Search Results (124)

Pectin is a multifunctional polysaccharide whose structural attributes, including degree of esterification (DE), molecular weight (MW), and branching, directly affect its gelling, emulsifying, and bioactive properties. Conventional pectin extraction relies on acid- or alkali-based methods that degrade the pectin structure, generate chemical waste, and alter its physicochemical and functional properties. Although novel methods such as ultrasound-assisted extraction (UAE), microwave-assisted extraction (MAE), and enzyme-assisted extraction (EAE) are recognized as environmentally friendly alternatives, they frequently use acids or alkalis as solvents. This review focuses on pectin extraction methods that do not involve acidic or alkaline solvents such as chelating agents, super/subcritical water, and deep eutectic solvents (DESs) composed of neutral components. This review also discusses how these alternative extraction methods can preserve or modify the key structural features of pectin, thereby influencing its monosaccharide composition, molecular conformation, and interactions with other biopolymers. Furthermore, the influence of these structural variations on the rheological properties, gelling behaviors, and potential applications of pectin in the food, pharmaceutical, and biomedical fields are discussed. This review provides insights into alternative strategies for obtaining structurally intact and functionally diverse pectin by examining the relationship between the extraction conditions and pectin functionality. Full article

As solid-state devices continue to advance, vacuum electron devices maintain critical importance due to their superior high-frequency power handling, long-term reliability, and operational efficiency. Among these, traveling-wave tubes (TWTs) excel in high-power microwave (HPM) applications, offering exceptional bandwidth and gain. However, developing THz-range TWT slow-wave structures (SWSs) presents significant design challenges. This work systematically outlines the SWS design methodology while addressing key obstacles and their solutions. As a demonstration, a staggered double vane (SDV) SWS operating at 1 THz (980–1080 GHz) achieves 650 mW output power, 23.35 dB gain, 0.14% electronic efficiency, and compact 21 mm length. Comparative analysis with deformed quasi-sine waveguide (D-QSWG) SWS confirms the SDV design’s superior performance for THz applications. Full article

American ginseng (Panax quinquefolium L.) residue from the extraction industry can be dried and mixed with rice bran as media for black truffle solid-state fermentation to enhance reuse and bioactive functions. Different ratios of rice bran (R) and American ginseng residue (G) mixtures were used as solid-state media for 5 weeks of black truffle fermentation, and then their bio-component contents and whitening effects were analyzed. Finally, four drying methods—hot air drying (HA), microwave drying (MW), hot air-assisted radio frequency (HARF) drying, and radio frequency vacuum (RFV) drying—were assessed to optimize drying efficiency for fermented medium. The results showed that using a 3:1 ratio of rice bran and American ginseng residue as the medium increased the crude polysaccharide and flavonoid contents by approximately threefold and enhanced the ginsenoside Rg3 content about twelvefold. Additionally, the 100 µg/mL ethanol extract of the fermented product inhibited 70% of tyrosinase activity and reduced the melanin area on zebrafish embryos by 42.74%. In the drying study, RFV drying R2G1 required only 13 min without exceeding 70 °C, demonstrating superior drying efficiency, temperature control, and low energy consumption. Overall, this study demonstrates the potential of black truffle fermentation of solid-state media from rice bran and American ginseng residue mixtures for whitening applications and highlights RFV drying as an efficient method for by-products. Full article

Tomato waste (TW) was employed as a sustainable source for the synthesis of fluorescent carbon dots (CDs) via a microwave-assisted hydrothermal carbonization (Mw-HTC) method, aiming at its valorization. Several amines were used as nitrogen additives to enhance the fluorescence quantum yield (QY) of CDs, and a set of reaction conditions, including additive/TW mass ratio (0.04–0.32), dwell time (15–60 min), and temperature (200–230 °C) of the HTC process, were scrutinized. The structural analysis of the tomato waste carbon dots (TWCDs) was undertaken by FTIR and ¹H NMR techniques, revealing their most relevant features. In solid state, transmission electron microscopy (TEM) analysis showed the presence of nearly spherical nanoparticles with an average lateral size of 8.1 nm. Likewise, the topographical assessment by atomic force microscopy (AFM) also indicated particles’ heights between 3 and 10 nm. Their photophysical properties, revealed by UV–Vis, steady-state, and time-resolved fluorescence spectroscopies, are fully discussed. Higher photoluminescent quantum yields (up to 0.08) were attained when the biomass residues were mixed with organic aliphatic amines during the Mw-HTC process. Emission tunability is a characteristic feature of these CDs, which display an intensity average fluorescence lifetime of 8 ns. The new TWCDs demonstrated good antioxidant properties by the ABTS radical cation method (75% inhibition at TWCDs’ concentration of 5 mg/mL), which proved to be related to the dwell time used in the CDs synthesis. Moreover, the synthesized TWCDs suppressed the growth of Escherichia coli and Staphylococcus aureus at concentrations higher than 2000 μg/mL, encouraging future antibacterial applications. Full article

In this study, a novel improved ultra-wideband (UWB) antipodal Vivaldi antenna suitable for breast cancer detection via microwave imaging was designed. The antenna was made more directional by adding three pairs of nestings to the antenna fins by adding elliptical patches. The frequency operating range of the proposed antenna is UWB 3.6–13 GHz, its directivity is 11 dB, and its gain is 9.27 dB. The antenna is designed with FR4 dielectric material and dimensions of 34.6 mm × 33 mm × 1.6 mm. It was demonstrated that the bandwidth, gain, and directivity of the proposed antenna meet the requirements for UWB radar applications. The Vivaldi antenna was tested on an imaging system developed using the CST Microwave Studio (CST MWS) program. In CST MWS, a hemispherical heterogeneous breast model with a radius of 50 mm was created and a spherical tumor with a diameter of 0.9 mm was placed inside. A Gaussian pulse was sent through Vivaldi antennas and the scattered signals were collected. Then, adaptive Wiener filter and image formation algorithm delay-multiply-sum (DMAS) steps were applied to the reflected signals. Using these steps, the tumor in the breast model was scanned at high resolution. In the simulation application, the tumor in the heterogeneous phantom was detected and imaged in the correct position. A monostatic radar-based system was implemented for scanning a breast phantom in the prone position in an experimental setting. For experimental measurements, homogeneous (fat and tumor) and heterogeneous (skin, fat, glandular, and tumor) breast phantoms were produced according to the electrical properties of the tissues. The phantoms were designed as hemispherical with a diameter of 100 mm. A spherical tumor tissue with a diameter of 16 mm was placed in the phantoms produced in the experimental environment. The dynamic range of the VNA device used allowed us to image a 16 mm diameter tumor in the experimental setting. The developed microwave imaging system shows that it is suitable for the early-stage detection of breast cancer by scanning the tumor in the correct location in breast phantoms. Full article

Intensive industrial activities have led to severe polycyclic aromatic hydrocarbon (PAH) contamination of adjacent lands. Remediating such contaminated soil is crucial for maintaining long-term ecological health and sustainable development. This study systematically assessed the performance of a microwave-activated persulfate (MW/PS) oxidation method in remediating pyrene-contaminated soil. Under conditions of 80 °C and a persulfate concentration of 23.8 mg/g, this system achieved 85.3% pyrene degradation within 30 min, significantly outperforming both single microwave and thermal-activated persulfate (TH/PS) systems. Key factors influencing the oxidation efficiency included the temperature, persulfate and pyrene concentrations, moisture, and humic acid content. An electron paramagnetic resonance analysis confirmed the generation of reactive oxygen species, including ^•OH, SO₄^•− and ¹O₂, in the MW/PS system, while O₂^•− was exclusive to the TH/PS system. However, further experiments revealed that ¹O₂ had a negligible impact on pyrene degradation, suggesting that its role may have been overestimated in previous studies. The high MW/PS performance was attributed to the synergistic effects of both thermal and non-thermal (molecular vibration) mechanisms. Based on these findings, the pathways of pyrene degradation were proposed, with intermediate products exhibiting reduced toxicity and bioaccumulation potential. This study provides valuable insights into the application of MW/PS systems in the remediation of PAH-contaminated soils. Full article

The rapid detoxification and mineralization of Cr(VI) in aqueous environments hold critical importance for emergency response and resource recovery yet remain technically challenging. Herein, we report the synthesis of FeS₂/ZVI composites through ethanol-assisted wet ball-milling and their application in Cr(VI) removal under microwave (MW) irradiation. This study systematically investigates the effects of MW irradiation on the removal efficiency of Cr(VI) using FeS₂/ZVI composites, with particular focus on key parameters including composite dosage, initial pH, MW temperature, and Cr(VI) concentration. Notably, 1 g/L FeS₂/ZVI composites achieved near-complete removal (>99%) of 50 mg/L Cr(VI) within 7 min at a MW irradiation temperature of 333 K, which exhibited 5.9-fold and 13.1-fold superior performance compared to pure pyrite and ZVI, respectively. Additionally, there is a 96.1% reduction in reaction time in comparison to non-MW irradiation system. In real electroplating wastewater samples, Cr(VI) concentration was reduced from 38.93 to 0.42 mg L⁻¹ by MW irradiation-assisted treatment, validating its potential for practical applications in industrial Cr(VI) pollution control. The activation energy determined by fitting the Arrhenius equation showed a 39.7% reduction for the MW-assisted FeS₂/ZVI system (16.0 kJ mol⁻¹) compared to conventional thermal heating (from 25.6 kJ mol⁻¹), indicating that MW irradiation induced catalytic enhancement of FeS₂/ZVI, thereby lowering the energy barrier for Cr(VI) reduction. Moreover, MW irradiation-assisted processes facilitated the mineralization of reduced Cr(III) to stable spinel FeCr₂O₄. These findings collectively establish a synergistic mechanism between MW activation and FeS₂/ZVI composites, offering innovative pathways for efficient Cr(VI) detoxification and resource recovery from high-strength industrial wastewaters. Full article

Carasau bread (CB) is a traditional Sardinian flatbread with significant market potential, driving the need for advanced quality monitoring solutions in its production. Recent advancements in automation and engineering have enhanced process control, but a comprehensive understanding of CB dough properties remains essential. Dielectric spectroscopy (DS), particularly in the microwave (MW) range, has emerged as a non-destructive, cost-effective tool for food characterization, providing insights into microstructure and composition. MW DS has been applied to assess fermentation dynamics and ingredient influence in CB doughs, with previous studies modeling dielectric properties using a third-order Cole–Cole model up to 8.5 GHz and later extending to 20 GHz. Despite these advancements, the repeatability, reliability, and consistency of MW DS measurements on CB doughs have not been systematically assessed. This study aims to fill this gap by analyzing MW DS measurements on ten CB dough samples with standard composition (water 50%, yeast 1.5%, salt 1.5%) in the 0.5–6 GHz range, both before and after leavening, for 10 different samples and a total of 100 measurements. Even though the correlation between spectra is high, and even if the coefficient of variation is below 5% before leavening, the z-score analysis and the kernel density estimation highlighted that the distribution of dielectric data is heterogeneous, showing that variability across samples exists, especially after leavening. Finally, the influence of pressure, temperature, and relative humidity was excluded. This statistical evaluation of MW DS measurement provided critical insights into the robustness of MW DS for industrial applications. Full article

In this paper, citrus pomace was used as a source of pectin and polyphenols extracted in one pot solution by microwave-assisted extraction (MAE) and conventional extraction (CE) methods. MAE parameters were optimized to maximize yield and adjust in situ final physicochemical properties of extracted pectins, such as the methylation degree (DM), significantly influencing pectin functionality and application. Citric acid (CA) and acetic acid (Hac) were employed as solvents to mitigate pectin degradation. Extracted pectins were structurally (GPC and FTIR-ATR), morphologically (SEM), and thermally (TGA) characterized. From the reaction batch, the bioactive compounds (AOs) were separated and recovered, and their yield and antioxidant activities were evaluated with a DPPH assay. Moreover, by strategically selecting pH and solvents, this research enabled precise control over the final properties of pectin. The various characterization techniques employed show that the extraction conditions significantly influence the physicochemical and morphological properties of the material. Molecular weight (Mw) values range from 218 kDa to 567 kDa, surface morphology varies from compact/aggregated structures to three-dimensional network-like formations, and the DM spans from 34% (low DM) to 83% (high DM). This highlights a novel approach for predicting and tailoring in situ characteristics of extracted pectin to meet specific application requirements. Full article

This paper demonstrates that potential oscillations in various frequency bands of monolithic microwave integrated circuits (MMICs) can be effectively suppressed using well-designed dual RC traps in the bias networks. The proposed approach is applied to the design and development of a highly stable W-band low-noise amplifier (LNA) MMIC for high-precision millimeter-wave applications. The amplifier is fabricated using the 0.1 µm GaAs pHEMT process from Win Semiconductors. The cascaded four-stage design consists of two low-noise-optimized stages, followed by two high-gain-tuned stages. Stability is enhanced through the integration of dual RC traps in the bias networks, which is rigorously evaluated using stability factors (K and μ) and network determinant function (NDF) encirclement analysis. In low-noise mode, the developed low-noise amplifier MMIC achieves a noise figure of 5.6−6.2 dB and a linear gain of 17.8−19.8 dB over the 90−98 GHz frequency range, while only consuming a DC power of 96 mW. In high-gain mode, it has a noise figure of 6.2−6.9 dB and a linear gain of 19.8−21.7 dB. Full article

Microwave photonics (MWP) applications often require a high optical input power (>100 mW) to achieve an optimal signal-to-noise ratio (SNR). However, conventional silicon spot-size converters (SSCs) are susceptible to high optical power due to the two-photon absorption (TPA) effect. To overcome this, we introduce a silicon nitride (SiN) SSC fabricated on a silicon-on-insulator (SOI) substrate. When coupled to a tapered fiber with a 4.5 μm mode field diameter (MFD), the device exhibits low coupling losses of <0.9 dB for TE modes and <1.4 dB for TM modes at relatively low optical input power. Even at a 1W input power, the additional loss is minimal, at approximately 0.1 dB. The versatility of the SSC is further demonstrated by its ability to efficiently couple to fibers with MFDs of 2.5 μm and 6.5 μm, maintaining coupling losses below 1.5 dB for both polarizations over the entire C-band. This adaptability to different mode diameters makes the SiN SSC a promising candidate for future electro-optic chiplets that integrate heterogeneous materials such as III-V for gain and lithium niobate for modulation with the SiN-on-SOI for all other functions using advanced packaging techniques. Full article

This study presents the synergistic application of ultrasound- and microwave-assisted extraction (UAE–MAE) as a novel and efficient method for recovering bioactive compounds from the medicinal plants oregano, rosemary, Hypericum perforatum, and chamomile. Extraction parameters, including microwave (MW) power, ultrasound (US) power, and extraction time, were optimized using the response surface methodology (RSM), with ethanol as the solvent. Extracts were evaluated for total phenolic content (TPC) via the Folin–Ciocalteu method and antioxidant activity (IC50) using the DPPH assay. High-performance liquid chromatography with diode array detection (HPLC–DAD) identified the main bioactive compounds contributing to their antioxidant and therapeutic potential. The optimized UAE–MAE conditions enhanced phenolic recovery and antioxidant potential across all plants. Notably, Hypericum perforatum exhibited the highest TPC (53.7 mg GAE/g) and strongest antioxidant activity (IC50 29.8 mg extract/g) under 200 W MW, 450 W US, and 12 min, yielding 14.5%. Rosemary achieved the highest yield (23.36%) with a TPC of 26.35 mg GAE/g and an IC50 of 40.75 mg extract/g at 200 W MW, 700 W US, and 8 min. Oregano’s optimal conditions (500 W MW, 700 W US, 12 min) produced a TPC of 34.99 mg GAE/g and an IC50 of 50.31 mg extract/g. Chamomile extracts demonstrated lower phenolic content and antioxidant activity but achieved significant yields under 500 W MW, 700 W US, and 5 min. This study highlights UAE–MAE’s superior efficiency, showcasing its potential to maximize phenolic recovery sustainably, making it a promising technique for industrial and therapeutic applications. Full article

The demand for safer, sustainable, and economical energy storage devices has motivated the development of lithium dual-ion batteries (Li_DIBs) for large-scale storage applications. For the Li_DIBs, expanded graphite (EG) cathodes are valuable as anion intercalation host frameworks to fabricate safer and more cost-effective devices. In this study, three different carbon cathode materials, including microwave-treated expanded graphite (MW-EG), ball-milled expanded graphite (BM-EG), and high-temperature-carbonized carbon nanoflakes (CNFs), were developed by different synthesis methods. Li_DIBs were configured by employing 4 M of LiPF₆ in a dimethyl carbonate electrolyte and MW-EG/BM-EG/CNF as an anion host cathode. After 600 cycles, a Li-MW-EG Li_DIB exhibited a reversible capacity of 66.1 mAh/g with a high Coulombic efficiency of 96.2% at a current rate of 0.05 A/g and an outstanding average energy density of 298.97 Wh/kg (with an output voltage of 4.62 V). The remarkable electrochemical results are associated with (i) moderate structural defects with a very low I_D/I_G ratio (0.848), (ii) degree of graphitization, which improves the mechanical stability and conductivity, and (iii) large pore volume and pore diameter, easy facilitating the accumulation of PF₆⁻ ions. The energy density characteristics demonstrate the feasibility of utilizing MW-EG as a promising cathode for energy-related Li_DIB applications. Full article

The triboelectric nanogenerator (TENG) has demonstrated exceptional efficiency in harvesting diverse forms of mechanical energy and converting it into electrical energy. This technology is particularly valuable for powering low-energy electronic devices and self-powered sensors. Most traditional TENGs use single-sided patterned friction pairs, which restrict their effective contact area and overall performance. Here, we propose a novel TENG that incorporates microwave patterned aluminum (MC-Al) foil and microcone structured polydimethylsiloxane (MC-PDMS). This innovative design utilizes two PMMA molds featuring identical micro-hole arrays ablated by a CO₂ laser, making it both cost-effective and easy to fabricate. A novel room imprinting technique has been employed to create the micromorphology of aluminum (Al) foil using the PMMA mold with shallower micro-hole arrays. Compared to TENGs with flat friction layers and single-side-patterned friction layers, the double-side-patterned MW-MC-TENG demonstrates superior output performance due to increased cone deformation and contact area. The open-circuit voltage of the MW-MC-TENG can reach 141 V, while the short-circuit current can attain 71.5 μA, corresponding to a current density of 2.86 µA/cm². The power density reaches 1.4 mW/cm² when the resistance is 15 MΩ, and it can charge a 0.1 μF capacitor to 2.01 V in 2.28 s. In addition, the MW-MC-TENG can function as an insole device to harvest walking energy, power 11 LED bulbs, monitor step speed, and power a timer device. Therefore, the MW-MC-TENG has significant application potential in micro-wearable devices. Full article

Epimedium is used in traditional Chinese medicine. Epimedium polysaccharides have a variety of physiological properties. This study compared three different processes for the extraction of polysaccharides from Epimedium spp., including ultrasonic, aqueous enzymatic, and microwave extraction, to optimize the extraction conditions and determine the optimal extraction method. The optimal parameters for each method were analyzed. The results showed that the optimal process for ultrasonic extraction was an ultrasonic power of 250 W, an extraction time of 60 min, a temperature of 50 °C, and a solid–liquid ratio of 1:35. The optimal conditions for the aqueous enzymatic method were a papain concentration of 70 U/mL, extraction time of 70 min, a temperature of 50 °C, and a material-to-liquid ratio of 1:30, while those for microwave extraction were a microwave power of 650 W, an extraction time of 50 min, a temperature of 40 °C, and a material-to-liquid ratio of 1:25. The polysaccharide yields were 4.85%, 4.72%, and 3.98% for the three methods, respectively, indicating that ultrasonic extraction resulted in the highest yield of polysaccharides from Epimedium brevicornum. After purification with DEAE-cellulose, the polysaccharide yields were 4.13%, 3.67%, and 3.12%, respectively. A comprehensive comparison demonstrated the superiority of the ultrasonic extraction method in terms of both extraction yield and purification efficiency. Characterization of the extracted Epimedium polysaccharides showed the presence of five monosaccharides, i.e., glucose, galactose, mannose, galacturonic acid, and rhamnose, and a number average molecular weight Mn of 1.65 × 10⁵ Da and weight average molecular weight Mw of 6.61 × 10⁵ Da. These results provide a scientific basis for the in-depth study and application of Epimedium polysaccharides. Full article