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Mini-EUSO is a wide-angle fluorescence telescope that registers ultraviolet (UV) radiation in the nocturnal atmosphere of Earth from the International Space Station. Meteors are among multiple phenomena that manifest themselves not only in the visible range but also in the UV. We present two simple artificial neural networks that allow for recognizing meteor signals in the Mini-EUSO data with high accuracy in terms of a binary classification problem. We expect that similar architectures can be effectively used for signal recognition in other fluorescence telescopes, regardless of the nature of the signal. Due to their simplicity, the networks can be implemented in onboard electronics of future orbital or balloon experiments. [ABSTRACT FROM AUTHOR]

We investigate the effect of pure darkness and UV illumination on the corrosion process of 3Ni weathering steels involved in both marine atmospheric environments. The corrosion behavior of 3Ni steel in both environments was assessed by cyclic acceleration experiments, electrochemical measurements, morphological analysis and physical phase analysis. The results show that UV illumination affects the corrosion process through the photovoltaic effect of the corrosion products, with photoelectrons and photo-vacancies participating in the redox reaction between the substrate and the atmospheric environment, thereby affecting the corrosion rate of 3Ni steel, the physical composition of the corrosion products and the denseness of the rust layer. [ABSTRACT FROM AUTHOR]

This study focuses on the fabrication and characterization of nanostructured zinc oxide films deposited on glass substrates using sol–gel dip-coating methods. The thin films are functionalized with silver ions at various Ag+ concentrations (10−2, 10−3, 10−4 M) through room temperature ion fixation process with and without ultraviolet (UV) illumination. Physicochemical characterization techniques, such as employing Scanning Electron Microscopy with Energy-dispersive X-ray spectroscopy (SEM-EDX), X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), Ultraviolet–Visible Spectroscopy and Electron Paramagnetic Resonance (EPR) techniques. The SEM-EDX and XRD confirmed a characteristic ganglia-like structure with a hexagonal crystalline structure. The photocatalytic performance and available surface area of the pure and Ag films are investigated in the removal of methylene blue dye under UV and visible light illumination and in darkness. It is observed that the photocatalytic activity increases proportionally to the Ag+ ion concentration: ZnO < Ag(10−4 M)/ZnO, < Ag(10−3 M)/ZnO < Ag(10−2 M)/ZnO. Moreover, the catalysts modified under UV illumination during the fixation treatment (Ag-UV/ZnO) exhibited a higher photocatalytic efficiency and degraded the dye in comparison with those without a light source (Ag/ZnO). The experimental results are confirmed using total organic carbon (TOC) analysis. The optimal silver concentration (10−2 M) is established, which shows the highest photocatalytic efficiency (in both cases of ion fixation treatment). The results can be used as a guideline for the development of co-catalyst-functionalized semiconductor photocatalysts. [ABSTRACT FROM AUTHOR]

The porosity of die-cast aluminum alloys is a determining factor for the quality of the product. In this paper, we studied the porosity of a selected part of a die-cast AlSi9Cu3(Fe) compressor part by computer tomography and metallography. In the case of this part, the achievable resolution by CT, a non-destructive testing method, was 30 μm—this method could not detect smaller cavities. Based on metallographic analysis, the percentage of defects larger than 30 μm ranges from 10 to 30% of the total number of defects, which represents 75–95% of the defective area (area ratio). Impregnation with methacrylate resin (used to seal cavities to prevent leakage) can be detected with UV-illuminated optical microscopic examination on metallographically prepared specimens. As confirmed by scanning electron microscopy, partial filling and partial impregnation can occur in a system of shrinkage cavities. [ABSTRACT FROM AUTHOR]

GaN high-electron-mobility transistors (HEMTs) have attracted widespread attention for high-power microwave applications, owing to their superior properties. However, the charge trapping effect has limitations to its performance. To study the trapping effect on the device large-signal behavior, AlGaN/GaN HEMTs and metal-insulator-semiconductor HEMTs (MIS-HEMTs) were characterized through X-parameter measurements under ultraviolet (UV) illumination. For HEMTs without passivation, the magnitude of the large-signal output wave ( X 21 FB ) and small-signal forward gain ( X 2111 S ) at fundamental frequency increased, whereas the large-signal second harmonic output wave ( X 22 FB ) decreased when the device was exposed to UV light, resulting from the photoconductive effect and suppression of buffer-related trapping. For MIS-HEMTs with SiN passivation, much higher X 21 FB and X 2111 S have been obtained compared with HEMTs. It suggests that better RF power performance can be achieved by removing the surface state. Moreover, the X-parameters of the MIS-HEMT are less dependent on UV light, since the light-induced performance enhancement is offset by excess traps in the SiN layer excited by UV light. The radio frequency (RF) power parameters and signal waveforms were further obtained based on the X-parameter model. The variation of RF current gain and distortion with light was consistent with the measurement results of X-parameters. Therefore, the trap number in the AlGaN surface, GaN buffer, and SiN layer must be minimized for a good large-signal performance of AlGaN/GaN transistors. [ABSTRACT FROM AUTHOR]

Antifogging surfaces with unique properties to migrate severe fog formation have gained extensive interest, which is of particular interest for transparent substrates to obtain high visibility and transparency. To date, a large number of strategies including superhydrophilic or superhydrophobic surfaces and titanium dioxide (TiO2)-based composite coatings have been developed based on different mechanisms. Although these surfaces exhibit effective antifogging properties, the rigid nanostructures, cumbersome preparation, and the need for UV light excitation largely limit their widespread applications. Herein, we report a zwitter-wettable antifogging and frost-resisting coating through a fast UV-curable cross-linking of copolymer with benzophenone groups. A series of random copolymers consisting of hydrophilic hydroxyethyl methacrylate (HEA), hydrophobic methyl methacrylate (MMA), and benzophenone-based acrylate units are developed by thermally triggered free-radical polymerization. Upon UV light irradiation, a highly efficient antifogging/frost-resisting coating is covalently bonded on a polycarbonate plate surface, maintaining a light transmission higher than 85%, which was confirmed in both high and low temperature anti-fog tests. Moreover, the wetting behaviors reveal that the antifogging performance exhibited by the zwitter-wettable surface mainly relies on its surface water-adsorbing capability to imbibe condensed water vapor on the surface outmost layer. Notably, the antifogging/frost-resisting behaviors can be well regulated by adjusting the hydrophilic/hydrophobic units, due to the proper balance between the water-adsorption and coating stability. Owing to its simplicity, low-cost preparation and high efficiency, this UV-curable acrylate antifogging coating may find a wide range of applications in various display devices in analytical and detection instruments. [ABSTRACT FROM AUTHOR]

Taking advantage of the outstanding properties of a naphthalenediimide-based entangled porous coordination polymer, a simple strategy for the achievement of white light emission is herein presented. The dynamic structural transformation of the [Zn2(bdc)2(dpNDI)]n metal-organic framework enhances the interactions with aryl-guests giving rise to different luminescence colors upon UV (ultraviolet) illumination. Thus, through the rational selection of those small aromatic guest molecules with different electron donor substituents at the appropriate proportion, the emission color was tuned by mixture ratio of guest molecules and even white light emission was achieved. Furthermore, domains in large crystals with a complementary response to linearly polarized light were noticed. [ABSTRACT FROM AUTHOR]

ZnO film was deposited by the magnetron sputtering method. The thickness of ZnO film is approximately 2 μm. The influence of UV light illumination on C2H5OH sensing properties of ZnO film was investigated. Gas sensing results revealed that the UV-illuminated ZnO film displays excellent C2H5OH characteristics in terms of high sensitivity, excellent selectivity, rapid response/recovery, and low detection limit down to 0.1 ppm. The excellent sensing performance of the sensor with UV activation could be attributed to the photocatalytic oxidation of ethanol on the surface of the ZnO film, the planar film structure with high utilizing efficiency of UV light, high electron mobility, and a good surface/volume ratio of of ZnO film with a relatively rough and porous surface. [ABSTRACT FROM AUTHOR]

Ultraviolet (UV) radiation has been considered a deleterious agent that living organisms must avoid. However, many of the acclimation changes elicited by UV induce a wide range of positive effects in plant physiology through the elicitation of secondary antioxidant metabolites and natural defenses. Therefore, this fact has changed the original UV conception as a germicide and potentially damaging agent, leading to the concept that it is worthy of application in harvested commodities to take advantage of its beneficial responses. Four decades have already passed since postharvest UV radiation applications began to be studied. During this time, UV treatments have been successfully evaluated for different purposes, including the selection of raw materials, the control of postharvest diseases and human pathogens, the elicitation of nutraceutical compounds, the modulation of ripening and senescence, and the induction of cross-stress tolerance. Besides the microbicide use of UV radiation, the effect that has received most attention is the elicitation of bioactive compounds as a defense mechanism. UV treatments have been shown to induce the accumulation of phytochemicals, including ascorbic acid, carotenoids, glucosinolates, and, more frequently, phenolic compounds. The nature and extent of this elicitation have been reported to depend on several factors, including the product type, maturity, cultivar, UV spectral region, dose, intensity, and radiation exposure pattern. Even though in recent years we have greatly increased our understanding of UV technology, some major issues still need to be addressed. These include defining the operational conditions to maximize UV radiation efficacy, reducing treatment times, and ensuring even radiation exposure, especially under realistic processing conditions. This will make UV treatments move beyond their status as an emerging technology and boost their adoption by industry. [ABSTRACT FROM AUTHOR]

A two-dimensional (2D) Dy2O3-Pd-PDA/rGO heterojunction nanocomposite has been synthesised and tested for hydrogen (H2) gas sensing under various functioning conditions, including different H2 concentrations (50 ppm up to 6000 ppm), relative humidity (up to 25 %RH) and working temperature (up to 200 °C). The material characterisation of Dy2O3-Pd-PDA/rGO nanocomposite performed using various techniques confirms uniform distribution of Pd NPs and 2D Dy2O3 nanostructures on multi-layered porous structure of PDA/rGO nanosheets (NSs) while forming a nanocomposite. Moreover, fundamental hydrogen sensing mechanisms, including the effect of UV illumination and relative humidity (%RH), are investigated. It is observed that the sensing performance is improved as the operating temperature increases from room temperature (RT = 30 °C) to the optimum temperature of 150 °C. The humidity effect investigation revealed a drastic enhancement in sensing parameters as the %RH increased up to 20%. The highest response was found to be 145.2% towards 5000 ppm H2 at 150 °C and 20 %RH under UV illumination (365 nm). This work offers a highly sensitive and selective hydrogen sensor based on a novel 2D nanocomposite using an environmentally friendly and energy-saving synthesis approach, enabling us to detect hydrogen molecules experimentally down to 50 ppm. [ABSTRACT FROM AUTHOR]

Nanocarbon materials have the advantages of biocompatibility, thermal stability and chemical stability and have shown excellent electrical properties in electronic devices. In this study, Al/MWCNT:GQD/ITO memristors with rewritable nonvolatile properties were prepared based on composites consisting of multiwalled carbon nanotubes (MWCNTs) and graphene quantum dots (GQDs). The switching current ratio of such a device can be tuned in two ways. Due to the ultraviolet light sensitivity of GQDs, when the dielectric material is illuminated by ultraviolet light, the charge capture ability of the GQDs decreases with an increasing duration of illumination, and the switching current ratio of the device also decreases with an increasing illumination duration (103–10). By exploiting the charge capture characteristics of GQDs, the trap capture level can be increased by increasing the content of GQDs in the dielectric layer. The switching current ratio of the device increases with increasing GQD content (10–103). The device can be programmed and erased more than 100 times; the programmable switching state can withstand 105 read pulses, and the retention time is more than 104 s. This memristor has a simple structure, low power consumption, and enormous application potential for data storage, artificial intelligence, image processing, artificial neural networks, and other applications. [ABSTRACT FROM AUTHOR]

UV-B illumination facilitates aggregation of alpha-lactalbumin (α-LA) by intramolecular disulfide bond cleavage followed by intermolecular thiol-disulfide exchange reactions. However, long term exposure to UV-B illumination may induce undesired oxidative modifications of amino acid residues in the protein. The purpose of this study was to examine the effect of UV-induced aggregation of apo-α-LA (a calcium-depleted form of α-LA) under aerobic and anaerobic conditions and by addition of tryptophan (Trp) as a photosensitizer. The addition of Trp to apo-α-LA illuminated under anaerobic conditions facilitated the highest level of free thiol release and disulfide-mediated aggregation as compared to without addition of Trp under both anaerobic and aerobic conditions. Addition of Trp under aerobic condition resulted in the lowest level of free thiols and disulfide-mediated aggregation and the aerobic conditions caused oxidation of the free Trp with formation of kynurenine and 5-hydroxy-Trp. Minor levels of the Trp oxidation product, 3-hydroxy-kynurenine (2% converted from Trp), was formed in apo-α-LA with added Trp under both aerobic and anaerobic conditions after UV-B treatment. [ABSTRACT FROM AUTHOR]

Tin sulfide (SnS) is known for its effective gas-detecting ability at low temperatures. However, the development of a portable and flexible SnS sensor is hindered by its high resistance, low response, and long recovery time. Like other chalcogenides, the electronic and gas-sensing properties of SnS strongly depend on its surface defects. Therefore, understanding the effects of its surface defects on its electronic and gas-sensing properties is a key factor in developing low-temperature SnS gas sensors. Herein, using thin SnS films annealed at different temperatures, we demonstrate that SnS exhibits n-type semiconducting behavior upon the appearance of S vacancies. Furthermore, the presence of S vacancies imparts the n-type SnS sensor with better sensing performance under UV illumination at room temperature (25 °C) than that of a p-type SnS sensor. These results are thoroughly investigated using various experimental analysis techniques and theoretical calculations using density functional theory. In addition, n-type SnS deposited on a polyimide substrate can be used to fabricate high-stability flexible sensors, which can be further developed for real applications. [ABSTRACT FROM AUTHOR]

Green synthesis of ZnO nanoparticles has attracted research attention as a sustainable method of avoiding the destructive effect of chemicals. We synthesized a flower-shaped zinc oxide (ZnO) nanoflower (NF) from sea buckthorn fruit (SBT) by co-precipitation and characterized it using X-ray powder diffraction (XRD), X-ray photo electronic microscopy (XPS), photoluminescence (PL), field emission transmission electron microscopy (FE-TEM), and Fourier-transform infrared (FT-IR) spectroscopy. The ability of the ZnO/NF to degrade cationic and anionic dyes, including malachite green (MG), Congo red (CR), methylene blue (MB), and eosin Y (EY), under ultraviolet illumination was studied. The photocatalyst degraded approximately 99% of the MG, MB, CR and EY dyes within 70, 70, 80, and 90 min of contact time, respectively, at a dye concentration of 15 mg/L, 5 mg/L, SBT-ZnO/NF degraded 100% of the MG, MB, CR and EY dyes within 23, 25, 28, and 30 min, respectively. The results indicate that SBT-ZnO/NFs as synthesized is an inexpensive, non-toxic, rapid, and reusable photocatalyst that can play an enhanced role in wastewater treatment. [ABSTRACT FROM AUTHOR]

In this paper, the UV illumination effect for microwave gas sensors based on the tin dioxide was verified. A UV LED with emission wavelength close to the absorption edge of the SnO2 gas-sensing layer was selected as the UV source. The developed gas sensors were tested under exposure to acetone in the 0–200 ppm range at room temperature. The sensor's complex reflection coefficient corresponding to target gas concentration was measured with the use of a five-port reflectometer system exhibiting enhanced uncertainty distribution, which allows for the detection of low gas concentration. The UV illumination significantly emphasizes the sensors' response in terms of both magnitude and phase for low gas concentrations, in contrast to previously reported results, in which only the reflection coefficient's phase was affected. The highest responses were obtained for modulated UV illumination. [ABSTRACT FROM AUTHOR]