| 171. |
- Wang, Ze, et al.
(author)
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Experimental investigation of internal structures of NH3/H2/O2/N2 premixed jet flames using multi-scalar imaging
- 2024
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In: Proceedings of the Combustion Institute. - 1540-7489. ; 40:1-4
-
Journal article (peer-reviewed)abstract
- Ammonia-hydrogen (NH3-H2) blends stand as a promising carbon-neutral fuel alternative. This study delves into the variation in the internal structure of NH3-H2 flames with varying Lewis numbers (Le) and turbulence intensities. Simultaneous multi-scalar imaging of NH3/NH/OH was performed to characterize the structures of turbulent jet flames with the same unstretched laminar flame speed (30.8 cm/s) but different H2 contents. Internal flame structures were characterized by isocontours of NH3, NH (both inner and outer edges, NHi and NHo), and OH to delimit the reaction zone. The parallelism of the selected isocontours (i.e., NH3, NHi, and NHo) with the OH baseline was quantified by calculating the probabilities, P(δp), of the selected isocontours overlapping with the OH baseline shifted by a distance of δp along its normal direction. On the one hand, results have revealed that increasing turbulence disrupts the parallelism of the selected isocontours with the OH baseline, leading to a larger and FWHM, as well as a reduced skewness of the P(δp) profiles. On the other hand, flames with higher H2 content and lower Le exhibit great resistance to turbulence but experience enhanced wrinkling due to the differential diffusion effect, which can also cause deviations in scalar parallelism at low turbulence intensity. For flames with reduced Le numbers, the NH3 isocontours are observed to be located even downstream of the NHi isocontours, which belong to the reaction zone. The extent of parallelism for the selected isocontours within the reaction zone is found to respond to turbulence and Le differently, deviating from an idealized picture of the flamelet manifold.
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| 172. |
- Wang, Zhenkan, et al.
(author)
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Investigation of OH and CH2O distributions at ultra-high repetition rates by planar laser induced fluorescence imaging in highly turbulent jet flames
- 2018
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In: Fuel. - : Elsevier BV. - 0016-2361. ; 234, s. 1528-1540
-
Journal article (peer-reviewed)abstract
- For better understanding of the transient behavior of the flow/flame interaction in highly turbulent premixed flames, measurement techniques with sufficient temporal resolution are required. Using a burst-mode laser pumped optical parametric oscillator system, the present work demonstrated an ultra-high-speed diagnostic, for the first time, capable of visualizing hydroxyl radicals (OH) and formaldehyde (CH2O) distributions in a highly turbulent flame at repetition rates up to 140 kHz (i.e. with a temporal resolution of 7.1 μs) to access the Kolmogorov time scales of flames in the distributed/broken reaction zone regime (Ka ≥ 100). More than 100 consecutive images were recorded in the present work for OH planar laser induced fluorescence (PLIF) measurement at 100 kHz. Systematic temporal and spatial evolution of the flame structure is clearly resolved over long sequences, e.g. 1.2 ms for OH PLIF and 10 ms for CH2O PLIF respectively. The Kolmogorov time scale for all the cases at x/d = 10 and x/d = 30 are estimated with the minimum Kolmogorov time scale of 7.5 μs, indicating that nearly all time-scales of the flow are resolved with the present experimental setup. The axial velocity of the CH2O structure at its outer layer at different flame height positions, UCH2O, is obtained. The velocity UCH2O is compared with the LDV results, which shows a good agreement with the mean flow velocity. By comparing UCH2O with the local axial velocity, different mechanisms responsible for the large-scale wrinkle structures in the reaction zone and the propagation of CH2O structure along the flame height are discussed. Power spectral density and autocorrelation function based on the CH2O outer layer fluctuation in the radial direction are illustrated. Quantitative analysis of the ultra-high-speed diagnostics data further augments the understanding of turbulent combustion down to Kolmogorov scale experimentally.
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| 173. |
- Wang, Zhenkan, et al.
(author)
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Structure and burning velocity of turbulent premixed methane/air jet flames in thin-reaction zone and distributed reaction zone regimes
- 2019
-
In: Proceedings of the Combustion Institute. - : Elsevier BV. - 1540-7489. ; 37:2, s. 2537-2544
-
Journal article (peer-reviewed)abstract
- A series of turbulent premixed methane/air jet flames are studied using simultaneous planar lase diagnostic imaging of OH/CH/temperature and CH/OH/CH2O. The Karlovitz number of the flames ranges from 25 to 1500, and the turbulence intensity ranges from 16 to 200. These flames can be classified as highly turbulent flames in the thin reactions zone (TRZ) regime and distributed reaction zone (DRZ) regime. The aims of this study are to investigate the structural change of the preheat zone and the reaction zone as the Karlovitz number and turbulent intensity increase, to study the impact of the structural change of the flame on the propagation speed of the flame, and to evaluate the turbulent burning velocity computed in different layers in the preheat zone and reaction zone. It is found that for all investigated flames the preheat zone characterized with planar laser-induced fluorescence (PLIF) of CH2O is broadened by turbulent eddies. The thickness of the preheat zone increases with the turbulent intensity and it can be on the order of the turbulent integral length at high Karlovitz numbers. The reaction zone characterized using the overlapping layer of OH and CH2O PLIF signals is not significantly broadened by turbulence eddies; however, the CH PLIF layer is found to be broadened significantly by turbulence. The turbulent burning velocity is shown to monotonically increase with turbulent intensity and Karlovitz number. The increase in turbulent burning velocity is mainly due to the enhanced turbulent heat and mass transfer in various layers of the flame, while the contribution of flame front wrinkling to the turbulent burning velocity is rather minor.
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| 174. |
- Wen, Bo, et al.
(author)
-
IPeak : An open source tool to combine results from multiple MS/MS search engines
- 2015
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In: Proteomics. - : Wiley-VCH Verlagsgesellschaft. - 1615-9853 .- 1615-9861. ; 15:17, s. 2916-2920
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Journal article (peer-reviewed)abstract
- Liquid chromatography coupled tandem mass spectrometry (LC-MS/MS) is an important technique for detecting peptides in proteomics studies. Here, we present an open source software tool, termed IPeak, a peptide identification pipeline that is designed to combine the Percolator post-processing algorithm and multi-search strategy to enhance the sensitivity of peptide identifications without compromising accuracy. IPeak provides a graphical user interface (GUI) as well as a command-line interface, which is implemented in JAVA and can work on all three major operating system platforms: Windows, Linux/Unix and OS X. IPeak has been designed to work with the mzIdentML standard from the Proteomics Standards Initiative (PSI) as an input and output, and also been fully integrated into the associated mzidLibrary project, providing access to the overall pipeline, as well as modules for calling Percolator on individual search engine result files. The integration thus enables IPeak (and Percolator) to be used in conjunction with any software packages implementing the mzIdentML data standard. IPeak is freely available and can be downloaded under an Apache 2.0 license at https://code.google.com/p/mzidentml-lib/.
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| 175. |
- Whiddon, Ronald, et al.
(author)
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Vapor phase tri-methyl-indium seeding system suitable for high temperature spectroscopy and thermometry.
- 2015
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In: Review of Scientific Instruments. - : AIP Publishing. - 1089-7623 .- 0034-6748. ; 86:9
-
Journal article (peer-reviewed)abstract
- Tri-methyl-indium (TMI) is used as an indium transport molecule to introduce indium atoms to reactive hot gas flows/combustion environments for spectroscopic diagnostics. A seeding system was constructed to allow the addition of an inert TMI laden carrier gas into an air/fuel mixture burning consequently on a burner. The amount of the seeded TMI in the carrier gas can be readily varied by controlling the vapor pressure through the temperature of the container. The seeding process was calibrated using the fluorescent emission intensity from the indium 6(2)S1/2 → 5(2)P1/2 and 6(2)S1/2 → 5(2)P3/2 transitions as a function of the calculated TMI seeding concentration over a range of 2-45 ppm. The response was found to be linear over the range 3-22.5 ppm; at concentrations above 25 ppm there is a loss of linearity attributable to self-absorption or loss of saturation of TMI vapor pressure in the carrier gas flow. When TMI was introduced into a post-combustion environment via an inert carrier gas, molecular transition from InH and InOH radicals were observed in the flame emission spectrum. Combined laser-induced fluorescence and absorption spectroscopy were applied to detect indium atoms in the TMI seeded flame and the measured atomic indium concentration was found to be at the ppm level. This method of seeding organometallic vapor like TMI to a reactive gas flow demonstrates the feasibility for quantitative spectroscopic investigations that may be applicable in various fields, e.g., chemical vapor deposition applications or temperature measurement in flames with two-line atomic fluorescence.
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| 176. |
- Wu, Bo, et al.
(author)
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Strong self-trapping by deformation potential limits photovoltaic performance in bismuth double perovskite
- 2021
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In: Science Advances. - : American Association for the Advancement of Science. - 2375-2548. ; 7:8
-
Journal article (peer-reviewed)abstract
- Bismuth-based double perovskite Cs2AgBiBr6 is regarded as a potential candidate for low-toxicity, high-stability perovskite solar cells. However, its performance is far from satisfactory. Albeit being an indirect bandgap semiconductor, we observe bright emission with large bimolecular recombination coefficient (reaching 4.5 +/- 0.1 x 10(-11) cm(3) s(-1)) and low charge carrier mobility (around 0.05 cm(2) s(-1) V-1). Besides intermediate Frohlich couplings present in both Pb-based perovskites and Cs2AgBiBr6, we uncover evidence of strong deformation potential by acoustic phonons in the latter through transient reflection, time-resolved terahertz measurements, and density functional theory calculations. The Frohlich and deformation potentials synergistically lead to ultrafast self-trapping of free carriers forming polarons highly localized on a few units of the lattice within a few picoseconds, which also breaks down the electronic band picture, leading to efficient radiative recombination. The strong self-trapping in Cs2AgBiBr6 could impose intrinsic limitations for its application in photovoltaics.
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| 177. |
- Wu, Bo, et al.
(author)
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Structure, Magnetism, and Electronic Properties of Inverse Heusler Alloy Ti2CoAl/MgO(100) Herterojuction: The Role of Interfaces
- 2018
-
In: Applied Sciences. - : MDPI. - 2076-3417. ; 8:12
-
Journal article (peer-reviewed)abstract
- In this study, the interface structures, atom-resolved magnetism, density of states, and spin polarization of 10 possible atomic terminations in the Ti2CoAl/MgO(100) heterojunction were comprehensively investigated using first-principle calculations. In the equilibrium interface structures, the length of the alloy-Mg bond was found to be much longer than that of the alloy-O bond because of the forceful repulsion interactions between theHeusler interface atoms andMg atoms. The competition among d-electronic hybridization, d-electronic localization, and the moving effect of the interface metal atoms played an important role in the interface atomic magnetic moment. Unexpected interface states appeared in the half-metallic gap for all terminations. The "ideal" half-metallicity observed in the bulk had been destroyed. In TiAl-Mg and AlAl-O terminations, the maximal spin polarization of about 65% could be reserved. The tunnel magnetoresistance (TMR) value was deduced to be lower than 150% in the Ti2CoAl/MgO(100) heterojunction at low temperature.
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| 178. |
- Xia, Xiaoyan, et al.
(author)
-
Effect of a two-stage intervention package on the cesarean section rate in Guangzhou, China: A before-and-after study.
- 2019
-
In: PLoS medicine. - : Public Library of Science (PLoS). - 1549-1676. ; 16:7
-
Journal article (peer-reviewed)abstract
- The cesarean section (CS) rate has risen globally during the last two decades. Effective and feasible strategies are needed to reduce it. The aim of this study was to assess the CS rate change after a two-stage intervention package that was designed to reduce the overall CS rate in Guangzhou, China.This intervention package was implemented by the Health Commission of Guangzhou Municipality in 2 stages (October 2010-September 2014 and October 2014-December 2016) and included programs for population health education, skills training for healthcare professionals, equipment and technical support for local healthcare facilities, and capacity building for the maternal near-miss care system. A retrospective repeated cross-sectional study was conducted to evaluate influences of the intervention on CS rates. A pre-intervention period from January 2008 to September 2010 served as the baseline. The primary outcome was the CS rate, and the secondary outcomes included maternal mortality ratio (MMR) and perinatal mortality rate (PMR), all obtained from the Guangzhou Perinatal Health Care and Delivery Surveillance System (GPHCDSS). The Cochran-Armitage test was used to examine the trends of the overall CS rate, MMR, and PMR across different stages. Segmented linear regression analysis was used to assess the change of the CS rate over the intervention period. A total of 1,921,932 records of births and 108 monthly CS rates from 2008 to 2016 were analyzed. The monthly CS rate declined across the intervention stages (Z = 75.067, p < 0.001), with an average rate of 42.4% at baseline, 39.8% at Stage 1, and 35.0% at Stage 2. The CS rate declined substantially among nulliparous women who delivered term singletons, with an accelerating decreasing trend observed across Stage 1 and Stage 2 (the difference in slopes: -0.09 [95% CI -0.16 to -0.02] between Stage 1 and baseline, p = 0.014; -0.11 [95% CI -0.20 to -0.02] between Stage 1 and Stage 2, p = 0.017). The CS rate in the remaining population increased during baseline and Stage 1 and subsequently decreased during Stage 2. The sensitivity analysis suggested no immediate impact of the universal two-child policy on the trend of the CS rate. The MMR (Z = -4.368, p < 0.001) and PMR (Z = -13.142, p < 0.001) declined by stage over the intervention period. One of the main limitations of the study is the lack of a parallel control group. Moreover, the influence of temporal changes in the study population on the CS rate was unknown. Given the observational nature of the present study, causality cannot be confirmed.Apparent decline in the overall CS rate was observed in Guangzhou, China, after the implementation of a two-stage intervention package. The decline was most evident among nulliparous women who delivered term singletons. Despite some limitations for causal inference, Guangzhou's experience in controlling the CS rate by implementing composite interventions with public health education and perinatal healthcare service improvement could have implications for other similar areas with high rates of CS.
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| 179. |
- Xu, Ning, et al.
(author)
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Adenovirus virus-associated RNAII-derived small RNAs are efficiently incorporated into the RNA-induced silencing complex and associate with polyribosomes
- 2007
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In: Journal of Virology. - 0022-538X .- 1098-5514. ; 81:19, s. 10540-10549
-
Journal article (peer-reviewed)abstract
- Adenovirus type 5 encodes two highly structured short RNAs, the virus-associated (VA) RNAI and RNAII. Both are processed by Dicer into small RNAs that are incorporated into the RNA-induced silencing complex (RISC). We show here, by cloning of small RNAs, that approximately 80% of Ago2-containing RISC immunopurified from late-infected cells is associated with VA RNA-derived small RNAs (mivaRNAs). Most surprisingly, VA RNAII, which is expressed at 20-fold lower levels compared to that of VA RNAI, appears to be the preferred substrate for Dicer and accounts for approximately 60% of all small RNAs in RISC. The mivaRNAs are derived from the 3' strand of the terminal stems of the VA RNAs, with the major fraction of VA RNAII starting at position 138. The small RNAs derived from VA RNAI were more heterogeneous in size, with the two predominant small RNAs starting at positions 137 and 138. Collectively, our results suggest that the mivaRNAs are efficiently used for RISC assembly in late-infected cells. Potentially, they function as miRNAs, regulating translation of cellular mRNAs. In support of this hypothesis, we detected a fraction of the VA RNAII-derived mivaRNAs on polyribosomes.
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| 180. |
- Yang, Junkai, et al.
(author)
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A mechanism of timing variability underlying the association between the mean and SD of asynchrony
- 2019
-
In: Human Movement Science. - : Elsevier. - 0167-9457 .- 1872-7646. ; 67
-
Journal article (peer-reviewed)abstract
- Sensorimotor timing behaviors typically exhibit an elusive phenomenon known as the negative asynchrony. When synchronizing movements (e.g. finger taps) with an external sequence (e.g. a metronome), people’s taps precede event onsets by a few tens of milliseconds. We recently reported that asynchrony is less negative in participants with lower asynchrony variability. This indicates an association between negative asynchrony and variability of timing. Here, in 24 metronome-synchronization data sets, we modeled asynchrony series using a sensorimotor synchronization model that accounts for serial dependence of asynchronies. The results showed that the modeling well captured the negative correlation between the mean and SD of asynchrony. The finding suggests that serial dependence in asynchronies is an essential mechanism of timing variability underlying the association between the mean and SD of asynchrony.
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