Theoretical Analysis of the IR and Visible Absorption Spectral Change by the Phase Transition of the Crystals of 2,3-Diphenylthio- and 2,3-Di(p-chlorothiophenyl)-1,4-Naphthoquinones

1996 ◽  
Vol 286 (1) ◽  
pp. 317-322
Author(s):  
Kouichi Mogi ◽  
Masashi Tanaka ◽  
Hisahiro Hayashi
Keyword(s):  
Phase Transition ◽  
Theoretical Analysis ◽  
Spectral Change ◽  
Visible Absorption

Ferroelasticity of SrCo0.8Fe0.2O3–δperovskite-related oxide with mixed ion–electron conductivity

2015 ◽  
Vol 48 (1) ◽  
pp. 179-188 ◽  
Author(s):  
I. Belenkaya ◽  
A. Matvienko ◽  
A. Nemudry
Keyword(s):  
Phase Transition ◽  
Theoretical Analysis ◽  
Mechanical Load ◽  
Electron Conductivity ◽  
Transmission Electron ◽  
Lamellar Texture ◽  
The Common ◽  
Common Nature ◽  
Means Of Transmission ◽  
Group Theoretical Analysis

A group-theoretical analysis was carried out to determine the possible orientation states of domains formed as a result of the `perovskite–brownmillerite' phase transition in SrCo0.8Fe0.2O2.5oxide with mixed ion–electron conductivity (MIEC). The results of the theoretical analysis agree with the experimental data obtained in the study of the SrCo0.8Fe0.2O2.5microstructure by means of transmission electron microscopy. Brownmillerite SrCo0.8Fe0.2O2.5(BM) has a lamellar texture composed of 90° twins 60–260 nm in size; the 〈010〉BMand 〈101〉BMdirections are linked through twinning in accordance with the predictions of the group-theoretical analysis. The presence of twins and their switching under mechanical load provide evidence that the perovskite–brownmillerite phase transition in SrCo0.8Fe0.2O2.5is ferroelastic. Comparative analysis of the phenomena observed for ferroelectrics and MIEC oxides indicates their similarity based on the common nature of ferroelectricity and ferroelasticity, and allows us to suppose that nonstoichiometric SrCo0.8Fe0.2O3−δwith compositional disorder may be considered (in terms of its microstructural features) a `relaxor ferroelastic'.

Influence of the Size Effect on Magnetic Susceptibility in Ultrathin Films

2015 ◽  
Vol 233-234 ◽  
pp. 639-642
Author(s):  
Leonid L. Afremov ◽  
Aleksandr A. Petrov
Keyword(s):  
Experimental Data ◽  
Phase Transition ◽  
Magnetic Susceptibility ◽  
Theoretical Analysis ◽  
Ultrathin Films ◽  
Transition Point ◽  
Finite Size ◽  
Phase Transition Point ◽  
Shape Curve ◽  
Good Agreement

The magnetic susceptibility dependence on temperature near phase transition point was investigated by theoretical analysis. It is shown that with decreasing of the film thickness the magnetic susceptibility shape curve becomes more rounded finite-size function, centered about the lowered temperature Tc (L). The obtained results are in good agreement with experimental data.

scholarly journals Turkey liver xanthine dehydrogenase. Reactivation of the cyanide-inactivated enzyme by sulphide and by selenide

1974 ◽  
Vol 143 (2) ◽  
pp. 331-340 ◽  
Author(s):  
William F. Cleere ◽  
Michael P. Coughlan
Keyword(s):  
Absorption Spectrum ◽  
Xanthine Dehydrogenase ◽  
Intramolecular Electron Transfer ◽  
Visible Absorption Spectrum ◽  
Spectral Change ◽  
Rapid Loss ◽  
Active Centre ◽  
Visible Absorption ◽  
Partial Restoration ◽  
First Order

1. Turkey liver xanthine dehydrogenase engaged in catalysing the oxidation of xanthine by dichlorophenol–indophenol was progressively inactivated by methanol. This inactivation was reversible by NAD+. 2. Reaction with arsenite and with cyanide, in each case first-order with respect to enzyme, resulted in characteristic alterations in the visible absorption spectrum of the enzyme. The rate of spectral change on reaction with either agent paralleled the rate of loss of enzyme activity. 3. Cyanide inactivation was accompanied by elimination from the enzyme of sulphur as thiocyanate. Partial restoration of activity was effected by incubation with sulphide or with selenide. The results suggest that turkey liver xanthine dehydrogenase, like milk xanthine oxidase (Massey & Edmonson, 1970), contains at the active centre a cyanolysable persulphide group essential to catalytic activity and that selenium may replace sulphur in this group to give an active enzyme. 4. Incubation of the native enzyme with sulphide or with selenide resulted in the rapid loss of half of the xanthine-oxidizing activity, apparently by disrupting the molybdenum and (Fe/S)II loci. This may indicate non-equivalence of the intramolecular electron-transfer systems.

scholarly journals The Li2SO4–Na2SO4 System for Thermal Energy Storage

Materials ◽  
2019 ◽  
Vol 12 (22) ◽  
pp. 3658 ◽  
Author(s):  
Stefania Doppiu ◽  
Jean-Luc Dauvergne ◽  
Angel Serrano ◽  
Elena Palomo del Barrio
Keyword(s):  
Phase Transition ◽  
Energy Storage ◽  
Solid State ◽  
Theoretical Analysis ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Solid Phase ◽  
Eutectoid Reaction ◽  
Durability Analysis ◽  
Solid Phase Transition

In this paper, the system Li2SO4–Na2SO4 is proposed as a candidate material for thermal energy storage applications at high temperatures (450–550 °C). Depending on the composition, the thermal energy can be stored by using a eutectoid reaction and solid–solid phase transition. In these types of systems, all the components (reagent and products) are in the solid state. This work includes the theoretical analysis (based on the Calphad method) of the system selected obtaining all the theoretical parameters (for example, enthalpies of reaction, transition temperatures, volume expansion, and the heat capacities) necessary to determine the theoretical performance in terms of thermal energy storage. The theoretical analysis allowed to identify two compositions (Li2SO4/Na2SO4 79/21 and 50/50) in the phase diagram with the most promising theoretical enthalpy of transformation (270 J/g and 318 J/g, respectively) corresponding to a eutectoid reaction and a solid–solid phase transition (stoichiometric compound LiNaSO4). The experimental analysis carried out allowed to confirm the great potential of this system for TES application even if some discrepancies with the theoretical calculation have been observed experimentally (energy densities lower than expected). For the two compositions studied, 79/21 and 50/50, the enthalpies of reaction are 185 J/g and 160 J/g, respectively. The reactivity of the system was tested under different experimental conditions preparing materials with a different degree of nanocrystallization to favor the diffusion in the solid state, testing the reactivity of the materials under controlled atmosphere and under air, and performing preliminary durability analysis (cycling behavior up to 20 cycles) to test the stability and reversibility.

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