Anthropogenic aerosol emissions lead to an increase in the amount of cloud condensation nuclei and consequently an increase in cloud droplet number concentration and cloud albedo. The corresponding negative radiative forcing due to aerosol cloud interactions (RFaci) is one of the most uncertain radiative forcing terms as reported in the 5th Assessment Report of the Intergovernmental Panel on Climate Change (IPCC). Here we show that previous observation-based studies underestimate aerosol-cloud interactions because they used measurements of aerosol optical properties that are not directly related to cloud formation and are hampered by measurement uncertainties. We have overcome this problem by the use of new polarimetric satellite retrievals of the relevant aerosol properties (aerosol number, size, shape). The resulting estimate of RFaci = −1.14 Wm 2 (range between −0.84 and −1.72 Wm 2) is more than a factor 2 stronger than the IPCC estimate that includes also other aerosol induced changes in cloud properties.

The efficiency of an internal combustion engine is highly dependent on the peak pressure at which the engine operates. A new compound engine concept, the double compression expansion engine (DCEE), utilizes a two-stage compression and expansion cycle to reach ultrahigh efficiencies. This engine takes advantage of its high-integrity structure, which is adapted to high pressures, and the peak motored pressure reaches up to 300 bar. However, this makes the use of conventional combustion cycles, such as the Seiliger–Sabathe (mixed) or Otto (isochoric) cycles, not feasible as they involve a further pressure rise due to combustion. This study investigates the concept of isobaric combustion at relatively high peak pressures and compares this concept with traditional diesel combustion cycles in terms of efficiency and emissions. Multiple consecutive injections through a single injector are used for controlling the heat release rate profile to achieve isobaric heat addition. In this study, the intake pressure is varied to enable a comparison between the isobaric cases with different peak pressures, up to 150 bar, and the mixed cycle cases. Tests are performed at several different levels of EGR. The experiments are performed on a 12.8 L displacement 6-cylinder Volvo D13C500 engine utilizing a single cylinder with a standard 17-compression-ratio piston. In this study, the cylinder represents the high-pressure unit of the DCEE. The fuel used in all the experiments is a standard EU diesel. In each target condition, the different injection strategies are compared with the total amount of fuel kept relatively constant. The results prove that the isobaric combustion concept is feasible with a traditional injection system and can achieve gross indicated efficiencies close to or higher than those of a conventional diesel combustion cycle. Moreover, the results show that with an isobaric cycle, heat transfer losses can be reduced by over 20%. However, the exhaust energy is higher, which can eventually be recovered in the second stage of expansion. Thus, this cycle could be suitable for the DCEE concept. The CO, UHC and soot emission levels are proven to be fairly similar to those of the conventional diesel combustion. However, the NOx emissions are significantly lower for the isobaric combustion.

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, in fulfilment of requirements for the degree of Master of Science. October 2014. / Domestic fuel burning activities have become a major source of urban air pollution. Studies have indicated that domestic burning activities, specifically in low-income settlements and townships, contribute greatly to the air quality problems experienced by most developing urban centres. Low-income households that exist within townships in South Africa, house a large portion of the South African population. These households burn vast quantities of coal, wood, paraffin as well as other substances in order to provide for their energy needs. Pollution emitted as a result of domestic burning activities is estimated to be one of the leading causes of respiratory illnesses, prevalent in inhabitants of low-income settlements. To better understand the relationship that exists between domestic burning and the resultant pollutants, a method of quantifying these pollutants has been developed for a completely un-electrified settlement, near Johannesburg, using the quantities and type of fuel consumed. A study, carried out in Zenzele during the winter months, in addition to a month before and a month after this period, allowed for the analysis of some of the more harmful winter fuels. Common fuel types consumed were identified through the analysis of census data and information gathered from questionnaires. In un-electrified households, paraffin and liquid petroleum gas (LPG), used specifically for cooking and lighting, are the most commonly used fuel types during the warmer months. During the colder months, however, residents of households in low-income settlements prefer to use solid fuels such as wood and coal. Factors such as seasonality, the availability and price of fuels as well as cultural aspects all have a bearing on residents’ fuel choices and the quantity consumed. Emissions were quantified based on the quantities of wood and coal burnt in 15 households in Zenzele, using emission factors for SO2, PM10, CO2 and CO. As the temperature declines, the rate at which these solid fuels are consumed increases. The most significant observations identified in this study are the diurnal and seasonal trends associated with domestic burning.

Das Prostatakarzinom (PCa) stellt derzeit in Deutschland die häufigste Krebserkrankung der männlichen Bevölkerung dar und steht bei den tödlich verlaufenden Malignomen an zweiter Stelle. Aktuell umfasst die Diagnostik immer öfter auch eine molekulare Bildgebung mittels PET/CT und den Tracern [18F]Cholin und [68Ga]PSMA. Letzterer detektiert selektiv das prostataspezifische Membranantigen (PSMA), welches in Prostatakarzinomzellen häufig überexprimiert ist. Das Wachstum von PCa geschieht in der Regel androgenabhängig, wobei sich auch teilweise eine androgenunabhängige Entwicklung findet. Für das bei kastrationsresistenten Karzinomen und fortgeschrittenen Stadien eingesetzte Chemotherapeutikum Docetaxel, werden immer wieder Resistenzentwicklungen beobachtet, wodurch dieses nur unzureichend effektiv ist. Ziel dieser Arbeit war es, die Eignung verschiedener PET-Tracer ([18F]FDG, [18F]Cholin und [68Ga]PSMA) zur Bildgebung androgenabhängiger und -unabhängiger Prostatakarzinomzellen zu testen sowie ihr Potential zur Beurteilung des Therapieansprechens auf Docetaxel zu untersuchen. Weiterhin sollte untersucht werden, ob die [68Ga]PSMA-Retention mit der PSMA-Expression korreliert. Im zweiten Teil wurde ein Zusammenhang zwischen der Expression von PSMA und der Resistenzentwicklung gegen Docetaxel untersucht. Methoden: Für die in-vitro Experimente wurden die hormonabhängige Zelllinie LNCaP sowie die hormonunabhängige Zelllinie LNCaP C4-2 verwendet. Im zweiten Teil wurden zusätzlich PSMA-negative PC-3 Zellen eingesetzt. Die aufgenommene bzw. gebundene Traceraktivität wurde mittels Gammacounter gemessen. Die Untersuchung der PSMA-Expression erfolgte mit Western-Blot und Durchflusszytometrie. Ein PSMA-Knockdown-System wurde mittels siRNA in LNCaP-Zellen etabliert. Ergebnisse: Die PSMA-Expression und die Sensitivität gegenüber Docetaxel waren bei LNCaP Zellen tendenziell erhöht gegenüber der LNCaP C4-2 Zelllinie. Nach Docetaxelbehandlung zeigte sich in beiden Zellreihen eine unveränderte PSMA-Expression. Der PSMA-spezifische PET-Tracer zeigte, im Vergleich zu den metabolischen Tracern [18F]FDG und [18F]Cholin, eine nur sehr geringe Retention. Im Vergleich der Zelllinien untereinander nahmen LNCaP C4-2 Zellen ca. 50 % mehr [18F]FDG auf als LNCaP Zellen. Die Aufnahme von [18F]Cholin unterschied sich nicht signifikant. Der Tracer [68Ga]PSMA zeigte eine höhere Bindung an LNCaP Zellen im Vergleich zu LNCaP C4-2 Zellen. In weiteren Versuchen konnte gezeigt werden, dass sowohl [18F]FDG als auch [18F]Cholin, nicht jedoch [68Ga]PSMA in vitro ein Therapieansprechen auf Docetaxel durch verminderte Traceraufnahme in beiden Zelllinien aufzeigen. Es konnte zudem eine direkte Korrelation zwischen der [68Ga]PSMA-Bindung und der PSMA-Expression nachgewiesen werden. Nach einer siRNA-vermittelten Verminderung der PSMA-Expression in LNCaP Zellen (Knockdown-Zellen) zeigte sich eine deutlich geringere Sensitivität für Docetaxel. Gleichzeitig war jedoch die Docetaxelsensitivität von PSMA-negativen PC-3 Zellen höher als die von LNCaP Knockdown-Zellen. Schlussfolgerung: Insgesamt zeigten unsere Untersuchungen, dass sich die PET-Tracer [18F]FDG und [68Ga]PSMA zur Unterscheidung des androgenabhängigen Zellmodells vom androgenunabhängigen Modell eignen. Außerdem ermöglicht der [68Ga]PSMA-Tracer eine Einschätzung der PSMA-Expression. Die Tracer [18F]FDG und [18F]Cholin eignen sich in vitro für die Beurteilung des Therapieansprechens einer Docetaxeltherapie, [68Ga]PSMA dagegen nicht. Die PSMA-Expression scheint ein entscheidender, aber nicht alleinstehender Faktor für die Sensitivität von LNCaP Zellen gegenüber Docetaxel zu sein. Es scheinen hierbei allerdings eher der Verlust von PSMA, wie im Knockdown-Modell induziert, sowie bislang unbekannte Faktoren eine wichtige Rolle zu spielen. / Prostate carcinoma (PCa) is currently the most frequent cancer in men in Germany and is the second leading cause of cancer deaths. Currently, diagnostics more and more often include molecular imaging using PET/CT and the tracers [18F]choline and [68Ga]PSMA. The latter selectively detects the prostate-specific membrane antigen (PSMA), which is often overexpressed in prostate cancer cells. The growth of PCa is usually androgen-dependent, although it is sometimes also developing independently of androgen. For the chemotherapeutic agent docetaxel, which is used for castration-resistant carcinomas and advanced stages, the development of resistance is observed again and again, resulting in insufficient efficacy. The aim of this work was to evaluate the potential of different PET tracers ([18F]FDG, [18F]Choline and [68Ga]PSMA) for the imaging of androgen-dependent and independent prostate carcinoma cells as well as their potential for the assessment of therapy response to docetaxel. Furthermore, it should be investigated whether [68Ga]PSMA uptake correlates with PSMA expression. In the second part, an association between the expression of PSMA and the development of resistance to docetaxel was investigated. Methods: For the in vitro experiments the hormone-dependent cell line LNCaP and the hormone-independent cell line LNCaP C4-2 were used. In the second part PSMA-negative PC-3 cells were additionally used. The tracer uptake and binding activity was measured by gamma counter. PSMA expression was determined by Western blot and flow cytometry. A PSMA knockdown system was established in LNCaP cells using siRNA. Results: PSMA expression and sensitivity to docetaxel were increased in LNCaP cells compared to the LNCaP C4-2 cells. After docetaxel treatment, both cell lines showed unchanged PSMA expression. Compared to the metabolic tracers [18F]FDG and [18F]choline, the PSMA-specific PET tracer showed very low uptake. In comparison of the cell lines, LNCaP C4-2 cells took up about 50 % more [18F]FDG than LNCaP cells. The uptake of [18F]choline did not differ significantly. The tracer [68Ga]PSMA showed a higher binding to LNCaP cells compared to LNCaP C4-2 cells. In further experiments it was observed that both [18F]FDG and [18F]choline, but not [68Ga]PSMA, in vitro showed a therapy response to docetaxel by reduced tracer uptake in both cell lines. A direct correlation between [68Ga]PSMA binding and PSMA expression was also found. After a siRNA-mediated reduction of PSMA expression in LNCaP cells (knockdown cells), a significantly lower sensitivity for docetaxel was observed. At the same time, however, the docetaxel sensitivity of PSMA-negative PC-3 cells was higher than that of LNCaP knockdown cells. Conclusion: Overall, our investigations showed that the PET tracers [18F]FDG and [68Ga]PSMA are suitable for differentiating the androgen-dependent cell model from the androgen-independent model. In addition, the [68Ga]PSMA tracer allows an assessment of PSMA expression. The tracers [18F]FDG and [18F]choline are suitable for in vitro assessment of response to docetaxel therapy, whereas [68Ga]PSMA is not. PSMA expression seems to be a critical, but not unique, factor for the sensitivity of LNCaP cells to docetaxel. However, the loss of PSMA, as induced in the knockdown model, as well as unknown factors seem to play an important role.

The addition of Tier 2 standards by United States Environmental Protection Agency (EPA) has increased focus on light-duty vehicle emissions. In this study, a diesel-electric hybrid vehicle was used for testing under the Challenge X program. The diesel engine was powered by a 20% soy-based biodiesel - 80% diesel blend, and the electric motor received its energy from a 330 volt Nickle Metal Hydride battery pack. The diesel engine, notorious for high emissions of nitrogen oxides (NOx) and particulate matter (PM), requires aftertreatment of these emissions to achieve Tier 2 EPA compliance. The primary focus of this thesis is use of a urea injection selective catalytic reduction (SCR) system to reduce NOx emissions. Also, a diesel particulate filter (DPF) was employed for PM reduction purposes. Significant decreases in both NOx and PM emissions were achieved.

Stringent government mandates for the fuel economy and emissions of light-duty consumer vehicles have forced manufacturers to focus on improvements in these areas. Increased consumer pressure has also shifted the automobile market towards higher efficiency vehicles. This study investigates the use of intelligent engine peripheral control to improve fuel efficiency and reduce vehicle emissions. The conventional automotive alternator control strategy contributes to higher overall vehicle losses and increased fuel consumption through indiscriminate loading of the engine. The improved method focuses on the selective reduction of engine loading and the recapture of vehicle energy during braking using intelligent control of the alternator system. The concept was demonstrated on the Mississippi State University Challenge X hybrid vehicle. The fuel economy and NOx emissions of the vehicle were improved by 6.6% and 10.5% respectively over the drive cycle developed by the 2006 Mississippi State University Challenge X team to evaluate emissions.

No description available.

No description available.

Atmospheric pollution resulting from an open-cast coal mine situated 10 km southwest of Witbank (Mpumalanga, South Africa) was investigated during summer and winter 2004. Industrial and urban activities in and around Witbank release large amounts of toxic and criteria pollutants into the atmosphere. Spontaneous combustion from the many collieries in the Witbank area contributes to this problem. Direct, automated, and continuous in situ measurements of trace gas concentrations and prevailing meteorological parameters were carried out by a mobile monitoring unit and an automatic weather station. The data collected show that spontaneous combustion is a source of CO, NO, SO2 and H2S. Summer daily averages of SO2, NO, NO2 and O3 concentrations ranged between 1 and 18 ppb, 0.3 and 40 ppb, 12 and 75 ppb and 0.9 and 19 ppb respectively. Winter daily concentrations of SO2 and O3 were much higher, ranging between 15 and 180 ppb and 14 and 30 ppb respectively. NO and NO2, in contrast, were lower in winter (0.8 to 15 ppb and 2 to 28 ppb for daily means). Winter daily average concentrations of H2S, CO and CO2 ranged between 16 and 217 ppb, 2100 and 5100 ppb and 322 and 436 ppm). Synoptic circulations over the Highveld were found to affect pollutant concentrations. During winter, temperature inversions played a significant role in increasing the pollutant concentrations in the early morning hours until about 10:00. Although considerable amounts of NO, NO2 and O3 were captured; their concentrations were within the South African Department of Environmental Affairs and Tourism’s permissible levels as contained in the National Environmental Management: Air Quality Act (2004). SO2 concentrations during winter 2004 exceeded the allowed standards. Elevated concentrations of pollutants were mostly observed when the wind blew from the SE, SSE, S and WSW directions, implicating the 2A south pits of the open-cast mine investigated as the major source of the emissions.

Biomass fast pyrolysis liquid (bio-oil) is a cellulose based alternative fuel with the potential to displace fossil fuels in stationary heat and power applications. To better understand the combustion behavior and emissions of bio-oil, a 10 kW spray burner was designed and constructed. The effect of swirl, atomization quality, ignition source (pilot) energy, air/fuel preheat and equivalence ratio on the stability and emissions of bio-oil spray flames was investigated. A blend of 80% pyrolysis liquid and 20% ethanol by volume was used during the tests and the results were compared to burner operation with diesel. It is important to have good atomization, thorough mixing and high swirl in order to stabilize ignition, promote the burnout of bio-oil and decrease CO, hydrocarbon and particulate matter emissions. The total amount of primary air and atomizing air that can be used to improve turbulence, mixing, droplet burnout and overall combustion quality is limited by the distillable fraction and narrow lean blow-out limit associated with pyrolysis liquid. Air and fuel preheat are important for reducing hydrocarbon and CO emissions, although subsequent fuel boiling should be avoided in order to maintain flame stability. The NOx produced in bio-oil flames is dominated by the conversion of fuel bound nitrogen. The particulate matter collected during bio-oil combustion is composed of both carbonaceous cenosphere residues and ash. Under good burning conditions, the majority consists of ash. Pilot flame energy and air/fuel preheat have a weak effect on the total particulate matter in the exhaust. Generally, these results suggest that available burner parameters can be adjusted in order to achieve low hydrocarbon, CO and carbonaceous particulate matter emissions when using pyrolysis liquid. Total particulates can be further mitigated by reducing the inherent ash content in bio-oil. Comparative burner tests with diesel reveal much lower emissions for this fuel at most of the operating points considered. This is due to the fully distillable nature, better atomization and improved spray ignition characteristics associated with diesel. Because of its superior volatility, diesel can also operate over a much wider range of primary air and atomizing air flow rates compared to bio-oil.