Search Results (3,233)

Despite its wide acceptance, one of the most critical limitations of Terahertz wave technology is its high sensitivity to moisture. This limitation can, in turn, be exploited for use in moisture detection applications. This work presents a quantitative, non-invasive characterization of moisture content in standard gypsum drywall using Terahertz Time-Domain Spectroscopy (THz-TDS). With an increase in the moisture content of the drywall sample, experimental results indicated an increase in the dielectric properties such as the refractive index, permittivity, absorption coefficient, extinction coefficient, and dissipation factor. The demonstrated sensitivity to moisture establishes THz-TDS as a powerful tool for structural monitoring, hidden defect detection, and electromagnetic modeling of real-world building environments. Beyond material diagnostics, these findings have broader implications for THz indoor propagation studies, especially for emerging sub-THz and low THz communication technologies in 5G/6G and THz imaging of objects hidden behind the wall. Full article

Improving the efficiency of photocatalysts for hydrogen production while minimizing the amount of noble metals used is a pressing issue in modern green energy. This study examines the effect of ultra-small Pt additives on increasing the efficiency of the CuO_x-dark TiO₂ photocatalyst used in the hydrogen evolution reaction (HER). Initially, Pt was photoreduced from the hydroxonitrate complex (Me₄N)₂[Pt₂(OH)₂(NO₃)₈] onto the surface of nanodispersed CuO_x powder obtained by pulsed laser ablation. Then, the obtained Pt-CuO_x particles were dispersed on the surface of highly defective dark TiO₂, so that the mass content of Pt in the samples varied in the range from 1.25 × 10⁻⁵ to 10⁻⁴. The prepared samples were examined using HRTEM, XRD, XPS, and UV-Vis DRS methods. It has been established that in the Pt-CuO_x particles, platinum is mainly present in the form of single atoms (SAs), both as Pt²⁺ (predominantly) and Pt⁴⁺ species, which should facilitate electron transfer and contribute to the manifestation of the strong metal–support interaction (SMSI) effect between SA Ptⁿ⁺ and CuO_x. In turn, in the Pt-CuO_x-dark TiO₂ samples, surface defects (O_v) and surface OH groups on dark TiO₂ particles act as “anchors”, promoting the spontaneous dispersion of CuO_x in the form of sub-nanometer clusters with the reduction of Cu²⁺ to Cu¹⁺ when localized near such O_v defects. During photocatalytic HER in aqueous glycerol solutions, irradiation was found to initiate a large number of catalytically active Pt⁰-CuO_x-O_v-dark TiO₂ centers, where the SMSI effect causes electron transfer from titania to SA Pt, thus promoting better separation of photogenerated charges. As a result, ultra-small additives of Pt led to up to a 1.34-fold increase in the amount of released hydrogen, while the maximum apparent quantum yield (AQY) reached 65%. Full article

As emergent material candidates for extreme environments, refractory high-entropy alloys (HEAs) or refractory multi-principal-element alloys (RMPEAs) comprising refractory metals feature qualities such as high radiation tolerance, corrosion resistance, and mechanical strength. A set of MoNbTi-based RMPEA samples with Al, Cr, V, and Zr additions are prepared by spark plasma sintering and investigated for their response to irradiation using 10 MeV Si⁺ ions with a dose of $1.43\times {10}^{15}$ ions/cm². Positron annihilation spectroscopy and transmission electron microscopy are employed as atomic- and meso- scale techniques to reveal how chemical complexity, nanotwinning, and phase fractions play an important role in radiation-induced defect accumulation and damage tolerance. The study provides experimental evidence of nanotwinning acting as an effective sink for radiation-induced point defects. Full article

This study investigates the interfacial structural origin of enhanced optical performance in InP-based quantum dots (QDs) employing a 2-step ZnSe shelling strategy. By comparing InP/ZnSe/ZnS QDs synthesized via 1-step and 2-step shelling methods using identical InP cores, we demonstrate that the 2-step approach results in improved core–shell lattice matching, more favorable carrier dynamics, and enhanced thermal stability. These enhancements are attributed to the formation of an initial thin ZnSe interfacial layer, which facilitates uniform shell growth and suppresses interfacial defect formation. High-resolution transmission electron microscopy and elemental mapping via energy-dispersive X-ray spectroscopy analyses confirm the improved crystallinity and reduced oxygen-related trap states in the 2-step samples. The findings highlight the critical role of interfacial control in determining QD performance and establish the 2-step ZnSe shelling strategy as an effective route to achieving structurally and optically robust QD emitters for advanced optoelectronic applications. Full article

To address the issue of missed detection of abnormal images caused by scarcity of defect samples and inadequate model training that characterize the current substation image inspection methods, this paper proposes a new substation image inspection method based on visual communication and combination of normal and abnormal samples. In this new method, the quality of substation equipment images is first evaluated, and images are recaptured when they are defocused and underexposed. Images are then preprocessed to eliminate the impact of noise on the algorithm. Image feature alignment is then performed to mitigate camera displacement errors that could degrade algorithmic accuracy. Subsequently, normal-labeled images are used to train the model, and a normal sample database is thus established. Built upon visual communication infrastructure with low-level quantization, the visual feature discrepancy between the current inspection images and those in the normal sample database is calculated using the Learned Perceptual Image Patch Similarity (LPIPS) metric. Through this process, the normal images are filtered out while abnormal images are classified and reported. Finally, this new method is validated at a municipal power supply company in China. When the abnormal image reporting rate is 18.9%, the abnormal image reporting accuracy rate is 100%. This demonstrates that the proposed method can significantly decrease the workload of substation operation and maintenance personnel in reviewing substation inspection images, reduce the time required for a single inspection of substation equipment, and improve the efficiency of video-based substation inspections. Full article

Kalach (KL) is a glyphosate (G)-based herbicide extensively used in agricultural and urban areas in Tunisia. It has been reported that G crosses the placenta in pregnant rats, potentially disrupting organ function in offspring. The present study examined the effects of prenatal and lactational exposure to KL on thyroid function, bone integrity, and phosphocalcic homeostasis in rat offspring. Pregnant rats were divided into two groups, group A (control group) and group B, exposed to KL (each mother rat received 0.07 mL of KL diluted in 1 mL of water by gavage). On postnatal day 14, plasma samples were analyzed for thyroid hormones, calcium, and phosphorus. Histology and immunohistochemical study of bone and thyroid, Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy assessed alterations. Additionally, we complemented the in vivo study with an in silico study. We found that KL induced hypothyroidism, necrosis in thyroid tissue, and phosphocalcic imbalance, leading to skeletal abnormalities. Structural and mineralization defects in bone were confirmed by FTIR and XRD analysis. The in silico study revealed that G bids to growth hormone receptors and thyroglobulin with good affinity, corroborating the in vivo findings. In conclusion, KL may interfere with bone tissue, growth hormone receptors, and thyroglobulin, impair hypothyroidism, and function as an endocrine disruptor exposure. Consequently, KL induces disorganization of the femoral growth plate. Full article

The objective of this study was to investigate the influence of additive manufacturing parameters, specifically using laser powder bed fusion (LPBF), and surface finishing methods on the corrosion rate and behavior of maraging steel M350 components. Samples were fabricated via LPBF employing varying laser powers (80 W, 100 W, and 120 W) and subsequently subjected to mechanical polishing. Corrosion performance was evaluated through 450 h immersion tests in a 3.5% aqueous NaCl solution and potentiodynamic polarization measurements. Microstructural characterization and surface topography assessments were performed using optical microscopy, scanning electron microscopy coupled with energy-dispersive spectroscopy (SEM-EDS), and profilometry. The results demonstrate a strong influence of temperature, manufacturing parameters, and polishing on corrosion processes. At room temperature, higher laser power reduced corrosion rates due to better powder consolidation and lower porosity, whereas at 45 °C, the trend reversed, with the highest corrosion rates observed for samples produced at 120 W. Mechanical polishing significantly reduced surface roughness (Ra from ~7–10 μm to ~0.6–1 μm) but did not improve corrosion resistance; in some cases, it increased corrosion rates, likely due to stress redistribution and exposure of subsurface defects. Potentiodynamic tests confirmed that higher laser power reduced corrosion current density for unpolished surfaces, but polishing increased current density at 80 W more than twofold. The findings indicate that optimizing LPBF process parameters is crucial for improving the corrosion resistance of M350 steel. High laser power (≥120 W) is beneficial at ambient conditions, while lower powers (80–100 W) perform better at elevated temperatures. Mechanical polishing alone is insufficient for enhancing resistance and should be combined with stress-relief and porosity-reduction treatments. These results provide guidelines for tailoring additive manufacturing strategies to ensure reliable performance of M350 steel in chloride-rich environments. Full article

It was demonstrated that various defects can be induced in halide crystals by irradiation with swift heavy ions. Here, we irradiated barium fluoride (BaF₂) single crystals with 220 MeV xenon ions at room temperature and performed stepwise thermal annealing up to the temperature of 825 K to study the kinetics of ion-induced defects at different temperatures. Optical spectroscopy was utilized for the measurement of the wide range of absorption spectra from NIR to VUV. A sharp decrease in the F₂ absorption peak was observed for the samples annealed in the temperature range of 400–450 K. This result can be explained by their recombination with anion interstitials during thermal decay of the complex hole centers. The mobile interstitials, those did not recombine with the F₂ centers, increase the absorption peaks in the 9–10 eV region, which can be associated with interstitial aggregates. Full article

Replication-defective adenoviruses are widely used as vectors for vaccines, but their efficacy may be compromised by the prevalence of pre-existing neutralizing antibodies from natural infections or prior vaccination with adenovirus-based vaccines. To overcome these limitations, less common human adenovirus (HAdV) types and simian adenoviruses (SAdV) have been explored as alternative vectors to the widely prevalent HAdV-C5. Despite their importance, there is limited information on the epidemiology of adenovirus immunity in many countries and geographical regions, including Mexico. In this study, we analyzed 2488 serum samples from healthy adults across all 32 states of Mexico to assess the prevalence of both total and neutralizing antibodies against various HAdV types from species A-F, and three related SAdVs. Our findings indicate a high prevalence of neutralizing antibodies against HAdV-C5 and HAdV-C6, with significant cross-reactivity observed among related adenoviruses. Notably, HAdV-D26 exhibited a lower prevalence of neutralizing antibodies, suggesting its potential suitability as a vector for vaccine development in populations with high pre-existing immunity to more common HAdV types. These results provide critical insights for optimizing adenovirus-based vaccine strategies in Mexico. Full article

A gas turbine engine is a technological system consisting of a compressor, a combustion chamber, and other modules. All these components are subjected to dynamic and cyclic loads, which lead to fatigue cracks and mechanical damage. The aim of this work is to repair the worn surfaces of a series of DR-59L high-pressure turbine blades by laser powder cladding. A number of technological parameters of laser cladding were tested to obtain a defect-free structure on the witness sample. The metal powder of the cobalt alloy Stellite 21 was used as a filler material. By modeling the process of restoring rotor blades, the operating mode of laser powder cladding was determined. No defects were detected during capillary control of the restored surfaces of the rotor blades. The results of the uniaxial tension test of the restored rotor blades showed increased tensile strength and elongation. With the use of laser powder cladding technology, it was possible to restore the worn surfaces of a series of rotor blades of the DR-59L high-pressure turbine, thereby increasing the life cycle of power plant products. Full article

This study sought to evaluate the inhibitory effect of pulsed electromagnetic field (PEMF) therapy on bone resorption in a mouse model of lipopolysaccharide (LPS)-induced osteoporosis. A total of 40 mice were divided into four groups: control, LPS, LPS + alendronate, and LPS + PEMF. Blood and spleen samples were analyzed using RT-PCR and ELISA, while calvaria and femurs were assessed by micro-computed tomography (CT) and histological analysis. Serum analysis revealed that, compared with the control group, calcium levels in the PEMF group showed no significant difference, but alkaline phosphatase (ALP) levels were significantly increased, whereas tartrate-resistant acid phosphatase (TRAP) levels were significantly decreased. Moreover, blood cytokine analysis showed reduced expression of TNF-α and IL-1β and increased expression of BMP-2 in the PEMF group. Spleen tissue analysis further demonstrated significant upregulation of IFN-γ and IL-10 expression in the PEMF group. Micro-CT confirmed that PEMF inhibited femoral bone loss and promoted bone regeneration in calvarial defects. Histological evaluation with hematoxylin and eosin and Masson–Goldner trichrome staining confirmed enhanced bone formation in both the femur and calvaria. In conclusion, PEMF effectively alleviates bone loss and promotes bone regeneration in LPS-induced osteoporosis. Furthermore, PEMF exhibits anti-osteoclastogenic activity by reducing inflammatory cytokines and enhancing IFN-γ and IL-10 expression in the spleen. Full article

Spinels like Co₃O₄ have acquired relevance because of their photocatalytic, electrocatalytic, optical and magnetic properties. In this context, we investigated the defect structure evolution of compounds synthetized using the nitrate precursor method and after annealing cycles at temperatures ranging from 260 to 650 °C by means of thermogravimetric analysis (TGA), neutron powder diffraction (NPD), X-ray powder diffraction (XRPD) coupled to Pair Distribution Function (PDF) analysis, and Density Functional Theory (DFT) calculations. Deuterated and hydrogenated precursors were adopted to produce the samples for NPD and XRPD experiments, respectively. TGA measurements displayed weight losses, the extent of which increased on lowering the preparation annealing temperature, suggesting that the adopted wet synthesis introduces structural water in the sample. Both XRPD and NPD revealed the presence of vacancies in tetrahedral cobalt sites ($V_{Co1}^{″}$) whose concentration at RT decreases on raising the annealing temperatures, while octahedral cobalt and oxygen sites were fully occupied in all the samples. In addition, the $V_{Co1}^{″}$ presence induces a shrinking of the volume of the CoO₄ tetrahedra. The combination of DFT calculation and diffraction revealed that deuterium/hydrogen ions ($D_i^{•}$/$H_i^{•}$), introduced during the synthesis by the nitrate precursor balanced the $V_{Co1}^{″}$. Finally, DFT calculations revealed that ($D_i^{•}$/$H_i^{•}$) in Co₃O₄ forms hydroxyl groups. Full article

Magnetic resonance techniques are powerful, nondestructive, non-invasive tools with broad applications in radiation dosimetry. Electron paramagnetic resonance (EPR) enables direct quantification of dose-dependent radiation-induced paramagnetic defects, while nuclear magnetic resonance (NMR) reflects the influence of such defects through changes in line width and nuclear spin relaxation. To date, these methods have typically been applied independently. Their combined use to probe radiation damage in the same material offers new opportunities for comprehensive characterization and preferred dosimetry techniques. In this work, we apply both EPR and NMR to investigate radiation damage in lithium carbonate (Li₂CO₃). A detailed EPR analysis of γ-irradiated samples shows that the concentration of paramagnetic defects increases with dose, following two distinct linear regimes: 10–100 Gy and 100–1000 Gy. A gradual decay of the EPR signal was observed over 40 days, even under cold storage. In contrast, ⁷Li NMR spectra and spin–lattice relaxation times in Li₂CO₃ exhibit negligible sensitivity to radiation doses up to 1000 Gy, while ¹H NMR results remain inconclusive. Possible mechanisms underlying these contrasting behaviors are discussed. Full article

AlSi10Mg has been one of the most studied and employed aluminum alloys for additive manufacturing via laser powder-bed fusion (L-PBF). The optimization of manufacturing parameters is important for reducing internal defects, including porosity and inadequate surface finishes. In addition, heat treatments, such as T6, are often applied to this alloy, but they degrade the characteristic microstructure obtained via L-PBF additive manufacturing—the fine cellular structures—which may, in turn, detrimentally affect the material’s properties. In this context, a new alternative to this treatment, direct aging (DA), has shown promise in improving the mechanical properties of AlSi10Mg parts produced via L-PBF, since it preserves the cellular microstructure, precipitating silicon-rich nanoparticles within the cells. Understanding how different temperatures and heat treatment times influence the microstructure and, consequently, the properties remains a field to be explored in order to optimize the treatment conditions and achieve better mechanical properties. Thus, the objective of this study was to evaluate the influence of manufacturing parameters and heat treatments on the microstructure and mechanical properties of AlSi10Mg alloy. The optimized manufacturing conditions were 300 W power, 800 mm/s scan speed, 30 µm layer thickness, and an argon atmosphere, which led to lower porosity and better finishing. Samples were heat-treated via DA at 150 °C and 170 °C for different times, as well as undergoing a T6 treatment (solution at 520 °C followed by aging at 150 °C and 170 °C). Initially, the aging curves show higher hardness values for the direct aging condition, compared to the T6 and as-built conditions, reaching a peak hardness of 195 HV for 6h of direct aging. In this way, it was followed with microstructural characterization, which demonstrated that DA maintained the fine cell microstructure of L-PBF and promoted the precipitation of Si nanoparticles, which certainly contributed to the increase in hardness compared to T6, which promoted a structure with coarser precipitates. DA at 170 °C for 6 h increased the tensile strength to 430 MPa, compared to the as-built condition, with a slight loss of ductility. Full article

As IoT (internet of things) devices grow in prominence, safeguarding them from cyberattacks is becoming a pressing challenge. To bootstrap IoT security, device identification or authentication is crucial for establishing trusted connections among devices without prior trust. In this regard, radio frequency fingerprinting (RFF) is gaining attention because it is more efficient and requires fewer computational resources compared to resource-intensive cryptographic methods, such as digital signatures. RFF works by identifying unique manufacturing defects in the radio circuitry of IoT devices by analyzing over-the-air signals that embed these imperfections, allowing for the identification of the transmitting hardware. Recent studies on RFF often leverage advanced classification models, including classical machine learning techniques such as K-Nearest Neighbor (KNN) and Support Vector Machine (SVM), as well as modern deep learning architectures like Convolutional Neural Network (CNN). In particular, CNNs are well-suited as they use multidimensional mapping to detect and extract reliable fingerprints during the learning process. However, a significant limitation of these approaches is that they require large datasets and necessitate retraining when new devices not included in the initial training set are added. This retraining can cause service interruptions and is costly, especially in large-scale IoT networks. In this paper, we propose a novel solution to this problem: RFF using Siamese networks, which eliminates the need for retraining and allows for seamless authentication in IoT deployments. The proposed Siamese network is trained using in-phase and quadrature (I/Q) samples from 10 different Software-Defined Radios (SDRs). Additionally, we present a new algorithm, the Similarity-Based Embedding Classification (SBEC) for RFF. We present experimental results that demonstrate that the Siamese network effectively distinguishes between malicious and trusted devices with a remarkable 98% identification accuracy. Full article