Consolidation of advanced composites having volatile generation

Processing polyimide-based thermosetting matrix composites is complicated because of gaseous volatiles produced during the polymerization and crosslinking reactions. This process involves complex interactions between part geometry, temperature and force cycles, and matrix/fiber properties. A simple model for the consolidation process that treats these composites as a three-phase system consisting of fiber, resin, and volatile has been developed. This model has been applied to compression molding process for constant thickness laminates and the predictions agree well with experiments. Further extension to handle three-dimensional parts and the required numerical techniques have also been developed.     

Development of a method employing reversed‐phase thin‐layer chromatography for establishing milk fat purity with respect to adulteration with vegetable oils

A systematic study was conducted using reversed‐phase thin‐layer chromatography wherein unsaponifiable matter of samples namely, pure cow and buffalo milk fats, vegetable oils (groundnut oil, soya bean oil and sunflower oil) and milk fats adulterated with vegetable oils (≥1%) were run along with the reference standards using two new solvent systems to detect adulteration in milk fat. The results of the study revealed that adulteration at even a 1% level could easily be detected using this rapid, reliable and reproducible method based on the presence of β‐sitosterol as a marker and some additional spots ascribable to their occurrence in vegetable oils only.     

Chemopreventive Effect of Different Ratios of Fish Oil and Corn Oil in Experimental Colon Carcinogenesis

n-3 Polyunsaturated fatty acids (PUFA) have a chemopreventive effect while n-6 PUFA promote carcinogenesis. The effect of these essential fatty acids may be related to oxidative stress. Therefore, the study was designed to evaluate the effect of different ratios of fish oil (FO) and corn oil (CO) in the prevention of colon cancer. Male Wistar rats were divided into control, dimethylhydrazine dihydrochloride (DMH) treated, FO + CO (1:1) and FO + CO (2.5:1). All the groups, except the control received a weekly injection of DMH for 4 weeks. The animals were sacrificed either 48 h later (initiation phase) or kept for 16 weeks (post initiation phase). DMH treatment in the initiation phase animals showed mild to moderate inflammation, decreased ROS and TrxR activity, increased antioxidants, apoptosis and ACF multiplicity. The post initiation study showed severe inflammation with hyperplasia, increased ACF multiplicity and ROS levels, a decrease in antioxidants and apoptosis. The FO + CO (1:1) treated animals showed severe inflammation, a decrease in ROS, an increase in antioxidants and apoptosis in the initiation phase. FO + CO (1:1) in the post initiation phase and FO + CO (2.5:1) in the initiation showed mild inflammation, increased ROS, apoptosis and decreased antioxidants. There was a decrease in ACF multiplicity and ROS levels, increased antioxidants and apoptosis in the post initiation phase study. The present study suggests that FO has a dose- and time-dependent chemopreventive effect in colon cancer mediated through oxidative stress and apoptosis.     

Friction stir scribe welding technique for dissimilar joining of aluminium and galvanised steel

Friction stir scribe technology, a derivative of friction stir welding, was applied for the dissimilar lap welding of an aluminium alloy and galvanised mild steel sheets. During the process, the rotating tool with a cobalt steel scribe first penetrated the top material – aluminium – and then the scribe cuts the bottom material – steel. The steel was displaced into the upper material to produce a characteristic hook feature. Lap welds were shear tested, and their fracture paths were studied. Welding parameters affected the welding features, including hook height, which turned out to be highly related to fracture position. Therefore, in this paper, the relationships among welding parameters, hook height, joint strength and fracture position are presented. In addition, the influence of zinc coating on joint strength was also studied.     

A biopolymer-based composite hydrogel for rhodamine 6G dye removal: its synthesis,adsorption isotherms and kinetics

The present study reports the preparation and application of a novel biopolymer-based composite hydrogel (BCH) for removal of synthetic dye rhodamine 6G (Rh6G). BCH was prepared from biopolymer chitosan and acrylic acid monomer, in the presence of initiator (K₂S₂O₈) and cross-linker thiourea using microwave irradiation. Synthesized chitosan-based composite hydrogel was characterized by using analytical techniques including Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), derivative thermogravimetric analysis (DTA) and differential thermal analysis (DTG). The stability of the adsorbent was demonstrated from its water uptake capacity. The dynamics of water sorption study showed the Fickian behavior. The investigations were continued to assess the adsorption potential of BCH for removal of Rh6G from aqueous solution. The effect of process parameters affecting the adsorption of rhodamine 6G (Rh6G), such as adsorbent dose, initial concentration of pollutant, contact time and pH of the solution was evaluated. Removal efficiency of chitosan-based composite hydrogel (BCH) was found to be 87.31% at pH 7 for BCH dose of 1 g/L after 8 h. The obtained data were fitted to adsorption isotherms and kinetics models. The adsorption equilibrium isotherm and kinetics studies indicated that the pseudo-second-order model and the Freundlich model well described the adsorption equilibrium of Rh6G on BCH.     

Role of Direct Reduced Iron Fines in Nitrogen Removal from Electric Arc Furnace Steel

Electric arc furnace steel contains about 70‐120 ppm nitrogen. There is no suitable method for nitrogen removal from electric arc furnace steel up to the level desired for good quality bars and flat rolled products (30 ppm max). The existing process based on vacuum degassing can remove only up to 20% of nitrogen in steel. In the present study DRI fines have been injected into a steel bath which can drift out nitrogen in steel through production of fine CO bubbles in‐situ on reaction with residual FeO in DRI fines and C in bath. For high and medium carbon steel, nitrogen got reduced to 30 ppm and 60 ppm respectively where initial nitrogen was 150 – 200 ppm in steel. Nitrogen removal also depends upon bath depth and addition level of DRI.     

Engineering polypyrrole nanotubes by 100 MeV Si9 + ion beam irradiation: Enhancement of antioxidant activity

In this work, the effect of 100 MeV Si^9 + ion beam with four different fluences on antioxidant and structural properties of polypyrrole nanotubes has been investigated. Polypyrrole nanotubes have been synthesized by reactive self degrade template method. Fragmentation of the polypyrrole nanotubes at higher fluence is revealed from the high resolution transmission electron micrograph (HRTEM) and X-ray diffraction (XRD) results. The decrease in characteristics band of polypyrrole in Fourier transmission of infrared spectra (FTIR) spectra suggests the main chain scission of polypyrrole during irradiation. The free radical scavenging activity of pristine and irradiated samples are evaluated by using α, α-diphenyl-β-picrylhydrazyl (DPPH) assay. The decline of the UV–visible absorbance at 516 nm suggests the neutralization of DPPH free radicals through the reaction with polypyrrole. Significant increase in antioxidant activity of polypyrrole nanotubes is observed with increase in ion fluence.     

Admissibility of a test procedure based on preliminary test of significance for life data

Necessary and sufficient condition for admissibility of a test procedure based on preliminary test of significance for life data has been obtained.