In-Vacuo thermal processing of α-Al2O3 single crystals in boron ambience and its implication on TL & OSL response

Single crystals of α-Al₂O₃ (10×10 mm², 0.4 mm thick) were annealed in vacuum at about 1500 °C in the ambience of boron. The OA studies on these samples showed bands at 203, 232 and 258 nm signifying that such a treatment leads to the formation of F and F⁺ centers in significant concentrations, these bands, however, were not found in the Al₂O₃ crystals processed in the similar manner in the absence of boron. The Al₂O₃:B samples were irradiated to different absorbed doses of ⁹⁰Sr/⁹⁰Y β-source and the continuous wave OSL (CW-OSL) was recorded on the samples using 470 nm blue light stimulation. These samples have shown a linear TL and CW-OSL response in the dose range of 20 mGy to 15 Gy. The minimum detectable dose, corresponding to 3σ limit of the variation of the output of the unirradiated dosimeters, was found to be 100 μGy. Irradiated samples stored in dark at room temperature for a period of two months show negligible fading. The TL and OSL sensitivities of the samples were found to be strongly dependent on process temperature and time. The TL response is marked by the absence of low temperature peak (<100 °C), unlike the case of α-Al₂O₃:C, implying that the boron doping does not lead to formation of shallow traps. The Al₂O₃:B samples show faster photoionisation cross-section as compared to α-Al₂O₃:C. This approach of processing of single crystal Al₂O₃ in the boron ambience thus represents a potential way of introducing dosimetrically pertinent defects in Al₂O₃ single crystals.     

Lattice size induced moment formation on isolated Fe atoms in nanocrystalline Nb

Measurements of the local susceptibility and 3d spin relaxation rate for single Fe impurities embedded in a nanocrystalline Nb host indicates the emergence of a local moment on Fe at and below a critical size of 11?nm. Our ab?initio electronic structure calculations show that the moment formation occurs due to Stoner enhancement arising from a size dependent lattice expansion and a consequent shift in the Fermi level. We also show that a size-induced positive host spin polarization of the Nb-4d band electrons strongly influences the fluctuation rate of the Fe moment.     

Electron beam induced green luminescence and degradation study of CaS:Ce nanocrystalline phosphors for FED applications

Green luminescence and degradation of Ce³⁺ doped CaS nanocrystalline phosphors were studied with a 2 keV, 10 μA electron beam in an O₂ environment. The nanophosphors were synthesized by the co-precipitation method. The samples were characterized using X-ray diffraction, Transmission electron microscopy, Scanning electron microscopy/electron dispersive X-ray spectroscopy and Photoluminescence (PL) spectroscopy. Cubic CaS with an average particle size of 42 ± 2 nm was obtained. PL emission was observed at 507 nm and a shoulder at 560 nm with an excitation wavelength of 460 nm. Auger electron spectroscopy and Cathodoluminescence (CL) were used to monitor the changes in the surface composition of the CaS:Ce³⁺ nanocrystalline phosphors during electron bombardment in an O₂ environment. The effect of different oxygen pressures ranging from 1 × 10⁻⁸ to 1 × 10⁻⁶ Torr on the CL intensity was also investigated. A CaSO₄ layer was observed on the surface after the electron beam degradation. The CL intensity was found to decrease up to 30% of its original intensity at 1 × 10⁻⁶ Torr oxygen pressure after an electron dose of 50 C/cm². The formation of oxygen defects during electron bombardment may also be responsible for the decrease in CL intensity.     

Determination of Traces of Uranium and Thorium in Environmental Matrices by Neutron Activation Analysis

Radioactive elements like ²³²Th and ²³⁸U along with their daughter products, form part of all environmental matrices and are getting transferred to living beings by different pathways, leading to a continuous radiation exposure and need to be monitored. This paper presents an analytical methodology, highlighting the need to separate interfering beta- and gamma-emitters from the analytes, when neutron activation analysis is employed for the determination of traces of uranium and thorium in soil and plant materials. The method has been applied to the soil and plant materials from selected regions of India, along with standard reference materials to verify the validity of the proposed separation scheme. The overall reproducibility of the procedure was 2–10%. The concentration values of uranium and thorium so obtained, have been used to calculate transfer factors from soil to various parts of wheat plant.     

Vibration based damage detection in a uniform strength beam using genetic algorithm

Cantilever steel beams of uniform strength are having various industrial applications. In particular when it is used as leaf spring it undergoes very large deflection in comparison to beam of uniform cross section. The damage occurs in these beams mainly due to fatigue loading. Early detection of damage in such type of beams is very essential to avoid a major failure or accident. In this paper, firstly formulation of an objective function for the genetic search optimization procedure along with the residual force method are presented for the identification of macroscopic structural damage in an uniform strength beam. Two cases have been investigated here. In the first case the width is varied keeping the strength of beam uniform throughout and in the second case both width and depth are varied to represent a special case of uniform strength beam. The developed model require experimentally determined data as input and detect the location and extent of the damage in the beam. Here, experimental data are simulated numerically by using finite element models of structures with inclusion of random noise on the vibration characteristics. It has been shown that the damage may be identified for the said problems with a good accuracy.     

An efficient,one-pot synthesis of trithiocarbonates from alcoholic tosylates using the Cs<Subscript>2</Subscript>CO<Subscript>3</Subscript>/CS<Subscript>2</Subscript> system

A single-step novel protocol for the preparation of symmetrical trithiocarbonates from a corresponding variety of primary, secondary, and tertiary alcoholic tosylates using the Cs₂CO₃/CS₂ system, was developed. This protocol is mild and more efficient than the reported methods. Correspondence: Devdutt Chaturvedi, Bio-Organic Chemistry Division, Indian Institute of Integrative Medicine, Canal Road, Jammu-Tawi-18000, J&K, India.     

Triton-B catalyzed, efficient one-pot synthesis of carbazates

A quick and efficient, one-pot synthesis of carbazates was accomplished in high yields by the reaction of various primary, secondary, and tertiary alkyl halides with a variety of substituted hydrazines using the benzyltrimethylammonium hydroxide (Triton-B)/CO₂ system. The reaction conditions are mild with simpler work-up procedures than the reported methods. Correspondence: Devdutt Chaturvedi, Bio-Organic Chemistry Division, Indian Institute of Integrative Medicine, Canal Road, Jammu-Tawi 18000, J&K, India.     

Synthesis, characterizations and applications of some nanomaterials (TiO2 and SiC nanostructured films, organized CNT structures, ZnO structures and CNT-blood platelet clusters)

TiO₂ nanostructured films have been synthesized by the hydrolysis of Ti[OCH(CH₃)₂]₄ as the precursor. These films have been utilized for the dissociation of phenol contaminant in water. Free-standing nanostructured film of silicon carbide (SiC) has been synthesized, employing a simple and new route of spray pyrolysis technique utilizing a slurry of Si in hexane. Another study is done on organized carbon nanotube (CNT) structures. These are made in the form of hollow cylinders (50 mm length, 4 mm diameter and 1.5 mm wall thickness). These CNT-based cylinders are made of conventional CNT and bamboo-shaped CNT. The filtrations of heavy hydrocarbons andE. coli bacteria from water have been carried out. In addition to this, ZnO nanostructures have also been studied. Another study concerns CNT-blood platelet clusters.     

Duality for Multiple Objective Fractional Subset Programming with Generalized (, ρ, σ, θ)-V-Type-I Functions

In this paper, we use a new class of generalized convex n-set functions, called (,ρ, σ, θ)-V-Type-I and related non-convex functions to establish appropriate duality theorems for three parametric and three semi-parametric dual models to the primal problem. This work extends an earlier work of Zalmai [Computer and Mathematics with Applications 43 (2002) 1489–1520] to a wider class of functions.This research is supported by the Department of Science and Technology, Ministry of Science and Technology, Government of India, under the Fast Track Scheme for Young Scientist through grant No. SR/FTP/MS-22/2001     

Working group report: Heavy-ion physics and quark-gluon plasma

This is the report of Heavy Ion Physics and Quark-Gluon Plasma at WHEPP-09 which was part of Working Group-4. Discussion and work on some aspects of quark-gluon plasma believed to have created in heavy-ion collisions and in early Universe are reported.