Search Results (683)

Purple celery (Apium graveolens L.) is a high-value functional vegetable rich in anthocyanins, but achieving a balanced optimization between biomass accumulation and nutritional quality in plant factories remains challenging due to species-specific spectral trade-offs, and current research lacks integrated light recipes that simultaneously optimize photosynthetic efficiency, antioxidant defenses, and functional quality while suppressing nitrate accumulation. This study evaluated five LED treatments over 30 days: white light (CK), monochromatic red (R), and red-to-blue photon flux density ratios of 5:5, 7:3, and 8:2. Red light induced stem elongation but suppressed root development. Conversely, 8R2B delivered the best performance, significantly elevating leaf, petiole, root, and total fresh biomass and increasing total dry weight by 68.8% over CK. It also markedly enhanced chlorophyll a, b, total chlorophyll, and carotenoids, as well as improved PSII quantum yield (YII), photochemical quenching (qP), and electron transport rate (ETR), while reducing non-photochemical heat dissipation (NPQ) by 61.0%, indicating superior light-use efficiency. Furthermore, 8R2B upregulated CAT and POD activities promoted soluble sugars (up 688.4% in leaves), soluble proteins, and ascorbic acid accumulation, yet reduced leaf nitrate by 28.5%. Principal component analysis confirmed 8R2B as the most effective formulation across all growth, photochemical, defense, and quality traits. These findings provide a novel, evidence-based 8:2 red-to-blue LED light recipe for high-yield, high-quality, and commercially viable purple celery production in controlled environment agriculture. Full article

This study investigates the flow and economic valuation of recyclable materials across fifteen Secondary Transfer Stations (STSs) in Dhaka North City Corporation (DNCC), Bangladesh, with the aim of understanding how market dynamics influence material recovery and circular economy potential. Primary data were collected through field surveys, structured questionnaires administered to 50 waste workers, five waste dealers and five local traders. Recovered materials were classified into six major categories, paper, plastic, metal, glass, electronic waste (e-waste), and other materials with further sub-categorization, to capture price variations and material characteristics. The results reveal a highly differentiated recycling market, with prices varying by more than an order of magnitude across materials. High-value materials, including copper wire, scrap aluminum, scrap metal, and electrical wire, are consistently recovered, whereas medium-value materials such as HDPE, PET, polypropylene, PVC, LDPE, Styrofoam, plastic crates, and mixed plastics are recovered selectively depending on market demand. In contrast, low-value materials, including packaging cartons, white paper, glass items, mixed LDPE, damaged LED lights, and mixed wastepaper, are frequently discarded due to weak economic incentives. Despite spatial and socioeconomic differences across STSs, price variability remains relatively low, indicating an integrated city-wide recycling market driven by active trader networks and broader commodity trends. To the best of our knowledge, this is one of the first studies to integrate recyclable material flow with economic valuation across multiple STSs in Dhaka. The findings highlight that recovery efficiency is strongly governed by economic value and informal practices, with limited segregation efficiency and inadequate occupational safety conditions. Enhancing source segregation, improving storage infrastructure, and introducing targeted market and policy interventions for low-value materials are critical for advancing Dhaka’s transition toward a circular and resource-efficient urban waste management system. Full article

This study examines the effects of nitrogen (N₂), cold storage (CS), yellow LED irradiation, and their combined application (N₂+LED+CS) on the quality of Sichuan pepper during storage. While individual treatments have been reported, their combined effect remains unexplored; this approach simultaneously targets temperature, oxygen, and light. The research focused on how these methods influence qualitative characteristics, including the preservation of OH-α-sanshool (the numbing component), total polyphenol content (TPC), total flavonoid content (TFC), and flavor compounds over a 60-day storage period. Preliminary screening of individual storage factors (temperatures: 5, 10, 20, 40 °C; O₂ levels: 0%, 10%, 20%, 40%; and LED colors: white, red, blue, yellow) showed that 5 °C and 0% O₂ significantly slowed degradation of TPC, TFC, and flavor compounds, while yellow LED notably preserved OH-α-sanshool. The combined N₂+LED+CS approach was particularly effective, reducing losses in TPC and TFC by 46.88% and 57.00%, respectively, compared to the control group. Additionally, OH-α-sanshool levels under N₂+LED+CS conditions were maintained at 19.04 mg/g, representing a 115.38% reduction in loss. The study concludes that the N₂+LED+CS method is a simple and efficient strategy that does not rely on chemical preservatives, offering a potentially sustainable approach to Sichuan pepper preservation. Full article

Greenhouse strawberry production has rapidly increased around the world, since greenhouse production allows for protection from adverse weather events and optimized climate control. During the winter months, supplemental electric lighting is essential to maintain production. However, the use of supplemental lighting can account for up to 30% of operating expenses, impacting the profitability of production. In addition, strawberries are prized for their taste, so maintaining fruit quality during production is essential. This study examined the impact four different supplemental overhead LED spectral lighting treatments (red–blue (95% red, red-rich), pink, warm white, and white) and two different irrigation electrical conductivity (EC) levels (low = 2 mS cm⁻¹ and high = 3 mS cm⁻¹) on morphology, physiology, fruit quality and electricity costs in two strawberry cultivars—cv. ‘Albion’ and cv. ‘Favori’—grown in rockwool during the 2023–2024 winter greenhouse season in Harrow, Ontario, Canada. The results showed that plants exposed to a board spectrum generally had higher photosynthetic rates and vegetative biomass. However, a threshold was observed when the green light fraction was above 24% (i.e., plants grown under the white-light treatment), resulting in reductions in photosynthesis and vegetative biomass. Although differences in photosynthetic capacity and biomass were observed, there was no impact of the light spectrum or irrigation EC on yield in either cultivar. Compared to the red–blue spectrum, plants grown under pink and warm white were observed to have lower titratable acidity (TA) and higher ratios of total soluble solids (TSSs) relative to TA. Importantly, it was determined that due to the higher efficacy of the red–blue supplemental lighting fixtures, the red-rich spectrum resulted in the lowest estimated lighting electricity cost per kilogram under the tested conditions. This study suggests that the use of supplemental high-efficacy, narrow wavelength, red-rich supplemental lighting can maintain yield and improve economic feasibility for greenhouse-grown strawberries. Full article

Singlet oxygen is produced by light-dependent excitation of molecular oxygen using photosensitizers. Using blue light and riboflavin (RF) or riboflavin phosphate (RFP) as photosensitizers, we studied the reaction of singlet oxygen with tertiary amines in aqueous solution because many are used as biochemical buffers and as electron donors in photoreduction reactions. The reactions of singlet oxygen with multiple tertiary amines, including ethylenediamine tetraacetic acid (EDTA), bicine, and triethanolamine (TEOA), produced micromolar hydrogen peroxide (H₂O₂) as the stable end product. For bicine and TEOA, but not EDTA, H₂O₂ yield increased as pH increased due to their higher amine pKa values. A white LED used in conjunction with riboflavin and tertiary amines also produced H₂O₂, a contaminant likely to form during tissue culture manipulations. Direct photoreduction of 2,6-dichlorophenolindophenol and 2,3-dimethoxy-5-methyl-p-benzoquinone was achieved using blue light, RF or RFP, and tertiary amines as electron donors. With RF, EDTA was the optimal electron donor for both substrates, whereas with RFP, bicine and TEOA were superior to EDTA. Photochemical redox cycling of both quinones produced H₂O₂ via singlet oxygen-dependent re-oxidation of reduced quinols. Several amine buffers, including HEPES and PIPES, reacted with singlet oxygen to produce H₂O₂ but did not function as electron donors in quinone photoreduction assays. Full article

This study investigated the effects of far-red (FR, 740 nm) and ultraviolet-A (UV-A, 370 nm) supplementation on the growth and nutritional quality of pak choi (Brassica rapa ssp. chinensis ‘Xiawang’) under different light intensities. Plants were grown under a white LED background light (6500 K) at two light intensities (100 and 400 μmol·m⁻²·s⁻¹) either without (T100 and T400) or with an additional 40 μmol·m⁻²·s⁻¹ of FR or UV-A radiation (T100FR, T100UV-A, T400FR, and T400UV-A). The results demonstrated a significant interactive effect between light intensity and FR/UV-A supplementation. Under low light intensity (T100), both FR and UV-A significantly enhanced biomass accumulation, the net photosynthetic rate, and the content of soluble proteins, soluble sugars, and cellulose. Under a high light intensity (T400), FR and UV-A primarily promoted morphological development (leaf expansion and thickening), photosynthetic performance, and carbohydrate accumulation. Specifically, FR notably promoted petiole elongation while reducing photosynthetic pigment content, whereas UV-A markedly increased the vitamin C content while decreasing nitrate accumulation. In conclusion, both FR and UV-A supplementation effectively improve the growth and quality of pak choi, but, through light-intensity-dependent mechanisms. FR acts mainly via morphological and photosynthetic optimization, whereas UV-A acts as a physiological and nutritional regulator. These findings highlight the complementary roles of FR and UV-A, providing practical guidance for optimizing spectral strategies in controlled environment agriculture (CEA). Full article

Sorrel (Rumex acetosa L.) is a promising leafy vegetable for controlled-environment production, but integrated information on its growth, structural quality, optical traits, and photochemical responses to light-emitting diode (LED) spectra remains limited. To our knowledge, this study provides the first systematic comparison of five contrasting LED spectral conditions in sorrel using morphological, biomass, structural-quality, reflectance-based, and chlorophyll-fluorescence indicators. Plants were grown for six weeks under red light (RL), green light (GL), blue light (BL), purple-phyto light (PL) containing red, blue, and far-red components, or white light (WL) at a color temperature of 6500 K. Sorrel responses differed markedly among spectral environments and could not be explained by a single growth parameter. WL produced the highest mean shoot dry weight (505 mg), which was approximately 30.5% higher than that under PL (387 mg), although the difference between the two treatments was not statistically significant. WL also produced 46.5% greater leaf area than PL (50.1 versus 34.2 cm²) and showed the highest mean PI_ABS value (4.00). In contrast, PL showed the highest mean root dry weight (25.5 mg) and Dickson quality index (9.4), together with a relatively low shoot-to-root ratio (17.7) and top-heavy index (20.0), indicating a less shoot-biased structural pattern. BL restricted growth and leaf development and was associated with lower soil plant analysis development units, normalized difference vegetation index, photochemical reflectance index, F_v/F_m, and PI_ABS, indicating that BL alone may have limited suitability for sorrel cultivation under the present experimental conditions. Under the tested conditions, WL appeared more suitable for yield-oriented production, whereas PL may be considered when shoot–root structural balance is prioritized. Full article

White LEDs are widely used in fields such as lighting and display. However, existing white light devices suffer from excessively broad emission spectra full width at half maximum (FWHM) and severe leakage of pump blue light. Hence, this study proposes a theoretical design for an ultra-narrow-band white LEDs based on an asymmetric Fabry-Pérot (F-P) microcavity. The microcavity employs a dual-DBR configuration with asymmetric optical responses: the bottom DBRs utilize a ZnS/MgF₂ ($d_L$/2-$d_H$-$d_L$/2)⁵ stack, providing a low reflectance of ~20% at 457 nm for efficient blue light transmission and quantum dot excitation; conversely, the final device incorporating top DBRs with a TiO₂/MgF₂ ($d_H$/2-$d_L$-$d_H$/2)⁴-stacked structure achieved a high reflectivity of approximately 89% at 457 nm, effectively decreasing the excessive blue light in the output spectrum. The intermediate emissive layer uses polymethyl methacrylate (PMMA) as the quantum dot host. By precisely tuning the cavity thickness, the resonant modes of the F-P microcavity—specifically the fourth-order (626 nm) and fifth-order (534 nm)—are aligned with the emission peaks of the red and green quantum dots, respectively. Simulation results demonstrate that the structure leverages the cavity filtering effect to compress the FWHM of the red and green emissions from initial values of 36.5 nm and 29.8 nm down to 2.2 nm and 1.9 nm, respectively, representing an order-of-magnitude improvement in color purity. Through the co-optimization of the top-DBR’s central wavelength, cavity optical thickness, and the doping ratio of red/green quantum dots, standard white light emission with CIE coordinates of (0.32, 0.33) was achieved, accompanied by emission efficiencies of 6.3% (green) and 22.3% (red) for the QDs. However, strict manufacturing tolerances and narrow observation angles limit the applicability of the device. This work provides theoretical research for developing white light sources. Full article

This study evaluated LED-supported speed-breeding conditions for two registered soybean cultivars (‘Sonya’ and ‘Victoria’; approximately Maturity Groups III–IV) by testing four constant photoperiod regimes (10, 14, 18, and 22 h light) combined with four LED spectral treatments differing in high red (HR; 640–660 nm), deep blue (DB; 450–460 nm), far-red (FR; 720–730 nm), cool white (CW; 6500 K; 400–700 nm) and warm white (WW; 3000 K; 400–700 nm) components. Photoperiod treatments were implemented as sequential runs in a controlled growth-chamber (28 ± 2 °C; ≥50% RH; 400–600 µmol·m⁻²·s⁻¹ PPFD), and performance was compared with a field trial in Antalya, Türkiye. Developmental timing (R1, R6), plant height, stem dry weight, pod number, seed oil concentration, fatty acid composition, and seed germination were analyzed using mixed-effects and generalized linear mixed models. Photoperiod exerted dominant control over developmental timing. The 10 h photoperiod regime produced the fastest progression (R1 ≈ 24.5 DAS; R6 ≈ 50 DAS), whereas 18 h markedly delayed R1 and R6 (with one LED treatment within 18 h failing to reach R6), and 22 h did not reach R6. LED spectral treatment did not affect R1 or R6 within photoperiods, but influenced plant height, stem dry weight, total seed oil, and germination. Field-grown plants produced substantially higher biomass and pod number than growth chamber-grown plants, consistent with greater branching and pod set under open-field, direct-sown conditions. Total seed oil concentration differed by environment and cultivar with no environment × cultivar interaction, while centered log-ratio PERMANOVA indicated largely stable fatty acid proportional composition across environments and LED treatments. Germination analyses (restricted to 10 h and 14 h due to insufficient seed production) showed significant effects of LED treatment and harvest timing, with the highest germination under LED–3. Overall, our results indicate that a constant 10 h photoperiod, combined with immature seed harvest from approximately R6 + 20 onward, provides an effective strategy for accelerating soybean generation turnover while maintaining high germination capacity. LED spectral design can also be used to modulate plant architecture and seed quality without substantially altering developmental timing. Full article

This study investigates the degradation mechanisms of 2835-packaged white LEDs commonly used in residential lighting scenarios under various environmental conditions and explores how standard ageing tests compare to those that better reflect real-world use cases. The samples consist of commercially available LED strips, both cool and warm white. The luminous output of each LED on a strip is spectrally measured individually before ageing, then aged under particular conditions for a certain time and measured individually again. The measurements for a given LED are then analysed from multiple aspects, including material degradation processes during ageing, for example by following changes in phosphor efficiency. Full article

Junction temperature (T_j) is a key parameter that directly governs the optical performance and operational reliability of light-emitting diodes (LEDs), which have become indispensable in modern illumination and display systems. Accurate real-time T_j monitoring is critical for ensuring device longevity and consistent light output. Although the forward voltage method (FVM) remains the industry benchmark, its practical implementation is hindered by the need for costly high-speed switching modules and ultra-low-current calibration sources, restricting its deployment in real-time and cost-sensitive scenarios. To overcome these limitations, we introduce and experimentally validate a non-contact optical method for T_j determination that leverages the normalized integral width (NIW) of the LED emission spectrum as a temperature-sensitive spectral parameter. The underlying principle is that spectral broadening—arising from enhanced carrier thermal excitation and temperature-induced bandgap shrinkage—exhibits a robust and quantifiable linear correlation with T_j. Both theoretical analysis and experimental data confirm that this mechanism underpins the excellent linear correlation between NIW and T_j observed across a wide range of LED types, including monochromatic (red, green, blue) and phosphor-converted white LEDs. A rigorous theoretical analysis establishes the mathematical framework linking NIW to T_j. Experimentally, a measurement system centered on a modified commercial spectrometer was constructed. Extensive testing on a diverse array of power LEDs consistently demonstrates an excellent linear correlation (R² > 0.998) between NIW and T_j under normal drive conditions (e.g., typical operating currents). A comparative analysis against the benchmark FVM, conducted using a Mentor Graphics T3Ster system, demonstrates that the proposed method achieves comparable measurement accuracy, with a maximum deviation of merely 2.1 °C, while substantially reducing system cost and complexity. Validation across diverse LED types confirmed excellent linearity and high repeatability. A comparative analysis with established optical methods (e.g., peak wavelength, blue-white ratio, Raman thermography) further underscores the advantages of the NIW method in terms of cost-effectiveness, measurement speed, and broader applicability. Subsequent evaluation of critical factors, including self-heating, ambient light interference, and spectrometer resolution, demonstrates its robustness. Consequently, the NIW method presents a practical solution for real-time, non-intrusive thermal monitoring, well-suited for industrial LED production and quality control. Full article

Supplemental light spectrum strongly influences crop physiology, quality, and marketability in controlled-environment horticulture. This study evaluated greenhouse-grown basil (Ocimum basilicum L.) under natural daylight supplemented with 250 µmol m⁻² s⁻¹ of multi-band WHITE or narrow-band RED, GREEN, and BLUE LEDs, compared with non-supplemented controls (CNT). Diurnal gas exchange, cumulative photosynthetic activity, quality, sensory traits, and productive responses were assessed to identify spectrum-specific effects. WHITE supplementation produced the highest net photosynthesis (P_n) throughout the photoperiod, increasing carbon assimilation by up to 90% during active supplementation compared with CNT, while improving stomatal–photosynthetic coordination and titratable acidity. BLUE light promoted the highest stomatal conductance and transpiration, whereas RED induced faster stomatal closure without affecting the plant’s final biomass. GREEN supplementation showed intermediate physiological responses while enhancing fresh biomass, leaf brightness, and greenness. Spectral treatments significantly affected chlorophyll content, colorimetric parameters, sensory descriptors, aroma typicity, and texture, although antioxidant activity and overall consumer acceptability remained largely stable. WHITE and CNT samples achieved the highest sensory appreciation, while BLUE supplementation increased bitterness and reduced aromatic typicality. Overall, no single spectrum optimized all production objectives. WHITE provided the most balanced strategy for maximizing photosynthetic efficiency and premium-quality traits, whereas RED, GREEN, and BLUE offered more specialized benefits related to biomass increase, visual quality, or pigmentation. These findings highlight precision spectral management as an effective tool for tailoring basil production to specific agronomic and commercial targets in protected cultivation systems. Full article

A low-complexity Hall-based measurement system implementing a dark/illuminated differential estimator of the majority-carrier photoconductive response is assessed on n-type crystalline silicon wafers with contrasting doping concentrations. The setup combines a Van der Pauw configuration, permanent neodymium magnets, a characterized white LED source, and a source–measure unit to extract an apparent Hall-derived differential indicator—not a calibrated majority-carrier density—under dark and illuminated steady-state conditions. At $1.81\mathrm{mW}{\mathrm{cm}}^{-2}$, the lightly doped wafer ($N_D\approx {10}^{14}{\mathrm{cm}}^{-3}$) shows a resolved response ($\Delta {\sigma }_{n,H}=29.61\pm 3.406\mathrm{mS}{\mathrm{cm}}^{-1}$), reported as mean ± sample standard deviation from 15 dark/light cycles. The heavily doped wafer ($N_D\approx {10}^{17}{\mathrm{cm}}^{-3}$) gives a nominal below-threshold response ($\Delta {\sigma }_{n,H}=1.167\pm 0.140\mathrm{mS}{\mathrm{cm}}^{-1}$) from the same cycling protocol; it should be interpreted only as an unresolved trend-level indication because it lies below the instrumental detection threshold. The contrast is qualitatively consistent with the expected doping dependence, but no quantitative performance ratio is claimed for the heavily doped wafer. A Macdonald–Cuevas comparison is used only as a qualitative physical-consistency benchmark. No independent QSSPC, SSPC, $\mu$-PCD, or carrier-resolved photo-Hall measurement was available for the same wafers; therefore, the system serves as a complementary low-cost screening tool for comparative trend analysis, not a replacement for calibrated photoconductance or photo-Hall techniques, and it does not constitute a new measurement principle. Full article

A novel Dy³⁺-doped self-activated Sr₂NaMg₂V₃O₁₂ (SNMVO) phosphor was synthesized via a high-temperature solid-state reaction method. Its microstructure, surface morphology, valence state, and luminescence properties were investigated. The results showed that the prepared phosphor exhibited bright green emission at 521 nm and yellow emission at 575 nm under 345 nm excitation. The luminescence intensity showed a strong concentration dependence, with an optimal Dy³⁺ ion doping concentration of 0.05 mol, and the concentration quenching (CQ) mechanism was dipole–dipole (d-d) interaction. Energy transfer between vanadate and Dy³⁺ was observed, with a maximum transfer efficiency of 63.5%. The thermal activation energy (0.1859 eV) indicated good thermal stability. Furthermore, this phosphor can be used as a yellow phosphor for white light-emitting diodes (wLEDs) and for anti-counterfeiting patterns. Full article

Bacopa monnieri (Brahmi), a valuable medicinal herb, faces challenges in consistent production and quality under natural cultivation. To overcome these limitations, this study investigated the impact of different light qualities (warm-white, red, blue, and green) on the in vitro growth, chlorophyll content, and accumulation of bacosides in B. monnieri using a temporary immersion system (TIS). The results revealed that green and blue light significantly enhanced biomass accumulation, with green light promoting the highest number of new shoots (24.2 shoots/clump) and blue light inducing the development of longer shoots with extended internodes (2.6 cm/internode). Interestingly, while green light resulted in the lowest chlorophyll content, it led to the highest accumulation of bacoside A3 (0.39% DW). In contrast, no significant differences were observed in bacopaside II content across all light treatments. However, bacopasaponin C production was significantly enhanced by warm-white and red light. These results demonstrate the potential of manipulating light quality within a TIS to optimize specific growth parameters and bioactive compound production in B. monnieri, offering valuable insights for enhancing the quality and yield of this important medicinal plant for industrial applications. Full article