Ventilation in underground mines is vital to creating a safe working environment. Though there have been numerous improvements in mine ventilation, it is still difficult to ascertain data on the state of the ventilation system following a disaster in which ventilation controls have been potentially damaged. This information is important when making the decision to send rescue personnel into the mine. By utilizing tracer gas techniques, which are powerful techniques for monitoring ventilation systems, especially in remote or inaccessible areas, analysis of the ventilation system immediately following a mine emergency can be more rapidly ascertained. However, the success of this technique is largely dependent on the accuracy of release and sampling methods. Therefore, an analysis of sampling methods is crucial for rapid response and dependable results during emergencies. This research project involves evaluating and comparing four well-accepted sampling techniques currently utilized in the mining industry using sulfur hexafluoride, an industry standard, as the tracer gas. Additionally, Solid Phase Microextraction (SPME) fibers are introduced and evaluated as an alternative sampling means. Current sampling methods include plastic syringes, glass syringes, Tedlar bags, and vacutainers. SPME fibers have been successfully used in a variety of industries from forensics to environmental sampling and are a solvent-less method of sampling analytes. To analyze these sampling methods, samples were taken from a 0.01% standard mixture of SF6 in nitrogen and analyzed using electron capture gas chromatography (GC). The technical and practical issues surrounding each sampling method were also observed and discussed. Furthermore, the use of multiple tracer gases could allow for rapid assessment of the functionality of ventilation controls. This paper describes experimentation related to the determination of a novel mine tracer gas. Multiple tracer gases greatly increase the level of flexibility when conducting ventilation surveys to establish and monitor controls. A second tracer would substantially reduce the time it takes to administer multiple surveys since it is not necessary to wait for the first tracer to flush out of the mine which can take up to a few days. Additionally, it is possible to release different tracers at different points and follow their respective airflow paths, analyzing multiple or complex circuits. This would be impossible to do simultaneously with only one tracer. Three different tracer gases, carbon tetrafluoride, octofluoropropane, and perfluoromethlycyclohexane, were selected and evaluated on various GC columns through utilizing different gas chromatographic protocols. Perfluoromethylcyclohexane was selected as the novel tracer, and a final protocol was established that ensured adequate separation of a mixture of SF6 and perfluoromethylcyclohexane. Since there is limited literature comparing sampling techniques in the mining industry, the findings and conclusions gained from the sampling comparison study provide a benchmark for establishing optimal sampling practices for tracer gas techniques. Additionally, the determination of a novel tracer gas that can be used with and separated from SF6 using the same analytical method increases the practicality and robustness of multiple mine tracer gas techniques. This initial work will contribute to the larger project scope of determining a methodology for the remote characterization of mine ventilation systems through utilizing multiple mine tracer gases and computational fluid dynamics (CFD). This will be completed through several phases including initial laboratory testing of novel tracer gases in a model mine apparatus to develop a methodology for releasing, sampling, and modeling a mine ventilation plan and tracer gas dispersion in CFD and eventually completing field trials to validate and enhance the multiple tracer gas methodology. / Master of Science

Interwell tracers help us understand flow patterns within the reservoir and in getting reliable information of the reservoir continuity. Thus, one can obtain different information about the reservoir barriers, fractures and productivity from the amount of tracer produced at each tracer. The main objective of this study is an attempt to model interwell connectivity by analytically calculating missing tracer data in oil fields for the next step of the calculation of swept volume. The feasibility of using analytical solutions to estimate early data and check differences was carried out. In general; all of these applications refer to the applicability and relative ease of using tracers in oil field. The idea is to determine if it is possible to get a good estimate of the swept pore volumes at an early time before the tracer flood is finished since it often takes a long time to capture the complete tracer tail and there is great value in being able to get an early estimate of the results Results indicate that the extrapolation of tracer tail and using the residence time distribution method give accurate sweep volume predictions without the need to wait for long times to get the full tracer profile. / text

No description available.

No description available.

No description available.

Gas fluidised beds are important components in many process industries, e.g. coal combustors and granulators, but not much is known about the movement of the solids. Positron Emission Particle Tracking (PEPT) enables the movement of a single, radioactive tracer particle to be followed rapidly and faithfully. Experiments were carried out in columns sized between 70 and 240mm diameter, operating in the bubbling regime at ambient process conditions using particles of group B and D (Geldart Classification). Particle motion was tracked and the data applied to models for particle movement at the gas distributor as well as close to other surfaces and to models for particle circulation in beds of cohesive particles. In the light of these data, models for particle and bubble interaction, particle circulation, segregation, attrition, erosion, heat transfer and fluidised bed scale-up rules were reassessed. Particle motion is directly caused by bubble motion, and their velocities were found to be equal for particles travelling in a bubble. PEPT enables particle circulation to be measured, giving a more accurate correlation for future predictions. Particle motion follows the scale-up rules based on similarities of the bubble motion in the bed. A new group of parameters was identified controlling the amount ofattrition in fluidised beds and a new model to predict attrition is proposed.

A basic phenomenon modeled computationally is tracer transport in a flow field, such as in porous medium simulation. We analyze the stability and convergence of a fully conservative characteristic method, the Volume Corrected Characteristics-Mixed Method [4] (VCCMM) applied to advection of a dilute tracer in an incompressible flow. Numerical tests for the optimal convergence rate match the results of our theoretical proof. We avoid the CFL constraint on the time step size and obtain a higher order convergence rate compared with Godunov's method. We describe the implementation of the VCCMM, where we feature and define a polyline class for the volume computation of trace-back regions. Some numerical examples show that large time steps can be used in practice, no overshoot or undershoot arises in the solution, and less numerical diffusion is produced compared with Godunov's method. An application to a nuclear waste disposal problem is also presented, where we simulate the processes of advection, reaction, and diffusion of radioactive elements in a simplified far field model. Finally, an extension of the VCCMM is developed for compressible flows, and a stability and convergence analysis is presented. / text

Master of Science / Department of Mechanical and Nuclear Engineering / Mohammad H. Hosni / Byron W. Jones / Due to the high occupant density and large number of travelers on commercial aircraft, it is crucial to limit the transport of contaminants and pathogens amongst passengers. In order to minimize the exposure of passengers to various contaminants of different sizes and characteristic, all mechanisms influencing airflow movement within an aircraft cabin need to be understood. The use of personal gaspers on commercial aircraft and their relation to airborne contaminants and pathogens transport is one such mechanism that was investigated. Tracer gas testing using carbon dioxide (CO[subscript]2) was conducted in a wide-body, 11-row Boeing 767 aircraft cabin mockup using actual aircraft components for air distribution. Three separate experiments were conducted investigating the effect of gaspers on the transport of contaminants. The first series of experiments focused on the effect of gaspers on longitudinal transport patterns within an aircraft cabin environment by measuring the concentration of tracer gas along the length of the aircraft cabin. The second experiment investigated what fraction of air a passenger inhales originates from a gasper in relation to the overall cabin ventilation. The final set of experiments determined if gaspers could limit close range person-to-person transmission of exhaled contaminants. Three separate sets of conclusions were drawn, one for each series of experiments. The first conclusion is that gaspers disrupt the longitudinal transport of contaminants within the aircraft cabin. The second conclusion is that less than 5% of the air inhaled by a passenger is originating from a gasper even with a gasper directed at the passenger's face. This low percentage is a result of the turbulent airflow within the aircraft cabin causing the gasper jet to quickly mix with the overall cabin ventilation air. The last conclusion is that gaspers can reduce person-to-person transmission of exhaled contaminants as much as nearly 90% in some cases. In other cases the gaspers are found to have negligible or negative impact on the transmission of contaminants. These conclusions are dependent upon where the tracer gas plume emanated from, the sampling location, and the configuration of gaspers around the tracer gas release point.

A dificuldade na detecção precoce de focos infecciosos específicos causados por bactérias tem aumentado a necessidade de pesquisar novas técnicas para este fim, uma vez que estes focos necessitam de tratamento prolongado com antibióticos e, em alguns casos, até mesmo drenagem ou, se for o caso, a remoção de próteses ou enxertos. A detecção de infecções bacterianas por cintilografia teria a vantagem de uma imagem de corpo inteiro, desde que traçadores específicos estejam disponíveis. Esse estudo visa a obtenção de aptâmeros específicos para identificação de bactérias para uso futuro como radiofármaco. A metodologia SELEX (do inglês Systematic Evolution of Ligands by Exponential Enrichment) pode gerar oligonucleotídeos (aptâmeros) que são capazes de se ligar com alta afinidade e especificidade a alvos específicos, desde pequenas moléculas até proteínas complexas, usando ciclos de enriquecimento e amplificação. Aptâmeros podem ser marcados com diferentes radionuclídeos tais como 99mTc, 18F e 32P. Aptâmeros anti-peptideoglicano, o principal componente da parede celular externa bacteriana, foram obtidos através da SELEX. Células inteiras de Staphylococcus aureus também foram utilizadas para a realização da SELEX para células (cell-SELEX). A seleção dos aptâmeros foi realizada por meio de dois procedimentos distintos. Esses foram o processo A em que foram realizados 15 ciclos da SELEX nos quais a separação dos oligonucleotídeos ligados ao peptideoglicano dos não ligados foi efetuada por filtração e o processo B em que foram realizados 15 ciclos com a separação realizada por centrifugação, seguidos de 5 ciclos de cell-SELEX. A SELEX teve início com um pool de ssDNA (DNA de fita simples). Para o processo A, inicialmente a biblioteca de ssDNA foi incubada com o peptideoglicano e a amplificação dos oligonucleotídeos que foram capazes de se ligar ao peptideoglicano foi realizada por PCR (Polymerase Chain Reaction). Os oligonucleotídeos amplificados foram novamente incubados com o peptideoglicano, amplificados e purificados. Ao fim de 15 ciclos de seleção, os oligonucleotídeos selecionados foram clonados. O produto de recombinação foi utilizado para transformar a bactéria Escherichia coli Top10F. O DNA plasmidial de 40 colônias selecionadas foram extraídos e quantificados. Os plasmídeos foram sequenciados, duas sequências diferentes (Antibac1 e Antibac2) foram obtidas e as estruturas secundárias determinadas. Os aptâmeros obtidos foram sintetizados e marcados com 32P. Os aptâmeros marcados foram incubados com células de S. aureus e a quantidade de ssDNA ligado às bactérias foi determinado por espectrometria de cintilação líquida. A biblioteca de oligonucleotídeos marcada com 32P foi usada como controle. Para o aptâmero Antibac1 a radiação foi 28 vezes maior do que a obtida com o controle e para o aptâmero Antibac2 22 vezes. Um ensaio de especificidade foi conduzido com os aptâmeros marcados utilizando-se células de S. aureus, E.coli, Candida albicans e fibroblastos humanos. Para os dois aptâmeros (Antibac1 e Antibac2) a ligação às células bacterianas foi significativamente superior à verificada para C. albicans e fibroblastos, demonstrando a especificidade dos mesmos para identificação de bactérias. Para o processo B após os 15 ciclos da SELEX foi realizada a cell-SELEX que começou com o produto do 15o ciclo sendo incubado com células de S.aureus. Ao fim de 5 ciclos de seleção, os oligonucleotídeos selecionados foram clonados e sequenciados como no processo A. Onze diferentes sequências foram obtidas de 21 clones e as estruturas secundárias foram determinadas. Os aptâmeros obtidos pelo processo A apresentaram alta afinidade e especificidade para bactérias. Os aptâmeros obtidos pelo processo B serão avaliados quanto a estes parâmetros em trabalhos futuros. / The difficulty in early detection of specific foci caused by bacteria in the bacterial infection has raised the need to search for new techniques for this purpose, since these foci require prolonged treatment with antibiotics and in some cases even drainage or, if applicable, removal of prostheses or grafts. Detection of bacterial infections by scintigraphy had the advantage that a whole body image could be obtained, since specific tracers were available. This study aims to obtain aptamers specific for bacteria identification for future use as radiopharmaceutical. The SELEX (Systematic Evolution of Ligands by Exponential Enrichment) methodology can generate oligonucleotides (aptamers) that are able to bind with high affinity and specificity to a specific target, from small molecules to complex proteins, by using rounds of enrichment and amplification. Aptamers can be labeled with different radionucleotides such as 99mTc, 18F and 32P. In this study, aptamers anti-peptidoglycan, the main component of the bacterial outer cell wall, were obtained through SELEX. Whole cells of Staphylococcus aureus were also used to perform the SELEX to cells (cell-SELEX). The selection of aptamers was performed by two different procedures (A and B). The A process has been accomplished by 15 SELEX rounds in which the separation of the oligonucleotides bound to the peptidoglycan of unbound ones was performed by filtration. In the B process 15 SELEX rounds were performed using the centrifugation for this separation, followed by 5 rounds cell-SELEX. The SELEX started with a pool of ssDNA (single stranded DNA). For A process, initially a library of ssDNA was incubated with peptidoglycan and the amplification of oligonucelotides that were able to bind to peptidoglycan was performed by PCR (Polymerase Chain Reation). The amplified oligonucleotides were again incubated with peptidoglycan, amplified and purified. At the end of 15 selection rounds the selected oligonucleotides were cloned. The product of recombination was used to transform Escherichia coli Top10F. The plasmid DNA from 40 selected colonies were extracted and quantified. The plasmids were sequenced, two different sequences (Antibac1 and Antibac2) were obtained and their secondary structures determined. The aptamers obtained were synthesized and labeled with 32P. The labeled aptamers were incubated with S. aureus cells and the amount of radiolabeled ssDNA was determined by liquid scintillation spectrometry.

While restoring hyporheic flowpaths has been cited as a benefit to stream restoration structures, little documentation exists confirming that constructed restoration structures induce hyporheic exchange comparable to natural stream features. This study compares a stream restoration structure (cross-vane) to a natural feature (riffle) concurrently in the same stream reach using time-lapsed electrical resistivity (ER) tomography. Using this hydrogeophysical approach, I am able to quantify hyporheic extent and transport beneath the cross-vane structure and riffle. I interpret from the geophysical data that the cross-vane and natural riffle induced spatially and temporally unique hyporheic extent and transport, and the cross-vane created both spatially larger and temporally longer hyporheic flowpaths than the natural riffle. Tracer from the 4.67-hr injection was detected along flowpaths for 4.6-hrs at the cross-vane and 4.2-hrs at the riffle. The spatial extent of the hyporheic zone at the cross-vane was 12% larger than at the riffle. I compare ER results of this study to vertical fluxes calculated from temperature profiles and conclude significant differences in the interpretation of hyporheic transport from these different field techniques. Results of this study demonstrate a high degree of heterogeneity in transport metrics at both the cross-vane and riffle and significant differences between the hyporheic flowpath networks at the two different features. Our results suggest that restoration structures may be capable of creating sufficient exchange flux and residence times to achieve the same ecological functions as natural features, but engineering of the physical and biogeochemical environment may be necessary to realize those benefits.