Rhodium nanoparticles intercalated into montmorillonite for hydrogenation of aromatic compounds in the presence of thiophene

Rhodium metal nanoparticles intercalated into montmorillonite (Rh-MMT) have been prepared and used for the hydrogenation of benzene and other aromatic compounds. Rh-MMT was characterized by PXRD, TEM and ICP-AES. The crystallite size of the rhodium particles was 6.9 nm using PXRD and the particle size by TEM was 25.6 ± 2.5 nm. Benzene hydrogenation was carried out at different substrate/catalyst mass ratios, temperature and pressure to optimize the reaction conditions. The benzene is completely hydrogenated with 100% selectivity to cyclohexane at 453 K and 6.2 MPa. The catalyst was poisoned by thiophene, and benzene hydrogenation decreased with increasing thiophene concentration. Hydrogenation of toluene, o,m,p-xylenes, naphthalene and anthracene were also carried out at the optimized reaction conditions.     

Optimization of Oxidation Temperature for Commercially Pure Titanium to Achieve Improved Corrosion Resistance

Thermal oxidation of commercially pure titanium (cp-Ti) was carried out at different temperatures, ranging from 200 to 900 °C to achieve optimum corrosion resistance of the thermally treated surface in simulated body fluid. Scanning electron microscopy, x-ray diffraction, Raman spectroscopy and electrochemical impedance spectroscopy techniques were used to characterize the oxides and assess their protective properties exposed in the test electrolyte. Maximum resistance toward corrosion was observed for samples oxidized at 500 °C. This was attributed to the formation of a composite layer of oxides at this temperature comprising Ti₂O₃ (titanium sesquioxide), anatase and rutile phases of TiO₂ on the surface of cp-Ti. Formation of an intact and pore-free oxide-substrate interface also improved its corrosion resistance.     

Antimicrobial properties of uncapped silver nanoparticles synthesized by DC arc thermal plasma technique

We, herein, report the antimicrobial properties of uncapped silver nanoparticles for a Gram positive model organism, Bacillus subtilis. Uncapped silver nanoparticles have been prepared using less-explored DC arc thermal plasma technique by considering its large scale generation capability. It is observed that the resultant nanoparticles show size as well as optical property dependent antimicrobial effect.     

Antibacterial activities of polyethylene glycol, tween 80 and sodium dodecyl sulphate coated silver nanoparticles in normal and multi-drug resistant bacteria

Antibacterial activity of silver nanoparticles coated with different functionalizing agents i.e., polyethylene glycol, tween 80 and sodium dodecyl sulphate were evaluated on both normal and multi-drug resistant strains of bacteria. Under the same reaction conditions, these functionalizing agents were added separately to coat silver nanoparticles. Among these, polyethylene glycol coated nanoparticles were most effective in killing all the bacterial strains which includes Escherichia coli DH5a, Bacillus subtilis, Micrococcus luteus, Staphylococcus aureus and multi-drug resistant clinical isolates of Shigella spp. (flexneri, boydii, sohnea) and Vibrio cholerae. The minimum inhibitory concentration of polyethylene glycol coated silver nanoparticles was also less compared to the other two sets of nanoparticles. Consistence with that polyethylene glycol coated nanoparticles produced more intracellular reactive oxygen species in bacteria. Moreover, when human cell lines MCF7 and Chang Liver were incubated in presence of these nanoparticles for 18 h with same concentrations as used for bacteria, no toxicity was observed. But significant increase in cell killing was observed with longer incubation time. Thus our present investigation implicates the potential therapeutic use of silver nanoparticles as antibacterial agent particularly the polyethylene glycol coated one.     

Novel down link rain fade mitigation technique for Ka‐band multibeam systems

Rain fades at Ka‐Band degrades the link quality and performance significantly. Several rain fade mitigation techniques for Ka‐band satellite systems are being investigated to improve the channel capacity. Methods such as power control and adaptive waveform techniques have been proposed for use in the uplink as they are capable of straightforward implementation. A novel down link power control technique for multi‐beam Ka‐band system has been proposed in this paper. It is based on the use of multi‐port amplifier, which is commonly used for dynamic power sharing of the beams depending upon the traffic. Payload architecture for multi‐beam coverage using multi‐port amplifiers has been designed for the proposed technique. The simulation results to compensate for the rain fade attenuation of one beam by sharing the unused power from other beams have been presented Copyright © 2006 John Wiley & Sons, Ltd.     

A binomially distributed photonic bandgap structure (PBGS) and its application to bandpass filter

Conventional hole‐patterned photonic bandgap structures (PBGSs) yield distinct and wide stopband, but suffer from a significant ripples in the passband beyond the optimized filling factor (FF) of 0.25. Binomial distribution in PBGSs can yield improved performance beyond this value. The optimum FF of binomially distributed PBGSs has been ivestigated at multifrequencies in the X‐band, namely, at 9, 10.5, and 12 GHz. It can be seen that 0.4 may be considered as the optimum FF for binomially distributed PBGSs at different frequencies within X‐band operations. Finally, binomially PBGSs with this optimium FF are applied in a bandpass filter (BPF) for suppresing the intrinsic spurious harmonics of a BPF. The various experimental investigations reveal that the variation in number of PBG elements and their locations affect the performance of harmonic suppression. Binomially distributed PBGSs are found to be potential candidate to suppress the harmonic signal and to improve the return‐ and insertion‐loss bandwidths. © 2006 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2006.     

Planar electromagnetic bandgap structures

This article presents various novel and conventional planar electromagnetic bandgap (EBG)‐assisted transmission lines. Both microstrip lines and coplanar waveguides (CPWs) are designed with circular, rectangular, annular, plus‐sign and fractal‐patterned EBGs and dumbbell‐shaped defected ground structure (DGS). The dispersion characteristics and the slow‐wave factors of the design are investigated. © 2006 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2006.     

Grafted hydroxypropyl guargum: Development, characterization and application as flocculating agent

Synthesis of hydroxypropyl guargum-g-polyacrylamide was carried out by ceric ion induced redox polymerization technique at 28±1°C. The graft copolymer was characterized by IR and thermal analysis. The flocculation performance of graft copolymer was tested in 1 wt% coal suspension.     

Effect of Loading Rate Upon Conventional Ceramic Microindentation Hardness

The world standards for conventional ceramic hardness have varying requirements for control of loading rate during the indentation cycle. A literature review suggests that loading rate may affect measured hardness in some instances. In view of the uncertainty over this issue, new experiments over a range of indentation loading rates were performed on a steel, sintered silicon carbide, and an aluminum oxynitride. There was negligible effect upon Vickers hardness when loading rate was varied by almost four orders of magnitude from approximately 0.03 N/s to 10 N/s.     

Millimeter wave attenuation in relation to rain rate distribution over a tropical station

Rain, perhaps, is the worst offender for utilising Millimeterwaves in practice. This paper describes the rain rate distribution from which millimeterwave attenuation distribution have been attempted. Results reveal that in our location (Calcutta: lat 23°N long 88.5°E) the rain rate distribution fits well with normal distribution. The cumulative distribution of rain rate also prompted the present authors to find out rain attenuation cumulative distribution for both terrestrial and earth-space paths in millimeterwave band.