Search Results (2,282)

Direct metal laser sintering (DMLS) is an advanced powder bed fusion (PBF) technology widely utilized in the medical device and aerospace sectors for the production of intricate and high-value components. The powdered metal materials used in the DMLS process can be expensive, and it is uncommon for a single build to exhaust an entire batch of powder. As a result, the un-melted powder characterized by differences in particle size and morphology compared to fresh virgin powder is recommended to be recycled for use in subsequent builds. This comprehensive review delves into the essential role that powder quality plays in the realm of DMLS with a particular focus on effective and sustainable powder recycling strategies. In this study, the effects of recycling stainless steel powder, specifically used in the DMLS process, are rigorously investigated in relation to the quality of the finished components. This paper monitors critical powder material characteristics, including particle size, particle morphology, and the overall bulk chemical composition throughout the recycling workflow. Furthermore, this review brings to light significant challenges associated with the recycling of stainless steel powders, such as the need to maintain consistency in particle size and shape, manage contamination risks, and mitigate the degradation effects that can arise from repeated usage, including wear, fragmentation, and oxidation of the particles. In addition, this paper explores a variety of recycling techniques aimed at rejuvenating powder quality. These techniques, including sieving, blending, and plasma spheroidization, are emphasized for their vital role in restoring the integrity of recycled powders and facilitating their reuse in innovative and efficient manufacturing processes. Full article

Plastic microbeads, widely incorporated into personal care and cleansing products, have emerged as a pervasive contaminant in freshwater systems, including in North America. Historical estimates indicate that North American consumers alone contributed trillions of microbeads daily to municipal wastewater, with global usage reaching quadrillions per day. Regulatory actions in 2017 in Canada and the USA to ban microbeads in personal care products appear to have greatly reduced microbead contamination levels, including a decrease in microbead proportion from 2 to 5% to 0.003%, and an 86% reduction in PE microbead discharge from wastewater treatment plants. Yet these particles still persist in the environment due to their resistance to degradation and continued release from unregulated sources, including industrial abrasives and certain cleaning agents. Studies across the Great Lakes, one of the world’s largest freshwater systems, have documented widespread microbead contamination in surface waters, sediments, and shorelines, highlighting their persistence and accumulation. This review synthesizes findings from key studies conducted between 2013 and 2017 to establish a pre-ban baseline of microbead distribution in the Great Lakes, and presents new data collected from 2018 to 2021 as a post-ban contamination assessment. The review emphasizes the unique challenges posed by microbeads within the broader context of microplastic pollution. We also hope that this paper underscores the critical role of polymer chemists and engineers in developing innovative materials and removal strategies to mitigate future contamination. Full article

Additive manufacturing (AM), or 3D printing, has a significant, largely beneficial influence on climate change by decreasing material waste and requiring less energy use. The application of AM in the construction and industrial sectors has the potential to reduce carbon emissions. This goal may be accomplished by using material and energy-saving measures, improving manufacturing processes, designing lightweight structures, and reducing transportation operations. While 3DP has the potential to help reduce environmental degradation, it is crucial to recognize the inherent setbacks associated with the technology. Certain AM processes have the potential to emit volatile organic compounds, which contribute to air pollution and hence need improved control. Industrial 3D printers can be excessively expensive, greatly increasing the initial expenditure required to begin a project. Despite these limitations, AM can reduce greenhouse gas emissions, generate better-built environments, and provide a means to reduce energy usage while supporting global carbon neutrality objectives. Governments should extend financial assistance in the form of subsidies to help reduce equipment purchase costs. Furthermore, AM’s capacity to foster a circular economy and minimize overall environmental effects is dependent on the improvement of material recycling and scalability. Full article

At present, the contamination of wastewater by persistent organic pollutants is a problem causing significant concern. Advanced oxidation processes have emerged as effective and innovative technologies for the degradation of these pollutants. In these processes, the synthesis and usage of an appropriate catalyst is essential to enhance the generation of reactive species and improve treatment efficiency. In this sense, the use of greener solvents in the synthesis procedure has attracted great interest in recent years, improving the catalyst performance and reducing the associated synthesis impact. Among them, deep eutectic solvents stand out for the synthesis of catalytic materials in advanced oxidation processes for water treatment, offering a sustainable alternative to traditional methods due to their unique properties and low environmental impact. This review summarizes recent advances in this field, highlighting primarily the methods for preparing new catalytic materials using deep eutectic solvents and their application in different types of advanced oxidation processes. Full article

The growing demand for floating offshore structures calls for lightweight, impact-resilient, and sustainable design approaches. This study explores the optimization of composite fibree layup in a 30 m hull subjected to slamming-type hydrodynamic loads. Although based on a recreational vessel, the model serves as a transferable case for offshore applications such as wave energy devices, offshore wind platforms, and floating PV systems. A finite element method (FEM) model was developed using shell elements and a sinusoidal time-dependent pressure to simulate slamming events on the wet surface of the hull. The response was evaluated under different fiber orientation schemes, aiming to reduce structural mass while maintaining stress levels within safety margins. Results showed that strategic layup optimization led to a measurable reduction in total material usage, without compromising structural integrity. These outcomes suggest multiple advantages, including an approximately 14% reduction in raw material demand, which in turn facilitates for potential downsizing of propulsion systems and transportation energy due to lighter structures. Such improvements contribute indirectly to reduced emissions and operational costs. The methodology presented offers a replicable approach to composite optimization under transient marine loads, with relevance for sustainable offshore structural design. Full article

Cemented granular materials (CGMs) represent a transitional class of geomaterials where mechanical behavior is governed by the interplay between a discrete granular skeleton and a continuous cementitious matrix. While previous studies have focused on idealized spherical particles, this study aims to quantify the influence of the cement filling ratio (ranging from 10% to 100%) on the mechanical constitutive behavior of CGMs fabricated with large, irregular granitic aggregates (14–20 mm). Unconfined compressive tests and splitting tensile tests were conducted to evaluate the evolution of strength, stiffness, and failure modes. The results reveal a distinct mechanical transition governed by the cement filling ratio (${\rho }_m$). The elastic modulus and splitting tensile strength exhibited a linear increase with ${\rho }_m$ (R2 > 0.95), indicating a direct dependence on the volume fraction of the binding phase. In contrast, the unconfined compressive strength (UCS) and peak strain displayed a bilinear growth pattern with a critical inflection point at ${\rho }_m$ = 80%. For the specific irregular granitic aggregate skeleton investigated, this threshold marks the transition from contact-dominated stability to matrix-dominated continuum behavior. Below this threshold, strength gain is limited by the stability of discrete particle contacts; above 80%, the material behaves as a continuum, with UCS increasing rapidly to a maximum of 41.78 MPa at 100% filling. Furthermore, the dispersion of stress–strain responses significantly decreased as ${\rho }_m$ exceeded 50%, attributed to the homogenization of stress distribution within the specimen. These findings provide a quantitative basis for optimizing cement usage in ground reinforcement applications, identifying 80% as a critical design threshold. Full article

Background and Objectives: Pilonidal Sinus Disease shows an increasing incidence. Surgical interventions are often necessary; thus, we wanted to analyze whether the usage of methylene blue (MB) for staining the PSD fistulas for better visualization during surgery shows an effect concerning recurrence rates. Materials and Methods: A thorough data search and cross-study data synthesis of publications in the time period of 1833 to 2023 lead to a total of 7936 studies focusing on PSD. The data sets were scanned for the eligibility criteria, namely treatment information, follow-up, recurrence data, and the use of MB in surgery. The data were sorted into different surgical treatment groups, and the recurrence rates were analyzed using Kaplan–Meier-survival curves. Results: A total of 1192 studies involving 130,677 patients were eligible for analysis. A total of 263 studies were performed with MB (22.1%, n = 25,602 patients) and 929 studies without MB (77.9%, n = 105,075 patients). Overall, there was a highly significant difference in RR between the group of MB-stained patients and those without (p < 0.0001), even if analyzed separately for treatments. Primary open approach, primary midline closure, primary asymmetric closure, and Limberg/Dufourmentel all showed a significantly lower RR when MB was used (p < 0.0001). The use of MB in Bascom/Karydakis-Flap showed a statistically significant disadvantage concerning RR (p < 0.0001), and Other Flaps showed less RR with the use of MB (p = 0.011); both groups showed a notable loss of follow-up data, diminishing the meaning of these p values. Conclusions: This study shows that the use of MB as a staining technique in PSD surgery may be beneficial regarding recurrence rates. Therefore, the routinely use of MB staining in PSD surgery should be considered. Full article

Background and Objectives: E-cigarette use among middle and high school students steadily increased in the last decade, raising significant public health concerns. It is argued that e-cigarettes contain a lower level of toxicants than combustible tobacco cigarettes. This perception has contributed to the growing popularity of e-cigarettes among youth. However, lower level of toxicants does not mean addiction is less likely. In this study, we examine trends in the usage of electronic cigarettes among middle and high school students in the U.S. from 2018 to 2023, compare these patterns with traditional cigarette use over the same period and population, and explore the underlying reasons driving e-cigarette use within this demographic. Understanding patterns and motivations are essential for developing effective prevention and intervention strategies. Materials and Methods: Data were derived from the National Youth Tobacco Survey (NYTS), administered by the Centers for Disease Control and Prevention (CDC). Population-level estimates and standard errors were calculated to facilitate comparisons across subgroups and time points. Results: A declining trend in e-cigarette use was observed over the study period. The proportion of students who reported exclusive e-cigarette use was significantly higher than that of those who used combustible cigarettes exclusively. Among reported motivations, anxiety consistently ranked among the top three reasons for vaping for current users. Conclusions: The downward trend in youth e-cigarette experimentation is encouraging. However, the period from 2020 to 2023, which includes the COVID-19 pandemic (2020 and 2021) era, may have impacted usage patterns. Alarmingly, the number of students who vape exclusively is approximately five times greater than that of those who smoke only cigarettes. This finding contradicts claims by e-cigarette manufacturers that their products facilitate smoking cessation. Further rising e-cigarette smoking exclusively is of public health concern, which warrants targeted intervention. Full article

Accurate immobilization is critical in head and neck (H&N) radiotherapy to ensure precise dose delivery while minimizing irradiation of surrounding healthy tissues. However, conventional thermoplastic masks cannot secure 100% replicas of the patient’s surface and are often limited by mechanical weakness, patient discomfort, and workflow inefficiencies. Recently, the best replicas of the patient’s face have been obtained by exploring personal CT or MRI scans of patients that are used for manufacturing of immobilization masks. This study aimed to design and evaluate customizable immobilization masks using acrylonitrile butadiene styrene (ABS)-based composites reinforced with bismuth oxide (Bi₂O₃) and to compare their mechanical performance against commercial thermoplastic masks. ABS and ABS/Bi₂O₃ composite filaments (5, 10, and 20 wt%) were fabricated and characterized by tensile testing. A patient-specific virtual mask was modeled and subjected to finite element analysis (FEA) under clinically relevant loading scenarios, including neck flexion and lateral bending. Results were benchmarked against two commercial thermoplastic masks. ABS and ABS-based composites exhibited significantly higher stiffness (1.7–2.5 GPa) and yield strength (20–25 MPa) compared to commercial thermoplastics (0.25–0.3 GPa, ~7 MPa; p < 0.001). FEA simulations revealed markedly reduced displacement in ABS masks (1–5 mm at 2 mm thickness; <1 mm at 4 mm thickness) relative to commercial masks, which exceeded 20 mm under lateral load. Hybrid configurations with reinforced edges further optimized rigidity while limiting material usage. Customized ABS-based immobilization masks outperform conventional thermoplastics in mechanical stability and displacement control, with the potential to reduce planning margins and improve patient comfort. In addition, ABS-based masks can be recycled, and Bi₂O₃-filled composites can be reused for printing new immobilization masks, thus contributing to a reduced amount of plastic waste. These findings support their promise as next-generation immobilization devices for precision radiotherapy, warranting further clinical validation, workflow integration and sustainable implementation within a circular economy. Full article

This study contributes to the advancement of circular economy practices in polymer manufacturing by applying machine learning algorithms (MLA) to predict the tensile strength of recycled low-density polyethylene (LDPE) building films. As the construction and packaging industries increasingly seek eco-efficient and low-carbon materials, recycled LDPE offers a valuable route toward sustainable resource management. However, ensuring consistent mechanical performance remains a challenge when reusing polymer waste streams. To address this, tensile tests were conducted on LDPE films produced from recycled granules, measuring tensile strength, strain, mass per unit area, thickness, and surface roughness. Three established machine learning algorithms—feed-forward Neural Network (NN), Gradient Boosting Machine (GBM), and Extreme Gradient Boosting (XGBoost)—were implemented, trained, and optimized using the experimental dataset using R statistical software (version 4.4.3). The models achieved high predictive accuracy, with XGBoost providing the most robust performance and the highest level of explainability. Feature importance analysis revealed that mass per unit area and surface roughness have a significant influence on film durability and performance. These insights enable more efficient production planning, reduced raw material usage, and improved quality control, key pillars of sustainable technological innovation. The integration of data-driven methods into polymer recycling workflows demonstrates the potential of artificial intelligence to accelerate circular economy objectives by enhancing process optimization, material performance, and resource efficiency in the plastics sector. Full article

Water polluted by dye colorants has been on the rise in the last decade. This is due to the over reliance on the textile industry, and it is holding a high economic value in most countries. This industry is the highest consumer of fresh water whilst also discharging several natural and synthetic pollutants to the environment. Several methods have been used for the removal of these pollutants and one of the most efficient technologies to be developed includes the photocatalysis method, via advanced oxidation processes. This review highlights the developments of green iron oxide nanoparticles as photocatalysts in the last decade. It was noted that tuning and controlling the phytochemical concentration and synthesis conditions, can assist with forming uniform and non-agglomerated materials, as this has limited the vast usage of these materials in major applications. Also, upon controlling the synthesis conditions, improved surface area and charge separation efficiency was noted. Their limitations and need for modification through forming composites are highlighted. Moreover, future perspectives are given on the use of green IONPs as photocatalysts. Full article

This study establishes a systematic and reproducible workflow for topology optimization (TO) of indexable face milling cutter bodies with integrated internal coolant channels, designed for Additive Manufacturing (AM) of metallic parts. Grounded in Design for Additive Manufacturing (DfAM) principles, the workflow combines displacement-based TO and computational fluid dynamics analysis to generate simulation-driven tool geometries tailored to the constraints of AM. By leveraging iterative design knowledge, the proposed methodology enhances the scalability and repeatability of the design process, reducing development time and supporting rapid adaptation across various tool geometries. AM is explicitly exploited to integrate support-free internal coolant channels directed toward the insert cutting edge, thereby achieving a 20% mass reduction relative to the initial milling tool designs, and improving material usage efficiency at the design stage. The workflow yields numerically optimized geometries that maintain simulated global stiffness under the considered loading conditions and exhibit coolant flow distributions that effectively target the exposed cutting edges. These simulation results demonstrate the feasibility of an AM oriented, workflow-based approach for the numerical design of milling tools with internal cooling, mass reduction and provide a focused basis for subsequent experimental validation and comparison with conventionally manufactured counterparts. Full article

Bacterial infections remain a major challenge to human health, especially in wound healing, where they can cause prolonged inflammation, delayed recovery, and severe complications. Current research is increasingly focused on developing innovative antimicrobial materials capable of overcoming the limitations of conventional antibiotics, whose effectiveness has declined due to the rise in bacterial resistance. Among the various alternatives, silver nanoparticles have gained particular attention for their broad-spectrum antibacterial properties and have already been successfully applied in the functionalization of commercial wound dressings. The aim of this study was to optimize the functionalization of commercial cotton gauzes based on in situ UV-assisted reduction of silver nanoparticles, reducing methanol usage and identifying the minimal silver nitrate precursor concentration to achieve antimicrobial efficacy while maintaining biocompatibility. Different precursor concentrations were then evaluated through cytocompatibility assays (MTT, Live/Dead, and scratch tests on fibroblasts) and antimicrobial analyses against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus (including an antibiotic-resistant strain), and Candida albicans. The results demonstrated that a 0.5% w/w silver nitrate concentration provided strong antimicrobial and antibiofilm activity without compromising textile properties or cytocompatibility. Furthermore, this optimized process reduced material waste, highlighting its potential for scalable production of antimicrobial wound dressings. Full article

Existing office buildings in Australia contribute to 24% of the nation’s electricity consumption and 10% of greenhouse gas emissions, with energy use projected to rise by 84%. Meeting the 2050 sustainability target and United Nations (UN) 17 Sustainable Development Goals (SDGs) requires improving sustainability within existing office buildings. This systematic review examines net zero energy and climate resilience strategies in these buildings by analysing 74 studies from scholarly literature, government reports, and industry publications. The literature search was conducted across Scopus, Google Scholar, and Web of Science databases, with the final search in early 2025. Studies were selected based on keywords and research parameters. A narrative synthesis identified key technologies, evaluating the integration of net zero principles with climate resilience to enhance energy efficiency through HVAC modifications. Technologies like heat pumps, energy recovery ventilators, thermal energy storage, and phase change materials (PCMs) have been identified as crucial in reducing HVAC energy usage intensity (EUI). Lighting control and plug load management advancements are examined for reducing electricity demand. This review highlights the gap between academic research and practical applications, emphasising the need for comprehensive field studies to provide long-term performance data. Current regulatory frameworks influencing the net zero transition are discussed, with recommendations for policy actions and future research. This study links net zero performance with climate adaptation objectives for existing office buildings and provides recommendations for future research, retrofit planning, and policy development. Full article

In response to the growing interest in sustainable and material-efficient architectural solutions, this study focuses on innovative applications of engineered timber in lightweight structural systems. It investigates the material optimization and structural performance of engineered timber thin-shell structures through an integrated parametric design approach. The study compares three prefabricated, panelized building systems, gridshell, segmented full-plate shell, and ribbed shell, to evaluate their efficiency in terms of material intensity, stiffness, and geometric behavior. Using Rhinoceros and Grasshopper environments with Karamba3D, Kiwi3D, and Kangaroo plugins, a comprehensive parametric workflow was developed that integrates geometric modeling, structural analysis, and material evaluation. The results show that segmented ribbed shell and two segmented gridshell variants offer up to 70% reduction in material usage compared with full-plate segmented timber shells, with hybrid timber shells achieving the best balance between stiffness and mass, offering functional advantages (roofing without additional load). These findings highlight the potential of parametric and computational design methods to enhance both the environmental efficiency (LCA) and digital fabrication readiness of timber-based architecture. The study contributes to the ongoing development of computational timber architecture, emphasizing the role of design-to-fabrication strategies in sustainable construction and the digital transformation of architectural practice. Full article