Study on the Constituents of Roots of Aceriphyllum rossii

A new stereoisomer of a tetrahydrofuranoid lignan, acerifuranoid A ( 1 ), and two new oleanane‐type triterpenoids, aceriphyllic acids J and K ( 2 and 3 ), were isolated from the roots of Aceriphyllum rossii. Their structures were elucidated on the basis of spectroscopic analyses and chemical evidence. These isolated compounds exhibited weak cytotoxic activity against various cancer cell lines with IC₅₀>150 μM .     

A numerical study of the flow of Bingham-like fluids in two-dimensional vane and cylinder rheometers using a smoothed particle hydrodynamics (SPH) based method

In this paper, a Lagrangian formulation of the Navier–Stokes equations, based on the smoothed particle hydrodynamics (SPH) approach, was applied to determine how well rheological parameters such as plastic viscosity can be determined from vane rheometer measurements. First, to validate this approach, a Bingham/Papanastasiou constitutive model was implemented into the SPH model and tests comparing simulation results to well established theoretical predictions were conducted. Numerical simulations for the flow of fluids in vane and coaxial cylinder rheometers were then performed. A comparison to experimental data was also made to verify the application of the SPH method in realistic flow geometries. Finally, results are presented from a parametric study of the flow of Bingham fluids with different yield stresses under various applied angular velocities of the outer cylindrical wall in the vane and coaxial cylinder rheometers. The stress, strain rate and velocity profiles, especially in the vicinity of the vane blades, were computed. By comparing the calculated stress and flow fields between the two rheometers, the validity of the assumption that the vane could be approximated as a cylinder for measuring the rheological properties of Bingham fluids at different shear rates was tested.     

Application of sputter-deposited amorphous and anatase TiO2 as electron-collecting layers in inverted organic photovoltaics

We demonstrate the deposition of amorphous and anatase TiO₂ on indium tin oxide (ITO) substrates via the process of sputtering, and the use of these materials as electron-collecting layers (ECLs) in inverted-type organic photovoltaics (OPVs). Anatase TiO₂ was obtained via vacuum-annealing of as-deposited amorphous TiO₂ at 300 °C. No deterioration of optical and electrical properties of ITO was observed after both sputter-deposition of TiO₂ and annealing process. The anatase TiO₂ proved to be an effective ECL when employed in inverted OPVs using bulk heterojunction photoactive layer of poly(3-hexylthiophene) and [6,6]-phenyl-C61-butyric acid methyl ester, achieving a power conversion efficiency of 3.3% (J_SC = 9.0 mA cm^?2, V_OC = 0.62 V and FF = 0.60).     

Bubble velocity jump discontinuity in polyacrylamide solutions: a photographic study

 It has been established that in the presence of elastic as well as surface tension forces, a jump can occur in the bubble velocity-bubble volume plot. It was proposed that this phenomenon was the result of an elastic instability at the bubble interface, which drastically changes the local boundary conditions. The origin of this change was mainly attributed to the magnitude of the elastic forces, which can extract surface active impurities at the gas-liquid interface. The purpose of this paper is to present photographic evidence of this hypothesis and to confirm past results. Received: 4 December 1998 Accepted: 17 February 1999     

Optimization of hydrothermal growth ZnO Nanorods for enhancement of light extraction from GaN blue LEDs

In this study, we report on the enhancement in the light extraction efficiency of GaN blue LEDs topped with ZnO nanorods. The ZnO nanorods were grown by a two-step hydrothermal synthesis with pre-coated ZnO nanoparticles under optimized condition to give the appropriate size and quality, giving an increase in the light output efficiency of 66%. This improvement is attributed to the optimal rod size and spacing with improved thermal dissipation as compared to light extraction from plain GaN surface. During the ZnO growth on the LEDs, 0.55 M of NH₃ was added and the ZnO sample was later annealed at 475 °C in N₂ ambient, to drive out interstitial oxygen atoms from the tetrahedral unstable site. As a result, a high ratio of UV to orange defect band emission was achieved. The two-step growth of ZnO nanorods on GaN LEDs was effective in generating array of ZnO nanorods which serve as reflector to enhance light extraction from LEDs.     

Chemical defects in the highly fluorescent conjugated polymer dots

We present strong evidence for the oxidation of conjugated polymers in the formation of conjugated polymer dots (CPdots) using Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Although recent studies show that folding of the polymer chain into a compact 3D structure is involved in the formation of these nanoparticles, the process by which these intrinsically hydrophobic nanoscale particles circumvent aggregation in water is still not well understood. Zeta potential results show that these dots have a negatively charged surface at neutral pH, with a zeta potential and surface charge density of approximately -40 mV and (1.39 - 1.70) × 10(-2) C/m(2), respectively. In addition, quantitative elemental analysis of CPdots indicates that oxygen composes 7-13% of these nanoparticles. The overall results support the presence of chemical defects in forming a hydrophilic surface of CPdots. As a consequence, the charged surface contributes to inhibiting the aggregation of CPdots in water, leading to colloidal stability.     

Effect of fullerene coating on silicon thin film anodes for lithium rechargeable batteries

To improve the electrochemical performances of Si thin film anodes for lithium rechargeable batteries, fullerene thin films are prepared by plasma-assisted evaporation methods to be used as coating materials. Analyses via Raman and X-ray photoelectron spectroscopy indicate that amorphous polymeric films originated from fullerene are formed on the surface of the silicon thin film. The electrochemical performance of these fullerene-coated silicon thin film as an anode material for rechargeable lithium batteries has been investigated by cyclic voltammetry, charge/discharge tests, and electrochemical impedance spectroscopy. The fullerene-coated Si thin films demonstrated a high specific capacity of above 3,000 mAh g⁻¹ as well as good capacity retention for 40 cycles. In comparison with bare silicon anodes, the fullerene-coated silicon thin film showed superior and stable cycle performance which can be attributed to the fullerene coating layer which enhances the Li-ion kinetic property at the electrode/electrolyte interface.     

Electrochemical performance of silicon thin film anodes covered by diamond-like carbon with various surface coating morphologies

Four different kinds of diamond-like carbon (DLC) coating morphologies on the surface of silicon films were prepared directly on a copper foil by using radio frequency plasma-enhanced chemical vapor deposition at 200 °C. A thin double layer film consisting of DLC (60 nm) and silicon film (250 nm) was fabricated for use as the anode material of lithium secondary batteries, and its electrochemical performance was also examined with special attention being paid to the surface coverage of the DLC film. The full coverage of silicon by the DLC film resulted in poor capacity due to the ensuing low reactivity with the lithium ions. On the other hand, the partial coating of the DLC film on the silicon film not only reduced the capacity fading, but also increased the discharge capacity during the charge/discharge cycles. These results indicated that the good dispersion of the DLC coating, obtained by using a smaller coating sector on the silicon film, improved the integrity of the electrode structure, thus giving higher capacities and reduced capacity fading.