Sustained High Temperatures Research Articles

Micro/Meso Scales Characterization of Alkali-Activated Fly Ash-Slag Concrete Under Sustained High-Temperatures with X-CT, MIP, and SEM Tests

Based on X-CT, MIP, and SEM tests, the micro/meso scales evolutions of alkali-activated fly ash-slag (AAFS) concrete under sustained high temperatures are studied. The results show that the water loss of the C-S-H and C-A-S-H gel phases at 60°C is continuous (about 60d). The variation law of meso-scale pore volume based on the X-CT test is consistent with that of micro-scale pore volume obtained by the MIP test. The 2D fractal dimension can be used to qualitatively evaluate the internal micro-cracks and microstructure complexity of AAFS concrete after sustained high-temperature action. The mass loss rate can reach stability within 3d-7d under the action of 100°C, 150°C, and 200°C, and there is no cumulative effect of micro-cracks and pores caused by initial water loss. Under sustained high-temperatures, the internal pore structure, micro-cracks, and microstructure changes of AAFS concrete are persistent, and these persistent changes lead to a significant change in the mechanical properties of AAFS concrete.

Nanoarchitecture via Synchronic Stacking of Metallic and Nonmetallic Two-Dimensional Nanosheets for Optimal Light-Driven Ion Transport.

The exceptional selectivity and responsive ion transport in biological channels inspire technology breakthrough in energy, environmental, and resource sectors. However, existing nanofluidic systems with a high photothermal conversion efficiency often exhibit excessive thermal conductivity, which impedes the creation of effective temperature gradients and results in a low ion transport efficiency. In this study, a strategy based on the synchronic stacking of metallic and nonmetallic two-dimensional (2D) nanosheets was presented to construct heterogeneous nanofluidic channels. This specific nanoconfined architecture sustained high temperatures in the illuminated area while maintaining low temperatures in the nonilluminated area, thus obtaining a robust driving force from sunlight for directional ion transport. As a result, our light-responsive ion transport system demonstrated significant potential in solar energy conversion and osmotic energy harvesting, surpassing those of all previously reported nanofluidic systems. Additionally, although it is still at the proof-of-concept stage, it shows great promise in light signal monitoring. This work provides an effective strategy for developing advanced light-responsive ion transport systems and their important applications.

Study on the global and nano-scale characterization of heat-induced changes in ordinary Portland cement paste

Cement-based composite materials can be damaged by distributed micro-cracking and degradation of hydration products when exposed to sustained high temperatures. In this study, a nano-scale characterization tool (dynamic nanoindentation) and global mechanical methods (vibration resonance frequency and damping) are employed to better understand the degradation of ordinary Portland cement paste subjected to high temperature exposures. A connection between the methods is demonstrated.

Comparative study on the compressive performance of NSC and HSC with preload under 24-hour high temperatures

This study explores the compressive performance of normal strength concrete (NSC) and high strength concrete (HSC) with preload under 24-hours sustained high temperature (SHT). A unique test setup was designed to accomplish the compressive tests of concrete under high temperatures. The effects of temperature, concrete strength and preloading are given attention. Besides, microscopic tests were carried out to reveal the variation mechanism of concrete performance. The results show that the degradation of the compressive strength of concrete under SHT is significantly more severe than under short-term high temperatures. At the same temperature and initial load level, HSC shows greater strength degradation than NSC. Pre-loaded concrete generates considerable creep under SHT, and its effect on the peak strain of concrete cannot be ignored. The peak strain of NSC and HSC is most significantly affected by the initial load level and temperature, respectively. At temperatures not higher than 350 °C, the deterioration of the compressive performance of concrete is mainly attributed to the dehydration decomposition of calcium silicate hydrate and the cracking of interface transition zone. Preloading can inhibit these reactions and improve the compressive performance of concrete under SHT. Further, a general model for the compressive stress-strain relationship of concrete under SHT considering concrete strength and preloading was developed, which can be used for the design and analysis of concrete structures serving at high-temperature environments.

Effect of 60 °C sustained temperature conditions on the mechanical properties and microstructure of alkali-activated fly ash-slag pastes and mortars

The temperature effect has been proven to affect the mechanical properties and microstructure of alkali-activated materials greatly. The research on the long-term complex high-temperature environment for alkali-activated materials remains blank. In this paper, the actual working temperature is selected to study the effects of long-term exposure at 60 °C on the mechanical properties of static/impact load, quality, shrinkage deformation, hydration products, pore structure, and microscopic morphology of alkali-activated fly ash-slag (AAFS). The results show that the mass loss rate of AAFS tends to be stable, the shrinkage deformation rate decreases, and the compressive strength decreases after 28d of sustained high-temperature action. The sustained high temperature causes changes in the hydration product phase, mean chain length (MCL) of the gel phase, pore structure, and micro-morphology. When the duration for 7d and 28d at 60 °C temperature, the compressive strength under static and impact loads increases, which is related to the increase of diffraction peak and MCL of the gel phase; when the duration is 60d and 90d, the compressive strength under static/impact loads decreases, which is related to the increase of cumulative pore volume and the decrease of MCL. Sustained high temperature refines the pore diameter of AAFS samples.

Flexible, breathable, and durable superhydrophobic cotton fabric modified by behenic acid, tung oil, and ZIF-8 with anti-icing and self-cleaning properties

Textiles with self-cleaning and anti-icing capabilities in cold climates are essential for outdoor workers and enthusiasts. Superhydrophobic modification of textile surfaces is effective in imparting these characteristics. Although there are numerous methods available for manufacturing superhydrophobic textiles, careful consideration is warranted for environmental concerns over fluorochemicals, stability of superhydrophobic coatings, and fabric breathability. In this work, we utilized biomass resources such as tung oil and behenic acid, along with zeolitic imidazolate framework (ZIF-8), to modify cotton fabrics, thereby creating an innovative behenic acid/tung oil/ZIF-8 modified cotton (BTZC) fabric with anti-icing and self-cleaning features. This material manifests a unique nanoflower-shaped surface morphology, demonstrating exceptional superhydrophobicity with a static water contact angle (CA) of 162° and a sliding angle (SA) of 2°. Moreover, BTZC excels in its thermal stability, breathability, and resistance to icing. Equally impressive is its robust stability, as evidenced through rigorous testing under continuous washing and abrasion, sustained high and low temperatures, extreme pH environments, and immersion in various chemical solvents. BTZC presents as a fluorine-free, durable, economically viable alternative for outdoor textile applications, marking substantial progress in the utilization of biomass and metal-organic framework materials in the textile industry and promising implications for value enhancement.

The influence of plant water stress on vegetation–atmosphere exchanges: implications for ozone modelling

Abstract. Evapotranspiration is important for Earth's water and energy cycles as it strongly affects air temperature, cloud cover, and precipitation. Leaf stomata are the conduit of transpiration, and their opening is sensitive to weather and climate conditions. This feedback can exacerbate heat waves and can play a role in their spatiotemporal propagation. Sustained high temperatures strongly favour high ozone levels, with significant negative impacts on air quality and thus on human health. Our study evaluates the process representation of evapotranspiration in the atmospheric chemistry–climate European Centre for Medium-Range Weather Forecasts – Hamburg(ECHAM)/Modular Earth Submodel System (MESSy) Atmospheric Chemistry model. Different water stress parameterizations are implemented in a stomatal model based on CO2 assimilation. The stress factors depend on either soil moisture or leaf water potential, which act on photosynthetic activity, and mesophyll and stomatal conductance. The new functionalities reduce the initial overestimation of evapotranspiration in the model globally by more than an order of magnitude, which is most important in the Southern Hemisphere. The intensity of simulated warm spells over continents is significantly improved. For ozone, we find that a realistic model representation of plant water stress suppresses uptake by vegetation and enhances photochemical production in the troposphere. These effects lead to an overall increase in simulated ground-level ozone, which is most pronounced in the Southern Hemisphere over the continents. More sophisticated land surface models with multi-layer soil schemes could address the uncertainties in representing plant dynamics representation due to too-shallow roots. In regions with low evaporative loss, the representation of precipitation remains the largest uncertainty.

Research on the residual compressive properties of concrete with preload after sustained high temperatures

The containment vessel of nuclear power plants, concrete structures near the furnaces and roller lines, and chimneys, are exposed to high temperatures (120 °C to 350 °C) for long term. Research on the compressive properties of concrete after short-term high temperatures (usually within 3 h) has been widely conducted, while that of concrete after sustained high temperatures is scarce. In this research, the effects of temperature (120 °C to 350 °C), heating duration (3 h to 32 h) and initial stress level (0.2 to 0.6, ratio of initial applied stress to compressive strength at room temperature) on the failure mode, compressive strength, peak strain and stress-strain relationship of concrete after sustained high temperatures were studied. The results show that with increasing temperature and heating duration, concrete compressive strength gradually decreases, while concrete peak strain gradually increases. At heating duration of 24 h, the properties of concrete have basically stabilised. Preloading helps the concrete to resist the adverse effects of high temperatures by inhibiting the dehydration of cement matrix and the cracking of interfacial transition zone. For concrete with preload, transient thermal strain and short-term creep at high temperatures could not be recovered after cooling, which causes a significant increase in the peak strain of concrete. A compressive stress-strain model for concrete with preload after sustained high temperatures was developed, which consists of pre-creep ascending segment, creep segment, post-creep ascending segment and descending segment. Comparison of the prediction results with the test results proves that the model has high accuracy.

Triggers for multiple glacier detachments from a low-angle valley glacier in the Amney Machen Range, eastern Tibetan Plateau

Large-scale ice avalanches initiated from low-angle glaciers (also known as glacier detachment) remain a scarcely studied and poorly understood phenomenon. Here we re-evaluated the repeat glacier detachments of a low angle (~14°) surging valley glacier in the Amney Machen Range, eastern Tibetan Plateau. Four glacier detachments recorded over a 15-year period (2004–2019) are described in detail based on the combination of satellite image analyses, additional terrain profile analyses and field data. To identify what triggered these high magnitude events, the glacier fluctuations, seismicity, lithology, and regional climate were examined. We find that the factors favouring glacier detachments were anomalous warming, subglacial hydrology, repeated glacier surging, a soft glacier bed, and ice-rock loading from the glacier headwall, though the relative influence of each factor varied in the four events we studied. We confirmed the observation of Paul (2019) that additional ice-rock debris loadings from the headwall were the most important factor for all events. The 2004 event probably was a delayed response to ice-rock loading during the preceding months. The latter three events may have been affected by short-term climate anomalies. The events of 2007 and 2016 were associated with anomalously high temperature: abrupt warming preceded the 2007 event and 2016 was the warmest year on record. The 2019 event followed sustained precipitation and high summer temperatures. Based on the spatial patterns in glacier change, we suggest that climate warming played a limited role in initiation.

Tolerance and Acclimation of the Leaves of Nine Urban Tree Species to High Temperatures

To prepare and manage urban greenspace for a hotter future, we must select trees that can tolerate or acclimate to high temperatures. Here, we compared tolerance and acclimation to high temperatures among nine urban tree species in Japan. Saplings were exposed to heat from different times (early and mid-summer) during the growing season in a greenhouse. With the exception of Ginko, heating in early summer did not affect whole-tree health, suggesting that most urban tree species may be able to acclimate to higher temperatures during the early growing season. However, continued exposure to higher temperatures, as well as heating from mid-summer, had negative effects on tree health, leading to wilting/browning, especially for evergreen broadleaved species whose leaves mature slowly. Cornus florida, Styrax japonicus and Morella rubra were the most vulnerable to heating, such that all heated saplings had died by the end of summer. At the leaf level, leaf maturation of the deciduous species and Morella was negatively affected by heating, whereas that of Eurya emarginata and Euonymus japonicas were not affected. These two species also showed heat tolerance, having a higher T50 (temperature where leaf quantum yield declined to 50% of maximum value due to heat stress) compared to other species, as well as heat acclimation, where T50 was higher for the heated saplings compared to the control. Our results indicate that, while some species that cannot recover from heat damage in early summer could die, others can acclimate to sustained high temperatures, as well as to late summer heat. As heatwaves are expected to become more frequent and severe due to global warming, tree species need to be screened individually to assess their ability to tolerate or acclimate to high temperature.

Development and Mechanism Analysis of High Temperature Resistant Nanocomposite Modified Asphalt

With the intensification of global warming, continuous extreme high temperature weather occurs frequently, and asphalt materials are prone to softening under continuous high temperature conditions, which can easily cause traffic accidents. Therefore, it is necessary to develop a high-temperature resistant modified asphalt. This study focuses on the research and development of high-temperature resistant nanocomposite modified asphalt under sustained extreme high temperature weather conditions, selects nanocomposite modification schemes, conducts aging, dynamic shear creep, bending small beam, and segregation tests on nanocomposite modified asphalt, comprehensively analyzes the aging resistance, segregation resistance, and high and low temperature performance of nanocomposite modified asphalt, and analyzes the mechanism of nanocomposite modified asphalt from the perspective of molecular dynamics. The research results indicate that the nano/polymer composite modification scheme for sustained extreme high temperature areas is: 3% ZnO+0.5% TiO2+3.5% SBS; The aging resistance and high temperature resistance of nanocomposite modified asphalt are obviously better than that of base asphalt; At a temperature of 413K (160℃), a more stable structure can be formed between asphalt and SBS. At a temperature of around 140℃, each interaction can reach its maximum value, and the modification effect is good.

Changes in the structure of polysaccharides under different extraction methods

Changes in the structure of polysaccharides under different extraction methods

Prospects for Eocene potash deposition in the East Tethyan domain: New evidence from fluid inclusions and chlorine isotope of halite crystals in the Kuqa Basin, NW China

The level of the Tethys Sea increased several times during the deposition of Mesozoic to Cenozoic sediments in the Kuqa Basin in the Tarim Block. The basin contains Paleogene to Neogene units containing evaporite-rich layers, which are favourable sources for economic concentration of potash (K-rich salt). However, the basin’s geology is poorly understood, lacking knowledge of the source of the brine, paleo-water temperatures, and the degree of evaporation. As a result, the exploration for potash mineralisation has been limited. This study documents the geochemistry, fluid inclusions, and Cl-isotope of Early Eocene halite crystals from the Kuqa Basin. The results show that the homogenisation temperatures of primary fluid inclusions in halite range between 20° and 57 °C, which is close to the temperature range of the seawater in the Tethyan sea during the same period. The average value of ∼ 32 °C is taken as the average temperature of the salt-forming brine in the Early Eocene. The homogenisation temperatures of the inclusions are generally high, with a maximum temperature of ∼ 57 °C, which is consistent with the global Paleocene–Eocene thermal maximum (PETM) climatic event, indicating that the salt-forming brine has experienced long-term and sustained high temperatures and short-term extremely high temperatures. This is consistent with the high temperatures recorded during the deposition of potash in other parts of the earth, such as ∼ 59 °C for the Silurian Michigan Basin in the USA and ∼ 58 °C for the Quaternary Lop Nur region in Mongolia. In addition, the Br content of the halite samples is between 58 and 125 ppm, and the Br × 103/Cl value is between 0.11 and 0.21, which is consistent with the evaporation curve of seawater, indicating that there is a marine environment favourable for potash deposition. The value of δ37Cl is between −0.7 and −0.14 ‰ showing that the salinity of the brine evolved to a higher concentration, especially during the later stage of potash deposition. This indicates that the potential for the presence of potash deposits in the Early Eocene Kuqa Basin is high.

Hydrometeorological triggering of periglacial debris flows using a Bayesian approach: a case study of the Hailuogou Gully region, China

Many debris flows have occurred in small basins with a small glacier cover or snow cover in periglacial areas, suddenly caused high mortality and great damage. The hydrometeorological conditions that caused such debris flows are complex, making forecasting and early warning difficult. Previous studies for these small-glacial-covered basins have primarily considered rainfall as the only inducing factor of debris flows, and often the effects of temperature are neglected. Thus, we carried out a probabilistic analysis of variables derived from hydrometeorological factors for the Mount Gongga region, Sichuan, China, where debris flows were recorded on 14 days between 1988 and 2019. By analyzing hydrological characteristics when debris flows occurred, three distinct dominant trigger types could be identified. The results show that seven (50%) of the observed debris flow events during the study period, high-intensity rainfall was the dominant trigger, snowmelt by high temperature was identified as the dominant trigger for 2 (14%). Furthermore, five (36%) debris flow events could be attributed to the combined effects of long-lasting (or short-medium) rainfall and sustained higher temperatures. We find that the differences between the trigger types are statistically significant, and a susceptibility prediction differentiating between trigger types can outperform simple rainfall-only situations. This study contributes to an improved understanding of the hydrometeorological impact on debris flow initiation in high elevation watersheds.

Quad Fever after Acute Traumatic Spinal Cord Injury

Quad fever is a rare and sometimes fatal condition characterised by sustained high temperatures of 40.8° C (105.4° F) and above, in spinal cord injury patients. Patients are often unresponsive to routine antipyretics and diagnosis is usually one of exclusion after other causes of fever are ruled out. This condition is understood to be secondary to autonomic dysfunction leading to thermoregulatory impairment. In the present case report, a 53-year-old male patient developed a fever of 104°F two days after a traumatic spinal cord injury involving C6-C7 segments. The fever did not respond to paracetamol, empirical broad-spectrum antibiotics or thromboprophylaxis. After ruling out both infectious and non infectious causes of fever, the hyperthermia was attributed to quad fever, a type of neurogenic fever. The patient continued to have non relapsing high fever and died five days after presentation. The case highlights the need to be aware of this differential in cases of high fever following traumatic spinal cord injury, in order to better prognosticate and also avoid unnecessary antimicrobial usage.

Simulation research on thermal protection performance of firefighting robots and design of protection system

In response to manufacturing strategy demand, fire accidents in petroleum, chemical, forestry, and high-rise buildings are on the rise. Although the firefighting robot can replace fire rescue workers who come into the dangerous rescue site, electronic devices’ thermal failure problem caused by high temperatures in the whole electronic equipment problem is bigger. The proportion of electronic device thermal failure has a significant impact on the normal operation of electronic equipment. How to dissipate heat quickly and avoid local high temperatures becomes a key problem. Most domestic and foreign scholars only study the influence of thermal protection materials themselves on robot protection systems, and few study the influence of heat insulation materials and heat dissipation materials on robot protection systems through appropriate structure combinations. Therefore, the establishment of comprehensive high-temperature fire situations on the fire protection robot automatic detection of smoke concentration and temperature of heat insulation material and heat dissipation material composition of folded tensile structure and liquid nitrogen cooling system thermal protection model of robot thermal protection performance research is of great significance, at the same time through COMSOL Multiphysics software to simulate the proposed model, Select the best heat dissipation materials and heat insulation materials, protect the internal electronic components in the fire accident sustained high temperature, can adjust the temperature as soon as possible, make it adapt to the change of temperature field, for the rescue process to gain 2~15 minutes time duration.

Constant High Temperature Promotes Early Changes in Testis Development Associated with Sexual Maturation in Male Atlantic Salmon (Salmo salar L.) Post-Smolts

Sexual maturation of post-smolts is a concern for Atlantic salmon producers, and its occurrence is dependent upon factors such as water temperature and energy availability, among others. The present study was designed to investigate the effect of different temperatures and feeding regimes on testis development and local regulation of spermatogenesis in salmon post-smolts. A 3 × 2 factorial design was used, with three temperatures (8 °C, 12.5 °C, and 18 °C) and two feed regimes (100% and 67% ration). Salmon (1800 parr, initial mean weight 23.1 ± 7.2 g) were reared from 28 October 2018 to 30 May 2019 in a freshwater flow-through system under continuous light (LD24:0), except for a 5-week winter signal (LD12:12) introduced on 4 February 2019. Testis histology, transcription of follicle-stimulating hormone receptor (fshr) and luteinizing hormone receptor (lhr), and transcription of testis proteins involved in spermatogenesis regulation such as gonadal-soma-derived factors 1 (gsdf1) and 2 (gsdf2), anti-Müllerian hormone (amh), and insulin-like growth factor-3 (igf3), were analyzed. Results showed that high temperature alone (18 °C), irrespective of the feed regime, promoted early presence of type B spermatogonia and reduced transcript levels of the proliferation-inhibitory factor amh in males still considered immature, of groups 18–100% and 18–67% that later matured in high proportion (~100%). This effect was also present to some degree in the group 12.5–100% (40% maturation), and absent in 12.5–67%, 8–100%, and 8–67% (groups with little or no maturation). Later, at onset of rapid testis growth, high temperature was linked to a pronounced downregulation of amh and of the self-renewal factors gsdf1 and gsdf2, as well as to a pronounced upregulation of the proliferation-stimulating factor igf3. Overall, the present findings demonstrate that rearing salmon at high temperatures can stimulate an early activation of the brain–pituitary–gonad axis before actual onset of rapid testis growth, enhancing and accelerating the mechanisms that control initiation and progression of maturation, while the feed regime has a minor impact. This poses a challenge for current salmon aquaculture practices that use sustained high temperature to maximize growth, since these practices increase the risk of early post-smolt maturation.

Interaction of temperature and feed ration on male postsmolt maturation of Atlantic salmon (Salmo salar L.)

Early maturation of Atlantic salmon male postsmolts is undesirable in aquaculture due to its negative impact on growth, welfare and seawater adaptation, however it is an increasing problem under intensive rearing conditions. The effect of temperature and feeding ration on sexual maturation during the induction of smoltification was tested with a 3 × 2 factorial design including three temperatures (8, 12.5 and 18 °C) and two feeding rations (100% and 67%), from 28 October 2018 to 30 May 2019. Fish in the six resulting treatments (1800 parr, initial mean weight 23.1 ± 7.2 g) were reared in flow-through under continuous light (LD24:0) except for a 5-week winter signal (LD12:12) introduced on 4 February 2019 to induce smoltification. A major effect of temperature determining the life history pattern of each group was observed. At 18 °C, a majority of the males were maturing in May under both rations (100% males in 18–100% and 88.9% males in 18–67%). Fish at 18 °C experienced an early activation of the BPG (Brain-Pituitary-Gonad) axis and displayed very poor signs of smoltification. At 12.5 °C, early maturation was also present, although at lower proportion than at 18 °C and more dependent upon feed ration (40% of males maturing in 12.5–100%, 8.6% in 12.5–67%). Salmon at 12.5 °C displayed the best growth within each feed regime, some early signs of smolting but subsequent low Na+, K+- ATPase activity after the winter signal. At 8 °C, salmon showed best signs of smoltification and lowest growth, while no males matured. The feed restriction had a minor effect on maturation at 18 °C but a greater impact at 12.5 °C, evidenced by significant differences between 12.5–100% and 12.5–67% in gonadosomatic index, plasma 11-ketotestosterone, insulin-like growth factor-I, and pituitary fshb (follicle stimulating hormone β-subunit gene) transcription. Onset of maturation was associated with the photoperiod change from short to long daylength, which probably also induced a slight activation of the BPG axis in non-maturing groups. Our results suggest that postsmolt producers must be cautious when using sustained high water temperatures, or the risk of early maturation and poor hypo-osmoregulatory performance will increase significantly. In addition, reducing the feeding ration will not help decrease incidence of maturation without significantly affecting growth.

Effect of long-term temperature stress on the intestinal microbiome of an invasive snail.

The gut microbiome is vital to the physiological and biochemical functions of the host, and changes in the composition of these microbial communities may affect growth and adaptability to the environment. Pomacea canaliculata is an invasive freshwater snail which has become a serious agricultural pest. Temperature adaptation is considered an important reason for the widespread distribution of this species. To date, the contribution of the gut microbes to host fitness of P. canaliculata during long-term temperature stress is not well understood. In this study, the morphological changes and intestinal microbiome of P. canaliculata under long-term stress at low temperature (15°C) and high temperature (35°C) were investigated with laboratory experiments. Compared with control group (25°C), the alpha diversity increased and pathogenic bacteria enriched changed under high and low temperature stress. The effect of high temperature stress on the intestinal microbiome of P. canaliculata was more significant than that of low temperature stress. A sustained high temperature environment led to an increase in the abundance of pathogenic bacteria, such as Aeromonas and Enterobacter, and a decrease in the abundance of immune-related bacteria such as Bacteroidetes, Firmicutes, and Lactococcus. These intestine microbiome changes can increase the risk of diseases like intestinal inflammation, and lead to more deaths at high temperature environments. In addition, with the extension of stress time from 14 to 28 days, the beneficial bacteria such as Bacteroidetes, Firmicutes, and Lactococcus were significantly enriched, while potential pathogenic bacteria such as Pseudomonas, Acinetobacter, Shivalella, and Flavobacterium decreased, suggesting that intestinal microbiota may play an important role in host response to heat stress. These results are consistent with previously reported results that the survival rate of both male and female P. canaliculata no longer significantly reduced after 21 days of high temperature stress, suggesting that the surviving P. canaliculata had gradually adapted to high temperature environments under long-term high temperature stress.

The importance of considering the duration of extreme temperatures when investigating responses to climate change.

The frequency and duration of heatwaves are increasing because of human activities. To cope with the changes, species with longer generation times may have to rely on plastic responses. The probability that their responses are adaptive is higher if the species have experienced temperature fluctuations also in their evolutionary past. However, experimental studies investigating responses to heatwaves often use exposure times that are significantly shorter than recent heatwaves. We show that this can lead to faulty conclusions and that the duration of higher temperature has to be considered in experimental designs. We recorded the response of threespine stickleback to prolonged duration of higher temperature during the breeding season, using a population that has experienced large fluctuations in temperature in its past and, hence, is expected to endure temperature changes well. We found males to adaptively adjust their reproductive behaviours to short periods of higher temperature, but not to longer periods that extended across two breeding cycles. Males initially increased their reproductive activities-nest building, courtship and parental care-which ensured high reproductive success during the first breeding cycle, but decreased their reproductive activities during the second breeding cycle when exposed to sustained high temperature. This reduced their courtship success and resulted in fewer offspring. Thus, a species expected to cope well with higher temperature suffers fitness reductions when the duration of high temperature is prolonged. The results stress the importance of considering the duration of extreme environmental conditions when investigating the impact that human activities have on species. Responses to short-term exposures cannot be extrapolated to assess responses to longer periods of extreme conditions.