Gasket temperature: an alternate technique for estimating sample temperature in a multi-anvil apparatus

It is common for sample temperatures to be estimated by the power input to the furnace in multi-anvil experiments in which a thermocouple cannot be used or the thermocouple failed during heating. Uncertainties using this technique are often on the order of ±85°C or larger. This paper describes a new method for estimating sample temperature using a second thermocouple outside all pressure media. Temperatures recorded at this external (gasket) thermocouple trend linearly with the internal (sample) thermocouple temperature. Because of thermal lag, it is necessary to determine the first gasket temperature (T₀) corresponding to the desired sample temperature. Accurate prediction of T₀ for the desired sample temperature can come from relatively few (5–6) gasket-temperature measurements made during the initial temperature ramp over a small temperature range (500–600°C). Using this method and manually ramping to T₀ allows for uncertainties in sample temperature estimation as small as ±20°C.     

Electrophysical parameters of variband AlGaAs films made in a temperature gradient

Results are presented on the distributions of the carriers and the hole mobility in undoped Al_zxGa_1–xAs variband films made by zone recrystallization in a temperature gradient on n-GaAs or p-GaAs crystals. It is shown that this method can give a structure of p⁺-n-p type with the n-p junction in the variband layer and a compensated n region.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 63–66, July, 1984.     

Thermoluminescence response as a function of irradiation temperature

Thermoluminescence response at different irradiation temperatures and photon energies has been studied. Analyses of the glow curve and the peak height of TLD 200, 600, 700 and CaSO₄:Dy for irradiations using ⁶⁰Co, ¹³⁷Cs and ²²⁶Ra were made.     

Quantum properties of a bonsonic membrane at nonzero temperature

The thermodynamics of a quasiclassical bosonic membrane is discussed. Based on the S representation, an attempt is made to construct the F representation for the free energy, and a comparison is made with the analogous analysis in field theory. The question of the possibility of dual symmetry of free energy is studied, and a dual-symmetric generalization of the free energy is constructed. The dependence of the Hagedorn temperature on the cutoff parameter is noted.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 66–71, September, 1991.The author is grateful to A. A. Bytsenko and I. M. Likhttsier for discussing a number of subjects.     

Surface acoustic waves in a piezo-electric with a resonant high temperature superconductor planar structure

We have analyzed the propagation of SAW in a periodic planar structure made from a granular high-temperature superconductor formed on the surface of a piezoelectric material. A number of essential features in the properties of the SAW were revealed. In the region of the N-S transition in a band where the Josephson current at the intergranular junctions of the superconductor is dominant the frequency and temperature dependences of the SAW parameters can have a resonant character. An estimate showed that the resonant damping peak can reach 100 dB/cm while the shift ΔV/V of the SAW velocities in the resonance region exceeds 10⁻². The sharp temperature dependences of these parameters allow one to use the effect to make bolometric acoustoelectronic photodetectors and other transducers. Tomsk State Academy for Control Systems and Radio Electronics. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 32–41, August, 1996.     

Simulation of temperature fields in a superconducting microstrip bridge

The temperature distribution in a microstrip bridge made of a high-temperature superconductor (HTSC) as a result of nonuniform heating by a microwave current is analyzed. Differential equations of heat conduction are solved in the one-and two-dimensional approximations. The size of a localized normal region is estimated. Comparative analysis of the results is performed.     

Realization of a flux-driven memtranstor at room temperature

The memtranstor has been proposed to be the fourth fundamental circuit memelement in addition to the memristor,memcapacitor, and meminductor. Here, we demonstrate the memtranstor behavior at room temperature in a device made of the magnetoelectric hexaferrite(Ba_(0.5)Sr_(1.5)Co_2Fe_(11) AlO_(22)) where the electric polarization is tunable by external magnetic field. This device shows a nonlinear q–р relationship with a butterfly-shaped hysteresis loop, in agreement with the anticipated memtranstor behavior. The memtranstor, like other memelements, has a great potential in developing more advanced circuit functionalities.     

Exact finite temperature quantum statistics of single atom electrodynamics in a cavity of arbitrary Q

We report a complete and exact analysis of the steady-state physical properties characterising a single radiating atom in a cavity of arbitrary Q. Solutions are in terms of multitime correlation functions and no approximation is made in terms of Q, temperature, or strength of field-atom coupling g. Results are import also to fundamental concepts of statistical mechanics such as adiabatic following and Markov approximations.     

Fine fluorescence and absorption spectra of hypericin in a polymer matrix at a temperature of 4.2 K

Monochromatic photoexcitation and selective registration in bands of purely electronic S₁↔S₀ transitions resulted in fine fluorescence and absorption (fluorescence excitation) spectra of hypericin in polyvinylbutyral at a temperature of 4.2 K. Vibration analysis of the spectra is done and conclusions are made about the form of many normal vibrations. It is found that the formation of intramolecular hydrogen bonds in the hypericin structure has a substantial effect on the relative position of the electronic vibrational levels of the pigment molecule. Institute of Molecular and Atomic Physics of the National Academy of Sciences of Belarus, 70, F. Skorina ave., Minsk 200072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 4, pp. 539–545, July–August, 1998.     

Line shape in far wings and water vapor absorption in a broad temperature interval

Despite the long-term history of extensive studies on water vapor continuum absorption it can hardly be said that an exhaustive consideration has been given to this problem both from experimental and theoretical viewpoints. For instance, deficiency remains concerning the precise data on the absorption coefficient as a function of temperature, especially at reduced temperatures. New experimental data on water vapor continuum absorption in the 800-1250 cm⁻¹ spectral region at temperatures from 311 to 363 K have become available quite recently [15]. Two advanced variants of the line wing theory - asymptotic and quasistatic - are briefly outlined. The asymptotic line wing theory has been used successfully to describe the absorption coefficient both at elevated temperatures of the Baranov study and at the temperatures of earlier experimental data. Comparison is made with the results obtained from the quasistatic line wing theory.     

Parametric excitation of temperature oscillations in a high-Q dielectric microwave resonator in liquid helium vapor

We study the threshold conditions of the parametric excitation of temperature oscillations using pulsed microwave pumping in three-mode regime for high-Q ferroelectric cryogenic resonators made of SrTiO₃ and KTaO₃. Comparative analysis is performed for the threshold power of the excitation of temperature oscillations and the threshold power of the ponderomotive parametric excitation of acoustic oscillations in the resonator. It is shown that in three-mode regime, temperature oscillations can develop under a rather moderate pump power of about 0.1–8 μW, depending on the combination of interacting temperature and electromagnetic modes. The calculated low threshold powers allow one to apply resonators in practice as high-sensitivity infrared sensors, resonant bolometers, and parametric amplifiers. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 52, No. 2, pp. 172–180, February 2009.     

A cheap and practical FBG temperature sensor utilizing a long-period grating in a photonic crystal fiber

A whole temperature sensor in one package utilizing a fiber Bragg grating (FBG) made in a conventional single-mode fiber and which uses a long-period grating (LPG) made in a photonic crystal fiber is proposed and experimentally demonstrated. The function of the interrogation is that the wavelength change of the FBG with environmental temperature is transferred to the intensity of the output via the LPG. Utilizing the temperature-insensitivity of the LPG in the PCF, the interrogation is stable and enables a cheap and practical temperature measurement system with a wide dynamic range.     

Estimating gas temperature in the channel of a high-temperature jet discharge in air

Consideration is made of determining gas temperature in the channel of a high-frequency jet discharge in air over the intensity distribution of lines for the rotational spectrum band for the transition A² X²II (0-0) in the radiation of hydroxyl. It is shown that the branches R₂ and Q₁ of this band are the most useful for temperature measurements at atmospheric pressure. Within error limits, the temperature in the discharge channel as determined from the lines of the R₂-branch is T_gas = (3120 ± 70) and (3380 ± 90) K in the cross sections of the discharge at a distance of 3 and 30 mm, respectively.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 3–7, February, 1987.     

Semiclassical treatment of induced schwinger processes at a finite temperature

The induced pair production in an external field at a finite temperature is considered. An one-loop correction to the Green’s function of a meson is calculated semiclassically within the framework of a saddle-point analysis of the Schwinger proper time integrals. This correction appears to be exponentially small in terms of an inverse temperature dependence. The low-temperature limit is shown to be in full agreement with previously obtained zero-temperature results. The corrections in the low-temperature limits are estimated up to the leading exponential and preexponential terms. A comparison is made to earlier calculations of the vacuum decay. The text was submitted by the authors in English.     

Simulation parameters of temperature in the process of manufacturing a glass-metal composite

A mathematical model is proposed for solving the problem of the glass cylinder deformation under the action of temperature and pressure in a confined region. Experimental investigations were made to confirm modeling parameters.     

Remote sensing of temperature by a TGS pyroelectric detector

Use of a TGS pyroelectric detector has been made for remote sensing of temperature. Radiant power is measured in terms of electrical quantities. The system is so designed that the ambient conditions do not effect the measurements.     

Dependence of hot carriers temperature on lattice temperature in CdS

Non-equilibrium carrier distributions were obtained in CdS at various temperatures from 77 to 400K. A study is made of the influence of the lattice temperature on the carrier temperature. It is found that the higher the lattice temperature the lower is the difference between carrier and lattice temperatures, though carriers are always thermalized among themselves. The results can be accounted for by carrier relaxation through optical polar phonon emission.     

Nonequilibrium measures which exhibit a temperature gradient: Study of a model

We give some rules to define measures which could describe heat flow in homogeneous crystals. We then study a particular model which is explicitly solvable: the one dimensional nearest neighborhood Ising model. We analyze two cases. In the first one the spins at the two boundaries interact with reservoirs at different temperatures; in the thermodynamical limit the measure we introduce converges locally to Gibbs measures and a temperature profile is so derived. We obtain an explicit expression for the thermal conductivity coefficient which depends on the temperature. In the second case we study the asymptotic behavior starting from an initial state in which each half of the space is at a different temperature. We find again a temperature profile which asymptotically obeys the heat equation with the thermal conductivity coefficient previously derived. From a mathematical point of view, the analysis of the invariant measure is made possible by studying a time-reversed process related to a graphical representation of an associated process. This provides us with an explicit formula for then-fold correlation function and we study the limiting behavior using both this representation (for proving an exchangeability result) and a Donsker-type, spacetime renormalization procedure.Partially supported by CNPq grant No. 402876/79Laboratoire de Recherche Associé au CNRS No. 169     

Oxidation of iron in the vicinity of its Curie temperature

The oxidation kinetics of iron have been investigated in the vicinity of its Curie temperature θ_c = 1043 K using a gravimetric technique. Large differences were found in the oxidation kinetics above and below θ_c. A comparison is made between our results and those previously reported by Measor and Afzulpurkar.     

Superfluid transition temperature in a Fermi gas with repulsion allowing for higher orders of perturbation theory

Higher-order perturbation-theory corrections to the superfluid transition temperature in a weakly nonideal Fermi gas with repulsion are determined. This involves calculating the contribution of third-and fourth-order diagrams in terms of the gas parameter ap _F to the effective interaction which determines the super-fluid transition temperature and also allowing for effects associated with retardation and renormalization of the polar part of the Green’s function. The expressions obtained provide evidence in support of attraction in the effective interaction in the second, third, and fourth orders of perturbation theory. It is shown that the critical temperature is mainly determined by second-and third-order terms of perturbation theory. Calculations are made of the superfluid transition temperature for a gas comprising neutral Fermi particles in a magnetic field. The limits of validity of the theory are analyzed and the possibility of applying the results to dilute solutions of ³He in ⁴He and neutral-particle Fermi gases in magnetic traps is discussed.