Thermometry Method Research Articles

Primary state standard of the temperature in the range from 0 to 3200 °С, GET 34-2020: practical implementation of the new definition of kelvin

The article considers the necessity of ways of modernization the Primary standard of the temperature GET 34-2007. Special attention is paid to the transition to a new definition of kelvin. Taking into account that the new definition of kelvin does not directly affect the status of the current international temperature scales ITS-90 and PLTS-2000, but there are significant advantages for measuring thermodynamic temperatures below 20 K and above ~1300 K, the main focus of the modernization of the GET 34-2007 in the range from 273.15 K to 1235 K was focused on improving the methods and means of implementing the International Temperature Scale ITS-90. As part of the modernization of the Primary standard in the range above 1235 K, a set of equipment has been created that allows the reproduction of kelvin in accordance with its new definition by two methods recommended by the Consultative Committee: the method of absolute primary radiometric thermometry and the method of relative primary radiometric thermometry. The basic principles of the implementation of these methods, composition and metrological characteristics of the Primary standard are described. The results of key comparisons of the developed standard in the range from 273.16 K to 692.477 K and the results of temperature measurements of a number of high-temperature fixed points and a comparison of the results with the published results of leading national metrological institutes are presented.

A simplified method of measuring thermal conductivity of β-Ga2O3 nanomembrane

In this work, we report a simplified method to measure thermal conductivity from the typical Raman thermometry method by employing a much simpler dispersion relationship equation and the Debye function, instead of solving the heat equation. Unlike the typical Raman thermometry method, our new method only requires monitoring of the temperature-dependent Raman mode shifting without considering laser power-dependent Raman mode shifting. Thus, this new calculation method offers a simpler way to calculate the thermal conductivity of materials with great precision. As a model system, the β-Ga2O3 nanomembrane (NM) on a diamond substrate was prepared to measure thermal conductivity of β-Ga2O3 NMs at different thicknesses (100 nm, 1000 nm, and 4000 nm). Furthermore, the phonon penetration depth was investigated to understand how deep phonons can be dispersed in the sample so as to guide the dimensional design parameter of the device from the thermal management perspective.

RF heating measurement using MR thermometry and field monitoring: Methodological considerations and first in vivo results.

A MR thermometry (MRT) method with field monitoring is proposed to improve the measurement of small temperature variations induced in brain MRI exams. MR thermometry experiments were performed at 7 Tesla with concurrent field monitoring and RF heating. Images were reconstructed with nominal k-space trajectories and with first-order spherical harmonics correction. Experiments were performed in vitro with deliberate field disturbances and on an anesthetized macaque in 2 different specific absorption rate regimes, that is, at 50% and 100% of the maximal specific absorption rate level allowed in the International Electrotechnical Commission normal mode of operation. Repeatability was assessed by running a second separate session on the same animal. Inclusion of magnetic field fluctuations in the reconstruction improved temperature measurement accuracy in vitro down to 0.02°C. Measurement precision in vivo was on the order of 0.15°C in areas little affected by motion. In the same region, temperature increase reached 0.5 to 0.8°C after 20 min of heating at 100% specific absorption rates and followed a rough factor of 2 with the 50% specific absorption rate scans. A horizontal temperature plateau, as predicted by Pennes bioheat model with thermal constants from the literature and constant blood temperature assumption, was not observed. Inclusion of field fluctuations in image reconstruction was beneficial for the measurement of small temperature rises encountered in standard brain exams. More work is needed to correct for motion-induced field disturbances to extract reliable temperature maps.

Multispectrum rotational states distribution thermometry: application to the 3ν1 + ν3 band of carbon dioxide

In this paper we propose multispectrum rotational states distribution thermometry as an optical method for primary thermometry. It relies on a global fitting of multiple absorption lines of the same band at different pressures. The approach allows leveraging both the temperature-dependent Doppler width and the temperature-dependent distribution of line intensities across the ro-vibrational band. We provide a proof-of-principle demonstration of the approach on the 3ν1 + ν3 band of CO2, for which several accurate line-strength models of both theoretical and experimental origin are available for the global fitting. Our experimental conditions do not allow to test the methodology beyond a combined uncertainty of 530 ppm, but the comparative analysis between different line-strength models shows promise to reduce the error budget to few tens of ppm. As compared to Doppler-broadening thermometry, the approach is advantageous to mitigate systematic errors induced by a wrong modelling of absorption line-shapes and to reduce, for a given experimental dataset, the statistical uncertainty by a factor of 2. When applied in a reverse way, i.e. using a gas of known temperature, the approach becomes a stringent testbed for the accuracy of the adopted line-strength model.

Thermometry in a Multipole Ion Trap

We present a characterization of the ions’ translational energy distribution in a multipole ion trap. A linear mapping between the energy distribution of the trapped ions onto the ions’ time-of-flight (TOF) to a detector is demonstrated. For low ion temperatures, a deviation from linearity is observed and can be attributed to the emergence of multiple potential minima. The potential landscape of the trapped ions is modeled via the finite element method, also accounting for subtleties such as surface-charge accumulation. We demonstrate the validity of our thermometry method by simulating the energy distribution of the ion ensemble thermalized with buffer gas using a Molecular Dynamics (MD) simulation. A comparison between the energy distribution of trapped ions in different multipole trap configurations—i.e., with hyperbolic rods, cylindrical rods, and cylindrical wires—is provided. With these findings, one can map the temperature of the trapped ions down to the Kelvin regime using their TOF distributions. This enables future studies on sympathetic cooling and chemical reactions involving ions in multipole traps.

Петрология и геохимия массива Ташлы-Тау, худолазовский дифференцированный комплекс, Южный Урал

Введение: Массив Ташлы-Тау представляет собой небольшой шток оливин-роговообманковых габбро, отвечая наиболее ранним по времени проявления продуктам дифференцированного магматизма худолазовского комплекса. Комплекс имеет сложное геологическое строение, поэтому детальные петролого-геохимические исследования отдельных массивов с привлечением численного моделирования параметров кристаллизации позволяют выявить особенности формирования худолазовского комплекса в целом. Цель статьи – реконструкция петрогенезиса габброидов массива Ташлы-Тау, имеющая важное значение ещё и в связи с его сульфидным Cu-Ni оруденением. Методика: Породообразующие минералы габброидов исследовались в оптическом микроскопе Axioskop 40 и на сканирующем электронном микроскопе Tescan Mira 3. Химический состав пород определялся с помощью рентгенофлуоресцентного анализа и масс-спектрометрии с индуктивно-связанной плазмой. Изотопный состав Sr и Nd изучался с помощью термоионизационной спектрометрии. Для разработки модели петрогенезиса использовалось численное COMAGMAT-моделирование и метод геохимической термометрии. Результаты и обсуждение: Выполнено петролого-геохимическое изучение пород массива Ташлы-Тау. В них отмечается широкое развитие роговой обманки – титанистого магнезиогастингсита (~50 мас. %). Габброиды характеризуются относительной обогащённостью крупноионными литофильными элементами (Cs, Rb, Sr, Ba) и обеднённостью высокозарядными элементами (Nb, Ta, Zr, Hf, REE). На основе геохимических данных сделан вывод о том, что магматический расплав являлся слабодифференцированным. Численное моделирование показало, что породы формировались из магмы, состоящей из ~20 мас. % вкрапленников оливина (Fo 76) и водонасыщенного базальтового расплава (~1.7 мас. % H2O), характеризующегося высокой глинозёмистостью, железистостью и умеренной магнезиальностью. Sr-Nd изотопный состав пород свидетельствует в пользу слабой коровой контаминации исходного расплава. Для них характерны высокие положительные значения εNd(Т) (+5.2...+10.3) и пониженное содержание радиогенного стронция. В качестве источника материнского расплава мог служить мантийный резервуар типа PREMA. Заключение: Полученные результаты важны для понимания природы формирования сложно дифференцированного худолазовского комплекса, специализированного на сульфидное оруденение. Для Урала этот комплекс является уникальным. Показано, что применение численного моделирования для водонасыщенных базальтовых систем может быть вполне эффективно до момента кристаллизации гидроксилсодержащих породообразующих минералов (роговой обманки).

Microstructure dependent thermal conductivity measurement of Zircaloy-4 using an extended Raman thermometry method

In this work, microstructural dependence of thermal conductivity of two polycrystalline zircaloy-4 samples was analyzed by using an extended Raman thermometry method. The thermal conductivity values in examined microstructures were found to vary spatially from 11 to 13 W m−1K−1. These values are in the range reported by other bulk measurements that do not consider spatial distribution. The Kapitza thermal resistance model is shown to describe the measured dependence of thermal conductivity as a function of grain size. Thermal resistance from grain boundaries and inhomogeneities are identified as two potential contributors to the thermal conductivity reduction. Nanoindentation tests were performed to obtain the local elastic modulus distribution in the analyzed samples. The thermal conductivity values increase with elastic modulus increasing in each sample. This result indicates a possibility that at room temperature phonon thermal conductivity makes a non-negligible contribution to the total thermal conductivity in zircaloy-4.

The infrared thermometry: registration of healing process of the free gingival graft

Relevance. The main aim of this article is determining the possibilities of clinical application of the infrared thermometry method in order to identify, predict and correct early complications such as ischemic and necrotic process after vestibuloplasty surgery using free gingival graft.Purpose. To determine the possibility of using the infrared thermometry method to study the regeneration processes of the mucous graft after vestibuloplasty surgery using free gingival graft.Materials and methods. 34 patients with a thin biotype and a small vestibule of the oral cavity. The vestibuloplasty was indicated. Depending on the choice of the method of surgical treatment, vestibuloplasty with/ or without free gingival graft, all patients were divided into 2 groups. And the 3rd (control) group consisted of patients with similar clinical picture for control data. Particular attention was paid to the healing process in the early postoperative period on days 1, 3, 7, 14. Patients were examined using a CEM-ThermoDiagnostics infrared thermometer.Results. The study confirmed the high clinical efficacy the both surgical methods of vestibuloplasty with/ or without free gingival graft. We did not registrate negative temperature values indicating the development of ischemic process which can lead to necrosis. We have diagnosed correlation between temperature values and clinical pictures.Conclusion. Using of IR-thermometry is an effective method for examination of the healing process after vestibuloplasty using with/ or without free gingival graft. It can show processes of revascularization of free gingival graft and examine some inflammation. This is the additional method of research, but in combination with clinical picture, it can be proposed as an accurate criterion for predicting early ischemic complications.

The Effect of Auditory Verbal Hallucinations on the Relationship between Spontaneous Brain Activity and intraventricular Brain Temperature in Patients with Drug-Naïve Schizophrenia

Our recent study reported that adolescent-onset schizophrenia showed an uncoupling between intraventricular brain temperature (iBT) and local spontaneous brain activity (SBA). While auditory verbal hallucinations (AVH) are common in schizophrenia, the role of AVH in the iBT-SBA relationship is unclear. The current study recruited 24 drug-naïve schizophrenia patients with AVH, 20 patients without AVH and 30 matched healthy controls (HC). We used a diffusion-weighted imaging (DWI) based thermometry method to calculate the iBT for each participant and used both regional homogeneity and amplitude of low-frequency fluctuation methods to assess the SBA. One-way ANOVA was used to detect group differences in iBT, and a partial correlation analysis controlling for lateral ventricles volume, sex and age was applied to detect the relationships between iBT and SBA across the three groups. The results demonstrated that the AVH group showed a significant coupling between iBT and SBA in the bilateral lingual gyrus, left superior occipital gyrus and caudate compared with the other two groups, and no uncoupling was found in the two patients groups relative to HCs. These findings suggest that AVH may modulate the relationship between iBT and SBA in schizophrenia-related regions.

Measurement of temperature and wavelength-dependent emissivity distributions using multi-wavelength radiation thermometry

A multi-wavelength radiation thermometry method used to determine the temperature and wavelength-dependent emissivity according to spectroscopic radiation intensities is presented. Over a predetermined temperature range, with a set step size, the method traverses the temperature range, and for each temperature, inversely fits a spectral line according to the intensity in the middle of the wavelength region, based on the Rayleigh approximation. The temperature with the spectral line closest to the measured spectral line is considered to be the optimum temperature at that accuracy level. Then, near that optimum temperature, the temperature range and step size are narrowed, to determine the optimum temperature at higher levels of accuracy. Iterating on this method until reaching the required accuracy level, the temperature can be achieved, and the wavelength-dependent emissivity can also be determined. Simulation verification was conducted showing good anti-noise performance and rapid processing capacity. Temperature and emissivity distributions for six heights of an axisymmetric laminar diffusion flame with 194 mL/min ethylene and 240 L/min air were given. Results show that along the line of sight, the radiation temperatures exhibit an average effect of the local temperatures, while the emissivity exhibits a cumulative effect of the absorption coefficients.

Temperature and emissivity measurements from combustion of pine wood, rice husk and fir wood using flame emission spectrum

Biomass combustion for heat and power generation is one of the best ways for substituting fossil fuels. It is necessary to develop in situ temperature and emissivity measurement technology for biomass volatile flame. In this study, combustion experiments on three biomass pellets of pine wood, rice husk and fir wood were carried out in a laboratory biomass burner at two A/F flowrates. A multi-wavelength radiation thermometry method was proposed to calculate temperature and wavelength-dependent emissivity based on Rayleigh approximation. The results showed that the temperature and emissivity of pine wood combustion were higher than those of rice husk and fir wood volatile flames. Though the emissivity of rice husk was less than that of fir wood, the temperature of rice husk combustion was higher than that of fir wood due to the latter's higher moisture content. The temperatures measured by the spectrometer system agreed well with the thermocouple data. The normalized emissivities of the three different biomass show the same trend, indicating the radiative properties of biomass volatile flames do not change with biomass species and combustion conditions.

Dye-Doped ZnO Microcapsules for High Throughput and Sensitive Optofluidic Micro-Thermometry.

The main objective of this work is to show the proof of concept of a new optofluidic method for high throughput fluorescence-based thermometry, which enables the measure of temperature inside optofluidic microsystems at the millisecond (ms) time scale (high throughput). We used droplet microfluidics to produce highly monodisperse microspheres from dispersed zinc oxide (ZnO) nanocrystals and doped them with rhodamine B (RhB) or/and rhodamine 6G (Rh6G). The fluorescence intensities of these two dyes are known to depend linearly on temperature but in two opposite manner. Their mixture enables for the construction of reference probe whose fluorescence does not depend practically on temperature. The use of zinc oxide microparticles as temperature probes in microfluidic channels has two main advantages: (i) avoid the diffusion and the adsorption of the dyes inside the walls of the microfluidic channels and (ii) enhance dissipation of the heat generated by the focused incident laser beam thanks to the high thermal conductivity of this material. Our results show that the fluorescence intensity of RhB decreases linearly with increasing temperature at a rate of about −2.2%/°C, in a very good agreement with the literature. In contrast, we observed for the first time a nonlinear change of the fluorescence intensity of Rh6G in ZnO microparticles with a minimum intensity at a temperature equal to 40 °C. This behaviour is reproducible and was observed only with ZnO microparticles doped with Rh6G.

Recent technological advancements in thermometry.

Thermometry is the key factor for achieving successful thermal therapy. Although invasive thermometry with a probe has been used for more than four decades, this method can only detect the local temperature within the probing volume. Noninvasive temperature imaging using a tomographic technique is ideal for monitoring hot-spot formation in the human body. Among various techniques, such as X-ray computed tomography, microwave tomography, echo sonography, and magnetic resonance (MR) imaging, the proton resonance frequency shift method of MR thermometry is the only method currently available for clinical practice because its temperature sensitivity is consistent in most aqueous tissues and can be easily observed using common clinical scanners. New techniques are being proposed to improve the robustness of this method against tissue motion. MR techniques for fat thermometry were also developed based on relaxation times. One of the latest non-MR techniques to attract attention is photoacoustic imaging.

High-temperature spectral thermometry in conditions of intense microwave electromagnetic fields

In this paper, a practical application variant of the high-temperature spectral thermometry method for controlling the temperature of a dielectric object heated in a high-intensity microwave electromagnetic field is proposed. The advantages of using the spectral pyrometry method over the methods of color and brightness pyrometry when registering high temperatures (from 500 °C and above) are described. The optical fiber cable used in this method, which receives thermal radiation from an object heated in the microwave field, is subject to the negative influence of the electromagnetic field, which leads to its unacceptable heating and failure. To eliminate this phenomenon, a non-standard use of an cutoff waveguide placed not outside, but inside the microwave heating chamber is proposed. It is shown that this solution completely eliminates the negative influence of the electromagnetic field on the fiber optic cable and allows placing the receiving end of the cable in close proximity to the object being heated. The calculation of geometric parameters of the cutoff waveguide for the operating frequency of the electromagnetic field of 2450 MHz is given.

Temperature Measurements in Neonates: Assessing the Agreement of Two Methods

Background: Neonatal temperature response during illness is unpredictable. Whereas accurate temperature measurement is an important diagnostic step in Neonatal practice. Abnormalties in temperature pattern may be a pointer to a sinister condition especially in neonates, whose thermoregulatory mechanism is immature. There are several methods of temperature measurements and the search for a suitable thermometry method in neonates continues. This study compared the forehead non touch infra-red thermometer (NTIT) with the axilllary mercury-in-glass (MIGT) method of temperature measurement in neonates. Method: Four hundred babies aged 1 to 28 days were recruited from the immunization clinic of the University of Ilorin Teaching Hospital between August 2016 and May 2017. Temperatures were taken using both NTIT and MIGT in the standard way and recorded. Result: The mean age and SD was 5.10 ± 4.28 days. Pearson correlation showed a positive correlation between the Axillary Mercury-in-Glass and Forehead Non-Touch Infra-red thermometry readings (r = 0.426, p 0.001). Bland-Altman method revealed a good agreement between both methods of thermometry as 95.5% of the readings were within the limits of agreement. Conclusion: Axillary Mercury-in-Glass thermometer and Forehead Non touch Infra-red thermometers have a good agreement and can be used interchangeably in neonates.

Multinuclear absolute magnetic resonance thermometry

Non-invasive measurement of absolute temperature is important for proper characterization of various pathologies and for evaluation of thermal dose during interventional procedures. The proton (hydrogen nucleus) magnetic resonance (MR) frequency shift method can be used to map relative temperature changes. However, spatiotemporal variations in the main magnetic field and the lack of local internal frequency reference challenge the determination of absolute temperature. Here, we introduce a multinuclear method for absolute MR thermometry, based on the fact that the hydrogen and sodium nuclei exhibit a unique and distinct characteristic frequency dependence with temperature and with electrolyte concentration. A one-to-one mapping between the precession frequency difference of the two nuclei and absolute temperature is demonstrated. Proof-of-concept experiments were conducted in aqueous solutions with different NaCl concentrations, in agarose gel samples, and in freshly excised ex vivo mouse tissues. One-dimensional chemical shift imaging experiments also demonstrated excellent agreement with infrared measurements.

Modeling of brightness temperature in biological tissue

Microwave radiothermometry is a passive and non-invasive technique which is used to measure the depth temperature of biological tissue. The method of microwave radio thermometry is based on measuring the intensity of the own electromagnetic radiation of the internal tissues of the patient in the ultra-high frequency range. The temperature measured by the instrument is called brightness. Modeling the brightness temperature is carried out to research the effectiveness of the method of medical diagnostics based on microwave radiothermometry data. A mathematical model of the distribution of the electromagnetic and temperature fields in the mammary gland was built. A numerical simulation of the electromagnetic and temperature fields for models differing in internal structure was carried out. The structure of the mammary gland is a multicomponent, heterogeneous environment and consists of the following types of biological tissues: skin, adipose tissue, muscle tissue, milk lobules, blood flow. The contribution of the electromagnetic field to the formation of the brightness temperature was determined. The dependence of the brightness temperature on the radius of the tumor is presented.

Linestrength ratio spectroscopy as a new primary thermometer for redefined Kelvin dissemination

Experimental methods for primary thermometry, after Kelvin unit redefinition on May 2019, become based on a known value of the Boltzmann constant rather than by measuring temperature with respect to a reference point. In this frame, we propose linestrength ratio thermometry (LRT) as a candidate method for primary thermometry in the 9–700 K temperature range. Temperature accuracies at the ppm level are prospected for LRT applied to optical transitions of the CO molecule in the range 80–700 K and of a rare-earth-doped crystal in the 9–100 K one. Future implementations of this technique can contribute to measure the calibration-discrepancies in the ITS-90 metrological scale of thermodynamic temperature which can have a measurable impact in applications ranging from fundamental-physics to meteorology and climatology.

Intra-pulse H2O absorption diagnostic for temperature sensing in a rapid compression machine

An in-situ temperature diagnostic based on intra-pulse absorption spectroscopy has been developed using two pulsed quantum cascade lasers (QCLs) centered at 5.46 and 5.60 μm for rapid compression machine (RCM) experiments. Pulsed mode operation of the QCLs yielded a broad spectral tuning range (1.8–2.3 cm−1), through which spectral line-shapes of two H2O ro-vibrational transitions were resolved at high pressure conditions in the RCM (15–20 bar). Based on the resolved line-shapes, a calibration-free two-line thermometry method was used to determine the gas temperature. A high temporal resolution of 10 μs was achieved through a pulse repetition frequency of 100 kHz. The diagnostic was validated through measurements of temperature rise during the first-stage ignition of n-pentane/air mixtures. Thereafter, temperature rise during the first-stage ignition of iso-octane/air mixtures was quantified for the first time and compared with the calculated temperature rise using a chemical kinetic model.

A method for ultrasound thermal image distribution reconstruction

This paper presents an ultrasonic thermometry method for thermal image distribution reconstruction in a heating environment. It is based on determining the time-of-flight (ToF) of ultrasonic waves along a large number of effective paths in a measured area, these ToFs depend on the temperature along the paths. On this basis, thermal image temperature distribution can be reconstructed by some appropriate methods. During the reconstruction process, an ultrasonic flight time measurement system based on the ultrasonic analog front end TDC1000 and time-to-digital converter TDC7200 is built to obtain the ToF data, and a reliable method for thermal image distribution reconstruction based on multiquadric-radial basis function (MQ-RBF) is proposed in this paper. Furthermore, the digital sensor DS18B20 temperature measurement system is developed to evaluate the performance of the reconstruction methods. The results indicate that the proposed method enjoys a relatively greater performance of temperature distribution reconstruction and higher robustness than the least squares method and the RBF, the common reconstruction methods.