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The explosive boiling characteristics of water on the copper surface are studied based on molecular dynamics simulation. The effects of the size, number and shape of nanostructures on the heat transfer performance of water explosive boiling are analysed. The results show that the heat transfer performance and boiling rate of liquid film increase with the increase of nanostructure size. At the same volume concentration of nanostructures, the boiling rate of the liquid film increases with the increase of the number of nanostructures. Compared with the spherical nanostructure, the water heating rate is higher and the heat flux of water is larger after the cylindrical nanostructure is adopted. Therefore, using cylindrical nanostructures and increasing, the uniformity of nanostructures on the surface can effectively improve the boiling heat transfer performance of water on the copper surface. [ABSTRACT FROM AUTHOR]

The characteristic plasticity associated with the deformation of helium bubbles and voids in aluminium under shock compression is investigated by molecular dynamics (MD) simulations. The scenarios indicate that the emission of shear dislocation loops rather than prismatic loops is the mechanism by which helium bubbles and voids collapse. The tendency to favour dislocation nucleation and emission at the trailing side of a void but at both sides of a helium bubble is attributed to the distribution of the resolved shear stress along (111) planes. Under the same loading strength, the resolved shear stress of the leading side of a helium bubble is larger than that of a void due to the internal pressure of the bubble; therefore, the dislocation nucleation at the leading side of a helium bubble is easier than that for a void. Based on the Virial theorem, we find that the locations of the calculated maximum resolved shear stress are in good agreement with the locations of dislocation nucleation. The elastic model clearly shows that the resolved shear stress increases with the internal pressure of the helium bubble but that the location of the maximum resolved shear stress is not affected. The results from the model nicely explain the scenarios that emerged in our MD simulations. The detailed studies of the microscopic mechanism of plastic deformation are important to deeply understand the mechanical properties of irradiated materials. [ABSTRACT FROM AUTHOR]

PcoC is a small soluble protein and is considered as a kind of copper carrier in the periplasm. The PcoC protein from E. coli possesses a β-barrel fold with two metal-binding sites of Cu2+ and Cu+. In this work, different spectroscopic techniques were adopted to clarify the stability of PcoC and metals' binding property. As demonstrated in results, Ag+ and Cu2+ are capable of binding with PcoC in a proportion of 1:1. The constant for PcoC and Cu2+ was (7.27 ± 0.21) × 1013 L/mol. In addition, we have explored how the cofactors affect the PcoC stability, finding that Cu2+ coordination affects both protein stability and unfolding pathway. The intermediate appeared during PcoC-Cu2+ unfolding. Further, the intermediate could be formed as CTAB interacted with PcoC. As found, the intermediate's C-terminal structure was unfolded, whereas the N-terminal was almost unaffected. Furthermore, the capability of the different unfolding degree protein with Cu2+ also indicated that the N-terminal exhibited a strong stability. Based on the anisotropy decay, tryptophan moved at a higher concentration of urea, also showing that the N-terminal was highly stable. In addition, the steered molecular dynamics simulations were performed, showing the rigidness of the N-terminal. The structure of the intermediate was considered as unfolded C-terminal and unchanged N-terminal. The binding capacity of Cu2+ was unchanged basically until 5 M urea. Unlabelled Image • The intermediate was obtained by the unfolding of PcoC induced by CTAB. • The intermediate corresponds to the unfolding of C terminal structure. • The binding capacity of Cu2+ was unchanged basically until 5 M urea. • The unfolding process was simulated by NAMD using constant velocity stretching. [ABSTRACT FROM AUTHOR]

Moleculardynamics simulations in conjunction with multiscale shocktechnique (MSST) are performed to study the initial chemical processesand the anisotropy of shock sensitivity of the condensed-phase HMXunder shock loadings applied along the a, b, and clattice vectors. A self-consistent charge density-functionaltight-binding (SCC-DFTB) method was employed. Our results show thatthere is a difference between lattice vector a(or c) and lattice vector bin the response to ashock wave velocity of 11 km/s, which is investigated through reactiontemperature and relative sliding rate between adjacent slipping planes.The response along lattice vectors aand care similar to each other, whose reaction temperature is up to 7000K, but quite different along lattice vector b, whosereaction temperature is only up to 4000 K. When compared with shockwave propagation along the lattice vectors a(18 Å/ps)and c(21 Å/ps), the relative sliding rate betweenadjacent slipping planes along lattice vector bis only0.2 Å/ps. Thus, the small relative sliding rate between adjacentslipping planes results in the temperature and energy under shockloading increasing at a slower rate, which is the main reason leadingto less sensitivity under shock wave compression along lattice vector b. In addition, the C–H bond dissociation is the primarypathway for HMX decomposition in early stages under high shock loadingfrom various directions. Compared with the observation for shock velocities Vimp= 10 and 11 km/s, the homolytic cleavageof N–NO2bond was obviously suppressed with increasingpressure. [ABSTRACT FROM AUTHOR]

• UNIFAC-IL model is extended to cover R410A refrigerant blend (R-32 and R-125). • CAILD is performed to rationally design ILs for separating R410A blend. • MD simulations are conducted to elucidate the rationality of CAILD results. The selective separation of refrigerants could facilitate their reclamation and reduce emissions of hydrofluorocarbons (HFC) with high global warming potential. R410A, a near azeotropic mixture comprising equimass difluoromethane (R-32) and pentafluoroethane (R-125), is required to be phased out and shortly replaced by more efficient and sustainable refrigerants. Under this background, the recovery of R-32 and R-125 by using ionic liquids (ILs) as the solvent is considered as a promising approach. In this work, the rational selection of ILs for enhancing the R410A separation is presented. To this end, 873 refrigerant-in-IL solubility data (573 for R-32, 300 for R-125) are firstly adopted for the extension of the UNIFAC-IL model to cover the R410A system. With the obtained UNIFAC-IL model, a computer-aided IL design (CAILD) task is cast as a mixed-integer nonlinear programming (MINLP) problem, which is solved to identify three top-ranked ILs. Following that, molecular dynamics (MD) simulations of the selected IL-refrigerant systems are conducted, which well elucidate the reliability of the CAILD results. [ABSTRACT FROM AUTHOR]

[Display omitted] • Solute effect on extraction of LCO components is systematically unraveled. • Four extraction parameters are evaluated based on liquid–liquid equilibria. • Mechanism is analyzed from interaction and interface behavior by MD simulation. • Extraction process simulation is performed with well-regressed NRTL model. • High extraction performance is achieved for LCO containing more diaromatics. Unravelling solute effect on extractive separation of aromatics and alkanes is highly required toward its rational incorporation into economical upgrading of light cycle oil (LCO). This work systematically examines the effect of aromatic and alkane structures on extraction performance from experimental and theoretical perspectives. Liquid-liquid extraction experiments demonstrate that the distribution coefficient and extraction efficiency strongly depend on the aromatic structure, whereas the selectivity and theoretical purity of aromatics significantly rely on the alkane structure. The extraction mechanism is elucidated from interaction strength and interfacial thickness analysis using molecular dynamics simulation. The diaromatics of 1-methylnaphthalene has stronger affinity to deep eutectic solvent (DES) than the monoaromatics of tetralin, while longer alkyl-chain in hexadecane enhances its repulsive interaction with DES than dodecane. Extraction process simulation was then carried out with well-regressed parameters of NRTL thermodynamic model. Process simulation confirms that a high extraction performance can be achieved for model LCO containing more diaromatics. Therefore, it is preferable to incorporate aromatics-alkanes extractive separation into the pre-hydrotreating step of LCO upgrading process. [ABSTRACT FROM AUTHOR]

• Phytosterols showed greater bioaccessibility when loaded in solid lipid nanoparticles. • Amounts of phytosterols in micelle was positively correlated with lipid lipolysis. • Affinities of phytosterols and lipids affected the arrangement of nanoparticles. • Compact arrangements were conducive to greater stability and slower release. The lipid matrix plays a key role in solid lipid nanoparticles (SLNs) embedding active ingredients. To investigate the influence of lipid matrix structure on arrangement, release, and stability of solid lipid nanoparticles, three phytosterols formulations with different carrier glycerides [glycerol monostearate (GMS), glycerol distearate (GDS), and glycerol tristearate (GTS)] were prepared and evaluated. X-ray diffraction and differential scanning calorimetry revealed the lowest crystallinity of phytosterols in the GMS matrix, corresponding to the maximum bioaccessibility (40.2%) in vitro experiments. Sustained release and better stability were observed from GDS and GTS matrices, which could be attributed to strong molecular interactions or a core-rich structure inside the nanoparticles. Molecular dynamics simulations demonstrated that the affinity between phytosterols and glycerides decreased in the order GDS > GTS > GMS, as well as explaining the release and storage capacities of the three nanoparticles. This study would facilitate the rational design of SLNs in functional foods. [ABSTRACT FROM AUTHOR]

In order to explore the interaction between nitrocellulose (NC) and nitroglycerine (NG) of composite modified double-base (CMDB) propellants, the radius of gyration of NC molecules and radial distribution function for different atoms of NC and NC/NG blends were calculated by using molecular dynamics simulation( MD) . It was found that the radius of gyration of NC molecules was independent on the temperature, while the number of NG molecules increased greatly with temperature. Besides, according to the radial distribution function of the models, it was revealed that the H-bond could be formed between NG and NC molecules instead of H-bond in the individual NC molecule, which could decrease the interaction force inside NC molecules, thus increase the radius of gyration of NC. [ABSTRACT FROM AUTHOR]

Abstract: The helium bubble has significant consequence to the mechanical properties of irradiated materials. The influence of embedded helium bubble to the elastic properties of aluminum has been investigated by molecular dynamics (MD) simulations. The interaction between aluminum atoms and the interaction between helium atoms are described by an embedded-atom-method (EAM) many-body potential and a pair potential, respectively. Another pair potential, which is parameterized based on ab initio calculation, is used to describe the interaction between aluminum and helium atoms, and its validation under pressure up to 10GPa is reasonable demonstrated by the electron density calculation. For the composite system consisting of 62,500 aluminum atoms and one helium bubble with various diameters, its elastic constants are calculated properly by stress–strain relation rather than by energy–strain relation. The results show that elastic constants c 11, c 12 and c 44 decrease with increasing of the volume of the helium bubble, and remain almost invariable with the internal pressure of the helium bubble. The main reason is under high-pressure the helium is softer than aluminum, and the soft effect overwhelms the hard effect of internal pressure of helium bubble. [Copyright &y& Elsevier]