Observation of first and third harmonic responses in two-dimensional AlGaAs/GaAs HEMT devices due to plasma wave interaction

Plasma waves are oscillations of electron density in time and space, and in deep submicron field effect transistors, typical plasma frequencies, _ωp${\omega }_p$, lie in the terahertz (THz) range and do not involve any quantum transitions. Hence, using plasma wave excitation for detection and/or generation of THz oscillations is a very promising approach. In this paper, the investigation of plasma wave interaction between the plasma waves propagating in a short-channel High-Electron-Mobility Transistor (HEMT) and the radiated electromagnetic waves was carried out. Experimentally, we have demonstrated the detection of the terahertz (THz) radiation by an AlGaAs/GaAs HEMT up to third harmonic at room temperature and their resonant responses show very good agreement with the calculated results.     

Simulation model of the fractal patterns in ionic conducting polymer films

Normally polymer electrolyte membranes are prepared and studied for applications in electrochemical devices. In this work, polymer electrolyte membranes have been used as the media to culture fractals. In order to simulate the growth patterns and stages of the fractals, a model has been identified based on the Brownian motion theory. A computer coding has been developed for the model to simulate and visualize the fractal growth. This computer program has been successful in simulating the growth of the fractal and in calculating the fractal dimension of each of the simulated fractal patterns. The fractal dimensions of the simulated fractals are comparable with the values obtained in the original fractals observed in the polymer electrolyte membrane. This indicates that the model developed in the present work is within acceptable conformity with the original fractal.     

Comparative studies on the structure and electromagnetic properties of Ni−Zn ferrites prepared via co-precipitation and conventional ceramic processing routes

The magnetic and physical properties of ferrites are very sensitive to microstructure, which in turn critically depends on the manufacturing process. In this study, nickel zinc ferrite powder with composition Ni_0.8Zn_0.2Fe₂O₄ has been prepared via conventional ceramic processing and co-precipitation methods. The toroidal and pellet form samples were sintered at various temperatures such as 1100, 1200 and 1300 °C. The microstructure, magnetic and dielectric properties of both samples were studied. The X-ray diffraction patterns confirm the formation of single-phase cubic spinel structure for the co-precipitation technique after sintering. The microstructure studies of Ni_0.8Zn_0.2Fe₂O₄ show the grain size increases and the porosity decreases with temperature for both methods. The controlled permeability with small loss and wide operational frequency range are found in the co-precipitation samples. Dielectric constants decrease with increase of frequency and increase with sintering temperature in both methods. Consequently, the homogenous microstructure with the low-loss high-performance of nickel zinc ferrite has been discovered by means of co-precipitation method.     

The Effect of Volume Shape Factor on the Crystal Size Distribution of Fragments due to Attrition

The effect of volume shape factor on crystal size distribution (CSD) is usually ignored to simplify the analysis of population balance equation. In the present work, the CSD of fragments generated from a mechanically stirred crystallizer as the result of attrition mechanism has been reported when the volume shape factor conforms to normal distribution. The physical model of GAHN and MERSMANN which relates the attrition resistance of a crystalline substances to its mechanical properties has been employed. The simulation of fragment size distribution was performed by Monte Carlo (MC) technique. The results are compared with those reported by GAHN and MERSMANN.     

ATP-Responsive Nanoparticles Covered with Biomolecular Machine “Chaperonin GroEL”

Herein, we report an ATP-responsive nanoparticle (^GroELNP) whose surface is fully covered with the biomolecular machine “chaperonin protein GroEL”. ^GroELNP was synthesized by DNA hybridization between a gold NP with DNA strands on its surface and GroEL carrying complementary DNA strands at its apical domains. The unique structure of ^GroELNP was visualized by transmission electron microscopy including under cryogenic conditions. The immobilized GroEL units retain their machine-like function and enable ^GroELNP to capture denatured green fluorescent protein and release it in response to ATP. Interestingly, the ATPase activity of ^GroELNP per GroEL was 4.8 and 4.0 times greater than those of precursor ^cysGroEL and its DNA-functionalized analogue, respectively. Finally, we confirmed that ^GroELNP could be iteratively extended to double-layered NP.