The heat of hydration of the proton in the gas and liquid phases

The literature data on the experimental heats of hydration in the sequential addition of water molecules to the proton in the gas phase and the integral heat of solution of the proton in water are analyzed. The integral heat of hydration of the proton in the gas phase was found to exceed the heat of solution of the proton in water by no less than 40.1 kcal/mol. The suggestion was made that this energy was spent for the rearrangement of the system of H-bonds in water caused by the solution of the proton.     

Specific heat studies on Ru substituted FeSi Kondo Insulator

The temperature dependent specific heat studies of a Ru substituted Fe_1−xRu_xSi Kondo Insulating system has been carried out in the 77 to 300 K range. The specific heat has been analyzed based on contributions from an electronic part and a lattice part. For the electronic part a Gaussian density of states model, which incorporates the effect of correlation, band structure and disorder in its defining parameters is used. The lattice part of specific heat is described in the Debye model. Parameters that define the electronic density of states and the Debye temperature are extracted from fits of the temperature dependent specific heat data and are compared with earlier resistivity measurements that employed a similar analysis.     

Specific heat of delta-Pu stabilized by Am

Detailed specific heat C(p) measurements of delta-Pu stabilized by Am (8%-20%) were performed in the temperature range 4.5-300 K. The coefficient of the electronic specific heat gamma, which reflects the quasiparticle density of states at the Fermi level E(F), is smaller than originally assumed and, depending on the estimate of phonon contributions, a value between 35 and 55 mJ/mol K2 can be deduced for Pu-8% Am. For higher Am concentrations, which expand the lattice, gamma decreases slightly with the Am content. An applied magnetic field of 9 T had no effect on C(p). The results strongly suggest that itinerant 5f states at E(F) are not appropriate for describing delta-Pu.     

Surface and quantum-size effects on the specific heat of layered and nonlayered nanotubes

A detailed analysis of room temperature specific heat of unrelaxed layered and nonlayered nanotubes is presented. Our results exhibit a close interplay between surface and quantization contributions of specific heat, i.e. C_surface and C_quantum. The calculated specific heat of single-layer and multi-layer layered nanotubes increases with diameter regardless of the species. However, slowly increasing C_quantum and rapidly decreasing C_surface with diameter result in the decrease of specific heat of nonlayered nanotubes. Moreover, our theoretical results are compared with experimental observation and physical mechanisms are discussed. These results imply that the existence of surface in nonlayered nanotubes has an important influence on specific heat.     

A study of the structural and thermodynamic properties of water by the molecular dynamics method

The thermodynamic and structural properties of four rigid water models were studied by the molecular dynamics method over a wide temperature range. Two three-center (SPC/E and TIP3P) and two five-center (ST4 and TIP5P) models were considered. The results discussed include the boiling and condensation temperatures, VT phase transition diagrams, three-dimensional spatial distributions of atoms, the temperature dependences of the total energy, density, heat capacity, the number of H-bonds per molecule, the distribution of H-bonds over the ∠HOO angle, the self-diffusion coefficient, and the radial distribution functions. The boiling points of all the models did not correspond to 100°C and were noticeably different from each other. The condensation points were also different. The data on the structural parameters led us to conclude that the TIP5P model reproduced the local structure of water most correctly. However, if the reproduction of the local structure is not a necessary condition, less resource consuming three-center models can be used.     

Magnetische Suszeptibilität von Chrom und Chrom-Legierungen

The magnetic susceptibility of chromium and b.c.c. binary alloys of Cr-Re, Cr-Ru, Cr-Os, Cr-Mo and Cr-W has been measured in the temperature range of 4,2°K to 700°K. These alloys exhibit a reduced spin susceptibility in the antiferromagnetic state. The comparison of the results with the electronic specific heat of the same samples yields an estimate of the different contributions to the susceptibility and of the influence of electron interactions.     

The Bellamy relationship and the nature of the H-bond. Heteroassociates of alcohols

IR spectroscopic data are used to demonstrate that the donor ability of alcohols in H-bonds is determined by the molecular conformation and the universal interaction of subunits of the H-bond complex in homological series. The observed regularities can be employed for empirical separation of the contributions of electrostatic and covalent components in the formation energy of the H-complex.     

Heat Capacity of Erbium-Doped Gallium-Gadolinium Garnet

In this paper, we compared the results of a heat capacity study of an erbium-doped gallium gadolinium garnet crystal with data for an undoped garnet. The measurements were carried out in the temperature range from 1.9 to 220 K and in magnetic fields from 0 to 9 T. The temperature dependences of the specific heat were interpreted with allowance for the Schottky contributions due to the Gd³⁺ and Er³⁺ ions and the contributions of the thermal vibrations of the crystal lattice. The values of entropy and magnetic entropy are calculated.     

Effect of electrostatics techniques on the estimation of thermal conductivity via equilibrium molecular dynamics simulation: application to methane hydrate

Equilibrium molecular dynamics (MD) simulations for three system sizes of fully occupied methane hydrate have been performed at around 265 K to estimate the thermal conductivity using the Ewald, Lekner, reaction field, shifted-force and undamped Fennell–Gezelter methods. The TIP4P water model was used in conjunction with a fully atomistic methane potential with which it had been parameterized from quantum simulation. The thermal conductivity was evaluated by integration of the heat flux autocorrelation function (ACF) derived from the Green–Kubo formalism; this approach vas validated by estimation of the average phonon mean free path. The thermal conductivities predicted by non-periodic techniques were in reasonable agreement with the experimental results of 0.62 and 0.68 W/m K, although it was found that the estimates by the non-periodic techniques were up to 25% larger than those of Lekner and Ewald estimates, particularly for larger systems. The results for the Lekner method exhibited the least variation with respect to system size. A decomposition of the heat flux vector into its respective contributions revealed the importance of electrostatic interactions, and how different electrostatic treatments affect the contribution to the thermal conductivity.     

聚苯胺的低温比热研究

测量了聚苯胺的中间氧化态以及掺杂盐酸后的样品在1.8至45K范围内的比热，比热数据可以用非晶态和晶态两部分的贡献来解释.利用声子-分形子模型成功地解释了低温下比热高于德拜理论趋势的反常现象.从本文的实验数据来看，没有观察到电子对比热容的贡献. 关键词： 低温比热 聚苯胺 分形     

Calorimetric investigation of electronic and lattice excitations of the icosahedral quasicrystal in the range of moderate temperatures

The precise measurements of the specific heat and the linear expansion coefficient of polygrain samples of the ordered icosahedral phase Al₆₃Cu₂₅Fe₁₂ have been performed in the temperature range 1.8–400.0 K. The deviations from the Grüneisen law, according to which the temperature dependences of the lattice specific heat at constant volume and the linear expansion coefficient are identical to each other, have been analyzed. The proofs that the specific heat of the quasicrystals contains latent electronic and lattice contributions of the Schottky type have been obtained. The revealed contributions can be thermodynamic consequences of the fractal energy spectra.     

硅藻土表面羟基的漫反射红外光谱(DRIFT)研究

运用傅里叶变换漫反射红外光谱（DRIFT）及氘化技术,研究了硅藻土的表面羟基结构及其在热处理中的变化。     

INFLUENCE OF RELATIVE DENSITY AND PARTICLE SIZE ON THE SPECIFIC HEAT OF NANOCRYSTALLINE IRON

The specific heats of two nanocrystalline iron samples with different structures have been measured in the temperature range from 2 to 26 K. Experimental results show that the specific heat of nanocrystalline iron samples exhibits abnormal characteristic compared with that of standard bulk iron. The contributions of quantum size effect, surface mode and Einstein mode have been observed in the measurement. Through analyses, it is discovered that the relative density and particle size have a great influence on specific heat of nanocrystalline iron at low temperature.     

燃料电池中质子交换膜干涸的热物理机制

本文首次应用有内热源的多孔介质中流体流动与换热理论,对直接甲醇燃料电池中PEM中的传热过程和干涸 现象进行定量研究。建立了相应的数学物理模型并进行了数值求解。计算结果表明:反映水的热容量和膜的内部产热量的 两个无因次参数D和N是影响PEM中传热的主要因素;水的质量流率小和电流密度过高是造成膜干涸的主要原因。     

评估固体激光器对流换热系数的方法

 为提高固体激光器的热管理效果,提出了一种使用316L不锈钢片代替激光晶体评估固体激光器表面对流换热系数的方法。在低冷却水温的条件下,使用快响应热电偶对替代片和出口水流的动态温度进行测量,应用有限元方法计算不同对流换热系数下替代片的动态温度,讨论了对流换热系数对重频大能量激光器热效应的影响。通过寻找测量值和计算值的最小方差,得到该冷却结构下的激光器表面对流换热系数为3 500 W·m^-2·K^-1。     

Mechanism of formation of simple optical structures in nonlinear fizeau interferometry

Explanations are suggested for the specific shapes of simple structures, generated in nonlinear interferometry. This is done within the mathematical model of dynamics of nonlinear phase clamping, developed by A. S. Akhmanov and M. A. Vorontsov. The basis of the analysis is an estimate of the contributions of diffusion and relaxation effects, as well as that of the Kerr effect, to the rates of phase dynamics.Tomsk State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 77–81, June, 1995.     

Water-proton-spin-lattice-relaxation dispersion of paramagnetic protein solutions

The paramagnetic contributions to water-proton-spin-lattice relaxation rate constants in protein systems spin-labeled with nitroxide radicals were re-examined. As noted by others, the strength of the dipolar coupling between water protons and the protein-bound nitroxide radical often appears to be larger than physically reasonable when the relaxation is assumed to be controlled by 3-dimensional diffusive processes in the vicinity of the spin label. We examine the effects of the surface in biasing the diffusive exploration of the radical region and derive a relaxation model that incorporates 2-dimensional dynamics at the interfacial layer. However, we find that the local 2-dimensional dynamics changes the shape of the relaxation dispersion profile but does not necessarily reproduce the low-field relaxation efficiency found by experiment. We examine the contributions of long-range dipolar couplings between the paramagnetic center and protein-bound-water molecules and find that the contributions from these several long range couplings may be competitive with translational contributions because the correlation time for global rotation of the protein is approximately 1000 times longer than that for the diffusive motion of water at the interfacial region. As a result the electron-proton dipolar coupling to rare protein-bound-water-molecule protons may be significant for protein systems that accommodate long-lived-water molecules. Although the estimate of local diffusion coefficients is not seriously compromised because it derives from the Larmor frequency dependence, these several contributions confound efforts to fit relaxation data quantitatively with unique models.     

Heat conduction in highly oriented polyethylene

The variety of structures found in polymers makes it impossible to thoroughly understand all the mechanisms affecting heat conduction. With the example of polyethylene it is shown that highly oriented polymers can be treated as strong anisotropic continua in the defect scattering limit. Using direction dependent sound velocities from Brillouin scattering we find elastic contributions to be dominated by the angular dependence of the phonon density. The direction dependence of the specific heat contributions is accounted for by using the Debye formalism inq-space. The cut off wave vector is determined by fitting the low temperature specific heat. The resulting relaxation lengths turn out to be largely temperature independent in agreement with the assumption of predominant structure scattering. At 8 K<T<40 K a minimum in the relaxation length parallel to the chain molecules indicates resonance scattering by local modes. They have been identified as the so called longitudinal acoustic eigenmodes (LA-modes) of the very small crystals.     

Static properties of two-component kink in a non-linear discrete polarizability model

We study analytically, in the low-velocity regime, the static properties of two-component kink in a discrete polarizability model with a quartic electron–ion interaction in one ionic species. Using a discretized Hamiltonian formalism, we derive the exact equations of motion for the two-component kink centre of the mass X(t) and coupled field variables. Numerical analysis is performed to estimate the amplitude of the dressing and its effects on the static properties of the discrete lattice for the potassium selenate (K₂SeO₄) at T=40 K. We find that dressing has important effects on dynamical quantities such as the pinning frequency and the depth of the Peierls–Nabarro potential. Two-component kink contributions to the specific heat have been also analysed both in the continuum and the discrete limits.