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Luminescence methods for non-contact temperature monitoring have evolved through improvements of hardware and sensor materials. Future advances in this field rely on the development of multimodal sensing capabilities of temperature probes and extend the temperature range across which they operate. The family of Cr-doped oxides appears particularly promising and we review their luminescence characteristics in light of their application in non-contact measurements of temperature over the 5–300 K range. Multimodal sensing utilizes the intensity ratio of emission lines, their wavelength shift, and the scintillation decay time constant. We carried out systematic studies of the temperature-induced changes in the luminescence of the Cr3+-doped oxides Al2O3, Ga2O3, Y3Al5O12, and YAlO3. The mechanism responsible for the temperature-dependent luminescence characteristic is discussed in terms of relevant models. It is shown that the thermally-induced processes of particle exchange, governing the dynamics of Cr3+ ion excited state populations, require low activation energy. This then translates into tangible changes of a luminescence parameter with temperature. We compare different schemes of temperature sensing and demonstrate that Ga2O3-Cr is a promising material for non-contact measurements at cryogenic temperatures. A temperature resolution better than ±1 K can be achieved by monitoring the luminescence intensity ratio (40–140 K) and decay time constant (80–300 K range).

Understanding the coordination of cell-division timing is one of the outstanding questions in the field of developmental biology. One active control parameter of the cell-cycle duration is temperature, as it can accelerate or decelerate the rate of biochemical reactions. However, controlled experiments at the cellular scale are challenging, due to the limited availability of biocompatible temperature sensors, as well as the lack of practical methods to systematically control local temperatures and cellular dynamics. Here, we demonstrate a method to probe and control the cell-division timing in Caenorhabditis elegans embryos using a combination of local laser heating and nanoscale thermometry. Local infrared laser illumination produces a temperature gradient across the embryo, which is precisely measured by in vivo nanoscale thermometry using quantum defects in nanodiamonds. These techniques enable selective, controlled acceleration of the cell divisions, even enabling an inversion of division order at the two-cell stage. Our data suggest that the cell-cycle timing asynchrony of the early embryonic development in C. elegans is determined independently by individual cells rather than via cell-to-cell communication. Our method can be used to control the development of multicellular organisms and to provide insights into the regulation of cell-division timings as a consequence of local perturbations.

Cardiac radiofrequency ablation (RFA) has received substantial attention for the treatment of multiple arrhythmias. In this scenario, there is an ever-growing demand for monitoring the temperature trend inside the tissue as it may allow an accurate control of the treatment effects, with a consequent improvement of the clinical outcomes. There are many methods for monitoring temperature in tissues undergoing RFA, which can be divided into invasive and non-invasive. This paper aims to provide an overview of the currently available techniques for temperature detection in this clinical scenario. Firstly, we describe the heat generation during RFA, then we report the principle of work of the most popular thermometric techniques and their features. Finally, we introduce their main applications in the field of cardiac RFA to explore the applicability in clinical settings of each method.

A nanoscale thermometry technique that uses coherent manipulation of the electronic spin associated with nitrogen–vacancy colour centres in diamond makes it possible to detect temperature variations as small as 1.8 millikelvin in ultrapure samples and to control and map temperature gradients within living cells. A nanothermometer for cells A nanoscale thermometer capable of subdegree temperature resolution and of integration within living cells could provide a powerful new tool for many areas of biological and medical research. This paper describes a new probe for nanoscale thermometry that achieves just that. The device uses quantum manipulation of nitrogen–vacancy colour centres in diamond nanocrystals. These harbour single electron spins and have specific fluorescence properties that are sensitively dependent on the local temperature. The authors show that they can be accurately measured with a spatial resolution down to 200 nm. By introducing both nanodiamonds and gold nanoparticles into a single human embryonic fibroblast, they demonstrate temperature-gradient control and mapping at the subcellular level. Sensitive probing of temperature variations on nanometre scales is an outstanding challenge in many areas of modern science and technology 1 . In particular, a thermometer capable of subdegree temperature resolution over a large range of temperatures as well as integration within a living system could provide a powerful new tool in many areas of biological, physical and chemical research. Possibilities range from the temperature-induced control of gene expression 2 , 3 , 4 , 5 and tumour metabolism 6 to the cell-selective treatment of disease 7 , 8 and the study of heat dissipation in integrated circuits 1 . By combining local light-induced heat sources with sensitive nanoscale thermometry, it may also be possible to engineer biological processes at the subcellular level 2 , 3 , 4 , 5 . Here we demonstrate a new approach to nanoscale thermometry that uses coherent manipulation of the electronic spin associated with nitrogen–vacancy colour centres in diamond. Our technique makes it possible to detect temperature variations as small as 1.8 mK (a sensitivity of 9 mK Hz −1/2 ) in an ultrapure bulk diamond sample. Using nitrogen–vacancy centres in diamond nanocrystals (nanodiamonds), we directly measure the local thermal environment on length scales as short as 200 nanometres. Finally, by introducing both nanodiamonds and gold nanoparticles into a single human embryonic fibroblast, we demonstrate temperature-gradient control and mapping at the subcellular level, enabling unique potential applications in life sciences.

Fluorescent nanothermometers can probe changes in local temperature in living cells and in vivo and reveal fundamental insights into biological properties. This field has attracted global efforts in developing both temperature-responsive materials and detection procedures to achieve sub-degree temperature resolution in biosystems. Recent generations of nanothermometers show superior performance to earlier ones and also offer multifunctionality, enabling state-of-the-art functional imaging with improved spatial, temporal and temperature resolutions for monitoring the metabolism of intracellular organelles and internal organs. Although progress in this field has been rapid, it has not been without controversy, as recent studies have shown possible biased sensing during fluorescence-based detection. Here, we introduce the design principles and advances in fluorescence nanothermometry, highlight application achievements, discuss scenarios that may lead to biased sensing, analyze the challenges ahead in terms of both fundamental issues and practical implementations, and point to new directions for improving this interdisciplinary field. This Review on nanothermometry introduces the many types of nanothermometers and their cellular and in vivo applications, as well as best practices for accurate measurements.

Despite great technical capabilities, the theory of non-contact temperature measurement is usually not fully applicable to the use of measuring instruments in practice. While black body calibrations and black body radiation thermometry (BBRT) are in practice well established and easy to accomplish, this calibration protocol is never fully applicable to measurements of real objects under real conditions. Currently, the best approximation to real-world radiation thermometry is grey body radiation thermometry (GBRT), which is supported by most measuring instruments to date. Nevertheless, the metrological requirements necessitate traceability; therefore, real body radiation thermometry (RBRT) method is required for temperature measurements of real bodies. This article documents the current state of temperature calculation algorithms for radiation thermometers and the creation of a traceable model for radiation thermometry of real bodies that uses an inverse model of the system of measurement to compensate for the loss of data caused by spectral integration, which occurs when thermal radiation is absorbed on the active surface of the sensor. To solve this problem, a hybrid model is proposed in which the spectral input parameters are converted to scalar inputs of a traditional scalar inverse model for GBRT. The method for calculating effective parameters, which corresponds to a system of measurement, is proposed and verified with the theoretical simulation model of non-contact thermometry. The sum of effective instrumental parameters is presented for different temperatures to show that the rule of GBRT, according to which the sum of instrumental emissivity and instrumental reflectivity is equal to 1, does not apply to RBRT. Using the derived models of radiation thermometry, the uncertainty of radiation thermometry due to the uncertainty of spectral emissivity was analysed by simulated worst-case measurements through temperature ranges of various radiation thermometers. This newly developed model for RBRT with known uncertainty of measurement enables traceable measurements using radiation thermometry under any conditions.

Titanium and zirconium analyses of quartz and rutile from blueschist samples from the eclogite–blueschist unit (EBU) in northern Sifnos, Greece, have been evaluated to determine the extent to which the intersection of the Ti-in-quartz (TitaniQ) and zirconium-in-rutile (ZiR) thermometers reflect peak metamorphic P–T conditions. Ti concentrations range from 100 to 530 ppb and Zr concentrations range from 14 to 44 ppm; there is no significant zoning observed in any grains and no significant differences in concentrations in samples south and north of the Vroulidia shear zone (VSZ). Lines of equal Keq from the TitaniQ and ZiR thermometers intersect at around 450–500 °C and 2.2–2.4 GPa, which is similar to the peak metamorphic conditions of 530 °C, 1.9 GPa for samples north of the VSZ. However, the intersection is inconsistent with the peak metamorphic conditions of 525 °C, 1.1–1.4 GPa for samples south of the VSZ even when TitaniQ temperatures are corrected for reduced activity of TiO 2 . Rather, TitaniQ temperatures are consistent with Ti values being incorporated into quartz during prograde metamorphism along a subduction geotherm of 10–12 deg/km at around 300 °C. ZiR temperatures are consistent with rutile nucleation and growth at around 450–500 °C along a similar metamorphic geotherm after the rutile-in reaction was overstepped by around 1 kJ/mol-O. The TitaniQ and ZiR thermometers do not, therefore, reflect peak metamorphic P–T conditions in these rocks but rather record recrystallization or growth processes during prograde subduction.

•Cold chain equipment is ageing and temperature exposure might impact vaccine potency.•Automatic recording devices appeared to be efficient monitoring and assessment tools.•Current monitoring tools such as Fridge-Tag©, and vaccine vial monitors are underused.•EPI staff needs adapted and continuing training on equipment and procedures.•The country’s Gavi approved five year cold chain supply plan should be accelerated. Abnormal temperatures are a major issue for vaccines within the Expanded Program of Immunization in tropical climates. Prolonged exposure to temperatures outside the standard +2 °C/+8 °C range can impact vaccine potency. The current study used automatic temperature recording devices (Testostore 171-1©) to monitor cold chain in remote areas of Western Burkina Faso. A series of 25 randomly selected health centers representing 33% of the existing 176 EPI facilities in Western Burkina Faso were prospectively assessed for eight months in 2015. Automatic measurements were compared to routine temperature loggers and vaccine vial monitors (VVM). The median age for all refrigerators was 9 years with 10/25 (42%) older than 10 years. Adverse temperatures were recorded in 20/24 (83%) refrigerators and ranged from −18.5 °C to +34.2 °C with 12,958/128,905 (10%) abnormal hourly records below +2 °C and 7357/128,905 (5.7%) above +8 °C. Time of day significantly affected the rate of temperature excursions, with higher rates from 00 am to 06 am (p < 0.001) for low temperatures and 10–12 am (p < 0.001) and 13–16 pm (p < 0.001) for high temperatures. Abnormal temperatures lasted from 1 h to 24 h below +2 °C and 13–24 h above +8 °C. Standard manual registers reported only 182/2761 (7%) inadequate temperatures and VVM color change detected only 133/2465 (5%) disruptions. Reliability of the refrigerators ranged from 48% to 98.7% with a median of 70%. Risk factors for excursions were old age of the refrigerators, the months of April and May, hours of high activity during the day, and health staff-associated factors such as inappropriate actions or insufficient knowledge. Important cold chain reliability issues reported in the current study in Western Burkina Faso raise concern about vaccine potency. In the absence of systematic renewal of the cold chain infrastructure or improved staff training and monitoring, antibody response assessment is recommended to study levels of effective immunization coverage.

The in vivo temperature monitoring of a microenvironment is significant in biology and nanomedicine research. Luminescent nanothermometry provides a noninvasive method of detecting the temperature in vivo with high sensitivity and high response speed. However, absorption and scattering in complex tissues limit the signal penetration depth and cause errors due to variation at different locations in vivo. In order to minimize these errors and monitor temperature in vivo, in the present work, we provided a strategy to fabricate a same-wavelength dual emission ratiometric upconversion luminescence nanothermometer based on a hybrid structure composed of upconversion emissive PbS quantum dots and Tm-doped upconversion nanoparticles. The ratiometric signal composed of two upconversion emissions working at the same wavelength, but different luminescent lifetimes, were decoded via a time-resolved technique. This nanothermometer improved the temperature monitoring ability and a thermal resolution and sensitivity of ~0.5 K and ~5.6% K −1 were obtained in vivo, respectively. Traditional ratiometric temperature monitoring is challenging due to the variation in tissue absorption and scattering of different wavelengths. Here, the authors show improved accuracy by using emission at the same wavelength, but different luminescent lifetimes decoded by a time-resolved technique.

The use of sensors in the real world is on the rise, providing information on medical diagnostics for healthcare and improving quality of life. Optical fiber sensors, as a result of their unique properties (small dimensions, capability of multiplexing, chemical inertness, and immunity to electromagnetic fields) have found wide applications, ranging from structural health monitoring to biomedical and point-of-care instrumentation. Furthermore, these sensors usually have good linearity, rapid response for real-time monitoring, and high sensitivity to external perturbations. Optical fiber sensors, thus, present several features that make them extremely attractive for a wide variety of applications, especially biomedical applications. This paper reviews achievements in the area of temperature optical fiber sensors, different configurations of the sensors reported over the last five years, and application of this technology in biomedical applications.