Phonons, electrons and thermal transport in Planckian high Tc materials

The room-temperature thermal diffusivity of high Tc materials is dominated by phonons. This allows the scattering of phonons by electrons to be discerned. We argue that the measured strength of this scattering suggests a converse Planckian scattering of electrons by phonons across the room-temperature phase diagram of these materials. Consistent with this conclusion, the temperature derivative of the resistivity of strongly overdoped cuprates is noted to show a kink at a little below 200 K that we argue should be understood as the onset of a high-temperature Planckian T-linear scattering of electrons by classical phonons. This kink continuously disappears toward optimal doping, even while strong scattering of phonons by electrons remains visible in the thermal diffusivity, sharpening the long-standing puzzle of the lack of a feature in the T-linear resistivity at optimal doping associated with the onset of phonon scattering.

Advanced method for determining the steady temperature and constant heating time of electric apparatus

The article proposes an improvement in the method for determining the steady-state heating temperature of current-carrying parts of an electrical apparatus and its time constant in the case of real measurements of temperature values made with some error. In accordance with the specified method, at a known ambient temperature, the apparatus is turned on with the measurement of its heating temperature at regular intervals; based on the measurement data, a graph of the temperature derivative is plotted over time; according to the data of the graph, the steady-state temperature and the constant heating time are determined. It is shown that inaccuracies in temperature measurement can significantly distort the dependences obtained for determining the time constant and the steady-state heating temperature, and for a correct estimation of the parameters, the form of the approximating function of the temperature derivative with respect to time must be known a priori - a linear function. This method can significantly reduce the time for testing electrical devices for heating in continuous operation. This method is illustrated by the example of determining the heating of the coil over time by measuring the active resistance. On the basis of the obtained and processed experimental data, the power overload coefficients are also determined in the long-term operation mode, as well as in the short-term and intermittent modes, which makes it possible to correctly operate the electrical apparatus.

Adsorption of Toxic Indigo Carmen Dyestuff from Aqueous Solution by Chitosan and Chitosan Phthalate

Toxic indigo carmen dyestuff was removed from the aqueous solution by adsorption. Adsorption was examined kinetically and thermodynamically based on temperature. Derivative of chitosan which is called chitosan phthalate was synthesized and used in removal of indigo carmen from aqueous solution. Some kinetic and thermodynamic parameters were calculated. Adsorption isotherms were drawn. Lastly, the adsorption of indigo carmen from the aqueous solution by chitosan and chitosan phthalate were compared.

On the Heat Capacity of a Quasi-Two-Dimensional Electron Gas

Numerical and analytical results of the investigation of the thermodynamic properties of a quasi-2D electron gas are presented. The density of states, the temperature derivative of the chemical potential, and the heat capacity of the gas at the resonance points and away from it are analyzed. It is shown that, in the dependence of the heat capacity on the chemical potential, there are additional steps at the resonance points. The width of the additional steps increases with temperature. With the increase in temperature, when the main steps are practically blurred, there are still visible marks from the additional steps.

Fluctuation induced magneto-conductivity of Y3Ba5Cu8O18±x and YBa2Cu3O7−d

A comparative study of the fluctuation magneto-conductivity in [Formula: see text] (noted [Formula: see text]) and [Formula: see text] (noted [Formula: see text]) polycrystalline samples was carried out. Samples were synthesized in oxygen atmosphere using a standard solid state reaction technique. Phases and microstructure have been systematically investigated using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The magneto-conductivity was measured in a magnetic field ranging from 0 T to 7 T applied perpendicular to the current path direction. The magneto-conductivity data were analyzed in terms of the temperature derivative of the resistivity and the logarithmic temperature derivative of the conductivity [Formula: see text], where [Formula: see text] is the fluctuation conductivity. Analyses of the magneto-conductivity data reveal that [Formula: see text] possesses a better quality of intrinsic Josephson junction compared to [Formula: see text] one while in the former one the depression in superconducting temperature is more pronounced. The applied magnetic field narrowed substantially the three dimensions (3D) Gaussian regime and for [Formula: see text] sample this regime is vanished for high magnetic field ([Formula: see text][Formula: see text]1 T). Results are discussed in relation with the difference in the structure and microstructure [Formula: see text] and [Formula: see text]. The upper critical and the irreversibility magnetic fields were estimated and were found to be higher in the [Formula: see text] sample.