Solar radiation makes the human body feel warm through energy absorption
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Scientific literature and reference texts indicate that solar radiation absorption warms biological surfaces, such as simulated skin and animal bodies.
Abstract Increasingly serious electromagnetic radiation pollution puts forward higher demands on wearable fabrics: high electromagnetic interference (EMI) shielding effectiveness. Besides, the ability for the fabrics to keep the human body warm is also important in a frigid environment. However, there have been few reports on fabrics simultaneously with the two functions so far. Here, a flexible wearable fabric with both excellent EMI shielding and passive radiation heating functions was developed through integrating silver nanowire (AgNW), ferroferric oxide (Fe3O4) nanoparticles, and polydimethylsiloxane (PDMS) onto a commercial fabric. The conductive AgNW networks endowed the fabric with a super-high EMI shielding property of 100.9 dB at the thickness of 450 μm – one noticeable advantage. The passive radiation heating ability was achieved by regulating the spectral selectivity of the fabric (a high solar energy absorptivity of 80.5% at 250–2500 nm, a low mid-infrared emissivity of 0.21 at 7 − 14 μm), so no electric power is needed for the fabric to heat the human body – another prominent advantage. The fabric resulted in a 20.6 °C temperature enhancement of the simulated skin under sunlight in the daytime and a 6.4 °C temperature enhancement in nighttime compared with traditional cotton fabric with the same thickness. Thus, the prepared multifunctional fabric can effectively protect the human body from electromagnetic radiation harm and injury caused by cold climate. This work holds great potential to enlarge the application scope of current EMI shielding fabrics.
Solar radiation intensity affects both subjective reactions and physiological functions, especially for people who exercise heavily. Field experiments including a questionnaire survey at various ambient temperatures were performed; outdoor activities under shading (irradiance I = 50 ± 20 W/m2) and non-shading (I = 700 ± 50 W/m2) conditions during summer in Xi'an were recorded. The results of questionnaires indicated that when the human body reached an extremely hot state, the corresponding environmental temperature was 3.7 °C lower under the non-shading condition, and the range of actual acceptable temperatures was narrower. In terms of thermal sensation, there was a significant difference for people who exercise heavily and those who do not. The results also showed that the curve of fatigue sensation exhibited an inverse Gaussian distribution. Namely, fatigue was promoted under both colder and hotter conditions. Moreover, under non-shading condition, the lowest fatigue incidence was higher, and the corresponding ambient temperature was lower. Changes in objective physiological responses indicated that the solar radiation might cause heat stress. Therefore, when the ambient temperature was higher than 32 °C, physiological stress was higher. Under the same exercise load, the blood pressure was higher under the non-shading condition and systolic blood pressure increased with ambient temperature.
Some turtles also have a posterior respiratory sac that opens off the hindgut that aids in the diffusion of gases. Most reptiles are ectotherms, animals whose main source of body heat comes from the environment; however, some crocodilians maintain elevated thoracic temperatures and thus appear to be at least regional endotherms. This is in contrast to true endotherms, which use heat produced by metabolism and muscle contraction to regulate body temperature over a very narrow temperature range, and thus are properly referred to as homeotherms. Reptiles have behavioral adaptations to help regulate body temperature, such as basking in sunny places to warm up through the absorption of solar radiation, or finding shady spots or going underground to minimize the absorption of solar radiation, which allows them to cool down and prevent overheating. The advantage of ectothermy is that metabolic energy from food is not required to heat the body; therefore, reptiles can survive on about 10 percent of the calories required by a similarly sized endotherm. In cold weather, some reptiles such as the garter snake brumate.
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