Search Results (349)

Harmful algal blooms (HABs) caused by the dinoflagellate Karenia brevis present serious ecological and public health concerns due to the production of brevetoxins (BTX). Clay flocculation and sedimentation of cells, particularly with polyaluminum chloride (PAC)-modified clays, is a promising HAB mitigation approach. This study evaluated the efficacy of Modified Clay-II (MCII), a PAC-modified kaolinite clay, in reducing K. brevis cell abundance in mesocosm experiments and examined the bioavailability of BTX potentially released from settled floc back into the water column and sediment over the first 72 h after treatment. Additionally, we quantified trace metals in benthic clams (Mercenaria mercenaria) exposed to the floc post-treatment to assess metal accumulation and potential toxicological effects from MCII application. MCII treatment (0.2 g/L) resulted in a 91% reduction in K. brevis cell density and a 50% decrease in waterborne brevetoxins after 5 h. Brevetoxins accumulated in sediment post-flocculation, with BTX-B5 emerging as the dominant congener. Clams exposed to MCII-treated floc showed comparable tissue BTX levels to controls and significantly elevated aluminum concentrations, though without mortality. The aluminum accumulations in this study do not raise concerns for the health of the clams or the humans who eat them, given other dietary exposures. These findings support the potential of MCII for HAB mitigation while underscoring the need for further evaluation of exposure risks to all benthic species. Full article

Lake Salda in Türkiye serves as a valuable Earth analog for studies of the properties of Mars due to its mineralogical and microbiological similarities to Jezero Crater on Mars. This study investigated the role of sulfate-reducing bacteria (SRB) enrichment culture isolated from Lake Salda on the microbiologically influenced corrosion (MIC) of an aluminum alloy (AA7075) using electrochemical, microbiological, molecular, and spectroscopic methods. Potentiodynamic polarization (PDP) tests confirmed SRB-enriched biofilm significantly accelerated corrosion. Fourier Transformed Infrared Spectroscopy (FTIR) further distinguished the control and biotic surfaces, showing the replacement of a 980 cm⁻¹ polysaccharide band with a 1075 cm⁻¹ cyclic polysaccharide vibration in SRB-colonized coupons. This spectral transition reflects biofilm maturation and EPS accumulation, providing molecular evidence for SRB-driven MIC. Molecular analysis identified Proteobacteria and Firmicutes as dominant phyla, and Desulfofustis limnaeus was detected in Lake Salda for the first time. Moreover, benthic foraminifera and ostracods were observed, some with morphological anomalies. These results provide mechanistic insight into the biochemical and electrochemical interactions driving SRB-induced corrosion, highlighting Lake Salda’s importance for studying microbial–material interactions in extreme environments. Full article

Composite materials are widely utilized for their excellent properties; however, the mismatch in phase response during processing often induces surface and subsurface damage. While reducing the cutting depth is a common strategy to improve quality, it shifts the material removal mechanism from shear to ploughing–extrusion, which can, in fact, degrade the final surface integrity. Energy field assistance is a promising approach to suppress this issue, yet its underlying mechanism remains insufficiently understood. This study investigates high-silicon aluminum alloy by combining turning experiments with molecular dynamics simulations to elucidate the origin and evolution of damage under different energy fields, establishing a correlation between microscopic processes and observable defects. In conventional turning, damage propagation is driven by particle accumulation and dislocation interlocking. Ultrasonic vibration softens the material and confines plastic deformation to the near-surface region, although excessively high transient peaks can lead to process instability. Laser remelting turning disperses stress within the remelted layer, significantly inhibiting defect expansion, but its effectiveness is highly sensitive to variations in cutting depth. The hybrid approach, laser remelting ultrasonic vibration turning, leverages the dispersion buffering effect of the remelted layer and the localized plastic deformation from ultrasonication to reduce peak loads, control deformation depth, and suppress defects, while simultaneously mitigating the depth sensitivity of damage and maintaining removal efficiency. This work clarifies the mechanism by which a composite energy field controls damage in the micro-cutting of high-silicon aluminum alloy, providing practical guidance for the high-quality machining of composite materials. Full article

Selenium (Se) is an essential trace element for human health, which is crucial for antioxidant defense, immune function, and disease prevention. Se deficiency affects around 40 countries worldwide, with China being one of the most severely impacted. While previous research has explored factors influencing soil Se content, such as the parent material, climate, and soil properties, the dominant controlling mechanisms across different spatial scales remain a subject of debate, especially in the Se-rich coastal regions of southeastern China. This study focuses on Fujian Province, using hotspot analysis and geographically weighted regression (GWR) to systematically examine the spatial distribution of soil Se and its key influencing factors. Hotspot analysis reveals multi-scale patterns in Se distribution: at the 1 km scale, Se hotspots are closely linked to metal minerals like sulfide and coal deposits; at the 2 km scale, Se-rich carbonate rocks and carbonaceous mudstones dominate; and, at the 10 km scale, Se accumulation is mainly controlled by organic matter and low-temperature conditions in high-altitude areas (≥1200 m). GWR analysis further clarifies the nonlinear relationships between soil Se and key environmental factors: organic matter strongly correlates with Se in coastal regions but weakly in land, indicating that this relationship is modulated by factors such as weathering intensity and clay content. The mobility of Se increases in alkaline soils (pH > 8.5), thus reducing its content; meanwhile, in acidic soils (pH < 4.5), its fixation is more complex. In acidic, low-aluminum settings, iron oxides adsorb Se effectively, whereas organic matter becomes the main carrier under alkaline conditions. Precipitation affects Se via atmospheric deposition and leaching, temperature promotes sulfide substitution through deposition but also accelerates the breakdown of organic matter, and altitude influences Se through hydrothermal variations. This study provides the first comprehensive analysis of the multi-factor mechanisms controlling soil Se in the Se-rich coastal areas of southeastern China at a regional scale, offering a scientific basis for the sustainable use of Se-enriched land resources. Full article

Load spectrum enhancement is a pivotal accelerated fatigue testing methodology employed to substantially reduce test duration and associated costs. This technique operates by strategically elevating load amplitudes while ensuring the preservation of the original failure mechanism. In this study, a novel fatigue life prediction model for variable amplitude loading is developed by integrating the theories of Equivalent Initial Flaw Size (EIFS) and the Equivalent Plastic Zone (EPZ). This integrated approach explicitly accounts for both the small crack effect and load interaction effects, which are critical yet often oversimplified aspects of fatigue damage accumulation. The model is subsequently applied to quantitatively establish the relationship between the Load Enhancement Factor (LEF) and the test time or compression ratio. Finally, fatigue tests on typical 2A14 aluminum alloy structures under variable amplitude loading are conducted to validate the proposed model. The results demonstrate a significant life reduction with increasing LEF, achieving a remarkable test time reduction of over 50% at an LEF of 1.2. All experimental data fall within a scatter band of three, relative to the model prediction. Additionally, the predicted mean compression ratio exhibits approximate agreement with the experimental data, with errors within an acceptable range. This work provides a physically grounded and practically validated framework for implementing efficient and reliable load spectrum enhancement. Full article

Mangrove forests provide critical ecosystem services, including carbon sequestration, shoreline protection, and serving as a food resource for coastal communities. However, these ecosystems face increasing environmental risks due to industrial and urban pollution, particularly contamination by heavy metals. This study assessed environmental quality in mangrove areas of Babitonga Bay, southern Brazil, using biomonitoring with the oyster Crassostrea rhizophorae and the mangrove tree Laguncularia racemosa. Sediment analyses revealed significantly elevated concentrations of copper, nickel, aluminum, and iron in Vila da Glória compared to Espinheiros, exceeding Brazilian environmental guidelines for copper and zinc. Biomonitoring results indicated high accumulation of arsenic and zinc in L. racemosa leaves, while oysters from Espinheiros exhibited higher concentrations of multiple heavy metals and smaller anatomical dimensions compared to those from Vila da Glória. Strong negative correlations were found between metal concentrations in oyster tissues and sediments, suggesting complex bioavailability dynamics. The study demonstrates the applicability of C. rhizophorae and L. racemosa as possible bioindicators of metal contamination in mangrove ecosystems. These findings underscore the importance of integrating biomonitoring approaches into coastal environmental health assessments to inform public health policies and conservation strategies aimed at promoting balanced ecosystem and human health. Full article

Spirulina and Chlorella are nutrient-rich microalgae widely consumed as dietary supplements; however, their high biosorption capacity raises concerns regarding the accumulation of environmental contaminants. This study analyzed 52 commercially available Spirulina and Chlorella products (29 conventional, 23 organic) to assess the co-occurrence of heavy metals and pharmaceutical residues, as these two classes of contaminants represent distinct yet complementary indicators of environmental pollution—heavy metals reflect long-term inputs from natural and industrial sources, while pharmaceuticals signal more recent contamination linked to human activity and wastewater discharge. To the best of our knowledge, this is the first study to investigate the presence of pharmaceutical residues—including cardiovascular drugs, antidepressants, antibiotics, and sulfonamides—in both conventional and organic formulations of microalgae-based dietary supplements. The analyses were performed using Inductively Coupled Plasma Mass Spectrometry and liquid chromatography coupled to tandem mass spectrometry. Aluminum, manganese, strontium, and zinc were the dominant trace elements. All samples complied with EU regulatory limits for toxic metals. More importantly, a wide range of pharmaceutical residues was detected in the supplements. Caffeine was the most frequently found compound, followed by metronidazole, carbamazepine, benzocaine, and tramadol. Particular concern is raised by the calculated TWI (% of tolerable weekly intake) for aluminum. Principal Component Analysis revealed significant compositional differences between Spirulina and Chlorella products, with vanadium notably elevated in conventionally cultivated Spirulina. Surprisingly, no significant differences were observed between organic and conventional products within each algal type. Our findings provide a novel contribution to the field by highlighting the presence of pharmaceutical residues in microalgae-based supplements and addressing a critical knowledge gap concerning potential chronic exposure to these contaminants through dietary intake. Full article

Understanding the microstructure–property relationship in aluminum extrusions is crucial to leverage their potential in automotive lightweighting. The sensitivity of the processing history to the microstructure and through-thickness variations poses a major challenge since it leads to strong directionality in plasticity and fracture. Reliable characterization of the mechanical response under relevant stress states is crucial for the development of modeling strategies and performance ranking in alloy design. To this end, tensile and 3-point bend tests were performed for an aluminum extrusion produced on a laboratory-scale extrusion press at Rio Tinto Aluminium. Direct measurements of surface strains during bending using stereoscopic digital image correlation revealed that a larger bend angle in the VDA238-100 test does not necessarily imply a higher fracture strain. The T4 sample tested in the extrusion direction sustained a bend angle of 104° compared to 68° in T6 for the same nominal bend severity (ratio of sheet thickness to punch radius), despite comparable major fracture strains of 0.60 and 0.58, respectively. It is proposed that the work-hardening behavior governs the strain distribution on the outer bend surface. The higher hardening rate in the T4 condition helped distribute deformation in the bend zone more uniformly. This delayed fracture to larger bend angles since strain is accumulated at a lower rate. To assess whether the effect of the hardening behavior is manifest at a microstructural lengthscale, microcomputed tomography (μ-CT) scans were conducted on interrupted bend samples. The distribution and severity of damage in the form of cracks on the outer bend surface were distinct to the temper and thus the hardening rate. Full article

Wire Arc Additive Manufacturing (WAAM) offers high deposition rates and cost-effective production of large metal components but suffers from poor surface quality, particularly surface waviness, which increases post-processing requirements and limits industrial adoption. Since waviness directly impacts structural integrity, resource efficiency, and industrial applicability, understanding how process parameters govern this feature is critical for reducing post-processing requirement. This study systematically investigated the influence of voltage, travel speed, and wire feed speed on surface waviness in aluminum alloy walls fabricated by WAAM. A two-level factorial design with 16 experiments was conducted, and surface waviness was quantified using height gauge measurements relative to the expected bead height. Statistical analyses, including ANOVA and multiple linear regression, were applied to evaluate parameter significance. The results revealed that wire feed speed was the most influential parameter, showing a strong positive correlation with waviness due to excess material deposition. Voltage exhibited a weaker, stabilizing effect, with higher values marginally reducing waviness through improved arc stability, while travel speed had negligible influence within the studied range. The regression model achieved an $R^2$ 0.389, with validation tests indicating reasonable predictive accuracy. These findings demonstrate that controlling wire feed speed is critical for minimizing waviness, while higher voltage may serve as a secondary stabilizing factor. The study was limited to surface waviness; however, future work should consider the role of thermal accumulation, inter-pass temperature, and external disturbances on surface stability. Such insights could enable adaptive parameter control strategies to further reduce post-processing needs and enhance the industrial viability of WAAM. Full article

Reliable modeling and prediction of the long-term strength of materials are relevant, as they allow for accurate determination of the service life of structures and components made from these materials. The aim of this work is to develop models of the long-term strength of rheonomic materials under constant stress and step loading using the principle of damage accumulation, as well as a model for predicting their long-term strength under constant stress based on short-term test data. Using the developed models, the long-term strength of optical fiber with a moisture of 30% and 85% under constant stress from 1600 to 2100 MPa and aluminum alloy under a step change of stress at a temperature of 180 °C were predicted with high accuracy; the long-term strength of pearlitic steel was predicted based on short-term tests under constant stress at temperatures from 98 °C to 293 °C. The developed models have important practical significance, as they can be used for modeling and predicting the long-term strength of rheonomic materials in practice, particularly in cases where the conditions of their operation and loading history are known. Full article

This study aimed to determine the stress mechanisms induced by foliar methyl jasmonate (MeJA) application in Vaccinium corymbosum cultivars subjected to water deficit (WD) and aluminum toxicity (Al). Two V. corymbosum cultivars, Star and Legacy, were subjected to different treatments in an Andisol: control (80% field capacity and low Al saturation), combined WD + Al (50% field capacity and 85% Al saturation), and different concentrations of foliar MeJA application (10 μM, 50 μM, and 100 μM) under WD + Al conditions. The determination of photosynthetic pigments, osmolytes, and organic acids, as well as the auxin levels and the expression of Aluminium-Activated Malate Transporter (ALMT) and Multidrug and Toxic Compound Extrusion (MATE) genes, was analyzed at 7 and 21 days. Foliar MeJA application increased chlorophyll a, b, and carotenoid levels, mainly at 50 µM, exhibiting early Star responses with up to 1.5-fold higher pigment accumulation, and a later increase in Legacy with up to 1.4-fold higher accumulation. Proline increases up to 2.2-fold in roots and sugar by 1.4-fold in leaves of both cultivars. The MeJA application increases the auxin levels by up to 2.3-fold in Star roots at 7 days and by up to 1.4-fold in Legacy leaves at 21 days. MeJA-induced upregulation of ALMT and MATE gene expression facilitated Al detoxification, with malate and citrate levels increasing up to 2-fold. Hierarchical clustering confirmed that the Star cultivar activated resistance mechanisms early, while the Legacy cultivar exhibited delayed but sustained resistance mechanisms. MeJA improves V. corymbosum resistance to combined WD + Al stress by modulating photosynthetic pigments, osmolytes, organic acids, and hormone regulation. This finding underscores the biotechnological potential of MeJA application to improve stress resilience and optimize crop performance under adverse environmental conditions. Full article

Generally, atomic doping is an effective method to address the weak bonding strength of the graphene/aluminum (Gr/Al) composite interface structure caused by physical adsorption, thereby enhancing the mechanical properties of the interface structure. In this paper, the nanoscopic influence mechanisms of atomic (M, including 12 types of atoms (elements)) doping in the aluminum matrix (Al) on the ideal strength of the Gr/Al interface structures are investigated based on density functional theory. The analysis of the electronic properties of the typical interface structures reveals that doping with scandium (Sc), copper (Cu) and manganese (Mn) atoms can all improve the interface binding energy of the Gr/Al structures, but their effects on the ideal strength are different. Sc doping disrupts the symmetry of the graphene structure so as to enhance the interface binding energy, but the ideal strength of the Gr/Al structures is decreased. For Cu doping it shows good compatibility with the Al matrix and the interface binding energy is enhanced through Cu alloying with the Al matrix, while the ideal strength of the interface remains basically unchanged. As for Mn doping, it causes the charge to accumulate around the Mn atoms and a resonance peak between the d_Z² orbitals of Mn and the p_x orbitals of Al to form, thereby improving the ideal strength of the interface structure. This study provides valuable insights for the design of Gr/Al composites by elucidating the underlying mechanisms for enhancing interface mechanical properties. Full article

On acid soils, aluminum (Al³⁺) is typically toxic to plants, though certain species like Pogostemon cablin (patchouli) show growth stimulation. This study reveals that Al functions as a root development stimulant in patchouli under acidic conditions. Treatment with 1.0 mM AlCl₃ for 34 days significantly enhanced root architecture, increasing total root length by 172.12% and root dry weight by 161.75%, without affecting shoot biomass. Structural analysis showed Al accumulation in root tip meristems and lateral root primordia, triggering a 103.77% increase in meristem activity and a 111.9% promotion of cell elongation. Physiological assays showed that Al treatment reduced H₂O₂ and malondialdehyde (MDA) levels by 49.2% and 67.6%, respectively, while boosting glutathione (GSH) content by 187.5%, thereby mitigating oxidative membrane damage mainly through the non-enzymatic antioxidant system. Moreover, Al deprivation impaired lateral root elongation, highlighting its functional importance. Gene expression profiling further indicated that Al regulated pathways related to cell proliferation, cell wall remodeling, and lateral root development. Taken together, our findings uncover a novel mechanism by which Al, traditionally regarded as toxic, acts as a stimulator of root development in patchouli, providing new insights into the molecular networks underlying plant abiotic stress responses. Full article

The development of advanced energy materials is critical for the safety and efficiency of next-generation nuclear energy systems. Aluminum alloys present a compelling option due to their excellent neutronic properties, notably a low thermal neutron absorption cross-section. However, their historically poor high-temperature performance has limited their use in commercial power reactors. This makes them prime candidates for specialized, lower-temperature but high-radiation environments, such as research reactors, spent fuel storage systems, and spallation neutron sources. In these applications, mitigating radiation damage—particularly swelling and embrittlement from helium produced during irradiation—remains a paramount challenge. Grain Boundary Engineering (GBE) is a potent strategy to mitigate radiation damage by increasing the fraction of low-energy Coincident Site Lattice (CSL) boundaries. These interfaces act as effective sinks for radiation-induced point defects (vacancies and self-interstitials), suppressing their accumulation and subsequent clustering into damaging dislocation loops and voids. By controlling the defect population, GBE can substantially reduce macroscopic effects like volumetric swelling and embrittlement, enhancing material performance in harsh radiation environments. In this article we evaluate the efficacy of GBE in an AlSi10Mg alloy, a candidate material for nuclear applications. Samples were prepared via KOBO extrusion, with a subset undergoing subsequent annealing to produce varied initial grain sizes and grain boundary character distributions. This allows for a direct comparison of how these microstructural features influence the material’s response to helium ion irradiation, which simulates damage from fission and fusion reactions. The resulting post-irradiation defect structures and their interaction with the engineered grain boundary network were characterized using a combination of Transmission Electron Microscopy (TEM) and High-Resolution Transmission Electron Microscopy (HRTEM), providing crucial insights for designing next-generation, radiation-tolerant energy materials. Full article

Anodic sludges generated in the production of aluminum profiles pose both an environmental and economic problem due to their accumulation in municipal landfills. This study investigates their valorization as a raw material for industry through leaching and calcination processes. The solid residue was characterized both physically and chemically. In the leaching process, concentrations of NaOH (1–2.5 M) and solid percentages (10–30%) were evaluated, achieving a 93.7% recovery of aluminum as sodium aluminate with 2 M NaOH and 10% solids. In the calcination process, the sludges were treated at temperatures ranging from 200 to 1600 °C, and different particle sizes (−3 + 1 mm, −1000 + 400 μm, −400 + 200 μm). The best result from calcination was obtained at 1600 °C, producing a refractory material composed of corundum (α-Al₂O₃) and diaoyudaoite (NaAl₁₁O₁₇). Full article