Dissertations / Theses on the topic 'Particle'

Second phase particles play an important role in the recrystallization of aluminium alloys. They give rise to high level of local lattice misorientation around the particle, in particle deformation zone (PDZ) during processing. These can act as potent nucleation sites for new recrystallized grains in a process known as particle stimulated nucleation (PSN). This mechanism is essential to produce material with a more random texture and small grain size, which helps e.g. ductility and formability. A new HRDIC technique is used here in combination with EBSD to investigate the evolution of deformation structures by linking the local deformation (by Digital Image Correlation, DIC) to the lattice orientation before and after deformation by EBSD measurements and compared with the CPFEM predictions. The results show that strain is very heterogeneous during deformation and concentrates mainly in slip bands. The spacing between these bands is affected by several factors: applied strain, crystallographic orientation and the existence of small dispersoids. Thus, the relationship between the strain, particle size and rotation in the deformation zone is much more complex than predicted by existing models.

Laser flare can often be a major issue in particle image velocimetry (PIV) involving solid boundaries in a flow or a gas-liquid interface. The use of fluorescent light from dye-doped particles has been demonstrated in water applications, but reproducing the technique in an airflow is more difficult due to particle size constraints and safety concerns. The following thesis is formatted in a hybrid manuscript style, including a full paper presenting the applications of fluorescent Kiton Red 620 (KR620)-doped polystyrene latex microspheres in PIV. These particles used are small and monodisperse, with a mean diameter of 0.87 μm. The KR620 dye exhibits much lower toxicity than other common fluorescent dyes, and would be safe to use in large flow facilities. The first sections present a general introduction followed by a validation experiment using a standard PIV setup in a free jet. This work was the first to demonstrate PIV using fluorescent KR620-doped microspheres in an airflow, and results from the experiment were compared to similar data taken using standard PIV techniques. For the free jet results, Mie-scattered and fluorescent PIV were compared and showed average velocities within 3% of each other at the nozzle exit. Based on the PIV validation requirements used, this was deemed to be more of an indication of nozzle unsteadiness rather than an error or bias in the data. Furthermore, fluorescent PIV data obtained vector validation rates over 98%, well above the standard threshold of 95%. The journal article expands on the introductory work and analyzes testing scenarios where fluorescent PIV allows for velocity measurements much closer to a solid surface than standard, Mie-scattered PIV. The fluorescent signal from the particles is measured on average to be 320 ± 10 times weaker than the Mie scattering signal from the particles. This fluorescence-to-Mie ratio was found to be nonuniform, with the typical signal ratio for a single particle expected to fall between 120 and 870. This reduction in signal is counterbalanced by greatly enhanced contrast via optical rejection of the incident laser wavelength. Fluorescent PIV with these particles is shown to eliminate laser flare near surfaces, in one case leading to 63 times fewer spurious velocity vectors than an optimized Mie scattering implementation in a region more than 5 mm from an angled surface. In the appendix, a brief summary of an experiment to characterize the temperature sensitivity of the KR620 dye is included. This experiment concluded that the KR620 particles did not exhibit sufficient temperature sensitivity to warrant further investigation at the time.
Master of Science

Cette these presente une etude de la production et de la desintegration semi-electronique des particules charmees dans la diffusion profondement inelastique de neutrinos mu. L'analyse est basee sur l'ensemble des evenements mu- e+, selectionnes a partir des donnees enregistrees par l'experience nomad dans le faisceau de neutrinos du cern au cours de l'annee 1995. Afin de reduire drastiquement le bruit de fond des evenements mu- e+, nous avons elabore une premiere selection sur les donnees. Puis, une etude d'evenements neutrinos simules dans nomad nous a permis de controler la qualite de la simulation, et d'affiner la selection sur les donnees. Nous avons mesure un signal charme mu- e+. Le nombre total de candidats mu- e+, ainsi que ses distributions cinematiques sont sensibles a la structure interne du nucleon. Par comparaison des distributions cinematiques du signal extrait sur les donnees et des evenements charmes simules, nous avons mesure le contenu en quarks etranges du nucleon. La these comporte une partie instrumentale principalement sur le detecteur a rayonnement de transition (drt), qui contribue a l'identification des electrons dans l'experience. Cependant, pour utiliser au mieux ses capacites de discrimination l'uniformite de la reponse de l'ensemble de ses elements est necessaire. Ce travail a permis d'une part de mesurer et d'ajuster l'uniformite du drt sur l'ensemble de la surface de ses 9 plans, et d'autre part d'etre a meme de controler en permanence cette uniformite au cours de la prise de donnees.

The regular transmittance of light or similar radiation through a flowing suspension of particles fluctuates because of the random occurrence of particles in the beam.In the work presented here, a theory for this fluctuating behaviour with the emphasison dispersions of mm-length slender cylindrical particles having circular crosssections is given. The particles in question are wood pulp fibres, which as a first approximation are considered to have a cylinder shape. Four possible measurementprinciples are described theoretically and experimentally. The four principles are for the measurement of concentration, length distribution characterized as lengthclasses, mean length, and mean width. The usefulness in industrial process monitoring of two of these principles is exemplified with pulp measurements. In order to estimate model errors, numerical simulations were used. Although other techniques such as image analysis may compete, the technique presented here is attractive because of the simplicity of the measurement device used.
QC 20100806

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2008.
Includes bibliographical references (p. 51).
Using the the SLIC simulator software and the org.lcsim reconstruction framework package, the performance of Mat Charles' NonTrivialPfa.java PFA for several different detector variations was found by determining the mass resolution for a given detector geometry. The variations tested included the layering of the hadronic calorimeter, the radius of the calorimeter, the interaction material utilized in the hadronic calorimeter and the type of read-out used in the calorimeter. Based on the performance of the PFA for the different variations, the optimal detector specifications for use with the PFA were discovered. The optimal detector was found to use scintillator as the sensitive layer and steel as the interaction material in the hadronic calorimeter. A general trend in increased performance with more layering was also observed for the calorimeter. Also illuminated in the study was the discovery of unexpected performance for radius variations.
by Lawrence Fernando Bronk.
S.B.

Filtration is the most efficient method of aerosol monitoring and control. A number of theories (Bradley, 1932); (Hamaker, 1937); (Johnson et al., 1971); (Wang and Kasper, 1991); (Dahneke, 1995); (Wall et al., 1990) have been developed to describe the particle interaction with surface of a filter and to estimate the probability of the particle adhesion onto a surface. A range of the particle, filter and process parameters could contribute to the strength of the adhesion. Some of them are: hardness and cross-sectional shape of the fiber, smoothness of either the fiber or particle, air humidity, the effect of particle shape and many others. Obviously, the particle size (and correspondingly the surface area) also plays a crucial role in the bouncing processes. However, despite its importance in the research field the detailed mechanisms of the particle-fiber collision and possibility for the particle to bounce or to be re-entrained have not been fully explored. Therefore, there is a need for a theoretical and experimental knowledge concerning the influence of particle bouncing on filtration and separation processes. Although, some work on the effect of particle shape on filtration process has been done, there is still need for further research regarding the influence of motion of the particles of different shape along a fiber...
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Engineering
Science, Environment, Engineering and Technology
Full Text

Le but de cette thèse est de développer les techniques et les connaissances en imagerie par particules chargées pour l’application en radiothérapie par hadrons. Dans un premier temps, les techniques d’estimation de parcours sont étudiées de façon phénoménologique et subséquemment retrouvée depuis une approache physique théorique, pour chaque ion depuis le proton jusqu’au carbone. Les techniques prenant en compte la connaissance préalable du milieu ont aussi été étudiées pour obtenir l’estimé de parcours le plus précis pour toute particule chargée. À l’aide de cet estimé de parcours précis et rapide, nous nous sommes par la suite penchés sur le problème de la reconstruction tomographique par particules chargées. La première étape de ce processus était l’inclusion de l’algorithme d’estimation de parcours développé précédemment dans les techniques conventionnelles de reconstruction itérative tomographique, telle que la reconstruction algébrique itérative, par particules chargées. Nous nous sommes rapidement aperçus de la lenteur du processus de reconstruction itérative et des problèmes de convergence reliés à ce type d’optimisation. Face à ces difficultés, nous avons décidé de développer notre propre algorithme de reconstruction tomographique dont la principale différence est l’optimisation individuelle des projections radiographiques. L’idée principale de notre algorithme est de diviser l’objet de la reconstruction en voxels et de retrouver le pouvoir d’arrêt d’une colonne de voxels de façon à ce qu’il maximise la probabilité de l’énergie perdue des protons qui la traversent. Le parcours des protons dans chaque colonne de voxels est calculé par l’algorithme de prédiction de parcours développé au début de la thèse. De cette façon, nous optimisons la résolution spatiale des radiographies individuellement. Les nouvelles radiographies peuvent par la suite être utilisées comme données d’entrée dans un algorithme conventionnel de reconstruction tomographique. La reconstruction tomographique nécessite un grand nombre de projections et celles-ci peuvent être longues à acquérir, ce qui est problématique dans un contexte clinique où le temps de faisceau est précieux et limité. Il existe donc une exigence d’efficacité et d’optimisation de la procédure. Dans cette optique, la prochaine partie de cette thèse s’est concentrée sur l’utilisation d’un ensemble limité de radiographies pour retrouver les paramètres de pouvoir d’arrêt dans les tissus, et ce de façon spécifique à un patient. La rationnelle de ce projet est que les radiographies peuvent être acquises rapidement, directement avant le traitement. Nous avons étudié la possibilité de combiner cet ensemble limité de radiographies avec l’image tomodensitométrique à simple énergie acquise lors du diagnostic. Une méthode permettant d’effectuer ce processus à été développée et évaluée sur différents fantômes anthropomorphiques représentant différentes sections du corps humain. Il a été prouvé qu’avec un nombre limité de radiographies, acquérable rapidement avant le traitement, il est possible de retrouver le pouvoir d’arrêt massique dans les tissus spécifiques à un patient avec une grande précision (< 1% d’erreur par rapport à la référence). Pour terminer la thèse, nous avons procédé à l’application expérimentale des différents algorithmes développés théoriquement. En collaboration avec le DKFZ (Deutsches Krebsforschungszentrum, Heidelberg, Allemagne), le HIT (Heavy Ion Therapy facility, Heidelberg, Allemagne) et la collaboration proton-CT (Loma Linda University, University of California San Francisco, University of California Santa Cruz, University Baylor, États-Unis) nous avons mis en place une expérience de tomographie par particules d’hélium. Nous avons pu utiliser le synchrotron du HIT en combinaison avec le détecteur proton-CT développé par la collaboration éponyme pour produire et détecter à la fois en entrée et en sortie un faisceau de particules chargées traversant un médium pré-déterminé. Cette étude nous a permis d’évaluer le bruit et la précision atteignable en imagerie tomographique par particules chargées.
The goal of this thesis is to develop methodology and knowledge in charged particle imaging for application in hadron radiotherapy. First, the various existing algorithm to estimate the path of a charged particle crossing a medium have been studied as a function of their efficiency and accuracy. To find an optimal solution for those two constraints, a phenomenological model has been developed that predict the most likely particle path in a medium. It was subsequently grounded in a solid physical background and extended to every ion up to carbon. Furthermore, prior-knowledge techniques were introduced to obtain the highest accuracy in the path estimate prediction for any ions. With these techniques in hand, we then approached the problem of tomographic reconstruction of charged particle radiographies. The first step of the work was to introduce the aforementioned path estimate method into a conventional charged particle reconstruction algorithm such as the algebraic reconstruction technique. This process requires a large calculation time that prevents an efficient reconstruction in a clinical work-flow, and suffer from convergence problems that leave the images with a high-noise level. Thus, it was decided to develop our own tomographic reconstruction algorithm in which the main difference resided in the optimization of individual projections. In our algorithm, the object was discretized into voxels and the average relative stopping power through voxel columns defined from the source to the detector pixels is optimized such that it maximizes the likelihood of the proton energy loss. The length spent by individual protons in each column is calculated through the path estimate. In this way, the spatial resolution of individual radiographies is optimized. The new radiographies can then be fed into a conventional X-ray tomographic algorithm, such as FDK, for a high resolution pCT reconstruction. The tomographic reconstruction requires a large number of projections and each can be individually long to acquire. This might cause problem into a clinical context where the beam time is costly and limited. There is a demand for efficiency in the procedure, which requires optimization of the algorithms. In this context, the next part of the thesis consisted on developing a method to utilize a subset of proton radiographies to retrieve stopping power parameters specific to the patient. This was done because a fewer number of radiographies can be acquired rapidly prior to the treatment. We studied the possibility of combining those subset of proton radiographies (usually either a single radiography or a pair) with single-energy X-ray tomographic images acquired prior for diagnostic. A new algorithm was develop to combine these two types of images and evaluated against various anthropomorphic phantoms that represents three body sites, the lung, the pelvis and the head. It has been shown that with a limited number of radiographies, it is possible to retrieve stopping power specific to the patient with an RMS error to the ground truth below 1%. The last part of the work was the experimental validation of the various algorithms developed. In collaboration with the (Deutsches Krebsforschungszentrum, Heidelberg), the HIT (Heavy Ion Therapy facility, Heidelberg) and the pCT collaboration (Loma Linda University, University of California San Francisco, University of California Santa Cruz, University Baylor), we designed an experiment to acquire charged particle tomographic images. To do so, we used the HIT’s synchrotron to produce a collimated beam of charged particle combined with the pCT detector to detect the particle before and after having crossed a pre-determined medium. This study allowed us to evaluate the noise, the spatial resolution and the precision achievable with charged particle imaging tomography.

Thesis: Ph. D. in Atmospheric Chemistry, Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2017.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 197-219).
This thesis explores ways in which single particle mass spectrometry can be extended, whether through hardware improvements, or through the use of advanced data processing techniques to provide new kinds of aerosol chemistry measurements. Most of this work has been carried out using the Particle Analysis by Laser Mass Spectrometry (PALMS) instrument, an aircraft deployable mass spectrometer that uses intense (~10 9 Wcm -2 ) UV laser pulses to vaporize and ionize single particles and measures their mass spectra using a time-of-flight mass spectrometer. Near-term and long-term hardware improvements as well as advanced data analysis techniques are explored in order to extract new chemical information from the thus obtained single particle mass spectra. Hardware improvements to PALMS are explored, such as the use of a high-powered femtosecond laser to obtain single particle mass spectra and a new high resolution compact mass analyzer. Also, a new commercial mass spectrometer LAAPToF is characterized and compared to PALMS. In addition to hardware improvements, novel data analysis techniques for analysis of single particle mass spectra were developed as a part of this work. In particular, a new method to identify biologically-derived particles is presented and used to derive vertical profiles of bioaerosol from near-surface to the upper troposphere.
by Maria Anna Zawadowicz.
Ph. D. in Atmospheric Chemistry

Thesis (M.S.)--University of Akron, Dept. of Mathematics, 2009.
"May, 2009." Title from electronic thesis title page (viewed 7/28/2009) Advisor, Dmitry Golovaty; Faculty Readers, Gerald Young, Patrick Wilber; Department Chair, Joseph Wilder; Dean of the College, Chand Midha; Dean of the Graduate School, George R. Newkome. Includes bibliographical references.

The understanding of human exposure to indoor particles of all sizes is important to enable exposure control and reduction, but especially for smaller particles since the smaller particles have a higher probability of penetration into the deeper parts of the respiratory tract and also contain higher levels of trace elements and toxins. Due to the limited understanding of the relationship between particle size and the health effects they cause, as well as instrument limitations, the available information on submicrometer (d < 1.0 µm) particles indoors, both in terms of mass and number concentrations, is still relatively limited. This PhD project was conducted as part of the South-East Queensland Air Quality program and Queensland Housing Study aimed at providing a better understanding of ambient particle concentrations within the indoor environment with a focus on exposure assessment and control. This PhD project was designed to investigate comprehensively the sources and sinks of indoor aerosol particles and the relationship between indoor and outdoor aerosol particles, particle and gaseous pollutant, as well as the association between indoor air pollutants and house characteristics by using, analysing and interpreting existing experimental data which were collected before this project commenced, as well as data from additional experiments which were designed and conducted for the purpose of this project. The focus of this research was on submicrometer particles with a diameter between 0.007 - 0.808 µm. The main outcome of this project may be summarised as following: * A comprehensive review of particle concentration levels and size distributions characteristics in the residential and non-industrial workplace environments was conducted. This review included only those studies in which more general trends were investigated, or could be concluded based on information provided in the papers. This review included four parts: 1) outdoor particles and their effect on indoor environments; 2) the relationship between indoor and outdoor concentration levels in the absence of indoor sources for naturally ventilated buildings; 3) indoor sources of particles: contribution to indoor concentration levels and the effect on I/O ratios for naturally ventilated buildings; and 4) indoor/outdoor relationship in mechanically ventilated buildings. * The relationship between indoor and outdoor airborne particles was investigated for sixteen residential houses in Brisbane, Australia, in the absence of operating indoor sources. Comparison of the ratios of indoor to outdoor particle concentrations revealed that while temporary values of the ratio vary in a broad range from 0.2 to 2.5 for both lower and higher ventilation conditions, average values of the ratios were very close to one regardless of ventilation conditions and of particle size range. The ratios were in the range from 0.78 to 1.07 for submicrometer particles, from 0.95 to 1.0 for supermicrometer particles and from 1.01 to 1.08 for PM2.5 fraction. Comparison of the time series of indoor to outdoor particle concentrations showed a clear positive relationship existing for many houses under normal ventilation conditions (estimated to be about and above 2 h-1), but not under minimum ventilation conditions (estimated to be about and below 1 h-1). These results suggest that for normal ventilation conditions and in the absence of operating indoor sources, outdoor particle concentrations could be used to predict instantaneous indoor particle concentrations but not for minium ventilation, unless air exchange rate is known, thus allowing for estimation of the "delay constant". * Diurnal variation of indoor submicrometer particle number and particle mass (approximation of PM2.5) concentrations was investigated in fifteen of the houses. The results show that there were clear diurnal variations in both particle number and approximation of PM2.5 concentrations, for all the investigated houses. The pattern of diurnal variations varied from house to house, however, there was always a close relationship between the concentration and human indoor activities. The average number and mass concentrations during indoor activities were (18.2±3.9)×10³ particles cm-³ and (15.5±7.9) µg m-³ respectively, and under non-activity conditions, (12.4±2.7)x10³ particles cm-³ (11.1±2.6) µg m-³, respectively. In general, there was a poor correlation between mass and number concentrations and the correlation coefficients were highly variable from day to day and from house to house. This implies that conclusions cannot be drawn about either one of the number or mass concentration characteristics of indoor particles, based on measurement of the other. The study also showed that it is unlikely that particle concentrations indoors could be represented by measurements conducted at a fixed monitoring station due to the large impact of indoor and local sources. * Emission characteristics of indoor particle sources in fourteen residential houses were quantified. In addition, characterizations of particles resulting from cooking conducted in an identical way in all the houses were measured. All the events of elevated particle concentrations were linked to indoor activities using house occupants diary entries, and catalogued into 21 different types of indoor activities. This enabled quantification of the effect of indoor sources on indoor particle concentrations as well as quantification of emission rates from the sources. For example, the study found that frying, grilling, stove use, toasting, cooking pizza, smoking, candle vaporizing eucalyptus oil and fan heater use, could elevate the indoor submicrometer particle number concentration levels by more than 5 times, while PM2.5 concentrations could be up to 3, 30 and 90 times higher than the background levels during smoking, frying and grilling, respectively. * Indoor particle deposition rates of size classified particles in the size range from 0.015 to 6 µm were quantified. Particle size distribution resulting from cooking, repeated under two different ventilation conditions in 14 houses, as well as changes to particle size distribution as a function of time, were measured using a scanning mobility particle sizer (SMPS), an aerodynamic particle sizer (APS), and a DustTrak. Deposition rates were determined by regression fitting of the measured size-resolved particle number and PM2.5 concentration decay curves, and accounting for air exchange rate. The measured deposition rates were shown to be particle size dependent and they varied from house to house. The lowest deposition rates were found for particles in the size range from 0.2 to 0.3 µm for both minimum (air exchange rate: 0.61±0.45 h-1) and normal (air exchange rate: 3.00±1.23 h-1) ventilation conditions. The results of statistical analysis indicated that ventilation condition (measured in terms of air exchange rate) was an important factor affecting deposition rates for particles in the size range from 0.08 to 1.0 µm, but not for particles smaller than 0.08 µm or larger than 1.0 µm. Particle coagulation was assessed to be negligible compared to the two other processes of removal: ventilation and deposition. This study of particle deposition rates, the largest conducted so far in terms of the number of residential houses investigated, demonstrated trends in deposition rates comparable with studies previously reported, usually for significantly smaller samples of houses (often only one). However, the results compare better with studies which, similarly to this study, investigated cooking as a source of particles (particle sources investigated in other studies included general activity, cleaning, artificial particles, etc). * Residential indoor and outdoor 48 h average levels of nitrogen dioxide (NO2), 48h indoor submicrometer particle number concentration and the approximation of PM2.5 concentrations were measured simultaneously for fourteen houses. Statistical analyses of the correlation between indoor and outdoor pollutants (NO2 and particles) and the association between house characteristics and indoor pollutants were conducted. The average indoor and outdoor NO2 levels were 13.8 ± 6.3 ppb and 16.7 ± 4.2 ppb, respectively. The indoor/outdoor NO2 concentration ratio ranged from 0.4 to 2.3, with a median value of 0.82. Despite statistically significant correlations between outdoor and fixed site NO2 monitoring station concentrations (p = 0.014, p = 0.008), there was no significant correlation between either indoor and outdoor NO2 concentrations (p = 0.428), or between indoor and fixed site NO2 monitoring station concentrations (p = 0.252, p = 0.465,). However, there was a significant correlation between indoor NO2 concentration and indoor submicrometer aerosol particle number concentrations (p = 0.001), as well as between indoor PM2.5 and outdoor NO2 (p = 0.004). These results imply that the outdoor or fixed site monitoring concentration alone is a poor predictor of indoor NO2 concentration. * Analysis of variance indicated that there was no significant association between indoor PM2.5 and any of the house characteristics investigated (p > 0.05). However, associations between indoor submicrometer particle number concentration and some house characteristics (stove type, water heater type, number of cars and condition of paintwork) were significant at the 5% level. Associations between indoor NO2 and some house characteristics (house age, stove type, heating system, water heater type and floor type) were also significant (p < 0.05). The results of these analyses thus strongly suggest that the gas stove, gas heating system and gas water heater system are main indoor sources of indoor submicrometer particle and NO2 concentrations in the studied residential houses. The significant contributions of this PhD project to the knowledge of indoor particle included: 1) improving an understanding of indoor particles behaviour in residential houses, especially for submicrometer particle; 2) improving an understanding of indoor particle source and indoor particle sink characteristics, as well as their effects on indoor particle concentration levels in residential houses; 3) improving an understanding of the relationship between indoor and outdoor particles, the relationship between particle mass and particle number, correlation between indoor NO2 and indoor particles, as well as association between indoor particle, NO2 and house characteristics.

The understanding of human exposure to indoor particles of all sizes is important to enable exposure control and reduction, but especially for smaller particles since the smaller particles have a higher probability of penetration into the deeper parts of the respiratory tract and also contain higher levels of trace elements and toxins. Due to the limited understanding of the relationship between particle size and the health effects they cause, as well as instrument limitations, the available information on submicrometer (d < 1.0 µm) particles indoors, both in terms of mass and number concentrations, is still relatively limited. This PhD project was conducted as part of the South-East Queensland Air Quality program and Queensland Housing Study aimed at providing a better understanding of ambient particle concentrations within the indoor environment with a focus on exposure assessment and control. This PhD project was designed to investigate comprehensively the sources and sinks of indoor aerosol particles and the relationship between indoor and outdoor aerosol particles, particle and gaseous pollutant, as well as the association between indoor air pollutants and house characteristics by using, analysing and interpreting existing experimental data which were collected before this project commenced, as well as data from additional experiments which were designed and conducted for the purpose of this project. The focus of this research was on submicrometer particles with a diameter between 0.007 - 0.808 µm. The main outcome of this project may be summarised as following: * A comprehensive review of particle concentration levels and size distributions characteristics in the residential and non-industrial workplace environments was conducted. This review included only those studies in which more general trends were investigated, or could be concluded based on information provided in the papers. This review included four parts: 1) outdoor particles and their effect on indoor environments; 2) the relationship between indoor and outdoor concentration levels in the absence of indoor sources for naturally ventilated buildings; 3) indoor sources of particles: contribution to indoor concentration levels and the effect on I/O ratios for naturally ventilated buildings; and 4) indoor/outdoor relationship in mechanically ventilated buildings. * The relationship between indoor and outdoor airborne particles was investigated for sixteen residential houses in Brisbane, Australia, in the absence of operating indoor sources. Comparison of the ratios of indoor to outdoor particle concentrations revealed that while temporary values of the ratio vary in a broad range from 0.2 to 2.5 for both lower and higher ventilation conditions, average values of the ratios were very close to one regardless of ventilation conditions and of particle size range. The ratios were in the range from 0.78 to 1.07 for submicrometer particles, from 0.95 to 1.0 for supermicrometer particles and from 1.01 to 1.08 for PM2.5 fraction. Comparison of the time series of indoor to outdoor particle concentrations showed a clear positive relationship existing for many houses under normal ventilation conditions (estimated to be about and above 2 h-1), but not under minimum ventilation conditions (estimated to be about and below 1 h-1). These results suggest that for normal ventilation conditions and in the absence of operating indoor sources, outdoor particle concentrations could be used to predict instantaneous indoor particle concentrations but not for minium ventilation, unless air exchange rate is known, thus allowing for estimation of the "delay constant". * Diurnal variation of indoor submicrometer particle number and particle mass (approximation of PM2.5) concentrations was investigated in fifteen of the houses. The results show that there were clear diurnal variations in both particle number and approximation of PM2.5 concentrations, for all the investigated houses. The pattern of diurnal variations varied from house to house, however, there was always a close relationship between the concentration and human indoor activities. The average number and mass concentrations during indoor activities were (18.2±3.9)×10³ particles cm-³ and (15.5±7.9) µg m-³ respectively, and under non-activity conditions, (12.4±2.7)x10³ particles cm-³ (11.1±2.6) µg m-³, respectively. In general, there was a poor correlation between mass and number concentrations and the correlation coefficients were highly variable from day to day and from house to house. This implies that conclusions cannot be drawn about either one of the number or mass concentration characteristics of indoor particles, based on measurement of the other. The study also showed that it is unlikely that particle concentrations indoors could be represented by measurements conducted at a fixed monitoring station due to the large impact of indoor and local sources. * Emission characteristics of indoor particle sources in fourteen residential houses were quantified. In addition, characterizations of particles resulting from cooking conducted in an identical way in all the houses were measured. All the events of elevated particle concentrations were linked to indoor activities using house occupants diary entries, and catalogued into 21 different types of indoor activities. This enabled quantification of the effect of indoor sources on indoor particle concentrations as well as quantification of emission rates from the sources. For example, the study found that frying, grilling, stove use, toasting, cooking pizza, smoking, candle vaporizing eucalyptus oil and fan heater use, could elevate the indoor submicrometer particle number concentration levels by more than 5 times, while PM2.5 concentrations could be up to 3, 30 and 90 times higher than the background levels during smoking, frying and grilling, respectively. * Indoor particle deposition rates of size classified particles in the size range from 0.015 to 6 µm were quantified. Particle size distribution resulting from cooking, repeated under two different ventilation conditions in 14 houses, as well as changes to particle size distribution as a function of time, were measured using a scanning mobility particle sizer (SMPS), an aerodynamic particle sizer (APS), and a DustTrak. Deposition rates were determined by regression fitting of the measured size-resolved particle number and PM2.5 concentration decay curves, and accounting for air exchange rate. The measured deposition rates were shown to be particle size dependent and they varied from house to house. The lowest deposition rates were found for particles in the size range from 0.2 to 0.3 µm for both minimum (air exchange rate: 0.61±0.45 h-1) and normal (air exchange rate: 3.00±1.23 h-1) ventilation conditions. The results of statistical analysis indicated that ventilation condition (measured in terms of air exchange rate) was an important factor affecting deposition rates for particles in the size range from 0.08 to 1.0 µm, but not for particles smaller than 0.08 µm or larger than 1.0 µm. Particle coagulation was assessed to be negligible compared to the two other processes of removal: ventilation and deposition. This study of particle deposition rates, the largest conducted so far in terms of the number of residential houses investigated, demonstrated trends in deposition rates comparable with studies previously reported, usually for significantly smaller samples of houses (often only one). However, the results compare better with studies which, similarly to this study, investigated cooking as a source of particles (particle sources investigated in other studies included general activity, cleaning, artificial particles, etc). * Residential indoor and outdoor 48 h average levels of nitrogen dioxide (NO2), 48h indoor submicrometer particle number concentration and the approximation of PM2.5 concentrations were measured simultaneously for fourteen houses. Statistical analyses of the correlation between indoor and outdoor pollutants (NO2 and particles) and the association between house characteristics and indoor pollutants were conducted. The average indoor and outdoor NO2 levels were 13.8 ± 6.3 ppb and 16.7 ± 4.2 ppb, respectively. The indoor/outdoor NO2 concentration ratio ranged from 0.4 to 2.3, with a median value of 0.82. Despite statistically significant correlations between outdoor and fixed site NO2 monitoring station concentrations (p = 0.014, p = 0.008), there was no significant correlation between either indoor and outdoor NO2 concentrations (p = 0.428), or between indoor and fixed site NO2 monitoring station concentrations (p = 0.252, p = 0.465,). However, there was a significant correlation between indoor NO2 concentration and indoor submicrometer aerosol particle number concentrations (p = 0.001), as well as between indoor PM2.5 and outdoor NO2 (p = 0.004). These results imply that the outdoor or fixed site monitoring concentration alone is a poor predictor of indoor NO2 concentration. * Analysis of variance indicated that there was no significant association between indoor PM2.5 and any of the house characteristics investigated (p > 0.05). However, associations between indoor submicrometer particle number concentration and some house characteristics (stove type, water heater type, number of cars and condition of paintwork) were significant at the 5% level. Associations between indoor NO2 and some house characteristics (house age, stove type, heating system, water heater type and floor type) were also significant (p < 0.05). The results of these analyses thus strongly suggest that the gas stove, gas heating system and gas water heater system are main indoor sources of indoor submicrometer particle and NO2 concentrations in the studied residential houses. The significant contributions of this PhD project to the knowledge of indoor particle included: 1) improving an understanding of indoor particles behaviour in residential houses, especially for submicrometer particle; 2) improving an understanding of indoor particle source and indoor particle sink characteristics, as well as their effects on indoor particle concentration levels in residential houses; 3) improving an understanding of the relationship between indoor and outdoor particles, the relationship between particle mass and particle number, correlation between indoor NO2 and indoor particles, as well as association between indoor particle, NO2 and house characteristics.

Atmospheric ultrafine particles play an important role in affecting human health, altering climate and degrading visibility. Numerous studies have been conducted to better understand the formation process of these particles, including field measurements, laboratory chamber studies and mathematical modeling approaches. Field studies on new particle formation found that formation processes were significantly affected by atmospheric conditions, such as the availability of particle precursors and meteorological conditions. However, those studies were mainly carried out in rural areas of the northern hemisphere and information on new particle formation in urban areas, especially those in subtropical regions, is limited. In general, subtropical regions display a higher level of solar radiation, along with stronger photochemical reactivity, than those regions investigated in previous studies. However, based on the results of these studies, the mechanisms involved in the new particle formation process remain unclear, particularly in the Southern Hemisphere. Therefore, in order to fill this gap in knowledge, a new particle formation study was conducted in a subtropical urban area in the Southern Hemisphere during 2009, which measured particle size distribution in different locations in Brisbane, Australia. Characterisation of nucleation events was conducted at the campus building of the Queensland University of Technology (QUT), located in an urban area of Brisbane. Overall, the annual average number concentrations of ultrafine, Aitken and nucleation mode particles were found to be 9.3 x 103, 3.7 x 103 and 5.6 x 103 cm-3, respectively. This was comparable to levels measured in urban areas of northern Europe, but lower than those from polluted urban areas such as the Yangtze River Delta, China and Huelva and Santa Cruz de Tenerife, Spain. Average particle number concentration (PNC) in the Brisbane region did not show significant seasonal variation, however a relatively large variation was observed during the warmer season. Diurnal variation of Aitken and nucleation mode particles displayed different patterns, which suggested that direct vehicle exhaust emissions were a major contributor of Aitken mode particles, while nucleation mode particles originated from vehicle exhaust emissions in the morning and photochemical production at around noon. A total of 65 nucleation events were observed during 2009, in which 40 events were classified as nucleation growth events and the remainder were nucleation burst events. An interesting observation in this study was that all nucleation growth events were associated with vehicle exhaust emission plumes, while the nucleation burst events were associated with industrial emission plumes from an industrial area. The average particle growth rate for nucleation events was found to be 4.6 nm hr-1 (ranging from 1.79-7.78 nm hr-1), which is comparable to other urban studies conducted in the United States, while monthly particle growth rates were found to be positively related to monthly solar radiation (r = 0.76, p <0.05). The particle growth rate values reported in this work are the first of their kind to be reported for the subtropical urban area of Australia. Furthermore, the influence of nucleation events on PNC within the urban airshed was also investigated. PNC was simultaneously measured at urban (QUT), roadside (Woolloongabba) and semi-urban (Rocklea) sites in Brisbane during 2009. Total PNC at these sites was found to be significantly affected by regional nucleation events. The relative fractions of PNC to total daily PNC observed at QUT, Woolloongabba and Rocklea were found to be 12%, 9% and 14%, respectively, during regional nucleation events. These values were higher than those observed as a result of vehicle exhaust emissions during weekday mornings, which ranged from 5.1-5.5% at QUT and Woolloongabba. In addition, PNC in the semi-urban area of Rocklea increased by a factor of 15.4 when it was upwind from urban pollution sources under the influence of nucleation burst events. Finally, we investigated the influence of sulfuric acid on new particle formation in the study region. A H2SO4 proxy was calculated by using [SO2], solar radiation and particle condensation sink data to represent the new particle production strength for the urban, roadside and semi-urban areas of Brisbane during the period June-July of 2009. The temporal variations of the H2SO4 proxies and the nucleation mode particle concentration were found to be in phase during nucleation events in the urban and roadside areas. In contrast, the peak of proxy concentration occurred 1-2 hr prior to the observed peak in nucleation mode particle concentration at the downwind semi-urban area of Brisbane. A moderate to strong linear relationship was found between the proxy and the freshly formed particles, with r2 values of 0.26-0.77 during the nucleation events. In addition, the log[H2SO4 proxy] required to produce new particles was found to be ~1.0 ppb Wm-2 s and below 0.5 ppb Wm-2 s for the urban and semi-urban areas, respectively. The particle growth rates were similar during nucleation events at the three study locations, with an average value of 2.7 ± 0.5 nm hr-1. This result suggested that a similar nucleation mechanism dominated in the study region, which was strongly related to sulphuric acid concentration, however the relationship between the proxy and PNC was poor in the semi-urban area of Rocklea. This can be explained by the fact that the nucleation process was initiated upwind of the site and the resultant particles were transported via the wind to Rocklea. This explanation is also supported by the higher geometric mean diameter value observed for particles during the nucleation event and the time lag relationship between the H2SO4 proxy and PNC observed at Rocklea. In summary, particle size distribution was continuously measured in a subtropical urban area of southern hemisphere during 2009, the findings from which formed the first particle size distribution dataset in the study region. The characteristics of nucleation events in the Brisbane region were quantified and the properties of the nucleation growth and burst events are discussed in detail using a case studies approach. To further investigate the influence of nucleation events on PNC in the study region, PNC was simultaneously measured at three locations to examine the spatial variation of PNC during the regional nucleation events. In addition, the impact of upwind urban pollution on the downwind semi-urban area was quantified during these nucleation events. Sulphuric acid was found to be an important factor influencing new particle formation in the urban and roadside areas of the study region, however, a direct relationship with nucleation events at the semi-urban site was not observed. This study provided an overview of new particle formation in the Brisbane region, and its influence on PNC in the surrounding area. The findings of this work are the first of their kind for an urban area in the southern hemisphere.

Thesis (S.M.)--Massachusetts Institute of Technology, Computation for Design and Optimization Program, 2009.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 57-59).
This thesis outlines adaptivity schemes for particle-based methods for the simulation of nearly incompressible fluid flows. As with the remeshing schemes used in mesh and grid-based methods, there is a need to use localized refinement in particle methods to reduce computational costs. Various forms of particle refinement have been proposed for particle-based methods such as Smoothed Particle Hydrodynamics (SPH). However, none of the techniques that exist currently are able to retain the original degree of randomness among particles. Existing methods reinitialize particle positions on a regular grid. Using such a method for region localized refinement can lead to discontinuities at the interfaces between refined and unrefined particle domains. In turn, this can produce inaccurate results or solution divergence. This thesis outlines the development of new localized refinement algorithms that are capable of retaining the initial randomness of the particles, thus eliminating transition zone discontinuities. The algorithms were tested through SPH simulations of Couette Flow and Poiseuille Flow with spatially varying particle spacing. The determined velocity profiles agree well with theoretical results. In addition, the algorithms were also tested on a flow past a cylinder problem, but with a complete domain remeshing. The original and the remeshed particle distributions showed similar velocity profiles. The algorithms can be extended to 3-D flows with few changes, and allow the simulation of multi-scale flows at reduced computational costs.
by Nikhil Galagali.
S.M.

Particle-laden flow in a microchannel resulting in aggregation of microparticles was investigated to determine the dependence of the cluster growth rate on the following parameters: suspension void fraction, shear strain rate, and channel-height to particle-diameter ratio. The growth rate of an average cluster was found to increase linearly with suspension void fraction, and to obey a power-law relationships with shear strain rate as S^0.9 and channel-height to particle-diameter ratio as (h/d)^-3.5. Ceramic liposomal nanoparticles and silica microparticles were functionalized with antibodies that act as targeting ligands. The bio-functionality and physical integrity of the cerasomes were characterized. Surface functionalization allows cerasomes to deliver drugs with selectivity and specificity that is not possible using standard liposomes. The functionalized particle-target cell binding process was characterized using BT-20 breast cancer cells. Two microfluidic systems were used; one with both species in suspension, the other with cells immobilized inside a microchannel and particle suspension as the mobile phase. Effects of incubation time, particle concentration, and shear strain rate on particle-cell binding were investigated. With both species in suspension, the particle-cell binding process was found to be reasonably well-described by a first-order model. Particle desorption and cellular loss of binding affinity in time were found to be negligible; cell-particle-cell interaction was identified as the limiting mechanism in particle-cell binding. Findings suggest that separation of a bound particle from a cell may be detrimental to cellular binding affinity. Cell-particle-cell interactions were prevented by immobilizing cells inside a microchannel. The initial stage of particle-cell binding was investigated and was again found to be reasonably well-described by a first-order model. For both systems, the time constant was found to be inversely proportional to particle concentration. The second system revealed the time constant to obey a power-law relationship with shear strain rate as τ∝S^.37±.06. Under appropriate scaling, the behavior displayed in both systems is well-described by the same exponential curve. Identification of the appropriate scaling parameters allows for extrapolation and requires only two empirical values. This could provide a major head-start in any dosage optimization studies.

2010 - 2011
The following doctoral thesis, titled “A particle-centred approach on Italian Verb Particle Constructions” (hereinafter VPCs) aims at showing that the particle characterizing Italian Phrasal verbs such as su (up), giù (down), fuori (out), dentro (in/inside) and so on plays a key role in the constructions both syntactically and semantically. The framework adopted is based on the main syntactic theories developed by Z.Harris (1976) as well as on the Lexicon Grammar Method as pointed out by M. Gross (1981). I will suggest, gradually during the dissertation, that the spatial, aspectual and metaphorical meaning of a large portion of Italian VPCs such as scappare fuori di casa (to escape out of the house), tirare via un chiodo (to pull out the nail from the wall), mettere dentro il ladro (to put the thief inside), portare avanti un progetto (to carry out a project), tagliare fuori qualcuno da un discorso (to cut sb.out from a discussion) - are embedded only into the particle slot as the head verb can vary into a finite range of possibilities or it not occur at all. The head verb is in other words ‘week’ while the particle represents the powerful element (or ‘operator’ in lexicon-grammar terms) so that it cannot be considered a small added element (lat. ‘particula’): the particle affects the argument structure of the verb and carries the aspectual or spatial or idiomatic meaning. Moreover its syntactic autonomy is demonstrated by the fact that it can also occur without the head verb, in sentences such as su le mani (hand up), via di qui (away from here), fuori i soldi (money out), giù il governo (down with the government), Lazio avanti (Lazio ahead) that are defined “verbless particle constructions”. The thesis provides an in depth syntactic and semantic analysis of Italian VPCs, with interesting evidence from dictionaries and corpora, stressing the need to substitute the traditional “Verbocentrism” with an original Particle-Centred Approach. Finally the theoretical and applicative implications of such a change of perspective are pointed out. [edited by author]
La tesi analizza i verbi sintagmatici dell’italiano – come tirare su, andare avanti, fare fuori - sulla base di un approccio trasformazionalista e distribuzionalista di matrice harrisiana (Harris 1976) e di una metodologia empirica di chiara derivazione grossiana (Gross 1992, Elia 2013). Un primo lemmario di più di 700 lemmi Verbo + particella locativa è stato collezionato a partire da una decina di opere lessicografiche. La nozione di lemma è stata poi sostituita con quella di ‘uso lessicale’ permettendo di distinguere con un costante processo di ‘moltiplicazione delle entrate’ due macroclassi ci costruzioni, composizionali e idiomatiche, per un totale di circa 800 usi lessicali diversi. Le costruzioni idiomatiche di tipo transitivo (213 entrate) sono state poi classificate entro nove distinte classi lessico-grammaticali. Queste costruzioni sono stata proiettate sul corpus LIP al fine di verificare empiricamente la presenza e la distribuzione di frequenza delle costruzioni V + particella (sia composizionali che idiomatiche) nel parlato dell’italiano. L’esplosione di usi idiomatici ha spinto ad indagare il fenomeno dell’ambiguità con maggiore acutezza fino a sostituire il verbocentrsmo delle prime analisi con un approccio del tutto particle-centred: la particella lungi dall’essere considerate un piccolo elemento inerte (lat. ‘particula’) svolge un ruolo centrale all’interno dell’enunciato, comportandosi harrisianamente da operatore cioè da elemento pienamente predicativo che seleziona il numero e la tipologia di argomenti e che determina il significato dell’intera costruzione. La parte finale della tesi è dedicata ad uno specifico set di costruzioni assolute con particella predicativa ma prive di verbo come su le mani, via di qui, avanti il prossimo, giù il Governo, definite ‘verbless-particle constructions’. [a cura dell'autore]
X n.s.

This thesis presents the study of laminar to turbulent transition of particle laden flows. When a flow becomes turbulent, the drag increases one order of magnitude compared to a laminar flow, therefore, much research is devoted to understand and influence the transition. Previous research at the Linne Flow Centre at KTH has concentrated on the understanding of the bypass transition process of single-phase fluids. Though there are still questions, the principles of this process are now, more or less, known. However, little is known of the influence of particles on transition. While experiments in the 1960s already showed that particles can reduce the friction in turbulent channel flows significantly. The question explored in this thesis is whether this can be attributed to their influence on transition. The initial onset of transition has been investigated with both modal and non-modal linear stability analysis in a Poiseuille flow between two parallel plates. Particles are introduced as a second fluid and they are considered to be solid, spherical and homogeneously distributed. When the fluid density is much smaller than the particle density, ξ (≡ ρf/ρp) << 1, an increase of the critical Reynolds number is observed. However, transient growth of streamwise vortices resulting in streaks is not affected by inclusion of particles. Particles with ξ ∼ 1 hardly seem to have an effect on stability. Although linear analysis shows that particles hardly influence the transient growth of disturbances, they might affect other (non-linear) stages of transition. To investigate such effects, the full Navier-Stokes equations for 3D Poiseuille flow between two parallel plates are numerically solved and particles are introduced as points with two-way coupling. For particles in a channel flow with ξ<<1, results show that the transition to turbulence is delayed for mass fractions ƒ (=mp N / ρf) larger than 0.1. For a mass fraction of ƒ=0.4 the initial disturbance energy needed to get a turbulent flow increases with a factor of four. Even if lower particle mass fractions ƒ are used, locally there could be large particle mass fractions. Therefore, the next step is to investigate the generation of local large particle mass fractions ƒ. Such particle clusters can be as large as the typical flow structures in the flow, like streak width and vortex size. Then they might change the flow field and (in)stability mechanisms. Numerical simulations of bypass transition in a boundary layer flow are used to determine whether particles cluster and where they tend to cluster. It is found that point particles with ξ<<1 and a large particle relaxation time tend to move in the low speed regions of the flow. In case of streaks, the low speed streaks are most favourable. For smaller particle relaxation times, particles act as tracers and do not have a preferential position and are homogeneously distributed. For particles with ξ∼1 the linear stability analysis showed no transition effect at any ƒ. However, one effect neglected until now is that of particle size. For particles with dimensions of the same order of magnitude of the flow disturbance, particles might influence the flow field. To investigate whether such particles migrate towards positions where they can affect transition some exploratory numerical simulations and experiments are performed. Numerically, the lateral migration of large particles (H/d=5) with ξ=1 in a 3D Poiseuille flow between two parallel plates is investigated. In laminar channel flow, large particles tend to move laterally due to shear to an equilibrium position. For a single large particle some key parameters for migration are identified: the size of the particle and the velocity of the fluid. When multiple particles are present, they tend to form particle trains. If particles are close, they influence each other and the equilibrium position shifts towards the wall, where the final position is dependent on the inter particle spacing. Also, not one steady equilibrium position is present, but particles move around an equilibrium position. Experimentally, migration of particles in bypass transition with ξ=1 is investigated to find out whether neutrally buoyant particles have a preferential position within streaks. The first results with tracer particles (d∼50μm) and few large particles (d∼200μm) do not show detectable preferential positioning.

QC 20131030

Phase transitions and other intrinsic properties (shape, size, architecture) of molecularly structured aerosol particles are important for understanding their role in planetary atmospheres and for technical applications. By combining bath gas cooling with time resolved mid-infrared spectroscopy and modeling, information is obtained on dynamic processes and intrinsic properties of fluoroform and ethane aerosol particles. The distinct infrared spectral features of fluoroform aerosol particles make it a particularly suitable model system. Homogeneous crystallization rates of the sub-micron sized aerosol particles are determined (JV = 10⁸ - 10¹⁰ cm-³s-¹ or JS = 10³ – 10⁵ cm-²s-¹ at a temperature of T = 78 K), and the controversial question regarding volume versus surface nucleation in freezing aerosols is addressed. It is demonstrated that current state of the art measurements of droplet ensembles cannot distinguish between the two mechanisms due to inherent experimental uncertainties. The evolution of particle shape from spherical supercooled droplets to cube-like crystalline particles and eventually to elongated crystalline particles is recorded and analyzed in detail with the help of vibrational exciton model calculations. Phase behaviour of pure ethane aerosols and ethane aerosols formed in the presence of other ice nuclei under conditions mimicking Titan’s atmosphere provide evidence for the formation of supercooled liquid ethane aerosol droplets, which subsequently crystallize. The observed homogeneous freezing rates (JV = 10⁷ – 10⁹ cm-³s-¹) imply that supercooled ethane could play a similar role in ethane rich regions of Titan’s atmosphere as supercooled water does in the Earth’s atmosphere.

Colloidal particles and surfactants are commonly used, either individually or combined, as stabilisers of emulsions and foams. While the properties of surfactants and particles under a range of conditions and concentrations are relatively well known, there are some areas that require further investigation. The wettability of colloidal particles is one of the main factors that determine how they behave in a given system but determining the wettability is difficult due to the small size of the particles. The Film Calliper Method (FCM) has been proposed as a simple technique for the direct measurement of the contact angles of micrometer and submicrometer particles in their natural environment. One of the main aims of this work was to develop the Film Calliper Method for measuring contact angles at oil -water interfaces. The FCM was therefore used to measure the contact angles at oil - water interfaces for a range of particles, such as latex and silica particles, in different systems. For the first time directly measured contact angles are linked to the types of emulsions stabilised by the particles. The FCM was also used to directly measure the contact angles of silica particles in cationic surfactant solutions at air and oil interfaces for the first time. The stability of foams and emulsions made with particle - surfactant mixtures were investigated and related to the particle contact angles. Janus particles are a special category of particles which have different properties on each hemisphere. A method for making Janus particles was developed using template silica particles masked with a polymerised Pickering emulsion. The portion of surface exposed for treating can be tuned by controlling the inherent wettability of the template particles as proven with fluorescence microscopy. Emulsions stabilised by amphiphilic Janus particles made with the method are compared with emulsions stabilised by homogeneous particles with similar wettability.

La turbulence est connue pour sa capacité à disperser efficacement de la matière, que ce soit des polluantes dans les océans ou du carburant dans les moteurs à combustion. Deux considérations essentielles s’imposent lorsqu’on considère de telles situations. Primo, l’écoulement sous-jacente pourrait avoir une influence non-négligeable sur le comportement des particules. Secundo, la concentration locale de la matière pourrait empêcher le transport ou l’augmenter. Pour répondre à ces deux problématiques distinctes, deux dispositifs expérimentaux ont été étudiés au cours de cette thèse. Un premier dispositif a été mis en place pour étudier l’écoulement de von Kàrmàn, qui consiste en une enceinte fermé avec de l’eau forcé par deux disques en contra-rotation. Cette écoulement est connu pour être très turbulent, inhomogène, et anisotrope. Deux caméras rapides ont facilité le suivi Lagrangien des particules isodenses avec l’eau et petites par rapport aux échelles de la turbulence. Ceci a permis une étude du bilan d’énergie cinétique turbulente qui est directement relié aux propriétés de transport. Des particules plus lourdes que l’eau ont aussi été étudiées et montrent le rôle de l’anisotropie de l’écoulement dans la dispersion des particules inertielles. Un deuxième dispositif, un écoulement de soufflerie ensemencé avec des gouttelettes d’eau micrométriques a permis une étude de l’effet de la concentration locale de l’eau sur la vitesse de chute des gouttelettes grâce à une montage préexistant. Un modèle basé sur des méthodes théorique d'écoulements multiphasiques a été élaboré enfin de prendre en compte les effets collectifs de ces particules sedimentant dans un écoulement turbulent. Les résultats théoriques et expérimentaux mettent en évidence le rôle de la polydispersité et du couplage entre les deux phases dans l’augmentation de la sédimentation des gouttelettes
Turbulence is well known for its ability to efficiently disperse matter, whether it be atmospheric pollutants or gasoline in combustion motors. Two considerations are fundamental when considering such situations. First, the underlying flow may have a strong influence of the behavior of the dispersed particles. Second, the local concentration of particles may enhance or impede the transport properties of turbulence. This dissertation addresses these points separately through the experimental study of two different turbulent flows. The first experimental device used is the so-called von K\'arm\'an flow which consists of an enclosed vessel filled with water that is forced by two counter rotating disks creating a strongly inhomogeneous and anisotropic turbulence. Two high-speed cameras permitted the creation a trajectory data base particles that were both isodense and heavier than water but were smaller than the smallest turbulent scales. The trajectories of this data base permitted a study of the turbulent kinetic energy budget which was shown to directly related to the transport properties of the turbulent flow. The heavy particles illustrate the role of flow anisotropy in the dispersive dynamics of particles dominated by effects related to their inertia. The second flow studied was a wind tunnel seeded with micrometer sized water droplets which was used to study the effects of local concentration of the settling velocities of these particles. A model based on theoretical multi-phase methods was developed in order to take into account the role of collective effects on sedimentation in a turbulent flow. The theoretical results emphasize the role of coupling between the underlying flow and the dispersed phase

An investigation has been conducted into factors affecting the interparticulate cohesion profile of three micronised drugs, as a function of humidity. An atomic force microscope (AFM) colloid probe technique was correlated with physico-chemical properties and in-vitro performance. Briefly, micronised drug particles of salbutamol sulphate, triamcinolone acetonide (TAA) and disodium cromoglycate (DSCG) were mounted onto Vshaped tipless cantilevers using a developed micromanipulation technique. Interactions between the AFM ‘drug probes’ and a series of model drug surfaces were conducted at a 15,30, 45, 60 and 75% relative humidity using a custom built perfusion apparatus connected to the AFM. As expected, separation energy distributions for drug probe interactions were dependent on the surface rugosity of the drug model surfaces. Separation energy measurements conducted between drug probes and individual micronised drug particles (mounted in polymer resin) suggested large variations in separation energy. Further analysis of such data suggested a lognormal separation energy distribution, however, limitations in individual particle measurements (finite particle measurements per experiment) allowed restricted statistical analysis.

This thesis is primarily concerned with understanding how the rate and extent of membrane permeation of a drug is affected by switching the donor delivery vehicle for different permeants and membranes. The project is funded by an industrial Collaborative Awards in Science and Engineering (CASE) award with an additional sponsorship by GlaxoSmithKline (GSK). The interest of GSK in this research is in the understanding of how the various types of topical formulation available, such as solutions, ointments, dispersions and emulsions, influence the characteristics of drug transport across a membrane. The rate and extent of membrane permeation from various types of topical formulation is experimentally investigated through the use of a developed automated method which is shown to be accurate and highly reproducible. The developed method incorporates stirred donor and re-circulating receiver compartments and continuous monitoring of the permeant concentration in the receiver phase. In a theoretical model based on rate-limiting membrane diffusion, an explicit set of equations are derived showing how the permeation extent and rate depend mainly on the membrane-donor and membrane-receiver partition coefficients of the permeant. The permeation of drug molecules from simple, single phase donor solutions are first investigated. The experimental permeation results for systems containing all possible combinations of hydrophilic or hydrophobic donor solvent, permeant and polymer membrane are measured using the developed method and are then compared to the calculated theoretical results. A quantitative comparison of model and experimental results from the widely-differing permeation systems successfully enables the systematic elucidation of all possible donor solvent effects in membrane permeation. For the experimental conditions used here, most of the permeation systems are in agreement with the model, demonstrating that the model assumptions are valid. In these cases, the dominant donor solvent effects arise from changes in the relative affinities of the permeant for the donor and receiver solvents and the membrane and are quantitatively predicted using the separately measured partition coefficients. It is also shown how additional donor solvent effects can arise when switching the donor solvent causes one or more of the model assumptions to be invalid. These effects include a change in rate-limiting step, permeant solution non-ideality and others. The development of a new type of formulation is investigated whereby the preparation of waterless, particle-stabilised emulsions is reported upon. The prepared emulsions incorporate a non-aqueous polar liquid phase, an immiscible oil phase and are stabilised by solid nanoparticles. Variation of the incorporated oil, polar liquid and particle hydrophobicity allow for the preparation of stable emulsions containing a wide range of liquids of both oil-in-polar liquid and polar liquid-in-oil emulsion types. The prepared formulations show great potential as vehicles for use in drug delivery in the pharmaceutical industry. These waterless emulsions provide several advantages such as high emulsion stability, aesthetic textures for topical application, aesthetic appearances (including the preparation of transparent emulsions through matching of the refractive index of the liquid phases) and the capability of containing very high hydrophobic drug concentrations dissolved within due to the absence of an aqueous liquid phase. The permeation of a drug molecule from more complex multiphase donor formulations, such as particle dispersions and particle stabilised emulsions, is also investigated. The delivery of a permeant across a synthetic membrane from both conventional oil-water and the developed waterless emulsions is discussed. The same experimental technique as that used to investigate the membrane permeation from single phase donor solutions is employed and a comparison of the experimental results to those calculated using the derived theoretical model is given. The theoretical model is adapted to account for the additional partioning of the permeant between the multiple phases present in these more complex donor formulations, but maintains the same set of underlying assumptions and fundamental principles of diffusion. The model successfully accounts for the experimental observations and reveals information regarding the mechanism of drug delivery from particle-stabilised emulsions. It is conclusively illustrated that permeant delivery from particle-stabilised emulsions occurs via partitioning of the drug between the dispersed and continuous emulsion phases prior to partitioning to the membrane exclusively from the emulsion continuous phase (i.e. dispersed emulsion droplet adhesion onto the surface of the membrane does not occur). Through analysis of the derived theoretical model, the extent and rate of membrane permeation of a permeant are correctly predicted to be independent of the emulsion type (i.e. oil-in-water or water-in-oil) and emulsion dispersed volume fraction for a given emulsion composition.

Interactions at elevated temperatures between solid particles occur in a wide range of industrial processes, for instance, in the filtering of hot gases, in the drying of pharmaceutical granules, in the curing of ceramics, in the combustion of solid fuels and regeneration of nuclear waste. Often these interactions can cause major problems in the operation of such processes. For example, it is well established that the fluidisation behaviour of certain powders is significantly affected by the presence of strong interparticle forces that, in turn, are the cause of both agglomerate formation and possible operative problems within the reactor. On the other hand, not much is known about the mechanisms of agglomeration, other than that it is mainly due to interfacial phenomena. High temperature adhesion forces arise from the formation of material bridges, usually due to the particle surfaces changing phase through either chemical reaction or simply melting. Moreover, thin liquid layers of sticky material, which may be present on particle surfaces, such as during reactive coating or drying processes, may also enhance strong interparticle bonds leading to solidification. It is obvious that for the reliable operation of high-temperature processes a good under standing of the fundamental mechanisms of adhesion and cohesion between particles at elevated temperatures is required. Here, adhesion is meant as the force that holds the particles together, after which they exhibit cohesive behaviour. Unfortunately, the level of understanding has been hampered by the lack of techniques available to observe and measure such interactions. However, recent developments in microscopic analysis techniques now mean that high temperature particle interactions can be studied directly, which will lead to the development of new predictive models. The main aim of the work described in this thesis is to provide experimental evidence and justification of particle-particle interactions at high temperature and to deliver original insights of the underlying mechanisms, which play a fundamental role in particulate cohesion in relation to fluidisation process. In order to fulfill this goal, a novel device, termed a High Temperature Micro-Force Balance, has been designed and developed which combines force and direct observation measurements operated through an adapted micro manipulator technique. The flexibility of use for the HTMFB represents its strongest design advantage, permit ting experimental investigations over different types of particle interactions at a small scale (crystallization of liquid binders, reactive coating, sintering and composite materials interactions). Results reported in this work provide an original contribution towards academic and industrial understanding of the micro-scale mechanisms of agglomeration and material properties at different operative conditions.

The particle filter is usually used as a tracking algorithm in non-linear under the Bayesian tracking framework. However, the problems of degeneracy and impoverishment degrade its performance. The particle filter is thereafter enhanced by evolutionary optimization, in particular, Particle Swarm Optimization (PSO) is used in this thesis due to its capability of optimizing non-linear problems. In this thesis, the PSO enhanced particle filter is reviewed followed by an analysis of its drawbacks. Then, a novel sampling mechanism for the particle filter is proposed. This method generates particles via the PSO process and estimates the importance distribution from all the particles generated. This ensures that particles are located in high likelihood regions while still maintaining a certain level of diversity. This sampling mechanism is then used together with the marginal particle filter. The proposed method?s superiority in performance over the conventional particle filter is then demonstrated by simulations.

The physical separation of micro-particles is very important in many research field as diverse as chemistry and medicine. The main goal of the current separation techniques is to extract micro-particles such as cells at a high processing rates and purity. Chromatography, for instance, is commonly applied for the detection and enrichment of pathogens, which is useful for the medical diagnostics of parasitic infections. Many separation techniques have been developed over the years, applying physical phenomena of different kinds and/or taking advantage of unique physical properties of the particles themselves. From all of these techniques, one that has remained popular over the years is Dielectrophoresys(DEP). One of the main reasons for its popularity is that it does not require markers of any kind; it takes advantage of differences in the particle’s polarizability, size and shape. Another distinctive characteristic of dielectrophoresis is its selectivity due to its capacity to be controlled using frequency and voltage amplitude and its suitability for small microfluidic systems. In very general terms the work I have done during my PhD studies was oriented towards the development of novel and robust technology for aiding in the micro-particle sorting and bio-particle recognition by using computer tools. The ideas and concepts I will be introducing throughout this document were allowed total freedom to evolve and change to better fulfill the main goals of the project and also to better adapt to the many technical challenges I had to face during my research. As well as developing a new dielectrophoresis method I have also tried to maximize the impact of this work by doing it in a truly accessible way for anyone, regardless if they are interested in basic research, a possible application or just looking to adapt this concepts and tools for a different purpose. The central work in this PhD thesis focuses on two main topics: - Computerized bio-particle tracking and identification using a machine-learning algorithm that incorporates a number of predictors, including colour histogram comparison. - A portable dielectrophoresis(DEP) electronic device able to tailor the potential across a microfluidic channel for particle separation. The first project is about computerized vision system designed to track and identify micro-particles of interest through the use of video microscopy, machine learning and other video processing tools. This system uses a novel particle recognition algorithm to improve specificity and speed during the tracking and identification process. We show the detection and classification of different types of cells in a diluted blood sample using a machine-learning algorithm that makes use of a number of predictors, including shape and color histogram comparison. This software can be considered as a stand alone piece of work. Its open source nature makes it ideal for scientific purposes or as a starting point for a different application. In the context of this PhD thesis, however, it is an invaluable tool for validating and quantifying experimental results obtained from the micro-particle separator experiments presented in Chapter 4. The central piece of work in this PhD thesis is introduced in Chapter 4. This project is about the development of a all-in-one continuous flow DEP based microparticle separator which uses a system of individually addressable electrodes to shape and control the particle’s potential energy profile across the entirety of a microfluidic channel. These tailored potential landscapes are created by averaging the electric field generated by 64 individual electrodes, where the electronic device has complete control over each electrode’s on/off state, frequency, AC voltage amplitude and pulse duration. All the characteristics of the potential landscapes are controlled wirelessly through a mobile phone application. These specially designed potential landscapes allow us to make lateral sorting and/or concentration of a binary mixture of particles at the same time they move through a microfluidic channel; all this without the need for buffer flows or additional external forces. One of the outstanding characteristics of this new sorting technique is that it relays exclusively on negative DEP. Most previous techniques require a combination of positive and negative DEP and possibly and external force of different nature to achieve particle sorting; all of which requires the use of a crossover frequency and hence a careful control of the conductivity of the suspending medium. Here by using only negative DEP we eschew the careful control over the conductivity of the suspending medium and the use of any other external force; all this contributes to make our device small and robust. In addition to this, our electronic device was designed to include all the supporting electronics it needs in a small and robust printed circuit board that can also be operated by batteries. We present simulation results to illustrate the physics behind this new technique along with experimental results demonstrating the separation of polystyrene beads.

Die Benetzbarkeit und Nichtbenetzbarkeit von Oberflächen durch eine Flüssigkeit sind faszinierende und wichtige Phänomene in Wissenschaft und Technologie. Jüngst wurde entdeckt, dass Partikel die Benetzung einer Wasseroberfläche durch ein Öl unterstützen können. Es wurde eine Theorie entwickelt, das Prinzip der zu beschreiben. In der vorliegenden Doktorarbeit wurde diese Theorie im Experiment sowohl qualitativ als auch quantitativ untersucht, wobei zwei Arten von Kieselgelpartikeln Verwendung fanden. Mit Hilfe einer Reihe unregelmäßig geformter Partikel mit variierender Hydrophobie wurde der Einfluss der Oberflächenhydrophobie der Partikel auf die partikel-assistierte Benetzung untersucht. Es wurde herausgefunden, dass die Partikel mit höchster Hydrophilie Linsen aus reinem Öl bilden, während die Partikel in die Wasserphase abtauchen. Die Partikel mit größter Hydrophobie hingegen bewirken die Ausbildung von kleinen Bereichen, in denen Öl und Partikel eine stabile homogene Schicht formen. Für Partikel mit mittlerer Hydrophobie wurden beide Phänomene beobachtet. Diese drei verschiedenen Beobachtungen bestätigen, dass die Oberflächenhydrophobie der Partikel das Benetzungsverhalten des Öls auf der Wasseroberfläche bestimmen. Für die unregelmäßig geformten Partikel war aufgrund des unbekannten Kontaktwinkels ein direkter Vergleich zur Theorie nicht möglich. Um die Theorie quantitativ zu prüfen, wurden sphärische Partikel synthetisiert und ihre Oberflächen mit Hilfe von zehn Silanisierungsmittel modifiziert. Anschließend wurde ein Vergleich der experimentellen Ergebnisse mit dem entsprechenden theoretischen Phasendiagramm durchgeführt. Die Untersuchungen zeigten, dass die theoretischen Vorhersagen zum Großteil mit den experimentellen Ergebnissen übereinstimmen. Es wurden alle Fälle der Benetzung beobachtet, die auch in der theoretischen Beschreibung berücksichtigt wurden. Darüber hinaus wurden auch Abweichungen von der Theorie festgestellt. Haben die Partikel ähnliche Affinitäten zur Luft/Öl- und Öl/Wasser-Grenzfläche, hängt die Beschaffenheit der Benetzungsfilme zusätzlich vom Oberflächendruck ab. Deshalb könnte es notwendig sein, die einfache Theorie zu erweitern um den beschriebenen Beobachtungen Rechnung zu tragen
Wetting and de-wetting of surfaces by a liquid are fascinating and important phenomena in science and technology. Recently, it was discovered that particles can assist the wetting of a water surface by an oil, and a theory describing the principle behind particle assisted wetting was developed. In this thesis, the theory was experimentally investigated qualitatively and quantitatively by using two series of silica particles. The influence of the surface hydrophobicity of the particles on particle assisted wetting was investigated by a series of irregular shaped particles with varying hydrophobicity. By applying mixtures of particles and oil to a water surface, it was found that for the most hydrophilic particles, only lenses of pure oil formed, with the particles being submerged into the aqueous phase. The most hydrophobic particles helped to form patches of stable homogenous mixed layers composed of oil and particles. For particles with intermediate hydrophobicity, lenses and patches of mixed layers were observed. These three different observations verified that the hydrophobicity of the particle surface determines the wetting behaviour of the oil at the water surface. For the irregular shaped particles with unknown contact angles with liquid interfaces, no direct comparison to the theory was possible. To test the theory quantitatively, a series of spherical particles was synthesized and their surfaces were modified by ten kinds of silane coupling agents; then the experimental results were compared with the corresponding theoretical phase diagram. It indicated that the theory agrees at large with the experimental results. All scenarios of wetting layers taken into account in the theoretical description were observed. In the fine print, deviations from the theory were also observed. If the particles have similar affinities to air/oil and oil/water interfaces, the experimentally observed morphology of the wetting layers depends in addition on the surface pressure. It might therefore be necessary to extend the simple theoretical picture to take these observations into accounts

This dissertation presents a robust method of modeling objects and forces for computer animation. Within this method objects and forces are represented as particles. As in most modeling systems, the movement of objects is driven by physically based forces. The usage of particles, however, allows more artistically motivated behavior to be achieved and also allows the modeling of heterogeneous objects and objects in different state phases: solid, liquid or gas. By using invisible particles to propagate forces through the modeling environment complex behavior is achieved through the interaction of relatively simple components. In sum, 'macroscopic' behavior emerges from 'microscopic' modeling. We present a newly developed modeling framework expanding on related work. This framework allows objects and forces to be modeled using particle representations and provides the details on how objects are created, how they interact, and how they may be displayed. We present examples to demonstrate the viability and robustness of the developed method of modeling. They illustrate the breaking and fracturing of solids, the interaction of objects in different phase states, and the achievement of a reasonable balance between artistic and physically based behaviors.

The aim of this thesis was to identify and evaluate critical factors for protein particle analysis and to apply this knowledge for the development of novel standardized protein-like particles. Thorough analysis of particles in therapeutic protein formulations is crucial due to regulatory requirements, the potential immunogenicity of protein aggregates and particles, and the need for quality and stability control of the product. The introduction gives a comprehensive overview of analytical methods for particle characterization in therapeutic protein formulations based on the currently available literature. Within the thesis, the performance of novel techniques or instruments for (protein) particle counting, sizing, or characterization was assessed. Micro-Flow Imaging (MFI) and resonant mass measurement (RMM) were tested for the differentiation of protein particles and silicone oil droplets which is highly relevant especially for pharmaceutical products in prefilled syringes. Four different flow imaging microscopy systems (MFI4100, MFI5200, FlowCAM VS1, and FlowCAM PV) were subjected to a detailed investigation of particle quantification, characterization, image quality, differentiation of protein particles and silicone oil droplets, and handling of the systems. A material screening of proteinaceous and non-proteinaceous materials for the development of novel standardized protein-like particles revealed gelatin and PTFE particles as promising materials for light-based applications. The density of protein particles, as a crucial particle parameter for weight-based techniques like RMM, was determined by two newly developed methods. The relevance of the refractive index (RI), which is closely related to transparency, was investigated and a novel method for RI determination of protein particles was developed. As protein particles became “invisible”, i.e. not detectable anymore by light-based systems at increased RI values - e.g. due to high protein concentration and/or sugars as excipients - potential solution strategies were evolved. Taken together, this thesis provides new insight into the analysis of particles in therapeutic protein formulations. In this regard, potential candidates for the development of novel standardized protein-like particles identified in this study are very valuable and can help to improve protein particle analysis in the future.

In order to increase the validity of numerical models of the detonation of heterogeneous titanium explosives, experimental results are needed. The combustino of titanium is studied using two experimental techniques. The first technique is the study of the burn time for a single particle over a wide range of initial diameters while altering the oxygen concentration. To accomplish this a new flat flame burner to study particle burn time has been designed. Luminous tracks caused by the light emitted by the combustion of the particles are analyzed and burn time is inferred. Burn time in air and in an oxygen enriched atmosphere were determined. A second experiment involves the study of large scale detonation of heterogeneous charges. The charges are filled with nitromethane and a packed bed of titanium particles. The titanium particles varied in morphology and particles size. A critical charge diameter for charge ignition (CDPI) was found for irregularly shaped particles but was not found for spherical particles.
Pour augmenter la validit des modles numriques sur dtonation d'explosifs htrognes contenants du titane , des rsultats exprimentaux sont ncessaires. Le combustino de titane est tudi en utilisant deux techniques exprimentales. La premire technique est l'tude du temps brle pour une particule sur une large gamme de diamtres initiaux en changeant la concentration d'oxygne. Pour l'accomplir un nouveau brleur de flamme plat pour tudier la particule brle le temps a t conu. Les empreintes lumineuses provoques par la lumire mise par la combustion des particules sont analyses et brlent le temps est dduit. Brlez le temps dans l'air et dans l'atmosphre enrichie d'un oxygne ont t dtermins. Une deuxime exprience implique l'tude de grande dtonation d'chelle de charges htrognes. Les charges sont remplies de nitromethane et un lit emball de particules de titane. Les particules de titane variaient dans la grandeur de particules et la morphologie. Un diamtre de charge critique pour l'ignition de charge (CDPI) a t trouv pour les particules irrgulirement en forme de, mais n'a pas t trouv pour pour les particules irrgulirement en forme de mais n'a pas t trouv pour les particules sphriques.

Since its introduction in the late 1970s by Lucy [11] and Gingold and Monaghan [4], smoothed particle hydrodynamics (SPH) has been used in many areas. It has grown into a widely-recognized technique with many practical applications. In this thesis, we present a new application of the SPH method: a new algorithm for computing a null divergence velocity field using SPH for incompressible flow - a pure SPH solution of the Helmholtz-Hodge decomposition. Also, a new version of the Laplacian for SPH is proposed and the advantages and disadvantages of different gradient and Laplacian approximation formulas used in SPH are also discussed. A new treatment of boundary conditions is proposed for the whole solution procedure. Throughout the thesis, a brief historical overview is presented, along with some fundamental notions about SPH and computational fluid dynamics.

The ability to analyse, interpret and make inferences about evolving dynamical systems is of great importance in different areas of the world we live in today. Various examples include the control of engineering systems, data assimilation in meteorology, volatility estimation in financial markets, computer vision and vehicle tracking. In general, the dynamical systems are not directly observable, quite often only partial information, which is deteriorated by the presence noise, is available. This naturally leads us to the area of stochastic filtering, which is defined as the estimation of dynamical systems whose trajectory is modelled by a stochastic process called the signal, given the information accumulated from its partial observation. A massive scientific and computational effort is dedicated to the development of various tools for approximating the solution of the filtering problem. Classical PDE methods can be successful, particularly if the state space has low dimensions (one to three). In higher dimensions (up to ten), a class of numerical methods called particle filters have proved the most successful methods to-date. These methods produce approximations of the posterior distribution of the current state of the signal by using the empirical distribution of a cloud of particles that explore the signal’s state space. In this thesis, we discuss a more general class of numerical methods which involve generalised particles, that is, particles that evolve through spaces larger than the signal’s state space. Such generalised particles include Gaussian mixtures, wavelets, orthonormal polynomials, and finite elements in addition to the classical particle methods. This thesis contains a rigorous analysis of the approximation of the solution of the filtering problem using Gaussian mixtures. In particular we deduce the L2-convergence rate and obtain the central limit theorem for the approximating system. Finally, the filtering model associated to the Navier-Stokes equation will be discussed as an example.

The thesis is concerned with the study of particles by impact voltammetry. The use of the particle-impact technique is developed and extended beyond quantitative sizing of spherical metallic nanoparticles to complex systems involving quasi-spherical nanoparticles, reversible agglomeration processes and extremely low levels of analyte. Initially the assumption that the particles are spherical is challenged and a system of quasi-spherical citrate-capped nanoparticles has been analyzed. The combination of SEM imaging and electrochemical nano-impact experiments was demonstrated to allow sizing and characterization of the geometry of single silver nanoparticles and determine an icosahedral geometry. Next the agglomeration/aggregation state of silver nanoparticles is studied in a media of high ionic strength. Distinguishing agglomeration (reversible clustering of the particles) and aggregation (irreversible clustering) is a challenging task for conventional techniques, especially at arbitrary concentrations. Using the nano-impact technique in conjunction with light scattering techniques (nanoparticle tracking analysis and dynamic light scattering) it was demonstrated that even in high ionic strength environments, particles develop equilibria between agglomerated and monomeric species, which in practice means the transport behavior is dominated by the presence of fast-diusing monomers with high chemical reactivity. Having developed an understanding of the agglomeration and aggregation state of the particles and underlying mass transport, the causes of agglomeration were considered and developed using the idea of entropy of mixing driven clustering, a concept hitherto unexplored and an entirely new perspective. Through the use of maximization of entropy of mixing the expected agglomeration population in the absence of any enthalpy eects and the contribution to the entropy from the formation of dimers, trimers etc., was predicted even though their formation causes an overall reduction in particle numbers. For a system of citrate-capped silver nanoparticles entropy was shown to play a dominant role in the observed size distributions. The distribution predicted by the model and the experimentally observed particle size distributions demonstrated the strong entropy contribution. The last chapter is concerned with the design of an approach for the most sensitive electrochemical detection of nanoparticles, yet realized. The limit of detection is dependent on the mass transport of the particles to the electrode and the electroactive area of the electrode. The use of a hydrodynamic walljet flow causes high mass transport. Larger electroactive area increases the observed current magnitude but in order to detect individual particles low capacitance is a required and as a result traditional macroelectrodes cannot be used. Hence in order to increase the surface area and reduce the associated increase in capacitance we chose to use a random assembly of microelectrodes (RAM) which consist of hundreds of carbon fiber microelectrodes connected in parallel to a current collector, which results in large electroactive area and relatively low capacitance. Using this in-house manufactured cell we were able to demonstrate femtomolar limit of detection for 50 nm silver citrate-capped nanoparticles, which is substantially the lowest limit detection reported in the literature to date.

The subject of this thesis is the improvement of particle tracking through the identification and correction of small systematic errors in particle "hit" locations due to positioning of tracking detectors. These errors call be as large or larger than the statistical spatial resolution of tracking detectors themselves, and therefore must be corrected. The focus is on identification and correction of errors due to rotations and beam axis translations.An algorithm is developed for use with proportional wire chamber and drift chamber detectors in experiment E683 at the Wideband facility of Fermi National Laboratory. In this experiment, high energy (tens of GeV) particles, primarily mesons, were produced when photons with energies of 40-400 GeV struck a metal or liquid target.At the present time, the method and code developed for this thesis has not been applied to real data, although an analysis of its effectiveness as a function of detector resolution has been investigated with Monte-Carlo simulations.
Department of Physics and Astronomy

Background The foamy virus (FV) replication cycle displays several unique features, which set them apart from orthoretroviruses. First, like other B/D type orthoretroviruses, FV capsids preassemble at the centrosome, but more similar to hepadnaviruses, FV budding is strictly dependent on cognate viral glycoprotein coexpression. Second, the unusually broad host range of FV is thought to be due to use of a very common entry receptor present on host cell plasma membranes, because all cell lines tested in vitro so far are permissive. Results In order to take advantage of modern fluorescent microscopy techniques to study FV replication, we have created FV Gag proteins bearing a variety of protein tags and evaluated these for their ability to support various steps of FV replication. Addition of even small N-terminal HA-tags to FV Gag severely impaired FV particle release. For example, release was completely abrogated by an N-terminal autofluorescent protein (AFP) fusion, despite apparently normal intracellular capsid assembly. In contrast, C-terminal Gag-tags had only minor effects on particle assembly, egress and particle morphogenesis. The infectivity of C-terminal capsid-tagged FV vector particles was reduced up to 100-fold in comparison to wild type; however, infectivity was rescued by coexpression of wild type Gag and assembly of mixed particles. Specific dose-dependent binding of fluorescent FV particles to target cells was demonstrated in an Env-dependent manner, but not binding to target cell-extracted- or synthetic- lipids. Screening of target cells of various origins resulted in the identification of two cell lines, a human erythroid precursor- and a zebrafish- cell line, resistant to FV Env-mediated FV- and HIV-vector transduction. Conclusions We have established functional, autofluorescent foamy viral particles as a valuable new tool to study FV - host cell interactions using modern fluorescent imaging techniques. Furthermore, we succeeded for the first time in identifying two cell lines resistant to Prototype Foamy Virus Env-mediated gene transfer. Interestingly, both cell lines still displayed FV Env-dependent attachment of fluorescent retroviral particles, implying a post-binding block potentially due to lack of putative FV entry cofactors. These cell lines might ultimately lead to the identification of the currently unknown ubiquitous cellular entry receptor(s) of FVs.

The purpose of this study is to numerically investigate the turbulence modulation of polydisperse particles in a square particle-laden jet. Turbulence modulation describes the effects of fluctuating velocity and intensity when the particles and continuous fluid interact in a turbulent flow field. The rate at which turbulence modulation is altered is dependent upon parameters such as particle size, mass loading, Stokes number, coupling, volume fraction and mechanisms of turbulence modulation. This study modifies the analytical model developed by Yarin and Hetsroni (1993) to account for the transitional drag regime for coarse polydisperse particles. The particles under study are dilute, inert and spherical, with relatively high Stokes numbers, and classified as having two-way coupling with the fluid. The new analytical model is compared to numerical results using the Computational Fluid Dynamics (CFD) software FLUENT (ANSYS, Inc.). The turbulence model employed is the standard k-ε model. This study will analyze the effects of varying mass content and particle ratios to investigate how turbulence modulation is influenced. The new model and the CFD results show good agreement in the cases where the mass contents of each particle size are equal. This study will also look into the effects of polydispersion, and the concentration distribution, for indoor air applications. It was found that, in certain cases, the monodisperse assumption slightly over-predicts the concentration distribution in the enclosed region.
Master of Science