An Investigation towards Coupling Molecular Dynamics with Computational Fluid Dynamics for Modelling Polymer Pyrolysis

Building polymers implemented into building panels and exterior façades have been determined as the major contributor to severe fire incidents, including the 2017 Grenfell Tower fire incident. To gain a deeper understanding of the pyrolysis process of these polymer composites, this work proposes a multi-scale modelling framework comprising of applying the kinetics parameters and detailed pyrolysis gas volatiles (parent combustion fuel and key precursor species) extracted from Molecular Dynamics models to a macro-scale Computational Fluid Dynamics fire model. The modelling framework was tested for pure and flame-retardant polyethylene systems. Based on the modelling results, the chemical distribution of the fully decomposed chemical compounds was realised for the selected polymers. Subsequently, the identified gas volatiles from solid to gas phases were applied as the parent fuel in the detailed chemical kinetics combustion model for enhanced predictions of toxic gas, charring, and smoke particulate predictions. The results demonstrate the potential application of the developed model in the simulation of different polymer materials without substantial prior knowledge of the thermal degradation properties from costly experiments.

Thermal Decomposition of 3-Nitro-1,2,4-Triazole-5-One (NTO) and Nanosize NTO Catalyzed by NiFe2O4

Nanosize Nickel ferrite (NiF) was synthesized by the co-precipitation methods and its effect as a 5 % by mass additive was studied on the thermal decomposition of micrometer and nanometer size NTO. In the presence of 5 % NiF additive, the thermal decomposition peak temperature of NTO was decreased from 276.36 to 260.18 oC and that of nano NTO was decreased from 261.38 to 258.89 oC (β=10 oC min-1). The kinetics parameters confirms the catalytic activity of NiF for the thermal decomposition of NTO, and nNTO as the parameters such as activation energy (NTO=~25.45 % and nNTO=~45.94 % decrement), and pre-exponential factor (NTO=~21.94 % and nNTO=~43.12 % decrement) were decreased when 5 % NiF additive was added to NTO, and nNTO. The rate of the decomposition process was increased in the presence of 5 % NiF catalyst, indicating the faster thermal decomposition of both NTO, and nNTO in the presence of nickel catalyst.

Sterol Extraction from Isolated Plant Plasma Membrane Vesicles Affects H+-ATPase Activity and H+-Transport

Plasma membrane H+-ATPase is known to be detected in detergent-resistant sterol-enriched fractions, also called “raft” domains. Studies on H+-ATPase reconstituted in artificial or native membrane vesicles have shown both sterol-mediated stimulations and inhibitions of its activity. Here, using sealed isolated plasma membrane vesicles, we investigated the effects of sterol depletion in the presence of methyl-β-cyclodextrin (MβCD) on H+-ATPase activity. The rate of ATP-dependent ∆µH+ generation and the kinetic parameters of ATP hydrolysis were evaluated. We show that the relative sterols content in membrane vesicles decreased gradually after treatment with MβCD and reached approximately 40% of their initial level in 30 mM probe solution. However, changes in the hydrolytic and H+-transport activities of the enzyme were nonlinear. The extraction of up to 20% of the initial sterols was accompanied by strong stimulation of ATP-dependent H+-transport in comparison with the hydrolytic activity of enzymes. Further sterol depletion led to a significant inhibition of active proton transport with an increase in passive H+-leakage. The solubilization of control and sterol-depleted vesicles in the presence of dodecyl maltoside negated the differences in the kinetics parameters of ATP hydrolysis, and all samples demonstrated maximal hydrolytic activities. The mechanisms behind the sensitivity of ATP-dependent H+-transport to sterols in the lipid environment of plasma membrane H+-ATPase are discussed.

In-situ Combustion Simulation from Laboratory to Field Scale

In-situ combustion simulation from laboratory to field scale has always been challenging, due to difficulties in deciding the reaction model and Arrhenius kinetics parameters, together with erroneous results observed in simulations when using large-sized grid blocks. We present a workflow of successful simulation of heavy oil in-situ combustion process from laboratory to field scale. We choose the ongoing PetroChina Liaohe D block in-situ combustion project as a case of study. First, we conduct kinetic cell (ramped temperature oxidation) experiments, establish a suitable kinetic reaction model, and perform corresponding history match to obtain Arrhenius kinetics parameters. Second, combustion tube experiments are conducted and history matched to further determine other simulation parameters and to determine the fuel amount per unit reservoir volume. Third, we upscale the Arrhenius kinetics to the upscaled reaction model for field-scale simulations. The upscaled reaction model shows consistent results with different grid sizes. Finally, field-scale simulation forecast is conducted for the D block in-situ combustion process using computationally affordable grid sizes. In conclusion, this work demonstrates the practical workflow for predictive simulation of in-situ combustion from laboratory to field scale for a major project in China.

A Comparison of Combustion Properties in Biomass–Coal Blends Using Characteristic and Kinetic Analyses

This paper presents comparative research on the combustion of coal, wheat, corn straw (CS), beet residues after extracting sugar (BR), and their blends, coal–corn straw blends (CCSBs), coal–wheat blends (CWBs), and coal–beet residue blends (CBRBs), using thermogravimetric (TG) analysis under 10, 20, 30, 40 and 50 °C/min. The test results indicate that CS and wheat show better combustion properties than BR, which are recommended to be used in biomass combustion. Under the heating rate of 20 °C/min, the coal has the longest thermal reaction time when compared with 10 and 30 °C/min. Adding coal to the biomass can improve the burnout level of biomass materials (BM), reduce the burning speed, and make the reaction more thorough. The authors employed the Flynn–Wall–Ozawa (FWO) method and the Kissinger–Akahira–Sunose (KAS) method to calculate kinetics parameters. It was proven that overall, the FWO method is better than the KAS method for coal, BM, and coal–biomass blends (CBBs), as it provides higher correlations in this study. It is shown that adding coal to wheat and BR decreases the activation energy and makes conversion more stable under particular α. The authors selected a wider range of biomass raw materials, made more kinds of CBB, and conducted more studies on different heating rates. This research can provide useful insights into how to choose agricultural residuals and how to use them.

388 Haemodynamic arterial changes in heart failure: a proposed new paradigm of heart and vessels failure. The Copernican revolution?

Aims Although heart failure (HF) is one of the most common conditions affecting the heart, little attention has been placed on the role of arteries in contributing to the progression of this disease. We sought to determine the haemodynamic change of arteries in HF patients subdivided according to left ventricular ejection fraction. The major goal was to establish the active compensatory role of arteries in HF. Methods and results Using sphygmography, we systematically studied a cohort of 228 HF patients and 52 healthy controls. We focused on the common carotid as the main elastic artery and the posterior tibial as the main muscular artery (Figure 1). Moreover, we categorized the three HF groups, HFrEF, HFmrEF, HFpEF, into two subgroups (A and B) according to the presence or absence of HF signs at baseline. We discovered that all the parameters of measured arterial kinetics, i.e. work, power, acceleration, and speed, were significantly increased (P < 0.001 by one-way ANOVA) in the groups without HF signs. In contrast, all the arterial kinetics parameters were significantly reduced (P < 0.001) in the groups exhibiting HF signs. Similar results were obtained in both types of arteries and were consistently observed across all the three different types of HF, although with some differences in magnitude. Finally, we discovered that HFpEF patients exhibited more compromised arterial function vis-à-vis HFrEF patients [Figure 2: Patients disposition (Top) and quantification of arterial kinetics and haemodynamic parameters (Down) from the common carotid artery (A) and the posterior tibial artery (B)]. Conclusions We provide the first documentation of an active compensatory role of arteries during HF. Mechanistically, we explain these findings by a dual activity of large arteries accomplished via an active propulsive work and a concurrent haemodynamic suction. These underestimated arterial functions partially compensate for the heart dysfunction in HF, underlining a key interplay between the heart and the vessels. We propose a new paradigm that we define as ‘heart and vessels failure’ that explicitly focuses on both heart and vessels’ interaction during the progression of HF.

Transamination-Like Reaction Catalyzed by Leucine Dehydrogenase for Efficient Co-Synthesis of α-Amino Acids and α-Keto Acids

α-Amino acids and α-keto acids are versatile building blocks for the synthesis of several commercially valuable products in the food, agricultural, and pharmaceutical industries. In this study, a novel transamination-like reaction catalyzed by leucine dehydrogenase was successfully constructed for the efficient enzymatic co-synthesis of α-amino acids and α-keto acids. In this reaction mode, the α-keto acid substrate was reduced and the α-amino acid substrate was oxidized simultaneously by the enzyme, without the need for an additional coenzyme regeneration system. The thermodynamically unfavorable oxidation reaction was driven by the reduction reaction. The efficiency of the biocatalytic reaction was evaluated using 12 different substrate combinations, and a significant variation was observed in substrate conversion, which was subsequently explained by the differences in enzyme kinetics parameters. The reaction with the selected model substrates 2-oxobutanoic acid and L-leucine reached 90.3% conversion with a high total turnover number of 9.0 × 106 under the optimal reaction conditions. Furthermore, complete conversion was achieved by adjusting the ratio of addition of the two substrates. The constructed reaction mode can be applied to other amino acid dehydrogenases in future studies to synthesize a wider range of valuable products.

Estimation of viral kinetics model parameters in young and aged SARS-CoV-2 infected macaques

The SARS-CoV-2 virus disproportionately causes serious illness and death in older individuals. In order to have the greatest impact in decreasing the human toll caused by the virus, antiviral treatment should be targeted to older patients. For this, we need a better understanding of the differences in viral dynamics between SARS-CoV-2 infection in younger and older adults. In this study, we use previously published averaged viral titre measurements from the nose and throat of SARS-CoV-2 infection in young and aged cynomolgus macaques to parametrize a viral kinetics model. We find that all viral kinetics parameters differ between young and aged macaques in the nasal passages, but that there are fewer differences in parameter estimates from the throat. We further use our parametrized model to study the antiviral treatment of young and aged animals, finding that early antiviral treatment is more likely to lead to a lengthening of the infection in aged animals, but not in young animals.