Microscopic Reaction Mechanism of Formic Acid Generated During Pyrolysis of Cellulosic Insulating Paper

The full text of this preprint has been withdrawn, as it was submitted in error. Therefore, the authors do not wish this work to be cited as a reference. Questions should be directed to the corresponding author.

Overview of Molecular Dynamics Simulation of Natural Gas Hydrate at Nanoscale

As a dynamic research method for molecular systems, molecular dynamic (MD) simulation can represent physical phenomena that cannot be realized by experimental means and discuss the microscopic reaction mechanism of things from the molecular level. In this paper, the previous research results were reviewed. First, the MD simulation process was briefly described, then, the applicability of different molecular force fields in the natural gas hydrate (NGH) system was discussed, and finally, the application of MD simulation in the formation and decomposition law of NGH was summarized from the perspective of NGH mining. The results show that the selection of water molecular force field has a great influence on the simulation results, and the evaluation of water model applicable to the simulation of NGH under different thermodynamic states is still an open research field that needs to be paid attention to. The effect of surface properties of porous media (such as crystallinity and hydrophilicity) on hydrate needs to be further studied. Compared with thermodynamic inhibitors, kinetic inhibitors (such as amino acids) have more promising research prospects, and further research can be carried out in the screening of efficient kinetic inhibitors in the future.

Nascent clathrin lattices spontaneously disassemble without sufficient adaptor proteins

Clathrin-coated structures must assemble on cell membranes to perform their primary function of receptor internalization. These structures show marked plasticity and instability, but what conditions are necessary to stabilize against disassembly have not been quantified. Recent in vitro fluorescence experiments have measured kinetics of stable clathrin assembly on membranes as controlled by key adaptor proteins like AP-2. Here, we combine this experimental data with microscopic reaction-diffusion simulations and theory to quantify mechanisms of stable vs unstable clathrin assembly on membranes. Both adaptor binding and dimensional reduction on the 2D surface are necessary to reproduce the cooperative kinetics of assembly. By applying our model to more physiologic-like conditions, where the stoichiometry and volume to area ratio are significantly lower than in vitro, we show that the critical nucleus contains ~25 clathrin, remarkably similar to sizes of abortive structures observed in vivo. Stable nucleation requires a stoichiometry of adaptor to clathrin that exceeds 1:1, meaning that AP-2 on its own has too few copies to nucleate lattices. Increasing adaptor concentration increases lattice sizes and nucleation speeds. For curved clathrin cages, we quantify both the cost of bending the membrane and the stabilization required to nucleate cages in solution. We find the energetics are comparable, suggesting that curving the lattice could offset the bending energy cost. Our model predicts how adaptor density controls stabilization of clathrin-coated structures against spontaneous disassembly, and shows remodeling and disassembly does not require ATPases, which is a critical advance towards predicting control of productive vesicle formation.

Microscopic Reaction Process of Cement with Asphalt emulsion and Its Influence on Macroscopic Properties of Binder

This research aimed at studying the reaction process between cement and asphalt emulsion from a microscopic view and the variations of macroscopic properties with cured time. The microstructure of cement asphalt emulsion (CAE) with a mass ratio of cement to asphalt (C/A) of 0.6 was scanned with SEM and its functional groups were measured with FTIR after being cured for 7 days. Six CAEs with different C/A ratios were prepared and cured for different days, then DSR tests and BBR tests were conducted to evaluate their macroscopic performance. The results indicated that emulsion residue was relative porous. Hydration reaction occurred between cement and water secreted by demulsification of asphalt emulsion, hydrates would gradually fill the voids. Asphalt and hydrates were interrelated into a cross-linking structure. As the rigidity of hydrates increased with cured time, the rutting resistance of CAE was improved, but its low-temperature performance and fatigue resistance were reduced.

Imaging the chemical activity of single nanoparticles with optical microscopy

Chemical activity of single nanoparticles can be imaged and determined by monitoring the optical signal of each individual during chemical reactions with advanced optical microscopes. It allows for clarifying the functional heterogeneity among individuals, and for uncovering the microscopic reaction mechanisms and kinetics that could otherwise be averaged out in ensemble measurements.

Molecular Dynamic Simulation of Hydrogen Production by Catalytic Gasification of Key Intermediates of Biomass in Supercritical Water

Supercritical water gasification (SCWG) is an efficient and clean conversion of biomass due to the unique chemical and physical properties. Anthracene and furfural are the key intermediates in SCWG, and their microscopic reaction mechanism in supercritical water may provide information for reactor optimization and selection of optimal operating condition. Density functional theory (DFT) and reactive empirical force fields (ReaxFF) were combined to investigate the molecular dynamics of catalytic gasification of anthracene and furfural. The simulation results showed that Cu and Ni obviously increased the production of H radicals, therefore the substance SCWG process. Ni catalyst decreased the production of H2 with the residence time of 500 ps while significantly increased CO production and finally increased the syngas production. Ni catalyst was proved to decrease the free carbon production to prohibit the carbon deposition on the surface of active sites; meanwhile, Cu catalyst increased the production of free carbon.