Effects Of Ultraviolet Exposure Research Articles

Effect of ultraviolet exposure and thermal treatment on NaF micro-crystallization mechanism in photo-thermo-refractive glasses

Photo-thermo-refractive (PTR) glass is a promising recording medium for volume-holographic devices. The recording processes involve a series of steps including ultraviolet (UV) exposure, nucleation, and crystallization thermal treatment. Sodium fluoride (NaF) microcrystals precipitate after crystallization, and modulate the refractive index locally of the glass matrix. In this study, to simulate the volume Bragg grating recording processes and study the effect of photothermal-induced processes on the crystallization kinetics in PTR glass, Si-Al-Na-Zn-K PTR glasses with and without Br− ions were prepared using the melt-quenching method. The UV exposure duration, thermal treatment temperature and crystallization time were regulated during subsequent treatment. During these processes, Br-free samples were used for comparison to demonstrate the potential roles of Br−ion in the nucleation and crystallization. The Ag nanoparticle (NP) nuclei surrounded by AgBr (AgF) microcrystals were characterized using UV–visible absorption spectroscopy and transmission electron microscopy, and the changes in the precipitated NaF were characterized using X-ray diffraction, Raman spectroscopy as well as XPS. The mechanism of NaF micro-crystallization is disclosed based on above experimental results. It is found the formation of Ag nanoparticle surrounded by AgBr (AgF) microcrystals inhibits the crystallization kinetics of NaF microcrystals in PTR glass.

Effect of ultraviolet exposure and palm fibre/fibreglass direction on composite

Effect of ultraviolet exposure and palm fibre/fibreglass direction on composite

The Effect of UV Exposure on the Service-life of Thermochromic Microcapsules Integrated into the Epoxy Matrix

The effect of ultraviolet (UV) exposure on the service-life of thermochromic microcapsules integrated into the epoxy matrix was investigated. The microcapsules of the formaldehyde shell contain the core of thermochromic leuco dye. Seven sets of epoxy resin samples filled with concentrations from 0 to 10 wt.% of microcapsules were investigated. The composite samples were exposed to UV for approximately 1000 h. For the quantitative evaluation of colour change under UV, a fast and simple original procedure based on samples’ image treatment was developed. With the exposure time intervals of 50 h, samples were taken out from the UV light chamber to evaluate the exposure effect on their reversible thermochromic ability and mechanical properties. Periodical evaluation of the UV light effect on mechanical properties during the exposure was performed by microhardness tests. Tensile tests of the samples till the fracture were performed every 200 h. The critical time under the exposure of the UV lamp that destroys the reversible thermochromic reaction of the microcapsules was defined as 200 h. At the same time, it has been found that the mechanical properties of the epoxy resin under the same UV source were not strongly affected after 1000 h of irradiance and changed in the frame of ~ 10 %.

Inactivation of marine bivalve parasites using UV-C irradiation: Examples of Perkinsus olseni and Bonamia ostreae

Diseases represent a major threat for the bivalve production industry. Their control relies on biosecurity measures to prevent their introduction and limit their spread. When maintained in hatcheries, nurseries and depuration centers, bivalves can become infected from the surrounding water and might release pathogens through wastewater effluents. A major effort was done in controlling the safety of bivalves for human consumption, but, on the other hand, information regarding the resistance of mollusc pathogens to water treatment is scarce. The effect of ultraviolet exposure was tested on two protozoan parasites of marine bivalves, the non-culturable parasite Bonamia ostreae and Perkinsus olseni culturable in DMEM/HAM´s medium. UV exposure experiments were carried out first at the bench scale and then, for P. olseni, at a larger scale mimicking depuration plants, hatcheries and nurseries conditions. At the bench scale, our study indicated that up to 40% of B. ostreae cells and 85% of P. olseni cells died 24 h and 21 days respectively after an exposure to 94 mJ/cm2 of UV-C. After 40 mJ/cm2 exposure, P. olseni density increased between 15 and 21 days of culture suggesting that the parasite is able to recover from low UV intensity exposure. At large scale, no signs of UV recovery were seen in P. olseni cultures, but, at lower intensity (216–244 mJ/cm2), 15% of the parasites remained alive 21 days post exposure. Finally, a minimum dose of 94 mJ/cm2 seems required to inhibit proliferation of parasites and 450 mJ/cm2 to completely kill all parasites. Taken this into account, a dose higher than 450 mJ/cm2 is suggested to properly treat water to avoid dispersion of bivalve protozoan parasites such as P. olseni.

A field‐friendly method of measuring faecal glucocorticoid metabolite concentration as a simple stress checker in snow leopards

Abstract The hormonal analysis of excrement has been employed to non‐invasively assess the physiological conditions of domestic, experimental, zoo and wild animals to. However, conventional hormone analysis techniques require frozen and refrigerated reagents, and laboratory equipment; therefore, it is almost impossible to obtain the results on‐site. This study attempted to establish a method for the simple and rapid quantitative on‐site analysis of faecal glucocorticoid metabolite (fGM) concentrations; this method involved using hand‐shaking for faecal hormone extraction, and immunochromatography using test strips and a smartphone application. This study focused specifically on snow leopards and developed a new, simple fGM measurement method to evaluate their stress levels on‐site. First, the effects of ultraviolet exposure and bacterial activity on fGM concentration, including sample age, were evaluated using faeces from a captive snow leopard. Second, a field‐friendly hormone extraction method was evaluated; this method does not require storage of faeces in the field because the hormones are extracted by hand‐shaking of faeces in ethanol at the time of collection. In addition, to measure hormone concentrations on‐site, a simple immunochromatography measurement kit was used. The concentrations were measured by quantifying the colour reactions using a smartphone application. There was no consistent increase or decrease in fGM concentration with ultraviolet irradiation time. In addition, a high correlation was observed between concentrations extracted using the conventional method (using a vortex mixer and methanol extraction) and those from the field‐friendly method (r = 0.812, p < 0.05). Changes in fGM concentration measured using immunochromatography were also highly consistent with those measured using the conventional method (enzyme immunoassay; r = 0.825, p < 0.05). The analytical validation of immunochromatography also showed high accuracy, that is parallelism (ANCOVA: F = 0.597, df = 1, p = 0.445) and recovery tests (98.2% ± 5.1% and 107.5% ± 18.7%). Further, for biological validation, the change in fGM concentration was examined before and after the transportation of the snow leopards to another zoo. This field‐friendly hormone analysis method is expected to contribute as a simple and rapid stress evaluation tool to manage conservation and animal welfare by monitoring the stress levels.

Effects of ultraviolet exposure on physicochemical and mechanical properties of bio-modified rubberized bitumen: Sustainability promotion and resource conservation

Promoting the use of scrap tire rubber and bio-modifiers in outdoor construction such as road pavements requires an in-depth understanding of their resistance to solar radiation which causes premature aging in outdoor constructions. Aging changes bitumen's colloidal stability, increasing the content of asphaltenes, and decreasing the content of aromatics as aging progresses. Bitumen's changes during aging include oxidation, aromatization, chain scission, and carbonization, which alter bitumen's chemical, physical, and mechanical properties. Here, we examine how exposure to ultraviolet radiation changes the physicochemical and mechanical properties of bio-modified rubberized bitumen (BMR) containing various bio-modifiers. To do so, the physicochemical and mechanical properties of rubberized bitumen specimens containing bio-modifiers from castor oil (CO), corn stover oil (CS), miscanthus oil (MS), wood pellets oil (WP), and waste vegetable oil (WVO) were examined before and after they were exposed to ultraviolet radiation for 50, 100, and 200 h. The study results showed that the resistance of the abovementioned bitumens to aging caused by ultraviolet exposure was highly dependent on the source of the bio-modifier. The aging resistance was highest for CO-BMR and WP-BMR, followed by WVO-BMR, CS-BMR, and MS-BMR. This was attributed to the presence of unsaturated groups in CO and WP, which acted as sacrificial agents. In the case of WP, the improvement can also be attributed to the presence of high content of furfural. It should be noted that furfural has been used as a specialty antiaging chemical in industry. The study outcomes help manufacturers select modifiers for rubberized bitumen to enhance its resistance to UV aging and promote sustainability in construction.

Effects of ultraviolet solar radiation on the properties of particulate-filled epoxy based polymer coating

Exposure to solar ultraviolet (UV) radiation causes photochemical damage near the exposed surface, which results in the degradation of composite reinforcing elements. To minimise the UV degradation, epoxy polymers are being applied as protective coatings to composite materials to retain properties during their design service life. In this study, the effects of UV exposure on the physical, mechanical, and thermo-mechanical properties, including the microstructure particulate-filled epoxy-based polymer coating, were investigated. The polymer coating contains up to 60% by volume of hydrated alumina powder fire retardant (FR) and fillers such as an industrial waste like fly ash (FA) and is exposed to simulated UV conditions either 1000 h or 2000 h. Physical observations showed yellowing at the surface of neat epoxy coating after UV exposure but the presence of particulate FR and FA fillers minimised fading and weight loss. Similarly, no reduction in the flexural strength was observed for polymer coating containing at least 40% fillers, indicating that the FR and FA retained the structural performance of the coating. SEM observation revealed formation of microcracks in the surface of the neat epoxy resin but a dense microstructure in particulate filled epoxy resin after exposure to UV radiation. FTIR analyses indicated that photo-degradation due to UV radiation was limited only on the thin surface of the coating. From the results of this study, a coating thickness of at least 11 mm is required for epoxy based polymer coating with 60% by volume fillers, which is 5 times thinner than neat epoxy resin, to provide 100 years of UV resistance.

A study looking at UV exposure and genetic risks in relation to melanoma

British Journal of DermatologyVolume 183, Issue 2 p. e39-e39 Plain Language Summary Free Access A study looking at UV exposure and genetic risks in relation to melanoma First published: 02 August 2020 https://doi.org/10.1111/bjd.19273 AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinked InRedditWechat Abstract Melanomas are common cancers among people of European ancestry, accounting for 1·6% of all new cancer cases and 0·6% of all cancer deaths worldwide in 2018. The only environmental factor consistently implicated as a cause of melanoma is ultraviolet (UV) radiation, but the relationship is complex, and little is known about how genetic factors influence the association between UV and melanoma. The effects of UV exposure are affected by ‘host factors’ (meaning factors that are specific to the individual, such as their genes), and by ‘host behaviours’ (such as their patterns of sun exposure and history of sunburns). The aim of this study was to examine whether melanoma risk varies according to reported levels of sun exposure, even within populations exposed to year-round high levels of sunlight (i.e. Queensland, Australia). More particularly, the authors sought to determine whether the associations with sunlight differ according to a person's inherent genetic risk. In a large Australian study, country of birth, age at migration and sunburns during all periods of life were all strongly associated with melanoma risk. People who had a past history of other types of skin cancer (specifically, BCC or SCC) and of other skin lesions caused by sun exposure had a higher risk of developing melanoma than people without sun-related skin lesions. The authors found evidence for gene-environment interactions that are consistent with the ‘divergent pathway’ hypothesis for melanoma development, which almost 20 years ago proposed that people with a high genetic susceptibility (i.e. at higher risk of melanoma, genetically) may only need modest levels of sun exposure to trigger melanoma development, whereas those with low genetic susceptibility require continued high levels of sun exposure to trigger melanoma development. In line with this hypothesis, the authors found that people who were at low genetic risk for melanoma, but who did eventually develop melanoma, were more likely to have been treated for sun-related skin lesions than people at high genetic risk. In other words, the people at low genetic risk who developed melanoma appeared to need a much larger dose of sun exposure than those at high genetic risk. In contrast, among people at high genetic risk, markers of high-level early life ambient exposure were relatively more important. These findings may help to identify and inform people at high risk of melanoma who stand to benefit most from adopting sun protective behaviours. Linked Article: Olsen et al. Br J Dermatol 2020; 183:303–310. Volume183, Issue2August 2020Pages e39-e39 RelatedInformation

Effect of ultra-violet exposure on production of mycosporine-like amino acids and lipids by Lyngbya purpurem

Cyanobacteria can have high lipid content, are amenable to metabolic engineering, and contain valuable materials, such as ultraviolet (UV) protectants and antioxidants. Maximizing the production and harvesting of several valuable products at the same time is an important objective. UV exposure was evaluated as a strategy to induce synthesis of UV protectants, higher lipid productivity, and a high lipid-saturation index in the cyanobacterium Lyngbya purpurem UTEX LB 2716. While UVA stimulated the highest production of lipids and the largest amount of mycosporine-like amino acids (MAAs), UVB lead to greater generation of MAAs, which correlated to higher antioxidant activity. UVB also showed a shift towards saturated fatty acids, such as C16:0 and C18:0, over unsaturated fatty acids, whereas UVA showed a shift towards the unsaturated fatty acids. In summary, UVB induced the highest MAAs production, anti-oxidant activity, and lipid saturation, and its yield of crude lipids and extracted FAME was only slightly lower than with UVA.

Xeroderma pigmentosum: when the sun burns the eyes

We report the case of a two-month-old male infant from a consanguine marriage. He had pigmented lesions on the skin of the eyelids, the face, and the neck, alternating with areas of depigmentation. An erosive appearance was found on the nose skin and lower labial mucosa. Ophthalmologically, the ocular tracking reflex was present, blepharitis was found with inflammatory palpebral swelling and bilateral ectropion; associated with conjunctival hyperemia, mucous secretions and severe dry eyes with corneal ulceration (exposure keratitis). The rest of the eye exam was normal. The prescribed treatment is based on sun protection, moistening, healing and antibiotic eye drops in both eyes, with close monitoring. Xeroderma pigmentosum (XP) is a rare genetic disease, with an autosomal recessive transmission, common in the Maghreb due to the high rate of consanguine marriage. The diagnosis of XP is clinical, defined by pigment abnormalities of skin exposed to the sun, skin neoplasia; XP is linked to a defect in the enzymes involved in repairing the oncogenic effects of ultraviolet exposure. Ocular neoplasia is most often located at the limb, cornea and conjunctiva. Prevention of tumors requires protection from sunlight. Surgical removal of tumors and self-healing of skin not exposed to the sun are the most important therapeutic measures. Treatment of complications (hyperemia, infections, and corneal opacification) is symptomatic, waiting for the arrival of the gene therapy.

Моделювання експериментального бактеріального кератиту та увеїту

When developing new protocols and methods for treating eye diseases, there is a need to set up an experiment with modeling a particular pathology in vivo. Currently, there are several methods for modelling keratitis and uveitis, however, their effectiveness remains unclear. In our research, under the experimental conditions on laboratory animals (rabbits), were applied three action methods of pathological factors causing inflammation and morphofunctional changes in eye tissues. The first method included the effect of ultraviolet exposure for 3 min using a DRT-240 mercury lamp, followed by infecting damaged corneal surface with the pathogenic Staphylococcus aureus strain 1×105 CFU/ml. The second method consisted of the introduction of the S. aureus pathogenic strain by injection of 1×105 CFU/ml into the anterior chamber of the eye. The third method is the application of filter paper 5 mm in diameter and soaked in 1% sodium hydroxide (NaOH) solution for 30 s on the surface of the eye cornea. In order to compare the degree of damage to the eye tissues after using various pathological factors, intravital diagnostic methods were used, in particular, the Shimmer test, the Seidel fluorescence test, non-contact face-to-face tonometry, biomicroscopy in focal light, ultrasound eye diagnostics, photo fixation. On the 7th day of the experiment, the animals were taken out of the experiment and histological studies of the enucleated eyeballs were carried out. It was found that all the factors that were used cause pathological processes, expressed to varying degrees. According to a complex of clinical and histological studies, it was found that the first method turned out to be the most effective, since the exposure of ultraviolet long-wave UVA rays caused a burn, and the next infecting with a pathogenic strain of S. aureus caused the development of total keratitis and uveitis. When a bacterial pathogen was injected into the anterior chamber of the eye, acute inflammation occurred inside the chamber, filling it with purulent exudate and melting the surrounding tissues, but did not cause keratitis on the cornea outer surface. In the group where chemical burns were used, according to the sum of the evaluation criteria and other studies, keratitis was found, but the eye barrier systems prevented the occurrence of uveitis.

Rearrangement of inhomogeneous distribution of ionic multiplets in ethylene ionomer induced by artificial weathering

An effect of ultraviolet exposure over the inhomogeneous structure of ionomer was investigated by using small-angle X-ray scattering (SAXS). Ionomer sheet laminated in between two sheets of glass was artificially weathered using a xenon lamp in an Atlas Ci4000 weatherometer. Though no significant changes were detected by chemical, thermal and optical analysis approach, SAXS identified changes at a low-angle upturn in the region of q < 0.01 Å−1 (where q is the magnitude of the scattering vector) after xenon light irradiation. Power law, I ∼ q−α, was employed to study the changes in the upturn and found α changed from 3.0 to 1.7, indicating a change in the micron-sized X-ray scatterers. A relationship between differences in the low-angle upturn and the inhomogeneous structure is interpreted as a rearrangement of cation distribution induced by xenon light irradiation.

Investigation of ultraviolet radiation effects on thermomechanical properties and shape memory behaviour of styrene-based shape memory polymers and its composite

In recent years, shape memory polymers (SMP) have been researched extensively for space applications, such as deployable solar panels and antenna reflectors. Space applications cause SMP components to be severely exposed to ultraviolet (UV) light which may results in material degradation which may causes catastrophic failures and costs substantial amount of public money. This paper investigates the effect of UV light exposure on thermomechanical properties and shape memory effect (SME) of the Styrene-based SMP and its Glass fibre shape memory polymer composites (SMPC). Dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA), have been used to investigate the thermomechanical properties, SMEs and thermal stability before and after the UV exposure. Further, Fourier transform infrared spectroscopy (FTIR) was performed to analyse the after effect of UV exposure on the polymer's chemical structure. Results have revealed that UV exposure had different impacts on the SMP samples. UV exposure have degraded the mechanical properties, lowered the glass transition temperature (Tg), considerably reduced shape recovery rate, and programming and recovery stresses in all samples. However, the exposure had no considerable effect on the fixity ratio and relaxation modulus of the neat SMP sample, and it slightly increased the fixity ratio of the SMPC samples.

NGF protects corneal, retinal, and cutaneous tissues/cells from phototoxic effect of UV exposure.

Based on evidence that nerve growth factor (NGF) exerts healing action on damaged corneal, retinal, and cutaneous tissues, the present study sought to assess whether topical NGF application can prevent and/or protect epithelial cells from deleterious effects of ultraviolet (UV) radiation. Eyes from 40 young-adult Sprague Dawley rats and cutaneous tissues from 36 adult nude mice were exposed to UVA/B lamp for 60min, either alone or in the presence of murine NGF. Corneal, retinal, and cutaneous tissues were sampled/processed for morphological, immunohistochemical, and biomolecular analysis, and results were compared statistically. UV exposure affected both biochemical and molecular expression of NGF and trkANGFR in corneal, retinal, and cutaneous tissues while UV exposure coupled to NGF treatment enhanced NGF and trkANGFR expression as well as reduced cell death. Overall, the findings of this in vivo/ex vivo study show the NGF ability to reduce the potential UV damage. Although the mechanism underneath this effect needs further investigation, these observations prospect the development of a pharmacological NGF-based therapy devoted to maintain cell function when exposed to phototoxic UV radiation.

Yellow Perch Sperm Motility, Cryopreservation, and Viability of Resulting Larvae and Juveniles

AbstractThe sperm of Yellow Perch Perca flavescens of two different age‐classes, age 0 and 3, were cryopreserved using two different cryoprotectants (dimethylsulfoxide [DMSO] and methanol [MetOH]) with two freezing methods (pellet and vial). The viability and quality of the progenies obtained from fertilization with cryopreserved sperm were then examined. The motility of Walleye Sander vitreus sperm was examined following cryopreservation and ultraviolet (UV) irradiation, with the aim of using heterologous cryopreserved sperm to inseminate Yellow Perch eggs to ensure gynogenesis. The first experiment compared the motility of fresh sperm and pellet method cryopreserved sperm devoid of salmon seminal plasma. Despite the high motility of fresh sperm—75% and 100%—of males age 0 and 3, respectively, the postthaw motility of seminal plasma devoid cryopreserved sperm was 0%. The second experiment addressed the efficiency of pellet and vial freezing methods with DMSO and MetOH supplemented with salmon seminal plasma. Cryopreserved sperm was thawed and motility measured. Sperm motility was not significantly different between pellet (13.3 ± 10.4%) and vial (10.3 ± 12.9%) methods in the absence of sperm extender; however, sperm motility of the pellet method was further improved (20 ± 8.7%) with the addition of sperm extender after thawing, while motility of the vial method sperm (10 ± 7.1%) was not. Cryopreserved sperm was further evaluated based on fertilization rate and ultimate survival and growth of larvae and juveniles through 14 d posthatch. Effects of UV exposure on fresh and pellet method cryopreserved sperm following UV irradiation were also examined. The motility of control sperm cryopreserved with DMSO and MetOH, and UV‐exposed sperm cryopreserved with DMSO decreased from 100% motility before cryopreservation (fresh sperm) to 75% following cryopreservation, while UV‐exposed sperm cryopreserved with MetOH decreased from 100% to 50%. This experiment provides significant new data to improve the effectiveness of straightforward cryopreservation techniques for Yellow Perch.

Impact of UV irradiation on multiwall carbon nanotubes in nanocomposites: Formation of entangled surface layer and mechanisms of release resistance

Multiwall carbon nanotubes (MWCNTs) are nanofillers used in consumer and structural polymeric products to enhance a variety of properties. Under weathering, the polymer matrix will degrade and the nanofillers may be released from the products potentially impacting ecological or human health. In this study, we investigated the degradation of a 0.72% (by mass) MWCNT/amine-cured epoxy nanocomposite irradiated with high intensity ultraviolet (UV) light at various doses, the effects of UV exposure on the surface accumulation and potential release of MWCNTs, and possible mechanisms for the release resistance of the MWCNT surface layer formed on nanocomposites by UV irradiation. Irradiated samples were characterized for chemical degradation, mass loss, surface morphological changes, and MWCNT release using a variety of analytical techniques. Under 295 nm–400 nm UV radiation up to a dose of 4865 MJ/m2, the nanocomposite matrix underwent photodegradation, resulting in formation of a dense, entangled MWCNT network structure on the surface. However, no MWCNT release was detected, even at very high UV doses, suggesting that the MWCNT surface layer formed from UV irradiation of polymer nanocomposites resist release. Four possible release resistance mechanisms of the UV-induced MWCNT surface layer are presented and discussed.

Dynamic properties of ultraviolet-exposed polyurea

Polyurea is used in military and civilian applications, where exposure to the sun in long durations is imminent. Extended exposure to ultraviolet radiation from the sun can deteriorate its mechanical performance to suboptimal levels. This study reports on the dynamic mechanical properties of polyurea as a function of ultraviolet radiation exposure duration. Six sets of samples were continuously exposed to ultraviolet radiation for different durations up to 18 weeks. Control samples were also tested that did not receive ultraviolet exposure. The dynamic properties were measured using a dynamic mechanical analyzer. Exposed samples exhibited significant color changes from transparent yellow to opaque tan after 18 weeks of exposure. Changes of color were observed as early as 3 weeks of exposure. The dynamic properties showed an initial increase in the dynamic modulus after 3 weeks of exposure, with no further significant change in the stiffness thereafter. The ultraviolet exposure had a significant impact at relatively short loading times or low temperature, for example, up to 6 decades of time. As loading time increases or polyurea operates at high temperature, the effect of ultraviolet exposure and temperature on the performance become highly coupled.

Effects of accelerated environmental aging on glass fiber reinforced thermoset polyurethane composites

Abstract In the present study, the effects on the microstructure and the impact behavior of thermoset polyurethane composite material, exposed to an accelerated aging environment, were assessed. A combined hygrothermal and ultraviolet (UV) chamber is used in an accelerated aging procedure to simulate temperate climate conditions. The samples were manufactured using a vacuum assisted resin transfer molding (VARTM) technique using a novel two-part polyurethane resin (Methylene diphenyl diisocyanate/Polyol) infused into plane weave E-glass fiber mats. Samples were exposed to the UV/moisture rich environment for 250, 500, 750 and 1000 h. Effect of UV exposure on color change of composite specimens was evaluated using colorimetry. The rate of color change and the total change in color for the fiber reinforced composite was shown to be much less than that of pure polyurethane. Optical microscopy observations revealed that the color change was limited to surface discoloration due to the fiber reinforcement limiting degradation to the surface polymer matrix microstructure even after extended UV-exposure. The accelerated aging effect on the glass fiber reinforced polyurethane was examined using low velocity impact tests to evaluate impact properties of the material throughout the aging process. The test showed that the bulk composite material was resistant to the UV aging by demonstrating no significant change in impact properties due to the accelerated aging process.

Effect of Ultraviolet Exposure on Impact Resistance of Ophthalmic Lenses.

To investigate the effect of ultraviolet radiation (UVR) on the impact resistance of organic ophthalmic lens materials. Plano power CR39, Phoenix, Trilogy, and polycarbonate lenses with various scratch-resistant (SR) and/or antireflection (AR) coatings were obtained in batches of 40 units. All lenses had a nominal thickness of 2 mm. Half of each batch was conditioned following the European Standard EN 168 protocol for the test of resistance to UVR (exposed group). The remaining lenses comprised an unexposed group for that combination of lens substrate and coating treatment. Each group was subjected to ballistic impact with 6-mm steel balls following the ZEST protocol to determine its mean breakage velocity. The difference in mean breakage velocity between exposed and unexposed groups of each combination of lens substrate and coating was assessed for statistical significance. Exposed uncoated CR39 showed a reduction in fracture velocity of 10.3 m/s whereas CR39 with ultra hard coat had a reduction of 3.5 m/s and CR39 with AR and SR coating had a reduction of 4.1 m/s. Scratch-resistant coated Phoenix had a reduction of 4.8 m/s whereas AR-coated Phoenix had a reduction of 3.7 m/s. The corresponding reductions for Trilogy were 3.9 and 17.8 m/s. All differences were significant at the p level of less than 0.05. Although we were unable to break unexposed SR-coated polycarbonate lenses with our test apparatus, exposed SR-coated polycarbonate had a mean breakage velocity of 142 m/s. Our data suggest that extended UVR exposure causes a significant reduction in the impact resistance of the ophthalmic lens substrates commonly used for occupational eye protectors. Protective lenses that have been exposed to high levels of UVR for extended periods should be replaced regularly to maintain optimal impact protection, even if they do not show visible damage owing to wear and tear.

Using 2D NMR spectroscopy to assess effects of UV radiation on cell wall chemistry during litter decomposition

Litter chemistry is one of the most studied controls on decomposition in terrestrial ecosystems. Solar radiation has been shown to increase litter decomposition rates in arid ecosystems through the process of photodegradation. However, it remains unclear how photodegradation affects litter chemistry, especially the abundance and composition of lignin, which is thought to play a key role in photodegradation. Using two-dimensional nuclear magnetic resonance (2D NMR) spectroscopic methods, we quantified the molecular-level changes in litter chemistry associated with photodegradation. Litter of Bromus diandrus was exposed in the field to two levels of radiation [with and without ultraviolet (UV) wavelengths] and two durations of exposure (2.5 months during summer, and 1 year). Through fiber analysis by sequential digestion, we found that the litter hemicellulose fraction decreased significantly from 31.6 to 24.9 % after 1 year of decomposition. In litter exposed for 1 year, the hemicellulose fraction was significantly lower in litter with UV exposure compared to litter without UV exposure (23.8 vs. 25.9 %). These results indicate that UV photodegradation has a small but significant effect on litter chemistry compared to other decomposition processes. Even though fiber analysis showed no loss of total lignin, 2D NMR analysis demonstrated that UV exposure reduced the major lignin structural units containing β-aryl ether inter-unit linkages by 9 % and decreased the relative abundance of lignin p-hydroxyphenyl units by 20 %. The 2D NMR analysis also revealed that lignin guaiacyl units were preferentially lost after 1 year of decomposition relative to the reference material, but no effects of UV exposure on guaiacyl units were observed. These results suggest that photodegradation causes partial degradation, not necessarily complete breakdown, of lignin structures. Our data also demonstrate that applications of 2D NMR methods are valuable for acquiring detailed information on lignin and polysaccharide chemistry during both biotic and abiotic decomposition processes.