Search Results (17,908)

In fundamental physics, sensors operating below liquid helium temperatures are highly vulnerable to vibrations, which can affect the sensitivity, for example, of high-performance particle detectors. Pulse-tube refrigerators, while generating vibrations lower than those of conventional systems, may still introduce several disturbances. Hence, flexible thermal connections are a commonly used mechanical solution to mitigate these undesirable effects. Among the materials that can be used, ultra-high-purity aluminum (UHP-Al) has attracted the attention for low-amplitude-vibration cryogenic applications, including gravitational wave interferometry, quantum information systems, precision space instrumentation, and cryogenic resonators. Thus, the aim of the paper is the characterization of the mechanical and microstructure properties of three UHP-Als (i.e., 5N—99.999 wt%, 5N5—99.9995 wt% and 6N—99.9999 wt%) intended for the production of thermal flexible connections with low stiffness, specifically designed to reduce vibration transmission in cryogenic environments. Mechanical properties were evaluated through standard tensile tests from room (+25 °C) to low temperature (i.e., −150 °C), providing insights into yield strength, ultimate tensile strength, elongation and elastic modulus. In addition, the dynamic elastic modulus of material loads, at cryogenic conditions (i.e., about −180 °C), was determined by measuring the natural resonance frequency, thereby assessing the material’s response to vibrational. Moreover, an extensive microstructural analysis was conducted using electron backscatter diffraction and x-ray diffraction. The correlation between the observed microstructure and the elastic properties was systematically examined. The results underscore the pivotal role of microstructural characteristics in dictating the elastic behavior of UHP Als. Eventually, the analysis provides valuable guidelines for the materials employment inside cryogenic systems, where severe vibration control is critical to maintain high operational performance. Full article

The chemical and mineral composition, physical and mechanical properties, and pozzolanic activity of ancient bricks from Hubei Province, China were investigated in this study. X-ray diffraction (XRD), thermogravimetric analysis (TG-DSC), X-ray fluorescence analysis (XRF) and scanning electron microscopy–energy dispersive spectroscopy (SEM-EDS) were adopted to characterize the chemical composition, crystalline minerals and microstructure of the ancient bricks. The results show that quartz is the dominant component in most ancient bricks, with a content exceeding 70% in samples BB-2, BB-5, BB-6 and BB-7. Some bricks contain minor non-clay minerals such as calcite, dolomite and albite. On some points in the SEM image, substances such as gypsum, calcite, and quartz can be clearly seen. The calcining temperature of the ancient bricks from Yupan Village, Xiantao City (sample BB-1), does not exceed 600 °C, while that of other samples ranges from 800 to 1100 °C. The compressive strength of most ancient bricks is around 10 MPa, with the highest value of 14.3 MPa (BB-6) and the lowest of 1.2 MPa (BB-3). The apparent density of all samples is approximately 2.2 g/cm³, and the water absorption rate ranges from 6.5% to 23.1%. The pozzolanic activity index of some samples reaches 76% at 28 days, with the 150-year-old sample BB-7 showing the best activity. This study provides a reliable experimental basis for analyzing the weathering resistance and deterioration mechanism of ancient bricks in Hubei Province, offers technical support for the restoration of local ancient buildings, and lays a foundation for the development of antique-style brick craftsmanship. Full article

Background: Qualitative motion analysis revealed that the cervical spine moves according to a consistent pattern. Current data analysis methods are limited by the extensive time required to process the retrieved data. A previous study demonstrated the feasibility of using a deep-learning model to automate analysis methods. However, segmentation accuracy needed to be improved. This study aims to improve segmentation model performance to enable reliable motion analysis. Methods: Four nnU-Net configurations were tested: baseline (A), pre-trained (B), with histogram equalization (C), and pre-trained with histogram equalization (D). Segmentation performance was evaluated using Dice Similarity Coefficient (DSC), Intersection over Union (IoU) and 95th percentile Hausdorff Distance (HD95). Vertebral rotation was estimated using mean shapes. Reliability was assessed using the Intraclass Correlation Coefficient (ICC). Sensitivity analyses were conducted. Results: Across all models, mean DSC ranged from 0.67 to 0.92, mean IoU from 0.55 to 0.85, and mean HD95 from 2.35 to 19.67 mm. After sensitivity analysis for low segmental range of motion (sROM) and low-quality recordings, the mean ICC ranged from 0.617 to 0.837 for model A, from 0.609 to 0.780 for model B, from 0.409 to 0.689 for model C, and from 0.480 to 0.835 for model D. Conclusions: This study shows that Models A and B can accurately analyze cervical motion patterns. High image contrast and an adequate sROM are essential for robust model performance. It also marks an important step toward automated qualitative motion analysis, increasing the accessibility of motion pattern evaluation. Full article

The urgent need to mitigate carbon dioxide (CO₂) emissions from fossil-fuel-based electricity generation has driven research into advanced materials for post-combustion carbon capture. This paper presents a modified solvothermal technique to synthesize zinc (Zn) and magnesium (Mg) based MOF-74 suitable for CO₂ capture from coal-fired power plants. The materials were synthesized through a solvothermal method using N,N-dimethylformamide (DMF) as the primary solvent, and subsequently characterized using Brunauer–Emmett–Teller (BET) surface area analysis, Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX), and thermogravimetric analysis (TGA). Both MOFs contained oxygen-containing functional groups and were thermally stable up to 430 °C and 600 °C respectively, making them ideal for carbon capture. The low-pressure N₂-BET surface areas were 55 m²/g and 24.73 m²/g. In conclusion, the Zn material had a mesoporous structure, making it more favorable for carbon capture. It was found that prolonged synthesis time weakened the MOF structure. Future work should experimentally evaluate CO₂ capture from coal-derived flue gas using Zn/Mg-MOF-74 materials, investigating adsorption behavior and kinetics through isotherm and kinetic models, while also assessing the effect of varying Zn: Mg ratios under optimized synthesis conditions. Full article

We report the synthesis, spectroscopic characterization, and single-crystal X-ray structures of 5-methyl-3-phenylbenzo[e][1,2,4]triazine (I) and its precursor N′-(3-methyl-2-nitrophenyl)benzohydrazide (IV). Compound IV was obtained by nucleophilic aromatic substitution of 1-fluoro-3-methyl-2-nitrobenzene with benzohydrazide and was converted to I through a reductive cyclodehydration/oxidative aromatization sequence. The present study provides a concise route to the 5-methyl regioisomer together with full structural characterization and examines how methyl substitution at the 5-position influences molecular geometry and crystal packing relative to the previously reported 6- and 8-methyl analogs. X-ray analysis shows that IV adopts a conjugated hydrazide framework with a twisted N–N linkage and an out-of-plane nitro group. In the crystal, it forms one-dimensional N–H⋯O hydrogen-bonded chains further assembled by weaker intermolecular contacts. By contrast, I displays an essentially planar benzo[e][1,2,4]triazine core with an almost coplanar phenyl substituent and packs into slipped π-stacked columns reinforced by secondary C–H⋯N contacts. Comparison with the previously reported methyl regioisomers shows that relocation of the methyl group to the 5-position has little effect on the intrinsic molecular geometry of the benzo[e][1,2,4]triazine scaffold, while subtly modulating the stacking arrangement and secondary packing interactions in the solid state. These results further define the role of methyl-substituent position in shaping the supramolecular organization of 3-phenylbenzo[e][1,2,4]triazines. Full article

This study investigates the hydrophobic properties of hexamethyldisiloxane (HMDSO)-based coatings deposited by atmospheric pressure plasma-enhanced chemical vapor deposition (AP-PECVD). The objective of this procedure is to enable the extraction of molded components from the mold cavity. The test specimen geometry employed in the present investigation were made of tool steel 1.2311, a material that is frequently utilized in industrial applications. A series of experiments was conducted to assess the coating performance. Initially, surface energy measurements based on contact angle analysis were performed to determine the polar and dispersive surface components. Finally, energy-dispersive X-ray spectroscopy (EDX) and scanning electron microscope (SEM) images are used to perform an exact measurement of the elemental composition and an optical comparison of the surface. The results of the work indicate that the material composition on the surface of silicon and oxygen is of particular importance. In addition, the results indicate that the use of argon as a carrier gas has a positive effect on reducing surface energy and increasing the contact angle to water drops. Full article

This research aims to investigate the modifications of the structural, dielectric, and sensing properties of CaFeO_3−δ ceramics produced by solid-state reaction induced by varying sintering temperatures in the range of 1000–1200 °C. A single crystallographic orthorhombic (Pcmn) structure was revealed by X-ray diffraction with Rietveld analysis, both for the powders and sintered ceramics, irrespective of the sintering temperature. The increase in the sintering temperature induces better densification and a larger grain size. Dielectric measurements reveal a pronounced enhancement of the relative permittivity, reaching 2 × 10⁵ at 1 kHz and 330 °C for the sample sintered at 1200 °C/4 h. This composition also displays the highest electrical conductivity, 0.4 S/m at 1 MHz. Cole–Cole analysis indicates a clear deviation from ideal Debye behavior, while the relaxational features of the dielectric permittivity suggest a strong correlation between the dielectric response and Fe-related conduction mechanisms. Gas sensing tests show that the ferrite ceramics exhibit consistent ethanol response trends. The ceramic sintered at 1200 °C/4 h achieved the highest sensitivity, of 56.28%, which can be attributed to its higher density, larger ceramic grains, and reduced low-frequency conductivity. The CaFeO_3−δ ceramic sintered at 1200 °C/4 h shows a combination of high permittivity, enhanced conductivity, and strong ethanol sensitivity, making it a promising material for dielectric components, capacitive devices, and gas sensing applications. Full article

Permeability is affected by nanopores and pore structure, and anisotropic permeability is the result of shale lamination, orientation, and stratification of minerals. To understand the reasons for permeability anisotropy, the pore networks of over-mature shale has been studied. The mineral compositions, petrophysical properties, and pore structures of the Lower Cambrian Niutitang Formation shales were analyzed using subcritical gas adsorption, field-emission scanning electron microscopic, and X-ray micro-computed tomographic methods. Quartz, clay minerals, and carbonate are the dominant minerals in the shales. The bedding-parallel and bedding-perpendicular permeabilities are 1.25–46.21 × 10⁻² and 1.38–6.62 × 10⁻² mD, respectively. The anisotropy of permeability, which is the ratio between the bedding-parallel and bedding-perpendicular permeability, is 0.21–26.87. The micropore and Barrett–Joyner–Halenda pore volumes are 0.54–3.62 and 0.05–0.69 mL/100 g, respectively. The bedding-parallel permeability is correlated positively with the micropore and Barrett–Joyner–Halenda pore volumes. Thin-section observations indicate the shales exhibit a bedding-parallel alignment of phyllosilicate minerals and planar deformation bands. The scanning electron microscopy shows deformation of the lamination and parallel alignment of the clay minerals due to compaction or differential compaction over coarser-grained quartz grains. The scanning electron microscopy images and subcritical gas adsorption data indicate that the pore fracture system is parallel to bedding and formed after diagenesis. Furthermore, X-ray micro-computed tomographic analysis shows that the micro-fractures are also preferentially oriented, parallel to bedding. Full article

This study examines the carbonation behavior and CO₂ storage potential of a Ca-rich alkali-activated binder produced entirely from industrial residues-ladle furnace slag (LFS), coal ash (CA), and cement kiln dust (CKD). The system was designed as a one-part alkali-activated material (AAM), with CKD acting as an internal activator, and subjected to ambient curing, water curing, and accelerated CO₂ curing at ambient pressure. Phase evolution, microstructural development, and pore-structure characteristics were investigated using X-ray diffraction, FTIR spectroscopy, DSC–TG analysis, scanning electron microscopy, and X-ray micro-computed tomography, together with measurements of density, water absorption, and compressive strength. Loss-on-ignition measurements combined with chemical analysis were further used to quantify CO₂ uptake and evaluate the degree of carbonation of the binder system. CO₂ curing fundamentally altered the reaction pathway of the binder, shifting it from hydration-dominated to carbonation-controlled phase evolution, leading to the decomposition of calcium-bearing hydrates and complete carbonation of non-hydraulic γ-belite with the formation of vaterite, aragonite, and calcite. These transformations induced pronounced microstructural densification, reflected in a near-doubling of compressive strength (>48 MPa), increased apparent density, reduced water absorption, and simplified pore-network topology. A preliminary carbon footprint assessment indicates that the production of 1 m³ of the developed LFS–CA–CKD concrete generates about 14.36 kg CO₂-eq, while the carbonation process enables significant CO₂ sequestration, resulting in a net negative carbon balance. The results demonstrate that controlled carbonation is an effective post-treatment strategy for waste-derived alkali-activated binders, enabling simultaneous performance enhancement and permanent CO₂ sequestration. Full article

Carnosine (or β-alanyl-L-histidine) is an endogenous compound playing very important roles in human organisms as antiglycation and antioxidant agents, and, in addition, helping to mitigate illnesses such as cancer and neurodegenerative diseases. Aiming to explore the chelating ability of carnosine, based on its coordinating possibilities, we started to investigate the metal complexes of essential copper(II), zinc(II), and iron(II) ions coordinated to this dipeptide. Different compounds were isolated in the solid state by adding stoichiometric amounts of metal salts to carnosine at controlled pH or under a controlled atmosphere, with the formation of mono-, bi- and polynuclear species. These complexes were subsequently characterized mainly by spectroscopic techniques (UV–Vis, IR, EPR), in addition to elemental analysis. A binuclear species was isolated with copper(II) and had its structure determined by X-ray diffraction, improving previously reported data in the literature. Two insoluble correlated trinuclear species were isolated with zinc(II) ions, using perchlorate or chloride as counter-ions. In the case of iron, a mononuclear species was verified with Fe(II) ions, obtained under an inert atmosphere. Further, the antioxidant properties of free carnosine and the copper–carnosine complex were verified by their scavenging activity toward the ABTS^•+ radical, using Trolox as a reference, showing significant activity. The carnosine–metal complexes were also tested as potential antineoplastic agents, in comparison to the free ligand, after 24 h of incubation at 37 °C, using malignant HeLa, SKMEL 28 and SKMEL 147, and non-tumor fibroblast cells. Results indicated neglected or poor anti-proliferative properties of these metal complexes, when compared to other similar compounds described in the literature. Full article

A Cu-containing FeCrMnNiAl multi-principal element alloy was processed by laser-based and electron beam-based powder bed fusion (PBF-LB/M and PBF-EB/M) to investigate processing–microstructure–property relationships. In focus were alloy variants with a relatively high Cu content. Two PBF-LB/M scan strategies, employing a Gaussian beam with and without a re-scan with a laser featuring a flat-top profile, were compared to PBF-EB/M processing, followed by heat-treatments between 300 °C and 1000 °C. The phase constitution, elemental partitioning and grain boundary characteristics were analyzed by X-ray diffraction, electron backscatter diffraction and energy-dispersive X-ray spectroscopy. Mechanical behavior was assessed by hardness and tensile testing. Both manufacturing routes promoted the evolution of stable multi-phase microstructures composed of face-centered-cubic (FCC)- and body-centered-cubic (BCC)-type phases across all heat-treatment conditions. PBF-LB/M processing resulted in finer, dendritic microstructures and suppressed formation of a Cu-rich FCC phase due to higher cooling rates, whereas PBF-EB/M promoted the evolution of Cu-rich FCC segregates and equiaxed grain morphologies. Heat-treatment above 700 °C led to recrystallization, accompanied by an increase of the FCC phase fraction, grain coarsening, and recovery. At lower heat-treatment temperatures, the changes in microstructure are different. Here, it is assumed that small, non-clustered Cu-rich precipitates formed at the grain and sub-grain boundaries, although this assumption is only based on the assessment of the mechanical properties. The size of these precipitates is below the resolution limit of the techniques applied for analysis in the present work. Additional structures seen within the Cu-rich areas of PBF-EB/M-manufactured samples treated at lower temperatures also seem to have an influence on the hardness and yield strength. All of the conditions investigated exhibited pronounced brittleness, limiting reliable tensile property evaluation and indicating the need for further optimization of processing strategies and microstructural control for high-Cu-fraction-containing multi-principal element alloys. Full article

Serial femtosecond crystallography (SFX) using X-ray free electron lasers (XFELs) enables the determination of room-temperature structures of biological macromolecules without radiation damage. The accuracy of detector geometry parameters, including the crystal-to-detector distance (CTDD), is critical for reliable data processing. In SFX experiments, the CTDD may shift during data collection due to changes in the experimental setup or installation of the sample delivery system. Such CTDD variations can affect the quality of SFX datasets; however, their impact has not been fully elucidated in the context of SFX data processing. In this study, we investigated the influence of CTDD variations on SFX datasets collected at Pohang Accelerator Laboratory X-ray Free Electron Laser (PAL-XFEL) with thermolysin, lysozyme, and glucose isomerase crystals processed by four indexing algorithms. At the optimized CTDD, the distribution of unit cell parameters exhibited a Gaussian pattern; however, it became distorted as the CTDD deviated further from the optimal value. Data analysis indicated that the CTDD tolerance for successful data processing and structure determination was approximately ±3–5 mm from the optimized CTDD. These findings provide insight into indexing behavior in SFX data processing at PAL-XFEL and offer practical guidance for improving data processing efficiency. Full article

Blended nanocomposite solid polymer electrolytes are gaining considerable attention as next-generation materials for use in flexible lithium-ion battery systems. These materials help ensure a more uniform distribution of lithium ions at the electrode–electrolyte interface, contributing to the development of a stable interfacial layer that mitigates lithium dendrite formation. In this study, solid polymer electrolytes were synthesized using a binary polymer matrix composed of polyethylene oxide (PEO) and polymethyl methacrylate (PMMA), with lithium iodide (LiI) as the ionic salt. Zirconium dioxide (ZrO₂) nanoparticles were introduced as nanofillers in varying concentrations to investigate their influence on the physical and functional characteristics of the polymer matrix. Characterization was carried out using Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), and X-ray Diffraction (XRD). SEM images indicated that ZrO₂ nanoparticles remained well-dispersed up to 3 wt%, while higher loadings showed slight agglomeration. FTIR analysis revealed noticeable changes in absorption bands, suggesting strong interactions among polymer chains and the nanofillers. XRD data confirmed the semi-crystalline behavior of the PEO/PMMA blend system. The inclusion of ZrO₂ nanofillers enhanced the structural integrity and ionic conductivity of the polymer matrix, making them promising candidates for applications in electrochemical energy storage and advanced material interfaces. The systematic incorporation of ZrO₂ nanofillers into the PEO/PMMA matrix significantly improved the microstructural uniformity, polymer–filler interactions, and ionic transport behavior of the solid polymer electrolytes. Full article

The study investigates the catalytic activity of vanadium-containing catalysts in the selective oxidation of 4-methylpyridine (4-MP) in the gas phase. V-Cr, V-Ti, and V-Ti-Cr catalysts were synthesised and studied. The phase composition and structural features of the catalysts were determined by X-ray diffraction (XRD) and Raman spectroscopy, and their thermal stability was investigated using thermogravimetric analysis (TGA/DTA). Textural characteristics were evaluated by low-temperature nitrogen adsorption–desorption (BET, BJH), surface morphology was studied using scanning electron microscopy (SEM), and the distribution of elements was investigated using energy-dispersive X-ray spectroscopy (EDX). The chemical composition of the catalysts was determined using inductively coupled plasma atomic emission spectrometry (ICP-OES) and catalytic activity was evaluated in the selective gas-phase oxidation reaction of 4-methylpyridine in the temperature range 280–380 °C. It was found that an increase in temperature is accompanied by an increase in the conversion of 4-methylpyridine, but at the same time, deep oxidation reactions intensify. The best result is achieved on the V-Ti-Cr catalyst, for which the conversion of 4-MP reaches 86.88% and the selectivity is 73.06% at 320 °C. However, V-Ti provides moderate stable performance, while V-Cr demonstrates relatively low efficiency. Thus, it can be concluded that the nature of the temperature dependence of 4-methylpyridine conversion reflects the different nature of the active centres and their stability. Full article

Glasses with compositions (52.5 − x/2)B₂O₃:(12.5 − x/2)SiO₂:25La₂O₃:5ZnO:5CaO:0.5Eu₂O₃:xWO₃, x = 0, 2.5, 5, 7.5, 10, 20 (mol%) were prepared by conventional melt-quenching method and investigated by X-ray diffraction analysis, DSC analysis, DR-UV-Vis spectroscopy and photoluminescence spectroscopy. Physical parameters like density, molar volume, oxygen molar volume and oxygen packing density were also determined. Their values, as well as DR-UV-Vis spectroscopy results, indicate that the tungstate ions incorporate into the base borosilicate glass as tetrahedral WO₄ and octahedral WO₆ groups. With increasing WO₃ content over 5 mol%, WO₆ units are progressively linked to each other by W-O-W bonds, leading to the formation of a more connected and homogeneous glass network. Glasses are characterized by a high glass transition temperature (over 650 °C) and good thermal stability. The emission intensity of the Eu³⁺ ion increases with the introduction of WO₃ due to the occurrence of non-radiative energy transfer from the tungstate groups to the active ion. The most intense luminescence peak observed at 612 nm suggests that the glasses are potential materials for red emission. Full article