Metabolic Heating Research Articles

Influence of air stability and metabolic rate on exhaled flow.

The characteristics of contaminant transport and dispersion of exhaled flow from a manikin are thoroughly studied in this article with respect to the influence of two important factors: air stability conditions and metabolic rates. Four cases with the combinations of stable and neutral conditions as well as lower (1.2 met) and higher (2 met) metabolic rates for a breathing thermal manikin are employed. The exhaled contaminant is simulated by smoke and N2 O to visualize and measure the contaminant distribution both around and in front of the manikin. The results show that the microenvironment around the manikin body can be affected by different air distribution patterns and metabolic heating. Under stable conditions, the exhaled contaminant from mouth or nose is locked and stratified at certain heights, causing potentially high contaminant exposure to others. In addition, velocity profiles of the pulsating exhaled flow, which are normalized by mean peak velocities, present similar shapes to a steady jet. The outlet velocity close to the mouth shows decrement with both exhalation temperature and body plume. The velocity decay and concentration decay also show significant dependence on air stability and metabolic level.

Cone thermogenesis and its limits in the tropical Cycas micronesica (Cycadaceae): Association with cone growth, dehiscence, and post‐dehiscence phases

Thermogenesis is a prominent pollination-related feature of cycad cones and is generally assumed to play a role in pollination. Although typically studied just before, during, and immediately after the cones' pollination phase, thermogenesis may be present in other cone developmental phases. • We assayed thermogenesis in Cycas micronesica, Guam's endangered cycad, over successive cone developmental phases by measuring temperatures in shaded and unshaded in situ cones for up to 7 wk. We also studied the effect of ambient conditions on cone thermogenesis in laboratory experiments and estimated the cones' metabolic heating rates. • Pollen cones exhibit a continuous, but small, metabolically generated thermogenesis for multiple weeks, including a single thermogenic peak temperature greater than peak ambient each day. The magnitudes of those daily peak temperature elevations above ambient reach maxima twice during cone development: a few days before dehiscence and approximately 1 wk post-dehiscence. Excised cones in dark, fixed temperature environments generated multiple thermogenic events (∼24 h period) over ∼10 d. Cones appear to initiate a protective temperature regulatory response at temperatures ≥∼38°C. • Cycas micronesica pollen cones exhibit several thermogenic attributes not reported in other cycads, including continuous thermogenesis for many weeks. These cones grow in a hot tropical environment that likely confines their metabolically generated temperature increases to a small thermogenic window beyond which they encounter heat stress. These findings suggest the presence of thermogenic functions not strictly related to pollination and a potential vulnerability to warming climates.

Vegetation cover predicts temperature in nests of the hawksbill sea turtle: implications for beach management and offspring sex ratios

Whether a sea turtle embryo develops into a male or a female depends, as with many other reptiles, on the temperature during incubation of the eggs. With sea turtles, warm tempera- tures produce 100% females and, thus, increasing global temperatures have the potential to sig- nificantly alter offspring sex ratios. Nest-site selection provides a potential mechanism by which females might adjust the sex of their offspring, but necessitates a reliable cue which provides information about the thermal properties of a nest. Overstory vegetation cover was found to sig- nificantly predict temperatures in nests of the hawksbill sea turtle Eretmochelys imbricata. Nests placed under high vegetation cover are significantly cooler and remain within the male-producing range of temperatures throughout incubation. Interestingly, metabolic heating of the developing clutch is less pronounced under vegetation, further reinforcing the importance of this nesting habitat with respect to the production of males. This underscores the importance of preserving natural vegetation cover at hawksbill nesting beaches in order to maintain the thermal diversity of nesting sites and, potentially, mitigate the impacts of increasing global temperatures.

Emergence Success and Sex Ratio of Natural and Relocated Nests of Olive Ridley Turtles from Alas Purwo National Park, East Java, Indonesia

The nest environment, in particular sand temperature, is critical to the breeding ecology of sea turtles which lack parental care during their early stages of life. We investigated the effects of sand temperature on emergence success and sex ratio of Olive Ridley (Lepidochelys olivacea) hatchlings in in situ and relocated nests in Alas Purwo National Park (APNP), East Java, Indonesia. Over two years of observation no in situ nests survived due to predation, while emergence success in relocated nests varied between the years. Temperatures above 34°C experienced by the nests over at least three consecutive days during incubation (T3dm) had decreased emergence success in both years. These high temperatures occurred as a result of metabolic heating of developing embryos combined with high sand temperatures. The indirect method of determining sex ratios from nest temperature profiles indicated that the hatchery at APNP generated more male hatchlings than female. Our study provides justification for on-going eg...

Mathematical model of cycad cones’ thermogenic temperature responses: Inverse calorimetry to estimate metabolic heating rates

A mathematical model based on conservation of energy has been developed and used to simulate the temperature responses of cones of the Australian cycads Macrozamia lucida and Macrozamia. macleayi during their daily thermogenic cycle. These cones generate diel midday thermogenic temperature increases as large as 12°C above ambient during their approximately two week pollination period. The cone temperature response model is shown to accurately predict the cones’ temperatures over multiple days as based on simulations of experimental results from 28 thermogenic events from 3 different cones, each simulated for either 9 or 10 sequential days.The verified model is then used as the foundation of a new, parameter estimation based technique (termed inverse calorimetry) that estimates the cones’ daily metabolic heating rates from temperature measurements alone. The inverse calorimetry technique’s predictions of the major features of the cones’ thermogenic metabolism compare favorably with the estimates from conventional respirometry (indirect calorimetry). Because the new technique uses only temperature measurements, and does not require measurements of oxygen consumption, it provides a simple, inexpensive and portable complement to conventional respirometry for estimating metabolic heating rates. It thus provides an additional tool to facilitate field and laboratory investigations of the bio-physics of thermogenic plants.

Ranking of parameters in bioheat transfer using Taguchi analysis

Modeling bioheat transfer plays an important role in the treatment planning of cancer therapy. Historically, Pennes bioheat equation has been used for bioheat transfer modeling in living tissue because of its simplicity, effectiveness and ease of application. It is imperative that the effect of each parameter involved in the bioheat transfer be known. The ultimate goal of a cancer treatment is to maximize the damage to the cancer affected tissue and minimize the collateral damage to the normal tissue surrounding it. This study takes into account six 3-level factors namely blood perfusion rate in healthy tissue and tumor, frequency, applied voltage, metabolic heating rate in healthy tissue and tumor. The purpose of this study is to rank the parameters involved in electromagnetic heating and determine the factors which affect the bioheat transfer the most. Maximum obtained temperature was taken as the response variable and Taguchi orthogonal arrays were used to obtain required data with minimum number of numerical experiments required. Calculations were performed in Minitab statistical software. The results show that the applied voltage has the largest effect on the maximum achieved temperature followed by frequency of the electromagnetic radiation.

Sex ratios of leatherback turtles: hatchery translocation decreases metabolic heating and female bias

Many sea turtle nesting colonies are in decline worldwide, and a common conserva- tion practice maximizes hatchling production by translocating eggs from threatened nests to pro- tective beach hatcheries. Typically, translocated eggs are 'doomed', or at risk of death due to tidal inundation, predation, or poaching. Sea turtles exhibit temperature-dependent sex determination. We determined how primary sex ratios, estimated from incubation temperatures, were affected by egg clutch translocation to a beach hatchery. We monitored incubation temperatures of eastern Pacific leatherback turtles Dermochelys coriacea in hatchery and in situ clutches at Playa Grande, Costa Rica, throughout each nesting season from 1998 to 2007. In situ clutches were estimated to be 90% female, whereas hatchery clutches (9% of clutches) were estimated to be 64% female. Taking into account differences in hatching success of in situ and hatchery nests, the overall sex ratio was 83% female. The Playa Grande hatchery abiotic environment (sand temperatures, water inputs) was similar to that in situ. However, metabolic heating was significantly reduced in hatch- ery clutches. The most likely explanation is that temperatures in hatchery clutches were cooler (less female-biased) due to decreases in the number of metabolizing embryos since hatchling suc- cess was lower in hatchery clutches than in situ clutches. Alteration of both primary sex ratios and hatching success is the tradeoff for reducing the risk of death to egg clutches by translocation to a hatchery. This tradeoff is not unique to Playa Grande leatherback turtles, and it is a strong indica- tion that hatchery translocation should be used cautiously.

Incubation Temperatures and Metabolic Heating of Relocated and In Situ Loggerhead Sea Turtle (Caretta caretta) Nests at a Northern Rookery

Miniature temperature loggers were used to better understand the incubation temperatures, patterns in metabolic heating, and potential implications for sex determination of relocated and in situ loggerhead sea turtle clutches near the northern extent of their nesting range. All sea turtles display temperature-dependent sex determination, with cooler nests producing males and warmer nests producing females. Analysis of the factors that affect incubation temperatures provides insight into variation in hatchling sex ratios over temporal and spatial scales and may help to guide management measures for the imperiled loggerhead sea turtle. Although no temperature difference was detected between relocated and in situ clutches during the thermal sensitive period, relocated nests hatched more quickly and incubated at warmer temperatures than in situ clutches for the entire incubation period. Metabolic heating was apparent in all clutches, beginning during the middle third of incubation, with the greatest gradient between nest temperature and surrounding sand temperatures (x ¯ = 1.5 ± 0.05°C) that occur during the final third of incubation. The magnitude of metabolic heating was not different between relocated and in situ clutches. Diel temperature fluctuations within nests were significantly less pronounced than in adjacent sand, which implies a degree of thermal buffering within the nest chamber. During the thermosensitive period, all nests incubated at a mean temperature above that of the estimated pivotal temperature (29.2°C), which implies a strongly female-biased hatchling sex ratio during the portion of the nesting season monitored. Potential impacts on incubation temperature and resultant sex ratios should be considered and explored on a beach-by-beach basis before adopting nest relocation as a conservation measure.

Modeling Bioheat Transport at Macroscale

Macroscale thermal models have been developed for biological tissues either by the mixture theory of continuum mechanics or by the porous-media theory. The former uses scaling-down from the global scale; the latter applies scaling-up from the microscale by the volume averaging. The used constitutive relations for heat flux density vector include the Fourier law, the Cattaneo–Vernotte (Cattaneo, C., 1958, “A Form of Heat Conduction Equation Which Eliminates the Paradox of Instantaneous Propagation,” Compt. Rend., 247, pp. 431–433; Vernotte, P., 1958, “Les Paradoxes de la Théorie Continue de I’equation de la Chaleur,” Compt. Rend., 246, pp. 3154–3155) theory, and the dual-phase-lagging theory. The developed models contain, for example, the Pennes (1948, “Analysis of Tissue and Arterial Blood Temperature in the Resting Human Forearm,” J. Appl. Physiol., 1, pp. 93–122), Wulff (1974, “The Energy Conservation Equation for Living Tissues,” IEEE Trans. Biomed. Eng., BME-21, pp. 494–495), Klinger (1974, “Heat Transfer in Perfused Tissue I: General Theory,” Bull. Math. Biol., 36, pp. 403–415), and Chen and Holmes (1980, “Microvascular Contributions in Tissue Heat Transfer,” Ann. N.Y. Acad. Sci., 335, pp. 137–150), thermal wave bioheat, dual-phase-lagging (DPL) bioheat, two-energy-equations, blood DPL bioheat, and tissue DPL bioheat models. We analyze the methodologies involved in these two approaches, the used constitutive theories for heat flux density vector and the developed models. The analysis shows the simplicity of the mixture theory approach and the powerful capacity of the porous-media approach for effectively developing accurate macroscale thermal models for biological tissues. Future research is in great demand to materialize the promising potential of the porous-media approach by developing a rigorous closure theory. The heterogeneous and nonisotropic nature of biological tissue yields normally a strong noninstantaneous response between heat flux and temperature gradient in nonequilibrium heat transport. Both blood and tissue macroscale temperatures satisfy the DPL-type energy equations with the same values of the phase lags of heat flux and temperature gradient that can be computed in terms of blood and tissue properties, blood-tissue interfacial convective heat transfer coefficient, and blood perfusion rate. The blood-tissue interaction leads to very sophisticated effect of the interfacial convective heat transfer, the blood velocity, the perfusion, and the metabolic reaction on blood and tissue macroscale temperature fields such as the spreading of tissue metabolic heating effect into the blood DPL bioheat equation and the appearance of the convection term in the tissue DPL bioheat equation due to the blood velocity.

Field lethal incubation temperature of olive ridley sea turtle Lepidochelys olivacea embryos at a mass nesting rookery

Hatching success in olive ridley mass nesting arribada beaches is typically low. We con- ducted a short study to understand whether incubation temperature in dry months accounts for exceedingly low hatching success at Ostional Beach, Costa Rica, a mass nesting rookery. We mea- sured in situ incubation temperatures in nests from 4 arribadas recorded in October to December 2008, and January 2009. Mean incubation temperatures for all months exceeded the upper lethal limit of 35°C, and no nests produced hatchlings when incubated at this or higher temperatures. Embryo development was inversely related to mean incubation temperature. Hatching success was low (2%) for the study period, and only 5 of 37 marked nests produced hatchlings. Mean incubation temperature for successful nests was <35°C. Since incubation temperatures of 32°C and higher recorded during the gonadal thermosensitive period were above the mean pivotal temperature of 30.5°C, the few hatchlings produced were presumably female. Incubation temperatures were signif- icantly higher during the second and third trimesters of incubation during all months as a result of metabolic heating. However, during January to March when embryos did not develop, higher incu- bation temperatures of in situ nests relative to controls indicated that heating was a result of micro- bial activity associated with egg decomposition. Our study demonstrates that after the onset of the dry season, incubation temperatures at this beach become lethal.

Selection of winter roosts in the Great Tit Parus major: influence of microclimate

The success in energy saving in roosting Great Tits (Parus major) is potentially influenced by roost microclimatic characteristics. We tried to learn about the pattern in cavity microclimate influence on night roosting of birds, under natural weather conditions. An experimental aviary offered two artificial tree-roosts with different microclimatic conditions which varied according to the outdoor conditions (mainly due to solar radiation) and microclimate retention capability of roosts. Birds actively explored roosts before the final choice of sleeping site. Two hours prior to sunset, there were significant differences between the roosts (n = 11 adult males tested, each six nights). Selected roosts had higher average temperature (Wilcoxon matched pairs test, P = 0.017) and temperature at the time of sunset (P = 0.028). Simultaneously, inside temperature decreased slowly (P = 0.047). During the night, when birds slept in one of the roosts, the average temperature was higher (P < 0.001) and the fluctuation range of temperatures was smaller (P = 0.003) there. Moreover, at the morning twilight, the temperature of the occupied roost was higher (P < 0.001). Humidity did not have a significant influence at all. The effect of metabolic heating was demonstrated. When birds slept in the insulated roost (n = 30 nights), the indoor average temperature significantly differed from the non-insulated and outdoor temperatures (Kruskal–Wallis ANOVA, P = 0.0001). Selection of an actually warmer and thermally more stable roost according to the course of weather indicates demand for a wide spectrum of potential roosts in the natural environment.

Unstable, self‐limiting thermochemical temperature oscillations in Macrozamia cycads

Field measurements and laboratory experiments on the Australian cycads Macrozamia lucida and Macrozamia macleayi demonstrate that their cones' diel peak thermogenic temperature increase varies systematically with cone stage, with single thermogenic temperature peaks occurring daily for up to 2 weeks and reaching 12 degrees C above ambient at midstage. The initiation, magnitude and timing of those peaks are strongly modulated by ambient temperature; the period between successive thermogenic temperature peaks is not circadian, and light is neither necessary nor sufficient to initiate a thermogenic event. A mathematical analysis is developed that provides a unified explanation of the experimental results. It describes these unstable, self-limiting thermogenic events in terms of conservation of energy and a first-order chemical reaction rate model that includes an Arrhenius equation dependence of the cone's metabolic heating rate on the cone temperature.

Effects of Nest Depth, Shading, and Metabolic Heating on Nest Temperatures in Sea Turtle Hatcheries

This study investigated the effects of hatchery shading, nest depth, and metabolic heating on the temperature of Chelonia mydas clutches incubated in hatcheries at Ma'Daerah, Terengganu, Malaysia. Metabolic heating was found to be the most influential factor on nest temperature; the number of completely developed eggs explained nearly half of the variation in mean nest temperature. The degree of hatchery shading (70% vs. 100%) and nest depth (50 vs. 75 cm) had little influence on nest temperatures, with mean nest temperatures between 28° and 28.6°C in the first third of incubation (before metabolic heating of the clutch began to have an effect). Nests at a depth of 75 cm had significantly lower daily temperature ranges than nests at a depth of 50 cm, but a maximum mean daily range of 0.5°C (50 cm depth in 70% shade hatchery) resulted in calculated constant temperature equivalents (CTE) being identical to observed mean nest temperatures. The results of this study indicate that, under current climatic conditions in this area, shading between 70% and 100% and nest depths between 50 and 75 cm will incubate green turtle clutches within the optimal temperature range for development. However, this information is site-specific and could vary significantly between locations due to the complex interaction of biological, chemical, and physical factors that influence sea turtle nest temperature.

Sand and nest temperatures and an estimate of hatchling sex ratio from the Heron Island green turtle (Chelonia mydas) rookery, Southern Great Barrier Reef

Sand and nest temperatures were monitored during the 2002–2003 nesting season of the green turtle, Chelonia mydas, at Heron Island, Great Barrier Reef, Australia. Sand temperatures increased from ∼ 24°C early in the season to 27–29°C in the middle, before decreasing again. Beach orientation affected sand temperature at nest depth throughout the season; the north facing beach remained 0.7°C warmer than the east, which was 0.9°C warmer than the south, but monitored nest temperatures were similar across all beaches. Sand temperature at 100 cm depth was cooler than at 40 cm early in the season, but this reversed at the end. Nest temperatures increased 2–4°C above sand temperatures during the later half of incubation due to metabolic heating. Hatchling sex ratio inferred from nest temperature profiles indicated a strong female bias.

Metabolic heating in Mediterranean loggerhead sea turtle clutches

Offspring sex ratio is an important demographic parameter and, given its determination by incubation temperature in sea turtles, might be a key factor for their conservation under climate warming. An appealing approach to estimate hatchling sex ratios is to measure sand temperatures at nest depth and deduce hatchling sex ratios from a beforehand-established relationship of hatchling sex ratio and sand temperature. Such estimates will only be accurate though if metabolic heat produced by the embryos is considered. Judging whether metabolic heating has a potential effect on hatchling sex ratios without actually measuring temperature within clutches would greatly facilitate monitoring protocols. We tested for a relationship between the amount of metabolic heating and the number of developed embryos as well as clutch size in the largest known loggerhead sea turtle ( Caretta caretta) population of the Mediterranean on Zakynthos (Greece). Temperatures were measured within 20 nests as well as at a reference site in the sand at nest depth. Metabolic heating was detected, but only during the last third of the incubation period did nests heat up considerably (1.6 °C on average) above the temperature of the surrounding sand. During the middle third of incubation, when sex is determined, the amount of metabolic heating was negligible. The amount of metabolic heating during the last third of the incubation duration was significantly correlated to the number of offspring developed to at least about 75% of incubation duration. This factor explained nearly 50% of variation in metabolic heating. Metabolic heating was also significantly correlated to clutch size. Given that clutch size within the Mediterranean is largest in Zakynthos loggerheads, we conclude that metabolic heating can be ignored in the estimate of hatchling sex ratios in Mediterranean loggerhead populations. These results thus provide the basis for a feasible monitoring of hatchling sex ratios in the loggerhead sea turtle in the Mediterranean.

Evolução do estado fisiológico da parte aérea do morangueiro durante a armazenagem em câmara frigorífica

O objetivo deste trabalho foi avaliar o estado fisiológico da parte aérea das plantas de morangueiro das cultivares Gariguette e Elsanta durante estocagem em câmara fria (-2ºC), de janeiro a agosto. Pelo teste biológico, a capacidade de crescimento manteve-se alta, sem evolução significativa durante a estocagem. O fluxo de calor metabólico (Q) e a intensidade respiratória (RCO2) dos tecidos da zona apical, medidos pela microcalorimetria na saída da câmara fria, não evoluíram significativamente, mas aumentaram após 48 e 72 horas de aclimatação a 20ºC. Existiu um estreito paralelismo entre os valores de Q e RCO2 e da umidade ponderal (UP) dos tecidos. A parte aérea das plantas manteve a capacidade de crescimento mesmo após oito meses de estocagem.

HOT BUGS: BODY TEMPERATURE OF INSECTS IN SUNSHINE

![Figure][1] It is always tempting to see the past as a dark and primitive age or a golden and heroic one. Peter Digby's classic paper, after half a century, can perhaps be viewed from both perspectives. Either way it represents, if not a turning point, certainly a substantial stride toward

Effects of hatchery shading and nest depth on the development and quality of Chelonia mydas hatchlings: implications for hatchery management in Peninsular, Malaysia

One of the decisions made by hatchery managers around the world is what degree of shading and nest depth are required to maximise the production of high-quality hatchlings at optimal sex ratios. The primary objectives of this study were to determine the effects of (1) hatchery shading and nest depth on nest temperatures and emergence lag, and (2) nest temperatures and nest depth on hatchling sex ratio and quality. In 2001, 26 Chelonia mydas clutches from Ma’Daerah beach, Terengganu, Malaysia, were relocated alternatively at depths of 50 cm and 75 cm into a 70%-shaded and a 100%-shaded hatchery. Data loggers were placed into the centre of each relocated clutch to record the temperature every hour over the course of incubation. When the hatchlings emerged, a sample of the clutch was run, measured and weighed and a separate sample was examined histologically for sex characteristics. Nest temperatures ranged between 28°C and 30°C and generally showed increases over the second half of incubation due to metabolic heating of the clutch. There was no significant correlation found between nest temperature and any of the hatchling parameters measured. Hatchlings from 75-cm-deep nests had a longer emergence lag (46.4 (±10.2) h) than hatchlings from 50-cm-deep nests. Hatch and emergence success were similar to those of natural populations and hatchling sex ratios were male dominant, with an average of 72% males. There was a poor correlation between mean middle-third incubation temperatures and sex ratio. Hatchlings from 75-cm-deep nests had similar running speeds but lower condition index than their conspecifics from 50-cm-deep nests.

Metabolic heating of embryos and sex determination in the american alligator, Alligator mississippiensis

1.The potential for metabolic heating by embryonic reptiles to influence temperature-dependent sex determination (TSD) has not been examined in a controlled environment.2.In a laboratory experiment conducted within a single background environment, eggs of the American Alligator (Alligator mississippiensis) arranged in a small cluster (“clutch”) yielded a sex ratio (73% male) that differed appreciably from the sex ratio (15% male) in a matched set of eggs in an open arrangement.3.The apparent cause of the difference in sex ratio was metabolic heating, which caused much higher temperatures in the cluster than in the open arrangement.

Incubation Environment and Nest Success of the Flatback Turtle (Natator depressus) from a Natural Nesting Beach

The thermal and hydric environment during incubation of turtle eggs influences hatchling size, sex, energy reserves, and thus their quality. Information on the natural nest environment of flatback turtles (Natator depressus) is lacking. Therefore, the current study investigated the thermal and hydric environment of their nest chambers and nesting beach (at Peak Island, east coastal Queensland during the 1996/1997 and 1997/1998 nesting seasons). The temperature of nest chambers and the nesting beach showed temporal and spatial variation. Beach temperature increased through the nesting season as summer progressed and showed significant vertical and lateral variation. The temperature in the core of nest chambers increased as incubation progressed (on average 7 C) apparently because of both metabolic heating and the natural seasonal increase in sand temperature. The temperature range of nests was 25.5–36.5 C, with many nests exposed to temperatures above 35 C for extended periods. Water content of sand surrounding nest chambers at the beginning of incubation ranged from 2.6–7.8% (w/w), varying with date of laying and location on the beach. Natator depressus eggs may be more tolerant of high incubation temperatures and severe moisture stress than those of most other sea turtle species. Nest success was not influenced by the position of the nest on the beach but was positively related to clutch size. Neither nest success nor clutch size varied significantly between subsequent clutches of an individual female. Hatchling sex ratio at this beach possibly depends on the date of egg laying. Because high density nesting occurs when beach temperature appears to produce almost all female hatchlings, the hatchling sex ratio at Peak Island is likely to be biased toward females. Data gathered in the current study will assist in the development of management strategies to protect this endemic species.