8 research outputs found
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Temperature, velocity and Species Profile Measurements for Reburning in a Pulverized, Entrained Flow, Coal Combustor
Measurements of effluent NO{sub x}, CO, and O{sub 2} have been obtained for various reburning locations in the controlled profile reactor. the location of the reburning zone and tertiary air zone have been varied to find an optimal location for detailed reburning profile measurements. No{sub x} reduction of greater than 70% has been seen with natural gas injection in and just below the primary combustion zone. Strategic injection of the natural gas for reburning reduces the total No{sub x} reduction capability of reburning. Modeling efforts continue in trying to match the modeling solution to the detailed baseline data taken in previous measurement. The use of more accurate measured boundary conditions did not appear to improve the model predictions greatly but the use of more detailed turbulence models was found to improve the predictions, the predictions are still far from matching the combustion measurements
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Temperature, velocity and species profile measurements for reburning in a pulverized, entrained flow, coal combustor
Nitrogen oxide emissions from pulverized coal combustion have been and will continue to be a regulated pollutant for electric utility boilers burning pulverized coal. Full scale combustion models can help in the design of new boilers and boiler retrofits which meet emissions standards, but these models require validation before they can be used with confidence. The objective of this work was to obtain detailed combustion measurements of pulverized coal flames which implement two NO reduction strategies, namely reburning and advanced reburning, to provide data for model validation. The data were also compared to an existing comprehensive pulverized coal combustion model with a reduced mechanism for NO reduction under reburning and advanced reburning conditions. The data were obtained in a 0.2 MW, cylindrical, down-fired, variable swirl, pulverized coal reactor. The reactor had a diameter of 0.76 m and a length of 2.4 m with access ports along the axial length. A Wyodak, sub-bituminous coal was used in all of the measurements. The burner had a centrally located primary fuel and air tube surrounded by heated and variably swirled secondary air. Species of NO, NO{sub x}, CO, CO{sub 2} and O{sub 2} were measured continuously. Aqueous sampling was used to measure HCN and NH{sub 3} at specific reactor locations. Samples were drawn from the reactor using water quenched suction probes. Velocity measurements were obtained using two component laser doppler anemometry in back-scatter mode. Temperature measurements were obtained using a shielded suction pyrometer. A series of six or more radial measurements at six or more axial locations within the reactor provided a map of species, temperature, and velocity measurements. In total, seven reactor maps were obtained. Three maps were obtained at baseline conditions of 0, 0.5 and 1.5 swirl and 10% excess air. Two maps were obtained under reburning conditions of 0.78 stoichiometric ratio and 1.5 swirl and 0.9 stoichiometric ratio and 0.5 swirl. And finally, two maps were obtained under advanced reburning conditions both at the same operating condition of 1.05 stoichiometric ratio in the reburning zone followed by ammonia injection. Numerous effluent measurements were obtained to study the affect of natural gas injection location, stoichiometric ratio, and injection velocity on effluent NO. For advanced reburning, effluent measurements were obtained for a similar matrix of operating conditions with the additional variable of ammonia nitrogen to nitrogen in NO or nitrogen stoichiometric ratio (NSR)
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Temperature, velocity, and species profile measurements for reburning in a pulverized, entrained flow, coal combustor. Semi-annual report, April 30, 1996--October 31, 1996
The capability of LDA measurements for future reburning experiments has now been demonstrated. Measurements of mean and turbulent gas and particle velocity have been obtained using Laser Doppler Anemometry (LDA) in the near burner and quart region of the pulverized coal reactor. The mean and turbulent velocity at the burner outlet, or top of the quart were obtained under non-reacting conditions in order to obtain realistic boundary conditions for comprehensive combustion modeling. Also, under cold flow it was determined that little error occurred in measuring mean velocities with LDA using pulverized coal as the seed particle. Thus, for mean velocities, coal particle and gas velocities were similar. Coal particle velocity profiles were obtained at three swirls and three axial locations. Gas species, and temperature maps for the reactor have now also been completed at three swirl settings in addition to the LDA data. Gas species obtained include CO, CO 2, O{sub 2} and NO. Calibration of the HCN and NH{sub 3} measurement has been successfully completed but no measurements in the reactor have been obtained. The design and fabrication of fuel and air injectors to be used for reburning are complete. The injectors have not yet been tested
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Temperature, velocity and species profile measurements for reburning in a pulverized, entrained flow, coal combustor. Semi-annual report, October 30, 1995--April 30, 1996
Data for mean velocity and temperature have been obtained over a baseline matrix operating conditions for pulverized coal without reburning. The data show the reactor to be symmetrical about the axial centerline. Effluent NO{sub x} data have been seen to correlate with measured and modeled results of flow patterns within the reactor. At low swirl the fuel jet creates a downward flow at the centerline with some upward recirculation at the perimeter of the reactor near the walls. This recirculation pattern reverses as swirl is increased, changing the flame from a long toroidal shape to a flat annulus. The NO{sub x} data show a local minimum at a swirl number of 1.0 which may be primarily the result of the direction and magnitude of the recirculation zone. Gas species and coal char burnout data have begun but have not yet been completed. Velocity data and modeling results have been used in the process of validating the comprehensive combustion code and in designing the reburning hardware. The details concerning storing and delivering the reburning fuel (natural gas) have been completed and the fabrication of the hardware is underway
Hydrodynamics of DNA confined in nanoslits and nanochannels
Modeling the dynamics of a confined, semiflexible polymer is a challenging problem, owing to the complicated interplay between the configurations of the chain, which are strongly affected by the length scale for the confinement relative to the persistence length of the chain, and the polymer-wall hydrodynamic interactions. At the same time, understanding these dynamics are crucial to the advancement of emerging genomic technologies that use confinement to stretch out DNA and “read” a genomic signature. In this mini-review, we begin by considering what is known experimentally and theoretically about the friction of a wormlike chain such as DNA confined in a slit or a channel. We then discuss how to estimate the friction coefficient of such a chain, either with dynamic simulations or via Monte Carlo sampling and the Kirkwood pre-averaging approximation. We then review our recent work on computing the diffusivity of DNA in nanoslits and nanochannels, and conclude with some promising avenues for future work and caveats about our approach
Is there an Ironic Tone of Voice?
Research on nonverbal vocal cues and verbal irony has often relied on the concept of an ironic tone of voice. Here we provide acoustic analysis and experimental evidence that this notion is oversimplified and misguided. Acoustic analyses of spontaneous ironic speech extracted from talk radio shows, both ambiguous and unambiguous in written form, revealed only a difference in amplitude variability compared to matched nonironic speech from the same sources, and that was only among the most clear-cut items. In a series of experiments, participants rated content-filtered versions of the same ironic and nonironic utterances on a range of affective and linguistic dimensions. Listeners did not rely on any set of vocal cues to identify verbal irony that was separate from other emotional and linguistic judgments. We conclude that there is no particular ironic tone of voice and that listeners interpret verbal irony by combining a variety of cues, including information outside of the linguistic context. © Kingston Press Ltd
Hydrodynamics of DNA confined in nanoslits and nanochannels
Modeling the dynamics of a confined, semi exible polymer is a challenging problem, owing to the complicated interplay between the configurations of the chain, which are strongly affected by the length scale for the confinement relative to the persistence length of the chain, and the polymer-wall hydrodynamic interactions. At the same time, understanding these dynamics are crucial to the advancement of emerging genomic technologies that use confinement to stretch out DNA and “read” a genomic signature. In this mini-review, we begin by considering what is known experimentally and theoretically about the friction of a wormlike chain such as DNA confined in a slit or a channel. We then discuss how to estimate the friction coefficient of such a chain, either with dynamic simulations or via Monte Carlo sampling and the Kirk-wood pre-averaging approximation. We then review our recent work on computing the diffusivity of DNA in nanoslits and nanochannels, and conclude with some promising avenues for future work and caveats about our approach
Safety and immunogenicity of ChAdOx1 nCoV-19 vaccine administered in a prime-boost regimen in young and old adults (COV002): a single-blind, randomised, controlled, phase 2/3 trial
Background
Older adults (aged ≥70 years) are at increased risk of severe disease and death if they develop COVID-19 and are therefore a priority for immunisation should an efficacious vaccine be developed. Immunogenicity of vaccines is often worse in older adults as a result of immunosenescence. We have reported the immunogenicity of a novel chimpanzee adenovirus-vectored vaccine, ChAdOx1 nCoV-19 (AZD1222), in young adults, and now describe the safety and immunogenicity of this vaccine in a wider range of participants, including adults aged 70 years and older.
Methods
In this report of the phase 2 component of a single-blind, randomised, controlled, phase 2/3 trial (COV002), healthy adults aged 18 years and older were enrolled at two UK clinical research facilities, in an age-escalation manner, into 18–55 years, 56–69 years, and 70 years and older immunogenicity subgroups. Participants were eligible if they did not have severe or uncontrolled medical comorbidities or a high frailty score (if aged ≥65 years). First, participants were recruited to a low-dose cohort, and within each age group, participants were randomly assigned to receive either intramuscular ChAdOx1 nCoV-19 (2·2 × 1010 virus particles) or a control vaccine, MenACWY, using block randomisation and stratified by age and dose group and study site, using the following ratios: in the 18–55 years group, 1:1 to either two doses of ChAdOx1 nCoV-19 or two doses of MenACWY; in the 56–69 years group, 3:1:3:1 to one dose of ChAdOx1 nCoV-19, one dose of MenACWY, two doses of ChAdOx1 nCoV-19, or two doses of MenACWY; and in the 70 years and older, 5:1:5:1 to one dose of ChAdOx1 nCoV-19, one dose of MenACWY, two doses of ChAdOx1 nCoV-19, or two doses of MenACWY. Prime-booster regimens were given 28 days apart. Participants were then recruited to the standard-dose cohort (3·5–6·5 × 1010 virus particles of ChAdOx1 nCoV-19) and the same randomisation procedures were followed, except the 18–55 years group was assigned in a 5:1 ratio to two doses of ChAdOx1 nCoV-19 or two doses of MenACWY. Participants and investigators, but not staff administering the vaccine, were masked to vaccine allocation. The specific objectives of this report were to assess the safety and humoral and cellular immunogenicity of a single-dose and two-dose schedule in adults older than 55 years. Humoral responses at baseline and after each vaccination until 1 year after the booster were assessed using an in-house standardised ELISA, a multiplex immunoassay, and a live severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) microneutralisation assay (MNA80). Cellular responses were assessed using an ex-vivo IFN-γ enzyme-linked immunospot assay. The coprimary outcomes of the trial were efficacy, as measured by the number of cases of symptomatic, virologically confirmed COVID-19, and safety, as measured by the occurrence of serious adverse events. Analyses were by group allocation in participants who received the vaccine. Here, we report the preliminary findings on safety, reactogenicity, and cellular and humoral immune responses. This study is ongoing and is registered with ClinicalTrials.gov, NCT04400838, and ISRCTN, 15281137.
Findings
Between May 30 and Aug 8, 2020, 560 participants were enrolled: 160 aged 18–55 years (100 assigned to ChAdOx1 nCoV-19, 60 assigned to MenACWY), 160 aged 56–69 years (120 assigned to ChAdOx1 nCoV-19: 40 assigned to MenACWY), and 240 aged 70 years and older (200 assigned to ChAdOx1 nCoV-19: 40 assigned to MenACWY). Seven participants did not receive the boost dose of their assigned two-dose regimen, one participant received the incorrect vaccine, and three were excluded from immunogenicity analyses due to incorrectly labelled samples. 280 (50%) of 552 analysable participants were female. Local and systemic reactions were more common in participants given ChAdOx1 nCoV-19 than in those given the control vaccine, and similar in nature to those previously reported (injection-site pain, feeling feverish, muscle ache, headache), but were less common in older adults (aged ≥56 years) than younger adults. In those receiving two standard doses of ChAdOx1 nCoV-19, after the prime vaccination local reactions were reported in 43 (88%) of 49 participants in the 18–55 years group, 22 (73%) of 30 in the 56–69 years group, and 30 (61%) of 49 in the 70 years and older group, and systemic reactions in 42 (86%) participants in the 18–55 years group, 23 (77%) in the 56–69 years group, and 32 (65%) in the 70 years and older group. As of Oct 26, 2020, 13 serious adverse events occurred during the study period, none of which were considered to be related to either study vaccine. In participants who received two doses of vaccine, median anti-spike SARS-CoV-2 IgG responses 28 days after the boost dose were similar across the three age cohorts (standard-dose groups: 18–55 years, 20 713 arbitrary units [AU]/mL [IQR 13 898–33 550], n=39; 56–69 years, 16 170 AU/mL [10 233–40 353], n=26; and ≥70 years 17 561 AU/mL [9705–37 796], n=47; p=0·68). Neutralising antibody titres after a boost dose were similar across all age groups (median MNA80 at day 42 in the standard-dose groups: 18–55 years, 193 [IQR 113–238], n=39; 56–69 years, 144 [119–347], n=20; and ≥70 years, 161 [73–323], n=47; p=0·40). By 14 days after the boost dose, 208 (>99%) of 209 boosted participants had neutralising antibody responses. T-cell responses peaked at day 14 after a single standard dose of ChAdOx1 nCoV-19 (18–55 years: median 1187 spot-forming cells [SFCs] per million peripheral blood mononuclear cells [IQR 841–2428], n=24; 56–69 years: 797 SFCs [383–1817], n=29; and ≥70 years: 977 SFCs [458–1914], n=48).
Interpretation
ChAdOx1 nCoV-19 appears to be better tolerated in older adults than in younger adults and has similar immunogenicity across all age groups after a boost dose. Further assessment of the efficacy of this vaccine is warranted in all age groups and individuals with comorbidities.
Funding
UK Research and Innovation, National Institutes for Health Research (NIHR), Coalition for Epidemic Preparedness Innovations, NIHR Oxford Biomedical Research Centre, Thames Valley and South Midlands NIHR Clinical Research Network, and AstraZeneca