Separation Of Beta-Apocarotenals And Related Compounds By Reversed-Phase Paper And Thin-Layer Chromatography

Tlie sclxuntion and clraractcrization of vitamins Al and An nnd related compoundsby reversed-pllasc paper cliromatogrnpl~y as well as ly thin-lqxr chromategraphy have hen rcportccl carlicrl * $. Thin-lnycr chromatography has also been used for the separatinn and charncterizatio11 of carotenoids from natural sourccs3~ ‘1. I-Iowcver, 130tr.rc,1~1~ofib scrvccl that carotenoid misturcs cannot be separated on a sin& aclsorhnt with ;1 sin& solvent. The scparntion and clctermi1wtion of carotenoid alclclydes from plants, microorganisms and animnl tissues have lxxn carriecl out by nicans of thin-layer clirf.~li~ato~apI~~U. Apocarotcnals awl apocarotcnoic acid have been detected in ornnges by the same technique’*

Investigation of activated transport in hole doped rare earth manganites in the high temperature paramagnetic regime

Electronic transport in the high temperature paramagnetic regime of the colossal magnetoresistive oxides, La(1-x)A(x)MnO(3), A=Ca, Sr, Ba, x similar or equal to 0.1-0.3, has been investigated using resistivity measurements. The main motivation for this work is to relook into the actual magnitude of the activation energy for transport in a number of manganites and study its variation as a function of hole doping (x), average A-site cation radius (< r(A)>), cationic disorder (sigma(2)) and strain (epsilon(zz)). We show that contrary to current practice, the description of a single activation energy in this phase is not entirely accurate. Our results clearly reveal a strong dependence of the activation energy on the hole doping as well as disorder. Comparing the results across different substituent species with different < r(A)> reveals the importance of sigma(2) as a metric to qualify any analysis based on (r(A)). (c) 2006 Elsevier Ltd. All rights reserved.

Effect of disorder on the exponent in the coherence region in high temperature superconductors

Effect of disorder on the electrical resistance near the superconducting transition temperature in the paracoherence region of high temperature YBa2CU3O7-delta (YBCO) thin film superconductor is reported. For this, c-axis oriented YBa2Cu3O7-delta thin films having superconducting transition width varying between 0.27 K and 6 K were deposited using laser ablation and high pressure oxygen sputtering techniques. Disorder in these films was further created by using 100 MeV oxygen and 200 MeV silver ions with varying fluences. It is observed that the critical exponent in the paracoherence region for films with high transition temperature and small transition width is in agreement with the theoretically predicted value (gamma = 1.33) and is not affected by disorder, while for films with lower transition temperature and larger transition width the value of exponent is much larger as compared to that theoretically predicted and it varies from sample to sample and usually changes with disorder induced by radiation. This difference in the behaviour of the exponent has been explained on the basis of differences in the strength of weak links and the transition between temperatures T. and T, is interpreted as a percolation like transition with disorder. (c) 2006 Elsevier B.V. All rights reserved.

Ambient temperature, zinc ion-conducting, binary molten electrolyte based on acetamide and zinc perchlorate: Application in rechargeable zinc batteries

Binary room temperature molten electrolytes based on acetamide and zinc perchlorate have been prepared and characterized. The electrolytes are found to be highly zinc ion-conducting with very favorable physicochemical and electrochemical characteristics. Raman and infrared spectroscopic studies reveal the presence of large free-ion concentration in the molten liquid. This is corroborated by the high conductivity observed under ambient conditions. Rechargeable zinc batteries assembled using gamma-MnO2 as the cathode and Zn as the anode with the molten electrolyte show high discharge capacities over several cycles, indicating excellent reversibility. This unique class of acetamide-based, room temperature molten liquids may become viable and green alternative electrolytes for rechargeable zinc-based secondary batteries. (C) 2009 Elsevier Inc. All rights reserved.

Effect of mode of rolling on development of texture and microstructure in two-phase (alpha plus beta) brass

The evolution of microstructure and texture during deformation of two-phase (alpha + beta) brass was studied for different initial microstructure and texture. The deformation processing involved unidirectional and multi-step cross-rolling. The bulk textures were determined by measuring the pole figures and calculating the orientation distribution function ODF for both alpha (fcc) and beta (bcc) phases, while the microstructure and other microstructural parameters were measured through optical microscopy and scanning electron microscopy with electron back scatter diffraction (SEM-EBSD). Results indicate that textures developed after unidirectional rolling and multi-step cross-rolling are significantly different. The variation in initial texture had a pronounced effect on the development of texture in the alpha phase during subsequent deformation. (C) 2010 Elsevier B.V. All rights reserved.

Robust/optimal temperature profile control using neural networks

An approximate dynamic programming (ADP) based neurocontroller is developed for a heat transfer application. Heat transfer problem for a fin in a car's electronic module is modeled as a nonlinear distributed parameter (infinite-dimensional) system by taking into account heat loss and generation due to conduction, convection and radiation. A low-order, finite-dimensional lumped parameter model for this problem is obtained by using Galerkin projection and basis functions designed through the 'Proper Orthogonal Decomposition' technique (POD) and the 'snap-shot' solutions. A suboptimal neurocontroller is obtained with a single-network-adaptive-critic (SNAC). Further contribution of this paper is to develop an online robust controller to account for unmodeled dynamics and parametric uncertainties. A weight update rule is presented that guarantees boundedness of the weights and eliminates the need for persistence of excitation (PE) condition to be satisfied. Since, the ADP and neural network based controllers are of fairly general structure, they appear to have the potential to be controller synthesis tools for nonlinear distributed parameter systems especially where it is difficult to obtain an accurate model.

Crystal structures and photocatalysis of the triclinic polymorphs of BiNbO4 and BiTaO4

The high-temperature polymorphs of two photocatalytic materials, BiNbO4 and BiTaO4 were synthesized by the ceramic method. The crystal structures of these materials were determined by single-crystal X-ray diffraction. BiNbO4 and BiTaO4 crystallize into the triclinic system P (1) over bar (No. 2), with a = 5.5376(4) angstrom, b = 7.6184(3) angstrom, c = 7.9324(36) angstrom, alpha = 102.565(3)degrees, beta = 90.143(2)degrees, gamma = 92.788 (4)degrees, V = 326.21 (5) angstrom(3). Z = 4 and a = 5.931(1) angstrom, b = 7.672(2) angstrom, c = 7.786(2) angstrom, alpha = 102.94 (3)degrees, beta = 90.04(3)degrees gamma = 93.53(3)degrees, V = 344.59(1) angstrom(3) and Z = 4, respectively. The structures along the c-axis, consist of layers of [Bi2O2] units separated by puckered sheets of (Nb/Ta)O-6 octahedra. Photocatalytic studies on the degradation of dyes indicate selectivity of BiNbO4 towards aromatics containing quinonic and azo functional groups

High temperature mechanical properties of thermal barrier coated superalloy applied to combustor liner of aero engines

High temperature load controlled fatigue, hot tensile and accelerated creep properties of thermal barrier coated (TBC) Superni C263 alloy used as a candidate material in combustor liner of aero engines are highlighted in this paper. Acoustic emission technique has been utilised to characterise the ductile-brittle transition teperature the bond coat. Results revealed that the DBTT (ductile to brittle transition temperature) of this bond coat is around 923 K, which is in close proximity to the value reported for CoCrAlY type of bond coat. Finite element technique, used for analysing the equivalent stresses in the bond coat well within the elastic limit, revealed the highest order of equivalent stress at 1073 K as the bond coat is ductile above 923 K. The endurance limit in fatigue and the life of TBC coated composite under accelerated creep conditions are substantially higher than those of the substrate material. Fractographic features at high stresses under fatigue showed intergranular cleavage whereas those at low stresses were transgranular and ductile in nature. Delamination of the bond coat and spallation of the TBC at high stresses during fatigue was evident. Unlike in the case of fatigue, the mode of fracture in the substrate at very high stresses was transgranular whereas that at low stresses was intergranular in creep.

Structural studies of model peptides containing beta-, gamma- and delta-amino acids

The crystal structures of five model peptides Piv-Pro-Gly-NHMe (1), Piv-Pro-beta Gly-NHMe (2), Piv-Pro-beta Gly-OMe (3), Piv-Pro-delta Ava-OMe (4) and Boc-Pro-gamma Abu-OH (5) are described (Piv:pivaloyl; NHMe: N-methylamide; beta Gly:beta-glycine; OMe:O-methyl ester; delta Ava:delta-aminovaleric acid; gamma Abu:gamma-aminobutyric acid). A comparison of the structures of peptides 1 and 2 illustrates the dramatic consequences upon backbone homologation in short sequences. 1 adopts a type II beta-turn conformation in the solid state, while in 2, the molecule adopts an open conformation with the beta-residue being fully extended. Piv-Pro-beta Gly-OMe (3), which differs from 2 by replacement of the C-terminal NH group by an O-atom, adopts an almost identical molecular conformation and packing arrangement in the solid state. In peptide 4, the observed conformation resembles that determined for 2 and 3, with the delta Ava residue being fully extended. In peptide 5, the molecule undergoes a chain reversal, revealing a beta-turn mimetic structure stabilized by a C-H center dot center dot center dot O hydrogen bond.

Effectiveness of a Differential Temperature Controller on a Solar Water Heating System: An Experimental Study

A differential temperature controller is incorporated in a solar water heating system to study the influence of its set points on system performance. The effectiveness of the controller set points DeltaT ON and DeltaT OFF on the pump cycling and energy collection has been studied experimentally and the results are presented in this paper.

Epitaxial growth of Co3O4 films by low temperature, low pressure chemical vapour deposition

The growth of strongly oriented or epitaxial thin films of metal oxides generally requires relatively high growth temperatures or infusion of energy to the growth surface through means such as ion bombardment. We have grown high quality epitaxial thin films of Co3O4 on different substrates at a temperature as low as 400 degreesC by low-pressure metalorganic chemical vapour deposition (MOCVD) using cobalt(II) acetylacetonate as the precursor. With oxygen as the reactant gas, polycrystalline Co3O4 films are formed on glass and Si (100) in the temperature range 400-550 degreesC. Under similar conditions of growth. highly oriented films of Co3O4 are formed on SrTiO3 (100) and LaAlO3 (100). The activation energy for the growth of polycrystalline films on glass is significantly higher than that for epitaxial growth on SrTiO3 (100). The film on LaAlO3 (100) grown at 450 degreesC shows a rocking curve FWHM of 1.61 degrees, which reduces to 1.32 degrees when it is annealed in oxygen at 725 degreesC. The film on SrTiO3 (100) has a FWHM of 0.33 degrees (as deposited) and 0.29 (after annealing at 725 degreesC). The phi -scan analysis shows cube-on-cube epitaxy on both these substrates. The quality of epitaxy on SrTiO3 (100) is comparable to the best of the perovskite-based oxide thin films grown at significantly higher temperatures. A plausible mechanism is proposed for the observed low temperature epitaxy. (C) 2001 Published by Elsevier Science B.V.