Dissertations / Theses on the topic 'Emission factors'

Welding is a common industrial practice that has the potential to emit air pollutants. Emission factors are useful indicators to help in the understanding of the extent of pollution from a process and managing them to reduce or minimize health impacts. The objective of this thesis is to determine emission factors applicable to the gas metal arc welding (GMAW), under varying current and voltage conditions. The most used base metals and an electrode for the shipbuilding industry were considered. A weld fume chamber was used to achieve the project goals along with standard sampling and analytical procedures. Three test runs were performed for each sampling scenario to ensure repeatability. The EPA EF average for MS experiments with the ER70S-6 electrode is 5.2 g/kg, and for SS experiments with the ER316L-Si electrode is 3.2 g/kg, while the average results for this study were 6.81 g/kg and 3.28 g/kg respectively.

The purpose of this research is to demonstrate a methodology for quantifying the variability and uncertainty in emission factors and emission inventories. Emission inventories are used for various policy-making purposes, such as characterization of temporal emission trends, emissions budgeting for regulatory and compliance purposes, and the prediction of ambient pollutant concentration using air quality models. Failure to account for variability and uncertainty in emission inventories may lead to erroneous conclusions regarding source apportionment, compliance with emission standards, emission trends, and the impact of emissions on air quality. Variability is the heterogeneity of values of a quantity with respect to time, space, or across a population while uncertainty arises due to lack of knowledge about the true value of a quantity. The sources of variability and uncertainty are distinct and hence variability and uncertainty affect policy- making in different ways. For example, variability in emissions arises from differences in operating conditions among different power plants. Uncertainty arises due to measurement errors, systematic errors, and random sampling errors. It is possible to reduce uncertainty by taking more accurate and precise measurements (i.e. reducing measurement error) or by taking a larger number of measurements (i.e. random sampling error). However, it is not possible to reduce variability. Therefore, in this research variability and uncertainty are treated separately. A methodology for simultaneous characterization of variability and uncertainty in emission and activity factors and their propagation through an emission inventory model is described. Variability was characterized using probability distributions developed on the basis of data analysis. The uncertainty due to random sampling error was characterized using parametric bootstrap simulation. A methodology for the quantification of variability and uncertainty in censored data sets containing below detection limit values was developed. This methodology is demonstrated for three case studies. In Case Study 1, the variability and uncertainty in the activity and emission factors for NO x emissions from selected coal-fired power plant systems was quantified based on data obtained from the U.S. Environmental Protection Agency. An illustrative partial probabilistic NO x emission inventory was developed for the state of North Carolina. In Case Study 2, the variability and uncertainty in the total short-term average emissions and in annual emissions of nine hazardous air pollutants (HAP) from a power plant was quantified by propagating the probability distributions for coal concentrations, boiler partitioning factors, and fabric filter partitioning factors through an emissions model. In Case Study 3, the effect of various levels of censoring on the variability and uncertainty in CO and HC emission factor data sets for diesel transit buses was studied. The main findings regarding the methodology demonstrated in this research include: (1) uncertainty due to random sampling error is substantial and in many cases was found to be of the same order of magnitude as the variability in the data set; and (2) the methodology developed for quantifying the variability and uncertainty in censored data sets is reasonably robust and accurate. The main insights obtained from the application of the methodology include: (1) the uncertainty in the total NO x emissions from selected power plants in North Carolina is ± 25 percent around the nominal value; (2) the uncertainty in the short-term average emissions of all HAPs from a power plant is substantially high in the upper percentiles (e.g., the width of the 95 percent confidence interval on the 95th percentile is 385 lb) than in the lower percentiles (e.g., the width of the 95 percent confidence interval on the median value is 60 lb) ; (3) the range of uncertainty in the annual average emissions is much wider than the range of variability in annual average emissions from one year to another; and (4) the uncertainty in the median value of censored CO and HC emission factor data sets increases as the level of censoring increases.

Generation of hydrogen sulfide (H2S) is a common phenomenon from wastewater collection, transport, and treatment processes. Impacts of H2S emissions from wastewater include corrosion and reduction in the service life of wastewater infrastructure, odor nuisance in the community, and health impacts on wastewater operations and maintenance personnel (Neilsen, et al. WEFTEC 2006). Conventional odor control studies performed by municipalities to design their individual odor/corrosion control strategies largely depend on establishing a dilution to detection threshold (D/T) ratio and ascertaining the recognition threshold (R/T) for air samples collected from the study area. These conventional odor studies based on grab samples using R/T and D/T technique using a few days of data have a number of limitations and potentially lead to inaccurate conclusions. However, H2S emission studies using continuous air monitoring is expensive and time consuming. The objective of this research is to understand the feasibility of utilizing emission factors as a tool to predict hydrogen sulfide emissions from headworks of four different Jefferson Parish, Louisiana wastewater treatment plants (WWTP). Proposed model(s) developed for predicting H2S emission factors that depend on wastewater parameters should be convenient for the municipalities to use as the data required is monitored routinely. Use of H2S emission models should assist rapid identification of H2S emission hot spots, optimize H2S control strategies, predict potential health risks, prevent community odor nuisance, and ascertain infrastructure corrosion. This dissertation attempts to; i) develop a research methodology, ii) identify instruments required, iii) generate emission factor ranges and compare their sensitivity to wastewater parameters, iv) generate preliminary empirical emission models based on flow treated, population serviced and area served by a treatment plant for each sampling location and v) provide a roadmap for future research opportunities to refine the models generated as part of this dissertation. Key words: emission model, emission factor, emission ranges, hydrogen sulfide, odor control, air quality, wastewater treatment.

Introduction
Current instrumentation makes it possible to measure vehicle emissions with high temporal resolution. But the increased resolution of emissions signals does not equate with increased accuracy. A prerequisite for the derivation of accurate emission factors from instantaneous vehicle emissions data is a fine allocation of measured mass emissions to recorded engine or vehicle states. This poses a technical challenge, because vehicle emission test facilities are not designed to support instantaneous emissions modelling, and they introduce distorting effects that compromise the instantaneous accuracy of the measured signals.

Methodology
These distorting effects can be compensated through a combination of physical modelling and data post-processing. The main original contribution of this dissertation is a novel methodology for the compensation of instantaneous emission signals, which is fully described herein. Whereas previous methodologies relied on systems theory modelling, and on comprehensive testing to model the sub-systems of the measurement setup, the alternative approach uses CO2 as a tracer of the distortions brought about by the measurement setup, which is modelled as a 'lump' system.

Conclusions
The main benefits of this methodology are its low burden of experimental work and its flexibility. Furthermore, it has been fully implemented in the 'esto' software tool, which can perform the compensation of emission signals with minimal user intervention and speed up the creation of engine emission maps.

Crop production is a significant contributor to greenhouse gas emissions because cropping inputs and cultivation lead to the formation of nitrous oxide (N2O) in soils. This research measured the baseline N2O emissions from apple, cherry, processing tomato and babyleaf spinach production in Australia and assessed the impacts of crop management practices on these emissions. Nitrous oxide emissions were measured using static chambers, and the impact of management practices including crop residue mulches, cover crops, composts and irrigation management on emissions was assessed; and, the data compared to estimated emissions calculated using the Intergovernmental Panel on Climate Change (IPCC) and the Cool Farm Tool (CFT) models. In Vietnam N2O emissions were measured in preliminary studies on vegetables crops, and the effectiveness of technical extension guidelines to mitigate N2O emissions were analysed. Average N2O emissions from fruit orchards and vegetable crops in Australia were low (less than 10 g N2O-N ha-1 day-1), while the emissions for choy sum, mustard and cabbage crops in Vietnam were higher, ranging from 12 g to 40 g N2O-N ha-1 day-1. Compost and lucerne straw additions increased N2O emissions in orchards while wheat straw mulch or bare soils did not. Sub-surface drip irrigation, legumes and ryegrass cover crops and low nitrogen fertiliser inputs were identified as potential strategies for mitigating N2O emissions in baby leaf spinach and processing tomatoes. The CFT and IPCC default values tended to overestimate measured N2O emissions. Technical guidelines for vegetable production in Vietnam focus on economic benefits rather than managing greenhouse gas emissions. Avoiding overuse of urea, using NPK, organic, slow-release urea fertilisers, and establishing permanent beds with small tractors were identified and ways to reduce GHG emissions in Vietnam.

In Tunisia, the National Agency for the Environment is encouraging the creation of a carbon footprint method specifically adapted to the Tunisian context. In cooperation with the French National Agency for the Environment, the adaptation of the French carbon footprint method is realised and has to go along with an adaptation of the emission factors. In this framework, this master thesis aims at presenting the emission factors adaptation process led to adapt the accounting tool. First, a literature review enables to present the main notions useful to understand the precise definition of emission factor. Then, a preliminary study of the main carbon footprint tools is presented so as to identify the main characteristics of a carbon footprint method. A comparison is then done to present the differences which can occur between the previous methods. Finally, for each category of emission factor, the adaptation process is presented showing three different ways to adapt emission factors: a replacing of the data in the calculations, an adaptation based on local studies and a more difficult adaptation requiring to develop a new method.

Mining generates great deal of particulate matter, especially for surface mining. The principle of dust generation is based on the theory of soil wind erosion. This thesis theoretically and experimentally dealt with mining dust. In chapter 1 the development of study on soil erosion by wind and mining dust were introduced. Chapter 2 elaborated the process of soil wind erosion. Soil motion during wind erosion is classified into three categories which are creeping, saltation and suspension. Threshold wind velocity, which initiates particle motion, depends on particle size, soil moisture, roughness element etc. Roughness element refers to non erodible fraction in a soil. A test on erodible fraction was included in this research.Chapter 3 presented effects and sources of mining dust. Sources include haul road, stockpiles, open surfaces, overburden removal etc. Malmberget mine operated by LKAB is one of the most important iron mines in Sweden. The mining area includes an area with huge open pit and current industrial center area. Both areas are surrounded by residential areas where people are suffering from dust problem. In this research the collected dust from 26 measuring stations during the time period Aug. 2009 to Aug. 2010 were used to calculate the dust fallout and distribution using surfer 9.0 software. It was concluded that two sources for dust generation were spotted. One was located close to the open pit, and the other was located nearby the current mining industrial center. It should be mentioned that the concentration of dust was varying with time. The maximum value happened on May in 2010. The value suddenly became extremely high compared with the other months. This was attributed to a road construction at that time. Analysis results have shown dust production around Malmberget mine was attributed to three reasons: wind erosion of the exposed area closed to the open pit, trucks transportation on haul roads, and wind erosion of stockpiles. Since the mining activities were relatively going at a constant level, the variations of dust level were mostly attributed to the climatic factor. During the research erodible fractions for surface samples from the open surface nearby the open pit were measured. The result showed an erodibility index of 4.69kg/m2 per year. Because the index value indicated relatively low intrinsic soil erodibility, the dust problem might be more contributed by wind erosion of stockpiles and truck travelling on haul roads.Chapter 4 introduced how US EPA developed dust emission factors for various mining activities. Accordingly recommendations and the future plans for the establishment of the dust emission factors for Malmberget mine in Sweden were given and highlighted in chapter 5. Chapter 6 finalizes the thesis with a conclusive paragraph.
Godkänd; 2011; 20110516 (qijia); LICENTIATSEMINARIUM Ämnesområde: Geoteknik/Soil Mechanics and Foundation Engineering Examinator: Professor Sven Knutsson, Institutionen för samhällsbyggnad och naturresurser, Luleå tekniska universitet Diskutant: Professor John McManus, St. Andrews University, United Kingdom Tid: Måndag den 3 oktober 2011 kl 10.30 Plats: F531, Luleå tekniska universitet

Indoor air quality is a growing concern in the world. People spend a considerable amount of time in indoor environments such as homes, workplaces, shopping malls, stores, and so on. Indoor sources like incense and candle burning, cooking contribute a significant amount of indoor air pollutants such as particulate matter, carbon monoxide (CO), volatile organic compounds. Exposure to these kinds of pollutants can result in adverse health effects. The purpose of this research is to determine the particulate matter and carbon monoxide emission factors (EFs) from incense stick burning. A test chamber with a rectangular exhaust duct, a fan to exhaust air with pollutants in it, and pollutant sensors were used to achieve the project goals. Several experiments were performed with different cases/scenarios to accurately estimate the EFs and several test runs were conducted for each case to test the repeatability of the results. The CO, PM2.5 (mass), PM2.5 (number), PM10 (mass), PM10 (number) EFs developed in this research are between 110-120 mg/g of incense, 2.5-3 mg/g of incense, 800-1100 #particles/µg of incense, 32-33 mg/g of incense, 1200-1400 #particles/µg of incense respectively.

This dissertation analyzes the basis for and magnitudes of discount factors based on the characteristics of greenhouse gas emission (GHGE) offsets that are applied to the GHGE reduction projects, concentrating on agricultural projects. Theoretical approaches to discount factors, estimation and incorporation of discount factors procedures are developed. Discount factors would be imposed by credit purchasers due to noncompliance with regulatory program of the credits with GHG program including consideration of shortfall penalties and limited durations. Discount factors are proposed for (i) additionality, (ii) leakage, (iii) permanence, and (iv) uncertainty. Additionality arise when the region where an AO project is being proposed would have substantial adoption of the AO practice in the absence of GHG programs (business as usual GHGE offset). Leakage arises when the effect of a program is offset by an induced increase in economic activity and accompanying emissions elsewhere. The leakage effect depends on demand and supply elasticities. Permanence reflects the saturation and volatility characteristics of carbon sequestration. Carbon is stored in a volatile form and can be released quickly to the atmosphere when an AO practice is discontinued. The permanence discount depends on the project design including practice continuation after the program and the dynamic rate of offset. Also, consideration of multiple offsets is important. Uncertainty arises due to the stochastic nature of project quantity. The uncertainty discount tends to be smaller the larger the size of the offset contract due to aggregation over space and time. The magnitude of these discounts is investigated in Southeast Texas rice discontinuation study. The additionality and the leakage discounts are found to play an important role in case of rice lands conversion to other crops but less so for pasture conversions and yet less for forest conversions. The permanence discount is important when converting to other crops and short rotation forestry. When all discounts are considered, rice lands conversion to forest yields claimable credits amounting to 52.8% ~ 77.5% of the total offset. When converting rice lands to pasture, the claimable credits 45.1% ~ 64.2%, while a conversion of rice lands to other crops yields claimable credits 38.9% ~ 40.4%.

The purpose of this project was to monitor ammonia emissions and develop updated ammonia emission factors for land application of poultry manure under British Columbia conditions. Field experiments were performed at the Agassiz Research Station in 2005 and 2006, which involved four types of poultry manure as the fertilizer materials and four varying heights of the grass canopy. Proceeding manure application, ammonia emission rates were determined using wind tunnels, the emitted ammonia captured using acid traps and analyzed with a flow injection analyzer. For all trials, the highest emissions occurred within the first day, and gradually declined over the next 2-3 weeks. Cumulative ammonia emission in all treatments did not exceed the initial amount of ammonia-nitrogen present in manure. Ammonia emission rates were significantly different among the manure types (p < 0.005). The percent total loss of ammonia with time was positively correlated with manure pH. Ammonia emission rates were generally higher in both of the spring trials than the fall trial. The ammonia-nitrogen emission rate was found to decrease as the grass height increase. The proposed revised ammonia emission factors of 0.12 and 0.16 kg-NH3-N/initial kg-N for the two major types of poultry - broiler and layer are in line with current emission factors adopted by Environment Canada. However, current and revised emission factors (0.38 versus 0.11 kg-NH3-N/initial kg-N) were substantially different for turkey manure.
Applied Science, Faculty of
Chemical and Biological Engineering, Department of
Graduate

The objectives of this study are to measure the non-methane volatile organic carbon (NMVOC'
s) emissions from passenger cars in Turkey having gasoline engines, to determine emission factors of these vehicles for BTEX compounds and comparison of emission factors obtained in this study with the emission factors of the other countries. This study was conducted in two parts: The first part was to determine the categories of passenger cars widely used in Turkey, and also to determine the average carbon monoxide (CO) and hydrocarbon (HC) emissions at idle condition for these car types based on the exhaust emission measurements of Ankara Ç
evre Koruma Vakfi (ANÇ
EVA). The second part of the study was to analyze the gas composition of exhaust gasses at different road conditions for BTEX components by using gas chromatography. The results of the study have shown that the cars named under &lsquo
&lsquo
Tofas&rsquo
&rsquo
constitute 31.5% and &lsquo
&lsquo
Fiat&rsquo
&rsquo
13.1% of the total cars in Turkey and they are manufactured by the same company. Therefore, studies have been performed with &lsquo
&lsquo
Tofas/Fiat&rsquo
&rsquo
cars. The highest emission factors among hydrocarbons investigated in this study were found for toluene and m-xylene. Generally, as driving speed increases the emissions of HC&rsquo
s are found to decrease in concentration. It was interesting to note that the highest emissions occur at 30 km/hr speed which is the mostly used speed in crowded streets and busy intersections. Therefore, it was concluded that it is very important to take measures for emissions in the city traffic. Cold start emissions were also found to be higher than the hot start emissions.

Transport of wastewater in sewer networks causes potential problems associated with gases which include ammonia, carbon dioxide, carbon monoxide, hydrogen sulfide and methane, in regard to odor nuisance, irritation, toxicity, and microbially induced corrosion. The extent of these problems depends on the emission rates of gases in the sewer atmosphere. To limit these kinds of problems an estimate of the gases emitted from the sewer network is to be known. In consideration to the above mentioned problems, a research has been taken up to estimate the two gases, namely, carbon dioxide and hydrogen sulfide from sewer wet wells. In this method, using Landtec GEM-2000 plus a multi-gas analyzer, the sample gases were collected from the wet well of pump stations for five days. Using the collected samples the emission rates of carbon dioxide and hydrogen sulfide are estimated.

An efficient management of organic fertilizers (here animal manure and digestate) is of large concern in today´s agriculture. When evaluating the efficiency of alternative management systems, differences in nutrient losses (emissions) must be taken into consideration. Those can be rather specific for e.g. a geographical region and agricultural system. This literature study aimed at identifying emission factors and uncertainty ranges, that are relevant to use in comparative system studies of different organic fertilizer management systems in South Swedish climate. Emissions from manure and digestate storage, application and field losses were considered. For carbon, the sequestration of organic carbon in the soil was considered instead of the carbon dioxide emissions from manure/digestate decomposition in soils. The values were very variable, and the median value was used as the selected emission factor. From storage of liquid cow manure, the ammonia emission for storage with cover was 3 % of the ammonium content, and 10 % without cover. It was about the same for both liquid pig manure (8 %) and solid cattle manure (10 %). The methane emissions during storage were 10 % of the maximum methane potential. Ammonia emissions during application ranged from 10-20 % of ammonium-nitrogen. Two studies of manure carbon sequestration were found that was applicable for the Swedish climate. They indicated that about 8-11 % of the carbon applied as solid manure was sequestered, compared to about 4 % for liquid manure.

From constructing buildings to manufacturing ships, welding is the structural backbone to numerous industries. With over one hundred welding techniques, primarily driven by the base metals, filler rods, electrodes, and environmental factors, welding is a major process used in industry, commerce, and service sectors. The focus of this research is to understand the fumes generated by the Tungsten Inert-Gas (TIG) welding on Aluminum-Lithium Alloy (Al-Li Alloy), estimate applicable emission factors, and identify the heavy metal concentrations of lead, manganese, and chromium. Although there are numerous metals and various welding procedures this study will focus on three main factors: 1. Base metals comprised of Aluminum Lithium Alloy 2195 and 2219 an agehardened copper containing aluminum alloy 2. Weld wire 4043 comprised of aluminum silicone and 2319 comprised of copper silicone 3. Weld techniques of Variable Polarity Plasma Arc (VVPA) and Tungsten inertgas (TIG).

Dry abrasive blasting is one of the most widely used methods of surface preparation. Air emissions from this process include particulate matter (PM) and metals. Spent abrasive generated from this process may be hazardous in nature. With increasing concern on health effects due to silica emissions from sand, use of alternative materials is suggested by health and regulatory agencies. The objective of this research was to evaluate performance of expendable abrasives and determine PM emission factors. Dry abrasive blasting was performed in an enclosed chamber and total PM samples were collected. Three commonly used expendable abrasives, coal slag, copper slag and specialty sand, were used to evaluate cleaner alternatives. Blast pressure and abrasive feed rate, two important process conditions were varied to study their effect on performance of an abrasive. Productivity, consumption and emission factors (performance parameters) were calculated and their variation with pressure and feed rate was evaluated. Two dimensional and three dimensional predicted models were developed to estimate the performance at intermediate blast pressure and feed rate conditions. Performance of the three abrasives was compared with respect to emission potential, productivity and consumption. Emission factors developed in this research will help in accurate estimation of total PM emissions and to select cleaner abrasives and optimum process conditions that will results in minimum emissions and reduced health risk. The productivity and consumption models will help is estimating life cycle costs including material cost, equipment cost, energy cost, labor costs, waste disposal cost, and compliance costs. Consumption models will also help in determining the quantity of spent abrasive generated, identify abrasives with lower material consumption, and identify process conditions that generate minimum spent abrasives. In addition, these models will help industries in making environmentally preferable purchasing (EPP), which results in pollution prevention and cost reduction.

Les flors emeten compostos orgànics volàtils (VOCs) per tal d’atreure pol·linitzadors i estimular la fecundació creuada. Alguns volàtils florals però juguen altres funcions, com ara la defensa contra els herbívors. Aquesta dualitat de rols que tenen les olors florals les converteix en complexes mescles de compostos amb múltiples efectes sobre diferents organismes. La complexitat de comprendre i caracteritzar les emissions florals augmenta quan considerem que són variables en el temps i l’espai. A aquestes fonts de variabilitat cal afegir diversos factors ambientals biòtics i abiòtics que modifiquen les emissions de COVs florals de diverses maneres. L’objectiu principal d’aquesta tesi és esclarir quins són els factors que determinen les emissions florals de volàtils, i veure de quina manera les afecten a elles i a les seves funcions ecològiques. En el primer capítol de la tesi hem revisat el coneixement actual sobre les emissions florals de VOCs i hem identificat les qüestions que necessitaven ser investigades en aquest camp de recerca. Les emissions florals estan determinades en primer lloc per la diversitat de compostos que les espècies són capaces de produir, els seu potencial biosintètic i la seva capacitat d’emissió, que estan fortament lligades a la biologia de l’espècie. Hem testat i demostrat que les plantes pol·linitzades per insectes solen presentar major diversitat de volàtils florals i emeten una major quantitat d’aquests que les plantes pol·linitzades pel vent, que no necessiten volàtils florals per funcions d’atracció. Hem testat si els patrons estacionals de disminució de la competència que ocorren cada any entre plantes d’una mateixa comunitat vegetal han donat lloc a la selecció d’un patró de disminució de les emissions i les recompenses florals al llarg del període de floració de cada espècie. També hem observat que les plantes adapten la seva fisiologia per optimitzar les seves emissions florals sota les condicions climàtiques de la seva època de floració. Les emissions florals de COVs es veuen afectades per factors ambientals al nivell d’organisme o de teixit. Hi ha diversos estats fisiològics de la planta que poden modificar substancialment la composició i la quantitat de les emissions florals de COVs. Els nostres experiments han demostrat que la microbiota floral pot jugar un rol crucial sobre la quantitat i composició de les emissions florals de COVs. També hem mostrat que l’herbivoria de flors per part d’erugues de Pieris brassicae sobre plantes de Diplotaxis erucoides indueixen augments immediats de les emissions de compostos amb funcions defensives. A més, l’herbivoria de flors i fulles combinada va mostrar un efecte sinèrgic que augmenta la resposta defensiva. La recerca sobre els canvis que poden experimentar les emissions florals en resposta a diversos agents del Canvi Global són de gran interès degut als diversos efectes que aquests canvis poden tenir sobre les interaccions que s’estableixen mitjançant els COVs florals. Els nostres resultats revelen que els augments de temperatura previstos per al segle següent deguts a l’Escalfament Global poden conduir a augments significatius de les emissions totals de COVs i també a canvis importants en la composició relativa de les olors florals. També hem observat que l’ozó causa una degradació significativa dels compostos florals i provoca canvis en la composició relativa de les olors. Els testos de resposta indiquen que els canvis observats en les olors florals exposades a ozó resulten en la pèrdua de l’atracció de pol·linitzadors. Aquesta tesi proporciona una nova visió sobre els factors que determinen les emissions florals de volàtils i les seves repercussions sobre les interaccions planta-pol·linitzador, i garanteix una major consideració dels factors biòtics i abiòtics que afecten la química i l’ecologia de les olors florals en un ambient contínuament canviant.
Flowers emit volatile organic compounds (VOCs) to attract pollinators and stimulate reproductive outcrossing. Some floral volatiles can play roles other than attraction, such as defense against herbivores. This duality of roles of flower emissions converts floral scents into complex mixtures of compounds with multiple effects on different organisms. The complexity of understanding and characterising floral emissions increases when considering that they are variable in time and space. To all these sources of variability we can add diverse biotic and abiotic environmental factors that modify floral VOC emissions in many different ways. The main objective of this thesis was to shed light on which are the factors that determine floral volatile emissions, and how do they affect these emissions and their ecological functions. In the first chapter of this thesis we reviewed the current knowledge on floral VOC emissions. We identified the open questions that still needed to be addressed or investigated in more detail in the research field of floral VOC emissions. Floral emissions are first determined by the array of compounds that the species are able to produce and their potential biosynthetic and emission capacities, which are strongly related to the species biology. We tested and demonstrated that flowering plants pollinated by insects usually present higher diversities of floral volatiles and emit higher amounts of them, than do plants pollinated by wind which do not need floral volatiles for attractive purposes. We tested whether well-known seasonal patterns of decreasing competition occurring every year in a community among co-flowering plants for pollinators led to the selection of a pattern of decreasing emission of floral volatiles and decreasing production of floral rewards along the flowering period of each species. We also observed that plants adapt their physiology to optimize their floral emissions under the climatic conditions of the flowering period. Floral VOC emissions of the species are affected by environmental factors at the individual (organism) or tissular level. There are diverse physiological states of the plant that can substantially modify the emission profiles and amounts of floral VOCs. Our experiments demonstrated that floral microbiota can play a crucial role in the quantity and quality of floral VOC emissions. We also showed that flower herbivory by Pieris brassicae caterpillars on Diplotaxis erucoides plants induced immediate increases in floral emission rates of few compounds with known defensive functions. Leaf herbivory caused no changes in the emissions of intact flowers, but the combination of leaf herbivory with flower herbivory showed a synergistic effect with enhanced defensive response. The research on the potential changes that floral emissions could experience in response to diverse drivers of Global Change are of critical interest because of the diverse effects that such changes can have on the interactions that floral VOCs mediate. Our results revealed that temperature increases as those predicted for the next century as a result of Global Warming can lead to significant total increases in floral VOC emissions and also to important changes in floral scent relative composition. We also detected that ozone caused significant degradation of floral compounds and changes in their relative composition. Behavioural tests indicated that all the changes observed in floral chemical cues when exposed to ozone resulted in the loss of attraction effect on pollinators. This thesis thus provides new insights on the factors that determine floral volatile emissions and their repercussions on plant-pollinator interactions and warrant deep consideration of both biotic and abiotic factors driving floral scent chemistry and floral scent ecology in a continuously changing environment.

Dry abrasive blasting is a commonly used surface preparation operation by many process industries to clean up metallic surfaces and achieve surface finishes suitable for future adhesion. Abrasives used in this process can be recyclable or expendable. This study was undertaken to evaluate the performance of three recyclable abrasives: garnet, barshot and steel grit/shot in terms of productivity (area cleaned per unit time), consumption (amount of abrasive used per unit area cleaned) and uncontrolled total particulate matter (TPM) emission factors (in terms of mass of pollutant emitted per unit area cleaned and mass of pollutant emitted per unit mass of abrasive consumed). Though there have been various attempts in the past to evaluate the performance of these abrasives, there has not been a streamlined approach to evaluate these parameters in the commonly used range of process conditions, or to identify and model the influences of key process variables on these performance parameters. The first step in this study was to evaluate the performance of these three abrasives in blasting painted steel panels under enclosed blasting conditions and using USEPA recommended protocols. The second step was to model the influences of blast pressure and abrasive feed rate, two most critical parameters on productivity, consumption and emission factors. Two and three dimensional models were obtained using multiple linear regression techniques to express productivity, consumption and TPM emission factors in terms of blast pressure and abrasive feed rate. Barshot was found to have high productivities over all and steel grit/shot demonstrated the least emission potential at almost all of the tested pressure and feed rate conditions. The data will help fill the gaps in literature currently available for dry abrasive blasting performance. The models obtained will help industries, the research community and the regulatory agencies to make accurate estimates of the performance parameters. Estimating productivity and consumption will help industries identify best management practices by optimizing the process conditions to achieve high productivity and low consumption rates. Emission factor determination will help in reducing the emissions to the atmosphere by choosing process conditions corresponding to minimum emissions. The performance parameters once optimized can result in reduction in material, labor, energy, emission and disposal costs, lower resource utilization and hence reduction in overall life cycle costs of dry abrasive process. The developed models will help industries in making environmentally preferable purchases thereby promoting source reduction options. PM emissions estimated using the models presented here will aid studies on health risk associated with inhalation of atmospheric PM.

In recent decades, life cycle assessment (LCA) has become a commonly used approach worldwide when studying environmental impacts linked to waste management systems. These systems are of a complex nature which includes everything from technical solutions, the environmental influence, and various stakeholders. To facilitate studies within this area of research, different LCA models are often utilised. WAMPS is a software specifically developed for assessing the environmental and economic impacts for a waste management system. During recent years, the work to bring the model up to date has begun as the software has not been modernised since it was developed in the early 2000s. The purpose of this degree project is to propose new emission factors for recycling and virgin production of glass, aluminium, steel, and plastic. In addition to this, the study intends to investigate how the implementation of the new figures may affect the results obtained in WAMPS.  To fulfil the purpose of the thesis, LCI datasets were collected for each material and evaluated according to three DQIs (Temporal representativeness, geographical representativeness, and documentation). New emission factors were developed based on the evaluation and discussions within the project group, to ensure that all relevant activities of the studied life cycles were included. The implications from implementing the new emission factors were investigated through a comparison with the old values. This was conducted through comparing the obtained results from WAMPS per one tonne of material as well as for a simple scenario.  The evaluation of the collected LCI data shows that many of the datasets represent average production in countries within Europe and that the data were generally older than five years old. The results show that the datasets were primarily well documented according to the criterion utilised in this study. Processes from EcoInvent were mainly used to develop the proposed emission factors. The implementation of the new emission factors in WAMPS resulted in significant change in potential environmental impact per tonne of material. Especially for the impact category photooxidation formation. For the scenario, the results indicated that a significant change in potential environmental burden is received when implementing the new emission factors. A reduction in total impact was obtained for all categories where eutrophication showed the largest absolute difference.  The developed emission factors are considered appropriate based on the design of this thesis. However, it is concluded that these have several limitations that are important to take into account if these were to be implemented in WAMPS in the future. In addition, it is considered established that an update may be considered reasonable based on the result obtained.
Under de senaste decennierna har livscykelanalys (LCA) blivit ett vanligt tillvägagångssätt världen över vid analyser av potentiella miljöeffekter kopplade till avfallshanteringssystem. Dessa system är av komplex natur och inkluderar allt från teknologiska lösningar, miljöpåverkan samt flera intressenter. För att underlätta dessa studier används idag ofta olika LCA-modeller. WAMPS är ett program som är särskilt utvecklad för att bedöma både miljömässiga- och ekonomiska konsekvenser kopplat till avfallshanteringssystem. Under de senaste åren har arbetet med att uppdatera modellen påbörjat eftersom programvaran inte har uppdaterats sedan början av 2000-talet. Syftet med detta examensarbete är att föreslå nya emissionsfaktorer för återvinning och jungfrulig produktion av glas, aluminium, stål, och plast. Utöver detta avser studien att studera hur implementeringen av de nya siffrorna inverkar på resultatet som erhålls i WAMPS.  För att uppfylla tesen av detta arbete samlades LCI data in för varje material och utvärderades enligt tre DQI:er (Temporal representativitet, geografisk representativitet och dokumentation). Nya utsläppsfaktorer utvecklades baserat på utvärderingen och genom diskussioner inom projektgruppen. Framförallt för att säkerhetsställa att alla relevanta aktiviteter i de studerade livscyklerna är inkluderade. Konsekvenserna av implementeringen av utsläppsfaktorerna undersöktes genom en jämförelse av resultat som erhölls i WAMPS då de nya samt de tidigare faktorerna nyttjas. Detta gjordes både per ton material samt genom ett enkelt scenario.  Utvärderingen av den insamlade LCI datan påvisar att många av dataseten representerar genomsnittlig produktion inom Europa och att datan generellt var insamlad för minst 5 år sedan. Resultatet påvisar att dataseten är väldokumenterad enlig indikatorn som ställts upp i denna studie. Främst användes processer från EcoInvent för att utveckla de nya emissionsfaktorerna. Implementeringen av emissionsfaktorerna i WAMPS resulterade i signifikanta skillnader i potentiell miljöpåverkan per ton material, främst för bildning av fotooxid. För fallet med scenariot indikerade studiens resultat att en betydande förändring av den potentiella miljöbelastningen erhålls när de nya utsläppsfaktorerna implementeras. Dessutom påvisades en minskning av miljöeffekterna för alla kategorier varav eutrofiering visade den största absoluta skillnaden.  Slutligen anses de utvecklade emissions faktorerna vara lämpliga utifrån utformningen av denna tes. Dock dras slutsatsen att dessa har flertalet begränsningar som är viktiga att ta i hänsyn ifall dessa implementeras i WAMPS i framtiden. Dessutom anses det vara fastställt att en fortsatt uppdatering kan anses rimlig utifrån det erhållna resultatet.

Positron emission tomography (PET) allows the accurate quantitation of blood flow measurement non-invasively. Four mathematical methods of calculating blood flow from PET scan data of H215O bolus injections were implemented. No gold standard method for determining blood flow exists, so the accuracy and precision of estimates must be found using alternative methods. To this end a computer model of the scanner was used to study various effects on flow including the arterial time delay and dispersion, tissue inhomogeneity, incorrect partition coefficient estimation, scan duration and weighting functions. However, computer models do not adequately describe all of the physical problems. Physical models were therefore built and imaged in an analogous manner to patients. They highlighted some of the physical problems with data collection, including deadtime of both the arterial -detector and the PET scanner. Suitable correction procedures were developed and implemented. The physical models were used to determine the optimal scan duration. For the autoradiographic method, the optimal scan duration is 132 seconds and for the weighted methods, 264 seconds. The best weighting functions for the weighted methods were 1 and t . Sophisticated optimisation methods were unable to give consistent optimal weights. The estimates of flow for the physical models were typically within 5&'37 of the true values. When flows were calculated from patient data, the flow estimates fell as the scan duration increased. This was due to a blood volume component where the activity in the blood does not diffuse into the tissue spaces. The conclusion is that the single compartment tissue model enables blood flow to be estimated with an accuracy of about 10&'37, but for higher accuracy, the non-exchanging blood volume component must be considered.

Brown adipose tissue (BAT) is a unique organ in existence in mammals. It can induce non-shivering thermogenesis to control body temperature and energy balance through the expression of uncoupling protein 1 (UCP1). In our study, we aimed to evaluate the prevalence of BAT, as detected by fluorine 18-fluorodeoxyglucose (18F-FDG) positron emission tomography combined computer tomography (PET/CT), in a Hong Kong Chinese population. We also assessed the influence of age and sex to BAT in Hong Kong Chinese population. We also determined the factors associated with it, in particular, its relationship with overweight and other metabolic disorders such as diabetes mellitus. We analyzed 1765 consecutive 18F-FDG PET-CT scans of 1442 Chinese for the presence of BAT. Comparison of the variables between positive and negative BAT scans was performed using Student’s t-test. The association between maximum value of standardized uptake value (SUVmax) and variables were explored by Spearman correlation. The predictors of observed BAT were analyzed by multiple logistic regression to determine the significant predictors of positive BAT. The relationship between the monthly numbers of subjects with BAT and the respective mean monthly outdoor temperature was evaluated by Pearson’s correlation co-efficient. P < 0.05 was considered to be statistically significant. Brown adipose tissue was detected in 66 out of 1442 subjects (4.6%). BAT was significantly more commonly found in younger (43.7±13.5 years old vs. 61.4±14.2 years old, P<0.001) and female (59% vs. 46%, P<0.05) subjects. BAT also existed more frequently in subjects with lower body mass index (BMI) (21.2±3.1 kg/m2 vs. 22.4±3.7 kg/m2, P<0.01) and lower blood glucose level (5.9±0.9 mmol/L vs. 6.4±1.6 mmol/L, P<0.01). Also, BAT was detected only in subjects with no history of diabetes meallitus (DM) (0 vs. 10%, P<0.01). Moreover, lower outdoor temperature (21.6±4.6。C vs. 23.4±4.7。C, P<0.005) resulted in higher prevalence of detected BAT. In the multiple logistic regression test, age and mean monthly temperatures were the significant independent predictors of the presence of BAT (P< 0.001 and P=0.001). Age was also significantly correlated to SUVmax (P< 0.001). The monthly prevalence of positive BAT correlated negatively with mean monthly temperature by Pearson’s correlation (r = -0.79; P<0.01). To summarize, BAT was more commonly found in young, female subjects with lower BMI and blood glucose levels, and non-diabetes subjects. Age was the most important factor associated with the prevalence of BAT in humans. Lower outdoor temperature in winter can increase the prevalence of BAT even in Hong Kong’s sub-tropical climates. Also, there was an association of BAT with normal BMI (<=23) and lower blood sugar levels supporting the notion that BAT may potentially be a therapeutic target for obesity and diabetes.
published_or_final_version
Diagnostic Radiology
Master
Master of Philosophy

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2016.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 155-160).
Due to their advantages in higher fuel efficiency and torque compared to conventional port fuel injection (PFI) engines, direct injection spark ignition (DISI) engines have become dominant in gasoline-fueled engines. However, DISI engines have a significant drawback in particulate matter (PM) emission: the PM emission of DISI engines is at least an order of magnitude higher than that of PFI engines. The objective of this study is to investigate PM emission in DISI engines, mainly focusing on particulate number (PN) emission. The study aims to assess, respectively, the plausible PM formation mechanisms: non-fuel originated sources (e.g., lubricant), flame propagation in rich mixture and the pyrolysis of the vapor from liquid fuel film. Through a series of experiments, it has been found that non-fuel contribution is less important than the other two mechanisms. For all operating conditions, the absolute amount of the non-fuel contribution is much smaller than the total emission. In case of PM generated by flame propagation in rich mixture, there is a threshold air-fuel equivalence ratio below which PM starts to form rapidly. The threshold is influenced by the combustion temperature. PM starts to form at lower equivalence ratio when the combustion temperature was lower. Contrary to the PM generated from flame propagation in fuel-rich mixture case, that from the liquid fuel film is suppressed by lowering the combustion temperature. Transmission electron microscopy (TEM) imaging shows that the sizes of primary particles and agglomerated particles become larger as engine load increases, but particulates from different mechanisms have different morphology.
by Changhoon Oh.
Ph. D.

Welding is a metal joining process widely used in many manufacturing facilities around the world. It involves the process of heating the base and filler metals to a high temperature that leads to the formation of fumes. Welding emissions consist of gaseous pollutants and micron and sub-micron particles consisting of different heavy metals. Health risks associated with exposures to weld fume is well recognized in the literature. This research evaluates emissions and emission factors applicable to gas metal arc welding (GMAW) on AH 36 (mild steel) and 316 L (stainless steel). Emission factors evaluated consisted, total fume, chromium, cobalt, lead, manganese, and nickel. A weld fume chamber is used to capture the welding fumes onto a filter and then further analyzed to quantify the total fume and heavy metal emissions. Critical operating parameters such as current, voltage, shielding gas, welding speed, and contact tube to work distance (CTWD) were considered while evaluating emissions and emission factors. The parameters with greater influence on emissions are selected, and then the heavy metal emissions are quantified by varying those parameters using inductively coupled plasma atomic emission spectrometry (ICP-AES) and portable XRF (X-Ray Fluorescence) analyzer. The heavy metal results from the ICP-AES and XRF are compared to explore the feasibility of using XRF analyzer in quantifying the heavy metals in welding fumes. Using the heavy metal emissions, the lifetime carcinogenic and non-carcinogenic risks are evaluated for the GMAW process. The mild steel (MS) and stainless steel (SS) statistical analysis results indicate current and voltage are most influencing parameters in generating the fumes in GMAW. This research found a significant linear relationship between ICP-AES and XRF heavy metal results. The lifetime carcinogenic and non-carcinogenic risks results indicate high potential health risks if not properly managed.

Dissertação para obtenção do Grau de Mestre em Engenharia do Ambiente Perfil de Gestão de Sistemas Ambientais
Plants are emitting chemical-signals to the atmosphere in response to stress factors - Volatile Organic Compounds (VOCs). VOCs have higher influence on atmosphere chemistry: they are acting as photochemical precursors in tropospheric ozone formation. Present work studies VOCs emission released by rice (Oryza sativa L cv. Aríete) cycle in paddy fields, in aleatory schemes with three replicates, in two separate soil plots with different textures (silty clay and loamy sand), studying open field conditions and open top chambers (OTCs) under influence of treatments with induced abiotic stress (increase temperature and simultaneously temperature and CO2 atmospheric concentration enhancement). VOCs were extracted from plant by solid phase micro extraction (SPME) and stem distillation extraction (SDE), and analyzed by gas chromatography coupled to mass spectrometry (GC/MS) using two GC capillary columns with different polarities, one non-polar (DB-5) and other polar (DB-WAX). A total of 33 VOCs using a non-polar column and 22 VOCs using a polar column, in both set of results were identified the three main classes of compounds: green leaf volatiles (GLV), monoterpenes and sesquiterpenes. Between rice cycle VOCs vary their trend and on vegetative stage were observed more VOCs, followed by ripening and lesser on reproductive. Silty clay soil demonstrated higher amount of VOCs released if compared with loamy sand texture. Between OTCs, more compounds were released by increasing temperature than simultaneously temperature and CO2. In Intergovernmental Panel for Climate Change (IPCC) scenarios with emergent trend of increasing temperature and CO2 atmospheric concentration, two effects are inherent to rice VOCs emission, one negative with higher emission related with temperature and other positive with less emission associated CO2. Field data measurements addictions in air quality models will help achievements of realistic previsions and better understand the effect of climate change in air quality on a global scale.
Portuguese Foundation for Science and Technology; FCT-UNL and partners from INIAV and UTAD, on a project named PTDC/AGR-AAM/102529/2008

An increased awareness about the global warming has created a demand for more information on how the climate is affected by different activities.This master thesis was initiated by Tricorona, a Swedish company that offers its customers analysis and calculation of their climate impact. Tricorona also supplies climate neutralisation with CERs, in accordance with the Kyoto protocol and controlled by the UN. This work demands updated emission factors for greenhouse gases. An emission factor gives information about the greenhouse gasintensity of a service or a product [kg CO2-eq./ functional unit].The purpose of this thesis is to examine how electricity, district heating, hotels, taxis, food and materials affect the climate and how emission factors for these areas can be calculated.This was done by reviewing and comparing different studies and by interviewing experts. The information was evaluated and recommendations on calculations and emission factors were made.The consumption of energy is the main source of greenhouse gas emissions for district heating, electricity, hotels, taxis and materials. For food production the biogenic greenhousegas emissions are also important, such as the emissions of carbon dioxide and nitrous oxide from land use and the methane emissions from ruminants.For climate impact assessment of electricity, district heating, hotels and taxis it is recommended that the calculations should be based on an average consumption of energy. All types of energy carriers should be included in the calculations and the emission factors used should be based on Life Cycle Assessments. Climate impact assessments based on energy consumption is a simplification that underestimates the real greenhouse gas emissions. The recommended emission factors are associated with some uncertainties that originate from the quality of the data used, the assumptions made and the system boundaries that were chosen.Despite that, the recommended emission factors can be considered representative since they are based on the best available data. For food and materials it is recommended that emissionfactors from Life Cycle Inventories should be used.

BAMMI, SACHIN. Quantitative Analysis of Variability and Uncertainty in On-Road and Non-Road Mobile Source Emission Factors. (Under the direction of Dr. H Christopher Frey.) The goal of this research is to demonstrate a methodology for quantifying variability and uncertainty in mobile source emissions. Emission factors and emission estimates are subject to both variability and uncertainty. Variability in emissions deals with real differences in emissions among multiple emission sources at any given time or over time for any individual emission source. Variability is the heterogeneity of values of a quantity with respect time space or across a population. Uncertainty in emissions on the other hand implies the lack of knowledge regarding the true value of emissions. In this research variability and uncertainty are treated separately since their sources are different and as such they affect the decision making process in a different way. For example, sources of variability in mobile source emissions include: vehicle make; ambient temperature; vehicle model; fuel used; vehicle age; and/or driving behavior. Sources of uncertainty may include: small sample sizes; lack of precision and/or accuracy in measurements; non-representativeness; or lack of data. In this work a methodology for simultaneous characterization of variability and uncertainty in mobile source emission factors is described. Variability is characterized by fitting probability distributions to the data sets. Uncertainty due to random sampling error is characterized by using the parametric Bootstrap technique.This methodology is demonstrated for emission factors for three categories: (1) Onroad mobile source exhaust air toxic emissions (2) nonroad lawn and garden equipment emissions and (3) nonroad construction farm and industrial equipment emissions. For the first category a database of vehicular exhaust emissions developed by the California Air Resources Board (CARB) was used. For the second and third categories emission factor databases were developed by reviewing reports and/or technical papers from U.S. Environmental Protection Agency (EPA), Southwest Research Institute (SwRI), CARB and Society of Automotive Engineers (SAE).The main results regarding the demonstrated methodology and related statistical analysis in this research include: (1) emission factor groupings were determined statistically (e.g. by engine size for lawn and garden engines); (2) substantial inter-engine variability in emissions was discovered; and (3) large ranges of uncertainty in mean emissions were found in many cases. In particular, uncertainty ranges for the mean emission factors were in excess of ±20 percent in most cases and as high as minus 49 percent to plus 89 percent.

Vehicle type approval CO2 emission figures form the basis for many countries’ national policy to reduce transport's contribution to anthropogenic climate change. However, it has become increasingly apparent that the vehicle type approval testing procedure used in Europe is not fit for purpose. There is, therefore, a need for representative real world emission factors that can be used to inform consumers, aid policy makers and provide an accurate benchmark from which type approval figures can be compared. In this work, two methods are explored to assess their feasibility to provide robust CO2 emission figures. The first is on-road vehicle activity tracking, using data collected from the vehicle controller area network. This method was chosen as it has the potential to provide large quantities of cheap, reliable data and has been demonstrated by recording over 40 parameters during testing of a third-generation Toyota Prius. This data has been used to analyse the vehicle powertrain control and provide a clear understanding of the control mechanisms that balance the engine and electrical power systems, present a comparison of the emissions of conventional and hybrid taxis giving local policy makers the underlying evidence required to introduce strong policies to reduce urban emissions from taxis and build a microscale emission model for accurate and detailed emission forecasts. The second method is microscale vehicle modelling, defined as very short time step models (1 second or less) that capture vehicle and location specific details within the model. The model requires vehicle speed and road gradient data as input and outputs second-by-second cumulative and total fuel consumed and CO2 emissions. The model has been validated against independent data (chassis dynamometer data collected by Argonne National Laboratory) and is now a powerful tool to help assess the effects of local policies (geofences, changes in the speed limit, incentives for hybrid vehicle uptake) or schemes (eco-driving) on the CO2 emissions from hybrid vehicles. This work has further developed these two methods in two ways. Firstly, by demonstrating the accuracy of controller area network data collected in vehicle activity tracking. Secondly, by demonstrating the precision of emission models built using real-world data, despite the data noise caused by real world conditions. In conclusion, these methods are well suited to providing representative real world CO2 emission factors, especially if the methods are combined. This is because vehicle activity tracking can provide the large amount of data needed for vehicle modelling and a vehicle model can provide situation specific emission factors, which, in contrary to many current emissions factors, are not only dependent on vehicle average speeds.

The rapid industrialization, population growth, urbanization and economic and social development cause many environmental problems, such as climate change which is the result of the increase in the emission of greenhouse gases (GHGs) especially CO2. Combustion of fossil fuels, particularly from electricity generation, has the major responsibility for CO2 emissions. Decreasing the amount of CO2 emission requires a significant shift from our present energy use pattern toward one of lesser reliance on fossil fuels. Using renewable energy sources is one of the ways to supply some of the electricity demand reducing the associated GHG emissions and thus decreasing the adverse effects of climate change. In this study, generated electricity associated CO2 emissions and the specific CO2 emission factors are calculated based on IPCC methodology for each fuel type and each thermal power plant for Turkey between 2001 and 2008. The electricity demand of Turkey is estimated to increase about 7% annually till to 2019. Based on the planned power plant data obtained from EMRA, it was found that the total electricity supply (planned + existing) will not be sufficient to provide the estimated demand between 2011 and 2019. To overcome supply deficiency problem, four different scenarios are developed and the mitigation potential of CO2 emission from electricity generation based on these scenarios are examined. The results from these scenarios show that there is a significant decrease in the amount of CO2 emission from electricity generation. Renewable Energy Scenario which is the best scenario in terms of mitigation of CO2 emissions, provides to mitigation of 192 millions of CO2 emissions between 2009 and 2019. with respect to BAU scenario

Detta är en studie om klimatpåverkan i samband med anläggandet av järnvägsbroar i syfte att ta fram nyckeltal (moment, material, mängder) för att effektivt kunna reducera utsläppen av växthusgaser. Till grund för studien har vi arbetat med Trafikverkets verktyg klimatkalkyl 2.0. Det har granskats utifrån användarvänlighet och riktighet i indata och emissionsomräkningsfaktorer. Det för att se till skillnaden mellan modellen och ett unikt anläggningsprojekt, var skiljer sig Trafikverkets typvärden mot de projektspecifika förutsättningarna samt vilka blir dess konsekvenser? Studien har kommit fram till att utan viss försiktighet vid arbete i klimatkalkyl 2.0 finns risk för inkorrekta resultat. Dessutom har studien påvisat tvivelaktiga standardvärden för betydande poster. Utöver dessa resultat har studien konstaterat att de mest betydande delarna för det unika anläggningsprojektets utsläpp är reduktion av mängden stål och betong samt att hitta leverantörer som kan bevisa låga emissionsfaktorer. Med relativt enkla åtgärder skulle det unika anläggningsprojektets totala utsläpp av koldioxidekvivalenter minskas med nästan 20%.
This is a study on the climate impacts associated with the construction of railway bridges in order to develop key performance indicators such as operation, material and amounts to effectively reduce greenhouse gas emissions. The basis of the study has been work in Trafikverkets tool klimatkalkyl 2.0. It has been reviewed on the basis of ease of use and accuracy of input data and emission conversion factors. That’s because we wanted to see the difference between the model and a unique project. What was different and why? This study has concluded that without some care and work in klimatkalkyl 2.0 is a risk of incorrect results. In addition the study demonstrated questionable defaults for significant items. In addition to these results the study found that the most significant parts of the unique projects emissions is reducing the amount of steel and concrete and to find suppliers who can demonstrate low emission factors. With relatively simple measures could the unique projects total carbon emissions be reduced by almost 20%

Mineral dust aerosols can impact air quality, climate change, biological cycles, tropical cyclone development and flight operations due to reduced visibility. Dust emissions are primarily limited to the extensive arid regions of the world, yet can negatively impact local to global scales, and are extremely complex to model accurately. Within this dissertation, the Dust Entrainment And Deposition (DEAD) model was adapted to run, for the first known time, using high temporal (hourly) and spatial (0.3°x0.3°) resolution data to methodically interrogate the key parameters and factors influencing global dust emissions. The dependence of dust emissions on key parameters under various conditions has been quantified and it has been shown that dust emissions within DEAD are largely determined by wind speeds, vegetation extent, soil moisture and topographic depressions. Important findings were that grid degradation from 0.3ºx0.3º to 1ºx1º, 2ºx2.5º, and 4°x5° of key meteorological, soil, and surface input parameters greatly reduced emissions approximately 13% and 29% and 64% respectively, as a result of the loss of sub grid detail within these key parameters at coarse grids. After running high resolution DEAD emissions globally for 2 years, two severe dust emission cases were chosen for an in-depth investigation of the root causes of the events and evaluation of the 2°x2.5° Goddard Earth Observing System (GEOS)-Chem and 0.3°x0.3° DEAD model capabilities to simulate the events: one over South West Asia (SWA) in June 2008 and the other over the Middle East in July 2009. The 2 year lack of rain over SWA preceding June 2008 with a 43% decrease in mean rainfall, yielded less than normal plant growth, a 28% increase in Aerosol Optical Depth (AOD), and a 24% decrease in Meteorological Aerodrome Report (METAR) observed visibility (VSBY) compared to average years. GEOS-Chem captured the observed higher AOD over SWA in June 2008. More detailed comparisons of GEOS-Chem predicted AOD and visibility over SWA with those observed at surface stations and from satellites revealed overall success of the model, although substantial regional differences exist. Within the extended drought, the study area was zoomed into the Middle East (ME) for July 2009 where multi-grid DEAD dust emissions using hourly CFSR meteorological input were compared with observations. The high resolution input yielded the best spatial and temporal dust patterns compared with Defense Meteorological Satellite Program (DMSP), Moderate Resolution Imaging Spectroradiometer (MODIS) and METAR VSBY observations and definitively revealed Syria as a major dust source for the region. The coarse resolution dust emissions degraded or missed daily dust emissions entirely. This readily showed that the spatial scale degradation of the input data can significantly impair DEAD dust emissions and offers a strong argument for adapting higher resolution dust emission schemes into future global models for improvements of dust simulations.

Heavy duty on-road vehicles represent one of the largest sources of NO _x emissions and fuel consumption in North America. Heavy duty vehicles are predominantly fueled with diesel, with the recent interest in natural gas (NG) systems. As emissions and greenhouse gas regulations continue to tighten new opportunities for advanced fleet specific heavy duty vehicles are becoming available with improved fuel economy. NO_x emissions have dropped 90% for heavy duty vehicles with the recent 2010 certification limit. Additional NO_x reductions of another 90% are desired for the South Coast Air basin to meet its 2023 NO_x inventory requirements and the California optional low NO_x standard in 2015.

One of the difficulties in quantifying NO_x emissions at the levels proposed in this research (90% of the 2010 certification level ~ 0.02 g/bhp-hr) is the measurement methods are approaching their detection limit to sufficiently quantify NO_x emissions. Three upgraded NO _x measurement methods were considered which include a raw NO_x measurement integrated with real time exhaust flow, a real-time ambient correction approach, and a trace level ambient analyzer for accurate bag analysis. In summary the improved methods varied in their success where the raw sampling approach showed to be the most accurate and precise over the rage of conditions tested.

The ISL G NZ 8.9 liter NG engine met and exceeded the target NO _x emissions of 0.02 g/bhp-hr. This engine significantly reduced 97%–100% of NO_x emissions compared with previous ISL G 8.9 engines. The NO_x emissions decreased as the duty cycle was decreased which was the opposite trend for the diesel vehicles. It is expected NG vehicles could play a role in the reduction of the south coast NO_x inventory problem given their near zero emission factors demonstrated.

This study was aimed at understanding the environmental performance of two abrasives, coal slag and garnet which are commonly used by shipyards and many other industries in surface preparation of metallic surfaces. Environmental performance evaluated in this study included, (1) productivity (ft2/hr), (2) consumption and or used-abrasive generation rate (ton/2000 ft2; lb/ ft2), (3) particulate emission factors (mg/ft2; mg/lb; lb/lb; lb/kg; lb/ton). In order to achieve the study objectives, an emission test facility was built and necessary equipment and materials were procured. Blasting was performed on rusted steel panels inside the test facility and emissions were measured using EPA Source Test Method to quantify particulate emissions. By measuring the area cleaned, blasting time, and the abrasive consumed, environmental performance of coal slag and garnet was evaluated. Simple mathematical models were developed to predict performance based on feed rate and blast pressure. Garnet was observed to be more productive, less consuming, and more environmentally-friendly compared to coal slag. These study findings will valuable in reducing costs, improving productivity, and protecting the environment.

Right ventricular function (RV) is one of the most important predictors of prognosis in many cardiovascular disease states. Despite the significance of RV function to survival, there are no therapies that directly nor selectively improve RV function. As well, the basis for RV failure is poorly understood. This is particularly relevant for patients with pulmonary arterial hypertension (PAH), where RV failure in the setting of pressure overload is the leading cause of death. PAH will be introduced in the 2nd chapter of this thesis by comparing and refining contemporary mortality risk assessment strategies. I will then explore 1) RV neurohormonal function and, 2) RV energetics, two molecular pathways thought to be involved in the pathogenesis and progression of maladaptive RV failure. I employed small animal molecular imaging using positron emission tomography (PET) to non-invasively investigate these pathways. The PET imaging techniques employed in this thesis have the unique potential for translation to human studies, to further explore disease mechanisms.

Este trabalho teve como objetivo avaliar o impacto da mudança dos fatores de emissão veicular na formação de ozônio troposférico na Região Metropolitana de São Paulo (RMSP), Brasil, comparando os anos de 2004 e 2011. Essa avaliação foi realizada por meio de modelagem numérica com o modelo de qualidade do ar Weather Research and Forecasting with Chemistry (WRF-Chem), configurado sobre um domínio com 4 grades aninhadas: 27, 9, 3 e 1 km; e com o mecanismo químico considerado, o RADM2, acionado apenas nas grades de 3 e 1 km. Os inventários de emissão foram baseados em informações estimadas de número de veículos, fatores de emissão de compostos químicos e número médio de quilômetros percorridos por dia pelos distintos tipos de veículos considerados. Os períodos de estudo 06 a 09 de setembro de 2004 e 12 a 15 de novembro de 2011 foram selecionados, principalmente, por apresentarem episódios de altas concentrações de ozônio e pela existência de dados experimentais de determinação de fatores de emissão. Para avaliar a performance das simulações foram utilizados dados observados de temperatura, umidade relativa, vento, concentração de ozônio, óxidos de nitrogênio e monóxido de carbono das estações de qualidade do ar da rede de monitoramento da Companhia de Tecnologia de Saneamento Ambiental (CETESB). Os resultados mostraram que as configurações físicas e químicas estabelecidas no modelo conseguiram representar adequadamente os ciclos de formação do ozônio, no entanto, com defasagens e intensidades máximas menores, características relacionadas com o cálculo das distribuições espaço/temporal das emissões como também pelo transporte não só do ozônio, mas também de seus precursores desde regiões externas à RMSP. Por outro lado, dadas as características de emissão em 2004 e 2011, encontrou-se que a atmosfera da RMSP estava caracterizada por um regime COV-limitante naqueles anos, principalmente no ano 2004. Finalmente, o cenário de emissão para 2011 considerando os mesmos fatores de emissão de 2004 mostrou um grande impacto na formação do ozônio troposférico, considerando a grade de 1 km de espaçamento. Esse resultado foi 8 produto do estabelecimento de uma razão média COV/NOx mais eficiente em termos de formação de ozônio, apesar das emissões dos seus precursores ter diminuído em relação a 2004.
The objective of this work was to evaluate the impact of vehicular emission factors change on tropospheric ozone formation in the Metropolitan Area of São Paulo (MASP), Brazil for 2004 and 2011. Weather Research and Forecasting with Chemistry (WRF-Chem) model was used as the photochemical modeling tool. WRF-Chem was set up to run with four nested grid cells: 27, 9, 3 and 1 km. The Regional Acid Deposition Model (RADM) version 2 was the chemical mechanism considered, turned it on barely in 3 and 1 km grid cells. The emission inventories were based on the estimated information of number of vehicles, emission factors and average driving kilometers for vehicle per day. The study periods September 06-09, 2004 and November 12-15, 2011 were chosen due to the high ozone concentrations observed, and the experimental data available for these periods. Observation of temperature, relative humidity, winds, and O3, CO and NOx concentrations from the air quality monitoring network of Companhia de Tecnologia de Saneamento Ambiental do Estado de São Paulo (CETESB) were used to evaluate WRF-Chem simulations performance. The results showed that the chemical and physics configurations in WRF-Chem represented adequately the ozone formation cycles; however, with mismatches and maximum concentrations lower than observations, characteristics related with the estimative of the spatial and temporal distributions of the emissions as well as by the transportation of ozone and its precursors from external regions to MASP. On the other hand, given the characteristics of emission in 2004 and 2011, we found that MASP was under a strong COV-limited regime, principally in 2004. Finally, the scenario considering the emission factor of 2004 valid for 2011 in MASP showed a great impact in tropospheric ozone formation with high concentrations calculated for 2011 considering 1 km grid cell (with the most realistic vehicular activity), as result of a more efficient COV/NOx ratio calculation in terms of ozone formation.

Brazil is one of the world\'s largest producers and exporters of soybeans. The oil and meal obtained from grains are important components of biodiesel and animal feed chains. In recent years, international standards and certifications were developed to promote sustainability in the agricultural supply chain. In this context, greenhouse gases (GHG) emissions in the products life cycle has been the main point of interest to the scientific community and consumers. Few studies have evaluated the GHG emissions in soybean cultivation with specific data for the Brazilian reality. The aim of this study was to evaluate the main sources of GHG in soybean production in the State of Mato Grosso, Brazil. We evaluated 55 farms in the crop years of 2007/08, 2008/09 and 2009/10, accounting for 180,000 hectares of soybean cultivation area and totaling 114 individual situations. The results indicated that the largest source of GHG in the soybean production is the decomposition of crop residues (36%), followed by fuel use (19%), fertilizer application (16%), liming (13%), pesticides (7%), seeds (8%) and electricity consumed at the farms (<1%). The average GHG emissions considering the three crop years were 0.186 kg of CO2eq kg-1 of soybean produced. Based on these results, field experiments were conducted to quantify N2O emissions from the decomposition of soybean crop residues in different climatic regions and harvest periods in Brazil. Our results show that, in field conditions, the contribution of N2O emissions from senesced and desiccated residues that remain on field after soybean harvest are unlikely to represent a significant source of N2O loss above normal background soil emissions. These results were also supported by the laboratory incubation experiment, indicating that the IPCC methodology for estimating N2O emissions from soybean crop residues may provide overestimations for the Brazilian conditions. The results of this study provide relevant and specific information to producers, industry and scientific community regarding the environmental impacts associated with soybean production in Brazil
O Brasil é um dos maiores produtores e exportadores mundiais de soja. O óleo e farelo obtidos dos grãos são componentes importantes das cadeias do biodiesel e ração animal. Nos últimos anos, normas e certificações internacionais foram desenvolvidas para promover a sustentabilidade na cadeia de produção agrícola. Nesse contexto, as emissões de gases de efeito estufa (GEE) no ciclo de vida dos produtos tem sido o principal ponto de interesse para a comunidade científica e consumidores. Poucos estudos avaliaram as emissões de GEE no cultivo da soja com dados específicos para a realidade brasileira. O objetivo deste estudo foi determinar as principais fontes de GEE na produção de soja em Mato Grosso, principal estado produtor brasileiro. Foram coletados dados de 55 fazendas nos anos-safra de 2007/08, 2008/09 e 2009/10, totalizando 114 avaliações. Os resultados indicaram que a maior fonte de GEE na produção de soja é a decomposição de resíduos culturais (36%), seguido pelo uso de combustível (19%), aplicação de fertilizantes (16%), calagem (13%), pesticidas (7%), sementes (8%) e eletricidade consumida nas fazendas (<1%). A emissão média considerando os três anos-safra avaliados foi 0,186 kg de CO2eq kg-1 de soja produzido. Com base nesses resultados, foram desenvolvidos experimentos em campo para quantificação das emissões de N2O proveniente da decomposição dos resíduos culturais da soja em diferentes regiões climáticas e períodos de colheita no Brasil. Adicionalmente, foram realizadas incubações em laboratório com materiais de soja em diferentes estágios de desenvolvimento. Os resultados indicaram que resíduos culturais de soja que permanecem no campo após a colheita não representam uma fonte significativa de N2O. Os resultados obtidos neste estudo fornecem informações relevantes para produtores, indústria e comunidade científica quanto aos impactos ambientais associados à cultura da soja no Brasil

Grade 2 gliomas are malignant brain tumours affecting otherwise healthy adults. Although the long-term prognosis is poor, many patients are well and may have a high quality of life for several years. There is, however, a large variability in the natural course of the disease which makes it essential to identify patients who might benefit from early surgery or radio-therapy. The aim of the present thesis was to define new and clinically useful prognostic markers that may assist in the initial treatment decision and in patient follow-up.

A retrospective study of 189 patients with gliomas WHO grade 2 showed no advantage in survival of early tumour resection or radiotherapy, and confirmed that histological subtype and patient age are the most important predictors of survival (I). In 89 patients, the pre-treatment uptake of 11C-methionine (MET) measured with positron emission tomography (PET) was identified as a prognostic marker for survival (II). At the time of tumour progression, irradiated tumours demonstrated signs of a residual radiotherapeutic effect that correlated with the pre-treatment uptake of MET (III). Pre-treatment uptake of MET may, therefore, be important both in predicting the natural course of the disease and the response after treatment. Immunohistochemical staining of 40 tumour samples showed an inverse association between the number of tumour cells expressing platelet-derived growth factor alpha receptor (PDGFRa) and survival (IV). Also, a reduction was observed in the number of receptor-positive cells after malignant transformation, supporting the prognostic value of PDGFRa.

Lumbar puncture was performed in eight patients with newly diagnosed low-grade gliomas to identify three important growth factors in tumour development. Neither PDGF nor vascular endothelial growth factor (VEGF) were detected in the cerebrospinal fluid (CSF), and fibroblast growth factor 2 (FGF-2) was measurable at extremely low concentrations in two of the patients (V). A proteome screening of the CSF, using two-dimensional gel electrophoresis and mass spectrometry, detected alpha 2-HS glycoprotein at significantly higher concentrations than in a control group (VI). This glycoprotein emerges as a novel substance in glioma research and may be of great interest because of its suggested involvement in the embryonic development of the neocortex.

This research developed an Unmanned Aerial Vehicle System for atmospheric pollution assessment, contributing new methodology and knowledge to the fields of air quality, human health and human exposure. This system was tested, validated and employed to characterize gaseous and particle pollutant concentration generated by traffic from a motorway in open space within the atmospheric column, and emitted from a ship while operating at sea, to develop ship emission factors. It allows measurements of air pollution under conditions where sampling with the existing techniques is not feasible or poses too high risk.

The growing consensus among scientists and governments on the need for immediate action to avoid the dangerous impacts of climate change has resulted in many industries starting to prepare for a carbon-constrained world, in order to analyse the effectiveness of industry response, this research has developed a theoretical framework to categorise corporate strategies on climate change in developing and industrialized countries. The framework classifies the corporate response into four sets of strategies based on their operational and management activities. The empirical data was collected from 180 companies trough a questionnaire survey in Pakistan and the UK. Twenty-four interviews with representatives from industries and other stakeholder groups were also conducted to triangulate and complement the survey results. An analysis of the empirical data indicates that corporate responses towards climate change can be characterized in four categories: indifferent, beginner, emerging and active which validates the theoretical framework. The research found that business responses to this international challenge depend on national policies, economic, social, and technological related factors. However, the strength and content of these factors varies between industrialized and developing countries, where corporate environmentalism is a relatively new phenomenon. For Pakistan, the findings suggest that, in the absence of regulatory and societal pressure, the only effective incentive for organizations is cost-savings tlirough energy efficiency projects. However, their response is shaped by the prevalence of obstacles and a lack of external pressure that prevent a different picture to emerge. The situation is different for the UK. Due to regulatory pressure, UK firms are actively involved in GHG management activities. However, climate policies concerning industries for instance, EU ETS, do not provide sufficient incentives to companies to change from 'business as usual' because of its short-term outlook, uncertainty, complexity and the generous allocation of allowances, hence very low carbon price.

Les incendies de végétation sont caractérisés par de nombreuses échelles de temps et d’espace. Une approche multi-physique et multi-échelle est donc nécessaire pour aborder la complexité de ces phénomènes. Ce travail de thèse est une contribution expérimentale à l’étude des effets d’échelle et du système sur la dynamique de combustion des végétaux et les fumées émises. Notre objectif principal a été de déterminer quels protocoles expérimentaux et plus particulièrement quelles échelles permettent de caractériser au mieux la combustion des végétaux en laboratoire. Nous avons ainsi étudié le comportement au feu des aiguilles de deux espèces de pin représentatives de l’écosystème méditerranéen, Pinus pinaster et Pinus laricio. Les litières d’aiguilles de pin représentent un enjeu important car elles entretiennent la propagation des incendies et elles participent à la transition d’un feu de surface à un feu total. Trois configurations expérimentales ont été étudiées au cours de cette thèse, l’échelle du cône calorimètre, l’échelle du grand calorimètre ou LSHR (permettant la combustion statique de masses plus importantes que le cône) et enfin, la propagation dans le LSHR permettant d’étudier l’effet du système sur la dynamique de la combustion et sur la production des fumées. Pour comparer ces trois configurations les protocoles expérimentaux ont été adaptés tout en maintenant la charge de combustible. Différents paramètres ont été étudiés pour analyser la dynamique de combustion tels que l’efficacité de la combustion, l’énergie dégagée ou encore la vitesse de perte de masse. La production des fumées a été étudiée par la mesure du coefficient d’extinction qui caractérise leur opacité et permet d’obtenir le facteur d’émission des suies. Les facteurs d’émissions des principaux composés émis lors de la combustion de ces deux types d’aiguilles de pin ont été mesurés en continu à partir d’un analyseur Infrarouge à Transformée de Fourier et d’un analyseur Infrarouge Non Dispersif. Des analyses par chromatographie en phase gazeuse couplée à un détecteur à ionisation de flamme et un spectromètre de masse nous ont permis de compléter ces mesures. Un bilan massique de carbone a également été réalisé afin de quantifier le carbone total mesuré dans nos analyses. Les principales contributions de notre travail sont les suivantes : l’étude du comportement au feu des aiguilles de P. pinaster a révélé des différences importantes pour la puissance dégagée aux échelles du cône calorimètre et du LSHR. En revanche, le système de combustion (propagation) n’influence pas cette grandeur. L’efficacité de la combustion est apparue peu dépendante de l’échelle et du système de combustion. Nous avons observé une influence de l’échelle de combustion sur la production totale des fumées (RSR) et sur le facteur d’émission des suies. Nous avons également montré que le système de combustion (la propagation) influence la dynamique et la valeur des facteurs d’émission de dioxyde et de monoxyde de carbone, composés majoritairement émis par ces combustions. Une influence de l’échelle et du système est également à noter sur les facteurs d’émissions des composés azotés et des COV émis pour les trois configurations expérimentales. Nous avons attribué les différences observées aux valeurs de températures des fumées. Enfin, une influence de la géométrie des particules a été mise en évidence par comparaison des combustions réalisées avec le cône calorimètre et le LSHR pour les deux types d’aiguilles de pin. La dynamique de combustion des aiguilles de Pinus laricio est moins affectée par le changement d’échelle que celle des aiguilles de Pinus pinaster (plus faible variation de la puissance de combustion). Nous avons également observé que les aiguilles de Pinus laricio, thermiquement plus fines que les aiguilles de Pinus pinaster présentent une valeur plus faible pour le facteur d’émission des suies
Wildfires are characterized by a lot of scales of time and space. A multi-physics and multi-scale approach is required to consider the complexity of these phenomena. This thesis is an experimental contribution to the study of the scale effects and the effects of the system on the combustion dynamics of forest fuels and smoke emission. The aim of this work was to determine which experimental protocols and specifically which scales can be used to characterize the combustion of vegetal fuels in the laboratory. The reaction to fire of pine needles species representative of the Mediterranean ecosystem, (Pinus pinaster and Pinus laricio) has been studied. Litters of pine needles are an important issue because they sustain fire spread and are involved in the transition from a surface fire to a total fire.Three experimental configurations were studied in this thesis: the cone calorimeter scale; the large scale calorimeter or LSHR (allowing static combustion with larger masses than used with the cone); a fire spread in the LSHR, allowing to study the effect of the system on the dynamics of combustion and release of smoke. To compare these configurations, experimental protocols have been elaborated while keeping the same fuel load. Different parameters were studied to analyze the combustion dynamics such as combustion efficiency, heat released rate and mass loss rate. Smoke production was studied by measuring the coefficient of extinction to characterize their opacity and an estimation of the soot emission factor was derived. The emission factors of the main compounds emitted during the combustion of these two pines needles were measured with a Fourier Transform Infrared analyzer and a Non-dispersive infrared analyzer. Analysis by gas chromatography coupled with a flame ionization detector and a mass spectrometer allowed us to complete these measurements. A mass balance of carbon was also performed to quantify the total carbon measured through our analyzes.The main contributions of our work can be summarized as follow: the study of the burning of Pinus pinaster needles reveals significant differences for heat release rate (HRR) at both cone calorimeter and LSHR scales. However, the combustion system (fire spread) does not influence the HRR value at the LSHR scale. The combustion efficiency appeared to be independent with regard to the scale and the system. We observed a wide influence on the rate of smoke release and the emission factor of soot. We also shown that the combustion system (fire spread) influences the dynamics and value of emissions factors of carbon dioxide and carbon monoxide (major compound emitted for these combustions). An influence of the three experimental configurations on the emission factors of nitrogen compounds and VOC emissions was also noted. This difference was attributed to the level of smoke temperature. Finally, an effect of particles geometry was also pointed out by the comparison between the burnings performed with the cone calorimeter and the LSHR for both types of pine needles. The combustion dynamics of Pinus laricio needles was slighlty affected by changing scale in comparison to needles of Pinus pinaster (weak variation of HRR). We also observed that Pinus laricio’s needles, which are thermally thiner than Pinus pinaster ones have the lowest soot emission factor