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Chemical reaction network has been a model of interest to both theoretical and applied computer scientists, and there has been concern about its physical-realisticity which calls for study on the atomic property of chemical reaction networks. Informally, a chemical reaction network is “atomic” if each reaction may be interpreted as the rearrangement of indivisible units of matter. There are several reasonable definitions formalizing this idea. We investigate the computational complexity of deciding whether a given network is atomic according to each of these definitions. Primitive atomic, which requires each reaction to preserve the total number of atoms, is shown to be equivalent to mass conservation. Since it is known that it can be decided in polynomial time whether a given chemical reaction network is mass-conserving (Mayr and Weihmann, in: International conference on applications and theory of petri nets and concurrency, Springer, New York, 2014), the equivalence we show gives an efficient algorithm to decide primitive atomicity. Subset atomic further requires all atoms be species, so intuitively this type of network is endowed with a “better” property than primitive atomic (i.e. mass conserving) ones in the sense that the atoms are not just abstract indivisible units, but also actual participants of reactions. We show that deciding if a network is subset atomic is in NP, and “whether a network is subset atomic with respect to a given atom set” is strongly NP-complete. Reachably atomic, studied by Adleman et al. (On the mathematics of the law of mass action, Springer, Dordrecht, 2014. 10.1007/978-94-017-9041-3_1), and Gopalkrishnan (2016), further requires that each species has a sequence of reactions splitting it into its constituent atoms. Using a combinatorial argument, we show that there is a polynomial-time algorithm to decide whether a given network is reachably atomic, improving upon the result of Adleman et al. that the problem is decidable. We show that the reachability problem for reachably atomic networks is PSPACE-complete. Finally, we demonstrate equivalence relationships between our definitions and some cases of an existing definition of atomicity due to Gnacadja (J Math Chem 49(10):2137, 2011). [ABSTRACT FROM AUTHOR]

The hierarchical flower-like Zn-doped SnO 2 (FLZn-SnO 2 ) architectures composed of curved sheets are synthesized by a hydrothermal method at 180 °C for 8 h. We can obtain the morphological evolution of FLZn-SnO 2 by a series of control experiments. Based on the nucleation and self-assembly process, a possible formation mechanism is proposed. The FLZn-SnO 2 architectures exhibit higher photocatalytic activity in the degradation of Rhodamine B than pure SnO 2 under visible light irradiation. [ABSTRACT FROM AUTHOR]

In this paper, to analyse the rider's effects on the motion of a motorcycle, we model a rider–motorcycle system by taking into account the leaning motion of the rider's upper torso and his/her arm connection with the handlebars. The nonlinearity of the tyre force is introduced by utilising hyperbolic tangent functions to approximate a Magic Formula tyre model. On the basis of a derived nonlinear state-space model, we analyse the effects of not only the rider's arms but also his/her postures during steady turning by simulations. The rider's postures including lean-with, lean-in and lean-out are realised by adding the lean torque to the rider's upper torso. The motorcycle motion and the rider's effects are analysed in the case where the friction coefficient of the road surface changes severely during steady turning. In addition, a linearised state-space model is derived during steady turning, and a stability analysis of the rider–motorcycle system is performed. [ABSTRACT FROM PUBLISHER]

Abstract: In this work, three-dimensional (3D) hierarchical silver microparticles (HSMP) composed of 2D nanoflakes were synthesized on the anode of a galvanic cell. A copper plate immersed in CuSO4 solution and a platinum-coated silicon plate immersed in AgNO3 solution served as the cathode and anode, respectively. The two half-cells were linked by a salt bridge. The presence of poly(N-vinyl pyrrolidone) (PVP) in the AgNO3 electrolyte, an optimum AgNO3 concentration and an appropriate reaction time are crucial for the formation of a hierarchical nanostructure. The evolution of the products during growth was tracked to study the formation and metamorphosis mechanisms. The catalytic activity of HSMP was studied via promotion of Rhodamine B reduction by NaBH4. [Copyright &y& Elsevier]

Abstract: In this paper, the shape evolution and thermal stability of Ag nanoparticles (NPs) on spherical SiO2 substrates were investigated by means of in situ transmission electron microscopy (TEM) imaging and differential scanning calorimetry (DSC). The initial Ag NPs at room temperature were semispherical-like, with an average size of 9nm in half-height width, well-dispersed on spherical SiO2 substrates. No obvious shape change was observed when the semispherical NPs of Ag were heated at temperature lower than 550°C. The shape of the semispherical Ag NPs changed gradually into a spherical one in the temperature range of 550–700°C, where surface diffusion and surface premelting took place. When the heating temperature was increased up to 750°C, the spherical Ag NPs were found to desquamate from the substrates due to the decreases of the contact area and the binding force between Ag NPs and SiO2 substrates. A possible mechanism for the desquamation of Ag NPs from the SiO2 sphere surface is proposed according to the results of in situ TEM observation and DSC analysis. [Copyright &y& Elsevier]

The continuous gas displacement in unconsolidated sandstone gas reservoirs will necessarily result in the pore structure and rock permeability variations, which cannot be neglected in the gas development process. However, the variations have not been comprehensively addressed yet, especially for the rock structure in pore scale. This work presented the quantitative results of pore structure in microscale and permeability variations during gas displacement in unconsolidated sandstone reservoirs through computed tomography (CT) reconstruction analysis. The results indicated that a more than 3% increase in porosity after gas displacement resulted from the enlargement of the pore and throat with a diameter of more than 20 μm and 3 μm, respectively, owing to the release and migration of clay and fine particles, in spite of the distribution frequency decline of both pore and throat with a small diameter. The pore connectivity would be enhanced by the increase of the connected pores as well as the enlargement of the pore and throat sizes. However, the pore-throat coordination number could only change with slight improvement. In terms of permeability and relative permeability changes with pore structure, the improvement of permeability after gas displacement was higher than that of porosity, and the continuous gas displacement would broaden gas-water flow region and lower irreducible water saturation and residual gas saturation, and then, the equal phase relative permeability point would shift to the right. These investigations will contribute to more accurate reserve evaluation and productivity prediction. [ABSTRACT FROM AUTHOR]

Abstract: A visible-light-active mesoporous Cr-doped TiO2 photocatalyst with worm-like channels was synthesized using an evaporation-induced self-assembly approach and characterized by X-ray powder diffraction, nitrogen adsorption–desorption, X-ray photoelectron spectroscopy, transmission electron microscope, and UV–vis diffuse reflectance, respectively. The effect of Cr3+ doping concentration on the photocatalytic activity of mesoporous TiO2 was investigated from 0.1 to 1mol%. The characterizations indicated that the photocatalysts possessed a homogeneous pore diameter of about 8nm with high surface area of 117m2/g and a crystalline anatase pore wall doped by Cr3+. Compared with pure mesoporous TiO2, the Cr-doped TiO2 extended the photoabsorption edge into the visible light region. The results of gaseous acetaldehyde photodecomposition showed that mesoporous Cr-doped TiO2 exhibited higher photocatalytic activities than pure mesoporous TiO2 and nonporous Cr-doped TiO2 under visible light irradiation. [Copyright &y& Elsevier]

Abstract: Silica–silver core–shell composite particles with uniform thin silver layers were successfully synthesized by a facile and one-step ultrasonic electrodeposition method. By electrolysis of the slurry consisting of preformed silica spheres and silver perchlorate without any additives, the homogenous composite particles can be prepared. The average size of single silver crystals in the composite is about 12nm and the thickness of silver layer is 14±2nm. Moreover, the continuity of Ag distribution, the surface roughness and the thickness of silver layer are controllable by adjusting the current density (I), the concentration of electrolyte (C) and the reaction time (t). Optical properties of the composite particles with different silver content were also investigated. [Copyright &y& Elsevier]

Abstract A facile hydrothermal method is developed to prepare hierarchical dahlia-like SnO 2 nanostructures (HDSNs). They have been successfully synthesized without using any templates or surfactants. We find that the hierarchical architectures of SnO 2 are assembled by a number of regular-shaped nanosheets and nanoparticles, which are cross-linked in the interior of the micro-flower. Based on the nucleation and self-assembly process, a possible formation mechanism is proposed. The effect of NaCl on the product is also studied. In addition, the product exhibits excellent photocatalytic activity to Rhodamine B (RhB) aqueous solution and possess good stability and reusability under visible light. This study will provide valuable experimental data for further study of nanomaterials and their photocatalytic properties. Highlights • Novel HDSNs are successfully fabricated without using any templates and surfactants. • Combined with time-dependent experiments and characterization, we present a possible growth mechanism for the products. • The HDSNs exhibit excellent photocatalytic activity to Rhodamine B under visible light irradiation. [ABSTRACT FROM AUTHOR]

Novel three-dimensional octagonal-like CuO micro-/nanostructures with diameters ranging from 10 to 15 μm have been successfully prepared by hydrogen peroxide-assisted hydrothermal method and subsequent calcination. The product morphology can be changed by simply ordering the amount of hydrogen peroxide (H 2 O 2 ). When the amounts of H 2 O 2 is increased, the length of the corner portion is increased and the width is narrower. The obtained octagonal CuO nanostructures were evaluated for their ability for the degradation of hazardous organic contaminants in water under visible-light irradiation. Comparing with commercial CuO and other CuO products, the CuO octagonal nanostructures exhibit excellent performance for photocatalytic decomposition of RhB (Rhodamine B). It is well established that effective photocatalytic performance results from its unique 3D octagonal nanostructures. We believe that the present work will provide some ideas for further fabrication of other novel nanostructures and exploration of their applications. [ABSTRACT FROM AUTHOR]

Novel hierarchical flower-like SnO 2 (HFL-SnO 2 ) nanostructures are successfully synthesized through the hydrothermal method. We find that the hierarchical architectures of SnO 2 is assembled by a number of regular-shaped nanosheets, which are cross-linked in the interior of the micro-flower. The product also has a high specific surface area of about 78.8 m 2 g −1 . Based on the nucleation and self-assembly process, a possible formation mechanism is proposed. The effects of SDS and NaCl on the product are also studied. Moreover, the product exhibits excellent photocatalytic activity and take possession of good stability and reusability under visible light. This study provides valuable experimental data for further study of nanomaterials and their photocatalytic properties. [ABSTRACT FROM AUTHOR]

Abstract: The shape-controlled synthesis of silver nanostructures (NSs) via sonoelectrochemistry has been investigated in aqueous solution of AgClO4 with the assistance of poly(N-vinylpyrrolidone) (PVP). The morphology of silver NSs depends strongly on the current density (J) and the molar ratio (R) of PVP monomer to Ag+. By controlling reaction conditions, not only zero-dimensional silver nanoparticles (NPs) of spherical and oval shapes, but also 3D silver NSs composed of dendritic rod, dendritic sheet and flower-like dendrites (consisting of staggered nanosheets) were successfully prepared. We discuss the growth process as being mainly dependent on the adjustable driving force of electroreduction while being modulated by PVP that contributes mainly to the finer structure in the shape-controlled synthesis. [Copyright &y& Elsevier]