Synthesis and characterization of polyaniline–ZnO composite and its dielectric behavior

Films of polyaniline (PANI) and PANI–zinc oxide (ZnO) composites have been synthesized by solution cast and spin coating technique. The ZnO powder of particle size 100–200 nm was synthesized by sol–gel technique and the polyaniline was synthesized by chemical oxidative polymerization of aniline. The composite films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infra red (FTIR) and the results were compared with polyaniline films. Dielectric properties of PANI and PANI–ZnO composite films have been investigated between frequency ranges of 8.5 and 13.0 GHz. The ‘a’ lattice parameter of ZnO was found to increase and the ‘c’ lattice parameter was found to decrease after ZnO–PANI composite formed. The characteristic FTIR peaks of PANI were found to shift to higher wave number in ZnO–PANI composite. These observed effects have been attributed to interaction of ZnO particles with PANI molecular chains. Dielectric constant of PANI–ZnO composite film was found to be smaller than the PANI film. The decrease of dielectric constant in PANI–ZnO films as compared to PANI was attributed to the interfaces formed between ZnO particles and PANI.     

Experimental investigations on flame stabilization behavior in a diverging micro channel with premixed methane–air mixtures

In the present paper, experimental investigations on the characterization of flame stabilization behavior in a 2.0 mm wide diverging channel are carried out with premixed methane–air mixtures. The effect of mixture equivalence ratio (Ф) and flow rate on flame shape, position, stability and emissions are reported in this work. The diverging portion of channel is preheated from the bottom side with a sintered metal burner to provide a positive temperature gradient along the direction of fluid flow which helps in stabilizing a flame in the channel. For a range of velocities and equivalence ratios, different types of stable and partially stable flame propagation modes were observed. Flames obtained for rich mixtures exhibited more stable nature as compared to lean mixtures. The flame stability limits were observed to vary between 0.2 m/s and 1.9 m/s for a range of mixture equivalence ratios.     

Toxicological evaluation of aspartame against Madin–Darby canine kidney cells

Aspartame is most widely used as artificial sweeteners in more than 6000 food varieties. Aspartame digested into aspartic acid, phenylalanine, and methanol, and several peroxides, superoxide molecules also generated together. The kidney is the secondary site for the cellular metabolism. The present study examined whether the treatment of aspartame induces oxidative stress in the Madin–Darby kidney cells (MDCK). The effects of aspartame on MDCK cell viability were investigated by the sulphorhodamine-B assay and flow cytometry. Morphology of MDCK cells following aspartame exposure was observed. Mitochondria-derived reactive oxygen species (ROS) was also determined using 2′,7′-dichlorodihydrofluorescein diacetate. Lipid peroxidation (LPO), glutathione reduced (GSH) levels and activities of superoxide dismutase (SOD), and catalase enzymes were also determined. Cell viability was significantly altered following aspartame exposure. Morphology of MDCK cells did not change significantly. However, there was a marginal morphological change, including rounding, sporadic distribution and loss of adherence were observed at higher doses of aspartame exposure. Mitochondria-derived ROS was increased in a dose-dependent manner following aspartame exposure. A significant increase in LPO levels, whereas GSH level was reduced after 48 and 72 h of aspartame exposure. SOD and catalase enzyme activities were significantly reduced in a dose- and time-dependent manner. Taking all these data together, it is concluded that aspartame may induce oxidative stress in the MDCK cells.     

Wavelet Modulus Maxima for Single Switch Open Fault in Multi-level Inverter

The multi-level inverter is widely used in high-power and high-voltage applications. Multi-level inverters use a large number of switches for high power conversion, resulting in increased system's fault probability. To ensure stable operation of the system, several fault diagnosis methods have been carried out by researchers. In this article, a fault diagnostic system in a multi-level inverter using wavelet modulus maxima is developed. The working situation of the power devices of a five-level diode-clamped multi-level inverter drive system under an open-circuit fault is analyzed through MATLAB (The MathWorks, Natick, Massachusetts, USA) simulation. The wavelet modulus maxima of output phase voltages are used to detect faulty phase (leg), and wavelet modulus maxima of DC bus currents are used to detect fault type and fault switch. Wavelet analysis is used for feature extraction, which can be used as input to the expert system to develop a fault identifier. The open-circuit fault on the five-level diode-clamped multi-level inverter of power devices is carried out experimentally. The experimental prototype is developed to validate the fault analysis with simulation results.     

A tool supported approach for brightness preserving contrast enhancement and mass segmentation of mammogram images using histogram modified grey relational analysis

Multidimensional Systems and Signal Processing - Mammography is a tool that uses X-rays to create mammograms. This tool is mainly used to find early signs of breast cancer. Usually, mammogram image...     

Micromechanical Hardness of Strontium Tartrate Trihydrate Crystals

The effect of load variation on the microhardness and microcracks of SrC₄H₄O₆·3H₂O (STT) single crystals has been studied. The crystals are grown by using a controlled chemical reaction in silica hydrogel medium. We confirm the applicability of Hays and Kendall's law. There is some anisotropy in the hardness observed on different faces. We show different types of cracking in the crystal during loading. Fracture toughness, brittleness index, and yield strength of the grown crystals have also been determined using the fracture mechanism.     

Efficient Near Infrared to Visible and Near‐Infrared Upconversion Emissions in Transparent (Tm3+, Er3+)‐α‐Sialon Ceramics

Intense visible and near‐infrared frequency upconversion and a frequency downconversion photoluminescence have been reported for the first time in Tm³⁺ and Er³⁺ co‐doped transparent α‐Sialon ceramics under 980 nm excitation. The α‐Sialon ceramics were prepared by hot‐press sintering technique. Intense upconversion bands at 554, 678, 803 nm, and a downconversion band at 1530 nm were observed as a result of the efficient energy transfer between Er³⁺ and Tm³⁺ ions. The quadratic dependence of upconversion intensities on the excitation power indicates that the upconversion process is governed by two‐photon absorption process. The sintered samples of thickness 0.20 mm have transparency above 80% in the range of 2000 to 4200 nm and it reaches as high as 82% at 3350 nm. Moderately low phonon energy was found with the highest frequency band at 828 cm^?1. These novel properties manifest the potential applications of transparent α‐Sialon ceramics as a multifunctional material.     

Augmenting the photocatalytic performance of cobalt ferrite via change in structural and optical properties with the introduction of different rare earth metal ions

In the present study, synthesis of different rare earth (RE) doped cobalt ferrite nanoparticles was done via facile sol-gel auto-combustion method using four different RE metal ions: Eu, Gd, Dy and Nd. The RE substituted cobalt ferrite nanoparticles were then characterized using FT-IR, powder XRD, HR-TEM, SAED, EDX, VSM and DRS techniques. From the characterization results, a significant variation in the structural, magnetic and optical properties of pure cobalt ferrite was observed with the introduction of different RE metal ions. This change in the properties was emerged due to the distortion of the ferrite crystal lattice due to replacement of smaller ionic radii Fe³⁺ ions with the comparatively larger ionic radii RE³⁺ metal ions. The catalytic activity of the fabricated RE doped cobalt ferrite nanoparticles was studied for the photo-Fenton degradation of cationic and anionic dyes. Under visible light irradiation, the as prepared RE doped nanoparticles exhibited great enhancement in the photo-Fenton degradation of dye molecules as compared to pure cobalt ferrite nanoparticles. The enhancement in the degradation rate was ascribed to the generation of defects in the crystal lattice, lower crystallite size and reduced band gap energy values which facilitated the facile transfer of photo-generated holes and electrons. Best catalytic results were obtained for CoNd_0.08Fe_1.92O₄ for SO dye (k?=?2.23?×?10^?1 min^?1) which were found to be around 9 times higher than the pure cobalt ferrite nanoparticles (k?=?0.23?×?10^?1 min^?1).     

Load‐Controlled Roll Transfer of Oxide Transistors for Stretchable Electronics

A stretchable and transparent In‐Ga‐Zn‐O (IGZO) thin film transistors with high electrical performance and scalability is demonstrated. A load‐controlled roll transfer method is realized for fully automated and scalable transfer of the IGZO TFTs from a rigid substrate to a nonconventional elastomeric substrate. The IGZO TFTs exhibit high electrical performance under stretching and cyclic tests, demonstrating the potentiality of the load‐controlled roll transfer in stretchable electronics. The mechanics of the load‐controlled roll transfer is investigated and simulated, and it is shown that the strain level experienced by the active layers of the device can be controlled to well below their maximum fracture level during transfer.