Dissertations / Theses on the topic 'In situ chemical'
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Darnell, Jason Ellis. "IN-SITU LEAD IMMOBILIZATION USING PHOSPHATE BASED BINDERS." MSSTATE, 2004. http://sun.library.msstate.edu/ETD-db/theses/available/etd-07072004-145059/.
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The purpose of this study was to determine the optimum phosphate treatment method to stabilize lead contaminated soil from a firing range. Seven different phosphate sources at five different concentrations were added to soil collected from a firing range on a military base. A series of tests were performed to determine a generic phosphate treatment method. The selected generic phosphate treatment was compared to an untreated control soil sample and to four commercially available treatments provided by invited vendors selected from industry. The four vendors processes, control, and generic treatments were subjected to a series of physical and chemical tests at 0, 14, and 28 days of curing time to determine the effectiveness of each treatment. The generic treatment using Hydroxyapatite developed in the MSU laboratory was competitive with three vendors? treatments. The fourth vendor?s treatment was more effective at reducing the lead leachability of the contaminated soil.
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Maphutha, Malebelo. "In situ sintering study of model nickel catalysts." Master's thesis, University of Cape Town, 2014. http://hdl.handle.net/11427/13326.
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Includes bibliographical references.Lipid catabolism plays a significant role in the survival of M.tb inside the host. The development of analytical techniques such as gas chromatography mass spectroscopy (GCMS) and liquid chromatography mass spectroscopy (LC-MS) has become popular as metabolomics tools in the study of such catabolic pathways. The development of biomarkers and internal standards to perform quantitative and qualitative analysis of metabolites in the catabolic pathway would be an attractive tool. Thus, cholesterol derivatives were synthesized as thia-, fluoro- and deuterium labeled analogs. Sulfur was incorporated into cholesterol at positions, C3 as well as C23. The 3â-mercaptocholest-5-ene was synthesized to block the initial stage of cholesterol catabolism and evaluate whether side chain degradation can still occur. Fluorine was integrated into the cholesterol backbone at C3 to evaluate the side-chain degradation in the absence of cholesterol oxidase activity. Steroids with fluorine at C6 are known to have good biological activity and were for this reason also synthesized. Deuterium labeled compounds were synthesized and used as internal standards for GC-MS analysis. As an alternative to cholesterol catabolism, fatty acids like stearic acid are important in producing building blocks for long chain mycolic acids which provides protection to the mycobacterium. For this reason thiastearic acid derivatives were synthesized and evaluated as biomarkers.
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Clark, Peter. "Towards in-situ characterisation of formulated products." Thesis, University of Birmingham, 2016. http://etheses.bham.ac.uk//id/eprint/6973/.
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Recently, the ability to characterise a formulated product during its manufacture has become very desirable due to the importance of maintaining control over its structure and electro-mechanical properties. The fields of process tomography and spectroscopy are set to play an important role in new technologies yielding in-situ characterisation of a product during chemical processing. This study has investigated such techniques with the aim to apply these tools to a relevant Johnson Matthey manufacturing line. Water, being a high di-electric, can be detected at very low concentrations using Electrical Capacitance Tomography (ECT). This relationship has been exploited to monitor drying and phase boundaries of a packed bed in both two and three dimensions. A comparison with MRI has yielded similar results for the drying profile of a similar packed bed demonstrating technique robustness. Electrical Resistance Tomography (ERT) has been used to discriminate gas and solid phases within a three phase system. The measured conductivity of the multi-phase system at 300 Hz is different than at 9600 Hz and allows for the identification of conductive particles from air bubbles. The application of wideband impedance spectroscopy to ceramic suspensions has shown that electrical and structural properties are inter-related. This work has driven forward the research and improved the range of applications of electrical process analytics.
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Rogozinski, Jeffrey David. "In-situ frequency-dependent electromagnetic sensing for monitoring physical and chemical attributes during chemical processing." W&M ScholarWorks, 2000. https://scholarworks.wm.edu/etd/1539623978.
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The objective of this research was to develop an in-situ sensing technique that monitors the molecular-level response of ions and dipoles to an applied electric field in order to characterize the changes in state of a polymer resin during chemical processing. This technique needs to be capable of monitoring the reaction progress not only in the laboratory setting but also in-situ in the processing tool or reaction environment. Frequency Dependent Electromagnetic Sensing (FDEMS) was selected for this task.;This dissertation investigates the applicability of FDEMS to monitoring two types of processing methods: reactive and batch reactor. The reactive processing system examined involves the processing of a high glass transition thermoplastic, either polyethylene ether or polyether imide blended with a thermoset, diglycidyl ether of bisphenol-A and 4,4'-methylene bis (3-chloro 2,6-diethylaniline]. The batch reactor processing systems examined involve the in-situ process control of an industrial batch reactor process involving five different systems: epoxy acrylic, polyester, latex, emulsion for lotions and surfactants.
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Bahri, Syaiful. "In situ combustion for upgrading of heavy oil." Thesis, University of Salford, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.248917.
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Adewusi, Victor Adesegun. "Heavy oil recovery by forward in-situ combustion." Thesis, University of Bath, 1986. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.370660.
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Tripathi, Ashok Burton Goodwin David G. "In-situ diagnostics for metalorganic chemical vapor deposition of YBCO /." Diss., Pasadena, Calif. : California Institute of Technology, 2001. http://resolver.caltech.edu/CaltechETD:etd-09262005-143545.
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Rai, Yugal. "In-situ interface chemical characterisation of a boundary lubricated contact." Thesis, University of Leeds, 2015. http://etheses.whiterose.ac.uk/12191/.
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An increasing demand for improved fuel efficiency and more reliable automotive engines has seen a number of approaches made to further improve the tribological performance in automotive engine parts. Engine oil lubricants extend the life of the moving parts operating under different conditions and also preventing any damages to these parts. However, although its applications are beneficial towards the moving parts, the environmental implications of these lubricants are somewhat harmful, leading to stricter regulations against its emissions. Strict emission requirements have led to a greater interest in understanding the tribological performance of these lubricant additives. Hence, in order to develop more environmentally friendly additives, it is necessary to understand the tribochemical mechanism that occur at the lubricated systems. However, to date despite considerable efforts, a model to predict friction coefficient is only limited to elastohydrodynamic and hydrodynamic lubrication systems. Under boundary and mixed lubrication conditions, the friction and wear behaviour of the tribological system are characterised by the surface asperities of real contact and with the formation of thin surface films. Thus, sophisticated and reliable experimental techniques are required to investigate and assess the tribological systems under this conditions. In-situ approaches can greatly enhance our understanding on the progressive developments between the contacting interfaces, including the detailed chemical, structural and physical interactions governing friction and wear. The research focuses on developing a methodology for in situ and real time boundary lubricated surface optical and chemical characterisation with the aid of Raman Spectroscopy. The techniques are developed with the lubricant additive of Molybdenum Dialkyldithiocarbamate (MoDTC) and used to experimentally evaluate the interface phenomena occurring in a bench tribometer. MoDTC under defined tribological conditions forms MoS2 tribofilms which reduces friction. Surface analytical methodology of ex-situ and in-situ analysis is applied for the lubricant additive to understand the tribochemical process occurring at the tribological contacts.
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Merchant, Akber. "In-situ fluidization for remediation of contaminated sand." Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=32966.
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Experiments were carried out to study the effects of jet velocity and the jet insertion depth on the characteristics of the fluidized region obtained when vertical and inclined water jets were submerged below the surface of saturated sand. Experiments were conducted using sand of mean particle size 507 mum. Water was injected into the sand through a tube of semicircular cross-section (internal diameter 0.55 cm) located at the wall of the tank, forming a half jet. At sufficiently high flowrate a U-shaped fluidized region formed around the jet tube. The fluidized zone was characterized by measuring scour depth, diameter of the fluidized region at the jet insertion depth and diameter of the fluidized region at half the jet insertion depth. For a fixed jet insertion depth, increasing the jet velocity increased the scour depth, the diameter of the fluidized region at the jet insertion depth, and the diameter at half the jet insertion depth. For a fixed jet velocity, the scour depth was independent of the insertion depth, however the two diameters of the fluidized region decreased with increasing jet insertion depth. The profiles obtained for inclined jets were more asymmetric than those for vertical jets.The effectiveness of the 'up-flow washing' technique for the removal of a water-soluble contaminant (CuSO4) from a saturated bed of sand was investigated for a vertical jet at jet velocities of 213 cm/s and 320 cm/s and jet insertion depths of 5.5 cm and 7.5 cm. Up-flow washing removed the contaminant from the sand bed. The cleaned region extended well beyond the boundary of the fluidized region as jet liquid leaked from the fluidized region and percolated through the fixed bed region. An approximate model for the leakage suggested that 10--20% of the jet liquid leaked from the fluidized region to the fixed bed region.
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Indrijarso, Surat. "Development of pressurized thermogravimetry for in-situ combustion studies." Thesis, University of Salford, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.261489.
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Löfgren, Martin. "Diffusive properties of granitic rock as measured by in-situ electrical methods." Doctoral thesis, KTH, Chemical Engineering and Technology, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-121.
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Diffusion into the rock matrix has been identified as one of the most important retention mechanisms for dissolved contaminants in fractured crystalline rock. In this thesis the diffusive properties of granitic rock, described by the formation factor, have been investigated by electrical methods. These methods are based on the Einstein relation between diffusivity and ionic mobility. Formation factors have been obtained both in the laboratory and in deep lying rock in-situ.
At present, two locations in Sweden, Forsmark and Oskarshamn, are undergoing site investigations for the siting of a repository for spent nuclear fuel. As a part of these investigations, the formation factor of the rock surrounding five, 1000 m deep boreholes has been investigated. More than 250 rock samples, taken from the bore cores, have been investigated in the laboratory and around 50 000 formation factors have been obtained in-situ. The results have been treated statistically and it appears that the formation factor is lognormally distributed. The mean and standard deviation of the obtained log-normal distributions vary from site to site, depending on the geology. For intact granitic rock, the obtained formation factors range between 2.2·10-7 and 2.5·10-2.
The results suggest that diffusion into open, but hydraulically non-conductive fractures may have a significant influence on radionuclide retention by way of increasing it. Therefore, the fractured rock formation factor was introduced in addition to the traditional rock matrix formation factor. The retardation capacity of crystalline rock is strongly associated with the pore connectivity. In this thesis, it is shown that the micropore network of granitic rock is connected on, at least, a metre scale in-situ.
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Trnka, Jeremiah. "Treatability study for the in situ chemical oxidation treatment of groundwater." Pullman, Wash. : Washington State University, 2009. http://www.dissertations.wsu.edu/Thesis/Summer2009/j_trnka_071609.pdf.
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Thesis (M.S. in environmental engineering)--Washington State University, August 2009.Title from PDF title page (viewed on Sept. 10, 2009). "Department of Civil and Environmental Engineering." Includes bibliographical references (p. 14-17).
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ANJOS, ANDREA CRISTINA CARVALHO DOS. "ANALYSIS OF AN IN SITU TABULATION STRATEGY OF COMBUSTION CHEMICAL KINETICS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2011. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=19456@1.
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COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIORA simulação numérica de processos de combustão é uma ferramenta cada vez mais utilizada para o projeto, a análise e a otimização de turbinas, motores e fornos de combustão, entre outros. No entanto, um dos principais inconvenientes que limitam a descrição fiel da realidade de modelos de combustão é o esforço computacional necessário para a solução das equações de transporte das propriedades do escoamento reativo, como frações de massa das espécies químicas, que incluem um termo fonte não linear associado à lei de Arrhenius. A rigidez e a carga computacional relacionadas com a determinação deste termo domina o custo de simulações que empregam modelos detalhados da cinética química da combustão. Esta dissertação descreve um estudo cujo objetivo é reduzir tais custos mediante a utilização de uma técnica de tabulação automática da evolução termoquímica da mistura. Assim, este trabalho apresenta a discussão do estado da arte da técnica denominada tabulação adaptativa in situ, que exibe desempenho considerável em termos de tempo computacional, na determinação dos termos fontes químicos, e propõe uma modificação do algoritmo atrasando o início da tabulação, para evitar o armazenamento de composições existentes apenas no estado transiente da queima, as quais não são representativas do regime estatisticamente estacionário. Um estudo dos resultados obtidos, em um reator parcialmente agitado com CO/O2, mostra ganhos superiores a 95 por cento na altura da árvore binária utilizada para tabulação, isso se reflete no custo de armazenamento e na acurácia dos resultados. Uma análise do tempo computacional caracteriza situações em que a nova estratégia de tabulação pode levar à redução do mesmo, quando comparado com a estratégia original. Seu desempenho é confirmado pelo estudo do sistema químico CH4/ar.
The numerical simulation of combustion processes is an important tool used for design, analysis and optimization of turbines, combustion engines and furnaces, among others. However, one of the major drawbacks that limit the faithful description of reality of combustion models is the computational effort required for the transport equations solution of reactive flow properties such as chemical species mass fractions, which include a nonlinear source term associated to the Arrhenius law. The stiffness and the computational burden related to the determination of such term, largely dominate the cost of simulations that employ detailed models of chemical kinetics combustion. This dissertation describes a study whose objective is to reduce these costs by using a of automatic tabulation technique of the mixture’s thermochemical evolution. Hence, this work presents a state of the art discussion of the technique named in situ adaptive tabulation – ISAT, which shows considerable performance in terms of computational time for the determination of the chemical sources terms, and proposes a modification in the algorithm by delaying the table start to avoid the storage of compositions that exist only in transient state, and which are not statistically representative of the stationary regime. A systematic study of the results in a partially stirred reactor with CO/O2, shows more than 95 per cent gains at the binary tree height used for tabulation, the gains are also optimistic in the storage demand and the results accuracy. A computational time analysis characterizes situations in which the new strategy tabulation could reduce it, when compared to the original algorithm. The strategy performance is confirmed by the study of the chemical system CH4/ar.
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Badmaarag, Ulzii-Orshikh. "Optical Chemical Sensing Device for In-situ Non-Invasive Gas Monitoring." University of Cincinnati / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1583155117533193.
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Mangesana, Nobathembu. "Developing a methodology for characterising in-situ viscosity profiles in tumbling mills." Master's thesis, University of Cape Town, 2012. http://hdl.handle.net/11427/16917.
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Milling is the most expensive operation in a mineral processing circuit and accounts for the highest amount of energy utilized. The efficiency of the milling process is affected by the rate of breakage of bigger rocks and the rate of transport of the slurry within and out of the mill. The transport of material in the mill is dependent on the rheological properties of the slurry such as viscosity. Viscosity is therefore one of the important parameters that influences the transport of the material in the mill. Slurries in tumbling mills are known to exhibit non-Newtonian behaviour. This means slurry viscosity is not constant but is a function of shear rate. To characterize slurry transport in the mill it is necessary to study the viscosity distributions in order to determine regions of high and low resistance to flow in the mill. To determine the influence of slurry viscosity on the transport of particles it is important to quantify the typical shear rate ranges that occur inside the tumbling mill. The aim of this project w as to develop a methodology for characterising viscosity distributions inside a tumbling mill using in-situ shear rate distributions obtained from PEPT at different solids concentrations and mill speeds. The P EPT technique was used to study the in-situ mot ion of slurry particles with in tumbling mill charge using a single radioactive tracer. Rheology experiments were conducted using a U-tube rheometer. The rheometer experiments were performed to characterise the rheological behaviour of the El Soldado slurry at a wide range of shear rates. The PEPT results provided information about the typical shear rate ranges that occur inside the mill. The combination of these results enabled the quantification of viscosity distribution from the slope of the rheogram at typical shear rates found in the tumbling mill. The rheology results indicated that the Bingham model is the rheological model which gives the best description of the rheology of El Sol dado slurry. It had the highest R² adjusted values at all tested solids concentrations concentration ranges. The rheological behaviour of El Soldado slurry with a particle size fraction of -75+53 microns can be described as Newtonian. This means that the viscosity is constant and does not vary with shear rate. At low solids concentrations up to 30wt%, the viscosity values attained are equivalent to that of water at room temperature at 0.001 Pa.s. At higher solids concentrations up to 60wt%, the viscosity increases to 0.007 Pa.s for the shear rate range tested. The Bingham viscosity and yield stress increases in an exponential form with increasing solids concentration. PEPT experiments were conducted to quantify and characterise in-situ shear rates in a laboratory scale tumbling mill. The highest shear rates were obtained at the lowest solids concentration for both mill speeds. It was 30s-¹ at 60% critical mill speed and 36s-¹ at 75% critical mill speed. Mill shear rates decreased with increasing slurry solids concentration. This was attributed to increased particle-particle interactions and reduced voidage. There is less volume available for particle shearing. The magnitude of the maximum shear rate is higher for the 75% critical mill speed at all slurry solids concentrations compared to the shear rates at the lower mill speed. At a higher speed the mill charge is fairly dilated by the strong centrifugal effects that oppose the natural packing structure which results in an overall decrease in bulk density. The increased voidage allows more volume for relative motion, producing an overall increase in shear rate. The narrow shear rate range and the Bingham rheological behaviour of the slurry resulted in a constant viscosity value that could be used in a viscosity model provided the solids concentration is uniform across all regions of the mill. Viscosity is more significantly impacted by solids concentration than shear rate distributions in the tumbling mill. Work should be done to study the solids concentration profiles in the tumbling mill to provide better insight on areas of active transport.
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Kim, Hyung Rae. "Chemical Looping Process for Direct Conversion of Solid Fuels In-Situ CO2 Capture." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1250605561.
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Na, Jeong-Seok. "Nanoscale Assembly for Molecular Electronics and In Situ Characterization during Atomic Layer Deposition." NCSU, 2009. http://www.lib.ncsu.edu/theses/available/etd-07062009-143027/.
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The work in this dissertation consists of a two-part study concerning molecular-based electronics and atomic layer deposition (ALD). As conventional âtop-downâ silicon-based technology approaches its expected physical and technical limits, researchers have paid considerable attention to âbottom-upâ approaches including molecular-based electronics that self assembles molecular components and ALD techniques that deposit thin films with atomic layer control. Reliable fabrication of molecular-based devices and a lack of understanding of the conduction mechanisms through individual molecules still remain critical issues in molecular-based electronics. Nanoparticle/molecule(s)/nanoparticle assemblies of âdimersâ and âtrimersâ, consisting of two and three nanoparticles bridged by oligomeric ethynylene phenylene molecules (OPEs), respectively, are successfully synthesized by coworkers and applied to contact nanogap electrodes (< 70 nm) fabricated by an angled metal evaporation technique. We demonstrate successful trapping of nanoparticle dimers across nanogap electrodes by dielectrophoresis at 2 VAC, 1 MHz, and 60 s. The structures can be maintained electrically connected for long periods of time, enabling time- and temperature-dependent current-voltage (I-V) characterization. Conduction mechanisms through independent molecules are investigated by temperature dependent I-V measurements. An Arrhenius plot of log (I) versus 1/T exhibits a change of slope at ~1.5 V, indicating the transition from direct tunneling to FowlerïNordheim tunneling. Monitoring of the conductance is also performed in real-time during trapping as well as during other modification and exposure sequences after trapping over short-term and long-term time scales. The real-time monitoring of conductance through dimer structures during trapping offers immediate detection of a specific fault which is ascribed to a loss of active molecules and fusing of the nanoparticles in the junction occurring mostly at a high applied voltage (â¥3 VAC). After successful trapping, the sample exposure to air reveals a small rapid decrease in current, followed by a slower exponential increase, and eventual current saturation. This work also reports on the dependence of electron transport on molecular length (2 to 4.7 nm) and structure (linear-type in dimers and Y-type in trimers). The extracted electronic decay constant of ~0.12/à and effective contact resistance of ~4 Megaohmï indicate a strong electronic coupling between the chain ends, facilitating electron transport over long distances. A three terminal molecular transistor is also demonstrated with trimers trapped across nanogap electrodes. The source-drain current is modulated within a factor of 2 with a gate bias voltage of -2 to +2 V. A subthreshold slope of ~110 mV/decade is obtained. Finally, we report on both fundamental understanding and application of atomic layer deposition. First, in situ analysis tools such as quartz crystal microbalance and electrical conductance measurements are combined to reveal direct links between surface reactions, charge transfer, and dopant incorporation during ZnO and ZnO:Al ALD. Second, the ability of ALD to form uniform and conformal coating onto complex nanostructures is explored to improve the ambient stability of single molecules/nanoparticle assemblies using Al2O3 ALD as an encapsulation layer. In addition, the ability to shield the surface polarity of ZnO nanostructures using Al2O3 + ZnO ALD, leading to hierarchical morphology evolution from one-dimensional ZnO nanorods to three-dimensional ZnO nanosheets with branched nanorods during hydrothermal growth is investigated.
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Mandal, Anasuya. "An alternative diagnostic method using microneedles for sampling the immune system in situ." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/111414.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemical Engineering, 2017.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 109-123).
Current protocols for immune system monitoring involve the collection of cells from blood or cerebrospinal fluid. However, since major populations of immune cells reside within tissues, these invasively-obtained body fluid samples are, at best, indirect indicators of the status of the immune system. Direct tissue sampling through biopsies is difficult to incorporate into long-term, repetitive, longitudinal immune monitoring. Whereas delayed-type hypersensitivity tests (e.g., Mantoux tuberculin test) query the presence of antigen-specific cells in the skin, but do not provide information about the phenotype and functional characteristics of responding immune cells. Here we present a technology that addresses several of these challenges simultaneously, with the synergistic goals of providing enhanced diagnostic methods for sampling and analyzing the function of the immune system, and providing a greater insight into the status of the immune system than state-of-the-art assays. We designed hydrogel-coated, immune-monitoring, sampling microneedles that are capable of sampling non-recirculating immune cell populations present in the skin and permitting the quantification of biomarkers present in collected dermal interstitial fluid, thus enabling the parallel monitoring of both cellular and humoral immune responses. We focused, first, on optimizing the materials for fabricating sampling microneedles with the requisite properties of mechanical integrity and robustness, reproducible fabrication, effective skin penetration, ability to include bioactive cell-signaling molecules in the MN sampling platform and a compartment within the platform for sample collection and retention. Next, we utilized two animal models: an immunization model in which mice were vaccinated with model antigen ovalbumin, and an infection model in which mice were infected, via tail-skin scarification, with vaccinia-virus expressing SIVgag. We established that including adjuvants and antigen as cargo in lipid nanocapsules embedded in the hydrogel coating of the microneedles elicit the recruitment and sampling of not only antigen-specific cells, but also non-recirculating tissue resident memory cells. In both models, we demonstrated that even at long times post antigen exposure, sampling microneedles consistently recruited for higher proportions of antigen-specific cells than those present in blood. Finally, we also showed that the dermal interstitial fluid collected via sampling microneedles, could be reliably quantified for biomarkers such as antigen-specific IgG. The technology of sampling microneedles allows ex vivo analysis of cells retrieved directly from the local tissue environment and enables the investigation of antigen-specific cells for diagnostic purposes as well as answering spatio-temporal questions related to immunology in local tissue environments. This simple, painless and minimally-invasive sampling approach should facilitate longitudinal monitoring of antigen-specific immune cell populations in the skin relevant for a variety of infectious and autoimmune diseases, and aid the process of vaccine design.
by Anasuya Mandal.
Ph. D.
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Xiong, Rentian. "In situ sensing for chemical vapor deposition based on state estimation theory." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/22711.
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Thesis (Ph. D.)--Chemical and Biomolecular Engineering, Georgia Institute of Technology, 2008.Committee Chair: Gallivan, Martha; Committee Member: Ferguson, Ian; Committee Member: Henderson, Cliff; Committee Member: Hess, Dennis; Committee Member: Lee, Jay.
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Li-Pook-Than, Andrew. "In situ Raman spectroscopy of carbon nanotube growth by chemical vapor deposition." Thesis, University of Ottawa (Canada), 2010. http://hdl.handle.net/10393/28500.
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In situ Raman spectroscopy was used to track the growth of carbon nanotubes grown by chemical vapor deposition. The dynamic evolution of three kinds of Raman bands, namely the G, D, and RBM bands, was analyzed. The evolution of nanotube diameter and crystallinity was analyzed from the RBM and D/G band evolution, respectively. A characteristic growth sequence consisting of four distinct stages of growth was consistently observed. The growth rate of each stage was found to decrease with increasing temperature, possibly due to parasitic, competing reactions, and energy scales for each stage are extracted. The evolution and nanotube distribution of samples grown with and without alumina support layers is contrasted and the role of alumina is discussed.
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Williamson, Alex Stewart. "Dielectric Sensor In-Situ Control of the RTM Composite Fabrication Process." W&M ScholarWorks, 1990. https://scholarworks.wm.edu/etd/1539625589.
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Salim, Sateria. "In-situ Fourier transform infrared spectroscopy of chemistry and growth in chemical vapor deposition." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/11378.
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Cho, Soon. "Real-Time In-Situ Chemical Sensing in AlGaN/GaN Metal-Organic Chemical Vapor Deposition Processes for Advanced Process Control." College Park, Md. : University of Maryland, 2004. http://hdl.handle.net/1903/1798.
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Thesis (Ph. D.) -- University of Maryland, College Park, 2004.Thesis research directed by: Material Science and Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Khasu, Motlokoa. "In situ study of Co₃O₄ morphology in the CO-PROX reaction." Master's thesis, University of Cape Town, 2017. http://hdl.handle.net/11427/24905.
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The preferential oxidation (PROX) reaction is an effective process for the removal of trace amounts of carbon monoxide from a reformate stream. Tricobalt tetraoxide (Co₃O₄) is the candidate for CO-PROX in a H₂ rich gas and could be an alternative to the rare and expensive PGMs. This study investigates the effect of different Co₃O₄ morphologies in the preferential oxidation of carbon monoxide in H₂ rich gas. Reports have shown morphology dependency in CO oxidation in the absence of hydrogen, no study has investigated the morphology dependency in H₂ rich atmospheres. Different morphologies of nanocubes, nanosheets and nanobelts were prepared using hydrothermal mn and precipitation. Conventional spherical nanoparticles from our group were included to compare the activity of conventional nanoparticles with nanoparticles of different morphology. The model catalysts were supported on silica spheres which were also prepared. The CO-PROX experiments were conducted in the in situ UCT-developed magnetometer and PXRD capillary cell instruments by induced reduction at temperatures between 50 and 450°C. Catalyst tests showed two distinct temperature regions with maximum activity. In the range of 150 – 175ᵒC, activity decreased from nanoparticles > amine nanosheets > nanobelts. However, the surface area specific rate of CO₂ formation displayed an inverse trend. In the region of 225 – 250ᵒC, nanocubes > NaOH nanosheet > HCl nanocubes showed maximum activity. The surface area specific rate was the same for amine nanocubes and NaOH nanosheets. None of the model catalysts retained their morphology after the temperature was ramped from 50ᵒC to 450ᵒC, and back to 50ᵒC. The catalysts were partially reduced to metallic Coo (other phase being CoO). Figure 1: In situ PXRD analysis and kinetics of CH4, CO and CO₂ showing the behaviour of Co₃O₄/SiO₂ (amine nanocubes) under CO-PROX conditions
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Nyathi, Thulani Mvelo. "Supported Cobalt Oxide Catalysts for the Preferential Oxidation of Carbon Monoxide: An in situ Investigation." Doctoral thesis, Faculty of Engineering and the Built Environment, 2021. http://hdl.handle.net/11427/33946.
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The study presented in this thesis has placed great focus on Co3O4-based catalysts for producing CO-free H2-rich gas streams for power generation using proton-exchange or polymer electrolyte membrane fuel cells (PEMFCs). The removal of CO (0.5 – 2%) is essential as it negatively affects the performance of the Pt-based anode catalyst of PEMFCs. Among the various CO removal processes reported, the preferential oxidation of CO (CO-PrOx) to CO2 is a very attractive catalytic process for decreasing the CO content to acceptable levels (i.e.,< 10 ppm) for operating the PEMFC. Co3O4-based catalysts have shown very good catalytic activity for the total oxidation of CO in the absence of H2, H2O and CO2. More specifically, the performance of Co3O4 is known to be influenced by numerous factors such as particle size, particle shape, and the preparation method. As a result, there has also been growing interest in Co3O4 as a cheaper alternative to noble metals for the CO-PrOx reaction. However, the H2 (40 – 75%) in the CO-PrOx feed can also react with O2 (0.5 – 4%) to produce H2O, which consequently decreases the selectivity towards CO2 (based on the total O2 conversion). Aside from H2, the CO-PrOx feed also contains H2O and CO2 which may affect the CO oxidation process as well. The use of Co3O4 as the active catalyst for CO-PrOx can have shortcomings – the main one being its relatively high susceptibility to reduction by H2, forming less active and selective Co-based phases (viz., CoO and metallic Co). Particularly over metallic Co, the conversion pathway of CO can change from oxidation to hydrogenation, forming CH4 instead of CO2. Therefore, the first objective of the work carried out was to investigate the effect of the gas feed components (viz., H2, H2O and CO2; co-fed individually and simultaneously) on the progress of the CO oxidation reaction and the phase stability of Co3O4 over a wide temperature range (50 – 450 °C). It should be noted that the presence of these three gases can also introduce more side reactions, viz., the forward and reverse water-gas shift, respectively, as well as CO and CO2 methanation, respectively. In the supported state, the choice of support, as well as the nature and/or strength of the interaction between the Co3O4 nanoparticles and the support can influence catalytic performance and phase stability. CO oxidation over metal oxides such as Co3O4, is believed to proceed via the Mars-van Krevelen mechanism, which depends on the surface of the catalyst being reducible in order to release lattice oxygen species. Generally, strong metal-support interactions (MSIs) or nanoparticlesupport interactions (NPSIs) can hinder the removal of surface (and bulk) oxygen species, which can negatively affect the catalytic performance. Strong interactions can also promote the solidstate reaction between the species from the nanoparticle with those from the support, leading to the formation of metal-support compounds (MSCs). The supports SiO2, TiO2 and Al2O3 are well known for this phenomenon, and consequently, allow for the formation of silicates, titanates and aluminates, respectively. Support materials such as CeO2, ZrO2 and SiC, are not known for interacting strongly with nanoparticles and often do not react to form MSCs. Therefore, the second objective of this Ph.D. study was to investigate the effect of different support materials (viz., CeO2, ZrO2, SiC, SiO2, TiO2 and Al2O3) on the catalytic performance and phase stability of Co3O4 under different CO-PrOx reaction gas environments. Before carrying out the lab-based experiments, theoretical evaluations were performed by means of thermodynamic calculations based on the Gibbs-Helmholtz Equation. The calculations helped determine the equilibrium conversions of each gas-phase reaction, revealing the extent to which a certain reaction can be expected to take place between 0 and 500 °C. Thermodynamic calculations were also performed to predict the stability of Co3O4, CoO and metallic Co at different temperatures and partial pressure ratios of H2-to-H2O. In the case of supported nanoparticles, the formation of the Co-support compounds - Co2SiO4, CoTiO3 and CoAl2O4 from SiO2, TiO2 and Al2O3, respectively - was shown to be thermodynamically feasible in H2-H2O mixtures. Unsupported Co3O4 nanoparticles were synthesised using the reverse microemulsion technique, while supported Co3O4 nanoparticles were prepared using incipient wetness impregnation. In situ PXRD- and magnetometry-based CO-PrOx catalytic testing was performed in different gas environments as depicted in Figure S.1. The different conditions chosen allowed for the effect of H2, H2O and CO2 on the progress of the CO oxidation reaction and on the reducibility of Co3O4 to be studied. For the first time, this work has identified all the possible gas-phase side reactions (in addition to CO oxidation) that can take place under CO-PrOx conditions. Each reaction could be linked to a specific Co-based phase which is responsible for its occurrence. Furthermore, the temperatures and the extent to which these reactions take place were in-line with the predictions from the thermodynamic calculations. The presence of a support does stabilise the Co3O4 (and CoO) phase over a wide temperature range. Over the weakly-interacting supports (i.e., ZrO2 and SiC), high CO conversions (91.5% and 80.8%, respectively) and O2 selectivities (55.2% and 55.9%, respectively) to CO2 could be obtained, in addition to the improved phase stability of Co3O4. In agreement with the thermodynamic predictions, the presence of Co2SiO4 (7.7%), CoTiO3 (13.8% (from TiO2- anatase) and 8.9% (from TiO2-rutile)), and CoAl2O4 (26.6%) was confirmed using ex situ X-Ray Absorption Spectroscopy in the spent samples of Co3O4/SiO2, Co3O4/TiO2-anatase, Co3O4/TiO2- rutile and Co3O4/Al2O3, respectively, after CO-PrOx. These three samples also exhibited relatively low CO oxidation activities and selectivities, as well as low Co3O4 reducibility.
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Forsey, Steven. "In situ Chemical Oxidation of Creosote/Coal Tar Residuals: Experimental and Numerical Investigation." Thesis, University of Waterloo, 2004. http://hdl.handle.net/10012/1275.
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Coal tar, coal tar creosote and oily wastes are often present as subsurface contaminants that may migrate below the water table, leaving a widely distributed residual source of contaminants leaching to the ground water. In situ chemical oxidation is a potentially viable technology for the remediation of aquifers contaminated with creosote and coal tars. The oxidant of choice would be flushed through the contaminated area to oxidize aqueous contaminants and enhance the mass transfer of contaminants from the oil phase. A series of batch and column experiments were performed to assess the ability of a chemical oxidizing reagent to oxidize creosote compounds and to increase mass transfer rates. Results from the column experiments were then simulated using a reactive transport model that considered 12 different creosote compounds undergoing dissolution, oxidation and advective-dispersive transport. Three strong chemical oxidizing reagents, Fenton's Reagent, potassium persulfate with ferrous ions, and potassium permanganate were tested with batch experiments to determine their reactivity towards creosote compounds. All three reagents successfully decomposed aqueous creosote compounds and were able to reduce the mass of the monitored creosote compounds within the oil phase. However, both the Fenton's and persulfate reagents required large molar ratios of iron and peroxide because the precipitation of iron continually removed the iron catalyst from the aqueous phase. Fenton's and persulfate reagents could be used in systems that are allowed to become acidic to solubilize the iron, but the cost of adjusting the pH, potential impact on aquifer geochemistry and the short lived free radical reaction make these reagents less practical than KMnO4. KMnO4 oxidizes a wide variety of creosote compound, can be used at very high concentrations, and its concentration will not be reduced significantly as it moves through the zone of contamination. The feasibility of using potassium permanganate as an oxidizing reagent for in situ treatment of creosote residuals was investigated using batch column experiments. Column experiments were conducted at a neutral pH in a carbonate rich sand matrix with creosote at 8 % saturation. The columns were treated intermittently with simulated ground water or KMnO4 dissolved in simulated ground water (8 g/L) for 172 days. Under these experimental conditions the KMnO4 decreased the initial mass of the monitored creosote compounds by 36. 5%, whereas in the control column (no oxidizer) only 3. 9% was removed. To remove all of the monitored creosote compounds from the columns it was calculated that the volume needed would be 40 times less for the KMnO4 solution, compared to flushing alone with simulated ground water. To evaluate the potential effectiveness of in situ chemical oxidation at field sites, numerical model simulations need to incorporate relevant chemical oxidation rates to assess system performance and to provide design guidance. In-depth kinetic studies were performed to determine rate constants and to gain insight into the oxidation of creosote compounds with KMnO4. The study examined the kinetics of the oxidative treatment of a selected group of creosote/coal tar compounds in water using excess potassium permanganate and investigated the correlation between reactivity and physical/chemical properties of the organic pollutants. The oxidation of naphthalene, phenanthrene, chrysene, pyrene, 1-methylnapthalene, 2-methylnaphthalene, acenaphthene, fluorene, carbazole, isopropylbenzene, ethylbenzene and methylbenzene closely followed first-order reaction kinetics, enabling calculation of second-order rate constants. Fluoranthene was only partially oxidized by permanganate and the oxidation of anthracene was too fast to be measured. Biphenyl, dibenzofuran, benzene and tert-butylbenzene failed to react in this study. Comprehensive column experiments complemented by numerical modeling revealed an unequal enhancement of the removal of creosote compounds from the oil phase. For the more readily oxidizable compounds such as pyrene and naphthalene, a significant increase in the mass transfer rates was observed in the oxidation columns, compared to the oxidant free column. For non-oxidizable compounds such as biphenyl and dibenzofuran, an increase in the rate of mass removal was also observed in the oxidation columns, even though their aqueous concentrations were not reduced in the column. This was due to the rapid removal of the more readily oxidizable compounds from the oil, which increases the mole fraction of the non-oxidizable compounds. Thus according to Raoult's Law, the concentration in the aqueous phase becomes closer to its pure phase liquid solubility and its aqueous concentration increases. The most significant result of the experiments is the observed increase in the rate of removal of those compounds that have low aqueous solubilities and are readily oxidized, such as pyrene and fluorene. Compounds that have low aqueous solubilities and are not readily oxidizable, such as chrysene, may still take a long period of time to be removed, but the removal time is greatly reduced with oxidation compared to flushing the area with water alone.
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Harden, John Michael. "Elucidation of key interactions between in situ chemical oxidation reagents and soil systems." Diss., Mississippi State : Mississippi State University, 2006. http://sun.library.msstate.edu/ETD-db/ETD-browse/browse.
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Baraga, Joseph J. (Joseph John). "In situ chemical analysis of biological tissue--vibrational Raman spectroscopy of human atheroschlerosis." Thesis, Massachusetts Institute of Technology, 1992. http://hdl.handle.net/1721.1/12875.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Whitaker College of Health Sciences and Technology, 1992.Includes bibliographical references (leaves 209-223).
by Joseph John Baraga.
Ph.D.
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Kazi, Rafiq Akhtar. "A high pressure kinetic study of the in-situ combustion process for oil recovery." Thesis, University of Salford, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.261611.
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Cunha, Alaine Santos da. "Aplicação de técnicas químicas de remediação em áreas contaminadas por compostos organoclorados." Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/44/44138/tde-08012011-183046/.
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Grande parte das áreas contaminadas conhecidas atualmente advém de práticas passadas onde os cuidados com a proteção à saúde humana e ao meio ambiente eram desconhecidos ou ignorados. O uso indiscriminado de produtos solventes clorados fez com que tais compostos se tornassem uma das principais fontes de contaminação no setor industrial. Por serem compostos de alta toxicidade, quando presentes na água subterrânea, mesmo em baixas concentrações, a tornam imprópria para o consumo. Técnicas de remediação como atenuação natural, ou que envolvam bombeamento e tratamento de água subterrânea contaminada por solventes clorados, vêm sendo substituídas por metodologias químicas destrutivas, por apresentarem resultados satisfatórios em um período de tempo inferior às técnicas utilizadas anteriormente. Este trabalho objetiva apresentar os resultados obtidos em duas áreas industriais onde foram aplicadas técnicas de remediação, envolvendo a redução química in situ, através da injeção de polisulfeto de cálcio e a oxidação química in situ, com a injeção de permanganato de potássio. Em ambas as áreas, os contaminantes organoclorados são os principais compostos de interesse presentes na água subterrânea. A redução química in situ é uma metodologia que utiliza um agente químico para reduzir óxidos de ferro III, presentes naturalmente no aquífero sedimentar, e transformá-los em ferro II que, por sua vez reduzirá contaminantes organoclorados. A principal característica desta metodologia é a eliminação contígua de dois átomos de cloro das moléculas dos contaminantes, o que tende e diminuir ou eliminar o acúmulo de subprodutos tóxicos como cloreto de vinila. Na oxidação química in situ, o agente promove a transferência de elétrons, onde os íons Cl- das moléculas dos contaminantes são substituídos por H+. Devido à baixa reatividade entre o permanganato de potássio e a matriz do aquífero durante as reações de oxidação química, este oxidante pode ser transportado pelos processos advectivo e dispersivo juntamente com o fluxo da água subterrânea e persistir por um período maior de tempo, reagindo com os contaminantes orgânicos. Ensaios de bancada com solo saturado contaminado de uma das áreas de estudo mostraram excelentes resultados na utilização do polisulfeto de cálcio, mas o mesmo não foi observado no teste piloto realizado em campo. Embora tenha sido observada dispersão do produto nas proximidades de pelo menos um dos pontos onde a solução foi injetada, notou-se que não houve redução significativa dos contaminantes, evidenciando que o ferro II não foi eficaz no processo de degradação. Isto pode ter sido ocasionado por uma série fatores, como possíveis reações, características hidráulicas, ou geológicas do meio. Portanto, o prosseguimento desta metodologia como alternativa de remediação para toda a área impactada foi descontinuado, tornando necessário novos estudos para avaliar a melhor técnica aplicável na área. Quanto à área onde foi aplicada a oxidação química, a remediação foi considerada eficiente. Ao longo do período de vinte e dois meses, quando foram realizadas atividades de monitoramento da água subterrânea, observou-se a presença do permanganato de potássio nas áreas mais impactadas das plumas de contaminação, fato que permitiu o processo de transferência de elétrons e consequentemente a oxidação dos contaminantes. Vinte e dois meses após as atividades de injeção, o principal contaminante identificado na área, o 1,-1-dicloroeteno, foi detectado em apenas um ponto com concentração superior a meta de remediação obtida anteriormente à injeção. Considerando que durante a sequência das atividades relacionadas à remediação, este contaminante sofreu alterações em seus valores toxicológicos estabelecidos pela Agência de Proteção Ambiental dos Estados Unidos, e passou a ser considerado um composto não carcinogênico, todos os poços apresentaram-se com concentrações inferiores a nova meta de remediação calculada. Como efeito colateral, foi observado o aumento das concentrações de metais dissolvidos, como: alumínio, bário, cromo e ferro. Tal mobilização de metais para a água subterrânea pode ser considerada temporária. Após o total consumo do permanganato de potássio pelos contaminantes ainda presentes no meio, as características físico-químicas do aquífero retornarão à situação identificada naturalmente, permitindo a precipitação dos metais.Most of the currently known contaminated areas are the result of past practices, where precautions regarding protection of human health and the environment were either unknown or ignored. The indiscriminate use of chlorinated solvents is the driving factor that has led to such compounds becoming one of the main sources of contamination in the industrial sector. Chlorinated solvents are highly toxic and, when present at even low concentrations in groundwater, they make this resource unfit for human consumption. Such remediation techniques as natural attenuation, or that involve pumping and treatment of groundwater contaminated by chlorinated solvents, are currently being replaced by destructive chemical methods, as they show satisfactory results in a shorter period of time than previously used techniques. This study has the objective of showing the results obtained at two industrial sites where remediation techniques have been used involving in-situ chemical reduction, through injection of calcium polysulfide, and in-situ chemical oxidation, with injection of potassium permanganate. At both sites, organochlorine contaminants are the main compounds of concern present in groundwater. In-situ chemical reduction is a methodology that uses a chemical agent in order to reduce iron III oxides, naturally present in the sedimentary aquifer, and transform them into iron II which, in turn, reduces the organochlorine contaminants. The principal characteristic of this methodology is that of contiguous elimination of two chlorine atoms from contaminant molecules, which tends to reduce or eliminate accumulation of such toxic byproducts as vinyl chloride. In in-situ chemical oxidation, the chemical agent brings about a transfer of electrons, where the Cl- ions of contaminant molecules are replaced by H+ ions. Due to the low degree of reactivity between potassium permanganate and the aquifer matrix during chemical oxidation reactions, this oxidizing agent can be transported via groundwater flow, by advective and dispersive processes, and persist for a longer period of time, reacting with organic contaminants. Bench tests performed with contaminated saturated soil from one of the sites under study showed excellent results through the use of calcium polysulfide; however, the same results were not observed during a pilot test performed in the field. Although product dispersion was observed in the vicinity of at least one of the points where the solution had been injected, it was found that there was no significant reduction of contaminants, showing that iron II was not effective in enhancing the degradation process. This could have been the result of a series of factors, for example, possible reactions or the hydraulic or geological characteristics of the medium. Therefore, it was decided not to continue with use of this methodology as a remediation alternative for the whole impacted area, making it necessary for further studies in order to assess the best technique applicable at the site. With respect to the site where a chemical oxidation approach was adopted, remediation was considered to be effective. Over a period of twenty-two months, during which groundwater monitoring activities were performed, the presence of potassium permanganate was observed in the most impacted areas of the contamination plumes, a fact that allowed for the electron transfer process and, consequently, contaminant oxidation. Twenty-two months after initiation of injection activities, the main contaminant identified at the site (1,1-dichloroethene) was only detected at one point at a concentration exceeding the post-remediation target value established prior to commencing these activities. Considering that, during the sequence of activities related to the remediation process, this contaminant underwent changes in its toxicological values established by the United States Environmental Protection Agency, and came to be considered a non-carcinogenic compound, all wells showed concentrations below the new calculated post-remediation target. As a collateral effect, there was found to be an increase in concentrations of such dissolved metals as aluminum, barium, chromium and iron. Such mobilization of metals to groundwater can be considered a temporary effect. Following complete consumption of potassium permanganate by contaminants still present in the medium, the physical-chemical characteristics of the aquifer will return to the situation occurring naturally, allowing for the precipitation of these metals.
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Kong, Wei. "Reactive processing methods for functionalisation of polymers and in-situ compatibilisation of poly(ethylene terephthalate)-based blends." Thesis, Aston University, 2001. http://publications.aston.ac.uk/9629/.
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One of the main objectives of this study was to functionalise various rubbers (i.e. ethylene propylene copolymer (EP), ethylene propylene diene terpolymer (EPDM), and natural rubber (NR)) using functional monomers, maleic anhydride (MA) and glycidyl methacrylate (GMA), via reactive processing routes. The functionalisation of the rubber was carried out via different reactive processing methods in an internal mixer. GMA was free-radically grafted onto EP and EPDM in the melt state in the absence and presence of a comonomer, trimethylolpropane triacrylate (TRlS). To optinuse the grafting conditions and the compositions, the effects of various paranleters on the grafting yields and the extent of side reactions were investigated. Precipitation method and Soxhlet extraction method was established to purifY the GMA modified rubbers and the grafting degree was determined by FTIR and titration. It was found that without TRlS the grafting degree of GMA increased with increasing peroxide concentration. However, grafting was low and the homopolymerisation of GMA and crosslinking of the polymers were identified as the main side reactions competing with the desired grafting reaction for EP and EPDM, respectively. The use of the tri-functional comonomer, TRlS, was shown to greatly enhance the GMA grafting and reduce the side reactions in terms of the higher GMA grafting degree, less alteration of the rheological properties of the polymer substrates and very little formation of polyGMA. The grafting mechanisms were investigated. MA was grafted onto NR using both thermal initiation and peroxide initiation. The results showed clearly that the reaction of MA with NR could be thermally initiated above 140°C in the absence of peroxide. At a preferable temperature of 200°C, the grafting degree was increased with increasing MA concentration. The grafting reaction could also be initiated with peroxide. It was found that 2,5-dimethyl-2,5-bis(ter-butylproxy) hexane (TIOI) was a suitable peroxide to initiate the reaction efficiently above 150°C. The second objective of the work was to utilize the functionalised rubbers in a second step to achieve an in-situ compatibilisation of blends based on poly(ethylene terephthalate) (PET), in particular, with GMA-grafted-EP and -EPDM and the reactive blending was carried out in an internal mixer. The effects of GMA grafting degree, viscosities of GMAgrafted- EP and -EPDM and the presence of polyGMA in the rubber samples on the compatibilisation of PET blends in terms of morphology, dynamical mechanical properties and tensile properties were investigated. It was found that the GMA modified rubbers were very efficient in compatibilising the PET blends and this was supported by the much finer morphology and the better tensile properties. The evidence obtained from the analysis of the PET blends strongly supports the existence of the copolymers through the interfacial reactions between the grafted epoxy group in the GMA modified rubber and the terminal groups of PET in the blends.
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Coffel, Joel. "Implementation and modeling of in situ magnetic hyperthermia." Diss., University of Iowa, 2016. https://ir.uiowa.edu/etd/2058.
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Health-care associated infections (HAIs) on medical implant surfaces present a unique challenge to physicians due to their existence in the biofilm phenotype which defends the pathogen from antibiotics and the host’s own immune system. A 2004 study in the U.S. showed that 2 to 4% of implanted devices become infected and must be treated via surgical explantation—a process that is both expensive and dangerous for the patient. A potential, alternative strategy to antibiotics and surgery is to use heat delivered wirelessly by a magnetic coating. This thermal treatment strategy has the potential to kill these HAIs directly on the implanted surface and without the patient requiring surgery.
This thesis introduces an iron oxide nanoparticle composite coating that is wirelessly heated using energy converted from an alternating magnetic field. Iron oxide nanoparticle composites are demonstrated to be remotely heated in both hydrophilic and hydrophobic polymer composites. In designing the composite coating, multiple parameters were investigated for how they impact the normalized heating rate of the material. Specifically, the amount of iron in the coating, the coating thickness, the polymer type, and the orientation of the coating relative to the applied magnetic field were investigated. Power output was shown to increase proportionally with iron loading whereas nearly two times the amount of power output was observed for the same coatings positioned parallel to magnetic field lines versus those positioned perpendicular—a result believed to be due to magnetic shielding from neighboring particles.
Microscope slides coated with 226 µm of composite delivered up to 10.9 W cm⁻² of power when loaded with 30.0% Fe and positioned parallel in a 2.3 kA m⁻¹AMF. Pseudomonas aeruginosa biofilms were grown directly on these coatings and heated for times ranging from 1 to 30 min and temperatures from 50 to 80 °C. Less than one order of magnitude of cell death was observed for temperatures less than 60 °C and heat shock times less than 5 min. Up to six orders of magnitude reduction in viable bacteria were observed for the most extreme heat shock (80 °C for 30 min).
Introducing this wirelessly heated composite into the body has the potential to kill harmful bacteria but at the risk of thermally damaging the surrounding tissue and organs if the treatment is not designed and predicted intelligently. Thermal energy will propagate differently depending on the surrounding heat sink, with convective heat sinks (i.e. those due to blood flow) requiring much more power to reach the same surface temperature than a conduction-only heat sink. To study how heat is transferred in biological tissues, a robust, poly(vinyl alcohol) tissue phantom was developed that can be poured to accommodate any geometry, is volume stable in water and under thermal stress, and can be modified with inert particle fillers to adjust its thermal conductivity from 0.475 to 0.795 W m⁻¹°C⁻¹. In vitro heat transfer was measured through this hydrogel tissue phantom with at least 10 °C of temperature rise, penetrating 5 mm of tissue in less than 120 sec for an 80 °C boundary condition.
A computational model was used to solve three-dimensional energy transfer through a combined fluid mimic/tissue mimic heat sink spanning the same surface boundary condition. The model was validated with experimental models using a custom designed heat transfer station. This scenario is applicable in the instance where the same coating is subject to starkly different heat sinks: half subject to convective heat loss, half to conductive heat loss. Based on these conditions, a magnetic coating would need to be designed that has a power gradient up to 15 times larger on the fluid half versus the other.
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Carabante, Ivan. "Study of arsenate adsorption on iron oxide by in situ ATR-FTIR spectroscopy." Licentiate thesis, Luleå tekniska universitet, Industriell miljö- och processteknik, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-26159.
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Stabilization of arsenic contaminated soils by iron oxides has been proposed as a remediation technique to prevent leaching of arsenate into the environment. However, fundamental studies are needed to establish under which conditions the complexes formed are stable. A new method based on ATR-FTIR spectroscopy was adapted to study the adsorption of arsenate species on iron oxides. The measurements required the use of D2O as solvent. The amount of arsenate complexes adsorbed on the iron oxide increased with decreasing pD in the range studied, viz. pD 4-12. Arsenate complexes adsorbed at pD 4 desorbed from the film to some extent as the pD was increased to 8.5 or 12. The stability of arsenate complexes adsorbed on the iron oxide evidently changed with the change in pD, most likely due to the electrostatic repulsion between the negatively charged oxoanion and the more negatively charged iron oxide as the pD increased. From competitive adsorption experiments it was found that arsenate species were more strongly bonded to the iron oxide than phosphate species. Furthermore, it was found that two different phosphate complexes formed on the iron surface at pD 4, one deuterated and the other one de-deuterated. The complexes showed very different stability. The deuterated phosphate complex was desorbed easily from the iron oxide film as arsenate was added to the system whereas the de-deuterated phosphate complex only desorbed slightly from the film upon adding arsenate.This work has increased the fundamental knowledge of the iron oxide/arsenate/phosphate system, which will be of importance for the development of more effective soil remediation techniques.Godkänd; 2009; 20090905 (ivacar); LICENTIATSEMINARIUM Ämnesområde: Kemisk teknologi/Chemical Technology Examinator: Professor Jonas Hedlund, Luleå tekniska universitet Tid: Fredag den 2 oktober 2009 kl 10.00 Plats: C 305, Luleå tekniska universitet
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Miller, Duane D. "In Situ Infrared Spectroscopy Study of Gold Oxidation Catalysis." University of Akron / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=akron1152205534.
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Turner, Jessica S. "Investigating marine particle distributions and processes using in situ optical imaging in the Gulf of Alaska." Thesis, University of Alaska Fairbanks, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=1605427.
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The Gulf of Alaska is a seasonally productive ecosystem surrounded by glaciated coastal mountains with high precipitation. With a combination of high biological production, inputs of suspended sediments from glacial runoff, and contrasting nutrient regimes in offshore and shelf environments, there is a great need to study particle cycling in this region. I measured the concentrations and size distributions of large marine particles (0.06-27 mm) during four cruises in 2014 and 2015 using the Underwater Vision Profiler (UVP). The UVP produces high resolution depth profiles of particle concentrations and size distributions throughout the water column, while generating individual images of objects >500 μm including marine snow particles and mesozooplankton.
The objectives of this study were to 1) describe spatial variability in particle concentrations and size distributions, and 2) use that variability to identify driving processes. I hypothesized that UVP particle concentrations and size distributions would follow patterns in chlorophyll a concentrations. Results did not support this hypothesis. Instead, a major contrast between shelf and offshore particle concentrations and sizes was observed. Total concentrations of particles increased with proximity to glacial and fluvial inputs. Over the shelf, particle concentrations on the order of 1000-10,000/L were 1-2 orders of magnitude greater than offshore concentrations on the order of 100/L. Driving processes over the shelf included terrigenous inputs from land, resuspension of bottom sediments, and advective transport of those inputs along and across the shelf. Offshore, biological processes were drivers of spatial variability in particle concentration and size. High quantities of terrigenous sediments could have implications for enhanced particle flux due to ballasting effects and for offshore transport of particulate phase iron to the central iron-limited gyre. The dominance of resuspended material in shelf processes will inform the location of future studies of the biological pump in the coastal Gulf of Alaska. This work highlights the importance of continental margins in global biogeochemical processes.
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Chaudhry, Zahra. "A study of optical, physical and chemical properties of aerosols using in-situ measurements." College Park, Md.: University of Maryland, 2009. http://hdl.handle.net/1903/9512.
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Thesis (Ph.D.) -- University of Maryland, College Park, 2009.Thesis research directed by: Dept. of Atmospheric and Oceanic Sciences. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Chen, James. "In-situ study of the chemical composition of photochromic Yttrium Oxy-Hydrides thin films." Thesis, Uppsala universitet, Tillämpad kärnfysik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-389390.
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Ng, Kar Wei. "Enhancements in light output power by MOCVD patterned growth and in situ roughening /." View abstract or full-text, 2007. http://library.ust.hk/cgi/db/thesis.pl?ECED%202007%20NG.
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Menghao, Chen. "Developing a novel in-situ polymerisation process for fully bioresorbable fibre reinforced composites." Thesis, University of Nottingham, 2018. http://eprints.nottingham.ac.uk/49215/.
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In recent decades, fully bioresorbable polymer composites with appropriate biocompatibility and mechanical properties have provided an exciting opportunity to replace conventional metal alloy implants. This work explores the development of a novel, one-step in-situ polymerisation (ISP) process for the manufacture of fully bioresorbable phosphate based glass fibre (PGF) reinforced composites with matrix materials of polycaprolactone (PCL), polycaprolactone-polylactic acid copolymer (PLA-PCL) and polylactic acid (PLA). Composites produced via conventional laminate stacking (LS) process were used as the comparison to demonstrate the advantages that ISP can provide in composites quality. In-vitro degradation in phosphate buffered saline (PBS) at 37 °C, flexural property retention and cytocompatibility were investigated for both LS and ISP composites. Additionally, the composites were degraded under representative flexural loading for high cycle fatigue analysis to understand and predict their lifetime in service and their likely mechanisms of failure. Significantly more robust fibre/matrix interface and uniform fibre distribution along the cross section of the composites were achieved via ISP compared to LS. These enhancements resulted in considerably higher initial mechanical properties (~450 MPa and ~24 GPa for flexural strength and modulus, close to the upper range of human cortical bone properties), prolonged mechanical retention, less and slower water uptake and mass loss profiles for the ISP composites. The flexural fatigue life of the ISP composites was at least 10 times longer than the LS composites counterpart within both dry and wet (within PBS at 37 °C) testing environments. Furthermore, positive cytocompatibility was also found for both the LS and ISP PLA/PGF composites. Conclusively, ISP composites exhibited considerably enhanced mechanical retention and drastically improved media resistance, making those fully bioresorbable composites significantly more favourable as materials for bioresorbable bone fracture fixation devices.
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Aberg, Christopher Mark. "Modification of Polymer Membranes: A Study of Crosslinking and In-Situ Growth of Palladium-Containing Nanoparticles in Polymer Matrices." NCSU, 2008. http://www.lib.ncsu.edu/theses/available/etd-07092008-182305/.
Full textAbstract:
A crucial step in obtaining pure hydrogen is separating it from other compoundsâmainly CO2âthat often accompany hydrogen in industrial chemical reactions. Advanced membrane technology may prove to be the key to the successful, economical production of molecular hydrogen for the eventual consumer market. Size-sieving glassy polymer membranes can separate H2 on the basis of its small size. Alternatively, reverse-selective rubbery polymers can expedite the passage and, hence, removal of CO2 due to its relatively high solubility in such membranes alone or in conjunction with dissociative chemical reactions. Transition-metal membranes and their alloys can adsorb H2 molecules, dissociate the molecules into H atoms for transport through interstitial sites, and subsequently recombine the H atoms to form molecular H2 again on the opposite membrane side. Microporous amorphous silica and zeolite membranes comprising thin films on a multilayer porous support exhibit good sorption selectivity and high diffusion mobilities for H2, leading to high H2 fluxes. Finally, carbon-based membranes, including carbon nanotubes, may be viable for H2 separation on the basis of selective surface flow and molecular sieving. One approach to achieve higher gas selectivity is to cross-link polymer membranes, thus restricting the ability of gases of various sizes to readily permeate at an unimpeded rate. Cross-linking can occur through a number of means: UV and ion irradiation, plasma treatment, or chemical and thermal techniques. In this study, a chemical technique has been chosen to cross-link the polyimide Matrimid®. Polyimides are well-established as gas-separation membranes due to their intrinsically low free-volume and correspondingly high H2 selectivity relative to other gases such as CO2. Prior studies have established that H2/CO2 selectivity can be improved by cross-linking polyimides with diamines differing in spacer length. In this first set of work, we follow the evolution of macroscopic and microscopic properties of a commercial polyimide over long cross-linking times (tx) with 1,3-diaminopropane. According to spectroscopic analysis, the cross-linking reaction saturates after ~24 h, whereas tensile, nanoindentation and stress-relaxation tests reveal that the material stiffens, and possesses a long relaxation time that increases, with increasing tx. Although differential scanning calorimetry shows that the glass transition temperature decreases systematically with increasing tx, permeation studies indicate that the permeabilities of H2 and CO2 decrease, while the H2/CO2 selectivity increases markedly, with increasing tx. At long tx, the polyimide becomes impermeable to CO2, suggesting that it could be used as a barrier material. Alternatively, polymer nanocomposites continue to receive considerable attention as multifunctional hybrid materials, with most nanocomposites fabricated by physical dispersion of surface-functionalized nanoscale objects. In the second study, we explore the viability of growing Pd-containing nanoparticles from Na2PdCl4 in two different polymers â hyper-cross-linked polystyrene (HPS) and an aromatic polyimide (PIm). In HPS, single Pd-containing nanoparticles possessing a relatively narrow size distribution (ca. 1-4 nm) are observed to form upon reduction of the divalent PdCl4-2 ions and cluster more readily if the reducing agent is introduced as a liquid. Single nanoparticles with a broad size distribution ranging from ~2 to 16 nm develop in PIm, which simultaneously undergoes chemical cross-linking during ion reduction. The conditions yielding Pd incorporation in PIm are explored through the use of instrumental neutron activation analysis. Such Pd-containing hybrid materials hold promise in molecular catalysis and gas separations. Results from these studies give prospect that these materials, with a great deal of future research, could be developed for H2 separations applications.
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Tumuluri, Uma. "In-Situ Spectroscopic Investigation of CO2 and SO2 Adsorption Mechanisms on Amine Sorbents." University of Akron / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=akron1407743891.
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Jacobs, Kelvin Stephen. "Investigation of the activity and selectivity of the MoO3/AI2O3 catalyst and the structural investigation using in-situ raman." Master's thesis, University of Cape Town, 2002. http://hdl.handle.net/11427/5314.
Full textAbstract:
Bibliography: leaves 89-94.Metathesis is a very versatile reaction, which allows the conversion of Simple, relatively inexpensive olefins into specialty, high-purity olefins which are useful intermediates in the fragrance, agricultural and many other specialty chemical industries. Supported molybdenum on alumina is an active heterogeneous catalyst for the metathesis of olefins. Its activity, as a function of time, passes a maximum. It is known that the activity of molybdenum-based catalyst increases up to monolayer capacity. Catalysts with various Mo-Ioadings were prepared by controlled adsorption method using ammonium heptamolybdate as a precursor. A catalyst using a new slurry impregnation method was also prepared for comparative reasons. Before the metathesis process, the molybdenum catalysts are activated at 550°C under N2 in a fixed bed reactor. The loading of the prepared catalysts was below and above monolayer capacity. It was observed that up to a loading 0.3 g Mo03 per g Ab03 the initial conversion increases more than proportional to the Mo03- loading. The catalysts with a Mo03-loading higher than 0.3 g Mo03 per gram AIz03 show initially a lower activity, ie. The activity per molybdenum atom in the catalyst decreases. With increasing time-on-stream the activity of the catalysts declines. The decline is much stronger over the catalysts with a rligher initial activity.
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Waldemer, Rachel H. "Determination of the rate of contaminant oxidations by permanganate : implications for in situ chemical oxidation (ISCO) /." Full text open access at:, 2004. http://content.ohsu.edu/u?/etd,20.
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Petersson, Karsten. "Combined formulations based on prodrugs and in situ gelling systems : design and pharmaceutical chemical characterisation /." [Cph.] : The Danish University of Pharmaceutical Sciences, Department of Pharmaceutics, 2004. http://www.dfh.dk/phd/defences/karstenpetersson.htm.
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Fuhrig, Leland T., and Leland T. Fuhrig. "In-situ chemical oxidation of 1,1-DCE in a low-conductivity zone using potassium permanganate." Thesis, The University of Arizona, 2006. http://hdl.handle.net/10150/626911.
Full textAbstract:
Injection of potassium permanganate (KMn04) was conducted in an effort to
remediate a Superfund Site contaminated with 1, 1-Dichloroethene (1, 1-DCE) at the
Samsonite building area of the Tucson International Airport in Tucson, AZ. In-situ
chemical oxidation such as this has been an effective method of source zone remediation
for several other sites contaminated with chlorinated compounds due to its ability to
destroy the compounds relatively quickly and effectively. Laboratory tests were done to
determine the correct amount ofKMn04 to use based on the levels of 1,1-DCE present in
the soil. Once this specific mass of KMn04 was established, it was injected into eight
wells out of nine in a square grid over 21 days and allowed to break down 1, 1-DCE over
time. A 3-dimensional profile of hydraulic conductivity values was generated using a
regression equation that predicted them from sediment classifications. The program
MODFLOW-2000 was employed, using the hydraulic conductivity values along with
additional physical parameters from the site to simulate the KMn04 injection. This
model can be used in conjunction with MT3DMS, a program designed to simulate solute
transport, as a tool that can be used to predict the behavior and extent of KMn04
distribution over a given time period.
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Huang, Dan. "In Situ Infrared Studies of Photooxidation of Ethanol and Bacteria on TiO2-Based Catalysts." University of Akron / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=akron1398093214.
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Xu, Xiuyuan. "Interaction of Chemical Oxidants with Aquifer Materials." Thesis, University of Waterloo, 2006. http://hdl.handle.net/10012/2891.
Full textAbstract:
In situ chemical oxidation (ISCO) is a leading-edge technology for soil and groundwater remediation, and involves injecting a chemical oxidant (e. g. , permanganate, hydrogen peroxide, or persulfate) into the subsurface to deplete contaminant mass through oxidation. Since the delivery of the chosen oxidant to the target treatment zone must occur in situ, the interaction between the injected oxidant and the aquifer material is a key controlling factor for a successful ISCO application. While many published ISCO studies have focused on the interaction between an oxidant and target contaminants, many questions still remain on the interaction between a potential oxidant and the aquifer material. Through a series of bench-scale experiments with aquifer materials collected from 10 sites throughout North America, the research presented in this thesis provides insight into the interaction between these aquifer materials and two widely used ISCO oxidants; permanganate and hydrogen peroxide. The investigation into the interaction between aquifer materials and permanganate consisted of three series of bench-scale experiments: (1) long-term batch experiments which were used to investigate permanganate consumption in response to fundamental geochemical properties of the aquifer materials, (2) short-term batch experiments which were designed to yield kinetic data that describe the behavior of permanganate in the presence of various aquifer materials, and (3) column experiments which were used to investigate permanganate transport in a system that mimics the subsurface environment. The long-term experiments which involved more than 180 batch reactors monitored for ~300 days showed that the unproductive permanganate consumption by aquifer materials or natural oxidant demand (NOD) is strongly affected by the initial permanganate concentration, permanganate to solid mass ratio, and the reductive components associated with each aquifer material. This consumption cannot be represented by an instantaneous reaction process but is kinetically controlled by at least a fast and slow reactive component. Accordingly, an empirical expression for permanganate NOD in terms of aquifer material properties, and a hypothetical kinetic model consisting of two reaction components were developed. In addition, a fast and economical permanganate NOD estimation procedure based on a permanganate COD test was developed and tested. The investigation into short-term permanganate consumption (time scale of hours) was based on the theoretical derivation of the stoichiometric reaction of permanganate with bulk aquifer material reductive components, and consisted of excess permanganate mass experiments and excess aquifer material mass experiments. The results demonstrated that permanganate consumption by aquifer materials can be characterized by a very fast reaction on the order of minutes to hours, confirming the existence of the fast reaction component of the hypothetical kinetic model used to describe the long-term permanganate NOD observations. A typical experimental column trial consisted of flushing an aquifer-material packed column with the permanganate source solution until sufficient permanganate breakthrough was observed. The permanganate column results indicated the presence of a fast and slow consumption rate consistent with the long-term batch test data, and an intermediate consumption rate affecting the shape of the rising limb of the breakthrough curve. Finally, a comparison of the experimental results between batch and column systems indicated that permanganate NOD was significantly overestimated by the batch experiments; however, permanganate consumption displayed some similarity between the batch and column systems and hence an empirical expression was developed to predict permanganate consumption in physically representative column systems from batch reactor data.
The interaction between hydrogen peroxide and aquifer materials was also investigated with both batch and column experiments. A series of batch experiments consisting of a mixture of 2% hydrogen peroxide and 15 g of aquifer materials was used to capture the overall hydrogen peroxide behavior in the presence of various aquifer materials. The results indicated that the decomposition of hydrogen peroxide in the presence of various aquifer materials followed a first-order rate law, and was strongly affected by the content of amorphous transition metals (i. e. , Fe and Mn). Although hydrogen peroxide decomposition is related to the total organic carbon (TOC) content of natural aquifer materials, the results from a two-week long exposure to hydrogen peroxide suggests that not all forms of natural organic matter contributed to this decomposition. A multiple linear regression analysis was used to generate predictive relationships to estimate hydrogen peroxide decomposition rate coefficients based on various aquifer material properties. The enhanced stability of hydrogen peroxide was investigated under six scenarios with the addition of chelating reagents. The impact of a new green chelating reagent, S,S'-ethylenediaminedisuccinate (EDDS), on the stability of hydrogen peroxide in the presence of aquifer materials was experimentally examined and compared to that of the traditional and widely used chelating reagent, Ethylenediaminetetraacetic (EDTA). The results demonstrated that EDDS was able to significantly increase the stability of hydrogen peroxide, especially for aquifer materials with low TOC contents and/or high dissolvable Fe and Mn contents. Finally, to complement and expand the findings from the batch experiments, column experiments were conducted with aquifer materials from five representative sites. Each column was flushed with two types of source solutions (with or without EDDS addition) at two flow rates. The column experiments showed that the use of EDDS resulted in an earlier breakthrough and a higher stable concentration of hydrogen peroxide relative to the case without the addition of EDDS. The hydrogen peroxide decomposition rate coefficients generated from the column data were significantly higher than those generated from the batch test data and no correlation between hydrogen peroxide decomposition coefficients obtained from column and batch experiments was observed. Based on the column experimental results, a one-dimensional transport model was also calibrated to capture the hydrogen peroxide breakthrough process.
Data from bench-scale tests are routinely used to support both ISCO design and site screening, and therefore the findings from this study can be used as guidance on the utility of these tests to generate reliable and useful information. In general, the behavior of both permanganate and hydrogen peroxide in the presence of aquifer materials in batch and the column systems clearly indicates that the use of batch test data for ISCO system design is questionable since column experiments are believed to mimic in situ conditions better since column systems provide more realistic aquifer material contact. Thus the scaling relationships developed in this study provide meaningful tools to transfer information obtained from batch systems, which are widely employed in most bench-scale studies, to column systems.
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Lin, Feng. "Preparation and Characterization of Polymer TiO2 Nanocomposites via In-situ Polymerization." Thesis, University of Waterloo, 2006. http://hdl.handle.net/10012/2849.
Full textAbstract:
Polymer nanocomposites are already a part of many important of worldwide businesses: automotive (molded part in cars), electronics and electrical engineering, household products, packaging industry, aircraft interiors, appliance components, security equipments. Among many nanocomposite precursors, TiO2 nanopowder is increasingly being investigated due to its special properties. The objective of this work is to synthesize and characterize polymer-TiO2 hybrid nanocomposites. When dispersed at the nanoscale level TiO2 could act as visually transparent UV filters and high-thermomechanical-performance materials. The synthesis strategy involved two steps. Firstly, aggregated TiO2, as received, was modified by 3-trimethoxysilyl propylmethacrylate aimed at altering its surface characteristics. The effect of modifier concentration on changing the physicochemical properties of TiO2 surface was evaluated. Size distribution of unmodified and modified TiO2 nanopowders was measured using a particle size analyzer. The qualitative and quantitative grafting of vinyl groups on TiO2 surface was investigated with Fourier transform-infrared (FTIR) and proton nuclear magnetic resonance (1H-NMR) spectroscopy. Secondly, styrene monomer was then added to carry out copolymerization with vinyl groups on the modified TiO2 by free radical initiator 2,2-azobis isobutyronitrile (AIBN) in bulk medium. FTIR spectra confirmed the formation of nanocomposites with polystyrene chains chemically linked to the surface of TiO2 nanopowders. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) indicated that the resulting nanocomposites displayed higher thermal stability and maintained similar glass transition temperatures (Tg) compared with pure PS. Ultraviolet ?visible spectroscopy (UV-Vis) investigated that these nanocomposites have improved optical properties potentially acting as visually transparent UV filters. Such incremented properties were attributed to the nancoscale dispersion (20-50nm size) of TiO2 into polystyrene matrix, which morphology was observed by scanning electron microscopy (SEM).
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Slopek, Ryan Patrick. "In-situ Monitoring of Photopolymerization Using Microrheology." Thesis, Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/7194.
Full textAbstract:
Photopolymerization is the basis of several multi-million dollar industries including films and coating, inks, adhesives, fiber optics, and biomaterials. The fundamentals of the photopolymerization process, however, are not well understood. As a result, spatial variations of photopolymerization impose significant limitations on applications in which a high spatial resolution is required.
To address these issues, microrheology was implemented to study the spatial and temporal effects of free-radical photopolymerization. In this work a photosensitive, acrylate resin was exposed to ultraviolet light, while the Brownian motion of micron sized, inert fluorescent tracer particles was tracked using optical videomicroscopy. Statistical analysis of particle motion yielded data that could then be used to extract rheological information about the embedding medium as a function of time and space, thereby relating UV exposure to the polymerization and gelation of monomeric resins.
The effects of varying depth, initiator concentration, inhibitor concentration, composition of the monomer, and light intensity on the gelation process were studied. The most striking result is the measured difference in gelation time observed as a function of UV penetration depth. The observed trend was found to be independent of UV light intensity and monomer composition. The intensity results were used to test the accuracy of energy threshold model, which is used to empirically predict photo-induced polymerization.
The results of this research affirm the ability of microrheology to provide the high spatial and temporal resolution necessary to accurately monitor the photopolymerization process. The experimental data provide a better understanding of the photo-induced polymerization, which could lead to expanded use and improved industrial process optimization. The use of microrheology to monitor photopolymerization can also aid in the development of predictive models and offer the ability to perform in-situ quality control of the process.
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Quig, Lauren Dekker. "Transport of Heat Activated Persulfate and Its Application for In-situ Chemical Oxidation of Residual Trichloroethylene." PDXScholar, 2015. https://pdxscholar.library.pdx.edu/open_access_etds/2629.
Full textAbstract:
In situ chemical oxidation is a promising technology for the remediation of persistent subsurface contamination. Increasingly, the persulfate ion is being studied for use in these systems, both on its own as a strong oxidant and as the precursor to the even more reactive sulfate radical. Persulfate has been shown to treat a wide range of contaminants, from traditional Superfund contaminants such as chlorinated solvents to emerging pharmaceutical contaminants. Additionally, persulfate ISCO can be tailored to site and pollutant specific characteristics based on the method of persulfate activation (e.g., energy and catalysis activation) to the sulfate radical. Thermal activation of persulfate is particularly promising because it can be easily controlled, requires no additional reagents, and commonly creates only non-toxic end products. While persulfate in-situ chemical oxidation technology is being commercially used, a mechanistic study of the physical and chemical processes controlling the effectiveness of this remedial approach is not well documented in the literature. Published work characterizing persulfate ISCO largely focuses on reactions in aqueous, batch systems, which fail to provide crucial design data when working with ever transient, multi-phase groundwater systems.
The purpose of this research was twofold. Initial studies characterized the overall transport behavior of unactivated and thermally-activated persulfate (20, 60, and 90°C) in one-dimensional soil column systems packed with a natural sandy porous media. This necessitated the development of a flow-through, temperature-controlled, continuous-injection system for the delivery of heat-activated persulfate. Finally, as a proof of concept, experiments were conducted to investigate persulfate ISCO as a remedial approach for residual-phase trichloroethylene (TCE), a commonly detected, persistent subsurface contaminant.
At all activation temperatures investigated, persulfate exhibited ideal transport behavior with negligible differences in the observed breakthrough curves of persulfate ion and nonreactive tracers in miscible displacement experiments. Additionally, moment analysis of the breakthrough curves measured for persulfate ion in solution indicated negligible interaction of persulfate with the sandy material under steady-state flow (average retardation factor equaled 1.00 ± 0.021). Persulfate ISCO for residual-phase trichloroethylene (TCE) was characterized at two flow rates, 0.2 mL/min and 0.5 mL/min, resulting in two degrees of apparent persulfate activation, 39.5% and 24.6%, respectively. Both ISCO soil column systems showed an initial, long-term plateau in effluent concentrations measured for TCE indicating steady-state dissolution of pure phase TCE. Effluent concentrations of TCE began decreasing after 75 and 100 pore volumes (normalized for the residual fraction of TCE in individual soil columns) in the 39.5% and 24.6% activated persulfate columns as compared to 110 pore volumes in the control study (flushed with electrolyte only). Pseudo first-order rate constants for the decreasing TCE concentrations were calculated using log-linear regression analysis. The measured reaction rate constants for the control, the 0.2 mL/min (39.5% activation) study, and the 0.5 mL/min (24.6% activation) study equaled 0.044, 0.063, and 0.083 hr-1, respectively. Additionally, moment analysis of the complete dissolution of TCE in the persulfate/activated persulfate remediation systems indicated approximately 33% degradation/oxidation of TCE mass present.
As shown by this and other work, persulfate has enormous potential as a subsurface remediation technology. A more thorough understanding of the physical and chemical mechanisms controlling the behavior and application of persulfate in the subsurface, especially under transient conditions, is necessary for the growth of this technology. By characterizing heat-activated persulfate under dynamic conditions, describing the overall transport of persulfate/activated persulfate in a natural porous media, as well as a proof of concept for the ISCO treatment of a residual nonaqueous phase liquid, this work aids in improving the implementation of persulfate ISCO systems.