Dissertations / Theses on the topic 'Dust'

Dust originating from dry lakes contributes harmful and toxic elements to downwind urban areas and mountain snowpack that is compounded by local contaminant inputs from anthropogenic sources. To evaluate dust contributions to an urban area from regional playas, we sampled playa dust sources, urban dust deposition, and snow dust deposition in central Utah, USA. Samples were analyzed for grain size, mineralogy, and chemistry. Bulk mineralogy between playa, urban, and snow dust samples was similar, with silicate, carbonate, and evaporite minerals. Grain size distribution between fine playa, urban, and snow dust particles was also similar. Elements found at high concentrations in playas include Li, Na, Mg, Ca, Sr, and U, and most other elements were found at higher concentrations in urban and snow deposition samples. Particularly enriched elements in dust deposition include Cu, Se, Ag, Cd, Sb, and La, which are sourced from industrial activity, mining, and vehicular emissions and wear. Based on results from mass balance modeling, a large majority of the dust mass deposited on the Wasatch Front is from playa sources. Urban and playa dust sources largely remain constant seasonally, although spikes in playa-associated element concentrations during a particular seasonal sample may indicate frequent and/or more intense dust events. Among the highly environmentally available elements B, Ca, Sr, and U, are Cd and Se, both of which present toxicity concerns for humans and environments. This is the first study describing heavy metal contamination and sources in Utah, USA.

Thesis (Ph.D.)--University of Toledo, 2005.
Typescript. "A dissertation [submitted] as partial fulfillment of the requirements of the Doctor of Philosophy degree in Physics." Bibliography; leaves 209-225.

In July 2012, I left America for the first time to travel to Madurai, India, for a month-long journalism internship. The inspiration for the poetry in this work is deeply rooted in my experiences while in India, mentally, physically, and spiritually. Not knowing why I chose India to travel to for my first time abroad, I realized much later that I needed to be there in order to transition into the next stage of my life. I always wanted to experience what life was like without the amenities the Western world is accustomed to (hot showers, washers and dryers, reliable electricity, etc.). Through isolating myself from the familiar I woke up to a simpler, happier perspective on life. This isolation also stirred mixed emotions in me that I wasn't aware of until I began writing about the experience in these poems. The feeling of being watched by everyone was common and sometimes frightening or disturbing. This vulnerability was uncomfortable even though the experiences and realizations I had outweighed the negativity while I was in India. The intent of this thesis is to explore how I've grown and what I took from the trip while comparing my Indian experience to life before and after my visit. With unconventional structural elements, I set out to put life and movement on the page to represent the chaotic, beautiful India and the emotions that carried the weight of each poem. Just from one month of being surrounded by strangers who stared with stone eyes, a language I didn't understand and memories of a life I didn't miss as much as I thought I would, this thesis follows the imaginative perceptions of a sleeping person through her evolution into a waking life.
B.A.
Bachelors
Arts and Humanities
English

El presente proyecto se basa en la producción y comercialización de fertilizante natural y biodegradable, que sirve como bio-estimulante para las plantas ornamentales, teniendo como valor adicional ser un retenedor de agua de riego durante 20-21 días aplicando una sola vez el producto. Elaborado a base de cáscara de naranja y palta, nuestro negocio va dirigido a habitantes de Lima Moderna correspondientes a los estilos de vida conservador, moderno y sofisticado que posean plantas y/o pequeños jardines pertenecientes a los niveles socioeconómicos (NSE) A, B y C, además de mostrar preocupación por el medio ambiente. El empaque del producto va a ser una bolsa de papel kraft biodegradable con una capacidad 250 gramos. Se realizó una total de entrevistas a 30 personas para validar la existencia del problema encontrado y el interés e intención de uso del producto de nuestros posibles clientes. Además, con fines de hacer este proyecto escalable para el rubro de la agricultura, se contactó a dos expertos en agronomía para validar el producto y algunos aspectos sobre la posible escalabilidad de este. El desarrollo del proyecto se encuentra dividido en dos puntos, los cuales son la validación del plan de negocio y desarrollo del plan de negocio. Para la ejecución del proyecto se requirió una inversión de 21,454 soles, obtenidos a base de capital propio de los accionistas, quienes estiman recuperar dicha inversión en el primer año de operación. La rentabilidad brindada a los accionistas es de 249% lo cual hace nuestro proyecto un negocio rentable.
The present project is based on the production and commercialization of natural and biodegradable fertilizer, which serves as a bio-stimulant for ornamental plants, with the additional value of being a water retainer for 20-21 days by applying the product once. Made with orange and avocado peel, our business is aimed at inhabitants of Modern Lima corresponding to conservative, modern and sophisticated lifestyles that have plants and / or small gardens belonging to socioeconomic levels (NSE) A, B and C, in addition to showing concern for the environment. The product packaging is going to be a biodegradable kraft paper bag with a capacity of 250 grams. A total of interviews were conducted with 30 people to validate the existence of the problem encountered and the interest and intention of using the product of our potential customers. In addition, in order to make this project scalable for the field of agriculture, two agronomy experts were contacted to validate the product and some aspects of its possible scalability. The development of the project is divided into two points, which are the validation of the business plan and development of the business plan. For the execution of the project, an investment of 21,454 soles was required, obtained based on the shareholders' own capital, who consider recovering said investment in the first year of operation. The profitability provided to shareholders is 249% which makes our project a profitable business.
Trabajo de investigación

Les nombreux avantages que présenteraient la fusion thermonucléaire, en particulier la configuration tokamak, en font un candidat idéal en vue de la transition énergétique. Cependant, un certain nombre de difficultés technologiques et physiques restent à résoudre avant que l'étape d'une centrale électrique à fusion puisse voir le jour. La production de poussières est l'une des principales difficultés rencontrées dans les tokamaks. Ces petites particules composées de matériaux présents dans les parois de la machine sont créées par l'érosion de ces parois par le plasma dans lequel les réactions de fusion doivent avoir lieu. Les poussières peuvent être transportées dans le plasma et y libérer de grandes quantités d'impuretés, ce qui a pour conséquence de baisser les performances de la machine (en augmentant les pertes radiatives et en créant des instabilités), et qui peut mettre en danger les composants face au plasma. Dans le but de comprendre le transport de ces poussières, des expériences d'injection sont réalisées sur le tokamak coréen \KSTAR. Les trajectoires des poussières dans le plasma sont observées par des caméras rapides et sont extraites des films à l'aide de routines de traitement d'images. Un code numérique implémentant les derniers modèles d'interactions plasma-poussières est développé, et des comparaisons avec les données expérimentales sont faites, confirmant la tendance générale de ces modèles à la sous-estimation de la longueur des trajectoires des poussières. Des pistes d'amélioration sont présentées. Concernant les sources et puits de poussières, l'accent est porté sur l'adhésion et remise en suspension de particules sur les parois de la machine
Thermonuclear fusion could play an important role amongst the numerous alternative energy sources, especially though the tokamak configuration. It could be a prime candidate for the energy transition, owing to its significant advantages (fuel abundance, low amount of wastes generated, low risks of accidents). However, a certain amount of technological and physical challenges require solving before any fusion power plant can be built. Dust production is one of the major difficulties encountered in tokamaks. These small particles, made out of wall material, are created by erosion of the plasma-facing components by the plasma, where the fusion reactions occur. Dust particles can be transported in the plasma, thereby unleashing large amounts of impurities, which in turn reduces the plasma performances (by raising radiative losses and generating instabilities) and can even jeopardize plasma-facing components. Aiming to understand dust transport, injection experiments are performed on the Korean tokamak \KSTAR. Trajectories are recorded on film via fast cameras and are extracted by image processing routines. A numerical tool implementing the latest models for dust-plasma interactions is developed, and comparisons with experimental data is made, confirming the overall tendency of these models to underestimate the trajectory lengths. Leads of improvements are presented. Concerning dust sources and sinks, the focus is made on dust adhesion and resuspension of dust on the machine walls

Les nombreux avantages que présenteraient la fusion thermonucléaire, en particulier la configuration tokamak, en font un candidat idéal en vue de la transition énergétique. Cependant, un certain nombre de difficultés technologiques et physiques restent à résoudre avant que l'étape d'une centrale électrique à fusion puisse voir le jour. La production de poussières est l'une des principales difficultés rencontrées dans les tokamaks. Ces petites particules composées de matériaux présents dans les parois de la machine sont créées par l'érosion de ces parois par le plasma dans lequel les réactions de fusion doivent avoir lieu. Les poussières peuvent être transportées dans le plasma et y libérer de grandes quantités d'impuretés, ce qui a pour conséquence de baisser les performances de la machine (en augmentant les pertes radiatives et en créant des instabilités), et qui peut mettre en danger les composants face au plasma. Dans le but de comprendre le transport de ces poussières, des expériences d'injection sont réalisées sur le tokamak coréen \KSTAR. Les trajectoires des poussières dans le plasma sont observées par des caméras rapides et sont extraites des films à l'aide de routines de traitement d'images. Un code numérique implémentant les derniers modèles d'interactions plasma-poussières est développé, et des comparaisons avec les données expérimentales sont faites, confirmant la tendance générale de ces modèles à la sous-estimation de la longueur des trajectoires des poussières. Des pistes d'amélioration sont présentées. Concernant les sources et puits de poussières, l'accent est porté sur l'adhésion et remise en suspension de particules sur les parois de la machine
Thermonuclear fusion could play an important role amongst the numerous alternative energy sources, especially though the tokamak configuration. It could be a prime candidate for the energy transition, owing to its significant advantages (fuel abundance, low amount of wastes generated, low risks of accidents). However, a certain amount of technological and physical challenges require solving before any fusion power plant can be built. Dust production is one of the major difficulties encountered in tokamaks. These small particles, made out of wall material, are created by erosion of the plasma-facing components by the plasma, where the fusion reactions occur. Dust particles can be transported in the plasma, thereby unleashing large amounts of impurities, which in turn reduces the plasma performances (by raising radiative losses and generating instabilities) and can even jeopardize plasma-facing components. Aiming to understand dust transport, injection experiments are performed on the Korean tokamak \KSTAR. Trajectories are recorded on film via fast cameras and are extracted by image processing routines. A numerical tool implementing the latest models for dust-plasma interactions is developed, and comparisons with experimental data is made, confirming the overall tendency of these models to underestimate the trajectory lengths. Leads of improvements are presented. Concerning dust sources and sinks, the focus is made on dust adhesion and resuspension of dust on the machine walls

Ces travaux de thèse sont consacrés à l’examen du rôle du rayonnement thermique dans le processus de propagation des flammes issues de la combustion des particules d’aluminium dans l’air. Le sujet étant complexe et d’un intérêt industriel, il nécessite de prendre en compte le couplage de nombreux phénomènes physico-chimiques afin de prédire finement les conséquences des explosions de poussières. Une analyse bibliographique approfondie est proposée, concernant les mécanismes d’inflammation et de combustion des particules d’aluminium et aussi concernant les connaissances relatives à la propagation des flammes de poussières. La question spécifique de la nature des échanges thermiques et de l’influence du rayonnement thermique est étudiée. La revue bibliographique souligne les approximations et les hypothèses simplificatrices utilisées dans la littérature permettant donc de définir les pistes d’améliorations. Compte tenu des limitations importantes concernant la physique de ces flammes, un outil de simulation de physique numérique nommé « RADIAN », proche de la simulation numérique directe, a été développé proposant un couplage fin entre les différents modes d’échanges thermiques et la combustion pour modéliser la propagation de la flamme dans un nuage de poussières. La méthode des éléments discrets (MED) est utilisée pour modéliser numériquement les échanges radiatifs entre les particules et les échanges conductifs entre gaz et particules. La méthode des différences finies est utilisée pour modéliser numériquement la conduction thermique dans la phase gazeuse et la combustion. Un modèle radiatif est proposé se basant sur la théorie de Mie sur les interactions rayonnement-particules. Les résultats des simulations sont comparés avec des solutions analytiques et des données expérimentales de la littérature. Mais en plus, une étude expérimentale est aussi conduite afin de mesurer la distribution du flux radiatif devant la flamme et la vitesse de combustion laminaire pour des flammes Méthane-Sic, Méthane-Alumine et Al-air. Un bon accord entre les simulations et les expériences est démontré. La loi de Beer-Lambert relative au transfert radiatif devant le front de flamme s’avère inapplicable et une nouvelle solution analytique est proposée. La présence de particules absorbantes du rayonnement promeut la propagation de la flamme. En particulier, il a été montré expérimentalement et confirmé numériquement que les mélanges riches d’AL-air sont susceptibles d’accélérer rapidement
In this thesis, the role of thermal radiation in aluminum-air flames propagation is studied. The subject being complex and of industrial interest, it requires the coupling of many physiochemical phenomena to accurately predict the consequences of dust explosions. A thorough literature review is proposed about the ignition and the combustion of aluminum particles and about the available theoretical models of dust flames propagation. The specific question of the nature of thermal exchanges and the influence of thermal radiation is studied. The bibliographic review underlines the simplifying assumptions and hypotheses used in the literature making possible the definition of improvement areas. Because of the limited amount of knowledge available to address these questions, a numerical tool “RADIAN” is developed enabling an accurate coupling between the different modes of heat exchange and combustion. The Discrete Element Method (DEM) is used to numerically model the radiative exchanges between particles and the gas-particle thermal conduction. The Finite Difference method is used to numerically model the thermal conduction through the gas phase and combustion. A radiative model based on Mie theory for radiation-particles interactions is incorporated. The results of the simulations are compared with available analytical solutions and experimental data. An original experimental study is also conducted to measure the distribution of irradiance ahead of the flame front and the laminar burning velocity for methane-air-Sic, methane-air-alumina and Al-air flames. A good agreement between numerical simulations and experiments is demonstrated. The Beer-Lambert’s law for radiative transfer in front of the flame front is found to be inapplicable and a new analytical solution is proposed. The presence of absorbing particles may promote the flame propagation. In particular, it is shown experimentally and confirmed theoretically/numerically that Al-air rich mixtures are likely to rapidly accelerate

In laboratory experiments, I study strongly-coupled dusty plasma levitated in a glow-discharge plasma. Dusty plasma is an arrangement of small dust particles in a plasma background of electrons, ions, and neutral gas. The dust particles are negatively charged because they collect electrons and ions from the background plasma. Depending on the experimental setup, the plasma's electric field can help to balance the dust particles against gravity. The high dust charge causes dust particles to repel each other, while confinement forces prevent their escape. The dust particles cannot easily move past one another, and instead organize themselves into highly-ordered structures. The neutral gas also plays a key role in these experiments. Depending on the relative motion between gas and dust particles, the neutral gas can either impede dust motion or it can drive the dust into motion. In this thesis, I report the findings of three separate experiments. In the first experiment, I use a spherically-shaped dusty plasma (Yukawa ball) as an indicator of a flow of neutral gas, called thermal creep flow. In the second and third experiments, I study naturally occurring dust-density waves, which propagate within the volume of a dusty plasma that has many horizontal layers. In Ch.2 of this thesis, I study thermal creep flow (TCF), which is a flow of gas driven by a temperature gradient along a solid boundary. Stripes on a glass box are heated by laser beam absorption, leading to both TCF and a thermophoretic force. A stirring motion of the dust particle suspension is observed. By eliminating all other explanations for this motion, I conclude that TCF at the boundary couples by drag to the bulk gas, causing the bulk gas to flow, thereby stirring the suspension of dust particles. This result provides an experimental verification that TCF in the slip-flow regime causes steady-state gas flow in a confined volume. In Ch.3, I observe the growth of a naturally occurring dust-density wave (DDW) using high-speed imaging. This low-frequency wave (∼ 25 Hz) grows in amplitude as it propagates downward through a dusty plasma. I measure the wave's linear growth rate using a phase-sensitive analysis method. For the conditions studied here, the growth rate increases as gas pressure decreases. At a critical gas pressure that I observe, a balance between an ion-flow instability and dissipation by neutral gas drag determines a threshold for wave propagation. A linear dispersion relation is derived, taking into account effects of strong coupling, to compare to the experiment. In Ch.4, I observe the development of nonlinearity in the naturally occurring dust-density wave by measuring harmonics of the fundamental. Using high-speed imaging, I measure amplitudes, wave numbers and growth rates for the fundamental and its harmonics. The amplitudes of the harmonics exhibit a strong exponential increase with diminishing gas pressure, and they saturate at lower gas pressures. My measurements show that the wave numbers and growth rates of harmonics are near integer multiples of the fundamental.

Interstellar dust affects our view of the Universe, with half of the starlight emitted since the Big Bang being absorbed by dust grains and re-radiated in the Infra-Red. This thesis is concerned with understanding the origin of interstellar dust and determining the relative importance of different dust formation sites in the Universe. The sources and maximum amount of dust in early galaxies are investigated using published extended atmosphere models, stellar evolution tracks and nucleation conditions. A chemical evolution model is modified to include the estimated condensation efficiencies. The implications are investigated and we show that a supernovae source is required to produce large amounts of dust in galaxies. The atmospheres of AGB stars evolve too slowly to be responsible for high redshift dust. If SNe are not responsible for dust, then significant dust masses can only be generated at z > 5 by galaxies with very efficient star formation and no dust destruction. The first sub-millimetre analysis of the galactic remnant Kepler is presented with 0.3 3 M0 of dust, depending on the absorption properties. This a 1000 times more than previous Infra-red observations found. The sub-mm emission anti-correlates with the other wavelengths, including the warm dust and the most likely origin is from freshly synthesised dust in the supernova and dust formed from the interaction of the supernova shock with the ambient medium. Iron needles as a possible origin of the sub-mm emission are investigated. Finally, the sub-mm observations of the massive LBV star, rj Carinae are presented to show that the winds of massive stars may also be important contributors to the dust budget. We conclude that supernovae, or their massive star progenitors, are a dominant contributor to interstellar dust and make suggestions for future work.

We present results studying the distribution and properties of the diffuse dust in the Milky Way Galaxy using large optical surveys—specifically, the Sloan Digital Sky Survey (SDSS) and the Panoramic Survey Telescope and Rapid Response System 1 (Pan-STARRS1). This work has resulted in accurate measurements of dust reddening in regions of low extinction over large regions of sky. We present maps of reddening from dust covering the footprint of the SDSS, which covers one quarter of the sky. We present preliminary maps of dust covering the Pan-STARRS1 footprint, which covers three-quarters of the sky, including most of the plane of our Galaxy. We use these maps of dust to decisively exclude some simple parameterizations of dust extinction (Cardelli et al., 1989) in favor of others (Fitzpatrick, 1999). We show that the extinction predicted by the widely-used far-infrared dust map of Schlegel et al. (1998) is overestimated by 18%, and recalibrate that map using our extinction measurements. We further map variation in the properties of the dust, as indicated by variation in the amount of extinction relative to the amout of far-infrared dust extinction, and by variation in the ratio of dust extinction at different frequencies. We confirm these results by measuring reddening using two independent techniques and data sets, the SDSS photometry and spectroscopy. We further present the photometric calibration of the Pan-STARRS1 data—a necessary step to studying the dust with that ongoing survey. We achieve photometric precision unprecedented in a large optical survey, accurate to better than 1%. We additionally show the suitability of the calibrated photometry for studying the distribution of dust. Finally, we present preliminary three-dimensional maps of the dust in the Galaxy using our calibrated data from Pan-STARRS1. These maps will provide by far the most extensive information yet achieved about the three-dimensional distribution of extinction in the Galaxy.
Physics

Dust storms have a great many environmental implications in the world's dry lands where they are particularly common. Four main classes of dust event are identified and defined: dust storms, dust haze, blowing dust and dust devils. The geography of dust storms is analysed in each of eight major world regions: Africa, the Middle East, South-west Asia, Europe and the USSR, China, Australia, North America and Latin America. Terrestrially observed meteorological data and data from remote sensing platforms are employed to identify the major source areas in each region, their seasonality, diurnal patterns of activity and trajectories of long-range transport. Among the important controls on the frequency distribution of dust storm activity are the meteorological conditions that generate dust-raising winds, and a number of meteorological systems commonly cause dust storms in all global regions. These include low pressure fronts with intense baroclinal gradients, pressure gradient winds between moving or stationary air masses, katabatic winds and convectional cells. The nature of the surface upon which deflation occurs is also important; typical dust-producing geomorpholological units include alluvial spreads, lacustrine deposits, desert depressions, loess deposits and reactivated fossil dunes. Dust storm activity is prone to considerable variation. The seasonal characteristics are explicable with reference to the meteorological systems generating dust, the state of ground cover, particularly vegetation, and the effects of seasonal rainfall. Substantial variations also occur from year to year, and land use and climatic variations can substantially affect their occurrence.

Les minéraux absorbent la lumière proche des UV (comme TiO2, Fe2O3, MgO) présents dans les aérosols minéraux interagissent avec les gaz traces présents dans l'atmosphère et peuvent initier une nouvelle chimie hétérogène photo-induite potentiellement significative et actuellement peu documentée. Cette thèse vise à aborder différentes questions sur la réactivité des poussières minérales vers les composés organiques et évaluer l'impact de ces interactions sur plusieurs aspects des sciences de l'atmosphère. Nous avons étudié expérimentalement l'interaction physico-chimique d'aérosols minéraux, purs ou revêtus de matériaux organiques/inorganiques avec des gaz traces de plusieurs familles chimiques (alcools, cétones, acides carboxyliques), dans des conditions simulées proches de l'environnement reel (concernant l'humidité, la concentration en phase gazeuse, la longueur d'onde et l'intensité de l'irradiation, la pression et la température) évaluant les effets des conditions ambiantes sur la cinétique de capture et la génération de produits en phase gazeuse. Dans l'ensemble, nos résultats montrent clairement que les reactions photochimique des poussières minérales doit être considéré comme une source de composés réactifs et comme un processus clé affectant leur action sur la nucléation de la glace et les noyaux de condensation des nuages
Minerals that absorb light near UV/Vis present in dust aerosols interact with trace gases in the atmosphere and can initiate a new and potentially significant photo-induced heterogeneous chemistry, which is currently poorly documented. This thesis aims to address different issues of mineral dust reactivity towards organic compounds and, therefore, assesses the impact of these interactions on several aspects of atmospheric sciences. We investigated experimentally the physicochemical interaction of mineral aerosols (synthetic and natural), pure or coated with organic/inorganic materials with trace gases from several chemical families (alcohols, ketones, carboxylic acids, etc.), under simulated conditions close to the real environment (regarding to humidity, concentration in the gas phase, wavelength and intensity of irradiation, pressure and temperature). In a first approach, we studied the uptake of oxygenated organics onto different dust proxies such as SiO2, TiO2 and Arizona test dust (ATD) evaluating the effects of ambient conditions on the uptake kinetics and product generation. Then, we discussed the chemistry of 5 dicarboxylic acids (C4-C8) on ATD particles upon UV-A irradiation monitoring products in the gas phase as well as those whose stay adsorbed on the particulate phase. Lastly, we investigated the influence of nitrate anions on the uptake of acetone on ATD and SiO2 and in the photochemical product formation of glutaric acid on ATD. Overall, our results clearly show that photochemical processing of dust aerosols should be considered as a source of reactive compounds and as a key process affecting their action as ice nucleation and cloud condensation nuclei

This thesis work is done for the department of Electronic System at The Institute of Technology at Linköping University (Linköpings Tekniska Högskolan). Study's focus is to design and implement a protocol for smart dust networks to improve the energy consumption algorithm for this kind of network. Smart dust networks are in category of distributed sensor networks and power consumption is one of the key concerns for this type of network. This work shows that by focusing on improving the algorithmic behavior of power consumption in every network element (so called as mote), we can save a considerable amount of power for the whole network. Suggested algorithm is examined using Erlang for one mote object and the whole idea has put into test for a small network using SystemC.

We shall not starve. We shall not lack shelter. We shall have a hearth. Awake self reliance! Our art is for feeding, warmth, protection. Ceramics– our temporal salvation. Clay– our material life-force. Transformed by fire we arise with the skills of the ancients! No longer will we live in obscurity. To the deskilled, your fate is at hand! You have chosen alienation, distraction, banality, and sloth. Embrace your digital false Gods and die or be reborn to the natural physical world. Now, together we complete our reason for being. We create a new world of kinship. A hope for the utopia not of rigid modernism but one of a new world, a rediscovery of the natural order.

ABSTRACT Occupational exposure to wood dust and biohazards associated with wood dust (endotoxins, (1->3)-b-D-glucans, Gram (-)ve bacteria and fungi), their correlation to respiratory function, and symptoms among woodworkers have been investigated in the present study. Wood dust, endotoxins, and allergenic fungi are the main hazards found in woodworking environments. Relatively very few studies have been done on wood dust exposure. The present study was designed to comprehensively investigate the health effects of wood dust exposure, and in particular provide new information regarding: Exposure to (1->3)-b-D-glucans in an occupational environment; Levels of exposure to wood dust and biohazards associated with wood dust in different woodworking environments; Correlations among personal exposures, especially correlations between (1->3)-b-D-glucans and fungi exposures, and endotoxins and Gram (-)ve bacteria exposures; Effects of personal exposure to biohazards on lung function; Effects of personal exposure to biohazards on work-related symptoms; and Determinants of inhalable exposures (provide which factors in the environment influence the personal inhalable exposures). Workers at four different woodworking processes; two logging sites, four sawmills, one major woodchipping operation and five joineries situated in the state of New South Wales in Australia were studied for personal exposure to inhalable dust (n=182) and respirable dust (n=81), fungi (n=120), Gram (-)ve bacteria (n=120), inhalable endotoxin (n=160), respirable endotoxin (n=79), inhalable (1->3)-b-D-glucan (n=105), and respirable (1->3)-b-D-glucan (n=62). The workers (n=168) were also tested for lung function. A questionnaire study (n=195) was carried out to determine the prevalence of work-related symptoms. The geometric mean inhalable exposure at logging sites was 0.56 mg/m3 (n=7), sawmills 1.59 mg/m3 (n=93), the woodchipping mill 1.86 mg/m3 (n=9) and joineries 3.68 mg/m3 (n=66). Overall, sixty two percent of the exposures exceeded the current standards. Among joineries, 95% of the hardwood exposures and 35% of the softwood exposures were above the relevant standards. Compared with green mills, the percentage of samples, which exceeded the hardwood standard was high for dry mills (70% in dry mills, 50% in green mills). The respirable dust exposures were high at the joineries compared with the other worksites. Exposure levels to fungi at logging sites and sawmills were in the range 103-104 cfu/m3, woodchipping 103-105 cfu/m3 and joineries 102-104 cfu/m3. The predominant fungi found at sawmills were Penicillium spp. High exposure levels of Aureobasidium pullulans were also found at two sawmills. At the woodchipping mill the predominant species were Aspergillus fumigatus, Penicillium spp., and Paecilomyces spp. The sawmills, which employed kiln drying processes, had lower exposure levels of fungi compared with the green mills. Those workplaces which had efficient dust control systems showed less exposure to fungi and bacteria. Although mean endotoxin levels were lower than the suggested threshold value of 20 ng/m3, some personal exposures at sawmills and joineries exceeded the threshold limit value. The mean inhalable (1->3)-b-D-glucan level at the woodchipping mill was 2.32 ng/m3, at sawmills 1.37 ng/m3, at logging sites 2.02 ng/m3, and at joineries 0.43 ng/m3. For the respirable size fraction, mean endotoxin and mean (1->3)-b-D-glucan concentrations were much lower, being similar to observed dust concentrations. Significant correlations were found between mean inhalable endotoxin and Gram (-)ve bacteria levels (p<0.0001), and mean airborne inhalable (1->3)-b-D-glucan and fungi levels (p=0.0003). The correlations between mean respirable endotoxin levels vs Gram (-)ve bacteria exposure levels (p=0.005), and respirable (1->3)-b-D-glucan exposure levels vs total fungi levels (p=0.005) were also significant. Significant correlations were found between lung function and personal exposures. Multivariate analyses showed that the effect of all the personal exposures on cross-shift decrements in lung function was more prominent among sawmill and chip mill workers compared with joinery workers. Woodworkers had markedly high prevalence of cough, phlegm, chronic bronchitis, frequent headaches, throat and eye irritations, and nasal symptoms compared with controls. Among the woodworkers, smokers had a high prevalence of chronic bronchitis (20%) compared with non-smokers (10%). Some workers also reported a variety of allergy problems due to exposure to various types of wood dust. Both joinery workers and sawmill and chip mill workers revealed significant correlations between work-related symptoms and personal exposures. Chronic bronchitis was significantly correlated with personal exposure to wood dust, endotoxin, (1->3)-b-D-glucan, fungi, and Gram (-)ve bacteria among joinery workers. Whereas among sawmill workers chronic bronchitis was significantly correlated with personal exposure to endotoxin, (1->3)-b-D-glucan, and fungi. Woodworkers showed significant positive correlations between percentage cross-shift change (decrease) in lung function and respiratory symptoms. Significant inverse correlations were also found among percentage predicted lung function and respiratory symptoms. The elevated inhalable dust exposures observed in this study can be explained by a combination of factors, including: lack of awareness of potential health effects of wood dust exposure among both management and workers, aging equipment, inadequate and ineffective dust extraction systems or usually none especially for hand held tools, poor maintenance of the ventilation system in some, non-segregation of dusty processes, dry sweeping, and the use of compressed air jets. The determinant-of-exposure analysis confirmed the field observations. The significant determinants of personal inhalable dust exposures (n=163) were found to be: local exhaust ventilation, job title, use of hand-held tools, cleaning method used, use of compressed air, and green or dry wood processed. Type of wood processed was not found to be statistically significant. A majority of workers (~90%) did not wear appropriate respirators approved for wood dust, while the workers who did wear them, used them on average less than 50% of the time. Workers should be protected by controlling dust at its source. When exposure to wood dust cannot be avoided, engineering controls should be supplemented with the use of appropriate personal protective equipment.

ABSTRACT Occupational exposure to wood dust and biohazards associated with wood dust (endotoxins, (1->3)-b-D-glucans, Gram (-)ve bacteria and fungi), their correlation to respiratory function, and symptoms among woodworkers have been investigated in the present study. Wood dust, endotoxins, and allergenic fungi are the main hazards found in woodworking environments. Relatively very few studies have been done on wood dust exposure. The present study was designed to comprehensively investigate the health effects of wood dust exposure, and in particular provide new information regarding: Exposure to (1->3)-b-D-glucans in an occupational environment; Levels of exposure to wood dust and biohazards associated with wood dust in different woodworking environments; Correlations among personal exposures, especially correlations between (1->3)-b-D-glucans and fungi exposures, and endotoxins and Gram (-)ve bacteria exposures; Effects of personal exposure to biohazards on lung function; Effects of personal exposure to biohazards on work-related symptoms; and Determinants of inhalable exposures (provide which factors in the environment influence the personal inhalable exposures). Workers at four different woodworking processes; two logging sites, four sawmills, one major woodchipping operation and five joineries situated in the state of New South Wales in Australia were studied for personal exposure to inhalable dust (n=182) and respirable dust (n=81), fungi (n=120), Gram (-)ve bacteria (n=120), inhalable endotoxin (n=160), respirable endotoxin (n=79), inhalable (1->3)-b-D-glucan (n=105), and respirable (1->3)-b-D-glucan (n=62). The workers (n=168) were also tested for lung function. A questionnaire study (n=195) was carried out to determine the prevalence of work-related symptoms. The geometric mean inhalable exposure at logging sites was 0.56 mg/m3 (n=7), sawmills 1.59 mg/m3 (n=93), the woodchipping mill 1.86 mg/m3 (n=9) and joineries 3.68 mg/m3 (n=66). Overall, sixty two percent of the exposures exceeded the current standards. Among joineries, 95% of the hardwood exposures and 35% of the softwood exposures were above the relevant standards. Compared with green mills, the percentage of samples, which exceeded the hardwood standard was high for dry mills (70% in dry mills, 50% in green mills). The respirable dust exposures were high at the joineries compared with the other worksites. Exposure levels to fungi at logging sites and sawmills were in the range 103-104 cfu/m3, woodchipping 103-105 cfu/m3 and joineries 102-104 cfu/m3. The predominant fungi found at sawmills were Penicillium spp. High exposure levels of Aureobasidium pullulans were also found at two sawmills. At the woodchipping mill the predominant species were Aspergillus fumigatus, Penicillium spp., and Paecilomyces spp. The sawmills, which employed kiln drying processes, had lower exposure levels of fungi compared with the green mills. Those workplaces which had efficient dust control systems showed less exposure to fungi and bacteria. Although mean endotoxin levels were lower than the suggested threshold value of 20 ng/m3, some personal exposures at sawmills and joineries exceeded the threshold limit value. The mean inhalable (1->3)-b-D-glucan level at the woodchipping mill was 2.32 ng/m3, at sawmills 1.37 ng/m3, at logging sites 2.02 ng/m3, and at joineries 0.43 ng/m3. For the respirable size fraction, mean endotoxin and mean (1->3)-b-D-glucan concentrations were much lower, being similar to observed dust concentrations. Significant correlations were found between mean inhalable endotoxin and Gram (-)ve bacteria levels (p<0.0001), and mean airborne inhalable (1->3)-b-D-glucan and fungi levels (p=0.0003). The correlations between mean respirable endotoxin levels vs Gram (-)ve bacteria exposure levels (p=0.005), and respirable (1->3)-b-D-glucan exposure levels vs total fungi levels (p=0.005) were also significant. Significant correlations were found between lung function and personal exposures. Multivariate analyses showed that the effect of all the personal exposures on cross-shift decrements in lung function was more prominent among sawmill and chip mill workers compared with joinery workers. Woodworkers had markedly high prevalence of cough, phlegm, chronic bronchitis, frequent headaches, throat and eye irritations, and nasal symptoms compared with controls. Among the woodworkers, smokers had a high prevalence of chronic bronchitis (20%) compared with non-smokers (10%). Some workers also reported a variety of allergy problems due to exposure to various types of wood dust. Both joinery workers and sawmill and chip mill workers revealed significant correlations between work-related symptoms and personal exposures. Chronic bronchitis was significantly correlated with personal exposure to wood dust, endotoxin, (1->3)-b-D-glucan, fungi, and Gram (-)ve bacteria among joinery workers. Whereas among sawmill workers chronic bronchitis was significantly correlated with personal exposure to endotoxin, (1->3)-b-D-glucan, and fungi. Woodworkers showed significant positive correlations between percentage cross-shift change (decrease) in lung function and respiratory symptoms. Significant inverse correlations were also found among percentage predicted lung function and respiratory symptoms. The elevated inhalable dust exposures observed in this study can be explained by a combination of factors, including: lack of awareness of potential health effects of wood dust exposure among both management and workers, aging equipment, inadequate and ineffective dust extraction systems or usually none especially for hand held tools, poor maintenance of the ventilation system in some, non-segregation of dusty processes, dry sweeping, and the use of compressed air jets. The determinant-of-exposure analysis confirmed the field observations. The significant determinants of personal inhalable dust exposures (n=163) were found to be: local exhaust ventilation, job title, use of hand-held tools, cleaning method used, use of compressed air, and green or dry wood processed. Type of wood processed was not found to be statistically significant. A majority of workers (~90%) did not wear appropriate respirators approved for wood dust, while the workers who did wear them, used them on average less than 50% of the time. Workers should be protected by controlling dust at its source. When exposure to wood dust cannot be avoided, engineering controls should be supplemented with the use of appropriate personal protective equipment.

In this Thesis, we investigate the chemical and dust evolution of the different galactic environments we encounter during the cosmic history, from the high-redshift Universe to the Milky Way. The study of the evolution of galaxies is performed by means of detailed chemical evolution models that predict the abundances of single chemical elements in the interstellar medium as well as the condensation into dust of the chemical elements. In the first part of the Thesis, we concentrate on the study of moderate to high-redshift systems. We start focusing on high-redshift starburst galaxies, whose extreme conditions pose questions on the universality of the initial mass function (IMF) as well as on the processes regulating the ISM dust. For these reasons, we test the the impact of the IMF shape on high-redshift environments by applying the so-called Integrated Galactic IMF (IGIMF) theory in models specifically suited for starburst galaxies. In this way, we look at the interplay between the IMF and dust processes in shaping the observed gas abundance patterns as well as global dust quantities. This analysis highlights the degenerate effect of the IGIMF and dust on abundance patterns and suggests that the IGIMF can explain the dust masses observed in some high-redshift star forming objects. To get a more complete picture about dust through cosmic evolution, we also investigate how dust quantities evolve at larger volume scales. To this aim, we present a novel method to compute the redshift evolution of dust mass in galaxy clusters. This is done by integrating the predictions of chemical and dust evolution models for individual galaxies over the galaxy cluster luminosity function (LF), assuming suitable cosmological scenarios for the LF evolution. By applying this method, we reproduce the dust amounts observed in low and intermediate-redshift galaxy clusters and we answer to some questions about dust in cluster. In particular, we find that spiral galaxies are the most important dust producers within clusters and that galactic ejecta can account alone for the observed intracluster dust. In the second part of the Thesis, instead, we focus on study of the local Universe and in particular of the MW Galaxy. We start investigating the evolution of the MW thick and thin discs by comparing MW models with recent survey data. In particular, we discuss the formation of abundance gradients in the MW and the main physical parameters influencing this process, concluding that inside-out disc formation should act together with radial gas flows and variable efficiency of star formation. Moreover, we suggest that to reproduce the observed [α/Fe] dichotomy/bimodality (i.e., the presence of two distinct data sequences in the [α/Fe] vs. [Fe/H] diagram) at different Galactocentric distances, one should assume a prolonged gap between the formation of the thick and thin discs and a chemically enriched gas accretion in the innermost thin disc. Finally, we study the impact of different Type Ia SN yields on the evolution of Fe-peak elements in our Galaxy. To this aim, we apply to our chemical models for the MW a large compilation of Type Ia SN yields from the recent literature, sampling different explosion mechanisms. The obtained results are compared with those obtained with classical Type Ia SN prescriptions adopted in previous studies. In addition, we allow combinations of of Type Ia SN yields from different progenitor classes to assess their role in terms of the chemical enrichment. We find that the chemical abundance patterns strongly depend not only on the explosion mechanism but also on other conditions. Moreover, the comparison with the observed abundance trends suggests that a combination of different classes of explosion is necessary to reproduce the data.
In this Thesis, we investigate the chemical and dust evolution of the different galactic environments we encounter during the cosmic history, from the high-redshift Universe to the Milky Way. The study of the evolution of galaxies is performed by means of detailed chemical evolution models that predict the abundances of single chemical elements in the interstellar medium as well as the condensation into dust of the chemical elements. In the first part of the Thesis, we concentrate on the study of moderate to high-redshift systems. We start focusing on high-redshift starburst galaxies, whose extreme conditions pose questions on the universality of the initial mass function (IMF) as well as on the processes regulating the ISM dust. For these reasons, we test the the impact of the IMF shape on high-redshift environments by applying the so-called Integrated Galactic IMF (IGIMF) theory in models specifically suited for starburst galaxies. In this way, we look at the interplay between the IMF and dust processes in shaping the observed gas abundance patterns as well as global dust quantities. This analysis highlights the degenerate effect of the IGIMF and dust on abundance patterns and suggests that the IGIMF can explain the dust masses observed in some high-redshift star forming objects. To get a more complete picture about dust through cosmic evolution, we also investigate how dust quantities evolve at larger volume scales. To this aim, we present a novel method to compute the redshift evolution of dust mass in galaxy clusters. This is done by integrating the predictions of chemical and dust evolution models for individual galaxies over the galaxy cluster luminosity function (LF), assuming suitable cosmological scenarios for the LF evolution. By applying this method, we reproduce the dust amounts observed in low and intermediate-redshift galaxy clusters and we answer to some questions about dust in cluster. In particular, we find that spiral galaxies are the most important dust producers within clusters and that galactic ejecta can account alone for the observed intracluster dust. In the second part of the Thesis, instead, we focus on study of the local Universe and in particular of the MW Galaxy. We start investigating the evolution of the MW thick and thin discs by comparing MW models with recent survey data. In particular, we discuss the formation of abundance gradients in the MW and the main physical parameters influencing this process, concluding that inside-out disc formation should act together with radial gas flows and variable efficiency of star formation. Moreover, we suggest that to reproduce the observed [α/Fe] dichotomy/bimodality (i.e., the presence of two distinct data sequences in the [α/Fe] vs. [Fe/H] diagram) at different Galactocentric distances, one should assume a prolonged gap between the formation of the thick and thin discs and a chemically enriched gas accretion in the innermost thin disc. Finally, we study the impact of different Type Ia SN yields on the evolution of Fe-peak elements in our Galaxy. To this aim, we apply to our chemical models for the MW a large compilation of Type Ia SN yields from the recent literature, sampling different explosion mechanisms. The obtained results are compared with those obtained with classical Type Ia SN prescriptions adopted in previous studies. In addition, we allow combinations of of Type Ia SN yields from different progenitor classes to assess their role in terms of the chemical enrichment. We find that the chemical abundance patterns strongly depend not only on the explosion mechanism but also on other conditions. Moreover, the comparison with the observed abundance trends suggests that a combination of different classes of explosion is necessary to reproduce the data.

From the beginning of the 20th entury astronomers started to move their studies toward that parti ular omponent whi h ould be responsible of the reddening and the extin tion of stars radiation. They agreed that this omponent must be represented by a population of mi ros opi parti les named interstellar dust, that it must be mixed with the interstellar gas. Later on, in the se ond half of the entury, dust was re ognized to play very many important roles in the Milky Way and other galaxies. These ndings hanged the astronomer's view of the interstellar spa e, that is now fully onsidered as an a tive element in gala ti evolution. For this reason to a hieve a more reliable understanding of the nature of interstellar dust is ne essary to take into a ount the response of dust to the physi al onditions of the regions in whi h dust grains are embedded. Over the years astronomers used the variation of extin tion respe t to wavelength, the interstellar extin tion urve, to study osmi dust. In this thesis I elaborate a physi al and hemi al model of dust, to investigate the remarkable variety of gala ti interstellar extin tion urves. In Chapter 1 I introdu e the roles of the interstellar dust, its pro essing in the interstellar medium, and the tools to address the problem of its nature. In Chapter 2 I present the exploited model in a simpli ed version, and an appli ation to some pe uliar lines of sight in our galaxy. In Chapter 3 the omplete version of the model is put forward, and, together with its simpli ed version, applied to a large sample of Milky Way interstellar extin tion urves. All di erent avours of observed extin tion urves, ranging from the average gala ti extin tion urve to very pe uliar pro les, an be des ribed by su h a model. I show that a mixture of ore mantle sili ate/ arbon grains together with a relatively small number (54 spe ies in four harge states) of poly y li aromati hydro arbons an reprodu e the features of the extin tion urve in the ultraviolet, dismissing an old obje tion to the ontribution of poly y li aromati hydro arbons to the interstellar extin tion urve. In Chapter 4 I ompare an evolutionary model of the physi al properties of arbona eous grain mantles with their determination through the tting pro edure outlined in Chapter 3. The results of su h omparison demonstrates, that in the framework of the adopted dust model, the whole sample of gala ti extin tion urves are in striking agreement with the proposed evolutionary s enario, requiring physi al onditions fully onsistent with standard values of density, temperature, radiation eld intensity, and average age of di use interstellar louds. The results of this thesis show that the present model is able to re on ile the great variety of observed interstellar extin tion urves within an uni ed evolutionary s enario, without making drasti hanges to stru tural properties of dust grains.

Mineral dust is ubiquitous in the atmosphere and represents a dominant type of particulate matter by mass. Despite its well-recognized importance, assessments of dust impacts on clouds and climate remain highly uncertain. This thesis addresses the role of dust as cloud condensation nuclei (CCN) and giant CCN (GCCN) with the goal of improving our understanding of dust-warm cloud interactions and their representation in climate models. We investigate the CCN-relevant properties of mineral dust samples representative of major regional dust sources experimentally in the laboratory conditions to determine their respective affinity to water. Based on the experimental exponent derived from the dependence of critical supersaturation with particle dry diameter, we determine the dominant physics of activation (i.e., adsorption activation theory (AT) or traditional Köhler theory (KT)) for dust particles from different global regions. Results from experimental measurements are used to support the development of a new parameterization of cloud droplet formation from dust CCN for climate models based on adsorption activation mechanism. The potential role of dust GCCN activating by AT within warm stratocumulus and convective clouds is also evaluated.

Mineral dust aerosols play an important role in climate and the Earth's energy budget. However, the nature and complexity of dust sources is poorly understood. Traditional techniques used for mapping the Sahara dust sources like the analysis of surface dust observations, back trajectory analysis of isobar data, and mineral tracers all tell a different story regarding the location of dust sources, they only agree that the Bodélé Depression and western Hoggar Mountains are important sources. Remote sensing techniques have more recently been used to identify Saharan dust sources and the different methods provide more agreement about more Saharan dust sources and also identify the Bodélé Depression and the western Hoggar Mountains as important source of dust. While there are several remote sensing techniques that can be used to identify desert dust sources yet no comprehensive comparison has yet been done to evaluate their utility. This thesis has evaluated the utility of nine different methods that can be employed to detect dust using MODIS have been investigated by comparing them to sun-photometer aerosol optical thickness (AOT) measurements at a wavelength of 1020μm from Banizoumbou (Niger). The five established techniques that were evaluated, these were: Ackerman (1989), Miller (2003), Handley (2004), Hansell et al., (2007) and the Deep Blue NASA aerosol product Hsu et al., (2003). Many of these methods employ brightness temperature differences (BTD). To determine the effectiveness of this approach all possible MODIS BTD’s were computed and evaluated, these were: BTD (12 μm-11 μm), BTD (3.7 μm-12 μm), BTD (8.6 μm-11 μm), and BTD (8.6 μm-12 μm). To evaluate the accuracy of these dust indices the correlation between the sun-photometer AOT and the result of each MODIS dust index were determined. The results show that the Deep Blue Algorithm gives the highest correlation (R²= 0.91), however the deep blue product has a 10km spatial resolution and thus is not good at locating dust sources, the ultimate aim of this project, furthermore the cloud mask applied to the product routinely masks out most of the dust. The other methods all have a spatial resolution of 1km and thus are more appropriate for this purpose. Of these methods the Ackerman (1989) shows a high R2 value (R²= 0.71) as do many other methods. The effect of different surface materials on dust detection was evaluate by studying five different backgrounds in order to see how the dust can be distinguished from these backgrounds using the M test. Over Limestone background, Miller (2003) has got the highest M value followed by Deep Blue and Ackerman (1989), excluding Deep Blue due to the poor cloud mask and visually difficult to trace the dust to their sources, Ackerman (1989) comes second and has an M value close to Miller (2003). However, Ackerman (1989) shows the best result visually. Based on the five tested backgrounds result using different techniques (visually, M test, and statistically) Deep Blue, Miller, and Ackerman present reasonable results. Based on these results Ackerman (1989) was selected to detect the dust sources over Cyrenaica (Libya) with using MODIS and SEVIRI data. SEVIRI images are also used to study the meteorology of the dust storms in order to provide more information on the wind direction, cause, and lifetime of dust storm. The highest percentage of the dust storms generated from Cyrenaica are caused by Anticyclone 70%. The majority last for six hours, starting at 8:00 am and ending at 14:00 pm. MODIS is used to detect the location of the dust sources and Landsat and Google Earth images are used to identify the geomorphology of the dust sources. Total of 53 dust sources are detected during 2008, 45% from alluvial fans, 15% from lake, 13% from alluvial plains, 6% from agriculture, 6% from river, 2% from multiple landforms in a single MODIS pixel and thus their nature could not be determined, while 13% were diffuse and no source could be detected. Alluvial fans were the most active sources and almost half of these dust sources are located at one large fan located south east of Benghazi.