Small-angle neutron scattering investigations on sintering behavior of combustion synthesized La0.8Sr0.2CrO3

Pore morphology of La0.8Sr0.2CrO3 (LSC) powder compacts, sintered between 1200 degrees C and 1450 degrees C for a fixed time, has been characterized by small-angle neutron scattering (SANS) in the scattering wave vector 'q' range, 0.003-0.17 nm(-1) of a double crystal based instrument. Scattering profile of green compact exhibits fractal scaling at two regions of 'q' with magnitudes of fractal dimensionality 1.8 and 2.36. Scattering profiles of sintered pellets have been modeled assuming a random distribution of near spherical pores in the solid matrix. Estimated pore size distributions of sintered pellets indicate decrease in pore volume has taken place by progressive elimination of smallest pores and growth of relatively larger pores with increasing sintering temperature. SANS results are supplemented by light scattering measurement and TEM image of powder and SEM image of the fracture surface of sintered pellet.     

Measurement of yarn hairiness by digital image processing

In their effort to measure yarn hairiness at high speed, the commercially available yarn hairiness testers resort to indirect techniques. Measurement of true length of all hairs can only be done by observing the yarn under a microscope and obtaining a trace of hairs. An attempt was made in this work to automate this task using digital image processing. The challenges were two-fold. The first was development of an algorithm capable of analysing yarn images taken under varying lighting conditions and varying yarn positions. The second was determination of minimum requirement of the image-capturing instrument. Both of these have been reported in this work. A new hairiness index has been proposed and suggested as a better indicator of hairiness than the traditional definition.     

Performance metrics in a hybrid MPI–OpenMP based molecular dynamics simulation with short-range interactions

We discuss the computational bottlenecks in molecular dynamics (MD) and describe the challenges in parallelizing the computation-intensive tasks. We present a hybrid algorithm using MPI (Message Passing Interface) with OpenMP threads for parallelizing a generalized MD computation scheme for systems with short range interatomic interactions. The algorithm is discussed in the context of nano-indentation of Chromium films with carbon indenters using the Embedded Atom Method potential for Cr–Cr interaction and the Morse potential for Cr–C interactions. We study the performance of our algorithm for a range of MPI–thread combinations and find the performance to depend strongly on the computational task and load sharing in the multi-core processor. The algorithm scaled poorly with MPI and our hybrid schemes were observed to outperform the pure message passing scheme, despite utilizing the same number of processors or cores in the cluster. Speed-up achieved by our algorithm compared favorably with that achieved by standard MD packages.     

Nanofluidic preconcentration and detection of nanoparticles

The fast detection and characterization of nanoparticles, such as viruses or environmental pollutants, are important in fields ranging from biosensing to quality control. However, most existing techniques have practical throughput limitations, which significantly limit their applicability to low analyte concentrations. Here, we present an integrated nanofluidic scheme for preconcentration and subsequent detection of nanoparticle samples within a continuous flow-through system. Using a Brownian ratchet mechanism, we increase the nanoparticle concentration ～27-fold. Single nanoparticles are subsequently detected and characterized by optical heterodyne interferometry. A wide range of potential applications can be foreseen, including real-time analysis of clinically relevant virus samples and contamination control of processing fluids used in the semiconductor industry.     

In vitro antioxidant study of vegetable oils containing conjugated linolenic acid isomers

The study aimed to evaluate the antioxidant activity (in vitro) of vegetable oils containing conjugated linolenic acid (CLnA) isomers such as α-eleostearic and punicic acid and also to evaluate the comparative effectiveness of these vegetable oils due to presence of cis–trans isomers in variable amount. Different in vitro methods were used to evaluate the free radical scavenging activity, hydroxyl radical scavenging activity, metal chelating activity and reducing activity of oils at different concentrations of CLnA isomers such as 125, 250 and 375 μg/mL. Inhibition on lipid peroxidation was evaluated by measuring thiobarbituric acid responsive substance (TBARS) and conjugated diene formation at 125 and 250 μg/mL concentrations of CLnA. Both the oils showed potent free radical scavenging activity at 375 μg/mL concentration. In contrary, these oils showed higher hydroxyl radical scavenging, metal chelation and reducing activity at lower concentration i.e. 125 μg/mL. TBARS formation and conjugated diene formation was lower i.e. inhibition of lipid peroxidation was maximum at 125 μg/mL of both CLnA isomers. Overall, both the oils showed better antioxidant activity at lower concentration due to better oxidative stability and bitter gourd oil showed more prominent antioxidant activity than snake gourd oil due to presence of higher trans content.     

Initial biocompatibility and enhanced osteoblast response of Si doping in a porous BCP bone graft substitute

Granular shape biphasic calcium phosphate (BCP) bone grafts with and without doping of silicon cations were evaluated in regards to biocompatibility and MG-63 cellular response. To do this we studied Cellular cytotoxicity, cellular adhesion and spreading behavior and cellular differentiation with alizarin red S staining. Gene expression in MG-63 cells on the implanted bone substitutes was also examined at different time points using RT-PCR. In comparison, the Si-doped BCP granule showed more cellular viability than the BCP granule without doping in MTT assay. Moreover, cell proliferation was much higher when Si doping was employed. The cells grown on the silicon-doped BCP substitutes had more active filopodial growth with cytoplasmic webbing that proceeded to the flattening stage, which was indicative of well cellular adhesion. When these cells were exposed to Si-doped BCP granules for 14 days, well differentiated MG-63 cells were observed. Osteonectin and osteopontin genes were highly expressed in the late stage of differentiation (14 days), whereas collagen type I mRNA were found to be highly expressed during the early stage (day 3). These combined results of this study demonstrate that silicon-doped BCP enhanced osteoblast attachment/spreading, proliferation, differentiation and gene expression.     

Microstructural characterization of the V-doped nano-titania

A new modified sol–gel method has been developed to synthesize undoped nano-titania and vanadium-doped nano-titania. XRD data and the Raman spectra indicate that even after 10 mol% doping of vanadium in the crystal lattice sites of TiO₂, the samples are phase pure with the anatase structure. The average particle size of these materials is about 11.5 nm, as calculated from the XRD peak broadening and TEM. Small angle X-ray scattering (SAXS) was also used for the determination of the particle size of these vanadium-doped titania samples. The SAXS parameters were determined assuming near spherical particle shape. The SAXS results were in agreement with the particle size as obtained by TEM. A negligible variation in the particle size was observed as a function of doping percentage upto a limiting value of 5 mol% doping of vanadium in the TiO₂ lattice. The results of the SAXS are in good agreement with the XRD and the TEM results.     

Influence of cooling field on the magnetic properties of Ni/NiO nanostructure

Nanoparticles of Ni/NiO structure were prepared by sol–gel route followed by the annealing in presence of controlled oxygen and argon gas mixture. When the sample was cooled down to 5 K from room temperature in a static magnetic field, a systematic shift of the magnetic hysteresis loop was observed. The shift was absent when the sample was cooled in zero field. For cooling the sample in field-cooled mode a small horizontal shift was noticed along with a moderate vertical shift of the hysteresis loop at the saturation of magnetization, which indicates the typical manifestation of exchange bias effect. The horizontal shift increases with decreasing particle size retaining almost unchanged relative vertical shift, where vertical shift is found to be uncorrelated with the horizontal shift. The exchange bias like effect in the Ni/NiO nanostructure is suggested at the Ni/NiO interface, where Ni is ferromagnetic and NiO is in the disordered magnetic state.