Search Results (1,891)

This article presents an experimental investigation of the effect of water aging on the static mechanical behavior and damage mechanisms of bio-based sandwich structures with auxetic cores using acoustic emission (AE) monitoring. Both the skins and the core are manufactured by 3D printing using polylactic acid (PLA) reinforced with short flax fibers. Four auxetic core configurations, differing in the number of unit cells across the core width, are considered. The specimens are immersed in water at room temperature to characterize their absorption behavior, which follows a Fickien’s diffusion law model with different saturation levels. Static three-point bending tests are performed at various immersion times to evaluate the influence of moisture on mechanical performance. The results show a progressive degradation of mechanical properties with increasing water exposure time, with the four-cell core configuration exhibiting the highest mechanical performance. Acoustic emission (AE) monitoring is employed to analyze damage evolution as a function of hydrothermal aging. AE parameters such as amplitude, energy, and cumulative event count are used to identify and classify the different damage mechanisms. This approach highlights the effectiveness of acoustic emission for structural health monitoring and for assessing the durability of auxetic core sandwich structures subjected to moisture. Full article

This paper proposes and experimentally validates a label-free microdroplet concentration detector based on a quad-resonator metamaterial. The device exploits the linear relationship between the dielectric constant of a binary mixed solution and its concentration, mapping concentration information to absorption frequency shifts with a sensitivity of 28.53 GHz/RIU. System modeling was performed through full-wave simulation. Experimental results demonstrate a highly linear relationship between resonance frequency shift and concentration across ethanol, water, and ethanol–water solutions. The relative deviation between simulation and measurement is less than 3%, validating the model’s reliability and the robustness of the detection principle. This detector supports rapid non-contact sample replacement without requiring chemical labeling or specialized packaging. It can be mass-produced on standard PDMS substrates, with each unit reusable for >50 cycles. With a single measurement time of <30 s, it meets high-throughput detection demands. Featuring low power consumption, high precision, and scalability, this device holds broad application prospects in point-of-care diagnostics, online process monitoring, and resource-constrained scenarios. Future work will focus on achieving simultaneous multi-component detection via multi-resonator arrays and integrating chip-level wireless readout modules to further enhance portability and system integration. Full article

Advanced oxidation processes using porphyrin-based heterogeneous catalysts hold promise for removing hazardous pollutants from wastewater. Their high visible-light absorption coefficients enable absorption of light from the solar spectrum. Moreover, their conjugated aromatic skeletons and intrinsic electronic properties facilitate the delocalization of photogenerated electrons during photodegradation. Delaying the recombination of photogenerated electron–hole pairs by introducing specific materials increases efficiency, as separated charges have more time to participate in redox reactions, boosting photocatalytic activities. However, applying these photocatalysts for wastewater treatment is challenging owing to facile agglomeration, deactivation, and recovery of the photocatalyst for reuse, which can significantly increase the overall cost. Therefore, new photocatalytic systems comprising porphyrin molecules must be developed. For this purpose, porphyrins can be conjugated to nanomaterials to create hybrid materials with photocatalytic efficiencies superior to those of free-standing starting porphyrins. Various transition metal oxides (TiO₂, ZnO, and Fe₃O₄) nanoparticles, main-group-element oxides (Al₂O₃ and SiO₂) nanoparticles, metal plasmons (silver nanoparticles), carbon-based platforms (graphene, graphene oxide, and g-C₃N₄), and polymer matrices have been used as nanostructured solid supports for the successful fabrication of porphyrin-conjugated hybrid materials. The conjugation of porphyrin molecules to solid supports improves the photocatalytic degradation activity in terms of visible-light conversion ability, recyclability, active porous sites, substrate mobility, separation of photogenerated charge species, recovery for reuse, and chemical stability, along with preventing the generation of secondary pollution. This review discusses the ongoing development of porphyrin-conjugated hybrid nanomaterials for the heterogeneous photocatalytic degradation of organic dyes, pharmaceutical pollutants, heavy metals, pesticides, and human care in water. Several important results and advancements in the field allow for a more efficient wastewater remediation process. Full article

Lightweight concretes have gained great momentum in construction in the last decade, due to the large number of sustainable characteristics and construction advantages associated with them. The sustainability of lightweight concrete depends mainly on the application of sustainable aggregates, such as the amorphous opalized tuff, found in large quantities in Eastern Macedonia. It is economically viable, easy to extract from surface mines, and easy to process. The physical, chemical, and mechanical properties, porosity, and water absorption of the tuff as a stone aggregate were examined as the aim of this study, with the objective of assessing its potential application in lightweight concrete. The tuff showed an average bulk density 87.2% lower than that of limestone. The compressive strength of the tested opalized tuff samples was 41.16 MPa, or 48.5% of the average strength of limestone rock (84.88 MPa). Furthermore, three concrete mixes with different aggregates were tested: with 100% limestone, with 50% tuff and 50% limestone, and with 100% tuff. The increase in the amount of tuff in the concrete mix required a larger amount of water, due to the high porosity of the tuff; the high water absorption of the tuff aggregate reduced the consistency of the concrete mix, so the bulk density decreased significantly with increasing tuff content. The concrete with 100% tuff aggregate was 44% lighter than concrete with 100% limestone aggregate, which means that concrete–tuff mixes can be classified as lightweight concrete. Our results further showed that by increasing the amount of opalized tuff aggregate in the concrete, the compressive strength of the hardened concrete decreased. The 50:50 mix showed an average compressive strength of 25.68 MPa at 28 days, i.e., 42% lower than the average compressive strength for limestone concrete (44.27 MPa). The tuff-only mix exhibited a compressive strength of 10.46 MPa that was 76.4% lower than limestone-only concrete. The increase in the amount of tuff in the concrete was shown to reduce the thermal conductivity; i.e., concrete with tuff aggregate showed a thermal conductivity coefficient of 0.3585 W/m·K, which is 5.58 times lower than that of conventional concrete with limestone aggregate. The results from the laboratory analyses provide guidance for the application of the local amorphous opalized tuff as a natural stone and as a filler for producing lightweight mortars and concretes. Every alternative and possibility for its application would contribute to reducing waste, reducing energy consumption in buildings, and thus creating an ecologically safe environment. The application of opalized tuff in lightweight concrete will support green jobs and the circular economy using locally available, alternative material, through reducing transportation emissions and decreasing waste. Full article

Oily sludge is a complex emulsified waste consisting of water, oil, and solid particles. Conventional treatments are often inefficient, energy-intensive, and prone to causing secondary pollution. This study proposes a green demulsification technology based on ozone micro–nanobubbles (O₃MNBs) by constructing an experimental system to analyze its effects and mechanisms of action on oily sludge treatment. The O₃MNBs exhibited a mean particle size of 831 nm and generated a substantial amount of hydroxyl radicals (·OH, 250.4 μmol·L⁻¹) in situ. Compared with conventional aeration, the dissolved ozone concentration and residence time in water of O₃MNBs increased by 192% and 213%, respectively. During bubble collapse, intense pressure waves and high-speed microjets were generated to disrupt sludge aggregates, promoting the dispersion of sludge particles while simultaneously stripping oil films. Thus, the oil removal rate reached 41.5%, demonstrating the high demulsification efficiency of O₃MNBs. Furthermore, ozone and ·OH attacked alkane C-H bonds in the oil phase, oxidizing hydrophobic films into hydrophilic products and decomposing surfactants that stabilize emulsions. This process promoted oil droplet coalescence and degradation into small organic molecules. After O₃MNB treatment, the absorption peak of alkane C-H bonds gradually reduced, while a new C=O absorption peak appeared. This study provides a theoretical foundation and technical support for environmentally sustainable treatment of oily sludge by O₃MNB application, offering an effective alternative to chemical demulsification without secondary pollution. Full article

The discharge of dye-contaminated effluents from textile industries into water bodies poses a severe threat to aquatic ecosystems and human health. To address this challenge, cellulose and interpenetrating polymer network (IPN) hydrogels based on cellulose and poly(vinyl alcohol) (PVA) were developed via an in situ synthesis method. The cellulose solution was obtained by cold dissolving the polysaccharide in NaOH, then dissolving PVA. The IPN hydrogels were obtained by co-cross-linking the two polymers in an alkaline medium using ECH. To optimize the hydrogels, synthesis parameters like time (4–7 h), temperature (50–80 °C), and cross-linking ratio (ECH = 50–125% w/w) were varied. Different hydrogel compositions (Cel/PVA = 90/10 to 60/40 w/w) were tested for their absorption efficiency in removing Tubantin Blue (DB 78) dye under varying initial concentrations and temperatures. Hydrogels exhibit varying adsorption capacities for DB78, depending on their IPN composition, synthesis parameters, and dye concentration. Specifically, IPN adsorption capacity ranges from 8.8 to 38.1 mg DB78/g hydrogel (7.5–36.2% efficiency). At high effluent concentrations, IPN can reach a retention capacity of 217.7 mg/g, achieving a retention efficiency of 58.4%. Cellulose and cellulose/PVA IPN hydrogels show promise as sustainable adsorbents for treating dye-contaminated wastewater. Full article

Background/Objectives: Enhancing excipient functionality through environmentally friendly and scalable processing methods is essential for improving the manufacturability and performance of orally disintegrating tablets (ODTs). Microwave-assisted wet granulation enables controlled microstructural modification without chemical alteration of excipient components. This study aimed to develop and evaluate a rice starch (RS)–mannitol co-processed excipient using microwave-assisted wet granulation for direct compression of ODTs. Methods: RS and mannitol were co-processed by wet granulation followed by microwave treatment under varying power levels and irradiation times. The effects of processing conditions on granule morphology, solid-state properties, porosity, powder flow, compressibility, wettability, and disintegration behavior were systematically investigated. The optimized excipient was further evaluated in ODT formulations containing chlorpheniramine maleate and piroxicam and benchmarked against a commercial co-processed excipient (Starlac^®). Results: Microwave treatment generated internal vapor pressure that promoted pore formation and particle agglomeration, resulting in enhanced powder flowability (compressibility index 8.4–10.8%). Partial crystallinity reduction and microstructural modification improved compressibility and surface wettability compared with non-microwave-treated materials. The optimized formulation (MW-RM-H-30) exhibited rapid wetting (25 s), high water absorption (90.5%), low contact angle (42°), and fast tablet disintegration (31 s). ODTs prepared with MW-RM-H-30 showed rapid disintegration (42 s for chlorpheniramine maleate and 32 s for piroxicam) and dissolution behavior comparable to Starlac^®. Conclusions: Microwave-assisted wet granulation provides an efficient, scalable, and environmentally friendly strategy for engineering starch-based co-processed excipients with enhanced functionality for direct compression ODT applications. The developed excipient demonstrates strong potential for solid dosage form manufacturing. Full article

Emerging landslides and severe floods highlight the urgent need to analyse and support predictive models and early warning systems. Soil moisture is a crucial parameter and it can now be determined from space with a resolution of a few tens of meters, potentially leading to the continuous global monitoring of landslide risk. We address this issue by determining the volumetric water content (VWC) of a testbed in Southern Italy (bare soil with significant flood and landslide hazard) through the comparison of two different satellite observations on the same day. In the first observation (Sentinel-1 mission of the European Space Agency, C-band Synthetic Aperture Radar (SAR)), the back-scattered radar signal is used to determine the VWC from the dielectric constant in the microwave range, using a time-series approach to calibrate the algorithm. In the second observation (hyperspectral PRISMA mission of the Italian Space Agency), the short-wave infrared (SWIR) reflectance spectra are used to calculate the VWC from the spectral weight of a vibrational absorption line of liquid water (wavelengths 1800–1950 nm). As the main result, we obtained a Pearson’s correlation coefficient of $0.4$ between the VWC values measured with the two techniques and a separate ground-truth confirmation of absolute VWC values in the range of 0.10–0.30 within $\pm 0.05$. This overlap validates that both SAR and hyperspectral data can be well calibrated and mapped with 30 m ground resolution, given the absence of artifacts or anomalies in this particular testbed (e.g., vegetation canopy or cloud presence). If hyperspectral data in the SWIR range become more broadly available in the future, our systematic procedure to synchronise these two technologies in both space and time can be further adapted to cross-validate the global high-resolution soil moisture dataset. Ultimately, multi-mission data integration could lead to quasi-real-time hydrogeological risk monitoring from space. Full article

In this work, highly water-soluble silk fibroin (SF) is first prepared by recrystallizing degummed silkworm cocoon fibers in concentrated CaCl₂ solution (replacing the conventional Ajisawa’s reagent), and then used as both stabilizing and reducing agents to synthesize copper nanoclusters (Cu@SF NCs) at pH = 11. Due to the existence of unreacted Cu²⁺ ions, the resulting SF-templated Cu NCs form slight aggregates, yielding a purple-colored solution with blue fluorescence. Interestingly, upon adding the pesticide 2,4-dichlorophenoxyacetic acid (2,4-D), the Cu NCs aggregates disassemble and the fluorescence is significantly enhanced, creating a “fluorescence-on” sensor for 2,4-D with a detection limit of 0.65 μM. In contrast, the pollutant p-nitrophenol (p-NP) quenches the fluorescence of Cu NCs via a fluorescence resonance energy transfer mechanism (with a detection limit as low as 1.35 nM), which is attributed to the large overlap between absorption spectrum of p-NP and excitation spectrum of Cu NCs. Other tested analytes (i.e., pyrifenox, carbofuran and melamine) produce negligible fluorescence changes. The distinct sensing mechanisms are elucidated with experimental evidence and density functional theory (DFT) calculations. The evolutions of fluorescence as a function of incubation time and analyte concentration are systematically investigated, demonstrating a versatile platform for sensitive and selective detection of target analytes. These findings provide an effective strategy for optimizing the optical properties of metal nanoclusters and improving their performance in environmental applications. Full article

Recycling wastewater from washing concrete trucks in concrete production addresses both economic and sustainability needs. In the present article, wastewater from washing concrete trucks was added to cement pastes made with two different types of cement for comparison. OPC type CEM I 42.5 was compared to pozzolanic cement type CEM IV/B (P-W) 32.5 in terms of hydration behavior and compressive strength development. The hydration of ordinary Portland cement (CEM I 42.5) was accelerated, while the hydration of pozzolanic cement (CEM IV 32.5) showed a relatively lower total normalized heat. Cement pastes were produced from both cement types, and compressive strength, thermal analysis, and setting time tests were performed for their characterization. The early-age kinetics and compressive strength development of CEM I 42.5 pastes indicate that hydration with wastewater leads to a slight increase in compressive strength. Test concrete prepared with pozzolanic cement (CEM IV 32.5) exhibited increased capillary voids, which contributed to less favorable mechanical and durability performance. Compared to the reference concrete, compressive strength was reduced by 7% at 28 days. Wastewater utilization increased the initial absorption rate by approximately 20%, but the calculated chloride content at the exposed concrete surface decreased after the addition of wastewater compared to the control mix. The carbonation depth of concrete with wastewater increased by 1–2 mm, with an uneven penetration zone, but the compressive strength after carbonation increased. Overall, the type of cement used appears to significantly influence the performance of concrete prepared with wastewater. For wastewater collected from sedimentation tanks, replacing fresh water at a 100% rate and using it with pozzolanic cement to produce concrete, it seems that the mechanical properties and durability are only slightly affected. Full article

Temperature and relative humidity can significantly affect quality of paddy rice during storage. Limited studies established the link between storage time, environmental fluctuations, changes in grain and flour physicochemical properties, and culinary performances. In a West African context, IR 841 paddy rice variety was stored under humid–sub-humid (HSH), and dry (DRY) conditions for 12 months. Over 12 months, rice stored under DRY conditions experienced greater environmental fluctuations than rice stored under HSH conditions. Grain water absorption capacity (WAC) increased during storage under DRY conditions, rising from 3.3 ± 0.3 to 3.8 ± 0.3 g/g DM between 0 and 12 months. Flour amylose content and soluble solids remained relatively stable from month 0 to 6 in all conditions, and further under HSH conditions. The observed changes led to improved grain cooking performance after 6 months of storage under DRY conditions. After 12 months, a decrease in rice flour WAC and a peak in viscosity were observed, while mean particle size increased from 42 ± 1 to 67 ± 3 μm under HSH conditions and from 31 ± 3 to 83 ± 3 μm under DRY conditions. Storage time may reduce the breadmaking capacity of rice flour. Overall, environmental fluctuations under DRY conditions strongly affected rice grain and flour properties. Full article

Underwater optical images often exhibit severe color distortion, weak texture, and uneven illumination due to light absorption and scattering in water. These issues result in unstable feature detection and inaccurate image registration. To address these challenges, this paper proposes an underwater image stitching method that integrates ORB (Oriented FAST and Rotated BRIEF) feature extraction with a fixed-ratio constraint matching strategy. First, lightweight color and contrast enhancement techniques are employed to restore color balance and improve local texture visibility. Then, ORB descriptors are extracted and matched via a KNN (K-Nearest Neighbors) nearest-neighbor search, and Lowe’s ratio test is applied to eliminate false matches caused by weak texture similarity. Finally, the geometric transformation between image frames is estimated by incorporating robust optimization, ensuring stable homography computation. Experimental results on real underwater datasets show that the proposed method significantly improves stitching continuity and structural consistency, achieving 40–120% improvements in SSIM (Structural Similarity Index) and PSNR (peak signal-to-noise ratio) over conventional Harris–ORB + KNN, SIFT (scale-invariant feature transform) + BF (brute force), SIFT + KNN, and AKAZE (accelerated KAZE) + BF methods while maintaining processing times within one second. These results indicate that the proposed method is well-suited for real-time underwater environment perception and panoramic mapping on low-cost, micro-sized underwater robotic platforms. Full article

This study investigated the effect of fermentation time (24 and 48 h) on the pH, titratable acidity (TTA), phytochemicals, antioxidants, phenolic compounds, colour, functional, pasting, and thermal properties of flours from selected legumes (mung beans, haricot beans, butter beans, and black beans). The pH dropped significantly (p ≤ 0.05) after 48 h (6.61–4.91) of fermentation, with a corresponding increase in TTA, which ranged from 0.3 to 1.28 g lactic acid/100 g sample. Colour analysis showed that fermentation caused a decrease in L* values (2.97–23.86% reduction), with the highest reduction observed in black bean flour (23.86% at 24 h), along with an increase in the browning index. The total phenolic content increased significantly (p ≤ 0.05) in all the samples, with the most pronounced increase observed in mung bean 24 h (6.85 mg GAE/g). Similarly, the values for total flavonoid increased from 2.26 to 6.48 mg QE/g, and antioxidant activities such as DPPH ranged from 45.04 to 74.51%, FRAP from 1.65 to 8.03 Mm TE/g, and ABTS from 60.86 to 90.01%. Ultra-high performance liquid chromatography–photodiode array quantification of the targeted phenolic compounds showed a significant increase, with the highest notable increase for trans-ferulic acid in mung bean (330% after 48 h). Water absorption capacity generally showed an increase, whereas bulk density ranged from 0.55 to 0.91 g/cm³ and decreased in all legumes. There were differences in the pasting properties of the selected legumes. The peak time of unfermented butter bean was 33.08 min and remained constant at 33.15 min at 24 and 48 h of fermentation. Thermal analysis indicated the alteration of gelatinization parameters, with a decrease in peak temperature, whereas higher gelatinization enthalpy was observed. Findings from this study show that fermentation with the starter cultures can significantly improve the bioactive compound and functional properties of legume flours and thus act as potential ingredients in functional food development. Full article

Diabetes is a developing global health concern that cannot be cured, necessitating frequent blood glucose monitoring and dietary management. Photoacoustic Spectroscopy (PAS) in the mid-infrared (MIR) region has recently emerged as a viable noninvasive blood glucose monitoring technique. However, MIR-PAS confronts significant challenges: (i) Water absorption, which reduces light penetration, and (ii) interference from other blood components. This paper systematically analyzes the background of photoacoustic signal generation and proposes a differential PAS (DPAS) in the MIR region for removing the background signals arising from water and other interfering components of blood, which improves the overall detection sensitivity. A detailed mathematical model with an explanation for choosing two suitable MIR quantum cascade lasers for this differential scheme is presented here. For single-wavelength PAS (SPAS), a detection sensitivity of $1.537$ µPa mg⁻¹ dL was obtained from the proposed model. Alternatively, $2.333$µPa mg⁻¹ dL detection sensitivity was found by implementing the DPAS scheme, which is about 1.5 times higher than SPAS. Moreover, DPAS facilitates an additional parameter, a differential phase shift between two laser responses, that has an effective correlation with the glucose concentration variation. Thus, MIR-based DPAS could be an effective way of monitoring blood glucose levels noninvasively in the near future. Full article

In this work, kaolin/chitin (K/Ch) composite aerogels with different mass ratios were successfully fabricated via a freeze–drying approach. The influence of kaolin content on the microstructure, properties and hemostatic performance of the composite aerogels was systematically investigated. The results demonstrated that the incorporation of kaolin endowed the chitin-based aerogels with tunable porous structures, excellent water absorption capacity (up to 4282% for K_0.25/Ch₂), and enhanced water retention (73.7% for K₂/Ch₂ at 60 min). Moreover, the K/Ch composite aerogels exhibited good biodegradability, no cytotoxicity (cell viability > 91.9%), and no hemolysis (hemolysis rate < 1.5% at all test concentrations). In vitro hemostatic evaluations revealed that the composite aerogels exhibited rapid blood coagulation (blood clotting time of 16 s for K₂/Ch₂) with a blood coagulation index (BCI) as low as 0.5%, which was attributed to the synergistic effect of the physical adsorption of chitin and the coagulation cascade activation by kaolin. These findings indicated that the K/Ch composite aerogels could be used as novel natural hemostatic materials for potential effective and rapid hemostasis. Full article