Thermal Plasticity Research Articles

Analysis of grain structure, precipitation and hardness heterogeneities, supported by a thermal model, for an aluminium alloy 7075 deposited by solid-state multi-layer friction surfacing

Thermomechanical cycles during multi-layer friction surfacing (MLFS) cause microstructural and mechanical heterogeneities in the deposited high-strength Al alloy, 7075. The thermal profile and heat accumulation were investigated in this study using a multilayer numerical thermal model of the MLFS process; additionally, these variables were linked to experimentally observed microstructural heterogeneities. Compared with the feedstock, grain sizes decreased by 55–80%. The mean grain size at the bottom and top areas of a given layer was finer than that in the middle of the layer because of the enhanced recrystallisation, which resulted from the friction and shear deformation experienced by the deposited material. The differences in the thermal cycle and plastic strain rate of the bottom and top areas along the layers resulted in a gradual increase in the grain size at the bottom of each layer and a reduction in the grain size at the top of each layer. The grain growth and continuous dynamic recrystallisation mechanisms are governed by the temperature and strain rate, those mechanisms determine the intra- and inter- layer grain sizes. The accumulated heat, owing to subsequent experimental deposition, resulted in excessive growth of the precipitates in the bottom layers. The strengthening of the solid-solution and Guinier-Preston zones significantly increased the microhardness of the top layer. Post-deposition T6 heat treatments confirmed the restoration of a uniform distribution of microhardness.

Greater plasticity in CTmax with increased climate variability among populations of tailed frogs.

Temporally variable climates are expected to drive the evolution of thermal physiological traits that enable performance across a wider range of temperatures (i.e. climate variability hypothesis, CVH). Spatial thermal variability, however, may mediate this relationship by providing ectotherms with the opportunity to behaviourally select preferred temperatures (i.e. the Bogert effect). These antagonistic forces on thermal physiological traits may explain the mixed support for the CVH within species despite strong support among species at larger geographical scales. Here, we test the CVH as it relates to plasticity in physiological upper thermal limits (critical thermal maximum-CTmax) among populations of coastal tailed frogs (Ascaphus truei). We targeted populations that inhabit spatially homogeneous environments, reducing the potentially confounding effects of behavioural thermoregulation. We found that populations experiencing greater temporal thermal variability exhibited greater plasticity in CTmax, supporting the CVH. Interestingly, we identified only one site with spatial temperature variability and tadpoles from this site demonstrated greater plasticity than expected, suggesting the opportunity for behavioural thermoregulation can reduce support for the CVH. Overall, our results demonstrate one role of climate variability in shaping thermal plasticity among populations and provide a baseline understanding of the impact of the CVH in spatially homogeneous thermal landscapes.

Comparison of Mitochondrial Genome Expression Differences among Four Skink Species Distributed at Different Latitudes under Low-Temperature Stress.

Continual climate change strongly influences temperature conditions worldwide, making ectothermic animals as suitable species for studying the potential impact of climate change on global biodiversity. However, the study of how lizards distributed at different latitudes respond to climate change at the transcriptome level is still insufficient. According to the Climatic Variability Hypothesis (CVH), the range of climate fluctuations experienced by terrestrial animals throughout the year increases with latitude, so individuals at higher latitudes should exhibit greater thermal plasticity to cope with fluctuating environments. Mitochondria, as the energy center of vertebrate cells, may indicate species' plasticity through the sensitivity of gene expression. In this study, we focused on the changes in transcript levels of liver mitochondrial protein-coding genes (PCGs) in skinks from the genus Plestiodon (P. capito and P. elegans) and the genus Scincella (S. modesta and S. reevesii) under low-temperature conditions of 8 °C, compared to the control group at 25 °C. Species within the same genus of skinks exhibit different latitudinal distribution patterns. We found that the two Plestiodon species, P. elegans and P. capito, employ a metabolic depression strategy (decreased transcript levels) to cope with low temperatures. In contrast, the two Scincella species show markedly different patterns: S. modesta exhibits significant increases in the transcript levels of six genes (metabolic compensation), while in S. reevesii, only two mitochondrial genes are downregulated (metabolic depression) compared to the control group. We also found that P. capito and S. modesta, which live at mid-to-high latitudes, exhibit stronger adaptive responses and plasticity at the mitochondrial gene level compared to P. elegans and S. reevesii, which live at lower latitudes. We suggest that this enhanced adaptability corresponds to more significant changes in a greater number of genes (plasticity genes).

Variation in the thermal plasticity of avian embryos is produced by the developmental environment, not genes.

Limited evidence suggests that variation in phenotypic plasticity within populations may arise largely from environmental sources, thereby constraining its evolvability. This is of concern for temperature-sensitive metabolism in the face of climate change. We quantified the relative influence of the developmental environment versus genes on the metabolic plasticity of avian embryos to temperature. We partially cross-fostered 602 house sparrow eggs (Passer domesticus), measured the heart rate plasticity of these embryos to egg temperature and partitioned variance in plasticity. We found that the foster (incubation) environment was the sole meaningful source of variance in embryonic plasticity (not genes, pre-laying effects or ambient conditions). In contrast to heart rate plasticity, offspring growth was influenced by the foster environment, genes/pre-laying parental effects and ambient conditions. Although embryonic plasticity to temperature varied in this population, these results suggest that it is unlikely to evolve quickly. Nevertheless, the expression of this plasticity may be able to shift between generations in response to changes in the developmental environment. Whether the multidimensional plasticity of heart rate to both current temperature and the developmental environment is itself an adaptive, evolved trait allowing avian embryos to optimize their metabolic plasticity to their current environment remains to be tested.

Breeding phenology drives variation in reproductive output, reproductive costs and offspring fitness in a viviparous ectotherm.

Phenological advances are a widespread response to global warming and can contribute to determine the climate vulnerability of organisms, particularly in ectothermic species which are highly dependent on ambient temperatures to complete their life cycle. Yet, the relative contribution of breeding dates and temperature conditions during gestation on fitness of females and their offspring is poorly documented in reptiles. Here, we exposed females of the common lizard Zootoca vivipara to contrasting thermal scenarios (cold versus hot treatment) during gestation and quantified effects of parturition dates and thermal treatment on life-history traits of females and their offspring for one year. Overall, our results suggest that parturition date has a greater impact than thermal conditions during gestation on life history strategies. In particular, we found positive effects of an earlier parturition date on juvenile survival, growth and recruitment suggesting that environmental dependent selection and/or differences in parental quality between early and late breeders underlie seasonal changes in offspring fitness. Yet, an earlier parturition date compromised the energetic condition of gravid females, which suggests the existence of a mother-offspring conflict regarding the optimisation of parturition dates. While numerous studies focused on the direct effects of alterations in incubation temperatures on reptile life-history traits, our results highlight the importance of considering the role of breeding phenology in assessing the short- and long-term effects of thermal developmental plasticity.

Long-term thermal acclimation enhances heat resistance of Hong Kong catfish (Clarias fuscus) by modulating gill tissue structure, antioxidant capacity and immune metabolic pathways

The rapid temperature changes caused by global warming significantly challenge fish survival by affecting various biological processes. Fish generally mitigate stress through physiological plasticity, but when temperature changes exceed their tolerance limits, even adaptable species like Siluriformes can experience internal disruptions. This study investigates the effects of extreme thermal climate on Hong Kong catfish (Clarias fuscus), native to tropical and subtropical regions. C. fuscus were exposed to normal temperature (NT, 26 ℃) or high temperature (HT, 34 ℃) condition for 90 days. Subsequently, histological, biochemical, and transcriptomic changes in gill tissue were observed after exposure to acute high temperatures (34 ℃) and subsequent temperature recovery (26 ℃). Histological analysis revealed that C. fuscus in the HT group exhibited less impact from sudden temperature shifts compared to the NT group, as they adapted by reducing the interlamellar cell mass (ILCM) and lamellae thickness (LT) of gill tissue, thereby mitigating the aftermath of acute heat shock. Biochemical analysis showed that catalase (CAT) activity in the high temperature group continued to increase, while malondialdehyde (MDA) levels decreased, suggesting establishment of a new oxidative balance and enhanced environmental adaptability. Transcriptome analysis identified 520 and 463 differentially expressed genes in the NT and HT groups, respectively, in response to acute temperature changes. Enrichment analysis highlighted that in response to acute temperature changes, the NT group inhibited apoptosis and ferroptosis by regulating the activity of alox12, gclc, and hmox1a, thereby attenuating the adverse effects of heat stress. Conversely, the HT group increased the activity of pfkma and pkma to provide sufficient energy for tissue repair. The higher degree of heat shock protein (Hsp) response in NT group also indicated more severe heat stress injury. These findings demonstrate alterations in gill tissue structure, regulation of oxidative balance, and the response of immune metabolic pathways to acute temperature fluctuations in C. fuscus following thermal exposure, suggesting potential avenues for further exploration into the thermal tolerance plasticity of fish adapting to global warming.

Within the optimal thermal range, temperature fluctuations with similar means have little effect on offspring phenotypes: A comparison of two approaches that simulate natural nest conditions

Temperature influences nearly every aspect of organismal function. Because aspects of global change such as urbanization and climate change influence temperature, researchers must consider how altering thermal regimes will impact biodiversity across the planet. To do so, they often measure temperature in natural and/or human-modified habitats, replicate those temperatures in laboratory experiments to understand organismal responses, and make predictions under models of future change. Consequently, accurately representing temperature in the laboratory is an important concern, yet few studies have assessed the consequences of simulating thermal conditions in different ways. We used nest temperatures for two urban-dwelling, invasive lizards (Anolis sagrei and A. cristatellus) to create two egg incubation treatments in the laboratory. Like most studies of thermal developmental plasticity, we created daily repeating thermal fluctuations; however, we used different methods to create temperature treatments that differed in the magnitude and breadth of thermal cycles, and then evaluated the effects of these different approaches on embryo development and hatchling phenotypes. Additionally, we measured embryo heart rate, a proxy for metabolism, across temperature to understand the immediate effects of treatments. We found that treatments had minimal effect on phenotypes likely because temperatures were within the optimal thermal range for each species and were similar in mean temperature. We conclude that slight differences in thermal treatments may be unimportant so long as temperatures are within a range appropriate for development, and we make several recommendations for future studies of developmental plasticity.

Effects of Three Different Kinds of Foaming Medium on the Properties of Expanded Thermal Plastic Polyurethane Prepared via Supercritical Carbon Dioxide Foaming.

Hot air, water, and glycerol were studied as foaming mediums for the production of ETPU to evaluate their influence on the behavior of the foam and compare the optimal particles for each of the foaming temperatures selected. The results showed that the times of water foaming and glycerol foaming were shorter by about 2/3 than with hot-air foaming. The best foaming temperatures for hot-air foaming, glycerol foaming, and water foaming are 110-115 °C, 75 °C, and 90 °C, respectively. The particles of glycerol foam have a matte appearance and their gloss is not very good. However, the particles in hot-air foaming are light, and the gloss is very satisfactory. The gloss of the surface of water-foaming particles is dim. At the same time, there is a faint matte appearance. Particles made with glycerol foaming and water foaming are more even than those made with hot-air foaming. The density of foaming materials from glycerol foaming, hot-air foaming, and water foaming are raised accordingly, while the hardness of foaming materials from glycerol foaming, water foaming, and hot-air foaming are successively increased.

Ecological consequences of body size reduction under warming.

Body size reduction is a universal response to warming, but its ecological consequences across biological levels, from individuals to ecosystems, remain poorly understood. Most biological processes scale with body size, and warming-induced changes in body size can therefore have important ecological consequences. To understand these consequences, we propose a unifying, hierarchical framework for the ecological impacts of intraspecific body size reductions due to thermal plasticity that explicitly builds on three key pathways: morphological constraints, bioenergetic constraints and surface-to-volume ratio. Using this framework, we synthesize key consequences of warming-induced body size reductions at multiple levels of biological organization. We outline how this trait-based framework can improve our understanding, detection and generalization of the ecological impacts of warming.

A multiaxial thermo-mechanical damage model for concrete including Load Induced Thermal Strain (LITS)

In the current study, a multiaxial LITS model of concrete was innovatively developed. This model can predict the behavior of concrete subjected to wide applied load level ranges from 20 % to 80 % and temperatures up to 800 °C. A 3D LITS model is developed through a triaxial compression stress confinement implementation and Poisson's ratio. Considering the water evaporation of concrete under high temperature, a third order polynomial LITS derivative function and an exponential derivative function were proposed to characterize the effects of the stress confinement and thermal effect. In order to comprehensively predict the performance of concrete subjected to multiaxial compressive loads in fire, an orthotropic triaxial compression thermo-mechanical damage model for concrete is developed. The effect of LITS on the multiaxial stress-strain response was considered in the multiaxial model. The coupling thermo-mechanical contributions containing the development of LITS among thermal effect, stress confinement, damage and plastic hardening evolution were creatively considered in the potential function within thermodynamics framework. The numerical calculations of this proposed model were conducted for validation. The effect of LITS on the multiaxial stress-strain response was studied. The nonlinear stress-strain responses of concrete were accurately captured at temperatures ranges from 20 °C to 1000 °C through the comparative study with test results in literatures, which indicates the accuracy and applicability of the proposed model.

In Hot Water: Current Thermal Threshold Methods Unlikely to Predict Invasive Species Shifts in NW Atlantic.

As global temperatures continue to rise, accurate predicted species distribution models will be important for forecasting the movement of range-shifting species. These predictions rely on measurements of organismal thermal tolerance, which can be measured using classical threshold concepts such as Arrhenius break temperatures and critical thermal temperatures, or through ecologically relevant measurements such as the temperature at which reproduction and growth occur. Many species, including invasive species, exhibit thermal plasticity, so these thresholds may change based on ambient temperature, life stage, and measurement techniques. Here, we review thermal thresholds for 15 invertebrate species invasive to the Gulf of Maine. The high degree of variability within a species and between applied conceptual frameworks suggests that modeling the future distribution of these species in all ecosystems, but especially in the rapidly warming northwest Atlantic and Gulf of Maine, will be challenging. While each of these measurement techniques is valid, we suggest contextualization and integration of threshold measurements for accurate modeling.

Limited thermal plasticity in high mountain tropical water bear

Limited thermal plasticity in high mountain tropical water bear

An Optimized Strain-Compensated Arrhenius Constitutive Model of GH4169 Superalloy Based on Hot Compression.

A precise constitutive model is essential for capturing the deformation characteristics of the GH4169 superalloy in numerical simulations of thermal plastic forming processes. Hence, the aim of this study was to develop a precise modified constitutive model to describe the hot deformation behavior exhibited by the GH4169 superalloy. The isothermal cylindrical uniaxial compression tests of the GH4169 superalloy were carried out at temperatures of 950~1100 °C and strain rates of 0.01~10 s-1 using a Thermecmastor-200KN thermal-mechanical simulator. The original strain-stress curves were corrected by minimizing the effects of plastic heat and interfacial friction. Based on the true stress-strain curves, the original strain-compensated Arrhenius constitutive model was constructed using polynomial orders of 3, 5, and 10, respectively. The results showed that once the polynomial order exceeds the 5th, further increasing the order has little contribution to the accuracy of the model. To improve prediction ability, a higher precision Arrhenius constitutive model was established by extending a series of material parameters as functions that depend on temperature, strain, and strain rate, in which the error can be reduced from 4.767% to 0.901% compared with the classic strain-compensated Arrhenius constitutive model.

The role of species thermal plasticity for alien species invasibility in a changing climate: A case study of Lophocladia trichoclados

The Mediterranean Sea provides fertile ground for understanding the complex interplay between invasive species and native habitats, particularly within the context of climate change. This thermal tolerance study reveals the remarkable ability of Lophocladia trichoclados, a red algae species that has proven highly invasive, to adapt to varying temperatures, particularly thriving in colder Mediterranean waters, where it can withstand temperatures as low as 14 °C, a trait not observed in its native habitat. This rapid acclimation, occurring in less than a century, might entail a trade-off with high temperature resistance. Additionally, all sampled populations in the Mediterranean share the same haplotype, suggesting a common origin and the possibility that we might be facing an exceptionally acclimatable and invasive strain. This high degree of acclimatability could determine the future spread capacity in a changing scenario, highlighting the importance of considering both acclimation and adaptation in understanding the expansion of invasive species' ranges.

Thermal plasticity in protective wing pigmentation is modulated by genotype and food availability in an insect model of seasonal polyphenism

Abstract Phenotypic variation in natural populations results from complex interactions between organisms and their changing environments. The environment shapes both phenotypic frequencies (during adaptation) and organismal phenotypes (through phenotypic plasticity). Developmental plasticity, in particular, refers to the phenomenon whereby an organism's phenotype depends on the environmental conditions during development. It can match phenotype to ecological conditions and help organisms to cope with environmental heterogeneity, including differences between alternating seasons. Experimental studies of developmental plasticity often focus on the impact of individual environmental cues and do not take explicit account of genetic variation. In contrast, natural environments are complex, comprising multiple variables with combined effects that are poorly understood and may vary among genotypes. We investigated the effects of multifactorial environments on the development of the seasonally plastic eyespots of Bicyclus anynana butterflies. Eyespot size depends on developmental temperature and is involved in alternative seasonal strategies for predator avoidance. In nature, both temperature and food availability undergo seasonal fluctuations. However, our understanding of how thermal plasticity in eyespot size varies in response to food availability and across genotypes remains limited. To address this, we investigated the combined effects of temperature (T; two levels: 20°C and 27°C) and food availability (N; two levels: control and limited) during development. We examined their impact on wing and eyespot size in adult males and females from multiple genotypes (G; 28 families). We found evidence of thermal and nutritional plasticity and temperature‐by‐nutrition interactions (significant T × N) on the size of eyespots in both sexes. Food limitation resulted in relatively smaller eyespots and tempered the effects of temperature. Additionally, we found differences among families for thermal plasticity (significant G × T effects), but not for nutritional plasticity (non‐significant G × N effects) nor for the combined effects of temperature and food limitation (non‐significant G × T × N effects). Our results reveal the context dependence of thermal plasticity, with the slope of thermal reaction norms varying across genotypes and across nutritional environments. We discuss these results in the light of the ecological significance of pigmentation and the value of considering thermal plasticity in studies of the biological impact of climate change. Read the free Plain Language Summary for this article on the Journal blog.

Thermal tolerance plasticity and dynamics of thermal tolerance in Eublepharis macularius: Implications for future climate-driven heat stress

The intensity and duration of heat waves, as well as average global temperatures, are expected to increase due to climate change. Heat waves can cause physiological stress and reduce fitness in animals. Species can reduce overheating risk through phenotypic plasticity, which allows them to raise their thermal tolerance limits over time. This mechanism could be important for ectotherms whose body temperatures are directly influenced by available environmental temperatures. Geckos are a large, diverse group of ectotherms that vary in their thermal habitats and times of daily activity, which could affect how they physiologically adjust to heat waves. Data on thermal physiology are scarce for reptiles, with only one study in geckos. Understanding thermal tolerance and plasticity, and their relationship, is essential for understanding how some species are able to adjust or adapt to changing temperatures. In this study, we estimated thermal tolerance and plasticity, and their interaction, in the crepuscular gecko, Eublepharis macularius, a species that is emerging as a model for reptile biology. After estimating basal thermal tolerance for 28 geckos, thermal tolerance was measured for each individual a second time at several timepoints (3, 6, or 24 h) to determine thermal tolerance plasticity. We found that thermal tolerance plasticity (1) does not depend on the basal thermal tolerance of the organism, (2) was highest after 6 h from initial heat shock, and (3) was negatively influenced by individual body mass. Our findings contribute to the increasing body of work focused on understanding the influence of biological and environmental factors on thermal tolerance plasticity in organisms and provide phenotypic data to further investigate the molecular basis of thermal tolerance plasticity in organisms.

Phenotypic plasticity and thermal efficiency of temperature responses in two conspecific springtail populations from contrasting climates

Temperature drives adaptation in life-history traits through direct effects on physiological processes. However, multiple life-history traits co-evolve as a life-history strategy. Therefore, physiological limitations constraining the evolution of trait means and phenotypic plasticity can be larger for some traits than the others. Comparisons of thermal responses across life-history traits can improve our understanding of the mechanisms determining the life-history strategies. In the present study, we focused on a soil microarthropod species abundant across the Northern Hemisphere, Folsomia quadrioculata (Collembola), with previously known effects of macroclimate. We selected an arctic and a temperate population from areas with highly contrasting climates — the arctic tundra and a coniferous forest floor, respectively — and compared them for thermal plasticity and thermal efficiency in growth, development, fecundity, and survival across four temperatures for a major part of their life cycle. We intended to understand the mechanisms by which temperature drives the evolution of life-history strategies. We found that the temperate population maximized performance at 10–15 °C, whereas the arctic population maintained its thermal efficiency across a wider temperature range (10–20 °C). Thermal plasticity varied in a trait-specific manner, and when considered together with differences in thermal efficiency, indicated that stochasticity in temperature conditions may be important in shaping the life-history strategies. Our study suggests that adopting a whole-organism approach and including physiological time considerations while analysing thermal adaptation will markedly improve our understanding of plausible links between thermal adaptation and responses to global climate change.

Higher thermal plasticity in flowering phenology increases flowering output.

Ongoing climate change poses an increasing threat to biodiversity. To avoid decline or extinction, species need to either adjust or adapt to new environmental conditions or track their climatic niches across space. In sessile organisms such as plants, phenotypic plasticity can help maintain fitness in variable and even novel environmental conditions and is therefore likely to play an important role in allowing them to survive climate change, particularly in the short term. Understanding a species' response to rising temperature is crucial for planning well-targeted and cost-effective conservation measures. We sampled seeds of three Hypericum species (H. maculatum, H. montanum, and H. perforatum), from a total of 23 populations originating from different parts of their native distribution areas in Europe. We grew them under four different temperature regimes in a greenhouse to simulate current and predicted future climatic conditions in the distribution areas. We measured flowering start, flower count, and subsequent seed weight, allowing us to study variations in the thermal plasticity of flowering phenology and its relation to fitness. Our results show that individuals flowered earlier with increasing temperature, while the degree of phenological plasticity varied among species. More specifically, the plasticity of H. maculatum varied depending on population origin, with individuals from the leading range edge being less plastic. Importantly, we show a positive relationship between higher plasticity and increased flower production, indicating adaptive phenological plasticity. The observed connection between plasticity and fitness supports the idea that plasticity may be adaptive. This study underlines the need for information on plasticity for predicting species' potential to thrive under global change and the need for studies on whether higher phenotypic plasticity is currently being selected as natural populations experience a rapidly changing climate.

Testing metabolic cold adaptation and the climatic variability hypothesis in two latitudinally distant populations of a supratidal water beetle

Temperature significantly impacts ectotherm physiology, with thermal tolerance and metabolic traits typically varying with latitude across species ranges. The drivers of this variation remain unclear, however, despite obvious consequences for population persistence and conservation in the face of ongoing global change. This study explored local adaptation and phenotypic plasticity of metabolic rates and thermal limits in the supratidal rockpool beetle Ochthebius lejolisii. Using populations from localities at different ends of the species range that experience contrasting thermal variability, we simultaneously tested two of the major paradigms of spatial physiological ecology: metabolic cold adaptation (MCA) and the climatic variability hypothesis (CVH). Reciprocal acclimation was conducted under spring temperature regimes of both localities, incorporating local diurnal variation. Metabolic rates were measured by closed respirometry, and thermal tolerance limits estimated through thermography. In line with MCA, the higher-latitude population (colder climate) showed higher metabolic rates and temperature coefficients (Q10s) at lower temperatures than the lower-latitude population. As predicted by the CVH, the lower-latitude population (more variable climate) showed higher upper thermal tolerance but only the higher-latitude population was able to acclimate upper thermal limits. This result suggests trade-offs between physiological thermal limits and thermal plasticity in this species. A limited acclimation capacity could make populations on Mediterranean coasts especially vulnerable in the face of projected increases in extreme temperatures under ongoing climate change.

Surface Interaction and Wear Due to Sliding Electrical Contact of Materials

This article reports a research study on sliding electrical contacts of copper–diamond materials, involving modeling and validation, contact status simulations, and parametric studies. The simulation model includes the analyses of both mechanical and electrical heat sources, evaluations of heat partition and temperature, and the capture of material thermal softening, plastic deformation, and material removal. The simulation model is validated through result comparison with experimental average temperature and measured wear. With this model, temperature variation and surface wear accumulation were numerically predicted under the influences of material property variations. Factors influencing wear of the copper surfaces were explored, and parameter sensitivity was investigated by means of the Taguchi L18 matrix. The results reveal that thermally related parameters of the contact interface strongly affect the wear of the copper pin, and thermal conductivity of its mating surface material is of critical importance. The research also suggests that the electromagnetic field change due to switching the polarity of the power supply does not affect the friction and wear results; however, the polarity change influences material electrochemistry, which results in a difference in friction and wear.