Search Results (221)

Designing the high-performance polyimides (PIs) for the biomimetic structures, which are used in extreme conditions, remains greatly challenging, due to the conflict between processability and thermal stability. Here, we report a series of silicon–alkyne-functionalized diamine-based polyimides that exhibit remarkable processability and thermal stability. The incorporation of bulky siloxy groups disrupts chain packing and increases free volume, enabling excellent solubility in polar solvents, while the rigid fluorene core enhances chain stiffness. DFT calculations confirm twisted molecular geometries (Si bond angle ≈ 103°, dihedral angle ≈ 89°) which weak π–π stacking, while heterogeneous electrostatic potentials enable favorable noncovalent interactions (e.g., C–F···H–C), promoting solvent diffusion. After thermal curing, the obtained product shows a high decomposition temperature (T_d5% = 560 °C), char yield of 72.0% at 800 °C, and glass transition temperature (T_g) of 354.6 °C. Meanwhile, locally planar fluorene units retain inherent thermal stabilization benefits through constrained rotational mobility. These results demonstrate a spatially decoupled siloxy–alkyne design that synergistically enhances molecular flexibility, disorder, and electronic stability, offering a molecular strategy for tailoring PI-based matrices to meet the demands of emerging biomimetic architectures and other high-performance composites operating under severe thermal loads. Full article

Liver function plays a pivotal role in the management of hepatocellular carcinoma (HCC). Consequently, managing HCC requires a dual focus on both tumour staging and liver function assessment to guide therapeutic decisions. Comprehensive liver function evaluation involves clinical tools such as the Child–Pugh classification and the Model for End-Stage Liver Disease (MELD) score. This is supplemented by newer metrics, including the MELD-Na score, the albumin–bilirubin (ALBI) grade and liver stiffness measurements. These assessments are integral to tailoring treatments, ranging from curative approaches such as surgical resection and liver transplantation to locoregional options (percutaneous ablation, transarterial chemoembolisation and radioembolisation), and systemic therapies. This review explores strategies for balancing the aggressiveness of cancer therapy with the need to preserve hepatic function, particularly in patients with advanced liver dysfunction. A multidisciplinary approach, incorporating expertise from hepatology, oncology, radiology and surgery, is essential for optimising outcomes. Advanced imaging techniques and biochemical markers also improve decision-making and ensure individualised care. Full article

Rapid characterization of high-cycle fatigue behaviour is of great interest, since conventional methods for developing S-N curves for longer fatigue lives are both costly in time and financial resources. Ultrasonic fatigue testing offers a promising alternative by enabling S-N curve evaluation in a fraction of the time, often hundreds of times faster, due to its high testing frequencies. Nevertheless, this technique presents specific challenges, including material overheating and limitations in specimens’ geometry. Most ultrasonic fatigue studies employ hourglass specimens; however, this geometry restricts the testing of sheets and thin-walled components, which are increasingly used for their reduced mass and high stiffness-to-mass ratio. To overcome this limitation, the present work introduces a methodology for designing and testing flat specimens and corresponding gripping systems tailored to such components. The procedure is demonstrated for an aluminium alloy (6082), and preliminary experimental fatigue results are presented and compared with literature. Full article

Background: Soft tissue tumors (STTs) represent a heterogeneous group of rare lesions that frequently mimic bone sarcomas in both clinical and radiologic appearance. Accurate differentiation between benign and malignant lesions is critical for appropriate treatment planning, yet conventional imaging often remains inconclusive. Ultrasound (US) elastography, a non-invasive method that quantifies tissue stiffness, has recently emerged as a potential adjunct to standard musculoskeletal imaging for improving diagnostic confidence and guiding biopsy. Methods: A systematic review was conducted in accordance with PRISMA guidelines. PubMed, Web of Science, and Cochrane Library were searched using the keywords “elastography”, “sonoelastography”, and “soft tissue tumor”. Twelve studies encompassing 1554 patients met the inclusion criteria, assessing the diagnostic accuracy of strain, compression, and shear wave elastography for differentiating benign from malignant STTs. Results: Elastography alone demonstrated limited specificity when used as a single diagnostic technique. However, its integration into multiparametric ultrasound approaches—combining grayscale, Doppler, and contrast-enhanced imaging—significantly improved diagnostic performance. Several studies reported sensitivities and specificities exceeding 85% when elastographic parameters were incorporated into composite diagnostic scores. Conclusions: Ultrasound elastography shows promise as a quantitative imaging biomarker for the preoperative evaluation of musculoskeletal tumors, particularly in distinguishing soft tissue from bone-related lesions. Although not a substitute for histopathological confirmation, its application within multimodal ultrasound protocols may reduce unnecessary biopsies, enhance diagnostic accuracy, and facilitate tailored management of bone and soft tissue sarcomas. Full article

This study examines the effect of geometrically controlled anisotropy on the compressive behaviour of additively manufactured Voronoi cellular structures. Three configurations—an isotropic reference and two anisotropic variants generated by scaling the design domain along the Z-axis—were fabricated by stereolithography using a tough photopolymer resin. All specimens exhibited an approximate nominal porosity of 80%. Compressive tests were conducted along the X, Y, and Z directions in accordance with ASTM D1621. The elongated structure showed enhanced stiffness and strength when loaded parallel to the scaling axis, whereas the compressed structure exhibited improved performance in the transverse directions. The isotropic structure displayed similar responses in all axes. These results demonstrate that geometric scaling effectively induces directional mechanical anisotropy without altering relative density, offering a simple route to tailor the load-bearing behaviour of lightweight architected materials. Full article

Background/Objectives: Metabolic dysfunction-associated steatotic liver disease (MASLD) is now the most prevalent chronic liver disorder among children and adolescents, mirroring the rise in pediatric obesity. The Mediterranean diet (MD) has demonstrated anti-inflammatory, antioxidant, and beneficial effects on different health outcomes across different life stages. The MD’s effect has been explored in adult MASLD, but there is limited information on the pediatric population. However, evidence on pediatric MASLD should be explored given its rising prevalence. Therefore, the aim of this review is to collect human studies assessing the effect of MD interventions on pediatric MASLD, focusing on key pathophysiological mechanisms. It also examines other interventions, including specific energy/macronutrient prescriptions, nutrition education or counseling, and physical activity components. Methods: A comprehensive search of PubMed, Scopus, and Web of Science was conducted using terms related to the Mediterranean diet, nutrition education, physical activity, pediatrics, and MASLD/NAFLD. Pre-determined inclusion and exclusion criteria were used to collect eligible studies to be included in the review. Study quality was assessed using the Academy of Nutrition and Dietetics Quality Criteria Checklist. Screening, data extraction, and appraisal were performed independently, with discrepancies resolved through discussion, and the findings were synthesized qualitatively. Results: This review synthesizes findings from eight human studies evaluating the impact of the MD, alone or integrated with structured exercise and nutrition education, on pediatric MASLD. Interventions consistently demonstrated reductions in hepatic steatosis, liver stiffness, and fibrosis markers, alongside improvements in inflammatory cytokines, oxidative stress defenses, and liver enzymes. The MD also enhanced lipid and glycemic profiles, lowering triglycerides, total cholesterol, and insulin resistance indices. Nutrition education and family-centered approaches improved adherence, while structured, enjoyable physical activity enhanced outcomes and long-term sustainability. Conclusions: Collectively, the MD, particularly when combined with exercise and tailored education, offers a safe, effective, and comprehensive lifestyle intervention for pediatric MASLD. Nonetheless, current evidence remains limited by small sample sizes, heterogeneity in protocols, and short follow-ups. Larger, multicenter randomized trials with standardized designs are needed to establish best practices and long-term efficacy. Full article

Graphene oxide (GO), with its high surface area, tunable chemistry, and exceptional mechanical, thermal, and electrical properties, is rapidly advancing as a transformative material in both composite engineering and membrane technology. In composite systems, GO serves as a multifunctional reinforcement, significantly improving strength, stiffness, thermal stability, and conductivity when integrated into polymeric, ceramic, or metallic matrices. These enhancements are enabling high-performance solutions across electronics, aerospace, automotive, and construction sectors, where lightweight yet durable materials are in demand. In addition, GO-based membranes are revolutionizing water purification, desalination, and other high-end separation technologies. The layered structure, adjustable interlayer spacing, and abundant oxygen-containing functional groups of GO allow precise control over permeability and selectivity, enabling efficient transport of desired molecules while blocking contaminants. Tailoring GO morphology and surface chemistry offers a pathway to optimized membrane performance for both industrial and environmental applications. This paper gives a comprehensive overview of the latest developments in GO-based composites and membranes, highlighting the interplay between structure, morphology, and functionality. Future research directions toward scalable fabrication, performance optimization, and integration into sustainable technologies are discussed, underscoring GO’s pivotal role in shaping next-generation advanced materials. Full article

This study investigates the influence of epichlorohydrin (EPCH) concentration on the rheological, mechanical, and swelling properties of lignin/PVA hydrogels. Hydrogels were prepared with EPCH concentrations ranging from 2.5% to 7.5%, and their viscoelastic properties were characterized through oscillatory strain and frequency sweep rheology. Increasing the EPCH concentration led to a substantial rise in mechanical stiffness, with the compressive modulus increasing from 21 kPa (2.5%) to 275 kPa (7.5%), accompanied by a marked reduction in swelling capacity from 460% to 190%. This behavior is attributed to the formation of a denser and more interconnected network structure with increasing cross-linking density. Furthermore, a strong correlation was observed between EPCH concentration and gelation kinetics, with higher concentrations generally leading to faster gelation times. In all formulations, gel time consistently decreased as the temperature increased from 10 to 50 °C. The optimal EPCH concentration for achieving a balance between mechanical properties and processability was determined to be 3.5%. At this concentration, the hydrogels exhibited a favorable combination of mechanical strength, shape recovery, and processability, while maintaining desirable swelling behavior. These findings provide valuable insights into the critical role of cross-linking density in determining the physicochemical properties of lignin/PVA hydrogels, paving the way for the development of these bio-based materials with tailored properties for diverse applications. Full article

We are witnessing a global commitment to sustainable mobility that requires advanced materials and manufacturing techniques, such as fused filament fabrication (FFF), to create lightweight, durable, and recyclable machine components. Acknowledging that friction and wear significantly contribute to energy loss globally, developing high-performance polymeric materials with customizable properties is essential for greener mechanical systems. FFF inherently drives resource efficiency and offers the geometric freedom necessary to engineer complex internal structures, such as the gyroid pattern, enabling substantial mass reduction. This study evaluates the tribological performance of FFF-printed thermoplastic polyurethane (TPU 82A) specimens fabricated with three distinct gyroid infill densities (10%, 50%, and 100%). Ball-on-disc testing was conducted under dry sliding conditions against a 100Cr6 spherical ball, with a constant normal load of 5 N, resulting in an initial maximum theoretical Hertz contact pressure of 231 MPa, over a total sliding distance of 300 m. Shore A hardness and surface roughness (R_a) were also measured to correlate mechanical and structural characteristics with frictional response. Results reveal a non-monotonic relationship between infill density and friction, with a particular absence of quantifiable mass loss across all samples. The intermediate 50% infill (75.9 ± 1.80 Shore A) exhibited the peak mean friction coefficient of $\overline{\mu }=1.002$ (${\mu }_{\max }=1.057$), which can be attributed to its balanced structural stiffness that promotes localized surface indentation and an increased real contact area during sliding. By contrast, the rigid 100% infill (86.3 ± 1.92 Shore A) yielded the lowest mean friction ($\overline{\mu }$ = 0.465), while the highly compliant 10% infill (44.3 ± 1.94 Shore A) demonstrated viscoelastic energy damping, stabilizing at $\overline{\mu }$ = 0.504. This work highlights the novelty of using FFF gyroid architectures to precisely tune TPU 82A’s tribological behavior, offering design pathways for sustainable mobility. The ability to tailor components for low-friction operations (e.g., μ ≈ 0.465 for bushings) or high-grip requirements (e.g., μ ≈ 1.002 for anti-slip systems) provides eco-efficient solutions for automotive, railway, and micromobility applications, while the exceptional wear resistance supports extended service life and material circularity. Full article

Serial-parallel hybrid manipulators featuring remote actuation via parallelogram mechanisms are highly valued for their low inertia and high stiffness. However, the complex nonlinear errors introduced by their multi-stage transmission chains pose significant challenges for high-precision calibration. To address this, this paper proposes a hierarchical and decoupled calibration framework specifically tailored for such parallelogram-driven hybrid manipulators. The method first independently calibrates the pose error of the 3-DOF serial main arm using a composite error model that integrates transmission chain constraints. Subsequently, the 2-DOF parallel wrist is accurately calibrated employing a joint-space error identification strategy based on inverse kinematics, thereby circumventing the intractability of solving the parallel mechanism’s forward kinematics. Experimental validation was performed on a self-developed 5-DOF robot prototype using an optical tracker and an attitude sensor. Results from the validation dataset demonstrate that the proposed method reduces the robot’s average positioning error from 2.199 mm to 0.658 mm (a 70.1% improvement) and the average attitude error from 0.8976 deg to 0.1767 deg (an 80.3% improvement). Furthermore, comparative experiments against the standard MDH model and polynomial fitting models confirm that the proposed composite error model and multi-stage transmission error model are essential for achieving high accuracy. This research provides crucial theoretical insights and practical solutions for the high-precision application of complex remote-driven hybrid manipulators. Full article

Lightweight lattice sandwich panels combine high stiffness-to-weight ratios with tailored vibration performance, making them ideal for aerospace structures. However, exact dynamic analysis of these structures remains computationally intensive and is frequently constrained by simplified boundary condition assumptions. This study proposes a novel solution framework that combines the asymptotic homogenization method (AHM) with the finite integral transform (FIT) method. The framework (1) uses the AHM to model a periodic lattice sandwich panel as an equivalent orthotropic thin plate, and (2) derives analytical natural frequency and mode shape solutions under non-Lévy-type boundary conditions via the FIT method. Comprehensive experimental and numerical validation demonstrates the accuracy and reliability of the AHM when applied to equivalent property prediction of lattice sandwich structures. All FIT-based analytical results achieve convergence to 5 significant digits within 15 terms, and demonstrate a maximum error of less than 1% when compared with the results from the finite element method-based equivalent model. Full article

This observational study aims to assess both the posture and muscle tone characteristics of the upper and lower limbs in patients with hemiparesis following a cerebrovascular accident. Measurements will be taken comparatively between the affected and non-affected sides. The study will include patients with both ischemic and hemorrhagic strokes. Assessments will be conducted at months 1, 3, and 6 after the stroke event. In order to ensure the homogeneity of the study group, all patients will follow a physical exercise program tailored to their clinical stage of recovery. Myotonometric evaluation will be performed using the Myoton PRO Digital Palpation Device, which allows the assessment of muscle tone, elasticity, dynamic stiffness, tension state, relaxation time, and deformation ratio during muscle relaxation. Postural assessment will be conducted using the GaitON device by Auptimo. In addition to these instrumental evaluations, the following clinical scales will be applied: the Modified Ashworth Scale, Barthel Index, Instrumental Activities of Daily Living and the Modified Rankin Scale. Based on the three successive evaluations (at one, three, and six months after stroke event) we expect that with the spasticity decrease and the improvement of the posture of patients participating in the physical exercise program, both the objectively assessed parameters and the scores obtained from clinical scales will evolve in favor of better functioning. Full article

Recently, significant attention has been paid to the use of multirole materials in additive manufacturing (AM). Polyvinylidene fluoride (PVDF) is an ideal candidate material that has been selected for examination because of its unique characteristics. This study establishes a correlation between the macroscopic mechanical behavior and microscopic structural mechanisms, enabling the utilization of the deformation rate in tailoring the mechanical response of printed PVDF components. This research focuses on testing AM PVDF samples under different strain rates (10–300 mm/min), aiming to report their behavior under loading conditions compatible with the stochastic nature of real-life applications. The thermal (thermogravimetric analysis and differential scanning calorimetry) and rheological (viscosity and melt flow rate) properties were investigated along with their morphological characteristics (scanning electron microscopy). The response under combined dynamic and thermal loading was investigated through dynamic mechanical analysis, and the structural characteristics were investigated using spectroscopic techniques (Raman and energy-dispersive spectroscopy). The properties examined were the ultimate and yield strengths, modulus of elasticity, and toughness. Sensitivity index data are also provided. For completeness, the flexural strength, Charpy impact strength, and Vickers hardness were also evaluated, suggesting that the AM PVDF samples exhibit a resilient nature even when subjected to extremes regarding their strain rate versus their overall mechanical characteristics. PVDF exhibited a strain-hardening response with an increase in its strength of up to ~25% (300 mm/min) and a stiffness of ~15% (100 mm/min) as the loading speed of testing increased. Full article

The growing demand for sustainable materials has intensified research on biodegradable polymers, particularly poly(ε-caprolactone) (PCL), poly(lactic acid) (PLA), and their blends. PLA and PCL offer biocompatibility and biodegradability, making them attractive for biomedical, packaging, and agricultural applications; however, their practical utility remains limited owing to intrinsic drawbacks. PLA has low impact strength and poor thermal resistance, while PCL suffers from low tensile strength and slow degradation kinetics. Blending PLA with PCL can complement their properties, providing a tunable balance of stiffness and flexibility. Further improvements can be achieved through the incorporation of micro- and nanocellulose (NC), which act as reinforcements, nucleating agents, as well as compatibilizers. We critically examine fabrication strategies for NC-reinforced PLA, PCL, and their blends, highlighting NC extraction, surface modification, processing strategies, and dispersion techniques that prevent agglomeration and facilitate uniform distribution. Comparative insights into composite and nanocomposite systems reveal that NC incorporation significantly enhances mechanical properties, thermal resistance, crystallization, and biodegradation kinetics, particularly at low filler loadings, owing to its high surface area, specific strength, and hydrophilicity. The review underscores the potential of PLA/PCL-based nanocomposites as eco-friendly biomaterials with tunable properties tailored for diverse sustainable applications. Full article

Gas bearings are attractive for sustainable, high-speed, and cryogenic applications, where gases replace liquid lubricants. This study numerically analyzed hybrid gas journal bearings lubricated with hydrogen, nitrogen, air, and helium, and quantifies the impact of circumferential micro-grooves. The compressible Reynolds equation was solved by the finite element method with constant-flow valve restrictors, while Gauss–Seidel iterations were used for convergence. The model was verified against published theoretical and experimental data with maximum deviations below 6%, and mesh independence is confirmed. The parametric results show that the gas type and texturing jointly controlled static and dynamic performance. Helium (highest viscosity) yielded the largest minimum film thickness, whereas hydrogen (lowest viscosity) attained higher peak pressures at a lower film thickness for a given load. Grooves redistributed pressure and reduced both the maximum pressure and the minimum film thickness, but they also lowered the frictional torque. Quantitatively, the hydrogen-lubricated grooved bearing reduced the frictional torque by up to 50% compared with the non-grooved air-lubricated bearing at the same load. Relative to air, hydrogen increased stiffness and damping by up to 10% and 50%, respectively, and raised the stability threshold speed by 110%. Conversely, grooves decreased the stiffness, damping, and stability threshold speed compared with non-grooved surfaces, revealing a trade-off between friction reduction and dynamic stability. These findings provide design guidance for selecting gas media and surface texturing to tailor hybrid gas journal bearings to application-specific requirements. Full article