Fabrication and electrochemical performance of La<Subscript>0.5</Subscript>Sr<Subscript>0.5</Subscript>CoO<Subscript>3</Subscript> impregnated porous YSZ cathode

La_0.5Sr_0.5CoO₃-yttria-stabilized zirconia (LSCO-YSZ) composite cathode for solid oxide fuel cell (SOFC) has been fabricated by wet impregnation method. Nitrate precursors of La, Sr, and Co have been impregnated into the pre-sintered porous YSZ matrix, which is converted into LSCO phase after calcination at 850 °C in the presence of glycine as confirmed from X-ray diffraction. LSCO of 5, 7, and 10 wt% impregnated porous YSZ have been electrochemically characterized using 2-probe AC conductivity method. Maximum ionic conductivity of 0.27 S/cm at 800 °C and activation energy of 0.15 eV between 600 and 800 °C have been observed for 10 wt% LSCO-YSZ cathode. Area-specific resistance of 1.01 Ω cm² at 800 °C is estimated for the electrolyte-supported half-cell (10 wt% LSCO-YSZ/YSZ). After testing the LSCO-YSZ cathode matrix, the electrolyte-supported full cell (10 wt% LSCO-YSZ/YSZ/NiO-YSZ) has been tested and produced maximum power density 51.12 mW/cm² (109.38 mA/cm²) at 800 °C. The electrolyte-supported full cell exhibited 6 Ω cm² electrode polarization at 800 °C in H₂, which is in higher side leading to low performance. LSCO-YSZ/YSZ/NiO-YSZ SOFC found to give stable performance up to 2 h and scanning electron microscopy analysis has been carried out before and after cell testing to assess the morphological changes.     

Tandem mass spectra of transition-metal ion adducts of glycosyl dithioacetals; distinction among stereoisomers

Electrospray ionization mass spectra of some glycosyl dithioacetals recorded in the presence of transition-metal chlorides, XCl2 (where X = Co, Mn and Zn), give abundant adduct ions such as [M+XCl]+ and [2M-H+X]+ and minor ions such as [M-H+X]+ and [2M+XCl]+. The tandem mass spectra of these adducts show characteristic elimination of neutral molecules such as H2O, HCl, EtSH, CH2O, C2H4O2/C2H4O. [M+XCl]+ ions fragment readily and the fragmentation appears to be stereochemically controlled as the relative abundances of the fragments are different for three stereoisomers. The added metal is lost as neutral molecules in the form of XCl(OH) and XCl(SEt). This is a predominant pathway in the ZnCl+ adducts. [2M+XCl]+ ions fragment preferentially by elimination of HCl, indicating strong metal interactions in the resulting dimeric [2M-H+X]+ ion. As there are several electron-rich centers in the molecule, the dimeric complex [2M-H+X]+ can have several structures and the observed fragmentations may reflect the sum of those of all these structures. The dimeric complexes fragment by elimination of neutral molecules leaving the dimeric interactions intact. The extent of fragmentation varies for the stereoisomers, leading to stereochemical differentiation.     

A class of exact solutions for coupled electromagnetic and scalar fields for einstein-rosen metric. I

A class of rigorous solutions for the Einstein-Rosen nonstatic cylindrically symmetric metric in the presence of combined electromagnetic and scalar meson fields has been obtained. Some of these solutions reduce to the solutions obtained by Misra and Radhakrishna [Proc. Nat. Inst. Sci. India Part A 28 (1962), 632] when the scalar field is not present.     

Use of cyanobacterial diazotrophic technology in rice agriculture

Applied Biochemistry and Biotechnology -     

Effect of metallic side walls on field distribution of generalized, single and coupled dielectric wave guide

The effect of metallic side walls on the field distribution of generalized single and coupled dielectric guide has been theoretically computed for even and odd modes using mode matching technique in E^Ymn configuration. It is concluded that the field E^Ymn is not symmetrical due to presence of side walls.     

Green function theory of a Heisenberg ferromagnet with dipole-octupole interactions

The effect of dipole-octupole interaction on different magnetic parameters for the spinS=3/2 system in the presence of biquadratic exchange has been investigated. The Green function technique with random phase approximation (RPA) has been employed to obtain analytical results. These results are in good agreement with the results of the molecular field approzimation (MFA).     

A search for mechanoluminophors capable of pressure-induced thermal population of excited states

During the process of deforming a crystal, a high pressure is developed near the tip of mobile cracks, which may in turn produce a new ground state by thermal electron transfer. Upon sudden release of pressure, the electron can either relax to one atmosphere ground state or remain in the excited state potential well long enough to relax to one atmosphere and radiatively transfer back to the ground state. For analysing the pressure induced thermal population of the excited state, the mechanoluminescence(ML) and high pressure photoluminescence(PL) of several organic and inorganic crystals were measured. The study indicated that usual pressure coefficient of energy shift of the order of 50–100 cm⁻¹/kbar and the stress at the crack-tip of the order of 5–10 kbar, are not sufficient to cause the thermal population of the excited state. If by any means the product of pressure coefficient and stress at the mobile crack-tip can be increased by 50 to 100 times, then the thermal population of the excited states may take place. Using the pressure coefficient of energy shift and the difference in ML and PL spectra, and using independently the change in relative intensities of the vibronic peaks, the pressure at the emitting mechanoluminescent crystal sites is evaluated and it is found to be of the order of several kbar which varies from crystal to crystal.     

A class of exact solutions for coupled electromagnetic and scalar fields for Einstein-Rosen metric. Part IA

In the previous work [1] we have obtained a class of exact solutions for the nonstatic cylindrically symmetric Einstein-Rosen metric in the presence of combined electromagnetic and zero-rest-mass scalar meson fields. But, these solutions are restricted because of assuming certain conditions on the scalar field. The present work deals with all the solutions obtained in the previous paper without any such restriction. The class of exact solutions obtained thus is more general than that given in [1].     

Debye-Waller factor of gold

The temperature dependence of the exponent of Debye-Waller factor of gold for the temperature range extending from 50 to 900°K has been studied using a theoretical model where the interactions are treated in realistic manner. The results are found to be in reasonable agreement with the experimental ones.