Computational fluid dynamic-discrete element method coupling analysis of particle transport in branched networks

An understanding of the particle transport characteristics in a branched network helps to predict the particle distribution and prevent undesired plugging in various engineering systems.Quantitative analysis of particle flow characteristics is challenging in that experiments are expensive and particle flow is difficult to detect without disturbing the flow.To overcome this difficulty,man-made fractal tree-like branched networks were built,and a coupled computational fluid dynamic and discrete element method model was applied.A series of numerical simulations was carried out to analyze the influence of fractal structure parameters of networks on the particle flow characteristics.The joint influence of inertial,shunt capacity and superposition from upstream branches on particle flow was investigated.The injection position at the inlet determined the particle velocity and its future flow path.The particle density ratio,particle size and bifurcation angle had a greater influence on the shunting of K2 branches than that in the K1 level and N_k22/N_k21 reached a maximum at 60°.Compared with a network with an even number of branches,there was a preferential branch when the branch number was odd.The preferential branch effect or asymmetry degree of the level(K2)branches had a more significant impact on particle shunting than that from the upstream branches(K1).     

β-cyclodextrin Sensitized Spectrofluorimetry for the Determination of Abiraterone Acetate and Abiraterone

A novel spectrofluorimetric method to determine abiraterone acetate and its active metabolite, abiraterone was developed, based on the fact that fluorescence intensity of abiraterone acetate and abiraterone could be enhanced in β-cyclodextrin (β-CD) due to the formation of the inclusion complex. The inclusion interaction of β-CD and abiraterone acetate and the β-cyclodextrin sensitized spectrofluorimetry was examined. The various factors influencing fluorescence were discussed in details. The results showed that under the optimized conditions, the linear range of calibration curve for the determination of biraterone acetate and abiraterone was 0.20?~?6.0 μg/mL, and the detection limit (LOD) was 6.8 (r?=?0.997) or 6.6 ng/mL (r?=?0.996), respectively. No interference was observed from common co-existing substances or pharmaceutical excipient. The method was successfully applied to the analysis of abiraterone acetate in pharmaceutical formulation and abiraterone in human serum/urine.     

A theoretical study on the structure and hygroscopicity of ammonium dinitramide

Density functional theory (DFT) and the dispersion corrected DFT have been used to investigate the hygroscopicity of ammonium dinitramide (ADN). Calculation results show that the gaseous ADN has a strong hydrogen bond. But the ionic pair structure NH₄ ⁺ · N(NO₂)^? is stabilized upon the addition of water molecules. Natural bond orbital calculations suggest that the intra- and intermolecular orbital interactions LP(O) → σ*(N–H) or LP(O) → σ*(O–H) make the system stabilized as a whole. En energy decomposition analysis reveals that the interactions between ADN and H₂O are dominated by the electrostatic and orbital interactions. The formation reactions become more spontaneous with the increasing number of water molecules but can be weakened by the growing temperature from 200 to 400 K. Moreover, the molecular dynamic method is applied to explore a more realistic cluster model to study the interactions between ADN and H₂O.     

Optical guided-wave study of a homeotropically aligned ferroelectric liquid crystal

Abstract

The excitation of optical modes is used to study the optical tensor configuration in a thin ferroelectric liquid crystal layer, cooled from the initially homeotropically aligned nematic phase. By monitoring the angular dependent reflectivity for plane polarized radiation coupled into the guided modes in the smectic C* layer and subsequently fitting the recorded data to predictions from multilayer optics theory, the optical tensor configuration in the layer is fully evaluated. Iteratively modelling the full tilt/twist profile in the cell, progressively converging the predicted reflectivity to experimental data, gives a complete and very well specified picture of the optical tensor throughout the cell. By studying the cell at various temperatures, the temperature dependence of the tilt of the major axis of the optic tensor (which may be related to the cone angle if the smectic layers are parallel to the cell surface) has been established. The temperature dependent optical dielectric constants have also been obtained.     

In situ self-assembly synthesis of gold nanoparticle arrays on polystyrene microspheres and their surface plasmon resonance

Gold (Au) nanoparticle arrays with tunable morphology and optical characteristics were synthesized by in-situ self-assembly process that occurred on the surface of aniline-modified polystyrene (PS) microspheres. The method can be used to control the growth of both single and aggregated Au nanoparticle arrays on PS microsphere surface. This method could also be adapted for synthesis of other noble metals hybrid materials, which opens exciting opportunities for their practical applications.     

Transition metal-free synthesis of primary amides from aldehydes and hydroxylamine hydrochloride

Primary aromatic amides can be synthesized from aldehydes and hydroxylamine hydrochloride in the presence of Cs₂CO₃. Various aromatic aldehydes (include some heteroaromatic aldehydes) are able to generate the corresponding aromatic amides in moderate to excellent yields.     

C?H Functionalization/Asymmetric Michael Addition Cascade Enabled by Relay Catalysis: Metal Carbenoid Used for C?C Bond Formation

A combination of either ruthenium(II) or rhodium(II) complexes and quinine‐derived squaramide enables 3‐diazooxindoles, indoles, and nitroalkenes to undergo highly efficient asymmetric three‐component reactions, thus affording optically active 3,3′‐bis(indole)s through a consecutive C C bond‐forming sequence, which turned out to be applicable to the facile total synthesis of (−)‐folicanthine.     

Single-crystal structure of two-dimensional organic framework based on donor-acceptor interactions with charge-transfer effect

Two charge-transfer single crystals induced by donor-acceptor interactions were obtained. The presence of different solvent molecules led to 1D(linear) or 2D self-assembly modes. More interestingly, the 2 D organic framework, a layer-by-layer 2D organic framework single crystal, showed a stronger charge-transfer effect than the 1D cocrystal.     

Dynamically maintained spike timing sequences in networks of pulse-coupled oscillators with delays

We demonstrate the widespread occurrence of dynamically maintained spike timing sequences in recurrent networks of pulse-coupled spiking neurons with large time delays. The sequences occur in transient, quasistable phase-locking states. The system spontaneously jumps between these states. This collective dynamics enables the system to generate a large number of distinct precise spike timing sequences. Distributed time delays play a constructive role by enhancing the dominance in parameter space of the dynamics responsible for producing the large variety of spike timing sequences.