Animal thermoregulation: a review of insulation, physiology and behaviour relevant to temperature control in buildings

Birds and mammals have evolved many thermal adaptations that are relevant to the bioinspired design of temperature control systems and energy management in buildings. Similar to many buildings, endothermic animals generate internal metabolic heat, are well insulated, regulate their temperature within set limits, modify microclimate and adjust thermal exchange with their environment. We review the major components of animal thermoregulation in endothermic birds and mammals that are pertinent to building engineering, in a world where climate is changing and reduction in energy use is needed. In animals, adjustment of insulation together with physiological and behavioural responses to changing environmental conditions fine-tune spatial and temporal regulation of body temperature, while also minimizing energy expenditure. These biological adaptations are characteristically flexible, allowing animals to alter their body temperatures to hourly, daily, or annual demands for energy. They exemplify how buildings could become more thermally reactive to meteorological fluctuations, capitalising on dynamic thermal materials and system properties. Based on this synthesis, we suggest that heat transfer modelling could be used to simulate these flexible biomimetic features and assess their success in reducing energy costs while maintaining thermal comfort for given building types

Bright light decreases peripheral skin temperature in healthy men:A forced desynchrony study under dim and bright light (II)

Human thermoregulation is strictly regulated by the preoptic area of the hypothalamus, which is directly influenced by the suprachiasmatic nucleus (SCN). The main input pathway of the SCN is light. Here, thermoregulatory effects of light were assessed in humans in a forced desynchrony (FD) design. The FD experiment was performed in dim light (DL, 6 lux) and bright white light (BL, 1300 lux) in 8 men in a semi-randomized within-subject design. A 4 × 18 h FD protocol (5 h sleep, 13 h wake) was applied, with continuous core body temperature (CBT) and skin temperature measurements at the forehead, clavicles, navel, palms, foot soles and toes. Skin temperature parameters indicated sleep-wake modulations as well as internal clock variations. All distal skin temperature parameters increased during sleep, when CBT decreased. Light significantly affected temperature levels during the wake phase, with decreased temperature measured at the forehead and toes and increased navel and clavicular skin temperatures. These effects persisted when the lights were turned off for sleep. Circadian amplitude of CBT and all skin temperature parameters decreased significantly during BL exposure. Circadian proximal skin temperatures cycled in phase with CBT, while distal skin temperatures cycled in anti-phase, confirming the idea that distal skin regions reflect heat dissipation and proximal regions approximate CBT. In general, we find that increased light intensity exposure may have decreased heat loss in humans, especially at times when the circadian system promotes sleep

Water conservation strategies of large African ungulates

A thesis submitted to the Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy Johannesburg, South Africa, 2017Ecosystems in the southern hemisphere are limited mainly by water availability, a resource predicted to become increasingly scarce in the region in the face of anthropogenic climate change. Understanding how the artiodactyls (e.g., sheep, goats, cattle, antelope and camels), an important grouping of animals regionally, conserve body water to facilitate their survival, is therefore of importance. The idea that selective brain cooling conserves body water has been advanced for more than 20 years, without any definitive proof that ungulates, naturally making use of selective brain cooling, actually save body water as a result of implementing selective brain cooling. Using implanted biologgers I simultaneously measure carotid arterial and hypothalamic temperature in Dorper sheep Ovis aries. The concomitant determination of water turnover, based on the washout rates of the stable hydrogen isotope deuterium oxide (D2O), allowed me to measure the volume of water that a dehydrated Dorper sheep conserves during a day when exposed to heat. Artiodactyls differ in their water requirements though, and may have selective brain cooling capabilities relative to their level of water dependency. I therefore undertook the first comparative investigation into selective brain in free-living artiodactyls by implanting, with the assistance of colleagues, biologgers to measure carotid arterial and hypothalamic temperatures in three large, sympatric artiodactyl species with varying water dependencies. Despite a clear water-dependency gradient across species, I found no difference in the magnitudes of selective brain cooling, iii the proportion of time that selective brain cooling was used, or the threshold temperatures for selective brain between the gemsbok Oryx gazella, red hartebeest Alcelaphus buselaphus or blue wildebeest Connochaetes taurinus in an environment where the animals had free access to water. I found greater variability in selective brain cooling within species, than between species and conclude that all three species had the same underlying ability to make use of selective brain cooling. Artiodactyls, however, are likely to rely on range of water conservation mechanisms in the face of climate change. A variable body temperature and the use of appropriate microclimates are two additional strategies that could be important in the quest to conserve body water. I therefore investigated the 24h nychthemeral body temperature rhythms of the gemsbok, red hartebeest and blue wildebeest, in combination with their 24h microclimate use patterns, during the five months of a southern hemisphere calendar year most challenging physiologically: the end of the dry season through the peak of summer. I found no species differences in the 24h nychthemeral body temperature rhythms of the gemsbok, the red hartebeest or the blue wildebeest. All three species, however, were heterothermic over about the first 50 days of the study, as a result of elevated maximum and depressed minimum body temperatures. Although subtle differences were detected in microclimate use, all three species used behavioural thermoregulation and accessed microclimates cooler than that available in the full sun. Such behaviour was enhanced during the hottest days, compared to the coolest days. In conclusion, I have investigated some of the water conservation strategies relied upon by large African ungulates in their current environments. These strategies are not mutually exclusive and will all benefit these species in the face of climate change. The long-term monitoring of these water conservation strategies will allow us to tease out the relative contributions that selective brain cooling, heterothermy and microclimate use makes to body water conservation and how that translates to individual fitness.DH201

The Assessment of Practical Per-Cooling Targeting Peripheral Limbs During Exercise in Hot and Humid Environments

When excess body heat generation owing to the performance of exercise coincides with the heat dissipation limitations presented by hot and humid environments, the body’s ability to maintain thermal balance is compromised, and internal temperatures can rise to dangerous levels. Individuals who exercise in hot environments commonly look to acute cooling strategies to provide thermoregulatory assistance in order to avoid the health risks and performance decrements brought about by elevated thermal stress. Many cooling techniques aim to apply cold surfaces to large areas of skin on the torso, head, or neck to extract heat directly from core regions of the body. These locations, however, are often difficult to access without disrupting movement. In many exercise modalities including cycling, paddle sports, or wheelchair sports, however, peripheral regions such as the upper or lower limbs remain almost stationary, and may present a convenient location to apply cooling garments/equipment without disrupting required movements. The research studying the impact of practically applicable cooling techniques at these locations, however, is limited and inconclusive, prompting the present work. This document first outlines the quantifiable heat transfer principles that determine human thermal behaviour, and discusses the effects of thermal stress and acute cooling interventions. It then outlines practical considerations regarding the applications of cooling techniques, motivating the proposal of a novel technique that does not interfere with exercise performance by targeting the volar forearm skin of cyclists during exercise. The impacts of forearm cooling are then assessed experimentally during cycling ergometry exercise in a hot and humid environment. The cooling was observed to reduce the rate of core temperature rise by 0.43 ± 0.34°C/hr (p=0.002), while also eliciting significant reductions in heart rate drift and rating of thermal comfort. Computational modelling of the human thermal system was then employed to extend the experimental investigation and assess what impact the cooling may have during true cycling applications outside of the laboratory setting. Model outcomes suggest that the effects of the outdoor environment may reduce the effectiveness of the applied cooling slightly, but that the cooling will still be capable of providing quantifiable benefits. The impact of the cooling was also simulated across a range of ambient conditions, and the cooling was generally observed to be more impactful in hotter air temperatures and at higher ambient humidity levels

Aspects of age, growth, demographics and thermal biology of two lamniform shark species

Age and growth rates for salmon sharks (Lamna ditropis) in the eastern North Pacific (ENP) were estimated from seasonally formed bands in the vertebrae, and compared to previously published life history parameters for this species from the western North Pacific (WNP). Results of this study show that salmon sharks in the ENP achieve their maximum length at a faster rate, reach sexual maturity at an earlier age and achieve a greater weight-at-length than those in the WNP. Additionally, this dissertation shows that adult salmon sharks maintain a specific body temperature independent of changes in ambient temperature through a combination of physical and physiological means, and essentially function as homeotherms. Due to uncertainty in previous life history parameter estimates for sand tiger sharks (Carcharias taurus) in the western North Atlantic, age and growth rates were re-estimated using a larger sample size and captive individuals injected with oxytetracycline (OTC), a fluorescent skeletal marker. The results support a hypothesis that this species forms one pair of growth bands annually in the vertebral centra, whereas previous growth rate estimates were based on the formation of two bands per year. as such, the growth rate of this species is considerably slower than previously predicted and the population more susceptible to fishing mortality. Demographic analyses were conducted for salmon sharks in the ENP and WNP, and for sand tiger sharks (based on new life history parameter estimates) with uncertainty in vital rates incorporated via Monte Carlo simulations. Density-dependent compensation was included in models where fishing mortality was imposed by increasing sub-adult survivorship from output values generated by a previously published Intrinsic Rebound Potential model. The results indicate that both species are extremely vulnerable to fishing mortality and that no fishery should be implemented for sand tiger sharks or salmon sharks in the WNP. Salmon sharks in the ENP were the only population examined that indicated the potential to tolerate any fishing mortality. A comparison of growth completion rates and other life history parameters of ectothermic and endothermic sharks did not indicate that endothermic sharks achieve their maximum length at a faster rate than ectothermic sharks

Aerospace medicine and biology: A continuing bibliography with indexes (supplement 343)

This bibliography lists 125 reports, articles and other documents introduced into the NASA Scientific and Technical Information System during January, 1989. Subject coverage includes: aerospace medicine and psychology, life support systems and controlled environments, safety equipment, exobiology and extraterrestrial life, and flight crew behavior and performance

Aerospace Medicine and Biology: A cumulative index to the 1980 issues

A cumulative index to the abstracts contained in the Supplements 203 through 214 of Aerospace Medicine and Biology: A Continuing Bibliography is presented. It includes three indexes--subject, personal author, and corporate source

Medical Laser-Induced Thermotherapy - Models and Applications

Heat has long been utilised as a therapeutic tool in medicine. Laser-induced thermotherapy aims at achieving the local destruction of lesions, relying on the conversion of the light absorbed by the tissue into heat. In interstitial laser-induced thermotherapy, light is focused into thin optical fibres, which are placed deep into the tumour mass. The objective of this work was to increase the understanding of the physical and biological phenomena governing the response to laser-induced thermotherapy, with special reference to treatment of liver tumours and benign prostatic hyperplasia. Mathematical models were used to calculate the distribution of light absorption and the subsequent temperature distribution in laser-irradiated tissues. The models were used to investigate the influence on the temperature distribution of a number of different factors, such as the design of the laser probe, the number of fibres, the optical properties of the tissue, the duration of irradiation, blood perfusion and boundary conditions. New results concerning transurethral microwave thermotherapy were obtained by incorporating the distribution of absorbed microwaves into the model. Prototypes of new laser applicators for anatomically correct treatment of benign prostatic hyperplasia were developed and tested ex vivo. Experimental work on liver tumours pointed to the importance of eliminating the blood flow in the liver during treatment to reduce convective heat loss. In addition, it was shown that hepatic inflow occlusion during treatment increased the thermal sensitivity of tumour tissue. The dynamic influence of interstitial laser thermotherapy on liver perfusion was investigated using interstitial laser Doppler flowmetry. Vessel damage after the combined treatment of laser-induced heat treatment and photodynamic therapy was studied