Search Results (26,536)

CubeSat missions increasingly rely on microwave-band communication systems, whose antennas often exhibit directional radiation patterns. As a result, multiple antennas are commonly used to improve coverage; however, a quantitative method to evaluate their performance across all spacecraft attitudes has been lacking. This paper introduces the Coverage Ratio of CubeSat Attitude (CRCA), a metric that quantifies the proportion of orientations for which the antenna gain exceeds a required threshold. CRCA is introduced and demonstrated using the S-band command antenna system of the 6U CubeSat VERTECS. The proposed metric is then used to quantitatively compare multiple antenna placement configurations, clarifying the effect of mounting faces on attitude-dependent coverage. Electromagnetic simulations and three-dimensional radiation pattern measurements using a metal CubeSat enclosure show good agreement when splitter and cable losses are taken into account. The combined radiation pattern achieves greater than $-8.0$ dBic in 90% of attitudes in simulation, and greater than $-10.0$ dBic of attitudes in 90% in measurement. Furthermore, a CRCA-based link budget analysis demonstrates that sufficient uplink margin can be conservatively maintained under tumbling conditions. The proposed CRCA framework provides a practical and generalizable approach for evaluating antenna omnidirectionality and attitude-dependent communication performance in CubeSat missions. Full article

Vanadium dioxide (VO₂) is a highly promising material for infrared laser protection due to the pronounced optical switching effect during its metal–insulator transition (MIT). However, due to the relatively high MIT temperature of VO₂ and the low transmittance contrast before and after the MIT, practical applications face challenges in modulation depth and response time. In this study, we address these issues using a wafer-scale VO₂/GaN/Al₂O₃ heterostructure fabricated by oxide molecular beam epitaxy. The conductive GaN interlayer enables local Joule heating of the VO₂ film, permitting direct control of the MIT via an external bias with a threshold of 4.7 V. This structure exhibits a substantial resistance change of four orders of magnitude and enables adaptive limiting of a 3.7 μm laser, reducing transmittance from 60% to 10%. Our work demonstrates a practical, wafer-scale laser-protection device and introduces a pre-excitation strategy via external biasing to enhance response performance. Full article

To address the bottleneck issues of traditional ultrasonic polishing—such as unclear material removal mechanisms for ductile metals and difficulties in controlling machining outcomes—this paper employs a combined approach of computational fluid dynamics (CFD) simulation and non-contact fixed-point polishing experiments to systematically reveal the intrinsic relationship between the dynamic characteristics of the polishing flow field and the evolution of the material surface. Numerical simulations demonstrate that the cavitation effect significantly regulates the flow field structure: it not only confines the minimum pressure near the saturated vapor pressure but also markedly reduces the pressure peak while concurrently causing an overall decrease in flow velocity, forming a strongly coupled multi-parameter system of pressure, cavitation, and flow velocity. Experimental results indicate a clear spatial differentiation in the material removal mechanism: the central region is dominated by cavitation erosion, resulting in numerous pits and a 33.6% increase in residual compressive stress; the edge region is primarily governed by fluid-mechanical scraping, effectively improving surface finish and increasing residual stress by 22.3%; the transition zone, influenced by synergistic mechanisms, shows the smallest stress increase (19.7%). The enhancement of residual compressive stress can significantly improve the fatigue resistance of materials and prolong their fatigue life. This study comprehensively elucidates the multi-mechanism synergistic material removal process involving “cavitation impact, mechanical scraping, and fatigue spallation” in ultrasonic polishing, providing a key theoretical basis and process optimization direction for sub-micrometer ultra-precision machining. Full article

Sabkhas, hypersaline ecosystems along Kuwait’s coastal zone, are extreme environments that harbor diverse halophilic microorganisms with significant biotechnological potential. Despite this, they remain underexplored, particularly in the context of enzymes that can function under high salinity. The aim of this study is to identify bacterial isolates from Kuwait’s sabkhas that produce α-amylase under extreme environmental conditions and to purify and characterize the resulting halotolerant α-amylase. Among the seven α-amylase-producing isolates, Priestia sp. W243, isolated from Mina Abdullah, exhibited the highest enzyme production under optimal growth conditions of pH 9.0, 37 °C, and 7.5% NaCl. A novel halotolerant α-amylase with a remarkably high specific activity (8112.1 U/mg) was purified from this isolate using ultrafiltration, ion-exchange chromatography, and gel-filtration. The purified enzyme, with a molecular weight of 25 kDa, showed optimal activity at 40 °C, pH 8, and 3% NaCl. Notably, the enzyme remained active in the absence of salt and up to 15% NaCl, demonstrating exceptional halotolerance. Metal ion profiling revealed that enzyme activity was significantly enhanced by Co²⁺, whereas Ca²⁺ had a comparatively moderate effect on enzyme activity. When the effects of metal chelators were examined, EDTA, a strong metal chelator, inhibited the enzyme. However, the enzyme remained active when Ca²⁺ was specifically removed using EGTA, suggesting that this α-amylase may be a cobalt-dependent metalloenzyme, which is an unusual characteristic among known α-amylases. Additionally, the enzyme retained its catalytic activity under reducing conditions (e.g., in the presence of DTT and β-mercaptoethanol), indicating structural stability is independent of disulfide bonds. These unique properties distinguish this α-amylase from typical salt- or calcium-dependent counterparts and highlight its potential for industrial applications in high-salt food processing, baking, brewing, and environmental remediation. Full article

In this study, novel Mo-decorated core–shell zeolite composites, namely ZSM-5@SAPO-34 and SAPO-34@ZSM-5, were synthesized and evaluated as catalysts for methane dehydroaromatization (MDA). Core–shell structures were effectively fabricated via sequential hydrothermal synthesis, utilizing SAPO-34 and ZSM-5 as cores, which were subsequently subjected to hydrothermal growth in ZSM-5 and SAPO-34 reacting solution, respectively. Catalysts with varying SAPO-34/ZSM-5 mass ratios and Mo loadings were thoroughly characterized by the XRD, BET, SEM-EDS, and NH₃-TPD techniques. The catalytic performance in the MDA reaction revealed a strong correlation between composite architecture, acidity, Mo dispersion, and product selectivity. Introducing H⁺SAPO-34 into both core–shell composites enhanced ethylene-to-benzene conversion due to the acidic confinement provided by SAPO-34. In contrast, non-protonated SAPO-34@ZSM-5 showed limited activity as a result of its weak acidity and inadequate Mo dispersion. Among all catalysts, H⁺ZSM-5@SAPO-34 with a 3:1 core–shell mass ratio delivered the highest benzene yield and stability, outperforming the benchmark, H⁺ZSM-5. This work highlights the potential of tailored core–shell zeolite composites in optimizing acid–metal interactions and improving catalytic performance in hydrocarbon transformations. Full article

Background: Gum Arabic (GA) is a natural polysaccharide widely recognized for its antioxidant and anti-inflammatory properties; however, its functional behavior as a biopolymeric gel and the mechanisms underlying its selective effects on cancer-related redox microenvironments remain insufficiently characterized. It is imperative to note that the interaction between its physicochemical properties and its biological activity in colorectal cancer remains to be fully clarified. Methods: This study aimed to evaluate the antineoplastic potential of GA in human colorectal cancer (CRC) cell lines (HT-29 and HCT-116) compared to normal fibroblasts (MRC-5) using the MTS assay. Oxidative stress-related molecular responses were assessed by quantitative PCR analysis of GPX4, GSTA2, CAT, NFKB, and SOD1 expression. In parallel, extracellular concentrations of key metal ions (Fe²⁺, Zn²⁺, Mn²⁺, Mg²⁺, Cu²⁺, and Al³⁺) were quantified following GA exposure. To establish its functional gel characteristics, rheological measurements were performed to assess viscosity and shear-dependent behavior, and USP-compliant in vitro kinetic studies were conducted to evaluate time-dependent release properties. Results: GA induced dose-dependent cytotoxicity in HT-29 and HCT-116 colorectal cancer cells, while MRC-5 fibroblasts exhibited comparatively higher viability across the tested concentration range, indicating reduced sensitivity in normal cells. Rheological analysis revealed concentration- and ion-dependent viscoelastic behavior, identifying a 10% (w/w) GA formulation as optimal due to its balanced low-shear viscosity and controlled shear-thinning properties. Kinetic studies demonstrated a defined, diffusion-governed release profile under physiologically relevant conditions. At the molecular level, significant upregulation of GPX4 and GSTA2 was observed in both cancer cell lines, whereas NFKB expression increased selectively in HT-29 cells, with no notable changes in CAT or SOD1 expression. Additionally, GA treatment resulted in marked increases in Fe²⁺, Zn²⁺, and Mn²⁺ levels, indicating modulation of the redox–ionic microenvironment. Conclusions: These findings demonstrate that GA functions as a natural, ion-responsive biopolymeric system with defined rheological and kinetic properties, capable of selectively targeting colorectal cancer cells through coordinated genetic and ionic regulation of oxidative stress. Collectively, the results position GA as a promising functional gel-based platform for future redox-modulated therapeutic strategies in colorectal cancer. Full article

Oxidative stress seems to be part of many deranged processes in the organism, affecting multiple degenerative conditions at a cellular and tissue level. Coumarins and flavonoids comprise two main categories of naturally derived compounds with multiple effects and applications. Our aim in this paper is the design of compounds with increased antioxidant activity with the conjugation of two moieties with highly antioxidant potency in the frame of one molecule. A series of novel derivatives, comprising fusion of 7-hydroxycoumarin (Umbelliferone) and Quercetin (flavonol) have been synthesized using classical organic chemistry methods. Additionally, one novel flavone derivative was prepared for comparison. The novel compounds were tested for their radical, reactive oxygen and nitrogen species (ROS and RNS) scavenging, their reductive activity, and their labile metal chelating potency, as well as with in silico tools. All of them were more active, in most cases, than reference molecules Trolox and vitamin C. The most active compound 2 reached IC₅₀ of 4.03 and 43.75 μM for ABTS and DPPH, respectively (up to three times lower than that of Trolox). Compound 1 was of equal to vitamin C activity in H₂O₂ scavenging, whilst compound 3 was up to 6.4 times more active than Trolox in NO scavenging. Since our designed compounds seem to exhibit high antioxidant potential, scavenging reactive nitrogen and oxygen species, which are accumulated and promote the progression of inflammatory conditions, and have reductive and metal chelating abilities, they can be considered as potential candidates for protection in cases of oxidative stress derived toxicity. Full article

The field of developing effective catalysts for heterogeneous catalysis has recently focused on controlling the structures of catalysts themselves to optimise the density and energy of crystal lattice defects. This can significantly influence catalytic activity in terms of both reaction rates and reaction mechanisms, and thus the selective production of desired substances as well. In many cases, these crystal lattice defects manifest themselves as so-called electron traps (ETs) and thus significantly influence charge transfer between the catalyst and reactants. ETs provide the missing electronic link between atomic-scale defects and macroscopic performance in heterogeneous catalysis. Therefore, the importance of ETs for catalysis is particularly evident in areas where charge transfer plays a fundamental role in the reaction mechanism, such as photocatalysis and electrocatalysis. In the field of thermally initiated reactions, the importance of ETs in heterogeneous catalysis has not yet been fully appreciated. However, several studies have already addressed the importance of ETs for this type of reaction. This review consolidates and extends the concept of ETs to purely thermal-initiated reactions, with a focus on CO₂ hydrogenation using typical transition metal catalysts. Firstly, in this review, ETs are defined as band gap states associated with internal and external defects, and their depth, density, spatial location, and dynamics are then coupled with key steps in thermocatalytic cycles, including charge storage/release, reactant activation, intermediate stabilisation, and redox turnover. Secondly, electron trap detection is reviewed based on advanced spectroscopic techniques, including reversed double-beam photoacoustic spectroscopy (RDB-PAS), thermally stimulated current (TSC), deep-level transient spectroscopy (DLTS), thermoluminescence (TL), electron paramagnetic resonance (EPR), and photoluminescence (PL), highlighting how each method describes trap energetics and populations under realistic operating conditions. Finally, case studies on the application of metal oxides and supported metals are discussed, as these are typical catalysts for the reaction mentioned above. This review highlights how oxygen vacancies (OVs), polarons, and metal–support interfacial sites act as robust electron reservoirs, lowering the barriers for CO₂ activation and hydrogenation. By reframing thermocatalysts through the lens of ET chemistry, this review identifies ETs as actionable targets for the rational design of next-generation materials for CO₂ hydrogenation and related high-temperature transformations. Full article

Negative refraction of nanolight (e.g., polaritons, hybrid light, and matter excitation) provides a promising building block for nanophotonics, as it paves the way for developing cutting-edge nanoscale applications, such as super-resolution and subwavelength imaging. In the visible regime, negative refraction of surface plasmon polaritons has been extensively studied in conventional plasmonic and metamaterial systems; however, the inherent metallic losses remain a challenge that hinders their practical applications. Herein, we demonstrate negative refraction of low-loss and highly confined hyperbolic plasmon polaritons (HPPs) in a lateral heterojunction of a natural hyperbolic van der Waals material, molybdenum dioxide chloride (MoOCl₂). Owing to the exotic and ray-like propagating properties of HPPs, the negative refraction-inspired superlens can easily reach into the deep subwavelength scale, with spatial confinement of 800 nm near-infrared light wavelengths to below 150 nm focal spots. By elaborately adjusting the orientation directions of two-sided MoOCl₂, the mirror-symmetric superlensing effect can be tilted, and therefore, the focal spots are tuned and steered to deviate from the vertical interfacial lines. Our results applying the concepts of in-plane negative refraction with vdW materials achieve deep subwavelength light confinement and manipulation, offering new possibilities for constructing efficient and compact nanophotonic and opto-electronic devices. Full article

Per- and polyfluoroalkyl substances (PFASs) are persistent and mobile contaminants of global concern, and, while granular activated carbon (GAC) is widely used for their removal, it is limited by the high regeneration and disposal costs. This study investigates surface-modified clinoptilolite zeolites as low-cost and thermally regenerable alternatives to GAC for PFAS removal from water. Natural clinoptilolite was modified through acid washing, ion exchange with Fe³⁺ or La³⁺, grafting with aminosilane (APTES) or hydrophobic silane (DTMS), dual APTES + DTMS grafting, and graphene oxide coating. The adsorption performance was evaluated for perfluorooctanoic acid (PFOA, C8) and perfluorobutanoic acid (PFBA, C4) at 100 µg L⁻¹ in single- and mixed-solute systems, with an additional high-concentration PFOA test (1 mg L⁻¹). PFAS concentrations were quantified by liquid chromatography–tandem mass spectrometry (LC–MS/MS) using a SCIEX 7500 QTRAP system coupled to a Waters ACQUITY UPLC I-Class. Raw zeolite showed limited PFOA removal (4%), whereas dual-functionalized APTES + DTMS zeolites achieved up to 93% removal, comparable to GAC (97%) and superior to single-silane or metal-exchanged variants. At lower concentrations, modified zeolites effectively removed PFOA but showed limited PFBA removal (<25%), highlighting ongoing challenges for short-chain PFASs. Overall, the results demonstrate that dual-functionalized clinoptilolite zeolites represent a promising and scalable platform for PFAS remediation, particularly for mid- to long-chain compounds, provided that strategies for enhancing short-chain PFAS binding are further developed. Full article

This study explores a sustainable synthesis route for FAU-type zeolite X using acid-treated ladle slag as a silicon source and waste aluminum cans as an alternative aluminum precursor. Conventional zeolite synthesis relies on high-purity reagents, which are costly and environmentally intensive to produce. Previous research has rarely addressed the valorization of ladle slag and metallic aluminum waste for zeolite formation, leaving their potential largely unexplored. The study focuses on the effective utilization of industrial and post-consumer wastes—acid-treated ladle slag and aluminum cans—as precursors for FAU-type NaX zeolite, demonstrating their feasibility as alternative silicon and aluminum sources. Here, zeolite X was synthesized hydrothermally from treated slag combined with either dissolved aluminum cans and commercial sodium aluminate at 90 °C for 6 h. FAU-type zeolite X was successfully synthesized using both aluminum sources, with a SiO₂/Al₂O₃ ratio of approximately 1.4. The results demonstrate that waste-derived precursors can effectively replace conventional chemicals, yielding predominantly NaX zeolite with high crystallinity and minor NaA impurity (as observed by XRD), with experimental yields of 1.47 g for aluminum cans and 1.266 g for sodium aluminate. The obtained zeolite X samples were structurally and texturally characterized by XRD, FTIR, XRF, BET surface area analysis, and thermogravimetric analysis (TG). Full article

Phosphogypsum, the primary solid waste from the wet-process phosphoric acid industry, poses significant environmental and health risks due to large-scale stockpiling. To promote its resource utilisation, this study systematically evaluated the solidification and stabilisation performance of phosphogypsum–coal fly ash cementitious material (PAC) for Cr(VI)-contaminated soil under high-chloride conditions. Phosphogypsum reactivity was enhanced via mechanical activation and high-temperature calcination. An orthogonal experimental design was employed to analyse the effects of multiple factors—including calcination temperature and duration—on compressive strength and heavy metal leaching behaviour. Results show that PAC prepared from coal ash calcined at 600 °C for 3 h exhibits excellent mechanical properties and Cr(VI) stabilisation efficacy under high-chloride conditions, achieving a maximum compressive strength of 28.75 MPa and a Cr(VI) leaching concentration as low as 15.69 μg/L. Microstructural characterisation revealed the synergistic formation of a dense framework between C–S–H gel and calcium aluminate, conferring superior mechanical strength. Substitution and chelation mechanisms of Cl⁻ ions played a key role in enhancing corrosion resistance. This study provides theoretical support and technical guidance for the high-value utilisation of phosphogypsum-based materials in remediating saline–alkali-contaminated soils. Full article

Nanocellulose, a biodegradable and renewable nanomaterial derived from biomass, has emerged as a promising sustainable building block for flexible functional devices due to its renewability, low density, excellent mechanical strength, tunable surface chemistry, and outstanding film-forming capability. This paper provides a critical review of the evaluations and synthesis of recent progress in the manufacturing, functionalization, and incorporation of nanocellulose and its composite materials for electronic devices and electrical systems applications. The paper also highlights the contributions of nanocellulose to performance, durability, and environmental sustainability, along with its potential uses in flexible electrical equipment, energy storage devices, sensors, and conductive components. Furthermore, the review examines the combined effects of nanocellulose with metallic nanoparticles, carbon-based materials, and polymers in developing superior electrically conductive composites. In addition, the article highlights research gaps and suggests future directions for advancing sustainable, high-performance conductive materials. Finally, the paper critically analyzes key challenges such as reliability, interface compatibility, and long-term stability, and proposes strategies to address these limitations. Full article

Wire Arc Additive Manufacturing (WAAM) is a cost-effective method for fabricating large aluminum components; however, it tends to suffer from heat accumulation and coarse anisotropic microstructures, which can limit the part’s performance. In this study, a wall is fabricated using a hybrid unified additive deformation manufacturing process (UAMFSP) method, which integrates friction stir processing (FSP) into WAAM, and is compared with a Metal Inert Gas (MIG)-based WAAM wall. Infrared (IR) thermography revealed progressive heat buildup in MIG walls, with peak layer temperatures of about 870 to 1000 °C. In contrast, in the UAMFSP process, heat was redistributed through mechanical stirring, maintaining more uniform sub-solidus profiles below approximately 400 °C. Also, optical microscopy and quantitative image analysis showed that MIG walls developed coarse, dendritic grains with a mean grain area of about 314 µm², whereas the UAMFSP produced refined, equiaxed grains with a mean grain area of about 10.9 µm². Microhardness measurement (Vickers HV0.2, 200 gf) confirmed that the UAMFSP process can improve the hardness by 45.8% compared to the MIG process (75.8 ± 7.7 HV vs. 52.0 ± 1.3 HV; p = 0.0027). In summary, the outcomes of this study introduce the UAMFSP process as a method for addressing the thermal and microstructural limitations of WAAM. These findings provide a framework for further extending hybrid additive–deformation strategies to thicker builds, alternative alloys, and service-relevant mechanical evaluations. Full article

Successful establishment of resource-efficient perennial crops that can thrive and produce economically viable yields under metal stress conditions requires a clear understanding of macronutrient uptake and metal detoxification regulation mechanisms particularly during crop establishment period. Therefore, this study aimed to evaluate the partitioning of macronutrients and metals in miscanthus and switchgrass grown on metal-contaminated soils, and to evaluate the effect of biostimulant treatments on early crop establishment and biomass productivity. Field trials were conducted with two perennial C₄ grasses, miscanthus (Miscanthus lutarioriparius) and switchgrass (Panicum virgatum L.), under three treatments: control (CK), humic acid (HA), and humic acid combined with microbial inoculants (HAM). At final growth stages, agronomic traits, biomass quality, and macronutrient (N, P, K) and metal (Cd, Cr, Pb, Cu, Zn) contents were analyzed. To investigate metal and macronutrient partitioning dynamics, samples were collected from October to December. The HAM treatment significantly enhanced biomass yield and morphological parameters in both species, particularly in miscanthus. Both HA and HAM improved cellulose and hemicellulose while reducing the lignin content, thereby improving biomass quality. For both crops, roots served as the primary organ for metal accumulation across growth stages. In miscanthus roots from October to December, the proportions of Cd, Cr, and Pb increased (10.5%, 10.8%, 13.6%), while Zn and Cu decreased (6.5%, 11.6%). Over the same period, Pb increased slightly (4.4%), but Cd, Cr, and Cu declined (26%, 1.9%, 12.9%) in switchgrass roots. Coupling and principal component analyses revealed weak macronutrient–metal synchronization in both miscanthus and switchgrass across growth stages. Full article