Search Results (3,093)

To explore the influence of reaction wheel perturbations on the image quality of a space optical telescope, a comprehensive dynamic model of a precision optical system was established, and an optical-mechanical integrated analysis approach was adopted to calculate the line-of-sight (LOS) error of the optical telescope under reaction wheel disturbances and determine the key mode that contributes the most significantly to the LOS error based on the entire satellite hierarchy. The rigid body displacements and mirror deformations generated by the optical reflector under reaction wheel perturbations were analyzed in synergy with the optical system to illuminate the impact of reaction wheel perturbations on the imaging quality of the optical imaging system. Finally, a satellite micro-vibration experiment was conducted, and the relative errors between the simulation and the experiment of the optical telescope’s object space axis of LOS error under key modes were 9.34% and 6.52% respectively, thereby validating the accuracy of the simulation analysis. The analysis outcomes offer direct engineering guidance for the structural layout and vibration isolation design of on-orbit optical satellites. The core innovations of this study are primarily manifested in three aspects: First, a full-link optomechanical integrated analysis framework is established, which synergistically accounts for the coupled effects of mirror rigid-body displacement and surface deformation on imaging performance, thereby addressing the limitations of single-factor analysis in existing research. Second, the framework is validated through satellite micro-vibration experiments, with the relative errors between simulation and experimental results both below 10%, ensuring the engineering reliability of the proposed method. Third, the scope of micro-vibration analysis is extended across scales from macroscopic space optical systems to micro/nano-scale precision optical devices. Beyond its application to space telescopes, this framework can be directly generalized to micro-optical systems sensitive to micro-vibrations, including augmented reality (AR) near-eye displays, microlithography objectives, and MOEMS-based micro-devices. The proposed framework is universal and can be directly extended to micro-optical systems such as MOEMS-based devices, near-eye display modules, and photonic crystal optomechanical systems, providing a standardized analytical approach for anti-vibration design in micro-system engineering. Full article

The effect of A-site substitution on the morphological and electrochemical properties of La_1-xSr_xMnO₃ (x = 0, 0.25, 0.50) perovskites was investigated to evaluate their potential as electrode materials for supercapacitors. X-ray diffraction analysis confirmed the formation of the perovskite structure, with minor peak shifts and distortion of crystal structure induced by Sr substitution. Scanning electron microscopy analysis revealed irregularly shaped particulate morphology across all perovskite compositions. The increasing amount of Sr as in La_0.5Sr_0.5MnO₃ (LSM-50) favored the formation of nanosized particles, and energy dispersive X-ray (EDX) analysis confirmed the presence of all constituent elements; EDX elemental mapping also showed a uniform distribution of all elements in the various perovskite compositions. Among all compositions, La_0.75Sr_0.25MnO₃ (LSM-25) possessed the highest specific capacitance (C_sp) of 483 Fg⁻¹ at 1 Ag⁻¹ current density in 3 M KOH electrolyte, as determined by electrochemical analysis. This perovskite material also exhibited a capacitance retention of 87.8% after 5000 charge–discharge cycles. Electrochemical impedance spectroscopy revealed that LSM-25 showed the lowest solution resistance (0.68 Ω*cm²) and charge transfer resistance (1.52 Ω*cm²), indicating strong electrode–electrolyte interaction. Detailed analysis of cyclic voltammetry data revealed that the predominant charge storage mechanism was diffusive in nature, with 88% of the diffusive contribution registered for LSM-25. These findings demonstrate that Sr substitution at the A-site significantly enhances the energy storage performance of LaMnO₃, making it a promising candidate for supercapacitor applications. Full article

This study investigated the improvement of the pozzolanic activity of pumice, perlite, and farin through mechanochemical activation (MCA). The properties of the materials were determined by performing XRF, XRD, and particle size and specific surface area analyses. The MCA of three different materials sourced from Türkiye was performed using a planetary ball mill, and their pozzolanic reactivity was systematically investigated. R³ test (bound water measurement) and strength activity index (SAI) test were used to evaluate pozzolanic activity. Based on the results, following MCA, the crystal structure was significantly disrupted, particularly in perlite and pumice, and the amount of amorphous phase increased more compared to farin, as confirmed by the decrease in XRD peak intensities. The amount of bound water tended to increase by increasing grinding time and grinding speed. The highest amount of bound water (7.5%) was obtained by grinding the pumice sample at 500 rpm, with ball-to-powder ratio (BPR) of 10 for 60 min. For the same material, the highest activity index (106%) was determined at 500 rpm, with a BPR of 15 and a grinding time of 60 min. In the perlite sample, the highest amount of bound water (7.07%) and the highest strength activity index (98%) were measured in the sample ground at 500 rpm for 60 min with a BPR of 15. In the farin sample, the highest amount of bound water (3.40%) was obtained at 500 rpm for 40 min with a BPR of 15, while the highest strength activity index (71.05%) was observed at 500 rpm for 40 min with a BPR of 10. The results show that the applied MCA process increases the activity of the materials. Full article

Porous, crystalline gamma-Al₂O₃ coatings with a thickness of (6 ± 0.5) μm and a uniform distribution of rare earth (RE) dopants are synthesized by plasma electrolytic oxidation of aluminum at a current density of 150 mA/cm² in a boric acid and borax (BB) solution containing added RE oxide particles (Ho₂O₃, Tb₄O₇, and Pr₆O₁₁) at concentrations of 1, 2, and 4 g/L. The concentration of RE oxide particles in the BB solution determines the amount of RE elements incorporated into the coatings but does not significantly affect their surface morphology, crystal structure, or light absorption properties. The coatings exhibit high absorption in the middle/near-ultraviolet region, characteristic of Al₂O₃. Typical 4f-4f transitions of Ho³⁺, Tb³⁺, and Pr³⁺ are observed in the photoluminescence spectra. Photocatalytic evaluations using methyl orange degradation under simulated solar irradiation show that RE doping significantly enhances photocatalytic efficiency. Peak degradation efficiencies are achieved at a concentration of 4 g/L for all RE oxides. After 8 h of irradiation, maximum degradation reaches 88%, 92%, and 85% with pseudo-first-order rate constants (k_app) of about 0.274 h⁻¹, 0.339 h⁻¹, and 0.232 h⁻¹ for coatings synthesized in BB with 4 g/L Ho₂O₃, Tb₄O₇, or Pr₆O₁₁, respectively. In comparison, the pristine Al₂O₃ coating achieves only about 50% degradation (k_app ≈ 0.087 h⁻¹). Photoluminescence indicates that RE³⁺ ions serve as effective charge-carrier traps, suppressing electron–hole pair recombination. RE-doped Al₂O₃ coatings demonstrate exceptional structural stability and reusability over six cycles, highlighting their potential for sustainable wastewater remediation. Full article

Colloidal crystals are periodic arrays of monodisperse particles that exhibit optical stopbands, which can be experimentally observed as a Bragg reflection characterized by a specific Bragg wavelength and width. Precise control of these characteristic parameters is essential for applications in structural color materials, sensors, and tunable photonic crystals. Although the Bragg reflection wavelength can be widely tuned by adjusting the lattice spacing via changes in particle size and concentration, controlling the width over a wide range—such as through expansion—is challenging because it is intrinsically determined by the refractive index contrast between the colloidal particles and their surrounding medium. In this study, the Bragg reflection width of non-close-packed colloidal crystals immobilized in an elastomer film was successfully expanded by adjusting the photoinitiator concentration and ultraviolet light intensity for photopolymerization. Expansion was attributed to the superposition of Bragg reflections at different wavelengths, resulting from spatial variations in the lattice spacings of the non-close-packed colloidal crystals formed during photopolymerization. Owing to the solvent-free and highly flexible nature of the elastomer-immobilized, non-close-packed colloidal crystal film, the Bragg reflection wavelength was readily tuned by mechanical compression while maintaining the expanded Bragg reflection width, thereby advancing the practical applications of structural color materials. Full article

In this study, TiO₂ nanoparticles (NPs), CdS NPs and TiO₂/CdS nanocomposite were synthesized via the sol–gel, hydrothermal and ex situ method, respectively. The synthesized materials were characterized using XRD, UV–vis DRS, FTIR, SEM, and EDX analysis. XRD analysis confirmed the crystalline structure of the as-prepared samples, while the bandgap energy of TiO₂ NPs, CdS NPs, and TiO₂/CdS nanocomposite were determined to be 2.98, 1.94, and 2.27 eV, respectively. Photocatalytic efficiency of TiO₂ NPs, CdS NPs, and TiO₂/CdS nanocomposite was systematically evaluated by photocatalytic degradation of crystal violet (CV) dye under visible-light irradiation. Under optimized reaction conditions of [CV concentration] = 20 mg/L, [catalyst dosage] = 0.25 g/L, and pH = 6, TiO₂/CdS nanocomposite achieved 86.3% removal of CV within 180 min, outperforming pure TiO₂ NPs (16.4%) and CdS NPs (66.9%). The enhanced performance of TiO₂/CdS nanocomposite as compared to CdS NPs is attributed to improved charge separation via heterojunction formation, while significantly superior performance over TiO₂ demonstrates successful visible-light activation. Further optimization study revealed that maximum removal efficiency of CV (97.1%) was achieved at lower dye concentration (10 mg/L). Photocatalytic degradation of CV followed pseudo-first-order kinetics. Moreover, scavenger experiments confirmed hydroxyl radicals (^•OH) as dominant reactive species. Furthermore, the TiO₂/CdS nanocomposite demonstrated good reusability with minimal activity loss after five runs. Additionally, the as-prepared nanocomposites showed significant antibacterial activity against Pseudomonas aeruginosa (P. aeruginosa). The present study indicated that TiO₂/CdS nanocomposite could be simultaneously used for degradation of organic pollutants as well as for removal of microorganisms while targeting environmental sustainability and water purification. Full article

As a part of our research on the presence of conglomerates among the aryl benzyl sulfoxides, racemic-benzimidazolyl pentafluorobenzyl sulfoxide was synthesised, and its crystal structure was determined by a single crystal X-ray diffraction experiment. The main interactions building up the crystal structure were recognised and compared with those of similar compounds. Since the crystal structures of racemic and enantiopure benzimidazolyl pentafluorobenzyl sulfoxides are different, the presence of a conglomerate is excluded in the present case. Full article

To develop a high-performance inorganic fireproof coating suitable for steel structures, this study utilized magnesium phosphate cement (MPC) as the matrix and introduced expanded perlite (EP) as a lightweight aggregate. The effects of EP content (40–55%) and magnesium-to-phosphorus ratio (M/P = 4:1–7:1) on the dry density, compressive strength, bond strength, and fire resistance of the coating were systematically investigated. X-ray diffraction (XRD), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA) were employed to reveal the phase evolution and microstructure evolution mechanisms at high temperatures. The results indicate that increasing EP content significantly reduces the dry density and thermal conductivity of the coating, enhancing thermal insulation performance. However, excessive incorporation leads to the deterioration of mechanical properties, with an optimal EP content of 45%. The M/P ratio influences the interfacial bond strength and high-temperature structural stability by regulating the proportion of the hydration product K-struvite (KMgPO₄·6H₂O) and residual MgO. Compressive strength peaked at M/P = 6:1 (0.80 MPa), while bond strength was optimal at M/P = 5:1 (0.097 MPa), corresponding to the best fire resistance (back-side temperature of 180.4 °C). At high temperatures, K-struvite dehydrates and transforms into anhydrous KMgPO₄, which, together with residual MgO and crystallized SiO₂ from EP, forms a dense ceramic skeleton, ensuring the structural integrity of the coating. Comprehensive performance evaluation determined the optimal mix ratio as M/P = 5:1 and EP content = 45%. The coating with this ratio exhibits a dry density of approximately 560 kg/m³, a 14-day compressive strength of 0.53 MPa, a bond strength of 0.097 MPa, and a back-side temperature of 180.4 °C under flame exposure, demonstrating a favorable balance of lightweight character, mechanical integrity, and thermal insulation performance suitable for steel structure fire protection applications. Full article

Physically unclonable functions (PUFs) are critical security primitives used in authentication and cryptographic key generation. Among these, structural color-based PUFs offer distinct advantages, including fade resistance and the ability to conceal multi-dimensional information. However, current fabrication methods rely heavily on wet processes and laser ablation. Consequently, there is a significant need for flexible PUF labels capable of being produced through a facile and dry process. Here, we present stress-relief modulated photonic crystal PUF labels designed for multi-level dynamic encryption. We achieve random patterning of nanograting-based photonic crystals by leveraging curved pinning edge-induced interruptions and the uncontrolled bulking of the polymeric elastomer due to the uneven adhesion force from the tape. Using artificial intelligence-based deep learning algorithms, we authenticate the labels by extracting structural color, brightness, and saturation, which are determined by the grating periodicity, depth, and orderliness of each pixel. Furthermore, we integrated these photonic crystal patterns with dynamically modulated optical erasure to extend encryption capacity from the spatial to the temporal dimension. We anticipate this approach will enable advanced wearable anti-counterfeiting labels and multi-level digital encryption systems. Full article

A novel derivative from carotene-type sesquiterpene, (1S,2R,3aR,6S,8aS)-1-isopropyl-3a,6-dimethyldecahydroazulene-1,2,6-triol (1), was successfully isolated from filamentous fungus Trichoderma virens NBRC 31959. The structure and molecular formula of 1 were determined by interpretation of 1D and 2D NMR and HRMS data. The absolute configuration was established unambiguously by single-crystal X-ray diffraction, with the Flack parameter supporting the assignment. This study adds to the chemical diversity of sesquiterpene-type CAF603 derivatives of Trichoderma virens. Full article

LaFeO₃ nanofibers and Ag-doped LaFeO₃ nanofibers were fabricated via an approach combining electrospinning with calcination. Their crystal structures, micro-morphologies, and chemical compositions were determined by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, and Fourier-transform infrared spectroscopy. In addition, the conduction mechanisms and magnetic properties of the two samples were investigated using a semiconductor analyzer and a vibrating sample magnetometer. Rietveld refined X-ray diffraction analyses confirmed the orthorhombic structure. The two samples showed a nanofibrous structure. For Ag-doped LaFeO₃, the conduction was dominated by the ohmic conduction mechanism in a low-resistance state, while it was governed by space-charge-limited current conduction in a high-resistance state. It also showed a high on/off ratio of 3.6 × 10³. The coercivity and remanence values of Ag-doped LaFeO₃ were 200 Oe and 0.000404 emu g⁻¹. This, thus, indicates the considerable application potential of Ag-doped LaFeO₃ for resistive random-access memory devices and magnetoresistive random-access memory devices. Full article

Synthetic derivatives of testosterone known as 17α-alkylated anabolic–androgenic steroids have been developed to retain anabolic effects while enabling oral administration. Here, we present newly identified hydrated solid forms of three agents: oxandrolone hemihydrate (C₁₉H₃₀O₃·0.5H₂O), fluoxymesterone hydrate (C₂₀H₂₉FO₃·H₂O), and methandienone hemihydrate (C₂₀H₂₈O₂·0.5H₂O). Their crystal structures were determined using single-crystal X-ray diffraction, supplemented by powder X-ray diffraction and thermal analyses. Computational methods were employed to investigate molecular interactions and crystal packing. Lattice energy evaluations revealed that the hydrated forms are energetically less stable than their anhydrous counterparts, with significantly less negative values (e.g., −113.4 kJ/mol for oxandrolone hemihydrate vs. −164.4 kJ/mol for the anhydrous form). Energy decomposition analysis indicates that while water molecules participate mostly in electrostatic-driven hydrogen bonding, they disrupt the dispersive packing efficiency found in the anhydrous phases. Specifically, intermolecular interaction energies show that host–host hydrogen bonds (up to −62.2 kJ/mol in oxandrolone) dominate over weaker host–water couplings (−8.9 to −34.9 kJ/mol). The newly reported crystal structures contribute to the expanding catalog of solid-state forms for 17α-alkylated steroids and provide important details regarding their metastable nature and the dehydration-driven phase transformations observed under climatic stress conditions. Full article

Microorganisms provide critical lead compounds for drug development, yet most biosynthetic gene clusters remain silent under standard culture conditions. The OSMAC strategy activates these clusters by adjusting cultivation parameters, thereby enabling the discovery of novel compounds from a single strain. Here, we applied OSMAC to explore the metabolic potential of the soft coral-derived fungus Aspergillus sclerotiorum SCSIO 41031. Three different culture media were employed for the large-scale fermentation process. After isolation by chromatography, the compounds were structurally characterized using NMR, MS, and X-ray single-crystal diffraction, and their absolute configurations were determined by electronic circular dichroism (ECD) calculations. In total, three new compounds, named 6,6′-diacetyl-1,1′-dihydroxy-3,3′-dimethoxydibenzyl ether (1), esterwortmannolol (17) and pestalpolyol I (20), along with 19 known compounds (2–16, 18–19 and 21–22) were obtained. This study validates the efficacy of the OSMAC strategy and underscores that A. sclerotiorum SCSIO 41031 serves as a valuable resource for producing structurally diverse natural products with potent biological activities. Full article

Three multicomponent crystals of metformin were investigated to elucidate factors governing crystal architecture. Structures were determined by X-ray diffraction and analyzed using the Atoms-in-Molecules (AIM) approach, focusing on critical points and electron density topology. Three types of crystals were obtained: salt, cocrystal salt solvate and mixed salt with both organic and inorganic anions. Protonation of nitrogen atoms in metformin alters bond lengths and electron density, while strong intramolecular hydrogen bonds in hydrogenmaleate anions stabilize the structures and define the preferred anion geometry. Comparison with monoprotonated metformin revealed similar topological features despite differing protonation states. Mechanochemical synthesis via liquid-assisted grinding (LAG) enabled selective formation of specific crystalline forms, with the solvent type and acid polymorph influencing product distribution. These results highlight the critical roles of protonation, hydrogen bonding, and synthetic methodology in designing and controlling multicomponent metformin crystal structures. Full article

Titanium dioxide (TiO₂) is a versatile material that exhibits a high refractive index, strong light-scattering capability, effective UV-absorption, wide band gap semiconductor behavior (3.0–3.2 eV), and excellent chemical stability. Owing to this unique combination of properties, TiO₂ is widely used in applications such as cosmetic and healthcare products, architectural and automotive coatings, and photocatalytic degradation of environmental pollutants. In photocatalytic applications, the crystal structure, phase composition and electronic properties of TiO₂ play a critical role in determining its performance. In the present study, TiO₂ nanotubes were synthesized by anodization of Ti° coatings deposited via a semi-industrial arc-PVD process. A post-anodization heat treatment was carried out at 430 °C for 1 h to promote the formation of the anatase phase within the TiO₂ nanotube structures. The structural characterization of the synthesized film was performed using X-ray diffraction (XRD) and Rietveld refinement. This methodology enabled the identification of the formed oxide phases, structure, and crystalline, confirming the formation of mixed oxides in the coating. To address the difficulty of refinement of these crystalline phases, the Le Bail method was applied. This refinement strategy allowed the identification of the crystalline phases that are present in the Ti_xO_y coating, including a hexagonal structure characteristic of α-Ti (space group P63/mmc, No. 194), the tetragonal anatase TiO₂ (space group I41/amd, No. 141) phase, and the trigonal Ti₂O₃ phase (space group R-3/c No. 167). Key crystallographic parameters such as lattice constants, bond lengths and angles, crystallite sizes, unit cell distortion and electron density were systematically evaluated for each phase. In addition, the Wyckoff positions and interatomic distances of the constitutive atoms were calculated, providing a comprehensive description of the TiO₂+Ti₂O₃/Ti° crystallographic system. The topographic and surface oxidation states were recorded by using profilometry and X-ray photoelectron spectroscopy, respectively. Full article