera) ou pouvant être généré par croisement avec la microvigne fut analysée. Dans un dernier volet, la caractérisation physiologique de génotypes issus d’un croisement entre V. vinifera et M. rotundifolia présentant un caractère de faible accumulation en sucres durant la maturation des raisins fut approfondie.Les résultats principaux de ce travail indiquent :1) Il est possible d’apprécier le développement d'une population de baies tant en asynchronie (bains densimétriques) qu’en hétérogénéité (Dyostem). La couleur du fruit n’était pas un bon indicateur du début de la maturation, apparaissant 1 à 5 jours après les premier signes de ramollissement des baies. Par ailleurs, les suivis réalisés à l'échelle de population de baies ont montré que pour des analyses fines, il était préférable d’analyser le fruit unique.2) Il existe une grande diversité chez V. vinifera pour ce qui concerne la compositions en métabolites primaires des baies et leurs dilutions. La possibilité de ségréger indépendamment l'accumulation d'eau, des sucres, des acides et des cations fut révélée, ouvrant d’intéressantes perspectives en termes d'innovation variétale.3) L’analyse du caractère faible teneur en sucres chez des descendants de V. vinifera et M. rotundifolia montre que ce caractère ne résulte ni d’une limitation ou d'un décalage de l'accumulation, ni d’une plus grande hétérogénéité/asynchronie des baies. Les résultats suggèrent qu'il existe des différences mécanistiques entre niveau de croissance et pression osmotique du fruit lors de la maturation entre génotypes. Cette découverte soulève de nombreuses questions : existe-t-il des différences dans les structures des parois cellulaires ou de leurs enzymes associées ? Est-ce que les cellules des baies des génotypes à faible teneur en sucres sont plus grosses ou plus nombreuses que les variétés traditionnelles ?Deux de ces descendants ont été croisés avec la microvigne pour détecter les QTLs associés à ce caractère dans l'objectif d'identifier les fonctions contrôlant ce trait d'intérêt agronomiqueUntil recently, varieties used for wine production (mainly V. vinifera) have been selected for high sugar accumulation and secondary metabolism compounds (aromas, tannins, anthocyanins). Some climate change parameters (temperatures, CO2) accentuate the trend towards higher sugar levels at harvest, resulting in more alcoholic wines. The increase in wine alcohol content is a global phenomenon, with annual increases of 0.16%. This alters the qualitative profile, in particular by impacting the alcohol/acidity balance and poses a problem for consumer health.The grape is a non-climacteric fleshy fruit that develops in two phases. The first is the herbaceous phase during which malic and tartaric acids accumulate mainly accumulate. During this phase, the berry grows by mitosis and vacuolar expansion. The second phase of growth is associated with the massive import of hexoses, water and potassium. At the end of the second growth phase, the phloem stops unloading and the berry concentrates its main metabolites by evaporation. Some oenological practices make it possible to reduce the sugar content of must or alcohol wines content (CEE-606/2009 and CEE-53/2011), but are partial or costly and can have an impact on the wines quality. Cultivation practices do not sufficiently modify the development of the grape to be effective, except that they degrade the quality potential of the harvest. In the long term, the most promising approach is the variety selection.The latter aspect was addressed in the thesis project. First, new phenotyping strategies/tools were developed to characterize grape development. Then, the diversity for the accumulation of primary metabolites in grapes (V. vinifera) or that can be generated by crossing with the microvine was analysed. In the last part, the physiological characterisation of genotypes resulting from a cross between V. vinifera and M. rotundifolia with a low sugar accumulation character during grape ripening was further developed.The main results of this work indicate:1) It is possible to assess the development of a berries population both in asynchrony (densimetric baths) and in heterogeneity (Dyostem). The colour of the fruit was not a good indicator of the beginning of ripening, appearing 1 to 5 days after the first signs of berry softening. In addition, monitoring at the berry population level has shown that for fine analyses, it is preferable to analyse the single fruit.2) There is a great diversity in V. vinifera with regard to the composition of primary berry metabolites and their dilutions. The possibility of independently segregating the accumulation of water, sugars, acids and cations was revealed, opening up interesting prospects for varietal innovation.3) Analysis of the low sugar concentration trait in descendants of V. vinifera and M. rotundifolia shows that this characteristic does not result from a limitation or delay in accumulation or from greater heterogeneity/asynchrony of the berries. The results suggest that there are mechanistic differences between growth level and osmotic pressure of the fruit during maturation between genotypes. This discovery raises many questions: are there differences in the cell wall structures or their associated enzymes? Are berry cells of low sugar genotypes larger or more numerous than traditional varieties?Two of these descendants were crossed with the microvine to detect the associated QTLs to this trait in order to identify the functions controlling this agronomic interest trait
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Söderman, Fredrik. "Comparative Population Ecology in Moor Frogs with Particular Reference to Acidity." Doctoral thesis, Uppsala University, Department of Ecology and Evolution, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-6828.
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This thesis is an attempt to describe how different environmental factors influence life history traits in different populations, sexes and developmental stages in the moor frog, Rana arvalis. The studied populations are located along 1100 km latitudinal gradient, with pH varying between 4.0 and 8.5. I have used data from both natural populations and common garden experiments.
Reproducing moor frogs were larger and older at high latitudes, indicating a selective advantage of large size at high latitudes and/or earlier reproduction at low latitudes. When controlling for age I found that frogs were older and smaller at low pH, which may be a result of a reduced growth rate due to acid stress. The both sexes respond differently to different environments, with the lowest sexual dimorphism in body size found in the acid environments. This is possibly caused by a trade-off between growth and reproduction. Being large is considered to be advantageous, in females due to increased fecundity, and in males due to higher ability to compete for mates, while the cost of high growth is a reduced possibility to survive until the next mating season. Moor frog embryos originating from an acid population survived better under acid stress than embryos from a neutral population. Using quantitative genetic techniques I found strong maternal effects and small additive genetic variation for the traits in acid and non acid populations. The variation in acid stress tolerance owed largely to non-genetic effects. Females from acid localities lay larger eggs, which probably improves the performance of tadpoles under acid conditions. The trade-off between egg size and fecundity was stronger in acid populations indicating that females in acid populations reduced fecundity to increase offspring size. Finally, frogs from acidified environments were more asymmetric in skeletal traits further indicating the developmental stress created by acidification.
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Fölster, Jens. "Catchment hydrochemical processes controlling acidity and nitrogen in forest stream water /." Uppsala : Swedish Univ. of Agricultural Sciences (Sveriges lantbruksuniv.), 2001. http://epsilon.slu.se/avh/2001/91-576-6074-3.pdf.
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Bishop, Kevin Harold. "Episodic increases in stream acidity, catchment flow pathways and hydrograph separation." Thesis, University of Cambridge, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239601.
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Stone, Carol E. "Rhizobium strain selection by white clover under conditions of acidity stress." Thesis, Queen's University Belfast, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.335442.
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Brooks, Jenkins Gareth. "Amelioration of acidity in fresh waters : individual to ecosystem level responses." Thesis, Queen Mary, University of London, 2015. http://qmro.qmul.ac.uk/xmlui/handle/123456789/8981.
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The extensive acidification of fresh waters across Europe and North America during the 20th century led to extensive and widespread loss of species, which fundamentally changed the structure of resident communities. While attempts to limit or halt acidifying emissions have been successful in reversing the chemical consequences of acidification, any corresponding biological recovery has been patchy at best. The main aim of this thesis was to investigate potential ecological constraints on this biological recovery, ranging from interactions between individuals to ecosystem-level processes, using a model stream system that has been extensively studied for over 40 years. I used a combination of long-term survey data and experiments, both in the field and the laboratory, to provide evidence that the lag in recovery of acidified aquatic communities is due to intrinsic resistance to re-colonisation by acid-sensitive species, as a result of both direct and indirect interactions between predators and prey. However, there is also evidence of recovery at an ecosystem level, with rates of microbial decomposition increasing – a key link in the transfer of energy to higher trophic levels, which could be facilitating population increases in large-bodied predators. These findings increase our understanding of the drivers which govern the structure and function of ecological networks in response to an important climatic stressor. This is especially relevant given the rapid industrialisation of countries such as India and China, which could well soon experience anthropogenic acidification on a significant scale.
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Weber, Reinier Willem. "The characterization and elimination of the external acidity of ZSM-5." Master's thesis, University of Cape Town, 1993. http://hdl.handle.net/11427/18301.
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The zeolite ZSM-5 is well-known for its unique intersecting channel system. This channel system has a great bearing on the shape-selective properties and the long life-times of ZSM-5. In this study, ZSM-5 was modified in various ways to eliminate the external acidity of the catalyst to further improve these properties, and the success and effects of these modifications were investigated primarily using temperature programmed desorption techniques. The internal surface of ZSM-5, a medium pore zeolite, plays a major role in the shape selective properties of this catalyst, due to the diffusional restrictions imposed by the channel system on bulky molecules. Even though the number of acid sites on the external surface is small compared to the total number of acid sites, these easily accessible and non-shape selective acid sites may provide a high turnover rate for non-shape selective reactions. Furthermore, the main cause of deactivation of ZSM-5 is thought to be the formation of polyaromatic molecules on the external surface, which block access to the channels of the catalyst.
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Demaret, Coralie. "Mise en forme de zéolithes : contrôle des propriétés acides des zéolithes et description de l’interface zéolithe / liant." Thesis, Lyon, 2019. http://www.theses.fr/2019LYSE1042.
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Les zéolithes sont des aluminosilicates cristallins possédant une microporosité organisée et régulière de taille moléculaire. Les zéolithes ZSM-5 sont largement employées dans l’industrie comme catalyseurs acides mais leur application commerciale requiert des objets de taille millimétrique pour leur résistance mécanique, pour diminuer la perte de charge dans les réacteurs et pour diluer l’acidité de la zéolithe, principalement par ajout de liant, peptisant... La mise en forme est l’étape clé dans le processus d’industrialisation d’un catalyseur car les additifs peuvent modifier les propriétés intrinsèques de la zéolithe après mise en forme. Les objectifs de la thèse sont donc d’identifier et de rationaliser les conséquences physico-chimiques de la mise en forme sur les propriétés des zéolithes en étudiant l’accessibilité, la concentration et la force de leurs sites acides, ainsi que de décrire la nature de l’interface zéolithe/liant. Pour cela, une approche multi-techniques a été mise en œuvre. Elle combine des mises en forme modèles, tout en faisant varier la nature du liant et de la zéolithe ZSM-5, des caractérisations texturales, spectroscopiques (infra-rouge, RMN) et de microscopies, de l’acidité (adsorption-désorption de molécules sondes suivies par analyses thermiques et spectroscopiques), et tests catalytiques modèles. La caractérisation des propriétés des zéolithes utilisées dans cette étude (de différentes tailles de cristaux et de différents rapports Si/Al) a été menée préalablement à celles des matériaux mis en forme. Les grands cristaux de zéolithes se sont révélés plus acides mais moins actifs en catalyse. Une partie des Al des petits cristaux forment des aluminols dont l’acidité est plus faible que celle des sites pontés. De plus, l’ensemble des sites pontés ne contribue pas à la réaction catalytique, seule une partie du cristal est efficace. Durant ce travail, deux types de liants ont été utilisés : l’alumine et la silice qui sont largement employées dans l’industrie. Le but a été de mettre en évidence, dans un premier temps, les effets de la mise en forme sur une zéolithe et un liant donné puis d’estimer l’impact de la nature de la zéolithe (taille de cristal et rapport Si/Al). Pour le liant de type alumine, un bouchage partiel de la microporosité est suspecté indépendamment de la taille des cristaux et du rapport Si/Al de la zéolithe. Un phénomène d’alumination de la structure de la zéolithe par création de sites pontés a été mis en évidence. Pour le liant de type silice, le paramètre critique à prendre en considération lors de la mise en forme est sa teneur en cations sodium. Le phénomène d’échange ionique a été mis en évidence, les propriétés acides et catalytiques des catalyseurs s’effondrent mais de manière réversible. Cet effet augmente quand la taille des cristaux de zéolithes diminue et quand le rapport Si/Al augmenteZeolites are crystalline and microporous aluminosilicates with an ordered and regular structure of molecular dimension. ZSM-5 zeolites are widely used in the industry as acid catalysts but their commercial application requires millimeter-sized bodies for mechanical strength and dilution of the zeolite acidity mainly, by addition of binder, peptizer... Shaping of zeolite is the key step of the process for the industrialization of a catalyst because the additives may modify the intrinsic properties of zeolites after shaping. The aims of this PhD thesis are to identify and rationalize the physico-chemical impacts of shaping on the zeolite properties by studying the accessibility, the concentration and the strength of acid sites, as well as to describe the zeolite/binder interface. To do this, a multi-technical approach was set up. It combines model shaped materials, by varying the type of binder and ZSM-5 zeolite, textural, spectroscopic (IR, NMR) and acid characterizations, microscopy and catalytic testing. The characterization of zeolites used in this study (various crystal sizes and Si/Al ratios) was carried out prior of those of shaped materials. Large crystals have been shown more acid but less active in catalysis. Some of Al of the small crystals form aluminols whose acidity is weaker than that of bridging sites. Moreover, all the bridging sites do not contribute to the catalytic reaction, only a part of the crystal is efficient. During this work, two types of binders were used: alumina and silica which are widely used in the industry. The strategy was to highlight, in a first step, the shaping impacts on a ZSM-5 and a given binder and then, to estimate the impact of the zeolite nature (crystal size and Si/Al ratio). For the alumina-type binder, a partial pore blocking is suspected, independently of the crystal size and the Si/Al ratios. A phenomenon of alumination of the zeolite structure was found. For the silica-type binder, the critical parameter is the content of sodium cations inside the binder before the shaping. An ion exchange phenomenon was highlighted and the acid and catalytic properties of the materials collapse but in a reversible way. This impact increases when the crystal size decreases and when the Si/Al ratio increases
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Durán-Klie, Gabriela. "Étude du comportement de l’uranium et de l’iode dans le mélange de fluorures fondus LiF-ThF₄ à 650 °C." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS268/document.
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Le Réacteur Nucléaire à sel fondu à spectre rapide (Molten Salt Fast Reactor, MSFR) est un concept innovant de quatrième génération développé par le CNRS depuis 2004 et actuellement étudié dans le cadre du projet européen SAMOFAR de H2020. Le MSFR fonctionne avec un combustible nucléaire liquide constitué d’un mélange de sels fluorures LiF-ThF₄-(UF₄/UF₃) (77,5-20-2,5) mol% fondus à haute température (700-900°C). Ce réacteur est particulièrement intéressant pour le cycle de combustible du thorium (²³²Th-²³³U). Ce concept propose un retraitement intégré du combustible nucléaire basé sur des méthodes pyrochimiques afin d’extraire la matière fissile et de séparer les actinides des produits de fission.Un schéma de traitement du sel combustible, proposé lors d’un précédent projet européen (EVOL, FP7), est basé sur les propriétés redox et acido-basiques des éléments produits par les réactions de fission et de capture ayant lieu dans le cœur du réacteur. La base d’évaluation de ce schéma a été dans un premier temps thermodynamique. Une validation expérimentale est actuellement en cours qui consiste à étudier le comportement chimique et électrochimique du sel fondu et des éléments qui y sont solubilisés. Les études précédentes sur les réacteurs sels fondus ne peuvent être utilisées que partiellement pour ce concept car la composition du sel du MSFR définie par le projet européen EVOL est différente en nature et composition des sels proposés jusqu’à présent pour ce type de réacteurs. Or, les coefficients de diffusion et d’activité dépendent des propriétés physico-chimiques du sel fondu (en particulier de la solvatation) et nous avons, lors d’études précédentes, montré que les propriétés de solvatation des sels fondus dépendent fortement de leur nature et de leur composition.Les objectifs de ce travail de thèse sont l’étude du mélange fondu LiF-ThF₄ et du comportement électrochimique de l’uranium et de l’iode dans ce mélange.L’étude électrochimique du comportement de l’uranium a montré la stabilité de deux espèces solubles (UF₄ et UF₃) de cet élément dans le milieu fondu et la possibilité de le réduire à l’état métallique. Ce point est d’importance car la co-existence de ces deux composés permettra de contrôler le potentiel du sel combustible dans le cœur du réacteur et de limiter les réactions de corrosion avec les matériaux de structure. Les coefficients d’activité de U(IV) et de U(III) ont été déterminés. Les valeurs obtenues montrent que la solvatation de l’uranium au degré d’oxydation (IV) par les ions fluorure est beaucoup plus importante que celle de l’uranium au degré (III), ce qui est en accord avec des observations ultérieures dans d’autres sels fluorures. Notre choix pour l’étude des produits de fission dans le sel combustible s’est porté sur l’iode. Dans le cœur du réacteur, la forme stable de l’iode est la forme halogénure soluble I- et dans le schéma général de traitement du sel combustible, il est prévu d’extraire l’iode par une étape de fluoration qui permet de produire le gaz I₂. Cette étude a montré la contribution d’une réaction chimique à l’oxydation des ions iodures en iode gazeux. Cette réaction chimique d’oxydo-réduction correspond à l’oxydation des ions iodures par l’oxygène. Cette réaction n’est expliquée que par l’existence d’un oxyfluorure de thorium soluble ThOF₂. Une efficacité d’extraction de I₂ (g) supérieure à 95 % a été obtenue par électrolyse à potentiel contrôlé. Ces électrolyses, qui simulent la fluoration, permettent de valider l’étape d’extraction de l’iode dans le schéma de traitement.Ce travail de recherche a permis d’acquérir une meilleure connaissance de la stabilité du sel et du comportement chimique et électrochimique de différents composés (U et I) dans le selThe Molten Salt Fast Reactor (MSFR) is an innovative concept of GEN IV developed by the CNRS since 2004. It is currently studied in the framework of the European project SAMOFAR of H2020. The MSFR operates with a liquid nuclear fuel consisting of a mixture of fluoride salts LiF-ThF₄- (UF₄ / UF₃) (77.5-20-2.5) mol% melted at high temperature (700-900° C). This reactor is particularly advantageous for the thorium fuel cycle (²³²Th-²³³U). This concept proposes an integrated reprocessing of the nuclear fuel based on pyrochemical methods in order to extract the fissile material and to separate the actinides from the fission products.A scheme for the treatment of the fuel salt, proposed in a previous European project (EVOL, FP7), is based on the redox and acido-basic properties of the elements produced by the fission and capture reactions occurring in the reactor core. The baseline for this scheme was initially thermodynamic. Experimental validation is currently under way to study the chemical and electrochemical behavior of the molten salt and the elements solubilized therein. Previous studies on molten salt reactors can only be partially used for this concept because the composition of the MSFR salt defined by the European EVOL project is different from the composition of the salts proposed up to now for this type of reactor. However, the diffusion and activity coefficients depend on the physicochemical properties of the molten salt (in particular solvation) and in previous studies we have shown that the solvation properties of molten salts are strongly dependent on their nature and their composition.The objectives of this thesis are the electrochemical characterization of the molten mixture LiF-ThF₄ and the study of the electrochemical behavior of uranium and iodine.The electrochemical study of the behavior of uranium shows the stability of two soluble species (UF₄ and UF₃) of this element in the molten medium and the possibility of its reduction to the metallic state. This point is important because the co-existence of these two compounds will make possible to control the potential of the fuel salt in the core of the reactor in order to limit the corrosion reactions with the structural materials. The activity coefficients of U (IV) and U (III) were determined. The values obtained show that the solvation of uranium to the degree of oxidation (IV) by fluoride ions is much greater than that of uranium to degree (III), which is in agreement with subsequent observations in other fluoride salts.Our choice for the study of fission products in the fuel salt has focused on iodine. In the core of the reactor, the stable form of the iodine is the soluble halide form I- and in the general scheme of treatment of the fuel salt, it is planned to extract iodine by a fluorination step in order to produce the gaseous compound I₂. The electrochemical study shows the contribution of a chemical reaction to the electrochemical oxidation of iodide ions in gaseous iodine. This redox chemical reaction corresponds to the oxidation of the iodide ions by oxygen. This reaction is explained for the existence of a soluble thorium oxifluoride ThOF₂. Extraction efficiencies of I₂ (g) greater than 95% were obtained by electrolysis at controlled potential. These electrolysis, which simulate fluorination process, make it possible to validate the method for the extraction of the iodine in the reprocessing scheme.This research has led to a better understanding of salt stability and of the chemical and electrochemical behavior of several compounds (U and I) in the molten salt
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Keenan, Matthew. "The influence of dopants on the surface properties of zirconia." Thesis, Nottingham Trent University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389703.
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Webb, Steven D. "Mathematical oncology and periodic wave train forcing." Thesis, Heriot-Watt University, 2000. http://hdl.handle.net/10399/521.
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Washington, N. "In vitro and in vivo evaluation of antacid and anti-reflux formulations." Thesis, University of Nottingham, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.376161.
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Heathcote, David M. "The reactivity of courmaran-2-ones in aqueous solution." Thesis, University of Huddersfield, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.285667.
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Chung, Meng-Chen. "Chemical composition and transport of ambient aerosols." Thesis, University of Essex, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.298838.
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Santos, Ricardo Filipe Reis dos. "A cultivar e o local de produção influenciam a qualidade do melão "pele de sapo"." Master's thesis, ISA/UL, 2015. http://hdl.handle.net/10400.5/11111.
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Mestrado em Engenharia Agronómica - Instituto Superior de AgronomiaThis study sought to assess the influence of cultivar and site quality of “Pele de Sapo” melon types. The cultivars studied where “MP 3177”, “Hidalgo”, “Rabal” and “Ruidera”. For this purpose were conducted three trials in Santarem, in Évora and in Amareleja. After the harvest, the melons were to three types of procedures, to determine the quality of the fruit of the twelve combinations Location x Cultivar, in first place the measurement of soluble solids content and titratable acidity, in second sensory tests, and at last the correlations performed between the first two. One of the conclusions is that the melons with a soluble solids content higher than 13º Brix are well accepted by consumers, it also concluded that to determine the exact date of harvest should be carried out sampling and it is recommended to Harvesting when the SSC is above 13ºBrix. Analysing the data, another conclusion obtained, is that the fruits” ripeness is central to their organoleptic characteristics and their acceptance by the consumer. We can also say that the “Rabal” cultivar is excluded, either by poor performance on consumer due to the weak resistance to fungus, on the other hand the cultivar "Ruidera" proved susceptible to mildew attack leading to low production and fruits of lesser quality. The “Hidalgo” and “MP3177” were the most resistant to powdery mildew. In other varieties it was necessary to harvest only plants not attacked for not affect the quality of melon. It is recommended that the cultivar "Hidalgo" can begin to be planted in early May to begin to be harvested in mid-July, while the "MP3177" can be planted until mid-July, ensuring crops until October
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Jin, Xiaojing. "Preparation of amorphous silica-aluminas with enhanced acidic properties and spectroscopic identification of their acid sites." Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066355/document.
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Des silice-alumines (SA) avec des propriétés acides améliorées et une fraction plus élevée d’aluminium acides ont été préparées en utilisant deux stratégies de synthèse. Leurs propriétés texturales ont été étudiées par physisorption de N2 et leurs propriétés acides par suivi FTIR de l’adsorption de molécules sondes (pyridine ou CO). Par ailleurs, la réaction d’isomérisation du 33DMB1 a été utilisée pour caractériser leurs performances catalytiques et leurs propriétés acides. La première stratégie de synthèse a été de désaluminer des silice-alumines commerciales avec de l’acetylacetone ou de l’acide citrique (CA). CA est plus actif et plus sélectif que Acac et permet de retirer jusqu’à 87% des Al initialement présents tout en augmentant la quantité de sites acides (jusqu’à 41%) et en multipliant par 5 la fraction d’Al acides. La seconde stratégie a été de greffé des précurseurs d’aluminium (Al(OPri)xL3-x, TIBA, DiBAH) sur des silices. Toutes les SA obtenues par greffage présentent une activité catalytique plus élevées que les SA commerciales et la zéolithe, mais seules certaines de SA obtenues par greffage de DiBAH ont des sites acides de Bronsted forts. Des SA représentatives de ces deux séries ont été caractérisées par RMN, avec comme objectif d’étudier la structure des sites acides en utilisant des séquences RMN 1D et 2D, homo- et héteronucléaires impliquant 1H et 27Al. Cette étude a mis en évidence: (i) la présence, pour la plupart des SA, de deux phases, l’une d’alumine, l’autre de silice alumine (27Al DQ-SQ NMR); (ii) une localisation des atomes d’Al près de la surface sur la base de leur flexibilité de coordination 27Al NMR (DP and 3Q MAS); (iii) l’implication possible des AlV (en plus des AlIV) dans les sites acides de Bronsted (27Al-1H D-HMQC 2D NMR); (iv) la probable différence de structure des sites acides des SA par rapport à ceux des zéolithes (1H-27Al REAPDOR)ASAs with enhanced acidity and a higher fraction of acidic Al were prepared by two experimental strategies. Their textures have been investigated by N2 adsorption–desorption and their acidic properties by FTIR of adsorbed probe molecule (pyridine or CO). Besides, isomerization of 33DMB1 was selected as model reaction to check their activity and characterize their acidity. The first strategy is based on dealumination of commercial ASAs with acetylacetone (Acac) or citric acid (CA). CA is superior to Acac for selective dealumination. It allows removing up to 87% of Al, increases total acidity up to 41%, and fraction of acidic Al by a 5 fold factor. The second strategy is based on the grafting Al precursor (Al(OPri)xL3-x, TIBA, DiBAH) on silica. All the grafted ASAs display better performance for 33DMB1 isomerization than commercial ASA and zeolite, but strong Brønsted acid sites are observed solely for some DiBAH derived samples. Representative samples of these two series were selected as model ASAs for advanced NMR characterization, with the purpose to investigate the structure of acid sites by a combination of one and two-dimensional homo- and heteronuclear 1H and 27Al NMR. On most ASAs, two separate phases are present: alumina and silica-alumina (27Al DQ-SQ NMR). Localization of most of the Al atoms was evidenced based on the flexibility of their coordination (27Al NMR DP and 3Q MAS). Brønsted acidity may be associated with both AlIV and AlV (27Al-1H D-HMQC 2D NMR) but the structure of these sites is probably different from those of zeolites (1H-27Al REAPDOR)
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Smith, Carol M. S. "Assessment of critical loads of acidity for selected U.K. upland organic soils." Thesis, University of Aberdeen, 1993. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU555089.
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The use of critical loads of acidity to quantify damage to sensitive components of terrestrial and aquatic ecosystems has developed rapidly over the last decade. While much work has focused on defining damage to forested ecosystems, surface waters and groundwaters, there has been little work done on defining critical loads of acidity for ombrotrophic and minerotrophic peat. This thesis presents a modelling approach to quantify damage to ombrotrophic peat ecosystems, since such damage can result in a decline in both surface water quality and the ability of peat to act as an absorbent to aerial pollutants. Initial investigations were concerned with the factors which could be included in investigations of critical loads of N and acidity to the surface organic horizons of forest and moorland soils. The modelling approach was then developed from a series of laboratory-based simulation experiments to investigate the effect of contents of H&'43 , Ca2&'43 and Mg2&'43 in rainfall upon the chemistry of the peat ion exchange complex. The basic tenet of the modelling approach was that ion exchange equilibria for peat is rapid, mineral input to the surface of ombrotrophic peat from mineral weathering is negligible and that atmospheric inputs of wet and dry deposition will dominate the peat chemistry. These simulation experiments provided peat pH values resulting from equilibration with the simulated rainfall. By combining these with databases of atmospheric depositon for the U.K., critical loads of acidity and the present day peat pH were calculated and mapped. The critical load values for peat thus obtained were incorporated in the U.K. Critical Load mapping program, which was used to support the on-going European negotiations of emission reduction within the United Nations Convention on Long-range Transboundary Air Pollution (U.N. E.C.E. C.L.T.A.P.).
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Wu, Xianchun. "Acidity and catalytic activity of zeolite catalysts bound with silica and alumina." Diss., Texas A&M University, 2003. http://hdl.handle.net/1969.1/561.
Full textAbstract:
Zeolites ZSM-5 (SiO2/Al2O3=30~280) and Y(SiO2/Al2O3=5.2~80) are bound with silica gel (Ludox HS-40 and Ludox AS-40) and alumina (γ- Al2O3 and boehmite) by different binding methods, namely, gel-mixing, powder-mixing and powder-wet-mixing methods. The acidities of the bound catalysts and the zeolite powder are determined by NH3-TPD and FTIR. The textures of these catalysts are analyzed on a BET machine with nitrogen as a probe molecule. The micropore surface area and micropore volume are determined by t-plot method. Micropore volume distribution is determined by Horvath-Kawazoe approach with a cylindrical pore model. Mesopore volume distribution is determined by BJH method from the nitrogen desorption isotherm. Silica from the binder may react with extra-framework alumina in zeolites to form a new protonic acid. SiO2-bound catalysts have less strong acidity, Bronsted acidity and Lewis acidity than the zeolite powder. Also, the strength of strong acid sites of the zeolites is reduced when silica is embedded. Micropore surface area and micropore volume are reduced by about 19% and 18%, respectively, indicating some micropores of ZSM-5 are blocked on binding with silica. SiO2-bound ZSM-5 catalysts have less catalytic activity for butane transformation (cracking and disproportionation) and ethylene oligomerization than ZSM-5 powder. When alumina is used as a binder, both the total acid sites and Lewis acid sites are increased. Micropore surface area and micropore volume of ZSM-5 powder are reduced by 26% and 23%, respectively, indicating some micropores of ZSM-5 are blocked by the alumina binder. Alumina-bound catalysts showed a lower activity for butane transformation and ethylene oligomerization than ZSM-5 powder. Alkaline metals content in the binder is a crucial factor that influences the acidity of a bound catalyst. The metal cations neutralize more selectively Bronsted acid sites than Lewis acid sites. Alkaline metal cations in the binder and micropore blockage cause the bound catalysts to have a lower catalytic activity than the zeolite powder.