UV-filtered Light Research Articles

The Impact of Accelerated Light Ageing on MS3 for Use as a Picture Varnish

ABSTRACT This study provides an evaluation of MS3, a reduced polycyclohexanone resin, with key considerations for use as a picture varnish including solubility, removability, colour, and gloss and the stability of these factors. MS3 was first produced in 2016 as a replacement for the discontinued MS2A resin which was widely used as a conservation-grade picture varnish. Films of MS3 resin were artificially aged using UV-containing and UV-filtered light, representing the effects of daylight filtered through glass, and indoor museum lighting conditions respectively. Changes in colour and gloss of light-aged samples vs. control samples were measured, and solubility/removability was evaluated using selected solvents applied by hand-rolled swabs. FTIR spectroscopy was used to explore chemical changes of the varnish films following light ageing with respect to control samples. Empirical observations were made regarding the handling properties of MS3 dissolved in Stoddard solvent, and its behaviour as a retouching medium and varnish. The results suggest that MS3 exhibits a slight yellowing and a moderate increase in the polarity of solvent required for removal. No significant colour or solubility changes were observed in MS3 varnish films artificially aged using non-UV light. The results suggest that MS3 is a good substitute for MS2A resin for use as a picture varnish or retouching medium, based on the parameters measured.

UV Dosage Unveils Toxic Properties of Weathered Commercial Bioplastic Bags.

Previous studies indicated that weathered conventional plastics and bioplastics pose ecotoxicological risks. Here, the effects of artificial and natural weathering on the ecotoxicity of three compostable bags and a conventional polyethylene (PE) bag are investigated. With that aim, a 21-day artificial indoor weathering experiment featuring UV light, UV-filtered light, and darkness was run simultaneously to a 120-day outdoor littoral mesocosm exposure featuring natural light, UV-filtered light, and shaded conditions. Acute toxicity of so-weathered plastic specimens was tested in vivo using the sensitive Paracentrotus lividus sea-urchin embryo test. PE was nontoxic from the beginning and did not gain toxicity due to UV weathering. In contrast, for bioplastics, dry artificial UV weathering increased toxicity in comparison to the dark control. Weathering in outdoor mesocosm led to a rapid loss of toxic properties due to leaching in rainwater. With a higher UV dosage, a plastic-type-dependent regain of toxicity was observed, most likely driven by enhanced availability or transformation of functional additives or due to bioplastic degradation products. PE showed moderate UV absorbance, while bioplastics showed high UV absorbance. This study highlights the potential of biodegradable plastics to pose enhanced ecotoxicological risk due to weathering under environmentally relevant conditions.

Influence of ambient water coloration on habitat and conspecific choice in the female Lake Malawi cichlid, Metriaclima zebra.

Female cichlid fish living in African great lakes are known to have sensory systems that are adapted to ambient light environments. These sensory system adaptations are hypothesized to have influenced the evolution of the diverse male nuptial coloration. In rock-dwelling Lake Malawi mbuna cichlids, however, the extent to which ambient light environments influence female sensory systems and potentially associated male nuptial coloration remains unknown. Yet, the ubiquitous blue flank coloration and UV reflection of male mbuna cichlids suggest the potential impacts of the blue-shifted ambient light environment on these cichlid's visual perception and male nuptial coloration in the shallow water depth in Lake Malawi. In the present study, we explored whether and how the sensory bias of females influences intersexual communication in the mbuna cichlid, Metriaclima zebra. A series of choice experiments in various light environments showed that M. zebra females 1) have a preference for the blue-shifted light environment, 2) prefer to interact with males in blue-shifted light environments, 3) do not show a preference between dominant and subordinate males in full-spectrum, long-wavelength filtered, and short-wavelength filtered light environments, and 4) show a "reversed" preference for subordinate males in the UV-filtered light environment. These results suggest that the visual perception of M. zebra females may be biased to the ambient light spectra in their natural habitat by local adaptation and that this sensory bias may influence the evolution of blue and UV reflective patterns in male nuptial coloration.

Role of light in methylmercury photodegradation: From irradiation to absorption in the presence of organic ligands

Photochemical degradation acts as the principal sink for methylmercury (MeHg) in surface water, which is regulated by light and solution matrix (especially the presence of dissolved organic matter, DOM). The spectral composition of light irradiation and the light absorption properties of reaction media (often exerted by DOM) are important in MeHg photodegradation, which has not yet been clearly resolved. Aiming to understand the role of light in MeHg photodegradation from the perspectives of both light irradiation and absorption, we investigated the photodegradation of MeHg under different simulated sunlight sources, with and without DOM model compounds of different molecular structures. The results show that the photodegradation of MeHg under different sunlight irradiation yields distinct first-order date constant, mainly due to the slight difference in UVB composition. The degradation of MeHg without DOM under a light source with high intensity in the UV region and no MeHg degradation under the UV-filtered light even in the presence of DOM showed the importance of UV lights in MeHg photodegradation. The use of ultrapure water as a reaction medium may be subject to MeHg loss through vessel adsorption, not just photolysis. Additionally, this work found that the type and position of coexisting substituents on aromatic thiols play a critical role in improving the photodegradation of MeHg, following amino > hydroxyl > carboxyl, para > meta > ortho. Based on the characterization of ultraviolet-visible absorption spectra and our previous work, it was concluded that the presence of DOM could induce red-shift in light absorption and reduce the electronic transition energy of the CHg bond, facilitating MeHg photodegradation. The structures of DOM affect the light absorption properties, which are related to MeHg photodegradation.

Evaluating Five Consolidants for Black-Dyed Māori Textile Artefacts

ABSTRACT This article reports testing of the efficacy of five consolidants (sodium alginate, zinc alginate, Paraloid® B-72, TRI-Funori™, Methocel® A4C) used by conservators for consolidation. The consolidants were tested for potential use on deteriorated black-dyed plant fibres, specifically paru-dyed muka (iron-tannate dyed fibre from harakeke; New Zealand flax, Phormium tenax), building on previous experimental work. Paru-dyed test fibres were pre-aged (light, with UV) to simulate museum artefacts, and then consolidated, after which their colour stability, strength retention, and acidity were measured. Consolidated test fibres were then artificially light-aged (UV-filtered) to test the stability of the consolidants over time (10 MLux hours; UV-filtered light), with colour stability, strength retention, and acidity re-measured after this ageing stage. A full factorial experimental design with four factors was used for testing: dye type, consolidant type, consolidant concentration, and accelerated light-ageing. Data were analysed using generalised linear models (GLM) coupled with analysis of variance (ANOVA) and simple effects procedures to test for interactions between factors and determine significant differences. Overall, this study found that using criteria of pH, strength, colour stability, and visual properties, that 0.5% w/v Methocel® A4C™ in H2O and TRI-Funori™ 0.5% w/v in H2O were recommended for further exploration for use on deteriorated paru-dyed muka.

Apparent spring swarming beaviour of Lesser Horseshoe Bats (Rhinolophus hipposideros)

Black-dyed artefacts are found in museums worldwide, many produced using an iron-tannate compound. Deterioration of iron-tannate dyed artefacts is an international preservation issue: in New Zealand the deterioration of paru (iron-tannate) dyed Māori textiles is widespread. This article reports experimental work testing the efficacy of sodium alginate, a consolidant developed for deteriorated paru-dyed muka (fibre from harakeke; Phormium tenax). The colour stability, strength retention, and acidity of paru-dyed muka consolidated with sodium alginate (0.25, 0.5, and 1% w/v in water) was tested pre- and post-artificial light ageing. This study found that sodium alginate had no negative effect on paru-dyed muka and in some cases provided benefit. Interestingly, the colour of paru-dyed muka is substantially more stable in UV-filtered light than previously recognised. Also microfading results were in agreement with visual assessments of colour change at 1 Mlux hour exposure, providing confidence in this relatively new technique to assess colour change.

Consolidation of Black-dyed Māori Textile Artefacts: Evaluating the Efficacy of Sodium Alginate

ABSTRACTBlack-dyed artefacts are found in museums worldwide, many produced using an iron-tannate compound. Deterioration of iron-tannate dyed artefacts is an international preservation issue: in New Zealand the deterioration of paru (iron-tannate) dyed Māori textiles is widespread. This article reports experimental work testing the efficacy of sodium alginate, a consolidant developed for deteriorated paru-dyed muka (fibre from harakeke; Phormium tenax). The colour stability, strength retention, and acidity of paru-dyed muka consolidated with sodium alginate (0.25, 0.5, and 1% w/v in water) was tested pre- and post-artificial light ageing. This study found that sodium alginate had no negative effect on paru-dyed muka and in some cases provided benefit. Interestingly, the colour of paru-dyed muka is substantially more stable in UV-filtered light than previously recognised. Also microfading results were in agreement with visual assessments of colour change at 1 Mlux hour exposure, providing confidence in this relatively new technique to assess colour change.

Photo-enhanced toxicity of two weathered Macondo crude oils to early life stages of the eastern oyster (Crassostrea virginica)

Polycyclic aromatic hydrocarbons (PAHs) have been reported to absorb ultraviolet (UV) light, resulting in enhanced toxicity. Early developmental stages of bivalves may be particularly susceptible to photo-enhanced toxicity during oil spills. In the current study, toxicity tests were conducted with sperm and three larval ages of the eastern oyster (Crassostrea virginica) to evaluate the photo-enhanced toxicity of low-energy water-accommodated fractions (WAFs) of two weathered Macondo crude oils collected from the Deepwater Horizon incident. Larvae exposed to oil WAFs under UV-filtered light demonstrated consistently higher survival and normal development than larvae exposed to WAFs under UV light. The phototoxicity of weathered Macondo oil increased as a function of increasing UV light intensity and dose. Early developing oyster larvae were the most sensitive to photo-enhanced toxicity, whereas later shelled prodissoconch larvae were insensitive. Comparisons between two weathered crude oils demonstrated that toxicity was dependent on phototoxic PAH concentration and UV light intensity.

On the mechanism of nanoparticulate CeO2 toxicity to freshwater algae

The factors affecting the chronic (72-h) toxicity of three nanoparticulate (10–34nm) and one micron-sized form of CeO2 to the green alga, Pseudokirchneriella subcapitata were investigated. To characterise transformations in solution, hydrodynamic diameters (HDD) were measured by dynamic light scatter, zeta potential values by electrophoretic mobility, and dissolution by equilibrium dialysis. The protective effects of humic and fulvic dissolved organic carbon (DOC) on toxicity were also assessed. To investigate the mechanisms of algal toxicity, the CytoViva hyperspectral imaging system was used to visualise algal–CeO2 interactions in the presence and absence of DOC, and the role of reactive oxygen species (ROS) was investigated by ‘switching off’ ROS production using UV-filtered lighting conditions.The nanoparticulate CeO2 immediately aggregated in solution to HDDs measured in the range 113–193nm, whereas the HDD and zeta potential values were significantly lower in the presence of DOC. Negligible CeO2 dissolution over the time course of the bioassay ruled out potential toxicity from dissolved cerium. The nanoparticulate CeO2 concentration that caused 50% inhibition of algal growth rate (IC50) was in the range 7.6–28mg/L compared with 59mg/L for micron-sized ceria, indicating that smaller particles were more toxic. The presence of DOC mitigated toxicity, with IC50s increasing to greater than 100mg/L. Significant ROS were generated in the nanoparticulate CeO2 bioassays under normal light conditions. However, ‘switching off’ ROS under UV-filtered light conditions resulted in a similar IC50, indicating that ROS generation was not the toxic mechanism. The CytoViva imaging showed negligible sorption of nanoparticulate CeO2 to algal cells in the presence of DOC, and strong sorption in its absence, suggesting that this was the toxic mechanism. The results suggest that DOC in natural waters will coat CeO2 particles and mitigate toxicity to algal cells.

The Effect of UV-absorbing Plastic Sheet on the Attraction and Host Location Ability of Three Parasitoids: Aphidius colemani, Diglyphus isaea and Eretmocerus mundus

The effect of ultra violet (UV)-absorbing plastic sheets on the host location ability of three commercially available parasitoids Aphidius colemani Viereck (Hymenoptera: Braconidae), Diglyphus isaea Walker (Hymenoptera: Eulophidae) and Eretmocerus mundus Mercet (Hymenoptera: Aphelinidae) – was tested in the laboratory and in field trials. The parasitoids’ preference between natural light and UV-filtered light was tested under laboratory conditions in a Y-shaped pipe system. The vast majority of all three species were strongly attracted to non-UV-filtered light. In field trials parasitoid’s ability to locate a host-infested plant from a distance (approximately 10 m.) was tested. Host location by A. colemani and D. isaea, expressed by parasitization rates, was not affected by greenhouse covering plastic type (regular versus UV-absorbing plastic). E. mundus, on the other hand, was unable to locate the host-infested plant when the latter was placed in the center of the UV-absorbing plastic covered greenhouses. When the host-infested plants were located in the corners of the greenhouses and the wasps were released at the center, the parasitization rates were lower under the UV-absorbing plastic than under the regular plastic covered greenhouses. The significance of UV light to E. mundus host location process and the practical implications it has on the parasitoid’s application in the field are discussed.

Modeling Photoinduced Algal Toxicity of Polycyclic Aromatic Hydrocarbons

The influence of light conditions on the toxicity of polycyclic aromatic hydrocarbons (PAHs) to different organisms has long been recognized. The aim of this study was to investigate whether previously proposed models can be used to qualitatively and quantitatively predict photoinduced toxicity to the green algae Scenedesmus vacuolatus. For this purpose 14 different PAH compounds were tested under three different light conditions for their effects on the algae reproduction. Illumination conditions comprised standard algae growth light, simulated sunlight aiming to mimic environmental light conditions, and UV-filtered light in order to minimize light influence on PAH toxicity. Models proposed for the prediction of photoinduced toxicity were modified in order to account for different exposure conditions and toxic endpoints used in the bioassay. The results of this study show that the gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) proposed as an indication for photoinduced toxicity to Daphnia magna can be used as a qualitative indication of a potential photoinduced toxicity to the green algae Scenedesmus vacuolatus. The impact of light conditions on PAH toxicity can be quantified by a linear model which allows the estimation of the ED50 of each compound from the amount of absorbed photons and an empirically determined relative phototoxic efficacy value of the compound.

Effect of H2O on the partial photo-oxidation of ethylene over Cu/SiO2 photocatalyst

Ethylene can be catalytically photo-oxidised with water as an oxidant over silica-supported copper oxide evacuated at 973 K. Presence of Cu+ cations in the catalyst is evidenced by X-ray Absorption Near-Edge Structure (XANES). Ethylene oxide is formed at 278 K with a selectivity higher than 80% by the irradiation with UV-filtered light longer than 280 nm.

Partial Photooxidation of Ethylene with Water as Oxidant over Copper Oxide Supported on Silica

Ethylene can be photooxidized selectively with water as an oxidant via irradiation with UV light over copper oxide supported on silica after evacuation at 973 K. Ethylene oxide was formed by irradiation of UV-filtered light at a wavelength longer than 280 nm, and a high selectivity to ethylene oxide (82.5%) with an ethylene conversion of 1.6% was obtained at 278 K for 5 h of irradiation. However, irradiation of UV-unfiltered light results in the disappearance of ethylene oxide, while carbon dioxide, acetaldehyde, ethanol, ethane, and C3 and C4 hydrocarbons are formed. X-ray absorption near-edge structure (XANES) spectroscopy showed the presence of Cu+ cations in the pore structure of the catalyst, suggesting that a mild oxidant can be generated from water on Cu+ sites by UV light irradiation.

Ultraviolet Filter Photography to Demonstrate the Fluorescence of Animal Lenses with Different Cataract Models

Ultraviolet (UV) filter photography with the Topcon SL-45 Scheimpflug camera has provided valuable informations about age-related and cataract-type-dependent changes in the spectral properties of the human lens. The present study deals with the same phenomenon in normal lenses of the Brown-Norway rat and in those with true diabetic and naphthalene cataracts. The lenses of all animals of the 3 groups were photographed at the middle and final examination of a 6-week experiment on Kodak Tri-X-pan ASA 400 black-and-white film, using visible light (xenon flash) and UV-filtered light (320-390 nm transmission) from the same light source for recording. The results clearly demonstrate that both cataract models exhibit characteristic fluorescence properties, different from each other and from normal rat lenses. The naphthalene cataract shows the most drastic increase in fluorescence in the cortex, compared to the increase in scattering with visible light. The versatility of the method in preclinical research and the versatility of the cataract models open new aspects of drug-related research in drug toxicity studies.