Search Results (160)

Global warming is associated with an increased frequency and intensity of heat waves, which severely threaten crop production and sustainable agriculture. As sessile organisms, plants evolved complex heat stress memory mechanisms to cope with recurring heat waves. Heat shock transcription factors (HSFs) are at the core of plant heat stress responses and memory. They regulate basal thermotolerance, acquired thermotolerance, and the maintenance of acquired thermotolerance. These processes involve multiple mechanisms, including temperature perception, activation of heat shock protein expression, and integration of hormonal and epigenetic signals. Here, we review the pivotal role HSFs play in the formation of heat stress memory, their structural characteristics, functional differentiation, and signal perception and transcriptional regulatory mechanisms. We further discuss the functional conservation and the diversity of HSFs across multiple species—for instance, HSFA2 acts as a conserved regulator of heat stress memory in Arabidopsis, tomato, wheat, and barley—and outline future research directions, including the functional characterization of heat shock transcription factor (HSF) subfamilies, investigation of their roles under stress combination, and strategies to balance stress tolerance with growth and development. We hope that our review will provide a theoretical foundation for the genetic improvement of crop thermotolerance as well as contribute to efforts directed at ensuring food security in the face of climate change. Full article

Thermally responsive shape memory polymer materials are the most widely used type of intelligent materials and have found applications in numerous fields. However, their practical utility is often limited by poor heat conduction. Carbon nanotubes (CNTs), renowned for their exceptional thermo-conductive and photothermal properties, provide a promising solution. In this study, CNTs were integrated into polyurethane prepared by stepwise polymerization method, using hydroxyl terminated polycaprolactone (PCL-diOH), poly(ethylene glycol) (PEG) and hexamethylene diisocyanate (HDI). The resulting polyurethane composite material exhibits remarkable mechanical strength, enhanced thermal conductivity, and superior shape memory performance. Notably, it demonstrates a form of training enhancement phenomenon, which shows higher mechanical properties. And the composite could achieve stress-free two-way shape memory behavior after cyclic stretching process. Additionally, this composite material can exhibit “vitrimer” material properties at higher temperatures (110 °C), allowing for shape reprogramming. The carbon nanotube-reinforced composite material can achieve remote and precise manipulation under light stimulation. By combining the composite material with a metal thermally conductive layer, a multi-layer structure with shape memory properties can be prepared, which can achieve two-way shape memory behavior under electrical and light stimulation, further expanding the application potential of the composite material in the real world. Full article

Shape-memory polymers (SMPs) are gaining significant attention for their ability to recover predefined shapes via external stimuli. Among thermally activated systems, biodegradable blends of polylactic acid (PLA) and polycaprolactone (PCL) are particularly promising for biomedical devices and soft actuators. This study develops a thermo-mechanical theoretical model to investigate the shape-memory behavior of a PLA/PCL composite blend under controlled thermal cycling. The framework integrates transient heat transfer, temperature-dependent elasticity, and viscoelastic dynamics to predict temperature evolution, deformation, and internal stress. The thermal response is computed via Newton’s law of convection, while the mechanical transition is described by a sigmoidal temperature- and crystallinity-dependent Young’s modulus. Beam bending theory is employed to evaluate the spatial distribution of strain and stress. A parametric sensitivity analysis was performed to evaluate the influence of different parameters, including the crystallinity grade, convective heat transfer coefficient, glass transition temperature, and viscoelastic recovery constant. The theoretical study accurately reproduces the shape-memory cycle, quantifying performance through fixation and recovery ratios. This model provides a robust tool for the rational design and optimization of biodegradable smart polymer structures. Full article

Temperature stress strongly affects plant metabolism, and recurrent heat exposure can modify physiological responses depending on developmental stage. This study examined the biochemical and physiological adjustments of Senecio madagascariensis subjected to single (naïve) or repeated (primed) heat stress at 40 °C during vegetative and reproductive stages. Sampling was conducted after the second heat stress and after the subsequent recovery period. Principal component analyses (PCAs) revealed marked stage-specific contrasts. In the vegetative stage, PCA1 and PCA2 explained 75.7% of total variance, clearly separating treatments: naïve plants were associated with elevated proline, soluble sugars, phenolics, glycine betaine, hydrogen peroxide (H₂O₂) and lipid peroxidation, whereas primed plants were linked to enhanced superoxide dismutase (SOD) and ascorbate peroxidase (APX) activities and reduced oxidative markers. Under stress, naïve plants showed substantial increases in soluble sugars (+198%) and proline (+66.9%), whereas primed plants exhibited attenuated oxidative responses and reduce phenolic accumulation. After recovery, primed plants exhibited markedly reduced H₂O₂ levels (−57.5%) and lipid peroxidation, alongside higher SOD activity. In the reproductive stage, PCA indicated more subtle priming effects, with overlapping clusters among treatments. Primed plants accumulated the highest soluble sugar levels under stress (+276.5%), while naïve plants showed higher proline and glycine betaine levels. Following recovery, osmolyte levels were similar among groups. Senecionine remained unchanged during the vegetative stage but increased in both naïve (+21.4%) and primed (+19.1%) plants during the reproductive stage after recovery. Oxidative markers revealed contrasting patterns, with primed reproductive plants showed the lowest superoxide under stress but the highest H₂O₂ and lipid peroxidation at both time points. Overall, the findings demonstrate that heat-stress responses in S. madagascariensis are developmentally regulated, with stronger priming effects during vegetative growth and phenology-dependent metabolic adjustments during reproduction. All results are directly supported by the measured biochemical and physiological data. Full article

Bioethanol production from lignocellulosic biomass remains energy-intensive, and its energy performance can be affected by equipment degradation, utility disturbances, and operating variability. This study developed a degradation-aware mechanistic–AI framework for energy forecasting, anomaly detection, maintenance-oriented interpretation, and multi-objective optimization in bioethanol production under limited-data conditions. Reduced-order energy models were formulated for pretreatment, hydrolysis–fermentation, and ethanol purification. Equipment deterioration was represented through heat-transfer fouling, column-efficiency decline, and pump-efficiency decay. Condition-dependent modifiers were introduced to account for load-related degradation and intervention-related partial recovery. Benchmark-constrained synthetic time-series datasets were generated under baseline, accelerated-degradation, condition-dependent, stress, and data-quality perturbation scenarios. Empirical baselines and machine-learning models were compared for specific energy consumption prediction, with uncertainty reported using confidence intervals. The long short-term memory model achieved the lowest prediction errors under both baseline and stress conditions. Robustness testing showed that sensor drift, missing values, and outliers increased forecasting and anomaly-detection uncertainty. Sensitivity analysis identified degradation coefficients, seasonal disturbance, and anomaly-threshold selection as influential factors. Multi-objective optimization revealed trade-offs among specific energy consumption, ethanol purity, and equipment-health penalty. The proposed framework should be interpreted as a benchmarked methodological platform rather than a plant-validated maintenance or control system. Plant-specific deployment requires calibration with operating records, maintenance logs, cleaning records, and sensor-quality assessment. Full article

RNA N⁶-methyladenosine (m⁶A) is a prevalent epitranscriptomic modification that governs plant growth, development, and environmental adaptation. This review synthesizes recent advances in understanding the molecular mechanisms and biological functions of m⁶A in plants. The m⁶A landscape is dynamically regulated by methyltransferases (writers), demethylases (erasers), and m⁶A-binding proteins (readers), which collectively influence mRNA stability, translation efficiency, alternative polyadenylation (APA), and chromatin crosstalk. Functionally, m⁶A integrates diverse developmental processes—including embryogenesis, organogenesis, flowering, fruit ripening, and leaf senescence—with abiotic stress responses such as salt, drought, cold, and heat. Notably, m⁶A modification exhibits remarkable species-, cultivar-, and tissue-specific plasticity, enabling precise spatiotemporal gene regulation. Recent breakthroughs have revealed bidirectional crosstalk between m⁶A and histone modifications, forming a multi-layered regulatory network, while emerging concepts including phase separation, RNA structure dynamics, and stress memory further expand the functional repertoire of m⁶A. Despite significant progress, plant epitranscriptomics remains mechanistically underexplored, with critical gaps persisting in our understanding of translation initiation mechanisms, upstream regulatory signals controlling writers/erasers activities, and the functional significance of individual m⁶A sites. This review provided systematic insights into the complexity and specificity of m⁶A regulation in plants, offering a theoretical foundation for future efforts to decipher and ultimately manipulate this epitranscriptional layer for crop improvement. Full article

Concrete and cementitious composites exhibit brittle failure under shear stress, limiting their resilience in seismic and high-load applications; this study investigates whether crimped NiTi shape memory alloy (SMA) fibers can enhance pure shear strength and ductility of mortar specimens, with particular focus on the effect of thermal activation. Z-shaped mortar specimens were prepared with SMA fiber volume fractions of 0%, 1.0%, and 1.25%, tested under both non-heated and heated conditions using a Universal Testing Machine, with deformation monitored via LVDTs and Digital Image Correlation. SMA fiber reinforcement increased peak shear strength by 13% and 14.5% for 1.0% and 1.25% fiber volumes, respectively, under ambient conditions, reaching up to 22% enhancement after thermal activation due to recovery-stress-induced prestressing; the 1.0% fiber volume achieved the highest ductility index of 4.05 compared to 1.03 for plain mortar, while SMA fibers had negligible influence on initial shear modulus but substantially improved post-cracking response and crack bridging. These findings demonstrate that crimped SMA fibers effectively improve shear resilience of cementitious composites, with 1.0% fiber content offering the optimal balance between strength and ductility, though activation protocols require careful calibration to minimize thermal degradation of the matrix. Full article

The increasing frequency of high-temperature episodes associated with climate change poses challenges to crop productivity. Stress priming could help to mitigate these effects, with the capacity to enhance plant resilience through metabolic adjustments and memory mechanisms. We evaluated the efficacy of the Stress Memory Encoder biofertilizer (SME, TIMAC Agro) as a seed treatment to induce heat stress (HS) memory in soybean plants [Glycine max (L.) Merrill]. In Experiment 1, plants with SME (0, 2, and 4 mL kg⁻¹) were exposed to HS (35 °C for 48 h) at V3 and V6 vegetative stages. The 4 mL kg⁻¹ dose at V6 under HS consistently improved photosynthetic traits and reductions in reactive oxygen species and lipid peroxidation. Non-enzymatic antioxidants were detected to this dose at V3. Multivariate analysis revealed patterns consistent with dose-dependent physiological adjustments and potential memory acquisition. In Experiment 2, plants treated with SME were exposed to HS (34 °C for 48 h) consecutively (V3 + V6). The SME-primed plants had a higher expression of transcript factors and genes related to HS. Overall, the findings indicate that SME may act as a priming agent capable of inducing somatic memory and enhancing adaptive responses to HS in soybean. Full article

Across Africa, drought seldom occurs alone. Rainfall deficits often coincide with heat, rapid soil moisture loss and reduced streamflow, producing compound events whose impacts exceed those of any single driver. This review synthesises station observations, satellite and reanalysis products, and climate model simulations to clarify where such events are most common, how they form, how they affect societies and ecosystems, and how risks are changing. A practical tiered definition tailored to African conditions is outlined and applied to identify five recurrent hotspots: the Sahel, the Greater Horn of Africa, southern Africa, the margins of the Congo Basin and the Guinea Coast. The review sets out a physically consistent sequence that links basin-scale sea surface temperature anomalies to shifts in monsoon circulation, and then to land processes that amplify and prolong heat and dryness through reduced evapotranspiration and soil-moisture memory. Documented impacts include lower crop and pasture productivity, pressure on rivers, reservoirs and groundwater, stress on hydropower and wider consequences for food and energy security. Compound drought frequency across these hotspots has risen by 18–55% since 1980, with the probability of the most severe events roughly doubling at 1.5 °C of global warming and tripling at 3 °C. The review highlights near-term priorities, including compound-aware monitoring, sub-seasonal-to-seasonal early warning and conjunctive water management. Full article

In this paper, a novel high-shielding-effectiveness energy-selective surface (HSE–ESS) is proposed. In previous solutions regarding energy-selective surfaces (ESSs) presented in the literature, PIN diodes are usually employed as nonlinear transmission components; however, these diodes may be burnt by powerful high-power microwave (HPM) beams, causing ESSs to lose their shielding effectiveness (SE). To date, no studies have focused on maintaining the SE performance of ESSs after PIN diode failure. To address these limitations, we introduce shape memory alloys (SMAs) into ESS design. The consequences of PIN diode failure are offset by the physical deformation of SMA components caused by high-amplitude-current heating. This characteristic, featuring 30 dB SE, can be defined as high shielding effectiveness (HSE). After completing the design and performing accurate numerical simulations, we fabricated a prototype using PCB technology and characterized it in an anechoic environment, verifying the overall method. In particular, the SMA components proved to be an effective medium for guaranteeing electrical continuity under thermal stress conditions, thus paving the way for their extended adoption in ESSs by substituting or acting as a back-up for PIN diodes. Overall, this approach enhances the reliability and SE of ESSs by adding SMA components. Full article

Iron-based shape memory alloy (Fe-SMA) fibers can enhance cementitious composites through both crack bridging and thermally activated recovery stresses. Since fiber pull-out governs load transfer at the micro scale, understanding the combined effects of fiber geometry, inclination, and thermal treatment is essential. This study experimentally investigated the pull-out behavior of hooked-end Fe-SMA fibers embedded in high-performance concrete (HPC). A total of 54 ASTM C307-type briquette specimens were tested using single-hook (3D) and double-hook (4D) fibers at inclination angles of 60°, 75°, and 90° under ambient, 100 °C, and 200 °C conditions. Additional flexural, compressive, and direct tensile tests were conducted on plain HPC exposed to the same thermal regime. At ambient temperature, 4D fibers showed 50–70% higher peak pull-out forces than 3D fibers. Heating to 100 °C further increased pull-out resistance by about 6–17%, and the 4D-60-100 configuration achieved the highest performance. In contrast, exposure to 200 °C reduced pull-out resistance by about 5–12% below ambient values. Overall, a 60° inclination generally provided a better response, while 90° produced the lowest. The results confirm that moderate thermal activation combined with double-hook geometry is the most effective strategy for maximizing Fe-SMA fiber–matrix load transfer in HPC. Full article

Against frequent extreme heat, landscaped green spaces cool, humidify, and mitigate urban heat islands, also boosting thermal comfort. Classical Chinese garden “gray spaces” are transitional gathering zones with strong microclimate-regulating potential, yet systematic research on their mechanisms in Western Sichuan memorial gardens remains limited. This study first reveals their thermal characteristics; establishes a refined classification system; uncovers nonlinear links between garden elements, spatial form, and thermal comfort; and proposes optimization strategies. Key findings: (1) Gray spaces show notable microclimate regulation. Internal air temperatures drop by 0.8–4.3 °C, relative humidity rises by 2.2–22.33%, and average PET decreases by 3.1 °C, effectively relieving thermal stress. (2) Thermal comfort is closely related to gray space types, with open halls performing best due to their strong sense of enclosement and shading. (3) Plant-dominated and hybrid spaces are superior to water-dominated ones. PET is negatively correlated with 40–70% plant canopy and 20–30% water coverage, while excess water leads to stuffiness. Hybrid spaces reach ideal blue–green synergy at 50–60% canopy and 20–30% water. (4) The summer PET comfort threshold for Western Sichuan gray spaces is 29.1–31.5 °C (neutral at 30.2 °C), higher than European standards, reflecting local adaptation to a hot–humid climate and guiding microclimate-adaptive design. Full article

Climate change has transformed extreme heat from a transient environmental perturbation into a persistent threat that worsens cardiovascular outcomes. Epidemiological studies show a lag between heat exposure and peaks in acute myocardial infarction (AMI) mortality, indicating a subclinical, latent vulnerability. This latent vulnerability likely originates at the level of the microvasculature, as cardiac microvascular endothelial cells (CMECs)—the heart’s primary “thermal sensors”—are uniquely susceptible to proteotoxic stress. The existing literature suggests that this sensitivity may be mediated by thermodynamically gated activation of the activating transcription factor 6 (ATF6) branch of the unfolded protein response (UPR), which could function as a master switch that reprograms endothelial cells from a pro-repair to a maladaptive, anti-angiogenic phenotype. However, this mechanism is derived primarily from preclinical studies and lacks direct validation in humans. The resulting “endothelial memory” is sustained by epigenetic modifications and organelle uncoupling; it persists beyond the initial insult and impairs subsequent neovascularization. As a result, ischemia occurs later in a compromised microenvironment, promoting a fibrosis–conduction mismatch that drives infarct expansion and arrhythmic risk. Thus, the post-exposure latent phase emerges as a novel therapeutic window: Precision targeting of the ER stress–angiogenesis axis during this period offers a focused strategy to protect heat-vulnerable individuals Full article

The behavior of shape memory alloy (SMA) materials is more complex than linear isotropic metals because of their nonlinear thermomechanical coupling. When an SMA material is mechanically stressed or joule-heated, phase transformation happens in the material, and accordingly some material properties dramatically change. In any loading or unloading scenario, the initial state of the material should be known because it significantly affects its behavior. Stress and strain alone are not enough to describe such materials. Temperature and martensitic fraction are also required to simulate SMA materials accurately. This paper presents a MATLAB application, called “SMA Simulator,” that was developed to simulate the nonlinear behavior of SMA wires under mechanical or thermal loads. This tool is very effective in helping users understand the shape memory and pseudoelastic effects in such smart materials, as it allows for plotting the loading path in the 3D stress–strain–temperature space while monitoring the evolution of the martensitic fraction. Any load–unload scenario can be studied, including multiple consecutive partial loading cycles. Since the application is not based on any numerical method that would require extensive meshing, the computational time is minimal, allowing users to perform more simulations and acquire results instantaneously. Full article

A large number of existing studies show that fiber-reinforced concrete (FRC) and ultra-high-performance concrete (UHPC) have improved crack resistance relative to conventional concrete, but there is limited research on further advancing the structural performance of FRC and UHPC through prestressing and self-healing. This study addresses this knowledge gap by introducing shape memory alloy (SMA) bars as reinforcement. Existing studies on using SMA bars for prestressing or healing are focused on conventional concrete. Thus, this study experimentally evaluates SMA bars in FRC and UHPC. Small-scale flexural specimens are fabricated for this purpose. Three mix designs are considered, corresponding to mortar, FRC, and UHPC. The prestrained and embedded SMA bars are employed in two different ways. The first method is to activate the SMA to prestress the concrete, thereby delaying cracking. The second is to activate the SMA after cracks develop, thereby closing and “healing” the cracks. Additionally, different heating methods are considered. Heating with electricity is compared to heating by electromagnetic induction to study their efficiency and safety. The experimental results validate the use of SMA for prestressing the different types of concrete. The concept of healing is also validated for all three types of concrete. Reductions in crack width as high as 80%, 90%, and 84% are measured in the mortar, FRC, and UHPC specimens, respectively. Full article