Thermal Stress Research Articles

Can Fecal T3 Metabolite Level Fluctuations in European Roe Deer (Capreolus capreolus) Give Insights on Body Condition and Thermal Stress?

Mammals can use a variety of physiological mechanisms to adapt to changes in their environment. Thyroid hormones (THs) are key modulators of growth and mediators of environmental conditions by regulating developmental processes and metabolism in animals. In recent years, advancements in non-invasive sampling have allowed monitoring of the fluctuations of THs and their metabolites in wild mammals. Triiodothyronine (T3) represents the major metabolite of THs excreted in feces so that it can be monitored in fecal samples. In this study, fecal samples collected during the hunting season from legally culled European roe deer (Capreolus capreolus; n = 160) were assayed to investigate the potential fluctuations of fecal TH metabolites (FTMs) in response to environmental (e.g., the temperature, local densities) and individual (e.g., sex, age, body, and nutritional conditions) variables. For this aim, we validated a TH enzyme immunoassay in the feces of roe deer. Our results show that FTMs can be successfully measured with satisfactory accuracy and precision. Extraction recovery (70%-120%), intra- and inter-day repeatability (<15%), linearity dilutions (80%-120%), and parallelism (<20%) were consistent with international guidelines. Environmental temperature (p < 0.001) showed a strong inverse correlation with FTM levels. THs can thus represent a reliable indicator in studying animals' adaptative responses to environmental temperature changes, providing perspectives for the study of the impact of climate change on ungulates and mammals. Further analyses, comparing samples collected all year round, are needed to investigate the correlations of TH values versus the other investigated variables.

Novel bisection-method laser scanning strategy for laser powder bed fusion

ABSTRACT Laser scanning strategy is one of the most factors affecting on the temperature gradient for the laser powder bed fusion (L-PBF). In this work, we propose a new Bisection-Method Scanning Strategy (BM-SS) based on dichotomous approximation, to reduce the heat accumulation effect between paths. The results show that BM-SS can effectively optimize the temperature gradient of the sample compared with that of the traditional sequential scanning strategy (TS-SS). The temperature gradient significantly optimizes as the n value increase, and the highest temperature is reduced by about 85K. Further experiments and numerical simulation indicate that BM-SS can effectively increase the cooling time between adjacent paths to reduce the temperature gradient and thermal stress of the sample from both time and space dimensions. The warpage of the sample reduces by up to 5 times without losing the mechanical properties. This BM-SS provides a new insight to improve the temperature gradient during L-PBF.

Effect of Wall, Roof, and Window‐to‐Wall Ratio on the Cooling and Heating Load of a Building in India

Effect of Wall, Roof, and Window‐to‐Wall Ratio on the Cooling and Heating Load of a Building in India

Temperature influences resource selection and predation risk tolerance in a climate generalist

ContextThermal conditions can influence animal behavior and predator–prey dynamics. Understanding the effects of temperature on animals and their interactions is of increasing importance given predictions for global warming.ObjectivesWe determined how temperature influenced avoidance of risky areas and habitat selection in a climate generalist, white-tailed deer (Odocoileus virginianus; hereafter “deer”), and how the effect varied between night and day in a system characterized by extreme heat and high predation risk from Florida panther (Puma concolor coryi).MethodsWe collected GPS locations of 224 (79 M, 145F) deer from June through September 2015–2018 in southwestern Florida, USA. We fit step-selection functions with interactions between ambient temperature and covariates including landcover and a spatial model of predation risk informed by panther kill sites.ResultsAvoidance of high-risk areas decreased with rising temperatures during night and day, indicating deer were less predation risk averse when balancing higher thermoregulatory costs. As temperatures increased during the day, deer increased avoidance of marshes and hardwood hammocks. However, temperature had weaker effects on habitat selection at night with only a moderate increase in selection of marshes with increasing temperatures.ConclusionsIn systems characterized by extreme heat, thermal conditions can have strong effects on animal behavior and species interactions. While climate generalists like deer have high tolerances to thermal stress, temperature still influenced predation risk tolerance and habitat selection of deer during both day and night periods. These responses are likely even stronger in species with narrower thermal tolerances (i.e., climate specialists). Thermal conditions are an important and potentially underappreciated driver of species interactions that is likely to become more significant with climate change.

Corticotropin-releasing hormone receptor 1 mediates the enhanced locomotor activity and metabolic demands to an acute thermal stress in adult zebrafish.

We recently showed that Crh-Crhr1 signalling is essential for acute stress-related locomotor activity in zebrafish larvae. However, the possibility that Crhr1 activation may also initiate the acute metabolic demands for stress coping was unexplored. Here, we tested the hypothesis that Crhr1 signalling is essential for the thermal stressor-induced increases in the acute metabolic rate, a key response for coping with the enhanced energy demands during stress. We tested this by using a wildtype (WT) and a ubiquitous Crhr1 knockout (crhr1-/-) zebrafish and subjecting them to an acute thermal stressor (TS: +5°C above ambient for 60 min). The TS induced the heat shock proteins response in both genotypes, but the elevated cortisol response observed in the WT was absent in the crhr1-/- mutant. The TS also increased the locomotor activity and the metabolic rate in the WT fish, but this response was inhibited in the crhr1-/- mutants. To test if this was due to a lack of TS-induced cortisol elevation in the crhr1-/- mutant, we mimicked the response in the WT fish by treating them with metyrapone, an 11β-hydroxylase inhibitor. While metyrapone inhibited the TS-induced cortisol elevation in the WT, it did not affect the metabolic rate. The lack of Crhr1 also reduced the swimming performance, and the lower Ucrit in the mutants corresponded with alterations in muscle energy metabolism. Together, our results indicate that Crh-Crhr1 signalling, independent of downstream cortisol action, is essential for the TS-induced acute hyperlocomotor activity and the associated increases in the metabolic demand for stress coping.

Better Transcriptomic Stability and Broader Transcriptomic Thermal Response Range Drive the Greater Thermal Tolerance in a Global Invasive Turtle Relative to Native Turtle.

Greater thermal tolerance of invasive species benefits their survival and spread under extreme climate events, especially under global warming. Revealing the mechanisms underlying the interspecific differences in thermal tolerance between invasive and native species can help understand the invasion process and predict potential invaders. Here, we link the changes in global transcriptomics and antioxidant defense at multiple temperatures with the differences in thermal limits in the juveniles of a successful globally invasive turtle, Trachemys scripta elegans, and a native turtle in China, Mauremys reevesii. The two species show different thermal tolerances and have co-existed in habitats with the risk of overheating. The majority of the transcriptional response to thermal stress is conserved in the two turtle species, including protein folding or DNA damage responses activated under relatively moderate thermal stress and regulation of the cell cycle and apoptosis during severe thermal stress. Greater thermal tolerance of T. scripta elegans can be associated with a more stable global transcriptome during thermal stress, except for necessary stress responses, and a broader thermal range of continuous up-regulation of the core mechanisms promoting survival under thermal stress, mainly protein folding and negative regulation of apoptosis. Under extreme hot conditions, the opposite change trends of genes involved in survival mechanisms during thermal stress between invasive and native turtles can be due to differences in energy turnover. The present study provides insights into the mechanisms of physiological differences between invasive and native species given global transcriptional changes and helps understand successful invasion and predict potential invasive species.

Gcn2 rescues reprogramming in the absence of Hog1/p38 signaling in C. neoformans during thermal stress.

The fungus Cryptococcus neoformans is an opportunistic pathogen of humans that reprograms its translatome to facilitate adaptation and virulence within the host. We studied the role of Hog1/p38 in reprogramming translation during thermal stress adaptation and found that this pathway acts on translation via crosstalk with the Gcn2 pathway, a well-studied regulator of general translation control. Using a combination of molecular assays and phenotypic analysis, we show that increased output from the Gcn2 pathway in a Hog1 deletion mutant is associated with rescue of thermal stress adaptation at both molecular and phenotypic scales. We characterize known outputs of the Hog1 pathway during thermal stress as either Gcn2-dependent or Gcn2-independent and demonstrate that Hog1 activation regulates the Gcn2 pathway even in the absence of thermal stress. Finally, we implicate this phenomenon in another Hog1-regulated process, morphogenesis, and recapitulate Hog1-Gcn2 crosstalk in the distantly related fungal pathogen, Candida albicans. Our results point to an important link between the stress response machinery and translation control and clarify the etiology of phenotypes associated with Hog1 deletion. More broadly, this study highlights complex interplay between core conserved signal transduction pathways and the utility of molecular assays to better understand how these pathways are connected.IMPORTANCECryptococcus neoformans is an opportunistic pathogen of humans that causes deadly cryptococcal meningitis, which is is responsible for an estimated 19% of AIDS-related mortality. When left untreated, cryptococcal meningitis is uniformly fatal, and in patients receiving the most effective antifungal regimens, mortality remains high. Thus, there is a critical need to identify additional targets that play a role in the adaptation to the human host and virulence. This study explores the role of the stress response kinases Hog1 and Gcn2 in thermoadaptation, which is a pre-requisite for virulence. Our results show that compensatory signaling occurs via the Gcn2 pathway when Hog1 is deleted, and that disruption of both pathways increases sensitivity to thermal stress. Importantly, our study highlights the insufficiency of using single-gene deletion mutants to study gene function, since many phenotypes associated with Hog1 deletion were driven by Gcn2 signaling in this background, rather than loss of direct Hog1 activity.

Enhancing the Thermal Stability of Organic Solar Cells by Locking Morphology with Ethyl Cellulose Additive

The morphology of active layer of the organic solar cells (OSCs) tends to transition toward its lowest energy conformation under thermal stress, significantly limiting the stability of OSCs. In this study, ethyl cellulose (EC) is utilized as an additive in the active layer of the typical PM6:Y6 and other systems. Due to the strong interaction between the hydroxyl groups of EC and the heteroatoms in the organic semiconductors, their bulk heterojunction nanomorphology is locked, thereby enhancing device thermal stability. Under thermal stress at 65 °C for 1,000 h, the PM6:Y6 device incorporating EC demonstrates excellent stability nearly without performance loss. Furthermore, compared to the control device, the device exhibits improved thermal stability under a range of more stringent aging conditions. Additionally, the EC additive shows broad applicability in various active layer systems, effectively enhancing their thermal stability. This work offers a promising approach for developing stable nanomorphology structures in OSCs.

Validation of Damage Analysis Techniques for Non-Metallic Materials Due to Laser Irradiation

In this study, the laser damage analysis model for metallic materials was applied to non-metallic materials. The analysis results showed that the damage levels of germanium and silicon were relatively lower compared to the experimental results. It is suggested that crack and crater formation increased the absorption coefficient and structural changes due to thermal stress contributed to the observed damage.

Distribution of perfluorooctanoic acid in exposed female post-pubertal pigs in thermal neutral or heat stressed conditions.

Perfluorooctanoic acid (PFOA), a legacy perfluoroalkyl substance with immuno- and repro-toxicant effects, has poorly characterized bioaccumulation and distribution patterns in female pigs. The potential for heat stress to influence PFOA partitioning, potentially through intestinal hyperpermeability and alterations in systemic blood flow, also warrants investigation. This study investigated PFOA uptake, accumulation, and distribution in thermal neutral and heat-stressed gilts. Pigs (n = 48) were estrus synchronized and experienced thermal neutral (TN; 20 °C) or heat stress (HS; 26.6 to 32.2 °C) conditions during which they consumed 70 ng/kg bodyweight PFOA via cookie dough as vehicle control daily. Plasma was collected on d 1, 15, and 20. Liver, ovary, and follicular fluid were collected at euthanasia (d 20). Post-exposure, PFOA was detected in serum, liver, ovary, and follicular fluid. Heat stress increased (P < 0.05) plasma PFOA compared to TN pigs on d 15, but on d 20, plasma PFOA levels in TN and HS pigs were similar. Liver PFOA concentrations were similar between TN and HS pigs. Ovarian PFOA levels tended (P = 0.06) to be higher in TN relative to HS pigs, with an opposing pattern in follicular fluid, in which PFOA concentrations were greater (P < 0.05) in HS pigs. These findings suggest that PFOA apportions to plasma, liver, ovary, and follicular fluid of exposed pigs and that heat stress alters PFOA distribution, which could negatively impact reproductive health. This study underscores the need to consider the interaction of heat stress and toxicant exposure in environmental health risk assessments.

The effect of an exercise- and passive-induced heat stress on autophagy in young and older males.

While activation of autophagy is vital for cellular survival during exposure to ambient heat and exercise, it remains unclear if autophagic activity differs between these heat stress conditions and if aging mediates this response. Young (n=10, mean [SD]: 22 [2] years) and older males (n=10, 70 [5] years) performed 30 min of semi-recumbent cycling (70% maximal oxygen uptake). On a separate day, participants were immersed in warm water for 30 min, with the water temperature adjusted to induce the same increase in core temperature (rectal) as the prior exercise bout. Proteins associated with autophagy, inflammation, apoptosis, and the heat shock response (HSR) were assessed in peripheral blood mononuclear cells via Western blot before and after each exposure and during a 6-hour seated recovery in a temperate environment (∼22°C). No differences in core temperature occurred at end-exposure to exercise or passive heating in either group (both, p≥0.999). Older adults exhibited greater autophagic regulation (significant LC3-II accumulation) to exercise when compared to passive heating at all timepoints (all, p≤0.022). However, passive heating alone may have impaired autophagy (elevated p62; p=0.044). Pro-inflammatory IL-6 was elevated during both conditions (p<0.001) in older adults. Conversely, greater autophagic initiation (i.e., beclin-2) occurred in young adults at end-exercise and 3h recovery when compared to passive heating (both, p≤0.024). The HSR and apoptotic responses were similar between conditions in both groups. While brief exercise stimulates autophagy, exposure to ambient heat stress of an equivalent heat load may underlie autophagic dysregulation in older adults.

Multiphysical Field Coupling Model for Simulating Thermal Stress and Deformation in Ferronickel Submerged Arc Furnace

To address the issue of thermal expansion and stress concentration in furnace body, a 3D multiphysical field coupling model of electromagnetics, fluid flow, and temperature is developed to predict the interaction mechanisms between temperature, thermal stress, and deformation during submerged arc furnace operation. This model integrates electromagnetism, electrothermal conversion, mass and heat transfer, and multiphase flow within a unified computational framework using user‐defined functions. Additionally, it conducts thermal mechanical coupling analyses to describe the thermal deformation and stress concentration behavior in the furnace body. The results indicate that the multiphysical field exhibits strong coupling and nonuniformity. Due to the high thermal resistance of the furnace body material, the temperature between the inner wall of the furnace lining and furnace shell decreases from 1212 to 467 K. When the electrode insertion depth increases from 1.8 to 2.2 m, the maximum temperature of furnace shell increases from 456 to 498 K, and the maximum deformation of furnace shell gradually increases from 28.0 to 30.1 mm. The maximum deformation position occurs at the height of z = 2.45 m. As the electrode insertion depth increases, the stress concentration phenomena in the rib plates, the bottom of furnace shell, and the central area of furnace bottom are enhanced.

Synergistic lubrication effect of texture and copper on cutting performance for broaching tool

Abstract The broaching process is a heavy-duty and highly efficient metal cutting technique. The heavy load encounters significant thermal and mechanical stresses on the tool during broaching, resulting in considerable friction within the tool-chip contact area. The friction adversely affects both workpiece quality and tool life. To address this issue, laser technology is utilized in this study to create three distinct textures on the rake face of the broach. Subsequently, an innovative rotary covering device is developed to cover a solid lubricant (copper) onto both surfaces and grooves of cutting tool. Broaching test is conducted to evaluate the impact of different textures and copper on chip morphology, including chip deformation and burr width. The findings demonstrate that employing a stripe-textured broach reduces the chip deformation coefficient by 16.1% compared to its non-textured counterpart. Furthermore, covering copper through rotational friction leads to an additional reduction of 7.7% in the chip deformation coefficient. Copper not only repairs surface defects but also forms a lubricating film during cutting operations, thereby serving as an effective solid lubricant. The synergistic interaction between texture and copper enhances heat dissipation during cutting processes, consequently reducing temperatures within the tool-chip contact area. The temperature reduction alleviates plastic deformation in localized regions of the workpiece, resulting in narrower burrs. Therefore, the use of rotary friction for covering copper onto the rake face of a broaching tool represents a straightforward yet cost-effective strategy for optimizing frictional conditions and enhancing the cutting performance.

Effects of lighting on task performance, stress and thermal sensation in working environments

Studies have shown that the correlated colour temperature (CCT) of light significantly influences individuals engaged in study and work activities. However, the impact of CCT on stress and task performance, particularly when considering subjective preferences and experiences, has been explored only to a limited extent. This study aims to investigate the relationship between CCT, thermal sensation vote, stress levels and task performance. Forty-two healthy participants (21 female and 21 male, aged 20 to 53 years) participated in the experimental study. Participants completed a paper-based task and subjective questionnaires across three sessions, each conducted under different CCTs (2700 K, 4000 K and 6500 K). During these sessions, electroencephalogram (EEG) and heart rate variability were monitored to objectively assess stress levels. The study primarily focused on the activity of EEG alpha and theta waves in response to varying CCT degrees. Notably, significant activity was observed in the frontal lobes at 2700 K, particularly related to the frontal theta wave. Statistical significance was also identified in different brain regions in both alpha and theta waves among participants who demonstrated successful task performance. Additionally, participants reported optimal thermal comfort at 2700 K, which was associated with enhanced task performance and reduced stress levels.

Coral reef thermal microclimates mapped from the International Space Station

Abstract Satellite sea surface temperature (SST) is critical for describing marine environments. Traditional SST data, such as those provided by the Group for High Resolution Sea Surface Temperature (GHRSST) program, are valuable, but have a relatively coarse spatial resolution for mapping coral reef thermal environments. Hence, fine resolution SST from orbit would be of great utility to the coral reef research community and speed the pathway to an increased understanding of how, when, and where thermal stress afflicts individual reefs. Such data would support adaptive management, especially so for the design of marine protected areas. Flying aboard the International Space Station, the NASA ECOsystem Spaceborne Thermal Radiometer Experiment on Space Station (ECOSTRESS) instrument may already fill this niche with a spatial resolution 204 times finer than GHRSST. To evaluate ECOSTRESS thermal data over reef environments, we deployed 21 temperature loggers over three years across two reef sites in the Red Sea. We compared temperature retrievals from both the coarse resolution GHRSST and the fine resolution, experimental, ECOSTRESS, to this in-situ logger dataset. While temperature data from both orbital platforms correlated strongly with the logger recordings, only ECOSTRESS, with its 70-m pixels, could construct thermal microclimate maps capturing the dynamic temperature fluctuations experienced by our studied reefs. We contend that ECOSTRESS represents a significant advancement in the capability to monitor heat stress on reefs from orbit.

Research on Turbulence Inhibitor Strengthening in Fluid–Thermal–Stress Coupling Modes for a Tundish

Research on Turbulence Inhibitor Strengthening in Fluid–Thermal–Stress Coupling Modes for a Tundish

Distortion and Residual Stress Reduction Using Asynchronous Heating Sources for Multi-Robot Coordinated Wire-Arc Directed Energy Deposition

Multi-robot coordinated wire-arc directed energy deposition (MRC-WA-DED) has proliferated in recent decades, employing asynchronous independent heating sources to deposit material simultaneously. Beyond enhancing efficiency, MRC-WA-DED introduces a synergic effect between the heating sources, resulting in a controllable thermal field on the deposit component. This research aims to investigate if the synergic effect is beneficial for residual stress and distortion reduction and how it can be applied to enhance the quality of MRC-WA-DEDed parts. A finite element model was developed to compare the thermodynamic response of WA-DED when both coordinated heating sources (CHSs) and a single heating source (SHS) are applied. Simulation and deposition experiments were carried out to clarify the influence of different coordination strategies on the fabricated component’s thermal behavior, stress distribution, and distortion conditions. The results indicate that the synergic effect of CHSs leads to a smoother temperature gradient than that accomplished by a SHS, reducing the maximum distortion of a single layer by 49.1%. As validated by actual depositions, the residual stress, maximum distortion, and hardness of a ten-layer component were reduced by 6.5%, 11.2%, and 18.6%, respectively.

Prior heat waves improve survival of field but not domesticated populations of tobacco hornworm exposed to repeated bacterial infections

Abstract In insects and other invertebrates, prior pathogen exposures can improve immune responses and survival to subsequent infections through immune priming. Alternatively, stress and metabolic costs of multiple infections can impair host immunity and survival. The effects of high‐temperature extremes on host–pathogen interactions are not well understood despite the increasing occurrence of heat waves caused by climate change. The response of insects to heat waves and pathogens depends on recent evolutionary history with selective pressures. Domestication of insect pests has occurred in lab colonies of model species, reducing selective pressures for immune and heat stress responses. Lab strains are often used in immunological or heat stress experiments to represent wild field strains, but the efficacy of this approach is seldom evaluated. Using the tobacco hornworm (Manduca sexta), we tested the impact of a heat wave during initial pathogen exposure on survival of a secondary infection with Bacillus thuringiensis bacteria. We used a domesticated lab population and a naturally occurring field population of M. sexta to evaluate the impacts of recent domestication on immune and thermal responses. A heat wave during initial infection significantly increased survival of the secondary B. thuringiensis infection in the field, but not the lab population of M. sexta. In the field population, survival of the repeated infection was temperature dependent: exposure to an initial infection event reduced survival of the secondary infection at the control temperature regime, consistent with a stress effect. However, a heat wave during the initial infection event increased survival of the secondary infection, consistent with immune priming effects. The results of this study demonstrate that (a) insect response to thermal stress and pathogens can depend on recent domestication and (b) responses of hosts to repeat pathogen exposures can be temperature‐dependent, suggesting that cross‐talk between the heat stress and immune memory pathways may have important consequences for host–pathogen outcomes under heat wave events. Read the free Plain Language Summary for this article on the Journal blog.

Predicting the impact of climate change on building energy consumption by using data-driven approaches

Buildings are complex thermodynamic entities that account for a large proportion of energy consumption. This work explores the application of data-driven models in order to forecast the building energy consumption over long time horizons. Long Short-Term Memory and Random Forest are used to forecast hourly heating and cooling energy consumption in the Urban Sciences Building, which is located in the city of Newcastle upon Tyne, UK. A synthetic time-series dataset is constructed using (a) a validated EnergyPlus model and (b) operational data hosted by Newcastle Urban Observatory. The energy consumption forecast is made using future climate data that represent a high emission future scenario during a typical year, that is 2030, and 2080. The experimental results suggest that, on average over the next six decades, there will be a 45% reduction in annual heating load, accompanied by a 680% increase in annual cooling load. These early findings indicate a notable shift in building thermal performance, a rise in overall building energy demand under the more drastic future weather scenarios, and a sharper emphasis on designing building envelopes and energy systems to include decarbonised cooling solutions.

Effects of chronic cold stress and thermal stress on growth performance, hepatic apoptosis, oxidative stress, immune response and gut microbiota of juvenile hybrid sturgeon (Acipenser baerii ♀ × A. schrenkii ♂)

The current study was conducted to investigate the effects of chronic cold stress and thermal stress on the growth performance, hepatic oxidative status, immune response, apoptosis and gut microbiota in juvenile hybrid sturgeon. The fish (initial mean weight: 21.4±0.3g) was reared at three temperatures (14°C, 22°C, and 30°C) for 16d, which were termed as low temperature group (LT), moderate temperature group (MT), and high temperature group (HT), respectively, and the second group was regarded as control group in this study. Each group was assigned randomly to three tanks with 15 fish per replica. The results indicated that cold stress resulted in a significant reduction of growth metrics and a significant increase of feed conversion ratio in fish compared with MT group. Interestingly, cold stress increased hepatocyte apoptosis revealed by TUNEL staining, along with nuclear disappearance in H&E-stained sections and elevated serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels. Transcriptional levels of apoptosis-related genes and toll-like receptor signaling pathway components were significantly up-regulated in liver under cold stress. Compared with control group, in terms of thermal stress, the growth performance and feed utilization of fish were declined to some extent compared with MT group. Moreover, high temperature significantly elevated hepatic productions of malondialdehyde and hydrogen peroxide, as well as increased activities of some antioxidant enzymes in liver. In addition, low and high temperature induce changes in the composition of gut microbiota. Overall, the results suggested that cold stress decelerated growth performance, induced hepatocyte apoptosis, and enhanced innate immunity in hybrid sturgeon to cope with additional stressors. Whereas, thermal stress resulted in hepatic oxidative stress in liver and the protective responses in the antioxidant enzymes in fish were activated. These results provided insights into the different physiological adaptation strategies in responsive to cold stress and thermal stress in this cold-water fish.