Structural evolution in nanocrystalline Fe-10 Wt pct Cr alloy powder produced by mechanical alloying—An atomic-force microscopy study

A mechanical alloying (MA) method was used to synthesize Fe-10 wt pct Cr alloy powder. The formation of an Fe-Cr solid solution during milling was studied using atomic-force microscopy (AFM), with the help of an atomic-force microscope in acoustic AC (AAC) mode. The AFM amplitude images indicated that the interlamellar spacing in the structure decreased with an increase in the milling time, and finally gave way to a nonlamellar structure. For structures obtained by milling up to 40 hours, AFM phase-contrast images showed regions of inhomogeneity. Surface-topography images of the granular milled powder showed that the powder surfaces were not smooth, but consisted of a typical hills-and-valley structure. The mean height of the hills decreased with an increase in the milling time. Powders milled up to 20 hours showed a structure that contained grains and subgrains. However, as the interlamellar spacing in granules was reduced, the clear definition of the grains disappeared. Only subgrains were observed in powders milled for time intervals ≥40 hours. With the milling time ≥40 hours, the subgrains not only got more and more refined, they also got elongated in the direction of granular flow. The subgrains in the powder milled for 100 hours were found to have an aspect ratio of 2.5 to 3.0; their smaller dimensions varied from 5 to 30 nm.     

Accidental death and disability in India: A stocktaking

Studies on accidental death and disability are not common in the low income countries and accurate data are difficult to obtain. In this paper data from official sources and spot studies of small populations in India have been used to extrapolate for the whole country to get an estimate of the magnitude of the problem. The results indicate that injuries in India may be as much of a health problem for individuals 5 yr old and above as in the high income countries.     

Oxygen deficiency dependence of transition temperature in (Sm, Er) Ba2Cu3O7−δ superconductors

We have investigated the effects of oxygen deficiency (δ) on the transition temperature (T _c) of (Sm, Er)Ba₂Cu₃O₇₋ δ superconductors by incorporating the effects of the two dimensional (2D) acoustic phonons and plasmons in the framework of strong coupling theory. The proposed approach for yttrium cuprates properly takes care of the double CuO₂ plane in a unit cell and has been found earlier to be successful in describing the pairing mechanism as well as the variation ofT _c withδ in Y Ba₂Cu₃O₇₋ δ system. The coupling strength (λ), the screening parameter (μ*) and the two dimensional acoustic phonon (plasmon) energyħω ₋(ω₊) as a function of oxygen deficiency is worked out. Finally, the transition temperature is evaluated and is found to be consistent with the earlier experimental data on yttrium cuprates. Thus, coupled phonon-plasmon mechanism is adequate to understand the nature of pairing mechanism and oxygen deficiency dependence of transition temperature in 90 K (Sm, Er)Ba₂Cu₃O₇₋ δ superconductors.     

Ionic conductivity and Raman investigations on the phase transformations of Na4P2O7

The ionic conductivity and thermo-Raman spectra of anhydrous sodium pyrophosphate Na₄P₂O₇ were measured dynamically in the temperature range from 25 to 600 °C with a heating rate of 2 °C min⁻¹ to understand the structural evolution and phase transformation involved. The DSC thermogram was also measured in the same thermal process for the phase transformation investigation. The spectral variations observed in the thermo-Raman investigation indicated the transformation of Na₄P₂O₇ from low temperature phase () to high temperature phase () proceeded through pre-transitional region from 75 to 410 °C before the major orientational disorder at 420 °C and minor structural modifications at 511, 540 and 560 °C. The activation energies and enthalpies of the proposed phase transformations were determined. The possible mechanism for temperature dependent conductivity in Na₄P₂O₇ was discussed with the available data.     

Integration of electrokinetic-based multidimensional separation/concentration platform with electrospray ionization-Fourier transform ion cyclotron resonance-mass spectrometry for proteome analysis of Shewanella oneidensis

This work focuses on the development of a multidimensional electrokinetic-based separation/concentration platform coupled with electrospray ionization-Fourier transform ion cyclotron resonance mass spectrometry (ESI-FTICR-MS) for achieving the high resolution and ultrasensitive analysis of complex protein/peptide mixtures. A microdialysis junction is employed as the interface for on-line combination of capillary isoelectric focusing (CIEF) with transient capillary isotachophoresis/zone electrophoresis (CITP/CZE) in an integrated platform. Besides the excellent resolving power afforded by both CIEF and CZE separations, the electrokinetic focusing/stacking effects of CIEF and CITP greatly enhance the dynamic range and detection sensitivity of MS for protein identification. The constructed multidimensional separation/concentration platform is demonstrated for the analysis of Shewanella oneidensis proteome, which has considerable implications toward the bioremediation of environmental pollutants. The electrokinetic-based platform offers the overall peak capacity comparable to those obtained using multidimensional chromatography systems, but with a much shorter run time and no need for column regeneration. Most importantly, a total of 1174 unique proteins, corresponding to 26.5% proteome coverage, are identified from the cytosolic fraction of S. oneidensis, while requiring <500 ng of proteolytic digest loaded in the CIEF capillary. The ultrasensitive capabilities of electrokinetic-based proteome approach are attributed to the concentration effect in CIEF, the electrokinetic stacking of CITP, the nanoscale peak volume in CZE, the "accurate mass tag" strategy for protein/peptide identification, and the high-sensitivity, high-resolution, and high-mass measurement accuracy of FTICR-MS.     

Synthesis of carbon nanotubes by arc discharge in open air

In this work Carbon nanotubes have been synthesized by arc discharge in open air. A TIG welding ac/dc inverter was used as the power source for arc discharge. During each run of the arc discharge based synthesis, the anode was a low purity (approximately 85% C by weight) graphite rod. The effect of varying the atmosphere on the yield of soot of the carbon nanotube containing carbon soot has been studied. Various soots were produced, purified by oxidation and characterized to confirm formation of carbon nanotubes and their relative quality, using transmission electron microscopy, Raman spectroscopy, and XRD. It was found that the yield of soot formed on the cathode is higher when synthesis is carried out in open air than when carried out in a flowing argon atmosphere. When synthesized in open air, using a 7.2-mm-diameter graphite rod as anode, the yield of soot was around 50% by weight of the graphite consumed. Current and voltage for arcing were at identical starting values in all the experiments. This modified method does not require a controlled atmosphere as in the case of a conventional arc discharge method of synthesis and hence the cost of production may be reduced.     

Burn properties of fabrics and garments worn in India

A full-scale human form dummy was designed for studying the burning of common dress assemblies (i.e. combination of garments) worn in India. The dummy was made in eight parts; each made of a steel shell filled with water so as to replicate properties of skin-tissue combination. Four thermocouples were fixed on the dummy for measuring torso, neck and face temperatures. The dummy was clothed separately in three women's dress assemblies (saree, salwar-khameez and nightgown) and men's dress assemblies (kurta-pyjama, shirt-pant and lungi), and ignited at the feet by a flat flame. The tests showed that loose fitting garments burnt easily. Once completely burnt, all dress assemblies result in third degree burns over most of the body. The burning process of synthetics is radically different from cottons or cotton-polyester blends. However, flame duration and temperatures produced on the skin are not radically different, suggesting that on the whole synthetics are no worse than cotton garments. Thick garments, such as, jeans and khadi, do not ignite easily and are inherently safer than similar garments made of light fabric. The studies show that results of standard flammability tests using single fabric strips do not correlate with the burning observed in garments as part of a dress where multilayering is common. Standards/codes for fire safety of garments and garment-dress assembly combinations need to be evolved to adequately address their fire safety.     

Analysis of SC networks using continuous-time four-port equivalents

A method of deriving a continuous-time equivalent of an SC network is considered. This method is based on LDI transformation.