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Infrared observations of the interstellar medium have unveiled the existence of numerous solid-phase molecules. The recent detection of uracil within the (162173) Ryugu asteroid has opened new prospects for the discovery of additional compounds, including nitrogenous bases, in the near future. To facilitate the comprehension, identification, and observation of these substances within astrophysical environments, precise measurements of their infrared band strengths are crucial. In this study, we present the outcomes of laboratory experiments conducted to investigate the behavior of adenine at various temperatures. The measured band strength from 3600 to 1970 cm−1 was determined to be 3.21⋅10−16 cm molecule−1. Additionally, as the temperature decreased, its behavior exhibited a well-fitted second-degree polynomial function. Notably, the experiments indicated no permanent phase changes or hysteresis during the cool-down and warm-up processes, further elucidating the thermal properties of adenine. [ABSTRACT FROM AUTHOR]

For CuInP2S6 layered crystal the temperature anomalies of the heat capacity and entropy at the ferrielectric ordering are explained based on the theoretical studies which predict the appearance of a critical endpoint and a bicritical endpoint on the phase diagram. Thus, the splitting of the anomaly of the heat capacity in Ag0.1Cu0.9InP2S6 mixed crystal can be interpreted as a transformation of the ferrielectric first-order phase transition, that is observed for CuInP2S6, into the sequent paraelectric–ferrielectric second-order phase transition and the isostructural first-order transition with a sharp change of the polarization in the ferrielectric phase. [ABSTRACT FROM AUTHOR]

The field dependence of magnetization at T = 4.2 K and in magnetic fields of up to 70 kOe, temperature dependences of magnetization (2 K < T < 300 K), heat capacity (2 K < T < 30 K) and magnetic susceptibility (2 K < T < 1000 K) for Mn1.99Co0.96Al1.05 and Mn1.79Co1.25Al0.96 alloys, closed in composition to the Mn2CoAl spin gapless semiconductor, were studied. Alloys studied were demonstrated to be the band ferromagnets. Their high-field (H > 11 kOe) magnetization is described in the Stoner models with the Rhodes-Wohlfarth parameter pRW = 1.3 for Mn1.99Co0.96Al1.05 and pRW = 2.3 for Mn1.79Co1.25Al0.96. When the composition deviates from the stoichiometric Mn2CoAl, the spontaneous moment decreases slightly, the effective moment, on the contrary, increases. In this case, a negative sign of the temperature-independent component of the paramagnetic susceptibility is observed. The density of states n(EF) at Fermi level and the Debye temperature ΘD of studied alloys have the usual values for 3d-metal alloys. [ABSTRACT FROM AUTHOR]

The Mayer group expansion for solids proposed earlier is applied in prediction of the location of polymorphic phase transition line between the cubic and layered phases of polymeric nitrogen. The comparison with existing measurements revealed that theoretical calculations based on the proposed potential model calibrated on ab initio energy calculations are in agreement with existing experimental data. Predicted location of the polymorphic transition line and specific behavior of thermal properties of both phases in a wide temperature range is discussed. [ABSTRACT FROM AUTHOR]

The observation of the thermoelectric effect, which is the spontaneous electric polarization of a cell with liquid He II during the thermal excitation of standing second-sound waves, has been confirmed [Low Temperature Physics 30, 1321 (2004)]. The relationship of this effect with the thermal and hydrodynamic properties of He II is studied in detail in the temperature range of 1.4 K < T < 2 K. It is established that the dependence of the amplitude of electric potential oscillations on the excitation intensity changes significantly during the thermal vibrations' transition from the laminar to the turbulent regime. The threshold value of the excitation power w = w0 (T) is recorded: in the region w < w0, the potential oscillations are regular and their amplitude increases in proportion to the power; at w > w0, the electric response becomes random in nature as the fluctuations increase and the amplitude decreases to zero, with a peculiar electromagnetic "noise" being observed. The experimental results are compared with the conclusions drawn from the theory of flexoelectric polarization of liquid helium. The polarization of liquid helium upon excitation of the first-sound waves, as well as pressure and temperature shock waves, has also been discussed. [ABSTRACT FROM AUTHOR]

A model of a one-dimensional nonideal gas in an external transverse force field is used to interpret the experimentally observed thermodynamic properties of xenon deposited in grooves on the surface of carbon nanobundles. A nonideal gas model with pairwise interactions is not entirely adequate for describing dense adsorbates (at low temperatures), but makes it easy to account for the exchange of particles between the 1D adsorbate and the 3D atmosphere, which is an important factor at intermediate (on the order of 35K for xenon) and, especially, high (∼100 K) temperatures. In this paper, we examine a 1D real gas taking only the one-dimensional Lennard-Jones interaction into account, but under exact equilibrium with respect to the number of particles between the 1D adsorbate and the 3D atmosphere of the measurement cell. The low-temperature branch of the specific heat is fitted independently by an elastic chain model so as to obtain the best agreement between theory and experiment over the widest possible region, beginning at zero temperature. The gas approximation sets in after temperatures for which the phonon specific heat of the chain essentially transforms to a one-dimensional equipartition law. Here the basic parameters of both models can be chosen so that the heat capacity C(T) of the chain transforms essentially continuously into the corresponding curve for the gas approximation. Thus, it can be expected that an adequate interpretation of the real temperature dependences of the specific heat of low-dimensionality atomic adsorbates can be obtained through a reasonable combination of the phonon and gas approximations. The main parameters of the gas approximation (such as the desorption energy) obtained by fitting the theory to experiments on the specific heat of xenon correlate well with published data.VC [ABSTRACT FROM AUTHOR]

The thermal conductivity of three single crystal samples of n-type gallium nitride with electron densities of 4.0 × 1016, 2.6 × 1018, and 1.1 × 1020 cm-3 has been determined in the temperature range 4-320K. The measurements were carried out within the ab plane using the stationary method. The thermal conductivity depends strongly on the donor concentration. The analysis within the Callaway approach and the Debye model shows a significant influence of phonon-electron scattering on the thermal conductivity of the samples. In addition, some preliminary results obtained along the c axes of GaN layered samples are presented. The latter measurements have been carried out using the 3ω method. [ABSTRACT FROM AUTHOR]

Creep in solid 4He at temperatures of ~100-1000 mK is studied experimentally by detecting the flow of helium through a frozen porous membrane under a constant external force. Creep curves are measured for different temperatures and mechanical stresses. This method has made it possible to detect low creep rates in helium down to the lowest temperatures in these experiments. It is found that throughout this temperature range, creep is thermally activated and the activation energy decreases with falling temperature and increasing mechanical stress. An analysis shows that for temperatures above ≈500 mK, Nabarro-Herring diffusive creep takes place in solid helium with mass transfer by self diffusion of atoms and a counterflow of vacancies. The experimental data have been used to obtain the self-diffusion coefficient as a function of temperature for different stresses. At temperatures below ≈500 mK creep takes place at a very low flow rate (~10-13 cm/s) and a very low activation energy (~0.5-0.7 K), while the creep mechanism remains unclear. [ABSTRACT FROM AUTHOR]

A reduction in the transmission of terahertz radiation through a periodically modulated slab of layered superconductor owing to diffraction of the incident wave and resonance excitation of eigenmodes is predicted and studied theoretically. The slab thickness is assumed to be much less than the skin depth and when there is no modulation the slab transmission is close to unity. [ABSTRACT FROM AUTHOR]

The effect of combined deformation, including equal-channel multiangle pressing (ECMAP), lowtemperature (77 K) drawing, and thermal processing, on the critical current density of superconducting wires based on Nb-Ti alloys is investigated. Reasonable parameters are established for deformation-thermal processing of NT-50 alloy using ECMAP that will ensure improved functionality of superconductors based on this alloy. Vortex pinning on structural inhomogeneities of these alloys is analyzed qualitatively. [ABSTRACT FROM AUTHOR]

Polycrystalline samples of fullerite C60 with different concentrations of molecular nitrogen impurity are studied by luminescence spectroscopy at temperatures of 20-230 K. The photoluminescence characteristics of the C60-N2 solutions vary significantly. At T = 20 K there is a significant contribution to the luminescence from emission centers ("deep X-traps") determined by the concentration of N2 molecules in octahedral voids of the fcc C60 lattice. The experimentally observed differences in the effect of nitrogen impurities on the structural and luminescence characteristics of C60-N2 solutions show that the filling of the lattice voids into the depth (from the surface) of the samples is substantially inhomogeneous. The temperature dependences of the integrated emission intensity from samples with different nitrogen concentrations are studied. N2 molecules are found to have little effect on the formation of fullerite orientational glass. A tendency for the vitrification temperature of these C60-N2 solutions to fall with increasing impurity concentration is observed experimentally. [ABSTRACT FROM AUTHOR]

Polycrystalline samples of fullerite C60 with different concentrations of molecular nitrogen impurity are studied by luminescence spectroscopy at temperatures of 20-230 K. The photoluminescence characteristics of the C60-N2 solutions vary significantly. At T = 20 K there is a significant contribution to the luminescence from emission centers ("deep X-traps") determined by the concentration of N2 molecules in octahedral voids of the fcc C60 lattice. The experimentally observed differences in the effect of nitrogen impurities on the structural and luminescence characteristics of C60-N2 solutions show that the filling of the lattice voids into the depth (from the surface) of the samples is substantially inhomogeneous. The temperature dependences of the integrated emission intensity from samples with different nitrogen concentrations are studied. N2 molecules are found to have little effect on the formation of fullerite orientational glass. A tendency for the vitrification temperature of these C60-N2 solutions to fall with increasing impurity concentration is observed experimentally. [ABSTRACT FROM AUTHOR]