Search Results (94)

The development of high-impact denture base formulations that are suitable for digital light processing (DLP) 3D printing is demanding. Indeed, a combination of high flexural strength/modulus and high fracture toughness is required. In this contribution, eight urethane macromonomers (UMs1-8) were synthesized in a one-pot, two-step procedure. Several rigid diols were first reacted with two equivalents of trimethylhexamethylene diisocyanate. The resulting diisocyanates were subsequently end-capped with a free-radically polymerizable monomer bearing a hydroxy group. UMs1-8 were combined with the monofunctional monomer (octahydro-4,7-methano-1H-indenyl)methyl acrylate and a poly(ε-caprolactone)-polydimethylsiloxane-poly(ε-caprolactone) (PCL-PDMS-PCL) triblock copolymer (BCP1) as a toughening agent. The double-bond conversion, glass transition temperature (T_g), and mechanical properties (flexural strength/modulus, fracture toughness) of corresponding light-cured materials were measured (cured in a mold using a light-curing unit). The results showed that the incorporation of BCP1 was highly efficient at significantly increasing the fracture toughness, as long as the obtained networks exhibited a low crosslink density. The structure of the urethane macromonomer (nature of the rigid group in the spacer; nature and number of polymerizable groups) was demonstrated to be crucial to reach the desired properties (balance between flexural strength/modulus and fracture toughness). Amongst the evaluated macromonomers, UM1 and UM2 were particularly promising. By correctly adjusting the BCP1 content, light-cured formulations based on those two urethane dimethacrylates were able to fulfill ISO20795-1:2013 standard requirements regarding high-impact materials. These formulations are therefore suitable for the development of 3D printable high-impact denture bases. Full article

The monitoring of peripheral electrical bioimpedance (EBI) variations is a promising method that has the potential to replace invasive or burdensome techniques for cardiovascular measurements. Segmental or continuous recording of peripheral pulse waves can serve as a basis for calculating prognostic markers like pulse wave velocity (PWV) or include parameters such as pulse transit time (PTT) or pulse arrival time (PAT) for noninvasive blood pressure (BP) estimation, as well as potentially novel cardiovascular risk indicators. However, several technical, analytical, and interpretative aspects need to be resolved before the EBI method can be adopted in clinical practice. Our goal was to investigate and improve the application of EBI, executing its comparison with other cardiovascular assessment methods in patients hospitalized for coronary catheterization procedures. Methods: We analyzed data from 44 non-acute patients aged 45–74 years who were hospitalized for coronary catheterization at East Tallinn Central Hospital between 2020 and 2021. The radial EBI and electrocardiogram (ECG) were measured simultaneously with central and contralateral pressure curves. The Savitzky–Golay filter was used for signal smoothing. The Hankel matrix decomposer was applied for the extraction of cardiac waveforms from multi-component signals. After extracting the cardiac component, a period detection algorithm was applied to EBI and blood pressure curves. Results: Seven points of interest were detected on the pressure and EBI curves, and four with good representativeness were selected for further analysis. The Spearman correlation coefficient was low for all but the central and distal pressure curve systolic upstroke time points. A high positive correlation was found between PWV measured both invasively and with EBI. The median value of complimentary pulse wave velocity (CPWV), a parameter proposed in the paper, was significantly lower in patients with normal coronaries compared to patients with any stage of coronary disease. Conclusions: With regard to wearable devices, the EBI-derived PAT can serve as a substrate for PWV calculations and cardiovascular risk assessment, although these data require further confirmation. Full article

To enhance the performance of state-of-the-art lithium-ion batteries, high-capacity silicon is increasingly introduced as active material for anodes. Furthermore, advanced batteries with new electrode architectures—so-called 3D architectures—can provide significantly enhanced electrochemical performance compared to state-of-the-art batteries. To facilitate and speed up the architectural development, the laser-induced forward transfer (LIFT) process was applied as a digital additive manufacturing method. As polyvinylidene fluoride (PVDF), the binder commonly used in the LIFT process, is not a suitable binder for silicon-containing electrodes due to its weak binding forces, polyacrylic acid (PAA) was introduced as a binder for use in printable electrode pastes. Since water as a solvent in such pastes evaporates quickly and the corresponding printing time would be too short, glycerol was added to the solvent mixture in different amounts. The silicon in the printed electrodes reaches a specific capacity of more than 3000 mAh$·{\mathrm{g}}^{–1}$ for most of the printed anodes. To further improve the electrochemical performance of the printed electrodes, as well as the rheology of the slurries, two different conductive additives with different particle sizes were used. Full article

STap2Go is the first purely digital strategy-based method for the training of executive functions, making its evaluation relevant. This study assesses the effectiveness of this intervention in children with (at risk) and without (no-risk) psychosocial risk, which refers to socio-educational vulnerability, and examines whether its impact differs between groups. A total of 124 children (9–12 years old) were randomly assigned to either an experimental or an active control group. Individual assessments and family questionnaires were administered (FDT, WISC-V, RIST, BRIEF-2). Both groups received a 12-week intervention. The experimental group showed significant improvements in executive functions, processing speed, IQ, academic performance, and emotional and behavioral regulation compared to the controls. Notably, IQ, metacognition, and working memory continued improving at follow-up, suggesting lasting effects. While both groups benefited, the effects were more pronounced in at-risk children, particularly in BRIEF-2 (Inhibition, Metacognition, Behavioral Regulation) and academic performance in mathematics and language. Moreover, the psychosocial risk control group showed a trend toward deterioration over time. The far transfer achieved thanks to digital strategy-based training seems to have a greater effect on at-risk children, and can be used to compensate for their difficulties. Full article

Chemical looping combustion (CLC), a promising technology employing oxygen carriers to realize cyclic oxygen transfer between reactors, represents a transformative approach to CO₂ capture with near-zero energy penalties. Among oxygen carriers, Fe-based materials have emerged as the predominant choice due to their cost-effectiveness, environmental compatibility, and robust performance. The reaction kinetics of oxygen carriers are crucial for both material development and the rational design of CLC systems. This comprehensive review synthesizes experimental and theoretical advances in kinetic characterization of Fe-based oxygen carriers, encompassing both natural and synthetic materials, while different models corresponding to specific reaction stages and their intrinsic relationships with microstructural transformations are systematically investigated. The kinetic characteristics across various reactor types and experimental conditions are analyzed. The differences between fixed bed thermogravimetric analysis and fluidized bed analysis are revealed, emphasizing the notable impacts of attrition on the kinetic parameters in fluidized beds. Furthermore, the effects of temperature and gas concentration on kinetic parameters are profoundly examined. Additionally, the significant performance variation of oxygen carriers due to their interaction with ash is highlighted, and the necessity of a quantitative analysis on the competing effects of ash is emphasized, providing actionable guidelines for advancing CLC technology using kinetics-informed material design and operational parameter optimization. Full article

Background: Recent studies have highlighted the neuroprotective effects of polyphenols, particularly their role in enhancing brain-derived neurotrophic factor (BDNF) and cAMP response element-binding protein (CREB) activity. This study aimed to evaluate the relationship between BDNF and CREB levels and cognitive performance in individuals undergoing a polyphenol-rich dietary intervention. Methods: A randomized, crossover, double-blind, placebo-controlled clinical trial was conducted with 92 participants. The intervention involved the daily intake of an encapsulated concentrate of fruit, vegetable, and berry juice powders (Juice Plus+ Premium^®) over two 16-week periods, separated by a 4-week washout phase. Cognitive function was assessed using the Stroop Test, Trail Making Test, and Reynolds Intellectual Screening Test (RIST). The plasma levels of CREB and BDNF were measured using ELISA. Results: The polyphenol-rich product significantly improved cognitive performance, as evidenced by higher scores in the Stroop Test and RIST, compared to the placebo. Additionally, the plasma levels of CREB and BDNF were notably elevated in the product condition, indicating enhanced neuroprotective activity. Conclusions: The findings suggest that polyphenol-rich nutraceuticals can modulate neurobiological mechanisms underlying cognitive improvements, primarily through the reduction of oxidative stress and the regulation of signaling pathways associated with synaptic plasticity. These results support the potential of dietary polyphenols in promoting cognitive health and preventing neurodegenerative diseases. Full article

This study addresses the critical challenge of carbon corrosion in proton exchange membrane fuel cells (PEMFCs) by developing hybrid supports that combine the high surface area of carbon black (CB) with the superior crystallinity and graphitic structure of carbon nanofibers (CNFs). Two commercially available CB samples were physically activated and composited with two types of CNFs synthesized via chemical vapor deposition using different carbon sources. The structure, morphology, and crystallinity of the resulting CNF–CB hybrid supports were characterized, and the performances of these hybrid supports in mitigating carbon corrosion and enhancing the PEMFC performance was evaluated through full-cell testing in collaboration with a membrane electrode assembly (MEA) manufacturer (VinaTech, Seoul, Republic, of Korea), adhering to industry-standard fabrication and evaluation procedures. Accelerated stress tests following the US Department of Energy protocols revealed that incorporating CNFs enhanced the durability of the CB-based hybrid supports without compromising their performance. The improved performance of the MEAs with the hybrid carbon support is attributed to the ability of the CNF to act as a structural backbone, facilitate water removal, and provide abundant edge plane sites for anchoring the platinum catalyst, which promoted the oxygen reduction reaction and improved catalyst utilization. The findings of this study highlight the potential of CNF-reinforced CB supports for enhancing the durability and performance of PEMFCs. Full article

The hydrodeoxygenation (HDO) of biomass pyrolysis oil (BPO) was evaluated in the presence of two commercial alumina-supported transition metal catalysts, NiMo/alumina-1 (NM1) and NiMo/alumina-2 (NM2). The study explored two characteristic aspects: how HDO reaction conditions affected the oxygen content, density, and boiling point distribution of BPO with varying temperature and HDO reaction time, and the roles of catalysts. Characterizations of HDO-treated oils included elemental analysis, GC-MS, SIMDIS, ¹³C NMR, and ¹H NMR, and characterizations of catalysts included NH₃-TPD, XRF, and TPO-MS analysis. The results show that both NM1 and NM2 catalysts removed oxygenated compounds effectively, which led to decreases in density and shifts toward higher boiling point distributions of BPO. Compared to the NM1 catalyst, NM2 had a higher acidity and enhanced HDO activity. The best HDO reaction performance was achieved in the presence of the NM2 catalyst at 300 °C. Furthermore, HDO reactions showed a significant amount of CO₂, CH₄, C₂H₆, and C₃H₈, which suggests that HDO reactions proceeded via a series of reactions of decarboxylation, water–gas shift, and methanation. In addition, hydrocarbon fraction tests suggested a favorable potential for the blending of HDO-treated biomass pyrolysis oil (HDO-BPO) with petroleum-derived fractions. Full article

This study investigates the potential of graphite waste (GW) from the Acheson furnace as a sustainable and cost-effective anode material for lithium-ion batteries (LIBs). Conventional anode materials face challenges such as energy-intensive production processes and reliance on virgin graphite resources, leading to high costs and environmental concerns. GW from the Acheson furnace, which already possesses high carbon purity (98.5%–99.9%) and crystallinity (93.5%), offers a promising alternative by eliminating the need for graphitization and extensive purification. Through spheronization and carbon coating, GW was successfully optimized to achieve electrochemical properties comparable to commercial anode materials (CAM), including an initial Coulombic efficiency of 85.1% and a specific capacity of 348.9 mAh/g. These findings suggest that GW from the Acheson furnace represents a viable pathway toward cost-effective and environmentally friendly LIB anodes. Full article

Recently, due to the rapid increase in the demand for artificial graphite, there has been a strong need to improve the productivity of artificial graphite. In this study, we propose a new efficient process by eliminating the carbonation stage from the existing process. The conventional graphite manufacturing process usually involves a series of stages: the pulverization of needle-type coke, the granulation of pitch and coke premix, carbonation, graphitization, and surface treatment to compensate voids formed within particles. The process seems time-consuming and costly. Therefore, in our proposed shortened process, we have eliminated the carbonization stage. Instead of petroleum-derived pitch, coal tar pitch was employed. Coal tar pitch has a lower softening point than binder pitch. Apart from the cost-effectiveness of the process, it has enhanced the properties of artificial graphite by a uniform coating using a lower amount of hard carbon. In addition, the whole manufacturing time and cost was reduced by 12 h and 20% due to the skipped manufacturing step, respectively. It was observed that the artificial graphite produced by the newly proposed shortened process had improved physical properties related to the density and graphitization degree, and also showed an improvement in electrochemical performance. Raman 3D mapping and the electrochemical evaluation of artificial graphite were mainly used to compare the physical properties. This shortened process not only reduces the manufacturing cost, but also contributes to the improved performance of lithium-ion battery anode material. Full article

Detecting defects in plates is crucial across various industries due to safety risks. While ultrasonic bulk waves offer point-by-point inspections, they are time-consuming and limited in coverage. In contrast, guided waves enable the rapid inspection of larger areas. Array transducers are typically used for more efficient coverage, but conventional excitation methods require sufficient time delays between the excitation of array elements that prolong inspection time, necessitating data acquisition time optimization. Reducing time delays can lead to signal overlapping, complicating signal separation. Conventional frequency domain or time-domain filtering methods often yield unsatisfactory separation results due to the signal overlapping in both domains. This study focuses on the application of the Fractional Fourier Transform (FrFT) for separating overlapping ultrasonic signals, leveraging the FrFT’s ability to distinguish signals that overlap in both the time and frequency domains. Numerical simulations and experiments were conducted to investigate the FrFT’s separation performance for guided waves inspection with array transducers. Results showed that a smaller time delay worsened separation, while using a chirp signal with a broader bandwidth improved separation for signals of fixed duration. Additionally, the effect of signal dispersion on the results was minimal. The findings confirm that the FrFT can effectively separate overlapping signals, enhancing time efficiency in guided wave inspections using array transducers. Full article

In Wire Arc Additive Manufacturing (WAAM), solidification grain morphology in titanium alloy tends to be columnar rather than equiaxed due to heat dissipation and repeated thermal cycles. This study demonstrates improved microstructure and anisotropic properties in Ti-6Al-4V specimens fabricated by WAAM and treated with hammer peening, resulting in a transition from columnar grains to fine equiaxed grains (~300 μm) in both single-pass and four-bead WAAM walls. The anisotropic elongation decreased by approximately 7%, and tensile strength along the building direction decreased by ~50 MPa for a single-pass wall. Additionally, small and large equiaxed prior-β grains appeared alternately due to the combined effect of hammer peening and welding deposition. The region can be categorized into three parts (MAX, MED, MIN) based on the degree of plastic strain characterized by KAM mapping of EBSD data. In current WAAM parameters, the ratio of strong (~1.5 mm) deformation field (MAX) is about 50% within one deposition layer (MAX+MIN), suggesting a new approach for producing equiaxed prior-β grains. We expect that this method will be applicable for transforming the prior-β grains from columnar to equiaxed. Furthermore, the distribution of plastic strain and phase transformation mechanisms offers innovative approaches to optimize the hammer peening process, with potential applications to optimize the process for more complex components in the aerospace and power plant industries. Full article

This study examined the role of fluoroethylene carbonate (FEC) in stabilizing the solid electrolyte interphase (SEI) and enhancing the electrochemical performance of SiOx-based composite negative electrodes in lithium-ion batteries. Two electrolyte systems were used: 1.0 mol dm⁻³ (M) LiPF₆ in a mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) with 0.5 wt.% VC, and 1.0 M LiPF₆ in a mixture of EC and EMC with 1.0 wt.% VC and 10 wt.% FEC. These systems enabled the investigation of how FEC contributes to SEI stabilization and cycling stability. FEC promotes the formation of a LiF-rich SEI layer, which mitigates volume expansion and enhances capacity retention. Additionally, the accumulation of Li₂CO₃ and Li₂O in the SEI was found to increase interfacial resistance, as observed through electrochemical impedance spectroscopy (EIS). Among the SiOx contents tested (0%, 3%, and 7.8%), the 3% SiOx content exhibited the best balance between SiOx and carbon nanotubes, resulting in improved SEI formation and enhanced electrochemical performance. These results offer insights into the optimization of electrolyte formulations for long-term cycling stability in SiOx-based lithium-ion batteries. Full article

Color stability is crucial for dental materials to ensure they perfectly match a patient’s tooth color. This is particularly challenging in photoresist-based additive manufacturing. Although some studies have addressed this issue, the exact causes of discoloration and ways to minimize it remain unclear. In this study, the intrinsic causes of discoloration in materials intended for 3D printing are investigated by examining thin-film samples (1200 µm) of various compositions, which are stored under different conditions. The samples are evaluated by measuring the UV-Vis absorption spectra at regular intervals to monitor changes. The findings reveal that both the composition of the formulations and the storage conditions significantly influence the discoloration behavior. Furthermore, methods have been developed to reduce or completely prevent discoloration. The use of photoinitiators with sterically demanding benzoyl moieties, as well as the addition of stabilizers, effectively decreases the intensity of emerging discoloration. Furthermore, incorporating the oxidizing agent cumene hydroperoxide (CHP) results in materials that maintain color stability. Full article

Analysis of the heavy fractions in crude oil has been important in petroleum industries. It is well known that heavy fractions such as vacuum gas oils (VGOs) include heteroatoms, of which sulfur and nitrogen are often characterized in many cases. We conducted research regarding the molecular species analysis of VGOs. Further refine processes using VGOs are becoming important when considering carbon recycling. In this work, we attempted to classify compounds within VGOs provided by Kuwait Institute for Scientific Research. Two VGOs were priorly distillated from Kuwait Export crude and Lower Fars crude. Quantitative analysis was performed mainly using matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOFMS). MALDI-TOF-MS has been developed for analyzing high-molecular-weight compounds such as polymer and biopolymers. As matrix selection is one of the most important aspects in MALDI-TOFMS, the careful selection of a matrix was firstly evaluated, followed by analysis using a Kendrick plot with nominal mass series (z*). The objective was to evaluate if this work could provide an effective classification of VGOs compounds. The Kendrick plot is a well-known method for processing mass data. The difference in the Kendrick mass defect (KMD) between C_nH_2n−14S and C_nH_2n−20O is only 0.0005 mass units, which makes it difficult in general to distinguish these compounds. However, since the z* value showed effective differences during the classification of these compounds, qualitative analysis could be possible. The analysis using nominal mass series showed the potential to be used as an effective method in analyzing heavy fractions. Full article