Anomalies In Temperature Dependence Research Articles

Interaction of carriers with soft ferroelectric mode and temperature dependence of conductivity

Comparative role is discussed of various interactions leading to the anomaly of temperature dependence of electrical conductivity near ferroelectric phase transition. For the first time, spin dependent interaction of carriers with the soft mode is taken into account and is shown to be of importance for interpretation of some experimental data.

Ultrasound absorption near the critical point of SO2+CCl4liquid mixtures

Ultrasonic absorption and velocity have been measured in several liquid mixtures of S${\mathrm{O}}_{2}$ + C${\mathrm{Cl}}_{4}$. Special emphasis was given to the homogeneous-solution region near the critical mixing point. Near the critical point it was found that high absorption and strong frequency dependence were characteristic of the ultrasound, unlike its behavior outside of the critical region. The frequency dependence of the absorption measurements near the critical point and along the critical isochore can be satisfactorily fit with the Kawasaki multiple-relaxation calculation by the adjustment of three fit parameters. Near the critical point the background absorption was found to be independent of frequency over the range of investigation (2 to 66 MHz). Including an adjustable single-relaxation term in the absorption fit indicated that the best fit was obtained as the amplitude of the single-relaxation term went to zero. The characteristic-frequency and amplitude parameters, taken from fits of the Kawasaki calculation to the data nearest the critical point, were scaled in reduced temperature. The characteristic-frequency data are consistent with a scaling exponent of 1.89\ifmmode\pm\else\textpm\fi{}1 if a critical temperature is chosen for the scaling that is slightly lower than the observed phase separation temperature, i.e., if the presence of a pseudospindodal curve is assumed. This is the exponent value that is predicted by the mode-mode coupling and Ising lattice-gas theories. Neither dispersion nor temperature-dependent anomalies were observed for the ultrasonic velocity.

Surface magnetism in 3He: Thermodynamics

A phenomenological formulation of the enhancement of the susceptibility of liquid 3He in contact with a dielectric surface is presented. The effective Hamiltonian includes a surface term consisting of both the quadratic and the quartic dependence on the surface order parameter. The partition function for this system is calculated using a novel application of the transfer matrix methods. We find a susceptibility that contains the Curie-Weiss-like surface contribution as well as the appropriate field dependence in agreement with experiments. In addition, we find a weak temperature-dependent anomaly in specific heat as well.

Normal and superconducting properties ofCsxWO3

The resistivity, Seebeck coefficient, superconducting transition temperature, and upper critical field have been measured in Cs/sub x/WO/sub 3/ for 0.19< or =x< or =0.30. In contrast to Rb/sub x/WO/sub 3/, no temperature-dependent anomalies were observed in either the normal resistivity or the Seebeck coefficient. The superconducting transition temperature, T/sub c/, increases monotonically with decreasing x from 2 K at x = 0.30 up to 6.7 K at x=0.20, with an inflection near 0.24. The resistivity as a function of x increases monotonically with decreasing x and also has an inflection near x=0.24.

Conduction properties of the hexagonal tungsten bronze,RbxWO3

Studies of the electrical transport properties---resistivity, Hall effect, and Seebeck coefficient---of the hexagonal tungsten bronze ${\mathrm{Rb}}_{x}\mathrm{W}{\mathrm{O}}_{3}$ for $0.16l~xl~0.33$ are reported for the temperature range from 1.5 to 300 K. In the normal state, these properties show temperature-dependent anomalies which suggest a phase transition with temperature. The temperature at which this transition occurs is shown to depend on the Rb concentration, exhibiting a sharp maximum near $x=0.25$. As the Rb concentration is decreased below $x=0.33$ the superconducting transition temperature first increases above the value of 1.94 K at $x=0.33$ and then decreases to less than 1 K at $x=0.24$. As the Rb concentration is lowered further a second increase in ${T}_{c}$ is observed. This behavior appears to be associated with a phase transition at a composition near $x=0.25$. The nature of neither the transition with temperature nor the transition with concentration could be precisely determined. The superconducting state shows a large temperature-independent 60\ifmmode^\circ\else\textdegree\fi{} anisotropy in ${H}_{c2}$ in the plane perpendicular to the hexagonal axis and positive curvature in the temperature dependence of ${H}_{c2}$ near ${T}_{c}$.

Raman spectroscopic studies of temperature dependent anomalies of strontium, barium, lead, and calcium nitrate

Raman studies of normal and 18O-substituted Sr(NO 3) 2 have been performed over a range of temperatures (77 to 580°K) to investigate the anomalous component previously observed in the symmetric stretching region. The results suggest that the peak may have a hot band origin. Impurity ions, N 18O 16O − 2 and vibrationally excited ∗NO − 3 ions, give rise to local modes (deep-well impurity centers) in the ν 1 and ν 4 (N 18O 16O − 2 only) regions but delocalized modes (shallow-well impurity centers) in the other internal and external mode regions. The host lattice was able to tolerate a large fraction of this type of impurity without interference with the dynamical coupling. Anomalous properties previously reported appear to be due to freezing out of the hot band. A less complete study of Ca(NO 3) 2, Ba(NO 3) 2 at room temperature and at temperature near 500°K suggests behavior similar to Sr(NO 3) 2.

Temperature dependent anomalies of dielectric properties of naturally disordered photoconductive lead oxides

Polarizing processes in lead monoxide were investigated. Certain anomalies were discovered in the temperature dependence of the permittivity and tg fi in the high temperature region near the phase transition. At low temperatures, in addition to these anomalies, intrinsic unipolar pyrocurrents were noted. The crystallographic structure analysis of the PbO modifications was investigated. Some space symmetry groups referred to lead monoxide are characteristic of ferroelectrics semiconductors. As a result of the experimental data analysis, it can be assumed that there is the probability of the formation of a ferroelectric situation in lead monoxide.

溶融金2元合金系におけるスズの活量

Activities of tin in liquid gold-tin alloys have been determined for NSn=0.17∼0.90, over the temperature range of 944∼1256 K, by the following E.M.F. method:(This article is not displayable. Please see full text pdf.) The activities of both components for the Au-Sn system demonstrate a considerable negative deviation from Raoult’s law over the whole concentration range.In the alloys with NSn=0.30∼0.80, there are remarkable variations in partial enthalpy and entropy of tin with temperature, as discussed with reference to previous investigations. The reason for this is considered to be due to the ordered structure of the alloy which persists above the liquidus temperature.These strongly temperature dependent anomalies are explained by the existence of AuSn, AuSn2, AuSn4-compound clusters in the melt.With increasing temperature the clusters dissociate and the anomalies disappear. The effects of compound cluster formation in liquid alloys on thermodynamic properties are discussed.In addition, other thermodynamic functions are calculated on the basis of the results obtained.

The Anomaly in Temperature Dependence of the Yield Stress of Silver Base Solid Solutions

The Anomaly in Temperature Dependence of the Yield Stress of Silver Base Solid Solutions

The Anomalies in Temperature Dependence of the Yield Stress of Cu Base Solid Solutions

Yield stress of Cu and Cu base solid solutions is measured from room temperature down to 1.6 K. Two kinds of anomalous behavior of the yield stress of the solid solutions are observed below 50 and 10 K. From theoretical considerations, these anomalies are attributed to dynamical motion of dislocation and to dynamical production of point defects due to climb motion of the dislocation, respectively. Hysteresis behavior of the temperature dependence of the yield stress, which is due to the dynamically produced point defects, is observed in very low temperature region. Criterion for applicability of chemical rate process to the motion of dislocation is discussed.

Thermal Conductivity, Anomaly in Temperature-dependence for Liquids

Most empirical equations express the thermal conductivity of normal simple liquids as linear functions of temperature. The majority of measurements to date, except water, support such a description. Very precise new measurements on toluene over the complete liquid range at 1 atm (0.299 &lt; Tr &lt; 0.645) show a substantial pre-freezing anomaly. At the freezing point (tf) there is a depression of the expected conductivity of 7.9 × 10−3 W/m °K. This tf behavior is attributed to cluster formation.

Temperature-dependent anomalies in the growth of microorganims.

Davey, C. B. (North Carolina State University, Raleigh), Raymond J. Miller, and Larry A. Nelson. Temperature-dependent anomalies in the growth of microorganisms. J. Bacteriol. 91:1827-1830. 1966.-Water in the liquid phase (0 to 100 C) has been shown, by others, to undergo subtle changes in its physical structure at approximately 15, 30, 45, and 60 C. It has been suggested that these temperature-dependent anomalies in the structure of water may have biological implications. After incubation in a polythermostat, direct cell counts were made to determine temperature-growth interactions for the four bacteria which were used to cover the temperature range from 5 to 70 C: Pseudomonas fragi, 5 to 25 C; Streptococcus faecalis, 20 to 40 C; Bacillus coagulans, 35 to 55 C; and B. stearothermophilus 1518 smooth, 50 to 70 C. In all cases, growth was suppressed at the predicted temperatures, suggesting a strong interaction between the structure of water and biological activity.

ポリビニルアルコールの部分および高度フォルマール化物の応力緩和挙動

The stress relaxation behavior of partly to highly formalized polyvinyl alcohol polymers has been investigated over ranges of time scale from 10 to 7000 seconds and of temperature from 80 to 160°C, in order to obtain informations about the effects of succesive changes in the polymer structure from quasi-crystalline to amorphous state upon the temperature dependence of the relaxation processes.The results obtained are summerized as follows:(1) The so-called master relaxation curve can be composed without difficulty from relaxation curves at various temperatures by using the ordinary time-temperature superposition method, but the temperature dependence of the shift factor log aT above the glass transition temperature is no longer expressed by the simple WLF equation, but by a combination of at least two WLF type equations.(2) The temperature dependence of the apparent activation energy for the relaxation process evaluated from the shift factor shows not only an extreme maximum at the glass transition temperature as observed for many other amorphous polymers, but also another small maximum at the higher temperature than Tg. With the increase of the degree of formalization, the temperature becomes higher while the maximum activation energy (ΔHa)max at becomes smaller except for an unusually large (ΔHa)max for PVF-80. The existence of the small maximum, which disappears with increasing degree of formalization, corresponds to that of the second temperature dispersion of the dynamic modulus which is observed at a temperature Tg2 higher than the glass transition temperature Tg under a constant frequency of 3×10-3 cps.The anomaly of the temperature dependence of the shift factor revolting from the simple WLF equation correlates with the existences of the small maximum on the apparent activation energy and of the second temperature dispersion on the dynamic modulus and may suggest the existence of another type of relaxation process.(3) The relaxation spectrum for each polymer has been obtained from the master curve by using the customary method of Swarzl-Staverman's 2nd approximation. With decreasing degree of formalization the relaxation spectrum at a reference temperature of 110°C not only shifts to shorter times but also changes the shape systematically in such a way as decreasing the slope of the wedge portion, increasing the height as well as the width of the box portion and revealing a new bump in the middle of the wedge portion. The new bump may correlate with the anomaly of temperature dependence of the shift factor due to the existence of another type of relaxation process mentioned above. It is hoped that the new bump is separated from the apparent relaxation spectrum.