Facile and Green Synthesis of Starfruit-Like ZIF-L,and Its Optimization Study

Due to its excellent characteristics, zeolitic imidazole framework-L (ZIF-L) is widely used in various applications, such as drug delivery, wastewater treatments and energy storage. In the synthesis of ZIF-L, the molar ratio of ligand to metal, the reaction time and the temperature are essential parameters to produce excellent ZIF-L. In this work, ZIF-L was synthesized using a facile and green synthesis method. It was statistically investigated and optimized to obtain the best operating conditions. The optimization was carried out toward the amount of adsorbed crystal violet (CV) dye (q) as the response in the statistics. The optimal ZIF-L was obtained using a molar ratio of ligand to metal of 8.2220 for 97 min at 29 °C, where the q value of the CV adsorption onto this optimal ZIF-L reached 823.02 mg/g. The obtained ZIF-L was characterized using SEM, XRD, FTIR and TGA analyses to ensure its excellent characteristics.     

Stereo PIV measurement of a finite, flapping rigid plate in hovering condition

Qualitative and quantitative flow visualizations were performed on a flapping rigid plate to establish a quantitative method for flow observation and evaluation of the force in the near field of a flapping wing. Flow visualization was performed qualitatively with dye visualization and quantitatively with velocity measurements using stereo particle image velocimetry (PIV) on three planes near the tip of the plate along its chord and oriented normally. By ensemble averaging the velocity fields of the same phase angles, they represent a portion of the volume near the tip. Measurements were conducted with two flapping frequencies to compare the flow structure. The second invariant of the deformation tensor visualized the leading edge and mid-chord vortices around the plate appearing due to flow separation behind the plate while other vortical structures were visualized by streamlines. These structures appear to be related to the dynamics of the leading edge vortex. Force analysis by integrating the phase-averaged velocity field within a chosen control volume showed increases in the maxima of the magnitudes of the non-dimensional unsteady force terms on the edge of the plate at the angles after the end of each stroke. The non-dimensional phase-averaged momentum flux was similar for both flapping frequencies.     

Beat structure in spectrally resolved four-wave mixing under crosslinear polarization in GaAs quantum wells

The polarization dependence of beat structure in spectrally resolved four-wave mixing was investigated on 50 Å GaAs multiple quantum wells. Under crosslinear polarization we observed a beating structure at higher energy region of the main spectral peak due to biexciton–exciton transition. The beat has a period of 0.95 ps and is constructive at delay time T=0 ps, which suggests the corresponding double Feynman diagrams to be of the same type. By shortening the central wavelength of the sub-ps laser, we observed the distinctive peak corresponding to the beat period. Even in GaAs system, which is generally believed to have a small biexcitonic effect, there are two effective 2-exciton states with well-defined energies which are required to describe the third-order optical nonlinearly.     

The estimation of pressure on the surface of a flapping rigid plate by stereo PIV

The method to estimate the dynamic load of a flapping wing by the integration of pressure on the wing’s surface is discussed. The flapping wing was modeled as a plate flapping sinusoidally in hovering condition. The flow around the flapping plate was measured using stereo PIV on multiple measurement planes along the out-of-plane direction. The phase-averaged velocity field of each measurement plane was calculated so that three-dimensional analyses could be applied. The phase-averaged pressure field was obtained from the integration of the three-dimensional Poisson equation for pressure using the available information acquired from stereo PIV measurements. The pressure field is visualized on the measurement planes. In this study, the estimated load was the torque of the axis of rotation. This torque was compared with the result from strain gauge measurements. The torque estimation, although only on a partial surface of the plate, is within reasonable agreement with the measured torque. The integration of the Poisson equation based on stereo PIV measurements and estimations of the torque shows that an increase in the torque at the start of a flapping stroke is caused by the stagnation on the surface of the plate from the flow that is induced by the leading-edge vortices.     

Studies on temperature dependent kinetics of <Emphasis Type="Italic">Aspergillus awamori</Emphasis> feruloyl esterase in water solutions

The initial reaction rate (V ₀) for the esterification reaction of feruloyl esterase (FAE-II) at different temperatures (288, 298, 308, 318, 328, 338, 348, and 358 K) and various ethyl ferulate concentrations [(2, 4, 6, 8, 10, 12, 14, and 16) × 10⁻⁴ mol l⁻¹ of ethyl ferulate in water] were determined. The Lineweaver-Burk double reciprocal plot yielded the kinetic parameters (maximal velocity V _max, Michaelis constant K _m, and second order rate constant V/K). The effects of temperature on those 3 kinetic parameters were presented and discussed. The thermodynamic parameters ΔH* (enthalpy of activation), ΔG* (free energy of activation), ΔS* (entropy of activation), ΔG _E-S (free energy change of substrate binding), ΔG _E-T (free energy change of transition state formation), related to that biochemical process were determined and discussed from van’t Hoff plot, Arrhenius plot, and Eyring plot.     

Statistically Optimum HKUST-1 Synthesized by Room Temperature Coordination Modulation Method for the Adsorption of Crystal Violet Dye

Due to its excellency and versatility, many synthesis methods and conditions were developed to produce HKUST-1 ([Cu₃(BTC)₂(H₂O)₃]_n). However, the diversity of HKUST-1 was actually generated both in terms of characteristics and morphologies. Hence, the consistency of HKUST-1 characteristics and morphologies needs to be maintained. The statistical analysis and optimization provide features to determine the best synthesis condition. Here, a room-temperature coordination modulation method was proposed to maintain the morphology of HKUST-1 while reducing energy consumption. In addition, response surface methodology (RSM) was used to demonstrate the statistical analysis and optimization of the synthesis of HKUST-1. The molar ratio of ligand to metal, reaction time, and acetic acid concentration were studied to determine their effects on HKUST-1. The optimum HKUST-1 was obtained by the synthesis with a molar ratio of ligand to metal of 0.4703 for 27.2 h using 5% v/v acetic acid concentration. The statistical analysis performed a good agreement with the experimental data and showed the significance of three desired parameters on HKUST-1. The optimum HKUST-1 had the adsorption capacity of 1005.22 mg/g with a removal efficiency of 92.31% towards CV dye. It could be reused up to 5 cycles with insignificant decrease in performance.     

Velocity measurements of streamwise roll cells in rotating plane Couette flow

For the first time, quantitative velocity measurements in rotating plane Couette flow are demonstrated. Particle image velocimetry is used at a low Reynolds number with anti-cyclonic, i.e. destabilising rotation, where the instability is expected to give rise to steady streamwise-oriented roll cells. The streamwise and spanwise velocities of the roll cells were measured on the centreplane of the flow and at two planes on either side. The streamwise velocity is spanwise periodic with an amplitude variation approximately ±42 % of half the velocity difference between the moving walls. The wall-normal velocity was estimated by assuming steady, laminar and streamwise-independent flow. Despite the large amplitude of the disturbance, both the spanwise wave length and amplitude ratio between the streamwise and wall-normal components were close to what is obtained from linear theory. A splitting event of a roll cell was also captured by the velocity measurements and its development followed in time.