The influence of UV radiation on silk fibroin

An investigation into the influence of UV-irradiation on regenerated silk fibroin dissolved in water was carried out using UV-Vis and fluorescence spectroscopy. It was found that the absorption of regenerated silk fibroin in solution increased during UV-irradiation of the sample, most notably between 250 and 400 nm. Moreover, after UV-irradiation a wide peak emerged between 290 and 340 nm with maximum at about 305 nm. The new peak suggests that new photoproducts are formed during UV-irradiation of regenerated silk fibroin.The fluorescence of regenerated silk fibroin was observed at 305 nm, at 480 nm and at 601 nm after excitation at 275 nm. UV-irradiation caused fluorescence fading at 305 nm and at 601 nm. The increase of fluorescence was observed at 480 nm, probably due to formation of new photoproducts. After excitation at 305 nm the fluorescence of regenerated silk fibroin was observed at 340 nm and at 400 nm. UV-irradiation caused fluorescence fading at 340 nm. FTIR spectroscopy showed that primary structure of regenerated silk fibroin was not significantly affected by UV radiation. SDS-PAGE chromatography showed alterations of molecular weight of silk after UV exposure.     

Interaction between UV radiation and filled polytetrafluoroethylene (PTFE). I. Degradation processes

The first part of a series of two, this paper analyzes the degradation of pure and filled PTFE under high energy UV radiation. The polymer morphology is first investigated using differential scanning calorimetry, highlighting the respective nucleating efficiency of TiO₂ and CaF₂ during polymer crystallization. Then, the various polymers are exposed to excimer laser radiation and observed under an optical microscope. The results indicate that the degradation is closely connected with microstructural parameters. In pure PTFE, scattering by crystallites and reflection on piles of lamellae control the nature and extent of the degradation. In filled PTFE, nature and concentration of fillers are the most important features governing degradation. When absorbing particles are added to PTFE, the damage is restricted to the surface and photothermal processes can modify the degradation from heterogeneous to ablative, depending on the filler content. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2057–2067, 1998     

Interaction between UV radiation and filled polytetrafluoroethylene (PTFE). II. A multiple scattering analysis

The second part of the series, this article analyzes the way UV light propagates through pure and filled PTFE. We investigated the diffusiveness of the semicrystalline matrix as well as the effect of scattering and absorbing fillers (CaF₂ and TiO₂) on the attenuation. The UV-visible absorption curves have been determined by spectrophotometry. A theoretical calculation based on a four-flux multiple scattering approach allowed us to satisfactorily reproduce the experimental results, highlighting the respective importance of the coherent and the diffuse fields. In light of this model, we discuss the influence of multiple scattering on the extent of degradation when PTFE is exposed to a high energy UV radiation. This approach provides of a comprehensive view of the damaging effect of UV light on PTFE, showing a good agreement with the experimental results of the previous article. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2069–2083, 1998     

Rat lens glycolysis after in vivo exposure to narrow band UV or blue light radiation

UV radiation and short wavelength visible light are known to damage various tissues in the eye. This paper investigates the effect on rat lens glycolysis after in vivo exposure with 90 kJ m⁻² narrow band UV radiation (UVB, 300 nm) and 90 kJ m⁻² blue light (435 nm) radiation. After exposure, all lenses were incubated in Medium 199. Samples of culture medium were withdrawn after 2, 4, 6 h and 5, 10, 20 h in two UVB studies and after 5, 10 and 20 h in a blue light study. Lactate is the major end product of lens glycolysis. Lactate was determined with a modified enzymatic-photometric method. Intralenticular lactate was determined in one UVB experiment. In the UVB experiments we found a lower lactate production in the exposed lenses 2–6 h after exposure. There was an accumulation of lactate inside UVB-exposed lenses after 6 h incubation compared with their contralateral lenses. No significant effect on lactate production was observed in the blue light experiment. Conclusions. UVB induced a reversible inhibition of glycolysis. UVB also induced an accumulation of lactate inside the lens. Blue light tended to increase glycolysis.     

Effect of UV radiation on the dyeing of cotton fabric with reactive blue 13

For the present study, the cotton fabric and dye solution were irradiated to UV radiation for different times. Dyeing was performed using un-irradiated and irradiated cotton with un-irradiated and irradiated reactive blue dye. Different dyeing parameters such as temperature, pH and time were optimized using irradiated dye and irradiated cotton. The data of colour report were obtained from un-irradiated and irradiated cotton dyed with reactive blue dye using spectra flash (SF650). Colourfastness properties show that UV radiation of both cotton and dye powder has improved the grading of fastness from fair to good. It is found that UV irradiation has not only enhanced the strength of dye on irradiated fabric but also improved the dyeing properties.     

Degradation of ROMP-based bio-renewable polymers by UV radiation

The degradation of a bio-renewable polymer under UV exposure was studied using various methods. Degradation of the bio-renewable polymer increased with increasing exposure time. Enhanced cross-link density in the early stage of degradation was confirmed by Soxhlet extraction. Tensile testing showed a transition from ductile failure to brittle fracture. Surface cracks and embrittlement were primary reasons for most reductions in mechanical properties, such as tensile strength and breaking strain. The effects of degradation were confined to the surface of thick bio-based polymer specimens, confirmed by both SEM and PAS-FTIR. Depth profile studies of degraded samples showed that the concentration of oxidation products, such as hydroxyl and carbonyl groups, varied with depth depending on the diffusion of oxygen.     

Adjusting timing of weathering test to account for seasonal variations in UV exposure

Satellite-derived UV climatology has been used to design a timetable for the outdoor UV exposure of polymeric material specimens. By pre-exposure computation, fixed time increments are transformed into a schedule with a predicted average accumulation of UV dose. The method was applied to produce a timetable for an ongoing exposure programme in a network of seven European test sites over the latitude range 28.5-67.4°N. The effect of the average seasonal variability of solar UV irradiance on the predicted accumulated UV exposure is shown to be notably diminished by the method. Relative underestimations of 5-82% of cumulative UV stress are estimated to be avoided by extensions of 6-167 days exposure durations as suggested by the adjustment procedure. Hence, more reproducible degradation data are expected to be obtainable for exposures that are not multiples of the full annual cycle of UV, especially for those with a duration <1 year.     

丙烯酸在牙釉质表面的紫外光共辐射接枝

龋坏的过程是牙釉质脱矿和再矿化长期交替进行的过程,当脱矿大于再矿化时,就导致了釉质脱矿从而引起龋病的发生[1]。本文设想在牙釉质表面接枝一些羧基活性官能团,为进一步在牙釉质表面引入牙釉蛋白分子提供活性基团和接位空穴,并为深入探讨牙釉蛋白诱导牙釉质的再矿化提供基础     

A mini-review on limitations associated with UV filters

Ultraviolet light from the sun can produce long-term skin damage and cancer. The use of sunscreen products containing one or more UV filters is encouraged by health professionals for preventing the damaging effects resulting from sun exposure. However, recently there have been increasing concerns about the use of sunscreens and their safety for both humans and the environment. The sunscreen manufacturers should take the initiative in testing of the products for possible short-term skin toxicity and long-term health effects that might occur due to the absorption of UV filters through the skin. Published studies have shed light on this topic by investigating the harmful effects of UV filters such as oxybenzone on the hormone system of aquatic animals and humans. Currently, in vitro and in vivo animal models are being used to determine the mechanistic and cellular effects these products produce. With growing awareness of adverse effects posed by UV filters on the environment and exposed organisms, several jurisdictions are prohibiting their use in sunscreens. To our knowledge, very few reviews summarized the potential toxicities associated with UV filters. Therefore, the current reported findings are rather controversial due to the lack of nonclinical safety assessment data to determine the clinical significance of such exposure.     

紫外辐射诱导C60聚合的扫描隧道显微研究

C60的聚合反应是近年来C60研究的热点．Yeretzian等[1]首先在质谱中观察到了C60在激光作用下的聚合反应，我们也曾以激光真空溅射技术制备了丰富的C60与C70的聚合物[2]．进一步研究还发现，C60在紫外光照射下也能聚合成膜[3]．为更深入地了解C60的聚合过程，本文以扫描隧道显微（STM）技术跟踪观察了C60在紫外光辐射下所发生的形态变化．1实验部分C60吸附在Au（111）面上时能够铺展成单分子层[4]．因此，我们选择Au（111）面作基底，将C60配成一定浓度的甲苯溶液滴在金表面上，待甲苯挥发后制得C60的单分子层．实验所用的紫外光源为…     

The Shielding Effect of Nano TiO2 on Collagen under UV Radiation

The shielding effect of nano TiO₂ on collagen under UV radiation was investigated using UV spectrophotometry. The results indicate that the shielding of collagen under UV radiation in the presence of nano TiO₂ is significant. For 2.5 wt.‐% of TiO₂, there is a greater shielding effect of UV radiation than that for 0.5 wt.‐% of TiO₂. In addition, this study gives hints that a novel tanning agent with a UV shielding function can be formulated by using nano TiO₂.

UV absorption of collagen under UV radiation after adding 2.5 wt.‐% TiO₂.     

UV radiation induced graft copolymerization of allyl acetate onto poly(ethylene terephthalate) (PET) films for fuel cell membranes

Ultraviolet (UV)-induced graft copolymerization of allyl acetate (AA) monomer onto poly(ethylene terephthalate) (PET) films and the subsequent sulfonation on the monomer units in the grafting chain using chlorosulfonic acid (C1SO3H) were carried out to prepare proton exchange membranes (PEMs) for fu     

Characterization of a clear coating cured by UV/EB radiation

The quality and performance of the polymeric materials cured by ultraviolet (UV)/electron beam (EB) radiation depends on the components of coating formulation, as well as the type of radiation used in the curing process. The aim of this study was to establish the correlation between the cure degree of a clear coating irradiated with different radiation doses of UV or EB and the tensile properties of the polymeric films obtained. The cure degree was measured by DSC and FTIR.     

Rapid estimation of global sugars by UV photodegradation and UV spectrophotometry

The UV/UV method developed for the measurement of specific wastewater pollution parameters (ammonium, Kjeldahl nitrogen, total phosphorus) is adapted to the determination of sugars in fruit juices and soft drinks. The procedure is based on the UV spectrophotometric detection of by-products of UV photodegradation of carbohydrates. Time of analysis is greatly reduced by using specific pH conditions and diluted samples.     

Excited-State Evolution of Keto-Carotenoids after Excess Energy Excitation in the UV Region

Carotenoids are molecules with rich photophysics that are in many biological systems involved in photoprotection. Yet, their response to excess energy excitation is only scarcely studied. Here we have explored excited state properties of three keto-carotenoids, echinenone, canthaxanthin and rhodoxanthin after excess energy excitation to a singlet state absorbing in UV. Though the basic spectral features and kinetics of S₂, hot S₁, relaxed S₁ states remain unchanged upon UV excitation, the clear increase of the S* signal is observed after excess energy excitation, associated with increased S* lifetime. A multiple origin of the S* signal, originating either from specific conformations in the S₁ state or from a non-equilibrated ground state, is confirmed in this work. We propose that the increased amount of energy stored in molecular vibrations, induced by the UV excitation, is the reason for the enhanced S* signal observed after UV excitation. Our data also suggest that a fraction of the UV excited state population may proceed through a non-sequential pathway, bypassing the S₂ state.     

Investigation of some commercial TLD chips/discs as UV dosimeters

Using a deuterium UV source, we have investigated the response of a number of commercially available thermoluminescence (TL) dosimeters (TLDs) to UV radiation (UVR), including LiF : Mg, Cu, P (TLD-100 H), CaF₂ : Dy (TLD-200), CaF₂ : Mn (TLD-400), Al₂O₃ (TLD-500), ⁷LiF : Mg, Cu, P (TLD-700 H) and CaSO₄ : Dy (TLD-900). The intrinsic method was used to detect UVR, while trap depth and frequency factors were estimated using the initial rise method. We have studied TL intensity as a function of exposure time, observing high sensitivity of TLD-500 to UVR. Conversely, TLD-400 displays weak sensitivity to these same radiations. Although TLD-900 and TLD-200 are both less sensitive to UVR than TLD-500, they each provide a linear response to UVR. The possible use of these phosphors as UV dosimeters has been further appraised, examining thermal fading effects and fading due to light exposure.     

Synthesis,UV photo‐polymerization and degradation study of PEG containing polyester polyol acrylates

Succinic acid‐co‐polyethylene glycol polyester polyol acrylates, capable of in situ polymerization with UV radiation, were synthesized and characterized. Effect of structural changes such as internal branching, external crosslinking on their polymerization and degradation properties were investigated. Use of external crosslinkers reduced the polymerizability of the polymer. Lipases of different origins expedited the degradation to different extents and lipase isolated from porcine pancreas appeared to be more efficient than lipases from other sources. Copyright © 2004 John Wiley & Sons, Ltd.     

Significance of grafting in curing processes initiated by UV, excimer and ionising radiation sources

The grafting of a typical methacrylate monomer (MMA) to polypropylene (PPE) and cellulose initiated by UV and ionising radiation is reported. The effect of additives which constitute components in radiation curing on the grafting process is examined. Additives studied include photoinitiators (PIs), multifunctional acrylates and methacrylates and acrylate oligomers. Synergistic effects when these additives are combined in the same solution are reported. The photografting studies have been extended to include grafting with charge transfer (CT) complexes involving donor/acceptor (DA) monomers to PPE, cellulose and wool. The importance of this work in conventional and PI free curing is discussed, particularly the significance of concurrent grafting during curing.     

Induction and repair of cyclobuta-dithymidine photoproducts in hamster skin by solar-simulated UV radiation

The induction and repair of cyclobuta-dithymidine (T less than greater than T) photoproducts in hamster skin was measured following exposure to artificial solar radiation. DNA extracted from irradiated hamster epidermis was analyzed by enzyme-linked immunosorbent assay (ELISA) using a monoclonal antibody specific for T less than greater than T photoproducts. Between 49% and 58% of T less than greater than T antibody binding sites were eliminated from DNA by 24 h after radiation exposures comparable with approximately 60 - 120 min of midday sunlight, whereas all detectable T less than greater than T binding sites were eliminated by 24 h after a radiation exposure comparable with 30 min of sunlight.