Similar Thermal Responses Research Articles

Accident tolerant fuels behavior analysis for Pressurized Water reactor in steady state and transient conditions

Nuclear Fission Technology (NFT) is constantly developing to seek an increasingly safer operation and, consequently, increase the public acceptance of nuclear energy generation. Therefore, the development of new types of nuclear fuels and the search for different materials for cladding fuel rods has been the subject of research mainly to provide better efficiency in to carry energy in nuclear reactors and also to reduce possible damages in accident situations. In this way, this work aimed to compare the thermal response and behavior of Zircaloy 4, SiC reinforced with Hi-Nicalon type S (HNS) and FeCrAl alloy when they were considered as fuel cladding at steady state and transient conditions during operation of a PWR (Pressurized Water Reactor). Two thermal hydraulic models using the RELAP5 MOD3.3 and RELAP5-3D v. 4.3.4 codes and the reference data from the document Final Safety Analysis Report of Angra 2 PWR were used to perform the investigations. The work was developed in two steps. In the first one, the results of the Angra 2 nodalization in steady state conditions were compared with the Angra 2 reference data, obtaining good agreement. In the second step, the thermal response, when the cladding materials were changed, was evaluated in steady state and transient situations. The transients LOFA (Loss of Flow Accident), LBLOCA (Large Break - Loss of Coolant Accident), and coolant channel blockage were simulated in extreme conditions. The results have shown that substituting Zircalloy 4 alloy by FeCrAl or ceramic cladding SiC HNS presented a similar and better thermal response. Moreover, in another simulation, UO2 fuel has been replaced by U3Si2. The results showed lower temperatures at the fuel center in the rods with U3Si2 than those using UO2 as nuclear fuel, demonstrating the advantages of using U3Si2 fuel concerning the radial heat transfer in the rod.

Patterns of thermal adaptation in a globally distributed plant pathogen: Local diversity and plasticity reveal two-tier dynamics.

Plant pathogen populations inhabit patchy environments with contrasting, variable thermal conditions. We investigated the diversity of thermal responses in populations sampled over contrasting spatiotemporal scales, to improve our understanding of their dynamics of adaptation to local conditions. Samples of natural populations of the wheat pathogen Zymoseptoria tritici were collected from sites within the Euro‐Mediterranean region subject to a broad range of climatic conditions. We tested for local adaptation, by accounting for the diversity of responses at the individual and population levels on the basis of key thermal performance curve parameters and “thermotype” (groups of individuals with similar thermal responses) composition. The characterization of phenotypic responses and genotypic structure revealed the following: (i) a high degree of individual plasticity and variation in sensitivity to temperature conditions across spatiotemporal scales and populations; and (ii) geographic variation in thermal response among populations, with major alterations due to seasonal patterns over the wheat‐growing season. The seasonal shifts in functional composition suggest that populations are locally structured by selection, contributing to adaptation patterns. Further studies combining selection experiments and modeling are required to determine how functional group selection drives population dynamics and adaptive potential in response to thermal heterogeneity.

Flexible Janus Functional Film for Adaptive Thermal Camouflage

AbstractWith the increasing development of infrared (IR) detection technologies for both military and civil applications, IR anti‐detection technologies, also known as thermal camouflage technologies, have attracted great attention in recent years. Decreasing the surface emissivity may be effective for high‐temperature targets, but fails for adaptive thermal camouflage in dynamic scenes where the background temperature varies. In this work, we demonstrate a flexible Janus functional film (JFF) for adaptive thermal camouflage. The JFF consists of a low emissivity (low‐ε) layer and a high heat capacity (high‐C) layer. The low‐ε layer can effectively suppress the IR radiation of the objects, thus reducing the temperature of the objects in IR camera, while the high‐C layer can make similar thermal response as the background. According to different environmental conditions, different surfaces of JFF can be selected as camouflage surface to achieve static or dynamic thermal camouflage effect. What's more, the substrate materials of JFF (i.e., high‐density polyethylene (HDPE), silica gel (SG)) enable the film with good flexibility and realize the encapsulation of the functional filler, thus improving its reliability of resisting water and oxygen. Such flexible JFF with high reliability, easy scalability, and low cost may hold great promise for broad applications in adaptive thermal camouflage.

Evaluation of interface pressure and temperature management in five wheelchair seat cushions and their effects on user satisfaction

BackgroundFactors such as the manufacturing materials, shape or even the mechanical and thermal response of sitting Pressure Redistribution Support Surfaces (PRSS) can be potential contributors to pressure ulcers. However, few studies have compared a number of characteristics of the most frequently used devices. ObjectiveTo compare three potential contributors to pressure ulcers in five commercial PRSS: pressure redistribution, temperature and perceived comfort. Method: Study with a cross-over randomized design in healthy volunteer participants. Data was collected in a temperature and relative humidity controlled environment. To assess thermal response, the temperature (Flir-E60) of the region of interest was captured before and after use of each PRSS for further analysis. The region of interest was the gluteal zone. To assess the pressure redistribution a pressure mat (XSensor®) was used between the 5 cushion and each study participant using a standardized method. Finally, a subjective perception questionnaire recorded comfort, adaptability and thermal sensation parameters. Data analysis levels of significance were set at 0.05. ResultsA total of 22 participants completed the assessments. There were no statistically significant differences in baseline temperatures between PRSS (>0.05). Pressure redistribution analysis showed significant differences between all PRSS in all variables evaluated except in the maximum and peak pressure index al sacrum. The subjective assessment suggested no major user-perceived differences between PRSS. ConclusionSeat cushions made of open cell polyurethane foam blocks of variable hardness and the horseshoe cushion (also open cell polyurethane foam) seem to provide a more effective pressure relief characteristic than those injected with polyurethane foam and gel in most of the studied pressure variables. However, the cushions provide similar thermal response and perceived comfort.

Choosing source populations for conservation reintroductions: lessons from variation in thermal tolerance among populations of the imperilled redside dace1

Reintroduction is an increasingly common conservation tool used to recover populations of imperilled species, but its success depends on the suitability of the introduced animals’ phenotype for their new habitat. For fishes, thermal tolerance may be a key trait in urbanized habitats. We compared thermal tolerance (CTmax) among three lineages (western, central, eastern) of imperilled redside dace (Clinostomus elongatus). CTmax of eastern adults was 3–4 °C lower than that of the other lineages, but adults of each lineage had similar thermal acclimation responses. In contrast, the acclimation response of juveniles differed by ∼80% between the central and western lineages. Using these data, we predicted how each lineage would fare in a hypothetical reintroduction to relatively warm urbanized habitats. Owing to the differences in juvenile acclimation responses, predicted thermal safety margins for the central lineage were double those predicted for the western lineage. Overall, we suggest that CTmax is a useful trait to incorporate into the source population selection process; however, there is an urgent need for the establishment of captive experimental research populations of imperilled species to address remaining uncertainties.

Fabrication and performance of shape‐stable phase change materials based on epoxy group crosslinking

AbstractShape‐stable phase change materials (SSPCMs) have attracted increased attention as they can be used in applications such as solar energy storage materials and smart textiles. Hexadecyl acrylate (HDA) was free‐radical copolymerized with allyl glycidyl ether (AGE) to form a copolymer with epoxy groups. It was further solidified with diethylenetriamine to form a series of novel SSPCMs. HDA could be limited to a stable 3D cross‐linking network constructed from epoxy groups, giving PCM excellent shape stability. Infrared spectroscopy and hydrogen nuclear magnetic spectroscopy showed the successful fabrication of poly(hexadecyl acrylate) (PHDA) with epoxy group. The maximum enthalpies of the SSPCMs with 5 wt% AGE during heating and cooling were 86 and 86 J/g, respectively, which indicated that they have good thermal energy storage densities. The initial melting and freezing temperatures were 32 and 29°C, respectively, which were within the comfortable temperature range of human body. In addition, the thermal decomposition temperature of SSPCMs was higher than 270°C. After 50 thermal cycles, the materials still showed excellent phase change performances. Moreover, the specimen with low degree of cross‐linking had similar temperature control and thermal response capabilities to PHDA. These SSPCMs exhibited excellent thermal performance, thermal reliabilities, and stabilities. Therefore, they were expected to be applied in various applications, including solar energy storage, energy‐saving buildings, and wearable temperature control textiles.

Multi-Tissue Analysis on the Impact of Electroporation on Electrical and Thermal Properties.

Tissue electroporation is achieved by applying a series of electric pulses to destabilize cell membranes within the target tissue. The treatment volume is dictated by the electric field distribution, which depends on the pulse parameters and tissue type and can be readily predicted using numerical methods. These models require the relevant tissue properties to be known beforehand. This study aims to quantify electrical and thermal properties for three different tissue types relevant to current clinical electroporation. Pancreatic, brain, and liver tissue were harvested from pigs, then treated with IRE pulses in a parallel-plate configuration. Resulting current and temperature readings were used to calculate the conductivity and its temperature dependence for each tissue type. Finally, a computational model was constructed to examine the impact of differences between tissue types. Baseline conductivity values (mean 0.11, 0.14, and 0.12S/m) and temperature coefficients of conductivity (mean 2.0, 2.3, and 1.2 % per degree Celsius) were calculated for pancreas, brain, and liver, respectively. The accompanying computational models suggest field distribution and thermal damage volumes are dependent on tissue type. The three tissue types show similar electrical and thermal responses to IRE, though brain tissue exhibits the greatest differences. The results also show that tissue type plays a role in the expected ablation and thermal damage volumes. The conductivity and its changes due to heating are expected to have a marked impact on the ablation volume. Incorporating these tissue properties aids in the prediction and optimization of electroporation-based therapies.

Skin Temperature Response to a 1 km Swim Performed in Normal and Cold‐Water

Cold‐water swimming is a recreational activity that may become a future Winter Olympic event. However, unintentional cold‐water exposure can lead to hypothermia or death. Changes in body temperature are known to diminish swimming performance in persons experiencing hypothermia, although thermal changes during recreational exposure are not well characterized. This study examined skin temperature responses to a one‐kilometer swim in normal and cold‐water. Competitive swimmers (2 male and 2 female; age 44±17 years; BMI 24±2) completed a one‐kilometer swim (22 laps × 75 foot lengths) under free‐living indoor (25.5°C water and 25.0°C air) and cold outdoor (10.9°C water and 6.5°C) conditions. Skin temperature was determined with a digital infrared camera on the center of right palm, cubital fossa of arm, lateral aspect of pectoral muscle, cheek, and average of the four locations at 8.7±1.7 minutes before the swim (pre), then 0.6±0.2 and 6.4±2.1 minutes after the swim. Data (mean±SD) was analyzed with repeated measures ANOVA with significance if P<0.05. Swimmers completed the indoor and outdoor swim events in 20.7±1.7 and 21.8±1.1 minutes respectively. Average indoor skin temperature at −8.7, +0.6 and +6.4 minutes was 94.0±1.7, 85.3±1.9, and 88.1±2.2°C. Average outdoor skin temperature at −8.7, +0.6 and +6.4 minutes was 83.0±3.6, 53.5±2.3, and 67.7±2.0°C. At all times average outdoor skin temperature was lower than indoor, with the lowest temperature 0.6 minutes post‐swim. Palm indoor temperature at −8.7, +0.6 and +6.4 minutes was 91.6±3.9, 83.1±0.5, and 87.3±5.0°C. Palm outdoor temperature at −8.7, +0.6 and +6.4 minutes was 75.1±7.9, 47.4±2.7, and 58.1±2.7°C. At all times outdoor palm temperature was lower than indoor, with the lowest temperature 0.6 minutes post‐swim. Similar thermal responses were observed in the cheek, cubital fossa and pectoral locations. While time to complete the indoor and outdoor one km swims were similar, swimming in cold water was associated with delayed rewarming in the palm and cheek relative to cubital fossa and pectoral muscle.

Not all cicadas increase thermal tolerance in response to a temperature gradient in metropolitan Seoul

Rapid anthropogenic alterations caused by urbanization are increasing temperatures in urban cores, a phenomenon known as the urban heat island (UHI) effect. Two cicada species, Cryptotympana atrata and Hyalessa fuscata (Hemiptera: Cicadidae), are abundant in metropolitan Seoul where their population densities correlate strongly with UHI intensities. Such a positive correlation between cicada density and UHI intensity may be possible if cicada abundance is linked to a certain thermal tolerance. We tested this hypothesis by investigating variation in morphology and thermal responses of two cicada species along a thermal gradient in Seoul and surrounding areas. The morphological responses were measured by metrics such as length, thorax width and depth, and mass. The thermal responses were measured in terms of minimum flight temperature, maximum voluntary temperature and heat torpor temperature. First, we observed a species-specific variation in thermal responses, in which C. atrata displayed a higher thermal threshold for maximum voluntary and heat torpor temperatures than H. fuscata. Second, a positive association between temperature conditions and body sizes were displayed in females H. fuscata, but not in either conspecific males or C. atrata individuals. Third, C. atrata exhibited similar thermal responses regardless of habitat temperature, while H. fuscata in warmer areas showed an increase in heat tolerance. In addition, H. fuscata individuals with bigger thorax sizes were more heat-tolerant than those with smaller thoraxes. Overall, our research is the first to detect a variation in thermal responses and body size of H. fuscata individuals at a local scale. More investigations would be needed to better understand the adaptation mechanisms of insects linked to UHI effects.

Thermal Response of Mortar Panels with Different Forms of Macro-Encapsulated Phase Change Materials: A Finite Element Study

This paper presents a numerical investigation of thermal response of mortar panels, incorporating macro-encapsulated paraffin in different forms. Two types of macro capsules were fabricated and tested in this study using an instrumented hot plate device. The experimental results show that macro encapsulated paraffin reduced the temperature and increased time lag in the mortar panels due to the latent heat capacity of paraffin. Finite element models adopting the effective heat capacity method to model phase change effects were able to capture the overall thermal response of panels incorporated with paraffin well. Then, a parametric study was conducted using the validated finite element (FE) modelling technique to investigate the effects of different forms of macro capsules, the quantity of paraffin and the position of macro capsules. It was found that the tube and sphere macro capsules showed similar thermal responses, while the plate shaped capsules may cause a non-uniform temperature distribution in mortar panels. The quantity and position of paraffin have significant effects on the thermal response of the mortal panels. A higher paraffin content results in a significantly longer temperature lag and a lower temperature during the phase transition of paraffin. Furthermore, placing the paraffin away from the heating face can cause a longer temperature lag on the other face, which is desirable for building façade applications.

Thermal Niche Differentiation in the Benthic Diatom Cylindrotheca closterium (Bacillariophyceae) Complex.

Coastal waters are expected to undergo severe warming in the coming decades. Very little is known about how diatoms, the dominant primary producers in these habitats, will cope with these changes. We investigated the thermal niche of Cylindrotheca closterium, a widespread benthic marine diatom, using 24 strains collected over a wide latitudinal gradient. A multi-marker phylogeny in combination with a species delimitation approach shows that C. closterium represents a (pseudo)cryptic species complex, and this is reflected in distinct growth response patterns in terms of optimum growth temperature, maximum growth rate, and thermal niche width. Strains from the same clade displayed a similar thermal response, suggesting niche conservation between closely related strains. Due to their lower maximum growth rate and smaller thermal niche width, we expect the polar species to be particularly sensitive to warming, and, in the absence of adaptation, to be replaced with species from lower latitudes.

High soil temperatures alter the rates of nitrification, denitrification and associated N2O emissions

The responses of nitrification and denitrification are not well characterised at temperatures above 35 °C, which is the focus of our study. Soils collected from two dairy pastures (Victoria, Australia) were incubated at 10 to 45 °C in the dark for 5 to 10 days following amendment with 100 μg N g−1 either as NH4NO3, 14NH415NO3 or 15NH415NO3 (10 atom% 15N excess) at 50% water-filled pore space. To detect N2O from heterotrophic nitrification, acetylene (0.01% v/v) was used in a subset of samples amended with 15NH415NO3. Atom% 15N enrichments of NO3ˉ, N2O and N2 were measured during the experiment to evaluate the responses of nitrification and denitrification to temperature. N2O production from the two soils increased with rising temperature and peaked between 35 and 40 °C. N2O production from nitrification and denitrification both had similar thermal responses, which were different to N2 production. The N2O/N2 ratio decreased from > 4 at 35–40 °C to 0.5 at 45 °C, due to greater N2 than N2O production in the Dermosol. Heterotrophic nitrifiers oxidised NH4+ and released N2O at 35–40 °C, suggesting a role for heterotrophs in N cycling under warm climates. Topt for nitrification was between 35 and 40 °C, which is higher than reported previously. A short-term effect of high temperatures could provide NH4+ for the growth of crops but may also decrease soil C pools. Increasing temperature above 35 °C altered the rates of nitrification, denitrification associated N2O and N2 production. Nitrification and denitrification peaked at 35–40 °C in the Chromosol and Dermosol. The production of N2 increased rapidly above 40 °C, which may be related to high soil respiration rates that likely decreased O2 availability, thus expanding the anaerobic microsites; such circumstances increased the reduction of N2O to N2 production from the Dermosol.

Effect of Delivery Platforms Structure on the Epidermal Antigen Transport for Topical Vaccination.

Transdermal immunization is highly attractive because of the skin's accessibility and unique immunological characteristics. However, it remains a relatively unexplored route of administration because of the great difficulty of transporting antigens past the outermost layer of skin, the stratum corneum. In this article, the abilities of three poly( N-vinylcaprolactam) (PVCL)-based thermoresponsive assemblies-PVCL hydrogels and nanogels plus novel film forming PVCL/acrylic nanogels-to act as protein delivery systems were investigated. Similar thermal responses were observed in all systems, with transition temperatures close to 32 °C, close to that of the skin surface. The investigated dermal delivery systems showed no evidence of cytotoxicity in human fibroblasts and were able to load and release ovalbumin (OVA), a well-studied antigen, in a temperature-dependent manner in vitro. The penetration of OVA into ex vivo human skin following topical application was evaluated, where enhanced skin delivery was seen for the OVA-loaded PVCL systems relative to administration of the protein alone. The distinct protein release and skin penetration profiles observed for the different PVCL assemblies were here discussed on the basis of their structural differences.

A metabolic syndrome in terrestrial ectotherms with different elevational and distribution patterns

The metabolic performance of ectotherms is expected to be driven by the environment in which they live. Ecologically similar species with contrasting elevation distributions occurring in sympatry at mid‐elevations, provide good models for studying how physiological responses to temperature vary as a function of adaptation to different elevations. Under sympatry, at middle elevations, where divergent species ranges overlap, sympatric populations are expected to have similar thermal responses, suggesting similar local acclimation or adaptation, while observed differences would suggest adaptation to each species’ core range. We analysed the metabolic traits of sympatric species pairs from three ectotherm groups: reptiles (Reptilia: Lacertidae), amphibians (Amphibia: Salamandridae) and beetles (Coleoptera: Carabidae), living at different elevations, in order to test how adaptation to different elevations affects metabolic responses to temperature. We experimentally tested the thermal response of respiration rate (RR) and estimated potential metabolic activity (PMA) at three temperature regimes surrounding the groups’ optimal activity body temperatures. RR was relatively similar among groups and showed a positive response to increasing temperature, which was more pronounced in the high‐elevation species of reptiles and beetles. Relative to RR, PMA displayed a stronger and more consistent positive response to increased temperature in all three groups. For all three groups, the average biochemical capacity for metabolism (PMA) was higher in the range‐restricted, high‐elevation species, and this difference increased at higher temperatures in a consistent manner. These results, indicating consistent pattern in three independently evolved animal groups, suggest a ubiquitous adaptive syndrome and represent a novel understanding of the mechanisms shaping spatial biodiversity patterns. Our results also highlight the importance of geographic patterns for the mechanistic understanding of adaptations in physiological traits, including species’ potential to respond/adapt to global climate changes.

The role of fracture in the impact initiation of Ni-Al intermetallic composite reactives during dynamic loading

Mechanical initiation of reactions in powder systems involve complex interactions that can yield unexpected results. Two materials that exhibit similar thermal responses can behave very differently under the same loading conditions due to differences in their mechanical properties. Reactive composite powders with small characteristic dimensions can exhibit short ignition delays and reduced thermal ignition thresholds; however, a full understanding of the response of these powders to rapid mechanical loading is still unclear. This work seeks to clarify the role of mechanical properties in impact induced ignition by considering the response of nanolaminate (NL) powders and high energy ball milled (HEBM) Ni-Al powders subjected to impact loading. The selected materials have nearly identical thermal ignition temperatures, but contrast a relatively complex microstructure (HEBM) with a simple ordered microstructure (NL) while maintaining comparable length scales (approximately 50–100 nm diffusion distances). The powders were placed into a windowed enclosure and mechanically loaded using a light gas gun, which allowed the resulting reactions to be observed using high-speed imaging. Even though the thermal ignition temperatures for the two powders are within 30 °C of each other, it was observed that the NL powders reacted on the microsecond timescale, immediately following the compaction wave for a short distance before decoupling from the compaction front. In contrast, the HEBM powders reacted after a several millisecond delay and clearly propagated as a deflagration front. Microindentation showed that the HEBM powders are much more ductile than those of NL. This suggests that the primary difference between the behavior of these materials on impact results from the ability and degree of the material to fracture, illustrating that the mechanical properties of a reactive material can have a dramatic effect on ignition during impact loading.

Improvements on Infrared-Camera Calibration for Accurate Surface Temperature Measurements in Arcjet Facilities

Ground testing of thermal protection systems play an essential role for understanding the response of candidate materials for thermal shields. Nonintrusive surface temperature measurements are necessary to map the temperature distribution for the correct interpretation of the results obtained in wind-tunnel facilities. An accurate calibration of the infrared camera to be used for a planned experimental campaign on variable transpiration cooling is described in detail. A prototype carbon–carbon cone has been used for both the calibration procedure and experiments. For this application, standard calibration procedures, based on the combined use of blackbody radiators for the calibration of the camera sensor together with tests for emissivity characterization, would not allow for the determination of the accurate surface temperature distribution. This is due to the diversified surface finish and localized defect characteristics of a typical component. The calibration procedure described here, which is based on simultaneous measurements of the local temperature and radiance, allows determination of the local surface temperatures independent of the material emissivity. The calibration curves reveal similar surface thermal response. A higher temperature variance on the calibration curve related to the thermocouple located near the tip of the cone has been detected due to local surface defects.

Adaptation of rammed earth to modern construction systems: Comparative study of thermal behavior under summer conditions

Buildings should be understood as a process that consumes energy in all their phases (design, construction, use and end-of-life) and, more specifically, the building envelope is clearly involved in all of them. For this reason, the International Energy Agency defines in its latest publication the improvement of building envelopes as one of the key points to reduce the energy consumption in buildings. In the present study, two sustainable construction systems based on rammed earth walls are adapted to modern requirements to be thermally tested and compared against three Mediterranean conventional systems under summer conditions. The experimentation was done by performing several experiments in free floating and controlled temperature conditions at real scale in five cubicle-shape buildings with inner dimensions 2.4×2.4×2.4m. The purpose of this study is to demonstrate that more sustainable construction systems can be used instead of conventional ones, with higher embodied energy, and achieve similar thermal response. Results show that the reduction of rammed earth wall thickness strongly penalizes its thermal behavior. However, similar thermal response than conventional systems is reached when 6cm of wooden insulation panels are added in the outer face of the cubicle-shape building.

Transgenic sickle cell trait mice do not exhibit abnormal thermoregulatory and stress responses to heat shock exposure

There remains controversy over whether individuals with sickle cell trait (SCT) are vulnerable to health risks during physical activity in high temperatures. We examined thermoregulatory and stress-related responses to heat exposure in SCT and wild-type (WT) mice. No significant differences in core temperature (Tc) were observed between SCT and WT mice during heat exposure. There was no correlation between peak Tc during heat exposure and levels of hemoglobin S in SCT mice. Basal levels of circulating inflammatory and stress-related markers were not significantly different between SCT and WT mice. Although heat exposure caused significant increases in plasma interleukins 1β and 6, and 8-isoprostane in SCT and WT mice, no differences were found between SCT and WT mice with similar thermal response profiles during heat exposure. SCT mice had significantly higher expression of heat shock protein 72 in heart, liver and gastrocnemius muscle than WT mice under control and post-heat conditions. In conclusion, there is neither thermoregulatory dysfunction nor abnormal stress-related response in SCT mice exposed to moderate heat. The hemoglobin variant in mice is associated with altered tissue stress protein homeostasis.

Correlation between skin temperature and heart rate during exercise and recovery, and the influence of body position in these variables in untrained women

It was known that the thermal response varies according to some variables. Until now, there are no studies that have investigated the relationship of skin temperature and heart rate during and after the workout, either the thermal behavior during postural changes. Objective: the aim of this study was to evaluate the behavior of skin temperature and heart rate, during exercise and up to an hour of recovery (with postural change), performed in two different intensities sessions (70% and 85% of 10 repetitions maximum) and observe the correlation between them. Method: This was a short longitudinal study, carried out with women aged from 18 to 30years. A sample of 31 untrained women, aged 18 and 30 was used. The volunteers were randomized into two groups: Biceps Group (BG), with 15 women, and Quadriceps Group (QG) with 16 women. Results: During and after completion of the exercise session, there was a significant reduction in skin temperature on the active muscles in both groups (BG and QG), with similar thermal responses for the two intensities studied (70% and 85%) to the minute 15 (which marks the end of the recovery in the standing position). From minute 15 to minute 20–60, the skin temperature increases abruptly and significantly, returning to levels close to those observed before exercise. Conclusion: There were no statistical differences in thermal response to exercises in 70% or 85% of 10RM. There is a negative correlation between heart rate and skin temperature when untrained women perform anaerobic exercise. It was observed that after a change of posture (from a standing position to a sitting posture) skin temperature increased abruptly and significantly.

Hormonal and metabolic responses to upper temperature extremes in divergent life-history ecotypes of a garter snake.

Extreme temperatures constrain organismal physiology and impose both acute and chronic effects. Additionally, temperature-induced hormone-mediated stress response pathways and energetic trade-offs are important drivers of life-history variation. This study employs an integrative approach to quantify acute physiological responses to high temperatures in divergent life-history ecotypes of the western terrestrial garter snake (Thamnophis elegans). Using wild-caught animals, we measured oxygen consumption rate and physiological markers of hormonal stress response, energy availability and anaerobic respiration in blood plasma across five ecologically relevant temperatures (24, 28, 32, 35 and 38°C; 3h exposure). Corticosterone, insulin and glucose concentrations all increased with temperature, but with different thermal response curves, suggesting that high temperatures differently affect energy-regulation pathways. Additionally, oxygen consumption rate increased without plateau and lactate concentration did not increase with temperature, challenging the recent hypothesis that oxygen limitation sets upper thermal tolerance limits. Finally, animals had similar physiological thermal responses to high-temperature exposure regardless of genetic background, suggesting that local adaptation has not resulted in fixed differences between ecotypes. Together, these results identify some of the mechanisms by which higher temperatures alter hormonal-mediated energy balance in reptiles and potential limits to the flexibility of this response.