Kinetic studies on saponification of ethyl acetate using an innovative conductivity‐monitoring instrument with a pulsating sensor

An innovative conductometric measurement technique using a nonconventional but high‐performance (high‐precision, high‐resolution, rapid response features for online graphic display) in house–built pulsating conductivity monitoring instrument has been deployed to study the kinetic behavior during the reaction of ethyl acetate and NaOH. A laboratory‐made constant temperature reaction bath with the facility of continuous stirring of solution for homogeneous mixing was used to carry out experiments at desired solution temperatures. Rate constants of the saponification reaction in the temperature range at various temperatures (30–55°C) were determined, and the results were compared with the reported values. Although the reported data exhibit wide scatter, our data are in agreement with some of the literature data. From these data, thermodynamic parameters such as activation energy, activation enthalpy, activation entropy, and activation free energy have been evaluated. With the introduction of this novel conductometric measurement technique, the determination of rate constants at various solution temperatures becomes much simpler and faster. © 2011 Wiley Periodicals, Inc. Int J Chem Kinet 43: 648–656, 2011     

Rare-earth doped III-nitride semiconductors for semiconductor spintronics

InGaGdN layers and InGaGdN/GaN superlattice (SL) structures were grown by plasma-assisted molecular beam epitaxy. InGaGdN layers exhibited photoluminescence emission at room temperature and its peak wavelength was red-shifted with the increase of In composition. Clear hysteresis and saturation were observed in the magnetization versus magnetic field curves at room temperature for the InGaGdN layers. Si co-doping into InGaGdN layers increased the electron carrier concentration and enhanced the magnetization. In the InGaGdN/GaN SL samples, enhanced magnetization was also observed. Si doping into wide bandgap GaN layers in these SL structures further increased the magnetization, where InGaGdN layers were not doped with Si. All these results can be understood with the carrier-mediated ferromagnetism.     

A novel injection method for high-speed proteome analysis by capillary electrophoresis

We have developed a new sample injection method for capillary electrophoresis (CE) that reduces the required migration time. We demonstrated a pressurization technique that was performed with buffer in the outlet after the electrokinetic sample injection with no buffer in the outlet. To reduce the migration time, the sample injection had to be performed with no buffer in the outlet; water should be pressurized while the buffer is in the outlet. Though the resolution was slightly decreased using this method, the addition of a separation carrier (curdlan) to the run buffer restored the resolution without delaying the migration time. The use of our new sample injection method combined with our high-quality separation carrier will enable us to improve the efficiency of the high-throughput screening (HTS) system for proteome analysis.     

Giant improvement of time-delayed feedback control by spatio-temporal filtering

Control of spatio-temporal chaos by the time-delay autosynchronization method is improved by several orders of magnitude. Unstable time periodic patterns are efficiently stabilized if one employs filters and couplings which originate from the Floquet eigenvalue problem of the unstable orbit. We illustrate our scheme by an application to a globally coupled reaction-diffusion model which describes charge transport in semiconductor devices.     

Large four-wave mixing of spatially extended excitonic states in thin GaAs layers

We study the size dependence of the nonlinear response of weakly confined excitons for the size region beyond the long wavelength approximation regime. The observed degenerate-four-wave mixing signal of GaAs thin layers exhibits an anomalous size dependence, where the signal is resonantly enhanced at a particular thickness region. The theoretical analysis elucidates that this enhancement is due to the size-resonant enhancement of the internal field with a spatial structure relevant to the nondipole-type excitonic state. These results establish the formerly proposed new type of size dependence of nonlinear response due to the nonlocality induced double resonance.     

207Pb chemical shift thermometer at high temperature for magic angle spinning experiments

The temperature dependence of 207Pb chemical shift in magic angle spinning (MAS) NMR spectrum of Pb(NO3)2 provides a sensitive method to calibrate sample temperatures in MAS NMR. The temperature dependence is uniform in the temperature range between 30 degrees C and 400 degrees C. The NMR sensitivity and the line width are also favorable.