Dissertations / Theses on the topic 'Bulk chemical'

PEDOT:PSS was investigated, using the dopants TWEEN 80 and MEK. The mixture was applied as a thin film on a PET substrate using three techniques, spincoating, dipcoating and spraycoating, with an aim to produce a bulk manufacturing conductive material. The dopants also improved the film forming of PEDOT:PSS. There was a problem with adhesion and durability of the film to the substrate. Several different materials were investigated to solve this problem. The adhesion problem was solved by adding a layer of methyl cellulose between the substrate and the PEDOT:PSS layers which acted as an adhesion promotor. One of the aims of this project was to determine a bulk manufacturing method which is viable for PEDOT:PSS. Three manufacturing techniques were investigated to see how this affected the film quality, film conductivity, thickness, orientation, and durability. Spincoating gave thinner films with a final thickness of 1- 2 µm and was more conductive than films manufactured using dipcoating or spraycoating. Spincoated films made using the dopants enhanced the bulk conductivity of the starting material by two orders of magnitude from 1494 Ωcm for the 100 % PEDOT:PSS dispersion used as a starting material, to 25 Ωcm for the doped 97.22 % PEDOT:PSS. The dipcoated and spraycoated samples were enhanced by three orders of magnitude, although, overall the spincoated samples were the most conductive. The enhanced 95 % to 98 % PEDOT:PSS dispersion with additives TWEEN 80 and MEK samples, remained more conductive than the starting material even after 62 weeks of storage under air. It was found that storage under air caused an increase in resistivity over the stored time period in doped PEDOT:PSS and 100% PEDOT:PSS films. High voltage studies up to 50V proved the material withstands repeated high voltage application over a period of 62 weeks. The mechanism of charge transport in the 97 % and 98 % PEDOT:PSS samples was found, using UV, to be due to the formation of polarons. Polaron charge carriers were formed when the polymer became ionised, lost an electron, and formed a positive charge on the polymer chain. In order to stabilise this the PEDOT molecule changes shape from the aromatic to the quinoid conformation. The most conductive films were found to be predominantly in the quinoid form whereas the less conductive films were mainly aromatic.

Phthalocyanines films have been noted for their use as chemical sensors by measuring changes in conductivity when a gas is adsorbed at the surface. The sensing mechanism is not well understood. This work uses iron phthalocyanine as a model in an attempt to understand the gas sensing mechanism of metal phthalocyanines. The alpha and beta polymorphs of iron phthalocyanine (FePc) have been synthesised and then studied using infra-red spectroscopy, scanning electron microscopy (SEM), gas sensing experiments and Mossbauer spectroscopy. Infra red spectroscopy indicates that a phase change occurs at 205°C and SEM work confirms this since the microcrystallite size changes at this temperature. Gas sensing work has shown that FePc responds to NO[2] and Cl[2] at room temperature. Variable temperature transmission mode Mossbauer spectroscopy of both phases showed that the alpha phase has a lower recoil free fraction at room temperature than the beta phase suggesting that the beta phase has a more rigid structure i.e. it is less free to vibrate in the lattice than the alpha phase. This also explains the difficulties experienced in attempts to collect backscatter spectra from alpha FePc. Backscatter Mossbauer spectroscopy has been used in vitro to show a difference at ambient temperature and pressure, of beta FePc before and after exposure to a gas. Conversion electron Mossbauer spectroscopy indicates that NO[2] adsorbs on to the surface of the FePc film preventing the escape of conversion electrons, and conversion x-ray experiments have shown that the NO[2] penetrates the near surface causing a chemical change.

Garnets are major silicates from the upper mantle to the transition zone. Elastic properties of garnets are essential to interpret the variation of seismic velocities at different depths and construct a model of the Earth’s composition. Due to the chemical flexibility at octahedron sites of the crystal structures, garnets usually exist with multiple components and have many composition variations. Pyrope is an important member in the garnet group. Fe2+-Mg2+ substitution in pyrope is one of the common solid solutions. We have synthesized and measured three synthetic solid solutions samples (Py83Alm17, Py54Alm46 and Py30Alm70). Equations of state yielded their isothermal bulk moduli K0 to be 172(4)GPa, 174(2)GPa, and 183(2)GPa, respectively, which confirmed that almandine content (Fe2+ substitution) increased the bulk modulus of the garnet. A relation between the bulk modulus and the almandine mole fraction (n) was derived to be K0 = 170 + 15 n, showing it is a nearly ideal mixing model. Another factor that also significantly influences the elasticity of pyrope is water. Water is transported to the deep Earth by subduction slabs and mainly exists in nominally anhydrous minerals (NAM) as hydroxyl (OH-). Its content in minerals varies as depth increases. We therefore investigated pressure influence on water solubility in pyrope. A suite of pyrope single crystals was synthesized in a water-saturated environment at 6, 7, 9 and 12GPa and water was characterized by FTIR. IR spectra showed a typical peak at 3630 cm-1. At 9 and 12GPa, new peaks at 3572 cm-1 and 3504 cm-1 appeared and indicated that a new substitution mechanism, other than hydrogarnet substitution SiO4=(OH)4, was adopted in the pyrope crystal structure. Water solubility in pyrope reached 0.2wt% at 7GPa. From 4-7GPa, water solubility increased. At 9GPa, water content dropped to 0.07wt% and increased to 0.3wt% at 12GPa, where a cubic to tetragonal phase transition was observed. Water showed a weakening effect on the bulk moduli of hydrous pyrope. Their bulk moduli were 166GPa, 173GPa and 161GPa with water contents of 0.07wt%, 0.1wt% and 0.2wt%, respectively. An approximate linear relationship was proposed about the bulk modulus as a function of water content.

Thesis (M. Eng. in Logistics)--Massachusetts Institute of Technology, Engineering Systems Division, 2003.
"June 2003."
Includes bibliographical references (leaves 99-100).
A logistics cost model is developed for a chemical distribution system from a single plant using bulk and packaged transportation strategies. The purpose of this research is to provide a tool that helps understand the cost trade offs in the operation of a logistics system at a strategic level for large scale systems and complex distribution systems. An analytical modeling approach was used to determine variables that define transportation, storage and material handling costs in the system. Several distribution strategies were evaluated and benchmarked in terms of costs against the current. Savings offered by the packaged distribution system for a single plant were marginal; extension of the current model to evaluate cost reduction opportunities across the complete network of plants and distribution centers is proposed for further research effort.
by Jose Joaquin Hernandez Lopez.
M.Eng.in Logistics

Modelling and simulation play an essential role in developing, optimizing and understanding the steps involved in the production of polymers. A simulator was designed in order to model free-radical bulk and solution homopolymerizations, as well as multi-component polymerizations. Several optional models were incorporated in to the simulator, such as several glass transition temperature models, and the penultimate model. Java(TM) was selected as the programming language because of its object-oriented nature, providing high flexibility and ensuring easy extension of the code. Once the simulator was validated against experimental data and another simulator, it was used to model three systems: butyl acrylate/vinyl acetate (BA/VAc), styrene/butyl acrylate (Sty/BA), and butyl acrylate/methyl methacrylate/vinyl acetate (BA/MMA/VAc). (Abstract shortened by UMI.)

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemical Engineering, February 2016.
Cataloged from PDF version of thesis.
Includes bibliographical references.
The self-assembly of globular protein-polymer diblock copolymers represents a promising technology for protein nanopatterning. The self-assembled materials have a high density of proteins and internal nanostructures that serve as continuous transport pathways for substrates, products, cofactors, and/or charges. The polymer block can act as a protective matrix for the protein, improving its stability and longevity in materials. The self-assembly of protein-polymer diblock copolymers is substantially different from that of traditional synthetic diblock copolymers due to the globular and rigid shape, heterogeneous composition, and anisotropic interactions of proteins. This thesis focuses on the control of nanostructures in self-assembled materials with a goal to gain a better understanding of the governing principles in self-assembly. This thesis presents experimental studies on the effect of modulated interactions between protein and polymers on the self-assembly of globular protein-polymer block copolymers. Bioconjugates composed of a model red fluorescent protein, mCherry, and a synthetic homopolymer with different chemical moieties are synthesized. Modulated interactions between protein and polymer by introducing polymer blocks with different hydrogen bonding capabilities change order-disorder transition concentrations in solution and the type of nanostructures formed. Bioconjugates with a weakly segregating polymer block are found to form a double gyroid structure with Ia3d symmetry, as opposed to perforated lamellae of bioconjugates with a strongly segregating polymer block. Common phase behaviors are also revealed, including the order of lyotropic order-order transitions and a re-entrant disordering behavior at high concentrations. Birefringence of the disordered solutions with increasing protein fraction suggests the formation of a nematic liquid crystalline phase arising from protein interactions. Self-assembly of proteinzwitterionic polymer bioconjugates shows that electrostatic segregation of mCherry constitutes one of the major driving forces for microphase separation. Nanostructures of the conjugates are further controlled by changing solvent selectivity. Important considerations in preparing bioconjugate thin films are also presented and discussed. Surface effects as well as kinetics such as solvent evaporation rate and film coating speed are shown to have a large impact on the long-range order of self-assembled nanostructures.
by Dongsook Chang.
Ph. D.

Industrial biotechnologies allow today to obtain both fine and bulk chemicals and yeasts as cell factories can produce many products belonging to both field (Branduardi et al., 2008, Porro and Branduardi, 2009). Among yeasts, Saccharomyces cerevisiae still represents the microorganism of election to develop such cell factories. As regard bioethanol production, yeasts utilization is well established for its natural fermentation ability, but new generation biofuels require the development of strain more and more robust, able to face conditions imposed by the process that should be as cheaper and more profitable as possible. In this direction, processes that use lignocellulosic feedstock for bioethanol production (the so called second generation biofuels) are still in development (NEMO project-Novel high performance Enzymes and Micro-Organisms for conversion of lignocellulosic biomass to ethanol, seventh framework program). This means that the cell factory has to be deeper and deeper investigated in structures and pathways trying to find good targets for improving the robustness. Among the many different functions, cell cytoplasmic membrane plays a key role in cell homeostasis and is deeply involved in facing and reacting to stressing conditions, so it can represent a good target for direct improvements of laboratory as well as industrial strains. Fishing in Arabidopsis thaliana genome, a potentially interesting gene was found, codifying for a Temperature Induced Lipocalin, named TIL. As it has positive effects in plants in unfavourable situations (Charron et al., 2008), TIL was expressed in S. cerevisiae and the recombinant strains compared with the parental counterpart under some of the stresses typical of industrial processes. The recombinant yeasts show an increased tolerance towards heat shock and to the presence of hydrogen peroxide and organic acids. In detail TIL expressing strain generate lower levels of ROS and accumulate less amounts of reactive electrophile species generated after membrane lipids fragmentation. Another industrial field that is gaining more and more importance is represented by bioplastics not coming from petrochemical sources. Vegetable oils derived fatty acids are interesting as bulk compounds for the synthesis of biopolymers, even if they have to be previously modified to possess two chemically reactive groups at molecules extremities. High catalytic activity and stability together with high versatility in reaction of performed by bacteria cytochromes answered to this need. The heterologous expressed B. subtilis cytochrome CYP102A2 in S. cerevisiae showed some activity, measured in terms of NADPH consumption towards fatty acids of different chain length, interestingly also towards short chain fatty acids. However as CYP is able to catalyze different type of reaction involving NADPH consumption (hydroxylation, oxidation and epooxidation as example), the products will be further characterized to understand what kind of modifications are carried out on the tested substrates. Considering the valuable reactions that cytochromes P450 are able to catalyze on a vast variety of substrates (fatty acids, steroids and a multitude of non natural compounds such as drugs, organic solvents and hydrocarbon products), their successful expression in yeast could open the possibility to develop sustainable processes in alternative to classical chemical synthesis. Because of the nice and positive results, S. cereviasiae potential as cell factory was deeper exploited for the expression of a whole plant biosynthetic pathway. In detail, yeast was engineered to express the pathway leadind to the formation of glucobrassicin, a nutraceutical indicated as a potential cancer chemoprotective agent. In this work we describe the construction of a recombinant S. cerevisiae strain able to produce glucobrassicin. Despite some investigation about possible strain optimization through the employment of multicopy plasmids, the final producer will exploit only integrative vectors and the described findings and the process of production were deposited as patent application [Mauro Magnani, E. Bartolucci, Danilo Porro, Paola Branduardi, Vera Codazzi, Umberto Benatti, Gianluca Damonte, Giovanni Schippa e Stefano Bianchini Sviluppo di una cell factory ricombinante per la produzione di Glucobrassicina]. Specific analysis on biosynthetic intermediates suggest steps on which focusing the attention to further improve the glucobrassicin production levels. Despite the number of biotechnological processes based on engineered microorganisms for the production of metabolites is still limited in comparison with the potentiality expressed at lab scale, the studies about strain robustness and heterologous pathway optimization are going to change that situation very soon.

Polyethylene terephthalate (PET) films can be advantageously utilised to replace both glass and metal in photovoltaic (PV) devices. However, there remain aspects of their performance in outdoor applications which may be improved upon to meet PV device requirements more efficiently. DuPont Teijin Films (DTF) employ artificial weathering techniques to investigate PET film degradation processes, such as UV degradation and hydrolysis, which occur during the outdoor application of PET films. In this Thesis, a thorough investigation into the modification of PET film properties with exposure to various artificial weathering techniques has been conducted. Techniques including infra-red spectroscopy, gel permeation chromatography, atomic force microscopy and nano-indentation have been employed to improve the understanding of the effects of artificial weathering on PET films. The effects of exposure to high intensity simulated solar radiation have also been investigated and compared with those of the combined degradation agents present during ISO standard accelerated environmental weathering. Surface modifications have been compared with those of the bulk, in particular, surface roughening and microcracking have been investigated in much greater detail than previously in the literature. Finally, the stabilizing effects of including an organic ultraviolet absorber on weathered PET film bulk and surface properties have also been assessed.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2012.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (p. [139]-146).
Understanding the ways that matter deforms and flows, which is the focus of the branch of science known as rheology, is essential for the efficient processing and proper function of such practically and technologically important materials as plastics, paints, oil-drilling fluids, and consumer products. Rheology is also powerful from a scientific perspective because of the correlation between rheological properties and the structure and behavior of matter on microscopic and molecular scales. The developing sub-field of microrheology, which explicitly examines flow and deformation behavior on microscopic length scales, provides additional clarity to this connection between rheology and microstructure. Aging materials, whose rheological properties evolve over time, are one class of materials that are of significant scientific and practical interest for their rheological behavior. Also, the unique field-responsive rheological properties of magnetorheological (MR) suspensions, which can be tuned with an applied magnetic field, have been used to create active vibration damping systems in such diverse applications as seismic vibration control and prosthetics. A material that undergoes rheological aging and that has received much attention from soft matter researchers is the synthetic clay Laponite® . This material is attractive as a rheological modifier in industrial applications and consumer products because a rich array of rheological properties, including a yield stress, viscoelasticity, and a shear-thinning viscosity, can be achieved at very low concentrations in aqueous dispersions (~ 1 w%). Though this behavior has been investigated extensively using traditional 'bulk' rheology, a number of important questions remain regarding the nature of the dispersion microstructure. The techniques of microrheology, in which rheological properties are extracted from the motion of embedded microscopic probe particles, could help to elucidate the connection between microstructure and rheology in this material. Microrheological studies can be performed using passive techniques, in which probes are subject only to thermal motion, and active techniques, in which external forces are applied to probes. Because aqueous Laponite® dispersions exhibit a significant yield stress, they could be beneficial as novel matrix fluids for magnetorheological suspensions. MR fluids consist of a suspension of microscopic magnetizable particles in a non-magnetic matrix fluid. When an external magnetic field is applied, the particles attract each other and align in domain-spanning chains of particles, resulting in significant and reversible changes in rheological properties. Because of the typically large density difference between the matrix fluid and the suspended magnetic particles, however, sedimentation is often problematic in MR fluids. A yield stress matrix fluid such as an aqueous Laponite® dispersion could help address this issue. In this thesis, bulk rheology and microrheology experiments are combined in order to provide a thorough characterization of the rheological properties of aqueous Laponite® dispersions. Multiple Particle Tracking (MPT), a passive microrheology technique, is used to explore the gelation properties of dilute dispersions, while an active magnetic tweezer microrheology technique is used to examine the yield stress and shear-thinning behavior in more concentrated dispersions. MPT results show strong probe-size dependence of the gelation time and the viscoelastic moduli, implying that the microstructure is heterogeneous across different length scales. We also demonstrate the first use of magnetic tweezers to measure yield stresses at the microscopic scale, and show that yield stress values determined from bulk and micro-scale measurements are in quantitative agreement in more concentrated Laponite® dispersions. With a thorough understanding of the clay rheology, we study the magnetorheology of MR suspensions in a yield stress matrix fluid composed of an aqueous Laponite® dispersion. Sedimentation of magnetic particles is prevented essentially indefinitely, and for sufficient magnetic field strengths and particle concentrations the matrix fluid yield stress has negligible effect on the magnetorheology. Using particle-level simulations, we characterize the ability of the matrix fluid yield stress to arrest the growth of magnetized particle chains. The methods and results presented in this thesis will contribute to the fundamental understanding of the rheology and microstructure of aqueous Laponite® dispersions and provide researchers with new techniques for investigating complex fluids on microscopic length scales. Additionally, our characterization of the effects of a matrix fluid yield stress on magnetorheological properties will aid formulators of MR fluids in achieving gravitationally stable field-responsive suspensions, and provide a new method for manipulating the assembly of particle building blocks into functional structures.
by Jason P. Rich.
Ph.D.

In 1998, the Virginia Department of Transportation (VDOT) adopted standards for soil handling and amendments to improve created non-tidal wetland soil conditions. This study was conducted in sites where these new reconstruction practices were supposedly being implemented. Specific objectives were (i) to determine the relative effects of soil reconstruction practices on mitigation site soils, (ii) to assess the degree to which hydric soil indicators were present, and (iii) to evaluate the relative edaphic potential of mitigation site soils. Soil physical, chemical and morphological properties were analyzed in ten mitigation wetlands located in Virginiaâ s Piedmont and Coastal Plain. Surface soil pH was high due to liming, although some sites demonstrated low subsoil pH, indicating the presence of sulfidic materials. Nutrient levels varied, while C:N ratios were low (<25:1), suggesting a high quality organic matter complex. Organic amendments were generally applied at a rate of 4% soil organic matter content. Actual measured carbon content was <2.6% (<50 Mg ha-1). Sites not receiving organic materials and associated tillage had root-limiting bulk densities at the surface, while the majority of sites had root-limiting subsoil (30 cm) bulk densities due to weakly developed soil structure and a lack of deep ripping practices. Many sites also contained high sand content (>50%), which may negatively affect other soil properties. Nine sites had confirmed Hydric Soil Indicators, with their occurrence in a site as high as 70%. Soil reconstruction methods need to incorporate higher organic amendment rates and/or routine disking/ripping practices to improve mitigation wetland soil conditions.
Master of Science

Orientador: Simonides Consani
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba
Made available in DSpace on 2018-08-26T13:35:05Z (GMT). No. of bitstreams: 1 Fugolin_AnaPaulaPiovezan_D.pdf: 4905643 bytes, checksum: 75a91fcf559fc00359be8feeeb2d2a0c (MD5) Previous issue date: 2015
Resumo: Novos compósitos bulk-fill, autoadesivos e de menor contração foram desenvolvidos propondo mudanças na técnica restauradora incremental preconizada. Os objetivos desta pesquisa foram: 1) analisar os compósitos Tetric EvoCeram Bulk Fill (TEC), Surefil SDR (SDR), Vertise Flow (VF), Filtek Low Shrinkage (SIL) e compará-los com o compósito convencional Z100 (Z100) quanto à contração volumétrica, tensão de contração, grau de conversão, cinética, resistência à flexão e módulo de elasticidade; 2) avaliar a profundidade de polimerização e a resistência da união à tração de cavidades de Classe II restauradas com diferentes técnicas e diversas associações de materiais submetidas à ciclagem mecânica; e 3) analisar a adaptação marginal por microscopia eletrônica de varredura de restaurações de Classe II antes e após ciclagem mecânica e resistência coesiva. No capitulo 1, a contração volumétrica foi avaliada por dilatômetro de mercúrio e bonded disc (n=5) e a tensão de contração com Bioman (n=5). O grau de conversão foi analisado com espectroscopia de infravermelho próximo (NIR) (n=5) e a cinética por meio de optical bench (n=5). Resistência à flexão e módulo de elasticidade foram mensurados em ensaio com três pontos de apoio após 10 e 60 minutos da fotoativação. Os dados foram analisados por ANOVA e teste de Tukey (5%). VF apresentou os maiores valores de contração volumétrica e tensão de contração, enquanto que SIL obteve os menores. SDR apresentou a maior taxa de polimerização e os maiores valores de grau de conversão. VF apresentou os maiores valores de resistência à flexão após 10 e 60 minutos e Z100 os maiores valores de módulo de elasticidade. No capítulo 2, cavidades de Classe II ocluso-distais em terceiros molares humanos extraídos foram restauradas usando sistema adesivo convencional ¿ XP Bond (XP) ou à base de silorano (SSA) associado aos compósitos TEC, SDR, VF, SIL e Z100 inseridos por meio da técnica incremental (I) e bulk (B). Os grupos experimentais testados foram: XP-Z-B, XP-Z-I, SSA-Z-B, SSA-Z-I, XP-TEC-B, XP-TEC-I, XP-SDR-Z100, SSA-SDR-Z100, VF-Z-B e SSA-SIL-B (n=8). Metade do total das amostras foi preparada para obtenção de palitos e submetida ao teste de resistência da união à microtração após sete dias de armazenagem, enquanto outra metade foi submetida à ciclagem mecânica antes do ensaio de resistência da união. A profundidade de polimerização foi mensurada em restaurações com 4,0 mm de profundidade removidas da cavidade e submetidas ao ensaio de dureza Knoop (n=3). Os resultados foram analisados por ANOVA e teste de Tukey (5%). Quanto à resistência de união o grupo XP-SDR-Z apresentou os maiores valores em ambas as superfícies (oclusal e cervical) nos grupos ciclados ou não. Os menores valores foram exibidos por VF-Z-B em ambas as superfícies para os grupos não ciclados e SSA-SDR-Z para os ciclados. Em relação à profundidade de polimerização, VF apresentou a maior redução da dureza, enquanto os demais compósitos apresentaram valores de redução menores do que 20%. No capítulo 3, as cavidades de Classe II restauradas seguiram as mesmas etapas dos grupos experimentais apresentados no capítulo 2 (n=5) e foram submetidas ao ensaio de ciclagem mecânica; porém, foram previamente moldadas para obtenção de replicas para análise da integridade marginal em microscopia eletrônica de varredura. As imagens foram analisadas pelo software Image J para verificar a porcentagem de fendas. Os compósitos utilizados para restaurar as cavidades foram submetidos ao teste de resistência coesiva (n=5). Os resultados foram analisados por ANOVA e teste de Tukey (5%). A análise da adaptação marginal qualitativa e quantitativa mostrou alteração significativa antes e após a ciclagem mecânica apenas para todos o grupo SSA-Z-B. Os resultados de resistência coesiva mostraram que Z100, SDR e SIL apresentaram os maiores valores, seguido de TEC. VF apresentou os menores valores. Concluiu-se que os novos compósitos apresentam propriedades comparáveis e, em algumas situações, melhores quando comparado ao compósito convencional
Abstract: New bulk-fill, self-adhering and low shrinkage materials were developed and purposed significant changes in the preconized incremental restorative technique. The aims of this research were: 1) analyze the new composites represented by Tetric EvoCeram Bulk Fill (TEC), Surefil (SDR), Vertise Flow (VF), Filtek Low Shrinkage (SIL) and compare them with the conventional composite Z100 (Z100) in relation to volumetric shrinkage, stress of polymerization, degree of conversion, kinetics, flexural strength and modulus; 2) evaluate depth of cure of different composites and microtensile bond strength of Class II cavities filled by different restorative techniques and materials association submitted to mechanical fatigue-cycling test; and 3) analyze marginal adaptation by scanning electron microscopy (SEM) of Class II restoration before and after mechanical cycling, and ultimate tensile strength. In the charter 1, the volumetric shrinkage was evaluated by mercury dilatometer and bonded-disc techniques (n=5) and stress of polymerization by Bioman instrument (n=5). Degree of conversion was analyzed with NIR-spectroscopy (n=5) and the kinetics by the optical bench (n=5). Flexural strength and modulus were carried out using a three-point bending test after 10 and 60 minutes after photocuring. Results were analyzed by ANOVA and Tukey¿s test (5%). VF showed the highest values of volumetric shrinkage and stresses of polymerization and SIL the lowest ones. SDR obtained the highest rate of polymerization and the highest degree of conversion values. VF presented the highest values of flexural strength in both tested times, and Z100 the highest values of modulus. In the charter 2, Class II occluso-distal cavities (6 x 2 x 4 mm) in extracted human molars were restored using a etch-and-rinse adhesive system ¿ XP Bond (XP) or silorane-based (SSA) associated to TEC, SDR, VF, SIL and Z100 composites placed by incremental (I) or bulk (B) technique. The tested experimental groups were: XP-Z-B, XP-Z-I, SSA-Z-B, SSA-Z-I, XP-TEC-B, XP-TEC-I, XP-SDR-Z100, SSA-SDR-Z100, VF-Z-B e SSA-SIL-B (n=8). Half of the samples were prepared to obtain sticks and submitted to the microtensile bond strength test after 7 days of storage. The other samples were submitted to the mechanical fatigue-cycling test before the microtensile bond strength test. Depth of cure was carried out in restorations with 4.0 mm of depth, removed and submitted to Knoop hardness test (n=3). Results were statistically analyzed by ANOVA and Tukey¿s test (5%). In relation to microtensile bond strength, in overall, XP-SDR-Z showed the highest values in both analyzed surfaces (occlusal and cervical) in cycling and no-cycling groups. The lowest values were exhibited by VF-Z-B in both analyzed surfaces in no-cycling groups and SSA-SDR-Z in cycling groups. In relation to depth of cure, VF obtained the lowest top-to-bottom ratio, while the other tested composites exhibited less than 20% of reduction. In the charter 3, Class II cavities were prepared following the same steps described in charter 2 (n=5) and were carried out to mechanical fatigue-cycling test. However, impressions were made before and after to obtain replicas to SEM analysis of the marginal integrity. The micrographs were analyzed by Image J software to measure the discontinuity percentage. The composites used in the cavities were submitted to the ultimate tensile strength (UTS) (n=5). Results were statistically analyzed by ANOVA and Tukey¿s test (5%). Marginal adaptation analysis did not show significant alteration before and after cycling for all groups except to SSA-Z-B where cracks and gaps were found in the adhesive interface. In relation to UTS results Z100, SDR and SIL showed the highest results, followed by TEC. VF exhibited the lowest values. It is possible to conclude that new composites show comparable properties and in some situation better than conventional material
Doutorado
Materiais Dentarios
Doutora em Materiais Dentários

As wastewater is transported in a sewer system, in-sewer transformations occur that allow the sewer system to be considered as a pipeline reactor. Domestic wastewater from the local wastewater treatment facility was monitored for a 3 day period to simulate the bulk phase of sewer flow. Aerobic and anoxic reactive environments were studied to determine the change in organic matter and size distribution. Aerobic and anoxic conditions showed similar treatment of organic matter with an average of 55% of the total chemical oxygen demand (CODt) removed in 72 hours. The CODt consumption rate increased to a mean maximum of 8.4 mg/L/h a mean experiment time of 24 hours. The majority of the organic removal occurred in the first 42 hours. Aerobic conditions led to the formation of larger microbial flocs than anoxic conditions demonstrated by an increasing trend of mean area particle diameter (D a) with the mean increase 8 microns compared to a 3 micron decrease for anoxic conditions. Initial substrate and biomass quality strongly influenced the observed transformations.

Master of Science
Department of Chemical Engineering
James H. Edgar
Boron nitride is a purely synthetic material that has been known for over 150 years but only recently has sparked interest as a semiconductor material due to its potential in ultraviolet lasing and neutron detection. Thin-layer hexagonal boron nitride (hBN) is probably most attractive as a complementary material to graphene during its intense research endeavors. But for hBN to be successful in the realm of semiconductor technology, methods for growing large single crystals are critical, and its properties need to be accurately determined. In this study, hBN crystals were grown from metal solvents. The effects of soak temperature, soak time, source materials and their proportions on hBN crystal size and properties were investigated. The largest crystals of hBN measured five millimeters across and about 30 micrometers thick by precipitation from BN powder dissolved in a nickel-chromium solvent at 1700°C. High temperatures promoted outward growth of the crystal along the a-axis, whereas low temperatures promoted growth along the c-axis. Crystal growth at high temperatures also caused bulk hBN to adopt a triangular habit rather than a hexagonal one. A previously unreported method of synthesizing hBN was proven successful by substituting BN powder with elemental boron and a nitrogen ambient. XRD and Raman spectroscopy confirmed hBN from solution growth to be highly crystalline, with an 8.0 cm[superscript]-1 FWHM of the Raman peak being the narrowest reported. Photoluminescence spectra exhibited peaks mid-gap and near the band edge, suggesting impurities and defects in the hBN samples. However, high-purity reactants and post-growth annealing showed promise for synthesizing semiconductor-grade hBN. Several etchants were explored for defect-selective etching of hBN. A molten eutectic mixture of KOH/NaOH was the most effective defect-selective etchant of hBN at temperatures of 430-450°C for about one minute. The two prevalent hexagonal etch pit morphologies observed were deep, pointed-bottom pits and shallow, flat-bottom pits. TEM and SAED confirmed basal plane twists and dislocations in hBN crystals, but due to the highly anisotropic nature of hBN, their existence may be inevitable no matter the growth technique.

Mestrado em Engenharia Florestal e dos Recursos Naturais - Instituto Superior de Agronomia
The goal of this report is to characterize the bark of five industrially important forest species in Europe - Eucalyptus globulus, Betula pendula, Picea abies, Pinus sylvestris e Pinus pinea and to define their potential use as a source of value added chemical products. It was performed the anatomical characterization of bark tissues (dissociated elements), the selective fractionation (size distribution, characterization of particle shape, separation of density and determination of bulk density), the average of basic chemical composition and particle size of three reference fractions (ash, extractives, suberin, Klason lignin, acid soluble lignin, holocellulose and 1% NaOH extraction). The anatomical study shows that there is no differential separation of the cellular elements of the tissues of the bark in seven particle size fractions. The physical process of fractioning showed that, for all barks, over 50% of the mass of material consisted of coarse particles with 6 mm average diameter. On the other hand, there was no direct correlation between the values of bulk density and particle diameter. It has only been possible to separate the birch bark and scots pine by difference in density fluctuations in water. The mean values of the chemical composition brought out that the barks of softwood showed higher content of total extractives, lignin and yield of 1% NaOH extraction. Considering the three different particle size fractions, the fine fraction showed a higher content of ash, total extractives and 1% NaOH extraction. There was no significant change in the content of suberin and holocellulose.

Reformulation of blended particulate materials has been always a problem for powder industry because formulators have difficulty in measuring, controlling and/or modifying the bulk flow properties of powders. A recently developed powder flow tester (PFT) by The Wolfson Centre for Bulk Solids Handling Technology, University of Greenwich is now available for industry to measure quickly and accurately the flow behaviour of single and blended particulate materials. This new powder flow tester helps to characterise quantitatively the blends which show good flow behaviour in the industrial process lines and define the desirable standards for blends with poor flow behaviour. However, the current process of reformulation is basically a trial and error procedure based on the prior experience of the formulator with other blends reformulated. There is clearly a lack of practical understanding of the links between the particle and bulk scale of powders and how changes in the particle properties and/or blend compositions would affect the flow behaviour of blended powders. The aim of this research work was to develop an “empirical understanding” of the links between the particle properties and bulk flow properties in order to predict the bulk flow properties of blended powders based on changes to the particle properties or blend components. This has been achieved evaluating analytical well-established models found in the literature linking particle and bulk scale for practical purposes in industry, developing new empirical models to predict the flow behaviour of single and blended powders based on the experimental work undertaken in this research and identifying methods or techniques that formulators in industry could use to predict the flow behaviour of their blended powders. The solution provided is a test protocol which in combination with the standard characterisation tests commonly used in industry and the prediction tool called Virtual Powder Blending Laboratory (recently developed by The Wolfson Centre for Bulk Solids Handling Technology using the experimental and modelling work undertaken in this work) will help formulators and process engineers to formulate the composition of blended powders with the desirable flow behaviour in industrial process lines.

Doctor of Philosophy
Department of Chemical Engineering
James H. Edgar
The sublimation recondensation crystal growth of aluminum nitride, titanium nitride, and yttrium nitride were explored experimentally and theoretically. Single crystals of these nitrides are potentially suitable as substrates for AlGaInN epitaxial layers, which are employed in ultraviolet optoelectronics including UV light-emitting diodes and laser diodes, and high power high frequency electronic device applications. A thermodynamic analysis was applied to the sublimation crystal growth of aluminum nitride to predict impurities transport (oxygen, carbon, and hydrogen) and to study the aspects of impurities incorporation for different growth conditions. A source purification procedure was established to minimize the impurity concentration and avoid degradation of the crystal’s properties. More than 98% of the oxygen, 99.9% of hydrogen and 90% of carbon originally in the source was removed. The AlN crystal growth process was explored in two ways: self-seeded growth with spontaneous nucleation directly on the crucible lid or foil, and seeded growth on SiC and AlN. The oxygen concentration was 2 ~ 4 x 1018cm-3, as measured by secondary ion mass spectroscopy in the crystals produced by self-seeded growth. Crystals grown from AlN seeds have visible grain size expansion. The initial AlN growth on SiC at a low temperature range (1400°C ~1600°C) was examined to understand the factors controlling nucleation. Crystals were obtained from c-plane on-axis and off-axis, Si-face and C-face, as well as m-plane SiC seeds. In all cases, crystal growth was fastest perpendicular to the c-axis. The growth rate dependence on temperature and pressure was determined for TiN and YN crystals, and their activation energies were 775.8±29.8kJ/mol and 467.1±21.7kJ/mol respectively. The orientation relationship of TiN (001) || W (001) with TiN [100] || W [110], a 45o angle between TiN [100] and W [100], was seen for TiN crystals deposited on both (001) textured tungsten and randomly orientated tungsten. Xray diffraction confirmed that the YN crystals were rock-salt structure, with a lattice constant of 4.88Å. Cubic yttria was detected in YN sample from the oxidation upon its exposed to air for limited time by XRD, while non-cubic yttria was detected in YN sample for exposures more than one hour by Raman spectra.

The aim of this work is to investigate: enhancement of the oxygen reduction reaction at the PrCoO3-δ/Pr2NiO4+ δ (PCO113/PNO214), inteface; and the mechano-chemical effect in mechanically strained lattice mismatched PCO113 films on Ce0.9Gd0.1O2/8-mol% YSZ(002) fabricated using pulsed laser deposition, PLD, and chemically strained A-site deficient PCO113 (Pr1-xCO3- δ) samples. PCO113 films on Si(004) and Ce0.9Gd0.1O2(200)/8-mol% YSZ(002) single crystal substrates were deposited by PLD. Out-of-plane compressive PCO113 lattice strains, calculated from the PCO113(002) reflection, between -0.39% to -0.99% were measured. Single phase PNO214 films could not be deposited for the PLD conditions tested in this work. Isothermal measurements of PNO214 at 800°C in air showed the gradual formation of Pr6O11 and Pr4Ni3O10, suggesting that this process is kinetically limited. Subsequently, investigation of the mechano-chemical effect was limited to the mechanically and chemically strained PCO113 systems. The chemical expansion on introducing Pr-deficiency, x, in PCO113 was attributed to the formation of Pr vacancies, which effect was large enough to offset the decrease in ionic radii as the oxidation state of Co3+ increased to Co4+. High temperature XRD indicated a thermo-chemical expansion wherein oxygen uptake at high temperatures affected the expansion of the PCO113 lattice as a function of temperature. A comparison of the thermos-chemical expansion between the Pr-deficient PCO113 samples confirmed an increase in oxygen vacancy concentration with Pr-deficiency. 18O diffusion profiles of the Pr-deficient PCO113 samples were fitted using Crank's solution for diffusion in a semi-infinite plane. D* and k* values varied between 1.36-2.26 ×10-16 cm2/s and 4.48-10.1×10-10 cm/s. D* and electrical conductivity was found to increase with Pr-deficiency. Visual analysis of 18O diffusions profiles of the strained PCO113 films suggested that the mechano-chemical effect was present and the introduction of a compressive out-of-plane strain inhibited oxide ion diffusion.

Doctor of Philosophy
Department of Chemical Engineering
James H. Edgar
Hexagonal boron nitride (hBN) is a wide bandgap III-V semiconductor that has seen new interest due to the development of other III-V LED devices and the advent of graphene and other 2-D materials. For device applications, high quality, low defect density materials are needed. Several applications for hBN crystals are being investigated, including as a neutron detector and interference-less infrared-absorbing material. Isotopically enriched crystals were utilized for enhanced propagation of phonon modes. These applications exploit the unique physical, electronic and nanophotonics applications for bulk hBN crystals. In this study, bulk hBN crystals were grown by the flux method using a molten Ni-Cr solvent at high temperatures (1500°C) and atmospheric pressures. The effects of growth parameters, source materials, and gas environment on the crystals size, morphology and purity were established and controlled, and the reliability of the process was greatly improved. Single-crystal domains exceeding 1mm in width and 200μm in thickness were produced and transferred to handle substrates for analysis. Grain size dependence with respect to dwell temperature, cooling rate and cooling temperature were analyzed and modeled using response surface morphology. Most significantly, crystal grain width was predicted to increase linearly with dwell temperature, with single-crystal domains exceeding 2mm in at 1700°C. Isotopically enriched ¹⁰B and ¹¹B hBN crystal were produced using a Ni-Cr-B flux method, and their properties investigated. ¹⁰B concentration was evaluated using SIMS and correlated to the shift in the Raman peak of the E[subscript 2g] mode. Crystals with enrichment of 99% ¹⁰B and >99% ¹¹B were achieved, with corresponding Raman shift peaks at 1392.0 cm⁻¹ and 1356.6 cm⁻¹, respectively. Peak FWHM also decreased as isotopic enrichment approached 100%, with widths as low as 3.5 cm⁻¹ achieved, compared to 8.0 cm⁻¹ for natural abundance samples. Defect selective etching was performed using a molten NaOH-KOH etchant at 425°C-525°C, to quantify the quality of the crystals. Three etch pit shapes were identified and etch pit width was investigated as a function of temperature. Etch pit density and etch pit activation energy was estimated at 5×10⁷ cm⁻² and 60 kJ/mol, respectively. Screw and mixed-type dislocations were identified using diffraction-contrast TEM imaging.

Continuous scaling down of the dimensions of electronic devices has made present day computers more powerful. In the front end of line, the minimum lateral dimensions in a transistor have shrunk from 45 nm in 2007 to 22 nm currently, and the gate oxide film thickness is two to three monolayers. This reduction in dimensions makes surface preparation an increasingly important part of the device fabrication process. The atoms or molecules that terminate surfaces function as passivation layers, diffusion barriers, and nucleation layers. In the back end of line, metal layers are deposited to connect transistors. We demonstrate a reproducible process that deposits a monolayer of aminopropyltrimethoxysilane molecules less than one nanometer thick on a silicon dioxide surface. The monolayer contains a high density of amine groups that can be used to deposit Pd and Ni and subsequently Co and Cu to serve as the nucleation layer in an electroless metal deposition process. Because of the shrinking device dimensions, there is a need to find new transistor channel materials that have high electron mobilities along with narrow band gaps to reduce power consumption. Compound III--V channel materials are candidates to enable increased performance and reduced power consumption at the current scaled geometries. But many challenges remain for such high mobility materials to be realized in high volume manufacturing. For instance, low defect density (1E7 /cm²) III--V and Ge on Si is the most fundamental issue to overcome before high mobility materials become practical. Unlike Si, dry etching of III-V semiconductor surfaces is believed to be difficult and uncontrollable. Therefore, new wet etching chemistries are needed. Si has been known to passivate by etching in hydrofluoric acid, but similar treatments on III--Vs are known to temporarily hydrogen passivate the surfaces. However, any subsequent exposure to the ambient reoxidizes the surface, resulting in a chemically unstable and high defect density interface. This work compares old and new wet etching chemistries and investigates new methods of passivating the III--V semiconductors.

In this study, bulk conductivity of commercial base paper impregnated with different ionic liquids blends and additives, through bench coating was investigated. Bulk conductivity of base paper, ion conductive paper and surface sized ion conductive papers with and without the influence of calendering were evaluated at different concentrations of ionic liquids using at resistivity cell and four point probe technique. It was shown that bulk conductivity of base paper was increased by increasing the amount of ionic liquids. Nano fibril cellulose also showed positive influence on the bulk conductivity of coated papers. By increasing the line load in the calendering machine, a positive influence on the bulk conductivity was observed. The tensile index of all the coated papers was lower than that of the base paper.

A funnel-shaped alteration pipe in Archean tholeiitic to transitional rhyolite and andesite underlying massive Zn-Cu sulphide ore at the Norbec mine in northwestern Quebec was outlined from drill core samples. Geochemical parameters, including mass changes and mobile element ratios were used with normative alteration mineralogy and thin section petrography to determine the extent of the alteration. The alteration was initially characterised by a peripheral zone of sericite-chlorite-quartz and a central chlorite-quartz zone. Isochemical metamorphism of the alteration pipe within the contact aureole of the Lac Dufault stock has converted these assemblages to cordierite-anthophyllite-biotite bearing rocks.
Bulk oxygen isotope data for the altered rhyolite suggest that the Norbec deposit formed at temperatures between 200$ sp circ$C and 300$ sp circ$C, with highest temperatures in the central chloritic zone of the alteration pipe. Calculations using SiO$ sb2$, K and Fe solubilities in typical sea-floor hydrothermal fluids suggest that water/rock ratios of 250 to 900 were necessary to introduce the added mobile elements to the alteration pipe.

As the solar nebula condensed, evaporated and fractionated to form the nascent Earth, the bulk elemental composition of the Earth was established. To first order, the Earth is a devolatilized sample of the solar nebula. Similarly, rocky exoplanets are also likely devolatilized samples of the stellar nebulae out of which they and their host stars formed. If this assumption holds, we can estimate the chemical composition of rocky exoplanets by applying a devolatilization algorithm based on the elemental abundances of their host stars. This thesis is an investigation of this potentially universal devolatilization pattern, from which exoplanetary chemistry and habitability are then derived. To quantify (in broad terms) the chemical relationships between the Earth, the Sun and other bodies in the Solar System, the elemental abundances of the bulk Earth are required. The key to comparing Earth’s composition with those of other objects is to have a determination of the bulk composition with an appropriate estimate of un- certainties. We present concordance estimates (with uncertainties) of the elemental abundances of the bulk Earth, by compiling, combining, and renormalizing a large set of heterogeneous literature values of the primitive mantle and of the core. The weighting factor for the concordance estimates comes from our new estimate of the core mass fraction of the Earth: 32.5±0.3 wt% (weight percent). The uncertainties on our elemental abundances usefully calibrate the unresolved discrepancies between standard Earth models made under various geochemical and geophysical assump- tions. We then extend our assessment of terrestrial abundances to the modeling of pro- tosolar abundances based on the latest estimates of solar photospheric abundances and primitive meteoritic abundances. We compare our new protosolar abundances with our estimates of bulk Earth composition, thereby quantifying the devolatiliza- tion of the solar nebula that led to the formation of the Earth. As a function of elemental 50% condensation temperatures (TC), we fit the Earth-to-Sun abundance ratios f to the linear trend log( f ) = a log(TC ) + b. The best fit coefficients are: a = 3.676 ± 0.142 and b = 11.556 ± 0.436. The quantification of the slope a provides an empirical observation upon which modeling of the devolatilization processes can be based. These coefficients determine a critical devolatilization temperature for the Earth TD(E) = 1391 ± 15 K. The resultant devolatilization pattern allows inferences to be made concerning the depletions of elements in the early solar system and is potentially useful for estimating the chemical composition of rocky exoplanets from their known host stellar abundances. We apply the devolatilization pattern to nearby planetary systems to infer the bulk elemental composition of rocky exoplanets – particularly those within the cir- cumstellar habitable zones – from the known host stellar elemental abundances. The estimated bulk planetary composition (rather than the host stellar abundances) is then used as a principal constraint to model the interior composition and structure of such exoplanets. We apply these constraints to four planet host stars: Kepler-10, Kepler-20, Kepler-21 and Kepler-100, to model the interiors including the mantle and core compositions as well as core mass fraction for potential terrestrial exoplanets orbiting these host stars. With respect to the estimates of the interiors, we conclude that a potential terrestrial exoplanet orbiting Kepler-21 would be the most Earth-like while one orbiting Kepler-10 would be the least.

The research project has been focused on the preparation and characterization of Mg(b1-xCx)2 powder and bulk samples using chemical vapour coated boron and silica coated boron by sol-gel method. The chemical vapour deposition of carbon on boron powder was achieved by reacting ethylene gas on high purity nano-sized boron particles (20-100nm diameter) with varying deposition temperatures and partial pressures. Undoped and carbon doped boron was then reacted with magnesium rod to produce both Mg(b1-xCx)2 powder and bulk samples. Transmission electron microscopy showed that the chemical vapour deposition achieved a uniformly thick carbon-rich layer on each particle, regardless of particle size. In addition, the analusis of the diffraction peaks and the characterization of the magnetisation has evidenced the coexistence of phases with different levels of carbon resulting in multiple current paths within the Mg(B1-xCx)2 samples. The study of the preparation process for bulk Mg(B1-xCx)2 samples has evidenced that reducing the difference between the time constant of reaction and the time constant of diffusion is crucial to opbtain well-sintered samples devoid of cracks. Doping with carbon has shown significant improvements in the field dependence of K for the MG(B1-xCx)2 bulk samples reaching values comparable with the best literature-reported data for bulk samples. However, the K values of the MG(B1-xCx)2 bulk samples were observed to be noticeably lower when compared with the beszt liter4arture-reported data for wires and tapes, owing to the greater density achievable in the latter. In contrast to the carbon doping, the coating with silica via sol-gel process was found to impair the in-field Jc properties of Mg(B1-xCx)2 bulk samples, presumably due to the huge amount of silica loaded onto the boron powder and to the formation of carbonate and silicate impuritis within their reacted microstructure.

L'objet de ce travail de thèse porte sur la synthèse originale en milieu fluide supercritique (FSC) de précurseurs « bulk » de catalyseurs d'hydrodésulfuration (HDS) à haute surface spécifique (SBET), destinés à l'HDS de composés soufrés réfractaires tels que le 4,6 diméthyldibenzothiophène (4,6¬ DMDBT). Ce projet a été réalisé en collaboration entre l'Institut de Chimie de la Matière Condensée de Bordeaux (ICMCB-CNRS) et l'Instituto de Tecnología Química de Valencia (ITQ-CSIC) dans le cadre du réseau européen d'excellence Functional Advanced Materials and Engineering of Hybrids and Ceramics (FAMEnoe). Les études à l'ICMCB se sont portées sur l'optimisation des paramètres de synthèse en milieu FSC de NixCo1-xMoO4 (0 ≤ x ≤ 1) (précurseurs métalliques, solvant, température, pression). Des poudres de précurseurs « bulk » majoritairement composées de la phase hydratée (NiMoO4.0,75H2O) - phase la plus active en HDS - de composition contrôlée et pouvant atteindre près de 200 m2.g-1 ont été obtenues et caractérisées. Les propriétés catalytiques de ces précurseurs « bulk » après sulfuration ont ensuite été testées à l'ITQ sur la réaction de Deep-HDS d'un mélange modèle et d'une fraction pétrolière réelle. L'étude souligne plus particulièrement leurs meilleures capacités d'hydrogénation et de catalyse de l'HDS du 4,6 DMDBT que le catalyseur commercial utilisé comme référence dans ces travaux.

The present work demonstrates the application of molecular simulations (MD) in two different areas: proton transport in bulk water and estimation of the dipole moment of polar organic compounds. In both areas, relatively few successful and robust methodologies exist. In the first part, a new polarizable water model is developed for MD simulations of the proton transport process. The model was parametrized from a combination of quantum chemical calculations and experimental water properties. The model was implemented in MD simulation studies of liquid water at room temperature, as well as with excess protons. For pure water the model gave good agreement with experimental properties. The proton transport rate for a single excess proton also gave a good match with the experimental value. The water model was further extended to include chloride ions. At 0.2 M concentration the resulting density and structure agreed well with experiment, and the proton transport rate was found to be slightly reduced. The model was further extended to include multiple excess protons. For the second part of the project, an open source ab initio MD program, SIESTA, was used to perform simulations of several organic compounds which potentially have multiple stable conformations, to determine their average dipole moments. A series of methods was developed. The most robust method involved modifications to the SIESTA code and statistical analysis of the resulting configurations, in order to more accurately predict the average dipole moment. The resulting dipole moments were in good agreement with the experimental values for cases in which experimental values were reliable. Based on this study, a general method to estimate the average dipole moment of any compound is proposed.

Durante il triennio di dottorato è stato studiato l'effetto del cambio di temperatura sulle proprietà chimiche e biochimiche di due componenti di suoli sotto faggio (Fagus sylvatica) dell'Appennino centrale (Italia): la rizosfera e il topsoil (orizzonti organici e il primo orizzonte minerale). Il disegno sperimentale ha considerato un transetto altitudinale (800 e 1000 m), con una differenza di temperatura media annua dell'aria di 1°C, e un transetto latitudinale, dove non si hanno differenze di temperatura media annua, ma ve ne sono in termini di escursione termica estate-inverno. La ricerca è stata preceduta dalla messa a punto di un metodo strumentale per ottenere più rapidamente dati di carbonio e azoto totali (TN) che siano affidabili e non distruttivi (Paper I). Risultati significativi sono stati ottenuti analizzando la rizosfera che, soprattutto a 1000 m, ha mostrato maggiori contenuti di carbonio organico totale (TOC), di sostanza organica estraibile in acqua (WEOM) e P disponibile del suolo bulk. Con l'aumento di 1°C si potrebbe così verificare un'accelerazione del ciclo dei nutrienti negli ambienti forestali a 1000 m (Paper II). Questo risultato è stato confermato da un maggior contenuto di zuccheri, fenoli solubili e tannini nella WEOM degli stessi suoli (Paper III). Comparando i risultati lungo la latitudine, gli orizzonti minerali sottosuperficiali sono risultati molto simili. Al contrario, il topsoil ha mostrato differenze chimiche e biochimiche attribuibili all’escursione di temperatura estate-inverno, con differenti andamenti delle attività enzimatiche secondo il ruolo degli enzimi nella degradazione della lettiera. In ogni caso, nel topsoil e negli orizzonti sottosuperficiali, l'altitudine è responsabile dell’incremento del TOC, del TN e dello spessore degli orizzonti organici, confermando che l'aumento di temperatura a queste quote potrebbe accelerare la velocità di mineralizzazione della sostanza organica (Paper IV).
The research conducted during the three years doctoral activity was focused on the effect of temperature change on chemical and biochemical properties of two different soil components of beech (Fagus sylvatica) forest soils from central Apennines (Italy): i) rhizosphere, which was contrasted with the bulk soil, and ii) organic horizons (OLn, OLv, OH) and the first mineral horizon (A). In the experimental design a small altitudinal transect (800 and 1000 m) with a different mean annual air temperature of 1°C was considered, together with a latitudinal transect with no difference in the mean annual air temperature but different for the summer-winter thermal excursion. The research was preceded by the development of a method to obtain data of total carbon and nitrogen with non-destructive and less time-consuming instruments in order to develop rapid and reliable field analyses (Paper I). Significant results were obtained with the rhizosphere, which showed marked differences with respect to the bulk at 1000 m, particularly for the greater content of total organic carbon (TOC), water extractable organic matter (WEOM), and available P concentration due to rhizodeposition processes. The enriched micro-environment of the rhizosphere also fosters a rapid nutrients' cycle (Paper II). This was confirmed by the higher content of sugars, soluble phenols and tannins in the rhizosphere WEOM at 1000 m (Paper III). Comparing results along the latitudinal transect, in the subsoil only small differences were recorded. Conversely, the topsoil (O+A horizons) showed chemical and biochemical differences ascribable to the summer-winter thermal excursion trend, with different behaviors of the enzymatic activities depending on their role in litter decomposition. However, in both topsoil and subsoil, horizons thickness and the TOC and total nitrogen contents were higher at 1000 than at 800 m, so confirming that an increase of temperature at these altitudes will increase the mineralization rate (Paper IV).

A biorefinery should ideally integrate biomass conversion processes to produce a range of fuels, power, materials, and chemicals from biomass. The term biorefinery is derived both from the raw material feedstock which is renewable biomass and also from the bioconversion processes often applied in the treatment and processing of the raw materials. Renewable sources are the basis of the alternative energy, fuels and compound obtained in a biorefinery-based way to meet the energy demand in a world where petrol fuels are becoming scarce and more expensive. The current biorefinery schemes are mainly based on hexose sugars (first generation) or lignocellulosic-based material (second generation) as feedstocks and depend on microbial cell factories for obtaining the products of interest. In most cases, the substrate utilization is not optimized jet: at the end of the process in addition to the main product, by-products such as huge quantity of lignin and some C5 sugars (deriving from incomplete utilization of lignocellulose) but also proteins (mainly the exhausted biomass at the end of the production) are still available. Focusing the attention on proteins, they are nowadays mainly absorbed as animal feed, but the quantities produced exceed the demand. Considering the implication related to GMO utilization and the increasing number of biorefineries, it can be stated that proteins could represent an interesting Abstract - 2 - “no-cost” starting material to produce more biofuel, bioproducts or biopower in a biorefinery-based way. This study has the aim to present some examples of production by using the protein side-stream of a biorefinery. In particular, we report the possible destiny of two aminoacids released from said proteins: glycine, to obtain butanol and isobutanol, and glutamate, to produce succinic acid. Butanol represents the most feasible alternative to gasoline, but, differently from ethanol, microbial fermentations are not enough developed to sustain the market demand. The natural producers, different species of the Gram positive group of Clostridia, present many and different limitations which are challenging the scientific communities in finding alternative hosts. Among the different alternative hosts, yeasts can present attractive features, being the most relevant the existence of industrial plants based on Saccharomyces cerevisiae fermentation for the production of ethanol. Up to now, in S. cerevisiae the production of butanol has been obtained by expressing heterologous genes from Clostridia. The best reported butanol titer is only 2.5 mg/L, probably mainly depending on problems related to the overexpression of heterologous prokaryotic enzymes. On the contrary, the isobutanol production is obtained at high level (0.63 g/L) in S. cerevisiae by using and optimizing an endogenous valine degradation pathway. We present an alternative and novel way to produce butanol and isobutanol using glycine as substrate, through a new identified and Abstract - 3 - biochemically characterized pathway. Starting from 15 g/L of glycine we have obtained 92 mg/L of butanol and 58 mg/L of isobutanol. Considering that the pathway has been just discovered and no optimization has been designed or applied, the obtained results has to be considered extremely positive. Since one of the most common stresses that microorganisms have to face during productions is the toxicity of the final product, we investigated also the possibility to use the glycine as protective agent for the cells. This idea originated from different studies that explain how the use of aminoacids, among which glycine, can help the cells to better respond to different stresses, such as high ethanol concentration and hydrogen peroxide. As never reported in literature, we have notably found that butanol causes a sort of oxidative stress, peroxidising the membrane lipids. Moreover, we have demonstrated that glycine can help the cells to better tolerate the presence of hydrogen peroxide, acetic acid, ethanol and butanol. The succinic acid occurs naturally in humans, animals, plants, and microorganisms as TCA cycle intermediate. Its use as a precursor to produce many important commodity chemicals used to make a wide assortment of products such as solvents, fiber and polymer production make it one of the most important relevant bulk chemicals. The microbial production of succinic acid via reductive TCA cycle using engineered Saccharomyces cerevisiae is nowadays on the market commercialised by Reverdia (Cassano Spinola, Italy). Abstract - 4 - Here we investigated the possibility to exploiting the glutamate degradation pathway through the γ-aminobutyric acid (GABA) intermediate as an additional way of obtaining succinate when a source of glutamate is feeded to the cells. Since this pathway, also called GAD/GABA shunt, is transcriptionally controlled, we transcriptionally up-regulated it through the constitutive overexpression of the involved genes, GAD1, UGA1 and UGA2. Even if the pathway was clearly overexpressed, as revealed by transcriptional analysis, the obtained amount of succinic acid did not reflect this modification. Further investigating the possible reason of that, we have demonstrated that, despite the higher transcription levels, the corresponding enzymatic activities of the pathway did not increased. We can argue that posttranslational regulations occur in the pathway, what at the moment impaired the initial aim of our work. However, the data add new and relevant information for the comprehension of the role and the regulation of this pathway in S. cerevisiae. It cannot be excluded that the production of succinic acid in yeasts might be in a future optimized by exploiting the GAD/GABA pathway, once it will be fully characterized. We have finally investigated the possibility to produce succinic acid in a strain of S. cerevisiae deleted in the gene encoding the enzyme glutamate synthase, GLT1. During this study we have tested different growing conditions, since the target gene of deletion is located in a critical node of the nitrogen sensing and utilization, which is related to cellular plasticity and adaptability in perturbed environment. We could demonstrate that Abstract - 5 - when cells are growing in low salts concentration medium, the deleted strain compared to wild type strain is able to accumulate more reduced products, such as succinic acid, malate/fumarate, glycerol and ethanol, indicating a sort of necessity to reduce the excess of NAD(P)H generated by the GLT1 deletion. Regarding this preliminary study, deeper investigations have to be performed to find a fine tuned way to intentionally redirect the metabolic flux and obtain the product of interest, which in turn could be succinic acid, but also malic or fumaric acid, or again ethanol, being this last the product that has the responsibility to prove that bio-based second generation processes can effectively and positively have an impact on our future society.

Thesis (M. Eng. in Logistics)--Massachusetts Institute of Technology, Engineering Systems Division, 2011.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 29-30).
U.S. petrochemical manufacturers operate in a very challenging environment on account of the recent economic crisis, volatility in crude oil prices, rising capacity in the Middle East, etc. Recently, there has been a focus on logistics costs and, in particular, capacity utilization as a means to retain a competitive edge. This thesis focuses on marine dock optimization for a major bulk chemicals manufacturer. The authors have surveyed the research literature to find commonalities in various approaches to the problem of dock optimization- in the petrochemical shipping industry as well as in allied operational environments such as container shipping. They discuss the inputs that would be needed to build a decision-support-system designed for the express purpose of measuring dock utilization. Following a review of the industry context and relevant literature, the authors develop a demonstrative framework that captures the key variables and constraints affecting loading and unloading operations. The authors speculate that multiple simulation and optimization techniques could sufficiently address the quantification of operational uncertainties at the marine dock. However, emphasis is placed upon the need for thorough data gathering and correct prioritization of variables and constraints affecting efficiency of dock operations.
by Gaurav Nath and Brian Ramos.
M.Eng.in Logistics

In the tuberculosis patients, Mycobacterium tuberculosis can stimulate production of hydrogen peroxide in the host as a result of immune response. The H2O2 accumulate in pulmonary cells, causing oxidative stress that could lead to the cancer. We select TB patients for this study which investigates the effects of quercetin as there is an increased incidence of latent TB among the migrant population in the past few years and TB can increase the risk of cancer. Sperm and lymphocytes were treated with DNA damage inducers and quercetin (10µM, 25µM and 100µM), the responses evaluated using the Comet and micronucleus techniques. The gene expressions of COX1, COX2, P53 and Bcl-2 and catalase protein expression were investigated using the qPCR and Western blot techniques. The results showed that a substantial reduction of DNA damage in lymphocytes from TB patients and sperm from healthy donors from * P ≤ 0.0283 to *** P≤0.001in the Comet assay. In the MNi assay, the effect of quercetin in lymphocytes was more significant in reduce DNA damage, whereas the DNA damage induced by a food mutagen was significant, from *p 0.0405 to ***p 0.001. The qPCR showed significance down-regulation of COX1 and Bcl-2 gene expression, rated between *p 0.045 and **p 0.0074. However, the catalase protein was up-regulated by the nano form of quercetin when using lymphocytes from TB patients and showed significant changes at *p 0.0236. In conclusion, the nano form was found to be more efficient at the reduction of DNA damage in the Comet and micronucleus assays. Also, it down-regulated COX1 and Bcl-2 and up-regulated the catalase proteins indicating a possible role for quercetin, in genoprotection to TB through its enzyme modulating effect.
Libyan Embassy

Purpose:Development of a stability-indicating high-performance liquid chromatography (HPLC) method for pyrimethamine analysis, with subsequent application of that method to assess the 90-day stability of a pyrimethamine suspension compounded from bulk USP-grade pyrimethamine powder, is described. Methods:A stability-indicating method of HPLC with ultraviolet detection specific to pyrimethamine was developed according to pharmacopeial recommendations and validated. The method was applied to investigate the stability of a 2-mg/mL pyrimethamine suspension in a vehicle consisting of Ora-Plus and Ora-Sweet (Perrigo) over a period of 90 days. Three replicate test preparations were stored at room temperature or refrigerated at 4.3–5.2 °C, and samples were analyzed in duplicate immediately after preparation and on study days 1, 2, 4, 7, 10, 14, 21, 30, 48, 60, 75, and 90. Results:The 2-mg/mL suspension of pyrimethamine in Ora-Plus and Ora-Sweet retained 90–110% of the labeled potency to 90 days at both temperature ranges. However, color changes in the samples stored at room temperature observed at day 60 indicated that a beyond-use date less than 90 days from the preparation date should be specified when the suspension is to be stored at room temperature. Conclusion:The study demonstrated that USP-grade pyrimethamine powder can be formulated as a 2-mg/mL suspension in a vehicle of Ora-Plus and Ora-Sweet and is stable when stored at room temperature and when refrigerated, in amber plastic bottles, for 48 and 90 days, respectively.

Thesis (Ph. D.)--Industrial and Systems Engineering, Georgia Institute of Technology, 2005.
I. A. Karimi, Committee Member ; Shabbir Ahmed, Committee Member ; Faiz Al-Khayyal, Committee Chair Chelsea (Chip) C. White III, Committee Member ; Earl Barnes, Committee Member. Includes bibliographical references.

An increasing number of chemicals are being transported by ships along the Swedish coastline. Many of these chemicals may pose a threat to the environment. Accidents and spills are luckily rare, but nonetheless it is important to be prepared for a possible chemical spill. The Swedish Coast Guard is responsible for responding to chemical spills at sea, and has both equipment and trained personnel for the purpose. In order to prepare for a possible accident one also needs to know what is currently being transported at sea. The aim of this project is therefore to survey the chemical transports in Swedish waters.

The survey shows that many of the chemicals transported at sea are environmentally harmful and may harm the environment in the event of a spill. The number of accidents that occur is difficult to determine since not all of the smaller ones are reported. It is clear, however, that the main reasons for accidents are groundings and collisions. The collection of information about chemical transports has been difficult because many of the companies and ports are unwilling to give their information. This is part because of concurrence and part due to the fact that it is considered too much work to gather the data.

The project also aims to make a risk analysis for chemical transports at sea. Because of the insufficient data the risk analysis has only dealt with qualitative assessments for certain chemicals. These assessments show that chemicals which are less environmentally harmful may still pose a threat because of the safety issues for the personnel may delay or even prevent a response action.

International regulations for transports at sea can sometimes be complicated to apply because of the vast number of different chemicals. The classification process takes time because of the extensive research which is needed. Furthermore, many of the chemicals transported are classified in different systems and these do not always correspond. It is therefore difficult to conclude which chemicals that are actually a threat to the environment.

Varje år transporteras allt större mängder kemikalier med fartyg längs Sveriges kust. Många av dessa kan vara farliga för miljön. Olyckor och utsläpp sker lyckligtvis ganska sällan men det krävs ändå en beredskap för att kunna ta hand om ett eventuellt utsläpp. I Sverige har Kustbevakningen ansvaret för miljöräddningstjänst till sjöss och har både utrustning och personal som är speciellt utbildad för att bekämpa just kemikalieutsläpp. För att kunna förbereda sig på en eventuell olycka måste man dock också ha en aktuell bild av vilka kemikalier det är som transporteras till sjöss. Detta projekt har därför syftat till att kartlägga kemikalietransporterna i svenska farvatten.

Kartläggningen visar att flera av de kemikalier som transporteras till sjöss är miljöfarliga och kan skada miljön vid ett utsläpp eller en olycka. Hur många olyckor som sker är svårt att veta eftersom många av de mindre olyckorna inte rapporteras. Däremot kan man tydligt se att de vanligaste olycksorsakerna är kollisioner och grundstötningar. Att få tag i uppgifter om hur mycket kemikalier som transporteras har visat sig vara svårt eftersom flera företag och hamnar inte vill tala om hur mycket som transporteras. Det beror dels på konkurrensen mellan kemikalieföretag och dels på att man tycker att det är för jobbigt att behöva sammanställa informationen.

Projektet har också syftat till att göra en riskanalys över kemikalietransporterna. På grund av det bristfälliga underlaget har riskanalysen endast behandlat kvalitativa bedömningar av ett antal olika kemikalier. Dessa bedömningar visar att även kemikalier som är mindre miljöfarliga kan utgöra en stor risk eftersom de säkerhetsmässiga riskerna för insatspersonalen kan försena eller till och med förhindra en bekämpningsinsats.

De internationella reglerna kring transporter till sjöss kan ibland vara svåra att tillämpa eftersom det finns ett stort antal olika kemikalier. Klassningen av de olika kemikalierna tar också lång tid då det krävs omfattande underlag. Många av kemikalierna som transporteras är dessutom klassade enligt flera olika system och det är inte alltid dessa system överensstämmer. Det kan därför vara svårt att ta reda på vilka kemikalier som egentligen kan anses vara miljöfarliga.

The management and disposal of huge volumes of coal combustion by products such as fly ash has constituted a major challenge to the environment. In most cases due to the inadequate alternative use of coal fly ash, the discarded waste is stored in holding ponds, slag heaps, or stock piled in ash dumps. This practice has raised concerns on the prospect of inorganic metals release to the surface and groundwater in the vicinity of the ash dump. Acceptable scientific studies are lacking to determine the best ash disposal practices. Moreover, knowledge about the mobility patterns of inorganic species as a function of mineralogical association or pH susceptibility of the dry disposed ash dump under natural weathering conditions are scarce in the literature. Fundamental understanding of chemical interactions of dry disposed ash with ingressed CO2 from atmosphere, percolating rain water and brine irrigation within ash disposal sites were seen as key areas requiring investigation. The mineralogical association of inorganic species in the dry disposed ash cores can be identified and quantified. This would provide a basis for understanding of chemical weathering, mineralogical transformations or mobility patterns of these inorganic species in the dry ash disposal scenario. The current study therefore aims to provide a comprehensive characterisation of weathered dry disposed ash cores, to reveal mobility patterns of chemical species as a function of depth and age of ash, with a view to assessing the potential environmental impacts. Fifty-nine samples were taken from 3 drilled cores obtained respectively from the 1 year, 8 year and 20-year-old sections of sequentially dumped, 
weathered, dry disposed ash in an ash dump site at Tutuka - a South African coal burning power station. The core samples were characterized using standard analytical procedures viz: X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier transforms infrared (FTIR) techniques, Scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS) and Acid neutralisation capacity (ANC) test. A modified sequential extraction (SE) method was used in this study. The chemical partitioning, mobility and weathering patterns in 1 year, 8 year and 20-year-old sections of the ash dump were respectively investigated using this modified sequential extraction scheme. The sequence of the extractions was as follows: (1) water soluble, (2) exchangeable, (3) carbonate, (4) iron and manganese and (5) residual. The results obtained from the 5 steps sequential extraction scheme were validated with the total metal content of the original sample using mass balance method. The distribution of major and trace elements in the different liquid fractions obtained after each step of sequential extraction of the 59 drilled core samples was determined by inductively coupled plasma mass spectrometry (ICPMS). The data generated for various ash core samples were explored for the systematic analysis of mineralogical transformation and change in ash chemistry with ageing of the ash. Furthermore, the data was analyzed to reveal the impact of ingressed CO2 from atmosphere, infiltrating rain water and brine irrigation on the chemistry of ash core samples. Major mineral phases in original ash core samples prior to extraction are quartz (SiO2) and mullite (3Al2O3·
2SiO2). Other minor mineral phases identified were hematite (Fe2O3), calcite (CaCO3), lime (CaO), anorthite (CaAl2Si2O8), mica (Ca (Mg, Al)3 (Al3Si) O10 (OH)2), and enstatite (Mg2Si2O6). X-ray diffraction results show significant loss of crystallinity in the older ash cores. The presence of minor phases of calcite and mica in dry disposed ash cores are attributed to reduction in the pore water pH due to hydration, carbonation and pozzolanic reactions. The X-ray diffraction technique was unable to detect Fe-oxyhydroxide phase and morealuminosilicate phases in ash core samples due to their low abundance and amorphous character. X-ray fluorescence results of the original ash core samples showed the presence of major oxides, such as SiO2, Al2O3, Fe2O3, while CaO, K2O, TiO2, Na2O, MnO, MgO, P2O5, and SO3 occur in minor concentrations. The ratio of SiO2/Al2O3 classified the original core samples prior to extraction as a silico-aluminate class F fly ash. The ternary plot of major elements in 1-year-old ash core samples was both sialic and ferrocalsialic but 8 year and 20-year-old ash core samples were sialic in chemical composition. It is noteworthy that the mass % of SiO2 varies through the depth of the core with an increase of nearly 3 %, to 58 mass % of SiO2 at a depth of 6 m in the 1-year-old core whereas in the case of the 8-year-old core a 2 % increase of SiO2 to a level of 57.5 mass % can be observed at levels between 4-8 m, showing dissolution of major components in the matrix of older ash cores.. The Na2O content of the Tutuka ash cores was low and varied between 0.6-1.1 mass % for 1-year-old ash cores to around 0.6-0.8 mass % for 8-year-old ash cores. Sodium levels were higher in 1-year-old ash cores compared to 8 year and 20-year-old ashcores. Observed trends indicate that quick weathering of the ash (within a year) leached out Na+ from the ash dump. No evidence of Na+ encapsulation even though the ash dump was brine irrigated. Thus the dry disposal ash placement method does not result in a sustainable salt sink for Na-containing species over time. The total content of each of the elements in 1 year and 20-year-old ash cores was normalised with their total content in fresh ash from same power station to show enrichment and depletion factor. Major elements such as K+, Mn showed enrichment in 1-year-old ash cores whereas Al, Si, Na+, Ti, Ca, Mg, S and Fe showed depletion due to over time erosion. Trace elements such as Cr, Sr, P, Ba, Pb, V and Zn showed enrichment but Ni, Y, Zr showed depletion attributed to over time erosion. In 20-year-old ash cores, major elements such as Al, Na+ and Mn showed enrichment while Si, K+, Fe, Mg and Ca showed depletion highlighting their mobility. Trends indicated intensive flushing of major soluble components such as buffering constituents (CaO) by percolating rain water. The 1-year-old and 20-year-old coal ash cores showed a lower pH and greater loss/depletion of the soluble buffering constituents than the 2-week-old placed ash, indicating significant chemical weathering within a year. Based 
on ANC results the leaching behaviours of Ca, Mg, Na+, K+, Se, Cr, and Sr were found to be controlled by the pH of the leachant indicating high mobility of major soluble species in the ash cores when in contact with slightly acid rain water. Other investigated toxic metals such as As, Mo and Pb showed amphoteric behaviour with respect to the pH of the leachant. Chemical alterations and formation of transient minor secondary mineral phases was found to have a significant effect on the acid susceptibility and depletion pattern of chemical species in the core ash samples when compared to fresh ash. These ANC results correlated well with the data generated from the sequential extraction scheme. Based on sequential extraction results elements, showed noticeable mobility in the water soluble, exchangeable and carbonate fractions due to adsorption and desorption caused by variations in the pore water pH. In contrast, slight mobility of elements in the Fe and Mn, and residual fractions of dry disposed fly ashes are attributed to the co-precipitation and dissolution of minor amount of less soluble secondary phase overtime. The 1-year-old dry disposed ash cores were the least weathered among the 3 drilled ash cores. Therefore low concentration of toxic metals in older ash cores were ascribed to extensive weathering with slower release from residual mineral phases over time. Elements were found to associate with different mineral phases depending on the age or depth of the core samples showing greater heterogeneity in dispersion. For instance the average amount of total calcium in different mineral associations of 1-year-old ash cores is as follows
water soluble (10.2 %), exchangeable (37.04 %), carbonate (37.9 %), Fe and Mn (7.1 %) and residual (2.97 %). The amount of total Na+ in different mineral phases of 1-year-old ash cores followed this trend: water soluble (21 %), exchangeable (11.26 %), carbonate (2.6 %), Fe and Mn (4.7 %) and residual (53.9 %). The non-leachable portion of the total Na+ content (namely that contained in the residual fraction) in the 1-year-old ash core samples under conditions found in nature ranged between 5-91 %. This non-leachable portion of the Na+ showed the metastability of the mineral phases with which residual Na+ associates. Results showed older ash cores are enriched in toxic elements. Toxic elements such as As, B, Cr, Mo and Pb are enriched in the residual fraction of older ash cores. For instance As concentration in the residual fraction varied between 0.0003- 0.00043 mg kg-1 for 1-year-old ash cores to around 0.0003-0.0015 mg kg-1 for 20-year-old ash cores. This suggests that the older ash is enriched in toxic elements hence dust from the ash dump would be toxic to human health. The knowledge of mobility and ecotoxicological significance of coal fly ash is needed when considering its disposal or reuse in the environment. The mobility and ecotoxicology of inorganic metals in coal fly ash are determined by (i) mineralogical associations of inorganic species (ii) in-homogeneity in the ash dumps (iii) long and short term exposure to ingress CO2 and percolating rain water. Management issues such as inconsistent placement of ash in the dumps, poor choice of ash dump site, in-homogeneity in brine irrigation, no record of salt load put on the ash dumps and lack of proper monitoring requires improvement. The thesis provides justification for the use of the modified sequential extraction scheme as a predictive tool and could be employed in a similar research work. This thesis also proved that the dry ash disposal method was not environmental friendly in terms of overall leaching potential after significant chemical weathering. Moreover the study proved that the practice of brine co-disposal or irrigation on ash dumps is not sustainable as the ash dump did not act as a salt sink.