Master of Science

thesisAerosol particulates are one of a variety of products generated by coal combustion. The objectives of this study were to elucidate ash particulate formation during oxy-fuel pulverized coal combustion compared to O2/N2 combustion. Oxy-fuel coal combustion conditions provide exhaust gas with a high concentration of CO2 versus CO2/N2 due to the recycled flue gas. Understanding fine particle formation is important for predicting emissions and understanding potential deposition. The hypothesis for CO2 affect the particulate formation is that this high CO2 concentration reduces the vaporization of refractory oxides from combustion according to the reaction: MOn(s) + CO(g) CO2(g) +MOn-1(g). This research experimentally investigated particulate formation in a laboratory laminar flow drop tube furnace with well controlled combustion conditions under different flue gas scenarios. Ash particulate formation has been studied as a function of temperature, coal type, and gas phase conditions, namely, CO2 versus N2. Two bituminous coals, Utah Skyline and Illinois #6, and one sub-bituminous coal, Powder River Basin (PRB) black thunder were reported. During the experiments, the furnace temperature was set at 1373 K and 1500 K to study the effect of the combustion temperature on particle size distributions (PSDs). A single particle model was developed for coal char to predict char particle temperatures and to illustrate the temperature differences between conditions. A Scanning Mobility Particle Sizer (SMPS) and an Aerodynamic Particle Sizer (APS) were utilized for ash PSDs in size ranges between 14.3nm to 20 microns. In addition, particles were collected on an eleven-stage, Berner Low Pressure Impactor (BLPI) for elemental analysis using Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). It is found that temperature was the driving mechanism for increasing the amount of ultrafine formation. Increases in predicted particle temperature yielded an increase in mass. As a second order effect, the combustion in an O2/CO2 environment yielded smaller masses of ultrafine particles than combustion in an O2/N2 environment. EDS results supported theSMPS/APS data as well and showed that, as expected, the coarse composition did not change significantly for the coals, but the ultrafine compositions were dependent upon the silicon, for Utah, and calcium, for PRB

Doctor of Philosophy

dissertationA gasifier's temperature is the primary characteristic that must be monitored to ensure its performance and the longevity of its refractory. One of the key technological challenges impacting the reliability and economics of coal and biomass gasification is the lack of temperature sensors that are capable of providing accurate, reliable, and long-life performance in an extreme gasification environment. This research has proposed, demonstrated, and validated a novel approach that uses a noninvasive ultrasound method that provides real-time temperature distribution monitoring across the refractory, especially the hot face temperature of the refractory. The essential idea of the ultrasound measurements of segmental temperature distribution is to use an ultrasound propagation waveguide across a refractory that has been engineered to contain multiple internal partial reflectors at known locations. When an ultrasound excitation pulse is introduced on the cold side of the refractory, it will be partially reflected from each scatterer in the US propagation path in the refractory wall and returned to the receiver as a train of partial echoes. The temperature in the corresponding segment can be determined based on recorded ultrasonic waveform and experimentally defined relationship between the speed of sound and temperature. The ultrasound measurement method offers a powerful solution to provide continuous real-time temperature monitoring for the occasions that conventional thermal, optical, and other sensors are infeasible, such as the impossibility of insertion of temperature sensors, harsh environment, unavailable optical path, and more. Our developed ultrasound system consists of an ultrasound engineered waveguide, ultrasound transducer/receiver, and data acquisition, logging, interpretation, and online display system, which is simple to install on the existing units with minimal modification on the gasifier or to use with new units. This system has been successfully tested with a 100 kW pilot-scale downflow oxyfuel combustor, capturing in real-time temperature changes during all relevant combustion process changes. The ultrasound measurements have excellent agreement with thermocouple measurements, and appear to be more sensitive to temperature changes before the thermocouples response, which is believed to be the first demonstration of ultrasound measurements segmental temperature distribution across refractories

Experimental investigation of dielectric barrier impact on breakdown voltage enhancement of copper wire-plane electrode systems

Non-pressurized air is extensively used as basic insulation media in medium / high voltage equipments. An inherent property of air-insulated designs is that the systems tend to become physically large. Application of Dielectric barrier can increase the breakdown voltage and therefore decrease the size of the equipments. In this paper, the impact of dielectric barrier on breakdown voltage enhancement of a copper wire-plane system is investigated. For this purpose, the copper wire is covered with different dielectric materials. Depending on the air gap and dielectric strength of the barrier the breakdown can be initiated in the solid or gas dielectric. Theoretically, free charges are affected by the electric field between the electrodes and accumulated at the dielectric surface, this leads to the reduction of electric field in air gap and enhancement of the ifield in the dielectric layer. Therefore, with appropriate selection of the barrier thickness and material, it is possible to increase the breakdown voltage of the insulation system. The influence of different parameters like inter-electrode spacing, and dielectric material on the break-down voltage is investigated for applied 50 Hz AC and DC voltages. The results indicate that up to 240% increase of the breakdown voltage can be achieved

Ku80 cooperates with CBP to promote COX-2 expression and tumor growth.

Cyclooxygenase-2 (COX-2) plays an important role in lung cancer development and progression. Using streptavidin-agarose pulldown and proteomics assay, we identified and validated Ku80, a dimer of Ku participating in the repair of broken DNA double strands, as a new binding protein of the COX-2 gene promoter. Overexpression of Ku80 up-regulated COX-2 promoter activation and COX-2 expression in lung cancer cells. Silencing of Ku80 by siRNA down-regulated COX-2 expression and inhibited tumor cell growth in vitro and in a xenograft mouse model. Ku80 knockdown suppressed phosphorylation of ERK, resulting in an inactivation of the MAPK pathway. Moreover, CBP, a transcription co-activator, interacted with and acetylated Ku80 to co-regulate the activation of COX-2 promoter. Overexpression of CBP increased Ku80 acetylation, thereby promoting COX-2 expression and cell growth. Suppression of CBP by a CBP-specific inhibitor or siRNA inhibited COX-2 expression as well as tumor cell growth. Tissue microarray immunohistochemical analysis of lung adenocarcinomas revealed a strong positive correlation between levels of Ku80 and COX-2 and clinicopathologic variables. Overexpression of Ku80 was associated with poor prognosis in patients with lung cancers. We conclude that Ku80 promotes COX-2 expression and tumor growth and is a potential therapeutic target in lung cancer

Clinical and molecular profiling of EGFR-mutant lung adenocarcinomas transformation to small cell lung cancer during TKI treatment

IntroductionSmall cell lung cancer (SCLC) transformation serves as a significant mechanism of resistance to tyrosine kinase inhibitors (TKIs) in advanced non-small cell lung cancer (NSCLC) with epidermal growth factor receptor (EGFR) mutations. To address this clinical challenge, we conducted a retrospective analysis at Zhejiang University School of Medicine, the First Affiliated Hospital, focusing on patients with EGFR sensitizing mutations.MethodsA total of 1012 cases were included in this retrospective analysis. The cohort primarily consisted of patients with EGFR sensitizing mutations. Biopsy-confirmed small cell transformation was observed in seven patients, accounting for 0.7% of the cases. All patients in this subset were initially diagnosed with stage IV adenocarcinoma (ADC), with four cases classified as poorly differentiated and three as moderately to poorly differentiated ADC. EGFR exon 19 deletions were identified in five of these cases. Next-generation sequencing (NGS) was performed on seven cases, revealing mutations in the tumor protein p53 (TP53) gene in four cases and loss of the retinoblastoma1 (RB1) gene in three cases.ResultsThe median duration from the initial diagnosis to small cell transformation was 35.9 months (interquartile range: 12.1–84 months). Following small cell transformation during EGFR inhibition, all patients received etoposide/platinum-based treatment, leading to a median progression-free survival (PFS) of 4.7 months (interquartile range: 2.7–10.1 months). Notably, most patients in this series had poorly differentiated adenocarcinomas at the outset. TP53 mutations and RB1 loss were common genetic alterations observed in patients with small cell transformation in this cohort.DiscussionThe findings underscore the clinical significance of SCLC transformation as a resistance mechanism to EGFR TKIs in NSCLC with EGFR mutations. The observed genetic alterations, including TP53 mutations and RB1 loss, suggest potential associations with the transformation process and warrant further investigation. Understanding the genetic landscape and clinical outcomes in patients experiencing small cell transformation can contribute to improved strategies for managing resistance in EGFR-mutant NSCLC

The interactions between phytoplankton and pollutants in eutropic freshwater : sufferer and vector

The present thesis focused on two aspects of the interactions between phytoplankton and chemical pollution in aquatic systems. On the one hand, phytoplankton suffers from a diverse array of pollutants in aquatic systems. In this thesis, the growth inhibition of three groups of biocides towards two groups of phytoplankton was systematically investigated. The three cyanobacteria were generally more tolerant than the three green algae in response to the five herbicides and two fungicides (p<0.05). In contrast, the sensitivity of the two groups of phytoplankton to antibiotics was more complex. Significant differences were observed for clarithromycin, thiamphenicol, tetracycline and trimethoprim (p<0.001), while no significant difference for sulfamethoxazole was seen. Meanwhile, a non-targeted metabolomic approach was employed to gain more insight into the different responses of cyanobacteria and green algae under herbicide exposures (i.e., to atrazine and diuron). Among the major metabolic changes observed in response to herbicide exposure was the alteration of amino acids metabolism, such as phenylalanine, tyrosine, methionine, asparagine, glycine and serine. In comparison to Microcystis, the green algae were more sensitive to the herbicides as the cells resorted to amino acid catalysis pathways to obtain energy when the photosynthesis is constrained. A rapid response in central carbon metabolism was observed in green algae but not in Microcystis. In general, metabolites in the TCA cycle, CBB cycle, and pentose phosphate pathway were up-regulated while the levels of glycolysis pathway metabolites were decreased. Moreover, the accumulation of glycolate and glycoxylate in the photorespiration pathway were increased in the Microcystis but decreased in the green algae in response to high exposures of the herbicides. On the other hand, chemicals-tolerant phytoplankton taxa might act as vectors of the pollutants, especially in eutrophic freshwaters where a high biomass of phytoplankton is often observed. In this thesis, firstly endocrine disruptive compounds (EDCs) of varied mechanisms of action were chemically and bioanalytically investigated in different matrices from Taihu Lake (China). Results from cell-based bioassays suggested the occurrence of estrogenic, anti-estrogenic, anti-androgenic, and anti-glucocorticogenic activities, while no androgenic and glucocorticogenic activities were observed in the samples. Results from the chemical analysis suggested that EDCs were widely distributed in water, sediment and cyanobacterial bloom samples. In order to further evaluate the role of cyanobacterial blooms in the distribution of EDCs in eutrophic freshwaters, endocrine disruptive potentials in phytoplankton samples were evaluated throughout a year-long surveillance. Results of the Spearman correlation analysis concluded that the concentrations of ten EDCs were negatively correlated with cyanobacteria biomass, suggesting the potential occurrence of biomass dilution effects of EDCs due to the huge biomass of cyanobacteria during bloom season. The present study provides complementary information about the potential endocrine disruptive risks of cyanobacteria blooms in eutrophic freshwaters. Moreover, the vector effects of cyanobacterial bloom on inorganic pollutants were also evaluated. Besides the wide detection of several metals in cyanobacteiral blooms, biomass dilution effects were also found. Overall, this thesis constitutes the basis for a comprehensive understanding of the interactions between chemical pollution and phytoplankton for the management of eutrophic freshwaters

Ash Particulate Formation from Pulverized Coal under Oxy-Fuel Combustion Conditions

Aerosol particulates are generated by coal combustion. The amount and properties of aerosol particulates, specifically size distribution and composition, can be affected by combustion conditions. Understanding the formation of these particles is important for predicting emissions and understanding potential deposition. Oxy-fuel combustion conditions utilize an oxygen-enriched gas environment with CO₂. The high concentration of CO₂ is a result of recycle flue gas which is used to maintain temperature. A hypothesis is that high CO₂ concentration reduces the vaporization of refractory oxides from combustion. A high-temperature drop-tube furnace was used under different oxygen concentrations and CO₂ versus N₂ to study the effects of furnace temperature, coal type, and gas phase conditions on particulate formation. A scanning mobility particle sizer (SMPS) and aerodynamic particle sizer (APS) were utilized for particle size distributions ranging from 14.3 nm to 20 μm. In addition, particles were collected on a Berner low pressure impactor (BLPI) for elemental analysis using scanning electron microscopy and energy dispersive spectroscopy. Three particle size modes were seen: ultrafine (below 0.1 μm), fine (0.1 to 1.0 μm), and coarse (above 1 μm). Ultrafine mass concentrations were directly related to estimated particle temperature, increasing with increasing temperature. For high silicon and calcium coals, Utah Skyline and PRB, there was a secondary effect due to CO₂ and the hypothesized reaction. Illinois #6, a high sulfur coal, had the highest amount of ultrafine mass and most of the sulfur was concentrated in the ultrafine and fine modes. Fine and coarse mode mass concentrations did not show a temperature or CO₂ relationship. (The table of contents graphic and abstract graphic are adapted from ref 27.

Simultaneous elimination of cyanotoxins and PCBs via mechanical collection of cyanobacterial blooms: An application of "green-bioadsorption concept"

In this study, the distribution, transfer and fate of both polychlorinated biphenyls (PCBs) and cyanotoxins via phytoplankton routes were systematically investigated in two Chinese lakes. Results indicated that PCB adsorption/bioaccumulation dynamics has significantly positive correlations with the biomass of green alga and diatoms. Total lipid content of phytoplankton is the major factor that influences PCB adsorption/bioaccumulation. Cyanobacterial blooms with relatively lower lipid content could also absorb high amount of PCBs due to their high cell density in the water columns, and this process was proposed as major route for the transfer of PCBs in Chinese eutrophic freshwater. According to these findings, a novel route on fates of PCBs via phytoplankton and a green bioadsorption concept were proposed and confirmed. In the practice of mechanical collections of bloom biomass from Lake Taihu, cyanotoxin/cyanobacteria and PCBs were found to be removed simultaneously very efficiently followed this theory. (C) 2016 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V