Search Results (15)

The broadband spectrum of solar radiation is commonly characterized by indices such as the average photon energy (APE) and the blue fraction (BF). This work explores the effectiveness of the two indices in a narrower spectral band, namely the ultraviolet (UV). The analysis is carried out from two perspectives: sensitivity to the changes in the UV spectrum and the uniqueness (each index value uniquely characterizes a single UV spectrum). The evaluation is performed in relation to the changes in spectrum induced by the main atmospheric attenuators in the UV band: ozone and aerosols. Synthetic UV spectra are generated in different atmospheric conditions using the SMARTS2 spectral solar irradiance model. The closing result is a new index for the signature of the solar UV radiation spectrum. The index is conceptually just like the BF, but it captures the specificity of the UV spectrum, being defined as the fraction of the energy of solar UV radiation held by the UV-B band. Therefore, this study gives a new meaning and a new utility to the common UV-B/UV ratio. Full article

In this study, an ultra-wideband absorber spanning from UV-B to middle-IR was designed and analyzed using a novel structure. The multilayer metamaterial, arranged from bottom to top, consisted of an Al metal layer, a lower SiO₂ layer, a graphite layer, another SiO₂ layer, a thin Ti layer, and a top SiO₂ layer. The top layer of SiO₂ had a 200 nm square cavity etched out, and then a square Ti nanopillar and a square Ti hollow outside a Ti nanopillar were embedded. This specific arrangement was chosen to maximize the absorption properties across a broad spectrum. The absorption spectrum of the designed absorber was thoroughly analyzed using the commercial finite element analysis software COMSOL Multiphysics^® (version 6.0). This analysis confirmed that the combination of these various components achieved perfect absorption and an ultra-wideband response. The synergistic interaction between the layers and the nanopillars structure contributed significantly to the absorber’s efficiency, making it a promising candidate for applications requiring broad-spectrum absorption. The comprehensive analyses of the parameters for different structures demonstrated that the effects of guided-mode resonance, coupling resonance, optical impedance matching, and propagating surface plasmon resonance existed in the investigated structure. The optimal model, determined through analyses using COMSOL Multiphysics^®, showed that the broadband absorption in the range of 270 to 3600 nm, spanning from UV-B to middle-IR, exceeded 90.0%. The average absorption rate within this range was 0.967, with the highest reaching a near-perfect absorptivity of 99.9%. We also compared three absorption spectra in this study: the t1–t6 flat structure, the t1–t5 flat structure with t6 featuring a square cavity, and the structure proposed in this study. This demonstrates that a square nanopillar and a square hollow embedded in a square cavity can enhance the absorptive properties of the absorber. Full article

In plants, secondary metabolites change in response to environmental conditions. These changes co-regulate resilience to stressful environmental conditions, plant growth and development, and interactions between plants and the wider ecosystem, while also affecting soil carbon storage and atmospheric and climatic conditions. The objective of this study was to determine the association between UV exposure and the contents of key metabolites, including amino acids, phenolics, flavonoids, terpenoids, carotenoids, tocopherols, and phytosterols. Mentha spicata plantlets were grown in tissue culture boxes for 30 days and then exposed to a low dose of broadband UV-B (291–315 nm; 2.8 kJm⁻² biologically effective UV) enriched light for eight days. Metabolite contents were quantified either immediately after the final UV exposure, or after seven days of recovery under photosynthetically active radiation. It was found that UV promoted the production of flavonoids (1.8-fold) ahead of phenolic acids (unchanged). Furthermore, the majority of monoterpenes and sesquiterpenes, constituents of valuable mint essential oil, were significantly increased through UV treatment (up to 90-fold for α-linalool). In contrast, the contents of carotenoids and tocopherols did not increase following UV exposure. A comparison between plants sampled immediately after UV exposure and after seven days of recovery showed that there was an overall increase in the content of carotenoids, mono- and sesquiterpenes, phenolics, and amino acids following recovery, while the contents of sterols and tocopherols decreased. These UV-induced changes in metabolite profile may have important consequences for agriculture, ecology, and even the global climate, and they also provide an exciting opportunity to enhance crop value, facilitating the development of improved products with higher levels of essential oils and added benefits of enhanced flavour, colour, and bioactive content. Full article

Retrotransposons have played an important role in evolution through their transposable activity. The largest and the only currently active human group of mobile DNAs are the LINE-1 retrotransposons. The ectopic expression of LINE-1 has been correlated with genomic instability. Narrow-band ultraviolet B (NB-UVB) and broad-band ultraviolet B (BB-UVB) phototherapy is commonly used for the treatment of dermatological diseases. UVB exposure is carcinogenic and can lead, in keratinocytes, to genomic instability. We hypothesize that LINE-1 reactivation occurs at a high rate in response to UVB exposure on the skin, which significantly contributes to genomic instability and DNA damage leading to cellular senescence and photoaging. Immortalized N/TERT1 and HaCaT human keratinocyte cell lines were irradiated in vitro with either NB-UVB or BB-UVB. Using immunofluorescence and Western blotting, we confirmed UVB-induced protein expression of LINE-1. Using RT-qPCR, we measured the mRNA expression of LINE-1 and senescence markers that were upregulated after several NB-UVB exposures. Selected miRNAs that are known to bind LINE-1 mRNA were measured using RT-qPCR, and the expression of miR-16 was downregulated with UVB exposure. Our findings demonstrate that UVB irradiation induces LINE-1 reactivation and DNA damage in normal keratinocytes along with the associated upregulation of cellular senescence markers and change in miR-16 expression. Full article

In this study, a fractal absorber was designed to enhance light absorptivity and improve the efficiency of converting solar energy into electricity for a range of solar energy technologies. The absorber consisted of multiple layers arranged from bottom to top, and the bottom layer was made of Ti metal, followed by a thin layer of MgF₂ atop it. Above the two layers, a structure comprising square pillars formed by three layers of Ti/MgF₂/Ti was formed. This pillar was encompassed by a square hollow with cylindrical structures made of Ti material on the exterior. The software utilized for this study was COMSOL Multiphysics^® (version 6.0). This study contains an absorption spectrum analysis of the various components of the designed absorber system, confirming the notion that achieving ultra-wideband and perfect absorption resulted from the combination of the various components. A comprehensive analysis was also conducted on the width of the central square pillar, and the analysis results demonstrate the presence of several remarkable optical phenomena within the investigated structure, including propagating surface plasmon resonance, localized surface plasmon resonance, Fabry–Perot cavity resonance, and symmetric coupling plasma modes. The optimal model determined through this software demonstrated that broadband absorption in the range of 276 to 2668 nm, which was in the range of UV-B to near-infrared, exceeded 90.0%. The average absorption rate in the range of 276~2668 nm reached 0.965, with the highest achieving a perfect absorptivity of 99.9%. A comparison between absorption with and without outer cylindrical structures revealed that the resonance effects significantly enhanced absorption efficiency, as evidenced by a comparison of electric field distributions. Full article

Several studies have highlighted the ability of snail mucus in maintaining healthy skin conditions due to its emollient, regenerative, and protective properties. In particular, mucus derived from Helix aspersa muller has already been reported to have beneficial properties such as antimicrobial activity and wound repair capacity. In order to enhance the beneficial effects of snail mucus, a formulation enriched with antioxidant compounds derived from edible flower waste (Acmella oleracea L., Centaurea cyanus L., Tagetes erecta L., Calendula officinalis L., and Moringa oleifera Lam.) was obtained. UVB damage was used as a model to investigate in vitro the cytoprotective effects of snail mucus and edible flower extract. Results demonstrated that polyphenols from the flower waste extract boosted the antioxidant activity of snail mucus, providing cytoprotective effects in keratinocytes exposed to UVB radiation. Additionally, glutathione content, reactive oxygen species (ROS), and lipid peroxidation levels were reduced following the combined treatment with snail mucus and edible flower waste extract. We demonstrated that flower waste can be considered a valid candidate for cosmeceutical applications due to its potent antioxidant activity. Thus, a new formulation of snail mucus enriched in extracts of edible flower waste could be useful to design innovative and sustainable broadband natural UV-screen cosmeceutical products. Full article

In the present study, continuous measurements of solar global (G) and ultraviolet-B (UVB) radiation are taken in Kuwait for 2014–2019 for all weather conditions. Hourly curves show a sinusoidal behavior for both G and UVB radiation. Statistical analysis indicates that there is a good agreement between hourly G and hourly UVB as the coefficients of determination (R²) for all years are larger than 0.91 and the root-mean-square error (RMSE) and mean bias error (MBE) are very small. The hourly percentage ratio (UVB/G) is found to decrease with G due to cloudy sky conditions. In addition, the ratio (UVB/G) tends to decrease with global clearness index (K_T), indicating that a higher ratio of (UVB/G) can be obtained for a cloudier atmosphere. Another interesting finding is that K_T and the UVB index (K_TUVB) are directly proportional, and a third-order polynomial fit gives an acceptable formula (R² = 0.859). Daily G and UVB values are very well correlated as R² is very close to unity for all years. The values of RMSE and MBE obtained from daily analysis are greatly enhanced as the values of RMSE and MBE are almost zero. The maximum G and UVB radiation obtained is 27.94 MJ/m² and 0.0044 MJ/m², respectively, with both occurring in June 2015. Finally, there is an excellent linear fit between the monthly G and monthly UVB radiation as R² is almost equal to unity and RMSE and MBE are negligible. Thus, the predicted daily or monthly empirical formula can be utilized with a very high accuracy to predict both daily and monthly UVB values at locations in Kuwait where G is measured. Full article

Background: The sun is a natural source of UV radiation. It can be divided into three bands, UVA (315–400 nm), UVB (280–315 nm) and UVC (100–280 nm), where the radiation up to 290 nm is very effectively eliminated by the stratospheric ozone. Although UV radiation can have a beneficial effect on our organism and can be used in the treatment of several skin diseases, it must primarily be considered harmful. Methods: In the presented work, we focused on the study of the longer-wavelength UV components (UVA and UVB) on the human epidermal keratinocyte line HaCaT. As UVA and UVB radiation sources, we used commercially available UVA and UVB tubes from Philips (Philips, Amsterdam, The Netherlands), which are commonly employed in photochemotherapy. We compared their effects on cell viability and proliferation, changes in ROS production, mitochondrial function and the degree of DNA damage. Results: Our results revealed that UVB irradiation, even with significantly lower irradiance, caused greater ROS production, depolarization of mitochondrial membrane potential and greater DNA fragmentation, along with significantly lowering cell viability and proliferative capacity. Conclusions: These results confirm that UV radiation causes severe damages in skin cells, and they need to be protected from it, or it needs to be applied more cautiously, especially if the component used is UVB. Full article

Supplemental narrow-band 311 nm UV-B radiation was applied in order to study the effect of this specific wavelength on tobacco as a model plant. UV-B at photon fluxes varying between 2.9 and 9.9 μmol m⁻² s⁻¹ was applied to supplement 150 μmol m⁻² s⁻¹ photosynthetically active radiation (PAR) for four hours in the middle of the light period for four days. Narrow-band UV-B increased leaf flavonoid and phenolic acid contents. In leaves exposed to 311 nm radiation, superoxide dismutase activity increased, but phenolic peroxidase activity decreased, and the changes were proportional to the UV flux. Ascorbate peroxidase activities were not significantly affected. Narrow-band UV-B caused a dose-dependent linear decrease in the quantum efficiency of photosystem II, up to approximately 10% loss. A parallel decrease in non-regulated non-photochemical quenching indicates potential electron transfer to oxygen in UV-treated leaves. In addition to a flux-dependent increase in the imbalance between enzymatic H₂O₂ production and neutralization, this resulted in an approximately 50% increase in leaf H₂O₂ content under 2.9–6 μmol m⁻² s⁻¹ UV-B. Leaf H₂O₂ decreased to control levels under higher UV-B fluxes due to the onset of increased non-enzymatic H₂O₂- and superoxide-neutralizing capacities, which were not observed under lower fluxes. These antioxidant responses to 311 nm UV-B were different from our previous findings in plants exposed to broad-band UV-B. The results suggest that signaling pathways activated by 311 nm radiation are distinct from those stimulated by other wavelengths and support the heterogeneous regulation of plant UV responses. Full article

In recent years, research on natural products has gained considerable attention, particularly in the cosmetic industry, which is looking for new bio-active and biodegradable molecules. In this study, cosmetic properties of cyanobacteria and red macroalgae were analyzed. The extractions were conducted in different solvents (water, ethanol and two combinations of water:ethanol). The main molecules with antioxidant and photoprotective capacity were mycosporine-like amino acids (MAAs), scytonemin and phenolic compounds. The highest contents of scytonemin (only present in cyanobacteria) were observed in Scytonema sp. (BEA 1603B) and Lyngbya sp. (BEA 1328B). The highest concentrations of MAAs were found in the red macroalgae Porphyra umbilicalis, Gelidium corneum and Osmundea pinnatifida and in the cyanobacterium Lyngbya sp. Scytonema sp. was the unique species that presented an MAA with maximum absorption in the UV-B band, being identified as mycosporine-glutaminol for the first time in this species. The highest content of polyphenols was observed in Scytonema sp. and P. umbilicalis. Water was the best extraction solvent for MAAs and phenols, whereas scytonemin was better extracted in a less polar solvent such as ethanol:_dH₂O (4:1). Cyanobacterium extracts presented higher antioxidant activity than those of red macroalgae. Positive correlations of antioxidant activity with different molecules, especially polyphenols, biliproteins and MAAs, were observed. Hydroethanolic extracts of some species incorporated in creams showed an increase in the photoprotection capacity in comparison with the base cream. Extracts of these organisms could be used as natural photoprotectors improving the diversity of sunscreens. The combination of different extracts enriched in scytonemin and MAAs could be useful to design broad-band natural UV-screen cosmeceutical products. Full article

The study shows an analysis of a 7-year data set measuring Ultraviolet-B (UVB) irradiance values and ultraviolet index TABLEUVI) values derived from ground-based broadband irradiance measurements, satellite-derived total ozone, and UVB solar irradiance recorded in Valladolid (Central Spain). Ultraviolet-B (UVB) solar irradiance measurements in the range (280–315 nm) carried out during the period 2013–2019 at a continental Mediterranean solar station, located in Valladolid (Spain), were analyzed. UVB data recorded using a YES UVB-1 pyranometer were used to estimate erythemal irradiance, ultraviolet erythemal irradiance (UVER), UVI, cumulative dose, and sun protection. Hourly UVER data in January (minimum values) and June (maximum values) were analyzed as an average year for the measurement station. Differences between UVI values at solar noon and the maximum daily value were minimal. It was found that on certain summer days, maximum daily UVI and SED (cumulative daily dose) could be over 12 and 60, respectively. The cumulative dose on the horizontal surface was calculated at the station for different skin types. It was observed that over 45% of the annual dose is received in summer, about 30% in spring, over 15% in autumn, and less than 10% in winter. In addition, the relationship between the maximum daily UVI and the annual accumulated dose in SEDs was studied to provide information on sun protection under low UVI conditions. Full article

Phototherapy using narrowband ultraviolet-B (NB-UVB) has been shown to be more effective than conventional broadband UVB (BB-UVB) in treating a variety of skin diseases. To assess the difference in carcinogenic potential between NB-UVB and BB-UVB, we investigated the cytotoxicity via colony formation assay, genotoxicity via sister chromatid exchange (SCE) assay, mutagenicity via hypoxanthine phosphoribosyltransferase (HPRT) mutation assay, as well as cyclobutane pyrimidine dimer (CPD) formation and reactive oxygen species (ROS) generation in Chinese hamster ovary (CHO) and their NER mutant cells. The radiation dose required to reduce survival to 10% (D₁₀ value) demonstrated BB-UVB was 10 times more cytotoxic than NB-UVB, and revealed that NB-UVB also induces DNA damage repaired by nucleotide excision repair. We also found that BB-UVB more efficiently induced SCEs and HPRT mutations per absorbed energy dosage (J/m²) than NB-UVB. However, SCE and HPRT mutation frequencies were observed to rise in noncytotoxic dosages of NB-UVB exposure. BB-UVB and NB-UVB both produced a significant increase in CPD formation and ROS formation (p < 0.05); however, higher dosages were required for NB-UVB. These results suggest that NB-UVB is less cytotoxic and genotoxic than BB-UVB, but can still produce genotoxic effects even at noncytotoxic doses. Full article

Zinc oxide (ZnO) nanoparticles have gained widespread interest due to their unique properties, making them suitable for a range of applications. Several methods for their production are available, and of these, controlled synthesis techniques are particularly favourable. Large-scale culturing of Chlorella vulgaris produces secretory carbohydrates as a waste product, which have been shown to play an important role in directing the particle size and morphology of nanoparticles. In this investigation, ZnO nanorods were produced through a controlled synthesis approach using secretory carbohydrates from C. vulgaris, which presents a cost-effective and sustainable alternative to the existing techniques. Fourier transform infrared (FTIR) spectroscopy, X-ray powder diffraction (XRD) analysis, transmission electron microscopy (TEM), and UV-Vis spectroscopy were used to characterise the nanorods. The prepared nanorods exhibited a broad range of UV absorption, which suggests that the particles are a promising broadband sun blocker and are likely to be effective for the fabrication of sunscreens with protection against both UVB (290–320 nm) and UVA (320–400 nm) radiations. The antimicrobial activity of the prepared nanorods against Gram-positive and Gram-negative bacteria was also assessed. The nanostructures had a crystalline structure and rod-like appearance, with an average length and width of 150 nm and 21 nm, respectively. The nanorods also demonstrated notable antibacterial activity, and 250 μg/mL was determined to be the most effective concentration. The antibacterial properties of the ZnO nanorods suggest its suitability for a range of antimicrobial uses, such as in the food industry and for various biomedical applications. Full article

Ascorbic acid 2-glucoside (AA2G), glucosylated ascorbic acid (AA), has superior properties for bioavailability and stability compared to AA. Although AA2G has shown radioprotective properties similar to AA, effects for UV light, especially UVC and UVB, are not studied. AA2G was tested for cytotoxicity and protective effects against ionizing radiation, UVC, and broadband and narrowband UVB in Chinese hamster ovary (CHO) cells and compared to AA and dimethyl sulfoxide (DMSO). Pretreatment with DMSO, AA, and AA2G showed comparative protective effects in CHO wild type and radiosensitive xrs5 cells for cell death against ionizing radiation with reducing the number of radiation-induced DNA damages. Pretreatment with AA and AA2G protected CHO wild type and UV sensitive UV135 cells from UVC and broadband UV, but not from narrowband UVB. DMSO showed no protective effects against tested UV. The UV filtration effects of AA and AA2G were analyzed with a spectrometer and spectroradiometer. AA and AA2G blocked UVC and reduced short wavelengths of UVB, but had no effect on wavelengths above 300 nm. These results suggest that AA2G protects cells from radiation by acting as a radical scavenger to reduce initial DNA damage, as well as protecting cells from certain UVB wavelengths by filtration. Full article

Human exposure to healthy doses of UV radiation is required for vitamin D synthesis, but exposure to excessive UV irradiance leads to several harmful impacts ranging from premature wrinkles to dangerous skin cancer. However, for countries located in the global dust belt, accurate estimation of the UV irradiance is challenging due to a strong impact of desert dust on incoming solar radiation. In this work, a UV Index forecasting capability is presented, specifically developed for dust-rich environments, that combines the use of ground-based measurements of broadband irradiances UVA (320–400 nm) and UVB (280–315 nm), NASA OMI Aura satellite-retrieved data and the meteorology-chemistry mesoscale model WRF-Chem. The forecasting ability of the model is evaluated for clear sky days as well as during the influence of dust storms in Doha, Qatar. The contribution of UV radiation to the total incoming global horizontal irradiance (GHI) ranges between 5% and 7% for UVA and 0.1% and 0.22% for UVB. The UVI forecasting performance of the model is quite encouraging with an absolute average error of less than 6% and a correlation coefficient of 0.93. In agreement with observations, the model predicts that the UV Index at local noontime can drop from 10–11 on clear sky days to approximately 6–7 during typical dusty conditions in the Arabian Peninsula—an effect similar to the presence of extensive cloud cover. Full article