Elevated Temperatures Research Articles

Can Hediste diversicolor Speed Up the Breakdown of Cigarette Butts in Marine Sediments?

Cigarette butts (CBs) are non-biodegradable harmful residues of synthetic origin and are widespread in marine environments around the world. Although environmental factors are often primarily responsible for the fragmentation of microplastics in the marine environment, biotic factors have recently been shown to be equally important in plastic debris. This study evaluates the role of the Hediste diversicolor polychaete in the fragmentation of CBs in the marine environment. Polychaetes were exposed to three concentrations of CB (0 (as the control), 0.25, and 1 butt L−1) at two different temperatures (15 °C and 23 °C) for 28 days. At each temperature, aquaria without polychaetes were used to study the effect of the burrowing activity of the polychaete on CB fragmentation. Toxicants analysed from exposed sediments increased their concentration in a dose-dependent manner to the CB concentration at a temperature of 15 °C but not at 23 °C. CBs did not directly decrease Hediste survival, but prolonged elevated temperatures increased the polychaetes’ susceptibility. The negative effects of CBs on burial success and burrowing behaviour could not be offset by the reduced start time caused by elevated temperatures. Regardless of temperature, both the weight loss and physical fragmentation of CBs buried in polychaete-contaminated sediments were significantly higher than those without Hediste, with no differences between the two concentrations tested. FTIR-ATR analysis used to evaluate CB degradation in relation to cellulose acetate decomposition showed a greater degradation of this compound in treatments with Hediste than in those without polychaetes (~2.75 times), but these differences were not significant. This study is a promising initial step for future research, as any factor that facilitates the fragmentation of this prevalent and hazardous waste must be carefully studied to extract the maximum benefit to help to reduce CBs in the marine environment.

Impact of oxygen scavenger, temperature, and packaging materials on freshness quality of packaged green teas during storage

AbstractGreen tea is renowned for its exceptional freshness; nevertheless, preserving its freshness poses a formidable challenge during storage due to its susceptibility to environmental factors. However, the effect of storage factors on freshness quality of green tea remains unclear, particularly with a lack of research studies regarding aroma quality and associated volatiles. In this study, we investigated the effects of oxygen scavenger, temperature, and packaging materials on freshness quality of packaged green teas during storage. The sensory freshness and corresponding volatile metabolites of the samples were investigated; the sensory‐chemical changes among packaged green teas during storage under different treatments were further explored. The freshness preservation in packaged green teas can be effectively achieved through the implementation of low‐temperature storage, packaging with oxygen scavenger and utilizing packaging with minimal oxygen permeability. A total of 151 volatile compounds were detected in all samples, among which 104 volatiles were identified as key contributors for distinguishing sample groups under 3 different treatments. The presence of volatiles with green, spicy, minty, and vegetable notes was found to be positively correlated with high freshness quality observed in packaged green tea. Conversely, an increase in volatiles characterized by fruity, sweet, fatty, and alkane notes was associated with the freshness deterioration. The volatiles changes that lead to freshness deterioration occurred especially under conditions of elevated temperature and increased oxygen levels, predominantly involving fat degradation, lipid oxidation, the Maillard reaction, carotenoids degradation, and dehydration reactions. The findings provide a theoretical foundation for the advancement of storage technology in packaged green teas.

Metabolic rate of two invasive Ponto‐Caspian goby species and their native competitors in the context of global warming

Abstract In connection with the expansion of alien gobies in European waters, a question arises whether this process can be enhanced or inhibited by global warming. The gobies are of Ponto‐Caspian origin, where the climate is warmer than in invaded European areas. Therefore, they are likely to cope physiologically with climate warming better than native species. Our aim was to identify differences in metabolic traits under elevated summer temperature between the invasive gobies and their native counterparts. Using a laboratory respirometer, we compared the effect of elevated summer temperature (25 vs. 17°C) on the metabolic responses of fish in two species pairs consisting of an invasive goby versus its native counterpart from the same ecological guild: the invasive racer goby Babka gymnotrachelus versus native European bullhead Cottus gobio, and the invasive monkey goby Neogobius fluviatilis versus native gudgeon Gobio gobio. The paired species share functional traits, including morphological characteristics, despite belonging to different fish families. After 4 weeks of acclimation, standard metabolic rate (SMR), maximum metabolic rate (MMR) and aerobic scope (AS = MMR–SMR) of the fish were determined. We found that SMR increased under elevated temperature irrespective of species, yet it was always lower in the gobies than in natives. The MMR of the racer goby was lower than that of the bullhead across all temperatures, whereas no differences in MMR were found between the gudgeon and monkey goby. On the one hand, the elevated temperature did not affect the AS of the racer goby and bullhead. However, the AS of the racer goby was consistently lower than that of the bullhead across all temperatures. On the other, elevated temperature caused a decrease in AS in both the monkey goby and gudgeon. However, this temperature‐induced change in AS was higher in the gudgeon than in the monkey goby. In terms of AS, the invaders did not always outperform the natives at higher temperatures. However, the invaders had lower living costs by maintaining a lower SMR. These results suggest that invasion by gobies may be facilitated by global warming, which is likely to increase their occurrence and effect on local fish communities in freshwater temperate systems.

Analyzing cutting force and vibration amplitude in high-speed milling of SKD11 steel with thermal assistance

In the realm of machining, the optimization of cutting conditions stands as a paramount pursuit for enhancing both efficiency and precision. This study embarks on a pioneering investigation delving into the intricate interplay among workpiece temperature, Thermal-Assisted High-Speed Machining (TA-HSM), cutting force dynamics, and vibration amplitudes during the milling process of SKD11 steel. Beyond a mere exploration, this research endeavors to unveil not only the impact of temperature and velocity on machining dynamics but also to delineate regions characterized by elevated temperature and velocity that exhibit the potential to mitigate cutting forces and vibrations, thereby refining machining methodologies. Experimental inquiries encompassing diverse temperature regimes, coupled with variations in cutting speeds, offer valuable insights into the nexus among temperature, cutting force and vibration amplitude. Of particular significance are the high-speed milling trials conducted under the most elevated admissible support temperature, which furnish elucidation on the ramifications of high speeds on cutting forces and vibrations. This inquiry constitutes a substantive contribution to the field by elucidating the correlation between cutting force and vibration amplitude under the thermal influence and high-speed milling within thermally demanding environments. Moreover, this study extends practical utility by proffering actionable insights into the optimal temperature range and cutting speeds requisite for effecting desired enhancements in machining productivity. By discerning and delineating these optimal parameters, this research endeavors to furnish tangible guidelines for practitioners seeking to optimize their machining processes, thus fostering advancements in both efficiency and precision within the machining domain.

Temperature-dependent dielectric and electromechanical properties of co-modified calcium bismuth titanate (CaBi4Ti4O15) ceramics

Bismuth layer-structured ferroelectrics (BLSFs), Aurivillius-type ceramics, are of great interest primarily due to their exceptionally high Curie temperature (Tc), rendering them invaluable in various applications such as sensors, actuators, transducers, and micro-electro-mechanical systems designed for elevated temperature operations, including ferroelectric Random-Access Memory applications. This study delves into the dielectric and electromechanical properties of Cobalt-modified Calcium Bismuth Titanate (CaBi4Ti4O15, CBT) (CBT-xCo, with x = 2, 4, and 6 mol%) prepared using a conventional solid-state route followed by sintering. By incorporation of Co, insignificant structural changes were observed, disclosed by X-ray Diffraction analysis. Scanning Electron Microscope micrographs unveiled highly anisotropic grains. The sintered density measured by Archimedes method was maximum for x = 6 mol% with value of 99.1 %. A temperature-dependent dielectric study disclosed that the Curie temperature of the CBT ceramics improved with the increase in Co concentration. Notably, CBT-4Co exhibited the lowest dielectric loss of 0.0967 at 1 MHz and the highest resistivity value of 0.1975 × 105 (Ω cm) at a temperature of 775 °C. Moreover, the electromechanical coupling (kp) and mechanical quality factor (Qm) measured at elevated temperatures unveiled distinctive properties, asserting the potential of the ceramics for high-temperature piezoelectric applications up to 450 °C. CBT-4Co demonstrated the highest kp, with a negligible variation at high temperature, although Qm declined. Results confirmed that CBT-4Co stands distinguished showcasing high Tc, minimal dielectric loss, and consistent electromechanical properties making it the prime candidate for electromechanical applications spanning the gamut from room temperature to elevated temperatures.

Thermo-mechanical fatigue crack growth in a nickel-based powder metallurgy superalloy

Fatigue crack growth is studied in a nickel-based powder metallurgy (PM) superalloy (FGH4099) subjected to in-phase (IP) and out-of-phase (OP) thermo-mechanical fatigue (TMF), as well as isothermal fatigue (IF) at peak temperature. The crack growth rate and path are evaluated for both coarse grain (CG) and fine grain (FG) FGH4099, especially the effects of phase angle and polycrystalline microstructure. The results show that the TMF crack propagation is mainly transgranular in OP condition; while in IP condition, fatigue crack propagates intergranularly at low ΔK and transforms to transgranular after passing the transition region. The crack propagation resistance for FG microstructure is lower than that for CG microstructure at elevated temperature, as a result of secondary cracks and grain boundary weakening effect. Crystallographic slip controls the crack propagation process, while the twin boundaries (TB) and special grain boundaries also exert a significant influence on crack deflection. The formation of secondary cracks is closely related to local misorientation and crystallographic deformation during TMF crack propagation. The crack deflection in a single grain reveals a competition mechanism between crystallographic slip and grain boundary effect, which explains the lower crack growth rate for OP when compared to IP or IF.

Mechanochromic Polymer Film with High Sensitivity toward Tensile Strain by the Post-Curing Ring-Closure Induced Pre-Stretching.

Mechanochromic materials has received broad research interests recently, owing to its ability to monitor the in-situ stress/strain in polymer materials in a straight forward way. However, one major setback that hinder the practical application of these materials is their low sensitivity toward tensile strain. Here we show a new strategy for pre-stretching of the mechanochromic agent in a polymer film on the molecular scale, which can effectively enhance the mechanochromic sensitivity of a polymer film toward tensile strain. In-situ fluorescent measurement during tensile test showed an early activation of the mechanochromic agent at tensile strain as low as 50%. The pre-stretching effect is realized by firstly inducing ring-opening of the mechanochromic agent by molecular functionalization, and then compelling the ring-closure process in the cured film by elevated temperature. This post-curing ring-closure process will result in pre-stretched mechanochromic agent in a crosslinked network. The mechanism for mechanochromic activation of polymer films with different composition was elaborated by visco-elastic measurements, and the effect of pre-stretching was further confirmed by polymer films with other compositions. Combined with the simplicity of the method developed, we believe this work will offer an alternative strategy to enhance the sensitivity of different mechanochromic agents toward tensile strain. This article is protected by copyright. All rights reserved.

Revealing intact neuronal circuitry in centimeter-sized formalin-fixed paraffin-embedded brain.

Tissue-clearing and labeling techniques have revolutionized brain-wide imaging and analysis, yet their application to clinical formalin-fixed paraffin-embedded (FFPE) blocks remains challenging. We introduce HIF-Clear, a novel method for efficiently clearing and labeling centimeter-thick FFPE specimens using elevated temperature and concentrated detergents. HIF-Clear with multi-round immunolabeling reveals neuron circuitry regulating multiple neurotransmitter systems in a whole FFPE mouse brain and is able to be used as the evaluation of disease treatment efficiency. HIF-Clear also supports expansion microscopy and can be performed on a non-sectioned 15-year-old FFPE specimen, as well as a 3-month formalin-fixed mouse brain. Thus, HIF-Clear represents a feasible approach for researching archived FFPE specimens for future neuroscientific and 3D neuropathological analyses.

Community structure and function during periods of high performance and system upset in a full-scale mixed microalgal wastewater resource recovery facility

Microalgae have the potential to exceed current nutrient recovery limits from wastewater, enabling water resource recovery facilities (WRRFs) to achieve increasingly stringent effluent permits. The use of photobioreactors (PBRs) and the separation of hydraulic retention and solids residence time (HRT/SRT) further enables increased biomass in a reduced physical footprint while allowing operational parameters (e.g., SRT) to select for desired functional communities. However, as algal technology transitions to full-scale, there is a need to understand the effect of operational and environmental parameters on complex microbial dynamics among mixotrophic microalgae, bacterial groups, and pests (i.e., grazers and pathogens) and to implement robust process controls for stable long-term performance. Here, we examine a full-scale, intensive WRRF utilizing mixed microalgae for tertiary treatment in the US (EcoRecover, Clearas Water Recovery Inc.) during a nine-month monitoring campaign. We investigated the temporal variations in microbial community structure (18S and 16S rRNA genes), which revealed that stable system performance of the EcoRecover system was marked by a low-diversity microalgal community (DINVSIMPSON = 2.01) dominated by Scenedesmus sp. (MRA = 55 %-80 %) that achieved strict nutrient removal (effluent TP < 0.04 mg·L-1) and steady biomass concentration (TSSmonthly avg. = 400–700 mg·L−1). Operational variables including pH, alkalinity, and influent ammonium (NH4+), correlated positively (p < 0.05, method = Spearman) with algal community during stable performance. Further, the use of these parameters as operational controls along with N/P loading and SRT allowed for system recovery following upset events. Importantly, the presence or absence of bacterial nitrification did not directly impact algal system performance and overall nutrient recovery, but partial nitrification (potentially resulting from NO2− accumulation) inhibited algal growth and should be considered during long-term operation. The microalgal communities were also adversely affected by zooplankton grazers (ciliates, rotifers) and fungal parasites (Aphelidium), particularly during periods of upset when algal cultures were experiencing culture turnover or stress conditions (e.g., nitrogen limitation, elevated temperature). Overall, the active management of system operation in order to maintain healthy algal cultures and high biomass productivity can result in significant periods (>4 months) of stable system performance that achieve robust nutrient recovery, even in winter months in northern latitudes (WI, USA).

Effects of eyestalk ablation and seawater temperature on D-glutamate levels in the reproductive tissues of male kuruma prawn Marsupenaeus japonicus.

D-Glutamate, a novel D-amino acid found in animal tissues, exclusively exists in the male reproductive tissues of kuruma prawn, Marsupenaeus japonicus. Herein, changes in the D-glutamate content were determined in the male reproductive tissues of M. japonicus, during acclimation with breeding seawater temperature of 18°C-22°C and unilateral eyestalk ablation. The D-glutamate content in the testis increased with increasing seawater temperature, and with unilateral eyestalk ablation. This suggests that both stimulations induced D-glutamate synthesis in the testis. Although the D-alanine content in the testis increased after unilateral eyestalk ablation, it did not change with elevated seawater temperature. Furthermore, we determined the D-glutamate distribution in the M. japonicus spermatophore. This indicates that D-glutamate is crucial in prawn fertilization.

Solvent-Responsive Nonporous Adaptive Crystals Derived from Pyridinium Hydrochloride and the Application in Iodine Adsorption.

Nonporous adaptive crystals (NACs) are crystalline nonporous materials that can undergo a structural adaptive phase transformation to accommodate specific guest via porous cavity or lattice voids. Most of the NACs are based on pillararenes because of their flexible backbone and intrinsic porous structure. Here a readily prepared organic hydrochloride of 4-(4-(diphenylamino)phenyl)pyridin-1-ium chloride (TPAPyH), exhibiting the solvent dimension-dependent adaptive crystallinity is reported. Wherein it forms a nonporous α crystal in a solvent with larger dimensions, while forming two porous β and γ crystals capable of accommodating solvent molecules in solvent with small size. Furthermore, the thermal-induced single-crystal-to-single-crystal (SCSC) transition from the β to α phase can be initiated. Upon exposure to iodine vapor or immersion in aqueous solution, the nonporous α phase transforms to porous β phase by adsorbing iodine molecules. Owing to the formation of trihalide anion I2Cl- within the crystal cavity, TPAPyH exhibits remarkable performance in iodine storage, with a high uptaking capacity of 1.27 g g-1 and elevated iodine desorption temperature of up to 110 and 82°C following the first and second adsorption stage. The unexpected adaptivity of TPAPyH inspires the design of NACs for selective adsorption and separation of volatile compound from organic small molecules.

A 3.2V Binary Layered Oxide Cathode for Potassium-Ion Batteries.

Potassium-ion batteries (KIBs) can offer high energy density, cyclability, and operational safety while being economical due to the natural abundance of potassium. Utilizing graphite as an anode, suitable cathodes can realize full cells. Searching for potential cathodes, this work introduces P3-type K0.5Ni1/3Mn2/3O2 layered oxide as a potential candidate synthesized by a simple solid-state method. The material works as a 3.2V cathode combining Ni redox at high voltage and Mn redox at low voltage and exhibits highly reversible K+ ion (de)insertion at ambient and elevated (40-50°C) temperatures. First-principles calculations suggest the ground state in-plane Mn-Ni ordering in the MO2 sheets is strongly correlated to the K-content in the framework, leading to an interwoven and alternative row ordering of Ni-Mn in K0.5Ni1/3Mn2/3O2. Postmortem and electrochemical titration reveal the occurrence of a solid solution mechanism during K+ (de)insertion. The findings suggest that the Ni addition can effectively tune the electronic and structural properties of the cathode, leading to improved electrochemical performance. This work provides new insights in the quest to develop potential low-cost Co-free KIB cathodes for practical applications in stationary energy storage.

Study on the extraction, purification, stability, free radical scavenging kinetics, polymerization degree and characterization of proanthocyanidins from Pinus koraiensis seed scales

To efficiently harness resources from Pinus koraiensis seed scales, a type of forestry waste, rigorous studies on the extraction, purification, stability, and free radical scavenging capacity of the proanthocyanidins derived from these seed scales were conducted. Kinetic models showed that under ultrasonic conditions, the proanthocyanidins content reached 2.66 mg/g within 0.5 h. The optimal storage parameters include darkness, 4 °C, and pH 4. The degrees of polymerization of the mixture and the high- and low-polymer components were 4.89, 7.42 and 3.07, respectively, with the low-polymer component exhibiting the highest radical scavenging activity. Through HPLC–QE-MS/MS, 1H NMR, and FT-IR analyses, we identified proanthocyanidin B1, proanthocyanidin B2, (−)-epicatechin, and polymeric trimer esters. The Pinus koraiensis proanthocyanidins exhibited a high molecular weight, a complex internal molecular structure, and commendable stability, with crystallization requiring elevated temperatures. Therefore, the proanthocyanidins from Pinus koraiensis seed scales have emerged as highly promising novel natural antioxidants.

Effects of high-temperature stress on gene expression related to photosynthesis in two jujube (Ziziphus jujuba Mill.) varieties

ABSTRACT Elevated temperatures critically impact crop growth, development, and yield, with photosynthesis being the most temperature-sensitive physiological process in plants. This study focused on assessing the photosynthetic response and genetic adaptation of two different heat-resistant jujube varieties ‘Junzao’ (J) and ‘Fucuimi’ (F), to high-temperature stress (42°C Day/30°C Night). Comparative analyses of leaf photosynthetic indices, microstructural changes, and transcriptome sequencing were conducted. Results indicated superior high-temperature adaptability in F, evidenced by alterations in leaf stomatal behavior – particularly in J, where defense cells exhibited significant water loss, shrinkage, and reduced stomatal opening, alongside a marked increase in stomatal density. Through transcriptome sequencing 13,884 differentially expressed genes (DEGs) were identified, significantly enriched in pathways related to plant-pathogen interactions, amino acid biosynthesis, starch and sucrose metabolism, and carbohydrate metabolism. Key findings include the identification of photosynthetic pathway related DEGs and HSFA1s as central regulators of thermal morphogenesis and heat stress response. Revealing their upregulation in F and downregulation in J. The results indicate that these genes play a crucial role in improving heat tolerance in F. This study unveils critical photosynthetic genes involved in heat stress, providing a theoretical foundation for comprehending the molecular mechanisms underlying jujube heat tolerance.

Influence of elevated temperatures on the mechanical behavior of one-part coal ash geopolymer concrete with sodium metasilicate pentahydrate and sodium metasilicate anhydrous as alkaline activators

Geopolymers can be synthesized through either a one-part or two-part combination methodology. The aluminosilicate precursor is blended with an alkaline activator solution in the two-part mixture. Conversely, the one-part mixture technique incorporates water directly into the dry composite comprising the aluminosilicate precursor and solid activator. Using one-part geopolymer concrete (OPGC) stands out as a beacon of sustainability, presenting a compelling alternative to conventional cement concrete in construction projects. A noticeable gap exists in the extant literature on investigations on the response of OPGC when subjected to elevated temperatures. The study aims to evaluate the effect of elevated temperatures on the mechanical behavior of OPGC. Sodium metasilicate pentahydrate (SMP) and sodium metasilicate anhydrous (SMA) are the two types of one-part alkaline activators used to make OPGC. Fly ash was applied as a precursor, and bottom ash was varied from 25 % to 100 % as a substitute for sand in the mix designs of the OPGC specimens. The concrete specimens were characterized by their workability, compressive strength, microstructures, mineralogical properties, and thermal stability. The results revealed that OPGC specimens with SMP and SMA activators containing bottom ash, exposed to 100 °C, exhibited increased compressive strength by 7.31 % and 39.09 %, respectively, compared to those exposed to 30 °C. This trend persisted, with the highest enhancements observed at 200 °C, reaching 37.62 % and 72.39 % for SMP and SMA, respectively. However, compressive strength declined at higher temperatures, with the most significant drop occurring at 800 °C. X-ray Diffraction results and microstructural analysis confirmed that the optimized geopolymer concrete is characterized by a binding product in Sodium Aluminosilicate Hydrate (N-A-S-H) gels, forming a robust three-dimensional geopolymer network. This behaviour implies a high level of toughness for the optimized geopolymer concrete. The study underscored the importance of comprehending the bonding mechanism of geopolymer concrete activated with SMP and SMA against high temperatures, as it clarifies the scientific underpinnings of its thermal resilience and resistance to deterioration, thus guiding the advancement of durable and eco-friendly construction materials.

Compressible Hydrogels with Stabilized Chirality from Thermoresponsive Helical Dendronized Poly(phenylacetylene)s

Fabrication of chiral hydrogels from thermoresponsive helical dendronized phenylacetylene copolymers (PPAs) carrying three‐fold dendritic oligoethylene glycols (OEGs) is reported. Three different temperatures, i.e. below or above cloud point temperatures (Tcps) of the copolymers, and under freezing condition, were utilized, affording thermoresponsive hydrogels with different morphologies and mechanical properties. At room temperature, transparent hydrogels were obtained through crosslinking among different copolymer chains. Differently, opaque hydrogels with much improved mechanical properties were formed at elevated temperatures through crosslinking from the thermally dehydrated and collapsed copolymer aggregates, leading to heterogeneity for the hydrogels with highly porous morphology. While crosslinking at freezing temperature synergistically through ice templating, these amphiphilic dendronized copolymers formed hydrogels with highly porous lamellar structures, which exhibited remarkable compressible properties as human articular cartilage with excellent fatigue resistance. Amphiphilicity of the dendronized copolymers played a pivotal role in modulating the network formation during the gelation, as well as morphology and mechanical performance of the resulting hydrogels. Through crosslinking, these dendronized copolymers featured with typical dynamic helical conformations were transformed into hydrogels with unprecedently stabilized helicities due to the restrained chain mobilities in the three‐dimensional networks.

Compressible Hydrogels with Stabilized Chirality from Thermoresponsive Helical Dendronized Poly(phenylacetylene)s.

Fabrication of chiral hydrogels from thermoresponsive helical dendronized phenylacetylene copolymers (PPAs) carrying three-fold dendritic oligoethylene glycols (OEGs) is reported. Three different temperatures, i.e. below or above cloud point temperatures (Tcps) of the copolymers, and under freezing condition, were utilized, affording thermoresponsive hydrogels with different morphologies and mechanical properties. At room temperature, transparent hydrogels were obtained through crosslinking among different copolymer chains. Differently, opaque hydrogels with much improved mechanical properties were formed at elevated temperatures through crosslinking from the thermally dehydrated and collapsed copolymer aggregates, leading to heterogeneity for the hydrogels with highly porous morphology. While crosslinking at freezing temperature synergistically through ice templating, these amphiphilic dendronized copolymers formed hydrogels with highly porous lamellar structures, which exhibited remarkable compressible properties as human articular cartilage with excellent fatigue resistance. Amphiphilicity of the dendronized copolymers played a pivotal role in modulating the network formation during the gelation, as well as morphology and mechanical performance of the resulting hydrogels. Through crosslinking, these dendronized copolymers featured with typical dynamic helical conformations were transformed into hydrogels with unprecedently stabilized helicities due to the restrained chain mobilities in the three-dimensional networks.

Investigation and analysis of the macro- and micro-responses of bentonite-sand mixtures to temperature

Bentonite-sand mixture has been proposed as a buffer material of high-level radioactive waste (HLW) repositories in many countries. The elevated temperature in HLW repositories significantly influences the properties and behaviour of the surrounding buffers. However, to date the mechanism of temperature effects on the behaviour of the bentonite buffer is not well understood. This study is aimed at clarifying the macro- and micro-responses of bentonite-sand mixtures by conducting cone penetration test, rheometer test, flask volumetric test, scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP) at different temperatures. The results from macro-experiments show that the liquid limit and yield stress increased while bound water content decreased with increasing temperature. The normalized relationships disclose the sand content dramatically affects the degree of temperature influence on the macro-behaviour. SEM and MIP results present that the contact manner between particles converted from edge-to-face to the edge-to-edge association and some intra-aggregate pores merged to form inter-aggregate pores as temperature increases. The mechanisms of the increasing temperature influence on the responses of bentonite-sand mixtures can be inferred that: 1) the diffuse double layer is supposed to decrease since more ions were electrolyzed from montmorillonite particles, thereby, increasing the ion concentration and changing the ion valence; 2) the slight shrinkage of diffuse double layer produced nano-fissures, causing water-hold capacity to increase; 3) the temperature-induced transition from bound water into free water results in an increase of liquid volume; 4) increasing temperature led to increased inter-particle repulsive force. Furthermore, an empirical model was proposed to predict the yield stress of bentonite dispersion incorporating the combined effects of sand content and temperature.

Optimizing Micro Friction Stir Spot Welding (mFSSW) of Aluminum Alloy AA1100 Using Neural Network Model

This study explores the optimization of Micro Friction Stir Spot Welding (mFSSW) by investigating the influence of tool profiles on welding outcomes, using aluminum alloy AA1100 with a 0.42 mm thickness as the specimen material. Monitoring temperature and RPM during welding with thermocouples and tachometers, mechanical properties are assessed through tensile shear tests, microhardness measurements, and macrostructural observations. The findings serve as the basis for developing Neural Network models using Rapidminer software, marking a transformative development that positions Neural Networks as potent tools for optimizing welding processes, potentially leading to achieving optimal weld quality. The investigation also delves into three welding tool configurations – the two-stage pin, one-stage pin, and pinless mFSSW probes – highlighting their distinct impacts on tensile shear test values and overall welding quality. Notably, the two-stage pin configuration emphasizes the significance of larger pin diameters and controlled heat generation for enhanced weld strength, while the one-stage pin configuration underscores the pivotal role of pin diameter and elevated temperatures in improving weld quality. The pinless mFSSW probe configuration, on the other hand, emphasizes the importance of shoulder diameter and temperature control for superior tensile shear test results. Leveraging Neural Network modeling for optimization, this study advances our understanding of parameter interactions and underscores the efficacy of Neural Networks in achieving superior tensile shear test values and welding quality in mFSSW, offering valuable insights for future endeavors in the field..

Plant diversity in the understory of Eucalyptus plantations on Hainan Island and its response to environmental factors

Research on understory plant diversity and its response to environmental factors helps in the sustainable development of plantation forests. We investigated the characteristics of understory plant diversity in Eucalyptus plantation forests located in Dongfang, Ding'an, Tunchang, and Lingao on Hainan Island by leveraging the plot survey method, and analyzing how the understory plant diversity in these Eucalyptus plantation forests responds to environmental factors. The results showed that a total of 124 plant species belonging to 62 families and 112 genera were recorded in the sampled plots of the Dongfang, Ding’an, Tunchang, and Lingao regional sites on Hainan Island, among which species of Fabaceae and Poaceae comprised the largest number of plants. The number of species and plant diversity indices of the shrub layer and herb layer in Eucalyptus plantation forests varied at different sites, The richest understory vegetation in Tunchang, located in the center of Hainan Island, and the highest α-diversity whether gauged by species or phylogenetically. The similarity of the understory plant community species was greatest between Ding’an and Tunchang, whereas the difference in composition was largest between Dongfang and the other three sites. Phylogenetically, the understory plant community at Ding’an had the most distant affinities among species, whereas that at Tunchang had the closest affinities among species. The results of the Mantel test and redundancy analysis revealed differing correlations between plant diversity in the shrub layer versus herb layer and various environmental factors. In particular, elevation and annual average temperature are the two main factors influencing plant diversity in the shrub layer, and soil available nitrogen and annual average sunshine duration are the two main factors influencing plant diversity in the herb layer. Variance decomposition showed that the combined effect of soil, climate, and topography factors is the main driver shaping plant diversity in the shrub layer of the understory in Eucalyptus plantation forests, while the combined effect of climate and soil factors is the main one determining plant diversity in their herb layer.