High-intensity Ultraviolet Radiation Research Articles

Rheological and microscopic characterization and correlation analysis of asphalt under high-intensity ultraviolet radiation

The lower radiation intensity (2–20 W/m2) was widely used for asphalt ultraviolet (UV) aging. The effect of high-intensity radiation on asphalt properties and microscopic morphology is unknown. This study investigated the rheological behavior, microscopic characterization, and correlation analysis of SBS modified asphalt under high-intensity UV radiation. Rheological properties tests encompassed temperature sweep (TS), multiple stress creep recovery (MSCR), and frequency sweep (FS). Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and Gel Permeation Chromatography (GPC) tests were performed to reveal the microscopic characterization. In the early stages of UV aging, the rutting factor of asphalt was increased. The increment decreased as the UV aging time increased. The UV aging process did not alter the temperature sensitivity of asphalt. The complex shear modulus was influenced by UV radiation duration and loading frequency. Extended exposure to high-intensity UV radiation resulted in the formation of microcracks on the surface of the asphalt. The maximum molecular weight of the UV-aged asphalt was higher than that of the original asphalt. The degraded SBS modifier deteriorated the homogeneity of asphalt. The sulfoxide aging index, carbonyl aging index, number-average molecular weight (Mn), weight average molecular weight (Mw), and polymer dispersity index (PDI) presented a better correlation with rheological behavior indexes. The correlation between small molecule size (SMS), medium molecule size (MMS), and large molecule size (LMS) with rutting factor and complex shear modulus was poor. It was worth mentioning that the correlation between the MSCR test results and microscopic performance indicators was the best. Especially for the recovery rate and Jnr at 3.2 kPa, the mean absolute value of the correlation coefficient was 0.953.

Effects of high-intensity ultraviolet irradiation on the structure and mechanical properties of Sisal fibers

Abstract To explore the impact of high-intensity ultraviolet light on the structure and mechanical properties of sisal fibers, the article uses chemical methods in the sisal fiber surface silver-plated, untreated, and alkali-treated sisal fibers as a comparison, with the help of scanning electron microscopy, infrared spectroscopy on the fiber surface topography, the molecular structure of the research, determination of high-intensity ultraviolet irradiation under the mechanical tensile properties of the fiber. Exposure to high-intensity ultraviolet radiation for a brief period results in a reduction in the tensile strength, fracture elongation, and elastic modulus of untreated, alkali-treated, and chemically silver-plated sisal fibers by 95.2%, 77.7%, 55.9%, 92.8%, 76.9%, 42.1%, and 89.4%, 70.2%, 34.2%, respectively.

Evaluation of Micro-Needling Followed by Tranexamic Acid Cream versus Micro-Needling Followed by Tranexamic Acid Solution in Treatment of Melasma: A Comparative Split Face Study

Abstract Background Melasma is a common pigmentary disorder clinically characterized by symmetric light brown to bluish-gray macules and patches with irregular, sharp borders that affect cutaneous areas, particularly the face and neck. It is commonly identified in women of reproductive ages and more commonly described in darker-skinned patients with Fitzpatrick skin types IV to VI residing in high-intensity ultraviolet radiation worldwide. It causes significant cosmetic disfigurement, psychosocial stress, and embarrassment, affecting patients’ quality of life. Objectives To evaluate the efficacy and safety of microneedling followed by tranexamic acid (TXA) cream application versus microneedling followed by tranexamic acid solution in the treatment of facial melasma. Patients and Methods This prospective split-face comparative study included thirty female patients with different types of melasma, their ages ranged from 25 to 40 years. They were recruited from the Dermatology outpatient clinic of Ain Shams University Hospitals. All patients have been treated with TXA for 3 sessions; one session every month (the right side of the face was treated by microneedling followed by TXA 5 % cream while the left side of the face was treated by microneedling followed by TXA solution 5%). Additionally, the right side of the face was treated with TXA 5% cream, and the left side applied with placebo cream twice daily for 3 months. Assessment was done by Hemi Melasma Area and Severity Index score (Hemi -MASI), patients’ satisfaction score, clinical digital photography, dermoscopic examination and area percentage of melanin concentration assessed by histopathological examination. Results Our findings showed significant improvement in different types of melasma regarding Hemi MASI score, patients’ satisfaction score, and area percentage of melanin concentration assessed by histopathological examination by Fontana-Masson stain (FM) one month after 3rd treatment session in both sides of the face. However, a minor melasma recurrence was observed two months after 3rd treatment session on both sides of the face. Meanwhile, no significant difference was observed in the treatment response of microneedling followed by TXA cream versus microneedling followed by TXA solution one month after 1st and 2nd sessions regarding Hemi MASI score, while a significant difference was observed one month after the 3rd session. Conclusion Topical TXA appears to be a promising therapeutic option in the treatment of melasma without serious adverse effects. Topical TXA cream, which was applied twice daily by the patient combined with microneedling sessions with TXA cream, has better results in comparison with microneedling sessions with TXA solution with placebo cream.

Superdurable and fire-retardant structural coloration of carbon nanotubes

Carbon nanotubes (CNTs) are promising candidates for numerous cutting-edge fields because of their excellent properties. However, the inherent black color of CNTs cannot satisfy the aesthetic/fashion requirement, and the flammability of CNTs severely restricts their application in high-temperature environments with oxygen. Here, we realized a structural coloration of CNTs by coating them with amorphous TiO2 layers. By tuning the TiO2 coating thickness, both CNT fibers and membranes exhibited controllable and brilliant colors, which exhibited remarkable superdurability that could endure 2000 cycles of laundering tests and more than 10 months of high-intensity ultraviolet irradiation. The TiO2-coated CNTs exhibited a notable fire-retardant performance and could endure 8 hours of fire burning. The structural coloration of CNTs with excellent fire retardance substantially improves their performance and broadens their applications.

Virucidal activity of pulsed ultraviolet radiation of continuous spectrum against SARS-CoV-2 coronavirus

The effect of pulsed ultraviolet (UV) radiation of a continuous spectrum on the inactivation of the novel SARS-CoV-2 coronavirus on metal surfaces was studied. The ability of generators of pulsed UV radiation of a continuous spectrum to completely inactivate the causative agent of COVID-19 within 3 minutes (Alpha-06) and 6 minutes and 45 seconds (Alpha-09) of the installation was confirmed. It has been shown that the use of high-intensity pulsed UV radiation of a continuous spectrum in the general complex of sanitary and hygienic measures for a long time (5 months) allows the personnel of medical organizations, in particular, employees of the laboratory PCR centre, to be protected from the disease of the new coronavirus infection COVID-19.

Characterization of chromophoric dissolved organic matter in lakes across the Tibet-Qinghai Plateau using spectroscopic analysis

Fluorescent dissolved organic matter (FDOM) has a significant influence on global inland water carbon cycling and biogeochemical processes. The alpine lakes on Tibet-Qinghai Plateau (TQP) are exposed to high-intensity ultraviolet radiation, long retention time with less anthropogenic influences. Yet, limited studies were conducted on FDOM of lakes on the highest plateau in the world with unique aquatic environments. Spatiotemporal variations of FDOM components from 63 lakes (32 fresh lakes, N = 135; 31 brackish lakes, N = 109) were grouped according to salinity across the TQP collected during 2014–2017. FDOM were examined using excitation-emission matrix spectra (EEM) and fluorescence regional integration (FRI). CDOM absorption and FDOM fluorescence indices, average fluorescence intensities of the five fluorescent components (φi,i = I, II, III, IV, V) and total fluorescence intensities (φT) are significantly different between brackish and freshwater lakes (p < 0.05). High correlations (−0.51** < r < −0.86**, p < 0.01) were revealed between FDOM and dissolved organic carbon (DOC) concentrations with salinity > 10‰. A comparatively prolonged retention time and terrestrial allochthonous inputs caused higher DOC accumulation in brackish water. Strong UV radiation resulted in an important effect on CDOM photo-absorption characteristics, and that contributed to DOC variability and fate. Likewise, average CDOM spectroscopic indices in each basin with different land covers showed a moderate correlation between DOC and normalized humic-like φV for 20 basins (r = −0.46**, p < 0.01). The results suggest that studies on the highest alpine lakes across the TQP should focus on the impact of the evapo-concentration, ultraviolet irradiance and landscape features within different basins on FDOM characteristics. It demonstrated that the FDOM was dominated by the allochthonous sources in brackish lakes from the TQP and had a similarity to those observed in marine environments.

Efficacy of 308-nm excimer laser versus high-intensity ultraviolet radiation for the treatment of active localized vitiligo

Objective To investigate the efficacy and safety of 308-nm excimer laser compared to high-intensity ultraviolet radiation for the treatment of active localized vitiligo, and to observe changes in skin lesions before and after the treatment by confocal laser scanning microscopy. Methods Sixty patients with 203 skin lesions of active localized vitiligo and were enrolled into this study, and the vitiligo disease activity (VIDA) score of these patients ranged from 2 to 3. We selected more than 3 skin lesions from a same anatomical site of each patient, one of lesions served as a control and the other skin lesions (≥ 2) were randomly treated with 308-nm excimer laser (laser group) or high-intensity ultraviolet radiation (ultraviolet group) . The treatment was conducted twice a week for 25 sessions, and a 3-month follow-up was performed. Results A total of 48 patients with 169 skin lesions completed the trial. The marked response rate was significantly higher in the laser group[66.15% (43/65) ]than in the ultraviolet group[44.64% (25/56) , χ2= 8.28, P < 0.01]. The patients with a VIDA score of 2 showed a significantly higher marked response rate[67.69% (44/65) ]compared with those with a VIDA score of 3[44.64% (25/56) , χ2= 6.80, P < 0.01]. During the 3-month follow-up, no relapse was observed. Confocal laser scanning microscopy showed that the number of inflammatory cells increased at the dermal-epidermal junction of the intra- and extra-marginal lesional skin. After treatment, the number of inflammatory cells markedly decreased and returned to normal level in lesions. Conclusion Both 308-nm excimer laser and high-intensity ultraviolet radiation are effective in the treatment of active localized vitiligo, but the 308-nm excimer laser shows a more rapid onset of action and a better therapeutic effect. Key words: Vitiligo; Lasers, excimer; Ultraviolet therapy; Microscopy, confocal

A macroscopically nondestructive method for characterizing surface mechanical properties of polymeric coatings under accelerated weathering

The surface of coatings and plastics is the first target in any degradation process initiated by ultraviolet (UV) radiation or mechanical stress (via scratch and abrasion). Surface damage can lead to changes in optical, morphological, and mechanical properties and can result in pathways for ingress of moisture and corrosive agents. Current test methods for monitoring performance of protective coatings focus on chemical properties and optical properties, such as color and gloss measurements, or invasive tests such as abrasion and cross-cut adhesion. In this study, a macroscopically nondestructive performance protocol using nanoindentation metrology via a well-controlled scratch test was applied to evaluate the scratch resistance and monitor the surface mechanical property changes in a protective coating under accelerated weathering. Polyurethane (PU) coatings with different polyol compositions were chosen for this study. Coating specimens were exposed to high-intensity UV radiation at 55°C and 75% RH conditions. Exposed specimens were removed at specified UV exposure times for surface modulus/hardness and scratch resistance characterization via nanoindentation and scratch test. The effect of polyol type and UV radiation dose on the scratch damage (scratch morphology) was investigated and correlated with the surface hardness and modulus of the materials.

Assessing the effects of ultraviolet radiation on the photosynthetic potential in Archean marine environments

AbstractIn this work, the photosynthesis model presented by Avilaet al. in 2013 is extended and more scenarios inhabited by ancient cyanobacteria are investigated to quantify the effects of ultraviolet (UV) radiation on their photosynthetic potential in marine environments of the Archean eon. We consider ferrous ions as blockers of UV during the Early Archean, while the absorption spectrum of chlorophyllais used to quantify the fraction of photosynthetically active radiation absorbed by photosynthetic organisms. UV could have induced photoinhibition at the water surface, thereby strongly affecting the species with low light use efficiency. A higher photosynthetic potential in early marine environments was shown than in the Late Archean as a consequence of the attenuation of UVC and UVB by iron ions, which probably played an important role in the protection of ancient free-floating bacteria from high-intensity UV radiation. Photosynthetic organisms in Archean coastal and ocean environments were probably abundant in the first 5 and 25 m of the water column, respectively. However, species with a relatively high efficiency in the use of light could have inhabited ocean waters up to a depth of 200 m and show a Deep Chlorophyll Maximum near 60 m depth. We show that the electromagnetic radiation from the Sun, both UV and visible light, could have determined the vertical distribution of Archean marine photosynthetic organisms.

UV resistance of polystyrene co-butyl acrylate (PSBA) encapsulated lignin–saponite nanohybrid composite film

Protecting biological systems and organic materials from high ultraviolet (UV) radiation is a significant issue for engineering materials in both terrestrial and space applications. In this study, the synthesized composites of polystyrene butyl acrylate (PSBA) encapsulated lignin based nanohybrid were evaluated as UV resistant cladding materials for both applications. The UV transmittance of the composite films and their physical, thermal, and chemical degradation after prolonged exposure to high UV radiation (10 Earth days and 30 Mars equivalent days) at low temperatures of 3.4°C were examined. The results showed that the composite films blocked the UV radiation and there was no significant effect of UV radiation on film integrity, mechanical and thermal properties of the composite films when they were exposed to high intensity UV radiation (132W/m2) within 24h. Further, FTIR spectra of the composite films before and after UV radiation demonstrated that the films did not have notable oxidation degradation, although the glass transition temperature was slightly decreased with increased exposure time.

Research on the Micro-Injection of UV Curing

Based on the traditional injection molding technology, micro-injection molding of UV curing experiments has been conducted. The injection molding and repeatability of the parts which have micro-structure were mainly studied. The experimental results show that: the mold-ability and repeatability of micro-structure are significantly infected by UV radiation energy and forming temperature. In order to achieve a good repeatability, it is necessary to use a sufficiently high intensity ultraviolet radiation and appropriate molding temperature during micro-injection of UV curing.

Impact-generated endolithic habitat within crystalline rocks of the Haughton impact structure, Devon Island, Canada.

The colonization of rocks by endolithic communities is an advantageous trait, especially in environments such as hot or cold deserts, where large temperature ranges, low water availability, and high-intensity ultraviolet radiation pose a significant challenge to survival and growth. On Mars, similar conditions (albeit more extreme) prevail. In these environments, meteorite impact structures could provide refuge for endolithic organisms. Though initially detrimental to biology, an impact event into a rocky body can favorably change the availability and habitability of a substrate for endolithic organisms, which are then able to (re)colonize microfractures and pore spaces created during the impact. Here, we show how shocked gneisses from the Haughton impact structure, Devon Island, Canada, offer significant refuge for endolithic communities. A total of 28 gneiss samples representing a range of shock states were analyzed, collected from in situ, stable field locations. For each sample, the top centimeter of rock was examined with confocal scanning laser microscopy, scanning electron microscopy, and bright-field microscopy to investigate the relationship of biomass with shock level, which was found to correlate generally with increased shock state and particularly with increased porosity. We found that gneisses, which experienced pressures between 35 and 60 GPa, provide the most ideal habitat for endolithic organisms.

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The Effect of High Intensity UV Irradiation on Color Behavior of Poly(Vinyl Chloride)

A detailed study of color change in poly(vinyl chloride) (PVC) sheets due to high intensity ultraviolet (UV) irradiation was undertaken, focusing on the first 50 h of change. Color changes were monitored with a Datacolor check spectrophotometer and compared with a set of controls. Measurements were taken after 1, 3, 5, 10, 15, and 20 h of irradiation, then at 10 h intervals for the next 40 h. Further measurements were conducted at 100, 240, and 480 h. Data were analyzed using the reflectance spectra (350–800 nm) as well as the CIE (International Commission on Illumination) L* a* b* color values (L*, a*, and b* are lightness value, redness-greenness value, and yellowness-blueness value, respectively) and the total color change (ΔE). The majority of color changes were found to occur within the first 50 h. After 50 h, the color change slowed and began to reverse toward 480 h. Surface microstructure properties, such as morphology, surface tension and oxidized products, were characterized to allow a comparison of sensitivity between the color monitoring methods and a comprehensive understanding of the color change. The results show that color evolution was attributable to the competition between the formations of polyene sequences (dehydrochlorination reaction) and their subsequent oxidation (photobleaching), which was slightly different from the behavior under a xenon arc lamp. According to the color behavior and the microstructure analysis a general scheme accounting for the mechanism of ageing behavior of PVC under high intensity UV irradiation is proposed.

UV radiation elevates arylalkylamine N-acetyltransferase activity and melatonin content in the two-spotted spider mite, Tetranychus urticae

Ultraviolet (UV) radiation produces reactive oxygen species (ROS) in mammals, where melatonin plays the role of a ROS scavenger. The melatonin synthetic enzyme arylalkylamine N-acetyltransferase (NAT) is a significant element in a possible ROS removal system. Changes in NAT activity and melatonin content were determined in the two-spotted spider mite Tetranychus urticae by irradiating it with monochromatic light using the Okazaki Large Spectrograph at the National Institute for Basic Biology, Okazaki, Japan. The NAT activity and melatonin content were suppressed by blue light (450 nm). No effects of red light (650 nm) on the NAT activity and melatonin content were observed. UV radiation had intensity-dependent dual effects on the NAT activity and melatonin content. In the UV-B (300 nm) treatment, the NAT activity and melatonin content were suppressed at the intensity below 1 μmol m −2 s −1 but elevated when the intensity was as high as 10 μmol m −2 s −1. In the UV-A (350 nm) treatment, the melatonin content was elevated when the intensity was as high as 10 μmol m −2 s −1, though the NAT activity and melatonin content were suppressed at the intensity below 10 and 1 μmol m −2 s −1, respectively. Elevation of the NAT activity and melatonin content by high intensity UV irradiation may indicate that the UV signals initiate melatonin synthesis for ROS removal in mites.

Role of Free Cadmium and Selenium Ions in the Potential Mechanism for the Enhancement of Photoluminescence of CdSe Quantum Dots Under Ultraviolet Irradiation

The present study describes an enhancement of the photoluminescence of CdSe quantum dots under long-term ultraviolet irradiation in organic solvents. The photoenhancement effect followed multiexponential kinetics and was found to depend on several factors: intensity of ultraviolet light, polarity of the solvent, presence of capping agents on the nanocrystal surface, and presence of free Cd and Se ions in the solution. High intensity ultraviolet irradiation provoked a rapid enhancement of the photoluminescence of CdSe nanocrystals, reaching the maximum with subsequent photoluminescence decay. Low-intensity ultraviolet irradiation provoked a comparatively slow enhancement of the photoluminescence of CdSe nanocrystals, reaching saturation after 5-6 hours of irradiation in organic solvents (butanol and chloroform). The photoenhancement effect was reversible or irreversible depending on the additional ingredients. The role of free Cd and Se in these processes was clarified. The results are discussed in the context of ultraviolet induced liberation of free Cd and Se ions from the nanocrystal surface and their hypothetical reversible deposition with trapping of the surface holes and influencing the efficiency of radiative versus nonradiative exciton decay during the enhancement of photoluminescence.

Accelerated UV weathering device based on integrating sphere technology

An ultraviolet (UV) weathering device based on integrating sphere technology has been designed, fabricated, and implemented for studying the accelerated weathering of polymers. This device has the capability of irradiating multiple test specimens with uniform, high intensity UV radiation while simultaneously subjecting them to a wide range of precisely and independently controlled temperature and relative humidity environments. This article describes the integrating sphere-based weathering system, its ability to precisely control temperature and relative humidity, and its ability to produce a highly uniform UV irradiance.

Polycrystalline diamond position sensitive detector for excimer laser UV radiation

To overcome any difficulty related to the fabrication of diamond ultraviolet (UV) sensors based on p–n junction, in this work we describe the realisation and characterisation of a very simple chemical vapour deposited diamond position sensitive detector based on a voltage-division structure. The photosensor, tested under UV excimer laser illumination, shows a non-linearity of the output signal vs. the beam position of approximately 6% but the response repeatability under stable excitation conditions indicates an rms signal fluctuation as low as 1%. A very low sensitivity to light intensity variation has been also evidenced. Moreover, the device shows a high stability and preliminary results seem to indicate a good robustness to repetitive use. Compared to silicon, the high thermal conductivity and the large threshold energy for radiation damage of diamond would largely extend the lifetime of the device under high intensity UV irradiation.

Oxidative decoloration of dyes by pulsed discharge plasma in water

Degradation of organic dyes by the pulsed discharge plasma between needle-to-plane electrodes in contaminated water has been investigated in three discharge modes: (i) streamer, (ii) spark, (iii) spark–streamer mixed mode. The process of the decoloration has been found to be most effective if the discharge operates in the spark–streamer mixed mode in dye solutions. The decoloration rate during the pulsed discharge plasma treatment was dependent on the initial pH values. The decoloration rate was increased when more acidic condition was used, especially in the case of streamer discharge mode. The decoloration rate at the pH value of 3.5 was found to be approximately three times higher than that at a pH value of 10.3. A small effect of initial pH during the decoloration process by spark and spark–streamer discharge mode means that the physical effects, such as shock-wave and ultraviolet radiation, may play an important role in the oxidation process. It was found that the decoloration rates in the case of spark and spark–streamer mixed discharge modes, which are characterized by high intensity ultraviolet radiation, were found to be much higher than that in the case of streamer discharge that is characterized by low intensity ultraviolet radiation. In addition, the considerable increase in the decoloration efficiency of H 2O 2 containing solutions can be attributed to the increase in hydroxyl radicals’ concentration. These are produced by ultraviolet light photo-dissociation of H 2O 2 molecules in water surrounding the plasma channel.

IR optical properties of ZnS/ZnSe-modified high-density polyethylene

The goal of this work was to find practical materials for infrared motion sensors that are more selective for IR radiation of human origin. Motion sensors used for security purposes can be vulnerable to false alarms. Along with sensitivity to infrared radiation produced by human intruders, they also sense white radiation from a number of common environmental sources. One material used for sensor optics is high-density polyethylene (HDPE). Since pigments alter the IR absorption properties of materials, the focus of the research was to produce pigmented HDPE and to determine the optical and mechanical characteristics of the resulting materials. Different pigments added to HDPE produced varying results. One pigment, a mixture of zinc sulfide and zinc selenide, performed well in eliminating white radiation, while attenuating the IR transmittance minimally. Accelerated weathering by exposure to high-intensity ultraviolet radiation gave information on the usefulness of the pigmented plastics for actual sensor installations. Accelerated weathering of clear HDPE and plastic pigmented with ZnS/ ZnSe produced a negligible loss. Impact testing for assessment of the embrittlement of the aged plastics showed that the clear HDPE and the ZnS/ZnSe pigmented polymer failed only at high impact and long simulated aging times.