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24 pages, 4967 KiB  
Article
CatBoost-Optimized Hyperspectral Modeling for Accurate Prediction of Wood Dyeing Formulations
by Xuemei Guan, Rongkai Xue, Zhongsheng He, Shibin Chen and Xiangya Chen
Forests 2025, 16(8), 1279; https://doi.org/10.3390/f16081279 - 5 Aug 2025
Abstract
This study proposes a CatBoost-enhanced hyperspectral modeling approach for accurate prediction of wood dyeing formulations. Using Pinus sylvestris var. mongolica veneer as the substrate, 306 samples with gradient dye concentrations were prepared, and their reflectance spectra (400–700 nm) were acquired. After noise reduction [...] Read more.
This study proposes a CatBoost-enhanced hyperspectral modeling approach for accurate prediction of wood dyeing formulations. Using Pinus sylvestris var. mongolica veneer as the substrate, 306 samples with gradient dye concentrations were prepared, and their reflectance spectra (400–700 nm) were acquired. After noise reduction and sensitive band selection (400–450 nm, 550–600 nm, and 600–650 nm), spectral descriptors were extracted as model inputs. The CatBoost algorithm, optimized via k-fold cross-validation and grid search, outperformed XGBoost, random forest, and SVR in prediction accuracy, achieving MSE = 0.00271 and MAE = 0.0349. Scanning electron microscopy (SEM) revealed the correlation between dye particle distribution and spectral response, validating the model’s physical basis. This approach enables intelligent dye formulation control in industrial wood processing, reducing color deviation (ΔE < 1.75) and dye waste by approximately 25%. Full article
(This article belongs to the Section Wood Science and Forest Products)
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20 pages, 2990 KiB  
Article
Examination of Interrupted Lighting Schedule in Indoor Vertical Farms
by Dafni D. Avgoustaki, Vasilis Vevelakis, Katerina Akrivopoulou, Stavros Kalogeropoulos and Thomas Bartzanas
AgriEngineering 2025, 7(8), 242; https://doi.org/10.3390/agriengineering7080242 - 1 Aug 2025
Viewed by 140
Abstract
Indoor horticulture requires a substantial quantity of electricity to meet crops extended photoperiodic requirements for optimal photosynthetic rate. Simultaneously, global electricity costs have grown dramatically in recent years, endangering the sustainability and profitability of indoor vertical farms and/or modern greenhouses that use artificial [...] Read more.
Indoor horticulture requires a substantial quantity of electricity to meet crops extended photoperiodic requirements for optimal photosynthetic rate. Simultaneously, global electricity costs have grown dramatically in recent years, endangering the sustainability and profitability of indoor vertical farms and/or modern greenhouses that use artificial lighting systems to accelerate crop development and growth. This study investigates the growth rate and physiological development of cherry tomato plants cultivated in a pilot indoor vertical farm at the Agricultural University of Athens’ Laboratory of Farm Structures (AUA) under continuous and disruptive lighting. The leaf physiological traits from multiple photoperiodic stress treatments were analyzed and utilized to estimate the plant’s tolerance rate under varied illumination conditions. Four different photoperiodic treatments were examined and compared, firstly plants grew under 14 h of continuous light (C-14L10D/control), secondly plants grew under a normalized photoperiod of 14 h with intermittent light intervals of 10 min of light followed by 50 min of dark (NI-14L10D/stress), the third treatment where plants grew under 14 h of a load-shifted energy demand response intermittent lighting schedule (LSI-14L10D/stress) and finally plants grew under 13 h photoperiod following of a load-shifted energy demand response intermittent lighting schedule (LSI-13L11D/stress). Plants were subjected also under two different light spectra for all the treatments, specifically WHITE and Blue/Red/Far-red light composition. The aim was to develop flexible, energy-efficient lighting protocols that maintain crop productivity while reducing electricity consumption in indoor settings. Results indicated that short periods of disruptive light did not negatively impact physiological responses, and plants exhibited tolerance to abiotic stress induced by intermittent lighting. Post-harvest data indicated that intermittent lighting regimes maintained or enhanced growth compared to continuous lighting, with spectral composition further influencing productivity. Plants under LSI-14L10D and B/R/FR spectra produced up to 93 g fresh fruit per plant and 30.4 g dry mass, while consuming up to 16 kWh less energy than continuous lighting—highlighting the potential of flexible lighting strategies for improved energy-use efficiency. Full article
(This article belongs to the Topic Digital Agriculture, Smart Farming and Crop Monitoring)
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18 pages, 12329 KiB  
Article
Red Cabbage Anthocyanin-Loaded Bacterial Cellulose Hydrogel for Colorimetric Detection of Microbial Contamination and Skin Healing Applications
by Hanna Melnyk, Olesia Havryliuk, Iryna Zaets, Tetyana Sergeyeva, Ganna Zubova, Valeriia Korovina, Maria Scherbyna, Lilia Savinska, Lyudmila Khirunenko, Evzen Amler, Maria Bardosova, Oleksandr Gorbach, Sergiy Rogalsky and Natalia Kozyrovska
Polymers 2025, 17(15), 2116; https://doi.org/10.3390/polym17152116 - 31 Jul 2025
Viewed by 252
Abstract
Developing innovative, low-cost halochromic materials for diagnosing microbial contamination in wounds and burns can effectively facilitate tissue regeneration. Here, we combine the pH-sensing capability of highly colorful red cabbage anthocyanins (RCAs) with their healing potential within a unique cellulose polymer film that mimics [...] Read more.
Developing innovative, low-cost halochromic materials for diagnosing microbial contamination in wounds and burns can effectively facilitate tissue regeneration. Here, we combine the pH-sensing capability of highly colorful red cabbage anthocyanins (RCAs) with their healing potential within a unique cellulose polymer film that mimics the skin matrix. Biological activities of RCA extract in bacterial cellulose (BC) showed no cytotoxicity and skin-sensitizing potential to human cells at concentrations of RCAs similar to those released from BC/RCA dressings (4.0–40.0 µg/mL). A decrease in cell viability and apoptosis was observed in human cancer cells with RCAs. The invisible eye detection of the early color change signal from RCAs in response to pH alteration by bacteria was recorded with a smartphone application. The incorporation of RCAs into BC polymer has altered the morphology of its matrix, resulting in a denser cellulose microfibril network. The complete coincidence of the vibrational modes detected in the absorption spectra of the cellulose/RCA composite with the modes in RCAs most likely indicates that RCAs retain their structure in the BC matrix. Affordable, sensitive halochromic BC/RCA hydrogels can be recommended for online monitoring of microbial contamination, making them accessible to patients. Full article
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19 pages, 4569 KiB  
Article
Tailored Magnetic Fe3O4-Based Core–Shell Nanoparticles Coated with TiO2 and SiO2 via Co-Precipitation: Structure–Property Correlation for Medical Imaging Applications
by Elena Emanuela Herbei, Daniela Laura Buruiana, Alina Crina Muresan, Viorica Ghisman, Nicoleta Lucica Bogatu, Vasile Basliu, Claudiu-Ionut Vasile and Lucian Barbu-Tudoran
Diagnostics 2025, 15(15), 1912; https://doi.org/10.3390/diagnostics15151912 - 30 Jul 2025
Viewed by 143
Abstract
Background/Objectives: Magnetic nanoparticles, particularly iron oxide-based materials, such as magnetite (Fe3O4), have gained significant attention as contrast agents in medical imaging This study aimsto syntheze and characterize Fe3O4-based core–shell nanostructures, including Fe3O4 [...] Read more.
Background/Objectives: Magnetic nanoparticles, particularly iron oxide-based materials, such as magnetite (Fe3O4), have gained significant attention as contrast agents in medical imaging This study aimsto syntheze and characterize Fe3O4-based core–shell nanostructures, including Fe3O4@TiO2 and Fe3O4@SiO2, and to evaluate their potential as tunable contrast agents for diagnostic imaging. Methods: Fe3O4, Fe3O4@TiO2, and Fe3O4@SiO2 nanoparticles were synthesized via co-precipitation at varying temperatures from iron salt precursors. Fourier transform infrared spectroscopy (FTIR) was used to confirm the presence of Fe–O bonds, while X-ray diffraction (XRD) was employed to determine the crystalline phases and estimate average crystallite sizes. Morphological analysis and particle size distribution were assessed by scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX) and transmission electron microscopy (TEM). Magnetic properties were investigated using vibrating sample magnetometry (VSM). Results: FTIR spectra exhibited characteristic Fe–O vibrations at 543 cm−1 and 555 cm−1, indicating the formation of magnetite. XRD patterns confirmed a dominant cubic magnetite phase, with the presence of rutile TiO2 and stishovite SiO2 in the coated samples. The average crystallite sizes ranged from 24 to 95 nm. SEM and TEM analyses revealed particle sizes between 5 and 150 nm with well-defined core–shell morphologies. VSM measurements showed saturation magnetization (Ms) values ranging from 40 to 70 emu/g, depending on the synthesis temperature and shell composition. The highest Ms value was obtained for uncoated Fe3O4 synthesized at 94 °C. Conclusions: The synthesized Fe3O4-based core–shell nanomaterials exhibit desirable structural, morphological, and magnetic properties for use as contrast agents. Their tunable magnetic response and nanoscale dimensions make them promising candidates for advanced diagnostic imaging applications. Full article
(This article belongs to the Section Medical Imaging and Theranostics)
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12 pages, 1829 KiB  
Article
Flexible Color Filter Using Lithium Niobate Metamaterial with Ultrahigh Purity and Brightness Characteristics
by Siqiang Zhao, Daoye Zheng, Yunche Zhu, Shuyan Zou and Yu-Sheng Lin
Photonics 2025, 12(8), 768; https://doi.org/10.3390/photonics12080768 - 30 Jul 2025
Viewed by 230
Abstract
We propose a simulation-based design for a flexible color filter (FCF) using a lithium niobate metamaterial (LNM) to investigate its color filtering potential. The FCF is composed of three periodically arranged half-ellipse LN arrays on a polydimethylsiloxane (PDMS) substrate, denoted as LNM-1, LNM-2, [...] Read more.
We propose a simulation-based design for a flexible color filter (FCF) using a lithium niobate metamaterial (LNM) to investigate its color filtering potential. The FCF is composed of three periodically arranged half-ellipse LN arrays on a polydimethylsiloxane (PDMS) substrate, denoted as LNM-1, LNM-2, and LNM-3. The electromagnetic responses of the FCF can be controlled by adjusting the periods of the LNMs. Our simulations predict high-quality (Q) factors in transmission spectra, ranging from 100 to 200 for LNM-1, 290 to 360 for LNM-2, and 140 to 300 for LNM-3. When the FCF is exposed to the surrounding environments with different refractive indexes, it exhibits a theoretical figure of merit (FOM) up to 900 RIU−1 and a sensitivity reaching 130 nm/RIU. The electromagnetic field distributions reveal strong confinement within the LNM nanostructures, confirming an efficient light–matter interaction. These results indicate that the proposed LNM-based FCF presents a promising design concept for high-performance color sensing and filtering applications. Full article
(This article belongs to the Special Issue Photonics Metamaterials: Processing and Applications)
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17 pages, 7508 KiB  
Article
Supramolecular Graphene Quantum Dots/Porphyrin Complex as Fluorescence Probe for Metal Ion Sensing
by Mariachiara Sarà, Andrea Romeo, Gabriele Lando, Maria Angela Castriciano, Roberto Zagami, Giovanni Neri and Luigi Monsù Scolaro
Int. J. Mol. Sci. 2025, 26(15), 7295; https://doi.org/10.3390/ijms26157295 - 28 Jul 2025
Viewed by 233
Abstract
Graphene quantum dots (GQDs) obtained by microwave-induced pyrolysis of glutamic acid and triethylenetetramine (trien) are fairly stable, emissive, water-soluble, and positively charged nano-systems able to interact with negatively charged meso-tetrakis(4-sulfonatophenyl) porphyrin (TPPS4). The stoichiometric control during the preparation affords a [...] Read more.
Graphene quantum dots (GQDs) obtained by microwave-induced pyrolysis of glutamic acid and triethylenetetramine (trien) are fairly stable, emissive, water-soluble, and positively charged nano-systems able to interact with negatively charged meso-tetrakis(4-sulfonatophenyl) porphyrin (TPPS4). The stoichiometric control during the preparation affords a supramolecular adduct, GQDs@TPPS4, that exhibits a double fluorescence emission from both the GQDs and the TPPS4 fluorophores. These supramolecular aggregates have an overall negative charge that is responsible for the condensation of cations in the nearby aqueous layer, and a three-fold acceleration of the metalation rates of Cu2+ ions has been observed with respect to the parent porphyrin. Addition of various metal ions leads to some changes in the UV/Vis spectra and has a different impact on the fluorescence emission of GQDs and TPPS4. The quenching efficiency of the TPPS4 emission follows the order Cu2+ > Hg2+ > Cd2+ > Pb2+ ~ Zn2+ ~ Co2+ ~ Ni2+ > Mn2+ ~ Cr3+ >> Mg2+ ~ Ca2+ ~ Ba2+, and it has been related to literature data and to the sitting-atop mechanism that large transition metal ions (e.g., Hg2+ and Cd2+) exhibit in their interaction with the macrocyclic nitrogen atoms of the porphyrin, inducing distortion and accelerating the insertion of smaller metal ions, such as Zn2+. For the most relevant metal ions, emission quenching of the porphyrin evidences a linear behavior in the micromolar range, with the emission of the GQDs being moderately affected through a filter effect. Deliberate pollution of the samples with Zn2+ reveals the ability of the GQDs@TPPS4 adduct to detect sensitively Cu2+, Hg2+, and Cd2+ ions. Full article
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24 pages, 8612 KiB  
Article
Experimental Investigation of the Seismic Behavior of a Multi-Story Steel Modular Building Using Shaking Table Tests
by Xinxin Zhang, Yucong Nie, Kehao Qian, Xinyu Xie, Mengyang Zhao, Zhan Zhao and Xiang Yuan Zheng
Buildings 2025, 15(15), 2661; https://doi.org/10.3390/buildings15152661 - 28 Jul 2025
Viewed by 267
Abstract
A steel modular building is a highly prefabricated form of steel construction. It offers rapid assembly, a high degree of industrialization, and an environmentally friendly construction site. To promote the application of multi-story steel modular buildings in earthquake fortification zones, it is imperative [...] Read more.
A steel modular building is a highly prefabricated form of steel construction. It offers rapid assembly, a high degree of industrialization, and an environmentally friendly construction site. To promote the application of multi-story steel modular buildings in earthquake fortification zones, it is imperative to conduct in-depth research on their seismic behavior. In this study, a seven-story modular steel building is investigated using shaking table tests. Three seismic waves (artificial ground motion, Tohoku wave, and Tianjin wave) are selected and scaled to four intensity levels (PGA = 0.035 g, 0.1 g, 0.22 g, 0.31 g). It is found that no residual deformation of the structure is observed after tests, and its stiffness degradation ratio is 7.65%. The largest strains observed during the tests are 540 × 10−6 in beams, 1538 × 10−6 in columns, and 669 × 10−6 in joint regions, all remaining below a threshold value of 1690 × 10−6. Amplitudes and frequency characteristics of the acceleration responses are significantly affected by the characteristics of the seismic waves. However, the acceleration responses at higher floors are predominantly governed by the structure’s low-order modes (first-mode and second-mode), with the corresponding spectra containing only a single peak. When the predominant frequency of the input ground motion is close to the fundamental natural frequency of the modular steel structure, the acceleration responses will be significantly amplified. Overall, the structure demonstrates favorable seismic resistance. Full article
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24 pages, 5866 KiB  
Article
Multiscale Characterization of Thermo-Hydro-Chemical Interactions Between Proppants and Fluids in Low-Temperature EGS Conditions
by Bruce Mutume, Ali Ettehadi, B. Dulani Dhanapala, Terry Palisch and Mileva Radonjic
Energies 2025, 18(15), 3974; https://doi.org/10.3390/en18153974 - 25 Jul 2025
Viewed by 259
Abstract
Enhanced Geothermal Systems (EGS) require thermochemically stable proppant materials capable of sustaining fracture conductivity under harsh subsurface conditions. This study systematically investigates the response of commercial proppants to coupled thermo-hydro-chemical (THC) effects, focusing on chemical stability and microstructural evolution. Four proppant types were [...] Read more.
Enhanced Geothermal Systems (EGS) require thermochemically stable proppant materials capable of sustaining fracture conductivity under harsh subsurface conditions. This study systematically investigates the response of commercial proppants to coupled thermo-hydro-chemical (THC) effects, focusing on chemical stability and microstructural evolution. Four proppant types were evaluated: an ultra-low-density ceramic (ULD), a resin-coated sand (RCS), and two quartz-based silica sands. Experiments were conducted under simulated EGS conditions at 130 °C with daily thermal cycling over a 25-day period, using diluted site-specific Utah FORGE geothermal fluids. Static batch reactions were followed by comprehensive multi-modal characterization, including scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS), X-ray diffraction (XRD), and micro-computed tomography (micro-CT). Proppants were tested in both granular and powdered forms to evaluate surface area effects and potential long-term reactivity. Results indicate that ULD proppants experienced notable resin degradation and secondary mineral precipitation within internal pore networks, evidenced by a 30.4% reduction in intragranular porosity (from CT analysis) and diminished amorphous peaks in the XRD spectra. RCS proppants exhibited a significant loss of surface carbon content from 72.98% to 53.05%, consistent with resin breakdown observed via SEM imaging. While the quartz-based sand proppants remained morphologically intact at the macro-scale, SEM-EDS revealed localized surface alteration and mineral precipitation. The brown sand proppant, in particular, showed the most extensive surface precipitation, with a 15.2% increase in newly detected mineral phases. These findings advance understanding of proppant–fluid interactions under low-temperature EGS conditions and underscore the importance of selecting proppants based on thermo-chemical compatibility. The results also highlight the need for continued development of chemically resilient proppant formulations tailored for long-term geothermal applications. Full article
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23 pages, 3875 KiB  
Article
Soil Water-Soluble Ion Inversion via Hyperspectral Data Reconstruction and Multi-Scale Attention Mechanism: A Remote Sensing Case Study of Farmland Saline–Alkali Lands
by Meichen Liu, Shengwei Zhang, Jing Gao, Bo Wang, Kedi Fang, Lu Liu, Shengwei Lv and Qian Zhang
Agronomy 2025, 15(8), 1779; https://doi.org/10.3390/agronomy15081779 - 24 Jul 2025
Viewed by 570
Abstract
The salinization of agricultural soils is a serious threat to farming and ecological balance in arid and semi-arid regions. Accurate estimation of soil water-soluble ions (calcium, carbonate, magnesium, and sulfate) is necessary for correct monitoring of soil salinization and sustainable land management. Hyperspectral [...] Read more.
The salinization of agricultural soils is a serious threat to farming and ecological balance in arid and semi-arid regions. Accurate estimation of soil water-soluble ions (calcium, carbonate, magnesium, and sulfate) is necessary for correct monitoring of soil salinization and sustainable land management. Hyperspectral ground-based data are valuable in soil salinization monitoring, but the acquisition cost is high, and the coverage is small. Therefore, this study proposes a two-stage deep learning framework with multispectral remote-sensing images. First, the wavelet transform is used to enhance the Transformer and extract fine-grained spectral features to reconstruct the ground-based hyperspectral data. A comparison of ground-based hyperspectral data shows that the reconstructed spectra match the measured data in the 450–998 nm range, with R2 up to 0.98 and MSE = 0.31. This high similarity compensates for the low spectral resolution and weak feature expression of multispectral remote-sensing data. Subsequently, this enhanced spectral information was integrated and fed into a novel multiscale self-attentive Transformer model (MSATransformer) to invert four water-soluble ions. Compared with BPANN, MLP, and the standard Transformer model, our model remains robust across different spectra, achieving an R2 of up to 0.95 and reducing the average relative error by more than 30%. Among them, for the strongly responsive ions magnesium and sulfate, R2 reaches 0.92 and 0.95 (with RMSE of 0.13 and 0.29 g/kg, respectively). For the weakly responsive ions calcium and carbonate, R2 stays above 0.80 (RMSE is below 0.40 g/kg). The MSATransformer framework provides a low-cost and high-accuracy solution to monitor soil salinization at large scales and supports precision farmland management. Full article
(This article belongs to the Special Issue Water and Fertilizer Regulation Theory and Technology in Crops)
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26 pages, 9566 KiB  
Article
How Does Energy Harvesting from a Fluttering Foil Influence Its Nonlinear Dynamics?
by Dilip Thakur, Faisal Muhammad and Muhammad Saif Ullah Khalid
Energies 2025, 18(15), 3897; https://doi.org/10.3390/en18153897 - 22 Jul 2025
Viewed by 221
Abstract
This study investigates the nonlinear aeroelastic behavior and energy harvesting performance of a two-degrees-of-freedom NACA 0012 airfoil under varying reduced velocities and electrical load resistances. The system exhibits a range of dynamic responses, including periodic and chaotic states, governed by strong fluid–structure interactions. [...] Read more.
This study investigates the nonlinear aeroelastic behavior and energy harvesting performance of a two-degrees-of-freedom NACA 0012 airfoil under varying reduced velocities and electrical load resistances. The system exhibits a range of dynamic responses, including periodic and chaotic states, governed by strong fluid–structure interactions. Nonlinear oscillations first appear near the critical reduced velocity Ur*=6, with large-amplitude limit-cycle oscillations emerging around Ur*=8 in the absence of the electrical loading. As the load resistance increases, this transition shifts to higher Ur*, reflecting the damping effect of the electrical load. Fourier spectra reveal the presence of odd and even superharmonics in the lift coefficient, indicating nonlinearities induced by fluid–structure coupling, which diminishes at higher resistances. Phase portraits and Poincaré maps capture transitions across dynamical regimes, from periodic to chaotic behavior, particularly at a low resistance. The voltage output correlates with variations in the lift force, reaching its maximum at an intermediate resistance before declining due to a suppressing nonlinearity. Flow visualizations identify various vortex shedding patterns, including single (S), paired (P), triplet (T), multiple-pair (mP) and pair with single (P + S) that weaken at higher resistances and reduced velocities. The results demonstrate that nonlinearity plays a critical role in efficient voltage generation but remains effective only within specific parameter ranges. Full article
(This article belongs to the Section A3: Wind, Wave and Tidal Energy)
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17 pages, 2607 KiB  
Article
One-Pot Synthesis of Phenylboronic Acid-Based Microgels for Tunable Gate of Glucose-Responsive Insulin Release at Physiological pH
by Prashun G. Roy, Jiangtao Zhang, Koushik Bhattacharya, Probal Banerjee, Jing Shen and Shuiqin Zhou
Molecules 2025, 30(15), 3059; https://doi.org/10.3390/molecules30153059 - 22 Jul 2025
Viewed by 284
Abstract
Glucose-responsive insulin delivery systems that effectively regulate insulin retention and release in response to real-time fluctuation of glucose levels are highly desirable for diabetes care with minimized risk of hypoglycemia. Herein, we report a class of glucose-sensitive copolymer microgels, prepared from a simple [...] Read more.
Glucose-responsive insulin delivery systems that effectively regulate insulin retention and release in response to real-time fluctuation of glucose levels are highly desirable for diabetes care with minimized risk of hypoglycemia. Herein, we report a class of glucose-sensitive copolymer microgels, prepared from a simple one-pot precipitation copolymerization of 4-vinylphenylboronic acid (VPBA), 2-(dimethylamino) ethyl acrylate (DMAEA), and oligo(ethylene glycol) methyl ether methacrylate (Mw = 300, MEO5MA), for gated glucose-responsive insulin release within the physiologically desirable glucose level range. The composition of the p(VPBA-DMAEA-MEO5MA) copolymer microgels were analyzed using NMR and FTIR spectra. The cis-diols of glucose can reversibly bind with the −B(OH)2 groups of the VPBA component in the microgels, resulting in the formation of negatively charged boronate esters that induce the volume phase transition of the microgels. The DMAEA component is incorporated to reduce the pKa of VPBA, thus improving the glucose sensitivity of the microgels at physiological pH. The neutral hydrophilic MEO5MA component is used to tune the onset of the glucose responsiveness of the microgels to the physiologically desirable levels. The more the MEO5MA component copolymerized in the microgels, the greater the glucose concentration required to initiate the swelling of the microgels to trigger the release of insulin. When the onset of the glucose response was tuned to 4−5 mM, the copolymer microgels retained insulin effectively in the hypo-/normo-glycemic range but also released insulin efficiently in response to the elevation of glucose levels in the hyperglycemic range, which is essential for diabetes management. The copolymer microgels display no cytotoxicity in vitro. Full article
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20 pages, 1461 KiB  
Article
Vulnerability-Based Economic Loss Rate Assessment of a Frame Structure Under Stochastic Sequence Ground Motions
by Zheng Zhang, Yunmu Jiang and Zixin Liu
Buildings 2025, 15(15), 2584; https://doi.org/10.3390/buildings15152584 - 22 Jul 2025
Viewed by 232
Abstract
Modeling mainshock–aftershock ground motions is essential for seismic risk assessment, especially in regions experiencing frequent earthquakes. Recent studies have often employed Copula-based joint distributions or machine learning techniques to simulate the statistical dependency between mainshock and aftershock parameters. While effective at capturing nonlinear [...] Read more.
Modeling mainshock–aftershock ground motions is essential for seismic risk assessment, especially in regions experiencing frequent earthquakes. Recent studies have often employed Copula-based joint distributions or machine learning techniques to simulate the statistical dependency between mainshock and aftershock parameters. While effective at capturing nonlinear correlations, these methods are typically black box in nature, data-dependent, and difficult to generalize across tectonic settings. More importantly, they tend to focus solely on marginal or joint parameter correlations, which implicitly treat mainshocks and aftershocks as independent stochastic processes, thereby overlooking their inherent spectral interaction. To address these limitations, this study proposes an explicit and parameterized modeling framework based on the evolutionary power spectral density (EPSD) of random ground motions. Using the magnitude difference between a mainshock and an aftershock as the control variable, we derive attenuation relationships for the amplitude, frequency content, and duration. A coherence function model is further developed from real seismic records, treating the mainshock–aftershock pair as a vector-valued stochastic process and thus enabling a more accurate representation of their spectral dependence. Coherence analysis shows that the function remains relatively stable between 0.3 and 0.6 across the 0–30 Rad/s frequency range. Validation results indicate that the simulated response spectra align closely with recorded spectra, achieving R2 values exceeding 0.90 and 0.91. To demonstrate the model’s applicability, a case study is conducted on a representative frame structure to evaluate seismic vulnerability and economic loss. As the mainshock PGA increases from 0.2 g to 1.2 g, the structure progresses from slight damage to complete collapse, with loss rates saturating near 1.0 g. These findings underscore the engineering importance of incorporating mainshock–aftershock spectral interaction in seismic damage and risk modeling, offering a transparent and transferable tool for future seismic resilience assessments. Full article
(This article belongs to the Special Issue Structural Vibration Analysis and Control in Civil Engineering)
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16 pages, 4720 KiB  
Article
Optical Response Tailoring via Morphosynthesis of Ag@Au Nanoparticles
by David Oswaldo Romero-Quitl, Siva Kumar Krishnan, Martha Alicia Palomino-Ovando, Orlando Hernández-Cristobal, José Concepción Torres-Guzmán, Jesús Eduardo Lugo and Miller Toledo-Solano
Nanomaterials 2025, 15(14), 1125; https://doi.org/10.3390/nano15141125 - 19 Jul 2025
Viewed by 330
Abstract
We present a simple method for customizing the optical characteristics of gold-core, silver-shell (Au@Ag) nanoparticles through controlled morphosynthesis via a seed-mediated chemical reduction approach. By systematically adjusting the concentration of cetyltrimethylammonium chloride (CTAC), we obtained precise control over both the thickness of the [...] Read more.
We present a simple method for customizing the optical characteristics of gold-core, silver-shell (Au@Ag) nanoparticles through controlled morphosynthesis via a seed-mediated chemical reduction approach. By systematically adjusting the concentration of cetyltrimethylammonium chloride (CTAC), we obtained precise control over both the thickness of the Ag shell and the particle shape, transitioning from spherical nanoparticles to distinctly defined nanocubes. Bright field and high-angle annular dark-field scanning transmission electron microscopy (BF-STEM and HAADF-STEM), and energy-dispersive X-ray spectroscopy (EDS) were employed to validate the structural and compositional changes. To link morphology with optical behavior, we utilized the Mie and Maxwell–Garnett theoretical models to simulate the dielectric response of the core–shell nanostructures, showing trends that align with experimental UV-visible absorption spectra. This research presents an easy and adjustable method for modifying the plasmonic properties of Ag@Au nanoparticles by varying their shape and shell, offering opportunities for advanced applications in sensing, photonics, and nanophotonics. Full article
(This article belongs to the Section Nanophotonics Materials and Devices)
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18 pages, 11678 KiB  
Article
Inclusions, Chemical Composition, and Spectral Characteristics of Pinkish-Purple to Purple Spinels from Mogok, Myanmar
by Danyu Guo, Geng Li, Liqun Weng, Meilun Zhang and Fabian Dietmar Schmitz
Crystals 2025, 15(7), 659; https://doi.org/10.3390/cryst15070659 - 19 Jul 2025
Viewed by 213
Abstract
With the increasing market demand for spinels of various colors, purple spinel—long regarded as a symbol of nobility—has attracted growing attention. In this study, pinkish-purple to purple spinels from the Mogok region of Myanmar were systematically examined using conventional gemological, spectroscopic, and chemical [...] Read more.
With the increasing market demand for spinels of various colors, purple spinel—long regarded as a symbol of nobility—has attracted growing attention. In this study, pinkish-purple to purple spinels from the Mogok region of Myanmar were systematically examined using conventional gemological, spectroscopic, and chemical analytical techniques. Raman analysis reveals that these spinels commonly contain octahedral inclusions composed of calcite, dolomite, magnesite, and graphite. Chemically, the samples are primarily magnesia-alumina spinels. Color variation is influenced by trace elements: increasing Cr and V contents enhance the red hue, while higher Fe concentrations intensify the purple tone. UV–Vis spectra show that Cr3+ and V3+ jointly contribute to absorptions at 388 nm and 548 nm, with Fe2+ and Fe3+ responsible for the bands at 371 nm and 457 nm, respectively, together controlling the pink-to-purple color variation. Most samples display four Cr3+-related peaks near 700 nm; however, these are absent in deeply purple spinels. In contrast, light pink spinels show weaker absorption at 371 nm and 457 nm, attributed to Fe2+ and Fe3+. Fluorescence spectra confirm characteristic Cr3+ emission bands at 673 nm, 684 nm, 696 nm, 706 nm, and 716 nm, indicating a strong crystal field environment. Raman spectra have peaks mainly around 312 cm−1, 406 cm−1, 665 cm−1, and 768 cm−1. The peaks of the infrared spectrum mainly appear around 840 cm−1, 729 cm−1, 587 cm−1, 545 cm−1, and 473 cm−1. Full article
(This article belongs to the Collection Topic Collection: Mineralogical Crystallography)
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23 pages, 4894 KiB  
Article
Evaluating Copper-Induced Oxidative Stress in Germinating Wheat Seeds Using Laser Photoacoustic Spectroscopy and EPR Techniques
by Mioara Petrus, Cristina Popa, Ana-Maria Bratu, Alexandra Camelia Joita and Vasile Bercu
Toxics 2025, 13(7), 604; https://doi.org/10.3390/toxics13070604 - 18 Jul 2025
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Abstract
Copper is an essential micronutrient for plants, but excessive levels can induce toxicity and impair physiological functions. This study evaluates the toxic effects of copper sulfate (CuSO4) on the germination of common wheat (Triticum aestivum), with emphasis on the [...] Read more.
Copper is an essential micronutrient for plants, but excessive levels can induce toxicity and impair physiological functions. This study evaluates the toxic effects of copper sulfate (CuSO4) on the germination of common wheat (Triticum aestivum), with emphasis on the gas emission dynamics and oxidative stress biomarkers. Seeds were germinated in agar and exposed to CuSO4 at concentrations of 1 µM, 100 µM, 1 mM, and 10 mM; distilled water served as the control. Ethylene and ammonia emissions were quantified using CO2 laser photoacoustic spectroscopy, while electron paramagnetic resonance (EPR) spectroscopy was employed to detect free radicals and Cu2+ complexes. Exposure to Cu concentrations ≥ 1 mM significantly inhibited germination and biomass accumulation. Enhanced ethylene and ammonia emissions, particularly at 10 mM, indicated stress-related metabolic responses. The EPR spectra confirmed the presence of semiquinone radicals and Cu2+ complexes under higher Cu levels. These results demonstrate that photoacoustic and EPR techniques are effective tools for the early detection of metal-induced phytotoxicity and offer a non-invasive approach to environmental toxicity screening and plant stress assessment. Full article
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