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As hydrogen (H 2) gains attention as a clean alternative to conventional fuels, understanding its effect on engine processes becomes necessary. This is especially challenging in dual-fuel applications combining H 2 and carbon-based fuels so that flexibility in combustion can be extended to emissions control. In this study, the real-driving conversion efficiency of CO and HC in Pt and Pt/Pd oxidation catalysts is investigated in the presence of H 2 applying an experimental–computational approach. The analysis of the experimental data drives to propose a reaction mechanism that accounts for alternative pathways for CO and HC oxidation when H 2 is present. This mechanism is then implemented in a one-dimensional model for dual-layer washcoat honeycomb catalytic converters. Firstly, the model is calibrated against experimental temperature-ramp tests to assess the sensitivity of CO and HC light-off temperature and selectivity to O 2 and H 2 depending on the catalytic formulation. Then, the H 2 effects on the conversion efficiency are analysed under real driving conditions considering a wide range of H 2 content. Finally, the changes in the catalyst response and the differences between Pt and Pt/Pd samples as a function of a variety of simple post-injection strategies are discussed in terms of cumulative conversion efficiency benefits against H 2 consumption. [Display omitted] • H 2 is studied as a CO and HC oxidation promoter in Pt and Pt/Pd catalysts. • Pt and Pt/Pd affinity to ⋅ OH radicals affects selectivity to O 2 along the monolith. • H 2 highly enhances CO light-off and cumulative conversion under real driving. • Pt optimises the balance between CO conversion increase and H 2 consumption. • Adsorption and O 2 interplay limit the benefits of HC conversion from H 2 presence. [ABSTRACT FROM AUTHOR]

The potential for ammonia/hydrogen (NH 3 /H 2) blends as fuel in modern, turbocharged, gas engines is evaluated by comparing the combustion properties of these blends with those of methane. To ensure proper combustion phasing in existing spark-ignited (SI) engines, the laminar burning velocity (LBV) is used, while the ignition delay times (IDT) of the mixtures are compared to assess the risk of engine knock. The chemical mechanisms used for the computation of IDT and/or LBV of NH 3 /H 2 mixtures are selected from 8 chemical mechanisms based on their ability to predict experimental data. The application of a turbocharger is shown to "boost" the temperature in the cylinder after compression to values that admit the use of NH 3 /H 2 mixtures in natural-gas SI engines without increasing the compression ratio (CR). The analysis also identifies regions of temperature and H 2 fraction that increase the risk of knock. Using the conditions in a practical turbocharged SI engine as an example, 40–50% H 2 in NH 3 yields combustion phasing equivalent to that obtained with methane, while avoiding the risk of knock. Analysis of the IDT for the conditions in a high-pressure direct-injection natural-gas engine also shows that the use of a turbocharger in compression-ignition (diesel-type) engines strongly reduces the demands on CR for achieving the conditions necessary for reliable ignition of NH 3 /H 2 mixtures. Increasing the temperature by only a few tens of degrees above the conditions studied will yield an IDT for ∼20% H 2 in NH 3 that satisfies the ignitibility requirements for use in a turbocharged diesel engine. • Turbocharging facilitates the use of NH 3 /H 2 mixtures in gas engines. • The risk of engine knock limits the "boost" temperature and maximum H 2 fraction. • 40–50% H 2 in NH 3 mimics CH 4 combustion without knocking in the SI engine considered. • Modest preheating enables the use of NH 3 with 20% H 2 in a turbocharged CI engine. • The methodology used is readily applied to different fuels and engine conditions. [ABSTRACT FROM AUTHOR]

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]

• A smog chamber was designed and comprehensively characterized. • The wall loss of gases and particles are smaller than other chambers. • The chamber can provide high quality data for gas-phase oxidation and SOA formation. Smog chambers provide a potent approach to explore the secondary organic aerosol formation under varied conditions. This study describes the construction and characterization of a new smog chamber facility for studying the formation mechanisms of gas-phase products and secondary organic aerosol from the photooxidation of volatile organic compounds. The chamber is a 5.4 m3 Fluorinated Ethylene Propylene (FEP) Teflon reactor with the potential to perform photooxidation experiments at controlled temperature and relative humidity. Detailed characterizations were conducted for evaluation of stability of environmental parameters, mixing time, background contamination, light intensity, and wall losses of gases and particles. The photolysis rate of NO 2 (J NO2) ranged from (1.02−3.32) ×10−3 sec−1, comparable to the average J NO2 in ambient environment. The wall loss rates for NO, NO 2 , and O 3 were 0.47 × 10−4, 0.37 × 10−4, and 1.17 × 10−4 min−1, while wall loss of toluene was obsoletely found in a 6 hr test. The particle number wall loss rates are (0.01−2.46) ×10−3 min−1 for 40−350 nm with an average lifetime of more than one day. A series of toluene photooxidation experiments were carried out in absence of NO x under dry conditions. The results of the simulation experiments demonstrated that the chamber is well designed to simulate photolysis progress in the atmosphere. [Display omitted] [ABSTRACT FROM AUTHOR]

A small proportion of nephropathy patients administered gadolinium contrast agents for nuclear magnetic resonance have been reported to develop nephrogenic systemic fibrosis (NSF). This paper introduces the mechanism of the transformation and deposition of NSF, aiming to reveal the chemical nature of the gadolinium phosphate bioparticles in nephrogenic system fibrosis. This research will provide an important theoretical basis for future studies on the occurrence, development, and formation of nephrogenic system fibrosis and the removal of sediment residues. Moreover, a new idea for introducing a biocompatible second chelating agent into the gadolinium contrast agent system has been proposed, which aims to improve the safe use of gadolinium contrast agent. [ABSTRACT FROM AUTHOR]

This paper presents two recent simulation studies conducted at NSW Department of Planning and Environment on the impact on air quality across NSW and the Greater Metropolitan Region (GMR) urban areas due to a dust storm in February 2019 and Covid 19 lock down in NSW in 2021. These studies highlight the importance of using suitable air quality models to simulate the emissions and transport of air pollutants over a region to assess the impact of events on air quality and population exposure. The WRF-Chem model is used for the large-scale dust storm event and the WRF-CMAQ is used for assessing emission changes in the GMR due to the Covid-19 lockdown on the urban air quality. Both WRF-Chem and WRF-CMAQ are regional chemical transport models and require high-end Linux-based computing resources. The advantage and disadvantage of applying each of the two models to conduct a particular air quality study will be discussed. [ABSTRACT FROM AUTHOR]

In present work, two types of substrates for the surface enhanced Raman scattering (SERS) spectroscopy based on silver-coated porous silicon (por-Si) and HfOx/por-Si are engineered. The por-Si samples are formed by electrochemical etching the monocrystalline silicon and have a mean pore diameter of 850 nm and a porous layer thickness of 5 µm. Deposition of the hafnium oxide film on the por-Si surface is performed by atomic layer technique, while the SERS-active silver particles are grown by the chemical "silver mirror" method. The HfOx-free substrates demonstrate better SERS-activity but result in changes of the analyte molecule (Ellman's reagent) spectra, which is supposed to associate with their thermal degradation. Oppositely, the Ag/HfOx/por-Si samples provide sufficient and stable enough SERS-activity during at least 1-min SERS-measurements. We assume the observed stability of the analyte on the substrates containing HfOx can be caused by the faster heat dissipation from the laser spot due to more uniform and conformal silver coating than that on HfOx-free sample. The conformal deposition of silver is provided by passivation of the por-Si surface with auxiliary HfOx layer. An analytical enhancement factor for the Ag/HfOx/por-Si substrate equals to 2·103. Therefore, the SERS-active substrate containing HfOx provided athermal effect on analyte. [ABSTRACT FROM AUTHOR]

[Display omitted] • Both AgNPs and Ag-decorated g-C 3 N 4 show excellent SERS activity. • Charge transfer calculations confirm that electrons drift towards the drug from the substrates. • Energy gap of the drug is reduced upon the incorporation of the substrates. • A low limit of detection of 10-12 M was successfully achieved. Herein, silver nanoparticles (AgNPs) and silver-loaded graphitic carbon nitride (Ag@g-C 3 N 4) nanocomposites have been synthesized and used as an effective surface-enhanced Raman scattering (SERS) substrates for the detection of low concentrations (10-14 M) of ciprofloxacin (CIP), a commonly bioactive medication used to treat bacterial illnesses. A combined approach of vibrational spectroscopy and density functional theory (DFT) has been developed to understand the possible modes of analyte (CIP) and SERS substrate (AgNPs and Ag@g-C 3 N 4) interactions. Furthermore, it has been noticed that the behavior of drug molecules in terms of SERS response and energetics of interaction changed significantly when interacted with the noble metal AgNPs decorated onto the g-C 3 N 4 framework in comparison to only AgNPs as substrate. The most prominent interaction scenario between AgNPs and CIP is likely to be through the –NH moiety of drug molecule with an interaction energy of −306 kcal/mol. Whereas, the CIP molecules adsorbed onto Ag@g-C 3 N 4 nanocomposite were more flexible with interaction energy of −107 kcal/mol, suggesting a greater association of analyte with the skeletal modes of substrate leading to Raman enhancements in the low wavenumber region i.e. below 600 cm−1. Hence, the Ag@g-C 3 N 4 nanocomposite-based SERS substrates investigated served two distinct spectral ranges, making them complementary of each other in terms of SERS detection of CIP. The characteristics of the computed frontier molecular orbitals indicated a pronounced amount of charge transfer between the drug and the substrate, highlighting the significance of the chemical mechanism of the overall process. These results represent a successful approach to have an extended spectral range that covers lower wavenumber shifts by applying simple and meaningful modifications to the normally utilized noble metal-based nanoparticles, which can lead to more effective and reliable detection of bioactive drugs. [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]

Changes in chemical composition during food processing and handling are crucial for the alteration of food flavor and function, and accurate characterization of key chemical reaction pathways in complex food matrices is one of the core challenges in food chemistry research. Here, this study attempts to establish a strategy for sensitive characterization of chemical reactions during food processing based on on-line extraction electrospray ionization mass spectrometry (oEESI-MS). The process of making garlic into black garlic, a traditional global flavor food, was chosen as an exemplary research template. The direct MS characterization of raw garlic as well as black garlic samples with different processing times was achieved by using the self-constructed oEESI-MS device. Benefiting from the high tolerance of oEESI-MS to complex matrix interferences, all samples can be fingerprinted directly without any pre-processing or pre-separation. As a result, oEESI-MS achieved a sensitive characterization of the changes of key substances during the preparation of black garlic. Further, a new chemical reaction pathway, the degradation of γ-L-glutamyl-S-allyl-L-cysteine to S-allyl-l-cysteine, was completely demonstrated by analyzing the differential substances before and after the treatment, and verified by standard substances and chemical theory calculations. In conclusion, a complete oEESI-MS-based strategy for tracking the substance changes in food processing was established in this study, which has a widely applicable prospect for the precise setting of food processing time and parameters, and the innovation of processing technology. • Strategy for studing chemical mechanism of food processing using oEESI-MS was created. • Composition changes in the garlic processing was directly monitored by oEESI-MS. • GSAC was firstly found degraded into SAC, Glu and PGA by a non-enzymatic pathway. • The non-enzymatic pathway was verified by both experimental and theoretical studies. [ABSTRACT FROM AUTHOR]

Volatile organic compounds (VOCs) oxidation processes play a very important role in atmospheric chemistry, and the chemical reactions are expressed in various manners in chemical mechanisms. To gain an improved understanding of VOCs evolution during oxidation processes and evaluate the discrepancies of VOCs oxidation schemes among different mechanisms, we used the total VOC reactivity as a diagnostic and evaluated tool to explore the differences for six widely used chemical mechanisms. We compared the total VOC reactivity evolution under high-NO x conditions for several sets of precursors, including n-pentane, toluene, ethene, isoprene and a mixture of 57 Photochemical Assessment Monitoring Stations (PAMS) species in a 0-D photochemical box model. Inter-comparison of total VOC reactivity of individual precursor simulations showed discrepancies to different extent of the oxidation schemes among the studied mechanisms, which are mainly attributed to the different lumping approaches for organic species. The PAMS simulation showed smaller discrepancy than individual precursor cases in terms of total VOC reactivity. SAPRC07 and RACM2 performances are found to better match the MCM for simulation of total VOC reactivity. Evidences suggest that the performance in simulating secondary organic products, OH concentrations and NO x concentrations are related to the OH reactivity discrepancies among various chemical mechanisms. Information in this study can be used in selection of chemical mechanisms to better model OH reactivity in different environments. The results in this study also provide directions to further improve the ability in modelling total VOC reactivity with the chemical mechanisms. [Display omitted] [ABSTRACT FROM AUTHOR]

Few atom thick, twisted bilayer graphene (tBLG) possesses a rotation angle (θ) dependent van Hove singularity (vHs). Fine-tuning vHs serves a potential method to enhance charge transfer (CT) in surface enhanced Raman spectroscopy. This study shows that tBLG having a specific θ promotes as high as a 1.7 times enhancement of the Raman signals of copper phthalocyanine (CuPc) as compared to that caused by single layer graphene (SLG). The results of a combination of reflection imaging spectroscopy and widefield Raman provide spatial and spectral information about both tBLG with θ ranging from 10.9 to 13.7° and the corresponding vHs. Comparison of Raman spectra of CuPc in presence and absence of tBLG demonstrates that a significant enhancement of certain CuPc vibrational modes occurs when the underlying tBLG possesses a θ = 12.2°, showing as high as 6.8 and 1.7 times enhancements of certain vibrational mode as compared to those of CuPc on bare and SLG substrates, respectively. Theoretical calculations indicate that a match between the energies of vHs of tBLG with those of frontier orbitals of CuPc facilitates CT from the distant SLG to CuPc. [Display omitted] [ABSTRACT FROM AUTHOR]

The prospects of 2-methylfuran (2MF) as a biofuel and gasoline blend stock are quite high. Therefore, a skeletal chemical kinetic mechanism – containing 238 species and 1156 reactions – for the simulation of premixed flames involving isooctane (representing gasoline)/2MF blends is proposed in the present work. The proposed model has been validated against a wide range of experimental data at various pressures, temperatures and compositions. It is demonstrated in the present work that the proposed mechanism can predict the concentrations of gaseous soot precursors as well. Moreover, the compatibility of the NOx sub-mechanism in the present model has been assured through validations against a wide range of recent experimental data. The results obtained in this work suggest that there are little chances of co-oxidation reactions among the species generated from the initial decomposition of both isooctane and 2MF. Furthermore, there is around 26% variation in the peak laminar burning velocity when the mole fraction of 2MF is increased from 10% to 90% in isooctane/2MF blend. [ABSTRACT FROM AUTHOR]

Lightweight embankment is an effective method for soft foundation treatment, while decreasing its cement usage can protect environment, save resource and reduce cost. This study aims to develop a lightweight cement composite (LC) containing fly ash and sand to provide guidance for filling the sustainable embankment. The chemical mechanism, micro-morphology, mechanical strength and workability of lightweight cement composites were evaluated through macro-micro tests, as well as life cycle assessment was performed to analyze the sustainability, and determine the optimal mixing ratio. The results showed that the moderate amount of fly ash was beneficial to enhance the mechanical strength of LC, while adding sand further improved its ductility, toughness, workability and sustainability. When the replacement rate of fly ash and sand were 10 % and 20 %, the energy absorption and fluidity of LC increased by 57 % and 7 %, and its ductility index, carbon emission and construction cost decreased by 34 %, 46 % and 35 %, respectively. Fly ash reacted with calcium hydroxide produced by cement hydration to generate more calcium silicate gels, which reduced the large pore of LC and improved its internal structure, while sand played a certain skeleton role. • Developing an eco-friendly and practical lightweight cement composite. • The applicability and chemical mechanism of lightweight cement composites are assessed. • Utilizing fly ash and sand in cement composite shows better sustainability. [ABSTRACT FROM AUTHOR]

[Display omitted] • Graphene monolayers are transferred successfully onto glass substrates from Cu substrate using the polymer-assisted exfoliation method. • Raman spectra of crystal violet (CV) and IR-780 Iodide molecules dispersed on the monolayer graphene film (MGF) are recorded. • In the CV-MGF system, the irreversible charge transfer is observed irrespective of the laser spot position. • Interestingly, for the first time, the reversible charge transfer observed in the IR-780 iodide-MGF system strongly depends upon the laser spot position. Herein, we report the Raman spectroscopy of crystal violet (CV) and IR-780 Iodide molecules dispersed on the monolayer graphene film (MGF). In the CV-MGF system, the enhancement in the Raman scattering of CV molecules is observed irrespective of the location probed during the spectral measurements. This enhancement is due to the charge transfer from the MGF to CV molecules. However, in the case of the IR-780 Iodide – MGF system, the enhancement of Raman scattering of dye molecules or MGF is observed strongly depending upon the probed location. These observations indicate that the charge transfer is irreversible and reversible in the CV-MGF and IR-780 Iodide–MGF systems, respectively. Importantly, for the first time, this experimental study revealed that enhancing the Raman scattering of MGF is possible through the "chemical mechanism" with suitable dye molecules apart from the "electromagnetic mechanism" with plasmonic hot spots of the metal nanoparticles and photonic nanojets of single dielectric microparticles. [ABSTRACT FROM AUTHOR]

• The ammonia and toluene reference fuel semi-detailed kinetic mechanism was proposed. • The NH 3 /TRF mechanism was validated by ignition delay time and laminar burning velocity. • Sensitivity and reaction pathway analysis was performed for the addition of NH 3 combustion. • The auto-ignition process in NH 3 /TRF blend mixture is dominated by NH 3 chemistry. C-free fuel ammonia has a high auto-ignition temperature and low flame speed compared to conventional hydrocarbon fuels, which limits its application in internal combustion engines (ICEs). Blending ammonia (NH 3) with a highly reactive fuel can effectively solve this problem, and traditional macromolecular hydrocarbon fuels are a good choice because of their practicality and economy. However, the chemical reaction mechanism for the combustion of NH 3 /macromolecular hydrocarbons is not yet fully understood. In this study, a detailed kinetic mechanism for NH 3 and toluene reference fuel (TRF) is proposed with 250 species and 4272 reactions. The developed NH 3 /TRF mechanism was validated by a single component (NH 3 , n-heptane, iso -octane, and toluene) and multiple components (NH 3 /n-heptane, NH 3 / iso -octane, NH 3 /toluene) with ignition delay time, laminar burning velocity, and key intermediate component distribution. The current NH 3 /TRF mechanism showed good performance compared with previous mechanisms. The co-combustion of NH 3 /TRF blends was performed with different NH 3 energy fractions, and sensitivity and reaction pathway analyses were performed to reveal the effect of TRF addition on NH 3 combustion. The results showed that the OH radical is mainly produced through N-containing reactions rather than C-containing reactions under T = 1000 K, P = 40 atm, and ϕ = 1 with more than 30 % NH 3 addition. The HO 2 radical is the most important radical for NH 3 ignition, in addition to OH radicals, and its reactions with N-containing radicals (NH 2, H 2 NO, and NO) contribute to the majority of OH radicals. [ABSTRACT FROM AUTHOR]

Summary: The pyrolysis gas consisting of 29.4% CH4, 21.3% C2H4, 30.8% C2H6, and 18.5% C3H6 in mole fraction is presented, as the surrogate of the actual gaseous pyrolysis products. At the conditions of TC = 877.7‐963 K, PC = 3.22‐4.37 MPa, φ = 0.5 and 1.0, the ignition delays of pyrolysis gas/air (diluted with 52% Ar) have been measured. With TC or PC increasing, the ignition delay time decreases. The auto‐ignition of φ = 1.0 is faster than that of φ = 0.5. Furthermore, two widely used small hydrocarbons chemical mechanisms are validated with the measured results. The USC‐II mechanism can well predict experimental results at high‐T regimes, but fails at low‐T regimes. By sensitivity analysis of temperature, the two elementary reactions C2H6 + OH = C2H5 + H2O (negative sensitivity coefficient) and C3H6 + OH = aC3H5 + H2O (positive sensitivity coefficient) have been identified, which have higher reactivity at low‐T and lower reactivity at high‐T. Considering the extreme uncertainty of rate constants of C3H6 + OH = aC3H5 + H2O, the kinetic parameters have been modified for improving the predictions. The validated results indicate that the optimized mechanism improves predictions of the auto‐ignition behavior at low temperature regimes. [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]

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]

A new state-of-the-art indoor smog chamber facility (CAPS-ZJU) has been constructed and characterized at Zhejiang University, which is designed for chemical mechanism evaluation under well-controlled conditions. A series of characterization experiments were performed to validate the well-established experimental protocols, including temperature variation pattern, light spectrum and equivalent intensity (J NO2), injection and mixing performance, as well as gases and particle wall loss. In addition, based on some characterization experiments, the auxiliary wall mechanism has been setup and examined. Fifty chamber experiments were performed across a broad range of experimental scenarios, and we demonstrated the ability to utilize these chamber data for evaluating SAPRC chemical mechanism. It was found that the SAPRC-11 can well predict the O 3 formation and NO oxidation for almost all propene runs, with 6 hr Δ(O 3 – NO) model error of –3% ± 7%, while the final O 3 was underestimated by ~20% for isoprene experiments. As for toluene and p -xylene experiments, it was confirmed that SAPRC-11 has significant improvement on aromatic chemistry than earlier version of SAPRC-07, although the aromatic decay rate was still underestimated to some extent. The model sensitivity test has been carried out, and the most sensitive parameters identified are the initial concentrations of reactants and the light intensity as well as HONO offgasing rate and O 3 wall loss rate. All of which demonstrated that CAPS-ZJU smog chamber could derive high quality experimental data, and could provide insights on chamber studies and chemical mechanism development. Image, graphical abstract [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]

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]

Abstract The consensus on mechanisms responsible for how chloride-based salts attack concrete has yet not been achieved. This work exposed laboratory-fabricated concrete samples to MgCl 2 solutions of various concentrations along with freeze/thaw and wet/dry cycles, with NaCl solutions as the control. The laboratory investigation revealed a new chemical mechanism during the MgCl 2 -induced deterioration of concrete, i.e., the formation of multi-phase nano-sized crystals, including CaCl 2 , Mg(OH) 2 , and Mg 3 (OH) 5 Cl·(H 2 O) 4. This mechanism was further corroborated by the testing of concrete samples cored from several selected concrete bridge decks, where cumulative exposure to MgCl 2 deicer resulted in significantly compromised splitting tensile strength (as high as 50%) as well as reductions in microhardness (up to 60%, often at a depth of 25 to 50 mm). This study provides new insights into the risks of MgCl 2 to the concrete-built environment. It also alerts that visual inspection could be misleading for condition assessment of concrete exposed to MgCl 2. Highlights • A new chemical mechanism during the MgCl 2 -induced deterioration of concrete. • Formation of nano-sized crystals of CaCl 2 , Mg(OH) 2 , and Mg 3 (OH) 5 Cl·(H 2 O) 4. • This mechanism was further corroborated by the testing of field cores. • Field exposure significantly compromised splitting tensile strength (as high as 50%), and caused a reduction in microhardness (up to 60%). • The degradation often peaked inside concrete, thus elusive to visual inspection. [ABSTRACT FROM AUTHOR]

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]

The prospects of 2,5-dimethylfuran (DMF) as a bio-derived fuel that can be blended with gasoline are believed to be impressive. However, the effects of blending DMF on the key combustion parameters like the laminar burning velocity and ignition delay time of gasoline/air mixture need to be studied extensively for the successful implementation of the fuel mixture in spark ignition engines. Therefore, a skeletal chemical kinetic mechanism, comprising of 999 reactions among 218 species, has been developed in the present work for this purpose. The proposed chemical kinetic model has been validated against a wide range of experimental data for the laminar burning velocity and ignition delay time of isooctane (representing gasoline), DMF and their blends. It has been found from the present study that the thermal diffusivity of the unburnt gas mixture changes by a very small amount from the corresponding value for the pure isooctane/air mixture when DMF is added. Unlike isooctane, the DMF molecule does not consume H radicals during its primary breakup. Therefore, the maximum laminar burning velocity increases marginally when 50% DMF is blended with isooctane due to the increased presence of H radicals in the flame. The negative temperature coefficient behaviour in the ignition delay time of the isooctane fuel vanishes when 30% DMF (v/v) is blended to it. [ABSTRACT FROM AUTHOR]

Abstract The arylalkylamine N -acyltransferases (AANATs) are enzymes that catalyze the acyl-CoA-dependent formation of N -acylarylalkylamides: acyl-CoA + arylalkylamine → N -acylarylalkylamides + CoA-SH. Herein, we describe our study of a previously uncharacterized AANAT from Bombyx mori : Bm -iAANAT3. Bm -iAANAT3 catalyzes the direct formation of N -acylarylalkylamides and accepts a broad range of short-chain acyl-CoA thioesters and amines as substrates. Acyl-CoA thioesters possessing an acyl chain length >10 carbon atoms are not substrates for Bm -iAANAT3. We report that Bm -iAANAT3 is a "versatile generalist", most likely, functioning in amine acetylation – a reaction in amine inactivation/excretion, cuticle sclerotization, and melanism. We propose a kinetic and chemical mechanism for Bm -iAANAT3 that is consistent with our steady-state kinetic analysis, dead-end inhibition studies, determination of the pH-rate profiles, and site-directed mutagenesis of a catalytically important amino acid in Bm -iAANAT3. These mechanistic studies of Bm -iAANAT3 will foster the development of novel compounds targeted against this enzyme and other insect AANATs for the control of insect pests. Graphical abstract Image 1 Highlights • Bm -iAANAT3 exhibits promiscuous substrate specificity for acyl-CoA and amine substrates. • Acetylation occurs via ordered sequential mechanism, with acetyl-CoA binding first and acetylated amine released last. • pH-activity profiles for Bm -iAANAT3 suggest a chemical mechanism with Glu-27 functioning as a base during catalysis. [ABSTRACT FROM AUTHOR]

Monoamine oxidases (MAOs) catalyse the oxidation of neurotransmitter amines and a wide variety of primary, secondary and tertiary amine xenobiotics, including therapeutic drugs. While inhibition of MAO activity in the periphery removes protection from biogenic amines and so is undesirable, inhibition in the brain gives vital antidepressant and behavioural advantages that make MAO a major pharmaceutical target for inhibitor design. In neurodegenerative diseases, MAO inhibitors can help to maintain neurotransmitter levels, making it a common feature in novel multi-target combinations designed to combat Alzheimer’s disease, albeit not yet proven clinically. Vital information for inhibitor design comes from an understanding of the structure, mechanism, and kinetics of the catalyst. This review will summarize the kinetic behaviour of MAO A and B and the kinetic evaluation of reversible inhibitors that transiently decrease catalysis. Kinetic parameters and crystal structures have enabled computational approaches to ligand discovery and validation of hits by docking. Kinetics and a wide variety of substrates and inhibitors along with theoretical modelling have also contributed to proposed schemes for the still debated chemical mechanism of amine oxidation. However, most of the marketed MAO drugs are long-lasting irreversible inactivators. The mechanism of irreversible inhibition by hydrazine, cyclopropylamine, and propargylamine drugs will be discussed. The article finishes with some examples of the propargylamine moiety in multi-target ligand design to combat neurodegeneration. [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]

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]

A numerical study has been carried out to investigate the impact of adding syngas into JP-8 fuel. A new chemical mechanism has been assembled from existing mechanism of JP-8 and syngas and has been examined by comparing with the experimental data from literatures. The mechanism was then applied to Cantera zero-dimension constant internal energy and constant volume model and one-dimensional (1D) freely propagating flame model to calculate the ignition delay time and laminar burning speed, respectively. The simulations were carried out over a large range of temperature (700-1000 K), blending ratio (0-20% syngas), and H2/CO ratio (10/90 to 50/50). Simulation results showed that the blending syngas with JP-8 will slightly increase the ignition delay time and laminar burning speed. [ABSTRACT FROM AUTHOR]

As an octane enhancer in commercial gasoline, ethanol is widely used by its oxygenated and renewable natures. In this study, five gasoline-ethanol blended fuels are studied with anti-knock index of 87–92: (1) Haltermann CARB LEV III E10 gasoline, (2) FACE C gasoline with 7% ethanol (by vol), (3) FACE C with 14% ethanol (by vol), (4) FACE J with 23% ethanol (by vol), (5) FACE J with 36% ethanol (by vol). First, surrogate models are formulated for the five fuels. By conducting a Jacobian-aided directed relation graph with error propagation (DRGEP) approach, a much improved performance is shown over the original counterpart for the multiple heavy fuel surrogate mechanism reduction. Based on the analysis, skeletal mechanisms generated after a hump region with an acceptable error in graph-based approaches is shown to deteriorate the further reduction potential. Starting from a detailed 1134-species mechanism, a 130-species skeletal mechanism and an 80-species reduced mechanism are finally developed with high fidelity under gasoline compression ignition (GCI) engine conditions, combining the DRGEP, target search algorithm (TSA) and quasi-steady state assumption (QSSA) approaches. Additionally, the low temperature heat releases in homogeneous charge compression ignition (HCCI) engine are validated under wide ranges of intake temperatures and pressures. [ABSTRACT FROM AUTHOR]

In this letter, we report the in situ growth of N-doped graphene (NG) thin films by ultraviolet pulsed laser deposition (PLD) in the presence of nitrogen. Based on this approach, the concentration of nitrogen-doping can be easily controlled via the nitrogen gas pressure during the PLD process. XPS results confirm that the nitrogen atoms have been successfully doped into graphene lattice. Moreover, the NGs show improved chemical enhancement for Raman spectra of absorbed Rhodamine 6G (R6G) molecules as compared to the pristine graphene (PG). The relative enhancement factor varies with the nitrogen content in the graphene, and the maximum value is about 2.5. The results show that the NG is a promising material for applications in chemical and biological detection because of its excellent enhanced Raman scattering performance. [ABSTRACT FROM AUTHOR]

In this study, the mechanism of the xanthine oxidase (XO) inhibitory activity of pyrogallol, the main inhibitor found in roasted coffee, was investigated. Pyrogallol was unstable and readily converted to purpurogallin in a pH 7.4 solution, a physiological model of human body fluids. The XO inhibitory activity of the produced purpurogallin was higher than that of pyrogallol, as evidenced by comparing their IC 50 values (0.2 µmol L −1 for purpurogallin, 1.6 µmol L −1 for pyrogallol). The XO activity of pyrogallol was enhanced by pre-incubation in pH 7.4 solution. Although the initial XO inhibitory activity of 4-methylpyrogallol was weak (IC 50 33.3 µmol L −1 ), its XO inhibitory activity was also enhanced by pre-incubation in the pH 7.4 solution. In contrast, 5-methylpyrogallol, which could not be transformed into corresponding purpurogallin derivatives, did not show XO inhibitory activity before or after incubation in pH 7.4 solution. Molecular docking simulations clarified that purpurogallins have stronger affinities for XO than corresponding pyrogallols. These results revealed that the potent XO inhibitory activity seemingly observed in pyrogallol is actually derived from its chemical conversion, under alkaline conditions, into purpurogallin. [ABSTRACT FROM AUTHOR]

2D transition metal dichalcogenide (TMD) materials have been recognized as active platforms for surface-enhanced Raman spectroscopy (SERS). Here, the effect of crystal structure (phase) transition is shown, which leads to altered electronic structures of TMD materials, on the Raman enhancement. Using thermally evaporated copper phthalocyanine, solution soaked rhodamine 6G, and crystal violet as typical probe molecules, it is found that a phase transition from 2H- to 1T-phase can significantly increase the Raman enhancement effect on MoX2 (X = S, Se) monolayers through a predominantly chemical mechanism. First-principle density functional theory calculations indicate that the significant enhancement of the Raman signals on metallic 1T-MoX2 can be attributed to the facilitated electron transfer from the Fermi energy level of metallic 1T-MoX2 to the highest occupied molecular orbital level of the probe molecules, which is more efficient than the process from the top of valence band of semiconducting 2H-MoX2. This study not only reveals the origin of the Raman enhancement and identifies 1T-MoSe2 and 1T-MoS2 as potential Raman enhancement substrates, but also paves the way for designing new 2D SERS substrates via phase-transition engineering. [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]

Pesticide residues create an ecological ecosystem that is incredibly dangerous and presents major risks to human health. To solve this issue, scientists are concentrating on creating extremely effective composites with superior photocatalytic performance. Even if several efforts have been made to remove pesticides and dangerous compounds using adsorption, the development of novel adsorbents with large adsorption capabilities is still very desirable. Here, the photocatalytic of carbamate pesticides in aqueous solution under simulated sunlight irradiation in the existence of Fe 3 O 4 , CuO/Cu 2 O, MIL-125-NH 2 , Fe 3 O 4 @MIL-125-NH 2 and CuO/Cu 2 O@MIL-125-NH 2 were investigated. The photocatalytic process may be credited with the effective electron-hole separation and wider area of light response. Moreover, the mechanism of pesticide photocatalytic process was discovered as mineralization of pesticides to carbon dioxide, water, sulphate, and ammonia. Total organic carbon (TOC) analysis was used to quantify the mineralization of pesticides while UV spectroscopy was used to measure the rates of pesticides photocatalytic activity. CuO/Cu 2 O@MIL-125-NH 2 and Fe 3 O 4 @MIL-125-NH 2 composite demonstrated the maximum pesticide photocatalytic efficiency and outstanding cycle stability. The antimicrobial potency was increased and the inhibition zone was minimised when treated by a parent MIL-125-NH 2 and its composites, which is surprising data when employing CuO/Cu 2 O@MIL-125-NH 2 and Fe 3 O 4 @MIL-125-NH 2 nanocomposite as an anti-bacterial material. [Display omitted] • Fe 3 O 4 and CuO/Cu 2 O were attached to MIL-125-NH 2 using self assembly protocol. • First example of the Fe 3 O 4 /MIL-125-NH 2 and CuO/Cu 2 O/MIL-125-NH 2 composite for pesticide degradation was applied. • Unique adsorption/photolysis mechanism of Fe 3 O 4 and CuO/Cu 2 O incorporated onto MIL-125-NH 2 was proposed. • Enhancing the photocatalytic activity performance on photolysis of pesticide was observed. • Fantastic antimicrobial activity was appeared for the prepared photocatalysts. [ABSTRACT FROM AUTHOR]

Gas-to-liquid (GTL), an alternative synthetic jet fuel derived from natural gas through Fischer–Tropsch (F–T) process, has gained significant attention due to its cleaner combustion characteristics when compared to conventional counterparts. The effect of chemical composition on key performance aspects such as ignition delay, laminar burning speed, and emission characteristics has been experimentally studied. However, the development of chemical mechanism to predict those parameters for GTL fuel is still in its early stage. The GTL aviation fuel from Syntroleum Corporation, S-8, is used in this study. For theoretical predictions, a mixture of 32% iso-octane, 25% n-decane, and 43% n-dodecane by volume is considered as the surrogate for S-8 fuel. In this work, a detailed kinetics model (DKM) has been developed based on the chemical mechanisms reported for the GTL fuel. The DKM is employed in a constant internal energy and constant volume reactor to predict the ignition delay times for GTL over a wide range of temperatures, pressures, and equivalence ratios. The ignition delay times predicted using DKM are validated with those reported in the literature. Furthermore, the steady one-dimensional premixed flame code from CANTERA is used in conjunction with the chemical mechanisms to predict the laminar burning speeds for GTL fuel over a wide range of operating conditions. Comparison of ignition delay and laminar burning speed shows that the Ranzi et al. mechanism has a better agreement with the available experimental data, and therefore is used for further evaluation in this study. [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]

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]

A combined modeling approach using kinetic Monte Carlo and molecular dynamics simulations is applied to investigate both chemical and mechanical degradation of Nafion membranes on the molecular level. In different hydration conditions, two major degradation reactions are identified to be the main chain unzipping and the side chain scission. The dissolution process of Nafion is evaluated in terms of weight loss, production emission rate and evolution of functional groups. Further, the complicated structural deformation is preliminarily investigated by imposing linear strain on degraded Nafion membrane. Different craze patterns are compared before and after chemical degradation, and the mechanism of crack propagation is proposed. Finally, prospective applications of our modeling approach are addressed for future studies of membrane degradation phenomena under fuel cell operation conditions. [ABSTRACT FROM AUTHOR]

The present review is focused on understanding the enhancement mechanisms in surface-enhanced Raman scattering (SERS) from the point of view of the various spectral changes, which have brought considerable confusion in this research field and have obstructed practical SERS applications. The electromagnetic mechanism provides us with the quantitative explanation of unexpected SERS spectral changes, such as larger Raman intensities for anti-Stokes peaks than for Stokes peaks and overtone peak intensities comparable with fundamental ones. Other mechanisms classified as chemical effects, i.e. the resonance Raman and the charge transfer mechanisms, are also introduced to explain the spectral changes in SERS. These mechanisms may explain the emergence of non-totally symmetric vibrational modes in SERS spectra, which is usually forbidden in Raman spectra. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

To elucidate the evolution process of PAHs (polycyclic aromatic hydrocarbons) in GDI (gasoline direct injection) engines, a reduced chemical model with 17 species and 40 reactions for PAHs formation was developed and integrated into a skeletal TRF (toluene reference fuels) oxidation mechanism to predict PAHs emissions. The final mechanism consisted of 85 species and 232 reactions. The new mechanism was validated for ignition delays and laminar flame speeds for gasoline/air and TRF/air mixtures under engine-like conditions, and good agreement was obtained for most of the experiments. Laminar premixed flames were simulated to validate the small species related to PAHs formation, as well as PAHs profiles up to A4 in flames, and the experimental trends were reproduced well. The combustion processes of GDI engines can be reproduced well using the new mechanism. PAHs were sampled from exhaust and analyzed by GC–MS, and PAHs with more than four rings were primary observed in particulate matter, while two and three ring polyaromatic hydrocarbons mainly existed in the vapor-phase PAHs. The vapor-phase PAHs released from the exhaust pipe were predicted, and the results indicated that the current mechanism could be used as a valuable tool to meet the needs of CFD (computational fluid dynamics) simulation for PAHs evolution in GDI engine combustion. [ABSTRACT FROM AUTHOR]

Arylalkylamine N -acyltransferase like 2 (AANATL2) catalyzes the formation of N -acylarylalkylamides from the corresponding acyl-CoA and arylalkylamine. The N -acylation of biogenic amines in Drosophila melanogaster is a critical step for the inactivation of neurotransmitters, cuticle sclerotization, and melatonin biosynthesis. In addition, D . melanogaster has been used as a model system to evaluate the biosynthesis of fatty acid amides: a family of potent cell signaling lipids. We have previously showed that AANATL2 catalyzes the formation of N -acylarylakylamides, including long-chain N -acylserotonins and N -acyldopamines. Herein, we define the kinetic mechanism for AANATL2 as an ordered sequential mechanism with acetyl-CoA binding first followed by tyramine to generate the ternary complex prior to catalysis. Bell shaped k cat,app – acetyl-CoA and (k cat /K m ) app – acetyl-CoA pH-rate profiles identified two apparent pK a,app values of ∼7.4 and ∼8.9 that are critical to catalysis, suggesting the AANATL2-catalyzed formation of N -acetyltyramine occurs through an acid/base chemical mechanism. Site-directed mutagenesis of a conserved glutamate that corresponds to the catalytic base for other D . melanogaster AANATL enzymes did not produce a substantial depression in the k cat,app value nor did it abolish the pK a,app value attributed to the general base in catalysis (pK a ∼7.4). These data suggest that AANATL2 catalyzes the formation of N -acylarylalkylamides using either different catalytic residues or a different chemical mechanism relative to other D . melanogaster AANATL enzymes. In addition, we constructed other site-directed mutants of AANATL2 to help define the role of targeted amino acids in substrate binding and/or enzyme catalysis. [ABSTRACT FROM AUTHOR]

NO X is one of the main compositions in the modern engine emissions and the reduction requirements of NO X have turned to be more stringent. To control NO X emissions better, the technologies of NO X sensors are forced to achieve much faster response and higher accuracy. In this paper, the correlation between ion current signals and NO X emissions is studied by both experiments and simulations in a direct-injection controlled auto-ignition (CAI) engine. The investigation provides the possibility of a novel method of cycle-by-cycle NO X emissions detection. The simulation results present this positive correlation based on the chemical kinetics theory, and also directly reflect the formation order of the chemical products and the influence of temperature on the rates of main ionization and NO X generated reactions. Furthermore, the distributions of both ions and NO products are shown with the CFD results, illustrating their in-cylinder space correlation. Combined with the simulation results, the experimental results not only validate the positive correlation between two different fuel types, but also provide the evidences of linear fitting function. Based on the fitting results, the cycle-based NO X emissions could be estimated. [ABSTRACT FROM AUTHOR]

Fourteen chemical-kinetic steps are identified, and their associated reaction-rate parameters are given, that enable an existing short chemical-kinetic mechanism (the San Diego mechanism) to be expanded to include the ignition and combustion of dimethyl-ether, over a range of conditions that includes both low-temperature and high-temperature chemistry, as well as both high and low pressures, extending to normal atmospheric pressure. This entails introducing five additional chemical species. Tests of predictions against measured ignition delays, laminar burning velocities, and flow-reactor and jet-stirred-reactor data are reported, that support the success of the mechanism. The results therefore can be useful in combustion computations, especially when larger mechanisms are too time-consuming to be accommodated. [ABSTRACT FROM AUTHOR]

In the framework of the AQMEII initiative WRF-Chem has been applied over Europe adopting two chemical configurations for the calendar year 2010. The first one employed the RADM2 gas-phase chemistry and MADE/SORGAM aerosol module, while the second one implemented the CBM-Z gaseous parameterization and MOSAIC aerosol chemistry. Configurations shared the same domain, meteorological setups and input data. The Comparison demonstrated that CBM-Z has a more efficient ozone-NO titration than RADM2 in regions with sufficiently high levels of NOx and VOCs. At the same time, CBM-Z is found to have a more effective NO 2 + OH reaction. The parameterization of the relative humidity of deliquescence point has a strong impact on HNO 3 and NO 3 concentrations over Europe, particularly over the sea. The MADE approach showed to be more efficient than MOSAIC. Differently, particulate sulfate and SO 2 ground concentrations proved to be more influenced by the heterogeneous SO 2 cloud oxidation. PM10 and PM2.5 have shown similar results for MOSAIC and MADE/SORGAM, even though some differences were found in the dust and sea salt size partitioning between modes and bins. Indeed, in MADE the sea salt was distributed only in the coarse fraction, while the dust emissions were distributed mainly in the fine fraction. Finally, different chemical mechanisms give different Aerosol Optical Depths (AOD). WRF-Chem is found to under predict the AODs in both configurations because of the misrepresentation of the dust coarse particle, as shown by the analysis of the relationship between the Angström exponent and the AOD bias. Differently, when the AOD is dominated by fine particles, the differences in model performance are more evident, with MADE/SORGAM generally performing better than MOSAIC. Indeed the higher availability of both sulfate and nitrate has a significant influence on reconstruction of the AOD estimations. This paper shows the great importance of chemical mechanisms in both gaseous and aerosols predictions, as well as in the calculation of aerosol optical properties. [ABSTRACT FROM AUTHOR]

Computational Fluid Dynamics (CFD) study of flameless combustion condition is carried out by solving the Reynolds-Averaged Navier-Stokes (RANS) equations in the open-source CFD package of OpenFOAM 2.1.0. Particular attention is devoted to the comparison of three global and detailed chemical mechanisms using the Partially Stirred Reactor (PaSR) combustion model for the turbulence-chemistry interaction treatment. The OpenFOAM simulations are assessed against previously published CFD results using the Eddy Dissipation Concept (EDC) combustion model as well as the experimental data available in the literature. Results show that global chemical mechanisms provide acceptable predictions of temperature and major species fields in flameless mode with much lower computational costs comparing with the detailed chemical mechanisms. However, incorporation of detailed chemical mechanisms with proper combustion models is crucial to account for finite-rate chemistry effects and accurately predict net production of minor species. [ABSTRACT FROM AUTHOR]