http://localhost:8080/xmlui/handle/123456789/672 2009 Publications Sat, 11 Apr 2026 05:55:24 GMT 2026-04-11T05:55:24Z http://localhost:8080/xmlui/handle/123456789/2898 Doping Dependent Metal to Insulator Transition in the (Bi, Pb)-2212 System: The Evolution of Structural and Electronic Properties with Europium Substitution Shabna, R; Sarun, P M; Vinu, S; Syamaprasad, U The present work investigates the effect of europium substitution on the (Bi, Pb)-2212 system in the concentration range 0.5 ≤ x ≤ 1.0. Phase analysis and lattice parameter calculations on the powder diffraction data and the elemental analysis of EDX show that the Eu atoms are successfully substituted into the (Bi, Pb)-2212 system. Resistivity measurements (64–300 K) reveal that the system exhibits superconductivity at x ≤ 0.5 and semiconductivity at x > 0.5. With the complete suppression of superconductivity which is known to be a quasi-two dimensional phenomenon in these materials, a metal to insulator transition takes place at x = 0.6 and the predominant conduction mechanism is found to be variable range hopping between localized states, resulting in macroscopic semiconducting behaviour. The results of electrical and structural properties of the doped (Bi, Pb)-2212 compounds suggest that the decrease of charge carrier concentration and the induced structural disorder are the more effective and dominant mechanisms in the origin of the metal to insulator transition and suppression of superconductivity due to Eu substitution at its Sr site. Tue, 01 Sep 2009 00:00:00 GMT http://localhost:8080/xmlui/handle/123456789/2898 2009-09-01T00:00:00Z http://localhost:8080/xmlui/handle/123456789/2897 Reactions of Morita–Baylis–Hillman Acetates with Huisgen Zwitterions: A Novel Strategy for the Synthesis of b-Amino Acid Derivatives Anu, J; Paul, R R; Resmi, M; Smitha, C M; Biju, A T; Suresh, E; Vijay Nair, G The reaction of Huisgen Zwitterion with Morita–Baylis–Hillman acetates afforded β-amino acid derivatives. Thu, 01 Jan 2009 00:00:00 GMT http://localhost:8080/xmlui/handle/123456789/2897 2009-01-01T00:00:00Z http://localhost:8080/xmlui/handle/123456789/2896 Immobilized Bacterial α-amylase for Effective Hydrolysis of Raw and Soluble Starch Dhanya, G; Nampoothiri, K M; Swetha, S; Pandey, A The major concern in an enzymatic process is the instability of the enzyme under repetitive or prolonged use and inhibition by high substrate and product concentration. Immobilization is a very effective alternative in overcoming problems of instability and repetitive use of enzymes. Entrapment method of immobilization is advantageous over other methods as they do not involve chemical modification of the enzyme. α-Amylase produced by Bacillus amyloliquefaciens ATCC 23842 was immobilized in calcium alginate beads and used for the effective hydrolysis of soluble and raw potato starch which was comparable to the free enzyme. The levels of parameters (sodium alginate, calcium chloride and curing time) that significantly influence the immobilization of α-amylase in calcium alginate were analyzed and optimized using response surface methodology. Reactor studies were performed to study the reusability and operational stability of the beads. The alginate beads retained more than 60% of their initial efficiency after five batches of successive use and 40% of efficiency was exhibited in the 6th and 7th batch run of 6 h duration. Fri, 01 May 2009 00:00:00 GMT http://localhost:8080/xmlui/handle/123456789/2896 2009-05-01T00:00:00Z http://localhost:8080/xmlui/handle/123456789/2611 Pyrochlore Type Semiconducting Ceramic Oxides in Ca–Ce–Ti–M–O System (M = Nb or Ta)—Structure, Microstructure and Electrical Properties Deepa, M; Prabhakar Rao, P; Radhakrishnan, A N; Sibi, K S; Peter Koshy A new series of pyrochlore type ceramic semiconducting oxides in Ca–Ce–Ti–M–O (M = Nb or Ta) system has been synthesized by the conventional ceramic route. The electrical conductivity measurements show that these oxides exhibit semiconducting behavior and the conductivity increases with the Ce content in the compound. Activation energy of the current carriers is in the range of 0.5–1.6 eV. The electrical conductivity in these oxides is due to the presence of Ce3+, which remains in the reduced state without being oxidized to Ce4+ by structural stabilization. The photoluminescence and X-ray photoelectron spectroscopy analysis corroborate the presence of Ce in the 3+ state. Impedance spectral analysis is carried out to evaluate the transport properties and indicates that the conduction in these compounds is mainly due to electronic contribution. The X-ray powder diffraction and Raman spectroscopy analysis establishes that these oxides belong to a cubic pyrochlore type structure. Wed, 01 Jul 2009 00:00:00 GMT http://localhost:8080/xmlui/handle/123456789/2611 2009-07-01T00:00:00Z