SciCombinator

Discover the most talked about and latest scientific content & concepts.

Concept: Thermal radiation

238

Although studies have provided estimates of premature deaths attributable to either heat or cold in selected countries, none has so far offered a systematic assessment across the whole temperature range in populations exposed to different climates. We aimed to quantify the total mortality burden attributable to non-optimum ambient temperature, and the relative contributions from heat and cold and from moderate and extreme temperatures.

Concepts: Demography, Climate, Temperature, Thermodynamics, Heat, Entropy, Cold, Thermal radiation

33

Control of the thermal emission spectra of emitters will result in improved energy utilization efficiency in a broad range of fields, including lighting, energy harvesting, and sensing. In particular, it is challenging to realize a highly selective thermal emitter in the near-infrared-to-visible range, in which unwanted thermal emission spectral components at longer wavelengths are significantly suppressed, whereas strong emission in the near-infrared-to-visible range is retained. To achieve this, we propose an emitter based on interband transitions in a nanostructured intrinsic semiconductor. The electron thermal fluctuations are first limited to the higher-frequency side of the spectrum, above the semiconductor bandgap, and are then enhanced by the photonic resonance of the structure. Theoretical calculations indicate that optimized intrinsic Si rod-array emitters with a rod radius of 105 nm can convert 59% of the input power into emission of wavelengths shorter than 1100 nm at 1400 K. It is also theoretically indicated that emitters with a rod radius of 190 nm can convert 84% of the input power into emission of <1800-nm wavelength at 1400 K. Experimentally, we fabricated a Si rod-array emitter that exhibited a high peak emissivity of 0.77 at a wavelength of 790 nm and a very low background emissivity of <0.02 to 0.05 at 1100 to 7000 nm, under operation at 1273 K. Use of a nanostructured intrinsic semiconductor that can withstand high temperatures is promising for the development of highly efficient thermal emitters operating in the near-infrared-to-visible range.

Concepts: Photon, Fundamental physics concepts, Light, Electromagnetic radiation, Temperature, Semiconductor, Black body, Thermal radiation

32

Beaks are increasingly recognised as important contributors to avian thermoregulation. Several studies supporting Allen’s rule demonstrate how beak size is under strong selection related to latitude and/or air temperature (Ta). Moreover, active regulation of heat transfer from the beak has recently been demonstrated in a toucan (Ramphastos toco, Ramphastidae), with the large beak acting as an important contributor to heat dissipation. We hypothesised that hornbills (Bucerotidae) likewise use their large beaks for non-evaporative heat dissipation, and used thermal imaging to quantify heat exchange over a range of air temperatures in eighteen desert-living Southern Yellow-billed Hornbills (Tockus leucomelas). We found that hornbills dissipate heat via the beak at air temperatures between 30.7°C and 41.4°C. The difference between beak surface and environmental temperatures abruptly increased when air temperature was within ~10°C below body temperature, indicating active regulation of heat loss. Maximum observed heat loss via the beak was 19.9% of total non-evaporative heat loss across the body surface. Heat loss per unit surface area via the beak more than doubled at Ta > 30.7°C compared to Ta < 30.7°C and at its peak dissipated 25.1 W m-2. Maximum heat flux rate across the beak of toucans under comparable convective conditions was calculated to be as high as 61.4 W m-2. The threshold air temperature at which toucans vasodilated their beak was lower than that of the hornbills, and thus had a larger potential for heat loss at lower air temperatures. Respiratory cooling (panting) thresholds were also lower in toucans compared to hornbills. Both beak vasodilation and panting threshold temperatures are potentially explained by differences in acclimation to environmental conditions and in the efficiency of evaporative cooling under differing environmental conditions. We speculate that non-evaporative heat dissipation may be a particularly important mechanism for animals inhabiting humid regions, such as toucans, and less critical for animals residing in more arid conditions, such as Southern Yellow-billed Hornbills. Alternatively, differences in beak morphology and hardness enforced by different diets may affect the capacity of birds to use the beak for non-evaporative heat loss.

Concepts: Temperature, Thermodynamics, Heat, Heat transfer, Thermal radiation, Toucan, Hornbill, Tockus

28

To map skin temperature kinetics, and by extension skin blood flow throughout normal or abnormal repair of full-thickness cutaneous wounds created on the horse body and limb, using infrared thermography.

Concepts: Scar, Wound healing, Healing, Temperature, Horse, Black body, Thermography, Thermal radiation

27

BACKGROUND/PURPOSE: Infrared thermography (IRT) is a useful tool for assessing skin temperature abnormalities in patients with complex regional pain syndrome (CRPS). Although determining regions of interest (ROIs) is an essential process for interpreting thermographic images, there are no validated and standardized guidelines to determine ROIs. Therefore, ROIs may be determined differently by each observer even for the same IRT images, which can result in an important issue for IRT reliability. The purpose of this study was to investigate the interexaminer reliability of IRT in patients with CRPS. METHODS: Infrared thermographic images of 28 patients diagnosed with CRPS were reviewed by three independent examiners. The shapes, sizes, and the detailed locations of the ROIs were determined by the investigator’s own opinion based on patient history and symptoms. After maximal skin temperature of the ROI was obtained for each patient, the degree of agreement among the three examiners limbs was assessed. RESULTS: The intraclass correlation coefficient among the three independent raters was 0.865 (95% confidence interval, 0.748-0.933), indicating a high degree of reliability (P < 0.001). CONCLUSIONS: The reliability of IRT for assessing skin temperature abnormalities in CRPS was high when the ROIs were determined based on patient history and symptoms.

Concepts: Temperature, Covariance and correlation, Black body, Infrared, Thermography, Thermal radiation, Infrared thermometer, Thermographic camera

26

To evaluate the surface temperature rise using an infrared thermal imaging camera on roots with and without simulated internal resorption cavities; during canal filling with injectable (Obtura II), carrier-based (Soft-Core) gutta-percha and continuous wave of condensation (System B) techniques.

Concepts: Temperature, Heat transfer, Black body, Infrared, Thermography, Thermal radiation, Infrared thermometer, Thermographic camera

15

Saharan silver ants, Cataglyphis bombycina, forage under extreme temperature conditions in the African desert. We show that the ants' conspicuous silvery appearance is created by a dense array of uniquely shaped triangular hairs with two thermoregulatory effects. They enhance not only the reflectivity of the ant’s body surface in the visible and near-infrared range of the spectrum, where solar radiation culminates, but also the emissivity of the ant in the mid-infrared. The latter effect enables the animals to efficiently dissipate heat back to the surroundings via blackbody radiation under full daylight conditions. This biological solution for a thermoregulatory problem may lead to the development of biomimetic coatings for passive radiative cooling of objects.

Concepts: Electromagnetic radiation, Sun, Thermodynamics, Heat transfer, Black body, Infrared, Thermal radiation, Emissivity

12

Acute stress triggers peripheral vasoconstriction, causing a rapid, short-term drop in skin temperature in homeotherms. We tested, for the first time, whether this response has the potential to quantify stress, by exhibiting proportionality with stressor intensity. We used established behavioural and hormonal markers: activity level and corticosterone level, to validate a mild and more severe form of an acute restraint stressor in hens (Gallus gallus domesticus). We then used infrared thermography (IRT) to non-invasively collect continuous temperature measurements following exposure to these two intensities of acute handling stress. In the comb and wattle, two skin regions with a known thermoregulatory role, stressor intensity predicted the extent of initial skin cooling, and also the occurrence of a more delayed skin warming, providing two opportunities to quantify stress. With the present, cost-effective availability of IRT technology, this non-invasive and continuous method of stress assessment in unrestrained animals has the potential to become common practice in pure and applied research.

Concepts: Time, Chicken, Black body, Red Junglefowl, Phasianidae, Grey Junglefowl, Thermography, Thermal radiation

9

Synthetic systems cannot easily mimic the color-changing abilities of animals such as cephalopods. Soft machines–machines fabricated from soft polymers and flexible reinforcing sheets–are rapidly increasing in functionality. This manuscript describes simple microfluidic networks that can change the color, contrast, pattern, apparent shape, luminescence, and surface temperature of soft machines for camouflage and display. The color of these microfluidic networks can be changed simultaneously in the visible and infrared–a capability that organisms do not have. These strategies begin to imitate the functions, although not the anatomies, of color-changing animals.

Concepts: Function, Energy, Temperature, Thermodynamics, Entropy, Black body, Thermal radiation, Kelvin

8

In this work, we leverage graphene’s unique tunable Seebeck coefficient for the demonstration of a graphene-based thermal imaging system. By integrating graphene based photo-thermo-electric detectors with micro-machined silicon nitride membranes, we are able to achieve room temperature responsivities on the order of ~7-9 V/W (at λ=10.6 μm), with a time constant of ~23 ms. The large responsivities, due to the combination of thermal isolation and broadband infrared absorption from the underlying SiN membrane, have enabled detection as well as stand-off imaging of an incoherent blackbody target (300-500K). By comparing the fundamental achievable performance of these graphene-based thermopiles with standard thermocouple materials, we find extrapolate that graphene’s high carrier mobility can enable improved performances with respect to two main figures of merit for infrared detectors: detectivity (>8x10(8) cmHz(½)W(-1)) and noise equivalent temperature difference (<100 mK). Furthermore, even average graphene carrier mobility (<1000 cm(2)/Vs) is still sufficient to detect the emitted thermal radiation from a human target.

Concepts: Temperature, Black body, Infrared, Thermography, Thermal radiation, Infrared photography, Emissivity, Thermocouple