Administration of medication directly to diseased lungs reduces adverse systemic side effects. For cystic fibrosis, jet nebulizers are the standard aerosol delivery system since they can aerosolize drugs that require relatively large volumes of liquid. Selection of the appropriate nebulizer for a given drug is crucial to ensure delivery of the therapeutic dose. This selection, ideally, requires knowledge of the pulmonary drug deposition (PDD). The gold standard for accurately measuring PDD is nuclear medicine techniques, which exposes the subject to radiation and therefore cannot be used repeatedly to test multiple devices. An alternative is to characterize the nebulizer using in vitro experiments and estimate the device’s in vivo performance. However these techniques are time-consuming and can only collect data for one breathing pattern and drug-device combination. Therefore this study is to formulate mathematical models for jet nebulizers that can estimate PDD based on the drug-device combination and patient’s breathing patterns.

The advent of satellite limb scatter measurements has allowed the stratosphere to be studied at a scope unparalleled by previous observational techniques, affording the opportunity to study structures on both small spacial and temporal scales. Utilizing these measurements to their fullest has fueled the development of radiative transfer models to simulate the measurements, but also inversion techniques to retrieve atmospheric parameters. The limb scatter instrument OSIRIS, onboard the Odin satellite, is currently used in conjunction with the SASKTRAN radiative transfer model and multiplicative algebraic reconstruction technique to retrieve stratospheric aerosol extinction. In this work, the aerosol information content of limb scatter measurements is explored and an improved version of the aerosol retrieval is developed through the simultaneous retrieval of a second aerosol parameter, the Angstrom coefficient, which is related to particle size. The sensitivity of limb scatter measurements to aerosol is investigated through forward modelling of OSIRIS measurements as a function of wavelength, satellite geometry and particle size. Information content of the measurements is investigated to determine the feasibility of retrieving various aerosol size parameters and a simple linear inversion technique is tested. Results from this study are used to develop a non-linear inversion technique with minimal sensitivity to the required assumptions. Incorporation of longer wavelength data into the retrieval allows for the determination of the wavelength dependence of the scattered signal, which when combined with a lognormal particle size distribution of constant mode width allows for the retrieval of aerosol number density and mode radius. Conversion of these parameters to extinction and the Angstrom coefficient provides retrieved quantities with minimal dependence on the assumed size distribution. Application of this technique to the OSIRIS data set shows improved extinction results through both internal comparisons of the data and when compared with other results from SAGE II, III and CALIPSO satellite measurements. Although the retrieved Angstrom coefficient shows some bias due to the required assumptions, comparisons with the SAGE II data set show considerable improvement over the apriori estimate.

The recent development of satellite observations of limb scattered sunlight at optical wavelengths has afforded a new opportunity to measure the vertical structure of atmospheric composition from the upper troposphere to the mesosphere, on a global scale. The determination of profiles of atmospheric composition from observed limb radiance profiles requires two elements, a forward radiative transfer model and a species specific inversion algorithm. In this work, the development of a new, fully spherical, successive orders radiative transfer model, SASKTRAN, for the analysis of limb scattered sunlight is presented. The model is incorporated into a novel relaxation algorithm that employs spectral ratios to retrieve profiles of stratospheric aerosols from limb radiance measurements collected by the Canadian OSIRIS instrument on the Odin satellite.<p>The SASKTRAN forward model results compare favorably with both OSIRIS observations as well as with other radiative transfer model calculations while remaining computationally practical for the operational inversion of large satellite data sets.<p>The spectral ratio relaxation algorithm is able to retrieve aerosol number density profiles at stratospheric altitudes from limb radiance profiles assuming the height profile of the aerosol particle size distribution is known. The equivalent aerosol extinction derived from the OSIRIS measurements at visible wavelengths agrees with coincident occultation measurements from other satellite instrumentation to within 15% when a size distribution appropriate for background aerosol conditions is used. Finally, it is demonstrated that the incorporation of simultaneous infra-red observations at 1530 nm into the inversion yields a useful proxy for the aerosol size distribution parameters.

An understanding of gas-liquid two-phase interactions, aerosol particle deposition, and heat transfer is needed. Computational Fluid Dynamics (CFD) is becoming a powerful tool to predict aerosol behavior for related design work. In this study, FLUENT 6 is used to analyze the performance of aerosol sampling and concentration devices including inlet components (impactors), cyclones, and virtual impactors. The ω − k model was used to predict particle behavior in Inline Cone Impactor (ICI) and Jet-in-Well impactor (JIW). Simulation provided excellent agreement with experimental test results for a compact ICI. In the JIW, compound impaction is shown to cause the device to have a smaller cutpoint Stokes number than the single impaction unit. The size ratio of the well-to-jet was analyzed to find its influence on the total and side collections. Simulation is used to analyze liquid film, flow structure, particle collection, pressure drop, and heating requirements for a bioaerosol sampling cyclone. A volume of fluid model is used to predict water film in an earlier cyclone. A shell-volume is developed to simulate thin liquid film in large device. For the upgraded version cyclone, simulation is verified to successfully predict cutpoint and pressure drop. A narrowing-jet is shown to describe the flow evolution inside the axial flow cyclone. Turbulent heat transfer coefficients and surface temperatures are analyzed and heaters are designed for this cyclone. A double-outlet cyclone was designed and its pressure drop decreased about 25%, compared with a single-outlet cyclone. A scaled-down 100 L/min cyclone was also designed and tested based on the 1250 L/min unit. CFD is used to design a Circumferential Slot Virtual Impactor (CSVI) which is used for concentration of bioaerosol particles. Simulations showed a 3-D unstable flow inside an earlier version CSVI, which could explain acoustic noise and particle loss observed in the experiment. A smaller CSVI unit was designed using simulation and its flow was shown to be stable. CFD was then used to analyze the wake flow downstream of the posts to reduce particle losses and eliminate flow instabilities caused by wakes. A successful solution, moving the posts outside was developed by the use of CFD.

This work investigates the effects of anthropogenic aerosols on deep convective clouds and the associated radiative forcing in the Houston area. The Goddard Cumulus Ensemble model (GCE) coupled with a spectral-bin microphysics is employed to investigate the aerosol effects on clouds and precipitation. First, aerosol indirect effects on clouds are separately investigated under different aerosol compositions, concentrations and size distributions. Then, an updated GCE model coupled with the radiative transfer and land surface processes is employed to investigate the aerosol radiative effects on deep convective clouds. The cloud microphysical and macrophysical properties change considerably with the aerosol properties. With varying the aerosol composition from only (NH4)2SO4, (NH4)2SO4 with soluble organics, to (NH4)2SO4 with slightly soluble organics, the number of activated aerosols decreases gradually, leading to a decrease in the cloud droplet number concentration (CDNC) and an increase in the droplet size. Ice processes are more sensitive to the changes of aerosol chemical properties than the warm rain processes. The most noticeable effect of increasing aerosol number concentrations is an increase of CDNC and cloud water content but a decrease in droplet size. It is indicated that the aerosol indirect effect on deep convection is more pronounced in relatively clean air than in heavily polluted air. The aerosol effects on clouds are strongly dependent on RH: the effect is very significant in humid air. Aerosol radiative effects (ARE) on clouds are very pronounced for mid-visible single-scattering albedo (SSA) of 0.85. Relative to the case without the ARE, cloud fraction and optical depth decrease by about 18% and 20%, respectively. The daytime-mean direct forcing is about 2.2 W m-2 at the TOA and -17.4 W m-2 at the surface. The semi-direct forcing is positive, about 10 and 11.2 W m-2 at the TOA and surface, respectively. Aerosol direct and semi-direct effects are very sensitive to SSA. The cloud fraction, optical depth, convective strength, and precipitation decrease with the increase of absorption, resulting from a more stable atmosphere due to enhanced surface cooling and atmospheric heating.

A code for the quasi-stationary solution of the coupled heat and mass transport equations for aerosols in a finite volume was developed. Both mass and heat are conserved effectively in the volume, which results in a competitive aerosol condensation growth computational model. A further model that couples this competitive aerosol condensation growth computational model with computational fluid dynamics (CFD) software (ANSYS FLUENT) enables the simulation of the realistic atmospheric environment. One or more air parcels, where the aerosols reside, are placed in a very big volume in order to mimic the large atmospheric environment. Mass (water vapor) and heat transportat between the air parcels and the environment facilitates the growth and prevents the parcels from unrealistically overheating. The suppression of cloud condensation nuclei (CCN) growth by high number densities was quantified by our model study. Model study with organic particles (Lmalic acid and maleic acid) indicates that when these organic species and ammonium sulfate are internally mixed, the particles can grow much more than if they are separately associated with distinct particles. Moreover, by using more multiple air parcels, which are randomly assigned with different initial relative humidity values according to a power law distribution, we studied the effects of atmospheric stochastic RH distribution on the growth of CCN.

In the event of a hypothetical nuclear reactor accident, the combination of plant design, operator training, and safety procedures result in low level risks to the general public; however, an additional offsite consequence mitigation system has the poten- tial to substantially decrease the amount of radioactive material that could reach a population zone in a postulated accident scenario. An experimental and numerical investigation of airborne particulate scavenging by water sprays was conducted as part of a consequence mitigation study. Previous researchers have experimentally studied the removal of aerosols by sprays, but only in a confined region. The ex- periment conducted in this research used an expansive region where sprays could significantly affect the flow fields in the spray region. Experimentation showed an expected trend of higher particle collection efficien- cies with increased residency time within the spray region, with the highest average overall collection efficiency found to be 70.6+/-3.2% at an air flow rate of 0.53 m/s and a water flow rate of 0.84 gpm. This general trend is expected because a longer resi- dency time leads to an increased probability of particle-drop interaction. Collection efficiencies were also found to increase with increased particle number density. The numerical investigation was done using a deterministic method and a Monte Carlo method. Each model shows promise based on theoretical limitations of drop size for the experimental conditions. The theory demonstrates that particle-drop relative velocity as well as the sizes significantly affect collection efficiency. An alternative study was conducted to determine the collection efficiency of non-wettable particles since the dust used in the experiment is hydrophobic. Computational Fluid Dynam- ics (CFD) models were also performed to determine the flow fields that developed within the experiment spray region and substantiate differences in the experimental and numerical models.

A single-ultrafine-particle mass spectrometer was constructed and deployed for size-resolved ultrafine aerosol composition measurements during the winter of 2002-2003 in College Station, Texas. Three separate experiments were held between December and March with six week intervals. Almost 128,000 mass spectra, corresponding to particles with aerodynamic diameters between 35 and 300 nm, were collected and classified. Fifteen statistically significant classes were identified and are discussed in this paper. Nitrate, potassium, carbon, and silicon/silicon oxide were the most frequently observed ions. Nitrate was present in most of the particles, probably due to the agricultural activity in the vicinity of the sampling site. The nitrate detection frequency was found to be sensitive to the ambient temperature and relative humidity. Another particle class, identified as an amine, exhibited strong relative humidity dependence, appearing only during periods of low relative humidity. There is evidence that some of the detected particles originated from the large urban centers, and were coated with nitrate, sulfate, and organics during transport.

Soot particles released from fossil fuel combustion and biomass burning have a large impact on the regional/global climate by altering the atmospheric radiative properties and by serving as cloud condensation nuclei (CCN). However, the exact forcing is affected by the mixing of soot with other aerosol constituents, such as sulfuric acid. In this work, experimental studies have been carried out focusing on three integral parts: (1) heterogeneous uptake of sulfuric acid on soot; (2) hygroscopic growth of H2SO4-coated soot aerosols; (3) effect of H2SO4 coating on scattering and extinction properties of soot particles. A low-pressure laminar-flow reactor, coupled to ion driftchemical ionization mass spectrometry (ID-CIMS) detection, is used to study uptake coefficients of H2SO4 on combustion soot. The results suggest that uptake of H2SO4 takes place efficiently on soot particles, representing an important route to convert hydrophobic soot to hydrophilic aerosols. A tandem differential mobility analyzing (TDMA) system is employed to determine the hygroscopicity of freshly generated soot in the presence of H2SO4 coating. It is found that fresh soot particles are highly hydrophobic, while coating of H2SO4 significantly facilitates water uptake on soot even at sub-saturation relative humidities. The results indicate that aged soot particles in the atmosphere can potentially be an efficient source of CCN. Scattering and extinction coefficient measurements of the soot-H2SO4 mixed particles are conducted using a threewavelength Nephelometer and a multi-path extinction cell. Coating of H2SO4 is found to increase the single scattering albedo (SSA) of soot particles which has impact on the aerosol direct radiative effect. Other laboratory techniques such as transmission electron microscopy (TEM) and Fourier transform infrared spectrometry (FTIR) are utilized to examine the morphology and chemical composition of the soot-H2SO4 particles. This work provides critical information concerning the heterogeneous interaction of soot and sulfuric acid, and how their mixing affects the hygroscopic and optical properties of soot. The results will improve our ability to model and assess the soot direct and indirect forcing and hence enhance our understanding of the impact of anthropogenic activities on the climate.

The chemical transport model PMCAMx was extended to investigate the eddects of partitioning and photochemical aging of primary biomass burning emissins on organic aerosol (OA) concentrations. A source-resolved version of the model was developed, PMCAMx-SR, in which biomass burning OA (bbOA) and its oxidation products are represented seperately from the other OA sources. The volatility distribution of bbOA was simulates using recent measurements. According to PMCAMx-SR, during the early summer period simulated, the contribution of bb emissions to total OA levels is approximately 4%. During winter the same contribution is nearly 28% due to both extensive residential wood combustion and wildfires in Portugal and Spain. The magnitude of these impacts also depends on the emissions of intermediate volatility organic compounds during biomass burning. In order to evaluate PMCAMx-SR performance, its predictions were compared with aerosol mass spectrometer measurements that took place in several sites around Europe. The new version of the model does have improved performance over the original PMCAMx in most sites. / Το μοντέλο χημικής μεταφοράς PMCAMx επεκτάθηκε ώστε να μελετήσουμε την επίδραση της φωτοχημικής γήρανσης των εκπομπών από καύση βιομάζας στην συγκέντρωση του οργανικού αεροζόλ (ΟΑ). Μια νέα έκδοση του μοντέλου αναπτύχθηκε, PMCAMx-SR, στην οποία το οργανικό αεροζόλ από καύση βιομάζας και τα προιόντα οξείδωσης του παρουσιάζονται ξεχωριστά από τις υπόλοιπες πηγές ΟΑ. Η κατανομή πτητικότητας του οργανικού αεροζόλ από καύση βιομάζας προσομοιώνεται χρησιμοποιώντας πρόσφατες μετρήσεις. Σύμφωνα με το PMCAMx-SR, κατά την καλοκαιρινή περίοδο προσομοίωσης, η συνεισφορά των εκπομπών από καύση βιομάζας στα συνολικά επίπεδα ΟΑ είναι περίπου 4%. Κατά την διάρκεια του χειμώνα η ίδια συνεισφορά είναι περίπου 28% εξαιτίας εκτεταμένης οικιακής καύσης ξύλου και πυρκαγιών στην Πορτογαλία και την Ισπανία. Σημαντικός είναι και ο ρόλος των εκπομπών οργανικών σωματιδίων ενδιάμεσης πτητικότητας από καύση βιομάζας. Για να αξιολογήσουμε το PMCAMx-SR, οι προβλέψεις του συγκρίθηκαν με τις μετρήσεις ΑΜS που έλαβαν χώρα σε αρκετά μέρη στην Ευρώπη. Η νέα έκδοση του μοντέλου έχει βελτιώσει την απόδοση του αρχικού μοντέλου PMCAMx σε αρκετά μέρη ανά την Ευρώπη.