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Volatile organic compound (VOC) emissions to the atmosphere cause air pollution associated with adverse health outcomes. Volatile chemical products (VCPs) have emerged as a VOC emission category that is poorly characterized by air pollution models. VCPs are present throughout developed economies in manufactured products that include paints, cleaning agents, printing inks, adhesives and pesticides. Air quality models must accurately represent the atmospheric chemistry of VCPs to develop reliable air quality plans. We develop a chemical mechanism for oxidant formation by VCP compounds that is compatible with version 6 of the Carbon Bond (CB6) mechanism. We analyzed a recent U.S. VCP emission inventory and found that ~67% of the emissions mass can be well-represented by existing CB6 mechanism species but ~33% could be better represented by adding 16 emitted VCP species including alcohols, ethers, esters, alkanes and siloxanes. For larger alkanes, an important VCP category, our mechanism explicitly represents temperature-dependent organic nitrate formation and autoxidation via 1,6 H-shift reactions consistent with current knowledge. We characterized the ozone forming potential of each added VCP species and compared it to the current practice of representing VCP species by surrogate species. Nine of the sixteen added VCP species are less reactive than the current practice, namely i-propanol, dimethyl ether, methyl formate, ethyl formate, methyl acetate, larger esters, i-butane, large alkanes and siloxanes. These less reactive VCP species are characterized by having OH-reactions that form un-reactive products. A total of 7 of the 16 VCP species are more reactive than current practice, namely n-propanol, ethylene glycol, propylene glycol, larger alcohols, diethyl ether, larger ethers and ethyl acetate. These more reactive VCP species are characterized as containing functional groups that promote faster OH-reaction. The VCP chemical mechanism for CB6 can improve how VCP impacts to oxidants are represented and will be incorporated to CB7. Changes in oxidant formation resulting from the mechanism update will depend on how VCP emissions are speciated for modeling, which is uncertain, and impacts may go in opposite directions for specific categories of VCP emissions that have unique chemical speciation characteristics. We provide guidance to help modelers implement the VCP mechanism update. [ABSTRACT FROM AUTHOR]

The flavoenzyme glycolate oxidase oxidizes glycolic acid to glyoxylate and the latter, more slowly, to oxalate. It is a member of an FMN‐dependent enzyme family that oxidizes l‐2‐hydroxy acids to keto acids. There has been a controversy concerning the chemical mechanism of substrate oxidation by these enzymes. Do they proceed by hydride transfer, as observed for NAD‐dependent enzymes, or by initial formation of a carbanion that transfers the electrons to the flavin? The present work describes a comparison of the reactivity of glycolate, lactate and trifluorolactate with recombinant human glycolate oxidase, by means of rapid‐kinetics experiments in anaerobiosis. We show that trifluorolactate is a substrate for glycolate oxidase, whereas it is known as an inhibitor for NAD‐dependent enzymes, as is trifluoroethanol for NAD‐dependent alcohol dehydrogenases. Unexpectedly, it was observed that, once reduced, a flavin transfers an electron to an oxidized flavin, so that the end species is a flavin semiquinone, whatever the substrate. This phenomenon has not previously been described for a glycolate oxidase. Altogether, considering that another member of this flavoenzyme family (flavocytochrome b2, a lactate dehydrogenase) has also been shown to oxidize trifluorolactate (Lederer F et al. (2016) Biochim Biophys Acta 1864, 1215–21), this work provides another important piece of evidence which is hardly compatible with a hydride transfer mechanism for this flavoenzyme family.

A kinetic model was developed for the prediction of HTL product yields based on a chemical mechanism. The model was developed after experimental studies on food wastes and food processing wastes. The model parameters were determined by training the model on experimental data on HTL of food wastes. Two other models from the literature were also tested. The calculated yields were compared with a large range of experimental data from the literature. Yields of bio-oil and char can be predicted from the process conditions, temperature, holding time, dry matter content, and the biochemical composition of the resource. Differences in the experimental recovery procedure and polarity of the extraction solvent are taken into account. This study shows that a kinetic model based on compositions allows a more detailed representation of the hydrothermal reactions than models purely based on resources and products. The precision of any model remains, however, largely dependent on the quality of the input data.

The flavoenzyme glycolate oxidase oxidizes glycolic acid to glyoxylate and the latter, more slowly, to oxalate. It is a member of an FMN‐dependent enzyme family that oxidizes l‐2‐hydroxy acids to keto acids. There has been a controversy concerning the chemical mechanism of substrate oxidation by these enzymes. Do they proceed by hydride transfer, as observed for NAD‐dependent enzymes, or by initial formation of a carbanion that transfers the electrons to the flavin? The present work describes a comparison of the reactivity of glycolate, lactate and trifluorolactate with recombinant human glycolate oxidase, by means of rapid‐kinetics experiments in anaerobiosis. We show that trifluorolactate is a substrate for glycolate oxidase, whereas it is known as an inhibitor for NAD‐dependent enzymes, as is trifluoroethanol for NAD‐dependent alcohol dehydrogenases. Unexpectedly, it was observed that, once reduced, a flavin transfers an electron to an oxidized flavin, so that the end species is a flavin semiquinone, whatever the substrate. This phenomenon has not previously been described for a glycolate oxidase. Altogether, considering that another member of this flavoenzyme family (flavocytochrome b2, a lactate dehydrogenase) has also been shown to oxidize trifluorolactate (Lederer F et al. (2016) Biochim Biophys Acta 1864, 1215–21), this work provides another important piece of evidence which is hardly compatible with a hydride transfer mechanism for this flavoenzyme family. [ABSTRACT FROM AUTHOR]

A kinetic model was developed for the prediction of HTL product yields based on a chemical mechanism. The model was developed after experimental studies on food wastes and food processing wastes. The model parameters were determined by training the model on experimental data on HTL of food wastes. Two other models from the literature were also tested. The calculated yields were compared with a large range of experimental data from the literature. Yields of bio-oil and char can be predicted from the process conditions, temperature, holding time, dry matter content, and the biochemical composition of the resource. Differences in the experimental recovery procedure and polarity of the extraction solvent are taken into account. This study shows that a kinetic model based on compositions allows a more detailed representation of the hydrothermal reactions than models purely based on resources and products. The precision of any model remains, however, largely dependent on the quality of the input data. [ABSTRACT FROM AUTHOR]

We have structure, a wealth of kinetic data, thousands of chemical ligands and clinical information for the effects of a range of drugs on monoamine oxidase activity in vivo. We have comparative information from various species and mutations on kinetics and effects of inhibition. Nevertheless, there are what seem like simple questions still to be answered. This article presents a brief summary of existing experimental evidence the background and poses questions that remain intriguing for chemists and biochemists researching the chemical enzymology of and drug design for monoamine oxidases (FAD-containing EC 4.1.3.4).

The antifungal mechanism of plant essential oil has always been a concern in the agriculture and forestry science field. In this investigation, besides the evaluation of inhibitory activities of twenty-three essential oils against Candida albicans in vitro, identification and quantification of the chemical composition of Litsea cubeba essential oil by gas chromatography-mass spectrometry were investigated. Further development, we assessed the mechanism of L. cubeba essential oil against C. albicans by molecular docking. Litsea cubeba essential oil displayed the strongest inhibitory activity among these oils and the diameter of the circle against C. albicans was more than 50 mm. Maximum three components were identified with transcitral (33.6%), cis-citral (30.3%), d-limonene (8.2%). Secretory aspartate protease (SAP5) and β-1,3-glucan synthase (β-1,3-GS) are two key enzyme proteins that inhibit the growth of C. albicans. Molecular docking studies reveal chemical binding forces of cis-citral, trans-citral and d-limonene to SAP5 are -21.76 kJ/mol, -22.18 kJ/mol and -24.27 kJ/mol, to β-1,3-GS are -23.01 kJ/mol, -25.52 kJ/mol and -23.85 kJ/mol, respectively. The most preferable binding mechanism was observed against SAP5 and β-1,3-GS due to hydrophobic interaction, as well as hydrogen bonding between citral molecules. The research results suggest the mechanism of chemical components in L. cubeba essential oil inhibits the growth of C. albicans, which provides a reference to the development and utilization of essential oil. [ABSTRACT FROM AUTHOR]

Moderate or Intense Low–oxygen Diluted (MILD) combustion is a promising technology with interesting ‎properties such as high efficiency and zero-emission. The biogas-syngas mixture is also considered a ‎promising new renewable biofuel with low emissions. This work aims to examine the effects of several ‎parameters on the biogas-syngas flame structure and emissions under MILD conditions in the Jet in Hot ‎Co flow (JHC) burner. The turbulence is modeled by the modified standard k-ε model; whereas ‎combustion-turbulence interaction is handled by the Eddy Dissipation Concept (EDC) in conjunction with ‎three detailed reaction mechanisms, namely: GRI-Mech 3.0, GRI-Mech 2.11, and DRM 2.11. Effects of ‎biogas-syngas composition, temperature, and oxygen concentration in the hot co-flow and Reynolds ‎number of the fuel jet have been elucidated. Results show that flame structure is more sensitive to the ‎increase of hydrogen in syngas than that of methane in biogas. An increase of oxygen concentration or ‎temperature in the co-flow stream leads to more NO formation whereas Reynolds number augmentation ‎reduced them. Furthermore, NO species production is globally governed by the NNH route‎‎.

For source apportionment by tracer method of secondary organic aerosol (SOA), the ratios of aerosol tracer to total SOA mass (fSOA) were determined during the oxidation of toluene, naphthalene, α-pinene, and isoprene by a series of laboratory experiments. Seven anthropogenic SOA tracers maintaining an aromatic ring structure, including 4-nitrophthalic acid and 3,5-dinitrosalicylic, were newly investigated as a chamber study together with 21 traditional aerosol tracers of anthropogenic and biogenic SOA. Experiments of the OH-initiated oxidation of anthropogenic VOCs were conducted as a function of the initial VOC/NOx ratio. No significant dependence on the VOC/NOx ratio was observed for the fSOA of 2,3-dihydroxy-4-oxopentanoic acid from toluene and phthalic acid from naphthalene, whereas the fSOA of nitroaromatic compounds such as 5-nitrosalicylic acid, 3,5-dinitrosalicylic acid, and 4-nitrophthalic acid increased with decreasing VOC/NOx ratio. Among seven newly evaluated anthropogenic SOA tracers, we concluded that 3,5-dinitronsalicylic can be used as a toluene SOA tracer, whereas 4-nitrophthalic acid can be used as a naphthalene SOA tracer. Results of kinetic calculations suggest that naphthalene is a major source of 5-nitrosalicylic acid under urban and rural conditions of previous observation studies. The ozonolysis and NO3-initiated oxidation of biogenic VOCs were investigated in addition to OH-initiated oxidation of biogenic VOCs. As for biogenic SOA tracers such as pinic acid and 2-methyltetrols, the fSOA value measured for the NO3-intiated reaction was lower than that of the OH-initiated oxidation and the fSOA value measured for the ozonolysis was not necessarily close to that of the OH-initiated oxidation. These results suggest that daytime and nighttime biogenic SOA formation events are interpreted by using different sets of the fSOA values.

Atomic layer deposition (ALD) has become an indispensable thin-film technology in the contemporary microelectronics industry. The unique self-limited layer-by-layer growth feature of ALD has outstood this technology to deposit highly uniform conformal pinhole-free thin films with angstrom-level thickness control, particularly on 3D topologies. Over the years, the ALD technology has enabled not only the successful downscaling of the microelectronic devices but also numerous novel 3D device structures. As ALD is essentially a variant of chemical vapor deposition, a comprehensive understanding of the involved chemistry is of crucial importance to further develop and utilize this technology. To this end, we, in this review, focus on the surface chemistry and precursor chemistry aspects of ALD. We first review the surface chemistry of the gas–solid ALD reactions and elaborately discuss the associated mechanisms for the film growth; then, we review the ALD precursor chemistry by comparatively discussing the precursors that have been commonly used in the ALD processes; and finally, we selectively present a few newly-emerged applications of ALD in microelectronics, followed by our perspective on the future of the ALD technology.

Moderate or Intense Low–oxygen Diluted (MILD) combustion is a promising technology with interesting properties such as high efficiency and zero-emission. The biogas-syngas mixture is also considered a promising new renewable biofuel with low emissions. This work aims to examine the effects of several parameters on the biogas-syngas flame structure and emissions under MILD conditions in the Jet in Hot Co flow (JHC) burner. The turbulence is modeled by the modified standard k-ε model; whereas combustion-turbulence interaction is handled by the Eddy Dissipation Concept (EDC) in conjunction with three detailed reaction mechanisms, namely: GRI-Mech 3.0, GRI-Mech 2.11, and DRM 2.11. Effects of biogas-syngas composition, temperature, and oxygen concentration in the hot co-flow and Reynolds number of the fuel jet have been elucidated. Results show that flame structure is more sensitive to the increase of hydrogen in syngas than that of methane in biogas. An increase of oxygen concentration or temperature in the co-flow stream leads to more NO formation whereas Reynolds number augmentation reduced them. Furthermore, NO species production is globally governed by the NNH route. [ABSTRACT FROM AUTHOR]

We have structure, a wealth of kinetic data, thousands of chemical ligands and clinical information for the effects of a range of drugs on monoamine oxidase activity in vivo. We have comparative information from various species and mutations on kinetics and effects of inhibition. Nevertheless, there are what seem like simple questions still to be answered. This article presents a brief summary of existing experimental evidence the background and poses questions that remain intriguing for chemists and biochemists researching the chemical enzymology of and drug design for monoamine oxidases (FAD-containing EC 4.1.3.4). [ABSTRACT FROM AUTHOR]

Surface enhanced Raman scattering (SERS) is a fingerprint spectral technique whose performance is highly dependent on the physicochemical properties of the substrate materials. In addition to the traditional plasmonic metal substrates that feature prominent electromagnetic enhancements, boosted SERS activities have been reported recently for various categories of non-metal materials, including graphene, MXenes, transition-metal chalcogens/oxides, and conjugated organic molecules. Although the structural compositions of these semiconducting substrates vary, chemical enhancements induced by interfacial charge transfer are often the major contributors to the overall SERS behavior, which is distinct from that of the traditional SERS based on plasmonic metals. Regarding charge-transfer-induced SERS enhancements, this short review introduces the basic concepts underlying the SERS enhancements, the most recent semiconducting substrates that use novel manipulation strategies, and the extended applications of these versatile substrates.

Abstract The Community Earth System Model version 2 (CESM2) includes a detailed representation of chemistry throughout the atmosphere in the Community Atmosphere Model with chemistry and Whole Atmosphere Community Climate Model configurations. These model configurations use the Model for Ozone and Related chemical Tracers (MOZART) family of chemical mechanisms, covering the troposphere, stratosphere, mesosphere, and lower thermosphere. The new MOZART tropospheric chemistry scheme (T1) has a number of updates over the previous version (MOZART‐4) in CESM, including improvements to the oxidation of isoprene and terpenes, organic nitrate speciation, and aromatic speciation and oxidation and thus improved representation of ozone and secondary organic aerosol precursors. An evaluation of the present‐day simulations of CESM2 being provided for Climate Model Intercomparison Project round 6 (CMIP6) is presented. These simulations, using the anthropogenic and biomass burning emissions from the inventories specified for CMIP6, as well as online calculation of emissions of biogenic compounds, lightning NO, dust, and sea salt, indicate an underestimate of anthropogenic emissions of a variety of compounds, including carbon monoxide and hydrocarbons. The simulation of surface ozone in the southeast United States is improved over previous model versions, largely due to the improved representation of reactive nitrogen and organic nitrate compounds resulting in a lower ozone production rate than in CESM1 but still overestimates observations in summer. The simulation of tropospheric ozone agrees well with ozonesonde observations in many parts of the globe. The comparison of NOx and PAN to aircraft observations indicates the model simulates the nitrogen budget well.

Alkyl and multifunctional nitrates (RONO2, Sigma ANs) have been observed to be a significant fraction of NOy in a number of different chemical regimes. Their formation is an important free radical chain termination step ending production of ozone and possibly affecting formation of secondary organic aerosol. Sigma ANs also represent a potentially large, unmeasured contribution to OH reactivity and are a major pathway for the removal of nitrogen oxides from the atmosphere. Numerous studies have investigated the role of nitrate formation from biogenic compounds and in the remote atmosphere. Less attention has been paid to the role Sigma ANs may play in the complex mixtures of hydrocarbons typical of urban settings. Measurements of total alkyl and multifunctional nitrates, NO2, total peroxy nitrates (Sigma PNs), HNO3 and a representative suite of hydrocarbons were obtained from the NASA DC-8 aircraft during spring of 2006 in and around Mexico City and the Gulf of Mexico. Sigma ANs were observed to be 10-20% of NOy in the Mexico City plume and to increase in importance with increased photochemical age. We describe three conclusions: (1) Correlations of Sigma ANs with odd-oxygen (O-x) indicate a stronger role for Sigma ANs in the photochemistry of Mexico City than is expected based on currently accepted photochemical mechanisms, (2) Sigma AN formation suppresses peak ozone production rates by as much as 40% in the near-field of Mexico City and (3) Sigma ANs play a significant role in the export of NOy from Mexico City to the Gulf Region.

A new path for hydroxyl radical formation via photo-excitation of nitrogen dioxide (NO2) and the reaction of photo-excited NO2 with water is evaluated using the UCI-CIT model for the South Coast Air Basin of California (SoCAB). Two separate studies predict different reaction rates, which differ by nearly an order of magnitude, for the reaction of photo-excited NO2 with water. Impacts of this new chemical mechanism on ozone and particulate matter formation, while utilizing both reaction rates, are quantified by simulating two summer episodes. First, sensitivity simulations are conducted to evaluate the uncertainty in the rate of reaction of photo-excited NO2 with water reported in the literature. Results indicate that the addition of photo-excited NO2 chemistry increases peak 8-h average ozone and particulate matter concentrations. The importance of this new chemistry is then evaluated in the context of pollution control strategies. A series of simulations are conducted to generate isopleths for ozone and particulate matter concentrations, varying baseline nitrogen oxides (NOx) and volatile organic compounds (VOC) emissions. Isopleths are obtained using 1987 emissions, to represent past conditions, and 2005, to represent current conditions in the SoCAB. Results show that the sensitivity of modeled pollutant control strategies due to photoexcitation decreases with the decrease in baseline emissions from 1987 to 2005. Results show that including NO2 photo-excitation, increases the sensitivity of ozone concentration with respect to changes in NOx emissions for both years. In particular, decreasing NOx emissions in 2005 when NO2 photo-excitation is included, while utilizing the higher reaction rate, leads to ozone relative reduction factors that are 15% lower than in a case without photo-excited NO2. This implies that photoexcitation increases the effectiveness in reducing ozone through NOx emissions reductions alone, which has implications for the assessment of future emission control strategies. However, there is still disagreement with respect to the reaction rate constant for the formation of OH. Therefore, further studies are required to reduce the uncertainty in the reaction rate constant before this new mechanism is fully implemented in regulatory applications.

While fuel combustion in oxygen-enriched environments provides a number of significant advantages, such as reduced nitrogen oxide emissions and high carbon dioxide purity for carbon sequestration, it is characterized by different physico-chemical oxidation behavior than combustion in air. Compared to nitrogen, carbon dioxide has different specific heat and effective Lewis number, and is chemically more active. Therefore, chemical mechanisms developed for the oxidation of fuel/air mixtures can fail to predict targets of interest for oxy-combustion accurately. In this study, a chemical mechanism of methane, which has been previously validated with data from experiments using air, is evaluated in terms of its prediction accuracy at oxy-conditions by comparing against available literature data. The validation takes various combustion properties into account, including ignition delay times, laminar burning velocities, and extinction strain rates, and covers a wide range of experimental conditions with respect to temperature, pressure, equivalence ratio, and carbon dioxide concentration. As additional targets, extinction strain rates of non-premixed oxy-methane flames are determined in a counterflow burner at conditions, where literature data have not yet been reported. The extensive validation demonstrates that the mechanism is able to describe oxy-methane combustion with reasonable prediction accuracy. For further insights into the underlying kinetics of diffusion flames of methane in oxy-atmosphere compared to its oxidation in air, reaction path and sensitivity analyses are performed using the validated mechanism. Notable differences between both combustion regimes are observed in the branching ratios of H-abstraction reactions by OH and H radicals and in the consumption channels of singlet methylene, which is a key species in the formation of polycyclic aromatic hydrocarbons. [ABSTRACT FROM AUTHOR]

Graph‐theoretical methods have revolutionized the exploration of complex systems across scientific disciplines. Here, we demonstrate their applicability to the investigation and comparison of three widely used atmospheric chemical mechanisms of varying complexity: the Master Chemical Mechanism v3.3, GEOS‐Chem v12.6, and the Super‐Fast chemical mechanism. We investigate these mechanisms using a class of graphical models known as species‐reaction graphs and find similarities between these chemical reaction systems and other systems arising in nature. Several graph theoretical properties are consistent across mechanisms, including strong dynamical system disequilibrium and clustering of chemically related species. This formalism also reveals key differences between the mechanisms, some of which have characteristics inconsistent with domain knowledge; e.g., isoprene and peroxy radical chemistry exhibit substantially different graph properties in each mechanism. Graph‐theoretical methods provide a promising set of tools for investigating atmospheric chemical mechanisms, complementing existing computational approaches, and potentially opening new avenues for scientific discovery. Plain Language Summary: A type of math known as "graph theory" provides a set of tools for scientific discovery in a variety of contexts. These include the study of social networks, the power grid, and the human brain. In this paper, we apply these tools to the study of the chemical reactions that occur in the atmosphere. We investigate and intercompare several different descriptions of these reactions, and find that these new graph theory‐based techniques provide information consistent with existing scientific techniques, and potentially allow for new avenues for scientific discovery. Key Points: We investigate three atmospheric chemical mechanisms of varying complexity and process representation using graph‐theoretical techniquesResults are consistent with existing computational approaches, demonstrating key similarities and differences between the mechanismsThese techniques provide chemical state independent, structural insights into existing mechanisms, and methods for new mechanism development [ABSTRACT FROM AUTHOR]

There is a growing need to design fuel flexible combustors. This require understanding of the combustion and emission characteristics of the combustors under varying fuel compositions. In the present study, the combustion characteristics and emission of methane and syngas flames were investigated numerically in a swirl stabilized combustor. The numerical model was developed using ANSYS-fluent software and validated using experimental values of temperature, CO2 and NOx emissions. A two-step chemical mechanism was used to model methane-air combustion. Results of the numerical validation showed similar trend between the experimental and predicted temperature along the combustor axis with about 5 % over prediction of the temperature. Syngasair combustion was thereafter modeled using a 21 step chemical mechanism. Syngas compositions studied were: syngas A (67% CO: 33% H2), syngas B (50% CO: 50% H2) and syngas C (33% CO: 67% H2). Results showed that for pure methane, a V-shaped flame was observed with the flame attached to the fuel nozzle, while a lifted flame was observed for case of syngas A composition. CO gas with higher ignition temperature and flammability as compared to H2 gas is the dominant gas in syngas A fuel composition. Jet flames were observed for syngas B and syngas C. Carbon monoxide is a slow burning gas. Therefore syngas with low CO content has a low tendency of emission of CO from the combustor. This suggests that syngas with high CO content such syngas A may require more residence time to completely combust the CO gas. The NOx emission was observed to have the same trend as that of the combustor maximum temperature. Syngas C flame had the highest NOx emission, while, syngas A flame had no NOx emission. This is due to low combustor temperature observed in the case of syngas A flame. [ABSTRACT FROM AUTHOR]

The Community Earth System Model version 2 (CESM2) includes a detailed representation of chemistry throughout the atmosphere in the Community Atmosphere Model with chemistry and Whole Atmosphere Community Climate Model configurations. These model configurations use the Model for Ozone and Related chemical Tracers (MOZART) family of chemical mechanisms, covering the troposphere, stratosphere, mesosphere, and lower thermosphere. The new MOZART tropospheric chemistry scheme (T1) has a number of updates over the previous version (MOZART‐4) in CESM, including improvements to the oxidation of isoprene and terpenes, organic nitrate speciation, and aromatic speciation and oxidation and thus improved representation of ozone and secondary organic aerosol precursors. An evaluation of the present‐day simulations of CESM2 being provided for Climate Model Intercomparison Project round 6 (CMIP6) is presented. These simulations, using the anthropogenic and biomass burning emissions from the inventories specified for CMIP6, as well as online calculation of emissions of biogenic compounds, lightning NO, dust, and sea salt, indicate an underestimate of anthropogenic emissions of a variety of compounds, including carbon monoxide and hydrocarbons. The simulation of surface ozone in the southeast United States is improved over previous model versions, largely due to the improved representation of reactive nitrogen and organic nitrate compounds resulting in a lower ozone production rate than in CESM1 but still overestimates observations in summer. The simulation of tropospheric ozone agrees well with ozonesonde observations in many parts of the globe. The comparison of NOx and PAN to aircraft observations indicates the model simulates the nitrogen budget well. Plain Language Summary: The set of chemical reactions for tropospheric chemistry used in the Community Earth System Model version 2 (CESM2) has been updated significantly over CESM1 in the Community Atmosphere Model with chemistry (CAM‐chem) and Whole Atmosphere Community Climate Model (WACCM) configurations. The emissions used for the CESM2 simulations are documented here, with anthropogenic and biomass burning emissions based on the specified inventories for Climate Model Intercomparison Project 6 (CMIP6), and emissions of biogenic compounds, lightning NO, dust, and sea salt are calculated online and dependent on the simulated meteorology. Evaluation of the CAM‐chem and WACCM configurations of CESM2 with observations indicate an underestimate of anthropogenic emissions of a variety of compounds, including carbon monoxide and hydrocarbons. The updated chemistry leads to an improvement in the simulation of tropospheric ozone. Key Points: This paper fully documents the significant updates to the chemistry mechanisms in version 2 of the Community Earth System ModelThe new tropospheric chemistry scheme improves representation of isoprene oxidation as well as other ozone precursors over earlier versionsThe simulation of tropospheric ozone is improved in comparison to observations [ABSTRACT FROM AUTHOR]

To distinguish the effects of chemical mechanisms and meteorological factors on air pollution in the megacity of Beijing, the sensitive numerical experiments with the third-generation air quality modeling system (WRF-SMOKE-CMAQ) are designed for a one-year simulation in 2018. The results indicate that: 1) the modeling system plays well in performance in the megacity of Beijing in 2018. The correlation coefficient of the simulated PM 2.5 concentration and the observation value reaches 0.74, while the normal mean bias is −14%–32% in the National Standard Air Quality observation stations in Beijing. 2) The impact of chemical mechanisms on pollutants such as ANO 3 is significant, reaching 1075%. However, there is almost no impact on AEC, or ASO 4 from the chemical mechanisms. The impact of chemical mechanisms on NO and O 3 concentration is between the aforementioned two, with a relatively small degree of impact. The influence of chemical mechanisms on PM 2.5 concentration is 35%, while the meteorological factors are 65% under the experiments. 3) For the photochemical species, the peak frequencies of NO 2 concentration in the two experiments are 27.1 ppbV and 5.9 ppbV, respectively, and the peak frequency of NO 2 observed concentration is 19.1 ppbV, near to the simulation in the baseline group, which illustrates that the chemical mechanism includes a large amount of NO 2 generation. The numerical model is a good tool to quantify the effect of chemical mechanisms and meteorological factors. In addition, the concentration of NO 2 in Beijing is decreasing from urban to exurb areas in terms of spatial distribution, and the spatial variation of PM 2.5 is also the same. • The influence of chemical mechanisms on PM 2.5 concentration is 35%, while the influence of meteorological factors is 65%. • The chemical mechanisms have varying impact on the PM components, a significant on ANO 3 , while a little impact on ASO 4. • The difference in the peak frequency of the normal distribution on NO 2 between the two experiments reached 8 ppbV. [ABSTRACT FROM AUTHOR]

We investigated the kinetics, mechanism and secondary organic aerosols formation of the ozonolysis of trans-2-pentenal (T2P) using four different reactors with Fourier Transform InfraRed (FTIR) spectroscopy and Gas Chromatography (GC) techniques at T = 298 ± 2 K and 760 Torr in dry conditions. The rate coefficients and branching ratios were also evaluated using the canonical variational transition (CVT) state theory coupled with small curvature tunneling (CVT/SCT) in the range 278–350 K. The experimental rate coefficient at 298 K was (1.46 ± 0.17) × 10−18 cm3 molecule−1 s−1, in good agreement with the theoretical rate. The two primary carbonyls formation yields, glyoxal and propanal, were 57 ± 10% and 42 ± 12%, respectively, with OH scavenger compared to 38 ± 8% for glyoxal and 26 ± 5% for propanal without OH scavenger. Acetaldehyde and 2-hydroxypropanal were also identified and quantified with yields of 9 ± 3% and 5 ± 2%, respectively, in the presence of OH scavenger. For the OH production, an upper limit of 24% was estimated using mesitylene as OH tracer. Combining experimental and theoretical findings enabled the establishment of a chemical mechanism. Finally, the SOA formation was observed with mass yields of about 1.5%. This work provides additional information on the effect of the aldehyde functional group on the fragmentation of the primary ozonide.

To better understand precursors of dicarboxylic acids in ambient secondary organic aerosol (SOA), we studied C4–C9 dicarboxylic acids present in SOA formed from the oxidation of toluene, naphthalene, α-pinene, and isoprene. C4–C9 dicarboxylic acids present in SOA were analyzed by offline derivatization gas chromatography–mass spectrometry. We revealed that C4 dicarboxylic acids including succinic acid, maleic acid, fumaric acid, malic acid, DL-tartaric acid, and meso-tartaric acid are produced by the photooxidation of toluene. Since meso-tartaric acid barely occurs in nature, it is a potential aerosol tracer of photochemical reaction products. In SOA particles from toluene, we also detected a compound and its isomer with similar mass spectra to methyltartaric acid standard; the compound and the isomer are tentatively identified as 2,3-dihydroxypentanedioic acid isomers. The ratio of detected C4–C5 dicarboxylic acids to total toluene SOA mass had no significant dependence on the initial VOC/NOx condition. Trace levels of maleic acid and fumaric acid were detected during the photooxidation of naphthalene. Malic acid was produced from the oxidation of α-pinene and isoprene. A trace amount of succinic acid was detected in the SOA produced from the oxidation of isoprene.

To analyze the performance of different chemical mechanisms on the prediction under moderate and intense low-oxygen dilution combustion environment, six different kinds of mechanisms were tested by solving the Reynolds averaged Navier- Stokes equations in a 2-D domain with the eddy dissipation concept model by FLUENT software. Temperature and the species concentration of OH, CO, and H2O were compared with the experiment data. The experiment results showed some similarities for each chemical mechanism as well as discrepancies. The comparison of CH4 oxidation route between the GRI2.11 and GRI3.0 mechanisms was made by Chemkin code. Reaction 95 and 147 were responsible for low temperature region for GRI2.11 mechanism at downstream area. [ABSTRACT FROM AUTHOR]

Encouraged by the diversity of n-dodecane chemical mechanisms currently available, this investigation focuses on analysing the impact of using different fuel oxidation schemes on the diesel-like Engine Combustion Network (ECN) Spray A flame structure, simulated by means of an Unsteady Flamelet Progress Variable (UFPV) combustion model. The present research discusses systematically the characteristics of four n-dodecane chemical mechanisms in perfectly stirred reactors and counterflow laminar diffusion flames (flamelets) before the final evaluation in turbulent reacting sprays in order to describe the effects of adding different physical levels of complexity to the ignition of the mixtures. In addition, this analysis is complemented with the description of the effect of the boundary conditions on the flame structure. Results evidence the extreme importance of the low temperature chemistry including the period for which the cool flame extends. The different prediction of this stage between mechanisms leads to noticeable different laminar flame structures which in turn produce substantially distinct turbulent flames, especially in the vicinity of the lift-off length (LOL) in terms of reactivity and positioning in the Z-T map. Finally, simulations confirm the strong effect of the boundary conditions, especially for the ambient temperature, on the ignitable mixtures which directly impacts on the soot precursors formation. [ABSTRACT FROM AUTHOR]

Arylalkylamine N-acyltransferases (AANATs) catalyze the formation of an N-acylamide from an acyl-CoA thioester and an amine. One well known example is the production of N-acetylserotonin from acetyl-CoA and serotonin, a reaction in the melatonin biosynthetic pathway from tryptophan. AANATs have been identified from a variety of vertebrates and invertebrates. Considerable efforts have been devoted to the mammalian AANAT because a cell-permeable inhibitor specifically targeted against this enzyme could prove useful to treat diseases related to dysfunction in melatonin production. Insects are an interesting model for the study of AANATs because more than one isoform is typically expressed by a specific insect and the different insect AANATs (iAANATs) serve different roles in the insect cell. In contrast, mammals express only one AANAT. The major role of iAANATs seem to be in the production of N-acetyldopamine, a reaction important in the tanning and sclerotization of the cuticle. Metabolites identified in insects including N-acetylserotonin and long-chain N-fatty acyl derivatives of dopamine, histidine, phenylalanine, serotonin, tyrosine, and tryptophan are likely produced by an iAANAT. In vitro studies of specific iAANATs are consistent with this hypothesis. In this review, we highlight the current metabolomic knowledge of the N-acylated aromatic amino acids and N-acylated derivatives of the aromatic amino acids, the current mechanistic understanding of the iAANATs, and explore the possibility that iAANATs serve as insect “rhymezymes” regulating photoperiodism and other rhythmic processes in insects.

Abstract The accuracy of atmospheric chemical mechanisms used in air quality models is critical for robustly predicting the production and decay of air pollutants and developing strategies to reduce concentrations that are above levels harmful to humans and ecosystems. In this study we document, evaluate and analyze an application of the CB6r3 chemical mechanism in a 3-D air quality model, the Community Multiscale Air Quality (CMAQ) model, and demonstrate the impact of this updated chemical mechanism on predictions of ozone, oxidized nitrogen and formaldehyde. In general, CMAQ-CB6 slightly improves the predictions of ozone over much of the dynamic range, while providing updates that are more consistent with current scientific understanding. For these reasons, CMAQ-CB6 is recommended in place of earlier versions available in CMAQ. Nitric acid is generally overpredicted in both winter and summer, and ongoing work continues to address this overprediction and update other aspects of the mechanism. Highlights • The CB6 chemical mechanism has been included in CMAQ with modifications. • Predictions are analyzed against observations of several pollutants. • CMAQ-CB6 performance for ozone is similar to previous CB05 mechanisms. [ABSTRACT FROM AUTHOR]

Abstract Uncertainty was evaluated in four chemical mechanisms pertaining to O 3 concentrations predicted over Japan by the Community Multiscale Air Quality Model (CMAQ) to investigate factors contributing to model overestimation of O 3 concentration. The model setting and meteorological and emissions input data were obtained from a Japanese model inter-comparison project, Japan's Study for Reference Air Quality Modeling (J-STREAM). The compared gas-phase chemical mechanisms included the Carbon Bond Mechanism (CB05TUCL), Regional Atmospheric Chemical Mechanism (RACM2), and two mechanisms developed by the State Air Pollution Research Center (SAPRC), namely SAPRC07TC and SAPRC99. The O 3 concentrations produced by CB05TUCL were low compared to those from SAPRC07TC. The RACM2 concentrations were similar to those from SAPRC07TC over inland Japan and lower over the sea. The concentrations from SAPRC99 were higher than those from SAPRC07TC in urban areas and lower in other areas. At most of the monitoring sites in Japan, the modeled O 3 concentrations were higher than those from observations. Module overestimation can be ranked in the order of SAPRC99 > SAPRC07TC > RACM2 > CB05TUCL for urban sites and SAPRC07TC > SAPRC99 > RACM2 > CB05TUCL for rural sites. The concentration differences between the chemical mechanisms were within 10 ppb, whereas those between the observed and simulated O 3 concentrations reached 40 ppb. Differences in O 3 concentrations between the chemical mechanisms accounted for only a part of the model overestimation, while the rest remained unexplained. To investigate factors influencing the differences in O 3 concentration between the chemical mechanisms, domain- and 10-vertical-layer-average hourly integrated process rates (IPRs) and integrated reaction rates (IRRs) were calculated using process analysis in CMAQ. The O 3 chemical IPRs from SAPRC07TC were higher than those from CB05TUCL and RACM2. The SAPRC99 IPRs were higher than those from SAPRC07TC in urban areas and lower in other areas. The IRR differences in the chemical mechanisms showed that IRRs for the O 3 and NO reactions were responsible for the differences in the O 3 chemical IPR. The coefficients of determination between the O 3 chemical process IPR and IRR differences in the chemical mechanisms were highest for the HO 2 -NO reaction in CB05TUCL and SAPRC99 and the RO 2 -NO reaction in RACM2. Differences in reaction rate constants and lumped volatile organic compounds may have caused some of the differences in O 3 production between the chemical mechanisms. Highlights • O 3 concentrations from different chemical mechanisms were within 10 ppb. • Of the mechanisms, CB05 O 3 concentrations were lowest and closest to observations. • Whole-model O 3 overestimation was not explained by differences in the mechanisms. [ABSTRACT FROM AUTHOR]

Recently, diesel/biodiesel/alcohol blend fuels have attracted tremendous attention as a potential alternative fuel in internal combustion engines, because of their beneficial effects on pollution emission and engine performance. However, there are few chemical mechanisms to forecast combustion characteristics of the ternary blends, especially for those blending with long-chain alcohols, such as butanol and pentanol. The objective of this paper is to develop a combined reduced combustion mechanism for the combustion simulation of diesel/biodiesel/alcohol (up to n-pentanol). This new combined mechanism, consisting of 229 species and 902 elementary reactions, was constructed by integrating two separated reduced mechanisms; one is the PRF-alcohols’ mechanism (Liu et al., 2016), and another is the biodiesel mechanism (Luo et al., 2012). The new combined mechanism reproduced well predictions of fuel ignition and flame speed compared with those obtained using the original ones. Extensive validations were performed against various experimental data for 0-D homogenous systems, 1-D freely propagating premixed flames and 3-D spray combustion flames. The proposed combined mechanism was shown to be versatile and robust, successfully integrating the biodiesel reaction mechanism and the long-chain alcohol reaction mechanisms into a single reaction scheme. Coupling with advanced simulation technology, it could be a powerful numerical tool in the design and optimization of new generation engines which are fueled with clean alternative fuels, especially when concerning long-chain alcohols. In addition, the effects of adding biodiesel and different kinds of alcohols on fundamental combustion characteristics of diesel/biodiesel/alcohol blend fuels were investigated using the proposed combined mechanism. [ABSTRACT FROM AUTHOR]

Graphene is a two-dimensional (2D) material consisting of a single sheet of sp2 hybridized carbon atoms laced in a hexagonal lattice, with potentially wide usage as a Raman enhancement substrate, also termed graphene-enhanced Raman scattering (GERS), making it ideal for sensing applications. GERS improves upon traditional surface-enhanced Raman scattering (SERS), combining its single-molecule sensitivity and spectral fingerprinting of molecules, and graphene’s simple processing and superior uniformity. This enables fast and highly sensitive detection of a wide variety of analytes. Accordingly, GERS has been investigated for a wide variety of sensing applications, including chemical- and bio-sensing. As a derivative of GERS, the use of two-dimensional materials other than graphene for Raman enhancement has emerged, which possess remarkably interesting properties and potential wider applications in combination with GERS. In this review, we first introduce various types of 2D materials, including graphene, MoS2, doped graphene, their properties, and synthesis. Then, we describe the principles of GERS and comprehensively explain how the GERS enhancement factors are influenced by molecular and 2D material properties. In the last section, we discuss the application of GERS in chemical- and bio-sensing, and the prospects of such a novel sensing method.

In this study, numerical analysis of fuel structures on engine soot particles’ mass and size were done by CFD combustion modelling using diesel and different levels of unsaturated biodiesel fuels through the KIVA4-CHEMKIN platform. The proposed numerical approach, with a quad-component skeletal mechanism of biodiesel blend surrogates along with a multi-step phenomenological soot particle model, could capture the soot particle characteristics of test fuels with acceptable accuracy under engine combustion conditions. The reduction of exhaust soot from biodiesel combustion, compared to diesel fuel, was attributed to the suppressed soot precursors formation and lower number of particles in total. However, it was concluded that the biodiesel fuel with a higher fraction of unsaturated FAMEs (more double carbon bonds C C) contributed more to the formation of soot precursors, thus producing a higher amount of soot particles in mass and numbers as a consequence of accelerated soot particle nucleation and soot surface growth. [ABSTRACT FROM AUTHOR]

The component of marine diesel fuel is complex. The muti-component mechanism with aromatic hydrocarbon can more accuracy the combustion of marine diesel engine. The new reduced n-tetradecane-toluene mechanism of marine diesel engine has been developed in this paper. The established model consists of 85 species and 317 reactions without cross reaction. This paper discuss the cross reaction on the effect of marine diesel engine for different mechanism, the new mechanism and the mechanism with 15% toluene content. The results show that the computed ignition delay time with the new mechanism was agreement with the data of mechanism with cross reaction. The in-cylinder pressure are almost same for all case. However, the heat release rate is higher at the end of for the mechanism with cross reaction. The error of CO2 and NOx is minimum using the mechanism with 15% toluene content added cross reaction. The cross reactions has large effect on the emission of marine diesel engine. [ABSTRACT FROM AUTHOR]

Radiation modeling and combustion chemistry are critical to accurate numerical predictions of oxy-combustion characteristics. The presence of carbon dioxide (CO 2 ) in oxy-fuel combustion acts as diluents and significantly changes the radiative properties of the combustion gases in comparison to air combustion. In this regard, three global reaction mechanisms: Westbrook-Dryer (3 equations), Jones-Lindstedt (5 equations) and Jones-Lindstedt (7 equations) for oxy-fuel combustion of methane were combined with different weighted sum of gray gas radiation models (WSGGM) available in literature to determine the most accurate combination for methane-oxy-fuel combustion modeling and simulation. This study was carried out in a non-premixed swirl stabilized model gas turbine combustor at a firing rate of 4MW/m 3 -bar. The modified Westbrook-Dryer (WD-oxy) mechanism could not predict the flame attachment to the fuel nozzle at 35% CO 2 addition. The combinations of Jones-Lindstedt (5 equations) reaction mechanism and WSGGM model proposed by Bordbar gave the closest approximation to our experimental observations and predicted the flame attachment to the fuel nozzle. [ABSTRACT FROM AUTHOR]

The physical properties and chemical mechanisms have direct relationship with combustion. The physical properties of different alternative fuels are researched on the effect of performance of marine diesel engine in this paper. The effect of in-cylinder pressure, emission products and the main species are compared. It can provides a direction for the researchers in established the CFD model. The results show that the in-cylinder pressure and temperature have large difference for different alternative fuels. The in-cylinder pressure and temperature are lower for the heavy oil. Due to the worse combustion, the soot mass has maximum value for heavy oil. The C14H30 and O2 mass have higher value at the start of combustion for the heavy oil. It also explains the combustion process of heavy oil. [ABSTRACT FROM AUTHOR]

The accuracy of determining atmospheric chemical mechanisms is a key factor in air pollution prediction, pollution-cause analysis and the development of control schemes based on air quality model simulations. However, the reaction of NH 3 and OH to generate NH 2 and its subsequent reactions are often ignored in the MOZART-4 chemical mechanism. To solve this problem, the gas-phase chemical mechanism of NH 3 was updated in this study. Response surface methodology (RSM), integrated gas-phase reaction rate (IRR) diagnosis and process analysis (PA) were used to quantify the influence of the updated NH 3 chemical mechanism on the O 3 simulated concentration, the nonlinear response relationship of O 3 and its precursors, the chemical reaction rate of O 3 generation and the meteorological transport process. The results show that the updated NH 3 chemical mechanism can reduce the error between the simulated and observed O 3 concentrations and better simulate the O 3 concentration. Compared with the Base scenario (original chemical mechanism simulated), the first-order term of NH 3 in the Updated scenario (updated NH 3 chemical mechanism simulated) in RSM passed the significance test (p < 0.05), indicating that NH 3 emissions have an influence on the O 3 simulation, and the effects of the updated NH 3 chemical mechanism on NOx-VOC-O 3 in different cities are different. In addition, the analysis of chemical reaction rate changes showed that NH 3 can affect the generation of O 3 by affecting the NOx concentration and NOx circulation with radicals of OH and HO 2 in the Updated scenario, and the change of pollutant concentration in the atmosphere leads to the change of meteorological transmission, eventually leading to the reduction of O 3 concentration in Beijing. In conclusion, this study highlights the importance of atmospheric chemistry for air quality models to model atmospheric pollutants and should attract more research focus. [Display omitted] • The chemical reaction of NH 3 in the chemical mechanism of MOZART-4 was updated. • Impact of updated NH 3 chemical mechanism on O 3 formation further investigated. • Improved O 3 simulation by updating NH 3 chemical mechanism. • Updated NH 3 chemical reaction affects NOx-VOC-O 3 differently in different cities. • Updated scenario lowers Beijing's O 3 concentrations via chemistry and meteorology. [ABSTRACT FROM AUTHOR]

Recycling Sn from waste liquid crystal display (LCD) is crucial to alleviate resource shortage and prevent environmental pollution. However, the disposal of waste LCD is a complex coupling process affected by multi-factors. The lack of mature harmless and resource-based treatment process restricts the development of industrialization. Therefore, an environmentally sound process focusing on resource recovery was proposed to recover Sn efficiently and remove toxic substances from waste LCD in this study. The reaction mechanism and leaching kinetics were discussed assisted by mechanical activation, and the statistical and mathematical method (Box-Behnken Design (BBD) model) was adopted to optimize the leaching process. The results showed that the mechanical activation could improve the physical and chemical properties of ITO glass. The essence of the leaching reaction mechanism was that the H+ in H 2 SO 4 combined with O2− in the lattice of In 2 O 3 to form OH−, resulting in Sn–O bond broking and Sn4+ entering the aqueous solution. Furthermore, the Zeta potential results showed that the Zeta potential of SiO 2 particles less than 0.035 mm was close to zero near pH 2, resulting in agglomeration between SiO 2 particles under the action of Coulomb force. The leaching kinetics was well expressed by the shrinking core model. The BBD model showed satisfactory correlation between the predicted and actual results, and the particle size was the most critical factor affecting the leaching efficiency. The maximum leaching efficiency was 87.6% which was obtained under the following optimal condition: 6 mol/L H 2 SO 4 , 108 min, 88 °C, and 0.035 mm ITO glass powder. Our findings demonstrated that the developed recovery process was both efficient and environmentally sound, which had the potential in the industrialization of waste LCD recycling system. [Display omitted] • An eco-friendly process with experimental analysis and prediction model was proposed. • The process maximally recovered tin while treating hazardous liquid crystal display. • The shrinking core model was applied for the assessment of leaching kinetics. • Prediction model clarified the interaction and optimization of experiment parameters. • Besides the high efficiency the process proved to sustainability and practicality. [ABSTRACT FROM AUTHOR]

The accuracy of determining atmospheric chemical mechanisms is a key factor in air pollution prediction, pollution-cause analysis and the development of control schemes based on air quality model simulations. However, the reaction of NH 3 and OH to generate NH 2 and its subsequent reactions are often ignored in the MOZART-4 chemical mechanism. To solve this problem, the gas-phase chemical mechanism of NH 3 was updated in this study. Response surface methodology (RSM), integrated gas-phase reaction rate (IRR) diagnosis and process analysis (PA) were used to quantify the influence of the updated NH 3 chemical mechanism on the O 3 simulated concentration, the nonlinear response relationship of O 3 and its precursors, the chemical reaction rate of O 3 generation and the meteorological transport process. The results show that the updated NH 3 chemical mechanism can reduce the error between the simulated and observed O 3 concentrations and better simulate the O 3 concentration. Compared with the Base scenario (original chemical mechanism simulated), the first-order term of NH 3 in the Updated scenario (updated NH 3 chemical mechanism simulated) in RSM passed the significance test (p < 0.05), indicating that NH 3 emissions have an influence on the O 3 simulation, and the effects of the updated NH 3 chemical mechanism on NOx-VOC-O 3 in different cities are different. In addition, the analysis of chemical reaction rate changes showed that NH 3 can affect the generation of O 3 by affecting the NOx concentration and NOx circulation with radicals of OH and HO 2 in the Updated scenario, and the change of pollutant concentration in the atmosphere leads to the change of meteorological transmission, eventually leading to the reduction of O 3 concentration in Beijing. In conclusion, this study highlights the importance of atmospheric chemistry for air quality models to model atmospheric pollutants and should attract more research focus., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

The formation process of algae is described inaccurately and water blooms are predicted with a low precision by current methods. In this paper, chemical mechanism of algae growth is analyzed, and a correlation analysis of chlorophyll-a and algal density is conducted by chemical measurement. Taking into account the influence of multi-factors on algae growth and water blooms, the comprehensive prediction method combined with multivariate time series and intelligent model is put forward in this paper. Firstly, through the process of photosynthesis, the main factors that affect the reproduction of the algae are analyzed. A compensation prediction method of multivariate time series analysis based on neural network and Support Vector Machine has been put forward which is combined with Kernel Principal Component Analysis to deal with dimension reduction of the influence factors of blooms. Then, Genetic Algorithm is applied to improve the generalization ability of the BP network and Least Squares Support Vector Machine. Experimental results show that this method could better compensate the prediction model of multivariate time series analysis which is an effective way to improve the description accuracy of algae growth and prediction precision of water blooms. [ABSTRACT FROM AUTHOR]

A C 1 –C 3 short chemical-kinetic mechanism (the San Diego mechanism), which involves 235 elementary reactions among 40 such species, is extended to C 4 by adding 22 chemical-kinetic steps, among 7 additional species, with their associated reaction-rate parameters, to include the ignition and combustion of n-butane over a range of conditions that encompasses both low-temperature and high-temperature chemistry, as well as both high and low pressures. Tests of predictions against measured ignition delays and laminar burning velocities are reported, as are comparisons with recent measurements in jet-stirred reactors, supporting the predictions of the mechanism, which may be useful in combustion computations, especially when larger mechanisms would be too time-consuming to be accommodated. [ABSTRACT FROM AUTHOR]

Air pollutants emitted from vehicles in street canyons may be reactive, undergoing mixing and chemical processing before escaping into the overlying atmosphere. The deterioration of air quality in street canyons occurs due to combined effects of proximate emission sources, dynamical processes (reduced dispersion) and chemical processes (evolution of reactive primary and formation of secondary pollutants). The coupling between dynamics and chemistry plays a major role in determining street canyon air quality, and numerical model approaches to represent this coupling are reviewed in this article. Dynamical processes can be represented by Computational Fluid Dynamics (CFD) techniques. The choice of CFD approach (mainly the Reynolds-Averaged Navier-Stokes (RANS) and Large-Eddy Simulation (LES) models) depends on the computational cost, the accuracy required and hence the application. Simplified parameterisations of the overall integrated effect of dynamics in street canyons provide capability to handle relatively complex chemistry in practical applications. Chemical processes are represented by a chemical mechanism, which describes mathematically the chemical removal and formation of primary and secondary species. Coupling between these aspects needs to accommodate transport, dispersion and chemical reactions for reactive pollutants, especially fast chemical reactions with time scales comparable to or shorter than those of typical turbulent eddies inside the street canyon. Different approaches to dynamical and chemical coupling have varying strengths, costs and levels of accuracy, which must be considered in their use for provision of reference information concerning urban canopy air pollution to stakeholders considering traffic and urban planning policies. [ABSTRACT FROM AUTHOR]

This paper improves the tetraethoxysilane (TEOS) oxidation mechanism proposed by Nurkowski et al. (2015) [17] by refining the rate parameters of the key reaction channels in the mechanism. A skeletal version of the mechanism is proposed for hydrogen–oxygen environment. The rates of ethylene-loss from (tetra-, tri-, di- and dimethyldi-) ethoxysilane are computed using transition state theory. The energetics of the main pathways are refined by performing detailed ab initio calculations using the CBS-Q technique. An analysis of ethanol formation via silicates is also performed resulting in the addition of 27 new silica species to the model. Thermodynamic properties for these species are calculated via the balanced reactions method. Reasonably good agreement between the improved model and available experimental data is observed. The subsequent elimination of unimportant species and reactions is achieved via a three-stage reduction procedure. The first and second stages involve the Direct Relation Graph with Error Propagation (DRGEP) method, whereas the third stage analyses rate of progress of each reaction. The investigated conditions are taken from the experimental studies of TEOS oxidation in oxygen–hydrogen flames. The final skeletal mechanism comprises 70 species and 457 reactions and retains good reproduction of the key model properties across the chosen operating conditions as compared to the full mechanism. [ABSTRACT FROM AUTHOR]