Assessing NO2-Hydrocarbon Interactions during Combustion of NO2/Alkane/Ar Mixtures in a Shock Tube Using CO Time Histories

Modern gas turbines use combustion chemistry during the design phase to optimize their efficiency and reduce emissions of regulated pollutants such as NOx. The detailed understanding of the interactions during NOx and natural gas during combustion is therefore necessary for this optimization step. To better assess such interactions, NO2 was used as a sole oxidant during the oxidation of CH4 and C2H6 (the main components of natural gas) in a shock tube. The evolution of the CO mole fraction was followed by laser-absorption spectroscopy from dilute mixtures at around 1.2 atm. The experimental CO profiles were compared to several modern detailed kinetics mechanisms from the literature: models tuned to characterize NOx-hydrocarbons interactions, base-chemistry models (C0–C4) that contain a NOx sub-mechanism, and a nitromethane model. The comparison between the models and the experimental profiles showed that most modern NOx-hydrocarbon detailed kinetics mechanisms are not very accurate, while the base chemistry models were lacking accuracy overall as well. The nitromethane model and one hydrocarbon/NOx model were in relatively good agreement with the data over the entire range of conditions investigated, although there is still room for improvement. The numerical analysis of the results showed that while the models considered predict the same reaction pathways from the fuels to CO, they can be very inconsistent in the selection of the reaction rate coefficients. This variation is especially true for ethane, for which a larger disagreement with the data was generally observed.

Signaling pathways in the regulation of cytokine release syndrome in human diseases and intervention therapy

Cytokine release syndrome (CRS) embodies a mixture of clinical manifestations, including elevated circulating cytokine levels, acute systemic inflammatory symptoms and secondary organ dysfunction, which was first described in the context of acute graft-versus-host disease after allogeneic hematopoietic stem-cell transplantation and was later observed in pandemics of influenza, SARS-CoV and COVID-19, immunotherapy of tumor, after chimeric antigen receptor T (CAR-T) therapy, and in monogenic disorders and autoimmune diseases. Particularly, severe CRS is a very significant and life-threatening complication, which is clinically characterized by persistent high fever, hyperinflammation, and severe organ dysfunction. However, CRS is a double-edged sword, which may be both helpful in controlling tumors/viruses/infections and harmful to the host. Although a high incidence and high levels of cytokines are features of CRS, the detailed kinetics and specific mechanisms of CRS in human diseases and intervention therapy remain unclear. In the present review, we have summarized the most recent advances related to the clinical features and management of CRS as well as cutting-edge technologies to elucidate the mechanisms of CRS. Considering that CRS is the major adverse event in human diseases and intervention therapy, our review delineates the characteristics, kinetics, signaling pathways, and potential mechanisms of CRS, which shows its clinical relevance for achieving both favorable efficacy and low toxicity.

Enhanced Performance of Natural Polymer Coagulants For Dye Removal From Wastewater: Coagulation Kinetics, And Mathematical Modelling Approach

This study explores the potentials of Brachystegia eurycoma coagulant (BEC) and Vigna subterranean coagulant (VSC) as natural organic polymers (NOPs) for the decolourisation of Crystal Ponceau 6R (AR 44) in wastewater. Materials characterisation studies were done on the precursors. Detailed kinetics study was employed. The decolourisation procedures were evalu­ated through time-dependent reduction in the concentration of particles, with the variation of the independent parameters. The proximate analysis showed protein contents of 19.77% and 18.15% for BEC and VSC, respectively. The functional test shows the presence of –OH, N–H, and C=H. Surface morphological study reveals that some rough surfaces, different pores sizes, and compact-net structures were evidenced. The order of removal efficiency was VSC > BEC with an optimum of 88.8% and 73.3%, respectively. The values of K and α obtained for BEC and VSC were 6.38 x 10-4 Lmg-1min-1, 1.8 and 4.03 x 10-3 L/mg-1min-1, 1.9, respectively. The coagulation time, Tag of 31.35 and 26.96 min for BEC and VSC respectively disclosed a quick coagulation. The coagulation-flocculation kinetics demonstrated that the process conforms to the pseudo-second-order model with R2 >0.997, suggesting that the rate-controlling mechanism is governed by chemisorption. The experimental data were well predicted by the cross-validation test, with percentage mean relative deviation modulus (M%) of 3.26 and 2.54 for BEC and VSC, respectively. These coagulants have added meaningful progress in wastewater treatment by coagulation-flocculation while displaying significant adsorption features. Likewise, the usage of kinetics studies and particle behaviour modelling should be a prerequisite in water treatment processes.

Kinetic Regularities of Methane Dry Reforming Reaction on Nickel-Containing Modified Ceria–Zirconia

The Ni-containing catalysts based on ceria–zirconia doped with Ti and Ti+Nb were prepared by the solvothermal method in supercritical fluids. Ni deposition was carried out by incipient wetness impregnation and the one-pot technique. All materials were investigated by a complex of physicochemical methods (XRD, BET, TEM, H2-TPR). Samples catalytic properties were studied in methane dry reforming in the plug-flow reactor. Conversions of CH4 and CO2, H2/CO ratio, and CO and H2 yields were measured, and detailed kinetics analysis was carried out. The influence of Ni loading method and support modification on the catalytic behavior in the methane dry reforming process was studied. The preparation method of catalysts affects the textural characteristics. For one-pot samples, pore volume and surface area are lower than for impregnated samples. For catalysts on modified supports, strong metal–support interaction was shown to increase catalytic activity. A reduction pretreatment of samples was shown to have significant influence on their catalytic properties. The kinetic parameters such as reaction rate constant at 700 °C, effective activation energy, and TOF were estimated and analyzed.

Comparison of soot models for reacting sprays in diesel engine-like conditions

Stringent emission legislations and growing health concerns have contributed to the evolution of soot modeling in diesel engines from simple empirical relations to methods involving detailed kinetics and complex aerosol dynamics. In this paper, four different soot models have been evaluated for the high temperature, high pressure combusting dodecane spray cases of engine combustion network (ECN) spray A which mimics engine-relevant conditions. The soot models considered include an empirical, a multistep, a method of moments based, and a discrete sectional method soot model. Two experimental cases with ambient oxygen volume of 21% and 15% have been modeled. A good agreement between simulations and experiments for vapor penetration and heat release rate has been obtained. Quasi-steady soot volume fraction contours for the four soot models have been compared with experiments. Contours of the species and source terms involved in soot modeling have also been compared for a better understanding of soot processes. The empirical soot model results in higher magnitude and spread of soot due to a lack of modeling framework for oxidation through OH species. Among the four models studied, the multistep soot model has been observed to provide the most promising agreement with the experimental data in terms of distribution of soot and location of peak soot volume fraction. Due to a two-way coupling of soot models, the detailed models predict an upstream location for soot as compared to the multi-step soot model which is one way coupled. A significant difference (of an order of magnitude) in the concentration of PAH (polycyclic aromatic hydrocarbons) precursor between multistep and detailed soot models has been observed because of precursor consumption due to the coupling of detailed soot models with chemical kinetics. It is recommended that kinetic schemes, especially those concerning PAH, be validated with experimental data with a kinetics-coupled soot model.

Interleukin 8 Elicits Rapid Physiological Changes in Neutrophils That Are Altered by Inflammatory Conditions

A sufficient response of neutrophil granulocytes stimulated by interleukin (IL)-8 is vital during systemic inflammation, for example, in sepsis or severe trauma. Moreover, IL-8 is clinically used as biomarker of inflammatory processes. However, the effects of IL-8 on cellular key regulators of neutrophil properties such as the intracellular pH (pH_i) in dependence of ion transport proteins and during inflammation remain to be elucidated. Therefore, we investigated in detail the fundamental changes in pH_i, cellular shape, and chemotactic activity elicited by IL-8. Using flow cytometric methods, we determined that the IL-8-induced cellular activity was largely dependent on specific ion channels and transporters, such as the sodium-proton exchanger 1 (NHE1) and non-NHE1-dependent sodium flux. Exposing neutrophils in vitro to a proinflammatory micromilieu with N-formyl-Met-Leu-Phe, LPS, or IL-8 resulted in a diminished response regarding the increase in cellular size and pH. The detailed kinetics of the reduced reactivity of the neutrophil granulocytes could be illustrated in a near-real-time flow cytometric measurement. Last, the LPS-mediated impairment of the IL-8-induced response in neutrophils was confirmed in a translational, animal-free human whole blood model. Overall, we provide novel mechanistic insights for the interaction of IL-8 with neutrophil granulocytes and report in detail about its alteration during systemic inflammation.

Electrochemical Nozaki–Hiyama–Kishi Coupling: Scope, Applications, and Mechanism

One of the most oft-employed methods for C–C bond formation involving the coupling of vinyl-halides with aldehydes catalyzed by Ni and Cr (Nozaki–Hiyama–Kishi, NHK) has been rendered more practical using an electroreductive manifold. Although early studies pointed to the feasibility of such a process those precedents were never applied by others due to cumbersome setups and limited scope. Here we show that a carefully optimized electroreductive procedure can enable a more sustainable approach to NHK, even in an asymmetric fashion on highly complex medicinally relevant systems. The e-NHK can even enable non-canonical substrate classes, such as redox-active esters, to participate with low loadings of Cr when conventional chemical techniques fail. A combination of detailed kinetics, cyclic voltammetry, and in situ UV-vis spectroelectrochemistry of these processes illuminates the subtle features of this mechanistically intricate process.

Electrochemical Nozaki–Hiyama–Kishi Coupling: Scope, Applications, and Mechanism

One of the most oft-employed methods for C–C bond formation involving the coupling of vinyl-halides with aldehydes catalyzed by Ni and Cr (Nozaki–Hiyama–Kishi, NHK) has been rendered more practical using an electroreductive manifold. Although early studies pointed to the feasibility of such a process those precedents were never applied by others due to cumbersome setups and limited scope. Here we show that a carefully optimized electroreductive procedure can enable a more sustainable approach to NHK, even in an asymmetric fashion on highly complex medicinally relevant systems. The e-NHK can even enable non-canonical substrate classes, such as redox-active esters, to participate with low loadings of Cr when conventional chemical techniques fail. A combination of detailed kinetics, cyclic voltammetry, and in situ UV-vis spectroelectrochemistry of these processes illuminates the subtle features of this mechanistically intricate process.

Fate of elemental Selenium in Sulfur dominated environments

<p>Selenium (Se) is an essential yet toxic trace element with one of the narrowest nutritional optimums of all elements. Se speciation plays a crucial role in its mobility, bioavailability, bioaccumulation, and toxicity. The current perception of Se environmental cycling encompasses a linear series of successive, bi-directional redox processes. Elemental Se is seen as a central species thermodynamically favored in redox conditions found in most environments. Most studies on Se environmental transformations focused on systems characterized by high Se concentrations. In nature though, sulfur (S) concentrations are in general orders of magnitude higher than those of Se. This work investigated elemental selenium reactivity in sulfur dominated environments. A set of laboratory experiments were conducted to determine the reaction rates of elemental selenium with sulfur in various environmental conditions. Our data clearly indicates that an abiotic reaction was occurring between elemental Se and S at neutral to alkaline conditions under anaerobic conditions, solubilizing elemental Se. At neutral pH (pH = 7), the reaction rates were low, whereas at high pH (pH = 12), the reaction was fast and all elemental Se was consumed by the reaction within 12 h. We present for the first time the detailed kinetics of reaction at various environmental conditions and discuss the control exerted by sulfur on selenium cycling.</p>

Anti-inflammatory dopamine- and serotonin-based endocannabinoid epoxides reciprocally regulate cannabinoid receptors and the TRPV1 channel

The endocannabinoid system is a promising target to mitigate pain as the endocannabinoids are endogenous ligands of the pain-mediating receptors—cannabinoid receptors 1 and 2 (CB1 and CB2) and TRPV1. Herein, we report on a class of lipids formed by the epoxidation of N-arachidonoyl-dopamine (NADA) and N-arachidonoyl-serotonin (NA5HT) by epoxygenases. EpoNADA and epoNA5HT are dual-functional rheostat modulators of the endocannabinoid-TRPV1 axis. EpoNADA and epoNA5HT are stronger modulators of TRPV1 than either NADA or NA5HT, and epoNA5HT displays a significantly stronger inhibition on TRPV1-mediated responses in primary afferent neurons. Moreover, epoNA5HT is a full CB1 agonist. These epoxides reduce the pro-inflammatory biomarkers IL-6, IL-1β, TNF-α and nitrous oxide and raise anti-inflammatory IL-10 cytokine in activated microglial cells. The epoxides are spontaneously generated by activated microglia cells and their formation is potentiated in the presence of anandamide. Detailed kinetics and molecular dynamics simulation studies provide evidence for this potentiation using the epoxygenase human CYP2J2. Taken together, inflammation leads to an increase in the metabolism of NADA, NA5HT and other eCBs by epoxygenases to form the corresponding epoxides. The epoxide metabolites are bioactive lipids that are potent, multi-faceted molecules, capable of influencing the activity of CB1, CB2 and TRPV1 receptors.