Rising temperatures driven by global warming and industrial thermal pollution are threatening the survival of both wild and farmed fish, which has emerged as one of the central concerns in international aquaculture. Understanding the physiological and behavioral responses of fish to heat exposure is critical for enhancing their survival. However, most studies rely on bulk-omic analyses at the tissue level which fail to reveal cellular heterogeneity. In the present study, ultrastructural observation and single-nuclei RNA sequencing (snRNA-seq) were applied to systematically study the physiological changes and the mechanisms of the Hucho bleekeri under acute heat stress. Histological analysis showed focal hemorrhage and lamellae broken in gill after heat stress. Ultrastructural observation revealed that after heat exposure, gill epithelial cells shed and the morphology of cell organelle damaged in pavement and mitochondria-rich cells. SnRNA-seq of gill generated 28 clusters, with the number of cells in each cluster ranging from 129 to 5590. After heat stress, epithelial (GobC) and endothelial cell proportion decreased significantly while neutrophil increased. Specifically, the change of cell proportion and pseudotime analysis indicated the occurrence of endothelial-to-mesenchymal transition during heat stress, and the expression of inflammation-related genes increased along the pseudotime axis. Differentially expressed genes (DEGs) analysis revealed that genes in heat shock protein and haemoglobin families were up-regulated in most cell type, whereas each cell also displayed specific DEGs profiles. Transcription factors analysis revealed increased activity of CEBPD, JUNB and CEBPA in most of the cell type after heat stress. Cell communication analysis showed interactions of CXCL12A-CXCR4B as well as CLDN11A-CLDN11A after heat stress. In addition, the results of snRNA-seq were validated through real-time PCR and fluorescence in situ hybridization analysis. Our study provides insights into cellular heterogeneity and physiological changes of H. bleekeri in response to heat stress, and lay a foundation for future studies on the mechanism of environmental stress on salmonid fish.
In several engineering systems, wavy surfaces are utilized to enhance thermal distribution such as heat exchangers and aerodynamics and drag control. However, when radiative heat transfer, heat generation and magnetic fields are considered, velocity and thermal distribution become more difficult, making it significant to understand their combined influences for improved heat transfer. Therefore, this problem focuses on the flow rate, isotherms, streamlines and thermal distribution of the hydromagnetic fluid flow over a wavy surface subjected to a constant heat flux with radiative heat transfer and magnetic fields influence. The impermeable wavy texture is considered to be heated via a constant heat flux, which supplies the fluid a consistent source of heating energy. The transformed nonlinear governing equations are solved numerically using a robust and efficient computational scheme known as the Spectral Quasi-Linearization Method (SQLM), implemented in Wolfram Mathematica to ensure precise and reliable solutions to the physical problem. The numerical outcomes obtained in the present study are validated through comparison with previously published results, showing excellent agreement and good concordance. This consistency confirms the reliability, effectiveness, and accuracy of the adopted numerical methodology. The findings display that radiation-conduction parameter enhance the thermal distribution within the boundary layer, whereas the amplitude of waviness tends to reduce the fluid velocity.
Mitochondrial protein synthesis is a critical component of OXPHOS complexes, vital for both mammals and Schizosaccharomyces pombe. In our study, we investigated the effect of heat stress on mitochondria, analyzed the mitochondrial proteome and found that during heat stress, the translation of all mtDNA-encoded transcripts was impaired, leading to a reduction in the steady-state levels of mtDNA-encoded proteins, suggesting that heat stress plays a general role in mitochondrial protein synthesis. We also found that heat stress affects the association of mitochondrial translation initiation factors to mitoribosomal small subunits. Interestingly, ago1 deletion compensates for the heat-induced disruption of the interaction between mitochondrial translation initiation factor and mitoribosomes, leading to partial recovery of both translation and steady-state levels of mtDNA-encoded proteins in S. pombe. Under heat stress, Ago1 accumulates in the mitochondrial matrix. C-terminal truncation ablates this localization and abolishes rescue of translational suppression, confirming mitochondrial targeting is essential for regulatory function. Furthermore, our data demonstrate that Ago1's small RNA-loading related N-terminal domain is required for heat-induced translational suppression and that Ago1 physically engages with mitochondrial RNAs, collectively indicating potential RNA interference (RNAi) activity within mitochondria. These findings provide insight into the regulation of mitochondrial protein synthesis in heat stress.
The oscillatory motion of titanium dioxide (TiO2) nanoparticles in water-based fluid for heat and mass transfer performance over vertical plate has been investigated. The novelty of this work evaluates the steady and periodical behavior of heat and mass transfer using TiO2-water nanofluid, magnetic field and mixed convection. The artificial neural network on dissipative Maxwell TiO2-water nanofluid is applied to predict the accuracy and convergence of velocity profile under defined boundary conditions. The oscillatory flow pattern is applied to develop the fluctuating layers in heating frequency and mass transmission. This model converts the mathematical equations into steady, real and imaginary forms using stokes and primitive transformations. Several authors solved the fluid models by converting into ordinary-differential form but this model presents direct unsteady partial differential equations. Implicit finite-difference approach is used to convert the mathematical model into algebraic system in the presence of Gaussian elimination simulation. It is noticed that the rate of velocity amplitude increases as radiation, Maxwell index, and heat dissipation increase. The lowest training mean square error (1.77 × 10⁻10), close validation, testing errors, small gradient (9.82 × 10⁻8) at fewer epochs (636) are observed for magnetic number Mf = 3.0. The steady behavior of heat and mass rate increases as Schmidt number and thermal radiation are enhanced. The amplitude of oscillatory heat and mass transfer intensifies as magnetic number and Richardson number are increased. The increasing skin friction rate is observed at each value of Maxwell parameter and Eckert number.
Heat shock is a hallmark of clinical malaria, where Plasmodium falciparum parasites are exposed to recurrent febrile episodes exceeding 40 °C and imposing acute proteotoxic stress. Parasite survival under these conditions relies on efficient proteostasis mechanisms and molecular chaperones, yet how stress resilience is coordinated beyond chaperone responses remains poorly understood.Here, we identify a stress-associated role for extracellular vesicles (EVs) in parasite heat shock adaptation linked to PfVps60-dependent vesicular trafficking, an Endosomal Sorting Complex Required for Transport (ESCRT) protein. Using a PfVps60 knockout (PfVps60KO) line, we show that disruption of ESCRT-dependent vesicular trafficking compromises EV cargo composition during thermal stress. Proteomic profiling revealed that 44.8% of EV-associated proteins from P. falciparum 3D7 overlapped with a previously defined set of aggregation-prone proteins. Loss of PfVps60 impaired EV-mediated export of the chaperones PfHsp70-x and PfHsp110, altered aggregation dynamics and induced the redistribution of protein aggregates near the parasitophorous vacuole, reduced induction of the cytosolic chaperone PfHsp70-1, and resulted in early loss of parasite viability following heat shock. Supplementation of PfVps60KO parasites with EVs derived from heat-stressed 3D7 parasites partially rescued heat shock tolerance in a dose-dependent manner. EVs released shortly after thermal stress were enriched in aggregation-prone proteins and associated with neighboring uninfected erythrocytes, suggesting EV-mediated intercellular communication during febrile episodes. Together, these findings support a role for EV-associated cargo as a previously unexplored component of P. falciparum proteostasis during heat shock adaptation, identifying stress-induced EVs as a potential parasite vulnerability for malaria intervention.
Agricultural workers endure physically demanding, high heat work daily, increasing the risk of kidney injury and reduced kidney function. However, few studies have examined individual measures of heat exposure and risk of kidney injury and impaired function. We assessed the association between measures of heat exposure with acute kidney injury and kidney functioning among agricultural workers, compared to a group of office workers in the same region. We recruited 77 adult males working in agriculture and 21 adult males in office jobs in Sonora, Mexico in 2019. We administered a demographic questionnaire to participants. A proxy physiological strain index (PSI), based on point measurements of heart rate and tympanic temperature, was used to estimate individual heat exposure. Kidney function was measured using the estimated glomerular filtration rate (eGFR). Kidney injury was assessed via urinary neutrophil gelatinase-associated lipocalin (uNGAL). We compared uNGAL and eGFR over time in the two study groups. We assessed proxy PSI associations with uNGAL and eGFR using linear mixed-effects models, adjusting for age, body mass index, and urinary specific gravity factor. We observed statistically significant differences between agricultural and office workers for eGFR (GM: 121.85 vs. 115.66 mL/min/1.73 m2, p = .04). Among agricultural workers, creatinine-adjusted uNGAL levels rose in summer compared to spring (GM: 4.47 vs. 1.98 mg/g creatinine, p < .01), and eGFR declined during the same period GM:(108.41 vs. 122.38 mL/min/1.73 m2, p < .01). In mixed models, proxy PSI was inversely associated with eGFR (β-coefficient:-2.87, 95% CI: -4.02, -1.72). Season and proxy PSI predicted kidney functioning in agricultural workers in this study. As climate warming continues, high-risk occupational groups such as agricultural workers will face increasing heat-related health risks.
Heat waste is a bottleneck in the development of green information technologies and much effort has been devoted to suppress the heating effect in both electronic and spintronic devices. Here, we take an alternative approach and show that controllable heating at the nanoscale can actually benefit information processing. In particular, we study a hybrid nanostructure consisting of a metallic square frame and an antiferromagnetic (AFM) thin film and show that the plasmonic heating can reversibly switch two perpendicularly oriented AFM domains without the assistance of magnetic fields and electric currents. The required switching energy is at the order 1 nJ, 3 to 6 orders of magnitude lower than the current-driven AFM switching. The physical mechanism arises from the thermal-induced strain fields inside the frame, which couple to and manipulate the magnetic orientation via magnetoelastic effect. The strain field direction can be well controlled by selectively exciting the longitudinal and transverse plasmon modes by varying the polarization of the waves, which readily allows for a reversible switching of the AFM vector. Our findings provide tremendous opportunities for optically manipulating the magnetism with ultralow energy consumption and may further promote the interdisciplinary study of photonics, acoustics, and spintronics.
In this paper, a simplified heat and mass transfer model for a pork burger cooked in an electric oven is presented. The aim was to relate model predictions to physicochemical and quality properties, providing a basis for optimizing electric oven cooking processes. The burgers were cooked for several times, and the numerical simulations showed good precision with experimental data, supporting the applicability of the proposed model. The heat transfer analysis identified three characteristic stages of temperature evolution at the burger center: initial slow heating, exponential increase, and a final constant temperature phase. For mass transfer, the drying curve confirmed that the process occurs exclusively in the falling rate period, with internal water diffusion being the predominant mechanism, suggesting that the meat protein-lipid emulsion may hinder moisture transport. The analysis of physicochemical and quality properties-including mass loss, pH, moisture, extractable lipids, surface color, and shear force-revealed complex interactions in the burger matrix. A positive and significant (P < 0.05) Pearson's correlation was found between cooking time and pH decrease, higher lipid extractability, redness loss, and yellowness increase. However, tenderness did not show a correlation with the cooking process during the studied periods. Overall, the proposed approach highlights thermal control as a strategic tool for studying physicochemical changes during cooking. These results provide insights into process design and thermal treatments, which could also improve product quality and consumer acceptability, and also maximizing yield.
To compare heat generation within bone during the collection of autologous bone grafts using two different collection systems under controlled laboratory conditions. Forty D2-type bovine rib fragments were collected from an authorized slaughterhouse after the animals had been slaughtered for food. The samples were randomly divided into two groups: OSBC and Artifol. In each group, two types of drills (Ø4 mm and Ø5 mm) and two irrigation temperatures (room temperature and 10 °C) were tested. Perforation was controlled and temperature was measured with a Fluke TiS55 + thermal imaging camera. Statistical analysis included normality tests (Shapiro-Wilk), comparison of means (Student's t-test), and multiple linear regression, all with a 95% confidence level and using Stata 17.0. The findings from the regression analysis indicated that using the Artifol System resulted in an increase in intra-osseous temperature by approximately + 0.92 °C (95% CI 0.30-1.55; p = 0.005). There was also a borderline increase in temperature produced with a Ø4 mm bur compared to a Ø5 mm bur (+ 0.32 °C; 95% CI 0.00-0.64; p = 0.048). When using cooled irrigation (10 °C), there were no longer any significant differences between the two systems and the OSBC system showed a slight decrease in temperature (- 0.18 °C; p = 0.301). In order to help establish this model further, the intercepts for both models showed baseline intraosseous temperatures of 13.40 °C and 14.82 °C, under ambient and cooled conditions respectively, providing further evidence of the superiority of irrigation as a means of thermal management. The type of collector system and the size of the bur will affect heat generation in bone, especially if the cold irrigation is discontinued. The continued application of irrigation at 10 °C has a strong effect on heat generation by the drill bur and results in the reduction of differences generated by devices and reinforcing its utility as a preventative technique in bone surgery.
Maillard reaction-induced modifications at lysine and arginine residues severely compromise trypsin-based LC-MS quantification of allergens in heat-processed foods. This study developed a chymotrypsin-based LC-HRMS strategy that cleaves at aromatic amino acids resistant to thermal modifications, bypassing Maillard reaction interference. Following comprehensive screening of target proteins and signature peptides across 11 major allergens (milk, egg, peanut, soybean, sesame, and six tree nuts), parallel reaction monitoring (PRM) was optimized for multiplexed quantification in baked goods. Thermally stable signature peptides devoid of lysine/arginine achieved limits of quantification of 2-15 mg/kg, well below regulatory reference doses, with recoveries of 76.4-104.5% and precision <14.3%. Comparative evaluation demonstrated superior accuracy versus trypsin-based methods in heat-treated samples. Application to 25 commercial baked goods revealed undeclared allergen contamination in 32% of samples, with concentrations exceeding clinical risk thresholds. This approach provides a robust analytical framework for allergen risk assessment in thermally processed foods.
The push for global plastic bans highlights the dual environmental crises of "white pollution" and greenhouse gas emissions from conventional petroleum-based plastics, intensifying the pursuit of high-performance bio-based polymers. Polylactic acid (PLA) is a prominent candidate, yet its broad application is constrained by fundamental material properties such as slow crystallization and low heat resistance. In this study, we proposed a "sheet-particle-whisker" multi-scale reinforcement strategy via melt spinning to simultaneously improve PLA's heat resistance and mechanical properties. Nacre-like calcium carbonate (CaCO3) sheets were successfully prepared from waste mussel shells through a combined calcination and ultrasonication process. The incorporation of these CaCO3 sheets, together with montmorillonite (MMT) and potassium titanate whiskers (PTW), into the PLA matrix at an appropriate ratio facilitated the formation of a ternary network structure. This resulted in bio-based fibers exhibiting a significant enhancement in properties, with a degree of crystallinity of 57.10% and a tensile strength of 29.14 cN·dtex-1 compared to those of neat PLA. Moreover, this performance enhancement was achieved without compromising the inherent biodegradability of the material. This work thus establishes a green, low-cost and scalable strategy for the production of high-performance bio-based PLA fibers.
Transposable elements play a pivotal role in genome evolution and phenotypic variation in numerous eukaryotic species1. Helitrons, a recently identified category of transposons, remain poorly understood in terms of epigenetic regulation and real-time mobilization in plants2,3. Here our study reveals that reduced DNA methylation combined with heat stress promotes the mobilization of the Xuan-Feng Helitron family in wheat. Activation is marked by transcription, extrachromosomal circular DNA formation and novel somatic insertions. Genetic segregation and heterologous reconstitution establish Feng8 as the autonomous driver of the Xuan-Feng family mobilization. These findings represent a step forward in the study of active Helitrons and their potential biological functions as well as their role in genome dynamics and their potential use in crop breeding.
The preparation of dental cavities generates heat through friction that can affect the internal structure of the tooth, especially the dentin. This study explores the infrared thermal emissivity in enamel and dentin, with and without irrigation, using different types of rotary burs to identify safer practices during dental procedures. An in vitro experimental study was developed following the CRIS Guidelines in the Orthodontics Laboratory at UNFV. Human premolars extracted for orthodontic reasons (n = 20 per group) were used and randomly assigned to conditions with or without irrigation in the enamel and dentin. The cavities were prepared with round and cylindrical burs using a KaVo high-speed turbine. The surface temperatures were recorded with a Fluke TiS55 + thermal imaging camera, calibrated and focused at 1 m. Statistical analysis included Student's t-tests and multiple linear regression models in Stata 17.0. Dentin without the use of irrigation had a higher thermal emissivity than enamel (up to 39.5 °C compared to enamel 32.05 °C), indicating that dentin has greater sensitivity to friction. Irrigation was able to reduce the temperature to approximately 22 °C in both tissues with no significant difference between bur types. The statistical model demonstrated that for every 1 °C increase in enamel temperature, dentin temperature rose by an additional 0.40 °C (p < 0.05). In contrast, variations in bur geometry did not exert a significant influence on dentin heat generation, underscoring that tissue response was primarily driven by thermal transfer rather than instrument design. Irrigation demonstrated strong efficacy as a thermal regulator, significantly reducing dentin temperature during cavity preparation. These results underscore the critical role of irrigation in preserving the integrity of internal dental tissues-particularly in clinical scenarios where direct cooling is not applied.
This study employed deacetylated nanochitin (NCh) and urea to fabricate chitin-based hydrogels via a heat-treatment (121 °C,1 h). The gel formation was attributed to heat-triggered urea decomposition, which releases ammonia that neutralizes acetic acid in the nanochitin suspension. This neutralization induced deprotonation of amino groups (-NH3+ → -NH2) on the nanochitin surface, reducing electrostatic repulsion, promoting nanofiber entanglement and physical crosslinking, and ultimately forming a stable three-dimensional network. At a fixed nanochitin concentration of 0.4% and urea dosage of 0.2 M, pH 4 was found to be the optimal condition for preparing composite hydrogels with better mechanical performance. Increasing the urea concentration to 2 M at a pH 4 could maximize the mechanical strength, approaching 3500 Pa. Soil amendment with the NCh(0.4)/Urea(0.5) hydrogel over a 30-day incubation period significantly revealed the increased abundance of functional genes related to carbon fixation and phosphorus solubilization, as well as the populations of Actinobacteria and Bacillus, with average increases of 39.5%, 33.0%, 35.5%, and 37.0%, respectively. This work provided a theoretical foundation and technical support for the controlled preparation of high-performance chitin-based hydrogels and their application as potential slow-release fertilizers to enhance soil health.
As urban areas host a large portion of the world's population, high-resolution gridded meteorological data within cities is required to answer impactful questions across fields including epidemiology and environmental sciences. Urban areas have complex land surface characteristics which significantly impact interactions between the urban surface and atmosphere. We develop a 1 km2 grid spacing meteorological dataset for 2010-2023 using a coupled atmosphere-land-urban modeling system (WRF-Urban) over the Atlanta metropolitan area with the Local Climate Zone (LCZ) classification urban map. We then apply a multivariate machine learning bias correction technique to the WRF-urban temperature and moisture variables that learn shared dependencies, which is critical for heat exposure applications. The bias correction is well validated for air temperature but shows reduced spatial transferability for dew point. We also compute several common heat exposure indices such as National Weather Service heat index, Humidex index, wet bulb globe temperature index, universal thermal climate index, and apparent temperature. The dataset can be used to estimate population exposure to heat and quantify relationships between heat exposure and health endpoints in epidemiologic research, as input to quantitative risk assessments and economic evaluation of heat-health implications, and other microclimate applications.
Transpired solar collectors (TSCs) preheat ventilation air and reduce conductive heat loss through the building envelope, thereby acting as dynamic insulation. Direct outdoor comparisons of glazed and unglazed TSC modules operating under identical conditions remain limited. A systematic experimental study was conducted on two façade-mounted modules with the same perforated galvanised-steel absorber and 110 mm plenum: an unglazed TSC (UTSC) and a glazed TSC (GTSC) fitted with 4 mm low-iron tempered glass. The system was tested outdoors in Amman, Jordan, under clear-sky conditions (January-March 2025) at specific airflow rates of 18-144 m3/(h·m2) and solar irradiance of 200-1000 W/m2. Passive natural-convection operation of the GTSC was also evaluated at several cavity heights. Performance was quantified using physically bounded metrics covering thermal performance, heat exchange, exergy, wall heat-loss recapture, ventilation load reduction, and economic return. Across the tested range, the GTSC achieved thermal efficiency of 48-75% and exergy efficiency up to 12%, outperforming the UTSC (42-65%) by 6-9% points. The UTSC wall heat-loss recapture index decreased from 93% at low irradiance to 63% at peak irradiance, consistent with dynamic-insulation behaviour, while GTSC ventilation load reduction increased monotonically from 60% to 90%. Under passive operation, the GTSC reached 55% efficiency at 3.0 m cavity height without fan energy. Economic assessment using Jordanian energy prices indicated payback periods of 4.4 years (UTSC) and 5.2 years (GTSC). The results provide experimentally grounded guidance on when glazing is justified for sustainable ventilation preheating in buildings.
Thermal management has emerged as a materials bottleneck for three-dimensional integrated circuits, which are being actively explored to enable dense vertical connectivity and mitigate interconnect delay and energy consumption. Unlike 2D-structure chips, stacked tiers confine dissipation within a boundary-rich back-end-of-line (BEOL) heterostructure. Heat must cross ultrathin dielectrics, porous interlayers, and numerous metal/dielectric and bonding interfaces. Consequently, interfacial resistance and thin-film size effects often determine temperature increase and reliability margins. This perspective highlights the materials physics underlying thermal limits and relates it to integration and design considerations. First, lattice heating is described by a carrier-phonon relaxation pathway in which the optical phonon bath serves as a transient energy reservoir and modulates ultrafast thermal responses. Second, heat transport in nanoscale BEOL multilayer stacks is discussed with emphasis on thickness-dependent conduction and finite thermal penetration that filters temperature transients across tiers. Then, vertical heat removal is governed by interfacial thermal boundary conductance (TBC) and via-network electrothermal coupling with parasitic Joule heating. Finally, thermal pathways are discussed, including thermally conductive insulating dielectrics and heat spreaders, TBC enhancing interlayers, low-temperature bonding and alternative metallization, and functional via architectures consistent with the BEOL thermal budget.
This study evaluated the effects of moisture-wicking clothing and spacer garments on heat strain among Royal Netherlands Marechaussee personnel. In a within-subject design, 19 participants (4 females, 15 males) stationed in the Dutch Caribbean participated in the study; were scheduled to complete 4 shifts while wearing their usual gear, a spacer garment, a moisture-wicking garment, or both a spacer garment and a moisture-wicking garment. Thermal sensation and comfort were assessed hourly, and skin temperatures were continuously monitored. Linear mixed models showed that moisture-wicking clothing without a spacer garment improved thermal comfort (-3 to +3) by 0.49 points (95% CI: 0.16 to 0.82) without affecting mean skin temperature, while standard gear with a spacer garment reduced thermal comfort by 0.36 points (95% CI: -0.68 to -0.04) and increased chest skin temperature by 0.41 °C (95% CI: 0.04 to 0.78). Moisture-wicking clothing enhances perceived comfort, whereas spacer garments may increase thermal strain. This study examined how different gear configurations affect heat strain in Royal Netherlands Marechaussee personnel. Findings show that moisture-wicking clothing enhances perceived comfort, while spacer garments may increase thermal strain. Practical implications highlight the need for simple, implementable clothing strategies to mitigate heat strain without reducing operational effectiveness.
Abies beshanzuensis M. H. Wu is a critically endangered conifer endemic to cool, high-elevation forests; its narrow range renders it vulnerable to climate warming and associated heat and water stress. We simulated climate warming by growing seedlings along an elevational gradient (500-1200 m) to assess physiological and molecular stress responses. Seedlings at mid-high elevation (1000-1200 m) grew optimally, whereas low-elevation (500 m) seedlings showed stress symptoms. At 500 m, Yield and ETR declined sharply; stomatal conductance also dropped, and NPQ collapsed entirely, dropping below the 1550 m baseline, proving quantitatively insufficient to prevent massive photoinhibition. Consequently, leaf chlorophyll content and biomass peaked at 1000 m and declined precipitously toward 500 m. Low-elevation leaves accumulated significantly higher levels of proline, soluble sugars, and proteins. However, this robust osmotic adjustment was physically insufficient to counteract the severe drought and heat stress, culminating in elevated MDA content and severe cellular damage. Antioxidant enzyme activities were highest at 1000 m and decreased at lower elevations. Transcriptome profiling and analysis of DEGs revealed altitude-dependent gene regulation. At 500 m, structural hub genes driving oxidative phosphorylation, glutathione metabolism, flavonoid biosynthesis (CSF7, MDMC, CHS), circadian rhythms, and heat-shock proteins were strongly upregulated. In contrast, genes for photosystems, primary hormone signaling, brassinosteroid biosynthesis, and pathogen defense were suppressed. Simulated warming induced pronounced stress responses, with photosynthesis and growth severely compromised, overwhelming osmotic adjustment and antioxidant defenses. These findings underscore the extreme climate vulnerability of A. beshanzuensis, establish 1000 m as a lower survival threshold, and highlight the urgent need to protect its high-elevation habitat and implement assisted conservation strategies.
The part produced via Laser Directed Energy Deposition (LDED) generates defects such as lack of fusion, porosity, cracking, inhomogeneous microstructure etc. Thermal behavior of the molten pool and solidification procedures plays a vital role in the quality of the fabricated part and enhances performance. In recent years, ultrasonic vibration-assisted (UV-A) LDED has applied to overcome the challenges associated with conventional LDED. Even though the previous studies stated that UV-A LDED have positive impacts on molten pool thermal behavior, the principal innovation of this study is to examine the impacts of different ultrasonic frequencies on molten pool thermal and mechanical behavior. In order to do that, two high performance engineering materials (17-4 PH stainless steel and IN718 superalloys) were used to fabricate single-track multi-layer parts to investigate molten poolgeometry, temperature variation, cooling rate, interlayer temperature distribution, residual stress, and microhardness. The findings indicatedthat varying ultrasonic frequencies significantly affect the thermal and mechanical properties of the molten pool in UV-A LDED process. Higher frequency impactedtemperature gradients, cooling rates, and interlayer heat transfer, resulting in more uniform thermal profiles and diminished residual stresses. Microhardness exhibiteda continuous enhancement under ultrasonic vibrations. Scanning electron microscopy (SEM) observations further revealed a transition from columnar to finer equiaxed microstructures under ultrasonic vibration. Finally, ultrasonic frequency has been found an efficient process parameter for improving heat control, reducing residual stress and strengthening mechanical performance.