Theoretical and experimental studies of doping effects on thermodynamic properties of (Dy, Y)-ZrO2

Ionic oxide materials play a vital role in technical applications owing to their high-temperature capability and when used as thermal barrier coating (TBC) materials, for example, they have environmentally friendly effects such as improved fuel efficiency and reduced emissions. Doped ZrO2 based solid solution is attracting attention, whereas doping effects on thermodynamic properties are not well understood. This work reports the synthesis and characterization of doped ZrO2 with Dy3+ and Y3+ via a sol-gel route. The relationship between chemical composition and thermodynamic properties is investigated via experiment and molecular dynamics (MD) simulation. MD simulation has been employed to theoretically explore the crystal structure and to calculate the intrinsic thermal conductivity, which agrees well with the experiment measurement. The thermal conductivity of dense samples is lower than that of conventional 6–8 wt.% Y2O3 stabilized ZrO2 (equivalent to 4 mol% Y2O3 stabilized ZrO2, 4YSZ) at room temperature. The coefficient of thermal expansion is higher due to the doping Dy3+ ion compared with that of 4YSZ. The thermochemical compatibility of Dy0.06Y0.072Zr0.868O1.934 with Al2O3 which is critical for the durability of the TBC system has been studied and can be maintained up to 1500 °C

Hot electrons in low-dimensional phonon systems

A simple bulk model of electron-phonon coupling in metals has been surprisingly successful in explaining experiments on metal films that actually involve surface- or other low-dimensional phonons. However, by an exact application of this standard model to a semi-infinite substrate with a free surface, making use of the actual vibrational modes of the substrate, we show that such agreement is fortuitous, and that the model actually predicts a low-temperature crossover from the familiar T^5 temperature dependence to a stronger T^6 log T scaling. Comparison with existing experiments suggests a widespread breakdown of the standard model of electron-phonon thermalization in metals

Regeneration of fertile transgenic indica (group 1) rice plants following microprojectile transformation of embryogenic suspension culture cells

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The Dynamics of Sustained Reentry in a Loop Model with Discrete Gap Junction Resistance

Dynamics of reentry are studied in a one dimensional loop of model cardiac cells with discrete intercellular gap junction resistance ($R$). Each cell is represented by a continuous cable with ionic current given by a modified Beeler-Reuter formulation. For $R$ below a limiting value, propagation is found to change from period-1 to quasi-periodic ($QP$) at a critical loop length ($L_{crit}$) that decreases with $R$. Quasi-periodic reentry exists from $L_{crit}$ to a minimum length ($L_{min}$) that is also shortening with $R$. The decrease of $L_{crit}(R)$ is not a simple scaling, but the bifurcation can still be predicted from the slope of the restitution curve giving the duration of the action potential as a function of the diastolic interval. However, the shape of the restitution curve changes with $R$.Comment: 6 pages, 7 figure