Effect of surface sterilization, fumigation and gamma irradiation on the microflora and germination of barley seeds.

Sodium hypochlorite (NaOCl) and mercuric chloride (HgCl2) surface sterilization, methyl bromide and propylene oxide fumigation and gamma irradiation treatments were compared for their effectiveness in killing microorganisms on or within barley seeds. Surface sterilization with 12.5, 25 or 50% (v/v) NaOCl for 5, 15 or 30 min, decreased Fusarium spp., Epicoccum purpurascens, and Bacillus spp. but did not kill Alternaria alternata. However, surface sterilization with 0.1 or 0.2% (w/v) HgCl2 for 3 min significantly decreased A. alternata, Fusarium spp. and E. purpurascens but Bacillus spp. were only killed by 0.3% (w/v) HgCl2 used for 10 min, which also decreased seed germination. Aspergillus flavus inoculated onto barley seeds as spores, was completely killed by surface sterilization with NaOCl but not with HgCl2, while Fusarium culmorum was killed by both NaOCl and HgCl2 treatments. Fumigation with methyl bromide yielding a concentration-time product of 3000 mg h l-1 or with propylene oxide giving a concentration-time product of 2400 mg h l-1 eliminated all filamentous fungi but Bacillus spp. and yeasts survived, and both treatments adversely affected seed germination. Gamma irradiation at a dose of 4 kGy eliminated most Alternaria, Fusarium and Epicoccum spp. but a dose of 12 kGy was required to kill Bacillus spp., yeasts and Aureobasidium pullulans. Germination was improved slightly up to a dose of 8 kGy but gradually decreased with increase in dosage to 15 kGy of gamma irradiation.     

Electron microscopic observations of Bi and Tl bearing cuprate high temperature superconductors

The second generation of high temperature superconductors typified by Bi₂Sr₂Ca _n−1Cu _n O_2n+4 and Tl₂Ba₂Ca _n−1Cu _n O_2n+4 exhibits curious structural properties which have direct relevance to the superconducting behaviour particularly transition temperature (T _c ). The present paper reports on investigations of structural properties at microlevel in Bi-bearing HTCS. We have found curious structural characteristics which manifests itself in the form of transformation froma _p ×a _p ×c to (2)^1/2 a _p ×(2)^1/2 a _p ×c through the loss of calcium atoms and the formation of five-fold modulated phase alongb through the loss of Ca and Sr atoms. We have also found the evidence of high periodicities (n=4) Bi₂Sr₂Ca₃Cu₄O₁₂. The microstructural characteristics of HTCS showing the higherT _c (R=0) ∼ 120 K exhibits unusual characteristics.     

Studies on EVA‐Based Wax Fuel for Launch Vehicle Applications

A fuel for the hybrid rocket system was developed. The attempts made to improve the mechanical properties of wax by adding EVA (ethylene vinyl acetate) are illustrated. It was observed that the mechanical properties obtained by adding EVA to wax were dependent on the process of curing the fuel specimen. A proprietary method of curing the fuel specimen was established. The percentage elongation obtained with 20 % EVA and 80 % of wax was around 17 %, which was much higher than the values obtained with pure wax (4 %). It was observed from the study that the higher the percentage of EVA content in wax was, the better the mechanical properties were. Regression rate studies with EVA and wax combination were carried out. It was observed that the regression rate decreased upon addition of EVA in wax. This reduction was compensated by using a bluff body at the head end. The regression rate obtained with 20 % EVA and 80 % wax even with the use of bluff body is lower than that obtained with pure wax, but is around 3.5 times the regression rate obtained with polymeric fuels.     

Influence of copper substitution on magnetic and electrical properties of MgCuZn ferrite prepared by microwave sintering method

Polycrystalline MgCuZn ferrites with chemical formula Mg_0.50-xCu_xZn_0.50Fe₂O₄ (x = 0.00, 0.05, 0.10, 0.15, 0.20, 0.25 and 0.30) were prepared by microwave sintering method. These powders were calcined, compacted and sintered at 950 °C for 30 min. Structural, microstructural and elemental analyses were carried out using X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive X-ray spectrometry (EDS), respectively. The lattice parameter is found to increase with increasing copper content. A remarkable densification is observed with the addition of Cu ions in the ferrites. The sintered ferrite was characterized for initial permeability, dielectric constant and dielectric loss tangent and ac conductivity measurements. The temperature variation of the initial permeability of these samples was carried out from 30 °C to 200 °C. The dielectric constant, dielectric loss tangent and ac conductivity have been measured in the frequency range of 100 Hz to 1 MHz. Initial permeability and dielectric constant were found to increase and dielectric loss decreased with Cu substitution for Mg, up to x = 0.20. The ferrite powder prepared is suitable for the application in multilayer chip inductor due to its low-temperature sinterability, good magnetic properties and low loss at high frequency.     

The processing electronics system for the pointed mode operation ofIXAE on the Indian satellite IRS-P3

Indian Remote Sensing Satellite-P3 (IRS-P3: 1996-017A) was launched into a near-Earth, polar, Sun-synchronous orbit by India's Polar Satellite Launch Vehicle (PSLV-D3) on March 21, 1996. The Indian X-ray Astronomy Experiment (IXAE) is one of the prime payloads onboard IRS-P3. IXAE has two sets of detectors: three pointed-mode proportional counters (PPCs) and one X-ray Sky Monitor (XSM). IRS-P3 is configured to operate in two modes, namely, Earth-pointing mode and stellar-pointing mode. In Earth-pointing mode the remote sensing payloads are in operation; in addition, XSM maps the sky for bright X-ray sources and X-ray transients. In stellar mode, the PPCs observe several Galactic, bright X-ray, and extragalactic sources. The microprocessor-based processing electronics system was designed and developed for PPC data-handling and telemetering the stored data to the ground station. The system has been working well from the day the IXAE was commissioned. The processing electronics system for the PPCs, its interfaces, and the in-orbit instrument performance are described. Some results of the pointed mode observations are also presented     

Third-order optical nonlinear studies of Cobalt (II) Schiff base complex bearing triphenylphosphine using Differential Optical Kerr Gate and Z-scan studies

The third-order optical nonlinearity of the composite film of coordination complex [CoLPPh₃Cl] (L = N-(2-pyridyl)-N′-(salicylidene)hydrazine) and PMMA has been investigated by using Differential Optical Kerr Gate (DOKG) and Z-scan measurements. Large value of the third-order nonlinear optical susceptibility (χ⁽³⁾) of the order of 10^?10 esu was measured and its nonlinear response time was found to be faster than or comparable to the laser pulse width (90 fs) used. The single beam Z-scan technique was used to investigate the nonlinear absorption property of the composite near 800 nm. The sample exhibit saturable absorption. The nonlinear absorption coefficient of sample is found to be ?32 cm/GW.