Structural impact of tungsten ions on ZnO-Sb2O3-As2O3 glass system

Five glasses in the quaternary system 5 ZnO-(50 − x) As₂O₃-45 Sb₂O₃: x WO₃ with the values of x ranging from 0 to 20 mol% (in steps of 5 mol%) are prepared. The samples are characterized by X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy (EDS) and differential thermal analysis (DTA) techniques. The DTA studies have indicated that the glass forming ability decreases with the increasing content of WO₃. A number of studies, like, spectroscopic (optical absorption, IR, Raman, ESR spectra) and dielectric studies (dielectric constant ?, loss tan δ, a.c. conductivity σ_a.c.) over a wide range of frequency and temperature and dielectric break down strength at room temperature, have been carried out and are analysed in the light of different oxidation states and environment of tungsten ions in these glasses. These glasses have potential photonic applications.     

Effect of deposition time on optical and luminescence properties of ZnS thin films prepared by photo assisted chemical deposition technique

Photo assisted chemical deposition method (PCD) is a new procedure for the deposition of compound semiconducting materials which is less explored. In this method the deposition is carried out with the irradiation of UV light on the reaction bath. PCD scores advantages for its low cost, use of flexible substrates and capability of large area deposition compared to other chemical methods like chemical bath deposition (CBD), electro chemical deposition (ECD), etc. Zinc sulfide films have been deposited on glass substrate by aqueous alkaline solution comprised of zinc nitrate, hydrazine hydrate, ammonium nitrate, ammonia and thiourea. The samples were prepared under UV illumination for different durations and characterized. The thickness of the samples increases with the deposition time. XRD patterns revealed the crystalline nature of samples with more number of dips. Optical study showed a low absorbance and constant transparency throughout the visible region disclosing the stiochiometric nature of the film. Obtained band gap energies were in good agreement with the theoretical value. Photoluminescence spectra showed two blue emission bands around 450 and 470 nm, and the intensity was found to depend on the thickness of the films.     

Synthesis,Characterization, and Evaluation of Mesoporous MCM-41-supported Molybdenum Hydrotreating Catalysts

Abstract

Mesoporous MCM-41 material with high surface area and narrow pore size distribution was synthesized and used as a support for Mo, CoMo, and NiMo catalysts. The molybdenum loading was varied from 2–14 wt% on MCM-41. On 10 wt% Mo/MCM-41, the promoter Co or Ni concentration was varied from 1–5 wt%. All the catalyst samples were characterized by surface area, low temperature oxygen chemisorption, x-ray diffraction (XRD), and temperature programmed reduction methods. Characterization results show that Mo is well dispersed on MCM-41 up to 10 wt%. The catalytic activities were evaluated for thiophene hydrodesulphurization (HDS), cyclohexene hydrogenation (HYD), and furan hydrodeoxygenation (HDO). All three catalytic functionalities vary in a similar manner to that of oxygen chemisorption as a function of Mo loading, indicating that there is a correlation between oxygen uptake and catalytic sites. The activities of these catalysts were compared with γ-Al₂O₃- and amorphous SiO₂-supported catalysts. It was found that MCM-41-supported Mo catalysts displayed superior activities.     

Properties of brush plated CdxZn1−xTe thin films

Cd_xZn_1−xTe (0  x  0.5) thin films were deposited for the first time by the brush plating technique using cadmium sulphate, zinc sulphate and tellurium dioxide precursors. The deposition current density was maintained at 100 mA cm⁻². X-ray diffraction studies indicated the formation of cubic phase with (1 1 1), (2 2 0), (3 1 1) orientations. From optical absorption measurements the band gaps of the films are found to be direct. AFM studies indicate a surface roughness around 54 Å. Density of the films of different composition has been estimated. Laser Raman studies indicated CdTe like LO and TO phonons.     

A Study on Process Parameters of Ultrasonic Assisted Micro EDM Based on Taguchi Method

Experimental investigation of ultrasonic assisted micro electro discharge machining was performed by introducing ultrasonic vibration to workpiece. The Taguchi experimental design has been applied to investigate the optimal combinations of process parameters to maximize the material removal rate and minimize the tool wear. Analysis of variance (ANOVA) was performed and signal-to-noise (S/N) ratio was determined to know the level of importance of the machining parameters. Based on ANOVA, ultrasonic vibration at 60% of the peak power with capacitance of 3300 PF was found to be significant for best MRR. The machining time plays a significant role in the tool wear. The results were confirmed experimentally at 95% confidence interval.     

Fabrication and testing of natural fibre composites: Vakka, sisal, bamboo and banana

A study has been carried out to investigate the tensile, flexural and dielectric properties of composites made by reinforcing vakka as a new natural fibre into a polyester resin matrix. The fibres extracted by retting and manual processes have been used to fabricate the composites. These composites are tested for tensile, flexural and dielectric properties and compared with those of established composites like sisal, bamboo and banana made under the same laboratory conditions. The composites are fabricated up to a maximum volume fraction of fibre of 0.37 in the case of tensile testing, and 0.39 for flexural and dielectric testing. It has been observed that the tensile properties increase with respect to volume fraction of fibre for vakka fibre composite and are also more than those of sisal and banana composites and comparable to those of bamboo composites. The flexural strength of vakka fibre composite is more than that of banana composite and is closer to sisal fibre composite with respect to the volume fraction of fibre, where as the flexural modulus is much higher than those of banana and sisal fibre composites and also very much closer to bamboo fibre composites. The dielectric strength of vakka fibre composite increases with increase in volume fraction of fibre in the composite unlike the case of sisal, bamboo and banana composites. The dielectric strength being a unique feature of vakka fibre composite, can be suggested for electrical insulation applications.     

Photoelectrochemical properties of brush plated Cd x Zn1−x Se films

Cd _x Zn_1−x Se films(0 ≤ x ≤ 1) were deposited for the first time by the brushplating technique at room temperature from an aqueous bath containing zincsulphate, cadmium sulphate and selenium oxide. The deposition current densitywas varied in the range of 50–250 mA cm⁻². The as deposited films exhibitedcubic structure. Composition of the films was estimated by EDAX studies. XPSstudies indicated the binding energies corresponding to Zn(2p_3/2), Cd(3d_5/2 and 3d_3/2) and Se(3d_5/2 and 3d_3/2). Optical band gap of the films varied from 1.72 to 2.70 eV as the composition varied from CdSe to ZnSe side. Atomic forcestudies indicated grain size in the range of 20–150 nm. Photoelectrochemical cells were made with polysulphide as the redox electrolyte. The output was maximum for the photoelectrodes of composition Cd_0.9Zn_0.1Se.     

Induced crystallization and physical properties of Li2O–CaF2–P2O5:TiO2 glass system: Part I. Characterization, spectroscopic and elastic properties

Li₂O–CaF₂–P₂O₅ glasses mixed with different concentrations of TiO₂ (ranging from 0 to 0.8 mol%) were crystallized at 500 °C. The samples are characterized by X-ray diffraction, scanning electron microscopy and differential thermal analysis techniques. Spectroscopic properties (IR and Raman) and elastic properties (viz., Young's modulus E, shear modulus G and micro-hardness H) at room temperature are studied. The X-ray diffraction and the scanning electron microscopic studies revealed the presence of lithium phosphate, lithium titanium phosphate and titanium phosphate crystal phases. The differential thermal analysis traces of these samples exhibit three crystalline temperatures. The IR and Raman spectra of these samples have exhibited bands due to TiO₄ and TiO₆ structural units in addition to the conventional bands due to various phosphate structural groups. The analysis of these results indicated that the sample crystallized with 0.6 mol% of TiO₂ possesses the highest density, high mechanical strength and more compact network.     

Designing fault-tolerant real-time computer systems with diversified bus architecture for nuclear power plants

Fault-tolerant real-time computer (FT-RTC) systems are widely used to perform safe operation of nuclear power plants (NPP) and safe shutdown in the event of any untoward situation. Design requirements for such systems need high reliability, availability, computational ability for measurement via sensors, control action via actuators, data communication and human interface via keyboard or display. All these attributes of FT-RTC systems are required to be implemented using best known methods such as redundant system design using diversified bus architecture to avoid common cause failure, fail-safe design to avoid unsafe failure and diagnostic features to validate system operation. In this context, the system designer must select efficient as well as highly reliable diversified bus architecture in order to realize fault-tolerant system design. This paper presents a comparative study between CompactPCI bus and Versa Module Eurocard (VME) bus architecture for designing FT-RTC systems with switch over logic system (SOLS) for NPP.     

Reduced VDAC1, Maintained Mitochondrial Dynamics and Enhanced Mitochondrial Biogenesis in a Transgenic Tau Mouse Model of Alzheimer’s Disease

Alzheimer’s disease (AD) is one of the most common forms of neurodegeneration, defined by reduced cognitive function, which is caused by the gradual death of neurons in the brain. Recent studies have shown an age-dependent rise in the levels of voltage-dependent anion channel 1 (VDAC1) in AD. In addition, we discovered an aberrant interaction between VDAC1 and P-TAU in the brains of AD patients, which led to abnormalities in the structural and functional integrity of the mitochondria. The purpose of our study is to understand the protective effects of reduced VDAC1 against impaired mitochondrial dynamics and defective mitochondrial biogenesis in transgenic TAU mice. Recently, we crossed heterozygote VDAC1 knockout (VDAC1^+/−) mice with transgenic TAU mice to obtain double-mutant VDAC1^+/−/TAU mice. Our goal was to evaluate whether a partial decrease in VDAC1 lessens the amount of mitochondrial toxicity in transgenic Tau (P301L) mice. We found that mitochondrial fission proteins were significantly reduced, and mitochondrial fusion and biogenesis proteins were increased in double-mutant mice compared to TAU mice. On the basis of these discoveries, the current work may have significance for the development of reduced-VDAC1-based treatments for individuals suffering from AD as well as other tauopathies.