Search

At the LHC, experimental data from proton collisions are compared to theoretical predictions of the SM. These predictions are often evaluated using Monte Carlo simulations. In order to ensure the long term success of the LHC it is necessary to improve the theoretical accuracy and computational efficiency of these simulations. This is especially pertinent in the era of the High-Luminosity LHC, where it is important to take advantage of the improved precision of experimental data. In this thesis we present three projects that will help towards this goal, all of which focus on the computation of perturbative physics. The first of these projects is the development of a new phase space generator called SingularPhasespace. Rather than attempting to simulate nature, this generator is used to populate the singular regions of phase space in a controlled and predictable way. This will allow developers to quickly understand any unexpected behaviour in their NLO simulations and so make it easier to improve them. The second project is a restructuring of the MadGraph5_aMC@NLO code, designed to improve its computational efficiency. This optimisation focussed on the evaluation of the fixed-order matrix element. We ensure that the program recycles duplicate parts of the helicity amplitude calculation instead of re-evaluating them. This results in a speed-up of a factor of ~2x for complex processes. We have dubbed this optimisation helicity recycling. The third project is a study of Higgs plus jet(s) simulations at NLO. We used Herwig's internal implementation of both subtractive and multiplicative matching methods to combine NLO fixed-order matrix elements with both the angular-ordered and dipole shower. We find good agreement between the showers but disagreement between the matching methods for certain observables. In particular we focus on the azimuthal angle between jets and Higgs pT distributions. We conclude that the multiplicative matching method is giving the more theoretically accurate description.

The angle γ is a fundamental parameter of the Standard Model, within which it quantifies the degree to which CP violation is permitted. It is presently one of the least well-constrained parameters of the CKM sector, which embodies the description of quark interactions. This thesis details work undertaken by the author at the LHCb experiment with the aim of reducing the uncertainty in γ. In addition, work undertaken to ensure the continued performance of the RICH subdetectors of LHCb is described. These subdetectors form a crucial part of the particle-identification system of LHCb, whose accuracy allows the precise study of processes with hadronic final states, such as the decays mentioned above.

In this thesis, the search for the production of the Higgs boson in associationwith two top quarks is presented. The main focus of this work is on the analysis optimised for the decay of the Higgs boson to a b-quark pair. The analysis is performed using 36.1 fb−1 of ppcollision data at a centre of mass energy sqrt(s)=13 TeV collected by the ATLAS detector at the Large Hadron Collider during 2015 and 2016. The signal strength of ttH in relation to the Standard Model prediction for a Higgs boson with a mass of 125 GeV is measured to be mu(ttH) = 0.87 +0.64−0.61, with signal strengths greater than 2.0 excluded at the 95% confidence level. The combination of this analysis with searches targeting additional Higgs boson decay modes is subsequently presented. The measured signal strength in relation to the Standard Model prediction is mu(ttH) = 1.2 +/-0.3. This correspondsto an observed (expected) significance for ttH of 4.2sigma (3.8sigma), constituting evidence for the ttH production mode. Finally, a study into the ability to observe and model the colour connection of b-quarks in ttH(bb) and ttbar+jets events is presented. The jet pull angle observable is used to investigate the effect of colour connection on jet substructure. Such an observable is found to be sensitive to the underlying colour structure in events, showing differences between b-quarks which decay from a colour singlet in comparison to a colour octet. However, the effect is found to be small and a larger dataset is required to measure the effect in ttH events.

The IceCube Neutrino Observatory at the South Pole is the world's largest neutrino detector with over 1km^3 of instrumented Antarctic ice. While it has been primarily designed to observe astrophysical neutrinos, this size also allows it to collect vast quantities of atmospheric neutrinos. These high-statistics datasets allow for measurements of the properties of neutrinos, in particular the phenomena of neutrino oscillation. One of the outstanding questions in this field is that of the neutrino mass ordering (NMO). The Precision IceCube Next Generation Upgrade (PINGU) is a proposed low-energy extension to IceCube for which a determination of the NMO is a priority science goal. The current low-energy atmospheric neutrino experiment at the South Pole, DeepCore, has been successfully collecting data since 2011. In this thesis the potential of this existing data to determine the NMO has been explored. While it was not expected to have a large sensitivity, this work has explored a Feldman-Cousins treatment for converting the delta-chi^2 between the two discrete mass ordering hypotheses into the standard Gaussian significance metric. Using 2.7 years of data from the DeepCore detector, the inverted mass ordering was preferred at the level of 0.05sigma. The second aspect of this thesis was to study the impact of the systematic uncertainties on the NMO determination. This particular analysis was actually statistics-limited and so the only impactful systematic uncertainties were the parameters that govern atmospheric neutrino oscillations, theta_23 and Deltam^2_31. Therefore, to improve the NMO results, these parameters were constrained by including the global information on them in the fits, yielding a new NMO sensitivity of 0.29sigma. This new global fit also yields measurements of the oscillation parameters of Deltam^2_32,NO=(2.443+/-0.037)e-3eV^2 and sin^2theta_23,NO=0.442+0.026-0.018 for the hypothesis of the normal mass ordering and Deltam^2_32,IO=(-2.510+/-0.036)e-3eV^2 and sin^2theta_23,IO=0.579+0.019-0.021 for the hypothesis of the inverted mass ordering. In addition to the work on the neutrino mass ordering, this thesis also investigated two issues related to predictions of the flux of atmospheric particles. The first related to the treatment of the predictions of the atmospheric neutrino flux, provided in binned tables. Crucially, these contain values representative of the integral of the flux across that bin and so an integral-preserving interpolation must be used. One such method will be presented along with a discussion of how it performs in the two-dimensional case of the atmospheric neutrino flux. The second issue related to quantifying uncertainties on the background muon distributions observed with the IceCube detector coming from the uncertainties on the initial cosmic ray flux. This involved performing a global fit on the available cosmic ray flux measurements and then propagating these uncertainties in to the muon distributions. To finalise this section, the exact manner in which these uncertainties can be included in the physics analyses of IceCube will be discussed.

So far the characteristics and mechanisms of particle adhesion have not been clearly understood and this hinders the development of methods for reducing particle adhesion. This thesis aims to understand the characteristics and mechanisms of particle adhesion and to develop some simple and passive methods for reducing particle adhesion in cyclones. Firstly, particle adhesion patterns in a cyclone are examined in a single cyclone experiment. They include the large scale spiral patterns (SPs), small scale wave patterns (WPs) and the thick adhesion layer (TAL) near the cyclone tip. The formation and development of these patterns are investigated with the aid of CFD simulations and the Barchan sand dune mechanism. It is found that the SPs are the footprint of the spiral band of particle trajectories in the cyclone. The backward creeping motion of the WPs is caused by the build-up of particles on their windward side, which is comparable to the movement of the Barchan sand dune. The precessional bent vortex end (PBVE) near the cyclone tip is supposed to be responsible for formation of the TAL. CFD simulations have been undertaken to gain an insight of the cause of particle adhesion. However, CFD simulations tend to overestimate particle velocities in the wall boundary layer, because sizes of mesh cells in the near-wall region are much larger than the particle size. In order to obtain a more accurate prediction of particle dynamic motion in the wall boundary layer and hence particle adhesion, a 2D mesh-free simulation of particle motions within the cross section of the cyclone is developed and validated with the experimental data. The results of the 2D mesh-free simulation show that the centrifugal force has little impact on particle adhesion, because the flow velocity near the wall is close to zero as the result of the non-slip condition. Instead, the radius of cyclone, particle charge, inlet velocity, coefficient of restitution (CoR) and the coefficient of friction (CoF) are found to affect particle adhesion considerable. During the experiment on a Dyson vacuum cleaner with a multi-cyclone configuration, a massive reduction of particle adhesion (about 94% reduction) is achieved by adding a small wedge in the inlet of the cylindrical chamber of the Dyson vacuum cleaner. A series of experiments were then carried out to identify the reasons for this reduction. It is found that the particle inlet location is significantly changed by the wedge. The author believed that the particle inlet position would affect the aerodynamic force on the particle in the cyclone. In this way, the particle adhesion is reduced by the wedge. The effect of particle inlet position is examined further in a single cyclone to investigate the detailed mechanisms on particle adhesion. The results show that there is a relation between particle adhesion and pressure drop of the cyclone. A high pressure drop is found to be associated with a small amount of particle adhesion. This finding confirms that particle inlet position affects the aerodynamic force on the particle. Combining the experimental results with CFD simulation results, a hypothesis is hence proposed to explain the mechanism behind the effect of particle inlet position.

The introduction of the Enhanced Actinide Removal Plant (EARP) at Sellafield in 1994 was designed to decontaminate radioactive effluents produced during nuclear fuel reprocessing. Through the action of flocculation with iron, followed by filtration, the effluents are decontaminated before being discharging to sea. The plant has been in successful operation for the past 20 years, and has made a significant difference to the level of radioactivity of the waste. However, little is known about the formed flocs. Particular concern focuses around future changes to the effluent compositions to be processed through EARP. These future feeds will potentially contain significantly less iron, thus potentially impacting upon the flocculation process and the efficiency of the decontamination process. The effluents currently treated contain significant concentrations of iron, stemming from the Magnox fuel reprocessing plant, along with actinides, fission and corrosion products. The flocculation of these acidic radioactive ferric feeds results in the formation of solid iron hydroxide flocs with encapsulated radioactivity. The flocs are then filtered, encapsulated and stored. It is envisioned that by characterising the floc properties, both physically and chemically a greater understanding of EARP can be obtained, ultimately leading to a maintained process efficiency with alternative feed compositions. The effect of a reduction in iron concentration on the chemical and physical properties of the flocs has been studied. The presence of any iron in the mock effluents was found to beneficially increase the contaminant decontamination factors (DF). However, the efficacy of this increase varied between contaminates. The DFs of group I and II metals ranged from 7.10 to 1.19 while lead ranged from 4x105 to 1.60, dependent upon iron concentration. Transition metal and lanthanide contaminants were marginally affected. With the use of agar embedding, the 'liquid form' of the flocs has been retained for two and three dimensional observations. SEM/EDX analysis has allowed for the inspection and chemical characterisation of the flocs while 2D microscope image analysis has allowed for the study of floc size and shape. A range of diameters, 300 - 1500 micro metre were found. Three dimensional X-ray Computer Tomography (3D X-ray CT) conducted at the Manchester X-ray Imaging Facility (MXIF) has led to the physical characterisation and classification of the flocs. Further, by studying the 3D shape it has been possible to classify a floc as a granule, fibre, chip or blade according to the Zingg classification with the majority of formed flocs being classified as granules.

Here is presented the top-quark pair plus photon production cross section measured in pp collisions at a centre-of-mass energy of √ s = 8 TeV with the CMS detector at the Large Hadron Collider, using data recorded in 2012 corresponding to an integrated luminosity of Lint = 19:6 fb−1. The measurement is performed in the dilepton decay channel. The fiducial region is defined by the final state of the process pp → W⁺W⁻b bl γ, with a minimum photon transverse energy of ET( γ) > 25 GeV and lies within a pseudorapidity range of η ( γ)| < 1:4442, with a separation of ∆R(γ; all) > 0:3 between the photon and quarks or leptons in η - space. Signal events are simulated using the MadGraph event generator. Data-driven templates are constructed in order to measure the photon identification efficiency using the supercluster footprint removal technique, and a fit to the charged hadron isolation is performed. The ratio of tt + γ cross section relative to the inclusive t t cross section, R = t t+ t t, is exploited in order to cancel various sources of systematic uncertainties. The combination of dilepton final state decay channels ratio in the fiducial area is measured to be R = 0:00115 ± 0:00023(stat:). Using a recent CMS t t cross section measurement at 8 TeV in the dilepton channel of t t = 245:6± 1:3(stat:)± +6:6/5:5 (syst:) ± 6:5(lumi:) pb, the top pair plus photon production cross section is calculated to be CMS / t t+γ = 944 154(stat:+syst:) fb. Being in agreement with the t t+γ SM expectation of SM / t t+γ = 861 ± 71(scale) ± 30(PDF) fb, this is the most accurate measurement of the t t +γ process to date, and the first at a centre-of-mass energy of 8 TeV in the dilepton channel.

Same- and opposite-sign charge asymmetries are measured in lepton+jets top anti-top events in which a b-hadron decays semileptonically to a soft muon, using data corresponding to an integrated luminosity of 20.3 fb-1 from proton-proton collisions at a centre-of-mass energy of √s = 8 TeV collected by the ATLAS detector at the Large Hadron Collider at CERN. The charge asymmetries are based on the charge of the lepton from the top-quark decay and the charge of the soft muon from the semileptonic decay of a b-hadron and are measured in a fiducial region corresponding to the experimental acceptance. Four CP asymmetries (one mixing and three direct) are measured and are found to be compatible with zero and consistent with the Standard Model.

Respirable coal mine dust (RCMD) still poses serious occupational health hazards to coal miners and can lead to incurable lung diseases such as coal workers' pneumoconiosis (CWP, also referred to as "black lung"). Further, CWP can develop into a more severe form known as progressive massive fibrosis (PMF). There has been a resurgence of PMF since the late 1990s. Coal miners are also exposed to crystalline silica, which can lead to a lung disease known as silicosis. While coal mining related disease is on the rise, the historic dust monitoring data does not indicate such a striking resurgence. As a result, there has been an increased interest in research surrounding RCMD to understand exposure as well as prevent health effects. Scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX) is a powerful tool that can analyze RCMD on a particle-level. The images produced by the SEM can size and characterize morphology of micron and submicron-sized particles. In addition, the EDX can determine elemental content, which can be used to infer mineralogy. However, particle classification can be impacted by interferences due to particle loading density (PLD) and agglomeration. PLD refers to the number of particles per unit area of substrate, while agglomeration describes clustered or overlapping particles. This thesis includes two studies aimed at exploring the effects of both PLD and agglomeration on SEM-EDX analysis. Study 1 includes an investigation into the effect of PLD on RCMD classification by SEM-EDX analysis. Dust recovered from the sample parent filters under low and high PLD conditions were used to isolate the effect of PLD. The comparison between the low and high PLD filters was then used to establish modified classification criteria to correct for high PLD. When the modified criteria were then applied to RCMD particles analyzed direct-on-filter, minimal change was observed in the apparent mineralogy distributions for most samples. These results suggest that particle agglomeration may have substantial effects on the particle classification of respirable dust analyzed direct-on-filter. Study 2 includes an investigation into the effect of particle agglomeration on RCMD by SEM-EDX analysis. Automated and manual SEM-EDX analysis was performed on paired filters collected from a parent filter. The manual analysis targeted respirable silica containing agglomerates. Each pair consisted of a filter analyzed directly and a filter that underwent a recovery process to deposit dust particles onto a new filter. The mineralogy distributions from the automated analysis suggest that agglomeration affects sizing and particle classification. Based on the manual analysis, there was an apparent increase in independent silica and a decrease in respirable silica-containing agglomerates after the recovery process. A limited collection of passive samples revealed more agglomerates than on the filters that were collected using a pump and size-selector cyclone. The work in this thesis is relevant to the research efforts aimed at the resurgence of coal mining related lung diseases, as the use of SEM-EDX can characterize RCMD by geographic region, geology, and location within a mine. Future work in this area of study might look at methods to estimate PLD in the field, other dust recovery methods, and a comparison of sampling methods.

This dissertation is ordered into three Parts. Part I is an investigation into identity, indiscernibility and individuality in logic and metaphysics. In Chapter 2, I investigate identity and discernibility in classical first-order logic. My aim will will be to define four different ways in which objects can be discerned from one another, and to relate these definitions: (i) to the idea of symmetry; and (ii) to the idea of individuality. In Chapter 3, the four kinds of discernibility are put to use in defining four rival metaphysical theses about indiscernibility and individuality. Part II sets up a philosophical framework for the work of Part III. In Chapter 4, I give an account of the rational reconstruction of concepts, inspired chiefly by Carnap and Haslanger. I also offer an account of the interpretation of physical theories. In Chapter 5, I turn to the specific problem of finding candidate concepts of particle. I present five desiderata that any putative explication ought to satisfy, in order that the proposed concept is a concept of particle at all. Part III surveys three rival proposals for the concept of particle in quantum mechanics. In Chapter 6, I define factorism and distinguish it from haecceitism. I then propose an amendment to recent work by Saunders, Muller and Seevinck, which seeks to show that factorist particles are all at least weakly discernible. I then present reasons for rejecting factorism. In Chapter 7, I investigate and build on recent heterodox proposals by Ghirardi, Marinatto and Weber about the most natural concept of entanglement, and by Zanardi about the idea of a natural decomposition of an assembly. In Chapter 8, I appraise the first of my two heterodox proposals for the concept of particle, varietism. I define varietism, and then compare its performance against the desiderata laid out in Chapter 5. I argue that, despite its many merits, varietism suffers a fatal ambiguity problem. In Chapter 9, I present the second heterodox proposal: emergentism. I argue that emergentism provides the best concept of particle, but that it is does so imperfectly; so there may be no concept of particle to be had in quantum mechanics. If emergentism is true, then particles are (higher-order) properties of the assembly, itself treated as the basic bearer of properties.

This thesis presents a study of the preparation and characterisation of microgels (MGs) and microgel-based systems which contain a high proportion of primaryamine groups. This is carried out with the aim of being used as the precursor materials for the development of an enzyme responsive system. The particle preparations discussed in this thesis begin with a particle dispersion prepared by a polymer-polymer interaction between partially oxidised dextran (Dexox) and poly(allylamine)(PA) or poly(vinylamine) (PVAM). The particle dispersions did show good tunability of properties by altering certain variables, such as extent of oxidation which resulted in the largest  -potential change with pH. However, these particles were not viable for further work as the largest swelling ratio by volume, Q value measured was only around 1.25, not sufficient for a pH responsive property swelling change (e.g. fluid-to-gel transition or drug delivery). MG particles were prepared using a non-aqueous dispersion polymerisation of Nvinylformamide (NVF), glycidylmethacrylate (GMA) and a crosslinker, 2-(Nvinylformamido)ethyl ether (NVEE). The PNVFx-GMAy-NVEEz particles were then hydrolysed to expose the primary amine groups in the resulting PVAMx-GMAy-BEVAMEz core-shell MGs. The shell, made up of GMA and NVF prevented hydrolysis taking place on the inside of the MGs, resulting in a PVAM rich shell. These hydrolysed MGs were cationic at low pH and were shown to have polyampholyte behaviour, caused by hydrolysis of some of the GMA groups. The inclusion of the NVEE crosslinker led to increased integration of the GMA and NVF into one homogenous phase in the shell and prevented hydrolytic fragmentation. The final system studied here concerns the macroscopic gel formation between the amine-rich MGs, poly(vinylamine-co-bis(ethyl vinylamine)ether) (PVAMBEVAME)and Dexox. These mixed dispersion gels were prepared and characterised. The MGs were externally crosslinked with the Dexox in order to form an elastically effective network. This was done by forming imine bonds by reaction between the primary amine groups present on the MGs and the aldehyde groups of the Dexox. These networks displayed high storage modulus (G’) and yield strains(*) of up to 140% and the G’ values for the MG-Dexox gels increased with mass ratio (MR) of Dexox to MG. The yield strains determined from rheology remained high (~125%) with increased MR. As the imine bonds formed were not reduced, they became unstable at low pH. This was exploited in order to investigate pH-triggered gel disruption of the network. This work demonstrates that new MG/aldehyde mixtures form ductile and versatile colloidal gels and our new method provides a route to increasing ductility of hydrogels containing MG particles. This research has led to the formation of amine rich MGs, as well as an injectable gel system. These materials are well placed to be developed for enzyme responsive materials in the future.

This thesis presents measurements of the the spin correlation strength in top anti-top quark pair production at the LHC using the ATLAS detector. The data used corresponds to 4.6 fb−1 of integrated luminosity taken during 2011 at the LHC at a center of mass energy of 7 TeV. The spin correlation is studied utilising different observables with different sensitivities to the production mechanism, in particular to gluon-gluon fusion in the like or unlike helicity state, quark anti- quark annihilation in the unlike helicity state, or a combination of the three. In addition cuts are made on the invariant mass of the ttbar system to enhance or suppress contributions from different initial state production mechanisms. The analysis presented is a precision test of both ttbar production and decay in the SM. These measurements are compared to the most current theoretical predictions. No deviation from the SM expectation was observed. In a subset of the data, corresponding to an integrated luminosity of 2.1 fb−1, the hypothesis of zero spin correlation is excluded at 5.1 standard deviations.

This thesis presents an investigation of pH-responsive, redox-sensitive poly(MMA-co- MAA) and poly(EA-co-MAA) hollow particles for the repair of load-bearing soft tissues, such as articular cartilage and the intervertebral disc. Hollow particles continue to attract major interest due to their numerous potential applications. The new method for hollow particle preparation presented in this thesis does not require the use of a colloidal template and is well suited for scaling up. Hollow particles were formed using linear poly(MMA-co-MAA) and poly(EA-co-MAA) aliphatic copolymers synthesised using free-radical chain copolymerisation performed in solution. These copolymers were dissolved in dichloromethane using methanol as a cosolvent and emulsified in water. Diffusion of the methanol into the aqueous phase prompts precipitation of the copolymer at the droplet/water interface. The more hydrophobic copolymers containing less MAA showed improved morphology compared to copolymers containing more MAA. Also, poly(EA-co-MAA) hollow particles had a more spherical morphology than poly(MMA-co-MAA) hollow particles with equivalent MAA contents. This was attributed to the lower Tg of the EA structural monomer, which resulted in more flexible particle shells. Unusually, during potentiometric titration of uncrosslinked hollow particles, the pH of the system decreased with increasing neutralisation. This behaviour is thought to be due to the unfolding of copolymer chains, exposing shielded carboxyl groups. The random structure of the copolymers is believed to be necessary for this behaviour. Crosslinked particles became swollen when the pH was increased using buffers. Concentrated dispersions formed self supporting gels, due to steric confinement, at 5 wt.%. The crosslinking process was performed by functionalising with cystamine using carbodiimide chemistry. This introduced disulphide crosslinks; which could be cleaved under reducing conditions at high pH, dissolving the gels. This ability to reduce the hollow particle shells to their constituent linear copolymer chains gives potential for natural removal from the body via extraction by the renal system. pH-triggered loading and release of a hydrophilic dye using crosslinked hollow particles was demonstrated. The similarity of the particle formation process to traditional solvent evaporation also allowed the loading of a hydrophobic dye. However, these particles were not crosslinked so release following swelling could not be investigated. Cystamine-crosslinked systems suffered from degradation due to thiol-disulphide exchange at high pH (~ pH 8). Crosslinking of one system was performed using 2-amino ethyl methacrylate (AEM). This introduced covalent, vinyl intra-shell crosslinking; which did not break down at high pH. Additional AEM was also used to allow inter-particle UVcrosslinking to form doubly crosslinked (DX) hollow-particle hydrogels. These gels did not re-disperse in buffer. To our knowledge, this is the first example of a covalent hydrogel formed from pH-responsive hollow particles. The DX gels offer improved mechanical properties compared to the singly crosslinked, physical gels. Freeze-dried samples of all of the gels produced during this study showed highly porous structures when observed using SEM. The rapid diffusion of FITC-dextran through a sample of DX gel indicates that these pores were interconnected. This is beneficial as it encourages tissue ingrowth, in addition to allowing the rapid diffusion of nutrients, oxygen and cell waste in vivo.

Quantum chromodynamics (QCD) is the branch of fundamental particle physics that studies the strong interaction, which is responsible for binding quarks and gluons into the familiar protons and neutrons that compose almost all ordinary matter. One of the most exciting predictions of this theory is the existence of a new state of matter, known as the quark-gluon plasma (QGP). At extreme temperatures and densities, protons and neutrons dissolve into their constituent quarks and gluons, forming a soup-like plasma of deconfined partons. This QGP is thought to have existed in the early universe, thus studying its formation and properties can help answer questions about the evolution of the universe and the nature of the strong force. However, recreating the extreme conditions of the early universe can be achieved by smashing together heavy nuclei at very high energies. This can only be done at the world’s most powerful particle accelerators. Unfortunately, QGP produced in these collisions only lasts for around 10⁻²³ seconds, making it impossible to study the plasma directly. Instead, there are a few key experimental observables that are associated with the characteristics of this plasma which can be studied. One such signature of QGP formation is known as strangeness enhancement, where the production of strange quarks within the QGP is enhanced relative to the standard up and down quarks that compose protons and neutrons. Previously believed to be unique to heavy-ion collisions, recent measurements have indicated that this enhancement is also present in high multiplicity proton-proton (pp) and proton-lead (p–Pb) systems as well. These measurements hint at the formation of a QGP in these smaller collision systems, calling into question the prediction that the formation of this plasma is only possible in heavy-ion collisions. While statistical and phenomenological models are capable of describing this enhancement in these smaller collision systems, the microscopic origins of strangeness enhancement are not well understood. Jets, which are streams of hadrons produced by an initial hard scattering of the partons within the colliding nuclei, can be used to illuminate the underlying processes that produce these strange particles. By measuring the angular correlation between a high-momentum trigger hadron (as a proxy for a jet axis) and a lower momentum strange hadron, it is possible to differentiate the strangeness-producing mechanisms between hard (jet-like) and soft (underlying event) processes. This angular correlation technique can be used to study the production of strangeness as a function of multiplicity in these regimes, giving insight into the origins of the observed enhancement. This thesis presents the first results utilizing azimuthal angular correlations to measure the production of Λ baryons—which are composed of an up, a down, and a strange quark (uds)—in p–Pb collisions at √sNN = 5.02 TeV using the ALICE detector at the LHC. The correlation measurements are used to extract the Λ jet-like and underlying event yields, as well as obtain the widths of the jets to provide more context for the observed jet production. These results are studied as a function of the Λ momentum and collision multiplicity, which are used to quantify the enhancement of strange quark production in these different kinematic regimes. Comparisons with theoretical predictions are also made to provide a framework for interpreting the results of this thesis. Moreover, these yield measurements are compared with published measurements of the ϕ(1020) meson (ss̄), which utilized similar techniques, to investigate the differences between open (|S| > 1) and hidden (|S| = 0) strangeness production. These strange measurements provide new insight into the production of strangeness in smaller collision systems, thus further constraining the microscopic origins of strangeness enhancement.

Virtual impactors are aerosol-concentrating devices composed of a nozzle and downstream receiving tube. The majority aerosol flow accelerated through the nozzle is diverted from transmitting through the receiving tube, yet particles inertially maintain trajectory into the tube, thereby increasing their concentrations. This study investigated the effect of nozzle geometry on particle focusing, a phenomenon wherein particles not only inertially enter the receiving tube but are radially confined to center streamlines. Specifically, the study aimed to understand how modifications to the nozzle's geometry can improve particle focusing. For this purpose, around 300 nozzles were simulated, with both fluid flow and particle trajectories modeled. The extent of focusing was quantified via a score metric determined by the fraction of particles confined to the inner 10% of the nozzle exit. The study found that shorter nozzles and simple geometries, such as those with a ratio of inlet radius to radius of curvature of around two, tend to have higher scores for particle focusing. The study also suggested the development of a two-stage nozzle to focus larger and smaller particles separately but concluded that the two stages cannot be selected independently of each other. It is suggested that the addition of a straight section between the two stages may allow for independent selection. Two focusing-optimized virtual impactor geometries were experimentally tested and compared to a reference geometry not optimized for focusing. All three impactor geometries were also simulated, and their penetration curves were compared to experimental data. Experimental data points were found to match well with their simulated curves, indicating accurate predictions of impactor performance. One of the optimized geometries showed slightly worse performance at small particle diameters, but no overfocusing at larger particle diameters, when compared to the reference geometry. The other optimized geometry showed similar performance at small particle diameters, but significantly improved penetration at larger particle diameters. Comparing the overfocusing via the receiving tube collection efficiencies, the two optimized virtual impactors showed 60% and 80% reductions in receiving tube losses, indicating improved particle focusing. The study concludes that the trajectory of particles can be controlled solely via the modification of nozzle geometry, which can be used in conjunction with a virtual impactor to improve the overall ability of the impactor to concentrate particles.

Understanding the dynamics and mechanical properties of complex fluid-fluid interfaces is of great importance in various industrial applications such as food processing, drug delivery, and coating. In this thesis, my research efforts focus on studying the interfacial rheology of particle-laden fluid interfaces with a custom-built device. Despite the high demand for the characterization of interfacial rheology in academic and industrial research, the study of interfacial rheology is still scarce compared to its counterpart of bulk rheometry and is limited only to specialized laboratories. One of biggest hurdles impeding the broad application of interfacial rheometry is the delicate design and the high cost of interfacial rheometers. In the first part of the thesis, a novel apparatus of the in-situ interfacial rheometer would be introduced. The simple design substantially reduces its dimension, making the new device highly portable and cost-effective for any laboratories that have access to optical microscopes for a wide range of interfacial rheology studies. Using the newly-developed interfacial rheometer, we study the rheology and microstructure of particle-laden fluid interfaces. In particular, the possibility of using Janus particles to tune the rheological response of particle-laden fluid interfaces is explored. Janus particles are heterogeneous colloids composed of two or more distinct regions with different surface properties. We find that the addition of a small amount of Janus particles can lead to a significant increase in surface moduli with enhanced elasticity, which greatly improves the stability of the interface. This drastic change in interfacial rheology is associated with the formation of local particle clusters surrounding each Janus particle. The origin of particle clusters is explained by considering the interparticle interactions at the interface. These experiments demonstrate a new way to tune the microstructure and mechanical properties of fluid-fluid interfaces. We then relate the microscopic dynamics of those particle clusters to their profound effects on the macroscopic rheology of particle-laden interfaces. By analyzing the local affine deformation of particles, we show that particles in those localized clusters experience substantially lower shear-induced stretching than their neighbors outside clusters. Such heterogeneous dynamics increase the effective surface coverage of particles, which in turn enhance the moduli of the interface, consistent with direct interfacial rheological measurements. Our findings open up an avenue for designing interfacial materials with improved mechanical properties via the control of the formation of localized particle clusters.

Los flujos granulares se observan con frecuencia en procesos naturales e industriales. El enfoque de este trabajo se dirige a la comprensión de cómo el cambio de las diferentes propiedades de los granos (forma, fricción y rigidez) influye en el caudal de los silos. Complementariamente, se analiza la dinámica del calentamiento de un gas granular de partículas alargadas. En todos estos escenarios, las simulaciones se combinan con experimentos para calibrar y validar las herramientas numéricas empleadas. En primer lugar, el análisis numérico de la descarga de granos blandos-lisos de un contenedor indicó el desarrollo de un caudal másico dependiente de la altura, lo cual no es habitual en los medios granulares. Nuestro estudio sistemático examinó el espacio de parámetros de fricción y rigidez de las partículas, explorando detalladamente la respuesta macroscópica de este sistema. Complementariamente, el análisis de los campos medios nos ayudó a explicar cuándo y por qué el caudal depende de la altura de la columna. La explicación general incluye: la respuesta del material a los gradientes de presión en el orificio de salida, pero también la forma en que se transmiten los esfuerzos en el sistema. Los resultados nos permitieron proponer argumentos teóricos simples, conectando el caudal macroscópico con el gradiente de presión en el orificio. Como resultado, hemos encontrado una explicación bien razonada de los valores de caudal dependiente de la altura, lo cual ha sido encontrado, experimental y numéricamente, para granos blandos de baja fricción. En segundo lugar, realizamos una investigación numérica del flujo en un silo bidimensional, usando una de mezclas de granos blandos-lisos y duros-rugosos. Partiendo de un sistema homogéneo de granos blandos-lisos, nuestros resultados numéricos reproducen el alto impacto que produce la inclusión de solo un 5% de los granos duros, en el flujo del conjunto de partículas. Además, resaltaron la importancia de la fricción entre granos de diferente tipo, en le desarrollo de este proceso. Cuando los granos durosrugosos son agregados al sistema, el flujo se vuelve más lento, los atascos resultan más frecuentes y la fuerza medida sobre el fondo disminuye. Además, resulta que estos efectos se potencian cuando aumenta la fricción entre especies. También estudiamos, sistemáticamente, la introducción de esfuerzos cortantes, imponiendo la rotación del fondo de un silo plano. Estas condiciones de contorno producen un efecto sorprendente en la descarga de partículas alargadas: el caudal se reduce significativamente, hasta en un 70%. Nuestras simulaciones y la aplicación de los métodos de promediación espacio-temporales revelan las razones subyacentes de esta observación. La velocidad de salida de las partículas es el principal factor que contribuye a esta caída, lo cual correlaciona con la orientación vertical de los granos. Nuestra herramienta numérica permitió explorar la dependencia del caudal del tamaño del orificio . En el límite de los orificios grandes, se reprodujo la clásica correlación de ley de potencia ∼ 5/2. Sin embargo, para aberturas pequeñas obtuvimos una ley de potencia pero con un exponente notablemente mayor. Además, también se encontró que el tamaño de la región denominada ”arco de caída libre” disminuye debido a la rotación. Finalmente, se ha estudiado numéricamente un gas granular agitado formado por partículas alargadas. Este sistema fue estudiado experimentalmente con anterioridad, y nuestro estudio proporciona información adicional sobre el proceso. Por ejemplo, describiendo el comportamiento del sistema en la dirección de calentamiento asimétrico, al que no se accedió experimentalmente. Se estudiaron las distribuciones de velocidad de las partículas, encontrando que ajustan muy bien con distribuciones exponenciales con colas largas, lo cual está en acuerdo con experimentos previos. Además, en la dirección no accesible experimentalmente, obtuvimos colas asimétricas. El colapso de las distribuciones de velocidad nos lleva a concluir que la energía media del sistema escala con el cuadrado de la velocidad característica de la pared.

Inhalation of ultra-fine particles is a major health hazard in industries involving powder and aerosol generation. The National Institute of Occupational Safety and Health (NIOSH) is conducting a series of experiments to quantify the risk of inhalation exposure for certain powder handling activities. For robust experimental predictions and to improve the design of powder handling and clean-up activities, the present Computational Fluid Dynamics study closely models the NIOSH setup. A mannequin, representing an operator, and a table are placed in a cuboidal airflow domain. The study considers massless as well as material particles introduced into the system, using multiphase flow simulations to model their dispersion and track their movement around the room in established airflow conditions. The mannequin wears an inhalable sampler and a respirable sampler, which capture some of the introduced particles, while the airflow sweeps many particles away from the mannequin.Initial simulations model the airflow around the mannequin and the table with no sampler suction involved, to study recirculation and stagnation zones around the objects in the room. Subsequent simulations are conducted with the samplers turned on, sucking the surrounding air in and giving us a visual outline of all the air streamlines entering the samplers. In the final set of the simulations, massless and material particles are introduced as a set of points in a vertical plane, with the position of the plane varying with each simulation. These simulations are conducted for different mannequin placements, namely up-stream, side-stream and down-stream of the table, different sampler arrangements on the mannequin’s body, and different particle sizes, to understand their effect on particle capture. For every simulation, particles being captured by the samplers are tracked to reveal their overall trajectory, original position, and the time of capture. The overall capture efficiency is then estimated as the ratio of number of particles captured over the total particles introduced. Additional simulations investigate different particle plane orientations such as horizontal particle arrangements, as well as different airflow speeds. An experimental powder dispenser is additionally introduced to study effects of the apparatus on the overall capture trends.The findings of this study quantify spatial and temporal dependence on inhalation risk, and help eliminate some operator orientations with minimal exposure risk. This is valuable information for experimental design, and stands in contrast to the industrial hygiene paradigm of considering average sampling in a well-mixed environment.

A number of recent experiments have been able to successfully measure the parityviolating asymmetry of electron-nucleus scattering and use its value to constrain thenuclear structure. The most recent of these, the Calcium Radius Experiment (CREX),finished taking data in Hall A of Jefferson Lab in 2021, and successfully extracted aneutron radius for 48Ca. While the main measurements of these experiments are parityviolating, there is an increasing amount of interest in the parity conserving Beam NormalSingle Spin Asymmetry (BNSSA) systematic. If not properly suppressed, the BNSSA cancompete with or exceed the parity violating measurement. Recent attempts to model thecontributions from standard model suppressed higher order diagrams have struggled topredict behavior of BNSSA for all nuclei.This document reports new measurements of the BNSSA at a beam energy of 2.18 GeVfor 12C, 40Ca, 48Ca, and 208Pb from the CREX running period. The values for 12C, 40Ca,and 48Ca are found to agree with model predictions. The two values of calcium agree witheach other, indicating no strong isotopic scaling. The value for 208Pb is consistent withzero, in stark disagreement with model predictions. This thesis contains a discussion ofhow these values were measured, as well as a proposed method to phenomenologicallyscale models to bring them into closer agreement with world data at lower energies.

In this study, the interaction of a shock with various gas and particle interfaces is analyzed through simulations using a new, GPU capable, multi-species flow solver, FIESTA (Fast, Interface Evolution, Shocks, and Transport in the Atmosphere), de- veloped for this research. The cases studied include the interaction between a shock and i) a two-dimensional (2D), circular cloud of a dense gas; ii) a 2D curtain of a dense gas; iii) a three-dimensional (3D) cylinder of a dense gas, and iv) a 3D curtain of solid particles. In simulations of a 2D gas curtain and a 3D gas column, the curtain and column were inclined with respect to the shock. In such flow geometries a shock-driven Kelvin-Helmholtz instability (SDKHI) develops on the curtain/column surface as observed in experiments. Additionally a perturbation develops near the foot and head of the curtain/column. In this study, these phenomena, observed in experiments, are confirmed numerically for the first time. Using simulation data, the effects of varying Mach number, initial angle and curtain/column width are explored in detail for 2D flows with inclined curtains and 3D flows with inclined columns. This work also examines the effect of SDKHI on various mixing characteristics for 3D flows with an inclined column. FIESTA is then extended to include Lagrangian particle transport capabilities and the particle mechanism is validated against experimental data. Performance characteristics of FIESTA are also compared on several computa- tional platforms utilizing CPU and GPU architectures. Exceptional performance is demonstrated on GPU clusters with speedups over 77X.

The composition and physical properties of atmospheric particles play a critical in Earth’s radiativebalance and are major sources of uncertainty in understanding our global climate. Atmospheric particles are produced through a variety of processes and their atmospheric impacts depend on multiple factors, like the composition, size and number concentration. Particularly, the composition, formation and growth of ultrafine particles, defined as particles with a diameter less than 100 nm, are of particular interest to investigate due to their ability to directly serve as cloud condensation nuclei (CCN). However, these various chemical and physical properties of ultrafine particles are largely dependent upon the environment they originate from. Therefore, studying the composition of ultrafine particles across various locales is extremely important and these results can be incorporated into building better global prediction models of climate. This dissertation investigates the chemical composition of ultrafine particles across the Amazon Basin, commonly referred to as the "green ocean," and over marine environments, or the "blue ocean."In Chapter 2, we measured the composition of ultrafine particles in the Amazon Basin using ThermalDesorption Chemical Ionization Mass Spectrometry (TDICMS) during the Green Ocean Amazon (GoAmazon2014/5) field experiment. The most abundant compounds detected in the positive and negative ion modes were measured. Two time periods arose over a ten day period of analysis, related to air mass back trajectories bringing different air masses to the sampling location. The first sampling period, deemed the anthropogenic period due to air masses originating over a metropolitan area, was characterized by higher particle number concentrations and larger amounts of particulate bisulfate. The background period, characterized by air masses arriving to the sampling site from northern forested areas, had 3-methylfuran as the dominant species, a thermal decomposition product of a particulate-phase isoprene epoxydiol (IEPOX). Additional statistical analysis was performed to compare the sources and composition of ultrafine particles to larger submicron particles. Hierarchical clustering separated ultrafine particle chemical components from the submicron particle chemical components, indicating that different processes or sources impact ultrafine particle formation and growth compared to larger submicron-sized particles.Next, in Chapters 3 and 4, we measured the composition of ultrafine particles from both primaryand secondary marine sources using TDCIMS analysis during the Sea Spray Chemistry and Particle Evolution (SeaSCAPE) experiment. Primary marine aerosol, known as sea spray aerosol, is directly emitted into marine environments through wave breaking and bubble bursting. Using coastal water obtained from Scripps Pier in San Diego, CA, primary sea spray was generated using a wave flume. The measured trends in inorganic, NaCl, and organic fractions were dependent on active biological activity, with the organic fraction peaking with the total abundance of heterotrophic bacteria. At low phytoplankton activity, ultrafine particulate mass was mainly comprised of NaCl. Positive ion fragments characteristic of polysaccharides and fatty acids likely were of bacterial origin, were measured in ultrafine particles but not in larger sea spray aerosol (∼100-200 nm). Additionally, in Chapter 4, we report the general composition of ultafine secondary marine aerosol during times of high biological activity and mass fractions of particle phase ammonium, sulfate, methanesulfonic acid (MSA), dimethylamine (DMA) and iodine. Secondary marine ultrafine particles were formed using a potential aerosol mass oxidative flow reactor and oxidizing gaseous emissions from the wave flue with ∼1 day equiv. aging of OH. These measurements were paired with gas phase measurements of volatile organic compounds (VOCs) directly emitted from the wave flume to assess the formation pathways of secondary marine aerosol. More ultrafine secondary marine aerosol was produced during times of high biological activity, when sulfur containing VOCs were at their highest, leading to roughly 40% of the mass fraction being composed of the TDCIMS calibrated species listed above. We hypothesize that particulate DMA and ammonium are neutralized by sulfuric acid, MSA and organic acids. The general composition of secondary ultrafine particles during peak biological activity suggest influence from nitrogen and sulfur containing organic species and low volatility organics that can contribute to new particle formation.

Aerosol generators are often used to suspend small particles in air for various applications within industry. Particle sizes ranging from tens of nanometers to hundreds of microns offer unique properties at this scale that can be leveraged for surface coatings, biochemical testing, and environmental technology development. The objective of this research is to provide a robust, cost-effective method for dry-powder aerosol generation for use within a controlled laboratory environment. The proposed device utilizes a hypocycloid mechanism to aerosolize dry-powder via agitation through a strainer. The device was developed, tested, and refined to fulfill all functional requirements outlined by the National Strategic Research Institute including a consistent, repeatable, and tunable output. Advisor: Benjamin Terry

Abstract: The PICO-60 experiment offers world leading sensitivity to the spin-dependent WIMP search, looking for the direct measurement of dark matter nuclear recoils with protons. The primary background in moderately super-heated C3F8 bubble chambers are neutrons, which can produce a signal indistinguishable from a dark matter candidate. To study the detectors response to neutrons, I show the relationship between bubble multiplicity and neutron energy is non-linear; meaning there is insufficient information in multi-bubble events to reconstruct the primary energy. This observation is explained by nuclear reactions at energies above 1.5 MeV, from fast neutrons depositing more energy above threshold into a single bubble event. Studying the acoustic energy emitted from nuclear reactions, I predict that these fast neutrons can be identified in the tail of the acoustic parameter (AP) distribution, which PICO originally uses to identify background alphas associated with the decay of222Rn. In an attempt to reconstruct direction, a technique to assign 3D coordinates to multi-bubble events is described using PICO-60 data and compared with Monte-Carlo simulations. The result is inconclusive, primarily because of a lack of statistics in the neu-tron calibration data. Finally, the commissioning of the PICO-40L detector at SNOLAB is discussed, focusing on my contributions to the thermal and camera installation. The new detector offers increased sensitivity to the dark matter search, and will continue the neutron AP and direction analysis presented.

This thesis covers the intensive research effort to elucidate the role of elevated temperature in deposition. Several experimental campaigns were conducted in this pursuit. The testing explored high temperature deposition with 0-10 micron Arizona Road Dust (ARD) with the intent of creating a yield strength model that included temperature effects and could be incorporated into the existing OSU deposition model.Experimental work was first conducted in the impulse kiln facility where small amounts of the test dust were placed on ceramic targets and rapidly exposed to temperatures between 1200K and 1500K. Trends in the packing factor confirmed the existence of two threshold values (1350K and 1425K) that could be linked to strength characteristics of the dust when exposed to high temperatures. Using the information obtained from the kiln experiments, HTDF testing was conducted between 1325K and 1525K. Exit temperatures were set at 25K intervals in this region with a constant jet velocity of 150 m/s. The capture efficiency data showed this trend with temperature and indicated a softening temperature and melting temperature of 1362K and 1512K respectively. With these critical values in hand, the Ohio State University Molten Model was created to modify yield strength with particle velocity and temperature. The model was tested using CFD and showed a good capability for capturing particle temperature effects in deposition from an impinging particle-laden jet.A subsequent test campaign was conducted to explore the effect of varying surface temperature on deposition. Hastelloy coupons with Thermal Barrier Coatings (TBCs) were subjected to a constant jet at 1600K jet and 200 m/s while being cooled via a backside impingement jet. Surface temperatures between 1455K and 1125K were impacted with 0-10 micron ARD while an IR camera monitored the surface. Coupons with higher coolant flowrates (lower surface temperature) saw significantly lower deposition rates than the higher surface temperatures. CFD simulations using the newly vetted OSU Molten Model were not able to account for the strong decrease in deposition with boundary layer cooling. Therefore, it was posited that the model should eventually incorporate both particle and surface temperatures in its formulation.

A one-dimensional kinetic particle-in-cell (PIC) MATLAB simulation was created to demonstrate the time-evolution of various plasma distributions. Building on previous plasma PIC programs written in FORTRAN and Python, this work recreates the computational and diagnostic tools of these packages in a more user- and educational-friendly development environment.Plasma quantities such as plasma frequency and species charge-mass ratios are arbitrarily defined. A one-dimensional spatial environment is defined by total length and number and size of spatial grid points. In the first time-step, charged particles are given initial positions and velocities on a spatial grid. After initialization, the program solves for the electrostatic Poisson equation at each time step to compute the force acting on each particle. Using the calculated force on each particle and the “leap-frog” method, the particle positions and velocities are updated and the motion is tracked in phase-space. Modifying parameters such as spatial perturbation, number of particles, and charge-mass ratio of each species, the time-evolution for various distributions are examined.The simulated distributions examined are categorized as the following: Cold Electron Stream, Electron Plasma Waves, Two-Stream Electron Instability, Landau Damping, and Beam-Plasma. The time evolution of the plasma distributions was studied by several methods. Tracking the electric field, charge density and particle velocities through each time step yields insight into the oscillations and wave propagation associated with each distribution. One key diagnostic missing from the original FORTRAN code was the electric field dispersion relation. The numerical dispersion relation allows for further insight into modelling plasma oscillations/waves in addition to the kinetic/field energies and electric field tracking present in the original code. Simulated results show agreement with other kinetic simulations as well as plasma theory.

Abstract: V1309 Sco was observed in 2008 as a luminous red nova and presents as some of the best time-resolved spectral data of a contact binary merger. However, the parameters of its progenitor and the physics behind the morphology of its light curve remain uncertain. We use the Smoothed Particle Hydrodynamics (SPH) code StarSmasher to model the progenitor primary star, using a MESA model at the base of the red giant branch with M = 1.52 Msun, R = 3.715 Rsun and total particle numbers N = 1x10^5, N = 2x10^5, and N = 3x10^5. We vary spatial resolutions in each of the models to find total energy profiles that match the initial MESA model well near the surface. We analyze all three models using a new code we developed called FluxCal, which solves the radiative transfer problem in SPH simulations using an envelope fitting method for inherently optically thick particles and a Runge-Kutta ray tracing method in the LTE approximation. FluxCal allows for the first time ever the calculation of spectral properties at SPH simulation boundaries with optically thick particles. We observe an accuracy improvement of ~2 orders of magnitude in the effective temperature of an SPH stellar model over a traditional ray tracing method. We simulate a contact binary merger with the M = 1.52 Msun, R = 3.715 Rsun, N = 2x10^5 red giant primary and a M = 0.16 Msun, R = 0.203 Rsun, N = 1x10^4 secondary with StarSmasher out to ~14 days (~4 months wall time) to model the V1309 Sco merger. We use FluxCal to calculate the effective temperatures in 10 hour intervals which we use to calculate luminosities. The merger in our simulations evolved on timescales shorter than expected from observations. This may be due to the primary's envelope artificially expanding during relaxation to a larger radius than the initial MESA model, which leads to Roche lobe overflow and loss of angular momentum at larger separations. Calculated luminosities peak at values similar to that observed in V1309 Sco. We require additional simulation time or a simulation with lower resolution to view late-time spectrotemporal dynamics.

Natural supersymmetry has earned a unique focus in the search for new physics, in part because of its solution to the hierarchy problem. Minimizing fine tuning in this solution often puts the superpartners of the Higgs boson (higgsino) and top quark (stop) well within LHC reach. In the most natural scenario, the higgsino and stop masses are expected to be close to the masses of their Standard Model partners. Additionally, in the case of higgsinos with multiple mass eigenstates, these masses should be close to each other. Such small mass splittings are known as a compressed spectrum. In a decay chain this presents several experimental challenges, since the final state objects are very soft and there is little missing energy. In order to build a sensitive analysis around these difficulties, a variety of new techniques are utilized, including improvements with ISR-assisted topologies using the Recursive Jigsaw Reconstruction (RJR) method. In this thesis, these novel strategies and the idea of naturalness are used as a lens to interpret the status of stop and higgsino searches with ATLAS at the conclusion of the Large Hadron Collider Run II.

Access to clean water is a fundamental human need and one of the most important and essential elements to health. Despite the worldwide efforts to improve water purification systems, the World Health Organization reported that tens of millions of people are fatally sick and 1.6 million people die every year due to water-related diseases. The diseases are caused by excessive amounts of particulate contaminants, which are derived from industrial chemicals, agricultural runoff and natural pollutants. To reduce such toxic liquid-borne particles suspended in the aqueous environment, liquid filtration techniques using membrane filters have been considered one of the most effective treatments. The membrane techniques have been also widely used to produce a compound with a high level of purity in many industries such as semiconductor manufacturing, drug-related industry and wastewater treatment. The objectives of this thesis are to 1) explore characterization methods for the evaluation of liquid filtration membranes and 2) investigate particle retention behaviors of small nanoparticles through various membrane filters.

This dissertation critically compares the two German focus particles eben and gerade. It has been repeatedly noted in the relevant literature that the two display an intriguing yet challenging near-synonymy. However, factors motivating this relationship have not been sufficiently explained to date. This study argues that the particles’ ostensible partial overlap is systematic and non-trivial in nature and that it can be explained by positing two distinct speaker motivations for uttering each particle to mark a constituent in a sentence: While the particle eben marks a constituent as conform-to-expectation, gerade marks a constituent as counter-to-expectation. Each marking is prompted by the discourse situation: If there is (extra)linguistic evidence that the interlocutor is inclined to select the same constituent as the speaker for completing a sentence, then eben is the appropriate marker. Alternatively, if no contrary evidence exists, eben may still be the appropriate marker. In the absense of favorable evidence, the speaker relies on assumptions about human communicative strategies and biases for arriving at the constituent choice matching the speaker’s and may still be prompted to utter eben. Conversely, the speaker utters gerade to mark a constituent as counter-to-expectation when there is (extra)linguistic evidence that a different constituent is more likely to be selected, or has been selected. Alternatively, if at least no (extra)linguistic evidence exists that the identical constituent is selected, assumptions about human communicative strategies and biases for arriving at a different constituent choice as the speaker’s prompt the use of gerade. The hypothesis is supported by two analyses: a minimal pair analysis employing substitution, elimination, and continuation tests as well as a synchronic, large-scale corpus-based analysis of syntactico-semantic features that frequently occur as the particles’ constituents. The former is employed to do away with compartmentalized interpretation suggestions for the particles, contaminated by adjacent elements, and suggests the underlying meanings of the particles to interact with said elements in generating the interpretations. The latter analysis presents a selection of syntactico-semantic features with which each particle frequently occurs in natural language and offers new insights on their functions based on interactions with eben and gerade.

Protein targeting is a fundamental cellular process that directs proteins from their site of synthesis to the site where they function. The signal recognition particle (SRP) dependent targeting pathway is conserved in both eukaryotes and prokaryotes where it co-translationally targets polypeptide chains emerging from ribosomes to the endoplasmic reticulum (eukaryotes) or cytoplasmic membrane (prokaryotes). A structurally unique form of SRP is found in chloroplasts where it functions to post-translationally bind and target a subset of integral thylakoid membrane proteins, the light harvesting chlorophyll binding proteins (LHCPs). Mature LHCPs bind chlorophyll a/b and function in photosynthetic light capture. Like many other chloroplast proteins, LHCPs are nuclear encoded and synthesized in the cytosol. Following their import into the chloroplast stroma, LHCPs associate with chloroplast SRP (cpSRP), which maintains LHCP solubility and initiates targeting of LHCP to the thylakoid membrane via an cpSRP receptor (cpFtsY) at the thylakoid membrane. Both cpSRP and cpFtsY are GTPases and associate at the thylakoid by a mechanism that requires GTP binding by both proteins. Subsequent insertion of LHCP into the lipid bilayer is mediated by a protein insertase Albino3 (Alb-3), which binds cpSRP to stimulate LHCP release from cpSRP and GTP hydrolysis by both cpSRP and its receptor. Work here has focused on studies to understand mechanistic details of the cpSRP targeting pathway and better understand the timing of targeting events at the membrane. The results provide support for a structure-based chronology of protein interactions between LHCP targeting substrates, cpSRP, cpFtsY, and Alb-3. They also demonstrate that GTP hydrolysis by cpSRP and its receptor at the membrane is not necessary for LHCP insertion by Alb-3, but serves to maintain an available pool of Alb-3 insertase at the membrane by stimulating the exit of cpSRP targeting components following release of LHCP from cpSRP to Alb-3.

This dissertation presents a measurement of the top quark mass (Mt) in the dileptonic decay channel using data from proton-proton collisions at √s = 8 TeV recorded by the CMS experiment at the LHC, corresponding to an integrated luminosity of 19.7 ± 0.5 fb−1. The analysis is based on three observables whose distributions are sensitive to the value of Mt. The Mbl invariant mass and MT2 'stransverse mass' observables are employed in a simultaneous fit to determine the value of Mt and an overall jet energy scale factor (JSF). In a complementary approach, the MT2-assisted on-shell reconstruction technique is used to construct an Mblv invariant mass observable that is combined with MT2 to measure Mt. The shapes of the observables, along with their evolutions in Mt and JSF, are modeled by a non-parametric Gaussian process regression technique. The sensitivity of the observables to the value of Mt is investigated using a Fisher information density function. The top quark mass is measured to be 172.22 ± 0.18 (stat) ± 0.91 (syst) GeV. This dissertation also presents a missing transverse momentum (MET) significance variable, which is used to estimate the compatibility of the reconstructed MET with a zero nominal value. This variable may be used to discriminate between events containing real MET due to undetected particles and spurious MET due to object misreconstruction, finite detector resolution, or detector noise. The MET significance variable is tuned using data-driven techniques, and its performance is evaluated using the CMS Run 1 and Run 2 datasets.

The decay of the Higgs boson to two photons is one of the major analysis channels for Higgs physics studied at the LHC. Together with the four-lepton decay channel, it provided the most statistically robust signal leading to the Higgs discovery in 2012. Although the particle has been extensively studied at 7 TeV and 8 TeV, research into higher collision energies (13 TeV) is necessary for further characterization. The two-photon collaboration in CMS has developed analysis tools to investigate these high-energy collision events. Important resultsare a measured signal strength of σobs/σtheoretical = 1.16+0.11−0.10 and a measured mass of mH=125.09 GeV with 9.3σ significance.

The search for and detailed study of new particles and forces with the Compact Muon Solenoid (CMS) detector at the Large Hadron Collider (LHC) of CERN is fundamentally dependent on the precise measurement of the rate at which proton-proton collisions produce any particles, the so-called luminosity. Therefore, a new detector, the Pixel Luminosity Telescope (PLT), dedicated to measure the luminosity at high precision was added to the CMS experiment in 2015. It measures the inclusive charged particle production from each collision of proton bunches in the LHC. Additional charged particles which are observed by the instrument but produced from sources other than collisions are characterized by measurements of particle trajectories and subtracted from the luminosity. Methods were developed to calculate the corrections to the luminosity measurement of the PLT.

Particle emissions from motor vehicles are an increasing source of atmospheric pollution. Operating conditions that produce significant particle number emissions in light duty vehicles were the focus of this study. Extremely cold conditions cause engines to use significant fuel enrichment during starting and warm-up and thus are prone to high particle emissions. In gasoline direct injection engines, this can lead to even higher soot formation due to liquid fuel impingement on the cold surfaces of the combustion chamber and piston. Humans can be exposed to high particle concentration from cold starting vehicles in parking ramps or any busy traffic areas due to higher vehicle density and poor ventilation. Separating ambient particle emissions according to engine type allows for the identification of vehicles that have the highest tailpipe emissions or contribute to high ambient particle number (PN) concentration. This thesis presents the results of two studies. The first study shows that the average PN emitted during 180 seconds by GDI and PFI vehicles after a cold-cold start were 3.09E+13 and 2.12E+13 particles respectively, based on tailpipe out emissions. The high particle emissions highlight the need for better particle control strategies to reduce particle emissions during engine startup in cold ambient temperatures. Meanwhile, the ambient study conducted at the exit of a parking ramp found that GDI vehicles (only 12% of the vehicle population in this study) contributed to about 50% of the increase of particle concentrations associated with vehicles. Thus, the increasing number of GDI vehicles in the future is expected to lead to an increase in particle concentrations in parking ramps and similar facilities.

When biological cells approach regions with high strain-rates, the membrane deformation can surpass the yielding point, leading to cell lysis. In the interest of enhancing such effects, drop dynamics is studied. Here, bending stiffness and viscoelastic area compression of the membrane are not considered. Surface-tension force is used to model planar tensile stresses instead. Breakup of drops has been shown to depend on the type of flow, the Reynolds number, Re , the capillary number, Ca , the viscosity ratio, the density ratio, and the Stokes number (particulate flows). In simple shear flows at low Re and low Ca, breakup is not possible. The main purpose of this work is to find conditions that enhance drop disruption under such flows. While the deformation of drops and elastic capsules in simple shear flows and particulate flows have been subject of research, less attention has been given to the deformation of drops in particulate simple shear flows that are initially quiescent. The effects of rigid particles on drops are studied numerically for several flow conditions and the deformation is analyzed using the particle-particle distance. It is observed a decrease in deformation as Re (moderate regime) increases for different initial position of the particles. Drop deformation increases with Ca, meanwhile larger and denser particles are preferred to induce drop puncturing. Without particles, the conditions for drop breakup are found when the walls are closely located. Similarly, a gravity-driven particulate flow is studied and the dependence on the Bond number is shown. The problem of drop splitting in sudden expansions is also analyzed, showing dependence on the expansion ratio. The conservation laws are solved numerically using finite volumes and the Crank-Nicolson scheme. Velocities are corrected with SIMPLEC. The interface is tracked with the volume-of-fluid method, reconstructed with the piecewise linear interface calculation algorithm (PLIC), and fluxed based on the defined donating region (DDR). A High-Resolution technique (SMART) is employed to discretize advection terms. A continuum surface force (CSF) models surface tension. Rigid particles are introduced in the domain with the Lagrange multiplier method.

An inclusive search for new physics is performed with a 13 TeV dataset from the CMS detector (May-November 2015, corresponding to 2.32/fb) using events with at least two leptons with the same electrical charge, missing transverse energy, and significant hadronic activity. No significant excesses are reported above the Standard Model background predictions. Constraints are set on a number of new physics models. As motivation, a thorough pedagogical review of the Standard Model and its shortcomings is presented in the first two chapters.

Elevated concentrations of diesel exhaust have been linked to adverse health effects. Filtering facepiece respirators (FFRs) are widely used as a form of respiratory protection against diesel particulate matter (DPM) in occupational settings. The objective of this study was to evaluate NIOSH-certified R95 and P95 electret respirators challenged with Diesel exhaust and get a better understanding of the factors that influence penetration. Two techniques were employed for the measurement of penetration: (a) particle counting technique using a Scanning Mobility Particle Sizer (SMPS, TSI Inc.) which measures particle size distribution, and (b) Gravimetric analysis using polyfluortetraethylene (PTFE) and polypropylene (PP) filters. Gravimetric measurements using PP filters were variable compared to SMPS measurements and biased high as a result of the adsorption of gas-phase semi-volatile material. Relatively inert PTFE filters adsorbed less semi-volatile material resulting in more accurate measurements. To attempt to correct for these artifacts associated with adsorption of semi-volatile material, primary and secondary filters were used in series upstream and downstream of the FFR. Correcting for adsorption by subtracting the secondary mass from the primary mass improved the result for both PTFE and PP filters but this correction is subject to “equilibrium” conditions that depend on sampling time and the concentration of particles and semi-volatile material. Overall, the results demonstrate that great care must be taken when using filters to determine filtration efficiency of FFRs challenged with diesel exhaust. Pure PTFE or other filters that minimize adsorption of semi-volatile artifacts and two filters should be used in tandem to allow correction for adsorbed artifacts. Analysis of SMPS measurements indicated that the respirators behave differently for Diesel exhaust generated at light and heavy load on engine. At light load, the penetration of the R-95 and P-95 respirators showed a steep increase with time, exceeding the maximum allowed penetration of 5% after about 40 minutes. Whereas at heavy load, the respirators were found to have a relatively unchanging penetration (less than 5%) throughout the 90-minute test duration. This difference was attributed to the presence of a high concentration of organic carbon (OC) in Diesel exhaust which has a tendency to degrade the electric charges on the respirators, thus reducing the filtration enhancement from electrostatic attraction forces. To account for the complex nature of DPM and its varying properties with changes in operating and sampling condition, an oxidation-dilution tunnel was designed to produce Diesel exhaust with a controlled set of properties: elemental carbon (EC) concentration, OC concentration, EC/OC ratio and volume flow rate. This device was used to evaluate R-95 and P-95 respirators for solid Diesel exhaust aerosol. The methodology proved to be effective in controlling the EC concentration and total volume flow rate. Results showed that the R-95 and P-95 respirators were more than 95% efficient for solid Diesel exhaust aerosol. This thesis is divided into two parts. The first focuses on the measurement of penetration of FFRs for Diesel exhaust, the second on the development of a standard DPM generator for testing filtration systems.

Atmospheric aerosol particles have been known to influence the Earth's climate directly and indirectly. The magnitude of these effects strongly depends on their size, morphology, and their interaction with water at different relative humidities, yet our knowledge of them is largely limited. Moreover, many industrial processes such as food, personal care, and pharmaceuticals require a general knowledge of particles' size and morphology. Therefore, an investigation of these characteristics is essential to both industrial and atmospheric applications. Different techniques have been used to study these physical characteristics of particles; nevertheless, these studies did not extend their analysis to the effects of different drying rates. Drying rates in this thesis are referring to different drying processes with different starting droplets and conditions. It was not the objective of this study to quantify the drying rates; therefore, the term was used to generally simplify the descriptions of two different drying processes. The thesis' goal was to investigate the effect of drying rate on size and morphology of a few inorganic, amino acid and dicarboxylic acid (C3-C7) nanoparticles through the use of a scanning mobility particle spectrometer and an atomic force microscope. The hypothesis was that some chemical compounds resulted in different morphologies depending on the drying rates. Experimental results confirmed this hypothesis. Particularly, the even dicarboxylic acid particles (C4 and C6) did not change while the odd dicarboxylic acid particles (C3, C5 and C7) did. Both amino acids (glutamic acid and L-leucine) results showed that their size stayed the same. However, AFM images of glutamic acid showed some changes in their morphology. Finally, CaCl2 and NH4Cl exhibited no change while NH4NO3 results indicated that the particles might have crystallized into two forms depending on the drying rates.

This thesis reports a theoretical study of polymers in the presence of particles. An analytical theory is used to describe the potential of mean force between spheres for the case where the polymer molecular weight dispersity is described by the Schulz-Flory distribution. Exact results are derived for systems where the particle radius (RS) is small in comparison to the radius of gyration (Rg) of the polymer molecules. Numerical results are obtained in the case of particles immersed in a solution of polymers. It is shown that when q = Rg/RS ≥ 10 a spherical approximation can be used to describe the potential of mean force. This result has significant consequences on the many-body interactions mediated by polymers between particles in the particle/polymer mixtures. The theory is then applied to study the phase behaviour of particle/polymer mixtures in electrolyte solutions wherein the particles are charged. Thus the particles have a combination of depletion attraction and screened electrostatic repulsion. We show that a generalized potential of mean force is an accurate and computationally efficient means by which to treat this system. In addition to the two studies above, we also consider the case of an equilibrium polymer consisting of associating co-monomers. We generalize the density functional theory of polymers to describe this scenario and study the case where the polymer is in the vicinity of an attractive surface. Interestingly, A surface phase transition is observed in ideal polymers, which is suppressed when monomers exclude each other. We use this theory to model the formation of linear peptide aggregates on the surfaces of particles. In particular, we consider a specific model for an amyloidal peptide responsible for Alzheimer disease. The thesis concludes with a discussion on possible theoretical developments in the future.

Indoor jets considerably dominate air movement and distribution of temperature and velocity, as well as transport of particles and other pollutants. Indoor air temperature and velocity distribution substantially impact occupants’ thermal comfort and productivity, heat and mass transfer on indoor surfaces. In addition, jets produced by human respiratory activities, such as coughing and sneezing, enhance the spread of particles that might carry bacteria or viruses. Understanding and characterizing indoor jets and their impacts on air distribution, temperature and velocity fields, and particle transport are crucial for advancing heating, ventilation, and air conditioning (HVAC) systems when considering thermal comfort and developing strategies for exposure mitigation. This dissertation contributes to the scientific understanding regarding to indoor air distribution and particle transport associated with indoor air jets. Current HVAC system design defines indoor air distribution related to the selection of diffusers/ grilles that distribute supply air jets, according to the specifics of the space and internal heating and cooling loads. However, current design guidance was developed over 40 years ago. It requires expansion of diffuser/ grille types and the update for air distribution by diffuser/ grille air jets supplying warm air at heating mode. Unlike jets from diffusers/ grilles, jets created by human activities are inherently transient in nature and might perform quite differently from steady-state ones. Understanding the dynamics of unsteady-state jets, such as coughs, enhances the current state of understanding of the mechanisms of respiratory disease transmission, which enables development of exposure reduction measures. The investigations presented in this dissertation extend the state-of-the-art knowledge on indoor jets and analyze the effect of steady-state and unsteady-state jets on particle transport in indoor environments. Figure 1 illustrates the two objectives and six investigations conducted in this dissertation. The first objective includes four investigations that address air distribution and particle transport associated with steady-state jets created by diffusers/ grilles, and the remaining two investigations relate to the second objective on unsteady-state cough jets. The first objective of this dissertation characterizes air distribution and particle transport in a space with steady-state jets created by diffusers/ grilles. One of the major contributions of this objective to the-state-of-the-art knowledge on indoor air distribution is the newly developed method for diffuser performance assessment and design when considering heating mode. It advances the current diffuser/ grille selection guide that was outdated decades ago. Furthermore, based on 650 experimental set-ups this objective provides a systematic analysis of indoor air velocity that can be further used in indoor heat transfer and pollutant emission and transport. The second objective investigates velocity fields in unsteady-state cough jets and transport of coughed particles. This objective provides a theoretical analysis of the dynamics of cough jets and examines how human thermal plume affects the exposure to coughed particles when considering different particle sizes. Ultimately, these investigations fill the knowledge gaps in indoor air distribution and particle transport associated with steady-state and unsteady-state jets in spaces using all-air HVAC systems. The newly developed diffuser guideline will improve HVAC design for both heating and cooling conditions when considering thermal discomfort or air stagnant zones caused by a wrong diffuser selection. In addition, the systematic analysis of indoor air velocity will improve the prediction of indoor heat transfer, mass transfer, particle resuspension rate, pollutant emission rate from the floor and other indoor surfaces. Finally, the theoretical analysis of unsteady-state jets contributes the knowledge for fluid dynamics of unobstructed human coughs and also transport of coughed particles, including the distribution in the vicinity of an exposed person.

The purpose of this thesis is to examine the potential for a more comprehensive method of analysis of coal mine dust. Respirable dust is specifically of interest due to its ability to cause occupational lung disease when miners are overexposed to airborne concentrations. A detailed standard methodology to characterize respirable mine dust is carefully investigated with the use of scanning electron microscopy with energy dispersive x-ray (SEM-EDX). In addition to a thorough description of the developed particle level characterization approach, the method is demonstrated with underground respirable dust samples collected from an underground coal mine in Central Appalachia. Results of this thesis indicate that a comprehensive dust characterization method is possible and can be efficient and effective, when standardized. This analytical approach uses measured compositions, dimensions, and shapes to produce an abundance of data in even a single sample of dust. Verification results show the method is suitable for analysis of respirable particles of common coal mine mineralogy and analysis of many samples in a timely manner. The results obtained from the underground samples in Central Appalachia reveal the quantity of information which can be generated using the developed method. The amount of data which is acquired using the more comprehensive dust characterization method may aid in understanding the health effects of various dust characteristics.

We study the motivation and groundwork for the construction of a Light-Shell Effective Theory, an effective field theory for describing the matter emerging from high-energy collisions and the accompanying radiation. We begin in chapter 2 with a simple electrodynamics calculation to motivate the picture of the ``light-shell," in which all electric and magnetic fields lie on a spherical shell that moves outward at the speed of light. The result turns out to do more than motivate, as it also hints at an important feature of the theory, namely the gauge in which we subsequently choose to do calculations, called Light-Shell Gauge.

This dissertation describes three computational models developed to simulate important aspects of low-temperature plasma devices, most notably ring-cusp ion discharges and thrusters. The main findings of this dissertation are related to (1) the mechanisms of cusp confinement for micro-scale plasmas, (2) the implementation and merits of magnetic field aligned meshes, and (3) an improved method for describing heavy species interactions. The Single Cusp (SC) model focuses on the near-cusp region of the discharge chamber to investigate the near surface cusp confinement of a micro-scale plasma. The model employs the multi-species iterative Monte Carlo method and uses various advanced methods such as electric field calculation and particle weighting algorithm that are compatible with a non-uniform mesh in cylindrical coordinates. Three different plasma conditions are simulated with the SC model, including an electron plasma, a sparse plasma, and a weakly ionized plasma. It is found that the scaling of plasma loss to the cusp for a sparse plasma can be similar to that for a weakly ionized plasma, while the loss mechanism is significantly different; the primary electrons strongly influence the loss structure of the sparse plasma. The model is also used, along with experimental results, to describe the importance of the local magnetic field on the primary electron loss behavior at the cusp.Many components of the 2D/3D hybrid fluid/particle model (DC-ION) are improved from the original version. The DC-ION code looks at the macroscopic structure of the discharge plasma and can be used to address the design and optimization challenges of miniature to micro discharges on the order of 3 cm to 1 cm in diameter. Among the work done for DC-ION, detailed steps for the magnetic field aligned (MFA) mesh are provided. Solving the plasma diffusion equation in the ring-cusp configuration, the benefit of the MFA mesh has been fully investigated by comparing the solution with a uniform mesh. It is found that the MFA mesh can still produce a relatively large error due to the misalignment at the domain boundary but still provides a significant improvement in the bulk plasma region. The mesh generation routine can be further improved by enhancing the smoothness of the near-boundary grid elements.The Ion Beam (IB) model is similar to the SC model but primarily focuses on heavy species. The model implements detailed calculation of the heavy species collisions, solving the classical scattering equation with higher order interaction potentials for different collision pairs. A parametric study has been conducted, and the simulation results have shown very good agreement with the experimental results when using an appropriate value for the secondary electron yield. Further study on the elastic collision has shown that the initial atom velocity should not be neglected in order to accurately compute the post-collision CEX ion velocity. The knowledge gained has led to an improvement on the current method by defining an effective elastic collision cross-section and significantly reducing the frequency of the collision calculation. The same method can be applied to collisions between fast and slow atoms.

The use of membranes with a single pore to measure particles as they pass through is a promising method to allow the rapid determination of properties of individual particles in solution. However, this will involve an understanding and control of the forces that these particles undergo while in the pore. In this work we use single cylindrical pores in PET membranes to test and compare the translocations of deformable hydrogel particles and rigid polystyrene spheres. We find that the hydrogel particles cause a characteristic initial increase in current, pass by electroosmosis, and can also undergo dehydration and deformation in pores of smaller diameter. We also show that the force on a particle by an applied hydrostatic pressure gradient can be sufficiently balanced with a transmembrane voltage that is dynamically triggered when the particle enters the pore, and the subsequent fluctuations in the current from the particle diffusing within the pore can be observed for tens of seconds. Finally, we show that repeated translocations of a single particle can be performed using a set rising edge or falling edge triggered voltage wave, or an even greater number of repetitions can be achieved by subtracting in real time the capacitance effects based on a previous test pulse.

The simultaneous production of two J/psi mesons has been significantly observed in proton-proton collisions at a center-of-mass energy of 7 TeV with the CMS detector. The two J/psi mesons are fully reconstructed in their decay to muons. The signal yield is extracted with an extended maximum likelihood fit based on four event variables. A method was developed to correct for detector acceptances and efficiencies based on the measured momenta of the J/psi and their decay muons to maintain the least model dependence possible. The measurement is performed in an acceptance region defined by the individual J/psi transverse momentum and rapidity. From the measured signal yield of 446 events corresponding to an integrated luminosity of 4:7 inverse femtobarn. The total cross section is found to be 1:49 nanobarn, with 0:07 statistical and 0:13 nb systematic error, and unpolarizaed production was assumed. Most predictions for particle production at the LHC assume dominance of single parton interaction for proton-proton collisions, which can be tested with the final state measured in this analysis. The differential cross section is measured in bins of the double J/psi invariant mass, the double J/psi transverse momentum, and the absolute difference in rapidity of the two J/psi. The reconstruction of the four charged muon trajectories heavily relies on the Pixel subdetector located close to the beampipe. Systematic studies with cosmic muons and tracks from collision events are presented. The development of the Pixel RawToDigi package, data quality monitoring packages, commissioning studies of Pixel data and tracks in first collisions, and realistic simulations of decay signals in the pixel subdetector were all performed as a part of this dissertation work.

Nanoparticles are often found in liquid-borne dispersed phases, in addition to the airborne and surface-borne phases. Characterization techniques for nanoparticles are needed for the environmental, health and safety studies of nanomaterials. On the other hand, membrane filtration has been demonstrated to be effective for the removal of liquid-borne nanoparticles. Such technique has found many applications, including: 1) contamination control in liquids used in industries which require high level of cleanliness, 2) control of the release of engineered nanoparticles for environmental health and safety and 3) drinking water purification and disinfection. For evaluating filtration performance of nanometer-rated filters, reliable techniques for counting and sizing liquid-borne nanoparticles are desirable. The objectives of this thesis are to 1) explore methods for characterizing liquid-borne nanoparticles and 2) apply these methods to study nanoparticle filtration problems. In Chapter 2, calibration results of the Nanoparticle Tracking Analysis (NTA) technique in our lab are reported. The concentration measurements agree well with that estimated by suspension mass concentration within the range of 108-1010 particles/ml. To ensure the concentration measurements are made within the linear valid range, a single sample should be diluted and the NTA concentration measurements for the original and diluted samples should agree. Applying the NTA technique, the size distribution and concentration of nanoparticles in the water used in Abrasive Waterjet Machining (AWM) and Electrical Discharge Machining (EDM) processes were measured. The particles generally have a most probable size of 100-200 nm. The filtration systems of the AWM and EDM processes were found to remove of 70 and 90 % the nanoparticles present, respectively. However, the particle concentration of the filtered water from the AWM was still four times higher than that found in regular tap water. These nanoparticles are mostly agglomerated, according to the microscopy analysis. Since AWM and EDM are widely used, the handling and disposal of used filters collected with nanoparticles, release of nanoparticles to the sewer and potential use of higher performance filters for these processes will deserve further considerations. The development of an aerosolization technique to measure liquid-borne nanoparticles down to 30 nm and its application to filter evaluation is discussed in Chapter 3. This technique involves dispersing nanoparticle suspensions into airborne form with an atomizer or electrospray aerosol generator, and measuring the size and concentration by a differential mobility analyzer coupled to a condensation particle counter. With the electrospray aerosol generator, residue particles can be controlled to be less than 10 nm, allowing particles as small as 30 nm to be clearly distinguished from the size distribution measurements. Calibrations with 30, 50, 125 and 200 nm polystyrene latex particles showed that liquid-borne and airborne particle concentrations are proportionally related. This provides an effective way to quantify liquid-borne particles as small as 30 nm, which cannot be analyzed by state-of-the-art liquid particle counters. Comparing to NTA, the aerosolization technique gives more accurate representation for polydisperse size distribution. The aim of Chapter 4 is to study the filtration process of a model membrane filter, the nuclepore filter. Initial filtration efficiency experimentally measured using the aerosolization and NTA techniques are comparable with each other. The capillary tube model modified from that developed for aerosol filtration was found to be useful to represent the experimental results, when a sticking coefficient of 0.15 is incorporated. This suggests that for the polystyrene latex (PSL) particles-nuclepore filter-water system, only 15% of the particle collisions with the filter results in successful attachment. The small sticking coefficient found can be explained by the unfavorable surface interactions between the particles and the filter medium. The sieving mechanism, in which particles are removed when they are larger than the filter pore size, is primarily used to describe the filtration process. The capture of particles smaller than the pore size, by adsorption via diffusion and interception, becomes effective when the combined electrostatic and van der Waals interactions between particle and filter surface are favorable. In Chapter 5, retention efficiency of a 50 nm- rated Polytetrafluoroethylene (PTFE) filter against nanoparticles of different materials (gold, PSL and silica), sizes (80, 50 and 30 nm), concentrations (2×109 to 4×1011 particles/ml) and size distributions (monodisperse and polydisperse) was measured. The decreasing trend of retention efficiency as a function of particle loading can be readily explained by the sieving mechanism. Among different particle materials, silica shows much lower retention efficiency compared to PSL and gold particles of the same size. This observation can be explained with the DLVO theory, which suggests that higher ionic strength of PSL and gold suspensions causes a decrease in the magnitude of energy barrier and favors their adsorption to the filter surface. In addition, this study observed higher retention efficiency for mixed particles compared to monodisperse ones and there is less than 10% of re-entrainment of particles collected by adsorption. In Chapter 6, numerical simulations for change in membrane filter's retention efficiency in the presence of a particle previously captured within the filter are reported. Because of the complex porous structure of the membrane, the filter model is simplified into two cases: 1) capillary tube model and 2) single fiber model. Simulations for the capillary tube model show that a particle captured near the pore opening can increase the collection efficiency of 30 nm particles due to impaction and interception by about two times, depending on the relative size of the particles to the pore. From the single fiber model, a particle attached on the fiber can increase the combined impaction-interception single fiber efficiency by 10 times, depending on the location of the particle attached. The capillary tube simulation results can be incorporated into pore blockage model which considers filters as multiple layers of parallel pores. The single fiber simulations can explain the higher collection efficiency due to a previously captured particle. However, the single fiber theory alone cannot account for the observed decreasing trend with particle loading.

When water droplets precipitate under the action of gravity and frictional forces, they will collide with smaller aerosol particles and fall to the ground. Usually, either droplets or aerosol particles carry some electric charges, and some may be highly charged. Therefore, the electrostatic effect is a very important factor in particle scavenging. Wet scrubbers as air pollution control devices use the same theory as scavenging to remove both particulate and gas contaminants from the industrial exhaust streams. Electrostatic wet scrubbers were developed in an attempt to improve collection efficiency by raising the attraction force between droplets and particles. Very few numerical models have been developed to describe the phenomenon of particle collection by highly charged droplets when electrostatic force is dominant. In an attempt to understand the physics of scavenging, a new three-dimensional model has been developed to simulate neutral or charged particles collected by a group of neutral or charged droplets. The model can simulate the particle traveling through a matrix of droplets. Both the inertial effect and the electrostatic effect on particle scavenging have been considered. The collection efficiency can be estimated by utilizing this developed model. The effect on the collection efficiency by the size of the particle and of the droplet, the charges of the particle the droplet, and droplet distance have been investigated. A validation approach has also been developed and the study results have achieved good agreement with published data.

In the past 10 years there has been a significant amount of research into two-phase particle transport. The terrorist events of September 11, 2001 sparked a series of studies analyzing particle entrainment and deposition in turbulent airflows. One area of research needing further attention has been the study of particles entrained in axisymmetric air jets. An experimental rig was designed and built to study entrainment properties and deposition of Newtonian particles, after injection into a turbulent axisymmetric free air jet. Newtonian spherical particles, ranging from 1mm to 6mm in diameter, were injected into a turbulent airstream and blown through a nozzle into a large, open space. As the particles fell out of the jet stream, their linear distances, from nozzle to initial-ground-contact, were recorded and analyzed. The experiments conducted indicated particle size and density to be significant factors when considering Newtonian particle entrainment. Additionally, particle deposition distribution revealed a consistent positive skewness, as opposed to an expected Gaussian form. The data presented in this paper provide a starting point for understanding entrainment of Newtonian spherical particles in jets. The simple experimental rig geometry and results also provide an opportunity for computational fluid dynamics models to be validated, answering a call from the 2006 Annual Review of Fluid Mechanics.

The work herein details an optical droplet measurement system based on planar multi-angle Mie scattering. Sizing information consists of a mean droplet diameter and droplet distribution estimates for every individual point within a planar (2D) area of interest. The planar method makes possible the fast acquisition of data within a large field of interest, and uses relatively inexpensive instrumentation. As presented, the method demonstrated the ability to measure water droplets from a typical simplex spray nozzle, across the range of 5-50 micrometers within +/-10% of known values, and in addition return an estimate of the shape and width of the size distribution at each location within the planar region of interest. Measurements demonstrating the agreement between results from this current method and known PDA data were successfully completed for a 1-gallon-per-hour spray nozzle, and repeatability was demonstrated in 2.5-gallon-per-hour and 4.5-gallon-per-hour nozzles. Additionally the limits of the technique are explored with simulated data. Conclusions from these exercises show that the multi-angle planar Mie scattering method is capable of measuring droplet distribution characteristics and means within a nominal range of 0.3 micrometers up to 150 micrometers.