Search

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.

Surface-enhanced Raman spectroscopy (SERS) is an ultrasensitive surface analysis technique that is widely used in chemical sensing, bioanalysis, and environmental monitoring. The design of the SERS substrates is crucial for obtaining high-quality SERS signals. Recently, 2D transition metal dichalcogenides (2D TMDs) have emerged as high-performance SERS substrates due to their superior stability, ease of fabrication, biocompatibility, controllable doping, and tunable bandgaps and excitons. In this review, a systematic overview of the latest advancements in 2D TMDs SERS substrates is provided. This review comprehensively summarizes the candidate 2D TMDs SERS materials, elucidates their working principles for SERS, explores the strategies to optimize their SERS performance, and highlights their practical applications. Particularly delved into are the material engineering strategies, including defect engineering, alloy engineering, thickness engineering, and heterojunction engineering. Additionally, the challenges and future prospects associated with the development of 2D TMDs SERS substrates are discussed, outlining potential directions that may lead to significant breakthroughs in practical applications., (© 2024 Wiley‐VCH GmbH.)

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]

The development of carbon materials as highly efficient and durable substrates for surface-enhanced Raman scattering (SERS) is of great importance for realizing practical application of molecular sensing through Raman spectroscopy. In this report, we demonstrate the fabrication, by low-temperature pyrolysis, of high-quality, iron–nitrogen-doped carbon nanosheets and nanorods from spin-coated poly-(4-vinylpyridine) (P4VP) polymer thin films and electrospun polymer nanofibers, respectively. As P4VP chains have functional pyridine rings available to bind with metal precursor ions through favorable interactions, iron (Fe) atoms can be incorporated into the carbon nanostructures with the aid of Fe-(II) acetate during the synthesis. The incorporation of a metal salt can decrease the thermal stability of pyridinic groups so that the pyrolysis produces carbon nanostructures with high degree of graphitization and with iron- and nitrogen-doped species. The codopants in these carbon nanostructures introduce surface dipole moments, affect the DOS of valence bands, and decrease the work function. The electronic structure of carbon nanomaterials can be finely tuned to enable the vibronic coupling of the conduction band and valence band states of carbon nanostructures with the excited and ground states of the probed molecules of Rhodamine 6G and crystal violet. The vibronic coupling enables a superior enhancement in SERS with the detection limit concentration being as low as 10–7 M and the maximum enhancement factor being 3.8 × 104 through a charge transfer (CT) process. The polymer-templated carbon nanostructures offer great promise for the implementation of this system in a next-generation SERS substrate for molecular sensing. [ABSTRACT FROM AUTHOR]

A reaction mechanism called Mech23 for gas-phase monomethylhydrazine and nitrogen tetroxide (MMH/NTO) containing 23 species and 20 reactions is developed and validated and then introduced into the numerical simulation of a small MMH/NTO liquid rocket engine. The ignition delay and equilibrium temperature predicted with Mech23 are in accordance with theoretical data within wide ranges of the MMH/NTO ratio, initial pressure, and temperature. Critical reactions are identified by the sensitivity analysis on the hypergolic ignition process of MMH/NTO mixtures. It is demonstrated that more precise predictions of thrust, specific impulse, and chamber pressure can be achieved with Mech23 than with the one-step global mechanism. Differences in the temperature distribution and gas species between the two chemical reaction mechanisms result in various performances. It is shown that the reaction mechanism plays an important role in the simulation of the engine combustion chamber. [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]

Pervaporation is an energy-efficient membrane technology for separating liquid molecules of similar physical properties, which may compete or combine with distillation separation technology in a number of applications. With the rapid development of new membrane materials, the pervaporation performance was significantly improved. Fundamental understanding of the mass transport mechanisms is crucial for the rational design of membrane materials and efficient intensification of pervaporation process. Based on the interactions between permeate molecules and membranes, this review focuses on two categories of mass transport mechanisms within pervaporation membranes: physical mechanism (solution-diffusion mechanism, molecular sieving mechanism) and chemical mechanism (facilitated transport mechanism). Furthermore, the optimal integration and evolution of different mass transport mechanisms are briefly introduced. Material selection and relevant applications are highlighted under the guidance of mass transport mechanisms. Finally, the current challenges and future perspectives are tentatively identified. [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]

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]

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]

Copyright of Shipin Kexue/ Food Science is the property of Food Science Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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]

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]

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]

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]

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]

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]

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.)

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]

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]

Using accurate multi-component diffusion treatment in numerical combustion studies remains formidable due to the computational cost associated with solving for diffusion velocities. To obtain the diffusion velocities, for low density gases, one needs to solve the Stefan–Maxwell equations along with the zero diffusion flux criteria, which scales as O ( N 3 ) , when solved exactly. In this paper, we propose an accurate, fast, direct and robust algorithm to compute multi-component diffusion velocities. We also take into account the Soret effect, while computing the multi-component diffusion velocities. To our knowledge, this is the first provably accurate algorithm (the solution can be obtained up to an arbitrary degree of precision) scaling at a computational complexity of O ( N ) in finite precision. The key idea involves leveraging the fact that the matrix of the reciprocal of the binary diffusivities, V , is low rank, with its rank being independent of the number of species involved. The low rank representation of matrix V is computed in a fast manner at a computational complexity of O ( N ) and the Sherman–Morrison–Woodbury formula is used to solve for the diffusion velocities at a computational complexity of O ( N ) . Rigorous proofs and numerical benchmarks illustrate the low rank property of the matrix V and scaling of the algorithm. [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]

Bauxite residue is a hazardous solid waste produced during the production of alumina. Its high alkalinity is a potential threat to the environment which may disrupt the surrounding ecological balance of its disposal areas. China is one of the major global producers of alumina and bauxite residue, but differences in alkalinity and associated chemistry exist between residues from China and those from other countries. A detailed understanding of the chemistry of bauxite residue remains the key to improving its management, both in terms of minimizing environmental impacts and reducing its alkaline properties. The nature of bauxite residue and the chemistry required for its transformation are still poorly understood. This review focuses on various transformation processes generated from the Bayer process, sintering process, and combined Bayer-sintering process in China. Problems associated with transformation mechanisms, technical methods, and relative merits of these technologies are reviewed, while current knowledge gaps and research priorities are recommended. Future research should focus on transformation chemistry and its associated mechanisms and for the development of a clear and economic process to reduce alkalinity and soda in bauxite residue. [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]