Thermodynamic Properties Of Ca Research Articles

Thermodynamic evaluation and optimization of the Ca−Si system

All available phase equilibria and thermodynamic data for the Ca−Si system were collected and critically evaluated. In a first step, the thermodynamic properties of Ca(g) were obtained from experimental vapor pressure data over pure Ca. The new vapor pressure of calcium over pure solid and liquid was used as a new reference to model the thermodynamic properties of the intermediate stoichiometric Ca−Si compounds together with other thermodynamic and phase diagram data found in the literature (liquidus temperatures, heat capacities, pressures of Ca, and heats of reaction). Optimization was performed to obtain the parameters of one set of model equations for the different solid and liquid phases to best reproduce all the experimental data simultaneously. In this way, the data are rendered self-consistent, discrepancies among the data are identified, and extrapolations and interpolations can be performed. For the liquid phase, the Modified Quasichemical Model in the Pair Approximation for short-range ordering was used.

Thermodynamic properties of [formula omitted] in magnetic fields

We have studied the influence of a magnetic field on the thermodynamic properties of Ca 2 - x Sr x RuO 4 in the intermediate metallic region with tilt and rotational distortions ( 0.2 ⩽ x ⩽ 0.5 ) . We find strong and anisotropic thermal expansion anomalies at low temperatures, which are suppressed and even reversed by a magnetic field. The metamagnetic transition of Ca 1.8 Sr 0.2 RuO 4 is accompanied by a large magnetostriction. Furthermore, we observe a strong magnetic-field dependence of c p / T and that can be explained by magnetic fluctuations.

Temperature Dependence and Thermodynamic Properties of Ca 2+ Sparks in Rat Cardiomyocytes

To elucidate the temperature dependence and underlying thermodynamic determinants of the elementary Ca 2+ release from the sarcoplasmic reticulum, we characterized Ca 2+ sparks originating from ryanodine receptors (RyRs) in rat cardiomyocytes over a wide range of temperature. From 35°C to 10°C, the normalized fluo-3 fluorescence of Ca 2+ sparks decreased monotonically, but the Δ[Ca 2+] i were relatively unchanged due to increased resting [Ca 2+] i. The time-to-peak of Ca 2+ sparks, which represents the RyR Ca 2+ release duration, was prolonged by 37% from 35°C to 10°C. An Arrhenius plot of the data identified a jump of apparent activation energy from 5.2 to 14.6 kJ/mol at 24.8°C, which presumably reflects a transition of sarcoplasmic reticulum lipids. Thermodynamic analysis of the decay kinetics showed that active transport plays little role in early recovery but a significant role in late recovery of local Ca 2+ concentration. These results provided a basis for quantitative interpretation of intracellular Ca 2+ signaling under various thermal conditions. The relative temperature insensitivity above the transitional 25°C led to the notion that Ca 2+ sparks measured at a “warm room” temperature are basically acceptable in elucidating mammalian heart function.