The Experts below are selected from a list of 324 Experts worldwide ranked by ideXlab platform
Heinz Koeppl - One of the best experts on this subject based on the ideXlab platform.
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scalable inference of Heterogeneous Reaction kinetics from pooled single cell recordings
Nature Methods, 2014Co-Authors: Christoph Zechner, Michael Unger, Serge Pelet, Matthias Peter, Heinz KoepplAbstract:This paper describes a method for statistical inference of unobserved molecular states from single-cell time-lapse data.
Hong He - One of the best experts on this subject based on the ideXlab platform.
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Heterogeneous Reaction of so2 on manganese oxides the effect of crystal structure and relative humidity
Scientific Reports, 2017Co-Authors: Weiwei Yang, Jianghao Zhang, Yan Zhao, Hong HeAbstract:Manganese oxides from anthropogenic sources can promote the formation of sulfate through catalytic oxidation of SO2. In this study, the kinetics of SO2 Reactions on MnO2 with different morphologies (α, β, γ and δ) was investigated using flow tube reactor and in situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS). Under dry conditions, the reactivity towards SO2 uptake was highest on δ-MnO2 but lowest on β-MnO2, with a geometric uptake coefficient (γobs) of (2.42 ± 0.13) ×10–2 and a corrected uptake coefficient (γc) of (1.48 ± 0.21) ×10−6 for the former while γobs of (3.35 ± 0.43) ×10−3 and γc of (7.46 ± 2.97) ×10−7 for the latter. Under wet conditions, the presence of water altered the chemical form of sulfate and was in favor for the Heterogeneous oxidation of SO2. The maximum sulfate formation rate was reached at 25% RH and 45% for δ-MnO2 and γ-MnO2, respectively, possibly due to their different crystal structures. The results suggest that morphologies and RH are important factors influencing the Heterogeneous Reaction of SO2 on mineral aerosols, and that aqueous oxidation process involving transition metals of Mn might be a potential important pathway for SO2 oxidation in the atmosphere.
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Heterogeneous Reaction of acetic acid on MgO, α-Al2O3, and CaCO3 and the effect on the hygroscopic behaviour of these particles
Physical Chemistry Chemical Physics, 2012Co-Authors: Qingxin Ma, Yongchun Liu, Chang Liu, Hong HeAbstract:PCCP View Article Online / Journal Homepage / Table of Contents for this issue Dynamic Article Links Cite this: Phys. Chem. C hem. P hys ., 2012, 14, 8403–8409 www.rsc.org/pccp PAPER Heterogeneous Reaction of acetic acid on MgO, a-Al2O3, and CaCO3 and the effect on the hygroscopic behaviour of these particlesw Qingxin Ma, Yongchun Liu, Chang Liu and Hong He* Received 18th February 2012, Accepted 2nd April 2012 DOI: 10.1039/c2cp40510e Mixtures of organic compounds with mineral dust are ubiquitous in the atmosphere, whereas the formation pathways and hygroscopic behavior of these mixtures are not well understood. In this study, in situ DRIFTS, XRD, and a vapor sorption analyzer were used to investigate the Heterogeneous Reaction of acetic acid on a-Al2O3, MgO, and CaCO3 particles under both dry and humid conditions while the effect of Reactions on the hygroscopic behavior of these particles was also measured. In all cases, formation of acetate is significantly enhanced in the presence of surface water. However, the Reaction extent varied with the mineral phase of these particles. For a-Al2O3, the Reaction is limited to the surface with the formation of surface coordinated acetate under both dry and humid conditions. For MgO, the bulk of the particle is involved in the Reaction and Mg(CH3COO)2 is formed under both dry and humid conditions, although it exhibits a saturation effect under dry conditions. In the case of CaCO3, acetic acid uptake is limited to the surface under dry conditions while it leads to the decomposition of the bulk of CaCO3 under humid conditions. While coordinated surface acetate species increased the water adsorption capacity slightly, the formation of bulk acetate promoted the water absorption capacity greatly. This study demonstrated that Heterogeneous Reaction between CH3COOH and mineral dust is not only an important sink for CH3COOH, but also has a significant effect on the hygroscopic behavior of mineral dust. 1.
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Temperature dependence of the Heterogeneous Reaction of carbonyl sulfide on magnesium oxide.
Journal of Physical Chemistry A, 2008Co-Authors: Hong He, Qingxin MaAbstract:The experimental determination of rate constants for atmospheric Reactions and how these rate constants vary with temperature remain a crucially important part of atmosphere science. In this study, the temperature dependence of the Heterogeneous Reaction of carbonyl sulfide (COS) on magnesium oxide (MgO) has been investigated using a Knudsen cell reactor and a temperature-programmed Reaction apparatus. We found that the adsorption and the Heterogeneous Reaction are sensitive to temperature. The initial uptake coefficients (γt(Ini)) of COS on MgO decrease from 1.07 ± 0.71 × 10-6 to 4.84 ± 0.60 × 10-7 with the increasing of temperature from 228 to 300 K, and the steady state uptake coefficients (γt(SS)) increase from 5.31 ± 0.06 × 10-8 to 1.68 ± 0.41 × 10-7 with the increasing of temperature from 240 to 300 K. The desorption rate constants (kdes) were also found to increase slightly with the enhancement of temperature. The empirical formula between the uptake coefficients, desorption rate constants and temp...
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Mechanism of Heterogeneous Reaction of Carbonyl Sulfide on Magnesium Oxide
Journal of Physical Chemistry A, 2007Co-Authors: Hong He, Wenqing Xu, Yunbo YuAbstract:Heterogeneous Reaction of carbonyl sulfide (OCS) on magnesium oxide (MgO) under ambient conditions was investigated by in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), quadrupole mass spectrometer (QMS), and density functional theory (DFT) calculations. It reveals that OCS can be catalytically hydrolyzed by surface hydroxyl on MgO to produce carbon dioxide (CO2) and hydrogen sulfide (H2S), and then H2S can be further catalytically oxidized by surface oxygen or gaseous oxygen on MgO to form sulfite (SO32-) and sulfate (SO42-). Hydrogen thiocarbonate (HSCO2-) was found to be the crucial intermediate. Surface hydrogen sulfide (HS), sulfur dioxide (SO2), and surface sulfite (SO32-) were also found to be intermediates for the formation of sulfate. Furthermore, the surface hydroxyl contributes not only to the formation of HSCO2- but also to HSCO2- decomposition. On the basis of experimental results, the Heterogeneous Reaction mechanism of OCS on MgO was discussed.
Jing Shang - One of the best experts on this subject based on the ideXlab platform.
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Heterogeneous Reaction of NO2 on the surface of montmorillonite particles
Journal of Environmental Sciences-china, 2012Co-Authors: Zefeng Zhang, Jing Shang, Hongjun Li, Defeng Zhao, Chunxiang YeAbstract:Abstract The studies on Heterogeneous Reactions over montmorillonite, which is a typical 2:1 layered aluminosilicate, will benefit to the understanding of Heterogeneous Reactions on clay minerals. Montmorillonite can be classified as sodium montmorillonite or calcium montmorillonite depending on the cation presented between the different layers. Using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), the Heterogeneous Reaction mechanism of NO 2 on the surface of montmorillonite was firstly investigated. Results showed that the Reaction of NO 2 on the surface of sodium and calcium montmorillonite fit a first-order kinetics, and the Reaction duration of calcium montmorillonite was longer than that of sodium montmorillonite under the dry condition. For either sodium or calcium montmorillonite, the uptake coefficient decreased as humidity increased.
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Heterogeneous Reaction of formaldehyde on the surface of γ-Al2O3 particles
Atmospheric Environment, 2011Co-Authors: Bingye Xu, Jing Shang, Xiaoyan TangAbstract:Abstract Formaldehyde is one of the most important carbonyl organic compounds. Heterogeneous Reactions of formaldehyde on the surface of oxides of crustal elements could be an important sink for formaldehyde in the atmosphere. In this study, the kinetics of the Heterogeneous Reaction of formaldehyde on the surface of γ-Al 2 O 3 was investigated in situ by diffuse reflectance infrared Fourier-transform spectroscopy (DRIFTS) combined with ion chromatography (IC), X-ray diffraction (XRD), and field emission environmental scanning electron microscope (ESEM). The adsorbed species, formate, dioxymethylene, polyoxymethylene, and formaldehyde, on γ-Al 2 O 3 particles, were identified by infrared spectroscopy. On the surface of γ-Al 2 O 3 particles, formaldehyde is first oxidized to dioxymethylene, which is further oxidized to formate. The Reaction order was determined as 0.74 ± 0.05, and the initial reactive uptake coefficients at room temperature were calculated with the geometric and Brunauer–Emmett–Teller specific surface areas as (3.6 ± 0.8) × 10 −4 and (1.4 ± 0.31) × 10 −8 , respectively. The influences of oxygen concentration, humidity, and temperature on the Reaction products and reactive uptake coefficients were studied. The results indicated the Reaction is independent of the O 2 concentration within the range used in this experiment, and humidity is negatively correlated with the uptake of formaldehyde by the particles. Temperature not only plays a role on the Heterogeneous Reaction products but also is positively correlated with the uptake rate of formaldehyde by γ-Al 2 O 3 particles in the troposphere. The apparent activation energy of the Reaction was determined.
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Heterogeneous Reaction of SO2 on TiO2 particles
Science China-chemistry, 2010Co-Authors: Jing Shang, Jia LiAbstract:The Heterogeneous Reaction of SO2 on TiO2 particles was studied using in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The influences of the oxygen concentration, relative humidity (RH), and ultraviolet (UV) light illumination (λ ≈ 365 nm) intensity on the Reaction were investigated. The main product of the Heterogeneous Reaction of SO2 on TiO2 particles was sulfate with UV illumination and sulfite without it. The production of sulfate was promoted significantly with UV illumination or water, and there was a synergistic effect when both were present. In the dry system without UV, the Heterogeneous Reaction of SO2 on TiO2 particles was found to be second-order for SO2 and the initial uptake coefficient, γBET, was determined to be 1.94 × 10−6. With UV and RH = 40%, the Reaction order was first-order and the initial uptake coefficient was 1.35 × 10−5.
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Heterogeneous Reaction of NO 2 with sea salt particles
Science China-chemistry, 2010Co-Authors: Chunxiang Ye, Jing Shang, Hongjun Li, Zefeng Zhang, Defeng ZhaoAbstract:To understand how NO2 reacts with sea salt particles in the atmosphere of Mega-cities in coastal zones, the Heterogeneous Reaction of NO2 on the surface of wet sea salt was investigated with diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and ion chromatography (IC). Kinetic measurements indicated that nitrate formation on sea salt was second order in NO2 concentration and reactive uptake coefficients were (5.51 ± 0.19) × 10−7 and 1.26 ± 10−6 respectively under 0% and 20% relative humidity (RH) at NO2 molecular concentration of 1.96 × 1015 mol/cm3. The results showed that liquid water was formed at the site of MgCl2·6H2O, CaCl2·2H2O on the surface of sea salt and made the Reaction more sustainable by releasing hydrated water and absorbing water from air even under a low RH (⩽ 30%). Therefore, pure NaCl particles should not be used to represent sea salt in studies of the Heterogeneous Reaction with NO2.
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Heterogeneous Reaction of formaldehyde on the surface of TiO2 particles
Science China-chemistry, 2010Co-Authors: Bingye Xu, Xiaoyan Tang, Jing ShangAbstract:The Heterogeneous Reaction of formaldehyde (HCHO) on the surface of titanium dioxide (TiO2) was investigated in situ using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) combined with ion chromatography (IC), X-ray diffraction (XRD), and transmission electron microscopy (TEM). Formate, dioxymethylene, methoxy, and polyoxymethylene were observed in the infrared spectra of TiO2 particles during the Reaction. On the surface of TiO2, the adsorbed HCHO was first oxidized to dioxymethylene and further oxidized to formate. The effects of temperature and ultraviolet radiation (UV) on the Reaction products and reactive uptake coefficients were studied, and the results indicate that the Reaction rate can be accelerated at increasing temperatures as well as under UV. The Heterogeneous Reaction mechanisms of HCHO on the surface of TiO2 in the dark and under UV irradiation are proposed. Kinetic measurements show that formate formation on TiO2 is second order in HCHO concentration and the initial reactive uptake coefficients at room temperature calculated with the Brunauer-Emmett- Teller specific surface area are (0.5–5) × 10−8 ([HCHO]: 1 × 1013−2 × 1014 molecules/cm3). A linear function relationship exists between the uptake coefficient and the concentration. The apparent activation energy of the Reaction was also determined.
H Puxbaum - One of the best experts on this subject based on the ideXlab platform.
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secondary organic aerosol formation in the atmosphere via Heterogeneous Reaction of gaseous isoprene on acidic particles
Geophysical Research Letters, 2003Co-Authors: Andreas Limbeck, Markku Kulmala, H PuxbaumAbstract:[1] Water-soluble macromolecular substances with spectral properties of “humic-like substances” (HULIS) were recently found to form the major identified fraction of the organic aerosol at urban and rural sites in Europe. With primary sources identified so far (e.g., biomass combustion) it is not possible to explain the observed HULIS levels in Europe, therefore there is an ongoing search for other sources - which form HULIS in situ in the atmosphere. Here we show that secondary aerosol formation of atmospheric polymers occurs by Heterogeneous Reaction of isoprenoid or terpenoid emissions in the presence of a sulfuric acid aerosol catalyst. Competing oxidants such as ozone or the presence of humidity decreased the Reaction yield, but the formation of humic–like substances was not disabled. Calculations indicate that the presented Reaction pathway could be an additional source for HULIS in the continental aerosol.
Precious Sibanda - One of the best experts on this subject based on the ideXlab platform.
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spectral quasi linearization method for casson fluid with homogeneous Heterogeneous Reaction in presence of nonlinear thermal radiation over an exponential stretching sheet
Multidiscipline Modeling in Materials and Structures, 2019Co-Authors: Hiranmoy Mondal, Prabir Kumar Kundu, Precious SibandaAbstract:Purpose The focus of the paper is only on the contributions toward the use of entropy generation of non-Newtonian Casson fluid over an exponential stretching sheet. The purpose of this paper is to investigate the entropy generation and homogeneous–Heterogeneous Reaction. Velocity and thermal slips are considered instead of no-slip conditions at the boundary. Design/methodology/approach Basic equations in form of partial differential equations are converted into a system of ordinary differential equations and then solved using the spectral quasi-linearization method (SQLM). Findings The validity of the model is established using error analysis. Variation of the velocity, temperature, concentration profiles and entropy generation against some of the governing parameters are presented graphically. It is to be noted that the increase in entropy generation due to increase in Heterogeneous Reaction parameter is due to the increase in heat transfer irreversibility. It is further noted that the Bejan number decreases with Brinkman number because increase in Brinkman number reduces the total entropy generation. Originality/value This paper acquires realistic numerical explanations for rapidly convergent temperature and concentration profiles using the SQLM. Convergence of the numerical solutions was monitored using the residual error of the PDEs. The resulting equations are then integrated using the SQLM. The influence of emergent flow, heat and mass transfer parameters effects are shown graphically.
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homogeneous Heterogeneous Reactions in micropolar fluid flow from a permeable stretching or shrinking sheet in a porous medium
Boundary Value Problems, 2013Co-Authors: Sachin Shaw, Peri K Kameswaran, Precious SibandaAbstract:The effects of a homogeneous-Heterogeneous Reaction on steady micropolar fluid flow from a permeable stretching or shrinking sheet in a porous medium are numerically investigated in this paper. The model developed by Chaudhary and Merkin (Fluid Dyn. Res. 16:311-333, 1995) for a homogeneous-Heterogeneous Reaction in boundary layer flow with equal diffusivities for reactant and autocatalysis is used and extended in this study. The uniqueness of this problem lies in the fact that the solutions are possible for all values of the stretching parameter λ > 0, while for λ < 0 (shrinking surface), solutions are possible only for a limited range of values. The effects of physical and fluid parameters such as the stretching parameter, micropolar parameter, permeability parameter, Schmidt number, strength of homogeneous and Heterogeneous Reaction parameter on the skin friction, velocity and concentration are analyzed, and these results are presented through graphs. The solute concentration at the surface is found to decrease with the strength of the homogeneous Reaction, and to increase with Heterogeneous Reactions, the permeability parameter and stretching or shrinking parameters. The velocity at the surface was found to increase with the micropolar parameter.
